• Title/Summary/Keyword: 극좌표계

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Performance Improvement Approach to Naval Gun Fire Control System Based on Linear Target Tracking Filter with Radar Line-of-sight Measurements (레이다 시선 측정치를 활용하는 선형 표적 추적필터 기반 함포 사격제원계산장치 성능향상 방법)

  • Uisuk Suh
    • Journal of the Korea Institute of Military Science and Technology
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    • v.27 no.4
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    • pp.446-456
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    • 2024
  • This paper addresses a novel approach to performance enhancement of the naval gun fire control system(FCS) by using the projectile tracking filter without any distortion of radar measurements. Under the assumption that the maneuvering between the projectile and the ship equipped with the radar is not quite large, this method is based on the concept of polar-coordinate target tracking, which separates the range estimation filter and the direction cosine estimation filter. Note that using polar-coordinates allows tracking to be performed in the same coordinate system from which the radar line-of-sight(LOS) measurements are obtained, unlike the conventional tracking process in Cartesian. Also, it is easy to implement in real-time and guarantees consistent estimates due to its linear filter structure. With the help of the above method, therefore, the proposed filter is able to improve the overall performance of FCS which requires stability of projectile estimates within a short engagement time. The effectiveness of the presented scheme is validated through computer simulations.

A Study for Evaluating of Voltage Stability Margin Considering Shunt Capacitor (조상설비를 고려한 전압안정성 여유전력의 평가에 관한 연구)

  • 김세영
    • Journal of Energy Engineering
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    • v.7 no.1
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    • pp.65-72
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    • 1998
  • This paper presents a fast calculation method for evaluating of voltage stability margin (MW) using the line flow equation in polar form. Here, Line flow equations $(P_{ij},\;Q_{ij}$ are comprised of state variable, $V_i,\;{\Delta}_i,\;V_j$ and ${Delta}_j$, and line parameter, r and x. using the feature of polar coordinate, these becomes one equation with two variables, $V_j,;V_j$. Moreover, if bus j is slack or generator bus, which is specified voltage magnitude in load flow calculation, it becomes one equation with one variable $V_ i $ that is, may be formulated with the second-order equation for $V^2_i$. Therefore, multiple load flow solutions may be obtained with simple computation. The obtained load flow multiple solutions are used for evaluating of voltage stability through sensitivity analysis or its closeness. Also, the method is proposed to calculate for voltage stability margin considering shunt capacitor, which is important element for evaluating of voltage stability. The proposed method was validated to sample systems.

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The Rotating Multiple Display Signage System (회전형 멀티 디스플레이 사이니지 시스템)

  • Kang, Ye-Jin;Park, Goo-Man
    • Journal of Broadcast Engineering
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    • v.23 no.5
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    • pp.636-641
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    • 2018
  • Recently, the digital signages display not only the rectangular shapes but also the various shapes and sizes. The high-resolution large-screen display monitors have evolved to multi-vision modes in which several screens are connected to one another. In this paper, we present the structure of an atypically shaped signage system in which the ROI changes with the rotation of the multiple displays. The inclination angle of the monitor is calculated by taking the output value of the gyro sensor inter-locked with the Arduino, and an image in which the position of the four corners is varied according to the rotation angle by using the polar coordinate system. In order to display images in the multi-screen environment, multiple displays with a gyro sensor were controlled using serial communication. As the result, we have obtained the flexibly moving monitor systems with associated images fitting in them.

Face Recognition Based on Polar Coordinate Transform (극좌표계 변환에 기반한 얼굴 인식 방법)

  • Oh, Jae-Hyun;Kwak, No-Jun
    • Journal of the Institute of Electronics Engineers of Korea SP
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    • v.47 no.1
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    • pp.44-52
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    • 2010
  • In this paper, we propose a novel method for face recognition which uses polar coordinate instead of conventional cartesian coordinate. Among the central area of a face, we select a point as a pole and make a polar image of a face by evenly sampling pixels in each direction of 360 degrees around the pole. By applying conventional feature extraction methods to the polar image, the recognition rates are improved. The polar coordinate delineates near-pole area more vividly than the area far from the pole. In a face, important regions such as eyes, nose and mouth are concentrated on the central part of a face. Therefore, the polar coordinate of a face image can achieve more vivid representation of important facial regions compared to the conventional cartesian coordinate. The proposed polar coordinate transform was applied to Yale and FRGC databases and LDA and NLDA were used to extract features afterwards. The experimental results show that the proposed method performs better than the conventional cartesian images.

A SNR Estimation Algorithm for Digital Satellite Transponder (디지털 위성트랜스폰더를 위한 SNR 추정 알고리즘)

  • Seo, Kwang-Nam;Choi, Seung-Woon;Kim, Chong-Hoon
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.35 no.9C
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    • pp.729-734
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    • 2010
  • In the initial stage of the communications between a base station and a satellite transponder, the base station transmits the frequency-sweeping un-modulated up-link carrier within a certain frequency range to acquire the doppler frequency shift and signal power between the base station and the satellite in orbital flight. The satellite transponder acquires and tracks the carrier in order to initialize the communication. To control such initialization process, the satellite receiver should analyze the input carrier signal in various ways. This paper presents an SNR estimation algorithm to control the initialization process. The proposed algorithm converts the input signal into the baseband polar coordinate representation and estimates the SNR via the statistics of the angular signal components as well as the status parameters to control the receiver. The Monte-Carlo simulations shows the validity of the estimation proposed.

Analytical Investigation on Elastic Behaviors of Isotropic Annular Sector Plates Subjected to Uniform Loading (등분포하중을 받는 등방성 환형 섹터판의 탄성 거동에 대한 해석적 연구)

  • Kim, Kyung-Sik
    • Journal of Korean Society of Steel Construction
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    • v.22 no.3
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    • pp.241-251
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    • 2010
  • This paper presents the development of a new analytical solution to the governing differential equation for isotropic annular sector plates subjected to uniform loading in a three-dimensional polar coordinate system. The 4th order governing partial differential equation (PDE) was converted to an ordinary differential equation (ODE) by assuming the Levy-type series solution form and the subsequent mathematical operations. Finally, a series-type solution was assembled with homogeneous and nonhomogeneous solution parts after operating real values and complex conjugates derived from the characteristic equation. To demonstrate the convergence rate and the accuracy of the featured method, several examples with various sector angles were selected and solved. The deflections and internal moments in the example annular sector plates that were obtained from the proposed solution were compared with those obtained from other analytical studies and numerical analyses using the finite element analysis package program, ABAQUS. Very good agreement with the results of other analytical and numerical methodologies was shown.

Numerically Efficient Evaluation of MoM Matrix in Conjunction with the Closed-form Green s Functions in Analysis of Multi-layered Planar Structures (다층 평판구조체 해석시 Closed-form 그린함수와 함께한 모멘트 행렬의 효율적인 수치계산)

  • 이영순;김병철;조영기
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.12 no.1
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    • pp.92-98
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    • 2001
  • When analyzing the scatting problem of multi-layered planar structures using closed-form Green's function, one of the main difficulties is that the numerical integrations for the evaluation of diagonal matrix elements converge slowly and are not so stable. Accordingly, even when the integration fur the singularity of type $e^{-jkr}/{\gamma}$, corresponding to the source dipole itself, is performed using such a method, this difficulty persists in the integration corresponding to the finite number of complex images. In order to resolve this difficulty, a new technique based upon the Gaussian quadrature in polar coordinates for the evaluation of the two-dimensional generalized exponential integral is presented. Stability of the algorithm and convergence is discussed. Performance is demonstrated for the example of a microstrip patch antenna.

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Calculation of Satellite's Power Generation by the Earth Albedo (지구 알베도에 의한 위성의 생산전력 계산)

  • Choi, Won-Sub;Kim, Kiduck;Kim, Hae-Dong
    • Journal of Space Technology and Applications
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    • v.1 no.1
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    • pp.76-84
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    • 2021
  • Because solar panels of normal satellites are faced to the sun, the power generation by the Earth Albedo is almost neglected in satellite's power analysis. However, many cubesats don't have deployable solar panels and in this case the Earth Albedo is not negligible because solar panels are in six sides facing different directions. In this paper, we calculated satellite's power generation by the Earth Albedo. We divided the Earth's surface into grids based on polar coordinate system. We modeled power generation in each solar cell by reflection on these grids. We simulated 1 U cubesat which flies in sun synchronous orbit and 500 km altitude so that we calculated satellite's power generation by the Earth Albedo.

Feature Extraction in 3-Dimensional Object with Closed-surface using Fourier Transform (Fourier Transform을 이용한 3차원 폐곡면 객체의 특징 벡터 추출)

  • 이준복;김문화;장동식
    • Journal of the Institute of Convergence Signal Processing
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    • v.4 no.3
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    • pp.21-26
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    • 2003
  • A new method to realize 3-dimensional object pattern recognition system using Fourier-based feature extractor has been proposed. The procedure to obtain the invariant feature vector is as follows ; A closed surface is generated by tracing the surface of object using the 3-dimensional polar coordinate. The centroidal distances between object's geometrical center and each closed surface points are calculated. The distance vector is translation invariant. The distance vector is normalized, so the result is scale invariant. The Fourier spectrum of each normalized distance vector is calculated, and the spectrum is rotation invariant. The Fourier-based feature generating from above procedure completely eliminates the effect of variations in translation, scale, and rotation of 3-dimensional object with closed-surface. The experimental results show that the proposed method has a high accuracy.

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Projection-type Fast Spin Echo Imaging (프로젝션 타입 고속 스핀 에코 영상)

  • 김휴정;김치영;김상묵;안창범
    • Investigative Magnetic Resonance Imaging
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    • v.4 no.1
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    • pp.42-51
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    • 2000
  • Purpose: Projection-type Fast Spin Echo (PFSE) imaging is robust to patient motion or flow related artifact compared to conventional Fast Spin Echo (FSE) imaging, however, it has difficulty in controlling $T_2$ contrast. In this paper, Tz contrast in the PFSE method is analyzed and compared with those of the FSE method with various effective echo times by computer simulation. The contrasts in the FSE and PFSE methods are also compared by experiments with volunteers. From the analysis and simulation, it is shown that ${T_2}-weighted$ images can well be obtained by the PFSE method proposed. Materials and methods: Pulse sequence for the PFSE method is implemented at a 1.0 Tesla whole body MRI system and $T_2$ contrasts in the PFSE and FSE methods are analyzed by computer simulation and experiment with volunteers. For the simulation, a mathematical phantom composed of various $T_2$ values is devised and $T_2$ contrast in the reconstructed image by the PFSE is compared to those by the FSE method with various effective echo times. Multi-slice ${T_2}-weighted$ head images of the volunteers obtained by the PFSE method are also shown in comparison with those by the FSE method at a 1.0 Tesla whole body MRI system. Results: From the analysis, $T_2$ contrast by the PFSE method appears similar to those by the FSE method with the effective echo time in a range of SO-lOOms. Using a mathematical phantom, contrast in the PFSE image appears close to that by the FSE method with the effective echo time of 96ms. From experiment with volunteers, multi-slice $T_2-weighted$ images are obtained by the PFSE method having contrast similar to that of the FSE method with the effective echo time of 96ms. Reconstructed images by the PFSE method show less motion related artifact compared to those by the FSE method. Conclusion: The projection-type FSE imaging acquires multiple radial lines with different angles in polar coordinate in k space using multiple spin echoes. The PFSE method is robust to patient motion or flow, however, it has difficulty in controlling $T_2$ contrast compared to the FSE method. In this paper, it is shown that the PFSE method provides good $T_2$ contrast (${T_2}-weighted$ images) similar to the FSE method by both computer simulation and experiments with volunteers.

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