• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2004년도 하계종합학술대회 논문집(1)
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• pp.321-324
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• 2004

In this paper, attenuation characteristics of silica-based variable optical attenuator (VOA) with heat insulating structures are investigated by variations of structural parameters and heating power at wavelength 1.55${\mu}m$. The characteristics of power dissipation and attenuation at this VOA was optimized in terms of heating insulating width, under-cladding height and over-cladding height. The optimized maximum attenuation of this VOA was achieved about 31dB at heating power 150mW.

• 한국정밀공학회지
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• 제23권6호
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• pp.143-150
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• 2006

Recently, in proportion to increased demand on environmentally-friendly heat source, efficient management of district heating(DH) system becomes one of important issue. The objectives of this paper are to systematize data processing of transition temperature, investigate the effect of temperature variations on thermal fatigue and find out a way to improve design fractures of Korean DH pipes. For this purpose, reliable fatigue lift evaluation procedures are examined and applied to quantify thermal fatigue lives. Also, as a prototypal optimization analysis results, mean value of original cross sectional area of selected pipes was reduced 18.6% sustaining their sufficient margins against fatigue failure. So, it is anticipated that the output of this research can be used as useful information of optimal design and operation in the future.

• KIEAE Journal
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• 제3권2호
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• pp.17-24
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• 2003

The purpose of this study is to present rational methods of multi-criteria optimization of the envelope of buildings. The object is to determine the optimum R-value of the envelope of a building, based on the following criteria: minimum building costs (including the cost of materials and construction) and yearly heating costs. Mathematical model described heat losses and gains in a building during the heating season. It takes into consideration heat losses through wall, roof, floor and windows. Particular attention was paid to have a more detailed description of heat gains due to solar radiation. On the assumption that shape of building is rectangle in order to solve the problem, optimum R-value of the envelope of a building is determined by using non-linear programing methods(Kuhn-Tucker Conditions). The results constitute information for designers on the optimum R-value of a building envelope for energy saving buildings.

• KIEAE Journal
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• 제3권2호
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• pp.51-58
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• 2003

The purpose of this study is to present rational methods of multi-criteria optimization of the shape of energy saving buildings. The object is to determine the optimum dimension of the shape of a building, based on the following criteria: minimum building costs (including the cost of materials and construction) and yearly heating costs. Mathematical model described heat losses and gains in a building during the heating season. It takes into consideration heat losses through wall, roof, floor and windows. Particular attention was paid to have a more detailed description of heat gains due to solar radiation. On the assumption that shape of building is rectangle in order to solve the problem, the proportions of wall length and building height are determined by using non-linear programing methods(Kuhn-Tucker Conditions). The results constitute information for designers on the optimum proportions of wall lengths, height, and the ratios of window to wall areas for energy saving buildings.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 하계종합학술대회 논문집(5)
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• pp.63-66
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• 2002

This paper has been studied the parallel resonant inverter which controlling the constant power and tracking the load resonant frequency with PLL is possible, in order to minimize switching losses. The current-fed full-bridge type parallel resonant inverter of an induction heating system was composed of IGBT in switching device. For regulating the output power of an induction heating system, the Fuzzy controller is used. The Fuzzy controller makes the control signal for a stable power regulating control and when reference is changed, it is superior to adaptability. It has been evaluated a stable behavior for a noise with switching and a load disturbance.

• 대한산업공학회지
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• 제23권1호
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• pp.115-127
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• 1997

A GDHS(Geothermal District Heating System) is a heating system supplying a group of districts with heat extracted from geothermal sources. The advantages of GDHS include saving fuel consumption as well as reducing air pollution. This paper presents a case study for the economic feasibility model and analysis of a GDHS with which central/individual heating systems are replaced. Configuring to a simplified GDHS which consisits of subsurface systems, surface systems, and transmission/distribution systems, we find out the properties of the system and the model parameters affecting the initial investment/operating costs in order to develop a classical economic feasibility model given geothermal temperature. Based on our model parameter space, we analyzed the geothermal development project of the Jejoo Island probabilistically given prior information such as the expected geothermal power, the demand size and the length of transmission/distribution pipes.

• 대한기계학회논문집
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• 제19권7호
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• pp.1709-1719
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• 1995

The primary objective of the paper is to obtain the basic information of the natural convection of a stratified with various parametric conditions related to rotating speed, temperature and concentration gradient. For the purpose of it, experiments are performed in a stably stratified salt-water solution with lateral heating in a stationary or rotating annulus. The experiment covers the ranges of Ar=2, Le=100, R $a_{\ta}$=2 10$^{5}$ and Ta=0, 10$^{5}$ - 2.5*10$^{8}$ . Many interesting flow phenomena are observed and rotation effects are examined. Particularly as Taylor number increases (rotation increases) at a given R $a_{\ta}$, the generation of rolls at hot wall is inhibited and the formation and merging process of layers are delayed.

• 대한건축학회논문집:구조계
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• 제36권2호
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• pp.175-180
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• 2020

The purpose of this study was to clarify precautions during the design and operation phases for energy reduction in a public office building. To check the operation status of the building, we measured the indoor temperature and humidity in the office space of the building installed central heating and cooling systems. And we analyzed these data and annual BEMS data. As a result, we found six problems related to decreasing system efficiency. Based on these, we presented the information to improve the efficiency of the system from the design and operation phase. Also, we present the need for a system to support the decision-making of operational managers in real-time for the energy efficiency of the building.

• 대한설비공학회지:설비저널
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• 제15권3호
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• pp.292-298
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• 1986

The new f-chart capable of estimating long-term thermal performance of solar space and water heating systems was developed. The system comprise a flat plate solar collector, heat exchanger, storage tank filled with water, auxiliary fuel fired heater, and a house structure. The information obtained from many simulations of solar heating systems has been used to develop this f-chart. Actual hourly meteorological data collected in Seoul, Daejeon, Kwangju and Daegu, Korea from 1979 to 1983 have been utilized in these simulations. The new f-equation is as follows: $$f=1.034Y_{-}0.0968X_{-}0.2235Y^2+0.0043X^2+0.0144Y^3$$. The system performance estimates obtained from the developed f-chart are in close agreement with the results of experiment.

• 한국주거학회논문집
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• 제17권4호
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• pp.101-109
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• 2006

The purpose of this study was to suggest ways on reducing the cooling and heating energy cost of the officetel building with the multiple glazing windows according to Life Cycle Costing. This study consisted of an hour-by hour energy simulation program and further data from the EnergyPlus V1-2-2 to the four pane type windows that were applied with 2 low-e polyester film and krypton gas to the officetel model building. It was determined that the four panes type windows that had 2 low-e polyester film and krypton gas applied to, them showed a cooling and heating cost reduction over traditional double glazed windows that were filled with air. According to this study, as well as the information from chart 4.5 and the LCC it was determined that the present value of the four panes of windows that had 2 low-e polyester film and krypton gas applied to them showed. a 11.4% reduction in heating and cooling in comparison to the traditional double glazed windows that were filled with air.