HWE(Hot Wall Epitaxy)에 의한 CuGaSe₂/GaAs epilayer 성장과 광전기적 특성

홍광준,정준우,백형원,정경아,방진주,진윤미,김소형 조선대학교 기초과학연구소 2001 自然科學硏究 Vol.24 No.-

수평 전기로에서 CuGaSe₂ 다결정을 합성하여 HWE(Hot Wall Epitaxy) 방법으로 CuGaSe₂/GaAs epilayer를 반절연성 GaAs(100)기판 위에 성장하였다. CuGaSe₂/GaAs epilayer는 증발원의 온도를 610℃, 기판의 온도를 450℃로 하였다. CuGaSe₂/GaAs epilayer의 결정성의 조사에서 20K에서 광발광(photoluminescence) 스펙트럼이 672.6nm(1.8432eV)에서 엑시톤 방출 스펙트럼이 가장 강하게 나타났으며, 이중결정 X-선 요동곡선(DCRC)의 반폭치(FWHM)도 138 arcsec로 가장 작아 최적 성장 조건임을 알 수 있었다. Hall 효과는 van der Pauw 방법에 의해 측정되었으며, 온도에 의존하는 운반자 농도와 이동도는 293K에서 각각 4.87×10^(23) electron/m³, 1.29×10² m²/v-s 였다. CuGaSe₂/GaAs epilayer의 광전류 단파장대 봉우리들로부터 20K에서 측정된 ΔCr(Crystal field splitting)은 약 0.09 eV ΔSo(spin orbit coupling)는 0.2498 eV였다. 20K의 광발광 측정으로부터 고품질의 결정에서 볼 수 있는 자유 엑시톤 (free exciton)과 매우 강한 세기의 중성 받개(acceptor) 구속 엑시톤 (bound exciton)등의 피크가 관찰되었다. 이때 받개 구속 엑시톤 (bound exciton)의 반치폭과 결합에너지는 각각 8meV와 93.2meV 였다. 또한 Haynes rule에 의해 구한 불순물의 활성화 에너지는 466meV였다. The stochiometric mixture of evaporating materials for the CuGaSe₂/GaAs epilayer was prepared from horizontal furnace. Using extrapolation method of X-ray diffraction patterns for the polycrystal CuGaSe₂, it was found tetragonal structure whose lattice constant a_(0) and c_(0) were 5.615 Å and 11.025 Å, respectively. To obtain the CuGaSe₂/GaAs epilayer, CuGaSe₂ mixed crystal was deposited on throughly etched GaAs(100) by the Hot Wall Epitaxy(HWE) system. The source and substrate temperature were 610 ℃ and 450 ℃ respectively. The crystalline structure of CuGaSe₂/GaAs epilayer was investigated by the double crystal X-ray diffraction(DCXD). Hall effect on this sample was measured by the method of van der pauw and studied on carrier density and mobility depending on temperature. From Hall data, the mobility was likely to be decreased by pizoelectric scattering in the temperature range 30 K to 150 K and by polar optical scattering in the temperature range 150 K to 293 K. From the photocurrent spectra by illumination of polarized light of the CuGaSe₂/GaAs epilaye. We have found that values of spin orbit coupling ΔSo and crystal field splitting ΔCr was 0.0900 eV and 0.2498 eV, respectively. From the photoluminescence measurement of CuGaSe₂/GaAs epilayer, we observed free excition(Ex) observable only in high quality crystal and neutral acceptor-bound exciton (A^(0); X) having very strong peak intensity. And, the full width at half maximum and binding energy of neutral donor bound excition were 8 meV and 93.2 meV, respectively. By Haynes rule, an activation energy of impurity was 466 meV.

Hydrophobic Coating of Y2O3:Eu Phosphors by Using HMDSO/Toluene Plasma at Low Pressure and Their Wettability

Han S. Uhm,Kyung H. Lee,Soon C. Cho,Sung Y. Jo,Chan U. Bang,Dong K. Lee 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.2

Surface treatments of Y2O3:Eu phosphors for improving the hydrophobic property were carried out using plasmas generated from a O-(Si(CH3)3)2 (HMDSO) in a low-pressure environment. The super-hydrophobic properties of the treated Y2O3:Eu phosphors were investigated. The samples treated by using the HMDSO/toluene glow plasma were analyzed by FTIR and OES and analyzed in terms of their contact angles (CAs). The effects of the HMDSO/toluene plasma treatments on the Y2O3:Eu phosphors were investigated in terms of the total surface free energy by using probe liquids to measure their contact angles (CAs). The total surface free energy of the Y2O3:Eu phosphors before and after a surface treatment with the HMDSO/toluene plasma, as estimated via the Owens-Wendt equation, was found to decrease from 82.2 mJ/m2 to 0.021 mJ/m2. This represents a significant improvement of the hydrophobicity of the Y2O3:Eu phosphors after the plasma treatment.

The PPARα activator fenofibrate inhibits voltage-dependent K⁺ channels in rabbit coronary arterial smooth muscle cells

Li, H.,Shin, S.E.,Seo, M.S.,An, J.R.,Jung, W.K.,Ha, K.S.,Han, E.T.,Hong, S.H.,Bang, H.,Bae, Y.M.,Firth, A.L.,Choi, I.W.,Park, W.S. North-Holland 2017 European journal of pharmacology Vol.812 No.-

<P>We examined the effects of the PPAR alpha activator fenofibrate on voltage-dependent K+ (Kv) channels using a patch clamp technique in native rabbit coronary arterial smooth muscle cells. Kv current was inhibited by application of fenofibrate in a concentration-dependent manner, with an apparent IC50 value of 6.39 +/- 0.53 mu M and a slope value (Hill coefficient) of 1.63 +/- 0.10. Fenofibrate accelerated the decay rate of Kv channel inactivation. The rate constants of association and dissociation for fenofibrate were 0.81 +/- 0.05 mu M-1 s(-1) and 4.70 +/- 0.47 s(-1), respectively. Although fenofibrate did not affect the steady-state activation curves, fenofibrate shifted the inactivation curves toward a more negative potential. Application of train pulses (1 or 2 Hz) progressively increased the fenofibrate-induced inhibition of the Kv channel, and the recovery time constant from inactivation was increased in the presence of fenofibrate, which suggested that the inhibitory effect of fenofibrate is use-dependent. Another PPAR alpha activator, bezafibrate and PPARa inhibitor, GW 6471, did not affect the Kv current and also did not change the inhibitory effect of fenofibrate on the Kv current. From these results, we suggest that fenofibrate inhibited Kv current in a state-, time-, and use-dependent manner, completely independent of PPAR alpha activation.</P>

한우 배최장근 단면적의 초음파 측정

윤주용,방극승,김영길 ( J . Y . Yoon,K . S . Bang,Y . K . Kim ) 한국축산학회 1997 한국축산학회지 Vol.39 No.2

One hundred eight Hanwoo cows were evaluated ultrsonically for longissimus muscle depth and muscle width over the 13th rib before slaughter. Carcass measurement of muscle area, muscle depth and muscle width were also obtained. The correlation coefficient between muscle area and muscle depth were 0.78 while correlation coefficient between muscle area and muscle width was 0.51. A linear regression model to predict muscle area(y) by ultrasonic measured muscle depth(x) was developed as follows: y=15.2 + 7.17 x, (R²=0.44).

간호대생과 의대생의 간호사 이미지 비교

구민진,김수영,방정민,서아영,양희진,윤소람,이윤재,이재은,이지연,정윤경,최수정 이화여자대학교 간호과학대학 2014 이화간호학회지 Vol.- No.48

Purpose: This study aims to analyze the difference in the perception that nursing students and medical students have regarding the image of nurses. Method: The sampling group for this study was made up of 111 nursing students and 117 medicine students, conducted from the 19th August 2013 to 3rd September 2013. The tool used for this study is the “Nurse Image Scale”. The data is analyzed using the SPSS 21.0 program, technical stats, t-test and ANOVA with Scheffe test. Result: There was a notable difference in the results(t=6.94, p<001), with the average image perception score of nurses at 3.84±0.34 amongst nursing students being higher than the 3.50±0.38 amongst Medicine students. The average score of the 4 areas tested, “Qualification of a Nurse”, “Role of a Nurse”, “Social Participation of a Nurse” and “Interpersonal Skills of a Nurse” were all marked higher by the nursing students than the medicine students. The average score became notably higher as the period of practice became shorter with nursing students (F=4.21, p=.043). Furthermore, the average score for the “Qualification of a Nurse” was notably higher as the period of practice became shorter (F=3.98, p=.049). Medical students gave an average score for the “Qualification of a Nurse”(F=3.72, p=.027) and the “Interpersonal Skills of a Nurse”(F=4.11, p=.019) which was relative to the development of a nurse’s image, while the average score for the “Role of a Nurse” was notably higher with a longer period of practice(F=6.65, p=.011). Conclusion: The results of this study suggest that the image perception of a nurse can vary depending on the experience in period of practice. Therefore, together with this study conducted with nursing students and medicine students, there is a need for further studies conducted on image perception of nurses with various experience in period of practice.

Phase II study and biomarker analysis of cetuximab combined with modified FOLFOX6 in advanced gastric cancer

Han, S-W,Oh, D-Y,Im, S-A,Park, S R,Lee, K-W,Song, H S,Lee, N-S,Lee, K H,Choi, I S,Lee, M H,Kim, M A,Kim, W H,Bang, Y-J,Kim, T-Y Nature Publishing Group 2009 The British journal of cancer Vol.100 No.2

<P>This prospective study was conducted with the Korean Cancer Study Group to evaluate the efficacy and safety of cetuximab combined with modified FOLFOX6 (mFOLFOX6) as first-line treatment in recurrent or metastatic gastric cancer and to identify potential predictive biomarkers. Patients received cetuximab 400 mg m<SUP>−2</SUP> at week 1 and 250 mg m<SUP>−2</SUP> weekly thereafter until disease progression. Oxaliplatin (100 mg m<SUP>−2</SUP>) and leucovorin (100 mg m<SUP>−2</SUP>) were administered as a 2-h infusion followed by a 46-h continuous infusion of 5-fluorouracil (2400 mg m<SUP>−2</SUP>) every 2 weeks for a maximum of 12 cycles. Biomarkers potentially associated with efficacy were analysed. Among 38 evaluable patients, confirmed response rate (RR) was 50.0% (95% CI 34.1–65.9). Median time-to-progression (TTP) was 5.5 months (95% CI 4.5–6.5) and overall survival (OS) 9.9 months. Eleven patients having tumour EGFR expression by immunohistochemistry with low serum EGF and TGF-<I>α</I> levels showed a 100% RR compared to 37.0% in the remaining 27 patients (<I>P</I><0.001). Moreover, ligand level increased when disease progressed in seven out of eight patients with EGFR expression and low baseline ligand level. No patient exhibited EGFR amplification or K-ras mutations. Gastric cancer patients with EGFR expression and low ligand levels had better outcomes with cetuximab/mFOLFOX6 treatment.</P>

KSTAR 전류전송계통 진공배기계 구축 및 시운전

우인식,송낙형,이영주,곽상우,방은남,이근수,김정수,장용복,박현택,홍재식,박영민,김양수,최창호,Woo, I.S.,Song, N.H.,Lee, Y.J.,Kwag, S.W.,Bang, E.N.,Lee, K.S.,Kim, J.S.,Jang, Y.B.,Park, H.T.,Hong, Jae-Sik,Park, Y.M.,Kim, Y.S.,Choi, C.H. 한국진공학회 2007 Applied Science and Convergence Technology Vol.16 No.6

KSTAR (Korea Superconducting Tokamak Advanced Research) 전류전송계 (Current Feeder System)는 4.5 K의 저온에서 운전되는 초전도자석과 300 K의 실온에서 운전되는 전원장치 (Magnet Power Supply)를 전기적으로 연결하는 장치이다. 전류전송계는 최대 35 kA의 DC 전류가 인가되는 TF 자석용 및 350초간 20$\sim$26 ㎄의펄스 전류가 인가되는 PF 자석용으로 분리되어 있으며 리드박스 내부는 전류인입선, 초전도버스라인, 열차폐체 및 냉각라인 등이 설치되어 있다. 리드박스와 초전도버스라인 진공덕트는 KSTAR 주장치와는 별도로 진공배기 시스템이 구축되어있으며, 전체적으로 아령 형상을 하고 있는 진공공간을 효율적으로 진공배기하기 위하여 버스라인 덕트와 주장치 저온용기 사이에 진공 분리막 (Vacuum Separator)이 설치되어 있다. 진공배기를 위한 초벌배기계는 로터리펌프 및 부스터펌프 (Mechanical Booster Pump)로 구축되었으며 고진공 배기계는 4대의 크라이오펌프 (Cryo-pump)로 구축되었다. 진공장치 운전을 위해 PLC 기반의 로컬 제어시스템을 구축하였고 장치 안전을 위한 자체 인터록과 중앙인터록 시스템 및 중앙제어연계시스템이 함께 구축되어 있다. 전류전송계 설치완료 후 진공배기 시운전을 통해 배기시스템의 자가진단 및 리드박스 내부에 설치되어 있는 헬륨배관의 진공누설검사를 완료하였으며, 액체질소를 사용하여 전류인입선 냉각시험을 완료하였다. Current feeder system (CFS) for Korea superconducting tokamak advanced research(KSTAR) project plays a role to interconnect magnet power supply (MPS) and superconducting (SC) magnets through the normal bus-bar at the room temperature(300 K) environment and the SC bus-line at the low temperature (4.5 K) environment. It is divided by two systems, i.e., toroidal field system which operates at 35 kA DC currents and poloidal field system wherein 20$\sim$26 kA pulsed currents are applied during 350 s transient time. Aside from the vacuum system of main cryostat, an independent vacuum system was constructed for the CFS in which a roughing system is consisted by a rotary and a mechanical booster pump and a high vacuum system is developed by four cryo-pumps with one dry pump as a backing pump. A self interlock and its control system, and a supervisory interlock and its control system are also established for the operational reliability as well. The entire CFS was completely tested including the reliability of local/supervisory control/interlock, helium gas leakage, vacuum pressure, and so on.

KSTAR 전류인입선 및 헬륨냉매 제어시스템 제작 및 설치

송낙형,우인식,이영주,곽상우,방은남,이근수,김정수,장용복,박현택,홍재식,박영민,김양수,최창호,Song, N.H.,Woo, I.S.,Lee, Y.J.,Kwag, S.W.,Bang, E.N.,Lee, K.S.,Kim, J.S.,Jang, Y.B.,Park, H.T.,Hong, J.S.,Park, Y.M.,Kim, Y.S.,Choi, C.H. 한국진공학회 2007 Applied Science and Convergence Technology Vol.16 No.5

KSTAR (Korea Superconducting Tokamak Advanced Research) 전류인입선(CL; Current Lead)은 4.5 K의 저온에서 운전되는 초전도 버스라인과 300 K의 실온에서 운전되는 MPS (Magnet Power Supply)를 전기적으로 연결하는 장치이다. 초기 플라즈마 발생시험을 위하여 TF (Toroidal Field) 및 PF (Poloidal Field) 리드박스에 전류인입선이 설치된다. TF 자석용 CL은 17.5 kA급 4 개의 CL에 최대 35 kA의 DC 전류가 인가되며, PF 자석용은 13 kA급 14 개의 CL에 350초간 $20\;{\sim}\;26\;kA$의 펄스 전류가 인가된다. 각각의 전류인입선은 TF 및 PF 자석에 전류를 인가하기 위한 버스라인이 연결되어 있으며, 전류인입선을 통해 초전도 버스라인으로 전달되는 전도열 및 전류인가시 발생되는 주울(Joule) 열을 차단하기 위한 헬륨냉매 제어시스템이 KSTAR 주장치와는 별도로 설치되어 있다. 리드박스 내 외부의 배관 및 제어시스템 설치완료 후 고진공 배기, 헬륨 누설검사, 전류인입선 유량 검사 및 액체질소 냉각시험을 실시하여 장치의 성능검증을 완료하였다. KSTAR (Korea Superconducting Tokamak Advanced Research) current lead system (CLS) has a role to interconnect magnet power supply (MPS) in room temperature (300 K) and superconducting (SC) bus-line, electrically. For the first plasma experiments, it should be assembled 4 current leads (CL) on toroidal field (TF) current lead box (CLB) and 14 leads on poloidal field (PF) CLB. Two current leads, with the design currents 17.5 kA, and SC bus-lines are connected in parallel to supply 35 kA DC currents on TF magnet. Whereas, it could supply $20\;{\sim}\;26\;kA$ to each pairs of PF magnets during more than 350 s. At the cold terminals of the leads, there are joined SC bus-lines and it was constructed helium coolant control system, aside from main tokamak system, to protect heat flux through current leads and enhanced Joule heat due to supplied currents. Throughout the establishment processes, it was tested the high vacuum pumping, helium leak of the helium lines and hardwares mounted between the helium lines, flow controls for CL, and liquid nitrogen cool-down of possible parts (current leads, CL helium lines, and thermal shield helium lines for CLB), for the accomplishment of the required performances.

열간성형해석을 위한 유동응력의 변형열 보정에 대한 연구

方源珪,鄭載榮,張榮遠 대한금속재료학회 2001 대한금속·재료학회지 Vol.39 No.12

Dynamic deformation of metallic materials mostly accompanies substantial amounts of deformation heating. Since the flow stress of deformation is sensitive to temperature, implication of heat due to plastic work is essential to the evaluation of constitutive relations. In this study, a series of compression tests were conducted for SAF 2507 super duplex stainless steel at various temperatures and strain rates. The accumulation of plastic work was integrated through conventional analytic method and numerical method proposed in this study. Subsequent logarithmic interpolation deduced isothermal flow surfaces, which were primary input data of finite element analysis. Two compensation methods showed definite difference in resulting flow stress, especially at high strain level, which mainly due to the underestimated strain hardening by conventional one. Simple closed die forging process was analyzed and optimized with commercial FEM code applying both raw and calibrated material database. The effect of accounting deformation heat was more noticeable in high-speed forming process.

스퍼터링으로 증착된 Na ionic conductive thin film을 이용한 CO₂센서의 제작 및 특성

방영일,송갑득,주병수,임채근,권오식,배재철,허증수,이덕동 경북대학교 센서기술연구소 2002 센서技術學術大會論文集 Vol.13 No.1