• Proceedings of the Korean Society of Computational and Applied Mathematics Conference
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• 2003.09a
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• pp.5.3-5
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• 2003

The boundary of a typical period-2 component in the degree-3 bifurcation set is formulated by a parametrization of its image which is the unit circle under the multiplier map, Some properties on the geometry of the boundary are investigated including the root point, the cusp, the component center and the length as well as the area bounded by the boundary curve. An algorithm drawing the boundary curve with Mathematica codes is proposed and its implementation exhibits a good agreement with the analysis presented here.

• Geophysics and Geophysical Exploration
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• v.19 no.4
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• pp.236-248
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• 2016

In this review, the basic concepts of geodetic coordinate system and map projection are explained to practitioners in exploration geophysicists to enhance the understanding of geographic and projected coordinate system. The fundamental elements such as earth ellipsoid, geoid, geocentric and geodetic latitudes, rhumb line, and great circle are dealt with in detail. The geocentric and geodetic coordinate systems are also summarized neatly, together with coordinate conversion formulae. In addition, the concept and technique for datum transforms between local and world datum are presented, with special emphasis on Korean Geodetic System.

• The Journal of Korea Robotics Society
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• v.12 no.1
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• pp.86-93
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• 2017

The Expanded Guide Circle (EGC) method has been originally proposed as the guidance navigation method for improving the efficiency of the remote operation using the sensory information. The previous algorithm is, however, concerned only for the omni-directional mobile robot, so it needs to suggest a suitable one for a mobile robot with non-holonomic constraints. The ego-kinematic transform is a method to map points of $R^2$ into the ego-kinematic space which implicitly represents non-holonomic constraints for admissible paths. Thus, robots with non-holonomic constraints in the ego-kinematic space can be considered as "free-flying object". In this paper, we propose an effective obstacle avoidance method for mobile robots with non-holonomic constraints by applying EGC method in the ego-kinematic space using the ego-kinematic transformation. This proposed method shows that it works better for non-holonomic mobile robots such as differential-drive robot than the original one. The simulation results show its effectiveness of performance.

• The Journal of Korean Institute of Next Generation Computing
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• v.15 no.3
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• pp.25-30
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• 2019

Magnetic sensors have the disadvantage that their vector values differ depending on the direction. In this paper, we propose a magnetic vector calibration method for geomagnetic-based indoor localization estimates. The fingerprinting technique used in geomagnetic-based indoor localization the position by matching the magnetic field map and the magnetic sensor value. However, since the moving direction of the current user may be different from the moving direction of the person who creates the magnetic field map at the collection time, the sampled magnetic vector may have different values from the vector values recorded in the field map. This may substantially lower the positioning accuracy. To avoid this problem, the existing studies use only the magnitude of magnetic vector, but this reduces the uniqueness of the fingerprint, which may also degrade the positioning accuracy. In this paper we propose a vector calibration algorithm which can adjust the sampled magnetic vector values to the vector direction of the magnetic field map by using the parametric equation of a circle. This can minimize the inaccuracy caused by the direction mismatch.

• Journal of Institute of Control, Robotics and Systems
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• v.13 no.5
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• pp.434-443
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• 2007

Presently, the exploration of an unknown environment is an important task for thee new generation of mobile service robots and mobile robots are navigated by means of a number of methods, using navigating systems such as the sonar-sensing system or the visual-sensing system. To fully utilize the strengths of both the sonar and visual sensing systems. This paper presents a technique for localization of a mobile robot using fusion data of multi-ultrasonic sensors and vision system. The mobile robot is designed for operating in a well-structured environment that can be represented by planes, edges, comers and cylinders in the view of structural features. In the case of ultrasonic sensors, these features have the range information in the form of the arc of a circle that is generally named as RCD(Region of Constant Depth). Localization is the continual provision of a knowledge of position which is deduced from it's a priori position estimation. The environment of a robot is modeled into a two dimensional grid map. we defines a vision-based environment recognition, phisically-based sonar sensor model and employs an extended Kalman filter to estimate position of the robot. The performance and simplicity of the approach is demonstrated with the results produced by sets of experiments using a mobile robot.

• Journal of the Korean Geographical Society
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• v.43 no.4
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• pp.638-654
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• 2008

A questionnaire survey is conducted to identify the middle school students' abilities to recognize the proportional symbolic maps. After analyzing the data from the respondents, three facts could be concluded. First, the trends of under-estimation are represented as the power function and the degree of under-estimation is increased as the sequence of line, square, circle, sphere symbols. Second, the estimations of symbol size are effected by the number of symbols in the legend(3, 5, 7), the presentation methods of legends(linear, nested), and the system to scale the symbol size(mathematical, perceptual). Lastly, the size of symbols on the map tends to be over-estimated comparing to the symbols in the legend, and the differences between the first year and third year students to recognize the proportional symbol maps are not identified.

• Journal of Institute of Control, Robotics and Systems
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• v.18 no.7
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• pp.658-663
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• 2012

An accurate outdoor localization method using line/arc features is suggested for mobile robots with LRFs (Laser Range Finders) and odometry. Localization is a key process for outdoor mobile robots which are used for autonomous navigation, exploration and so on. In this paper, an accurate pose correction algorithm is proposed for mobile robots using LRFs, which use three feature types: line, circle, and arc. Using this method we can reduce the number of singular cases that robots couldn't find their pose. Finally we have got simulation results to validate the proposed algorithm.

• Proceedings of the Korea Information Processing Society Conference
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• 2006.05a
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• pp.1415-1418
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• 2006

최근 정보 관련 산업 발달과 더불어 공간 정보의 중요성이 점점 강조되어, 국가 차원의 지리정보체계가 구현되고 있다. 국토지리정보원이 구축하고 있는 수치지도는 DXF로 제작되는데, 이 DXF맵은 GIS분야에서 필요한 속성정보나 위상정보를 갖지 못하여 지리정보 통합에 어려움이 있다. 지리정보의 여러 분야에 걸쳐 효율적인 데이터의 공유가 가능하도록 DXF파일에서 공간 개체를 추출하는 연구는 매우 중요하다. 본 논문에서는 DXF 파일에서 다양한 공간 개체를 추출하는 효율적인 공간 개체 추출기를 제안한다. 공간 개체 추출기는 DXF파일을 구성하는 요소들 중에 POLYLINE, POINT, CIRCLE, TEXT, ARC, LINE의 수치값을 비교하여 그에 해당하는 좌표값을 DAT 파일에 저장한다. 제안된 시스템은 웹상에서도 사용할 수 있다. 사용자는 단순히 웹서버에 DXF 파일을 업로드해서 공간 개체 추출기를 실행하여 결과를 다운로드 받아 활용할 수 있다.

• Bulletin of the Korean Mathematical Society
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• v.57 no.1
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• pp.251-274
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• 2020

We study a dynamical system that was originally defined by Romik in 2008 using an old theorem of Berggren concerning Pythagorean triples. Romik's system is closely related to the Farey map on the unit interval which generates an additive continued fraction algorithm. We explore some number theoretical properties of the Romik system. In particular, we prove an analogue of Lagrange's theorem in the case of the Romik system on the unit quarter circle, which states that a point possesses an eventually periodic digit expansion if and only if the point is defined over a real quadratic extension field of rationals.

• Korean System Dynamics Review
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• v.14 no.3
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• pp.5-23
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• 2013

This paper explores a structural mechanism underlying governmental reformulation. Studying cases of governmental reorganizations occurred during past 60 years, this paper constructs a causal map containing a principle of small government, an integrative organization of the government, and a committee organization. A positive feedback loop linking these factors produces an increase in the number of the committee organization in the government. Also, this paper points out that there might be a hidden self fullfilling prophecy that reinforces the principle of small government. Open experiment toward a big government is proposed to overcome the vicious circle of small government curse.