• International Journal of Precision Engineering and Manufacturing
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• 제5권4호
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• pp.61-68
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• 2004

Necessity to address engineering system uncertainties in design processes has long been acknowledged. To obtain quality of product, a safety factor is traditionally used by many design engineers due to its easy of use and comprehension. However, the safety factor approach often yields either conservative or unreliable designs, since it ignores the type of probability distribution and the mechanism of uncertainty propagation from the input to the output. For a consistent reliability-based design, two fundamental issues must be investigated thoroughly. First, the design-decision process that clearly identifies a mechanism of uncertainty propagation under system uncertainties needs to be developed, which must be an efficient and accurate process. To identify the mechanism more effectively, an adaptive probability analysis is proposed by adaptively setting probability levels through a posteriori error estimation. The second is to develop the design process that not only yields a high quality design but also a cost-effective optimum design from manufacturing point of view. As a result, a response surface methodology is specially developed for RBDO, thus enhancing numerical challenges of efficiency and complicatedness. Side crashworthiness application is used to demonstrate the integrated design process for product and manufacturing process design.

• 한국경영과학회지
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• 제20권2호
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• pp.39-60
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• 1995

In this paper, an integration of stochastic dynamic programming (SDP), integer goal programming (IGP) and analytic hierarchy process (AHP) is proposed to handle multiobjective-multicriteria sequential decision making problems under uncertainty inherent in R & D investment planning. SDP has its capability to handle problems which are sequential and stochastic. In the SDP model, the probabilities of the funding levels in any time period are generated using a subjective model which employs functional relationships among interrelated parameters, scenarios of future budget availability and subjective inputs elicited from a group of decision makers. The SDP model primarily yields an optimal investment planning policy considering the possibility that actual funding received may be less than anticipated one and thus the projects being selected under the anticipated budget would be interrupted. IGP is used to handle the multiobjective issues such as tradoff between economic benefit and technology accumulation level. Other managerial concerns related to the determination of the optimal project portifolio within each stage of the SDP model. including project selection, project scheduling and annual budget allocation are also determined by the IGP. AHP is proposed for generating scenario-based transformation probabilities under budgetary uncertainty and for quantifying the environmental risk to be considered.

• Earthquakes and Structures
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• 제17권5호
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• pp.463-475
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• 2019

In this paper, a procedure to develop fragility curves of structures equipped with semi-active tuned mass dampers (SATMDs) considering multiple failure criteria has been presented while accounting for the uncertainties of the input excitation, structure and control device parameters. In this procedure, Latin hypercube sampling (LHS) method has been employed to generate 30 random SATMD-structure systems and nonlinear incremental dynamic analysis (IDA) has been conducted under 20 earthquakes to determine the structural responses, where failure probabilities in each intensity level have been evaluated using Monte Carlo simulation (MCS) method. For numerical analysis, an eight-story nonlinear shear building frame with bilinear hysteresis material behavior has been used. Fragility curves for the structure equipped with optimal SATMDs have been developed considering single and multiple failure criteria for different performance levels and compared with that of uncontrolled structure as well as structure controlled using passive tuned mass damper (TMD). Numerical analysis has shown the capability of SATMDs in significant enhancement of the seismic fragility of the nonlinear structure. Also, considering multiple failure criteria has led to increasing the fragility of the structure. Moreover, it is observed that the influence of the uncertainty of input excitation with respect to the other uncertainties is considerable.

• Wind and Structures
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• 제11권1호
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• pp.51-70
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• 2008

CFD is applied to evaluate pedestrian wind comfort at outdoor platforms in a high-rise apartment building. Model validation is focused on generic building sub-configurations that are obtained by decomposition of the actual complex building geometry. The comfort study is performed during the design stage, which allows structural design changes to be made for wind comfort improvement. Preliminary simulations are performed to determine the effect of different design modifications. A full wind comfort assessment study is conducted for the final design. Structural remedial measures for this building, aimed at reducing pressure short-circuiting, appear to be successful in bringing the discomfort probability estimates down to acceptable levels. Finally, the importance of one of the main sources of uncertainty in this type of wind comfort studies is illustrated. It is shown that the uncertainty about the terrain roughness classification can strongly influence the outcome of wind comfort studies and can lead to wrong decisions. This problem is present to the same extent in both wind tunnel and CFD wind comfort studies when applying the same particular procedure for terrain relation contributions as used in this paper.

• 대한산업공학회지
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• 제10권1호
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• pp.27-36
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• 1984

This paper examines the influence of the uncertainty in demand and lead time on the relative performances of ten well-known single stage lot-sizing rules in a rolling schedule environment. Two other factors, coefficient of variation and time between orders, which may affect the performances of the rules are also considered. To compare the rules under an identical condition, 100% service level is set by introducing safety stocks. The effects of various factor levels are checked statistically by the pairwise t-test and the results show that the uncertainty of the environment has a strong influence on the performance of the rules.

• Ocean Systems Engineering
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• 제2권1호
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• pp.1-16
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• 2012

Offshore wind turbines are complex structural and mechanical systems located in a highly demanding environment. This paper proposes a multi-level system approach for studying the structural behavior of the support structure of an offshore wind turbine. In accordance with this approach, a proper numerical modeling requires the adoption of a suitable technique in order to organize the qualitative and quantitative assessment in various sub-problems, which can be solved by means of sub-models at different levels of detail, both for the structural behavior and for the simulation of loads. Consequently, in a first place, the effects on the structural response induced by the uncertainty of the parameters used to describe the environmental actions and the finite element model of the structure are inquired. After that, a meso-level FEM model of the blade is adopted in order to obtain the detailed load stress on the blade/hub connection.

• 한국유통학회지:유통연구
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• 제2권1호
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• pp.115-141
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• 1997

This study examines the effects of economic and relational dimensions of supplier-distributor relationship on distributors intents to leave. A survey of 121 computer hardware distributors revealed that distributors commitment to the relationship and their transaction-specific investment would decrease directly the level of withdrawal intention. Other relational dimensions such as the procedural and distributive fairness, the morality of aspiration, and economic dimensions such as the transaction-specific investment made by the supplier and distributors expectations fo future performance increase indirectly the level of withdrawal intension via affecting either trust or commitment. The present study also found that perceived uncertainty and relative dependence might moderate the effects the economic and relational dimensions on distributors intents to leave. Relational dimensions, when compared to economic dimensions, tend to have stronger impacts on withdrawal intentions under high levels of uncertainty and relative dependence.

• 한국방사성폐기물학회:학술대회논문집
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• 한국방사성폐기물학회 2005년도 춘계 학술대회
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• pp.49-55
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• 2005

Unconditional clearance levels were derived for fifteen short-lived radionuclides. Due to the uncertainty of long-term radiological impact analysis, alpha emitting nuclides and nuclides with half-lives longer than 30 years (except for C-14) were excluded from the scope of this study. The candidate waste streams are solid wastes and waste oil generated from nuclear power reactors. The clearance levels were derived by generic assessment for enveloping scenarios, along with specific assessment for each detailed scenario such as landfill, incineration and recycling. The derived values lie in the range from 0.01 to 100 Bq/g.

• 기술혁신학회지
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• 제12권1호
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• pp.212-236
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• 2009

본 연구는 차세대 컨버전스서비스를 대상으로 고객, 기술, 사업자, 규제의 4대 이슈별로 환경 불확실성요인을 규명하고, 이들 환경 불확실성요인 중 특히 핵심이 되는 불확실성 요인을 도출하였다. 이어 도출된 핵심불확실성요인(KUF: Key Uncertainty Factor)을 중심으로 환경의 잔여불확실성 수준에 대한 평가를 시나리오 플래닝에 의해 실시하고, 이를 기반으로 차세대 컨버전스서비스의 진입전략 수립을 위한 방향을 제시하였다. 본 연구의 차세대 컨버전스서비스 사업의 불확실성 평가 및 진입 시나리오 구성에 대한 연구결과를 종합하면 다음과 같다. 2가지 잔여 불확실성 수준(선택 가능한 미래 수준, 예측 범위의 미래 수준)의 6개 시나리오를 대상으로 각각의 전략적 속성을 평가한 결과 시장 진입의 성공 요소로 2가지 핵심성공요인(KSF: Key Success Factor)을 도출하였다. 즉, 고객수요추세, 광고규제 완화를 핵심성공요인(KSF: Key Success Factor)으로 도출하였으며, 이를 토대로 4가지 전략적 시나리오 유형 및 각 시나리오 별 요구되는 사업자 대응역량에 대한 방향성을 제시하였다. 본 연구의 결과는 컨버전스 시장의 활성화는 물론 관련 사업자의 자원의 효율적 배분, 진입형태, 진입 적정시기 등 진입전략 수립에 많은 시사점을 제공할 것이다.

• 한국콘텐츠학회논문지
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• 제13권7호
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• pp.168-180
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• 2013

본 연구는 한국 TV 드라마 제작 산업을 대상으로 하여 환경 변화에 따른 드라마 제작자의 대응 전략 변화를 분석하였다. 구체적으로 본 연구에서는 전략적 상황이론에 근거하여, 상이한 환경특성을 가진 두 시기 사이에 드라마 제작자들이 제작한 드라마의 장르 다양성 수준에 차이가 있는지를 검증하였다. 실증분석결과, 안정적인 환경특성의 시기(1994년-2002년)보다 불확실성이 높은 환경특성의 시기(2003년-2009년)에 장르 다양성 수준이 높은 것으로 나타났다. 이러한 결과는 드라마 제작자가 안정적인 환경에서는 동일한 장르를 반복적으로 활용하여 효율을 추구하는 반면, 불확실한 환경에서는 장르의 다양성을 높여 혁신을 추구하는 방식으로 환경특성에 적합한 전략을 사용한다는 것을 시사하고 있다.