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Search Results: 1 - 10 of 687 matches for " Hideyuki Momono "
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The Corrosion Behavior of Ni3Al/Ni3V Two-Phase Intermetallic Compounds in Various Acidic Solutions
Gadang Priyotomo,Hideyuki Momono,Sanat Wagle,Kenji Okitsu,Akihiro Iwase,Yasuyuki Kaneno,Rokuro Nishimura,Takayuki Takasugi
International Journal of Corrosion , 2012, DOI: 10.1155/2012/626240
Abstract: The corrosion behavior of the Ni3Al/Ni3V two-phase intermetallic compounds with and without minor elements (Nb, Co, and Cr) to be composed of L12 phase (Ni3Al) and a mixed phase of L12 (Ni3Al) and D022 (Ni3V) has been investigated by using an immersion test in 0.5?kmol/m3 HCl, H2SO4, and HNO3 solutions. The surface morphology was observed before and after the immersion test by scanning electron microscope (SEM). The results were compared to those of the L12 single-phase Ni3(Si,Ti) and austenitic stainless steel type 304. In all acidic solutions, preferential dissolution of ( ) phase was found in Ni3Al/Ni3V, but no intergranular attack, whereas the attacks took place on Ni3(Si,Ti). The Ni3Al/Ni3V showed a higher corrosion resistance in HCl solution and a lower resistance in HNO3 solution than Ni3(Si,Ti) and type 304. The addition of the minor elements enhanced corrosion resistance in HNO3 solution, but not clearly in HCl and H2SO4 solutions. In HCl and H2SO4, their weight losses during the immersion test were almost the same. 1. Introduction Recently, Ni-Al-V intermetallic compounds with a two-phase microstructure of Ni3Al (L12) and Ni3V (D022) phases have been developed by Takasugi et al. [1–13] and are confirmed to exhibit a highly coherent interface between these constituent phases. They have superior mechanical properties (i.e., high creep rapture life, high hardness, low thermal expansion, and better thermal conductivity) and also have high tensile strength and fracture toughness over a broad range of temperature in comparison with those of Inconel 750, Inconel 718 and Hastelloy [1–13]. Therefore, the Ni3Al/Ni3V two-phase intermetallic compounds are a candidates as materials in land-based, marine-based, and aero-gas turbine industries (turbine blade), high strength nut and bolt, and high temperature bearing or high temperature tool [8, 9, 14]. However, many studies revealed that the intermetallic compounds containing aluminum are very susceptible to hydrogen embrittlement [15–18], where hydrogen embrittlement takes place with permeation of atomic hydrogen formed by corrosion reaction into the compounds. Hence, to suppress this environmental embrittlement a small amount of boron was added to these compounds. However, it was reported that the boron segregation at grain boundaries became the preferential dissolution site and led to the intergranular attack in the L12 single-phase Ni3(Si,Ti) [19]. Furthermore, Ni base intermetallic compounds such as single-phase Ni3(Si,Ti) have attractive properties for high-temperature structural material (e.g., high
Multi-Name Extension to the Credit Grades and an Efficient Monte Carlo Method  [PDF]
Hideyuki Takada
Journal of Mathematical Finance (JMF) , 2014, DOI: 10.4236/jmf.2014.43017
Abstract:

In this paper, we present a multi-name incomplete information structural model which possess the contagion mechanism and its efficient Monte Carlo algorithm based on Interacting Particle System. Along with the Credit Grades, which is industrially used single-name credit model, we suppose that investors can observe firm values and defaults but are not informed of the threshold level at which a firm is deemed to default. Additionally, in order to model the possibility of crisis normalization, we introduce the concept of memory period after default. During the memory period after a default, public investors remember when the previous default occurred and directly reflect that information for updating their belief. When the memory period after a default finish, investors forget about that default and shift their interest to recent defaults if exist. One of the variance reduction techniques, relying upon Interacting Particle System, is combined with the standard Monte Carlo method to address the rare but critical events represented by the tail of loss distribution of portfolio.

Effect of Ultrasonic Output Power on Refining the Crystal Structures of Ingots and Its Experimental Simulation
Junwen LI,Tadashi MOMONO,
Tadashi
,MOMONO

材料科学技术学报 , 2005,
Abstract: In this study, a series of tests were conducted by using aluminum-based alloy to determine the formation of grain refining structure based on the ultrasonic vibration (UV). Furthermore, the simulation test and effect of ultrasonic output power were studied using ammonium chloride. Finally, the mechanism of grain refinement was investigated.The results show that: (1) By applying the UV to aluminum-base alloy, the grain refining rate of ingots tended to increase with the increase of the output value of UV. (2) It was confirmed that time from after the pour to the beginning of crystallization as well as cloudiness tended to decrease with increasing the ultrasonic power value of UV. Moreover, it can be seen from each cooling curve that a uniform temperature gradient existed in the melt as the power of UV increased, that made the melt strongly stirred. (3) It was also considered that the grain refining effect of ingots, which was observed from the simulation tests, resulted from nucleation action and stirring division action by applying the UV.
Interactive Evolutionary Computation for Analyzing Human Awareness Mechanisms
Hideyuki Takagi
Applied Computational Intelligence and Soft Computing , 2012, DOI: 10.1155/2012/694836
Abstract: We discuss the importance of establishing awareness science and show the idea of using interactive evolutionary computation (IEC) as a tool for analyzing awareness mechanism and making awareness models. First, we describe the importance of human factors in computational intelligence and that IEC is one of approaches for the so-called humanized computational intelligence. Second, we show examples that IEC is used as an analysis tool for human science. As analyzing human awareness mechanism is in this kind of analyzing human characteristics and capabilities, IEC may be able to be used for this purpose. Based on this expectation, we express one idea for analyzing the awareness mechanism. This idea is to make an equivalent model of an IEC user using a learning model and find latent variables that connect inputs and outputs of the user model and that help to understand or explain the inputs-outputs relationship. Although there must be several definitions of awareness, this idea is based on one definition that awareness is to find out unknown variables that helps our understanding. If we establish a method for finding the latent variables automatically, we can realize an awareness model in computer. 1. Introduction The number of papers using the keywords context awareness, power awareness, location awareness, and situation awareness in the SciVerse Scopus database of Elsevier is, respectively, 6,383, 1,749, 1,688, and 257 as of February 2012. Engineering interest in these areas has increased. These engineering approaches call obtaining unknown knowledge or facts awareness. However, how do these engineering approaches differ from data mining or knowledge acquisition? Although these kind of applications are useful and important, we need other scientific approaches not only to support the engineering applications of awareness but also to extend awareness science and engineering. One such scientific approach would be analyzing the awareness mechanisms of human beings and/or animals and constructing awareness models based on these mechanisms. Once we establish their core technologies, we may be able to make a computer with using such a model be aware of something. As the result, we can expect not only to develop data mining-like applications as has been done until now but also to progress human-machine communications, the monitoring of social networks, and new areas. Analyzing awareness mechanisms and modeling them are the first important step to research performed in this direction. It is important to integrate ideas from and cooperate with those in ethology,
Photoinduced Surface Relief Grating Formation for a Single Crystal of 4-Aminoazobenzene
Hideyuki Nakano
International Journal of Molecular Sciences , 2010, DOI: 10.3390/ijms11041311
Abstract: Photoinduced surface relief grating (SRG) formation for a single crystal of 4-aminoazobenzene was investigated. It was found that SRG could be inscribed on the (001) surface of the crystal, which might suggest that the photoinduced SRG formation is a general phenomenon observed for single crystals of azobenzene-based molecules as well as for azobenzene-based amorphous systems. In addition, the dependences of the SRG formation upon the orientation of the sample crystal and upon the polarization of the writing beams were found to be different from those observed for previously reported crystalline systems.
Effect of aqueous vitamin B on the growth of blister blight pathogen, Exobasidium vexans
Hideyuki Nagao
Songklanakarin Journal of Science and Technology , 2012,
Abstract: The effect of three aqueous solution of biotin, thiamine and calcium pantothenate, on the growth of Exobasidiumvexans was examined in vitro. The germination process of basidiospores of E. vexans differed from those of the otherExobasidium species. Basidiospore germination commenced after 19.5 hr incubation and chlamydospore-like bodies wereformed after 96 hr of incubation. Addition of biotin, calcium pantothenate, and thiamine to Difco PDA and Czapek’s mediumdid not affect the proportion of germinating basidiospores. The length of germ tubes was enhanced only by addition ofthiamine in the media. Larger size germ tubes (thick germ tubes) were occasionally observed among the ordinary hyphae.Most germlings of basidiospores developed chlamydospore-like bodies or autolysed on the media. Thick germ tubesfrequently appeared on the calcium pantothenate amended media and developed into a colony when these hyphae weretransferred to new calcium pantothenate amended media. However, further transfer of colonies did not successfully bring anew colony to grow on the calcium pantothenate amended media. Vitamin B5, calcium pantothenate, was only partially effective in generating the thick germ tubes and to induce the initial colony formation, whereas amendment of biotin and thiamineto the media did not induce visible colony growth.
TOPICAL REVIEW: Structural control of Fe-based alloys through diffusional solid/solid phase transformations in a high magnetic field
Hideyuki Ohtsuka
Science and Technology of Advanced Materials , 2008,
Abstract: A magnetic field has a remarkable influence on solid/solid phase transformations and it can be used to control the structure and function of materials during phase transformations. The effects of magnetic fields on diffusional solid/solid phase transformations, mainly from austenite to ferrite, in Fe-based alloys are reviewed. The effects of magnetic fields on the transformation temperature and phase diagram are explained thermodynamically, and the transformation behavior and transformed structures in magnetic fields are discussed.
Vacuum State of Lattice Gauge Theory with Fermions in 2+1 Dimensions
Hideyuki Abe
Physics , 1996, DOI: 10.1142/S0217751X97001948
Abstract: We investigate the vacuum state of the lattice gauge theory with fermions in 2+1 dimensions. The vacuum in the Hermite form for the fermion part is obtained; the vacuum in the unitary form has been proposed by Luo and Chen. It is shown that the Hermite vacuum has a lower energy than the unitary one through the variational method.
Physics of stars understood/expected from asteroesismology
Hideyuki Saio
Physics , 2011,
Abstract: What can be learned about the physics of stellar interiors from studying stellar oscillations? This review address the potential to improve our understandings of convective core overshoot and of more general convection-related effects, microscopic diffusion, rotation and magnetic fields, and finally evolution-induced period changes.
Prospects for asteroseismology of rapidly rotating B-type stars
Hideyuki Saio
Physics , 2013, DOI: 10.1007/978-3-642-33380-4_8
Abstract: In rapidly rotating stars Coriolis forces and centrifugal deformations modify the properties of oscillations; the Coriolis force is important for low-frequency modes, while the centrifugal deformation affects mainly p-modes. Here, we discuss properties of g- and r-mode oscillations in rotating stars. Predicted frequency spectra of high-order g-modes (and r-modes) excited in rapidly rotating stars show frequency groupings associated with azimuthal order $m$. We compare such properties with observations in rapidly rotating Be stars, and discuss what is learnt from such comparisons.
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