• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.6 no.4
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• pp.307-327
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• 2008

Geochemical study on the rocks and minerals of the Gyeongju low and intermediate level waste repository was carried out in order to provide geochemical data for the safety assessment and geochemical modeling. Polarized microscopy, X-ray diffraction method, chemical analysis for the major and trace elements, scanning electron microscopy(SEM), and stable isotope analysis were applied. Fracture zones are locally developed with various degrees of alteration in the study area. The study area is mainly composed of granodiorite and diorite and their relation is gradational in the field. However, they could be easily distinguished by their chemical property. The granodiorite showed higher $SiO_2$ content and lower MgO and $Fe_2O_3$ contents than the diorite. Variation trends of the major elements of the granodiorite and diorite were plotted on the same line according to the increase of $SiO_2$ content suggesting that they were differentiated from the same magma. Spatial distribution of the various elements showed that the diorite region had lower $SiO_2,\;Al_2O_3,\;Na_2O\;and\;K_2O$ contents, and higher CaO, $Fe_2O_3$ contents than the granodiorite region. Especially, because the differences in the CaO and $Na_2O$ distribution were most distinct and their trends were reciprocal, the chemical variation of the plagioclase of the granitic rocks was the main parameter of the chemical variation of the host rocks in the study area. Identified fracture-filling minerals from the drill core were montmorillonite, zeolite minerals, chlorite, illite, calcite and pyrite. Especially pyrite and laumontite, which are known as indicating minerals of hydrothermal alteration, were widely distributed in the study area indicating that the study area was affected by mineralization and/or hydrothermal alteration. Sulfur isotope analysis for the pyrite and oxygen-hydrogen stable isotope analysis for the clay minerals indicated that they were originated from the magma. Therefore, it is considered that the fracture-filling minerals from the study area were affected by the hydrothermal solution as well as the simply water-rock interaction.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2016.05a
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• pp.13-14
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• 2016

This study is aimed to analyze temperature history at each section of mat foundation concrete applying double bubble sheets. The results of the study are as follows. Firstly, the results of measuring the temperature history indicate that the lowest external temperature has been recorded at -5.6℃ for the three-day measurement period. For the central section, the result indicates that the lower, center and upper part have all secured the concrete curing temperature of 18℃ or higher. This results are believed to have resulted from excellent heat insulation performance of double bubble sheets. For the edge section between the edge form and the concrete interface, the temperature has been measured, on average, approximately 12℃ lower than the central section. However, all measured sections have indicated the temperature of 5℃ or higher. Meanwhile, an analysis has been conducted through the estimation equation of compressive strength of maturity during the curing period in order to examine the possibility of early frost damage and the aspect of securing strength. It has been confirmed that the compressive strength is higher than 50°D·D, namely, 5MPa, on the 3rd day of the aging process, which allows early frost damage to be avoided.

• Solar Energy
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• v.11 no.2
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• pp.63-69
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• 1991

A Steady laminar natural convection heat transfer from two isothermal square beams attached to a vertical adiabatic plate has been studied numerically. The results have been obtained for dimensionless beam spacings, $0.5{\le}D/L{\le}3.0$, and for Gr=5000-10000 at ${\phi}_2/{\phi}_1=1.0$. 1. The local Nusselt number from the beam surface is increased with the dimension-less beam spacing D/L. but that of the downward surface of the lower beam is almost same as the D/L increases. And, the local Nusselt number from the upward surface of a lower beam is greatly increased with D/L. 2. The beam spacings of the maximum mean Nusselt number for the downward surface of an upper beam and the upward surface of a lower beam occur at. D/L =2.6 and 2.0 respectively. 3. The beam spacing for the maximum total mean Nusselt number occurs at D/L = 2.6.

• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.4
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• pp.356-362
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• 2016

Light-weight concrete uses forming agents for reducing weight and high heat insulation property. However, the forming agents make problems of decreased volume and compressive strength of the concrete. This research aims to having weight-reduction and securing heat insulation property using recycled wasted form polyurethane without any forming agents. A small quantity of admixture used for constructability and avoiding material segregation. We picked admixtures from two different companies which shows evenly dispersed of wasted form polyurethane. This research conducts a study on the effect of mixing ratio of admixture on the light-weight concrete used wasted form polyurethane. As a result of the test, increased mixing ratio of the admixtures results reduced fluidity of concrete. On the other hand, percentage of moisture content and compressive strength are increased slightly. Combustibility performance and sound insulation performance are also secured, as well.

• Journal of the Korea Institute of Building Construction
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• v.15 no.2
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• pp.177-183
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• 2015

In this study, the thermal conductivity, physical and mechanical properties of lightweight aggregate concretes with hollow micro sphere(HMS) are experimentally examined as a basic research for the development of structural insulation concrete. As the results of this experiment, in the case of concrete mixed with HMS, the value of slump has been reduced, so it is found that the dosage of superplasticizer should be increased. As the replacement ratio of HMS increases, it has shown that the compressive strength is somewhat decreased due to the low interfacial adhesion strength of HMS. But the thermal conductivity is found to be greatly improved with the replacement ratio of HMS increases, the thermal conductivity of HMS shows the lower value of 68% at lightweight aggregate concrete and 32% of normal concrete. Also it is found that the compressive strength is decreased and thermal conductivity is increased as the water-cement ratio increases. The most outstanding for insulation performance is observed when using 20% of HMS and 50% of water-cement ratio.

• Journal of the Korea Institute of Building Construction
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• v.20 no.1
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• pp.35-41
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• 2020

The thin coating material used in the outer insulation finishing method is a finishing material mainly based on acrylic emulsion. In this study, the properties of silane modified acrylic emulsion and silica dispersed acrylic emulsion were evaluated. Experimental results showed that the silane modified acrylic emulsion had no significant effect on improving tensile strength, but was effective in improving the performance of adhesion strength, water absorption coefficient, and hot and cold repeat resistance. Silica-dispersed acrylic emulsions were effective in improving tensile strength, and at 10% substitution rate, they were effective in improving the performance of adhesion strength, water absorption coefficient and hot / cold resistance. Through this, it was judged that a composite emulsion capable of improving the performance of the acrylic emulsion could be prepared.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.617-622
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• 2001

This paper presents the effectiveness of cold weather concreting by applying both anti-freeze agent and insulating forms developed through previous study investigating insulating effects on the concrete and the strength gain. According to test results, in $-10^{\circ}C$ of air temperature, when euroforms are applied, the temperature of plain concrete drops below $0^{\circ}C$ and maintains its temperature during early 24 hours. However, when insulating forms are applied, the temperature of concrete keeps 8~$13^{\circ}C$ during first 24 hours. Insulating forms has better performance on insulating effects than existing euroforms. Concrete containing anti-freeze agent shows temperature rising effects about $1^{\circ}C$ compared to plain concrete. Strength gain of core concrete shows higher when insulating forms is applied.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.913-918
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• 2001

This paper investigates insulating effects and strength properties of concrete under cold climate carrying out the experiment with insulating forms on the slab member. According to test results, under $-10^{\circ}C$ of outer temperature, the surface of concrete exposed to outer temperature goes below zero after 10hours since exposed. And, the surface of concrete covered with vinyl and blanket goes below zero after 42hours. However, the surface of concrete covered with insulating materials such as polystyrene foam does not drop below zero until 55hours. And, according to coring sample strength test, compressive strength cured with insulation shows much higher strength than no insulation curing condition and vinyl and blanket curing condition.

• Proceedings of the KAIS Fall Conference
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• 2009.12a
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• pp.167-170
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• 2009

최근 에너지 사용이 획기적으로 증가함에 따라 효율적인 에너지 사용이 필요하게 되었다. 특히 건물에서 벽체보다 에너지 손실이 많이 발생하는 창호의 경우 단열성능이 좋은 고효율 진공유리의 사용이 절실하나, 가격 및 성능 등의 문제로 보급화가 늦어지고 있는 실정이다. 본 연구에서는 저가형 고효율 진공유리 개발을 위한 기초 연구로써 유리 용접용 수소-산소 혼합가스 토치 개발하기 위한 열해석을 수행하였다. 주로 토치의 형상, 노즐 배치 및 직경 변경을 통한 토치 최적화를 수행하였다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1993.04b
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• pp.166-171
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• 1993

절삭공구에의한 절삭가공은 오늘날 가장 보편화된 가공기술중의 하나이다. 그런데, 최근들어 각종 첨단산업의발전과 함께 초정밀 부품제작이 필수선결 조건으로 부상하고 있으며, 이에대한 해결방안중의 하나로 초정밀가공 기 술로 크게 대두되고 있다. 최근 컴퓨터 기술의 발달에 따라 구조해석분야의 해석방법론의 개발 및 보완에 힘입어 Klemecki(1973)에 의해유한요소법을 이용한 Chip생성기구 해석에 관한 연구가수행되었으며, Stevenson(1983) 등에의해단열조 건하에서 변형률과 온도 상태에서의 Chip형상, 잔류응결-변형율에 대한 연구가 이루어졌다. 본 연구에서는 유한요소법을 이용하여 미소절삭기구를 모델링하고, 절삭인자규명을 중심으로 응력-변형률 해석을 실시함으로써, 미소절삭시의 Chip 생성기구 및 전단면 생성 원리, 공구와 Chip간의 마찰기구의 고찰을 통해기본 Mechanism 이해와 적절한 절삭유한요소모델 제시의 기초자료로 삼고자 한다. 특히 본 보고서에서는 미소 절삭기구의 적정한 Constitutive Deformation Law 마찰계수 등 주요절삭인자변경에 따른 미소절삭기구 해석에 주안점을 두어 연구한 결과를 기술하였다.