• Proceedings of the KSAR Conference
• /
• 2003.06a
• /
• pp.81-81
• /
• 2003

돼지 정액의 동결보존은 돼지 정자가 내동성이 약한 특성을 가지고 있어 아직 만족할만한 결과를 얻지 못하여 액상정액을 이용하여 인공수정을 실시하고 있는 실정이다. 돼지 정액의 동결보존을 효과적으로 이룩한다면 돼지 인공수정의 효율성을 증대시킬 수 있고, 우수한 종돈의 보호 및 국제적 돼지 품종의 교류를 증진시킬 수 있을 것이다. 본 실험은 돼지 정액 동결시 동결온도와 시간, 항산화제로 알려진 Taurine의 농도별 첨가, 동해보호제 및 융해조건이 돼지 정액의 동결 융해후 생존성에 미치는 영향을 검토하고자 수행되었다.

• 한국방재학회:학술대회논문집
• /
• 2010.02a
• /
• pp.90.1-90.1
• /
• 2010

우리나라는 계절적 특성으로 인하여 겨울에서 봄에 이르기까지 도로포장의 동결 융해가 반복되어 도로 파손을 유발 시키고 있다. 동결 융해로 인한 피해를 줄이기 위하여 도로포장 설계시 동상방지층을 별도로 설치를 하고 있으나 실효성 검증 없이 무분별하게 적용되고 있어 국가적으로 예산을 낭비하고 있다. 본 연구에서는 효과적인 동상방지층의 설계를 목적으로 계측된 온도 및 함수비 데이터를 효율적으로 관리하고 모니터링하는 기반을 마련하고자 한다.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.12 no.6
• /
• pp.599-608
• /
• 2000

One dimensional numerical modeling was carried out for the melting behavior of dry snow and the unsaturated flow when heat was supplied from the bottom surface. Discrepancy between the previous experimental data and the present numerical results is substantially reduced by considering the density change of water permeation layer due to the infiltration of meltwater. In the parametric study for effective thermal conductivity, it was found that the effect of this parameter to the behavior of snow melting is minor. Sensitivity analysis showed that the melting time is most sensitive to changes in supplied heat flux, snow temperature, and bulk density, whereas snow bulk density and residual saturation have a significant effect on the height of water permeation layer in snow.

• Korean Journal of Poultry Science
• /
• v.45 no.4
• /
• pp.237-244
• /
• 2018

In this study, to increase the survival rate of frozen/thaw rooster semen, standard protocols of semen thawing procedures were tested by computer-assisted sperm assay (CASA). We tested 4 different thawing protocols for frozen semen, $5^{\circ}C$ for 2 min, $35^{\circ}C$ for 30 s, $54^{\circ}C$ for 13 s, and $70^{\circ}C$ for 7 s. The pooled semen from 5 to 8 Ogye rooster line was diluted in the HS-1 diluent and frozen in 8% methylacetamide (MA) in liquid nitrogen vapors. To determine standard thawing method, straws were plunged into different temperatures and times. The resulting motilities were recorded by the CASA system. The results of this study showed that the best viability of the spermatozoa was shown by exposure at $5^{\circ}C$ for 2 min. Moreover, the longevity test of thawed sperm at $5^{\circ}C$ for 2 min also supported the higher viability under low temperature preservation of $17^{\circ}C$ for 1 hr. Further research is needed to increase the motility of thawed rooster semen for field application. In addition, the in vivo tests for different rooster lines are also needed for the establishment of avian genetic resource bank.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.19 no.6
• /
• pp.1059-1075
• /
• 2017

The objective of this study was to evaluate the freezing and thawing resistance of the existing drainage system for leakage treatment of underground concrete structures operating in cold regions. The freezing and thawing test was conducted on 4 types of drainage system specimens to evaluate the freezing and thawing resistance of the drainage system. The freezing and thawing resistance was evaluated on 4 types of Hotty-gel, as a waterproofing material, connection methods and on two methods to fix the drainage board with Hotty-gel on the surface of cement concrete specimen. One cycle of the freeze-thaw testing was 48 hours (24 hours of freezing and 24 hours of thawing), and the temperatures of freezing and thawing were at $-18^{\circ}C$ and $10^{\circ}C$, respectively. Among the 4 types of Hotty-gel connection methods, leakage occurred after 28 cycles (8 weeks) of freeze-thawing only in the Hotty-gel connection method with the 'V' groove applied to the corner of the drainage board. No leakage occurred in the 3 types of Hotty-gel connection methods. In two fixing methods, leakage occurred in the method of fixing the drainage board on the cement concrete specimen using the washer, screw and plastic wall plug. Leakage occurred at one point after 10 cycles (3 weeks) of freezing and thawing. After 28 cycles (8 weeks) of freezing and thawing, leakage point increased to 5 points. As time passed, the leak point was not increased, but the amount of leakage was increased at each leak point. The Hotty-gel connection method with cross-sectional diagonal shape was evaluated to be the highest in the production efficiency considering the production time and manufacturing method of the Hotty-gel connection shape. In the construction efficiency considering the construction time and construction method, the fixing method of air nailer, fixed nail and washer was superior to that of the washer, screw and plastic wall plug.

• Korean Journal of Animal Reproduction
• /
• v.24 no.1
• /
• pp.89-95
• /
• 2000

This study was to establish an effective dilution technique in a vitrification of bovine blastocysts for the field trial. For vitrification, blastocysts were exposed in glycerol (G) and ethylene glycol (EG) mixture in m-DPBS supplemented with 10% FBS. Blastocysts were first exposed to 10% (v/v) G for 5 min, and subsequently were transferred to 10% G plus 20% EG (v/v) for 5 min. Finally, embryos were transferred to 25% G plus 25% EG (v/v) for 30 see and were placed in nitrogen vapor for 3 min, and then were plunged into L$N_2$. At thawing, the straw containing blastocysts was placed in air for 10 sec, and then plunged into a water bath at $25^{\circ}C$ until all ice had disappeared. They were placed in $25^{\circ}C$ and 36$^{\circ}C$ water according to treatment group for different time. Also, in vitro survival was assessed by the re-expansion and hatched rates at 24 hand 48 h postwarming, respectively. The results obtained in these experiments were summarized as follows; 1) In the survival rates of vitrified bovine blastocysts according to different dilution time at thawing, the data of 1 min group (86.6, 56.6%) were higher than those of other treatment groups (2 min; 93.5, 35.4%, 2.5 min; 76.9, 30.7%, 3 min; 88.8, 36.1% and 3.5 min; 83.7, 8.1%). 2) When the in vitro survival of vitrified groups according to different developmental stage was examined at 48 h after thawing using 1 min dilution method, the hatching rates of fast developed embryos (expanded blastocyst: 81.3%: early hatching blastocyst: 86.2%) were higher than that of delayed developed one (early blastocyst: 46.6%). 3) In addition, when the in vitro survival of vitrified groups according to different embryo age was compared, the hatched rates at 48 h after thawing of Day 7 (66.6%) and Day 8 embryos (60.0%) were significantly higher than that of Day 9 embryos (22.7%) (P＜0.05). These results demonstrate that vitrified bovine IVM/IVF/IVC blastocysts can be successfully survived in vitro using one-step dilution (1 min) method.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.7 no.4
• /
• pp.438-444
• /
• 2019

In this study, the effect of polypropylene fiber on the freeze-thaw damage of mortar was evaluated experimentally. The effects of the reinforcing of polypropylene fiber on the compressive and bending performance of mortar after 300 cycles of freeze-thaw test were evaluated by comparing the normal mortar and the mortar with polyvinyl alcohol fiber. In addition, the mass loss, relative dynamic elastic modulus, and cumulated pore volume of mortar were measured by each cycle of freeze-thaw test. As a result, it was confirmed that the fiber reinforced mortar, regardless of the fiber type, was effective not only in maintaining the performance of the compressive strength and the bending strength but also suppressing the mass loss after the freeze-thaw test of 300 cycles. Meanwhile, it was confirmed that not only polyvinyl alcohol fibers but also polypropylene fibers can effectively act to suppress the damage of the mortar by freeze-thaw. However, in order to improve the freeze-thaw resistance of mortar mixed with polypropylene fiber, it is necessary to increase the bonding performance with the cement matrix which can be expected from polyvinyl alcohol fiber.

• Resources Recycling
• /
• v.19 no.4
• /
• pp.35-40
• /
• 2010

Existing porous concrete has problems with reduction of strength due to freezing and thawing and exfoliation of aggregate at joints. In this study, a method for increasing strength and durability of porous concrete by using fine aggregate, silica-fume and high-range water-reducing agent was proposed by laboratory tests. Mixing ratio between silica-fume (10%) and fine aggregate (0%, 7%, 15%) was selected as a major test factor, and laboratory tests for compressive strength, flexural strength, permeability coefficient, porosity, freezing and thawing were conducted. Compressive strength and flexural strength were increased as the mixing ratio of fine aggregate was increased. However, permeability and freezing-thawing resistance were decreased due to reduction of porosity. Therefore, the ratio of fine aggregate should be limited to increase strength and durability of the porous concrete, while the mixing ratio of silica-fume should be over 10%.

• International Journal of Highway Engineering
• /
• v.9 no.4
• /
• pp.171-184
• /
• 2007

Chemical admixture stabilization has been extensively used in both shallow and deep stabilization in order to improve inherent properties of the soil such as strength and deformation behavior. An increment in strength, a reduction in compressibility, an improvement of the swelling or squeezing characteristics and increasing the durability of soil are the main aims of the admixtures for soil stabilization. Recently, the various advanced cement stabilizer mixing technique was developed. Advanced cement stabilizer mixing technique is environmentally-friendly and has an excellent mixing property and outstanding mixing speed. In this study, to develop the rural road pavement technology using cement stabilizer, compaction and unconfined compression test were performed with various mixing ratio and two types of soil(clay and silty soil). And the freezing/thaw test and bending strength test performed to develop suitable cement stabilizer material for stabilization of rural road. Based on the test results, the liquid types of cement stabilizer material and silty soil mixture are most suitable for rural road construction and although the mixing ratio is low, cement stabilizer mixture is effective for durability of rural road surface layer.

• Clinical and Experimental Reproductive Medicine
• /
• v.37 no.4
• /
• pp.307-319
• /
• 2010

Objective: Vitrification requires a high concentration of cyroprotectant (CPA) and an elevated cooling speed to avoid ice crystal formation. We have evaluated the effect of different combinations of cooling rate and CPA on embryonic integrity (developmental competence) in order to increase the efficiency of vitrification without impairing embryo viabilit. We hypothesized that the combination of CPA or the increase of cooling rates can reduce the concentration of toxic CPA for vitrification. As consequently, we performed experiments to evaluate the effect of various composition of CPA or slush nitrogen ($SN_2$) on the mouse embryonic development following vitrification using low CPA concentration. Methods: Vitrification of mouse embryos was performed with EM grid using liquid nitrogen ($LN_2$) or $SN_2$ and different composition of CPAs, ethylene glycol (EG) and dimethylsulfoxide (DMSO). After vitrification-warming process, their survival and blastocyst formation rates were examined. For analyzing long-term effect, these blastocysts were transferred into the uterus of foster mothers. Results: Survival and blastocyst formation rates of vitrified embryos were higher in EG+DMSO group than those in EG only. Furthermor, the group using $SN_2$ with a lower CPA concentration showed a higher survival of embryos and developmental rates than group using $LN_2$. Conclusion: The combination of EG and DMSO as CPAs may enhance the survival of mouse embryos and further embryonic development after vitrification. $SN_2$ can generate high survival and developmental rate of vitrified/warmed mouse embryos when a lower concentration of CPA was applied. Therefore, these systems may contribute in the improvement of cryopreservation for fertility preservation.