• Journal of KIISE:Computing Practices and Letters
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• v.9 no.3
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• pp.341-351
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• 2003

Digital image watermarking is the method that can protect the copyright of the image by embedding copyright information, which is called watermark. Watermarking must have robustness to intentional or unintentional data changing, called attack. The conventional watermarking schemes are robust to waveform attacks such as image compression, filtering etc. However, they are vulnerable to geometrical attacks such as rotation, scaling, translation, and cropping. Accordingly, this paper proposes new watermarking scheme that is robust to geometrical attacks by using invariant centroid. Invariant centroid is the gravity center of a central area in a gray scale image that remains unchanged even when the image is attacked by RST including cropping and proposed scheme uses invariant centroids of original and inverted image as the template. To make geometrically invariant domain, template and angle compensated Log -Polar Map(LPM) is used. Then Discrete Cosine Transform(DCT) is performed and the watermark is embedded into the DCT coefficients. Futhermore, to prevent a watermarked image from degrading due to interpolation during coordinate system conversion, only the image of the watermark signal is extracted and added to the original image. Experimental results show that the proposed scheme is especially robust to RST attacks including cropping.

• Korean Journal of Remote Sensing
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• v.35 no.5_1
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• pp.705-714
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• 2019

Precision positioning is necessary for various use of high-resolution UAV images. Basically, GCP is used for this purpose, but in case of emergency situations or difficulty in selecting GCPs, the data shall be obtained without GCPs. This study proposed a method of improving positional accuracy for x, y coordinate of UAV based 3 dimensional point cloud data generated without GCPs. Road vector file by the public data (Open Data Portal) was used as reference data for improving location accuracy. The geometric correction of the 2 dimensional ortho-mosaic image was first performed and the transform matrix produced in this process was adopted to apply to the 3 dimensional point cloud data. The straight distance difference of 34.54 m before the correction was reduced to 1.21 m after the correction. By confirming that it is possible to improve the location accuracy of UAV images acquired without GCPs, it is expected to expand the scope of use of 3 dimensional spatial objects generated from point cloud by enabling connection and compatibility with other spatial information data.

• Journal of Broadcast Engineering
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• v.26 no.5
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• pp.553-565
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• 2021

Point cloud is a set of points for representing a 3D object, and consists of geometric information, which is 3D coordinate information, and attribute information, which is information representing color, reflectance, and the like. In this way of expressing, it has a vast amount of data compared to 2D images. Therefore, a process of compressing the point cloud data in order to transmit the point cloud data or use it in various fields is required. Unlike color information corresponding to all 2D geometric information constituting a 2D image, a point cloud represents a point cloud including attribute information such as color in only a part of the 3D space. Therefore, separate processing of geometric information is also required. Based on these characteristics of point clouds, MPEG under ISO/IEC standardizes V-PCC, which imitates point cloud images and compresses them into 2D DCT-based 2D image compression codecs, as a compression method for high-density point cloud data. This has limitations in accurately representing 3D spatial information to proceed with compression by converting 3D point clouds to 2D, and difficulty in processing non-existent points when utilizing 3D DCT. Therefore, in this paper, we present 3D Discrete Cosine Transform-based Point Cloud Compression (3DCT PCC), a method to compress point cloud data, which is a 3D image by utilizing 3D DCT, and confirm the efficiency of 3D DCT compared to V-PCC based on 2D DCT.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.28 no.2
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• pp.123-130
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• 2015

This paper presents a new formulation for transient simulations of microwave propagation in heterogeneous unbounded domains. In particular, perfectly-matched-layers(PMLs) are introduced to allow for wave absorption at artificial boundaries used to truncate the infinite extent of the physical domains. The development of the electromagnetic PML targets the application to engineering mechanics problems such as structural health monitoring and inverse medium problems. To formulate the PML for plane electromagnetic waves, a complex coordinate transformation is introduced to Maxwell's equations in the frequency-domain. Then the PML-endowed partial differential equations(PDEs) for transient electromagnetic waves are recovered by the application of the inverse Fourier transform to the frequency-domain equations. A mixed finite element method is employed to solve the time-domain PDEs for electric and magnetic fields in the PML-truncated domain. Numerical results are presented for plane microwaves propagating through concrete structures, and the accuracy of solutions is investigated by a series of error analyses.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.11
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• pp.1437-1446
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• 2000

A numerical analysis on the freeze coating process of a non-isothermal finite dimensional plate with a binary alloy is performed to investigate the growth and decay behavior of the solid and the mushy layer of the freeze coat and a complete procedure to calculate the process is obtained in this study. The continuously varying solid and mushy layers are immobilized by a coordinate transform and the resulting governing differential equations are solved by a finite difference technique. To account for the latent heat release and property change during solidification, proper phase change models are adopted. And the convection in the liquid melt is modeled as an appropriate heat transfer boundary condition at the liquid/mushy interface. The present results are compared with analytic solutions derived for the freeze coating of infinite dimensional plates and the discrepancy is found to be less than 0.5 percent in relative magnitude for all simulation cases. In addition the conservation of thermal energy is checked. The results show that the freeze coat grows proportional to the 1.2 square of axial position as predicted by analytic solutions ar first. But after the short period of initial growth, the growth rate of the freeze coat gradually decreases and finally the freeze coat starts to decay. The effects of various non-dimensional processing parameters on the behavior of freeze coat are also investigated.

• Journal of Broadcast Engineering
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• v.18 no.3
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• pp.380-392
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• 2013

A method to classify a golf swing motion into 7 sections using a Kinect sensor and a fuzzy system is proposed. The inputs to the fuzzy logic are the positions of golf club and its head, which are extracted from the information of golfer's joint position and color information obtained by a Kinect sensor. The proposed method consists of three modules: one for extracting the joint's information, another for detecting and tracking of a golf club, and the other for classifying golf swing motions. The first module extracts the hand's position among the joint information provided by a Kinect sensor. The second module detects the golf club as well as its head with the Hough line transform based on the hand's coordinate. Using a fuzzy logic as a classification engine reduces recognition errors and, consequently, improves the performance of robust classification. From the experiments of real-time video clips, the proposed method shows the reliability of classification by 85.2%.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.27 no.1
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• pp.677-682
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• 2009

According to the revised law of survey, all the geographic information data including 1/1,000 digital topographic maps have to be converted to world geodetic reference system by the end of 2009. National Geographic Information Institute (NGII) formulated the policy to promote the conversion from local geodetic reference system to world geodetic reference system. However, the current conversion rate is lower than planned due to some impeding factors. Therefore, in this paper, those impeding factors are investigated and then efficient conversion strategies are established and provided. The research involves the validation of affine transformation, the determination of critical value for outlier detection and optimal number of common control points for coordinate conversion, and the treatment of old and new control points.

• Journal of Astronomy and Space Sciences
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• v.2 no.1
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• pp.19-33
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• 1985

The singularities of differential Newtonian equation of motion in three body problem cause the loss of accuracy and the considerable increase of the computer time. These singularities could be eliminated during the process of regularization to transform the independent variables and the coordinate of Newtonian equations of motion. In this study, we calculated the positions and velocities of three body along the time scale to find out the unique solution of regularized Newtonian equations of motion with the $5^{th}$ order Runge-Kutta method by assuming the suitable initial velocities and positions. As the results of these calculations it is shown that the tripe stellar system eventually distintegrated, two of them formed a binary, and the last one escaped from this system with a hyperbolic orbit. This may suggest one possible explanation for the binary formation.

• Journal of Astronomy and Space Sciences
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• v.31 no.2
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• pp.159-167
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• 2014

Solar variability is widely known to affect the interplanetary space and in turn the Earth's electromagnetical environment on the basis of common periodicities in the solar and geomagnetic activity indices. The goal of this study is twofold. Firstly, we attempt to associate modes by comparing a temporal behavior of the power of geomagnetic activity parameters since it is barely sufficient searching for common peaks with a similar periodicity in order to causally correlate geomagnetic activity parameters. As a result of the wavelet transform analysis we are able to obtain information on the temporal behavior of the power in the velocity of the solar wind, the number density of protons in the solar wind, the AE index, the Dst index, the interplanetary magnetic field, B and its three components of the GSM coordinate system, $B_X$, $B_Y$, $B_Z$. Secondly, we also attempt to search for any signatures of influence on the space environment near the Earth by inner planets orbiting around the Sun. Our main findings are as follows: (1) Parameters we have investigated show periodicities of ~ 27 days, ~ 13.5 days, ~ 9 days. (2) The peaks in the power spectrum of $B_Z$ appear to be split due to an unknown agent. (3) For some modes powers are not present all the time and intervals showing high powers do not always coincide. (4) Noticeable peaks do not emerge at those frequencies corresponding to the synodic and/or sidereal periods of Mercury and Venus, which leads us to conclude that the Earth's space environment is not subject to the shadow of the inner planets as suggested earlier.

• Journal of the Korean Society for Nondestructive Testing
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• v.22 no.5
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• pp.523-531
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• 2002

This study is concentrated on the development of high speed multi-object image processing algorithm in real time. Recently, the use of vision system is rapidly increasing in inspection and robot's position control. To apply the vision system, it is necessary to transform the physical coordinate of object into the image information acquired by CCD camera. Thus, to use the application of the vision system to the inspection and robot's position control in real time, we have to know the position of object in the image plane. Particularly, in case of rigid body using multi-cue to identify its shape, the each position of multi-cue must be calculated in an image plane at the same time. To solve these problems, the image processing algorithm on the position of multi-cue is developed.