Vol.34 (2019)

Bulletin of Research Center for Computing and Multimedia Studies
Vol.34, 2019 ISSN 1882-7694

Densities in Liquid-Vapor Equilibrium by Molecular Dynamics Simulation
Yoduke Kataoka
Received: March 5, 2019    PDF   Abstract
The equilibrium densities of liquid and gas of argon were calculated by molecular dynamics simulation. The method was based on Maxwell construction. The calculated phase diagram was compared with the results by Lennard-Jones equation of state satisfactory.
Gas-liquid phase boundary of nitrogen by molecular dynamics simulation
Yusuke Goto, Yosuke Kataoka, Hironori Ogata
Received: March 5, 2019    PDF   Abstract
Molecular dynamics (MD) simulation was applied to find the gas-liquid phase boundary of nitrogen. A value close to the critical volume was estimated as the third intersection point in the Maxwell construction. Vapor pressure was obtained by MD simulation at this point. Calculated results were consistent with the experiment.
Liquefaction process and spinodal line by molecular dynamics simulation
Yoduke Kataoka
Received: March 5, 2019    PDF   Abstract
The spinodal line of Lennard-Jones system was calculated by molecular dynamics simulation as a function of temperature. The relaxation processes were compared in the metastable and unstable states. The structure in the short term was nonlocal and different from the relaxed liquid structure.
Stability of FCC Structure in the Charged Colloidal Dispersion by Molecular Dynamics Simulations -2
Yoduke Kataoka
Received: March 5, 2019    PDF   Abstract
The stability of the FCC structure was compared with that of the liquid structure in the charged colloidal dispersion by molecular dynamics simulations. The effective potential of Sogami-Ise theory was assumed. In the case of the low volume fraction (1%), the FCC structure was more stable than the liquid structure for a typical charge distribution at room temperature. The melting point was estimated as about 676K.
Simulation for Compression Test of Sand by Distinct Elment Method
Yuya Maru, Nagayuki Yoshida
Received: March 12, 2019    PDF   Abstract
The purpose of this study is to simulate the direct shear test using the Distinct Element Method (DEM), and to investigate the characteristics of DEM. We performed the shear tests based on two conversion methods for the tangential force in contact, which is evaluated by the tangential distance between two particles or the tangential spring constant. The angle of shear resistance is obtained by use of these two methods, and numerical results are compared and examined.
A study on Identification Method by Using Real Observation of Buildings
Kazuhiro Suezaki, Nagayuki Yoshida
Received: March 13, 2019    PDF   Abstract
The aim of this paper is to examine the efficacy of identification method by using real observation of the building. We have analyzed the single degree of freedom model for the simulation testing of identification. This time we try to use the real building as the identification target. From the observed data, the natural period and the damping factor are estimated by MOESP method and FFT analysis as the dynamic characteristics of the building.
Influence of Cut-off Distance of Interaction on Molecular Dynamics Simulation to Obtain Gas-Liquid Phase Equilibrium
Yuri Yamada, Azumi Iijima, Shunya Yamazaki, Reki Tsuda
Received: March 13, 2019    PDF   Abstract
In molecular simulation of gas-liquid or solid-gas equilibrium, if cut-off distance of the interaction is unduly short, an appropriate phase boundary can not be estimated. In this study, gas-liquid equilibrium simulations of Lennard-Jones 12-6 and 10-5 system were performed using constant-pressure molecular dynamics calculation based on direct-coexistence method, and influence of cut-off distance on the equilibrium temperature is investigated. If the cut-off distance is too short, the gas-liquid equilibrium temperature estimated from the simulations will be higher than the appropriate value. It was also found that the cut-off distance required to estimate an appropriate gas-liquid equilibrium temperature can not be determined uniquely because it varies depending on the setting of the potential function and pressure.
Dihedral-angle dependency of the through-resonance effect operating on a,a- dimethylbenzyl cations
Kazuhide Nakata, Mizue Fujio
Received: March 15, 2019    PDF   Abstract
Substituent effects on gas-phase stabilities of a,a-dimethylbenzyl cations having fixed dihedral angle f between the benzene ring and the side chain planes that was varied from 0˚ to 90˚ by steps of 10˚ were determined by computational chemistry together with that of fully optimized cations, and were analyzed by means of Yukawa-Tsuno equation. Comparison of obtained r+ values with geometrical indices such as bond distances and angles gave support to the operation of the through-resonance effect even in the 90˚-fixed cation. To examine the inducement mechanism of the through-resonance effect in this cationic framework, natural bond orbital (NBO) analyses were performed. NBO interactions that correspond to electron donation from the p orbital of the benzene p-electron system to the p* orbital of the side chain operate at the maximum efficiency in the planer structure and those that correspond to electron donation from the p orbital of the benzene p-electron system to the s* orbital of the side chain operate at the maximum efficiency in the orthogonal structure. Sum of these orbital interactions were found to determine the through-resonence effect of this cationic system at any f.
Quantum Double-slit Interference using SSPH
Fumiaki Hirono, Misako Iwasawa, Satoru S. Kano, Yasunari Zempo
Received: March 15, 2019    PDF   Abstract
Symmetric smoothed particle hydrodynamics (SSPH) method is applied to the electric structure calculation in real space, which is described by the time dependent Schrödinger equation. In the process of time evolution, we employed the Bohmian expression. Since the propagation is represented by trajectories, we can directly recognize the propagation as the particle movement. We have been studying this technique to be applied to the analysis of interference and diffraction of the double-slit. We compared the solution by SSPH with that of analytical one. Both results have a good agreement, and SSPH has enough accuracy and stability to use practical applications. We report our present status of the development SSPH for the electronic structure calculation.
Quantification of Relationship between Environmental Performance of Buildings and Distance from Nearest Train Station
Rei Nara, Ayuta Yamaguchi, Shun Kawakubo, Kiyotaka Deguchi
Received: March 15, 2019    PDF   Abstract
Assessment tools for buildings are developed in many countries in these days. A tool called Comprehensive Assessment System for Built Environment Efficiency (CASBEE) is one of them and it is used for assessing building environmental performance. Initially, CASBEE assessment results data is collected from 24 Japanese local governments in this study. Secondly, relationship among CASBEE assessment results, distance from stations and population density are clarified using Geographic Information System (GIS). Network analysis was conducted to identify area that can be reached within 5, 10- and 15-minutes’ walk from the nearest station to consider more actual conditions of residents. The study has identified that environmental performance of buildings are affected by various regional characteristics.
Shock Pattern in Two-dimensional Flow Field of Transonic Axial Turbine Cascade
Hoshio Tsujita, Masanao Kaneko
Received: March 16, 2019    PDF   Abstract
The improvement of aerodynamic performance of turbine components constituting the gas turbine engine is required to reduce environmental load. Then, it is very important to investigate the aerodynamic performance of an axial turbine at practical transonic compressible flow conditions, where the shock/boundary layer interaction significantly influences on the loss generation. In this study, two-dimensional steady compressible flows in an axial turbine cascade were analyzed numerically with the parameter of exit Mach number by using a commercial CFD code. The present computed results clarified the variations of shock pattern with the increase of exit Mach number and the associated profile loss generation.
Creep Characteristics of Ni/ZrO2 Functionally Graded Materials Investigated by Coupled Thermal-Structural Analysis
Kyoko Kameya, Syota Ando, Hideaki Tsukamoto
Received: March 29, 2019    PDF   Abstract
Functionally graded materials (FGMs) are a new kind of composite materials which have been expected to effectively relax thermal stress. In order to fully utilize the advantages of FGMs, it is important to better understand the details of heat conduction, thermal stress and creep strain proceeding in FGMs. In this study, a numerical analysis of creep characteristics of FGMs is presented. Finite element analysis which deals with thermal shock testing of the metal-ceramic FGMs is addressed. Furthermore, heat resistance, thermal stress and creep behaviors of FGMs are discussed by comparing FGMs with conventional materials. As a result, it is revealed that FGMs are effective to suppress thermal deformation and avoid thermal stress fracture.
Cellular Automata Traffic Flow Analysis for Walking People at the Passage in Public Space
Kohei Misue, Kohei Kobayashi, Keichirou Kawamoto, Tomoyuki Kido, Motohisa Hirano
Received: March 31, 2019    PDF   Abstract
This study constructs the cellular automata (CA) model for walking people traffic flow observed in public passages to elucidate how local interactions between neighboring walking people affect the global behavior of pedestrian group. By using the CA model, we have discussed to clarify how the daily walking rules in station yards and annoying acts such as smartphone texting while walking influence the global behavior of pedestrian group, thus discussing how to reduce traffic congestion that occurs at cross roads and stairs, to ensure physical safety, and to alleviate mental stress.
Performance Evaluation for Bubble Eliminator with CFD
Sayako Sakama, Ryo Takamizawa, Yutaka Tanaka
Received: April 19, 2019    PDF   Abstract
Air bubbles in working fluids greatly influence the performance of hydraulic systems. The bubble in working hydraulic fluids may cause major problems because of bulk modulus change, cavitation and aeration inception, degradation of lubrication, noise generation, oil temperature rise and deterioration of oil quality. An active “bubble eliminator” that uses swirl flow to remove air bubbles can be used to mitigate these problems. The purpose of this paper is to evaluate an adequate computational model and mesh with CFD analysis according to the numerical simulation of the bubble eliminator. It has been numerically verified that the performance of the bubble removal for the bubble eliminator depends on particle sizes of bubbles by Euler multiphase model. It is also confirmed that the numerical results have good agreement with experimental results.
Quantitative Text Analysis of PBL Lesson Free-form Questionnaires By Using KH Coder (Educational Approach for Improving PBL Lesson done at the Department Mechanical Engineering)
Yasunobu Uchio, Kyoko Kameya, Takao Mutobe, Yuki Kondo, Ichiro Yoshida, Tatsuhito Aihara, Motohisa Hirano
Received: March 19, 2019    PDF   Abstract
This article discusses the quantitative text analysis, i.e., text mining of the PBL lesson free-form questionnaires by using KH Coder in order to examine the educational effects of the lesson done at Department of Mechanical Engineering. To do this end, we have conducted a statistical analysis of the texts written in the student questionnaires for PBL lessons that were conducted in two semesters in 2017 and 2018. It has been discussed whether this lesson project has been effective for attaining the class goals to acquire the fundamental academic ability that can tackle the project solution.