• 대한산업공학회지
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• 제30권2호
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• pp.130-145
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• 2004

This paper addresses the integrated problem of process planning and scheduling in FMS (Flexible Manufacturing System). The integration of process planning and scheduling is important for an efficient utilization of manufacturing resources. In this paper, a new method using an artificial intelligent search technique, called asymmetric multileveled symbiotic evolutionary algorithm, is presented to handle the two functions at the same time. Efficient genetic representations and operator schemes are considered. While designing the schemes, we take into account the features specific to each of process planning and scheduling problems. The performance of the proposed algorithm is compared with those of a traditional hierarchical approach and existing evolutionary algorithms. The experimental results show that the proposed algorithm outperforms the compared algorithms.

• 제어로봇시스템학회논문지
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• 제16권6호
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• pp.572-578
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• 2010

In this paper, the final fitness results of the satellite mission scheduling algorithm, which is designed by using the genetic algorithm, are simulated and compared with respect to the control constants. Heuristic algorithms, including the genetic algorithm, are good to find global optima, however, we have to find the optimal control constants before its application to a problem, because the algorithm is strongly effected by the control constants. In this research, the satellite mission scheduling algorithm is simulated with different crossover probability and mutation probability, which is major control constant of the genetic algorithm.

• 한국멀티미디어학회논문지
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• 제9권1호
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• pp.119-126
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• 2006

멀티 프로세서 시스템에서 스케쥴링은 매우 중요한 부분이지만, 최적의 해를 구하는 것이 복잡하여 최근 다양한 휴리스틱 방법들에 의한 스케쥴링 알고리즘들이 제안되고 있다. 본 논문에서는 유전 알고리즘을 이용한 새로운 스케쥴링 알고리즘을 제시한다. 또한, 해를 구하는 과정에서 시뮬레이티드 어닐링 (simulated annealing)의 확률을 이용하여 유전 알고리즘의 성능을 개선시킨다. 제시된 알고리즘은 태스크들의 최종 수행 완료 시간 (makespan)을 최소화하는 것을 목표로 한다. 모의 실험을 통하여 제시된 알고리즘이 다른 알고리즘보다 최종 수행 완료 시간이 작음을 확인할 수 있었다.

• 한국CDE학회논문집
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• 제15권1호
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• pp.1-10
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• 2010

Recently, a shipyard is making every effort to efficiently manage equipments of resources such as a gantry crane, transporter, and so on. So far block lifting scheduling of a gantry crane has been manually performed by a manager of the shipyard, and thus it took much time to get scheduling results and moreover the quality of them was not optimal. To improve this, a block lifting scheduling system of the gantry crane using optimization techniques was developed in this study. First, a block lifting scheduling problem was mathematically formulated as a multi-objective optimization problem, considering the minimization of travel distance at an idle state and wire replacement during block lifting. Then, to solve the problem, a meta-heuristic optimization algorithm based on the genetic algorithm was proposed. To evaluate the efficiency and applicability of the developed system, it was applied to an actual block lifting scheduling problem of the shipyard. The result shows that blocks can be efficiently lifted by the gantry crane using the developed system, compared to manual scheduling by a manager.

• International Journal of Aeronautical and Space Sciences
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• 제17권1호
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• pp.89-100
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• 2016

Given the unpredictability of the space environment, satellite communications are manually performed by exchanging telecommands and telemetry. Ground support for orbiting satellites is given only during limited periods of ground antenna visibility, which can result in conflicts when multiple satellites are present. This problem can be regarded as a scheduling problem of allocating antenna support (task) to limited visibility (resource). To mitigate unforeseen errors and costs associated with manual scheduling and mission planning, we propose a novel method based on a genetic algorithm to solve the ground support problem of multiple satellites and antennae with visibility conflicts. Numerous scheduling parameters, including user priority, emergency, profit, contact interval, support time, remaining resource, are considered to provide maximum benefit to users and real applications. The modeling and formulae are developed in accordance with the characteristics of satellite communication. To validate the proposed algorithm, 20 satellites and 3 ground antennae in the Korean peninsula are assumed and modeled using the satellite tool kit (STK). The proposed algorithm is applied to two operation modes: (i) telemetry, tracking, and command and (ii) payload. The results of the present study show near-optimal scheduling in both operation modes and demonstrate the applicability of the proposed algorithm to actual mission control systems.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제17권4호
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• pp.1100-1122
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• 2023

Scheduling user-submitted cloud tasks to the appropriate virtual machine (VM) in cloud computing is critical for cloud providers. However, as the demand for cloud resources from user tasks continues to grow, current evolutionary algorithms (EAs) cannot satisfy the optimal solution of large-scale cloud task scheduling problems. In this paper, we first construct a large- scale multi-objective cloud task problem considering the time and cost functions. Second, a multi-objective optimization algorithm based on multi-factor optimization (MFO) is proposed to solve the established problem. This algorithm solves by decomposing the large-scale optimization problem into multiple optimization subproblems. This reduces the computational burden of the algorithm. Later, the introduction of the MFO strategy provides the algorithm with a parallel evolutionary paradigm for multiple subpopulations of implicit knowledge transfer. Finally, simulation experiments and comparisons are performed on a large-scale task scheduling test set on the CloudSim platform. Experimental results show that our algorithm can obtain the best scheduling solution while maintaining good results of the objective function compared with other optimization algorithms.

• 한국멀티미디어학회논문지
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• 제14권11호
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• pp.1478-1490
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• 2011

멀티코어 프로세서는 멀티미디어 스트리밍에 있어서 비교적 낮은 비용에 높은 성능을 보인다는 장점 때문에 스마트폰, 스마트 TV, 셋톱박스 등 관련 산업계에서 큰 관심을 받고 있다. 멀티미디어 데이터를 처리하기 위해서는 주기적인 태스크의 시간 제약성을 만족시킬 수 있는 스케줄링 알고리즘이 필요하다. Pfair 스케줄링 알고리즘은 이론상으로 멀티코어 상에서 모든 태스크의 시간 제약성을 만족하는 동시에 100%의 이용률을 달성할 수 있지만 코어간에 태스크의 빈번한 이동이 필요하고 매 스케줄링 시점에 시스템 전역에 대한 동기화가 필요하는 등 스케줄링을 위한 오버헤드가 매우 높다. 이러한 문제점을 개선하기 위해 본 논문에서는 코어 간의 이동이 꼭 필요할 경우에만 전체 코어의 스케줄링을 수행하고 평상시에는 각 코어별로 독립적인 스케줄링을 수행하도록 하는 HPGP 스케줄러를 제안한다. 시뮬레이터를 통한 실험 결과 기존의 Pfair 알고리즘에 비해 스케줄링 오버헤드가 현격히 감소하는 것을 알 수 있으며 80% 이하의 이용률을 갖는 태스크 집합에서는 스케줄링 오버헤드가 거의 발생하지 않는 것을 확인하였다.

• 한국멀티미디어학회논문지
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• 제4권5호
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• pp.371-376
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• 2001

연속적인 미디어 특성을 가진 데이터들은 시간적인 제약조건을 가진다. 일반적인 실시간 스케쥴링 알고리즘은 연속적인 미디어 특성을 고려하지 아니하므로 멀티미디어 스케줄링에 적절하지 않다. 스트라이드 스케줄러를 기본으로 하여 설계된 비율조정 비례지분 스케쥴러는 연속 미디어의 시간 제약적인 특성을 고려한 스케줄링 알고리즘이다. 일반적인 태스크를 위해 설계된 스트라이드 스케쥴러는 자원 할당에 있어서 공정성과 예측가능성을 보장한다. 비율조정 비례지분 스케쥴러에서 연속 미디어의 특성을 고려하기 위해 도입한 비율조정 기는 태스크가 지분보다 더 많은 자원을 할당받지 않도록 조정해 준다. 그러나 엄격한 비율조정 기로 인해 비율조정 비례지분 스케쥴러는 자원 할당의 공정성을 보장하지 못하다. 본 논문에서 제시하는 수정된 비례지분 스케줄러는 연속성, 시간 제약성과 같은 연속 미디어의 특성을 고려한다. 본 논문에서 제시하는 스케줄링 알고리즘은 자원 할당의 공정성을 유지하여 과부하시에 성능이 점진적으로 저하됨을 보였고 비율조정 비례지분 스케쥴러보다 문맥교환에 있어 좀 더 나은 성능을 보였다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 추계종합학술대회 논문집(1)
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• pp.445-448
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• 2000

This paper considers a scheduling algorithm for high-speed routers, where the router has an N x N port input-queued switch and the input queues are composed of N VOQ(Virtual Output Queue)s at each input port. The major concern of the paper is on the scheduling mechanism for the router. The paper discusses the preferred levels of the performance measures and then develope a non-linear mixed integer programming. Additionally, the paper suggests a heuristic scheduling algorithm for efficient and effective switching.

• 한국정밀공학회지
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• 제15권3호
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• pp.82-87
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• 1998

In order to provide a manufacturing system with efficiency and flexibility to cope with the changes in shop floor status, the integration of process planning and operations scheduling is required. In this paper, an integrated system of process planning and operations scheduling based on the concept of process net model and genetic algorithm is suggested. The process net model includes the alternative process plans. The integrated system is applied for prismatic parts.