• Information Systems Review
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• v.7 no.1
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• pp.115-136
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• 2005

Recently Internet portals contend with each other to expand their customer base by providing customers with a much amount of e-mail storage. But This strategy may not be successful because of customers' switching cost following site moving. Therefore, in order to reveal whether their strategy makes sense, this study investigates the direct and contingency factors affecting customer switching intension of e-mail services in portal sites. The research results show that attractiveness of alternatives, switching cost, and customer satisfaction have a significantly direct impact on customer switching intension of e-mail services. Also, attractiveness of alternatives alone has an moderated effect on customer switching intension but switching cost does not. Thus, Internet portals may reap the harvest from their recent aggressive action.

• Korean Journal of Construction Engineering and Management
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• v.18 no.3
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• pp.105-116
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• 2017

In recent years, large Korean construction companies have suffered serious losses in their overseas business. Many practitioners and researchers have analyzed causes of cost overrun in these projects. However, these arguments have not been empirically verified based on acutal project cases. This study investigated cost overrun rate, contingency, allowance, predicted risk before bidding, and actual and residual risk after award in the 67 international infrastructure projects conducted by 13 large construction companies. The causes of cost overruns are derived as follows. First, they identified the possibility of cost overrun to some extent before the bidding, but did not reflect the enough risk money to bid price. In particular, this behavior was more severe in badly cost-overrun projects. Second, the causes of cost overrun were more influenced by external environmental risk than internal capability risk. However, the internal risk in badly cost-overrun projects was relatively high compared to cost-underrun projects. Third, badly cost-overrun projects failed to mitigate risk. However, cost underrun projects were affected more by low exterior risk conditions than by well mitigated risk. This study provides more informed knowledge in controlling project costs in international infrastructure projects.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.4
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• pp.679-685
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• 2010

As the electrical power industry is restructured, the electrical power exchange is becoming extended. One of the key information used to determine how much power can be transferred through the network is known as available transfer capability (ATC). To calculate ATC, traditional deterministic approach is based on the severest case, but the approach has the complexity of procedure. Therefore, novel approach for ATC calculation is proposed using cost-optimization method, well-being method and risk-benefit method in this paper. This paper proposes the optimal transfer capability of HVDC system between mainland and a separated island in Korea through these three methods. These methods will consider production cost, wheeling charge through HVDC system and outage cost with one depth (N-1 contingency).

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.5
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• pp.848-853
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• 2007

This paper presents a methodology of estimating incomplete information in electricity markets for analyzing the gaming behavior of Generating Companies (GENCOs). Each GENCO needs to model its opponents' unknown information of strategic biddings and cost functions. In electricity markets with complete information, each GENCO knows its rivals' payoff functions and tries to maximize its own profit at Nash equilibriurnl Nli) by acknowledging the rivals' cost function. On the other hand, in the incomplete information markets, each GENCO lacks information about its rivals. Load patterns can change continuously due to many factors such as weather, price, contingency, etc. In this paper, we propose the method of the estimation of the opponents' cost function using market price, transaction quantities. and customer load patterns. A numerical example with two GENCOs is illustrated to show the basic idea and effectiveness of the proposed methodology.

• KIEE International Transactions on Power Engineering
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• v.5A no.3
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• pp.303-308
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• 2005

The restructure of the electrical power industry is accompanied by the extension of the electrical power exchange. One of the key pieces of information used to determine how much power can be transferred through the network is known as available transfer capability (ATC). The traditional ATC deterministic approach is based on the severest case and it involves a complex procedure. Therefore, a novel approach for A TC calculation is proposed using cost optimization in this paper. The Jeju Island interconnected HVDC system has inland KEPCO (Korean Electric Power Corporation) systems, and its demand is increasing at the rate of about $\10[%]$ annually. To supply this increasing demand, the capability of the HVDC system must be enlarged. This paper proposes the optimal transfer capability of the HVDC system between Haenam in the inland and Jeju in Cheju Island through cost optimization. The cost optimization is based on generating cost in Jeju Island, transfer cost through Jeju-Haenam HVDC system and outage cost with one depth (N-1 contingency).

• The Bulletin of The Korean Astronomical Society
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• v.40 no.1
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• pp.84.2-84.2
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• 2015

There are probabilistic forecast models for solar flare occurrence, which can be evaluated by various skill scores (e.g. accuracy, critical success index, heidek skill score, true skill score). Since these skill scores assume that two types of forecast errors (i.e. false alarm and miss) are equal or constant, which does not take into account different situations of users, they may be unrealistic. In this study, we make an evaluation of a probabilistic flare forecast model (Lee et al. 2012) which use sunspot groups and its area changes as a proxy of flux emergence. We calculate daily solar flare probabilities from 1996 to 2014 using this model. Overall frequencies are 61.08% (C), 22.83% (M), and 5.44% (X). The maximum probabilities computed by the model are 99.9% (C), 89.39% (M), and 25.45% (X), respectively. The skill scores are computed through contingency tables as a function of forecast probability, which corresponds to the maximum skill score depending on flare class and type of a skill score. For the critical success index widely used, the probability threshold values for contingency tables are 25% (C), 20% (M), and 4% (X). We use a value score with cost/loss ratio, relative importance between the two types of forecast errors. We find that the forecast model has an effective range of cost/loss ratio for each class flare: 0.15-0.83(C), 0.11-0.51(M), and 0.04-0.17(X), also depending on a lifetime of satellite. We expect that this study would provide a guideline to determine the probability threshold for space weather forecast.

• The Journal of Asian Finance, Economics and Business
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• v.9 no.5
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• pp.475-486
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• 2022

The purpose of this paper is to examine the use of material flow cost accounting (MFCA) in Vietnam's coal-fired thermal power plants. This study is based on the contingency and system theories to explain the application of management tools and analyze steps of input, output, and process in manufacturing. Costs in producing process-based MFCA include material cost, energy cost, system cost, and waste management cost. The exploratory case study methodology is used to describe and answer two questions, namely "How coal flow cost is recognized?" and "Why waste in material consumption can be harmful to the environment?". By analyzing the Quang Ninh and Pha Lai coal-fired thermal power plants that are the typical plants, this paper identifies the flow of primary material in these plants as a basis for determining losses for the business. The material flow of coal-fired thermal power plants provides the basis for the use of the MFCA. The manufacturing of electrical items in these plants is divided into four stages, each with its own set of losses. As a result, some phases in the application of MFCA are suggested, as well as some other elements required for MFCA application in coal-fired thermal power plants.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.195_196
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• 2009

As the electrical power industry is restructured, the electrical power exchange is becoming extended. One of the key information used to determine how much power can be transferred through the network is known as available transfer capability (ATC). To calculate ATC, traditional deterministic approach is based on the severest case, but the approach has the complexity of procedure. Therefore, novel approach for ATC calculation is proposed using cost-optimization method in this paper, and is compared with well-being method and risk-benefit method. This paper proposes the optimal transfer capability of HVDC system between mainland and a separated island in Korea through these three methods. These methods will consider production cost, wheeling charge through HVDC system and outage cost with one depth (N-1 contingency).

• Proceedings of the KIEE Conference
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• 1999.11b
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• pp.213-215
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• 1999

This paper presents a transmission cost allocation through application of a new reliability index in transmission pricing in competitive electric industry. The proposed method allocates a fair use of transmission system charge given separately to individual generator by capacity usage, based on the contribution of individual generator considering N-1 contingency in reliability margin of transmission capacity, and offers more alternatives of pricing in using transmission capacity and transmission margin.

• Journal of Electrical Engineering and Technology
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• v.8 no.1
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• pp.53-63
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• 2013

To guide the decision making of the expert engineer specialized in power system operation and control; the practical OPF solution should take in consideration the critical situation due to severe loading conditions and fault in power system. Differential Evolution (DE) is one of the best Evolutionary Algorithms (EA) to solve real valued optimization problems. This paper presents simple Differential Evolution (DE) Optimization algorithm to solving multi objective optimal power flow (OPF) in the power system with shunt FACTS devices considering voltage deviation, power losses, and power flow branch. The proposed approach is examined and tested on the standard IEEE-30Bus power system test with different objective functions at critical situations. In addition, the non smooth cost function due to the effect of valve point has been considered within the second practical network test (13 generating units). The simulation results are compared with those by the other recent techniques. From the different case studies, it is observed that the results demonstrate the potential of the proposed approach and show clearly its effectiveness to solve practical OPF under contingent operation states.