• 한국통신학회논문지
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• 제34권10C호
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• pp.955-960
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• 2009

본 논문에서는 주파수영역에서 음향학적 반향 억제 (AES, acoustic echo suppression) 성능을 개선시키기 위해 tracking echo-presence uncertainty (TEPU) 기법에 근거한 새로운 잔여 반향 억제 (RES, residual echo suppression) 알고리즘을 제안한다. 제안된 방법은 RES를 위해 마이크로폰 입력신호 대 원단의 반향신호가 제거된 결과신호의 전력 비 (ratio)를 문턱 (threshold) 값에 의한 decision rule에 적용하여 추정된 echo-presence uncertainty를 RES 필터로 이용한다. 제안된 알고리즘은 각각의 주파수 채널에서 echo-presence uncertainty를 도출하여 용이하게 잔여 반향신호를 제거하는 장점을 가진다. 실제로 잔여 반향신호를 제거하기 위한 기존의 방법과 객관적인 실험을 통해 비교 평가한 결과 우수한 성능을 보였다.

• 한국압력기기공학회 논문집
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• 제19권2호
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• pp.130-139
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• 2023

This paper examines the quantification of uncertainty for welding residual stresses in dissimilar metal welds used in nuclear power plants. A mock-up of a dissimilar metal weld pipe, consisting of carbon and stainless steel pipes, was fabricated to measure the residual stress. A Round-Robin analysis was conducted by Korean institutions to assess the welding residual stress. The analysis was carried out in the second order, and the data obtained by each institution was evaluated based on the information provided. Using the Round-Robin results, the distribution of uncertainty in welding residual stresses among Korean institutions was evaluated. The quantification of uncertainty for Korean institutions was found to have a wider range compared to the distribution of welding residual stresses observed in overseas institutions. This study is considered useful in the establishment of comprehensive strategies for evaluating welding residual stress analysis methods used by domestic institutions.

• 한국분말재료학회지
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• 제14권6호
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• pp.410-414
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• 2007

Carbon contamination from the binder resin is an inherent problem with the metal powder injection molding process. Residual carbon in the W-Cu compacts has a strong impact on the thermal and electric properties. In this study, uncertainty was quantified to evaluate determination of carbon in a W-15%Cu MIM body by the combustition method. For a valid generalization about this evaluation, uncertainty scheme applied even to the repeatability as well as the uncertainty sources of each analyse step and quality appraisal sources. As a result, the concentration of carbon in the W-Cu part were measured as 0.062% with expanded uncertainty of 0.003% at 95% level. This evaluation example may be useful to uncertainty evaluation for other MIM products.

• 한국항공우주학회지
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• 제43권12호
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• pp.1116-1123
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• 2015

정지궤도위성의 수명은 추진제 잔여량에 좌우되고 정확한 잔여추진제량 측정은 조기 수명종료로 야기되는 경제적 손실을 완화시킬 뿐만 아니라 후속위성의 대체나 위성망 운용계획 등에 매우 중요하다. 본 논문에서는 열질량법과 그 불확실성 추정방법에 대한 기본이론에 대해 소개한다. 열질량법 잔여추진제 분석은 무궁화위성 데이터를 기초로 분석하였고 이러한 열질량법 불확실성 분석은 몬테카를로 방법을 사용하여 수행하였다. 이러한 연구 결과를 통해 열질량법을 사용한 잔여추진제 추정의 중요 파라미터를 알 수 있다.

• 한국신뢰성학회지:신뢰성응용연구
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• 제3권1호
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• pp.83-92
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• 2003

We studied the trend change of failure rate function and uncertainty of residual life function in terms of location of their trend change points. It is shown that the trend change of uncertainty of residual life takes place before the failure rate changes its trend. Like DIFR(IDFR) does not necessary implies IDMRL(DIMRL), we find the fact that DIFR(IDFR) does not always imply IDURL(DIURL) under certain conditions, through the exponentiated-weibull distribution.

• Nuclear Engineering and Technology
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• 제48권3호
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• pp.765-772
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• 2016

In analyzing residual radiation, researchers generally use a two-step Monte Carlo (MC) simulation. The first step (MC1) simulates neutron transport, and the second step (MC2) transports the decay photons emitted from the activated materials. In this process, the stochastic uncertainty estimated by the MC2 appears only as a final result, but it is underestimated because the stochastic error generated in MC1 cannot be directly included in MC2. Hence, estimating the true stochastic uncertainty requires quantifying the propagation degree of the stochastic error in MC1. The brute force technique is a straightforward method to estimate the true uncertainty. However, it is a costly method to obtain reliable results. Another method, called the adjoint-based method, can reduce the computational time needed to evaluate the true uncertainty; however, there are limitations. To address those limitations, we propose a new strategy to estimate uncertainty propagation without any additional calculations in two-step MC simulations. To verify the proposed method, we applied it to activation benchmark problems and compared the results with those of previous methods. The results show that the proposed method increases the applicability and user-friendliness preserving accuracy in quantifying uncertainty propagation. We expect that the proposed strategy will contribute to efficient and accurate two-step MC calculations.

• 한국항공우주학회지
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• 제39권12호
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• pp.1107-1114
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• 2011

본 논문에서는 레이저 피닝(Laser peening) 구조물에 대한 피로 수명을 예측하였다. 레이저 피닝에 의해 생성된 압축잔류응력(Compressive residual stress)을 계산하기 위해서 유한 요소 시뮬레이션(Finite element simulation)을 수행하였고, 피로 수명 예측 시에 압축잔류응력 효과를 고려하기 위해서 수정된 Goodman 식을 사용하였다. 또한, S-N 선도 모델 불확실성(Model uncertainty)을 고려한 피로 수명 예측을 위해 부가 적응 인자 접근법(Additive adjustment factor approach)을 적용하여 예측된 피로 수명의 신뢰 구간(Reliable bounds)을 결정하였다.

• Journal of Information Technology Applications and Management
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• 제11권2호
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• pp.15-27
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• 2004

Most software projects inevitably involve various types and degrees of uncertainty. Without proper risk assessment and coordination, software projects can easily run out of control and consume significant additional resource. Thus, risk management techniques are critical issues to information system researchers. Previous empirical studies of U.S. software firms support the adoption of development standardization and user requirement analysis techniques in risk-based software project management. Using data collected from software projects developed in Korea during 1999-2000, we conduct a comparative study to determine how risk management strategies impact software product and process performance in countries with dissimilar IT capabilities. In addition, we offer an alternative conceptualization of residual performance risk. We show that the use of residual performance risk as an intervening variable is inappropriate in IT developing countries like Korea where the role of late stage risk control remedies are critical. A revised model is proposed that generates more reliable empirical implications for Korean software projects.

• Journal of applied mathematics & informatics
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• 제41권1호
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• pp.71-82
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• 2023

In this article, we find the approximate solutions of Abel differential equation (ADE) with uncertainty using residual power series (RPS) method. This method helps to calculate the sequence of solutions of ADE. Finally, numerical illustrations demonstrate the applicability of the method.

• 대한기계학회논문집A
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• 제40권3호
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• pp.281-288
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• 2016

복합재는 재료 불균질성에 의해 고속 충돌 시 방호성능 자료가 산포한다. 본 연구에서는 다수의 충돌시험으로 복합판재 잔류속도 산포를 확보하고 수치해석으로 예측하는 방법을 정립하였다. 먼저 10개의 동일 시편으로 인장시험을 수행하여 파단변형률 산포를 얻었다. 같은 재료로 제작된 4ply([0/90]s)와 8ply([0/90/0/90]s) GFRP(Glass Fiber Reinforced Plastic) 복합판재에 FSP(Fragment Simulating Projectile) 고속 충돌시험을 동일 조건에서 다수 수행하여 잔류속도 산포를 얻었다. 인장시험에서 얻어진 파단 변형률 분포를 이용하여 수치해석을 수행하였다. 충돌속도는 4ply와 8ply 각각 411.7m/s와 592.5m/s이다. 시험 결과와 비교하여 적절한 잔류속도의 산포를 예측할 수 있었다. 추가적으로 복합판재의 경우 Solid요소 대비 Layered Solid요소로 모델링하면 계산시간이 감소되었다.