• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.717-720
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• 2000

Event-driven communication protocols such as CAN(Controller Area Network) have inherent packet delays due to the contention process for the use of network medium. These delays are stochastic in nature because most packets arrive at random time instants. The stochastic property of the delay adversely influences the control system's performance in terms of stability, responsiveness and steady-state error. Another problem for safety-critical application such as brake-by-wire systems is the reliability of the communication modules that can fail abruptly. This paper deals with two methods to overcome the above problems : (i) scheduling method that can maintain packet delays under some acceptable level, and (ii) redundancy management of communication modules that prescribes dual-redundancy modules' behavior when one of them fails.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.8 s.179
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• pp.2115-2122
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• 2000

The understanding of impact-induced delamination is important in safety and reliability of composite structure. In this study, a model for arrest toughness is proposed in consideration of fracture behavior of composite materials. Also, the probabilistic model is proposed to describe the variability of arrest toughness due to the nonhomogeneity of material. For these models, experiments were conducted on the Carbon/Epoxy composite plates with various thickness using the impact hammer. The elastic work factor used in J-Integral is applicable to the evaluation of energy release rate. The fracture behavior can be described by crack arrest concept and the arrest toughness is independent of the delamination size. Additionally, a probabilistic characteristics of arrest toughness is well described by the Weibull distribution function. A variation of arrest toughness increases with specimen thickness.

• Korean Journal of Organic Agriculture
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• v.22 no.1
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• pp.67-80
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• 2014

The objective of the study is to investigate factors affecting consumers' purchase intention toward imported organic agricultural products. To accomplish the goal of the study a consumer survey was administered for randomly selected households residing in capital area. Results show that the more consumers trust a safety of domestic products and a certification system, the less they purchase the imported products. In addition, it is demonstrated that educated consumers are relatively less reluctant to imported organic agricultural products. Finally, an improvement of domestic certification system, decrease of price of environmentally friendly agricultural products, and aggressive promotion are required to enhance the competitiveness of the domestic environmentally friendly agricultural products.

• Computational Structural Engineering
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• v.7 no.1
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• pp.125-134
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• 1994

Response variability of reinforced concrete frame subjected to material property randomness has been evaluated with the aid of the finite element method. The spatial variation of Young's modulus is assumed to be a two-dimensional homogeneous stochastic process. Young's Modulus of concrete material has been investigated based on the uiaxial strength of concrete cylinder. Direct Monte Carlo simulation method is used to investigate the response of reinforced concrete frame due to the variation of Young's modulus with the Neumann expansion method and the pertubation method. The results by three analytic methods are compared with those by deterministic finite element analysis. These stochastic technique may be an efficient tool for evaluating the structural safety and reliability of reinforced concrete structures.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.3
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• pp.68-74
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• 2014

As the number of ECUs (Electronic control units) are increasing, reliability and functional stability of a software in an ECU is getting more important. Therefore the application of functional safety standards ISO 26262 is making the software more reliable. Software fault injection test (SFIT) is required as a verification technique for the application of ISO 26262. In case of applying SFIT, an artificial error is injected to inspect the vulnerability of the system which is not easily detected during normal operation. In this paper, the basic concept of SFIT will be examined and the application of SIFT based on ISO26262 will be described.

• Proceedings of the Korean Society for Quality Management Conference
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• 2004.04a
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• pp.261-265
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• 2004

As a car is a combination of a lot of components, it is necessary to consider safety and durability. Even there are lots of components for a car, the connector is one of the most important one since it connects functional electric signal. Usually automotive connector is tested under each car maker's test specification, which should have dependability characteristic. In this paper, we aim to review the current test specifications in view of dependability, and propose an accelerated life test for the automotive connector.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2011.11a
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• pp.151-154
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• 2011

법률 중심적인 사양위주 설계의 한계를 극복하고자 국내 외 다양한 분야에서 성능위주 설계가 사용되고 있다. 국내에 도입된 소방 설비에 대한 성능위주 설계는 도입단계로 볼 수 있어, 선진국의 사례를 통해 도입 초기인 현재 발생할 수 있는 문제점과 대안을 분석하였다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.05a
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• pp.99-100
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• 2006

철도안전법의 제정 및 시행에 즈음하여 철도안전관리에 대한 인식이 제고되고 있는 시점에서 인적요소를 고려한 전기철도안전관리기법을 제시한다. 이를 위해서는 인적신뢰성분석이 필요하나 현재로서는 세계적으로도 이에 관한 규격이 정비되어 가고 있는 실정으로서 국내에서는 규격 적합성 인증 제도가 아직 구축되어 있지 못하고 따라서 규격 정비의 진행에 따라 위험성정보교환에 관련된 대책의 필요성이 증가하고 안전성의 확률론적 정량적평가가 보다 중요시 될 것으로 예상된다. 본고에서는 시스템 위험도분석을 통한 안전공학적 절차를 준수함으로써 위험도를 정량적으로 평가하고 정량적으로 평가된 위험도를 적정 수준으로 관리함으로써 철도시스템 안전관리체계를 향상시킬 수 있는 기법으로서 최근 주목받고 있는 인적신뢰성분석기법과 위험도정보교환에 대한 기본 개념을 제시한다.

• 한국항공운항학회:학술대회논문집
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• 2015.11a
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• pp.242-246
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• 2015

항공기 엔진 체계의 신뢰성과 안전성을 분석하는 것은 RAM 분석이라고 한다. RAM은 제작자가 개발한 시스템의 지속가능성 혹은 그 체계의 수명주기비용(Lice Cycle Cost)에 중대한 영향을 줄 수 있는 시스템 설계특성을 의미한다. 또한 RAM은 시스템이 개발될 당시에 의도된 임무를 수행할 수 있는 능력 혹은 임수수행을 성공할 수 있도록 담보하는 중요한 역할을 한다. RAM은 1970년대 이후 미국 군수분야에서는 군수지원성분석(LSA, Logistic Support Analysis) 과 밀접히 연계되어 활용되어 왔으며, RAM과 LSA를 통합하여 종합군수지원체계(ILS, Integrated Logistics Support)라고 부른다. 본 연구에서는 항공기 엔진에 대한 신뢰성 분석에 Weibull 분포를 활용하였다. Weibull 분포는 2개의 변수 적용에서 다음과 같이 정의된다. 변수가 그 계의 어떤 값을 나타내느냐에 따라 분포도 곡선의 특성 의미는 변수에 의존된다. 예를 들어 시험성적, 사회적 특성을 표현하는 인지도, 산업 제품의 고장이나 결함을 나타내는 고장관련 모수(변수) 등에 따라 그 특징을 나타내게 된다. 항공기 엔진의 신뢰성 분석을 통해 항공기 엔진의 수명 판단이 가능해졌으며 임무 불가능 수준의 In-Flight Shut-Down 비율이 현격히 감소됨을 확인할 수 있었다.

• Computational Structural Engineering
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• v.10 no.1
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• pp.173-183
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• 1997

In this paper a method is suggested for the probabilistic analysis of impact buckling failure time of cylinder with random axisymmetric geometric imperfection under axial impact. Failure is assumed as axisymmetric radial deformation exceeds the given criteria for the first time. For the generation of random geometric initial imperfection, random field theory by mean function and autocorrelation function of geometric imperfection is used. Suggested method is useful for the treatment of the randomness of realistic geometric imperfection and can be used for the structural safety analysis of cylinder considering its effect.