• Proceedings of the KIEE Conference
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• 2004.11c
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• pp.69-71
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• 2004

DC servo motors have a defect that they need a periodical maintenance because of a brush commutation and also they have a difficulty at high speed operation. In this reason, the use of AC Servo motors are increasing these days. In this paper, a proposed neuro observer is applied to speed control of AC servo motor. The proposed observer complement a problem that occur from increase of gain of High-gain observer in proportion to the square number of observable state variables. And also, the proposed observer can tune the gain obtained by differentiating observational error automatically by using the backpropagation training method to stabilize the observational speed. The excellence and feasibility of the proposed observer is proved by making a comparison test between the proposed observer and the others applied to the same AC servo motor.

• Proceedings of the KIEE Conference
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• 2005.05a
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• pp.69-71
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• 2005

DC servo motors have a defect that they need a periodical maintenance because of a brush commutation and also they have a difficulty at high speed operation. In this reason, the use of AC Servo motors are increasing these days. In this paper, a proposed neuro observer is applied to speed control of AC servo motor. The proposed observer complement a problem that occur from increase of gain of High-gain observer in proportion to the square number of observable state variables. And also, the proposed observer can tune the gain obtained by differentiating observational error automatically by using the backpropagation training method to stabilize the observational speed. The excellence and feasibility of the proposed observer is proved by making a comparison test between the proposed observer and the others applied to the same AC servo motor.

• Journal of the Ergonomics Society of Korea
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• v.25 no.2
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• pp.51-62
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• 2006

In assessing risks related to working posture, pictures of postures are taken from various directions, which can be a source of observation error. Joint postures of the neck, lower back, knee, shoulder, and elbow were taken from 7 different viewing angles and 19 observers estimated joint angles by observing the pictures in 2-dimensional display. The joint angles were also measured using an optoelectronic motion measurement system. The estimation error increased as the viewing angle varies from the right side of the human body, but the patterns differ according to which joint angles were being observed. Guidelines to increase the validity of observation of joint angles were presented based on the results. In general, it is recommended to maintain the viewing angle within 20 degrees from the right side of the human body, while different ranges of viewing angle are recommended for each joint angle.

• Atmosphere
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• v.33 no.1
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• pp.33-47
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• 2023

In this study, for the application of observation errors to the Korean Integrated Model (KIM) to utilize the Constellation Observing System for Meteorology, Ionosphere & Climate-2 (COSMIC-2) new satellites, the observation errors were diagnosed based on the Desroziers method using the cost function in the process of variational data assimilation. We calculated observation errors for all observational species being utilized for KIM and compared with their relative values. The observation error of the calculated the Global Navigation Satellite System Radio Occultation (GNSS RO) was about six times smaller than that of other satellites. In order to balance with other satellites, we conducted two experiments in which the GNSS RO data expanded by about twice the observation error. The performance of the analysis field was significantly improved in the tropics, where the COSMIC-2 data are more available, and in the Southern Hemisphere, where the influence of GNSS RO data is significantly greater. In particular, the prediction performance of the Southern Hemisphere was improved by doubling the observation error in global region, rather than doubling the COSMIC-2 data only in areas with high density, which seems to have been balanced with other observations.

• Journal of Korea Multimedia Society
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• v.18 no.7
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• pp.886-894
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• 2015

In this paper, we conduct sensitivity analysis of parameters used for inverse modeling in order to estimate the PM₁₀ emissions from the 16 areas in East Asia accurately. Parameters used in sensitivity analysis are R, the observational error covariance matrix, and B, a priori (background) error covariance matrix. In previous studies, it was used with the predetermined parameter empirically. Such a method, however, has difficulties in estimating an accurate emissions. Therefore, an automatically determining method for the most suitable value of R and B with an error measurement criteria and posteriori emissions accuracy is required. We determined the parameters through a sensitivity analysis, and improved the accuracy of posteriori emissions estimation. Inverse modeling methods used in the emissions estimation are pseudo inverse, NNLS (Nonnegative Least Square), and BA(Bayesian Approach). Pseudo inverse has a small error, but has negative values of emissions. In order to resolve the problem, NNLS is used. It has a unrealistic emissions, too. The problems are resolved with BA(Bayesian Approach). We showed the effectiveness and the accuracy of three methods through case studies.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.5 no.2
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• pp.56-64
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• 1987

The concept of standard error ellipse and confidence ellipse is vtilized in the detection of displaced station which are uncluded in the observational network. In this paper, the influences on the accuracy of unknown stations according to the varied selection and geometrical conditions of fixed stations were evaluated. And then the displaced stations were detected by error ellipse concept, and the amounts of displacement were determined by coordinate differences between epochs which were calculated by fixed point adjustment and free network adjustment. As a result, it is found that the free network adjustment is more efficient in the detection and displacement calculation of displaced stations.

• Journal of the Korean Society of Earth Science Education
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• v.5 no.2
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• pp.139-147
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• 2012

The purpose of this study was to explain how extraordinary the scientific technology or our ancestor was from the modern perspective by remodeling the most unique astronomical instrument, So-ganui (小簡儀), developed in the Sejong Period (世宗時代) after being examined with contemporary and the principles of the science and observational technology would be properly understood and measured directly. When measuring the altitude of the sun and azimuth using So-ganui, it was adjusted with the horizontal coordinate system and measured using Jipyeonghwan (地平環), Ipeunhwan (立運環) and Guyhyeong (窺衡). Based such measuring principles, the measurement accuracy proposed using So-ganui are as follows. The remodeled So-ganui produced approximately ${\pm}0.29$ degrees error on average at high altitude while in measuring the azimuth degrees, there was difference of ${\pm}0.35$ degrees. Since the theoretically, the measurement error for So-ganui was ${\pm}0.5$ degrees, the remodeled So-ganui could accurately measure at the high altitude compared to So-ganui from the Sejong period. In the study, So-ganui, which has disappeared, has been remodeled in modern perspective to be used as the educational material to accurately understand the principles of science and measurement technology from the Sejong period. The findings could contribute to raising the reputation in the astronomical observations from the documents from the Sejong period. Furthermore, this study has materialized the celestial and sky our ancestors have viewed with the observational principles of their times, on the computer screen via a webcam, bringing out interest in the traditional science for the students.

• Journal of Climate Change Research
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• v.6 no.4
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• pp.331-344
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• 2015

A long-term gridded historical data at 3 km spatial resolution has been generated for practical regional applications such as hydrologic modelling. However, overly high or low values have been found at some grid points where complex topography or sparse observational network exist. In this study, the Inverse Distance Weighting (IDW) method was applied to properly smooth the overly predicted values of Improved GIS-based Regression Model (IGISRM), called the IDW-IGISRM grid data, at the same resolution for daily precipitation, maximum temperature and minimum temperature from 2001 to 2010 over South Korea. We tested various effective distances in the IDW method to detect an optimal distance that provides the highest performance. IDW-IGISRM was compared with IGISRM to evaluate the effectiveness of IDW-IGISRM with regard to spatial patterns, and quantitative performance metrics over 243 AWS observational points and four selected stations showing the largest biases. Regarding the spatial pattern, IDW-IGISRM reduced irrational overly predicted values, i. e. producing smoother spatial maps that IGISRM for all variables. In addition, all quantitative performance metrics were improved by IDW-IGISRM; correlation coefficient (CC), Index Of Agreement (IOA) increase up to 11.2% and 2.0%, respectively. Mean Absolute Error (MAE) and Root Mean Square Error (RMSE) were also reduced up to 5.4% and 15.2% respectively. At the selected four stations, this study demonstrated that the improvement was more considerable. These results indicate that IDW-IGISRM can improve the predictive performance of IGISRM, consequently providing more reliable high-resolution gridded data for assessment, adaptation, and vulnerability studies of climate change impacts.

• Journal of Astronomy and Space Sciences
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• v.24 no.1
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• pp.31-38
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• 2007

We have investigated the evolutionary status of 85 Peg within the framework of standard evolutionary theory. 85 Peg has been known to be a visual and spectroscopic binary system in the solar neighborhood. In spite of the accurate information of the total mass (${\sim}1.5M_{\odot}$) and the distance (${\sim}12pc$) from the HIPPARCOS parallax, it has been undetermined an individual mass, therefore the evolved status of the system. Moreover, the coupled uncertainties of chemical composition and age, make matters worse in predicting an evolutionary status of the system. Nevertheless, we computed the various possible models for 85 Peg, and then calibrated stellar parameters by adjusting to the recent observational data. Our modelling computation has included recently updated input physics and stellar theory such as opacity, equation of state, and chemical diffusion. Through a statistical assessment, we have derived a confident parameter set as the best solution which minimized $X^{2}$ within the observational error domain. Most of all, we found that 85 Peg is not a binary system but a triple system with an unseen companion 85 Peg $B_{b}\;{\sim}0.16M_{\odot}$. The aim of the present paper is (1) to provide a complete modelling of the stellar system based on the evolutionary theory, and (2) to constrain the physical dimensions such as mass, metallicity and age.

• Journal of Astronomy and Space Sciences
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• v.35 no.4
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• pp.295-308
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• 2018

In this study, orbit determination (OD) simulation for the Korea Pathfinder Lunar Orbiter (KPLO) was accomplished for investigation of the observational arc-length effect using a sequential estimation algorithm. A lunar polar orbit located at 100 km altitude and $90^{\circ}$ inclination was mainly considered for the KPLO mission operation phase. For measurement simulation and OD for KPLO, the Analytical Graphics Inc. Systems Tool Kit 11 and Orbit Determination Tool Kit 6 software were utilized. Three deep-space ground stations, including two deep space network (DSN) antennas and the Korea Deep Space Antenna, were configured for the OD simulation. To investigate the arc-length effect on OD, 60-hr, 48-hr, 24-hr, and 12-hr tracking data were prepared. Position uncertainty by error covariance and orbit overlap precision were used for OD performance evaluation. Additionally, orbit prediction (OP) accuracy was also assessed by the position difference between the estimated and true orbits. Finally, we concluded that the 48-hr-based OD strategy is suitable for effective flight dynamics operation of KPLO. This work suggests a useful guideline for the OD strategy of KPLO mission planning and operation during the nominal lunar orbits phase.