National Institute of Technology, Ube College

Yamaguchi, Japan

National Institute of Technology, Ube College

Yamaguchi, Japan
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Inagaki T.,Hiroshima University | Kimura D.,National Institute of Technology, Ube College | Kohyama H.,Kyungpook National University
International Journal of Modern Physics A | Year: 2014

The Nambu-Jona-Lasinio model is investigated in the 1/Nc expansion with the dimensional regularization. At the four-dimensional limit, the meson propagators have simple forms in the leading order of the 1/N c expansion. Thus, the next to leading order calculation reduces to an ordinary one loop calculation. Here we obtain an explicit form of the 1/Nc correction and numerically evaluate the Nc dependence for the gap equation. © 2014 World Scientific Publishing Company.

Nishida K.,National Institute of Technology, Ube College | Ahmed T.,Assiut University | Nakaoka M.,Kyungnam University
IEEE Transactions on Industry Applications | Year: 2011

In this paper, a novel grid integration system for a variable-speed wind turbine using an interior permanent-magnet synchronous generator (IPMSG) is developed. The power conditioner system (PCS) consists of a series-type 12-pulse uncontrolled diode rectifier powered by a phase-shifting transformer and then cascaded to a pulsewidth-modulated (PWM) voltage source inverter. The active current of the grid-side PWM inverter is only controlled to follow the optimal active current reference which is determined by using a simple maximum power point tracking (MPPT) control strategy. The MPPT algorithm requires only three sensors in order to track the maximum power of the wind turbine. The most significant advantage of the proposed system is that the passive filter together with a series-type 12-pulse rectifier provides high efficiency by compensating the power factor angle of the IPMSG and suppresses distortions presented in the IPMSG voltages and currents. The laboratory results indicate that the proposed construction and scheme are simple, cheap, and efficient. © 2010 IEEE.

Kohyama H.,National Taiwan University | Kimura D.,National Institute of Technology, Ube College | Inagaki T.,Hiroshima University
Nuclear Physics B | Year: 2015

We study the regularization dependence on meson properties and the phase diagram of quark matter by using the two flavor Nambu-Jona-Lasinio model. The model also has the parameter dependence in each regularization, so we explicitly give the model parameters for some sets of the input observables, then investigate its effect on the phase diagram. We find that the location or the existence of the critical end point highly depends on the regularization methods and the model parameters. Then we think that regularization and parameters are carefully considered when one investigates the QCD critical end point in the effective model studies. © 2015.

Haruyama O.,Tokyo University of Science | Nakayama Y.,Tokyo University of Science | Wada R.,Tokyo University of Science | Tokunaga H.,National Institute of Technology, Ube College | And 3 more authors.
Acta Materialia | Year: 2010

The structural relaxation in a Zr55Cu30Ni5Al10 bulk metallic glass was investigated by volume and enthalpy relaxation at various temperatures. The relaxation kinetics was well described by a stretched exponential relaxation function, Φ (t) = exp [- (t / τ)β]. The Kohlrausch index, β, ranged from 0.35 to 0.69, while the temperature dependence of relaxation time, τ was best fitted by the Vogel-Fulcher-Tanmmann formula, τ (T) = τ0 exp fenced(D* T0 / (T - T0)), with τ0 = 1.1 × 10-14 s, D* = 44.2 and T0 = 311 K. Atomic volumes in the equilibrium liquid region were measured by the electrostatic levitation method and these volumes, together with volumes of relaxed glasses, were better described by the Cohen-Grest model than by the Cohen-Turnbull model. © 2009 Acta Materialia Inc.

Ishikawa S.,Kyushu Institute of Technology | Kubota R.,National Institute of Technology, Ube College | Horio K.,Kyushu Institute of Technology
Expert Systems with Applications | Year: 2015

In this paper, we propose a new optimization technique, the hierarchical multi-space competitive distributed genetic algorithm (HmcDGA), which is effective for the hierarchical optimization problem. It is an extension of the multi-space competitive distributed genetic algorithm (mcDGA), which was proposed by the authors. The mcDGA efficiently finds an optimal solution with a low computational cost by increasing the number of individuals in a solution space in which it is likely to exist. An optimization method that is divided into several levels of hierarchy is called a hierarchical optimization. Several hierarchical optimization techniques have been proposed, including the hierarchical genetic algorithm (HGA). In hierarchical optimization, a complex problem is divided into a hierarchical collection of simpler problems, and each level is optimized independently. In this way, complex problems can be solved without the need to develop problem-specific operators. However, in the conventional HGA, this results in a high computational cost because the genetic algorithm (GA) is repeated many times at upper and lower level. The HmcDGA is a hybrid of the mcDGA and HGA, and it has some of the advantages of each one; for example, the HmcDGA can find an optimal solution at low computational cost and without requiring special operations. This allows it to be applied to a wide variety of optimization problems. Therefore, the HmcDGA may become the powerful optimization algorithm that can solve various problems. In this paper, we apply the proposed HmcDGA to the flexible job-shop scheduling problem (FJSP) which is one of the complex combinational optimization problem and confirm its effectiveness. Simulation results show that the HmcDGA can find solutions that are comparable to those found by using GAs developed specifically for the FJSP, the HmcDGA is not required a lot of computational costs comparing to the HGA. © 2015 Elsevier Ltd. All rights reserved.

Yoshida M.,National Institute of Technology, Ube College
Materials Transactions | Year: 2012

Titanium diboride (TiB 2) has been sintered using spark plasma sintering (SPS) with the addition of titanium tri-aluminide (Al 2Ti) at the temperature between 1273 and 1573 K. By the X-ray diffraction measurements, it has been shown that TiB 2Al 2Ti composites can be obtained by the sintering at 1273 K. Vickers hardness of the specimen increases as the amount of Al 2Ti increases up to 30% by the sintering at 1273 K, and TiB 230 mass% Al 2Ti composite has the relative density of around 96% and Vickers hardness as high as 2100 Hv. On the other hand, Al 2Ti evaporates during sintering above 1473 K. TiB 2 sintered with 10 mass% Al 2Ti at 1573K has the relative density of 94% and Vickers hardness 2100 Hv, while TiB 2 sintered without Al 2Ti has the relative density as low as 76%. This fact indicates that Al 2Ti accelerates the diffusion of TiB 2 causing densification of sintered TiB 2 specimens in the sintering above 1473 K. © 2012 The Japan Institute of Metals.

Mitani Y.,National Institute of Technology, Ube College | Hamamoto Y.,Yamaguchi University
Proceedings of the SICE Annual Conference | Year: 2010

In remote sensing, it is important to acquire high-resolution images. A pan-sharpen technique artificially produces a high-resolution image by image fusion techniques using high-resolution panchromatic and low-resolution multispectral images. Thus, the appearance of the color image can improve. However, the effectiveness of pan-sharpen techniques is little studied. In this paper, the effectiveness of three pan-sharpening methods based on the HSI transform approach is investigated. Furthermore, the influence of smoothing the low-resolution multispectral image is also investigated. © 2010 SICE.

Yoshida M.,National Institute of Technology, Ube College
16th European Conference on Composite Materials, ECCM 2014 | Year: 2014

Titanium diboride added with NiAl of up to 80wt% has been sintered using spark plasma sintering (SPS) at temperature between 1273K and 1673K. By the x-ray diffraction measurements it has been shown that TiB2 and NiAl co-exist in equilibrium at the temperature up to 1673K. By the SEM observation it has been shown that NiAl fills the space between TiB2 grains and dense samples are obtained. The grain size of TiB2 is around several microns which is the same as that of the starting TiB2 powders. The highest Vickers hardness of 1600Hv has been obtained for TiB2-40wt%NiAl, which has bending strength of as high as 730MPa. The highest bending strength of 990MPa has been obtained for TiB2-80wt%NiAl. On the other hand, the bending strength of monolithic NiAl and TiB2 sintered at 1573K is as low as 370MPa and 250MPa, respectively.

Nagamine Y.,National Institute of Technology, Ube College
Physical Review E | Year: 2016

To demonstrate that phase separation is a main mechanism of pattern formation for one of the spatiotemporal patterns emerging in the Ag and Sb electrodeposition system, I performed numerical simulations to model the mixed system of conductive and insulative materials under a steady electric field. For such a dissipative system, I derived the extended Cahn-Hilliard equation using Onsager's variational principle. My results demonstrate that conductive and insulative materials phase separate spatially under the constant-current mode. © 2016 American Physical Society.

Kubota R.,National Institute of Technology, Ube College | Suetake N.,Yamaguchi University
Journal of the Franklin Institute | Year: 2011

We present a novel switching median filter for the removal of random-valued impulse noise on a color image. The present filter consists of a new noise detector with auto-tuning function, and a vector type noise remover avoiding the occurrence of the color artifacts after the noise removal. The detector has a parameter, which is automatically tuned only by using the distribution information of the noise signal without any training signals, and detects the pixel corrupted by the random-valued impulse noise with the parameter. And the detector operates in each channel independently. As a noise remover, the ordinary vector median filter is employed to interpolate only the pixel which is detected as noisy one by the detector. Through the experiments using some digital color images, the validity and the effectiveness of the present method are verified. © 2011 The Franklin Institute.

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