• 한국자동차공학회논문집
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• 제11권5호
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• pp.89-94
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• 2003

Rolling stock structures such as bogie frame and car body play an important role for the support of vehicle leading. In general, more than 25 years' durability is needed for them. A lot of study has been carried out for the prediction of the fatigue life of the bogie frame and car body in experimental and theoretical domains. One of the new methods is a probabilistic fatigue lift evaluation. The objective of this paper is to estimate the fatigue lift of the bogie frame of an electric car, which was developed by the Korea Railroad Research Institute (KRRI). We used two approaches. In the first approach probabilistic distribution of S-N curve and limit state function of the equivalent stress of the measured stress spectra are used. In the second approach, limit state function is also used. And load spectra measured by strain gauges are approximated by the two-parameter Weibull distribution. Other probabilistic variables are represented by log-normal and normal distributions. Finally, reliability index and structural integrity of the bogie frame are estimated.

• International Journal of Human Ecology
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• 제7권2호
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• pp.85-95
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• 2006

The purpose of this study was to examine mothers' ideal and actual parenting behaviors toward their infants in three parenting domains; social, didactic, and limit setting. A total of 264 mothers of young children under age three from Seoul, Korea completed Parental Style Questionnaires (PSQ). Mothers' self report on their ideal and actual parenting were explored as a function of child sex, age, and birth order. As expected, there were significant differences between mothers' ideal and actual behaviors in all three parenting domains: Mothers' ideal behaviors such as social interaction, didactic interaction and limit setting were higher than those of their actual behaviors. For mothers' ideal parenting, results revealed neither significant main effects nor interaction effects. However, the Parenting Domain x Birth-Order 2-way interaction and the Parenting Domain x Child Age 2-way interaction were significant for mothers' actual behaviors. Specifically, mothers reported more social and didactic behaviors with their first-born than later born children, but not for limit setting behavior. It was also found that higher limit setting behaviors were apparent for their 2- and 3-year-old than 1-year old children whereas lower social interactions were found for 3-year-old than for 1-year-old. In light of universality and uniqueness, mothers' parenting behavior toward young children has been discussed.

• 한국정보과학회논문지:소프트웨어및응용
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• 제31권11호
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• pp.1474-1482
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• 2004

본 논문에서는 적응적 가중치 함수를 이용하여 블록 단위의 모션 벡터를 필터링하는 방법을 제안한다. 제안하는 방법에서는 먼저 인접한 영상을 받아 들여 가변적 크기의 블록 정합 방법을 이용하여 모션 벡터를 추출한다. 그리고 추출된 모션 벡터를 강건 예측에 적용하여 아웃라이어(outlier)를 제거함으로써 강건 예측에서 사용하는 동작 모델에 근접한 모션 벡터만을 추출한다. 제안된 적응적 강건 예측은 연속적인 시그모이드 가중치 함수를 사용하여 정상 자료와 아웃라이어의 소속 정도를 보다 효과적으로 표현한다. 또한, 최소화 기법의 반복 단계에서 잔여에러가 감소함에 따라 점진적으로 시그모이드 가중치 함수를 조율함으로써 정상 자료와 아웃라이어를 보다 유연하게 분리한다. 실험에서는 카메라의 동작이 포함된 비디오 데이타를 입력 받아 성능을 비교 분석함으로써 제안한 방법의 우수함을 보인다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제8권6호
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• pp.602-614
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• 2016

It is necessary to develop an efficient optimization technique to perform optimum designs which have given design spaces, discrete design values and several design goals. As optimization techniques, direct search method and stochastic search method are widely used in designing of ship structures. The merit of the direct search method is to search the optimum points rapidly by considering the search direction, step size and convergence limit. And the merit of the stochastic search method is to obtain the global optimum points well by spreading points randomly entire the design spaces. In this paper, Pareto Strategy (PS) multi-objective function method is developed by considering the search direction based on Pareto optimal points, the step size, the convergence limit and the random number generation. The success points between just before and current Pareto optimal points are considered. PS method can also apply to the single objective function problems, and can consider the discrete design variables such as plate thickness, longitudinal space, web height and web space. The optimum design results are compared with existing Random Search (RS) multi-objective function method and Evolutionary Strategy (ES) multi-objective function method by performing the optimum designs of double bottom structure and double hull tanker which have discrete design values. Its superiority and effectiveness are shown by comparing the optimum results with those of RS method and ES method.

• 한국전산구조공학회논문집
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• 제26권3호
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• pp.183-189
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• 2013

본 논문에서는 불확실성을 확률변수로 가정하고 구조물의 파손기준을 한계상태식(Limit State Equation)으로 정의하였다. 한계상태식을 Fleishman의 3차 다항식으로 근사하고 이론적인 확률 모멘트(Moments)를 계산하였다. Fleishman은 표준정규 분포 확률변수에 대해서만 3차 다항식을 제시하였으나, 본 논문에서는 이를 확장하여 베타, 감마, 균일 분포 등 다양한 확률 변수에 적용하였다. 확률 모멘트를 계산하기 위해서 누률(Cumulants)과 정규화된 한계상태식을 활용하였으며, 피어슨 시스템(Pearson System)을 통해 한계상태식의 확률분포를 근사하였다.

• 한국구조물진단유지관리공학회 논문집
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• 제11권1호
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• pp.171-180
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• 2007

처짐, 응력 및 휨강도 한계상태에 대한 PSSC(prestressed steel and concrete)거더의 신뢰도해석을 수행한다. PSSC 거더는 시공비용과 형하공간의 확보 면에서 지간 40m이상인 교량에 적용하는데 커다란 장점을 가지고 있는 형식이다. 이 논문에서는 다양한 지간, 단면 및 설계 응력수준을 가지는 PSSC 거더를 설계하여 중앙점 처짐, 응력 및 단면 휨모멘트 해석을 수행하고, 각각에 대한 한계상태를 가정한 후, Monte-Carlo 시뮬레이션과 Rackwitz-Fiessler 방법을 이용하여 신뢰도지수를 구한다. 결과를 분석하면 PSSC 거더에 대한 처짐한계상태는 응력한계상태보다 적절하게 큰 신뢰도지수 값을 보이며, 휨강도에 대한 신뢰도지수가 매우 큼을 알 수 있다.

• 대한수학회지
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• 제51권1호
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• pp.1-15
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• 2014

A conditional version of the classical central limit theorem is derived rigorously by using conditional characteristic functions, and a more general version of conditional central limit theorem for the case of conditionally independent but not necessarily conditionally identically distributed random variables is established. These are done anticipating that the field of conditional limit theory will prove to be of significant applicability.

• 품질경영학회지
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• 제23권3호
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• pp.20-32
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• 1995

This paper is concerned with the economic selection of both the lower limit and the process mean for a continuous production process. Consider a production process where items are produced continuously. All of the items are subject to acceptance inspection. The items for which the measured values of the quality characteristic are larger than the lower limit are accepted, and those smaller than the lower limit are rejected and excluded from shipment. The process mean may be set higher to reduce the costs incurred by imperfect quality. Using a higher process mean, however, results in a higher production cost when production cost is an increasing function of the quality characteristic. Assuming that the quality characteristic is normally distributed with known variability, cost models are constructed which involve production cost, cost incurred by imperfect quality, rejection cost, and inspection cost. Methods of finding optimal values of the lower limit and the process mean are presented and numerical examples are given.

• 소성∙가공
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• 제22권6호
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• pp.328-333
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• 2013

The current study aims to determine the limit strains more accurately and reasonably when producing a forming limit curve (FLC) from experiments. The international standard ISO 12004-2 in its recent version (2008) states that the limit major strain should be determined by using the best-fit inverse second-order parabola through the experimental strain distribution. However, in cases where fracture does not occur at the center of the specimen, due to insufficient lubrication, the inverse parabola does not give a realistic fit because of its intrinsic symmetry in shape. In this study it is demonstrated that an inverse quartic function can give a much better fit than an inverse parabola in almost all FLC test samples showing asymmetric strain distributions. Using a quartic fit creates more reliable FLCs.

• 품질경영학회지
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• 제20권2호
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• pp.11-20
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• 1992

We discuss the feed back control of the on-line QC in the Taguchi method. Taguchi(1982) used the assumptions that the quality characteristics follow an uniform distribution and the Brownian motion to draw the loss function and proposed ${\Delta}/3$ or ${\Delta}$ for the initial control limit. Adams and Woodall(1989) also proposed a different procedure but using the same loss function. We propose, in this paper the new loss function under the assumption of mainly Brownian motion and compare the results with the results of the above.