Obara S.,Kitami Institute of Technology |
Watanabe S.,National Institute of Technology, Kushiro College
International Journal of Hydrogen Energy | Year: 2012
A microgrid requires a stable supply of electric power and heat, which is achieved by the cooperative operation of two or more pieces of equipment. The equipment capacity and the operational method of the equipment were optimized using a newly developed orthogonal array-GA (genetic algorithm) hybrid method for an independent microgrid accompanied by a fuel cell cascade system, solar water electrolysis, battery, and heat storage. This type of system had not been hardly developed until now. The objective function of the proposed system was the minimization of the total amount of equipment and fuel cost over ten years. For the first step in the proposed analysis method, the capacity of each piece of equipment and the operational method, which are considered to be close to the optimal solution of the system, are combined using the orthogonal array and factorial-effect chart, which are an experimental design technique. In the next step, the combination described above provides the initial values to the GA, and the GA searches for the optimal capacity and operational method for each piece of equipment in question. Compared with a simple GA, the convergence characteristic improves greatly using the proposed analysis method developed in this study. Copyright © 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
Obara S.,Kitami Institute of Technology |
Watanabe S.,National Institute of Technology, Kushiro College |
Rengarajan B.,International Advanced Research Center for Powder Metallurgy And New Materials
Energy | Year: 2011
A completely energy-independent microgrid (green microgrid) was examined in this work with the aims of abating greenhouse gas emissions by spreading the use of green energy, providing energy backup systems for disaster, and increasing the energy utilization efficiency with the use of exhaust heat. This paper analyzed the energy supply to six houses in a cold region. The green microgrid consisted of photovoltaics, water electrolyzers, proton-exchange membrane fuel cells (PEFCs), and heat pumps. To investigate the operation method and the capacity of each piece of equipment in the arrangement, a distributed system with two or more sets of equipment and a central system with one set of equipment were analyzed by a genetic algorithm. By introducing the prior energy need pattern of a cold region into the proposed system, the operation method and equipment capacity based on the power and heat balance were clarified. By introducing the partial load performance of a water electrolyzer and a PEFC into the analysis program, the operation method of each system was investigated. It was found that the area of a solar cell of a distributed system could be reduced by 12% as compared to a central system. © 2011 Elsevier Ltd.
Suda J.,National Institute of Technology, Kushiro College |
Zverev P.G.,RAS A.M. Prokhorov General Physics Institute
Vibrational Spectroscopy | Year: 2012
The phonon-dispersion relations of BaWO 4 crystal are calculated using the lattice dynamical calculations approach. Spontaneous Raman spectra in the BaWO 4 were measured in the temperature range from 10 K to 295 K, and the temperature dependence of the linewidth of the E g (72 cm -1) and A g (926 cm -1) Raman modes were analyzed using the lattice dynamical perturbative approach. We found that different behaviors of these two modes in the case of temperature broadening could be attributed to the large energy band gap in the one-phonon density of states (PDOS) resulting in different anharmonic interactions. This phonon band gap limits the number of relaxation mechanisms for internal vibronic modes, i.e., anharmonic processes between the A g (926 cm -1) Raman modes and lower energy modes in BaWO 4. This leads to a dephasing effect on the A g (926 cm -1) mode and the dephasing processes are increased only at high temperatures. © 2012 Elsevier B.V.
Fumoto K.,National Institute of Technology, Kushiro College |
Kawaji M.,University of Toronto |
Kawanami T.,Kobe University
Journal of Electronic Packaging, Transactions of the ASME | Year: 2010
This paper discusses a pulsating heat pipe (PHP) using a self-rewetting fluid. Unlike other common liquids, self-rewetting fluids have the property that the surface tension increases with temperature. The increasing surface tension at a higher temperature can cause the liquid to be drawn toward a heated surface if a dry spot appears and thus to improve boiling heat transfer. In experiments, 1-butanol and 1-pentanol were added to water at a concentration of less than 1 wt % to make self-rewetting fluid. A pulsating heat pipe made from an extruded multiport tube was partially filled with the self-rewetting fluid water mixture and tested for its heat transport capability at different input power levels. The experiments showed that the maximum heat transport capability was enhanced by a factor of 4 when the maximum heater temperature was limited to 110°C. Thus, the use of a self-rewetting fluid in a PHP was shown to be highly effective in improving the heat transport capability of pulsating heat pipes. © 2008 IEEE.
Ishibashi N.,University of Tsukuba |
Murakami K.,National Institute of Technology, Kushiro College
Journal of High Energy Physics | Year: 2016
Abstract: It is possible to formulate light-cone gauge string field theory in noncritical dimensions. Such a theory corresponds to conformal gauge worldsheet theory with nonstandard longitudinal part. We study the longitudinal part of the worldsheet theory on higher genus Riemann surfaces. The results in this paper shall be used to study the dimensional regularization of light-cone gauge string field theory. © 2016, The Author(s).
Sako A.,National Institute of Technology, Kushiro College
Advances in Mathematical Physics | Year: 2010
We review recent developments in noncommutative deformations of instantons in ℝ4. In the operator formalism, we study how to make noncommutative instantons by using the ADHM method, and we review the relation between topological charges and noncommutativity. In the ADHM methods, there exist instantons whose commutative limits are singular. We review smooth noncommutative deformations of instantons, spinor zero-modes, the Green's functions, and the ADHM constructions from commutative ones that have no singularities. It is found that the instanton charges of these noncommutative instanton solutions coincide with the instanton charges of commutative instantons before noncommutative deformation. These smooth deformations are the latest developments in noncommutative gauge theories, and we can extend the procedure to other types of solitons. As an example, vortex deformations are studied. Copyright © 2010 Akifumi Sako.
Miyake A.,National Institute of Technology, Kushiro College |
Miyake A.,Meiji Gakuin University |
Ohta K.,Meiji Gakuin University |
Sakai N.,Tokyo Woman's Christian University
Progress of Theoretical Physics | Year: 2011
We evaluate volume of moduli space of BPS vortices on a compact genus h Riemann surface σh by using topological field theory and localization technique developed by Moore, Nekrasov and Shatashvili. We apply this technique to Abelian (ANO) vortex and show that the volume of moduli space agrees with the previous results obtained by integrating over the moduli space metric. We extend the evaluation to non-Abelian gauge groups and multiflavors. We also compare our results with the volume of the Kähler quotient space inspired by the brane configuration.
Tsuyoshi-Takahashi,National Institute of Technology, Kushiro College |
Sasaki K.,Hokkaido University
Procedia Engineering | Year: 2010
To meet several marketing demands, development of new aluminum alloys which can be used for future high-efficiency diesel engines has been widely pursued. Especially, cylinder heads (hereafter referred to as "head(s)") are used at high combustion pressure and very high temperature, which makes it difficult to achieve a structure with light weight and high rigidity. In this study, aluminum alloy A356 (Al-Si-Mg series) which is a major head material, were conducted the thermal fatigue tests. Thus, the authors focused on the changing of material characteristics (hardness and stress-strain curves as for macroscopic characteristic and microstructure as for microscopic characteristic) during the test. This paper deals with the effects of artificial aging on two aluminum alloys A356, which have been often used for engine cylinder heads. The aluminum alloys were artificially aged under several different conditions after T6 heat treatment. The alloys were tested for fatigue characteristics as thermo-mechanical fatigue failure. The microstructure was observed by TEM to see the effects on microstructure in terms of fatigue failure. In addition, we examined the microstructure of an actual head after a durability test, and tried to find out whether material test conditions above mentioned were reasonable. Finally, the relationship between the microstructure changes and the low cycle thermal fatigue is discussed. © 2010 Published by Elsevier Ltd.
Kishi N.,National Institute of Technology, Kushiro College |
Mikami H.,Sumitomo Mitsui Construction
ACI Structural Journal | Year: 2012
To establish an impact-resistant design procedure for reinforced concrete (RC) structures based on the performance-based design concept, an evaluation method for the impact-resistant capacity of the structures needs to be developed. Until now, a particular method for beams has not yet been specified worldwide. To achieve this, falling-weight impact tests on a total of 36 beams with varying section parameters were conducted and the key factors for better representing the impact behavior of the beams were investigated. Two empirical equations were derived based on the experimental results. By using these equations, the required static flexural load-carrying capacity of an RC beam may be determined by specifying the limit state with the maximum and residual deflections of the beam. Copyright © 2012, American Concrete Institute. All rights reserved.
Kawanami T.,Kobe University |
Hirano S.,Kobe University |
Fumoto K.,National Institute of Technology, Kushiro College |
Hirasawa S.,Kobe University
Applied Thermal Engineering | Year: 2011
This paper deals with the cooling characteristics of a magnetocaloric cooling technique refrigerator an active magnetic regenerator (AMR). The AMR-based refrigeration cycle, which has a thermal storage process and a regeneration process, realizes a practical magnetic refrigerator running near room temperature. The AMR cycle has four sequential processes: adiabatic magnetization, fluid flow, adiabatic demagnetization, and fluid flow. We devise an appropriate simulation model of the cyclic heat transfer process inside the particle bed as the target AMR. Then, the temperature profile inside the AMR particle bed and the cooling characteristics of the room-temperature magnetic regenerator are studied analytically. In addition, the validity of the analytical model by molecular field approximation theory is verified by comparing the experimental results with the analytical results. The results show that, when a higher magnetic field is applied to the magnetocaloric material, a greater temperature difference is obtained. © 2010 Elsevier Ltd. All rights reserved.