• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.5 s.248
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• pp.472-479
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• 2006

Recently, various methods have been developed to improve the performance of gas turbines for combined cycle power plants. This paper especially focused on the gas turbine with a reheat process. The purpose of this study is to analyze performance characteristics of a reheat-cycle gas turbine on both a design point and off-design operations. Results of the parametric study of this model show how operating and design parameters influence on the performance of the gas turbine. Moreover, possibilities for the analysis of off-design performance based on a self-generated compressor performance characteristic map are presented.

• Korean Management Science Review
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• v.20 no.2
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• pp.17-31
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• 2003

A workflow management system is a software system to support accurate execution, control and management of business processes. It has been known that the system automatically executes complex processes and effectively manages them to improve the productivities. However though existing systems assure the automatic execution of an individual process, there is a room for enhancement from the view of efficient execution of all the processes. In this paper, we propose a method of executing business processes efficiently by introducing the PERT/CPM techniques in the workflow management systems. We first consider the differences between workflow process models and PERT/CPM models, and then develop a method of calculating the critical path and slack time in workflow processes. This leads us to develop a dispatching rule that can guide task performers to prioritize their tasks to increase the efficiency of ail the processes. We have carried out a set of simulation experiments and analyzed the results to demonstrate the effectiveness of the proposed method.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.12 no.20
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• pp.47-53
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• 1989

This paper presents an algorithm CAPFACT to evaluate the reliability of a capacitated two terminal network such as a communication network, a power distribution network, and a pipeline network. The network is good(working) if and only if it is possible to transmit successfully the required system capacity from one specified terminal to the other. This paper defines new Capacitated series-parallel reduction to be applied to a series-parallel structure of the network. New Capacitated factoring method is applied to a non-series-parallel structure. The method is based on the factoring theorem given by Agrawal and Barlow. According to the existing studies on the reliability evaluation of the network that the capacity is not considered, the factoring method using reduction is efficient. The CAPFACT is more efficient than Aggarwal algorithm which enumerated and combined the paths. The efficiency is proved by the result of testing the number of operations and cpu time on FORTRAN compiler of VAX-11/780 at Hanyang University.

• International Journal of Fluid Machinery and Systems
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• v.2 no.3
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• pp.248-253
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• 2009

This paper presents a numerical study for unsteady flows in a high-pressure steam turbine with a partial admission stage. Compressible Navier-Stokes equations are solved by the high-order high-resolution finite-difference method based on the fourth-order compact MUSCL TVD scheme, Roe's approximate Riemann solver, and the LU-SGS scheme. The SST-model is also solved for evaluating the eddy-viscosity. The unsteady two-dimensional flows through whole nozzle-rotor cascade channels considering a partial admission are numerically investigated. 108 nozzle passages with two blockages and 60 rotor passages are simultaneously calculated. The influence of the flange in the nozzle box to the lift of rotors is predicted. Also the efficiency of the partial admission stage changing the number of blockages and the number of nozzles is parametrically predicted.

• THE INTERNATIONAL COMMERCE & LAW REVIEW
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• v.12
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• pp.349-376
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• 1999

The objective of this paper is to identify the problems of Korean inland transportation system and suggest the improvement plan for reducing the export logistics cost. The results are as follows: (1) Expansion of logistics hub facilities : Logistics hub facilities- integrated freight terminal and ICD, etc. can shorten the empty leg and reduce the logistics cost. (2) Design for CVO(Commercial Vehicle Operations) : CVO has various functions that improve the efficiency and effectiveness of freight transportation. (3) Rationalization of freight transportation industry : In particular, the deregulation of the motor freight industry and the privatization of the railway industry induce the competition among their firms and undercut the transportation rates in the long run. (4) Use of third-party logistics : The benefits of TPL are system reliability, improved customer service, and more efficient cost performance.

• Korean Management Science Review
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• v.26 no.3
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• pp.11-21
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• 2009

In this paper, we proposed some valuable analysis results of cultivation campaign marketing in A mobile telephone company. The cultivation campaign marketing is a new outbound TM campaign strategy composed of 4 steps for new subscribers. During the analyses, attrition rate of A mobile company, outbound TM rejection rate, contact rate/call success rate and additional service attrition rate after subscription are measured as an effect of cultivation campaign. The results showed that there were no statistical significance in improving retention rate between customers experienced 4 step cultivation campaign and control group. However, the cultivation campaign had a better effect on improving response rate and success of selling additional service product of mobile company compared to general selling campaign. This is because cultivation campaign group had been taking care of from subscription time. It is suggested that cultivation campaign had better confined customers more likely to buy additional service to outbound TM for the sake of financial efficiency.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.8
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• pp.52-59
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• 1996

Conventionally, grinding of stainless steel, aluminium ally, copper alloy, and titanum alloy are difficult to obtain the high quality finish, because they have the mechanical properties such as low hardness, high toughness which result in the loading of wheel and the poor surface finish. Inorder to perform the grinding operations for these sorts of materials easily, the discontinuous grinding wheel with multi-porous grooves has newly been developed. The multi-porous grooves were formed during wheel production. This discontinous grinding wheel increases the grinding performance. It is desirable to use the discontinuous grinding wheel when grinding materials wiht high efficiency and accuracy which is impossible by conventional wheels. In this paper, the constructing and manufacturing method of grinding wheel with multi-proous grooves are explained, and the grinding charateristics of discontinuous grinding wheel are also illustrate.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1996.06c
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• pp.999-1008
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• 1996

The development and improvement of the originally designed direct rice sowing machine were carried out for the specific purpose of saving labor and increasing the efficiency of field operations in rice cultivation in the northern part of Japan. the prototype super wide spreader has a unique mechanism which propels rice seeds by compressed air and spreads them from the pivoting nozzle while the machine is in motion. The effective field capacity of sowing operation is about 6 ha/h. This spreader can also handle granular chemicals such as fertilizers, herbicides, pesticides and insecticides.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.33 no.1
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• pp.24-32
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• 2010

The first full-scale u-City operation has started in Dongtan u-City. As local cities take over and operates the u-City, unexpected issues arise such as securing the budget of operating costs and self-providing the costs with business models utilizing the u-City assets. The paper presents a strategy for solving these issues. The strategy provides a foundation(infrastructure) for long-term operation models which may reduce the long-term operation costs. In order to establish the economic operating framework of u-City, suggested are some cost-reduction models based on the operating costs structure. For each model, a base framework with comparative analysis of operating costs is provided. With these models, each u-City may select a relevant model according to the characteristics of it. We hope that the framework provides the foundation for efficient and sustainable u-City operations.

• International Journal of Reliability and Applications
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• v.7 no.2
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• pp.187-201
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• 2006

In this paper, we derive recurrence relations for the single and product moments of progressively Type-II right censored order statistics from half logistic distribution. Next, we derive the maximum likelihood estimators (MLEs) of the location and scale parameters of the half logistic distribution. In addition, we use the setup proposed by Balakrishnan and Aggarwala (2000) to compute the approximate best linear unbiased estimates (ABLUEs) of the location and scale parameters. Finally, we point out a simulation study to compare between the efficiency of the techniques considered for the estimation.