• Smart Structures and Systems
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• 제29권6호
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• pp.799-805
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• 2022

Permanent magnet synchronous motors (PMSMs) are widely used in systems requiring high control precision, efficiency, and reliability. Predicting the remaining useful life (RUL) with health monitoring of PMSMs prevents catastrophic failure and ensures reliable operation of system. In this study, a model-based method for predicting the RUL of PMSMs using phase current and vibration signals is proposed. The proposed method includes feature selection and RUL prediction based on a particle filter with a degradation model. The Paris-Erdogan model describing micro fatigue crack propagation is used as the degradation model. An experimental set-up to conduct accelerated life test, capable of monitoring various signals was designed in this study. Phase current and vibration data obtained from an accelerated life test of the PMSMs were used to verify the proposed approach. Features extracted from the data were clustered based on monotonicity and correlation clustering, respectively. The results identify the effectiveness of using the current data in predicting the RUL of PMSMs.

• Smart Structures and Systems
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• 제14권6호
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• pp.1055-1079
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• 2014

Substructure shake table testing is a class of real-time hybrid simulation (RTHS). It combines shake table tests of substructures with real-time computational simulation of the remaining part of the structure to assess dynamic response of the entire structure. Unlike in the conventional hybrid simulation, substructure shake table testing imposes acceleration compatibilities at substructure boundaries. However, acceleration tracking of shake tables is extremely challenging, and it is not possible to produce perfect acceleration tracking without time delay. If responses of the experimental substructure have high correlation with ground accelerations, response errors are inevitably induced by the erroneous input acceleration. Feeding the erroneous responses into the RTHS procedure will deteriorate the simulation results. This study presents a set of techniques to enable reliable substructure shake table testing. The developed techniques include compensation techniques for errors induced by imperfect input acceleration of shake tables, model-based actuator delay compensation with state observer, and force correction to eliminate process and measurement noises. These techniques are experimentally investigated through RTHS using a uni-axial shake table and three-story steel frame structure at the Johns Hopkins University. The simulation results showed that substructure shake table testing with the developed compensation techniques provides an accurate and reliable means to simulate the dynamic responses of the entire structure under earthquake excitations.

• 정보처리학회논문지:소프트웨어 및 데이터공학
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• 제8권4호
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• pp.137-144
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• 2019

무기체계 기술의 국산화 과정에서 경험과 기술이 부족한 상태로 개발 중인 체계에 대한 테스트 기술의 성숙도는 매우 중요하다. 테스트에서 발견하지 못한 결함은 시스템 운용 중 막대한 영향을 미친다. 잠수함에서 실시간 정보공유 체계는 신속한 지휘결심과 임무능력으로 이어진다. 데이터 분산 시스템은 매우 중요한 정보 공유체계이며 제조사나 데이터 형태가 다른 체계들 간에 이루어진다. 본 논문에서는 데이터 분산 시스템의 데이터 분산 특성을 분석하여 데이터별 체계를 그룹핑하고, 경로 테스트 기법에 트리순회 방법인 후위트리순회, 전위트리순회를 이용하여 테스트케이스 생성기법을 제시한다. 제시한 기법은 기존기법들에 비해 73.7% 테스팅 리소스를 감소시킬 수 있다.

• 한국정보처리학회논문지
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• 제4권5호
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• pp.1211-1220
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• 1997

다수 공급에 의해 제공되는 여러 구현들간의 상호운용성 시험은 비용을 초래할 뿐아니라 실제 상황에서 때로는 그 자체가 불가능하다. 적합성 시험이나 적합성 시험을 확정한 방법들 만으로는 효과적으로 상호운용성을 보장할 수 없다 본 논문 에서는 실시간 시스템인 통신망의 구성 요소들을 매우 훌륭하게 추상화 할 수 있는 실시간 객체 모형을 기반으로 한 프로토콜 상호운용성 시험 방법을 제시한다. 이 방법 에서는 RTO.k 객체 모형을 이용하여 IUT(lmplementation Under Test)와 시험 환경을 추상화하고 그 결과 얻어진 객체들을 실행 환경인 DREAM 커널 상에 지역 모니터와 전역 모니터를 두어 수행시킨다. 지역 모니터는 관찰과 제어를 주요 임무로 하고 전역 모니터는 시험 과정을 주관한다. 시험 방법의 검증을 위하여 B-ISDN UNI Q.2931 의 예를 들어 호 연결 제어 프로토콜 상호운용성 시험을 실험야 하였다. 이 방법으로 높은 결함 발견율을 얻을 수 있다.

• Journal of the Korean Data and Information Science Society
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• 제24권6호
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• pp.1551-1559
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• 2013

In this paper, we analyze the Korean Won/Japanese 100 Yen exchange rate data based on the ARMA-GARCH model, and perform the test for detecting the parameter changes. As a test statistics, we employ the cumulative sum (CUSUM) test for ARMA-GARCH model, which is introduced by Lee and Song (2008). Our empirical analysis indicates that the KRW/JPY exchange rate series experienced several parameter changes during the period from January 2000 to December 2012, which leads to a fitting of AR-IGARCH model to the whole series.

• International Journal of Reliability and Applications
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• 제15권1호
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• pp.65-76
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• 2014

In this article, a new model based on Lomax distribution is introduced. This new model is both useful and practical in areas such as economic, reliability and life testing. Some statistical properties of this model are presented including moments, hazard rate, reversed hazard rate, mean residual life and mean inactivity time functions, among others. It is also shown that the distributions of the new model are ordered with respect to the strongest likelihood ratio ordering. The method of moment and maximum likelihood estimation are used to estimates the unknown parameters. Simulation is utilized to calculate the unknown shape parameter and to study its properties. Finally, to illustrate the concepts, the appropriateness of the new model for real data sets are included.

• 한국재료학회지
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• 제15권1호
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• pp.6-13
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• 2005

Copper based leadframe sheets were immersed in two kinds of hot alkaline solutions to form brown-oxide or blackoxide layer on the surface. The oxide-coated leadframe sheets were molded with epoxy molding compound (EMC). After post mold curing, the oxide-coated EMC-leadframe joints were machined to form sandwiched double-cantilever beam (SDCB) specimens. The SDCB specimens were used to measure the fracture toughness of the EMC/leadframe interfaces under quasi-Mode I loading conditions. After fracture toughness testing, the fracture surface were analyzed by various equipment to investigate failure path. An adhesion model was suggested to explain the failure path formation. The adhesion model is based on the strengthening mechanism of fiber-reinforced composite. The present paper deals with the introduction of the adhesion model. The explanation of the failure path with the proposed adhesion model was introduced in the companion paper.

• 한국전자거래학회지
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• 제9권1호
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• pp.1-19
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• 2004

시간적 금전적 압박으로 최근의 웹 응용에서는 체계적인 시험작업이 종종 간과되곤 한다. 게다가 효과적인 웹 응용 시험 방법이 많지 않아 웹 응용에 기존의 시험 방법들을 적용하면서 개발자들은 많은 어려움을 겪고 있다. 빠르고 효과적 인 시험을 위하여 웹 페이지간의 메시지를 모델링한 UML 순차도(Sequence Diagram)로부터 웹 응용을 위한 시험사례를 추출하는 방법을 제안한다. 웹 응용을 위한 시험사례들은 UML의 순차도에서 자기 호출 메시지 (Self-Call Messages)를 포함한 메시지들로부터 추출된다. 시험사례는 시험할 대상인 메시지와 스크립트 함수, 서버 페이지와 추가적인 시험값들로 구성된다. 또한, 웹 응용 시험을 지원하기 위한 간단한 도구를 제시한다. 이 시험 도구는 웹 응용을 시험하기 위한 URL을 생성하고 이를 실행하여 그 결과를 보인다. 생성된 URL은 시험할 서버 페이지의 주소와 추가적인 시험값들로 구성된다. 이 도구는 마이크로소프트 비주얼 베이직으로 작성하였다. 회원 관리 기능을 수행하는 웹 응용개발 과제에 제안하는 시험사례 추출방법과 시험 지원 도구를 적용하였으며 그 유용성을 확인하였다.

• Computers and Concrete
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• 제18권1호
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• pp.1-16
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• 2016

In this study, an Artificial Neural Network (ANN) and Adaptive Network-based Fuzzy Inference Systems (ANFIS) prediction models for flexural strength of the cement mortars have been developed. For purpose of constructing this models, 12 different mixes with 144 specimens of the 2, 7, 28 and 90 days flexural strength experimental results of cement mortars containing pure Portland cement (PC), blast furnace slag (BFS), waste tire rubber powder (WTRP) and BFS+WTRP used in training and testing for ANN and ANFIS were gathered from the standard cement tests. The data used in the ANN and ANFIS models are arranged in a format of four input parameters that cover the Portland cement, BFS, WTRP and age of samples and an output parameter which is flexural strength of cement mortars. The ANN and ANFIS models have produced notable excellent outputs with higher coefficients of determination of $R^2$, RMS and MAPE. For the testing of dataset, the $R^2$, RMS and MAPE values for the ANN model were 0.9892, 0.1715 and 0.0212, respectively. Furthermore, the $R^2$, RMS and MAPE values for the ANFIS model were 0.9831, 0.1947 and 0.0270, respectively. As a result, in the models, the training and testing results indicated that experimental data can be estimated to a superior close extent by the ANN and ANFIS models.

• 한국신뢰성학회지:신뢰성응용연구
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• 제4권2호
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• pp.73-90
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• 2004

We performed the heat aging test to predict the useful lifetime of Elastomeric Bearing Chloroprene Rubber (CR) used for supporting bridge. During the test, we measured elongation that are influenced by temperature and aging time. The failure of a test piece is defined as the point at which the elongation reaches to 75% of the initial value. This failure criterion is based on KS F 4420: 1998 (Elastomeric Bearing for bridge). Through the accelerated heat aging test, we found that the Arrhenius relationship and the Weibull lifetime distribution are appropriate as the life-temperature relationship and lifetime distribution of the CR, respectively. Using the Arrhenius -Weibull model, the parameters of the model are estimated and the lifetime of the CR at use condition is predicted.