• 설비공학논문집
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• 제17권5호
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• pp.459-467
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• 2005

The effect of anti freezing solution liquid film on the frost prevention is experimentally investigated. It is desirable that the antifreezing solution spreads widely on the heat exchanger surface forming thin liquid film to prevent frost nucleation and reduce the thermal resistance across the film. A porous layer coating technique is adopted to improve the wettedness of the anti freezing solution on a parallel plate heat exchanger. The antifreezing solution spreads widely on the heat exchanger surface with 100 $\mu$m thickness by the capillary force resulting from the porous structure. It is observed that the antifreezing solution liquid film prevents a parallel plate heat exchanger from frosting. The reductions of heat and mass transfer rate caused by thin liquid film are only $1\~2\%$ compared with those for non-liquid film surface.

• 한국축산식품학회지
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• 제38권5호
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• pp.959-969
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• 2018

This study investigated the effects of deep freezing and storage temperature ($-50^{\circ}C$, $-60^{\circ}C$, and $-80^{\circ}C$) on the quality and freshness of lamb. To compare the qualities of deep frozen and stored lamb, fresh control and normal freezing conditions ($-18^{\circ}C$) were adopted. As quality and freshness parameters, drip loss (thawing loss and cooking loss), water-holding capacity (WHC), texture profile analysis (TPA), thiobarbituric acid reactive substances (TBARS), and total volatile basic nitrogen (TVBN) were evaluated during 5 months of storage. Temperature influenced the drip loss and WHC, and deep freezing minimized the moisture loss during frozen storage compared to the normal freezing condition. Lamb frozen and stored at deep freezing temperature showed better tenderness than that stored in normal freezing conditions. In particular, lamb frozen at lower than $-60^{\circ}C$ exhibited fresh lamb-like tenderness. Regardless of temperature, evidence of lipid oxidation was not found in any frozen lamb after 5 months, while TVBN was dependent on the applied temperature. Therefore, this study demonstrated that deep freezing could potentially be used to maintain freshness of lamb for 5 months. From the quality and economic aspects, the freezing and storage condition of $-60^{\circ}C$ is estimated as the optimum condition for frozen lamb.

• 정보처리학회논문지:컴퓨터 및 통신 시스템
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• 제4권9호
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• pp.307-314
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• 2015

최근 보조기억장치 스토리지 시장 추세는 HDD와 SSD가 혼용되어 사용되고 있다. 미래에는 HDD보다 SSD가 보조기억장치 역할로 더욱 많이 사용될 것으로 예상되고 있다. SSD 기술이 발달하면서 이를 효율적으로 사용하기 위해 TRIM 명령기법이 나오게 되었다. TRIM 명령기법은 과거 SSD의 문제점인 Freezing 현상을 해결하기 위해 나온 명령으로 운영체제와 SSD가 협동하여 작동한다. TRIM 명령기법은 사용자가 데이터를 삭제하였을 때 SSD 내부에서도 실제로 삭제하는 기법으로 유휴시간에 수행한다. 하지만, 디지털 포렌식 관점에서 본다면 디지털 범죄는 매년 급증하지만 데이터 미복구로 인한 검거율은 미흡하다. 본 논문에서는 기존 TRIM 명령의 장점인 안정성(Freezing Solution)과 쓰기 속도를 최대한 지원하며 선별적으로 데이터를 관리하여 삭제하는 기법을 제안한다. 실험을 통해 기존 기법과 선별된 기법의 성능을 측정하여 검증한다.

• 한국수정란이식학회지
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• 제12권2호
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• pp.141-149
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• 1997

This study was carried out to investigate the effect of vitrification and slow freezing methods on the post-thaw developmental rate of rabbit zygotes. After exposing rabbit zygotes in EFS solution for 0.5, 1, 2, 3 and S min at room temperature, they were washed with 0.5 M sucrose solution, D-PBS and TCM-199 and then cultured in TCM-199 plus 10% FBS with bovine oviduct epithelial cells(BOEC) to examine whether the cryoprotectant induced injury during the various exposure periods. The embryo development rates to hatched blastocyst after exposing in EFS solution for 3 and 5 min(40.0 and 16.7%) were significantly lower than in 0.5, 1 and 2 min(63.0, 72.0 and 54.5%), respectively. The post-thaw development rates to hatched blastocyst were significantly(P<0.05) higher in in vivo morula with intact mucin coat(85.2%) and mucin seperated morula(77.8%) than those of in vitro morula(58.5%) and zygote(5.9%), hut no difference was shown between in vitro morulae and mucin separated morula. The cryoprotectant dilution procedures showed no effects on the post-thaw development rates to hatched blastocyst under the present culture conditions. The post-thaw development to hatched blastocyst in the rabbit zygotes was not significantly different between the slow freezing(12.8%) and vitrification(5.9%). These results indicated that the rabbit frozen zygotes could he successfully developed in vitro to hatched blastocysts, though their developmental rate was very low, compared with morula stage embryos, in either vitrification or slow freezing procedure under the present conditions.

• 설비공학논문집
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• 제19권9호
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• pp.647-653
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• 2007

In dynamic ice storage system(DISS), ice slurry is formed not only from solution freezing by mechanical removing parts but also supercooled solution. However, in order to perform continuous ice formation in the system without mechanical moving parts, supercooled aqueous solution should be formed stable through cooling heat exchanger and be dissolved uniformly in storage tank. In previous study, the time of ice slurry increased as the pressure of the cooling heat exchanger(PHX) increased. In this study, a cooling experiment of an ethylene glycol 7mass% solution was performed with various inlet temperature of the PHX, which has constant brine inlet temperature of $-7^{\circ}C$. The temperature in the storage tank maintained to freezing point of the solution. At results, the time of ice slurry formation increased as the supercooling degree decreased and the cooling rate increased.

• 설비공학논문집
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• 제14권12호
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• pp.1063-1070
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• 2002

To resist ice adhesion on cooling wall is concerned to continuous ice formation in thermal storage system. In this study, ice slurries were formed with two ecological aqueous solution, one is ethanol+silanol and the other is propylene glycol+silanol. By freezing under stirring the solution of $300m\ell$ in a stainless steel vessel which was immersed and cooled in a temperature controlled bath, the shape of ice slurry and the strength of ice adhesion on wall was observed with measuring the temperature and stirring load variation. As the concentration is smaller and the supercooling degree is larger, the ice adhesion is easy to occur. When the stirring load is larger than$ 2.1\times10^{-5}W$, the ice adhesion occurred.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.530-533
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• 2008

Refrigerators have some frost related problems in a freezing compartment. The frost formation in the refrigerator gives customers a bad impression concerning quality problems. Therefore, many engineers have been studying the optimum solution to avoid frost formation. But the problem of frost formation is very complex and hard to approach to the answer. The frost generation of a household refrigerator have been widely known that is closely related to the distribution of temperature inside the compartment. The distribution depends on the cold air circulation inside the refrigerator. So frost problem can be reduced and energy consumption efficiency also improved through optimization of air flow fields inside the freezing compartment. In this paper, numerical simulation has been carried out to check fluid flow. The variation of temperature at the walls was measured and quantitative analysis of frost generated from the freezing compartment was carried out. Through comparison between simulation and experiment, some correlation revealed.

• Current Research on Agriculture and Life Sciences
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• 제6권
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• pp.163-169
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• 1988

본 연구는 식품의 동결시 동결기구의 설계 및 동결에너지의 효율적인 운용등을 위하여 동결상태에서 과일쥬스의 농도 및 온도변화에 따른 밀도변화를 예측하기 위하여 수행되었다. 10, 15, 20, 25, 30, 35, 40%농도의 Orange Juice, Apple Juice, Grape Juice 및 Sucrose Solation을 시료로 하여 온도강하에 의해 동결팽창되는 부위를 제거하므로써 거기에 따른 무게변화를 $-5^{\circ}C$에서 $-40^{\circ}C$까지의 온도범위에서 $5^{\circ}C$ 간격으로 각각 측정하여 밀도를 산출하였다. 그리고, Heldman의 식을 이용하여, 위의 농도와 온도범위에서 각 과일쥬스와 Sucrose Solution의 Unfrozen water fraction을 계산하였다. 실험을 통해 측정된 밀도데이타와 Unfrozen water fraction 데이타를 최적화 컴퓨터 프로그램을 이용하여 10%에서 40%까지의 농도범위와 $-5^{\circ}C$에서 $-40^{\circ}C$까지의 온도범위에서 Orange Juice, Apple Juice, Grape Juice 및 Sucrose Solution의 밀도를 예측할 수 있는 모델을 수립하였다.

• Clinical and Experimental Reproductive Medicine
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• 제46권2호
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• pp.67-75
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• 2019

Objective: Sperm cryopreservation has been widely used in assisted reproductive technology, as it offers great potential for the treatment of some types of male infertility. However, cryopreservation may result in changes in membrane lipid composition and acrosome status, as well as reductions in sperm motility and viability. This study aimed to evaluate sperm DNA fragmentation damage caused by conventional freezing using the sperm chromatin dispersion test. Methods: In total, 120 fresh human semen samples were frozen by conventional methods, using SpermFreeze Solution as a cryoprotectant. Routine semen analysis and a Halosperm test (using the Halosperm kit) were performed on each sample before freezing and after thawing. Semen parameters and sperm DNA fragmentation were compared between these groups. Results: There was a significant decrease in sperm progressive motility, viability, and normal morphology after conventional freezing (32.78%, 79.58%, and 3.87% vs. 16%, 55.99%, and 2.55%, respectively). The sperm head, midpiece, and tail defect rate increased slightly after freezing. Furthermore, the DNA fragmentation index (DFI) was significantly higher after thawing than before freezing (19.21% prior to freezing vs. 22.23% after thawing). Significant increases in the DFI after cryopreservation were observed in samples with both normal and abnormal motility and morphology, as well as in those with normal viability. Conclusion: Conventional freezing seems to damage some sperm parameters, in particular causing a reduction in sperm DNA integrity.

• 한국수정란이식학회지
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• 제13권1호
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• pp.1-9
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• 1998

In order to improve the cryopreservation by vitrification or slow freezing of nuclear transplant rabbit embryos, the effects of factors affecting embryo cryopreservation such as cryoprotectants, equilibration, cooling rate and post-thaw dilution on post-thaw survial and development were determined using intact embryos of morular stage. And the post-thaw development of nuclear transplanted embryos cryopreserved under the optimal conditions examined was compared between vitrification and slow freezing. The cryoprotectant solution used was ethyleneglycol-ficoll-sucrose (EFS) or ethyleneglycol-poly-vinylpyrrolidone-galactose- I (EPG- I ) for vitrification, and EPG- II for slow freezing. To examine the viability of frozen-thawed embryos, the nuclear transplanted embryos were co-cultured in TCM-199 plus 10% FBS with bovine oviduct epithelial cells(BOEC) for 24 hrs and the intact morulae were co-cultured with BOEC for 5 days and 3 days to hatching blastocyst stage in 39 ˚C 5% $CO_2$ incubator. The results obtained were as follows: Following vitrification with EFS, the post-thaw development of rabbit morulae to hatching blastocyst was significantly(P<0.05) higher in compacted stage(82.4%) than in early morular stage(60.0%). The post-thaw development of compacted morulae to hatching blastocyst was similarly high in vitrification with EFS(82.4%), EPG- I (85.0%) and in slow freezing with EPG- II (83.3%). Following vitrification with EPG- I, the post-thaw development of intact rabbit morulae to hatching blastocyst was similar as 78.0% and 85.0% in 1-step and 2-step post-thaw dilution, respectively. The post-thaw development of nuclear transplanted rabbit embryos of compacted morulae stage to hatching blastocyst was similarly 43.6% and 40.0% in vitrification with EPG- Iand slow freezing with EPG- II, respectively. These results indicated that the rabbit nuclear transplant and intact embryos of morulae stage could be well cryopreserved with either vitrification or slow freezing procedure.