• 한국농공학회논문집
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• 제58권1호
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• pp.19-26
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• 2016

This study was performed to evaluate the strength and durability properties of modified epoxy composites with waste tire chip, recycled coarse aggregate, filler and modified epoxy to improve elongation and elasticity of epoxy. Additionally, for comparing to modified epoxy and unsaturated polyester resin as a binder, unsaturated polyester resin composites were developed in the same condition. The mix proportions were determined to satisfy the requirement for the workability and slump according to aggregate size and binder content. Tests for the compressive and flexural strength, freezing and thawing and durability for 20 % sulfuric solution were performed. The compressive and flexural strength of modified epoxy composites were in the range of 34.9~61.6 MPa and 10.2~18.3 MPa at the curing 7 days, respectively. Also, the compressive and flexural strength of unsaturated polyester resin composites were in the range of 44.2~77.8 MPa and 11.3~20.8 MPa at the curing 7 days, respectively. After 300 cycles of freezing and thawing, weight decrease ratio and durability factor of modified epoxy composites were in the range of 0.8~1.9 % and 95~98, respectively. Accordingly, modified epoxy composites will greatly improve the durability of concrete.

• 대한의용생체공학회:의공학회지
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• 제39권4호
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• pp.161-167
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• 2018

Polyvinyl alcohol/sodium carboxymethyl cellulose (PVA/NaCMC) hydrogels were prepared by physical crosslinking (cyclic freezing/thawing) and gamma (${\gamma}$)-ray irradiation to evaluate the effect of NaCMC concentration (2~8 wt%) on the mechanical properties and the biocompatibility of the PVA/NaCMC hydrogels. The swelling rate of PVA/NaCMC hydrogels regardless of irradiation rose with increasing NaCMC content from 2 wt% to 8 wt%, while the gelation rate was the reverse. As the NaCMC content increased from 2 wt% to 6 wt%, the compressive strength of the hydrogels increased dramatically from $8.5{\pm}2.0kPa$ to $52.7{\pm}2.5kPa$ before irradiation and from $13.5{\pm}2.9kPa$ to $65.5{\pm}8.7kPa$ after irradiation. When 8 wt% NaCMC was added afterwards, the compressive strength decreased however. The irradiated PVA/NaCMC hydrogels containing 6 wt% NaCMC exhibited the tailored properties of the swelling rate of $118{\pm}3.7%$, the gelation rate of $71.4{\pm}1.3%$, the strength of $65.5{\pm}8.7kPa$, respectively, and no cytotoxicity was observed.

• Computers and Concrete
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• 제3권2_3호
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• pp.163-175
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• 2006

This research was conducted to determine effect of pumice aggregate ratio, cement dosage and slumps on freeze-thaw resistance, density, water absorption and elasticity of concrete. In the first batch, $300kg/m^3$ cement dosage were kept constant and pumice ratios were changed as 25%, 50%, 75% and 100% of replacement for normal aggregate by volume for $3{\pm}1cm$, $5{\pm}1cm$ and $7{\pm}1cm$ slumps. Other batches were prepared with $200kg/m^3$, $250kg/m^3$, $350kg/m^3$, $400kg/m^3$ and $500kg/m^3$ cement dosages and 25% pumice aggregate +75% normal aggregate at a constant slump. Test results showed that when pumice-aggregate ratio decreased the density and freeze-thaw resistance of concretes increased. With increasing of cement dosage in the mixtures, density of the concretes increased, however, freeze-thaw resistance of concretes decreased. Water absorption of the concrete decreased with increasing cement dosage but increased with the pumice ratio. Water absorption of the concrete also decreased after freeze-thaw cycles. Freeze-thaw resistance of concretes was decreased with increasing the slumps.

• 상하수도학회지
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• 제22권5호
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• pp.561-569
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• 2008

We analyzed contents of cations and anions for the domestic bottled drinking water. Results showed that total cation content was 45.81 mg/L and contained 40% of Ca. The content of cations were decreased in the order of Ca>Si>Na>Mg>K. Total anion content was 12.20 mg/L and contained 90% of ${SO_4}^{2-}$ and $Cl^-$. $F^-$ and $NO_{3-}N$ were a little contained. While Si content was reduced 2.3~75.7%(mean value:38.5%) after freezing, Ca content was reduced 45.2% after boiling. It showed that water containing higher Ca content was significantly decreased after boiling. Precipitates formed by freezing and boiling is composed of minerals such as Si and Ca. Compared to minerals from food intake, concentrations of minerals from water intake are expected to be less influenced. It is recommended Bottled Water that contains more than 20 mg/L of Ca(exceeding water-quality standard for turbidity) is safe to drink without thawing and boiling.

• 한국농공학회:학술대회논문집
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• 한국농공학회 2005년도 학술발표논문집
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• pp.381-386
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• 2005

In order to have compressive strength tests and frost heaving tests, two sorts of soil samples at Chonbuk-Do area were used. According to this research, the compressive strength of soil which was mixed by quick lime, was largely increased until 28 days but after 28 days, the increment of strength was seldom found and its maximum compressive strength increasing rate for content of quick lime was $10{\sim}15%$ scope. In the mixed rates of quick lime and briquette ash, the compressive strength of soil which was mixed by quick lime and briquette ash, was increased by increasing mixed rates of quick lime and its compressive strength was increased by additional quantity. The compressive strength of mixed soil within freezing-thawing 1 cycle was diminished around 30% compared to non-freezing soil's 28 days compressive strength but there were no movements after 2 cycle.

• 한국수정란이식학회지
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• 제18권3호
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• pp.195-201
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• 2003

본 실험은 실험견의 정액 동결 시 희석 액에 첨가되는 Glycerol 농도, 동결속도, 동결보존액 첨가후 평형시간, 융해온도와 시간에 따라 정자의 생존성과 운동성을 조사하여 최적의 동결조건을 확립하기 위해 실시하였다. 1. 각기 다른 Glycerol 농도를 함유한 동결보존액에서 동결보존 후 융해하였을 때 4%의 Gly-cerol 농도에서 각각 68.8$\pm$7.4%, 73.2$\pm$8.3%로서 다른 군보다 유의하게 높은 생존율과 운동성 나타냈다(P<0.05). 2. 희석 액 I 을 첨가한 정액을 상온에서 4$^{\circ}C$까지 각각 30, 60, 120분간 속도로 하강 시켜 동결보존 후 융해하였을 때 60분간의 속도로 하강시킨 군에서 생존성은 70.6$\pm$6.8%, 운동성은 72.8$\pm$8.4%로서 다른 군보다 유의하게 높은 생존율과 운동성을 나타냈다(P<0.05). 3. 희석 액 I 을 상온에서 4$^{\circ}C$까지 60분의 속도로 하강시킨 후 희석 액 II를 첨가하여 각각 30, 60, 120분 동안 평형을 유지시킨 후 동결보존 하였을 때 60분 동안 평형을 유지시킨 군에서 생존성은 71.4$\pm$7.3%, 운동성은 74.6$\pm$7.5%로서 다른 군보다 유의하게 높은 생존율 및 운동성을 나타냈다(P<0.05). 4. 정액을 동결함에 있어 액체질소의 표면에서 각각 3, 5, 7, 9cm의 높이에서 정치시킨 후 동결을 실시하였을 때 액체질소의 표면 5cm의 높이에서 동결을 실시한 군에서 융해 후 생존성과 운동성은 각각 77.0$\pm$7.0%, 80.2$\pm$6.3% 로서 다른 군보다 유의하게 높은 생존율과 운동성을 나타냈다(P <0.05). 5. 일정기간 보존된 동결정액을 융해 시 융해온도에 따른 정자의 생존성과 운동성은 37$^{\circ}C$의 온도에서 120초 동안의 기간에 녹였을 때 각각 77.0$\pm$7.0%, 80.2$\pm$6.3%로서 다른 군보다 유의하게 높은 생존율을 나타냈다(P<0.05).

• Clinical and Experimental Reproductive Medicine
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• 제28권2호
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• pp.121-129
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• 2001

Objective: The aim of this study is to compare the efficiency of a method for the cryopreservation of mouse blastocyst.. Methods: Mouse embryos were obtained at 2-cell stage and cultured to blastocyst stage in T6 medium supplemented with 10% fetal bovine serum. Morphologically normal blastocysts were collected and randomly divided to one control and four experimental groups. In control group, blastocysts were cultured in vitro continuously for additional two days. In group 2, blastocysts were exposed to vitrification solution (ethylene glycol) only without cryopreservation (exposure only group). In group 3, 4 and 5, blastocysts were cryopreserved by slow-freezing procedure with glycerol (slow-fteezing group) or by vitrification procedure using EM grids (EM grids group) and cryoloop (cryoloop group), respectively. Frozen blastocysts were thawed and cultured for additional two days. Twenty four hours after thawing, some blastocysts were fixed and stained with Hoechst 33342 (bisbenzimide) and the number of nuclei in each blastocysts were counted to confirm the survival of bias to cysts in experimental groups. Results: Survival rate and hatching rate of the blastocysts in slow-freezing group (24 h: 72.4% and 66.0%, 48 h: 63.2% and 64.6%) and EM grids group (24 h: survival rate 77.3%, 48 h: 70.1% and 71.4%) were significantly lower ($X^2$-test p<0.05) than those of control group (24 h: 93.4% and 86.0%, 48 h: 88.5% and 90.7%). In contrast, the survival rate and hatching rate of the blastocysts in cryoloop group (24 h: 84.1% and 84.1%,48 h 79.3% and 87.7%) is well compared with those in the control group. The mean (${\pm}SD$) cell number of blastocyst in the exposure only ($89.2{\pm}11.5$), EM grids ($85.0{\pm}10.3$) and cryoloop ($89.0{\pm}11.0$) groups, except slow-freezing group ($79.0{\pm}10.0$), were not significantly different from that of control group ($93.1{\pm}13.9$) 24 h after thawing (Student's t-test). Conclusion: This study demonstrates that higher survival rate of vitrified-thawed mouse blastocyst can be obtained using cryoloop as the embryo container at freezing rather than slow-freezing or vitrification using EM grids. The results of this study suggest that vitrification using cryoloop (with ethylene glycol) may be a preferable procedure for mouse blastocyst cryopreservation and could be applied to the human blastocyst cryopreservation.

• 한국축산식품학회지
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• 제38권5호
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• pp.959-969
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• 2018

This study investigated the effects of deep freezing and storage temperature ($-50^{\circ}C$, $-60^{\circ}C$, and $-80^{\circ}C$) on the quality and freshness of lamb. To compare the qualities of deep frozen and stored lamb, fresh control and normal freezing conditions ($-18^{\circ}C$) were adopted. As quality and freshness parameters, drip loss (thawing loss and cooking loss), water-holding capacity (WHC), texture profile analysis (TPA), thiobarbituric acid reactive substances (TBARS), and total volatile basic nitrogen (TVBN) were evaluated during 5 months of storage. Temperature influenced the drip loss and WHC, and deep freezing minimized the moisture loss during frozen storage compared to the normal freezing condition. Lamb frozen and stored at deep freezing temperature showed better tenderness than that stored in normal freezing conditions. In particular, lamb frozen at lower than $-60^{\circ}C$ exhibited fresh lamb-like tenderness. Regardless of temperature, evidence of lipid oxidation was not found in any frozen lamb after 5 months, while TVBN was dependent on the applied temperature. Therefore, this study demonstrated that deep freezing could potentially be used to maintain freshness of lamb for 5 months. From the quality and economic aspects, the freezing and storage condition of $-60^{\circ}C$ is estimated as the optimum condition for frozen lamb.

• 한국식품영양과학회지
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• 제42권3호
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• pp.403-409
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• 2013

신율미, 연황미 및 연미를 사용하여 원적외선 오븐으로 제조한 냉동 군고구마의 품질 특성을 연구하였다. 군고구마의 제조는 원적외선 오븐을 사용하여 $250^{\circ}C$에서 40분 동안 굽기를 실시하였으며, 냉동 군고구마는 군고구마를 $-18^{\circ}C$에서 30일간 냉동 후 microwave oven을 사용하여 3분간 해동하였다. 원료고구마의 일반성분은 수분 함량을 제외한 조지방 및 조단백질 함량이 신율미 및 연미보다 연황미에서 높았다. 세 품종 모두 굽기에 따라 총당, 환원당, sucrose 및 maltose 함량이 증가하였다. 명도 및 적색도, 황색도는 굽기 및 냉해동에 따라 감소하였으며, ${\beta}$-carotene 함량 또한 굽기 및 냉해동에 의해 감소하였다. 군고구마의 냉해동에 따른 조직감은 신율미와 연황미에서 견고성, 검성 및 응집성이 감소하였다. 관능검사 결과 신율미가 외관, 풍미, 감미 및 전반적 기호도에서 가장 높은 선호도를 보여 냉동 군고구마의 제조에 가장 적합한 품종은 신율미로 판단되었다.

• 한국동물위생학회지
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• 제18권3호
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• pp.1-12
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• 1995

To investigate effect of seeding on post-thaw motility and viability of canine spermatozoa, the semen from male dogs which had been proved to be fertile in the past were frozen and seeded during freezing process. Post-thaw motility and viability of canine sperm which were frozen and seeded were investigated according to different seeding temperatures of $-5^{\circ}C$, $-10^{\circ}C$, or $-l5^{\circ}C$ and also according to different concentration of glycerol of 2%, 5% and 10%. In addition, post-thaw motility of canine sperm frozen by direct freezing in a deep freezer or programmed freezing in a programmed cell freezer was investigated. Post-thaw motility of canine sperm was compared according to different seeding temperatures : The sperm seeded at $-5^{\circ}C$ showed considerably higher post-thaw motility than that of non-seeding, and that seeded at $-10^{\circ}C$, or $-l5^{\circ}C$, respectively, in 2% and 5% glycerol groups on both 2 and 7day after freezing(p<0.05). In 10% concentration of glycerol, the sperm seeded at each seeding temperature showed considerably higher post-thaw motility than that of non-seeding group on day 7 after freezing(p<0.01). Post-thaw viability of canine sperm was compared according to different seeding temperatures : The sperm seeded at $-5^{\circ}$ showed significantly higher post-thaw motility than that of non-seeding, and that seeded at $-10^{\circ}C$, or $-l5^{\circ}C$, in 5% and 10% glycerol groups on day 7 after freezing(p< 0.05). In comparison of post-thaw motility of canine sperm seeded according to different concentration of glycerol, 5% glycerol group and 10% glycerol group showed considerably higher post-thaw motility than 2% glycerol group without difference between those two groups in all seeding temperatures($-5^{\circ}C$, $-10^{\circ}C$ and $-l5^{\circ}C$) on day 2 and 7 after freezing(p<0.01). In comparison of post-thaw viability of canine sperm seeded according to different concentration of glycerol, 5% glycerol group and 10% glycerol group showed the same considerably higher post-thaw viability than 2% glycerol group on each thawing day(p<0.01). The canine sperm frozen and seeded by programmed freezing method showed considerably higher post-thaw motility than that frozen by direct freezing method in all different seeding temperatures($-5^{\circ}C$, $-10^{\circ}C$ and $-l5^{\circ}$). These results indicated that the higher post-thaw motility and viability was obtained in the spermatozoa seeded than that of non-seeding, that among different seeding temperatures of $-5^{\circ}C$, $-10^{\circ}C$ and $-l5^{\circ}C$, the sperm seeded at $-5^{\circ}C$ showed higher post-thaw motility and viability than the other temperatures, also among different concentrations fof glycerol of 2%, 5% and 10%, the sperm frozen and seeded in 5% and 10% concentration of glycerol showed higher post-thaw motility and viability than that in 2% of glycerol, and that the sperm frozen and seeded by programmed freezing method showed higher motility than that by direct freezing method.