Daisuke Sakurai | Last modified date：2022.06.22 |

Graduate School

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##### https://kyushu-u.pure.elsevier.com/en/persons/daisuke-sakurai

Reseacher Profiling Tool Kyushu University Pure

Academic Degree

PhD

Field of Specialization

Topological Analysis, Visualization

Total Priod of education and research career in the foreign country

02years07months

Research

**Research Interests**

- Computational geometry, topological analysis, visualization

keyword : Computational geometry, topological analysis, visualization

2019.05～2022.03.

**Academic Activities**

**Papers**

1. | Makoto Hasegawa, Daisuke Sakurai, Aki Higashijima , Ichiro Niiya, Keiji Matsushima, Kazuaki Hanada, Hiroshi Idei, Takeshi Ido, Ryuya Ikezoe, Takumi Onchi, Kengo Kuroda, Towards automated gas leak detection through cluster analysis of mass spectrometer data, Fusion Engineering and Design, 180, 1-9, 2022.06, [URL], In order to generate high-performance plasma for future fusion power generation, it is desirable to keep high quality vacuum during experiment. Mass spectrometer is commonly used to monitor the vacuum quality and to record the amount of atoms and molecules in the vacuum vessel. Leak is the most serious accident to avoid that can nullify an experiment and even harm researchers. Detecting leaks are ever more important since it can be easily overlooked, e.g., when the deterioration in the vacuum degree is modest. This forces the researcher to carefully observe the vacuum and mass spectrometer data. This article presents a way to suggest potential leaks in the vacuum vessel by analyzing mass spectrometer data. This is done by utilizing the Euclidean distance between composition ratios at different times for the clustering using the daily composition ratio. We show that our cluster analysis is an effective way of separating these two cases, which results in a semi-automatic determination of leaks is more efficient than the current norm, which is to check many measures to find a small abnormality in the data manually. We plan further model improvements for long-term evaluation.. |

2. | Shigeo Takahashi, Daisuke Sakurai, Miyuki Sasaki, Hiroko M. Miyamura, Yukihisa Sanada, Visual Analysis of Geospatial Multivariate Data for Investigating Radioactive Deposition Processes, The Visual Computer, 37, 12, 3039-3050, 2021.07. |

3. | Daisuke Sakurai, Osamu Saeki, Hamish Carr, Hsiang-Yun Wu, Takahiro Yamamoto, David Duke, Shigeo Takahashi, Interactive Visualization for Singular Fibers of Functions f: R3 → R2, IEEE Transactions on Visualization and Computer Graphics, https://doi.org/10.1109/TVCG.2015.2467433, 22, 1, 945-954, 2016.01, Scalar topology in the form of Morse theory has provided computational tools that analyze and visualize data from scientific and engineering tasks. Contracting isocontours to single points encapsulates variations in isocontour connectivity in the Reeb graph. For multivariate data, isocontours generalize to fibers - inverse images of points in the range, and this area is therefore known as fiber topology. However, fiber topology is less fully developed than Morse theory, and current efforts rely on manual visualizations. This paper presents how to accelerate and semi-automate this task through an interface for visualizing fiber singularities of multivariate functions R3 → R2. This interface exploits existing conventions of fiber topology, but also introduces a 3D view based on the extension of Reeb graphs to Reeb spaces. Using the Joint Contour Net, a quantized approximation of the Reeb space, this accelerates topological visualization and permits online perturbation to reduce or remove degeneracies in functions under study. Validation of the interface is performed by assessing whether the interface supports the mathematical workflow both of experts and of less experienced mathematicians.. |

4. | Daisuke Sakurai, Kenji Ono, Hamish Carr, Jorji Nonaka, and Tomohiro Kawanabe, Flexible Fiber Surface : A Reeb-Free Approach, Topological Methods in Data Analysis and Visualization V, 2020.10, The fiber surface generalizes the popular isosurface to multi-fields, so that pre-images can be visualized as surfaces. As with the isosurface, however, the fiber surface suffers from visual occlusion. We propose to avoid such occlusion by restricting the components to only the relevant ones with a new component-wise flexing algorithm. The approach, flexible fiber surface, generalizes the manipulation idea found in the flexible isosurface for the fiber surface. The flexible isosurface in the original form, however, relies on the contour tree. For the fiber surface, this corresponds to the Reeb space, which is challenging for both the computation and user interaction. We thus take a Reeb-free approach, in which one does not compute the Reeb space. Under this constraint, we generalize a few selected interactions in the flexible isosurface and discuss the implication of the restriction.. |

5. | Daisuke Sakurai, Takahiro Yamamoto, Visually Evaluating the Topological Equivalence of Bounded Bivariate Fields, Topological Methods in Visualization VI - Theory, Applications, and Software, 181-196, 2021.11, We apply visualization to evaluating a new topological equivalence rela-tion, which we call thetopologicalB+-equivalence. It has been used in our separate,yet ongoing, study in mathematics. The equivalence is a building block for thetopological study of maps of bounded manifolds into the plane (akabounded bivari-ate fields). In that study, we have introduced a few invariants that approximate theequivalence, which is hard to treat directly. In this chapter dedicated to the visual-ization community, we show that visualizing the Reeb space gives us a near-instantway of evaluating the invariants. The process has traditionally required an unpre-dictable amount of time due to manual analysis of high-order polynomials, whichwas necessary to obtain the invariant values. Our Reeb space visualization revealsthe topological information necessary for evaluating the invariants, and, doing so,the topologicalB+-equivalence itself. Previously, the visualization had been foundto serve as an introductory learning tool for studying examples of singular fibers.The present article goes further to demonstrate professional use cases.. |

6. | Daisuke Sakurai and Takahiro Yamamoto, Investigating Topological Invariants in Bounded Bivariate Fields, Proceedings of TopoInVis 2019, 2019.06. |

7. | Tomohiro Kawanabe, Jorji Nonaka, Daisuke Sakurai, Kazuma Hatta, Shuhei Okayama and Kenji Ono, Showing Ultra-High-Resolution Images in VDA-Based Scalable Displays, Cooperative Design, Visualization, and Engineering: 16th International Conference, CDVE 2019, Mallorca, Spain, October 6–9, 2019, Proceedings, 2019.10. |

**Presentations**

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