Kyushu University Academic Staff Educational and Research Activities Database
List of Papers
Junya Suehiro Last modified date:2021.10.28

Professor / Applied Energy Engineering / Department of Electrical Engineering / Faculty of Information Science and Electrical Engineering


Papers
1. H. Lee, J. Suehiro, M. Hara, D. Lee, M. So, Optimal Condition of Waveforms for Electrical Sterilization of {?it Escherichia coli?/} by HV Impulse, 静電気学会誌, Vol.24, No.4, pp.213-217, 2000.04.
2. Manipulation and Detection of Bacteria Using Dielectrophoresis.
3. Applications of dielectrophoresis in life science.
4. Dielectrophoretic manipulation of nanomaterials and its application to device fabrication.
5. NisarutPhansiri, Daichi Maenosono, Masafumi Inaba, Michihiko Nakano, Junya Suehiro, Hidefumi Sato, Detection of Decomposition Products of CF₄/SF₆ Gas Mixture Generated by Partial Discharge Using a SnO₂ Gas Sensor Fabricated by Dielectrophoresis, 電気学会研究会資料. HV = The papers of technical meeting on high voltage engineering, IEE Japan, 2020, 51, 59-63, 2020.01.
6. T. Okada, M. Ueda, J. Nishimura, J. Guo, M. Higashihata, Junya Suehiro, Optical characteristics of ZnO nanowires synthesized by nanoparticle-assisted deposition and their application to sensors, Zinc Oxide Materials and Devices II Zinc Oxide Materials and Devices II, 10.1117/12.698854, 2007.05, ZnO nano-nails which consist of the nanowire at the top of nanorods have been synthesized by the nanoparticle-assisted deposition technique. When the nanowire was excited by the third harmonics of a Q-switched Nd:YAG laser, the ultraviolet stimulated emission was clearly observed from single nanowire, indicating the high crystalinity of the nanowire. The highly sensitive ultraviolet photo-detectors were successfully fabricated by trapping these nanowires between electrodes using the dielectrophoresis technique..
7. J. Suehiro, K. Imasaka, Solubilization of carbon nanotubes using microplasma generated in water, Transactions of the Materials Research Society of Japan, Vol. 32, No. 2, pp. 517-522, 2007.06.
8. K. Imasaka, Y. Kanatake, Y. Ohshiro, J. Suehiro, M. Hara, Production of carbon nanoonions and nanotubes using an intermittent arc discharge in water, Thin Solid Films, Vol.506/507, pp.250-254, 2006.05, [URL].
9. K. Imasaka, Y. Kanatake, Y. Ohshiro, J. Suehiro, M. Hara, Production of carbon nanoonions and nanotubes using an intermittent arc discharge in water, Thin Solid Films, 10.1016/j.tsf.2005.08.024, 506-507, 250-254, 2006.05, An intermittent arc discharge in water, which has several millisecond pulse width, was used to produce carbon nanoparticles. High-resolution TEM observation revealed that the aggregated nanoonions were obtained as the floating powders on the water surface and the rest products which contains multiwalled carbon nanotubes were found at the base of the water. Production efficiency of carbon soot which contains the carbon nanoonions and multiwalled nanotubes to consumption mass of carbon electrodes was also investigated. Production efficiency of carbon soot was increased about 3 times in comparison with a direct current (DC) arc discharge method in water..
10. Yasin Khan, Junya Suehiro, Masanori Hara, Shigemitsu Okabe, Particle-initiated Breakdown Characteristics around Spacer under Lightning Impulse Voltage Superimposed on Pre-stressed DC, The transactions of the Institute of Electrical Engineers of Japan.A, 10.1541/ieejfms.124.547, 124, 7, 547-552, 2004.07, This paper deals with the effect of the magnitude and polarity on the particle initiated breakdown characteristics around a simple shaped spacer in quasi-uniform field gap under lightning impulse voltage superimposed on pre-stressed DC voltage. The results are discussed on the dust figure technique and also on the breakdown voltage / delay time characteristics, while keeping in view the magnitude of the pre-stressed DC applied voltage. Consequently, it was found that the surface charges accumulated on the spacer in the vicinity of the particle tip under the pre-stressed DC voltage play an important role in the particle initiated breakdown phenomenon..
11. Kiminobu Imasaka, Yuki Kato, Junya Suehiro, Effects of gas bubbling on water-solubilization of carbon nanotube using microplasma generated in water, Surface and Coatings Technology, 10.1016/j.surfcoat.2008.06.068, 202, 22-23, 5271-5274, 2008.08, In this study, influences of gas bubbling on water-solubility of single-walled carbon nanotubes (SWCNTs) based on microplasma treatment in water were investigated. Oxygen (O2), argon (Ar), nitrogen (N2) and carbon dioxide (CO2) were used as the bubbling gases. Bubbling of O2, Ar and N2 enhanced the O* and H* radicals produced by the microplasma in water and the solubility of SWCNT was increased more than two times compared to that without gas bubbling. On the other hand, the solubility was very poor in case of CO2. The negative effect of CO2 on the solubility might be due to the decrease of radicals, which were scavenged by carbonate ion generated by dissociation of CO2 in water, and caused by the reaction of radicals with CO2 or CO rather than those with SWCNT..
12. K. Imasaka, Y. Kato and J. Suehiro, Effects of gas bubbling on water-solubilization of carbon nanotube using microplasma generated in water, Surface & Coatings Technology, Volume 202, Issues 22-23, Pages 5271-5274, 2008.08, [URL].
13. J. Suehiro, M. Shutou, T. Hatano, M. Hara, High sensitive detection of biological cells using dielectrophoretic impedance measurement method combined with electropermeabilization, Sensors and Actuators B: Chemical, 10.1016/S0925-4005(03)00517-3, 96, 1-2, 144-151, Vol.96, No.1/2, pp.144-151, 2003.11, [URL].
14. J. Suehiro, G. Zhou, M. Hara, Detection of partial discharge in SF6 gas using a carbon nanotube-based gas sensor, Sensors and Actuators B, Chemical, 10.1016/j.snb.2004.05.050, 105, 2, 164-169, Vol.105, pp.164-169, 2004.07, [URL].
15. J. Suehiro, T. Hatano, M. Shutou and M. Hara, Improvement of electric pulse shape for electropermeabilization-assisted dielectrophoretic impedance measurement for high sensitive bacteria detection, Sensors and Actuators B, Chemical, 10.1016/j.snb.2004.12.048, 109, 2, 209-215, Vol.109, pp.209-215, 2005.01, [URL].
16. J. Suehiro, G. Zhou, H. Imakiire, W. Ding, M. Hara, Controlled fabrication of carbon nanotube NO2 gas sensor using dielectrophoretic impedance measurement, Sensors and Actuators B, Chemical, 10.1016/j.snb.2004.09.048, 108, 1-2, 398-403, Vol.108, pp.398-403, 2005.07, [URL].
17. J. Suehiro, H. Imakiire, S. Hidaka, W. Ding, G. Zhou, K. Imasaka, M. Hara, Schottky-type response of carbon nanotube NO2 gas sensor fabricated onto aluminum electrodes by dielectrophoresis, Sensors and Actuators B, Chemical, Vol.114, pp.943?949, 2006.04, [URL].
18. J. Suehiro, A. Ohtsubo, T. Hatano, M. Hara, Selective detection of bacteria by a dielectrophoretic impedance measurement method using an antibody-immobilized electrode chip, Sensors and Actuators B, Chemical, Vol.119, pp.319-326, 2006.11, [URL].
19. J. Suehiro, S. Hidaka, S. Yamane, K. Imasaka, Fabrication of interfaces between carbon nanotubes and catalytic palladium using dielectrophoresis and its application to hydrogen gas sensor, Sensors and Actuators B: Chemical, , Vol.127, No.2, pp.505–511, 2007.11, [URL].
20. M. Nakano, R. Hamada, H. Takayama, Y. Shonishi, T. Hisajima, L. Mao, J. Suehiro, Pretreatment of cell membranes for improved electropermeabilization-assisted dielectrophoretic impedance measurement, Sensors and Actuators B: Chemical, , 10.1016/j.snb.2012.07.078, 2012.08, [URL], We improved our previously reported highly sensitive bacteria detection method called
electropermeabilization-assisted dielectrophoretic impedance measurement (EPA-DEPIM), which
counts the number of bacteria by measuring changes in impedance. EPA-DEPIM involves two processes:
collection of bacteria by dielectrophoresis (DEP), followed by electropermeabilization (EP) of the
cell membranes. In DEP, bacterial cells in aqueous solution are collected on microelectrodes by the
dielectrophoretic force. In EP, a pulse-like rectangular wave is applied to the collected cells to disrupt
their membranes. This increases the signal sensitivity because the disrupted membranes release
intracellular ions that increase the change in impedance. However, the pulse-like EP wave creates a
strong electric field that causes metal ions to be released from the microelectrodes, increasing the blank
signal to levels comparable to that for a low-concentration Escherichia coli suspension (102 cells/ml). To
address this problem, we demonstrated the efficacy of two types of pretreatment applied before the EP
wave: chemical pretreatment by exposure to hydrogen peroxide, and physical pretreatment by a small
pulse-like voltage. Both pretreatments successfully intensified the change in impedance even at a lower
EP voltage..
21. Hamada Ryo, Takayama Hiroyuki, Shonishi Yasuhiko, Mao Leina, Suehiro Junya, A rapid bacteria detection technique utilizing impedance measurement combined with positive and negative dielectrophoresis, Sensors and Actuators, B: Chemical, 10.1016/j.snb.2013.02.030, 181, 439-445, 2013.05, In this study, a bacterial detection technique and device that utilizes advantages of both positive and negative dielectrophoresis (DEP) has been proposed and demonstrated. The device has two microelectrodes, which serve as a bacteria concentrator using negative DEP (n-DEP) and as a bacteria detector using positive DEP (p-DEP), respectively. Bacteria flowing into the device are repelled under action of n-DEP force exerted by the first microelectrode, and are pushed toward the second microelectrode situated at the downstream. Then concentrated bacteria are finally captured by p-DEP on the second microelectrode and detected by dielectrophoretic impedance measurement (DEPIM) method. The numerical simulations and experiments proved that n-DEP concentrator could make DEPIM sensitivity two times higher than that without n-DEP as a result of increased number of bacteria trapped on the p-DEP microelectrode..
22. Junya Suehiro, Shin Ichiro Hidaka, Shinji Yamane, Kiminobu Imasaka, Fabrication of interfaces between carbon nanotubes and catalytic palladium using dielectrophoresis and its application to hydrogen gas sensor, Sensors and Actuators, B: Chemical, 10.1016/j.snb.2007.05.002, 127, 2, 505-511, 2007.11, The authors have developed a novel fabrication method of a carbon nanotube (CNT) gas sensor using positive dielectrophoresis (DEP). One advantage of the DEP technique is that one can readily build up interfaces between electrodes and CNT, or between CNT and other nanomaterials. In this paper, the DEP technique was employed to fabricate interfaces between CNT and catalytic palladium (Pd) to realize a CNT-based hydrogen (H2) gas sensor. Two types of CNT/Pd interfaces were proposed and tested. For one type, CNTs were trapped onto a microelectrode made of Pd so that the CNT/Pd interfaces were formed at both ends of CNTs lying over the Pd electrode surface. The other type of gas sensor was fabricated by simultaneously trapping CNTs and Pd nanoparticles under action of the positive DEP. It was found that both types of the CNT/Pd gas sensors could respond to hydrogen, while the CNT sensor without the Pd functionalization could not. For the hydrogen gas diluted with dry air, the electrical resistance of the CNT/Pd sensors increased at the moment of hydrogen exposure, and then turned to decrease in the later stage. The resistance increase just after the H2 exposure was probably due to reduction of CNTs by H atoms, which were produced by dissociative adsorption of H2 molecules on the catalytic Pd surface. In the later stage, the dissociated H atoms might react with dissociated oxygen atoms to create H2O molecules accompanying heat generation..
23. Junya Suehiro, Akio Ohtsubo, Tetsuji Hatano, Masanori Hara, Selective detection of bacteria by a dielectrophoretic impedance measurement method using an antibody-immobilized electrode chip, Sensors and Actuators, B: Chemical, 10.1016/j.snb.2005.12.027, 119, 1, 319-326, 2006.11, This paper describes a selective detection method for specific bacteria by using a dielectrophoretic impedance measurement method in conjunction with an antigen-antibody reaction. The authors have previously demonstrated a bacteria detection technique called DEPIM (dielectrophoretic impedance measurement) and EPA-DEPIM (electropermeabilization-assisted DEPIM) using a positive dielectrophoretic force to capture bacteria in suspension onto an interdigitated electrode chip. It has also been demonstrated that a selective DEPIM detection of specific bacteria could be realized by taking advantage of agglutination phenomena, which were caused by an antigen-antibody reaction. In the present study, other combinations of the antigen-antibody reaction with DEPIM or EPA-DEPIM were demonstrated. Antibody molecules were immobilized on the electrode chip before the preliminary bacteria trapping by positive dielectrophoresis (DEP). The bacteria were attracted to the electrode gap under the action of the positive DEP force and finally brought into contact with the glass surface to be bound with the immobilized antibody. By appropriately adjusting the balance between the DEP force and the drag force caused by liquid flow, the target bacteria (Escherichia coli) could be selectively retained on the chip surface avoiding undesired non-specific binding. The retained bacteria were electrically detected by EPA-DEPIM. It was also confirmed that the proposed method realized selective detection of the target bacteria from a mixed suspension with nontarget bacteria..
24. Junya Suehiro, Hiroshi Imakiire, Shin Ichiro Hidaka, Weidong Ding, Guangbin Zhou, Kiminobu Imasaka, Masanori Hara, Schottky-type response of carbon nanotube NO 2 gas sensor fabricated onto aluminum electrodes by dielectrophoresis, Sensors and Actuators, B: Chemical, 10.1016/j.snb.2005.08.043, 114, 2, 943-949, 2006.04, Single-walled carbon nanotube (CNT) gas sensors were fabricated by dielectrophoresis onto microelectrodes made of Cr, Pd or Al. The Al/CNT sensor response to NO 2 (nitrogen dioxide) gas was characterized by fast and large resistance increase at the moment of NO 2 exposure, whereas the resistance of the other metal/CNT sensors monotonously decreased. It was suggested that the adsorbed NO 2 molecules might alter the Schottky barrier at the Al/CNT interface as well as the positive hole density in the p-type semiconducting CNT. The Al/CNT sensor response could be interpreted as a superposition of the Schottky contact resistance and the CNT resistance, which were differently influenced by the NO 2 adsorption and contributed to the overall sensor response. The Schottky response of the Al/CNT sensor was approximately one order of magnitude faster than the CNT response obtained using the other metal electrodes..
25. Junya Suehiro, Guangbin Zhou, Masanori Hara, Detection of partial discharge in SF6 gas using a carbon nanotube-based gas sensor, Sensors and Actuators, B: Chemical, 10.1016/S0925-4005(04)00415-0, 105, 2, 164-169, 2005.03, For electrical insulation diagnosis of gas-insulated switchgear (GIS), detection of partial discharge (PD) generated in sulfur hexafluoride (SF 6) gas is important. This paper describes a new detection method of PD generated in SF6 gas using a gas sensor composed of multiwall carbon nanotubes (MWCNTs). The gas sensor was fabricated by electrokinetic manipulation of semiconducting MWCNTs using positive dielectrophoresis. The MWCNT gas sensor and a point-to-plane electrode system were placed in a steel tank filled with SF6 gas at atmospheric pressure. AC high voltage was applied to the point electrode in order to generate PD while the electrical impedance of the MWCNT sensor was monitored. When the PD was generated, the electrical conductance of the MWCNT sensor gradually increased. The sensor response was reversible and was influenced by the PD intensity as well as by the relative position of the sensor to the point electrode. It was suggested that the sensor conductance increase was caused by an electronic interaction between MWCNTs and non-identified oxidative decomposition products. The faint PD, which could not be sensed by gas detecting tubes, was successfully detected by the MWCNT sensor on a real time basis..
26. M. Inaba, T. Oda, M. Kono, N. Phansiri, T. Morita, S. Nakahara, M. Nakano, J. Suehiro, Effect of mixing ratio on NO2 gas sensor response with SnO2-decorated carbon nanotube channels fabricated by one-step dielectrophoretic assembly, Sensors and Actuators, B: Chemical, 10.1016/j.snb.2021.130257, 344, 130257-1-130257-9, 2021.10, We fabricated nitrogen dioxide (NO2) gas sensors with p-type carbon nanotubes (CNTs) / n-type tin dioxide (SnO2) nanoparticle heterojunctions using one-step dielectrophoretic assembly and investigated the effect of CNT/SnO2 ratio on their NO2 gas detection properties. CNTs and SnO2 nanoparticles were mixed in various ratios, suspended in deionized water, and assembled by dielectrophoresis. The normalized response of fabricated CNT/SnO2 heterojunction gas sensors against 1 ppm NO2 was ∼80 in an N2 atmosphere and ∼20 in artificial air, where UV irradiation was used only for initialization. To reduce the effect of oxygen (O2), we also conducted continuous UV irradiation with various intensities during the initialization and gas detection. The CNT/SnO2 pn heterojunction gas sensor had a maximum normalized response of 19 for 1 ppm NO2 in artificial air, while that of the SnO2 sensor was 3. Furthermore, plotting the gas sensor response as a function of NO2 concentration reveals that the sensor detected an NO2 gas concentration as low as 20 ppb in artificial air. .
27. K. Imasaka, K. Kawazoe, Y. Kawauchi, S. Hara, J. Suehiro, M. Hara, Reduction of the Source Size of Gas-Puff Z-Pinch Plasmas Using an Inductive Pulsed Power System, Rev of Sci. Instrum, 10.1063/1.1322576, 71, 12, 4438-4444, Vol.71, No.12, pp.4438-4444, 2000.12.
28. R. Hamada and J. Suehiro, Optimization of electric field frequency on dielectrophoretic impedance measurement method for oral bacteria detection, Proceedings of the International Conference on Biomedical Electronics and Devices (Biodevices 2011), 125-129, 2011.01.
29. Michihiko Nakano, Ryoji Obara, Ding Zhenhao, Junya Suehiro, Detection of norovirus and rotavirus by dielectrophoretic impedance measurement, Proceedings of the International Conference on Sensing Technology, ICST, 374-378, Article number 6727678, 2013.12.
30. Ryoji Obara, Ding Zhenhao, Kenta Shinzato, Michihiko Nakano, Junya Suehiro, Higher throughput of optical detection of bacteria concentrated by negative dielectrophoresis, Proceedings of the International Conference on Sensing Technology, ICST, 275-278, Article number 6727658, 2013.12.
31. Michihiko Nakano, Ding Zhenhao, Hiromichi Kasahara, Junya Suehiro, DNA Detection using Microbeads-based Dielectrophoretic Impedance Measurement, Proceedings of the International Conference on Sensing Technology, ICST, 10.1109/ICSENS.2014.6985174, 2014-December, December, 12 December 2014, 1010-1013, Article number 6985174, 2014.12, A new electrical technique for rapid detection of DNA amplified by polymerase chain reaction (PCR) using dielectrophoresis (DEP) of microbeads was demonstrated. The amplicons were chemically immobilized on the microbeads. The DNA immobilization on the microbeads alters their DEP behavior in such a way that they are trapped on a microelectrode under the action of positive DEP, whereas pristine microbeads are not. Combining the dramatic alteration in DEP characteristics with impedance measurement leads to rapid and quantitative detection of the amplicon in a few seconds. The proposed microbead-based assay could be applicable for rapid, quantitative, and automated detection of virus infection..
32. J. Suehiro, K. Yamasaki, M. Hara, J. Gerhold, Liquid helium breakdown in the μs range, Proceedings of the IEEE 11th International Conference on Conduction and Breakdown in Dielectric Liquids (ICDL), 400-404, 1993.08, Information about breakdown time lags under pulsed voltage stress i is prerequisite to the insulation design of superconducting devices. Experiments have been carried out using a pulse generator with 200ns rise time and a long delay time constant of more than 1ms. This generator provides a step voltage to the gap in the μs range. The present experiments may bridge the information gap between time lag measurements in the ns range using extremely high field strengths, and existing data found with usual lightning impulse voltage. The test device is described in the paper, and some typical results are discussed in detail..
33. M. Hara, J. Suehiro, Breakdown behavior of insulation elements in superconducting magnet coils, Proceedings of the 3rd International Conference on Properties and Applications of Dielectric Materials, 411-414, 1992.08, The authors examine dielectric breakdown phenomena under some environments peculiar to superconducting coils, such as an internal high voltage and thermal bubbles in the coolant generated by the coil quench, as well as high magnetic field and low temperature. Breakdown mechanisms of vacuum, gaseous helium, and liquefied gas are also discussed..
34. T. Kurihara, J. Suehiro, M. Hara, Observation of residual surface charge distribution inside an artificial air-filled void due to partial discharge activities at room and liquid nitrogen temperatures, Proceedings of the 2004 IEEE International Conference on Solid Dielectrics ICSD 2004, 308-311, 2004.01, Partial discharge (PD) characteristics within an artificial air-filled void contained in a solid insulator were experimentally investigated under 60 Hz ac voltages at liquid nitrogen temperature (77 K) and room temperature of 298 K. The results show that the first PD inception voltage at 77 K is about twice higher than that at 298 K while successive values at both temperatures are almost the same. The results also show that PD charge magnitude noticeably decreases and PD pulse number remarkably increases with the decrease in the temperature from 298 K to 77 K. The latter results are further discussed based on the observed remarkable decrease in the charged area by a single PD on an inner void surface with the decrease in the temperature..
35. Zhenhao Ding, Michihiko Nakano, Junya Suehiro, DNA detection method based on the microbead velocity under traveling wave dielectrophoresis, Proceedings of the 12th International Joint Conference on Biomedical Engineering Systems and Technologies, 10.5220/0007341800210025, 1, 21-25, 2019.02.
36. Bok Yeol Seok, Hiroaki Komatsu, Junya Suehiro, Masanori Hara, Bubble behavior and PBD characteristics in the simulated electrode system of high temperature superconducting coils, Proceedings of the 1999 11th International Symposium on 'High Voltage Engineering' (ish99) IEE Conference Publication, 3.372.P4-3.375.P4, 1999.10, This paper deals with bubble behavior and electrical insulation at quenching state in superconducting coils. Bubble behavior in the simulated electrode system which consists of concentric coil layer-to-cylindrical electrode system with an insulation barrier and spacers immersed in liquid nitrogen was categorized into two types according to the cooling channel width (lc). In this study, bubble behavior and partial breakdown (PBD) characteristics are investigated with lc being narrower than the diameter of induced bubbles. Experimental results show that the bubbles are trapped in the groove between coil turns in the tested electrode system even at no applied voltage. Behavior of trapped bubbles depends on the applied voltage and shape of spacer which was installed for positioning of electrodes. The spacer having no aperture produces the most severe condition for electrical insulation: tight trap of bubble, excitation of electrohydrodynamic (EHD) instability on the surface of trapped bubble and lower inception voltage of partial breakdown in cooling channel than that with the spacer having an aperture. The pressurizing of liquid nitrogen is effective for suppression of active boiling and improvement of electrical insulation performance in the tested electrode system..
37. Junya Suehiro, Kouichi Tsutsumi, Daisuke Tsuji, Shinya Ohtsuka, Kiminobu Imasaka, Masanori Hara, Fast quench of superconducting wire by pulsed current and its application to pulsed power generation, Proceedings of the 1999 11th International Symposium on 'High Voltage Engineering' (ish99) IEE Conference Publication, 5.390.S26-5.393.S26, 1999.10, An inductive energy storage pulsed power generator needs an opening switch to immediately limit the circuit current and to achieve a high inductive voltage. Quench phenomena of a superconducting wire can be applicable to the opening switch because it provides a fast resistance increase of the wire. In this study, quench characteristics of a superconducting wire were investigated using pulsed current waveforms with various peak values. It has been found that quench of the wire occurred when the current exceeded a critical value. The resistance rise rate of the wire increases with the current peak and wire length. An inductive pulsed power generator, which used a solenoid coil of the superconducting wire as an opening switch, was constructed to demonstrate that the switch could principally work to generate pulsed voltage and power with a fast rising rate..
38. Shin ichiro Tsuru, Takumi Mine, Junya Suehiro, Masanori Hara, Partial discharge degradation of solid insulators with an air-filled void at liquid nitrogen temperature, Proceedings of the 1999 11th International Symposium on 'High Voltage Engineering' (ish99) IEE Conference Publication, 4.369.P2-4.372.P2, 1999.10, Degradation and Lifetime characteristics of solid insulators with an artificial air-filled void was investigated experimentally at liquid nitrogen temperature. As a result, it was found that the lifetime of a test sample decreased suddenly with increase in applied voltage. Observation of the PD characteristics showed that the decrease in lifetime at a higher applied voltage had a close relationship with the PD activity. The void surface subjected to the PDs was observed with SEM, and the degradation mechanism was discussed taking the experimental results into consideration..
39. S. Tsuru, M. Nakamura, T. Mine, J. Suehiro, M. Hara, Partial discharge inception characteristics in artificial air-filled voids at room and liquid nitrogen temperatures, Proceedings of the 1998 IEEE International Symposium on Electrical Insulation. Part 1 (of 2) Conference Record of IEEE International Symposium on Electrical Insulation, 1, 153-156, 1998.06, A part of gas substances in a void in solid insulators becomes liquid or solid at cryogenic temperature and the reduction in gas pressure in it may cause a decrease in partial discharge (PD) inception voltage. In this study, PD inception voltage and PD characteristics around the PD inception in artificial air-filled voids are investigated experimentally at room and liquid nitrogen temperatures. The results show that PD inception voltage decreases with decrease in ambient temperature due to the liquefaction of oxygen. PD characteristics just after the PD inception at liquid nitrogen temperature are affected by arrangement of test sample. Based on the simultaneous measurement of the current pulses and light images, PD characteristic dependence on the sample arrangement is discussed, taking account of the phase change of oxygen in the void..
40. Michihiko Nakano, Zhenhao Ding, Hiromichi Kasahara, Junya Suehiro, Rapid size determination of PCR amplified DNA by beads-based dielectrophoretic impedance spectroscopy, Proceedings of Transducers 2015, 10.1109/TRANSDUCERS.2015.7181228, 2015.11.
41. Y. Martin, Z. Li, T. Tsutsumi, J. Suehiro, K. Imasaka and S. Ohtsuka, Identification of DC corona generating SF6 decomposition gases adsorbed on CNT gas sensor using FTIR spectroscopy, Proceedings of TENCON 2010, 10.1109/TENCON.2010.5686640, 663-666, 2010.11.
42. J. Suehiro, S. Yamane and K. Imasaka, Carbon nanotube-based hydrogen gas sensor electrochemically functionalized with palladium
Proceedings of IEEE Sensors 2007, , Proceedings of IEEE Sensors 2007, art. no. 4388458, pp. 554-557, 2007.10, [URL].
43. Nakano Michihiko, Hisajima Takafumi, Mao Leina, Suehiro Junya, Electrical detection of norovirus capsid using dielectrophoretic impedance measurement method, Proceedings of IEEE Sensors, 10.1109/ICSENS.2012.6411163, 2012.10, In this work, we demonstrated an electrical detection technique of norovirus capsid in liquid by using dielectrophoretic impedance measurement (DEPIM). DEPIM is a method composing of capturing target particles by dielectrophoresis (DEP) in the gap of microelectrodes and measuring the impedance change of the microelectrodes caused by the captured particles. DEPIM has been successfully applied to bacteria detection by the present authors. This is the first report to extend scope of DEPIM inspection from bacteria to norovirus. Recombinant norovirus capsid was employed as target particles in experiments due to safety concerns. First, we showed virus capturing by DEP using fluorescent labeled norovirus capsid. Then, DEPIM of the capsid was carried out. As the result, DEPIM detected 2.5 ng/ml of the norovirus capsid in 300 sec. This implies that DEPIM has comparable sensitivity but shorter detection time than immunochromatography. .
44. Michihiko Nakano, Hiromichi Kasahara, Zhenhao Ding, Junya Suehiro, Sensitive and quantitative DNA detection by beads-based dielectrophoretic impedance measurement, Proceedings of IEEE Sensors 2015, 10.1109/ICSENS.2015.7370216, 2015.11.
45. R. Nakane, H. Kojima, J. Suehiro, H. Okubo, N. Hayakawa, Time Transition of Conductivity Distribution in Air by DC Partial Discharge for Air-solid Composite Insulation Systems, Proceedings of Conference on Electrical Insulation and Dielectric Phenomena, CEIDP, 10.1109/CEIDP49254.2020.9437492, 55-58, Article number 9437492, 2020.10, Toward the development of HVDC power apparatus, we investigate the charging process on solid insulator in terms of the time transition of conductivity distribution in air for air-solid composite insulation system from DC-on to DC steady-state. By using needle-air-PMMA-plane electrode configuration, we measure the time evolution of surface potential on PMMA due to partial discharge at the needle tip under negative DC voltage. We compare the measured surface potential distribution with the simulation result considering the charge behavior in air. Especially, a novel simulation model considering the charge supply due to DC partial discharge is built. As a result, in air-solid composite insulation system under negative DC application, the time transition of conductivity distribution in air corresponding to the charge accumulation is evaluated quantitatively..
46. Nisarut Phansiri, Daichi Maenosono, Masafumi Inaba, Michihiko Nakano, Junya Suehiro, Hidefumi Sato, A New Scheme for Residual CF4 Detection in Gas-Insulated Switchgear Using Plasma-induced CF4 Decomposition into CO2, Proceedings of 8th International Conference on Condition Monitoring and Diagnosis, 10.1109/CMD48350.2020.9287294, 54-57, 2020.12, This paper presents a new scheme for the detection of residual carbon tetrafluoride (CF 4 ) gas in gas-insulated switchgear (GIS) for its diagnosis. For the diagnosis of GIS, the decomposition gas species including CF 4 generated by partial discharges or breakdown are analyzed. Accumulation of the gas species indicates the history of the failure of GIS. However, most of the gas species are removed by an absorbent placed in a GIS vessel. The only CF 4 stays in GIS vessel for the long term. In this study, it is aimed to develop an easy and rapid CF 4 detection method. Because direct detection of CF 4 is difficult, an indirect detection method of CF 4 is proposed, in which CF 4 is processed by non-thermal plasma (NTP). In this paper, the conversion of CF 4 using dielectric barrier discharge (DBD) was examined. The infrared absorption band among SF 6 , CF 4 , and CO 2 was observed by Fourier transform infrared (FT-IR) spectroscopy. The amount of CO 2 generated in the case of CF 4 (10,000 ppm) and O 2 (10,000 ppm) diluted in Ar or SF 6 was analyzed. In the case of Ar dilution, CO 2 gradually increased with increasing time of DBD application by using a compact CO 2 NDIR sensor. In the case of SF 6 dilution, CO 2 , CO, O 2 , and SO 2 were detected by using a portable gas analyzer. The latter case showed a higher CO 2 generation rate of 400 ppm/hr, whereas the other showed 50 ppm/hr. In addition, a zeolite-filled column was installed for removing SO 2 from the processed gas..
47. Y. Khan, K. Sakai, S. Okabe, J. Suehiro, M. Hara, Importance of the Consideration of Electrical Gradient Force in the Deactivation of Free Conducting Particle under DC Voltage, Proc. of the IEEE/PES Transmission and Distribution Conf, 904-908, pp.904-908, 2002.10.
48. K. Sakai, D. L. Abella, J. Suehiro, M. Hara, Lateral Motion of Wire Particles toward Decreasing Electrode Gap Regions in Atmospheric Air, Proc. of the 6th Int. Conf. on Properties and Applications of Dielectric Materials, 817-820, pp.817-820, 2000.06.
49. S. Tsuru, M. Nakamura, K. Funaki, M. Iwakuma, J. Suehiro, M. Hara, Partial Discharge Characteristics in Artificial Air-Filled Voids Immersed in Liquid Nitrogen, Proc. of the 5th ICPADM, 228-231, pp.228-231, 1997.05.
50. H. K. Lee, J. Suehiro, M. H. So, M. Hara, D. C. Lee, Measurement of Excellent Condition to RLC Parameter for Electrical Sterilization on Escherichia coli, Proc. of the 5th ICPADM, pp.1136-1139, 1997.05.
51. K. Imasaka, Y. Kawauchi, K. Kawazoe, J. Suehiro, M. Hara, Numerical and Experimental Study of Behavior of Gas-Puff Z-Pinch Plasma Produced by Indutive Pulsed Power Generator, Proc. of the 15th Int. Conf. on High-Power Particle Beams, pp.printing, 1998.06.
52. K. Sakai, Y. Khan, Q. Zhang, J. Suehiro, M. Hara, Importance of the Consideration of Electrical Gradient Force Acting on Foreign Conducting Particle in the Insulation Design of GIS, Proc. of the 14th Conf. of the Electric Power Supply Industry, pp.7-12, 2002.11.
53. M. Hara, T. Kurihara, S. Kozuru, J. Suehiro, N. Hayashi, Estimation of partial Discharge Characteristics in Gases around Triple Junction, Proc. of the 14th Conf. of the Electric Power Supply Industry, pp.19-24, 2002.11.
54. Y. Khan, K. Sakai, E. Lee, J. Suehiro, M. Hara, A Basic Study of Deactivation Methods of Free Conducting Particles around Spacers between Non-parallel Plane Electrodes under DC Voltage, Proc. of the 14th Conf. of the Electric Power Supply Industry, pp.13-18, 2002.11.
55. H. K. Lee, J. Suehiro, M. H. So, M. Hara, D. C. Lee, Electrical Sterlization of Escherichia coli by HV Impulse and Effect of Voltage Waveforms, Proc. of Korea-Japan Sympo. on Electrical Discharge and High Voltage Engineering, pp.59-62, 1996.05.
56. K. Imasaka, S. Hara, H. Tokutomi, T. Akine, I. Nakamura, J. Suehiro, M. Hara, Compact Pulsed Power Generator and its Applications to Electrical Insulation Test, Proc. of Korea-Japan Sympo. on Electrical Discharge and High Voltage Engineering, pp.245-249, 1996.05.
57. S. Ohtsuka, H. Ohtsubo, T. Nakamura, D. Tsuji, J. Suehiro, M. Hara, Feasibility Study on a Mechanical Persistent Current Switch in SMES, Proc. of Int. Conf. on Electrical Engineering, pp.102-105, 1997.07.
58. R. Hamada, D. Noutomi, J. Suehiro, R. Yatsunami, M. Hara, Selective Detection of Viable and Non-viable Bacteria by Using Dielectrophoretic Impedance Measurement Method, Proc. of Int. Conf. on Electrical Engineering 2000, pp.1081-1084, 2000.07.
59. K. Imasaka, S. Hara, Y. Kawauchi, K. Kawazoe, J. Suehiro, M. Hara, Soft X-ray Emission from the Gas-puff Z-pinch Plasma Produced by an Inductive Pulsed Power Generator, Proc. of IEEE Int. Conf. on Pulsed Power, 845-850, pp.p1-59, 1997.06.
60. M. Miyama, T. Takahashi, K. Ohno, J. Suehiro, M. Hara, Size Effects and Breakdown Mechanism in Superfluid Helium, Proc. of 8th ACED, pp.203-1-203-4, 1996.10.
61. K. Imasaka, S. Hara, Y. Kawauchi, J. Suehiro, M. Hara, Gas-puff Z-pinch driven by a Fast Bank, Proc. of 8th ACED, pp.406-1-406-4, 1996.10.
62. S. Ohtsuka, H. Ohtsubo, T. Nakamura, J. Suehiro, M. Hara, Contact Resistance Characteristics of Mechanical Switch Made of NbTi, Proc. of 8th ACED, pp.711-1-711-4, 1996.10.
63. K. Imasaka, K. Takahashi, J. Suehiro, M. Hara, Polarity Effect on the Behavior of Gas-Puff Z-Pinch Plasma Produced by IPP System, Proc. of 28th IEEE Int. Conf. on Plasma Science and 13th IEEE Int. Pulsed Power Conf., 757-760, pp., 2001.06.
64. T. Kurihara, T. Nishioka, J. Suehiro, N. Hayashi, M. Hara, Experimental Study of PD Characteristics around a Triple Junction in Atmospheric Air, Proc. of 2002 Joint Conf. of ACED and K-J Sympo. on ED and HVE, pp.495-498, 2002.11.
65. G. Zhou, M. Imamura, J. Suehiro, M. Hara, Elimination of Fine particles Suspended in Liquid Using Dielectrophoresis, Proc. of 2002 Joint Conf. of ACED and K-J Sympo. on ED and HVE, pp.27-30, 2002.11.
66. Y. Khan, A. Oda, Q. Zhang, J. Suehiro, M. Hara, S. Okabe, Effect of Voltage Wavwform on Particle-triggered Pre-breakdown Phenomena in Diverging Air Gap with Simple Shaped Spacer, Proc. of 2002 Joint Conf. of ACED and K-J Sympo. on ED and HVE, pp.366-369, 2002.11.
67. T. Kurihara, S. Kozuru, J. Suehiro, M. Hara, H. Okamoto, Partial Discharge Inception in an Air-filled Void at Cryogenic Temperatures under Superimposed Sinusoidal Voltage, Proc. of 2001 Japan-Korea Joint Sympo. on Electrical Discharge and High Voltage Engineering, pp.25-28, 2001.11.
68. M. Hara, T. Kurihara, S. Kozuru, J. Suehiro, N. Hayashi, PD Onset Characteristics around a Triple Junction in Atmospheric Air at Room Temperature, Proc. of 2001 Japan-Korea Joint Sympo. on Electrical Discharge and High Voltage Engineering, pp.57-60, 2001.11.
69. K. Takahashi, K. Imasaka, J. Suehiro, M. Hara, Effects of the Voltage Polarity on the Gas-Puff Z-Pinch Characteristics in an IPP System, Proc. of 2001 Japan-Korea Joint Sympo. on Electrical Discharge and High Voltage Engineering, pp.273-276, 2001.11.
70. K. Sakai, Q. Zhang, Y. Khan, E. Lee, A. Oda, J. Suehiro, M. Hara, Dependence of Particle-Triggered Breakdown Voltage on N$_{2}$ and SF$_{6}$ Gas Pressure in DC Field between Non-Parallel Plane Electrodes, Proc. of 2001 Japan-Korea Joint Sympo. on Electrical Discharge and High Voltage Engineering, pp.269-272, 2001.11.
71. Y. Khan, E. Lee, A. Oda, K. Sakai, Q. Zhang, J. Suehiro, M. Hara, Characteristics of Corona and Surface Flashover Triggered by Free Conducting Particle around Simple Shaped Spacer under DC Voltage in Atmospheric Air, Proc. of 2001 Japan-Korea Joint Sympo. on Electrical Discharge and High Voltage Engineering, pp.101-104, 2001.11.
72. M. Hara, T. Kurihara, S. Kozuru, J. Suehiro, N. Hayashi, New Estimation Method of Partial Discharge Characteristics in Gas around a Triple Junction, Proc. of 2000 Korea-Japan Joint Sympo. on Electrical Discharge and High Voltage Engineering, pp.504-1 - 504-4, 2000.10.
73. K. Sakai, E. Lee, Y. Khan, J. Suehiro, M. Hara, Effect of Spacers on Free Conducting Particle Motion within Diverging Air Gap, Proc. of 2000 Korea-Japan Joint Sympo. on Electrical Discharge and High Voltage Engineering, pp.601-1 - 601-4, 2000.10.
74. K. Sakai, D. L. Abella, J. Suehiro, M. Hara, Mode of Free-Conducting Particle Motion and Particle-Triggered Breakdown Mechanism in Non-uniform Field Gaps, Proc. of 2000 IEEE Conference on Electrical Insulation and Dielectric Phenomena, 389-392, pp.389-392, 2000.10.
75. Wei Sun and Usama Khaled and Hironari Tomita and Kiminobu Imasaka and Junya Suehiro, Effects of ozone generated by dielectric barrier discharge on water-solubility of single-walled carbon nanotubes
author="Wei Sun and Usama Khaled and Hironari Tomita and Kiminobu Imasaka and Junya Suehiro",
booktitle="Proc. of 19th Int. Sympo. on Plasma Chemistry",
pages="P1.8.51",
month="7",
year="2009", Proc. of 19th Int. Sympo. on Plasma Chemistry, P1.8.51, 2009.07.
76. Wei Sun and Usama Khaled and Hironari Tomita and Kiminobu Imasaka and Junya Suehiro, Effects of ozone generated by dielectric barrier discharge on water-solubility of single-walled carbon nanotubes, Proc. of 19th Int. Sympo. on Plasma Chemistry, P1.8.51, 2009.07.
77. Kiminobu Imasaka and Usama Khaled and Wei Sun and Junya Suehiro, pH dependence of water-solubility of single-walled carbon nanotubes treated by microplasma in aqueous solution, Proc. of 19th Int. Sympo. on Plasma Chemistry, P2.15.08, 2009.07.
78. S. Tsuru, T. Kurihara, J. Suehiro, M. Hara, PD Characteristics in Air-Filled Void at Room Temperature under the Condition of Simulated Inverter Surges, Proc. of 1999 Japan-Korea Joint Sympo. on Electrical Discharge and High Voltage Engineering, pp.208-211, 1999.10.
79. D. L. Abella, K. Sakai, P. Attaviriyanupap, J. Suehiro, M. Hara, Free Conducting Particle Charging and Behavior in the Gap between Non-Parallel Bare and Coated Electrodes, Proc. of 1999 Japan-Korea Joint Sympo. on Electrical Discharge and High Voltage Engineering, pp.45-48, 1999.10.
80. H. K. Lee, J. Suehiro, M. Hara, M. H. So, D. C. Lee, Effect of Sterilization of Soya by HV Impulse Waveform, Proc. of 1999 Japan-Korea Joint Sympo. on Electrical Discharge and High Voltage Engineering, pp.204-207, 1999.10.
81. K. Sakai, D. L. Abella, P. Attaviriyanupap, J. Suehiro, M. Hara, Breakdown Triggered by Migration of Free Conducting Particles from Low to High Electric Field Regions, Proc. of 1999 Japan-Korea Joint Sympo. on Electrical Discharge and High Voltage Engineering, pp.239-242, 1999.10.
82. K. Imasaka, T. Masaki, J. Suehiro, M. Hara, Behavior of the Gas-Puff Z-Pinch Plasma Produced by Inductive Pulsed Power Generator and its Characteristics, Proc. of 1999 Japan-Korea Joint Sympo. on Electrical Discharge and High Voltage Engineering, pp.200-203, 1999.10.
83. B. Y. Seok, H. Komatsu, M. Kushinaga, J. Suehiro, M. Hara, A Study of PBD Phenomena Triggered by Induced Bubble in the Simulated Electrode System of Superconducting Coils, Proc. of 1999 Japan-Korea Joint Sympo. on Electrical Discharge and High Voltage Engineering, pp.301-304, 1999.10.
84. M. Hara, J. Suehiro, H. Maeda, H. Nakashima, DC Pre-Breakdown Phenomena and Breakdown Characteristics in the Presence of Metallic Particle in Liquid Nitrogen, Proc. of 1999 IEEE 13th Int. Conf. on Dielectric Liquids, pp.457-461, 1999.07.
85. T. Mine, S. Tsuru, J. Suehiro, M. Hara, PD Degradation of Solid Insulators with an Artificial Air-Filled Voids at Room and Liquid Nitrogen Temperatures, Proc. of 1998 Korea-Japan Joint Symp. on ED and HVE, pp.65-68, 1998.10.
86. H. K. Lee, J. Suehiro, M. Hara, D. C. Lee, Measurement of optima HV impulse Waveshape for electrical sterlization of Escherichia coli, Proc. of 1998 Korea-Japan Joint Symp. on ED and HVE, pp.179-182, 1998.10.
87. K. Kawazoe, T. Masaki, K. Imasaka, J. Suehiro, M. Hara, Gap Length Dependence of Soft X-ray Emission from Gas-Puff Z-Pinch Plasma Produced by Inductive Pulsed Power Generator, Proc. of 1998 Korea-Japan Joint Symp. on ED and HVE, pp.175-178, 1998.10.
88. M. Hisao, N. Hideki, J. Suehiro, M. Hara, D.c.Pre-Breakdown Phenomena and Breakdown Voltage Characteristics of a Parallel Plane Gap in the Presence of Free Conducting Particles in Liquid Nitrogen, Proc. of 1998 Korea-Japan Joint Symp. on ED and HVE, pp.111-114, 1998.10.
89. S. Tsuru, M. Nakamura, T. Mine, K. Sakai, J. Suehiro, M. Hara, Partial Discharge Mode and Mechanism in Artificial Air-Filled Voids at Room Temperature, Proc. of 1997 Japan-Korea Joint Sympo. on ED and HVE, pp.39-42, 1997.10.
90. H. K. Lee, M. H. So, J. Suehiro, M. Hara, D. C. Lee, Optimal RLC Condition to Electrical Sterilization of Escherichia coli by HV Impulse, Proc. of 1997 Japan-Korea Joint Sympo. on ED and HVE, pp.121-124, 1997.10.
91. S. Ohtsuka, T. Nakamura, D. Tsuji, J. Suehiro, M. Hara, Arc Discharge Characteristics Generated by Opening a NbTi Mechanical PCS, Proc. of 1997 Japan-Korea Joint Sympo. on ED and HVE, pp.141-144, 1997.10.
92. Y. Kawauchi, K. Kawazoe, K. Imasaka, J. Suehiro, M. Hara, Analysis of Pinching Process of Gas-Puff Z-Pinch Plasma Produced by Inductive Pulsed Power Generator, Proc. of 1997 Japan-Korea Joint Sympo. on ED and HVE, pp.129-132, 1997.10.
93. K. Funaki, M. Iwakuma, M. Takeo, K. Yamafuji, J. Suehiro, M. Hara, M. Konno, Y. Kasagawa, K. Okubo, Y. Yasukawa, S. Nose, M. Ueyama, K. Hayashi, K. Sato, Design and Construction of a 500 kVA-Class Oxide Superconducting Power Transformer Cooled by Liquid Nitrogen, Proc. of 16th Int. Cryo. Eng. Conf. / Int. Cryo. Mat. Conf., pp.1009-1012, 1997.03.
94. S. Ohtsuka, T. Nakamura, D. Tsuji, J. Suehiro, M. Hara, Quench Current Characteristics of Parallel Mechanical PCS, Proc. of 15th Int. Conf. on Magnet Technology, pp.PB-13, 1997.10.
95. S. Ohtsuka, T. Nakamura, D. Tsuji, J. Suehiro, M. Hara, Quench Current Characteristics of Parallel Mechanical PCSs, Proc. of 15th Int. Conf. on Magnet Technology, pp.551-554, 1998.10.
96. M. Hara, H. Nakagawa, J. Suehiro, T. Shinohara, Electrical Breakdown Triggered by Free Conducting Spherical Particle in Saturated Liquid HeI and HeII under Uniform Dc Field, Proc. of 14th Int. Conf. on Dielectric Liquids, 10.1109/ICDL.2002.1022703, 99-102, pp.99-102, 2002.07.
97. Y. Khan, K. Sakai, E. Lee, J. Suehiro, M. Hara, Free-Conducting Spherical Particle Motion around Different Shaped Spacers under DC Voltage, Proc. of 12th Int. Sympo. on High Voltage Engineering, pp.294-297, 2001.08.
98. T. Kurihara, S. Kozuru, J. Suehiro, M. Hara, Effect of Superimposed Sinusoidal Voltage on Partial Discharge Characteristics in an Artificial Air-Filled Void, Proc. of 12th Int. Sympo. on High Voltage Engineering, pp.1035-1038, 2001.08.
99. K. Sakai, Y. Khan, E. Lee, J. Suehiro, M. Hara, Effect of Microdischarge Occurrences on Spherical Conducting Particle Motion between Non-Parallel Plane Electrodes, Proc. of 12th Int. Sympo. on High Voltage Engineering, pp.302-305, 2001.08.
100. J. Suehiro, K. Ohno, T. Takahashi, M. Miyama, M. Hara, Statistical Characteristics of Electrical Breakdown in Saturated Superfluid Helium, Proc. of 12th ICDL, 320-323, pp.320-323, 1996.07.
101. S. Ohtsuka, D. Tsuji, K. Tsutsumi, J. Suehiro, M. Hara, Effect of Quench Time Lag on the Succeeding Quench in the Parallel Mechanical PCS Circuit, Proc. of 11th Int. Sympo. on Superconductivity, pp.SAP-28, 1998.11.
102. S. Tsuru, T. Mine, J. Suehiro, M. Hara, Partial Discharge Degradation of Solid Insulators with an Air-Filled Void at Liquid Nitrogen Temperature, Proc. of 11th Int. Sympo. on High-Voltage Engineering, pp.369-372, 1999.08.
103. J. Suehiro, K. Tsutsumi, D. Tsuji, S. Ohtsuka, K. Imasaka, M. Hara, Fast Quench of Superconducting Wire by Pulsed Current and its Application to Pulsed Power Generation, Proc. of 11th Int. Sympo. on High-Voltage Engineering, pp.390-393, 1999.08.
104. B. Y. Seok, H. Komatsu, J. Suehiro, M. Hara, Bubble Behavior and PBD Characteristics in the Simulated Electrode System of High Temperature Superconducting Coils, Proc. of 11th Int. Sympo. on High-Voltage Engineering, pp.372-375, 1999.08.
105. K. Imasaka, T. Masaki, K. Kawazoe, J. Suehiro, M. Hara, Spatial Distribution of Hot Spots Produced by Gas-Puff Z-Pinch Using Inductive Pulsed Power Generator, Proc. of 10th Asian Conf. on Electrical Discharge, pp.227-230, 2000.11.
106. T. Kurihara, S. Tsuru, J. Suehiro, M. Hara, Simulation of Partial Discharge in an Artificial Air-Filled Void under Superimposed Sinusoidal Voltages, Proc. of 10th Asian Conf. on Electrical Discharge, pp.123-126, 2000.11.
107. J. Maruyama, F. Shimokawa, G. B. Zhou, J. Suehiro, M. Hara, AC Electrical Tree Initiation and Growth Characteristics in XLPE under UV Irradiation, Proc. of 10th Asian Conf. on Electrical Discharge, pp.127-130, 2000.11.
108. K. Funaki, M. Iwakuma, M. Takeo, K. Yamafuji, J. Suehiro, M. Hara, M. Konno, Y. Kasagawa, K. Ohkubo, Y. Yasukawa, S. Nose, M. Ueyama, K. Hayashi, K. Sato, Design and Construction of A 500kVA-Class Oxide Superconducting Power Transformer Cooled by Liquid Nitrogen, Proc. ICEC16/ICMC, pp.1009-1012, 1997.02.
109. J. Suehiro, N. Nakagawa, S. Hidaka, M. Ueda, K. Imasaka, M. Higashihata, T. Okada, M. Hara, Dielectrophoretic fabrication and characterization of ZnO nanowire-based UV photosensor, Nanotechnology, Vol.17, pp.2567?2573, 2006.05, [URL].
110. K. Imasaka, J. Suehiro, Y. Kanatake, Y. Kato, M. Hara, Preparation of water-soluble carbon nanotubes using pulsed streamer discharge in water, Nanotechnology, Vol.17, pp.3421-3427, 2006.07, [URL].
111. K. Imasaka, Y. Kato, J. Suehiro, Enhancement of microplasma-based water-solubilization of single-walled carbon nanotubes using gas bubbling in water, Nanotechnology, Vol.18, 335602 (7pp), 2007.08, [URL].
112. Kiminobu Imasaka, Yuki Kato, Junya Suehiro, Enhancement of microplasma-based water-solubilization of single-walled carbon nanotubes using gas bubbling in water, Nanotechnology, 10.1088/0957-4484/18/33/335602, 18, 33, 2007.08, The authors have previously proposed a novel technique for the preparation of water-soluble carbon nanotubes (CNTs) using microplasma generated by a pulsed streamer discharge in water. This paper describes an improvement in the method of the microplasma-based CNT solubilization process by the use of gas bubbling in water. Oxygen, argon and nitrogen were used as bubbling gas in order to clarify the effects of the gas species on the single-walled CNT (SWCNT) solubilization efficiency. Ultraviolet-visible absorption spectra of the SWCNT suspensions revealed that the SWCNT solubility was increased by more than two times by using gas bubbling together with microplasma treatment. No significant difference was observed among the three gas species tested. Fourier transform infrared (FTIR)spectroscopy and x-ray photoelectron spectroscopy (XPS) analysis showed that the number of -OH groups, introduced on the SWCNT surface by the microplasma treatment, was increased by gas bubbling. Optical emission measurements also showed that the number of highly oxidative oxygen and hydrogen radicals, which were generated by the microplasma, was also increased by gas bubbling. These results indicate that gas bubbling has positive effects on microplasma-based SWCNT solubilization as a result of enhanced radical formation and functionalization of the SWCNT surface..
113. Kiminobu Imasaka, Junya Suehiro, Yusuke Kanatake, Yuki Kato, Masanori Hara, Preparation of water-soluble carbon nanotubes using a pulsed streamer discharge in water, Nanotechnology, 10.1088/0957-4484/17/14/013, 17, 14, 3421-3427, 2006.07, A novel technique for the preparation of water-soluble carbon nanotubes was demonstrated using a pulsed streamer discharge generated in water. The technique involved chemical reactions between radicals generated by the pulsed streamer discharge and carbon nanotubes. The pulsed streamer-treated carbon nanotubes were homogeneously dispersed and well solubilized in water for a month or longer. The mechanism of solubilization of carbon nanotubes by the pulsed streamer discharge is discussed based on FTIR spectroscopy and optical emission spectra measurements. FTIR spectroscopy revealed that -OH groups, which are known to impart a hydrophilic nature to carbon material, were introduced on the carbon nanotube surface. Optical emission spectra from the pulsed streamer plasma showed that highly oxidative O* and H* radicals were generated in water. These results suggest that the functionalization of the carbon nanotube surface by -OH group can be attributed to the O* and H* radicals. An advantage of the proposed method is that there is no need for any chemical agents or additives for solubilization. Chemical agents for solubilization are generated from the water itself by the electrochemical reactions induced by the pulsed streamer discharge..
114. Junya Suehiro, Nobutaka Nakagawa, Shin Ichiro Hidaka, Makoto Ueda, Kiminobu Imasaka, Mitsuhiro Higashihata, Tatsuo Okada, Masanori Hara, Dielectrophoretic fabrication and characterization of a ZnO nanowire-based UV photosensor, Nanotechnology, 10.1088/0957-4484/17/10/021, 17, 10, 2567-2573, 2006.05, Wide-gap semiconductors with nanostructures such as nanoparticles, nanorods, nanowires are promising as a new type of UV photosensor. Recently, ZnO (zinc oxide) nanowires have been extensively investigated for electronic and optoelectronic device applications. ZnO nanowires are expected to have good UV response due to their large surface area to volume ratio, and they might enhance the performance of UV photosensors. In this paper, a new fabrication method of a UV photosensor based on ZnO nanowires using dielectrophoresis is demonstrated. Dielectrophoresis (DEP) is the electrokinetic motion of dielectrically polarized materials in non-uniform electric fields. ZnO nanowires, which were synthesized by nanoparticle-assisted pulsed-laser deposition (NAPLD) and suspended in ethanol, were trapped in the microelectrode gap where the electric field became higher. The trapped ZnO nanowires were aligned along the electric field line and bridged the electrode gap. Under UV irradiation, the conductance of the DEP-trapped ZnO nanowires exponentially increased with a time constant of a few minutes. The slow UV response of ZnO nanowires was similar to that observed with ZnO thin films and might be attributed to adsorption and photodesorption of ambient gas molecules such as O2 or H 2O. At higher UV intensity, the conductance response became larger. The DEP-fabricated ZnO nanowire UV photosensor could detect UV light down to 10nWcm-2 intensity, indicating a higher UV sensitivity than ZnO thin films or ZnO nanowires assembled by other methods..
115. J. Suehiro, N. Ikeda, A. Ohtsubo and K. Imasaka, Fabrication of bio/nano interfaces between biological cells and carbon nanotubes using dielectrophoresis, Microfluidics and Nanofluidics, Volume 5, Number 6, Pages 741-747, 2008.12, [URL].
116. Michihiko Nakano, Zhenhao Ding, Junya Suehiro, Frequency-dependent conductance change of dielectrhophoretic-trapped DNA-labeled microbeads and its application in DNA size determinations, Microfluidics and Nanofluidics, 10.1007/s10404-018-2051-7, 22, 26, 2018.03.
117. M. Nakano, Z. Ding, J. Suehiro, Frequency-dependent conductance change of dielectrhophoretic-trapped DNA-labeled microbeads and its application in DNA size determinations, Microfluidics and Nanofluidics, 10.1007/s10404-018-2051-7, 22, 26, 2018.03.
118. Junya Suehiro, Naoki Ikeda, Akio Ohtsubo, Kiminobu Imasaka, Fabrication of bio/nano interfaces between biological cells and carbon nanotubes using dielectrophoresis, Microfluidics and Nanofluidics, 10.1007/s10404-008-0276-6, 5, 6, 741-747, 2008.03, The authors have previously demonstrated the manipulation of bacteria and carbon nanotubes (CNTs) using dielectrophoresis (DEP) and its application for various types of biological and chemical sensors. This paper demonstrates simultaneous DEP handling of bacteria and CNTs, which are mixed and suspended in water. The CNTs were solubilized in water using microplasma-based treatment. When a microelectrode was energized with an ac voltage in the suspension of Escherichia coli (E. coli) cells and multi-walled CNTs (MWCNTs), both of them were simultaneously trapped in the microelectrode gap. Scanning electron microscopy (SEM) images revealed that E. coli cells were trapped on the surface or the tip of MWCNTs, where the electric field strength was intensified due to high aspect ratio of MWCNTs. As a result, bio/nano interfaces between bacteria and MWCNTs were automatically formed in a self-assembly manner. A potential application of the DEP-fabricated bio/nano interfaces is a drug delivery system (DDS), which is realized by transporting drug molecules from CNTs to cells across the cell membrane, which can be electroporated by the local high electric field formed on the CNT surface..
119. J. Suehiro, H. Fujinobu, M. Hara, Reversible electrical breakdown of bilayer lipid membranes with a ramped voltage and the quantitative analysis based on a transient aqueous pore model, Memoirs - Kyushu University, Faculty of Engineering, 54, 4, 263-277, 1994.01, Reversible electrical breakdown of bilayer lipid membranes is observed by using the voltage-clamp method with ramped voltage waveforms. It is shown experimentally that the critical transmembrane voltage at which membrane conductance drastically increases depends on the ramp rate. The pore growing process is discussed quantitatively based on a transient pore model of the breakdown phenomena. The comparison between the experimental results and theoretical prediction shows that the model can describe the time course of the pore development and resultant increase in the membrane conductance. Effects of the voltage rising rate on the electroporation and the membrane conductance increase are discussed by using the transient pore model. (from Authors).
120. J. Suehiro, K. Imasaka, Y. Ohshiro, G. Zhou, M. Hara, N. Sano, Production of carbon nanoparticles using pulsed arc discharge triggered by dielectric breakdown in water
, Jpn. J. Appl. Phys., 10.1143/JJAP.42.L1483, 42, 12A, L1483-L1485, Vol.42, pp.L1483-L1485, 2003.12, [URL].
121. K. Imasaka, Y. Kato, U. Khaled and J. Suehiro, Effects of pH on water-solubilization of carbon nanotube using microplasma in aqueous solution, Jpn. J. Appl. Phys., Volume 48, No.6, Paper No.065004, 2009.06, [URL].
122. W. Sun, U. Khaled, H. Tomita, Z. Li, K. Imasaka and J. Suehiro, Solubilization of single-walled carbon nanotubes using ozone generated by dielectric barrier discharge, Jpn. J. Appl. Phys., 10.1143/JJAP.49.055002, 49, article No. 055002, 2010.05, [URL].
123. W. Sun, U. Khaled, H. Tomita, Z. Li, K. Imasaka and J. Suehiro, Solubilization of single-walled carbon nanotubes using ozone generated by dielectric barrier discharge, Jpn. J. Appl. Phys., 10.1143/JJAP.49.055002, 49, 055002, 2010.05, [URL].
124. W. Sun, U. Khaled, H. Tomita, Z. Li, K. Imasaka and J. Suehiro, Solubilization of single-walled carbon nanotubes using ozone generated by dielectric barrier discharge, Jpn. J. Appl. Phys., 10.1143/JJAP.49.055002, 49, 055002, 2010.05, [URL].
125. K. Imasaka, W. Sun, H. Tomita, Y. Kato, U. Khaled and J. Suehiro, Enhancement and stabilization of pulsed streamer discharge in water by adding carbon nanotubes, Jpn. J. Appl. Phys., 10.1143/JJAP.49.086203, 49, 086203, 2010.08, [URL].
126. M. Nakano, M. Fujioka, K. Mai, H. Watanabe, Y. Martin and J. Suehiro, Dielectrophoretic Assembly of Semiconducting Carbon Nanotubes Separated and Enriched by Spin Column Chromatography and Its Application to Gas Sensing, Jpn. J. Appl. Phys., 10.1143/JJAP.51.045102, 51, 045102 (6 pages), 2012.03, [URL].
127. U. Khaled, K. Imasaka and J. Suehiro, Enhancement of microplasma generated in water by adding carbon nanotubes, Journal of Plasma and Fusion Research Series, Volume 8, Pages 603-607, 2009.10, [URL].
128. R. Hamada, H. Takayama, Y. Shonishi, T. Hisajima, L. Mao, M. Nakano and J. Suehiro, Improvement of dielectrophoretic impedance measurement method by bacterial concentration utilizing negative dielectrophoresis, Journal of Physics: Conference Series, 307, 1, Art. no. 012031, 2011.12.
129. J. Suehiro, G. Zhou, M .Hara, Fabrication of a carbon nanotube-based gas sensor using dielectrophoresis and its application for ammonia detection by impedance spectroscopy, Journal of Physics D: Applied Physics, 10.1088/0022-3727/36/21/L01, 36, 21, L109-L114, Vol.36, No.21, pp.L109-L114, 2003.11, [URL].
130. W. Sun, H. Tomita, S. Hasegawa, Y. Kitamura, M. Nakano, J. Suehiro, An array of interdigitated parallel wire electrodes for preparing a large-scale nanocomposite film with aligned carbon nanotubes, Journal of Physics D: Applied Physics, 10.1088/0022-3727/44/44/445303, 44, 44, 2011.11, Application of high electric field is effective for the alignment of carbon nanotube (CNT) in a nanocomposite film. The conventionally used single pair of parallel plate electrodes is not applicable to large-sized nanocomposite fabrication due to limited output voltage of the high-voltage source. We have proposed an array of parallel wire electrodes to address this issue. The composite material was spread over a thin dielectric layer placed on the wire electrodes. The high electric field region can be extended over a wider area just by increasing the number of electrode pairs. Discrete electric field distribution bordered by the wire electrodes was avoided by linearly oscillated motion of the composite film. A CNT/epoxy resin composite film with a size of 15 cm × 15 cm was successfully fabricated..
131. Junya Suehiro, Ryuichi Yatsunami, Ryo Hamada, Masanori Hara, Quantitative estimation of biological cell concentration suspended in aqueous medium by using dielectrophoretic impedance measurement method, Journal of Physics D: Applied Physics, 10.1088/0022-3727/32/21/316, 32, 21, 2814-2820, 1999.11, We describe a new technique that realizes the quantitative estimation of the biological cell concentration in an aqueous medium. The proposed dielectrophoretic impedance measurement method utilizes the positive dielectrophoretic force to capture suspended biological particles onto an interdigitated micro-electrode array in pearl-chain formation. Higher cell concentration results in faster development of the pearl chains, which are electrically connected in parallel within the electrode gap to increase the conductance and capacitance between the electrodes. By monitoring temporal variation of the electrical impedance, it is possible to quantitatively evaluate the cell population according to a theoretical model of the cell collection process. It has been demonstrated that a suspension liquid of Escherichia coli could be accurately assayed in about 10 min at 105 cm-3 concentration..
132. J. Suehiro, K. Yamamoto, M. Hara, Mobilities of charge carriers generated by corona discharge in low temperature helium gas, Journal of Physics D: Applied Physics, 10.1088/0022-3727/24/8/019, 24, 8, 1360-1366, 1991.08, This paper describes a new method of apparent mobility measurement in a space charge flow field generated by corona discharge. The positive helium ion mobility at cryogenic temperatures down to 4.2 K is newly measured and the results obtained agree well with theoretical values for the atomic helium ion He+. The mobility of negative charge carriers is also obtained at 4.3 K. The results suggest the transition from free electron to electronic bubble in dense helium gas and support the discharge mechanism of a negative pulse corona in which an electronic bubble has the same space charge effect as a negative ion in electronegative gas..
133. K. Minamida, J. Suehiro, T. Toshimitu, T. Kawamoto, Laser System for Dulling Work Roll by Q Switched Nd:YAG Laser, Journal of Laser Applications, 10.2351/1.4745240, 1, 4, 15-20, 1989.10, A new dulling system for the work rolls used to roughen the surface of cold rolled steel sheet has been developed. Such sheets are used in various products, such as outer panels of automobiles, and decorative outer plates of electric appliances. In this process, several pulsed laser beams generated by Q switched Nd:YAG lasers produce small craters with rims around them. This process includes a longitudinal scanning system within the laser processing head and a rotation system for the work roll; consequently, the surface of the dulled roll consists of innumerable small craters. The main features of the system consist of: (1) a special way of controlling RF power applied to the acousto optic modulator for the Q switching to change the peak power, pulse duration, and low level CW power to fit the dulling condition, (2) a method to combine two or more pulse beams to control the profile of dulling craters. Immediate advantages of this process are: (1) timesaving (very high repetition rate of pulses by Q switching), (2) stable operation (without a mechanical chopper which is usually used with a CO2 laser to make pulsed beam), and (3) cost saving. This newly developed system is effectively applied to the production of cold rolled steel sheets..
134. Junya Suehiro, Noriaki Sano, Guangbin Zhou, Hiroshi Imakiire, Kiminobu Imasaka, Masanori Hara, Application of dielectrophoresis to fabrication of carbon nanohorn gas sensor, Journal of Electrostatics, 10.1016/j.elstat.2005.11.001, 64, 6, 408-415, 2006.06, This paper describes an electrokinetic fabrication method for a gas sensor composed of single-wall carbon nanohorns (SWCNHs) using dielectrophoresis (DEP). The authors have previously demonstrated that DEP manipulation of carbon nanotubes (CNTs) can be applied to the fabrication of a CNT gas sensor. In the present study, we further explored the possibility of electrokinetic manipulation of SWCNHs. The latter have different structures and properties compared to CNTs. The SWCNHs were synthesized using the 'arc in water with gas injection' method. The SWCNH aggregates were dispersed in ethanol and trapped in an interdigitated microelectrode gap under the action of positive DEP. After the DEP process, the ethanol was evaporated and the microelectrode retaining the SWCNHs was exposed to nitrogen dioxide (NO2) or ammonia (NH3) gas while the electrode impedance was monitored. It was found that conductance of the DEP-fabricated SWCNH sensor increased or decreased upon exposure to ppm-levels of NO2 or NH3, respectively. These results were similar to those previously obtained for CNT gas sensors and suggest that the SWCNH aggregate behaves as a p-type semiconductor. The comparison reveals that intrinsic NO2 sensitivity of the SWCNHs is lower than that of single-wall CNTs (SWCNTs) but comparable with the intrinsic sensitivity of multiple-wall CNTs (MWCNTs)..
135. Junya Suehiro, Ryo Hamada, Daisuke Noutomi, Masanori Shutou, Masanori Hara, Selective detection of viable bacteria using dielectrophoretic impedance measurement method, Journal of Electrostatics, 10.1016/S0304-3886(02)00124-9, 57, 2, 157-168, 2003.02, This paper describes a selective detection technique of viable bacteria based on dielectrophoresis and electrical impedance measurements. The authors have previously proposed a detection technique of biological particles called dielectrophoretic impedance measurement (DEPIM) method using positive dielectrophoretic force to capture biological cells in suspension onto an interdigitated microelectrode array. By combining antigen-antibody reaction with the DEPIM, selective detection of a particular species of bacteria was demonstrated. In this present work, the authors demonstrated another selective DEPIM method utilizing cell viability dependency of dielectrophoretic force without introducing the antigen-antibody reaction. It was found that dielectrophoresis of heat-treated Escherichia coli showed strong dependency on viability when applied field frequency was as high as 1 MHz. As a result, viable bacteria could be exclusively collected by positive dielectrophoresis and selectively detected by the DEPIM technique from a suspension also containing heat-treated nonviable cells. On the other hand, nonviable bacteria obtained by UV irradiation showed little dielectrophoresis dependency on viability. According to a theoretical analysis of the dielectrophoretic force, it is suggested that heat treatment alters the dielectric properties of treated cells. In particular, a decrease in cytoplasmic conductivity, which might be caused by heat-induced perforation of cell membrane, was expected to considerably affect dielectrophoresis characteristics. Proposed selective DEPIM method was also applied to evaluation of heat sterilization effect on a real time basis. It was experimentally proved that DEPIM could evaluate viable cell number variation with heat treatment time in a considerably shorter time than conventional microbiological method based on cell incubation..
136. Kiminobu Imasaka, Yuki Kato, Usama Khaled, Junya Suehiro, Effects of pH on water-solubilization of carbon nanotube using microplasma in aqueous solution, Japanese journal of applied physics, 10.1143/JJAP.48.065004, 48, 6, 2009.06, The authors have previously proposed a novel technique for the preparation of water-soluble carbon nanotubes (CNTs) using microplasma generated by a pulsed streamer discharge in water. This paper describes effects of pH values on water-solubility of single-walled CNT (SWCNT) treated by the microplasma. The SWCNT treated under basic conditions showed two times higher solubility compared to that treated under neutral condition, whereas the SWCNT solubility considerably decreased under acidic conditions. Based on optical emission measurements of microplasma showed that radical formation was not pH sensitive. Fourier transform infrared (FTIR) spectroscopy and Xray photoelectron spectroscopy (XPS) analysis showed that the microplasma treated SWCNT was functionalized with -COO- groups with little pH dependence. In contrary, clear pH dependence was observed for zeta potential of the microplasma-treated SWCNT. The lowest zeta potential was-46 mV, which was obtained with basic solution adjusted by NH3 (pH≈9). The SWCNT treated under basic conditions was more negatively charged due to suppressed protonation of -COO- groups. As a result, the electrostatic repulsion force between SWCNTs could overcome van der Waals force improving their solubility and dispersibility in water..
137. Masafumi Inaba, Shohei Hayashi, Henan Li, Mikoto Kamimura, Michihiko Nakano, Junya Suehiro, Dielectrophoretic properties of submicron diamond particles in sodium chloride aqueous solution, Japanese Journal of Applied Physics, 10.35848/1347-4065/ab7baf, 59, 4, 2020.04, Dielectrophoretic (DEP) manipulation of a diamond particle has potential application in the detection of DNA or other bio-molecules. We investigate the fundamental DEP and surface properties of submicron diamond particles. Diamond particles were dispersed in a NaCl solution and dropped on a castle-walled electrode. An AC electric field was applied to determine the DEP crossover frequency as a function of the solution conductivity. The surface conductance of the diamond particles was then evaluated from the parametrical fitting of the crossover frequencies. The diamond surface layer was shown to exhibit a rather high conductance, although bulk diamond is insulative..
138. Michihiko Nakano, Zhenhao Ding, Junya Suehiro, Dielectrophoresis and dielectrophoretic impedance detection of adenovirus and rotavirus, Japanese Journal of Applied Physics, 10.7567/JJAP.55.017001, 55, 1, 2016.01, The aim of this study is the electrical detection of pathogenic viruses, namely, adenovirus and rotavirus, using dielectrophoretic impedance measurement (DEPIM). DEPIM consists of two simultaneous processes: dielectrophoretic trapping of the target and measurement of the impedance change and increase in conductance with the number of trapped targets. This is the first study of applying DEPIM, which was originally developed to detect bacteria suspended in aqueous solutions, to virus detection. The dielectric properties of the viruses were also investigated in terms of their dielectrophoretic behavior. Although their estimated dielectric properties were different from those of bacteria, the trapped viruses increased the conductance of the microelectrode in a manner similar to that in bacteria detection. We demonstrated the electrical detection of viruses within 60 s at concentrations as low as 70 ng/ml for adenovirus and 50 ng/ml for rotavirus..
139. Junya Suehiro, Kiminobu Imasaka, Yutaka Ohshiro, Guangbin Zhou, Masanori Hara, Noriaki Sano, Production of carbon nanoparticles using pulsed arc discharge triggered by dielectric breakdown in water, Japanese Journal of Applied Physics, Part 2: Letters, 10.1143/jjap.42.l1483, 42, 12 A, L1483-L1485, 2003.12, This paper describes a simple production method for carbon nanoparticles by pulsed arc discharge in water, which is triggered by the electrical breakdown of water between graphite electrodes. High-resolution transmission electron microscopy (HRTEM) observation revealed that the main products obtained by the proposed method were onion-like nanoparticles; while carbon nanotubes were not formed. The carbon nanoonions uniformly dispersed in water forming micron-sized aggregates. The effects of the arc discharge mode (dc or pulse) on the nanoparticle formation mechanism are discussed..
140. Michihiko Nakano, Junya Suehiro, Time-resolved imaging of the electrical breakdown of planar microelectrode gap in atmospheric air, JOURNAL OF ELECTROSTATICS, 10.1016/j.elstat.2017.04.010, 87, 167-172, 2017.06.
141. J. Suehiro, R. Yatsunami, R. hamada, M. Hara, Quantitive Estimation of Biological Cell Concentration Suspended in Aqueous Medium by Using Dielectrophoretic Impedance Measurement Method, J.Phys. D: Appl. Phys., Vol.32, pp.2814-2820, 1999.11, [URL].
142. J. Suehiro, P. Pethig, The dielectrophoretic movement and positioning of a biological cell using a three-dimensional grid electrode system, J. Phys. D:Appl. Phys., 10.1088/0022-3727/31/22/019, 31, 22, 3298-3305, Vol.31, No.22, pp.3298-3305, 1998.06, [URL].
143. W. Sun, H. Tomita, S. Hasegawa, Y. Kitamura, M. Nakano and J. Suehiro, An array of interdigitated parallel wire electrodes for preparing a large-scale nanocomposite film with aligned carbon nanotubes, J. Phys. D: Appl. Phys., 44, 9, Article number 445303, 2011.11.
144. J. Suehiro , R. Hamada, D. Noutomi, M. Shutou, M. Hara, Selective etection of viable bacteria using dielectrophoretic impedance measurement method, J. Electrostatics, Vol.57, No.2, pp.157-168, 2003.02, [URL].
145. J. Suehiro, D. Noutomi, M. Shutou, M. Hara, Selective detection of specific bacteria using dielectrophoretic impedance measurement method combined with antigen-antibody reaction, J. Electrostatics, 10.1016/S0304-3886(03)00062-7, 58, 3-4, 229-246, Vol.58, No.3/4, pp.229-246, 2003.06, [URL].
146. J. Suehiro, N. Sano, G. Zhou, H. Imakiire, K. Imasaka, M. Hara, Application of dielectrophoresis to fabrication of carbon nanohorn gas sensor, J. Electrostatics, Vol.64, pp.408-415, 2006.06, [URL].
147. Nisarut Phansiri1, Xulin Liu, Kohei Miwa, Masafumi Inaba, Michihiko Nakano, Junya Suehiro, Hidefumi Sato, Indirect detection of residual CF4 in gas-insulated switchgear via conversion under dielectric barrier discharge, International Journal of Plasma Environmental Science and Technology, doi.org/10.34343/ijpest.2021.15.e02010, 15, 2, e02010-1-e02010 -11, 2021.08, [URL], In this paper, a new diagnosis method for SF6 gas-insulated switchgear (GIS) is proposed based on decomposition gas analysis. We focus on residual CF4 gas in GIS, which is a decomposition gas generated in GIS via partial or arc discharge. Unlike other decomposition gases, which can be removed by the gas absorbent, CF4 accumulates during in-service operation, enabling trend-based GIS condition monitoring. Because direct CF4 detection using commercially available gas sensors is difficult, we propose a novel indirect detection method in which CF4 is converted into CO and CO2 by a dielectric barrier discharge (DBD). A DBD-treated artificial gas mixture composed of CF4, O2, and SF6 was analyzed via Fourier transform infrared spectroscopy (FTIR). It was found that CO and CO2 are simultaneously generated when the CF4 gas concentration is higher than 100 ppm, which is close to the target CF4 concentration for GIS diagnosis. To demonstrate rapid, simple, and on-site diagnostic capabilities, a commercial electrochemical CO gas sensor was employed to detect DBD-converted CO gas. The CO concentration quantified by the calibrated gas sensor was almost identical to that obtained via FTIR. As the CF4-to-CO conversion rate is expected to improve with an optimum DBD reactor design, the proposed scheme could be applicable to GIS diagnosis..
148. Ryo Hamada, Junya Suehiro, Optimization of electric field frequency on dielectrophoretic impedance measurement method for oral bacteria detection, International Conference on Biomedical Electronics and Devices, BIODEVICES 2011 BIODEVICES 2011 - Proceedings of the International Conference on Biomedical Electronics and Devices, 125-129, 2011.07, A simple and rapid bacteria detection device for on-site evaluation of oral hygiene in hospitals and clinics was demonstrated. The developed device utilizes dielectrophoretic impedance measurement (DEPIM) method. We integrated a micro electrode chip on which bacteria were captured by dielectrophoresis (DEP), an AC voltage source to induce DEP force, and an impedance measurement circuit to a portable instrument that enables rapid and automated oral bacterial inspection in hospitals and clinics. Special considerations have been made on effects of high electrical conductivity of oral samples on DEP force and DEPIM results. It was shown experimentally and theoretically that using a higher electric field frequency for the DEP bacteria trap and the impedance measurement could realize DEPIM application to bacteria inspection from oral samples with higher conductivity. Based on these investigations, we optimized the frequency condition of the DEPIM suitable for inspecting an oral sample along with the design and development of a portable DEPIM apparatus for on-site inspection of oral bacteria..
149. J. Suehiro, N. Ikeda, A. Ohtsubo and K. Imasaka, Bacterial detection using a carbon nanotube gas sensor coupled with a microheater for ammonia synthesis by aerobic oxidization of organic components, IET Nanobiotechnology, Volume 3, Issue 2, pp.15-22, 2009.06, [URL].
150. R. Hamada, J. Suehiro, M. Nakano, T. Kikutani, K. Konishi, Development of rapid oral bacteria detection apparatus based on dielectrophoretic impedance measurement method, IET Nanobiotechnology, 10.1049/iet-nbt.2010.0011, 5, 2, 25-31, 2011.06, [URL], In this study, a bacteria detection apparatus based on dielectrophoretic impedance measurement (DEPIM) method was
demonstrated for rapid evaluation of oral hygiene. The authors integrated a micro electrode chip on which bacteria were captured
by dielectrophoresis (DEP), an AC voltage source to induce DEP force, and an impedance measurement circuit to a portable
instrument that enables rapid and automated oral bacterial inspection in hospitals and clinics. Special considerations have
been made on effects of high electrical conductivity of oral samples on DEP force and DEPIM results. It was shown
experimentally and theoretically that using a higher electric field frequency for the DEP bacteria trap and the impedance
measurement could realise DEPIM application to bacteria inspection from oral samples with higher conductivity. Based on
these investigations, the authors optimised the frequency condition of the DEPIM suitable for inspecting an oral sample along
with the design and development of a portable DEPIM apparatus for on-site inspection of oral bacteria. Under the optimised
frequency condition, DEPIM results were in good agreement with the conventional culture method showing significant
applicability of the DEPIM apparatus for practical rapid oral bacteria inspection..
151. Zhenhao Ding, Hiromichi Kasahara, Michihiko Nakano, Junya Suehiro, Bacterial detection based on polymerase chain reaction and microbead dielectrophoresis characteristics, IET Nanobiotechnology, 10.1049/iet-nbt.2016.0186, 2016.11.
152. Junya Suehiro, N. Ikeda, A. Ohtsubo, K. Imasaka, Bacterial detection using a carbon nanotube gas sensor coupled with a microheater for ammonia synthesis by aerobic oxidisation of organic components, IET Nanobiotechnology, 10.1049/iet-nbt.2008.0011, 3, 2, 15-22, 2009.06, In this study, the authors propose a new bacteria detection method using a carbon nanotube (CNT) gas sensor and a microheater, which were coupled into a Bio-MEMS (microelectromechanical systems)-type device. Bacteria were heated by the microheater in air so that ammonia (NH3) gas can be generated by the oxidation reaction of organic components of bacteria. Thus generated NH 3 gas was detected by using the CNT gas sensor, which was fabricated by dielectrophoresis (DEP) and combined with the microheater to form a small chamber. Cyclic pulsed heating operation was employed so that the CNT response to elevated temperature did not mask NH3 response. It was demonstrated that the proposed device could detect and quantify 107 bacteria cells (Escherichia coli). Possible application of DEP to trap and enrich target bacteria on the microheater was also discussed..
153. Zhenhao Ding, Hiromichi Kasahara, Michihiko Nakano, Junya Suehiro, Bacterial detection based on polymerase chain reaction and microbead dielectrophoresis characteristics, IET NANOBIOTECHNOLOGY, 10.1049/iet-nbt.2016.0186, 11, 5, 562-567, 2017.08.
154. Kohei Yaji, Kazuo Adachi, Junya Suehiro, Evaluation on insulation performance of snow accreted insulators by using artificial snow created in a laboratory - Complex impedance of artificial snow related to liquid water content, IEEJ Transactions on Fundamentals and Materials, 10.1541/ieejfms.137.590, 137, 10, 590-597, 2017.01, This paper provides electrical and dielectric properties of artificial snow produced at a defined condition in a climatic chamber. Complex impedance of the artificial snow block was measured varying its Liquid Water Content (LWC). An equivalent circuit of the electrode system was also discussed. It was revealed that the complex impedance of artificial snow decreased with increasing LWC. Moreover, it was suggested that the change in LWC would provide a change in dielectric properties of artificial snow depending on the source frequency..
155. Yuki Inoue, Michihiko Nakano, Junya Suehiro, Sensitivity improvement of dielectrophoretic impedance measurement by bacteria concentration using negative dielectrophoresis, IEEJ Transactions on Sensors and Micromachines, 10.1541/ieejsmas.136.148, 136, 5, 148-152, 2016.05, Dielectrophoretic impedance measurement (DEPIM) is a method to detect bacteria in an aqueous solution. DEPIM consists of two simultaneous processes: dielectrophoretic trapping of the target bacteria onto a microelectrode and measurement of impedance change caused by trapping bacteria. In this study, a new bacterial concentration process was combined with DEPIM to improve its sensitivity. The concentration process was based on negative dielectrophoresis of bacteria caused by specific configuration of parallel electrodes. A ditched dielectric thin layer deposited on one of the parallel electrodes causes non-uniform electric field resulting in occurring negative dielectrophoresis. Two electrode configurations, one is for the bacteria concentration and the other is for DEPIM, were fabricated in a microchannel. As a result, the detection sensitivity of DEPIM increased about 1.6 times by combining the concentration..
156. Junya Suehiro, Dielectrophoretic manipulation of nanomaterials and its application to device fabrication, IEEJ Transactions on Fundamentals and Materials, 10.1541/ieejfms.129.435, 129, 7, 435-438, 2009.09, The Dielectrophoresis (DEP) is electrokinetic motion of dielectrically polarized materials in non-uniform electric fields. DEP has been successfully applied to manipulation of nanomaterials including carbon nanotubes, metallic nanoparticles and semiconducting nanowires. Under positive DEP force, which attracts nanomaterials toward the higher field region, nanomaterials are trapped in the electrode gap and automatically establish good electrical connections between them and the external measuring circuit. This feature allows us a fast, simple and low-cost fabrication of nanomaterial-based sensors based on a bottom-up basis. This paper firstly presents a theoretical background of DEP phenomena and then reviews recent works of the present author, which were aimed to develop nanomaterial-based sensors, such as a carbon nanotube gas sensor and a ZnO nanowire photosensor, using DEP fabrication technique..
157. Kiminobu Imasaka, Yusuke Kanatake, Junya Suehiro, Masanori Hara, Production of magnetic iron oxide nanoparticles by using graphite arc discharge in Fe(OH) 3 colloidal solution, IEEJ Transactions on Fundamentals and Materials, 10.1541/ieejfms.126.349, 126, 5, 349-354, 2006.05, In this study, magnetic iron oxide nanoparticles were produced by thermal treatment of Fe(OH) 3 colloidal solution after graphite arc discharge in the solution. X-ray diffraction (XRD) pattern of the heat-treated powders showed that magnetic iron oxide nanoparticles (γ-Fe 2O 3 or Fe 3O 4) were produced by the phase transformation from α-Fe 2O 3 at the thermal treatment temperature over 500°C. The XRD pattern also indicated that the graphite powders produced by the arc discharge were contained in the Fe(OH) 3 colloidal solution, suggesting that the graphite powders contributed to the reduction process of α-Fe 2O 3..
158. Junya Suehiro, Masahiro Takahashi, Yuya Nishi, Weidong Ding, Kiminobu Imasaka, Masanori Hara, Improvement of the Ozone Generation Efficiency by Silent Discharge at Cryogenic Temperature, IEEJ Transactions on Fundamentals and Materials, 10.1541/ieejfms.124.791, 124, 9, 791-796, 2004.09, This paper describes a generation method of ozone using a silent discharge ozonizer, which is cooled down to cryogenic temperature by liquid nitrogen. The ozonizer was consisted of two metal electrodes and one dielectric barrier covering the lower electrode surface. In order to cool down the discharge space between the dielectric barrier and the upper electrode, the ozonizer was placed in an inner vessel of a metal cryostat whose outer vessel was filled with liquid nitrogen. It was found that the ozone concentration and ozone yield were increased with decreasing temperature. Especially, the cooling effects were remarkable in high specific energy region. The maximum ozone concentration of 146 g/m3 and ozone yield of 212.5 g/kWh were achieved at 170 K. Temperature distribution within the ozonizer was theoretically analyzed inorder to clarify the effects of the dielectric barrier material and the electrode gap space..
159. Takashi Kurihara, Takanori Nishioka, Junya Suehiro, Masanori Hara, Partial Discharge Characteristics in an Artificial Air-filled Void under Superimposed Sinusoidal Voltages at LN2 Temperature, IEEJ Transactions on Power and Energy, 10.1541/ieejpes.123.1280, 123, 11, 1280-1287, 2003.11, Partial discharge (PD) characteristics within an artificial air-filled void contained in a solid insulator were experimentally investigated under superimposed sinusoidal voltages of 60 and 600Hz at liquid nitrogen temperature (77K) to find the effects of the waveforms of distorted sinusoidal voltages on PD characteristics at 77K. The results show that PD inception voltage at 77K is independent of the applied voltage waveform. The results also show that, when the 600Hz component of the superimposed voltage is increased with its constant peak value, PD intensity seems to be independent of the voltage waveform, whereas PD pulse number increases. Since PD charge magnitude and pulse number at 77K were remarkably different from those at 298K, their mechanisms are discussed based on the observation results of residual charge distributions remaining on a void surface subjected to PDs under 60Hz ac voltages at both temperatures..
160. Yasin Khan, Akihito Oda, Junya Suehiro, Masanori Hara, Shigemitsu Okabe, Wire Particle Motion Behavior and Breakdown Characteristics around Different Shaped Spacers within Diverging Air Gap, IEEJ Transactions on Power and Energy, 10.1541/ieejpes.123.1288, 123, 11, 1288-1295, 2003.11, Free wire particle motion behavior and particle triggered breakdown characteristics around different shaped spacers between diverging conducting plane electrodes are studied experimentally in the laboratory air under DC and 60Hz AC voltages. Wire particle motion behavior was observed experimentally and is discussed on the basis of the results of field calculations. Consequently, it was found that a particle around spacer tends to move toward or away from the spacer depending on the field strength around the spacer, under both DC or AC voltages. Moreover, it was observed that a particle can hardly adheres to the spacer in case of corona discharge at wire particle ends under DC voltage and/or an oscillating wire particle in case of AC voltage and vicevcrsa. Also, the wire particle adhesion phenomenon and the characteristics of surface flashover triggered by free conducting wire particle around a simple shaped spacer in quasi uniform field is briefly discussed..
161. Masanori Hara, Junya Suehiro, Hidetaka Shigematsu, Shinsuke Yano, Methods for the improvement of electrical insulation in vacuum in the presence of transverse magnetic field, IEEJ Transactions on Fundamentals and Materials, 10.1541/ieejfms1972.109.375, 109, 9, 375-382, 1989.09.
162. Masanori Hara, Tadamitsu Kaneko, Junya Suehiro, Yuji Nakamura, Masanori Akazaki, The Similarity Relationship in Unipolar Ion Flow Fields with Rod-to-Plane Gaps, IEEJ Transactions on Fundamentals and Materials, 10.1541/ieejfms1972.107.233, 107, 5, 233-240, 1987.05.
163. Y. Martin, Z. Li, T. Tsutsumi, R. Shou, M. Nakano, J. Suehiro and S. Ohtsuka, Detection of SF6 decomposition products generated by DC corona discharge using a carbon nanotube gas sensor, IEEE Transactions on Dielectrics and Electrical Insulation, 10.1109/TDEI.2012.6180262, 19, 2, 671-676, 2012.04.
164. Junya Suehiro, Kiminobu Imasaka, Masanori Hara, Optical observations of partial discharge-induced bubbles generated in subcooled liquid nitrogen at atmospheric pressure, IEEE Transactions on Dielectrics and Electrical Insulation, 10.1109/TDEI.2008.4543097, 15, 3, 620-625, 2008.06, Composite insulation system of liquid nitrogen and solid insulator, which are widely employed in high 4TC superconducting equipment, can be deteriorated by partial discharge (PD) generated in highly stressed region. By subcooling the liquid nitrogen below the boiling point of 77 K at atmospheric pressure, the superconducting power device can obtain higher performance because the critical current density of the superconductor can be increased. The subcooled liquid nitrogen may also have better properties as electrical insulation medium than pool boiling one because gaseous bubble generation is suppressed. In this study, effects of subcooling temperature on PD characteristics were investigated at atmospheric pressure. Behavior of PD induced bubbles was optically investigated using a high speed digital imaging system as well as a laser light scattering method. These optical observations were synchronized with PD signal detection in order to clarify relationship between the PD intensity and bubble behavior. It was found that PD induced bubbles were strongly influenced by the PD energy as well as temperature of the subcooled liquid nitrogen..
165. Weidong Ding, Kohei Ochi, Junya Suehiro, Kiminobu Imasaka, Ryota Hayashi, Masanori Hara, Factors affecting PD detection in GIS using a carbon nanotube gas sensor, IEEE Transactions on Dielectrics and Electrical Insulation, 10.1109/TDEI.2007.369536, 14, 3, 718-725, 2007.06, The authors have previously demonstrated that a carbon nanotube (CNT) gas sensor can detect SF6 decomposition byproducts generated by partial discharges (PDs). There are several factors to be considered, however, before applying the CNT gas sensor to practical diagnosis of a gas-insulated switchgear (GIS). In this paper, three major factors, namely, the effects of operating temperature and installation location of the CNT gas sensor and SF 6/N2 gas mixture, were investigated. The stability of sensor conductance and the sensor response to PD were improved by controlling the sensor operating temperature. The maximum sensor response was obtained at about 70 °C. The CNT gas sensor, which was installed in an external pipe connected to the GIS tank, could detect PD generated in the tank, although the sensor response became lower and slower as the sensor was located further away from the PD source. It was found that the sensor response to PD showed a clear dependence on the mixing ratio of the SFS/N2 gas mixture. The maximum sensor response was achieved for SF6/N2 (20%/80%) gas mixture. This result was discussed based on Fourier transformation infrared (FTIR) analysis of PD decomposition byproducts adsorbed on the CNT surface..
166. Yulistya Negara, Kohei Yaji, Kiminobu Imasaka, Noriyuki Hayashi, Junya Suehiro, Masanori Hara, AC particle-triggered corona discharge in low pressure SF6 gas, IEEE Transactions on Dielectrics and Electrical Insulation, 10.1109/TDEI.2007.302876, 14, 1, 91-100, 2007.02, This paper deals with ac particle-triggered corona discharge as a follow-up to our previous research with dc voltage to clarify the particle-triggered corona discharge process in SF6 gas. Corona current pulses, charges associated with a corona current pulse, and corona light pulses were observed with an aluminum ellipsoidal particle suspended in a parallel plane electrode system under a SF6 gas pressure range of 30 kPa ≤ P ≤ 50 kPa by changing the particle position. Corona mode, phase (Φ)-charge (q) characteristics as well as corona discharge processes were discussed and the following results were obtained. Ac corona mode depended on the instantaneous applied voltage, voltage gradient as well as the particle position and then, the Φ-q characteristics were also affected by those parameters. Charges flow into the floating particle due to coronas on the both tips of particle and excite field fluctuations around the opposite side of particle in addition to the applied ac field. The field fluctuation in SF6 gas by the corona charges was about 4% of the applied field and much lower than that in air gap which was about 70%. That is, the corona development was suppressed effectively by high electron affinity of SF6 gas even in the case of floating particle. The less effective interference between coronas on the both side of particle in SF6 gas results in an obscure local minimum in the breakdown voltage characteristics as the particle is in the vicinity of electrode as contrasted with a drastic fall in the breakdown voltage by the particle in air..
167. Weidong Ding, Ryota Hayashi, Kohei Ochi, Junya Suehiro, Kiminobu Imasaka, Masanori Hara, Noriaki Sano, Eiichi Nagao, Tadao Minagawa, Analysis of PD-generated SF6 decomposition gases adsorbed on carbon nanotubes, IEEE Transactions on Dielectrics and Electrical Insulation, 10.1109/TDEI.2006.258191, 13, 6, 1200-1207, 2006.12, Chemical byproducts analysis has been recognized as a powerful diagnosis method for SF6 gas-insulated switchgear (GIS). The authors have previously demonstrated that a carbon nanotube (CNT) gas sensor could detect partial discharge (PD) generated in SF6 gas. However, PD-generated decomposition gas species, which were responsible for the CNT gas sensor response, have not been identified yet. In this paper, two kinds of experiments were conducted in order to identify the responsible decomposition gas species. At first, the decomposition gas molecules adsorbed on CNTs were analyzed by Fourier transformation infrared (FTIR) spectroscopy. FTIR absorbance was observed around 735 cm-1 after CNTs were exposed to PD generated in SF6. In the second experiment, the CNT gas sensor responses to typical SF6 decomposition products (HF and SF4) were examined. The CNT gas sensor responded to these gases in the same way as to PD generated in SF6. SF4 response was larger than HF response. Based on these results, SF4 and SOF2 emerged as candidates for the responsible decomposition gases. Electrochemical interactions between adsorbed gas molecules and CNT were discussed based on theoretical predictions of molecular orbital calculations. The calculation results suggested that both of SOF2 and SF4 could increase the CNT gas sensor conductance..
168. Yulistya Negara, Kohei Yaji, Junya Suehiro, Noriyuki Hayashi, Masanori Hara, DC corona discharge from floating particle in low pressure SF6, IEEE Transactions on Dielectrics and Electrical Insulation, 10.1109/TDEI.2006.258192, 13, 6, 1208-1216, 2006.12, The final objective of this research project is clarification of the particle-triggered corona mechanism in SF6 gas-insulated electrical equipment as well as development of high precision diagnostic method of foreign metallic particle in GIS insulated by SF6 gas using the electrical signal due to corona discharge. The following research steps are conducting to achieve our goal: 1) clarification of particle-triggered corona phenomena in air which is well-understood corona mechanism, 2) clarification of particle-triggered corona phenomena under dc and ac applied voltage in SF 6 gas at low pressure in which a stable corona occurred, and 3) clarification of the pressure effect on the particle-triggered corona mechanism. This study is the second step of our research series research, which focuses on characteristics and the mechanism of particle-triggered corona discharge in SF6 gas on the basis of measurements of corona current pulses at a pressure range of 30 kPa to 50 kPa under dc applied voltage. The identification of positive and negative corona pulses in SF6 gas from the waveform, amplitude and repetition rate of corona current pulses is difficult; thus, current and light pulses of coronas from the both tips of particle were measured simultaneously to discriminate the polarity of corona current pulses. Experiments showed that near the corona onset voltage, positive corona accompanied pulse current but negative corona tended to be glow-like corona. As the applied voltage was increased, negative corona changed into streamer type accompanying strong current pulse. Positive corona pulses maintained a small amplitude with an instantaneously high repetition rate, even if the field enhancement on the positive tip of particle occurred due to the positive-ion inflow to the particle produced by negative corona. On the basis of current pulse measurements, the mechanism of particle-triggered corona was discussed. Moreover, corona activity and breakdown voltage were investigated by changing the particle position. This study confirmed that the active corona development and fall in breakdown voltage were due to the effect of intermittent short-circuit arc in the minor gap between particle and electrode when the particle was in the vicinity of the electrode..
169. Masanori Hara, Yuji Maeda, Nobutaka Nakagawa, Junya Suehiro, Shuichi Yamada, DC breakdown voltage characteristics of saturated liquid helium in the presence of metallic particles, IEEE Transactions on Dielectrics and Electrical Insulation, 10.1109/TDEI.2006.1657957, 13, 3, 470-476, 2006.06, This paper deals with the breakdown voltage characteristics of saturated liquid helium in the presence of a needle-shaped or spherical metallic particle to obtain insulation design data for pool-cooled, low-temperature superconducting coils and to find the predominant factor affecting the breakdown voltage of liquid helium at a given state. The results show the following. (1) The generation of bubbles at the instant of collision of a particle with an electrode is caused mainly by the kinetic energy released from the moving particle to the liquid helium, while the electrostatic energy accompanying the microdischarge between the particle and the electrode has a lesser effect on it. (2) The lowest breakdown voltage at different particle conditions appears in the case of a free needle particle. The low breakdown voltage is caused by the bubble triggered by the particle collision, the high electric field at the tip of the needle particle, and the rich initial electrons supplied by the microdischarge..
170. Weidong Ding, Ryota Hayashi, Junya Suehiro, Guangbin Zhou, Kiminobu Imasaka, Masanori Hara, Calibration methods of carbon nanotube gas sensor for partial discharge detection in SF 6, IEEE Transactions on Dielectrics and Electrical Insulation, 10.1109/TDEI.2006.1624280, 13, 2, 353-360, 2006.04, The authors proposed a new type of gas sensor for high sensitive detection of decomposition products generated by partial discharge (PD) in SF 6 gas. The sensor employed carbon nanotubes (CNTs) as gas sensing transducer and was fabricated by electrokinetic manipulation of CNTs using dielectrophoresis. Due to complicated gas decomposition process of SF 6 gas, calibration of the CNT gas sensor is an essential and challenging subject in order to realize reliable and stable detection of PD under practical conditions. In this paper, two methods for the CNT gas sensor calibration were proposed and tested. The first method was based on initial conductance dependence of the CNT gas sensor response. The CNT gas sensor response to PD increased almost linearly with the amount of CNT trapped onto the sensor electrode, which could be quantified by the initial conductance of the sensor. However, the calibration accuracy of this method was about 50 % and was not high enough for practical use. The second method employed NO 2 (nitrogen dioxide) as calibration gas because of the similarity in the CNT sensor response to PD decomposition products and NO 2. It was found that the accuracy of the NO 2 calibration was about 10 % and far better than the first method. Finally, effectiveness of the NO 2 calibration was demonstrated by a PD monitoring test in which two CNT sensors were simultaneously exposed to SF 6 decomposition products with identical concentration..
171. Yasin Khan, Shigemitsu Okabe, Junya Suehiro, Masanori Hara, Proposal for new particle deactivation methods in GIS, IEEE Transactions on Dielectrics and Electrical Insulation, 10.1109/TDEI.2005.1394025, 12, 1, 147-156, 2005.02, This paper deals with consideration of particle motion control and its trapping in the deactivation of foreign contaminating moving particle in simulated GIS. The particle motion behavior in non-uniform field gap without/with different shaped spacers was investigated experimentally under dc and 60 Hz ac voltages. The obtained results were confirmed experimentally as well as by calculating the electrostatic force acting on the particle in the non-uniform field gap and are reported elsewhere. Whereas, in this paper, the observed particle motion behavior around simple shaped spacer is simulated by solving the particle motion equations analytically in the presence of electrical gradient and image forces. The simulation agreed fairly well with the experimental results. Furthermore, in the non-uniform electric field, the effect of dielectric coating on the grounded electrode on the particle motion and particle deactivation is also briefly discussed. On the basis of the obtained results of particle motion behavior without/with different shaped spacers and the effect of dielectric coating on the ground electrode, different methods of particle deactivation are suggested as well as confirmed experimentally..
172. Masanori Hara, Hiroshi Nakagawa, Junya Suehiro, Teruaki Shinohara, Electrical Breakdown Triggered by a Free Conducting Spherical Particle in Saturated Liquid He I and He II under Uniform dc Field, IEEE Transactions on Dielectrics and Electrical Insulation, 10.1109/TDEI.2003.1255780, 10, 6, 1022-1031, 2003.12, This paper is concerned with the pre-breakdown phenomena and the breakdown voltage characteristics, in the presence of a free moving conducting spherical particle, of saturated normal liquid helium (He I) and saturated superfluid liquid helium (He II) under uniform dc field. Experiments show that the particle lifts off around the theoretical value of the lift-off electric field, and the particle oscillates between the electrodes at higher applied voltages. In that case, the microdischarge appears just before the charged particle collides with the oppositely charged electrode, and the bubble is generated at the moment of every collision of the particle with the electrode. It is confirmed theoretically as well as experimentally that the maximum bubble radius in He II is nearly proportional to the Ein1/3, which is the released energy from the particle for the bubble generation. The insulation environment before the electrical breakdown suddenly changes at the λ-point since the bubble behavior in He I and He II greatly differs. In the characteristics of the breakdown voltage vs. liquid pressure, a clear discontinuity appears at the λ-point. Furthermore, the breakdown voltage in the parallel plane gap contaminated by a particle is lower than that in the rod-plane gap without a particle. It is found that the breakdown voltage characteristics are closely related to the trigger effect of the microdischarge and the bubble generation..
173. Koh Ichi Sakai, Dan Labrado Abella, Yasin Khan, Junya Suehiro, Masanori Hara, Experimental studies of free conducting wire particle behavior between non-parallel plane electrodes with ac voltages in air, IEEE Transactions on Dielectrics and Electrical Insulation, 10.1109/TDEI.2003.1207467, 10, 3, 418-424, 2003.06, When a spherical conducting particle exists in an electrode system where electrical gradient force acts along the electrode surface, the particle tends to move towards the high field region as reported in [1]. The possibility of appearance of this phenomenon is experimentally investigated with wire particles, which can easily produce the corona discharge on their ends resulting the action of a reactive force on the particle by a corona wind. The results show that a hovering particle travels deeper into the high electric field regions regardless of the corona discharge. Moreover, it is found that wire particle with corona discharge hovers near the negative electrode under dc voltage in atmospheric air due to different characteristics of corona discharge by the polarity. But under the ac voltage, the particle hovers near the bottom electrode only and invades in the high field region deeper than under the dc voltage..
174. Yasin Khan, Koh Ichi Sakai, Eun Kyung Lee, Junya Suehiro, Masanori Hara, Motion behavior and deactivation method of free-conducting particle around spacer between diverging conducting plates under dc voltage in atmospheric air, IEEE Transactions on Dielectrics and Electrical Insulation, 10.1109/TDEI.2003.1207471, 10, 3, 444-457, 2003.06, This paper deals with free conducting particle motion around different shaped spacers between diverging conducting plates under dc voltage in atmospheric air. Spherical particle motion was observed experimentally and the results were discussed on the basis of the electrostatic force acting on the particle with and without spacer. The results show that a particle around a spacer tends to move laterally towards or away from the spacer towards higher field regions, depending on the spacer configuration. It lifts at higher field positions and sometimes adheres to the spacer. The effects of spacer angle and spacer material (permittivity) on free conducting particle motion are also discussed. For comparing the results obtained with a sphere, a wire particle motion around different shaped spacers is also investigated. The obtained results suggest one of the methods to prevent/suppress the conducting particle from approaching or adhering to spacers, is to reduce the field strength in the vicinity of the triple junction of gas, solid dielectric and electrode in gas insulated system (GIS)..
175. Koh Ichi Sakai, Dan Labrado Abella, Yasin Khan, Junya Suehiro, Masanori Hara, Theoretical and experimental studies for spherical free-conducting particle behavior between non-parallel plane electrodes with ac voltages in air, IEEE Transactions on Dielectrics and Electrical Insulation, 10.1109/TDEI.2003.1207466, 10, 3, 404-417, 2003.06, This paper deals with free-conducting particle motion and particle-triggered breakdown in ac electric fields between non-parallel plane electrodes in atmospheric air. Spherical particle motion was investigated theoretically and experimentally under ac voltages with various frequencies, considering the effect of the electrical gradient force and the dependence of the Coulomb force magnitude on the distance between a particle and an electrode. The result shows that when the Coulomb force acting on a bouncing particle changes its direction periodically under ac voltage whose frequency is around commercial power frequency, the electrical gradient force can become effective in initiating particle motion toward decreasing electrode gap regions, causing the particle to trigger breakdown. Moreover, it was found that the direction in which a particle advances horizontally is greatly influenced by microdischarge occurrence when the particle bounces very near to the grounded electrode under high-frequency ac voltage, and that when a particle bounces on an electrode, particle-triggered breakdown voltage is decreased by the effect of microdischarge..
176. M. Hara, J. Suehiro, H. Maeda, H. Nakashima, DC pre-breakdown phenomena and breakdown characteristics in the presence of conducting particles in liquid nitrogen, IEEE Transactions on Dielectrics and Electrical Insulation, 10.1109/94.983880, 9, 1, 23-30, 2002.02, dc pre-breakdown phenomena and breakdown characteristics in the presence of free conducting particles in liquid nitrogen are studied experimentally. The results show that a microdischarge occurs when a charged particle is approaching an oppositely charged electrode. An intense microdischarge can trigger a complete breakdown of the gap. The breakdown voltage of a uniform field gap with a free metallic particle of mm size might be reduced well below that of a point-to-plane gap without a particle in liquid nitrogen. Heavy contamination by a metallic powder produces a large reduction in the breakdown voltage, with a horizontal spacer surface. However carbon powder is less hazardous compared to metallic powder..
177. Hee Kyu Lee, Junya Suehiro, Masanori Hara, Duck Chul Lee, Myung Hwan So, Energy efficiency improvement of electrical sterilization using oscillatory waveforms from a RLC discharging circuit, IEEE Transactions on Dielectrics and Electrical Insulation, 10.1109/94.892003, 7, 6, 872-874, 2000.12, This paper describes effects of pulsed HV waveforms on biological cell inactivation. A simple RLC circuit with various inductance values was employed to investigate the waveform effects on the electrical sterilization of Escherichia Coli. It has been found that the minimum value of cell survivability can be realized by choosing an appropriate inductance value, even when the initial energy stored in a capacitor is constant. In order to realize the higher energy efficiency than a conventional RC discharging network, circuit parameters should be determined so that amplitude and width of each pulse become larger than the critical values 15 kV/cm and 50 μs, respectively..
178. J. Suehiro, K. Yamasaki, H. Matsuo, M. Hara, J. Gerhold, Pulsed electrical breakdown in liquid helium in the μs range, IEEE Transactions on Dielectrics and Electrical Insulation, 10.1109/94.300281, 1, 3, 403-406, 1994.06, Information about breakdown time lags under pulsed voltage stress is prerequisite to the insulation design of superconducting devices. Experiments have been carried out using a pulse generator which provides a step voltage with 200 ns rise time and a long decay time constant of more than 1 ms. The present experiments may bridge the information gap between time lag measurements in the ns range using extremely high field strengths, and existing data found with usual lightning impulse voltage. The test device is described in the paper, and some typical results are discussed in detail..
179. M. Hara, J. Suehiro, T. Wakiyama, Deflection of Streamer Channels in High Magnetic Field, IEEE Transactions on Electrical Insulation, 10.1109/14.204869, 27, 6, 1179-1185, 1992.12, Streamer propagation on a dielectric film under transverse magnetic field produced by a superconducting magnet is investigated by using the Lichtenberg figure technique. The positive and negative streamer channels are deflected in the same direction due to the Lorentz force, which acts on electrons in the streamer head. The deflection angle of negative streamer is larger than that of the positive one and increases with the propagation in the radial direction. On the other hand, the deflection angle of positive streamer is almost constant along the path. A streamer propagation model is proposed taking account of the electric field in the space charge region left behind the streamer channel and the field enhancement effect at the streamer tip. Through comparison of the experimental results of the streamer deflection characteristics with the theoretical prediction, the electric field in the space charge region is supposed to reach a value of 2 to 3 kV/cm. The internal field causes voltage drop across the space charge region, while the electric field is enhanced in the concentrated positive streamer head. On the other hand, the negative steamer spreads uniformly and the field concentration effect at the tip is weak..
180. Masanori Hara, Junya Suehiro, Hisayuki Matsumoto, Tadamitsu Kaneko, Breakdown Characteristics of Cryogenic Gaseous Nitrogen and Estimation of its Electrical Insulation Properties, IEEE Transactions on Electrical Insulation, 10.1109/14.34195, 24, 4, 609-617, 1989.08, Electrical properties of liquid nitrogen and its vaporized gas have become of great interest again since the discovery of high-temperature superconducting materials. This paper presents breakdown characteristics of gaseous nitrogen from room temperature down to 74 K. With uniform field gap geometry, the validity of Paschen’s law is confirmed even under the saturated gas condition at 74 K. In the case of non-uniform field gap, there is a remarkable difference in the effect of positive and negative polarities on corona stabilization. A wider gap length is necessary for stable negative corona formation than for positive corona at temperatures < 100 K. Breakdown criteria are proposed on the basis of experimental results to give a practical and reliable procedure for the design of cryogenic insulating systems which use liquid nitrogen and the vaporized gas as the coolant..
181. M. G. Danikas, S. Tsuru, M. Nakamura, T. Mine, J. Suehiro, M. Hara, PD Characteristics and Mechanisms in Artificial Air-Filled Voids at Room and Liquid Nitogen Temperatures, IEEE Trans. on. Dielectrics and Electrical Insulation, Vol.7, No.6, pp.875-876, 2000.12.
182. H. Lee, J. Suehiro, D. Lee, M. So, M. Hara, Energy Efficiency Improvement of Electrical Sterilization Using Oscillatory Waveforms from a RLC Discharging Circuit, IEEE Trans. on. Dielectrics and Electrical Insulation, 7, 6, 872-874, Vol.7, No.6, pp.872-874, 2000.12.
183. J. Suehiro, G. Zhou, M. Imamura, M. Hara, Dielectrophoretic filter for separation and recovery of biological cells in water, IEEE Trans. on Industry Applications, 10.1109/TIA.2003.816535, 39, 5, 1514-1521, Vol.39, No.5, pp.1514-1521, 2003.09, [URL].
184. S. Tsuru, M. Nakamura, T. Mine, J. Suehiro, M. Hara, PD Characteristics and Mechanisms in Artificial Air-Filled Voids at Room and Liquid Nitrogen Temperatures, IEEE Trans. on Dielectrics and Electrical Insulation, 10.1109/94.752008, 6, 1, 43-50, Vol.6, No.1, pp.43-50, 1999.02.
185. B. Y. Seok, H. Komatsu, J. Suehiro, M. Hara, Partial and Complete Electrical Breakdown in Simulated High Temperature Superconducting Coils, IEEE Trans. on Dielectrics and Electrical Insulation, 10.1109/94.839344, 7, 1, 78-86, Vol.7, No.1, pp.78-86, 2000.02.
186. T. Kurihara, S. Kozuru, K. Imasaka, J. Suehiro, M. Hara, PD Characteristics in an Air-filled Void at Room Temperature under Superimposed Sinusoidal Voltages, IEEE Trans. on Dielectrics and Electrical Insulation, 10.1109/94.919953, 8, 2, 269-275, Vol.8, No.2, pp.269-275, 2001.04.
187. B. Y. Seok, H. Komatsu, M. Kushinaga, J. Suehiro, M. Hara, Pressurizing and Sub-cooling Effects on Electrical Breakdown of LN$_{2}$ in Modeled HTS Coils, IEEE Trans. on Dielectrics and Electrical Insulation, 10.1109/94.971460, 8, 6, 1016-1024, Vol.8, No.6, pp.1016-1024, 2001.12.
188. M. Hara, J. Suehiro, H. Maeda, H. Nakashima, PD Per-Breakdown Phenomena and Breakdown Characteristics in the Presence of Conducting Particles in Liquid Nitrogen, IEEE Trans. on Dielectrics and Electrical Insulation, Vol.9, No.1, pp.23-30, 2002.02.
189. K. Sakai, D. L. Abella, J. Suehiro, M. Hara, Charging and Behavior of a Spherically Conducting Particle on a Dielectrically Coated Electrode in the Presence of Electrical Gradient Force in Atmospheric Air, IEEE Trans. on Dielectrics and Electrical Insulation, 10.1109/TDEI.2002.1024436, 9, 4, 577-588, Vol.9, No.4, pp.577-588, 2002.08.
190. M. Hara, H. Nakagawa, T. Shinohara, J. Suehiro, Generation, Growth and Collapse of Bubbles on Collision of Particle with Electride in DC Electrically Stressed Liquid Helium, IEEE Trans. on Dielectrics and Electrical Insulation, 10.1109/TDEI.2002.1115484, 9, 6, 910-921, Vol.9, No.6, pp.910-921, 2002.12.
191. Y. Khan, S. Okabe, J. Suehiro, M. Hara, Proposal of new particle deactivation methods in GIS, IEEE Trans. on Dielectrics and Electrical Insulation, Vol.12, No.1, pp.147-159, 2005.02.
192. W. Ding, R. Hayashi, J. Suehiro, G. Zhou, K. Imasaka, M. Hara, Calibration methods of carbon nanotube gas sensor for partial discharge detection in SF6, IEEE Trans. on Dielectrics and Electrical Insulation, Vol.13, No.2, pp.353-361, 2006.04, [URL].
193. M. Hara, Y. Maeda, N. Nakagawa, J. Suehiro, S. Yamada, DC breakdown voltage characteristics of saturated liquid helium in the presence of metallic particles, IEEE Trans. on Dielectrics and Electrical Insulation, Vol.13, No.3, pp.470-476, 2006.06.
194. W. Ding, R. Hayashi, K. Ochi, J. Suehiro, K. Imasaka, M. Hara, N. Sano, E. Nagao, T. Minagawa, Analysis of PD-generated SF6 decomposition gases adsorbed on carbon nanotubes, IEEE Trans. on Dielectrics and Electrical Insulation, Vol.13, No.6, pp.1200-1207, 2006.12, [URL].
195. Y. Negara, K. Yaji, J. Suehiro, N. Hayashi, M. Hara, DC corona discharge from floating particle in low pressure SF6, IEEE Trans. on Dielectrics and Electrical Insulation, Vol.13, No.6, pp.1208-1216, 2006.12.
196. Y. Negara, K. Yaji, K. Imasaka, N. Hayashi, J. Suehiro, M. Hara, AC particle-triggered corona discharge in low pressure SF6 gas, IEEE Trans. on Dielectrics and Electrical Insulation, Vol.14, No.1, pp.91-100, 2007.02.
197. W. Ding, K. Ochi, J. Suehiro, K. Imasaka, R. Hayashi, M. Hara, Factors affecting PD detection in GIS using a carbon nanotube gas sensor, IEEE Trans. on Dielectrics and Electrical Insulation, Vol.14, No.3, pp.718-725, 2007.06, [URL].
198. J. Suehiro, K. Imasaka, M. Hara, Optical observations of partial discharge-induced bubbles generated in subcooled liquid nitrogen at atmospheric pressure, IEEE Trans. on Dielectrics and Electrical Insulation, Vol.15, No.3, pp.620-625, 2008.06, [URL].
199. J. Suehiro, K. Ohno, T. Takahashi, M. Miyama, M. Hara, Size Effect and Statistical Characteristics of DC and Pulsed Breakdown of Liquid Helium, IEEE Trans. on DEI, 10.1109/94.536729, 3, 4, 507-514, Vol.3, No.4, pp.507-514, 1996.08.
200. K. Funaki, K. Iwakuma, M. Takeo, K. Yamafuji, J. Suehiro, M. Hara, M. Konno, Y. Kasagawa, I. Itoh, S. Nose, M. Ueyama, K. Hayashi, K. Sato, Preliminary Tests of a 500kVA-Class Oxide Superconducting Transformer Cooled by Subcooled Nitrogen, IEEE Trans. on Applied Superconductivity, 10.1109/77.614630, 7, 2, 824-827, Vol.7, No.2, pp.824-827, 1997.06.
201. J. Suehiro, D. Tsuji, K. Tsutsumi, S. Ohtsuka, M. Hara, Quench Time Lag and its Statistical Characteristics of NbTi Mechanical PCS Measured with Pulsed Current, IEEE Trans. on Applied Superconductivity, 10.1109/77.783496, 9, 2, 1125-1128, Vol.9, No.2, pp.1125-1128, 1999.06.
202. S. Ohtsuka, T. Nakamura, D. Tsuji, J. Suehiro, M. Hara, Quench Characteristics of Parallel Circuit of Two Mechanical PCS's, IEEE Trans. on Applied Superconductivity, 10.1109/77.783486, 9, 2, 1085-1088, Vol.9, No.2, pp.1085-1088, 1999.06.
203. K. Funaki, M. Iwakuma, M. Takeo, K. Yamafuji, J. Suehiro, M. Hara, M. Konno, Y. Kasagawa, I. Itoh, S. Nose, M. Ueyama, K. Hayashi, K. Sato, Preliminary Tests of A 500 kVA-Class Oxide Superconducting Transformer Cooled by Subcooled Nitrogen, IEEE Trans. on Appl. Supercond., 10.1109/77.614630, 7, 2, 824-827, Vol.7, No.2, pp.824-827, 1997.07.
204. K. Funaki, M. Iwakuma, K. Kajikawa, M. Hara, J. Suehiro, T. Ito, Y. Takata, T. Bohno, S. Nose, M. Konno, Y. Yagi, H. Maruyama, T. Ogata, S. Yoshida, K. Ohashi, H. Kimura, K. Tsutsumi, Development of a 22kV/6.9kV Single-Phase Model for a 3MVA HTS Power Transformer, IEEE Trans. Appl. Supercond., 10.1109/77.920079, 11, 1, 1578-1581, Vol.11, No.1, pp.1578-1581, 2001.03.
205. Yoshihiko Obana, Michihiko Nakano, Junya Suehiro, Breakup of carbon nanotube aggregates under high electric field and its application to nanocomposite film, IEEE TENCON 2016, 10.1109/TENCON.2016.7848606, 3045-3048, 2017.02.
206. Hiroki Hayashi, Michihiko Nakano, Junya Suehiro, Detection of acetylene dissolved in insulation oil using pt-decorated ZnO gas sensor, IEEE TENCON 2016, DOI: 10.1109/TENCON.2016.7848262, 1485-1488, 2017.02.
207. Shota Inoue, Michihiko Nakano, Junya Suehiro, Dielectrophoretic modification of carbon nanotube with ZnO nanoparticles for NO2 gas sensing, IEEE TENCON 2016, 10.1109/TENCON.2016.7848608, 3054-3057, 2017.02.
208. Ning Wei, Wei Dong Ding, Yi Dong Zhu, Chun Qiang Su, Junya Suehiro, Single-walled carbon nanotube gas sensor used in partial discharge detection of GIS, Gaodianya Jishu/High Voltage Engineering, 37, 11, 2700-2706, 2011.11, This paper describes a realizable fabrication method to manufacture chemical gas sensors by using single-walled carbon nanotubes (SWCNTs). The sensors were tested for the monitoring of SF 6 decomposition gas produced by partial discharge (PD) in GIS tank. The results showed a superior sensitivity, favorable reliability and good reproducibility. For further clarifying the relativity between sensor response and partial discharge activity, the discharge in GIS tank was monitored simultaneously through conventional pulse current method and a SWCNTs gas sensor, and the measurement results were put together for comparative analysis in this paper. The sensor response showed a great dependence on partial discharge characteristics. The sensor response increased nearly linearly with limits when the energy of discharge was persistently accumulated. Partial discharge power had a great influence on the response rate and the time delay. With the increase of partial discharge power, the response rate augmented almost in proportion while the time delay gradually becomes shorter with limits. The results were quite favorable to assess the partial discharge intensity and duration to some extent. Compared with pulse current method, the sensor was predominant to detect partial discharge exposed to constantly high levels of noise. It was capable of detecting partial discharge which was too weak to be detected with pulse current method. However, the sensor response didn't show much dependency on the apparent discharge of partial discharge..
209. Kiminobu Imasaka, Yusuke Kanatake, Junya Suehiro, Masanori Hara, Production of magnetic iron oxide nanoparticles by using graphite ARC discharge in Fe(OH)3 colloidal solution, Electronics and Communications in Japan, 10.1002/ecj.10024, 91, 2, 55-62, 2008.02, In this study, magnetic iron oxide nanoparticles were produced by thermal treatment of Fe(OH)3 colloidal solution after graphite arc discharge in the solution. The X-ray diffraction (XRD) pattern of the heat-treated powders showed that magnetic iron oxide nanoparticles (γ-Fe2O 3 or Fe3O4) were produced by the phase transformation from α-Fe2O2 at the thermal treatment temperature over 500 °C. The XRD pattern also indicated that the graphite powders produced by the arc discharge were contained in the Fe(OH)3 colloidal solution, suggesting that the graphite powders contributed to the reduction process of a-Fe2O3..
210. Kiminobu Imasaka, Kazuki Takahashi, Junya Suehiro, Masanori Hara, Influence of gap length on the gas-puff z-pinch plasma produced by an inductive pulsed power system, Electrical Engineering in Japan (English translation of Denki Gakkai Ronbunshi), 10.1002/eej.10126, 144, 4, 1-8, 2003.09, In this study, an argon gas-puff z-pinch plasma was produced by an inductive pulsed power system. The gap length dependence of plasma characteristics such as the pinch plasma behavior, soft x-ray emissions, and spatial distribution of hot spots, was investigated. The soft x-ray output decreased with gap length, and hot spots generated by sausage instability were distributed along the z-axis for shorter delay times of the discharge onset. However, hot spots were distributed in the center of the gap space with increased delay times, regardless of the gap length, and the number of hot spots decreased..
211. Masanori Hara, Takashi Kurihara, Susumu Kozuru, Junya Suehiro, Noriyuki Hayashi, Estimation of partial discharge onset characteristics in gases around a triple junction, Electrical Engineering in Japan (English translation of Denki Gakkai Ronbunshi), 10.1002/eej.10175, 144, 1, 1-11, 2003.07, A new method of estimating partial discharge onset conditions in gases around a triple junction is proposed. The effectiveness of the method based on the Paschen curve and the potential distribution along the interface between a solid insulator and gas is confirmed experimentally in air at room temperature. The partial discharge onset conditions in air and SF6 gas under different pressures at room temperature and in cryogenic nitrogen and helium gases at saturation temperature and atmospheric pressure are estimated. The partial discharge intensity is discussed on the basis of the proposed method..
212. Junya Suehiro, Takuji Takahashi, Motohide Miyama, Masanori Hara, Influence of liquid temperature and electrode size on insulated breakdown characteristics in saturated superfluid helium, Electrical Engineering in Japan (English translation of Denki Gakkai Ronbunshi), 10.1002/(SICI)1520-6416(199908)128:3<16::AID-EEJ3>3.0.CO;2-N, 128, 3, 16-23, 1999.08, The dc breakdown strength and pulsed breakdown time lag of saturated superfluid liquid helium (HeII) at 1.4 and 1.85 K are measured over a wide range of electrode sizes and applied field strengths. The results of the measurements are statistically analyzed by using Weibull distribution functions. It is found that the area effect is dominant for dc and pulsed breakdown rather than the volume effect as in the case of liquid helium of 4.2 K (HeI). The shape parameter in the Weibull distribution function for dc breakdown strengths of HeII is smaller than that of HeI. As a result, dc breakdown in superfluid helium can take place in a wider electrode area than in normal liquid helium, while no remarkable differences in breakdown areas are observed between 1.85 and 1.4 K. On the other hand, the statistical time lag in HeII becomes shorter with a decrease in temperature. According to the Fowler-Nordheim theory, it is suggested that a higher electron mobility in HeII may increase the field-emitted electron kinetic energy to trigger liquid breakdown with a higher probability..
213. Koji Takano, Shunsuke Matsuura, Yan Jiang, Junya Suehiro, Masanori Hara, Effect of a thin insulation film on thermal bubble-triggered breakdown phenomena in liquid nitrogen, Electrical Engineering in Japan (English translation of Denki Gakkai Ronbunshi), 10.1002/(SICI)1520-6416(199906)127:4<18::AID-EEJ3>3.0.CO;2-J, 127, 4, 18-28, 1999.06, The effect of a thin insulation film on breakdown phenomena in liquid nitrogen in the presence of thermally induced bubbles is investigated with a cylinder-to-plane electrode. Bubbles were produced by a heater mounted in the cylinder, which is partially covered with an insulation film. The results show that the film's effect on the breakdown voltage is insignificant until a pore is formed on the film by a previous breakdown, but it becomes substantial after pore formation. The reduction rate in breakdown voltage after the pore formation depends on the gap length and heater power. The minimum breakdown voltage drops to the magnitude of the breakdown voltage in the gaseous phase at normal boiling temperature. The breakdown mechanism is discussed on the basis of bubble observation and numerical calculation of suspended-bubble motion..
214. Masanori Hara, Junya Suehiro, Hidetaka Shigematsu, Shinsuke Yano, Methods for the improvement of electrical insulation in vacuum in the presence of transverse magnetic field, Electrical Engineering in Japan, 10.1002/eej.4391100204, 110, 2, 27-35, 1990.02.
215. Masanori Hara, Junya Suehiro, Satoru Sumiyoshitani, Masanori Akazaki, Modes and characteristics of corona discharge in high‐temperature air, Electrical Engineering in Japan, 10.1002/eej.4391080302, 108, 3, 10-21, 1988.03.
216. Michihiko Nakano, Zhenhao Ding, Hiromichi Kasahara, Junya Suehiro, Rapid microbead-based DNA detection using dielectrophoresis and impedance measurement, EPL, 10.1209/0295-5075/108/28003, 108, 2, Article number 28003 (5 pages), 2014.10, Polymerase chain reaction (PCR) is a powerful tool for diagnostic procedures in bacterial and viral infections. The authors propose a new electrical technique for rapid detection of DNA amplified by PCR using dielectrophoresis (DEP) of microbeads. The method is based on dramatic alteration of DEP characteristics of microbeads caused by DNA labeling. DNA-labeled microbeads are trapped on a microelectrode under the action of positive DEP, whereas pristine ones are not. DEP-trapped microbeads are measured impedimetrically to realize rapid and quantitative detection of the amplified DNA. The validity of the proposed method was demonstrated by detection of PCR-amplified DNA of viruses..
217. K. Funaki, M. Iwakuma, K. Kajikawa, M. Takeo, J. Suehiro, M. Hara, K. Yamafuji, M. Konno, Y. Kasagawa, K. Okubo, Y. Yasukawa, S. Nose, M. Ueyama, K. Hayashi, K. Sato, Development of a 500 kVA-class oxide-supercon- ducting power transformer operated at liquid-nitrogen temperature, Cryogenics, 10.1016/S0011-2275(97)00134-3, 38, 2, 211-220, Vol.38, No.2, pp.211-220, 1998.02.
218. S. Ohtsuka, H. Ohtsubo, T. Nakamura, J. Suehiro, M. Hara, Characteristics of NbTi Mechanical Persistent Current Switch and Mechanism of Superconducting Connection at Contact, Cryogenics, 10.1016/S0011-2275(98)00079-4, 38, 9, 893-902, Vol.38, No.9, pp.893-902, 1998.09.
219. M. Hara, T. Kurihara, R. Nakano, J. Suehiro, Medium factors of electrical insulation systems in high temperature superconducting power apparatus with coil structure for equivalent ac withstand voltage test at room temperature, Cryogenics, 10.1016/j.cryogenics.2005.08.004, 45, 10-11, 705-717, Vol.45, pp.705-717, 2005.10.
220. Junya Suehiro, Masanori Hara, Quench time lag of NbTi mechanical PCS with ramped current waveforms, Cryogenics, 10.1016/S0011-2275(02)00150-9, 43, 1, 19-24, 2003.01, This paper describes characteristics and generation mechanism of quench time lag of NbTi mechanical persist current switch (PCS). The quench time lag tD was defined as a time delay between quench occurrence and the moment of the instantaneous value of the switch current exceeding a static quench current of the PCS. Quench time lag characteristics were investigated by using ramp current waveforms in order to clarify effects of the current sweep rate. It was found that the quench time lag decreased with increasing current sweep rate. A theoretical model was proposed in order to clarify the quench mechanism with a transient current waveform. In the model, the quench time lag was calculated by computing temperature rise of a superconducting connection bridge due to an AC loss and a flux flow loss. The simulation results of the quench time lag were in a good agreement with experimental data when cooling effects of liquid helium were taken into account..
221. S. Ohtsuka, T. Nakamura, D. Tsuji, J. Suehiro, M. Hara, Magnetic field dependence of transition current of NbTi mechanical PCS, Cryogenics, 10.1016/S0011-2275(98)00122-2, 38, 12, 1207-1212, 1998.12, This paper deals with magnetic field dependence of transition current of NbTi mechanical persistent current switch (PCS), which realizes zero contact resistance and consists of two contact pieces made of NbTi bulk, in parallel or perpendicular magnetic field. The transition current is defined as the quench current with which the contact resistance abruptly generates. It is found that the transition current decreases with the field strength. Using a theoretical model to explain the formation mechanism of a superconducting connection at the contact of the mechanical PCS, it is confirmed that the transition current varies according to Jc-B characteristics of the contact piece material NbTi. These findings prove that NbTi mechanical PCS has superconductive connection between the contact pieces in the closed state and can be operated in persistent current mode as a superconducting PCS..
222. B. J. Choi, S. Ohtsuka, J. Suehiro, M. Hara, Simulation test and theoretical analysis of surge propagation in superconducting magnet, Cryogenics, 10.1016/0011-2275(95)98218-P, 35, 8, 505-513, 1995.08, This paper deals with the surge propagation characteristics in a superconducting magnet in which arc discharge can be generated and extinguished to produce a high frequency oscillating voltage. Special attention is paid to the effects of conductor resistance in the high frequency range, which decreases with a lowering of temperature. Based on the results of simulation tests and theoretical considerations, it is shown that waveform shaping during surge travelling depends on an attenuation process due to electrical loss, as well as transmission and reflection phenomena at junctions with external circuits..
223. M. Hara, J. Suehiro, H. Matsumoto, Breakdown characteristics of cryogenic gaseous helium in uniform electric field and space charge modified non-uniform field, Cryogenics, 10.1016/0011-2275(90)90276-I, 30, 9, 787-794, 1990.09, D.c. breakdown characteristics of gaseous helium in uniform and non-uniform electric fields down to 4.2 K at atmospheric pressure have been investigated. Although helium is a nonelectronegative gas, a negative pulse corona is observed only near the normal boiling point due to the abrupt appearance of quasi-bubble state electrons. Positive ion space charge modifies the electric field distribution in the gap space considerably. The electric field strength on the non-corona electrode in the ion flow field is measured satisfactorily and analysed theoretically using a numerical electric field calculation technique. On the basis of experimental results, methods are proposed to give corona onset criteria and the breakdown voltage preceded by a positive glow corona..
224. G. Zhou, M. Imamura, J. Suehiro, M. Hara, A Dielectrophoretic Filter for Separation and Collection of Fine Particles Suspended in Liquid, Conf. Records of the 2002 IEEE Industry Applications Conf., 37th IAS Annual Meeting, 1404-1411, pp.1404-1411, 2002.10.
225. S. Tsuru, M. Nakamura, T. Mine, J. Suehiro, M. Hara, Partial Discharge Inception Characteristics in Artificial Air-Filled Voids at Room and Liquid Nitrogen Temperatures, Conf. Record of the IEEE Int. Sympo. on Electrical Insulation, 153-156, pp.153-156, 1998.06.
226. J. Suehiro, G. Zhou, M. Hara, NO2 gas sensing characteristics of carbon nanotube gas sensor fabricated by dielectrophoresis, Chemical Sensors, Vol.20, Supplement B, pp.454-455, 2004.07.
227. M. Hara, T. Kurihara, T. Nishioka, J. Suehiro, H. Okamoto, Determination method of equivalent insulation test voltage at room temperature for high temperature superconducting power apparatus with coil structure, CRYOGENICS, 10.1016/j.cryogenics.2003.12.001, 44, 4, 229-239, Vol.44, pp.229-239, 2004.04.
228. Michihiko Nakano, Zhenhao Ding, Junya Suehiro, Comparison of Sensitivity and Quantitation between Microbead Dielectrophoresis-Based DNA Detection and Real-Time PCR, Biosensors, 10.3390/bios7040044, 7, 4, 44, 2017.09.
229. Michihiko Nakano, Zhenhao Ding, Junya Suehiro, Comparison of Sensitivity and Quantitation between Microbead Dielectrophoresis-Based DNA Detection and Real-Time PCR, Biosensors, 10.3390/bios7040044, 7, 4, 44, 2017.09.
230. J. Suehiro, Fabrication and characterization of nanomaterial-based sensors using dielectrophoresis, Biomicrofluidics, 10.1063/1.3430535, 4, 3430535, 2010.06, [URL], Dielectrophoresis DEP is an electrokinetic motion of dielectrically polarized materials in nonuniform electric fields. DEP has been successfully applied to manipulation of nanomaterials including carbon nanotubes CNTs, metallic nanoparticles, and semiconducting nanowires. Under positive DEP force, which attracts nano materials toward the higher field region, nanomaterials are trapped in the electrode gap and automatically establish good electrical connections between them and the external measuring circuit. This feature allows us a fast, simple, and low-cost fabrication of nanomaterial-based sensors based on a bottom-up approach. This paper first presents a theoretical background of DEP phenomena and then reviews recent works of the present author, which were aimed to develop nanomaterial-based sensors, such as a CNT gas sensor and a ZnO nanowire photosensor, using DEP fabrication technique. It is also demonstrated that DEP technique enables self-formation of interfaces between various nano materials, which can be also applicable as novel sensing transducers..
231. M. Nakano, Z. Ding, K. Matsuda, J. Xu, M. Inaba, J. Suehiro, Simple microfluidic device for detecting the negative dielectrophoresis of DNA labeled microbeads, BIOMICROFLUIDICS, 10.1063/1.5124419, 13, 6, 2019.11.
232. T. Okada, J. Suehiro, Synthesis of nano-structured materials by laser-ablation and their application to sensors, Applied Surface Science, Vol. 253, No. 19, pp. 7840-7847, 2007.07, [URL].
233. T. Okada, J. Suehiro, Synthesis of nano-structured materials by laser-ablation and their application to sensors, Applied Surface Science, 10.1016/j.apsusc.2007.02.152, 253, 19, 7840-7847, 2007.07, We describe the synthesis of nano-structured materials of ZnO and Pd by laser ablation and their applications to sensors. The synthesis of ZnO nano-wires was performed by nano-particle assisted deposition (NPAD) where nano-crystals were grown with nano-particles generated by laser-ablating a ZnO sintered target in an Ar background gas. The synthesized ZnO nano-wires were characterized with a scanning electron microscopy and the photoluminescent characteristics were examined under an excitation with the third harmonics of a Nd:YAG laser. The nano-wires with a diameter in the range from 50 to 150 nm and a length of up to 5 μm were taken out of the substrate by laser blow-off technique and/or sonication. It was confirmed that the nano-wires showed the stimulated emission under optical pumping, indicating a high quality of the crystalinity. Pd nano-particles were generated by laser-ablating a Pd plate in pure water. The transmission electron microscope observation revealed that Pd nano-particles with a diameter in the range from 3 nm to several tens of nanometers were produced. Using these nano-structured materials, we successfully fabricated sensors by the dielectrophoresis techniques. In the case of the ultraviolet photosensor, a detection sensitivity of 10 nW/cm 2 was achieved and in the case of hydrogen sensing, the response time of less than 10 s has been demonstrated with Pd nano-particles..
234. R.Q. Guo, J. Nishimura, M. Matsumoto, M. Higashihata, D. Nakamura, J. Suehiro, T. Okada, Aligned growth of ZnO nanowires and lasing in single ZnO nanowire optical cavities, Applied Physics B: Lasers and Optics, Volume 90, Numbers 3-4, Pages 539-542, 2008.03, [URL].
235. R. Q. Guo, J. Nishimura, M. Matsumoto, M. Higashihata, Daisuke Nakamura, Junya Suehiro, T. Okada, Aligned growth of ZnO nanowires and lasing in single ZnO nanowire optical cavities, Applied Physics B: Lasers and Optics, 10.1007/s00340-007-2891-4, 90, 3-4, 539-542, 2008.03, Ordered ZnO nanowire arrays have been fabricated in N2 background gas by catalyst-free nanoparticle-assisted pulsed-laser deposition. A single ZnO nanowire was collected in an electrode gap by dielectrophoresis. Under the optical pumping above an exciting laser (λ=∈355 nm) threshold of ∼ 334 kW/cm2, ultraviolet lasing action in a single ZnO nanowire was observed at room temperature, indicating that the as-synthesized nanowires in pure N2 background gas are of high quality. The crystalline facets of both ends of the nanowire acted to form an optical cavity. Therefore, the mode spacings corresponding to cavity lengths of the respective nanowires were observed in photoluminescence spectra..
236. N. Sano, M. Kinugasa, F. Otsuki, J. Suehiro, Gas sensor using single-wall carbon nanohorns, Advanced Powder Technology, Vol. 18, No. 4, pp. 455–466, 2007.07.
237. Noriaki Sano, Masaru Kinugasa, Fumihiro Otsuki, Junya Suehiro, Gas sensor using single-wall carbon nanohorns, Advanced Powder Technology, 10.1163/156855207781389447, 18, 4, 455-466, 2007.07, We fabricated a gas sensor using single-walled carbon nanohorns (SWNHs) produced by the gas-injected arc-in-water method. This gas sensor consisted of agglomerated SWNHs as a coating film between Al electrodes on a glass substrate and the shift of the electric resistance of this coating film caused by gas adsorption was monitored. Its sensing property was examined for the detection of NH3 and O3 at room temperature. It was confirmed that the electrical resistance of the SWNHs film increases with adsorption of NH3, whereas the adsorption of O3 induced the decrease of the resistance. A model to correlate the gas concentration and the sensing property was proposed focusing on the detection of NH3 based on mono-layer adsorption and a second-order interaction of adsorbed gas molecules for charge transfer..
238. Michihiko Nakano, Masafumi Inaba, Junya Suehiro, Rapid and low-cost amplicon visualization for nucleic acid amplification tests using magnetic microbeads, ANALYST, 10.1039/d0an02349c, 2021.03.
239. M. Inaba, M. Kono, T. Oda, N. Phansiri, M. Nakano, J. Suehiro, Response properties of nitrogen dioxide gas sensors with tin oxide decorated carbon nanotube channel fabricated by two-step dielectrophoretic assembly, AIP ADVANCES, 10.1063/5.0008188, 10, 5, 2020.05.
240. M. Nakano, Z. Ding, M. Inaba, J. Suehiro, DNA-induced changes in traveling wave dielectrophoresis velocity of microparticles, AIP ADVANCES, 10.1063/1.5129725, 10, 1, 2020.01.
241. Zhenhao Ding, Hiromichi Kasahara, Michihiko Nakano, Junya Suehiro, Dielectrophoretic characteristics of microbeads labeled with DNA of various lengths, 8th International Conference on Biomedical Electronics and Devices, BIODEVICES 2015, 185-89, 2015.01, Polymerase chain reaction (PCR) is one of the most sensitive and specific detection methods of bacterial and viral infections. The authors proposed a new electrical technique for rapid detection of DNA amplified by PCR using dielectrophoresis (DEP) of microbeads. The method is based on dramatic alteration of DEP characteristics of microbeads caused by DNA labelling. DNA labeled microbeads are trapped on a microelectrode under the action of positive DEP, whereas pristine microbeads are not. DEP-trapped microbeads can be measured impedimetrically to realize rapid and quantitative detection of the amplified DNA. In this study, it was aimed to reveal how DNA length affects DEP characteristic of DNA-labeled microbeads. Dielectrophoretic crossover from the negative to the positive was measured for microbeads labeled with DNA length in 204 bp, 391 bp and 796 bp. After theoretical fitting of DEP crossover data, it was revealed that the surface conductance increased when the length of labeled DNA increased..
242. Zhenhao Ding, Hiromichi Kasahara, Michihiko Nakano, Junya Suehiro, Dielectrophoretic characteristics of microbeads labeled with DNA of various lengths, 8th International Conference on Biomedical Electronics and Devices, BIODEVICES 2015 BIODEVICES 2015 - 8th International Conference on Biomedical Electronics and Devices, Proceedings; Part of 8th International Joint Conference on Biomedical Engineering Systems and Technologies, BIOSTEC 2015, 10.5220/0005280701850189, 185-189, 2015.01, Polymerase chain reaction (PCR) is one of the most sensitive and specific detection methods of bacterial and viral infections. The authors proposed a new electrical technique for rapid detection of DNA amplified by PCR using dielectrophoresis (DEP) of microbeads. The method is based on dramatic alteration of DEP characteristics of microbeads caused by DNA labelling. DNA labeled microbeads are trapped on a microelectrode under the action of positive DEP, whereas pristine microbeads are not. DEP-trapped microbeads can be measured impedimetrically to realize rapid and quantitative detection of the amplified DNA. In this study, it was aimed to reveal how DNA length affects DEP characteristic of DNA-labeled microbeads. Dielectrophoretic crossover from the negative to the positive was measured for microbeads labeled with DNA length in 204 bp, 391 bp and 796 bp. After theoretical fitting of DEP crossover data, it was revealed that the surface conductance increased when the length of labeled DNA increased..
243. Junya Suehiro, Shinji Yamane, Kiminobu Imasaka, Carbon nanotube-based hydrogen gas sensor electrochemically functionalized with palladium, 6th IEEE Conference on SENSORS, IEEE SENSORS 2007 The 6th IEEE Conference on SENSORS, IEEE SENSORS 2007, 10.1109/ICSENS.2007.4388458, 554-557, 2007.12, Palladium (Pd) has been widely employed for conventional hydrogen sensors due to the catalytic nature. Pd has been incorporated also with carbon nanotube (CNT) gas sensors for hydrogen sensing. In this study, a liquid-phase electrochemical reaction was proposed to realize a simple and inexpensive fabrication method of a Pd-functionalized CNT hydrogen sensor. The single-walled CNTs were trapped onto a microelectrode under positive dielectrophoresis. The CNT-retaining microelectrode was immersed in a palladium acetate solution together with a graphite rod. DC voltage was applied between the microelectrode (cathode) and the graphite rod (anode) so that palladium acetate could be reduced and catalytic Pd could be electrodeposited on the CNT surface. The CNT sensor could reversibly respond to hydrogen gas in the air in the range of 0.01 % -1 % concentration at room temperature. It was also demonstrated that the Pdfunctionalized CNT gas sensor could be fabricated just by dipping the CNT-retaining microelectrode into an aqueous Pd salt solution without applying DC voltage (electroless redox reaction)..
244. Guangbin Zhou, Manabu Imamura, Junya Suehiro, Masanori Hara, A dielectrophoretic filter for separation and collection of fine particles suspended in liquid, 37th IAS Annual Meeting and World Conference on Industrial applications of Electrical Energy Conference Record - IAS Annual Meeting (IEEE Industry Applications Society), 2, 1404-1411, 2002.01, Dielectrophoresis (DEP) is the electrokinetic motion of dielectrically polarized particles in nonuniform electric fields. DEP has found many useful technological applications including separation, levitation and characterization of dielectric particles such as biological cells. In this study, the authors propose a new type of liquid filter, which utilizes dielectrophoretic force (DEP force) to capture fine particles suspended in liquid. The DEP filter consists of an electrode system that is filled up with many dielectric particles. These particles modify the electric field distribution in the electrode system so that strong DEP force is generated on their surfaces. If the DEP force is stronger than drag force exerted by liquid flow in the filter, the suspended particles can be trapped and eliminated from the flowing liquid. The DEP filter can control trapping and releasing process just by changing electrode energizing ac signal and the resultant DEP force. It was experimentally confirmed that the DEP filter could continuously eliminate yeast cells suspended in water. The cell density decreased from 106 cells/mL to 101 cells/mL in about an hour. The electrical conductivity of the medium was a crucial parameter that influenced the liquid temperature by Joule heating and DEP force. Further-more, the selective separation of viable and nonviable yeast cells was demonstrated by utilizing viability dependency of the DEP force..
245. J. Suehiro, D. Noutomi, R. Hamada, M. Hara, Selective detection of bacteria using dielectrophoretic impedance measurement method combined with antigen-antibody reaction, 36th IAS Annual Meeting -Conference Record of the 2001 Industry Applications Conference Record - IAS Annual Meeting (IEEE Industry Applications Society), 3, 1950-1955, 2001.01, This paper describes a new selective detection method of microorganisms such as bacteria by using dielectrophoresis together with antigen-antibody reaction. The authors had proposed the dielectrophoretic impedance measurement (DEPIM) method, which realized fast and easy detection of biological cells suspended in aqueous medium. However, highly selective detection of bacteria according to their species or strain, was rather difficult by utilizing only the dielectric property variation according to the cell type. In this paper, we propose a selective bacteria detection method using DEPIM combined with antigen-antibody reaction, which is widely used in clinical diagnosis. Two kinds of combinations of DEPIM with immunoassay are tested. In one method, agglutination of bacteria is employed to increase dielectrophoretic force. The other method utilizes antibody molecules immobilized onto the microelectrode surface. It is experimentally confirmed that both methods can leave peculiar bacteria on the electrode surface after preliminary dielectrophoretic enrichment. Furthermore, agglutinated bacteria can be electrically detected by residual increase of the electrode conductance. These findings suggest that target bacteria may be selectively detected from mixture of various bacteria by the improved DEPIM technique..
246. K. Imasaka, Koji Takahashi, Junya Suehiro, M. Hara, Polarity effect on the behavior of gas-puff z-pinch plasma produced by IPP system, 28th IEEE International Conference on Plasma Science and 13th IEEE International Pulsed Power Conference, PPPS 2001 PPPS 2001 - Pulsed Power Plasma Science 2001, 10.1109/PPPS.2001.01002207, 1, 757-760, 2015.01, Hot spots produced by gas-puff z-pinch plasma which are high energy density plasma regions radiate intensive soft x-rays. Gas-puff z-pinch is expected to industrial applications such as soft x-ray lithography, microscopy and laser. In these cases, the scattering of hot spots is important when the gas-puff z-pinch plasma is used as a point source of soft x-ray. Previous results in our study showed the reduction of radial displacement of hot spots in positive voltage shots by using an IPP (Inductive Pulsed Power) system. In this paper, the voltage polarity effects on the gaspuff z-pinch plasma behavior, spatial distribution of hot spots and soft x-ray emission are described..
247. K. Imasaka, K. Takahashi, J. Suehiro, M. Hara, Polarity effect on the behaviour of gas puff z-pinch plasma produced by IPP system, 28th IEEE International Conference on Plasma Science/ 13th IEEE International Pulsed Power Conference IEEE International Conference on Plasma Science, P1C18, 2001.01, Hot spots produced by gas-puff z-pinch plasma which are high energy density plasma regions radiate intensive soft x-rays. Gas-puff z-pinch is expected to industrial applications such as soft x-ray lithography, microscopy and laser, in these cases, the scattering of hot spots is important when the gas-puff z-pinch plasma is used as a point source of soft x-ray. Previous results in our study showed the reduction of radial displacement of hot spots in positive voltage shots by using IPP(inductive pulsed power) system. In this paper, the voltage polarities effect on the z-pinch plasma behaviour, soft x-ray emission and spatial distribution of hot spots are described..
248. Nisarut Phansiri, Daichi Maenosono, Takumi Furumoto, Hidefumi Sato, Michihiko Nakano, Junya Suehiro, Detection of CF4 Gas Using a Nanomaterial-Based Gas Sensor Fabricated by Dielectrophoresis, 21st International Symposium on High Voltage Engineering, ISH 2019 Proceedings of the 21st International Symposium on High Voltage Engineering - Volume 1, 10.1007/978-3-030-31676-1_46, 481-488, 2019.11, Partial and arc discharge in gas insulated switchgear (GIS), such as a switching component or circuit breaker, can lead decomposition gas generation of sulphur hexafluoride (SF6), which is generally used as an electrical insulation medium. The authors had demonstrated that SF6 decomposition products, such as HF, SO2, SOF2, can be detected by using a carbon nanotube (CNT) gas sensor, which was fabricated by dielectrophoresis. In this study, we selected carbon tetrafluoride (CF4) as a target decomposition gas to be detected by nanomaterial-based gas sensors. Because CF4 is hard to be removed by using a molecular sieve or absorbent, the decomposition product accumulates in a long time and can be used for GIS diagnosis. Three kinds of semiconducting nanomaterial, carbon nanotube, SnO2 nanoparticle, ZnO nanowires, were integrated on a microelectrode by dielectrophoresis respectively to fabricate a gas sensor. It was found that SnO2 gas sensor showed the highest response to CF4 gas at 1% concentration in SF6. The conductance of the SnO2 sensor gradually decreased with elapsed time after exposure to the CF4 gas depending on the operating temperature..
249. Hiroki Hayashi, Michihiko Nakano, Junya Suehiro, Detection of acetylene dissolved in insulation oil using pt-decorated ZnO gas sensor, 2016 IEEE Region 10 Conference, TENCON 2016 Proceedings of the 2016 IEEE Region 10 Conference, TENCON 2016, 10.1109/TENCON.2016.7848262, 1485-1488, 2017.02, Oil-insulated transformer is one of the important equipments in the current high-voltage transmission system and it has contributed to the reduction of transmission power loss. However, abnormal phenomena, such as over-heat, discharge and so on, would appear in the oil-insulated transformer. Currently, gas chromatography is the most common diagnosis technique for the transformer diagnosis which is not suitable for rapid detection in the operation field. Therefore, it is necessary to develop a more efficient diagnostic method to identify the abnormal phenomena. In this paper, we demonstrated a platinum modified ZnO gas sensor, which was fabricated by dielectrophoresis (DEP) integration method, to detect acetylene gas dissolved in the insulating oil after arc discharge occurred inside the insulating oil. In addition, the influence of discharge voltage to sensor response was investigated and the response was compared to quantitative analysis obtained by gas chromatography. Relationship between the sensor response and the concentration of acetylene gas dissolved suggested a possibility of quantitative analysis of acetylene by platinum (Pt) decorated ZnO sensor..
250. Yuki Inoue, Ryoji Obara, Michihiko Nakano, Junya Suehiro, Concentration of bacteria in high conductive medium using negative dielectrophoresis, 2015 IEEE International Conference on Industrial Technology, ICIT 2015, 10.1109/ICIT.2015.7125592, 2015-June, June, 16 June 2015, 3336-3340, Article number 7125592, 2015.06, Rapid and sensitive detection of pathogenic bacteria has been an important concern in various fields such as bioscience research, medical diagnosis and hazard analysis in the food industry. The requirement for highly efficient bacterial detection has pointed to the need for new and innovative sample concentration technologies. In this study, a new microfluidic device was demonstrated to enable concentration of bacteria by using negative dielectrophoresis (n-DEP) in high conductive medium. A special design of the electrode system, which was covered with patterned dielectric films, was tested in order to control the electric field distribution in the device so that n-DEP force could drive cells to a point for concentration as well as Joule heating of the suspension medium could be suppressed to avoid heat-induced cell damage. The electrode design was optimized using numerical calculation results of cell motion trajectories and the suspension medium temperature in the device. It was experimentally proved that proposed microfluidic device could concentrate E. coli cells in a continuous flow of cell suspension..
251. Hiromichi Kasahara, Zhenhao Ding, Michihiko Nakano, Junya Suehiro, Effect of DNA length on dielectrophoretic characteristics of DNA-labeled microbeads, 2015 IEEE International Conference on Industrial Technology, ICIT 2015, 10.1109/ICIT.2015.7125593, 2015-June, June, 16 June 2015, 3341-3346, Article number 7125593, 2015.06, Polymerase chain reaction (PCR) is a powerful tool for diagnostic procedures in bacterial and viral infections. We have developed a new electrical technique for rapid detection of DNA amplified by PCR using dielectrophoresis (DEP) of microbeads that are chemically labeled with the amplicons. The DNA immobilization on the microbeads alters their DEP behavior in such a way that they are trapped on a microelectrode under the action of positive DEP, whereas pristine microbeads are not. Combining the dramatic alteration in DEP characteristics with impedance measurement leads to rapid and quantitative detection of amplicons. The method is based on the surface conductivity dependence of microbeads DEP characteristics. It was expected that the surface conductivity would depend on the length of DNA fragments immobilized on a microbeads. In this study, it was found that the crossover frequency was dependent on the length of DNA..
252. Yuki Kawabe, Li Li, Michihiko Nakano, Suehiro Junya, Dielectrophoretic fabrication and chacterization of ZnO nanowire-based acetylene gas sensor, 2015 IEEE International Conference on Industrial Technology, ICIT 2015, 10.1109/ICIT.2015.7125298, 2015-June, June, 16 June 2015, 1433-1437, Article number 7125298, 2015.06, Wide-gap semiconductors with nanostructures such as nanoparticles, nanorods, nanowires are promising as a new type of gas sensor. Recently, ZnO (zinc oxide) nano-structures have been extensively investigated for acetylene (C2H2) gas sensing device applications. In this paper, a new fabrication method of a C2H2 gas sensor based on ZnO nanowires using dielectrophoresis is demonstrated. Dielectrophoresis (DEP) is the electrokinetic motion of dielectrically polarized materials in nonuniform electric fields. ZnO nanowires were trapped in the microelectrode gap where the electric field became higher. The trapped ZnO nanowires were aligned along the electric field line and bridged the electrode gap. Upon exposure to C2H2 gas, the conductance of the DEP-trapped ZnO nanowires increased. The ZnO nanowire gas sensor response to C2H2 gas was dependent on the temperature and the maximum response was obtained at 250 °C. It was confirmed that the sensor response was considerably improved by electrochemically decorating the ZnO nanowires with platinum nanoparticles..
253. Hideaki Watanabe, Hiroki Komure, Michihiko Nakano, Junya Suehiro, Solution-based fabrication of carbon nanotube gas sensor by using dielectrophoresis and spin-column chromatography , 2013 International Conference on Materials Science and Chemical Engineering, MSCE 2013, 10.4028/www.scientific.net/AMR.699.915, 699, 915-920, 2013.02.
254. Ryuta Shou, Kazuyoshi Hata, Michihiko Nakano, Junya Suehiro, Chemical detection of SF6 decomposition products generated by AC and DC corona discharges using a carbon nanotube gas sensor, 2013 International Conference on Materials Science and Chemical Engineering, MSCE 2013, 10.4028/www.scientific.net/AMR.699.909, 699, 909-914, 2013.02.
255. Takafumi Hisajima, Lina Mao, Kenta Shinzato, Michihiko Nakano, Junya Suehiro, Three dimensional bacteria concentration by negative dielectrophoresis, 2013 International Conference on Materials Science and Chemical Engineering, MSCE 2013, 10.4028/www.scientific.net/AMR.699.251, 699, 251-256, 2013.02.
256. Yu Kitamura, Hiroaki Tone, Michihiko Nakano, Junya Suehiro, Fabrication of a large-scale conductive composite film containing electrically aligned carbon nanotubes, 2013 International Conference on Materials Science and Chemical Engineering, MSCE 2013, 10.4028/www.scientific.net/AMR.699.513, 699, 513-518, 2013.02.
257. Michihiko Nakano, Ryoji Obara, Zhenhao Ding, Junya Suehiro, Detection of norovirus and rotavirus by dielectrophoretic impedance measurement, 2013 7th International Conference on Sensing Technology, ICST 2013 2013 7th International Conference on Sensing Technology, ICST 2013, 10.1109/ICSensT.2013.6727678, 374-378, 2013.12, Aim of this paper is to demonstrate virus detection by dielectrophoretic impedance measurement (DEPIM). DEPIM consists of two processes of dielectrophoretic trapping of target particles and measuring impedance change with increasing the number of trapped particles. DEPIM has been used to detect bacteria suspended in aqueous solution. In this study, norovirus and rotavirus, which cause gastroenteritis in human, were used as the target viruses. As the results, 50 ng/ml of norovirus and 10 ng/ml of rotavirus were detected within 100 s..
258. Ryoji Obara, Zhenhao Ding, Kenta Shinzato, Michihiko Nakano, Junya Suehiro, Higher throughput of optical detection of bacteria concentrated by negative dielectrophoresis, 2013 7th International Conference on Sensing Technology, ICST 2013 2013 7th International Conference on Sensing Technology, ICST 2013, 10.1109/ICSensT.2013.6727658, 275-278, 2013.12, The authors have proposed a new method to concentrate bacteria flowing in a microchannel by using negative dielectrophoretic force generated by using a thin dielectric layer. In this study, it was demonstrated application of the bacteria concentration to improve throughput of optical detection of bacteria in microchannel..
259. M. Fujioka, H. Watanabe, Y. Martin, M. Nakano, J. Suehiro, Separation and enrichment of semiconducting carbon nanotubes and its application to highly sensitive carbon nanotube gas sensor, 2011 IEEE Nanotechnology Materials and Devices Conference, NMDC 2011 2011 IEEE Nanotechnology Materials and Devices Conference, NMDC 2011, 10.1109/NMDC.2011.6155387, 403-407, 2011.12, We have previously demonstrated a fabrication method of single-walled carbon nanotubes (SWCNTs) based gas sensor by employing dielectrophoresis. Because this method uses the SWCNTs that are synthesized in bulk, it is a cheaper and more flexible method than that of on-site synthesized. This method can quantify the amount of trapped nanotubes on a real time basis by monitoring the electrical impedance of the sensor simultaneously with its fabrication. In this study, semiconducting SWCNTs, which served as transducer in gas detection, were separated from commercially available mixture of semiconducting and metallic ones, and were further enriched by using a spin column and dextran-based gel. The separation and enrichment of the semiconducting SWCNTs were confirmed by measuring their optical and electrical properties. The CNT gas sensor fabricated using separated semiconducting SWCNTs was highly sensitive against nitrogen dioxide gas, - more sensitive by two times than that fabricated using the pristine SWCNTs mixture..
260. M. Hara, Y. Maeda, Y. Nakagawa, J. Suehiro, S. Yamada, DC breakdown voltage characteristics in the presence of metallic particles in saturated liquid helium, 2005 IEEE International Conference on Dielectric Liquids, ICDL 2005, 373-376, 2005.01, This paper deals with breakdown voltage characteristics of saturated liquid helium, in the presence of a metallic particle in shape of needle or sphere to obtain insulation design data for the pool-cooled low temperature superconducting coil and to find the factors dominating the breakdown voltage. The results show that the lowest breakdown voltage appears at a free needle particle which produces bubble-generation, rich initial electrons and high stress electric field..
261. W. Ding, R. Hayashi, J. Suehiro, K. Imasaka, M. Hara, Observation of dynamic behavior of PD-generated SF6 decompositions using carbon nanotube gas sensor, 2005 Conference on Electrical Insulation and Dielectric Phenomena, CEIDP '05 2005 Annual Report Conference on Electrical Insulation and Dielectric Phenomena, CEIDP '05, 10.1109/CEIDP.2005.1560744, 561-564, 2005.01, The authors had proposed a new detection method for partial discharge (PD) occurring in sulfur hexafluoride (SF6) gas using a carbon nanotube (CNT) gas sensor. In the previous study, we had investigated the dependency of gas sensor response on applied voltage and gas sensor position. In this paper, a series of experiments was performed to observe dynamic behavior of decomposition gas using the CNT gas sensor. The gas sensor responses to PD under several SF6 gas pressures were measured. It was found that the sensor response normalized by PD power increased almost linearly with the gas pressure. The result is useful to understand the mechanism how the gas pressure influences the generation and diffusion of decomposition gas. Effects of absorbent placed inside the discharge chamber were also investigated. Finally, the gas sensor responses were measured with a time interval after PD was extinguished to check if an offline diagnosis was possible. Although the sensor response decreased with elapsed time after PD was extinguished, it was still possible to detect the residual decomposition gas using the CNT gas sensor..
262. Koh ichi Sakai, Dan Labrado Abella, Junya Suehiro, Noriyuki Hayashi, Masanori Hara, Mode of free-conducting particle motion and particle-triggered breakdown mechanism in non-uniform field gaps, 2000 IEEE Conference on Electrical Insulation and Dielectric Phenomena Conference on Electrical Insulation and Dielectric Phenomena (CEIDP), Annual Report, 1, 389-392, 2000.01, This paper deals with free-conducting particle motion and particle-triggered breakdown mechanism in AC and DC electric fields between non-parallel plane electrodes. Particle motion is divided into several modes, and particle-triggered breakdown mechanisms are discussed for each motion mode theoretically and experimentally. The obtained results suggest that several types of particle-triggered breakdown can occur in Gas Insulated System (GIS)..
263. M. Nakano, H. Kasahara, Z. Ding, J. Suehiro, Selective detection of DNA with different length using microbeads-based dielectrophoresis and impedance measurement, 18th International Conference on Miniaturized Systems for Chemistry and Life Sciences, MicroTAS 2014 18th International Conference on Miniaturized Systems for Chemistry and Life Sciences, MicroTAS 2014, 2101-2103, 2014.01, We proposed a new DNA detection method based on microbeads dielectrophoresis (DEP). In the method, the DNA-labeled microbeads are electrically detected. Only the DNA-labeled microbeads are trapped on a microelectrode by positive DEP, whereas the pristine ones are repelled In this paper, size selective detection of DNA using the method is described. It was found that the frequency response of DEP of the DNA-labeled microbeads depended on the DNA length. At high frequency only the long DNA-labeled microbeads were trapped, whereas the short DNA-labeled microbeads were repelled. This phenomena can realize selective detection of DNA with different length..
264. I. Myojo, M. Nakano, J. Suehiro, T. Iwaya, Y. Ishida, Electric field-induced alignment of thermal conductive filler in acrylic polymer for enhanced thermal conductivity, 18th European Conference on Composite Materials, ECCM 2018 ECCM 2018 - 18th European Conference on Composite Materials, 2020.01, A recent trend in the integration of electric power devices has caused problems of heat management because of high heat generation from the device. Therefore, studies of new materials having high thermal conductivity have been motivated. Polymer-based composites have been paid attention because of its flexibility and energy-saving productivity. In this study, nitride fillers, which have excellent thermal conductivity and electric insulating property, were used as a component of the polymer-based composites. To achieve high thermal diffusion with a small fraction of the fillers, the fillers were aligned by an electric field. Aluminum nitride (AlN) or boron nitride (BN) particles were dispersed in an acrylic polymer. An array of wire electrodes was used to form widely spread electric field. In-plane and through-plane alignment were carried out with varying arrangements of the electrode arrays. Thermal diffusivity in-plane direction of the AlN and BN composites increased about 1.2- and 1.7-fold by aligning the fillers as comparing with those without the alignment, respectively. To align the filler in through-plane detection, several kinds of the electrode arrangements were examined. As the best result, the through-plane thermal diffusivity of the aligned AlN composites became 30-fold compared to that without the alignment..
265. Zhenhao Ding, Kenichi Ida, Kenya Matsuda, Michihiko Nakano, Junya Suehiro, DNA detection microfluidic device based on negative dielectrophoresis of DNA labeled microbeads, 16th IEEE SENSORS Conference, ICSENS 2017 IEEE SENSORS 2017 - Conference Proceedings, 10.1109/ICSENS.2017.8234345, 2017-December, 1-3, 2017.12, In this study, we focus on the alteration of negative dielectrophoresis (n-DEP) caused by small amount of DNA labeling on the microbeads and propose a new design of microfluidic device for more sensitive DNA detection. In previous study, we proposed a new electrical technique for rapid detection of DNA amplified by polymerase chain reaction (PCR). The method is based on dramatic alteration of dielectrophoresis (DEP) characteristics of microbeads caused by DNA labeling. The DNA labeling of microbeads alters their DEP behavior in such a way that they are trapped on a microelectrode under the action of positive DEP (p-DEP), whereas bare microbeads are not, due to the n-DEP. However, this method requires at least 105 copies of DNA labelling on a microbead to alter the DEP behavior of microbeads from negative to positive. As a result, we are able to distinguish bare microbeads and microbeads labeled with DNA at DNA to microbead ratio of 3×103: 1 and 3×104: 1, based on the n-DEP alteration..
266. R. Hamada, H. Takayama, Y. Shonishi, T. Hisajima, L. Mao, M. Nakano, J. Suehiro, Improvement of dielectrophoretic impedance measurement method by bacterial concentration utilizing negative dielectrophoresis, 16th Conference in the Biennial Sensors and Their Applications Journal of Physics: Conference Series, 10.1088/1742-6596/307/1/012031, 307, 1, 2011.01, In this study, the concept design for the improvement of the bacterial detection sensitivity of the DEPIM (Dielectrophoretic Impedance Measurement) method has been proposed. The cells in the micro-chamber are repelled and concentrated by n-DEP (negative dielectrophosesis). The concentrated cells are captured by p-DEP (positive DEP) and detected by measuring the change in the electrical impedance. The numerical simulations and the preliminary test were performed to investigate the effectiveness of the n-DEP concentration. When n-DEP concentration was employed, the increase in the rate of the conductance became approximately two times higher than that obtained without n-DEP..
267. K. Imasaka, Y. Kawauchi, K. Kawazoe, J. Suehiro, M. Hara, Numerical and experimental study of behavior of gas-puff z-pinch plasma produced by inductive pulsed power generator, 12th International Conference on High-Power Particle Beams, BEAMS 1998 BEAMS 1998 - Proceedings of the 12th International Conference on High-Power Particle Beams, 10.1109/BEAMS.1998.816929, 611-614, 1998.01, Magnetohydrodynamic (MHD) instabilities, such as kink and sausage instabilities, appeared on the gas-puff z-pinch plasma during the pinching process prevent spatial stability of hot spots, which are high energy density plasma regions produced by those instabilities on the z-pinch plasma column locally. Spatial stabilization of hot spots in the axial direction is very important to have practical applications. In this study, radius and velocity of the inwardly tilted gas-puff z-pinch plasma during the compression and efficiency of energy conversion were analyzed theoretically by solving one dimensional snowplow model (1D-SPM) and circuit equations which considered inductive pulsed power generator. Those results were compared with experimental results measured with framing photograph of the pinching plasma. Efficiency of energy conversion of an input energy supplied from the inductive pulsed power generator into kinetic energy of the z-pinch plasma and final pinching velocity of the plasma exceeded that in comparison with fast bank method. These results received benefit from the fast and large pinching current transferred from the inductive pulsed power generator..
268. Y. Khan, S. Okabe, J. Suehiro, M. Hara, Particle-triggered breakdown characteristics around spacer under lightning impulse voltage superimposed on pre-stressed dc, Vol.124, pp.549-552, 2004.07.