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Search Results: 1 - 10 of 180 matches for " Akihito Hasuno "
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Improvement of die life in high speed injection die casting
Yasuhiro Arisuda,Akihito Hasuno,Junji Yoshida
China Foundry , 2008,
Abstract: High-speed injection die casting is an effi cient manufacturing technology for upgrading aluminum die-cast products. However, defi ciencies (such as die damage in early period) due to larger load on the molding die compared with conventional technology have brought new challenges. In this study, the cause of damage generated in super high-speed injection was investigated by the combination of experimental observation of the dies and CAE simulation (e.g. die emperature analysis, fl ow analysis and thermal stress analysis). The potential countermeasures to solve the above problems were also proposed.
Effects of Differential Item Discriminations between Individual-Level and Cluster-Level under the Multilevel Item Response Theory Model  [PDF]
Chalie Patarapichayatham, Akihito Kamata
Open Journal of Applied Sciences (OJAppS) , 2014, DOI: 10.4236/ojapps.2014.48039
Abstract: This study attempted to interpret differential item discriminations between individual and cluster levels by focusing on patterns and magnitudes of item discriminations under 2PL multilevel IRT model through a set of variety simulation conditions. The consistency between the mean of individual-level ability estimates and cluster-level ability estimates was evaluated by the correlations between them. As a result, it was found that they were highly correlated if the patterns of item discriminations were the same for both individual and cluster levels. The magnitudes of item discriminations themselves did not affect much on correlations, as far as the patterns were the same at the two levels. However, it was found that the correlation became lower when the patterns of item discriminations were different between the individual and cluster levels. Also, it was revealed that the mean of the estimated individual-level abilities would not be necessarily a good representation of the cluster-level ability, if the patterns were different at the two levels.
Fructophilic lactic acid bacteria inhabit fructose-rich niches in nature
Akihito Endo
Microbial Ecology in Health and Disease , 2012, DOI: 10.3402/mehd.v23i0.18563
Abstract: Fructophilic lactic acid bacteria (FLAB) are a special group of lactic acid bacteria (LAB), which prefer fructose but not glucose as growth substrate. They are found in fructose-rich niches, e.g. flowers, fruits, and fermented foods made from fruits. Quite recently, they were found in the gastrointestinal tracts of animals consuming fructose, which were bumblebees, tropical fruit flies, and Camponotus ants. These suggest that all natural sources that are rich in fructose are possible their habitats. Fructobacillus spp., formerly classified as Leuconostoc spp., are representatives of these microorganisms, and Lactobacillus kunkeei has also been classified as FLAB. They share several unique biochemical characteristics, which have not been found in LAB inhabited in other niches. FLAB grow well on fructose but very poor on glucose. These organisms grow well on glucose only when external electron accepters, e.g. pyruvate or oxygen, are available. LAB have been shown to have specific evolution to adapt to their niches and have several niche-specific characteristics. FLAB must have fructophilic evolution during adaptation to fructose-rich niches. FLAB are unique food-related LAB, suggesting a great potential for future food and feed applications.
An approach to first principles electronic structure calculation by symbolic-numeric computation
Akihito Kikuchi
QScience Connect , 2013, DOI: 10.5339/connect.2013.14
Abstract: There is a wide variety of electronic structure calculation cooperating with symbolic computation. The main purpose of the latter is to play an auxiliary role (but not without importance) to the former. In the field of quantum physics [1-9], researchers sometimes have to handle complicated mathematical expressions, whose derivation seems almost beyond human power. Thus one resorts to the intensive use of computers, namely, symbolic computation [10-16]. Examples of this can be seen in various topics: atomic energy levels, molecular dynamics, molecular energy and spectra, collision and scattering, lattice spin models and so on [16]. How to obtain molecular integrals analytically or how to manipulate complex formulas in many body interactions, is one such problem. In the former, when one uses special atomic basis for a specific purpose, to express the integrals by the combination of already known analytic functions, may sometimes be very difficult. In the latter, one must rearrange a number of creation and annihilation operators in a suitable order and calculate the analytical expectation value. It is usual that a quantitative and massive computation follows a symbolic one; for the convenience of the numerical computation, it is necessary to reduce a complicated analytic expression into a tractable and computable form. This is the main motive for the introduction of the symbolic computation as a forerunner of the numerical one and their collaboration has won considerable successes. The present work should be classified as one such trial. Meanwhile, the use of symbolic computation in the present work is not limited to indirect and auxiliary part to the numerical computation. The present work can be applicable to a direct and quantitative estimation of the electronic structure, skipping conventional computational methods.
Julia Clancy-Smith (éd.), North Africa, Islam, and the Mediterranean World : from the Almoravids to the Algerian War, London, Frank Cass, 2001, 202 p.
Akihito Kudo
Revue des Mondes Musulmans et de la Méditerranée , 2011,
Abstract: Cet ouvrage collectif est le résultat d’un colloque international organisé en 1998 conjointement par l’AIMS (American Institute for Maghrib Studies) et le CEMAT (Centres d'études Maghrébines à Tunis). Il s’agissait de se pencher sur le Maghreb dans l'optique de la "World History", un champ d'études largement méconnu des chercheurs francophones et maghrébins, comme le remarque la directrice de la publication, Julia Clancy-Smith. Il s'agit d'une approche visant à déconstruire non seulement le...
Multi-reference extension to virtual crystal approximation pseudo-potentials
Akihito Kikuchi
Physics , 2014,
Abstract: In this study a computational method of the multi-reference VCA(virtual crystal approximation) pseudo-potential generation is presented. This is an extension of that proposed Ramer and Rappe [J. Phys. Chem. Sol. 61, 315(2000)], the scheme of which is in want of the explicit incorporation of semi-core states. To compensate this drawback, a kind of fine tuning applied to the non-multi-reference VCA pseudo-potential; the form of the pseudo-potential is slightly modified within the cut-off radius in order that the agreements between the pseudo-potential and all-electron calculations are guaranteed both for semi-core and valence states. The improvement in the present work is validated by atomic and crystalline test calculations for the transferability and the lattice constant estimation.
An approach to first principles electronic structure calculation by symbolic-numeric computation
Akihito Kikuchi
Physics , 2013,
Abstract: This article is an introduction to a new approach to first principles electronic structure calculation. The starting point is the Hartree-Fock-Roothaan equation, in which molecular integrals are approximated by polynomials by way of Taylor expansion with respect to atomic coordinates and other variables. It leads to a set of polynomial equations whose solutions are eigenstate, which is designated as algebraic molecular orbital equation. Symbolic computation, especially, Gr\"obner bases theory, enables us to rewrite the polynomial equations into more trimmed and tractable forms with identical roots, from which we can unravel the relationship between physical parameters (wave function, atomic coordinates, and others) and numerically evaluate them one by one in order. Furthermore, this method is a unified way to solve the electronic structure calculation, the optimization of physical parameters, and the inverse problem as a forward problem.
A proposal to first principles electronic structure calculation: Symbolic-Numeric method
Akihito Kikuchi
Physics , 2012,
Abstract: This study proposes an approach toward the first principles electronic structure calculation with the aid of symbolic-numeric solving. The symbolic computation enables us to express the Hartree-Fock-Roothaan equation and the molecular integrals in analytic forms and approximate them as a set of polynomial equations. By use of the Grobner bases technique, the polynomial equations are transformed into other ones which have identical roots. The converted equations take more convenient forms which will simplify numerical procedures, from which we can derive necessary physical properties in order, in an a la carte way. This method enables us to solve the electronic structure calculation, the optimization of any kind, or the inverse problem as a forward problem in a unified way, in which there is no need for iterative self-consistent procedures with trials and errors.
Simplification of QPLDA: A practical method to the correction for the LDA band gap problem
Akihito Kikuchi
Physics , 2012,
Abstract: It is necessary to employ quasi-particle calculations to correct band gap problems in LDA. As an expedient way for the reliable but massive GWA, Quasi-Particle-LDA (QPLDA) is proposed by several authors, where the total computational cost scales with N. Historically, Sham and Kohn introduced the idea of the local mass operator based on local wavenumber similar to WKB, but did not execute actual numerical calculations. They took into account exchange interaction only, from which we could not expect precise treatments anyway. Later, Pickett and Wang had proposed a more qualitative method and had shown its potentiality in examples of semiconductors, such as silicon, diamond and GaP. They used a model analytic formula for the dialectic function and adopted a model energy dispersion, which is free-electron like one, except that, being accompanied with an artificial band-gap discontinuity. The latter method has two shortcomings. First, to execute the calculation, several parameters are needed, such as the macroscopic dielectric constant and the band gap, which should be evaluated by the calculation itself, rather than being prepared as parameters. Second, in their computation of the mass operator, two or three dimensional numerical integrations are needed on each point of the direct space mesh, which demand large computational costs in iterative procedures in determining local wavenumbers and quasi-particle energies. This may be the reason why QPLDA has not been widely used until now. The present work proposes a qualitative way of QPLDA which does not need any experimental parameters, being much speedier than the formalism of Picket and Wang, and more precise than that of Sham and Kohn. The computational method adopted by the present work is a modification of the original proposal by Sham and Kohn, rather than that of Picket and Wang.
Some special values of hypergeometric series related to central values of automorphic $L$-functions
Akihito Ebisu
Mathematics , 2013,
Abstract: In a recent work, H.Narita presented problems concerning the strict positivity of central values of certain automorphic $L$-functions in the form of questions regarding special values of the hypergeometric series. In this paper, we present partial answers to these questions using the theory of orthogonal polynomials and three term relations of the hypergeometric series.
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