• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 심포지엄 논문집 정보 및 제어부문
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• pp.59-61
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• 2004

Researches about scheduling distributed real-time systems have some weak points, not scheduling both sporadic and periodic tasks and messages or being unable to guaranteeing the end-to-end constraints due to omitting precedence relations between sporadic tasks. This paper describes the application model of sporadic tasks with precedence constraints in a distributed real-time system. It is shown that existing scheduling methods such as Rate Monotonic scheduling are not proper to be applied to the system having sporadic tasks with precedence constraints. So this paper proposes an end-to-end laxity-based priority assignment algorithm which considers the practical laxity of a task and allocates a proper priority to a task.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제1권1호
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• pp.35-53
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• 1997

This paper analyzes the time complexity of Genetic Algorithm based Task Scheduling (GATS) which is designed for the scheduling of parallel programs with diverse embedded parallelism types in a heterogeneous network systems. The analysis of time complexity is performed based on two representation methods (REIA, REIS) which are proposed in this paper to encode the scheduling information. And the heterogeneous network systems consist of a set of loosely coupled parallel and vector machines connected via a high-speed network. The objective of heterogeneous network computing is to solve computationally intensive problems that have several types of parallelism, on a suite of high performance and parallel machines in a manner that best utilizes the capabilities of each machine. Therefore, when scheduling in heterogeneous network systems, the matching of the parallelism characteristics between tasks and parallel machines should be carefully handled in order to obtain more speedup. This paper shows how the parallelism type matching affects the time complexity of GATS.

• 한국멀티미디어학회논문지
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• 제8권12호
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• pp.1589-1596
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• 2005

The imprecise real-time system provides flexibility in scheduling time-critical tasks. Most scheduling problems of satisfying both 0/1 constraint and timing constraints, while the total error is minimized, are NP complete when the optional tasks have arbitrary processing times. Liu suggested a reasonable strategy of scheduling tasks with the 0/1 constraint on uniprocessors for minimizing the total error. Song et al suggested a reasonable strategy of scheduling tasks with the 0/1 constraint on multiprocessors for minimizing the total error. But, these algorithms are all off-line algorithms. On the other hand, in the case of on line scheduling, Shih and Liu proposed the NORA algorithm which can find a schedule with the minimum total error for a task system consisting solely of on-line tasks that are ready upon arrival. But, for the task system with 0/1 constraint, it has not been known whether the NORA algorithm can be optimal or not in the sense that it guarantees all mandatory tasks are completed by their deadlines and the total error is minimized. So, this paper suggests an optimal algorithm to search minimum total error for the imprecise on-line real-time task system with 0/1 constraint. Furthermore, the proposed algorithm has the same complexity, O(N log N), as the NORA algorithm, where N is the number of tasks.

• 경영과학
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• 제30권1호
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• pp.15-24
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• 2013

We consider the single machine scheduling problem with a rate-modifying activity and time-dependent deterioration after the activity. The class of scheduling problems with rate-modifying activities and the class of scheduling problems with time-dependent processing times have been studied independently. However, the integration of these classes is motivated by human operators of tasks who has fatigue while carrying out the operation of a series of tasks. This situation is also applicable to machines that experience performance degradation over time due to mal-position or mal-alignment of jobs, abrasion of tools, and scraps of operations, etc. In this study, the integration of the two classes of scheduling problems is considered. We present a mathematical model to determine job-sequence and a position of a rate-modifying activity for the integration problem. Since the model is difficult to solve as the size of real problem being very large, we propose genetic algorithms. The performance of the algorithms are compared with optimal solutions with various problems.

• 한국통신학회논문지
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• 제30권6B호
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• pp.377-386
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• 2005

최근 들어, 실시간 디스크 스케줄링에서 단위 시간당 처리량을 최대화하기 위한 다양한 실시간 스케줄링 알고리즘들이 연구되고 있다. 특히, 실시간 디스크 스케줄링 알고리즘을 대표하는 EDF(Earliest Deadline First)에 스캔기법을 적용한 많은 알고리즘들이 연구되고 있다. 그러나 제안된 디스크 스케줄링 알고리즘들은 스캔 그룹을 생성할 때 계속되는 I/O 요구들을 고려해야 하기 때문에 많은 제약을 가지고 있다. 또한, 스캔 기법에서 서비스 방향의 고정으로 인하여 디스크의 효율성을 떨어뜨리는 결과를 초래하고 있다. 본 논문에서는 기존의 경성 실시간 시스템에서 사용되는 실시간 디스크 스케줄링 알고리즘들의 문제점을 해결하기 위해 삽입 기법과, 양방향 스캔기법을 기반으로 한 새로운 실시간 디스크 스케줄링 알고리즘을 제안하고 실험을 통해 제안 시스템의 시간당 처리량과 서비스 가능한 I/O 요구가 우수함을 증명한다.

• 한국컴퓨터정보학회논문지
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• 제29권1호
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• pp.1-9
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• 2024

본 논문에서는 LoRaEnergySim에 최적의 실시간 스케줄링 알고리즘으로 알려진 ED-H 스케줄링 알고리즘을 연동하여 LoRaWAN 클래스-A 단말기에 슈퍼 커패시터 기반의 에너지 하베스팅 시스템을 전원 공급 장치를 적용하였을 때 시간 제약성을 갖는 LoRaWAN 컨트롤러의 태스크와 응용 태스크의 실시간 스케줄링 알고리즘 간의 상호 시뮬레이션이 가능하도록 한다. 이를 위해 LoRaWAN의 상태와 상태 전환에 따른 시간과 에너지 특성을 로그 형태로 추출하고 타임 슬롯 기반의 ED-H 스케줄링 알고리즘에 적합하도록 태스크 모델을 수립하고 태스크가 CPU에 의해서 수행되는 특성에 따라 알고리즘이 시간 제약성을 만족하며 태스크를 수행할 수 있도록 확장하였다. 본 논문에서 제안한 기법의 평가를 위해 LoRaEnergySim 시뮬레이션 결과가 제시된 동일 환경에서 패킷 송수신이 수행되는 것과 동시에 10%에서 90%의 CPU 점유율을 갖는 다양한 시간과 에너지 특성을 갖는 태스크 집합에 대해 ED-H 스케줄링 알고리즘을 수행하였으며, 실험 결과로 스케줄링 알고리즘에 따라 시간 제약성의 만족을 위해 슈퍼 커패시터의 에너지가 고갈되지 않는 한 태스크의 시급성을 우선하여 사용하는 것을 확인하여 상호 시뮬레이션의 적용 가능성을 확인하였다.

• Journal of Electrical Engineering and information Science
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• 제3권3호
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• pp.396-401
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• 1998

An optimal algorithm is presented for feasibility test and scheduling of real-time tasks where tasks are preemptable and created dynamically. Each task has an arbitrary creation time, ready time, maximum execution time, and deadline. Feasibility test and scheduling are conducted via the same algorithm. Time complexity of the algorithm is O(n) for each newly created task where n is the number of tasks. This result improves the previous result of O(n log n). It is shown that the algorithm can be used for scheduling tasks with different levels of importance. Time complexity of the algorithm for the problem is O(n\ulcorner) which improves the previous results of O(n\ulcorner log n).

• Management Science and Financial Engineering
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• 제9권2호
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• pp.47-68
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• 2003

We consider the customer order scheduling problem with job capacity restriction where the number of jobs in the shop at the same time is fixed. In the customer order scheduling problem, each job is part of some batch (customer order) and the composition of the jobs (product) in the batch is pre-specified. The objective function is associated with the completion time of the batches instead of the completion time of the jobs. We first summarize the known results for the general customer order scheduling problems. Then, we establish some new properties for the problems with job capacity restriction. For the case of unit processing time with the objective of minimizing makespan, we develop a polynomial-time optimal procedure for the two machine case. For the same problem with a variation of no batch alternation, we also develop a polynomial-time optimal procedure. Then, we show that the problems with the objectives of minimizing makespan and minimizing average batch completion time become NP-hard when there exist arbitrary number of machines. Finally, We propose optimal solution procedures for some special cases.

• 산업경영시스템학회지
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• 제20권41호
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• pp.231-242
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• 1997

This paper describe an approximation method for solving the minimum makespan problem of job shop scheduling with fuzzy processing time. We consider the multi-part production scheduling problem in a job shop scheduling. The job shop scheduling problem is a complex system and a NP-hard problem. The problem is more complex if the processing time is imprecision. The Fuzzy set theory can be useful in modeling and solving scheduling problems with uncertain processing times. Lee-Li fuzzy number comparison method will be used to compare processing times that evaluated under fuzziness. This study propose heuristic algorithm solving the job shop scheduling problem under fuzzy environment. In This study the proposed algorithm is designed to treat opinions of experts, also can be used to solve a job shop environment under the existence of alternate operations. On the basis of the proposed method, an example is presented.

• 제어로봇시스템학회논문지
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• 제4권5호
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• pp.651-657
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• 1998

In this study, an intelligent scheduling with hybrid architecture, which integrates expert system and neural network, is proposed. Neural network is trained with the data acquired from simulation model of FMC to obtain the knowledge about the relationship between the state of the FMC and its best dispatching rule. Expert system controls the scheduling of FMC by integrating the output of neural network, the states of FMS, and user input. By applying the hybrid system to a scheduling problem, the human knowledge on scheduling and the generation of non-logical knowledge by machine teaming, can be processed in one scheduler. The computer simulation shows that comparing with MST(Minimum Slack Time), there is a little increment in tardness, 5% growth in flow time. And at breakdown, tardness is not increased by expert system comparing with EDD(Earliest Due Date).