• 경영과학
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• 제12권2호
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• pp.77-87
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• 1995

In this paper we develop an efficient heuristic algorithm for the problem of scheduling n sequence-dependent jobs on a basic processor to minimize makespan. Efficient solution methods are already known for the sequence- independent case. But for the sequence-dependent case, this problem belongs to a set of strong NP-complete problems. We present a heuristic which is similar to shortest setup time heuristic but opportunity cost of setup time rather than shortest setup time is used for choosing next job. This heuristic algorithm has same computational complexity and worst case ratio as the shortest setup time heuristic. We used Wilcoxon signed rank test to show that our heuristic is superior to nearest setup time heuristic in term of average behavior.

• 한국경영과학회지
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• 제18권1호
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• pp.119-126
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• 1993

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 sucessful with probability P$_{i}$. The setup is prone to failure, which results in the loss of expensive wafers. Therefore, a tiral 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 shead 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.d.d.

• Industrial Engineering and Management Systems
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• 제4권1호
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• pp.1-22
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• 2005

This paper presents new scheduling heuristics, namely Mean Progressive Weighted Tardiness Estimator (MPWT) Heuristic Method and modified priority rules with sequence-dependent setup times consideration. These are designed to solve job shop scheduling problems with new performance measures - progressive weighted tardiness penalties. More realistic constraints, which are inter-machine overlapping sequence-dependent setup times, are considered. In real production environments, inter-machine overlapping sequence-dependent setups are significant. Therefore, modified scheduling generation algorithms of active and nondelay schedules for job shop problems with inter-machine overlapping sequence-dependent setup times are proposed in this paper. In addition, new customer-based measures of performance, which are total earliness and progressive weighted tardiness, and total progressive weighted tardiness, are proposed. The objective of the first experiment is to compare the proposed priority rules with the consideration of sequence-dependent setup times and the standard priority rules without setup times consideration. The results indicate that the proposed priority rules with setup times consideration are superior to the standard priority rules without the consideration of setup times. From the second experiment and the third experiment to compare the proposed MPWT heuristic approach with the efficient priority rules with setup times consideration, the MPWT heuristic method is significantly superior to the Batched Apparent Tardiness Cost with Sequence-dependent Setups (BATCS) rule, and other priority rules based on total earliness and progressive weighted tardiness, and total earliness and tardiness.

• 제어로봇시스템학회논문지
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• 제3권5호
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• pp.532-541
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• 1997

This article derives an analytic solution to determine the optimal size of multiple noncontinuous process and storage units. The total cost to be minimized consists of the setup cost of noncontinuous processing units and the inventory holding cost of feedstock/product storages. A novel approach, which is called PSW(Periodic Square Wave) model, is applied to represent the material flow among non-continuous units and storages. PSW model presumes that the material flow between unit and storage is periodic square wave shaped. The resulting optimal unit size has similar characteristics with the classical economic lot sizing model such as EOQ(Economic Order Quantity) or EPQ(Economic Production Quantity) model in a sense that the unit size is determined as the balance between setup and inventory holding cost. However, the influence of inventory holding cost of PSW model is different from that of EOQ/EPQ model. EOQ/EPQ model includes only the product inventory holding cost but PSW model includes all inventory holding costs around the non-continuous unit with proportional contribution. PSW model is suitable for analyzing interlinked process-storage system. The optimal lot size of PSW model is smaller than that of EOQ/EPQ model. This is quitea remarkable result considering that the EOQ/EPQ model has been is widely used since last half century.

• 한국경영과학회지
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• 제30권1호
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• pp.27-41
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• 2005

This paper considers identical parallel machine scheduling problem. Each job has a processing time. due date. weight and family type. If a different type of job is followed by prior job. a family setup is incurred. A two phased heuristic is presented for minimizing the sum of weighted tardiness. In the first phase. using roiling horizon technique. group each job into same family and schedule each family. In the second phase. assign each job to machines using schedule obtained in the first phase. Extensive computational experiments and comparisons among other algorithms are carried out to show the efficiency of the proposed algorithm.

• 대한전자공학회논문지TC
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• 제41권12호
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• pp.41-49
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• 2004

최근 인터넷 사용자 수의 증가와 새로운 서비스의 등장으로 각 응용의 요구 대역폭이 증가하였다. 따라서 Internet 트래픽은 폭주하게 되었고, 고속의 백본(backbone) 네트워크가 필요하게 되었다. 이러한 요구는 IP packet switching과 wavelength switching 모두를 동시에 수행하면서 대용량의 대역폭을 지원할 수 있는 GMPLS(Generalized Multi-protocol Label Switching) 기반의 OXC(Optical cross-connects)에 의해 만족될 수 있다. 이러한 요구를 위해서는 Core망에 많은 수의 파장 변환기가 필요하고, 구축 및 운용비용(cost-effective)이 효율적일 뿐만 아니라 최적의 트래픽 전송제한을 받는 문제점을 갖고 있다. 따라서 본 논문에서는 GMPLS망에서 개선된 Lightpath setup을 위한 GMPLS의 RSVP-TE 시그널링을 제안하였다. 제안한 알고리즘은 setup 시그널링이 블로킹 되었을 때, edge router까지 PathErr 메시지를 전송하는 것이 아니라 파장 변환을 수행할 수 있는 최단거리에 위치한 람다 라우터를 찾고, 그 노드로부터 setup 시그널링을 다시 수행한다. 본 알고리즘은 Lightpath setup 시그널링의 블로킹 확률을 줄일 수 있으며, 적절한 파장 변환기 수를 산출하여 core망에서 람다 라우터의 효율적인 배치도 구현할 수 있을 것으로 사료된다.

• 산업공학
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• 제8권2호
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• pp.151-159
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• 1995

Two-dimensional cutting stock problem is to find a waste-minimizing method of cutting a single rectangular plane into a number of smaller pieces of known dimensions. In practice, besides wastes, setup cost taken during adjusting is of an important concern. We suggest 2-phased guillotine cutting method as a solution to the problem which minimize wastes and setup costs. Also, in order to reduce the computing time we apply techniques of discretization, cutoff, median. Experimental results show good performance of our algorithm.

• 산업경영시스템학회지
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• 제12권19호
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• pp.79-88
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• 1989

This characteristics of process industries are high capital intensity, relatively long and sequence dependent setup times, and extremely limited capacity resources. The lot sizing, sequencing and limited capacity resources factors must he considered for production scheduling in these industries. This paper presents a mixed integer programming model for production scheduling. The economic trade offs between capacitated lot sizing flow shop scheduling and sequence dependent setup times also be compared with SMITH-DANIELS's model. As a results, it is shown that this paper has lower total cost, more efficient throughput than SMITH-DANIELS's model.

• 한국인터넷방송통신학회논문지
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• 제21권2호
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• pp.169-175
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• 2021

로트 크기 문제(LSP)는 다항시간으로 최적 해를 찾을 수 있는 알고리즘이 알려져 있지 않은 NP-완전의 난제이다. LSP에 대해 다항시간으로 해를 구할 수 있는 W-W 알고리즘이 알려져 있지만, 이 알고리즘은 너무나 복잡하여 이해와 적용에 어려움이 있어 S-M의 휴리스틱 근사 알고리즘이 제안되었다. 본 논문에서는 LSP의 근사 해가 아닌 최적 해를 찾을 수 있는 간단한 공식을 가진 O(n)의 선형 복잡도 알고리즘을 제안하였다. 제안된 알고리즘은 t시점에서의 로트 크기(생산량) Xt∗은 비축 비가 절차 비를 초과하지 않는 t+k 시점을 결정하여 [t,t+k] 구간의 요구량 합으로 단순히 결정하였다. 제안된 알고리즘을 다양한 실험 데이터에 적용한 결과 모든 데이터에 대해 최적 해를 찾았다.

• 산업경영시스템학회지
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• 제38권3호
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• pp.117-126
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• 2015

This paper is to analyze an integrated production and inventory model in a single-vendor multi-buyer supply chain. The vendor is defined as the manufacturer and the buyers as the retailers. The product that the manufacturer produces is supplied to the retailers with constant periodic time interval. The production rate of the manufacturer is constant for the time. The demand of the retailers is constant for the time. The cycle time of the vendor is defined as the elapsed time from the start of the production to the start of the next production, while the cycle times of the buyer as the elapsed time between the adjacent supply times from the vendor to the buyer. The cycle times of the vendor and the buyers that minimizes the total cost in a supply chain are analyzed. The cost factors are the production setup cost and the inventory holding cost of the manufacturer, the ordering cost and the inventory holding cost of the retailers. The cycle time of the vendor is investigated through the cycle time that satisfies economic production quantity with the production setup cost and the inventory holding cost of the manufacturer. An integrated production and inventory model is formulated, and an algorithm is developed. An numerical example is presented to explain the algorithm. The solution of the algorithm for the numerical examples is compared with that of genetic algorithm. Numerical example shows that the vendor and the buyers can save cost by integrated decision making.