Language：English   Publishing type：Research paper (international conference proceedings)  

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DOI： 10.1109/ICSensT.2017.8304486

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DOI： 10.1016/j.compag.2016.04.025

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DOI： 10.13140/2.1.1643.8401

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圃場に設置された簡易モニタリング装置を用いて計測・収集される環境データは，作物の生育状況，病害虫の発生等の把握・予測のみならず，播種・移植，潅水，施肥，防除，収穫等の種々の農作業の最適化のための重要な情報となる．しかしながら，モニタリング装置の設置台数，さらには各装置に接続されたセンサー数の増加に伴い，データベースに保管されるた計測データは急速に増大していくすることが予想される．このため，これら膨大なデータの中から農業生産に必要なデータを効率的かつ迅速に抽出するための技術の開発が求められるている．本稿では，まず，圃場環境の常時監視，農業生産工程の最適化，農家間での生産情報の共有等を目的に著者らが開発を行ったハウス内環境の簡易モニタリングシステムについて概説する．次に，特異スペクトル変換と称される時系列データ解析手法に基づく特徴量抽出プログラムを開発し，同モニタリングシステムで計測されたハウス内環境情報の変化点の抽出，さらには，抽出した変化点情報と農作業履歴データとの比較・照査を行い，本解析手法ならびに自動検出された変化点情報の妥当性について検討を行った．

Language：English   Publishing type：Research paper (international conference proceedings)  

Field environmental information such as air temperature, humidity, and solar radiation would be important not only for evaluation of crop growth progress, status and quality or the occurrence of pests and diseases, but also for optimization of agricultural production processes such as plating, irrigation, fertilization, pest control, and harvesting. However, measured data stored in an agricultural information database, would be vast data with the increase in the number of monitoring devices and sensors installed in such devices. Thus, in order to extract feature values from such vast data, it is necessary to develop some numerical technologies and methods. In this study, the change point analysis based on Singular Spectrum Transformation (SST) was applied for extracting the difference of cultivation environmental conditions in each the tomato greenhouse. The change point scores were detected from the change of CO2 concentration data clearly. They agreed well with the farm work history recorded by a corporative farmer.

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Tillage is one of important operations to improve and maintain top soil condition in farmland. The soil condition is different according to soil types and region in general. Various kinds of the tillage methods and tools have been developed up to present. However, their developments have been often conducted by experience and sense using trial and error methods. From these backgrounds, developments of numerical analysis method have been tried to clarify the mechanism for soil-tillage interaction phenomena and to reduce the developing time and costs. In this study, the soil-tillage interaction simulation was established by a three-dimensional geometry of a disk plow and soil layer modeled by using discrete element method (DEM). Trac-tion resistances acting on the disk plow and soil cutting phenomena were estimated in the simulation. They were compared with the experimental results. The simulated results agreed qualitatively with the experimental results.

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Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

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PIV (Particle Image Velocimetry)

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Soil-Water Coupled Finite Element Analysis of Consolidation Test Consdering Frictional Sliding Phenomenon

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Elastoplastic finite element analysis on deformation behavior of ground surrounding anchor subjected to cyclic loading

Language：English   Publishing type：Research paper (international conference proceedings)  

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Elastoplastic finite element analysis on trap-door problem

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Studies on the measurement of the soil deformation by piv and the prediction for the stress in soil

Language：Japanese   Publishing type：Research paper (scientific journal)  

Elastoplastic finite element analysis on flow phenomena of powder and granular materials in silo

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Finite element analyses of frictional contact problems by the ｓubloading-ｆriction ｍodel

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An elastoplastic finite element analysis of soil-pile interaction by the subloading-friction model

Language：Japanese   Publishing type：Research paper (scientific journal)  

Deformation of over-consolidated soils under fill construction

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Lowering trap door simulation by finite element method introduced subloading surface model

Language：Japanese   Publishing type：Research paper (scientific journal)  

Friction theory based on the subloading surface concept

Language：English   Publishing type：Research paper (international conference proceedings)  

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Elastoplastic finite element analysis of ground deformation behavior due to uplifting of anchor

Language：Japanese   Publishing type：Research paper (scientific journal)  

Generalized rate-dependent inelastic constitutive equation (Application to metals)

Language：Japanese   Publishing type：Research paper (scientific journal)  

An advanced technique for displacement measurement of soils

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Deformation behavior of shirasu and its prediction by the subloading surface model

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Evaluation of typical conventional and unconventional plasticity models for prediction of softening behavior of soils

Language：Japanese   Publishing type：Research paper (scientific journal)  

A proposal for internet education on elastoplasticity

Language：English   Publishing type：Research paper (scientific journal)  

Time-dependent elastoplastic constitutive equation of soils and its application to fem implementation

Language：Japanese   Publishing type：Research paper (scientific journal)  

Elastoplastic finite element analysis for ground deformation behavior subjected to cyclic loading

Language：Japanese   Publishing type：Research paper (scientific journal)  

Evaluation of conventional and unconventional plasticity for prediction of softening behavior

Language：Japanese   Publishing type：Research paper (scientific journal)  

Development of fem program as a soil-water coupled finite deformation introducing the extended subloading surface model

Language：English   Publishing type：Research paper (international conference proceedings)  

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Time-dependent elastoplastic constitutive equation based on subloading surface model and its application to soils

Language：Japanese   Publishing type：Research paper (scientific journal)  

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Image processing on-line measurement for soil displacement

Language：English   Publishing type：Research paper (scientific journal)  

Time-dependent elastoplastic constitutive model

Language：Japanese   Publishing type：Research paper (scientific journal)  

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DOI： 10.1007/s42853-024-00237-w

Web of Science

Language：English   Publisher：Japanese Society of Agricultural Informatics  

<p>As robotic systems become increasingly integrated into plant phenotyping processes, the quality of images captured plays an increasingly crucial role in accurate data collection and analysis. Here we address the challenge of assessing and enhancing image quality in the context of plant phenotyping robot using a pan-tilt-zoom camera. We present a data-driven approach using machine learning, specifically the Random Forest classifier, to classify both blurred and sharp images. Our method involves feature extraction, data preprocessing, hyperparameter tuning, and cross-validation. The resulting model demonstrates promising performance as indicated by its accuracy, precision, recall, area under the curve (AUC), and feature importance analysis. Notably, our results support a highly accurate classifier, achieving a correct classification rate of 95% for sharp images and 92% for blurred ones, a receiver operating characteristic curve with an AUC of 0.93, and a precision-recall curve with an average precision of 0.91. Shapley Additive Explanations analysis identifies “edge density” and “mean gradient magnitude” as influential to the classifier, offering valuable insights for future feature engineering and model refinement. The classifier has a short inference time (2.8 s) on a Raspberry Pi 4B computer, both improving the quality of captured images and automatically eliminating blurred images. By enhancing image quality assessment, this research improves data reliability and the overall effectiveness of plant phenotyping robots. We discuss the implications of these findings and their practical relevance and suggest directions for future research.</p>

DOI： 10.3173/air.33.97

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Publisher：Scientia Horticulturae  

Harnessing the power of Vapor Pressure Deficit (VPD) control, this novel research illuminates a pathway to enhanced plant growth and yield within Micro-Plant Factory (McPF) and Urban Mini-Plant Factory (UMPF) environments. The research focused on the growth parameters of spinach microgreens, with the experimental data originating from each system's upper, central, and lower shelves. Results indicated significantly enhanced plant height and dry weight on the central shelves, attributed to optimal VPD control. Growth analysis also revealed higher relative growth rates (RGR) under tightly managed VPD conditions on the central shelves, even amidst varying environmental parameters. Most notably, effective VPD control translated these growth metrics into increased yields. For instance, a 71 % and 66 % increase in final plant dry weight over the lower and upper shelves was noted. These advances were mirrored in the plant height, which also saw 57 % and 103 % growth. Overall, the findings underscore the critical role of VPD control in plant growth and yield enhancement within structured environments like McPF and UMPF, offering significant insights for future research in manipulating VPD for optimal plant growth and productivity.

DOI： 10.1016/j.scienta.2024.113229

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Scopus

Publishing type：Research paper (scientific journal)   Publisher：Journal of Horticultural Science and Biotechnology  

We evaluate whether cumulative photosynthesis (A n,C) could predict the time of harvest in strawberry better than light (I C) or temperature (T a,C) as forecast indices. We monitored the daily dynamics of flowering, fruit set, and harvest in over 2,700 fruits across the growing season in a greenhouse in Japan. Photosynthesis was calculated using a biochemical model, and A n,C calculated by totalling the cumulative rate from flowering to harvest in each fruit. I C and T a,C were calculated by totalling daily cumulative light intensity and average temperature. A new index (D) was defined as the normalised variation of A n,C, I C, and T a,C, and a statistical analysis was conducted on the means for each index. The results showed that A n,C had the lowest D (0.114), suggesting that it was a better index for predicting the time of harvest. This study suggests the importance of considering the accumulation of photosynthates in individual fruit, which cannot be achieved by I C or T a,C, these results can be used to improve the forecasting and optimisation of yield. However, further research is required to substantiate these claims.

DOI： 10.1080/14620316.2023.2254759

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Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publisher：Japanese Society of Agricultural, Biological and Environmental Engineers and Scientists  

DOI： 10.2525/shita.36.2

CiNii Research

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

Abstract

CO₂ enrichment is an essential environmental control technology due to its significantly enhancing effect on crop production capacity. Despite being a key energy consumer in protected agriculture (i.e. greenhouse systems), CO₂ enrichment remains at a low energy use efficiency level, highlighting the need for developing more energy-efficiency strategies for CO₂ enrichment. Therefore, this study employed the computational fluid dynamics (CFD) simulation method to replicate the CO₂ diffusion process resulting from CO₂ enrichment in three commercial strawberry greenhouses with varying geometric characteristics. Based on the CFD-simulated CO₂ concentration distributions, the leaf photosynthetic rate was calculated using a mathematical model group. The CO₂ enrichment efficiency was then analysed by calculating the ratio of increased photosynthesis across the cultivation area to the amount of energy (in CO₂ equivalent) used. The efficiency peaked when the average CO₂ concentration was approximately 500 μmol mol⁻¹, thereby providing guidance for determining the target concentration of CO₂ enrichment in production. Although this study is limited as the CFD simulation only considered a typical short-period CO₂ enrichment event, future research will provide a broader analysis by considering changes throughout the day.

DOI： 10.1038/s41598-023-44200-9

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Other Link： https://www.nature.com/articles/s41598-023-44200-9

Language：Japanese   Publisher：Japanese Society of Agricultural, Biological and Environmental Engineers and Scientists  

DOI： 10.2525/shita.35.39

CiNii Research

Publishing type：Research paper (scientific journal)   Publisher：Journal of Cleaner Production  

In greenhouse cultivation, microclimate control is a highly energy-consuming process, and CO2 enrichment, which is a part of it, requires the direct consumption of fossil fuel energy. To achieve sustainable and economical greenhouse management, we must understand the performance and energy utilisation efficiency of CO2 enrichment in greenhouses. In this study, we conducted computational fluid dynamics (CFD) simulations for two CO2 enrichment methods in a strawberry greenhouse: (1) conventional overall greenhouse enrichment (‘Entire Enrichment’) and (2) crop-localised enrichment (‘Local Enrichment’). The spatial distribution of microclimate parameters was simulated using a CFD model; based on the results, the spatial distribution of the crop photosynthetic rate was also simulated using an environment–plant coupled model group. Furthermore, we quantitatively analysed the efficiency of CO2 enrichment (ECE) by calculating the changes in the photosynthetic carbon assimilation capacity of the crop canopy in relation to CO2 usage, which allowed us to propose a more efficient enrichment strategy. Compared with the Entire Enrichment method, the Local Enrichment method reduced the effects on greenhouse temperature and humidity but increased the average CO2 concentration inside the canopy by 264 μmol mol−1. As a result, Local Enrichment increased the average leaf photosynthetic rate inside the canopy by 1.48 μmol m−2 s−1. According to ECE analysis, Local Enrichment has huge advantages over Entire Enrichment; the mean ECE of Local Enrichment was approximately 4.4 times higher than that of Entire Enrichment (25.7 and 5.9 mmol mol−1, respectively). Moreover, scenario analysis indicated that the Local Enrichment system could be applied to larger greenhouses and improves ECE relative to that in a conventional system. Having compared the two enrichment methods comprehensively, we conclude that the Local Enrichment method could significantly improve the environmental parameters around the crop canopy in relation to photosynthesis and greatly enhance CO2 utilisation efficiency.

DOI： 10.1016/j.jclepro.2022.133465

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Language：English  

Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

Crop productivity is largely dependent on canopy photosynthesis, which is difficult to measure at farming sites. Therefore, real-time estimation of the canopy photosynthetic rate (Ac) is expected to facilitate effective farm management. For the estimation of Ac, two types of mathematical models (i.e., process-based models and empirical models) have been used, although both types have their own weaknesses. Process-based models inevitably require many model parameters that are difficult to identify, while empirical models, including artificial neural network (ANN) models, have a low predictive ability outside of the range of training datasets. To overcome these weaknesses, we developed a hybrid canopy photosynthesis model that included components of both process-based models and ANN models. In this hybrid model, the single-leaf photosynthetic rate (AL) and leaf area index (LAI) were first estimated from information easily obtainable at farming sites: AL was estimated by the process-based model of AL (i.e., the biochemical photosynthesis model of Farquhar et al. (1980)) from environmental data (photosynthetic photon flux density (PPFD), air temperature (Ta), humidity, and atmospheric CO2 concentration (Ca)), and the LAI was estimated by an analysis of crop canopy imagery. As highly explainable information for Ac, the estimated AL and LAI were input into the ANN model to estimate Ac. As such, the ANN model learned the logical relationships between the inputs (AL and LAI) and the output (Ac). Detailed validation analysis using nine spinach Ac datasets revealed that the hybrid ANN model can estimate Ac accurately throughout the whole growth period, even when training and test datasets were obtained in different seasons under different CO2 concentrations and based on training datasets of only three days. This study highlights the high generalizability of the hybrid ANN model, which is a prerequisite for practical application in environmentally controlled crop production.

DOI： 10.1016/j.agrformet.2022.109036

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Language：English   Publishing type：Research paper (international conference proceedings)  

Publishing type：Research paper (scientific journal)   Publisher：Scientia Horticulturae  

In protected strawberry (Fragaria × ananassa Duch.) cultivation, CO2 enrichment is essential to enhance both fruit quality and yield. Fuel burning generators are commonly used to supply CO2 to entire commercial greenhouse space. However, methods that are less fuel-based are desired for contemporary agricultural practices. A new crop-local CO2 enrichment system using a modified fuel-burning generator has been developed to increase yields and decrease the fuel required for CO2 enrichment in greenhouse strawberry production. This crop-local CO2 enrichment (CLC) method directly supplies CO2 from perforated tubes set in the interrow space of the plant canopy. The effects of this technique on fruit quality, fruit yield, and fuel use efficiency have been examined in comparison with conventional CO2 enrichment (CC) practices. The CLC method increased CO2 concentration inside the plant canopy by 100–200 μmol mol–1 when compared with CC under the ventilating conditions by a roof window. This resulted in significant increases of approximately 10–26% in the average fruit weight, 13% in the cumulative fruit number, and 22% in cumulative marketable yield when compared to CC. Furthermore, cumulative fuel consumption was approximately 27% lower with the CLC method when compared to CC. These results indicate that CLC improves fuel use efficiency when compared with CC as it increased yields and decreased fuel consumption.

DOI： 10.1016/j.scienta.2022.111104

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Language：English  

Publisher：Environmental and Experimental Botany  

Carbon export from leaves as translocation is a result of plant coordination of leaf carbohydrate availability. Carbohydrate availability coordination is actively studied in model plants (Arabidopsis) under regulated conditions and can be optimized to increase productivity. However, in horticultural crops grown under field conditions, carbon export dynamics and coordination are poorly understood. The objective of this study was to analyze the dynamics of carbon export from leaves and the effects of carbohydrate availability coordination on these dynamics in strawberry grown under field conditions. Through three different day/night cycles, we measured leaf carbohydrate concentrations and photosynthetic rates and evaluated the dynamics of carbon export based on the leaf carbon balance. During the daytime, when carbon resources are almost entirely supplied by photosynthesis, strawberry leaves stored sucrose and starch. Starch synthesis was remarkable when sucrose concentration exceeded 150 mmol m−2, and the carbon export rate tended to increase. In the nighttime, when carbon resources are supplied by leaf sucrose and starch stored during the daytime, the starch concentrations decreased linearly and the carbon export rate was lower than the daytime level. These results indicate that in the daytime, the coordination of leaf carbohydrate availability for starch storage and carbon export was affected by leaf sucrose concentration, whereas, at night, it was regulated by leaf carbon storage levels at dusk rather than sucrose concentration. Thus, this study elucidates the basis of carbon export dynamics in strawberry leaves under field conditions, advancing our understanding of the role of leaf carbohydrates in translocation.

DOI： 10.1016/j.envexpbot.2022.104806

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Language：Japanese   Publisher：The Japanese Agricultural Systems Society  

<p>Rice production in Japan faces concerns over yield reduction and poor grain quality owing to unstable weather conditions and the deterioration of soil fertility. In addition, it needs to increase competitiveness against foreign agricultural products and other food products. This situation requires to develop analytical methods to effectively use data regarding agriculture, which is becoming easily available with information and communication technologies. The objectives of this study were 1) to build the predictive model of three classes (low, middle, and high) of ripened brown rice yield using data collected in the production sites, 2) to clarify limiting factors of yield using the predictive model, and 3) to investigate measures to improve yield. We applied support vector machine to build the predictive model using data collected from 2011 to 2016 in a total of 90 paddy fields. The paddy fields where Hinohikari cultivar was cultivated were located in the city of Itoshima, Fukuoka Prefecture. The predictive model built included three explanatory variables: the number of rough rice, daily mean sunshine hours during the period from five days after heading to the late ripening period, and mineral nitrogen supply from the early panicle formation to the late ripening periods. The predictive model achieved the classification accuracy of 77.8%. Particularly, paddy fields categorized in the low yield class had small tiller number at the panicle initiation stage. As the result, small number of rough rice decreased yield. Some paddy fields, where their yield was categorized in the middle class and was categorized in the high class with the number of rough rice greater than 28 thousand m^-2, reduced yield because of shortage of mineral nitrogen supply during the ripening period. The measures to improve yield were as follows: for the paddy fields categorized in low yield class, to ensure appropriate number of rough rice by increasing tiller number during the vegetative growth stage, and for paddy fields where shortage of mineral nitrogen supply during the ripening period reduced yield, to apply topdressing two times to meet the standard nitrogen application rate in the surveyed region (3.6 kg/10a in total). This measure obtained for topdressing indicates that the analysis using survey data collected in rice production sites supported the standard that has been determined by local cultivation tests as well as trial and error in the production sites.</p>

DOI： 10.14962/jass.38.1_1

CiNii Research

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japanese Society of Agricultural, Biological and Environmental Engineers and Scientists  

<p> We designed and constructed a light-shielding, closed fruit chamber system that can easily measure the respiration rate of intact fruits. Intact strawberries (<i>Fragaria×ananassa</i> Duch. cv. Fukuoka S6) were placed in the newly-developed system, and the change in CO₂ concentration was measured. It was observed that this method was a valid means of determining the change in the CO₂ concentration. Also, the respiration rate of the intact fruits could be evaluated appropriately by fitting a theoretical equation to the change in CO₂ density for 180 s after closing the chamber measured by newly-developed system and obtaining the initial slope. This method was applied to intact strawberries at different ripening stages, and the effect of on the respiration rate was investigated. As the ripening stage progressed and the volume of fruits increased, the respiration rate per fruit at each ripening stage also significantly increased. However, there was no significant difference in the respiration rate per unit fruit volume at each ripening stage. These results suggest that newly-developed system is effective in measuring the respiration rate per fruit. This system would contribute to the comprehension of intact fruit respiration and photosynthate translocation to fruits.</p>

DOI： 10.2525/ecb.60.33

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Language：English  

Publisher：IOP Conference Series: Earth and Environmental Science  

A significant urban population increases with the rising demand for higher food quality and security. Adapting the current food chain system and our eating patterns are needed to make them more sustainable. Plant factories are one approach for making the food chain system more sustainable. However, plant factory systems typically require significant initial capital expenditure. As a result, a mini plant factory, which is more affordable and flexible, will be appropriate in urban areas. The objective of this study was to design, build, and evaluate a mini plant factory system for horticultural crop production. The mini plant factory system comprises a mini cultivation room with three growing shelves equipped with a microclimate sensor, nutrient dosing system, artificial growth light, and ventilation system. Sensors and actuators are integrated with the Agrieye Cloud system for monitoring and control and can autonomously execute data retrieval and actuation. Mini Plant Factory operates by automatically capturing monitoring data every five minutes; if a value exceeds the limit, the actuator control system activates to stabilize that value. The linear regression test yielded the most excellent R2 value of 0.999 for sensor calibration. The validation test was conducted using RMSE (Root Mean Square Error) and MAPE (Mean Absolute Percentage Error). The results show that the lowest RMSE values are 0.133, and the lowest MAPE values are 0.082%. The data logging system's performance is perfect. The control and scheduling system works well but does not function optimally since there are no interruptions throughout the data gathering process.

DOI： 10.1088/1755-1315/1116/1/012028

Scopus

Language：English   Publisher：Japanese Society of Agricultural Technology Management  

DOI： 10.20809/seisan.27.3_85

CiNii Research

Publishing type：Part of collection (book)   Publisher：Springer Nature Singapore  

DOI： 10.1007/978-981-19-1154-5_6

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Publisher：IOP Conference Series: Earth and Environmental Science  

Plant growth monitoring is an important aspect of precision agriculture implementation. The monitoring can be performed by estimating the volume by the result of Three-dimensional (3D) reconstruction by using Close-range Photogrammetry. However, to present the functionality of the system for plant growth behavior, it is necessary to evaluate its accuracy and performance. In this study, a plant growth estimation system based on non-contact measurement using the Close-Range Photogrammetry (CRP) method for volume estimation of Chinese cabbage was developed to measure the growth. The objective of this study was to apply a 3D reconstruction system using the CRP method for validating volume variation and estimate the rate of growth of Chinese cabbage. This system consists of Canon 700D's DSLR camera and camera stabilizer. The stage of image processing using 3DF's Zephyr Pro photogrammetric software for generating 3D models. For the validation purposes and its functionality for modelling and estimating volumetric objects, Chinese cabbage with four size variations at different ages was used (14, 21, 28, and 35 Days After Transplant). As the result, the developed system could observe and generate the plant in a three-dimensional manner resemble the actual plant model. Farther the volumetric validation could be obtained with the result of R2 of 0,9991, Root Mean Square Error (RMSE) = 26,08 cm3 and Mean Absolute Percentage Error (MAPE) = 10,43%. From the result, the system could be used for generating plants into 3D objects and its accuracy of measurement is quite good. Further improvements in accuracy need to be made for precise measurements as well as validation for other crop types.

DOI： 10.1088/1755-1315/1038/1/012051

Scopus

Publisher：IOP Conference Series: Earth and Environmental Science  

Limited land for agricultural cultivation in urban areas makes it difficult to fulfill for healthy and sustainable food. Mini Plant Factory is an alternative to produce food, especially vegetables. In the Mini Plant Factory, the distribution of air flow is one thing that must be considered because the air flow will affect the growth of the plants in it so it is necessary to do an analysis to determine the good air flow in the mini plant factory using Computational Fluid Dynamics (CFD) software. The purpose of this study was to analyse the aeration of the air flow in the mini plant factory using Computational Fluid Dynamics. This research was carried out at smart agriculture UGM, in this study using a mini plant factory measuring 70 x 40 x 150 cm, which is equipped with a temperature sensor (DHT 22) of 1 units in each shelf and 1 unit on the outside for measure environmental conditions, with a total number of 4 temperature sensors, the mini plant factory is also equipped with an automatic nutrition system that is integrated with the cloud, and is equipped with artificial lighting. CFD analysis was carried out using the Ansys 2022 software, the laptop specifications used were AMD Ryzen 7 4800 H, NVIDIA GeForce RTX 3050. Temperature data was measured during the observation period. The analysis method in CFD has several stages, namely preparation, meshing workflow, mesh, models, materials, boundary conditions, solution and post-processing. The last part is data validation, namely by making a comparison between the CFD results and the actual data, then calculating the error value using MAPE. The expected result are visualisation various distribution of aeration temperatures inside mini plant factory, optimum aeration design for mini plant factory.

DOI： 10.1088/1755-1315/1116/1/012029

Scopus

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (bulletin of university, research institution)  

Repository Public URL： https://catalog.lib.kyushu-u.ac.jp/opac_detail_md/?lang=0&amode=MD100000&bibid=4363556

Language：English   Publishing type：Research paper (bulletin of university, research institution)  

Repository Public URL： http://hdl.handle.net/2324/4363552

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (bulletin of university, research institution)  

Language：English   Publishing type：Research paper (scientific journal)  

To understand long-term association between canopy-scale photosynthesis and growth, we continuously and simultaneously measured the net photosynthetic rate (A_c) and leaf area index (LAI) of a spinach canopy from transplantation to harvesting. This long-term measurement was enabled by combining an open-type flux chamber method and image analysis of top-of-view canopy photographs. The photosynthetic photon flux density (PPFD) was the major determinant of A_c during a short-term period, but the change in A_c was significantly amplified by an increase in LAI during a long-term period. LAI, measured with reliable accuracy from gap fractions (projected non-leaf areas) of top-of-view photographs, increased exponentially through the growth period. These results indicate a positive feedback loop between photosynthesis and growth (i.e., the growth of leaves amplifies photosynthesis, and the amplified photosynthesis further accelerates the growth of leaves). Consequently, a linearity was found between cumulative canopy net photosynthesis (ΣA_c) and LAI, implying that throughout the growth period, a fixed proportion of dry matter was partitioned to the leaves and that the leaf area was expanded in proportion to the partitioned dry matter. This linearity between ΣA_c and LAI also suggests that growth of a leafy vegetable canopy can be predicted from canopy photosynthesis.

DOI： 10.2525/ecb.58.21

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

To understand long-term association between canopy-scale photosynthesis and growth, we continuously and simultaneously measured the net photosynthetic rate (A_c) and leaf area index (LAI) of a spinach canopy from transplantation to harvesting. This long-term measurement was enabled by combining an open-type flux chamber method and image analysis of top-of-view canopy photographs. The photosynthetic photon flux density (PPFD) was the major determinant of A_c during a short-term period, but the change in A_c was significantly amplified by an increase in LAI during a long-term period. LAI, measured with reliable accuracy from gap fractions (projected non-leaf areas) of top-of-view photographs, increased exponentially through the growth period. These results indicate a positive feedback loop between photosynthesis and growth (i.e., the growth of leaves amplifies photosynthesis, and the amplified photosynthesis further accelerates the growth of leaves). Consequently, a linearity was found between cumulative canopy net photosynthesis (ΣA_c) and LAI, implying that throughout the growth period, a fixed proportion of dry matter was partitioned to the leaves and that the leaf area was expanded in proportion to the partitioned dry matter. This linearity between ΣA_c and LAI also suggests that growth of a leafy vegetable canopy can be predicted from canopy photosynthesis.

DOI： 10.2525/ecb.58.21

Language：English   Publishing type：Research paper (other academic)  

Plant factory is an extensive cultivation that produce vegetable under a controllable environment. The concept of Precision Agriculture has been introduced to enhance the plant factory production by monitoring of crop growth intensively. Crop growth can be estimated using a mathematical model to determine the state of the plant during the growth period. However, the application of a crop growth model in plant factory has several challenges because every plant has a specific model to be observed. The objective of this study was to construct a crop growth prediction model for vegetative development phase. The activity covers the development of mathematical model and model validation using Chili (Capsicum frutescens) as a preliminary experiment. Four samples (S1, S2, S3, S4) of Chili with age of five weeks after planting were used and measured daily for 30 days to get the actual height (cm). Three crop height observation data set (S1, S1, S3), were used to develop a mathematical model and the rest dataset was for model validation and evaluation. Linear and polynomial model were applied to obtain the appropriate prediction. The model was validated and evaluated using the Root Mean Squared Error (RMSE) and Mean Absolute Percentage Error (MAPE). As a result, Determination coefficient (R²) of the Linear model was 0.9667, and the RMSE was 2.16; The Polynomial model shows R² 0.98755, and RMSE RMSE 1.68. The result of the model that is suitable for the Chili crop during the vegetative phase is the polynomial model with error rate of 1,68%.

DOI： 10.1063/1.5141717

Language：English   Publishing type：Research paper (other academic)  

Circadian rhythm is a biological rhythm in a plant that has a 24-hour period, which affects the plant activities, such as metabolism processes, physiology processes, and plant behavior. Generally, Circadian rhythm has two factors affecting the synchronizing the biological clock: Light and temperature cycle. In our previous studies, plant motion monitoring systems based on leaf movement have been developed to determine the circadian rhythms of a regular plant under the normal condition. However, the performance of the system to monitor the plant rhythm under abnormal conditions relating to the biological clock, lighting interval treatment, does not establish yet. The objective of this study was to implement a plant motion monitoring system to study plant behavior with 16-hour and 12-hour lighting interval treatment. The plant's motion of Chili (Capsicum annum L.) was observed in a growth chamber equipped with an infrared camera and raspberry pi, which is used to take pictures continuously at certain intervals using top projection view. Periode of circadian rhythms phase, the amplitude of the plant were analyzed and compared. As a result, plant motion monitoring system could be used to monitor the circadian rhythm on Chili (Capsicum annum L.) with the variation of lighting interval (12-h and 16-h). The amplitude of 16-hour lighting has higher and the period shift indicated late oscilation comparing the 12-hour lighting. The higher amplitude and late in oscilation is accordance with previous studies that environmental cues, such as light, can reset the clock and can also affect the rhythm output clock.

DOI： 10.1063/1.5141715

Language：English   Publishing type：Research paper (other academic)  

Plant Factory is a large-scale vegetable production method with limited, closed, and controlled space. This system is endeavored to support the sustainability of agricultural production system by applying the concept of precision agriculture. This concept is implemented to observe plant growth effectively and efficiently. Currently, in the conventional way monitoring carried out one by one, using the computer vision technology will help accelerate plant growth monitoring in the Plant Factory. However, in the application in a Plant Factory, it requires many cameras to be used for growth monitoring for each crop to support the precise measurement. So, it is necessary to have a system that supports the mobility of the camera module inside the plant factory. The objective of this study was to design the Mobile RoboVision using the stereo camera for automatic Crop Growth Monitoring. The system consists of three modules: Stereo camera positioning system using M1 Computer Numerical Control (1000mm x 1000mm of size) equipped with x and y motor for flexible movement; Image acquisition system using Raspberry Pi B+ as microcomputer unit installed Stereo Camera standard with quad IR Illuminator and sensors; Data collection system using Cloud Storage. The camera positioning system manages the position of the camera module to stop in every crop in specified coordinate C1..n = {(x1, y1), (x2, y2), ..(xn, yn)} and capture stereo images automatically. The captured image will be managed in a data collection system using Cloud System to provide flexible and convenient access for further analysis.

DOI： 10.1063/1.5141713

Language：English   Publishing type：Research paper (other academic)  

Circadian rhythm is a biological rhythm that has a period of 24 hours. Leaf movement is one of physical indicator that commonly used to detect the circadian rhythms in the plant. In its application, it is required to design a plant motion monitoring system that can work automatically and continuously to estimate the period of plant motion and quantify the circadian rhythm. Generally, a plant monitoring system uses a top view projection to monitor plant activity. To extend its functionality, the side view projection was also important to monitor the plant behavior from a horizontal point of view. The objective of this study was to design and evaluate the performance of the Top and Side view projection as multi-camera for continuous plant motion monitoring system. The system composed of two IR LED cameras with Top and Side view projection and connected to the microcomputer (Raspberry Pi3 B+). The data were analyzed by Optical Flow method using OpenCV Library applying Shi-Tomasi and Lucas Kanade. Estimation of circadian rhythms was using the FFT (Fast Fourier Transform) method. The multi-camera system was evaluated to monitor the motion of Chili (Capsicum annum L.) by observing the time series of circadian rhythm, Period, Amplitude, and Phase. As a result, the system could be used to monitor the circadian rhythm for both Top and Side view projection. The Frequency and Period have the same value 0,00001157 and 24-hour. The Top view projection has higher amplitude means, for the same object motion it could represent clear motion.

DOI： 10.1063/1.5141716

Language：English   Publishing type：Research paper (scientific journal)  

Tropical agriculture production is profoundly affected by the uncontrollable environmental condition. To obtain good agricultural products, farmers manage their farm to fit with the variation of weather and season. The farming managements are generally determined according to farmers personal knowledge, gained from the long-term experience from preceding years. Nowadays, climate change intensifies unpredictable weather and its unstable distribution. Consequently, conventional farming management considering the climate change factor should be considered. The farming management should face the dynamic change of weather condition as well as improve the farmer's knowledge towards the implementation of precision agriculture approach. The objective of this study was to introduce an appropriate adaptation of precision agriculture technology by the utilization of information and communication technology (ICT) to improve conventional farming management in tropical agriculture production. The framework is implementing cloud technology as a backbone, which can be extended with various knowledge such as data science, plant biology, plant physiology, biophysical, and biomechanical. The appropriate adaptation of precision agriculture represented by the improvement of the conventional farming method using the technological aspect by fostering their knowledge to adopt modern agriculture empowered with Information and Communication Technology (ICT). Learning process from data-information-knowledge on the application of precision agriculture will be documented at the PA Knowledge Management System.

DOI： 10.1088/1755-1315/355/1/012028

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Wireless Sensor Network (WSN) is widely used in field environmental monitoring recently, because of its ease of use and being able to simplify the complexity installation in real application. Indonesia is an agricultural country with more than 16.5 million of farming land, most of the farming land is located in a rural area. The problems on the implementation of IoT-based environmental monitoring system in a rural area is the limited signal and energy. Accordingly, the objective of this study was to develop an Environmental Monitoring System based on LoRa in a rural area with the implementation of the Local Management Subsystem (LMS) and Global Management Subsystem (GMS) framework to optimize the existing development of the Environmental Monitoring System with focused on optimum distance by measuring the RSSI, signal strength and packet loss. The research was conducted in Bulaksumur Universitas Gadjah Mada, Yogyakarta, with four zones and various obstacles. As the result, Zone D with line of sight was the best result for getting the affordable distance for data transmission. This Zone can reach over 800 m distance with only 20% packet loss.

DOI： 10.1088/1755-1315/355/1/012010

Language：English   Publishing type：Research paper (bulletin of university, research institution)  

Language：English   Publishing type：Research paper (bulletin of university, research institution)  

Language：English   Publishing type：Research paper (bulletin of university, research institution)  

Language：English   Publishing type：Research paper (scientific journal)  

A torque management model (TMM) focused on the close matching of driving requirements and operating conditions for electric tractors was developed. The TMM used the accelerator pedal output signal to establish the torque demand to adapt for two conditions – field traction and road driving. Further, the TMM uses the limitations of a time-based torque ramp, maximum motor torque at the current speed, and battery state of charge. To verify the performance of the TMM, a tractor control unit (TCU) to support the TMM was designed, and a test bench comprising both driving and loading devices was built. The bench provided the TMM/TCU with the necessary operating states needed as inputs to determine the torque demand. Experiments were performed under five specific manoeuvring cases. The test results showed that the TMM was capable of accurately converting pedal manipulations into torque demands both in the field traction and road driving conditions. The torque changes during testing were properly smoothed by limiting the rising and falling time of the target torque, which was favourable for eliminating impacts due to torque fluctuations. Overloading operations that would occur in case of excessive torque request were avoided by the torque capacity limitation both in the field traction and road acceleration tests. When the bus voltage was deliberately adjusted below the alarm threshold, the TMM could scale down the torque demand in real time according to the deviation between the actual voltage and the threshold, and therefore, it always kept the voltage above the safe level.

DOI： 10.1016/j.biosystemseng.2019.04.002

Language：English   Publishing type：Research paper (scientific journal)  

A torque management model (TMM) focused on the close matching of driving requirements and operating conditions for electric tractors was developed. The TMM used the accelerator pedal output signal to establish the torque demand to adapt for two conditions – field traction and road driving. Further, the TMM uses the limitations of a time-based torque ramp, maximum motor torque at the current speed, and battery state of charge. To verify the performance of the TMM, a tractor control unit (TCU) to support the TMM was designed, and a test bench comprising both driving and loading devices was built. The bench provided the TMM/TCU with the necessary operating states needed as inputs to determine the torque demand. Experiments were performed under five specific manoeuvring cases. The test results showed that the TMM was capable of accurately converting pedal manipulations into torque demands both in the field traction and road driving conditions. The torque changes during testing were properly smoothed by limiting the rising and falling time of the target torque, which was favourable for eliminating impacts due to torque fluctuations. Overloading operations that would occur in case of excessive torque request were avoided by the torque capacity limitation both in the field traction and road acceleration tests. When the bus voltage was deliberately adjusted below the alarm threshold, the TMM could scale down the torque demand in real time according to the deviation between the actual voltage and the threshold, and therefore, it always kept the voltage above the safe level.

DOI： 10.1016/j.biosystemseng.2019.04.002

Language：English   Publishing type：Research paper (bulletin of university, research institution)  

Language：English   Publishing type：Research paper (bulletin of university, research institution)  

Language：English   Publishing type：Research paper (bulletin of university, research institution)  

Language：English   Publishing type：Research paper (other academic)  

This paper presents an outline of our project, in which we develop an observation framework for integrating lecture and contextual learning in the field of crop cultivation. Specifically, we will use multi sensing of learners' activities in classrooms, and contextual learning in fieldwork, farm planting, and farming environments. The motivation for our project is twofold: First, crop cultivation provides a powerful illustration of educational technology. It requires both explicit knowledge (from lectures) and implicit knowledge (from contextual learning outside of class). Second, from a practical viewpoint, the number of Japanese farmers is shrinking due to low income and to aging population. Thus, in order to maintain crop yields, farming skills must be transferred efficiently to novice farm workers. Herein, the major features of our framework will be described.

Language：English   Publishing type：Research paper (scientific journal)  

This paper proposes a new approach to visualizing spatial variation of plant status in a tomato greenhouse based on farm work information operated by laborers. Farm work information consists of a farm laborer’s position and action. A farm laborer’s position is estimated based on radio wave strength measured by using a smartphone carried by the farm laborer and Bluetooth beacons placed in the greenhouse. A farm laborer’s action is recognized based on motion data measured by using smartwatches worn on both wrists of the farm laborer. As experiment, harvesting information operated by one farm laborer in a part of a tomato greenhouse is obtained, and the spatial distribution of yields in the experimental field, called a harvesting map, is visualized. The mean absolute error of the number of harvested tomatoes in each small section of the experimental field is 0.35. An interview with the farm manager shows that the harvesting map is useful for intuitively grasping the states of the greenhouse.

DOI： 10.3390/s18113906

Language：English   Publishing type：Research paper (scientific journal)  

This paper proposes a new approach to visualizing spatial variation of plant status in a tomato greenhouse based on farm work information operated by laborers. Farm work information consists of a farm laborer’s position and action. A farm laborer’s position is estimated based on radio wave strength measured by using a smartphone carried by the farm laborer and Bluetooth beacons placed in the greenhouse. A farm laborer’s action is recognized based on motion data measured by using smartwatches worn on both wrists of the farm laborer. As experiment, harvesting information operated by one farm laborer in a part of a tomato greenhouse is obtained, and the spatial distribution of yields in the experimental field, called a harvesting map, is visualized. The mean absolute error of the number of harvested tomatoes in each small section of the experimental field is 0.35. An interview with the farm manager shows that the harvesting map is useful for intuitively grasping the states of the greenhouse.

DOI： 10.3390/s18113906

Language：English   Publishing type：Research paper (scientific journal)  

Whole crop rice (WCR) is expected to establish a cultivation method using manure produced from animal wastes. Meanwhile, application methods of fertilizer and manure in the WCR cultivation are affected by availability of manure, available time for its application, and field drainage, and low market price of WCR. This raises concerns about soil fertility deterioration and yield reduction in the WCR cultivation. The objectives of this study were to investigate how different application methods of fertilizer and manure affected soil chemical properties and yield in the WCR cultivation. Field surveys were conducted in 2013 and 2014 at 10 fields cultivated by five different farmers in the Itoshima region, Fukuoka Prefecture, Japan. The surveyed fields included two application methods of manure (M) alone and chemical fertilizer (CF) alone. Clay plus silt content was significantly correlated with total nitrogen (TN), total phosphorus (TP), and exchangeable potassium (Exch. K), which indicated that soil texture partly contributed to the variations of these soil chemical properties. Meanwhile, clear gaps of TN, TP, Exch. K, K saturation degree, and available N between CF and M at around 40% of clay plus silt content strongly suggested that manure application contributed to increases in the soil chemical properties. Yearly differences of available N had relatively large negative values in CF fields. This result suggested a possible decrease in mineralizable part of soil TN in the WCR cultivation with CF alone, which needs to be clarified through long-term study. Significant relationships between potential N supply and straw weight (r = 0.698, p < 0.05 for 2013; r = 0.873, p < 0.01 for 2014) or yield of whole crop (r = 0.852, p < 0.01 for 2014) indicated that N mineralized from soil, which was enhanced by manure application, increased straw weight, resulting in an increase in yield of whole crop. However, excessive amounts of manure applied in surveyed fields can cause groundwater and surface water pollution. Thus, nutrient balances in a paddy field need to be analyzed further to determine an appropriate application amount of manure.

DOI： 10.1080/00380768.2018.1443399

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

The purpose of this study was to analyze the load of a transplanter PTO shaft during transplanting operations with respect to planting distances. To measure the loads on the PTO shaft of a transplanter, a load measurement system was constructed using a torque sensor and an embedded system. Field experiments were conducted at planting distances of 26,35,43, and 80 cm in a field with similar soil conditions. The load measured was converted from the time domain to the frequency domain using the rain-flow counting and SWT methods. The damage level of the transplanter to the working load with respect to the planting distance was calculated using Miner's rule, and the damage level was represented by ratio of the damage sum to the smallest damage sum among the planting distances. The damage level was increased by 199,493, and 708% when the planting distance gradually decreased from 80 to 43,35, and 26 cm, respectively. The results show that a shorter planting distance has a stronger effect on the transplanter PTO shaft than a longer planting distance. Therefore, it is known that transplanter PTO shafts should be designed while considering working loads with respect to planting distance.

Language：English   Publishing type：Research paper (scientific journal)  

This study conducted a factorial experiment with an experimental bench to analyze the separation performance of a card cleaner type separating system of pepper harvesters. The factors used for this study were the card arrangement (inline and staggered), slope angle (5° and 15°), and rotational speed (35, 50, and 65 rpm) of the card cleaner. The separation efficiency of peppers was influenced by the slope and rotational speed of the card cleaner in both types of card arrangement. In the inline arrangement, the mixing ratio of foreign materials was influenced by slope angle but not influenced by the rotational speed of the card cleaner. In the staggered arrangement, the mixing ratio of foreign materials was influenced by slope angle and the rotational speed of the card cleaner. The high separation efficiency in the staggered arrangement was obtained under the conditions of a slope of 5° and a rotational speed of 50 rpm. However, the mixing ratio of foreign materials was also high in this condition. The high separation efficiency in the inline arrangement was obtained under the conditions of a slope of 15° and a rotational speed of 50 rpm, and the mixing ratio of foreign materials was relatively low in this condition. Thus, the inline arrangement with a slope angle of 15°was recommended for a separating system of self-propelled pepper harvesters.

Language：English   Publishing type：Research paper (scientific journal)  

It has been identified that tractor stability can be affected by multiple factors, including configurational and environmental parameters. To improve tractor stability and enhance the resistance of the tractorimplement system to exterior disturbs, three tractor physical parameters were selected as the key control factors to examine their statistical significances and to find out the corresponding desired levels. In this study, a scaled experimental system consisting of a scaled tractor-implement model, force-sensing system, random road surfaces was developed. The tractor was operated to travel forward passing over two classes of rough road. Various tractor configuration patterns were assigned following the L27 orthogonal array according to the Taguchi design of experiment. Adopting the concept of lateral-load transfer ratio, the output voltage signals of the force sensing resistors were calculated for the stability indexes basing on tractor front and rear axles. Results showed that the type of tractor front tire and the ballast weight significantly varied the ground contact condition of the front tires, while the rear track width of the tractor predominantly determined the rear-axle-based vehicle stability.

Language：English   Publishing type：Research paper (scientific journal)  

The aim of this study was to analyze the fundamental lighting characteristics (spectrum distribution and light intensity) of a low-light LED unit and its effect on gas exchange in strawberry leaves. This unit was newly developed to provide low-cost supplemental lighting for greenhouses. The low-light LED unit was made using 24 LED module chips, each of which were 1 m in length and 43.2 W. The electricity consumption of this unit was only 55% of that of the high-light LED previously reported by Hidaka et al. (2013). The spectrum characteristics of low-light LED were measured using a portable spectro-radiometer. The photosynthetic photon flux density (PPFD) was measured using a photon sensor, and its distribution was measured at five different heights from a reference plane (110 cm x 150 cm). Gas exchange in strawberry leaves under low-light LED (Low LED treatment) supplemental lighting and no lighting (Control treatment) were measured using a leaf chamber system. The results demonstrated that the spectrum distribution patterns of the low-light LED and the high-light LED were similar; we found that the relative light intensity of both LEDs peaked once near a wavelength of 450 nm and again near a wavelength of 550 nm. The PPFD and its horizontal distribution showed that, as the height of the light source increased, the PPFD and lighting regions decreased and increased, respectively. On the other hand, as the height of 20 cm, PPFD under supplemental lighting with the low-light LED increased by 2.1 times than natural condition. As a result, stomatal conductance and transpiration rate increased by 1.5 times and 1.2 times, respectively; further photosynthetic rate increased by 2.2 times. Thus, the low-light LED was demonstrated to have suitable wavelength for crop production. Furthermore, applying supplemental lighting with the low-light LED significantly improved light intensity and accelerated photosynthesis in strawberry.

Language：English   Publishing type：Research paper (scientific journal)  

A program library for use on open-source hardware was developed in order to construct a low-cost environmental control system for greenhouses. The library facilitated the development of environmental sensing and control devices that conform to the protocols of the Ubiquitous Environment Control System (UECS). The open-source hardware used was the “Arduino Ethernet” and the “Arduino Mega 2560 with Ethernet Shield” microcontroller boards. UECS is a system for controlling greenhouse environments that communicates information via a local area network, and devices utilizing the library that we developed can perform the UECS defined communication tasks automatically. With the help of this library, device developers no longer need to program the communications aspects of the device and can concentrate on programming setting and control logic of the device. The library occupies about 29 kilobytes of the read only memory area of the target board. The library and associated open-source microcontroller boards are powerful tools for developing low-cost environmental control systems.

DOI： 10.2525/ecb.56.107

Language：English   Publishing type：Research paper (international conference proceedings)  

DOI： 10.1109/ICSensT.2017.8304451

Language：English   Publishing type：Research paper (international conference proceedings)  

DOI： 10.1109/ICCVW.2017.239

Language：English   Publishing type：Research paper (scientific journal)  

Measuring the area of combine-harvested field sections corresponding to a truckload of grain received at a grain elevator (LHA: load harvest area) allows the estimation of brown rice yield. The objective of this study was to evaluate the accuracy of LHA measured based on combine movement traces when the traces were recorded by a GPS or a GPS + Quasi-Zenith Satellite System (QZSS) receiver. For the measurements using a GPS receiver, the mean and standard deviation of relative errors of LHA were 4.7% and 8.1%. The center of the relative error distribution shifted toward positive because positioning errors of a GPS receiver shifted outer edges of harvested sections outward and resulted in measuring larger harvested area than a true value. For the measurements using a GPS + QZSS receiver, the mean and standard deviation of relative errors of LHA were 0.5% and 4.8%. The center of the relative error distribution was around 0% for its better positioning accuracy. The relative errors of LHA tended to be large when an LHA was measured from a field section where only the outer-part of a field is harvested or several small harvested sections. These cases of LHA measurements increased the sum of the perimeter of harvested sections and resulted in deteriorating the measurement accuracy. This result indicated that measurement accuracy of LHA can be further improved by correcting error, which can be estimated based on positioning errors and the perimeter of harvested sections.

DOI： 10.1016/j.eaef.2017.05.001

Language：English   Publishing type：Research paper (scientific journal)  

This study calculated the Mahalanobis' distance, which is a multidimensional space distance with correlations, from the time-series data of 3-axis translational acceleration and 3-axis rotational angular speed, and examined whether this could be used in judging the abnormalities of the agricultural machineries. As the result, using the Mahalanobis' distance to determine the abnormality of the data was not possible for the changes in not-so-big behaviors, such as turning and temporary stop, but determining the abnormality of the data using the Mahalanobis' distance was clearly possible for sudden changes to the operating status of the equipment, such as a roll over and passing obstacles through an experiment using the model car. We hypothesized in the beginning that the distribution of the Mahalanobis' distance at the signal space could be separated with the distribution of the Mahalanobis' distance at the unit space. However, unless there is a large-scale change to the behavior, such as a roll over, etc., complete separation is difficult in reality, and we determined realistically that conducting the abnormality determination from the significant difference viewpoint by placing a threshold value to the normalized distribution of the Mahalanobis' distance at the unit space is possible.

Language：English  

DOI： 10.1007/978-3-319-55345-0_12

Language：English   Publishing type：Research paper (scientific journal)  

Dry-seeded rice cultivation is an effective low-cost cultivation method in Japan, but preventing water leakage from cultivated rice fields remains a challenge. Here we assessed the efficiency of using a vibratory roller in a dry-seeded rice field for preventing water leakage. The tests were conducted at two different soil-water contents (WC: 32 and 39%) before roller compaction. We measured the acceleration response of the vibrating roller by using a micro-electro mechanical system (MEMS) accelerometer, and we determined the volume of water leakage from the field by using a rapid leakage capacity tester. We analyzed the changes in the soil structure by using a micro-focused X-ray CT scanner. We analyzed all of the resulting data to identify any correlation. We observed that water leakage from the field was sufficiently prevented when prior to roller compaction, soil moisture content was 39%. The shape of the soil pores that could efficiently prevent water leakage was flatter than that of the inefficiently compacted soil. In addition, the total porosity decreased, but the small-sized pore fraction increased. The vibration acceleration of the roller significantly increased with the decrease in the volume of water leakage. Thus, in addition to assessing the efficiency of vibratory rollers in reducing water leakage, our data suggest that it is to some extent possible to estimate the water leakage prevention effect from the acceleration response of a vibrating roller.

DOI： 10.1016/j.still.2016.09.011

Language：English   Publishing type：Research paper (scientific journal)  

In Bangladesh the demand of chemical free vegetables is increasing due to health hazards of conventional vegetables. However, the awareness of the farmers and supply of such vegetables are not sufficient. In this research, therefore, we focused on why agrochemical free vegetable production including marketing has been underdeveloped in Bangladesh as a growing business compared to conventional vegetable production. In order to collect the information, which can argue these reality of chemical free vegetable production, distribution and marketing in Bangladesh, we especially focused on widely cultivated winter vegetables such as cabbage, cauliflower and tomato. Data were collected targeting the activities of SENSE (Support to establish a new society of BOP farmers by using the power of ICT) project regarding production and marketing. The results indicated that the production of chemical free cauliflower and tomato were substandard compare to the cabbage. The reasons for getting substandard production were unavailability of proper production inputs such as appropriate organic pesticides, quality compost and lack of timely execution of the farming activities. Moreover, the selling results indicated that farmers got higher income from tomato compare to cabbage and cauliflower. Additionally, revenue (per kg) of the products sold in Dhaka market was more than the local markets. The differences of revenue (per kg) between Dhaka and locally sold cabbage, cauliflower and tomato were BDT 6.02, BDT 6.63 and BDT 10.22, respectively. However, the average selling percentage of cabbage, cauliflower and tomato in Dhaka market (10.06%) and local market (89.94%) indicated that chemical free vegetable production had high potential by selling more products in Dhaka market for high income generation of the resource poor farmers.

Language：English   Publishing type：Research paper (scientific journal)  

The purpose of this study was to develop parallel hybrid tractor. The hybrid tractor was constructed by adding major components of a hybrid driving system on a tractor. The tractor has 71 kW engine power and the major components included an EMG (electric motor/generator), an inverter, batteries, a battery management system (BMS), and a hybrid control unit (HCU). The hybrid tractor had three control modes: idle, power assist, and battery charge and it were determined by the workload which estimated by measuring engine rotational speed. Performance of the hybrid tractor was evaluated through the field tests of plowing. Performance tests were conducted by comparing the hybrid tractor and the conventional one, and one hybrid tractor was used for the experiment. The hybrid tractor used the hybrid system for the control of EMG, and the conventional tractor was driven by the engine not using the hybrid system. Performances of the hybrid tractor and the conventional tractor were similar at M2 which is low speed condition and it could work with low load, but the performance of the hybrid tractor was better than one of the conventional tractor at higher load condition (M3, M4). Fuel efficiency of the hybrid tractor at M2 was similar with the one of the conventional tractor, but it was lower at M3 and M4 than the one of the conventional tractor by 74%. Considering all results of this study, the developed parallel hybrid tractor is feasible to improve plowing performance of the conventional tractor.

Language：English   Publishing type：Research paper (scientific journal)  

In Bangladesh the demand of chemical free vegetables is increasing due to health hazards of conventional vegetables. However, the awareness of the farmers and supply of such vegetables are not sufficient. In this research, therefore, we focused on why agrochemical free vegetable production including marketing has been underdeveloped in Bangladesh as a growing business compared to conventional vegetable production. In order to collect the information, which can argue these reality of chemical free vegetable production, distribution and marketing in Bangladesh, we especially focused on widely cultivated winter vegetables such as cabbage, cauliflower and tomato. Data were collected targeting the activities of SENSE (Support to establish a new society of BOP farmers by using the power of ICT) project regarding production and marketing. The results indicated that the production of chemical free cauliflower and tomato were substandard compare to the cabbage. The reasons for getting substandard production were unavailability of proper production inputs such as appropriate organic pesticides, quality compost and lack of timely execution of the farming activities. Moreover, the selling results indicated that farmers got higher income from tomato compare to cabbage and cauliflower. Additionally, revenue (per kg) of the products sold in Dhaka market was more than the local markets. The differences of revenue (per kg) between Dhaka and locally sold cabbage, cauliflower and tomato were BDT 6.02, BDT 6.63 and BDT 10.22, respectively. However, the average selling percentage of cabbage, cauliflower and tomato in Dhaka market (10.06%) and local market (89.94%) indicated that chemical free vegetable production had high potential by selling more products in Dhaka market for high income generation of the resource poor farmers.

Language：English   Publishing type：Research paper (scientific journal)  

For stable year-round production of greenhouse crops with sustainability and high profitability, it is essential to establish a system that encompasses energy-saving and year-round environmental control via the application of renewable energy resources. One such renewable energy resource is the constant soil temperature layer, which is widespread and easily accessible in agricultural fields. However, owing to the low heat capacity and conductivity of media such as soil and air, heat exchange with the constant soil temperature layer has been considered insufficient for temperature control of the entire air volume inside a greenhouse. Therefore, we utilized a novel local temperature control system based on heat exchange between the constant soil temperature layer and the ambient air surrounding greenhouse crops. In the present study, we applied this system to the elevated bed system of strawberry crops with no-heating culture during the winter season. The system, that control the ambient air temperature of strawberry crops, increased fruits yield compared with no-heating, and was estimated 45% reduction of heating load to maintain 8°C or more.

DOI： 10.2525/ecb.55.37

Language：English   Publishing type：Research paper (scientific journal)  

In strawberry production, carbon dioxide (CO₂) enrichment is widely used to promote crop photosynthesis and to improve growth and yield of strawberry fruits. However, a standard CO₂ enrichment method has not been established clearly. For sustainable strawberry production with high profitability, it is essential to establish an efficient system for CO₂ enrichment. Therefore, in this study, we newly propose a local CO₂ enrichment system. The system enriches CO₂ only ambient to strawberry crops, not a whole greenhouse, and thereby enables efficient control of CO₂ concentration. We applied this system in a strawberry cultivation greenhouse with ventilating windows and examined the performance of system. During the daytime on clear days with opened greenhouse ventilation windows, the proposed system stabilized the ambient CO₂ concentration to strawberry crops at 800 ppm. Furthermore, when the day after CO₂ enrichment was begun, strawberry crop photosynthesis and photosynthate translocation from source leaves were promoted as the effects of short-term CO₂ enrichment. Nevertheless, the yields and quality of fruits was not affected by the system. It is considered that long-term CO₂ enrichment thickened source leaves and thereby caused down-regulation of photosynthesis. Further consideration will be needed on effect of long-term CO₂ enrichment on physiological function of crops.

DOI： 10.2525/ecb.55.165

Language：English   Publishing type：Research paper (scientific journal)  

In greenhouse production of strawberries (Fragaria×ananassa×Duch.) during winter season in Japan, unsuitable climate condition (low solar radiation, low temperature, etc.) for strawberry growth causes serious problems such as yield depression and low quality of fruits. For sustainable production with high profitability, it is keenly desired to establish a system for efficient environmental control based on physiological functions of crops. Translocation of photosynthate from leaves to fruits is a major physiological determinant for size and sugar content of strawberries. It is therefore essential to clarify the response of photosynthate loading to surrounding environment. In this study, we focused on light condition which strongly influences the photosynthesis, and analyzed effects of irradiation on dynamics of photosynthate loading. Furthermore, aiming at the estimation of dynamics of photostnthate loading in cultivation field, we simulated daily amount of photosynthate loading by kinetic model using a saturable Michaelis-Menten component in combination with an unsaturable component obeying first-order kinetics.

DOI： 10.2525/ecb.55.53

Language：English   Publishing type：Research paper (scientific journal)  

Statistics show that lateral overturns are the most frequent fatal accidents involving tractors. There is thus much research interest in improving tractor lateral stability. Previous research has discovered the effects of various factors on tractor dynamic responses. While these factors have been analysed separately, their relative significance with respect to other factors remain uncertain. Furthermore, the practical limits of what operators can do have not been considered. The present study assumed a possible case that a tractor operator has several spare tyres of different types and service condition. Additionally, the ballast weight, track width, and implement position can usually be controlled before operation. A scale model tractor was thus developed allowing changes to these factors. The model tractor was designated to pass over typical farming road surfaces. Moreover, the tractor lateral stability was evaluated in terms of the roll angle, lateral-load transfer ratio, and Phase I overturn index. Employing the Taguchi method, we arranged experiments and assessed the applicability of the three kinds of indexes regarding tractor Phase I overturn. Results revealed that the roll angle did not well reflect the initiations of overturns. Compared with the lateral-load transfer ratio, the Phase I overturn index had more convincing factorial effects on tractor stability. Further investigation of the suggested tractor configuration supported this conclusion by comparing predicted and experimental results. In practical cases, this approach may provide a reference for engineers to help operators improve driving safety with limited spare parts.

DOI： 10.1016/j.biosystemseng.2016.07.004

Language：English   Publishing type：Research paper (scientific journal)  

Precision agriculture has been implemented in various cultivation operations for various crops. Recently, autonomous mower tractor with variable rate fertilization has been tried. Variable rate fertilization requires quantification of grass growth level. Objective of this study was to compare the performance of potential sensors under different growth levels and sensor operation conditions. A CCD camera, an ultrasonic module, and an optical reflectance sensor (i.e., Crop Circle) were tested at fields with different grass growth levels. Effects of sensor mounting height and angle were investigated. Effects of vehicle (i.e., mower tractor) vibration and traveling were also investigated: under static, vibration and no traveling, and vibration with traveling conditions. Results showed that sensor mounting height had a little effect on the sensor performance, and grass growth level was successfully quantified. Camera angle of 90° showed the best performance with less noise. The ultrasonic sensor could work with less deviation under static condition, whereas, CCD camera proved the applicability under all operating conditions. Operation condition of the optical reflectance sensor showed a little effect on the grass growth detection results. This study would provide information useful for automated grass growth mapping and variable fertilization recommendation.

Language：English   Publishing type：Research paper (scientific journal)  

This study evaluated a DEM (Discrete Element Method) model through test results and analysis results for the simulation of the conveying performance of the separating system in a peanut harvester. With the validated DEM model, analysis under three conditions of slope angle of separating system compare with horizon (-7°, 0°, and 7°) was also conducted to examine the conveying performance. From the comparison between the test results and simulation results, the conveying performances of 0° and 7° were observed to be the same at the initial period and completion period; however, the gradient of 0° and 7° from the simulation were higher than the ones from the test by 8.9% (0°) and 9.2% (7°). The higher gradient means that the transport performance is better. The gradient of -7° from the simulation was higher than the one from the test by 3.6%, and the amount of the peanuts from the simulation was larger than the test by 500 g at the initial period of 5 seconds. The higher gradient of the simulation was due to the losses at the collecting part as 3.4% (0°), 3.1% (7°), and 2.0% (-7°). The error in the amount of the peanuts (500 g) at the initial period of 5 seconds with -7° was due to the initial input difference between the test and simulation.

Language：English   Publishing type：Research paper (international conference proceedings)  

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Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English  

Repository Public URL： http://hdl.handle.net/2324/1564100

Language：English   Publishing type：Research paper (scientific journal)  

Bangladesh is a country where people mostly depend on agriculture. The crop sub-sector of agriculture mainly depends on extensive agrochemicals to increase production and to ensure the national food security. Although, farmers have been using agrochemicals, the production was still found not to increase significantly due to the lack of knowledge about proper and modern cultivation technology. In addition, farmers are getting less income from agriculture compared to another profession, because of the inconsistent price of agricultural produces between the rural and urban area. In order to improve the situation, Kyushu University has conducted JICA (Japan International Cooperation Agency) grassroots technical cooperation project which aims at income generation for BOP (Bottom of Pyramid) farmers by producing and marketing the chemical free quality vegetables using ICT (Information and Communication Technology). The project has been conducted in five rural areas in Bangladesh. Here, the farmers are producing vegetables under a quality vegetable management center (QVMC) which is well equipped with ICT tools, and a quality vegetable entrepreneur (QVE) is helping them regularly to get the desired production and also ensuring the marketing of such vegetables. The project has targeted 100 farmers for producing chemical free vegetables and already got 42 interested farmers in 1.5 years of time. It is observed that farmers get better production under this QVMC in the winter season (called "Rabi" in Bangladesh) than summer season (called "Kharif-1" in Bangladesh).

Language：English   Publishing type：Research paper (scientific journal)  

Tractor overturning or rollover is a serious accident owing to its high fatality rate. Reviews of farm tractor rollover incidents indicate that overturns account for over 50% of all tractor-related deaths. To understand a tractor's performance on uneven terrain, a three-dimensional (3D) mathematical model describing the general bouncing and pitching motions of a tractor would be very useful. In this study, we design a rigid-body tractor system with the tires modeled as spring-damper units. To predict the tractor's motion on undulating surfaces, a half sine wave bump is adopted for the front and rear wheels on both the longitudinal and transverse slopes. The tractor's dimensional parameters and physical properties are taken from the work of Takeda et al. (2010). The passing over process is divided into four detailed phases and the attitude of the tractor is obtained by capturing the motion of the vehicle's center of gravity (COG). The displacement, pitch angle, and accelerations of the COG are numerically analyzed by applying the Runge-Kutta method. We introduce in this study three coordinates for the vehicle, slope and horizontal ground-based observations. The results are presented as factors of forward velocity, bump height, and slope gradient. Predictions show that there is a decrease in stability and an increase in danger at higher velocities, higher bump heights, and steep inclines. The specific cases indicating dangerous situations for the tractor are pointed out according to the results.

Language：English   Publishing type：Research paper (scientific journal)  

The purpose of this study was to evaluate fuel efficiency of tractor using working cycle. First, baler operation was conducted in Italian ryegrass farmlands and engine torque and fuel consumption were measured as field data. Second, baler operation cycle was developed using the field data. The arbitrary working cycles were generated by randomly selected micro-trips, ininimum working patterns. Some of the arbitrary working cycles were selected and baler operation cycle was determined considering sum of squared difference (SSD). The baler operation cycle was evaluated using performance value (PV) comparing with driving cycles. The results showed that PVs of the driving cycles were 67 - 109% of the baler operation cycle. Third, fuel efficiency of the baler operation was evaluated by dynamometer test using dynamometer system and the baler operation cycle. The fuel consumption and engine power were measured while the engine acted on the baler operation cycle and fuel efficiency was evaluated. The results of t-test showed no significant difference between fuel efficiency by the dynamometer test and fuel efficiency of each farmland by the field test. Considering all results of this study, the baler operation cycle is feasible to apply to evaluate fuel efficiency of tractor with dynamometer system.

Language：English   Publishing type：Research paper (scientific journal)  

In this study, tractor stability was discussed from the aspects of rollover initiation, vertical and lateral vibration characteristics considering tractor dynamics in Phase I overturn. As two of the key geometric parameters of a tractor, track width ratio and wheel base ratio were intro-duced into the mathematical model developed earlier as the independent variables. Results showed that both factors greatly reduced the risk of initializing tractor rollover with their in-creasing values. Higher track width ratios were found to generally enhance the contact condition between the sensitive tire and the ground, while higher wheel base ratios showed an effect of stabilizing the vehicle more rapidly after a disturbance. However, no obvious changes in tractor bounce acceleration were observed with the variation in track width ratio, nor were the changes in lateral acceleration found with different values of wheel base ratio.

Language：English   Publishing type：Research paper (scientific journal)  

This study conducted design parameter optimization for tillage blade of a crank-type rotavator (45 kW rated power, eight blades). Load, stress, and mass of the blade were obtained from field tests and a commercial program, and design parameter optimization was carried out with them. Selected design parameters were the heights of front and rear ribs, and thickness of the blade. And objective function was minimizing the mass of the blade. Optimization for the nominal tillage blade was conducted considering two different cases of thickness profile: constant thickness of tillage blade in the length direction and inclined thickness. In addition, it was conducted in two different cases of safety factor to consider the changes of tillage load depending on the soil characteristics: higher safety factor on the stress than the nominal tillage blade and lower safety factor. From the results of the optimization for the nominal tillage blade, the mass of the blade reduced by 3.2% under the same safety factor condition. And results of the optimizations with various conditions showed that higher safety factor increased the mass of the blade. The inclined blade also increased the mass of the blade to have the same safety factor. The results of the sensitivity analysis provided that the design parameter affected most on the stress and mass of the blade was thickness of the blade. Therefore, determining appropriate safety factor and thickness of the blade is important in designing the tillage blade. Design parameters of this study do not affect on the surface area of the blade, which is the important influence factor for the tillage performance. Thus, the process used in this study will contribute to the design of tillage blade in minimizing the mass while having similar tillage performance. Further studies on optimization of the shape of the frame and optimization of geometrical structure of the blade will be needed.

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Repository Public URL： http://hdl.handle.net/2324/1564097

Language：English  

Repository Public URL： http://hdl.handle.net/2324/1564099

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Tractor overturns are serious potential hazards for operators. While rollover protective structures (ROPS) protect operators passively, greater protection can be achieved through theoretical prediction of a potential overturn. Given effective warning, an operator can act to correct a tractor's motion when a tyre is about to lose contact with the ground. Such a loss of contact is associated with the initiation of a Phase I tractor overturn. However, it remains unclear how the initiation of tractor overturn is influenced by certain factors. Furthermore, the current mathematical models for tractors should be further extended for general utilisation. This study was conducted to develop stability indicators based on a more general model for dynamic Phase I tractor overturn. We considered practical tractor configurations and motion characteristics in a three-dimensional (3D) reference frame in formulating the mathematical model. Tractor stability indicators for overturn and sideslip were derived from force calculations. A parametric study was conducted using an example tractor. The tractor speed and slope angle were found to affect the overturning stability significantly. The coefficient of maximum static friction was found to be the main factor contributing to tractor sideslip. Critical tractor speeds for various ground conditions were identified by considering the zero values of the tractor stability indicators. The critical tractor speed was determined as a function of the maximum static friction and the slope angle. By providing a display device based on ergonomics principles, the results of this study can be further implemented in the form of guidance to operators.

DOI： 10.1016/j.biosystemseng.2015.03.016

Language：English   Publishing type：Research paper (bulletin of university, research institution)  

Repository Public URL： http://hdl.handle.net/2324/1526311

Language：English   Publishing type：Research paper (scientific journal)  

This study examined the performance of the separating system of a self-propelled peanut harvester by analyzing the relationship between a shaking screen and rotational speeds of winnowing. The shaking screen was manufactured to have rotational speeds of 370, 470, 570 rpm and winnowing was manufactured to have rotational speeds of 1,500, 1,760, 2,020 rpm by adjusting the pitch circle diameter of each pulley. The sample was prepared based on the yields of an actual self-propelled peanut harvester and analyzed with Statistical Analysis Software after measuring the weight of peanuts and stems. The stem separation ratio was high as 95.3% when rotational speeds were 570 rpm (shaking screen) and 2,020 rpm (winnowing). The peanut loss ratio was low as 0% when rotational speeds were 370 rpm (shaking screen) and 1,500 rpm (winnowing). The results indicated that the stem separation ratio was improved with high rotational speeds of shaking screen and winnowing; the peanut loss ratio was reduced with low rotational speeds of shaking screen and winnowing. However, the rotational speed of winnowing did not influence on the peanut loss ratio; as a result, separation performance was improved with low rotational speed of shaking screen and high rotational speed of winnowing. Low rotational speed of shaking screen, however, may cause congestion during process, thus follow-up studies are needed.

Language：English   Publishing type：Research paper (scientific journal)  

The cultivation area of rice for whole crop silage (WCS) has rapidly increased in the last decade in Japan due to increasing demand for domestic livestock feed as well as a measure for the use of redundant paddy field. On the other hand, the production cost of rice for WCS is largely supported by subsidy now, so it is required to reduce the production cost. Manure application is a prospective way to reduce the cost of fertilizer and to sustain soil fertility. Thus, we investigated the production of rice for WCS using manure in Itoshima region, Fukuoka Prefecture, Japan, from the aspects of soil fertility, plant growth, and dry matter weight. The fields where manure was applied showed relatively high TN contents in soil whereas fields where manure was not applied showed low TN contents. This result indicated that soil fertility can be deteriorated by the continuous production of rice for WCS when organic matter is not supplied by manure and other materials. Plant length (r=0.748^∗) and tiller number (r=0.891^∗∗) at panicle initiation stage were closely correlated with TN content in soil whereas SPAD readings (r=0.846^∗∗) at the same stage was closely correlated with mineralized N in soil. Dry matter weight was positively correlated with TN content in soil (r=0.767^∗∗). Fields where manure was not applied had small dry matter weight although nitrogen was supplied from fertilizer. These results indicated that dry matter weight was significantly affected by soil fertility.

Language：English   Publishing type：Research paper (scientific journal)  

Tractor stability predominantly determines operator's safety. For a tractor parking on lateral slopes, overturning accidents have been frequently discussed using mathematical models. While the existing static models remarkably contribute tractor overturning mechanisms, few of them have considered the stability from the perspective of tractor sideslip. In our study, a relatively precise quasi-static model presented recently was adopted as the base model. We expanded it by introducing potential tractor sideslips. While the original model pointed out the lateral slope angle as the main factor influencing tractor overturns, we investigated tractor slipping stability under the influences of the slope angle and the coefficient of friction. The dimensional parameters of the example tractor for simulation were set the same as those in the original work. It was found that the allowable friction forces of both the front and rear tires primarily depended on the coefficient of friction rather than the slope angle. By comparing the surfaces of the allowable friction forces and the corresponding friction forces, tractor slipping thresholds for the front and rear tires were identified. Caution areas implying certain ground conditions that will definitely cause tractor sideslip were marked accordingly. The results shown in this study provide a relatively comprehensive way to understand tractor static stability when both tractor sideslip and overturn are concerned.

Language：English   Publishing type：Research paper (scientific journal)  

A mathematical model for tractor dynamics was expanded by considering the rotatable tractor front end. The fundamental shortcoming of the simplified model was revealed by the loss of contact of the tire with a rigid horizontal surface in an obstacle-passing case. Further shortcomings of the simplified model arise from aspects of the motion and vibration characteristics. The improved model provides a better and more realistic representation of the tire-ground contact condition and is applicable to tractors on lateral slopes. The independent roll motions of the two main tractor parts (the front end and main body) significantly reduce the motions of the tractor and thus increase its stability. Furthermore, the effects of the forward tractor speed and obstacle height were studied for a tractor on a 10° lateral slope. By analyzing the motion amplitude and tire-ground contact condition, the tractor speed and obstacle height parameters associated with danger and risk were evaluated. The results suggest the greater capability of the improved model to predict tractor dynamic response in Phase I overturn.

Language：English   Publishing type：Research paper (scientific journal)  

The purpose of this study is to examine the usefulness of an MEMS sensor for measuring vibration of agricultural vehicle by obtaining serial data of vibration acceleration of agricultural vehicle using an MEMS sensor and translational accelerometer and thereby calculating RMS and PSD for comparison and analysis as a step before construction of measuring system which can identify operating conditions of agricultural packaging machinery at all times. Although there are differences between vertical acceleration RMS and pitching angular acceleration measured by an MEMS sensor and translational accelerometer due to disturbance factors and computation errors, both measurements obtained by the two methods typically increase as vehicle body moves faster. For PSD, likewise RMS, there were differences in measurements, but peak frequencies were almost matched between the two methods, so it was confirmed that an MEMS sensor could exactly detect vibration characteristics. Therefore, it was considered that instead of large and costly translational accelerometer, an MEMS sensor which can measure both translational acceleration (back-and-forth, lateral, and vertical) and angular acceleration (rolling, pitching, and yawing) only with a single unit could be properly used in identifying vibration characteristics of agricultural packaging machinery.

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

Language：English   Publishing type：Research paper (scientific journal)  

In recent years, it is becoming important to collect and utilize different data on rice production to achieve a high yield and high quality, and to transfer the skill to the next generation. The objective of this study was to investigate the validity of a regression tree for analysis of yield and quality determinants. Determinants of grain yield (yield), 1000-grain weight, and protein content of brown rice (protein) were analyzed by focusing on explanatory variables for the meteorological environment and conditions of rice growth and nutrition after the heading period. The spikelet number/m² was identified as a yield determinant by a regression tree and multiple regression analysis. However, the predictive accuracy was higher in multiple regression analysis due to a strong linear correlation between yield and spikelet number/m². For the analysis of the 1000-grain weight with nonlinear data structure, no reasonable determinant was identified in multiple regression analysis, while a regression tree implied the 1000-grain weight determinant by clarifying its relationship with SPAD readings about 20-d after heading (SPAD20). The SPAD20 was also identified as a protein determinant. Furthermore, it was indicated for data under the condition with high SPAD readings that protein was lowered by the high temperature during 5 to 30 days period after heading. A regression tree can clarify the relationship among parts of data by splitting data hierarchically, but multiple regression analysis can not.

DOI： 10.1626/jcs.83.143

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.20710/dohikouen.60.0_117_3

Language：English   Publishing type：Research paper (scientific journal)  

The threshing unit of a combine comprises a multiphase flow; therefore, it is essential to consider it on the basis of the flow model. In this study, flight simulation by DEM with fixed wind velocity was carried out. The grain and straw were considered to be ellipsoidal and cuboidal, respectively. A two-dimensional model coupling with a circle element was constructed. Each flight trajectory was reproduced in terms of the initial conditions and changes in winnowing velocity. The average flight velocity of the grain was 0.2 m/s higher than that measured in the experiment. It can simulate to closer phenomenon by mixing different particle mass and straw, analyzing the increase in particles and linking it with fluid analysis.

DOI： 10.1016/j.eaef.2013.12.006

Language：English   Publishing type：Research paper (scientific journal)  

A three-dimensional mathematical model of tractor on lateral slopes was developed in this study. The model considers the nonlinear geometric relationships of the arms of the ground supporting forces when the tractor passes over a half sine curve obstacle. It is subsequently ap-phcable to large rotations of a tractor. Meanwhile, the change of the direction of a supporting force due to the interaction between tractor pitch and roll motions and its result in corresponding tire deformation are the concern of this study. Given the transformation matrix, the tractor translations and rotational motions were observed in a global coordinate. According to the de-veloped model, one can obtain the tractor bounce displacement, the pitch angle, and the accel-eration characteristics. Furthermore, the supporting and lateral friction forces can be examined since they predominantly determine the tractor lateral rollover and sideslip which affect tractor safety to a great extent. Therefore, the lateral slope effect on these forces was investigated con-sidering a tractor speed of 0.5 m/s and an obstacle height of 0.08 m. Results showed that as the slope angle increases, both the supporting and lateral friction forces put the tractor to a situation closer to danger. In particular, a specific slope angle of 25' was highlighted as a warning parameter because the onset of rollover as well as tractor sideslip were discovered. It is also found that a tractor is more susceptible to sideslip than rollover along with the slope increasing.

Language：English   Publishing type：Research paper (other academic)  

Various constitutive models for soils and gravels have been developed in the last century. Among them unconventional plasticity theory is a key and necessary approach for describing cyclic deformation behavior of materials. The "subloading surface model" proposed by Hashiguchi, which belongs to the unconventional plasticity framework, does not assume a purely-elastic domain inside a yield surface and premises that an inelastic strain is induced by stress changes inside the yield surface. It is able to describe the mechanical behavior of materials such as not only smooth elastoplastic transition but also cyclic loading behavior. Thus, elastoplastic constitutive models for various materials based on this model have been developed up to present. Moreover computational analysis methods such as a finite element method (FEM) incorporating this constitutive model have been utilized for solving problems in geotechnical engineering fields. On the other hand, gravel such as ballast causes elastoplastic deformation in the proportional loading process. However the accumulation of the plastic deformation under a cyclic loading condition is smaller than that for typical soils such as sand and clay in general since the elastic property of ballast particle is high and the slip between each ballast is remarkably suppressed by the particles' packing. In this study, the subloading surface model is modified by assuming an existence of the elastic domain surface inside the subloading surface so as to realistically describe the inelastic deformation behavior of ballast including monotonic and cyclic loading conditions. The validity of the model is verified by the comparison with large-scale triaxial compression test data for both loading conditions.

Language：English   Publishing type：Research paper (scientific journal)  

A dynamic three-dimensional model of a tractor travelling through a half sine wave obstacle was developed considering bouncing, pitching, and rolling motions. Compared with the case of bouncing on a level road, setting the obstacle on a sideways slope under the upper side of the forwarding tractor could stimulates a much more dangerous scenario, which may lead to tractor overturn. In this model, the tractor was considered as a rigid body, except for the tires, which were regarded as spring-damper units. The entire passing-over process was divided into four periods as done by Yamamoto and Shimada (1957), and Takeda et al. (2010) for dissecting the influence of each specific travelling period on the tractor. Basic dimensional parameters and physical properties of the objective tractor, used as input parameters in our simulation, were cited directly from the work of Takeda et al. (2010). Dynamic behavior of the tractor was described by capturing the motion of its center of gravity, which includes vertical displacement, angle, and angular acceleration for the pitching and rolling phenomena. Using the Runge-Kutta method, the desired mathematical model was numerically simulated through programming in Visual Basic Application language within Microsoft Excel. Tractor dynamic predictions were presented as factors of forward constant speed and lateral slope. The simulation results show fluctuations and increase in danger levels owing to higher velocities and steep lateral slopes. Therefore, this model enables us to explore potential overturning judgment standards.

Language：English   Publishing type：Research paper (scientific journal)  

Rice production in Japan is facing problems of yield and quality instability owing to recent climate changes, aging of farmers, and a decrease in the farmer population. Thus, it is becoming important to develop an improved rice production technology that utilizes collected data about rice production rather than relying on the conventional technology that is based on the experience and knowledge of individual farmers. We developed predictive models for yield and protein content of brown rice that can provide useful knowledge to support farmer’s management decision-making, utilizing data sets from 47 paddy fields where rice was produced under various environments and management styles. Support vector machines (SVMs) were applied to build the predictive models based on explanatory variables representing the growth and nutrition conditions after the heading stage and the meteorological environment after the late spikelet initiation stage. The models achieved quantitative accuracy that was within approximately 1 t ha−1 in yield for 85.1% of the total data sets and within 0.8% in protein content for 76.6% of the total data sets, respectively. Further, patterns of explanatory variables classified in three classes of yield and protein content, which were visualized by the predictive models, were reasonable in terms of knowledge of crop science. We found that the predictive models using SVMs had the potential to describe a relation between yield or protein content and multiple explanatory variables that reflected diverse rice production in actual fields, and could provide useful knowledge for decision-making of topdressing and basal fertilization.

Keywords
Rice production; Yield; Protein content; Predictive model; Support vector machine; Pattern recognition

DOI： http://dx.doi.org/10.1016/j.compag.2013.09.003

Language：Japanese   Publishing type：Research paper (scientific journal)  

Effects of Partially Shallow Tilling and Sowing Method on the Growth and the Yield of Wheat (Triticum aestivum L.) and Labor-Saving Cultivation

Language：English   Publishing type：Research paper (scientific journal)  

Aging and feminization of farming population are a major burden on current agricultural sector, and some measures are demanding to adjust this trend. The agricultural mechanization has relieved farmers of most of the hard physical labor, but still work environments are poor, and there are a lot of harmful factors affecting human health. Therefore, improvement of safety and comfort in agricultural machinery is needed. In case of the most commonly used domestic agricultural machinery, agricultural tractors, operation device location and operating force are regulated by international rules such as ISO 4253, but the rule is not sufficient for domestic operators, since it was not developed for operator's comfort and was drawn out based on the westerners. In this study, we developed a technique that evaluates the conformability of tractor driving operation device for all Korean farmers including senior and women farmers. We also established evaluation equipments and inspection method of tractor operation conformability to promote dissemination of tractors that suit for Korean farmers' physique. In the future, the result allows tractor manufacturers to propose design guidelines for proper location and operating force of tractor operating device. It also allows domestic agriculture manufacturers to develop agricultural machinery that considered the conformability of farmers from the design stage.

Language：English   Publishing type：Research paper (scientific journal)  

In this study, the effects of tillage blade shape on tillage and power consumption characteristics were investigated for a crank-type rotavator. Three types of tillage blades were applied, i.e. standard blade, endsloped blade and narrow blade for the purpose of the study. Tillage operations were carried out using each blade with the same prime mover tractor and rotavator platforms in two different soil and Power Take-Off (PTO) speed conditions. During the operations, PTO speed and torque, soil pulverizing ratio and inversion ratio, actual work speed, and rotavating width and depth were measured, and the required power of the PTO shaft, field capacity and flow of tilled soil were calculated to compare the characteristics according to the tillage blade shape. Experimental results show that the rotavating width, actual work speed, field capacity, flow of tilled soil and soil inversion ratio were independent of the blade shape, whereas the rotavating depth and soil pulverizing ratio were influenced by the blade shape according to the soil condition. In the most commonly used tractor gear conditions of L2 and L3, the PTO power of the end-sloped blade and narrow blade were almost the same as each other, and significantly lower than the standard blade in the paddy field, whereas there were no significant differences among blades in the dry field. It can be concluded that if an adequate blade shape suitable for specific soil conditions is applied to the crank-type rotavator, power efficiency and good tillage performance operation can be achieved at the same time. Further research is needed to determine the optimal shape of tillage blade with certain soil properties.

Language：English   Publishing type：Research paper (scientific journal)  

In a farmer's strawberry greenhouse, seasonal changes in solar radiation and air conditions (temperature, humidity, and CO₂ concentration) were measured, and it became clear that the stable year-round production of strawberry was depressed by low temperature and low solar radiation in the cold season and by excessively high temperature in early autumn. Furthermore, dew formations during the nighttime and inappropriate application of CO₂ enrichment were also related to the depression of stable production. Therefore, a local environmental control system was newly developed for strawberry crops based on air circulation and heat exchange between the constant soil temperature layer and the ambient air. The system consisted of an underground air pipe (UAP) and perforated inter-row air ducts (IAD) connected to the UAP; the UAP was set at a depth of 1.5 m, where soil temperature remained suitable for year-round strawberry growth. The greenhouse air was drawn into the UAP, and the air flowing through the UAP exchanged heat with the constant soil temperature layer and was dispersed to the ambient environment of the strawberry crops through the perforated IAD. In the nighttime during the cold season, air flowing through the system was heated by 8°C, and a heating effect of 3°C was observed in the ambient air. The proposed system of applying the constant soil temperature layer can be expected to reduce the nighttime heating load by 50% and enable energy-saving environmental control.

DOI： 10.2525/ecb.51.89

Language：Japanese   Publishing type：Research paper (scientific journal)  

Effects of Partially Shallow Tilling and Sowing Method on the Growth and the Yield of Soybean (Glicine max L.) in Upland Filed Converted from Paddy Field

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

The empirical Gaussian-based mathematical model of the soil displacement increment under a traveling wheel was extended to be applicable to any depth of soil layer under the ground contact surface of the wheel. The unknown coefficients were obtained by least mean-square fitting with the soil displacement curve measured through a sophisticated laboratory soil bin test. Those coefficients were then re-derived as a function of depth. The movement of soil particles at the ground contact surface was modeled by dividing movement into two kinds; first, the free movement of soil particles before contact with the wheel and the movement of the particles after they are separated from the wheel surface and, second, soil movement during attachment to the wheel surface. By combining the models for the ground contact surface of the wheel with that for all soil layers, an extended model that can describe soil displacement increment in both vertical and horizontal directions using one equation was established. The predicted results obtained using the extended model fitted quite well with the measured values. The predicted strain increment distributions also show the same trends as the measured distributions.

DOI： http://dx.doi.org/10.1016/j.jterra.2012.06.001

Language：English   Publishing type：Research paper (scientific journal)  

This research was aimed at developing a hydroponie recycling system using a visible light- reactive titanium dioxide (TiO
₂
) photocatalyst. We made a sterilization system for the nutrient solution by utilizing the features of the filters coated with visible light-reactive titanium dioxide photocatalyst. The system is composed of a photocatalyst filter (300×300×20 mm), a 4-tier stair type processing channel (305 mm wide, 2,100 mm long, 30 mm high), a supply tank, a catchment tank, a water pump, a circulation control facility, an insolation sensor, and a data log. We also evaluated the sterilization performance using a number of filters, the initial density of spores in the nutrient solution, the species of spores, flow rates, and the amount of insolation. In the experiment with 20 filters, sterilization performance per 1 filter was 20.3% higher than one per 5 filters. Sterilization performance at a low initial density of spores (26 counts/0.9 mm3) is 23.9% higher than at a high initial density of spores (440.3 counts/0.9 mm3). Colletotrichum was more sensitive to the photocatalyst than Fusarium, and the slow flow rate (0.5 L/min) has more sterilization effects (9.0%) than the fast flow rate (1.0 L/min). The logarithmic relation of the average insolation and lethal intensity of unit spore density is correlated as 0.926 of the coefficient of determination (R2). These results provide valuable information for TlO
₂
photocatalytic treatment of waste nutrient solutions under solar light irradiation.

Language：English   Publishing type：Research paper (scientific journal)  

An impact-type threshing device that applies perpendicular force to rice ear was developed in this study. Threshing experiment was performed for a single ear and to a bundle of rice plants. Crop properties and collision conditions were used as input parameters in this experiment to perform multiple regression analysis, thereby estimating threshing rate and percentage of grains with rachis branch. Optimal regression model for estimating threshing rate and percentage of grains with rachis branch was obtained for both single ear and bundle of rice plants. Although all four regression models had low analytical error and verification error, but relative error was high due to insufficient number of datasets and accuracy was low as a result. However, certain extent of estimation was possible for threshing rate. Observing that threshing rate was highly correlated with transverse threshing force and transverse displacement, it was inferred that threshing of rice plant by impact-type threshing device is from perpendicular force acting on rice ears. Although estimation of percentage of grains with rachis branch had low absolute error, accuracy was low because of relative error that is enlarged due to low rate of occurrence. Since percentage of grains with rachis branch was negatively correlated with net's mesh size, we concluded that the mesh size must be made as low as possible to reduce percentage of grains with rachis branch.

Language：English   Publishing type：Research paper (scientific journal)  

In this study, we established a method to calculate inclination angle of moving vehicles from acceleration and angular velocity measured by microelectromechanical systems (MEMS) sensor, which is becoming popular recently due to its ultra-small size and low manufacturing cost. We applied the technique to measure inclination angle of semi-crawler tractor to validate its usefulness. Results from various methods to calculate inclination angle of a vehicle from acceleration and angular velocity data showed that moving average acceleration method and wavelet acceleration method produced results that significantly deviated from the actual inclination angle, while results from angular velocity method and acceleration-angular velocity method were close to the actual inclination angle. Inclination angle calculated by acceleration method in a static state was very similar to the measurement from inclination sensor and was highly accurate, but did not demonstrate sufficient accuracy in dynamic state as the estimated inclination angle was at maximum 10' smaller at inclination angle of 75". In the meanwhile, the inclination angle calculated by angular velocity method showed only small deviation from the sensor measurement even at dynamic state. As a result of measuring inclination of semi-crawler type tractor using MEMS sensor, it was determined that the angular velocity method is the most versatile of the four methods tested as it can not only produce very accurate time series of inclination angle but also be used to easily obtain angular displacement from the angular velocity data obtained. However, error of integration was shown to increase with longer measurement times and it must be addressed by an appropriate solution. Acceleration-angular velocity method also produced similar results as experiments were performed indoors where disturbance factors were few. The inclination angle measurement system using MEMS sensor established in this study can be applied to agricultural vehicles such as tractors as well as to almost all construction and general vehicles with drive system. We expect the system to contribute to development of a safety system that can prevent rollover accidents and quickly respond to them.

Language：English   Publishing type：Research paper (scientific journal)  

Onion is one of the major vegetables and is also the number one crop from the perspective of storage amount in South Korea. However, the postharvest processing for onions has been accomplished mainly with net package, causing high cost and low efficiency. Thus, development of a continuous and integrated processing system is required to ensure buyer satisfaction and marketing success. The objective was to determine factional properties and airflow resistance of onion, which are very important to understand the behavior of onions in developing its bulk handling system. Frictional properties of onions, friction coefficient and rolling resistance, were determined by the method of inclined surface. Those values were investigated on three different surfaces (rubber, plywood, and galvanized steel) for four size grades (extra-large, large, medium, small). The airflow resistance, or static pressure drop, was measured with different mixing rate of onion sizes, and equations were developed for prediction of pressure drop in bulk state. The static-friction coefficient ranged from 0.35 to 0.46 for all experiment condition. The highest value was obtained on the plywood surface (0.46+0.06) followed by the rubber (0.41±0.03) and galvanized steel surface (0.35±0.03). This friction coefficient decreased with the onion bulb size. The static-rolling resistance ranged from 8.4' to 17.6° for all sizes, and, unlike the friction coefficient, increased with the onion bulb size. The highest values of rolling angles were obtained on the rubber surface (15.43±4.78) followed by the plywood (13.77±3.77) and galvanized steel surface (10.84±4.26). The airflow resistance increased as the onion size decreased, and a low porosity produced a higher pressure drop in all mixing rate of onion size. The pressure drop in stacked onion was also proportional to the superficial air velocity. Equation developed for prediction of pressure drop with superficial air velocity (SV) and stacking depth (SD) (r2=0.99) was better than one with stacking depth (SD) (r2=0.95) only. These results are invaluable to design post-harvest bulk handling system of onions.

Language：English   Publishing type：Research paper (scientific journal)  

In a farmer's strawberry greenhouse, seasonal changes in solar radiation and air conditions (temperature, humidity and CO₂ concentration) were measured, and it became clear that the stable yearround production of strawberry was depressed by low temperature and low solar radiation in the cold season and excessively high daytime temperature in the warm season. Furthermore, dew formation in the nighttime, excessively low humidity in the fair daytime and the inappropriate application of CO₂ enrichment were also concerned with the depression of stable production. Therefore, a local environment control system was newly developed on the basis of the air circulation and the heat exchange between the constant soil temperature layer and strawberry inter-rows. The system was composed of an underground air pipe (UAP) and inter-row air ducts (IAD) connected to UAP, and UAP was set at a depth of 1.5m where the soil temperature is kept around a temperature suitable for the strawberry growth all the year round. The system can be expected to enable the energy-saving and local control of the ambient air condition of strawberry crops for the stable year-round production.

Language：Japanese   Publishing type：Research paper (scientific journal)  

Feature Extraction of Field Environmental Information Using the Change Point Analysis Method

DOI： 10.3173/air.22.174

Language：English   Publishing type：Research paper (scientific journal)  

Rice production in Japan is facing problems of yield and quality instability owing to recent climate changes, aging of farmers, and a decrease in the farmer population. Thus, it is becoming important to develop an improved rice production technology that utilizes collected data about rice production rather than relying on the conventional technology that is based on the experience and knowledge of individual farmers. We developed predictive models for yield and protein content of brown rice that can provide useful knowledge to support farmer's management decision-making, utilizing data sets from 47 paddy fields where rice was produced under various environments and management styles. Support vector machines (SVMs) were applied to build the predictive models based on explanatory variables representing the growth and nutrition conditions after the heading stage and the meteorological environment after the late spikelet initiation stage. The models achieved quantitative accuracy that was within approximately 1tha^-1 in yield for 85.1% of the total data sets and within 0.8% in protein content for 76.6% of the total data sets, respectively. Further, patterns of explanatory variables classified in three classes of yield and protein content, which were visualized by the predictive models, were reasonable in terms of knowledge of crop science. We found that the predictive models using SVMs had the potential to describe a relation between yield or protein content and multiple explanatory variables that reflected diverse rice production in actual fields, and could provide useful knowledge for decision-making of topdressing and basal fertilization.

DOI： 10.1016/j.compag.2013.09.003

Language：English   Publishing type：Research paper (scientific journal)  

The empirical Gaussian-based mathematical model of the soil displacement increment under a traveling wheel was extended to be applicable to any depth of soil layer under the ground contact surface of the wheel. The unknown coefficients were obtained by least mean-square fitting with the soil displacement curve measured through a sophisticated laboratory soil bin test. Those coefficients were then re-derived as a function of depth. The movement of soil particles at the ground contact surface was modeled by dividing movement into two kinds; first, the free movement of soil particles before contact with the wheel and the movement of the particles after they are separated from the wheel surface and, second, soil movement during attachment to the wheel surface. By combining the models for the ground contact surface of the wheel with that for all soil layers, an extended model that can describe soil displacement increment in both vertical and horizontal directions using one equation was established. The predicted results obtained using the extended model fitted quite well with the measured values. The predicted strain increment distributions also show the same trends as the measured distributions.

DOI： 10.1016/j.jterra.2012.06.001

Language：English   Publishing type：Research paper (scientific journal)  

There is growing concern to promote the use of aerobically fermented liquid fertilizer produced from human waste and sludge to reduce the cost, environmental load, and energy consumption in rice production. We tested the maturity accelerating effects on rice straw and effects as a nitrogen fertilizer by applying liquid fertilizer in 2009 and 2010. The maturity accelerating effects were not significant in terms of dry weight, total nitrogen content (T-N), and nitrogen uptake. When liquid fertilizer, which had an ammonium nitrogen (NH₄-N) ratio of approximately 70%, was incorporated into the plow layer of the soil as a basal fertilizer, the nitrogen fertilizer effect and panicle number were equivalent to those for chemical fertilizers. However, when liquid fertilizer with a low NH₄-N ratio was applied, the dry weight, T-N, and nitrogen uptake were lowered resulting in reduced panicle number. When applied as a top-dressing on the soil surface, nitrogen uptake decreased because of NH₄-N loss through volatilization. This decrease in nitrogen uptake may have reduced spikelet number. Nitrogen uptake slowed under the low NH₄-N ratio, and nitrogen nutrition conditions deteriorated during the ripening period. This may have lowered 1000-grain weight under the high average temperature conditions in 2010 (26.7°C during the 20-d period after heading). The yield tended to be low because of these reductions in yield components. Nitrogen fertilizer effects were affected by NH₄-N ratio, whose fluctuation is considered problematic.

DOI： 10.1626/jcs.82.325

Language：English   Publishing type：Research paper (scientific journal)  

Agriculture faces many challenges in the production system, such as climate and weather, field conditions, crop types, soils types and conditions, and so on. Farmers consider many aspects to optimize the "on-farm" process by their long-term experiences. Various informatization agricultural supporting systems have been developed using ICT (Information and Communication Technologies) to improve agricultural productivity. Authors have developed the ICT-based agricultural supporting system called the "Agri-eye" in which a field monitoring, crop growth and quality evaluation, work recording, and online data offering and sharing sub-systems were incorporated. On the other hand, an actuation subsystem for controlling and managing agricultural facilities in a greenhouse such as a heater, water pumps, circulation fans, a CO2 generator, etc. has been introduced. In this study, an actuation framework is developed as a useful method for monitoring and controlling local facilities and machineries. The method can be used for controlling particular device with adjusting parameter from Agri-eye server to meet the cultivation requirement. Furthermore, the validity of the developed framework was verified to monitor and control air temperature in laboratory test box.

Language：English   Publishing type：Research paper (scientific journal)  

In Japan, rice production technology must be developed to meet stable yield and quality targets. This objective is important because of the demand for high quality rice by consumers, the necessity of enhancing Japan's international competitive power, and a declining trend in the production of first grade rice. To achieve stable yield and quality, it is important to control panicle number appropriately since it is a primary factor to determine rice yield and quality. In this study, a multiple linear regression model was built to predict panicle number, which can support the decision-making process of farmers in agricultural practice. Surveys of 33 paddy fields were conducted in the Fukuoka Prefecture in 2010-2011. Data regarding influential factors on panicle number, such as solar radiation, water temperature, and exchangeable ammonium (eNHJ content in the soil, were collected and used for building the model as candidates of the explanatory variable. As the results, eNH, content in the soil at the beginning of tillering stage and accumulated amount of daily solar radiation during the tillering stage were selected as explanatory variables. The adjusted coefficient of determination was 0.448 and RMSECV was 2.49. In the prediction model, eNH, content in the soil at the beginning of the tillering stage was selected as an explanatory variable to represent inorganic nitrogen supply. In comparison, this variable does not reflect the inorganic nitrogen supplied throughout the tillering stage. This difference resulted in a large error in the field with organic fertilizer application, as the manner of inorganic nitrogen release is different to that of typical fields in the survey area that are subject-ed to chemical fertilizer application.

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (bulletin of university, research institution)  

Repository Public URL： http://hdl.handle.net/2324/22070

Language：English   Publishing type：Research paper (scientific journal)  

Corrugated board is an engineering structure, whose strength characteristics depend on the cross-section geometry and the material properties of liner and corrugated medium. Therefore, the board combination (combination of material for preparing corrugated board) of corrugated boards should be optimized with considering the quality characteristics of corrugated board demanded to achieve the optimum packaging design. The board combinations of corrugated boards can be determined by employing the configuration method for the paperboard stiffness and the basis weight. The results of board combinations can greatly affect the buckling resistance and compression strength of the box. ^11,15 In order to analyze the effect of the configuration method for the board stiffness and the basis weight on the flexural stiffness of corrugated board, we performed experiments based on cost- and time-consuming procedures. However, by using a simulation method such as finite element analysis (FEA) has the advantages such as saving of the time and cost in experiments and sample production as well as detailed analysis by adjusting several parameters. In the case of the simulation method, the estimation of reliability and reproducibility of the results should be strongly considered. In this study, we observed the strength-optimal design conditions for the corrugated board combinations by analyzing the flexural stiffness index (FSI). The FEA method was used in the study using the four-point loading conditions. We found that the difference between the FEA result and the test results were approximately 18-31%. However, it was estimated that the variations in FSI estimated by using both methods are similar. Therefore, we expect that the flexural balance for different board combinations would be successfully analyzed on the basis of the qualitative comparison of FSI values corresponding to the combinations when the stiffness for each of the liner and the corrugating medium are assumed to be with 2-3 levels.

Language：English   Publishing type：Research paper (scientific journal)  

It is necessary to develop a design theory of the knife driving system of combine harvesters in order to derive the control parameters of the balance weights used for vibration reduction. A collision vibration model of the knife driving system that is equipped with a slider-crank mechanism was constructed in order to examine the influence of the interspace that arises at the joint of the drive knife and the end of the link arm. The simulation result revealed that the harmonic frequency components varied with an increase in the width of the interspace although the highest harmonic frequency in the simulation without the interspace was three times the crank wheel rotation frequency. However, the vibration reduction by the balance weight was not dependent on the width of the interspace.

DOI： 10.1016/S1881-8366(12)80024-3

Language：English   Publishing type：Research paper (other academic)  

In the region of Japan, broadband network and informatization have spread. However the field of agriculture has not come willingly. The infrastructure that has not been enough in mountainous areas, but various initiatives of computerization are being started using production and distribution as the subjects. Since this began in reality, there are still insufficient matters that have been resolved in regards to the technical validations and cost effectiveness. Therefore necessitates pouring in a tremendous amount of expertise, possibility is ICT and its related technologies of sensors. In our research and developments, we create demo hardware for the experiment using in the farm collected data. On the other hand, making study group with farmers for accumulation of data and experience. That visualized information configure to the platform of knowledge management.

DOI： 10.1109/CISIS.2012.149

Language：English   Publishing type：Research paper (scientific journal)  

The flight of separated straws is thought to affect the cleaning wind of a combine harvester. To comprehend the turbulent flow characteristics of the cleaning wind and its passage through the grains, the cleaning wind velocity is measured by particle image velocimetry and laser Doppler velocimetry. The flow of the cleaning wind is blocked by the grains, and therefore the distribution of wind velocity changes. It is found that the energy loss of the cleaning wind is not a result of turbulent flow. The wall friction and the pressure change observed as a result of the shape and the friction loss in the grains are the main considerations while calculating the energy loss of the cleaning wind in combine harvester.

DOI： 10.1016/S1881-8366(12)80022-X

Language：English   Publishing type：Research paper (bulletin of university, research institution)  

Repository Public URL： http://hdl.handle.net/2324/20328

Language：English   Publishing type：Research paper (scientific journal)  

A dynamic three-dimensional model was constructed for a half-track tractor that considers its bounce, pitch, and roll motions in order to clarify the tractor's vibration characteristics. Driving experiments were conducted in which the tractor was driven on a solid asphalt road surface in order to investigate its vibration characteristics and to verify the validity of an analysis based on motion equations that were formulated from the proposed dynamic model. The experiments were conducted with a half-track tractor apparatus equipped with twelve accelerometers for the measurement of 6 DOF of acceleration of the tractor's centre of gravity. The discrete time series of the measured data was resolved and reconstructed by wavelet analysis. The model was verified using the fixed lug phase difference between the left and the right crawler systems for each combination of three location arrangements of the track rollers and seven levels of tractor speed. Results showed that the acceleration of the centre of gravity for the bounce, pitch, and roll motions was at a minimum when the track rollers were set equidistant from one another. The acceleration caused by the bounce and pitch motions decreased with an increase in the lug phase difference, while the acceleration caused by the roll motion increased with an increase in the lug phase difference. The results further suggested that the proposed three-dimensional dynamic model could be improved by incorporating into it the lug phase differences that change during actual tractor driving, instead of a constant lug phase difference.

DOI： 10.1016/j.biosystemseng.2011.07.013

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Corrugated fiberboard are typically lightweight and inexpensive with high stiffness-to-weight and strength-to-weight ratios as an environmental-friendly packaging materials. In order to optimize the application of corrugated paperboard for packaging cushioning materials, it is essential that both a vibration transmissibility test and drop shock test be completed for the transmissibility-frequency curve and dynamic cushion curve respectively. This paper deals with the characterization of properties of corrugated paperboard relevant to its application for protective packaging in transportation, such as vibration transmissibility, resonant frequency, damping ratio, and maximum dynamic stress. The main feature of the paper is the evaluation on the vibration transmissibility of corrugated paperboard with corrugation shape and the equilibrium atmospheric conditions by a sinusoidal sweep vibration test. Additionally, damping ratio and maximum dynamic stress were evaluated by linear vibration theory. All the works provide basic data relevant to its application for protective packaging in transportation.

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (other academic)  

Simple field monitoring system for optimizing and improving agricultural production process and management is developed by the built-in mail sender data logger unit with some weather and field monitoring sensors. In this monitoring system, all the monitoring data are once transferred and stored to mail servers. Thereafter the data are transferred periodically to the agricultural information database system. The database system was fully developed using open software such as apache (web server), MySQL, PHP, Java, CMS (Contents Management System) and so on. The stability of the monitoring system was verified using more than 20 monitoring units at four test sites where weather, crop type and farm size are different. On the other hand, work recording system to manage and optimize current production process was also developed and integrated to the developed database system. A list of farming processes and schedules was arranged flexibly by a farmer thorough a web browser. All the process data were entered into the information database by using mobile device and/or PC. The availability and validity of the developed recording system were verified by feasibility studies in the real farming sites.

Language：English   Publishing type：Research paper (other academic)  

Soil compaction is one of the major subjects in a well-mechanized modern agricultural system. In order to reduce the risk of soil compaction, the mechanical impacts to topsoil and subsoil during agricultural machinery operations have to be controlled. Soil compaction test using an off-road vehicle was conducted in the reclamation farmland at Isahaya bay, Nagasaki, Japan. The farmland was formed by sedimentary heavy clayey soil having high water-holding capacity and strong cohesion. In all the tests, the penetration resistance (cone index) of the soil and the bulk density before and after the vehicle running was measured in the field. The detail of soil mechanical properties was obtained from typical soil tests such as the standard compression, oedometer and triaxial compression test, respectively. On the other hand, an unconventional elastoplastic constitutive model for soils having the structure and cohesion was proposed by the superloading-yield/subloading surface model with Hashiguchi and Mase concept (2007). The validity of the model was evaluated by comparisons with the test data mentioned above.

Language：English   Publishing type：Research paper (other academic)  

The empirical Gaussian-based mathematical model of soil displacement increment under the traveling wheel was extended to be applicable to any depth of soil layer under the ground contact surface of the wheel. The unknown coefficients were obtained by least mean-square fitting with the soil displacement curve measured through laboratory sophisticated soil bin test. Then those coefficients were re-derived as a function of depth. The movement of soil particles at the ground contact surface was modeled by dividing into 2 kinds; first, the free movement of soil particles before contact with the wheel and the movement of the particles after they are separated from the wheel surface and the second type represent soil movement during attachment to the wheel surface. By combining the models for the ground contact surface of the wheel with that for all soil layers, the extended model that can describe soil displacement increment in both the vertical and horizontal directions using one equation was established. The predicted results obtained using the extended model fitted quite well with the measured values. The predicted strain increment distributions show the same trends as the measured distributions.

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

Experiments to measure the vertical dynamic loading forces acting on the track rollers of a half-tracked tractor were conducted by using strain gauges. In addition, a driving simulation model was constructed to predict the vertical dynamic loading forces acting on the track rollers as the tractor ran on an asphalt road surface. A twodimensional model to evaluate the vibration characteristics of the half-tracked tractor is discussed. It was modified and improved by considering the linear and nonlinear interactions of the rubber crawler with the track roller as well as the roller's location arrangement.

DOI： 10.1016/S1881-8366(10)80003-5

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

In order to analyze precisely not only the elastoplastic deformation phenomenon of saturated particle assembly such as soils, grains, powdered and tablet medicines or three dimensional cellular materials, but also the frictional sliding phenomenon between saturated particle assembly and other bodies, a particle assembly-water coupled finite element program, that incorporates both the subloading surface and the subloading-friction models, is developed. Subsequently, simulations of the compaction behavior of saturated particle assembly under strain rate control are performed. It is revealed by the numerical experiment adopting the finite element program that the frictional sliding behavior of the contact boundary influences both the deformation behavior and the pore water flow behavior in the saturated particle assembly.

Language：English   Publishing type：Research paper (scientific journal)  

The elastoplastic stress is first defined as the stress which evolves as the actual strain rate is induced in an imaginary quasi-static process of elastoplastic deformation, while internal variables evolve with the viscoplastic strain rate calculated by the viscoplastic constitutive equation. Further, the novel variable "overstress tensor" reaching the current stress from the elastoplastic stress is defined. Then, the overstress model is extended so as to describe also the tangential viscoplastic strain rate induced by the overstress tensor component tangential to the yield surface. Furthermore, the viscoplastic strain rate due to the change of stress inside the yield surface is incorporated by adopting the concept of the subloading surface which falls within the framework of the unconventional elastoplasticity describing the smooth elastic-plastic transition fulfilling the smoothness and continuity conditions.

Language：English   Publishing type：Research paper (scientific journal)  

This study is aimed at evaluation of the deformation behavior of Shirasu soil (volcanic sandy soil) for reclamation and embankment construction, using elastoplastic constitutive equation based on the subloading surface model with the rotational hardening. Test results for isotropic consolidation and monotonic/cyclic loading-unloading compression with several lateral stresses under the drained conditions for various initial void ratios are reported. Further, the simulation by the constitutive equation based on the extended subloading surface model is compared with the test results. High applicability of the constitutive equation for the prediction of mechanical behavior of Shirasu soil for a geo-material at the lowland in the southern Kyushu is verified by the comparison.

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Soil-wheel interaction especially soil deformation caused by the wheel motion was investigated experimentally using a sophisticated soil bin test apparatus and an on-line measurement system for soil displacement. Based on these test results, characteristics of soil deformation were summarized focusing on the behavior and distribution of displacement increment vectors. Mathematical models were examined in order to describe the displacements of soil particles. Properties of the displacement loci are described. The magnitude of the displacement increment vector, its horizontal and vertical components are discussed, and characteristics of these distributions with respect to the relative horizontal distance from the vertical centerline of the wheel to the target point are clarified. Shapes of these distribution curves were closely similar to those of the derivatives of a Gaussian function. A distribution curve of the horizontal displacement increment had two peaks and that of the vertical one had three peaks. Based on the results, mathematical models for those displacement increments were proposed by employing a Gaussian function through multiplication of a linear function and a quadratic function. Predicted distributions and displacement loci of the models agreed with high accuracy to the measured values. The mathematical models were extended taking into consideration the wheel slip. The predicted distributions according to test conditions agreed very well to the measured results.

DOI： 10.1016/j.jterra.2005.05.005

Language：English   Publishing type：Research paper (scientific journal)  

The conventional elastoplastic model premising that the interior of yield surface is a purely elastic domain is incapable of describing the plastic deformation by the rate of stress inside the yield surface. Thus, it is inapplicable to the description of cyclic loading behavior. Besides, the traditional elastoplastic model is independent of the stress rate component tangential to the yield surface. Therefore, it predicts an unrealistically high stiffness modulus for non- v proportional loading process deviating significantly from proportional one. The extended tangential-subloading surface model proposed by Hashiguchi and Tsutsumi (2001) would be capable of describing the cyclic loading behavior and the inelastic strain rate induced by the stress rate component tangential to the subloading surface. In this article, the extended tangential-subloading surface model is applied to the prediction of deformation behavior of sands subjected to various loading ranging from proportional to cyclic nonproportional loading. The validity is verified by comparing with the various test data. Then, it is revealed that the incorporation of the strain rate due to the stress rate component tangential to the subloading surface is of importance for the description of nonproportional loading behavior.

DOI： 10.3208/sandf.46.449

Language：English   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

A rate-dependent inelastic constitutive equation is formulated by extending the elastoplastic constitutive equation so as to retain the latter's mathematical structure and thus reduce to the latter equation at an infinitesimal rate of deformation. That structure differs substantially from that of the over-stress model, the best-known rate-dependent inelastic constitutive model. The proposed constitutive model is a type of superposition model, which is premised on the additive decomposition of the inelastic strain rate into the plastic and creep strain rates. The plastic strain rate is formulated so as to become suppressed as the rate of deformation increases but is induced even at the infinite rate of deformation. This is the distinguishing features of this model from the existing superposition models. The present model can describe realistically the rate-dependent inelastic deformation for a wide range of strain rates. On the other hand, the over-stress model cannot predict appropriately the difference of mechanical response due to the rate of deformation, especially being inapplicable to the description of deformation at high rate of deformation as known from the unrealistic prediction of the infinite strength at an infinite rate of deformation. The proposed model is applied to various metals, and its adequacy is verified through comparisons with various test data under a wide variety of strain rates and temperatures.

DOI： 10.1016/j.ijplas.2004.04.001

Language：English   Publishing type：Research paper (scientific journal)  

A constitutive model for the description of friction phenomena is formulated by incorporating the concept of the subloading surface [Hashiguchi, K., 1978. Plastic constitutive equations of granular materials. In: Proc. US-Japan Seminar Continuum Mech. Stast. Appr. Mech. Granular Materials, Sendai, pp. 321-329; Hashiguchi, K., 1980. Constitutive equations of elastoplastic materials with elastic-plastic transition. J. Appl. Mech. (ASME) 47 (1980) 266-272; Hashiguchi, K., 1989. Subloading surface model in unconventional plasticity. Int. J. Solids Struct. 25 (1989) 917-945] falling within the framework of unconventional plasticity [Drucker, D.C., 1988. Conventional and unconventional plastic response and representation. Appl. Mech. Rev. (ASME) 41 (1988) 151-167], which excludes the premise that the interior of a yield surface is a purely elastic domain. It describes the nonlinear relationship between the normal and tangential tractions on a contact surface. Furthermore, it predicts the gradual progress of sliding displacement with an increase in traction, and thus a judgment regarding the fulfillment of the sliding condition is not necessary. This is in contrast to a conventional friction model with a sliding surface enclosing an elastic domain, in which such gradual progress cannot be described and the judgment is required. Thus, a rough numerical calculation with large loading steps even in the explicit numerical method is allowed in the present friction model. In addition, typical friction boundary value problems are analyzed by the finite element method incorporating the present friction model.

DOI： 10.1016/j.ijsolstr.2004.08.006

Language：English   Publishing type：Research paper (scientific journal)  

A rate-dependent inelastic constitutive equation is formulated by extending the elastoplastic constitutive equation so as to retain the latter's mathematical structure and thus reduce to the latter equation at an infinitesimal rate of deformation. That structure differs substantially from that of the over-stress model, the best-known rate-dependent inelastic constitutive model. The proposed constitutive model is a type of superposition model, which is premised on the additive decomposition of the inelastic strain rate into the plastic and creep strain rates. The plastic strain rate is formulated so as to become suppressed as the rate of deformation increases but is induced even at the infinite rate of deformation. This is the distinguishing features of this model from the existing superposition models. The present model can describe realistically the rate-dependent inelastic deformation for a wide range of strain rates. On the other hand, the over-stress model cannot predict appropriately the difference of mechanical response due to the rate of deformation, especially being inapplicable to the description of deformation at high rate of deformation as known from the unrealistic prediction of the infinite strength at an infinite rate of deformation. The proposed model is applied to various metals, and its adequacy is verified through comparisons with various test data under a wide variety of strain rates and temperatures.

DOI： 10.1016/j.ijplas.2004.04.001

Language：English   Publishing type：Research paper (scientific journal)  

A constitutive model for the description of friction phenomena is formulated by incorporating the concept of the subloading surface [Hashiguchi, K., 1978. Plastic constitutive equations of granular materials. In: Proc. US-Japan Seminar Continuum Mech. Stast. Appr. Mech. Granular Materials, Sendai, pp. 321-329; Hashiguchi, K., 1980. Constitutive equations of elastoplastic materials with elastic-plastic transition. J. Appl. Mech. (ASME) 47 (1980) 266-272; Hashiguchi, K., 1989. Subloading surface model in unconventional plasticity. Int. J. Solids Struct. 25 (1989) 917-945] falling within the framework of unconventional plasticity [Drucker, D.C., 1988. Conventional and unconventional plastic response and representation. Appl. Mech. Rev. (ASME) 41 (1988) 151-167], which excludes the premise that the interior of a yield surface is a purely elastic domain. It describes the nonlinear relationship between the normal and tangential tractions on a contact surface. Furthermore, it predicts the gradual progress of sliding displacement with an increase in traction, and thus a judgment regarding the fulfillment of the sliding condition is not necessary. This is in contrast to a conventional friction model with a sliding surface enclosing an elastic domain, in which such gradual progress cannot be described and the judgment is required. Thus, a rough numerical calculation with large loading steps even in the explicit numerical method is allowed in the present friction model. In addition, typical friction boundary value problems are analyzed by the finite element method incorporating the present friction model.

DOI： 10.1016/j.ijsolstr.2004.08.006

Language：English   Publishing type：Research paper (scientific journal)  

A rate-dependent inelastic constitutive equation is formulated by extending the elastoplastic constitutive equation so as to retain the latter's mathematical structure and thus reduce to the latter equation at an infinitesimal rate of deformation. That structure differs substantially from that of the over-stress model, the best-known rate-dependent inelastic constitutive model. The proposed constitutive model is a type of superposition model, which is premised on the additive decomposition of the inelastic strain rate into the plastic and creep strain rates. The plastic strain rate is formulated so as to become suppressed as the rate of deformation increases but is induced even at the infinite rate of deformation. This is the distinguishing features of this model from the existing superposition models. The present model can describe realistically the rate-dependent inelastic deformation for a wide range of strain rates. On the other hand, the over-stress model cannot predict appropriately the difference of mechanical response due to the rate of deformation, especially being inapplicable to the description of deformation at high rate of deformation as known from the unrealistic prediction of the infinite strength at an infinite rate of deformation. The proposed model is applied to various metals, and its adequacy is verified through comparisons with various test data under a wide variety of strain rates and temperatures.

DOI： 10.1016/j.ijplas.2004.04.001

Language：English   Publishing type：Research paper (scientific journal)  

A constitutive model for the description of friction phenomena is formulated by incorporating the concept of the subloading surface [Hashiguchi, K., 1978. Plastic constitutive equations of granular materials. In: Proc. US-Japan Seminar Continuum Mech. Stast. Appr. Mech. Granular Materials, Sendai, pp. 321-329; Hashiguchi, K., 1980. Constitutive equations of elastoplastic materials with elastic-plastic transition. J. Appl. Mech. (ASME) 47 (1980) 266-272; Hashiguchi, K., 1989. Subloading surface model in unconventional plasticity. Int. J. Solids Struct. 25 (1989) 917-945] falling within the framework of unconventional plasticity [Drucker, D.C., 1988. Conventional and unconventional plastic response and representation. Appl. Mech. Rev. (ASME) 41 (1988) 151-167], which excludes the premise that the interior of a yield surface is a purely elastic domain. It describes the nonlinear relationship between the normal and tangential tractions on a contact surface. Furthermore, it predicts the gradual progress of sliding displacement with an increase in traction, and thus a judgment regarding the fulfillment of the sliding condition is not necessary. This is in contrast to a conventional friction model with a sliding surface enclosing an elastic domain, in which such gradual progress cannot be described and the judgment is required. Thus, a rough numerical calculation with large loading steps even in the explicit numerical method is allowed in the present friction model. In addition, typical friction boundary value problems are analyzed by the finite element method incorporating the present friction model.

DOI： 10.1016/j.ijsolstr.2004.08.006

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

The subloading-friction model is the unconventional elastoplastic friction model which allows the slip displacement due to the contact stress below the sliding surface. It is capable of describing the nonlinear relationship between the normal and the tangential stress on the contact surface and a gradual progress of relative tangential displacement with the increase of the contact stress. In this paper, the compression problem of rectangular block, the indentation problem of circular rigid roller and the cyclic friction problem for the elastic body under the plane strain condition are analyzed by the finite element program incorporating the subloading-friction model. It is revealed that the distribution of contact stress is predicted appropriately and the accumulation of relative displacement due to the cyclic loading of contact tangential traction below the sliding condition can be described. Besides, the computation time is shortened by the present finite element program compared with programs with the conventional friction model.

Language：English   Publishing type：Research paper (scientific journal)  

The subloading-friction model is the unconventional elastoplastic friction model which allows the slip displacement due to the contact stress below the sliding surface. It is capable of describing the nonlinear relationship between the normal and the tangential stress on the contact surface and a gradual progress of relative tangential displacement with the increase of the contact stress. In this paper, the compression problem of rectangular block, the indentation problem of circular rigid roller and the cyclic friction problem for the elastic body under the plane strain condition are analyzed by the finite element program incorporating the subloading-friction model. It is revealed that the distribution of contact stress is predicted appropriately and the accumulation of relative displacement due to the cyclic loading of contact tangential traction below the sliding condition can be described. Besides, the computation time is shortened by the present finite element program compared with programs with the conventional friction model.

Language：English   Publishing type：Research paper (scientific journal)  

The subloading-friction model is the unconventional elastoplastic friction model which allows the slip displacement due to the contact stress below the sliding surface. It is capable of describing the nonlinear relationship between the normal and the tangential stress on the contact surface and a gradual progress of relative tangential displacement with the increase of the contact stress. In this paper, the compression problem of rectangular block, the indentation problem of circular rigid roller and the cyclic friction problem for the elastic body under the plane strain condition are analyzed by the finite element program incorporating the subloading-friction model. It is revealed that the distribution of contact stress is predicted appropriately and the accumulation of relative displacement due to the cyclic loading of contact tangential traction below the sliding condition can be described. Besides, the computation time is shortened by the present finite element program compared with programs with the conventional friction model.

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Proposal of a phenome-nological friction model incorporating the subloading surface concept

Language：English   Publishing type：Research paper (scientific journal)  

A constitutive model for the description of friction phenomenon is formulated by incorporating the subloading surface concept proposed for the formulation of the unconventional plastic constitutive equation. It describes the nonlinearity of the relationship between the normal and the tangential forces on the contact boundary. Further, it describes the smooth relation of the contact force and the sliding distance, i.e. the smooth elastic-plastic transition and the thus the judgment for the fulfillment of friction condition is not needed, which is required in the conventional friction theory. Thus, a rough numerical calculation with large loading steps is allowed in the present model.

Language：English   Publishing type：Research paper (scientific journal)  

The rate-dependent inelastic constitutive equation was formulated by extending the subloading model such that the plastic strain rate is suppressed with the increase of strain rate and incorporating the creep strain rate in the previous article. It retains the mathematical structure of the subloading surface model and thus reduces to the model itself at infinitesimal strain rate. It belongs to the superposition model premising on the additive decomposition of the inelastic strain rate into the plastic and the creep strain rates. It is applied to metals, and its adequacy is verified comparing with various test data at a wide variety of strain rates and temperatures.

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

The description of the deformation behavior of Shirasu (volcanic sandy soil) by the elastoplastic constitutive equation is studied adopting a subloading surface model with rotational hardening. Also, test results for isotropic consolidation and triaxial compression with several lateral stresses under the drained and the undrained conditions for various initial void ratios are reported. Further, simulation by the constitutive equation is compared with the test results. High ability of the constitutive equation for the prediction of mechanical behavior of Shirasu is verified by the comparison.

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

Conventional elastoplasticity is based on the idealisation that the interior of the yield surface is a purely elastic domain. This idealisation would not lead to unrealistic prediction of hardening behaviour, but would cause unrealistic prediction of softening behaviour, which is observed typically in overconsolidated soils, whereas metals and normally consolidated soils exhibit hardening behaviour. By contrast, unconventional elastoplasticity that does not use this idealisation makes it possible to describe the plastic deformation due to the change of stress inside the yield surface exhibiting a smooth elastic-plastic transition, and is thus expected to describe softening behaviour more accurately. In this paper the capabilities of conventional and unconventional elastoplasticity for describing softening behaviour are examined, comparing the Drucker-Prager model as the conventional one and the subloading surface model as the unconventional one for predicting the deformation behaviour of overconsolidated soils. It is concluded that unconventional elastoplasticity has to be adopted for predicting softening behaviour.

DOI： 10.1680/geot.2002.52.8.561

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

Various constitutive models have been applied to the analyses of localized deformation of solids. However, most of them fall within the framework of the conventional plasticity premising that the interior of yield surface is an elastic domain and obeys the plastic potential theory in which the plastic stretching is independent of the stress rate component tangential to the yield surface. Therefore, they predict a stiff elastic response until the stress reaches the yield state and further a stiff elastoplastic response after yielding. On the other hand, the subloading surface model falling within the unconventional plasticity would be only the model capable of describing pertinently the plastic deformation induced by the rate of stress within the yield surface in general loading process including the unloading, reloading and inverse loading. Further, the numerical calculation by this model is quite efficient disusing the special algorism, e.g. the mean normal method and the radial return method in order to make the stress lie just on the yield surface in the plastic loading process since it contains the controlling function to make the stress approach automatically the yield surface in the plastic loading process. Further, this model is recently extended so as to describe the tangential stress rate effect, i.e. the inelastic deformation induced by the stress rate component tangential to the subloading surface. In this article the post-localized deformation of metal due to the shear band formation is analyzed by the finite element method incorporating the subloading surface model with the tangential stress rate effect. Thus, the influence of the tangential stress rate effect on the shear band formation is discussed exhibiting several examples of the deformation patterns.

Language：English   Publishing type：Research paper (scientific journal)  

Post-localization analysis by the subloading surface model with tangential stress rate effect

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

Mechanical response of the subloading surface model with tangential stretching

Language：Japanese   Publishing type：Research paper (scientific journal)  

Consideration of shear band formation by elastoplastic constitutive equation of soils with tangential stress rate effect

Language：English   Publishing type：Research paper (scientific journal)  

Various constitutive models for the description of time-dependent deformation behavior have been proposed. However, it is first verified in this article that a pertinent model applicable to the description of deformation for a wide range of stress below and over the elastic limit, i.e. the yield stress, has not been found up to the present. It should be noted that a stress goes out over the yield surface at a high rate of deformation, only elastic deformation being induced. The subloading surface model does not premise that a stress exists on the yield surface even in the plastic loading process and thus describes the plastic deformation induced by the rate of stress within the yield surface, exhibiting the smooth elastic-plastic transition. In this article the subloading surface model is extended so as to describe the time-dependence for a wide range of deformation rates by allowing the stress to go out from the yield surface based on the physical interpretation that a plastic deformation due to the mutual slip between microstructures is suppressed for the deformation at a high rate causing the increase of viscous resistance acting between the microstructures. Further, based on this, a time-dependent elastoplastic constitutive equation of soils is formulated by incorporating the secondary-consolidation phenomenon, and its ability to predict deformation behavior of soils is verified by comparisons with test data on fundamental time-dependent behavior with various deformation rates, creep and stress relaxation under the undrained condition.

DOI： 10.3208/sandf.40.4_19

Language：English   Publishing type：Research paper (scientific journal)  

The travelling performance of rigid wheels on sand stratum is measured using two kinds of surface material, i.e. steel and steel coated with rubber. A new method for measuring the displacement of soil beneath the wheel has been developed using small polyester film markers. The trajectories of soil particles beneath the wheels are approximated by an exponential function and the fluctuations in the drawbar pull are represented by a sinusoidal function. The amplitude and basic wavelength of the fluctuation in the drawbar pull are discussed for both types of wheels.

DOI： 10.1016/S0022-4898(99)00011-7

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

Precise measurement of soil deformation and fluctuation in drawbar pull for steel and rubber-coated rigid wheels

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

The subloading surface model does not premise that the stress exists on the yield surface and thus describes a plastic deformation even when the stress exists inside the yield surface. The measure describing the degree that the stress approaches the yield surface or goes out from the surface is involved in this model. It is extended so as to describe the time-dependent deformation behavior of materials by allowing the stress to go out from the yield surface and considering the fact that a plastic deformation requires time to occur, although an elastic deformation is induced momentarily. Further, based on it, the constitutive equation of soils is formulated by taking the secondary consolidation phenomenon into account.

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (scientific journal)  

The extension of the elastoplastic constitutive equation so as to describe the plastic stretching due to the stress rate component tangential to the yield or loading surface has been one of the most pressing problems in the elastoplasticity. To this aim, various models have been proposed in the past. However, a pertinent model applicable to a general loading process has not previously been proposed. In this article, the elastoplastic constitutive equation extended so as to describe a plastic stretching due to a stress rate component tangential to a yield or loading surface is formulated keeping a single and smooth yield surface. It would be a pertinent one which fulfills the mechanical requirements for elastoplastic constitutive equation and which is applicable to an arbitrary loading process. Based on this equation, a constitutive equation of metals with the isotropic-kinematic hardening is formulated.

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