• Title/Summary/Keyword: gradient algorithm

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Optimization of Image Tracking Algorithm Used in 4D Radiation Therapy (4차원 방사선 치료시 영상 추적기술의 최적화)

  • Park, Jong-In;Shin, Eun-Hyuk;Han, Young-Yih;Park, Hee-Chul;Lee, Jai-Ki;Choi, Doo-Ho
    • Progress in Medical Physics
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    • v.23 no.1
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    • pp.8-14
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    • 2012
  • In order to develop a Patient respiratory management system includinga biofeedback function for4-dimentional radiation therapy, this study investigated anoptimal tracking algorithmfor moving target using IR (Infra-red) camera as well as commercial camera. A tracking system was developed by LabVIEW 2010. Motion phantom images were acquired using a camera (IR or commercial). After image process were conducted to convert acquired image to binary image by applying a threshold values, several edge enhance methods such as Sobel, Prewitt, Differentiation, Sigma, Gradient, Roberts, were applied. The targetpattern was defined in the images, and acquired image from a moving targetwas tracked by matching pre-defined tracking pattern. During the matching of imagee, thecoordinateof tracking point was recorded. In order to assess the performance of tracking algorithm, the value of score which represents theaccuracy of pattern matching was defined. To compare the algorithm objectively, we repeat experiments 3 times for 5 minuts for each algorithm. Average valueand standard deviations (SD) of score were automatically calculatedsaved as ASCII format. Score of threshold only was 706, and standard deviation was 84. The value of average and SD for other algorithms which combined edge detection method and thresholdwere 794, 64 in Sobel, 770, 101 in Differentiation, 754, 85 in Gradient, 763, 75 in Prewitt, 777, 93 in Roberts, and 822, 62 in Sigma, respectively. According to score analysis, the most efficient tracking algorithm is the Sigma method. Therefore, 4-dimentional radiation threapy is expected tobemore efficient if threshold and Sigma edge detection method are used together in target tracking.

Thermal Analysis of Composite Satellite Antenna Structure in Space Environment (복합재 통신위성 안테나의 우주환경 열해석)

  • ;;;;Frank Gilles
    • Proceedings of the Korean Society For Composite Materials Conference
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    • 2002.05a
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    • pp.77-80
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    • 2002
  • Thermal analysis has been performed to evaluate the thermal effect on composite antenna (Ka-band) structure in space environment. The concepts of thermal control are also presented to maintain the antenna components within respective temperature limits. A steady-state algorithm of I-DEAS' thermal analysis software was utilized to predict both maximum and minimum temperature, maximum gradient temperature, and temperature distribution on each antenna component.

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A domain decomposition method applied to queuing network problems

  • Park, Pil-Seong
    • Communications of the Korean Mathematical Society
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    • v.10 no.3
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    • pp.735-750
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    • 1995
  • We present a domain decomposition algorithm for solving large sparse linear systems of equations arising from queuing networks. Such techniques are attractive since the problems in subdomains can be solved independently by parallel processors. Many of the methods proposed so far use some form of the preconditioned conjugate gradient method to deal with one large interface problem between subdomains. However, in this paper, we propose a "nested" domain decomposition method where the subsystems governing the interfaces are small enough so that they are easily solvable by direct methods on machines with many parallel processors. Convergence of the algorithms is also shown.lso shown.

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STRONG CONVERGENCE OF AN ITERATIVE ALGORITHM FOR SYSTEMS OF VARIATIONAL INEQUALITIES AND FIXED POINT PROBLEMS IN q-UNIFORMLY SMOOTH BANACH SPACES

  • Jeong, Jae Ug
    • Korean Journal of Mathematics
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    • v.20 no.2
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    • pp.225-237
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    • 2012
  • In this paper, we introduce a new iterative scheme to investigate the problem of nding a common element of nonexpansive mappings and the set of solutions of generalized variational inequalities for a $k$-strict pseudo-contraction by relaxed extra-gradient methods. Strong convergence theorems are established in $q$-uniformly smooth Banach spaces.

A LOGARITHMIC CONJUGATE GRADIENT METHOD INVARIANT TO NONLINEAR SCALING

  • Moghrabi, I.A.
    • Journal of the Korean Society for Industrial and Applied Mathematics
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    • v.8 no.2
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    • pp.15-21
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    • 2004
  • A Conjugate Gradiant (CG) method is proposed for unconstained optimization which is invariant to a nonlinear scaling of a strictly convex quadratic function. The technique has the same properties as the classical CG-method when applied to a quadratic function. The algorithm derived here is based on a logarithmic model and is compared to the standard CG method of Fletcher and Reeves [3]. Numerical results are encouraging and indicate that nonlinear scaling is promising and deserves further investigation.

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STRONG CONVERGENCE OF AN ITERATIVE ALGORITHM FOR A MODIFIED SYSTEM OF VARIATIONAL INEQUALITIES AND A FINITE FAMILY OF NONEXPANSIVE MAPPINGS IN BANACH SPACES

  • JEONG, JAE UG
    • Korean Journal of Mathematics
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    • v.23 no.3
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    • pp.409-425
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    • 2015
  • In this paper, a new iterative scheme based on the extra-gradient-like method for finding a common element of the set of fixed points of a finite family of nonexpansive mappings and the set of solutions of modified variational inequalities in Banach spaces. A strong convergence theorem for this iterative scheme in Banach spaces is established. Our results extend recent results announced by many others.

A METHOD FOR ADJUSTING ADAPTIVELY THE WEIGHT OF FEATURE IN MULTI-DIMENSIONAL FEATURE VECTOR MATCHING

  • Ye, Chul-Soo
    • Proceedings of the KSRS Conference
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    • v.2
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    • pp.772-775
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    • 2006
  • Muilti-dimensional feature vector matching algorithm uses multiple features such as intensity, gradient, variance, first or second derivative of a pixel to find correspondence pixels in stereo images. In this paper, we proposed a new method for adjusting automatically the weight of feature in multi-dimensional feature vector matching considering sharpeness of a pixel in feature vector distance curve. The sharpeness consists of minimum and maximum vector distances of a small window mask. In the experiment we used IKONOS satellite stereo imagery and obtained accurate matching results comparable to the manual weight-adjusting method.

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A station-keeping method considering satellite attitude (자세를 고려한 위성체 궤도유지 기법)

  • 박재훈;이장규;김유단;최재원
    • 제어로봇시스템학회:학술대회논문집
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    • 1993.10a
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    • pp.799-804
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    • 1993
  • In this paper, the scheme of combining the orbit correction and attitude control of a 3-axis stabilized satellite is suggested. Being coupled and complimentary, it is preferable to achieve the required orbit correction and the desired attitude control simultaneously. A solution of the probes simultaneous control of orbit correction and attitude of a satellite, is obtained by solving the two point boundary value problem numerically. The first-order gradient algorithm is used to solve the numerical problem. The simulation results show that the East-West station keeping process with the combined system of an orbit correction and an attitude control is satisfactory.

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Adaptive sliding-mode tracking control in the presence of unmodeled dynamics

  • Cho, Seung-Ho
    • 제어로봇시스템학회:학술대회논문집
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    • 1994.10a
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    • pp.267-270
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    • 1994
  • To increase the robustness of tile feedforward tracking control system, a new discrete time sliding function has been defined and utilized for the formulation of control law, In adaptive case the robustness is achieved by using both a normalized gradient algorithm with deadzone and a sliding function-based nonlinear feedback, while in nonadaptive case by using only a sliding function-based nonlinear feedback.

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