• Journal of the Computational Structural Engineering Institute of Korea
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• v.15 no.1
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• pp.1-8
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• 2002

When a body enters waters, its original kinetic energy or momentum is distributed among the body and surrounding water in the form of added mass. Due to the transfer of the energy or momentum, the bode is subjected to the hydrodynamic impact forces and acceleration. This impact behavior can be an important criterion of submersible vehicle launched to the air. In this paper, based on Life-boat model, an approximate method is proposed for the evaluation of the forces and responses of cylindrical rigid bode by water entry impact. The impact forces are calculated by yon Karman's momentum theory and motion responses the body, especially acceleration, are calculated by a numerical integration of the motion equations derived by hydrodynamic force equilibrium. The proposed method is expected to be a simple but efficient tool lot the preliminary design or motion analysis of a body subjected to water entry impact.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.49 no.4
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• pp.78-89
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• 2012

The generated torque of a switched reluctance(SR) motor is highly nonlinear, which makes it difficult to determine the reference current commands for minimum torque ripples. In this paper, we present a computationally simple and efficient method to minimize torque ripples of SR motors based on iterative learning control. The reference current command of each phase minimizing torque ripples is identified in 2-dimensional look-up table form. Our learning control algorithm does not require the torque model, so our method is not affected by model errors and hence is very accurate. In order to justify our work, we present some computer simulation results.

• Journal of KIISE
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• v.42 no.3
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• pp.281-288
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• 2015

A volcano disaster damage prediction system supports decision making for counteracting volcanic disasters by simulating meteorological condition and volcanic eruptions. In this system, a program called Fall3D generates predicted results for the diffusion of ash after a volcanic eruption on the basis of meteorological information. The relevant meteorological information is generated by a weather numerical prediction model known as Weather Research & Forecasting (WRF). In order to reduce the entire processing time without modifying these two simulation programs, pipelining can be used by partly executing Fall3D whenever the hourly (partial) results of WRF are generated. To reduce the processing time, successor programs such as Fall3D require that certain features be suspended until the part of the results that is based on prior calculation is generated by a predecessor. Even though Fall3D does not have a suspend or resume feature, pipelining effect can be produced by using the program's restart feature, which resumes simulation from the previous session. In this study, we suggest a workflow that can control the execution type.

• The Journal of the Acoustical Society of Korea
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• v.42 no.3
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• pp.189-202
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• 2023

In this study, the acoustic performance was analyzed by architectural shapes of the hall. There are four architectural shapes of halls. They are rectangular, horseshoe, surround, and fan-shape. Eight acoustic parameters were used to determine the acoustic performance. These are RT₆₀, EDT, C₈₀, BQI, LF, G_mid, G₁₂₅ and ITDG. First, measurement data of famous concert halls around the world were analyzed. The correlation coefficient R was obtained by regression analysis of the relationship between the subjective ranking of the halls and the acoustic parameters. It was found that BQI, G, and ITDG have higher correlation coefficients R. Also the average of acoustic parameters for each architectural shape were obtained. The total acoustic performance for each shape was calculated by using the correlation coefficient R as a weight for each acoustic parameters. As a result, rectangular halls and horseshoe halls showed good acoustical performances. Second, 3D models of each architectural shape were created and acoustic simulation had been performed. The simulation was performed by creating 3D models of each four shapes of concert halls with the same volume and sound absorption coefficient. Listening test was carried out using the sound source which is created from impulse responses of 3D model. As a result, rectangular hall and horseshoe hall showed the best performance however surround hall and fan-shaped hall showed relatively poor performance.

• Proceedings of the KIEE Conference
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• 2001.04a
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• pp.141-143
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• 2001

자기 부상력을 이용한 정밀 저울은 화학 실험실과 같이 정밀한 측정을 필요로 하는 곳에서 사용되고 있다. 이 정밀 저울은 저울의 측정대가 초기 위치로부터 이동하는 거리와 자속 밀도와의 상관관계를 이용하여 무게를 구하는 방식을 사용한다. 그런데 기존의 정밀저울은 힘이나 자속 밀도가 측정대의 이동하는 거리에 대해서 비선형적인 특성을 갖고 있기 때문에 거리에 대한 무게를 계산하는데 어려움이 있었고, 따라서 이동 가능 범위가 제한되어 있다는 단점이 있었다. 본 논문에서는 이런 문제점들을 해결하기 위해서 자기 부상형 정밀저울의 자석 표면에 부가적인 금속 구조를 덧붙인 새로운 모델을 제안하였고, 유한요소법과 진화 알고리즘을 사용하여 금속 구조의 형태를 최적화하였다. 그 결과 기존 자기 부상형 정밀 저울의 문제점인 비선형적 특성을 해결하고 이동 가능 범위도 향상시켜 더 간단하면서도 정화하게 무게를 계산할 수 있게 하였다.

• IE interfaces
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• v.8 no.3
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• pp.155-169
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• 1995

일반적인 CAD/CAM 시스템을 이용해서 생성한 NC-code는 오류의 가능성의 항시 내포되어 있으므로, 실 가공하기 전에 NC-code의 불량 여부를 검사할 필요가 있다. 본 논문에서는 Z-map 형태의 계산모형을 이용한 모의가공의 계산방법을 볼엔드밀, 평엔드밀, 라운드엔드밀에 대해서 도식적으로 설명하였다. 또, 모의가공 된 형상만으로 NC-code의 불량 여부를 검사하는 자체적인 검사방법과 모의가공 된 형상과 설계형상을 비교해서 불량여부를 판별하는 비교 검사방법을 제시하였다. Z-am 모델을 모의가공과 가공형상의 검증에 사용하면, 빠른 속도로 실제가공 상황을 재현 할 수 있고 육안 검증을 포함한 다양한 수치적 검증이 가능하다. 또, 간단한 데이터 구조이므로 필요한 앨고리즘을 효율적이고, 로버스트하게 구현할 수 있다.

• Journal of the Korea Society for Simulation
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• v.15 no.3
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• pp.103-114
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• 2006

Now distribution centers include an ASRS (Automated Storage and Retrieving System) and automated transfer systems such as conveyors and AGV (Automated Guided Vehicle). These automated distribution centers have lots of parameters to be considered fur operating performance. The general basic parameters in the distribution centers are specifications of storage equipment, system operating rules, configuration of storage area and unit load features. In this paper, an approach using simulation and metamodeling with response Surface method to optimize the design parameters of an automated distribution center model is presented. The simulation based metamodel will constitute an efficient approximation of the system function, and the approximate function will be used to design rapid optimal parameters of the distribution center model. This paper provides a comprehensive framework for economical material flow system design using the simulation and metamodeling.

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.983-983
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• 2012

EFDC의 수질모형인 HEM3D는 국내 해양수질모델링에는 적용된 사례가 많지만 담수에 적용된 사례는 거의 없으며, 우리나라 환경부 수질측정항목과 수질 INPUT 자료가 달라서 모델의 적용이 힘들었다. 그러나 HEM3D는 EFDC 수리모델을 연계하는 WASP에 비해 자체 3차원 수리동역학 모델이 있어 셀 개수의 제한이 없고 계산속도 또한 WASP 보다 2~3배 빠른 것으로 알려져 있다. 그러나 현재 우리나라의 수질측정항목은 HEM3D의 수질모의항목과 다소 차이가 있다. 특히 Carbon계열에서 실측수질항목은 BOD, COD인 반면 HEM3D의 모의가능항목은 RPOC, LPOC, DOC, COD로 바로 적용을 하기는 어렵다고 판단하였다. 따라서 환경부 수질자료를 HEM3D에 적용하기위해 문헌자료를 참고한 수질항목간의 분율을 사용하여 필요한 자료를 산출하였고, 환경부 수질자료의 HEM3D적용 결과를 알아보고 현재 자료 사용 시의 문제점과 향후 개선방안을 알아보고자 하였다. HEM3D의 모의 결과 TN, TP 보정에는 큰 문제가 없었으나 $BOD_5$와 세부수질항목의 영향을 많이 받는 조류 등의 항목 보정결과는 성공적이지 못했다. 이것은 분율을 적용해 각 유입지천의 세부항목별 수질 자료를 산출할 때 낙동강 전체 평균을 사용했기 때문에 조류성장에 직접적으로 영향을 받는 세부 항목별 영양염에 대한 실제 값과 산출된 농도 값 사이의 오차가 가장 큰 원인으로 판단된다. 한편 전체 대상지역중 일부구간에 대하여 동일한 수질입력자료를 이용하여 HEM3D와 WASP을 동시 적용하였다. 자료의 변환과정에서의 오차와 입력형태 및 각 모델 변수형태의 차이 등의 한계로 결과값에 차이가 있는 것으로 나타났으며, 본 연구결과 현재 확보된 수질측정망의 수질자료를 이용하여 HEM3D를 구축하는 것은 Carbon 계열과 조류(부영양화)모의에서 문제가 발생할 것으로 판단되며 추가 자료 확보가 필요할 것으로 보인다. 또한 필요한 입력자료가 충분히 확보가 된다면 추가연구결과에서 볼 수 있듯이 미국공변단과 미국 환경부수질모델 모두 동시적용이 가능하다고 판단되며 목적과 편의에 따라 선택적 모의가 가능하다고 판단된다.

• Journal of Internet Computing and Services
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• v.21 no.2
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• pp.121-130
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• 2020

This paper suggests evaluating the military closed network data as an image which is generated by Generative Adversarial Network (GAN), applying an image evaluation method such as the InceptionV3 model-based Inception Score (IS) and Frechet Inception Distance (FID). We employed the famous image classification models instead of the InceptionV3, added layers to those models, and converted the network data to an image in diverse ways. Experimental results show that the Densenet121 model with one added Dense Layer achieves the best performance in data converted using the arctangent algorithm and 8 * 8 size of the image.

• Journal of Korean Ophthalmic Optics Society
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• v.16 no.1
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• pp.107-116
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• 2011

Purpose: The review article was written to establish an excel program that could calculate minimal Dk of contact lens without $O^2$ deficiency and actual $O^2$ concentration on cornea when contact lens were being fitted by changing lens-related factors. Methods: An excel program was formulated to calculate the thickness of post-lens lacrimal layer, Dk of contact lens and $O^2$ concentration on cornea. Results: With the excel program established, minimal $O^2$ concentration needed on cornea could be calculated when the thickness of post-lens lacrimal layer was changed by varying lens-related factors. A different route in the excel program was needed to choose based on the shape of lacrimal layer. The thickness of lacrimal layer was determined by the shape of meniscus made of tear between lens edge and cornea with flat fit. Thus, the $O^2$ concentration showing negative number in calculation decreased on peripheral cornea with flatter fitting and actual $O^2$ concentration would be zero on cornea. With tight fitting, the thickness of post-lens lacrimal layer is much thicker than lens itself thus negative number in calculation by the excel program is shown indicating zero oxygen on cornea. It can cause $O^2$ deficiency regardless of Dk of contact lens. Conclusions: The calculation of thickness of post-lens lacrimal layer and $O^2$ concentration on cornea by the established excel program is suggested to avoid $O^2$ deficiency when fitting state is varied by changing lens-related factors.