• Journal of the Korean Geosynthetics Society
• /
• v.11 no.3
• /
• pp.27-35
• /
• 2012

In this paper, the frost heaving and thawing characteristics of flexible pavement structure were evaluated in the large scale freezer which have a specification of temperature range $-20^{\circ}C{\sim}10^{\circ}C$ and $3.2m(L){\times}3.2m(B){\times}2.4m(H)$ in size. The insulated steel box with the size of $0.9m(L){\times}0.9m(B){\times}0.9m(H)$ was used to simulate actual pavement road structure. The variation of temperature, frost heave amount and frost heave pressure were measured through the instrument of TDS-602 data logger. LFWD (light falling weight deflectometer) was used to determine the change of deflection due to the frost heaving and thawing. Furthermore, the influence of aggregate layer to the freezing of the subgrade soil was studied to verify the function and effectiveness of the anti-freezing layer.

• Food Science and Preservation
• /
• v.17 no.4
• /
• pp.507-512
• /
• 2010

The effects of pretreatment by freezing on juice expression and drying characteristics of Prunus mume fruit were investigated. Fresh fruit slices were frozen at $-20^{\circ}C$, thawed, and then either pressed (to yield juice) or dried. Fresh fruit slices were used as controls. Both juice yield and drying rate were higher when pre-frozen fruit was tested, compared to fresh fruit. The L and b color values were lower in the juice and dried powder of pre-frozen compared to fresh fruit. The a color value was higher in juice and powder prepared from pre-frozen fruit compared to fresh fruit. There was no significant difference in free sugar or organic acid content between juices and powders from pre-frozen and fresh fruit. None of soluble solid content, titratable acidity, or juice pH was affected by freezing pretreatment. The results suggest that such pretreatment may be useful to increase juice yield and drying rate. However, browning of juice and powder may be elevated.

• Journal of the Korea Concrete Institute
• /
• v.19 no.5
• /
• pp.647-653
• /
• 2007

In ready mixed concrete factory, in case of using the high molecular additive in winter especially the liquid additive for the early strength, it is required to check the stability. In this research, the freezing and gelling characteristics of the liquid additive for the early strength is reviewed, the material and mechanical solution are proposed to that the practical quality control method will be suggested. As the result, the Freezing temperature of the liquid additive for the early strength is $-11.8^{\circ}C$, and it is the lower than the temperature at which the strength is shown. By making with sodium silicate of $37{\pm}0.5%$ designed by $SiO_2\;and\;Na_2O$ in 0.31 of mol ratio, it minimizes the gelling at the lower temperature. On the other hand, facilities for storing and supplying the material should be set at $40^{\circ}C$ so the temperature distribution is well spreaded for practical operation.

• Journal of the Korean Electrochemical Society
• /
• v.6 no.1
• /
• pp.36-40
• /
• 2003

Freezing of water in a polymer electrolyte membrane fuel cell (PEMFC) may cause severe problems in driving a fuel cell vehicle during the winter time. Characteristics of PEMFC which suffered low temperatures below zero degree was examined with the thermal cycles from 80 to $-10^{\circ}C$. With the thermal cycles, the cell performance was degraded due to the phase transformation and volume changes of water. Effects of freezing of water in PEMFC on the electrode structure and polarization resistance were examined by BET analysis, cyclic voltammetry, and AC impedance spectroscopy.

• Journal of Biosystems Engineering
• /
• v.31 no.3 s.116
• /
• pp.168-174
• /
• 2006

The purpose of this study is to develop the cold chain system by developing optimal phase change materials (PCM). There are some benefits from developing this system such as keeping freshness of agriculture products, saving energy, etc. The major results are as follows. To decide a latent heat material, the characteristics of water, sodium, polyacrylate, ethanol and N-tetradecane are analysed. Also, an insulating material is made by mixing water, nucleating agent and latent heat material, using cementing method. In addition, the sensitivity analysis for developed latent heat material($K_l,\;K_2,\;K_3$) is conducted. For $K_l,\;K_2,\;K_3$ which cans keep latent heat temperature, ranging from $0\;to\;5^{\circ}C,\;5\;to\;10^{\circ}C,\;10\;to\;15^{\circ}C$. it can keeps latent heat temperature at radiant heat (5, 12, $17^{\circ}C$) and transportation latent heat container both melting temperature and amount of latent heat of Kl are $-1.6{\pm}1.0^{\circ}C$, 326.51 J/g, respectively and freezing temperature and latent heat are $-7.98{\pm}1.5^{\circ}C$ and 174.18 J/g. and $K_2$ are $7.41{\pm}1.5^{\circ}C$, 89.80 J/g, respectively and freezing temperature and latent heat are $-2.14{\pm}1.5^{\circ}C$ and 83.90 J/g. and $K_3$ are $9.54{\pm}1.0^{\circ}C$, 145.42 J/g, respectively and freezing temperature and latent heat are $0.21{\pm}1.0^{\circ}C$ and 152.48 J/g.

• Korean Journal of Food Science and Technology
• /
• v.20 no.2
• /
• pp.205-212
• /
• 1988

The effect of physicochemical characteristics on the freezing point depression of garlic bulb was studied to examine the reasons of cryoprotectivity in garlic bulb stored at subzero temperature. The composition of fresh garlic was characterized by having high soluble solids($40^{\circ}$ Brix; 90% on dry basis), comparing with $10^{\circ}$ Brix in case of other fruits and vegetables. Soluble solids were composed of 70% sugars, 20% protein, and 10% insoluble solids(including 3% of ash, 3% of crude fiber, and 4% of fat). The main component of sugars in garlic was fructosan with 1-29 degree of polymerization(D.P) and the fructosan of 4-5 D.P was over 50% of total fructosan. Freezing point of garlic bulb, which is a parameter of cryoprotectivity, was depressed as the concentration of soluble solids increased, and as the D.P value decreased in the same concentration of soluble solids.

• Journal of the Korean Geotechnical Society
• /
• v.38 no.8
• /
• pp.7-15
• /
• 2022

Most studies have conducted cryogenic triaxial compression tests with frozen specimens prepared in a separate mold by one-directional freezing. This method has the potential to generate residual stress in a frozen specimen and cannot be adopted to simulate the application of the artificial ground freezing method in the field. Therefore, in this study, novel equipment and procedure for the cryogenic triaxial compression test were proposed to overcome the limitations of existing test methods. Therefore, the mechanical characteristics of frozen sand, considering the effect of temperature and confining pressure, were evaluated. As the freezing temperature decreased, the brittleness of frozen sand increased, and the strength increased due to a decrease in the unfrozen water content and an increase in the ice strength. A higher confining pressure resulted in an increase in interparticle friction and the pressure melting phenomenon, which caused strength reduction. Thus, it was found that the mechanical behaviors of frozen sand were simultaneously affected by both temperature and confining pressure.

• Food Science and Preservation
• /
• v.23 no.3
• /
• pp.438-444
• /
• 2016

This study was performed to determine the optimal freezing point for the reliable cold storage of Korean agricultural products, and to provide basic data for determining the storage temperature based on the quality characteristics. Additional supercooling temperature analysis was conducted to explore the possibility of supercooling storage. To determine the effects of quality characteristics on the freezing point, the hardness, acidity, moisture and sugar content were analyzed. The crops were frozen using customized cooling unit and their freezing and supercooling points were determined based on their heat release points. The freezing temperatures of garlic, leek, cucumber, hot pepper, grape, oriental melon, netted melon, peach, cherry tomato, plum, daikon, sweet persimmon, apple, sweet potato, mandarin, pear, and strawberry were -1.6, -0.5, -0.5, -0.7, -1.6, -1.6, -1.3, -0.8, -0.3, -1.1, -0.3, -1.7, -1.5, -1.5, -0.8, -1.5, and -$0.9^{\circ}C$, respectively; otherwise, supercooling points were -7.8, -3.7, -3.3, -4.9, -5.7, -4.6, -2.8, -3.3, -5.9, -4.2, -0.8, -4.7, -3.2, -3.7, -4.7, -4.2, and -$3.4^{\circ}C$, respectively. These results suggest that the ideal freezing temperature of crops could be estimated through freezing point depression because of their sugar content, and this technique should be used to maintain an optimum storage temperature. However, cold storage is complicated and further study is required because of the effects of long-term cold storage on the crops.

• Food Science of Animal Resources
• /
• v.33 no.6
• /
• pp.723-729
• /
• 2013

In this study, the quality characteristics due to the influence of various thawing methods on electro-magnetic and air blast frozen beef were examined. The loin and round of second grade Hanwoo were sliced into 5-7 cm thickness and packed with aerobic packaging. The packaged beef samples, which were frozen by air blast freezing at $-45^{\circ}C$ and electro-magnetic freezing at $-55^{\circ}C$, were thawed by 4 thawing methods with refrigeration ($4{\pm}1^{\circ}C$), room temperature (RT, $25^{\circ}C$), cold water ($15^{\circ}C$), and microwave (2450 MHz). These samples were thawed to the point, which were core temperature reached $0^{\circ}C$. Analyses were carried out to determine drip and cooking loss, water holding capacity (WHC), moisture contents and sensory evaluation. Frozen beef thawed by microwave indicated a lower drip loss (0.66-2.01%) than the other thawing methods (0.80-2.50%). Cooking loss after electro-magnetic freezing indicated 52.0% by microwave thawing for round compared with 41.8% by refrigeration, 50.1% by RT, and 50.8% by cold water. WHC thawing by microwave with electro-magnetic freezing didn't showed any difference depending on the thawing methods, while moisture contents was higher thawing by microwave with electro-magnetic freezing than refrigeration (71.9%), RT (75.0%), and cold water (74.9%) for round. The texture of sensory evaluation for round thawed by microwave result was the highest than refrigeration (4.7 point), RT (6.4 point) and cold water (6.6 point), while sensory evaluation was no significant difference. Therefore, it was shown that microwave thawing is an appropriate way to reduce the deterioration of meat quality due to freezing.

• Journal of the Korean GEO-environmental Society
• /
• v.19 no.3
• /
• pp.5-13
• /
• 2018

Recently, construction disasters in thawing season are increasing due to the ground collapse and it is related to the improper compaction during winter season. Compaction at sub-zero temperature reduces the compaction effect and the research of mechanical properties of thawed soil after winter compaction can be used as useful data to understand the behavior of the ground in the thawing season. On the other hand, the research interest in the unsaturated soil mechanics has been increasing in the field of the geotechnical engineering. Therefore, it is expected that the research of unsaturated characteristics under the compaction of sub-zero temperature and freezing & thawing condition provides information to the researchers in the related fields. Therefore, in this research, unsaturated soil-water characteristics test and unsaturated uniaxial compression test were conducted on the specimens compacted at sub-zero temperature and continuous freezing & thawing condition to investigate change of unsaturated characteristics and matric suction. Based on the test results, the change of matric suction and the decrease of strength and stiffness were observed with the freezing & thawing conditions. Especially in case of the weathered soil, the strength and matric suction were significantly reduced with lower temperature and more repetition of freezing & thawing cycles. This result implies that compaction of sub-zero temperature and freezing & thawing cycles will have a considerable influence on the stability of the ground.