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Processing optimization, surface properties and wear behavior of HVOF spraying WC–CrC–Ni coating
Fang, W.,Cho, T.Y.,Yoon, J.H.,Song, K.O.,Hur, S.K.,Youn, S.J.,Chun, H.G. Elsevier 2009 Journal of materials processing technology Vol.209 No.7
<P><B>Abstract</B></P><P>In this work, the optimal coating process (OCP) designed by Taguchi program for high velocity oxy-fuel (HVOF) thermal spraying WC–CrC–Ni powder on Inconel 718 substrate (IN 718) is obtained by optimizing hardness (38 FMR oxygen flow rate, 53 FMR hydrogen flow rate, 25g/min powder feed rate and 7in. spray distance). Oxygen flow rate affects hardness mostly. The surface properties such as microstructure, crystalline phase, hardness, and porosity of WC–CrC–Ni coating have been investigated. The phase of coating has been changed during the OCP spraying because a portion of carbides, such as WC, Cr<SUB>7</SUB>C<SUB>3</SUB>, Ni<SUB>3</SUB>C decomposes to W<SUB>2</SUB>C, Cr, Ni and free carbon. Hardness (1150±50Hv) and porosity (1.2±0.2%) of the OCP coating have been improved by optimization. The friction and wear behaviors of the WC–CrC–Ni coating, electrolytic hard chrome (EHC) plating and IN 718 have been studied comparatively. The lubrication due to free carbon and metal oxide debris results in a decrease of friction coefficients of the WC–CrC–Ni, compared to EHC and IN 718 at both 25 and 450°C. It is concluded that HVOF WC–CrC–Ni coating performs more excellent anti-wear than others at both temperatures.</P>
SPECTRAL DIAGNOSTICS OF THE ENERGETIC PARTICLES IN SOLAR FLARES
FANG C.,DING M. D.,HENOUX J. C.,GAN W. Q. The Korean Astronomical Society 1996 Journal of The Korean Astronomical Society Vol.29 No.suppl1
Non-LTE calculations, with the non-thermal ionization effects included, indicated that for electron bombardment, the H$\alpha$ line is widely broadened and shows a strong central reversal. Significant enhancements at the line wings of Ly$\alpha$ and Ly$\beta$ are also predicted at the beginning of the impulsive phase of flares. For the proton bombardment, no strong broadening and no large central reversal are expected. However, due to proton-hydrogen charge exchange, the enhancements at the red wings of Ly$\alpha$ and Ly$\beta$ lines at the early impulsive phase of flares are significant. Our results show that the electron beam can also in some cases generate visible and UV continuum emission in white-light flares. However, at the onset phase, a negative flare may appear within several seconds, due to the increase of the H- opacity. Another spectroscopic signature of energetic particles, i.e. the impact polarization of atomic lines, is also mentioned.
Production of Chitosan- and Chitin-like Exopolymers by Acetobacter xylinum ATCC 10245
Lee,Jin W.,Deng,Fang,Yeomans,Walter G.,Allen,Alfred L.,Gross,Richard A.,Kaplan,David L. 한국생명과학회 1998 한국생명과학회 학술발표회 Vol.20 No.-
To biosynthesize modified cellulose, glucose analogs including 3-O-methyl-D-glucose, glucosamine, N-acetylglucosamine, and 2-deoxy-D-glucose were used separately as the carbon source. Incorporation of glucosamine and N-acetylglucosamine repeat units into cellulose by Acetobacter xylinum ATCC 10245 was confirmed by GC, GC/MS, FTIR and ¹H-NMR. Based on data, the average molar percentages of glucosamine and N-acetylglucosamine repeat units into exopolymers were 19% and 18%, respectively. The yields of exopolymers made with glucosamine and N-acetylglucosamine as carbon source after 7 day culture were 0.37 ㎎/㎖ and 0.67 ㎎/㎖ , respectively, whereas that of glucose was 3.9 ㎎/㎖. The yield of exopolymer made with the mixture of glucose (0.5%, v/v) and glucosamine (1.5%, v/v) as carbon sources was 1.75 ㎎/㎖, and the average molar percentage of glucosamine repeat unit into the exopolymer was 17%. Exopolymers made with glucosamine and N-acetylglucosamine were fractionated by 10% acetic acid and DW, respectively, The molar ratio of glucose to glucosamine in the acetic acid (10%, v/v) soluble fractionation of glucosamine incorporated exopolymer was 0.6: 1.0. The molar ratio of glucose to N-acetylglucosanune in the water soluble fraction of N-acetylglucosamine incorporated exopolymer was 0.8 : 1.0.
전극형상에 따른 제조공기(I-Air)의 절연파괴 특성에 관한 연구
이창훈(C.H. Lee),김도석(D.S. Kim),常超(C. Chang),이창욱(C.W. Lee),김영수(Y.S. Kim),方亞偉(Y.W. Fang),최은혁(E.H. Choi),임창호(C.H. Lim),김정배 (J.B. Kim),이광식(K.S. Lee) 한국조명·전기설비학회 2006 한국조명·전기설비학회 학술대회논문집 Vol.2006 No.11월
본 연구는 SF?를 대체하기 위한 제조공기(I-Air)의 특성을 연구할 목적으로 교류고전압 인가 시 압력(P)변화 및 갭 길이의 변화에 따른 절연파괴특성을 연구하였다. 본 연구를 통해 챔버 내의 P가 증가 할수록 절연파괴특성은 증가하는 것을 확인했다. 그리고 불평등전계 보다 평등전계에서 절연파괴특성이 더 증가하고 전극간거리(d)가 증가 할수록 절연파괴특성이 증가하는 것을 확인했다. 특히 평등전계에서 d 및 높은 P일수록 SF?의 절연파괴전압(V<SUB>B</SUB>)에 I-Air의 V<SUB>B</SUB>의 근접도가 큼을 알 수 있었다.
Biosynthesis of Novel Exopolymers by Aureobasidium pullulans
Lee,Jin W.,Deng,Fang,Yeomans,Walter G.,Allen,Alfred L.,Gross,Richard A.,Kaplan,David L. 한국생명과학회 1998 한국생명과학회 학술발표회 Vol.20 No.-
Exopolymers produced by A. pullulans ATCC 42023 under aerobic conditions with glucose, mannose, and glucose analogs including 3-O- methyl-D-glucose, glucosamine, N-acetylglucosamine, and 2-deoxy-D- glucose as carbon sources contained glucose and mannose. The molar ratio of glucose to mannose in exopolymers and the molecular weight of exopolymers varied with the carbon source and culture time. Exopolymers synthesized with glucose and mannose as carbon sources showed glucose contents of 87±3 and 89±2%, respectively, with a decreased molecular weight from 3.50 - 2.12 x 10^6 to 0.85 - 0.77 x 10^6 with culture time. The molar ratio of glucose to mannose in the exopolymer synthesized with glucosamine changed from 55±3 : 45±3 to 29±2 : 71±2 and its molecular weight increased from 2.73 x 10^6 to 4.86 x10^6 with culture time. The molar ratio of glucose to mannose in exopolymers ranged from 87±3 : 13±3 to 28±2 : 72±2 and can be controlled by carbon source. On the basis on the results from enzyme hydrolysis of the exopolymers and comparison of ¹H- and ^(13)C-NMR chromatograms, the mannose as a monomeric component is substituted for glucose without changing the structure of pullulan.