Faculty of Engineering, Okayama University Acta Medica Okayama 0475-0071 25 2 1991 Mesh Generation for Convex 3-Dimensional Domain 123 133 EN Takeo Taniguchi Chikashi Ohta /10.18926/15517 The aim of this investigation is the proposal of 3D mesh generation method based on the Delaunay triangulation. The method is valid for the finite element modelling of any convex 3D domain into tetrahedra with optimum geometrical configuration. This paper includes the mathematical background of the mesh generation method, its detail, proposal of some efficient tools for faster and more rigorous computations, and some examples of the mesh generation. No potential conflict of interest relevant to this article was reported.

Faculty of Engineering, Okayama University Acta Medica Okayama 0475-0071 25 2 1991 Nested Dissection Method on Transputer 115 122 EN Takeo Taniguchi 10.18926/15516 Nested dissection method is an elimination method for a set of linear algebraic equations with minimum fillins. Physically it divides a domain into four subdomains, and each subdomain is again divided into four. This procedure is repeated till all nodes are included in some subdomains. Using this characteristic, the authors examine the efficiency of the method on the transputer. No potential conflict of interest relevant to this article was reported.

Faculty of Engineering, Okayama University Acta Medica Okayama 0475-0071 25 2 1991 Analysis of Superconducting Microstructures: Critical Temperature of Two-Dimensional Structures 95 113 EN Hiroo Totsuji /10.18926/15515 Critical temperatures of two-dimensional microstructures with superconducting proximity effect in the dirty limit are evaluated for various geometrical constructions. As a numerical method, the finite element method is applied. Guidelines in estimating critical temperatures are given for the case where the decay of superconducting order parameter is either sufficiently slow or fast in comparison with the scale length of the structure. No potential conflict of interest relevant to this article was reported.

Faculty of Engineering, Okayama University Acta Medica Okayama 0475-0071 25 2 1991 Analysis of Superconducting Microstructures: Formulation 81 93 EN Hiroo Totsuji 10.18926/15513 Numerical methods for the analysis of the proximity effect in superconducting microstructures in the dirty limit are formulated on the basis of the finite element method. One- and two-dimensional cases are considered and third order Hermite shape functions are used. The results are also applicable to investigations of electronic states in semiconductor superlattice structures. No potential conflict of interest relevant to this article was reported.

Faculty of Engineering, Okayama University Acta Medica Okayama 0475-0071 25 2 1991 A Basic Study on Nonlinear Sound Propagation by Finite Element Simulation 69 80 EN Yukio Kagawa /10.18926/15512 A finite element approach to the calculation of nonlinear sound propagation is proposed. Under the assumption of a weak nonlinearity, a linearized one-dimensional equation is considered. The equation is discretized in space, and is then solved for time by using Newmark-β integration scheme, in which a numerical damping is devised. Some numerical demonstrations are made for the nonlinear sound propagation of a single-shot pulse in air. It is shown that the shock wave propagation is stably and accurately simulated by the introduction of the numerical damping. No potential conflict of interest relevant to this article was reported.

Faculty of Engineering, Okayama University Acta Medica Okayama 0475-0071 25 2 1991 A Procedure for Settling Multi-Criteria Problem by a Small Group of Decision Makers 55 67 EN Yoshimasa Kameyama Hayatoshi Sayama Kazuhiko Suzuki /10.18926/15511 AHP can handle decision-making problems involving several criteria when some of these are difficult or impossible to compare other than numerically. When a small group of decision makers settle the multi-criteria problem by AHP, the members of group could not often reach an agreement with hierarchic structure involving objectives, criteria, sub-criteria and alternatives because they have different positions, interests, and opinions. Further, the members have different importances for criteria and sub-criteria, and have dissimilar preferences for alternatives. In this article, we reveal the troubleness of AHP in case of being used by a small group of decision makers. Moreover, we proposed a procedure of AHP which the members of group could easily agree with the structure of problem and the weights of criteria etc. No potential conflict of interest relevant to this article was reported.

Faculty of Engineering, Okayama University Acta Medica Okayama 0475-0071 25 2 1991 Prediction of Transient and Steady Turbulent Free Subsonic Air Jets 39 54 EN Eiji Tomita Yoshisuke Hamamoto 10.18926/15510 Velocity distributions and related parameters of　transient and steady, turbulent air jets issuing under atmospheric conditions at Mach 0.14, 0.33 and 0.5 have been predicted using Navier-Stokes(N-S) equations for compressible flow and incompressible flow independently with the k-ε model. The closeness and consistence of the results predicted by the N-S equations for compressible and incompressible flows as well as with relevant measurement or similar prediction show that the incompressible flow assumption for at least some subsonic gas jets issuing at velocities higher than Mach 0.3, the general limit for incompressible fluid flow, can be reasonably accurate particularly in the main fully developed flow region. This suggests that the divergence term in source terms of the momentum, turbulence energy and its dissipation rate equations have negligible effects for some seemingly compressible high speed, subsonic free gas jets. The computation time is reduced by at least 18 % when incompressible flow assumption is used. No potential conflict of interest relevant to this article was reported.

Faculty of Engineering, Okayama University Acta Medica Okayama 0475-0071 25 2 1991 Numerical Calculation of a Transient Methane Gas Jet Discharging into Quiescent Atmosphere at Mach One 25 38 EN Eiji Tomiｔa Yoshisuke Hamamoto /10.18926/15508 A suddenly started cold methane gas jet issuing from a 1 mm diameter orifice into still air at Mach one has been predicted using the two-equation, high Reynolds number version of k-ε turbulence model and SIMPLE algorithm which employs so called primitive variables and a hybrid scheme for treating combined diffusion and convection. Global trends of predicted radial distributions of velocity, temperature, methane concentration in the steady rear part of the transient jet and axial jet tip penetration compare reasonably well with universal profiles representing measurement for the steady jet particularly in the fully developed turbulent core and semi-empirical relation for the transient jet respectively. The prediction scheme has shown reasonably good accuracy especially in prediction of main flow parameters of a transient, high speed compressible gas jet issuing into a dissimilar surrounding gas(binary gas mixture jet). No potential conflict of interest relevant to this article was reported.

Faculty of Engineering, Okayama University Acta Medica Okayama 0475-0071 25 2 1991 Fatigue Strength of Age-Hardened Al-Zn Alloys under Repeated Tensile Loading 17 23 EN Akira Sakakibara Teruto Kanadani Toshiaki Kaneeda Norio Hosokawa /10.18926/15506 Effect of the soft surface layer that was formed on low temperature aging of Al-Zn alloy on fatigue strength was studied under repeated tensile loading. Vickers microhardness test revealed that there existed less hardened region in the vicinity of grain boundary and surface, and that the region extends 50 to 100μm from the surface inward. From the plot of the stress amplitude against the number of cycles to failure, it is concluded that the presence of less hardened surface layer strengthens fatigue resistance of the age hardened Al-Zn alloys containing 8 to 16mass % Zn under the repeated tensile loading. No potential conflict of interest relevant to this article was reported.

Faculty of Engineering, Okayama University Acta Medica Okayama 0475-0071 25 2 1991 X-ray Topographs of Strain Field Induced by Locally Ion-Plated Films on Si Substrates 9 15 EN Masato Mikuni Moritaka Hida Norihide Nishida Akira Sakakibara Masuo Yamada /10.18926/15503 Strains induced in the Si substrates by TiN film were observed with X-ray topography. The image of the sample with TiN film 0.45μm thick was like that of a dislocation loop observed with transmission electron microscope. The images of the samples with TiN films 1.65, and 1.9μm thick were different; blackening spreaded in the <112> and <110> direction from the ring contrast in shape of four-lobed rosette pattern. Spreading extended 1.6 times longer than the radius of the ring contrast along the <112> direction. The strain field extended 0.1μm in depth from the top surface where TiN was plated. From the topographs of bent Si beam, it was found that the blackness was almost proportional to the strain. The strains induced by TiN film locally ion-plated were smaller than those observed previously when TiN was ion-plated on the whole top surface of the substrate. Fine structures were observed in the topographs which could not be explained by the kinematical theory. No potential conflict of interest relevant to this article was reported.

Faculty of Engineering, Okayama University Acta Medica Okayama 0475-0071 25 2 1991 Mechanical Characteristics of Cast Ti Fiber-Reinforced Mg Composite 1 8 EN Hiroyuki Okada Moritaka Hida Akira Sakakibara Yoshito Takemoto 10.18926/15500 Tensile strength and elongation of cast magnesium reinforced with titanium fiber were measured by tensile test. The pull-out test of a titanium rod partially embedded in a magnesium matrix was performed to evaluate interfacial bonding strength between magnesium and titanium. It was found that when the fiber volume fraction was changed from 1% to 14%, the tensile strength was improved with increase of volume fraction, while the improvement of elongation tended to be restrained beyond the volume fraction of 10%. The interfacial strength was revealed to be strong, and this was substantiated by the scanning electron microscopy showing an excellent wettability between the titanium fiber and the magnesium matrix. No potential conflict of interest relevant to this article was reported.