• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.2
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• pp.68-77
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• 2020

The purpose of the paper is to evaluate the pore structure and mechanical properties of early frost damaged concrete using electric arc furnace slag as aggregate. From the results, when the concrete is exposed to frost damage at an early age, the peak point of pores 100 to 150 ㎛ in diameter were transferred into larger one. When the freezing duration is not exceeded 24 hours, it is possible that the pore distribution of under the 200 ㎛ is maintained and pore size of over 500 ㎛ is not formed, and, the freezing resistance of concrete using EFG could be improved. When BFS was mixed in concrete using EFG as coarse aggregate, the relative strength is higher than that of natural coarse aggregate. Meanwhile, the elastic modulus and resonance frequency did not change significantly due to the early frost damage as compared with the compressive strength. So, it is necessary to analyze the correlation between the experimental results in order to evaluate the performance degradation due to early frost damage.

• Journal of the Korea Concrete Institute
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• v.15 no.1
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• pp.43-51
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• 2003

Recently, to consider financial and constructive aspect usage of Admixture such as Blast-Furnace Slag and Fly-Ash, are increased. Also the use of cold-weather-concrete is increased. Blast-Furnace Slag, a by-product of steel industry, have many advantage to reduce the heat of hydration, increase in ultimate strength and etc. But it also reduces early-age strength, so it is prevented from using of Blast-Furnace Slag at cold-weather-concrete. In this study, for the purpose of increasing usage of Blast-Furnace Slag at cold-weather-concrete, it is investigated the strength properties of concrete subjected to frost damage for the cause of early age curing. The factors of this experience to give early frost damaged were Freezing temperature(-1, -10, $-15^{\circ}C$), Early curing age(0, 12, 24, 48hour), Freezing times(0, 12, 24, 48hour). According to this study, if early curing is carried out before haying frost damage, the strength of concrete used admixture, subjected to frost damage, is recovered. And that properties are considered, the effect of using admixture like blast-furnace-slag, is very high

• Korean Journal of Food Science and Technology
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• v.38 no.4
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• pp.513-520
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• 2006

Spray-dried (SD) and freeze-dried (FD) takju powders were stored at 5, 15 and $25^{\circ}C$, and various quality characteristics such as moisture, amino nitrogen, color value, total viable cell count, total sugar, reducing sugar organic acid, and flavor compounds were measured for 50 days at 10-day intervals. After 50 days of storage, the moisture content was increased from an initial 6.64% to 7.24-7.38% in the SD powder, and from an initial 4.86 to 5.43-5.61% in the FD powder. pH, total acid content and total viable cell counts were slightly increased. Organic acid content was decreased in the SD powder from an initial 3,949.9 mg% to 805.9-922.3 mg%, and in the FD powder from an initial 5,171.5 mg% to 3,646.0-4,110.2 mg%. Amino nitrogen content was increased in the SD powder from an initial 1.2% to 1.9-2.2% and in the FD powder from an initial 1.9% to 2.2-2.5%. Total sugar and reducing sugar contents were increased in the SD powder from an initial 17.2% and 4.0% to 25.9-27.3% and 5.8-6.9%, and in the FD powder from an initial 19.1% and 5.2% to 29.2-30.2% and 8.3-8.8%, respectively. With increasing storage time, L and b values in the SD powder increased slowly, while L value in the FD powder tended to decrease and b value tended to increase. About 20 major volatile flavor components were identified in the SD and FD powders by GC-MS and all such component levels were decreased with increasing storage time.

• Journal of the Korean Society of Food Science and Nutrition
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• v.15 no.3
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• pp.213-221
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• 1986

Japanese spotted mackerels(Scomber tapeinoephalus) were stored at $0^{\circ}C$ for 7days as the maximum, and then, they were stored again at $-3.5^{\circ}C$(partial freezing) or $-20^{\circ}C$(freezing), respectively. During storage by partial freezing, the fishes with a longer period of prestorage at $0^{\circ}C$ showed an earlier increase in the number of bacterial cells on their skin, however, it was not apparent in the freezing storage. K value of the fishes with 7 days of prestorage increased from 20% to 65.4% for 36 days of partial freezing storage, that of the fishes prestored for 0 and 4 days were 39.9% and 53.2% respectively. On contrastly, no drastic increase in K value was observed in the fishes of freezing storage. Content of volatile nitrogen of the fish muscle prestored for 4 days gradually increased from 10mg% to 29.4mg% and 17.2mg% during 36 days of partial freezing and 83 days of freezing storage respectively, that of the fishes with 7 days of prestorage showed no significant increase, moreover, it was decreased within early period of both of the storages. Free drip from the fishes with partial fleering was higher almost 5 times than that from the fishes with freezing, the highest free drip was observed from the fishes with 4 days of prestorage.

• Journal of Dairy Science and Biotechnology
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• v.33 no.3
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• pp.203-207
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• 2015

The majority of food drying processes are based on the use of thermal energy. However, such methods may deteriorate the quality of the final product. Freeze-drying is one of the most useful processes for drying thermosensitive substances. Food that contains beneficial bacteria, for example, is susceptible to heat treatment, but during freeze-drying beneficial bacteria are preserved in these food items. The primary goals of this study were to develop yogurt snacks and to compare the viability of lactic acid bacteria (LAB) in yogurt snacks under different freeze-drying temperatures. In addition, the survival of LAB during storage was investigated. Survival of LAB in freeze-dried yogurt snacks gradually decreased over 16 weeks of storage. LAB had a residual viability of 25.5% after 16 weeks of storage at room temperature. LAB survived better in freeze-dried plain yogurt snacks than in freeze-dried strawberry yogurt snacks during storage. Freeze-dried yogurt snacks contained 11.9% fat, 57.1% carbohydrate, and 18.7% protein. In conclusion, the viability of LAB in freeze-dried yogurt snacks depends on the temperature during freeze-drying: the higher the freeze-drying temperature, the lower the viability of LAB in yogurt snacks. The viability of LAB in yogurt snacks was also dependent on the moisture content and nutritional value.

• The Korean Journal of Food And Nutrition
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• v.10 no.4
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• pp.553-558
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• 1997

Frozen cod fillet block(7.0$\times$4.6$\times$0.6cm, 18$\pm$0.5g) was purchased from a supermarket in Taegu area. Three experimental groups of fish fillet, frozen-thawed cod fillet refrigerated at 5$^{\circ}C$(R), frozen at -2$0^{\circ}C$(F) and repeated freezing and refrigerating(RFR) every other day, were incubated at each temperature. Changes in the viable counts of mesophiles and psychrotrops, the amount of free drip and pH of cod muscle during cold storage were 6.5$\times$104 and 7.4$\times$103 CFU/g of muscle, respectively. The viable counts of cod muscle R and FRF exceeded 107 CFU/g within 8 days and 16 days, respectively, while the viable counts of cod muscle F were not exceeded 107 cells/g throughout the storage period. The viable counts of psychrotrops exceeded that of mesophiles at the end of cold storage period. The viable counts of cod muscle showed positive correlation with pH(r=0.73-0.96,the highest in RFR) during cold storage. The amount of free drip in cod muscle R, F and RFR was 27.06$\pm$9.75, 27.56$\pm$8.02 and 33.97$\pm$10.70%, respectively. The amount of free drip in RFR increased as the progress of storage.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.19 no.1
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• pp.27-35
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• 1986

In succession to the previous paper, the present study was directed to investigate the effect of keeping freshness of conger eel (Astroconger myriaster) and yellowtail (Seriola quinqueradiata) by partial freezing, and the changes in the physical properties of fish meat paste product prepared with the muscle of conger eel during storage were also examined. The results obtained are summarized as follows: The period of keeping freshness (days in which k value reaches $20\%$) of conger eel and yellowtail by partial freezing was 10 days and 6 days, respectively. VBN content in the conger eel muscle showed 39.5 mg/100g by icing for 15 days, and did not show a great change by partial freezing and freezing, while that of yellowtail muscle reached at 32 mg/100g by icing, 20 mg/100g by partial freezing and 18 mg/100g by freezing for 15 days. The lipids extracted from the muscles of both fishes by icing were remarkably oxidized than those by partial freezing. The myofibrillar protein in the conger eel muscle during storage for 9 days decreased $3\%,\;10%\;and\;11\%$ by icing, partial freezing and freezing, respectively, and that of yellowtail muscle did $16\%,\;10%\;and\;4\%$ by icing, partial freezing and freezing, respectively. On the other hand, the alkali-soluble protein in both fishes increased with storage time. Gel strength of fish meat paste product prepared with the muscle of conger eel decreased to $35\%$ by icing, $74\%$ by partial freezing and $76\%$ by freezing for 10 days compared to control, and the expressible water increased 1.6 times, 1.2 times and 1.1 times by icing, partial freezing and freezing, respectively, as much as that of control product.

• International Journal of Highway Engineering
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• v.7 no.2 s.24
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• pp.87-95
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• 2005

To prevent the lowering of structural capability due to freezing and thawing in cold winter, numerous researches on frost heaving have been performed. As the result, the freezing index contour map of the Korea peninsula has been made for the design of the anti-freezing layer of pavements. However, the validity of the anti-freezing layer needs to be evaluated because systematic investigations on the variation of freezing depth with the thickness and material types of pavement layers and the configuration of the ground have been rarely performed. The freezing index of the Korea Highway Corporation test road site was calculated and the freezing depths of the concrete and asphalt pavements of the test road were investigated using the ambient and pavement temperature and water content. In addition, the investigated freezing depths were compared to the values estimated by existing freezing depth models. This is the preliminary study on the freezing-related data measured at the test road. The results with higher reliability will be produced by the long-term accumulation of the data and the analysis on it.

• Food Engineering Progress
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• v.14 no.4
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• pp.328-334
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• 2010

Recently the enhancement and development of makgeolli processing to extend shelf life are constantly accomplished. However, the standardization to restrict microorganisms including cold chain system and sterilizing system has not been established yet. Therefore, the objective of this study was to investigate the storage stability of makgeolli using quick freezing (QF) and slow freezing (SF) storage methods. The storage period was 40 days. Every 10 days, the samples were taken from the quick and slow freezing storage chamber. And then the samples were put into a $10^{\circ}C$ refrigerator for 24 hr to thaw them. The final samples were evaluated for chemical experiments and microbial cell counts. As a result, reducing sugar content was dramatically increased after 10 days for all of the samples. In titratable acidity and color values case, these values did not significantly change by storage time. In case of lactic acid bacteria and yeasts for all the samples, there was a decreasing tendency with storage time. Especially, in case of lactic acid bacteria, the changes from the beginning microbial cell counts ($4.1{\times}10^7$ CFU/mL) for QF and SF after 20 days were $3.6{\times}10^6$ CFU/mL and $1.8{\times}10^4$ CFU/mL, respectively. This result showed that the freezing methods could restrict the microbial growth in makgeolli.

• 한국정보통신설비학회:학술대회논문집
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• 2008.08a
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• pp.545-548
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• 2008

불포화 폴리에스테르 수지를 결합재로 사용하여 제작되는 폴리머 콘크리트 맨홀은 조기 고강도 발현, 접착성. 수밀성, 내동결융해성, 내약품성, 내마모성, 전기절연성이 우수하여 프리캐스트로 제작되는 많은 통신용 맨홀에 적용되고 있다. 폴리머 콘크리트의 결합재로 사용되는 불포화 폴리에스테르 수지는 열경화성수지로써, 자체 발열에 의해 거푸집을 탈형할 정도의 초기 경화 반응이 나타나지만, 구조물로서 요구되는 소요 강도를 발휘하기 위해서는 적정 온도에 의한 추가 양생이 반드시 필요하다. 이에 본 논문에서는 폴리머 콘크리트의 휨 강도 시험용 공시체를 사용하여, 다양한 양생 온도 조건 및 양생기간에 따른 휨 강도를 측정하였으며, 이를 가열 촉진 양생에 의한 휨 강도와 비교하여 콘크리트가 소요 강도를 발휘하는데 요구되는 적정 온도와 기간을 도출하였다. 이를 통해 폴리머 큰크리트 맨홀의 품질 확보를 위한 생산 관리와 제품 검사를 체계적이고 효율적으로 수행할 수 있도록 하였다.