• Earthquakes and Structures
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• 제3권3_4호
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• pp.341-363
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• 2012

The spectral representation method is a quick and versatile tool for the generation of spatially variable, response-spectrum-compatible simulations to be used in the nonlinear seismic response evaluation of extended structures, such as bridges. However, just as recorded data, these simulated accelerations require processing, but, unlike recorded data, the reasons for their processing are purely numerical. Hence, the criteria for the processing of acceleration simulations need to be tied to the effect of processing on the structural response. This paper presents a framework for processing acceleration simulations that is based on seismological approaches for processing recorded data, but establishes the corner frequency of the high-pass filter by minimizing the effect of processing on the response of the structural system, for the response evaluation of which the ground motions were generated. The proposed two-step criterion selects the filter corner frequency by considering both the dynamic and the pseudo-static response of the systems. First, it ensures that the linear/nonlinear dynamic structural response induced by the processed simulations captures the characteristics of the system's dynamic response caused by the unprocessed simulations, the frequency content of which is fully compatible with the target response spectrum. Second, it examines the adequacy of the selected estimate for the filter corner frequency by evaluating the pseudo-static response of the system subjected to spatially variable excitations. It is noted that the first step of this two-fold criterion suffices for the establishment of the corner frequency for the processing of acceleration time series generated at a single ground-surface location to be used in the seismic response evaluation of, e.g. a building structure. Furthermore, the concept also applies for the processing of acceleration time series generated by means of any approach that does not provide physical considerations for the selection of the corner frequency of the high-pass filter.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1987년도 한국자동제어학술회의논문집(한일합동학술편); 한국과학기술대학, 충남; 16-17 Oct. 1987
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• pp.827-831
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• 1987

The analysis of a certian example and simulations given in the previous sections show that the modified FKA is more stable than the standard FKA without loss of the performance of it. The general analysis of modified FKA's numerical stability is the open problem with more simulations in order to prove the stability of it.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2002년도 International Meeting on Information Display
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• pp.1077-1080
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• 2002

Present status of diagnostics and simulations on microplasmas for understandings of the discharge and VUV emission characteristics in a unit cell of plasma display panel is overviewed and their future perspective will be argued towards potential improvement of the characteristics.

• Bulletin of the Korean Chemical Society
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• 제27권2호
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• pp.325-328
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• 2006

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2763-2768
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• 2007

Recently, as the semiconductor production technology develops, there has been growing interest in the cooling system using micro fluid pump. Among the various types of micro fluid pump, the valve-less diffuser/nozzle has been extensively studied in recent years. However, the flat-walled diffuser/nozzle flow has not been clearly looked into due to its non-linear characteristics. In this paper, the flow characteristics of the flat-walled diffuser/nozzle have been analyzed using similitude model and simulations. Similitude models are designed so that the flow pattern is same as that of 1/10 scale flow by using high viscous fluid as working fluid. The results are compared to the simulations. It is shown that the flow characteristics of 2D simulation are different from 3D simulations at high Re region, and the measured pump efficiency is highly dependent on the pressure difference as well as the channel geometry. From these results, the desirable conditions for the efficient pump is discussed.

• Geomechanics and Engineering
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• 제23권3호
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• pp.189-206
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• 2020

The accurate modeling of boundary conditions is important in simulations of the discrete element method (DEM) and can affect the numerical results significantly. In conventional triaxial compression (CTC) tests, the specimens are wrapped by flexible membranes allowing to deform freely. To accurately model the boundary conditions of CTC, new flexible boundary algorithms for 2D and 3D DEM simulations are proposed. The new algorithms are computationally efficient and easy to implement. Moreover, both horizontal and vertical component of confining pressure are considered in the 2D and 3D algorithms, which can ensure that the directions of confining pressure are always perpendicular to the specimen surfaces. Furthermore, the boundaries are continuous and closed in the new algorithms, which can prevent the escape of particles from the specimens. The effectiveness of the proposed algorithms is validated by biaxial and triaxial simulations of granular materials. The results show that the algorithms allow the boundaries to deform non-uniformly on the premise of maintaining high control accuracy of confining pressure. Meanwhile, the influences of different lateral boundary conditions on the numerical results are discussed. It is indicated that the flexible boundary is more appropriate for the models with large strain or significant localization than rigid boundary.

• 한국해양공학회지
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• 제28권4호
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• pp.288-293
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• 2014

The IEC standard for onshore or offshore wind turbines requires additional dummy simulations (at least 5 s) for the transient responses due to initial conditions. An increase in the dummy time causes a considerable increase in the computational cost considering multiple design spirals with several thousand design load analysis cases. A time of 30 s is typically used in practical simulations for a wind turbine design with a fixed platform. However, 30 s may be insufficient for floating offshore wind turbines (FOWT) because the platforms have lower natural frequencies, and the transient responses will last much longer. In this paper, an initial condition application algorithm is implemented for WindHydro, and the appropriate dummy simulation time is investigated based on a series of dynamic simulations of a FOWT. As a result, it is found that more than 300 s is required for the platform to have stationary motion after the initial transient responses for the FOWT under the conditions considered.

• Macromolecular Research
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• 제12권2호
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• pp.178-188
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• 2004

We performed molecular dynamics (MD) simulations at 300 K on a series of poly(benzyl ether) (PBE) dendrimers having a different core functionalities. We used the rotational isomeric state Metropolis Monte Carlo (RMMC) method to construct the initial configuration in a periodic boundary cell (PBC) before the MD simulations were undertaken. To elucidate the effects that the structural features have on the chain dimension, the overall internal structure, and the morphology, we monitored the radii of gyration, R$\sub$g/ and the conformational changes during the simulations. The PBE dendrimers in a glassy state adopted less-extended structures when compared with the conformations obtained from the RMMC calculations. We found that R$\sub$g/ of the PBE dendrimer depends on the molecular weight, M, according to the relation, R$\sub$g/∼M$\^$0.22/. The radial distributions of the dendrimers were developed identically in the PBC, irrespective of the core functionality. A gradual decrease in radial density resulted from the fact that the terminal branch ends are distributed all over the molecule, except for the core region.

• 한국군사과학기술학회지
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• 제14권5호
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• pp.932-940
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• 2011

This study describes computational simulation results in 2-dimensional and 3-dimensional space concerning large scale gap test(LSGT) by using commercial hydrocode such as AUTODYN and LS-DYNA to analyze the detonation phenomenons of high explosives. To consider the possibilities of LSGT simulation, we used Lee - Tarver reaction rate model of PBX-9404 and Comp-B which were implemented AUTODYN's material library. Also we have tried the diverse numerical schemes such as Lagrangian, Eulerian and ALE(Arbitary Lagrangian Eulerian), SPH(Smoothed Particle Hydrodynamics) in LSGT simulations. After LSGT simulations, we compared the simulation results with published results to verify the LSGT simulations. According to the LSGT simulations, we have concluded as follows. In 2-dimensional and 3-dimensional space, Lagrangian solver provided the most reliable results based on analysis time and accuracy. When using two hydrocodes in 2-dimensional space, the simulation results are almost same except one explosive model. We have verified the modeling method and simulation results of the LSGT by using the commenrcial hydrocode in this study.

• 대한기계학회논문집A
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• 제33권9호
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• pp.938-948
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• 2009

In this paper, permanent magnets were used to remove magnetic sludge in the condenser of the power plant. To obtain the flow characteristics and magnetic information that are needed for determining a proper design of the magnetics sludge removal apparatus, numerical simulations were performed through the use of two commercial codes, ANSYS Workbench-Emag and CFX. Experiments were also performed on various kinds and sizes of magnets to obtain the magnetic information through a gauss meter. By analyzing the results of simulations and experiments, the minimum magnetic force that is able to remove the any size of the magnetic sludge in the condenser was calculated, and the design of the removal apparatus was confirmed. The test model which was confirmed by simulations and experiments was made. After testing, the test results were compared with those of numerical simulations and have good agreements.