• 한국수소및신에너지학회논문집
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• 제23권6호
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• pp.604-611
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• 2012

For the commercialization of fuel cell powered vehicle, it is highly important to improve the performance and efficiency of an automotive polymer electrolyte membrane fuel cell (PEMFC) system. The performance and efficiency of PEMFC systems are significantly influenced by their operating conditions. Among these conditions, the system operating pressure is considered as the one of the main factors. In this study, to investigate the effects of operating pressure on the performance and efficiency of automotive PEMFC systems, two types of high-pressure operating PEMFC systems adopting two different compressors (i. e. different performance maps) are modeled by using MATLAB/Simulink environment. The PEMFC system efficiency and parasitic compressor power are mainly analyzed and compared for the two types of high-pressure operating PEMFC systems under the same system net power conditions. It is expected that this kind of study can contribute to provide basic insight into the operating strategies of high-pressure operating PEMFC systems for automotive use.

• 대한전기학회논문지
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• 제39권11호
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• pp.1174-1182
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• 1990

A hgih efficiency and good dynamic performance drive system of an induction motor is presented in this paper using vector control technique. If the induction motor is driven under light loads with rated flux, the iron loss is excessively large compared with the copper loss, resulting in poor motor efficiency. High efficiency drive of an induction motor can be achieved by adjusting the flux level which leads the total motor loss to be a minimum value. Generally reducing the flux degrades the dynamic performance, but the dynamic performance of the proposed system is also maintained high. If the d-axis is coincident with rotor flux phasor in synchronous rotating reference frame, the stator current can be decoupled as flux component and torque component. At steady state, the developed motor torque is proportional to the product of the flux and torque component. The combination of the two components minimizing the motor loss could be found with numerical method. As the procedure to obtain the optimal combination is too hard, it is found experimentally. The system block diagram is suggested for maximum efficiency control. The proposed system is studied through digital simulation and verified with experiment. The experimental results show the possiblity of a high efficiency drive with good dynamic performance of maximum efficiency control.

• The Journal of Asian Finance, Economics and Business
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• 제8권5호
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• pp.231-239
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• 2021

The purpose of this study is to analyze the effect of risk efficiency, financial decisions, and financial performance on firm value due to advances in financial reporting technology. This research was conducted on all banking sub-sector companies listed on the Indonesian capital market during a period of eight years, namely 2012-2019 which were selected using the purposive sampling method. The advancement of financial reporting technology is measured by two indicators based on the Internet financial reporting approach. Risk efficiency is measured using three indicators with a risk proxy relative efficiency approach using value at risk. Financial decisions are measured by two indicators that represent funding decisions and investment decisions. Financial performance is measured by two indicators with the profitability approach, and firm value is measured by two indicators based on the investor perception approach. The data analysis technique in this study used multivariate analysis with SEM-PLS. The empirical findings of this study are the advances in financial reporting technology, financial decisions, and risk-based efficiency value have a significant effect on firm value, while financial performance does not have a significant effect on firm value. Banking companies reduce risk to achieve efficiency and result in lower profits.

• 유통과학연구
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• 제15권11호
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• pp.49-57
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• 2017

Purpose - In Korea, general super markets have a great impact on the market performance of traditional markets. We propose a modified two stage DEA model for evaluating the performance of traditional markets in Incheon, Korea by identifying the influence of external environmental factors including the presence of general super markets as non-discretionary variables in DEA. Research design, data, and methodology - After obtaining bias-corrected estimates of original DEA efficiency scores using the input and output data of 49 traditional markets, we regress them on several external environmental factors by bootstrap-truncated regression. Results - We obtain bias-corrected efficiency scores from the original DEA efficiency scores by bootstrap and among the five environmental factors, the residential population and the presence of general super markets or SSMs can be considered as the driving forces influencing bias-corrected efficiency scores, positively and negatively, respectively. Conclusions - When DEA efficiency scores tend to be overestimated, we need to use a biased-corrected efficiency score by bootstrap. It is important to note that the efficiency of traditional markets can be largely influenced by external environmental factors such as the presence of general super markets or SSMs that traditional markets can not control. Therefore, it is desirable to consider such environmental factors appropriately for a reasonable performance evaluation.

• 산업공학
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• 제22권3호
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• pp.192-204
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• 2009

Based on the characteristics of 'Korean electric power industry R&D programs', this study proposes a new performance evaluation framework where electric power industry related R&D projects are scrutinized. The abovementioned R&D programs have their own goals and especially they emphasize the effectiveness as well as the efficiency of each subordinate R&D project. Hence, in this framework, a performance evaluation procedure is established and then a mathematical model is developed according to the procedure. The model calculates performance evaluation indices for a set of R&D projects integrating the effectiveness with the efficiency of each R&D project. In a case study with an empirical dataset, statistical significance is tested on the integrated performance evaluation indices of R&D projects regarding organizational types and program categories considered.

• 한국자동차공학회논문집
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• 제3권2호
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• pp.130-135
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• 1995

In this paper, the numerical simulation of the method of characteristics for a two-stroke SI engine was carried out, and the scavenging efficiency and the performance of single engine with two types of exhaust system, that is, a pipe exhaust system and a tuned exhaust system, were predicted and compared. The conculusions are obtained as follows. (1) The method of characteristics of hometropic flow considering the friction and the variation of area is useful to predict the scavenging efficiency and the performance of the two-stroke engine. (2) The shape of exhaust system effects directly on the scavenging and the trapping efficiency. (3) A tuned exhaust system consisted of the diffuser and the convergent nozzle makes the plugging pulse and therefore enhances the scavenging and the trapping efficiency. (4) It may be possible to design the optimum exhaust system by using the plugging pulse.

• 한국컴퓨터정보학회논문지
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• 제23권11호
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• pp.9-15
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• 2018

The Ministry of National Defense announced 'Defense Reform 2.0' that aims to strengthen the country's security for decrease of regional uncertainties, growing requirements for advanced technologies, and a need for more efficiency in the Republic of Korea(RoK) Armed Forces this year. It said RoK Armed Forces have to change efficiently in preparation for rapid decline in military service resources as demographic cliff turning into reality, and the rapid evolution of the "battlefield environment" caused by developments in military science and technologies. RoK Navy combat Management System(CMS) made by domestic proprietary technology since 2000s and development centered on Agency for Defense Development require design changes for added requirements. So in this paper, I propose method of design a low cost and high efficiency navy CMS architecture based on high performance server and virtualization technology. And I create a test environment for analysis performance and compare the performance of proposed navy CMS and existing navy CMS.

• 한국태양에너지학회 논문집
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• 제31권3호
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• pp.57-66
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• 2011

A Photovoltaic/Thermal(PVT) solar system consists of PV module and thermal absorber plate which convert the absorbed solar radiation into electricity and heat. Meaningful researches and development (R&D) on the PVT technologies have been performed since the 1970s. This paper presents a review of the previous works covering the various types of PVT and their performance analysis in terms of electrical and thermal efficiency. This review compares electrical and thermal efficiency of the different types of PVT collectors and analyzes the parameters affecting PVT performance. Based on the literature review, box channel type PVT with unglazed, or flat plate PVT with glazed have the highest efficiency among them. From the literature review, R&D should be carried out aiming at improving their overall electrical and thermal efficiency, cutting down the cost, and making them more competitive in the energy consumption market.

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2011년도 춘계학술발표대회 논문집
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• pp.250-255
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• 2011

A Photovoltaic/Thermal(PVT) solar system consists of PV module and thermal absorber plate which convert the absorbed solar radiation into electricity and heat. Meaningful researches and development (R&D) on the PVT technologies have been performed since the 1970s. This paper presents a review of the previous works covering the various types of PVT and their performance analysis in terms of electrical and thermal efficiency. This review compares electrical and thermal efficiency of the different types of PVT collectors and analyzes the parameters affecting PVT performance. Based on the literature review, box charmel type PVT with unglazed, or flat plate PVT with glazed have the highest efficiency among them. From the literature review, R&D should be carried out aiming at improving their overall electrical and thermal efficiency and cutting down the cost, making them more competitive in the energy consumption market.

• International Journal of Automotive Technology
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• 제6권5호
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• pp.537-544
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• 2005

This paper presents the efficiency measurement and energy analysis for a parallel HEY. Using the HEV test rig, the efficiency of each powertrain component is measured for a given driving cycle including the regenerative braking system. Accompanied by the efficiency measurements, a detailed energy analysis is performed. Based on the efficiency measurement and energy analysis, a HEV performance simulator is developed. Using the simulator, the HEV performance is evaluated for a mild hybrid system. It is expected that the HEV simulator developed can be used to obtain further optimization potentials.