• 품질경영학회지
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• 제43권2호
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• pp.169-184
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• 2015

Purpose: This paper is concerned with optimally designing accelerated degradation test (ADT) plans based on a gamma process for the degradation model. Methods: By minimizing the asymptotic variance of the MLE of the q-th quantile of the lifetime distribution at the use condition, the test stress levels and the proportion of test units allocated to each stress level are optimally determined. Results: The optimal plans of ADT are developed for various combination of parameters. In addition, a method for determining the sample size is developed, and sensitivity analysis procedures are illustrated with an example. Conclusion: It is important to optimally design ADT based on a gamma process under the condition that a degradation process should be always nonnegative and strictly increasing over time.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 춘계학술대회 논문집
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• pp.552-558
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• 1995

Stereolithography is a process used to rapidly produce polymer components directly from a computer-representation of the part. There are several considerations to be made for the efficient use of te process. Especially, the build-up orientation of part critically affect to the part accuracy, total build time and the volume of support structures. Te purpose of this study is to determine the optimal build-up part orientation for the SLA process with improving part accuracy, minimizing total build time, and the volume of supprot structures. The first factor is related to the area of surfaces which have staircase protrusions after solidification, the second factor is related to the total number of layers, and the third factor is related to the area of the surfaces which need to be supported with support structures. An algorithm is developed to calculate the staircase area with quantifying the process planning errors that the volume of materials is supposed to be removed or added to the part, and the optimal layer thickness for the SLA system whichcan hadle the variable layer thickness in different orientations achieved by rotating the given part to the specified finite directions. So the optimal part orientation is determined based on the user's selections of primary criterion and the optimal thickness of layers is calculated at any part orientations.

• Korean Chemical Engineering Research
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• 제58권3호
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• pp.346-355
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• 2020

의약 중간체 제조 공장을 포함한 정밀 화학 산업에서 생산 계획 및 전사적 자원 관리(enterprise resource planning) 관한 의사 결정은 기업 운영 효율성 최적화에 매우 주요한 연구 주제이다. 기존의 의사 결정 시스템은 공장 간의 자원관리와 공장내 생산 계획이 분리되어, 전사적 관점에서의 전역 해를 도출하는데 한계가 있다. 본 연구에서는 무선 식별 시스템(Radio Frequency Identification; RFID) 기반의 실시간 물류 관리 시스템을 이용하여 의약품 중간체 산업의 전사적 자원 관리와 최적 생산 계획 수립을 동시에 수행할 수 있는 의사결정 플랫폼을 개발하고, 실제 제조 공정에 적용하여 그 효과를 분석한다. 기존의 분리된 운영 체제와는 달린 본 연구에서 제안하는 통한 의사결정 플랫폼은 원료 주문 및 운송 시간에 관한 정보가 RFID 기술을 통해 제조 공정 생산 계획 수립의 핵심 데이터로 사용됨으로써, 별도의 재고 관리 시설 없이 공장간 물류 현황에 대응하여 최적 생산 계획이 수립된다. 이를 위하여 제품 생산 시간 최소화를 목적 함수로 설정하고, 마감 기한 및 주문량에 대한 제약조건 등을 포함한 혼합정수선형계획 모델을 개발하였다. 이후 개발된 최적화 모델을 실제 의약품 중간체 생산 문제로 적용함으로써, 제안한 통합 의사결정 플랫폼의 효용성을 입증하였다. 본 연구 결과로 생산 시간 최적화를 위해 단순한 공정 조합을 필요로 하는 생산물이 먼저 제조되고 복잡한 공정 구조를 가진 생산물이 순차적으로 생산되는 생산 일정이 최적임을 확인하였다.

• 대한산업공학회지
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• 제8권2호
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• pp.3-14
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• 1982

The purpose of this study is to establish the function of a sub-system for System Alternatives Feasibility Estimation (SAFE) in R & D Project Planning Phase (RDPPL). It is the fundamental function of the RDPPL/SAFE that selected an optimal planning system alternative of all, considered at RDPPL/SAS, by logical means in view of feasibility. In this paper, improving the function of RDPPL/SAFE, mathmatical models in order to quantify methods determining and integrating the feasibility funtion in each terminal system with a multi-stage process are examined.

• 산업경영시스템학회지
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• 제40권2호
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• pp.111-120
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• 2017

This paper proposes an improved standard genetic algorithm (GA) of making a near optimal schedule for integrated process planning and scheduling problem (IPPS) considering tool flexibility and tool related constraints. Process planning involves the selection of operations and the allocation of resources. Scheduling, meanwhile, determines the sequence order in which operations are executed on each machine. Due to the high degree of complexity, traditionally, a sequential approach has been preferred, which determines process planning firstly and then performs scheduling independently based on the results. The two sub-problems, however, are complicatedly interrelated to each other, so the IPPS tend to solve the two problems simultaneously. Although many studies for IPPS have been conducted in the past, tool flexibility and capacity constraints are rarely considered. Various meta-heuristics, especially GA, have been applied for IPPS, but the performance is yet satisfactory. To improve solution quality against computation time in GA, we adopted three methods. First, we used a random circular queue during generation of an initial population. It can provide sufficient diversity of individuals at the beginning of GA. Second, we adopted an inferior selection to choose the parents for the crossover and mutation operations. It helps to maintain exploitation capability throughout the evolution process. Third, we employed a modification of the hybrid scheduling algorithm to decode the chromosome of the individual into a schedule, which can generate an active and non-delay schedule. The experimental results show that our proposed algorithm is superior to the current best evolutionary algorithms at most benchmark problems.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 하계학술대회 논문집
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• pp.707-710
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• 2000

Optimization of the biphenyl chloromethylation process with para-formaldehyde has been investigated in the presence of ZnCl$_2$with HCI gas by the Box-Wilson method of mathematical planning of experiment. The 4,4'- (dichloromethyl)-biphenyl yield dependence on the biphenyl para-formaldehyde ratio, temperature and reaction duration has been studied. A mathematical model of the process has been developed and optimal conditions for the biphenyl chloromethylation procedure has been determined.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2004년도 SMICS 2004 International Symposium on Maritime and Communication Sciences
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• pp.77-79
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• 2004

Optimization of the biphenile chloromethylation process with paraphormaldegide has been done in the presence of ZnCl$_2$ with HCI gas by the Box-Wilson method of mathematical planning of experiment. The 4, 4'-( dichloromethyl)-biphenile yield dependence on the biphenile - paraphormaldegide ratio, temperature and reaction duration has been studied. A mathematical model of the process has been developed and optimal conditions for the biphenile chloromethylation procedure has been determined

• 동굴
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• 제73호
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• pp.1-8
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• 2006

Optimization of the biphenile chloromethylation process with paraphormaldegide has been done in the presence of $ZnCl_2$ with HCl gas by the Box-Wilson method of mathematical planning of experiment. The 4,4'-(dichloromethyl)-biphenile yield dependence on the piphenile -paraphormaldegide ratio, temperature and reaction duration has been studied. A mathematical model of the process has been developed and optimal conditions for the biphenile chloromethylation procedure has been determined.

• International Journal of Precision Engineering and Manufacturing
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• 제1권2호
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• pp.35-42
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• 2000

To save time and cost in assembly process and to improve th quality of products, it is very important to choose and optimal assembly sequence. In this paper, we propose a methodology that generates an optimal assembly sequence by using various methods and the knowledge of experts. To illustrate the effectiveness of the proposed methodology, a knowledge-based system is developed, The built system is applied to the case of UBR(Unit Bath Room). The applying result showed the applicability of the developed system.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2004년도 춘계 학술발표대회 개요집
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• pp.18-20
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• 2004

This study is to find the optimal work plan of robot welding in the subassembly process of shipbuilding and to verify the found solution through 3-D simulation. The optimal work plan was established by evenly distributing the work amount to each stage and finding the shortest work sequence. The shortest work sequence was found by using the genetic algorithm. The result was compared with the practically adopted case and verified through the 3-D simulation.