Nagoya, Japan
Nagoya, Japan

Daido University is a private university in Minami-ku, Nagoya, Aichi Prefecture, Japan. The predecessor of the school was founded in 1939. The school is close to Daidōchō Station. Wikipedia.


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The n-dimensional homogeneous Lotka-Volterra (HLV) ladder equation possesses Lie symmetries that generate a Lie algebra isomorphic to sl n(K) [J. Phys. Soc. Jpn. 71 (2002) 2396 and 72 (2003) 973], where K = C or R. In this work, using the Lie algebraic structure of the HLV ladder equation, we derive new n-dimensional dynamical systems and prove their integrability from the viewpoint of Lie symmetries. © 2013 The Physical Society of Japan.


Oono Y.,Daido University | Sounai A.,National College of Technology, Suzuka College | Hori M.,Daido University
Journal of Power Sources | Year: 2012

The mechanism underlying the decline in cell voltage over time was investigated for high-temperature proton exchange membrane fuel cells. Five identical cells were prepared and long-term power generation tests were conducted at an operation temperature of 150 °C and a current density of 0.2 A cm -2 for periods of up to 17,860 h. Each of the cells was then analyzed using transmission electron microscopy and electron probe micro-analysis (EPMA). The results indicated that growth of the Pt catalyst particles occurred during operation, in addition to oxidation of the carbon support. Degradation of the catalyst layers was investigated by EPMA of cross sections of the membrane electrode assemblies, allowing the mechanism of cell performance reduction to be clarified. © 2012 Elsevier B.V. All rights reserved.


This paper consists of three parts. In the first part, we prove that the Bekenstein-Hawking entropy is the unique expression of black hole entropy. Our proof is constructed in the framework of thermodynamics without any statistical discussion. In the second part, intrinsic properties of quantum mechanics are shown, which justify the Boltzmann formula to yield a unique entropy in statistical mechanics. These properties clarify three conditions, one of which is necessary and others are sufficient for the validity of Boltzmann formula. In the third part, by combining the above results, we find a reasonable suggestion from the sufficient conditions that the potential of gravitational interaction among microstates of underlying quantum gravity may not diverge to negative infinity (such as Newtonian gravity) but is bounded below at a finite length scale. In addition to that, from the necessary condition, the interaction has to be repulsive within the finite length scale. The length scale should be Planck size. Thus, quantum gravity may become repulsive at Planck length. Also, a relation of these suggestions with action integral of gravity at semi-classical level is given. These suggestions about quantum gravity are universal in the sense that they are independent of any existing model of quantum gravity. © 2011 by the author.


The ductile fracture of nonferrous pure metals and alloys during notch tensile testing was predicted using an ellipsoidal void model. Simulated and experimental tensile tests were performed using four types of nonferrous sheets and bars. Two magnitudes of prestrain were induced in the sheets by rolling and in the bars by drawing. Six notched sheet specimens and thirteen notched bar specimens with different notch-root radii were prepared. A void configuration and void shape for pure metals and those for alloys were assumed. The effects of the prestrain and notch-root radius on the reduction in area calculated agreed reasonably well with those obtained experimentally. © 2015 Elsevier Ltd.


Komori K.,Daido University
Procedia Engineering | Year: 2014

A crack becomes stationary during blanking when the clearance between the punch and the die is relatively small. In this work, a simulation of the stationary crack during blanking was performed using the node separation method. When a crack becomes stationary, one fracture surface contacts another fracture surface in the region near the stationary crack. Therefore, a simplified simulation method is proposed for the material contact. Special attention was paid to the effect of the various kinds of ductile fracture criteria on crack initiation and crack propagation during blanking. The shapes of chips and holes and the relationship between punch displacement and punch force calculated from the simulation agree well with those obtained experimentally. © 2014 The Authors. Published by Elsevier Ltd.


Komori K.,Daido University
Computational Materials Science | Year: 2013

A void model that can be used for the evaluation of ductile fracture in the simulation of sheet metal-forming processes is proposed. This void model is an extension of the Thomason model of void coalescence, which is based on the internal necking of the matrix between voids. In sheet metal-forming processes, the material is subjected to a complex strain path. Hence, the prestrain should be considered for the evaluation of ductile fracture in the simulation of sheet metal-forming processes. In the present paper, the prestrain is first introduced in the proposed void model. The simulation of the hole expansion test, which is a fundamental material test in sheet metal forming, is performed while paying special attention to the void configuration and the void shape. Finally, the validity of the proposed void model is confirmed by comparing the simulation results with the experimental results. © 2011 Elsevier B.V. All rights reserved.


Komori K.,Daido University
International Journal of Mechanical Sciences | Year: 2013

A crack is arrested during blanking when the clearance between the punch and the die is relatively small. Simulation of the arrest of a crack during blanking is performed using the node separation method. When a crack is arrested, one fracture surface contacts another fracture surface in the region near the arrested crack. Therefore, a simplified simulation method is proposed for the material contact. Special attention is given to the effect of various kinds of ductile fracture criteria on crack initiation and propagation during blanking simulations. The shapes of the scraps and blanks and the relationship between the punch displacement and the punch force calculated by the simulation agree fairly with those obtained in the experiment. © 2013 Elsevier Ltd.


Komori K.,Daido University
Mechanics of Materials | Year: 2013

An ellipsoidal void model, which is based on a parallelogrammic void model, is proposed for simulating ductile fracture behavior. It is used to analyze ductile fracture behavior in three plastic deformation modes: plane strain tension, uniaxial tension, and simple shear. The relationship between the fracture strain and the initial void volume fraction in uniaxial tension calculated using the void model agrees with that calculated using a finite-element void cell and agrees reasonably well with experimentally determined relationships in previous studies. For a specified initial void volume fraction, plane strain tension and simple shear respectively have the smallest and largest nominal fracture strains of the three plastic deformation modes.© 2013 Elsevier Ltd. All rights reserved.


Imai K.,Daido University
Journal of the Physical Society of Japan | Year: 2014

In this paper, a new n-dimensional homogeneous Lotka-Volterra (HLV) equation, which possesses a Lie symmetry, is derived by the extension from a three-dimensional HLV equation. Its integrability is shown from the viewpoint of Lie symmetries. Furthermore, we derive dynamical systems of higher order, which possess the Lie symmetry, using the algebraic structure of this HLV equation. © 2014 The Physical Society of Japan.


Komori K.,Daido University
Mechanics of Materials | Year: 2014

The ductile fracture in the simulation of sheet-metal-forming processes is evaluated by the ellipsoidal void model previously proposed by the author. In the present study, the simulation and experiment of the hole expansion test are performed using six types of metals. For an alloy, the relationship between prestrain and hole expansion ratio calculated using the ellipsoidal void configuration and ellipsoidal void shape and that calculated using the ellipsoidal void configuration and circular void shape agree with the relationship obtained experimentally. For a pure metal, the relationship between prestrain and hole expansion ratio calculated using the average void configuration and average void shape agrees with that obtained experimentally. Furthermore, the method of introducing prestrain to an as-rolled sheet is proposed, and the prestrain in this sheet is estimated. © 2014 Elsevier Ltd. All rights reserved.

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