• Journal of Korean Society for Quality Management
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• v.31 no.3
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• pp.114-125
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• 2003

In this paper, we deal with the problem of modeling of agent-based robot manufacturing cell. Its role is becoming increasingly important in automated manufacturing systems. For Object Oriented & Queueing Petri Nets (OO&QPNs), an extended formalism for the combined quantitative and qualitative analysis of different systems is used for structure and performance analysis of mobile robotic cell. In the case study, the OO&QPN model of a mobile robotic cell is represented and analyzed, considering multi-class parts, non-preemptive priority and alternative routing. Finally, the comparison of performance values between Shortest Process Time (SPT) rule and First Come First Serve (FCFS) rule is suggested. In general, SPT rule is most suitable for parts that have shorter processing time than others.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2000.04a
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• pp.253-256
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• 2000

In general, Automated Storage/Retrieval Systems (AS/RS ) have racks of equal sized cells to utilize the concept of unit-load. Most of the techniques for the performance estimation of a unit-load AS/RS are a static model or computer simulation. Especially, their models were developed under assumption that the Storage/Retrieval (S/R) machine performs only single command (SC) or dual command (DC). In reality, defending on the operating policy and the status of the system at a particular time, the S/B machine performs a SC or a DC, or becomes .: idle. In order to resolve these weak points, we propose a stochastic model for the performance estimation of unit-load AS/RS by using a single-server queueing model. Expected numbers of waiting storage and retrieval commands are found

• Journal of Korean Institute of Industrial Engineers
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• v.27 no.1
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• pp.95-102
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• 2001

The design of automobile body assembly line is one of essential parts for improving the process performance. The major objective of this research is to develop a performance evaluation model for automobile assembly line using a closed queueing network(CQN) and simulation method. In this study we used a two-step approach to compute the performance of the assembly line : first, we used CQN model considering assembly line equipments and the line operating time under the assumption of no failure, and second we used a well-known simulator FACTOR/AIM. Finally we implemented this model on a K automobile company and we have shown the sample results of automobile body assembly line.

• Journal of Korean Institute of Industrial Engineers
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• v.30 no.4
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• pp.328-337
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• 2004

Tool costs can comprise a significant part of the total operating costs of Flexible Manufacturing Systems. We address the problem of determining the optimal processing times of individual operations and routing mix in FMSs with multiple routes for each part type in order to minimize tool cost, subject to meeting a throughput constraint for each part type. The problem is formulated as a nonlinear program superimposed on a closed queueing network of the FMSs under consideration. Numerical examples reveal the potential of our approach for significant saving in tool costs.

• Journal of the Korean Operations Research and Management Science Society
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• v.29 no.4
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• pp.175-187
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• 2004

We consider the simultaneous selection of part routes for multiple part types in Flexible Manufacturing Systems (FMSs). Using an optimization framework we investigate two alternative route assignment policies. The one, called routing mix policy in the literature, specifies the optimal proportion of each part type to be produced along its alternative routes, assuming that the proportions can be kept during execution. The other one, which we propose and call pallet allocation policy, partitions the pallets assigned to each part type among the routes. The optimization framework used is a nonlinear programming superimposed on a closed queueing network model of an FMS which produces multiple part types with distinct repeated visits to certain workstations. The objective is to maximize the weighted throughput. Our study shows that the simultaneous use of multiple routes leads to reduced bottleneck utilization, improved workload balance, and a significant increase in the FMS's weighted throughput, without any additional capital investments. Based on numerical work, we also conjecture that pallet allocation policy is more robust than routing mix policy, operationally easier to implement, and may yield higher revenues.

• Journal of applied mathematics & informatics
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• v.33 no.1_2
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• pp.77-87
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• 2015

Parallel lines are often used to increase production rate in many manufacturing systems where the main line splits into several lines in parallel, and after some operations, they merge into a main line again. Queueing networks with finite buffers have been widely used for modeling and analyzing manufacturing systems. This paper provides an approximation technique for multi-server two-stage networks with merge configuration and blocking which will be a building block for analysis of general manufacturing systems with parallel lines and merge configuration. The main idea of the method is to decompose the original system into subsystems that have two service stations with multiple servers, two buffers and external arrivals to the second stage are allowed. The subsystems are modeled by level dependent quasi-birth-and-death (LDQBD) process.

• Proceedings of the IEEK Conference
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• 2003.07a
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• pp.637-640
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• 2003

본 논문은 리눅스를 내장하며, 다양한 인터페이스와 서비스 어플리케이션을 갖는 홈게이트웨이 시스템에서 리얼타임 서비스를 보장하며, 각 서비스 클래스에 대한 공정성을 보장하는 동적 우선순위 큐잉에 관한 연구이다. 기존의 리눅스에서는 동일한 우선순위를 부여함으로써 리얼타임 서비스에 대한 보장을 지원하지 못한다. 또한 리얼타임 서비스에 정적인 우선순위를 부여한다면 비리얼타임 서비스의 지연이 크게 되거나 서비스를 받지 못하는 기아현상이 발생한다. 본 논문에서는 일반 리눅스 커널에 리얼타임 리눅스 커널을 포팅하고, 리얼타임 커널에 큐잉엔진을 구현한다. 큐잉엔진은 동적 우선순위를 부여하고 리얼타임 스케줄러에 의해 처리되도록 함으로써, 리얼타임 서비스을 보장하고, 비리얼타임 서비스의 기아현상을 제거하며, 각 응용 서비스 클래스에 대한 서비스 공정성을 보장함으로써, 홈게이트웨이 시스템의 성능을 향상 시킨다.

• Proceedings of the Korea Multimedia Society Conference
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• 2000.11a
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• pp.561-566
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• 2000

Computer-Communication System may be classified into two kinds of systems considering connection capability among terminal and computing facility : time sharing and distributed computer systems According to the different input characteristic, the buffer behavior of two systems is quite different. Here we restrict our study to the analysis of queueing behavior of a demultiplexing buffer of time sharing systems. The analysis shows that M/G/1 queueing model can be used model such behavior.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.4 no.4
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• pp.329-333
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• 2003

In this paper we analyze the performance of the low latency pre-registration handoff method of mobile IP by computer simulation. Packet losses and delays are evaluated in terms of system utilization. Foreign agents that participate in the handoff process can be modeled as queues representing input and output ports. Therefore, we propose an analytical model of pre-registration handoff by using open queueing network model. Simulation results are shown for validating analytical estimates.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.7 no.1
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• pp.15-23
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• 2003

ATM networks provide the various kinds of service which require the different Quality of Services(QoS) such as loss and delay. By statistically multiplexing of traffics and the uncertainty and fluctuation of source traffic pattern, the congestion may occur. The leaky bucket scheme is a representative policing mechanism for preventive congestion control. In this paper, we analyze the HOL(Head-of-Line) priority leaky bucket scheme. That is, traffics are classified into real-time and nonreal-time traffic. The real-time traffic has priority over nonreal-time traffic for transmission. For proposed mechanism, we obtain the system state distribution, finally the loss probability and the mean waiting time of real-time and nonreal-time traffic. The simple numerical examples also are presented.