• Journal of Embryo Transfer
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• v.21 no.1
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• pp.77-83
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• 2006

본 연구는 개 동결 정액 융해 시 straw 크기 및 융해 속도가 융해 정자의 질(quality)에 미치는 영향을 조사하고 최적의 융해 조건을 조사하는데 그 목적이 있다. 정상적인 번식능을 가진 비글 수컷 5마리에서 정액을 채취하여 원심 분리하여 정장을 버리고 남은 정자에 동결보호제인 glycerol이 첨가된 tris-glucose-egg yolk extender를 첨가하여 동결하고 액체질소에 보관한 후 융해하였다. 동결 융해 조건에 따른 효과를 알아보기 위해 straw는 0.25 ml과 0.5 ml크기를 사용하였고 융해 조건은 $75^{\circ}C$에 10초, $55^{\circ}C$에 12초 및 $37^{\circ}C$에서 120초로 하여 융해 후 정자의 활력도(vigor), 운동성(motility), Hypo-osmotic test(HOS test)를 이용한 생존성(viability) 및 $SperMac^{\circledR}$ 염색을 하여 정자의 membrane integrity를 비교 조사하였다. 조사 결과 0.5 ml 크기의 straw를 사용한 경우 $37^{\circ}C$ 융해가 $55^{\circ}C,\;75^{\circ}C$ 융해보다, 0.25 ml 크기의 straw를 사용한 경우에는 $37^{\circ}C,\;55^{\circ}C$ 융해가 $75^{\circ}C$ 융해보다 유의적으로 높은 활력 지수 및 생존성을 보였다(P<0.05). Straw크기에 따라 비교하였을 경우 0.5 ml 군에서 유의적으로 높은 활력도, 생존성 및 membrane integrity를 보였다(P<0.05). 결론적으로 개 정액이 동결 및 융해 시 0.5ml straw를 이용하여 동결한 후 $37^{\circ}C$에서 120초 동안 융해하는 것이 최적의 조건임이 사료된다.

• Tunnel and Underground Space
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• v.22 no.4
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• pp.276-283
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• 2012

Changes in rock properties due to freezing and thawing cycles ranging from $-20^{\circ}C$ to $10^{\circ}C$ were checked for the typical Korean rocks: granite (weathered), limestone, sandstone, tuff, shale and basalt. The porosity, seismic velocity, shore hardness and specific gravity were measured every 10 cycles for each type of rock up to 40 cycles. The specific gravity was rarely changed. Granite (w), shale and basalt decreased gradually in their shore hardness and seismic velocity values, these values for limestone, sandstone and tuff changed only a very little. The porosity increased in the granite (w), shale and basalt, whereas in the others it did not change. Due to the low tensile strength with high porosity, granite (w), shale and basalt were susceptible to the F-T cycles. A linear regression equation was calculated based on the experiment results according to properties and types of rock. The relationship between the freeze-thaw sensitivity (=initial porosity/initial tensile strength) and the coefficients of the regression equation was examined. With additional experimental data, the coefficients of the regression equation can be estimated using the F-T sensitivity. This makes it possible to predict the properties of rock as affected by freeze-thaw weathering by only measuring the initial properties without knowledge of the regression equation coefficients for each type of rock.

• Economic and Environmental Geology
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• v.52 no.6
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• pp.587-593
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• 2019

This study were subjected to accelerated weathering test under freeze-thaw and pressure conditions to observe initiation and propagation of cracks using CLSM. Applied stress was set at 50 MPa, 55 MPa, 70 MPa for 3 samples each by using compressor and freeze-thaw experiment was conducted while samples maintained that condition. In freeze-thaw experiments, a temperature range was set to -20~40℃ which was 1 cycle for 6 hours. The freeze-thaw cycle was composed of time which reached to set temperature for 1 hour and holding time for 2 hours. On the basis of this cycle, surface of samples was observed by CLSM after each 20 freeze-thaw cycle. From this research, according to increase freeze-thaw cycle, there were 7, 10, 19 each cracks and High pressured sample's accumulate length was longer than low pressured sample's. High pressured sample's crack velocities were also faster than low pressured sample's which were calculated by accumulate length and freeze-thaw cycle.

• Clinical and Experimental Reproductive Medicine
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• v.32 no.1
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• pp.65-70
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• 2005

본 연구는 이식 후 남은 잉여의 포배기 배아를 두 번의 냉동과 융해 과정을 반복적으로 실시한 후 이식한 결과에 관한 보고이다. 사람 포배기 배아의 동결보존에서 높은 생존율과 성공적인 임신율이 보고되고 있으나 미성숙 난자로부터 발달한 포배기 배아에 두 번의 초급속 냉동 방법을 실시한 후 이식한 보고는 되어 있지 않다. 이에 본 연구에서는 다낭성 난소 증후군 환자에게서 얻은 미성숙 난자로부터 발달한 포배기 배아를 artificial shrinkage 후 초급속 냉동함으로써 생존율을 높이는 방법을 이용하여 재냉동 이식하였을 때 임신에 성공한 증례를 보고하고자 한다. 29세의 환자로부터 채취한 55개의 미성숙 난자들(germinal vesicle stage oocytes)을 체외배양 하여 성숙한 37개의 난자들로부터 30개의 수정란을 얻을 수 있었다. 12개의 배아가 포배기 배아까지 발달하였으며 이 중 3개의 양질의 포배기 배아를 선별하여 이식하였고, 이식을 한 후에 남은 9개의 포배기 배아들은 artificial shrinkage의 과정을 마친 후에 초급속 냉동 방법을 이용하여 동결보존 하였다. 그 중, 4개의 포배기 배아들을 융해한 후 이식을 하지 않고 다시 재냉동을 하여 보관하였고 이 후 재냉동 되었던 4개의 포배기 배아들을 다시 융해 하여 이식을 한 결과 임신이 되어 건강한 남아를 분만하였다. 이로써 미성숙 난자로부터 얻은 포배기 배아가 두 번의 냉동과 융해의 과정을 통해 크게 손상을 입지 않고 생존할 수 있다는 것을 알 수 있었다. 그러므로 융해이식 후 남은 잉여의 포배기 배아를 다시 냉동 보관하여 다음 주기에 이용함으로써 축적된 임신율을 증가시킬 수 있을 것으로 사료된다.

• The Journal of Engineering Geology
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• v.24 no.1
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• pp.111-122
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• 2014

For accurate laboratory evaluations of soil deposits, it is essential that the samples are undisturbed. An artificial ground-freezing system is the one of the most effective methods for obtaining undisturbed samples from sand deposits. The objective of this study is to estimate the shear strengths and the characteristics of elastic waves of frozen-thawed and unfrozen specimens through the undrained triaxial compression test. For the experiments, Jumunjin standard sands are used to prepare frozen and unfrozen specimens with similar relative densities (60% and 80%). The water pluviation method is used to simulate the fully saturated condition under the groundwater table. When thawing the frozen specimens, the temperature is measured every minute. After the specimens are completely thawed, undrained triaxial compression tests are conducted using the same procedures as for the unfrozen specimens. During the triaxial tests (saturation, consolidation, and shear phase), compressional and shear waves are measured. The results show that the freeze-thaw process has minor effects on the peak deviatoric stress and shear strength values, and that the process does not affect the internal friction angle. The compressional wave velocity increases with increasing B-value to 1800 m/s in the saturation phase, but tends to remain constant in the process of consolidation and shearing. The shear wave velocity decreases with increasing B-value in the process of saturation, but changes velocity in accordance with the change in effective stress in the processes of consolidation and shearing. The compressional wave velocity has similar values regardless of the freeze-thaw process, but values of shear wave velocity are slighly lower in frozen-thawed specimens than in unfrozen specimens. This study is a preliminary experiment for estimating the shear strength and characteristics of elastic wave velocity in undisturbed frozen specimens that have been obtained using the artificial ground-freezing method.

• Journal of the Korean GEO-environmental Society
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• v.15 no.5
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• pp.47-56
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• 2014

In winter season, the pore water inside the ground freezes and thaws repetitively due to the cold air temperature. When the freezing-thawing processes are repeated on the ground, the change in soil particle structure occurs and thus the damage of the infrastructure may be following. This study was performed in order to investigate the stiffness change of soils due to the freeze-thaw by using elastic waves. Sand-silt mixtures are prepared with in the silt fraction of 40 %, 60 % and 80 % in weight and in the degree of saturation of 40 %. The specimens are placed into the square freezing-thawing cell by the temping method. For the measurement of the elastic waves, a pair of the bender elements and a pair of piezo disk elements are installed on the cell, and a thermocouple is inserted into soils for the measurement of the temperature. The temperature of the mixtures is decreased from $20^{\circ}C$ to $-10^{\circ}C$ during freezing, is maintained at $-20^{\circ}C$ for 18 hours, is gradually increased up to the room temperature of $20^{\circ}C$ to thaw the specimens. The shear waves, the compressional waves and the temperature are measured during the freeze-thaw process. The experimental result indicates that the shear and the compressional wave velocities after thawing are smaller than those of before freezing. The velocity ratio of after thawing to before freezing of shear wave is smaller than that of the compressional wave. As silt fraction increases from 40 % to 80 %, the shear and compressional wave velocities are gradually increased. This study suggests that the freezing-thawing process in unsaturated soil loosens the soil particle structure, and the shear wave velocity reflects the effect of freezing-thawing more sensitively than the compressional wave velocity.

• Economic and Environmental Geology
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• v.42 no.3
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• pp.261-272
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• 2009

An experimental study of the accelerated weathering was performed to investigate the variations of physicomechanical properties of deteriorated rocks due to freeze-thaw weathering for the Jurassic granite specimens from Wonju, Gangwon-do. Each complete cycle of freeze and thaw was lasted 24 hours, comprising 2 hours saturating in vacuum chamber, 8 hours freezing at -20$\pm1^{\circ}C$ and 14 hours thawing at room temperature. Freeze-thaw cycles were implemented with measuring the index physical properties as well as geometries of microfractures. The seismic velocity was found to decrease with increasing freeze-thaw cycles. On the other hand, absorption tends to increase with freeze-thaw cycles. In the end, it was concluded that variations of the index properties of deteriorated specimen depend on its initial properties and flaws in rock. The size and density of the traces of the microfracture on slab specimen were changed continuously with increasing freeze-thaw weathering. The results obtained in this study show that the box fractal dimension($D_B$) has the strong capability of quantifying the combined effect of size and density of the microfractures.

• Tunnel and Underground Space
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• v.19 no.2
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• pp.146-157
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• 2009

An experimental study of accelerated weathering on mudstone sample specimens from Haman, Gyeongnam was performed to investigate the variations of physico-mechanical properties of deteriorated rocks due to freeze-thaw weathering. Each complete cycle of freeze and thaw lasted 24 hours, comprising 2 hours of saturating in vacuum chamber, 8 hours of freezing at $-16{\pm}1^{\circ}C$ and 14 hours of thawing at room temperature. Total of 55 cycles of freeze-thaw were completed with measuring the index properties as well as geometries of microfractures. The measured specific gravity and P-wave velocity found to decrease with increasing freeze-thaw cycles. On the other hand, absorption ratio and effective porosity were continuously increased with increasing freeze-thaw cycles. It was found that the index properties of deteriorated sample specimen depend on its initial properties and flaws in rock. The size and density of the traces of the microfracture on slab specimen exhibited abrupt changes after 30 cycles of freeze-thaw weathering. The results obtained in this study show that the box fractal dimension($D_B$) given in this paper has the strong capability of quantifying the size and density of the microfracture.

• Tunnel and Underground Space
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• v.13 no.3
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• pp.215-224
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• 2003

Weathering in nature was simulated by freeze-thaw cyclic test which represents mechanical weathering. Measured physical properties were elastic wave velocities, absorption rate, volume change and weight change. Uniaxial compression tests were also conducted before and after the weathering tests. The change in weight and volume of the specimens were not clearly related to the weathering process, but P, S wave velocities, uniaxial compression strength and Young's modulus were clearly decreased as weathering progresses. Test result can be used for the assessment of long-term stability of rock slopes.

• Journal of Embryo Transfer
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• v.18 no.1
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• pp.51-59
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• 2003

This study was carried out to evaluate the effect of different freezing and thawing rates on the viability, motility and acrosomal changes of frozen canine spermatozoa. The ejaculated semen was extended with Tris-egg yolk buffer containing 8% glycerol and equilibrated for 60 min after cooled to 4$^{\circ}C$ for 58 min. The straws were cryopreserved gradually by slow-cooling at different distance(6, 10 and 17 cm, respectively) from the liquid nitrogen (L$N_2$) to achieve temperature rate of 3, 8.9 and 19$^{\circ}C$ /min. Thawing of the straws was performed in a water bath fur 2 min at 37$^{\circ}C$ and 55$^{\circ}C$ , respectively. The motility of frozen-thawed spermatozoa was assessed by phase-contrast microscopy. To assess their viability and acrosome content, spermatozoa were stained with a vital stain and Fluorescence conjugated lectin Pisum Savitum Agglutinin (FITC/PAS), respectively. Concentration of the ejaculated fresh semen was normal range of 3.44 $\times$ 10$^{8}$ /ml. Freezing temperature were reduced to -110, -70 and -35$^{\circ}C$, as higher distance from liquid nitrogen, 6, 10 and 17 cm, respectively. Freezing at 3$^{\circ}C$/min in distance of 17 cm from liquid nitrogen yielded better motility, viability and rate of intact acrosome than 8.9 or 19$^{\circ}C$/min and the optimal thawing was 37$^{\circ}C$ for 2 min.