• 반도체디스플레이기술학회지
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• 제21권4호
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• pp.65-70
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• 2022

In manufacturing and semiconductor industries, transfer robots increase productivity through accurate and continuous work. Due to the nature of the semiconductor process, there are environments where humans cannot intervene to maintain internal temperature and humidity in a clean room. So, transport robots take responsibility over humans. In such an environment where the manpower of the process is cutting down, the lack of maintenance and management technology of the machine may adversely affect the production, and that's why it is necessary to develop a technology for the machine failure diagnosis system. Therefore, this paper tries to identify various causes of failure of transport robots that are widely used in semiconductor automation, and the Prognostics and Health Management (PHM) method is considered for determining and predicting the process of failures. The robot mainly fails in the driving unit due to long-term repetitive motion, and the core components of the driving unit are motors and gear reducer. A simulation drive unit was manufactured and tested around this component and then applied to 6-axis vertical multi-joint robots used in actual industrial sites. Vibration data was collected for each cause of failure of the robot, and then the collected data was processed through signal processing and frequency analysis. The processed data can determine the fault of the robot by utilizing machine learning algorithms such as SVM (Support Vector Machine) and KNN (K-Nearest Neighbor). As a result, the PHM environment was built based on machine learning algorithms using SVM and KNN, confirming that failure prediction was partially possible.

• 정보처리학회논문지:소프트웨어 및 데이터공학
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• 제12권3호
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• pp.141-148
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• 2023

반도체 제품의 높은 수율을 달성하기 위해서는 정확한 오버레이 계측이 필수적이다. 오버레이 계측 성능은 오버레이 타깃 설계와 측정 방법에 많은 영향을 받는다. 따라서 오버레이 타깃은 성능 개선을 위해 다양한 타깃에 적용할 수 있는 측정 방법들이 요구된다. 본 연구는 이미지 기반의 오버레이를 측정할 수 있는 새로운 알고리즘을 제안한다. 제안하는 측정 알고리즘은 움직임 벡터를 이용하는 방법으로 서브 픽셀 단위의 위치를 추정할 수 있다. 움직임 벡터는 선택된 영역의 픽셀들을 이용하여 다항식 전개를 통해 2차 방정식의 모델을 생성한다. 그 후 모델을 이용하여 서브픽셀 단위의 위치를 추정할 수 있다. 움직임 벡터를 활용한 측정방법은 X축, Y축의 적층 오류를 각각 계산하는 기존 상관계수 기반의 측정방법과는 달리 한 번에 모든 방향의 적층 오류를 계산할 수 있다. 따라서 X축과 Y축의 관계를 반영하여 보다 정확한 오버레이 측정이 가능하다. 하지만 기존 상관계수 기반의 알고리즘보다 계산량이 증가하기 때문에 더 많은 연산시간이 사용될 수 있다. 본 연구에서는 기존 방법보다 개선된 알고리즘을 제시하는 것이 아닌 새로운 측정 방법의 방향을 제안하는 것에 목적을 두고 있다. 실험 결과를 통해 기존 방법과 유사한 정밀도의 측정 결과를 얻을 수 있음을 확인하였다.

• 대한수학회보
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• 제30권2호
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• pp.229-238
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• 1993

Let M be an n-dimensional compact Riemannian manifold with boundary .part.M. We consider the Neumann eigenvalue problem on M of the equation (Fig.) where .upsilon. is the unit outward normal vector to the boundary .part.M. due to the importance of Poincare inequality for analysis on manifolds, one wishes to obtain the lower bound of the first non-zero eigenvalue .eta.$_{1}$ of (1.1). For the purpose of applications, it is important to relax the dependency of the lower bound on the geometric quantities. For general compact manifolds with convex boundary, Li-Yau [3] obtained the lower bound of .eta.$_{1}$. Recently, Roger Chen [1] investigated the lower bound of the first Neumann eigenvalue .eta.$_{1}$ on compact manifold M with nonconvex boundary. We investigate the lower bound .eta.$_{1}$ with the same conditions as those of Roger chen. But, using the different auxiliary function, we have the following theorem.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.3197-3202
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• 2007

An analysis program for pedestrian flow has been developed to investigate the flow patterns of passenger in railway stations. Analysis algorithms for pedestrian flow based on DEM(Discrete Element Method) are newly developed. There are lots of similarity between particle-laden two phase flow and passenger flow. The velocity component of 1st phase corresponds to the unit vector of calculation cell, each particle to passenger, volume fraction to population density and the particle velocity to the walking velocity, etc. And, the walking velocity of passenger is also represented by the function of population density. Key algorithms are developed to determine the position of passenger, population density and numbering to each passenger. By using the developed program, we compared the simulation results of the effects of the location and size of exit and elapsed time.

• Kyungpook Mathematical Journal
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• 제57권4호
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• pp.683-699
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• 2017

We introduce the notion of Killing shape operator for real hypersurfaces in the complex hyperbolic quadric $Q^{m*}=SO_{m,2}/SO_mSO_2$. The Killing shape operator implies that the unit normal vector field N becomes A-principal or A-isotropic. Then according to each case, we give a complete classification of real hypersurfaces in $Q^{m*}=SO_{m,2}/SO_mSO_2$ with Killing shape operator.

• Communications for Statistical Applications and Methods
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• 제22권6호
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• pp.615-624
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• 2015

We consider the estimation of seasonal cointegration in the presence of conditional heteroskedasticity (CH) using a feasible generalized least squares method. We capture cointegrating relationships and time-varying volatility for long-run and short-run dynamics in the same model. This procedure can be easily implemented using common methods such as ordinary least squares and generalized least squares. The maximum likelihood (ML) estimation method is computationally difficult and may not be feasible for larger models. The simulation results indicate that the proposed method is superior to the ML method when CH exists. In order to illustrate the proposed method, an empirical example is presented to model a seasonally cointegrated times series under CH.

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2005년도 종합학술발표회 논문집 Vol.15 No.1
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• pp.153-156
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• 2005

This paper concerns an efficient iterative approach for eliminating coherent interference signals in linearly constrained adaptive arrays. The Alternate Mainbeam Nulling Algorithm[1] is implemented iteratively to find an optimum weight vector. The convergence parameters in the unit gain and null constraints are calculated using steepest descent method with gradient estimation. The nulling performance of the proposed method is compared with that of conventional ones. It is shown that the proposed method performs better than conventional ones when the power of the coherent signals is large compared with a desired signal. Also, it performs consistently well for more number of interferences.

• 한국경영과학회:학술대회논문집
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• 한국경영과학회 2007년도 추계학술대회 및 정기총회
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• pp.477-481
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• 2007

The purpose of this study is to provide the ideal forecasting model of cadastral survey work load through the Economeatric Analysis of Time Series, Granger Causality and VAR Model Analysis, it suggested the forecasting reference materials for the total amount of cadastral survey general work load. The main result is that the derive of the environment variables which affect cadastral survey general work load and the outcome of VAR(vector auto regression) analysis materials(impulse response function and forecast error variance decomposition analysis materials), which explain the change of general work load depending on altering the environment variables. And also, For confirming the stability of time series data, we took a unit root test, ADF(Augmented Dickey-Fuller) analysis and the time series model analysis derives the best cadastral forecasting model regarding on general cadastral survey work load. And also, it showed up the various standards that are applied the statistical method of econometric analysis so it enhanced the prior aggregate system of cadastral survey work load forecasting.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1992년도 하계학술대회 논문집 B
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• pp.1108-1113
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• 1992

In this paper, the high frequency twin resonant inverter using MOSFET is presented. The output control is excellent and the EMI noise is reduced, because the output appear as the vector sum of current in each unit inverter. The output voltage and the output current of the inverter are controlled by PLL. In this paper, the principle of the twin resonant method is described. And computer simulations and experimental results are shown.

• 한국미생물·생명공학회지
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• 제37권4호
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• pp.405-407
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• 2009

A Bacillus subtilis mannanase gene was subcloned into an Escherichia coli- Corynebacterium lactofermentum shuttle vector pHE83, and the resultant plasmid pHE83M was transferred into an endogenous plasmid-free strain of C. lactofermentum. Mannanase produced by the recombinant C. lactofermentum (pHE83M) was secreted extracellulary at the level of 86%, and the remaining activity of mannanase was detected in the cell-free extract. The maximum mannanase productivity of the recombinant strain reached 8.1 unit/mL in the culture filtrate of LB medium. According to the zymogram of mannanase on SDS-PAGE, it was found that the mannanase produced by the recombinant C. lactofermentum could be maintained stably with a migration identical to the mannanase produced by the parental strain, B. subtilis WL-3.