• Asia-Pacific Journal of Atmospheric Sciences
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• v.54 no.4
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• pp.527-544
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• 2018

This paper presents a nighttime sea fog detection algorithm incorporating unsupervised learning technique. The algorithm is based on data sets that combine brightness temperatures from the $3.7{\mu}m$ and $10.8{\mu}m$ channels of the meteorological imager (MI) onboard the Communication, Ocean and Meteorological Satellite (COMS), with sea surface temperature from the Operational Sea Surface Temperature and Sea Ice Analysis (OSTIA). Previous algorithms generally employed threshold values including the brightness temperature difference between the near infrared and infrared. The threshold values were previously determined from climatological analysis or model simulation. Although this method using predetermined thresholds is very simple and effective in detecting low cloud, it has difficulty in distinguishing fog from stratus because they share similar characteristics of particle size and altitude. In order to improve this, the unsupervised learning approach, which allows a more effective interpretation from the insufficient information, has been utilized. The unsupervised learning method employed in this paper is the expectation-maximization (EM) algorithm that is widely used in incomplete data problems. It identifies distinguishing features of the data by organizing and optimizing the data. This allows for the application of optimal threshold values for fog detection by considering the characteristics of a specific domain. The algorithm has been evaluated using the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) vertical profile products, which showed promising results within a local domain with probability of detection (POD) of 0.753 and critical success index (CSI) of 0.477, respectively.

• Journal of the Korean Association of Geographic Information Studies
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• v.18 no.2
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• pp.59-74
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• 2015

The purpose of this study is to analyze reasonable green area ratios for mitigating urban heat island considering various land use types. Land uses of 5 types such as single residential, multi residential, commercial area, public facility, and industrial area were considered. Green areas were extracted from the tree attribution of land cover. Effect of urban heat island was analysed by the surface temperature of ASTER thermal infrared radiance scanned daytime and nighttime. Mitigation effect of green area at daytime was higher than nighttime. Surface temperature of green area was low in single residential at daytime. But the difference of surface temperature by each land use type was small. The effect of surface temperature mitigation of green area was lower in industrial area. The results of reasonable green area ratios for mitigating urban heat island indicate that surface temperature was the lowest with green area ratio of 40~50% in single residential, multi residential, and commercial area at daytime. Surface temperature of nighttime was not changed much by green area ratios. Therefore, the results of this study will be suggested in urban development planning to construct effectively green area for mitigating urban heat island.

• Journal of the Korean Association of Geographic Information Studies
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• v.15 no.2
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• pp.113-125
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• 2012

This research is aimed at evaluating the land surface characterization of KOMPSAT-3A middle infrared (MIR) data. Airborne Hyperspectral Scanner (AHS) data, which has MIR bands with high spatial resolution, were used to assess land surface temperature (LST) retrieval and classification accuracy of MIR bands. Firstly, LST values for daytime and nighttime, which were calculated with AHS thermal infrared (TIR) bands, were compared to digital number of AHS MIR bands. The determination coefficient of AHS band 68 (center wavelength $4.64{\mu}m$) was over 0.74, and was higher than other MIR bands. Secondly, The land cover maps were generated by unsupervised classification methods using the AHS MIR bands. Each class of land cover maps for daytime, such as water, trees, green grass, roads, roofs, was distinguished well. But some classes of land cover maps for nighttime, such as trees versus green grass, roads versus roofs, were not separated. The image classification using the difference images between daytime AHS MIR bands and nighttime AHS MIR bands were conducted to enhance the discrimination ability of land surface for AHS MIR imagery. The classification accuracy of the land cover map for zone 1 and zone 2 was 67.5%, 64.3%, respectively. It was improved by 10% compared to land cover map of daytime AHS MIR bands and night AHS MIR bands. Consequently, new algorithm based on land surface characteristics is required for temperature retrieval of high resolution MIR imagery, and the difference images between daytime and nighttime was considered to enhance the ability of land surface characterization using high resolution MIR data.

• Magazine of the Korean Society of Agricultural Engineers
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• v.29 no.4
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• pp.117-123
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• 1987

This study was conducted to develop an automatic insulation system to reduce the heat loss through the wall of greenhouses during the nighttime in winter. A double covered model vinyl house was constructed, and blowers were used to fill or remove styrene pellets automatically the inside of the double-wall of the double covered vinyl house. The effects of insulation of the double covered vinyl house insulated with the styrene pellets were analyzed by comparing with the single covered vinyl house. The results obtained from this study can be summarized as follows : 1. The optimum thickness of the double-wall of the double covered vinyl house was found to be 5 to 10 cm. 2.When the outside temperature varied in the range of -8.3 to -1.5$^{\circ}C$ during the nighttime, the inside temperature of the double covered vinyl house insulated with the styrene pellets showed 7.7 to 11.7$^{\circ}C$ and the inside temperature of the single covered vinyl house showed -5.8 to 2.3$^{\circ}C$. Therefore, the effects of insulation of the double covered vinyl house insulated with the styrene pellets were confirmed to be excellent. 3. Also, the excessive increase of the inside temperature in the vinyl house was prevented by the shading effect of the double covered vinyl house insulated with the styrene pellets during the daytime. 4. When the outside temperature varied in the range of 17.7 to 30.0$^{\circ}C$ during the daytime, it was possible to keep the inside temperature at 30${\pm}$4$^{\circ}C$ in the double covered vinyl house by operating the insulation system. 5. The transmissivity of the double covered vinyl house with the styrene pellets removed was 52.4 % on the average.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.19 no.11
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• pp.797-802
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• 2007

The effects of window cover on the performance of the plate type radiant cooling test system are studied. The cover materials tested are 2mm, 1mm, 0.7mm glass, Cokin 007 filter, and PVC film. The measurements are performed during the September nights of 2005 at the rooftop of the building in Seoul. The equivalent height of the building is about a building with twelve floors. The radiant cooling performance of the black painted and aluminum film coated plate are compared under no cover condition. Also the results are compared when the system has cover over the plate. In general, the covers reduce the radiant cooling temperature differences during the nighttime. Among these covers, the PVC film cover shows the best performance. In some cases, the plate with PVC film cover shows lower temperatures than the system without cover.

• Journal of the Korean Society for Marine Environment & Energy
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• v.13 no.3
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• pp.165-173
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• 2010

A cloud detection method is introduced to improve the reliability of NOAA/AVHRR Sea Surface Temperature (SST) data processed during the daytime and nighttime in the TeraScan System. In daytime, the channels 2 and 4 are used to detect a cloud using the three tests, which are spatial uniformity tests of brightness temperature (infrared channel 4) and channel 2 albedo, and reflectivity threshold test for visible channel 2. Meanwhile, the nighttime cloud detection tests are performed by using the channels 3 and 4, because the channel 2 data are not available in nighttime. This process include the dual channel brightness temperature difference (ch3 - ch4) and infrared channel brightness temperature threshold tests. For a comparison of daytime and nighttime SST images, two data used here are obtained at 0:28 (UTC) and 21:00 (UTC) on May 13, 2009. 6 parameters was tested to understand the factors that affect a cloud masking in and around Korean Peninsula. In daytime, the thresholds for ch2_max cover a range 3 through 8, and ch4_delta and ch2_delta are fixed on 5 and 2, respectively. In nighttime, the threshold range of ch3_minus_ch4 is from -1 to 0, and ch4_delta and min_ch4_temp have the fixed thresholds with 3.5 and 0, respectively. It is acceptable that the resulted images represent a reliability of SST according to the change of cloud masking area by each level. In the future, the accuracy of SST will be verified, and an assimilation method for SST data should be tested for a reliability improvement considering an atmospheric characteristic of research area around Korean Peninsula.

• Journal of the Korean Solar Energy Society
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• v.40 no.2
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• pp.25-36
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• 2020

The Korean government has a plan to mandate zero-energy buildings in 2020 for public and 2025 for private buildings. In order to design a zero-energy building, insulation and airtightness, which are the most basic elements of passive house technology, are required, and the government has been accomplished this through step-by-step strengthening of related standards. In passive house with high thermal insulation and airtightness performance, the heat introduced into the building through solar radiation can be stored for a long time to keep the inside warm during winter. On the other hand, during summer, heat introduced into the building cannot be easily released to outside, so it is necessary to actively block solar radiation and high temperature outdoor air to prevent an increase of indoor temperature. Therefore, this study aims to derive an appropriate operation condition of passive house to maintain the indoor temperature at an suitable level according to the ventilation methods and solar shading conditions. As a result, under the conditions that the outdoor temperature was 28℃ or less, the ventilation using a heat recovery ventilation system at daytime and natural ventilation at nighttime were selected for the most appropriate operation method. In addition, in the case of solar shading, it was found that blocking solar radiation at daytime using the blind and open the blind at nighttime to ensure natural ventilation were selected for the most appropriate solar shading condition.

• Proceedings of the KIEE Conference
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• 1997.11a
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• pp.581-583
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• 1997

In this paper, we present a temperature characteristic in OPGW link due to meteological effects. we measured a temperature on a 2km OPGW using a distributed optical fiber temperature sensing system. The measurement showed that OPGW temperature was several degrees lower to ambient atmospheric temperature in the nighttime and several degrees higher than that in the daytime due to sunshine. It'll be used for a reference data of the transmission delay variations in OPGW link due to meteorological effects.

• Journal of Bio-Environment Control
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• v.13 no.4
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• pp.226-232
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• 2004

This experiment was conducted to investigate the effect of night and daytime temperatures on growth and yield of paprika 'Fiesta' and 'Jubilee' under soil culture experiment in the vinyl houses during the 2003 and 2004 season. Total fruit yield was greater in 'Fiesta' than 'Jubilee' Marketable yield was not different between two cultivars, due to lower $\%$ marketable fruits in 'Fiesta'. mean Fruit weight was not different between two cultivars. Difference of yield between cultivars was due to fruit number, harves time and root condition. It was caused by cracked fruits to decrease $\%$ marketable fruits. Total yield was greater in nighttime temperature of $18^{\circ}C\;than\;15^{\circ}C$ and marketable yield was considerably greater because of $\%$ marketable fruits was higher. Mean fruit weight was slightly greater in nighttime temperature of $15^{\circ}C\;than\;18^{\circ}C$. Difference of fruit yield in treatments of nighttime temperature was due to fruit number and harvest time. There was not significant difference of yield between daytime temperature of $28^{\circ}C\;and\;31^{\circ}C$, but in $34^{\circ}C$, total and marketable yields were the least and mean fruit weight was the smallest because of decreased $CO_2$ concentration in the house, accerated vegetative growth, and the least chlorophyll content. There were no significant difference in photosynthetic rate, transpiration rate, maximal photochemical efficiency and antioxidant enzyme activities of all temperature treatments in this experiment. However it was clear that a little difference in error range of these results affects the source of crops in any case. It was not acknowledged that compensation effect by high temperature in daytime to the low temperature treatment in nighttime.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.1300-1305
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• 2004

The purpose of this experiment is to study the radiant cooling effects by a plate directly viewing the nighttime sky. The measurements are performed at a rooftop of the Engineering building at the Dongguk University in Seoul during the month of August in 2004. The radiant cooling effects are compared using three different types of plate surfaces such as galvanized Iron, black painted, and aluminum film coated galvanized iron plate. Among these plates, the black painted surface show the lowest temperature that is lower than its ambient temperature. The maximum radiant cooling temperature difference, that is ambient temperature minus plate temperature, observed is about 5K..