• Elastomers and Composites
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• v.54 no.2
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• pp.123-127
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• 2019

Shrink film is currently being used for plastic container lavels to avoid the use of glue. Polyethylene terephthalate (PET) bottle lavels also use shrink films in the same PET materials for easy recycling of PET bottles. An air layer is generated between the shrink film and PET bottle surface due to the bent shape of the bottle surface. This air layer can insulate external heat, as air has a relatively lower thermal conductivity. In this study, the insulation property of the air layer was examined by computer simulation. Two PET bottle models were used, one with and the other without an air layer between the PET bottle surface and lavel. The two bottle models were filled with cold liquid and exposed to room temperature for 6 h, and the temperatures of the contents were then compared. The results showed that the temperature of the contents in the bottle with the air layer was lower than that without the air layer by at least $2^{\circ}C$. This study suggests an effective lavel design of PET bottles while ensuring that the temperature of the bottle contents is maintained.

• Journal of Welding and Joining
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• v.4 no.1
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• pp.32-39
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• 1986

This paper was studied about the influence of oxidized films on workability in cold pressure welding. In preceding studies, the principal foci of the studies about pressure welding were considered several factors(surface manufacturing methods, surface roughness, pressure welding speed and surface temperature). But the influence to the growth of oxidation have hardly known well. So the purpose of this paper consists in solving the question above and proposing the optimal states of the pressure welding. Therefore the results obtained is as the following; When the oxidation time is within about 2 minutes, the bonding strength is very good after surface manufacturing of the neighboring to be bonded. The more surfaces are fine the more bonding strength is excellent. Above all, the optimal condition of cold pressure welding is the state that the characteristic value is 38% with smooth surface and without oxidation.

• Atmosphere
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• v.26 no.4
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• pp.635-647
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• 2016

The effects of sea surface temperature (SST) gradient induced by the previous typhoon on the following typhoon motion over East Asia have been investigated using Weather Research and Forecasting (WRF) model for the previous Typhoon Bolaven (1215) and following Typhoon Tembin (1214). It was observed that Typhoon Bolaven remarkably reduced SST by about $7^{\circ}C$ at Yellow Sea buoy (YSbuoy). Using the WRF experiments for the imposed cold wake over West of Tembin (WT) and over East of Tembin (ET), this study demonstrates that the effects of eastward SST gradient including cold wake over WT is much significant rather than that over ET in relation to unexpected Tembin's eastward deflection. This difference between two experiments is attributed to the fact that cold wake over WT increases the magnitude of SST gradient under the eastward SST gradient around East Asia and the resultant asymmetric flow deflects Typhoon Tembin eastward, which is mainly due to the different atmospheric response to the SST forcing between ET and WT. Therefore, it implies that the enhanced eastward SST gradient over East Asia results in larger typhoon deflection toward the region of warmer SST according to the location of the cold wake effect. This result can contribute to the improvement of track prediction for typhoons influencing the Korean Peninsula

• Korean Journal of Food Science and Technology
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• v.38 no.5
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• pp.635-641
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• 2006

In an attempt to find ways of improving the quality and sanitary state of dried squid, this study compared artificial drying methods i.e. hot air drying and cold air drying with natural drying method. The drying rates of squid were in the order of hot air, cold air and natural drying. However, cold-air drying was slower than natural drying at $7^{\circ}C$. The drying rates increased with increasing drying temperature. When drying temperature was close to the dew point on a dehumidifier surface, which was the case with cold air drying at $7^{\circ}C$, the driving force for dehumidification was lower than under other drying conditions, which resulted in a lower drying rate. There were little color differences between the drying methods and temperature. Squid dried by cold air-drying had better mechanical texture and sensory qualities than with other drying methods. In addition, the cold air drying method maintained superior quality in terms of the contents of amino acids, taurine, EPA, DHA, other fatty acids and a low TBA value than the other drying methods.

• Proceedings of the KSME Conference
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• 2000.11b
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• pp.228-233
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• 2000

The Korean Next Generation Reactor(KNGR) is a Pressurized Water Reactor adopting direct vessel injection(DVI) to optimize the performance of emergency core cooling system(ECCS). In a certain accident, however, pressurized thermal shock(PTS) of the vessel due to the sudden contact with the injected cold water is expected. In this paper, an accident of Main Steam Line Break(MSLB) has been numerically investigated with direct vessel injections and an increased volume flow rate in some cold legs. Using FLUENT code, temperature distributions of the fluid in the downcomer and of reactor vessel including the core region have been calculated, together with the distribution of convective heat transfer coefficient(CHTC) at the cladding surface of the reactor vessel. The result shows that some parts of the core region of the reactor vessel have higher temperature gradient expressing higher thermal stress.

• 한국해양학회지
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• v.19 no.2
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• pp.125-132
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• 1984

The abnormal low water temperature phenomenon of the Yellow Sea Bottom Cold Water in summer, 1981 is studied on the basis of the oceanographical data collected by the National Fisheries University of Pusan in July, 1981 and Fisheries Research and Development Agency of Korea from 1960 to 1981 and meteorological data within the same 22 years. In winter, 1980 the northwesterly monsoon was vary predominant and the air temperature was lower than that of mean year by 1∼8$^{\circ}C$ and also the surface temperature was lower 1∼3$^{\circ}C$. And then the temperature of the Yellow Sea Bottom Cold Water in summer, 1981 became lower 2∼3$^{\circ}C$ than that of mean year and the influence of this cold water was extended to about 50 miles off the coast of Cheju Island. Comparing with mean year, the water temperature at 30m depth in February, 1981 was lower by 1∼2$^{\circ}C$ in entire regions except near sea of Sohuksando and at 50m depth in August, 1981, it was lower by about 3.5$^{\circ}C$. Particularly, the offshore of Hongdo shower value of 5$^{\circ}C$ than that of mean year. It was found that the abnormal low water temperature phenomenon of Yellow Sea Bottom Cold Water in summer, 1981 resulted from the sea surface cooling by the predominant northwestly monsoon and abnormally low air temperature in winter, 1980.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.24-27
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• 2002

The environmental problems by using coolant demanded the new cooling methods. As one of them, the studies on the finding with compressed cold air and oil mist have been done. The cooling method using compressed cold air was effective through going down the temperature of compressed air supplied below $-25^{\circ}$ and increasing the amount of compressed cold air, but had not enough cooling effect due to the low performance of lubrication. Therefore, the cooling methods using oil mist newly were suggested. This method can satisfy both cooling effect and lubrication with only small amount of coolant, also have the benefit in the point of decreasing the environmental pollution. This paper focused on analyzing the grinding characteristics of the cooling method using oil mist. The grinding test according to compressed cold air, oil mist spray pressure and oil mist supply direction were done.

• Korean Journal of Remote Sensing
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• v.39 no.6_1
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• pp.1235-1243
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• 2023

This study proposes the detection algorithm for the cold water mass (CWM) along the eastern coast of the Korean Peninsula using sea surface temperature (SST) data provided by the Korea Institute of Ocean Science and Technology (KIOST). Considering the occurrence and distribution of the CWM, the eastern coast of the Korean Peninsula is classified into 3 regions("Goseong-Uljin", "Samcheok-Guryongpo", "Pohang-Gijang"), and the K-means clustering is first applied to SST field of each region. Three groups, K-means clusters are used to determine CWM through applying a double threshold filter predetermined using the standard deviation and the difference of average SST for the 3 groups. The estimated sea area is judged by the CWM if the standard deviation in the sea area is 0.6℃ or higher and the average water temperature difference is 2℃ or higher. As a result of the CWM detection in 2022, the number of CWM occurrences in "Pohang-Gijang" was the most frequent on 77 days and performance indicators of the confusion matrix were calculated for quantitative evaluation. The accuracy of the three regions was 0.83 or higher, and the F1 score recorded a maximum of 0.95 in "Pohang-Gijang". The detection algorithm proposed in this study has been applied to the KIOST SST system providing a CWM map by email.

• Journal of the Korean Geographical Society
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• v.30 no.3
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• pp.230-241
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• 1995

The Characteristics of nocturnal temperature fields were analyzed to understand the factors of freezing-and-cold damages on orange orchards in Cheju Island. Temperatures were measured from January 7th through 27, 1995 at 25 sites in an area of 1x1.25$ extrm{km}^2$, Wasan-ri, Chochon-up, Pukcheju-kun located on the northeastern slope of Mt.Hanla. Several other weather elements such as wind and cloud were observed as supplementary data. Surface weather maps were also analyzed to clarify the influence of prevailing pressure patterns on the temperature fields. The vertical temperature profiles were obtained at the height from the ground up to 360 cm in 30 cm intervals at site 3, a frost hollow, and site 10 on the upper slope. The results show that freezing damages occured in the hollows, terrain depressions, rather than at the upper slope due to nocturnal radiation cooling as well as accumulation of cold airflow from Mt.Hanla. Windbreaks of densely planted Japanese ceders with stone-walls also roled as obstacles to the cold airflow in nights with Clear skies and light winds. The maximum intensity of temperature inversion in hollows, quasi-cold air lake, was 3.1$^{\circ}C$. Cold air from Mt.Hanla was trapped in the depressions up to a height of 90cm forming frost pocket. Man-made facilities such as shelterbelt or stone-wall which are built to prevent the penetration of cold north-westeries in winter aggravated the cold damage. The differance of daily minimum temperatures between before and behind shelterbelts was 2.$0^{\circ}C$. The man-made convection by smudgin which raised the temperatures up to 3.8$^{\circ}C$ can reduce the cold damage in the hellows.

• Atmosphere
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• v.27 no.2
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• pp.177-188
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• 2017

The development mechanisms of an unusual heavy snowfall event, which occurred in the coast of Jeju Island on 23 January 2016 were investigated through a thermodynamic approach. The formation of heavy snowfall was attributed to the enhanced thermal convection in two ways. First, the convection was enhanced by the air-sea temperature difference between the cold air advection in low-troposphere associated with the strengthening of the Siberian High and abnormal warm sea surface temperature, which is $1{\sim}2^{\circ}C$ higher than normal year over the Yellow Sea (YS). Second, the convective instability was increased by the vertical temperature gradient between the 7 days-sustained cold air advection in low-troposphere and the abrupt cold air intrusion in mid-troposphere induced by the southward shift of a cold cut-off vortex ($-45^{\circ}C$) at the formation stage. Compared to the twelve hours prior to the formation, the low-level moisture increased by 5% through the moisture supply from the YS, and the air-sea temperature difference increased from $18.5^{\circ}C$ to $28.5^{\circ}C$. Furthermore, the upward sensible (latent) heat flux increased 1.5 (1.2) times over the YS before the twelve hours prior to the formation. Thereafter, the sustained moisture supply and upward turbulent heat flux helped to maintain the snowstorm.