Updated on 2024/04/10

写真a

 
Obayashi Ippei
 
Organization
Center for Artificial Intelligence and Mathematical Data Science Professor
Position
Professor
External link

Degree

  • Ph. D. in science (mathematics) ( 2010.3   Kyoto University )

Research Interests

  • Topological data analysis

  • Persistent homology

  • Applied mathematics

  • Dynamical systems

Research Areas

  • Natural Science / Basic mathematics  / 位相的データ解析

  • Natural Science / Applied mathematics and statistics  / 位相的データ解析

  • Natural Science / Mathematical analysis  / 力学系

Education

  • Kyoto University   大学院理学研究科   数学・数理解析専攻

    2006.4 - 2010.3

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    Country: Japan

    Notes: 博士後期課程

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  • Kyoto University   大学院理学研究科   数学・数理解析専攻

    2004.4 - 2006.3

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    Country: Japan

    Notes: 修士課程

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  • Kyoto University   理学部  

    2000.4 - 2004.3

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Research History

  • Okayama University   Center for Artificial Intelligence and Mathematical Data Science   Professor

    2021.4

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  • RIKEN   RIKEN Center for advanced intelligence   Research Scientist

    2018.6 - 2021.3

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  • Tohoku University   Advanced Institute for Materials Research   Associate Professor

    2018.4 - 2018.5

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  • Tohoku University   Advanced Institute for Materials Research   Assistant Professor

    2015.4 - 2018.3

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  • Kyoto University   Graduate School of Science   Postdoctral researcher

    2010.4 - 2015.3

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Professional Memberships

  • The Japan Society for Industrial and Applied Mathematics

    2019.11

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  • THE MATHEMATICAL SOCIETY OF JAPAN

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Committee Memberships

  • 日本応用数理学会   位相的データ解析研究部会 主査  

    2021.4   

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    Committee type:Academic society

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Papers

  • Atomic and Electronic Structure in MgO–SiO2

    Yuta Shuseki, Shinji Kohara, Tomoaki Kaneko, Keitaro Sodeyama, Yohei Onodera, Chihiro Koyama, Atsunobu Masuno, Shunta Sasaki, Shohei Hatano, Motoki Shiga, Ippei Obayashi, Yasuaki Hiraoka, Junpei T. Okada, Akitoshi Mizuno, Yuki Watanabe, Yui Nakata, Koji Ohara, Motohiko Murakami, Matthew G. Tucker, Marshall T. McDonnell, Hirohisa Oda, Takehiko Ishikawa

    The Journal of Physical Chemistry A   2024.1

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    Publishing type:Research paper (scientific journal)   Publisher:American Chemical Society (ACS)  

    DOI: 10.1021/acs.jpca.3c05561

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  • Sharp changes in fractal basin of attraction in passive dynamic walking Reviewed

    Kota Okamoto, Nozomi Akashi, Ippei Obayashi, Kohei Nakajima, Hiroshi Kokubu, Kei Senda, Kazuo Tsuchiya, Shinya Aoi

    Nonlinear Dynamics   2023.11

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

    Abstract

    A passive dynamic walker is a mechanical system that walks down a slope without any control, and gives useful insights into the dynamic mechanism of stable walking. This system shows specific attractor characteristics depending on the slope angle due to nonlinear dynamics, such as period-doubling to chaos and its disappearance by a boundary crisis. However, it remains unclear what happens to the basin of attraction. In our previous studies, we showed that a fractal basin of attraction is generated using a simple model over a critical slope angle by iteratively applying the inverse image of the Poincaré map, which has stretching and bending effects. In the present study, we show that the size and fractality of the basin of attraction sharply change many times by changing the slope angle. Furthermore, we improved our previous analysis to clarify the mechanisms for these changes and the disappearance of the basin of attraction based on the stretching and bending deformation in the basin formation process. These findings will improve our understanding of the governing dynamics to generate the basin of attraction in walking.

    DOI: 10.1007/s11071-023-08913-w

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    Other Link: https://link.springer.com/article/10.1007/s11071-023-08913-w/fulltext.html

  • Structural-Order Analysis Based on Applied Mathematics

    Motoki Shiga, Ippei Obayashi

    The Materials Research Society Series   265 - 288   2023.10

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

    DOI: 10.1007/978-981-99-5235-9_11

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  • Analysis of Magnetization Reversal Process of Non-Oriented Electromagnetic Steel Sheet by Extended Landau Free Energy Model Reviewed

    Taniwaki, Michiki, Alexandre, Foggiatto Lira, Mitsumata, Chiharu, Yamazaki, Takahiro, Obayashi, Ippei, Hiraoka, Yasuaki, Igarashi, Yasuhiko, Mizutori, Yuta, Hossein, Sepehri Amin, Ohkubo, Tadakatsu, Kotsugi, Masato

    IEEE   2023.9

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    Language:English   Publishing type:Research paper (international conference proceedings)   Publisher:Michiki Taniwaki Tokyo Univ. of Sci. Foggiatto Lira Alexandre Tokyo Univ. of Sci. Chiharu Mitsumata Tokyo Univ. of Sci. Takahiro Yamazaki Tokyo Univ. of Sci. Ippei Obayashi Okayama Univ. Yasuaki Hiraoka Kyoto Univ. Yasuhiko Igarashi Tsukuba Univ. Yuta Mizutori Tsukuba Univ. Sepehri Amin Hossein NIMS Tadakatsu Ohkubo NIMS Masato Kotsugi Tokyo Univ. of Sci.  

    We analyzed the magnetization reversal process of non-oriented electromagnetic steel sheets using the extended Landau free energy model (eX-GL). The model is a new analysis approach that can connect the macroscopic function and the microscopic structure beyond the hierarchy by using data science technique. It can treat grain boundaries and defects, which frequently occur in actual magnetic materials, furthermore it can visualize the inhibiting factors of magnetization reversal back to the original image. As a result, we could draw the experimental energy landscape of an electromagnetic steel sheet for the first time, and the magnetic domain walls that contribute to magnetization reversal was selectively visualized.

    DOI: 10.1109/INTERMAGShortPapers58606.2023.10228817

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  • Persistent homology-based descriptor for machine-learning potential of amorphous structures Reviewed

    Emi Minamitani, Ippei Obayashi, Koji Shimizu, Satoshi Watanabe

    The Journal of Chemical Physics   159 ( 8 )   2023.8

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

    High-accuracy prediction of the physical properties of amorphous materials is challenging in condensed-matter physics. A promising method to achieve this is machine-learning potentials, which is an alternative to computationally demanding ab initio calculations. When applying machine-learning potentials, the construction of descriptors to represent atomic configurations is crucial. These descriptors should be invariant to symmetry operations. Handcrafted representations using a smooth overlap of atomic positions and graph neural networks (GNN) are examples of methods used for constructing symmetry-invariant descriptors. In this study, we propose a novel descriptor based on a persistence diagram (PD), a two-dimensional representation of persistent homology (PH). First, we demonstrated that the normalized two-dimensional histogram obtained from PD could predict the average energy per atom of amorphous carbon at various densities, even when using a simple model. Second, an analysis of the dimensional reduction results of the descriptor spaces revealed that PH can be used to construct descriptors with characteristics similar to those of a latent space in a GNN. These results indicate that PH is a promising method for constructing descriptors suitable for machine-learning potentials without hyperparameter tuning and deep-learning techniques.

    DOI: 10.1063/5.0159349

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  • Field Choice Problem in Persistent Homology Reviewed

    Ippei Obayashi, Michio Yoshiwaki

    Discrete & Computational Geometry   70 ( 3 )   645 - 670   2023.8

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

    Abstract

    This paper tackles the problem of coefficient field choice in persistent homology. When we compute a persistence diagram, we need to select a coefficient field before computation. We should understand the dependence of the diagram on the coefficient field to facilitate computation and interpretation of the diagram. We clarify that the dependence is strongly related to the torsion part of $$\mathbb {Z}$$ relative homology in the filtration. We show the sufficient and necessary conditions of the independence of coefficient field choice. An efficient algorithm is proposed to verify the independence. A slight modification of the standard persistence algorithm gives the verification algorithm. In a numerical experiment with the algorithm, a persistence diagram rarely changes even when the coefficient field changes if we consider a filtration in $$\mathbb {R}^3$$. The experiment suggests that, in practical terms, changes in the field coefficient will not change persistence diagrams when the data are in $$\mathbb {R}^3$$.

    DOI: 10.1007/s00454-023-00544-7

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    Other Link: https://link.springer.com/article/10.1007/s00454-023-00544-7/fulltext.html

  • Stable volumes for persistent homology Reviewed

    Ippei Obayashi

    Journal of Applied and Computational Topology   7 ( 4 )   671 - 706   2023.5

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

    Abstract

    This paper proposes a stable volume and a stable volume variant, referred to as a stable sub-volume, for more reliable data analysis using persistent homology. In prior research, an optimal cycle and similar ideas have been proposed to identify the homological structure corresponding to each birth-death pair in a persistence diagram. While this is helpful for data analysis using persistent homology, the results are sensitive to noise. The sensitivity affects the reliability and interpretability of the analysis. In this paper, stable volumes and stable sub-volumes are proposed to solve this problem. For a special case, we prove that a stable volume is the robust part of an optimal volume against noise. We implemented stable volumes and sub-volumes on HomCloud, a data analysis software package based on persistent homology, and show examples of stable volumes and sub-volumes.

    DOI: 10.1007/s41468-023-00119-8

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    Other Link: https://link.springer.com/article/10.1007/s41468-023-00119-8/fulltext.html

  • Persistent homology analysis with nonnegative matrix factorization for 3D voxel data of iron ore sinters Reviewed

    Ippei Obayashi, Masao Kimura

    JSIAM Letters   14   151 - 154   2022.12

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    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:The Japan Society for Industrial and Applied Mathematics  

    DOI: 10.14495/jsiaml.14.151

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  • Persistent Homology Analysis for Materials Research and Persistent Homology Software: HomCloud Reviewed

    Obayashi, I., Nakamura, T., Hiraoka, Y.

    Journal of the Physical Society of Japan   91 ( 9 )   2022.9

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    Publishing type:Research paper (scientific journal)   Publisher:Physical Society of Japan  

    DOI: 10.7566/JPSJ.91.091013

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  • Topological descriptor of thermal conductivity in amorphous Si Reviewed

    Emi Minamitani, Takuma Shiga, Makoto Kashiwagi, Ippei Obayashi

    The Journal of Chemical Physics   156 ( 24 )   244502 - 244502   2022.6

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

    Quantifying the correlation between the complex structures of amorphous materials and their physical properties has been a longstanding problem in materials science. In amorphous Si, a representative covalent amorphous solid, the presence of a medium-range order (MRO) has been intensively discussed. However, the specific atomic arrangement corresponding to the MRO and its relationship with physical properties, such as thermal conductivity, remains elusive. We solved this problem by combining topological data analysis, machine learning, and molecular dynamics simulations. Using persistent homology, we constructed a topological descriptor that can predict thermal conductivity. Moreover, from the inverse analysis of the descriptor, we determined the typical ring features correlated with both the thermal conductivity and MRO. The results could provide an avenue for controlling material characteristics through the topology of the nanostructures.

    DOI: 10.1063/5.0093441

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  • Contribution of Phase Resetting to Statistical Persistence in Stride Intervals: A Modeling Study Reviewed

    Kota Okamoto, Ippei Obayashi, Hiroshi Kokubu, Kei Senda, Kazuo Tsuchiya, Shinya Aoi

    Frontiers in Neural Circuits   16   2022.6

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    Publishing type:Research paper (scientific journal)   Publisher:Frontiers Media SA  

    Stride intervals in human walking fluctuate from one stride to the next, exhibiting statistical persistence. This statistical property is changed by aging, neural disorders, and experimental interventions. It has been hypothesized that the central nervous system is responsible for the statistical persistence. Human walking is a complex phenomenon generated through the dynamic interactions between the central nervous system and the biomechanical system. It has also been hypothesized that the statistical persistence emerges through the dynamic interactions during walking. In particular, a previous study integrated a biomechanical model composed of seven rigid links with a central pattern generator (CPG) model, which incorporated a phase resetting mechanism as sensory feedback as well as feedforward, trajectory tracking, and intermittent feedback controllers, and suggested that phase resetting contributes to the statistical persistence in stride intervals. However, the essential mechanisms remain largely unclear due to the complexity of the neuromechanical model. In this study, we reproduced the statistical persistence in stride intervals using a simplified neuromechanical model composed of a simple compass-type biomechanical model and a simple CPG model that incorporates only phase resetting and a feedforward controller. A lack of phase resetting induced a loss of statistical persistence, as observed for aging, neural disorders, and experimental interventions. These mechanisms were clarified based on the phase response characteristics of our model. These findings provide useful insight into the mechanisms responsible for the statistical persistence of stride intervals in human walking.

    DOI: 10.3389/fncir.2022.836121

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  • Relationship between local coordinates and thermal conductivity in amorphous carbon Reviewed

    Emi Minamitani, Takuma Shiga, Makoto Kashiwagi, Ippei Obayashi

    Journal of Vacuum Science & Technology A   40 ( 3 )   033408 - 033408   2022.5

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    Publishing type:Research paper (scientific journal)   Publisher:American Vacuum Society  

    To determine the correlation between local structure and thermal conductivity of amorphous carbon, we investigated heat conduction in 216-atom systems with different densities (2.0–3.4 g/cm3) using the ab initio molecular dynamics approach. By applying the Allen–Feldman theory with interatomic force constants from ab initio calculations, we report a significant correlation between the thermal conductivity and the density. To clarify which structural characteristics in the high- and low-density cases determine the magnitude of thermal conductivity, we performed geometrical and topological analyses. Coordination number analysis and ring statistics revealed that the sp/sp2/sp3 bond ratios and topological characteristics correlate with density. We also demonstrated that these structural characteristics can be quantified using persistent homology analysis, providing a predictive model of thermal conductivity.

    DOI: 10.1116/6.0001744

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  • Flow estimation solely from image data through persistent homology analysis Reviewed

    Anna Suzuki, Miyuki Miyazawa, James M. Minto, Takeshi Tsuji, Ippei Obayashi, Yasuaki Hiraoka, Takatoshi Ito

    Scientific Reports   11 ( 1 )   2021.12

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

    <title>Abstract</title>Topological data analysis is an emerging concept of data analysis for characterizing shapes. A state-of-the-art tool in topological data analysis is persistent homology, which is expected to summarize quantified topological and geometric features. Although persistent homology is useful for revealing the topological and geometric information, it is difficult to interpret the parameters of persistent homology themselves and difficult to directly relate the parameters to physical properties. In this study, we focus on connectivity and apertures of flow channels detected from persistent homology analysis. We propose a method to estimate permeability in fracture networks from parameters of persistent homology. Synthetic 3D fracture network patterns and their direct flow simulations are used for the validation. The results suggest that the persistent homology can estimate fluid flow in fracture network based on the image data. This method can easily derive the flow phenomena based on the information of the structure.

    DOI: 10.1038/s41598-021-97222-6

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    Other Link: https://www.nature.com/articles/s41598-021-97222-6

  • Structure and properties of densified silica glass: characterizing the order within disorder Reviewed

    Yohei Onodera, Shinji Kohara, Philip S. Salmon, Akihiko Hirata, Norimasa Nishiyama, Suguru Kitani, Anita Zeidler, Motoki Shiga, Atsunobu Masuno, Hiroyuki Inoue, Shuta Tahara, Annalisa Polidori, Henry E. Fischer, Tatsuya Mori, Seiji Kojima, Hitoshi Kawaji, Alexander I. Kolesnikov, Matthew B. Stone, Matthew G. Tucker, Marshall T. McDonnell, Alex C. Hannon, Yasuaki Hiraoka, Ippei Obayashi, Takenobu Nakamura, Jaakko Akola, Yasuhiro Fujii, Koji Ohara, Takashi Taniguchi, Osami Sakata

    NPG ASIA MATERIALS   12 ( 1 )   2020.12

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:NATURE RESEARCH  

    The broken symmetry in the atomic-scale ordering of glassy versus crystalline solids leads to a daunting challenge to provide suitable metrics for describing the order within disorder, especially on length scales beyond the nearest neighbor that are characterized by rich structural complexity. Here, we address this challenge for silica, a canonical network-forming glass, by using hot versus cold compression to (i) systematically increase the structural ordering after densification and (ii) prepare two glasses with the same high-density but contrasting structures. The structure was measured by high-energy X-ray and neutron diffraction, and atomistic models were generated that reproduce the experimental results. The vibrational and thermodynamic properties of the glasses were probed by using inelastic neutron scattering and calorimetry, respectively. Traditional measures of amorphous structures show relatively subtle changes upon compacting the glass. The method of persistent homology identifies, however, distinct features in the network topology that change as the initially open structure of the glass is collapsed. The results for the same high-density glasses show that the nature of structural disorder does impact the heat capacity and boson peak in the low-frequency dynamical spectra. Densification is discussed in terms of the loss of locally favored tetrahedral structures comprising oxygen-decorated SiSi4 tetrahedra.

    DOI: 10.1038/s41427-020-00262-z

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  • Structural changes during glass formation extracted by computational homology with machine learning Reviewed

    Akihiko Hirata, Tomohide Wada, Ippei Obayashi, Yasuaki Hiraoka

    Communications Materials   1 ( 1 )   2020.12

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

    <title>Abstract</title>The structural origin of the slow dynamics in glass formation remains to be understood owing to the subtle structural differences between the liquid and glass states. Even from simulations, where the positions of all atoms are deterministic, it is difficult to extract significant structural components for glass formation. In this study, we have extracted significant local atomic structures from a large number of metallic glass models with different cooling rates by utilising a computational persistent homology method combined with linear machine learning techniques. A drastic change in the extended range atomic structure consisting of 3–9 prism-type atomic clusters, rather than a change in individual atomic clusters, was found during the glass formation. The present method would be helpful towards understanding the hierarchical features of the unique static structure of the glass states.

    DOI: 10.1038/s43246-020-00100-3

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    Other Link: http://www.nature.com/articles/s43246-020-00100-3

  • Disappearance of chaotic attractor of passive dynamic walking by stretch-bending deformation in basin of attraction

    Kota Okamoto, Shinya Aoi, Ippei Obayashi, Hiroshi Kokubu, Kei Senda, Kazuo Tsuchiya

    2020 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS)   2020.10

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    Publishing type:Research paper (international conference proceedings)   Publisher:IEEE  

    DOI: 10.1109/iros45743.2020.9341800

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  • Inferring fracture forming processes by characterizing fracture network patterns with persistent homology Reviewed

    A. Suzuki, M. Miyazawa, A. Okamoto, H. Shimizu, I. Obayashi, Y. Hiraoka, T. Tsuji, P. K. Kang, T. Ito

    Computers and Geosciences   143   104550 - 104550   2020.10

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

    © 2020 The Author(s) Persistent homology is a mathematical method to quantify topological features of shapes, such as connectivity. This study applied persistent homology to analyze fracture network patterns in rocks. We show that persistent homology can detect paths connecting from one boundary to the other boundary constituting fractures, which is useful for understanding relationships between fracture patterns and flow phenomena. In addition, complex fracture network patterns so-called mesh textures in serpentine were analyzed by persistent homology. In previous studies, fracture network patterns for different flow conditions were generated by a hydraulic–chemical–mechanical simulation and classified based on additional data and on expert's experience and knowledge. In this study, image analysis based on persistent homology alone was able to characterize fracture patterns. Similarities and differences of fracture network patterns between natural serpentinite and simulation were quantified and discussed. The data-driven approach combining with the persistent homology analysis helps to infer fracture forming processes in rocks. The results of persistent homology analysis provide critical topological information that cannot be obtained by geometric analysis of image data only.

    DOI: 10.1016/j.cageo.2020.104550

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  • Fractal mechanism of basin of attraction in passive dynamic walking Reviewed

    Kota Okamoto, Shinya Aoi, Ippei Obayashi, Hiroshi Kokubu, Kei Senda, Kazuo Tsuchiya

    Bioinspiration & Biomimetics   15 ( 5 )   055002 - 055002   2020.7

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

    Abstract

    Passive dynamic walking is a model that walks down a shallow slope without any control or input. This model has been widely used to investigate how humans walk with low energy consumption and provides design principles for energy-efficient biped robots. However, the basin of attraction is very small and thin and has a fractal-like complicated shape, which makes producing stable walking difficult. In our previous study, we used the simplest walking model and investigated the fractal-like basin of attraction based on dynamical systems theory by focusing on the hybrid dynamics of the model composed of the continuous dynamics with saddle hyperbolicity and the discontinuous dynamics caused by the impact upon foot contact. We clarified that the fractal-like basin of attraction is generated through iterative stretching and bending deformations of the domain of the Poincaré map by sequential inverse images. However, whether the fractal-like basin of attraction is actually fractal, i.e., whether infinitely many self-similar patterns are embedded in the basin of attraction, is dependent on the slope angle, and the mechanism remains unclear. In the present study, we improved our previous analysis in order to clarify this mechanism. In particular, we newly focused on the range of the Poincaré map and specified the regions that are stretched and bent by the sequential inverse images of the Poincaré map. Through the analysis of the specified regions, we clarified the conditions and mechanism required for the basin of attraction to be fractal.

    DOI: 10.1088/1748-3190/ab9283

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    Other Link: https://iopscience.iop.org/article/10.1088/1748-3190/ab9283/pdf

  • Protein-Folding Analysis Using Features Obtained by Persistent Homology Reviewed

    Takashi Ichinomiya, Ippei Obayashi, Yasuaki Hiraoka

    Biophysical Journal   118 ( 12 )   2926 - 2937   2020.6

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

    DOI: 10.1016/j.bpj.2020.04.032

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  • Very sharp diffraction peak in non-glass forming liquid with the formation of distorted tetraclusters Reviewed

    C. Koyama, S. Tahara, S. Kohara, Y. Onodera, D. R. Småbråten, S. M. Selbach, J. Akola, T. Ishikawa, A. Masuno, A. Mizuno, J. T. Okada, Y. Watanabe, Y. Nakata, K. Ohara, H. Tamaru, H. Oda, I. Obayashi, Y. Hiraoka, O. Sakata

    NPG Asia Materials   12 ( 1 )   43-1 - 43-11   2020.6

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:NATURE PUBLISHING GROUP  

    Understanding the liquid structure provides information that is crucial to uncovering the nature of the glass-liquid transition. We apply an aerodynamic levitation technique and high-energy X-rays to liquid (l)-Er(2)O(3)to discover its structure. The sample densities are measured by electrostatic levitation at the International Space Station. Liquid Er(2)O(3)displays a very sharp diffraction peak (principal peak). Applying a combined reverse Monte Carlo - molecular dynamics approach, the simulations produce an Er-O coordination number of 6.1, which is comparable to that of another nonglass-forming liquid,l-ZrO2. The atomic structure ofl-Er(2)O(3)comprises distorted OEr4 tetraclusters in nearly linear arrangements, as manifested by a prominent peak observed at similar to 180 degrees in the Er-O-Er bond angle distribution. This structural feature gives rise to long periodicity corresponding to the sharp principal peak in the X-ray diffraction data. A persistent homology analysis suggests thatl-Er(2)O(3)is homologically similar to the crystalline phase. Moreover, electronic structure calculations show thatl-Er(2)O(3)has a modest band gap of 0.6 eV that is significantly reduced from the crystalline phase due to the tetracluster distortions. The estimated viscosity is very low above the melting point forl-ZrO2, and the material can be described as an extremely fragile liquid.

    DOI: 10.1038/s41427-020-0220-0

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  • Understanding diffraction patterns of glassy, liquid and amorphous materials via persistent homology analyses Reviewed

    Y. Onodera, S. Kohara, S. Tahara, A. Masuno, H. Inoue, M. Shiga, A. Hirata, K. Tsuchiya, Y. Hiraoka, I. Obayashi, K. Ohara, A. Mizuno, O. Sakata

    Journal of the Ceramic Society of Japan   127 ( 12 )   853 - 863   2019.12

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI  

    The structure of glassy, liquid, and amorphous materials is still not well understood, due to the insufficient structural information from diffraction data. In this article, attempts are made to understand the origin of diffraction peaks, particularly of the first sharp diffraction peak (FSDP, Q(1)), the principal peak (PP, Q(2)), and the third peak (Q(3)), observed in the measured diffraction patterns of disordered materials whose structure contains tetrahedral motifs. It is confirmed that the FSDP (Q(1)) is not a signature of the formation of a network, because an FSDP is observed in tetrahedral molecular liquids. It is found that the PP (Q(2)) reflects orientational correlations of tetrahedra. Q(3), that can be observed in all disordered materials, even in common liquid metals, stems from simple pair correlations. Moreover, information on the topology of disordered materials was revealed by utilizing persistent homology analyses. The persistence diagram of silica (SiO2) glass suggests that the shape of rings in the glass is similar not only to those in the crystalline phase with comparable density (alpha-cristobalite), but also to rings present in crystalline phases with higher density (alpha-quartz and coesite); this is thought to be the signature of disorder. Furthermore, we have succeeded in revealing the differences, in terms of persistent homology, between tetrahedral networks and tetrahedral molecular liquids, and the difference/similarity between liquid and amorphous (glassy) states. Our series of analyses demonstrated that a combination of diffraction data and persistent homology analyses is a useful tool for allowing us to uncover structural features hidden in halo pattern of disordered materials. (C) 2019 The Ceramic Society of Japan. All rights reserved.

    DOI: 10.2109/jcersj2.19143

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  • Origin of the mixed alkali effect in silicate glass Reviewed

    Yohei Onodera, Yasuyuki Takimoto, Hiroyuki Hijiya, Taketoshi Taniguchi, Shingo Urata, Seiji Inaba, Sanae Fujita, Ippei Obayashi, Yasuaki Hiraoka, Shinji Kohara

    NPG Asia Materials   11 ( 1 )   75 - 11   2019.12

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

    DOI: 10.1038/s41427-019-0180-4

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  • Persistent Homology and Structural Analysis in Materials Science Invited

    Yasuaki Hiraoka, Ippei Obayashi, Kazuto Akagi

    Artificial Intelligence   34 ( 3 )   330 - 338   2019.5

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

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  • Visualization of Topological Defect in Labyrinth Magnetic Domain by Using Persistent Homology Reviewed

    T. YAMADA, Y. SUZUKI, C. MITSUMATA, K. ONO, T. UENO, I. OBAYASHI, Y. HIRAOKA, M. KOTSUGI

    Vacuum and Surface Science   62 ( 3 )   153 - 160   2019.3

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    Language:Japanese   Publisher:Surface Science Society Japan  

    <p>We executed the topological data analysis of labyrinth magnetic domain structure to visualize pinning site during the magnetization reversal process. We utilized persistent homology to extract the topological feature of the magnetic domain structure, and principal component analysis was used to construct the correlation between persistence diagram and magnetic hysteresis loop. As a result, we could automatically visualize the pinning site as topological defect on the original magnetic domain structure.</p>

    DOI: 10.1380/vss.62.153

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  • Visualization of Topological Defect in Labyrinth Magnetic Domain by Using Persistent Homology Invited Reviewed

    YAMADA T., SUZUKI Y., MITSUMATA C., ONO K., UENO T., OBAYASHI I., HIRAOKA Y., KOTSUGI M.

    Vacuum and Surface Science   62 ( 3 )   153 - 160   2019.3

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    Language:Japanese   Publisher:The Japan Society of Vacuum and Surface Science  

    <p>We executed the topological data analysis of labyrinth magnetic domain structure to visualize pinning site during the magnetization reversal process. We utilized persistent homology to extract the topological feature of the magnetic domain structure, and principal component analysis was used to construct the correlation between persistence diagram and magnetic hysteresis loop. As a result, we could automatically visualize the pinning site as topological defect on the original magnetic domain structure.</p>

    DOI: 10.1380/vss.62.153

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  • Persistent Homology and Its Applications to Materials Science Reviewed

    Yasuaki Hiraoka, Ippei Obayashi

    Materia Japan   58 ( 1 )   17 - 22   2019.1

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    Publishing type:Research paper (scientific journal)   Publisher:Japan Institute of Metals  

    DOI: 10.2320/materia.58.17

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  • Ultrahigh-pressure form of SiO2 glass with dense pyrite-type crystalline homology Reviewed

    M. Murakami, S. Kohara, N. Kitamura, J. Akola, H. Inoue, A. Hirata, Y. Hiraoka, Y. Onodera, I. Obayashi, J. Kalikka, N. Hirao, T. Musso, A. S. Foster, Y. Idemoto, O. Sakata, Y. Ohishi

    Physical Review B   99 ( 4 )   2019.1

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    DOI: 10.1103/physrevb.99.045153

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  • パーシステントホモロジーの基礎と材料工学への適用例 Invited Reviewed

    平岡裕章, 大林一平

    日本金属学会会報「まてりあ」   58 ( 1 )   17 - 22   2019

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  • Hepatic tumor classification using texture and topology analysis of non-contrast-enhanced three-dimensional T1-weighted MR images with a radiomics approach Reviewed International journal

    A. Oyama, Y. Hiraoka, I. Obayashi, Y. Saikawa, S. Furui, K. Shiraishi, S. Kumagai, T. Hayashi, J. Kotoku

    Scientific Reports   9 ( 1 )   8764 - 8764   2019

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    The purpose of this study is to evaluate the accuracy for classification of hepatic tumors by characterization of T1-weighted magnetic resonance (MR) images using two radiomics approaches with machine learning models: texture analysis and topological data analysis using persistent homology. This study assessed non-contrast-enhanced fat-suppressed three-dimensional (3D) T1-weighted images of 150 hepatic tumors. The lesions included 50 hepatocellular carcinomas (HCCs), 50 metastatic tumors (MTs), and 50 hepatic hemangiomas (HHs) found respectively in 37, 23, and 33 patients. For classification, texture features were calculated, and also persistence images of three types (degree 0, degree 1 and degree 2) were obtained for each lesion from the 3D MR imaging data. We used three classification models. In the classification of HCC and MT (resp. HCC and HH, HH and MT), we obtained accuracy of 92% (resp. 90%, 73%) by texture analysis, and the highest accuracy of 85% (resp. 84%, 74%) when degree 1 (resp. degree 1, degree 2) persistence images were used. Our methods using texture analysis or topological data analysis allow for classification of the three hepatic tumors with considerable accuracy, and thus might be useful when applied for computer-aided diagnosis with MR images.

    DOI: 10.1038/s41598-019-45283-z

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  • Volume-Optimal Cycle: Tightest Representative Cycle of a Generator in Persistent Homology Reviewed

    Obayashi, I.

    SIAM Journal on Applied Algebra and Geometry   2 ( 4 )   508 - 534   2018.10

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    DOI: 10.1137/17M1159439

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  • Non-Empirical Identification of Trigger Sites in Image Data using Persistent Homology: Crack Formation during Heterogeneous Reduction of Iron-Ore Sinters Reviewed

    M. Kimura, I. Obayashi, Y. Takeichi, R. Murao, Y. Hiraoka

    Microscopy and Microanalysis   24 ( S2 )   540 - 541   2018.8

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    DOI: 10.1017/s1431927618014897

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  • Persistence diagrams with linear machine learning models Reviewed

    Obayashi, I., Hiraoka, Y., Kimura, M.

    Journal of Applied and Computational Topology   1 ( 3-4 )   421 - 449   2018.5

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    DOI: 10.1007/s41468-018-0013-5

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  • Non-empirical identification of trigger sites in heterogeneous processes using persistent homology Reviewed

    Masao Kimura, Ippei Obayashi, Yasuo Takeichi, Reiko Murao, Yasuaki Hiraoka

    Scientific Reports   8 ( 1 )   2018.2

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    DOI: 10.1038/s41598-018-21867-z

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  • Persistent homology analysis of craze formation Reviewed

    Takashi Ichinomiya, Ippei Obayashi, Yasuaki Hiraoka

    PHYSICAL REVIEW E   95 ( 1 )   2017.1

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    We apply a persistent homology analysis to investigate the behavior of nanovoids during the crazing process of glassy polymers. We carry out a coarse-grained molecular dynamics simulation of the uniaxial deformation of an amorphous polymer and analyze the results with persistent homology. Persistent homology reveals the void coalescence during craze formation, and the results suggest that the yielding process is regarded as the percolation of nanovoids created by deformation.

    DOI: 10.1103/PhysRevE.95.012504

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  • Inverse Problems for Persistence Diagrams Invited Reviewed

    Ippei Obayashi

    Bulletin of the Japan Society for Industrial and Applied Mathematics   26 ( 4 )   7 - 14   2017

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    DOI: 10.11540/bjsiam.26.4_7

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  • Chemical state mapping of heterogeneous reduction of iron ore sinter Reviewed

    M. Kimura, Y. Takeichi, R. Murao, I. Obayashi, Y. Hiraoka, Y. Liu

    X-RAY MICROSCOPY CONFERENCE 2016 (XRM 2016)   849   012015   2017

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    Iron ore sinter constitutes the major component of the iron-bearing burden in blast furnaces, and its reduction mechanism is one of the keys to improving the productivity of ironmaking. Iron ore sinter is composed of multiple iron oxide phases and calcium ferrites (CFs), and their heterogeneous reduction was investigated in terms of changes in iron chemical state: Fe-III, Fe-II, and Fe-0 were examined macroscopically by 2D X-ray absorption and microscopically by 3D transmission X-ray microscopy (TXM). It was shown that the reduction starts at iron oxide grains rather than at calcium ferrite (CF) grains, especially those located near micropores. The heterogeneous reduction causes crack formation and deteriorates the mechanical strength of the sinter. These results help us to understand the fundamental aspects of heterogeneous reduction schemes in iron ore sinter.

    DOI: 10.1088/1742-6596/849/1/012015

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  • A Cyclone Identification Algorithm with Persistent Homology and Merge-Tree Reviewed

    Masaru Inatsu, Hayato Kato, Yuta Katsuyama, Yasuaki Hiraoka, Ippei Ohbayashi

    SOLA   13   214 - 218   2017

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    <p>This paper addresses a cyclone identification algorithm with the superlevel set filtration of the persistent homology together with the merge-tree reconstruction of data. Based on the information of peaks and saddles of the scaler field, the newly developed algorithm divides the analysis area into several homology classes, each of which satisfies the peak-to-saddle difference larger than a criterion that should be set in advance. Applied to the 850-hPa relative vorticity in the western North Pacific at 1200 UTC on 2 March 2013, 3 homology classes were found with the criterion of 100 × 10−6 s−1 and 17 homology classes were found with the criterion of 50 × 10−6 s−1. The merge-tree restructuring clarified the neighbour relation among homology classes. The result suggests that the weak criterion detected too much homology classes, some of which are small peaks inside of a single cyclone. The climatology feature density provides the Pacific storm track with the strict criterion. Finally, a possible way to extend toward cyclone tracking with the persistent homology is discussed.</p>

    DOI: 10.2151/sola.2017-039

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  • Continuation of point clouds via persistence diagrams Reviewed

    Marcio Gameiro, Yasuaki Hiraoka, Ippei Obayashi

    PHYSICA D-NONLINEAR PHENOMENA   334 ( 1 )   118 - 132   2016.11

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    In this paper, we present a mathematical and algorithmic framework for the continuation of point clouds by persistence diagrams. A key property used in the method is that the persistence map, which assigns a persistence diagram to a point cloud, is differentiable. This allows us to apply the Newton-Raphson continuation method in this setting. Given an original point cloud P, its persistence diagram D, and a target persistence diagram D', we gradually move from D to D', by successively computing intermediate point clouds until we finally find a point cloud P' having D' as its persistence diagram. Our method can be applied to a wide variety of situations in topological data analysis where it is necessary to solve an inverse problem, from persistence diagrams to point cloud data. (C) 2015 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.physd.2015.11.011

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  • Formation mechanism of a basin of attraction for passive dynamic walking induced by intrinsic hyperbolicity Reviewed

    Ippei Obayashi, Shinya Aoi, Kazuo Tsuchiya, Hiroshi Kokubu

    PROCEEDINGS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES   472 ( 2190 )   20160028   2016.6

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    Passive dynamic walking is a useful model for investigating the mechanical functions of the body that produce energy-efficient walking. The basin of attraction is very small and thin, and it has a fractal-like shape; this explains the difficulty in producing stable passive dynamic walking. The underlying mechanism that produces these geometric characteristics was not known. In this paper, we consider this from the viewpoint of dynamical systems theory, and we use the simplest walking model to clarify the mechanism that forms the basin of attraction for passive dynamic walking. We show that the intrinsic saddle-type hyperbolicity of the upright equilibrium point in the governing dynamics plays an important role in the geometrical characteristics of the basin of attraction; this contributes to our understanding of the stability mechanism of bipedal walking.

    DOI: 10.1098/rspa.2016.0028

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  • Common formation mechanism of basin of attraction for bipedal walking models by saddle hyperbolicity and hybrid dynamics Reviewed

    Ippei Obayashi, Shinya Aoi, Kazuo Tsuchiya, Hiroshi Kokubu

    JAPAN JOURNAL OF INDUSTRIAL AND APPLIED MATHEMATICS   32 ( 2 )   315 - 332   2015.7

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    In this paper, we investigate the mathematical structures and mechanisms of bipedal walking from a dynamical viewpoint. Especially, we focus on the basin of attraction since it determines the stability of bipedal walking. We treat two similar but different bipedal walking models (passive and active dynamic walking models) and examine common mathematical structure between these models. We find that the saddle hyperbolicity and hybrid system play important roles for the shape of the basin of attraction in both models, which are quite common for more general bipedal models and important for understanding the stability mechanism of bipedal walking.

    DOI: 10.1007/s13160-015-0181-9

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  • Capturing the Global Behavior of Dynamical Systems with Conley-Morse Graphs Reviewed

    Zin Arai, Hiroshi Kokubu, Ippei Obayashi

    Advances in Cognitive Neurodynamics (III)   665   2013

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    DOI: 10.1007/978-94-007-4792-0_89

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  • Combinatorial-topological framework for the analysis of global dynamics Reviewed

    Justin Bush, Marcio Gameiro, Shaun Harker, Hiroshi Kokubu, Konstantin Mischaikow, Ippei Obayashi, Pawel Pilarczyk

    CHAOS   22 ( 4 )   047508   2012.12

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    We discuss an algorithmic framework based on efficient graph algorithms and algebraic-topological computational tools. The framework is aimed at automatic computation of a database of global dynamics of a given m-parameter semidynamical system with discrete time on a bounded subset of the n-dimensional phase space. We introduce the mathematical background, which is based upon Conley's topological approach to dynamics, describe the algorithms for the analysis of the dynamics using rectangular grids both in phase space and parameter space, and show two sample applications. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4767672]

    DOI: 10.1063/1.4767672

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  • Computer-Assisted Verification Method for Invariant Densities and Rates of Decay of Correlations Reviewed

    Obayashi Ippei

    SIAM JOURNAL ON APPLIED DYNAMICAL SYSTEMS   10 ( 2 )   788 - 816   2011

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    A new computer-assisted verification method for invariant densities and decay rates of correlations is proposed. This new method is based on the Hilbert cone technique.

    DOI: 10.1137/09077864X

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  • Exponential decay of correlations for surface semiflows with an expanding direction Reviewed

    Ippei Obayashi

    JOURNAL OF MATHEMATICS OF KYOTO UNIVERSITY   49 ( 2 )   427 - 440   2009

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    Dolgopyat [4] showed that a class of Axiom A flows has exponential decay of correlations for smooth observables, and Baladi-Vallee [2] gave a nice interpretation of it on suspension semiflows of one-dimensional expanding countable Markov maps. Avila-Gouezel-Yoccoz [1] extends the result of Baladi-Vallee to higher dimensional systems.
    In this paper we show that a class of non-Markov semiflows also has exponential decay of correlations.
    We prove that such exponential decay can be shown on an open dense condition for the suspensions of piecewise expanding maps.

    DOI: 10.1215/kjm/1256219166

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Books

  • 位相的データ解析から構造発見へ : パーシステントホモロジーを中心に

    池, 祐一, Emerson Gaw Escolar, 大林, 一平, 鍛冶, 静雄( Role: Joint author)

    サイエンス社  2023.9  ( ISBN:9784781915807

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  • マテリアルズインフォマティクス = Materials informatics

    吉田亮, 伊藤聡, 劉暢, Wu, Stephen, 野口瑶, 山田寛尚, 赤木和人, 大林一平, 山下智樹( Role: Joint author ,  第2章)

    共立出版  2022.8  ( ISBN:9784320072022

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    Total pages:ix, 186p, 図版 [2] p   Language:Japanese Book type:Textbook, survey, introduction

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MISC

  • ソフトウェア紹介:パーシステントホモロジーに基づくデータ解析ソフトウェア「HomCloud」による材料科学データ解析

    大林一平

    分子シミュレーション学会学会誌 アンサンブル   26 ( 1 )   83 - 90   2024

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  • 数理情報科学を用いた構造秩序解析

    志賀元紀, 森田秀利, 大林一平

    セラミックス   58   527 - 530   2023

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  • パーシステントホモロジーの optimal volume と stable volume について

    大林一平

    京都大学 数理解析研究所 講究録   ( 2209 )   2021.6

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  • パーシステントホモロジーに基づくデータ解析パッケージHomCloudの紹介 Invited

    大林一平

    京都大学 数理解析研究所 講究録   ( 2166 )   2020.7

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  • Understanding Diffraction from Disordered Materials and the Extraction of Topology Hidden in the Pairwise Correlations by Persistent Homology

    Shinji KOHARA, Osami SAKATA, Yohei ONODERA, Ippei OBAYASHI, Motoki SHIGA, Akihiko HIRATA, Yasuaki HIRAOKA

    Nihon Kessho Gakkaishi   62 ( 1 )   43 - 50   2020.2

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    Language:Abkhazian   Publishing type:Article, review, commentary, editorial, etc. (scientific journal)   Publisher:The Crystallographic Society of Japan  

    DOI: 10.5940/jcrsj.62.43

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  • パーシステントホモロジーによる材料科学データ解析

    大林 一平

    NewGlass   35 ( 1 )   17 - 23   2020

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  • ガラスの二体相関に隠れたトポロジーの抽出

    New Glass   35 ( 1 )   24 - 30   2020

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  • Multi Phase Field 法とパーシステントホモロジー解析による鉄鋼材料組織の特徴抽出

    沖直人, 山田拓洋, 山中晃徳, 大林一平, 平岡裕章, 赤木和人, 小嗣真人

    第66回応用物理学会春季学術講演会講演予稿集   11a-PA8-6   2019.3

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  • Chemical State Mapping Using X-ray Microscopes and Non-empirical Analysis of Trigger Sites Using Applied Mathematics

    Masao Kimura, Yasuo Takeichi, Ippei Obayashi, Reiko Murao, Yasuaki Hiraoka

    Materia Japan   57 ( 12 )   595 - 595   2018.12

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    Language:Japanese   Publishing type:Rapid communication, short report, research note, etc. (scientific journal)   Publisher:Japan Institute of Metals  

    DOI: 10.2320/materia.57.595

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  • 数値シミュレーションと組み合わせた構造解析による蛇紋岩の形成メカニズム推定

    宮澤美幸, 鈴木杏奈, 岡本敦, 清水浩之, 大林一平, 平岡裕章, 平岡裕章, 伊藤高敏

    日本地質学会学術大会講演要旨   125th   116   2018.9

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    J-GLOBAL

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  • Persistent homology and materials informatics Invited

    Mickaël Buchet, Yasuaki Hiraoka, Ippei Obayashi

    Nanoinformatics   75 - 95   2018.1

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    This paper provides an introduction to persistent homology and a survey of its applications to materials science. Mathematical prerequisites are limited to elementary linear algebra. Important concepts in topological data analysis such as persistent homology and persistence diagram are explained in a selfcontained manner with several examples. These tools are applied to glass structural analysis, crystallization of granular systems, and craze formation of polymers.

    DOI: 10.1007/978-981-10-7617-6_5

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  • An Attempt to Understand Global Structure of Dynamics in Nonlinear Phenomena Invited

    Hiroshi Kokubu, Ippei Obayashi

    The Brain & Neural Networks   22 ( 2 )   68 - 77   2015

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    Language:Japanese   Publishing type:Article, review, commentary, editorial, etc. (scientific journal)   Publisher:Japanese Neural Network Society  

    DOI: 10.3902/jnns.22.68

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  • 歩行と力学系 Invited

    数学セミナー2014年7月号   53 ( 7 )   36 - 41   2014.7

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    CiNii Article

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    Other Link: http://orcid.org/0000-0002-7207-7280

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Presentations

  • A data analysis framework with linear models and persistent homology Invited

    Ippei Obayashi

    TDA Week 2023  2023.8.2 

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    Event date: 2023.7.31 - 2023.8.4

    Language:English   Presentation type:Oral presentation (keynote)  

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  • パーシステントホモロジーのデータ解析への活用 Invited

    大林一平

    応用のためのトポロジカルデータ解析チュートリアル&ワークショップ  2020.6.18 

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    Event date: 2020.6.18 - 2020.6.19

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  • 位相的データ解析 - 理論,ソフトウェア,応⽤ Invited

    大林一平

    Topology Meets Data  2023.1.10 

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  • パーシステントホモロジーによるデータ解析 - 理論,応用,ソフトウェア Invited

    大林一平

    JST数学関連3領域連携WS「情報科学と拓く新しい数理科学」  2022.9.12 

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    Venue:札幌  

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  • Ippei Obayashi. Stable volumes for persistent homology Invited International conference

    Ippei Obayashi

    TDA Week  2022.2.14 

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    Venue:Online  

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  • 3D Data Analysis of X-Ray CT Images with Persistent Homology and Nonnegative Matrix Factorization Invited International conference

    Ippei Obayashi

    Perspectives on Artificial Intelligence and Machine Learning in Materials Science  2022.2.5 

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    Venue:Online  

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  • TDAの材料科学への応用とデータ解析ソフトウェアHomCloud Invited

    大林一平

    CREST 「現代の数理科学と連携するモデリング手法の構築」 成果報告公開シンポジウム  2021.9.21 

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  • Hands-on on topological analysis - Online tutorial of quantum beam PDF analysis and topological analysis for disordered materials Invited

    Ippei Obayashi, Motoki Shiga

    Tutorial by ICG TC29 (Quantum beam diffraction) and JSPS Hyper-ordered structures science  2021.9.17 

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  • Lecture on topological analysis - Online tutorial of quantum beam PDF analysis and topological analysis for disordered materials Invited

    Ippei Obayashi

    Tutorial by ICG TC29 (Quantum beam diffraction) and JSPS Hyper-ordered structures science  2021.9.13 

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  • Persistent homology: a descriptor of the shape of data Invited

    Ippei Obayashi

    RIMS Workshop Mathematical methods for the studies of flow, shape, and dynamics  2021.8.30 

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  • パーシステントホモロジーによるデータ解析の基本と材料科学への応用 Invited

    大林一平

    第52回ガラス部会夏季若手セミナー  2021.8.27 

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  • パーシステントホモロジーによる材料科学データ解析 Invited

    大林一平

    第99回千葉地域活動高分子交流講演会  2021.6.15 

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  • Volume-optimal cycles and stable volumes for persistent homology Invited

    大林 一平

    RIMS共同研究 一般位相幾何学の動向と諸分野との連携  2021.6.2 

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    Language:Japanese   Presentation type:Oral presentation (general)  

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  • Stable volumes for persistent homology Invited

    Ippei Obayashi

    Thematic Einstein Semester on Geometric and Topological Structure of Materials  2021.5.26 

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  • Inverse problems on persistence diagrams Invited

    Ippei Obayashi

    RIMS Workshop on "Recent developments on inverse problems for partial differential equations and their applications"  2021.1.7 

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  • Field choice problem in persistent homology Invited

    Ippei Obayashi

    Asia Pacific Seminar on Applied Topology and Geometry  2020.11.20 

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  • Software and applications of persistent homology Invited

    Ippei Obayashi

    2nd AIP Open Seminar  2020.11.18 

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  • パーシステントホモロジーによるデータ解析 - 材料科学への応用について Invited

    大林一平

    公益社団法人日本セラミックス協会 第 33 回秋季シンポジウム  2020.9.3 

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  • Theory, software, and applications of persistent homology Invited

    大林一平

    RIMS共同研究(公開型) 第16回生物数学の理論とその応用-生命現象の定量的理解に向けて-  2020.1.31 

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  • パーシステントホモロジーチュートリアル (パーシステントホモロジーの基礎と応用例の紹介, HomCloud体験チュートリアル) Invited

    大林一平

    TDA Tutorial  2019.11.28 

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  • Data Analysis by Persistent homology and Machine learning Invited

    Ippei Obayashi

    A3 foresight workshop "Modeling and Simulation of Hierarchical and Heterogeneous Flow Systems with Applications to Materials Science VI"  2019.6.28 

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  • Machine learning with persistent homology and its applications to materials science Invited International conference

    Ippei Obayashi

    TGDA@OSU TRIPODS Center Workshop - Structure in the Micro-world  2019.5.31 

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    Language:English   Presentation type:Oral presentation (invited, special)  

    Venue:Ohio State University, Columbus, Ohio, USA  

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  • パーシステントホモロジーの基礎と材料科学への応用 Invited

    大林 一平

    数学と諸分野の融合に向けた若手数学者交流会  2019.3.16 

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    Language:Japanese   Presentation type:Oral presentation (invited, special)  

    Venue:JST東京本部, 東京  

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  • Topological Data Analysis for Materials Science Invited International conference

    Ippei Obayashi

    ICMMA 2018  2019.2.12 

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    Venue:Meiji Univ., Tokyo  

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  • パーシステントホモロジーの理論と応用 Invited

    大林 一平

    Interaction between Pure and Applied Mathematics 2018 (IPA Math 2018)  2018.12.14 

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    Language:Japanese   Presentation type:Oral presentation (invited, special)  

    Venue:明治大学駿河台キャンパス, 東京  

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  • Theory and applications of persistent homology Invited International conference

    Ippei Obayashi

    Mathematical Progress in Expressive Image Synthesis 2018 (MEIS2018)  2018.12.12 

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    Language:English   Presentation type:Oral presentation (invited, special)  

    Venue:Shibaura Institute of technology, Tokyo  

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  • パーシステントホモロジーの理論と応用 Invited

    大林 一平

    第24回交通流と自己駆動粒子系のシンポジウム  2018.12.6 

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  • パーシステントホモロジー解析の(非)結晶学への展開 Invited

    大林 一平

    日本結晶学会 2018年度年会  2018.11 

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  • 位相的データ解析による材料科学データの不均一性の評価 Invited

    大林 一平

    X線顕微鏡による機能の可視化と多次元情報の活用 (X線顕微鏡研究会)  2018.11 

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  • The theory and applications of persistent homology Invited International conference

    Ippei Obayashi

    2018.11 

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  • パーシステントホモロジーの基礎から応用まで Invited

    大林一平

    応用物理学会 薄膜・表面物理分科会 基礎講座:データサイエンスを活用した固体材料・表面研究の最前線  2018.11  応用物理学会 薄膜・表面物理分科会

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    Language:Japanese   Presentation type:Public lecture, seminar, tutorial, course, or other speech  

    Venue:東京理科大学  

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  • パーシステントホモロジー - 数学と計算機科学の融合による「かたち」のデータ解析 Invited

    大林 一平

    2018年 日本数学会 秋季総合分科会  2018.9 

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  • Analysis of the shape of data by persistent homology and machine learning Invited International conference

    Ippei Obayashi

    Applied Geometry & Topology 2018  2018.7 

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  • パーシステントホモロジーの基礎から応用まで Invited

    大林 一平

    第 23 回 高分子計算機科学 研究会講座 - 材料開発のための AI システムとその応用  2018.6 

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  • Volume Optimal Cycles for Persistent Homology Invited

    大林 一平

    第10回福島応用数学研究集会  2018.3 

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  • Theory and Application of persistent homology Invited International conference

    Ippei Obayashi

    -LANDSCAPE OF APPLIED MATHEMATICS IN ENERGY PROBLEM- i2cner international workshop 2018  2018.2 

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  • Introduction to topological data analysis Invited International conference

    Ippei Obayashi

    Kavli IPMU-Berkeley Symposium "Statistics, Physics and Astronomy"  2018.1 

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  • 位相的データ解析ソフトウェア HomCloud の紹介 およびパーシステント図の逆問題について Invited

    大林 一平

    Encounter with Mathematics 第70回 パーシステントホモロジーとその周辺  2017.12 

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    Language:Japanese   Presentation type:Oral presentation (invited, special)  

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  • Introduction to Topological Data Analysis Invited International conference

    Ippei Obayashi

    INVA2017  2017.3 

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  • Analysis of digital image data from material science with Topological Data Analysis and Machine learning Invited International conference

    Ippei Obayashi

    The AIMR International Symposium 2017 (AMIS2017)  2017.2 

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  • 位相的データ解析の基礎と応用 - パーシステントホモロジーの計算ソフトウェアと発展的話題について Invited

    大林 一平

    統計数理研究所 2016年度公開講座  2017.2 

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  • パーシステントホモロジーによる材料科学データの空間構造解析について Invited

    大林 一平

    PF研究会「測定しているけど見えていない情報を引き出すためには?〜不可逆反応、不均一反応での情報科学/計算科学×計測技術の融合〜」  2017.1 

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  • Inverse problem from persistence diagrams to point clouds Invited

    Ippei Obayashi

    2016.3 

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  • Software for persistent homology Invited International conference

    Ippei Obayashi

    A3 Foresight Winter School on "Mathematics on Materials Science: Topological Data Analysis and Dynamics"  2016.2 

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  • トポロジカルデータ解析と形のインフォマティックス - Homcloudを用いたデータ解析について Invited

    大林 一平

    新化学技術推進協会 先端化学・材料技術部会 コンピュータケミストリ分科会講演会「マルチスケール材料開発のための幾何学的手法」  2016 

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  • 倒立/二重振子と受動歩行のモデリング Invited

    大林 一平

    「現象数理冬の学校」ーモデルを通して現象を視る  2014.2 

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  • Dynamics of simple walking models Invited International conference

    Ippei Obayashi

    Workshop: Dynamics and Applied Topology  2013.6 

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  • Time series analysis based on the idea of CM graphs Invited International conference

    Ippei Obayashi

    IV Developers Workshop on the Conley-Morse Database Project  2012.3 

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Awards

  • Award of the Outstanding Papers Published in the JCS-JAPAN in 2019

    2020.6   The Ceramic Society of Japan   Understanding diffraction patterns of glassy, liquid and amorphous materials via persistent homology analyses

    Yohei ONODERA, Shinji KOHARA, Shuta TAHARA, Atsunobu MASUNO, Hiroyuki INOUE, Motoki SHIGA, Akihiko HIRATA, Koichi TSUCHIYA, Yasuaki HIRAOKA, Ippei OBAYASHI, Koji OHARA, Akitoshi MIZUNO, Osami SAKATA

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  • 第11回 桜舞賞 研究奨励賞

    2020.3   理化学研究所   Development of topological data analysis software and its industrial applications

    大林一平

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  • 日本応用数理学会 2017 年度 ベストオーサー賞

    2017.9   日本応用数理学会  

    大林 一平

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    Award type:Honored in official journal of a scientific society, scientific journal 

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  • 第6回藤原洋数理科学賞 奨励賞

    2017.9  

    大林 一平

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  • 日本応用数理学会 2017 年度 論文賞

    2017.9   日本応用数理学会  

    大林 一平

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    Award type:Honored in official journal of a scientific society, scientific journal 

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  • AIMR International Symposium 2017 (AMIS2017) Best Poster Award

    2017.2   AIMR, Tohoku University  

    大林 一平

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    Award type:Award from international society, conference, symposium, etc. 

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Research Projects

  • Comprehensive analysis of hyper-ordered structures based on mathematics and informatics

    Grant number:20H05884  2020.11 - 2025.03

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Transformative Research Areas (A)  Grant-in-Aid for Transformative Research Areas (A)

    志賀 元紀, 松下 智裕, 大林 一平

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    Grant amount:\98670000 ( Direct expense: \75900000 、 Indirect expense:\22770000 )

    開始年度となる本年度では、まず、計上していた予算を用いて多数CPUコアおよびGPUを搭載した計算機を購入し計算機環境を整備し、また、研究データの整備および開発ソフトウェアの機能強化を行った。
    計測データから原子配列を推定する課題において、光電子ホログラフィーや蛍光X線ホログラフィーから原子像を再構成する理論が研究分野全体の鍵を握っている。蛍光X線ホログラフィーでは通常はBarton法が使われるが、これはX線の波長を変えながら、約10枚のホログラムを必要とする。理論が向上すれば、この測定量を減らすことが可能になる。そこで、L1正則化や最大エントロピー法を用いた方法の研究、また、リバースモンテカルロ法を用いて原子像再生をする理論の研究を行った。
    超秩序の記述法の課題において、トポロジーの概念を活用し、従来の手法では特徴付けが難しかった構造記述子の構築に取り組んだ。具体的には、孔や空隙の形や大きさ、ネットワーク構造など多体秩序の定量的記述を目指し、この目標のため、パーシステントホモロジー(PH)という数学的手法などを活用した。こうして超秩序構造のための記述子を構成し、それを利用して物性を予測する機械学習モデルを構築し、超秩序と物性の関係を明らかにするための理論およびソフトウェア整備を行った。さらに、他の計画班との連携によって、シリカガラスの化学結合ネットワークのトポロジー解析を行った。具体的には、様々な条件で合成されたシリカガラスにおける化学結合ネットワーク上のリング(閉ループ)を解析し、比較を行った結果をまとめて学術雑誌NPG Asia Materialsにおいて発表した。

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  • Development of a new method for data science via the fusion of dynamical systems and computational topology

    Grant number:19KK0068  2019.10 - 2025.03

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Fund for the Promotion of Joint International Research (Fostering Joint International Research (B))  Fund for the Promotion of Joint International Research (Fostering Joint International Research (B))

    荒井 迅, 平岡 裕章, 大林 一平, 竹内 博志

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    Grant amount:\18330000 ( Direct expense: \14100000 、 Indirect expense:\4230000 )

    本研究は,力学系と計算トポロジーを融合することにより,新しいデータ解析の手法を開発すること,また開発した手法を用いて様々な分野の具体的な応用問題に貢献することを目指す.さらに,具体的な問題への応用という観点から力学系の安定性理論を見直し,新しい力学系の安定性概念を提案することも目的とする.主な道具は,力学系理論からはコンレイ指数理論や分岐理論,一様双曲性証明アルゴリズムであり,計算トポロジー理論からはパーシステントホモロジー理論やその逆問題解析法などである.この目的のため,力学系の研究と位相的データ解析の双方の分野において世界的に指導的な役割を果たしてきた,米国ラトガース大学のミシャイコフ教授のグループと連携を進める.アルゴリズムの実装から具体的な応用まで幅広く相互に技術を交換し,データ解析の新しい枠組みを 展開することを目指す.ラトガース大学との直接の人的交流は新型コロナ感染拡大もあり思うように進んでいないものの,前回渡航時に検討した問題の解析を進め,基礎理論を構築しつつある.特に,動的なデータ解析を目指す上で重要な,サンプル写像に対するパーシステントホモロジー理論の基礎づけや,具体例への応用のための計算アルゴリズムについて進展が得られた.応用面では,このような位相幾何学的な手法と,統計的因果推論や,大域的な力学系解析手法などを組み合わせた手法について研究を進め,生物学や化学などの異分野から提供される様々な実データに対して適用できる手法の開発を進めている.

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  • パーシステントホモロジーによる位相高次構造抽出手法開発

    2019.10 - 2023.03

    Japan Science and Technology Agenc  PRESTO 

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    Authorship:Principal investigator 

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  • Determination of trigger sites for crack formation in aeronautical composite by combining X-ray microscopy and applied mathematics

    Grant number:19H00834  2019.04 - 2024.03

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (A)  Grant-in-Aid for Scientific Research (A)

    木村 正雄, 大林 一平, 武市 泰男, 丹羽 尉博

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    Grant amount:\45890000 ( Direct expense: \35300000 、 Indirect expense:\10590000 )

    (1) 昨年度、高度化に成功したX線顕微鏡による4次元/5次元観察により、高空間分解能(~50nm)で、応力負荷しながら(in situ)X-CTによる観察を行いCFRP (炭素繊維強化プラスチック)におけるき裂の発生、進展の挙動を調べた。
    その結果、Mode I (引っ張り)応力でのミクロ・ナノスケールでのき裂の発生・進展挙動は、 (A)樹脂内でのき裂発生と、(B)炭素繊維/樹脂界面での剥離、が競合して進行し、どちらが優位になるかは、炭素繊維の配列に大きく依存していることが新たに判明した。炭素繊維が離散的に配列し炭素繊維間の距離dがd≧1/2r(r:炭素繊維の半径)程度の領域では(A)モードでのき裂発生、炭素繊維が密に配列しd<1/2r程度の領域では(B)モードでのき裂発生が主体となることが初めて判明した。
    (2) 昨年度、高度化に成功した走査型X線顕微鏡(STXM)を用いた炭素の化学状態をナノスケールでマッピングする技術を用いて、CFRPの観察を実施した。炭素繊維内の黒鉛微結晶のC=C結合由来のπ軌道の配向分布を定量化するために、回転試料台を用いた観察技術を確立した。
    (3)顕微鏡ビッグデータの応用数学による解析として、不均一性のかたちをマルチスケールかつ定量的に特徴付ける手法であるパーシステントホモロジー(PH)の高度化に取り組んだ。現状は、解析の対象が二次元データに限られているため、アルゴリズムの改良と計算プログラムの高度化を継続して行った。鉄系酸化物の三次元顕微鏡データを用いて、解析が可能であることを確認し、更に可視化の高度化を推進中である。
    (4)なお、当初予定していた耐環境性セラミックスコーティング(EBC)の観察については、試料の製造が困難であることが判明し、代替として鉄系酸化物の還元過程のX線顕微鏡観察に取り組むこととし、その準備を進めた。

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  • ハイブリッド力学系としての二足歩行の吸引領域の形成メカニズムに注目した解析

    Grant number:16K17638  2016.04 - 2020.03

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Young Scientists (B)  Grant-in-Aid for Young Scientists (B)

    大林 一平

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    Grant amount:\3640000 ( Direct expense: \2800000 、 Indirect expense:\840000 )

    去年度の「今後の研究」の所に書いた通り、この年度は位相的データ解析の研究のほうに力を入れて研究した。
    パーシステントホモロジーと機械学習の組み合わせに関する論文がこの5月に出版された。パーシステントホモロジーはデータの形を定量的に抽出することができ、機械学習はデータに隠されたパターンを発見(学習)することができる。この2つの組み合わせによってデータの特徴的な幾何的パターンを抽出することが可能となる。さらにこれに逆解析という手法を組み合わせることでその特徴的パターンの起源を具体的なかたちとして取り出すこともできる強力な手法である。材料科学データへの応用例や他の画像解析手法との比較なども含まれ、実践的な応用がしやすい結果であると言える。
    また、10月にはパーシステントホモロジーの逆問題に関する論文も出版された。この問題では上に挙げた逆解析の新しい手法を提案する論文である。パーシステント図は2次元平面上のヒストグラムとして表現されるが、ヒストグラム上の各点はデータのホモロジー的構造(穴や空洞など)と対応している。この構造を抽出できれば(上の機械学習によるデータ解析のような)データ解析で有用であるが、それは数学的に容易な問題ではない。既存の手法として「ホモロジー最適化」と呼ばれる手法が用いられており、本論文ではそれをパーシステントホモロジーに適する形で利用した新しい手法を開発した。線形計画法で効率的に計算するアルゴリズムも提案し、それを利用可能なソフトウェア実装やそれによる計算例もこの論文で紹介している。

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  • Cross-cutting research of data- and model-driven methods by interlacing deductive and inductive cellular automata constructing method

    Grant number:16K13772  2016.04 - 2019.03

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Challenging Exploratory Research  Grant-in-Aid for Challenging Exploratory Research

    Nakano Naoto, OBAYASHI Ippei, HIROSE Sanpei

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    Grant amount:\3640000 ( Direct expense: \2800000 、 Indirect expense:\840000 )

    In this research, we studied empirical cellular automata (CA) construction method as a new modeling method for phenomena. We set the following two approaches to establish the empirical CA construction method: (A) numerical analysis on the selectivity of local rules of CA; (B) refinement of methodology for quantitative modelling. In (A), we investigated the relationship between solutions of CAs and PDEs by the use of interval operation and found the selection tendencies of resultant local rules of empirical CA mathematically. In (B), we constructed a model that mimics the solution behavior of nonlinear wave phenomena in a data driven manner. Furthermore, investigating the connection of our method with machine learning techniques and the method for analysis of global dynamics, we also obtained a novel method of modelling phenomenon.

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  • Study of Global Structures and Bifurcations of Dynamical Systems including Systems with Large Degrees of Freedom

    Grant number:21340035  2009 - 2012

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (B)

    KOKUBU Hiroshi, ARAI Zin, OKA Hiroe, OBAYASHI Ippei

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    Grant amount:\17160000 ( Direct expense: \13200000 、 Indirect expense:\3960000 )

    A great improvement of the Conley-Morse graph method, a computer-assisted method that analyzes global dynamics and bifurcations by combining a topological method and validated numerical computation has been done by developing a computer-algorithm for generating so-called clutching graphs which describe relation between Conley-Morse graphs on adjacent parameter domains. Another improvement is a method of non-uniform grid decomposition of the phase space in order to substantially decrease computational cost of the Conley-Morse graph method.A new approach to the bifurcation theory of dynamical systems from topological-computation theory viewpoint has been proposed which captures bifurcation of dynamics from changes of the corresponding Conley-Morse graphs. From this viewpoint, we have obtained a new mathematical framework for the crisis bifurcation.Moreover, we have studied the global dynamics of a Coupled Map Lattice system and a Coupled Oscillator system by using the Conley-Morse graph method, and have obtained the creation and bifurcations of some global dynamics such as unstable invariant tori and their connecting orbits.

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  • Basic Data Utilization (2023academic year) Third semester  - 月5~6,木3~4

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  • Seminar on Mathematical Science for Data Engineering (2023academic year) Late  - その他

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  • Seminar in Mathematical Science for Data Engineering B (2023academic year) Year-round  - その他

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Media Coverage

  • 岩石内の流体流動、実験いらずで直接予測 東北大 Newspaper, magazine

    日刊工業新聞社  日刊工業新聞  2021.9.24

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