• 한국식품과학회지
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• 제34권3호
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• pp.413-418
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• 2002

제빵에 이용 할 반죽을 발효하거나 발효하지 않은 상태로 다섯 가지의 다른 냉동 및 저장 환경에서 냉동하고 일주일간 저장하여 해동 한 후 제조된 빵의 품질을 비교하였다. 냉동속도가 빠르더라도 발효한 후 냉동된 반죽은 빵의 부피가 감소하였으며 이러한 문제점은 침지식 냉동 방식에서도 해결되지 않았다. $-70^{\circ}C$의 초저온 냉동은 $-20^{\circ}C$ 침지식 냉동고에 비하여 냉동 온도가 매우 낮으나, 냉동 속도도 느리고 해동 후 재 발효하여도 빵의 부피가 작아서 효과적인 냉동 방법이 되지 못하였다. 반면 냉동 속도는 느리지만 $-20^{\circ}C$ 공기 송풍식 냉동고가 $-70^{\circ}C$ 공시 송풍식 냉동고보다 냉동에 따른 장해가 적어서 반죽의 발효가 잘되었다. 동일한 온도일 때는 침지식 냉동이 더욱 효과적이었으며 침지식 가운데도 온도가 더 높은 $-10^{\circ}C$ 냉동이 가장 효과적이어서 발효하지 않고 냉동하여 재 발효 할 경우 대조구보다도 오히려 반죽의 발효가 잘되어 빵의 부피가 더 컸다. 따라서 본 연구에 이용한 방법 가운데 $-70^{\circ}C$ 공기 송풍식 냉동고에서 냉동, 저장하는 것이 가장 비효율적이며 침지식 냉동방법들이 냉동 온도가 높더라도 오히려 해동 후 발효 장해가 적어서 효율적이었다. 위의 실험 결과를 종합하였을 때, 냉동 전에 반죽을 발효하지 않고 $-10^{\circ}C$ 침지식 냉동고에서 냉동하여 저장하거나, $-20^{\circ}C$ 침지식 냉동고에서 초기에 냉동을 하고, $-20^{\circ}C$ air freezer에 저장하는 방법이 가장 효과적이었다.

• 콘크리트학회논문집
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• 제19권5호
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• pp.647-653
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• 2007

레디믹스트콘크리트 공장에서 동절기에 고분자 화학 혼화제, 특히 조기강도 확보를 위해 개발된 액상형 조강제를 사용할 경우, 해당 혼화제의 저장 안정성을 검토할 필요가 있다. 본 연구에서는 액상형 조강제의 동결 및 겔화 특성을 검토하고, 이를 방지할 수 있는 재료적, 설비적 해결 방안을 제시하여, 실무 적용시의 품질관리 방안으로 제시하고자 하였다. 검토 결과, 액상형 조강제의 동결온도는 $-11.8^{\circ}C$ 정도로 확인되어 콘크리트의 강도 발현 온도한계보다 낮은 온도 범위로서 안정적인 것을 확인하였으며, $SiO_2$와 $Na_2O$의 mol비를 0.31 수준으로 디자인한 sodium silicate를 $37{\pm}0.5%$ 포함시켜 제조함에 따라 저온에서의 겔화를 최소화하는 한편, 이의 저장 및 공급을 위해 고안된 설비 시설은 공급탱크의 온도를 $40^{\circ}C$ 정도로 설정하여 설비 전단계의 온도 분포가 실무 활용상 문제가 없음을 확인할 수 있었다.

• Journal of Biosystems Engineering
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• 제31권3호
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• pp.168-174
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• 2006

The purpose of this study is to develop the cold chain system by developing optimal phase change materials (PCM). There are some benefits from developing this system such as keeping freshness of agriculture products, saving energy, etc. The major results are as follows. To decide a latent heat material, the characteristics of water, sodium, polyacrylate, ethanol and N-tetradecane are analysed. Also, an insulating material is made by mixing water, nucleating agent and latent heat material, using cementing method. In addition, the sensitivity analysis for developed latent heat material($K_l,\;K_2,\;K_3$) is conducted. For $K_l,\;K_2,\;K_3$ which cans keep latent heat temperature, ranging from $0\;to\;5^{\circ}C,\;5\;to\;10^{\circ}C,\;10\;to\;15^{\circ}C$. it can keeps latent heat temperature at radiant heat (5, 12, $17^{\circ}C$) and transportation latent heat container both melting temperature and amount of latent heat of Kl are $-1.6{\pm}1.0^{\circ}C$, 326.51 J/g, respectively and freezing temperature and latent heat are $-7.98{\pm}1.5^{\circ}C$ and 174.18 J/g. and $K_2$ are $7.41{\pm}1.5^{\circ}C$, 89.80 J/g, respectively and freezing temperature and latent heat are $-2.14{\pm}1.5^{\circ}C$ and 83.90 J/g. and $K_3$ are $9.54{\pm}1.0^{\circ}C$, 145.42 J/g, respectively and freezing temperature and latent heat are $0.21{\pm}1.0^{\circ}C$ and 152.48 J/g.

• 한국축산식품학회지
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• 제42권2호
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• pp.341-349
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• 2022

The objective of this study was to examine the effect of temperature abuse prior to cold storage on changes in quality and metabolites of frozen/thawed beef loin. The aerobic packaged samples were assigned to three groups: refrigeration (4℃) (CR); freezing (-18℃ for 6 d) and thawing (20±1℃ for 1 d), followed by refrigeration (4℃) (FT); temperature abuse (20℃ for 6 h) prior to freezing (-18℃ for 6 d) and thawing (20±1℃ for 1 d), followed by refrigeration (4℃) (AFT). FT and AFT resulted in higher volatile basic nitrogen (VBN) values than CR (p<0.05), and these values rapidly increased in the final 15 d. Cooking loss decreased significantly with an increase in the storage period (p<0.05). In addition, cooking loss was lower in the FT and AFT groups than in the CR owing to water loss after storage (p<0.05). A scanning electron microscope (SEM) revealed that frozen/thawed beef samples were influenced by temperature abuse in the structure of the fiber at 15 d. Metabolomic analysis showed differences among CR, FT, and AFT from partial least square discriminant analysis (PLS-DA) based on proton nuclear magnetic resonance (¹H NMR) profiling. The treatments differed slightly, with higher FT than AFT values in several metabolites (phenylalanine, isoleucine, valine, betaine, and tyrosine). Overall, temperature abuse prior to freezing and during thawing of beef loin resulted in accelerated quality changes.

• 대한수의학회지
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• 제56권2호
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• pp.85-89
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• 2016

We tested a set of conditions for obtaining optimal tissue quality in preparation for histology in samples of mouse brain. C57BL/6J mice were sacrificed and perfused with 4% paraformaldehyde, after which the brains were removed and dehydrated in 30% sucrose solution. The brains were then divided into four groups according to freezing temperature and usage of optimal cutting temperature (OCT) compound. Next, we stained the sectioned brain tissues with Harris hematoxylin and eosin Y and immunohistochemistry was performed for doublecortin. The best quality tissue was obtained at $-25^{\circ}C$ and by not embedding with the OCT compound. When frozen at $-25^{\circ}C$, the embedded tissue was significantly damaged by crystals, while at $-80^{\circ}C$ there were no meaningful differences between qualities of embedded- and non-embedded tissues. Overall, we identified a set of conditions to obtain quality frozen brain sections. Our developed protocol will help resolve matters associated with damage caused to sectioned brain tissue by crystal formation during freezing.

• 한국산업융합학회 논문집
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• 제24권6_2호
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• pp.873-882
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• 2021

In this study, a study was conducted to develop a system for predicting/responding to black ice occurring on roads in winter. Tests conditions were studied by making models of cement concrete pavement and asphalt concrete pavement. In order to freeze water on the manufactured model package, an tests was conducted at a temperature below zero using a freezer, and the freezing process was photographed using a thermal imaging camera. Black ice is generated when water is present on the road surface and the temperature is below freezing or the road surface temperature is below the dew point temperature. Under sub-zero conditions, the pavement, water, and ice were classified with a thermal imaging camera. As a result of the tests, it was possible to distinguish with a thermal imaging camera at a temperature below freezing in the same freezer due to the difference in the emissivity of the packaging, water, and ice. In the process of changing from water to ice during the tests, it was analyzed that ice and water were clearly distinguished by the thermal imaging camera due to the difference in emissivity and reflectance, so black ice could be predicted using the thermal imaging camera.

• 대한건축학회논문집:구조계
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• 제34권6호
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• pp.55-61
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• 2018

This study aims to analyze the performance of Heated-nonslip using renewable energy to prevent nonslip freezing during winter. For this purpose, power generation system and congratulatory devices using solar energy are designed, and it is designed to provide regular electricity to heat up nonslip through Electrical storage system(ESS). In this study, It is intended to analyze the level of electrical energy suitable for nonslip using 24V or 48V, and to measure the temperature changes and temperature distribution according to the location of the test object. As a result of the experiment, nonslip's frame temperature was measured at $-7.5{\sim}-5^{\circ}C$ on average, and $-1{\sim}-2^{\circ}C$ on the heating cable during the supply of 24V and this could not be the solution for defrosting freezing nonslip in the winter. As a result of heating nonslip by supplying 48V with an electrical power of 8W, the temperature of the nonslip was shown to be between $5^{\circ}C$ and $11^{\circ}C$ to $13^{\circ}C$. Even if the power supply was switched on and off every minute, the temperature did not drop below $4^{\circ}C$ and the frozen ice melted on the nonslip without freezing.

• 한국환경과학회지
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• 제27권7호
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• pp.531-541
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• 2018

Road freezing caused by snowfall during wintertime causes traffic congestion and many accidents. To prevent such problems, we developed, in this study, a system to predict road freezing based on weather forecast data and the freezing generation modules. The weather forecast data were obtained from a high-resolution model with 1 km resolution for Jeju Island from 00:00 KST on December 1, 2017, to 23:00 KST on February 28, 2018. The results of the weather forecast data show that index of agreement (IOA) temperature was higher than 0.85 at all points, and that for wind speed was higher than 0.7 except in Seogwipo city. In order to evaluate the results of the freezing predictions, we used model evaluation metrics obtained from a confusion matrix. These metrics revealed that, the Imacho module showed good performance in precision and accuracy and that the Karlsson module showed good performance in specificity and FP rate. In particular, Cohen's kappa value was shown to be excellent for both modules, demonstrating that the algorithm is reliable. The superiority of both the modules shows that the new system can prevent traffic problems related to road freezing in the Jeju area during wintertime.

• 지질공학
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• 제11권1호
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• pp.13-23
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• 2001

도로나 철도 변에 나타나는 암반사면은 외부 기온에 영향을 받아 동절기부터 이른봄에 걸쳐 동결융해작용을 반복해서 받는다. 본 연구의 목적은 불연속성 암반이 동결융해작용을 반복하여 받을 경우 열화현상을 겪게 되고 이에 따른 암반의 안정성이 어떻게 변화되는가를 해석한다. 해석방법으로는 균질화법을 이용하여 불연속성 암반의 강도특성을 밝히고 파괴기준으로는 드러커-플래커 기준을 이용한다. 또한 실제 암석의 열화특성은 응회암을 채취하여 실내 동결융해실험에 의하여 열화특성을 정량화 하여 암반의 안정성 해석의 기초 자료로 이용한다. 현장사면에서 동결융해에 의한 열화의 깊이를 추정하기 위하여 일차원 열전도 방정식을 이용하여 온도에 영향을 받는 깊이를 구한다. 모델 사면의 동결융해 깊이를 결정한 후 모델 암반사면에서 암반의 강도 값의 변화양상을 해석한다. 암반의 작용하는 외력은 자중에 의한 중력만이 작용한다고 가정하고 안전율 해석을 실시한다. 그 결과 암반의 안정성 변화양상을 정량적으로 분석한다. 대상으로 하는 두 도시의 경우 동결융해 영향을 받는 깊이는 1.0m 내외 였으며 10년 경과 후에는 암반의 붕괴 조짐을 나타나는 것을 추측할 수 있다.

• 대기
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• 제25권3호
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• pp.389-405
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• 2015

In this study, the occurrence circumstances of 3 cases (12 Jan 2006, 11 Jan 2008, 22 Feb 2009) when the freezing rain was observed at more than two observatories in a day with more than three times each observatory, were investigated. Following the advanced study about the same cases, we have tried to find more delicate differences in using the Korea Local Analysis and Prediction System (KLAPS; 5 km reanalysis data) that has the smallest grid scale at current situation. As results, three common characteristics are found: (1) Just before the occurrence of the freezing rain, the wind direction was consistently continuous and the wind speed was constant or gradually increased for at least 3 hr more. (2) Surface air temperature (Relative humidity) was respectively $3.08^{\circ}C$ (28.76%), $0.47^{\circ}C$ (50.07%) and $-3.60^{\circ}C$ (71.07%) 3 hr ago to break out the freezing rain. It means the freezing rain occurs in a wide range of atmospheric environments. However, the closer it got to the occurrence time of the freezing rain, the closer the surface air temperature was to $0^{\circ}C$, and the bigger the humidity of the surface air was. (3) The liquid precipitation formed in the upper atmosphere, met a cold advection bellower than 950 hPa level and suspected to be changed to the super-cooled condition.