Theoretical and Applied Mechanics Japan
Online ISSN : 1349-4244
Print ISSN : 1348-0693
ISSN-L : 1348-0693
Volume 54
Displaying 1-41 of 41 articles from this issue
I. SOLID AND STRUCTURAL MECHANICS
  • Makoto SAKAMOTO, Koichi KOBAYASHI
    2005 Volume 54 Pages 3-15
    Published: 2005
    Released on J-STAGE: May 10, 2006
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    We study an axisymmetric contact problem of a transversely isotropic layer subjected to a tensile stress applied over a circular hole of a rigid plate. The problem is equivalent to a mixed boundary-value problem of the theory of elasticity, and an exact solution is obtained through an infinite system of simultaneous equations. Convergence can be achieved using 8 terms of the series. Significant effects of the material anisotropy and the layer thickness on the stress fields are demonstrated with numerical results. The problem is applied to a biomechanical model of an articulating joint which assumes that an articular cartilage is a transversely isotropic layer and a subchondral bone is a rigid foundation. Numerical examples of the normal displacement in the circular hole for anisotropic cartilage material property are also presented.
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  • Ying ZHENG, Eiichiro TSUCHIDA, Yoshio ARAI
    2005 Volume 54 Pages 17-29
    Published: 2005
    Released on J-STAGE: May 10, 2006
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    In the present paper, we investigate the steady state thermal stresses in an elastic thick plate containing an oblate spheroidal inclusion, when the circle regions of radius d of the upper surface is heated and the one of lower surface is cooled. The solution is deduced with using thermoelastic displacement potentials and Papcovich-Neuber displacement potentials. Numerical results are presented for different heat areas, inclusion shapes and sizes, and the stress distributions in the vicinity of the inclusion are illustrated graphically.
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  • Kenzo SATO
    2005 Volume 54 Pages 31-44
    Published: 2005
    Released on J-STAGE: May 10, 2006
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    The bending of an elliptical plate undergoing the combined action of uniform lateral load over its entire surface and uniform in-plane force distributed in its middle plane is treated in the present paper. The analysis is based on the small-deflection theory of the plate and performed in the elliptical coordinate system. The general solution, which satisfies perfectly the basic equation of deflection and the boundary condition, is presented in the form of an infinite series of Mathieu functions. In addition, the intensities of bending moments, twisting moment, shearing forces and effective shear force are rigorously formulated in the form of infinite series. A special case of a circular plate under the combined action of uniform lateral load and in-plane force is discussed in detail. Numerical calculation is also performed and the calculated results will be given in tables and figures.
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  • Hiroyuki KINOSHITA, Koichi KAIZU
    2005 Volume 54 Pages 45-52
    Published: 2005
    Released on J-STAGE: May 10, 2006
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    This paper aims to ascertain guidelines for obtaining the high joint strength in the riveting process. Presently, it is thought that in the riveting process the plate is fastened by the rivet head, as well as by the pressure between the rivet axis side and plate in the rivet hole generated as a result of the spreading of the rivet axis. In this paper, to clarify the influences of the work-hardening of rivet materials and the clearance in the rivet hole on the pressure between the rivet axis and plate, both elastic-plastic finite element simulations of the riveting process and extrusion tests of the rivet axis are carried out. The numerical and experimental results show that the pressure between the rivet axis side and plate increases when the rivet material with the greater work-hardening is used, and the pressure becomes lower when the clearance in the rivet hole is larger.
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  • Giora SHATIL, Li WANG
    2005 Volume 54 Pages 53-63
    Published: 2005
    Released on J-STAGE: May 10, 2006
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    This article is a summary of an extensive investigation carried out to assess the possible use of the local approach to ductile fracture in the design of service components. The investigation included ductile fracture simulation of structural steel(BS080M40) at room temperature using non-linear finite element analysis and several constitutive material damage models. It incorporated an experimental programme to calibrate and validate the simulation results and metallographic examinations of the material microstructure and fracture process. It concludes that local fracture approaches have the capacity to model fracture of structural steel components within specified limitations.
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  • Shigetoshi ARAKI, Akio SUGIMOTO
    2005 Volume 54 Pages 65-76
    Published: 2005
    Released on J-STAGE: May 10, 2006
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    Void growth in a viscous resin is analyzed by using the equivalent inclusion method combined with the Mori-Tanaka theorem. In modeling, we assume that a solid-state gas-forming agent dispersed in the matrix resin a priori sublimates into a gas at the prescribed temperature and the resultant voids are formed in the matrix resin. The pressure in the void is related with both its volume and the degree of temperature in it by using the Boyle-Charles law. The coefficient of viscosity of the matrix resin is assumed to change with temperature according to the so-called W.L.F. equation. By adopting the equivalent inclusion method to the model, the dilatational strain rate in the void, and hence, the differential equation for the volume of voids with respect to the elapsed time is derived as a function of the temperature. The differential equation is solved to a forming process made up of a heating process for forming of the void, followed by a retention process under the constant temperature for the void growth, before a cooling process for bringing a stop to the void growth. Consequently, the volume of void considerably increases with decrease in the viscosity of the matrix and with increase in the retention temperature.
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  • Yasutomo UETSUJI, Yusuke TODA, Kazuyoshi TSUCHIYA, Sei UEDA, Eiji NAKA ...
    2005 Volume 54 Pages 77-82
    Published: 2005
    Released on J-STAGE: May 10, 2006
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    For multi-scale modeling of advanced polycrystalline piezoelectric ceramics such as lead zirconium titanate (PZT), it is necessary to catch mechanical and electrical properties of crystal grain. In this paper, PZT crystal grain properties have been identified computationally from ones of PZT polycrystal by steepest decent method and multi-scale finite element modeling based on a crystallographic homogenization method. Crystal morphology of PZT polycrystal has been measured by SEM•EBSD technique, and it has been introduced to microscopic finite element model. Then, crystal grain properties were surveyed by steepest decent method to correspond its macroscopic homogenized ones to experimental values of PZT polycrystal. The proposed procedure has been applied to barium titanate (BT), and its validity has been proved by comparison of identified properties with already-known ones of BT single crystal. Finally, the identified properties such as elastic compliance, dielectric and piezoelectric constants were presented for PZT crystal grain.
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  • Mitsuhiro HASEGAWA, Shizuka IZAWA, Ming-Chien HSU, Makoto SUDO, Tetsuk ...
    2005 Volume 54 Pages 83-91
    Published: 2005
    Released on J-STAGE: May 10, 2006
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    There is a difficult problem that the present freezing and thawing test method indicates the structure-insensitive properties from the point of view of materials science concerning the specimen size, shape and exposure condition, in addition, the mass variation. The “surface defect ratio” as a new index in place of the above-mentioned factors has been proposed. The fundamental deterioration is dependent on the repetitional scaling of surface layer; further, it has been basically analyzed that the freezing and thawing action makes concrete neutralize from the outside by virtue of the environmental contact water. The wet and dry action as well as the freeze-thaw action is one of the principal deterioration causes and these are the extreme phenomena at both ends on the temperature axis. It has been already understood that the either action contributes to the neutralizing acceleration of concrete.
    The present paper particularly deals with the quantification of the concentration dilution of pore solution and the neutralization of matrix of concrete, from the viewpoint of the potential Hydrogen (pH) range of general environmental water.
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  • Masaki OMIYA, Kikuo KISHIMOTO
    2005 Volume 54 Pages 93-99
    Published: 2005
    Released on J-STAGE: May 10, 2006
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    The simple tensile tests under a confocal laser scanning microscope and in-situ observations of thin film were carried out to investigate the failure process of brittle thin film under tensile loading. The results show that cracks parallel to loading direction were firstly formed and, then, cracks vertical to the loading direction were formed due to Poisson's effect. We focused on the formation of vertical cracks and proposed the buckling induced delamination and cracking model to evaluate the interfacial strength between thin film and substrate. The interfacial strength obtained by that model agrees well with the interfacial strength obtained by Multi-stages peel test.
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  • Samadder Liton KUMAR, Yoshio ARAI, Eiichiro TSUCHIDA
    2005 Volume 54 Pages 101-112
    Published: 2005
    Released on J-STAGE: May 10, 2006
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    Characteristics of singular stress field around an interface free edge between elastic and elastic-plastic materials, especially for the ceramic/metal joints with a interlayer were investigated theoretically. Finite element simulations have also been conducted to accomplish the quantitative examinations of the theoretical results. Elastic/linear hardening predictions and elastic/power-law hardening predictions were considered in the analysis. The simulation results of stress distribution clearly showed that the singular fields exist around the interface free edge between the elastic and elastic-plastic materials. Variables separable form functions of stress distribution were examined around the interface free edge. The availability of the elastic/linear hardening materials interface edge prediction was discussed.
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II. DYNAMICS AND OPTIMIZATION
  • Yoichi MUKAI, Masaki FUJIMOTO
    2005 Volume 54 Pages 115-122
    Published: 2005
    Released on J-STAGE: May 10, 2006
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    Applicability of an "Active Powered-Mass Couplers (PMC)" system is discussed to improve aseismic efficiency of the seismic isolation buildings. The PMC is assembled by a moving-mass installed in an isolated story and dual connecting members to both the upper structure and the basement. One of connecting members is actively controlled so that "negative stiffness" can be apparently generated. Negative stiffness of the PMC can take the place of the control force by large volume of the additional mass as introduced on the general mass damper system. Appropriate designing method of the PMC is proposed by using the general tuning theory for "Tuned Mass Dampers (TMD)" systems. Response control effects of the PMC are investigated through numerical case studies. As a result, it is assured that the PMC can effectively reduce resonant responses of the seismic isolation buildings without spoiling vibration isolating efficiency for the acceleration responses.
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  • Harumi NISHIMURA, Eizaburo TACHIBANA
    2005 Volume 54 Pages 123-135
    Published: 2005
    Released on J-STAGE: May 10, 2006
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    The sliding base isolators are used for lightweight building structures because of their low dependence on contact pressure. Generally, the desirable frictional coefficients of sliding base isolators are 0.05~0.10. However, even in the case of 0.10~0.20, enough reduction of response can be expected at the time of a big earthquake (Maximum acceleration > 200 Gal). In this study, by using shaking table, the efficiencies of sliding base isolator made by stainless steel are examined. At first both static and dynamic frictional coefficients μs and μd are identified. As a result, the values are identified around 0.19 and 0.14, respectively. Then with these values, numerical simulations are executed and it appeared that the responses decrease to 20~50% for the case of multi-degree-of-freedom system model.
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  • Qin ZHU, Mitsuaki ISHITOBI
    2005 Volume 54 Pages 137-142
    Published: 2005
    Released on J-STAGE: May 10, 2006
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    In this study, the dynamic responses of a seven-degree-of-freedom non-linear ground vehicle model are investigated with numerical simulation. The model displays complicated dynamic responses including harmonic motions and chaos. The chaotic motion is confirmed by calculation of the dominant Lyapunov exponent. The results may be useful in dynamic design of the vehicle.
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  • Hiroyuki KOJIMA, Gustavo KATO
    2005 Volume 54 Pages 143-150
    Published: 2005
    Released on J-STAGE: May 10, 2006
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    In this paper, the dynamic behaviors of a two-joint articulated hopping robot with two stopper mechanisms are theoretically investigated. In the theoretical analysis, the four phases are used to model the dynamic behaviors of the two-joint articulated hopping robot. By the use of the principle of the conservation of momentum and angular momentum, the initial states in the periods of the phase-B and the phase-C are derived, and the equations of motion of the two-joint articulated hopping robot in the four phases are obtained. Furthermore, the numerical simulations have been carried out, and it is theoretically confirmed that the hopping and moving actions can be successfully performed.
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  • Noboru TANIMOTO
    2005 Volume 54 Pages 151-165
    Published: 2005
    Released on J-STAGE: May 10, 2006
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    Many investigations have been done on dynamic behavior of solids or on hypervelocity behavior of condensed matter. However, there exists a 1-dimensional basic problem of plane collision unresolved. In other words, general formulas have not been sufficiently established yet between two collision velocities before collision and physical quantities of two continuous bodies immediately after collision when two continuous bodies collide with faces perpendicular to the direction of motion. In the present paper, it is newly shown that relational formulas among physical quantities produced by plane collision are expressed in terms of two collision velocities, material constants and a slope of the relation between propagation speed of precursor and particle velocity of the compressive stress wave. And from those general formulas, theoretical equations in a few special cases are derived and onsidered. And approximate formulas and applicable conditions of those equations are given. And moreover, from the proposed same general formulas, theoretical equations are derived also in the case of hypervelocity collision which produces shock waves. And theoretical values are compared with experimental ones.
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  • Keiji SATOH, Kou YAMADA, Makoto KOWADA
    2005 Volume 54 Pages 167-173
    Published: 2005
    Released on J-STAGE: May 10, 2006
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    In this paper, we examine the parametrization of all stabilizing modified repetitive controllers for single-input/single-output time-delay systems with the specified input-output frequency characteristics. The parametrization of all stabilizing modified repetitive controllers for time-delay systems was considered by Yamada et al. However, using the parametrization of all stabilizing modified repetitive controllers for time-delay systems by Yamada et al., the input-output frequency characteristics cannot be settled easily. From a practical point of view, the input-output frequency characteristics of the control systems are required to be easily settled. In this paper, we expand the result by Yamada et al. and propose the parametrization of all stabilizing modified repetitive controllers for time-delay systems with the specified input-output frequency characteristics. Finally, a numerical example is shown to illustrate the effectiveness of the proposed parametrization.
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  • Kou YAMADA, Takashi OGIWARA
    2005 Volume 54 Pages 175-185
    Published: 2005
    Released on J-STAGE: May 10, 2006
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    In this paper, we propose a design method for robust servo controllers for nonlinear systems to which the exact linearization method is not applicable. In order for the output to follow the reference input without steady state error, the controller must include all modes of the reference input. Therefore we construct the augmented nonlinear systems with the plant and the pre-compensator that includes all modes of the reference input. Next, a state transformation matrix is settled, so that the augmented nonlinear system is transformed approximately into the controllable canonical form. A standard nonlinear linearization method is used to transform the controllable canonical form into a linear system. Since this method adopts an approximate linearization approach, in some cases, the approximate term makes the control system unstable. Next we present a design method for robust servo controllers that guarantee the stability of the control system even if the approximate term exists.
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III. HEAT TRANSFER AND FLUID DYNAMICS
  • Kenji TOMOEDA
    2005 Volume 54 Pages 189-194
    Published: 2005
    Released on J-STAGE: May 10, 2006
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    Numerical experiments suggest the interesting properties in the several fields. One of them is the occurrence of support re-splitting phenomena caused by the interaction between diffusion and absorption, where support splitting phenomena mean that the region occupied by the fluid becomes disconnected. From only numerical computations it is difficult to justify whether such phenomena are true or not, because the space mesh and the time step are sufficiently small but not zero. In this paper such phenomena are investigated by use of finite difference scheme, and justified from numerical and analytical points of view.
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  • Seiichiro NAGOYA
    2005 Volume 54 Pages 195-202
    Published: 2005
    Released on J-STAGE: May 10, 2006
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    The problem of free surface flow is considered, e.g. the tidal flow. Some conservative convection diffusion difference schemes for the problem are proposed. To establish the conservative property, the difference schemes will be formulated by semi-implicit technique.
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  • Kazuko MIYASHITA, Tetuya KAWAMURA
    2005 Volume 54 Pages 203-209
    Published: 2005
    Released on J-STAGE: May 10, 2006
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    The objective of the present study is to investigate performances of the first, the second and the third order accurate methods for the calculation of inviscid fluxes in the shallow water equations. For this purpose, Roe's flux difference splitting method with MUSCL interpolation scheme is applied to solve the two dimensional shallow water equations. In the above mentioned methods, minmod slope-limiter is applied. A partial dam-break problem and circular dam-break problem are analyzed in order to compare the performance among the presented schemes. The results indicate that differences between the first-order upwind scheme and higher order ones are clear while those between the second and the third are slight.
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  • Hiroshi KANAYAMA, Masao OGINO, Norifumi TAKESUE, A.M.M. MUKADDES
    2005 Volume 54 Pages 211-219
    Published: 2005
    Released on J-STAGE: May 10, 2006
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    We have constructed a parallel algorithm of the Balancing Domain Decomposition (BDD) in structural analysis, and succeeded in solving problems with over 100 million degrees of freedom. The results are released as an open source software, named ADVENTURE_Solid, from the ADVENTURE project. In this study, as an application of the parallel BDD algorithm of ADVENTURE_Solid to other fields, we apply it to a stationary Stokes solver. The effectiveness is shown with the consideration of applications to Navier-Stokes solvers.
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  • Masuo MIZUSHIMA
    2005 Volume 54 Pages 221-225
    Published: 2005
    Released on J-STAGE: May 10, 2006
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    A condenser cooling sea water discharged from coastal nuclear power plant has been diffused into the sea area at an outlet temperature-rise of the order of 7 °C in thermally-stratified turbulent shear flow. The purpose of this research is that the vertical thermal diffusion phenomenon and heat-flux interface stability mechanism in the thermal effluent is analyzed based on one-dimensional heat-flux turbulence models. An important applied hydrodynamic formula that is the relation between a local gradient Richardson number Ri and a dimensionless buoyancy parameter Bp is formulated, and it is seen to keep the buoyancy parameter Bp →∞ in the case of flow region of Ri ≥0.612. It is principal to perform the protection of environment.
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  • Masato FUKUTA, Shu TAKAGI, Yoichiro MATSUMOTO
    2005 Volume 54 Pages 227-234
    Published: 2005
    Released on J-STAGE: May 10, 2006
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    The lift force acting on a spherical bubble in a linear shear flow is studied by solving the Navier-Stokes equations in a three-dimensional orthogonal curvilinear coordinate system. It is well known that the characteristics of the bubble surface changes from shear-free to no-slip when the liquid is contaminated by surfactants, and this change affects the bubble motion. Focusing on the change of the boundary conditions on the surface, the lift force is investigated numerically when the no-slip condition is given at the rear region of the bubble surface. The present results show that the drag and lift forces change from those of a clean bubble to those of a rigid sphere. In the transient region, the dependences of the drag and lift forces on the cap angle are different and are discussed with respect to the contribution of the pressure to those forces.
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  • Tetsuya SUEKANE, Yoshihisa TSUKAMOTO, Shuichiro HIRAI
    2005 Volume 54 Pages 235-242
    Published: 2005
    Released on J-STAGE: May 10, 2006
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    Sequestration of CO2 to geological formations such as aquifers is considered as one of the possible options for the abatement of CO2 emission to the atmosphere. Understandings of microscopic two-phase flows in porous media are very important to assess the safety and long-term fate of sequestered CO2. We had developed a numerical code, which simulates two-phase flow of supercritical CO2 and water in porous media including the effect of interfacial tension, wettability, buoyancy, and viscosity ratio by means of the lattice Boltzmann method. We investigated effect of capillary number on flow patterns of two-phase flow in a microscopic model of porous media which have highly water-wet surfaces. A present study shows that the interfacial tension affects the relative permeability of CO2 to deviate from Darcy law at low capillary numbers. The interfacial tension that dominates over the viscous force results in the establishment of secondary flow in a CO2 bubble.
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  • Chihiro MATSUOKA, Katsunobu NISHIHARA
    2005 Volume 54 Pages 243-247
    Published: 2005
    Released on J-STAGE: May 10, 2006
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    We study temporal evolution of an interface in the Richtmyer-Meshkov instability numerically. The interface is treated as a vortex sheet and the Birkhoff-Rott equation is used in order to describe motion of a vortex sheet. We show that redistribution of grid points to equal arclength and the application of the Fourier series expansion for numerical differentiations and integrations make it possible to perform long-time caluculations. Successive profiles of a vortex sheet and the temporal evolution of the sheet strength are presented, and especially the evolution of the sheet strength of a vortex core, defined as a point at which the absolute values of the curvature and strength of a vortex sheet become maximum, is discussed. It is found that the sheet strength of a vortex core takes a maximal value at a finite time and turns to gradually decreasing when the Atwood number in the system is non-zero.
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  • Masato FUNATSU, Hiroyuki SHIRAI
    2005 Volume 54 Pages 249-254
    Published: 2005
    Released on J-STAGE: May 10, 2006
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    The governing equations for a relaxation region behind strong shock waves were presented based upon a four-temperature flow model and were solved numerically as a one-dimensional analysis of a two-boundary value problem. The transport properties for viscosity, diffusion, and thermal conductivity were taken into account in detail, because flow and thermal conditions just behind shock fronts were expected to vary steeply. The change of vibrational and rotational energies of molecules, and free-electron energy due to dissociation and recombination reaction of diatomic molecules were also included. The rotational and vibrational temperature distributions calculated agreed very well with the experiments of ISAS/JAXA, indicating that the physico-chemical model used in the present analysis was valid.
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  • Akihiko TAKADA
    2005 Volume 54 Pages 255-261
    Published: 2005
    Released on J-STAGE: May 10, 2006
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    We studied complex formation between carboxyl teminated telechelic polymer and organic amines such as aromatic and aliphatic amines and their mechanical properties. It turned out that aliphatic amines can form ionic complexes with the telechelic polymer. On the other hand, aromatic amines and pyridines did not form ionic complex with the polymer. Remarkable increase in viscosity was observed for the complex between the polymer and an aliphatic amine with two amino groups. The complex compound could flow and behave a viscoelastic network, even although all carboxyl groups of the polymer formed ionic complexes with equilibrium amount of amino groups of a diamino compound to form highly entangled network of long polymer chains and ring chains formed by association of original chains. The activation energy of flow process of the ionic complex was larger than that of the original telechelic polymer, which indicates that they have different flow mechanism. The flow property of the ionic complex should come from recombination process of ionic associates between carboxyl and amino groups.
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  • Hiroshi ITO, Yusuke YAGISAWA, Takushi SAITO, Toshiyuki YASUHARA, Takes ...
    2005 Volume 54 Pages 263-268
    Published: 2005
    Released on J-STAGE: May 10, 2006
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    Thin-wall injection molding of polypropylene (PP) was performed to clarify the structure and mechanical properties of micro-scale molded products. Effects of mold thickness and process conditions on processability in micro injection molding were evaluated. Furthermore, the structure and mechanical properties of molded products were analyzed using wide angle X-ray diffraction, birefringence, DSC measurements, and tensile testing. The molecular orientation in the vicinity of the gate was higher than that at any other positions. Birefringence increased with decreasing mold temperature, whereas crystallinity decreased with decreasing mold temperature. Results of cross-sectional observation also revealed a skin-core structure inside the molded products; spherulite structure at core region was not observed at thin cavity thickness at low mold temperature. The thickness ratio between the thickness of skin-shear layers and total cavity thickness increased at thinner cavity thickness. Elongation at break of the products with cavity thickness of 0.3 mm became higher with decreasing mold temperature.
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  • Tetsu MITSUMATA, Akiyasu NAGATA, Takashi TANIGUCHI, Jun-ichi TAKIMOTO
    2005 Volume 54 Pages 269-274
    Published: 2005
    Released on J-STAGE: May 10, 2006
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    Effects of magnetization on the complex modulus of magnetic gels have been investigated. The magnetic gel was made of natural polymers of κ-carrageenan and ferromagnetic particles of barium ferrite BaFe12O19. The volume fraction of the ferrite was varied up to 38 vol.%. Complex moduli of the magnetic gel were measured by dynamic viscoelastic measurements with a compressional strain. Storage modulus of the magnetic gel as obtained increased with increasing the volume fraction of ferrite. The magnetic gel was magnetized by applying the magnetic field of 1T. It was firstly observed that the storage modulus after being magnetized decreased compared to the modulus before one. The change in the modulus increased with increasing the ferrite volume fraction and it exceeded beyond 75% of the modulus before being magnetized. It was also found that the change in the modulus was nearly independent of a magnetization direction.
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  • Tetsu MITSUMATA, Tomohiro HACHIYA, Jun-ichi TAKIMOTO
    2005 Volume 54 Pages 275-280
    Published: 2005
    Released on J-STAGE: May 10, 2006
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    We have investigated the rheological properties of poly(vinyl alcohol) gels containing aluminum hydroxide particles with the mean diameter of ~1.4 μm. To find out the filler effect of the particle, the dynamic modulus of composite gels with the particle volume fraction φf<0.23 was measured by dynamic viscoelastic measurements with a compressional strain. The storage modulus of composite gels below φf<0.05 could be explained by Einstein's equation, however, an anomalous increase was observed above the particle volume fraction. It was also found that the storage modulus of composite gels with various cross-linking densities could be scaled by the particle volume fraction. Scanning electron microphotographs revealed that the composite gel had a network structure made of aluminum hydroxide with few microns. The network made of aluminum hydroxide would contribute the large increase in the storage modulus.
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  • Yuki TANIGUCHI, Michio YAMADA, Keiichi ISHIOKA
    2005 Volume 54 Pages 281-288
    Published: 2005
    Released on J-STAGE: May 10, 2006
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    Spontaneous formation of an eastward circumpolar jet is found in the course of time development in two-dimensional incompressible Navier-Stokes fluid on a rotating hemisphere with non-slip boundary at the equator, robustly from randomly chosen initial velocity fields. The formation of the eastward jet is in contrast with the robust formation of the westward jets in the full-sphere case.
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  • Yukiko YAMADA, Takeaki SAMPE, Yoshiyuki O. TAKAHASHI, Mayumi K. YOSHIO ...
    2005 Volume 54 Pages 289-297
    Published: 2005
    Released on J-STAGE: May 10, 2006
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    An aqua planet experiment is performed to investigate dependence of the model representation of the equatorial precipitation activities on horizontal and vertical resolution. The numerical model utilized is AFES, an AGCM optimized for the Earth Simulator. With a resolution of horizontal truncation at T39 and 48 vertical levels (referred to as the standard run), there appear precipitation disturbances of the scale of several grids, which are advected westward by the background wind. With the increase of the vertical resolution to 96 levels from the standard run, precipitation tends to have weak intensity but be widely distributed, and the westward propagating grid-scale disturbances are rarely observed. With the increase of the horizontal resolution to T159 from the standard run, a hierarchical structure appears. A large-scale eastward moving precipitation structure is superimposed on a small-scale westward moving structure.
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  • Norihiko SUGIMOTO, Keiichi ISHIOKA, Shigeo YODEN
    2005 Volume 54 Pages 299-304
    Published: 2005
    Released on J-STAGE: May 10, 2006
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    Continuous gravity wave radiation from unsteady rotational flow is investigated numerically in f-plane shallow water system for a wide range of Rossby number, Ro, and Froude number, Fr, using forced dissipative system. For large Ro, where the effect of the earth rotation is negligible, gravity wave flux is proportional to Fr, which is consistent with the aero-acoustic sound radiation theory (the Lighthill theory). However, this power law is not valid for relatively small Ro, where the effect of the earth rotation is important. The mechanism for the breakdown of the power law is also examined using temporal spectral analyses.
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IV. NUMERICAL COMPUTATIONS
  • Kentaro IIJIMA, Manabu NAKADA, Katsuyoshi SAITO, Kazuei ONISHI
    2005 Volume 54 Pages 307-317
    Published: 2005
    Released on J-STAGE: May 10, 2006
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    Real numbers are usually represented in the computer as hexadecimal floating point numbers with finite digits.Accordingly the numerical analysis is often suffered from rounding errors. The rounding errors particularly deteriorate the precision of numerical solution in inverse and ill-posed problems. We attempt to use a multiple-precision arithmetic for reducing the rounding error evil. In this paper we try to show effectiveness of the multiple-precision arithmetic by taking three typical examples; the Cauchy problem of the Laplace equation in two dimensions, the backward heat conduction problem in two dimensions, and the shape identification problem by inverse scattering in three dimensions. It is concluded from a few numerical examples that the multiple-precision arithmetic works well on the resolution of those numerical solutions, as it is combined with an arbitrary grid spectral method for the Cauchy problem and the backward heat conduction problem, and with the eigenfunction expansion method for the inverse scattering problem.
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  • Toshiki TAKEUCHI, Hitoshi IMAI, Hideo SAKAGUCHI
    2005 Volume 54 Pages 319-326
    Published: 2005
    Released on J-STAGE: May 10, 2006
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    In this paper a typical inverse problem called a backward heat conduction problem is simulated directly and globally. The bounding transform on time and a transform of the solution are used for the global simulation. The artificial condition is introduced for the estimation of the growth rate of the solution. Numerical results show that the simulation is performed globally in time. Moreover, they also show that the parameter in the transform of the solution can be used for the investigation of the growth rate of the solution.
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  • Noriyuki KUNOGI
    2005 Volume 54 Pages 327-332
    Published: 2005
    Released on J-STAGE: May 10, 2006
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    We consider the inverse obstacle scattering problem for the Maxwell equation in inhomogeneous media.Although the scattering operator is not unitary for the Maxwell equation, we reduce our problem to an equivalent one for another system that has a unitary scattering operator. Representing the scattering operator for the new system in explicit forms, we obtain results similar to those of the Lax-Phillips theory for the inverse obstacle scattering problem of the Maxwell equation.
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  • Toshinori MIYOSHI
    2005 Volume 54 Pages 333-339
    Published: 2005
    Released on J-STAGE: May 10, 2006
    JOURNAL FREE ACCESS
    We consider an inverse problem of determining an unknown crack by the two-dimensional wave equation from boundary measurements. To this end, we deal with the initial-boundary value problem of the wave equation in a domain with a crack as a direct problem, and consider uniqueness of a solution to our inverse problem. We show unique solvability of the initial-boundary value problem in weighted Sobolev spaces, and show uniqueness in the inverse problem for a straight crack case.
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  • Tomohiro TAKAKI, Tadashi HASEBE, Yoshihiro TOMITA
    2005 Volume 54 Pages 341-347
    Published: 2005
    Released on J-STAGE: May 10, 2006
    JOURNAL FREE ACCESS
    A phase-field model for self-assembled quantum dot formation has been developed in which the surface morphologies are determined to be dependent on the balance between the surface energy and the elastic strain energy caused by the lattice mismatch strain. The facet morphologies, which are often observed in semiconductor materials, have also been modeled using the generalized gradient correction coefficient for a crystal with a high anisotropy of surface energy. The variations of surface morphologies and energies have been examined by performing two-dimensional phase-field simulations for the annealing process of heteroepitaxial film. By taking sixteen-fold anisotropy into consideration, the multifaceted islands, which change shape with film thickness, can be created. The differences in morphological change and energy variations due to the mode number of the surface energy anisotropy have also been evaluated.
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  • Kazumi OMATA, Kenji YAMAMOTO
    2005 Volume 54 Pages 349-355
    Published: 2005
    Released on J-STAGE: May 10, 2006
    JOURNAL FREE ACCESS
    The microscopic-to-mesoscopic structure of the Lennard-Jones supercritical fluids is studied by carrying out Monte Carlo simulations and calculating the static structure factors. Based on the results, we investigate the density fluctuations and provide qualitative descriptions of the structure which depends on how far the thermodynamic condition is from the critical point.
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  • Dai OKANO, Masatoshi TERAZONO, Kaname AMANO, Hidenori OGATA
    2005 Volume 54 Pages 357-363
    Published: 2005
    Released on J-STAGE: May 10, 2006
    JOURNAL FREE ACCESS
    Usually, on computation of conformal mappings, different methods are used to obtain the mapping functions of two directions between a problem domain and a canonical domain.Amano proposed a method based on the numerical conformal mappings by the charge simulation method, and it offers the both mapping functions of simply connected problem domains and the canonical domains like the unit disk.However, his method cannot be used to obtain the mapping function on the canonical slit domains, which are important for the potential flow analysis of multiply connected domains.Here, we provide a solution to this difficulty, and propose a new method which improves the method of numerical conformal mappings by the charge simulation method, and expands the bi-directional applicability to the problem of multiply connected domains.
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  • Kouji MURAMATSU, Yoshitane SHINOHARA
    2005 Volume 54 Pages 365-371
    Published: 2005
    Released on J-STAGE: May 10, 2006
    JOURNAL FREE ACCESS
    The purpose of the paper is to present a global method of calculating the implied volatility via European put and to establish a verification theorem which verifies the existence and uniqueness of exact implied volatility and assures the number of accurate digits of numerical results. Our numerical analysis of implied volatility is efficient in both European call and put.
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