• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.10
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• pp.77-82
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• 2004

This paper presents polar converting logic(PCL) of BTT missiles against slowly moving or stationary targets. A guidance commands expressed in rectangular coordinates must be converted in the form of polar coordinates for BTT control. Since conventional PCL has nonlinear and discontinuous function, the missiles may lose controllability when pitch acceleration command equals to zero. Further, roll coupling may have a serious unstabilizing influence on homing guidance with two gimbals seeker. In this paper, a linear homotopy equation is introduced to improve the controllability and a command following performance at midcourse phase. We also design a PCL which is less sensitive to pitch acceleration command so that it may improve the stability of the homing loop. To substantiate our conclusion, results of the computer simulation have been illustrated.

• Journal of KIISE:Computer Systems and Theory
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• v.31 no.7
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• pp.414-420
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• 2004

Among the desirable properties of a piecewise linear parameterization, guaranteeing a one-to-one mapping (i.e., no triangle flips in the parameter plane) is often sought. A one-to-one mapping is accomplished by non-negative coefficients in the affine transformation. In the Floater's method, the coefficients were computed after the 3D mesh was flattened by geodesic polar-mapping. But using this geodesic polar map introduces unnecessary local distortion. In this paper, a simple variant of the original shape-preserving mapping technique by Floater is introduced. A new simple method for calculating barycentric coordinates by using straightest geodesics is proposed. With this method, the non-negative coefficients are computed directly on the mesh, reducing the shape distortion introduced by the previously-used polar mapping. The parameterization is then found by solving a sparse linear system, and it provides a simple and visually-smooth piecewise linear mapping, without foldovers.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.971-976
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• 2002

The differential equations governing free vibrations of the elastic arches with unsymmetric axis are derived in rectangular coordinates rather than in polar coordinates, in which the effect of rotatory inertia is included. Frequencies and mode shapes are computed numerically for parabolic arches with both clamped ends and both hinged ends. Comparisons of natural frequencies between this study and SAP 2000 are made to validate theories and numerical methods developed herein. The convergent efficiency is highly improved under the newly derived differential equations in Rectangular coordinates. The lowest four natural frequency parameters are reported, with and without the rotatory inertia, as functions of three non-dimensional system parameters: the rise to chord length ratio, the span length to chord length ratio, and the slenderness ratio. Also typical mode shapes of vibrating arches are presented.

• Journal of The Institute of Information and Telecommunication Facilities Engineering
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• v.2 no.1
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• pp.71-77
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• 2003

본 논문에서는 불량 하드디스크 드라이브의 수리판정 자동화를 위해 필요한 하드디스크 드라이브(Hard Disk Drive, HDD) 결함의 분포패턴의 분류에 관한 연구 결과를 소개한다. HDD 제조공정에서는 테스트 진행 중 검출된 결함에 관한 정보를 HDD 내부에 기록한다. 불량으로 판별된 HDD는 내부에 기록된 결함의 분포론 관찰한 후, 불량의 종류 및 그에 따른 처리방안을 결정한다. 본 논문에서는 효율적인 결함분포 패턴의 특징추출을 위해, 하드디스크의 물리적 특성에 대한 분석을 바탕으로 극좌표 (Polar Coordinates) 방식으로 표현된 결함 위치 데이터를 직교좌표(Cartesian Coordinates)로 변환한다. 그리고 디스크 상의 두 동심원 사이의 공간을 정해진 회전각별로 등분한 후, 나누어진 구간별로 결함 발생빈도 히스토그램 (Histogram) 분석을 수행하여 결함분포의 패턴을 분류하는 알고리즘을 제시한다. 설계된 알고리즘은 실제 HDD 제조공정에서 발생한 불량 HDD Set을 대상으로 적용한 결과, 그 효용성이 검증되었다.

• 한국가시화정보학회:학술대회논문집
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• 2004.12a
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• pp.81-90
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• 2004

A zonal embedded grid technique has been developed for computation of the two-dimensional Navier-Stokes equations with cylindrical coordinates. The fundamental idea of the zonal embedded grid technique is that the number of azimuthal grids can be made small near the origin of the coordinates so that the grid size is more uniformly distributed over the domain than with the conventional regular-grid system. The code developed using this technique combined with the explicit, finite-volume method was then applied to calculation of the spin-up flows within a semi-circular cylinder. It was shown that the numerical results were in good agreement with the experimental results both qualitatively and quantitatively.

• Journal of Korea Multimedia Society
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• v.22 no.2
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• pp.299-310
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• 2019

Most web documents are written in Cartesian coordinates, so the study of vertical arrangement of text has been well organized, while the study of circular arrangement is very early. With the recent development of circular display devices, the demand for circular arrangement of texts is increasing. Thus, we proposed a CSS3 extended specification of polar coordinate layout for the circular placement of text. First, we defined the concept of fan model for the text arrangement in polar coordinate which is corresponding to box model in Cartesian coordinate. And, we described new definition on the directions of sentence, paragraph and text orientation in polar coordinate. Based on this new definitions, we developed the extended specification consisting of three parts. A part for setting the fan model, a part for setting directions, and a part for setting typesetting properties. To verify the feasibility of the proposed specification in current web browsers, a preprocessor was developed and sample contents were examined. We compared the code length of the sample contents implemented using other JavaScript library CssWarp.js so as to verify the efficiency of the proposed specification.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.44 no.3
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• pp.48-60
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• 2007

In previous researches for iris feature extraction, they transform a original iris image into rectangular one by stretching and interpolation, which causes the distortion of iris patterns. Consequently, it reduce iris recognition accuracy. So we are propose the method that extracts iris feature by using polar coordinates without distortion of iris patterns. Our proposed method has three strengths compared with previous researches. First, we extract iris feature directly from polar coordinate circular iris image. Though it requires a little more processing time, there is no degradation of accuracy for iris recognition and we compares the recognition performance of polar coordinate to rectangular type using by Hamming Distance, Cosine Distance and Euclidean Distance. Second, in general, the center position of pupil is different from that of iris due to camera angle, head position and gaze direction of user. So, we propose the method of iris feature detection based on polar coordinate circular iris region, which uses pupil and iris position and radius at the same time. Third, we overcome override point from iris patterns by using polar coordinates circular method. each overlapped point would be extracted from the same position of iris region. To overcome such problem, we modify Gabor filter's size and frequency on first track in order to consider low frequency iris patterns caused by overlapped points. Experimental results showed that EER is 0.29%, d' is 5,9 and EER is 0.16%, d' is 6,4 in case of using conventional rectangular image and proposed method, respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.7
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• pp.774-781
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• 2014

The radar measurements are composed of range, Doppler and angles which are expressed as polar-coordinate components. An approach to match the measurements with the states of target dynamics which are modeled in cartesian coordinates is to use the pseudo-measurements or the extended Kalman filter in order to solve the mismatching problem. Another approach is that the states of dynamics are modeled in polar coordinates and measurement equation is linear. However, this approach bears that we have to deal with a time-varying dynamics. In this study, it is proposed that the states of dynamics are expressed as polar-coordinate component and the system matrix of the dynamic equation is modeled as a time-invariant. Nonlinear terms that appear due to the proposed modeling are regarded as a system input. The results of a series of simulation runs indicate that the tracking filter that uses the proposed modeling is viable from the fact that the Doppler measurement is easy to be augmented in the measurement equation.

• Bulletin of the Society of Naval Architects of Korea
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• v.2 no.1
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• pp.15-19
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• 1965

The stability curves are very important data to decide the seaworthiness of all kinds of ships among waves. Both statical and dynamical stability curves on a rectangular coordinate system have broadly been handled at ship yards or at the government concerned, up to data. As concerns a method of obtaining a statical stability curve on polar coordinate system, the papers were presented once. Also, it is of use to research the dynamical stability curve on polar coordinate system. Author treated of the dynamical stability curve by four different methods, and tried to set the stability indicator inboard, adopted those proposals, in order to give some aids for good navigation on the sea. Fig. 1. shows a drawing method in case of the position of centre of buoyancy can be previously pointed out on the line corresponding to its inclination. Fig. 2. shows a method used a statical stability curve on polar coordinate. Fig. 3. shows a method obtained by the most simplified means. Fig. 4. shows dynamical stability curve made by geometrical expression method, instead of dynamical lever. A simple stability indicator which was mechanized above characteristics is attempted by author as shown Fig. 5 and Fig.6. It is demanded at hand, for more advanced improvement of such indicator.

• Proceedings of the Korean Information Science Society Conference
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• 1999.10b
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• pp.545-547
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• 1999

본 논문에서는 불량 하드디스크 드라이브의 수리판정 자동화를 위해 필요한 하드디스크 드라이브(Hard Disk Drive, HDD) 결함이 분포패턴의 분류에 관한 연구 결과를 소개한다. HDD 제조공정에서는 테스트 진행중 검출된 결함에 관한 정보를 HDD 내부에 기록한다. 불량으로 판별된 HDD는 내부에 기록된 결함의 분포를 관찰한 후, 불량의 종류 및 그에 따르는 처리방안을 결정한다. 본 논문에서는 효율적인 결함분포 패턴의 특징추출을 위해, 하드디스크의 물리적 특성에 대한 분석을 바탕으로 극좌표(Polar Coordinates) 방식으로 표현된 결함 위치데이터를 직교좌표(Cartesian Coordinates)로 변환한다. 그리고 디스크 상의 두 동심원 사이의 공간을 정해진 회전각별로 등분한 후, 나누어진 구간별로 결함 발생빈도 히스토그램(Histogram) 분석을 수행하여 결함분포의 패턴을 분류하는 알고리즘을 제시한다. 설계된 알고리즘은 실제 HDD 제조공정에서 발생한 불량 HDD Set을 대상으로 적용한 결과, 그 효용성이 검증되었다.