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유사체액에서의 전기화학적 처리가 티타늄 표면의 인산갈슘 흡착에 미치는 영향
조국현,김문영,송광엽,배태성,이민호 大韓齒科器材學會 2002 대한치과재료학회지 Vol.29 No.3
This study was performed to examine the effect of electrochemical treatment on the precipitation of apatite-like calcium phosphate in a simulated body fluid. Titanium plates of 20×20×1 ㎣ in dimensions were polished sequentially from #600 to #2,000 emery paper and one surface of each specimen was received an additional polishing sequence through 0.1㎛ alumina paste. To improve the bioactivity of titanium plates, they were electrochemically treated at 100 mA for 20 min in an electrolyte containing the calcium and phosphate ions, and the Hanks' solution with pH 7.4 at 36.5℃ for 30 days, and the surfaces were examined with X-ray diffractometer(XRD), scanning electron microscope(SEM) and X-ray photoemission spectroscopy(XPS). Precipitation of calcium phosphate and CaO were observed on the electrochemically treated titanium surface in a simulated body fluid after treatment at 600℃. Precipitation of calcium phosphate was densified and coarsened with increasing the temperature of the electrolyte solution in the range of 20-80℃. The calcium phosphate contained phosphate in the form of Po₄^3-, HPO₄^2-, and H₂PO₄^-.
중학교 과학 교과서 분별 증류 실험의 비교 분석 및 개선
柳五鉉,崔文永,宋周眩,권정근,白盛惠,朴國泰 한국교원대학교 과학교육연구소 2001 청람과학교육연구논총 Vol.11 No.1
이 연구의 목적은 제 6차 교육과정에 의한 중학교 1학년 과학 교과서 분별 증류 실험의 문제점을 파악하고, 중학생들이 분별 증류 실험을 능률적으로 수행할 수 있는 실험 방법을 제시하고자 하는 것이다. 이를 위한 첫 번째 단계로서 현재 사용되고 있는 8종의 과학 교과서를 분별 증류 실험 장치와 액체 혼합물의 종류에 따라 6가지로 분류하였다. 두 번째 단계로서 액체 혼합물을 가열 방법에 따라 직접가열과 물 중탕 가열로 나누어 교과서 실험과정에 따라 같은 실험을 세 번 실시하였다. 세 번째 단계로서 실험 결과의 문제점을 해결하기 위한 대안 실험을 실시하였다. 대안 실험에서는 알코을 램프로 직접가열 하는 방법과 기름 중탕으로 가열하는 방법, 그리고 가열 맨틀을 사용하여 가열하는 방법을 사용하였다. 연구결과, 가지 달린 둥근 플라스크를 직접 가열하는 실험 결과가 가지 달린 시험관을 물 중탕으로 가열하는 실험 결과보다 이론적인 결과에 근접하였다. 그리고 가지 달린 둥근 플라스크를 직접 가열하는 실험에서 플라스크 윗 부분을 보온해 주는 실험이 보온하지 않은 실험보다 실험 결과가 더 나았다. 대안 실험에서는 액체 혼합물의 증류 온도 증가를 보면서 가열 맨틀의 가열 온도를 을려 준 실험의 결과가 이론적인 결과에 가장 가까웠다. 이러한 연구 결과로부터 가지 달린 시험관을 물 중탕으로 가열하는 분별 증류 실험 장치는 탐구실험 수업에 부적절한 것이므로 개선이 요구되며, 중학교 과학실 여건을 고려할 때, 액체 혼합물의 증류 온도 증가를 보면서 가열 맨틀의 가열 온도를 변화시키는 분별 증류 실험이 가장 능률적인 방법임을 알 수 있었다. The purpose of this study was to find out the problems on the fractional distillation experiments in the middle school science textbooks based on the 6th curriculum and to suggest an efficient experiment method for the middle school students. The first step was the classification of the experiments in 8 science textbooks according to heating apparatus and liquid mixtures. The second step was doing each experiment 3 times followed by the experimental process in the textbooks. The third step was developing the alternative experiments for solving the problems found in the second step. The heating method used in the alternative experiments were direct heating, oil bath, and heating mantle. The results of the second step showed that the direct heating experiment of branched round flask was more close to the theoretical prediction than the experiment of water bath heating of branched test tube. Also the direct heating experiment of thermally insulated branched round flask was better than the result of the experiment which was not insulated. The results of the third step showed that the experiment using heating mantle regulated heating power by observing the temperature of distillate gave the closest result to the theoretical prediction. From the above results, it is concluded that the experiment using branched test-tube with water bath heating is not adequate for the fractional distillation and an alternative experiment using insulated branched round flask with heating mantle regulated heating power during experiment is recommended.
Origin and Fate of Pendrin-Positive Intercalated Cells in Developing Mouse Kidney
Song, Hyun-Kuk,Kim, Wan-Young,Lee, Hyun-Wook,Park, Eun-Young,Han, Ki-Hwan,Nielsen, Soren,Madsen, Kirsten M.,Kim, Jin American Society of Nephrology 2007 Journal of the American Society of Nephrology Vol.18 No.10
<P>Pendrin is an apical anion exchanger found in type B and nonA-nonB intercalated cells that is involved in bicarbonate secretion. The purpose of this study was to establish the origin and fate of pendrin-positive intercalated cells in the mouse kidney. Using immunohistochemistry, we found that pendrin-positive cells first appeared in the connecting tubule at embryonic day 14 (E14) and subsequently in the medullary collecting duct at E18. Most of the pendrin-positive cells in the connecting tubule were nonA-nonB intercalated cells, wheras those in the medullary collecting duct were type B intercalated cells. In the cortical collecting duct, pendrin-positive cells appeared in the inner part at day 4 after birth and in the outer part at day 7. Pendrin-positive cells gradually disappeared by apoptosis from the inner part of the medullary collecting duct two weeks after birth. Using 5-bromo-2'deoxy-uridine (BrdU) to follow cell proliferation, we determined that selective proliferation of pendrin-positive intercalated cells does not occur; instead, these cells may arise from undifferentiated precursor cells from separate foci, one in the connecting tubule and one in the collecting duct.</P>
Enhancement of Grain Refinement and Mechanical Properties of Cross-Roll Rolled Pure Copper
Song, Kuk Hyun,Kim, Han Sol,Kim, Won Yong The Japan Institute of Metals 2011 Materials transactions Vol.52 No.5
<P>The aim of this work was to evaluate the effects of strain rate on the microstructural evolution of 5-mm-thick pure copper (99.99%) sheets subjected to conventional rolling (CR) and cross-roll rolling (CRR). The sheets were cold-rolled with a reduction ratio of 90% and then annealed at 400°C for 30 min to obtain the fully recrystallized microstructures. The resulting cold-rolled and annealed sheets had considerably finer grains than the initial sheets. In particular, the average grain size became smaller by CRR (6.5 μm) than by CR (9.8 μm). The mechanical properties of the sheets, i.e., Vickers microhardness and tensile strength, were more enhanced by CRR than by CR. The microstructural development in these processes was systematically discussed.</P>