• Journal of the Korean Society for information Management
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• v.24 no.4
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• pp.255-265
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• 2007

In this paper we analyzed regularity of daily patterns of distribution of Queries coming from internet search engine. And then, we proposed a Pareto distribution and Zipf law for identifying the query distribution and applied them to daily queries on the search engine during 2 week. We found that there is some evidence that Pareto and Zipf laws can be applied to evaluate the regularity of daily patterns of distribution of queries in search engine. Those results can be used to provide a better understanding of the social interests and trends using the query distribution patterns.

• The KIPS Transactions:PartA
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• v.10A no.3
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• pp.189-198
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• 2003

In this paper, we propose a method of analysis to show the heavy-tailed statistical distribution of file sizes in web servers, using TTT plot technique. TTT plot technique, a well-known method in the area of reliability engineering, determines that a distribution of samples fellows a heavy tailed one when their TTT statistical plots are lied on a straight line. We performed an intensive simulation using data gathered from real web servers. The simulation indicates that the proposed method is superior to Hill estimation technique or LLCD plot method in efficiency of data analysis. Moreover, the proposed method eliminates the possible decision error, which Pareto distribution or traditional method might cause.

• Journal of the Institute of Convergence Signal Processing
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• v.9 no.1
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• pp.39-45
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• 2008

This paper considers the multi-objective optimization of a multi-service arrayed waveguide grating-based single-hop WDM network with the two conflicting objectives of maximizing throughput while minimizing delay. This paper presents a genetic algorithm based methodology for finding the optimal throughput-delay tradeoff curve, the so-called Pareto-optimal frontier. Genetic algorithm based methodology provides the network architecture parameters and the Medium Access Control protocol parameters that achieve the Pareto-optima in a computationally efficient manner. The numerical results obtained with this methodology provide the Pareto-optimal network planning and operation solution for a wide range of traffic scenarios. The presented methodology is applicable to other networks with a similar throughput-delay tradeoff.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2000.04a
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• pp.357-360
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• 2000

본 논문은 철의장품(steel outfit) 조선기자재를 생산하는 업체들의 품질경영실태를 분석하여 한국의 철의장품 조선기자재 생산업체의 특성에 맞는 효과적이고 효율적인 품질경영시스템을 개발하고자 한다. 조사 대상업체는 ISO 9000 품질인증을 획득한 부산 경남 인근의 7개 업체로서 최근 99년까지 지난 3년간 실시한 본 심사와 예비심사에 나타난 심사자료를 근거로 분석하였다. 종업원수와 사급여부에 따라 7개 업체를 2개의 그룹으로 나누고 ISO 9000 품질인증의 요구항목별 지적사항의 수에 따른 파레토챠트를 작성하였다. 철의장품 조선기자재 생산업체의 품질경영시스템의 관리에서 ISO 9000 품질인증의 어느 요구항목이 가장 중요한 중점관리항목들인가를 찾아보고 SAS를 이용하여 중요 요구항목들과 업체들의 통계적 관련성을 살펴보았다. 한국 조선업의 세계적인 수주량 선점에도 불구하고 철의장품 조선기자재 산업체들의 수주조건 악화에 따른 단가의 하락으로 점차 열악해져 가는 조선기자재산업의 현실에 적합한 품질경영시스템을 개발하기 위해서 ISO 9001 요구항목에는 포함되지 않지만 조선기자재산업의 품질경영시스템의 특성상 반드시 포함되어야 할 중요한 추가 요구사항들의 구체적인 사례들을 제시하였다. 마지막으로 중요 요구항목별 심사자료 유형별 그룹별 통계적 관련성을 3원 분할표를 이용하여 설명하였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.7B
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• pp.1034-1042
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• 2010

As many researchers have been interested in Green IT, Energy Efficient Ethernet(EEE) with rate adaptation has recently begun to receive many attention. However, the rate adaptation scheme can have different energy efficiency and delay according to the characteristics of various traffic patterns. Therefore, in this paper, we analyze the impact of different traffic patterns on the energy efficiency and delay in Ethernet with rate adaptation. To do this, firstly we design a rate adaptation simulator which consists of Poisson based traffic generator, Pareto distribution based ON-OFF generator and Ethernet node with rate adaptation by using OPNET Modeler. Using this simulator, we perform the simulation in view of the total number of switching, transmission rate reduction, energy saving ratio and average queueing delay. Simulation results show that IP traffic patterns with high self-similarity affect the number of switching, rate reduction and energy saving ratio. Additionally, the transition overhead is caused due to the high self-similar traffic.

• Journal of the Korea Society for Simulation
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• v.20 no.2
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• pp.67-76
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• 2011

Order picking in automotive service parts warehouses is considered to be the most labor-intensive operation. Such warehouses contain hundreds of thousands of items, but normally 20% of products contribute to about 80% of turnover according to Pareto's 80-20 principle. Therefore most fast moving items are located near an outbound area which is called the "Golden Zone". Order picking routing efficiency is related to productivity and labor cost. However, most companies use simple methods. In this paper, we describe a series of computational experiments over a set of test cases where, we compared various previously existing routing heuristics to an optimal algorithm. We focus on examining the influence of the golden zone on the performance and selection of routing methods. The results obtained show that the optimal routing method increases the productivity at least 17.2%, and all the routing methods have better performance as the pick up rate from the golden zone increases.

• KDI Journal of Economic Policy
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• v.33 no.1
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• pp.125-148
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• 2011

Although the patient's problem with access to health information has been improved due to rapidly developing information technologies, such as the internet, some patients still do not have enough ability to understand, interpret, and analyze the health information. Given this view on the patient's asymmetric information problem, if a doctor provides sufficient effort to help patients understand and interpret medical information, the efficiency of patient's medical care use could be improved. This paper shows firstly that the patient's inefficient use of medical care originates from his information problems, such as the misperception of the effectiveness of medical care and secondly suggests that if the doctor makes sufficient effort to correct patient's information problems, the inefficiency can be ameliorated. This paper also suggests the manipulation of a doctor's payment method can lead a doctor to provide optimal level of efforts which can in turn lead patients to use the optimal level of medical care. With an optimal level of effort, a doctor can more easily achieve a patient's compliance with the newly recommended amount of medical care.

• KDI Journal of Economic Policy
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• v.36 no.4
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• pp.1-32
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• 2014

Auction is widely used in allocation and procurement of resources due to its desirable properties: efficiency and revenue maximization. It is well-known, however, that auction may fail to achieve efficiency when allocative externalities exist. Such a result may happen in the auction of the resources that are very scarce, for example, radio spectrum. This is because allocation of the resources has effects on competition of the firms in the aftermarket, and thus a firm that utilizes the resources less efficiently may make a higher bid to lessen competition. This paper shows first that efficient allocation may not be achieved by auction even when the number of bidders is 2, while it is shown in the literature that auction may result in inefficient allocation when the number of bidders is greater than or equal to 3. There exist 2 firms, who make a bid to win the scarce resources that increase the value or decrease the production cost of their own product. After the auction ends, the firms engage in Bertrand competition on the Hotelling line. Inefficient allocation may happen even under the second-price auction rule, and it happens only when the firms are different in the initial value or the initial cost of their products as well as in the value of the auctioned resources. The firm who has been the leader loses a large portion of the market if it fails to win the auction, and thus makes a high bid even when the other firm can use the resources more efficiently. Allocative efficiency Pareto improves when the smaller firm's bid counts more than the leader's bid. This paper suggests a modified rule that the smaller firm wins the auction when its bid multiplied by some constant is greater than the leader's bid. The multiplier can be calculated from the market shares. It is equal to 1 when the two firms are the same, and is increasing in the leader's market share. Allocation is efficient in a strictly larger set of parameters under the modified rule than under the standard second-price auction rule.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.4
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• pp.1239-1247
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• 2010

In this paper, we were researched decision problem called an optimal release policies after testing a software system in development phase and transferring it to the user. The applied model of release time exploited infinite failure non-homogeneous Poisson process This infinite failure non-homogeneous Poisson process is a model which reflects the possibility of introducing new faults when correcting or modifying the software. The intensity function used Gompertz, Preto and Log-logstic pattern which has the efficient various property. Thus, optimal software release policies which minimize a total average software cost of development and maintenance under the constraint of satisfying a software reliability requirement becomes an optimal release policies. In a numerical example, after trend test applied and estimated the parameters using maximum likelihood estimation of inter-failure time data, estimated software optimal release time.

• Journal of Korea Water Resources Association
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• v.41 no.1
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• pp.1-15
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• 2008

The purpose of this study is to propose a procedure that will be able to find the most efficient sets of weight coefficients for the Geum-River basin in Korea. The result obtained from multi-objective optimization model is inherently sensitive to the weight coefficient on each objective. In multi-objective reservoir operation problems, the coefficient setting may be more complicated because of the natural variation of inflow. Therefore, for multi-objective reservoir operation problems, it may be important for modelers to provide reservoir operators with appropriate sets of weight coefficients considering the inflow variation. This study presents a procedure to find an appropriate set of weight coefficients under the situation that has inflow variation. The proposed procedure uses GA-CoMOM to provide a set of weight coefficient sets. A DEA-window analysis and a cross efficiency analysis are then performed in order to evaluate and rank the sets of weight coefficients for various inflow scenarios. This proposed procedure might be able to find the most efficient sets of weight coefficients for the Geum-River basin in Korea.