Coating with boron nitride on SiC fiber using atomic substitution

Woo‑Seong Tak,Jin‑Uk Hwang,Young‑Keun Jeong,Woo‑Sik Kim 한국세라믹학회 2020 한국세라믹학회지 Vol.57 No.2

To increase the mechanical properties of ceramic matrix composite, it is important that formation of lubricant layer for crack deflection between matrix and fiber. Therefore, we fabricated uniform boron nitride (BN) lubricant layer using atomic substitution method. Silicon carbide (SiC) fiber surface was modified with amine groups using (3-amonipropyl)triethoxysilane to coat SiC fiber with BN as a solid lubricant. Then, surface was coated with graphene oxide (GO). Boric acid powder was supplied to the GO-coated fibers and the samples were heat-treated at 1200–1400 ℃ under N2 and NH3 atmospheres. An uniform BN layer could be coated on SiC fiber with 10 nm-1.11 μm. Crystallinity and thickness of BN layer could be controlled by reaction temperature. It was also confirmed that crystalline BN formed under process conditions of higher than 1400 ℃.

당뇨병 백서의 간세포에서 Glucokinase 활성도 및 유전자 발현에 대한 인슐린의 영향

강성이,팽정령,서광식,안규정,우정택,김성운,양인명,김진우,김영설,김광원,최영길 경희대학교 유전공학연구소 1993 遺傳工學論文集 Vol.5 No.-

목적 당대사의 조절 상태에 따른 생체 변화를 분자 수준에서 이해하고자 식이 조건을 달리한 정상 백서와 화학적으로 유도된 당뇨병 백서의 간조직에서 혈당수준과 인슐린치료 정도에 따라 나타나는 글루코키나제 활성도 및 유전자 발현을 분석하였다. 방법 스트렙토조토신 정맥투여 후 당뇨병의 유발을 확인하고, 인슐린을 1일 3회 3일간 복강내로 투여하여 상태를 안정시킨 후, 인슐린 투여군은 인슐린 투여 6시간이내에 그리고 인슐린 비투여군은 24시간 후 단두하여 채혈하고 복강을 열어 간조직을 채취하였다. 채취한 간조직에서 글루코키나제 활성도는 인산화된 포도당에서 NADH의 형성을 형광분광계로 측정하였으며, 글루코키나제 유전자 mRNA발현은 Northern 분석법을 이용하였다. 성적 정상 백서에서 공복상태와 식이를 섭취한 경우에 간조직의 글루코키나제 효소의 활성은 차이가 없었으나, 글루코키나제 유전자 mRNA 발현은 증가되었다. 당뇨병이 유발된 백서의 간조직에서 글루코키나제 효소의 활성 및 글루코키나제 유전자의 mRNA 발현은 정상 백서에 비하여 낮았다. 인슐린 투쳐 후 글루코키나제 효소의 활성 및 글루코키나제 유전자의 mRNA 발현이 증가되었고, 특히 혈당이 정상화된 경우에서 글루코키나제 유전자의 mRNA 발현이 증가도었다. 결론 인슐린에 의한 간조직에서 글루코키나제 효소의 활성 및 글루코키나제 유전자의 mRNA을 증가를 볼수 있었다. 당뇨병 백서에서 인슐린 투여 후에 혈당조절이 안된 경우 간조직의 글루코키나제 유전자의 mRNA 발현이 증가가 없는 것으로 보아 글루코키나제 mRNA의 발현에는 인슐린 이외의 다른 요소가 관여할 것으로 생각된다. The liver-specific hexokinase isoenzyme, referred to as glucokinase, is thought to play a key reglulatory role in hepatic glucose metabolism. The glucokinase gene is, therefore, of interest both because of its tissue-specific expression and because of the several regulatory processes that can be analyzed. The level of hepatic glucokinase activity appears to be determined essentially by regulation of the rate of enzyme synthesis, with insulin playing a leading role as an inducer. We investigated the role of insulin for the induction of glucokinase in the liver of diabetic rats. Experimental diabetes was induced by injection of streptozotocin 7 days before the experiment. Regular insulin was given by three days intraperitoneal injection at 8-h interval. The glucokinase mRNA in the liver was estimated by Nothern blot assay, as well as by fluorometric enzyme activity assay. Glucokinase activity was not reduced in the liver of normal fasting rats as compared to normal fed rats. And glucokinase activity was reduced in the liver of diabetic rats as compared to normal rats. In diabetic rats treated with insulin, glucokinase enzyme activity were increased. But glucokinase mRNA expression was only increased in normoglycemic diabetic rat with treated with insulin as compared to hyperglycemic rat. These data indicate that insulin stimulates hepatic glucokinase enzyme activity and mRNA expression. But other hormonal or metabolic factors may be contribute to regulation of glucokinase mRNA expression.

에어컨 냉각 팬용 브러쉬레스 DC 전동기의 역기전력 분석에 대한 연구

조정현,김지현,정정원,황흥식,이치우 경성대학교 공학기술연구소 2012 공학기술연구지 Vol.18 No.-

Compared to conventional dc motors having the combination of commutators and brushes, a brushless DC (BLDC) motor is one of the highly efficient motors due to its electrical commutation without a brush, and this feature allows the BLDC otor to be more suitable for an application requiring no maintenance due to mechanical wear between a commutator and a brush. Also, the BLDC motor has a few benefits over both a dc motor and an induction motor such as high dynamic response, high efficiency, logn life span, and low noise in wide speed-torque region. This paper investigates the variation of voltage induced in phase windings in a BLDC motor in several cases with respect to stack length, steel grade, and coil material. This study is numerically conducted and it is verified from the theoritical point of view by comparing the result of simulation with that of experimental measurement.

용융 알미늄합금의 산화피막 강도측정에 관한 연구

우정명,양중식,백영남 慶熙大學校 材料科學技術硏究所 1991 材料科學技術硏究論集 Vol.4 No.-

This study carrys out to determine the strength of oxide skins of Al alloy melts as the practical alloy for automobile piston. This has been observed by Rotational Die Movement Equiment for the temperature range from 600℃ to 750℃ and oxidation time range from 10min to 60min. This method was able to quantify the strength of oxide skins of the molten alloys and had ±3% experimence error range. This strength of oxide skins of the molten alloys were much more affected by oxidation temperature than oxidation time.

생체시료 중 스타틴계 약물 정량법의 최근 개발 동향

우경식,박정숙 충남대학교 약학대학 의약품개발연구소 2009 藥學論文集 Vol.24 No.-

Statins are reversible inhibitors of S-hydroxy-3-methyl glutaryl coenzyme A (HMG-CoA) reductase, widely used for the treatment of hyperlipidemia as well as atherosclerosis. Recently, various brands of cholesterol lowering statin drugs have been frequently prescribed and dispensed to the patients for reducing morbidity and mortality related to coronary heart disease. Therefore, demands for development of reliable and sensitive analytical methods for statins in biological fluid have been increased to monitor the plasma concentrations of drugs. A lot of chromatographic-mass spectrometric methods for the quantification of presently available seven statins such as atorvastatin, simvastatin, lovastatin, pravastatin, fluvastatin, rosuvastatin, and pitavastatin have already been published. Of analytical methods, high performance liquid chromatography (HPLC) with tandem mass spectrometry (MS/MS) is the analytical technique of choice for the quantification of statins in biological samples. This review covers most of the analytical method used for quantification of statins, which are applied for plasma sample and suitable for therapeutic drug monitoring.

木浦(나무벌)의 水生 및 濕生管束植物相과그들의 保護

鄭宇珪,孔榮植,梁運眞 경남대학교 환경문제연구소 1995 환경연구 Vol.17 No.-

1993년 7월 부터 1995년 5월 까지 9회에 걸쳐 慶南 昌寧郡準 梨房面 木浦(나무벌)의 水生 및 濕生植物과 그들의 生活形, 開花期 및 花色을 조사한 결과는 다음과 같았다. 1. 조사된 總 植物은 4目 31科 48屬 71種 14變種 2品種 總 87種類였다. 2. 이들 중 水生植物이 11目 20科 23屬 38種 9變種 1品種 總 48種類 55.2%이고, 挻水植物 22種類 45.8%, 浮??植物 15種類 31 3%, 沈水植物 8種類 9.2%, 浮生植物 3種類 6.3%였다. 3. 濕生植物은 10目 24科 25屬 33種 5變種 1品種 總 39種類 44.8%였다. 4. 木浦 植物相의 開花期는 7~8월에 가장 많이 開花하여 여름개화기 후형이었고 北半球 溫帶 氣候 開花期이었다. 5. 木浦 樵物相의 花色 多樣性에서 가장 많은 색은 綠色(33.3%)이었고 다음이 흰색(25.4%)이었다. 6. 溜池에는 마름이 優占種이었고, 가시연꽃이 準優占種이었으며 가시연꽃은 單一種으로 된 群落을 형성하고 있었다. 7. 늪지의 水生 및 濕生植物의 分布 즉 마름, 가시연꽃 자라풀, 수염마름 등의 分布가 논의되었으며 이들 濕地植物과 늪의 保護를 위한 課題도 논의되었다. The flora, distribution, life form, flowering period, and flower colors of hydrophytes and hygrophytes from Mokp,o swamp in Changny□ng-gun, Ky□ngsangnam-do, Korea were investigated at nine times from July, 1993 to August, 1995. The flora was composed of 16 orders, 31 families, 48 genera, 71 species, 14 varieties, and 2 forma; total 87 taxa. Among them, the vascular hydrophytes were composed of 11 orders, 20 families, 23 genera, 38 species. 9 varieties, and 1 forma, total 48 taxa, 55.2%. These were composed of 22 taxa emerged plants(45.8%), 15 taxa floating-leaves plants(31.3 %), 8 taxa submerged plants(9.2%), and 3 taxa free-floating plants(6.3%). The hygrophytes were composed of 10 orders, 13 families, 25 genera, 33 species, 5 varieties, and 1 foema: total 39 taxa, 44.8%. The peak of flowering period occurred in August. The most species in this swamp were flowering from July to August. The pattern of flowering period was responded summer flowering climate pattern and northern middle latitute region flowering climate pattern. In the study of flower color diversity of Mokp,o flora, the most abundunt colcr was green taxa(33.3%) and the white was second(26.4%). In Mokp.o swamp dominent species was Trapa japonica and subdominent was Euryale ferox on the whole. The distribution of hydrophytes: Euryale ferox, Trapa japonica, Hydrocharis dubia and Trapella sinensis var antenifera were discussed. Also the work for protection of the swamp and wetland plants in Mokp.o were discussed.

배·급수 시스템에서 부식방지제의 적용 평가 연구

우달식,문정기,구성은,최종헌,김주환,문광순 대한상하수도학회 2003 상하수도학회지 Vol.17 No.5

This study evaluated the effect of the corrosion inhibitors on the corrosion control performance in drinking water distribution system. A phosphate-zinc based inhibitor formulated was for the efficient corrosion control in drinking water distribution system. In a continuous-circulation test, 99% reduction in corrosion rate was achieved. The optimum concentration of the corrosion inhibitor was found to be 2.2㎎ PO₄/L. The effect of the corrosion inhibitor was significant for the pipes of carbon steel, galvanized steel and copper, but less for that of stainless steel. The corrosion inhibitor can be an effective cure for corrosion and red water problems by prevention the old pipes from further corrosion. Tap water in Mokpo and Kwangyang were more corrosive than the water in the rest of 4 other regions(Seoul, Pohang, Pusan, Puyeo). Tap water in Pusan was high in various ionic concentrations in general. The corrosion inhibitor reduced the corrosion rate by 76-94%, depending on the origin of the tap water.

BCG를 대량 투여 받은 생쥐 가슴샘 겉질의 미세구조

고정식,안의태,박경호,우성임,한영복,경홍기 대한해부학회 1997 Anatomy & Cell Biology Vol.30 No.3

박실지와 연당지의 植物相과 그들의 保護

鄭宇珪,孔榮植,金哲壽,梁運眞 경남대학교 환경문제연구소 1996 환경연구 Vol.18 No.-

1990년 7월부터 1996년 8월까지 16회에 걸쳐 慶南 陝川郡 龍州面 박실지와 연당지 및 그 周邊 地域의 水生植物과 植物相을 조사한 결과는 다음과 같았다. 1. 조사된 總 植物은 38目 107科 287屬 365種 1亞種 61變種 3品種 總 430種類로 구성되었다. 2. 이들 중 水生植物이 11目 22科 41種 10變種 1品目 總 52 種類 12.1%이고, 挻水植物 25種類 5.8%, 浮葉植物 15種類 3.5%, 沈水植物 9種類 2.5%, 浮生植物 3種類 0.8%였다. 3. 陸上植物은 36目 92科 269屬 324種 1亞種 51變種 2品種 總 378種類 87.0%였고, 이들 중에는 濕生植物이 50種類 13.2%, 水邊植物이 328種類 86.8%였다. 4. 박실지의 溜池에서 優占種은 마름, 準優占種은 줄이었고, 연당지에서의 優占種은 줄이었고 準優占種은 연이었다. 5. 희귀식물인 가시연꽃과 통발, 북방분자인 돌단풍과 도루박이 및 최근에 국내에 분포하는 것이 확인된 민초피나무의 분포가 논의되었다. The flora and distribution of hydrophytes and terrestrial plants from Paksil and Yundang swamp and their adjacent area in Hapchon-hun. Kyongsangnam-do were investigated at sixteen times from July. 1990 to August. 1996. The flora was composed of 38 orders. 107 families. 287 genera. 365 species. 1 subspecies, 61 varieties, and 3 forma, total 430 taxa. Among them, the vascular hydrophytes were composed of 11 orders. 22 families, 31 genera, 41 species, 10 varieties, and 1 forma, total 52 taxa. 12.1%. These were composed of 25 taxa emerged plants. 15 taxa floating-leaves plants. 9 taxa submerged plants, and 3 taxa free-floating plants. The terrestrial plants were composed of 36 orders. 92 families. 269 genera. 324 species. 1 subspecies. 51 varieties, and 2 forma. total 378 taxa. 87.9%. Among them, the hygrophytes and water side plants were 50 taxa, 13.2% and 328 taxa, 86.8%. In Paksil swamp dominent species was Trapa japonica and subdominent was Zizania latiforia on the whole. In Yundang swamp dominent species was Zizania latiforia and subdominent species was Nelumbo nucifera on the whole. The distribution of Euryale ferox. Scirpus radicans. Acerphyllum rossii. Utricularia Japonica. Xanthoxylum piperitum var. inerme. were discussed. Also the work protection of Paksil swamp were discussed.

저전력 BFSK 수신기의 FPGA 구현

하정우,이미진,변건식 東亞大學校 附設 情報技術硏究所 2007 情報技術硏究所論文誌 Vol.15 No.1

This paper is to implement a low power Frequency Shift Keying(FSK) receiver using xilinx System Generator. The receiver incorporates a 16 point Fast Fourier Transform(FFT) for symbol detection. The design units of the receiver are digital designs for better efficiency and reliability. The receiver functions on one bit data processing and supports data rates 10kbps. In addition CORDIC algorithm is used for avoiding complex multiplications while computing FFT, multiplication of twiddle factor is substituted by rotators. The design and simulation of the receiver is carried out in Simulink, then the simulink model is translated to a hardware model to implement FPGA using Xilinx System Generator and to verify performance.