• Title/Summary/Keyword: Real-Time Scheduling System

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The Efficient Buffer Management for a Multimedia File System (멀티미디어 파일 시스템을 위한 효율적 버퍼 관리)

  • Hong, Chul-Eui
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.15 no.8
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    • pp.1743-1749
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    • 2011
  • The multimedia data for video-on-demand(VOD) service has large, continuous and real time characteristics. The frequent disk I/O operations takes much time and decrease the system performance in multimedia services. Therefore the efficient buffer management is needed in order to reduce the disk accesses to multimedia data. This paper addresses how to increase the buffer hit ratio and the number of users in a multimedia service like VOD by increasing the utility of buffer. This paper also simulated various resource management algorithms and strategies and evaluated, compared and analyzed their performances.

Design and Implementation of Vehicle Delivery Planning System for the Improvement Logistics Services (물류 서비스 향상을 위한 배차계획 시스템의 설계 및 구현)

  • Lee Myeong-Ho
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.7 no.4
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    • pp.587-593
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    • 2006
  • Development of digital information and internet technology causes the changes of technology environments and companies, and the variety of customers needs has been dynamically changed in terms of integrating information system with customers satisfaction. Moreover a new logistics concept is needed through the sharing information between suppliers and consumers, which maximizes the customers service and its flexibility by changing functional-oriented to process-oriented. Many research papers on transportation studies have focused on the Vehicle Routing Problem (VRP) and Vehicle Scheduling Problem (VSP). However in the real world, it is known that it takes long time to build vehicle scheduling in the process of transporting the amount of orders from the logistics center to the vendors due to the realistic constraints. This paper presents a framework design for each process enabling delivery planning automatically using heuristic algorithm. In addition, an interactive delivery planning system is implemented utilizing the proposed algorithm.

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Analysis of Tour Information Services using Agent-based Simulation (시뮬레이션 모형을 통한 관광정보서비스 효과 분석)

  • Kim, Hyeon-Myeong;O, Jun-Seok
    • Journal of Korean Society of Transportation
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    • v.24 no.6 s.92
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    • pp.103-117
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    • 2006
  • This study develops an agent-based simulation model to evaluate tourist information systems under ubiquitous environment. In this study, individual tourist's activity chaining behavior is formulated as a utility maximization problem. The underlying assumption of the model is that tourists increase their activities within their time and budget constraints to maximize their utilities. The model seeks individual's optimal tour schedule by solving Prize-Collecting Multiple-Day Traveling Salesman Problem(PC MD TSP). The simulation-based evaluation framework allows investigating individual utility gains by their information type and the total expenditure at each tour attractions. The real-time tour activity scheduling system enables tourists to optimize their tour activities by minimizing their time loss and maximizing their opportunity to use high utility facilities.

An Efficient Genetic Algorithm for the Allocation and Engagement Scheduling of Interceptor Missiles (효율적인 유전 알고리즘을 활용한 요격미사일 할당 및 교전 일정계획의 최적화)

  • Lee, Dae Ryeock;Yang, Jaehwan
    • Journal of Korean Society of Industrial and Systems Engineering
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    • v.39 no.2
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    • pp.88-102
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    • 2016
  • This paper considers the allocation and engagement scheduling problem of interceptor missiles, and the problem was formulated by using MIP (mixed integer programming) in the previous research. The objective of the model is the maximization of total intercept altitude instead of the more conventional objective such as the minimization of surviving target value. The concept of the time window was used to model the engagement situation and a continuous time is assumed for flying times of the both missiles. The MIP formulation of the problem is very complex due to the complexity of the real problem itself. Hence, the finding of an efficient optimal solution procedure seems to be difficult. In this paper, an efficient genetic algorithm is developed by improving a general genetic algorithm. The improvement is achieved by carefully analyzing the structure of the formulation. Specifically, the new algorithm includes an enhanced repair process and a crossover operation which utilizes the idea of the PSO (particle swarm optimization). Then, the algorithm is throughly tested on 50 randomly generated engagement scenarios, and its performance is compared with that of a commercial package and a more general genetic algorithm, respectively. The results indicate that the new algorithm consistently performs better than a general genetic algorithm. Also, the new algorithm generates much better results than those by the commercial package on several test cases when the execution time of the commercial package is limited to 8,000 seconds, which is about two hours and 13 minutes. Moreover, it obtains a solution within 0.13~33.34 seconds depending on the size of scenarios.

Automated Schedulability-Aware Mapping of Real-Time Object-Oriented Models to Multi-Threaded Implementations (실시간 객체 모델의 다중 스레드 구현으로의 스케줄링을 고려한 자동화된 변환)

  • Hong, Sung-Soo
    • Journal of KIISE:Computing Practices and Letters
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    • v.8 no.2
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    • pp.174-182
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    • 2002
  • The object-oriented design methods and their CASE tools are widely used in practice by many real-time software developers. However, object-oriented CASE tools require an additional step of identifying tasks from a given design model. Unfortunately, it is difficult to automate this step for a couple of reasons: (1) there are inherent discrepancies between objects and tasks; and (2) it is hard to derive tasks while maximizing real-time schedulability since this problem makes a non-trivial optimization problem. As a result, in practical object-oriented CASE tools, task identification is usually performed in an ad-hoc manner using hints provided by human designers. In this paper, we present a systematic, schedulability-aware approach that can help mapping real-time object-oriented models to multi-threaded implementations. In our approach, a task contains a group of mutually exclusive transactions that may possess different periods and deadline. For this new task model, we provide a new schedulability analysis algorithm. We also show how the run-time system is implemented and how executable code is generated in our frame work. We have performed a case study. It shows the difficulty of task derivation problem and the utility of the automated synthesis of implementations as well as the Inappropriateness of the single-threaded implementations.

Development of Part Sales Agent Coupled with Virtual Manufacturing in Internet Environment (인터넷상의 가상생산 기반 부품판매 에이전트 개발)

  • Choi, Hyung-Rim;Kim, Hyun-Soo;Park, Young-Jae;Park, Byoung-Joo;Lee, Kyoung-Jun
    • Asia pacific journal of information systems
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    • v.12 no.4
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    • pp.193-213
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    • 2002
  • The sales activity of most of small manufacturing companies is based on orders of buyers. The process of promotion, negotiation, receipt and selection of orders of the manufacturers is closely coupled with the load status of the production lines. The decision on whether to accept an order or not, or the selection of optimal order set among excessive orders is entirely dependent on the schedule of production lines. However, in the real world, since the production scheduling activity is mainly performed by human experts, most of small manufacturers are suffer from being unable to meet due dates, lack of rapid decision on the acceptance of new order. Recently, Internet based Electronic Commerce is recognized as one of the alternatives for strengthening sales power of small and medium companies. However, small and medium manufacturers can't adjust properly to the new environment because they are in short of money, personnel, and technology. To cope with this problem, this paper deals with development of part sales agent coupled with virtual manufacturing in Internet environment that consist of selection agent, advertisement agent, selection agent, negotiation agent, and virtual manufacturing system. This paper develops a time-bounded negotiation mechanism for small and medium manufacturers in agent-based automated negotiation between customers and negotiation agents. Furthermore, to select optimal order set maximized profit, we first formulate the order selection problem with mixed integer programming, but the computation time of IP is not acceptable for real world scale problem. To overcome this problem and dynamic nature of virtual manufacturing, we suggest a genetic algorithm approach, which shows a reasonable computation time for real world case and good incremental problem solving capability.

An Improved Online Algorithm to Minimize Total Error of the Imprecise Tasks with 0/1 Constraint (0/1 제약조건을 갖는 부정확한 태스크들의 총오류를 최소화시키기 위한 개선된 온라인 알고리즘)

  • Song, Gi-Hyeon
    • 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.

Development of Intelligent ATP System Using Genetic Algorithm (유전 알고리듬을 적용한 지능형 ATP 시스템 개발)

  • Kim, Tai-Young
    • Journal of Intelligence and Information Systems
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    • v.16 no.4
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    • pp.131-145
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    • 2010
  • The framework for making a coordinated decision for large-scale facilities has become an important issue in supply chain(SC) management research. The competitive business environment requires companies to continuously search for the ways to achieve high efficiency and lower operational costs. In the areas of production/distribution planning, many researchers and practitioners have developedand evaluated the deterministic models to coordinate important and interrelated logistic decisions such as capacity management, inventory allocation, and vehicle routing. They initially have investigated the various process of SC separately and later become more interested in such problems encompassing the whole SC system. The accurate quotation of ATP(Available-To-Promise) plays a very important role in enhancing customer satisfaction and fill rate maximization. The complexity for intelligent manufacturing system, which includes all the linkages among procurement, production, and distribution, makes the accurate quotation of ATP be a quite difficult job. In addition to, many researchers assumed ATP model with integer time. However, in industry practices, integer times are very rare and the model developed using integer times is therefore approximating the real system. Various alternative models for an ATP system with time lags have been developed and evaluated. In most cases, these models have assumed that the time lags are integer multiples of a unit time grid. However, integer time lags are very rare in practices, and therefore models developed using integer time lags only approximate real systems. The differences occurring by this approximation frequently result in significant accuracy degradations. To introduce the ATP model with time lags, we first introduce the dynamic production function. Hackman and Leachman's dynamic production function in initiated research directly related to the topic of this paper. They propose a modeling framework for a system with non-integer time lags and show how to apply the framework to a variety of systems including continues time series, manufacturing resource planning and critical path method. Their formulation requires no additional variables or constraints and is capable of representing real world systems more accurately. Previously, to cope with non-integer time lags, they usually model a concerned system either by rounding lags to the nearest integers or by subdividing the time grid to make the lags become integer multiples of the grid. But each approach has a critical weakness: the first approach underestimates, potentially leading to infeasibilities or overestimates lead times, potentially resulting in excessive work-inprocesses. The second approach drastically inflates the problem size. We consider an optimized ATP system with non-integer time lag in supply chain management. We focus on a worldwide headquarter, distribution centers, and manufacturing facilities are globally networked. We develop a mixed integer programming(MIP) model for ATP process, which has the definition of required data flow. The illustrative ATP module shows the proposed system is largely affected inSCM. The system we are concerned is composed of a multiple production facility with multiple products, multiple distribution centers and multiple customers. For the system, we consider an ATP scheduling and capacity allocationproblem. In this study, we proposed the model for the ATP system in SCM using the dynamic production function considering the non-integer time lags. The model is developed under the framework suitable for the non-integer lags and, therefore, is more accurate than the models we usually encounter. We developed intelligent ATP System for this model using genetic algorithm. We focus on a capacitated production planning and capacity allocation problem, develop a mixed integer programming model, and propose an efficient heuristic procedure using an evolutionary system to solve it efficiently. This method makes it possible for the population to reach the approximate solution easily. Moreover, we designed and utilized a representation scheme that allows the proposed models to represent real variables. The proposed regeneration procedures, which evaluate each infeasible chromosome, makes the solutions converge to the optimum quickly.

A study of real-time media streaming delivery over P2P networks (P2P 환경에서 실시간 미디어스트리밍의 전송에 관한 연구)

  • Liu Xu-dong;Jo In-June
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • 2006.05a
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    • pp.538-541
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    • 2006
  • Recently researches of P2P media streaming have been actively published, but the research what kind of P2P overlay networks are better to delivering media data has not been attended. This paper designs a P2P streaming media system model. In this system, we constructs a Half-Structure P2P overlay protocol based on node's capability as the infrastructure of streaming application, which utilizes the heterogeneity of the nodes to maintain topology, presents a active contents diffusing algorithm and Two-stage search algorithm, make it possible for nodes in P2P system to collect information according their capacity and reduces the number of forwarding packet compared with flooding. Also, we give an optimal scheme to scheduling media data.

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A Knowledge-based Approach to Plant Construction Process Planning (지식 기반 플랜트 건설 공정 계획 시스템의 개발)

  • 김우주
    • Journal of Intelligence and Information Systems
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    • v.7 no.1
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    • pp.81-95
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    • 2001
  • Plant construction projects usually take much higher uncertainty and risks than the projects from other domains. This implies the importance of plant construction project management should be more emphasized than the other domain. Especially, the overall successes of the projects often depend on the performance of process planning and scheduling performed at the initial stage of the project. However, most plant construction projects suffer great difficulties in establishing proper process planning and scheduling timely because of unstructureness and dynamicity of environment of the project itself In this paper, we propose a knowledge-based process planning and scheduling approach in a plant construction domain to cope this problem. First, we modulize process planning knowledge and present the knowledge representation scheme. Second, we propose an inferencing mechanism to build a process planning for plant construction based on the represented process planning knowledge. Since our approach automate the initial process planning, which was usually done by manual way, it can improve the correctness and also completeness of the process plan and schedule by reducing the time to plan and allowing simulations on the various situation. We also design and implement this our approach as a real working system, and it is successfully applied to real plant construction cases from a leading construction company in Korea. Based on this success, we expect our approach can be easily applied to the projects of other areas, while contributing to enhancement in productivity and quality of project management.

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