• Journal of the Computational Structural Engineering Institute of Korea
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• v.22 no.4
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• pp.315-322
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• 2009

This paper presents a novel numerical method based on the extended moving least squares finite difference method(MLS FDM) for solving 1-D Stefan problem. The MLS FDM is employed for easy numerical modelling of the moving boundary and Taylor polynomial is extended using wedge function for accurate capturing of interfacial singularity. Difference equations for the governing equations are constructed by implicit method which makes the numerical method stable. Numerical experiments prove that the extended MLS FDM show high accuracy and efficiency in solving semi-infinite melting, cylindrical solidification problems with moving interfacial boundary.

• Journal of Embryo Transfer
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• v.9 no.1
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• pp.103-110
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• 1994

소 난포란의 체외성숙율과 체외수정후 분할율을 향상시키기 위하여 성숙배양액에 FCS 첨가 효과를 조사하였으며 FCS의 첨가수준은 5-20%였고 사용된 기본배양액은 Dn(-BSA), Ham's F10 및 TCM199이었다. 난포직경 2-6mm 난포로부터 채란된 수정란을 39$^{\circ}C$ 배양기에서 28시간 성숙시킨후 동결융해정자 또는 비동결정자로 체외수정시켰다. FCS 무첨가구보다는 첨가구 성숙유리 향상되었으나 FCS 첨가의DM(-BSA)와 Ham's F10간에, 그리고 FCS첨가수준간에는 성숙율의 차이가 없었다. FCS의 첨가로 성숙율은 향상되었으나 난할율에는 영향이 없었다. 체외수정 난포란의 난할율이 HIS 처리후 6시간 전배양한 동결정자와의 수정에서는 현저히 낮았으나 2시간 전배양과 정자에 의해서는 향상되었고 비동결정자이용시 더욱 향상되었다. FCS 첨가된 Ham's F10과 TCM199에서 성숙시킨 난자의 난할율이 DM(-BSA)+FCS보다 높았다. 본 연구 결과에서 난포란의 체외성숙이 FCS첨가로 개선되었으나 난할율에는 영향이 없었으며 난할율이 정자처리방법에 따라 차이가 많았고 Ham's F10과 TCM199에 FCS의 첨가가 보다 효과적이었다.

• Reproductive and Developmental Biology
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• v.29 no.3
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• pp.193-199
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• 2005

The cryopreservation of germ cells, sperm and embryos, has been largely used to increase the effect of artificial reproductive techniques for human infertility, but the efficiency of germ cell cryopreservation has been conkoversial till now. Thus, the effect of the cryopreservation of human sperm used for ICSI and the effect of the cryopreservation of embryos produced by ICSI on fertilizatiof development and pregnancy were investigated. Sperm freezing did not affect fertilizatiort development and pregnancy rates. Also, there was no significant difference between ejaculated and testicular sperm in ferclizatiort development and pregnancy. Embryo freezing methods, slow freezing and vitrificatior did not differ each other in viability and pregnncy rates. However, ICSI embryo freezing significantly decreased pregnancy rate compared to fresh embryos freezing (p<0.05). In conclusiof this result suggested that cryopreservation of sperm for ICSI did not affect on the resulted embryo development and pregnancy, but ICSI embryo cryopreservation would significantly inhibit pregnancy.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.26 no.1
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• pp.39-48
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• 2013

This paper develops a 2-D moving least squares(MLS) difference method for Stefan problem by extending the 1-D version of the conventional method. Unlike to 1-D interfacial modeling, the complex topology change in 2-D domain due to arbitrarily moving boundary is successfully modelled. The MLS derivative approximation that drives the kinetics of moving boundary is derived while the strong merit of MLS Difference Method that utilizes only nodal computation is effectively conserved. The governing equations are differentiated by an implicit scheme for achieving numerical stability and the moving boundary is updated by an explicit scheme for maximizing numerical efficiency. Numerical experiments prove that the MLS Difference Method shows very good accuracy and efficiency in solving complex 2-D Stefan problems.

• Journal of the Korea Concrete Institute
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• v.14 no.1
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• pp.16-23
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• 2002

In construction field, million tons of demolished concrete are produced in korea. It is urgently needed that they are used as recycled materials in order to prevent environment pollution and gain economic profits. However, existing recycling methods of demolished concrete have their limits for wide application. They have been only focused on the burying and banking. Therefore, in this paper, physical and mechanical properties of planting concrete using construction wastes for aggregates are described in order to investigate the validities of demolished concrete as recycled aggregates. The Properties of strength and durability are tested. According to the experimental results, compressive strength and freeze-thaw resistance of planting concrete using recycled aggregates shows worse performance than those using crushed stone concrete. But, it shows positive performance on the absorption ratio and thermal conductivity. Especially, considering the side of recycling of concrete wastes, it is recommended that recycled aggregates made with construction wastes is applied to planting concrete.

• Composites Research
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• v.21 no.3
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• pp.24-30
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• 2008

Durability problems may arise in the concrete, which is one of the major construction materials, used in the construction field. Bridge piers and foundation piles are usually made with concrete and they are exposed to the moisture and hence the durability of the concrete reduced significantly due to oxidization of re-bar and icing of concrete. To mitigate such problems, FRP tube has been developed and the concrete filled FRP tube (CFFT) has been investigated to find the confinement effect which is provided additionally. It was reported that if the concrete is wrapped with FRP, strength and chemical resistance are improved significantly. In order to apply such a member in the construction field, structural behavior and applicable design guideline or design criteria must be thoroughly investigated. In the experimental investigation, the results are compared with the previous research results and the relationship which can predict the ultimate strength and strain is suggested. In addition, some comments found at the compression tests are given briefly.

• Journal of the Korean GEO-environmental Society
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• v.13 no.2
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• pp.5-17
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• 2012

The amount of snow due to global warming and climate change has recently increased. The effective management of snow removal materials will be required. First, on the basis of domestic winter temperature, it is not necessary to get a baseline to less than the freezing point of $-52^{\circ}C$ for the calcium chloride($CaCl_2$) of 30%.. In terms of cost comparison between calcium chloride($CaCl_2$) and sodium chloride($NaCl$), the calcium chloride($CaCl_2$) is 2 to 3 times more expensive, and the supply of the calcium chloride($CaCl_2$) is not produced in domestic country and is in the conditions that have to imports all needed. Accordingly, the effective use scheme of snow removal materials should be considered to multifaceted ways. Thus, the objective of this study is to develop effective method and to replace from calcium choride($CaCl_2$) to sodium chloride($NaCl$) solution in the current snow removal operating system that uses a pre-wetted salt spreading method. The effective method that equals to the quality of the existing snow removal materials was developed in this study through performance tests for deicing chemicals, corrosion test of steel and freezing and thawing tests of concrete.

• Reproductive and Developmental Biology
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• v.31 no.1
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• pp.43-48
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• 2007

This study was conducted to examine the characteristics of fresh and frozen semen, proliferating efficiency by AI, and the coat color of offsprings in Korean Native Striped Cattle (Bos namadicus Falconer, Chikso). Semen were collected from 6 heads of tiger-coated male Chikso. In vitro fertilization (IVF) was conducted with frozen-thawed semen and in vitro matured Korean native brown cattle (general Hanwoo) oocytes. Total 18 heads of Hanwoo and Chikso were inseminated using Chikso semen. Coat colors of total 40 offsprings produced by AI were evaluated. The characteristics of the fresh and frozen-thawed Chikso semen did not differ among individuals. In vitro fertilization rate of Chikso semen was not different from that of general Hanwoo semen. However, developmental rate to the blastocyst stage of IVF embryos was higher in Chikso semen (25.9%) than in general Hanwoo semen (p<0.05). There was no difference in conception rate after AI between Chikso and general Hanwoo. The coat colors of offsprings varied, only 42.5% (17/40 heads) of offsprings had tiger coat color. Futhermore, only 55% of offsprings produced from the tiger-coated recipients had tiger coat color. This result shows that proliferation of Chikso by AI is possible, but further research approaches may be needed to enhance the productivity of tiger-coated Chikso.

• Proceedings of the Korean Society of Developmental Biology Conference
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• 2003.10a
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• pp.127-127
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• 2003

본 연구의 목적은 젖소에서 다배란유기법의 확립을 위해서 호르몬을 처리법을 달리한 결과이다. 난포의 발생을 자극하는 FSH 호르몬을 하루에 2번의 호르몬 주사를 하는 데, 이는 혈액내에 난포자극호르몬의 농도를 연속적으로 유지하여 난소에서 다난포 발생의 목적을 달성하고자 하는 방법이다. 하지만 빈번하게 호르몬을 주사하는 방법은 처리하는 노력이 필요하고 공란우도 스트레스로 작용한다. 이러한 단점을 극복하기 위해 한번에 많은 난포의 성숙을 유도하는 다배란처리법에 대한 보고가 많이 있어, 본 연구에서 이 다배란처리 효과를 비교하고자 젖소를 이용하였다. 방법으로는 다회주사법(8회)과 일회주사법(1회)에서 황체수와 수정란의 생산수 등을 조사하였다. 다회주사법은 생리식염수에 융해한 FSH를 1일 50mg씩 2회(12시간 간격)주사하는 법으로 CIDR 질내 주입 9일째부터 4일간 주사하였으며, 질내에 CIDR를 주입하고 11일째되는 날에 PG(25mg, 루텔라이스, 한국)를 주사하고, 12일째는 CIDR를 제거하여 일회주사법과 주기를 맞추었다. 일회주사법은 CIDR를 질내에 주입하고 나서 9일째 되는 날에 400mg의 FSH을 생리식염수에 융해하여 일회주사를 하고 다회주사법과 같이 인공수정과 채란시간을 맞추었다. 인공수정은 황체퇴행제(PG)를 주사하고 나서 48, 72시간에 2회 인공수정을 실시하여 1주일 후 수정란을 채란하였다. 인공수정시는 반드시 GnRH(2.5mg)를 동시에 주사하였다. 채란은 인공수정 후 7일째 되는 날에 비외과적으로 채란을 실시하여 우수한 수정란은 동결을 실시하였다. 다회주사법에서 14두, 일회주사법에서 14두를 공시하여 황체수, 회수수정란수, 배반포수, 동결란수를 조사하였다. 다회주사법에서는 황체수는 8.07$\pm$6.62개, 회수정란수는 6.78$\pm$5.96개, 배반포율은 58.9%, 동결란 생산율은 52.6%의 성적을 얻었으며, 일회주사법에서 황체수는 12.07$\pm$8.07개, 회수수정란수는 10.0$\pm$9.24개, 배반포율은 27.1%, 동결란 생산율은 25.0% 수준의 결과를 얻었으나 결과에 대한 통계분석시 다회주사법과 일회주사리법 간에 유의적인 차는 인정되지 않았다(student T-test, P<0.05). 본 실험의 결과에서 나타나듯이 생리식염수를 용매로 이용한 FSH 1회 주사법이 다회주사법과 비교하였을 때에 수정란 생산효율에서 유의적인 차이가 없으므로 이 방법을 이용한 다배란유기는 노동력과 공란우에 대한 스트레스를 경감할 수 있을 것으로 사료된다.

• Journal of the Korean GEO-environmental Society
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• v.10 no.4
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• pp.15-24
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• 2009

Korea is known to have seasonal frost during winter and the effect of low temperatures and water may cause a weakening of pavements. For that reason, frost protection layers have been constructed in pavements to avoid damage caused by frost action. The practies established in USA and Japan have been adopted as anti-frost design methods in Korea. However, the characteristics of Korean soils are different. Additionally, there is no formulation of a reasonable equation for frost penetration depth and the criterion to identify potentially frost-susceptible soils in present pavement design manuals in Korea. Therefore, adequate pavement design procedures in seasonal frost areas, as well as construction and maintenance practices are required. In this paper, frost penetration depths along national roads in Korea were measured and analyzed over several years. The frost penetration depth was analyzed with respect to the provinces of Korea and sunny/ shaded areas. Additionally, measurement results were compared to the formula of the US Army Corps of Engineers and Ifukube in Japan.