• 전기학회논문지
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• 제60권12호
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• pp.2392-2396
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• 2011

This paper deals with the power integration of large urban railway systems to improve regenerative energy utilization. Current regenerative energy utilization is low because there is no special plan for using this energy. If the railway system is integrated with other railway systems, the efficiency is expected to be improved. Through the case studies, to find the realistic effect of integrated operation, real system for the Seoul Metro lines, especially line 5 and 7, had been applied.

• 한국분말재료학회지
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• 제1권1호
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• pp.66-71
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• 1994

Optical microstructures and mechanical properties of Na gas atomized Al-20Si-5Fe alloying powder and its hot extrudates were studied on 3 different types of powder size distribution. This powder showed the size distribution of 10~210 $\mu\textrm{m}$. Also the microstructures of $\alpha$-Al, primary and eutectic Si and needle shaped intermetallic compounds were observed by optical microscope. These needle shaped intermetallic compounds were identified as ${\delta}Al_4FeSi_2$- by XRD and EDX analysis. The ultimate tensile strength(UTS) of these alloy extrudates was increased from 324 to 390 MPa with decreasing powder size range from 120~210 $\mu\textrm{m}$ to 10~64 $\mu\textrm{m}$. A value of Micro-vic-kers hardness was simillar to the result of UTS. These extrudates showed better wear resistance than those of Al-20Si-2X(X : Ni, Cr, Zr), although they are insensitive to the size distribution. These results indicate that the presentation of ${\delta}Al_4FeSi_2$ intermetallic compounds contributed to the wear resistance improvement.

• 복식
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• 제34권
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• pp.135-150
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• 1997

The purpose of this study was to inves-tigate the economic performance of the textile industry for the Korean traditional clothes. The content of this paper had two pars; The first part was for the macroeconomic aspects such as location production employments and the produc-tion facilities of the textile industries. The second part was for the microeconomic aspects such as business type branding method fabric type R&D efforts sourc-ing and the distributional channel The major results were as follows: 1.) Most textile firms for the korean traditional clothes were located in Gongju for man-made fibers and in Jinju for silk fabrics. 2) The size of the textile industry in terms of the number of business produc-tion amount the number of employee de-creased during 1994 and 1995 due to the decreasing demand. 3) Over the half of the textile firms produced raw fabric products while only 20% of them were involved in additional dyeing and /or printing finish which re-sulted in low value added production 4) The R&D effort of the textile indus-try for the Korean traditional clothes was very low due to the market uncertainty lack of technological knowledge and most of all small size of the firms 5) Most raw materials for the textile in -dustry were imported with high(25%) tariff rates resulting in price increase and thus low competitiveness in the market. 6) The textile producers sole about the 70% of their products to the wholesalers while selling the rest to the retailers di-rectly. This showed the dual structure of the distribution channel in the textile products. These results suggested some implica-tions for the firms the policy makers and the researchers. The firms should develop new and improved products to increase and create consumer demand by intensive R&D efforts. The government policy ma-kers should give financial supports the firms with R&D investment and legal help such as lowing tariff rate for the raw ma-terials. The researchers from the academy could help the textile industry with the advanced technological knowledge and up-date information for the consumer fashion demand.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제29권6호
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• pp.474-484
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• 2007

Purpose: The effect of platelet-rich plasma(PRP) on osteogenesis of marrow-derived osteoblasts on histomorphometric analysis in the mandible of rabbit was assessed. Materials and Method: Bone marrow cells were obtained from iliac bone of rabbits and were cultured in a Dulbecco's Modified Eagle's Medium(DMEM) with Dexamethasone, L-Ascortic acid, ${\beta}$-Glycerophosphate to proliferate and differentiate into osteoblasts for $4{\sim}5$ weeks. The expression of osteogenic mar-kers was detected by reverse transcription-polymerase chain reaction(RT-PCR) and silver nitrate stain. Then we prepared bony defects in the mandible of rabbit, 10.0mm in diameter and 4.0mm deep, by trephine bur. In the control group, the defects were filled with autogenous bone and cultured osteoblasts. In the experimental group, the defects were filled with autogenous bone, cultured osteoblasts and PRP. 2 weeks, 4 weeks, 8 weeks later, each group was evaluated with histological and histomorphometric analyses. Results: In vitro, osteoblasts were identified on RT-PCR and silver nitrate stain. According to histological observation, at 2 weeks well-developed anasto-mosing newly-formed woven bone was observed, at 4 weeks anastomosing newly-formed woven bone having osteoblastic activation was observed, and at 8 weeks thick newly-formed woven bone was observed in both control and experimental groups. According to histomorphometric analysis, there were 1.5% more newly-formed bone volume in experimental group than control group at 2 weeks, 28.4% more at 4 weeks, 4.3% more at 8 weeks. Particularly there were significant differences in bone volume at 4 weeks and 8 weeks new bone. Conclusion: Our results demonstrated PRP may enhance osteogenesis of marrow-derived osteoblasts at 4 weeks, 8 weeks.