• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.42.1-42.1
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• 2010

결정질 실리콘 태양전지의 전면 전극은 전극 면적으로 인한 손실(shading loss)를 줄이고 단락전류밀도(Jsc)를 높이기 위해 전극 너비를 줄이는 노력을 하고 있다. 하지만 전극 소성(firing) 시 전면 전극의 핑거(finger)와 버스바(busbar)의 너비 차이로 인해 전극 침투(fire-through) 정도가 달라질 수 있다. 본 연구에서는 전극 소성 공정 시 전면 전극의 너비에 따른 전극 침투 정도를 조사하기 위해 접촉 저항(specific contact resistance)과 재결정화(Ag recrystallite) 된 전면전극의 분포에 대해 비교하였다. 접촉 저항을 측정하기 위하여 transfer length method(TLM)를 이용하였다. 또한 전면 전극층을 제거한 후 실리콘 기판의 재결정 분포를 주사전자현미경(Scanning electron microscope : SEM)을 이용하여 관찰하였다.

• Archives of Reconstructive Microsurgery
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• v.22 no.2
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• pp.63-68
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• 2013

Purpose: In case of the failed replantation, if the patients want to preserve the length of amputated stump, toe transfer is the ideal choice. However, reconstruction of these amputated stump with a free flap can be a useful method when the patients refuse sacrificing their toe. Our purpose of this study is to evaluate availability of functional results and patient satisfaction after this procedure. Materials and Methods: From March 2008 to February 2012, we reconstructed the amputated stump with free flap by patients demand. Eleven patients were included, medial plantar artery perforator flap in seven cases and great toe pulp flap in five cases. Follow-up range 12 to 24 months and we evaluate patient satisfaction by using a visual analogue scale (VAS; 1=unsatisfied, 5=excellent) and functional recovery by measuring the range of motion of remaining joint at 12 months after operation. Results: During follow-up period, all transferred free flaps survived and no major complications were noted. Range of motion of remaining joint appeared satisfactory result ($15^{\circ}$ to $100^{\circ}$). The VAS patient satisfaction score for aesthetic were five in six patients, four in four patients, and three in one patient. Conclusion: In case of the failed digital replantation, if patient refuse toe transfer, it could be useful method to reconstruction with the free flap to preserving maximal length of amputated stump.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.96-96
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• 2011

ZnO는 실온에서 3.37 eV의 큰 밴드갭 에너지와 60 meV의 높은 exciton binding energy를 가지고 있어 광소자를 만드는데 큰 관심을 얻고 있다. 또한 최근에는 ZnO를 기반으로 한 동종접합 전광소자를 만드는데 성공하였다. 그러나 소자의 성능을 높이기 위해 여러 가지 개선할 사항이 있다. 그 중에 하나는 캐리어를 잘 주입 시키기 위한 금속-반도체 접합을 구현하는 것이다. 이러한 문제를 개선하기 위해서는 ZnO 기반으로 한 낮은 비저항을 가진 소자가 필요하다. 일반적으로 n-type ZnO Ohmic 접합에서 쓰이는 금속은 Ti/Au, Ta/Au, Al/Au 등이 있다. 실험방법은 c-plane 사파이어 기판 위에 펄스 레이저 증착 방법으로 3시간 동안 $500^{\circ}C$ 환경에서 ZnO 박막을 성장하고, 표면을 고르게 하기 위해 $1000^{\circ}C$에서 1분 동안 열처리를 진행하였다. 샘플 위에 photo-resist 코팅을 한 다음 transfer length method(TLM)를 이용하기 위해 포토리소그래피 장비를 통하여 샘플을 노광하였다. 그 위에 Ti/Au (30 nm/80 nm)를 E-beam/thermal evaporation으로 증착 하였다. 이는 일반적인 반도체 공정과 Lift-off방식을 이용하여 패터닝 하였다. 샘플을 열처리하는 것은 금속과 반도체의 접촉 접착과 전기적인 성질을 개선하고 응력과 계면 결함을 감소시키기 때문에 샘플을 100, 200, 300, 400, $500^{\circ}C$에서 각각 열처리하였다. 저항을 구하기 위해 각각 열처리된 샘플과 as-deposited의 전류, 전압 특성을 측정하고, 이러한 실험 방법으로 n-type ZnO의 Ohmic 접합을 구현하는 것이 목표이다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.3
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• pp.414-421
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• 2001

The present study is conducted to investigate the local heat/mass transfer characteristics on the shroud with blade tip clearances. The relative motion between blade and shroud has little influence on the overall heat transfer characteristics, except some local effects. Therefore, the relative motion between the blade and shroud is neglected in this study. A naphthalene sublimation method is employed to determine the detailed local heat/mass transfer coefficients on the surface of the shroud. The tip clearance is changed from 0.66% to 2.85% of the blade chord length. The flow enters the gap between the blade tip and shroud at the pressure side due to the pressure difference. Therefore, the heat/mass transfer characteristics on the shroud are changed significantly from those with endwall. At first, high heat/mass transfer occurs along the profile of blade at the pressure side due to the entrance effect and acceleration of the gap flow. Then, the heat/mass transfer coefficients on the shroud increase along the suction side of the blade because tip leakage vortices are generated and interact with the main flow. The results show that the heat/mass transfer characteristics are changed largely with the gap distance between the tip of turbine blade and the shroud.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.4
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• pp.388-397
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• 2000

Comparison of the heat conduction into a trapezoidal fin and the heat loss from the fin by convection is made in this study Also, the ratio of heat loss from each surface to the total heat loss and the temperature distribution are analyzed using a 3-D analytical method. A trapezoidal fin whose tip height is half the root height is chosen as the model. The results show that the heat transfer rates from the tip and from both sides are comparable with each other as the non-dimensional width and length vary while the heat transfer rate from the bottom and top is dominant.

• Architectural research
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• v.1 no.1
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• pp.41-46
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• 1999

The configuration factors in the flux transfer method are applied to calculate daylight factors reaching a station point. To analyze the window equipped with a louver system, geometrical correlation is used for the length shielded by the louver. The space in front of a window is assumed to be an imaginary outdoor space for calculating the luminance of the louver system. The data calculated from this study are compared with SUPERLlTE simulation data and the scale model data. Scale model data are collected on the roof of the Engineering building at Korea University in Seoul under the uniform sky condition.

• 유체기계공업학회:학술대회논문집
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• 2005.12a
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• pp.240-243
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• 2005

This study deals with the shape optimization of a wire spacer fuel assembly of Liquid Metal Reactors (LMRs). The Response Surface based optimization Method is used as an optimization technique with the Reynolds-averaged Navier-Stokes analysis of fluid flow and heat transfer using Shear Stress Transport (SST) turbulence model as a turbulence closure. Two design variables namely, pitch to fuel rod diameter ratio and lead length to fuel rod diameter ratio are selected. The objective function is defined as a combination of the heat transfer rate and the inverse of friction loss with a weighting factor. Three level full-factorial method is used to determine the training points. In total, nine experiments have been performed numerically and the resulting datas have been analysed for optimization study. Also, a comparison has been made between the optimized surface and the reference one in this study.

• Structural Engineering and Mechanics
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• v.71 no.3
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• pp.245-255
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• 2019

In this paper, an inverted-pendulum model consisting of a point supported by spring limbs with roller feet is adopted to simulate human walking load. To establish the kinematic motion of first and second single and double support phases, the Lagrangian variation method was used. Given a set of model parameters, desired walking speed and initial states, the Newmark-${\beta}$ method was used to solve the above kinematic motion for studying the effects of roller radius, stiffness, impact angle, walking speed, and step length on the ground reaction force, energy transfer, and height of center of mass transfer. The numerical simulation results show that the inverted-pendulum model for walking is conservative as there is no change in total energy and the duration time of double support phase is 50-70% of total time. Based on the numerical analysis, a dynamic load factor ${\alpha}_{wi}$ is proposed for the traditional walking load model.

• Journal of Industrial Technology
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• v.26 no.B
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• pp.29-34
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• 2006

A convective, radiating rectangular fin is analysed by using the one dimensional analytic method. Instead of constant fin base temperature, heat conduction from the inner wall to the fin base is considered as the fin base boundary condition. Radiation heat transfer is approximately linearized. For different fin tip length, temperature profile along the normalized fin position is shown. The fin tip length for 98% of the maximum heat loss with the variations of fin base length and radiation characteristic number is listed. The maximum heat loss is presented as a function of the fin base length, radiation characteristic number and Biot number.

• Journal of Welding and Joining
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• v.27 no.3
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• pp.67-72
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• 2009

The flux cored arc welding (FCAW) process is one of the most frequently employed and important welding process due to high productivity and excellent workability. The process is performed either as an automated process or as a semi-automatic process. In FCAW process, welding voltage has been considered as a qualitative indication of arc length. But it is necessary to let welding operators know, maintain and manage the arc length directly by estimating and displaying it. In this study, to develop arc length estimation technique, we measured a welding circuit resistance($R_sc$) and then we calculated welding circuit voltage drop($V_sc$). Also, we measured arc peak voltage($V_ap$). By subtracting $V_sc$ from $V_arc$, we can easily calculate net arc voltage drop($V_arc$). Consequently, we suggested arc length estimating equation and basic algorithm by regressive analyzing the relationship between net arc voltage drop($V_arc$) and real arc length(Larc) measured by high speed camera. Therefore, arc length can be predicted by just monitoring welding current and voltage.