• 한국구조물진단유지관리공학회 논문집
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• 제15권2호
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• pp.107-115
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• 2011

본 연구는 부착재료의 변화 및 동결융해에 따른 FRP-콘크리트구조물 경계면의 거동을 조사하였다. 실험 시 고려된 연구변수로는 부착경계면의 부착강도, 경계면 유효부착길이 등을 조사하였다. 경계면 부착재료에 따른 거동변화 실험체의 경우 FRP-구조물 부착경계면에 사용되는 에폭시의 종류를 각각 3가지로 분류하며 FRP-콘크리트간 다양한 부착길이를 고려하여 시편을 제작하였으며 동결융해에 따른 경계면 거동조사의 경우 0 cycle에서 300cycle까지 계속적으로 증가되는 주기에 대하여 실험체들을 제작, 장기거동 부착실험을 수행하였다. 본 실험결과, 적용 부착재료의 종류에 따라 최대 유효부착길이는 5~7% 차이가 있었으며 동결융해 주기증가에 따른 최대부착하중 및 유효부착길이의 경우 초기에 나타난 급격한 거동변화 이후 상대적으로 불규칙한 변화를 장기적으로 나타내었다.

• 한국초전도ㆍ저온공학회논문지
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• 제21권1호
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• pp.40-44
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• 2019

This study investigates mixtures of water and cryoprotectant agents (CPAs) to store high-grade cold energy. Although water is an ideal material for a cold thermal storage (CTS) due to its high specific heat, undesirable volume expansion may cause structural stresses during freezing. The volume expansion can be alleviated by adding the CPAs to water. However, the CPA aqueous solutions not only have different thermal properties but also transit to amorphous state different from pure water. Therefore, these characteristics should be considered when using them as material of the CTS. In experiments, glycerol and dimethyl sulfoxide (DMSO) are selected as the candidate CPA. The volume expansion of the solution is measured by an in-situ strain gauge in low temperature region. The specific heat capacity of the solution is also measured by differential scanning calorimetry (DSC). Both the amount of volume expansion and the specific heat capacity of the CPA aqueous solution decrease in the case of higher concentration of CPA. These characteristics should be contemplated to select optimal aqueous solution for CTS for liquid air energy storage system (LAES). The CPA solutions have advantages of having wide temperature range to utilize the latent heat of water and higher sensible heat of the CPA. The CPA solutions which can satisfy the allowable stress of the structure are determined. Consequently, among the CPA solutions investigated, DMSO 20% w/w solution is the most suitable for the CTS.

• 한국지형학회지
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• 제25권4호
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• pp.89-101
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• 2018

In Mt. Halla, an arctic-alpine plant Diapensia lapponica var. obovata largely clings to rock surfaces. We observed the rock-surface temperatures of a rocky ridge on the summit area of the mountain from late April 2009 to early May 2010 in order to examine the diurnal and annual temperature variations and the thermal amplitude. We also investigated temperature regimes such as the frequency of freeze-thaw cycles and the temperature change, which might endanger the habitat through frost weathering. For comparison of slope aspects, temperature monitoring was carried out on the north and south faces of the same rocky ridge. The south face experiences the high daily maximum rock-surface temperatures and the high thermal amplitudes during the unfreezing season of May to November 2009. The temperature regimes are considered to exert physiological stress to the arctic-alpine plant. In addition, the south face shows the high frequency of freeze-thaw cycles during the seasonal freezing period of December 2009 to April 2010. This indicates that the south face is susceptible the exfoliation and granular disintegration of rock surfaces, which results in habitat destruction. As a consequence, the south face is believed to be less favorable for the establishment and growth of the arctic-alpine plant than the north face on the summit area of Mt. Halla.

• 한국초지조사료학회지
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• 제26권4호
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• pp.267-276
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• 2006

월동기간 동안 zoysiauass [Zoysia matrella (L.) Merr]와 creeping bentgrass(Agrostis palustris Hunds)의 뿌리에서 저온 스트레스에 대한 생리학적 반응을 규명하기 위해 지질과산화 정도와 효소적 항산화 반응 및 탄수화물의 변화를 조사하였다. 1월 말 Creeping bentgrass의 뿌리 고사율은 zoysiagrass 보다 약 20% 현저히 높게 나타났다. Creeping bentgrass의 뿌리 성장은 온도변화와 거의 평행하게 변화하였으나 zoysiauass는 뿌리 성장에 거의 변화가 없이 4월 말까지 유지되었다. Polyssacharide(starch+fructan)의 함량은 두 품종에서 별다른 차이는 발견되지 않았으나 zoysiagrass의 총비구조적 탄수화물이 creeping bentgrass에 비해 약 10% 높게 나타났다. Malondialdehyde(MDA)의 농도는 creeping bentgrass에서 현저히 높게 나타났다. Creeping bentgrass의 peroxidase의 활성은 zoysiagrass에 비해 약 4.2 배 높았으나 superoxide(SOD)와 catalase(CAT)의 활성은 각각 22%와 67% 낮았다. 이상의 결과들은 creeping bentgrass 보다 zoysiagrass가 월동 기간 중 저온 내성 메커니즘을 우선적으로 작동시키며 저온 스트레스에 대해 덜 민감하다는 것을 잘 나타내고 있다.

• 한국자원식물학회:학술대회논문집
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• 한국자원식물학회 2010년도 정기총회 및 춘계학술발표회
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• pp.12-12
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• 2010

We developed droplet-vitrification protocol, a combination of droplet-freezing and solution-based vitrification, and applied to germplasm collections of garlic, potato, lily as well as cell lines, including hairy roots, somatic embryos. To establish a garlic cryobank, four Korean garlic field collections at Danyang, Suwon, Mokpo and Namhae were cryopreserved last five years. The protocol applied consisted of preculture for 3-4 days at $10^{\circ}C$ on solid MS medium with 0.3M sucrose, loading for 40 min in liquid medium with 35% PVS3, dehydration with PVS3 for 150 min, cooling in $5{\mu}l$ droplets of PVS3 placed on aluminum foil strips by dipping these strips in liquid nitrogen, warming them by plunging the foil strips into pre-heated($40^{\circ}C$) 0.8M sucrose solution for 30s. A total of over 900 accessions of garlic were stored in liquid nitrogen for long-term conservation using unripe inflorescences, cloves or bulbils. Twelve alternative plant vitrification solutions were designed by modifying cryoprotectant concentrations from the original PVS2 and PVS3. The results suggest that PVS2-based vitrification solutions with increased glycerol and sucrose and/or decreased DMSO and EG concentrations can be applied for medium size explants which are tolerant to chemical toxicity and moderately sensitive to osmotic stress. PVS3 and variants can be used widely when samples are heterogeneous, of large size and/or very sensitive to chemical toxicity and tolerant to osmotic stress.

• 한국지반환경공학회 논문집
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• 제13권11호
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• pp.51-60
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• 2012

동토지반의 기초구조물을 설계하는데 있어 기초의 안정성을 지배하는 설계정수인 동결토의 전단강도 및 동착강도를 측정하기 위하여 지난 50여 년 동안 많은 연구가 수행되어 오고 있다. 하지만, 아직까지 동결토의 전단강도 특성에 관한 많은 연구들은 토사 종류, 수직구속응력, 동결온도조건 등 여러 가지 영향인자 중 제한된 영향인자의 변화를 통해 수행되어 왔다. 동결토는 일반 토질과는 달리 토립자, 물, 공기뿐만 아니라 얼음을 포함한 4상으로 구성되어 있으며, 동토의 역학적인 성질의 변화는 일반적으로 온도, 수직구속응력, 동토의 구성물질에 따라 영향을 받는다. 이와 같은 동결토의 전단강도 특성을 측정하기 위하여 영하 30도의 저온환경에서도 동작이 가능하도록 설계된 동결토 직접전단시험기를 활용하였으며, 동토지역의 저온환경을 모사하기 위하여 대형 냉동챔버 내에 직접전단시험기를 설치하였다. 동결토의 전단강도 특성을 측정하기 위하여 비교적 균질한 입경분포를 지닌 주문진표준사 및 실리카모래와 입도분포가 좋은 화강풍화토를 활용하였다. 각각 세가지 시료에 대하여 전단시험은 세가지 동결온도 조건 및 수직구속응력 조건에서 수행되었으며, 그 결과를 바탕으로 동결온도조건 및 수직구속응력이 동결토의 전단강도에 미치는 영향을 분석하였다. 전반적으로 동결토의 전단강도는 동결온도가 낮아질수록 증가하는 경향을 보였으나, 수직구속응력에 의한 영향은 미미한 것으로 나타났다.

• 한국도로학회논문집
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• 제20권3호
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• pp.1-9
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• 2018

PURPOSES : In order to evaluate a crack resistance at cold joint, sealing tape was adopted to apply at cold joint instead of typical tack coat material(RSC-4). The sealing tape was made by hot sealing material. The crack resistance as function of environmental and traffic loading was measured with visual observation. METHODS : In this study, the crack resistance was evaluated as function of environmental and traffic loading. The freeze-thaw method was adopted for environmental loading of asphalt pavement. condition. The damage of cold joint under freeze-thaw action is initiated by ice expansion load and accelerated by the interfacial damage between new and old asphalt pavement. The traffic loading was applied with wheel tracking machine on the cold joint area of the asphalt pavement for 3 hours at $25^{\circ}C$. The evaluation of crack resistance was measured with visual observation. The freeze-thaw results shows that the sealing tape was significantly increased the crack resistance based on. RESULTS : To estimate the crack resistance at cold joint area due to the environmental loading, the Freeze-thaw test was conducted by exposing the product to freezing temperature(approximately $-18^{\circ}C$) for 24 hours, and then allowing it to thaw at $60^{\circ}C$ for 24 hours. The tack coat material(RSC-4) was debonded after 21 cycles of the Freeze-thaw test. The first crack was observed after 14 freeze-thaw cycle with RSC-4 material. But, the sealing tape was not debonded after 24 cycle test. Also, the sealing tape shows the better performance of the crack resistance under the traffic loading with wheel track test. The crack was generated the under traffic loading with RSC-4(tack coating), however, the crack was not shown with sealing tape. It indicates that the sealing tape has a strong resistance of tensile stress due to traffic loading. CONCLUSIONS :Based on limited laboratory test result, a performance of crack resistance using the sealing tape is better than that of general tack coat material(RSC-4). It means that the sealing tape is possible to extend a pavement service life because the crack, one of the main pavement distresses, will be delayed.

• 한국식품과학회지
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• 제19권2호
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• pp.81-88
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• 1987

동결속도를 달리하여 제조한 2종의 동결건조 분말고추장 재수화 현탁액의 리올리지 특성을 원료고추장을 대조구로 온도 $25{\sim}60^{\circ}C$, 고형물 함량 $47{\sim}56^{\circ}C$, 전단속도 $0.1965{\sim}1.9650\;sec^{-1}$의 범위에서 Brookfield 단 원통 회전점도계로 측정하였다. 급속동결 분말고추장 및 완만동결 분말고추장의 재수화 현탁액과 원료고추장은 모두 항복치를 지닌 의가소성을 나타내고. 전단초기 20분까지 Tiu의 모델에 따라 2차 반응속도식으로 붕괴되는 thixotropic거동을 보여주였으며. 분말고추장 현탁액의 구조붕괴 속도가 원료고추장 보다 빨랐다. 평형구조변수는 전단속도에 크게 영향받지 않았으며 그 값은 세가지 시료 모두 비슷하였다. 급속동결분말고추장 및 완만동결 분말고추장의 재수화 현탁액과 원료고추장의 곁보기점도의 온도 의존성은 Arrhenius식과 일치하였으며. 활성화 에너지의 값은 가각 2.21, 2.18, $2.32\;Kcal/g{\cdot}mole $이었다. 세가지 시료의 점조도지수는 온도의 증가에 따라 감소하었으며, 고형물 함량의 증가에 따라 증가하였으나, 유동거동지수는 온두 및 고형물 함량에 거의 영향을 받지 않았다. 급속동결 분말고추장과 완만동결 분말고추장의 러올로지 성질은 큰 차이가 없었다.

• Reproductive and Developmental Biology
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• 제40권3호
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• pp.27-31
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• 2016

The aim of this study was to evaluate effect of ${\alpha}$-linolenic acid (ALA) on viability, acrosome reaction and mitochondrial intact in frozen-thawed boar sperm. The boar semen was collected by gloved-hand method and cryopreserved in 20% egg yolk freezing extender containing ALA (0, 3, 5, and 10 ng/mL) with 0.05% ethanol. The frozen-boar spermatozoa were thawed at $37.5^{\circ}C$ for 45 sec in water-bath. The spermatozoa samples were evaluated the plasma membrane integrity, acrosome reaction, and mitochondrial integrity using flow cytometry. In results, population of live sperm with intact plasma membrane was significantly higher in control and 3 ng/mL ALA treatment group than ethanol group (p<0.05). In contract, dying sperms were higher in ethanol group than 3 ng/mL ALA treatment (p<0.05). Acrosomal membrane damage in all sperm population was reduced in 3 ng/mL ALA groups compared with ethanol treatment (p<0.05). However, acrosome damage in live sperm population was no significant difference among the all treatment groups. Mitochondrial integrity was not influenced by ALA treatments in both of live and all sperm population. In conclusion, this results show that supplement of ALA during the cryopreservation process could reduce the membrane damages including plasma and acrosomal membrane, whereas ALA did not influence to mitochondria in boar spermatozoa. Therefore, these results suggest that ALA can protect against the membrane damage derived cryo-stress, and cryopreservation efficiency of boar semen would be improved by use of ALA.

• 한국수정란이식학회지
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• 제6권2호
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• pp.1-17
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• 1991

It is widely recognized that the embryonic or fetal loss after breeding is common in the cattle and that it is an important factor affecting reproductive efficiency. The causes of this loss have been subject of extensive researches and the results indicate that the embryonic mortality may he primary factor responsible for low pregnancy rates in non-embryo transfer bovine populations as well as embryo transfer programs. However, it's causes are still not clearly understood. The embryonic mortality or pregnancy rate has been influenced by various embryonic and maternal effects related to genetic and environmental factors. The timing and extent of embryonic mortality vanes greatly according to authors and estimating methods, because it is difficult to make direct measurements. The major important factors that may influence the embryonic losses or pregnancy rates after embryo transfer can be summeirized. 1.When an embryo is transferred to unmated recipients, the contralateral transfer to corpus luteum results in a lower survival rate than ipsilateral deposition. When the embryos are transferred for the production of twin calves, their survivals and twin pregnancies have quite inconsistent according to the transfer methods either to the unmated-synchronized or already mated recipients and more works are needed to accurrately clarify the previous results. 2.Although embryos can be cultured in vitro some hours without the great declines in pregnancy rates, the rates differ markedly among culture times and media but may be improved by co-transfer systems. 3.Embryo developmental stages and quality grades clearly affect the survival rate following freezing and the pregnancy rate after transfer and the selection of embryos without chromosome abnormalities and of high fertile semen may also be considered to increase the pregnancy rates. 4.Many researches have attempted to relate the plasma progesterone levels to pregnancy rates and others have done either direct progesterone supplementation or luteal stimulation by hCG treatment in order to increase the pregnancy rates. However, these effects on pregnancy rates are inconsistent and also contradictory. 5.The asynchrony between donors or embryos and recipients may he a major cause of embryo death and low pregnancy rate and the sensitivity to uterine asynchyony differs in according to the quality and stages of embryos. 6.The extremes of poor or over nutrition during early pregnancy in the recipients are detrimental to the survival of embryos and the good body condition is required to prevent a reduejion of pregnancy rates. The uterine pathogens in embryonic mortality or fertility have been questioned but the infection of C.pyogenes and Campylobacter fetus is still important pathogens. 7.The heat stress during early pregnancy may reduce conceptus weight and possibly increase the embryonic mortality.