• 대한의용생체공학회:의공학회지
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• 제7권2호
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• pp.133-138
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• 1986

Abstract In a conventional digital sector scan system in the ultrasound medical imaging, the sampling space is in the polar coordinates while the display space is in the cartesian coordinates, which necessitates a coordinate transformation process resultion process resulting the overall system very complex and bulky. In this paper we propose a new architecture of the Digital-Scan-Converter (DSC) for the ultrasound sector scan system in which sampling space is the same as the display space, so the data are displayed as they are acquired without any interpola- tion process required. To implement the above real time DSC. two frequency synthesizes with very high switching time and a low-pass filter are required. The former determines the precise location of the data points and the latter fills the gap betw- een pixels in the horizontal direction.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 추계학술대회 논문집 학회본부
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• pp.222-224
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• 1995

This paper deals with 3-dimensional missile guidance law. This presents the general optimal solution of the state equation which includes the target maneuvering as the Gauss-Markov processing. The main results ore about the transformation between the Cartesian coordinates on which both the guidance law and the filter are bused and the polar coordinates system in real missile guidance and measurement information. And the extended Kalman filter and adjustment of the estimated target acceleration by triangular functions is proposed solution to this transformation problem. It is shown that this proposed transformation is valid in real 3-dimensional guidance problem by the computer simulation.

• Ocean and Polar Research
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• 제23권2호
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• pp.121-130
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• 2001

Geodetic datums define the size and shape of the earth and the origin and orientation of the coordinate systems used to map the earth. A lot of different datums have been developed and each nation uses its own datum as the basis for coordinate systems used to identify positions in geographic information systems. Recently GPS receivers are widely used to find out location and GPS is based on the World Geodetic System 1984(WGS-84) datum. Therefore the diversity of datums in use today requires accurate conversion between coordinates in different datums. In this study a coordinate conversion program on Windows is developed to transform between Tokyo Bessel(1941), which is the reference datum in Korea, and WGS-84. Several examples of coordinate conversion are presented and computed results are tested and proved to be correct.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1988년도 전기.전자공학 학술대회 논문집
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• pp.905-908
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• 1988

In recent, Kalman filter technique has been much used as one of technique for tracking of the moving target. But some problem are still remained to be resolved. For example, when Kalman filter technique is applied to nonlinear system, the technique is nonoptimal estimator. Therefore, extended Kalman filter is proposed to reduce modeling error for nonlinear system. In this study, an extended Kalman filter in Cartesian coordinates is described for moving target, when the radar sensor measures range, azimuth and elevation angle in polar coordinates. And an approximate gain computation algorithm is proposed. In this approach, Kalman gains are computed for three uncoupled filter and multiplied by a Jacobian transformation determined from the measured target position and orientation.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 하계학술대회 논문집 B
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• pp.556-558
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• 1995

This paper presents a new simplified method for finding the multiple load flow solutions and through their solutions the voltage stability can be evaluated. Line flow($P_{ij}$, $Q_{ij}$) may be formulated with the second-order equations for $V_{i}^{2}$ in polar coordinates or two circle equations for $e_{i}$ and $f_{i}$ in rectangular coordinates. Based on this feature, multiple load flow solutions are calculated with simple works, results of multiple load flow solutions are used for sensitivity analysis of voltage stability. Also, in the case that reactive power sources is considered, method of evaluating the voltage stability is introduced. The proposed method was validated to 2-bus and IEEE 6-bus system.

• Bulletin of the Korean Chemical Society
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• 제21권12호
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• pp.1227-1232
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• 2000

Near the conical intersection for the 1,2 $^{2}A'$ states of $H_3$ the derivative coupling vector is calculated and analyzed on the plane of internal coordinates, (U,V) or its polar coordinates $(S{\theta})$, based on the squares of the internuclear distances. It is shown that in the vicinity of the conical intersection the derivative coupling vector behaves like ${\theta}/2S$, which is responsible for the sign changes of the real-valued electronic wave function when the nuclear configuration traverses a closed path enclosing a conical intersection. The analytic property of the wave functions is studied and especially the observation of the sign change in the configuration state function (CSF) coefficients of the real-valued electronic wave functions is demonstrated.

• 융합보안논문지
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• 제6권2호
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• pp.71-80
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• 2006

센서네트워크는 매우 제한된 자원을 갖는 작은 노드들로 구성되어 온도, 진동 등의 지역적 정보를 수집하고 통신망을 통하여 이들 정보를 제공한다. 센서네트워크는 일반적으로 매우 작고 제한적인 자원을 갖는 노드들로 구성되므로 이러한 노드들에 보안 서비스를 추가하는 것은 상당히 어려운 문제이다. 센서네트워크의 안정성을 위해서는 일반 네트워크 노드들에 비하여 보다 더 효율적인 키 관리 기법이 필요하다. 본 논문에서는 원형 좌표계를 이용한 위치 정보를 기반으로 키 관리하는 기법을 제시한다. 원형좌표계의 원점을 중심으로 노드와 노드간의 상대적인 위치 정보를 이용하여 키를 생성하였다. 이러한 방법은 대칭적 위치 구조에 의해 키 생성이 다른 방법에 비하여 간결하면서도 효율적임을 보였다.

• 대한의용생체공학회:의공학회지
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• 제17권4호
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• pp.469-478
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• 1996

In the conventional digital ultrasound scanner, the reflected signal is sampled either in polar coordinates of R-$\theta$ method, or in Cartesian coordinates of uniform ladder algorithm (ULA). The R-$\theta$ scan method necessitates a coordinate transform process which makes hardware complex in comparison with ULA scan mrthoA In spite of this complexity, R-$\theta$ method has a good resolution in ultrasonographic (US) image, since scan direction of the US imaging is a radial direction. In this paper, a new digital scan converter is proposed, which is named the radius uniform ladder algorithm (RULA). The RULA has the rome scan direction as the US scanning in the radial direction and as the display space in the $\theta$ direction. In tllis new approach, sampled points we uniformly distributed in each horizontal line i.n well as in each radial ray so that the data are displayed in the Cartesian coordinates by the 1-D interpolation process. The propped algorithm has an uniform resolution in the periphery and the center field in comparison with equi-angle ULA and equi-interval ULA. To extend the scan angle, concentric square raster sampling (CSRS) is adopted with reduction of discontinuities on the junctions between horizontal scan and vertical scan. The discontinuities are reduced by using the hmction filtering along the $\theta$ direction.

• 한국소음진동공학회논문집
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• 제12권12호
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• pp.970-978
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• 2002

이제까지 아치의 자유진동에 관한 연구들은 모두 극좌표계에서 해석한 연구들이다. 이 논문은 극좌표계에서 아치의 해석을 지양하고, 직교좌표계에서 아치의 자유진동을 해석한 연구이다. 아치의 자유진동을 지배하는 미분방정식을 직교좌표계에서 유도하고. 이를 수치해석하여 고유진동수와와 진동형을 산출하였다. 미분방정식에는 회전관성 효과를 고려하고. 아치의 선형은 포물선으로 채택하였다. 실제 구조물에 대한 적용을 위하여 비대칭 축을 갖는 아치를 수치해석 하였다. 본 연구와 SAP 2000의 결과를 비교하여 본 연구의 타당성을 검증하였다. 수치해석의 결과로 아치의 무차원 변수들이 무차원 고유진동수에 미치는 영향을 분석하고. 전형적인 진동형의 예를 그림에 나타내었다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.191-193
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• 2006

This paper presents an analytical solution to predict magnetic field distribution of permanent magnet synchronous motor equipped with surface-mounted magnet by using transfer relations in terms of two-dimensional model in polar coordinates. The analytical results are validated by comparison with finite element analyses (FEA).