• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 하계학술대회 논문집 C
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• pp.1442-1444
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• 1995

In this study, we confirmed that the crystallinity and the mechanical properties of polycrystalline Silicon(poly-Si) deposited on the poly-oxide are better than those of poly-Si on the conventional sacrificial layers that is CVD oxide layer or PSG. But the etch rate of poly-oxide is poor than that of the CVD oxide layer or PSG. Therefore, to make the best use of small stress and fast etch rate, we fabricated the double oxide layer; 10%-thick poly-oxide on 90%-thick CVD oxide or PSG. To estimate structure deformation by stress, we fabricated the test structures; cantilever. bridge and ring/beam structure and estimated by SEM. As the results, all structure is expressed the deformed structure by residual stress(tensile stress) and the deformation of the structure layer on the double oxide layer is small compared with that of the structure layer on the CVD oxide layer or PSG. And, the etch rate of the double oxide layer is enhanced compared with that of the poly-oxide.

• Progress in Superconductivity
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• 제11권1호
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• pp.36-41
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• 2009

Superconducting quantum phenomena are getting attention from the field of metrology area. Following its first successful application of Josephson effect to voltage standard, piconewton force standard was suggested as a candidate for the next application of superconducting quantum effects in metrology. It is predicted that a micron-sized superconducting Nb ring in a strong magnetic field gradient generates a quantized force of the order of sub-piconewtons. In this work, we studied the design and fabrication of Nb superconducting quantum interference device (SQUID) on an ultra-thin silicon cantilever. The Nb SQUID and electrodes were structured on a silicon-on-insulator (SOI) wafer by dc magnetron sputtering and lift-off lithography. Using the resulting SOI wafer, we fabricated V-shaped and parallel-beam cantilevers, each with a $30-{\mu}m$-wide paddle; the length, width, and thickness of each cantilever arm were typically $440{\mu}m,\;4.5{\mu}m$, and $0.34{\mu}m$, respectively. However, the cantilevers underwent bending, a technical difficulty commonly encountered during the fabrication of electrical circuits on ultra-soft mechanical substrates. In order to circumvent this difficulty, we controlled the Ar pressure during Nb sputtering to minimize the intrinsic stress in the Nb film and studied the effect of residual stress on the resultant device.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.389-392
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• 2004

It is clinically well known that pre-tension of wires increases the fracture stability in ring or hybrid external fixation. In some cases, additional half pin should be necessary to increase the stability when soft tissue impalement occurs during fixation. In this paper, the fracture stability of a hybrid external fixator system with different pre-tension effects and additional half-pins was analysed using FEM to investigate the effects of these pre-tension and half pin on the system stability quantitatively. 3-D finite element models of five different fixator frames were developed using by beam elements. In axial compression analysis, the fracture stiffness was increased maximally 62％ as the pre-tension increased. In torsion analysis, in the other hand, there is little variations in the fracture stiffness. Additional half pin increased the system stiffness about 200 ％. From the results, proper pre-tension and additional half pin would provide good methods to increase the fracture stability of the hybrid external fixator and provide more surgical options to minimize soft tissue damage at the fracture site.

• 한국진공학회지
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• 제5권3호
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• pp.245-250
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• 1996

$Y_2O_3$ thin film on si(100) was successfully grown by ionized cluster beam(ICBD) technique at substrate temperature of around $500^{\circ}C$ and pressure of ~$10^{-5}$Torr.To prevent the oxidation of Si substrae, a very thin yttrium layer was deposited on Si before reactive depositing of oxygen and yttrium source. In asdeposited stage, b.c.c and h.c.p strucutres of $Y_2O_3$ were observed from S-ary analysis. From the observation of spots and ring patterns in selected area diffractin(SAD) patterns. crystallane formation and growth could be proceeded during the deposition. $Y_2O_3$/mixed layer/$SiO_2=170\AA/50\AA/10\AA$ structure were verified by high resolution transmition electron imcroscopy(HRTEM) image, and the formation of amorphous layer of SiO2 was discussed . Electricla charateristics of the film were also investigated . In as-deposited Pt/$Y_2O_3$/Si sturcuture, leakage current was less than $10^{-6}$A/$\textrm{cm}^2$ at 7MV/cm strength.

• 한국터널지하공간학회 논문집
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• 제17권3호
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• pp.363-382
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• 2015

본 연구는 수치해석을 통하여 TBM 세그먼트의 분할 수와 인접한 링의 이격각도가 라이닝의 부재력에 어떤 영향을 미치는 살펴보았다. 수치해석은 Midas civil 2012+ 프로그램을 사용하였고, 모델링은 2링빔 스프링 모델을 이용하였다. TBM 세그먼드 부재력은 다양한 요소에 의해 결정된다. 본 논문에서는 세그먼트 분할 수와 분포를 제외한 다른 요소인 이음부 스프링 계수, 지반반력계수를 통제하고 특정한 분할 수와 분할 특성을 통해 case를 선정함으로써 분할 수와 분포와 같은 분할 특성이 부재력에 미치는 영향을 분석하였다. 이로써 TBM 세그먼트 시공 설계시 구조적으로 유리하거나 불리한 이음부 특성을 확인할 수 있다.

• Journal of Chest Surgery
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• 제24권3호
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• pp.265-270
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• 1991

Since advent of the prosthetic cardiac valve replacement, much efforts for accurate assessing value function in-vivo have been attempted. To evaluate the postoperative functional and morphological status of the replaced cardiac valve prosthesis, 33 patients with valve replacement were studied by transthoracic and transesophageal 2-dimensional echocardiac imaging as well as by color Doppler flow velocity imaging. Twenty four patients had mitral valve replacement. 6 patients had aortic valve replacement and 3 patients had both mitral and aortic valve replacement. There were 34 mechanical and 2 biological prosthesis. Comparing to transthoracic echocardiography, transesophageal approach showed transvalvular regurgitant jet flow amid the prosthetic mitral valve ring during. systole and much clear visualization of cardiac chamber behind prosthesis which could give shadowing effect to ultrasound beam. According to the quantitative grading by the length and area of mitral regurgitant flow, 24 out of 27 mitral valves revealed mild degree regurgitation considered as physiological after prosthetic bileaflet valve replacement and the other 3 valves including 2 biological prosthesis had moderate degree regurgitation which was regarded as pathologic one. 2 cases of left atrial thromboses and 1 case of paravalvular leakage which were not visible by transthoracic approach were identified by transesophageal echocardiography in patients with mitral valve replacement and patients with aortic valve replacement respectively. We conclude that in patients with prosthetic mitral valve replacement, transesophageal 2-dimensional imaging with color Doppler can suggest reliable information beyond that available from the transthoracic access even though it gives patient some discomfort to proceed.

• 한국의학물리학회지:의학물리
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• 제9권1호
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• pp.29-35
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• 1998

There has been necessity of an air free ionization chamber using the gold-crystal-aluminium plates, henceforth called the crystal chamber. The crystal chamber formed of parallel plates is very small in size and has more response for absorbed dose of therapeutic radiation beams. The gold plate on the crystal facing the photon and electron beam acts as an intensifier of signals and crystal plate as an ionization medium respectively. Both the copper guard ring and the aluminum collecting electrode are connected to an electrometer. Using high energy photon (6, 15 MV) and electron (9, 12, 15, 18 MeV) beams, the responses of the crystal chamber are evaluated against a PTW Farmer-type chamber at a field size of 10${\times}$10cm$^2$ and 100 cm SSD. The responses of crystal chamber for therapeutic radiation electron and photon beams are greater in magnitude by several order than Farmer. The crystal chamber has good linearity without correction factor C$\_$t,p/ with respect to the signals, a reading reproduction with good accuracy and precision less than 0.5%, and has other useful functions in measuring radiation beams.

• Structural Engineering and Mechanics
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• 제61권5호
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• pp.593-603
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• 2017

A high-efficiency simplified modelling approach is proposed for investigating the nonlinear responses of reinforced concrete linings of shield tunnels. Material and geometric nonlinearities are considered in the analysis of the lining structures undergoing large deformation before ultimately losing the load-carrying capacity. A beam-spring element model is developed to capture the force-transfer mechanism between lining segments and radial joints. The developed model is validated by comparing analyzed results to experimental results of a single-ring lining structure under two loading conditions: the ground overloading and the lateral unloading respectively. The results show that the lining structure under the lateral unloading due to excavation on the both sides of the tunnel is more vulnerable compared to the case of ground overloading on the top of the tunnel. A parameter study is conducted and results indicate that the lateral pressure coefficient has the greatest influence on the behaviour of the lining structure.

• 대한화학회지
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• 제22권6호
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• pp.380-385
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• 1978

진공미량저울을 사용하여 Spheron 6 위에서 o-크실렌의 여러 온도에서의 흡착등온곡선을 얻고 이들로 부터 BET 방법을 써서 흡착분자 단면적을 구하였다. 이 단면적의 값은 $-15^{\circ}C$까지에서는 변화가 없었고 -15와 $-14^{\circ}C$ 사이에서 갑자기 변하여 $-14^{\circ}C$ 이상의 온도에서는 다시 일정한 값을 유지하였다. 이 결과는 $-15^{\circ}C$ 보다 낮은 온도에서는 촘촘히 쌓인 편재흡착이 일어나고 $-14^{\circ}C$ 이상의 온도에서는 벤젠고리를 중심으로한 하나의 회전자유도를 얻는 것으로 생각된다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 제39회 하계학술대회
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• pp.1697-1698
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• 2008

PLS(Pohang Light Source) is 2.5 Gev synchrotron radiation source in Pohang, Korea, which is under operation since 1995. The hardware and software of the old BPM(Beam Position Monitor) data acquisition system for the PLS storage ring was completely upgraded to increase its performance and stability. The new BPM data acquisition system is based on VME-based EPICS (Experimental Physics and Instrument Control System) IOC system. We used 16-bit resolution analog-to-digital conversion board to digitize analog BPM signals. We developed a data average software to average raw BPM data using reflective memory board. We also developed device drivers for VME I/O boards used, IOC database for PV's(Process Variables). The new BPM data acquisition system is currently running for routine operation with good performance and stability. In this paper, we present the hardware and software of the new BPM data acquisition system DTL water skid cooling system and Resonant Control Cooling.