• Journal of Astronomy and Space Sciences
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• v.30 no.3
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• pp.207-212
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• 2013

Ionosphere is one of the largest error sources when the navigational signals produced by Global Positioning System (GPS) satellites are transmitted. Therefore it is very important to estimate total electron contents (TEC) in ionosphere precisely for navigation, precise positioning and some other applications. When we provide ionospheric TEC values in real-time, its application can be expanded to other areas. In this study we have used data obtained from nine Global Navigation Satellite System (GNSS) reference stations which have been operated by Korea Astronomy and Space Science Institute (KASI) to detect ionospheric TEC over South Korea in real-time. We performed data processing that covers converting 1Hz raw data delivered from GNSS reference stations to Receiver INdependent Exchange (RINEX) format files at intervals of 5 minutes. We also analyzed the elevation angles of GPS satellites, vertical TEC (VTEC) values and their changes.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.2
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• pp.146-156
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• 1998

Thispapr proposes hybrid navigation parameter estimation using sequential aerial images. The proposed navigation parameter estimation system is composed of two parts: relative position estimation and absolute position estimation. the relative position estimation recursively computes the current velocity and absolute position estimation. The relative position estimation recursively computes the current velocity and position of an aircraft by accumulating navigation parameters extracted from two succesive aerial images. Simple accumulation of parameter values decreases reliability of the extracted parameters as an aircraft goes on navigating. therefore absolute position estimation is required to compensate for position error generated in the relative position step. The absolute position estimation algorithm combining image matching and digital elevation model(DEM) matching is presented. Computer simulation with real aerial image sequences shows the efficiency of the proposed hybrial algorithm.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2003.09a
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• pp.311-314
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• 2003

In radar tracking, since the sensor measures range, azimuth and elevation angle of a target, the measurement equation is nonlinear and the extended Kalman filter (EKF) is applied to nonlinear estimation. The conventional EKF has been widely used as a nonlinear filter for radar tracking, but the considerably large measurement error due to the linearization of nonlinear function in highly nonlinear situations may deteriorate the performance of the EKF. To solve this problem, a fuzzy-model-based Kalman filter (FMBKF) is proposed for radar tracking. The FMBKP uses a local model approximation based on a TS fuzzy model instead of a Jacobian matrix to linearize nonlinear measurement equation. The hybrid GA and RLS method is used to identify the premise and the consequent parameters and the rule numbers of this TS fuzzy model. In two-dimensional radar tracking problem, the proposed method is compared with the conventional EKF.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2002.10a
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• pp.273-276
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• 2002

Watershed boundary and stream network can be extracted from DEM(Digital Elevation Model) using GIS software such as ARC/INFO or ArcView Spatial Analyst. However, there exist many errors in the generated watershed boundary and stream network just by operating sink removal function of the present software. This paper present the error reducing method to delineate watershed boundary and generate stream network especially in plane areas by using stream burning techniques known as Fillburn and Agree bum. These preprocessing techniques of DEM dramatically decreased the errors comparing with the results by no-bum DEM.

• Proceedings of the KIEE Conference
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• 2005.07d
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• pp.2741-2743
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• 2005

In this paper, Elevator is designed for real time security & management. Security & Management System is designed for wireless communication between an Elevator and an manager, between Elevation and an manager. Also, to have remote control capability, embedded system platform with TCP/IP techniques are applied to process control system with independent open structure for the precise data transmission and without constraint of operating system. Security and Management system is designed to solve problem of network port by Bluetooth module. Moved recording, unworked table, life of device and replacement time of device are made database, database is applied to Fuzzy Rule for pre-detection unworked Elevator. Security & Management system is designed safety and convenience for customers using Elevator as well as rapidly treatment with unworked Elevator.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.2 s.191
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• pp.86-94
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• 2007

In this paper, a dual stage servo mechanism has been developed for image tracking system to improve control performances such as small rise time, small overshoot, small settling time, small stabilization error etc. A secondary stage, a platform, actuated by a pair of electro-magnets is mounted on a conventional elevation gimbal. In this mechanism, the gimbal provides large range but slow motion and the platform provides small range but fast positioning. A sliding mode control is applied to the platform positioning to attain robust performances and stability in the presence of the disturbance related to dynamic coupling of the gimbal and the platform. Results from experiments illustrate that the suggested dual stage mechanism controlled by the sliding mode control is effective in improving responses and attenuating the disturbance response related with dynamic coupling.

• Proceedings of the KSRS Conference
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• 2008.10a
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• pp.251-254
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• 2008

The German radar satellite TerraSAR was launched in 2007. In this study, interferogram is generated using TerraSAR-X data and DEM (Digital Elevation Model). Coregistration procedures used with SAR images (i.e. master and slave) in traditional method results in serious errors for high resolution TerraSARX data because of the mutual shift of the master and slave images due to topography. This error becomes more serious in mountainous areas in which the coherence between interferometric pairs is relatively low. Here we processed a geometric coregistration with DEM exploiting height information. Through the method, interferometry processing is fulfilled to generate a qualified interferogram and coherence is improved. This approach will help high resolution X-band SAR interferometry in mountainous area.

• Transactions of the Korean Society of Mechanical Engineers
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• v.9 no.4
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• pp.463-470
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• 1985

In this study a parametric analysis for the rewetting temperature was made with 572 data obtained from the single tube experiment. The rewetting temperature was also evaluated by measuring the vaporization time of a liquid drop on a hot surface at the elevated pressures. The results showed that the rewetting temperature increased with flooding rate, inlet subcooling pressure and initial wall temperature, and decreased with increasing axial elevation. Based on the results obtained, the rewetting temperature correlation was suggested. From the comparison of correlated rewetting temperatures with measured values, it showed that the correlated values fell within .+-.5% error from the measured values.

• Proceedings of the KIEE Conference
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• 1988.07a
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• pp.905-908
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• 1988

In recent, Kalman filter technique has been much used as one of technique for tracking of the moving target. But some problem are still remained to be resolved. For example, when Kalman filter technique is applied to nonlinear system, the technique is nonoptimal estimator. Therefore, extended Kalman filter is proposed to reduce modeling error for nonlinear system. In this study, an extended Kalman filter in Cartesian coordinates is described for moving target, when the radar sensor measures range, azimuth and elevation angle in polar coordinates. And an approximate gain computation algorithm is proposed. In this approach, Kalman gains are computed for three uncoupled filter and multiplied by a Jacobian transformation determined from the measured target position and orientation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.4
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• pp.1113-1120
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• 1998

This paper introduces a channel model that is a combination of Rice and log-normal statistics, with independent shadowing affectingeach direct and diffuse component, repectively. This model extends the channel model of a combined Rice and Log-normal, proposed by Corazza, to include the independent shadowing. The validity of model is confirmed by comparisons with the data collectedin the literature, the analytical model, and the computer model in terms of probability distribution of the evvelope of each model. The model turns out to be one of many well-known narrowband models in limiting cases, e.g. Rayleigh, Rice, log-normal, Suzuki, Loo, and Corazza. Finally, the examples of bit error probability evaluations for several values of the elevation angle in the channel are provided.