Updated on 2023/02/06

写真a

 
YAMAZAKI, Yoshihiro
 
Scopus Paper Info  
Paper Count: 0  Citation Count: 0  h-index: 5

Citation count denotes the number of citations in papers published for a particular year.

Affiliation
Faculty of Science and Engineering, School of Advanced Science and Engineering
Job title
Professor

Concurrent Post

  • Faculty of Education and Integrated Arts and Sciences   School of Education

  • Faculty of Science and Engineering   Graduate School of Advanced Science and Engineering

Research Institute

  • 2022
    -
    2024

    Waseda Research Institute for Science and Engineering   Concurrent Researcher

Education

  • 1996.04
    -
    1999.03

    京都大学大学院   理学研究科   物理学・宇宙物理学専攻  

  • 1994.04
    -
    1996.03

    京都大学大学院   理学研究科   物理学第1専攻  

  • 1990.04
    -
    1994.03

    Kyoto University   Faculty of Engineering  

Degree

  • 京都大学 1999年3月   博士(理学)

Research Experience

  • 2010.04
    -
    Now

    Waseda University   Faculty of Science and Engineering

  • 2007.04
    -
    2010.03

    Waseda University   Faculty of Science and Engineering

  • 2005.04
    -
    2007.03

    Waseda University   School of Science and Engineering

  • 2003.04
    -
    2005.03

    Waseda University   School of Science and Engineering

  • 2002.04
    -
    2003.03

    Chuo University   Faculty of Science and Engineering, Department of Physics

  • 2001.04
    -
    2002.03

    Chuo University   Faculty of Science and Engineering, Department of Physics

  • 1999.04
    -
    2001.03

    日本学術振興会 特別研究員   (広島大学大学院 理学研究科)   PD

▼display all

Professional Memberships

  •  
     
     

    THE JAPAN SOCIETY FOR INDUSTRIAL AND APPLIED MATHEMATICS

  •  
     
     

    THE ADHESION SOCIETY OF JAPAN

  •  
     
     

    日本物理学会

 

Research Areas

  • Mathematical physics and fundamental theory of condensed matter physics

Papers

  • Condition of Weak Discontinuity for Percolation Models with Edge Selection Rule Depending on Cluster Sizes

    Yamada Yuhei, Yamazaki Yoshihiro

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   87 ( 8 )  2018.08  [Refereed]

     View Summary

    With regard to rapid transition in percolation on graphs, a sufficient condition for cluster sizes to realize the weak discontinuity is derived. We focused on a group of models in which edges are added between nodes with a probability depending on their cluster sizes. It is found that the Erdos-Renyi model becomes weakly discontinuous depending on some initial condition.

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  • Transient properties of probability distribution for a Markov process with size-dependent additive noise

    Yuhei Yamada, Yoshihiro Yamazaki

    Journal of the Physical Society of Japan   87 ( 4 )  2018  [Refereed]

     View Summary

    This study considered a stochastic model for cluster growth in a Markov process with a cluster size dependent additive noise. According to this model, the probability distribution of the cluster size transiently becomes an exponential or a log-normal distribution depending on the initial condition of the growth. In this letter, a master equation is obtained for this model, and derivation of the distributions is discussed.

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  • 統計物理の眼で見るサッカー

    成塚拓真, 山崎義弘

    日本物理学会誌   72 ( 10 ) 747‐751  2017.10  [Refereed]

    DOI

  • Existence of thickness threshold for crystal growth rate of ascorbic acid from its thin solution film

    Yoshihiro Yamazaki, Hiroki Yoshino, Mitsunobu Kikuchi, Sakiko Kashiwase

    JOURNAL OF CRYSTAL GROWTH   468   43 - 45  2017.06  [Refereed]

     View Summary

    Growth rate of ascorbic acid crystal domains from its aqueous solution film depends on the film thickness. Existence of a thickness threshold is experimentally confirmed below which growth rate becomes quite low and is considered to almost stop. This threshold is one of the essential factors for the dynamical transition between uniform and rhythmic growth modes.

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    1
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  • Dynamical Transitions between Stick-Slip and Steady Motions of Bistable Units with Global and Asymmetric Local Interactions

    Yoshihiro Yamazaki

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   86 ( 4 )  2017.04  [Refereed]

     View Summary

    For a system consisting of bistable units with global and asymmetric local interactions, there exist two different types of dynamical transition between stick-slip and steady motions: continuous and discontinuous in the amplitude of stickslip motion. These two types are consistent with the experimental findings in a dry friction system. The dynamical phase diagram and other types of transition are also discussed.

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  • Statistical properties for directional alignment and chasing of players in football games

    Narizuka Takuma, Yamazaki Yoshihiro

    Europhys. Lett.   116 ( 6 )  2016.12  [Refereed]

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    4
    Citation
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  • ―身近な現象の物理―テープをはがして,考える―「粘着の物理」に向けて―

    山崎義弘

    日本物理学会誌   71 ( 5 ) 318‐322  2016.05  [Refereed]

  • A Cluster-Size Averaging Model for Strongly Discontinuous Percolation

    Yuhei Yamada, Yoshihiro Yamazaki

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   85 ( 5 )  2016.05  [Refereed]

     View Summary

    We propose a network percolation model, called cut-off model, which exhibits strongly discontinuous transition by an averaging effect of cluster sizes. In this model, a randomly selected bond is added if the size of the cluster formed by the bond is less than a times of the mean cluster size. It is shown that the model is strongly discontinuous when a is a finite constant.

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  • Cellular Automata for Spatiotemporal Pattern Formation from Reaction-Diffusion Partial Differential Equations

    Shousuke Ohmori, Yoshihiro Yamazaki

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   85 ( 1 )  2016.01  [Refereed]

     View Summary

    Ultradiscrete equations are derived from a set of reaction diffusion partial differential equations, and cellular automaton rules are obtained on the basis of the ultradiscrete equations. Some rules reproduce the dynamical properties of the original reaction-diffusion equations, namely, bistability and pulse annihilation. Furthermore, other rules bring about soliton-like preservation and periodic pulse generation with a pacemaker, which are not obtained from the original reaction-diffusion equations.

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    4
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  • Degree Distribution of Position-Dependent Ball-Passing Networks in Football Games

    Takuma Narizuka, Ken Yamamoto, Yoshihiro Yamazaki

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   84 ( 8 )  2015.08  [Refereed]

     View Summary

    We propose a simple stochastic model describing the position-dependent ball-passing network in football (soccer) games. In this network, a player in a certain area in a divided field is a node, and a pass between two nodes corresponds to an edge. Our stochastic process model is characterized by the consecutive choice of a node depending on its intrinsic fitness. We derive an explicit expression for the degree distribution and find that the derived distribution reproduces that for actual data reasonably well.

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    4
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    (Scopus)
  • Statistical properties of position-dependent ball-passing networks in football games

    Takuma Narizuka, Ken Yamamoto, Yoshihiro Yamazaki

    PHYSICA A-STATISTICAL MECHANICS AND ITS APPLICATIONS   412   157 - 168  2014.10  [Refereed]

     View Summary

    Statistical properties of position-dependent ball-passing networks in real football games are examined. We find that the networks have the small-world property, and their degree distributions are fitted well by a truncated gamma distribution function. In order to reproduce these properties of networks, a model based on a Markov chain is proposed. (C) 2014 Elsevier B.V. All rights reserved.

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    25
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  • Structure and modeling of the network of two-Chinese-character compound words in the Japanese language

    Ken Yamamoto, Yoshihiro Yamazaki

    PHYSICA A-STATISTICAL MECHANICS AND ITS APPLICATIONS   412   84 - 91  2014.10  [Refereed]

     View Summary

    This paper proposes a numerical model of the network of two-Chinese-character compound words (two-character network, for short). In this network, a Chinese character is a node and a two-Chinese-character compound word links two nodes. The basic framework of the model is that an important character gets many edges. As the importance of a character, we use the frequency of each character appearing in publications. The direction of edge is given according to a random number assigned to nodes. The network generated by the model is small-world and scale-free, and reproduces statistical properties in the actual two-character network quantitatively. (C) 2014 Elsevier B.V. All rights reserved.

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    6
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  • 粘着剤の進化と高機能化 粘着・剥離現象への物理的アプローチと粘着剤への展開

    山崎義弘

    月刊ファインケミカル   43 ( 9 ) 7 - 14  2014.09  [Refereed]

    DOI

  • Derivation of a stochastic cellular automaton model for the dynamics of bistable units with global and asymmetric local interactions

    Shousuke Ohmori, Yoshihiro Yamazaki

    PROGRESS OF THEORETICAL AND EXPERIMENTAL PHYSICS   ( 8 )  2014.08  [Refereed]

     View Summary

    By means of ultradiscretization and probabilistic treatment, we derive a stochastic cellular automaton (CA) model from a dynamical model for bistable units with global and asymmetric local interactions. The obtained CA model is composed of the elementary CA rule 254 with a probabilistic rule that regulates the average of the total cell states.

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    2
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  • Dynamical Properties in Uniform and Periodic Growth Modes of Ascorbic Acid Crystal Domain from Thin Solution Film

    Yoshihiro Yamazaki, Mitsunobu Kikuchi, Akihiko Toda, Jun-ichi Wakita, Mitsugu Matsushita

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   83 ( 6 )  2014.06  [Refereed]

     View Summary

    There exists a threshold-sensitive dynamical transition between uniform and periodic growth modes in the domain growth of ascorbic acid crystals from its aqueous supersaturated solution film. The crystal growth induces solution flow. Humidity controls the fluidity of the solution. The solution flow varies the film thickness. The threshold exists in the thickness of the solution film. If the thickness becomes lower than the threshold, the solution flow and the crystal growth almost stop.

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    4
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    (Scopus)
  • Apparent Transition in the Human Height Distribution Caused by Age-Dependent Variation during Puberty Period

    Takaki Iwata, Yoshihiro Yamazaki, Hiroto Kuninaka

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   82 ( 8 )  2013.08  [Refereed]

     View Summary

    In this study, we examine the validity of the transition of the human height distribution from the log-normal distribution to the normal distribution during puberty, as suggested in an earlier study [Kuninaka et al.: J. Phys. Soc. Jpn. 78 (2009) 125001]. Our data analysis reveals that, in late puberty, the variation in height decreases as children grow. Thus, the classification of a height dataset by age at this stage leads us to analyze a mixture of distributions with larger means and smaller variations. This mixture distribution has a negative skewness and is consequently closer to the normal distribution than to the log-normal distribution. The opposite case occurs in early puberty and the mixture distribution is positively skewed, which resembles the log-normal distribution rather than the normal distribution. Thus, this scenario mimics the transition during puberty. Additionally, our scenario is realized through a numerical simulation based on a statistical model. The present study does not support the transition suggested by the earlier study.

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    1
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  • MULTIFRACTAL ASPECTS OF AN EFFICIENT CHANGE-MAKING PROCESS

    Ken Yamamoto, Yoshihiro Yamazaki

    FRACTALS-COMPLEX GEOMETRY PATTERNS AND SCALING IN NATURE AND SOCIETY   21 ( 2 )  2013.06  [Refereed]

     View Summary

    In this paper, we focus on the "minimal payment" which minimizes the number of coins left after the payment. Two kinds of multifractal properties of the minimal payment are studied. The first one is a frequency distribution of change amounts, and the second one is a visiting probability on the delay plot of successive change amounts. When the face values of coins are power of two (1, 2, 4, 8, ... ), we find that these two distributions are related to well-known multifractal models, and derive analytical expressions of multifractal spectra.

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    1
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  • Preferential Migration and Random Mobility in Population Size Distribution of Municipalities

    Yoshihiro Yamazaki, Kenji Takamura

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   82 ( 6 )  2013.06  [Refereed]

    DOI

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    1
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  • Group-separation effect in cell-size distribution of origami crease patterns

    Ken Yamamoto, Yoshihiro Yamazaki

    Journal of the Physical Society of Japan   82 ( 4 )  2013.04  [Refereed]

     View Summary

    Some statistical properties of origami (the art of paper folding) are investigated. In a crease pattern of an origami work, a paper sheet is divided into many "cells" surrounded by creases. We compute the cell-size distributions of four origami works and find that they are described by the superposition of lognormal distributions with different averages and variances. This lognormal behavior can be explained by a successive-folding process that works as a multiplicative effect. To confirm this idea, we introduce a numerical model by only incorporating a successive-folding process, and discuss its analytical properties. Moreover, we show that a group-separation structure is also essential in origami, which is different from pure crumpling. © 2013 The Physical Society of Japan.

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    1
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  • 粘着・剥離の理論と実際~後編~剥離の時空間パターン

    山崎義弘

    コンバーテック   41 ( 3 ) 116 - 119  2013.03

  • 粘着・剥離の理論と実際~前編~剥離の非単調性

    山崎義弘

    コンバーテック   41 ( 2 ) 108 - 110  2013.02

  • Fractal behind coin-reducing payment

    Ken Yamamoto, Yoshihiro Yamazaki

    CHAOS SOLITONS & FRACTALS   45 ( 8 ) 1058 - 1066  2012.08  [Refereed]

     View Summary

    The 'minimal' payment-a payment method which minimizes the number of coins in a purse-is presented. We focus on a time series of change given back to a shopper repeating the minimal payment. By using the delay plot, the set of successive change possesses a fine structure similar to the Sierpinski gasket. We also estimate effectivity of the minimal-payment method by means of the average number of coins in a purse, and conclude that the minimal-payment strategy is the best to reduce the number of coins in a purse. Moreover, we compare our results to the rule-60 cellular automaton and the Pascal-Sierpinski gaskets, which are known as generators of the discrete Sierpinski gasket. (C) 2012 Elsevier Ltd. All rights reserved.

    DOI

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    3
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    (Scopus)
  • Spatiotemporal Patterns Formed by the Dynamics of Bistable Units with Global and Asymmetric Local Interactions

    Yoshihiro Yamazaki, Ken Yamamoto, Daisuke Kadono, Akihiko Toda

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   81 ( 4 )  2012.04  [Refereed]

     View Summary

    We propose the rule ''254'' cellular automaton model with a probabilistic global rule. The global rule regulates the proportion of total cell states. The model reproduces spatiotemporal patterns obtained by an experiment of peeling an adhesive tape. The statistical properties of the spatiotemporal patterns are characterized from the fractal point of view.

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    2
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  • Power-law behavior in a cascade process with stopping events: A solvable model

    Ken Yamamoto, Yoshihiro Yamazaki

    PHYSICAL REVIEW E   85 ( 1 )  2012.01  [Refereed]

     View Summary

    The present paper proposes a stochastic model to be solved analytically, and a power-law-like distribution is derived. This model is formulated based on a cascade fracture with the additional effect that each fragment at each stage of a cascade ceases fracture with a certain probability. When the probability is constant, the exponent of the power-law cumulative distribution lies between -1 and 0, depending not only on the probability but the distribution of fracture points. Whereas, when the probability depends on the size of a fragment, the exponent is less than -1, irrespective of the distribution of fracture points. The applicability of our model is also discussed.

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    10
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  • Fractal Structure of Isothermal Lines and Loops on the Cosmic Microwave Background

    Naoki Kobayashi, Yoshihiro Yamazaki, Hiroto Kuninaka, Makoto Katori, Mitsugu Matsushita, Satoki Matsushita, Lung-Yih Chiang

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   80 ( 7 )  2011.07  [Refereed]

     View Summary

    The statistics of isothermal lines and loops of the cosmic microwave background (CMB) radiation on the sky map is studied and the fractal structure is confirmed in the radiation temperature fluctuation. We estimate the fractal exponents, such as the fractal dimension D-e of the entire pattern of isothermal lines, the fractal dimension D-e of a single isothermal line, the exponent zeta in Korcak's law for the size distribution of isothermal loops, the two kind of Hurst exponents, H-e for the profile of the CMB radiation temperature, and H-c for a single isothermal line. We also perform fractal analysis of two artificial sky maps simulated by a standard model in physical cosmology, the WMAP best-fit Lambda cold dark matter (Lambda CDM) model, and by the Gaussian free model of rough surfaces. The temperature fluctuations of the real CMB radiation and in the simulation using the Lambda CDM model are non-Gaussian, in the sense that the displacement of isothermal lines and loops has an antipersistent property indicated by H-e similar or equal to 0.23 < 1/2.

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    9
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  • Collective Behavior of Bistable Units with Global and Asymmetric Local Interactions

    Yoshihiro Yamazaki

    PROGRESS OF THEORETICAL PHYSICS   125 ( 4 ) 641 - 652  2011.04  [Refereed]

     View Summary

    Competition between global and asymmetric local interactions among bistable units brings about the characteristic collective behavior: the state of each unit is nonsteady, while their average property remains almost constant. The existence of noise is necessary for sustaining this nonsteady bistable dynamics. In the dynamics, the interface motion between the two different stable states is characterized. The difference from the case with global and diffusive (symmetric) local interactions is discussed.

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    4
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  • Central Limit Theorem of the Bifurcation Ratio of the Horton-Strahler Analysis: Application to DLA Clusters

    Ken Yamamoto, Yoshihiro Yamazaki

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   80 ( 3 )  2011.03  [Refereed]

     View Summary

    The method of branch ordering evaluates the hierarchical structure of branching patterns, and the bifurcation ratio is an important variable in the topological analysis of branching patterns. In a simple mathematical model of a branching system called the random model, a central limit theorem for the inverse bifurcation ratio has been confirmed. In the present paper, we make a qualitative comparison between the random model and an ensemble of diffusion-limited aggregation (DLA) clusters from the viewpoint of the central limit theorem. From numerical data, we extrapolate asymptotic behaviors of the average and variance of the inverse bifurcation ratio of DLA clusters. These asymptotic properties are in good agreement with those of the random model qualitatively. Hence, the central limit theorem also holds for DLA clusters.

    DOI

  • 粘着・剥離に関する高分子化学の最近の進歩 粘着剤のフラクトグラフィ

    山崎義弘

    高分子   59 ( 12 ) 905 - 908  2010.12  [Refereed]

  • Topological Self-similarity on the Random Binary-Tree Model

    Ken Yamamoto, Yoshihiro Yamazaki

    JOURNAL OF STATISTICAL PHYSICS   139 ( 1 ) 62 - 71  2010.04  [Refereed]

     View Summary

    Asymptotic analysis on some statistical properties of the random binary-tree model is developed. We quantify a hierarchical structure of branching patterns based on the Horton-Strahler analysis. We introduce a transformation of a binary tree, and derive a recursive equation about branch orders. As an application of the analysis, topological self-similarity and its generalization is proved in an asymptotic sense. Also, some important examples are presented.

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    4
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  • Central limit theorem for the bifurcation ratio of a random binary tree

    Ken Yamamoto, Yoshihiro Yamazaki

    JOURNAL OF PHYSICS A-MATHEMATICAL AND THEORETICAL   42 ( 41 )  2009.10  [Refereed]

     View Summary

    In order to formulate and examine the central limit theorem for a binary tree numerically, a method for generating random binary trees is presented. We first propose the correspondence between binary trees and a certain type of binary sequences (which we call Dyck sequences). Then, the method for generating random Dyck sequences is shown. Also, we propose the method of branch ordering of a binary tree by means of only the corresponding Dyck sequence. We confirm that the method is in good consistency with the topological analysis of binary trees known as the Horton-Strahler analysis. Two types of central limit theorem are numerically confirmed, and the obtained results are expressed in simple forms. Furthermore, the proposed method is available for a wide range of the topological analysis of binary trees.

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    2
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  • Humidity-Temperature Dependence of Domain Growth of Ascorbic Acid Crystal

    Yoshihiro Yamazaki, Hiroki Yoshino, Machiko Izui, Yukiko Sato, Mitsugu Matsushita

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   78 ( 7 )  2009.07  [Refereed]

     View Summary

    Humidity-temperature conditions for the emergence of various domain patterns of ascorbic acid crystal are identified, where the crystal grows from its thinly spreading aqueous solution by solvent evaporation. In particular, under a low-humidity condition, the coexistent pattern is formed by two domains having different growth rates. In the faster growing domain, there exists a clear time delay between the crystal growth in the solution and the drying of the crystal surface. From the shape of the domain boundary in the coexistent pattern, the growth rate ratio between the two domains can be estimated.

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    3
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  • A network of two-Chinese-character compound words in the Japanese language

    Ken Yamamoto, Yoshihiro Yamazaki

    PHYSICA A-STATISTICAL MECHANICS AND ITS APPLICATIONS   388 ( 12 ) 2555 - 2560  2009.06  [Refereed]

     View Summary

    Some statistical properties of a network of two-Chinese-character compound words in the Japanese language are reported. In this network, a node represents a Chinese character and an edge represents a two-Chinese-character compound word. It is found that this network has properties of being "small-world" and "scale-free". A network formed by only Chinese characters for common use (joyo-kanji in Japanese), which is regarded as a subclass of the original network, also has the small-world property. However, a degree distribution of the network exhibits no clear power law. In order to reproduce the disappearance of the power-law property, a model for a selecting process of the Chinese characters for Common Use is proposed. (C) 2009 Elsevier B.V. All rights reserved.

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    11
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  • Spatiotemporal patterns formed by deformed adhesive in peeling

    Yoshihiro Yamazaki, Akihiko Toda

    American Chemical Society, Polymer Preprints, Division of Polymer Chemistry   49   811 - 812  2008.09  [Refereed]  [Invited]

  • Formulation and asymptotic properties of the bifurcation ratio in Horton's law for the equiprobable binary tree model

    Ken Yamamoto, Yoshihiro Yamazaki

    PHYSICAL REVIEW E   78 ( 2 )  2008.08  [Refereed]

     View Summary

    The bifurcation ratio for the equiprobable binary tree model is formulated. We obtain the exact expression of the kth moment of the second-order streams. We also obtain a recursive equation between rth and (r+1)th order streams. Horton's law is confirmed numerically by calculating this recursive equation and asymptotic properties of the bifurcation ratio are discussed.

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    4
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  • Reconstruction and extension of the family-vicsek scaling hypothesis for growing rough interfaces

    Yoshihiro Yamazaki, Kazuaki Saito, Naoki Kobayashi, Tatsuya Ozawa, Mitsugu Matsushita

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   76 ( 10 )  2007.10  [Refereed]

     View Summary

    A scaling hypothesis for the standard deviation sigma of the height of growing interfaces is proposed by extending the Family-Vicsek (FV) scaling hypothesis. A data-collapsing method is adopted for estimating values of three exponents alpha,beta, and z, which characterize, respectively, the roughness, growth, and dynamic properties of growing interfaces. The estimation is carried out through sigma, which is a function of both the time and the width of the interfaces. The advantages of the present extended scaling hypothesis are as follows: (A) The value of,B can be obtained even if the data for Q in terms of t are few so that its value is not determined precisely from the slope of the In a vs In t plot. (B) Different scaling relations can be obtained during the time evolution of interface growth. (C) By introducing a new exponent, which represents the time dependence of Q for a short width, a scaling argument is possible even for growing interfaces that do not satisfy the FV scaling relation. Successful applications are carried out to a few numerical models and a paper-wetting experiment.

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    2
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  • Modelling for collective motion of granular particles driven by motion of interfaces

    Shin-ya Komura, Yoshihiro Yamazaki

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   76 ( 8 )  2007.08  [Refereed]

     View Summary

    A model for the collective motion of granular particles induced by an interaction with interface motion is constructed. By numerical simulation, it is found that the model can qualitatively reproduce labyrinthine patterns that are quite similar to those experimentally obtained in the drying process of a water-granule mixture. It is found that the characteristic scale of the patterns is proportional to the inverse of the strength of dynamic friction for the particles. Moreover, the stick-slip motion of the interfaces is confirmed in our model.

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    3
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  • Spatiotemporal patterns formed by deformed adhesive in peeling

    Yoshihiro Yamazaki, Akihiko Toda

    INTERNATIONAL CONFERENCE ON SCIENCE OF FRICTION   89  2007  [Refereed]

     View Summary

    Dynamical properties of peeling an adhesive tape are investigated experimentally as an analogy of sliding friction. An adhesive tape is peeled by pulling an elastic spring connected to the tape. Controlling its spring constant k and pulling speed V, peel force is measured and spatiotemporal patterns formed on the peeled tape by deformed adhesive are observed. It is found that there exist two kinds of adhesive state in peeling front. The emergence of multiple states is caused by the stability of a characteristic structure (tunnel structure) formed by deformed adhesive. Tunnel structures are distributed spatiotemporally on adhesive tape after peeling. Based on the spatiotemporal distribution, a morphology-dynamical phase diagram is constructed on k-V space and is divided into the four regions: (A) uniform pattern with tunnel structure, (B) uniform pattern without tunnel structure, (C) striped pattern with oscillatory peeling, and (D) spatiotemporally coexistent pattern.

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  • Percolation in aggregation of granular particles formed by sweeping front dynamics

    Y Yamazaki, S Komura, K Suganuma

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   75 ( 4 )  2006.04  [Refereed]

     View Summary

    In the aggregation of granular particles caused by the motion of the sweeping front. percolation occurs in the universality class of two dimensions due to a change in the particle concentration corresponding to the occupation ratio. The collective motion of the granular particles is described as the process of self-avoiding invasion percolation. The cluster structure of the aggregated granular particles exhibits a scaling property in a wide range of the particle concentration.

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    6
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  • Pattern formation and spatiotemporal behavior of adhesive in peeling

    Y Yamazaki, A Toda

    PHYSICA D-NONLINEAR PHENOMENA   214 ( 2 ) 120 - 131  2006.02  [Refereed]

     View Summary

    We examined various spatiotemporal patterns evolving in deformed adhesives during peeling. The patterns are regarded as a spatiotemporal distribution of a tunnel structure formed by the deformed adhesive, and are classified into the following four types: (A) uniform pattern with tunnel structure, (B) uniform pattern without tunnel structure, (C) striped pattern alternating between A and B in time, and (D) spatiotemporal pattern made by the coexistence of two regions with and without the tunnel structure. We are able to reproduce these patterns and the mechanical and statistical behaviors by constructing a model with a state variable representing the stability of the tunnel structure. The essential factor of the pattern formation is the competition between a local asymmetric interaction and a global coupling of the state variables. (c) 2006 Elsevier B.V. All rights reserved.

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    Citation
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  • Model of earthquake generation exhibiting self-organized criticality with self-affine fault surfaces

    Tomohiro Hasumi, Shin-ya Komura, Masashi Kamogawa, Yoshihiro Yamazaki

    THIRD 21COE SYMPOSIUM: ASTROPHYSICS AS INTERDISCIPLINARY SCIENCE   31   237 - +  2006  [Refereed]

     View Summary

    Generation of earthquakes has not been still understood. However, some statistical properties of seismicity are established such as magnitude-frequency distribution indicating power law. In this study, we numerically investigate one-dimensional spring-block earthquake model, considering self-affine fault surfaces, in order to understand such statistical properties.

    DOI

    Scopus

    2
    Citation
    (Scopus)
  • Multi-affinity for growing rough interfaces of bacterial colonies

    N Kobayashi, T Ozawa, K Saito, Y Yamazaki, T Matsuyama, Matsushita, I

    PROGRESS OF THEORETICAL PHYSICS SUPPLEMENT   161 ( 161 ) 232 - 235  2006  [Refereed]

     View Summary

    We have examined whether rough interfaces of bacterial colonies are multi-affine. We have used the bacterial species called Bacillus subtilis, which has been found to exhibit a variety of colony patterns when varying both the concentration of nutrient and solidity of agar medium. Consequently, we have found that the colony interface on a nutrient-rich, solid agar medium is multi-affine. On the other hand, the colony interface on a nutrient-rich, semi-solid agar medium is self-affine.

    DOI

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    2
    Citation
    (Scopus)
  • Spatio-temporal patterns formed on adhesive tape in peeling

    Yoshihiro Yamazaki, Akihiko Toda

    Polymer Preprints, Japan   54   3948 - 3949  2005.12

     View Summary

    Our experimental results about the dynamical behavior of adhesive tape in peeling at a constant peel speed are reported. We focus our attention on spatio-temporal patterns formed by deformed adhesive in peeling on the tape. Because of the viscoelastic nature of adhesive, it is found that the patterns are classified into four types by changing both the peel speed and the stiffness of the system, which is controlled by a spring connected to the tape. In order to explain the experimental results, we propose a model for the pattern formation on adhesive tape in peeling by introducing the state variable representing the stability of a characteristic structure, which is called tunnel structure.

  • Extended dynamic scaling for growing interfaces

    N Kobayashi, K Saito, T Ozawa, Y Yamazaki, K Honda, M Matsushita

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   74 ( 10 ) 2712 - 2715  2005.10  [Refereed]

     View Summary

    We have extended dynamic scaling hypothesis to describe the wide range of experiments on growing rough interfaces. An alternative approach of original Family-Vicsek scaling hypothesis was not successfully applied to the growing interfaces of paper wetting in that we obtained unphysical values of roughness exponents. Since very nice data collapse suggested the existence of some kind of dynamic scaling, we have tried to extend the dynamic scaling hypothesis. It was found that the extended dynamic scaling hypothesis can be nicely applied to the growing rough interfaces in paper wetting, yielding values of roughness and growth exponents alpha similar or equal to 0.73, beta similar or equal to 0.60, respectively.

    DOI

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    5
    Citation
    (Scopus)
  • Periodic growth of bacterial colonies

    Y Yamazaki, T Ikeda, H Shimada, F Hiramatsu, N Kobayashi, J Wakita, H Itoh, S Kurosu, M Nakatsuchi, T Matsuyama, M Matsushita

    PHYSICA D-NONLINEAR PHENOMENA   205 ( 1-4 ) 136 - 153  2005.06  [Refereed]

     View Summary

    The formation of concentric ring colonies by bacterial species Bacillus subtilis and Proteus mirabilis has been investigated experimentally, focusing our attention on the dependence of local cell density upon the bacterial motility. It has been confirmed that these concentric ring colonies reflect the periodic change of the bacterial motility between motile cell state and immotile cell state. We conclude that this periodic change is macroscopically determined neither by biological factors (i.e., biological clock) nor by chemical factors (chemotaxis as inhibitor). And our experimental results strongly suggest that the essential factor for the change of the bacterial motility during concentric ring formation is the local cell density. (c) 2005 Elsevier B.V. All rights reserved.

    DOI

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    18
    Citation
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  • Directional crack propagation of granular water systems

    T Mizuguchi, A Nishimoto, S Kitsunezaki, Y Yamazaki, Aoki, I

    PHYSICAL REVIEW E   71 ( 5 )  2005.05  [Refereed]

     View Summary

    Pattern dynamics of directional crack propagation phenomena observed in drying process of starch-water mixture is investigated. To visualize the three-dimensional structure of the drying-fracture process two kinds of experiments are performed, i.e., resin solidification planing method and real-time measurement of water content distribution with MR instruments. A cross section with polygonal structure is visualized in both experiments. The depth dependency of cell size is measured. The phenomenological model for water transportation is also discussed.

    DOI

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    42
    Citation
    (Scopus)
  • Patterns of Expansion produced by a Structured Cell Population of Serratia marcescens in Response to Different Media

    Fumiko Hiramatsu, Jun-Ichi Wakita, Naoki Kobayashi, Yoshihiro Yamazaki, Mitsugu Matsushita, Tohey Matsuyama

    Microbes and Environments   20 ( 2 ) 120 - 125  2005  [Refereed]

     View Summary

    Characteristic patterns of expansion were generated by bacterial cell populations of Serratia marcescens on media with different concentrations of nutrient and agar. These patterns were classified as Eden-like, dense-branching-morphology-like, flower-like, concentric ring-like and diffusion-limited aggregation-like. Although flower-like was specific to Serratia marcescens, the other patterns were exhibited by Bacillus subtilis. Through macro- and microscopic tracing of the processes generating these patterns, physico-chemical principles of bacterial growth, collaborative and independent properties of bacteria, structural organization for population expansion, and the division of labor among bacterial cells (i.e., wall composer, pressure generator, and logistic supporter) were brought to light. © 2005, Japanese Society of Microbial Ecology &amp
    The Japanese Society of Soil Microbiology. All rights reserved.

    DOI

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    10
    Citation
    (Scopus)
  • Dynamic scaling of the growing rough surfaces

    N Kobayashi, O Moriyama, S Kitsunezaki, Y Yamazaki, M Matsushita

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   73 ( 8 ) 2112 - 2116  2004.08  [Refereed]

     View Summary

    We have numerically investigated the self-affinity of the bacterial colony model. In order to examine the growth exponent beta, we find a new approach to the dynamic scaling hypothesis for the growing rough surface. We have first investigated the self-affinity of the well-known Eden model to check the validity of the new approach. The obtained results of the exponents alpha congruent to 0.50 and beta congruent to 0.33 coincide with the wellknown values of the exponents of the Eden model. We have then applied it successfully to growing interfaces produced by the bacterial colony model. We have found that the self-affinity of the bacterial colony model is characterized as alpha congruent to 0.80 and beta congruent to 0.65.

    DOI

    Scopus

    5
    Citation
    (Scopus)
  • Stability of tunnel structure and relationship between peel load and spatiotemporal pattern by deformed adhesive during peeling

    Y Yamazaki, A Toda

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   73 ( 8 ) 2342 - 2346  2004.08  [Refereed]

     View Summary

    We investigated (i) the relationship between the spatiotemporal pattern of a deformed adhesive and peel load during peeling, and (ii) the dependence of the pattern formation on peel speed in the hard spring limit case. In the hard spring limit case, it is found that elastic and viscous peeling states coexist. It is also found that the occupation ratio of tunnel structures in a separation front is determined by the peel speed and is a monotonically decreasing function of peel speed. We experimentally confirmed that the value of peel load has a linear dependence on the occupation ratio of tunnel structures. An explanation of dynamical behavior is also given on the basis of the creation-annihilation dynamics of tunnel structures.

    DOI

    Scopus

    21
    Citation
    (Scopus)
  • Dependence of local cell density on concentric ring colony formation by bacterial species Bacillus subtilis

    H Shimada, T Ikeda, J Wakita, H Itoh, S Kurosu, F Hiramatsu, M Nakatsuchi, Y Yamazaki, T Matsuyama, M Matsushita

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   73 ( 4 ) 1082 - 1089  2004.04  [Refereed]

     View Summary

    The formation of concentric ring-like colonies by bacterial species Bacillus subtilis has been investigated, focusing our attention on the effect of local cell density upon the bacterial motility: (i) Neither any chemicals nor a pacemaker at the center of the ring takes part in the concentric ring formation. (ii) Phase entrainment between two colonies having different phase of concentric ring does not occur. (iii) From the measurement of lag-phase time when varying the initial cell density, the start of the first migration phase is found to depend on the cell density. (iv) When cutting the part of a colony which is behind a migration phase just after the start of migration, the migration phase becomes shorter. On the other hand, the following consolidation phase becomes longer. (v) By the replica-printing method, active bacteria move collectively from inside to outside of the outermost consolidation terrace. Our present experimental results are qualitatively consistent with the results of the other bacterial species P. mirabilis, although the individual cell motility is quite different from each other. The present results suggest that the essential factor of the change of the bacterial motility of B. subtilis during concetric ring formation is the local cell density.

    DOI

    Scopus

    23
    Citation
    (Scopus)
  • 粘着テープの剥離過程で形成される時空パターン

    日本物理学会誌   59; 1  2004.01  [Refereed]

    DOI

  • Bouncing gel balls: Impact of soft gels onto rigid surface

    Europhys. Lett.   63; 1  2003.07  [Refereed]

    DOI

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    14
    Citation
    (Scopus)
  • Morphological diversity in crystal growth of L-ascorbic acid dissolved in methanol

    M Ito, M Izui, Y Yamazaki, M Matsushita

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   72 ( 6 ) 1384 - 1389  2003.06  [Refereed]

     View Summary

    Morphological diagram with respect to crystal growth of L-ascorbic acid (C6H8O6; so-called vitamin C) from methanol solution on a flat glass dish is presented. Varying humidity and initial concentration of L-ascorbic acid in methanol solution, the following three distinct kinds of growing patterns have been observed: homogeneous disk, concentric ring and dendrite. In addition, in higher concentration clearly faceted small single crystals grow in any humidity less than 90%. Crossovers from one pattern to another were observed, too.

    DOI

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    12
    Citation
    (Scopus)
  • Modelling and numerical analysis of the colony formation of bacteria

    N Kobayashi, T Sato, Y Yamazaki, M Matsushita

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   72 ( 4 ) 970 - 971  2003.04  [Refereed]

    DOI

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    6
    Citation
    (Scopus)
  • Theory of aging phenomena in shape-memory alloys

    T Okuzono, Y Yamazaki, T Ohta

    PHYSICAL REVIEW B   67 ( 5 )  2003.02

     View Summary

    We formulate a theory for the aging phenomena in AuCd-type shape-memory alloys. The kinetics of the martensitic transformation is represented in terms of the local strain as the order-parameter field. We introduce a secondary slow variable coupled with the order parameter. This theory is an extension of the previous paper by one of the authors, where the secondary variable was assumed to be a nonconserved quantity. In the present paper, we explore the consequence that the secondary variable is conserved. It is shown that the conserved slow variable is more favorable to account for martensite stabilization after aging observed experimentally. In order to study the rubberlike elasticity, the stress-strain relation is also derived both by the direct simulations of the set of kinetic equations and by the interface (twin boundary) dynamics. We propose experiments to elucidate whether the slow variable is conserved or not.

    DOI

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    7
    Citation
    (Scopus)
  • Transition to density waves of granular particles flowing through a vertical pipe

    O Moriyama, N Kuroiwa, S Tateda, T Arai, A Awazu, Y Yamazaki, M Matsushita

    PROGRESS OF THEORETICAL PHYSICS SUPPLEMENT   150 ( 150 ) 136 - 146  2003  [Refereed]

     View Summary

    We show experimental results regarding how density waves of granular particles flowing through a vertical glass pipe emerge by controlling two kinds of parameters; air flow out of a flask attached to the bottom-end of the pipe and inflow of granular materials from a hopper attached to the top-end. It was found, by controlling the former parameter, that the most important factor for the onset of density waves is the strong interaction between granular particles and the air. It was also found, by changing the latter parameter, that there is a sharp transition from the uniform flow to the density waves at the threshold value of the inflow rate of granules. Power spectra of density waves show a clear power-law form S(f) similar to f(-alpha), where alpha similar or equal to 4/3. The value of alpha is robust in that, once density waves occurred, it was independent of the two parameters described above.

    DOI

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    6
    Citation
    (Scopus)
  • Dynamics of granular flow through a vertical pipe under the control of inflow rate

    Y Yamazaki, S Tateda, A Awazu, T Arai, O Moriyama, M Matsushita

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   71 ( 12 ) 2859 - 2862  2002.12  [Refereed]

     View Summary

    We present experimental results regarding the dynamical property of granular flow through a vertical glass pipe under the control of inflow rate. It was found that there exists a critical inflow rate for the formation of density waves. The power spectrum of the density waves exhibits clear power-law behavior, S(f) similar to f(-alpha), with alpha similar or equal to 4/3. This value of alpha is robust under variation of inflow rate.

    DOI

    Scopus

    6
    Citation
    (Scopus)
  • Dynamical-morphological property of adhesive tape in peeling

    Y Yamazaki, A Toda

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   71 ( 7 ) 1618 - 1621  2002.07  [Refereed]

     View Summary

    We experimentally investigated the dynamical behavior of adhesive tape in peeling with emphasis on the emergence of slow and fast peeling motions. The dynamical-morphological phase diagram for peeled adhesive tape as a function of peel speed and spring constant was obtained. The spatiotemporal patterns of peeled adhesive were classified into four types: low-speed pattern, high-speed pattern, oscillatory pattern, and spatiotemporal intermittent pattern.

    DOI

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    22
    Citation
    (Scopus)
  • Dynamical properties of transient spatio-temporal patterns in bacterial colony of Proteus mirabilis

    K Watanabe, J Wakita, H Itoh, H Shimada, S Kurosu, T Ikeda, Y Yamazaki, T Matsuyama, M Matsushita

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   71 ( 2 ) 650 - 656  2002.02  [Refereed]

     View Summary

    Spatio-temporal patterns emerged inside a colony of bacterial species Proteus mirabilis on the surface of nutrient-rich semisolid agar medium have been investigated. We observed various patterns composed of the following basic types: propagating stripe, propagating stripe with fixed dislocation, expanding and shrinking target, and rotating spiral. The remarkable point is that the pattern changes immediately when we alter the position for observation, but it returns to the original if we restore the observing position within a few minutes. We further investigated mesoscopic and microscopic properties of the spatiotemporal patterns. It turned out that whenever the spatio-temporal patterns are observed in a colony, the areas are composed of two superimposed monolayers of elongated bacterial cells. In each area they are aligned almost parallel with each other like a two-dimensional nematic liquid crystal, and move collectively and independently of another layer. It has been found that the observed spatio-temporal patterns are explained as the moire effect.

    DOI

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    14
    Citation
    (Scopus)
  • Target patterns in phase separation induced by cross-linking

    M Motoyama, Y Yamazaki, T Ohta

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   70 ( 3 ) 729 - 732  2001.03  [Refereed]

     View Summary

    We introduce a quite simple model for a phase-separating binary mixture where one of the components is cross-linked. It is shown by computer simulations that target patterns are generated. We use a Cahn-Hilliard equation with a bulk free energy density which varies as a molecular weight changes with time. Target patterns are obtained in the following way. We first quench the system, having an off-critical composition, into a spinodal region, and find that disconnected droplets emerge in the system. With cross-linking one of the components, the phase diagram of the system shifts to a location where a bicontinuous structure is formed. As a result, target patterns grow from the droplets without any additional nuclei.

    DOI

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    4
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    (Scopus)
  • Kinetics of cubic to tetragonal transformation under external field by the time-dependent Ginzburg-Landau approach

    T Ichitsubo, K Tanaka, M Koiwa, Y Yamazaki

    PHYSICAL REVIEW B   62 ( 9 ) 5435 - 5441  2000.09  [Refereed]

     View Summary

    Computer simulations based on the time-dependent Ginzbug-Landau approach have been performed for the formation of domain structure in the cubic-tetragonal transformation under an external field. The fcc-L1(0) ordering has been studied as a model case of the transformation, and the Landau free-energy function has been determined so as to reproduce the free energy calculated by the Monte Carlo simulation. The simulations have demonstrated the features observed in our experiments on FePd alloy under an external stress, and have clarified the formation mechanism of a single variant structure. The internal stress field developed by the preferential formation of a variant favored by the external stress further accelerates the trend cooperatively, and eventually leads to a single variant structure.

    DOI

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    60
    Citation
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  • Front aggregation and labyrinthine pattern in the drying process of two-dimensional wet granular systems

    Yoshihiro Yamazaki, Tsuyoshi Mizuguchi

    Journal of the Physical Society of Japan   69 ( 8 ) 2387 - 2390  2000  [Refereed]

     View Summary

    The aggregation process of granules driven by the motion of water-air fronts in the drying process of two-dimensional wet granular systems is experimentally studied. The fronts and aggregated granules interact with each other during this drying, and a labyrinthine pattern is formed as a result. A qualitative framework of the pattern formation is given, and topological and metrical properties of the pattern are also discussed.

    DOI

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    13
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  • Pattern Formations in Cubic-Tetragonal Structural Transitions

    Yoshihiro Yamazaki

    Journal of the Physical Society of Japan   67 ( 9 ) 2970 - 2973  1998  [Refereed]

     View Summary

    We performed numerical simulations for pattern formations in cubic-tetragonal structural transitions. Our model can reproduce a series of patterns which are quite similar to morphologies observed in experiments. And the evolution of patterns is consistent with the results of the interface dynamics. The mechanism of pattern formations is discussed from an elastic point of view.

    DOI

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    7
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    (Scopus)
  • Interface Dynamics for Cubic-Tetragonal Structural Transitions

    Yoshihiro Yamazaki

    Journal of the Physical Society of Japan   67 ( 5 ) 1587 - 1593  1998  [Refereed]

     View Summary

    Interface equations of motion for a single tetragonal nucleus growth and for twin formation under elastic fields in cubic-tetragonal structural transitions are derived. We give an expression to the elastic energy in the form of non-local, long-range interactions between nonconserved order parameters. We find that a single tetragonal nucleus grows anisotropically into oval or square and that twin structure is a stationary state in the coarsening process. These results are consistent with the numerical simulation.

    DOI

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    4
    Citation
    (Scopus)
  • Numerical Study of Elastic Effects by Cubic-Tetragonal Symmetry Breaking on the Ordering Kinetics

    Yoshihiro Yamazaki

    Journal of the Physical Society of Japan   66 ( 9 ) 2628 - 2637  1997  [Refereed]

     View Summary

    Elastic effects by cubic-tetragonal symmetry breaking on the ordering kinetics are investigated. We propose a coarse-grained model characterized by a Ginzburg-Landau free energy with non-conserved order parameters coupled to an elastic field. By numerical study we obtain an oval shaped domain and a square domain in two dimensions and a plate-like domain and a rod-like domain in three dimensions. And in the coarsening process, a striped pattern is obtained. These patterns are remarkably similar to morphologies observed in real cubic-tetragonal order-disorder alloys. Moreover, we study the dynamics during the coarsening process by analyzing the change of the total domain boundaries LDB(t). LDB(t) decreases as a power of time: t-α(α &gt
    0). The exponent a becomes small with increasing the magnitude of the elastic effects.

    DOI

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    5
    Citation
    (Scopus)
  • He I-He II coexistence near the superfluid transition

    Akira Onuki, Yoshihiro Yamazaki

    Journal of Low Temperature Physics   103 ( 3-4 ) 131 - 138  1996  [Refereed]

     View Summary

    We have made a numerical scheme of solving two fluid hydrodynamics near the λ point, which includes the mass density, momentum density, entropy density, and complex order parameter. In our model the normal fluid velocity vanishes at the boundaries due to finite viscosity. As preliminary examples we examine coexistence of a superfluid region and a normal fluid region in two space dimensions firstly in heat flow and secondly in gravity and heat flow. We observe formation of a vortex from a wall in the second case. © 1996 Plenum Publishing Corporation.

    DOI

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    7
    Citation
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▼display all

Research Projects

  • 高粘度薄膜溶液からの結晶成長における非線形ダイナミクスとパターン形成

    科学研究費助成事業(早稲田大学)  科学研究費助成事業(基盤研究(C))

  • ソフトマテリアルの粘着剥離過程における時空パターンとその制御

    科学研究費助成事業(広島大学)  科学研究費助成事業(特定領域研究)

  • 粘着運動の物理

    科学研究費助成事業(早稲田大学)  科学研究費助成事業(若手研究(B))

  • Formation Mechanism of Growing Random Patterns

  • Non-Equilibrium Structural Evolution in Crystallization from Viscoelastic Soft Matter

  • Competition between two dynamics : interface motion and collective motion of granular particles

  • Structure, Statistics and Dynamics of Complex Systems

  • Stability and fluidity of a highly viscous solution film during crystal growth

▼display all

Presentations

▼display all

Specific Research

  • 非平衡非線形系としての粘着現象の数理探求

    2021  

     View Summary

    粘着テープの剥離で見られるスティックスリップ(自励振動)はリミットサイクル振動として理解され、一般に連続変数に基づく常微分方程式系で議論される。我々は、リミットサイクル振動を有する連続力学系に対してトロピカル差分を行って得られた離散力学系に着目した研究を行った。具体的な実施事項は以下の通りである。(1)リミットサイクルを有するモデルとして、Selkovモデルに着目し、トロピカル差分化した離散力学系がNeimark-Sacker分岐を示すことを確認した。(2)このトロピカル差分化されたSelkovモデルに対して、超離散極限公式を用いて得られたmax-plus方程式(超離散Selkovモデル)もリミットサイクル振動することを確認した。

  • 対戦型スポーツにおける選手の到達距離を考慮した集団ダイナミクス

    2020   成塚拓真

     View Summary

    対戦型スポーツとしてサッカーに着目し、統計物理学の視点から選手の到達距離を考慮することによってフィールドに選手の影響力を表す量を導入した。そして、群れを構成している各要素の役割を評価する手法を確立した。具体的な実施事項は以下の通りである。(1)サッカーのトラッキングデータを用いて、選手の配置に依存した影響力をフィールドの各位置に定義した。(2)フィールドに対する影響力とこれまで研究してきたドロネー三角形分割により得られるネットワークを用いて各選手の攻撃・守備におけるパフォーマンスの評価を行った。本研究を通して、サッカーのみならず対戦型スポーツ全般において適用可能な評価手段の確率が期待される。

  • 対戦型スポーツを例としたデータベースに基づく時系列解析の方法

    2019   成塚拓真

     View Summary

    近年、生物系や社会系において、個体の運動・行動を追跡(トラッキング)したデータの取得が容易になった。それに伴い、集団(群れ)における各個体の位置関係を解析し、群れの内部構造(フォーメーション)を解析する手法の必要性が高まっている。本課題では、主に対戦型スポーツに着目し、統計物理学の視点から解析を行った。そして、群れを構成している系の詳細に依らない普遍的な解析手法を確立することを目的とした。具体的な実施事項は以下の通りである。(1)サッカーのトラッキングデータを用いてフォーメーション解析を行った。(2)より一般的な視点からフォーメーション解析を再考し、フィールドを領域への分割ではなく,各位置の重み付けと いう アプローチによる,新たなスペース評価の手法を提案した。領域への分割ではなく,各位置の重み付けと いう アプローチによる,新たなスペース評価の手法を提案する.

  • 少数多体系に対するフォーメーション解析の発展

    2018  

     View Summary

    少数多体系の集団的性質をフォーメーションとしてとらえ、主に以下の研究を実施した。(1) サッカーのトラッキングデータを用いてフォーメーション解析を行った。これまでの手法では、複数の試合を統一してフォーメーションの分類を行うことが困難であった。本研究では、この点を克服するため、ドロネー法の拡張を行った。(2) フォーメーション解析に対する一般的な手法を考案し、フェンシングを行っている選手の姿勢に関するデータベースを構築し、データベースに基づく時系列解析を行った。(3) フォーメーション解析をVicsek model に適用し、2つの自己駆動粒子が隣接関係となる時間の頻度分布に対する解析を行った。

  • 粘着が関与するパターン形成と非線形ダイナミクス

    2017  

     View Summary

    本研究では、スティックスリップ状態と定常状態との間で起こる動的転移の挙動について、我々が提案してきた力学系モデルを用いて考察を行った。その結果、スティックスリップ状態と定常状態との間の動的転移において、バネの張力が連続的に変化する場合と不連続な場合が存在することを示した。このモデルには、摩擦や粘着に関して具体的な系の詳細は含まれていない。従って、この結果は普遍的なものである。また、不連続転移において突発的な摩擦力・粘着強さの変化が引き起こされる可能性を示唆した。さらに、スティックスリップを示す関連した系として、摩擦が生じている状況での糸の引っ張り実験を行った。

  • 社会の行動様式に対する物理的動力学・統計物理学に基づくアプローチ

    2016  

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    種々の社会現象を、ルールと不確定性の競合により生じたものと捉え、社会現象から統計的に得られる「分布の普遍性」を解明することを目的として、統計物理学に基づいて研究を行ってきている。本研究課題では、特に、対戦型集団スポーツとしてサッカーに着目し、データスタジアム株式会社から提供を受けた、サッカー選手、および、ボールのトラッキングデータ、ならびに、申請者自身が試合の動画から抽出したパスのデータを用いて、チームや試合の詳細に依らない、サッカーという系自体が持つ普遍的性質を抽出するための枠組みを提示し、実際にその枠組みを用いて統計的性質を解析し、さらに、その意味について数理モデルを用いて考察した。

  • 社会の行動様式に観られる分布形成メカニズムへの統計物理学的アプローチ

    2015   山本健, 成塚拓真, 川島秀友

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    社会現象における我々の行動は、規範やルールに基づく不確定な要素の集団的振る舞いとして捉えられる。本研究課題では、種々の社会現象がルールと不確定性の競合により生じたものと捉え、統計的に得られる分布の普遍性に着目した。統計物理学の観点に基づき、現象の詳細に依存しない共通の分布形成メカニズムを明らかにすることを試みた。具体的に、以下の4項目を対象とした。(1)対戦型スポーツ:サッカーに対するネットワーク構造・選手の集団的振る舞い・選手間相互作用の解析(2)経済動向:映画の興行収入データに対する確率モデルの構築(3)言語体系:日本語の単語を構成する音声に潜む統計性の抽出(4)法体系:法令の階層構造における統計性の解明

  • 溶液の流動を伴う結晶成長の実験的研究

    2012  

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    点源からの周期成長の結果、その周期成長の起源が系により本質的に異なっているにもかかわらず、共通して同心円状パターンが生み出されることはよく知られている。例えば、BZ反応によるターゲットパターン、バクテリアの増殖・移動による同心円状コロニー形成、ゲル中での沈殿(析出)によるリーゼガング・リング、薄膜状になった有機分子溶液や高分子溶液からのリング状結晶成長といった様々な系で同心円状パターンを観察することができる。これまで、有機分子系の一つであるアスコルビン酸の薄膜状溶液からの結晶成長については、パターン形成の物理という観点に基づいた実験的研究の報告がいくつかなされてきた。これらの先行報告に従って、これまで確認されている(confirm)実験事実は以下の様にまとめられる。先ず、溶媒の蒸発により溶液が準安定状態となる。準安定状態となった溶液の流動性は低湿度下において極めて低くなり、soft solid、amorphous、glassyと表現される状態となっている。その後、核生成により結晶成長が開始する。ここで注目すべき点として、結晶の成長モードが環境の湿度に依存して変化することが挙げられる。実際、湿度が高くなるに従って、結晶の成長モードは二種共存、均一、周期、分岐へと変化することが分かっている。以上の実験事実は、水溶液、メタノール溶液いずれの場合も共通している。なお、アスコルビン酸の結晶成長における周期成長の先行研究においては、2002年に上坂らが周期成長の要因として次の2つの点を示唆した。(1)結晶(針状結晶)成長に伴い放出された溶媒による、成長フロントの近傍にあるガラス状溶液の局所的な流動化。(2)針状結晶の間に生じる隙間(ボイド)。彼らの解釈では、成長フロントの近傍で局所的に流動化した溶液が結晶間の隙間に吸収され、フロントの前方に溶液がなくなることで結晶成長が停止し、その後、部分的に結晶と接している溶液から再度結晶化が始まることで周期性が現れるとしている。さらに、均一成長においてはこのような溶液の局所的な流動化が観られなかったことから、上記の2点が周期的成長と均一成長の違いを引き起こしていると結論づけている。しかしながら、この解釈は次のような点において、周期成長の説明としては不十分ではないかと思われる。先ず、上記の解釈には各成長モードおよびその変化に対する湿度依存性が全く考慮されていない。また、結晶成長時の溶液全体の流動については詳細な報告がなされていない。以上の問題意識に基づいて、本課題研究では、薄膜状となったアスコルビン酸水溶液からの結晶成長について、均一成長から周期成長への変化について、溶液の流動性に着目して実験を行った。その結果、均一成長においても溶液は流動しており、湿度が高くなるに従って流動性が高くなるなることを確認した。さらに、均一成長・周期成長において、結晶成長先端の20~30μm前方に溶液の薄くなっている領域が形成し、10μm前方までは流動領域が存在することを確認した。これらの結果により、局所的な流動化領域の有無は転移に関係ないことが結論づけられる。

  • 粒子の集団運動と競合する多相系の界面ダイナミクス

    2008  

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    2枚のガラス板に挟まれた水と粉体の混合液をガラス板の隙間から乾燥させたとき、水-空気界面の進行が粉体の存在によって不安定化し、乾燥後に残った粉体領域が迷路のようなパターンになることが実験的に知られている。我々は、そのメカニズムを理解するために、粉粒体の運動と水-空気界面の振る舞いを記述するモデルを構築し、数値シミュレーションによってその妥当性を確認した。粉粒体の挙動には分子動力学法、水-空気界面の進行にはphase-field モデルを適用し、粉粒体が親水性を持つことによる界面との相互作用を考慮した。さらに、実験で観られる粉粒体のstick-slip 的な挙動を考慮し、粉粒体はガラス板から摩擦抵抗を受けるものとした。粉粒体領域の密度、水の相の安定性、摩擦係数をコントロールパラメータとしてシミュレーションを行ったところ、比較的乾燥が遅い場合または摩擦抵抗が小さい場合に粉体領域が孤立しにくくなり、迷路状のパターンが形成されることが分かった。その形成過程において、界面に運ばれた粉粒体が集まることで、界面からの力に抵抗して静止する様子が再現された。さらに摩擦抵抗を取り入れたことで、実験において見られるような、界面が至る所で進行と停滞を繰り返しながら空気領域が蛇行する場合と、界面全体が同時に進行しパターンに異方性が生じる場合の双方を同じモデルで再現することが出来た。また、パターン形成過程における界面の形状について、自己アフィン指数を求めることで、粉粒体の密度が大きくなるにつれて自己アフィンフラクタルから自己相似フラクタルに移り変わる現象が確認された。さらに、この乾燥パターンの持つ特徴的な統計的性質は侵入型パーコレーションを元にしたモデルによってある程度再現されることが確認されているが、我々のモデルにおいても、侵入型パーコレーションの関連性が再現されるかどうかを調べた。

  • 粘着体の剥離におけるパターン形成のダイナミクス

    2003  

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    粘弾性を有する粘着物質は、変形を加えた時間や温度に応じて多様な力学的性質を示し、粘着物質の運動を特徴付ける際には、運動が基板(壁)との接着および剥離を繰り返すことによって行われために、粘着物質および取り巻く環境を含むシステム全体の硬さや、変形に対する粘着物質の力学的応答、そして粘着物質と基板との相互作用が運動に対して重要な影響を及ぼすことに注意すべきである。そこで我々は、粘着物質の力学物性だけでなく、環境条件、運動様式(剥離の方法など)を含めたシステム全体の動的挙動として問題を構成し、粘着運動をパターン形成の物理として理解することを試みている。本研究では、粘着物質が粘性と弾性とを共存し得るような変形の時間領域で、テープ剥離による粘着物質の変形および変形した粘着物質によって形成されるパターンに着目し、実験を行ってきた。粘着テープを水平に置かれた基板に貼り、システムの硬さを制御するため、バネと粘着テープの一端を連結し、バネを基板と垂直方向に引き上げ、テープの剥離を行った。剥離の際、剥離速度とバネ定数をコントロールパラメータにして、基板からテープをはがす際に必要な荷重を測定した。また剥離後、テープに残された粘着物質の形態を観察した。我々の実験で用いた粘着テープには天然ゴム系の架橋粘着物質が使われている。 剥離によってテープと基板との間隔が広がるため、粘着物質は伸長し、変形する。ここで注目すべき点は、粘着物質は変形後もその変形によってできた形態を保つことと、界面剥離が1次元的な剥離先端で行われていることである。従って、剥離後の粘着テープには1次元空間で行われたテープ剥離の時間的推移が、変形した粘着物質がつくる形態の時空間パターンとして表現されていることになる。つまり、各時刻、各場所でどのような剥離が行われたかを剥離後の粘着テープを観察すれば理解できるのである。従って、テープの剥離現象をパターン形成の物理として理解することが可能になるのである。以上のパターンに着目し、剥離過程の動的挙動が一目でわかるようにまとめたもの動的相図を作成した。また、この相図は定常的な剥離が実現するために必要な時間とシステム固有の緩和時間に関する議論により、定性的には理解できることを示した。

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