• Atmosphere
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• v.30 no.3
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• pp.249-256
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• 2020

We investigate regional differences in the characteristics of cold surges that occurred over the South Korea during winter season (December-February, 1981/1982~2017/2018). A significant regional contrast of cold surge characteristics exists and we found that this is closely related to the spatially inhomogeneous distribution of winter-mean climatological surface temperature in association with the complex topography of the Korean peninsula. For the regions of the temperature below -1℃ (Region1; R1), the frequency of cold surges is inversely proportional to the surface temperature almost linearly. In case of the regions above -1℃ (Region2; R2), cold surge frequency does not exhibit any clear dependency on the surface temperature. Duration and number of occurrences of cold surge between the two regions showed clear difference. Dynamical evolution of cold surges before the onset showed a sharp contrast between R1 and R2. In R1, cold surface air temperature (SAT) was already predominant over East-Asia before the onset and the cold temperature was sustained after the occurrence. On the contrary, warm SAT was predominant over East-Asia before the onset in R2. The SAT suddenly drops just after the cold surge occurrence. We present different origin of wave activity and propagation characteristics between the two types: Wave-activity flux (WAF) was relatively weaker and wave disturbances moved eastward in R1 along with the WAF mainly directing eastward. In case of R2, WAF was stronger and directing southeastward in the upstream of South Korea movement erasing predominant warmer air eventually causing sudden temperature drops over southern provinces over South Korea.

• Journal of the Korean Academy of Clinical Electrophysiology
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• v.5 no.2
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• pp.61-72
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• 2007

INTRODUCTION: Local heat and cold application has been frequently used as means of muscle relaxation and blood circulation or reinforcing muscle strength, relaxing muscle tension in clinical situation. In particular, it has been known that long-term heat and cold application for relaxing muscle tension inhibits muscle spasticity or tension. But, it has been rarely reported that what influences of heat and cold application on activation of muscle action potential. Therefore, this study aims to analyze surface temperature and electromyography activities according to the heat and cold application. METHODE: Subjects of this research were 10 normal men and women (5 men, 5 women). Hot pack and cold pack was applied to vastus medialis muscle of thigh and rectus femoris muscle for 20 min. Surface temperature of vastus medialis muscle and rectus femoris muscle was measured, knee joint of subjects was in $45^{\circ}$ flexion, sitting on a chair, maximal isometric contraction was induced, surface electromyography (sEMG) signals were collected and root mean square (RMS) and median frequency (MOF) were analyzed. All measurements were conducted before and immediately after experiment, 10 min., 20 min. and 30 min. after experiment. Data were analyzed with SPSS 12.0 program, comparison of changes in superficial temperature and sEMG signals through repeated measurement was conducted with repeated measures ANOVA and significance level $\alpha$ was 0.05. RESULTS: Changes of surface temperature of vastus medialis muscle according to cold application were radically decreased immediately after application, but it was recovered after 30 min. of application and it showed significant difference (F4. 36=72.216, P<0.001). Surface temperature of rectus femoris also showed radical decrease immediately after application, but it was recovered after 30 min. of application and showed significant difference (F4. 36=88.930, P<0.001). Changes of surface temperature of vastus medialis muscle according to heat application were radically increased immediately after application, but it was recovered after 30 min. of application and it showed significant difference (F4. 36=27.267, P<0.001). Surface temperature of rectus femoris also showed radical decrease immediately after application, but it was recovered after 30 min. of application and showed significant difference (F4. 36=19.774, P<0.001). Changes of sEMG by heat and cold application were no statistical difference. Surface temperature of skeletal muscle after heat and cold application showed significant change for 30 min., but it was found that increase or decrease of surface temperature had not great influence on sEMG activities.

• Atmosphere
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• v.28 no.4
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• pp.383-392
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• 2018

This study investigates synoptic characteristics of cold surges over South Korea during winter season (December-February). A total of 63 cold events are selected by quantile regression analysis using daily mean temperature observations from 11 KMA stations for 38 years (1979/80-2016/17). Large-scale pressure pattern during the cold surges is well characterized by high over Siberia and low over Aleutian regions, which elucidates cold advection over the Korean peninsula. However, the large-scale pattern cannot successfully explain the observed sudden decrease of temperature during the cold surges. Composite analyses reveal that a synoptic-scale cyclone developing over the northern Japan is a key feature that significantly contribute to the enhancement of cold advection by increasing pressure gradient over the Korean peninsula. Enhanced sensible and latent heat fluxes are observed over the southern ocean of Korea and Japan during the cold surges due to temperature and humidity differences between the near surface and the lower atmosphere over the ocean. The evaporated water vapor transported toward the center of the surface cyclone and condenses in the lower-to-middle troposphere. The released energy likely promotes the development of the surface cyclone by inducing positive PV near the surface of the heating region.

• Journal of Korean Society for Geospatial Information Science
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• v.23 no.4
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• pp.11-16
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• 2015

Spatial and temporal information on near-surface air temperature is important for understanding global warming and climate change. In this study, the estimation algorithm of near-surface air temperature in Korea was developed by using spatial homogeneous surface information obtained from satellite remote sensing observations. Based on LST(Land Surface Temperature), NDWI(Normalized Difference Water Index) and NDVI(Normalized Difference Vegetation Index) as independent variables, the multiple regression model was proposed for the estimation of near-surface air temperature. The different regression constants and coefficients for warm and cold seasons were calculated for considering regional climate change in Korea. The near-surface air temperature values estimated from the multiple regression algorithm showed reasonable performance for both warm and cold seasons with respect to observed values (approximately $3^{\circ}C$ root mean-square error and nearly zero mean bias). Thus;the proposed algorithm using remotely sensed surface observations and the approach based on the classified warm and cold seasons may be useful for assessment of regional climate temperature in Korea.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2003.05a
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• pp.19-22
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• 2003

The purpose of this study is to analyze the curing effect of planar surface heater for concreting in cold weather. Some experiments were conducted to evaluate the temperature history of concrete structures cured with heating sheets. Results are as follows ; (1) The temperature of concrete showed continuously rising trend with the heating by planar surface heater under the cold environmental condition of 3~-12$^{\circ}C$. And after about 24 hours the maximum temperature of concrete was reached at 25~3$0^{\circ}C$. (2) The temperature of slab concrete heated by planar surface heater of 130W/$m^2$ was at least $25^{\circ}C$ higher than that of an exterior air, and the curing performance was much more effective than heating by hot wind machine. (3) Through the curing by planar surface heater for 48 hours, the concrete maturity of about 1.5 times to heating by hot wind machine was acquired.

• Journal of Forest and Environmental Science
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• v.35 no.4
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• pp.232-239
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• 2019

This study was carried out to establish an efficient selection condition for cold-tolerant individuals among evergreen Quercus spp. To select higher cold-tolerant individuals among four species of evergreen Quercus spp. (Q. acuta, Q. glauca, Q. myrsinaefoila, and Q. salicina), an-year-old seedlings of each species were exposed to low temperature in serial, and then examined for the death of cell tissue and the surface temperature was monitored. It was shown that the higher numbers of seedlings of Q. myrsinaefolia were survived than the others when those seedlings are exposed to cold stress. Thus, selection of the cold tolerant individuals was conducted on Q. myrsinaefolia seedlings. The limit low temperature condition for selecting cold-tolerant individuals was -6℃ for 24 hrs because no seedling of Q. myrsinaefolia was survived after exposed to -7℃ for 24 hours. It was shown that the leaf surface temperature of the selected individuals was higher than those of the non-selected individuals when they were exposed to cold-stress while monitoring them using thermal graphic camera. The results in this study can be used for expanding afforestation area of tree species of the warm temperate zone for preparation of climate change.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2003.05a
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• pp.7-11
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• 2003

This study investigate the hydration heat history with variation of surface insulating material in cold weather concreting. According to the results, the temperature of concrete lowers below zero in 24hours, so early frost damage occurs in the case of exposure and 1 fold bubble sheet, but the lowest temperature keeps above zero, so a adiabatic effect is very favorable in the case of double bubble sheet and 부직포. Compressive strength of core specimen at 7 and 28 days is highest In the case of double bubble sheet and 부직포. But, considering convenience of construction and economical efficiency, it is thought that the most effective surface insulating material is 1 fold bubble sheet +blanket.

• Journal of the Korean Society of Safety
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• v.14 no.1
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• pp.3-9
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• 1999

The vortex tube is a simple device which splits a compressed gas stream into a cold stream and a hot stream without any chemical reactions. Recently, vortex tube is widely used to local cooler of industrial equipments and air supply system. In this study, the insulation effect of surface on the efficiency of vortex tube was performed experimentally. The experiment is carried out for nozzle area ratio of 0.194, diameter ratio of cold end orifice of 0.6 and input pressure ranging from 0.2Mpa to 0.5Mpa. The purpose of this study is focused on the effect of surface insulation of vortex tube with the variation of cold air mass flow ratio. The results indicate that the temperature difference of cold and hot air are higher about 12% and 30% than that of not insulated vortex tube respectively. Furthermore, for the insulated vortex tube, the similarity relation for the prediction of cold end temperature as the function of cold air mass flow ratio and input pressure is obtained.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.3
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• pp.286-295
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• 2016

With the results of observations in 2013 and 2014 including ocean buoys, in-situ investigations and wind data, we examined the spatio-temporal variation of cold water masses along the eastern coast of Korea. Usually, a cold water mass first appears along the northern part of the eastern coast from May to July, and then along the southern part of the eastern coast from late June to mid-August. Cold water masses appear 3~5 times a year and remain for 5~20 days in the southwestern part of the East Sea. A distinctive cold water mass appeared usually in mid-July in this area, the surface temperature of which was below $10^{\circ}C$ in some cases. During the appearance of a cold water mass in the southwestern part of the East Sea, the horizontal temperature gradient was large at the surface and a significant low water temperature below $8^{\circ}C$ appeared at the bottom level. This appearance of cold water masses clearly corresponded to southwesterly winds, which generated coastal upwelling.

• The Korean Journal of Quaternary Research
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• v.33 no.1_2
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• pp.37-48
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• 2021

The cold surge is an important extreme weather in East Asia during winter, and is largely affected by behavior of the Siberian high Arctic Oscillation, which represents undulation of large-scale pressure pattern in the Arctic region. Recent studies also revealed that the synoptic low pressure system developing in the eastern boundary of the Asian continent is sensitive to sea surface temperature (SST) and plays an important role in strengthening the cold advection over the Korean Peninsula during cold surges. In this study, we analyzed the Arctic Oscillation affecting the large-scale background of cold surge in East Asia, and the sea surface temperature in the coast of East Asia is examined focusing on its role on synoptic low-inducing cold advection. For the analysis, the days with the bottom 3% of the average daily temperature, measured at five surface stations in Korean Peninsula during 49 years (1969/70-2017/18), were used for the cold surge cases. During the negative phase of the Arctic Oscillation, a strong trough is observed over East Asia, and the inflow of cold air from the polar region is strengthened, which lead to frequent cold surges. In addition, anomalously high SST in the eastern coast of Asia increases sensible and latent heat release from the ocean, therefore, it enlarges the likelihood of synoptic low-inducing extreme cold surges.