• JSTS:Journal of Semiconductor Technology and Science
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• 제17권2호
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• pp.288-293
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• 2017

Transient simulation capability with an implicit time derivation method is a missing feature in deterministic Boltzmann equation solvers. The H-transformation, which is critical for the stable simulation of nanoscale devices, introduces difficulties for the transient simulation. In this work, the transient simulation of graphene sheets is reported. It is shown that simulation of homogeneous systems can be done without abandoning the H-transformation, as much as a specially designed discretization method is employed. The AC mobility and step response of the graphene sheet on the $SiO_2$ substrate are simulated.

• International Journal of Aeronautical and Space Sciences
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• 제18권3호
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• pp.574-578
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• 2017

In order to achieve iterative design in early R&D period, a Distributed and Real-time Integrated Simulation System for avionics based on a Model-Based Systems Engineering (MBSE) method is proposed. The proposed simulation system includes driver, simulation model, monitor, flight visual model and aircraft external model.The effect of this simulation system in iterative design and system verification is testified by several use cases. The result shows that the simulation system, which can play an important role in iterative design and system verification, can reduce project costs and shorten the entire R&D period.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2006년도 PARALLEL CFD 2006
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• pp.107-112
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• 2006

A wind tunnel simulation requires high-performance computing power like supercomputers and deep knowledge of this subject. Those requirements make win tunnel simulation difficult. Grid technology will make these difficulties simpler by providing easy to use grid web portal. By using grid web portal, scientist can execute simulation and access to high-performance computing power without any serious difficulties. In this paper will present a grid web portal for a wind tunnel simulation that is used in Aerospace area.

• Nuclear Engineering and Technology
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• 제51권5호
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• pp.1436-1443
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• 2019

A fast gamma-ray dose rate assessment method for complex geometries based on stylized model reconstruction and point-kernel method is proposed in this paper. The complex three-dimensional (3D) geometries are imported as a 3DS format file from 3dsMax software with material and radiometric attributes. Based on 3D stylized model reconstruction of solid mesh, the 3D-geometrical solids are automatically converted into stylized models. In point-kernel calculation, the stylized source models are divided into point kernels and the mean free paths (mfp) are calculated by the intersections between shield stylized models and tracing ray. Compared with MCNP, the proposed method can implement complex 3D geometries visually, and the dose rate calculation is accurate and fast.

• International Journal of Naval Architecture and Ocean Engineering
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• 제13권1호
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• pp.877-888
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• 2021

The water entry behaviors of projectiles with different cone-headed angles were studied numerically, experimentally and theoretically, mainly focusing on the hydrodynamic impact in the initial stage. Based on MMALE algorithm, it was proposed a formula of impact deceleration, which relied on the initial entry velocity and cone-headed angle. Meanwhile, in order to verify the validity of the simulation model, experiments using accelerometer and high-speed camera were carried out, and their results were in a good agreement with simulation results. Also, theoretical calculation results of cavity diameter were compared with experiments and simulation results. It was observed that the simulation method had a good reliability, which would make forecast on impact deceleration in an engineering project.

• Journal of Internet Computing and Services
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• 제21권5호
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• pp.97-107
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• 2020

This paper introduces an online experiment environment based on a computational science platform that can be used for various purposes ranging from basic education to quantum chemistry and professional quantum chemistry research. The simulation environment was constructed using a simulation workbench and simulation workflow, which are execution environment services of Science App provided by the computational science platform. We developed an environment in which learners can learn independently without an instructor by selecting experiment topics that can be used in various areas of chemistry, and offering the learning materials of the topics in a form of e-learning content that includes theory and simulation exercises. To verify the superiority of the proposed system, it was compared with WebMO, a state-of-the-art web-based quantum chemistry simulation service.

• Bulletin of the Korean Space Science Society
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• 한국우주과학회 2009년도 한국우주과학회보 제18권2호
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• pp.26.2-26.2
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• 2009

The Solar and Space Weather Research Group (SOS) in Korea Astronomy and Space Science Institute (KASI) is constructing the Space Weather Prediction Center since 2007. As a part of the project, we are developing automatic real-time system of the global 3-D magnetohydrodynamics (MHD) simulation. The MHD simulation model of earth's magnetosphere is designed as modified leap-frog scheme by T. Ogino, and it was parallelized by using message passing interface (MPI). Our work focuses on the automatic processing about simulation of 3-D MHD model and visualization of the simulation results. We used PC cluster to compute, and virtual reality modeling language (VRML) file format to visualize the MHD simulation. The system can show the variation of earth's magnetosphere by the solar wind in quasi real time. For data assimilation we used four parameters from ACE data; density, pressure, velocity of solar wind, and z component of interplanetary magnetic field (IMF). In this paper, we performed some initial tests and made a animation. The automatic real-time system will be valuable tool to understand the configuration of the solar-terrestrial environment for space weather research.

• Wind and Structures
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• 제39권2호
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• pp.125-140
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• 2024

The simulation of non-stationary wind velocity is particularly crucial for the wind resistant design of slender structures. Recently, some data-driven simulation methods have received much attention due to their straightforwardness. However, as the number of simulation points increases, it will face efficiency issues. Under such a background, in this paper, a time-varying coherence matrix decomposition method based on Diagonal Proper Orthogonal Decomposition (DPOD) interpolation is proposed for the data-driven simulation of non-stationary wind velocity based on S-transform (ST). Its core idea is to use coherence matrix decomposition instead of the decomposition of the measured time-frequency power spectrum matrix based on ST. The decomposition result of the time-varying coherence matrix is relatively smooth, so DPOD interpolation can be introduced to accelerate its decomposition, and the DPOD interpolation technology is extended to the simulation based on measured wind velocity. The numerical experiment has shown that the reconstruction results of coherence matrix interpolation are consistent with the target values, and the interpolation calculation efficiency is higher than that of the coherence matrix time-frequency interpolation method and the coherence matrix POD interpolation method. Compared to existing data-driven simulation methods, it addresses the efficiency issue in simulations where the number of Cholesky decompositions increases with the increase of simulation points, significantly enhancing the efficiency of simulating multivariate non-stationary wind velocities. Meanwhile, the simulation data preserved the time-frequency characteristics of the measured wind velocity well.

• JSTS:Journal of Semiconductor Technology and Science
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• 제14권4호
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• pp.463-470
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• 2014

A Verilog model is proposed for transmission lines to perform the all-Verilog simulation of high-speed chip-to-chip interface system, which reduces the simulation time by around 770 times compared to the mixed-mode simulation. The single-pulse response of transmission line in SPICE model is converted into that in Verilog model by converting the full-scale analog signal into an 11-bit digital code after uniform time sampling. The receiver waveform of transmission line is calculated by adding or subtracting the single-pulse response in Verilog model depending on the transmitting digital code values with appropriate time delay. The application of this work to a USB 2.0 high-speed PHY interface reduces the simulation time to less than three minutes with error less than 5% while the mixed-mode simulation takes more than two days for the same circuit.

• Journal of Mechanical Science and Technology
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• 제15권12호
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• pp.1750-1756
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• 2001

Three-dimensional and unsteady flow analysis is a practical target of high performance computation. As recently advances of computers, a numerical prediction by the large eddy simulation (LES) are introduced and evaluated for various engineering problems. Its advanced methods for the complex turbulent flows are discussed by several examples applied for aerodynamic designs, analysis of fluid flow mechanisms and their interaction to complex phenomena. These results of time-dependent and three-dimensional phenomena are visualized by interactive graphics and animations.