• 한국농공학회:학술대회논문집
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• 한국농공학회 1998년도 학술발표회 발표논문집
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• pp.161-166
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• 1998

This experiment was on purpose to estimate freezing and thawing resistance concering with developing rice straw ash concrete which were mixed rice straw ash to cement as ratio of cement weight. Freezing and thawing test was done by Method A of KS F 2456. It could estimate change of original mass, pulse velocity and dynamic modulus of elasticity during test. Test results showed that 5% filled rice straw ash concrete had the highest durability factor(DF) as 86 and from 5% to 7.5% filled rice straw ash concrete showed higher DF than normal cement concrete.

• 한국초전도ㆍ저온공학회논문지
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• 제3권2호
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• pp.77-83
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• 2001

The thermal characteristics of solid nitrogen are investigated by experiment and analysis for the purpose of evaluating its feasibility as a cooling medium for HTS (high T$_{c}$ superconductor) magnets. A cryostat to refrigerate a liquid-nitrogen container well below its freezing temperature with a 2-stage GM cryocooler is designed and constructed. The spatial distribution of temperature is measure as a function of time during the freezing and melting processes. from which the thermal diffusivity of solid nitrogen can be approximately calculated. the freezing process is formulated and solved by the integral method with an assumption of phase equilibrium at the solid-liquid interface and experimental observation. It may be concluded that the thermal diffusion in solid phase is much slower than in liquid and the degree of super-saturation is quite severe in the solidification of nitrogen.n.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2010년도 춘계 학술대회 제22권1호
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• pp.383-384
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• 2010

본 연구에서는 방동제의 동결온도 측정방법 및 국내에서 시판되는 방동제의 동결온도 특성을 조사하였다. 방동제 종류는 아질(초)산계 방동제를 대상으로 하였으며, 방동제와 물의 희석비는 각 종류별 3개 수준으로 하였는데, 방동제와 물의 희석비가 1:3의 경우 $-4.9{\sim}-6.3^{\circ}C$, 1:5의 경우 $-3.3{\sim}-4.2^{\circ}C$, 1:7의 경우 $-2.1{\sim}-3.3^{\circ}C$의 범위를 나타내었다.

• 한국수정란이식학회지
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• 제10권3호
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• pp.243-250
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• 1995

Frozen storage of the oocytes has been used in a few mammalian species including mouse, hamster, human and cattle. However, frozen4hawed oocvtes show different sperm penetration on the levels of the zona pellucida and the plasma memhrane when compared with fresh oocytes. To elucidate biological changes occurring during freezing and thawing, we examined the kinetics of sperm penetration into frozen-thawed hamster oocytes. Oocytes obtained from superovulated female golden hamsters were frozen-thawed in an autofreezer according to an established method. Fresh and frozen4hawed oocytes were fertilized in vitro with capacitated hamster spermatozoa after removing the zona pellucida. The oocytes were examined at 1, 2, 3 and 6 h postinsemination. Sperm penetration found to be 1 h delayed in frozen-thawed oocytes. Other parameters such as degree of polyspermy and decondensing sperm heads were not affected by freezing and thawing. The results suggest that freezing and thawing may cause changes in the egg membrane surface and subsequently which leads to delay in the sperm-egg fusion.

• 한국방재학회:학술대회논문집
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• 한국방재학회 2008년도 정기총회 및 학술발표대회
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• pp.457-460
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• 2008

CFRP plates has been established as an effective method for rehabilitation and strengthening of concrete structures. The CFRP reinforcements are bonded to beams and slabs using structural adhesives. Adhesive strength can be affected by environmental exposure. During freezing-and-thawing cycling, temperature-induced stresses in the adhesive layer, due to differential thermal expansion between the CFRP and the substrate concrete, may lead to bond damage and contribute to or cause premature CFRP composite separation. This paper presents the results of experimental program undertaken to investigate the effects of freeze-thaw cycling (from -18 to $4^{\circ}C$) on the behavior and failure characteristics of RC beams strengthened in shear with CFRP plate using acoustic emission (AE) technique.

• Clinical and Experimental Reproductive Medicine
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• 제19권2호
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• pp.163-168
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• 1992

This study was carried out to set up the ovum bank for ovum donation and to determine the best freezing method for human immature oocytes. Human immature follicular oocytes were cryopreserved by slow freezing and rapid thawing method. Immature follicular oocytes were treated by propanediol(PROH) solution by 2 and 4 step method in protocols A & B, respectively. In protocol C, immature oocytes were exposed to sucrose prior to treatment of PROH by 4 step method. We compared survival rate, maturation rate, and fertilization rate of immature oocytes among three protocols. Results were as follows. 1. Oocytes treated by the protocol C showed the highest survival rate( 70.3 %) and maturation rate(34.6%) after thawing. 2. Survival rate of oocytes treated by the protocol C was significantly higher than that of the protocol B after thawing(p<0.05). In conclusion, treatment of oocytes with sucrose prior to expose PROH was the best freezing method. Sucrose may have reduced the toxic effect of cryoprotectant to oocytes. We failed to induce fertilization of oocytes, which were treated by any protocols, by conventional insemination method, but obtained 28.8% fertilization rate by using partial zona dissection(PZD) method. This result suggests that micromanipulation(PZD) of the thawed oocytes before insemination will improve the fertilization rate.

• 한국도로학회논문집
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• 제14권5호
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• pp.57-65
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• 2012

PURPOSES: It is important to consider the long-term performance of concrete pavement, because concrete pavement is more exposed to the various environmental conditions than any other concrete structures. One of the several methods to evaluate the long-term performance of concrete during winter is KS F 2456. Relative dynamic modulus of elasticity shows the resistance to freezing and thawing. METHODS: To measure relative dynamic modulus of elasticity, ultra sonic is generally used. But in this study, to measure the relative dynamic modulus of elasticity, both ultra sonic and shear wave were used and then compared each other. RESULTS: The results from the measurement by ultrasonic wave and shear wave were divided into three types. Type 1 : Specimens are good and relative dynamic modulus of elasticity did not decrease until 300 cycle. Type 2 : The relative dynamic modulus of elasticity decreased from the late cycle.(about 150 cycle later) Type 3 : The relative dynamic modulus of elasticity consistently decreased from the beginning. As a result of ANOVA, there is no difference according to measuring method, in type 2 and 3. But there is a difference according to measuring method, in type 1's relative dynamic modulus of elasticity. CONCLUSIONS: It is proved that shear wave can be used to understand the damage tendency of relative freezing and thawing and to measure the relative dynamic modulus of elasticity.

• 한국수산과학회지
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• 제19권4호
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• pp.356-362
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• 1986

This experiment was designed to evaluate effects of freezing and frozen storage on survival of sanitary indicative bacteria in seafoods. Culture of bacteria such as Escherichia coli type I, Citrobacter freundii type I, Klebsiella aerogenes type I and Streptococcus faecalis was inoculated into homogenates of pollack, shrimp, and sardine frozen in a contact plate freezer at $-40^{\circ}C$ and chest freezer at $-20^{\circ}C$, stored at $-20^{\circ}C$, and then survival of the inoculated bacteria was determined over a period of 95 days. Coliform group was highly sensitive to freezing and frozen storage showing survival of about $2\%$ after 95 days of frozen storage at $-20^{\circ}C$, whereas Streptococcus faecalis was relatively resistant with $20\%$ survival rate. The sanitary indicative bacteria count was rapidly decreased in the early stage of frozen storage revealing 90 to $95\%$ loss of coliform group and 40 to $70\%$ loss in case of Streptococcus faecalis after 10 days storage. In determining recovery rate, most probable number (MPN) method gave more reproducible recovery of the tested strain than did the selected agar plate method.

• Clinical and Experimental Reproductive Medicine
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• 제26권2호
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• pp.127-135
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• 1999

Cryopreservation is able to store the surplus pre-embryos for freezing and furthermore thawing and transfer in a subsequent cycle. Cryopreserving cells which are maintaining their viability are the very complex process. This study has been carried out in order to find the effects of cryopreservation steps, freezing media and embryonic stages on the rates of viability and development of cryopreserved mouse embryos. Female ICR mice ($6{\sim}8$ weeks old) were induced to superovulate by sequential intraperitoneal injection of 5 IU PMSG and 5 IU hCG 48h apart. Mouse embryos were collected according to its developmental stage after the injection of hCG. Embryos were cryopreserved not only by cryoprotectant step (1 step${\sim}$4 step) but also in a variety of media (HTF, IVF medium, D-PBS) and cell stage. The results were as follows: There is no clear advantage in these freezing media of rapid method, but 4 cell and 8 cell of slow method (2, 3, 4 step) have advantage in D-PBS. The development of embryos according to cell stage become greater in 8 cell stage. In the treatment steps of cryopreservation, the development of embryo to blastocyst was similar among rapid method, but the development of 4 cell and 8 cell embryos to blastocyst according to slow method was better than rapid method.

• Journal of Applied Biological Chemistry
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• 제58권1호
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• pp.55-60
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• 2015

수출용 냉동딸기 제조 시 미생물학적 안전성 확보를 위한 수단으로 이산화염소수와 acetic acid 병합처리를 최적 비가열 전처리 기술로써 적용하여 -20, -70, $-196^{\circ}C$로 냉동한 후 미생물 수, 품질변화 및 관능평가를 조사하였다. 냉동방법 및 세척 처리에 따른 색도 차이는 나타나지 않았고, 비타민 C 함량은 $-70^{\circ}C$ 냉동에서 35.33 mg/100 g FW로 가장 대조구와 유사하였으며, drip loss도 $-70^{\circ}C$ 냉동이 14.39%로 가장 낮게 나타났다. 관능평가 역시 $-70^{\circ}C$ 냉동이 -20, $-196^{\circ}C$ 냉동보다 높은 점수를 받았으며, 세척처리는 비타민 C 함량, drip loss 및 관능평가에 큰 영향을 끼치지 않는 것으로 나타났다. 또한, 냉동딸기에 50 ppm 이산화염소수와 1% acetic acid를 병합 처리하여 냉동 후 미생물 수 변화를 측정한 결과, 냉동 전과 같이 병합처리 된 딸기 시료에서 미생물이 검출되지 않았다. 따라서 저장성이 높은 수출용 냉동딸기 생산을 위해서는 gas nitrogen convection chamber를 이용한 $-70^{\circ}C$에서의 급속냉동 처리가 보다 효과적인 냉동방법이며, 냉동 처리만으로는 미생물 제어가 어렵기 때문에 냉동 전 비가열 전처리를 통해서 냉동딸기의 미생물학적 안전성을 확보해야 한다고 판단된다.