Papers by Keyword: Computer Simulation

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Authors: Chao Xu, Dong Chen
Abstract: Ab initio electronic structures for β-Ge3N4 are investigated using ultrasoft pseudo-potential method within the generalized gradient approximation functional. The lattice parameters are predicted theoretically, and are compared with available experimental data and the other theoretical results. The elastic constants calculations reveal that the phenacite structure is a stable phase in the pressure range of 020GPa. The high bulk modulus (B=180.2GPa) indicates that β-Ge3N4 is a relatively hard material. β-Ge3N4 has a direct band gap of 2.94eV, indicating its promising applications as a semiconductor in electronics and optical fibers. On the other hand, the density of states analysis is also included in this paper.* Corresponding author: CHEN Dong
Authors: Chao Xu, Dong Chen
Abstract: The structural and elastic properties of the cubic spinel Ge3N4 semiconductor have been investigated using the ab initio scheme within the generalized gradient approximation in the framework of density functional theory. Quantities such as lattice constants and elastic constants of interest are calculated. A good agreement is found between our results and the other data. Through the lattice dynamics, in which the finite displacement method is used, we have obtained successfully the thermal properties such as the phonon curve, free energy, heat capacity and Debye temperature in the whole temperature range from 0 to 1000K. It is the authors ambition that these results will inspire further experimental study on the Ge-based semiconductors. * Corresponding author: CHEN Dong
Authors: Sergey A. Aksenov, Irina V. Logashina, Eugene N. Chumachenko, Milan Kotas
Abstract: The subject of the paper is a study of the material behaviour during hot rolling. The process considered is a rolling of round bar in roughing mill group which consist of four passes. The computer simulation of the process shows that the local plastic deformations which appear in the material are extremely large. This fact can leads to extension of surface defects. The dependences of maximum local plastic deformation on geometrical parameters of the calibres have been obtained and analysed during this study. The investigations performed, led to the development of new roll pass design which almost halved the maximum value of local plastic deformation in the material during the rolling. Since full 3D FEM models needs significant amount of computer memory and CPU time, it was not suitable for the performed study which involves a bulk of simulations with different initial conditions. Therefore, the quick algorithms for simulation of rolling processes which based on so-called “2.5D” method have been used. This method, due to number of simplifications, is significant faster then conventional 3D FEM, and at the same time it allows to reach good accuracy of the model. The developed computer software SPLEN(Rolling) which implements “2.5D” FEM simulations was applied for computations and analysis of the results. This software is able to predict the shape evolution of rolled material, as well as distributions of strain, strain rate and temperature within the volume of deformation zone. It has been shown that computer simulation based on “2.5D” FEM with SPLEN(Rolling) software can by efficiently used for optimization of technological procedures in rolling industry.
Authors: Z.S. Nikolić, M. Yoshimura, S. Araki
Abstract: Two-dimensional numerical model is adopted to analyze the heat transfer process during solidification of the sample melted in an Arc-image furnace. Numerical solution of this complex problem enabled us to calculate the temperature distribution in both sample and substrate, including the phase change phenomena. Also, the effects of process parameters on the solidification of the sample melted on substrate that is cooled by water can be investigated numerically. The parameters include sample size, contact area size between the sample and the substrate, and degree of undercooling associated with rapid phase change and moving interface. The results obtained reveal that these parameters have strong effect on temperature distribution during solidification.
Authors: Yoshiki Komiya, Shoichi Hirosawa, Tatsuo Sato
Abstract: The formation of nanoclusters in the early aging stage is not fully clarified due to their extremely small sizes. To clarify the atomic-scale clustering of solute atoms, a three-dimensional atom probe (3DAP) analysis and a Monte Carlo computer simulation have been conducted together for Al-Zn alloys. The nanoclusters in the alloy aged at room temperature were successfully detected in the obtained 3DAP maps. From these maps the growth behavior of nanoclusters during aging was experimentally examined. In the Monte Carlo simulation, on the other hand, many-body nearest neighbor interactions between atoms and between atoms and a vacancy were taken into account. The Zn concentration of the clusters calculated in the 4-body interaction model best agreed with that obtained experimentally, suggesting the importance of many-body interactions. Therefore, it was confirmed that the combined analysis of 3DAP and the well-constructed Monte Carlo simulation is useful to make clear the nanocluster formation in alloys.
Authors: Cherng Shing Lin, Min Gen Wu, Sheng Min Tsai
Abstract: A large number of factories have been sequentially established in Taiwan following the economic take-off several decades ago. However, this growth in number has led to the prevalence of fire hazards. Factory fires typically cause substantial casualties and property losses, and have therefore become a focal point for research. In the present study, the researchers employed the Fire Dynamics Simulator (FDS) software developed by the National Institute of Standards and Technology (NIST) to simulate and evaluate a factory fire scene in Taiwan. The fire continued for approximately 74 h, rendering this outbreak the single longest building fire and rescue in Taiwan. By analyzing relevant data, the researchers established a numerical model of the fire scene to simulate, evaluate, and analyze the influences that temperature, smoke conditions, and smoke layer height parameters had on the fire scene. The findings enabled the researchers to better understand the damage conditions that occur during fire outbreaks. The results of this case study can serve as a reference for designing and improving future fire prevention and safety plans.
Authors: Yiming Li
Abstract: Quantum correction model features the correction of the inversion layer charge on different classical transport models in semiconductor device simulation. This approach has successfully been of great interest in the recent years. Considering a metal-oxide-semiconductor (MOS) structure in this paper, the Hänsch, the modified local density approximation (MLDA), the density-gradient (DG), the effective potential (EP), and our models are investigated computationally and compared systematically with the result of the Schrödinger-Poisson (SP) model. In terms of the accuracy for (1) the position of the charge concentration peak, (2) the maximum of the charge concentration, (3)the total inversion charge sheet density, and (4) the average inversion charge depth, these well-established models are examined simultaneously. The DG model requires the solution of a boundary value problem, the EP model overestimates the position of the charge concentration peak and the maximum of the charge concentration, our explicit model demonstrates good accuracy among models.
Authors: Yu.V. Truschin, R.A. Yankov, V.S. Kharlamov, D.V. Kulikov, D.N. Tsigankov, U. Kreissig, M. Voelskow, Jörg Pezoldt, Wolfgang Skorupa
Authors: A.C. Buriti, A.G.P. Silva, Uilame Umbelino Gomes
Authors: Hyung Soo Ahn, Il Hyung Park, Denis DiAngelo
Abstract: The biomechanical changes brought on by spine fusion and the artificial disc designs to restore physiologic motion were studied by using a cervical spine computer model. Fusion increased the motion compensation at the adjacent segment during flexion and extension. The global rotational stiffness and segmental disc forces were also increased after fusion. Among the three prosthetic disc designs, the PDD-III (5-DOF spherical joint in plane parallel with the C5-C6 disc level) maintained the normal motion and minimized load build up of adjacent segment.
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