• Journal of KIISE:Computer Systems and Theory
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• v.30 no.12
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• pp.736-748
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• 2003

Dynamic voltage scaling(DVS), which adjusts the clock speed and supply voltage dynamically, is an effective technique in reducing the energy consumption of embedded real-time systems. The energy efficiency of a DVS algorithm largely depends on the performance of the slack estimation method used in it. In this paper, we propose novel DVS algorithms for periodic hard real-time tasks based on an improved slack estimation algorithm. Unlike the existing techniques, the proposed method can be applied to most priority-driven scheduling policies. Especially, we apply the proposed slack estimation method to EDF and RM scheduling policies. The experimental results show that the DVS algorithms using the proposed slack estimation method reduce the energy consumption by 20∼40 % over the existing DVS algorithms.

• The KIPS Transactions:PartA
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• v.18A no.4
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• pp.143-150
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• 2011

This paper presents an EDF based scheduling algorithm for scheduling imprecise computation model where each task consists of mandatory part and optional part. Imprecise computation is useful to manage overload condition. In overload situation, some optional parts should be removed. The proposed DOP algorithm removes optional parts of earlier deadline tasks to enhance flexibly for newly arriving tasks. A simulation result shows that DOP has better performance than other algorithms.

• The KIPS Transactions:PartA
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• v.12A no.5 s.95
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• pp.355-364
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• 2005

With fast advances in computing power and network technologies, online streaming services of continuous media (CM) have been popularly implemented on the Web. To implement such services, a variety of CM streams need to be processed efficiently, so that the Sweep scheme was proposed. This scheme has several advantages such as hiccup-free playbacks and seek-time optimization. In this scheme, however, the entire CM streams are scheduled with a single scheduling period, called a cycle. Since only one scheduling period is allowed in this scheme, a significant amount of disk time is usually wasted because of its inflexible disk schedules. To solve this, we propose a new dynamic Sweep scheme. For this, we devise an algorithm that is able to expand scheduling periods of serviced CM streams and propose a new admission control mechanism guaranteeing hiccup-free playbacks. To show performance gains, we execute various simulation experiments. From the experimental results, we can see that the proposed scheme outperforms the Sweep scheme in terms of disk utilization and scheduling flexibility.

• Journal of KIISE:Computer Systems and Theory
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• v.34 no.10
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• pp.493-501
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• 2007

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 at 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. In the online scheduling, the NORA algorithm can find a schedule with the minimum total error for the imprecise online task system. In NORA algorithm, EDF strategy is adopted in the optional scheduling. On the other hand, for the task system with 0/1 constraint, EDF_Scheduling may not be optimal in the sense that the total error is minimized. Furthermore, when the optional tasks are scheduled in the ascending order of their required processing times, NORA algorithm which EDF strategy is adopted may not produce minimum total error. Therefore, in this paper, an online algorithm is proposed to minimize total error for the imprecise task system with 0/1 constraint. Then, to compare the performance between the proposed algorithm and NORA algorithm, a series of experiments are performed. As a conseqence of the performance comparison between two algorithms, it has been concluded that the proposed algorithm can produce similar total error to NORA algorithm when the optional tasks are scheduled in the random order of their required processing times but, the proposed algorithm can produce less total error than NORA algorithm especially when the optional tasks are scheduled in the ascending order of their required processing times.

• Proceedings of the Korean Information Science Society Conference
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• 2001.10b
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• pp.583-585
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• 2001

최근 들어 인터넷의 발달로 웹기반 교육시스템을 이용한 온라인 강좌는 컴퓨터 교육 시스템 분야의 이슈로 부각되고 있으며 이러한 웹기반 교육시스템의 보급과 더불어 사용자의 다양한 교육 서비스에 대한 욕구 증대에 따른 교육서비스를 응용한 연구가 활발히 진행되고 있다. 학습자와 교사간의 상호작용을 위한 도구들이 다양하게 지원되고 있지만, 교과과정을 개설하고 이를 운영하는 교사의 입장에서 볼 때 등록한 모든 학생들이 대면하게 되는 상황을 모두 접수하고, 그들의 학습 상태를 분석하여 학습자에게 가장 적합한 코스 구성 및 스케줄을 제공한다는 것은 어려운 일이다. 따라서, 이러한 웹기반 교육 시스템에서의 학습자에게 효과적인 학습 방법과 코스 구성, 그리고 코스 스케줄 등의 피드백을 제공할 수 있는 에이전트가 필요하게 되었다. 또한, 최근에 학습자의 요구에 맞는 코스웨어 주문이 증가되고 있는 추세이며 그에 따라 웹 기반 교육 시스템의 효율적이고 자동화된 교육 에이전트의 필요성이 인식되고 있다. 본 논문에서는 학습자의 학습 모니터링과 지속적인 학습 평가에 의하여 개인 학습자의 학습 성취도를 계산하여 학습자에게 적합한 코스 스케줄을 제공해 주는 코스 스케줄링 멀티 에이전트를 제안하고자 한다.

• Journal of the Korea Computer Industry Society
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• v.10 no.4
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• pp.115-120
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• 2009

Most reservation systems make a reservation without customer's preference on-line. These reservation systems had problems not to improve customer's preference in modern society. To solve these problems, we have tried to apply these problems to complex scheduling technique. The scheduling technique for performing art reservation proposed in this thesis is based on object-oriented concepts. To consider the over all satisfaction, the events of every object are alloted to the sitting plan board along its priority. We have scheduled to rise customer's satisfaction in the performing art reservation.

• Proceedings of the Korea Multimedia Society Conference
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• 2001.11a
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• pp.719-723
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• 2001

웹기반 교육시스템을 이용한 온라인 강좌는 인터넷의 발달과 더불어 컴퓨터 교육 시스템 분야의 이슈로 부각되고 있으며 이러한 웹기반 교육시스템의 보급과 더불어 사용자의 다양한 교육 서비스에 대한 욕구 증대에 따른 교육서비스를 응용한 연구가 활발히 진행되고 있다. 학습자와 교사간의 상호작용을 위한 도구들이 다양하게 지원되고 있지만, 교과과정을 개설하고 이를 운영하는 교사의 입장에서 볼 때, 등록한 모든 학생들이 대면하게 되는 상황을 모두 접수하고, 그들의 학습 상태를 분석하여 학습자에게 가장 적합한 코스 구성 및 스케줄을 제공한다는 것은 어려운 일이다. 따라서, 이러한 웹기반 교육 시스템에서의 학습자에게 효과적인 학습 방법과 코스 구성, 그리고 코스 스케줄 등의 피드백을 제공할 수 있는 에이전트가 필요하게 되었다. 또한, 최근에 학습자의 요구에 맞는 코스웨어 주문이 증가되고 있는 추세이며 그에 따라 웹 기반 교육 시스템의 효율적이고 자동화된 교육 에이전트의 필요성이 인식되고 있다. 본 논문에서는 학습자의 학습 모니터링과 지속적인 학습 평가에 의하여 개인 학습자의 학습 성취도를 계산하여 학습자에게 적합한 코스 스케쥴을 제공해 주는 코스 스케쥴링 멀티 에이전트를 제안하고자 한다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.3
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• pp.443-451
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• 2001

This paper addresses an on-line scheduling method for track systems in semiconductor fabrication. A track system is a clustered equipment performing photolithography process in semiconductor fabrication. Trends toward high automation and flexibility in the track systems accelerate the necessity of the intelligent controller that can guarantee reliability and optimize productivity of the track systems. This paper proposes an-efficient on-line scheduling method that can avoid deadlock inherent to track systems and optimize the productivity. We employ two procedures for the on-line scheduling. First, we define potential deadlock set to apply deadlock avoidance policy efficiently. After introducing the potential deadlock set, we propose a deadlock avoidance policy using an on-line Gantt chart, which can generate optimal near-optimal schedule without deadlock. The proposed on-line scheduling method is shown to be efficient in handling deadlock inherent to the track systems through simulation.

• Journal of the Korea Society of Computer and Information
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• v.10 no.4 s.36
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• pp.365-373
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• 2005

Ubiquitous learning environment needs various new model of e-learning as web based education system has been proposed. The demand for the customized courseware which is required from the learners is increased. the needs of the efficient and automated education agents in the web-based instruction are recognized. But many education systems that had been studied recently did not service fluently the courses which learners had been wanting and could not provide the way for the learners to study the learning weakness which is observed in the continuous feedback of the course. In this paper we propose a multi-agent system for course scheduling of learner-oriented using weakness analysis algorithm via personalized ubiquitous environment factors. First proposed system analyze learner's result of evaluation and calculates learning accomplishment. From this accomplishment the multi-agent schedules the suitable course for the learner. The learner achieves an active and complete learning from the repeated and suitable course.

• The Journal of the Korea Contents Association
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• v.7 no.1
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• pp.83-93
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• 2007

In this paper, we address a power-aware scheduling algorithm for a mixed real-time system which consists of periodic and sporadic tasks, each of which is characterized by its minimum period, worst-case execution requirement and deadline. We propose a dynamic voltage scaling algorithm called DVSMT(DVS for mixed tasks), which dynamically scales down the supplying voltage(and thus the frequency) using on-line distribution of the borrowed resources when jobs complete while still meeting their deadlines. With this scheme, we could reduce more energy consumption. As the proposed algorithm can be easily incorporated with RTOS(Real-Time Operating System), it is applicable for handhold devices and sensor network nodes that use a limited battery power. Simulation results show that DVSMT saves up 60% more than the existing algorithms both in the periodic-task and mixed-task systems.