• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
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• pp.753-756
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• 2005

Recently, the alkali activation of Fly-ash has become a significant field of research because it is possible to use these materials having highly chemical reaction property. Also, the product does not generate CO2 gas, unlike ordinary Portland cement(O.P.C). Therefore, the purpose of this paper is to design for improving mechanical and chemical properties using Fly-ash and Meta-kaolin. And additive(CaO) affected to control the strength behaviors and shrinkage rate.

• 한국세라믹학회지
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• 제27권7호
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• pp.877-882
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• 1990

Effects of metallic Al powder addition on basic and thermal properties of castable refractories were investigated. Generally, low grade prooperties were obtained by metallic Al powder addition with the increase of temperature, comparing with those of non-addition of Al powder. Especially, Al addtion showed severe shrinkage, corrosiion and low strength above 1000$^{\circ}C$. As a result of Al addition, lower strength of and higher corrosion resistance were shown for 2% addition, but it was reversed for above 4% addition. It was found that Al addition was excellent in the explosive spalling test regardless of Al quantity.

• International Journal of Industrial Entomology and Biomaterials
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• 제38권2호
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• pp.31-37
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• 2019

Silkworm larval mortality specifically during spinning stage leading to non-spinning with specific morphological symptoms was frequently complained by sericulturists in Karnataka, India during 2015. Survey was conducted and information collected through questionnaire from the identified farmers who faced the problem of non-spinning in both traditional and non-traditional areas of Karnataka. Survey results indicate that the problem is specific to the silkworm crop of those farmers' who shifted from other crops of agriculture/ horticulture/olericulture/ floriculture to Sericulture. Silkworm rearing performance of the batches fed with these leaves confirmed that the pesticide sprayed to the crops previous to mulberry, remain in the soil and when mulberry plantation is taken up in these gardens, the pesticide is absorbed by the roots of mulberry plants and transported to the leaves. Silkworms that feed on these mulberry leaves, grow and ripen normally but during spinning stage, larvae die with external symptoms like regurgitation, body shrinkage, rectal protrusion later become hook shaped leading to non-spinning or partial metamorphosis into pupa and death or spin flimsy cocoons. Larval mortality ranged from a minimum of twenty five percent to a maximum of hundred percent. The problem was noticed from the first harvest of leaves and lasted for a maximum period of 36 months. Cocoon crop loss depends on the concentration, duration and type of pesticides used previously for other crops.

• Clinical and Experimental Reproductive Medicine
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• 제42권3호
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• pp.94-100
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• 2015

Objective: The goal of this study was to ascertain optimal assisted hatching (AH) method in frozen embryo transfer. We compared the effect of depending on whether mechanical or laser-AH was performed before or after the vitrification of embryo development rate and blastocyst cell numbers. Methods: In order to induce superovulation, pregnant mare's serum gonadotropin followed by human chorionic gonadotropin were injected into 4- to 5-week-old female mice. 2-cell embryos were then collected by flushing out the oviducts. The Expanded blastocysts were recovered after the collected embryos were incubated for 48 hours, and were then subjected to artificial shrinkage (AS) and cross-mechanical AH (cMAH) or quarter-laser zona thinning-AH (qLZT-AH) were carried out using the expanded blastocysts before or after vitrification. After 48 hours of incubation, followed by vitrification and thawing (V-T), and blastocysts were fluorescence stained and observed. Results: The rate of formation of hatched blastocysts after 24 and 72 hours of incubation was significantly higher in the AS/qLZT-AH/V-T group than in the other groups (p<0.05). The cell number of the inner cell mass was higher in AS/V-T/non-AH and AS/V-T/cMAH groups than those of others (p<0.05). In the control group, the number of trophectoderm and the total cell number were higher than in the AS-AH group (p<0.05). Conclusion: The above results suggest that AS and AH in vitrification of expanded blastocysts lead to the more efficient formation of hatched blastocysts in mice.

• 콘크리트학회논문집
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• 제16권1호
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• pp.54-60
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• 2004

발포폴리스티렌(EPS)의 효율적인 재활용 기술개발의 일환으로서 폐 발포폴리스티렌을 중합성 모노머인 스티렌에 용해한 고분자 용액에 가교제, 개시제, 촉진제 등을 첨가하여 상온 중합성 결합재를 개발하였으며 이를 이용한 폴리스티렌 모르타르를 제조하여 그 중요한 경화특성인 사용가능시간, 건조양생재령에 따른 발열온도 및 길이변화 거동에 미치는 폐 발포폴리스티렌 용액농도 및 TMPTMA 첨가량의 영향에 대해서 검토하였다. EPS용액을 이용한 결합재 및 폴리스티렌 모르타르의 사용가능시간은 EPS용액 농도 및 TMPTMA 첨가율의 증가에 따라서 짧아지며, 또한 폴리스티렌 모르타르의 경화에 따른 길이변화는 EPS용액 농도 및 TMPTMA 첨가율에 크게 영향을 받는데 이를 적절히 조절하여 경화특성을 제어함으로써 저수축 혹은 무수축 폴리스티렌 모르타르의 제조가 가능하다는 것을 검증하고 있다.

• Elastomers and Composites
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• 제35권3호
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• pp.196-204
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• 2000

방수제로 사용하는 EVA 에멀젼 수지에 라텍스 형태의 아크릴 수지, 에폭시 수지, 우레탄 수지, SBR 수지를 전체 혼합물 중에 $0{\sim}50%$ 혼합하여 소포성, 기계적 물성, 내수성 등을 조사하였다. 소포제의 소포효과는 BYK-021이 가장 우수하였으며 적절한 사용량은 전체 혼합물에 대하여 0.3phr이었다. 수축율은 수지간의 상용성과 기공형성도에 영향을 받았으며 기계적 강도는 수지 분자간의 응집력, 수지와 시멘트의 결합력, 시멘트 입자간의 응집력 등에 영향을 받았다. 라텍스를 혼합한 것은 혼합하지 않은 것보다 수축율, 굴곡강도, 접착강도, 충격강도 등에서 우수한 물성을 나타내었다. EVA에 시멘트를 혼합했을 때에는 혼합하지 않았을 때보다 내수성이 떨어졌다.

• Archives of Plastic Surgery
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• 제35권3호
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• pp.248-254
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• 2008

Purpose: Human acellular dermal matrix(ADM) is widely used in the treatment of congenital anomalies and soft tissue deficiencies. But it is rapidly degraded in the body and does not provide satisfactory results. There is a need to improve collagen fiber stability through various methods and ultimately regulate the speed of degradation. Methods: The ADMs were added with various cross-linking agents called glutaraldehyde, dimethyl 3,3'-dithiobispropionimidate to produce cross-linked acellular dermal matrices. 1,4-butanediol diglycidyl ether solution was applied with a pH of 4.5 and 9.0, respectively. The stability of cross-linked dermal matrix was observed by measuring the shrinkage temperature and the degradation rates. The cross- and non-cross linked dermis were placed in the rat abdomen and obtained after 8, 12 and 16 weeks. Results: The shrinkage temperature significantly increased and the degradation rate significantly decreased, compared to the control(p<0.05). All of cross-linked dermises were observed grossly in 16 weeks, but most of non-cross linked dermis were absorbed in 8 weeks. Histologically, the control group ADM was found to have been infiltrated with fibroblasts and most of dermal stroma were transformed into the host collagen fibers. However, infiltration of fibroblasts in the experiment was insignificant and the original collagen structure was intact. Conclusion: Collagen cross-linking increases the structural stability and decreases degradation of acellular dermis. Therefore, decrease in body absorption and increase in duration can be expected.

• 한국염색가공학회지
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• 제23권4호
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• pp.233-240
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• 2011

A fineness range of 150 Nm-170 Nm has recently been applied to produce much finer wool products, so that processing techniques for the wool fabrics have been developed very rapidly. However, the worsted wool-like technique using polyester fiber has not been still implemented in general processing technique. Therefore, this research is to develop materials of side-by-side type with high finess, high shrinkage and stretchability. The mechanical properties of the produced fabrics were analyzed and the fundamental information were obtained for the new worsted wool-like products. The physical properties of a latent crimped yarns of side-by-side type with stretch function are analyzed. Also the mechanical properties of five kinds of fabrics are analyzed, which are produced with non-circular shape(+type) warp yarns of a twist of 1000(T/M) and with two kinds of latent weft yarns of a twist of 1000 T/M and DTY respectively.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1998년도 가을 학술발표논문집(II)
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• pp.258-261
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• 1998

Aggregate is cheaper than cement and confers considerable technical advantages on concrete, which has a higher volume stability and better durability than hydrated cement paste alone. and coarse aggregate is the largest particle size out of concrete and is much affect on the fruidity, compaction and non-segregation ability of high flowing concrete. As the compaction, fillingability and shrinkage of high flowing concrete, the volume ratio of coarse aggregate is prescribed by Japanese Architectural Standard Specificateon (JASS 5) : from 0.500 to 0.500㎥/㎥. It is the aim of this study to compare and analysis the fruidity, fillingability and non-segregation of high flosing concrete according to the volume ratio of coarse aggregate of concrete(G/Glim).

• Structural Engineering and Mechanics
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• 제15권3호
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• pp.345-365
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• 2003

The adoption of fibre reinforced polymer (FRP) rebars (whose behaviour is elastic-brittle) in reinforced concrete (RC) cross sections requires the assessment of the influence of time-dependent behaviour of concrete on the load-carrying capacity of these sections. This paper presents a method of computing the load-carrying capacity of sections that are at first submitted to a constant long-term service load and then overloaded up to ultimate load. The method solves first a non-linear visco-elastic problem, and then a non-linear instantaneous analysis up to ultimate load that takes into account the self-equilibrated stress distribution previously computed. This method is then adopted to perform a parametric analysis that shows that creep and shrinkage of concrete increase the load-carrying capacity of the cross section reinforced with FRP and allows for the suggestion of simple design rules.