arXiv subjects

Yoshinori Hayakawa

Publications and source records attributed to Yoshinori Hayakawa.

6 recordsLinked to original sources

arXiv2024

Inverse Magnus Effect Induced by Dilute Water Fog

The inverse Magnus effect is a phenomenon in which a spinning sphere experiences a lift force opposite to the conventional Magnus effect. This effect is typically observed in the flow higher than a critical Reynolds number or spin ratio. We experimentally studied the inverse Magnus effect on a spinning sphere in a flow containing suspended micrometer size droplets. The lift force was measured by injecting droplets into a closed return wind tunnel. We investigated the threshold of the inverse Magnus effect for several types of dispersed droplets. Our results indicate that the flow with suspended water droplets significantly affects the onset of the inverse Magnus effect, causing a decrease in the critical Reynolds number and spin ratio.

physics.flu-dyn↗

arXiv2017

Contact enhancement of locomotion in spreading cell colonies

The dispersal of cells from an initially constrained location is a crucial aspect of many physiological phenomena ranging from morphogenesis to tumour spreading. In such processes, the way cell-cell interactions impact the motion of single cells, and in turn the collective dynamics, remains unclear. Here, the spreading of micro-patterned colonies of non-cohesive cells is fully characterized from the complete set of individual trajectories. It shows that contact interactions, chemically mediated interactions and cell proliferation each dominates the dispersal process on different time scales. From data analysis and simulation of an active particle model, we demonstrate that contact interactions act to speed up the early population spreading by promoting individual cells to a state of higher persistence, which constitutes an as-yet unreported contact enhancement of locomotion. Our findings suggest that the current modeling paradigm of memoryless interacting active particles may need to be extended to account for the possibility of internal states and history-dependent behaviour of motile cells.

physics.bio-ph↗

arXiv2008

Bending-Filament Model for the Buckling and Coiling Instability of Viscous Fluid Rope

A simple model is proposed for the buckling and coiling instability of a viscous "fluid rope" falling on a plane. By regarding a fluid rope as a one-dimensional flow, this model accounts for only the axial and shared viscous forces. Our model successfully reproduces several experiments with no adjustable parameters, such as the existence of three distinct coiling regimes reported in Phys. Rev. Lett. 93, 214502 (2004). Our model allows for the discussion of unsteady motion. An expression for the critical fall height at which the coiling frequency changes from a decrease to increase was phenomenologically derived. It was found that the coil-uncoil transition shows remarkable hysteresis only for weak gravity condition.

cond-mat.stat-mech↗

arXiv2007

Reinforcement learning of recurrent neural network for temporal coding

We study a reinforcement learning for temporal coding with neural network consisting of stochastic spiking neurons. In neural networks, information can be coded by characteristics of the timing of each neuronal firing, including the order of firing or the relative phase differences of firing. We derive the learning rule for this network and show that the network consisting of Hodgkin-Huxley neurons with the dynamical synaptic kinetics can learn the appropriate timing of each neuronal firing. We also investigate the system size dependence of learning efficiency.

nlin.AO↗

arXiv2004

A theoretical and numerical approach to "magic angle" of stone skipping

We investigate oblique impacts of a circular disk and water surface. An experiment [ Clanet, C., Hersen, F. and Bocquet, L., Nature 427, 29 (2004) ] revealed that there exists a "magic angle" of 20 [deg.] between a disk face and water surface which minimize the required speed for ricochet. We perform 3-dimensional simulation of the water impacts using the Smoothed Particle Hydrodynamics (SPH) and analyze the results with an ordinal differential equation (ODE) model. Our simulation is in good agreement with the experiment. The analysis with the ODE model give us a theoretical insight for the ``magic angle" of stone skipping.

physics.flu-dyn↗

arXiv2002

Collision of One-Dimensional Nonlinear Chains

We investigate one-dimensional collisions of unharmonic chains and a rigid wall. We find that the coefficient of restitution (COR) is strongly dependent on the velocity of colliding chains and has a minimum value at a certain velocity. The relationship between COR and collision velocity is derived for low-velocity collisions using perturbation methods. We found that the velocity dependence is characterized by the exponent of the lowest unharmonic term of interparticle potential energy.

cond-mat.stat-mech↗