• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2015.10a
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• pp.53-54
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• 2015

The maritime industry is expanding at an alarming rate and as such there is a perpetual need to improve situation awareness in the maritime environment using new and emerging technology. Tracking is one of the numerous ways of enhancing situation awareness by providing information that may be useful to the operator. The tracking system described herein comprises determining existing states of own ship, state prediction and state compensation caused by random noise. The purpose of this paper is to analyze the process of tracking and develop a tracking algorithm by using ${\alpha}-{\beta}-{\gamma}$ tracking filter under a random noise or irregular motion for use in a warship. The algorithm involves initializing the input parameters of position, velocity and course. The actual positions are then computed for each time interval. In addition, a weighted difference of the observed and predicted position at the nth observation is added to the predicted position to obtain the smoothed position. This estimation is subsequently employed to determine the predicted position at (n+1). The smoothed values, predicted values and the observed values are used to compute the twice distance root mean square (2drms) error as a measure of accuracy of the tracking module.

• Journal of Aerospace System Engineering
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• v.15 no.2
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• pp.1-9
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• 2021

In this paper, a thickness compensation function is introduced to consider the shear deformation and warping effect resulting from increased thickness in the composite multi-cell wing box. The thickness compensation function is used to perform the structure optimization of the multi-cell. It is determined by minimizing the error of an analytical formula using solid mechanics and the Ritz method. It is used to define a structural performance prediction expression due to the increase in thickness. The parameter is defined by the number of spars and analyzed by the critical buckling load and the limited failure index as a response. Constraints in structural optimization are composed of displacements, torsional angles, the critical buckling load, and the failure index. The objective function is the mass, and its optimization is performed using a genetic algorithm.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.10
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• pp.27-33
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• 2004

In this paper, we present a carrier recovery circuit using the polarity-decision algorithm that recovers a phase and a frequency error simultaneously. The proposed algorithm catches a frequency error based on a differential of an angular velocity of the signal constellations. Using the differential of a phase error may compensate the frequency error. The symbol prediction method in the proposed algorithm accumulates the symbols, which makes easy to calculate a phase differential. The hardware size of the algerian is small since we use Q data or I only to get phase information. As a result, the algerian shows a pull-in range of normalized frequency error 0.5 under AWGN 15dB.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.10
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• pp.2112-2122
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• 1997

This paper presents a new video codec which is based on 2-D triangular mesh-based motion compensation and two step grid point motion estimation. With this approach the efficiency of compression and the quality of reconstructed images are improved. The compensation of motion for each triangular patch is performed by image warping using motion vectors at the grid points. The prediction error coding and the rate control meet MPEG-4 VM 3.0 specification. The experimental results show that the codec system proposed is simple in complexity and moreover, the quality of decoded images is improved.

• Journal of Institute of Control, Robotics and Systems
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• v.10 no.3
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• pp.273-279
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• 2004

This research is concerned with the development of an Internet-based robot system, which is insensitive to the unpredictable internet time delay. For this purpose, a simple mobile robot system that moves in response to the user s direct control on the internet has been developed. The time delay in data transmission is an important problem for the construction of this kind of system. Therefore, the PPS (Position Prediction Simulator) is suggested and implemented to compensate for the time delay problem of the internet. The simulation and experimental results show that the distance error can be reduced using the developed PPS.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.810-815
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• 2003

This research is concerned with the development of an Internet-based robot system, which is insensitive to the unpredictable Internet time delay. For that purpose, a simple mobile robot system that moves in response to the user' direct control on the Internet has been built. The time delay in data transmission is a big problem for the construction of this kind of system. Therefore, the PPS (Position Prediction Simulator) is suggested and implemented to compensate for the time delay problem of the Internet. The simulation and experimental result show that the distance error can be reduced using the developed PPS.

• Journal of the military operations research society of Korea
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• v.13 no.1
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• pp.1-18
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• 1987

This paper presents several adaptive linear predictive coding techniques based upon extension of recursive ladder filters. A 2-D recursive ladder filter is extended to a 3-D case which can adaptively track the variation of both spatial and temporal changes of moving images. Using the 2-D/3-D ladder filter and a previous farme predictor, two types of adaptive predictor-control schemes are proposed in which the prediction error at each pel can be obtained at or close to a minimum level. We also investigate several modifications of the basic encoding methods. Performance of the 2-D/3-D ladder filters, their adaptive control schemes, and variations in coding methods are evaluated by computer simulations on a real sequence and compared to the results of motion compensation and frame differential coders. As a validity test of the ladder filters developed, the error signals for the different predictors are compared and evaluated.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1186-1189
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• 2005

Focused Ion Beam machining is an attractive approach to produce nano-scale 3D structures. However, like other beam-based manufacturing processes, the redeposition of the sputtered material during the machining deteriorates the geometric accuracy of ion beam machining. In this research a new approach to reduce the geometric error in FIB machining is introduced. The observed redeposition phenomena have been compared with existing theoretical model. Although the redeposition effect has good repeatability the prediction of exact amount of geometric error in ion beam machining is difficult. Therefore, proposed method utilizes process control approach. Developed algorithm measures the redeposition amount after every production cycle and modifies next process plan. The method has been implemented to a real FIB machine and the experimental results demonstrated considerable improvement of five micrometer-sized pocket machining.

• Journal of Navigation and Port Research
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• v.40 no.2
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• pp.83-87
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• 2016

The maritime industry is expanding at an alarming rate hence there is a perpetual need to improve situation awareness in the maritime environment using new and emerging technology. Tracking is one of the numerous ways of enhancing situation awareness by providing information that may be useful to the operator. The tracking module designed herein comprises determining existing states of high dynamic target warship, state prediction and state compensation due to random noise. This is achieved by first analyzing the process of tracking followed by design of a tracking algorithm that uses ${\alpha}-{\beta}-{\gamma}$ tracking filter under a random noise. The algorithm involves initializing the state parameters which include position, velocity, acceleration and the course. This is then followed by state prediction at each time interval. A weighted difference of the observed and predicted state values at the $n^{th}$ observation is added to the predicted state to obtain the smoothed (filtered) state. This estimation is subsequently employed to determine the predicted state in the next radar scan. The filtering coefficients ${\alpha}$, ${\beta}$ and ${\gamma}$ are determined from a pre-determined value of the damping parameter, ${\xi}$. The smoothed, predicted and the observed positions are used to compute the twice distance root mean square (2drms) error as a measure of the ability of the tracking module to manage the noise to acceptable levels.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.10
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• pp.881-891
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• 2017

In this paper, we described the new TLE(Two Line Elements) generation method based on the compansation technique by using past TLEs(Two Line Elements) released by JSpOC(Joint Space Operation Center) in USA to reduce the orbit prediction error for long duration of SGP4(Simplified General Perturbations 4) which is a simplifed and analytical orbit propagator. The orbital residuals the orbital difference between two ephemeris for the first TLE only and for the all TLEs updated by JSpOC for the past some period was applied for this algorithm instead of general orbit determination software. Actually, in these orbital residuals, the trend of orbit prediction error from SGP4 is included. Thus, it is possible to make a simple residual function from these orbital residulas by using the fitting process. By using these residual functions with SGP4 prediction data for the currnet TLE data, the compansated orbit prediction can be reconstructed and the orbit prediction error for long duration of SGP4 is also reduced. And it is possible to generate new TLE data from it. In this paper, we demonstraed this algorithm in simple simulation, and the orbital error is decreased dramatically from 4km for the SGP4 propagation to 2km for it during 7 days as a result.