Tsuyoshi Mizuguchi

PROPORTION REGULATION OF BIOLOGICAL CELLS IN GLOBALLY COUPLED NONLINEAR SYSTEMS

As a model of proportion regulation in differentiation process of biological system, globally coupled activator-inhibitor systems are studied. Formation and destabilization of one and two cluster state are predicted analytically. Numerical simulations show that the proportion of units of clusters is chosen within a finite range and it is selected depend on the initial condition.

Numerical study of drying process and columnar fracture process in granule-water mixtures

The formation of three-dimensional prismatic cracks in the drying process of starch-water mixtures is investigated numerically. We assume that the mixture is an elastic porous medium which possesses a stress field and a water content field. The evolution of both fields is represented by a spring network and a phenomenological model with the water potential, respectively. We find that the water content distribution has a propagating front which is not explained by a simple diffusion process. The prismatic structure of cracks driven by the water content field is observed. The depth dependence and the coarsening process of the columnar structure are also studied. The particle diameter dependence of the scale of the columns and the effect of the crack networks on the dynamics of the water content field are also discussed.

Front Aggregation and Labyrinthine Pattern in the Drying Process of Two-Dimensional Wet Granular Systems.

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.

Proportion Regulation in Task Allocation Systems

Designable task allocation systems which consist of identical agents using stochastic automata are suggested. From the viewpoint of the group response and the individual behavior, the performances of a simple model and an improved one are compared numerically. Robots experiments are performed to compare between the two models.

Spatio-Temporal Structure of Hooded Gull Flocks

We analyzed the spatio-temporal structure of hooded gull flocks with a portable stereo camera system. The 3-dimensional positions of individuals were reconstructed from pairs of videos. The motions of each individual were analyzed, and both gliding and flapping motions were quantified based on the velocity time series. We analyzed the distributions of the nearest neighbor’s position in terms of coordinates based on each individual’s motion. The obtained results were consistent with the aerodynamic interaction between individuals. We characterized the leader-follower relationship between individuals by a delay time to mimic the direction of a motion. A relation between the delay time and a relative position was analyzed quantitatively, which suggested the basic properties of the formation flight that maintains order in the flock.

Collective Motion of Multi-Robot System based on Simple Dynamics

Multi-robot system is one of the most attractive systems in robotics, and many researchers have been investigating it from various viewpoints (Cao, 1997; Balch & Parker, 2002; Parker, 2003). Remarkable point of multi-robot system is that the robots are cooperatively able to complete a task that a single robot can hardly or cannot accomplish by itself. Especially, searching, transportation or conveyance, construction, and pattern formation are typical categories which are suitable for multi-robot system, and a lot of concrete tasks can be found in each category. Some approaches have been considered and proposed to accomplish them, and biology inspired robotics is one of the most effective method to develop useful multirobot system. Actually, many researchers have been applying this approach to design multirobot system (Bonabeau, 1999). In this article, we treat collective motion of motile elements which was inspired by living things such as fishes, birds and small insects, assuming to apply to real robot system. It is considered that the collective motion of the robots can be utilized for some significant tasks such as traffic control, ground/ocean surveillance (Ogen, 2004), and so on. This article is organized as follows. In section 2, we explain a fundamental kinetic model of collective behaviors based on the livings. Result of numerical simulation and analysis are shown in Section 3. In section 4, we show small scale of experiment based on the model.

Open and Closed Phase Jump Lines in Two-Dimensional Cellular Patterns

On the basis of topological arguments, it is shown that phase jump lines arise in two-dimensional cellular patterns. A phase jump line either ends at a phase singularity with a half-integer topological charge or it has no endpoints. As a simple model equation which exhibits such lines, a set of amplitude equations describing resonant interaction between two modes with wave numbers k and 2k is considered. Numerical simulations of the model equations show that these lines are spontaneously formed in ordering process of cellular structures.

Scytale decodes chaos: A method for estimating unstable symmetric solutions

A method for estimating a period of unstable periodic solutions is suggested in continuous dissipative chaotic dynamical systems. The measurement of a minimum distance between a reference state and an image of transformation of it exhibits a characteristic structure of the system, and the local minima of the structure give candidates of period and state of corresponding symmetric solutions. Appropriate periods and initial states for the Newton method are chosen efficiently by setting a threshold to the range of the minimum distance and the period.

Proportion regulation for division of labor in multi-robot system

Division of labor performed by social insects, such as ants and bees, is one of the most advanced functions that they have evolved. Although individual insects have the same inheritance, they are divided into certain groups in which they play specialized roles. For effective performance, the groups exhibit proportional regulation of population, which implies regulating their population to maintain their proportion; further the proportion of each group is regulated against external disturbances without aid from a special individual. In a multi-robot system, the division of labor is one of the most attractive and useful propositions. This paper addresses the proportion regulation of population in a homogenous multi-robot system, which is inspired by the task allocation practiced by social insects. We propose an extended probability model for proportion regulation, and confirm its performance by numerical simulation. We also experimentally validate its performance using a simple multi-robot system.

Coordinated Behaviour in Pigeon Flocks

We analysed pigeon flock flights using GPS trajectory data to reveal the most important kinematic aspects of flocking behaviour. We quantitatively investigated the internal motion of the flock based on pairwise statistics and found the following general relationships in all datasets: i) the temporal order of decisions characterised by the delay between directional changes is strictly related to the spatial order characterised by the longitudinal relative position within the flock; ii) during circling motion, pigeons use a mixture of two idealised and fundamentally different turning strategies, namely, parallel-path and equal-radius type turning. While pigeons tend to maintain their relative position within the flock on average, as in the parallel-path approximation, those who turn later also get behind as in the equal-radius case. Equal-radius type turning also tends to be expressed more during smaller radius turns.