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Search Results: 1 - 10 of 4254 matches for " Takashi Ichinomiya "
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Path-integral approach to the dynamics in sparse random network
Takashi Ichinomiya
Physics , 2005, DOI: 10.1103/PhysRevE.72.016109
Abstract: We study the dynamics involved in a sparse random network model. We extend the standard mean-field approximation for the dynamics of a random network by employing the path-integral approach. The result indicates that the distribution of the variable is essentially identical to that obtained from globally coupled oscillators with random Gaussian interaction. We present the results of a numerical simulation of the Kuramoto transition in a random network, which is found to be consistent with this analysis.
Power-law distribution in Japanese racetrack betting
Takashi Ichinomiya
Physics , 2006, DOI: 10.1016/j.physa.2005.12.027
Abstract: Gambling is one of the basic economic activities that humans indulge in. An investigation of gambling activities provides deep insights into the economic actions of people and sheds lights on the study of econophysics. In this paper we present an analysis of the distribution of the final odds of the races organized by the Japan Racing Association. The distribution of the final odds $P_o(x)$ indicates a clear power law $P_o(x)\propto 1/x$, where $x$ represents the final odds. This power law can be explained on the basis of the assumption that that every bettor bets his money on the horse that appears to be the strongest in a race.
Frequency synchronization in random oscillator network
Takashi Ichinomiya
Physics , 2004, DOI: 10.1103/PhysRevE.70.026116
Abstract: We study the frequency-synchronization of randomly coupled oscillators. By analyzing the continuum limit, we obtain the sufficient condition for the mean-field type synchronization. We especially find that the critical coupling constant $K$ becomes 0 in the random scale free network, $P(k)\propto k^{-\gamma}$, if $2 < \gamma \le 3$. Numerical simulations in finite networks are consistent with these analysis.
Impurity-induced Ferromagnetism in Doped Triplet Excitonic Insulator
Takashi Ichinomiya
Physics , 2000, DOI: 10.1103/PhysRevB.63.045113
Abstract: The theory of impurities in excitonic insulator is investigated in the light of the recent experiments on hexaborides. First, we study the bound state around the impurity and find that the bound state emerges when ${Re}\Delta$ is positive. Second, we study the continuum state using Abrikosov-Gor'kov's approach. We find that the energy gap is reduced strongly when ${Im}\Delta=0$. Finally, we solve Bogoliubov-de Gennes equations for excitonic insulator numerically. We get the results consistent with the analytic ones. We also find that incomplete ferromagnetism appears in doped triplet excitonic insulator with impurity. We make a short qualitative discussion on the ferromagnetism of doped hexaborides using our result.
Bouchaud-Mézard model on a random network
Takashi Ichinomiya
Physics , 2012, DOI: 10.1103/PhysRevE.86.036111
Abstract: We studied the Bouchaud-M\'ezard(BM) model, which was introduced to explain Pareto's law in a real economy, on a random network. Using "adiabatic and independent" assumptions, we analytically obtained the stationary probability distribution function of wealth. The results shows that wealth-condensation, indicated by the divergence of the variance of wealth, occurs at a larger $J$ than that obtained by the mean-field theory, where $J$ represents the strength of interaction between agents. We compared our results with numerical simulation results and found that they were in good agreement.
Wealth distribution on complex networks
Takashi Ichinomiya
Physics , 2012, DOI: 10.1103/PhysRevE.86.066115
Abstract: We study the wealth distribution of the Bouchaud--M\'ezard (BM) model on complex networks. It has been known that this distribution depends on the topology of network by numerical simulations, however, no one have succeeded to explain it. Using "adiabatic" and "independent" assumptions along with the central-limit theorem, we derive equations that determine the probability distribution function. The results are compared to those of simulations for various networks. We find good agreement between our theory and the simulations, except the case of Watts--Strogatz networks with a low rewiring rate, due to the breakdown of independent assumption.
Power-law exponent of the Bouchaud-Mézard model on regular random network
Takashi Ichinomiya
Physics , 2013, DOI: 10.1103/PhysRevE.88.012819
Abstract: We study the Bouchaud-M\'ezard model on a regular random network. By assuming adiabaticity and independency, and utilizing the generalized central limit theorem and the Tauberian theorem, we derive an equation that determines the exponent of the probability distribution function of the wealth as $x\rightarrow \infty$. The analysis shows that the exponent can be smaller than 2, while a mean-field analysis always gives the exponent as being larger than 2. The results of our analysis are shown to be good agreement with those of the numerical simulations.
Thermodynamic Characterization of Synchronization-Optimized Oscillator-Networks
Tatsuo Yanagita,Takashi Ichinomiya
Physics , 2014, DOI: 10.1103/PhysRevE.90.062914
Abstract: We consider a canonical ensemble of synchronization-optimized networks of identical oscillators under external noise. By performing a Markov chain Monte Carlo (MCMC) simulation using the Kirchhoff index, i.e., the sum of the inverse eigenvalues of the Laplacian matrix (as a graph Hamiltonian of the network), we construct more than 1,000 different synchronization-optimized networks. We then show that the transition from star to core-periphery structure depends on the connectivity of the network, and is characterized by the node degree variance of the synchronization-optimized ensemble. We find that thermodynamic properties such as heat capacity show anomalies for sparse networks.
Numerical Simulation of Flow over an Open Cavity with Self-Sustained Oscillation Mode Switching  [PDF]
Takashi Yoshida, Takashi Watanabe
Open Journal of Fluid Dynamics (OJFD) , 2016, DOI: 10.4236/ojfd.2016.64027
Abstract: Numerical simulations are used to investigate the self-sustained oscillating flows past an open cavity. The two-dimensional incompressible Navier-Stokes equations are solved directly by using the finite difference method for cavities with an upstream laminar boundary layer. A series of simulations are performed for a variety of cavity length-to-depth ratio. The results show the switching among some flow modes including non-oscillation mode, shear layer mode and wake mode. The variation of the Strouhal number is in favorable agreement with available experimental data. The results of flow fields in the cavity reveal the relationship between the cavity shear layer oscillation modes and recirculating vortices in the cavity.
External apical root resorption and the release of interleukin-6 in the gingival crevucular fluid induced by a self-ligating system  [PDF]
Ryoko Kawashima-Ichinomiya, Masaru Yamaguchi, Yasuhiro Tanimoto, Masaki Asano, Kunihiko Yamada, Ryo Nakajima, Shoji Fujita, Kazutaka Kasai
Open Journal of Stomatology (OJST) , 2012, DOI: 10.4236/ojst.2012.22021
Abstract: The aim of this study was to investigate the amount of external apical root resorption (EARR) and the release of interleukin (IL)-6 in the gingival crevicular fluid (GCF) in subjects treated with a low-force low-friction system. Sixty patients were assigned to two groups of thirty patients for each: one group received treatment with self-ligating brackets and the other with conventional ligated edgewise brackets. All patients were treated with extraction of the maxillary first premolars. The EARR of the maxillary central incisors was evaluated on the periapical radiographs and cephalograms, taken before and after orthodontic treatment. The GCF was also collected non-invasively from the mesial and distal sides of central incisors by using filter paper strips before and after orthodontic treatment. Enzyme-linked immunosorbent assay (ELISA) kits were used to determine the IL-6 levels in the GCF samples. A significant difference was found in the amount of EARR between the patients with self-ligating brackets and conventional brackets. The mean amount of EARR was significantly lower for self-ligating brackets than conventional brackets (p < 0.05). The GCF levels of IL-6 for the patients with self-ligating brackets appliance were significantly lower than for those with the conventional brackets (p < 0.05). These results show that the mean amount of EARR and the GCF levels of IL-6 were significantly lower in the patients treated using low-force low-friction appliances than conventional brackets. Therefore, self-ligating brackets may be a useful system for reducing inflammation and EARR.
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