• 전기학회논문지
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• 제62권4호
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• pp.566-572
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• 2013

A microgrid is a small scale power system. The microgrid is operated in two operation modes, the grid-connected mode and the islanded mode. In the islanded mode, the frequency of a microgrid should be maintained constantly. For this, the balance between power supply and power demand during islanded mode should be met. In general, energy storage systems (ESSs) are used to solve power imbalance. In this paper, the frequency control effect of a Lithium-ion battery energy storage system (Li-ion BESS) has been tested on the hardware-in-the loop simulation (HILS) system environment.

• Journal of Construction Engineering and Project Management
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• 제4권1호
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• pp.37-44
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• 2014

Comparatively, the construction industry has, on average, a higher rate of fatal and major injuries, work induced ill-health and damage to properties than other industrial sectors; and this is a source of concern to industry stakeholders. The study showed that although subcontracting could be contributory to an increase in workplace accidents in the construction industry, contractual aspects of subcontracting arrangements (such as the power imbalance that exist along the client-customer interface) also present opportunities for improvements in health and safety management (HSM) practices in organisations. This conclusion was reached after an analysis of a questionnaire survey (with a 27% response rate) that assessed the attitudes and perception to health and safety issues.

• 디지털산업정보학회논문지
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• 제9권3호
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• pp.99-106
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• 2013

There has been a lot of growth more than 10% in the information security industry. In accordance with the industrial growth, it increased needs for the information security manpower development as a national problem. But there is an imbalance between demand and supply of the information security manpower in terms of the quantity and quality. It is mainly caused by the curriculum of the information security is made considering for suppliers not for demanders. As a resolution to solve this problem, we suggest the curriculum of information security for vocational education and training. As the information security area is wide in view of required knowledge and technology, we design the curriculum by selecting major occupation type from the information security manpower distribution and products and then by investigating the job description using NCS(National Competency Standard). And we compared the curriculum to that of two or three year diploma courses in Korea.

• 한국GIS학회:학술대회논문집
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• 한국GIS학회 2010년도 추계학술대회
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• pp.291-291
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• 2010

Emerging global economic growth and increasing demand for energy supply and demand imbalance and the excessive use of fossil fuels existing the rapidly increasing greenhouse gas emissions and resource depletion of global energy crisis is deepening. Accordingly, improvement of living conditions around and through the natural ecological preservation and the need for a comfortable life for the meeting the importance of energy management and consumption are emerging. Many in the field of architecture for energy-saving measures and conducts research and analysis from the early stages to verify the energy performance of BIM (Building Information Model) technology development and commercialization through the building's energy performance to an objective technology forecasts Analysis of the existing building energy performance in waste management also possible that "BIM-based green building process, the possibility of" suggested. In this study, BIM through the analysis of information using the structures for the management of waste, energy and physical data collected by Mapping it can effectively plan resources for recycling were analyzed.

• 전력전자학회논문지
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• 제22권1호
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• pp.9-17
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• 2017

A parallel control algorithm of thyristor dual-converter power system for the DC power supply of railway is proposed. The circulating current and current imbalance generated during parallel operation can be limited to control the output voltage of each power system by using the proposed parallel control algorithm. The proposed control algorithm can also eliminate output current sensor to achieve the same output response without additional costs. The validity of the proposed algorithm is verified through simulation and experiment.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2000년도 전력전자학술대회 논문집
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• pp.739-743
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• 2000

With significant development of power electronics technology the proliferation of nonlinear loads such as such as static power converters has deteriorated power quality in power transmission distribution systems. Notably voltage harmonics resulting from current harmonies produced by the nonlinear loads have become a serious problem in many systems Moreover momentary interruptions and voltage sags are responsible for many of the power quality problems found in typical industrial plants. Int his paper proposed 3 phase hybrid series active power filter is not only for harmonic compensation but also for harmonic isolation between supply and load and for voltage regulation and imbalance compensation Through computer simulations we have verified the effectiveness of the proposed system.

• 한국시스템다이내믹스연구
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• 제11권1호
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• pp.5-26
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• 2010

To revitalize the trucking market, many studies are being done but it still has a lot of problems such as imbalance between supply and demand, poor profit structure of truck owners, ect. Therefore, it aims to study what kinds of prerequisite are needed to solve these problems through analyzing system structure and mechanism of the market. To achieve it, System Dynamics methodology, appropriate to make a simulation model and analyze dynamics of the system, is utilized. To obtain an empirical research point of view, time series data related on trucking market-provided by The Korea Transport Institute-are used. In addition, interview with a local representative logistics company and a ICD(Inland Container Depot) operation company is performed to find out technical and functional supporting factors to solve the existing problems in the market.

• Journal of Power Electronics
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• 제15권1호
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• pp.288-297
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• 2015

This paper presents a novel approach to diagnose interturn insulation faults in three-phase transformers that operate at different loading conditions. This approach is based on the loci of instantaneous symmetrical components and requires the measurement of three input primary winding currents and voltages to diagnose faults in the transformer. The effect of unbalance supply conditions, load variations, constructional imbalance, and measurement errors when this methodology is used is also investigated. Wing size or length determines the loading on the transformer. Wing travel and area determine the degree of severity of fault. Experimental results are presented for a 400/200 V, 7.5 kVA transformer to validate this method.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 추계학술대회 논문집 전력기술부문
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• pp.190-192
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• 2003

When generators trip on the occurrence of disturbance, the power system frequency declines by the amount of difference between demand and supply due to the imbalance between power generation and load. Even though the power system is operated with the same grid structure, generating capacity, and load, the resulting frequency decline and its recovery slope show different aspects according to the inertia constants of generators, spinning reserves, and the speed adjusting rates at the governors. From this point of view, we analysed differences of frequency decline at the various conditions in domestic power system.

• 한국수소및신에너지학회논문집
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• 제30권3호
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• pp.201-208
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• 2019

Recently, a fuel reforming plant for supplying high purity hydrogen is being applied to submarines. Since steam reforming is an endothermic reaction, it is necessary to continuously supply heat to the reactor. A fuel reforming plant for a submarine needs a multi-stage burner (MSB) to acquire heat and convert the combustion gas to $CO_2+H_2O$. The MSB has problems that the combustion imbalance occurs during start-up due to the temperature restriction of the combustion gas. This problems can be solved by burning $H_2O$ together with fuel and $O_2$. In this study, the simulation results of MSB were analyzed to determine the optimum flow rate of $H_2O$ supplied to the 6-stage burner. When the flow rate of $H_2O$ was low, combustion was concentrated on the burner#6 in comparison with the burner#1-#5. This combustion concentration improved as the supply amount of $H_2O$ increased. As a results, it was necessary to supply at least 4.9 kmol/h of $H_2O$ (per 1 kmol/h of fuel) to burner#1 in order to maintain the combustion gas temperature of each stage at $750^{\circ}C$ and to convert the final stage burner gas composition to $CO_2+H_2O$.