• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1996.03b
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• pp.7-15
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• 1996

A Manufacturing process of the power steering worm blank is analyzed by FEM aimulation. The process includes mainly three operations such as indentation, extrusion, and upsetting, which was designed bya forming equipment expert. The results of simulation are summarized in terms of load-stroke relationships, die pressure distributions, effective strain distribution, and deforming patterns for each forming operation. Also, Efforts are focused to get the reason that the tool expert designed the forming process in three operations. The results of the simulation are to be useful for the next advanced process planning in terms of good dimesional accuracy, savings in material and machining, no deforaming defects and imporvements in mechanical properties.

• Journal of Communications and Networks
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• v.10 no.4
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• pp.403-411
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• 2008

Energy consumption has been mostly neglected in network coding (NC) research so far. This work investigates several different properties of NC that influence the energy consumption and thus are important when designing NC systems for battery-driven devices. Different approaches to the necessary implementation of coding operations and Galois fields arithmetic are considered and complexity expressions for coding operations are provided. We also benchmark our own mobile phone implementation on a Nokia N95 under different settings. Several NC strategies are described and compared, furthermore expressions for transmission times are developed. It is also shown that the use of NC introduces a trade off between reduction in transmission time and increase in energy consumption.

• Journal of the Korean Institute of Intelligent Systems
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• v.21 no.3
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• pp.389-394
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• 2011

The notion of generalized intuitionistic fuzzy soft set theory is proposed. Our generalized intuitionistic fuzzy soft set theory is a combination of the generalized intuitionistic fuzzy set theory and the soft set theory. In other words, our generalized intuitionistic fuzzy soft set theory is an extension of the intuitionistic fuzzy soft set theory. The complement, "and" and "or" operations are defined on the generalized intuitionistic fuzzy soft sets. Their basic properties for the generalized intuitionistic fuzzy soft sets are also presented and discussed.

• Journal of the Korean Operations Research and Management Science Society
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• v.25 no.4
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• pp.1-14
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• 2000

The methods of sensitivity analysis for linear programming can be classified in two types: sensitivity analysis using an optimal solution, and sensitivity analysis using an approximate optimal solution. As the methods of sensitivity analysis using an optimal solution, there are three sensitivity analysis methods: sensitivity analysis using an optimal basis, positive sensitivity analysis, and optimal partition sensitivity analysis. Since they may provide different characteristic regions under degeneracy, it is not easy to understand and apply the results of the three methods. In this paper, we propose a generalized sensitivity analysis that can integrate the three existing methods of sensitivity analysis. When a right-hand side or a cost coefficient is perturbed, the generalized sensitivity analysis gives different characteristic regions according to the controlling index set that denotes the set of variables allowed to have positive values in optimal solutions to the perturbed problem. We show that the three existing sensitivity analysis methods are special cases of the generalized sensitivity analysis, and present some properties of the generalized sensitivity analysis.

• Journal of the Korean Operations Research and Management Science Society
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• v.36 no.1
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• pp.1-11
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• 2011

This article examines the impact of electronic commerce on environmental welfare. In particular, we analyze a game model of price competition between offline and online firms when consumption taxes are imposed on both offline and online transactions that produce environmental pollution. We investigate the properties of optimal taxation between offline and online markets and demonstrate that there is an optimal difference between the two taxes, depending upon not only the transaction cost between offline and online consumption, but also the environmental damage cost. We also investigate the effect of tax-free online transactions on tax revenues, and the financial feasibility of the optimal taxation.

• Journal of the Korean Operations Research and Management Science Society
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• v.19 no.1
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• pp.85-98
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• 1994

The distribution of random sum of i. i. d. exponential random variables is called GHP (Generalized Phase-Type) distribution. The class of GPH distributions is large enough to include PH (Phase-Type) distributions and has several properties which can be applied conveniently for computational purposes. In this paper, we show that any distribution difined on R$^{+}$ can be app-roximated by the GPH distribution and demonstrate the accuracy of the approximation through various numerical examples. Also, we introduce an efficient way to compute the delay and waiting various numerical examples. Also, we introduce an efficient way to compute the delay and waiting time distributions of the GPH/GPH/1 queueing system which can be used as an approximation model for the GI/G/1 system, and validate its accuracy through numerical examples. The theoretical and experimental results of this paper help us accept the usefulness of the approximations based on GPH distribution.n.

• IE interfaces
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• v.18 no.4
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• pp.418-430
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• 2005

We establish an efficient strategy for construction and operation of data consolidation center for multi-organization in public sector. First, we introduce important concepts on data consolidation center in public sector, and draw some success factors by analyzing several foreign and domestic cases. Second, we construct all the possible logical operational models of the center and investigate the properties and feasibility of the models. Third, we suggest a virtual operational environment for the two representative models selected by feasibility criteria among the possible logical models, and compare the two models in terms of operational cost. We also utilize AHP methodology to evaluate qualitative opinions on the two models from several experts in public information systems. As a result, we find the best alternative is the case in which all infrastructure and facilities for the center are provided by government, and common essential IT operations are integrated, associated data are consolidated and the whole operational work are outsourced to specialized IT operations service providers.

• Journal of the Korean Operations Research and Management Science Society
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• v.24 no.4
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• pp.111-122
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• 1999

In this paper, we consider a queueing network model. where the population constraint within each subnetwork is controlled by a semaphore queue. The total number of customers that may be present in the subnetwork can not exceed a given value. Each node has a constant service time and the arrival process to the queueing network is an arbitrary distribution. A major characteristics of this model is that the lower layer flow is halted by the state of higher layer. We present some properties that the inter-change of nodes does not make any difference to customer's waiting time in the queueing network under a certain condition. The queueing network can be transformed into a simplified queueing network. A dramatic simplification of the queueing network is shown. It is interesting to see how the simplification developed for sliding window flow control, can be applied to multi-layered queueing network.

• Journal of the Korean Operations Research and Management Science Society
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• v.36 no.2
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• pp.43-50
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• 2011

We consider the separation problem of the rank-1 Chvatal-Gomory (C-G) inequalities for the 0-1 knapsack problem with the knapsack capacity defined by an additional binary variable, which we call the fixed-charge 0-1 knapsack problem. We analyze the structural properties of the optimal solutions to the separation problem and show that the separation problem can be solved in pseudo-polynomial time. By using the result, we also show that the existence of a pseudo-polynomial time algorithm for the separation problem of the rank-1 C-G inequalities of the ordinary 0-1 knapsack problem.

• Journal of the Korean Operations Research and Management Science Society
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• v.8 no.2
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• pp.27-43
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• 1983

The purpose of this paper is to analyze the structure and properties of the patterns by extracting the general patterns on socio-economic development from huge data by statistical analysis. We collected data concerning socio-logical, economical and technological aspects. Indicators used for this study amounted to a total of 136, and among them 39 were on science & technology. What is more, these indicators were set up with the resent data for the first half of the 1970's mainly, and 141 nations were selected as the sample. Some rinkage patterns to the total indicators were abstracted by cluster analysis based on the correlation matrix. And some rinkage patterns to the total countries were educed by applying cluster analysis of centroid method to the respective indicators.