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Search Results: 1 - 10 of 231 matches for " Toshiharu Kishi "
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Non-Destructive Imaging of Water Permeation through Cementitious Materials Using MRI  [PDF]
Yuya Sakai, Yuki Yokoyama, Toshiharu Kishi
Open Journal of Civil Engineering (OJCE) , 2017, DOI: 10.4236/ojce.2017.73026
Abstract: In this study, water permeation through cementitious materials was observed using magnetic resonance imaging (MRI). The influence of cement type on the magnetic resonance signal was studied subsequent to determining the parameters required for imaging. Consequently, adequate imaging of water permeating through hardened cement paste (HCP) made with white Portland cement was achieved, while water permeation through ordinary Portland cement-based HCP yielded poor signal. HCPs maintained at various levels of relative humidity (RH) were observed, and the signal was detected only from those maintained at an RH of higher than 85%. The water permeation depths in HCP were observed by using MRI, and the measured depths were compared to those measured via a spraying water detector on the split surface of the specimens. As a result, good agreement was confirmed between the two methods. Additionally, MRI was applied to concrete specimens; although it was found that water was not detected when a lightweight aggregate was used, water permeation through concrete with limestone aggregate was detectable via MRI. MRI will help in understanding how water permeation causes and accelerates concrete deteriorations such as rebar corrosion and freezing and thawing.
A Role of Chaotic Phenomenon and the Central Place System in a Firm’s Location Selections  [PDF]
Toshiharu Ishikawa
Theoretical Economics Letters (TEL) , 2012, DOI: 10.4236/tel.2012.21019
Abstract: When a manufacturing firm has a plan to build a factory, the determination of the factory’s location site is one of the most important elements in the plan. Since the manufacturer does not have enough information of economic conditions of all potential location sites, the manufacturer cannot determine immediately its location site. A series of steps are taken to determine the location place. The firm makes range of searching area small step by step toward the site deter-mination; 1) Determination of a prospective region in a large space, 2) Selection of a potential area in that region, 3) Choice of an urban district in that area, 4) Decision of a site in the district. This paper proposes that chaotic phenome-non, which is appeared in the calculation processes to specify the optimal location site, may be used to identify a pro-spective region. And then, it is shown in the paper that the central place systems laid in the region play a role in the se-lection of a potential area for the factory location. This paper elucidates how a firm searches step by step an appropriate factory’s location within a large geographical area.
Fixed Point Theorem and Fractional Differential Equations with Multiple Delays Related with Chaos Neuron Models  [PDF]
Toshiharu Kawasaki, Masashi Toyoda
Applied Mathematics (AM) , 2015, DOI: 10.4236/am.2015.613192
Abstract: In this paper, we show a fixed point theorem which deduces to both of Lou’s fixed point theorem and de Pascale and de Pascale’s fixed point theorem. Moreover, our result can be applied to show the existence and uniqueness of solutions for fractional differential equations with multiple delays. Using the theorem, we discuss the fractional chaos neuron model.
Therapeutic Strategies for SLE Involving Cytokines: Mechanism-Oriented Therapies Especially IFN- Targeting Gene Therapy
Toshiharu Hayashi
Journal of Biomedicine and Biotechnology , 2010, DOI: 10.1155/2010/461641
Abstract: Systemic lupus erythematosus (SLE: lupus) is a chronic complicated autoimmune disease and pathogenesis is still unclear. However, key cytokines have been recognized. Interferon (IFN)- and also IFN/ are of particular importance. Depending on the concept that lupus is a helper T(Th)1 disease and that dendritic cells (DCs) determine the direction of lupus, balance shift of Th1/Th2 and immunogenic/tolerogenic DCs is reviewed for therapy. (IFN)-- and IFN-/-targeted (gene) therapies are introduced. These consist of Th1/Th2 balance shift and elimination of IFN- and IFN--related cytokines such as (interleukin)IL-12 and IL-18. Other approaches include suppression of immunocompetent cells, normalization of abnormal T-cell function, costimulation blockade, B lymphocyte stimulator (Blys) blockade, and suppression of nephritic kidney inflammation. Moreover, balance shift of IFN-/ and tumor necrosis factor (TNF)- together with regulatory T(Treg) cells are briefely introduced. Clinical application will be discussed.
Dysfunction of Lacrimal and Salivary Glands in Sj?gren's Syndrome: Nonimmunologic Injury in Preinflammatory Phase and Mouse Model
Toshiharu Hayashi
Journal of Biomedicine and Biotechnology , 2011, DOI: 10.1155/2011/407031
Abstract: Sjögren's syndrome (SjS) is a chronic autoimmune disorder characterized by dry eyes and dry mouth due to dacryoadenitis and sialoadenitis with SS-A/Ro and/or SS-B/La autoantibodies in genetically predisposed individuals. Destruction of lacrimal and salivary glands by autoimmune reactions may lead to clinical manifestation. However, the mechanisms behind the decreased volume of secretions in tears and saliva are complex and are not fully understood. Exocrine gland dysfunction may precede autoimmunity (acquired immunity) or represent a process independent from inflammation in the pathogenesis of SjS. The preceded functional and morphologic changes of those tissues by nonimmunologic injury before the development of inflammation at the sites of target organs have been implicated. This paper focuses on the several factors and components relating to glandular dysfunction and morphologic changes by nonimmunologic injury during the preinflammatory phase in mouse model, including the factors which link between innate immunity and adaptive immunity.
Poincaré gauge theory of gravity
Toshiharu Kawai
Physics , 1993, DOI: 10.1103/PhysRevD.49.2862
Abstract: A Poincar\'{e} gauge theory of (2+1)-dimensional gravity is developed. Fundamental gravitational field variables are dreibein fields and Lorentz gauge potentials, and the theory is underlain with the Riemann-Cartan space-time. The most general gravitational Lagrangian density, which is at most quadratic in curvature and torsion tensors and invariant under local Lorentz transformations and under general coordinate transformations, is given. Gravitational field equations are studied in detail, and solutions of the equations for weak gravitational fields are examined for the case with a static, \lq \lq spin"less point like source. We find, among other things, the following: (1)Solutions of the vacuum Einstein equation satisfy gravitational field equations in the vacuum in this theory. (2)For a class of the parameters in the gravitational Lagrangian density, the torsion is \lq \lq frozen" at the place where \lq \lq spin" density of the source field is not vanishing. In this case, the field equation actually agrees with the Einstein equation, when the source field is \lq \lq spin"less. (3)A teleparallel theory developed in a previous paper is \lq \lq included as a solution" in a limiting case. (4)A Newtonian limit is obtainable, if the parameters in the Lagrangian density satisfy certain conditions.
Exotic black hole solution in teleparallel theory of (2+1)-dimensional gravity
Toshiharu Kawai
Physics , 1994, DOI: 10.1143/PTP.94.1169
Abstract: A black hole solution in a teleparallel theory of (2+1)-dimensional gravity, given in a previous paper, is examined. This solution is also a solution of the three-dimensional vacuum Einstein equation with a vanishing cosmological constant. Remarkable is the fact that this solution gives a black hole in a \lq \lq flat-land" in the Einstein theory and a Newtonian limit. Coordinate transformations to \lq \lq Minkowskian" coordinates, however, are singular not only at the origin, but also on the event horizon. {\em In the three-dimensional Einstein theory, vacuum regions of space-times can be locally non-trivial}.
Generators of Internal Lorentz Transformations and of General Affine Coordinate Transformations in Teleparallel Theory of (2+1)-Dimensional Gravity --- Cases with Static Circularly Symmetric Space-Times---
Toshiharu Kawai
Physics , 1995, DOI: 10.1143/PTP.94.915
Abstract: In a teleparallel theory of (2+1)-dimensional gravity developed in a previous paper, we examine generators of internal Lorentz transformations and of general affine coordinate transformations for static circularly symmetric exact solutions of gravitational field equation. The \lq \lq spin" angular momentum, the energy-momentum and the \lq \lq extended orbital angular momentum" are explicitly given for each solution. Also, we give a critical comment on Deser's claim that neither momentum nor boosts are definable for finite energy solutions of three-dimensional Einstein gravity.
Energy-momentum and angular momentum densities in gauge theories of gravity
Toshiharu Kawai
Physics , 2000, DOI: 10.1103/PhysRevD.62.104014
Abstract: In the $\bar{\mbox{\rm Poincar\'{e}}}$ gauge theory of gravity, which has been formulated on the basis of a principal fiber bundle over the space-time manifold having the covering group of the proper orthochronous Poincar\'{e} group as the structure group, we examine the tensorial properties of the dynamical energy-momentum density ${}^{G}{\mathbf T}_{k}{}^{\mu}$ and the ` ` spin" angular momentum density ${}^{G}{\mathbf S}_{kl}{}^{\mu}$ of the gravitational field. They are both space-time vector densities, and transform as tensors under {\em global} $SL(2,C)$- transformations. Under {\em local} internal translation, ${}^{G}{\mathbf T}_{k}{}^{\mu}$ is invariant, while ${}^{G}{\mathbf S}_{kl}{}^{\mu}$ transforms inhomogeneously. The dynamical energy-momentum density ${}^{M}{\mathbf T}_{k}{}^{\mu}$ and the ` ` spin" angular momentum density ${}^{M}{\mathbf S}_{kl}{}^{\mu}$ of the matter field are also examined, and they are known to be space-time vector densities and to obey tensorial transformation rules under internal $\bar{\mbox{\rm Poincar\'{e}}}$ gauge transformations. The corresponding discussions in extended new general relativity which is obtained as a teleparallel limit of $\bar{\mbox{\rm Poincar\'{e}}}$ gauge theory are also given, and energy-momentum and ` ` spin" angular momentum densities are known to be well behaved. Namely, they are all space-time vector densities, etc. In both theories, integrations of these densities on a space-like surface give the total energy-momentum and {\em total} (={\em spin}+{\em orbital}) angular momentum for asymptotically flat space-time. The tensorial properties of canonical energy-momentum and ` ` extended orbital angular momentum" densities are also examined.
Precise Positioning of Pneumatic Artificial Muscle Systems  [PDF]
Shaofei Wang, Kaiji Sato, Toshiharu Kagawa
Journal of Flow Control, Measurement & Visualization (JFCMV) , 2014, DOI: 10.4236/jfcmv.2014.24016
Abstract: Pneumatic artificial muscles (PAMs) currently possess a high power-to-weight ratio, a high power-to-volume ratio, and a high degree of safety. They have therefore been applied to many power assist devices and positioning mechanisms such as bionic robots, welfare devices, and parallel manipulators. However, the significant nonlinear characteristics of PAM mechanisms limit their positioning accuracies. The accuracies are generally lower than 5 μm, which preclude the PAM from precision systems. Nevertheless, enhancing the positioning accuracy is desired to extend the application fields of PAMs. This study aims to clarify a practical controller design method to achieve the precise positioning of PAM systems. As the first step of this research, a linear motion mechanism with a pair of McKibben PAMs was constructed and a conventional dynamic model for this system is introduced. The dynamic model is used to explain the basic characteristics of the PAM mechanism and discuss the necessary characteristics for precise positioning. Then open-loop step and sinusoidal responses of the PAM mechanism were examined by experimental and simulated results. Next, for precise positioning, the practical controller design procedure is discussed and determined based on the measured open-loop responses. The proposed controller design procedure can be easily implemented into PAM mechanisms without an exact dynamic model. The positioning performance of such a system was experimentally evaluated. The experimental results show that although the positioning accuracy depends on the target position, the positioning error is lower than 1 μm even in the worst case and the positioning resolution can be set to 0.5 μm.
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