Server Assignment Policy for Minimizing the Output Variability of a Pull Serial Line : PULL 흐름라인의 산출량 변동성을 최소화하는 작업자 배정안

Choe Sang Woong(최상웅),金彩福, 윤재곤 한국산업경영학회 2003 한국산업경영학회 발표논문집 Vol.- No.-

Variability and unevenness in processing times create a problem of imbalance in the production system. So in a pull serial line, even though the product is expected to come out of the preceding cell ""Just In Time"", yet this imbalance creates different problems of unequal utilization of server, fluctuation of production rate, creation of temporary inventory, blocking and starvation in the line. The prior knowledge of these consequential results of different configurations of imbalance in a pull serial line will help the operations manager to control the production in more efficient ways such as the optimal ordering(assigning) of servers. Relatively much attention has being given by the research community to the assignment of servers in a push serial line. But little effort has been put toward such work in a pull serial line. In this study, we consider a pull serial line as tandem queueing networks with finite buffer capacities and address the issue of assigning the servers so that the variation of the output is minimized. For simplicity, we assume that each server can work on only one job at a time, that several servers can not work together on one job and that the number of cells equals the number of servers. Furthermore, assume that the service rates depend only on the servers. Without loss of generality, each server is cross-trained to work at all cells. Also, it is considered as given two boundary conditions that there is an infinite supply of raw materials to the cell (1) and external demands are permitted to be backlogged. Note that these boundary conditions are not required to support the theoretical results, but to help simplify the details. We can gain much by analyzing pull systems and obtaining theoretical results in a general environment. Particularly, valuable is the variability propagation property gained from the analysis; it is this property that helps in developing efficient assignment policies of servers. Based on the variability propagation property, we propose a policy - (RULE 1) for assigning the servers. (RULE 1) refers to the assignment of servers obtained by unbalancing a pull serial line such that the mean or the variance of service times decreases progressively from cell (1) to cell (m). Numeric results illustrate that (RULE 1) always agrees with the optimal assignment of servers.

Proof of the variability propagation principle in a pull serial line : existence and measurement

최상웅(Sang-Woong Choe) 한국경영과학회 2002 한국경영과학회 학술대회논문집 Vol.2002-A No.-

A pull serial line considered in this paper has an infinite supply of raw materials and permits backlogged demands in addition The ultimate objective of this study is to prove the vanability propagation principle in a pull serial line and is to measure it in terms of the first two moments of the inter-departure process subject to given service rate, demand rate and number of cards in each cell.<br/> Two preparations are required to achieve this objective The one is to derive a true lower bound of variance of the inter-departure process This lower bound can be used in any approximate distribution associated with performances under a general service scheme The other is to establish a constramed discrete minimax problem for the no backorder(backlogging) probability in each cell Necessary and sufficient conditions for the existence of optimal solution which enables us to get insight to the variability propagation prunciple in a pull serial line are theoretically provided Applying the implicit function theorem to this no backorder(backlogging) probability we may get some fundamental results necessary to a completion for the proof<br/> Finally, a numeric model used to measure the vallability propagation principle is proposed and solved.

공액구배법을 이용한 역전파 학습 알고리듬 수정 및 학습계수 최적화

최상웅(Sang Woong Choe),이진춘(Jinchoon Lee) 한국지능시스템학회 1999 한국지능시스템학회논문지 Vol.9 No.1

거래자료 기반의 능력계획

최상웅(Choe, Sang-Woong) 한국의사결정학회 2014 의사결정학연구 Vol.22 No.2

탐색적 자료분석 접근법을 이용하여, 높은 다양성으로 대표되는 주문생산 환경의 거래자료에 내포된 의미있는 현상들을 연구하고자 한다. 사용되는 거래자료에는 2년간(2012년-2013년)의 주문내역이 기록되어 있다. 주문내역은 주문도착시점, 주문인도시점, 주문명세(제품모델, 해당 모델의 총중량, 주문수량) 그리고 자체생산 혹은 하청생산 여부 등으로 구성된다. 생산능력 부족에 대처하는 방법들 중 하나인 하청생산을 함께 운영하는 주문생산시스템을 대상으로, 거래자료를 기반으로 하여 생산능력계획에 대한 대기행렬이론 관점을 소개하고자 한다. 이 논문에서는, 대기행렬을 직접 관찰하는 것이 아니라, 단지 거래자료에서 추론함으로써, 대기행렬 통계량(대표값)을 도출하는 방법을 제안한다. We use Exploratory Data Analysis to study transactional data, which contain significant phenomena in Make-to-Order environments characterized by high variety. The transactional data we obtained contain records of order, including its arrival time, departure time, arrival mode(product model, gross weight, quantity) and type of acceptance(in-housing or subcontracting) over a period of two years(2012-2013). We seek to introduce a queueing-theory perspective of a data-based production capacity planning in Make-to-Order systems, where subcontracting could be an important way of overcoming capacity shortages. In this paper, we propose a way to derive the queue statistics only by drawing inferences from the transactional data, not by observing the queue.

기술이전에 대한 동적 분석

최상웅(Choe, Sang-Woong) 한국의사결정학회 2014 의사결정학연구 Vol.22 No.2

이 논문에서는 기술선도주자(기술제공자)와 기술후발주자(기술도입자)의 동적 행태를 기술하는 연립미분방정식을 제안한다. 연립미분방정식의 해를 해석적으로 구하고, 이를 이용하여 상대기술수준과 기술격차를 정의한다. 향후 보다 세밀히 논의할 가치가 있는 두 가지 사실을 발견했다. 하나는 상대기술수준이 로지스틱 곡선을 형성한다는 사실이고, 다른 하나는 기술후발주자(기술도입자)의 내적 기술개발률(학습률)이 기술선도주자(기술제공자)의 그것보다 크거나 같을 때만 기술추월이 실행 가능하다는 사실이다. This article presents a system of differential equations to describe the dynamic behaviors of the technological leader(transferor) and follower (transferee). These coupled differential equations yield an analytic solution to technology levels of transferor and transferee, which relates the relative technology level(ratio) and the technological gap(difference) between transferor and transferee. We found two meaningful facts which are worthy of being explored in more detail from now on. First, the relative technology level has a logistic curve. Second, the technological leapfrog is practicable only if the indigenous rate of development(learning rate) for transferee is greater than equal to that for transferor.

활동기준원가계산과 불확실성을 이용한 제품배합 의사결정

류세걸(Ryu Se-Gul),최상웅(Choe Sang-Woong) 한국산업경영학회 2006 經營硏究 Vol.21 No.2

  본 연구에서는 활동기준원가계산과 제품배합 의사결정에 이용되는 정보의 불확실성을 결합한 방법론을 제안하고자 한다. 전통적 원가계산법에서는 제조간접비가 자의적으로 배부되므로 원가 왜곡 문제가 발생하지만, 활동기준원가계산은 원가동인을 사용하여 활동의 원가를 좀 더 정확히 원가계산대상에 할당함으로써 이러한 원가왜곡 문제를 해결하는데 일조할 수 있다. 불확실성은 과거실적자료 혹은 경험을 바탕으로 다양한 방법으로 구체화 될 수 있는데, 확률제약계획법도 불확실성을 구체화시키는 한 대안이다. 확률제약계획법은 위험이나 신뢰성척도를 구체화시키고 제품배합 분석을 수행하는데 간편하면서도 가치 있는 기법이다. 본 연구의 기여는 활동기준원가계산 정보를 사용하여 제품배합 분석을 수행하는 확률제약계획법 모형의 개발이다. 그리고 간단한 가설적 사례를 통하여본 연구에서 제안된 모형의 적용가능성을 모색하였다.   This study demonstrates the combined use of activity based costing(ABC) and uncertainty associated with the information used in product-mix decisions. The conventional costing systems allocate overhead costs arbitrarily, which causes product cost distortion. ABC provides a solution to this problem by assigning the costs of activities to cost objects more accurately by the use of cost drivers. Uncertainty can be modeled in a variety of ways based on the historical data and experiences. The chance constrained programming(CCP) can be an alternative to do that. The CCP provides a relatively easy method to incorporate risks or reliability measures and is a valuable technique for performing the analysis of product combinations. The contribution of this research is the CCP model for product mix analysis that uses ABC informations. A simple hypothetical case is prepared to show the applicability of the proposed model.

Proof of the Variability Propagation Principle in a Pull Serial Line : Existence and Measurement 존재와 측정

Choe, Sang-Woong 한국경영과학회 2002 韓國經營科學會誌 Vol.27 No.4

In this study, we consider infinite supply of raw materials and backlogged demands as given two boundary conditions. And we need not make any specific assumptions about the inter-arrival of external demand and service time distributions. Under these situations, the ultimate objective of this study is to prove the variability propagation principle in a pull serial line and is to measure it in terms of the first two moments of the inter-departure process subject to number of cards in each cell. Two preparations are required to achieve this objective: The one is to derive a true lower bound of variance of the inter-departure process. The other is to establish a constrained discrete minimax problem for the no backorder (backlogging) probabilities in each cell. We may get some fundamental results necessary to a completion for the proof through the necessary and sufficient conditions for existence of optimal solution of a constrained discrete minimax problem and the implicit function theorem. Finally, we propose a numeric model to measure the variability propagation principle. Numeric examples show the validity and applicability of our study.