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Takahashi T.,Niihama National College of Technology | Minamino Y.,Osaka University
Journal of Alloys and Compounds | Year: 2012

The binary interdiffusion coefficients D̃ (Ti-Fe) in β Ti-Fe alloy and D̃ (Ti-Al) in β Ti-Al alloy, Fe impurity diffusion coefficients D* Fe(Ti-Al) in β Ti-Al alloys, and ternary interdiffusion coefficients D̃ AlAl Ti, D̃ FeFe Ti, D̃ AlFe Ti and D̃ FeAl Ti in Ti-rich β Ti-Al-Fe alloys were determined at 1423 K using binary and ternary diffusion couples by ordinary and extended Matano methods and Hall's one. The D̃ (Ti-Al) values increase with Al concentration, and the D̃ (Ti-Fe) values show almost no concentration dependence. The D* Fe(Ti-Al) values in β Ti-Al alloys steeply decrease with Al concentration up to 7 at.%Al and become almost constant over about 7 at.%Al. In the ternary β Ti-Al-Fe alloys, the D̃ AlAl Ti, D̃ FeFe Ti, D̃ AlFe Ti and D̃ FeAl Ti values are positive, and the D̃ FeFe Ti and D̃ FeAl Ti values are larger than the D̃ AlAl Ti and D̃ AlFe Ti ones, respectively. They show the complicated dependence on concentrations of Al and Fe elements. The positive ratios of D̃ FeAl Ti/D̃ FeFe Ti and D̃ AlFe Ti/D̃ AlAl Ti indicate that the repulsive interactions exist between Al and Fe atoms in the ternary alloys, but the negative ratios of converted interdiffusion coefficients D̃ FeTi Al/D̃ FeFe Al show the attractive interactions between Ti and Al and between Ti and Fe atoms in this alloy. These diffusion coefficients and data suggest that Al diffusion occur by vacancy diffusion mechanisms and Fe diffusion takes place by some kind of interstitial diffusion mechanism in β Ti-Al-Fe alloys. © 2012 Elsevier B.V. All rights reserved. Source


DiFranzo A.,University of California at Irvine | Nagao K.I.,High Energy Accelerator Research Organization | Nagao K.I.,Niihama National College of Technology | Rajaraman A.,University of California at Irvine | Tait T.M.P.,University of California at Irvine
Journal of High Energy Physics | Year: 2013

We investigate simplified models in which dark matter particles, taken to be either Dirac or Majorana fermions, couple to quarks via colored mediators. We determine bounds from colliders and direct detection experiments, and show how the interplay of the two leads to a complementary view of this class of dark matter models. Forecasts for future searches in light of the current constraints are presented. © SISSA 2013. Source


Nakayama S.,Niihama National College of Technology | Sakamoto M.,Yamagata University
Solid State Ionics | Year: 2013

Apatite-type La9.33Ge6O26 single crystal as an oxide ionic conductor has been successfully prepared by a single crystallization of the sintered polycrystalline La9.33Ge 6O26 ceramics on the surface of seed single crystal without their melt. The crystal has a hexagonal crystal system with a space group of P63/m. Conductivity measurements revealed that the La 9.33Ge6O26 single crystal did not exhibit an anisotropy, in contrast with the previously reported La9.33Si 6O26 single crystal (hexagonal crystal system with a space group of P63/m), which apparently exhibited the anisotropy: conductivity component parallel to the c-axis was ca. 100 times higher than the perpendicular component. In order to discuss the difference between these apatite-type single crystals, their crystal structures were compared. Results implied that the conduction pathway perpendicular to the c-axis is rather important in the germanate apatite. © 2013 Elsevier B.V. Source


Matsuda K.,Niihama National College of Technology
Journal of Mathematical Physics | Year: 2012

We completely classify the rational solutions of the Noumi and Yamada system of type A 4 (1), which is a generalization of the fourth Painlevé equation. The rational solutions are classified to three by the Bäcklund transformation group. © 2012 American Institute of Physics. Source


Matsutomo S.,Niihama National College of Technology | Noguchi S.,Hokkaido University | Yamashita H.,Hiroshima Institute of Technology
IEEE Transactions on Magnetics | Year: 2012

To solve electromagnetic field problems by the finite element method, it is necessary for a user to make a mesh in preprocess. However, the made mesh is usually different from that made by the other users, since it depends on the user's experience and knowledge. The mesh strongly affects the accuracy of the analysis result. The adaptive finite element method has been researched in order to address this problem. In this paper, we propose a new mesh generation method utilizing magnetic flux lines in two-dimensional electromagnetic field problem. Utilizing the magnetic flux lines computed with a rough mesh, it is possible to distribute elements with different densities suitable for the electromagnetic field distribution. © 2012 IEEE. Source

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