• Journal of the Korea Organic Resources Recycling Association
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• v.18 no.2
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• pp.93-100
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• 2010

In this study, ways to help anaerobic digestion were studied and waste activated sludge were pretreated by grinding, thawing after freezing and grinding after freezing. The volumes of grinding sludge, thawing after freezing and grinding after freezing were decreased 2.08 times, 3.37 times, 3.54 times compared to the volume of sludge respectively and the larger decline in the sludge has been grinding after freezing, thawing after freezing, and grinding. In addition, when the concentrations of SCOD, SBOD and protein were compared, the concentration of freezing sludge was higher than others and the grinding after freezing method seems to be the highest concentration. When the TS, VS removal rates were compared, thawing after freezing method seems to be higher than others method. From these results, grinding after freezing method is very effective for the pretreatment of sludge and it can be expected grinding after freezing method can be an alternative method for prohibiting ocean dumping of sludge after 2012.

• Korean Journal of Food Science and Technology
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• v.20 no.2
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• pp.280-286
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• 1988

Freezing is becoming incressingly important in the food industry as a means of food preservation since the turn of the century. For quality, processing and economic reasons, it is important to predict the freezing time for foods. A number of models have been proposed to predict freezing time. However, most analytical freezing time prediction techniques apply only to specific freezing conditions. Therefore, it is necessary to develop an improved analytical method for freezing time prediction under various conditions. The objectives of this study, by reviewing previous experimental data obtained by uncertain freezing condition and thermo-physical data, were to develop simple and accurate analytical method for prediction freezing time, and to obtain the freezing time of various foodstuffs by still air freezing and immersion freezing method. The result of this study showed that the proposed method offered better results than the other complex method compared.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.38 no.4
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• pp.555-565
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• 2018

Nowadays, the artificial ground freezing (AGF) method has been used in many geotechnical engineering applications such as temporary excavation support, underpinning, and groundwater cutoff. The AGF method conducts the freezing process by employing a refrigerant circulating through a set of embedded freezing pipes to form frozen walls serving as an excavation support and cutoff wall. Two refrigerants of brine with the freezing temperature of $-20{\sim}-40^{\circ}C$ and liquid nitrogen with the freezing (evaporating) temperature of $-196^{\circ}C$ are commonly being used in geotechnical applications. This paper performed a series of field experiments to evaluate the freezing rate of marine clay in application of the AGF method. The field experiments consisted of the single freezing-pipe test and the frozen-wall formation test by circulating liquid nitrogen, which is a cryogenic refrigerant, into freezing pipes constructed at a depth of 3.2 m in the ground. The temperature of discharged liquid nitrogen was maintained through the automatic valve, and the temperature change induced by AGF method was measured at the freezing pipes and in the ground with time. According to the experimental results, the single freezing-pipe test consumed about 11.9 tons of liquid nitrogen for 3.5 days to form a cylindrical frozen body with the volume of about $2.12m^3$. In addition, the frozen-wall formation test used about 18 tons of liquid nitrogen for 4.1 days to form a frozen wall with the volume of about $7.04m^3$. The radial freezing rate decreased with increasing the radius of frozen body because the frozen area at a certain depth is proportional to the square of the radius. The radial freezing rate was formulated as a simple equation.

• Journal of Veterinary Clinics
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• v.8 no.2
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• pp.183-190
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• 1991

Pellet and straw methods in canine semen freezing are compared with respect to motility, viability and acrosome demage of sperm during each of the two major processing steps, to prior-freezing and to frozen-thawing. Senen was extended with a tris-buffered egg yolk contained 4% glycero1 Pellet freezing in the hole of dry ice and straw freezing on the surface of liquid nitrogen were carried out, respectively. The frozen semen 10 days after storage in liquid nitrogen container. wao thawed. In the comparison of two freezing methods, the straw freezing method with 42.7% in motility. 49.2% in viability and 0.186 acrosome score after thawing seems to be superior to the pellet freezing method with 31.2%, 34.5% and 0.314%, respectively. Sperm motility of processing step to frozen-thawing against decrease rate 12.67% to Prior freezing appeared of 33.84% and 49.37% in straw and pellet freezing and increase of 0.02 in acrsomal score to prior freezing appeared of 0.08 and 0.21 in straw and pellet freezing method to frozen-thawing

• Journal of the Korea institute for structural maintenance and inspection
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• v.5 no.1
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• pp.131-140
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• 2001

In general, the deterioration induced by the freezing and thawing cyclic in concrete structures often leads to the reduction in concrete durability by the cracking or surface spalling. If it can prediction of concrete deterioration subjected to cyclic freezing and thawing, we can rationally do the design of mix proportion in view of concrete durability and the maintenance management of concrete structures. Therefore in this study a prediction method of deterioration for concrete structures subjected to the irregular freezing and thawing is proposed from the results of accelerated laboratory freezing and thawing test using the constant temperature condition and the in-situ weathering data. Furthermore, to accurately predict the concrete deterioration, a method of modification for the effect of hydration increasing during rapid freezing and thawing test is investigated.

• Journal of Biosystems Engineering
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• v.33 no.1
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• pp.21-29
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• 2008

In this study, the thermal properties of peeled chestnuts were measured, and the mathematical prediction model of freezing time was also developed for various interior positions from center to rind (surface). The measured thermal properties were showed that heat conductivity is $0.43W/m^{\circ}C$, specific heat is $2.7206J/m^3^{\circ}C$, latent heat is $216.9{\times}10^6J/m^3$ and freezing point is $-2.8^{\circ}C$. The entire process about reaching to the freezing time of peeled chestnuts was analyzed with its each regular depth position using the finite difference method (FDM) based on computer simulation. In case of regular freezing temperature, it was showed an that surface (rind) position is more rapidly reached into the freezing point rather than the center position, and also reaching time to the freezing point is more fast at the lower freezing temperature. Comparison results between simulation and experiments showed linear relationship. In regularly varying condition for freezing temperature, this method would give an information to predict a freezing time of the interior points for peeled chestnuts and more similar agricultural products.

• Journal of the Korea Concrete Institute
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• v.11 no.4
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• pp.117-127
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• 1999

In concrete incorporating high volume ground granulated blast-furnace slag that has frozen at early age, to evaluated the results of resistance to freezing and thawing is very difficult because the hydration of the concrete increases over the duration of rapid freezing and thawing test. Hence, the dynamic modulus of elasticity of specimens after freezing and thawing will be favorable results unless the hydration effect is taken into consideration. In this study, a method of evaluating to the resistance to freezing and thawing of concrete subjected freezing at early age, in which the effect of hydration is modified for its increase during rapid freezing and thawing test, is investigated.

• Food Science and Preservation
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• v.10 no.4
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• pp.459-465
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• 2003

This study was carried out to investigate the changes in internal pressure according to various freezing methods, as basic research to protect the destruction of tissues when fruits and vegetables are frozen. The rate of weight loss, caused by the freezing of fruits and vegetables, was found to be the least (0.44∼1.38％) when the immersion freezing method was applied. The difference in the rate of weight loss was the highest when freezing methods were applied to watermelon, and the freezing rate of watermelon whose moisture contents were greater have relatively greater influence on the weight loss. The difference in internal pressures was the least and caused by the volume increase and decrease, when pear, apple, and melon were frozen using the immersion freezing method, while the diffeyence the greatest when the air-blast freezing method was used. As the freezing rate was greater, the internal pressure was less. However, the internal pressure of strawberry and watermelon was the greatest when the immersion freezing method was applied. Frozen without using the thermal equalizing method, the change in internal pressure of fruits was about 2 psig. In contrast, the internal pressure of watermelon applied with the thermal equalizing method was changed in a way similar to that of watermelon not applied with the method, but the former generated a certain level of internal pressure and maintained a significantly low level of internal pressure (about 1.3 psig). When thawed, the internal pressure of samples to which the thermal equalizing method was applied was less than that of what the thermal equalizing method was not applied to. In comparison with the application of multi-step thermal equalizing method, 3∼4 times of application of the thermal equalizing method to the freezing resulted in the decrease of fluctuation range of internal pressure.

• Journal of Embryo Transfer
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• v.23 no.1
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• pp.19-24
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• 2008

The purpose of this study was to compare the efficiency of slow freezing with that of vitrification method for the cryopreservation of human embryos. Human embryos were derived from in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) and the mixed solution of propanedial (1.5, 1.0, 0.5M PROH) and sucrose (0.1M), ethylene glycol (7.5, 15%), dimethyl sulfoxide (7.5, 15% DMSO), sucrose (0.5, 1.0M) and SPS (Serum Protein Substitute) was used for a cryoprotectant for slow freezing and vitrification solution, respectively. Rates of recovery after thawing, morphological normality, post-thaw viability, arrest, morphological abnormality and preimplantation development were compared between two protocols. After freezing-thawing, recovery and survial rate of slow freezing was (88.6% and 73.4%), whereas vitrification was (99.2% and 96.2%) (p<0.05). The arrest rate of slow freezing was significantly lower compared with those of vitrification(8.7% vs 29.9%) (p<0.05). Preimplantation development to the 2-cell (83.8% vs 67.7%), 4-cell (69.0% vs 47.2%) and 8-cell (62.4% vs 37.8%) stages 24, 48 and 72 h after thawing, respectively, were higher in the slow freezing than the vitrification. After slow freezing and vitrification of human embryo at 2-8cell stage, the rate of recovery rate, survival rate and partial damage rate were 92.0% vs 100%, 80.4% vs 96.2% and 52.2% vs 19.0%, respectively. And partial damage rate was significantly lower than those of slow freezing method (p<0.05). These results demonstrate that a slow freezing using PROH is more efficient than a vitrification for cryopreserving the human zygotes, although the vitrification yielded better recovery, survival and partial damage of frozen-thawed 2-8 cell stage embryos than slow freezing method.

• Culinary science and hospitality research
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• v.14 no.2
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• pp.286-292
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• 2008

The purpose of this study was to examine the effects of freezing and thawing methods on the quality of pork meat. The freezing methods for pork meat were the cryogenic freezing with liquid nitrogen gas, fast freezing at $-70^{\circ}C$ and normal freezing at $-20^{\circ}C$. The thawing methods were tested on low temperature thawing at refrigerative temperature($4^{\circ}C$), room temperature($20^{\circ}C$), high temperature($60^{\circ}C$) and using microwave. The quality of pork meat frozen by cryogenic methods was better than those of fast and normal freezing methods. The cooking hardness of pork meat frozen by cryogenic method showed the highest value as 1,898 g. In case of fast freezing, the hardness of pork meat was 1,472 g and that of normal frozen pork meat was 1,541 g. The high cooking hardness value of cryogenic frozen pork meat showed that the cryogenic freezing method made less freeze damage like textural softness. The drip-loss of pork meat thawed at refrigerative temperature($4^{\circ}C$), room temperature($20^{\circ}C$), high temperature($60^{\circ}C$) were shown lower than that of microwave thawing. The cooking hardness of pork meat that was thawed by microwave showed the lowest value among the thawing methods. The cryogenic freezing was the most useful freezing method for preserving quality, decreasing the freeze damage of pork meat. And thawing at refrigerative temperature was the most effective method to prevent quality loss and weight loss by drip-loss.