• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 1999.10a
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• pp.91-99
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• 1999

In Pusan Harbour, new port development projects are implemented such as the Extended Terminal adjacent to the Gamman Terminal, Pusan New Port, the Nary $\infty$ piers, etc. which will require new marine traffic environments in the Passage I of Pusan Harbour Specially, the turning basin of the Extended Terminal adjacent to the Gamman Terminal gas been designed to overlay the Passage I of Pusan Harbour, Which will interrupt the inbound traffic flow and the results will be worried to decrease the efficiency of port operation. Therefore, this paper will be aimed to evaluate the traffic congestion in the Pusan Passage I due to the opening of new ports within Pusan Harbour in 2006 and 2011 by using computer simulation based the queueing theory.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.9
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• pp.2415-2423
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• 2009

We consider organizational knowledge combination process. Previous literature investigated the issue from either managerial or social aspects, emphasizing on a part of the whole process and limiting to qualitative analyses. Here we propose an integrative and quantitative approach which considers knowledge combination process from engineering perspective. We employ a queueing network model and techniques to capture the process of interactions of entities in the knowledge combination environment. By doing so, we are able to understand the performance of the knowledge combination process. The performance measures derived can provide valuable implications for managerial decisions such as planning and controlling the knowledge combination process.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.8
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• pp.1420-1426
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• 2008

This paper derives medium access delay of each AC(Access Category) in a stationary station using inter-departure time of IEEE 802.11e WLAN(Wireless LAN). Inter-departure time of IEEE 802.11e WLAN is obtained using saturation throughput of IEEE 802.11e WLAN which was the topic of our prior work. By using a simple queueing model, we evaluate mean queue length and mean delay for each AC on stationary condition. We calculate performance of each AC using this simple model and validate results using simulation.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.11
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• pp.5269-5286
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• 2018

Task scheduling is one of the key issues in improving system performance and optimizing resource management in cloud computing environment. In order to provide appropriate services for heterogeneous users, we propose a novel task scheduling strategy with service differentiation, in which the delay sensitive tasks are assigned to the rapid cloud with high-speed processing, whereas the fault sensitive tasks are assigned to the reliable cloud with service restoration. Considering that a user can receive service from either local SaaS (Software as a Service) servers or public IaaS (Infrastructure as a Service) cloud, we establish a hybrid queueing network based system model. With the assumption of Poisson arriving process, we analyze the system model in steady state. Moreover, we derive the performance measures in terms of average response time of the delay sensitive tasks and utilization of VMs (Virtual Machines) in reliable cloud. We provide experimental results to validate the proposed strategy and the system model. Furthermore, we investigate the Nash equilibrium behavior and the social optimization behavior of the delay sensitive tasks. Finally, we carry out an improved intelligent searching algorithm to obtain the optimal arrival rate of total tasks and present a pricing policy for the delay sensitive tasks.

• The Transactions of the Korea Information Processing Society
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• v.5 no.10
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• pp.2627-2640
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• 1998

In this paper, we analyze the performance of the virtual cell system[1] for the transmission of IP datagrams in mobile computer communications. A virtual cell consistsof a group of physical cells shose base stationsl are implemented b recote bridges and interconnected via high speed datagram packet switched networks. Host mobility is supported at the data link layer using the distributed hierachical location information of mobile hosts. Given mobility and communication ptems among physical cells, the problem of deploying virtual cells is equivalent to the optimization cost for the entire system where interclster communication is more expesive than intracluster communication[2]. Once an iptimal partitionof disjoint clusters is obtained, we deploy the virtual cell system according to the topology of the optimal partition such that each virtual cell correspods to a cluser. To analyze the performance of the virtual cell system, we adopt a BCMP open multipel class queueing network model. In addition to mobility and communication patterns, among physical cells, the topology of the virtual cell system is used to determine service transition probabilities of the queueing network model. With various system parameters, we conduct interesting sensitivity analyses to determine network design tradeoffs. The first application of the proposed model is to determine an adequate network bandwidth for base station networking such that the networks would not become an bottleneck. We also evaluate the network vlilization and system response time due to various types of messages. For instance, when the mobile hosts begin moving fast, the migration rate will be increased. This results of the performance analysis provide a good evidence in demonsratc the sysem effciency under different assumptions of mobility and communication patterns.

• The Transactions of the Korea Information Processing Society
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• v.7 no.8
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• pp.2484-2496
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• 2000

High speed switches have been developing to interconnect a large number of nodes. It is important to analyze the switch performance under various conditions to satisfy the requirements. Queueing analysis, in general, has the intrinsic problem of large state space dimension and complex computation. In fact, The petri net is a graphical and mathematical model. It is suitable for various applications, in particular, manufacturing systems. It can deal with parallelism, concurrence, deadlock avoidance, and asynchronism. Currently it has been applied to the performance of computer networks and protocol verifications. This paper presents a framework for modeling and analyzing ATM switch using stochastic activity networks (SANs). In this paper, we provide the ATM switch model using SANs to extend easily and an approximate analysis method to apply A TM switch models, which significantly reduce the complexity of the model solution. Cell arrival process in output-buffered Queueing A TM switch with finite buffer is modeled as Markov Modulated Poisson Process (MMPP), which is able to accurately represent real traffic and capture the characteristics of bursty traffic. We analyze the performance of the switch in terms of cell-loss ratio (CLR), mean Queue length and mean delay time. We show that the SAN model is very useful in A TM switch model in that the gates have the capability of implementing of scheduling algorithm.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.24 no.66
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• pp.11-18
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• 2001

In this paper, we analyze an M/G/1 two-phase gated service model with threshold. We consider compound Poison arrival Process and general service time, where the server fives two different modes of services in order, batch and individual services. Server starts his service when the number of arrived customers reaches the predetermined threshold . We find the PGF of the number of customers in system and LST of waiting time, with which we obtain the means of them.

• Proceedings of the Korean Information Science Society Conference
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• 2012.06a
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• pp.288-289
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• 2012

이 논문에서는 Solid State Drives(SSD)의 구조적인 특성을 활용한 Native Command Queueing(NCQ) 스케줄링 기법을 제안하려 한다. SSD는 Hard Disk Drives(HDD)와 달리 접근시간이 매우 짧고, 읽기/쓰기 속도가 서로 다르다는 특성이 있다. 그리고 SSD 내부에는 HDD와 마찬가지로 버퍼캐시가 존재한다. 이런 특성들을 활용하여 커맨드가 처리되는데 걸리는 시간을 모델링할 수 있다. 이렇게 모델링한 처리시간을 짧은 순서대로 스케줄링 정책에 적용하여 응답속도를 개선할 수 있다.

• Proceedings of the IEEK Conference
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• 2000.11a
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• pp.287-290
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• 2000

This paper analyze link-sharing mechanisms in packet networks based on the hierarchical class based queueing. The CBQ outlines a set of flexible, efficiently implemented gateway mechanisms that can meet a range of service and link-sharing requirements. We have analyzed the Class level(B, C, D) using the EWMA (Exponential Weighted Moving Average) weight value and EWMA average limit value.

• East Asian mathematical journal
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• v.27 no.1
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• pp.23-33
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• 2011

Due to underutilization of spectrum under current inefficient and static spectrum management policy, various kinds of opportunistic spectrum access (OSA) strategies have appeared. Myopic policy is a simple and robust OSA strategy with reduced complexity that maximizes immediate throughput. In this paper, we propose mathematical models to evaluate the throughput and the MAC delay of a myopic policy under saturation tra c conditions. Using the MAC delay distribution, we evaluate the packet delay of secondary users under nonsaturation conditions. Numerical results are given to show the performance of the myopic policy in cognitive radio networks.