• 전자공학회논문지CI
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• 제39권6호
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• pp.36-46
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• 2002

본 논문에서는 웹서버를 탑재한 내장형 시스템에서 실시간 속성을 만족시킬 수 있는 스케줄링 기법을 제안한다. 내장형 시스템에 웹서버를 응용프로그램의 형태로 탑재하는 경우 운영체제와 웹서버간의 이원화된 스케줄링 때문에 우선 순위 역전 현상이 발생하여 실시간 속성을 만족시키지 못한다. 이에 본 논문에서는 웹서버의 일부 스케줄링 기능을 운영체제의 스케줄러와 통합 내장시켜 일관된 스케줄링 방법을 제공한다. 제안된 스케줄링 기법을 실험용 내장형 시스템에 적용한 결과, 웹서버를 일반 태스크로 구현한 경우와 달리 우선 순위 역전 현상이 발생하지 않았다. 또한 우선 순위에 따라 태스크별 응답 시간이 시스템 부하에 관계없이 일정하여 제안된 스케줄링 기법이 실시간 내장형 웹서버 시스템에 적합하다.

• 한국경영과학회:학술대회논문집
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• 대한산업공학회/한국경영과학회 1990년도 춘계공동학술대회논문집; 한국과학기술원; 28 Apr. 1990
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• pp.195-208
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• 1990

Flexible Manufacturing System(FMS) is an integrated, computer controlled complex of automated material handling devices and numerically controlled machine tools that can simultaneously process medium-sized volumes of a variety of part types. This paper discusses planning problems that can be solved for efficient use of an FMS and present an integrated decision support system for FMS production planning and scheduling problems. FMSDS(Flexible Manufacturing Systems Decision Support System) consists of data handling modules, part selection module, loading module, load adjusting module, scheduling module and simulation module etc. This paper presents the solution methodology of each subproblems and integrated interfaces between subproblems using hierarchical approaches and loop controls considering the relationships between subproblems. A case study by this model is presented.

• 산업공학
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• 제13권3호
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• pp.512-520
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• 2000

An integrated process planning and scheduling model considering outsourcing in manufacturing supply chain is proposed in this paper. The process planning and scheduling considering outsourcing are actually interrelated and should be solved simultaneously. The proposed model considers the alternative process plans for job types, precedence constraints of job operations, due date of production, transportation time and production information for outsourcing. The integrated states include:(1) Operations sequencing, (2) Machine selection, (3) Scheduling with outsourcing under the due date. To solve the model, a heuristic approach based on genetic algorithm(GA) is developed. The proposed approach minimizes the makespan considering outsourcing and shows the best operation-sequences and schedule of all jobs.

• Industrial Engineering and Management Systems
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• 제11권1호
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• pp.94-102
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• 2012

In this paper, an interactive planning and scheduling framework are proposed for optimising operations from pits to crushers in ore mining industry. Series of theoretical and practical operations research techniques are investigated to improve the overall efficiency of mining systems due to the facts that mining managers need to tackle optimisation problems within different horizons and with different levels of detail. Under this framework, mine design planning, mine production sequencing and mine transportation scheduling models are integrated and interacted within a whole optimisation system. The proposed integrated framework could be used by mining industry for reducing equipment costs, improving the production efficiency and maximising the net present value.

• 국제학술발표논문집
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• The 4th International Conference on Construction Engineering and Project Management Organized by the University of New South Wales
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• pp.395-398
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• 2011

This paper introduces stochastic cash-flow modeling integrated with simulation based scheduling. The system makes use of CPM schedule data exported from commercial scheduling software, computes the best fit probability distribution functions (PDFs) of historical activity durations, assigns the PDFs identified to respective activities, simulates the schedule network, computes the deterministic and stochastic project cash-flows, plots the corresponding cash flow diagrams, and estimates the best fit PDFs of overdraft and net profit of a project. It analyzes the effect of different distributions of activity durations on the distribution of overdrafts and net profits, and improves reliability compared to deterministic cash flow analysis.

• 한국산학기술학회논문지
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• 제20권10호
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• pp.149-158
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• 2019

본 논문에서는 다수의 구성품으로 구성된 시스템에 대해 Hidden Failure를 고려하여 최적의 계획 정비 스케줄링 문제에 대해 연구하였다. 계획 정비 스케줄링의 목적은 장기 운용 유지비용 최소화이다. 시스템 측면에서는 다수의 구성품을 그룹화하여 검사함으로써 시스템이 정지함으로 인해 발생할 수 있는 비용을 최소화 할 수 있다. 또한 각 구성품 별로 적절한 검사 주기를 선정하여 고장을 조기에 확인함으로써 고장 발생으로 인한 비용을 최소화 할 수 있다. 본 논문에서는 계산의 복잡성을 줄이기 위해 기존 연구에서 사용한 "Base interval approach"를 적용하였으며 추가적으로 다수 구성품의 동시 검사를 통한 검사비용 절감 효과를 고려하였다. 검사비용은 소요되는 시설, 장비 및 인력 비용으로 구성된다고 가정하였으며 유사한 구성품을 동시에 검사함으로써 검사비용이 절감되는 경우에 대한 분석을 실시하였다. 본 논문에서는 검사비용 절감 효과를 비교하기 위해 기존 연구에서 활용한 사례를 대상으로 분석을 실시하였고 이에 따른 비용 절감 효과를 시뮬레이션을 통해 비교하여 제시한다.

• 산업경영시스템학회지
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• 제40권2호
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• pp.111-120
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• 2017

This paper proposes an improved standard genetic algorithm (GA) of making a near optimal schedule for integrated process planning and scheduling problem (IPPS) considering tool flexibility and tool related constraints. Process planning involves the selection of operations and the allocation of resources. Scheduling, meanwhile, determines the sequence order in which operations are executed on each machine. Due to the high degree of complexity, traditionally, a sequential approach has been preferred, which determines process planning firstly and then performs scheduling independently based on the results. The two sub-problems, however, are complicatedly interrelated to each other, so the IPPS tend to solve the two problems simultaneously. Although many studies for IPPS have been conducted in the past, tool flexibility and capacity constraints are rarely considered. Various meta-heuristics, especially GA, have been applied for IPPS, but the performance is yet satisfactory. To improve solution quality against computation time in GA, we adopted three methods. First, we used a random circular queue during generation of an initial population. It can provide sufficient diversity of individuals at the beginning of GA. Second, we adopted an inferior selection to choose the parents for the crossover and mutation operations. It helps to maintain exploitation capability throughout the evolution process. Third, we employed a modification of the hybrid scheduling algorithm to decode the chromosome of the individual into a schedule, which can generate an active and non-delay schedule. The experimental results show that our proposed algorithm is superior to the current best evolutionary algorithms at most benchmark problems.

• 전기학회논문지
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• 제57권11호
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• pp.2124-2126
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• 2008

In the wireless communication systems, the demand of multimedia services is also increased. Unlike typical data packets, realtime service such as VoIP packets have delay bound and low loss rate requirement. In this paper we propose a new scheduling algorithm that be able to allocate resources to the different kinds of services such as VoIP and data packet. The proposed algorithm considers both time delay and channel condition toe determine the priority. Simulation results show that the proposed algorithm works more efficiently than the conventional algorithms.

• 산업공학
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• 제13권3호
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• pp.388-395
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• 2000

In this paper, we propose an approach for integrated process planning and scheduling through analysis of the alternative operations sequences and machine selection in supply chain with multiple plants. It takes into account such factors alternative machine, alternative operations sequences, setup time, transportation time between plants, along with other manufacturing factors. The objective of the model is to minimize makespan of machine schedules for all parts, determines operations sequence for each part, and selects a machine for each operation simultaneously. Examples are presented to demonstrate the effectiveness of the proposed approach.

• 한국경영과학회:학술대회논문집
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• 한국경영과학회 2006년도 추계학술대회
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• pp.273-276
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• 2006

At an integrated steel mill, various raw material such as coal and iron ore are unloaded from a large ship. The unloaded raw material is then transported to storage yards through a complex belt conveyer network. We propose an optimization model for scheduling the unloading operations under the limitations of available berths, unloading equipments and transportation capacity of the belt conveyer network. We show that the problem is NP-Hard and propose a heuristic approach to the problem.