• Management Science and Financial Engineering
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• v.4 no.2
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• pp.43-58
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• 1998

Packet switch is a key component in high speed digital networks. This paper investigates congestion phenomena in the packet switching with input buffers. For large value of switch size N, mathematical models have been developed to analyze asymptotic maximum switch throughput under nonuniform traffic. Simulation study has also been done for small values of finite N. The rapid convergence of the switch performance with finite switch size to asymptotic solutions implies that asymptotic analytical solutions approximate very closely to maximum throughputs for reasonably large but finite N. Numerical examples show that non-uniformity in traffic pattern could result in serious degradation in packet switch performance, while the maximum switch throughput is 0.586 when the traffic load is uniform over the output trunks. Window scheduling policy seems to work only when the traffic is relatively uniformly distributed. As traffic non-uniformity increases, the effect of window size on throughput is getting mediocre.

• Proceedings of the Safety Management and Science Conference
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• 2010.11a
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• pp.41-61
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• 2010

With increasing the quality of life in proportion to the national income, we have had cars as more convenient and safe means of transportation for a long time. The more we have the benefits from cars, the more seriously we should consider problems such as the destruction of the environment by air pollution, traffic accidents, parking problems, traffic congestion, etc. as social cost caused by the increase of cars. Among them, the traffic accidents are very serious, especially the accidents of the business cars occurs five times more than those of the private cars. Therefore if we analyze the cases of the various kinds of syst.em, test the results and apply them to business cars, we will reduce the traffic accidents of business cars.

• Journal of Korea Multimedia Society
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• v.19 no.2
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• pp.291-299
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• 2016

To enhance network efficiency, named-data networking (NDN) implements data caching functionality on intermediate network nodes, and then the nodes directly respond to request messages for cached data. Through the processing of request messages in intermediate node, NDN can efficiently reduce the amount of network traffic, also solve network congestion problems near data sources. Also, NDN provides a data authenticate mechanism so as to prevent various Internet accidents caused from the absence of an authentication mechanism. Hence, through applying NDN to various smart IT convergence services, it is expected to efficiently control the explosive growth of network traffic as well as to provide more secure services. Basically, it is important factors of NDN which data is cached and where nodes caching data is located in a network topology. This paper first analyzes previous works caching content based on the popularity of the content. Then ii investigates the hitting rate of caches in each node of a network topology, and then propose an improved caching scheme based on the result of the analyzation. Finally, it evaluates the performance of the proposal.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.22 no.1
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• pp.108-113
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• 2014

Recently increase in the number of aircraft caused the air traffic congestion and flight delays. If timely action to reform the air traffic system is not taken, these may result in added economic impact. As a result, the air traffic management should be changed in an innovative manner to modernize the existing air traffic control environment. This paper reviews the trends of airspace reforms such as integration of terminal control areas and flexible use of airspace introduced by foreign countries and compares their merits and demerits in order to provide a judgement to adopt the concept in domestic airspace in the future.

• Journal of the Korean Operations Research and Management Science Society
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• v.21 no.3
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• pp.1-10
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• 1996

In this paper, the problem of simultaneously allocating servers and loadings of stations in a class of manufacturing systems modelled as network of queues is considered. The throughput function of the closed network of queues is demonstrated as a Schur convex function of server allocation, that is, increasing the server allocation vector under majorization increases the performance in the ship in terms of the throughput. It also reduces the congestion in the open network of queues in terms of reducing the total number of jobs in the sense of likelihood ratio ordering. These are the extentions of the numerical results of Green and Guha (1995) in the service system with independent M/M/c systems to the network of queues. The results can be used to support production planning in certain manufacturing systems.

• International Journal of Advanced Culture Technology
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• v.8 no.3
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• pp.275-279
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• 2020

Due to the recent rapid industrialization worldwide, the number of pediatric asthma patients is increasing. And the fine dust containing heavy metals is linked to the characteristics of high toxic lead due to the increase heating in factory operation and automobile driving. It is the reason of arsenic increasing. In the treatment of pediatric asthma patients, drug administration, oral drug entry, and HMPC (Home Management Plan of Care) are used. In this paper, we analyze the relationship between the onset of asthma and the method of prescription for specific childhood asthma in the United States using EM (Expectation Maximization) and MDL (Minimum Description Length) algorithms. And the association is also analyzed by comparing the nature of specific congestion between the past prevalence of digestive asthma and the recent prevalence of environmental pollution.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1990.04a
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• pp.299-311
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• 1990

A computer simulation model is proposed for selecting effective agrees paths and estimating the evacuation time in case of evacuating all the residents of a building to the safe area. The physical structure of a building is formulated into a network. The followings are considered in the model : the congestion effect to the velocity, the behavioral pattern of the evacuees, and the probabilistic nature of the evacuation process. Coded in SLAM II/PC, the simulation model can generate the output such as evacuation time(max, average), utilization of exits, utilization of passages, floor clearance times, and bottleneck information. The "rigorous" validation of the proposed model is not completed yet but remains to be a future research topic.rch topic.

• Journal of Korea Society of Digital Industry and Information Management
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• v.14 no.3
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• pp.69-75
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• 2018

Recently, various convergence technologies are attracting attention due to the block chain innovation technology in the M2M environment. Although the block-chain-based technology is known to be secure in its own right, there are various problems such as security and weight reduction in various M2M environments connected with this. In this paper, we propose a new lightweight method for the hash tree generation of block chains to solve the lightweight problem. It is designed considering extensibility without affecting the existing block chain. Performance analysis shows that the computation performance increases with decreasing the existing hash length.

• Journal of Communications and Networks
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• v.4 no.2
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• pp.136-147
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• 2002

In this paper, the maximal capacity of the data network link has attempted to be exploited by using the dynamic allocation strategy. We propose a new methodology based on the economic models for competing traffic classes (classes of sessions) in packet networks. As the demand for network services accelerates, users' satisfaction to the service level might decrease due to the congestion at the network nodes. To prevent this, efficient allocation of a networks resources, such as available bandwidth and switch capacity, is needed. By using the so-called user profile as well as the utility (e.g., data rate) functions, it is possible to allocate data rates and other utilities using the arbitrary number of QoS classes, say $0.01,...,$10.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2002.05a
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• pp.120-127
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• 2002

The multicasting is defined as the distribution of the same information stream from one to many nodes concurrently. There has been an intensive research effort to design protocols and construct multicast routing graphs for a single multicast group. However. there have been few researches about the relation between multiple and concurrent multicast groups. In this paper, the multiple multicast tree allocation algorithm to avoid congestion is proposed. The multicast group with different bandwidth requirement is also considered. A two-phase algorithm is proposed. The first phase is for basic search and the second phase for further improvement. The performance of the proposed algorithm is experimented with computational results. Computational results show that the proposed algorithm outperforms an existing algorithm.