• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2008년도 춘계학술발표대회 논문집
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• pp.300-303
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• 2008

The stratification effect was investigated with four different types of diffuser shape in a thermal storage tank. For this study, experimental facility was constructed, which was composed of experimental thermal storage tank, hot and cold water storage tanks, boiler, chiller, data acquisition system, etc.. Visualization and lab scale experimental result showed that radial curved type diffuser was the highest degree of stratification among the four diffuser shapes.

• 터널과지하공간
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• 제23권1호
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• pp.78-85
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• 2013

열에너지를 성층화하여 저장하는 주된 목적은 에너지의 열역학적 질을 유지하기 위한 것으로서 열에너지의 성층화를 통해 필요시 원하는 온도에서 열에너지 활용이 가능하다. 저장소 내 열에너지의 온도에 따른 분리, 즉 열성층화는 이와 같은 열에너지의 활용에 영향을 미치는 핵심 인자이다. 본 논문에서는 열성층화의 정도를 평가할 수 있는 기존에 제안된 기법들을 소개하였으며, 특히 열에너지의 주입, 저장, 배출 과정 동안 열저장소의 성층화와 관련된 성능을 결정하는 데 사용될 수 있는 기법들을 중심으로 개념 및 특징을 살펴보았다. 또한 열성층화 지수를 이용하는 방법을 토대로 스웨덴 Lyckebo 암반공동 내 열에너지의 성층도를 비교 분석하여 기법의 적용성을 조사하였다.

• 설비공학논문집
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• 제24권4호
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• pp.336-342
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• 2012

Large-scale active solar heat systems are generally using heat exchanger between collector and storage tank loops to prevent damage by freezing. It is difficult to maintain stratification in a storage tank in the system owing to greater flow rate enhancing heat transfer. In the previous study, we introduced a spiral-jacketed storage tank and obtained good results to keep system performance of general level without better stratification. We added a scroll-shaped heat exchanger coil on the upper part in the spiral-jacketed storage tank. As a result of the experiment, it was verified that degree of stratification of the new type storage tank is higher than that of the previous one with a possibility of better collector efficiency and solar fraction.

• Communications for Statistical Applications and Methods
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• 제22권3호
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• pp.255-264
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• 2015

This paper addressed the problem of estimation of finite population mean in double sampling for stratification. This paper proposed a generalized ratio-cum-product type estimator of population mean. The bias and mean square error of the proposed estimator has been obtained upto the first degree of approximation. A particular member of the proposed generalized estimator was identified and studied from a comparison point of view. It is observed that the identified particular estimator is more efficient than usual unbiased estimator and Ige and Tripathi (1987) estimators. An empirical study was conducted in support of the theoretical findings.

• 복식문화연구
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• 제8권5호
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• pp.771-784
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• 2000

The purpose of this study was to investigate the casual relationships of self-monitoring, face satisfaction, and demographic variables on the purchasing behavior and use of cosmetics of women. Samples wre 479 women in their 20's to 50's in Seoul, Korea. Three factors of the purchase criteria of cosmetics derived by factor analysis : F.1 'intrinsic trait', F.2 'sales promotion and fashion', F.3 'economy. Women high in self-monitor purchased and used cosmetics more than those low in self-monitor. There were significant relationships between the purchasing behavior and use of cosmetics and age, education, and social stratification. Women in their 20's and 30's perceived purchase criteria associated with intrinsic trait such as color and becomingness as more important, 20's sales promotion and fashion, women with less education perceived economy more than did the others. Upper class women showed more concern for intrinsic trait such as quality and color of cosmetics than did lower class. Social stratification, age, self-monitoring, and education had a direct effect on the degree of cosmetics purchase. Self-monitoring and education had a direct effect on the degree of cosmetics use. Age, education, social stratification, and face satisfaction had an indirect effect on the degree of cosmetics purchase and use. The causal relationship of self-monitoring on the use of coloring cosmetics was stronger than the connection between self-monitoring and total cosmetics. The present findings provide that personal trait associated with self-monitoring of women is important variable in understanding of the purchasing behavior and use of cosmetics.

• 한국해안해양공학회지
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• 제14권4호
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• pp.295-307
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• 2002

진해ㆍ마산만에서 수온, 염도 및 DO농도를 연직방향으로 1년동안 측정하였다. 관측된 수온 및 염도 자료를 이용하여 성층화 특성을 분석하고, DO농도의 연직변화를 성층화 특성 및 저질오염도와 관련하여 분석하였다. 분석결과, 진해ㆍ마산만의 수온 성층화는 4월 이전에 시작되어 10월경에 종료되는 양상을 보이고 있는 것으로 판단되었다. 또한, 1998년 4월 연직방향의 평균 염도변화는 3.9(equation omitted) 정도로 증가되고, 1998년 8월 9.3(equation omited), 10월 4.3(equation omitted) 정도가 유지되어 가을철에도 염도 성층이지속되고 있는 것으로 파악되었다. 한편, DO 농도는 성층화가 시작되는 4월을 기점으로 연직방향 평균 DO농도변화도 2.6(mg/L)에서 6월 8.3(mg/L), 8월 5.9(mg/L), 9월 7.24(mg/L), 10월4.4(mg/L)으로 명확한 성층화 양상을 보이고 있다. DO 농도변화는 전체적으로 해역의 오염도와 밀접한 관련이 있으나. 성층화 기간동안 연직방향 DO 농도편차가 크게 나타나고 있는것은 수온 및 염도성층에 의한 표 저층간의 물질교환 저해에 의한 영향도 직접적인 요인으로 작용하고 있은 것으로 파악되었다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 추계학술대회
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• pp.188-192
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• 2006

This study is conducted to improve efficiency of thermal storage tank. The thermal storage tank was designed to store heat energy that obtained from solar or the others heat sources. However, it has difficulties in storing heat with uniform temperature through the entire tank with respect to vertical direction. This kind of maldistribution of the supplied heat to the storage tank effects on the system performance. In this study is focused on utilization of the thermal stratification to improve thermal comfort for people in the house. To enhance temperature stratification of the tank, a distributor was designed and Installed in the middle of the tank. The distributor is supplies hottest water to the top side of the tank which is very close to inlet of the supply line to the heating load. The hottest water that is accumulated on top side of the tank is firstly supplied to the load with higher temperature. Reminder water takes a little time to warming up until desired supply temperature reached. This kind alternating selection of the supply temperature is improve thermal comfort with moderated system performance.

• 한국안전학회지
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• 제33권5호
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• pp.164-169
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• 2018

A detailed fatigue evaluation procedure was developed to mitigate the excessive conservativeness of the conventional environmental fatigue evaluation method for the pressurizer spray line elbow of domestic new nuclear power plants. The pressurizer spray line is made of austenitic stainless steel, which is relatively sensitive to the environmentally assisted fatigue, and has a low degree of design margin in terms of environmentally assisted fatigue due to the thermal stratification phenomenon on the pipe cross section as a whole or locally. In this study, to meet the environmental fatigue design requirements of the pressurizer spray line elbow, the new environmental fatigue evaluation has been performed, which used the ASME Code NB-3200-based detailed fatigue analysis and the environmental fatigue correction factor instead of the existing NB-3600 evaluation method. As a result, the design requirements for environmentally assisted fatigue were met in all parts of the pressurizer spray line elbow including the fatigue weakened zones by thermal stratification.

• 한국태양에너지학회 논문집
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• 제27권4호
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• pp.43-49
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• 2007

This study is conducted to improve the efficiency of a thermal storage tank. The thermal storage tank was designed to store heat energy that obtained from the solar or the others heat sources. However, it has difficulties in storing heat with nonuniform temperature through the entire tank with respect to the vertical direction, This study is focused on the thermal stratification to improve thermal comfort for the resident in house. To enhance temperature stratification of the tank, a distributor was designed and installed in the middle of the storage tank vertically. The vertically designed distributor could supply the return water with stratified temperature in the storage tank with respect to the height. The water velocity from the distributor hole is the same with the other outlet in the distributor. However, gravity effect on the flow in the storage tank is much higher than that of the velocity effect due to that Froude Number is less than 1. During the heat charging process in the storage tank, temperature maintained with little difference with respect to the height. However the charging process takes long time to get a effective temperature for the heating or hot water supply because of all of water in the storage tank needs to be heated.

• 설비공학논문집
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• 제26권7호
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• pp.322-328
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• 2014

Return piping is used in a solar combi-system for heating and hot water supply. When the temperature of the lower side of a storage tank is low due to hot water usage, the returned hot water after heating is mixed with the lower side cold water of the tank, and the useful energy is reduced. We studied the degree of thermal stratification in the tank, using either a diffuser or a manifold to prevent mixing. Using the diffuser, mixing starts from the bottom of the storage tank. On the other hand, the manifold has the marked effect of preventing mixing. As a result of experiments with changing the diameter and number of holes in the manifold, the optimum condition is 8.5 mm diameter and 96 holes, under the condition of 0.3 lpm.