• International Journal of Computer Science & Network Security
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• v.21 no.12
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• pp.309-315
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• 2021

The purpose of the article is to analyze the functioning of economic systems in the context of the development of their potential in a circular economy. It is determined that the functioning of economic systems to ensure their sustainability should meet modern challenges and provide for the formation of competitive institutional architecture, the introduction of structural and regulatory innovations, the transition to an innovative model of development. The specific principles of functioning of economic systems include openness, nonlinearity, multivectority, dynamism, emergence, uncertainty about the development of economic processes. It is substantiated that the linear nature of development and equilibrium are not dominant in the functioning of economic systems, and increasing the level of economic efficiency should go hand in hand with minimizing the activities of enterprises, which necessitates the use of circular economy. The main prerequisites for the transition to a circular economy are analyzed. It is determined that the basic concept of the circular economy involves the development of a system of production and consumption, which is based on processing, reuse, repair, product sharing, change of consumption patterns and new business models and systems. The main elements of the circular economy include: a closed cycle, the use of renewable energy sources, systems thinking. The correlation of the principles of sustainable development and the peculiarities of the application of the circular economy is analyzed. It is determined that the circular economy contrasts with the traditional linear economic model, which is based on the model of "take-do-consume-throw away". The advantages and disadvantages due to the use of the principles of circular economy are given. Based on the study, steps are identified to accelerate the transition from a linear economy to a circular economy.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.1
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• pp.76-84
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• 2013

The renewable energy sources is raising for use of grid connected systems, for which higher power quality requirements are being issued. A grid connected converter requires a LC-filter stage, this one is lightly damped for efficiency constraints. Hence, it is subject to resonance if excited by the converter current harmonics or pre-exciting grid voltage harmonics. In this paper, an active damping technique employing notch filter for damping of the resonance frequency is introduced. This technique doesn't need to additional sensors. In addition, it is simple to apply for various systems. Monitoring of the resonance frequency ensures the stable operation of the proper connection and disconnection of the grid. This paper proposes the estimating method of a resonant frequency to determine the cut-off frequency of the notch filter. This method is validated by both simulation and experimental results.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.208.2-208.2
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• 2010

폐기물 가스화는 생산된 합성가스를 이용하여 발전 등 직접적인 에너지원으로 이용할 수 있으며, 고부가가치 화합물의 원료 공급원으로도 이용할 수 있다. 폐기물 가스화를 이용한 고부가가치 화합물 제조의 경우 기존 화합물 제조공정에 폐기물 가스화 공정이 연계되어, 하나의 복합시스템으로 운영이 된다. 따라서 기존 공정과 최적으로 연계될 수 있는 폐기물 가스화 시스템의 개발 또는 선정이 필요하며, 이를 위하여 폐기물 가스화 시스템에 대한 분석 평가가 적절하게 이루어져야 한다. 본 연구에서는 시스템공학 개념을 적용하여 폐기물 가스화 시스템의 체계적인 분석 평가를 위한 프레임워크를 개발하였다. 시스템공학은 요건분석, 기능분석, 합성(통합), 분석/관리 프로세스를 통하여 시스템을 성공적으로 구현하기 위한 다학제적인 접근방법이다. 이러한 시스템공학의 개념 및 기본 프로세스를 적용 조정하여 폐기물 가스화 분석 평가 프레임워크를 개발하였으며, 개발된 프레임워크는 계층구조로 표현이 된다. 계층구조는 분석관점, 분석항목, 분석지표로 구성이 되며 분석된 데이터에 대한 평가는 AHP를 통하여 계산된 가중치를 적용하여 이루어진다.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.90.1-90.1
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• 2010

The design and fabrication of a metallic bipolar plate-gasket assembly for polymer electrolyte fuel cells (PEMFCs) is defined. This bipolar plate-gasket assembly was prepared by inserting a previously prepared bipolar plate in the specially designed gasket mold. For this aim, a proprietary fluoro-silicone based rubber was injected directly into the bipolar plate borders. Gaskets obtained like this showed the chemically / physically stable and the good sealibilty in typically operating PEM fuel cell conditions. And also, this bipolar plate-gasket assembly shows lots of advantages with respect to traditional PEMFCs stack assembling systems: useful application to automative stacking due to easy handling, reduced fabrication time, possibility of quality control and failed elements substitution. This bipolar plate-gasket assembly was evaluated in the short fuel cell stack and met the leakage requirement for normal operation both in short-term and in long-term operation. Especially, it was confirmed that this gasket could be applied successfully even in the high pressure FEM fuel cell systems(over 2.0 bar in absolute pressure).

• Journal of Korea Multimedia Society
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• v.23 no.9
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• pp.1171-1180
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• 2020

The number of the PV systems installed in south korea has been gradually increasing. Interest of operation & management of PV System is rising up as PV System installation trends to increase. The vital function of operation & management is the monitoring system. Most monitoring systems are only available for equipment of suppliers and manufacturers. In this study, a monitoring system was implemented to support multi-domain equipment (inverter, junction box, water distribution board, environmental sensors) that are not limited to specific manufacturers. Monitoring system includes a visualization function, which makes it easy for users to check the power generation and the operation status of the equipment of PV System. In the future, this monitoring system will be utilized as an operation & maintenance foundation element in the PV system industry.

• Journal of Soil and Groundwater Environment
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• v.22 no.5
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• pp.112-127
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• 2017

Groundwater accounts for more than 10% of the total water supply in Korea. However, the contribution of groundwater to public water supply systems has been poorly played role throughout the country except for Jeju Island. Compared with the groundwater uses in foreign countries, the pattern of groundwater use in Korea seems to be very deformed and unreasonable. Currently, the development and use of groundwater in Korea are mostly carried out by the individuals, and public sectors such as central and local governments are not actively involved in such activities. Private groundwater use and management will continue to cause groundwater depletion and pollution problems. It is necessary to actively enhance the role of public authorities in groundwater managements by engaging precise hydrogeological surveys and proper economic evaluation in the development and operation of groundwater sources. Also, in order to solve the problems that public water supply systems overly rely on the surface water sources, it is necessary to take policies that require the water supply companies to secure a variety of water sources.

• The Transactions of the Korean Institute of Power Electronics
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• v.21 no.3
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• pp.254-259
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• 2016

Recently, DC distribution systems have become a hot issue because of the increase in digital loads and DC generation systems according to the expansion of renewable energy technologies. To obtain the practical usage of DC electricity, safety should be guaranteed. The main concerns for safety are twofold: one side is human protection against electric shocks, and the other is facility protection from short faults. "Effects of current on human beings and livestock" (IEC 60479) defines a human body impedance model in electric shock conditions that consists of resistive components and capacitive components. Although the human body impedance model properly works in AC electricity, it does not well match with the electric shock behavior in DC electricity. In this study, the contradiction of the human body impedance model defined by IEC 60479 in case of DC electricity is shown through experiments for the human body. From the analysis of experimental results, a novel unified human body impedance model in electric shock conditions is proposed. This model consists of resistive components, capacitive components, and an inductance component. The proposed human impedance model matches well for AC and DC electricity environments in simulation and experiment.

• Journal of Power Electronics
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• v.10 no.5
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• pp.498-504
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• 2010

The output power fluctuations of renewable energy power plants such as wind turbine generators and photovoltaic systems result in frequency deviations and terminal voltage fluctuations. Furthermore, these power fluctuations also affect the turbine shaftings of diesel generators and gas-turbine generators which are the main power generation systems on isolated islands. Therefore, it is important to achieve torsional torque suppression. Since the measurement of torsional torque is technically difficult, and there is an uncertainty in the mechanical constants of the shaft torsional system. This paper presents an estimation system that estimates torsional torque by using a developed $H_{\infty}$ observer. In addition to the above functions, the proposed shaft torque observer incorporates a parameter identification system that aims to improve the estimation accuracy. The simulation results validate the effectiveness of the proposed $H_{\infty}$ observer and the parameter identification.

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.466-469
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• 2007

Heat pumps are used for air-conditioning systems in commercial buildings, schools, and factories because of low operating and maintenance costs. These systems use the earth as a heat source in heating mode and a heat sink in cooling mode. Ground heat exchangers are classified by a horizontal type and vertical type according to the installation method. A horizontal type means that a heat exchanger is laid in the trench bored in 1.2 to 1.8 m depth. And a vertical type is usually constructed by placing small diameter high density polyethylene tube in a vertical borehole. Vertical tube sizes range from 20 to 40 mm nominal diameter. Borehole depth range between 100 and 200 m depending on local drilling conditions and available equipment. In this study, to evaluate the performance of single u-tube with bentonite grouting, single u-tube with broken stone grouting and double n-tube bentonite grouting of vertical ground heat exchangers, test sections are buried on the earth and experimental apparatus is installed. Therefore the heat transfer performance and pressure loss of these are estimated.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.514-519
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• 2009

The purpose of this study is to show the method of applying snow thermal storage system through the analysis of the cases in Japan. The results were as follows. (1) The systems in Japan were installed at the location whose annual mean air temperature was $14.6^{\circ}C$ or below and annual snowfall was 59 cm or above. (2) By analyzing the characteristics of the systems, meltwater circulation system with a backup chiller was confirmed to be most suitable for Korea. (3) For the first time in Korea, the system with the snow storage of 500 ton was designed at Muju after analyzing regional climate characteristics.