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Search Results: 1 - 10 of 1463 matches for " Hideki Arakawa "
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Reliability of Power Spectral Analysis of Surface Electromyogram Recorded during Sustained Vastus Medialis Isometric Contraction in Assessment of Muscle Fatigability  [PDF]
Yuta Minoshima, Yukihide Nishimura, Hiroyuki Tsuboi, Hideyuki Satou, Yoshi-ichiro Kamijo, Hideki Arakawa, Yuichi Umezu, Fumihiro Tajima
Open Journal of Therapy and Rehabilitation (OJTR) , 2017, DOI: 10.4236/ojtr.2017.52005
Abstract: The aim of this study was to determine the within-day and between-days reliability of surface electromyographic (EMG) power spectral analysis in assessing fatigability of the vastus medialis (VM) muscle during knee and hip flexion under constant load application. The subjects were 13 healthy adult men free of knee abnormalities. Surface EMG was recorded from vastus medialis obliquus (VMO) and vastus medialis longus (VML) during sustained isometric contractions at 60% of maximal voluntary contraction until exhaustion on the leg press machine (static leg press test). Linear regression analysis was applied to median frequency (MF) time series to calculate initial MF and MF slope. For VMO and VML, the initial MF showed moderate to high reliability, while the MF slope showed high reliability (Intraclass correlation coefficient (ICC) = initial MF: 0.63 - 0.92, MF slope: 0.70 - 0.86). The results demonstrated that spectral analysis of surface EMG recording during isometric VM muscle contraction has high within-day and between-days reliability in the assessment of fatigability of the VMO and VML.
Development of Charging Infrastructure and Subsidies for Promoting Electric Vehicles  [PDF]
Kiyoshi Arakawa
Theoretical Economics Letters (TEL) , 2018, DOI: 10.4236/tel.2018.811131
Abstract: This paper clarifies an effect of policy on the development of charging infrastructure and subsidies for promoting electric vehicles (EVs). Due to the long-term function of charging infrastructure, this paper constructs a multiple-period model to analyze policy effects on the diffusion of EVs from a long-term perspective. This paper shows that charging infrastructure and subsidy encourage innovation on increasing the battery capacity of EVs. Because intertemporal cost allocation can be executed in the development of a charging infrastructure with a subsidy, a policy with a long-term perspective can enhance the charging infrastructure and promote EVs effectively.
Dynamic Effect of Low-Cost Entry on the Conduct Parameter: An Early-Stage Analysis of Southwest Airlines and America West Airlines  [PDF]
Hideki Murakami
Modern Economy (ME) , 2013, DOI: 10.4236/me.2013.44032

The purpose of this research is to investigate the dynamic changes in the competition between air carriers by applying a revised conduct parameter method. We examine the cases of Southwest Airlines and America West Airlines due to the availability of data. Our interests are in what fashion a low-cost carrier entered the market, how the rival reacted, and whether the fashions of competition between two types of air carrier remained stable as time passed. Our empirical results show that the fashions of competition fell between Cournot and “P = MC” competition, and competitive fashions were sometimes stable but sometimes not.

Efficient Frontier via Production Functions and Mechanization  [PDF]
Hideki Nakamura
American Journal of Operations Research (AJOR) , 2017, DOI: 10.4236/ajor.2017.71004
Abstract: This study attempts to reconcile data envelopment analysis (DEA) with the production function approach in economics. We examine not only the inputs of capital and labor, but also the ranges of these inputs in production process steps, and endogenously derive a Leontief production function. The Leontief production functions shift northeasterly owing to mechanization, which is the replacement of labor inputs by capital inputs in some steps. Consequently, we describe the efficient frontier as the convex hull of the Leontief production functions. Furthermore, we consider the possibility of efficient production below the efficient frontier.
An Equilibrium Asset Pricing Model under the Dual Theory of the Smooth Ambiguity Model  [PDF]
Hideki Iwaki
Journal of Mathematical Finance (JMF) , 2018, DOI: 10.4236/jmf.2018.82031
Abstract: This paper considers an equilibrium asset pricing model in a static pure exchange economy under ambiguity. Ambiguity preference is represented by the dual theory of the smooth ambiguity model [6]. We show the existence and the uniqueness of the equilibrium in the economy and derive the state price density (SPD). The equilibrium excess return, which can be seen as an extension of the capital asset pricing model (CAPM) under risk to ambiguity, is derived from the SPD. We also determine the effects of ambiguity preference on the excess returns of ambiguous securities through comparative statics of the SPD.
Factor Substitution and Employment  [PDF]
Hideki Nakamura
Modern Economy (ME) , 2018, DOI: 10.4236/me.2018.97074
Abstract: This paper explores how employment among an educated workforce depends on production technology represented by factor substitution and factor-augmenting technical progress. We consider a variant of the Diamond overlapping generations model that can explain the empirical finding about the elasticity of substitution being less than unity observed in some developed economies. Depending on factor substitution, a decline in the wage rate has positive and negative effects on employment. When the elasticity of substitution is less than unity, a low wage rate can imply a low employment rate as well as a low human capital level. Given the elasticity of substitution, being less than unity, labor-augmenting technical progress can decrease the employment rate and human capital level via a decrease in the marginal product of labor.
Characterization of Quasispecies of Pandemic 2009 Influenza A Virus (A/H1N1/2009) by De Novo Sequencing Using a Next-Generation DNA Sequencer
Makoto Kuroda,Harutaka Katano,Noriko Nakajima,Minoru Tobiume,Akira Ainai,Tsuyoshi Sekizuka,Hideki Hasegawa,Masato Tashiro,Yuko Sasaki,Yoshichika Arakawa,Satoru Hata,Masahide Watanabe,Tetsutaro Sata
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0010256
Abstract: Pandemic 2009 influenza A virus (A/H1N1/2009) has emerged globally. In this study, we performed a comprehensive detection of potential pathogens by de novo sequencing using a next-generation DNA sequencer on total RNAs extracted from an autopsy lung of a patient who died of viral pneumonia with A/H1N1/2009. Among a total of 9.4×106 40-mer short reads, more than 98% appeared to be human, while 0.85% were identified as A/H1N1/2009 (A/Nagano/RC1-L/2009(H1N1)). Suspected bacterial reads such as Streptococcus pneumoniae and other oral bacteria flora were very low at 0.005%, and a significant bacterial infection was not histologically observed. De novo assembly and read mapping analysis of A/Nagano/RC1-L/2009(H1N1) showed more than ×200 coverage on average, and revealed nucleotide heterogeneity on hemagglutinin as quasispecies, specifically at two amino acids (Gly172Glu and Gly239Asn of HA) located on the Sa and Ca2 antigenic sites, respectively. Gly239 and Asn239 on antigenic site Ca2 appeared to be minor amino acids compared with the highly distributed Asp239 in H1N1 HAs. This study demonstrated that de novo sequencing can comprehensively detect pathogens, and such in-depth investigation facilitates the identification of influenza A viral heterogeneity. To better characterize the A/H1N1/2009 virus, unbiased comprehensive techniques will be indispensable for the primary investigations of emerging infectious diseases.
Representation Theory of Superconformal Algebras and the Kac-Roan-Wakimoto Conjecture
Tomoyuki Arakawa
Physics , 2004,
Abstract: We study the representation theory of the superconformal algebra $W_k(g,f_{\theta})$ associated with a minimal gradation of $g$. Here, $g$ is a simple finite-dimensional Lie superalgebra with a non-degenerate, even supersymmetric invariant bilinear form. Thus, $W_k(g,f_{\theta})$ can be one of the well-known superconformal algebras including the Virasoro algebra, the Bershadsky-Polyakov algebra, the Neveu-Schwarz algebra, the Bershadsky-Knizhnik algebras, the N=2 superconformal algebra, the N=4 superconformal algebra, the N=3 superconformal algebra and the big N=4 superconformal algebra. We prove the conjecture of V. G. Kac, S.-S. Roan and M. Wakimoto for $W_k(g,f_{\theta})$. In fact, we show that any irreducible highest weight character of $W_k(g,f_{\theta})$ at any level $k\in C$ is determined by the corresponding irreducible highest weight character of the Kac-Moody affinization of $g$.
Many-body effects on the resistivity of a multiorbital system beyond Landau's Fermi-liquid theory
Naoya Arakawa
Physics , 2015, DOI: 10.1142/S0217984915300057
Abstract: I review many-body effects on the resistivity of a multiorbital system beyond Landau's Fermi-liquid (FL) theory. Landau's FL theory succeeds in describing electronic properties of some correlated electron systems at low temperatures. However, the behaviors deviating from the temperature dependence in the FL, non-FL-like behaviors, emerge near a magnetic quantum-critical point. These indicate the importance of many-body effects beyond Landau's FL theory. Those effects in multiorbital systems have been little understood, although their understanding is important to deduce ubiquitous properties of correlated electron systems and characteristic properties of multiorbital systems. To improve this situation, I formulate the resistivity of a multiorbital Hubbard model using the extended \'{E}liashberg theory and adopt this method to the inplane resistivity of quasi-two-dimensional paramagnetic ruthenates in combination with the fluctuation-exchange approximation including the current vertex corrections arising from the self-energy and Maki-Thompson term. The results away from and near the antiferromagnetic quantum-critical point reproduce the temperature dependence observed in Sr$_{2}$RuO$_{4}$ and Sr$_{2}$Ru$_{0.075}$Ti$_{0.025}$O$_{4}$, respectively. I highlight the importance of not only the momentum and the temperature dependence of the damping of a quasiparticle but also its orbital dependence in discussing the resistivity of correlated electron systems.
Orbital-cooperative spin fluctuation and orbital-dependent transport in ruthenates
Naoya Arakawa
Physics , 2014, DOI: 10.1103/PhysRevB.90.245103
Abstract: Unusual transport properties deviating from the Fermi liquid are observed in ruthenates near a magnetic quantum-critical point (QCP). To understand the electronic properties of the ruthenates near and away from an antiferromagnetic (AF) QCP, I study the electronic structure and magnetic and transport properties for the $t_{2g}$-orbital Hubbard model on a square lattice in fluctuation-exchange approximation including Maki-Thompson (MT) current vertex correction (CVC). The results away from the AF QCP reproduce several experimental results of Sr$_{2}$RuO$_{4}$ qualitatively and provide new mechanisms about the enhancement of spin fluctuation at $Q_{\textrm{IC-AF}}\approx (0.66\pi,0.66\pi)$, larger mass enhancement of the $d_{xy}$ orbital than that of the $d_{xz/yz}$ orbital, and nonmonotonic temperature dependence of the Hall coefficient. Also, the results near the AF QCP explain the $T$-linear inplane resistivity in Sr$_{2}$Ru$_{0.075}$Ti$_{0.025}$O$_{4}$ and give an experimental test on the obtained temperature dependence of the Hall coefficient. I reveal spatial correlation including the self-energy of electrons beyond mean-field approximations is essential to determine the electronic properties of the ruthenates. I also show several ubiquitous transport properties near an AF QCP and characteristic transport properties of a multiorbital system by comparison with results of a single-orbital system near an AF QCP.
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