• Korean Journal of Optics and Photonics
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• v.35 no.5
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• pp.228-234
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• 2024

Modern infrared-guided weapons detect and destroy targets by seeking and tracking the infrared radiation emitted by the target. By covering the target with a material that has low infrared emissivity, the infrared signal can be reduced to evade tracking. However, this method is effective only when the target is hotter than the background. Since the temperature of the background varies significantly between day and night, target signals with low emissivity at night can be captured by the optical systems of guided weapons due to signal contrast, as they are smaller than the background signals. In this study, the optimal emissivity for implementing infrared stealth for ground targets is calculated based on the temperature and emissivity of the background, as well as the temperature of the target. The size of the signal received by the optical systems of guided weapons, the contrast value of the image, and the lock-on range were calculated for target signals that vary depending on the emissivity of the target. The effectiveness of the optimal emissivity was demonstrated by thermal imaging computer simulations using COMSOL Multiphysics software.

• Journal of Bio-Environment Control
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• v.28 no.4
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• pp.396-403
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• 2019

This study was conducted to investigate the growth of grafted cucumber seedlings in biodegradable paper pot trays influenced by seedling age, nutrient management before transplanting, and night temperature after transplanting. Grafted cucumber seedlings in paper pot trays were supplied with different nutrient solution concentrations of 0.5 x full strength (S) (EC $0.8dS{\cdot}m^{-1}$), 1.0S(EC $1.6dS{\cdot}m^{-1}$), 2.0S(EC $3.2dS{\cdot}m^{-1}$) two times a week until transplanting. 26, 33, 40, and 47 day-old cucumber grafted seedlings were transplanted and grown at three levels of night temperature (10, 15, and $25^{\circ}C$) during ten days. Increasing nutrient solution concentration enhanced the shoot length, number of leaves, leaf area, dry weight, and relative growth rate of seedlings. With increasing seedling age, the differences in growth were greater among nutrient treatments. The dry matter percentage increased with the seedling age, but was lower with higher nutrient concentration. The specific leaf area showed the opposite results. In cucumbers transplanted at 26- or 33-day seedling ages, night temperature did not affect the growth at ten days after transplanting. However, the growth of 40 or 47 day-old seedling decreased at $10^{\circ}C$. Compared with $25^{\circ}C$, the dry weight of cucumbers transplanted at 40- or 47-day seedling ages was depressed by 58% or 71%, respectively, at $10^{\circ}C$. Accordingly, it was concluded that the optimum nutrient solution concentrations and seedling age for the production of grafted cucumber seedlings in biodegradable paper pot trays can be 1.0S and about 30 days, respectively, and night temperature should be maintained at the range of $15-25^{\circ}C$ for promoting the growth after transplanting.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.5 no.4
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• pp.272-280
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• 1976

A natural ventilating type store was designed for the economic and effective storage of citrus fruits in Jejudo. The material used for the wall is scoria, widely distributed in Jejudo and known for high strength and insulation. Design condition was chosen for the period till March of a year and the dry bulb temperature was taken from TAC $5\%$ base. The temperature of the store can be maintained below the limiting temperature of $8^{\circ}C$ for the time length of $7\frac{1}{2}$ hours under the condition of the atmospheric temp, $15.3^{\circ}C$ and the solar insolation. The limiting temperature can he recovered to the initial temperature $(7^{\circ}C)$ by the natural ventilation for 8 hours in the night.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.60 no.2
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• pp.146-152
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• 2015

Early-maturing Korean Japonica cultivars and Jungmo1024 were used as plant materials to evaluate hightemperature tolerance during grain filling stage. National Institute of Crop Science (NICS) in Korea developed Jungmo1024, a mutant line from Namil (wild type) treated by using sodium azide (SA) as mutagen. To evaluate high-temperature tolerance, all cultivars were exposed to high-temperature (day $31.5{\pm}2.5^{\circ}C$/ night $27.5{\pm}1.3^{\circ}C$) and ordinary temperature (day $27.5{\pm}1.8^{\circ}C$/ night $24.7{\pm}1.6^{\circ}C$) during grain filling stage. In these conditions, we performed compared evaluation of grain shape such as length and width and grain quality by using a 1625 Cervitec grain inspector. High-temperature during grain filling stage caused decrease of grain shape. In grain shape such as length and width, the decrease rate of width (average 6.3%) was higher than the decrease rate of length (average 1.3%). Hence, high-temperature affected width of grain than length of grain. In addition, high-temperature showed a decided difference in rate of head rice between ordinary temperature (average 76.3%) and high-temperature (average 13.3%).As a result, Taebong, Ungwang, Manan, and Jungmo1024 seemed relatively a decent high-temperature tolerance than other cultivars. Especially, Jungmo1024 seemed remarkable rate of head rice (average $34.4{\pm}6.2%$) than other cultivars under high-temperature. It is considered that a genetic trait of Jungmo1024 can be useful to improve breeding for high-temperature tolerance.

• Journal of Applied Biological Chemistry
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• v.63 no.4
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• pp.347-355
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• 2020

Several sensors have been developed for soil and plants to assess plant stress due to climate change. Therefore, the objective of the study is to nondestructively evaluate temperature stress on plant by monitoring climatic and soil conditions and plant responses using various sensors. Plant responses were monitored by electrical conductivity in plant stem and sap flow rate. Electrical conductivity in plant stem reflects the physiological activity of plants including water and ion transport. Fully grown Brassica oleracea var. italica was exposed to 20/15 ℃ (day/night) with 16 h photoperiods as a control, low temperature 15/10 ℃, and high temperature 35/30 ℃ while climatic, soil, and plant conditions were monitored. Electrical conductivity in plant stem and sap flow rate increased during the day and decreased at night. Under low temperature stress, electrical conductivity in plant stem of Brassica oleracea var. italica was lower than control while under high temperature stress, it was higher than control indicating that water and ion transport was affected. However, chlorophyll a and b increased in leaves subjected to low temperature stress and there was no significant difference between high temperature stressed leaves and control. Free proline contents in the leaves did not increase under low temperature stress, but increased under high temperature stress. Proline synthesis in plant is a defense mechanism under environmental stress. Therefore, Brassica oleracea var. Italica appears to be more susceptible to high temperature stress than low temperature.

• Journal of Biosystems Engineering
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• v.12 no.2
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• pp.16-27
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• 1987

Greenhouse farming was introduced to the Korean farmers in the middle of 1950's and its area has been increased annually. The plastic greenhouse, which is covered with polyethylene or polyvinyl chloride film, has been rapidly spread in greenhouse farming since 1970. The greenhouse farming greatly contributed to the increase of farm household income and the improvement of crop productivity per unit area. Since the greenhouse farming is generally practiced during winter, from November to March, the thermal environment in the plastic greenhouse should be controlled in order to maintain favorable condition for plant growing. Main factors that influence the thermal environment in the plastic greenhouse are solar radiation, convective and radiative heat transfer among the thermal component of the greenhouse, and the use of heat source. The objective of this study was to develop a simulation model for thermal environment of the plastic greenhouse in order to determine the characteristics of heat flow and effects of various ambient environmental conditions upon thermal environments within the plastic greenhouse. The results obtained are summarized as follows: 1. Simulation model for thermal environment of the plastic greenhouse was developed, resulting in a good agreement between the experimental and predicted data. 2. Solar radiation being absorbed in the plant and soil during the daytime was 75 percent of the total solar radiation and the remainder was absorbed in the plastic cover. 3. About 83 percent of the total heat loss was due to convective and radiative heat transfer through the plastic cover. Air ventilation heat loss was 5 to 6 percent of total heat loss during the daytime and 16 to 17 percent during the night. 4. The effectiveness of thermal curtain for the plastic greenhouse at night was significantly increased by the increase of the inside air temperature of the greenhouse due to the supplementary heat. 5. When the temperature difference between the inside and outside of the greenhouse was small, the variation of ambient wind velocity did not greatly affect on the inside air temperature. 6. The more solar radiation in the plastic greenhouse was, the higher the inside air temperature. Because of low heat storage capacity of the plant and soil inside the greenhouse and a relatively high convective heat loss through the plastic cover, the increase of solar radiation during the daytime could not reduce the supplymentary heat requirement for the greenhouse during the night.

• Journal of Digital Convergence
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• v.14 no.5
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• pp.317-323
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• 2016

This paper suggests a system that can detect malfunctions of the temperature testing equipment, and then notify this information to surroundings using arduino. Precision electronics need a test under extremely high/low temperature using temperature called a chamber. If this chamber have a malfunction situation, the precision electronics under test is damaged and scrapped. Especially when the temperature test is automatically conducted at night with no representative, this system monitors the actual temperature of the tested product in real-time by attaching a temperature sensor to the inside of the test equipment. In case when it is out of the temperature range set up by the tester, the damage to high-priced products can be prevented in the condition of extremely high/low temperature, by turning off the power of the temperature testing equipment, and also notifying this information to the worker at night-time. Regardless of the equipment manufacturers, proposed system in this paper can be applied to all kind of temperature testing equipments, and it can be also produced for low cost.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.3
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• pp.352-363
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• 1999

Target detection by the infrared imager depends on the apparent temperature difference between the target and the background, so it is essential to predict apparent temperature variations for this purpose. In this study, thermal analysis program Including conduction, convection and radiation is developed and applied to a representative geometry adequate for examining the apparent temperature characteristics. The results show that the longwave emissivity in association with the background temperature affects the apparent temperature strongly but does not affect the physical temperature. It is revealed that the background temperature plays a role of tuning the apparent temperature. As the longwave emissivity decreases, the apparent temperature decreases when the target is hotter than the background, whereas it increases in the reversed situation. These findings imply that an effective surface treatment, such as painting of a less emissive material, may provide a less detection probability and contribute to preventing the target from being detected at night.

• Journal of Bio-Environment Control
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• v.24 no.2
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• pp.93-99
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• 2015

The purpose of this study was to determine the appropriate temperature for water curtain in greenhouses equipped with recirculated water curtain system. The study analyzed the changes in air temperature in non-heated greenhouses for strawberry cultivation based on outdoor temperature, water curtain temperature and night time. Three greenhouse units were used for this study: The first unit was assigned as a control (no water curtain system), two other greenhouses were equipped with recirculated water curtain system with water curtain temperatures of $10^{\circ}C$ and $15^{\circ}C$, respectively. Analysis showed that the indoor temperatures were directly correlated with the outdoor temperature in all experimental greenhouses. Heat insulating effect of $15^{\circ}C$ water curtain was increased by $1.3^{\circ}C$ compared to that in $10^{\circ}C$ water curtain system. The $15^{\circ}C$ water curtain treatment showed the highest average temperature and less temperature variation in comparison with control and $10^{\circ}C$ water curtain treatment. To maintain indoor temperature at $5^{\circ}C$, water curtain temperature of $10^{\circ}C$ was suitable when outdoor minimum and average temperatures were -1.3 and $1.5^{\circ}C$, and water curtain temperature of $15^{\circ}C$ was suitable when outdoor minimum and average temperatures were -4.7 and $-0.2^{\circ}C$, respectively. The highest temperature in greenhouses according to measurements in different periods of night time was observed after sunset (18:30-20:30), and the lowest temperature before sunrise (05:00-07:00). Water curtain maintained a target indoor temperature by acting as a layer of heat transfer insulator which decreased heat loss from greenhouses. Therefore, water temperature in recirculating water curtain systems should be determined by considering outdoor temperatures, changes in temperature at different periods of night time, and cultivated crop.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.6 no.1
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• pp.28-33
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• 2003

In this study, we observed air temperature to make clear that land coverage condition and stand form has a certain relationship to air temperature during the night in various green space. And with revolution analysis, we interpreted relationship of air temperature distribution in the green space, The way of analysis is this land coverage rate and air temperature, of number of tree volume of tree air temperature. With this experimental result, we can propose green plan, which is taking into consideration lower effect of air temperature. In this result, lower zone is formed in forest and water area, higher zone is formed in paved surface and barren ground. but this gap is a little. arbor+subarbor area, in the point of water area surrounded stand is formed relative lower air temperature. As a result to make up efficiency lower air temperature area, it is needed to make water area which has surrounded forest, and it is needed to make stand form lower air temperature 2~3 layer forest. In order of arbor, subarbor, shrub, the lower air temperature is more effect.