• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.2
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• pp.1-6
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• 2019

The objective of this study was to investigate performance characteristics of thermal management system(TMS) in a fuel cell electric vehicle with 100kW Fuel Cell(FC) system. In order to build up analytic modelling for TMS, each component was installed and tested under various operating conditions, such as water pump, radiator, 3-Way valve, COD heater, and FC stack etc. and as the results of them, correlations reflecting component's characteristics with flow rate, air velocity were developed. Developed analytic modelling was carried out under various operating conditions on the road. To verify modelling's accuracy, after prediction for optimum coolant flow rate was fulfilled under certain operating conditions, such as FC system, water pump speed, opening of 3-way valve, and pipe resistance, analytic and experimental values were compared and good agreement was shown. In order to predict cold-start operating performance for analytic modelling, coolant temperature variation was analyzed with $-20^{\circ}C$ ambient temperature and duration was predicted to rise in optimum temperature for FC. Because there is appropriate temperature difference between inlet and outlet of FC stack to operate FC system properly, related analysis was performed with respect to power consumption for TMS and heat rejection rate and performance map was depicted along with FC operating conditions.

• Journal of Korea Society of Industrial Information Systems
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• v.12 no.3
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• pp.86-94
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• 2007

In this paper, the electric characteristics in multilayer organic light emitting, diodes(OLEDs) are observed using a numerical device modeling method. The methode is applied to a general device structure, ITO/CuPC/${\alpha}-NPD$/ Alq3/LiF/Al, that has received broad attention in previous literature. The fitted current-voltage characteristics are quite consistent with the results which was experimentally determined in reference papers. This research approached results in a detailed understanding of the operating machanism of a multilayer OLEDs and applied to a set of real devices.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.5
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• pp.1022-1027
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• 2014

Based on the modeling of DGPS antenna and antenna site environment, the DGPS short-monopole antenna performance according to the antenna surrounding environment are analyzed in this paper. The DGPS antenna site modeling that considers the ground conductivity and radio wave obstacles is performed and the general requirements for DGPS antenna site are proposed. In case of antenna site with proper radials on the ground plane of the fixed scale, the effect for antenna matching network due to the ground conductivity and radio wave obstacles is small but the impact on the radiation efficiency is large. To provide the stable DGPS service, it is important to install the DGPS antenna on the flat ground plain with good conductivity and without radio wave obstacles.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.29 no.6
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• pp.382-388
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• 2017

This study performed an OpenFOAM-based numerical modeling for simulating performance of wave reduction by a floating vertical plate. Based on the Waves2FOAM library, an internal wave generation and energy dissipation with sponge layers schemes were further implemented. The performance of wave generation and dissipation was first tested with a simple two-dimensional analysis. Then, numerical simulation was carried out with the experimental data of Briggs et al. (2001) for the two regular wave cases. In general, the modeling results agreed well with the experimental data, showing better agreement than the numerical analysis by WAMIT that is included in Briggs et al. (2001).

• Proceedings of the KIEE Conference
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• 2006.10d
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• pp.12-15
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• 2006

모터의 설계를 위해서는 여러 가지 방법에 의해서 해석을 먼저 수행하는 것이 필수적이다. 이를 위해서는 시스템에 대한 최적 모델링이 필수적인데 모터의 전자기적인 해석에는 비선형성이 크기 때문에 최적의 모델링이 쉽지 않다. 특히 집중권선 방식을 이용한 유도기는 자속의 집중으로 인해 고조파 발생 등 많은 문제점을 안고 있어서 실제로 유도기 설계시 설계자들이 많은 어려움을 겪고 있으며, 많은 설계자들은 대부분 등가회로를 이용한 방법으로 시뮬레이션하고, 자신의 경험을 바탕으로 시행착오를 거쳐 가면서 설계를 하고 있다. 그러나 그렇게 설계된 제품이 최적의 설계인지도 의문시 되는 경우가 대부분이다. 따라서 본 논문에서는 모터의 최적설계를 위하여 기존 개발한 집중권 방식 유도기를 대상으로 신경회로망을 이용하여 시스템을 모델링하였고, 그 결과를 확인하기 위해 기존 개발한 집중권 유도기의 실측치와 신정회로망을 이용하여 모델링한 방법을 비교, 제시하였다.

• Journal of the Korean GEO-environmental Society
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• v.9 no.6
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• pp.5-12
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• 2008

In this research, the plate load tests on sand which is reinforced by Tirecell mat were simulated by finite element method (FEM). Tirecell mat made by waste tires has the same function and similar shape to Geocell for soil reinforcement and it can also be used for civil engineering structure. The results were compared with those of field plate load tests for evaluation of suitability of modeling method. From the comparison of both results, it can be seen that the settlements by FEM were very similar to test results with small margin under the ultimate bearing capacity. For the ultimate bearing capacities of two results, difference was very small. After the confirmation of the modelling, reinforcing effects with variation of cover depth and number of reinforcement layers by Tirecell were analyzed additionally. Reinforcing effect decreases with increasing soil cover depth, and this is similar to previous test results by soil cover depth. As the number of reinforcing layers increased, reinforcing effect increased. However at more than 2 reinforcing layers, reinforcing effect was negligible. In conclusion, the modeling method in this research might be used for analysis of reinforced structures using Tirecell mat.

• Geophysics and Geophysical Exploration
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• v.20 no.3
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• pp.121-128
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• 2017

Interpretation of time-domain electromagnetic (TEM) data has been made mostly based on one-dimensional (1-D) inversion scheme in Korea. A proper interpretation of TEM data should employ 3-D TEM forward and inverse modeling algorithms. This study developed a 3-D TEM modeling algorithm using a finite difference time-domain (FDTD) method with staggered grid. In numerically solving Maxwell equations, fictitious displacement current is included based on an explicit FDTD method using a central difference approximation scheme. The developed modeling algorithm simulated a small-coil source configuration to be verified against analytic solutions for homogeneous half-space models. Further, TEM responses for a 3-D anomaly are modeled and analyzed. We expect that it will contribute greatly to the precise interpretation of TEM data.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.12
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• pp.1160-1165
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• 2011

This study is focused on the structural dynamic responses, i.e., vibration analysis results of the high-accuracy observation multi-axial camera, which is installed and operated for the UAV (Unmanned Aerial Vehicle) and helicopter etc. And, the authors newly suggest a modeling technology of the ball bearing applied to the camera by using three-axis spring elements. The vibration analysis results well agreed to the randum vibration test results. Also, the vibration responses characteristics of the multi-axial camera through the time history analysis of the random vibration were analyzed and evaluated. The above results can be applied to the FE-modeling of the ball bearings used for the space cameras.

• Aerospace Engineering and Technology
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• v.9 no.1
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• pp.9-16
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• 2010

In this study, structural analyses were carried out on the composite sandwich panel which was tested under compression loading. In the structural analyses, three types of finite element modelling were considered and linear buckling analysis and nonlinear analysis were performed for each FE-model. Through the analyses, it was found that shell elements for face parts and solid elements for core part were appropriate for the better prediction of the buckling load of the panel. If the material failure of the face is critical than overall buckling of the sandwich panel, the use of one shell element through the thickness direction was suitable in the FE-model for the better predictions of failure location and failure load.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.2
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• pp.115-120
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• 2014

In this study, a module is developed for modeling and analyzing dynamic behavior of a wind turbine using RecurDyn, which is a commercial multi-body dynamics software developed by FunctionBay, Inc. The wind turbine consists of tower, nacelle, hub and blades. Tower and blades are regarded as flexible bodies for considering elastic effect using beam theory and spring force. In this paper, a constant speed wind was assumed and aerodynamic force is modeled using BEM theory. Dynamic analysis applying this aerodynamic force is carried out. To verify the validity of analysis results, these results are compared to those of GH-Bladed which is a commercial software for analyzing wind turbine system distributed by Garrad Hassan.