• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 2000년도 THE THIRD INTERNATIONAL CONFERENCE ON AGRICULTURAL MACHINERY ENGINEERING. V.II
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• pp.413-422
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• 2000

Samples of banana were dried in a two-stage heat pump dryer capable of producing stepwise control of the inlet drying air temperature while keeping absolute humidity constant. Two stepwise air temperature profiles were tested. The incremental temperature step change in temperature of the drying air about the mean air temperature of 30 $^{\circ}C$ was 5 $^{\circ}C$. The total drying time for each temperature-time profile was about 300 minutes. The drying kinetics and color change of the products dried under these stepwise variation of the inlet air temperature were measured and compared with constant air temperature drying. The stepwise air temperature variation was found to yield better quality product in terms of color of the dried product. Further, it was found that by employing a step-down temperature profile, it was possible to reduce the drying time to reach the desired moisture content.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2008년도 한국우주과학회보 제17권2호
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• pp.24.2-24.2
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• 2008

We have examined the relative contributions of representative space weather proxies (geomagnetic aa index) to global warming (Global temperature anomaly) and compared them with that of green house effect characterized CO2 content from 1868 to 2005. For this we used Hadcrut3 temperature anomaly (Ta) data, aa index taken at two anti-podal subauroral stations (Canberra Australia and hartland England), and the CO2 data come from historical ice core records. From the comparison between Ta and aa index, we found several interesting results: (1) the linear correlation coefficient between two parameters increases until 1990 and then decreases rapidly, and (2) the scattered plots between two parameters shows different patterns before and after 1990. A partial correlation of Ta and two quantities (aa, CO2) also shows that the geomagnetic effect (aa index) is dominant until about 1990 and the CO2 effect becomes much more important after then. These results imply that the green house effect become very important since at least 1990. For a further analysis, we simply assume that Ta (total) = Ta (aa) + Ta (CO2) and made a linear regression between Ta and aa index from 1868 to 1990. A linear model is then made from the linear regression between energy consumption (a proxy of CO2 effect) and Ta (total) - Ta (aa) since 1990. This linear model makes it possible to predict the temperature anomaly in 2030, about 1 degree higher than the present temperature, which is much larger than in the previous century.

• 동력기계공학회지
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• 제18권1호
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• pp.57-62
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• 2014

This paper present the performance characteristics of R404A two-stage compression refrigeration system. The operating parameters considered in this study include evaporating and condensing temperature, subcooling and superheating degree, compressor efficiency. The main results were summarized as follows: The COP of two-stage compression refrigeration system using R404A has an effect on the variation of evaporation temperature, condensation temperature, subcooling degree and compressor efficiency, but not an effect on the superheating degree. R404A two-stage compression refrigeration system is unstable because COP of this system is significantly changed when evaporating temperature and compressor efficiency decreased. In particular, when compressor efficiency decreased, COP is significantly decreased. This is inefficient for long-term use.

• 설비공학논문집
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• 제24권7호
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• pp.585-590
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• 2012

The objective of this study is to investigate the performance of a two-stage compression heat pump system for district heating. The experimental setup of heat pump consists of compressor, condenser, evaporator, expansion device, intercooler, flash tank, oil separator and accumulator. The experimental evaluations on the two-stage compression cycle were carried out under various operating conditions which were heat source temperature, the degree of compressor inlet superheat, and intermediate pressure. The temperature ranges of unutilized energy as the heat source were used in the test conditions. As the heat source temperature increased from $10^{\circ}C$ to $30^{\circ}C$, the COP and heating capacity of the heat pump system increased by 22.6% and 45.8%, respectively. The performance of the two-stage heat pump system increased by 5.2% with the variation of the intermediate pressure in the same heat source temperature conditions.

• Structural Engineering and Mechanics
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• 제78권1호
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• pp.23-30
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• 2021

In this paper, we established the generalized thermoelasticity phenomenon in an isotropic elastic medium considering the electromagnetic field, rotation and two-temperature. Three theories of generalized thermoelasticity have been applied: Lord-Shulman (one relaxation time), Green-Lindsay (two relaxation times), as well as the coupled theory. We discussed some particular cases in the context of the wave propagation phenomenon in thermoelasticity. From solving the fundamental equations, we arrived that there are three waves: P-, T- and SV-waves that we calculated their velocities. The boundary conditions for mechanical stress and Maxwell's stress and thermal insulated or isothermal have been applied to determine the amplitudes ratios (reflection coefficients) for P-, T - and SV waves. Some utilitarian aspects are obtained from the reflection coefficients, presented graphically, and the new conclusions have been presented. Comparisons are made for the results predicted by different theories (CT, LS, GL) in the absence and presence of the electro-magnetic field, rotation, as well as two-temperature on the reflection of generalized thermoelastic waves. The results obtained concluded that the external parameters as the angle of incidence, electromagnetic field, rotation as well as the theories parameters have strong effect on the phenomenon.

• 한국연초학회지
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• 제11권2호
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• pp.127-134
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• 1989

Several growth characteristics of two ornamental tobacco species, Nicotiana sanderae and N. affinis, were investigated in this study. Also effect of temperature and daylength on the flowering of the tobacco plants were evaluated to obtain basic information on breeding and cultivation. 1. The plants were great in high temperature-long day at the early stage and in low temperature-short day at the late stage of plant growth, for both Nicotana species. At the early growth stage the leaf length N. sanderae was great in high temperature-long day, and that of N. affinis was great in high temperature-short day period, while at the late stage of the plant growth the leaf lengths were more significantly effected by the temperature rather than daylength. Leaf width and leaf shape index were less sensitive to the conditions. 2. For both of the species, the total number of tobacco leaves not much influenced by the temperature and daylength. 3. There were no significant differences for budding and flowering period between the two species, both of which were sensitive to temperature and daylength with more influence by daylength than temperature. 4. Number of floral stalks, number of flower and flowering period were not much influenced by temperature and daylength; however, N. affinis had 2 more floral stalks, 31 more flowers, and 6 day longer flowering period than N. sanderae.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.1361-1365
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• 2003

There are two Clausius inequalities. One involves the temperature of external reservoir and the other involves the temperature at the system boundary. It is shown that the former Clausius inequality can be established from a direct application of the proposition regarding the efficiency of a Carnot cycle based on an apparatus with two reservoirs. A different apparatus which also has two thermal reservoirs is utilized to compare the cyclic integral of the former inequality with that of the latter, resulting in the proof of the latter inequality.

• Coupled systems mechanics
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• 제8권3호
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• pp.219-245
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• 2019

The present research deals in two dimensional (2D) transversely isotropic magneto generalized thermoelastic solid without energy dissipation and with two temperatures due to time harmonic sources in Lord-Shulman (LS) theory of thermoelasticity. The Fourier transform has been used to find the solution of the problem. The displacement components, stress components and conductive temperature distribution with the horizontal distance are calculated in transformed domain and further calculated in the physical domain numerically. The effect of two temperature are depicted graphically on the resulting quantities.

• 한국화재소방학회논문지
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• 제31권4호
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• pp.20-25
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• 2017

본 연구에서는 화염 내에 생성된 그을음 입자가 방사하는 복사 강도 분포를 측정하고, 이를 바탕으로 Jet A1 액적확산 화염의 온도 분포를 예측하였다. 이를 위해서 700 nm와 900 nm 각각의 파장에 대해서 화염 내 그을음 입자가 방사하는 복사 강도를 CCD 카메라로 측정하였고 Abel 변환을 통해 얻어진 국소 복사 강도 분포를 이색법(Two Color Method)에 적용하여 최종 화염의 온도 분포를 계산하였다. 그 결과 이색법에 의한 측정은 그을음의 복사 강도와 투영된 시각선의 간격에 따라서 약 2% 정도 이내의 deconvolution 오차가 발생할 수 있으며, 본 연구 결과에서 제시한 측정 방법을 통해 2000 K 기준 약 18 K 오차 범위 이내에서 화염온도 예측이 가능함을 확인하였다.

• 한국환경보건학회지
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• 제27권1호
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• pp.69-74
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• 2001

A study on temperature control of freezers & refrigerators in department stores and supermakets was conducted in Taegu are from July 15 through August 30 in order to determine how the temperature is effectively controled for food safety. Five departments and four supermarkets were selected randomly and fifty seven refrigerators and fifty nine freezers were inspected to observe temperature of thermometers and measure the temperature of the coolers by laser thermometer. The results are as follow; 1. Out of one hundred and sixteen coolers, eighty six (74.1%) were open type coolers and thirty (25.9%) were closed types (p<.05). 2. Twenty five (89.3%) of refrigerators and twenty three (82.1%) of freezers in department stores had thermometers and twenty seven refrigerators (93.1%) and twenty two (71%) of freezers in supermarkets had thermometers respectively (p<.01). 3. The measured temperatures of coolers increased in the afternoon to compared to the temperatures of them in the morning time (p<.01). The difference of temperatures of coolers between department stores and supermarkets was wider in the supermarkets and difference of temperatures of food items between refrigerators and freezers was wider in the refrigerators but the difference was not statistically significant. 4. The temperatures of forty four (84.6%) out of fifty two refrigerators within recommended ranges and those of forty two (93.3%) of forty five freezers higher than recommended ranges (p<.05).