• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 가을 학술발표회 논문집
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• pp.48-53
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• 2003

The steel slag, a by-product which is produced on the process of manufacturing steel by refining pig iron is mainly used as road materials after aging it. It is necessary to age steel slag for long time in air because the reaction with water and free-CaO in steel slag could make the volume expanded. Due to this reason it prevents steel slag from being used as aggregate of concrete. But steel slag used in this study is controled by a air-jet method which rapidly cools substance melted at a high temperature. Rapid cooling prevents from generating of free-CaO in steel slag. In this study, it was investigated that steel slag manufactured by air-jet method affects on concrete in the freezing and thawing. As results of this study, concrete mixed with steel slag was worse in the freezing and thawing than concrete mixed with sand in spite of using air entraining agent. To obtain durability of concrete in the freezing and thawing, it is desirable to mix 50% of steel slag in concrete per unit weight of volume.

• 동력기계공학회지
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• 제14권1호
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• pp.34-39
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• 2010

A side by side refrigerator is popularly used one among electric home appliances according to the rise of the customer's living standard. But the frost problem in freezing compartment comes out whenever we develop the high quality refrigerator. In this research, internal flow simulation and temperature measurement were carried out by using CFD and T-type thermocouple respectively in order to understand freezing mechanism. It was revealed that the amount of frost beneath the 1st and 2nd shelves is approximately 40% of total frost and the cause of frost generation is due to bad circulation of low speed cold flow. Using this analysis, the shapes of outlets under shelves are modified. So, the amount of frost in this modified model decreases 6% comparing to original one.

• 설비공학논문집
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• 제14권2호
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• pp.168-174
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• 2002

In order to obtain a new heat transfer fluid having a high thermal capacity, micro-capsules of a phase-change material can be a successful candidate to be added into water. In this study, 25, 50, 100, and $200\mu$m diameter micro-encapsulated Lauric acids were tested by a differential scanning calorimeter. The Lauric acid itself had a single freezing curve, but the micro-encapsulated Lauric acid had double freezing curves. The second freezing dominated for $25\mu$m diameter Lauric acids. But the first freeing energy became big as the size of the capsule increased.

• 한국철도학회논문집
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• 제8권1호
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• pp.57-62
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• 2005

The frost heaving pressure can be a problem for weakening of the railway roadbed material. This study was initiated to investigate the soils frost heaving pressure and physical characteristics(Liquid limit, permeability, SEM analysis) resulting from freezing and freezing-thawing cycle process. Therefore, upon freezing a saturated soil in a closed-system from the top, a considerable pressure was developed. Weathered granite soils, sandy soil were used in the laboratory freezing test which sometimes subjected to thermal gradients under closed-systems. The frost heaving pressure arising within the soil samples and the temperature of the samples inside were monitored with elapsed time. The degree of saturation versus heaving pressure curve is also presented for weathered granite soil and the maximum pressure is closely related to this curve. Based on the laboratory test results, fine-grained soils with strong attractive forces between soil grains md water molecules, and additional water is attracted into the pores leading to further volume changes and ice segregation.

• 한국터널지하공간학회 논문집
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• 제20권2호
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• pp.255-268
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• 2018

해저터널은 시공중 예측치 못한 고수압으로 인한 해수 침투가 발생할 가능성이 매우 크다. 이에 고수압조건에서 차수 및 보강효과가 탁월한 인공 동결 공법의 적용이 대두되고 있다. 본 연구에서는 인공 동결 공법에 필요한 냉매량을 산정하기 위해 열흐름 에너지 이론 모델에 의한 이론적인 값을 계산하고, 동결 챔버 실험결과 및 수치해석결과와의 비교를 통해 적정성을 검증하였다. 염분과 수압에 따른 열적 역학적 특성 변화를 규명하기 위해 동결용 챔버를 제작하여 염분과 수압 조건에 따라 사질토의 동결 시간을 파악하였다. 또한, 이론값과 수치해석 결과의 동결 시간은 유사한 경향을 확인하였다. 동결공법의 냉매량은 수치해석의 결과를 기반으로, 동결 챔버 실험을 통해 동결 효율의 결과와 이론식을 통한 동결 유지를 위한 에너지 비율을 적용하여 산정하였다. 동결유지를 위한 에너지 비율은 해저터널의 토피고와 해저면의 수온에 따라 좌우될 것으로 판단된다.

• 한국식품저장유통학회지
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• 제7권1호
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• pp.57-62
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• 2000

Ginseng was stored at a temperature lower than the freezing point after a treatment of freezing point depressing agents to extend its freshness. Respiration rate at freezing point of ginseng, -1.7${\pm}$0.1$^{\circ}C$, was inhibited 92% and 97% compared with those stored at 5$^{\circ}C$or 20$^{\circ}C$ , respectively. Sorbitol solution chosen as a freezing point depressing agent lowered the freezing point of ginseng to about -3.0$^{\circ}C$. Ginsengs treated with the sorbitol solution and packaged with 0.06mm LDPE was stored at -2$^{\circ}C$ , and the quality change was then compared with ginsengs stored at 0$^{\circ}C$ and 5$^{\circ}C$. Weight loss of ginsengs stored at -2$^{\circ}C$ for 100days was 1.5%, which is about 2.6times less than those stored at 5$^{\circ}C$. However, there were no significant difference between the ginsengs stored at -2$^{\circ}C$ and at 0$^{\circ}C$(1.9%). Spoilage rate of the ginsengs was 100% after 50 days of storage at 5$^{\circ}C$ and 25% after 100days at 0$^{\circ}C$respectively. but that of ginsengs stored at -2$^{\circ}C$ was 13%, which was half than that of ginsengs stored at 0$^{\circ}C$. Firmness and amount of monoscaccharides in ginsengs were decreased during storage at 5 or 0$^{\circ}C$ but ginsengs stored at -2$^{\circ}C$ showed better firmness and an increase in monosaccharides such as fructose and glucose. From above, when ginseng treated with freezing pont depressing agents were stored at -2$^{\circ}C$, the shelf life was extended to 2 or 3 times longer than those that were stored at 5 or 0$^{\circ}C$, respectively.

• 동아시아식생활학회지
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• 제16권4호
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• pp.429-437
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• 2006

The quality of Jeung-pyun made with frozen rice batter was evaluated according to variations in the freezing temperature of the batter. The physicochemical sensory and rheological characteristics of Jeung-pyun were analyzed. The rice batter was stored at -20$^{\circ}C$, -40$^{\circ}C$, and -70$^{\circ}C$ for up to 4 weeks. Statistical data analysis was completed using the SAS program. The pH, and brix percentage of Jeung-pyun batter decreased during the fermentation. In carbon dioxide evolution during fermentation, the levels of the sample stored at -40$^{\circ}C$:, and -70$^{\circ}C$ for 3$\sim$4 weeks were significantly higher than that of the sample stored at -20$^{\circ}C$. The Jeung-pyun moisture content was not significantly affected by freezing temperature or storage times. Specific volume of Jeung-pyun made with rice batter stored at -40$^{\circ}C$, and -70$^{\circ}C$ for 4 weeks was significantly higher than that stored at -20$^{\circ}C$. In sensory evaluation of the stored sample for 4 weeks, the overall quality of Jeung-pyun was not significantly different between with the control and the -20$^{\circ}C$ sample, and between the control and the -40$^{\circ}C$ sample. Among the rheological properties measured with a rheometer on Jeung-pyun made with batter stored sample for 4 weeks at -20$^{\circ}C$, -40$^{\circ}C$ and unfrozen batter, the hardness was increased over the storage time, but the difference was not significant. In conclusion, the most suitable freezing temperature of the rice batter for the manufacture of Jeung-pyun was proposed to be -40$^{\circ}C$.

• 터널과지하공간
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• 제20권4호
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• pp.241-251
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• 2010

극지는 학문적인 가치뿐만 아니라 무한한 자원의 공급처로서 각광받고 있는 추세이다. 극지와 극지 암석의 암석역학적 특성을 이해하기 위하여 남극대륙의 암석을 포함하여 극지 환경 조건에서 진행된 암석의 물성 변화에 관한 연구를 살펴보았다. 남극대륙은 바람이 매우 강하고 지구상에서 가장 기온이 낮으며 건조한 지역이다. 남극 현지 암석의 심도별 온도분포를 조사한 연구에서는 지표면과 가까운 얕은 심도에서는 동결-융해 과정이 반복되는 한편, 특정 깊이 이하에서는 항상 $0^{\circ}C$ 미만의 온도 분포를 나타내는 것으로 보고 하였다. 현지 암석의 온도분포와 대기 온도를 비교해 보았을 경우 상당한 차이를 나타내었다. 남극 사면의 기후에 의한 풍화정도를 알아보기 위하여 슈미트 반발경도와 taffoni의 분포를 조사한 연구가 있다. 그리고 실내 실험을 통해 암석 시료를 동결-융해 과정을 반복하여 풍화시킨 후 쇼어경도, 일축압축강도 등을 측정한 결과 동결-융해 횟수가 증가할수록 암석의 강도가 저하됨을 보고한 사례가 있다. 향후 극지암석에 대한 보다 상세한 암석역학적 물성 시험과 풍화에 관한 실내시험결과를 현장 암석의 물성변화에 적용시키는 연구가 필요할 것으로 판단된다.

• 한국수산과학회지
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• 제15권2호
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• pp.111-116
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• 1982

말쥐치를 보다 효과적으로 이용하기 위한 하나의 방법으로서 말쥐치 동건품의 가공사건 및 저장중의품질변화를 실험하였다. 동결온도 $-10^{\circ}C$이고 송풍해동조건이 온도 $56\pm2^{\circ}C$, 풍속 1 m/sec 일 때 동결시간 10시간, 해동시간2시각, 동결 및 해동포수는 5소파 가장 적합하였다. 이 때 제품의 수분사양은 $23.6\%$, 수율은 $10.2\%$였다. 상온에서 함기포장하여 저장한 결과 90일까지는 품질에 큰 변화 없이 저장 가능했다. Omission test결과 제품의 맛에는 유리아미노산과 5'-mononucleotide가 주된 구실을 한다는 것을 알 수 있었다. 또한 말쥐치 동건품과 시판 동건명태는 관능 검사결과 맛, 냄새, 텍스튜어 등이 거의 비슷하였다.

• Journal of Biosystems Engineering
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• 제33권3호
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• pp.167-172
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• 2008

The objective of this study was to investigate the adequate storage method that was able to maintain the high quality of rough rice according to storage methods and period. The quality change of the rough rice during the storage period was evaluated by storage method such as cooling bin using winter cold air, ordinary temperature bin, freezing, refrigeration and indoor storage. Moisture content, brown rice whiteness, hardness, crack ratio and germination ratio were measured in this study. Moisture content of rough rice stored in cooling bin using winter cold air and ordinary temperature bin were decreased by 0.07% and 0.42%, respectively, which were lower than the other storage method. The hardness of brown rice increased in order of storage method such as winter cooling bin, normal bin, freezing storage, refrigeration storage and indoor storage. Crack ratio by indoor and ordinary temperature bin storage were increased by 2.68% and 3.63%, respectively, whereas cooling bin using winter cold air, refrigeration and freezing storage showed below 1.0%. The highest germination rate was found in cooling bin using winter cold air. As a result, cooling bin using winter cold air can be evaluated for the adequate storage method of rough rice.