• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(II)
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• pp.505-508
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• 2005

Concrete has a void, which exists as one of defect in concrete. If the porosity of concrete increases, durability of concrete decreases. In this paper, to improve surface void of concrete, surface penetration sealers are applied to specimen. And it were investigated that the resistances of chloride penetration and freezing and thawing for concrete with surface penetration sealer of two types. According to the results, surface penetration sealer has not show a harmful influence on strength and resistance of freezing and thawing. Also, B type surface penetration sealer was more superior in resistance of chloride penetration.

• 한국주조공학회지
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• 제41권3호
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• pp.241-251
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• 2021

7000계 알루미늄 합금은 다른 Al 합금에 비해 강도가 우수하여 주목을 받고있으며, 7000계 알루미늄 빌렛은 일반적으로 Direct-Chill (DC) 주조 공정을 통해 제조된다. DC 주조 공정으로 제조된 알루미늄 빌렛의 표면 결함은 주로 Exudation과 Meniscus freezing 현상과 관련이 있으며, 이는 합금 성분, 주조 속도 및 주조 온도의 영향을 받는다. 특히, 7000계 알루미늄 합금은 응고 과정에서 응고 온도 범위가 넓어 주조 결함이 발생하기 쉽다. 본 연구에서는 DC 주조 공정에 의해 제조된 Al-8Zn-2Mg-2Cu 합금 빌렛에 대한 표면 결함 변화에 대하여 조사하였다. 빌렛의 표면은 "Wavy" 또는 "Dot" 표면으로 관찰되었다. Wavy 표면은 낮은 주조 속도(200mm/min)와 온도(655℃)에서 Meniscus freezing 현상에 의해 형성되었으며, Concave 영역에서 Meniscus freezing 현상으로 인한 조성작 과냉으로 인해 미세한 수지상 조직이 관찰되었다. 반면에, 주조 온도가 높은 조건(675℃)에서는 Dot 표면이 기공 형성에 의해 형성되었으며, 높은 주조 속도(230mm/min)에서 제조된 Dot 표면을 갖는 빌렛에서는 높은 금속 수두압에 의해 Exudation 층이 형성되었다. Exudation 층의 Dot 영역과 Smooth 영역은 각각 미세한 수지상 형태와 주상정 형태의 조직이 관찰되었으며 이는 Dot 영역에서 가스 기공의 형성에 의한 결과이다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1994년도 연약지반처리위원회 봄 학술발표회 논문집 연약지반처리
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• pp.13-46
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• 1994

Artificial ground freezing methods have been applied to geotechnical construction projects for stabilizing earth materials and controlling water seepage into the ground. However, this can result in frost heaving and causes the same engineering problems as encountered with the natural freezing of soil. In natural freezing, the ground freezes from the surface downward. When artificial ground freezing is applied at a deep location, however, freezing is limited locally. The soil condition differs between them as follows: Natural freezing - unsaturated and without overburden pressure. Artificial freezing -- saturated and under overburden pressure. The authors investigated the practical application of artificial ground freezing and examined the frost behaviour of a saturated soil under overburden pressure. This paper presents the results obtained from experiments concerning frost heaving and discusses frost heaving at the freezing site.

• 대기
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• 제25권1호
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• pp.31-49
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• 2015

From the hourly data of 75 Korean weather stations over a 12-year period (2001~2012), this study has chosen three cases (January 12, 2006; January 11, 2008; and February 22, 2009) of multiple freezing rains and investigated the atmospheric circulations that seemed to cause the events. As a result, the receding high pressure type (2006), prevailing high pressure type (2008), and warm front type (2009) are confirmed as synoptic patterns. In all three cases, freezing rain was found in regions with a strong ascending current near the end point of a low-level jet that carried the warm humid air from low latitudes. The strong ascending current resulted from lower-level convergence and upper-level divergence. In 2006 and 2009, the melting process was confirmed. In 2008, the supercooled warm rain process (SWRP) was confirmed. In contrast to existing SWRP theory, it was found that the cool air produced at the middle atmosphere and near the earth's surface led to the formation of freezing rain. The sources of this cool air were supposed to be the evaporative latent heat and the cold advection coming from the northeast. On the other hand, a special case was detected, in which the freezing rain occurred when both the soil surface temperature and surface air temperature were above $0^{\circ}C$. The thickness distributions related to freezing rain in Korea were found to be similar to those in North America. A P-type nomogram was considered for freezing rain forecasting; however, it was not relevant enough to Korea, and few modifications were needed.

• 한국농공학회지
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• 제38권5호
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• pp.116-124
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• 1996

The purpose of The work described in this paper is to clear up the initial moisture content, specific surface, air drying and freezing-thawing process on liquid limit of clayey soils distributed widely at estuary of three main rivers in the west coast. To this end, a series of tests were conducted on clayey soils samples with natural state and treated state. From the test results, the liquid limit was decreased with decrement of initial moisture content, air drying process, and freezing-thawing cycles and increased with increment of specific surface. The specific surface which influenced on the liquid limit is over $25 m^2$m$^2$/g, and their relationships are well formulated. Air drying process is expected to improve the engineering properties of the soils such the pro-water properties were changed to anti-water proper-ties through lowering of water holding as resulted to incline from A-7-5 to A-5 on the soil classificaction plastic chart. The freezing-thawing process decreased 20% of liquid limit, especially under the first cycle of the behavious, as a result of above mentioned reasons, phase change of soil-water system brought the decrement of specific surface and affected to the liquid limit.

• 한국응용과학기술학회지
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• 제38권6호
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• pp.1355-1369
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• 2021

본 연구는 도로 노면결빙 판정 알고리즘에 대해 알고리즘을 개선하고 실제 현장 측정 자료와 알고리즘 예측값을 비교하였을 때 알고리즘에 대한 적중률을 분석하였다. 분석을 위하여 포천시 신북면 금동리의 도로 및 기상을 측정하였다. 알고리즘은 기존 도로 결빙 알고리즘을 선정하여 실제 결빙 조건 및 측정 수치에 맞춰 4차 알고리즘까지 개선하였다. 최종적으로 응결에 의한 결빙, 강수에 의한 결빙, 적설에 의한 결빙, 결빙상태의 지속, 풍속에 의한 결빙 5개의 알고리즘을 제작하였다. 포천 현장에서 알고리즘을 활용하여 예측할 경우 경우 결빙 적중률이 93.22%까지 개선되었다. 결빙 알고리즘에 대한 조합 비율에 대해 도출하였을 때 응결에 의한 결빙과 결빙상태의 지속에 대한 알고리즘이 96%를 차지하였다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2010년도 춘계학술대회 논문집
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• pp.1077-1078
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• 2010

• 한국구조물진단유지관리공학회 논문집
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• 제5권1호
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• pp.131-140
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• 2001

In general, the deterioration induced by the freezing and thawing cyclic in concrete structures often leads to the reduction in concrete durability by the cracking or surface spalling. If it can prediction of concrete deterioration subjected to cyclic freezing and thawing, we can rationally do the design of mix proportion in view of concrete durability and the maintenance management of concrete structures. Therefore in this study a prediction method of deterioration for concrete structures subjected to the irregular freezing and thawing is proposed from the results of accelerated laboratory freezing and thawing test using the constant temperature condition and the in-situ weathering data. Furthermore, to accurately predict the concrete deterioration, a method of modification for the effect of hydration increasing during rapid freezing and thawing test is investigated.

• 대기
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• 제25권3호
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• pp.389-405
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• 2015

In this study, the occurrence circumstances of 3 cases (12 Jan 2006, 11 Jan 2008, 22 Feb 2009) when the freezing rain was observed at more than two observatories in a day with more than three times each observatory, were investigated. Following the advanced study about the same cases, we have tried to find more delicate differences in using the Korea Local Analysis and Prediction System (KLAPS; 5 km reanalysis data) that has the smallest grid scale at current situation. As results, three common characteristics are found: (1) Just before the occurrence of the freezing rain, the wind direction was consistently continuous and the wind speed was constant or gradually increased for at least 3 hr more. (2) Surface air temperature (Relative humidity) was respectively $3.08^{\circ}C$ (28.76%), $0.47^{\circ}C$ (50.07%) and $-3.60^{\circ}C$ (71.07%) 3 hr ago to break out the freezing rain. It means the freezing rain occurs in a wide range of atmospheric environments. However, the closer it got to the occurrence time of the freezing rain, the closer the surface air temperature was to $0^{\circ}C$, and the bigger the humidity of the surface air was. (3) The liquid precipitation formed in the upper atmosphere, met a cold advection bellower than 950 hPa level and suspected to be changed to the super-cooled condition.

• 한국임상수의학회지
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• 제8권2호
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• pp.183-190
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• 1991

Pellet and straw methods in canine semen freezing are compared with respect to motility, viability and acrosome demage of sperm during each of the two major processing steps, to prior-freezing and to frozen-thawing. Senen was extended with a tris-buffered egg yolk contained 4% glycero1 Pellet freezing in the hole of dry ice and straw freezing on the surface of liquid nitrogen were carried out, respectively. The frozen semen 10 days after storage in liquid nitrogen container. wao thawed. In the comparison of two freezing methods, the straw freezing method with 42.7% in motility. 49.2% in viability and 0.186 acrosome score after thawing seems to be superior to the pellet freezing method with 31.2%, 34.5% and 0.314%, respectively. Sperm motility of processing step to frozen-thawing against decrease rate 12.67% to Prior freezing appeared of 33.84% and 49.37% in straw and pellet freezing and increase of 0.02 in acrsomal score to prior freezing appeared of 0.08 and 0.21 in straw and pellet freezing method to frozen-thawing