• The Bulletin of The Korean Astronomical Society
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• v.44 no.2
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• pp.36.1-36.1
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• 2019

In this talk I will review the concept of the Cosmic Web which is behind our understanding of the filamentary structures in the matter distribution in our Universe at large scales, how it can be described geometrically, and some of its most basic properties.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.6C
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• pp.834-841
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• 2004

There can be lips transformed geometrically in the lip images according to the location or the pose of camera and speaker. This transformation of the lip images changes geometric information of original lip phases. Therefore, for enhancing global lip information by using partial information of lips to correct lip phases transformed geometrically, in this paper we propose a method that can geometrically correct lips. The method is composed of two steps - the feature-deciding step and the correcting step. In the former, it is for us to extract key points and features of source image according to the its lip model and to create that of target image according to the its lip model. In the latter, we decide mapping relation after partition a source and target image based on information extracted in the previous step into each 4 regions. and then, after mapping, we unite corrected sub-images to a result image. As experiment image, we use fames that contain pronunciation on short vowels of the Korean language and use lip symmetry for evaluating the proposed algorithm. In experiment result, the correcting rate of the lower lip than the upper lip and that of lips moving largely than little was highly enhanced.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.11
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• pp.2893-2912
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• 2013

The design of geometrically invariant watermarking is one of the most challenging work in digital image watermarking research area. To achieve the robustness to geometrical attacks, the inherent characteristic of an image is usually used. In this paper, a geometrically invariant image watermarking scheme using connected objects and gravity center is proposed. First, the gray-scale image is converted into the binary one, and the connected objects according to the connectedness of binary image are obtained, then the coordinates of these connected objects are mapped to the gray-scale image, and the gravity centers of those bigger objects are chosen as the feature points for watermark embedding. After that, the line between each gravity center and the center of the whole image is rotated an angle to form a sector, and finally the same version of watermark is embedded into these sectors. Because the image connectedness is topologically invariant to geometrical attacks such as scaling and rotation, and the gravity center of the connected object as feature points is very stable, the watermark synchronization is realized successfully under the geometrical distortion. The proposed scheme can extract the watermark information without using the original image or template. The simulation results show the proposed scheme has a good invisibility for watermarking application, and stronger robustness than previous feature-based watermarking schemes against geometrical attacks such as rotation, scaling and cropping, and can also resist common image processing operations including JPEG compression, adding noise, median filtering, and histogram equalization, etc.

• The Journal of Information Technology
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• v.4 no.3
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• pp.77-86
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• 2001

In this paper, Electromagnetic scattering problem by a resistive strip grating with 2 dielectric layers on a ground plane according as resistivity of resistive strip, relative permittivity and thickness of dielectric layers, and incident angles of a electric wave is analyzed by applying the PMM (Point Matching Method) known as a numerical procedure. The scattered electromagnetic fields are expanded in a series of floquet mode functions. The boundary conditions are applied to obtain the unknown field coefficients and the resistive boundary condition is used for the relationship between the tangential electric field and the electric current density on the strip. According as the relative permittivity and the thickness of layers are increased, the values of the geometrically normalized reflected power have a high value and the values of strip width are moved toward a high value going from left to right. When the resistivity of this paper has a value of zero, the numerical results of the geometrically normalized reflected power show in good agreement with those by the PMM of existing paper. Then, the most energys of the sharp variation point in minimum values of the geometrically normalized reflected power are scattered in direction of the other angles except incident angle.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.2
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• pp.125-135
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• 2011

The latest study for formulation of finite element method and computation techniques has progressed widely. The classical method in the formulation of frame elements for geometrically nonlinear analysis derives the geometric stiffness directly from the governing differential equation for bending with axial force. From the computational viewpoint of this paper, the most common approach is the finite element method. Commonly, the formulation of frame elements for geometrically nonlinear structures is based on appropriate interpolation functions for the transverse and axial displacements of the member. The formulation of flexibility-based elements, on the other hand, is based on interpolation functions for the internal forces. In this paper, a new method is used to suppose that interpolation functions for the displacements from the curvatures is Lagrangian interpolation. This paper derives flexibility matrix from that displacement functions and is considered the application of it. Using the flexibility matrix, this paper apply the program considered geometrically nonlinear analysis to common problems.

• Journal of Biosystems Engineering
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• v.17 no.1
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• pp.65-78
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• 1992

When using a computer vision system for a measurement, the geometrically distorted input image usually restricts the site and size of the measuring window. A geometrically distorted image caused by the image sensing and processing hardware degrades the accuracy of the visual measurement and prohibits the arbitrary selection of the measuring scope. Therefore, an image calibration is inevitable to improve the measuring accuracy. A calibration process is usually done via four steps such as measurement, modeling, parameter estimation, and compensation. In this paper, the efficient error calibration technique of a geometrically distorted input image was developed using a neural network. After calibrating a unit pixel, the distorted image was compensated by training CMLAN(Cerebellar Model Linear Associator Network) without modeling the behavior of any system element. The input/output training pairs for the network was obtained by processing the image of the devised sampled pattern. The generalization property of the network successfully compensates the distortion errors of the untrained arbitrary pixel points on the image space. The error convergence of the trained network with respect to the network control parameters were also presented. The compensated image through the network was then post processed using a simple DDA(Digital Differential Analyzer) to avoid the pixel disconnectivity. The compensation effect was verified using known sized geometric primitives. A way to extract directly a real scaled geometric quantity of the object from the 8-directional chain coding was also devised and coded. Since the developed calibration algorithm does not require any knowledge of modeling system elements and estimating parameters, it can be applied simply to any image processing system. Furthermore, it efficiently enhances the measurement accuracy and allows the arbitrary sizing and locating of the measuring window. The applied and developed algorithms were coded as a menu driven way using MS-C language Ver. 6.0, PC VISION PLUS library functions, and VGA graphic functions.

• Computational Structural Engineering
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• v.10 no.1
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• pp.201-211
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• 1997

A clearly consistent finite element formulation for geometrically non-linear analysis of space frames is presented by applying incremental equilibrium equations based on the updated Lagrangian formulation and introducing Vlasov's assumption. The improved displacement field for symmetric cross sections is introduced based on inclusion of second order terms of finite rotations, and the potential energy corresponding to the semitangential rotations and moments is consistently derived. For finite element analysis, elastic and geometric stiffness matrices of the space frame element are derived by using the Hermitian polynomials as shape functions. A co-rotational formulation in order to evaluate the unbalanced loads is presented by separating the rigid body rotations and pure deformations from incremental displacements and evaluating the updated direction cosines of the frame element due to rigid body rotations and incremental member forces from pure deformaions. Finite element solutions for the spatial buckling and post-buckling analysis of space frames are compared with available solutions and other researcher's results.

• Structural Engineering and Mechanics
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• v.15 no.1
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• pp.83-114
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• 2003

A new simple 3-node triangular flat-shell element with standard nodal DOF (6 DOF per node) is proposed for the linear and geometrically nonlinear analysis of very thin to thick plate and shell structures. The formulation of element GT9 (Long and Xu 1994), a generalized conforming membrane element with rigid rotational freedoms, is employed as the membrane component of the new shell element. Both one-point reduced integration scheme and a corresponding stabilization matrix are adopted for avoiding membrane locking and hourglass phenomenon. The bending component of the new element comes from a new generalized conforming Kirchhoff-Mindlin plate element TSL-T9, which is derived in this paper based on semiLoof constrains and rational shear interpolation. Thus the convergence can be guaranteed and no shear locking will happen. Furthermore, a simple hybrid procedure is suggested to improve the stress solutions, and the Updated Lagrangian formulae are also established for the geometrically nonlinear problems. Numerical results with solutions, which are solved by some other recent element models and the models in the commercial finite element software ABAQUS, are presented. They show that the proposed element, denoted as GMST18, exhibits excellent and better performance for the analysis of thin-think plates and shells in both linear and geometrically nonlinear problems.

• Journal of the Society of Naval Architects of Korea
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• v.29 no.4
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• pp.227-233
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• 1992

To study the large displacement and large rotation problems, geometrically nonlinear formulation of eccentric degenerated beam element has been developed, where the restrictions of infinitesimal rotation increments are removed and the incremental equations are derived using the Taylor series expansion of the displacement function at time t+dt. The geometrically nonlinear analyses are carried out for the cases of cantilever, square frame, shallow arch and 45-degree bend beam and all of them are compared with each of the other results published. The element developed in the present research can be efficiently utilized for analysis of the nonlinear behaviours of structures when displacements and rotations are large.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.17 no.5
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• pp.1339-1355
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• 2023

Localization is a hot research spot for many areas, especially in the mobile robot field. Due to the weak signal of the global positioning system (GPS), the alternative schemes in an indoor environment include wireless signal transmitting and receiving solutions, laser rangefinder to build a map followed by a re-localization stage and visual positioning methods, etc. Among all wireless signal positioning techniques, Wi-Fi is the most common one. Wi-Fi access points are installed in most indoor areas of human activities, and smart devices equipped with Wi-Fi modules can be seen everywhere. However, the localization of a mobile robot using a Wi-Fi scheme usually lacks orientation information. Besides, the distance error is large because of indoor signal interference. Another research direction that mainly refers to laser sensors is to actively detect the environment and achieve positioning. An occupancy grid map is built by using the simultaneous localization and mapping (SLAM) method when the mobile robot enters the indoor environment for the first time. When the robot enters the environment again, it can localize itself according to the known map. Nevertheless, this scheme only works effectively based on the prerequisite that those areas have salient geometrical features. If the areas have similar scanning structures, such as a long corridor or similar rooms, the traditional methods always fail. To address the weakness of the above two methods, this work proposes a coarse-to-fine paradigm and an improved localization algorithm that utilizes Wi-Fi to assist the robot localization in a geometrically similar environment. Firstly, a grid map is built by using laser SLAM. Secondly, a fingerprint database is built in the offline phase. Then, the RSSI values are achieved in the localization stage to get a coarse localization. Finally, an improved particle filter method based on the Wi-Fi signal values is proposed to realize a fine localization. Experimental results show that our approach is effective and robust for both global localization and the kidnapped robot problem. The localization success rate reaches 97.33%, while the traditional method always fails.