• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.3A
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• pp.215-225
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• 2011

In general, the precast columns can obtain its homogeneous quality as they are produced in a factory with a hollow concrete block type by using high strength concrete, so that they can generate the reduction of dead load. Such a method of precast hollow concrete columns is already implemented in USA and Japan and used for connecting between blocks which use PC tendons. However, it is inevitable to have uneconomical construction with excessive cost in early stage when PC tendons are used. This study aims to develop an economical precast column with high quality and constructability which consists of only splice sleeve and general reinforcing bar without using PC tendons in order to reduce the construction period and cost. To achieve this goal, this study tested the performance of total 5 minimized models in the experiment with the variables such as hollowness, diameter of main reinforcement bar and cross-sectional size for the cross section of precast column by using grouting type splice sleeve which is a new type joint rebar. And it also verified the performance of column in the experiment for a large-sized model in order to overview its applicability by excluding large scale effect.

• Proceedings of the Korean Society of Embryo Transfer Conference
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• 2002.11a
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• pp.88-88
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• 2002

인공수정 및 수정란기술의 활성화에 따라 소에 있어서 인공수정은 90%이상이 실시되고 있으나, 수정란이식은 수정란의 생산이 안정적이지 않아 활성화에 많은 지장을 초래하고 있다. 이의 원인은 수정란이식에 의한 수태율의 저하가 가장 크며, 수태율 향상을 위하여 수란우에 progesterone, hCG 등의 주사가 실시되고 있다. 그러나 이는 수정란의 착상에 있어서 자궁의 환경을 개선한다고 하나, 착상의 정확한 기전의 구명은 미미한 상태이다. 한편 비장유래 macrophage가 황체를 자극하고 TGF-$\beta$의 생산을 유도하는 것으로 보고되고 있으며, IL-I $\alpha$와 $\beta$에 따라 TGF-$\beta$ 생산에 있어서 약간의 차이를 보이는 것으로 보고되고 있다. 따라서 본 연구는 비장유래 macrophage가 TGF-$\beta$의 생산시 임신관련 Cytokine인 IL-I$\alpha$와의 관계를 조사하기 위하여 실시하였다. 임신 및 비임신 도축 암소의 비장을 채취하여 얼음에 채워 실험실로 운반한 후 비장의 표면을 70%의 알콜로 세척하고, 표피를 벗겨 비장조직을 세절하여 10% FBS+DMEM에 넣어 조직을 눌러 짜면서 조직속의 세포를 분리하였다. 세척한 배양액은 4-5$m\ell$를 100mm 유리 petri dish에 넣고 39$^{\circ}C$, 5% $CO_2$, 95% 공기인 배양기에서 2시간이상 배양하였으며, 배양 후 냉장된 buffer A 용액으로 세척하여 유리 petri dish의 바닥에 부착된 macrophage만을 cell scraper로 분리하였다. 분리한 macrophage는 0.5-1 $\times$ $10^{6}$ cells/$m\ell$가 되게 조정하여, IL-I 을 0.001, 0.01, 0.1 또한 1 ng/$m\ell$를 첨가하여 농도에 따른 효과를 조사하였고, 각각 24, 48, 72, 96 또한 120시간을 배양하여 시간에 의한 효과도 실시하였다. 각 배치구에서 얻어진 배양액은 TGF-$\beta$를 조사하기 전까지 -2$0^{\circ}C$에 동결 보존하였다. TGF-$\beta$의 측정은 TGF-$\beta$ kit(promega, USA)를 이용하여 실시하였으며, 통계학적 분석은 Anova test를 Statview program을 이용하여 분석하였다. 시험의 결과 대조구에 비해 IL-I 첨가구는 2-3배의 TGF-$\beta$생산을 보였으며, 배양시간에 따른 생산은 시간이 지남에 따라 약간 상승하는 경향을 보였으나, 유의적인 차이를 보이지는 않았다. 또한 IL-I의 농도에 따른 생산의 변화는 IL-I의 농도에 따라 약간의 차이를 보였고 유의적인 차이는 인정되지 않았다. 임신 및 비임신의 경우 임신우의 비장 macrophage가 비임신보다는 약간 상승하는 거스로 나타났다. 이상의 결과로 볼 때 IL-I $\alpha$ 는$\beta$subunit 보다 TGF-$\beta$ 생산에 있어서 서로 다른 양상을 보일 것으로 추정되며, IL-I은 macrophage의 직접적인 영향을 주기보다는 황체세포를 매개로 한 자궁에 TGF-$\beta$의 생산을 유도하는 것으로 사료되며, 임신관련 cytokine에 대한 다양한 연구가 요구되고 있다.

• Geotechnical Engineering
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• v.12 no.2
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• pp.71-84
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• 1996

In order to investigate the influence of slanting angle of reticulated root piles(RRP) on their bearing capacities, model tests of compressive and uplift loads on RRP with different slanting angles, which were installed in sandy soils with a relative density of 47%, were carried out. Each pile which is made of a steel bar of 5mm in diameter and 300mm in length, is coated with sand to be 6.5mm in diameter. One set of RRP consists of 8 piles which are installed in circular patterns forming two concentric circles, each of which has 4 piles. Slanting angles of RRP for load tests are 0$^{\circ}$, 5$^{\circ}$, 10$^{\circ}$, 15$^{\circ}$, 20$^{\circ}$, and 25$^{\circ}$. In addition, compressive load tests on circular footing whose diameter is the same as the outer circle of RRP were carried out. Test results show that maximum load bearing capacities of RRP by regression analysis are obtained at about 12$^{\circ}$ and 13$^{\circ}$ of slanting angles for compressive and uplift load tests, respectively. Maximum compressive bearing capacity is estimated to be 13oA bigger than that of the vertical RRP and 95% bigger than that of surface footing. Maximum uplift capacity is estimated to be 21% bigger than that of the vertical RRP. And it can be appreciated that increasing the slanting angle makes the load -Settlement behavior more ductile.

• Korean Journal of Food Science and Technology
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• v.16 no.4
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• pp.418-422
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• 1984

In order to determine the removal efficiency of pesticide residues in fruits and vegetables by washing processes, samples of lettuce, young Chinese radish, Chinese cabbage, green red pepper, strawberry and grape were artificially contaminated with malathion and washed according to the household practices. After three times washings with water, the remaining ratios of malathion residues in grape, green red pepper, strawberry, young Chinese radish, lettuce and Chinese cabbage were 9.7%, 25.2%, 28.0%, 29.7%, 38.9% and 57.5%, respectively. After washing with detergent solution followed by two times rinsing with water, the remaining ratios of malathion residues in the same food samples were 1.6%, 8.3%, 15.8%, 24.8%, 27.2% and 45.9%, respectively. The removal efficiency of malathion by detergent washing was significantly higher than the water washings only. The removal ratio of malathion residues was the highest in the first washing and the ratio fell greatly in the following washings. The removal efficiency was not quite different in the temperature range of $5-35^{\circ}C$ of the washing solution, but the efficiency at $100^{\circ}C$ was 2-3 times higher than other temperature ranges.

• Tunnel and Underground Space
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• v.28 no.1
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• pp.97-110
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• 2018

The application of sprayed waterproofing membrane with high adhesion and ductility is considered to be promising as a measure for repair and reinforcement of a tunnel structure. Therefore, a powder-type and one-component membrane prototype with high tensile and bond strengths was made in this study. Then, its reinforcement effect on a shield segment was evaluated by carrying out a series of full-scale loading tests of segment specimens on which the membrane was sprayed. From the tests, it was confirmed that the initial cracking loads increased by approximately 34% due to cracking retardation by membrane coating. Even though the increase of failure loads were not so high as cracking loads, the strain-softening behaviors were observed from specimens coated by the membrane. Therefore, it is expected that the membrane coated on the inner surface of a lining might be effective in preventing its brittle failure.

• Journal of The Korean Society of Grassland and Forage Science
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• v.37 no.4
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• pp.345-349
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• 2017

This study was conducted to investigate the effect of pasture grazing and barn feeding system on the growth performance, weight gain and velvet antler productivity in Elk. Twelve 5-year-old elk stags about 273 kg were stratified by weight and randomly assigned by feeding system (a pasture grazing and a barn feeding, n=6). The average feed intake were not signigicant difference between two groups. Average daily gain for grazing and barn feeding group was 0.25 g and 0.29 g respectively, showing no significant difference. Velvet antler yield for grazing and barn feeding group was 7,700 g and 6, 960 g respectively, with no significant difference. In conclusion grazing group was better than barn feeding group in feed intake, body weight gain and velvet antler productivity. However, there were no statistical significant difference between the two group. These results may serve as the basis for further study of deer feeding system in Korea and further study needed to examine the grazing intensity and economic efficiency.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.6A
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• pp.457-464
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• 2011

An experimental study was performed to evaluate the possibility of using stiff type PolyUrea(PU) on RC slab as a strengthening material. Stiff type PU(STPU) was sprayed on the bottom surface of the slab specimens, which were then attached with CFRP or GFRP sheets. Also the evaluation of the bond capacity, the single most influential parameter on strengthening of RC structures, was carried out the flexural capacity evaluation test results showed that the load carrying capacity of the PU specimen was greater and less than the unstrengthened and FRP sheet attached specimens, respectively. The STPU specimens showed a ductile flexural behavior in the plastic displacement range. With respect to bond capacity, the bond strength of all of the specimen exceeded the code required bond strength of 1.5 MPa. Also, the STPU sprayed specimen without using epoxy resin did not peel off when the tensile grip was applied for testing. The stability of the PU bond failure indicate a good bond strength of PU when applied to concrete.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.6
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• pp.1677-1685
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• 2014

Short discrete fibers compounded with concrete can enhance the tensile resistance and ductility of concrete. Recently, the effectiveness of the reinforcement has increased according to the increasing length of steel fiber. However, the lengthening of steel fiber requires reducing the ratio of the fiber content to remain the workability and quality of concrete. Thus, the present study evaluated the flexural performance of fiber reinforced concrete with less than l.0% fiber volume ratios of steel fiber, 30mm and 60mm long, and polypropylene fiber, being evaluated as a good reinforcing material with chemical stability, long-term durability, and cost effectiveness. Concrete with more than 0.25% steel and 0.5% polypropylene fibers improved the brittle failure of concrete after reaching cracking strength. Concrete reinforced with polypropylene exhibited deflection-softening behavior, but that with more than 0.5% polypropylene delayed stress reduction and recovered flexural strength by 60 to 80% after cracking strength. In conclusion, concrete reinforced with more than 0.75% polypropylene could improve structural flexural performance. In particular, energy absorption capacity of reinforced concrete with 1.0% polypropylene fiber was similar to that with 0.5% and 0.7% steel fibers.

• Journal of Korea Foundry Society
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• v.41 no.5
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• pp.411-418
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• 2021

In order to experimentally investigate the effect of Ni or Cu addition on microstructure and mechanical properties of high Si Solution Strengthened Ferritic Ductile cast Iron (SSF DI), a series of lab-scale sand casting experiment were conducted by changing initial concentration of Ni up to 3.0wt% or Cu up to 0.9wt% in the alloy. It was found that increase in Ni or Cu content in the alloy leads to increase in strength properties and hardness as well as decrease in ductility. The higher Ni or Cu content the SSF DI has, the higher fraction of pearlite was observed. At similar levels of Ni or Cu contents in the alloy, higher pearlite area fraction was observed in the Cu-containing SSF DI than that in the Ni-containing SSF DI. When the effect of the microstructure on the mechanical properties of Ni-containing SSF DI was considered, Ni-containing SSF DI was found to have excellent strength and hardness as well as good elongation when the pearlite fraction was controlled less than 10%. As the pearlite fraction in the Ni-containing SSF DI exceeds 10%, however, it shows drastic decrease in elongation. Meanwhile, gradual increase in strength and hardness, and decrease in elongation with respect to increase in pearlite fraction were observed in Cu-containing SSF DI. The different microstructure-mechanical property relationships between Ni-containing and Cu-containing SSF DI were due to the combined effect of the relatively weak pearlite stabilizing effect of Ni compared to that of Cu in high Si SSF DI, and matrix strengthening effect caused by the different amounts of those alloying elements required for similar pearlite fraction.

• Journal of Convergence for Information Technology
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• v.11 no.4
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• pp.111-121
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• 2021

In order to determine the possibility that Chrysanthemum indicum L. cultured with Lactococcus lactis (CILL) is a material for obesity suppression food, the body weight, body fat mass, and T cells were determined in C57BL/6 mice induced by a high fat diet. The CILL (25.15±2.44 g) demonstrated weight loss from week 4 onward and maintained a low weight gain from week 1 to week 8 (1.00±0.53 g). The 8-week body weight (30.38±4.17 g) indicated loss of 13.15% when compared to the HFD (60% high fat diet, 34.99±2.09 g). Fat mass decreased to 10.3022±2.8813 g, and the absolute liver weight decreased relative to that in the HFD. CD4+ T cells were 4.84±1.33%, CD8+ T cells 7.02±2.26%, and CD4+CD8+ T cells 1.46±0.81%, which were all higher than those in the HFD. As a result, CILL can be used as a material for preventing obesity as an effective measure toward reducing weight when consumed orally.