• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 추계학술대회 논문집 전력기술부문
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• pp.153-156
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• 2001

The transformer and the OF cable are cooled and insulated by insulating oils in their body. The insulating oil expands or contracts with the heat transfer according to the operating conditions of the electric facilities. So we install the $N_2$ gas tank connected with the insulating oil system to overcome the change. The change of the insulating oil volume for the operation temperature range must be calculated to decide the $N_2$ gas volume and to set the alarm point for safe operation. It is known that this change is proportional to the temperature change and to the insulating oil volume if the temperature change is small enough.[1][11] However this proportional formula has been accepted generally in the design of electric facilities for wide operation temperature range such as $40^{\circ}C{\sim}125^{\circ}C$. Hence, it makes large errors in calculation which car result in serious damage against safe operation of the electric facilities. This paper presents a improved method of calculating the accurate change of the insulating oil volume to insure the safe operation of electric facilities.

• 태양에너지
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• 제9권3호
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• pp.44-54
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• 1989

Heat transfer phenomena during inward melting process of the phase change material were studied experimentally. N-docosane paraffin [$C_{22}H_{46}$] is used for phase change material and its melting temperature is $42.5^{\circ}C$. Experiments were performed for melting of an initially no-sub cooled or subcooled solid in a horizontal cylinder, in order to compare and investigate the radial temperature distribution, ratio of melting and melted mass, various energy components stored from the cylinder wall, figure of the melting front in the horizontal cylinder. The solid-liquid interface motion during phase change was recorded photographically. The experimental results reaffirmed the dominant role played by the conduction at early stage, by the natural convection at longer time during inward melting in the horizontal cylinder. Ratio of melting and melted mass are more influenced by wall temperature, rather than by the initial temperature of solid. The latent energy is the largest contributor to the total stored energy.

• 설비공학논문집
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• 제23권6호
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• pp.441-448
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• 2011

The energy consumption of a condensing gas boiler may be greatly reduced by the effective operation of the unit. In this study, the supply water algorithm for a condensing gas boiler control was developed by using the fuzzy logic. This includes the supply water set temperature algorithm, and the control algorithms of a gas valve, a blower and a pump. For the set temperature algorithm, the outside air temperature and the return water temperature were used as input variables. The supply water temperature difference and its slope were used as input variables of the gas valve and blower control algorithm. And the supply water temperature and the return water temperature were used as input variables of the pump control algorithm. In order to analyse performances of these algorithms, the dynamic model of a condensing gas boiler was used. The initial start-up test, the supply water set temperature change test, the outside air temperature change test, and the return water temperature change test were performed. Simulation results showed that algorithms developed in this study may be practically applied for the effective control of a condensing gas boiler.

• 한국기후변화학회지
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• 제4권2호
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• pp.189-199
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• 2013

기상청 소속 60개 지점에서 관측한 1973년부터 2010년까지의 순별 평균기온을 조사기간의 평균값과 비교하는 평균편차법으로 이상고온과 이상저온의 출현횟수를 조사하고, 시 공간별로 분석하였다. 과거 38년간 이상기온의 출현횟수는 연 평균 1.8회(이상고온 0.65회, 이상저온 1.15회)로 조사되었다. 연도별로는 1998년에 이상고온의 출현횟수가 2.47회로 가장 많았고, 이상저온의 출현횟수는 1980년에 5.07회로 가장 많았다. 연대별 이상고온의 연간 출현횟수는 1980년대(1981~1990년)의 0.2회에서 2000년대(2001~2010년)의 1.0회로 5배 이상 크게 증가한 반면에, 이상저온의 연간 출현횟수는 1970년대(1973~1980년)의 2.06회에서 2000년대의 0.63회로 크게 감소하는 경향을 나타내서, 최근 우리나라에서의 온난화 현상을 나타내고 있었다. 농업기후지대로 구분하여 분석하면, 과거 38년간 이상고온의 출현횟수가 가장 많았던 농업기후지대는 태백고냉지대(대관령, 평창 등)로서 연평균 0.76회이었고, 동해안 북부지대(강릉, 속초 등)는 0.74회로 다음으로 많았다. 반면에, 이상고온의 출현횟수가 가장 적었던 농업기후지대는 동해안 남부지대(포항, 울산 등)로 0.45회였다. 과거 38년간 이상저온의 출현횟수가 가장 많았던 농업기후지대는 소백서부 내륙지대(청주, 대전 등)로 연평균 1.43회이었고, 이상저온의 출현횟수가 가장 적었던 농업기후지대는 동해안 중부지대(울진, 영덕 등)로 연 평균 0.64회이었다.

• Transactions on Control, Automation and Systems Engineering
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• 제3권2호
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• pp.133-138
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• 2001

This paper describes a system that can used to recognize an unknown material regardless of the change of ambient tem-perature using temperature response curve fitting and fuzzy neural network(FNN). There are some problems to realize the recogni-tion system using temperature response. It requires too many memories to store the vast temperature response data and it has to be filtered to remove noise which occurs in experiment. And the temperature response is influenced by the change of ambient tempera-ture. So, this paper proposes a practical method using curve fitting the remove above problems of memories and nose. And FNN is propose to overcome the problem caused by the change of ambient temperature. Using the FNN which is learned by temperature responses on fixed ambient temperature and known thermal conductivity, the thermal conductivity of the material can be inferred on various ambient temperature. So the material can be recognized by the thermal conductivity.

• International Journal of Air-Conditioning and Refrigeration
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• 제17권1호
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• pp.32-36
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• 2009

The ice storage system uses water for low temperature latent heat storage. However, a refrigerator capacity is increased and COP is decreased due to supercooling of water in the course of phase change from solid to liquid. This study investigates the cooling characteristics of the TMA-water clathrate compound including TMA (Tri-methyl-amine, $(CH_3)_3N$) of $20{\sim}25wt%$ as a low temperature latent heat storage material. The results showed that the phase change temperature and the specific heat is increased and the supercooling degree is decreased as the weight concentration of TMA increased. Especially, the clathrate compound containing TMA 25 wt% has the average phase change tempera ture of $5.8^{\circ}C$, the supercooling degree of $8.0^{\circ}C$ and the specific heat of 3.499 kJ/kgK in the cooling process. This can lead to reduction of operation time of refrigerator in low temperature latent heat storage system and efficiency improvement of refrigerator COP and overall system. Therefore, energy saving and improvement of utilization efficiency are expected.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2007년도 동계학술발표대회 논문집
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• pp.23-28
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• 2007

In most existing research, it is difficult to evaluate thermal comfort exactly because of reflecting individual ideal or psychological response by subjective questions. Physiological variable was selected in this study to evaluate objectively thermal comfort. MST was appeared very sensitively in indoor temperature and can express correctly thermal comfort of human body. The results of CSV are different each individual feeling sensation, so is difficult to evaluate detailedly thermal comfort unlike TSV. But the results of PP, AIx, ED, SEVR are greatly related to temperature change. So thermal comfort is evaluated more objectively by using PP, AIx, ED, SEVR on behalf of TSV, CSV. Human body was presented physiological feedback by temperature impetus and specially, tendency of heart rate agree with temperature change. Physiological reaction was showed sufficient possibility availing evaluation index of thermal comfort. In the future another one needs to review beside the selected physiological variable.

• 한국분무공학회지
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• 제16권3호
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• pp.126-133
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• 2011

In HCCI Engine, combustion is affected by change of compression speed corresponding to engine speed. The purpose of this study is to investigate the mechanism of influence of engine speed on HCCI combustion characteristics by using numerical analysis. At first, the influence of engine speed was shown. And then, in order to clarify the mechanism of influence of engine speed, results of kinetics computations were analyzed to investigate the elementary reaction path for heat release at transient temperatures by using contribution matrix. In results, as engine speed increased, in-cylinder gas temperature and pressure at ignition start increased. And ignition start timing was retarded and combustion duration was lengthened on crank angle basis. On time basis, ignition start timing was advanced and combustion duration was shortened. High engine speed showed higher robustness to change of initial temperature than low engine speed. Because of its high robustness, selecting high engine speed was efficient for keeping stable operation in real engine which include variation of initial temperature by various factors. The variation of engine speed did not change the reaction path. But, as engine speed increased, the temperature that each elementary reaction would be active became high and reaction speed quicken. Rising the in-cylinder gas temperature of combustion start was caused by these gaps of temperature.

• 한국농림기상학회지
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• 제3권1호
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• pp.55-70
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• 2001

It was unusual crop weather for 1998 and 1999 compared with normal in Korea. The consecutive days of the optimum ripening period for rice plant that had daily mean temperature 21~23$^{\circ}C$ for 40 days after flowering, increased with long anomalies in 1998~99. The air temperature during ripening period was much higher than the optimum temperature and lower sunshine hour than norm in the local adaptability tests of newly developed rice lines during those years. In response of rice cultivation to warming and cloudy weather during crop season, the yield shall be decreased. Most scientists agree that the rate of heating is accelerating and temperature change could become increasingly disruptive. Weather patterns should also become more erratic. Agrometeorologists could be analyzed yearly variations of temperature, sunshine hour and rainfall pattern focused on transient agroclimate change for last a decade. Rice agronomists could be established taking advantage of real time agricultural meteorology information system for fertilization, irrigation, pest control and harvest. Also they could be analyzed the characteristics of flowering response of the recommended and newly bred rice cultivars for suitable cropping plan such as cultural patterns and sowing or transplanting date. Rice breeders should be deeply considered introducing the characteristics of basic vegetative type of flowering response like Togil rices as prospective rice cultivars corresponding to global warming because of the rices needed higher temperature at ripening stage than japonica rices, photoperiod-sensitive and thermo-sensitive ecotypes.

• 대한지리학회지
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• 제46권2호
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• pp.152-167
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• 2011

이 연구에서는 서울의 1941~1970년(가 기간)과 1971~2000년(나 기간)의 일 평년 기온에 조화분석을 적용하여 계절 추이를 산출, 이의 변화 양상을 살피고, 계절 추이와 변화에 영향을 미치는 요인을 조사하였다. 그 결과 겨울철의 가장 낮은 기온이 가 기간에는 1월초 중순에 나타났으나 나 기간에는 1월 하순~2월 초순에 나타나 계절 추이가 변화되었음을 나타냈다. 이러한 변화는 12월 27일~1월 20일(전기)의 기온이 보다 많이 상승한 반면 1월 21일~2월 9일(후기)의 기온이 보다 적게 상승하였기 때문에 나타났다. 가 기간의 일 평년값에 대한 전기와 후기의 기온 펀치는 1970년 이전에는 큰 차이가 없었으나 1971년 이후에 차이가 컸다. 전기의 경우 시베리아 고기압이 근래에 뚜렷하게 약화되면서 우리나라 부근의 북풍이 약화되어 서울의 기온이 많이 상승하였다. 반면 후기의 경우 시베리아 고기압이 근래에 약화되었으나 알류샨 저기압이 발달하여 우리나라 부근의 북풍은 크게 약화되지 않아 서울 기온이 많이 상승하지 않았다.