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A Send-ahead Policy for a Semiconductor Wafer Fabrication Process
Moon, Ilkyeong 한국경영과학회 1993 韓國經營科學會誌 Vol.18 No.1
We study a manufacturing process that is quite common in semiconductor wafer fabrication of semiconductor chip production. A machine is used to process a job consisting of J wafers. Each job requires a setup, and the i_th setup for a job is successful with probability p_i. The setup is prone to failure, which results in the loss of expensive wafers. Therefore, a trial run is first conducted on a small batch. If the set up is successful, the test is passed and the balance of the job can be processed. If the setup is unsuccessful, the exposed wafers are lost to scrap and the mask is realigned. The process then repeats on the balance of the job. We call this as send-ahead policy and consider general policies in which the number of wafers that are sent ahead depend on the cost of the raw wafer, the sequence of success probabilities, and the balance of the job. We model this process and determine the expected number of good wafers per job, the expected time to process a job, and the long run average throughput. An algorithm, to minimize the cost per good wafer subject to a demand constraint is provided.
Multiple Product Single Facility Stockout Avoidance Problem(SAP) and Weighted Stockout Problem(WSP)
Moon, Ilkyeong 한국경영과학회 1992 韓國經營科學會誌 Vol.17 No.3
We study the Multiple Product Single Facility Stockout Avoidance Problem (SAP). That is the problem of determining, given initial inventories, whether there is a multiple product single facility production schedule that avoids stockouts over a given time horizon. The optimization version of the SAP where stockouts are penalized linerarly is also studied. We call this problem the Weighted Stockout Problem (WSP). Both problems are NP-hard in the strong sense. We develop Mixed Integer Linear Programming (MIP) formulations for both the SAP and the WSP. In addition, several heuristic algorithms are presented and performances are tested using computational experiments. We show that there exist polynomial algorithms for some special cases of the SAP and the WSP. We also present a method to phase into a target cyclic schedule for infinite horizon problems. These can be used as a practical scheduling tool for temporarily overloaded facilities or to reschedule production after a disruption.
Strategic inventory: Manufacturer vs. retailer investment
Moon, Ilkyeong,Dey, Kartick,Saha, Subrata Elsevier 2018 TRANSPORTATION RESEARCH PART E-LOGISTICS AND TRANS Vol.109 No.-
<P><B>Abstract</B></P> <P>This paper presents a two-period supply chain model under demand induced by selling price and investment effort in the presence of strategic inventory. We compared six different scenarios to identify optimal pricing decisions. An incremental quantity discount contract was applied to verify supply chain coordination. Our findings show that manufacturer-investment efforts cannot always persuade the retailer carrying strategic inventory to maintain harmony among supply chain participants; however, retailer-investment efforts can promote harmony when strategic inventory is used. The retailer’s decision to carry strategic inventory is catastrophic from the perspective of supply chain coordination, but benign for the decentralized supply chain.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Two-period supply chain models are studied to find impact of strategic inventory. </LI> <LI> The demand rate depends on price and investment effort. </LI> <LI> Retailer’s strategic inventory is not always a threat but can also prove beneficial. </LI> <LI> Strategic inventory is catastrophic from the perspective of supply chain coordination. </LI> </UL> </P>
문일경,김태우 한국경영과학회 1996 經營 科學 Vol.13 No.2
Due-data is an important factor in Flexible Manufacturing System scheduling. Even though most of researchers have focused part selection and loading problem using fixed due-date assignment rules, FMSs consist of multi-function machines which facilitate alternative processes. This research investigates interactions of three dispatching mechanisms, three NSS(Next Station Selection)rules and four due-date assignment rules using simulation. Both cost-based and time-based performance measures are considered in this research.
An Integer Program and a Hybrid Genetic Algorithm for the University Timetabling Problem
Yuna Lee,Ilkyeong Moon 대한산업공학회 2014 대한산업공학회 추계학술대회논문집 Vol.2014 No.11
The university timetabling problem (UTP) has been studied by numerous research groups for decades. The studies were conducted through various methods including linear algorithms, mathematical models, heuristics, and metaheuristics. In this paper, an integer program, a heuristic algorithm, and a hybrid genetic algorithm are used to solve the UTP characterized by real-world constraints such as periodicity and consecutiveness. The integer program can be used to efficiently alter constraints and improve accuracy. However, it is inefficient with large problems, because the UTP is NP-hard problem, so a heuristic algorithm with left upper strategy and a hybrid genetic algorithm were developed. The first experiment showed the effects of the periodicity and consecutiveness constraints ratio and the second experiment compared the performances of the heuristic and hybrid genetic algorithms with small, medium, and large problems. The integer program was coded in FICO Xpress-IVE version 7.3, and the heuristic and the hybrid genetic algorithm were implemented in Java programming language. The results illustrate that the higher ratio of the lectures with consecutiveness constraints deducted the better objectives. For larger problems, the IP could not reach the optimum within 7200 seconds, and the hybrid genetic algorithm yielded better solutions than the heuristic algorithm.