• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2014년도 춘계학술대회
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• pp.47-48
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• 2014

물체 내부구조 및 매질 정수의 분포를 측정하기 위한 비파괴 기술은 지하자원의 탐사, 지하 케이블 및 매설관의 식별, 의료 분야의 영상진단 등에서 폭넓게 적용될 수 있다. 본 연구에서는 문제의 단순화를 위해 2차원 전자파 산란문제를 대상으로 역산란에 대한 해를 구하기 위한 정식화 과정을 검토하고 이의 유효성을 검증하고자 한다.

• 한국전기전자재료학회논문지
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• 제15권11호
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• pp.1003-1008
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• 2002

In this paper, the estimation of lifetime with the various conditions of the interface between toughened epoxy and rubber which are consisting materials of underground power delivery system has been studied. After the measurement of the short time AC interfacial breakdown strength on macro interfaces at room temperature, the breakdown time at several voltages were measured under the constant voltages lower than the short time breakdown voltage. The long time breakdown voltage was calculated by using Inverse Power Law. Two types of interfaces was studied. One was the interface between toughened epoxy and EPDM(Ethylene Prorylene Diene Terpolymer). The other was the interface between toughened epoxy and silicon rubber. Interfacial pressure and roughness of interfaces was determined through the characteristic of short time AC interfacial breakdown strength. Oil condition was no oiled, low viscosity oiled and high viscosity oiled. High viscosity oiled interface between Toughened epoxy and silicon rubber had the best lifetime exponent, 20.69. and the breakdown voltage of this interface after 30 years was evaluated 19.27㎸.

• 상하수도학회지
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• 제25권4호
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• pp.547-554
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• 2011

In small-scale water systems, the measurement of quality of raw water in running water is generally implemented when the quality of water is stable and frequency of measurement is low. However, units such as water temperature and pH, which are easily monitored, are frequently measured. In establishing an improvement plan for a water treatment system, the range of concentration of the target material present in the raw water of the running water provides relevant information. If the concentration of target material can be specified by the quality of water of data items that are measured daily, inverse estimation of the range of concentration is possible as well. In this paper, we took note of manganese in the raw water from Ogasawara-mura, Tokyo, and estimated the manganese concentration in the raw water of the running water for the past five years. Based on the results obtained, we have proposed a manganese removal system, considering the current situation and geographical conditions of Ogasawara-mura.

• Transactions on Electrical and Electronic Materials
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• 제8권6호
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• pp.278-282
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• 2007

In the complex insulation system that is used in extra high voltage(EHV) devices, according to the trend for electric power equipment of high capacity and reduction of its size, macro interfaces between two different bulk materials which affect the stability of insulation system exist inevitably. In this paper, the dielectric strength decrease of the macro interfaces between epoxy and ethylene propylene diene terpolymer(EPDM) was estimated by using the applied voltage to breakdown time characteristics. Firstly, the AC short time dielectric strength of specimens was measured at room temperature. Then, the breakdown time was measured under the applied constant voltage which is 70% of short time breakdown voltage. With these processes, the life exponent n was determined by inverse power law, and the long time breakdown voltage can be evaluated. The best condition of the interface was LOS(low viscosity(350 cSt) silicone oil spread specimen). When 30 years last on the specimens, the breakdown voltage was estimated 44% of the short time breakdown voltage.

• Structural Engineering and Mechanics
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• 제12권5호
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• pp.527-540
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• 2001

A new sort of learning algorithm named whole learning algorithm is proposed to simulate the nonlinear and dynamic behavior of RC members for the estimation of structural integrity. A mathematical technique to solve the multi-objective optimization problem is applied for the learning of the feedforward neural network, which is formulated so as to minimize the Euclidean norm of the error vector defined as the difference between the outputs and the target values for all the learning data sets. The change of the outputs is approximated in the first-order with respect to the amount of weight modification of the network. The governing equation for weight modification to make the error vector null is constituted with the consideration of the approximated outputs for all the learning data sets. The solution is neatly determined by means of the Moore-Penrose generalized inverse after summarization of the governing equation into the linear simultaneous equations with a rectangular matrix of coefficients. The learning efficiency of the proposed algorithm from the viewpoint of computational cost is verified in three types of problems to learn the truth table for exclusive or, the stress-strain relationship described by the Ramberg-Osgood model and the nonlinear and dynamic behavior of RC members observed under an earthquake.

• Composites Research
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• 제36권1호
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• pp.59-67
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• 2023

항공우주산업에서 경량화를 위해 사용되는 CFRP 복합재료로 구성된 차체의 충격에 따른 파손은 탑승자의 안전과 직결된다. 따라서 충돌 상황에서 육안으로 확인하기 힘든 재료의 손상거동을 파악하는 것이 중요하며, 이를 구현할 수 있는 유한요소모델을 통한 연구가 필요하다. 본 연구에서는 일방향 적층 복합재료의 충돌 해석에 대해 파손 거동 예측에 적합한 유한요소모델을 구축하였다. 인공신경망 모델을 통해 LS-DYNA에서 제공하는 MAT_54 Enhanced Composite Damage 재료 모델의 교정 파라미터를 역추정하여 획득하였다. 획득한 파라미터에 대한 인공신경망 모델의 결과를 실험결과와 비교하여 신뢰성을 검증하였다. 그 결과, 교정 파라미터의 최적화를 통해 실험에 대한 정확도를 향상시킨 유한요소모델을 구축할 수 있음을 확인하였다.

• 한국지반신소재학회논문집
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• 제21권3호
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• pp.1-10
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• 2022

본 논문에서는 지반 구조물의 재료 물성치에 대한 추계장 세트를 이용하여 재료 물성치의 공간적 임의성 및 확률 특성을 역추정한다. 이러한 추정된 재료 물성치의 확률분포 및 확률특성을 이용하여 구조 형상에 대한 위상 최적화를 수행하고, 기존의 결정론적 위상 최적화 결과와 비교한다. 재료 물성치에 대한 한 세트의 추계장들을 생성하고, 각 추계장에서 재료 물성치의 공간적 임의성을 모사한다. 각 추계장에서 재료 물성치의 부분값들을 이용하여 실제 재료 물성치의 확률분포와 확률 특성을 추정한다. 추정된 실제 재료 물성치의 확률특성을 추계장 세트의 확률 특성과 비교한다. 또한, 임의성을 가진 재료탄성계수를 가지는 지반구조물의 최적화 응답변화도와 임의성이 없는 재료탄성계수를 가지는 지반구조의 응답변화도를 비교한다. 따라서, 실제 재료 물성치의 공간적 임의성을 고려한 정량화된 확률론적 위상 최적화 결과를 얻을 수 있다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.911-914
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• 2005

Soft tissue characterization and modeling based on living tissues has been investigated in order to provide a more realistic behavior in a virtual reality based surgical simulation. In this paper, we characterize the nonlinear viscoelastic properties of intra-abdominal organs using the data from in vivo animal experiments and inverse FE parameter estimation algorithm. In the assumptions of quasi-linear-viscoelastic theory, we estimated the nonlinear material parameters to provide a physically based simulation of tissue deformations. To calibrate the parameters to the experimental results, we developed a three dimensional FE model to simulate the forces at the indenter and an optimization program that updates new parameters and runs the simulation iteratively. The comparison between simulation and experimental behavior of pig intra abdominal soft tissue are presented to provide a validness of the tissue model using our approach.

• 대한기계학회논문집A
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• 제32권5호
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• pp.430-436
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• 2008

This paper proposes a way to predict electrical lifetime of a relay using Accelerated Life Testings (ALTs). The relay of interest mounting on printed circuit boards is usually under an inrush current stress. The inrush current is generated and accelerated through controlling a lamp switching device in the ALT. We find that the dominant failure mechanism under high levels of inrush current would be contact welding in the contact surface of the relay and the contact welding process is accelerated according to increase in inrush current. The electrical lifetime model based on Inverse Power Law in term of inrush current is proposed, and parameters characterizing relay's lifetime distribution are statistically estimated using ALTA 6 PRO software.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2003년도 학술대회지
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• pp.112-117
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• 2003

The purpose of this work is to general approach to numerically simulating wear in rolling and sliding contact area between wheel and rail interface based on the analysis of dynamics with general MBS package. A simulation scheme is developed that calculates the wear at a detailed level. The estimation of material removal follows Archard's wear equation which states that the reduction of volume is linearly proportional to the sliding distance, the normal applied load and the wear coefficient and inverse proportional to hardness. The main research application is the wheel-rail contact of Korea High Speed Railway.