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Czochralski법을 이용한 금속 단결정의 성장과 구조적, 전기적 성질에 관한 연구
박정훈,차수영,박상언,김성규,조채룡,박혁규,김형찬,정명화,정세영,Park, Jeung-Hun,Cha, Su-Young,Park, Sang-Eon,Kim, Sung-Kyu,Cho, Chae-Ryong,Park, Hyuk-K.,Kim, Hyung-Chan,Jeong, Myung-Hwa,Jeong, Se-Young 한국결정학회 2005 韓國結晶學會誌 Vol.16 No.2
It is well known that the general metals have a lot of grain boundaries. The grain boundaries play a negative role to increase the resistivity and to decrease the conductivity. The small resistivity and the large conductivity have been a goal of the material scientists, and no signal noise, perfect signal transfer, and the realization of the real sound are the dream of electronic engineers and audio manias. Generally, oxygen free copper (OFC) and Ohno continuous casting (OCC) copper cables have been used for the purpose of the precise signal transfer and low noise. However they still include a lot of grain boundaries. In our study, we have grown the single crystal by the Czochralski method and succeeded to produce single crystal wires from the crystal in the dimension of $0.5{\times}0.5{\times}2500mm$. The produced wire still possesses very good single crystal properties. We observed the structure of the wire, and measured the resistance and impedance. Glow Discharge Spectrometer (GDS) was used for analyzing the compositions of copper single crystals and commercial copper. Current-Voltage curve, resistance, total harmonic distortion and speaker frequency response were measured for comparing electrical and acoustic properties of two samples.
박정훈,유홍희,양현익,황요하,Park, Jeong-Hun,Yu, Hong-Hui,Yang, Hyeon-Ik,Hwang, Yo-Ha 대한기계학회 2000 大韓機械學會論文集A Vol.24 No.2
This paper presents a method for the dynamic analysis of constrained multibody systems undergoing abrupt collision. The proposed method uses a longer time interval to check collision than that of c onventional method. This reduces the computational effort significantly. To calculate collision points on two colliding rigid bodies, one may introduce constraints of contact. However, this causes reduction of degree of freedom and difficulty of numerical analysis. The proposed method can calculate collision points without above mentioned problems. Three numerical examples are given to demonstrate the computational efficiency and the usefulness of the proposed method.
주 유동의 난류특성이 원통 표면에서의 열전달에 미치는 영향에 관한 연구 - 수치 해석적 고찰 -
박정훈,최영기,유홍선,Park, J.H.,Choi, Y.K.,Ryou, H.S. 대한설비공학회 1991 설비공학 논문집 Vol.3 No.3
Numerical analysis has been performed to investigate the effects of the turbulence intensity and Prandtl number on the local heat transfer around a circular cylinder in crossflow. The governing equations were reformulated in a non-orthogonal coordinate system with Cartesian velocity components and discretised by the finite volume method with a non-staggered variable arrangement. For laminar flow, the calculations were performed for the Reynolds numbers 26 and 200. The results showed good agreement with the experimental results. For turbulent flow of the Reynolds number $1{\times}10^5$ and $2{\times}10^6$, the results showed that with an increase in the turbulent intensity in the main stream, the local Nusselt number increases in the front region of the circular cylinder. But the effect of turbulent intensity on the local Nusselt number diminishes in the wake region. The influence of Prandtl numbers show similar trend to that of turbulent intensity.
위승한격(胃勝寒格)을 시술한 안검경련환자 47례에 대한 임상적 고찰
박정훈,홍승욱,Park, Jung-Hoon,Hong, Seung-Ug 대한한방안이비인후피부과학회 2009 한방안이비인후피부과학회지 Vol.22 No.2
Objectives : This study was performed to observe 47 cases of patients with blepharospasm treated with Wisunghanggyeok(胃勝寒格). Methods : For 28 months from Sep. 2006 to Dec. 2008, we researched 47 blepharospasm patients treated with Wisunghanggyeok(胃勝寒格) who visited the author's clinic. Results & Conclusion: 1. It shows more female patients than male patients, and mostly patients in their fifties. 2. The lesion is shown more on the right side than on the left side, and the left side blepharospasm is cured more effective. 3. The causes of hemifacial spasm are mainly stress and overwork, and there is a 85% improvement of 39 cases from these two causes. 4. The disease period is mainly within 1 week, and that period is the most effective time. 5. The number of treatment is mainly under 5 times, and the effect of treatment over 4 times for week is more available. 6. There are 59.57% of excellent improvement and 23.4% of good improvement, and these make 82.97% improvement of 47cases.
La<sub>0.07</sub>Sr<sub>0.3</sub>Co<sub>0.2</sub>Fe<sub>0.8</sub>O<sub>3-δ</sub> 분리막의 제조 및 산소투과 특성
박정훈,김종표,백일현,Park, Jung Hoon,Kim, Jong Pyo,Baek, Il Hyun 한국공업화학회 2008 공업화학 Vol.19 No.5
$La_{0.7}Sr_{0.3}Co_{0.2}Fe_{0.8}O_{3-{\delta}$ oxide was synthesized by a citrate method and a typical dense membrane of perovskite oxide has been prepared using as-prepared powder by pressing and sintering at $1300^{\circ}C$. Precursor of $La_{0.7}Sr_{0.3}Co_{0.2}Fe_{0.8}O_{3-{\delta}$ prepared by citrate method was investigated by TGA and XRD. Metal-citrate complex in precursor was decomposed into perovskite oxide in the temperature range of $260{\sim}410^{\circ}C$ but XRD results showed $SrCO_3$ existed as impurity at less than $900^{\circ}C$. Electrical conductivity of membrane increased with increasing temperature but then decreased over $700^{\circ}C$ in air atmosphere ($Po_2=0.2atm$) and $600^{\circ}C$ in He atmosphere ($Po_2=0.01atm$) respectively due to oxygen loss from the crystal lattice. The oxygen permeation flux increased with increasing temperature and maximum oxygen permeation flux of $La_{0.7}Sr_{0.3}Co_{0.2}Fe_{0.8}O_{3-{\delta}$ membrane with 1.6 mm thickness was about $0.31cm^3/cm^2{\cdot}min$ at $950^{\circ}C$. The activation energy for oxygen permeation was 88.4 kJ/mol in the temperature range of $750{\sim}950^{\circ}C$. Perovskite structure of membrane was not changed after permeation test of 40 h and the membrane was stable without secondary phase change with 0.3 mol Sr addition. 구연산법을 이용하여 $La_{0.7}Sr_{0.3}Co_{0.2}Fe_{0.8}O_{3-{\delta}$ 산화물을 합성하였으며, 합성된 분말은 압축 성형 후 $1300^{\circ}C$에서 소결하여 치밀한 페롭스카이트 분리막을 제조하였다. 구연산법으로 제조한 $La_{0.7}Sr_{0.3}Co_{0.2}Fe_{0.8}O_{3-{\delta}$의 전구물질은 TGA와 XRD로 분석하였다. $260{\sim}410^{\circ}C$ 온도 영역에서 전구물질의 금속-구연산 복합체가 분해되며 페롭스카이트 산화물이 얻어지나 XRD 분석결과 $900^{\circ}C$ 이하에서는 $SrCO_3$가 불순물로 존재하였다. 분리막의 전기전도도는 온도가 증가함에 따라 증가하다. 결정격자의 산소 손실로 인해 공기분위기에서는 $700^{\circ}C$ ($Po_2=0.2atm$)부터, 헬륨분위기에서는 $600^{\circ}C$ ($Po_2=0.01atm$) 부터 각각 감소하였다. 산소투과량은 온도가 증가할수록 증가하였고, 두께 1.6 mm의 $La_{0.7}Sr_{0.3}Co_{0.2}Fe_{0.8}O_{3-{\delta}$ 분리막은 $950^{\circ}C$에서 $0.31cm^3/cm^2{\cdot}min$의 최대 투과도를 보였다. 산소투과에 대한 활성화 에너지는 $750{\sim}950^{\circ}C$ 온도 영역에서 88.4 kJ/mol이었다. 40 h의 투과실험 후에 분리막의 페롭스카이트 결정 구조는 변하지 않았으며 0.3 mol Sr doping 시 2차상이 생성되지 않고 안정하였다.
Sulfur removal from coal with supercritical fluid treatment
박정훈,Yong Ou Joung,Sang Do Park 한국화학공학회 2007 Korean Journal of Chemical Engineering Vol.24 No.2
Conversion and sulfur removal of coal in sub- and supercritical water was studied in a micro reactor in the temperature range of 340-400°C and water density 0-0.27 g/cm3 for 0-90 min under N2 atmosphere. The experiments were conducted to investigate the effect of reaction temperature, pressure, time and density of water on the sulfur removal in gaseous and liquid effluents, respectively. The results show that supercritical condition is more effective than sub-critical condition to remove the sulfur from coal. It is possible to reduce 57.42% of the original sulfur in coal for the reaction time of 90 min at 400°C and 30 MPa. The main gas containing sulfur in the gaseous effluent is not SO2 but H2S, irrespective of operating condition. The sulfur removal in liquid effluents is much greater than that in gas effluents. Compared with temperature, the influence of water density and pressure is less significant.