• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.11
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• pp.953-960
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• 2021

Korea Astronomy and Space Science Institute has been verifying the multipurpose laser tracking system with three functions of satellite laser tracking, adaptive optics and space debris laser tracking for not only scientific research but also national space missions. The system employs an optical telescope consisting of a 100 cm primary mirror and an altazimuth mount for fast and precise tracking. The precise pointing and tracking capability in a tracking mount is considered as one of important performance metrics in the fields of automatic tracking and precise application research. So it is required to analyze a mount model for investigating pointing error factors and compensating pointing error. In this study, we investigated various factors causing static pointing errors of tracking mount and analyzed the pointing accuracy of the tracking mount at Geochang observatory by estimating mount parameters based on the least square method.

• 한국지구물리탐사학회:학술대회논문집
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• 2005.05a
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• pp.227-232
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• 2005

Least squares (${\ell}^2-norm$) solutions of seismic inversion tend to be very sensitive to data points with large errors. The ${\ell}^p-norm$ minimization for $1{\le}p<2$ gives more robust solutions, but usually with higher computational cost. Iteratively reweighted least squares (IRLS) gives efficient approximate solutions of these ${\ell}^p-norm$ problems. I propose a simple way to implement the IRLS method for a hybrid ${\ell}^1/{\ell}^2$ minimization problem that behaves as ${\ell}^2$ fit for small residual and ${\ell}^1$ fit for large residuals. Synthetic and a field-data examples demonstrates the improvement of the hybrid method over least squares when there are outliers in the data.

• Journal of Korea Multimedia Society
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• v.13 no.3
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• pp.400-409
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• 2010

This paper presents a position error recognition system when the wafer is mounted in cleaning equipment among the wafer manufacturing processes. The proposed system is to enhance the performance in cost and reliability by preventing the wafer cleaning system from damaging by alerting it when it is put in correct position. The key algorithms are the calibration method between image acquired from camera and physical wafer, a infrared lighting and the design of the filter, and the extraction of wafer boundary and the position error recognition resulting from generation of circle based on least square method. The system is to install in-line process using high reliable and high accurate position recognition. The experimental results show that the performance is good in detecting errors within tolerance.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.6
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• pp.642-653
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• 2008

This study deals with modeling of head-related transfer functions(HRTFs) using principal components analysis(PCA) in the time and frequency domains. Four PCA models based on head-related impulse responses(HRIRs), complex-valued HRTFs, augmented HRTFs, and log-magnitudes of HRTFs are investigated. The objective of this study is to compare modeling performances of the PCA models in the least-squares sense and to show the theoretical relationship between the PCA models. In terms of the number of principal components needed for modeling, the PCA model based on HRIR or augmented HRTFs showed more efficient modeling performance than the PCA model based on complex-valued HRTFs. The PCA model based on HRIRs in the time domain and that based on augmented HRTFs in the frequency domain are shown to be theoretically equivalent. Modeling performance of the PCA model based on log-magnitudes of HRTFs cannot be compared with that of other PCA models because the PCA model deals with log-scaled magnitude components only, whereas the other PCA models consider both magnitude and phase components in linear scale.

• Journal of Korean Society of Transportation
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• v.18 no.6
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• pp.89-99
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• 2000

To cope with the limits of conventional O-D trip matrix collecting methods, several approaches have been developed. One of them is bilevel Programming method Proposed by Yang(1995), which uses Sensitivity Analysis Based(SAB) algorithm to solve Generalized Least Square(GLS) problem. However, the SAB a1gorithm has revealed two critical short-comings. The first is that when there exists a significant difference between target O-D matrix and true O-D matrix, SAB algorithm may not produce correct solution. This stems from the heavy dependance on the historical O-D information, in special when gravel Patterns are dramatically changed. The second is the assumption of iterative linear approximation to original Problem. Because of the approximation, SAB algorithm has difficulty in converging to Perfect Stackelberg game condition. So as to avoid the Problems. we need a more robust and stable solution method. The main purpose of this Paper is to show the problem of the dependency of Previous models and to Propose an alternative solution method to handle it. The Problem of O-D matrix estimation is intrinsically nonlinear and nonconvex. thus it has multiple solutions. Therefore it is necessary to require a method for searching globa1 solution. In this paper, we develop a solution algorithm combined with genetic algorithm(GA) , which is widely used as probabilistic global searching method To compare the efficiency of the algorithm, SAB algorithm suggested by Yang et al. (1992,1995) is used. From the results of numerical example, the Proposed algorithm is superior to SAB algorithm irrespective of travel patterns.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.4
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• pp.723-730
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• 2015

In this paper, a location tracking compensation algorithm based on the Least-Squares Method ($LCA_{LSM}$) was proposed to improve the autonomous tracking efficiency for the docent robot in exhibition hall, and the performance of the $LCA_{LSM}$ is analyzed by several practical experiments. The proposed $LCA_{LSM}$ compensates the collected location coordinates for the robot using the Least-Squares Method (LSM) in order to reduce the cumulated errors that occur in the Encoder/Giro sensor (E/G) and to enhance the measured tracking accuracy rates in the autonomous tracking of the robot in exhibition hall. By experiments, it was confirmed that the average error reduction rates of the $LCA_{LSM}$ are higher as 4.85% than that of the $LCA_{KF}$ in Scenario 1 (S1) and Scenario 2 (S2), respectively on the location tracking. In addition, it was also confirmed that the standard deviation in the measured errors of the $LCA_{LSM}$ are much more low and constant compared to that of the E/G sensor and the $LCA_{KF}$ in S1 and S2 respectively. Finally, we see that the suggested $LCA_{LSM}$ can execute more the stabilized location tracking than the E/G sensors and the $LCA_{KF}$ on the straight lines of S1 and S2 for the docent robot.

• Economic and Environmental Geology
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• v.36 no.3
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• pp.213-223
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• 2003

We estimated the Moho depth of Korean Peninsula from gravity anomalies and digital elevation model. The satellite radar altimetry-derived global free-air gravity model was used to ensure the homogeneity in both data and frequency domains of the original data. Two different methods were implemented to calculate the Moho depth; the wavenumber correlation analysis (Kim et al., 2000a) and the power spectrum analysis. The former method calculates depth-to-the-Moho by correlating topographic gravity effect with free-air gravity anomaly in the wavenumber domain under the assumption that the study area is not isostatically compensated. The latter one, on the other hand, considers the different density layers (i.e., Conrad and Moho), using complete Bouguer gravity anomaly in the Frequency domain of the Fourier transform. The correlation coefficient of the two Moho model is 0.53, and methodology and numerical error are mainly responsible for any mismatch between the two models. In order to integrate the two independentely-estimated models, we applied least-squares adjustment using the differenced depth. The resultant model has mean and standard deviation Moho depths of 32.0 km and 2.5 km with (min, max) depths of (20.3, 36.6) kms. Although this result does not include any topographic gravity effect, however, the validity of isostasy and the role of local stress field in the study area should be further studied.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2004.04a
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• pp.387-393
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• 2004

General purpose of cylindrical capacitive displacement sensor(CCS) is measuring run-out motion and deflection of rotor. If CCS has narrow sensing range, its sensitivity coefficients must be calibrated precisely. And x, y component of CCS output can be coupled. In this research, CCS calibration procedure is automated with automatic calibration program and PC-controlled stage. And, coupled-terms of CCS signals were removed and the errors between measured position and mapped CCS signal were reduced obviously by sensitivity matrix that linearly.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1117-1122
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• 2003

The paper on table deflection by stop state and move speed at loaded load, and the table deflection measured of static load. It is developed program for Date correction of LSM(Least Square Method). We experimented the method as following. The first a Laser setting and scan Experimental device measured curvature radius, The second A center of measurement object and curvature radius taking of LSC.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.10
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• pp.102-108
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• 2004

In this paper, we studied a vibration problem that is critical and common to most precision measurement systems. For micro mechanical part measurements, results obtained from the vision-based precision measurement system may contain errors due to the vibration. In order to defeat this generic problem, for the current study, a PC based image processing technique was used first, to assess the effect of the vibration to the precision measurement and second, to develop an in-situ calibration algorithm that automatically compensate the measurement results in real time. We used a set of stereoscopic CCD cameras to acquire the images for the dimensional measurement and the reference measurement. The mapping function was obtained through the in-situ calibration to compensate the measurement results and the statistical analysis for the actual results is provided in the paper. Based on the current statistical study, it is expected to obtain high precision results for the micro measurement systems.