• 정보관리학회지
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• 제19권2호
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• pp.5-29
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• 2002

본 연구는 국내 환경·에너지 공학 분야 연구기관을 대상으로 다양한 유형의 연구소 현황을 조사하고, 최근에 이루어진 연구결과의 데이터베이스 구축 등의 정보화 여부와 환경·에너지 R&D 정보 활용여부와 자원공유를 위한 연구기관들간의 협력적 네트워크 활용의 실태를 진단했다. 정보화와 정보 활용을 방해하는 역기능 요인 분석결과를 중심으로 21세기 핵심 R&D 정보활용과 보다 전문적이고 수준 높은 연구환경을 고무시킬 수 있는 방안을 제시했다.

• Journal of Power Electronics
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• 제15권3호
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• pp.652-659
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• 2015

This paper presents a new hybrid soft switching dc-dc converter with a low circulating current and high circuit efficiency. The proposed hybrid converter includes two sub-converters sharing two power switches. One is a three-level PWM converter and the other is a LLC converter. The LLC converter and the three-level converter share the lagging-leg switches and extend the zero-voltage switching (ZVS) range of the lagging-leg switches from nearly zero to full load since the LLC converter can be operated at f_sw (switching frequency) $\approx$ f_r (series resonant frequency). A passive snubber is used on the secondary side of the three-level converter to decrease the circulating current on the primary side, especially at high input voltage and full load conditions. Thus, the conduction losses due to the circulating current are reduced. The output sides of the two converters are connected in series. Energy can be transferred from the input voltage to the output load within the whole switching period. Finally, the effectiveness of the proposed converter is verified by experiments with a 1.44kW prototype circuit.

• 대한전기학회논문지:전력기술부문A
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• 제54권3호
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• pp.107-116
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• 2005

The paper addresses modeling and analysis of a grid-connected photovoltaic generation system (PV system). PSCAD/EMTDC, an industry standard simulation tool for studying the transient behavior of electric power system and apparatus, is used to conduct all aspects of model implementation and to carry out extensive simulation study. This paper is aimed at sharing with the PSCAD/EMTDC user community our user-defined model for PV system applications, which is not yet available as a standard model within PSCAD/EMTDC. An equivalent circuit model of a solar cell has been used for modeling solar array. A series of parameters required for array modeling have been estimated from general specification data of a solar module. A PWM voltage source inverter (VSI) and its current control scheme have been implemented. A maximum power point tracking (MPPT) technique is employed for drawing the maximum available energy from the PV array. Comprehensive simulation results are presented to examine PV array behaviors and PV system control performance in response to irradiation changes. In addition, dynamic responses of PV array and system to network fault conditions are simulated and analysed.

• 임상간호연구
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• 제22권3호
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• pp.314-326
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• 2016

Purpose: The purpose of this study was to understand the experience of emotional labor of clinical nurses in medical institutes. Methods: A total of 26 nurses from 11 hospitals participated in the study. Six focus groups were organized and 4 to 5 nurses took part in each group. The compositional factors of groups included clinical experience, age, gender, work place and position. Data collection was conducted through focus group interview and it was proceeded by the time of data saturation. In this qualitative study, content analysis was conducted. Results: Five themes, 14 categories, and 33 subcategories, were emerged. The themes were 'Restrain themselves', 'Communion to the patients', 'Working environment provoking emotional tension', 'Respond to emotional events', 'Recovery of emotional energy'. Conclusion: Results indicated that surface acting of emotional labor such as, repression of personal desire and presenting the emotions that the organization ask nurse to express was related to psychosomatic symptoms, depression, burnout, poor job performance, increased mistakes, and low job satisfaction which eventually leads to nurses' turnover. In order to reduce negative influence of emotional labor, it is necessary to build positive organizational culture, to provide support from managers and co-workers. It is also important to improve work environment in order to do more deep acting since sharing emotions with patients can reduce the negative influence of emotional labor.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권6호
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• pp.3029-3045
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• 2017

The main processes of a cognitive radio system include spectrum sensing, spectrum decision, spectrum sharing, and spectrum conversion. Experimental results show that these stages introduce a time delay that affects the spectrum sensing accuracy, reducing its efficiency. To reduce the time delay, the frequency spectrum prediction was proposed to alleviate the burden on the spectrum sensing. In this paper, the deep recurrent neural network (DRNN) was proposed to predict the spectrum of multiple time slots, since the existing methods only predict the spectrum of one time slot. The continuous state of a channel is divided into a many time slots, forming a time series of the channel state. Since there are more hidden layers in the DRNN than in the RNN, the DRNN has fading memory in its bottom layer as well as in the past input. In addition, the extended Kalman filter was used to train the DRNN, which overcomes the problem of slow convergence and the vanishing gradient of the gradient descent method. The spectrum prediction based on the DRNN was verified with a WiFi signal, and the error of the prediction was analyzed. The simulation results proved that the multiple slot spectrum prediction improved the spectrum efficiency and reduced the energy consumption of spectrum sensing.

• 한국공간구조학회논문집
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• 제14권4호
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• pp.47-54
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• 2014

This paper presents the structural model development and verification processes of wind turbine blade. The National Renewable Energy Laboratory (NREL) Phase VI wind turbine which the wind tunnel and structural test data has publicly available is used for the study. The wind turbine assembled by blades, rotor, nacelle and tower. The wind blade connected to rotor. To make the whole turbine structural model, the mass and stiffness properties of all parts should be clear and given. However the wind blade, hub, nacelle, rotor and power generating machinery parts have difficulties to define the material properties because of the composite and assembling nature of that. Nowadays to increase the power generating coefficient and cost efficiency, the highly accurate aerodynamic loading evaluating technique should be developed. The Fluid-Structure Interaction (FSI) is the emerging new way to evaluate the aerodynamic force on the rotating wind blade. To perform the FSI analysis, the fluid and structural model which are sharing the associated interface topology have to be provided. In this paper, the structural model of blade development and verifying processes have been explained for Part1. In following Part2 paper, the processes of whole turbine system will be discussing.

• 전기학회논문지
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• 제57권11호
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• pp.1954-1961
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• 2008

Microgrid usually consists of a cluster of distributed generators(DGs), energy storage systems and loads, and can operate in the grid-connected mode and the islanded mode. This paper presents detailed descriptions of two different options for controlling the active power of DGs in the microgrid. One is regulating the power injected by the unit to a desired amount(Unit output power control) and the other is to regulate the flow of active power in the feeder where the unit is installed to a constant(Feeder flow control). Frequency-droop characteristics are used to achieve good active power sharing when the microgrid operates in the islanded mode. The change in the frequency and the active power output of DGs are investigated according to the control mode and the configuration of DGs when the microgrid is disconnected from the main grid. From the analysis, this paper proposes a method to determine the droop constant of DGs operating in the feeder flow control mode. Simulation results using the PSCAD/EMTDC are presented to validate the approach, which shows good performance as opposed to the conventional one.

• 유통과학연구
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• 제18권5호
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• pp.71-81
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• 2020

Purpose: This case study illustrates the successful entry of Saudi Aramco in the Korean market and how it grows to become one of the world's largest integrated energy enterprises. Research design, data and methodology: This case investigates diverse secondary sources to examine the entry strategy of Aramco in Korea, such as several interviews including public and anonymous dialogues, periodicals, dispatches (i.e. news articles and magazines), annual reports, industrial reports, and others. Results: The main concern for the international strategic approaching of Saudi Aramco is to enter into Korean market by joint venture with SsangYong Oil (today's S-Oil Corporation) in 1991 and finally, ending by Acquisition of S-Oil in 2015. This acquisition of local No.3 company, S-Oil, in Korea is the successful case in Asian Markets overcoming liability of foreignness. Moreover, Saudi Aramco's global distribution strategy through localization in the Korean market is appropriate given the market conditions, timing, effectiveness, and efficiency by sharing their resources and collaborating. Conclusions: It would be valuable, unique, and real story to analyze global leading company's entry and globalization strategy in overseas market. In addition, this study provides decision-makers with a significant and more strategic implication for the overseas expansion of businesses.

• Nuclear Engineering and Technology
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• 제41권8호
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• pp.1005-1014
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• 2009

The Dual Unit Optimizer 2000 MWe (DUO2000) is put forward as a new design concept for large power nuclear plants to cope with economic and safety challenges facing the $21^{st}$ century green and sustainable energy industry. DUO2000 is home to two nuclear steam supply systems (NSSSs) of the Optimized Power Reactor 1000 MWe (OPR1000)-like pressurized water reactor (PWR) in single containment so as to double the capacity of the plant. The idea behind DUO may as well be extended to combining any number of NSSSs of PWRs or pressurized heavy water reactors (PHWRs), or even boiling water reactors (BWRs). Once proven in water reactors, the technology may even be expanded to gas cooled, liquid metal cooled, and molten salt cooled reactors. With its in-vessel retention external reactor vessel cooling (IVR-ERVC) as severe accident management strategy, DUO can not only put the single most querulous PWR safety issue to an end, but also pave the way to very promising large power capacity while dispensing with the huge redesigning cost for Generation III+ nuclear systems. Five prototypes are presented for the DUO2000, and their respective advantages and drawbacks are considered. The strengths include, but are not necessarily limited to, reducing the cost of construction by decreasing the number of containment buildings from two to one, minimizing the cost of NSSS and control systems by sharing between the dual units, and lessening the maintenance cost by uniting the NSSS, just to name the few. The latent threats are discussed as well.

• 한국주거학회논문집
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• 제24권6호
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• pp.189-197
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• 2013

The purpose of the study was to analyze the improvement elements depended on housing quality measurement tool related to mental health. The data for the analysis was collected through questionnaire survey method from November 1, 2012 to January 17, 2013, and the sample consisted of 720 respondents living in single detached houses, multi-families detached houses, apartments, and town houses in 4 cities, Seoul, Busan, Daejeon, and Kwangju. The data were analyzed using descriptive statistics. The results of improvement elements are as follows: 1) Pedestrian-threaten street from cars in physical safety 2) A secluded or dark spot and fear of walking at night in social security, 3) Indoor noise, outdoor noise, and evidence of abandoned trash heap/bottle in neighborhood in health & sanitation, 4) Illegal parking and heating control system in facility convenience, 5) Extra kitchen, number of bathrooms, and community spaces in space convenience, 6) Openness and spaciousness of indoor room, and satisfaction of house and neighborhood in comfort, 7) Management common/sharing space in maintenance, 8) Energy saving facility and environment friendly materials use in sustainability, 9) Burden on housing cost, asset value on house, and school district in economic value, 10) Reflection of residents style, surrounding building's number of layers, and neighborhood appearance of preference in housing environment image.