• Journal of Korean Society of Forest Science
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• v.28 no.1
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• pp.31-35
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• 1975

The present study explored the rapid effect of low temperature on the freezing resistance of dehardening twigs of three apple cultivars and sweet cherry. The effect of low temperature was depending upon the thawing treatment following to the low temperature treatment. When the freezing temperature to $-9^{\circ}C$ for three hours followed by thawing treatment ($5^{\circ}C$) was given repeatedly twice, the low temperature increased apparently the cold hardiness of apple and cherry by 3 to $9^{\circ}C$. On the other hand, when the freezing temperature ($-9^{\circ}C$) for ten hours was pretreated without thawing, the low temperature appeared not affecting the cold resistance of the twigs. The role of freezing-thawing temperature cycle in nature was discussed as a signal of environmental stimulus to which dehardening plant may be responding to increase their cold hardiness so as to adapt against the damage of late frost in early spring.

• Journal of Ginseng Research
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• v.20 no.2
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• pp.179-183
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• 1996

One exotherm was detected in the intact ginseng seeds containing more than 35% water, but in seeds with 20% there was no exotherm. The shapes of exotherm were remarkably uniform without relation to water content above 35%. The temperature at the initiation of freezing varied from -3.5$^{\circ}C$ to -9.6$^{\circ}C$ with the different water content in the seeds, and the Initial temperature of freezing delayed with the decrease of water content. The resistance damage at low temperature appeared in order of maln body, rhizome, lateral root of 3-year-old yearling rhizome, and fine root of 3-year-old. Ginseng roots didn't receive any damage at -5$^{\circ}C$ for 24 hours. Otherwise they received serious damage below -1$0^{\circ}C$ even for 5 hours'exposure. Hence, alternative low temperature gave more severe damage compared to constant low temperature. This result suggests that the Possibility of receiving injury at low temperature was higher during the thawing season of the early spring than in the winter.

• Journal of Biosystems Engineering
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• v.40 no.3
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• pp.271-276
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• 2015

Purpose: Quick freezing is widely used in commercial food storage. Well-known freezing techniques such as individual quick freezing require a low-temperature coolant and small cuts for the heat-transfer efficiency. However, the freezing method for bulk food resembles techniques used in the 1970s. In this study, electromagnetic (EM) heating was applied to improve the quick freezing of bulk food. Methods: During freezing, the surface of food can be rapidly cooled by an outside coolant, but the inner parts of the food cool slowly owing to the latent heat from the phase change. EM waves can directly heat the inner parts of food to prevent it from freezing until the outer parts finish their phase change and are cooled rapidly. The center temperature of garlic cloves was probed with optical thermo sensors while liquid nitrogen (LN) was sprayed. Results: When EM heating was applied, the center cooling time of the garlic cloves from freezing until $-10^{\circ}C$ was 48 s, which was approximately half the value of 85 s obtained without EM heating. For the white radish cubes, the center cooling time was also improved, from 288 to 132 s. The samples frozen by LN spray with EM heating had a closer hardness to the unfrozen samples than the samples frozen by LN only. Conclusions: The EM heating during quick freezing functions to maintain the hardness of fresh food by reducing the freezing time from 0 to $-10^{\circ}C$.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.4 no.3
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• pp.175-182
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• 1992

Freezing of the binary solution ($H_2O-NaCl$) saturating a packed bed of spheres is investigated experimentally. The system is cooled through its top surface, and the bottom is maintained at a temperature above the liquidus. Experiments are performed on the hypolutectic side, and the cold wall temperature is lower than the eutectic point. The effects of initial mixture concentration, superheat and glass bead diameter on temperature and concentration distributions are investigated. Supercooling was observed only at early times of the freezing process for experiments with 5% initial salt concentration. Flow visualization experiments and mushy-liquid interface position observations revealed natural convection in the liquid region. Remelting phenomena was not observed at both the solid-mushy and mushy-liquid interfaces.

• Korean Journal of Animal Reproduction
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• v.21 no.3
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• pp.287-292
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• 1997

This study was carried out to investigate the effects of concentration and kinds of cryoprotectants, equilibraction time, thawing temperature and time, sucrose concentration on the survival rates of frozen bovine demi-embryos. The bovine demi-embryos following dehydration by cryoprotectants a various concentration of sucrose were freezed by cell freezer and thawed in 3$0^{\circ}C$ water bath. Survival and in vitro developmental rates was defined as development rates on in vitro culture or FDA-test. The results are summarized as follows : 1. The high survival rates of demi-embryos after frozen-thawing in freezing medium was attained 2.0M glycerol. The high survival rates of demi-embryos after frozen-thawing in freezing medium was obtained using single cryoprotectant(25.0~30.0%) than mixed cryoprotectants(16.7~19.0%). 2. The survival rates of demi-embryos after frozen-thawing in freezing medium added 1.5M, 2.0M glycerol＋0.25M sucrose(37.5~33.3%) were higher survival rates than those of sucrose concentration of 0.50, 0.75M(12.5~26.7%). 3. The equilibration time on the survival rates of demi-embryos was attained after short period of time(30.0~35.0%) in the freezing medium higher than long period of time(21.1%). 4. The thawing temperature on the survival rates of demi-embryos was attained at 3$0^{\circ}C$ of thawing temperature(26.7~40.0%) higher than $25^{\circ}C$ or 37$^{\circ}C$ of thawing temperature(13.3~20.0%). 5. The thawing time on the survival rates of demi-embryos was attained at 1~5 minutes of thawing time(26.7~33.3%) in the freezing medium higher than 10 minutes of thawing time(13.3~18.8%).

• Journal of Advanced Marine Engineering and Technology
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• v.41 no.3
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• pp.176-181
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• 2017

This study attempted to examine a method of anti-freezing on a plate-type heat exchanger in a low-temperature environment. Freezing condition was observed after ultrasonic waves were generated. Data were recorded to determine the optimal conditions for freezing. Ethylene glycol, which is commonly used in antifreeze formulations, was used as the brine, and the temperature was varied between -8 and $-16^{\circ}C$. The water for freezing provided by the thickness of 1-3 mm. In addition, experiments were conducted by adjusting the output to identify the changes that occurred due to the incidence of ultrasonic energy. The results of the anti-freezing effect were brine temperature, freezing thickness, and frequency band of ultrasonic waves.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.24 no.5
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• pp.340-344
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• 1991

On heating and fleering food-stuffs, it is very important to obtain informations about thermophysical properties of fishes for designing of freezing and heating equipment and analyzing of physico-chemical reaction during storage. It is particularly necessary to measure denaturation enthalpy, temperature, latent heat of freezing, activation energy, enthalpy, entropy and free energy on freezing and heating rate. In this study, DSC was used to study effects of freezing and heating rate on thermophysical properties and denaturation temperature on scanning rate $2.5-10.0^{\circ}C/min$. On increasing scanning rate, denaturation temperature of protein and lipid incresed and freezing point, activation energy, enthalpy, entropy were decreased. In freezing process free energy of fishes were found to be $14.2-18.9 kcal/mol$.

• International Journal of Industrial Entomology and Biomaterials
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• v.47 no.2
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• pp.126-133
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• 2023

Genetic resources of mulberry trees are commonly preserved as trophosomes, which are vulnerable to environmental factors, such as natural disasters, diseases, and pests. This study establishes a basic protocol for ultra-low temperature cryopreservation of mulberry trees using a two-step freezing process. The procedure was established using the "Daeshim" variety and then tested on genetic resources from 24 other mulberry varieties. Samples were first dried to a moisture content of 33-43% in a low-temperature forced-air chamber at -5 ℃, then slowly frozen from -5 ℃ to -20 ℃, and preserved in liquid nitrogen (-196 ℃). To determine the regeneration rate, isolated dormant buds were inoculated into MS basal medium, and grown shoots were grafted onto 1-year-old rootstock via chip budding and then cultured. After freezing in liquid nitrogen, the "Daeshim" variety exhibited a survival and regeneration rate of more than 70% and 50%, respectively. Applying the two-step freezing process to genetic resources from 24 mulberry species yielded average survival and regeneration rates of 85.3% and 75.5%, respectively. Morus alba showed survival and regeneration rates of 100%, confirming the efficacy of the two-step freezing method. These results indicate the high feasibility of ultra-low-temperature cryopreservation through two-step freezing of dormant buds from mulberry genetic resources. Additional research is required into the variations in regeneration rates with freezing period in liquid nitrogen.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.1164-1171
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• 2010

Korea is considered to be a seasonal frozen soil area that is thawed in the spring, and most of the area is frozen in winter as to the characteristic of geography. In the current design codes for anti-freezing layer, the thickness of anti freezing layer is calculated by freezing depth against the temperature condition. Therefore, they have a tendency of over-design and uniform thickness without the considerations of thermal stability, bearing capacity and frost susceptibility of materials. So, it is essential for studying the appropriateness and bearing capacity besides the seasonal and mechanical properties of pavement materials to take a appropriate and reasonable design of the road structure. In this research, the evaluation of frost susceptibility on subgrade, ant-freezing layer, sub base was conducted by means of the mechanical property test and laboratory field road model downed scale experiment. The temperature, heaving amount, heaving pressure and unfrozen water contents of soil samples, the subgrade, anti-freezing layer, sub base soils of highway construction site, were measured to determine the frost susceptibility.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.11a
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• pp.543-550
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• 2000

Rock slopes along the road or railroad are affected by temperature and therefore experienced iterative freezing-thawing process between winter and early spring. The purpose of this study is to analyze the stability of rock slopes which are influenced by the deterioration due to the freezing-thawing. The analysis is the homogenization method which evaluates the strength property of discontinuous rock mass, and as a strength failure criterion, Drucker-Prager failure criterion is used. The deterioration property of real rock is obtained by a freezing-thawing laboratory test of tuff and this property of deterioration is quantitated and used as a basic data of stability analysis for rock mass. To evaluate the deterioration depth due to the freezing-thawing in situ rock slope, one dimensional heat conductivity equation is used and as the result I can find that the depth of which is affected by a temperature. After the freezing-thawing depth of model slope is determined, we analyze the pattern of rock mass stength value of rock slope model which excesses the limit of self-load.