• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(II)
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• pp.225-228
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• 2005

This paper was accomplished for analyzing the reason of the above deterioration happened on the deck of concrete bridge. The bridge was constructed at 660m above the sea level having more freezing and snowing days. Therefore, it is placed on the particular condition sprinkling $CaCl_2$ enough for keeping up with moderate traffic condition. When it is considered to the former condition, the bridge can be assumed to potentialities for combined deterioration with freezing-thawing under sprinkling deicing chemical. Core specimens were gathered from the concrete deck for clearing the reason of the above deterioration exactly, and it is used for various tests for measuring the compressive strength, elastic modulus, content of $Cl^-$, freezing-thawing at the fresh and salt water. As a result of freezing-thawing test, the specimen at the fresh water has over 90$\%$ of durability factor, but another specimen at 1$\%$ of salt water has 0$\%$ of durability factor at 140 cycles of the freezing-thawing. The result means that frost damage is sccelerated at the salt water. Therefore, the deterioration of the concrete deck is estimated to be occured by combined effects of freezing-thawing and chloride ion attack.

• 한국산림과학회지
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• 제103권4호
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• pp.528-536
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• 2014

최근 기후변화로 인해 관심이 증대되는 도시 녹지 내 난대상록활엽수의 동해피해 현황을 조사하여 그 특성을 분석하였다. 각 개체목의 주요 부위별 피해빈도를 분석한 결과, 줄기 피해는 동백나무가 59.6%로 가장 낮았으며, 후피향나무가 83.3%로 가장 많은 피해를 입은 것으로 나타났다. 피해도는 지역별로 진주지역이 가장 피해가 심하였으며(p<0.001), 식재구역의 경우 생태공원이 가장 높은 피해도를 보였다(p<0.001). 식재 환경별로 수하식재지(p<0.01), 단목식재(p<0.001), 평탄지(p<0.001) 및 유기물이 많은 곳(p<0.05)에서 피해도가 낮았다. 생육인자와 피해도와 간의 상관분석 결과 수고, 수관폭의 상관계수가 각각 -0.432, -0.470으로 피해도와 부의 상관관계로 나타났다. 따라서 효율적인 난대상록활엽수의 도시녹지 조성을 위해서는 수종, 입지환경 특성을 충분히 고려하여야 할 것으로 사료된다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 추계 학술발표회 제20권2호
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• pp.25-28
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• 2008

일반적으로 철근콘크리트 건축물은 외부의 기후에 노출되어 있어 겨울에서 이른 봄까지 동결과 융해의 반복적인 작용에 영향을 받는다. 이러한 동결융해 작용은 콘크리트의 균열을 발생시키거나 콘크리트 표면의 박리를 일으켜 내구성 저하의 원인이 된다$^{1),2)}$. 본 연구에서는 철근콘크리트보의 동결융해 경험에 따른 반복하중 하에서의 이력 특성의 평가를 위해 동결융해 사이클을 변수로 하여 철근콘크리트보의 반복하중 가력시 거동을 비교하고자 6개의 시험체를 제작, 실험하였다. 실험결과를 통해 동결 융해에 노출되어있는 철근콘크리트보의 반복하중하의 이력특성을 평가하는데 기초적인 자료를 제시하고자 하였다.

• 한국농공학회:학술대회논문집
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• 한국농공학회 1999년도 Proceedings of the 1999 Annual Conference The Korean Society of Agricutural Engineers
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• pp.294-300
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• 1999

After researching the physical properties of the concrete included Rice Husk Ash(RHA concrete) and workability of fresh concrete admixed RHA, we have tested durability of RHA-concrete against freeaing and thawing in the winter using rapid freezing and thawing test method(KS F 2456) . There aretwo hypotheses to explain the failure mechanism of a freezing and thawing action. First, the hydraulic pressure in the pores of freezing concrete make an internal stress of concrete structures outbreaking micro crack in the face of concrete, Second, Frost action causing damage to cement paste repeatedly come from soil frost action, freezing water in the capillaries. Initial Relative Dynamic Modulus of Elasticity (DME) was biggest in cae of unit binder weight 600kgf/㎥ and relative dynamic modulus of elasticity increased until 300cycles. In general , initial relative DME was proportional to unit binder weight . Relative DME was decreased in proportion to unit binder weight in the case of 300, 400, 500kgf/㎥ , but relative DME fo the others remained more than 90% until 300 cycles. It was not good effect of intermixed RHA to concrete in case of below unit binder weight 300kgf/㎥ and the resistance of freezing and thawing was not good either.

• 한국세라믹학회지
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• 제31권9호
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• pp.949-956
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• 1994

In order to investigate the relationship between pore size distribution and freezing-thawing resistance of mortars, polymer-cement mortars were prepared by using styrene-butadiene rubber latex, ethylene-vinyl acetate emulsion and polyacrylic ester emulsion with various polymer-cement ratios at constant flow. From the results of the test, polymer-cement mortars had a good pore size distribution for freezing-thawing resistance compared with unmodified mortars because of having a small pore volume in the pore radius range of 103~104 $\AA$ affecting on the frost damage. And the freezing-thawing resistance of polymer-cement mortars was improved with increasing polymer-cement ratio.

• Clinical and Experimental Reproductive Medicine
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• 제50권4호
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• pp.213-222
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• 2023

Cryopreservation is an option for the preservation of pre- or post-pubertal female or male fertility. This technique not only is beneficial for human clinical applications, but also plays a crucial role in the breeding of livestock and endangered species. Unfortunately, frozen germ cells, including oocytes, sperm, embryos, and spermatogonial stem cells, are subject to cryoinjury. As a result, various cryoprotective agents and freezing techniques have been developed to mitigate this damage. Despite extensive research aimed at reducing apoptotic cell death during freezing, a low survival rate and impaired cell function are still observed after freeze-thawing. In recent decades, several cell death pathways other than apoptosis have been identified. However, the relationship between these pathways and cryoinjury is not yet fully understood, although necroptosis and autophagy appear to be linked to cryoinjury. Therefore, gaining a deeper understanding of the molecular mechanisms of cryoinjury could aid in the development of new strategies to enhance the effectiveness of the freezing of reproductive tissues. In this review, we focus on the pathways through which cryoinjury leads to cell death and propose novel approaches to enhance freezing efficacy based on signaling molecules.

• 한국건설순환자원학회논문집
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• 제6권3호
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• pp.79-87
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• 2011

고로슬래그를 다량으로 혼입한 콘크리트를 동절기에 시공할 경우에는 배합에 따라서 응결과 경화가 현저히 지연되어 초기동해를 받을 위험성이 높다. 따라서 이 연구에서는 동절기에 고로슬래그를 다량으로 혼입한 콘크리트가 재령 초기에 동결을 받은 경우를 상정하여 초기동해가 콘크리트의 압축강도와 동결융해 저항성에 미치는 영향을 검토하였다. 그 결과, 고로슬래그를 다량으로 혼입한 콘크리트는 초기동해를 받음으로써 압축강도와 동결융해 저항성 모두가 현저히 저하되고, 고로슬래그를 혼입하지 않은 일반콘크리트에 비해서 특히 동결융해 저항성이 크게 저하되는 것으로 나타났다.

• 한국동물생명공학회지
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• 제35권1호
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• pp.58-64
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• 2020

This present study was conducted to investigate protective effect of discontinuous Percoll gradient containing alpha-linolenic acid (ALA) before freezing process on viability, acrosome damage, mitochondrial activity, and oxidative stress of frozen-thawed boar spermatozoa. The separation of spermatozoa by discontinuous Percoll gradient was performed by different concentration of Percoll solution (45/90%) containing ALA combined with bovine serum albumin (BSA), and collected sperm in each Percoll layer was cryopreserved. To evaluate viability, acrosome damage, mitochondrial activity, and reactive oxygen species (ROS) level of frozen-thawed sperm, flow cytometry was used. Morphological abnormalities were observed under light microscope. In results, viability of sperm from 90% Percoll layer was higher than control and 45% Percoll group (p < 0.05). Separated sperm in 90% Percoll layer had lower acrosome damage and morphological abnormalities than control as well as viability, whereas 45% Percoll group was higher (p < 0.05). Similar with acrosome damage and abnormalities, mitochondrial activity was slightly enhanced and the population of live sperm with high ROS level was decreased by 90% Percoll separation, however, there was no significant difference. Supplementation of 3 ng/mL ALA into Percoll solution increased sperm viability and decreased population of live sperm with high ROS compared to control (p < 0.05). In conclusion, discontinuous Percoll gradient before freezing process could improve efficiency of cryopreservation of boar sperm through selection of sperm with high freezing resistance, and supplement of ALA during Percoll gradient might contribute suppression of ROS generation via stabilizing of plasma membrane during cryopreservation.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1996년도 봄 학술발표회 논문집
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• pp.48-51
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• 1996

Recently, frost damage of storage tank for admixture agent caused by low temperature in winter and quality deterioration of admixture agent ofen happened. But, many problems are caused because of no applicable regulations of admixture agent facility and so on. Therefore, this study presents the reference data about using and quality control of admixture agent in practice and the judgement data about working out a counter plan of suitable heat insulation of injecion equipment of admixture agent exposed at outside in winter by measuring the freezing point of admixture agent for concrete.

• 한국식품영양과학회지
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• 제43권7호
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• pp.1055-1061
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• 2014

본 연구는 양파의 최적 냉동 분석 조건을 확립하기 위해 다양한 냉동속도가 양파의 이화학적 및 영양학적 특성 변화에 미치는 정도를 관찰함으로써 진행되었다. 본 실험에서는 강제송풍방식을 이용하였으며, 자연대류식($0.1^{\circ}C/min$), 저속 ($0.5^{\circ}C/min$) 및 고속($0.7^{\circ}C/min$)으로 냉동속도를 조절하여 $-12^{\circ}C$까지 냉동하였다. 냉동양파의 해동은 전자레인지를 이용하여 중심부의 온도가 $4^{\circ}C$가 될 때까지 400 W의 세기로 해동하였다. 분석 결과 양파의 강도는 데치기 처리된 양파(대조구)에 비해 냉 해동 후 현저히 감소하는 경향을 보였고, 냉동속도가 빠를수록 대조구와 유사하게 나타났다. 양파의 해동 감량은 냉동속도가 빠를수록 증가하였다. 양파의 색도는 냉동속도가 느릴수록 대조구와 현저한 차이를 보였다. 또한 전자현미경(SEM) 관찰 결과 냉동속도가 빠를수록 기공의 크기가 작았으며, 이는 빠른 냉동속도가 식품 조직의 손상을 방지하는 것으로 사료된다. 영양성분의 분석 결과 비타민 C의 경우 생 시료(대조구)에 비해 데치기 및 냉 해동처리 후 값은 감소하였지만 냉동속도에 따른 큰 차이는 나타나지 않았다. 유리당의 함량은 데치기 및 냉 해동 처리 후 감소하였으며, fructose, glucose 및 sucrose의 함량은 고속으로 냉동 시 가장 높았다. Citric acid, succinic acid 및 fumaric acid 함량은 냉동속도에 따른 차이는 없었고, malic acid 함량은 고속냉동 시에 가장 높은 값을 보였다. 본 연구결과 고속으로 양파를 냉동할 때 물리적 및 영양적 손실을 막아 품질을 유지하는데 효과적인 것으로 사료된다.