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류병기,Bong-Seo Kim,이지은,Sung-Jae Joo,Bok-Ki Min,이희웅,Su-Dong Park,Min-Wook Oh 한국물리학회 2016 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.68 No.1
Density functional calculations are performed to study the band structures of Bi2Te3-related binary (Bi2Te3, Sb2Te3, Bi2Se3, and Sb2Se3) and Sb/Se-doped ternary compounds [(Bi1−xSbx)2Te3 and Bi2(Te1−ySey)3]. The band gap was found to be increased by Sb doping and to be monotonically increased by Se doping. In ternary compounds, the change in the conduction band structure is more significant as compared to the change in the valence band structure. The band degeneracy of the valence band maximum is maintained at 6 in binaries and ternaries. However, when going from Bi2Te3 to Sb2Te3 (Bi2Se3), the degeneracy of the conduction band minimum is reduced from 6 to 2(1). Based on the results for the band structures, we suggest suitable stoichiometries of ternary compounds for high thermoelectric performance.
Work Function of Bismuth Telluride: First-Principles Approach
류병기 한국물리학회 2018 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.72 No.1
First-principles approach is demonstrated to calculate the work function of Bi2Te3. The reference potential and the vacuum energy levels are extracted from the Bi2Te3 (0001) surface structure using the reference potential method based on the density functional theory. The one-shot GOWO manybody perturbation theory is used to place the bulk band edge energies with respect to the reference level and the vacuum energy. At last, the work function of 5.301 - 5.131 eV is predicted for Bi2Te3 (0001) surface and compared to various elements.
Timoshenko 보 이론을 이용한 층상균열이 있는 보의 진동해석 및 비파괴적 평가
韓秉基,李晟熙,柳澤仁 弘益大學校 科學技術硏究所 1994 科學技術硏究論文集 Vol.5 No.-
A study of the natural vibrations of Timoshenko beam with a split is presented. An analytic model, based on the transverse and longitudinal vibration of beams is employed to determine the natural frequencies. The variations of natural frequencies with the changes of size and location of laminar tear are plotted for several thickness ratio. A specific example are given to show the effects of rotary inertia, and shear deformation on the natural frequencies of the beam with a split. A new skill for the presentation of relationship between the size and location of laminar tear and natural frequencies is presented.
메타형 실리사이드 신열전반도체 및 소자물성 측정 표준화 기술 개발
박수동,장정인,류병기,정재환,박종호,( Pawel Ziolkowski ) 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.1
최근 다양한 에너지재생 기술에 대한 관심이 커지면서 열전발전 분야에 대한 관심도 커져 가고 있다. 사실 열전과학은 가장 오래된 반도체에너지 기술로 고체상태에서 열에너지와 전기에너지가 변환되는 매우 원천적 과학이다. 현재까지 도모되고 있는 많은 연구 성과중 실제 응용화에 성공하고 있는 열전기술도 19세기에 시도되었던 기술적 응용과 매우 유사하다. 이것은 물질적 측면에서의 혁신적 도약, 산업적 측면에서의 실용적 표준 기술의 부재가 매우 큰 이유이다. 본 발표에서는 차세대 열전소재로 꾸준히 각광받고 있는 실리사이드계 열전화합물 반도체와 산업화에 큰 걸림돌인 소자화 기술 및 측정 표준화 기술 현황과 기술 개발 전략에 대해 소개한다.
진행성 위암을 동반한 복부 대동맥류의 치험예 : 1예 보고
김홍기,최창식,조창순,류병기 대한혈관외과학회 1992 Vascular Specialist International Vol.8 No.1
In the age group in which aneurysms of the abdominal aorta usually occur, malignant neoplasia has a high relative incidence. The coincidence of two potentially lethal lesions raises obvious problems of management, particularly as regards priority of treatment. We experienced a case of abdominal aortic aneurysm which had intra-abdominal malignancy, advanced stomach cancer, stage III. He was a 67-year-old man with cancer of the stomach and infra-renal impending abdominal aortic aneurysm, diagnosed preoperatively. He was treated by two-stage operation of them, I.e., aneurysmectomy was performed about 2 weeks prior to radical subtotal gastrectomy. Selection of the operative approaches for patients having both alimentary tract malignancy and an abdominal aortic aneurysm was difficult, although the initial surgical intervention for the more life-threatening lesion would be better justified. So, these case was presented with brief review of the literature.
Enhanced Thermoelectric Properties and Development of Nanotwins in Na-Doped Bi0.5Sb1.5Te3 Alloy
김현,이재기,박수동,류병기,이지은,김봉서,민복기,주성재,이희웅,조영래 대한금속·재료학회 2016 ELECTRONIC MATERIALS LETTERS Vol.12 No.2
We found that Na is a good source to develop twin structures in the Bi-Te system, such as Ag as noted in a previous study. The twinboundaries had a considerable influence on reductions of the latticethermal conductivity due to phonon scattering by the nano-orderedlayers and on reductions of the electrical resistivity owing to thedefects generated by the substitution of Na into the cation sites. Here,we report the enhanced thermoelectric properties of a Na-doped p-typeBi0.5Sb1.5Te3 alloy. Measurements show that the electrical resistivityand the Seebeck coefficient decrease with Na doping due to anincrease in the free carrier (hole) concentration and that the latticethermal conductivity decreases with Na doping. The achievedmaximum ZT value was 1.20 at 423 K, which is approximately 20%higher than that of Bi0.5Sb1.5Te3 under the same fabrication conditions. These results were achievable by controlling the morphology of thetwin structure and the carrier concentration by means of Na doping.