• Journal of Aerospace System Engineering
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• v.9 no.3
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• pp.39-46
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• 2015

An integrated simulation program for an artificial satellite's operation has been developed. The program integrates and simulates orbit mechanics, attitude control, power/energy transition and mass variation. In the early stages of satellite development, this program can be used as a communication tool among design engineers of different fields. As a result, the efficiency to design a satellite is expected to increase. This program has been coded by Modelica language which supports acausal and object oriented programming methods. Libraries are developed for satellite simulation, and simulation results are presented.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.16 no.4
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• pp.1266-1285
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• 2022

Compact E-cash is the first scheme which can withdraw 2^l coins within 𝒪(1) operations and then store them in 𝒪(𝑙) bits. Because of its high efficiency, a lot of research has been carried out on its basis, but no previous research pay attention to the privacy of payees and in some cases, payees have the same privacy requirement as payers. We propose a double-blind compact E-cash scheme, which means that both the payer and the payee can keep anonymous while spending. In our scheme, the payer and the bank cannot determine whether the payees of two different transactions are the same one and connect the payee with transactions related to him, in this way, the privacy of the payee is protected. And our protocols disconnect the received coin from previous transaction, then, the coin can be transferred into an unspent coin which belongs to the payee. The proposed e-cash scheme is secure within y-DDHI and LRSW assumption.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.171-171
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• 2010

An innovative design of a floating-buoy wave energy converter (WEC) using hydrostatic transmission (HST), named HSTWEC, is presented in this paper. The system is designed to convert ocean wave fluctuation into electricity by using the HST circuit and an electric generator. Based on the floating-buoy concept, the wave forces the sub-buoy to move up and down. Consequently, the electric power can be obtained from the generator in both the moving directions of the sub-buoy through the HST circuit as shown in Fig. 1. In order to investigate the HSTWEC operations, a mathematical model of the system is indispensible. In addition, the method to control the HSTWEC, including: pump displacement control, tension adjustment control and ballast weight control, is also discussed in this paper. Finally, the design concept as well as simulation results indicated that this HSTWEC design is an effective solution and possible to fabricate for wave energy generation.

• Journal of Energy Engineering
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• v.15 no.1 s.45
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• pp.67-73
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• 2006

A calculation method on performance impact of the controllable operations parameter such as GT inlet filter ${\Delta}P$, compressor efficiency, and condenser pressure was devised to achieve best performance of combined cycle power plant with the on-line performance monitoring system. This method calculates the performance impact on the deviation between 'Expected' values and 'Actual' values. Controllable parameter targets are determined based on achievable performance given existing equipments and control conditions.

• Korean Management Science Review
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• v.20 no.1
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• pp.125-139
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• 2003

City gas is becoming an essential resource in households due to its convenience and low price in comparison to other energy sources. However, in order to prepare for the gas market to be saturated, many city gas companies must pursue customer satisfaction management and develop happy call systems for a promising solution. In the development of the happy call systems, the difficult problem is that we cannot contact all customers because of limited resources and calling efficiency in the call center, We should find best customers according to their value. This paper suggests a methodology for the selection of happy call customers when city 9as companies consider two strategies. First, they should launch a new business area. Second, they must attempt to prevent current customers from moving from city gas to other fuels. We will discover important attributes and derive rules of weighting for the attributes through an exploration study that affect customer satisfaction and preference. Through a simulation model, we will show how many customers will be selected by our methodology.

• Korean Management Science Review
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• v.15 no.1
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• pp.13-31
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• 1998

In this paper, we examine the relationship between information type and new product development process. Information that was provided for new product development can be divided into two categories. One was relative information that could be used as a basis for comparison such as patent data. The other was absolute information that must be fulfilled in the new product such as key customers requirements. An experiment was conducted with staffs in an R＆D department in order to analyze the impact of the different information types on the development process of new product. It was found that the group with the absolute information recognized the given information repeatedly, which in turn results in a highly technical idea with good teamwork. The group with the relative information created a superior product with better application, appearance and product efficiency through the frequent refinements of given ideas. This paper concludes with the implications of the results to the new product development process and supporting information systems.

• Korean Management Science Review
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• v.14 no.2
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• pp.161-184
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• 1997

This research examines the importance of IT training/education, present situation and possible suggestion for the successful training/education. The research method adopts a comparative analytical approach based on questionnaire survey responses from three work groups - managers, employees, and union representatives - drawn from five sample Korean banks. The evidence indicates that all three groups agree that IT improves banking efficiency and reduces job repetitiveness, but their job satisfaction level with IT-based work is surprisingly very low. The main reasons are mainly lack of training/education and poor user manuals. Also the research shows that most respondents would like to get further training/education to more adequately fit them for their jobs. Those from banks which invested in continuing training/education revealed more positive work attitudes and higher job satisfaction.

• Knowledge Management Research
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• v.20 no.3
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• pp.107-117
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• 2019

Successful start-ups are driven by opportunities, teams, and the resources needed to grow the business. Systematic business process management is required to maximize the efficiency of business operations. However, the existing entrepreneurial process research has limitations that it is difficult to intuitively and dynamically provide the necessary information for start-up operation, and it is necessary to define necessary information (resources, stakeholders, activities). In this study, we suggest the "Start-up Process Repository System" which overcomes limitations of existing entrepreneurial process research. The architecture for the Start-up Process Repository System provides five layers and enables each layer to interact four interfaces between each layer. This study improves start-ups' accessibility to the start-up business process repository created from the existing repository architecture and increases the utility derived from it by providing methodologies for components that offer useful start-up knowledge.

• Korean Management Science Review
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• v.11 no.3
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• pp.13-26
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• 1994

In this paper we studied an integration scheme of some simplex algorithms and some efficient techniques to get the stable solution in linear programming code. And we developed a linear programming package (LPAK) by introducing this scheme and techniques. In LPAK three different algorithms were integrated, which were two primal simplex algorithms using Two phase method and big-M method respectively, and the dual simplex algorithm. LPAK introduces several heuristic techniques in each step of simplex method in order to enhance the stability and efficiency. They were new heuristic methods in structuring initial basis, choosing entering variable, choosing dropping variable and performing reinversion. The experimental results on the NETLIB problems showed that LPAK provided the stable solutions.

• Korean Management Science Review
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• v.17 no.1
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• pp.41-54
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• 2000

in the real world situations that some jobs need be processed only on certain limited machines frequently occur due to the capacity restrictions of machines such as tools fixtures or material handling equipment. In this paper we consider n-job non-preemptive and m parallel machines scheduling problem having two machines group. The objective function is to minimize the sum of earliness and tardiness with different release times and due dates. The problem is formulated as a mixed integer programming problem. The problem is proved to be Np-complete. Thus a heuristic is developed to solve this problem. To illustrate its suitability and efficiency a proposed heuristic is compared with a genetic algorithm and tabu search for a large number of randomly generated test problems in ship engine assembly shop. Through the experimental results it is showed that the proposed algorithm yields good solutions efficiently.