• Proceedings of the Korean Information Science Society Conference
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• 한국정보과학회 2008년도 한국컴퓨터종합학술대회논문집 Vol.35 No.1 (A)
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• pp.377-378
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• 2008

• Journal of Korean Society of Industrial and Systems Engineering
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• 제47권2호
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• pp.48-56
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• 2024

We examine a single machine scheduling problem with step-improving jobs in which job processing times decrease step-wisely over time according to their starting times. The objective is to minimize total completion time which is defined as the sum of completion times of jobs. The total completion time is frequently considered as an objective because it is highly related to the total time spent by jobs in the system as well as work-in-progress. Many applications of this problem can be observed in the real world such as data gathering networks, system upgrades or technological shock, and production lines operated with part-time workers in each shift. Our goal is to develop a scheduling algorithm that can provide an optimal solution. For this, we present an efficient branch and bound algorithm with an assignment-based node design and tight lower bounds that can prune branch and bound nodes at early stages and accordingly reduce the computation time. In numerical experiments well designed to consider various scenarios, it is shown that the proposed algorithm outperforms the existing method and can solve practical problems within reasonable computation time.

• Journal of applied mathematics & informatics
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• 제15권1_2호
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• pp.511-525
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• 2004

we model communication and computer systems that process interactive and several and several types of background jobs. The scheduling policy in use is to share the processor among all interactive jobs and, at most, one background job of each type at a time according to the process sharing discipline. Background jobs of each type are served on a first-come-first-served basis. Such scheduling policy is called Processor Sharing with Background jobs (PSBJ). In fact, the PSBJ policy is commonly used on many communication and computer systems that allow interactive usage of the systems and process certain jobs in a background mode. In this paper, the stability conditions for the PSBJ policy are given and proved. Since an exact analysis of the policy seems to be very difficult, an approximate analytic model is proposed to obtain the average job sojourn times. The model requires the solution of a set of nonlinear equations, for which an iterative algorithm is given and its convergence is proved. Our results reveal that the model provides excellent estimates of average sojourn times for both interactive and background jobs with a few percent of errors in most of the cases considered.

• Journal of the Korea Academia-Industrial cooperation Society
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• 제10권7호
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• pp.1702-1710
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• 2009

In this paper, we propose a problem space based search(PSBS) algorithm to solve parallel machine scheduling problem considering rework probabilities. For each pair of a machine and a job type, rework probability of each job on a machine can be known through historical data acquisition. Neighborhoods are generated by perturbing four problem data vectors (processing times, due dates, setup times, and rework probabilities) and evaluated through the efficient dispatching heuristic (EDDR). The proposed algorithm is measured by maximum lateness and the number of reworked jobs. We show that the PSBS algorithm is considerably improved from the result obtained by EDDR.

• Proceedings of the Korean Information Science Society Conference
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• 한국정보과학회 2006년도 가을 학술발표논문집 Vol.33 No.2 (A)
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• pp.162-166
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• 2006

선행스케줄링(pre-scheduling)은 정적인 작업(periodic job)과 동적인 작업(sporadic job)을 유연하게 처리하기 위해 제안된 스케줄링 방식이다. 이 방식은 오프라인 컴포넌트와 온라인 컴포넌트로 구성되며 오프라인 컴포넌트에서는 비주기적으로 도착하는 동적인 작업들을 고려하여 정적인 작업들을 여러 부분작업으로 분할하고, 그리고 각 부분작업들의 실행시간, 준비시간, 마감시간을 부여하고 실행순서를 결정한다. 온라인 컴포넌트에서는 이 정보들을 이용하여 정적인 작업들을 정해진 실행순서에 따라 스케줄하고, 동적인 작업이 도착하면 EDF(Earliest Deadline First) 스케줄링 방식으로 처리한다. 그러나 선행스케줄링에서는 자원공유문제를 고려하지 않고 실행시간을 부여하였으므로 여러 정적인 작업들이 하나의 자원을 공유할 경우에 배타적인 자원접근을 보장하지 못한다. 본 논문에서는 단일처리기 환경에서 여러 정적인 작업들의 자원공유를 고려하여 자원의 배타적 사용을 보장하는 선행스케줄 생성기법을 제시한다. 이 기법은 각 작업의 자원 방출시간을 예측하고 예측시간에 근거하여 각 작업의 자원사용구간이 중복되지 않도록 실행시간을 결정한다.

• Proceedings of the Korea Information Processing Society Conference
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• 한국정보처리학회 2014년도 춘계학술발표대회
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• pp.97-100
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• 2014

전자책 (E-Book)에 대한 수요가 커짐에 따라서 전자책 시장이 점점 커지고 있다. 이에 PDF 와 같은 다른 형태의 문서들을 전자책으로 변환하는 프로그램 및 서비스들에 대한 요구가 늘어가고 있다. 전자책의 공급 규모가 커지고 형식이 발전함에 따라서 대규모의 전자책들을 빠르고 효율적으로 변환 가능하게 하는 환경의 조성이 필요하게 되었다. 기존 시장에 배포되거나 출판된 PDF형식의 문서를 오픈소스 변환 라이브러리를 이용하여 변환할 수 있는 변환기를 작성하고, 이를 이용해 대규모 PDF 를 저장하고 있는 분산 저장 시스템에서 백그라운드 배치 작업으로 변환할 수 있는 구조를 설계 및 제안한다. 본 논문에서는 전자책의 효율적인 변환을 위한 분산 환경에서의 작업 배분방법을 다룬다.

• Journal of Korean Society of Industrial and Systems Engineering
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• 제24권66호
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• pp.1-10
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• 2001

Simulation-Based Expert System(SIMBES) is a very effective tool to solve complex antral hard problems. The SIMBES model includes a simulator, a feature extractor, a machine learning system, a performance evaluator, and a Knowledge-Based Expert System(KBES). Since SIMBES depends on Problem domains, a schedule-based material requirements planning problem, which is NP-hard, was selected to exemplify the SIMBES model. To implement the SIMBES application in Smalltalk paradigm, a system class hierarchy was constructed. The hierarchy consists of five large classes such as Job Generator, Job Scheduler, Job Evaluator, Inference Engine, and Executive System. Several classes inside these classes were identified. Additionally, instance protocols about all classes have been described in terms of messages and pseudo methods. These protocols can be implemented easily by any other object-oriented languages. Furthermore, these results may be used as a skeletal system to develop a new SIMBES efficiently, especially when the application is related to other scheduling problems.

• Journal of Korean Society of Industrial and Systems Engineering
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• 제44권4호
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• pp.32-42
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• 2021

The printing process can have to print various colors with a limited capacity of printing facility such as ink containers that are needed cleaning to change color. In each container, cleaning time exists to assign corresponding inks, and it is considered as the setup cost required to reduce the increasing productivity. The existing manual method, which is based on the worker's experience or intuition, is difficult to respond to the diversification of color requirements, mathematical modeling and algorithms are suggested for efficient scheduling. In this study, we propose a new type of scheduling problem for the printing process. First, we suggest a mathematical model that optimizes the color assignment and scheduling. Although the suggested model guarantees global optimality, it needs a lot of computational time to solve. Thus, we decompose the original problem into sequencing orders and allocating ink problems. An approximate function is used to compute the job scheduling, and local search heuristic based on 2-opt algorithm is suggested for reducing computational time. In order to verify the effectiveness of our method, we compared the algorithms' performance. The results show that the suggested decomposition structure can find acceptable solutions within a reasonable time. Also, we present schematized results for field application.

• The Transactions of the Korea Information Processing Society
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• 제6권4호
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• pp.959-968
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• 1999

several papers have reported that parallel heuristics or hybrid approaches combining several heuristics can get better results. However, the parallelization and hybridization of any search methods on the single CPU type computer need enormous computation time. that case, we need more elegant combination method. For this purpose, we propose Fast Model of Parallel Heuristics(FMPH). FMPH is based on the island model of parallel genetic algorithms and takes local search to the elite solution obtained form each island(sub group). In this paper we introduce how can we adapt FMPH to the job-shop scheduling problem notorious as the most difficult NP-hard problem and report the excellent results of several famous benchmark problems.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 한국정보통신학회 2014년도 추계학술대회
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• pp.624-627
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• 2014

In vehicular network, the basic goal is to provide vehicle safety service and commercial service such as ITS(Intelligent Transportation System) or video, etc on the road. And most research concentrated on transportation of safety message in congestion situation. It is important to allocate channel for safety message in congestion situation, but providing suitable service is also important problem in vehicular network. For this reason, IEEE 1609.4 allocate 4 multiple service channels (SCHs) for non-safety data transfer. But, in congestion situation with many vehicles, the contention for channel acquisition between services becomes more severe. So services are provided improperly because of lack of service channel. This paper suggests dynamic channel allocation algorithm. The proposed algorithm is that RSU(RaodSide Unit) maintain and manage the information about service and status of channels. On based of the SJF(Shortest Job First) scheduling using those information, RSU selects the most appropriate channel among the 4 SCHs allocated by IEEE 1609.4 in network congestion situation.