• 한국가시화정보학회지
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• 제9권1호
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• pp.17-19
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• 2011

The bubble oscillations play an important role in ultrasonic cleaning processes. In the ultrasonic cleaning of semiconductor wafers, the cleaning process often damages micro/nano scale patterns while removing contaminant particles. However, the understanding of how patterns in semiconductor wafers are damaged during ultrasonic cleaning is far from complete yet. Here, we report the observations of the motion of bubbles that induce solid wall damage under 26 kHz continuous ultrasonic waves. We classified the motions into the four types, i.e. volume motion, shape motion, splitting or jetting motion and chaotic motion. Our experimental results show that bubble oscillations get unstable and nonlinear as the ultrasonic amplitude increases, which may exert a large stress on a solid surface raising the possibility of damaging microstructures.

• Tribology and Lubricants
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• 제23권2호
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• pp.56-60
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• 2007

The main object of this study is to compare the results that have been concluded by the experiment and to estimate the temperature rise that can cause the contacting surface to be damaged. The former studies are based on the Blok and Jaeger formula. By these formulas we assume that two of the contacted objects are a kind of semi-infinite solid and with this assumption we can make a temperature analysis. But this method doesn't consider lubrication conditions and the calculation time requires a lot of time in that we have to face many difficulties in measuring the actual temperature rise. In this study we combines the semi-infinite solid method and the finite volume method to analyze the temperature of the contacting surface. And we measure temperature rise of the contact surface by dynamic thermocouple.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.879-885
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• 2000

This study is carried out to make clear the reason of occurrence of sudden acceleration incident of AT vehicle. The stepping motor is used to control the engine speed at idle by compensating the volume of air. By the way it's valve is contaminated by blow-by gas, deposit and back fire etc. This contamination could occur the load of motor at low temperature. This plays an important role in damaging the motor's coil with the motor's performance interfered. If it's coil is damaged the ISC could malfunction. If these phenomena occur, the speed of engine may increase or the engine may stall with hunting.

• 한국작물학회지
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• 제46권5호
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• pp.352-359
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• 2001

Cookie baking properties and relationships between cookie baking properties and flour characteristics were evaluated for two years, 1997 and 1998, and at two locations, Suwon and Deokso, with Korean winter wheat cultivars and lines. Cookie baking parameters, except for cookie diameter and top grain score, were influenced by locations and years. Chokwang, Suwon 274, Suwon 275, Suwon 277 and Urimil showed larger cookie diameter and excellent top grain score compared to the other Korean winter wheat cultivars and lines. Among the flour characteristics, protein content, damaged starch content, alkaline water retention capacity and flour swelling volume showed high positive correlation coefficients with cookie baking parameters. Friabilin-present lines showed larger cookie diameter, suitable surface structure of cookie and softer snapping force than the friabilin-absent lines.

• 품질경영학회지
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• 제29권1호
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• pp.1-10
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• 2001

We consider the problem of detecting special variations in multivariate $T^2$-control chart when two or more multivariate outliers are present. Since a multivariate outlier may reflect slippage in mean, variance, or correlation, it can distort the sample mean vector and sample covariance matrix. Damaged sample mean vector and sample covariance matrix have difficulty in examining special variations clearly, An alternative to detection outliers or special variations is to use robust estimators of mean vector and covariance matrix that are less sensitive to extreme observations than are the standard estimators $\bar{x}$ and $\textbf{S}$. We applied popular minimum volume ellipsoid(MVE) and minimum covariance determinant(MCD) method to estimate mean vector and covariance matrix and compared its results with standard $T^2$-control chart using simulated multivariate data with outliers. We found that the modified $T^2$-control chart based on the above robust methods were more effective in detecting special variations clearly than the standard $T^2$-control chart.

• 한국구조물진단유지관리공학회 논문집
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• 제4권4호
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• pp.211-218
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• 2000

Many bridges are severely damaged by the overloaded heavy vehicle and the trend will become more serious because the traffic volume is continuously increasing. Currently, the vehicles with gross weights over 40 tonf or axle weight over 10 tonf are not allowed on the public road. However, this regulation is not based on a systematic study on the bridge capacity and assumed to be much too conservative depending on the vehicle types and bridge types. In this study, the permit weights of heavy vehicles of diverse axle spacings and axle load distribution are calculated considering the structural characteristics of bridge superstructures. In order to consider the various load effects of heavy weight vehicle crossings, three conditions are considered in the calculation of permit vehicle load. From the results, the permit vehicle weights of the simple girder bridges are calculated.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 전력전자학술대회 논문집
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• pp.284-287
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• 2001

In the System-integrated modular advanced reactor(SMART), the motor for Control element drive mechanism(CEDM) requires high density power and simple drive mechanism to reduce volume because of restriction by install-space and must satisfy the reactor operating circumstances with high pressure and temperature. To Maximize the characteristics of the TFM, we chose the asymmetric bridge converter as the driving system for TFM. Because two switching devices are connected in series with the stator winding of each phases in the asymmetric bridge converter all the phases are not affected by another phase but controlled independently. Also, this converter has many advantages that the various control methods can be adopted, it is easy to control, and that in case that the switching devices of a phase are damaged, the affects can be minimized.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2015년도 학술발표회
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• pp.241-241
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• 2015

In this study, the simulations and analyses of flood flow due to a river inundation in a coastal urban area are carried out using a two-dimensional finite volume method with well-balanced HLLC scheme. The target area is a coastal urban area around Gohyun river which is located at Geoje city in Kyungnam province in Korea and was extremely damaged due to the heavy rainfall during the period of the typhoon "Maemi" in September 2003. For the purpose of the verification of the numerical model applied in this study, the simulated results are compared and analyzed with the inundation traces. Moreover, the flood flow in a urban area is simulated and analyzed based on the scenarios of inflow to the river with the increase and decrease of the intensity of the heavy rainfall.

• International Journal of Naval Architecture and Ocean Engineering
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• 제12권1호
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• pp.699-710
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• 2020

Pitting corrosion commonly shaped in hull structure due to marine corrosive environment seriously causes the deterioration of structural performance. This paper deals with the ultimate strength behaviors of stiffened ship panels damaged by the pits subjected to uniaxial compression. A series of no-linear finite element analyses are carried out for three stiffened panels using ABAQUS software. Influences of the investigated typical parameters of pit degree (DOP), depth, location and distribution on the ultimate strength strength are discussed in detail. It is found that the ultimate strength is significantly reduced with increasing the DOP and pit depth and severely affected by the distribution. In addition, the pits including their distributions on the web have a slight effect on the ultimate strength. Compared with regular distribution, random one on the panel result in a change of collapse mode. Finally, an empirical formula as a function of corrosion volume loss is proposed for predicting the ultimate strength of stiffened panel.

• 한국산학기술학회논문지
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• 제19권2호
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• pp.602-607
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• 2018

산림공간정보는 국가산림계획 및 산림정책 수립을 위한 기초자료로 주기적으로 구축 및 관리되고 있으며, 이 중 임야의 훼손에 대한 정보는 토사유출이나 산사태 등 추가적인 재해 발생의 위험이 있어 지속적인 관리가 필요하다. 하지만 기존의 목측 및 줄자에 의한 산림조사 방법은 많은 인력과 시간을 필요로 하기 때문에 업무의 효율성이 떨어진다. 최근 드론은 공간정보 구축 및 활용 분야에 효과적인 방법으로 관심이 증가하고 있으며, 드론 관련 산업 시장의 규모는 나날이 커지고 있다. 이에 본 연구에서는 드론을 활용하여 산림공간정보를 조사 및 분석함으로써 관련 업무의 효율성을 높이고자 하였다. 드론을 이용하여 연구 대상지역을 촬영하고, 데이터 처리를 통해 정사영상과 포인트클라우드 형태의 DSM(Digital Surface Model)을 생성하였으며, 성과물을 이용하여 훼손지역에 대한 분석을 수행하였다. 연구를 통해 임야훼손지역의 면적과 체적이 산출되었으며, 산림조사 분야에서 드론의 활용성을 제시할 수 있었다. 드론을 활용한 산림공간정보 조사 및 분석 방법은 기존 방법보다 인력과 시간을 절감할 수 있으며, 정량적인 분석이 가능하기 때문에 국가산림계획 및 정책 수립에 크게 기여할 것이다.