• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.421-421
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• 2012

Cu(In,Ga)$Se_2$ (CIGS) 화합물은 직접천이형 반도체로 열적으로 매우 안정하고 에너지밴드갭이 1.04 eV로 이상적인 값에 가깝고, 특히 높은 광흡수계수를 가지기 때문에 박막 태양전지로서 커다란 응용 잠재력을 갖고 있는 광흡수층 재료이다. CIGS 화합물 박막 태양전지의 효율은 연구실에서는 ~20%를 높은 효율을 보고하고 있으며, 모듈급에서도 ~13%의 효율을 보이고 있다. 그러나 CIGS 박막 태양전지를 대면적 또는 양산화에 적용하기 위해서는 20년 이상의 장기적인 수명을 보장할 수 있는 내구성을 갖추어야 한다. 본 연구에서는 CIGS 모듈의 장기적인 신뢰성을 평가하기 위해 CIGS PV 모듈을 대상으로 대표적인 고온 고습 조건인 IEC-61646 규격을 이용하여 $85^{\circ}C$/85% RH에서 1000시간 동안 가속시험이 수행되었고, 고온 환경하에서 모듈의 성능 저하에 미치는 영향을 고찰하기 위해 모듈을 $85^{\circ}C$에서 1000시간 노출시켰다. 두 종류의 가속 스트레스시험 후에 모듈들의 외형적인 노화현상 및 전기적 열화 성능을 분석하였다. 또한 모듈의 효율저하의 원인을 규명하기 위해 모듈 구성 재료 중 충진재료로 사용하는 EVA sheet와 투명전극 AZO를 대상으로 고장분석을 수행하였다. AZO의 미세구조 관찰, 결정상 분석, XPS 분석 및 전기적 분석과 EVA sheet의 FT-IR 분석과 TG-DSC 분석들을 종합하여 CIGS PV 모듈의 성능저하의 원인을 규명하였다.

• Journal of the Earthquake Engineering Society of Korea
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• v.11 no.1 s.53
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• pp.59-65
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• 2007

Site classification of IBC and KBC is based on the ft-kips unit system and is not friendly for the linear interpolation of the site coefficients due to the implicit relationship between a site class and site coefficients, defining a site class by the range of the soil properties, not by a single soil property. Also, the site class definition of KBC has too wide range of soil properties for each soil class. making the structural engineers difficult to estimate the site coefficients for the diverse soil layers. In this study, a new site classification in SI unit system was proposed for the seismic design codes of KBC etc., and the comparison of the site coefficients of $F_{a}\;and\;F_{v}$ was also performed to investigate the possibility of the linear interpolation of the site coefficients with the proposed new site classification. According to the study results, it was more reasonable for the linear interpolation of the site coefficients to utilize the proposed new site classification considered the Sl unit system and the soil characteristics of the 30m soil layer beneath the shallow embedded foundation, and the linear interpolation of the acceleration coefficients for the design spectrum can be performed more reasonably defining the site coefficients for the representative shear wave velocities of each site class. With the study results, a new site classification, and the linear interpolation permitted acceleration coefficients fer the design spectrum were proposed for the modification of the seismic design regulations of KBC.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.8
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• pp.62-68
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• 2016

The feeder cable assembly is an automotive part used for telecommunication. If it malfunctions, the control and safety of the automobile can be put at risk. ALT (Accelerated Life Testing) is a testing process for products in which they are subjected to conditions (stress, strain, temperatures, etc.) in excess of their normal service parameters in an attempt to uncover faults and potential modes of failure in a short amount of time. Failure is caused by defects in the design, process, quality, or application of the part, and these defects are the underlying causes of failure or which initiate a process leading to failure. Thermal shock occurs when a thermal gradient causes different parts of an object to expand by different amounts. Thermal shock testing is performed to determine the ability of parts and components to withstand sudden changes in temperature. In this research, the main causes of failure of the feeder cable assembly were snapping, shorting and electro-pressure resistance failure. Using the Coffin-Manson model for ALT, the normal conditions were from Tmax = $80^{\circ}C$ to Tmin = $-40^{\circ}C$, the accelerated testing conditions were from Tmax = $120^{\circ}C$ to Tmin = $-60^{\circ}C$, the AF (Acceleration Factor) was 2.25 and the testing time was reduced from 1,000 cycles to 444 cycles. Using the Bxlife test, the number of samples was 5, the required life was B0.04%.10years, in the acceleration condition, 747 cycles were obtained. After the thermal shock test under different conditions, the feeder cable assembly was examined by a network analyzer and compared with the Weibull distribution modulus parameter. The results obtained showed good results in acceleration life test mode. For the same reliability rate, the testing time was decreased by a quarter using ALT.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.1258-1261
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• 2004

ACSR전력선의 송전용량 증가를 위해 개발된 증용량저이도 송전선인 STACBUAW(Super Thermal-resistant Aluminum alloy Conductors, aluminum-clad Invar-Reinforced)전선은 초내열 Al도체 및 인바강선의 사용으로 비교적 고온에서의 안정적 운전이 가능하다. 그러나 고온 환경에서 장시간 노출된 STACIR/AW전선의 안정적 관리를 위해서는, 열화 된 STACIR/AW 전선의 인장강도, 각 구성소재의 탄성 계수, 비틀림 계수 둥과 같은 기계적 물성이 장기 운전 모의를 위해 설정된 열화온도, 열화시간 등에 대해 종합적으로 평가될 필요가 있다. 또한 크립 등과 같이 고온응력 부하상태에서의 변형거동과 탄성계수 및 선 팽창계수의 온도의존성 등은 전선의 이도관리와 예측을 위해서도 명확히 규명되어야할 중요한 관리 인자이다. 그러나 현재까지는 이들에 대해 수행한 어떠한 연구결과들도 보고 되어 있지 않은 실정이다. 본 연구에서는 STACIR/AW $410mm^2$ 송전선을 장시간 운전의 모의를 위해 가속열화 시키고 가속열화에 따른 STACIR/AW전선 및 그 구성소재의 강도, 비틀림 특성의 변화를 조사하여 장시간 운전에 따른 STACIR/AW전선의 안정성을 평가하여 보고하고자 하였다.

• Journal of Internet Computing and Services
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• v.10 no.3
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• pp.17-25
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• 2009

This paper presents a methodology for a fall detection using the feature extraction method based on the neural network with weighted fuzzy membership functions (NEWFM). The distributed non-overlap area measurement method selects the minimized number of input features by removing the worst input features one by one. Nineteen number of wavelet transformed coefficients captured by a triaxial accelerometer are selected as minimized features using the non-overlap area distribution measurement method. The proposed methodology shows that sensitivity, specificity, and accuracy are 95%, 97.25%, and 96.125%, respectively.

• Journal of Ocean Engineering and Technology
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• v.6 no.2
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• pp.76-84
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• 1992

In this study, corrosion fatigue test of SAPH45 steel was performed by the use of plane behavior of base metal (BM) and heat affected zone (HAZ) of SAPH45. The main results obtained are as follows: 1) The more aspect ratio (b/t) of corner crack decreases, the more aspect ratio (b/a) takes greatly effect by corrosion. 2) The correlation between the stress intensity factor range ($\Delta$k) and crack growth rate (da/dN) for weldment in seawater is given by Paris rule as follow: da/dN=C($\Delta$K) super(m). Where m is constant, and the value is 3.82-3.84. 3) The accelerative factor ($\alpha$) of BM and HAZ under seawater is about 1.1-1.9, and ($\alpha$) of HAZ increases more and more under the low $\Delta$K region. 4) HAZ is more susceptible to corrowion than BM because of potential of electrode (E sub(c)) of HAZ becomes more less noble potential than that of BM.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.1
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• pp.853-859
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• 2015

1-DOF shear building was designed, built and tested to investigate the interactions between the shear building and the shaking table excited harmonically by the electro-magnetic forces. In the experiments horizontal accelerations of the shaking table and the shear building were measured. To understand the experimental results experimental setting was modeled as an unconstrained 2-DOF system under the hormonic forces. The responses of the shear building and the shaking table of the unconstrained 2-DOF system were found with the equations of motions. The magnification factors of the table and the shear building with respect to the amplitude of the harmonic forces and the transmission of the shear building with respect to the table excitations were found and compared with the experimental results.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.6
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• pp.429-437
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• 2019

This paper deals with a ZEM (Zero-Effort-Miss) based guidance law for the interception of moving targets and characteristics of the guidance law according to time-to-go estimation methods. To derive the ZEM vector feedback guidance command, we introduce a polynomial function with unknown coefficient, and then we determine the coefficient to satisfy initial and terminal constraints. Since the directions of the guidance command and ZEM vectors are adjusted by the time-to-go, general time-to-go estimation methods are proposed, which can generate the vertical and horizontal guidance commands with respect to an arbitrary reference frame. By performing various numerical simulations, the performance and characteristics of the proposed methods are investigated.

• Korean Journal of Food Science and Technology
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• v.25 no.6
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• pp.643-648
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• 1993

A simple approximate model using equivalent time at a reference temperature ($t_{eq}$) was derived to predict quality changes caused by temperature fluctuations. The validity and effectiveness of this model have been assessed with experimental data of sucrose hydrolysis. Kinetic parameters of sucrose hydrolysis were estimated by one step method using equivalent time at a reference temperature with linearly increasing temperature profile. Sucrose hydrolysis was a first order reaction, and the activation energy was 25.84 kcal/mol. The extent of sucrose hydrolysis of liquid model system under accelerated test with sinusoidal temperature fluctuations were determined. The proposed model yielded accurate prediction with the correlation coefficient in the range of $0.92{\sim}0.99$.

• Journal of the Korea Society of Computer and Information
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• v.24 no.10
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• pp.33-39
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• 2019

In this paper, we propose a parametric model for analyzing the motion information obtained from the acceleration sensors to measure the activity of the human body. The motion of the upper body and the lower body does not occur at the same time, and the motion analysis method using a single motion sensor involves a lot of errors. In this study, the 3-axis accelerometer is attached to the arms and legs, the body's activity data are measured, the momentum of the arms and legs are calculated for each channel, and the linear predictive coefficient is obtained for each channel. The periodicity of the upper body and the lower body is determined by analyzing the correlation between the channels. The linear predictive coefficient and the periodic value are used as data to measure the type of exercise and the amount of exercise. In the proposed method, we measured four types of movements such as walking, stair climbing, slow hill climbing, and fast hill descending. In order to verify the usefulness of the parameters, the recognition results are presented using the linear predictive coefficient and the periodic value for each motion as the neural network input.