• Proceedings of the Safety Management and Science Conference
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• 2000.05a
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• pp.97-110
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• 2000

Production schedule and realization quantity of Large type bus [929(HD), 928, 928-A(SD), 937E/L, 937/L,] were analyzed in order to intruoduce FMS(Flexible Manufacturing System) appropriate for varities of customer desire and multi-item, small lot production. And this paper is aimed to propose introduction method of FMS, analyzing zig tools change times and idle times with production line and workers as an object. According to analysis results, only simple spec., depending on bus type, changed with decrease in production. For 929(HD), 928,928-A(SD), 937Eh, 937/L bus type, there was no harmony between schdule and realization. Therefore, it caused many difficulties in part supply. And there was loss of manpower and reduction of productibility due to idle time of process with bus type change. Production processes were operated inefficiently because tact time exceeded or shortaged of allow time.

• Journal of the Korean Operations Research and Management Science Society
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• v.27 no.2
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• pp.51-61
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• 2002

By using the arrival time approach of Chae et at. [6], we derive various performance measures including the queue length distributions (in PGFs) and the waiting time distributions (in LST and PGF) for both M$^{x}$ /G/1 and Geo$^{x}$ /G/1 queueing systems, both under the assumption that the server, when it becomes idle, takes multiple vacations up to a random maximum number. This is an extension of both Choudhury[7] and Zhang and Tian [11]. A few mistakes in Zhang and Tian are corrected and meaningful interpretations are supplemented.

• Proceedings of the Korea Information Processing Society Conference
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• 2006.05a
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• pp.1283-1286
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• 2006

본 논문에서는 관찰된 채널의 유휴 시간을 이용하여, ACK(Acknowledgement) 기반의 링크 적응 기술의 단점을 극복하는 새로운 알고리즘인 COLA 를 제안한다. COLA 는 광범위한 채널과 부하 상황에서 최적의 성능을 얻으며 RTS/CTS 메커니즘이나 하드웨어를 이용한 채널 SNR 측정과 같은 추가적인 옵션 혹은 별도의 프로토콜 메커니즘의 지원이 필요하지 않다. 또한 COLA 알고리즘은 단지 짧은 10 개의 critical 한 명령어를 사용함으로써 부하를 줄이며, 실제 동작 시 수반되는 heuristic 한 매개변수로부터 자유롭고, 따라서 실제 사용 시 장점을 가진다.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.3
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• pp.473-479
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• 2008

Generally, HDDs are widely used as data storage device in office, home and mobile machineries. So, it is used for various applications or tasks, such as file copy, file download, music and movie play etc., in various environment. In spite of this kind of varieties in tasks and environment in which HDDs perform, most commercial HDDs hardly control its operations adaptively to these varieties. Thus, it is preferred to optimize the performance and energy consumption of HDDs according to the task and/or the environment. So, this paper proposes a new fuzzy inference algorithm which adaptively controls HDDs operations and may also easily be implemented as the firmware of HDDs and run in the restricted environment such as embedded systems.

• Industrial Engineering and Management Systems
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• v.15 no.2
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• pp.123-130
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• 2016

We introduce a queueing system with general arrival stream and exponential service time under the N-policy, where customers may renege during idle period and arrival rates may vary according to the server's status. Probability distributions of the lengths of idle period and busy period are derived using absorbing Markov chain approach and a method to obtain the optimal control policy that minimizes long-run expected operating cost per unit time is provided. Numerical analysis is done to illustrate and characterize the method.

• Journal of the Korean Operations Research and Management Science Society
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• v.26 no.1
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• pp.87-96
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• 2001

This paper considers the transfer batch scheduling problem for a two-machine flow shop with setup times consisting of attached setup time and separate setup time. The attached setup is attached to the processing and can be scheduled in anticipation of arriving work. Two cases of the separate setup are addressed. One is the case that the separate setup can be done only when a machine is idle. The other is the case that the separate setup can be done even though the machine is idle. the other is the case that the separate setup can be done even though the machine is operating. A scheduling rule similar to Johnson\`s rule is suggested to minimize makespan. the scheduling rule developed can be applied to most of the two-machine flow shop scheduling problems if some parameters are adjusted. A numerical example is presented to illustrate the scheduling rule.

• Journal of Korea Multimedia Society
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• v.7 no.12
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• pp.1754-1764
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• 2004

Lately mobile handheld devices such as Personal Digital Assistant (PDA) and cellular phones are getting more popular for personal web surfing. However, today most mobile handheld devices have relatively poor web browsing capability due to their low performance so their users have to suffer longer communication latency than those of desktop Personal Computers (PCs). In this paper, we propose an effective pre-refresh mechanism for embedded web browser of mobile handheld devices to reduce this problem. The proposed mechanism uses the idle time to pre-refresh the expired web objects in an embedded web browser's cache memory. It increases the utilization of Central Processing Unit (CPU) power and network bandwidth during the idle time and consequently reduces the client's latency and web browsing cost. An experiment was done using a simulator designed by us to evaluate the efficacy of the proposed mechanism. The experiment result demonstrates that it has a good performance to make web surfing faster.

• Proceedings of the KIEE Conference
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• 1997.07b
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• pp.672-674
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• 1997

In this paper, we study the idle speed control of the spark ignition engine. Engine idle speed control is a difficult problem because of troublesome characteristics such as severe process nonlinearities, variable time delays, time-varying dynamics and unobservable internal system states and disturbances. We investigate the intelligent control algorithms such as neural network controller and fuzzy controller for 4-cylinder 4-stroke engine.

• Journal of Korean Institute of Industrial Engineers
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• v.22 no.3
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• pp.313-324
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• 1996

A new policy to determine the waiting position of an idle Automated Guided Vehicle(AGV) is proposed and its performance is compared with the existing waiting position policies. Unlike the existing policies, the queue length in the input buffer is considered in the new policy. As a result, the waiting position based on the new policy depends on the status of the system. The simulation result indicates that the proposed policy reduces the waiting time in both the input and the output buffers significantly, regardless of the number of AGVs in the system. Therefore, the manufacturing lead time can be minimized.

• Journal of the Korea Society for Simulation
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• v.11 no.4
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• pp.69-80
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• 2002

This study deals with the productivity improvement on a flow production system with the consideration of line-balancing. In a flow production system, similar product models are produced on a same assembly line, the predefined process order and the limitation of total worker number. The system can be increased the work-in -process(WIP) inventory and the worker's idle time. In this study, the worker assignment model is developed to assign evenly workload of process to each product model in such a manner that each process has the different number of worker. This worker assignment model is the mathematical model that determines worker number in each process such that the idle time of processes is reduced and the utilization of worker is improved. We use a simulation technique to simulate the production line proposed by the mathematical model and apply real production line. With the result of simulation, this study analyzes the propriety of production line and proposes the alternatives of new production line