• Prospectives of Industrial Chemistry
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• v.24 no.3
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• pp.28-41
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• 2021

고분자 시스템의 경우 매우 상이한 시간 및 길이 스케일(time and length scale)에 연관된 복잡한 내부 구조(internal structure)를 가지고 있기 때문에 전통적인 실험 방법만으로는 체계적이고 종합적인 연구가 쉽지 않다. 최근 다양한 시간 및 길이 스케일에 연관된 연구를 진행할 수 있는 다중 스케일 전산 모사(multiscale computer simulation) 방법은 이러한 고분자 시스템 연구에 있어서 새로운 대안으로 각광받고 있다. 본 논문에서는 최근 급격한 발전을 이룬 고분자 용액(polymeric liquid) 시스템에 대한 평형(equilibrium) 및 비평형(nonequilibrium) 전산 모사(computer simulation) 방법들에 관해 소개하고 이를 통합적으로 해석할 수 있는 다중 스케일 전산 모사 방법에 대해 여러 가지 사례를 들어 살펴보았다.

• Geomechanics and Engineering
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• v.13 no.1
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• pp.1-23
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• 2017

A coupled liquid-gas-solid three-phase model, linking two numerical codes (TOUGH2/EOS3 and $FLAC^{3D}$), was firstly established and validated by simulating an in-situ air flow test in Essen. Then the coupled model was employed to investigate responses of multiphase flow and soil skeleton deformation to compressed air or freshwater injection using the same simulation conditions in an aquifer of Tianjin, China. The simulation results show that with injecting pressurized fluids, the vertical effective stress in some area decreases owing to the pore pressure increasing, an expansion of soil skeleton appears, and land uplift occurs due to support actions from lower deformed soils. After fluids injection stops, soil deformation decreases overall due to injecting fluids dissipating. With the same applied pressure, changes in multiphase flow and geo-mechanical deformation caused by compressed air injection are relatively greater than those by freshwater injection. Furthermore, the expansion of soil skeleton induced by compressed air injection transfers upward and laterally continuously with time, while during and after freshwater injection, this expansion reaches rapidly a quasi-steady state. These differences induced by two fluids injection are mainly because air could spread upward and laterally easily for its lower density and phase state transition appears for compressed air injection.

• International Journal of Aeronautical and Space Sciences
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• v.17 no.4
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• pp.535-550
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• 2016

Securing the safety and the reliability of liquid-propellant rocket engines (LREs) for space vehicles is indispensable as engines consist of many complex components and operate under extremely high energy-dense conditions. Thus, health monitoring has become a mandatory requirement, especially for the reusable LREs that are currently being developed. In this context, a dynamic simulation program based on MATLAB/Simulink was developed in the current research on the Space Shuttle Main Engine (SSME), a partly reusable engine. Then, a series of fault simulations using this program was conducted: at a steady state operating condition (104% Rated Propulsion Level), various simulated fault conditions were artificially injected into the simulation models for the five major valves, the pumps, and the turbines of the SSME. The consequent effects due to each fault were analyzed based on the time responses of the major parameters of the engine. It is believed that this research topic is an essential pre-step for the development of fault detection and diagnosis algorithms for reusable engines in the future.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.733-738
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• 2006

As the film transistor-liquid crystal display (TFTLCD) panels become larger and provide higher resolution, the propagation delay of row and column lines, the voltage modulation of Vcom, and the response time of liquid crystal affect the display images now more than in the past. It is more important to understand the electrical characteristic of TFT-LCD panels these days. This paper describes the electrical model of a 15-inch XGA ($1024{\times}768$) TFT-LCD panel. The parasitic resistance and capacitance of its panel are obtained by 3D simulation of a sub pixel. The accuracy of these data is verified by the measured values in an actual panel [1]. The developed panel simulation platform, the equivalent circuit of a 15-inch XGA panel, is simulated by HSPICE. The results of simulation are compared with those of experiment, according to changing the width of signal. Especially, the proposed simulation platform for modeling TFTLCD panels can be applied to large size LCD TVs. It can help panel and circuit designers to verify their ideas without making actual panels and circuits.

• Journal of Korean Society of Water and Wastewater
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• v.32 no.5
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• pp.381-388
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• 2018

Microbubbles oxygen transfer to water was simulated based on experimental results obtained from the bubbles generation operated under varying liquid supply velocity to the multi-step orifices of the generator. It had been known that liquid supply velocity and bubble size are inversely related. In the oxygen transfer, a non-steady state was assumed and the pseudo stagnation caused the slow movement of bubbles from the bottom to the water surface. Two parameters were considered for the simulation: They represent a factor to correct the pseudo stagnation state and a scale which represented the amount of bubbles in supply versus time. The sum of absolute error determined by fitting regression to the experimental results was comparable to that of the American Society of Civil Engineers (ASCE) model, which is based on concentration differential as the driving force. Hence, considering the bubbles formation factors, the simulation process has the potential to be easily used for applications by introducing two parameters in the assumptions. Compared with the ASCE model, the simulation method reproduced the experimental results well by detailed conditions.

• Journal of Aerospace System Engineering
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• v.12 no.5
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• pp.8-15
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• 2018

The geostationary satellite uses a liquid apogee engine, to obtain a required velocity increment to enter a geostationary orbit. However, as the liquid apogee engine operates in the vacuum, a considerable disbursement of exhaust plume flow, from the liquid apogee engine can trigger a backflow. As this backflow may possibly collide with the satellite directly, it can cause adverse effects such as surface contamination, thermal load, and altitude disturbance, that can generate performance reduction of the geostationary satellite. So, this study investigated exhaust plume behavior of 400 N grade liquid apogee engine numerically. To analyze exhaust plume behavior in vacuum condition, the DSMC (Direct Simulation Monte Carlo) method based on Boltzmann equation is used. As a result, thermal fluid characteristics of exhaust plume such as temperature and number density, are observed.

• Journal of the Korea Computer Graphics Society
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• v.25 no.4
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• pp.1-8
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• 2019

In this paper, we propose a new framework that can express the detailed movement of liquid sprayed from wet hair or fur. In wet hair, not only the friction and adhesion of the hair but also the movement of the liquid has a distinctive motion compared to the dry hair. However, the recently proposed techniques only considered the contact force and friction of the hair and did not improve the movement of the liquid dispersed in the wet hair. This problem is detrimental to the quality of the result because it does not capture the detailed features expressed in the interaction of hair and liquid. The main point of this paper is to alleviate this problem and improve the quality of the result. As a result, we propose a combining framework that can efficiently express FLIP (Fluid-implicit particle) based fluid simulation and interaction of hair particles. The proposed method expresses the movement of the liquid sprayed in a curved shape which was not expressed in previous studies.

• Journal of the Optical Society of Korea
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• v.20 no.4
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• pp.510-514
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• 2016

The conventional liquid crystal displays (LCDs) have been using optically uniaxial liquid crystal (LC) medium and this often causes a significant image change at oblique viewing angles. We simulated the viewing angle properties of the biaxial nematic (N_b) phase of a bent-core liquid crystal (BLC) and compared the results with the vertically aligned (VA)- and the in-plane switching (IPS)-LCDs. The N_b phase of the BLC showed a smaller transmittance at the dark state as well as a greater contrast ratio at wide viewing angle. The viewing angle property of the N_b-mode without any compensation film was slightly superior to the IPS-mode with the compensation films eliminating the decross of the polarizers at oblique viewing angle.

• Nuclear Engineering and Technology
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• v.47 no.5
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• pp.588-595
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• 2015

This study presents an effective method for additional recovery of residual actinides in liquid electrodes after the electrowinning process of pyroprocessing. The major distinctive feature of this method is a reactor with multiple reaction cells separated by partition walls in order to improve the recovery yield, thereby using the interelement difference in diffusion coefficients within the liquid electrode and controlling the selectivity and purity of element recovery. Through an example of numerical simulation of the diffusion scenarios of individual elements, we verified that the proposed method could effectively separate the actinides (U and Pu) and rare-earth elements contained in liquid cadmium. We performed a five-step consecutive recovery process using a simplified conceptual reaction cell and recovered 58% of the initial amount of actinides (U + Pu) in high purity (${\geq}99%$).

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.8
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• pp.1793-1798
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• 2005

We model the nucleation and motion of defects in the liquid crystal display device with inhomogeneous surface by using fast Q-tensor method, which can calculate scalar order parameter S and nucleation of the defect in the liquid crystal director field. In order to model the defect, homeotropic aligned liquid crystal cell with step inhomogeneous electrode which has a height of $1{\mu}m$ is used. From the simulation, we can observe the nucleation and line of the defect from surface inhomogeneity and the experiment is performed for confirmation.