• Proceedings of the KIPE Conference
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• 2007.07a
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• pp.172-174
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• 2007

The AC-DC Adapter has been widely used in Mobile Phones, Note Book PC, LCD monitors, and portable electronic products. Recently, high-power-density Adapter was developed. This adapter increases power factor using a bridge diode rectifier and PFC, however, there are weak points that improving efficiency is limited. In the bridgeless rectifier circuit proposed in this paper, there is no PFC, however, the power factor and efficiency are improved by BCM and ZCS operations.

• Journal of Service Research and Studies
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• v.11 no.4
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• pp.43-55
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• 2021

This study analyzed the efficiency of medical services in OECD member countries by dividing it into operational efficiency and quality efficiency. For this purpose, data from 2017-2019 OECD Health Statistics were used. As the analysis method, super efficiency was measured by applying an output-oriented Variable Returns to Scale (VRS) model. As a result of the analysis, Switzerland, Korea, and Italy were included in the high group of operational efficiency, Canada, Greece, Denmark, etc. in the medium group, and Belgium, Germany, and Spain in the low group. Based on quality efficiency, Norway, Switzerland, and Spain are in the high group, and Greece, Denmark, Mexico, etc. are in the medium group, and the Netherlands, Germany, Belgium, etc. were included in the low group. As a result of comparative analysis of efficiency by OECD member countries as of 2018, it was found that Korea's operational efficiency was the most efficient and quality efficiency was inefficient. Korea (0.998) should improve life expectancy by 0.2 (0.2%) and subjective health perception by 44.2 (138.1%) by benchmarking Greece (0.422), Switzerland (0.207), and Spain (0.371) to improve quality efficiency. Unlike most previous studies that focused on operational efficiency, this study measured quality efficiency together and analyzed the efficiency of the medical service industry in each OECD member country. Through this, this study has implications in that it confirmed the international competitiveness of the domestic medical service industry and suggested ways to improve efficiency.

• Korean Management Science Review
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• v.16 no.2
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• pp.1-11
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• 1999

A well-designed location strategy is an integral and important part of corporate strategy for retail firms. The last five years witnessed major changes in retailing industry. A growing city population, rising income levels. and the emergence of suburb areas presented ratailers with new challenges. Mass discount merchandisers and supermarkets expanded rapidly, spreading from Seoul into smaller cities. The rapid increase of mass discount stores raised new concerns and gave rise to the need from a systematic approach to location analysis. In this paper, we present the mathematical background and characteristics of DEA(Data Envelopment Analysis) model, and give a short case study where we apply the DEA model to compute the relative efficiency of 11 Korean mass discount merchandisers. Interpretation of the result is also provided.

• The Transactions of the Korean Institute of Power Electronics
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• v.18 no.4
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• pp.359-366
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• 2013

This paper proposes a zero-current-transition(ZCT) synchronous buck converter using auxiliary circuit with soft-switching for light weight and high efficiency. In this scheme, an auxiliary circuit is added to the conventional synchronous rectifier buck converter and used to achieve soft-switching condition for both the main switch and synchronous switch. In addition, the switch in the auxiliary circuit operates under soft-switching conditions. Thus, the proposed converter provides a higher efficiency. The basic operations, in this paper, are discussed and design guidelines are presented. The usefulness of the proposed converter is verified on a 200KHz, 20 W prototype converter.

• Journal of Distribution Science
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• v.13 no.2
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• pp.5-13
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• 2015

Purpose - In recent years, concerns over privatization have been growing in some public sectors. Privatization in Britain offers lessons for those who have intended to privatize their industry, and in particular, the port industry. Therefore, it is useful for researchers to examine British port privatization in detail, particularly the implications of UK port privatization. Research design, data, and methodology - After reviewing the historical development of the UK port industry, the important factors determining the success of the British port privatization process were identified. The interpretations could be lessons for some other country to consider port privatization in near future. Results - The key factors in relation to port privatization are first, regulation; second, ownership; and third, utilities and operations, which includes autonomy, efficiency, and competitiveness. In addition, the UK port management system is a pure private port system, which has been successful. Conclusions - In Britain, after deciding to privatize the erstwhile public ports, they were fully privatized, focusing on the aforesaid key factors. This offers important lessons for the privatization of other ports in the world.

• Journal of information and communication convergence engineering
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• v.11 no.2
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• pp.118-123
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• 2013

This paper proposes an efficient hardware architecture for high efficiency video coding (HEVC), which is the next generation video compression standard. It adopts several new coding techniques to reduce the bit rate by about 50% compared with the previous one. Unlike the previous H.264/AVC 6-tap interpolation filter, in HEVC, a one-dimensional seven-tap and eight-tap filter is adopted for luma interpolation, but it also increases the complexity and gate area in hardware implementation. In this paper, we propose a parallel architecture to boost the interpolation performance, achieving a luma $4{\times}4$ block interpolation in 2-4 cycles. The proposed architecture contains shared operations reducing the gate count increased due to the parallel architecture. This makes the area efficiency better than the previous design, in the best case, with the performance improved by about 75.15%. It is synthesized with the MagnaChip $0.18{\mu}m$ library and can reach the maximum frequency of 200 MHz.

• Journal of Information Processing Systems
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• v.6 no.1
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• pp.43-52
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• 2010

In the secure communication areas, three-party authenticated key exchange protocol is an important cryptographic technique. In this protocol, two clients will share a human-memorable password with a trusted server, in which two users can generate a secure session key. On the other hand the protocol should resist all types of password guessing attacks. Recently, STPKE' protocol has been proposed by Kim and Choi. An undetectable online password guessing attack on STPKE' protocol is presented in the current study. An alternative protocol to overcome undetectable online password guessing attacks is proposed. The results show that the proposed protocol can resist undetectable online password guessing attacks. Additionally, it achieves the same security level with reduced random numbers and without XOR operations. The computational efficiency is improved by $\approx$ 30% for problems of size $\approx$ 2048 bits. The proposed protocol is achieving better performance efficiency and withstands password guessing attacks. The results show that the proposed protocol is secure, efficient and practical.

• Korean Management Science Review
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• v.23 no.2
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• pp.137-159
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• 2006

Maintenance equipments, tools, manuals and documents are needed to maintain weapon systems. At the time, a lot of technical materials are maintained and used individually at various places and organizations. Thus, maintenance engineers can rot get the necessary informations quickly and the efficiency of maintenance is low. In this paper, first we analyze maintenance processes in weapon systems and define the total measure to evaluate the maintenance efficiency of weapon systems. Second, we propose an implementation procedure to integrated maintenance system.

• Korean Management Science Review
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• v.5 no.1
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• pp.56-70
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• 1988

In this study, We reviewed the solution methods (for the heuristic and optimization method) for the single-item dynamic lot-sizing problem, and improved the efficiency (speed and optimality) of the conventional heuristic method by utilizing the inventory decomposition property. The iventory decomposition property decomposes the given original problem into several independent subproblems without violating the optimality conditions. Then we solve each decomposed subproblems by using the conventional heuristics such as LTC, LUC, Silver-Meal etc. For testing the efficiency of the proposed decomposition method, we adopted the data sets given in Kaimann, Berry and Silver-Meal. The computational results show that the suggested problem solving framework results in some promising effects on the computation time and the degree of optimality.

• Electronics and Telecommunications Trends
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• v.39 no.4
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• pp.32-41
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• 2024

Building energy management plays a crucial role in improving energy efficiency and optimizing energy usage. To achieve this, it is important to monitor and analyze energy-related data from buildings in real time using sensors to understand energy consumption patterns and establish optimal operational strategies. Because of the uncertainties in building energy-related data, there are challenges in analyzing these data and formulating operational strategies based on them. Artificial intelligence (AI) technology can help overcome these challenges. This paper investigates past and current research trends in AI technology and examines its future prospects for building energy management. By performing prediction and analysis based on energy consumption or supply data, the future energy demands of buildings can be forecasted and energy consumption can be optimized. Additionally, data related to the surrounding environment, occupancy, and other building energy-related factors can be collected and analyzed using sensors to establish operational strategies aimed at further reducing energy consumption and increasing efficiency. These technologies will contribute to cost savings and help minimize environmental impacts for building owners and operators, ultimately facilitating sustainable building operations.