SHIMOKAWA Michiko
Faculty Division of Natural Sciences Research Group of Physics | Associate Professor |
Last Updated :2025/04/27
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Profile Information
Name (Japanese)
SHIMOKAWAName (Kana)
MICHIKO
■Ⅱ.研究活動実績
Published Papers
- Refereed, Journal of the Physical Society of Japan, Physical Society of Japan, Transition of the Bifurcations in the Rotation of a Camphor-Coated Elliptical Paper Disk, Michiko Shimokawa; Junma Arimitsu; Hiroyuki Kitahata; Hidetsugu Sakaguchi, 15 Mar. 2024, 93, 3, Scientific journal, 10.7566/jpsj.93.034002
- Refereed, Journal of the Physical Society of Japan, Physical Society of Japan, Hula-Hoop-Like Motion and Subcritical Bifurcation of the Rotation of an Elliptical Paper Disk Coated with Camphor, Michiko Shimokawa; Hidetsugu Sakaguchi, 15 Jul. 2022, 91, 7, Scientific journal, 10.7566/jpsj.91.074002
- Refereed, Europhysics Letters, IOP Publishing, Observation and a simple model of plumose pattern on fracture surfaces of drying pastes, Hidetsugu Sakaguchi; Kazuki Yamada; Michiko Shimokawa, Abstract
Plumose pattern often appears on the fracture surface of drying pastes. We show a few experimental results of the crack propagation in the drying pastes. We find that the crack propagation sometimes exhibits jump motions. We have also performed an experiment of the crack propagation in a tilted container where the crack propagates from the deeper to shallower sides. This experimental result suggests the importance of the movement of water content. We propose a simple coupled map lattice model. In the numerical simulation, a plumose-like pattern appears owing to the instability of the flat surface of the fracture. The numerical simulation reproduces the jump motions in the crack propagation. We have performed another experiment where a vertical streak pattern appears when the crack propagates downward by cutting into the top surface of the drying paste., 01 Apr. 2022, 138, 1, 16002, 16002, Scientific journal, 10.1209/0295-5075/ac61b0 - Refereed, Europhysics Letters, IOP Publishing, Star-shaped patterns caused by colloidal aggregation during the spreading process of a droplet, Michiko Shimokawa; Hiroyuki Kitahata; Hidetsugu Sakaguchi, Abstract
In this study, we discovered that, when an acidic solution with a low surface tension spreads on the surface of a glycerol solution mixed with milk, a star-shaped pattern is spontaneously formed on the surface in the horizontal plane during the spreading process. We experimentally investigated the emergence of the star-shaped pattern caused by an interfacial instability by using glycerol and aqueous 2-methoxyethanol solutions, which are acidic solutions; we chose the viscosity of the glycerol solution and concentration of both solutions as free parameters. The result demonstrated that the star-shaped pattern emerged when the concentration of 2-methoxyethanol was high. We proposed a phenomenological model based on our experimental results, which explains the following three points: the spreading of the aqueous 2-methoxyethanol solution on the surface of the glycerol solution; colloidal aggregation of the milk protein colloids caused by the denaturation that occurs when mixed with 2-methoxyethanol; accumulation of the aggregates toward the dent regions of the moving interface by a sweeping effect. The model reproduced the star-shaped pattern, which was similar to the experimental one. Furthermore, the concentration of the 2-methoxyethanol solution and the viscosity of the glycerol solution were taken as control parameters in our experiments and were varied, and a phase diagram was obtained. The phase diagram was similar to that obtained from our experiments. The results suggest that the above three points are important for the formation of the star-shaped pattern., 01 Oct. 2020, 132, 1, 18002, 18002, Scientific journal, 10.1209/0295-5075/132/18002 - Refereed, Aug. 2017, 72, 8, 570, 575, Scientific journal, 10.11316/butsuri.72.8_570
- Refereed, Physical Review E, The American physical society, Breakup and deformation of a droplet falling in a miscible solution, Michiko Shimokawa; Ryosei Mayumi; Taiki Nakamura; Toshiya Takami; Hidetsugu Sakaguchi, 2016, 93, 062214(1), (6)
- Refereed, Modern physics letters B, World Scientific, Effect of fluid viscosity on surface patterns formed by gravitational instability, Michiko Shimokawa; Toshiya Takami, 2015, 29, 1550237(1), (11)
- Refereed, Physical Review E, The American physical society, Pattern formation in a sandpile of ternary granular mixtures, Michiko Shimokawa; Yuki Suetsugu; Ryoma Hiroshige; Takeru Hirano; Hidetsugu Sakaguchi, 2015, 91, 062205(1), (6)
- Refereed, Journal of the Physical Society of Japan, Wavelength Analysis of Interface between Two Miscible Solutions Observed in Formation of Fractal Pattern, Michiko Shimokawa; Toshiya Takami, 2014, 83, 044001(1), (5)
- Refereed, Physical Review E, The American physical society, Size distribution of cell pattern observed in gravitational instability, Michiko Shimokawa; Hiroyuki Kitahata; Tatsunari Sakurai, 2013, 87, 012903(1), (5)
- Refereed, Fractals, World Scientific, Annihilative fractals formed in Rayleigh-Taylor instability, Michiko Shimokawa; Shonosuke Ohta, 2012, 20, 97, 104
- Refereed, Journal of the Physical Society of Japan, Experimental Study on Transition in Fractal Patterns Derived from Vertical Flow, Michiko Shimokawa, 2012, 81, 094003(1), (5)
- Refereed, Physical Review E, The American physical society, Spontaneous formation of dual stratification patterns in a large quasi-two-dimensional sand pile, Michiko Shimokawa; Shonosuke Ohta, 2008, 77, 011305(1), (8)
- Refereed, Physics Letters A, ELSEVIER, Dual stratification of a Sand Pile formed by Trapped kink, Michiko Shimokawa; Shonosuke Ohta, 2007, 366, 591, 595
- Refereed, Proceedings of 8th Cross Straits Symposium on Materials, Energy and Environment Science, New Dual stratification in a Sand Pile formed by Trapped kink, Michiko Shimokawa; Shonosuke Ohta, 2006, 267, 268
- Refereed, Powder and Grains `05, Garcia-Rojo, The experimental study on a period of granular stratification pattern, Michiko Shimokawa; Shonosuke Ohta; Akio Nakahara, 2005, 1295, 1298
MISC
- Meeting Abstracts of the Physical Society of Japan, The Physical Society of Japan, Star shaped pattern formed by colloid aggregation, Shimokawa Michiko; Kitahata Hiroyuki; Sakaguchi Hidetsugu, 2019, 74.2, 2609, 2609, 10.11316/jpsgaiyo.74.2.0_2609
- Meeting Abstracts of the Physical Society of Japan, The Physical Society of Japan, Simulation on the control of pattern growth in paint coating, Omachi Rena; Shimokawa Michiko; Kudo Kazue, 2018, 73, 2635, 2635, 10.11316/jpsgaiyo.73.2.0_2635
- Meeting Abstracts of the Physical Society of Japan, The Physical Society of Japan, Star shaped pattern formed by magnetic fluid on milk, Shimokawa Michiko; Komiya Toshiki; Toshimitsu Akio; Kitahata Hiroyuki; Sakaguchi Hidetsugu, 2018, 73.1, 2978, 2978, 10.11316/jpsgaiyo.73.1.0_2978
- Meeting Abstracts of the Physical Society of Japan, The Physical Society of Japan, Pattern formation on doubly coated paints, Omachi Rena; Shimokawa Michiko; Kudo Kazue, 2018, 73, 2956, 2956, 10.11316/jpsgaiyo.73.1.0_2956
- 2018, 32, 1, 巻頭, Others
- Meeting Abstracts of the Physical Society of Japan, The Physical Society of Japan, Formation of wrinkles at surface of paint film observed in dry process, Shimokawa Michiko; Kudo Kazue, 2017, 72, 2840, 2840, 10.11316/jpsgaiyo.72.2.0_2840
- 2016
- 2016, SS16
- 2016, 225, 9
- Determination of Power Index on Scaling Law of Crater-size, 2016, 33, 59, 61
- 2015, 32, 23, 25
- 2013, 41, 51
- 2012, 67, 2
- 2008, 23, 2, 140, 141
- 9th Tamura symposium Frontiers in Dynamics: Physical and Biological Systems, Dual stratification of a Sand Pile formed by Trapped kink, Michiko Shimokawa; Shonosuke Ohta, 2006, 28, 3, 323, 334, 10.15017/14562
- Not Refereed, Meeting Abstracts of the Physical Society of Japan, The Physical Society of Japan, 27aPS-35 The stratification pattern formed from binary mixtures of grains, Shimokawa M.; Nishio Y.; Nakahara A.; Ohta S., 2005, 60, 0, 326, 326, 10.11316/jpsgaiyo.60.1.2.0_326_2
- 2004, Article No. 44
Presentations
- Michiko Shimokawa, Niels Bohr Institute seminar, Bifurcation of Rotational Motion of Elliptical Camphor Coated Disk, Public discourse, 04 Apr. 2025
- Oral presentation, 07 Mar. 2025, 07 Mar. 2025 - 08 Mar. 2025
- Michiko Shimokawa; Hiroyuki Kitahata, International Active Matter Workshop 2025, Bifurcation phenomena of a rotating camphor boat, Poster presentation, 24 Jan. 2025, 24 Jan. 2025 - 25 Jan. 2025
- Poster presentation, 30 Nov. 2024, 30 Nov. 2024 - 30 Nov. 2024
- Michiko Shimokawa, Warwick Mathematics Institute seminar, Bifurcation of rotational motion of an elliptical camphor-coated disk, Public discourse, 04 Nov. 2024
- Michiko Shimokawa, Nottingham Trent University seminar, Bifurcation of Rotational Motion of Elliptical Camphor Coated Disk, Public discourse, 23 Oct. 2024
- Oral presentation, 16 Sep. 2024, 16 Sep. 2024 - 19 Sep. 2024
- Michiko Shimokawa; Hidetsugu Sakaguchi, Dynamics and Design Conference 2024, Breakup and deformation of a droplet falling into a miscible solution, Oral presentation, 03 Sep. 2024, 03 Sep. 2024 - 06 Sep. 2024
- Poster presentation, 26 May 2024, 26 May 2024 - 31 May 2024
- Michiko Shimokawa, Active Matter Workshop 2024, Bifurcation of Rotational Motion of Elliptical Camphor Coated Disk, Invited oral presentation, 26 Jan. 2024
- Invited oral presentation, 21 Dec. 2023
- Oral presentation, 19 Sep. 2023
- Poster presentation, 17 Sep. 2023
- Michiko Shimokawa; Junma Arimitsu; Hiroyuki Kitahata; Hidetsugu Sakaguchi, XLIII Dynamics Days Europe, Bifurcation of rotational motion observed in experiments of elliptical camphor-coated disk, Poster presentation, 06 Sep. 2023, 03 Sep. 2023 - 08 Sep. 2023
- Oral presentation, Mar. 2022, Mar. 2022 - Mar. 2022
- Public discourse, 31 Jan. 2022, 31 Jan. 2022 - 31 Jan. 2022
- Michiko Shimokawa; Hiroyuki Kitahata; Hidetsugu Sakaguchi, Pacifichem2021, Star shaped pattern caused by colloidal aggregation during spreading of the acidic solution on the surface of milk solutions, Oral presentation, Dec. 2021, Dec. 2021 - Dec. 2021
- Oral presentation, Sep. 2021, Sep. 2021 - Sep. 2021
- Oral presentation, Sep. 2021, Sep. 2021 - Sep. 2021
- Oral presentation, Sep. 2020, Sep. 2020 - Sep. 2020
- Michiko Shimokawa; Hiroyuki Kitahata; Hidetsugu Sakaguchi, Dynamics days digital 2020, Online., Formation of star shaped pattern caused by colloidal aggregation, Oral presentation, Aug. 2020, Aug. 2020 - Aug. 2020
- Jul. 2020, Jul. 2020 - Jul. 2020
- Michiko Shimokawa, FAST (Fluides, Automatique et Systèmes Thermiques) seminar, Sand pile pattern formed by ternary mixed grains, Public discourse, Mar. 2020
- Michiko Shimokawa, ESPCI(Ecole supérieure de physique et de chimie industrielles de la ville de Paris) seminar, Pattern formation of a sand pile formed by mixed grains, Public discourse, Mar. 2020
- Michiko Shimokawa, Séminaire MSC (Complex Matter and Systems lab), Mode Selection of Breakup of Falling Droplet in Miscible Solution, Public discourse, Mar. 2020
- Oral presentation, Dec. 2019
- Invited oral presentation, Nov. 2019, 16 Nov. 2019 - 17 Nov. 2019
- Shimokawa Michiko; Kitahata Hiroyuki; Sakaguchi Hidetsugu, Meeting Abstracts of the Physical Society of Japan, Star shaped pattern formed by colloid aggregation, Oral presentation, Sep. 2019, Sep. 2019 - Sep. 2019, The Physical Society of Japan
- Michiko Shimokawa; Hidetsugu Sakaguchi, XXXIX Dynamics days Europe (DDEU 2019), Breakup of falling droplets by instability of vortex ring, Oral presentation, Sep. 2019, Sep. 2019 - Sep. 2019
- Michiko Shimokawa, BioComplexity meeting, Breakup of falling droplets by instability of vortex ring, Public discourse, Aug. 2019
- Michiko Shimokawa, Center for Fluid Dynamic seminar, Breakup of falling droplets by instability of vortex ring, Public discourse, Aug. 2019
- Michiko Shimokawa, Discussion meeting on Granular dynamics;Planetary terrain, Mode Selection of Breakup of Falling Droplet in Miscible Solution, Oral presentation, Aug. 2019
- Public discourse, Jun. 2019
- Public discourse, Jun. 2019
- Invited oral presentation, May 2019, 26 May 2019 - 30 May 2019
- Public discourse, May 2019
- Public discourse, May 2019
- Oral presentation, Mar. 2019, Mar. 2019 - Mar. 2019
- Michiko Shimokawa; Hidetsugu Sakaguchi, BIT’s Annual World Congress of Smart Materials 2019, Mode selection of Breakup of Falling Droplet in Miscible solution, Oral presentation, Mar. 2019, Mar. 2019 - Mar. 2019
- Oral presentation, Dec. 2018, Dec. 2018 - Dec. 2018
- Oral presentation, Dec. 2018, Dec. 2018 - Dec. 2018
- Michiko Shimokawa; Hidestugu Sakaguchi, International conference on Advances in Physics of Emergent orders in Fluctuations, Mode selection of the breakup of a droplet falling into a miscible solution, Oral presentation, Nov. 2018, Nov. 2018 - Nov. 2018
- Kazue Kudo; Michiko Shimokawa, International conference on Advances in Physics of Emergent orders in Fluctuations, Simulations of nonlinear buckling in coating, Oral presentation, Nov. 2018, Nov. 2018 - Nov. 2018
- Invited oral presentation, Sep. 2018, 01 Sep. 2018 - 02 Sep. 2018
- Omachi Rena; Shimokawa Michiko; Kudo Kazue, Meeting Abstracts of the Physical Society of Japan, Simulation on the control of pattern growth in paint coating, Oral presentation, Sep. 2018, Sep. 2018 - Sep. 2018, The Physical Society of Japan
- Shimokawa Michiko; Kitahata Hiroyuki, Meeting Abstracts of the Physical Society of Japan, Power law observed in the motion of an asymmetric camphor boat under viscous conditions, Oral presentation, Sep. 2018, Sep. 2018 - Sep. 2018, The Physical Society of Japan
- Michiko Shimokawa; Hidetsugu Sakaguchi, Gordon Research Seminar ―Oscillations and Dynamic Instabilities in Chemical Systems―, Mode selection on the breakup of a falling droplet in a miscible solution, Poster presentation, Jul. 2018, Jul. 2018 - Jul. 2018
- Michiko Shimokawa; Hiroyuki Kitahata, Gordon Research Conference ―Oscillations and Dynamic Instabilities in Chemical Systems―, Power law observed in the motion of an asymmetric camphor boat in viscous conditions, Poster presentation, Jul. 2018, Jul. 2018 - Jul. 2018
- Mar. 2018, Mar. 2018 - Mar. 2018
- Mar. 2018, Mar. 2018 - Mar. 2018
- Mar. 2018
- Dec. 2017
- Dec. 2017
- Dec. 2017
- Dec. 2017
- Dec. 2017
- Dec. 2017
- Dec. 2017
- Rena Omachi; Kazue Kudo; Michiko Shimokawa, International Symposium on Fluctuation and Structure out of Equilibrium 2017, Simulations of Buckling Patterns in Paint Coatings, Nov. 2017, Nov. 2017 - Nov. 2017
- Nov. 2017
- Nov. 2017
- Nov. 2017
- Nov. 2017
- Nov. 2017
- Nov. 2017
- Nov. 2017
- Shimokawa Michiko; Kudo Kazue, Meeting Abstracts of the Physical Society of Japan, Formation of wrinkles at surface of paint film observed in dry process, Sep. 2017, Sep. 2017 - Sep. 2017, The Physical Society of Japan
- Kazue Kudo; Michiko Shimokawa, IUMRS-ICAM 2017, Simulation of Nonlinear buckling in Coating, Aug. 2017, Aug. 2017 - Aug. 2017
- Michiko Shimokawa; Hidetsugu Sakaguchi, IUMRS-ICAM 2017, Breakup of a falling droplet in miscible viscous fluid, Aug. 2017, Aug. 2017 - Aug. 2017
- Michiko Shimokawa; Kazue Kudo, IUMRS-ICAM 2017, Emergence of wrinkles in double coating process, Aug. 2017, Aug. 2017 - Aug. 2017
- Aug. 2017
- Deformation and Breakup of a Droplet Falling into a Viscous Fluid, 2017, 2017 - 2017
- Dec. 2016
- Nov. 2016
- Sep. 2016, Sep. 2016 - Sep. 2016
- Shimokawa Michiko; Sakaguchi Hidetsugu, Meeting Abstracts of the Physical Society of Japan, Mode selection on breakup of a droplet falling in viscous fluid, Sep. 2016, Sep. 2016 - Sep. 2016, The Physical Society of Japan
- Michiko Shimokawa; Toshiya Takami; Hidetsugu Sakaguchi, STATPHYS 26, Origin of Instability derived, Jul. 2016, Jul. 2016 - Jul. 2016
- Jun. 2016
- May 2016
- Michiko Shimokawa; Hidetsugu Sakaguchi, Mini-symposium on cooperative phenomena in nonequilibrium systems, Breakup and deformation of a falling droplet in a miscible solution, 04 Mar. 2016, 04 Mar. 2016 - 04 Mar. 2016
- Jan. 2016
- Michiko Shimokawa; Ryu Egashira, The International Chemical Congress of Pacific Basin Societies 2015(Pacifichem 2015), Navigation speed of a camphor boat on bubbly water, Dec. 2015, Dec. 2015 - Dec. 2015
- Nov. 2015
- Oct. 2015
- Toshiya Takami; Michiko Shimokawa, Dynamics days Europe (DDEU 2015), Temporal parallel approach to nonlinear problems with multiple time-scales, Sep. 2015, Sep. 2015 - Sep. 2015
- Michiko Shimokawa; Toshiya Takami, Dynamics days Europe (DDEU 2015), Deformation and breakup process of a droplet, Sep. 2015, Sep. 2015 - Sep. 2015
- Michiko Shimokawa, BioComplexity meeting, Pattern formation in a sandpile of ternary granular mixtures, Sep. 2015
- Jul. 2015
- Jul. 2015
- Jun. 2015
- Shimokawa M.; Suetsugu Y.; Hiroshige R.; Hirano T.; Sakaguchi H., Meeting Abstracts of the Physical Society of Japan, 21aPS-25 Pattern formation on a sand pile of ternary grains, Mar. 2015, Mar. 2015 - Mar. 2015, The Physical Society of Japan (JPS)
- Mar. 2015
- Dec. 2014
- Nov. 2014
- Sep. 2014, Sep. 2014 - Sep. 2014
- Michiko Shimokawa; Toshiya Takami, International Conference on Statistical Physics (SigmaPhi 2014), Experimental study of fractal pattern observed in gravitational instability, Jul. 2014, Jul. 2014 - Jul. 2014
- Jul. 2014
- May 2014
- Mar. 2014, Mar. 2014 - Mar. 2014
- Nov. 2013
- Sep. 2013, Sep. 2013 - Sep. 2013
- Sep. 2013, Sep. 2013 - Sep. 2013
- Sep. 2013
- Toshiya Takami; Michiko Shimokawa; Hiroshi Fujisaki; Taizo Kobayashi, XXV IUPAP International Conference on Statistical Physics (Statphys25), Random Aggregation Models and Simulations for Coffee Fractals on Milk, Jul. 2013, Jul. 2013 - Jul. 2013
- Michiko Shimokawa; Toshiya Takami, XXV IUPAP International Conference on Statistical Physics (Statphys25), Transition between Fractal and Cell Patterns Derived from Vertical Convection, Jul. 2013, Jul. 2013 - Jul. 2013
- May 2013
- Mar. 2013, Mar. 2013 - Mar. 2013
- Feb. 2013
- Dec. 2012
- Dec. 2012
- Oct. 2012
- Sep. 2012, Sep. 2012 - Sep. 2012
- Sep. 2012, Sep. 2012 - Sep. 2012
- Sep. 2012, Sep. 2012 - Sep. 2012
- Michiko Shimokawa; Hiroyuki Kitahata; Tatsunari Sakurai, Dynamics Days Europe 32 (DDEU32), Size distribution of cell pattern formed in experiment of gravitational instability, Sep. 2012, Sep. 2012 - Sep. 2012
- Toshiya Takami; Michiko Shimokawa; Hiroshi Fujisaki; Taizo Kobayashi, Dynamics Days Asia/Pacific 7 (DDAP 7), Particle Simulations to Create Coffee Patterns on Milk, Aug. 2012, Aug. 2012 - Aug. 2012
- Aug. 2012
- Jul. 2012
- Mar. 2012, Mar. 2012 - Mar. 2012
- Jan. 2012
- Michiko Shimokawa, International symposium on complex systems 2011-Perspectives on the legacy of Torahiko Terada-, Surface pattern formed in Rayleigh-Taylor instability, Dec. 2011, Dec. 2011 - Dec. 2011
- Sep. 2011, Sep. 2011 - Sep. 2011
- Toshiya Takami; Michiko Shimokawa; Hiroshi Fujisaki; Taizo Kobayashi, Dynamics Days Europe 31 (DDEU31), Coffee Patterns Generated by Slow Dynamics, Jul. 2011, Jul. 2011 - Jul. 2011
- Sep. 2010, Sep. 2010 - Sep. 2010
- Sep. 2010, Sep. 2010 - Sep. 2010
- Toshiya Takami; Michiko Shimokawa; Hiroshi Fujisaki; Taizo Kobayashi, Dynamics Days Asia Pacific 6 (DDAP6), Deformation and Separation Dynamics of a Coffee Droplet in Milk, Jul. 2010, Jul. 2010 - Jul. 2010
- Feb. 2010
- Dec. 2009
- Nov. 2009
- Oct. 2009
- Sep. 2009, Sep. 2009 - Sep. 2009
- Jun. 2009
- Nov. 2008
- Sep. 2008, Sep. 2008 - Sep. 2008
- Sep. 2007, Sep. 2007 - Sep. 2007
- Michiko Shimokawa; Shonosuke Ohta, The 23rd International Conference on Statistical Physics (STATPHYS23), Dual stratification of a Sand Pile formed by Trapped kink, 2007, 2007 - 2007
- Michiko Shimokawa; Shonosuke Ohta, Statics and dynamics of granular media and colloidal suspensions, Dual stratification of a Sand Pile formed by Trapped kink, 2007, 2007 - 2007
- Apr. 2005
- Mar. 2005, Mar. 2005 - Mar. 2005
- Nov. 2004
- Sep. 2004, Sep. 2004 - Sep. 2004
Awards
- Langmuir poster award, The 15th international conference on Advanced materials (IUMRS-ICAM 2017), Aug. 2017, Emergence of wrinkles in double coating process
- ベストポスター賞, International Conference on Statistical Physics (SigmaPhi 2014), Jul. 2014, Experimental study of fractal pattern observed in gravitational instability
- Jul. 2012
- Mar. 2006
Research Projects
- 基盤研究(C), Apr. 2024 - Mar. 2027, 24K06978, 樟脳船を用いたアクティブマターの集団ダイナミクスの解明, 下川 倫子, 日本学術振興会, 科学研究費助成事業, 奈良女子大学, 4680000, 3600000, 1080000, kaken
- Sep. 2025 - Mar. 2026, Principal investigator, 墨割のパターン形成ダイナミクスに関する実験的研究 ―美術作品から創発されるソフトマター物理における普遍法則の探求―, 下川倫子, 公益財団法人山田科学振興財団, 海外研究援助
- Mar. 2023 - Dec. 2024, エクスプロラシオン・フランス2024, 下川倫子, フランス大使館
- Nov. 2023 - Nov. 2024, 樟脳船を用いた実験による渋滞現象の解明, 下川倫子, 公益財団法人住友財団 基礎科学研究助成
- Grant-in-Aid for Scientific Research (C), 01 Apr. 2021 - 31 Mar. 2024, 21K11789, A New Analytic Approach to Time-series of Collective Motion with Integrated Statistical and Mathematical Modeling Strategy, 高見 利也; 大城 英裕; 行天 啓二; 下川 倫子, Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C), Oita University, 4160000, 3200000, 960000, 本研究は、時系列情報をもとにシステムのモデル化を行い、人の動きや自己駆動粒子を含む複雑な運動の分析手法を開発することが最終的な目的である。初年度の研究では、ビデオ映像の分析技術に関しては、映像時系列分析手法の検討と映像分類を実施した。集団運動による時系列の例である心電図に関しては、心筋の振動モデルを実装した。以下、これらに関してそれぞれ記述する。
ビデオ映像に関する実績では、人の動きをとらえたビデオを分析し、動きによって分類するシステムを試作した。空間方向2次元と時間の方向を合わせて三次元のデータを分析するには、広く画像の分析に使われる2次元の畳み込みに加えて、時間方向の畳み込みを導入する必要があるが、まずは時間方向を特別視しない均質な三次元畳み込み層を導入して、その性能について検証を実施した。また、類似の運動を記録した二つの時系列データ間で、時間遅れの存在を検出するために、既存の動的時間伸縮法(Dynamic Time-Warping, DTW)を応用したシステムを検討した。今後、動的モード分解(Dynamic Mode Decomposition, DMD)を利用した時系列分割のシステムと融合する形で、自己駆動粒子の実験映像から得た時系列データの分析に使用していく予定である。
心電図については、心電図を再現することのできる数理モデルの一つを実装し、今後の詳細な分析のためのデータを作成した。心電図は集団的に振動する心筋細胞の表面電位を体表面で記録したものであるが、この時系列データから心筋細胞の運動を再現することは解析的な手法では不可能であり、いわゆる逆問題を解く必要がある。そこで、この逆問題を深層学習を利用して解決することが可能かどうかを検討するためのデータ作成を目的としたものである。このデータを利用した逆問題の分析手法の確立は、次年度以降に実施する。, kaken - 基盤研究(C), Apr. 2018 - Mar. 2024, 18K03572, 界面不安定性による多角形渦輪の形成メカニズム, 下川 倫子; 坂口 英継, 日本学術振興会, 科学研究費助成事業 基盤研究(C), 福岡工業大学, 4420000, 3400000, 1020000, 本研究の目的は、渦輪の多角形への変形メカニズムの解明を通して粘性流体における非平衡界面の変形現象を理解することである。粘性流体中を沈降する液滴は 沈降過程で渦輪に変形した後、自発的にいくつかの液滴に分裂する。日常生活で使用する万年筆のインクとグラスに注いだ水を使えば、誰でも簡単に観察できる身近な現象であるが、液滴の形状や沈降速度が時間とともに変化する非定常な系であるため、そのダイナミクスが十分に理解されているとは言えない。そこで、我々は液滴と粘性流体の界面で生じる不安定化についての研究を通して、そのダイナミクスを理解することを考えた。昨年度は、沈降する渦輪の不安定化によるモード選択の揺らぎについて、実験と数値計算の両方からアプローチした。今年度は、粘性流体の水深を浅くした条件下で起こる水平方向の界面不安定性に焦点を当てた。実験で、液滴に含まれる界面活性剤の濃度と溶液の粘度を変化させ、実験を行い、二流体界面で不安定化が起こる領域を調べた。次に、二流体の界面張力差による液滴溶液の駆動、二流体界面で生じるコロイド凝集、二流体界面で凝集されたコロイドのはきよせを考慮した現象論的モデルを提案した。現象論的モデルから、二流体界面での安定性を調べたところ、実験と同様の傾向が得られた。以上のことより、上記3要素が水平方向の不安定化において重要であることが分かった。昨年度に実施した渦輪の不安定化のモード選択については、国際学会や国内の学会で発表し、海外の研究室のセミナーで講演した。また、本年度実施した水平方向の不安定化に関しては、国内の学会で発表し、現在、学術論文を投稿中である。, kaken
- Grant-in-Aid for Scientific Research (C), 01 Apr. 2018 - 31 Mar. 2021, 18K11338, Construction of data-driven simulations through video analysis of self-propelled particle systems, Takami Toshiya, Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C), Oita University, 4420000, 3400000, 1020000, Research was conducted for the purpose of modeling complex particle systems and constructing simulation. First, we analyzed the time series of the self-driven particle system and showed that the change point of complex motion can be detected by a method applying dynamic mode decomposition. Furthermore, time-series data was extracted based on the experimental images, a mathematical model for expressing this motion was estimated, and statistical analysis including causal analysis was performed. As a result, we successfully established the procedure from video to the mathematical model even for unknown motion., kaken
- 2019 - 2019, 公益財団法人日本科学協会・第2期 海外発表促進助成, 下川倫子
- Grant-in-Aid for Scientific Research (C), 01 Apr. 2015 - 31 Mar. 2018, 15K04760, Construction and Validation of Multi-scale Simulations based on the Parallel-in-Time Method, Takami Toshiya; Toda Mikito; Takahashi Kin'ya; Fujisaki Hiroshi, Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C), Oita University, 4940000, 3800000, 1140000, Parallel computations by the use of multi-scale descriptions for quantum systems, two-phase fluids, and sound/fluid complex systems have been executed. Through these studies, it was established that the space-time parallel method is effective to systems described by non-parabolic partial differential equations. On the other hand, it was also revealed that systems under ordinary differential equations are difficult to be parallelized by the parallel-in-time method. This is because convergence property is poor and an application area is narrow. In this study, we demonstrated the poor convergence in self-propelled particle systems when we parallelize them with the parallel-in-time method., url
- Grant-in-Aid for Young Scientists (B), 01 Apr. 2015 - 31 Mar. 2018, 15K17723, Experimental study of a deformation of a droplet, SHIMOKAWA MICHIKO, Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Young Scientists (B), Fukuoka Institute of Technology, 4160000, 3200000, 960000, When a droplet falls into a viscous solution, the droplet breaks up spontaneoustly in the falling process. It was reported that the droplet deformed to a vortex ring and the instability of the vortex ring leaded to the breakup of the droplet.The origin of the instability, however, had not been clarified. In order to know the origin of the vortex instability, we investigated wavelengths of the instability in experiments. The wavelengths agreed with the wavelengths of Rayleigh Taylor instability, obtained from a numerical simulation. Thus, we considered that Rayleigh Taylor instability played an important role for the instability of the vortex ring., url
- Apr. 2015 - Mar. 2016, Principal investigator, 滴変形の動的ダイナミクスに関する実験的研究, 私学振興事業, 学術研究振興資金(若手研究者奨励金)
- Jan. 2012 - May 2014, Principal investigator, 重力不安定により形成される表面パターンの実験的研究, 住友財団, 基礎科学助成
- Grant-in-Aid for Scientific Research (C), 2011 - 2013, 23540454, Establishment of Multiscale Analysis for Daily Nonlinear Phenomena and its Application, TAKAMI Toshiya; FUJISAKI Hiroshi; SHIMOKAWA Michiko; KOBAYASHI Taizo; TODA Mikito; TAKAHASHI Kin'ya, Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C), Kyushu University, 4940000, 3800000, 1140000, We have experimentally studied daily nonlinear phenomena over the whole period of this research in order to simulate those phenomena on computer and to clarify the mechanism. In particular, we have found that the initial pattern formation of coffee fractals on milk is explained by viscous fingering. Since we have tried to analyze those phenomena 'as is', it is required to develop multiscale approach. In the field of the multiscale analysis, we showed efficiency of the multiscale method for time-direction, which leads to the next study on the multiscale analysis of nonlinear phenomena., url
- Apr. 2009 - Mar. 2010, Principal investigator, レイリーテーラー不安定性の中で見られる新しいフラクタル構造, 笹川科学研究助成
- Grant-in-Aid for Research Activity Start-up, 2009 - 2010, 21840054, Experimental study on granular phase transition, MICHIKO Shimokawa, Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research Grant-in-Aid for Research Activity Start-up, Setsunan University, 2028000, 1560000, 468000, When the external force is exceeded with one critical level, granular starts to move. From the view of the group motion of granular, this behavior is recognized as the granular phase transition. To understand the phase transition, the vibration experiments were conducted. The glass beads, which diameter is 0.1 mm, are poured into an inclined rectangular case, and are vibrated at the right angle to the slope of the case. In this experiment, granular climbs upward on the slope. In the process of the transport upward of the slope, surface patterns formed by grains are observed on the slope. According to the increasing of external force, the surface pattern changes; stripe pattern, cluster pattern, bubble pattern. And, vibration was added from both horizontal direction and vertical direction, which leads that the horizontal vibration is important to transport the granular upward of the slope. In addition, it was found that the interaction between granules is derived from the formation of surface patterns by the observation of high speed camera., url
- 特別研究員奨励費, 2006 - 2008, 06J09777, 粉体系の不可逆な偏析現象と非平衡定常状態における揺らぎの実験的研究, 下川 倫子, 日本学術振興会, 科学研究費助成事業 特別研究員奨励費, 九州大学, 2400000, 2400000, 本年度は研究課題のキーワードにある「粉体の揺らぎ」に焦点を当て、実験を行った。粉体は粉、粒はもちろん、コロイド、磁性流体もその対象である。1、2年目は粉体の代表例であるガラスビーズ、砂糖を使った実験を行った。本年度は特殊な粉体であるコロイド溶液を用い、重力不安定な条件の下、発生する揺らぎが作る構造について調べた。その結果、コーヒーが牛乳界面に作る新しいフラクタルパターンを発見した。コロイド溶液として、身近にある密度の大きいコーヒーと密度の小さい牛乳を用いた。実験方法は、円形容器に牛乳を入れ、放置した後、静止した牛乳表面の中央に0.2mlのコーヒーの滴を静かに置くというものである。初期条件で軽い牛乳の上に重いコーヒーを載せているので、初期的に重力不安定な状態を作っている。そのため、牛乳とコーヒー滴の界面で揺らぎが発生する。実験から得られた主な結果は以下の2つである。
(1)コーヒー滴を牛乳界面に置くと、滴は表面に沿って拡がり、約70秒後、表面パターンが観察された。画像処理で画像を2値化し、密度相関関数法とボックスカウント法を用いてフラクタル解析を行った結果、べき乗則に従うフラクタルパターンと判明した。フラクタル次元はコーヒー密度に依存せず、表面パターンが消滅する約400秒後まで、一定値1.88±0.06を示した。磁性流体の滴を用いて同様の実験を行い、コーヒーのパターンと一致するフラクタル次元1.88±0.04を得た。
(2)コーヒーのフラクタルパターンは、密度の大きい表面のコーヒーが鉛直方向に沈み、埋めつくされた空間から面要素がぬけることで形成される。そのため、無限時間の極限でパターン面積は0に収束する。この消滅的性質は数学モデルのシェルピンスキーカーペットと共通している。このモデルの面積が指数関数的に減少することにヒントを得て、コーヒーパターンの輝度を測定し、パターン密度の時間変化を求めた。パターン密度は指数関数的に減少し、その時定数は70秒であり、前に述べたフラクタル解析が可能となる約70秒と一致した。, kaken