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黃龍奎,秋惠容 圓光大學校 基礎自然科學硏究所 1991 基礎科學硏究誌 Vol.10 No.2
GaAs/AlAs/GaAs RTD's(Resonant Tunneling Diodes) have been fabricated and characterized. Peak to Valley Ratio has been found to be 3.16 at the room temperature for a RTD with the quantum well width of 45A and quantum barrier width of 40A. Peak voltage, peak current, valley voltage, and valley current have been measured to be 690㎷, 9.2㎃, 880㎷, and 2.9㎃, respectively. About 160㎷ out of 690㎷ for the peak voltage could be accounted for as being due to the contact resistance under the contact pads, about 240㎷ as being due to the voltage needed to lineup the quasibound energy level of the DBQW(Double Barrier Quantum Well) in the RTD to the bottom of the conduction band of the emitter. About 190㎷ could not be accounted for by the simplified calculation employed in the analysis. It will be needed to calculate accurately the electrostatic potential profile near the DBQW.
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밀도초함수밀접결합 방법을 이용한 Si(100) 표면의 탄화과정 연구
황용규 圓光大學校 基礎自然科學硏究所 2000 基礎科學硏究誌 Vol.18 No.1
DFT-TB방법을 이용하여 Si(100)표면에서의 탄화수소의 흡착과 탄화과정을 연구하였다. Si(100) 표면에 흡착된 CH_3 H하나가 이양체(dimer)를 구성하는 Si 원자중의 하나로 옮겨 붙으며 Si이양체의 중앙에 삽입되거나 Si원자에 Dimer바깥쪽으로 흡착되었다. 계속되는 CH_3의 흡착은 CH_4의 형태로 H를 떼어내어 C-C결합의 형성을 지연시키며 Si(100)면을 CH_2 또는 CH로 뒤엎히게 하고 Si원자가 공급되는 경우 SiC구조가 형성됨을 알 수 있었다. 이로부터 Si표면이 CH_3로 뒤덮힌 뒤, 계속되는 CH_3의 입사에도 불구하고 C-C결합이 형성되지 않고, 규소원자나 수소화규소의 입사가 있으면 Si-C결합이 형성되어 SiC의 성장이 이루어짐을 알 수 있었다. Carbonization of Si(100)surface has been studied using Self-consistent -Charge Density -Funhctional-Tight-Bindind method. When a CH_3 molecules adsorbs on the surface, a H atom moves away from CH_3 to form a bond with one of the Si atoms forming a dimer and the rest is inserted into the dimer. Or CH_3 adsorbs to one of the Si atoms forming the dimer. Subsequent absorption of CH_3 dessorbs H from CH_3 and CH_4, delaying the formation of C-C bonds. Eventually the surface is covered by either CH_2 or CH, and the adsorption of Si atoms or bhdrosilicon form Si-C bonds. adsorption of CH_3 on this C-terminated surface and the amount of Si supplied will result in the good crystalline quality of the carbonized layer. The growth of SiC may follow the above procedure, and is being studied by the same method.
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DFT Study for Substitution Patterns of C20H18X2 Regioisomers (X = F, Cl, Br, or OH)
황용규,Seol Lee,이기학 대한화학회 2012 Bulletin of the Korean Chemical Society Vol.33 No.2
We used the hybrid density-functional (B3LYP/6-31G(d,p)) method to analyze the substitution patterns of C20H18X2 derivatives (X = F, Cl, Br, or OH) obtained as disubstituted C20H20 cages. Our results suggest that the cis-1 regioisomers (1,2-dihalo derivatives) are less stable than the trans-1 regioisomers (1,20-dihalo derivatives), whereas in the case of the dihydroxy derivatives, the cis-1 regioisomer is more stable than the trans-1 regioisomer. This implies that in the dihalo-induced strain cages of C20H18X2, the strain effect would affect the relative energies, while in the dihydroxide, the hydrogen bonds have a stronger effect on the relative energies in cis-1 regioisomer than the strain effect do. Thus this supports the experimental result in which the bisvicinal tetrol was of particular preparative-synthetic interest as a substitute for the lacking bisvicinal tetrabromide. Further, the topologies of the HOMO and LUMO characteristics of all C20H18Cl2 and C20H18Br2regioisomers with the same symmetry are same, but they are different from those of C20H18F2 and C20H18(OH)2. This indicates that the five regioisomers of each C20H20 disubstituted derivative will have an entirely different set of characteristic chemical reactions.
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Hwang, Yong Gyoo 圓光大學校 基礎自然科學硏究所 1996 基礎科學硏究誌 Vol.14 No.2
순이론 분자동력학 방법을 이용하여 탄소로 끝난―SiC의 (100) 표면의 구조를 계산하여 보았다. 한 층에 8개의 원자가 있고 모두 7층의 두께를 갖는 판형 구조를 이용하고 위로부터 5층이내에 있는 원자들을 움직여 가며 가장 안정된 구조를 찾았다. 덩어리를 있는 그대로 잘라낸 이상적인 표면구조에 비하여 이양체가 형성된 (2가1) 재구성 구조의 에너지가 이양체 하나당 4.40 eV가 낮았으며, 엇갈린 이양체로 이루어진 c(2가2)재구성 구조 와 엇갈린 다리구조로 이루어진 c(2가2) 재구성 구조에 비해서는 각각 0.44 eV 와 0.95 eV 만큼 에너지가 높았다. 이양체는 대칭적이었으며 C―C 결합길이는 1.35 가이어서 이중결합구조임을 밝혔다. The structure of C―terminated (100) surface of cubic SIC has been studied by employing ab initio molecular dynamics method. A slab geometry of 7 atomic layers thick with 8 atoms in each os used to simulate the surface and upper 5 layers of atoms are allowed to relax. We find that total energy is 4.40 eV lower per dimer compared to the ideal surface, but 0.44 and 0.95 eV higher than the staggered dimer c(2×2) and staggerde bridge c(2×2) structures, respectively. The dimer os found to be symmetric and C―C bond length os 1.35Å, indicating it is doubly bonded.
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김병선,황용규,권철재,임영재 한국임상수의학회 1998 한국임상수의학회지 Vol.15 No.2
During the 5 years period(93-197) of Seoul racecourse Thoroughbred racing, 2i963 holies took an active part in Seoul Racecourse and 61,181 horses entered the racing.400 horses(305 : 1 time, 76 :2 times, 19 :3 times, total : 514 cases) had bled(EIPH) from their nostils after their races. Incidence of bleeding horses from the 21963 racehorses was 13.5%, and incidence of bleeding cases from the 61,181 horses was 0.84%. The average racing frequence (1.05 times/1 month) of bleeders was more than that(0.8 times/1 month) of total race-horses. There was tendency to higher incidence of bleeding at older in age, female in sex, England/ Ireland horses in origin, higher grade in performances heavier in body weight increased, larger in weight to be carried, mid or longer in racing distance, handicap race, spring in season. Relationship did not exist between bleeding and respiratory disease. These results suggested that frequent entering into the race should be controlled. And body weight regulation with conditioning is recommended far reducing incidence of EIPH. It is supposed to prevent bleeding that decrescent performance horses should not be entering long distance or handicap race.
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한상호,황용규 圓光大學校 基礎自然科學硏究所 1997 基礎科學硏究誌 Vol.15 No.2
반경험적 밀접 결합(emprical tight binding) 방법을 이용하여 깨끗한 C(100)표면과 수소화된 C(100) 표면의 구조적 특성을 연구하였다. 깨끗한 C(100) 표면의 경우, 표면은 대칭적 이양체를 형성하며 (2×1)구조를 나타내었으며, 이양체의 결합 길이는 1.39Å으로 ab initio 계산결과와 거의 일치하였다. 수소화된 C(100)표면에서는 수소의 피복률을 0.5 ML,1 ML,1.33 ML,1.5 ML,2 ML에 대하여 가능한 구조들을 고려하였다. 0.5 ML에 대해서는 지금까지 알려진 구조보다 안정한 새로운 구조를 (2×2)구조를 제시하였다. We studied the structural properties of clean and hydrogenated C(100)surfaces using the emprical tight binding method. The clean C(100)surface shows the (2×1)symmetry with symmetric dimers, and dimer bond length is 1.39Å in good agreement with the ab initio calculations. For hydrogenated C(100)surfaces, we considered various structures for the hydrogen coverages of 0.5 ML, 1 ML, 1.33 ML, 1.5 ML and 2 ML. For 0.5 ML we suggest a new structure with the (2×2) symmetry, which is more stable than reported structure.
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