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Dive into the research topics where Kwang Hee Ko is active.

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Featured researches published by Kwang Hee Ko.


IEEE Transactions on Industrial Electronics | 2009

Simple Pedestrian Localization Algorithms Based on Distributed Wireless Sensor Networks

Hyo-Sung Ahn; Kwang Hee Ko

This paper addresses simple algorithms for pedestrian localization based on the measurements from distributed wireless sensor networks (WSNs). It appears to be quite difficult to install a set of hardware sensors onto a human body; thus, traditional navigation sensors such as the inertial measurement unit cannot be employed for human tracking in a practical point of view. Recently, to minimize hardware installation onto the human body, WSNs have been actively investigated. However, there is a critical problem in WSNs associated with the measurement noises and signal disturbances. In this paper, we establish very simple localization algorithms that can reduce the noise effects as well as disturbances without a priori knowledge of them. Through actual experimental tests, the validity of the proposed methods is demonstrated.


Computer-aided Design | 2003

An algorithm for optimal free-form object matching

Kwang Hee Ko; Takashi Maekawa; Nicholas M. Patrikalakis

A novel method of matching for 3-D free-form objects (points vs. surface and surface vs. surface) is proposed. The method formulates the problem in terms of solution of a non-linear polynomial equation system, which can be solved robustly by the Interval Projected Polyhedron (IPP) algorithm. Two intrinsic surface properties, the Gaussian and the mean curvatures, are used as object features for matching. The related iso-curvature lines are used to establish the correspondence between two objects. The intersection points of these iso-curvature lines are calculated and sorted out to satisfy the Euclidean constraints from which the translation and rotation transformations are estimated. The performance of the proposed algorithm is also analyzed. This approach can cover global and partial matching, and be applied to automated inspection, copyright protection of NURBS models, and object recognition. Examples illustrate our technique.


Progress in Electromagnetics Research-pier | 2012

A COMPACT BEAM RECONFIGURABLE ANTENNA FOR SYMMETRIC BEAM SWITCHING

Woong Kang; Kwang Hee Ko; Kangwook Kim

In this paper, two radiation pattern-reconflgurable antennas are designed to operate near the frequency of 1.8GHz. The geometry of the proposed antennas is symmetric with respect to the vertical center line. The electrical shapes of the antennas are composed of a monopole-loaded loop and an open wire. The open wire functions as either a director or re∞ector for the two antennas. Depending on the switching state, the antennas can select between two beam directions with no input impedance difierence. The sizes of each antenna are then optimized to achieve beam switching capability using PIN diodes and FETs. The re∞ection coe-cients and gain patterns for two bias conditions using both switches are measured and compared with the simulated results. The measured results show that the proposed antennas can clearly alternate their beam directions using the switching components.


ACS Applied Materials & Interfaces | 2014

Anisotropic Adhesion of Micropillars with Spatula Pads

Seungwan Seo; Jehong Lee; Kwang-Seop Kim; Kwang Hee Ko; Jong-Hyun Lee; Jongho Lee

Natural gecko adhesive structures consisting of angled setae, branched into thin spatulas, have remarkable properties including easily attachable and releasable anisotropic adhesion. The geometrically asymmetric structures lead to anisotropic adhesive properties. Inspired by the gecko, we fabricated an array of micropillars with asymmetric spatula pads from elastomeric materials. This paper describes the anisotropic properties of the micropillars with spatula pads as established by experimental measurements and observation together with finite element analysis. The results indicate that the structural difference of the spatula pad at one edge of the micropillar provides the anisotropic adhesive properties.


Graphical Models \/graphical Models and Image Processing \/computer Vision, Graphics, and Image Processing | 2002

Surface construction by fitting unorganized curves

Takashi Maekawa; Kwang Hee Ko

We present a novel technique to construct a B-spline surface from unorganized curves in 3D space. Unlike the lofting or skinning methods, where the family of curves to be lofted form isoparametric lines of the resulting surface, our method relaxes this restriction and allows a set of curves to take arbitrary orientation and possibly intersect each other. We employ the concept of a curve on a surface which is used in obtaining the arc element of a curve on the surface in differential geometry. This novel technique is useful in surface construction or creation where surfaces are created based on sketches. The surface creation has applications in aesthetic shape design, reverse engineering, computer graphics, and computer animation. This technique is also useful in surface reconstruction where surfaces are constructed from stripes which are made of a series of points lined up in a sequential manner.


Graphical Models \/graphical Models and Image Processing \/computer Vision, Graphics, and Image Processing | 2005

Algorithms for optimal partial matching of free-form objects with scaling effects

Kwang Hee Ko; Takashi Maekawa; Nicholas M. Patrikalakis

A free-form object matching problem is addressed in this paper. Two methods are proposed to solve a partial matching problem with scaling effects and no prior information on correspondence or the rigid body transformation involved. The first method uses umbilical points, which behave as fingerprints of a surface and their qualitative properties can be used for matching purposes. The second method uses an optimization scheme based on the extension of the KH curvature matching method [Comput. Aided Design 35 (2003) 913], first introduced in the context of a matching problem without scaling effects. Two types of curvatures, the Gaussian and the mean curvatures, are used to establish correspondences between two objects. The curvature matching method is formulated in terms of minimization of an objective function depending on the unknown scaling factor, and the rigid body transformation parameters. The accuracy and complexity of the proposed methods as well as the convergence for the optimization approach are analyzed. Examples illustrate the two methods.


acm symposium on solid modeling and applications | 2003

Shape intrinsic fingerprints for free-form object matching

Kwang Hee Ko; Takashi Maekawa; Nicholas M. Patrikalakis; Hiroshi Masuda; Franz-Erich Wolter

This paper presents matching and similarity evaluation methods between two NURBS surfaces, and their application to copyright protection of digital data representing solids or NURBS surfaces. Two methods are employed to match objects: the moment and the curvature methods. The moment method uses integral properties, i.e. the volume, the principal moments of inertia and directions, to find the rigid body transformation as well as the scaling factor. The curvature method is based on the Gaussian and the mean curvatures to establish correspondence between two objects. The matching algorithms are applied to problems of copyright protection. A suspect model is aligned to an original model through the matching methods so that similarity between two models can be assessed to determine if the suspect model contains part(s) of the original model, which may be stored in an independent repository. Three types of tests, the weak, intermediate and strong tests, are proposed for similarity assessment between two objects. The weak and intermediate tests are performed at node points obtained through shape intrinsic wireframing. The strong test relies on isolated umbilical points which can be used as fingerprints of an object for supporting an ownership claim to the original model. The three tests are organized in two decision algorithms such that they produce systematic and statistical measures for a similarity decision between two objects in a hierarchical manner. Based on the systematic and statistical evaluation of similarity, a decision can be reached whether the suspect model is an illegal copy of the original model.


international symposium on ubiquitous virtual reality | 2008

Introduction of Physics Simulation in Augmented Reality

Changhun Chae; Kwang Hee Ko

In 3D computer graphics, it has been an important issue to describe a virtual object realistically and show it in a physically correct manner. Unlike the virtual reality(VR), the augmented reality (AR) is an environment containing virtual and real objects simultaneously. However, the difference in motion between the virtual and real objects is obvious, which makes it hard for AR to be realistic and attractive. To reduce this gap, we propose to apply physical attributes to each virtual object, which can be done by using a physics engine, a software library containing functions related with physics. For this purpose, an ODE (open dynamics engine) library is used. However, the direct use of the library in the AR environment poses a lot of problems. Most of all, the coordination of the coordinate systems between OSG (OpenSceneGraph) and ODE must be taken care of. Next the positions of markers are also needed to be considered. In this paper, such problems are addressed and solutions to them are discussed.


Progress in Electromagnetics Research-pier | 2013

Multi-feature based detection of landmines using ground penetrating radar

Kyungmi Park; Suncheol Park; Kangwook Kim; Kwang Hee Ko

In this paper, we present a method for detecting anti- tank or anti-personnel landmines buried in the ground. A set of data generated by a ground penetrating radar is processed to remove the surface re∞ection and clutter, yielding signals for possible landmines. In order to detect landmines in the signals, features are computed and compared against a database, which contains those of various landmines. Three features are proposed to use; principal components from principal component analysis, Fourier coe-cients and singular values from singular value decomposition method, each of which is chosen to represent each landmine uniquely. Detection is performed using Mahalanobis distance-based method. Examples show that the proposed method can efiectively detect landmines in various burial condition.


Computer-aided Design | 2010

Immersive modeling system (IMMS) for personal electronic products using a multi-modal interface

Yong-Gu Lee; Hyungjun Park; Woontack Woo; Jeha Ryu; Hong Kook Kim; Sung Wook Baik; Kwang Hee Ko; Han Kyun Choi; Sun-Uk Hwang; Duck Bong Kim; Hyun Soo Kim; Kwan H. Lee

In developing new personal electronic products, the development time has shortened to a few months due to high competition in the market. Now it has become very hard to meet the time to market by evaluating products by making physical prototypes. To overcome this problem, we propose an immersive modeling system (IMMS) that enables us to interact with a digital product model in the augmented virtual environment using a multi-modal interface. The IMMS allows the user to evaluate the product model realistically using visual, auditory, and tactile/force senses. The architecture and main modules of the system are described in detail. The integration problems encountered during the development of the test bed are discussed. Application examples to personal electronic products are also included.

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Nicholas M. Patrikalakis

Massachusetts Institute of Technology

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Hyo-Sung Ahn

Gwangju Institute of Science and Technology

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Kangwook Kim

Gwangju Institute of Science and Technology

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Kwan H. Lee

Gwangju Institute of Science and Technology

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Su-Jin Choi

Korea Aerospace Research Institute

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Dae-Won Chung

Korea Aerospace Research Institute

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Jung Seo Park

Samsung Heavy Industries

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Ok-Chul Jung

Korea Aerospace Research Institute

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Takashi Maekawa

Yokohama National University

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Jong Gye Shin

Seoul National University

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