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Study of Cryogenic Conduction Cooling Systems for an HTS SMES
Yeom, H.K.,Hong, Y.J.,Park, S.J.,Seo, T.B.,Seong, K.C.,Kim, H.J. IEEE 2007 IEEE transactions on applied superconductivity Vol.17 No.2
<P>Superconducting magnetic energy storage (SMES) is more fast response, economical, and environment-friendly than uninterruptible power supply (UPS) using the battery. And the SMES not only has the ability to control active and reactive power simultaneously, but also has a long life time because the superconducting magnet does not have degradation problem which the battery has. Therefore, the SMES is a candidate for instead of the UPS using the battery. The SMES needs cryogenic system without exception. A conduction cooling system that has a simple, light and small structure is well adapted to high temperature superconducting (HTS) SMES. The cryogenic conduction cooling system is needed some technologies such as insulation, vacuum, and thermal analysis. Conduction heat is mainly transferred by cooler port, access port, support bar, etc., and radiation heat is transferred by vacuum chamber, thermal shield and HTS coil surface. The heat loads through the conduction and radiation of cryostat are calculated. Radiation shield heat load, temperature of HTS coil and conduction copper plate are estimated and measured. A cryopumping effect of cooled radiation shield was observed. A current lead and HTS coil heat load was evaluated to maintain HTS coil temperature was under 20 K.</P>
Calculation of electron and hole impact ionization coeffcients in SiGe alloys
Yeom, K.,Hinckley, J.M.,Singh. J. 대전산업대학교 반도체기술연구소 1999 半導體技術硏究所報 Vol.1 No.-
Silicon-germanium alloys offer a system where the ratio of the electron impact ionization coefficiend (a) and hole impact ionization coefficient (B) varies from a value larger the unity (in high silicon content alloys), to a value smaller than unity (in high germanium content alloys). We report results for a and B for this alloy system. The electron results are based on a multivalley nonparabolic band structure. The hole results are based on a six-band k.p model for low energies coupled to an eight0band model for high energies. We find that for the alloy Si_0.4Ge_0.6, a~B. Alloy scattering is found to play an important role in determining the impact ionization coefficient. For compositions around Si_0.5Ge_0.5, the strong alloy scattering is found to suppress the impact ionization coefficient.
Seo, J. M.,Kim, K. J.,Yeom, H. W.,Park, Ch. 全北大學校 基礎科學硏究所 1994 基礎科學 Vol.17 No.-
The presence of metastable molecular precursor to dissociative oxygen chemisorption has been identified, for the first time, on Si(100) and Si(111) surfaces using ultraviolet photoelectron spectroscopy and x-ray photoelectron spectroscopy at 40 K. Density of valence states for such species shows three distinct peaks at 1.8, 3.4, and 4.9 eV below the Fermi energy of substrates. The precursor stabilized on Si(100) at 40 K induces a large work- function increase of 1.5 eV at saturation coverage. It also gives rise to a shoulder to O 1s photoemission spectrum that it located at 1.2 eV lower binding energy than the O 1s peak of stable and dissociated oxygen species. It has been concluded that the major reason of a larger work-function increment at 40 K is the existence of a molecular precursor, or peroxy radical type, on Si(100) and Si(111). These results strongly suggest that exists a general mechanism of oxygen adsorption onto silicon surfaces.
Kwon, H.J.,Yeom, S.J.,Park, C.S.,Oh, D.K. Society for Bioscience and Bioengineering, Japan ; 2010 Journal of bioscience and bioengineering Vol.110 No.1
The specific activity and catalytic efficiency (k<SUB>cat</SUB>/K<SUB>m</SUB>) of the recombinant putative protein from Providencia stuartii was the highest for d-lyxose among the aldose substrates, indicating that it is a d-lyxose isomerase. Gel filtration analysis suggested that the native enzyme is a dimer with a molecular mass of 44 kDa. The maximal activity for d-lyxose isomerization was observed at pH 7.5 and 45 <SUP>o</SUP>C in the presence of 1 mM Mn<SUP>2+</SUP>. The enzyme exhibited high isomerization activity for aldose substrates with the C2 and C3 hydroxyl groups in the left-hand configuration, such as d-lyxose, d-mannose, l-ribose, d-talose, and l-allose (listed in decreasing order of activity). The enzyme exhibited the highest activity for d-xylulose among all pentoses and hexoses. Thus, d-lyxose was produced at 288 g/l from 500 g/l d-xylulose by d-lyxose isomerase at pH 7.5 and 45 <SUP>o</SUP>C for 2 h, with a conversion yield of 58 % and a volumetric productivity of 144 g l<SUP>-1</SUP> h<SUP>-1</SUP>. The observed k<SUB>cat</SUB>/K<SUB>m</SUB> (920 mM<SUP>-1</SUP> s<SUP>-1</SUP>) of P. stuartiid-lyxose isomerase for d-xylulose is higher than any of the k<SUB>cat</SUB>/K<SUB>m</SUB> values previously reported for sugar and sugar phosphate isomerases with monosaccharide substrates. These results suggest that the enzyme will be useful as an industrial producer of d-lyxose.
상용 유한요소 프로그램에서 사용하는 보요소와 판요소의 대변형 거동에 관한 연구
진종태,이경식,염선일 울산대학교 1997 공학연구논문집 Vol.28 No.2
구조물 해석에 널리 쓰이는 상용 유한요소해석용 소프트웨어인 MSC/NASTRAN 과 NISA-Ⅱ를 사용하여 외팔보와 4변이 고정된 정사각형 평판 문제를 해석하고 그 결과를 각각의 이론해와 비교하였다. 미소변형일 경우 외팔보의 유한요소 해석의 결과는 본 연구에서 해석한 모든 경우에 요소수와 무관하게 이론해와 정확히 일치한다. 대변형일 경우에는 외팔보와 평판 문제 모두에서 요소수가 많을수록 또한 보의 길이나 판의 한 변의 길이가 두께에 비해 클수록 이론해에 근접해 가는 경향이 있다. 특히 길이가 높이에 비해 긴 외팔보의 경우요소수가 5 이상이면 이론해와 0.5% 이내의 오차를 보인다. 평판문제의 대변형 해석결과는 NISA-Ⅱ의 해석결과가 MSC/NASTRAN의 해석결과보다 더 이론해에 근접하다. The results of FE analysis of a uniform cantilever beam and a uniformly loaded square plate with all edges clamped, using commercial FE software( MSC/NASTRAN and NISA-Ⅱ), are compared with the analytical solutions. For small deformation in cantilever beam, the results of FE analysis for all the cases are identical with the analytic solutions regardless of the number of elements. For large deformation, the results of the FE analysis tends to approach close to the analytic solutions with the increase in the number of elements and the length to thickness ratios in both of two problems. In particular, for the case of the cantilever whose length is much longer than the depth, the errors are within 1% in cases of the number of elements are more than five. Comparing the results of the large deformation analysis of the square plate reveals that the result of the NISA-Ⅱ is closer to the analytical solution than that of the NSC/NASTRAN.
고온 압축변형된 니켈기 초내열 718 합금 결정립 조직의 EBSD 분석
나영상,이만형,염종택,박노광 대한금속재료학회 2003 대한금속·재료학회지 Vol.41 No.3
In order to characterize the dynamic change of microstructures in commercially-available superalloy 718, a series of compression tests were conducted by varying test temperature and strain rate. Orientation relationship and the misorientations between recrystallized grains as well as unrecrystallized grains were thoroughly investigated with EBSD technique. The dynamically-recrystallized grain size was similar regardless of the compression test condition except for the sample tested at 1066℃-0.005/sec condition, where the dynamically-recrystallized grain size was as large as 20 μm in average diameter. In case of the sample tested at 1066℃, flow stress drops caused by the strain softening were almost same at the strain rates of 0.5/sec and 0.005/sec in spite of the different fraction of dynamic recrystallization. It was concluded from the observation of the misorientation angle distribution that it was due to the active dynamic recovery in the unrecrystallized large grains at high temperature. It was also suggested from the variations of CSL boundary distribution that the characteristic redistribution of the dynamically-recrystallized grain boundary might be taken place during the compression at high temperature and low strain rate.
Interspecies transmission of the canine influenza H3N2 virus to domestic cats in South Korea, 2010
Song, D. S.,An, D. J.,Moon, H. J.,Yeom, M. J.,Jeong, H. Y.,Jeong, W. S.,Park, S. J.,Kim, H. K.,Han, S. Y.,Oh, J. S.,Park, B. K.,Kim, J. K.,Poo, H.,Webster, R. G.,Jung, K.,Kang, B. K. Microbiology Society 2011 The Journal of general virology Vol.92 No.10