• 산업경영시스템학회지
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• 제44권4호
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• pp.220-226
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• 2021

In supply chain, there are a variety of different uncertainties including demand, service time, lead time, and so forth. The uncertainty of demand has been commonly studied by researchers or practitioners in the field of supply chain. However, the uncertainty of upstream supply chain has also increased. A problem of uncertainty in the upstream supply chain is the fluctuation of the lead time. The stochastic lead time sometimes causes to happen so called the order crossover which is not the same sequences of the order placed and the order arrived. When the order crossover happens, ordinary inventory policies have difficult to find the optimal inventory solutions. In this research, we investigate the lead time distribution in case of the order crossover and explore the resolutions of the inventory solution with the order crossover.

• Communications for Statistical Applications and Methods
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• 제27권6호
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• pp.641-647
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• 2020

The 2 × 3 crossover design, a modified version of the 3 × 3 crossover design, is considered to compare the bioavailability of two generic candidates with a reference drug. The 2 × 3 crossover design is more economically favorable due to decrease in the number of sequences, rather than conducting a 3×3 crossover trial or two separate 2 × 2 crossover trials. However, when using a higher-order crossover trial, the risk of drop-outs and withdrawals of subjects increases, so the suitable statistical inferences for missing data is needed. The bioequivalence model of a of 2×3 crossover trial with missing data is defined and the statistical procedures of assessing bioequivalence is proposed. An illustrated example of the 2 × 3 trial with missing data is also presented with discussion.

• 응용통계연구
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• 제29권2호
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• pp.279-289
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• 2016

최근 식품의약품안전처는 의약품동등성시험기준에 고변동성 제제의 생물학적 동등성(생동성) 평가 기준을 넓혀주는 새로운 규정을 추가하면서 고차 교차설계법을 활용하여 생동성 평가를 하는 논의가 확대되고 있다. 확장된 생동성 기준을 적용하기 위해서는 3기간 이상의 교차설계법이 적용되어야 하지만 아직 관련된 논의가 많이 이루어지지 않고 있다. 본 연구에서는 $3{\times}3$ 교차설계법에 기초한 생동성 평가의 통계적 추론과정을 제시하고 논의한다. 또한 사례를 통해 $3{\times}3$ 교차설계법을 활용한 생동성 평가를 식품의약품안전처 의약품동등성시험기준에 따라 진행하고 그 의미를 논의한다.

• 대한산업공학회지
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• 제20권3호
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• pp.15-34
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• 1994

This paper considers the genetic algorithms(GAs) for the mixed model assembly line sequencing(MMALS) in which the objective is to minimize the overall line length. To apply the GAs to the MMALS, the representation, selection, genetic sequencing operators, and genetic parameters are studied. Especially, the existing sequencing binary operators such as partially map crossover(PMX), cycle crossover(CX), and order crossover (OX) are modified to be suitable for the MMALS, and a new sequencing binary operator called immediate successor relationship crossover (ISR) is introduced. These binary operators mentioned above and/or unary operators such as swap, insertion, inversion, displacement, and splice are compared to find operators which work well in the MMALS. Experimental results indicate that 1) among the binary operators ISR operator is the best, followed by the modified OX, and the modified PMX, with the modified CX being the worst, 2) among the unary operators inversion operator is the best, followed by displacement, swap, and insertion, with splice being the worst, and 3) in general, the unary operators perform better than the binary operators for the MMALS.

• Macromolecular Research
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• 제16권6호
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• pp.524-531
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• 2008

The mitigation or elimination of methanol crossover for perfluorosulfonic acid fuel cell membranes has been investigated extensively for direct methanol fuel cell applications with the aim of increasing the electrochemical performance and enhancing the utilization rate of methanol. Self-assembly modifications by applying an oppositely charged polyelectrolyte to Nafion membranes were attempted in order to block or reduce methanol crossover while maintaining the other advantageous properties of Nafion membranes. It was reported that anionic polyallylamine hydrochloride (PAH) was the most efficient polyelectrolyte in reducing methanol crossover, and considerable cell performance was obtained even at a methanol feed concentration of 10 M.

• 응용통계연구
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• 제20권1호
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• pp.39-52
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• 2007

협심증 치료의 신약에 대한 교차계획 임상시험(crossover clinical trials)에서 신약의 효능을 알아보는 운동테스트(treadmill exercise test) 결과는 중도절단 생존시간(censored survival times)으로 측정된다. 이 논문에서는 교차계획에서 수집된 중도절단 생존자료의 여러 가지 분석법에 대해 설명한다. 중도절단을 감안한 비모수적 방법들과 층화 Cox 비례위험모형 (stratified Cox proportional hazards model)에 근거한 분석법이 제시되었다. 한편, 교차계획의 두 시기에 걸쳐 수집된 생존시간의 차(difference)로부터 구간절단자료(interval censored data)가 생성되며 이에 근거한 분석법으로서 이 논문에서는 구간절단자료에 대한 Cox 비례위험모형 (proportional hazards model)의 가능성을 알아보며, 예제 자료로써 여러 방법들의 결과를 비교해 본다.

• 산업경영시스템학회지
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• 제39권4호
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• pp.81-89
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• 2016

Distributed genetic algorithm (DGA), also known as island model or coarse-grained model, is a kind of parallel genetic algorithm, in which a population is partitioned into several sub-populations and each of them evolves with its own genetic operators to maintain diversity of individuals. It is known that DGA is superior to conventional genetic algorithm with a single population in terms of solution quality and computation time. Several researches have been conducted to evaluate effects of parameters on GAs, but there is no research work yet that deals with structure of DGA. In this study, we tried to evaluate performance of various genetic algorithms (GAs) for the famous symmetric traveling salesman problems. The considered GAs include a conventional serial GA (SGA) with IGX (Improved Greedy Crossover) and several DGAs with various combinations of crossover operators such as OX (Order Crossover), DPX (Distance Preserving Crossover), GX (Greedy Crossover), and IGX. Two distinct immigration policies, conventional noncompetitive policy and newly proposed competitive policy are also considered. To compare performance of GAs clearly, a series of analysis of variance (ANOVA) is conducted for several scenarios. The experimental results and ANOVAs show that DGAs outperform SGA in terms of computation time, while the solution quality is statistically the same. The most effective crossover operators are revealed as IGX and DPX, especially IGX is outstanding to improve solution quality regardless of type of GAs. In the perspective of immigration policy, the proposed competitive policy is slightly superior to the conventional policy when the problem size is large.

• 전기화학회지
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• 제5권4호
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• pp.226-231
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• 2002

Power densities produced by the permeation of methanol through membranes were directly measured by inserting the membrane in front of anode in a membrane-electrode-assembly of a direct methanol fuel cell (DMFC). The power density was closely related to the loss of power in the DMFC and was strongly affected by temperature. As the cell temperature was increased, the power density resulting from methanol crossover was increased. The increase in methanol crossover had be attributed to diffusion caused or affected by temperature. Methanol crossover a major effect on the performance of a DMFC at a relatively low temperature with $26\%\;loss\;at\;30^{\circ}C$. In order to reduce methanol crossover, a conventional Nafion membrane was modified by the incorporation of Pt or Pd. The reduction in methanol crossover was investigated in these modified membranes by our cell performance measurement. Pt and Pd particles incorporated in the Nafion membranes block methanol pathway and prevent methanol transport through the membranes, which was proved by combining with liquid chromatography.

• 한국지능시스템학회논문지
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• 제14권5호
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• pp.563-570
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• 2004

Genetic algorithms have been successfully applied to various optimization problems belonging to NP-hard problems. The sequential ordering problems(SOP) and the job shop scheduling problems(JSP) are well-known NP-hard problems with strong influence on industrial applications. Both problems share some common properties in that they have some imposed precedence constraints. When genetic algorithms are applied to this kind of problems, it is desirable for genetic operators to be designed to produce chromosomes satisfying the imposed precedence constraints. Several genetic operators applicable to such problems have been proposed. We call such genetic operators precedence-preserving genetic operators. This paper presents three existing precedence-preserving genetic operators: Precedence -Preserving Crossover(PPX), Precedence-preserving Order-based Crossover (POX), and Maximum Partial Order! Arbitrary Insertion (MPO/AI). In addition, it proposes two new operators named Precedence-Preserving Edge Recombination (PPER) and Multiple Selection Precedence-preserving Order-based Crossover (MSPOX) applicable to such problems. It compares the performance of these genetic operators for SOP and JSP in the perspective of their solution quality and execution time.

• 한국엔터테인먼트산업학회논문지
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• 제14권6호
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• pp.151-160
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• 2020

클래식 음악은 '작곡가가 쓴 그대로 연주해야 한다'란 엄격함이 존재했다. 그러나 다양한 개성과 사고를 중시하는 21세기 포스트모더니즘 시대에 들어서면서 전통 클래식 무대를 제외하곤 그 엄격함의 무게가 더 이상 유의미하지 않게 되었다. 클래식의 기품은 간직한 채 엄격한 규칙대신 대중음악의 친숙함을 접목시키며 크로스오버 된 오페라 아리아는 그 동안 어렵게만 느껴졌던 오페라 아리아가 대중들에게 한층 쉽게 다가가며 클래식의 대중화를 이끌어내는 큰 역할을 하게 되었다. 그럼에도 불구하고 클래식 음악을 크로스오버 음악으로 탈바꿈시키는 편곡기법에 관한 연구는 부족한 상황이다. 따라서 본 연구는 객관적 음악분석 방법인 화성, 리듬, 악기 편성 중심으로 기존 선행연구의 연구범위를 확대한 오페라에 대한 크로스오버적 편곡기법을 연구하였다. 분석결과, 원곡과 팝페라 버전은 리듬, 화성에는 유사성을 보이고 있으나 악기 편성에서는 차이점을 보이고 있다. 재즈 버전은 아프로큐반 리듬의 발라드 계열인 볼레로 리듬, 재즈 어쿠스틱 악기 중심의 구성, Tension을 많이 사용한 Voicing을 통해 클래식컬한 느낌을 없애고 재즈의 느낌으로 연출하여 원곡과의 차별을 보이고 있는 것이 특징이었다. 본 연구가 클래식컬 크로스오버 편곡기법 연구 자료로서 유용하게 쓰이길 바란다.