• 전기학회논문지
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• 제59권3호
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• pp.485-491
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• 2010

Total Transfer Capability (TTC) should be pre-determined in order to estimate Available Transfer Capability (ATC). Typically, TTC is determined by considering three categories; voltage, stability and thermal limits. Among these, thermal limits are treated mainly in this paper on the evaluation of TTC due to the relatively short transmission line length of Korea Electric Power Corporation (KEPCO) system. This paper presents a new approach to evaluate the TTC using the Dynamic Line Rating (DLR) for the thermal limit. Since the approach includes not only traditional electrical constraints but also real-time environmental constraints, this paper obtains more cost-effective and exact results. A case study using KEPCO system confirms that the proposed method is useful for real-time operation and the planning of the electricity market.

• ETRI Journal
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• 제32권3호
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• pp.422-429
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• 2010

We present guaranteed dynamic priority assignment schemes for multiple real-time tasks subject to (m, k)-firm deadlines. The proposed schemes have two scheduling objectives: providing a bounded probability of missing (m, k)-firm constraints and maximizing the probability of deadline satisfactions. The second scheduling objective is especially necessary in order to provide the best quality of service as well as to satisfy the minimum requirements expressed by (m, k)-firm deadlines. We analytically establish that the proposed schemes provide a guarantee on the bounded probability of missing (m, k)-firm constraints. Experimental studies validate our analytical results and confirm the effectiveness and superiority of the proposed schemes with regard to their scheduling objectives.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2002년도 춘계학술발표논문집 (상)
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• pp.687-690
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• 2002

In this paper, we present a novel semaphore implementation scheme which shortens finish time of high priority tasks and improves reliability of a system. The real-time systems have time constraints. Especially, the task with hard real-time constraints must meet its deadline. Consequently, managing shared resources is considered guaranteeing mutual exclusion as well as meeting task's deadline under unfavorable condition. According to the number and sort of the locked semaphores under the event occurred, this paper presents the reduction of the finish time of high priority task by decision whether the context switched or not. The experimental results show that the proposed method gives performance improvements in finish time of high priority tasks of about 11% over zuberi[4] method.

• 한국정보처리학회논문지
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• 제1권2호
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• pp.244-253
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• 1994

컴퓨터 네트워크들은 여러 가지 다양한 서비스의 지원이 요구된다. 컴퓨터 네트 워크를 통해서 전송되는 음성, 화상 기타 긴급 전송과 관련된 메시지들은 명확한 전 송제한 시간을 갖는 실시간 통신 기법이 요구된다. 본 논문에서는 예약기법을 이용한 이중-링크 네트워크에서 사용하는 실시간 통신기법을 개선하여, 실시간 메시지 전송시 에 전송제한시간을 기초로하여 메시지 전송순위를 결정하는 스케듈링 기법을 제시한다. 제시된 기법의 성능을 비교 분석을 위해 SLAM II언어를 사용하여 시뮬레이션을 하였다. 시뮬레이션에서는 시스템 부하의 변화에 따른 메시지 상실률을 비교 분석 하였다.

• International journal of advanced smart convergence
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• 제11권1호
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• pp.28-35
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• 2022

This paper presents a performance evaluation of real-time Linux for industrial real-time platforms. On industrial platforms, multicore processors are popular due to their work distribution efficiency and cost-effectiveness. Multicore processors, however, are not designed for applications with real-time constraints, and their performance capabilities depend on their core configurations. In order to assess the feasibility of a multicore processor for real-time applications, we conduct a performance evaluation of a general processor and a low-power processor to provide an experimental environment of real-time Linux on both Xenomai and RT-preempt considering the multicore configuration. The real-time performance is evaluated through scheduling latency and in an environment with loads on the CPU, memory, and network to consider an actual situation. The results show a difference between a low-power and a general-purpose processor, but from developer's point of view, it shows that the low-power processor is a proper solution to accommodate low power situations.

• 대한전기학회논문지:전력기술부문A
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• 제48권6호
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• pp.781-788
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• 1999

In this paper, an expert system is proposed, which can be effectively applied to the large-scale systems with the diversity time constraints, the objectives and the unfixed system structure. The inference scheme of the expert system have the integrated structure composed of the intuitive inference module and logical inference module in order to support effectively the operating constraints of system. The intuitive inference module is designed using the pattern matching or pattern recognition method in order to search a same or similar pattern under the fixed system structure. On the other hand, the logical inference module is designed as the structure with the multiple inference mode based on the heuristic search method in order to determine the optimal or near optimal control strategies satisfing the time constraints for system events under the unfixed system structure, and in order to use as knowledge generator. Here, inference mode consists of the best-first, the local-minimum tree, the breadth-iterative, the limited search width/time method. Finally, the application results for large-scale distribution SCADA system proves that the inference scheme of the expert system is very effective for the large-scale system. The expert system is implemented in C language for the dynamic mamory allocation method, database interface, compatability.

• 한국멀티미디어학회논문지
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• 제10권12호
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• pp.1741-1751
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• 2007

The imprecise computation technique ensures that all time-critical tasks produce their results before their deadlines by trading off the quality of the results for the computation time requirements of the tasks. In the imprecise computation, most scheduling problems of satisfying both 0/1 constraints and timing constraints, while the total error is minimized, are NP-complete when the optional tasks have arbitrary processing times. In the previous studies, the reasonable strategies of scheduling tasks with the 0/1 constraints on uniprocessors and multiprocessors for minimizing the total error are proposed. But, these algorithms are all off-line algorithms. Then, in the on-line scheduling, NORA(No Off-line tasks and on-line tasks Ready upon Arrival) algorithm can find a schedule with the minimum total error. In NORA algorithm, EDF(Earliest Deadline First) strategy is adopted in the scheduling of optional tasks. On the other hand, for the task system with 0/1 constraints, NORA algorithm may not suitable any more for minimizing total error of the imprecise tasks. Therefore, in this paper, an on-line algorithm is proposed to minimize total error for the imprecise real-time task system with 0/1 constraints. This algorithm is suitable for the imprecise on-line system with 0/1 constraints. Next, to evaluate performance of this algorithm, a series of experiments are done. As a consequence of the performance comparison, it has been concluded that IOSMTE(Imprecise On-line Scheduling to Minimize Total Error) algorithm proposed in this paper outperforms LOF(Longest Optional First) strategy and SOF(Shortest Optional First) strategy for the most cases.

• 제어로봇시스템학회논문지
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• 제8권6호
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• pp.506-513
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• 2002

Distributed control systems(DCS) using fieldbus such as CAN have been applied to process systems but it is very difficult to design the DCS while guaranteeing the given end-to-end constraints such as precedence constraints, time constraints, and periods and priorities of tasks and messages. This paper presents a scheduling method to guarantee the given end-to-end constraints. The presented scheduling method is the integrated one considering both tasks executed in each node and messages transmitted via the network and is designed to be applied to a general DCS that has multiple loops with several types of constraints, where each loop consists of sensor nodes with multiple sensors, actuator nodes with multiple actuators and controller nodes with multiple tasks. An assignment method of the optimal period of each loop and a heuristic assignment rule of each message's priority are proposed and the integrated scheduling method is developed based on them.

• 대한전자공학회논문지SP
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• 제37권3호
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• pp.57-69
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• 2000

본 논문에서는 주행차량에 장착된 CCD 카메라를 통하여 획득되어진 영상으로부터 moving window를 사용하여 차선을 인식하고 장애물을 감지하는 방법을 제안한다 입력되는 동영상을 실시간에 처리하기 위해서는 하드웨어적으로 상당히 많은 제약을 초래한다. 이러한 문제점을 극복하고 영상을 사용하여 실시간에 차선 인식 및 장애물을 감지하기 위해, 도로조건과 차량상태에 바탕을 둔 최적의 window 크기를 결정하고 그 window 영상만을 처리하여 차선 인식 및 장애물 감지를 실시간에 가능하게 하는 기법을 제안한다 영상의 각 프레임에 대하여 moving window는 칼만필터에 의해 정확성이 향상된 예측방향으로 옮겨진다. 제안된 알고리즘의 효용성을 고속도로 주행영상을 사용한 실험을 통해 보여준다

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2009년도 추계학술대회
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• pp.966-968
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• 2009

IEEE 802.16 시스템에서는 실시간 및 비실시간의 다양한 서비스를 제공하고 있으며 효율적인 자원활용을 위해서는 적절하게 자원을 할당하는 것이 중요하다. 지금까지 OFDMA 환경에서 실시간 및 비실시간 패킷을 효율적으로 자원 할당하는 방법은 많이 연구되었으나, IEEE 802.16 시스템에 적용하기 위해서는 시스템의 특성에 맞게 적용해야 할 필요가 있다. 특히 IEEE 802.16에서는 여러 가지 QoS 제한조건을 가진 5가지 서비스 클래스를 지원하므로 이러한 클래스들의 특성을 고려하는 것이 중요하다. 따라서 본 논문에서는 IEEE 802.16 시스템에서 제공하는 서비스들의 QoS 제한조건을 고려하여 다양한 서비스들을 효율적으로 제공하는 스케줄링 기법을 제안하고자 한다.