핵연료 탄성계수 측정기의 시스템 교정

양재환,박창제,류호진,나상호,강권호 한국방사성폐기물학회 2009 한국방사성폐기물학회 학술논문요약집 Vol.7 No.1

방사성 아이오딘을 흡착한 AgX의 유리화 가능성 연구

양재환,신진명,박장진,김영자,이영순,이도연,박근일 한국방사성폐기물학회 2012 한국방사성폐기물학회 학술논문요약집 Vol.10 No.1

문제 특성과 알고리듬 수행 능력 간 관계에 관한 분석: 0-1 Knapsack 문제에 관한 사례 연구

양재환,김현수 한국경영과학회 2006 韓國經營科學會誌 Vol.31 No.1

We perform a computational study on 0-1 knapsack problems generated under explicit correlation induction. A total of 2000 100-variable test problems are solved. We use two solution methods:(1) a well known heuristic and (2) a representative branch and bound type algorithm. Two different performance measures are considered:(1) the number of nodes needed to find an optimal solution and (2) the relative error of the heuristic solution. We also examine the effect of different joint probability mass functions (pmfs) for the coefficient values on the performance of the solution procedure.

Customer Order Scheduling in a Two Machine Flowshop

양재환,Ph.K. 대한산업공학회 2011 대한산업공학회 춘계학술대회논문집 Vol.2011 No.5

Hybrid Flow Shop with Parallel Machines at the First Stage and Dedicated Machines at the Second Stage

양재환 대한산업공학회 2015 Industrial Engineeering & Management Systems Vol.14 No.1

In this paper, a two-stage hybrid flow shop problem is considered. Specifically, there exist identical parallel machines at stage 1 and two dedicated machines at stage 2, and the objective of the problem is to minimize makespan. After being processed by any machine at stage 1, a job must be processed by a specific machine at stage 2 depending on the job type, and one type of jobs can have different processing times on each machine. First, we introduce the problem and establish complexity of several variations of the problem. For some special cases, we develop optimal polynomial time solution procedures. Then, we establish some simple lower bounds for the problem. In order to solve this NPhard problem, three heuristics based on simple rules such as the Johnson’s rule and the LPT (Longest Processing Time first) rule are developed. For each of the heuristics, we provide some theoretical analysis and find some worst case bound on relative error. Finally, we empirically evaluate the heuristics.

No Tardiness Rescheduling with Order Disruptions

양재환 대한산업공학회 2013 Industrial Engineeering & Management Systems Vol.12 No.1

This paper considers a single machine rescheduling problem whose original (efficiency related) objective is minimizing makespan. We assume that disruptions such as order cancelations and newly arrived orders occur after the initial scheduling, and we reschedule this disrupted schedule with the objective of minimizing a disruption related objective while preserving the original objective. The disruption related objective measures the impact of the disruptions as difference of completion times in the remaining (uncanceled) jobs before and after the disruptions. The artificial due dates for the remaining jobs are set to completion times in the original schedule while newly arrived jobs do not have due dates. Then, the objective of the rescheduling is minimizing the maximum earliness without tardiness. In order to preserve the optimality of the original objective, we assume that no-idle time and no tardiness are allowed while rescheduling. We first define this new problem and prove that the general version of the problem is unary NP-complete. Then, we develop three simple but intuitive heuristics. For each of the three heuristics, we find a tight bound on the measure called modified z-approximation ratio. The best theoretical bound is found to be 0.5 −ε for some ε > 0, and it implies that the solution value of the best heuristic is at most around a half of the worst possible solution value. Finally, we empirically evaluate the heuristics and demonstrate that the two best heuristics perform much better than the other one

주택연금의 최적 수요자 계층분석을 통한 장수리스크 완화 효과에 관한 연구

양재환,여윤경 한국금융학회 2014 금융연구 Vol.28 No.4

The objective of this study is to examine how much longevity riskcan be alleviated by using the reverse mortgage loan system in Korea(JooTaekYeonKeum, JTYK). In details, we compare expected utility valueof JTYK users during the retirement period with that of non-JTYK users,and try to identify characteristics of the groups which earn most benefitsout of the JTYK in terms of the expected utility value. To achieve this goal,we used data from the 2011 Korean Retirement and Income Study (KReIS)of National Pension Research Institute and extracted relevant demographicdata of the households lead by a male householder, whose age is rangedfrom 60 to 65 years. For each household with a specific age of the headand value of the house its members reside, different monthly payment streamsfrom the JTYK according to four different payment types were obtained,and by using a mathematical model whose objective is to maximize expectedutility function during the retirement period, the maximum expected utilityvalues were calculated by assuming that (1) the household uses the JTYKand (2) the household does not use the JTYK and self-annuitizes the wealth. For analysis, we first define the difference of utility value from the twoassumptions, i.e. the utility value from the assumption (1) -utility valuefrom the assumption (2) as the amount of effect of longevity risk alleviationby using the JTYK. Then, ANOVA (analysis of variance) and multi-variateregression analyses were performed. The results of the ANOVA indicate that the effect of longevity riskalleviation by using the JTYK is significantly different among groups bynet wealth excluding house, income and consumption. The direction of the differences is opposite to the housing cost of non-JTYK users during theretirement period. Many effects in the multi-variate analyses are consistentwith major effects shown in the ANOVA. Specifically, the results of theregression, in which the other factors are controlled, show that the effectof longevity risk alleviation by the JTYK is significantly different as thevalue of house, net wealth except the house value, age of the householder,or public pension changes. Furthermore, the direction of the effect for thecases where the housing cost during the retirement period of non-JTYKusers is no larger than 30% of value of the house is opposite to that forthe cases where the housing cost of non-JTYK users is no less than 50%of value of the house. The results of this study suggest that the housingcost during the retirement be a crucial factor when individuals considerin opting for the JTYK and policy makers try to improve the design of the JTYK. 본 연구는 주택연금의 수요자 입장에서 주택연금을 활용함으로써 장수리스크를 얼마나 완화시킬수 있는가를 규명하고자 시도되었다. 구체적으로 주택연금의 이용자와 비이용자의 효용가치를비교함으로써 주택연금의 최적 수요자 집단의 특성을 분석하였다. 이러한 연구목적을 위하여국민연금연구원의 국민노후보장패널조사자료를 이용하여 연령이 60세~65세인 남성 가구주가구를 추출하였고 이들이 거주하고 있는 주택의 가치에 기초하여 주택연금액을 도출하고 이를기대효용 최적화모형에 적용시켜 주택연금 이용 시의 효용가치와 이용하지 않을 경우의 효용가치를추정하여 서로 비교하였다. 주택연금을 이용하였을 경우 증가 혹은 감소되는 효용가치를 주택연금의 장수리스크 완화효과로 정의하고 영향을 미치는 요인을 도출하기 위하여 분산분석과회귀분석을 실시하였다. 분산분석 결과 주택연금의 장수리스크 완화효과는 주택 외 순자산,공적연금, 소득, 소비수준의 집단별로 의미 있는 차이를 보이는 것으로 나타났는데 그것은 주택연금을 비이용자의 주거비 규모의 비중에 따라서 정반대의 방향성을 보였다. 회귀분석 결과에서도주택연금의 지급방식과 관계없이 주택연금의 장수리스크 감소효과에 영향을 미치는 변수들은주택가격, 주택 외 순자산, 가구주 연령, 공적연금소득으로 매우 일관성 있게 나타났다. 그러나주택연금 비이용자의 주거비 비중이 30% 이하인 경우와 50% 이상인 경우는 이러한 변수들의영향력이 상반되는 방향으로 작용하였다. 본 연구의 결과는 주택연금 가입에 관한 의사결정과향후 주택연금상품의 확장적 설계에 있어서 연금 가입자의 주거비 부분이 중요한 고려대상이되어야 함을 시사해 준다.

1단계에 전용 기계가 있는 2단계 하이브리드 Flow Shop

양재환 한국경영과학회 2013 한국경영과학회 학술대회논문집 Vol.2013 No.5

Customer Order Scheduling in a Two Machine Flowshop

양재환,Ph.K. 한국경영과학회 2011 한국경영과학회 학술대회논문집 Vol.2011 No.5

방사성 요오드 기체의 포집을 위한 비스무스와 요오드의 반응친화성 탐색

양재환,신진명,박장진,유재욱,백영희,박근일 한국방사성폐기물학회 2014 한국방사성폐기물학회 학술논문요약집 Vol.2014 No.05