A Parallel Nonrigid Registration Algorithm Based on B-Spline for Medical Images
Directory of Open Access Journals (Sweden)
Xiaogang Du
2016-01-01
Full Text Available The nonrigid registration algorithm based on B-spline Free-Form Deformation (FFD plays a key role and is widely applied in medical image processing due to the good flexibility and robustness. However, it requires a tremendous amount of computing time to obtain more accurate registration results especially for a large amount of medical image data. To address the issue, a parallel nonrigid registration algorithm based on B-spline is proposed in this paper. First, the Logarithm Squared Difference (LSD is considered as the similarity metric in the B-spline registration algorithm to improve registration precision. After that, we create a parallel computing strategy and lookup tables (LUTs to reduce the complexity of the B-spline registration algorithm. As a result, the computing time of three time-consuming steps including B-splines interpolation, LSD computation, and the analytic gradient computation of LSD, is efficiently reduced, for the B-spline registration algorithm employs the Nonlinear Conjugate Gradient (NCG optimization method. Experimental results of registration quality and execution efficiency on the large amount of medical images show that our algorithm achieves a better registration accuracy in terms of the differences between the best deformation fields and ground truth and a speedup of 17 times over the single-threaded CPU implementation due to the powerful parallel computing ability of Graphics Processing Unit (GPU.
Non-Rigid Image Registration Algorithm Based on B-Splines Approximation
Institute of Scientific and Technical Information of China (English)
ZHANG Hongying; ZHANG Jiawan; SUN Jizhou; SUN Yigang
2007-01-01
An intensity-based non-rigid registration algorithm is discussed, which uses Gaussian smoothing to constrain the transformation to be smooth, and thus preserves the topology of images. In view of the insufficiency of the uniform Gaussian filtering of the deformation field, an automatic and accurate non-rigid image registration method based on B-splines approximation is proposed. The regularization strategy is adopted by using multi-level B-splines approximation to regularize the dis-placement fields in a coarse-to-fine manner. Moreover, it assigns the different weights to the estimated displacements according to their reliabilities. In this way, the level of regularity can be adapted locally. Experiments were performed on both synthetic and real medical images of brain, and the results show that the proposed method improves the registration accuracy and robustness.
融合SIFT的B样条红外图像非刚性配准%B-spline non-rigid registration algorithm for infrared image based on SIFT
Institute of Scientific and Technical Information of China (English)
卢朝梁; 马丽华; 陈豪; 张薇; 于敏; 崔树民
2014-01-01
手持式广角镜头红外热像仪所拍摄的不同时刻红外图像具有刚性形变和非刚性形变，传统图像配准算法很难同时矫正刚性形变与非刚性形变，针对该问题，提出一种融合SIFT的B样条配准算法。首先在待配准图像中建立控制网格，其次运用SIFT算法寻找待配准与基准图像间的匹配点对，剔除错误匹配点对并计算出待配准图像与基准图像间的刚性变换参数，接着对控制点进行刚性变换，最后以局部强度和为测度函数，运用B样条非刚性配准算法对广角镜头引起图像的非线性进行矫正。对比实验结果表明，本文算法具有很高配准精度，能够满足实际工程精度要求。%Infrared images obtained by handheld infrared camera with wide-angle lens have rigid and non-rigid deform-ations. Tradition image registration algorithm is difficult to correct the rigid and non-rigid deformations. To solve this problem,B-spline non-rigid registration algorithm based on SIFT is proposed. At first,the control mesh is created in the input image. Then,matching points between input image and template image are found by SIFT algorithm. The rigid transformation parameters are calculated after ignoring the incorrect matching points. Next,the control points are transformed by rigid transformation parameters. Finally,the sum of pattern intensity is used as measurement,and the nonlinear transformation of the image that is caused by wide-angle lens is corrected by B-spline non-rigid registration algorithm. The results of comparison show that the new method has better registration accuracy and it also can meet the requirements of practical engineering accuracy.
Segmented Regression Based on B-Splines with Solved Examples
Directory of Open Access Journals (Sweden)
Miloš Kaňka
2015-12-01
Full Text Available The subject of the paper is segmented linear, quadratic, and cubic regression based on B-spline basis functions. In this article we expose the formulas for the computation of B-splines of order one, two, and three that is needed to construct linear, quadratic, and cubic regression. We list some interesting properties of these functions. For a clearer understanding we give the solutions of a couple of elementary exercises regarding these functions.
Fingerprint Representation Methods Based on B-Spline Functions
Institute of Scientific and Technical Information of China (English)
Ruan Ke; Xia De-lin; Yan Pu-liu
2004-01-01
The global characteristics of a fingerprint image such as the ridge shape and ridge topology are often ignored in most automatic fingerprint verification system. In this paper, a new representative method based on B-Spline curve is proposed to address this problem. The resultant B-Spline curves can represent the global characteristics completely and the curves are analyzable and precise. An algorithm is also proposed to extract the curves from the fingerprint image. In addition to preserve the most information of the fingerprint image, the knot-points number of the B-Spline curve is reduced to minimum in this algorithm. At the same time, the influence of the fingerprint image noise is discussed. In the end, an example is given to demonstrate the effectiveness of the representation method.
Chen, Jian; Tustison, Nicholas J.; Amini, Amir A.
2006-03-01
In this paper, an improved framework for estimation of 3-D left-ventricular deformations from tagged MRI is presented. Contiguous short- and long-axis tagged MR images are collected and are used within a 4-D B-Spline based deformable model to determine 4-D displacements and strains. An initial 4-D B-spline model fitted to sparse tag line data is first constructed by minimizing a 4-D Chamfer distance potential-based energy function for aligning isoparametric planes of the model with tag line locations; subsequently, dense virtual tag lines based on 2-D phase-based displacement estimates and the initial model are created. A final 4-D B-spline model with increased knots is fitted to the virtual tag lines. From the final model, we can extract accurate 3-D myocardial deformation fields and corresponding strain maps which are local measures of non-rigid deformation. Lagrangian strains in simulated data are derived which show improvement over our previous work. The method is also applied to 3-D tagged MRI data collected in a canine.
B-SPLINE-BASED SVM MODEL AND ITS APPLICATIONS TO OIL WATER-FLOODED STATUS IDENTIFICATION
Institute of Scientific and Technical Information of China (English)
Shang Fuhua; Zhao Tiejun; Yi Xiongying
2007-01-01
A method of B-spline transform for signal feature extraction is developed. With the B-spline,the log-signal space is mapped into the vector space. An efficient algorithm based on Support Vector Machine (SVM) to automatically identify the water-flooded status of oil-saturated stratum is described.The experiments show that this algorithm can improve the performances for the identification and the generalization in the case of a limited set of samples.
Dominant point detecting based non-uniform B-spline approximation for grain contour
Institute of Scientific and Technical Information of China (English)
ZHAO XiuYang; YIN YanSheng; YANG Bo
2007-01-01
Three-dimension reconstruction from serial sections has been used in the last decade to obtain information concerning three-dimensional microstructural geometry. One of the crucial steps of three-dimension reconstruction is getting compact and fairing grain contours. Based on the achievement of closed raw contours of ceramic composite grains by using wavelet and level set, an adaptive method is adopted for the polygonal approximation of the digitized raw contours. Instead of setting a fixed length of support region in advance, the novel method computes the suitable length of support region for each point to find the best estimated curvature. The dominant points are identified as the points with local maximum estimated curvatures. Periodic closed B-spline approximation is used to find the most compact B-spline grain boundary contours within the given tolerance. A flexible distance selection approach is adopted to obtain the common knot vector of serial contours consisting of less knots that contain enough degrees of freedom to guarantee the existence of a B-spline curve interpolating each contour. Finally, a B-spline surface interpolating the serial contours is generated via B-spline surface skinning.
Dominant point detecting based non-uniform B-spline approximation for grain contour
Institute of Scientific and Technical Information of China (English)
2007-01-01
Three-dimension reconstruction from serial sections has been used in the last decade to obtain information concerning three-dimensional microstructural ge-ometry. One of the crucial steps of three-dimension reconstruction is getting compact and fairing grain contours. Based on the achievement of closed raw con-tours of ceramic composite grains by using wavelet and level set, an adaptive method is adopted for the polygonal approximation of the digitized raw contours. Instead of setting a fixed length of support region in advance, the novel method computes the suitable length of support region for each point to find the best es-timated curvature. The dominant points are identified as the points with local maximum estimated curvatures. Periodic closed B-spline approximation is used to find the most compact B-spline grain boundary contours within the given tolerance. A flexible distance selection approach is adopted to obtain the common knot vector of serial contours consisting of less knots that contain enough degrees of freedom to guarantee the existence of a B-spline curve interpolating each contour. Finally, a B-spline surface interpolating the serial contours is generated via B-spline surface skinning.
Short-Term Wind Speed Forecast Based on B-Spline Neural Network Optimized by PSO
Directory of Open Access Journals (Sweden)
Zhongqiang Wu
2015-01-01
Full Text Available Considering the randomness and volatility of wind, a method based on B-spline neural network optimized by particle swarm optimization is proposed to predict the short-term wind speed. The B-spline neural network can change the division of input space and the definition of basis function flexibly. For any input, only a few outputs of hidden layers are nonzero, the outputs are simple, and the convergence speed is fast, but it is easy to fall into local minimum. The traditional method to divide the input space is thoughtless and it will influence the final prediction accuracy. Particle swarm optimization is adopted to solve the problem by optimizing the nodes. Simulated results show that it has higher prediction accuracy than traditional B-spline neural network and BP neural network.
Shape Parameterization in Aircraft Design: A Novel Method, Based on B-Splines
Straathof, M.H.
2012-01-01
This thesis introduces a new parameterization technique based on the Class-Shape-Transformation (CST) method. The new technique consists of an extension to the CST method in the form of a refinement function based on B-splines. This Class-Shape-Refinement-Transformation (CSRT) method has the same ad
A new wavelet-based thin plate element using B-spline wavelet on the interval
Jiawei, Xiang; Xuefeng, Chen; Zhengjia, He; Yinghong, Zhang
2008-01-01
By interacting and synchronizing wavelet theory in mathematics and variational principle in finite element method, a class of wavelet-based plate element is constructed. In the construction of wavelet-based plate element, the element displacement field represented by the coefficients of wavelet expansions in wavelet space is transformed into the physical degree of freedoms in finite element space via the corresponding two-dimensional C1 type transformation matrix. Then, based on the associated generalized function of potential energy of thin plate bending and vibration problems, the scaling functions of B-spline wavelet on the interval (BSWI) at different scale are employed directly to form the multi-scale finite element approximation basis so as to construct BSWI plate element via variational principle. BSWI plate element combines the accuracy of B-spline functions approximation and various wavelet-based elements for structural analysis. Some static and dynamic numerical examples are studied to demonstrate the performances of the present element.
B-spline image model for energy minimization-based optical flow estimation.
Le Besnerais, Guy; Champagnat, Frédéric
2006-10-01
Robust estimation of the optical flow is addressed through a multiresolution energy minimization. It involves repeated evaluation of spatial and temporal gradients of image intensity which rely usually on bilinear interpolation and image filtering. We propose to base both computations on a single pyramidal cubic B-spline model of image intensity. We show empirically improvements in convergence speed and estimation error and validate the resulting algorithm on real test sequences.
River Flow Lane Detection and Kalman Filtering-Based B-Spline Lane Tracking
Directory of Open Access Journals (Sweden)
King Hann Lim
2012-01-01
Full Text Available A novel lane detection technique using adaptive line segment and river flow method is proposed in this paper to estimate driving lane edges. A Kalman filtering-based B-spline tracking model is also presented to quickly predict lane boundaries in consecutive frames. Firstly, sky region and road shadows are removed by applying a regional dividing method and road region analysis, respectively. Next, the change of lane orientation is monitored in order to define an adaptive line segment separating the region into near and far fields. In the near field, a 1D Hough transform is used to approximate a pair of lane boundaries. Subsequently, river flow method is applied to obtain lane curvature in the far field. Once the lane boundaries are detected, a B-spline mathematical model is updated using a Kalman filter to continuously track the road edges. Simulation results show that the proposed lane detection and tracking method has good performance with low complexity.
Ship hull plate processing surface fairing with constraints based on B-spline
Institute of Scientific and Technical Information of China (English)
无
2005-01-01
The problem of ship hull plate processing surface fairing with constraints based on B-spline is solved in this paper. The algorithm for B-spline curve fairing with constraints is one of the most common methods in plane curve fairing. The algorithm can be applied to global and local curve fairing. It can constrain the perturbation range of the control points and the shape variation of the curve, and get a better fairing result in plane curves. In this paper, a new fairing algorithm with constraints for curves and surfaces in space is presented. Then this method is applied to the experiments of ship hull plate processing surface. Finally numerical results are obtained to show the efficiency of this method.
A Numerical Method Based on Daubechies Wavelet Basis and B-Spline Patches for Elasticity Problems
Directory of Open Access Journals (Sweden)
Yanan Liu
2016-01-01
Full Text Available The Daubechies (DB wavelets are used for solving 2D plane elasticity problems. In order to improve the accuracy and stability in computation, the DB wavelet scaling functions in 0,+∞ comprising boundary scaling functions are chosen as basis functions for approximation. The B-spline patches used in isogeometry analysis method are constructed to describe the problem domain. Through the isoparametric analysis approach, the function approximation and relevant computation based on DB wavelet functions are implemented on B-spline patches. This work makes an attempt to break the limitation that problems only can be discretized on uniform grids in the traditional wavelet numerical method. Numerical examples of 2D elasticity problems illustrate that this kind of analysis method is effective and stable.
Geometry Modeling of Ship Hull Based on Non-uniform B-spline
Institute of Scientific and Technical Information of China (English)
WANG Hu; ZOU Zao-jian
2008-01-01
In order to generate the three-dimensional (3-D) hull surface accurately and smoothly, a mixed method which is made up of non-uniform B-spline together with an iterative procedure was developed. By using the iterative method the data points on each section curve are calculated and the generalized waterlines and transverse section curves are determined. Then using the non-uniform B-spline expression, the control vertex net of the hull is calculated based on the generalized waterlines and section curves. A ship with tunnel stern was taken as test case. The numerical results prove that the proposed approach for geometry modeling of 3-D ship hull surface is accurate and effective.
One Fairing Method of Cubic B-spline Curves Based on Weighted Progressive Iterative Approximation
Institute of Scientific and Technical Information of China (English)
ZHANG Li; YANG Yan; LI Yuan-yuan; TAN Jie-qing
2014-01-01
A new method to the problem of fairing planar cubic B-spline curves is introduced in this paper. The method is based on weighted progressive iterative approximation (WPIA for short) and consists of following steps:finding the bad point which needs to fair, deleting the bad point, re-inserting a new data point to keep the structure of the curve and applying WPIA method with the new set of the data points to obtain the faired curve. The new set of the data points is formed by the rest of the original data points and the new inserted point. The method can be used for shape design and data processing. Numerical examples are provided to demonstrate the effectiveness of the method.
Directory of Open Access Journals (Sweden)
Shanshan He
2015-10-01
Full Text Available Piecewise linear (G01-based tool paths generated by CAM systems lack G1 and G2 continuity. The discontinuity causes vibration and unnecessary hesitation during machining. To ensure efficient high-speed machining, a method to improve the continuity of the tool paths is required, such as B-spline fitting that approximates G01 paths with B-spline curves. Conventional B-spline fitting approaches cannot be directly used for tool path B-spline fitting, because they have shortages such as numerical instability, lack of chord error constraint, and lack of assurance of a usable result. Progressive and Iterative Approximation for Least Squares (LSPIA is an efficient method for data fitting that solves the numerical instability problem. However, it does not consider chord errors and needs more work to ensure ironclad results for commercial applications. In this paper, we use LSPIA method incorporating Energy term (ELSPIA to avoid the numerical instability, and lower chord errors by using stretching energy term. We implement several algorithm improvements, including (1 an improved technique for initial control point determination over Dominant Point Method, (2 an algorithm that updates foot point parameters as needed, (3 analysis of the degrees of freedom of control points to insert new control points only when needed, (4 chord error refinement using a similar ELSPIA method with the above enhancements. The proposed approach can generate a shape-preserving B-spline curve. Experiments with data analysis and machining tests are presented for verification of quality and efficiency. Comparisons with other known solutions are included to evaluate the worthiness of the proposed solution.
Conformal interpolating algorithm based on B-spline for aspheric ultra-precision machining
Li, Chenggui; Sun, Dan; Wang, Min
2006-02-01
Numeric control machining and on-line compensation for aspheric surface are key techniques for ultra-precision machining. In this paper, conformal cubic B-spline interpolating curve is first applied to fit the character curve of aspheric surface. Its algorithm and process are also proposed and imitated by Matlab7.0 software. To evaluate the performance of the conformal B-spline interpolation, comparison was made between linear and circular interpolations. The result verifies this method can ensure smoothness of interpolating spline curve and preserve original shape characters. The surface quality interpolated by B-spline is higher than by line and by circle arc. The algorithm is benefit to increasing the surface form precision of workpiece during ultra-precision machining.
A new extension algorithm for cubic B-splines based on minimal strain energy
Institute of Scientific and Technical Information of China (English)
MO Guo-liang; ZHAO Ya-nan
2006-01-01
Extension ora B-spline curve or surface is a useful function in a CAD system. This paper presents an algorithm for extending cubic B-spline curves or surfaces to one or more target points. To keep the extension curve segment GC2-continuous with the original one, a family of cubic polynomial interpolation curves can be constructed. One curve is chosen as the solution from a sub-class of such a family by setting one GC2 parameter to be zero and determining the second GC2 parameter by minimizing the strain energy. To simplify the final curve representation, the extension segment is reparameterized to achieve C2-continuity with the given B-spline curve, and then knot removal from the curve is done. As a result, a sub-optimized solution subject to the given constraints and criteria is obtained. Additionally, new control points of the extension B-spline segment can be determined by solving lower triangular linear equations. Some computing examples for comparing our method and other methods are given.
The structure of uniform B-spline curves with parameters
Institute of Scientific and Technical Information of China (English)
Juan Cao; Guozhao Wang
2008-01-01
The shape-adjustable curve constructed by uniform B-spline basis function with parameter is an extension of uniform B-spline curve. In this paper, we study the relation between the uniform B-spline basis functions with parameter and the B-spline basis functions. Based on the degree elevation of B-spline, we extend the uniform B-spline basis functions with parameter to ones with multiple parameters. Examples show that the proposed basis functions provide more flexibility for curve design.
Non-Rigid Medical Image Registration with Joint Histogram Estimation Based on Mutual Information
Institute of Scientific and Technical Information of China (English)
LU Xuesong; ZHANG Su; SU He; CHEN Yazhu
2007-01-01
A mutual information-based non-rigid medical image registration algorithm is presented. An approximate function of Harming windowed sinc is used as kernel function of partial volume (PV)interpolation to estimate the joint histogram, which is the key to calculating the mutual information. And a new method is proposed to compute the gradient of mutual information with respect to themodel parameters. The transformation of object is modeled by a free-form deformation (FFD) based on B-splines. The experiments on 3D synthetic and real image data show that the algorithm can con-verge at the global optimum and restrain the emergency of local extreme.
Wen, W. B.; Duan, S. Y.; Yan, J.; Ma, Y. B.; Wei, K.; Fang, D. N.
2016-11-01
An explicit time integration scheme based on quartic B-splines is presented for solving linear structural dynamics problems. The scheme is of a one-parameter family of schemes where free algorithmic parameter controls stability, accuracy and numerical dispersion. The proposed scheme possesses at least second-order accuracy and at most third-order accuracy. A 2D wave problem is analyzed to demonstrate the effectiveness of the proposed scheme in reducing high-frequency modes and retaining low-frequency modes. Except for general structural dynamics, the proposed scheme can be used effectively for wave propagation problems in which numerical dissipation is needed to reduce spurious oscillations.
Institute of Scientific and Technical Information of China (English)
温伟斌; 蹇开林; 骆少明
2013-01-01
A new numerical manifold (NMM) method is derived on the basis of quartic uniform B-spline interpolation. The analysis shows that the new interpolation function possesses higher-order continuity and polynomial consistency compared with the conven-tional NMM. The stiffness matrix of the new element is well-conditioned. The proposed method is applied for the numerical example of thin plate bending. Based on the prin-ciple of minimum potential energy, the manifold matrices and equilibrium equation are deduced. Numerical results reveal that the NMM has high interpolation accuracy and rapid convergence for the global cover function and its higher-order partial derivatives.
Wen, W. B.; Duan, S. Y.; Yan, J.; Ma, Y. B.; Wei, K.; Fang, D. N.
2017-03-01
An explicit time integration scheme based on quartic B-splines is presented for solving linear structural dynamics problems. The scheme is of a one-parameter family of schemes where free algorithmic parameter controls stability, accuracy and numerical dispersion. The proposed scheme possesses at least second-order accuracy and at most third-order accuracy. A 2D wave problem is analyzed to demonstrate the effectiveness of the proposed scheme in reducing high-frequency modes and retaining low-frequency modes. Except for general structural dynamics, the proposed scheme can be used effectively for wave propagation problems in which numerical dissipation is needed to reduce spurious oscillations.
Quadrotor system identification using the multivariate multiplex b-spline
Visser, T.; De Visser, C.C.; Van Kampen, E.J.
2015-01-01
A novel method for aircraft system identification is presented that is based on a new multivariate spline type; the multivariate multiplex B-spline. The multivariate multiplex B-spline is a generalization of the recently introduced tensor-simplex B-spline. Multivariate multiplex splines obtain simil
Institute of Scientific and Technical Information of China (English)
Xiang Jiawei; He Zhengjia; Chen Xuefeng
2006-01-01
Based on B-spline wavelet on the interval (BSWI), two classes of truncated conical shell elements were constructed to solve axisymmetric problems, i.e. BSWI thin truncated conical shell element and BSWI moderately thick truncated conical shell element with independent slopedeformation interpolation. In the construction of wavelet-based element, instead of traditional polynomial interpolation, the scaling functions of BSWI were employed to form the shape functions through the constructed elemental transformation matrix, and then construct BSWI element via the variational principle. Unlike the process of direct wavelets adding in the wavelet Galerkin method, the elemental displacement field represented by the coefficients of wavelets expansion was transformed into edges and internal modes via the constructed transformation matrix. BSWI element combines the accuracy of B-spline function approximation and various wavelet-based lements for structural analysis. Some static and dynamic numerical examples of conical shells were studied to demonstrate the present element with higher efficiency and precision than the traditional element.
Adaptive Parametrization of Multivariate B-splines for Image Registration
DEFF Research Database (Denmark)
Hansen, Michael Sass; Glocker, Benjamin; Navab, Nassir;
2008-01-01
cost function. In the current work we introduce multivariate B-splines as a novel alternative to the widely used tensor B-splines enabling us to make efficient use of the derived measure.The multivariate B-splines of order n are Cn- 1 smooth and are based on Delaunay configurations of arbitrary 2D or 3......D control point sets. Efficient algorithms for finding the configurations are presented, and B-splines are through their flexibility shown to feature several advantages over the tensor B-splines. In spite of efforts to make the tensor product B-splines more flexible, the knots are still bound...... to reside on a regular grid. In contrast, by efficient non- constrained placement of the knots, the multivariate B- splines are shown to give a good representation of inho- mogeneous objects in natural settings. The wide applicability of the method is illustrated through its application on medical data...
A B-Spline-Based Colocation Method to Approximate the Solutions to the Equations of Fluid Dynamics
Energy Technology Data Exchange (ETDEWEB)
Johnson, Richard Wayne; Landon, Mark Dee
1999-07-01
The potential of a B-spline collocation method for numerically solving the equations of fluid dynamics is discussed. It is known that B-splines can resolve curves with drastically fewer data than can their standard shape function counterparts. This feature promises to allow much faster numerical simulations of fluid flow than standard finite volume/finite element methods without sacrificing accuracy. An example channel flow problem is solved using the method.
A B-Spline-Based Colocation Method to Approximate the Solutions to the Equations of Fluid Dynamics
Energy Technology Data Exchange (ETDEWEB)
M. D. Landon; R. W. Johnson
1999-07-01
The potential of a B-spline collocation method for numerically solving the equations of fluid dynamics is discussed. It is known that B-splines can resolve complex curves with drastically fewer data than can their standard shape function counterparts. This feature promises to allow much faster numerical simulations of fluid flow than standard finite volume/finite element methods without sacrificing accuracy. An example channel flow problem is solved using the method.
Büchmann, Bjarne
2000-05-01
An analysis is given for the accuracy and stability of some perturbation-based time-domain boundary element models (BEMs) with B-spline basis functions, solving hydrodynamic free-surface problems, including forward speed effects. The spatial convergence rate is found as a function of the order of the B-spline basis. It is shown that for all the models examined the mixed implicit-explicit Euler time integration scheme is correct to second order. Stability diagrams are found for models based on B-splines of orders third through to sixth for two different time integration schemes. The stability analysis can be regarded as an extension of the analysis by Vada and Nakos [Vada T, Nakos DE. Time marching schemes for ship motion simulations. In Proceedings of the 8th International Workshop on Water Waves and Floating Bodies, St. John's, Newfoundland, Canada, 1993; 155-158] to include B-splines of orders higher than three (piecewise quadratic polynomials) and to include finite water depth and a current at an oblique angle to the model grid. Copyright
Analysis of a Gyroscope's Rotor Nonlinear Supported Magnetic Field Based on the B-Spline Wavelet-FEM
Institute of Scientific and Technical Information of China (English)
LIU Jian-feng; YUAN Gan-nan; HUANG Xu; YU Li
2005-01-01
A supported framework of a gyroscope′s rotor is designed and the B-Spline wavelet finite element model of nonlinear supported magnetic field is worked out. A new finite element space is studied in which the scaling function of the B-spline wavelet is considered as the shape function of a tetrahedron. The magnetic field is spited by an artificial absorbing body which used the condition of field radiating, so the solution is unique. The resolution is improved via the varying gradient of the B-spline function under the condition of unchanging gridding. So there are some advantages in dealing with the focus flux and a high varying gradient result from a nonlinear magnetic field. The result is more practical. Plots of flux and in the space is studied via simulating the supported system model. The results of the study are useful in the research of the supported magnetic system for the gyroscope rotor.
Uniform trigonometric polynomial B-spline curves
Institute of Scientific and Technical Information of China (English)
吕勇刚; 汪国昭; 杨勋年
2002-01-01
This paper presents a new kind of uniform spline curve, named trigonometric polynomialB-splines, over space Ω = span{sint, cost, tk-3,tk-4,…,t,1} of which k is an arbitrary integerlarger than or equal to 3. We show that trigonometric polynomial B-spline curves have many similarV properties to traditional B-splines. Based on the explicit representation of the curve we have also presented the subdivision formulae for this new kind of curve. Since the new spline can include both polynomial curves and trigonometric curves as special cases without rational form, it can be used as an efficient new model for geometric design in the fields of CAD/CAM.
Energy Technology Data Exchange (ETDEWEB)
Soares Filho, Djalma Manoel; Eckhardt, Wietze; Braganca, Ricardo Silva Nunes de [PETROBRAS, Rio de Janeiro, RJ (Brazil). Centro de Pesquisas. Setor de Geofisica e Estratigrafia
1997-07-01
A gauss-Newton type method for seismic crosswell traveltime tomography based on B-splines products linear combinations for velocity field representation is presented. Knot points and order are established through Dierckx approximation technique according to the initial guess model parameters. The Frechet derivatives are contour integrations along the rays and the regularization factor is estimated using the concepts of condition number and Backus-Gilbert spread factor for normalized resolution matrices. A numerical example demonstrates the robustness of the method. (author)
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
In order to improve airfoil performance under different flight conditions and to make the performance insensitive to off-design condition at the same time,a multi-objective optimization approach considering robust design has been developed and applied to airfoil design. Non-uniform rational B-spline (NURBS) representation is adopted in airfoil design process,control points and related weights around airfoil are used as design variables. Two airfoil representation cases show that the NURBS method can get airfoil geometry with max geometry error less than 0.0019. By using six-sigma robust approach in multi-objective airfoil design,each sub-objective function of the problem has robustness property. By adopting multi-objective genetic algorithm that is based on non-dominated sorting,a set of non-dominated airfoil solutions with robustness can be obtained in the design. The optimum robust airfoil can be traded off and selected in these non-dominated solutions by design tendency. By using the above methods,a multi-objective robust optimization was conducted for NASA SC0712 airfoil. After performing robust airfoil optimization,the mean value of drag coefficient at Ma0.7-0.8 and the mean value of lift coefficient at post stall regime (Ma0.3) have been improved by 12.2% and 25.4%. By comparing the aerodynamic force coefficients of optimization result,it shows that: different from single robust airfoil design which just improves the property of drag divergence at Ma0.7-0.8,multi-objective robust design can improve both the drag divergence property at Ma0.7-0.8 and stall property at low speed. The design cases show that the multi-objective robust design method makes the airfoil performance robust under different off-design conditions.
Karimi, Hossein; Nikmehr, Saeid; Khodapanah, Ehsan
2016-09-01
In this paper, we develop a B-spline finite-element method (FEM) based on a locally modal wave propagation with anisotropic perfectly matched layers (PMLs), for the first time, to simulate nonlinear and lossy plasmonic waveguides. Conventional approaches like beam propagation method, inherently omit the wave spectrum and do not provide physical insight into nonlinear modes especially in the plasmonic applications, where nonlinear modes are constructed by linear modes with very close propagation constant quantities. Our locally modal B-spline finite element method (LMBS-FEM) does not suffer from the weakness of the conventional approaches. To validate our method, first, propagation of wave for various kinds of linear, nonlinear, lossless and lossy materials of metal-insulator plasmonic structures are simulated using LMBS-FEM in MATLAB and the comparisons are made with FEM-BPM module of COMSOL Multiphysics simulator and B-spline finite-element finite-difference wide angle beam propagation method (BSFEFD-WABPM). The comparisons show that not only our developed numerical approach is computationally more accurate and efficient than conventional approaches but also it provides physical insight into the nonlinear nature of the propagation modes.
Edge detection of molten pool and weld line for CO2 welding based on B-spline wavelet
Institute of Scientific and Technical Information of China (English)
薛家祥; 贾林; 李海宝; 张丽玲
2004-01-01
Due to the disturbances of spatters, dusts and strong arc light, it is difficult to detect the molten pool edge and the weld line location in CO2 welding processes. The median filtering and self-multiplication was employed to preprocess the image of the CO2 welding in order to detect effectively the edge of molten pool and the location of weld line. The B-spline wavelet algorithm has been investigated, the influence of different scales and thresholds on the results of the edge detection have been compared and analyzed. The experimental results show that better performance to extract the edge of the molten pool and the location of weld line can be obtained by using the B-spline wavelet transform. The proposed edge detection approach can be further applied to the control of molten depth and the seam tracking.
均匀B样条曲线曲面的小波表示%Wavelets-Based Representation of Uniform B-Spline Curves and Surfaces
Institute of Scientific and Technical Information of China (English)
赵罡; 穆国旺; 闫光荣; 朱心雄
2001-01-01
Wavelets-based representation provides a more flexible method for expressing curves and surfaces in different resolution levels. For uniform B-spline curves and surfaces, a unified expression can be adopted after decomposition to describe the wavelets for the interior and boundaries of the domain defined, and hence the multiplication is the only operation be needed to wavelets reconstruction. This results in high efficiency for the computation. The paper describes, from the point of geometry view, the principles and methods of realizing wavelets-based multiresolution representation of uniform cubic B-spline curves and surfaces.%小波基为曲线曲面带来了更为灵活的表达方式。均匀B样条曲线曲面在经过小波分解以后所得到的小波在定义域边界与内部可以采用统一的表达式，在进行小波重构时仅需作乘法运算，计算效率高。本文试图从几何概念出发由浅入深地论述基于小波的均匀三次B样条曲线曲面多分辨表示的原理及其实现。
A matrix method for degree-raising of B-spline curves
Institute of Scientific and Technical Information of China (English)
秦开怀
1997-01-01
A new identity is proved that represents the kth order B-splines as linear combinations of the (k + 1) th order B-splines A new method for degree-raising of B-spline curves is presented based on the identity. The new method can be used for all kinds of B-spline curves, that is, both uniform and arbitrarily nonuniform B-spline curves. When used for degree-raising of a segment of a uniform B-spline curve of degree k - 1, it can help obtain a segment of curve of degree k that is still a uniform B-spline curve without raising the multiplicity of any knot. The method for degree-raising of Bezier curves can be regarded as the special case of the new method presented. Moreover, the conventional theory for degree-raising, whose shortcoming has been found, is discussed.
Numerical Methods Using B-Splines
Shariff, Karim; Merriam, Marshal (Technical Monitor)
1997-01-01
The seminar will discuss (1) The current range of applications for which B-spline schemes may be appropriate (2) The property of high-resolution and the relationship between B-spline and compact schemes (3) Comparison between finite-element, Hermite finite element and B-spline schemes (4) Mesh embedding using B-splines (5) A method for the incompressible Navier-Stokes equations in curvilinear coordinates using divergence-free expansions.
三次均匀B样条与α-B样条的扩展%Extended Cubic Uniform B-spline and α-B-spline
Institute of Scientific and Technical Information of China (English)
徐岗; 汪国昭
2008-01-01
Spline curve and surface play an important role in CAD and computer graphics. In this paper, we propose several extensions of cubic uniform B-spline. Then, we present the ex- tensions of interpolating α-B-spline based on the new B-splines and the singular blending technique. The advantage of the ex- tensions is that they have global and local shape parameters. Furthermore, we also investigate their applications in data in- terpolation and polygonal shape deformation.
The Research of Obstacle-avoiding Problem based on Minimum Variation B-spline%基于最小变量的B-样条避障问题研究
Institute of Scientific and Technical Information of China (English)
彭辉; 曾碧
2011-01-01
为解决移动机器人在避障时的曲线优化问题，提出了基于最小变量的B-样条避障的方法．对该方法从数学模型上进行了推导，指出了该方法相对于其他弘样条方法的优点，并对该方法进行了优化，给出了相应的优化算法．研究表明：具有最小变量的B-样条函数比只用肛样条函数定义的曲线具有更优化的线性约束，其曲线具有更好的光滑性．%To solve the mobile robot in obstacle avoidance of curve optimization problems , and put for- ward based on the minimum variable B-spline obstacle-avoidance approach. The method is carried out from the derived mathematical model, that the method compared to other B-spline interpolation method has the advantage . The method was optimized, and its iterative optimization algorithm is given. Results of the em- pirical investigation indicated that the Minimum Variation B-spline problem which is a linearly constrained optimization problem over curves defined by B-spline functions only, Its curve has better smoothness.
PET/CT成像呼吸运动B样条校正%Respiratory motion correction of PET/CT imaging based on B-spline
Institute of Scientific and Technical Information of China (English)
潘李鹏; 贺建峰; 封硕; 崔锐; 马磊; 相艳; 易三莉; 张俊
2015-01-01
The degradation of image quality of PET/CT caused by respiratory motion will affect the physician’s diagnosis. The common developed technology of respiratory motion correction is gating, but it still has some limitations. This paper proposes a new method that using CT images extract the features of respiratory motion based on B-Spline to correct respi-ration. Firstly, it obtains the sequence of CT images corresponding with PET images within same respiratory motion cycle, and extracts the features of the motion of CT sequences within respiratory cycle by B-Spline. Next it transforms the feature parameters of CT sequences into the corresponding PET image sequences for the motion correction. The geometric defor-mation phantom and voxelised phantom tests show that the proposed method can obviously improve the quality of image of PET/CT for respiratory motion, and has a value of study further.%PET/CT成像中的人体呼吸运动会造成图像运动模糊，会严重影响图像质量，对医生的诊断造成影响。目前常用的呼吸门控技术能够在一定程度上改善图像质量，但是均存在其局限性。提出了一种基于CT图像提取呼吸运动特征的B样条方法，对呼吸运动图像进行校正。在PET/CT上获取与PET图像周期匹配的CT图像序列，通过B样条配准方式对在呼吸周期内的CT图序列像提取运动信息；对CT图像所匹配的PET图像做基于运动特征信息的校正变换进行运动校正。几何位移形变和像素人体模实验结果表明，提出的方法对PET/CT呼吸运动图像质量改进明显，具有研究价值。
A fast direct point-by-point generating algorithm for B Spline curves and surfaces
Institute of Scientific and Technical Information of China (English)
LI Zhong; HAN Dan-fu
2005-01-01
Traditional generating algorithms for B Spline curves and surfaces require approximation methods where how to increment the parameter to get the best approximation is problematic; or they take the pixel-based method needing matrix transformation from B Spline representation to Bezier form. Here, a fast, direct point-by-point generating algorithm for B Spline curves and surfaces is presented. The algorithm does not need matrix transformation, can be used for uniform or nonuniform B Spline curves and surfaces of any degree, and has high generating speed and good rendering accuracy.
RECONSTRUCTION OF SYMMETRIC B-SPLINE CURVES AND SURFACES
Institute of Scientific and Technical Information of China (English)
ZHU Weidong; KE Yinglin
2007-01-01
A method to reconstruct Symmetric B-spline curves and surfaces is presented. The symmetry property is realized by using Symmetric knot vector and Symmetric control points. Firstly, data points are divided into two parts based on the symmetry axis or symmetry plane extracted from data points. Then the divided data points are parameterized and a Symmetric knot vector is selected in order to get Symmetric B-spline basis functions. Constraint equations regarding the control points are deduced to keep the control points of the B-spline curve or surface to be Symmetric with respect to the extracted symmetry axis or symmetry plane. Lastly, the constrained least squares fitting problem is solved with the Lagrange multiplier method. Two examples from industry are given to show that the proposed method is efficient, robust and able to meet the general engineering requirements.
基于三次B样条函数的SEM图像处理%SEM Image Processing Based on Third- order B- spline Function
Institute of Scientific and Technical Information of China (English)
张健
2011-01-01
SEM images, for its unique practical testing significance, need in denoising also highlight its edges and accurate edge extraction positioning, So this paper adopts a partial differential method which can maintain the edges of the denoising and a extensive application of multi - scale wavelet analysis to detect edges, all based on third - order B - spline function as the core operator, for line width test of SEM image processing, This algorithm obtained the better denoising effect and maintained edge features for SEM images.%SEM图像由于其独特的实际测试意义,需要在去噪的同时突出边缘和准确的边缘提取定位,所以提出采用能够保持边缘的偏微分方法去噪和广泛应用的多尺度小波提取边缘,基于三次B样条函数作为核心算子,对用于线宽测试的SEM图像进行处理,获得了较好的去噪并保持边缘的效果以及清晰的图像边缘检测效果.
Institute of Scientific and Technical Information of China (English)
冯健; 叶伯生; 周向东
2012-01-01
针对FPGA的特点对三次B样条曲线插补算法进行优化,使用VHDL语言实现了三次B样条插补算法,并在FPGA中进行实际验证.%The paper optimizes the cubic B -spline interpolation algorithm based on the characteristics of the FPGA,and verify the algorithm implemented by VHDL language on FPGA.
Directory of Open Access Journals (Sweden)
Xiaogang Ji
2014-01-01
Full Text Available In the process of curves and surfaces fairing with multiresolution analysis, fairing accuracy will be determined by final fairing scale. On the basis of Dyadic wavelet fairing algorithm (DWFA, arbitrary resolution wavelet fairing algorithm (ARWFA, and corresponding software, accuracy control of multiresolution fairing was studied for the uncertainty of fairing scale. Firstly, using the idea of inverse problem for reference, linear hypothesis was adopted to predict the corresponding wavelet scale for any given fairing error. Although linear hypothesis has error, it can be eliminated by multiple iterations. So faired curves can be determined by a minimum number of control vertexes and have the best faring effect under the requirement of accuracy. Secondly, in consideration of efficiency loss caused by iterative algorithm, inverse calculation of fairing scale was presented based on the least squares fitting. With the increase of order of curves, inverse calculation accuracy becomes higher and higher. Verification results show that inverse calculation scale can meet the accuracy requirement when fitting curve is sextic. In the whole fairing process, because there is no approximation algorithm such as interpolation and approximation, faired curves can be reconstructed again exactly. This algorithm meets the idea and essence of wavelet analysis well.
Learning-Based Tracking of Complex Non-Rigid Motion
Institute of Scientific and Technical Information of China (English)
Qiang Wang; Hai-Zhou Ai; Guang-You Xu
2004-01-01
This paper describes a novel method for tracking complex non-rigid motions by learning the intrinsic object structure.The approach builds on and extends the studies on non-linear dimensionality reduction for object representation,object dynamics modeling and particle filter style tracking.First,the dimensionality reduction and density estimation algorithm is derived for unsupervised learning of object intrinsic representation,and the obtained non-rigid part of object state reduces even to 2-3 dimensions.Secondly the dynamical model is derived and trained based on this intrinsic representation.Thirdly the learned intrinsic object structure is integrated into a particle filter style tracker.It is shown that this intrinsic object representation has some interesting properties and based on which the newly derived dynamical model makes particle filter style tracker more robust and reliable.Extensive experiments are done on the tracking of challenging non-rigid motions such as fish twisting with selfocclusion,large inter-frame lip motion and facial expressions with global head rotation.Quantitative results are given to make comparisons between the newly proposed tracker and the existing tracker.The proposed method also has the potential to solve other type of tracking problems.
三次B样条曲线拟合的虹膜定位%Iris Localization Algorithm Based on Cubic B-spline Curve Fitting
Institute of Scientific and Technical Information of China (English)
叶永强; 沈建新; 周啸; 张敏
2011-01-01
采用圆检测定位虹膜内外边界的方法是当前虹膜定位的主流算法.当虹膜图像分辨率很高时,圆曲线不能准确地拟合虹膜真实边界,特别是受瞳孔收缩影响很大的内边界.而采用三次B样条曲线能够很好地拟合内边界.为了提高定位效率,首先运用质心探测方法分割出瞳孔区域,然后在瞳孔区域中搜索内边界点,采用三次B样条曲线精确拟合内边界；最后利用Canny算子检测外边界,并采用圆曲线的最小二乘拟合外边界.运用Bath大学虹膜库中的1000幅虹膜图像对该定位算法进行测试,内边界定位时间0.0203s、准确率99.2％；外边界定位时间2.0277s,准确率98.9％,满足准确、高效的定位要求.%The current important methods of iris localization are based on circle detection. But they could not fit the real boundary well when iris images are high-resolution, especially the inner boundary under the influence of pupil constriction. Proposed method based on cubic B-spline curve can figure out this problem. It locates the inner boundary area first, and then the outer boundary. To improve the efficiency and robustness for inner boundary localization, this paper has proposed a method to segment the pupil area first based centroid detection, then search inner edge in the segmented area. The outer boundary area is then determined by using Ihe parameter relations between inner and outer boundary. Finally, using canny operator delects the outer edge, and the outer boundary is fitted in the Least-square circle sense. The Experiment results based on the iris database of Bath University, with 99.2% accuracy and 0.022s positioning time of inner boundary, 98.9% and 2.027s of outer show that the proposed approach is efficient and robust.
Institute of Scientific and Technical Information of China (English)
梁锡坤
2011-01-01
为了丰富和发展B样条曲线理论,利用曲线线性组合的思想,将3次均匀B样条曲线进行了拓展,并讨论了拓展曲线的性质.研究表明,拓展曲线的基具有较简单的表达式;拓展曲线包含了原曲线的基本形式,比原曲线具有更强的描述能力,且保持曲线次数不变.利用曲线的形状因子可以调整曲线的局部形状;同时得到了一种闭曲线表示的新途径.%In order to develop the theory of B-spline curve, the representation of cubic uniform B-spline curve is extended to a general form based on linear combination of curves.Moreover, some properties of the extended curve are discussed in details.The research shows that the basis of the generalized curve is relative simple, and the extended curve includes the original B-spline curve and shows much better shape-control capability than the original curve.Meanwhile, the extended curve keeps the same degree of original one.It is easy to find that the curve can be reshape by adjusting the shape factor.Also, a new method of the representation of closed curve is given.
Regional Ionosphere Mapping with Kriging and B-spline Methods
Grynyshyna-Poliuga, O.; Stanislawska, I. M.
2013-12-01
This work demonstrates the concept and practical examples of mapping of regional ionosphere, based on GPS observations from the EGNOS Ranging and Integrity Monitoring Stations (RIMS) network and permanent stations near to them. Interpolation/prediction techniques, such as kriging (KR) and the cubic B-spline, which are suitable for handling multi-scale phenomena and unevenly distributed data, were used to create total electron content (TEC) maps. Their computational efficiency (especially the B-spline) and the ability to handle undersampled data (especially kriging) are particularly attractive. The data sets have been collect into seasonal bins representing June, December solstices and equinox (March, September). TEC maps have a spatial resolution of 2.50 and 2.50 in latitude and longitude, respectively, and a 15-minutes temporal resolution. The time series of the TEC maps can be used to derive average monthly maps describing major ionospheric trends as a function of time, season, and spatial location.
A B-spline method used to calculate added resistance in waves
Zangeneh, Razieh; Ghiasi, Mahmood
2017-01-01
Making an exact computation of added resistance in sea waves is of high interest due to the economic effects relating to ship design and operation. In this paper, a B-spline based method is developed for computation of added resistance. Based on the potential flow assumption, the velocity potential is computed using Green's formula. The Kochin function is applied to compute added resistance using Maruo's far-field method, the body surface is described by a B-spline curve and potentials and normal derivation of potentials are also described by B-spline basis functions and B-spline derivations. A collocation approach is applied for numerical computation, and integral equations are then evaluated by applying Gauss-Legendre quadrature. Computations are performed for a spheroid and different hull forms; results are validated by a comparison with experimental results. All results obtained with the present method show good agreement with experimental results.
基于小波的B样条曲线多分辨表示及编辑%Wavelets-Based Multiresolution Representation and Edit of B-Spline Curves
Institute of Scientific and Technical Information of China (English)
赵罡; 朱心雄
2001-01-01
Multiresolution representation provides a more flexible approach to edit curves and surfaces in different resolution levels. The paper describes, from the viewpoint of geometry, the principles and methods of realizing wavelets-based multiresolution representation of quasi-uniform cubic B-spline curves. An example is given to illustrate the editing of B-spline curves in multiresolution level.%多分辨表示方法为曲线提供了更为灵活的表达方式，使得我们可以在不同分辨率下对曲线进行编辑.小波技术是实现曲线多分辨表示的一种新颖方法，已有许多论文从理论上论述了这项技术.文中从几何概念出发,由浅入深地论述了基于小波的准均匀三次B样条曲线多分辨表示的原理及其实现，并通过实例描述了B样条曲线的多分辨编辑.
Cubic B-Spline Collocation Method for One-Dimensional Heat and Advection-Diffusion Equations
Joan Goh; Ahmad Abd. Majid; Ahmad Izani Md. Ismail
2012-01-01
Numerical solutions of one-dimensional heat and advection-diffusion equations are obtained by collocation method based on cubic B-spline. Usual finite difference scheme is used for time and space integrations. Cubic B-spline is applied as interpolation function. The stability analysis of the scheme is examined by the Von Neumann approach. The efficiency of the method is illustrated by some test problems. The numerical results are found to be in good agreement with the exact solution.
Aerodynamic Shape Optimization for Wing Based on Non-uniform Rational B-spline%基于NURBS方法的机翼气动外形优化
Institute of Scientific and Technical Information of China (English)
马晓永; 范召林; 吴文华; 杨党国
2011-01-01
飞行器气动外形优化就是将设计对象的空气动力学性能分析与最优化方法相结合,通过不断改变设计对象的外形,使其气动性能在满足一定约束条件下达到最优.气动外形优化是一个涉及几何参数化、动网格、流场计算和寻优算法的综合应用平台.随着计算流体力学(CFD)的发展以及高性能计算机的使用,气动外形优化在现代飞行器设计中的作用愈加重要.为此建立了基于非均匀有理B样条(NURBS)参数化方法的机翼气动外形优化平台.优化过程中采用弹性网格变形法,由雷诺平均Navier-Stokes方程组和Baldwin-Lomax代数湍流模型求解流场,并用离散伴随方法进行目标函数梯度求解,最后结合序列二次规划( SQP)方法进行优化迭代.通过对ONERA M6机翼在跨声速条件下进行优化分析,结果表明在保持升力系数和机翼容积不变,马赫数Ma =0.84、迎角α=3.06°时,优化后机翼表面压力系数有明显变化,上翼面λ激波明显减弱,相对于原始外形优化后机翼阻力系数减小0.002 5,降幅达13.1％；优化实例验证了该方法有效可行.%Aerodynamic design optimization is to find the optimum of aircraft aerodynamic performance under certain constraints by changing the shape of the designed object. It facilitates the design process by automating both the performance a-nalysis and the optimization method. Aerodynamic design optimization is an integrated application of geometry parameterization, grid update, flow field solver and optimization method, and it has contributed to the design of aircraft with the maturity of computational fluid dynamics (CFD) and the progress of computer performance. This paper presents an aerodynamic wing shape optimization method based on non-uniform rational B-spline (NURBS), in which the mesh deformation is used with a spring-based smoothing method. The Reynolds-averaged Navier-Stokes equations with an algebraic turbulence model of
Ng-Thow-Hing, Victor; Agur, Anne; Ball, Kevin A.; Fiume, Eugene; McKee, Nancy
1998-05-01
We introduce a mathematical primitive called the B-spline solid that can be used to create deformable models of muscle shape. B-spline solids can be used to model skeletal muscle for the purpose of building a data library of reusable, deformable muscles that are reconstructed from actual muscle data. Algorithms are provided for minimizing shape distortions that may be caused when fitting discrete sampled data to a continuous B-spline solid model. Visible Human image data provides a good indication of the perimeter of a muscle, but is not suitable for providing internal muscle fiber bundle arrangements which are important for physical simulation of muscle function. To obtain these fiber bundle orientations, we obtain 3-D muscle fiber bundle coordinates by triangulating optical images taken from three different camera views of serially dissected human soleus specimens. B-spline solids are represented as mathematical three-dimensional vector functions which can parameterize an enclosed volume as well as its boundary surface. They are based on B-spline basis functions, allowing local deformations via adjustable control points and smooth continuity of shape. After the B-spline solid muscle model is fitted with its external surface and internal volume arrangements, we can subsequently deform its shape to allow simulation of animated muscle tissue.
Han, In Su; Kim, Eung Sik; Min, Suk Won; Hur, Don; Park, Jong Keun
2004-10-01
In this paper, the electric field at the spacer in a 170 kV gas-insulated switchgear (GIS) is optimized. Initially, the tangential and total electric fields around the original shape of the 170 kV GIS produced by a Korean company are calculated using a combination of the charge simulation method (CSM) and surface charge method (SCM). The contour of the spacer in the 170 kV GIS is found using a non-uniform rational B-spline (NURB) curve the effectiveness of which has been proved. By moving some control points in the NURB curve, the initial shape of the 170 kV GIS can be determined so that we may begin to optimize the electric field. Owing to the proposed algorithm, the overall process has a stable convergence. The objects that we want to design are the upper and lower parts of the spacer. Finally, we can find the shapes in which the tangential and total electric fields are optimized.
Energy Technology Data Exchange (ETDEWEB)
Lamare, F [INSERM, U650, Laboratoire du Traitement de l' Information Medicale (LaTIM), Brest, F-29200 (France); Carbayo, M J Ledesma [ETSI Telecomunicacion Universidad Politecnica de Madrid, Ciudad Universitaria s/n 28040, Madrid (Spain); Cresson, T [INSERM, U650, Laboratoire du Traitement de l' Information Medicale (LaTIM), Brest, F-29200 (France); Kontaxakis, G [ETSI Telecomunicacion Universidad Politecnica de Madrid, Ciudad Universitaria s/n 28040, Madrid (Spain); Santos, A [ETSI Telecomunicacion Universidad Politecnica de Madrid, Ciudad Universitaria s/n 28040, Madrid (Spain); Rest, C Cheze Le [INSERM, U650, Laboratoire du Traitement de l' Information Medicale (LaTIM), Brest, F-29200 (France); Reader, A J [School of Chemical Engineering and Analytical Science, University of Manchester, Manchester (United Kingdom); Visvikis, D [INSERM, U650, Laboratoire du Traitement de l' Information Medicale (LaTIM), Brest, F-29200 (France)
2007-09-07
Respiratory motion in emission tomography leads to reduced image quality. Developed correction methodology has been concentrating on the use of respiratory synchronized acquisitions leading to gated frames. Such frames, however, are of low signal-to-noise ratio as a result of containing reduced statistics. In this work, we describe the implementation of an elastic transformation within a list-mode-based reconstruction for the correction of respiratory motion over the thorax, allowing the use of all data available throughout a respiratory motion average acquisition. The developed algorithm was evaluated using datasets of the NCAT phantom generated at different points throughout the respiratory cycle. List-mode-data-based PET-simulated frames were subsequently produced by combining the NCAT datasets with Monte Carlo simulation. A non-rigid registration algorithm based on B-spline basis functions was employed to derive transformation parameters accounting for the respiratory motion using the NCAT dynamic CT images. The displacement matrices derived were subsequently applied during the image reconstruction of the original emission list mode data. Two different implementations for the incorporation of the elastic transformations within the one-pass list mode EM (OPL-EM) algorithm were developed and evaluated. The corrected images were compared with those produced using an affine transformation of list mode data prior to reconstruction, as well as with uncorrected respiratory motion average images. Results demonstrate that although both correction techniques considered lead to significant improvements in accounting for respiratory motion artefacts in the lung fields, the elastic-transformation-based correction leads to a more uniform improvement across the lungs for different lesion sizes and locations.
基于三次B样条的曲线逼近算法及其收敛性%Approximate algorithm of curves and its convergence based on cubic B-spline
Institute of Scientific and Technical Information of China (English)
蒋勇; 李玉梅
2013-01-01
为了改进传统的插值样条曲线算法不易于后期处理和实时局部修改、B样条算法不能满足精度要求的缺点,提出了一种基于三次B样条的曲线逼近算法[1].该算法以三次B样条为基础对曲线的逼近领域进行了研究,通过大量的数值实验证明了该算法的可行性及高效性.该算法通过结合插值样条与B样条的各种优点,有效避免了传统算法的不足.同时,对该算法的收敛性进行了理论证明.数值实验表明了该算法具有收敛速度快、精度高且编程易实现等优点,为曲线研究提供了可供参考的有效算法.%In order to improve the shortcomings of the traditional interpolation spline that is not easy to solve the problems at the post-processing and to do the local modification in time,and to improve the disadvantage of the approximate spline which can not meet the accuracy requirements,the approximate algorithm based on the cubic B-Spline is put forward[1].The algorithm is based on the cubic B-Spline and makes some research on the area of the curve approximate.A large number of numerical experiments are made to illustrate the feasibility and the efficiency of the algorithm.The algrithm combines the advantages of the interpolation spline and the B-Spline.The shortcomings of the traditional algrithrn are prevented effectively.At the same time,the theoretical proof is put forward to demonstrate the convergence of the algorithm.And the numerical experiments show that this algorithm has fast convergence speed and high precision.And its programming is easy to implement.A effective algorithm is put forward for the curve research which can be use as a reference.
Institute of Scientific and Technical Information of China (English)
李小霞; 汪木兰; 刘坤; 蒋荣
2012-01-01
An interpolation method based on five degrees B-spline for manipulators trajectory planning in joint space is proposed to accomplish smooth trajectory adjustment. The B-spline interpolation algorithm can ensure the continuous of velocity, acceleration and jerk in joints moving process, also can achieve start and stop velocity, acceleration and jerk be any configuration. The manipulator trajectory is simulated out and the graphs of joints position-time, velocity-time and acceleration-time are drawn out through C + + 6. 0 development platform based on MFC framework class and OpenGL graphics library. Simulation results show that, the proposed algorithm supplied manipulators with smooth adjustment of trajectory and stable movement of joints.%为实现机械手作业轨迹平滑,关节轨迹的速度、加速度、加加速度保持连续,起始和停止的速度、加速度和加加速度可以任意配置,采用5次B样条曲线插值方法构造关节轨迹.推导了B样条曲线插值轨迹算法；通过VC ++6.0开发平台,基于MFC框架类和OpenGL图形库仿真出机械手的运动过程,并绘制出各关节的位置、速度、加速度时间曲线图.仿真结果表明,该方法使机械手关节调整平滑且运动平稳,运动性能显著优于传统的三次样条轨迹规划.
基于误差控制的自适应3次B样条曲线插值%Adaptive curve interpolation of cubic B-spline based on error control
Institute of Scientific and Technical Information of China (English)
叶铁丽; 李学艺; 曾庆良
2013-01-01
Aiming at the problem of the existing curve interpolation algorithm on data compression, an adaptive curve interpolation algorithm of cubic B-spline is presented. An initial cubic B-spline curve is interpolated by selected minimum data points. Based on the presented algorithm for calculating the minimum distance from point to a curve, all the interpolation errors corresponding to remaining data points are calculated, and the maximum interpolation error is obtained. If the maximum error is greater than the threshold value, the point with the maximum error is added to the data points to interpolate a new curve. The process continues until the maximum interpolation error is less than the threshold value. Comparing to the current curve interpolation methods, the proposed algorithm can compress data points greatly with the same precision.%针对现有曲线插值算法不能有效压缩型值点的缺陷,研究了一种自适应三次B样条曲线插值算法.从型值点序列中选用最少的点插值一条初始曲线,基于提出的点到曲线的最小距离计算方法,分别计算各非插值点对应的插值误差,并从中提取最大插值误差.若最大误差大于给定的误差阈值,则将其对应的型值点加入插值型值点序列,重新插值曲线,直到最大插值误差满足误差要求.与现有曲线插值算法相比,该算法可以在保证插值精度的前提下有效压缩数据量.
A Comparison of FFD-based Nonrigid Registration and AAMs Applied to Myocardial Perfusion MRI
DEFF Research Database (Denmark)
Ólafsdóttir, Hildur; Stegmann, Mikkel Bille; Ersbøll, Bjarne Kjær;
2006-01-01
Little work has been done on comparing the performance of statistical model-based approaches and nonrigid registration algorithms. This paper deals with the qualitative and quantitative comparison of active appearance models (AAMs) and a nonrigid registration algorithm based on free......-form deformations (FFDs). AAMs are known to be much faster than nonrigid registration algorithms. On the other hand nonrigid registration algorithms are independent of a training set as required to build an AAM. To obtain a further comparison of the two methods, they are both applied to automatically register multi......-slice myocardial perfusion images. The images are acquired by magnetic resonance imaging, from infarct patients. A registration of these sequences is crucial for clinical practice, which currently is subjected to manual labor. In the paper, the pros and cons of the two registration approaches are discussed...
Image Edge Detection Based on B-spline Wavelet%基于B样条小波的图像边缘检测
Institute of Scientific and Technical Information of China (English)
周何; 黄山; 盛贤
2011-01-01
研究图像边缘优化检测问题.针对图像边缘信息被噪声污染影响定位精度,经典的边缘检测方法Canny算法中的高斯平滑函数边缘定位精确度较低,导致图像缓变边缘信息丢失和假边缘的现象.为去除虚假边缘,在Canny最优边缘检测准则下,提出引入了渐进最优的B样条小波函数,采用小波变换应用于图像边缘检测中的基于模极大值的方法,并结合Kmeans聚类的自适应双阈值方法进行图像边缘检测仿真.仿真结果表明,改进的算法改善了噪声干扰情况下图像边缘提取效果,有效提高了边缘检测的准确性,得到较高的边缘检测图像质量,可为设计提供依据.%In order to improve the low positioning accuracy of image edge detection, a research on optimization of image edge detection was carried out. The Gaussian smoothing function of the classical Canny edge detection method has lower edge positioning accuracy, which causes the missing of slowly varying edges and the producing of feigned edges and the edge detection is not accurate enough. So under the Canny criteria of optimum edge detection, the asymptotically optimal B-spline wavelet function was introduced. The method of modulus maxima of wavelet transform and the method of self-adapting dual threshold of kmeans clustering was used in the edge detection experiments. The experiments proved that the new algorithm is of higher accuracy and improves the quality of the edge detection images.
Nonrigid Medical Image Registration Based on Mesh Deformation Constraints
Directory of Open Access Journals (Sweden)
XiangBo Lin
2013-01-01
Full Text Available Regularizing the deformation field is an important aspect in nonrigid medical image registration. By covering the template image with a triangular mesh, this paper proposes a new regularization constraint in terms of connections between mesh vertices. The connection relationship is preserved by the spring analogy method. The method is evaluated by registering cerebral magnetic resonance imaging (MRI image data obtained from different individuals. Experimental results show that the proposed method has good deformation ability and topology-preserving ability, providing a new way to the nonrigid medical image registration.
Multiple products of B-splines used in CAD system
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
The function upgrade of computer aided design (CAD) system requested that the multiple product of B-spline functions should be represented as a linear combination of some suitable (usually higher-degree) B-splines. In this paper, we apply the theory of spline space and discrete B-splines to deduce the representation of the coefficients of all terms of the linear combination, which can be directly applied to software coding in system development.
Trigonometric polynomial B-spline with shape parameter
Institute of Scientific and Technical Information of China (English)
WANG Wentao; WANG Guozhao
2004-01-01
The basis function of n order trigonometric polynomial B-spline with shape parameter is constructed by an integral approach. The shape of the constructed curve can be adjusted by changing the shape parameter and it has most of the properties of B-spline. The ellipse and circle can be accurately represented by this basis function.
Exponential B-splines and the partition of unity property
DEFF Research Database (Denmark)
Christensen, Ole; Massopust, Peter
2012-01-01
We provide an explicit formula for a large class of exponential B-splines. Also, we characterize the cases where the integer-translates of an exponential B-spline form a partition of unity up to a multiplicative constant. As an application of this result we construct explicitly given pairs of dual...
Cubic B-Spline Collocation Method for One-Dimensional Heat and Advection-Diffusion Equations
Directory of Open Access Journals (Sweden)
Joan Goh
2012-01-01
Full Text Available Numerical solutions of one-dimensional heat and advection-diffusion equations are obtained by collocation method based on cubic B-spline. Usual finite difference scheme is used for time and space integrations. Cubic B-spline is applied as interpolation function. The stability analysis of the scheme is examined by the Von Neumann approach. The efficiency of the method is illustrated by some test problems. The numerical results are found to be in good agreement with the exact solution.
Institute of Scientific and Technical Information of China (English)
祝恒佳; 严思杰; 刘学伟
2011-01-01
A method of modifying glass - shape curve based on cubic B - spline curve is studied. An algorithm of screening the effective data points in processing the sampling points is putted forward. As a result, the glass - shape curve can be generated by calculating the control points and interpolation. The curve can be modified directly by dragging the control point. And then calculate the space curve of the glass,and control the three axis linkage for molding movement. The algorithm effectively simplify the calculating process of modifying the glass - shape curve, and make the modifying convenience.%研究了一种基于三次B样条来进行镜框曲线修调策略.提出对镜框采样数据的有效型值点筛选算法,通过反求控制点、插值生成镜框平面曲线.直接通过拖动控制点来对平面曲线进行修调.进而计算镜框空间曲线,控制三轴联动来完成镜框成型运动.该算法能够有效简化曲线修调的计算过程,并使修调操作方便.
Non-rigid registration of medical images based on ordinal feature and manifold learning
Li, Qi; Liu, Jin; Zang, Bo
2015-12-01
With the rapid development of medical imaging technology, medical image research and application has become a research hotspot. This paper offers a solution to non-rigid registration of medical images based on ordinal feature (OF) and manifold learning. The structural features of medical images are extracted by combining ordinal features with local linear embedding (LLE) to improve the precision and speed of the registration algorithm. A physical model based on manifold learning and optimization search is constructed according to the complicated characteristics of non-rigid registration. The experimental results demonstrate the robustness and applicability of the proposed registration scheme.
MUTUAL INFORMATION BASED 3D NON-RIGID REGISTRATION OF CT/MR ABDOMEN IMAGES
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
A mutual information based 3D non-rigid registration approach was proposed for the registration of deformable CT/MR body abdomen images. The Parzen Windows Density Estimation (PWDE) method is adopted to calculate the mutual information between the two modals of CT and MRI abdomen images. By maximizing MI between the CT and MR volume images, the overlapping part of them reaches the biggest, which means that the two body images of CT and MR matches best to each other. Visible Human Project (VHP) Male abdomen CT and MRI Data are used as experimental data sets. The experimental results indicate that this approach of non-rigid 3D registration of CT/MR body abdominal images can be achieved effectively and automatically, without any prior processing procedures such as segmentation and feature extraction, but has a main drawback of very long computation time. Key words: medical image registration; multi-modality; mutual information; non-rigid; Parzen window density estimation
Cubic B-spline curve approximation by curve unclamping
Chen, Xiao-Diao; Ma, Weiyin; Paul, Jean-Claude
2010-01-01
International audience; A new approach for cubic B-spline curve approximation is presented. The method produces an approximation cubic B-spline curve tangent to a given curve at a set of selected positions, called tangent points, in a piecewise manner starting from a seed segment. A heuristic method is provided to select the tangent points. The first segment of the approximation cubic B-spline curve can be obtained using an inner point interpolation method, least-squares method or geometric H...
Cubic Trigonometric B-spline Galerkin Methods for the Regularized Long Wave Equation
Irk, Dursun; Keskin, Pinar
2016-10-01
A numerical solution of the Regularized Long Wave (RLW) equation is obtained using Galerkin finite element method, based on Crank Nicolson method for the time integration and cubic trigonometric B-spline functions for the space integration. After two different linearization techniques are applied, the proposed algorithms are tested on the problems of propagation of a solitary wave and interaction of two solitary waves.
Improving Feature-based Non-rigid Registration for Applications in Radiotherapy
E.M. Vásquez Osorio (Eliana)
2012-01-01
textabstractThis thesis describes the improvements of a feature-based non-rigid registration method that were essential for its application in radiotherapy. In addition, this thesis presents three practical applications of the improved method: 1) quantification of anatomical changes in 3D for head a
Constructing iterative non-uniform B-spline curve and surface to fit data points
Institute of Scientific and Technical Information of China (English)
LIN Hongwei; WANG Guojin; DONG Chenshi
2004-01-01
In this paper, based on the idea of profit and loss modification, we present the iterative non-uniform B-spline curve and surface to settle a key problem in computer aided geometric design and reverse engineering, that is, constructing the curve (surface)fitting (interpolating) a given ordered point set without solving a linear system. We start with a piece of initial non-uniform B-spline curve (surface) which takes the given point set as its control point set. Then by adjusting its control points gradually with iterative formula,we can get a group of non-uniform B-spline curves (surfaces) with gradually higher precision. In this paper, using modern matrix theory, we strictly prove that the limit curve (surface) of the iteration interpolates the given point set. The non-uniform B-spline curves (surfaces) generated with the iteration have many advantages, such as satisfying the NURBS standard, having explicit expression, gaining locality, and convexity preserving,etc.
Optimization and dynamics of protein-protein complexes using B-splines.
Gillilan, Richard E; Lilien, Ryan H
2004-10-01
A moving-grid approach for optimization and dynamics of protein-protein complexes is introduced, which utilizes cubic B-spline interpolation for rapid energy and force evaluation. The method allows for the efficient use of full electrostatic potentials joined smoothly to multipoles at long distance so that multiprotein simulation is possible. Using a recently published benchmark of 58 protein complexes, we examine the performance and quality of the grid approximation, refining cocrystallized complexes to within 0.68 A RMSD of interface atoms, close to the optimum 0.63 A produced by the underlying MMFF94 force field. We quantify the theoretical statistical advantage of using minimization in a stochastic search in the case of two rigid bodies, and contrast it with the underlying cost of conjugate gradient minimization using B-splines. The volumes of conjugate gradient minimization basins of attraction in cocrystallized systems are generally orders of magnitude larger than well volumes based on energy thresholds needed to discriminate native from nonnative states; nonetheless, computational cost is significant. Molecular dynamics using B-splines is doubly efficient due to the combined advantages of rapid force evaluation and large simulation step sizes. Large basins localized around the native state and other possible binding sites are identifiable during simulations of protein-protein motion. In addition to providing increased modeling detail, B-splines offer new algorithmic possibilities that should be valuable in refining docking candidates and studying global complex behavior.
Institute of Scientific and Technical Information of China (English)
张金芳; 许曼
2013-01-01
文章对动态系统的三维输出概率密度函数(PDF)进行了线性建模和控制器设计研究。首先选择合适的二维 B 样条函数，利用系统的输入输出数据通过递归最小二乘算法建立了基于二维 B 样条函数的三维输出 PDF 的线性动态模型；然后根据所建立的数学模型，选择跟踪性能指标，进行了控制器的设计；最后，选择动态输出分布系统，进行了动态系统三维输出PDF控制的仿真研究，仿真结果证实了控制算法的有效性。%Dynamic modeling and controller design for the three dimensional (3D) output probability density function (PDF) are studied in this paper. Through recursive least square algorithm, the dynamic model of 3D PDF is set up based on two dimensional (2D) B-spline basis function with output and input data of the system firstly, then a tracking performance index is chosen to design a controller based 3D PDF dynamic model, at last a dynamic output distribution system is constructed for simulation study, and the results verify the effectiveness of the presented controller.
Use of B-Spline in the Finite Element Analysis: Comparison with ANCF Geometry
2011-02-04
formulations developed in this paper. 15. SUBJECT TERMS Geometric discontinuities; Finite element; Multibody systems; B-spline; NURBS 16. SECURITY...Keywords: Geometric discontinuities; Finite element; Multibody systems; B-spline; NURBS . UNCLAS: Dist A. Approved for public release 3 1...developed by computational geometry methods such as B- spline and NURBS (Non-Uniform Rational B-Splines) representations. This fact has motivated
[Research on non-rigid medical image registration algorithm based on SIFT feature extraction].
Wang, Anna; Lu, Dan; Wang, Zhe; Fang, Zhizhen
2010-08-01
In allusion to non-rigid registration of medical images, the paper gives a practical feature points matching algorithm--the image registration algorithm based on the scale-invariant features transform (Scale Invariant Feature Transform, SIFT). The algorithm makes use of the image features of translation, rotation and affine transformation invariance in scale space to extract the image feature points. Bidirectional matching algorithm is chosen to establish the matching relations between the images, so the accuracy of image registrations is improved. On this basis, affine transform is chosen to complement the non-rigid registration, and normalized mutual information measure and PSO optimization algorithm are also chosen to optimize the registration process. The experimental results show that the method can achieve better registration results than the method based on mutual information.
Harmening, Corinna; Neuner, Hans
2016-09-01
Due to the establishment of terrestrial laser scanner, the analysis strategies in engineering geodesy change from pointwise approaches to areal ones. These areal analysis strategies are commonly built on the modelling of the acquired point clouds. Freeform curves and surfaces like B-spline curves/surfaces are one possible approach to obtain space continuous information. A variety of parameters determines the B-spline's appearance; the B-spline's complexity is mostly determined by the number of control points. Usually, this number of control points is chosen quite arbitrarily by intuitive trial-and-error-procedures. In this paper, the Akaike Information Criterion and the Bayesian Information Criterion are investigated with regard to a justified and reproducible choice of the optimal number of control points of B-spline curves. Additionally, we develop a method which is based on the structural risk minimization of the statistical learning theory. Unlike the Akaike and the Bayesian Information Criteria this method doesn't use the number of parameters as complexity measure of the approximating functions but their Vapnik-Chervonenkis-dimension. Furthermore, it is also valid for non-linear models. Thus, the three methods differ in their target function to be minimized and consequently in their definition of optimality. The present paper will be continued by a second paper dealing with the choice of the optimal number of control points of B-spline surfaces.
A Galerkin Solution for Burgers' Equation Using Cubic B-Spline Finite Elements
A.A. Soliman
2012-01-01
Numerical solutions for Burgers’ equation based on the Galerkins’ method using cubic B-splines as both weight and interpolation functions are set up. It is shown that this method is capable of solving Burgers’ equation accurately for values of viscosity ranging from very small to large. Three standard problems are used to validate the proposed algorithm. A linear stability analysis shows that a numerical scheme based on a Cranck-Nicolson approximation in time is unconditionally stable.
A Galerkin Solution for Burgers' Equation Using Cubic B-Spline Finite Elements
Directory of Open Access Journals (Sweden)
A. A. Soliman
2012-01-01
Full Text Available Numerical solutions for Burgers’ equation based on the Galerkins’ method using cubic B-splines as both weight and interpolation functions are set up. It is shown that this method is capable of solving Burgers’ equation accurately for values of viscosity ranging from very small to large. Three standard problems are used to validate the proposed algorithm. A linear stability analysis shows that a numerical scheme based on a Cranck-Nicolson approximation in time is unconditionally stable.
Construction of generalized magnetic coordinates by B-spline expansion
Energy Technology Data Exchange (ETDEWEB)
Kurata, Michinari [Dept. of Energy Engineering and Science, Graduate School of Engineering, Nagoya Univ., Nagoya, Aichi (Japan); Todoroki, Jiro [National Inst. for Fusion Science, Toki, Gifu (Japan)
2000-06-01
Generalized Magnetic Coordinates (GMC) are curvilinear coordinates ({xi},{eta},{zeta}) in which the magnetic field is expressed in the form B={nabla}{psi}({xi},{eta},{zeta}) x {nabla}{zeta} + H{sup {zeta}}({xi},{eta}){nabla}{xi} x {nabla}{eta}. The coordinates are expanded in Fourier series in the toroidal direction and the B-spline function in other two dimensions to treat the aperiodic model magnetic field. The coordinates are well constructed, but are influenced by the boundary condition in the B-spline expansion. (author)
Institute of Scientific and Technical Information of China (English)
王玉珠; 杨丹; 张小洪
2007-01-01
This paper presents a multi-scale curvature product corner detection technique in the framework of B-spline curvature scale space. A scale product function is derived from the curvature product of the contour at different scales. Corners are constructed as the local maxima by thresholding the curvature product results across several scales. Through scale product, the localization accuracy and detection performance can be notably improved in terms of CNN criteria. Experiments also demonstrate that proposed method shows robustness to high frequency details and provides promising detection results.
Börger, Klaus; Schmidt, Michael; Dettmering, Denise; Limberger, Marco; Erdogan, Eren; Seitz, Florian; Brandert, Sylvia; Görres, Barbara; Kersten, Wilhelm; Bothmer, Volker; Hinrichs, Johannes; Venzmer, Malte; Mrotzek, Niclas
2016-04-01
Today, the observations of space geodetic techniques are usually available with a rather low latency which applies to space missions observing the solar terrestrial environment, too. Therefore, we can use all these measurements in near real-time to compute and to provide ionosphere information, e.g. the vertical total electron content (VTEC). GSSAC and BGIC support a project aiming at a service for providing ionosphere information. This project is called OPTIMAP, meaning "Operational Tool for Ionosphere Mapping and Prediction"; the scientific work is mainly done by the German Geodetic Research Institute of the Technical University Munich (DGFI-TUM) and the Institute for Astrophysics of the University of Goettingen (IAG). The OPTIMAP strategy for providing ionosphere target quantities of high quality, such as VTEC or the electron density, includes mathematical approaches and tools allowing for the model adaptation to the real observational scenario as a significant improvement w.r.t. the traditional well-established methods. For example, OPTIMAP combines different observation types such as GNSS (GPS, GLONASS), Satellite Altimetry (Jason-2), DORIS as well as radio-occultation measurements (FORMOSAT#3/COSMIC). All these observations run into a Kalman-filter to compute global ionosphere maps, i.e. VTEC, for the current instant of time and as a forecast for a couple of subsequent days. Mathematically, the global VTEC is set up as a series expansion in terms of two-dimensional basis functions defined as tensor products of trigonometric B-splines for longitude and polynomial B-splines for latitude. Compared to the classical spherical harmonics, B-splines have a localizing character and, therefore, can handle an inhomogeneous data distribution properly. Finally, B-splines enable a so-called multi-resolution-representation (MRR) enabling the combination of global and regional modelling approaches. In addition to the geodetic measurements, Sun observations are pre
基于B样条空间等距线的机器人轨迹优化算法%Robot Trajectory Optimization Algorithm Based on Spatial Offset B-Spline
Institute of Scientific and Technical Information of China (English)
胡绳荪; 庹宇鲲; 申俊琦; 陈昌亮; 谷文; 李坚
2015-01-01
针对J形坡口焊接机器人轨迹示教中理论轨迹与实际轨迹偏差较大的问题,利用实际轨迹的空间等距线逼近下一道焊接轨迹,并设计了相贯线轨迹等距线的B样条逼近算法. 算法主要包括:基于等曲线弧长准则对原B样条曲线取样;利用向心算法计算取样点的等距点;计算插值于该等距点的3次B样条曲线;在给定的全局误差限内去除多余控制顶点. 试验结果表明:等距点的向心算法可以有效解决相贯线曲线局部修改后主法向量发散的问题;全局插值方法可以保留原曲线修改特征;全局误差限下去除多余控制顶点可以减少B样条曲线控制顶点数目.%For the problem of the large deviation between the theoretical trajectory and the real trajectory of the J-groove joint welding robot during trajectory teaching, a solution is proposed using the offset spline of the real trajec-tory to approximate the next welding trajectory. An approximation algorithm for offset B-spline of intersecting splines is designed, which includes the following steps: sampling the original B-spline with the uniform curve arc length crite-rion; calculating the offset points of the sample points with the centripetal algorithm; fitting a cubic B-spline with global interpolation; removing most control points under the global error bound. The experimental results are as fol-lows: the centripetal algorithm could solve the problem of the divergence of the principal normal vectors after local modification on the intersecting curve; the algorithm of global interpolating could retain the modification features of the original trajectory; the algorithm of removing control points under global error bound could remove most control points effectively and reduce the number of control points of B-spline.
Micropolar Fluids Using B-spline Divergence Conforming Spaces
Sarmiento, Adel
2014-06-06
We discretized the two-dimensional linear momentum, microrotation, energy and mass conservation equations from micropolar fluids theory, with the finite element method, creating divergence conforming spaces based on B-spline basis functions to obtain pointwise divergence free solutions [8]. Weak boundary conditions were imposed using Nitsche\\'s method for tangential conditions, while normal conditions were imposed strongly. Once the exact mass conservation was provided by the divergence free formulation, we focused on evaluating the differences between micropolar fluids and conventional fluids, to show the advantages of using the micropolar fluid model to capture the features of complex fluids. A square and an arc heat driven cavities were solved as test cases. A variation of the parameters of the model, along with the variation of Rayleigh number were performed for a better understanding of the system. The divergence free formulation was used to guarantee an accurate solution of the flow. This formulation was implemented using the framework PetIGA as a basis, using its parallel stuctures to achieve high scalability. The results of the square heat driven cavity test case are in good agreement with those reported earlier.
B-Spline Active Contour with Handling of Topology Changes for Fast Video Segmentation
Directory of Open Access Journals (Sweden)
Frederic Precioso
2002-06-01
Full Text Available This paper deals with video segmentation for MPEG-4 and MPEG-7 applications. Region-based active contour is a powerful technique for segmentation. However most of these methods are implemented using level sets. Although level-set methods provide accurate segmentation, they suffer from large computational cost. We propose to use a regular B-spline parametric method to provide a fast and accurate segmentation. Our B-spline interpolation is based on a fixed number of points 2j depending on the level of the desired details. Through this spatial multiresolution approach, the computational cost of the segmentation is reduced. We introduce a length penalty. This results in improving both smoothness and accuracy. Then we show some experiments on real-video sequences.
EVolution: an edge-based variational method for non-rigid multi-modal image registration
de Senneville, B. Denis; Zachiu, C.; Ries, M.; Moonen, C.
2016-10-01
Image registration is part of a large variety of medical applications including diagnosis, monitoring disease progression and/or treatment effectiveness and, more recently, therapy guidance. Such applications usually involve several imaging modalities such as ultrasound, computed tomography, positron emission tomography, x-ray or magnetic resonance imaging, either separately or combined. In the current work, we propose a non-rigid multi-modal registration method (namely EVolution: an edge-based variational method for non-rigid multi-modal image registration) that aims at maximizing edge alignment between the images being registered. The proposed algorithm requires only contrasts between physiological tissues, preferably present in both image modalities, and assumes deformable/elastic tissues. Given both is shown to be well suitable for non-rigid co-registration across different image types/contrasts (T1/T2) as well as different modalities (CT/MRI). This is achieved using a variational scheme that provides a fast algorithm with a low number of control parameters. Results obtained on an annotated CT data set were comparable to the ones provided by state-of-the-art multi-modal image registration algorithms, for all tested experimental conditions (image pre-filtering, image intensity variation, noise perturbation). Moreover, we demonstrate that, compared to existing approaches, our method possesses increased robustness to transient structures (i.e. that are only present in some of the images).
Numerical Solution of One-dimensional Telegraph Equation using Cubic B-spline Collocation Method
Directory of Open Access Journals (Sweden)
J. Rashidinia
2014-02-01
Full Text Available In this paper, a collocation approach is employed for the solution of the one-dimensional telegraph equation based on cubic B-spline. The derived method leads to a tri-diagonal linear system. Computational efficiency of the method is confirmed through numerical examples whose results are in good agreement with theory. The obtained numerical results have been compared with the results obtained by some existing methods to verify the accurate nature of our method.
B-spline soliton solution of the fifth order KdV type equations
Zahra, W. K.; Ouf, W. A.; El-Azab, M. S.
2013-10-01
In this paper, we develop a numerical solution based on sextic B-spline collocation method for solving the generalized fifth-order nonlinear evolution equations. Applying Von-Neumann stability analysis, the proposed technique is shown to be unconditionally stable. The accuracy of the presented method is demonstrated by a test problem. The numerical results are found to be in good agreement with the exact solution.
Left ventricular motion reconstruction with a prolate spheroidal B-spline model
Energy Technology Data Exchange (ETDEWEB)
Li Jin; Denney, Thomas S Jr [Electrical and Computer Engineering Department, 200 Broun Hall, Auburn University, AL 36849-5201 (United States)
2006-02-07
Tagged cardiac magnetic resonance (MR) imaging can non-invasively image deformation of the left ventricular (LV) wall. Three-dimensional (3D) analysis of tag data requires fitting a deformation model to tag lines in the image data. In this paper, we present a 3D myocardial displacement and strain reconstruction method based on a B-spline deformation model defined in prolate spheroidal coordinates, which more closely matches the shape of the LV wall than existing Cartesian or cylindrical coordinate models. The prolate spheroidal B-spline (PSB) deformation model also enforces smoothness across and can compute strain at the apex. The PSB reconstruction algorithm was evaluated on a previously published data set to allow head-to-head comparison of the PSB model with existing LV deformation reconstruction methods. We conclude that the PSB method can accurately reconstruct deformation and strain in the LV wall from tagged MR images and has several advantages relative to existing techniques.
Left ventricular motion reconstruction with a prolate spheroidal B-spline model
Li, Jin; Denney, Thomas S., Jr.
2006-02-01
Tagged cardiac magnetic resonance (MR) imaging can non-invasively image deformation of the left ventricular (LV) wall. Three-dimensional (3D) analysis of tag data requires fitting a deformation model to tag lines in the image data. In this paper, we present a 3D myocardial displacement and strain reconstruction method based on a B-spline deformation model defined in prolate spheroidal coordinates, which more closely matches the shape of the LV wall than existing Cartesian or cylindrical coordinate models. The prolate spheroidal B-spline (PSB) deformation model also enforces smoothness across and can compute strain at the apex. The PSB reconstruction algorithm was evaluated on a previously published data set to allow head-to-head comparison of the PSB model with existing LV deformation reconstruction methods. We conclude that the PSB method can accurately reconstruct deformation and strain in the LV wall from tagged MR images and has several advantages relative to existing techniques.
Numerical method using cubic B-spline for a strongly coupled reaction-diffusion system.
Directory of Open Access Journals (Sweden)
Muhammad Abbas
Full Text Available In this paper, a numerical method for the solution of a strongly coupled reaction-diffusion system, with suitable initial and Neumann boundary conditions, by using cubic B-spline collocation scheme on a uniform grid is presented. The scheme is based on the usual finite difference scheme to discretize the time derivative while cubic B-spline is used as an interpolation function in the space dimension. The scheme is shown to be unconditionally stable using the von Neumann method. The accuracy of the proposed scheme is demonstrated by applying it on a test problem. The performance of this scheme is shown by computing L∞ and L2 error norms for different time levels. The numerical results are found to be in good agreement with known exact solutions.
Numerical method using cubic B-spline for a strongly coupled reaction-diffusion system.
Abbas, Muhammad; Majid, Ahmad Abd; Md Ismail, Ahmad Izani; Rashid, Abdur
2014-01-01
In this paper, a numerical method for the solution of a strongly coupled reaction-diffusion system, with suitable initial and Neumann boundary conditions, by using cubic B-spline collocation scheme on a uniform grid is presented. The scheme is based on the usual finite difference scheme to discretize the time derivative while cubic B-spline is used as an interpolation function in the space dimension. The scheme is shown to be unconditionally stable using the von Neumann method. The accuracy of the proposed scheme is demonstrated by applying it on a test problem. The performance of this scheme is shown by computing L∞ and L2 error norms for different time levels. The numerical results are found to be in good agreement with known exact solutions.
Direct Numerical Simulation of Incompressible Pipe Flow Using a B-Spline Spectral Method
Loulou, Patrick; Moser, Robert D.; Mansour, Nagi N.; Cantwell, Brian J.
1997-01-01
A numerical method based on b-spline polynomials was developed to study incompressible flows in cylindrical geometries. A b-spline method has the advantages of possessing spectral accuracy and the flexibility of standard finite element methods. Using this method it was possible to ensure regularity of the solution near the origin, i.e. smoothness and boundedness. Because b-splines have compact support, it is also possible to remove b-splines near the center to alleviate the constraint placed on the time step by an overly fine grid. Using the natural periodicity in the azimuthal direction and approximating the streamwise direction as periodic, so-called time evolving flow, greatly reduced the cost and complexity of the computations. A direct numerical simulation of pipe flow was carried out using the method described above at a Reynolds number of 5600 based on diameter and bulk velocity. General knowledge of pipe flow and the availability of experimental measurements make pipe flow the ideal test case with which to validate the numerical method. Results indicated that high flatness levels of the radial component of velocity in the near wall region are physical; regions of high radial velocity were detected and appear to be related to high speed streaks in the boundary layer. Budgets of Reynolds stress transport equations showed close similarity with those of channel flow. However contrary to channel flow, the log layer of pipe flow is not homogeneous for the present Reynolds number. A topological method based on a classification of the invariants of the velocity gradient tensor was used. Plotting iso-surfaces of the discriminant of the invariants proved to be a good method for identifying vortical eddies in the flow field.
Vibration Analysis of Rectangular Plates with One or More Guided Edges via Bicubic B-Spline Method
Directory of Open Access Journals (Sweden)
W.J. Si
2005-01-01
Full Text Available A simple and accurate method is proposed for the vibration analysis of rectangular plates with one or more guided edges, in which bicubic B-spline interpolation in combination with a new type of basis cubic B-spline functions is used to approximate the plate deflection. This type of basis cubic B-spline functions can satisfy simply supported, clamped, free, and guided edge conditions with easy numerical manipulation. The frequency characteristic equation is formulated based on classical thin plate theory by performing Hamilton's principle. The present solutions are verified with the analytical ones. Fast convergence, high accuracy and computational efficiency have been demonstrated from the comparisons. Frequency parameters for 13 cases of rectangular plates with at least one guided edge, which are possible by approximate or numerical methods only, are presented. These results are new in literature.
A free-form deformation method based on B-splines surface control%一种基于B-样条曲面控制的自由变形方法
Institute of Scientific and Technical Information of China (English)
林金花; 李万龙; 王璐; 李鑫
2011-01-01
With Doo-Sabin subdivision mode,a control grid for the interpolation vertex position and the bi-quadratic B-spline surface is constructed to obtain the parametric representation of the interpolation surface.The model points are attached to the interpolation surface to get the local coordinates which keep constant during the transformation.As the subdivision can deal with random topology grid,the multi-resolution deformation of the 3D model is realized by editing the B-spline control grid.%利用Doo-Sabin细分模式构造插值顶点位置和法向双二次B样条曲面控制网格,得到插值曲面的参数表示,再将模型上的点参数化到插值曲面上,得到该点的局部坐标。由于局部坐标在变形过程中保持不变,并且细分方法具有处理任意拓扑网格的能力,从而通过编辑模型的B-样条曲面控制网格,实现了三维模型的多分辨率变形。
Generalized b-spline subdivision-surface wavelets and lossless compression
Energy Technology Data Exchange (ETDEWEB)
Bertram, M; Duchaineau, M A; Hamann, B; Joy, K I
1999-11-24
We present a new construction of wavelets on arbitrary two-manifold topology for geometry compression. The constructed wavelets generalize symmetric tensor product wavelets with associated B-spline scaling functions to irregular polygonal base mesh domains. The wavelets and scaling functions are tensor products almost everywhere, except in the neighborhoods of some extraordinary points (points of valence unequal four) in the base mesh that defines the topology. The compression of arbitrary polygonal meshes representing isosurfaces of scalar-valued trivariate functions is a primary application. The main contribution of this paper is the generalization of lifted symmetric tensor product B-spline wavelets to two-manifold geometries. Surfaces composed of B-spline patches can easily be converted to this scheme. We present a lossless compression method for geometries with or without associated functions like color, texture, or normals. The new wavelet transform is highly efficient and can represent surfaces at any level of resolution with high degrees of continuity, except at a finite number of extraordinary points in the base mesh. In the neighborhoods of these points detail can be added to the surface to approximate any degree of continuity.
Extended cubic B-spline method for solving a linear system of second-order boundary value problems.
Heilat, Ahmed Salem; Hamid, Nur Nadiah Abd; Ismail, Ahmad Izani Md
2016-01-01
A method based on extended cubic B-spline is proposed to solve a linear system of second-order boundary value problems. In this method, two free parameters, [Formula: see text] and [Formula: see text], play an important role in producing accurate results. Optimization of these parameters are carried out and the truncation error is calculated. This method is tested on three examples. The examples suggest that this method produces comparable or more accurate results than cubic B-spline and some other methods.
Isogeometric Divergence-conforming B-splines for the Darcy-Stokes-Brinkman Equations
2012-01-01
depicted in Figure 2. A geometrical mapping meeting our criteria could be defined utilizing B-splines or Non-Uniform Rational B- Splines ( NURBS ) on...the coarsest mesh Mh0 . For examples of such mappings, see Chapter 2 of [20]. NURBS mappings are especially useful as they can represent many...Compatible B-splines Two-dimensional Compatible B-splines: NURBS Mapped Domains On NURBS mapped domains, the Piola transform is utilized to map flow velocities
Institute of Scientific and Technical Information of China (English)
苏世栋; 刘鹏飞
2012-01-01
为了增强关节式工业机器人加工不规则工件的能力,将三次均匀B样条曲线应用于关节式机器人轨迹插补算法中,使机器人末端以三次B样条的曲线轨迹通过各加工点.在分析了三次均匀B样条曲线特性的基础上,给出了三次均匀B样条曲线的一般表达式.在增加曲线自由端点条件后,使用追赶算法快速反算出控制点.使用预估校正的方法推导出插补算法,该算法能使机器人末端遵循抛物线过渡型的加速-匀速-减速变化规律,给出了预测减速点的方法.对一个类花瓣型的加工对象进行仿真,证明文中方法的可行性.%To enhance capability of industry joint robot to machine irregular shape workpiece, the cubic uniform B - spline curve is introduced to manipulator trajectory interpolation. After reviewing characteristics of cubic uniform B-spline curve, the general expressions of such curve are proposed. A chasing method is used to calculate the control points,while conditions of two free endpoints are added to the solutions. A predict-correct method is used to derive the interpolation algorithm, which directs the velocity of end-effecter to follow a parabolic curve-accelerating, uniform and decelerating, and the prediction of deceleration point is presented. A simulation is tested in a flower-shaped workpiece and feasibility of manipulator trajectory interpolation algorithm is verified.
Cubic generalized B-splines for interpolation and nonlinear filtering of images
Tshughuryan, Heghine
1997-04-01
This paper presents the introduction and using of the generalized or parametric B-splines, namely the cubic generalized B-splines, in various signal processing applications. The theory of generalized B-splines is briefly reviewed and also some important properties of generalized B-splines are investigated. In this paper it is shown the use of generalized B-splines as a tool to solve the quasioptimal algorithm problem for nonlinear filtering. Finally, the experimental results are presented for oscillatory and other signals and images.
Testing for additivity with B-splines
Institute of Scientific and Technical Information of China (English)
2007-01-01
Regression splines are often used for fitting nonparametric functions, and they work especially well for additivity models. In this paper, we consider two simple tests of additivity: an adaptation of Tukey’s one degree of freedom test and a nonparametric version of Rao’s score test. While the Tukey-type test can detect most forms of the local non-additivity at the parametric rate of O(n-1/2), the score test is consistent for all alternative at a nonparametric rate. The asymptotic distribution of these test statistics is derived under both the null and local alternative hypotheses. A simulation study is conducted to compare their finite-sample performances with some existing kernel-based tests. The score test is found to have a good overall performance.
Data assimilation using Bayesian filters and B-spline geological models
Duan, Lian
2011-04-01
This paper proposes a new approach to problems of data assimilation, also known as history matching, of oilfield production data by adjustment of the location and sharpness of patterns of geological facies. Traditionally, this problem has been addressed using gradient based approaches with a level set parameterization of the geology. Gradient-based methods are robust, but computationally demanding with real-world reservoir problems and insufficient for reservoir management uncertainty assessment. Recently, the ensemble filter approach has been used to tackle this problem because of its high efficiency from the standpoint of implementation, computational cost, and performance. Incorporation of level set parameterization in this approach could further deal with the lack of differentiability with respect to facies type, but its practical implementation is based on some assumptions that are not easily satisfied in real problems. In this work, we propose to describe the geometry of the permeability field using B-spline curves. This transforms history matching of the discrete facies type to the estimation of continuous B-spline control points. As filtering scheme, we use the ensemble square-root filter (EnSRF). The efficacy of the EnSRF with the B-spline parameterization is investigated through three numerical experiments, in which the reservoir contains a curved channel, a disconnected channel or a 2-dimensional closed feature. It is found that the application of the proposed method to the problem of adjusting facies edges to match production data is relatively straightforward and provides statistical estimates of the distribution of geological facies and of the state of the reservoir.
B-Spline Filtering for Automatic Detection of Calcification Lesions in Mammograms
Bueno, G.; Sánchez, S.; Ruiz, M.
2006-10-01
Breast cancer continues to be an important health problem between women population. Early detection is the only way to improve breast cancer prognosis and significantly reduce women mortality. It is by using CAD systems that radiologist can improve their ability to detect, and classify lesions in mammograms. In this study the usefulness of using B-spline based on a gradient scheme and compared to wavelet and adaptative filtering has been investigated for calcification lesion detection and as part of CAD systems. The technique has been applied to different density tissues. A qualitative validation shows the success of the method.
Institute of Scientific and Technical Information of China (English)
成贤锴; 顾国刚; 陈琦; 于涌
2014-01-01
It is difficult and inefficient for an industrial robot to move along a particular complex track by teaching programming, for the control system is closed and independent. Thus, waiting process trajectory is planned in the image of workpiece surface. According to cubic B-spline interpolation algorithm, it needs some data processing to the planned trajectory path. Then, the format of data points converts to robot lan-guage by off-line programming. Complex curvilinear motion of industrial robot divides to linear motion and circular motion. During the experiment, the robot moves smoothly, and actual trajectory and planning traj-ectory are highly consistent. And the experimental results prove that the method is feasible.%工业机器人的控制系统是封闭且独立的，通过示教方式来在线编程是很难完成复杂的曲线运动，效率较低。为此在工件面型图像中对待加工轨迹进行规划，根据三次B样条曲线插值算法对规划好的加工路径轨迹进行数据处理，通过离线编程把加工轨迹数据点格式转换成机器人程序文件，把复杂的曲线运动分解成直线运动和圆弧运动，从而实现工业机器人的复杂曲线运动。实验过程中机器人运动流畅没有停顿，实际运动轨迹和规划运动轨迹吻合得很好，证明该方法有效可行。
Infrared image non-rigid registration based on regional information entropy demons algorithm
Lu, Chaoliang; Ma, Lihua; Yu, Ming; Cui, Shumin; Wu, Qingrong
2015-02-01
Infrared imaging fault detection which is treated as an ideal, non-contact, non-destructive testing method is applied to the circuit board fault detection. Since Infrared images obtained by handheld infrared camera with wide-angle lens have both rigid and non-rigid deformations. To solve this problem, a new demons algorithm based on regional information entropy was proposed. The new method overcame the shortcomings of traditional demons algorithm that was sensitive to the intensity. First, the information entropy image was gotten by computing regional information entropy of the image. Then, the deformation between the two images was calculated that was the same as demons algorithm. Experimental results demonstrated that the proposed algorithm has better robustness in intensity inconsistent images registration compared with the traditional demons algorithm. Achieving accurate registration between intensity inconsistent infrared images provided strong support for the temperature contrast.
Yang, Xiaofeng; Akbari, Hamed; Halig, Luma; Fei, Baowei
2011-03-01
We present a 3D non-rigid registration algorithm for the potential use in combining PET/CT and transrectal ultrasound (TRUS) images for targeted prostate biopsy. Our registration is a hybrid approach that simultaneously optimizes the similarities from point-based registration and volume matching methods. The 3D registration is obtained by minimizing the distances of corresponding points at the surface and within the prostate and by maximizing the overlap ratio of the bladder neck on both images. The hybrid approach not only capture deformation at the prostate surface and internal landmarks but also the deformation at the bladder neck regions. The registration uses a soft assignment and deterministic annealing process. The correspondences are iteratively established in a fuzzy-to-deterministic approach. B-splines are used to generate a smooth non-rigid spatial transformation. In this study, we tested our registration with pre- and postbiopsy TRUS images of the same patients. Registration accuracy is evaluated using manual defined anatomic landmarks, i.e. calcification. The root-mean-squared (RMS) of the difference image between the reference and floating images was decreased by 62.6+/-9.1% after registration. The mean target registration error (TRE) was 0.88+/-0.16 mm, i.e. less than 3 voxels with a voxel size of 0.38×0.38×0.38 mm3 for all five patients. The experimental results demonstrate the robustness and accuracy of the 3D non-rigid registration algorithm.
Non-rigid registration of medical images based on estimation of deformation states
Marami, Bahram; Sirouspour, Shahin; Capson, David W.
2014-11-01
A unified framework for automatic non-rigid 3D-3D and 3D-2D registration of medical images with static and dynamic deformations is proposed in this paper. The problem of non-rigid image registration is approached as a classical state estimation problem using a generic deformation model for the soft tissue. The registration technique employs a dynamic linear elastic continuum mechanics model of the tissue deformation, which is discretized using the finite element method. In the proposed method, the registration is achieved through a Kalman-like filtering process, which incorporates information from the deformation model and a vector of observation prediction errors computed from an intensity-based similarity/distance metric between images. With this formulation, single and multiple-modality, 3D-3D and 3D-2D image registration problems can all be treated within the same framework. The performance of the proposed registration technique was evaluated in a number of different registration scenarios. First, 3D magnetic resonance (MR) images of uncompressed and compressed breast tissue were co-registered. 3D MR images of the uncompressed breast tissue were also registered to a sequence of simulated 2D interventional MR images of the compressed breast. Finally, the registration algorithm was employed to dynamically track a target sub-volume inside the breast tissue during the process of the biopsy needle insertion based on registering pre-insertion 3D MR images to a sequence of real-time simulated 2D interventional MR images. Registration results indicate that the proposed method can be effectively employed for the registration of medical images in image-guided procedures, such as breast biopsy in which the tissue undergoes static and dynamic deformations.
Hodograph computation and bound estimation for rational B-spline curves
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
It is necessary to compute the derivative and estimate the bound of rational B-spline curves in design system, which has not been studied to date. To improve the function of computer aided design (CAD) system, and to enhance the efficiency of different algorithms of rational B-spline curves, the representation of scaled hodograph and bound of derivative magnitude of uniform planar rational B-spline curves are derived by applying Dir function, which indicates the direction of Cartesian vector between homogeneous points, discrete B-spline theory and the formula of translating the product into a summation of B-spline functions. As an application of the result above,upper bound of parametric distance between any two points in a uniform planar rational B-spline curve is further presented.
Automatic Shape Control of Triangular B-Splines of Arbitrary Topology
Institute of Scientific and Technical Information of China (English)
Ying He; Xian-Feng Gu; Hong Qin
2006-01-01
Triangular B-splines are powerful and flexible in modeling a broader class of geometric objects defined over arbitrary, non-rectangular domains. Despite their great potential and advantages in theory, practical techniques and computational tools with triangular B-splines are less-developed. This is mainly because users have to handle a large number of irregularly distributed control points over arbitrary triangulation. In this paper, an automatic and efficient method is proposed to generate visually pleasing, high-quality triangular B-splines of arbitrary topology. The experimental results on several real datasets show that triangular B-splines are powerful and effective in both theory and practice.
Non-Stationary Hydrologic Frequency Analysis using B-Splines Quantile Regression
Nasri, B.; St-Hilaire, A.; Bouezmarni, T.; Ouarda, T.
2015-12-01
Hydrologic frequency analysis is commonly used by engineers and hydrologists to provide the basic information on planning, design and management of hydraulic structures and water resources system under the assumption of stationarity. However, with increasing evidence of changing climate, it is possible that the assumption of stationarity would no longer be valid and the results of conventional analysis would become questionable. In this study, we consider a framework for frequency analysis of extreme flows based on B-Splines quantile regression, which allows to model non-stationary data that have a dependence on covariates. Such covariates may have linear or nonlinear dependence. A Markov Chain Monte Carlo (MCMC) algorithm is used to estimate quantiles and their posterior distributions. A coefficient of determination for quantiles regression is proposed to evaluate the estimation of the proposed model for each quantile level. The method is applied on annual maximum and minimum streamflow records in Ontario, Canada. Climate indices are considered to describe the non-stationarity in these variables and to estimate the quantiles in this case. The results show large differences between the non-stationary quantiles and their stationary equivalents for annual maximum and minimum discharge with high annual non-exceedance probabilities. Keywords: Quantile regression, B-Splines functions, MCMC, Streamflow, Climate indices, non-stationarity.
Generalized B-spline subdivision-surface wavelets for geometry compression.
Bertram, Martin; Duchaineau, Mark A; Hamann, Bernd; Joy, Kenneth I
2004-01-01
We present a new construction of lifted biorthogonal wavelets on surfaces of arbitrary two-manifold topology for compression and multiresolution representation. Our method combines three approaches: subdivision surfaces of arbitrary topology, B-spline wavelets, and the lifting scheme for biorthogonal wavelet construction. The simple building blocks of our wavelet transform are local lifting operations performed on polygonal meshes with subdivision hierarchy. Starting with a coarse, irregular polyhedral base mesh, our transform creates a subdivision hierarchy of meshes converging to a smooth limit surface. At every subdivision level, geometric detail can be expanded from wavelet coefficients and added to the surface. We present wavelet constructions for bilinear, bicubic, and biquintic B-Spline subdivision. While the bilinear and bicubic constructions perform well in numerical experiments, the biquintic construction turns out to be unstable. For lossless compression, our transform can be computed in integer arithmetic, mapping integer coordinates of control points to integer wavelet coefficients. Our approach provides a highly efficient and progressive representation for complex geometries of arbitrary topology.
B-splines as a Tool to Solve Constraints in Non-Hydrostatic Forecast Model
Subias, Alvaro
2016-01-01
Finite elements has been proven to be an useful tool to discretize the vertical coordinate in the hydrostatic forecast models allowing to define model variables in full levels so that no staggering is needed. In the non-hydrostatic case a constraint in the vertical operators appears (called C1) that does not allow to reduce the set of semi-implicit linear equations to a single equation in one variable as in the analytic case. Recently vertical finite elements based in B-splines have been used with an iterative method to relax the C1 constraint. In this paper we want to develop properly some representations of vertical operators in terms of B-splines in order to keep the C1-constraint. An invertibility relation between integral and derivative operators between vertical velocity and vertical divergence is also presented. The final scope of this paper is to provide a theoretical framework of development of finite element vertical operators to be implemented in the nh-Harmonie model
Directory of Open Access Journals (Sweden)
F. Steinbruecker
2012-01-01
the performance of a new nonrigid motion correction algorithm based on the optical flow method. For each of the small lesions, we extracted morphological and dynamical features describing both global and local shape, and kinetics behavior. In this paper, we compare the performance of each extracted feature set under consideration of several 2D or 3D motion compensation parameters for the differential diagnosis of enhancing lesions in breast MRI. Based on several simulation results, we determined the optimal motion compensation parameters. Our results have shown that motion compensation can improve the classification results. The results suggest that the computerized analysis system based on the non-rigid motion compensation technique and spatiotemporal features has the potential to increase the diagnostic accuracy of MRI mammography for small lesions and can be used as a basis for computer-aided diagnosis of breast cancer with MR mammography.
Efficient acceleration of mutual information computation for nonrigid registration using CUDA.
Ikeda, Kei; Ino, Fumihiko; Hagihara, Kenichi
2014-05-01
In this paper, we propose an efficient acceleration method for the nonrigid registration of multimodal images that uses a graphics processing unit. The key contribution of our method is efficient utilization of on-chip memory for both normalized mutual information (NMI) computation and hierarchical B-spline deformation, which compose a well-known registration algorithm. We implement this registration algorithm as a compute unified device architecture program with an efficient parallel scheme and several optimization techniques such as hierarchical data organization, data reuse, and multiresolution representation. We experimentally evaluate our method with four clinical datasets consisting of up to 512 × 512 × 296 voxels. We find that exploitation of on-chip memory achieves a 12-fold increase in speed over an off-chip memory version and, therefore, it increases the efficiency of parallel execution from 4% to 46%. We also find that our method running on a GeForce GTX 580 card is approximately 14 times faster than a fully optimized CPU-based implementation running on four cores. Some multimodal registration results are also provided to understand the limitation of our method. We believe that our highly efficient method, which completes an alignment task within a few tens of seconds, will be useful to realize rapid nonrigid registration.
Fast Selection of Spectral Variables with B-Spline Compression
Rossi, Fabrice; Wertz, Vincent; Meurens, Marc; Verleysen, Michel
2007-01-01
The large number of spectral variables in most data sets encountered in spectral chemometrics often renders the prediction of a dependent variable uneasy. The number of variables hopefully can be reduced, by using either projection techniques or selection methods; the latter allow for the interpretation of the selected variables. Since the optimal approach of testing all possible subsets of variables with the prediction model is intractable, an incremental selection approach using a nonparametric statistics is a good option, as it avoids the computationally intensive use of the model itself. It has two drawbacks however: the number of groups of variables to test is still huge, and colinearities can make the results unstable. To overcome these limitations, this paper presents a method to select groups of spectral variables. It consists in a forward-backward procedure applied to the coefficients of a B-Spline representation of the spectra. The criterion used in the forward-backward procedure is the mutual infor...
A B-spline Galerkin method for the Dirac equation
Froese Fischer, Charlotte; Zatsarinny, Oleg
2009-06-01
The B-spline Galerkin method is first investigated for the simple eigenvalue problem, y=-λy, that can also be written as a pair of first-order equations y=λz, z=-λy. Expanding both y(r) and z(r) in the B basis results in many spurious solutions such as those observed for the Dirac equation. However, when y(r) is expanded in the B basis and z(r) in the dB/dr basis, solutions of the well-behaved second-order differential equation are obtained. From this analysis, we propose a stable method ( B,B) basis for the Dirac equation and evaluate its accuracy by comparing the computed and exact R-matrix for a wide range of nuclear charges Z and angular quantum numbers κ. When splines of the same order are used, many spurious solutions are found whereas none are found for splines of different order. Excellent agreement is obtained for the R-matrix and energies for bound states for low values of Z. For high Z, accuracy requires the use of a grid with many points near the nucleus. We demonstrate the accuracy of the bound-state wavefunctions by comparing integrals arising in hyperfine interaction matrix elements with exact analytic expressions. We also show that the Thomas-Reiche-Kuhn sum rule is not a good measure of the quality of the solutions obtained by the B-spline Galerkin method whereas the R-matrix is very sensitive to the appearance of pseudo-states.
Combination of automatic non-rigid and landmark based registration: the best of both worlds
Fischer, Bernd; Modersitzki, Jan
2003-05-01
Automatic, parameter-free, and non-rigid registration schemes are known to be valuable tools in various (medical) image processing applications. Typically, these approaches aim to match intensity patterns in each scan by minimizing an appropriate distance measure. The outcome of an automatic registration procedure in general matches the target image quite good on the average. However, it may be inaccurate for specific, important locations as for example anatomical landmarks. On the other hand, landmark based registration techniques are designed to accurately match user specified landmarks. A drawback of landmark based registration is that the intensities of the images are completely neglected. Consequently, the registration result away from the landmarks may be very poor. Here we propose a framework for novel registration techniques which are capable to combine automatic and landmark driven approaches in order to benefit from the advantages of both strategies. We also propose a general, mathematical treatment of this framework and a particular implementation. The procedure computes a displacement field which is guaranteed to produce a one-to-one match between given landmarks and at the smae time minimizes an intensity based measure for the remaining parts of the images. The properties of the new scheme are demonstrated for a variety of numerical example. It is worthwhile noticing, that we not only present a new approach. Instead, we propose a general framework for a variety of different approaches. The choice of the main building blocks, the distance measure and the smoothness constraint, is essentially free.
Detection and correction of inconsistency-based errors in non-rigid registration
Gass, Tobias; Szekely, Gabor; Goksel, Orcun
2014-03-01
In this paper we present a novel post-processing technique to detect and correct inconsistency-based errors in non-rigid registration. While deformable registration is ubiquitous in medical image computing, assessing its quality has yet been an open problem. We propose a method that predicts local registration errors of existing pairwise registrations between a set of images, while simultaneously estimating corrected registrations. In the solution the error is constrained to be small in areas of high post-registration image similarity, while local registrations are constrained to be consistent between direct and indirect registration paths. The latter is a critical property of an ideal registration process, and has been frequently used to asses the performance of registration algorithms. In our work, the consistency is used as a target criterion, for which we efficiently find a solution using a linear least-squares model on a coarse grid of registration control points. We show experimentally that the local errors estimated by our algorithm correlate strongly with true registration errors in experiments with known, dense ground-truth deformations. Additionally, the estimated corrected registrations consistently improve over the initial registrations in terms of average deformation error or TRE for different registration algorithms on both simulated and clinical data, independent of modality (MRI/CT), dimensionality (2D/3D) and employed primary registration method (demons/Markov-randomfield).
van der Put, R. W.; Kerkhof, E. M.; Raaymakers, B. W.; Jürgenliemk-Schulz, I. M.; Lagendijk, J. J. W.
2009-12-01
External beam radiation treatment for patients with cervical cancer is hindered by the relatively large motion of the target volume. A hybrid MRI-accelerator system makes it possible to acquire online MR images during treatment in order to correct for motion and deformation. To fully benefit from such a system, online delineation of the target volumes is necessary. The aim of this study is to investigate the accuracy of rigid, non-rigid and semi-automatic registrations of MR images for interfractional contour propagation in patients with cervical cancer. Registration using mutual information was performed on both bony anatomy and soft tissue. A B-spline transform was used for the non-rigid method. Semi-automatic registration was implemented with a point set registration algorithm on a small set of manual landmarks. Online registration was simulated by application of each method to four weekly MRI scans for each of 33 cervical cancer patients. Evaluation was performed by distance analysis with respect to manual delineations. The results show that soft-tissue registration significantly (P treatment of cervical cancer, online MRI imaging will allow target localization based on soft tissue visualization, which provides a significantly higher accuracy than localization based on bony anatomy. The use of limited user input to guide the registration increases overall accuracy. Additional non-rigid registration further reduces the propagation error and negates errors caused by small observer variations.
B-splines on 3-D tetrahedron partition in four-directional mesh
Institute of Scientific and Technical Information of China (English)
SUN; Jiachang
2001-01-01
［1］ de Boor, C., Hllig, K., Riemannschneider, S. D., Box Splines, New York: Springer-Verlag, 1993.［2］ Dahmen, W., Micchelli, C. A., Recent Process in Multivariate Splines, Interpolating Cardinal Splines as Their Degree Tends to Infinity (ed. Ward, J.), New York: Academic Press, 1983, 27.［3］ de Boor, C., Topics in multivariate approximation theory, in Topics in Numerical Analysis, Lecture Notes in Mathematics (ed. Turner, P. R.), Vol. 965, New York: Springer-Verlag, 1982, 39.［4］ de Boor, C., B-form basics, in Geometric Modelling (ed. Farin, G.), Philadephia: SIAM, 1987, 131.［5］ Chui, C. K., Wang, R. H., Spaces of bivariate cubic and quartic splines on type-1 triangulations, J. Math. Anal. Appl., 1984, 101: 540.［6］ Jia, R. Q., Approximation order from certain spaces of smooth bivariate splines on a three-direction mesh, Trans. AMS, 1986, 295: 199.［7］ Dahmen, W., On multivariate B-splines, SIAM J. Numer. Anal., 1980, 17: 179.［8］ Sun Jiachang, The B-net structure and recurrence algorithms for B-splines on a three direction mesh, Mathematica Numerica Sinica, 1990, 12: 365.［9］ Sun Jiachang, Some results on the field of spline theory and its applications, Contemporary Mathematics, 1994, 163: 127.［10］ Sun Jiachang, Dual bases and quasi-interpolation of B-splines on S13 with three direction meshes, Acta Mathematicae Applicatae Sinica, 1991, 14: 170.［11］ Wang, R. H., He, T. X., Liu, X. Y. Et al., An integral method for constructing bivariate spline functions, J. Comp. Math., 1989, 7: 244.［12］ Wang, R. H., Shi, X. Q., A kind of C interpolation in the n-dimensional finite element method, J. Math. Res. And Exp., 1989, 9: 173.［13］ Shi, X. Q., Wang, R. H., The existence conditions of space S12(Δn), Chinese Science Bulletin, 1989, 34: 2015.
B-spline parameterization of spatial response in a monolithic scintillation camera
Solovov, V; Chepel, V; Domingos, V; Martins, R
2016-01-01
A framework for parameterization of the light response functions (LRFs) in a scintillation camera was developed. It is based on approximation of the measured or simulated photosensor response with weighted sums of uniform cubic B-splines or their tensor products. The LRFs represented in this way are smooth, computationally inexpensive to evaluate and require much less memory than non-parametric alternatives. The parameters are found in a straightforward way by the linear least squares method. The use of linear fit makes the fitting process stable and predictable enough to be used in non-supervised mode. Several techniques that allow to reduce the storage and processing power requirements were developed. A software library for fitting simulated and measured light response with spline functions was developed and integrated into an open source software package ANTS2 designed for simulation and data processing for Anger camera-type detectors.
The Analysis of Curved Beam Using B-Spline Wavelet on Interval Finite Element Method
Directory of Open Access Journals (Sweden)
Zhibo Yang
2014-01-01
Full Text Available A B-spline wavelet on interval (BSWI finite element is developed for curved beams, and the static and free vibration behaviors of curved beam (arch are investigated in this paper. Instead of the traditional polynomial interpolation, scaling functions at a certain scale have been adopted to form the shape functions and construct wavelet-based elements. Different from the process of the direct wavelet addition in the other wavelet numerical methods, the element displacement field represented by the coefficients of wavelets expansions is transformed from wavelet space to physical space by aid of the corresponding transformation matrix. Furthermore, compared with the commonly used Daubechies wavelet, BSWI has explicit expressions and excellent approximation properties, which guarantee satisfactory results. Numerical examples are performed to demonstrate the accuracy and efficiency with respect to previously published formulations for curved beams.
Vibration analysis of composite pipes using the finite element method with B-spline wavelets
Energy Technology Data Exchange (ETDEWEB)
Oke, Wasiu A.; Khulief, Yehia A. [King Fahd University of Petroleum and Minerals, Dhahran (Saudi Arabia)
2016-02-15
A finite element formulation using the B-spline wavelets on the interval is developed for modeling the free vibrations of composite pipes. The composite FRP pipe element is treated as a beam element. The finite pipe element is constructed in the wavelet space and then transformed to the physical space. Detailed expressions of the mass and stiffness matrices are derived for the composite pipe using the Bspline scaling and wavelet functions. Both Euler-Bernoulli and Timoshenko beam theories are considered. The generalized eigenvalue problem is formulated and solved to obtain the modal characteristics of the composite pipe. The developed wavelet-based finite element discretization scheme utilizes significantly less elements compared to the conventional finite element method for modeling composite pipes. Numerical solutions are obtained to demonstrate the accuracy of the developed element, which is verified by comparisons with some available results in the literature.
Symmetric alteration of four knots of B-spline and NURBS surfaces
Institute of Scientific and Technical Information of China (English)
LI Ya-juan; WANG Guo-zhao
2006-01-01
Modifying the knots ofa B-spline curve, the shape of the curve will be changed. In this paper, we present the effect of the symmetric alteration of four knots of the B-spline and the NURBS surfaces, i.e., symmetrical alteration of the knots of surface,the extended paths of points of the surface will converge to a point which should be expressed with several control points. This theory can be used in the constrained shape modification of B-spline and NURBS surfaces.
B-splines smoothed rejection sampling method and its applications in quasi-Monte Carlo integration
Institute of Scientific and Technical Information of China (English)
雷桂媛
2002-01-01
The rejection sampling method is one of the most popular methods used in Monte Carlo methods. It turns out that the standard rejection method is closely related to the problem of quasi-Monte Carlo integration of characteristic functions, whose accuracy may be lost due to the discontinuity of the characteristic functions. We proposed a B-splines smoothed rejection sampling method, which smoothed the characteristic function by B-splines smoothing technique without changing the integral quantity. Numerical experiments showed that the convergence rate of nearly O(N-1) is regained by using the B-splines smoothed rejection method in importance sampling.
B-splines smoothed rejection sampling method and its applications in quasi-Monte Carlo integration
Institute of Scientific and Technical Information of China (English)
雷桂媛
2002-01-01
The rejection sampling method is one of the most popular methods used in Monte Carlo methods. It turns out that the standard rejection method is closely related to the problem of quasi-Monte Carlo integration of characteristic functions, whose accuracy may be lost due to the discontinuity of the characteristic functions. We proposed a B-splines smoothed rejection sampling method, which smoothed the characteristic function by B-splines smoothing technique without changing the integral quantity. Numerical experiments showed that the convergence rate of nearly O( N-1 ) is regained by using the B-splines smoothed rejection method in importance sampling.
Isogeometric Divergence-conforming B-splines for the Steady Navier-Stokes Equations
2012-04-01
geometrical mapping meeting our criteria could be defined utilizing B-splines or Non- Uniform Rational B-Splines ( NURBS ) on the coarsest mesh Mh0 . For...examples of such mappings, see Chapter 2 of [13]. NURBS mappings are especially useful as they can represent many geometries of scientific and...complications that are beyond the scope of this work. We would like to note that all four assumptions hold if we employ a conforming NURBS multi-patch
Xiaolong Wang; Yi Wang; Zhizhu Cao; Weizhong Zou; Liping Wang; Guojun Yu; Bo Yu; Jinjun Zhang
2013-01-01
In general, proper orthogonal decomposition (POD) method is used to deal with single-parameter problems in engineering practice, and the linear interpolation is employed to establish the reduced model. Recently, this method is extended to solve the double-parameter problems with the amplitudes being achieved by cubic B-spline interpolation. In this paper, the accuracy of reduced models, which are established with linear interpolation and cubic B-spline interpolation, respectively, is verified...
A class of compactly supported symmetric/antisymmetric B-spline wavelets
Institute of Scientific and Technical Information of China (English)
YANG Shouzhi; LOU Zengjian
2005-01-01
An algorithm for constructing a class of compactly supported symmetric/antisymmetric B-spline wavelets is presented.For any m th order and k th order cardinal B-spline Nm (x), Nk (x), if m + k is an even integer, the corresponding m th order B-spline wavelets ψkm (x) can be constructed, which are compactly supported symmetric/antisymmetric. In addition, if ψkm (x), m ＞ 1 is m th Bspline wavelet associated with two spline functions Nm (x) and Nk (x), then (ψkm (x))′( x ) is m - 1th B-spline wavelet associated with Nm-1(x) and Nk+1(x), i.e. (ψkm(x))′(x) =22ψk+1m-1(x). Similarly, ∫x0 ψkm(t)dt, k ＞1 is m + 1th B-spline wavelet associated with Nm + 1 (x) and Nk-1 (x). Using this method, we recovered Chui and Wang' s spline wavelets. Since a class of B-spline wavelets are symmetric/antisymmetric, their linear phase property is assured. Several examples are also presented.
Lorenz, K S; Salama, P; Dunn, K W; Delp, E J
2012-02-01
Digital image analysis is a fundamental component of quantitative microscopy. However, intravital microscopy presents many challenges for digital image analysis. In general, microscopy volumes are inherently anisotropic, suffer from decreasing contrast with tissue depth, lack object edge detail and characteristically have low signal levels. Intravital microscopy introduces the additional problem of motion artefacts, resulting from respiratory motion and heartbeat from specimens imaged in vivo. This paper describes an image registration technique for use with sequences of intravital microscopy images collected in time-series or in 3D volumes. Our registration method involves both rigid and nonrigid components. The rigid registration component corrects global image translations, whereas the nonrigid component manipulates a uniform grid of control points defined by B-splines. Each control point is optimized by minimizing a cost function consisting of two parts: a term to define image similarity, and a term to ensure deformation grid smoothness. Experimental results indicate that this approach is promising based on the analysis of several image volumes collected from the kidney, lung and salivary gland of living rodents.
PetIGA-MF: a multi-field high-performance toolbox for structure-preserving B-splines spaces
Sarmiento, A.F.
2016-10-01
We describe a high-performance solution framework for isogeometric discrete differential forms based on B-splines: PetIGA-MF. Built on top of PetIGA, an open-source library we have built and developed over the last decade, PetIGA-MF is a general multi-field discretization tool. To test the capabilities of our implementation, we solve different viscous flow problems such as Darcy, Stokes, Brinkman, and Navier-Stokes equations. Several convergence benchmarks based on manufactured solutions are presented assuring optimal convergence rates of the approximations, showing the accuracy and robustness of our solver.
Mautz, R.; Ping, J.; Heki, K.; Schaffrin, B.; Shum, C.; Potts, L.
2005-05-01
Wavelet expansion has been demonstrated to be suitable for the representation of spatial functions. Here we propose the so-called B-spline wavelets to represent spatial time-series of GPS-derived global ionosphere maps (GIMs) of the vertical total electron content (TEC) from the Earth’s surface to the mean altitudes of GPS satellites, over Japan. The scalar-valued B-spline wavelets can be defined in a two-dimensional, but not necessarily planar, domain. Generated by a sequence of knots, different degrees of B-splines can be implemented: degree 1 represents the Haar wavelet; degree 2, the linear B-spline wavelet, or degree 4, the cubic B-spline wavelet. A non-uniform version of these wavelets allows us to handle data on a bounded domain without any edge effects. B-splines are easily extended with great computational efficiency to domains of arbitrary dimensions, while preserving their properties. This generalization employs tensor products of B-splines, defined as linear superposition of products of univariate B-splines in different directions. The data and model may be identical at the locations of the data points if the number of wavelet coefficients is equal to the number of grid points. In addition, data compression is made efficient by eliminating the wavelet coefficients with negligible magnitudes, thereby reducing the observational noise. We applied the developed methodology to the representation of the spatial and temporal variations of GIM from an extremely dense GPS network, the GPS Earth Observation Network (GEONET) in Japan. Since the sampling of the TEC is registered regularly in time, we use a two-dimensional B-spline wavelet representation in space and a one-dimensional spline interpolation in time. Over the Japan region, the B-spline wavelet method can overcome the problem of bias for the spherical harmonic model at the boundary, caused by the non-compact support. The hierarchical decomposition not only allows an inexpensive calculation, but also
BSR: B-spline atomic R-matrix codes
Zatsarinny, Oleg
2006-02-01
BSR is a general program to calculate atomic continuum processes using the B-spline R-matrix method, including electron-atom and electron-ion scattering, and radiative processes such as bound-bound transitions, photoionization and polarizabilities. The calculations can be performed in LS-coupling or in an intermediate-coupling scheme by including terms of the Breit-Pauli Hamiltonian. New version program summaryTitle of program: BSR Catalogue identifier: ADWY Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADWY Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland Computers on which the program has been tested: Microway Beowulf cluster; Compaq Beowulf cluster; DEC Alpha workstation; DELL PC Operating systems under which the new version has been tested: UNIX, Windows XP Programming language used: FORTRAN 95 Memory required to execute with typical data: Typically 256-512 Mwords. Since all the principal dimensions are allocatable, the available memory defines the maximum complexity of the problem No. of bits in a word: 8 No. of processors used: 1 Has the code been vectorized or parallelized?: no No. of lines in distributed program, including test data, etc.: 69 943 No. of bytes in distributed program, including test data, etc.: 746 450 Peripherals used: scratch disk store; permanent disk store Distribution format: tar.gz Nature of physical problem: This program uses the R-matrix method to calculate electron-atom and electron-ion collision processes, with options to calculate radiative data, photoionization, etc. The calculations can be performed in LS-coupling or in an intermediate-coupling scheme, with options to include Breit-Pauli terms in the Hamiltonian. Method of solution: The R-matrix method is used [P.G. Burke, K.A. Berrington, Atomic and Molecular Processes: An R-Matrix Approach, IOP Publishing, Bristol, 1993; P.G. Burke, W.D. Robb, Adv. At. Mol. Phys. 11 (1975) 143; K.A. Berrington, W.B. Eissner, P.H. Norrington, Comput
Pirpinia, K.; Bosman, P.A.N.; Sonke, J.-J.; van Herk, M.; Alderliesten, T.
2015-01-01
The use of gradient information is well-known to be highly useful in single-objective optimization-based image registration methods. However, its usefulness has not yet been investigated for deformable image registration from a multi-objective optimization perspective. To this end, within a previous
Institute of Scientific and Technical Information of China (English)
刘运峰; 宋寿鹏; 马晓鲲; 王成
2012-01-01
在超声检测中,液位、压力、应力等参数的测量实际上转化为超声信号度越时间的测量,如何有效地提取超声回波信号的波至时刻成为能否准确测量的关键.在分析了连续复小波变换的模极大值包络提取和小波的奇异点检测理论的基础上,提出了一种新的超声信号波至检测函数,并选用复频域B样条和高斯函数为小波基,在MATLAB上对仿真信号及原始超声信号分析处理.实验结果表明,此检测函数在较低的信噪比条件下也可有效地提取到超声回波信号的波至时刻.%In ultrasonic testing,the measurement of the liquid level,the pressure, the stress and so on is in fact the measurement of the time-of-flight of the ultrasonic signal. Then how to implement the extraction of ultrasonic signal arrival time precisely becomes so important. Based on envelop extraction of continuous complex wavelet transform and the singularity point detection theory , a new arrival time detection function is shown. Emulation and the real acquired ultrasonic data were processed with MATLAB u-sing complex frequency B-spline and Gaussian function as wavelet. It is proved that the function has good detection effect even under low SNR condition.
Nonrigid registration-based coronary artery motion correction for cardiac computed tomography
Energy Technology Data Exchange (ETDEWEB)
Bhagalia, Roshni; Pack, Jed D.; Miller, James V.; Iatrou, Maria [GE Global Research, Niskayuna, New York 12309 (United States); GE Healthcare, Hoboken, New Jersey 07030 (United States)
2012-07-15
Purpose: X-ray computed tomography angiography (CTA) is the modality of choice to noninvasively monitor and diagnose heart disease with coronary artery health and stenosis detection being of particular interest. Reliable, clinically relevant coronary artery imaging mandates high spatiotemporal resolution. However, advances in intrinsic scanner spatial resolution (CT scanners are available which combine nearly 900 detector columns with focal spot oversampling) can be tempered by motion blurring, particularly in patients with unstable heartbeats. As a result, recently numerous methods have been devised to improve coronary CTA imaging. Solutions involving hardware, multisector algorithms, or {beta}-blockers are limited by cost, oversimplifying assumptions about cardiac motion, and populations showing contraindications to drugs, respectively. This work introduces an inexpensive algorithmic solution that retrospectively improves the temporal resolution of coronary CTA without significantly affecting spatial resolution. Methods: Given the goal of ruling out coronary stenosis, the method focuses on 'deblurring' the coronary arteries. The approach makes no assumptions about cardiac motion, can be used on exams acquired at high heart rates (even over 75 beats/min), and draws on a fast and accurate three-dimensional (3D) nonrigid bidirectional labeled point matching approach to estimate the trajectories of the coronary arteries during image acquisition. Motion compensation is achieved by employing a 3D warping of a series of partial reconstructions based on the estimated motion fields. Each of these partial reconstructions is created from data acquired over a short time interval. For brevity, the algorithm 'Subphasic Warp and Add' (SWA) reconstruction. Results: The performance of the new motion estimation-compensation approach was evaluated by a systematic observer study conducted using nine human cardiac CTA exams acquired over a range of average heart
Directory of Open Access Journals (Sweden)
Xiaolong Wang
2013-01-01
Full Text Available In general, proper orthogonal decomposition (POD method is used to deal with single-parameter problems in engineering practice, and the linear interpolation is employed to establish the reduced model. Recently, this method is extended to solve the double-parameter problems with the amplitudes being achieved by cubic B-spline interpolation. In this paper, the accuracy of reduced models, which are established with linear interpolation and cubic B-spline interpolation, respectively, is verified via two typical examples. Both results of the two methods are satisfying, and the results of cubic B-spline interpolation are more accurate than those of linear interpolation. The results are meaningful for guiding the application of the POD interpolation to complex multiparameter problems.
B-Spline Finite Elements and their Efficiency in Solving Relativistic Mean Field Equations
Pöschl, W
1997-01-01
A finite element method using B-splines is presented and compared with a conventional finite element method of Lagrangian type. The efficiency of both methods has been investigated at the example of a coupled non-linear system of Dirac eigenvalue equations and inhomogeneous Klein-Gordon equations which describe a nuclear system in the framework of relativistic mean field theory. Although, FEM has been applied with great success in nuclear RMF recently, a well known problem is the appearance of spurious solutions in the spectra of the Dirac equation. The question, whether B-splines lead to a reduction of spurious solutions is analyzed. Numerical expenses, precision and behavior of convergence are compared for both methods in view of their use in large scale computation on FEM grids with more dimensions. A B-spline version of the object oriented C++ code for spherical nuclei has been used for this investigation.
Souto, Nelson; Thuillier, Sandrine; Andrade-Campos, A.
2016-10-01
Nowadays, full-field measurement methods are largely used to acquire the strain field developed by heterogeneous mechanical tests. Recent material parameters identification strategies based on a single heterogeneous test have been proposed considering that an inhomogeneous strain field can lead to a more complete mechanical characterization of the sheet metals. The purpose of this work is the design of a heterogeneous test promoting an enhanced mechanical behavior characterization of thin metallic sheets, under several strain paths and strain amplitudes. To achieve this goal, a design optimization strategy finding the appropriate specimen shape of the heterogeneous test by using either B-Splines or cubic splines was developed. The influence of using approximation or interpolation curves, respectively, was investigated in order to determine the most effective approach for achieving a better shape design. The optimization process is guided by an indicator criterion which evaluates, quantitatively, the strain field information provided by the mechanical test. Moreover, the design of the heterogeneous test is based on the resemblance with the experimental reality, since a rigid tool leading to uniaxial loading path is used for applying the displacement in a similar way as universal standard testing machines. The results obtained reveal that the optimization strategy using B-Splines curve approximation led to a heterogeneous test providing larger strain field information for characterizing the mechanical behavior of sheet metals.
A Cubic B-Spline Approach for Inter-Transformation Between Potential Field and Gradient Data
Wang, B.; Gao, S. S.
2008-12-01
Traditionally, algorithms involving Fast Fourier Transforms (FFT) are used to calculate gradients from field data and vise versa. Because the popular FFT differentiation algorithms are prone to noise, expensive field campaigns are increasingly utilized to obtain gradient data. In areas with both field and gradient data, transformation facilitates comparison. In areas with only one kind of data, transformation facilitates interpretation by transforming the measured data into another form of data. We advance unified formulae for interpolation, differentiation and integration using cubic B-splines, and propose new space-domain approaches for 2D and 3D transformations from potential field data to potential-field gradient data and vice versa. We also advance spline-based continuation techniques. In the spline-based algorithms, the spacing can be either regular or irregular. Analyses using synthetic and real gravity and magnetic data show that the new algorithms have higher accuracy, are more noise-tolerant and thus provide better insights into understanding the nature of the sources than the traditional FFT techniques.
2012-01-01
In this paper a new system identification algorithm is introduced for Hammerstein systems based on observational input/output data. The nonlinear static function in the Hammerstein system is modelled using a non-uniform rational B-spline (NURB) neural network. The proposed system identification algorithm for this NURB network based Hammerstein system consists of two successive stages. First the shaping parameters in NURB network are estimated using particle swarmoptimization (PSO) procedure. ...
Mittal, R. C.; Jain, R. K.
2012-12-01
In this paper, a numerical method is proposed to approximate the solution of the nonlinear parabolic partial differential equation with Neumann's boundary conditions. The method is based on collocation of cubic B-splines over finite elements so that we have continuity of the dependent variable and its first two derivatives throughout the solution range. We apply cubic B-splines for spatial variable and its derivatives, which produce a system of first order ordinary differential equations. We solve this system by using SSP-RK3 scheme. The numerical approximate solutions to the nonlinear parabolic partial differential equations have been computed without transforming the equation and without using the linearization. Four illustrative examples are included to demonstrate the validity and applicability of the technique. In numerical test problems, the performance of this method is shown by computing L∞andL2error norms for different time levels. Results shown by this method are found to be in good agreement with the known exact solutions.
n-dimensional non uniform rational b-splines for metamodeling
Energy Technology Data Exchange (ETDEWEB)
Turner, Cameron J [Los Alamos National Laboratory; Crawford, Richard H [UT-AUSTIN
2008-01-01
Non Uniform Rational B-splines (NURBs) have unique properties that make them attractive for engineering metamodeling applications. NURBs are known to accurately model many different continuous curve and surface topologies in 1- and 2-variate spaces. However, engineering metamodels of the design space often require hypervariate representations of multidimensional outputs. In essence, design space metamodels are hyperdimensional constructs with a dimensionality determined by their input and output variables. To use NURBs as the basis for a metamodel in a hyperdimensional space, traditional geometric fitting techniques must be adapted to hypervariate and hyperdimensional spaces composed of both continuous and discontinuous variable types. In this paper, they describe the necessary adaptations for the development of a NURBs-based metamodel called a Hyperdimensional Performance Model or HyPerModel. HyPerModels are capable of accurately and reliably modeling nonlinear hyperdimensional objects defined by both continuous and discontinuous variables of a wide variety of topologies, such as those that define typical engineering design spaces. They demonstrate this ability by successfully generating accurate HyPerModels of 10 trial functions laying the foundation for future work with N-dimensional NURBs in design space applications.
N-dimensional non uniform rational B-splines for metamodeling
Energy Technology Data Exchange (ETDEWEB)
Turner, Cameron J [Los Alamos National Laboratory; Crawford, Richard H [UT - AUSTIN
2008-01-01
Non Uniform Rational B-splines (NURBs) have unique properties that make them attractive for engineering metamodeling applications. NURBs are known to accurately model many different continuous curve and surface topologies in 1-and 2-variate spaces. However, engineering metamodels of the design space often require hypervariate representations of multidimensional outputs. In essence, design space metamodels are hyperdimensional constructs with a dimensionality determined by their input and output variables. To use NURBs as the basis for a metamodel in a hyperdimensional space, traditional geometric fitting techniques must be adapted to hypervariate and hyperdimensional spaces composed of both continuous and discontinuous variable types. In this paper, we describe the necessary adaptations for the development of a NURBs-based metamodel called a Hyperdimensional Performance Model or HyPerModel. HyPerModels are capable of accurately and reliably modeling nonlinear hyperdimensional objects defined by both continuous and discontinuous variables of a wide variety of topologies, such as those that define typical engineering design spaces. We demonstrate this ability by successfully generating accurate HyPerModels of 10 trial functions laying the foundation for future work with N-dimensional NURBs in design space applications.
Estimating kinetic parameters in TGA using B-spline smoothing and the Friedman method
Energy Technology Data Exchange (ETDEWEB)
Zhang, Xiaojie; Preto, Fernando [CANMET Energy Technology Centre (CETC), Natural Resources (Canada); de Jong, Wiebren [Faculty 3mE, Department of Process and Energy, ET Section, Delft University of Technology, Leeghwaterstraat 44, 2628 CD Delft (Netherlands)
2009-10-15
The pyrolysis of biomass occurs via several parallel/serial decomposition reactions. The kinetic parameters, namely the activation energy (E) and the pre-exponential factor (k{sub o}), do not remain constant during the pyrolysis process. A modified empirical method is introduced for calculating the activation energy (E) and the pre-exponential factor (k{sub 0}) based on the Friedman analysis [Friedman HL. Kinetics of thermal degradation of char-forming plastics from thermogravimetry - application to a phenolic plastic. [J Polym Sci C 1963;6: 183-95]. The kinetic parameters are expressed as a function of the conversion (x) during the biomass pyrolysis process. The reactions are assumed to be of first order. At least three data sets obtained at different dynamic heating rates are required. From the Friedman analysis, the conversion (x) related functions E = E(x) and k{sub o} = k{sub o}(x) can be obtained by a B-spline regression method. The pyrolysis can hence be described as: dx/ dt=k(1-x)=k{sub o}(x). exp (-E(x)/RT)(1-x). In this paper, the adapted method is applied to pyrolysis of cellulose and two biomass fuels (meat and bone meal, chicken litter). Experiments were carried out at 2, 10 and 50 K min{sup -1} by thermogravimetric analysis. A good fit of the calculated conversion with experimental data was found. (author)
Energy Technology Data Exchange (ETDEWEB)
Linsen, L; Pascucci, V; Duchaineau, M A; Hamann, B; Joy, K I
2002-11-19
Multiresolution methods for representing data at multiple levels of detail are widely used for large-scale two- and three-dimensional data sets. We present a four-dimensional multiresolution approach for time-varying volume data. This approach supports a hierarchy with spatial and temporal scalability. The hierarchical data organization is based on 4{radical}2 subdivision. The n{radical}2-subdivision scheme only doubles the overall number of grid points in each subdivision step. This fact leads to fine granularity and high adaptivity, which is especially desirable in the spatial dimensions. For high-quality data approximation on each level of detail, we use quadrilinear B-spline wavelets. We present a linear B-spline wavelet lighting scheme based on n{radical}2 subdivision to obtain narrow masks for the update rules. Narrow masks provide a basis for out-of-core data exploration techniques and view-dependent visualization of sequences of time steps.
Directory of Open Access Journals (Sweden)
Zhiwei Pan
2016-05-01
Full Text Available Global look-up table strategy proposed recently has been proven to be an efficient method to accelerate the interpolation, which is the most time-consuming part in the iterative sub-pixel digital image correlation (DIC algorithms. In this paper, a global look-up table strategy with cubic B-spline interpolation is developed for the DIC method based on the inverse compositional Gauss–Newton (IC-GN algorithm. The performance of this strategy, including accuracy, precision, and computation efficiency, is evaluated through a theoretical and experimental study, using the one with widely employed bicubic interpolation as a benchmark. The global look-up table strategy with cubic B-spline interpolation improves significantly the accuracy of the IC-GN algorithm-based DIC method compared with the one using the bicubic interpolation, at a trivial price of computation efficiency.
Institute of Scientific and Technical Information of China (English)
A. Zerarka; O. Haif-Khaif; K. Libarir; A. Attaf
2011-01-01
This research concerns with the development of a linear three-dimensional numerical model in a quantum environment. We use the semi inverse variational method together with B-spline bases to extract the structures of bound states of the Schr(o)dinger equation. The model performances are demonstrated for the Coulomb type problem. From realistic examples, some state configurations are presented to illustrate the effectiveness and the exactitude of the proposed method.
B-Spline with Symplectic Algorithm Method for Solution of Time-Dependent Schr(o)dinger Equations
Institute of Scientific and Technical Information of China (English)
BIAN Xue-Bin; QIAO Hao-Xue; SHI Ting-Yun
2006-01-01
@@ A B-spline with the symplectic algorithm method for the solution of time-dependent Schr(o)dinger equations(TDSEs) is introduced. The spatial part of the wavefunction is expanded by B-spline and the time evolution is given in a symplectic scheme.
Least square fitting of low resolution gamma ray spectra with cubic B-spline basis functions
Institute of Scientific and Technical Information of China (English)
ZHU Meng-Hua; LIU Liang-Gang; QI Dong-Xu; YOU Zhong; XU Ao-Ao
2009-01-01
In this paper,the least square fitting method with the cubic B-spline basis hmctioas is derived to reduce the influence of statistical fluctuations in the gamma ray spectra.The derived procedure is simple and automatic.The results show that this method is better than the convolution method with a sufficient reduction of statistical fluctuation.
Study of Microwave Multiphoton Transition of Rydberg Potassium Atom by Using B-Spline
Institute of Scientific and Technical Information of China (English)
JIN Cheng; ZHOU Xiao-Xin; ZHAO Song-Feng
2005-01-01
The B-spline expansion technique and time-dependent two-level approach are applied to study the interaction between the microwave field and potassium atoms in a static electric field. We obtain theoretical multiphoton resonance spectra that can be compared with the experimental data. We also obtain the time evolution of the final state in different microwave fields.
The use of B-splines in the assessment of strain levels associated with plain dents
Energy Technology Data Exchange (ETDEWEB)
Noronha Junior, Dauro B.; Martins, Ricardo R. [PETROBRAS, Rio de Janeiro, RJ (Brazil). Centro de Pesquisas (CENPES); Jacob, Breno P.; Souza, Eduardo [Coordenacao dos Programas de Pos-graduacao de Engenharia (COPPE/UFRJ), Rio de Janeiro, RJ (Brazil). Programa de Engenharia Civil. Lab. de Metodos Computacionais e Sistemas Offshore (LAMCSO)
2005-07-01
Most international pipeline codes consider plain dents injurious if they exceed a depth of 6% of the nominal pipe diameter. ASME B31.8 - Gas Transmission and Distribution Piping Systems - 2003 Edition gives an alternative to the above mentioned limit. According to this edition of the code, plain dents of any depth are acceptable provided strain levels associated with the deformation do not exceed 6% strain. In order to use the method for estimating strain in dents proposed in Appendix R of B31.8 Code, interpolation or other mathematical technique is usually necessary to develop surface contour information from in-line inspections (ILI) tools or direct information data. This paper describes the application of a piece-wise interpolating technique that makes use of fourth-order B-spline curves to approximating the dent profile in both longitudinal and circumferential directions. The results obtained using B-splines were tested against nonlinear finite analyses of dented pipelines and a distinct methodology proposed by Rosenfeld et al. (1998). The results obtained with the use of B-splines compared well with both techniques. Furthermore, the extension of the proposed methodology to the description of the topology of dents with more general shapes using B-spline surfaces is very promising. (author)
Calculations of Electron Structure of Endohedrally Confined Helium Atom with B-Spline Type Functions
Institute of Scientific and Technical Information of China (English)
QIAO HaoXue; SHI TingYun; LI BaiWen
2002-01-01
The B-spline basis set method is used to study the properties of helium confined endohedrally at thegeometrical centre of a fullerene. The boundary conditions of the wavefunctions can be simply satisfied with thismethod. From our results, the phenomenon of "mirror collapse" is found in the case of confining helium. The interestingbehaviors of confining helium are also discussed.
Directory of Open Access Journals (Sweden)
Binjie Qin
2009-12-01
Full Text Available This paper proposes a novel global-to-local nonrigid brain MR image registration to compensate for the brain shift and the unmatchable outliers caused by the tumor resection. The mutual information between the corresponding salient structures, which are enhanced by the joint saliency map (JSM, is maximized to achieve a global rigid registration of the two images. Being detected and clustered at the paired contiguous matching areas in the globally registered images, the paired pools of DoG keypoints in combination with the JSM provide a useful cluster-to-cluster correspondence to guide the local control-point correspondence detection and the outlier keypoint rejection. Lastly, a quasi-inverse consistent deformation is smoothly approximated to locally register brain images through the mapping the clustered control points by compact support radial basis functions. The 2D implementation of the method can model the brain shift in brain tumor resection MR images, though the theory holds for the 3D case.
Duddu, Ravindra
2011-10-05
We present a numerical formulation aimed at modeling the nonlinear response of elastic materials using large deformation continuum mechanics in three dimensions. This finite element formulation is based on the Eulerian description of motion and the transport of the deformation gradient. When modeling a nearly incompressible solid, the transport of the deformation gradient is decomposed into its isochoric part and the Jacobian determinant as independent fields. A homogeneous isotropic hyperelastic solid is assumed and B-splines-based finite elements are used for the spatial discretization. A variational multiscale residual-based approach is employed to stabilize the transport equations. The performance of the scheme is explored for both compressible and nearly incompressible applications. The numerical results are in good agreement with theory illustrating the viability of the computational scheme. © 2011 John Wiley & Sons, Ltd.
Knot Removing and Smoothing Method of Generalized B-Spline Curves%广义B样条曲线的节点去除与光顺算法
Institute of Scientific and Technical Information of China (English)
张莉; 葛先玉; 檀结庆
2016-01-01
广义B样条曲线具备了B样条曲线的各种优良性质，又因为其独具的核函数为形状设计带来更加丰富的可能性，文中提出了广义 B 样条曲线的节点去除与光顺算法。首先给出了构造广义 B 样条对偶基的新方法，其时间计算复杂度得到了很好的控制；其次摘除需去除的节点，再利用对偶基的最佳逼近性质，采用广义 B 样条的对偶基求得新的广义B样条曲线的控制顶点；在广义B样条曲线光顺中引入跳跃值的概念，如果某个节点附近的跳跃值较大，则去除相应的节点，从而实现在此节点处的光顺。最后通过大量的数值实例，展示了算法的有效性。%Generalized B-splines are not only compatible with classical B-splines but also provide plentiful shapes for geometric modeling systems because of their flexible core functions. The paper focuses on knots removal and smooth method of generalized B-splines. Firstly, the dual bases of generalized B-splines are constructed, and the complexity can be reduced a lot. Secondly, jump value is introduced, if jump values of some knots are too big, the corresponding knots are removed. At last, by the aid of best approximation prop-erty of the generalized B-splines’ dual bases, control points of new approximating generalized B-splines are obtained. Thus, knots removal and smooth of curves are realized. Numerical examples are given to illustrate the effectiveness of the method.
A Taylor-Galerkin finite element method for the KdV equation using cubic B-splines
Energy Technology Data Exchange (ETDEWEB)
Canivar, Aynur [Cemal Mumtaz Teachers Training Anatolian High School, 26210 Eskisehir (Turkey); Sari, Murat, E-mail: msari@pau.edu.t [Department of Mathematics, Pamukkale University, Denizli 20070 (Turkey); Dag, Idris [Department of Computer Engineering, Eskisehir Osmangazi University, Eskisehir 26480 (Turkey)
2010-08-15
In this paper, to obtain accurate solutions of the Korteweg-de Vries (KdV) equation, a Taylor-Galerkin method is proposed based on cubic B-splines over finite elements. To tackle this a forward time-stepping technique is accepted in time. To see the accuracy of the proposed method, L{sub 2} and L{sub {infinity} }error norms are calculated in three test problems. The numerical results are found to be in good agreement with exact solutions and with the literature. The applied numerical method has also been shown to be unconditionally stable. In order to find out the physical behaviour of more intricate models, this procedure has been seen to have a great potentiality.
Introduction of b-splines to trajectory planning for robot manipulators
Directory of Open Access Journals (Sweden)
Per E. Koch
1988-04-01
Full Text Available This paper describes how B-splines can be used to construct joint trajectories for robot manipulators. The motion is specified by a sequence of Cartesian knots, i.e., positions and orientations of the end effector of a robot manipulator. For a six joint robot manipulator, these Cartesian knots are transformed into six sets of joint variables, with each set corresponding to a joint. Splines, represented as linear combinations of B-splines, are used to fit the sequence of joint variables for each of the six joints. A computationally very simple, recurrence formula is used to generate the 8-splines. This approach is used for the first time to establish the mathematical model of trajectory generation for robot manipulators, and offers flexibility, computational efficiency, and a compact representation.
A Unified Representation Scheme for Solid Geometric Objects Using B-splines (extended Abstract)
Bahler, D.
1985-01-01
A geometric representation scheme called the B-spline cylinder, which consists of interpolation between pairs of uniform periodic cubic B-spline curves is discussed. This approach carries a number of interesting implications. For one, a single relatively simple database schema can be used to represent a reasonably large class of objects, since the spline representation is flexible enough to allow a large domain of representable objects at very little cost in data complexity. The model is thus very storage-efficient. A second feature of such a system is that it reduces to one the number of routines which the system must support to perform a given operation on objects. Third, the scheme enables easy conversion to and from other representations. The formal definition of the cylinder entity is given. In the geometric properties of the entity are explored and several operations on such objects are defined. Some general purpose criteria for evaluating any geometric representation scheme are introduced and the B-spline cylinder scheme according to these criteria is evaluated.
Energy Technology Data Exchange (ETDEWEB)
McCurdy, C. William; Horner, Daniel A.; Rescigno, Thomas N.; Martin, Fernando
2004-02-19
Calculations of absolute triple differential and single differential cross sections for helium double photoionization are performed using an implementation of exterior complex scaling in B-splines. Results for cross sections, well-converged in partial waves, are presented and compared with both experiment and earlier theoretical calculations. These calculations establish the practicality and effectiveness of the complex B-spline approach to calculations of double ionization of atomic and molecular systems.
Durmaz, Murat; Karslioglu, Mahmut Onur
2015-04-01
There are various global and regional methods that have been proposed for the modeling of ionospheric vertical total electron content (VTEC). Global distribution of VTEC is usually modeled by spherical harmonic expansions, while tensor products of compactly supported univariate B-splines can be used for regional modeling. In these empirical parametric models, the coefficients of the basis functions as well as differential code biases (DCBs) of satellites and receivers can be treated as unknown parameters which can be estimated from geometry-free linear combinations of global positioning system observables. In this work we propose a new semi-parametric multivariate adaptive regression B-splines (SP-BMARS) method for the regional modeling of VTEC together with satellite and receiver DCBs, where the parametric part of the model is related to the DCBs as fixed parameters and the non-parametric part adaptively models the spatio-temporal distribution of VTEC. The latter is based on multivariate adaptive regression B-splines which is a non-parametric modeling technique making use of compactly supported B-spline basis functions that are generated from the observations automatically. This algorithm takes advantage of an adaptive scale-by-scale model building strategy that searches for best-fitting B-splines to the data at each scale. The VTEC maps generated from the proposed method are compared numerically and visually with the global ionosphere maps (GIMs) which are provided by the Center for Orbit Determination in Europe (CODE). The VTEC values from SP-BMARS and CODE GIMs are also compared with VTEC values obtained through calibration using local ionospheric model. The estimated satellite and receiver DCBs from the SP-BMARS model are compared with the CODE distributed DCBs. The results show that the SP-BMARS algorithm can be used to estimate satellite and receiver DCBs while adaptively and flexibly modeling the daily regional VTEC.
Zhiwei Pan; Wei Chen; Zhenyu Jiang; Liqun Tang; Yiping Liu; Zejia Liu
2016-01-01
Global look-up table strategy proposed recently has been proven to be an efficient method to accelerate the interpolation, which is the most time-consuming part in the iterative sub-pixel digital image correlation (DIC) algorithms. In this paper, a global look-up table strategy with cubic B-spline interpolation is developed for the DIC method based on the inverse compositional Gauss–Newton (IC-GN) algorithm. The performance of this strategy, including accuracy, precision, and computation effi...
直线网格B样条混合滤波GPU光线投射%Rectilinear Grid GPU Raycasting with B-Spline Hybrid Filtering
Institute of Scientific and Technical Information of China (English)
袁斌
2013-01-01
To render rectilinear grid quickly to produce high quality image, this paper gives B-spline hybrid filtering and implementation speed grid that are applied to GPU-raycasting for rectilinear grid. Proposition about sign property of derivative of B-spline basics is proved. Furthermore, it is shown that there are significant errors in some cases when S&H method is used to compute derivative of B-spline. According to such a conclusion, in ray integration, S&H method is used if the condition is satisfied; otherwise B-spline basic equation is used. Moreover, proposition about range of derivatives of B-spline functions is proved, so that gradient magnitude modulation and speed grid are implemented in GPU; in ray integration, interfaces between materials are shown with gradient magnitude modulation and empty space is skipped with speed grid. As a result, GPU-raycasting with the hybrid method in this paper frees artifacts caused by generalized S&H algorithm; it is faster than stationary step GPU-raycasting based on B-spline basic equation; it can represent the true feature of things measured or simulated if they are smooth.%为了快速、高质量地绘制直线网格,提出B样条混合滤波方法,实现加速网格,并将其应用到直线网格GPU光线投射.证明了三次B样条基函数导数的符号性质,进而证明用快速三次滤波方法(S& H方法)计算非均匀B样条函数的导数会出现误差.据此,在光线积分计算中,如果条件允许,采用S & H方法；否则采用基于B样条基本公式的滤波方法.另外,证明三次B样条函数导数的范围,以实现梯度量调制和加速网格；在光线积分计算中,利用梯度量调制表现物质的分界面；利用加速网格,跳过无效积分步,加快绘制速度.实验结果表明,采用混合滤波的直线网格GPU光线投射方法能消除S&H方法导致的走样现象；与基于B样条基本公式的绘制方法相比,该方法更快；如果模拟
Energy Spectra of the Confined Atoms Obtained by Using B-Splines
Institute of Scientific and Technical Information of China (English)
SHI Ting-Yun; BAO Cheng-Guang; LI Bai-Wen
2001-01-01
We have calculated the energy spectra of one- and two-electron atoms (ions) centered in an impenetrable spherical box by variational method with B-splines as basis functions. Accurate results are obtained for both large and small radii of confinement. The critical box radius of confined hydrogen atom is also calculated to show the usefulness of our method. A partial energy degeneracy in confined hydrogen atom is found when the radius of spherical box is equal to the distance at which a node of single-node wavefunctions of free hydrogen atom is located.
A cubic B-spline Galerkin approach for the numerical simulation of the GEW equation
Directory of Open Access Journals (Sweden)
S. Battal Gazi Karakoç
2016-02-01
Full Text Available The generalized equal width (GEW wave equation is solved numerically by using lumped Galerkin approach with cubic B-spline functions. The proposed numerical scheme is tested by applying two test problems including single solitary wave and interaction of two solitary waves. In order to determine the performance of the algorithm, the error norms L2 and L∞ and the invariants I1, I2 and I3 are calculated. For the linear stability analysis of the numerical algorithm, von Neumann approach is used. As a result, the obtained findings show that the presented numerical scheme is preferable to some recent numerical methods.
System identification of Wiener systems with B-spline functions using De Boor recursion
Hong, X.; Mitchell, R. J.; Chen, S.
2013-09-01
In this article a simple and effective algorithm is introduced for the system identification of the Wiener system using observational input/output data. The nonlinear static function in the Wiener system is modelled using a B-spline neural network. The Gauss-Newton algorithm is combined with De Boor algorithm (both curve and the first order derivatives) for the parameter estimation of the Wiener model, together with the use of a parameter initialisation scheme. Numerical examples are utilised to demonstrate the efficacy of the proposed approach.
Uniform B-Spline Curve Interpolation with Prescribed Tangent and Curvature Vectors.
Okaniwa, Shoichi; Nasri, Ahmad; Lin, Hongwei; Abbas, Abdulwahed; Kineri, Yuki; Maekawa, Takashi
2012-09-01
This paper presents a geometric algorithm for the generation of uniform cubic B-spline curves interpolating a sequence of data points under tangent and curvature vectors constraints. To satisfy these constraints, knot insertion is used to generate additional control points which are progressively repositioned using corresponding geometric rules. Compared to existing schemes, our approach is capable of handling plane as well as space curves, has local control, and avoids the solution of the typical linear system. The effectiveness of the proposed algorithm is illustrated through several comparative examples. Applications of the method in NC machining and shape design are also outlined.
Csébfalvi, Balázs
2010-01-01
In this paper, we demonstrate that quasi-interpolation of orders two and four can be efficiently implemented on the Body-Centered Cubic (BCC) lattice by using tensor-product B-splines combined with appropriate discrete prefilters. Unlike the nonseparable box-spline reconstruction previously proposed for the BCC lattice, the prefiltered B-spline reconstruction can utilize the fast trilinear texture-fetching capability of the recent graphics cards. Therefore, it can be applied for rendering BCC-sampled volumetric data interactively. Furthermore, we show that a separable B-spline filter can suppress the postaliasing effect much more isotropically than a nonseparable box-spline filter of the same approximation power. Although prefilters that make the B-splines interpolating on the BCC lattice do not exist, we demonstrate that quasi-interpolating prefiltered linear and cubic B-spline reconstructions can still provide similar or higher image quality than the interpolating linear box-spline and prefiltered quintic box-spline reconstructions, respectively.
Marghany, Maged
2014-06-01
A critical challenges in urban aeras is slums. In fact, they are considered a source of crime and disease due to poor-quality housing, unsanitary conditions, poor infrastructures and occupancy security. The poor in the dense urban slums are the most vulnerable to infection due to (i) inadequate and restricted access to safety, drinking water and sufficient quantities of water for personal hygiene; (ii) the lack of removal and treatment of excreta; and (iii) the lack of removal of solid waste. This study aims to investigate the capability of ENVISAT ASAR satellite and Google Earth data for three-dimensional (3-D) slum urban reconstruction in developed countries such as Egypt. The main objective of this work is to utilize some 3-D automatic detection algorithm for urban slum in ENVISAT ASAR and Google Erath images were acquired in Cairo, Egypt using Fuzzy B-spline algorithm. The results show that the fuzzy algorithm is the best indicator for chaotic urban slum as it can discriminate between them from its surrounding environment. The combination of Fuzzy and B-spline then used to reconstruct 3-D of urban slum. The results show that urban slums, road network, and infrastructures are perfectly discriminated. It can therefore be concluded that the fuzzy algorithm is an appropriate algorithm for chaotic urban slum automatic detection in ENVSIAT ASAR and Google Earth data.
G1 Continuity Conditions of B-spline Surfaces%B样条曲面间的G1连续条件
Institute of Scientific and Technical Information of China (English)
车翔玖; 梁学章
2002-01-01
According to the B-spline theory and Boehm algorithm, this paper presents severalnecessary and sufficient G1 continuity conditions between two adjacent B-spline surfaces. In orderto meet the need of application, a kind of sufficient conditions of G1 continuity are developed, anda kind of sufficient conditions of G1 continuity among N(N ＞ 2) patch B-spline surfaces meetingat a common corner are given at the end.
Energy Technology Data Exchange (ETDEWEB)
Vijayan, Sinara, E-mail: sinara.vijayan@ntnu.no [Norwegian University of Science and Technology, 7491 Trondheim (Norway); Klein, Stefan [Norwegian University of Science and Technology, 7491 Trondheim, Norway and Biomedical Imaging Group Rotterdam, Department of Medical Informatics and Radiology, Erasmus MC, 3000 CA Rotterdam (Netherlands); Hofstad, Erlend Fagertun; Langø, Thomas [SINTEF, Department Medical Technology, 7465 Trondheim (Norway); Lindseth, Frank [Norwegian University of Science and Technology, 7491 Trondheim, Norway and SINTEF, Department Medical Technology, 7465 Trondheim (Norway); Ystgaard, Brynjulf [Department of Surgery, St. Olavs Hospital, 7030 Trondheim (Norway)
2014-08-15
Purpose: Treatments like radiotherapy and focused ultrasound in the abdomen require accurate motion tracking, in order to optimize dosage delivery to the target and minimize damage to critical structures and healthy tissues around the target. 4D ultrasound is a promising modality for motion tracking during such treatments. In this study, the authors evaluate the accuracy of motion tracking in the liver based on deformable registration of 4D ultrasound images. Methods: The offline analysis was performed using a nonrigid registration algorithm that was specifically designed for motion estimation from dynamic imaging data. The method registers the entire 4D image data sequence in a groupwise optimization fashion, thus avoiding a bias toward a specifically chosen reference time point. Three healthy volunteers were scanned over several breathing cycles (12 s) from three different positions and angles on the abdomen; a total of nine 4D scans for the three volunteers. Well-defined anatomic landmarks were manually annotated in all 96 time frames for assessment of the automatic algorithm. The error of the automatic motion estimation method was compared with interobserver variability. The authors also performed experiments to investigate the influence of parameters defining the deformation field flexibility and evaluated how well the method performed with a lower temporal resolution in order to establish the minimum frame rate required for accurate motion estimation. Results: The registration method estimated liver motion with an error of 1 mm (75% percentile over all datasets), which was lower than the interobserver variability of 1.4 mm. The results were only slightly dependent on the degrees of freedom of the deformation model. The registration error increased to 2.8 mm with an eight times lower temporal resolution. Conclusions: The authors conclude that the methodology was able to accurately track the motion of the liver in the 4D ultrasound data. The authors believe
Shao, Chenxi; Xue, Yong; Fang, Fang; Bai, Fangzhou; Yin, Peifeng; Wang, Binghong
2015-07-01
The self-controlling feedback control method requires an external periodic oscillator with special design, which is technically challenging. This paper proposes a chaos control method based on time series non-uniform rational B-splines (SNURBS for short) signal feedback. It first builds the chaos phase diagram or chaotic attractor with the sampled chaotic time series and any target orbit can then be explicitly chosen according to the actual demand. Second, we use the discrete timing sequence selected from the specific target orbit to build the corresponding external SNURBS chaos periodic signal, whose difference from the system current output is used as the feedback control signal. Finally, by properly adjusting the feedback weight, we can quickly lead the system to an expected status. We demonstrate both the effectiveness and efficiency of our method by applying it to two classic chaotic systems, i.e., the Van der Pol oscillator and the Lorenz chaotic system. Further, our experimental results show that compared with delayed feedback control, our method takes less time to obtain the target point or periodic orbit (from the starting point) and that its parameters can be fine-tuned more easily.
Energy Technology Data Exchange (ETDEWEB)
Shao, Chenxi, E-mail: cxshao@ustc.edu.cn; Xue, Yong; Fang, Fang; Bai, Fangzhou [Department of Computer Science and Technology, University of Science and Technology of China, Hefei 230027 (China); Yin, Peifeng [Department of Computer Science and Engineering, Pennsylvania State University, State College, Pennsylvania 16801 (United States); Wang, Binghong [Department of Modern Physics, University of Science and Technology of China, Hefei 230026 (China)
2015-07-15
The self-controlling feedback control method requires an external periodic oscillator with special design, which is technically challenging. This paper proposes a chaos control method based on time series non-uniform rational B-splines (SNURBS for short) signal feedback. It first builds the chaos phase diagram or chaotic attractor with the sampled chaotic time series and any target orbit can then be explicitly chosen according to the actual demand. Second, we use the discrete timing sequence selected from the specific target orbit to build the corresponding external SNURBS chaos periodic signal, whose difference from the system current output is used as the feedback control signal. Finally, by properly adjusting the feedback weight, we can quickly lead the system to an expected status. We demonstrate both the effectiveness and efficiency of our method by applying it to two classic chaotic systems, i.e., the Van der Pol oscillator and the Lorenz chaotic system. Further, our experimental results show that compared with delayed feedback control, our method takes less time to obtain the target point or periodic orbit (from the starting point) and that its parameters can be fine-tuned more easily.
Energy Technology Data Exchange (ETDEWEB)
Li, Xin; Miller, Eric L.; Rappaport, Carey; Silevich, Michael
2000-04-11
A common problem in signal processing is to estimate the structure of an object from noisy measurements linearly related to the desired image. These problems are broadly known as inverse problems. A key feature which complicates the solution to such problems is their ill-posedness. That is, small perturbations in the data arising e.g. from noise can and do lead to severe, non-physical artifacts in the recovered image. The process of stabilizing these problems is known as regularization of which Tikhonov regularization is one of the most common. While this approach leads to a simple linear least squares problem to solve for generating the reconstruction, it has the unfortunate side effect of producing smooth images thereby obscuring important features such as edges. Therefore, over the past decade there has been much work in the development of edge-preserving regularizers. This technique leads to image estimates in which the important features are retained, but computationally the y require the solution of a nonlinear least squares problem, a daunting task in many practical multi-dimensional applications. In this thesis we explore low-order models for reducing the complexity of the re-construction process. Specifically, B-Splines are used to approximate the object. If a ''proper'' collection B-Splines are chosen that the object can be efficiently represented using a few basis functions, the dimensionality of the underlying problem will be significantly decreased. Consequently, an optimum distribution of splines needs to be determined. Here, an adaptive refining and pruning algorithm is developed to solve the problem. The refining part is based on curvature information, in which the intuition is that a relatively dense set of fine scale basis elements should cluster near regions of high curvature while a spares collection of basis vectors are required to adequately represent the object over spatially smooth areas. The pruning part is a greedy
AHT Bézier Curves and NUAHT B-Spline Curves
Institute of Scientific and Technical Information of China (English)
Gang Xu; Guo-Zhao Wang
2007-01-01
In this paper, we present two new unified mathematics models of conics and polynomial curves, called algebraic hyperbolic trigonometric ( AHT) Bézier curves and non-uniform algebraic hyperbolic trigonometric ( NUAHT) B-sptine curves of order n, which are generated over the space span{sin t, cos t, sinh t, cosh t, 1, t,..., tn-5}, n ≥ 5. The two kinds of curves share most of the properties as those of the Bézier curves and B-spline curves in polynomial space. In particular, they can represent exactly some remarkable transcendental curves such as the helix, the cycloid and the catenary. The subdivision formulae of these new kinds of curves are also given. The generations of the tensor product surfaces are straightforward. Using the new mathematics models, we present the control mesh representations of two classes of minimal surfaces.
Frequency-modulated excitation of Rydberg potassium atoms by using B-spline
Institute of Scientific and Technical Information of China (English)
Li Xiao-Yong; Wang Guo-Li; Zhou Xiao-Xin
2012-01-01
By using the B-spline expansion technique and a model potential of the alkali atoms,the properties of frequencymodulated excitation of Rydberg potassium atoms in a static electric field and a microwave field are investigated by using the time-dependent two-level approach.We successfully reproduce the square wave oscillations in the low frequency,the stair step population oscillations in the intermediate frequency,and the multiphoton transitions in the high frequency with respect to the unmodulated Rabi frequency,which have been observed experimentally by Noel et al.[Phys.Rev.A 58 2265 (1998)].Furthermore,we also numerically obtain the discretized Rabi oscillations predicted in the Landau-Zener accumulation model.
Soldea, Octavian; Elber, Gershon; Rivlin, Ehud
2006-02-01
This paper presents a method to globally segment volumetric images into regions that contain convex or concave (elliptic) iso-surfaces, planar or cylindrical (parabolic) iso-surfaces, and volumetric regions with saddle-like (hyperbolic) iso-surfaces, regardless of the value of the iso-surface level. The proposed scheme relies on a novel approach to globally compute, bound, and analyze the Gaussian and mean curvatures of an entire volumetric data set, using a trivariate B-spline volumetric representation. This scheme derives a new differential scalar field for a given volumetric scalar field, which could easily be adapted to other differential properties. Moreover, this scheme can set the basis for more precise and accurate segmentation of data sets targeting the identification of primitive parts. Since the proposed scheme employs piecewise continuous functions, it is precise and insensitive to aliasing.
Collocation method with quintic b-spline method for solving hirota-satsuma coupled KDV equation
Directory of Open Access Journals (Sweden)
K. R. Raslan
2016-05-01
Full Text Available In the present paper, a numerical method is proposed for the numerical solution of a coupled system of KdV (CKdV equation with appropriate initial and boundary conditions by using collocation method with quintic B-spline on the uniform mesh points. The method is shown to be unconditionally stable using von-Neumann technique. To test accuracy the error norms, are computed. Three invariants of motion are predestined to determine the preservation properties of the problem, and the numerical scheme leads to careful and active results. Furthermore, interaction of two and three solitary waves is shown. These results show that the technique introduced here is easy to apply. We make linearization for the nonlinear term.
Efficient nonrigid registration using ranked order statistics
DEFF Research Database (Denmark)
Tennakoon, Ruwan B.; Bab-Hadiashar, Alireza; de Bruijne, Marleen
2013-01-01
Non-rigid image registration techniques are widely used in medical imaging applications. Due to high computational complexities of these techniques, finding appropriate registration method to both reduce the computation burden and increase the registration accuracy has become an intense area...... of research. In this paper we propose a fast and accurate non-rigid registration method for intra-modality volumetric images. Our approach exploits the information provided by an order statistics based segmentation method, to find the important regions for registration and use an appropriate sampling scheme...... to target those areas and reduce the registration computation time. A unique advantage of the proposed method is its ability to identify the point of diminishing returns and stop the registration process. Our experiments on registration of real lung CT images, with expert annotated landmarks, show...
RATIONAL QUADRATIC B-SPLINE INTERPOLATION OF FUNCTION SEGMENTS%函数的分段有理二次B样条插值
Institute of Scientific and Technical Information of China (English)
梁锡坤
2012-01-01
Based on the proper segmentation of complicated functions, the triangle convex hull of functions segment is introduced. We propose a scheme of control polygon determination by the tangent of the endpoints of the segment intervals. The algorithm of the segment rational quadratic B-spline interpolation of complicated functions is discussed in details. The interpolation keeps many important geometric features of the original function such as convexity, monotonicity and G1 continuity. The numerical experiments show that the algorithm provides an efficient approach to approximate representation of complicated functions.%0引 言 科学和工程计算中,函数的近似表示一直是一个重要课题.近似方法一般可归结为插值、逼近和拟合三种基本类型,经历长期发展,函数逼近方法[1-3]十分丰富.
Geometric Hermite Interpolation for Space Curves by B-Spline%空间曲线几何Hermite插值的B样条方法
Institute of Scientific and Technical Information of China (English)
朱春钢; 王仁宏
2005-01-01
在给定的GC2插值条件,利用de Boor的构造平面曲线的GC2-Hermite插值方法,构造了一条具有两个自由度的三次B样条插值曲线,并证明插值曲线是局部存在的且具有4阶精度.%This paper considers the space GC2 Hermite interpolation by cubic B-spline curve which is based on de Boor's idea for constructing the planar GC2 Hermite interpolation. In addition to position and tangent direction, the curvature vector is interpolated at each point. It is proved that under appropriate assumptions the interpolant exists locally with two degrees of freedom and the 4th order accuracy.
Jiwari, Ram
2015-08-01
In this article, the author proposed two differential quadrature methods to find the approximate solution of one and two dimensional hyperbolic partial differential equations with Dirichlet and Neumann's boundary conditions. The methods are based on Lagrange interpolation and modified cubic B-splines respectively. The proposed methods reduced the hyperbolic problem into a system of second order ordinary differential equations in time variable. Then, the obtained system is changed into a system of first order ordinary differential equations and finally, SSP-RK3 scheme is used to solve the obtained system. The well known hyperbolic equations such as telegraph, Klein-Gordon, sine-Gordon, Dissipative non-linear wave, and Vander Pol type non-linear wave equations are solved to check the accuracy and efficiency of the proposed methods. The numerical results are shown in L∞ , RMS andL2 errors form.
Hardy, David J; Wolff, Matthew A; Xia, Jianlin; Schulten, Klaus; Skeel, Robert D
2016-03-21
The multilevel summation method for calculating electrostatic interactions in molecular dynamics simulations constructs an approximation to a pairwise interaction kernel and its gradient, which can be evaluated at a cost that scales linearly with the number of atoms. The method smoothly splits the kernel into a sum of partial kernels of increasing range and decreasing variability with the longer-range parts interpolated from grids of increasing coarseness. Multilevel summation is especially appropriate in the context of dynamics and minimization, because it can produce continuous gradients. This article explores the use of B-splines to increase the accuracy of the multilevel summation method (for nonperiodic boundaries) without incurring additional computation other than a preprocessing step (whose cost also scales linearly). To obtain accurate results efficiently involves technical difficulties, which are overcome by a novel preprocessing algorithm. Numerical experiments demonstrate that the resulting method offers substantial improvements in accuracy and that its performance is competitive with an implementation of the fast multipole method in general and markedly better for Hamiltonian formulations of molecular dynamics. The improvement is great enough to establish multilevel summation as a serious contender for calculating pairwise interactions in molecular dynamics simulations. In particular, the method appears to be uniquely capable for molecular dynamics in two situations, nonperiodic boundary conditions and massively parallel computation, where the fast Fourier transform employed in the particle-mesh Ewald method falls short.
Online estimation of B-spline mixture models from TOF-PET list-mode data
Energy Technology Data Exchange (ETDEWEB)
Schretter, Colas; Kobbelt, Leif [RWTH Aachen Univ. (Germany). Computer Graphics Group; Sun, Jianyong [Nottingham Univ. (United Kingdom). Intelligent Modelling and Analysis Research Group
2011-07-01
In emission tomography, images are usually represented by regular grids of voxels or overlapping smooth image elements (blobs). Few other image models have been proposed like tetrahedral meshes or point clouds that are adapted to an anatomical image. This work proposes a practical sparse and continuous image model inspired from the field of parametric density estimation for Gaussian mixture models. The position, size, aspect ratio and orientation of each image element is optimized as well as its weight with a very fast online estimation method. Furthermore, the number of mixture components, hence the image resolution, is locally adapted according to the available data. The system model is represented in the same basis as image elements and captures time of flight and positron range effects in an exact way. Computations use apodized B-spline approximations of Gaussians and simple closed-form analytical expressions without any sampling or interpolation. In consequence, the reconstructed image never suffers from spurious aliasing artifacts. Noiseless images of the XCAT brain phantom were reconstructed from simulated data. (orig.)
Certified Approximation of Parametric Space Curves with Cubic B-spline Curves
Shen, Liyong; Gao, Xiao-Shan
2012-01-01
Approximating complex curves with simple parametric curves is widely used in CAGD, CG, and CNC. This paper presents an algorithm to compute a certified approximation to a given parametric space curve with cubic B-spline curves. By certified, we mean that the approximation can approximate the given curve to any given precision and preserve the geometric features of the given curve such as the topology, singular points, etc. The approximated curve is divided into segments called quasi-cubic B\\'{e}zier curve segments which have properties similar to a cubic rational B\\'{e}zier curve. And the approximate curve is naturally constructed as the associated cubic rational B\\'{e}zier curve of the control tetrahedron of a quasi-cubic curve. A novel optimization method is proposed to select proper weights in the cubic rational B\\'{e}zier curve to approximate the given curve. The error of the approximation is controlled by the size of its tetrahedron, which converges to zero by subdividing the curve segments. As an applic...
CT segmentation of dental shapes by anatomy-driven reformation imaging and B-spline modelling.
Barone, S; Paoli, A; Razionale, A V
2016-06-01
Dedicated imaging methods are among the most important tools of modern computer-aided medical applications. In the last few years, cone beam computed tomography (CBCT) has gained popularity in digital dentistry for 3D imaging of jawbones and teeth. However, the anatomy of a maxillofacial region complicates the assessment of tooth geometry and anatomical location when using standard orthogonal views of the CT data set. In particular, a tooth is defined by a sub-region, which cannot be easily separated from surrounding tissues by only considering pixel grey-intensity values. For this reason, an image enhancement is usually necessary in order to properly segment tooth geometries. In this paper, an anatomy-driven methodology to reconstruct individual 3D tooth anatomies by processing CBCT data is presented. The main concept is to generate a small set of multi-planar reformation images along significant views for each target tooth, driven by the individual anatomical geometry of a specific patient. The reformation images greatly enhance the clearness of the target tooth contours. A set of meaningful 2D tooth contours is extracted and used to automatically model the overall 3D tooth shape through a B-spline representation. The effectiveness of the methodology has been verified by comparing some anatomy-driven reconstructions of anterior and premolar teeth with those obtained by using standard tooth segmentation tools. Copyright © 2015 John Wiley & Sons, Ltd.
Quartic B-spline collocation method applied to Korteweg de Vries equation
Zin, Shazalina Mat; Majid, Ahmad Abd; Ismail, Ahmad Izani Md
2014-07-01
The Korteweg de Vries (KdV) equation is known as a mathematical model of shallow water waves. The general form of this equation is ut+ɛuux+μuxxx = 0 where u(x,t) describes the elongation of the wave at displacement x and time t. In this work, one-soliton solution for KdV equation has been obtained numerically using quartic B-spline collocation method for displacement x and using finite difference approach for time t. Two problems have been identified to be solved. Approximate solutions and errors for these two test problems were obtained for different values of t. In order to look into accuracy of the method, L2-norm and L∞-norm have been calculated. Mass, energy and momentum of KdV equation have also been calculated. The results obtained show the present method can approximate the solution very well, but as time increases, L2-norm and L∞-norm are also increase.
Directory of Open Access Journals (Sweden)
H. S. Shukla
2015-01-01
Full Text Available In this paper, a modified cubic B-spline differential quadrature method (MCB-DQM is employed for the numerical simulation of two-space dimensional nonlinear sine-Gordon equation with appropriate initial and boundary conditions. The modified cubic B-spline works as a basis function in the differential quadrature method to compute the weighting coefficients. Accordingly, two dimensional sine-Gordon equation is transformed into a system of second order ordinary differential equations (ODEs. The resultant system of ODEs is solved by employing an optimal five stage and fourth-order strong stability preserving Runge–Kutta scheme (SSP-RK54. Numerical simulation is discussed for both damped and undamped cases. Computational results are found to be in good agreement with the exact solution and other numerical results available in the literature.
Directory of Open Access Journals (Sweden)
H. S. Shukla
2014-11-01
Full Text Available In this paper, a numerical solution of two dimensional nonlinear coupled viscous Burger equation is discussed with appropriate initial and boundary conditions using the modified cubic B-spline differential quadrature method. In this method, the weighting coefficients are computed using the modified cubic B-spline as a basis function in the differential quadrature method. Thus, the coupled Burger equation is reduced into a system of ordinary differential equations. An optimal five stage and fourth-order strong stability preserving Runge–Kutta scheme is applied for solving the resulting system of ordinary differential equations. The accuracy of the scheme is illustrated by taking two numerical examples. Computed results are compared with the exact solutions and other results available in literature. Obtained numerical result shows that the described method is efficient and reliable scheme for solving two dimensional coupled viscous Burger equation.
外载荷的B样条曲线变形%Shape modification of B-spline curve via external loads
Institute of Scientific and Technical Information of China (English)
程仙国; 刘伟军
2011-01-01
运用能量优化的思想,提出一种B样条曲线变形的新方法,可用于B样条曲线的变形.首先将B样条曲线段类比为有限单元法中线单元,并将作用在B样条曲线段的外载荷等效成线单元的端点力,分别建立B样条曲线内部能量、外载荷能量函数方程;外载荷的改变将引起B样条曲线能量的变化,通过求解一个使曲线能量的变化量为最小的优化问题,得到变形后的B样条曲线.运用该方法实现了B样条曲线的局部、整体等变形操作.%Based on the idea of energy optimization, a new method for shape modification of the B-spine curve is proposed. First, using an analogy between the B-spline curve and the curve element of finite element method, and making the external load acting on the curve be equivalent to the end force into the element, the internal energy functional equation of the B-spline curve and the energy functional equation of the load are constructed respectively. The energy change of the Bspline curve with the change of the load, a new curve is generated by solving an optimization problem of the change of the energy. Using this approach, the local or total modification of the curve can be accomplished.
2013-04-01
surfaces consisting of Bezier curves and Nonuniform Rational B-spline Surfaces ( NURBS ). There are many times however, when both modeling approaches...have allowed the integration of free-form objects in CSG systems. This presentation will discuss the development and integration of NURBS into the...Ballistics Research Laboratory CSG modeling system. 15. SUBJECT TERMS NURBS , BSpline, raytracing, CSG, BRL-CAD 16. SECURITY CLASSIFICATION OF: 17
Directory of Open Access Journals (Sweden)
T Nikbakht
2012-12-01
Full Text Available Effects of quantum size and potential shape on the spectra of an electron and a hydrogenic-donor at the center of a permeable spherical cavity have been calculated, using linear variational method. B-splines have been used as basis functions. By extensive convergence tests and comparing with other results given in the literature, the validity and efficiency of the method were confirmed.
Geometric Construction of Algebraic Hyperbolic B-Spline%代数双曲B-样条的几何构造
Institute of Scientific and Technical Information of China (English)
朱平; 汪国昭
2009-01-01
样条曲线的升阶是CAD系统相互沟通必不可少的手段之一.由于双阶样条的升阶算法具有割角性质,因此具有鲜明的几何意义.以代数双曲B-样条为例,证明了样条曲线经过不断升阶之后,其控制多边形序列会像Bézier曲线一样收敛到初始的代数双曲B-样条曲线.利用文中得到的结果,就可以像Bézier曲线一样,通过几何割角法生成B-样条曲线﹑双曲线﹑悬链线等常用曲线.%Degree elevation of spline curves is an essential technique for communication between CAD systems. Since degree elevation algorithm by bi-order Spline can be interpreted as corner cutting process, degree elevation of Spline curve has obvious geometric meaning. Taking algebraic hyperbolic B-spline curve as an example, it is proved that Spline curve's control polygon sequence will converge to the initial algebraic hyperbolic B-spline curve after degree elevation continually. By this conclusion, common curves including B-spline, hyperbola and catenary curves can be obtained by geometric corner cutting as Bézier curves.
Nonrigid registration with tissue-dependent filtering of the deformation field
Energy Technology Data Exchange (ETDEWEB)
Staring, Marius; Klein, Stefan; Pluim, Josien P W [Image Sciences Institute, University Medical Center Utrecht, PO Box 85500, 3508 GA, Room Q0S.459, Utrecht (Netherlands)
2007-12-07
In present-day medical practice it is often necessary to nonrigidly align image data. Current registration algorithms do not generally take the characteristics of tissue into account. Consequently, rigid tissue, such as bone, can be deformed elastically, growth of tumours may be concealed, and contrast-enhanced structures may be reduced in volume. We propose a method to locally adapt the deformation field at structures that must be kept rigid, using a tissue-dependent filtering technique. This adaptive filtering of the deformation field results in locally linear transformations without scaling or shearing. The degree of filtering is related to tissue stiffness: more filtering is applied at stiff tissue locations, less at parts of the image containing nonrigid tissue. The tissue-dependent filter is incorporated in a commonly used registration algorithm, using mutual information as a similarity measure and cubic B-splines to model the deformation field. The new registration algorithm is compared with this popular method. Evaluation of the proposed tissue-dependent filtering is performed on 3D computed tomography (CT) data of the thorax and on 2D digital subtraction angiography (DSA) images. The results show that tissue-dependent filtering of the deformation field leads to improved registration results: tumour volumes and vessel widths are preserved rather than affected.
Energy Technology Data Exchange (ETDEWEB)
Yang, Xiaofeng, E-mail: xyang43@emory.edu; Rossi, Peter; Ogunleye, Tomi; Marcus, David M.; Jani, Ashesh B.; Curran, Walter J.; Liu, Tian [Department of Radiation Oncology and Winship Cancer Institute, Emory University, Atlanta, Georgia 30322 (United States); Mao, Hui [Department of Radiology and Imaging Sciences, Emory University, Atlanta, Georgia 30322 (United States)
2014-11-01
Purpose: The technological advances in real-time ultrasound image guidance for high-dose-rate (HDR) prostate brachytherapy have placed this treatment modality at the forefront of innovation in cancer radiotherapy. Prostate HDR treatment often involves placing the HDR catheters (needles) into the prostate gland under the transrectal ultrasound (TRUS) guidance, then generating a radiation treatment plan based on CT prostate images, and subsequently delivering high dose of radiation through these catheters. The main challenge for this HDR procedure is to accurately segment the prostate volume in the CT images for the radiation treatment planning. In this study, the authors propose a novel approach that integrates the prostate volume from 3D TRUS images into the treatment planning CT images to provide an accurate prostate delineation for prostate HDR treatment. Methods: The authors’ approach requires acquisition of 3D TRUS prostate images in the operating room right after the HDR catheters are inserted, which takes 1–3 min. These TRUS images are used to create prostate contours. The HDR catheters are reconstructed from the intraoperative TRUS and postoperative CT images, and subsequently used as landmarks for the TRUS–CT image fusion. After TRUS–CT fusion, the TRUS-based prostate volume is deformed to the CT images for treatment planning. This method was first validated with a prostate-phantom study. In addition, a pilot study of ten patients undergoing HDR prostate brachytherapy was conducted to test its clinical feasibility. The accuracy of their approach was assessed through the locations of three implanted fiducial (gold) markers, as well as T2-weighted MR prostate images of patients. Results: For the phantom study, the target registration error (TRE) of gold-markers was 0.41 ± 0.11 mm. For the ten patients, the TRE of gold markers was 1.18 ± 0.26 mm; the prostate volume difference between the authors’ approach and the MRI-based volume was 7.28% ± 0
Yang, Xiaofeng; Rossi, Peter; Ogunleye, Tomi; Marcus, David M.; Jani, Ashesh B.; Mao, Hui; Curran, Walter J.; Liu, Tian
2014-01-01
Purpose: The technological advances in real-time ultrasound image guidance for high-dose-rate (HDR) prostate brachytherapy have placed this treatment modality at the forefront of innovation in cancer radiotherapy. Prostate HDR treatment often involves placing the HDR catheters (needles) into the prostate gland under the transrectal ultrasound (TRUS) guidance, then generating a radiation treatment plan based on CT prostate images, and subsequently delivering high dose of radiation through these catheters. The main challenge for this HDR procedure is to accurately segment the prostate volume in the CT images for the radiation treatment planning. In this study, the authors propose a novel approach that integrates the prostate volume from 3D TRUS images into the treatment planning CT images to provide an accurate prostate delineation for prostate HDR treatment. Methods: The authors’ approach requires acquisition of 3D TRUS prostate images in the operating room right after the HDR catheters are inserted, which takes 1–3 min. These TRUS images are used to create prostate contours. The HDR catheters are reconstructed from the intraoperative TRUS and postoperative CT images, and subsequently used as landmarks for the TRUS–CT image fusion. After TRUS–CT fusion, the TRUS-based prostate volume is deformed to the CT images for treatment planning. This method was first validated with a prostate-phantom study. In addition, a pilot study of ten patients undergoing HDR prostate brachytherapy was conducted to test its clinical feasibility. The accuracy of their approach was assessed through the locations of three implanted fiducial (gold) markers, as well as T2-weighted MR prostate images of patients. Results: For the phantom study, the target registration error (TRE) of gold-markers was 0.41 ± 0.11 mm. For the ten patients, the TRE of gold markers was 1.18 ± 0.26 mm; the prostate volume difference between the authors’ approach and the MRI-based volume was 7.28% ± 0
Directory of Open Access Journals (Sweden)
Sandra P Mateus
2010-01-01
Full Text Available Dentro de las técnicas existentes de Inteligencia Artificial, se escogieron y adaptaron dos Redes Neuronales Artificiales (RNA para realizar el ajuste de uno de los elementos que definen una B-Spline Racional No Uniforme (NURBS y con ello obtener un modelado adecuado de la NURBS. Los elementos escogidos fueron los puntos de control. Las RNA utilizadas son las de Función de Base Radial y las de Kohonen o Mapas Auto-organizativos. Con base en el análisis de resultados y la caracterización de las RNA, la Función de Base Radial tuvo un desempeño más adecuado y óptimo para un número elevado de datos, lo cual es una desventaja de los Mapas Auto-organizativos. En este modelo se tiene que realizar procesos extras para determinar la neurona ganadora y realizar el reajuste de los pesos.In the existing techniques of Artificial Intelligence, two Artificial Neural Networks (ANN were selected and adapted to fit one of the elements that define a Non-Uniform Rational B-Spline (NURBS and thus obtaining an appropriate modeling of the NURBS. The selected elements were the checkpoints. The ANN used were the Radial Basis Function and the Kohonen model or Self-Organizing Maps. Based on the analysis of the results and characterization of the ANN the Radial Basis Function had a more appropriate and optimum performance for a large number of data, which is a disadvantage of the Self-Organizing Maps. In this model, additional processes must be done to determine the winning neuron and the weights must be refitted.
Institute of Scientific and Technical Information of China (English)
Zhang Yue-Xia; Meng Hui-Yan; Shi Ting-Yun
2008-01-01
The B-spline basis set plus complex scaling method is applied to the numerical calculation of the exact resonance parameters Er and I/2 of a hydrogen atom in parallel electric and magnetic fields.The method can calculate the ground and higher excited resonances accurately and efficiently.The resonance parameters with accuracies of 10-9 - 10-12 for hydrogen atom in parallel fields with different field strengths and symmetries are presented and compared with previous ones.Extension to the calculation of Rydberg atom in crossed electric and magnetic fields and of atomic double excited states in external electric fields is discussed.
Institute of Scientific and Technical Information of China (English)
XIONG Lei; LI haijiao; ZHANG Lewen
2008-01-01
The fourth-order B spline wavelet scaling functions are used to solve the two-dimensional unsteady diffusion equation. The calculations from a case history indicate that the method provides high accuracy and the computational efficiency is enhanced due to the small matrix derived from this method.The respective features of 3-spline wavelet scaling functions, 4-spline wavelet scaling functions and quasi-wavelet used to solve the two-dimensional unsteady diffusion equation are compared. The proposed method has potential applications in many fields including marine science.
Fillion-Gourdeau, F; Bandrauk, A D
2015-01-01
A Galerkin method is developed to solve the time-dependent Dirac equation in prolate spheroidal coordinates for an electron-molecular two-center system. The initial state is evaluated from a variational principle using a kinetic/atomic balanced basis, which allows for an efficient and accurate determination of the Dirac spectrum and eigenfunctions. B-spline basis functions are used to obtain high accuracy. This numerical method is used to compute the energy spectrum of the two-center problem and then the evolution of eigenstate wavefunctions in an external electromagnetic field.
Galerkin method for unsplit 3-D Dirac equation using atomically/kinetically balanced B-spline basis
Energy Technology Data Exchange (ETDEWEB)
Fillion-Gourdeau, F., E-mail: filliong@CRM.UMontreal.ca [Université du Québec, INRS – Énergie, Matériaux et Télécommunications, Varennes, J3X 1S2 (Canada); Centre de Recherches Mathématiques, Université de Montréal, Montréal, H3T 1J4 (Canada); Lorin, E., E-mail: elorin@math.carleton.ca [School of Mathematics and Statistics, Carleton University, Ottawa, K1S 5B6 (Canada); Centre de Recherches Mathématiques, Université de Montréal, Montréal, H3T 1J4 (Canada); Bandrauk, A.D., E-mail: andre.bandrauk@usherbrooke.ca [Laboratoire de Chimie Théorique, Faculté des Sciences, Université de Sherbrooke, Sherbrooke, J1K 2R1 (Canada); Centre de Recherches Mathématiques, Université de Montréal, Montréal, H3T 1J4 (Canada)
2016-02-15
A Galerkin method is developed to solve the time-dependent Dirac equation in prolate spheroidal coordinates for an electron–molecular two-center system. The initial state is evaluated from a variational principle using a kinetic/atomic balanced basis, which allows for an efficient and accurate determination of the Dirac spectrum and eigenfunctions. B-spline basis functions are used to obtain high accuracy. This numerical method is used to compute the energy spectrum of the two-center problem and then the evolution of eigenstate wavefunctions in an external electromagnetic field.
Institute of Scientific and Technical Information of China (English)
QIAO Hao-Xue; LI Bai-Wen
2002-01-01
A B-spline method has been used to calculate the electron structure of cndohedrally confined hydrogenlike atoms.The boundary conditions were conveniently satisfied with such the method.The evolution of the energy spectrum,as function of the depth of the confining well,exhibits a "mirror collapse".Ions with higher ionicity have more "collapse lines",the energies change more sharply at "collapse points",and the oscillator strengths change more violently with the depth of the confining well.
2014-01-01
Este documento de tesis tiene el propósito de describir una metodología para obtener nubes de puntos que representen a superficies (o parches de geometría compleja) de piezas mecánicas que pueden ser replicadas en la industria. Estos puntos se obtuvieron utilizando el método de interpolación superficial B-Spline que deben cumplir un margen de error conocido y controlado de acuerdo a las tolerancias de fabricación utilizados en estos procesos de fabricación. En primer lugar e...
Dealing with difficult deformations: Construction of a knowledge-based deformation atlas
DEFF Research Database (Denmark)
Thorup, Signe Strann; Darvann, T.A.; Hermann, N.V.
2010-01-01
was needed. We have previously demonstrated that non-rigid registration using B-splines is able to provide automated determination of point correspondences in populations of infants without cleft lip. However, this type of registration fails when applied to the task of determining the complex deformation...
Almeida, Nuno; Friboulet, Denis; Sarvari, Sebastian Imre; Bernard, Olivier; Barbosa, Daniel; Samset, Eigil; Dhooge, Jan
2016-02-01
Segmentation of the left atrium (LA) of the heart allows quantification of LA volume dynamics which can give insight into cardiac function. However, very little attention has been given to LA segmentation from three-dimensional (3-D) ultrasound (US), most efforts being focused on the segmentation of the left ventricle (LV). The B-spline explicit active surfaces (BEAS) framework has been shown to be a very robust and efficient methodology to perform LV segmentation. In this study, we propose an extension of the BEAS framework, introducing B-splines with uncoupled scaling. This formulation improves the shape support for less regular and more variable structures, by giving independent control over smoothness and number of control points. Semiautomatic segmentation of the LA endocardium using this framework was tested in a setup requiring little user input, on 20 volumetric sequences of echocardiographic data from healthy subjects. The segmentation results were evaluated against manual reference delineations of the LA. Relevant LA morphological and functional parameters were derived from the segmented surfaces, in order to assess the performance of the proposed method on its clinical usage. The results showed that the modified BEAS framework is capable of accurate semiautomatic LA segmentation in 3-D transthoracic US, providing reliable quantification of the LA morphology and function.
Energy Technology Data Exchange (ETDEWEB)
Vasconcelos, Geovane Vitor; Dantas, Carlos Costa, E-mail: geovitor@bol.com.b, E-mail: ccd@ufpe.b [Universidade Federal de Pernambuco (UFPE), Recife, PE (Brazil). Dept. de Energia Nuclear. Grupo de Radioquimica; Melo, Silvio de Barros; Pires, Renan Ferraz, E-mail: sbm@cin.ufpe.b, E-mail: rfp@cin.ufpe.b [Universidade Federal de Pernambuco (UFPE), Recife, PE (Brazil). Centro de Informatica
2009-07-01
The 3D tomography reconstruction has been a profitable alternative in the analysis of the FCC-type- riser (Fluid Catalytic Cracking), for appropriately keeping track of the sectional catalyst concentration distribution in the process of oil refining. The method of tomography reconstruction proposed by M. Azzi and colleagues (1991) uses a relatively small amount of trajectories (from 3 to 5) and projections (from 5 to 7) of gamma rays, a desirable feature in the industrial process tomography. Compared to more popular methods, such as the FBP (Filtered Back Projection), which demands a much higher amount of gamma rays projections, the method by Azzi et al. is more appropriate for the industrial process, where the physical limitations and the cost of the process require more economical arrangements. The use of few projections and trajectories facilitates the diagnosis in the flow dynamical process. This article proposes an improvement in the basis functions introduced by Azzi et al., through the use of quadratic B-splines functions. The use of B-splines functions makes possible a smoother surface reconstruction of the density distribution, since the functions are continuous and smooth. This work describes how the modeling can be done. (author)
Côrtes, A.M.A.
2016-10-01
The recently introduced divergence-conforming B-spline discretizations allow the construction of smooth discrete velocity-pressure pairs for viscous incompressible flows that are at the same time inf−supinf−sup stable and pointwise divergence-free. When applied to the discretized Stokes problem, these spaces generate a symmetric and indefinite saddle-point linear system. The iterative method of choice to solve such system is the Generalized Minimum Residual Method. This method lacks robustness, and one remedy is to use preconditioners. For linear systems of saddle-point type, a large family of preconditioners can be obtained by using a block factorization of the system. In this paper, we show how the nesting of “black-box” solvers and preconditioners can be put together in a block triangular strategy to build a scalable block preconditioner for the Stokes system discretized by divergence-conforming B-splines. Besides the known cavity flow problem, we used for benchmark flows defined on complex geometries: an eccentric annulus and hollow torus of an eccentric annular cross-section.
Institute of Scientific and Technical Information of China (English)
Joong-Hyun Rhim; Doo-Yeoun Cho; Kyu-Yeul Lee; Tae-Wan Kim
2006-01-01
We propose a method that automatically generates discrete bicubic G1 continuous B-spline surfaces that interpolate the curve network of a ship hullform. First, the curves in the network are classified into two types: boundary curves and "reference curves". The boundary curves correspond to a set of rectangular (or triangular) topological type that can be represented with tensor-product (or degenerate) B-spline surface patches. Next, in the interior of the patches,surface fitting points and cross boundary derivatives are estimated from the reference curves by constructing "virtual" isoparametric curves. Finally, a discrete G1 continuous B-spline surface is generated by a surface fitting algorithm. Several smooth ship hullform surfaces generated from curve networks corresponding to actual ship hullforms demonstrate the quality of the method.
C-B样条曲线的分割和拼接%Arbitrary Subdivision Algorithm and Joining of C-B-Spline
Institute of Scientific and Technical Information of China (English)
宋丽平
2011-01-01
曲线曲面造型中设计复杂的自由曲线时,单段曲线已不能满足外形设计的要求,因而在实际造型中,经常采用曲线的分割和拼接.C-B样条理论是曲线曲面造型的一项重要内容.在对C-B样条基函数及曲线端点特性分析的基础上,提出了C-B样条曲线的任意分割算法,并对C-B样条曲线间进行了G1拼接.给出了 B样条曲线和C-B样条曲线G1和G2光滑拼接的几何条件.采用分割和拼接技术会增加C-B样条曲线的灵活性,所得结论具有明确的几何意义,并可以进一步推广到C-B样条曲面造型中.%The single curve already can' t satisfy the requirements of shape design when designing complex free curve in curve/surface modeling. Thus in the actual modeling, C-B-spline theory is an important content of curve/surface modeling. Propose the algorithm of arbitrarily divided when analysing C-B-spline basis functions,then splicing between two C-B-spline. In addition,give geometry conditions about B-spline curves and C-B-spline curves. The results are benefit for the shape modification, and they can also be extended to surface modeling with C-B-spline.
Indhumathi, C; Cai, Y Y; Guan, Y Q; Opas, M; Zheng, J
2012-01-01
Confocal laser scanning microscopy has become a most powerful tool to visualize and analyze the dynamic behavior of cellular molecules. Photobleaching of fluorochromes is a major problem with confocal image acquisition that will lead to intensity attenuation. Photobleaching effect can be reduced by optimizing the collection efficiency of the confocal image by fast z-scanning. However, such images suffer from distortions, particularly in the z dimension, which causes disparities in the x, y, and z directions of the voxels with the original image stacks. As a result, reliable segmentation and feature extraction of these images may be difficult or even impossible. Image interpolation is especially needed for the correction of undersampling artifact in the axial plane of three-dimensional images generated by a confocal microscope to obtain cubic voxels. In this work, we present an adaptive cubic B-spline-based interpolation with the aid of lookup tables by deriving adaptive weights based on local gradients for the sampling nodes in the interpolation formulae. Thus, the proposed method enhances the axial resolution of confocal images by improving the accuracy of the interpolated value simultaneously with great reduction in computational cost. Numerical experimental results confirm the effectiveness of the proposed interpolation approach and demonstrate its superiority both in terms of accuracy and speed compared to other interpolation algorithms.
GA Based Rational cubic B-Spline Representation for Still Image Interpolation
Directory of Open Access Journals (Sweden)
Samreen Abbas
2016-12-01
Full Text Available In this paper, an image interpolation scheme is designed for 2D natural images. A local support rational cubic spline with control parameters, as interpolatory function, is being optimized using Genetic Algorithm (GA. GA is applied to determine the appropriate values of control parameter used in the description of rational cubic spline. Three state-of-the-art Image Quality Assessment (IQA models with traditional one are hired for comparison with existing image interpolation schemes and perceptual quality check of resulting images. The results show that the proposed scheme is better than the existing ones in comparison.
GA Based Rational cubic B-Spline Representation for Still Image Interpolation
Samreen Abbas; Malik Zawwar Hussain; Misbah Irshad
2016-01-01
In this paper, an image interpolation scheme is designed for 2D natural images. A local support rational cubic spline with control parameters, as interpolatory function, is being optimized using Genetic Algorithm (GA). GA is applied to determine the appropriate values of control parameter used in the description of rational cubic spline. Three state-of-the-art Image Quality Assessment (IQA) models with traditional one are hired for comparison with existing image interpolation schemes and perc...
PCA and level set based non-rigid image registration for MRI and Paxinos-Watson atlas of rat brain
Cai, Chao; Liu, Ailing; Ding, Mingyue; Zhou, Chengping
2007-12-01
Image registration provides the ability to geometrically align one dataset with another. It is a basic task in a great variety of biomedical imaging applications. This paper introduced a novel three-dimensional registration method for Magnetic Resonance Image (MRI) and Paxinos-Watson Atlas of rat brain. For the purpose of adapting to a large range and non-linear deformation between MRI and atlas in higher registration accuracy, based on the segmentation of rat brain, we chose the principle components analysis (PCA) automatically performing the linear registration, and then, a level set based nonlinear registration correcting some small distortions. We implemented this registration method in a rat brain 3D reconstruction and analysis system. Experiments have demonstrated that this method can be successfully applied to registering the low resolution and noise affection MRI with Paxinos-Watson Atlas of rat brain.
Bi-cubic non-uniform B-spline surface reconstruction for slice contours%断层轮廓的双三次非均匀B样条曲面重构
Institute of Scientific and Technical Information of China (English)
王瑜; 郑津津; 周洪军; 沈连婠
2011-01-01
A surface reconstruction method from the slice contours was proposed. First, feature points were extracted based on curvature feature, and they were resampled in order to get a unification of sampling points in each line (column). Then, the sampling points were interpolated to get a bi-cubic non-uniform B-spline surface. Finally, nodes were inserted on the surface based on distance feature at a certain control accuracy, and the new control points through the least-squares approximation method were calculated to get approximate surface within the permissible range error. Based on the characteristics of slice contours, B-spline cycle and non-cycle B-spline combined, and the calculation of closed and non-closed surface was discussed. It was found that the combination of interpolation and approximation makes the algorithm more rapid and practical.%针对断层图像数据,提出了一种曲面重构的方法.依据曲率特征首先提取各层特征点,对其重采样使每行(列)获得统一的采样点数;再对采样点插值得到非均匀双三次B样条曲面;最后,在一定控制精度下对曲面依据距离特征进行节点插入,通过最小二乘逼近法算出新的控制顶点,从而得到误差在容许范围内的逼近曲面.根据断层轮廓的特点,本算法综合运用了周期B样条和非周期B样条,讨论了封闭曲面和非封闭曲面的计算方法.另外插值和逼近的结合应用使该算法更快速、实用.
Nonrigid registration of volumetric images using ranked order statistics
DEFF Research Database (Denmark)
Tennakoon, Ruwan; Bab-Hadiashar, Alireza; Cao, Zhenwei
2014-01-01
Non-rigid image registration techniques using intensity based similarity measures are widely used in medical imaging applications. Due to high computational complexities of these techniques, particularly for volumetric images, finding appropriate registration methods to both reduce the computation...... burden and increase the registration accuracy has become an intensive area of research. In this paper we propose a fast and accurate non-rigid registration method for intra-modality volumetric images. Our approach exploits the information provided by an order statistics based segmentation method, to find...... the important regions for registration and use an appropriate sampling scheme to target those areas and reduce the registration computation time. A unique advantage of the proposed method is its ability to identify the point of diminishing returns and stop the registration process. Our experiments...
Real-Time Interactive Modification of B-Spline by PIA%基于PIA的B-Spline曲面实时交互修改方法
Institute of Scientific and Technical Information of China (English)
赵宇; 蔺宏伟
2011-01-01
交互修改是几何设计中一种常用的曲线曲面编辑手段,NURBS曲线曲面是CAD系统中曲线曲面的标准表示形式.现有的B-spline曲线曲面交互修改技术往往需要求解一个带约束的能量优化问题,当曲线曲面的控制顶点较多时,这个优化问题的求解过程较慢,难以满足交互操作的实时要求.为此,基于B-spline曲线曲面的局部迭代逼近(PIA)性质提出一种实时的B-spline曲面交互编辑方法.给定一张B-spline曲面和空间待插值目标点集,首先确定距待插值目标点位置最近的曲面上的点以及最近的控制顶点,构造对应于这2个点的主差向量,并将它们扩散到其他控制顶点；然后通过平均操作获得对应于每个控制顶点的差向量；最后通过PIA迭代生成新曲面.该迭代过程的极限曲面就是插值于给定目标点集的曲面.由于PIA迭代仅需调整若干控制顶点,不需求解约束优化问题,使得其在交互修改具有大规模控制网格的B-spline曲面时,在速度方面具有较大优势；同时,文中方法生成的曲面质量与采用能量优化方法得到的曲面质量相比差别不大.%Interactive design is widely used for curve and surface editing in geometric design. Currently, the methods for B-spline curve and surface modification usually involve solving a constrained energy optimization problem, which costs lots of time when the number of control points of curves or surfaces is large. So it hardly achieves real-time response in the modification operation. In this paper, we propose a real-time surface modification method based on progressive-iteration approximation (PIA). Suppose we are given a B-spline surface and an interpolated point set as input. First, we determine the points on the given surface, which are closest to the interpolated points, and the control points closest to the interpolated points. Then, we construct the main difference vectors, diffuse them to all of the
基于C-B样条的三角形和四边形曲面生成%Triangular and quadrilateral surface construction using C-B spline
Institute of Scientific and Technical Information of China (English)
李薇; 吴卓奇; 荻原一郎
2012-01-01
This paper provides a different solution to represent basic smooth elements like triangular and quadrilateral surface patches from mesh using C-B spline curves. C-B spline curves are developed by the basis {sin t, cos t, t, 1}, and it overcomes some shortcomings of the B-spline and non-uniform rational B-splines (NURBS) model, for example, they have to increase unnecessary control point in order to satisfy the data grid topology, their derivative and integral are complex and tedious, their degrees are too high, and it is difficult to discuss their continuous conditions. How to develop C-B spline curves into surface becomes an important problem. In this paper, the interpolation operators are constructed by using side-vertex method and a convex combination of these operators is achieved. The C-B spline curves are developed into triangular and quadrilateral surface patches which can be used in reverse engineering of CAD.%文章给出了基于C-B样条的由网格数据产生三角形和四边形曲面片的方法,C-B样条是由基底函数{sin t,cos t,t,1}导出的一种新型样条曲线,它可以克服现在正在使用的B样条和有理B样条为了满足数据网格的拓扑结构而增加多余的控制点,求导求积分复杂繁琐,阶数过高,从而讨论其连续拼接时增加了困难等缺点,如何将它推广成曲面就成为一个重要问题.作者利用边-顶点方法构造插值算子,再将这些算子进行凸性组合,将C-B样条曲线推广成三角形曲面片和四边形曲面片,它可以用于CAD的逆向工程中散乱数据的曲面重构.
Directory of Open Access Journals (Sweden)
Verónica S. Martínez
2015-12-01
Full Text Available Metabolic flux analysis (MFA is widely used to estimate intracellular fluxes. Conventional MFA, however, is limited to continuous cultures and the mid-exponential growth phase of batch cultures. Dynamic MFA (DMFA has emerged to characterize time-resolved metabolic fluxes for the entire culture period. Here, the linear DMFA approach was extended using B-spline fitting (B-DMFA to estimate mass balanced fluxes. Smoother fits were achieved using reduced number of knots and parameters. Additionally, computation time was greatly reduced using a new heuristic algorithm for knot placement. B-DMFA revealed that Chinese hamster ovary cells shifted from 37 °C to 32 °C maintained a constant IgG volume-specific productivity, whereas the productivity for the controls peaked during mid-exponential growth phase and declined afterward. The observed 42% increase in product titer at 32 °C was explained by a prolonged cell growth with high cell viability, a larger cell volume and a more stable volume-specific productivity.
Côrtes, A.M.A.
2015-02-20
The recently introduced divergence-conforming B-spline discretizations allow the construction of smooth discrete velocity–pressure pairs for viscous incompressible flows that are at the same time inf-sup stable and pointwise divergence-free. When applied to discretized Stokes equations, these spaces generate a symmetric and indefinite saddle-point linear system. Krylov subspace methods are usually the most efficient procedures to solve such systems. One of such methods, for symmetric systems, is the Minimum Residual Method (MINRES). However, the efficiency and robustness of Krylov subspace methods is closely tied to appropriate preconditioning strategies. For the discrete Stokes system, in particular, block-diagonal strategies provide efficient preconditioners. In this article, we compare the performance of block-diagonal preconditioners for several block choices. We verify how the eigenvalue clustering promoted by the preconditioning strategies affects MINRES convergence. We also compare the number of iterations and wall-clock timings. We conclude that among the building blocks we tested, the strategy with relaxed inner conjugate gradients preconditioned with incomplete Cholesky provided the best results.
Csébfalvi, Balázs
2013-09-01
In this paper, Cosine-Weighted B-spline (CWB) filters are proposed for interpolation on the optimal Body-Centered Cubic (BCC) lattice. We demonstrate that our CWB filters can well exploit the fast trilinear texture-fetching capability of modern GPUs, and outperform the state-of-the-art box-spline filters not just in terms of efficiency, but in terms of visual quality and numerical accuracy as well. Furthermore, we rigorously show that the CWB filters are better tailored to the BCC lattice than the previously proposed quasi-interpolating BCC B-spline filters, because they form a Riesz basis; exactly reproduce the original signal at the lattice points; but still provide the same approximation order.
带多个形状参数的三次均匀B样条曲线的扩展%Extension of Uniform Cubic B-Spline Curves withMultiple Shape Parameters
Institute of Scientific and Technical Information of China (English)
夏成林; 邬弘毅; 郑兴国; 彭凯军
2011-01-01
通过构造两类带多个形状参数的调配函数,生成三次均匀B样条基函数的扩展.基于给出的调配函数定义了两类带多个形状参数的分段多项式曲线.这些曲线具有三次均匀B样条曲线的绝大多数重要性质,能达到GC1或GC2连续.改变形状参数的值可以独立地调控各子段的端点的位置及其切矢的长度,对曲线进行整体或局部调整,甚至直接插值任何所需的控制点.%Two classes of blending functions with multiple shape parameters are presented in this paper. They are the extension of uniform cubic B-spline basic functions. Based on the given blending functions, the piecewise polynomial curves with shape parameters are defined. These curves inherit the most properties of uniform cubic B-spline curves with GCl or GC2 continuity.The position and the length of tangent vector at the end points of curve segments can be independently controlled by changing the values of the shape parameters. These curves can be adjusted totally or locally and interpolated by any given control points.
使用B样条无单元法进行梯形盖板受力分析%Stress Analysis of Trapezoidal Slabs by Using B-spline Meshless Method
Institute of Scientific and Technical Information of China (English)
李彬
2013-01-01
To meet the needs of stress analysis and evaluation of trapezoidal slabs of skew culvert,this paper puts forward a B-spline meshless method based on moderately thick slab theory.By using dual quartic and dual cubic B-spline to make interpolation for the deflection and the turning angle respectively,this paper deduces the stiffness matrix and equivalent load formulations,introduces the method of setting boundary condition by using penalty function,enumerates the key points of using both Matlab and Spline Toolbox in order to achieve this method,and gives numerical verification result.The results from research and calculation show that this method proposed has advantages such as concise formulation,simple post-processing,high precision and efficiency,and can facilitate the development of relevant specialized analysis program.%为满足对斜交涵洞梯形盖板进行受力分析与评估的需要,提出基于中厚板理论的B样条无单元方法.实现中对挠度和转角分别采用双四次和双三次B样条进行插值,使用变分原理推导相应的刚度矩阵和等效荷载列式,介绍利用罚函数施加边界条件的方法,列举使用Matlab及Spline Toolbox实现该方法时的一些要点,提供了数值验证结果.研究及计算结果表明,该方法列式简洁、后处理方便、精度好、效率高,为相关专用分析程序的开发提供一条方便的途径.
Inference in dynamic systems using B-splines and quasilinearized ODE penalties.
Frasso, Gianluca; Jaeger, Jonathan; Lambert, Philippe
2016-05-01
Nonlinear (systems of) ordinary differential equations (ODEs) are common tools in the analysis of complex one-dimensional dynamic systems. We propose a smoothing approach regularized by a quasilinearized ODE-based penalty. Within the quasilinearized spline-based framework, the estimation reduces to a conditionally linear problem for the optimization of the spline coefficients. Furthermore, standard ODE compliance parameter(s) selection criteria are applicable. We evaluate the performances of the proposed strategy through simulated and real data examples. Simulation studies suggest that the proposed procedure ensures more accurate estimates than standard nonlinear least squares approaches when the state (initial and/or boundary) conditions are not known.
Numerical solution of functional integral equations by using B-splines
Directory of Open Access Journals (Sweden)
Reza Firouzdor
2014-05-01
Full Text Available This paper describes an approximating solution, based on Lagrange interpolation and spline functions, to treat functional integral equations of Fredholm type and Volterra type. This method can be extended to functional dierential and integro-dierential equations. For showing eciency of the method we give some numerical examples.
Projection of curves on B-spline surfaces using quadratic reparameterization
Yang, Yijun
2010-09-01
Curves on surfaces play an important role in computer aided geometric design. In this paper, we present a hyperbola approximation method based on the quadratic reparameterization of Bézier surfaces, which generates reasonable low degree curves lying completely on the surfaces by using iso-parameter curves of the reparameterized surfaces. The Hausdorff distance between the projected curve and the original curve is controlled under the user-specified distance tolerance. The projected curve is T-G 1 continuous, where T is the user-specified angle tolerance. Examples are given to show the performance of our algorithm. © 2010 Elsevier Inc. All rights reserved.
On B-spline framelets derived from the unitary extension principle
Shen, Zuowei
2011-01-01
Spline wavelet tight frames of Ron-Shen have been used widely in frame based image analysis and restorations. However, except for the tight frame property and the approximation order of the truncated series, there are few other properties of this family of spline wavelet tight frames to be known. This paper is to present a few new properties of this family that will provide further understanding of it and, hopefully, give some indications why it is efficient in image analysis and restorations. In particular, we present a recurrence formula of computing generators of higher order spline wavelet tight frames from the lower order ones. We also represent each generator of spline wavelet tight frames as certain order of derivative of some univariate box spline. With this, we further show that each generator of sufficiently high order spline wavelet tight frames is close to a right order of derivative of a properly scaled Gaussian function. This leads to the result that the wavelet system generated by a finitely ma...
Lichter, J; Li, Hui; Sachse, Frank B
2016-10-01
Measurement of cell shortening is an important technique for assessment of physiology and pathophysiology of cardiac myocytes. Many types of heart disease are associated with decreased myocyte shortening, which is commonly caused by structural and functional remodeling. Here, we present a new approach for local measurement of 2-dimensional strain within cells at high spatial resolution. The approach applies non-rigid image registration to quantify local displacements and Cauchy strain in images of cells undergoing contraction. We extensively evaluated the approach using synthetic cell images and image sequences from rapid scanning confocal microscopy of fluorescently labeled isolated myocytes from the left ventricle of normal and diseased canine heart. Application of the approach yielded a comprehensive description of cellular strain including novel measurements of transverse strain and spatial heterogeneity of strain. Quantitative comparison with manual measurements of strain in image sequences indicated reliability of the developed approach. We suggest that the developed approach provides researchers with a novel tool to investigate contractility of cardiac myocytes at subcellular scale. In contrast to previously introduced methods for measuring cell shorting, the developed approach provides comprehensive information on the spatio-temporal distribution of 2-dimensional strain at micrometer scale.
Lu, Xuesong; Zhang, Su; Yang, Wei; Chen, Yazhu
2010-11-01
Non-rigid registration of ultrasound images takes an important role in image-guided radiotherapy and surgery. Intensity-based method is popular in non-rigid registration, but it is sensitive to intensity variations and has problems with matching small structure features for the existence of speckles in ultrasound images. In this paper, we develop a new algorithm integrating the intensity and feature of ultrasound images. Both global shape information and local keypoint information extracted by scale invariant feature transform (SIFT) are incorporated into intensity similarity measure as the body force of viscous fluid model in a Bayesian framework. Experiments were performed on synthetic and clinical ultrasound images of breast and kidney. It is shown that shape and keypoint information significantly improves fluid model for non-rigid registration, especially for alignment of small structure features in accuracy.
Level set motion assisted non-rigid 3D image registration
Yang, Deshan; Deasy, Joseph O.; Low, Daniel A.; El Naqa, Issam
2007-03-01
Medical imaging applications of rigid and non-rigid elastic deformable image registration are undergoing wide scale development. Our approach determines image deformation maps through a hierarchical process, from global to local scales. Vemuri (2000) reported a registration method, based on levelset evolution theory, to morph an image along the motion gradient until it deforms to the reference image. We have applied this level set motion method as basis to iteratively compute the incremental motion fields and then we approximated the field using a higher-level affine and non-rigid motion model. In such a way, we combine sequentially the global affine motion, local affine motion and local non-rigid motion. Our method is fully automated, computationally efficient, and is able to detect large deformations if used together with multi-grid approaches, potentially yielding greater registration accuracy.
Analysis and optimization of assembly variations for non-rigid parts
Institute of Scientific and Technical Information of China (English)
无
2005-01-01
Traditional variation analysis methods are not applicable to non-rigid assemblies due to possible part deformation during the assembly process. This paper presents the use of finite element methods to simulate assembly deformation. The relationship between the parts' variation and the variation of the key points in final assembly for quality control is set up by calculating the spring back deformation after assembly. Moreover, the optimization method for non-rigid assembly variations based on finite element analysis is presented. The optimal objective is to reduce the manufacturing cost. The approach is implemented by using ANSYS and MATLAB. The test example shows that the proposed method is effective and applicable.
Real-time Animation Technique for a Kind of Non-rigid Objects
Institute of Scientific and Technical Information of China (English)
无
2003-01-01
A real-time animation technique for a kind of non-rigid objects, flexible and thin objects, is proposed, which can update with stability the state of n mass points of the mass-spring (MS) model with time complexity of O(n). The new implicit numerical integration technique of the authors, which is based on a simple approximation of the linear system, has great advantages over the existing implicit integration methods. Moreover, experiment shows that the new technique is highly efficient in animating a kind of non-rigid objects, and suitable for the draping module of the 3D garment CAD system.
Personalized x-ray reconstruction of the proximal femur via a non-rigid 2D-3D registration
Yu, Weimin; Zysset, Philippe; Zheng, Guoyan
2015-03-01
In this paper we present a new approach for a personalized X-ray reconstruction of the proximal femur via a non-rigid registration of a 3D volumetric template to 2D calibrated C-arm images. The 2D-3D registration is done with a hierarchical two-stage strategy: the global scaled rigid registration stage followed by a regularized deformable b-spline registration stage. In both stages, a set of control points with uniform spacing are placed over the domain of the 3D volumetric template and the registrations are driven by computing updated positions of these control points, which then allows to accurately register the 3D volumetric template to the reference space of the C-arm images. Comprehensive experiments on simulated images, on images of cadaveric femurs and on clinical datasets are designed and conducted to evaluate the performance of the proposed approach. Quantitative and qualitative evaluation results are given, which demonstrate the efficacy of the present approach.
Numerical solution of Poisson equation by quintic B-spline interpolation%均匀二型剖分下的二元五次B样条基函数及其应用
Institute of Scientific and Technical Information of China (English)
张胜刚; 宋明威; 王仁宏; 李国荣; 唐晓; 刘启贵
2012-01-01
1975年王仁宏建立了任意剖分下多元样条函数的基本理论框架,即所谓光滑余因子方法.多元样条在函数逼近、计算机辅助几何设计、有限元及小波等领域中均有重要的应用.由于某些特殊剖分如均匀剖分的可研究性,1984年王仁宏给出均匀二型剖分下的二元三次一阶光滑样条空间S1((△(2)mn))的维数及其B样条基函数,在计算机辅助几何设计,微分方程数值解等方面应用广泛.在研究光滑余因子方法的基础上,分析均匀二型剖分下的二元五次三阶光滑样条空间(S35)((△(2)mn))函数空间,给出了(S35)((△(2)mn))的维数及其B样条基函数,满足曲面拟合和微分方程数值解等应用中对更高阶光滑性的要求.基于该组基函数,提出一种Poisson方程的数值解方法,通过数值实例检验该方法的精度.%Multivariate splines have wide applications in approximation theory, computer aided geometric design(CAGD) and finite element method. In 1975, Ren-Hong Wang established a new approach to study the basic theory on multivariate spline functions on arbitrary partition by presenting the so called Smoothing cofactor-conformality method. As the large applications in CAGD et al. , Ren-Hong Wang discussed the dimension and B-spline basis of the C1 cubic spline spaces on type-2 triangulation partition, which is denoted by S31(△(2)mn). Accordingly we analyze the C3 quintic spline spaces on type-2 triangulation partition S53 (△(2)mn). The dimension and one group of B spline basis of S53(△(2)mn)are given. High derivatives is satisfied in applications. Based on the basis one numerical scheme is proposed to simulate the Poisson equation. Numerical examples are given to show the validity of the scheme.
Sequential Non-Rigid Structure from Motion Using Physical Priors.
Agudo, Antonio; Moreno-Noguer, Francesc; Calvo, Begona; Montiel, Jose M Martinez
2016-05-01
We propose a new approach to simultaneously recover camera pose and 3D shape of non-rigid and potentially extensible surfaces from a monocular image sequence. For this purpose, we make use of the Extended Kalman Filter based Simultaneous Localization And Mapping (EKF-SLAM) formulation, a Bayesian optimization framework traditionally used in mobile robotics for estimating camera pose and reconstructing rigid scenarios. In order to extend the problem to a deformable domain we represent the object's surface mechanics by means of Navier's equations, which are solved using a Finite Element Method (FEM). With these main ingredients, we can further model the material's stretching, allowing us to go a step further than most of current techniques, typically constrained to surfaces undergoing isometric deformations. We extensively validate our approach in both real and synthetic experiments, and demonstrate its advantages with respect to competing methods. More specifically, we show that besides simultaneously retrieving camera pose and non-rigid shape, our approach is adequate for both isometric and extensible surfaces, does not require neither batch processing all the frames nor tracking points over the whole sequence and runs at several frames per second.
二次B样条曲面顶点及法向插值%Interpolation of Vertices and Their Normal Vectors with Quadratic B-Spline Surfaces
Institute of Scientific and Technical Information of China (English)
李桂清; 李现民; 李华
2001-01-01
Interpolation to vertex positions is an essential issue in surface modeling, and interpolation to normal vectors has also important applications in some CAD/CAM areas. Properties of bi-quadratic B-spline surface are investigated by the subdivision approach, and the control mesh of bi-quadratic B-spline surface is constructed by employing Doo-Sabin subdivision to derive the parametric representation of interpolation surface. For enhancing the efficiency of handling mesh with larger scale data, we first partition the mesh into a number of sub-meshes and compute their corresponding control nets satisfying interpolatory conditions, then the sub-nets are integrated to form a whole net such that its bi-quadratic B-spline surface interpolates all given vertices and normal vectors.%顶点位置插值是自由曲面造型的基本方法，法向插值在一些CAD/CAM系统中也有重要应用．文中利用子分曲面理论研究双二次B样条曲面的性质，在此基础上利用Doo-Sabin子分模式构造插值顶点位置和法向的双二次B样条曲面控制网格，得到插值曲面的参数表示．为了提高效率，对规模较大的网格数据，先把它划分成若干片子网格，分别求出满足与子网格相关的插值条件的控制网格. 最后再把它们整合在一起形成完整的控制网格，使得相应的二次B样条曲面插值所有顶点及法向.
An Improved Method for Airfoil Parameterization by B-Spline%一种改进的B样条翼型参数化方法
Institute of Scientific and Technical Information of China (English)
张骥; 朱春钢; 冯仁忠; 刘明明; 张恒洋
2016-01-01
翼型设计是空气动力学研究的一项重要内容，翼型的参数化结果将影响翼型的优化设计。为了减少翼型优化中的设计变量，保证优化结果的光滑性与C2连续，在优化过程中控制翼型几何特性的变化范围，提出了一种改进的B样条参数化方法。用一条三次非均匀B样条曲线表示翼型，翼型数据的参数化过程中主要运用了B样条曲线拟合算法，并且在一般的B样条曲线拟合算法的基础上加入了对曲线的法向约束，通过迭代得到最终的参数化结果。实验结果表明，该方法可以很好的拟合典型的翼型数据，得到的翼型参数化结果不仅光滑，满足 C2条件，而且所得翼型函数的参数个数比传统的参数化方法有了进一步的减少，更有利于之后翼型的优化设计。%Airfoil design is a crucial issue of aerodynamic research, the parameterization of airfoil will affect the airfoil optimization design. In order to reduce the number of variables in the airfoil optimization, eliminate the unfairness phenomenon, preserve theC2 continuity condition, and control the geometric characteristics of the airfoil in the optimization process, in this paper, we present an improved method for airfoil parameterization by B-spline. The method represents airfoil by a cubic non-uniform B-spline curve. Fitting of airfoil data by B-spline curve is mainly by least square method and the normal constraints. And the final result is obtained by iteration. Experiments show that the proposed method can be well fitted to the typical airfoil data, the resulting curve is fair andC2 continuity, and has few parameters of airfoil function compared with the classical airfoil parametric methods.
Nonrigid retrospective respiratory motion correction in whole-heart coronary MRA.
Schmidt, Johannes F M; Buehrer, Martin; Boesiger, Peter; Kozerke, Sebastian
2011-12-01
A nonrigid retrospective respiratory motion correction scheme is presented for whole-heart coronary imaging with interleaved acquisition of motion information. The quasi-periodic nature of breathing is exploited to populate a 3D nonrigid motion model from low-resolution 2D imaging slices acquired interleaved with a segmented 3D whole-heart coronary scan without imposing scan time penalty. Reconstruction and motion correction are based on inversion of a generalized encoding equation. Therein, a forward model describes the transformation from the motion free image to the motion distorted k-space data, which includes nonrigid spatial transformations. The effectiveness of the approach is demonstrated on 10 healthy volunteers using free-breathing coronary whole-heart scans. Although conventional respiratory-gated acquisitions with 5-mm gating window resulted in an average gating efficiency of 51% ± 11%, nonrigid motion correction allowed for gate-free acquisitions, and hence scan time reduction by a factor of two without significant penalty in image quality. Image scores and quantitative image quality measures for the left coronary arteries showed no significant differences between 5-mm gated and gate-free acquisitions with motion correction. For the right coronary artery, slightly reduced image quality in the motion corrected gate-free scan was observed as a result of the close vicinity of anatomical structures with different motion characteristics. Magn Reson Med, 2011. © 2011 Wiley Periodicals, Inc.
Infinitesimal nonrigidity of convex surfaces with planar boundary
Institute of Scientific and Technical Information of China (English)
LI Chunhe; HONG Jiaxing
2005-01-01
In the present paper infinitesimal nonrigidity of a class of convex surfaces with planar boundary is given. This result shows that if the image of the Gauss map of an evolution convex surface with planar boundary covers some hemisphere, this surface may be of infinitesimal nonrigidity for the isometric deformation of planar boundary.
Non-rigid image registration using bone growth model
DEFF Research Database (Denmark)
Bro-Nielsen, Morten; Gramkow, Claus; Kreiborg, Sven
1997-01-01
Non-rigid registration has traditionally used physical models like elasticity and fluids. These models are very seldom valid models of the difference between the registered images. This paper presents a non-rigid registration algorithm, which uses a model of bone growth as a model of the change b...
Non-rigid registration by geometry-constrained diffusion
DEFF Research Database (Denmark)
Andresen, Per Rønsholt; Nielsen, Mads
2001-01-01
Assume that only partial knowledge about a non-rigid registration is given: certain points, curves, or surfaces in one 3D image are known to map to certain points, curves, or surfaces in another 3D image. In trying to identify the non-rigid registration field, we face a generalized aperture problem...
Non-rigid body static model based miniature robotic arm pose estimation%基于非刚体静力模型的微型机械臂姿态估计
Institute of Scientific and Technical Information of China (English)
雷洋; 田书林; 程玉华
2012-01-01
A model based estimation approach is proposed to determine the real-time kinematic pose of a miniature cable driven robotic arm with ten passive planar rotation joints. A non-rigid body static equilibrium model is constructed, and the ten planar degree of freedom ( DOF) variables are transformed to one translational variable and one tensile force variable. An linear variable differential transformer(LVDT) sensor and a load cell are used in this robotic arm to measure the planar kinematic pose of its end actuator. The accuracy and error of the measurement results are analyzed; the advantage and insufficiency of this measurement approach are stated; and the proposed method is compared with other potential measurement schemes.%提出了一种针对具有10个被动平面转动关节的微型化柔索驱动机械臂运动姿态的实时估计方法.通过建立该微型机械臂的非刚体静力模型,将10个平面自由度变量转化为1个位移变量和1个张力变量.用一个线型差动变压位移传感器(linear variable differential transformer,LVDT)和一个微型载荷传感器(load cell)测量该微型机械臂终端执行器的平面运动姿态.通过对测量结果的精度和误差进行分析,指出了该测量方法的优势与不足,并与其他几种可能的测量方法进行了比较和讨论.
双二次B-样条插值图像缩放%Image resizing via bi-quadratic B-spline interpolation
Institute of Scientific and Technical Information of China (English)
李英明; 夏海宏
2011-01-01
双线性和各种双三次插值方法是图像缩放中常用方法,但是双二次插值函数却很少被人提起.本文提出了一种基于双二次B-样条局部插值的图像缩放方法,该算法在图像局部重构过程中对称地采用了4×4采样点,并通过对该函数进行重采样来实现图像的缩放,避免了二次函数在图像重构与采样中的相位失真问题,此算法是一个局部性算法,易于扩展.实验结果表明,本文算法得到的图像的峰值信噪比(PSNR)、MISSIM值比双线性插值、双三次卷积、Catmull-Rom三次插值、Dodgson插值算法都要好,接近于最好的双三次B-样条算法,视觉效果虽然不如双三次B-样条插值算法,但优于Dodgson方法,计算时间比双三次B-样条减少了近三分之一.由于该算法没有对图像边缘特征进行特殊处理,对于一些细节纹理比较丰富的图像,将进一步研究.%Bilinear interpolation and various bi-cubic interpolations are frequently adopted in image resizing. However the biquadratic function is rarely considered due to its phase distortion problem. In this paper, we propose an image resizing method via bi-quadratic B-spline interpolation, where 4x4 pixels are sampled symmetrically in the local image. The proposed algorithm is a local algorithm and can be easily extended. According to our experiment results, the proposed bi-quadratic B-spline interpolation algorithm has better image peak signal-to-noise ratio ( PSNR) and MISSIM than bi-linear interpolation, bi-cubic convolution, Catmull-Rom cubic interpolation, or the Dodgson interpolation algorithm. The results are comparable to the bi-cubic B-spline interpolation algorithm, though the visual effects are not as good as that, but still better than the Dodgson algorithm. The computing time is reduced by nearly one-third compared to the bi-cubic B-spline interpolation algorithm. Since the algorithm has not carried on the special handling to the image edge features
Application of Piecewise Cubic B-Spline%过两端点分段三次 B 样条方法应用研究*
Institute of Scientific and Technical Information of China (English)
王争争
2015-01-01
通过引入约束点 P0和常量 r，构建过两端点分段三次B样条曲线并推出衔接点光滑衔接条件。应用过两端点分段三次B样条方法可以构建直线、三角形、四边形及蛋形画法，并通过消齿光顺得到理想效果。实现图形的平移、缩放和旋转，通过逆时针、顺时针旋转计算消除偏差，保形效果理想。按顺时针方向生成闭曲线并记录轨迹点位置数据，方便平面上闭曲线对象间关系的计算，并得到布尔运算结果。应用该方法可以构建空间图形，实现颜色渐变效果理想。%By introducing the constraint point P0 and constant r ,two endpoints piecewise cubic B spline curve is built and some smooth cohesion terms are introduced .Application of two endpoints piecewise cubic B spline method can build straight lines ,triangles ,quadrilateral and egg painting .Through the elimination of tooth smoothing ,ideal effect is got . Translation ,scaling and rotation of graphics are achieved and eliminated by counterclockwise ,clockwise calculation devia‐tion ,conformal effect is ideal .Clockwise to generate closed curve trajectory point location and record data ,convenient plane closed curve calculation of relations between objects ,Boolean calculation results are obtained .The method can build space graphics ,make color gradient effect ideal .
Institute of Scientific and Technical Information of China (English)
无
2005-01-01
Some construct characteristics and composing material of the new Gyro's rotor are introduced. Some factors resulting in deformation of the rotor surface are analyzed. Under different loads such as the force of deflecting center, the change of temperature, the force of pressure and couple factors, the deformation of rotor is analyzed with the wavelet finite element simulation software. The vector distributing map of rotor reformation is given. The deformation resulting from the pressure force of photon is studied. Finally, the influence on Gyro's performance because of anomalous surface of rotor due to deformation of rotor is researched and the result is useful to forecast the performance of the drift of gyroscope. The disturbing moment resulting from the deformation of rotor can be compensated using the mathematic method, and provides an important reference for both design and optimization of the rotor.
Optimized imaging using non-rigid registration
Energy Technology Data Exchange (ETDEWEB)
Berkels, Benjamin, E-mail: berkels@aices.rwth-aachen.de [Interdisciplinary Mathematics Institute, 1523 Greene Street, University of South Carolina, Columbia, SC 29208 (United States); Binev, Peter, E-mail: binev@math.sc.edu [Interdisciplinary Mathematics Institute, 1523 Greene Street, University of South Carolina, Columbia, SC 29208 (United States); Department of Mathematics, 1523 Greene Street, University of South Carolina, Columbia, SC 29208 (United States); Blom, Douglas A., E-mail: doug.blom@sc.edu [NanoCenter, 1212 Greene Street, University of South Carolina, Columbia, SC 29208 (United States); Dahmen, Wolfgang, E-mail: dahmen@igpm.rwth-aachen.de [Interdisciplinary Mathematics Institute, 1523 Greene Street, University of South Carolina, Columbia, SC 29208 (United States); Institut für Geometrie und Praktische Mathematik, RWTH Aachen, Templergraben 55, 52056 Aachen (Germany); Sharpley, Robert C., E-mail: rcsharpley@gmail.com [Interdisciplinary Mathematics Institute, 1523 Greene Street, University of South Carolina, Columbia, SC 29208 (United States); Department of Mathematics, 1523 Greene Street, University of South Carolina, Columbia, SC 29208 (United States); Vogt, Thomas, E-mail: tvogt@mailbox.sc.edu [Interdisciplinary Mathematics Institute, 1523 Greene Street, University of South Carolina, Columbia, SC 29208 (United States); NanoCenter, 1212 Greene Street, University of South Carolina, Columbia, SC 29208 (United States); Department of Chemistry and Biochemistry, 631 Sumter Street, University of South Carolina, Columbia, SC 29208 (United States)
2014-03-01
The extraordinary improvements of modern imaging devices offer access to data with unprecedented information content. However, widely used image processing methodologies fall far short of exploiting the full breadth of information offered by numerous types of scanning probe, optical, and electron microscopies. In many applications, it is necessary to keep measurement intensities below a desired threshold. We propose a methodology for extracting an increased level of information by processing a series of data sets suffering, in particular, from high degree of spatial uncertainty caused by complex multiscale motion during the acquisition process. An important role is played by a non-rigid pixel-wise registration method that can cope with low signal-to-noise ratios. This is accompanied by formulating objective quality measures which replace human intervention and visual inspection in the processing chain. Scanning transmission electron microscopy of siliceous zeolite material exhibits the above-mentioned obstructions and therefore serves as orientation and a test of our procedures. - Highlights: • Developed a new process for extracting more information from a series of STEM images. • An objective non-rigid registration process copes with distortions. • Images of zeolite Y show retrieval of all information available from the data set. • Quantitative measures of registration quality were implemented. • Applicable to any serially acquired data, e.g. STM, AFM, STXM, etc.
Directory of Open Access Journals (Sweden)
Xiaocui Wu
2015-11-01
Full Text Available Fluid–structure interaction is an important issue for non-rigid airships with inflated envelopes. In this study, a wind tunnel test is conducted, and a loosely coupled procedure is correspondingly established for numerical simulation based on computational fluid dynamics and nonlinear finite element analysis methods. The typical results of the numerical simulation and wind tunnel experiment, including the overall lift and deformation, are in good agreement with each other. The results obtained indicate that the effect of fluid–structure interaction is noticeable and should be considered for non-rigid airships. Flow-induced deformation can further intensify the upward lift force and pitching moment, which can lead to a large deformation. Under a wind speed of 15 m/s, the lift force of the non-rigid model is increased to approximately 60% compared with that of the rigid model under a high angle of attack.
DEFF Research Database (Denmark)
Izquierdo-Garcia, David; Hansen, Adam E; Förster, Stefan
2014-01-01
. The method was validated on 16 new subjects with brain tumors (n = 12) or mild cognitive impairment (n = 4) who underwent CT and PET/MR scans. The μ maps and corresponding reconstructed PET images were compared with those obtained using the gold standard CT-based approach and the Dixon-based method available...... coregistered using a diffeomorphic approach. A similar procedure was used to coregister the anatomic MR data for a new subject to the template. Finally, the CT-like images obtained by applying the inverse transformations were converted to linear attenuation coefficients to be used for AC of PET data...... on the Biograph mMR scanner. Relative change (RC) images were generated in each case, and voxel- and region-of-interest-based analyses were performed. RESULTS: The leave-one-out cross-validation analysis of the data from the 15 atlas-generation subjects showed small errors in brain linear attenuation coefficients...
Automatic Detection of Wild-type Mouse Cranial Sutures
DEFF Research Database (Denmark)
Ólafsdóttir, Hildur; Darvann, Tron Andre; Hermann, Nuno V.;
, automatic detection of the cranial sutures becomes important. We have previously built a craniofacial, wild-type mouse atlas from a set of 10 Micro CT scans using a B-spline-based nonrigid registration method by Rueckert et al. Subsequently, all volumes were registered nonrigidly to the atlas. Using...
Craniofacial Statistical Deformation Models of Wild-type mice and Crouzon mice
DEFF Research Database (Denmark)
Ólafsdóttir, Hildur; Darvann, Tron Andre; Ersbøll, Bjarne Kjær;
2007-01-01
using B-spline-based nonrigid registration and subsequently, the atlas was nonrigidly registered to the cases being modelled. The parameters of these registrations were then used as input to a PCA. Using different sets of registration parameters, different models were constructed to describe (i...
Deng, Zhipeng; Lei, Lin; Zhou, Shilin
2015-10-01
Automatic image registration is a vital yet challenging task, particularly for non-rigid deformation images which are more complicated and common in remote sensing images, such as distorted UAV (unmanned aerial vehicle) images or scanning imaging images caused by flutter. Traditional non-rigid image registration methods are based on the correctly matched corresponding landmarks, which usually needs artificial markers. It is a rather challenging task to locate the accurate position of the points and get accurate homonymy point sets. In this paper, we proposed an automatic non-rigid image registration algorithm which mainly consists of three steps: To begin with, we introduce an automatic feature point extraction method based on non-linear scale space and uniform distribution strategy to extract the points which are uniform distributed along the edge of the image. Next, we propose a hybrid point matching algorithm using DaLI (Deformation and Light Invariant) descriptor and local affine invariant geometric constraint based on triangulation which is constructed by K-nearest neighbor algorithm. Based on the accurate homonymy point sets, the two images are registrated by the model of TPS (Thin Plate Spline). Our method is demonstrated by three deliberately designed experiments. The first two experiments are designed to evaluate the distribution of point set and the correctly matching rate on synthetic data and real data respectively. The last experiment is designed on the non-rigid deformation remote sensing images and the three experimental results demonstrate the accuracy, robustness, and efficiency of the proposed algorithm compared with other traditional methods.
Two kinds of quadratic trigonometric B-spline curves with uniform knot vectors%均匀结点情形下的两类二阶三角B-样条曲线
Institute of Scientific and Technical Information of China (English)
王晶昕; 王迪
2014-01-01
Two kinds of quadratic trigonometric B-spline basis functions with uniform knot vectors are presented in this paper ,their constructions and properties are analyzed .These two kinds of functions can be used to construct trigonometric B-spline functions and trigonometric B-spline curves .Every segment of the first kind of curves is determined by three control points w hen every segment of the second kind of curves is determined by four control points .The properties of the two kinds of curves and the relationship between them are discussed .The cases of multiple knots of the first kind of basis functions are defined ,and we show how the curves like in this situation .The comparisons of the one order trigonometric B-spline curves and the quadratic trigonometric spline curves are presented in this paper .We came to a conclusion that the quadratic trigonometric B-spline curves are closer to the con-trol polygon than the one order trigonometric B-spline curves .%给出两类均匀结点情形下二阶三角B-样条基函数的定义，分析它们的构造过程，性质，并分别用其生成二阶三角B-样条函数和二阶三角B-样条曲线。其中第一类曲线是三点分段的，即由前后相继3个控制点决定一段曲线，与二阶B-样条曲线类似，第二类曲线是四点分段的，即由前后相继4个控制点决定一段曲线，与三阶B-样条曲线类似。讨论这两类曲线的性质及它们之间的关系。针对第一类曲线，还给出了重结点情形下基函数的定义并分析了这种情形下曲线的情况。将第一类二阶三角B-样条曲线与一阶三角B-样条曲线进行了对比，得出相同结点向量下，二阶三角B-样条曲线更加接近控制多边形的结论。
Interactive Manipulation and Reuse of Geodesic B-spline Curves on Meshes%网格曲面上测地B样条曲线交互操作与重用
Institute of Scientific and Technical Information of China (English)
刘斌; 韩林; 林俊义; 黄常标; 江开勇
2012-01-01
针对现有曲面上自由曲线设计重用方法的不足,提出一种流形网格曲面上曲线几何变换方法,达到曲线重用与再设计的目的.网格曲面上的曲线用测地B样条表示,具有与欧氏空间中传统B样条相一致的明确数学模型；引入对数映射理论将给定的源曲线控制顶点映射到切空间,获得它们的法坐标,按照曲线迁移前后控制顶点法坐标保持不变的原则,建立曲线迁移前后控制顶点的对应关系,实现类似于欧氏空间中的平移、旋转和缩放等几何变换.以网格曲面上离散对数映射理论为基础,将欧氏空间中的对称定义拓展到曲面空间,提出曲面上曲线的广义镜像概念并给出具体的算法实现.法坐标很好地保持了控制顶点之间的测地距离和相对位置关系,因而也保证了曲线迁移重用过程中的形状保持性.试验结果表明,所介绍方法健壮、有效,能满足曲面上曲线的交互设计要求.%In allusion to the deficiencies of the existing methods of reuse designing free curve on the surface, a geometric transformation method of curves on Manifold triangulation surface is proposed to achieve the aim of curves reuse and redesign. The curve on the mesh surface is represented as Geodesic B- spline curve, which has the clear uniform mathematical model with the classical B-spline curves in Euclidean space; by introduction of the logarithmic mapping theory, the control points of source curves can be mapped into tangent space and its Normal Coordinates can be obtained. According to the principle of those Normal Coordinates of remained unchanged, establishing the corresponding relation between pre and post transfer of curves, and curve's translation, rotation and scaling could be realized similaring to its geometric transformation in Euclidean space. The symmetry definition in Euclidean space is expand to curved space based on discrete logarithmic mapping theory, the generalized mirror
On Knot Modifications of B-Spline or NURBS Surface%改变B样条曲面与NURBS曲面的节点
Institute of Scientific and Technical Information of China (English)
李亚娟; 汪国昭
2005-01-01
通过改变k×h阶B样条曲面和NURBS(Non-Uniform Rational B-spline)曲面的若干节点,分别产生一个B样条曲面族和NURBS曲面族,并指出:曲面族的包络是用相同控制顶点定义的(k-α)×(h-b)阶B样条曲面和NURBS曲面,其中α,b分别是两个方向上所改变的节点的重数.对于B样条曲面来说,曲面族与其包络的任意阶相同偏微分之间只相差一个因子,文中所得结果可以作为计算机辅助设计系统中曲面造型和形状修改的理论参考.
带形状调整参数的一阶三角B样条曲线%One order trigonometric B-spline curves with shape parameters
Institute of Scientific and Technical Information of China (English)
王晶昕; 张嘉洋; 郭丽霞
2013-01-01
给出了一阶三角B样条基函数的构造，讨论这种基函数的性质以及在具有重节点情形时的变化，并利用这类三角B样条基构造了相应的三角B样条函数及三角B样条曲线。还给出了用带调节参数的控制点方法生成一阶三角B样条曲线以便对曲线形状进行调整的方法。讨论了如何利用这类B样条基以及带参数的控制点方法生成可调形状的三角样条曲线的问题。%T he construction of the one order trigonometric B-spline basic functions is presented in this paper .The properties of the basic functions and the case of multiple knots of the basic functions are discussed .T his kind basic function can be used to construct trigonometric spline functions and trigo-nometric spline curves .By the method of control points trasformation ,a kind of spline curve with shape parameters is presented and discussed .
An information theoretic approach for non-rigid image registration using voxel class probabilities.
D'Agostino, Emiliano; Maes, Frederik; Vandermeulen, Dirk; Suetens, Paul
2006-06-01
We propose two information theoretic similarity measures that allow to incorporate tissue class information in non-rigid image registration. The first measure assumes that tissue class probabilities have been assigned to each of the images to be registered by prior segmentation of both of them. One image is then non-rigidly deformed to match the other such that the fuzzy overlap of corresponding voxel object labels becomes similar to the ideal case whereby the tissue probability maps of both images are identical. Image similarity is assessed during registration by the divergence between the ideal and actual joint class probability distributions of both images. A second registration measure is proposed that applies in case a segmentation is available for only one of the images, for instance an atlas image that is to be matched to a study image to guide the segmentation thereof. Intensities in one image are matched to the fuzzy class labels in the other image by minimizing the conditional entropy of the intensities in the first image given the class labels in the second image. We derive analytic expressions for the gradient of each measure with respect to individual voxel displacements to derive a force field that drives the registration process, which is regularized by a viscous fluid model. The performance of the class-based measures is evaluated in the context of non-rigid inter-subject registration and atlas-based segmentation of MR brain images and compared with maximization of mutual information using only intensity information. Our results demonstrate that incorporation of class information in the registration measure significantly improves the overlap between corresponding tissue classes after non-rigid matching. The methods proposed here open new perspectives for integrating segmentation and registration in a single process, whereby the output of one is used to guide the other.
Institute of Scientific and Technical Information of China (English)
吴扬扬; 李全海
2012-01-01
介绍了建立似大地水准面模型的原理，讨论了非均匀B样条函数方法的基本原理。根据中部某地区的已知点的大地高和正常高，分别用非均匀三次B样条函数和三次曲面函数对该地区的似大地水准面进行高程拟合，结果表明了该方法具有更好的精度和稳定性。%The principles of the quasi-geoid model is introduced, and the basic principles of non-uniform B-spline method is discussed in this paper. It fits height on the quasi-geoid of this region by using non-uniform three B-spline method and three surface method separately according to the geodetic height and normal height of the known points of a certain area in central. Results show that the non-uniform B-spline method has better accuracy and stability.
Automatic nonrigid registration of whole body CT mice images.
Li, Xia; Yankeelov, Thomas E; Peterson, Todd E; Gore, John C; Dawant, Benoit M
2008-04-01
Three-dimensional intra- and intersubject registration of image volumes is important for tasks that include quantification of temporal/longitudinal changes, atlas-based segmentation, computing population averages, or voxel and tensor-based morphometry. While a number of methods have been proposed to address this problem, few have focused on the problem of registering whole body image volumes acquired either from humans or small animals. These image volumes typically contain a large number of articulated structures, which makes registration more difficult than the registration of head images, to which the majority of registration algorithms have been applied. This article presents a new method for the automatic registration of whole body computed tomography (CT) volumes, which consists of two main steps. Skeletons are first brought into approximate correspondence with a robust point-based method. Transformations so obtained are refined with an intensity-based nonrigid registration algorithm that includes spatial adaptation of the transformation's stiffness. The approach has been applied to whole body CT images of mice, to CT images of the human upper torso, and to human head and neck CT images. To validate the authors method on soft tissue structures, which are difficult to see in CT images, the authors use coregistered magnetic resonance images. They demonstrate that the approach they propose can successfully register image volumes even when these volumes are very different in size and shape or if they have been acquired with the subjects in different positions.
2015-12-01
Island Boolean Hierarchy 12 7. Raytracing -Based Validation 13 8. Performance Implications 14 9. Conclusions and Future Work 15 10. References 16...Visualization provided by NIST, b) right is the same model imported and raytraced in BRL- CAD...geometry which, although providing a definite step forward, is typically slow compared to CSG raytracing . In general, there has been relatively little
Non-rigid registration using higher-order mutual information
Rueckert, D.; Clarkson, M. J.; Hill, D. L. G.; Hawkes, D. J.
2000-03-01
Non-rigid registration of multi-modality images is an important tool for assessing temporal and structural changesbetween images. For rigid registration, voxel similarity measures like mutual information have been shown to alignimages from different modalities accurately and robustly. For non-rigid registration, mutual information can besensitive to local variations of intensity which in MR images may be caused by RF inhomogeneity. The reasonfor the sensitivity of mutual information towards intensity variations stems from the fact that mutual informationignores any spatial information. In this paper we propose an extension of the mutual information framework whichincorporates spatial information about higher-order image structure into the registration process and has the potentialto improve the accuracy and robustness of non-rigid registration in the presence of intensity variations. We haveapplied the non-rigid registration algorithm to a number of simulated MR brain images of a digital phantom whichhave been degraded by a simulated intensity shading and a known deformation. In addition, we have applied thealgorithm for the non-rigid registration of eight pre- and post-operative brain MR images which were acquired withan interventional MR scanner and therefore have substantial intensity shading due to RF field inhomogeneities. Inall cases the second-order estimate of mutual information leads to robust and accurate registration.
Nonrigid Registration of Monomodal MRI Using Linear Viscoelastic Model
Directory of Open Access Journals (Sweden)
Jian Yang
2014-01-01
Full Text Available This paper describes a method for nonrigid registration of monomodal MRI based on physical laws. The proposed method assumes that the properties of image deformations are like those of viscoelastic matter, which exhibits the properties of both an elastic solid and a viscous fluid. Therefore, the deformation fields of the deformed image are constrained by both sets of properties. After global registration, the local shape variations are assumed to have the properties of the Maxwell model of linear viscoelasticity, and the deformation fields are constrained by the corresponding partial differential equations. To speed up the registration, an adaptive force is introduced according to the maximum displacement of each iteration. Both synthetic datasets and real datasets are used to evaluate the proposed method. We compare the results of the linear viscoelastic model with those of the fluid model on the basis of both the standard and adaptive forces. The results demonstrate that the adaptive force increases in both models and that the linear viscoelastic model improves the registration accuracy.
Directory of Open Access Journals (Sweden)
Floris H P van Velden
Full Text Available OBJECTIVES: Reusing baseline volumes of interest (VOI by applying non-rigid and to some extent (local rigid image registration showed good test-retest variability similar to delineating VOI on both scans individually. The aim of the present study was to compare response assessments and classifications based on various types of image registration with those based on (semi-automatic tumour delineation. METHODS: Baseline (n = 13, early (n = 12 and late (n = 9 response (after one and three cycles of treatment, respectively whole body [(18F]fluoro-2-deoxy-D-glucose positron emission tomography/computed tomography (PET/CT scans were acquired in subjects with advanced gastrointestinal malignancies. Lesions were identified for early and late response scans. VOI were drawn independently on all scans using an adaptive 50% threshold method (A50. In addition, various types of (non-rigid image registration were applied to PET and/or CT images, after which baseline VOI were projected onto response scans. Response was classified using PET Response Criteria in Solid Tumors for maximum standardized uptake value (SUV(max, average SUV (SUV(mean, peak SUV (SUV(peak, metabolically active tumour volume (MATV, total lesion glycolysis (TLG and the area under a cumulative SUV-volume histogram curve (AUC. RESULTS: Non-rigid PET-based registration and non-rigid CT-based registration followed by non-rigid PET-based registration (CTPET did not show differences in response classifications compared to A50 for SUV(max and SUV(peak, however, differences were observed for MATV, SUV(mean, TLG and AUC. For the latter, these registrations demonstrated a poorer performance for small lung lesions (<2.8 ml, whereas A50 showed a poorer performance when another area with high uptake was close to the target lesion. All methods were affected by lesions with very heterogeneous tracer uptake. CONCLUSIONS: Non-rigid PET- and CTPET-based image registrations may be used to classify response
GGO nodule volume-preserving nonrigid lung registration using GLCM texture analysis.
Park, Seongjin; Kim, Bohyoung; Lee, Jeongjin; Goo, Jin Mo; Shin, Yeong-Gil
2011-10-01
In lung cancer screening, benign and malignant nodules can be classified through nodule growth assessment by the registration and, then, subtraction between follow-up computed tomography scans. During the registration, the volume of nodule regions in the floating image should be preserved, whereas the volume of other regions in the floating image should be aligned to that in the reference image. However, ground glass opacity (GGO) nodules are very elusive to automatically segment due to their inhomogeneous interior. In other words, it is difficult to automatically define the volume-preserving regions of GGO nodules. In this paper, we propose an accurate and fast nonrigid registration method. It applies the volume-preserving constraint to candidate regions of GGO nodules, which are automatically detected by gray-level cooccurrence matrix (GLCM) texture analysis. Considering that GGO nodules can be characterized by their inner inhomogeneity and high intensity, we identify the candidate regions of GGO nodules based on the homogeneity values calculated by the GLCM and the intensity values. Furthermore, we accelerate our nonrigid registration by using Compute Unified Device Architecture (CUDA). In the nonrigid registration process, the computationally expensive procedures of the floating-image transformation and the cost-function calculation are accelerated by using CUDA. The experimental results demonstrated that our method almost perfectly preserves the volume of GGO nodules in the floating image as well as effectively aligns the lung between the reference and floating images. Regarding the computational performance, our CUDA-based method delivers about 20× faster registration than the conventional method. Our method can be successfully applied to a GGO nodule follow-up study and can be extended to the volume-preserving registration and subtraction of specific diseases in other organs (e.g., liver cancer).
Multi-modal 2D-3D non-rigid registration
Prümmer, M.; Hornegger, J.; Pfister, M.; Dörfler, A.
2006-03-01
In this paper, we propose a multi-modal non-rigid 2D-3D registration technique. This method allows a non-rigid alignment of a patient pre-operatively computed tomography (CT) to few intra operatively acquired fluoroscopic X-ray images obtained with a C-arm system. This multi-modal approach is especially focused on the 3D alignment of high contrast reconstructed volumes with intra-interventional low contrast X-ray images in order to make use of up-to-date information for surgical guidance and other interventions. The key issue of non-rigid 2D-3D registration is how to define the distance measure between high contrast 3D data and low contrast 2D projections. In this work, we use algebraic reconstruction theory to handle this problem. We modify the Euler-Lagrange equation by introducing a new 3D force. This external force term is computed from the residual of the algebraic reconstruction procedures. In the multi-modal case we replace the residual between the digitally reconstructed radiographs (DRR) and observed X-ray images with a statistical based distance measure. We integrate the algebraic reconstruction technique into a variational registration framework, so that the 3D displacement field is driven to minimize the reconstruction distance between the volumetric data and its 2D projections using mutual information (MI). The benefits of this 2D-3D registration approach are its scalability in the number of used X-ray reference images and the proposed distance that can handle low contrast fluoroscopies as well. Experimental results are presented on both artificial phantom and 3D C-arm CT images.
Constrained non-rigid registration for whole body image registration: method and validation
Li, Xia; Yankeelov, Thomas E.; Peterson, Todd E.; Gore, John C.; Dawant, Benoit M.
2007-03-01
3D intra- and inter-subject registration of image volumes is important for tasks that include measurements and quantification of temporal/longitudinal changes, atlas-based segmentation, deriving population averages, or voxel and tensor-based morphometry. A number of methods have been proposed to tackle this problem but few of them have focused on the problem of registering whole body image volumes acquired either from humans or small animals. These image volumes typically contain a large number of articulated structures, which makes registration more difficult than the registration of head images, to which the vast majority of registration algorithms have been applied. To solve this problem, we have previously proposed an approach, which initializes an intensity-based non-rigid registration algorithm with a point based registration technique [1, 2]. In this paper, we introduce new constraints into our non-rigid registration algorithm to prevent the bones from being deformed inaccurately. Results we have obtained show that the new constrained algorithm leads to better registration results than the previous one.
B-Spline Variational Method for Shape Reconstruction from Shading%由单幅图像重构表面形状的B样条变分法研究
Institute of Scientific and Technical Information of China (English)
熊汉伟; 张湘伟
2001-01-01
B-spline approach is used to solve shape from shading problem, removing the smoothness and integrability restrictions from the objective functional formulation. A new B-spline hierarchical basis function is introduced to accelerate the algorithm. Simulation results show the efficiency of new approach.%针对SFS(Shape From Shading)问题中的Lagrange乘子难题，经过B样条插值，将SFS问题的可积性、光滑性限制隐含，消除Lagrange乘子的不利影响，采用B样条变分法解决了SFS问题；并根据B样条特殊结构，设计了SFS问题变分格式的层次基变换共轭梯度加速算法.初步的计算实例表明，此方法在精度、速度上有所提高，效果令人满意.
非均匀三次B样条曲线插值的GS-PIA算法%Non-uniform Cubic B-spline Curve Interpolation Algorithm of GS-PIA
Institute of Scientific and Technical Information of China (English)
刘晓艳; 邓重阳
2015-01-01
提出了非均匀三次B样条曲线插值的GS-PIA算法。该算法与解线性方程组的高斯－赛德尔迭代法有同样的优点，即把已经更新的点参与到迭代过程来优化迭代过程；同时也具有渐进迭代逼近方法的优点，即有明确的几何意义，并能得到一系列逐次逼近插值点的非均匀三次 B样条曲线。%This paper presents a non-uniform cubic B-spline curve interpolation algorithm of GS-PIA.The algorithm and the Gauss-Seidel iterative method of solving linear equations have the same advantages , namely the points involved in the iterative process which has been updated to optimize the iterative process .At the same time, the algorithm also has the advantage of progressive iterative approximation method , namely, there is a clear geometric significance , and can make a series of non-uniform cubic B-spline curve approximation interpolation points .
3D nonrigid medical image registration using a new information theoretic measure
Li, Bicao; Yang, Guanyu; Coatrieux, Jean Louis; Li, Baosheng; Shu, Huazhong
2015-11-01
This work presents a novel method for the nonrigid registration of medical images based on the Arimoto entropy, a generalization of the Shannon entropy. The proposed method employed the Jensen-Arimoto divergence measure as a similarity metric to measure the statistical dependence between medical images. Free-form deformations were adopted as the transformation model and the Parzen window estimation was applied to compute the probability distributions. A penalty term is incorporated into the objective function to smooth the nonrigid transformation. The goal of registration is to optimize an objective function consisting of a dissimilarity term and a penalty term, which would be minimal when two deformed images are perfectly aligned using the limited memory BFGS optimization method, and thus to get the optimal geometric transformation. To validate the performance of the proposed method, experiments on both simulated 3D brain MR images and real 3D thoracic CT data sets were designed and performed on the open source elastix package. For the simulated experiments, the registration errors of 3D brain MR images with various magnitudes of known deformations and different levels of noise were measured. For the real data tests, four data sets of 4D thoracic CT from four patients were selected to assess the registration performance of the method, including ten 3D CT images for each 4D CT data covering an entire respiration cycle. These results were compared with the normalized cross correlation and the mutual information methods and show a slight but true improvement in registration accuracy.
Directory of Open Access Journals (Sweden)
Diego Mauricio Vasquez E.
2010-05-01
Full Text Available En este documento se presenta la descripción y los resultados de la estimación de la estructura a plazos de las tasas de interés en Colombia utilizando el método de funciones B-spline cúbicas. Adicionalmente, se llevan a cabo comparaciones entre los resultados obtenidos a través de esta metodología y los presentados por Arango, Melo y Vásquez (2002 respecto a los métodos de Nelson y Siegel, y de la Bolsa de Valores de Colombia. Se observa que el desempeño del método de estimación de funciones Bspline cúbicas es similar al de Nelson y Siegel, y estos dos métodos superan al de la Bolsa de Valores de Colombia.
Non-Rigid Object Tracking by Anisotropic Kernel Mean Shift
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
Mean shift, an iterative procedure that shifts each data point to the average of data points in its neighborhood, has been applied to object tracker. However, the traditional mean shift tracker by isotropic kernel often loses the object with the changing object structure in video sequences, especially when the object structure varies fast. This paper proposes a non-rigid object tracker by anisotropic kernel mean shift in which the shape, scale, and orientation of the kernels adapt to the changing object structure. The experimental results show that the new tracker is self-adaptive and approximately twice faster than the traditional tracker, which ensures the robustness and real time of tracking.
Full Non-Rigid Group and Symmetry of Dimethyltrichlorophosphorus
Institute of Scientific and Technical Information of China (English)
ASHRAFI; AliReza
2005-01-01
In this work, a simple method is described, by means of which it is possible to calculate character tables for the symmetry group of molecules consisting of a number of NH3 groups attached to a rigid framework. The full non-rigid group (f-NRG) of dimethyltrichlorophosphorus with the symmetry group D3h was studied. It has been proven that it is a group of order 216 with 27 conjugacy classes and its character table computed. Finally, the Permutation-lnversion group of this molecule was calculated.
Method of vector graphics digital watermarking based on B-spline%基于B-spline矢量图形数字水印方法
Institute of Scientific and Technical Information of China (English)
范铁生; 孟瑶; 房肖冰
2007-01-01
提出了一种针对矢量图形的数字水印算法,用于矢量图形的版权保护.算法利用了B-spline良好的持续逼近曲线形状的特点,将水印嵌入到B-spline的控制点坐标中.经实验证明,该算法对于通常的图形几何变换,如平移、旋转、缩放以及局部修改攻击,均有令人满意的鲁棒性.
基于三次B样条函数的话务量预测模型%Traffic Prediction Model Based on Cubic B Spline Interpolation
Institute of Scientific and Technical Information of China (English)
熊春波; 郭军峰
2009-01-01
针对某移动通信服务公司话务量预测的实际问题,利用三次B样条函数插值方法,建立了工作日和假日话务量预测模型,求解得出了移动电话的话务量随时间变化的规律性,并在某通信服务公司的话务量预测中得到了具体应用,结果是有效的.
Cardiac nonrigid motion analysis from image sequences
Institute of Scientific and Technical Information of China (English)
LIU Huafeng
2006-01-01
Noninvasive estimation of the soft tissue kinematics properties from medical image sequences has many important clinical and physiological implications, such as the diagnosis of heart diseases and the understanding of cardiac mechanics. In this paper, we present a biomechanics based strategy, framed as a priori constraints for the ill-posed motion recovery problema, to realize estimation of the cardiac motion and deformation parameters. By constructing the heart dynamics system equations from biomechanics principles, we use the finite element method to generate smooth estimates.of heart kinematics throughout the cardiac cycle. We present the application of the strategy to the estimation of displacements and strains from in vivo left ventricular magnetic resonance image sequence.
DEFF Research Database (Denmark)
Hansen, Michael Sass; Olafsdóttir, Hildur; Darvann, Tron Andre;
2007-01-01
of wild-type (normal) mice and Crouzon mice were investigated. We present for what we believe is the first time, a statistical deformation model based on independent component analysis (ICA). A set of deformation parameters for each mouse was calculated using a B-spline-based nonrigid registration. From...
Non-rigid registration of 3D point clouds under isometric deformation
Ge, Xuming
2016-11-01
An algorithm for pairwise non-rigid registration of 3D point clouds is presented in the specific context of isometric deformations. The critical step is registration of point clouds at different epochs captured from an isometric deformation surface within overlapping regions. Based on characteristics invariant under isometric deformation, a variant of the four-point congruent sets algorithm is applied to generate correspondences between two deformed point clouds, and subsequently a RANSAC framework is used to complete cluster extraction in preparation for global optimal alignment. Examples are presented and the results compared with existing approaches to demonstrate the two main contributions of the technique: a success rate for generating true correspondences of 90% and a root mean square error after final registration of 2-3 mm.
PROBABILISTIC NON-RIGID REGISTRATION OF PROSTATE IMAGES: MODELING AND QUANTIFYING UNCERTAINTY
Risholm, Petter; Fedorov, Andriy; Pursley, Jennifer; Tuncali, Kemal; Cormack, Robert; Wells, William M.
2012-01-01
Registration of pre- to intra-procedural prostate images needs to handle the large changes in position and shape of the prostate caused by varying rectal filling and patient positioning. We describe a probabilistic method for non-rigid registration of prostate images which can quantify the most probable deformation as well as the uncertainty of the estimated deformation. The method is based on a biomechanical Finite Element model which treats the prostate as an elastic material. We use a Markov Chain Monte Carlo sampler to draw deformation configurations from the posterior distribution. In practice, we simultaneously estimate the boundary conditions (surface displacements) and the internal deformations of our biomechanical model. The proposed method was validated on a clinical MRI dataset with registration results comparable to previously published methods, but with the added benefit of also providing uncertainty estimates which may be important to take into account during prostate biopsy and brachytherapy procedures. PMID:22288004
Non-rigid registration of breast surfaces using the laplace and diffusion equations
Directory of Open Access Journals (Sweden)
Ou Jao J
2010-02-01
Full Text Available Abstract A semi-automated, non-rigid breast surface registration method is presented that involves solving the Laplace or diffusion equations over undeformed and deformed breast surfaces. The resulting potential energy fields and isocontours are used to establish surface correspondence. This novel surface-based method, which does not require intensity images, anatomical landmarks, or fiducials, is compared to a gold standard of thin-plate spline (TPS interpolation. Realistic finite element simulations of breast compression and further testing against a tissue-mimicking phantom demonstrate that this method is capable of registering surfaces experiencing 6 - 36 mm compression to within a mean error of 0.5 - 5.7 mm.
Institute of Scientific and Technical Information of China (English)
胡良臣; 寿华好
2016-01-01
若是 B 样条拟合曲线的节点向量与控制顶点均为变量，则该问题变为一个带约束的多维多变量高度非线性的优化问题，反求方程系统的方法已经难以求得最优解。针对该类问题，提出一种带有法向约束的粒子群优化算法(PSO)求解曲线逼近问题的方法，首先将带有法向约束的非线性最优化问题以罚函数的方法转化为无约束的最优化问题，建立一个与数据点和法向同时相关且比较合适的适应度函数(误差函数)，然后以PSO调节节点向量，并使用最小二乘法求解在该节点向量下的最优拟合曲线，通过判断适应度函数值的优劣循环迭代，直到达到终止条件或者产生令人满意(误差容忍值)的拟合曲线为止。将文中算法产生的拟合曲线通过实验数据的对比与说明，突出了该方法的优越性，表明其用于解决带法向约束的逼近问题切实可行。%If the knot vector and control points of a B-spline curve are variable, the B-spline curve approxi-mation with normal constraint problem becomes a multidimensional, multivariate and highly nonlinear op-timization problem with normal constraints, the conventional method of inverse equation system is difficult to obtain the optimal solution. Aiming at this kind of problem, a particle swarm optimization (PSO) method is introduced to solve the curve approximation problem with normal constraints. Firstly, the penalty function method is used to transform the constrained optimization problem into an unconstrained optimization prob-lem. Secondly, a suitable fitness function which is closely related to both data points and normal constraints is constructed. Finally, PSO is applied to adjust the knot vector, and at the same time, the least square method is used to solve the optimal control points, do loop iteration until the best B-spline curve approxima-tion is produced. By a comparison with existing methods, the superiority of
Fernández-Menchero, L; Bartschat, K
2016-01-01
There are major discrepancies between recent ICFT (Intermediate Coupling Frame Transformation) and DARC (Dirac Atomic R-matrix Code) calculations (Fern\\'andez-Menchero et al. 2014, Astron. Astroph. 566 A104, Aggarwal et al. 2016 Mon. Not. R Astr. Soc. 461 3997) regarding electron impact excitation rates for transitions in several Be-like ions, as well as claims that DARC calculations are much more accurate and the ICFT results might even be wrong. To resolve possible reasons for these discrepancies and to estimate the accuracy of the various results, we carried out independent B-Spline R-Matrix (BSR) calculations for electron-impact excitation of the Be-like ion N$^{3+}$. Our close-coupling expansions contain the same target states (238 levels overall) as the previous ICFT and DARC calculations, but the representation of the target wave functions is completely different. We find close agreement among all calculations for the strong transitions between low-lying states, whereas there remain serious discrepanci...
带有切线多边形的三次B样条的α扩展曲线%α extension of the cubic B-spline curve with given tangent polygon
Institute of Scientific and Technical Information of China (English)
王成伟
2011-01-01
为了使三次均匀B样条的α扩展曲线与给定多边形相切,构造了一种与给定多边形相切的三次均匀B样条曲线的α扩展的算法.在算法中,所有的三次均匀B样条的α扩展曲线的控制点可以通过对多边形的顶点简单计算产生.所构造的曲线对多边形具有保形性,曲线可以局部修改.最后给出了2个算例.%In order to a expansion of the cubic uniform B-spline curve tangent to the given polygon,in this paper, an algorithm for constructing α extension of the cubic uniform B-spine curve which is tangent to the given polygon is described. The control points of α extension of the cubic uniform B-spine curve to be constructed are computed simply by the vertices of the given polygon. The constructed curve is shape-preserving to the polygon. The local modification to a extension of the cubic uniform B-spine curve can be completed by simply adjusting the corresponding control parameters. Two examples are included.
Atlas-Based Automatic Generation of Subject-Specific Finite Element Tongue Meshes.
Bijar, Ahmad; Rohan, Pierre-Yves; Perrier, Pascal; Payan, Yohan
2016-01-01
Generation of subject-specific 3D finite element (FE) models requires the processing of numerous medical images in order to precisely extract geometrical information about subject-specific anatomy. This processing remains extremely challenging. To overcome this difficulty, we present an automatic atlas-based method that generates subject-specific FE meshes via a 3D registration guided by Magnetic Resonance images. The method extracts a 3D transformation by registering the atlas' volume image to the subject's one, and establishes a one-to-one correspondence between the two volumes. The 3D transformation field deforms the atlas' mesh to generate the subject-specific FE mesh. To preserve the quality of the subject-specific mesh, a diffeomorphic non-rigid registration based on B-spline free-form deformations is used, which guarantees a non-folding and one-to-one transformation. Two evaluations of the method are provided. First, a publicly available CT-database is used to assess the capability to accurately capture the complexity of each subject-specific Lung's geometry. Second, FE tongue meshes are generated for two healthy volunteers and two patients suffering from tongue cancer using MR images. It is shown that the method generates an appropriate representation of the subject-specific geometry while preserving the quality of the FE meshes for subsequent FE analysis. To demonstrate the importance of our method in a clinical context, a subject-specific mesh is used to simulate tongue's biomechanical response to the activation of an important tongue muscle, before and after cancer surgery.
A Novel Prior- and Motion-Based Compressed Sensing Method for Small-Animal Respiratory Gated CT.
Directory of Open Access Journals (Sweden)
Juan F P J Abascal
Full Text Available Low-dose protocols for respiratory gating in cardiothoracic small-animal imaging lead to streak artifacts in the images reconstructed with a Feldkamp-Davis-Kress (FDK method. We propose a novel prior- and motion-based reconstruction (PRIMOR method, which improves prior-based reconstruction (PBR by adding a penalty function that includes a model of motion. The prior image is generated as the average of all the respiratory gates, reconstructed with FDK. Motion between respiratory gates is estimated using a nonrigid registration method based on hierarchical B-splines. We compare PRIMOR with an equivalent PBR method without motion estimation using as reference the reconstruction of high dose data. From these data acquired with a micro-CT scanner, different scenarios were simulated by changing photon flux and number of projections. Methods were evaluated in terms of contrast-to-noise-ratio (CNR, mean square error (MSE, streak artefact indicator (SAI, solution error norm (SEN, and correction of respiratory motion. Also, to evaluate the effect of each method on lung studies quantification, we have computed the Jaccard similarity index of the mask obtained from segmenting each image as compared to those obtained from the high dose reconstruction. Both iterative methods greatly improved FDK reconstruction in all cases. PBR was prone to streak artifacts and presented blurring effects in bone and lung tissues when using both a low number of projections and low dose. Adopting PBR as a reference, PRIMOR increased CNR up to 33% and decreased MSE, SAI and SEN up to 20%, 4% and 13%, respectively. PRIMOR also presented better compensation for respiratory motion and higher Jaccard similarity index. In conclusion, the new method proposed for low-dose respiratory gating in small-animal scanners shows an improvement in image quality and allows a reduction of dose or a reduction of the number of projections between two and three times with respect to previous PBR
A Condition Number for Non-Rigid Shape Matching
Ovsjanikov, Maks
2011-08-01
© 2011 The Author(s). Despite the large amount of work devoted in recent years to the problem of non-rigid shape matching, practical methods that can successfully be used for arbitrary pairs of shapes remain elusive. In this paper, we study the hardness of the problem of shape matching, and introduce the notion of the shape condition number, which captures the intuition that some shapes are inherently more difficult to match against than others. In particular, we make a connection between the symmetry of a given shape and the stability of any method used to match it while optimizing a given distortion measure. We analyze two commonly used classes of methods in deformable shape matching, and show that the stability of both types of techniques can be captured by the appropriate notion of a condition number. We also provide a practical way to estimate the shape condition number and show how it can be used to guide the selection of landmark correspondences between shapes. Thus we shed some light on the reasons why general shape matching remains difficult and provide a way to detect and mitigate such difficulties in practice.
Institute of Scientific and Technical Information of China (English)
蔡利栋
2001-01-01
The profit-and-loss revision technique may improve the accuracy of approximation to raw image data undergone a cubic B-spline smoothing. Comments are made on this technique from the viewpoint of image smoothing and restoration, giving highlights on the equivalence between spline smoothing and diffusion smoothing, and between profit-and-loss revision and inverse diffusion restoration; formulating the revision operators into a series of renewal recursions together with an estimation to the order of their deviations from the raw data; and exposing the numerical instability of both simple and renewal recursion of the profit and loss revision. Finally, a discussion is further made on the feasibility of applying the profit-and-loss revision to edge detection for images in the presence of noise.%以三阶B-样条作数据磨光时，引入盈亏修正可以在磨光的同时提高逼近原始数据的精度.通过从图象的平滑与恢复处理的角度出发来对盈亏修正技术进行评注，并进一步阐明了样条磨光与扩散平滑、盈亏修正与反扩散恢复在离散条件下的等价关系，给出了用于修正的更新迭代算子序列以及相应的偏差阶数估计，并且指出了盈亏修正的简单迭代和更新迭代都是数值上绝对不稳定的计算；最后讨论了盈亏修正技术在图象边缘探测中的适用性.
Fernández-Menchero, L.; Zatsarinny, O.; Bartschat, K.
2017-03-01
There are major discrepancies between recent intermediate coupling frame transformation (ICFT) and Dirac atomic R-matrix code (DARC) calculations (Fernández-Menchero et al 2014 Astron. Astrophys. 566 A104; Aggarwal et al 2016 Mon. Not. R. Astron. Soc. 461 3997) regarding electron-impact excitation rates for transitions in several Be-like ions, as well as claims that the DARC calculations are much more accurate and the ICFT results might even be wrong. To identify possible reasons for these discrepancies and to estimate the accuracy of the various results, we carried out independent B-spline R-matrix calculations for electron-impact excitation of the Be-like ion {{{N}}}3+. Our close-coupling (CC) expansions contain the same target states (238 levels overall) as the previous ICFT and DARC calculations, but the representation of the target wave functions is completely different. We find close agreement among all calculations for the strong transitions between low-lying states, whereas there remain serious discrepancies for the weak transitions as well as for transitions to highly excited states. The differences in the final results for the collision strengths are mainly due to differences in the structure description, specifically the inclusion of correlation effects, rather than the treatment of relativistic effects or problems with the validity of the three methods to describe the collision. Hence there is no indication that one approach is superior to another, until the convergence of both the target configuration and the CC expansions have been fully established.
Wielandts, Jean-Yves; De Buck, Stijn; Ector, Joris; Nuyens, Dieter; Maes, Frederik; Heidbuchel, Hein
2014-03-01
VT ablations could benefit from Dynamic 3D (4D) left ventricle (LV) visualization as road-map for anatomy-guided procedures. We developed a registration-based method that combines information of several cardiac phases to filter out noise and artifacts in low-dose 3D Rotational Angiography (3DRA) images. This also enables generation of accurate multi-phase surface models by semi-automatic segmentation (SAS). The method uses B-spline non-rigid inter-phase registration (IPR) and subsequent averaging of the registered 3DRA images of 4 cardiac phases, acquired with a slow atrial pacing protocol, and was validated on data from 5 porcine experiments. IPR parameter settings were optimized against manual delineations of the LVs using a composed similarity score (Q), dependent on DICE-coefficient, RMSDistance, Hausdorff (HD) and the percentage of inter-surface distances ≤3mm and ≤4mm. The latter are clinically acceptable error cut-off values. Validation was performed after SAS for varying voxel intensity thresholds (ISO), by comparison between models with and without prior use of IPR. Distances to the manual delineations at optimal ISO were reduced to ≤3mm for 95.6±2.7% and to ≤4mm for 97.1±2.0% of model surfaces. Improved quality was proven by significant mean Q-increase irrespective of ISO (7.6% at optimal ISO (95%CI 4.6-10.5,pmodels proved feasible, with sufficient accuracy for clinical applications, opening the perspective of more accurate overlay and guidance during ablation in locations with high degrees of movement.
Comparing nonrigid registration techniques for motion corrected MR prostate diffusion imaging
Energy Technology Data Exchange (ETDEWEB)
Buerger, C., E-mail: christian.buerger@philips.com; Sénégas, J.; Kabus, S.; Carolus, H.; Schulz, H.; Renisch, S. [Philips Research Hamburg, Hamburg 22335 (Germany); Agarwal, H. [Philips Research North America, Briarcliff Manor, New York 10510 and Molecular Imaging Program, NCI, National Institute of Health, Bethesda, Maryland 20892 (United States); Turkbey, B.; Choyke, P. L. [Molecular Imaging Program, NCI, National Institute of Health, Bethesda, Maryland 20892 (United States)
2015-01-15
Purpose: T{sub 2}-weighted magnetic resonance imaging (MRI) is commonly used for anatomical visualization in the pelvis area, such as the prostate, with high soft-tissue contrast. MRI can also provide functional information such as diffusion-weighted imaging (DWI) which depicts the molecular diffusion processes in biological tissues. The combination of anatomical and functional imaging techniques is widely used in oncology, e.g., for prostate cancer diagnosis and staging. However, acquisition-specific distortions as well as physiological motion lead to misalignments between T{sub 2} and DWI and consequently to a reduced diagnostic value. Image registration algorithms are commonly employed to correct for such misalignment. Methods: The authors compare the performance of five state-of-the-art nonrigid image registration techniques for accurate image fusion of DWI with T{sub 2}. Results: Image data of 20 prostate patients with cancerous lesions or cysts were acquired. All registration algorithms were validated using intensity-based as well as landmark-based techniques. Conclusions: The authors’ results show that the “fast elastic image registration” provides most accurate results with a target registration error of 1.07 ± 0.41 mm at minimum execution times of 11 ± 1 s.
Testing for additivity with B-splines
Institute of Scientific and Technical Information of China (English)
Heng-jian CUI; Xu-ming HE; Li LIU
2007-01-01
Regression splines are often used for fitting nonparametric functions, and they work especially well for additivity models. In this paper, we consider two simple tests of additivity: an adaptation of Tukey's one degree of freedom test and a nonparametric version of Rao's score test. While the Tukey-type test can detect most forms of the local non-additivity at the parametric rate of O(n-1/2), the score test is consistent for all alternative at a nonparametric rate. The asymptotic distribution of these test statistics is derived under both the null and local alternative hypotheses. A simulation study is conducted to compare their finite-sample performances with some existing kernelbased tests. The score test is found to have a good overall performance.
Xie, Zhongliu; Kitamoto, Asanobu; Tamura, Masaru; Shiroishi, Toshihiko; Gillies, Duncan
2016-03-01
Intensive international efforts are underway towards phenotyping the mouse genome, by knocking out each of its ≍25,000 genes one-by-one for comparative study. With vast amounts of data to analyze, the traditional method using time-consuming histological examination is clearly impractical, leading to an overwhelming demand for some high-throughput phenotyping framework, especially with the employment of biomedical image informatics to efficiently identify phenotypes concerning morphological abnormality. Existing work has either excessively relied on volumetric analytics which is insensitive to phenotypes associated with no severe volume variations, or tailored for specific defects and thus fails to serve a general phenotyping purpose. Furthermore, the prevailing requirement of an atlas for image segmentation in contrast to its limited availability further complicates the issue in practice. In this paper we propose a high-throughput general-purpose phenotyping framework that is able to efficiently perform batch-wise anomaly detection without prior knowledge of the phenotype and the need for atlas-based segmentation. Anomaly detection is centered on the combined use of group-wise non-rigid image registration and robust principal component analysis (RPCA) for feature extraction and decomposition.
Li, Xia; Dawant, Benoit M.; Welch, E. Brian; Chakravarthy, A. Bapsi; Freehardt, Darla; Mayer, Ingrid; Kelley, Mark; Meszoely, Ingrid; Gore, John C.; Yankeelov, Thomas E.
2009-02-01
Although useful for the detection of breast cancers, conventional imaging methods, including mammography and ultrasonography, do not provide adequate information regarding response to therapy. Dynamic contrast enhanced MRI (DCE-MRI) has emerged as a promising technique to provide relevant information on tumor status. Consequently, accurate longitudinal registration of breast MR images is critical for the comparison of changes induced by treatment at the voxel level. In this study, a nonrigid registration algorithm is proposed to allow for longitudinal registration of breast MR images obtained throughout the course of treatment. We accomplish this by modifying the adaptive bases algorithm (ABA) through adding a tumor volume preserving constraint in the cost function. The registration results demonstrate the proposed algorithm can successfully register the longitudinal breast MR images and permit analysis of the parameter maps. We also propose a novel validation method to evaluate the proposed registration algorithm quantitatively. These validations also demonstrate that the proposed algorithm constrains tumor deformation well and performs better than the unconstrained ABA algorithm.
Validation of TMJ osteoarthritis synthetic defect database via non-rigid registration
Paniagua, Beatriz; Pera, Juliette; Budin, Francois; Gomes, Liliane; Styner, Martin; Lucia, Cevidanes; Nguyen, Tung
2015-03-01
Temporomandibular joint (TMJ) disorders are a group of conditions that cause pain and dysfunction in the jaw joint and the muscles controlling jaw movement. However, diagnosis and treatment of these conditions remain controversial. To date, there is no single sign, symptom, or test that can clearly diagnose early stages of osteoarthritis (OA). Instead, the diagnosis is based on a consideration of several factors, including radiological evaluation. The current radiological diagnosis scores of TMJ pathology are subject to misdiagnosis. We believe these scores are limited by the acquisition procedures, such as oblique cuts of the CT and head positioning errors, and can lead to incorrect diagnoses of flattening of the head of the condyle, formation of osteophytes, or condylar pitting. This study consists of creating and validating a methodological framework to simulate defects in CBCT scans of known location and size, in order to create synthetic TMJ OA database. User-generated defects were created using a non-rigid deformation protocol in CBCT. All segmentation evaluation, surface distances and linear distances from the user-generated to the simulated defects showed our methodological framework to be very precise and within a voxel (0.5 mm) of magnitude. A TMJ OA synthetic database will be created next, and evaluated by expert radiologists, and this will serve to evaluate how sensitive the current radiological diagnosis tools are.
Fast pixel-wise adaptive visual tracking of non-rigid objects.
Duffner, Stefan; Garcia, Christophe
2017-03-01
In this paper, we present a new algorithm for realtime single-object tracking in videos in unconstrained environments. The algorithm comprises two different components that are trained "in one shot" at the first video frame: a detector that makes use of the generalised Hough transform with colour and gradient descriptors, and a probabilistic segmentation method based on global models for foreground and background colour distributions. Both components work at pixel level and are used for tracking in a combined way adapting each other in a cotraining manner. Moreover, we propose an adaptive shape model as well as a new probabilistic method for updating the scale of the tracker. Through effective model adaptation and segmentation, the algorithm is able to track objects that undergo rigid and non-rigid deformations and considerable shape and appearance variations. The proposed tracking method has been thoroughly evaluated on challenging benchmarks, and outperforms state-ofthe- art tracking methods designed for the same task. Finally, a very efficient implementation of the proposed models allows for extremely fast tracking.
DEFF Research Database (Denmark)
Kjer, Hans Martin; Fagertun, Jens; Vera, Sergio
2016-01-01
Better understanding of the anatomical variability of the human cochlear is important for the design and function of Cochlear Implants. Proper non-rigid alignment of high-resolution cochlear μCT data is a challenge for the typical cubic B-spline registration model. In this paper we study one way...... of incorporating skeleton-based similarity as an anatomical registration prior. We extract a centerline skeleton of the cochlear spiral, and generate corresponding parametric pseudo-landmarks between samples. These correspondences are included in the cost function of a typical cubic B-spline registration model...
Image-based motion estimation for cardiac CT via image registration
Cammin, J.; Taguchi, K.
2010-03-01
Images reconstructed from tomographic projection data are subject to motion artifacts from organs that move during the duration of the scan. The effect can be reduced by taking the motion into account in the reconstruction algorithm if an estimate of the deformation exists. This paper presents the estimation of the three-dimensional cardiac motion by registering reconstructed images from cardiac quiet phases as a first step towards motion-compensated cardiac image reconstruction. The non-rigid deformations of the heart are parametrized on a coarse grid on the image volume and are interpolated with cubic b-splines. The optimization problem of finding b-spline coefficients that best describe the observed deformations is ill-posed due to the large number of parameters and the resulting motion vector field is sensitive to the choice of initial parameters. Particularly challenging is the task to capture the twisting motion of the heart. The motion vector field from a dynamic computer phantom of the human heart is used to initialize the transformation parameters for the optimization process with realistic starting values. The results are evaluated by comparing the registered images and the obtained motion vector field to the case when the registration is performed without using prior knowledge about the expected cardiac motion. We find that the registered images are similar for both approaches, but the motion vector field obtained from motion estimation initialized with the phantom describes the cardiac contraction and twisting motion more accurately.
Directory of Open Access Journals (Sweden)
Rexilius Jan
2005-03-01
Full Text Available Abstract Background The visual combination of different modalities is essential for many medical imaging applications in the field of Computer-Assisted medical Diagnosis (CAD to enhance the clinical information content. Clinically, incontinence is a diagnosis with high clinical prevalence and morbidity rate. The search for a method to identify risk patients and to control the success of operations is still a challenging task. The conjunction of magnetic resonance (MR and 3D ultrasound (US image data sets could lead to a new clinical visual representation of the morphology as we show with corresponding data sets of the female anal canal with this paper. Methods We present a feasibility study for a non-rigid registration technique based on a biomechanical model for MR and US image data sets of the female anal canal as a base for a new innovative clinical visual representation. Results It is shown in this case study that the internal and external sphincter region could be registered elastically and the registration partially corrects the compression induced by the ultrasound transducer, so the MR data set showing the native anatomy is used as a frame for the US data set showing the same region with higher resolution but distorted by the transducer Conclusion The morphology is of special interest in the assessment of anal incontinence and the non-rigid registration of normal clinical MR and US image data sets is a new field of the adaptation of this method incorporating the advantages of both technologies.
Registration of 3D point clouds and meshes: a survey from rigid to nonrigid.
Tam, Gary K L; Cheng, Zhi-Quan; Lai, Yu-Kun; Langbein, Frank C; Liu, Yonghuai; Marshall, David; Martin, Ralph R; Sun, Xian-Fang; Rosin, Paul L
2013-07-01
Three-dimensional surface registration transforms multiple three-dimensional data sets into the same coordinate system so as to align overlapping components of these sets. Recent surveys have covered different aspects of either rigid or nonrigid registration, but seldom discuss them as a whole. Our study serves two purposes: 1) To give a comprehensive survey of both types of registration, focusing on three-dimensional point clouds and meshes and 2) to provide a better understanding of registration from the perspective of data fitting. Registration is closely related to data fitting in which it comprises three core interwoven components: model selection, correspondences and constraints, and optimization. Study of these components 1) provides a basis for comparison of the novelties of different techniques, 2) reveals the similarity of rigid and nonrigid registration in terms of problem representations, and 3) shows how overfitting arises in nonrigid registration and the reasons for increasing interest in intrinsic techniques. We further summarize some practical issues of registration which include initializations and evaluations, and discuss some of our own observations, insights and foreseeable research trends.
Q-Conjugacy character table for the non-rigid group of 2,3-dimethylbutane
Directory of Open Access Journals (Sweden)
MOHAMMAD REZA DARAFSHEH
2009-01-01
Full Text Available Maturated and unmaturated groups were introduced by the Japanese chemist Shinsaku Fujita, who used them in the markaracter table and the Q-conjugacy character table of a finite group. He then applied his results in this area of research to enumerate isomers of molecules. Using the non-rigid group theory, it was shown by the second author that the full non-rigid (f-NRG group of 2,3--dimethylbutane is isomorphic to the group (Z3×Z3×Z3×Z3:Z2 of order 162 with 54 conjugacy classes. Here (Z3×Z3×Z3×Z3:Z2 denotes the semi direct product of four copies of Z3 by Z2, where Zn is a cyclic group of order n. In this paper, it is shown with the GAP program that this group has 30 dominant classes (similarly, Q-conjugacy characters and that 24 of them are unmatured (similarly, Q-conjugacy characters such that they are the sum of two irreducible characters. Then, the Q-conjugacy character table of the unmatured full non-rigid group 2,3-dimethylbutane is derived.
Robust non-rigid point set registration using student's-t mixture model.
Directory of Open Access Journals (Sweden)
Zhiyong Zhou
Full Text Available The Student's-t mixture model, which is heavily tailed and more robust than the Gaussian mixture model, has recently received great attention on image processing. In this paper, we propose a robust non-rigid point set registration algorithm using the Student's-t mixture model. Specifically, first, we consider the alignment of two point sets as a probability density estimation problem and treat one point set as Student's-t mixture model centroids. Then, we fit the Student's-t mixture model centroids to the other point set which is treated as data. Finally, we get the closed-form solutions of registration parameters, leading to a computationally efficient registration algorithm. The proposed algorithm is especially effective for addressing the non-rigid point set registration problem when significant amounts of noise and outliers are present. Moreover, less registration parameters have to be set manually for our algorithm compared to the popular coherent points drift (CPD algorithm. We have compared our algorithm with other state-of-the-art registration algorithms on both 2D and 3D data with noise and outliers, where our non-rigid registration algorithm showed accurate results and outperformed the other algorithms.
Pursley, Jennifer; Risholm, Petter; Fedorov, Andriy; Tuncali, Kemal; Fennessy, Fiona M.; Wells, William M.; Tempany, Clare M.; Cormack, Robert A.
2012-01-01
Purpose: This study introduces a probabilistic nonrigid registration method for use in image-guided prostate brachytherapy. Intraoperative imaging for prostate procedures, usually transrectal ultrasound (TRUS), is typically inferior to diagnostic-quality imaging of the pelvis such as endorectal magnetic resonance imaging (MRI). MR images contain superior detail of the prostate boundaries and provide substructure features not otherwise visible. Previous efforts to register diagnostic prostate images with the intraoperative coordinate system have been deterministic and did not offer a measure of the registration uncertainty. The authors developed a Bayesian registration method to estimate the posterior distribution on deformations and provide a case-specific measure of the associated registration uncertainty. Methods: The authors adapted a biomechanical-based probabilistic nonrigid method to register diagnostic to intraoperative images by aligning a physician's segmentations of the prostate in the two images. The posterior distribution was characterized with a Markov Chain Monte Carlo method; the maximum a posteriori deformation and the associated uncertainty were estimated from the collection of deformation samples drawn from the posterior distribution. The authors validated the registration method using a dataset created from ten patients with MRI-guided prostate biopsies who had both diagnostic and intraprocedural 3 Tesla MRI scans. The accuracy and precision of the estimated posterior distribution on deformations were evaluated from two predictive distance distributions: between the deformed central zone-peripheral zone (CZ-PZ) interface and the physician-labeled interface, and based on physician-defined landmarks. Geometric margins on the registration of the prostate's peripheral zone were determined from the posterior predictive distance to the CZ-PZ interface separately for the base, mid-gland, and apical regions of the prostate. Results: The authors observed
Chappelow, Jonathan; Viswanath, Satish; Monaco, James; Rosen, Mark; Tomaszewski, John; Feldman, Michael; Madabhushi, Anant
2008-03-01
Computer-aided diagnosis (CAD) systems for the detection of cancer in medical images require precise labeling of training data. For magnetic resonance (MR) imaging (MRI) of the prostate, training labels define the spatial extent of prostate cancer (CaP); the most common source for these labels is expert segmentations. When ancillary data such as whole mount histology (WMH) sections, which provide the gold standard for cancer ground truth, are available, the manual labeling of CaP can be improved by referencing WMH. However, manual segmentation is error prone, time consuming and not reproducible. Therefore, we present the use of multimodal image registration to automatically and accurately transcribe CaP from histology onto MRI following alignment of the two modalities, in order to improve the quality of training data and hence classifier performance. We quantitatively demonstrate the superiority of this registration-based methodology by comparing its results to the manual CaP annotation of expert radiologists. Five supervised CAD classifiers were trained using the labels for CaP extent on MRI obtained by the expert and 4 different registration techniques. Two of the registration methods were affi;ne schemes; one based on maximization of mutual information (MI) and the other method that we previously developed, Combined Feature Ensemble Mutual Information (COFEMI), which incorporates high-order statistical features for robust multimodal registration. Two non-rigid schemes were obtained by succeeding the two affine registration methods with an elastic deformation step using thin-plate splines (TPS). In the absence of definitive ground truth for CaP extent on MRI, classifier accuracy was evaluated against 7 ground truth surrogates obtained by different combinations of the expert and registration segmentations. For 26 multimodal MRI-WMH image pairs, all four registration methods produced a higher area under the receiver operating characteristic curve compared to that
Registration Based Retrieval using Texture Measures
Directory of Open Access Journals (Sweden)
Swarnambiga AYYACHAMY
2015-09-01
Full Text Available The aim of the study presented in this manuscript was to develop and analyze registration based retrieval of medical image using texture measures. Three main methods are implemented in this work. The first method includes Affine transformation, Demons and Affine with B-spline. The second method implemented is medical image retrieval system using content based medical image retrieval. GLCM, LBP and GLCM with LBP are used for texture based retrieval. Shape based retrieval is processed using canny edge with the Otsu method. From registration based retrieval, Affine with B-Spline performs well and produces best result by increasing the retrieval rate and the next better performances are given by Demons and Affine registration. The results showed that the best results for registration based retrieval are given by Affine with B-Spline registration based retrieval using GLCM+LBP with (100/50. Based on more relevant retrieved images, Brain (100/50 and Knee (100/50 observed to have more relevant retrieved images.
Berkels, Benjamin; Deserno, Thomas; Ehrlich, Eva E.; Fritz, Ulrike B.; Sirazitdinova, Ekaterina; Tatano, Rosalia
2016-03-01
Quantitative light-induced fluorescence (QLF) is widely used to assess the damage of a tooth due to decalcification. In digital photographs, decalcification appears as white spot lesions, i.e. white spots on the tooth surface. We propose a novel multimodal registration approach for the matching of digital photographs and QLF images of decalcified teeth. The registration is based on the idea of contour-to-pixel matching. Here, the curve, which represents the shape of the tooth, is extracted from the QLF image using a contour segmentation by binarization and morphological processing. This curve is aligned to the photo with a non-rigid variational registration approach. Thus, the registration problem is formulated as minimization problem with an objective function that consists of a data term and a regularizer for the deformation. To construct the data term, the photo is pointwise classified into tooth and non-tooth regions. Then, the signed distance function of the tooth region allows to measure the mismatch between curve and photo. As regularizer a higher order, linear elastic prior is used. The resulting minimization problem is solved numerically using bilinear Finite Elements for the spatial discretization and the Gauss-Newton algorithm. The evaluation is based on 150 image pairs, where an average of 5 teeth have been captured from 32 subjects. All registrations have been confirmed correctly by a dental expert. The contour-to-pixel methods can directly be used in 3D for surface-to-voxel tasks.
3D prostate MR-TRUS non-rigid registration using dual optimization with volume-preserving constraint
Qiu, Wu; Yuan, Jing; Fenster, Aaron
2016-03-01
We introduce an efficient and novel convex optimization-based approach to the challenging non-rigid registration of 3D prostate magnetic resonance (MR) and transrectal ultrasound (TRUS) images, which incorporates a new volume preserving constraint to essentially improve the accuracy of targeting suspicious regions during the 3D TRUS guided prostate biopsy. Especially, we propose a fast sequential convex optimization scheme to efficiently minimize the employed highly nonlinear image fidelity function using the robust multi-channel modality independent neighborhood descriptor (MIND) across the two modalities of MR and TRUS. The registration accuracy was evaluated using 10 patient images by calculating the target registration error (TRE) using manually identified corresponding intrinsic fiducials in the whole prostate gland. We also compared the MR and TRUS manually segmented prostate surfaces in the registered images in terms of the Dice similarity coefficient (DSC), mean absolute surface distance (MAD), and maximum absolute surface distance (MAXD). Experimental results showed that the proposed method with the introduced volume-preserving prior significantly improves the registration accuracy comparing to the method without the volume-preserving constraint, by yielding an overall mean TRE of 2:0+/-0:7 mm, and an average DSC of 86:5+/-3:5%, MAD of 1:4+/-0:6 mm and MAXD of 6:5+/-3:5 mm.
Institute of Scientific and Technical Information of China (English)
李丽; 孙军; 王军
2009-01-01
讨论了旧的数控编程接口标准ISO6983的缺点,研究了基于新数控编程接口标准STEP-NC的数控系统中的NURBS曲面插补技术.介绍了STEP-NC标准中关于NURBS曲面的描述,详细讨论了NURBS插补原理,插补预处理,NURBS曲面加工路径规划和实时插补轨迹生成算法,并给出了实例和仿真结果.NURBS曲面插补技术的研究为进一步研究STEP-NC数控系统奠定基础.
Institute of Scientific and Technical Information of China (English)
杜慧茜; 郭林楠; 梅文博; 任彦芳
2008-01-01
各向异性扩散偏微分方程(PDE)的图像平滑方法能够在去噪的同时在一定程度上保持图像的边缘特征,但对图像细节的保持仍不理想.提出采用归一化的3次B样条作为扩散函数,给出了新的PDE模型算法,该算法能在除噪声的同时增强图像边缘细节,并可降低迭代次数,对加性和乘性噪声均有效.
Institute of Scientific and Technical Information of China (English)
刘洪臣; 冯勇; 杨旭强
2007-01-01
亚像元动态成像技术是实现遥感器高分辨、小型化的有效方法.将双三次B样条曲面插值方法应用于亚像元动态成像,利用待插值点周围邻域范围内16个像素点做一张B样条曲面,取曲面中点的值作为待插值点的像素值.文中推导了双三次B样条曲面插值亚像元图像的插值算式,对所提方法进行了计算机仿真研究,并与其他几种常用插值方法进行了性能比较,结果表明,本文算法得到的高分辨率图像效果更佳.
Institute of Scientific and Technical Information of China (English)
胡志刚
2000-01-01
运用三次均匀B样条曲线插值法分段构造凸轮曲线,给出任意插值点的三次均匀B样条闭曲线的B特征多边形顶点的反算公式,并导出由三次均匀B样条闭曲线构成的对心直动从动件盘形凸轮轮廓曲线上任一点处的压力角计算公式.
基于周期性延伸的三次B样条闭曲线插值%Interpolation of Cubic B-spline Closed Curve Based on Periodic Extension
Institute of Scientific and Technical Information of China (English)
李学艺; 王钊; 连小珉; 曾庆良
2009-01-01
针对闭曲线具有可周期性延伸的特点,提出了一种基于求解双列带阵线性方程组的三次B样条完全闭曲线插算法.通过节点向量和控制点在曲线闭合点两端的周期性延伸,使插值曲线在闭合点实现了理论上的完全封闭.针对曲线插值线性方程组中系数矩阵具有不完全带阵的特点,提出了一种双列带阵线性方程组求解算法.应用实例表明,算法性能稳定、效率高、可插值任意形状的复杂闭曲线,适于处理大数据量闭曲线插值运算.
The Real-time Interpolation of Cubic B-spline Curves Based on TMS320F2812%基于TMS320F2812的三次B样条曲线实时插补
Institute of Scientific and Technical Information of China (English)
李广涛; 薛重德; 侯小强
2008-01-01
为提高数控系统实时插补的准确性、加工速度和加工精度,采用在每个插补周期中保持进给速度不变的三次B样条曲线参变量非均匀变化实时插补算法.利用数字信号处理器(DSP)进行三次B样条曲线实时插补,可缩短插补计算时间;通过设定DSP的定时器中断来实现各轴控制脉冲的发送,可实现最大限度地减少折线状的插补轨迹的目的.结果表明,该算法能使所有的插补点都在理论曲线上,可以保证运动控制系统的高速高精度要求.
基于三次B样条插值的形状错误隐藏算法%Spatial shape error concealment method based on cubic B-spline interpolation
Institute of Scientific and Technical Information of China (English)
符祥; 郭宝龙; 杨占龙
2008-01-01
分析了基于Bézier插值的视频对象形状错误隐藏方法的不足,即计算附加控制点的过程复杂,隐藏结果受附加控制点影响大.针对这一问题,提出了一种基于三次B样条插值的错误隐藏算法.对三次B样条插值的矩阵公式进行了改进,保证目标轮廓的平滑性;直接对已知轮廓点插值,克服了传统方法的不足.与传统方法对比实验表明,新算法简单易实现,有较好的实用意义.
Terrain Reconstruction Algorithm Based on Bi-cubic B-spline Interpolation%基于双三次B-样条插值的大地形重构
Institute of Scientific and Technical Information of China (English)
张立民; 邹容平; 李一平; 陈敏
2007-01-01
提出一种基于双三次B-样条的DEM地形数据重构算法.根据用户对不同地形区域关注程度的不同而采用不同的地形分辨率,可有效地降低计算机负荷.采用该算法可以有效地对关注度较高的区域进行地形重构,提高该区域的地形分辨率.实践结果表明,该算法满足大地形视景仿真系统的需要.
Validation of a nonrigid registration framework that accommodates tissue resection
Risholm, Petter; Samset, Eigil; Wells, William, III
2010-03-01
We present a 3D extension and validation of an intra-operative registration framework that accommodates tissue resection. The framework is based on the bijective Demons method, but instead of regularizing with the traditional Gaussian smoother, we apply an anisotropic diffusion filter with the resection modeled as a diffusion sink. The diffusion sink prevents unwanted Demon forces that originates from the resected area from diffusing into the surrounding area. Another attractive property of the diffusion sink is the resulting continuous deformation field across the diffusion sink boundary, which allows us to move the boundary of the diffusion sink without changing values in the deformation field. The area of resection is estimated by a level-set method evolving in the space of image intensity disagreements in the intra-operative image domain. A product of using the bijective Demons method is that we can also provide an accurate estimate of the resected tissue in the preoperative image space. Validation of the proposed method was performed on a set of 25 synthetic images. Our experiments show a significant improvement in accommodating resection using the proposed method compared to two other Demons based methods.
Understanding geological processes: Visualization of rigid and non-rigid transformations
Shipley, T. F.; Atit, K.; Manduca, C. A.; Ormand, C. J.; Resnick, I.; Tikoff, B.
2012-12-01
Visualizations are used in the geological sciences to support reasoning about structures and events. Research in cognitive sciences offers insights into the range of skills of different users, and ultimately how visualizations might support different users. To understand the range of skills needed to reason about earth processes we have developed a program of research that is grounded in the geosciences' careful description of the spatial and spatiotemporal patterns associated with earth processes. In particular, we are pursuing a research program that identifies specific spatial skills and investigates whether and how they are related to each other. For this study, we focus on a specific question: Is there an important distinction in the geosciences between rigid and non-rigid deformation? To study a general spatial thinking skill we employed displays with non-geological objects that had been altered by rigid change (rotation), and two types of non-rigid change ("brittle" (or discontinuous) and "ductile" (or continuous) deformation). Disciplinary scientists (geosciences and chemistry faculty), and novices (non-science faculty and undergraduate psychology students) answered questions that required them to visualize the appearance of the object before the change. In one study, geologists and chemists were found to be superior to non-science faculty in reasoning about rigid rotations (e.g., what an object would look like from a different perspective). Geologists were superior to chemists in reasoning about brittle deformations (e.g., what an object looked like before it was broken - here the object was a word cut into many fragments displaced in different directions). This finding is consistent with two hypotheses: 1) Experts are good at visualizing the types of changes required for their domain; and 2) Visualization of rigid and non-rigid changes are not the same skill. An additional important finding is that there was a broad range of skill in both rigid and non-rigid
Changala, P Bryan
2016-01-01
We present a perturbative method for ab initio calculations of rotational and rovibrational effective Hamiltonians of both rigid and non-rigid molecules. Our approach is based on a curvilinear implementation of second order vibrational M{\\o}ller-Plesset perturbation theory (VMP2) extended to include rotational effects via a second order contact transformation. Though more expensive, this approach is significantly more accurate than standard second order vibrational perturbation theory (VPT2) for systems that are poorly described to zeroth order by rectilinear normal mode harmonic oscillators. We apply this method and demonstrate its accuracy on two molecules: Si$_2$C, a quasilinear triatomic with significant bending anharmonicity, and CH$_3$NO$_2$, which contains a completely unhindered methyl rotor. In addition to these two examples, we discuss several key technical aspects of the method, including an efficient implementation of Eckart and quasi-Eckart frame embedding that does not rely on numerical finite d...
Based on the Wavelet Function of Power Network Fault Location
Directory of Open Access Journals (Sweden)
Fan YU
2013-04-01
Full Text Available In order to improve the measurement accuracy, in the traditional measuring method based on, by avoiding wave speed influence on fault location of transmission line method, and compares it with the combination of wavelet transform. This article selects dBN wavelet and three B spline wavelet contrast, compared them with new methods, through the Xi'an City Power Supply Bureau of the actual fault data validation. The results show that, with3 B spline wavelet and the new method combined with the location results are closer to the actual distance, its accuracy is higher than that of db3wavelet transform and a new method derived from the results, the error is far less than the db3 wavelet function, location is satisfactory.
3D Visual Data-Driven Spatiotemporal Deformations for Non-Rigid Object Grasping Using Robot Hands.
Mateo, Carlos M; Gil, Pablo; Torres, Fernando
2016-05-05
Sensing techniques are important for solving problems of uncertainty inherent to intelligent grasping tasks. The main goal here is to present a visual sensing system based on range imaging technology for robot manipulation of non-rigid objects. Our proposal provides a suitable visual perception system of complex grasping tasks to support a robot controller when other sensor systems, such as tactile and force, are not able to obtain useful data relevant to the grasping manipulation task. In particular, a new visual approach based on RGBD data was implemented to help a robot controller carry out intelligent manipulation tasks with flexible objects. The proposed method supervises the interaction between the grasped object and the robot hand in order to avoid poor contact between the fingertips and an object when there is neither force nor pressure data. This new approach is also used to measure changes to the shape of an object's surfaces and so allows us to find deformations caused by inappropriate pressure being applied by the hand's fingers. Test was carried out for grasping tasks involving several flexible household objects with a multi-fingered robot hand working in real time. Our approach generates pulses from the deformation detection method and sends an event message to the robot controller when surface deformation is detected. In comparison with other methods, the obtained results reveal that our visual pipeline does not use deformations models of objects and materials, as well as the approach works well both planar and 3D household objects in real time. In addition, our method does not depend on the pose of the robot hand because the location of the reference system is computed from a recognition process of a pattern located place at the robot forearm. The presented experiments demonstrate that the proposed method accomplishes a good monitoring of grasping task with several objects and different grasping configurations in indoor environments.
3D Visual Data-Driven Spatiotemporal Deformations for Non-Rigid Object Grasping Using Robot Hands
Mateo, Carlos M.; Gil, Pablo; Torres, Fernando
2016-01-01
Sensing techniques are important for solving problems of uncertainty inherent to intelligent grasping tasks. The main goal here is to present a visual sensing system based on range imaging technology for robot manipulation of non-rigid objects. Our proposal provides a suitable visual perception system of complex grasping tasks to support a robot controller when other sensor systems, such as tactile and force, are not able to obtain useful data relevant to the grasping manipulation task. In particular, a new visual approach based on RGBD data was implemented to help a robot controller carry out intelligent manipulation tasks with flexible objects. The proposed method supervises the interaction between the grasped object and the robot hand in order to avoid poor contact between the fingertips and an object when there is neither force nor pressure data. This new approach is also used to measure changes to the shape of an object’s surfaces and so allows us to find deformations caused by inappropriate pressure being applied by the hand’s fingers. Test was carried out for grasping tasks involving several flexible household objects with a multi-fingered robot hand working in real time. Our approach generates pulses from the deformation detection method and sends an event message to the robot controller when surface deformation is detected. In comparison with other methods, the obtained results reveal that our visual pipeline does not use deformations models of objects and materials, as well as the approach works well both planar and 3D household objects in real time. In addition, our method does not depend on the pose of the robot hand because the location of the reference system is computed from a recognition process of a pattern located place at the robot forearm. The presented experiments demonstrate that the proposed method accomplishes a good monitoring of grasping task with several objects and different grasping configurations in indoor environments. PMID
Vásquez Osorio, Eliana M; Hoogeman, Mischa S; Bondar, Luiza; Levendag, Peter C; Heijmen, Ben J M
2009-07-01
Technical improvements in planning and dose delivery and in verification of patient positioning have substantially widened the therapeutic window for radiation treatment of cancer. However, changes in patient anatomy during the treatment limit the exploitation of these new techniques. To further improve radiation treatments, anatomical changes need to be modeled and accounted for Nonrigid registration can be used for this purpose. This article describes the design, the implementation, and the validation of a new framework for nonrigid registration for radiotherapy applications. The core of this framework is an improved version of the thin plate spline robust point matching (TPS-RPM) algorithm. The TPS-RPM algorithm estimates a global correspondence and a transformation between the points that represent organs of interest belonging to two image sets. However, the algorithm does not allow for the inclusion of prior knowledge on the correspondence of subset of points, and therefore, it can lead to inconsistent anatomical solutions. In this article TPS-RPM was improved by employing a novel correspondence filter that supports simultaneous registration of multiple structures. The improved method allows for coherent organ registration and for the inclusion of user-defined landmarks, lines, and surfaces inside and outside of structures of interest. A procedure to generate control points from segmented organs is described. The framework parameters r and lambda, which control the number of points and the nonrigidness of the transformation, respectively, were optimized for three sites with different degrees of deformation (head and neck, prostate, and cervix) using two cases per site. For the head and neck cases, the salivary glands were manually contoured on CT scans, for the prostate cases the prostate and the vesicles, and for the cervix cases the cervix uterus, the bladder, and the rectum. The transformation error obtained using the best set of parameters was below 1 mm
Energy Technology Data Exchange (ETDEWEB)
Vasquez Osorio, Eliana M.; Hoogeman, Mischa S.; Bondar, Luiza; Levendag, Peter C.; Heijmen, Ben J. M. [Department of Radiation Oncology, Daniel den Hoed Cancer Center, Erasmus Medical Center, Rotterdam 3075 (Netherlands)
2009-07-15
Technical improvements in planning and dose delivery and in verification of patient positioning have substantially widened the therapeutic window for radiation treatment of cancer. However, changes in patient anatomy during the treatment limit the exploitation of these new techniques. To further improve radiation treatments, anatomical changes need to be modeled and accounted for. Nonrigid registration can be used for this purpose. This article describes the design, the implementation, and the validation of a new framework for nonrigid registration for radiotherapy applications. The core of this framework is an improved version of the thin plate spline robust point matching (TPS-RPM) algorithm. The TPS-RPM algorithm estimates a global correspondence and a transformation between the points that represent organs of interest belonging to two image sets. However, the algorithm does not allow for the inclusion of prior knowledge on the correspondence of subset of points, and therefore, it can lead to inconsistent anatomical solutions. In this article TPS-RPM was improved by employing a novel correspondence filter that supports simultaneous registration of multiple structures. The improved method allows for coherent organ registration and for the inclusion of user-defined landmarks, lines, and surfaces inside and outside of structures of interest. A procedure to generate control points from segmented organs is described. The framework parameters r and {lambda}, which control the number of points and the nonrigidness of the transformation, respectively, were optimized for three sites with different degrees of deformation (head and neck, prostate, and cervix) using two cases per site. For the head and neck cases, the salivary glands were manually contoured on CT scans, for the prostate cases the prostate and the vesicles, and for the cervix cases the cervix uterus, the bladder, and the rectum. The transformation error obtained using the best set of parameters was below 1
A batch Algorithm for Implicit Non-Rigid Shape and Motion Recovery
DEFF Research Database (Denmark)
Bartoli, Adrien; Olsen, Søren Ingvor
2005-01-01
manner. There are several issues that have not been addressed yet, among which, choosing the rank automatically and dealing with erroneous point tracks and missing data. We introduce theoretical and practical contributions that address these issues. We propose an implicit imaging model for non......The recovery of 3D shape and camera motion for non-rigid scenes from single-camera video footage is a very important problem in computer vision. The low-rank shape model consists in regarding the deformations as linear combinations of basis shapes. Most algorithms for reconstructing the parameters...... of the subsequence, using a robust estimator incorporating a model selection criterion that detects erroneous image points. Preliminary experimental results on real and simulated data show that our algorithm deals with challenging video sequences....
Non-rigid image registration under non-deterministic deformation bounds
Ge, Qian; Lokare, Namita; Lobaton, Edgar
2015-01-01
Image registration aims to identify the mapping between corresponding locations in an anatomic structure. Most traditional approaches solve this problem by minimizing some error metric. However, they do not quantify the uncertainty behind their estimates and the feasibility of other solutions. In this work, it is assumed that two images of the same anatomic structure are related via a Lipschitz non-rigid deformation (the registration map). An approach for identifying point correspondences with zero false-negative rate and high precision is introduced under this assumption. This methodology is then extended to registration of regions in an image which is posed as a graph matching problem with geometric constraints. The outcome of this approach is a homeomorphism with uncertainty bounds characterizing its accuracy over the entire image domain. The method is tested by applying deformation maps to the LPBA40 dataset.
Energy Technology Data Exchange (ETDEWEB)
Chen, H; Zhen, X; Zhou, L [Southern Medical University, Guangzhou, Guangdong (China); Zhong, Z [The University of Texas at Dallas, Department of Computer Science, TX (United States); Pompos, A; Yan, H; Jiang, S; Gu, X [UT Southwestern Medical Center, Dallas, TX (United States)
2014-06-15
Purpose: To propose and validate a deformable point matching scheme for surface deformation to facilitate accurate bladder dose summation for fractionated HDR cervical cancer treatment. Method: A deformable point matching scheme based on the thin plate spline robust point matching (TPSRPM) algorithm is proposed for bladder surface registration. The surface of bladders segmented from fractional CT images is extracted and discretized with triangular surface mesh. Deformation between the two bladder surfaces are obtained by matching the two meshes' vertices via the TPS-RPM algorithm, and the deformation vector fields (DVFs) characteristic of this deformation is estimated by B-spline approximation. Numerically, the algorithm is quantitatively compared with the Demons algorithm using five clinical cervical cancer cases by several metrics: vertex-to-vertex distance (VVD), Hausdorff distance (HD), percent error (PE), and conformity index (CI). Experimentally, the algorithm is validated on a balloon phantom with 12 surface fiducial markers. The balloon is inflated with different amount of water, and the displacement of fiducial markers is benchmarked as ground truth to study TPS-RPM calculated DVFs' accuracy. Results: In numerical evaluation, the mean VVD is 3.7(±2.0) mm after Demons, and 1.3(±0.9) mm after TPS-RPM. The mean HD is 14.4 mm after Demons, and 5.3mm after TPS-RPM. The mean PE is 101.7% after Demons and decreases to 18.7% after TPS-RPM. The mean CI is 0.63 after Demons, and increases to 0.90 after TPS-RPM. In the phantom study, the mean Euclidean distance of the fiducials is 7.4±3.0mm and 4.2±1.8mm after Demons and TPS-RPM, respectively. Conclusions: The bladder wall deformation is more accurate using the feature-based TPS-RPM algorithm than the intensity-based Demons algorithm, indicating that TPS-RPM has the potential for accurate bladder dose deformation and dose summation for multi-fractional cervical HDR brachytherapy. This work is supported
Maguinness, Corrina; Newell, Fiona N
2015-04-01
There is growing evidence to suggest that facial motion is an important cue for face recognition. However, it is poorly understood whether motion is integrated with facial form information or whether it provides an independent cue to identity. To provide further insight into this issue, we compared the effect of motion on face perception in two developmental prosopagnosics and age-matched controls. Participants first learned faces presented dynamically (video), or in a sequence of static images, in which rigid (viewpoint) or non-rigid (expression) changes occurred. Immediately following learning, participants were required to match a static face image to the learned face. Test face images varied by viewpoint (Experiment 1) or expression (Experiment 2) and were learned or novel face images. We found similar performance across prosopagnosics and controls in matching facial identity across changes in viewpoint when the learned face was shown moving in a rigid manner. However, non-rigid motion interfered with face matching across changes in expression in both individuals with prosopagnosia compared to the performance of control participants. In contrast, non-rigid motion did not differentially affect the matching of facial expressions across changes in identity for either prosopagnosics (Experiment 3). Our results suggest that whilst the processing of rigid motion information of a face may be preserved in developmental prosopagnosia, non-rigid motion can specifically interfere with the representation of structural face information. Taken together, these results suggest that both form and motion cues are important in face perception and that these cues are likely integrated in the representation of facial identity.
Giyasov Botir Iminzhonovich; Kupriyanov Roman Valer’evich; Andrianov Konstantin Anatol’evich; Zubkov Anatoliy Fedorovich
2015-01-01
The construction quality of road surface of non-rigid type essentially depend on providing the temperature regimes in the process of laying and packing of hot asphalt concrete mixtures. In order to provide the required characteristics of asphalt concrete due to the surface width it is necessary to provide the temperature regimes of hot asphalt concrete mixture in the zones of lane connection. The hot mixture is promptly cooling right after laying within several minutes, which results, accordi...
Analysis and application of B-spline wavelet on interval hybrid stress element%区间B样条小波杂交应力元分析及其应用
Institute of Scientific and Technical Information of China (English)
刘艳红; 商中新
2013-01-01
Wavelet function is introduced into hybrid stress element. The scaling functions of BSWI are used to construct the rectangular and cubic wavelet element as interpolation function. The results obtained in this paper are compared with those by Abaqus. The numerical examples illustrate that the wavelet-based element method has higher accuracy and higher accuracy, while it's less sensitive to the density of elements.%将小波函数引入到杂交应力元中,以其尺度函数作为插值函数,构造了二维四节点和三维八节点的B样条小波杂交应力元.将数值算例结果与理论解和Abaqus软件计算结果相对比,本文所构造的新型单元具有计算精度高、对单元划分密度不敏感、收敛速度快的优点.
Evolutionary algorithm based offline/online path planner for UAV navigation.
Nikolos, I K; Valavanis, K P; Tsourveloudis, N C; Kostaras, A N
2003-01-01
An evolutionary algorithm based framework, a combination of modified breeder genetic algorithms incorporating characteristics of classic genetic algorithms, is utilized to design an offline/online path planner for unmanned aerial vehicles (UAVs) autonomous navigation. The path planner calculates a curved path line with desired characteristics in a three-dimensional (3-D) rough terrain environment, represented using B-spline curves, with the coordinates of its control points being the evolutionary algorithm artificial chromosome genes. Given a 3-D rough environment and assuming flight envelope restrictions, two problems are solved: i) UAV navigation using an offline planner in a known environment, and, ii) UAV navigation using an online planner in a completely unknown environment. The offline planner produces a single B-Spline curve that connects the starting and target points with a predefined initial direction. The online planner, based on the offline one, is given on-board radar readings which gradually produces a smooth 3-D trajectory aiming at reaching a predetermined target in an unknown environment; the produced trajectory consists of smaller B-spline curves smoothly connected with each other. Both planners have been tested under different scenarios, and they have been proven effective in guiding an UAV to its final destination, providing near-optimal curved paths quickly and efficiently.
A 3D MR-acquisition scheme for nonrigid bulk motion correction in simultaneous PET-MR
Energy Technology Data Exchange (ETDEWEB)
Kolbitsch, Christoph, E-mail: christoph.1.kolbitsch@kcl.ac.uk; Prieto, Claudia; Schaeffter, Tobias [Division of Imaging Sciences and Biomedical Engineering, King' s College London, London SE1 7EH (United Kingdom); Tsoumpas, Charalampos [Division of Imaging Sciences and Biomedical Engineering, King' s College London, London SE1 7EH, United Kingdom and Division of Medical Physics, University of Leeds, Leeds LS2 9JT (United Kingdom)
2014-08-15
Purpose: Positron emission tomography (PET) is a highly sensitive medical imaging technique commonly used to detect and assess tumor lesions. Magnetic resonance imaging (MRI) provides high resolution anatomical images with different contrasts and a range of additional information important for cancer diagnosis. Recently, simultaneous PET-MR systems have been released with the promise to provide complementary information from both modalities in a single examination. Due to long scan times, subject nonrigid bulk motion, i.e., changes of the patient's position on the scanner table leading to nonrigid changes of the patient's anatomy, during data acquisition can negatively impair image quality and tracer uptake quantification. A 3D MR-acquisition scheme is proposed to detect and correct for nonrigid bulk motion in simultaneously acquired PET-MR data. Methods: A respiratory navigated three dimensional (3D) MR-acquisition with Radial Phase Encoding (RPE) is used to obtain T1- and T2-weighted data with an isotropic resolution of 1.5 mm. Healthy volunteers are asked to move the abdomen two to three times during data acquisition resulting in overall 19 movements at arbitrary time points. The acquisition scheme is used to retrospectively reconstruct dynamic 3D MR images with different temporal resolutions. Nonrigid bulk motion is detected and corrected in this image data. A simultaneous PET acquisition is simulated and the effect of motion correction is assessed on image quality and standardized uptake values (SUV) for lesions with different diameters. Results: Six respiratory gated 3D data sets with T1- and T2-weighted contrast have been obtained in healthy volunteers. All bulk motion shifts have successfully been detected and motion fields describing the transformation between the different motion states could be obtained with an accuracy of 1.71 ± 0.29 mm. The PET simulation showed errors of up to 67% in measured SUV due to bulk motion which could be reduced to
Evrendilek, F.; Karakaya, N.
2014-06-01
Continuous time-series measurements of diel dissolved oxygen (DO) through online sensors are vital to better understanding and management of metabolism of lake ecosystems, but are prone to noise. Discrete wavelet transforms (DWT) with the orthogonal Symmlet and the semiorthogonal Chui-Wang B-spline were compared in denoising diel, daytime and nighttime dynamics of DO, water temperature, pH, and chlorophyll-a. Predictive efficacies of multiple non-linear regression (MNLR) models of DO dynamics were evaluated with or without DWT denoising of either the response variable alone or all the response and explanatory variables. The combined use of the B-spline-based denoising of all the variables and the temporally partitioned data improved both the predictive power and the errors of the MNLR models better than the use of Symmlet DWT denoising of DO only or all the variables with or without the temporal partitioning.
Institute of Scientific and Technical Information of China (English)
YAO LiNa; WANG Hong
2008-01-01
The task of robust fault detection and diagnosis of stochastic distribution control (SDC) systems with uncertainties is to use the measured input and the system output PDFs to still obtain possible faults information of the system. Using the ra-tional square-root B-spline model to represent the dynamics between the output PDF and the input, in this paper, a robust nonlinear adaptive observer-based fault diagnosis algorithm is presented to diagnose the fault in the dynamic part of such systems with model uncertainties. When certain conditions are satisfied, the weight vector of the rational square-root B-spline model proves to be bounded. Conver-gency analysis is performed for the error dynamic system raised from robust fault detection and fault diagnosis phase. Computer simulations are given to demon-strate the effectiveness of the proposed algorithm.
GPU accelerated non-rigid registration for the evaluation of cardiac function.
Li, Bo; Young, Alistair A; Cowan, Brett R
2008-01-01
We present a method for the fast and efficient tracking of motion in cardiac magnetic resonance (CMR) cines. A GPU accelerated Levenberg-Marquardt non-linear least squares optimization procedure for finite element non-rigid registration was implemented on an NVIDIA graphics card using the OpenGL environment. Points were tracked from frame to frame using forward and backward incremental registration. The inner (endocardial) and outer (epicardial) boarders of the heart were tracked in six short axis cines with approximately 25 frames through the cardiac cycle in 36 patients with vascular disease. Contours placed by two independent expert observers using a semi-automatic ventricular analysis program (CIM version 4.6) were used as the gold standard. The method took 0.5 seconds per frame, and the maximum Hausdorff errors were less than 2 mm on average which was of the same order as the expert inter-observer error. In conclusion, GPU accelerated Levenberg-Marquardt non-linear optimization enables fast and accurate tracking of cardiac motion in CMR images.
Pheiffer, Thomas S.; Ou, Jao J.; Miga, Michael I.
2010-02-01
Modality-independent elastography (MIE) is a method of elastography that reconstructs the elastic properties of tissue using images acquired under different loading conditions and a biomechanical model. Boundary conditions are a critical input to the algorithm, and are often determined by time-consuming point correspondence methods requiring manual user input. Unfortunately, generation of accurate boundary conditions for the biomechanical model is often difficult due to the challenge of accurately matching points between the source and target surfaces and consequently necessitates the use of large numbers of fiducial markers. This study presents a novel method of automatically generating boundary conditions by non-rigidly registering two image sets with a Demons diffusion-based registration algorithm. The use of this method was successfully performed in silico using magnetic resonance and X-ray computed tomography image data with known boundary conditions. These preliminary results have produced boundary conditions with accuracy of up to 80% compared to the known conditions. Finally, these boundary conditions were utilized within a 3D MIE reconstruction to determine an elasticity contrast ratio between tumor and normal tissue. Preliminary results show a reasonable characterization of the material properties on this first attempt and a significant improvement in the automation level and viability of the method.
Vuong, Quoc C; Friedman, Alinda; Read, Jenny C A
2012-03-16
Shape and motion are two dominant cues for object recognition, but it can be difficult to investigate their relative quantitative contribution to the recognition process. In the present study, we combined shape and non-rigid motion morphing to investigate the relative contributions of both types of cues to the discrimination of dynamic objects. In Experiment 1, we validated a novel parameter-based motion morphing technique using a single-part three-dimensional object. We then combined shape morphing with the novel motion morphing technique to pairs of multipart objects to create a joint shape and motion similarity space. In Experiment 2, participants were shown pairs of morphed objects from this space and responded "same" on the basis of motion-only, shape-only, or both cues. Both cue types influenced judgments: When responding to only one cue, the other cue could be ignored, although shape cues were more difficult to ignore. When responding on the basis of both cues, there was an overall bias to weight shape cues more than motion cues. Overall, our results suggest that shape influences discrimination more than motion even when both cue types have been made quantitatively equivalent in terms of their individual discriminability.
Myocardial kinematics based on tagged MRI from volumetric NURBS models
Tustison, Nicholas J.; Amini, Amir A.
2004-04-01
We present current research in which left ventricular deformation is estimated from tagged cardiac magnetic resonance imaging using volumetric deformable models constructed from nonuniform rational B-splines (NURBS). From a set of short and long axis images at end-diastole, the initial NURBS model is constructed by fitting two surfaces with the same parameterization to the set of epicardial and endocardial contours from which a volumetric model is created. Using normal displacements of the three sets of orthogonal tag planes as well as displacements of both tag line and contour/tag line intersection points, one can solve for the optimal homogeneous coordinates, in a least squares sense, of the control points of the NURBS model at a later time point using quadratic programming. After fitting to all time points of data, lofting the NURBS model at each time point creates a comprehensive 4-D NURBS model. From this model, we can extract 3-D myocardial displacement fields and corresponding strain maps, which are local measures of non-rigid deformation.
Non-rigid image registration to reduce beam-induced blurring of cryo-electron microscopy images
Energy Technology Data Exchange (ETDEWEB)
Karimi Nejadasl, Fatemeh; Karuppasamy, Manikandan [Leiden University Medical Center, PO Box 9600, 2300RC Leiden (Netherlands); Newman, Emily R.; McGeehan, John E. [University of Portsmouth, Portsmouth PO1 2DY (United Kingdom); Ravelli, Raimond B. G., E-mail: raimond.nl@gmail.com [Leiden University Medical Center, PO Box 9600, 2300RC Leiden (Netherlands)
2013-01-01
Cryo-electron microscopy images of vitrified large macromolecular complexes can become blurred due to beam-induced specimen alterations. Exposure series are examined, and rigid and non-rigid image registration schemes are applied to reduce such blurring. The typical dose used to record cryo-electron microscopy images from vitrified biological specimens is so high that radiation-induced structural alterations are bound to occur during data acquisition. Integration of all scattered electrons into one image can lead to significant blurring, particularly if the data are collected from an unsupported thin layer of ice suspended over the holes of a support film. Here, the dose has been fractioned and exposure series have been acquired in order to study beam-induced specimen movements under low dose conditions, prior to bubbling. Gold particles were added to the protein sample as fiducial markers. These were automatically localized and tracked throughout the exposure series and showed correlated motions within small patches, with larger amplitudes of motion vectors at the start of a series compared with the end of each series. A non-rigid scheme was used to register all images within each exposure series, using natural neighbor interpolation with the gold particles as anchor points. The procedure increases the contrast and resolution of the examined macromolecules.
Ahmad, Sahar; Khan, Muhammad Faisal
2015-12-01
In this paper, we present a new non-rigid image registration method that imposes a topology preservation constraint on the deformation. We propose to incorporate the time varying elasticity model into the deformable image matching procedure and constrain the Jacobian determinant of the transformation over the entire image domain. The motion of elastic bodies is governed by a hyperbolic partial differential equation, generally termed as elastodynamics wave equation, which we propose to use as a deformation model. We carried out clinical image registration experiments on 3D magnetic resonance brain scans from IBSR database. The results of the proposed registration approach in terms of Kappa index and relative overlap computed over the subcortical structures were compared against the existing topology preserving non-rigid image registration methods and non topology preserving variant of our proposed registration scheme. The Jacobian determinant maps obtained with our proposed registration method were qualitatively and quantitatively analyzed. The results demonstrated that the proposed scheme provides good registration accuracy with smooth transformations, thereby guaranteeing the preservation of topology.
Aitken, D J; Ongeri, S; Vallée-Goyet, D; Gramain, J C; Husson, H P
2001-03-12
A non-rigid cyclopropane-containing diamine analogue of CP-99,994 was synthesised and was found to have only moderate NK1 receptor binding affinity. Molecular dynamics calculations of the conformational space of the former compound gave good correlation between observed activity and a recently published pharmacophore model, lending predictive value to the latter.
Jasinschi, R; Rosenfeld, A; Araújo, H J
1993-01-01
The perception of luminance transparency for superimposed patterns depends on how luminance, figural, and topological conditions are simultaneously satisfied. Motion transparency or coherence for two superimposed patterns, which correspond to the perception of both patterns moving across one another or to the perception of compound motion of the regions of pattern intersection, depends on the relation between the local velocity, luminance, and shape information. This study analyzes how luminance, shape, and local velocity interact in the perception of motion transparency and coherence. Psychophysical experiments done with sinusoidally modulated bar patterns are presented which show that the perception of motion transparency or coherence can be described as the result of the interaction of two integration modules: the velocity-luminance and the velocity-shape processes. The velocity-luminance process describes the integration of the local velocity with luminance information. When the luminance transparency rules are satisfied this process always generates the perception of motion transparency independently of the shape or contour information. On the other hand, when the luminance transparency rules are violated one can either perceive motion coherence or non-rigid motion; one perceives motion coherence when the patterns have small or zero amplitude, and non-rigid motion when the patterns have large amplitude. The velocity-shape process describes the integration of local velocity with shape information, and this depends on the relation between the error in the extraction of the local velocity and the magnitude of the contour amplitude. As a result of these experiments it is conjectured that the velocity-luminance and the velocity-shape processes do interact constructively or destructively. The constructive interaction occurs when the luminance transparency rules are satisfied. The destructive interaction occurs when the luminance transparency rules are violated, and
Constrained reverse diffusion for thick slice interpolation of 3D volumetric MRI images.
Neubert, Aleš; Salvado, Olivier; Acosta, Oscar; Bourgeat, Pierrick; Fripp, Jurgen
2012-03-01
Due to physical limitations inherent in magnetic resonance imaging scanners, three dimensional volumetric scans are often acquired with anisotropic voxel resolution. We investigate several interpolation approaches to reduce the anisotropy and present a novel approach - constrained reverse diffusion for thick slice interpolation. This technique was compared to common methods: linear and cubic B-Spline interpolation and a technique based on non-rigid registration of neighboring slices. The methods were evaluated on artificial MR phantoms and real MR scans of human brain. The constrained reverse diffusion approach delivered promising results and provides an alternative for thick slice interpolation, especially for higher anisotropy factors.
Zuza, Andrew V.; Yin, An
2016-05-01
Collision-induced continental deformation commonly involves complex interactions between strike-slip faulting and off-fault deformation, yet this relationship has rarely been quantified. In northern Tibet, Cenozoic deformation is expressed by the development of the > 1000-km-long east-striking left-slip Kunlun, Qinling, and Haiyuan faults. Each have a maximum slip in the central fault segment exceeding 10s to ~ 100 km but a much smaller slip magnitude (~rigid-body motion and flow-like distributed deformation end-member models for continental tectonics. Here we propose a non-rigid bookshelf-fault model for the Cenozoic tectonic development of northern Tibet. Our model, quantitatively relating discrete left-slip faulting to distributed off-fault deformation during regional clockwise rotation, explains several puzzling features, including the: (1) clockwise rotation of east-striking left-slip faults against the northeast-striking left-slip Altyn Tagh fault along the northwestern margin of the Tibetan Plateau, (2) alternating fault-parallel extension and shortening in the off-fault regions, and (3) eastward-tapering map-view geometries of the Qimen Tagh, Qaidam, and Qilian Shan thrust belts that link with the three major left-slip faults in northern Tibet. We refer to this specific non-rigid bookshelf-fault system as a passive bookshelf-fault system because the rotating bookshelf panels are detached from the rigid bounding domains. As a consequence, the wallrock of the strike-slip faults deforms to accommodate both the clockwise rotation of the left-slip faults and off-fault strain that arises at the fault ends. An important implication of our model is that the style and magnitude of Cenozoic deformation in northern Tibet vary considerably in the east-west direction. Thus, any single north-south cross section and its kinematic reconstruction through the region do not properly quantify the complex deformational processes of plateau formation.
Connolly, C. M.; Konik, A.; Dasari, P. K. R.; Segars, P.; Zheng, S.; Johnson, K. L.; Dey, J.; King, M. A.
2011-03-01
Patient motion can cause artifacts, which can lead to difficulty in interpretation. The purpose of this study is to create 3D digital anthropomorphic phantoms which model the location of the structures of the chest and upper abdomen of human volunteers undergoing a series of clinically relevant motions. The 3D anatomy is modeled using the XCAT phantom and based on MRI studies. The NURBS surfaces of the XCAT are interactively adapted to fit the MRI studies. A detailed XCAT phantom is first developed from an EKG triggered Navigator acquisition composed of sagittal slices with a 3 x 3 x 3 mm voxel dimension. Rigid body motion states are then acquired at breath-hold as sagittal slices partially covering the thorax, centered on the heart, with 9 mm gaps between them. For non-rigid body motion requiring greater sampling, modified Navigator sequences covering the entire thorax with 3 mm gaps between slices are obtained. The structures of the initial XCAT are then adapted to fit these different motion states. Simultaneous to MRI imaging the positions of multiple reflective markers on stretchy bands about the volunteer's chest and abdomen are optically tracked in 3D via stereo imaging. These phantoms with combined position tracking will be used to investigate both imaging-data-driven and motion-tracking strategies to estimate and correct for patient motion. Our initial application will be to cardiacperfusion SPECT imaging where the XCAT phantoms will be used to create patient activity and attenuation distributions for each volunteer with corresponding motion tracking data from the markers on the body-surface. Monte Carlo methods will then be used to simulate SPECT acquisitions, which will be used to evaluate various motion estimation and correction strategies.
Energy Technology Data Exchange (ETDEWEB)
Heijkoop, Sabrina T., E-mail: s.heijkoop@erasmusmc.nl; Langerak, Thomas R.; Quint, Sandra; Bondar, Luiza; Mens, Jan Willem M.; Heijmen, Ben J.M.; Hoogeman, Mischa S.
2014-11-01
Purpose: To evaluate the clinical implementation of an online adaptive plan-of-the-day protocol for nonrigid target motion management in locally advanced cervical cancer intensity modulated radiation therapy (IMRT). Methods and Materials: Each of the 64 patients had four markers implanted in the vaginal fornix to verify the position of the cervix during treatment. Full and empty bladder computed tomography (CT) scans were acquired prior to treatment to build a bladder volume-dependent cervix-uterus motion model for establishment of the plan library. In the first phase of clinical implementation, the library consisted of one IMRT plan based on a single model-predicted internal target volume (mpITV), covering the target for the whole pretreatment observed bladder volume range, and a 3D conformal radiation therapy (3DCRT) motion-robust backup plan based on the same mpITV. The planning target volume (PTV) combined the ITV and nodal clinical target volume (CTV), expanded with a 1-cm margin. In the second phase, for patients showing >2.5-cm bladder-induced cervix-uterus motion during planning, two IMRT plans were constructed, based on mpITVs for empty-to-half-full and half-full-to-full bladder. In both phases, a daily cone beam CT (CBCT) scan was acquired to first position the patient based on bony anatomy and nodal targets and then select the appropriate plan. Daily post-treatment CBCT was used to verify plan selection. Results: Twenty-four and 40 patients were included in the first and second phase, respectively. In the second phase, 11 patients had two IMRT plans. Overall, an IMRT plan was used in 82.4% of fractions. The main reasons for selecting the motion-robust backup plan were uterus outside the PTV (27.5%) and markers outside their margin (21.3%). In patients with two IMRT plans, the half-full-to-full bladder plan was selected on average in 45% of the first 12 fractions, which was reduced to 35% in the last treatment fractions. Conclusions: The implemented
Chen, Haibin; Zhong, Zichun; Liao, Yuliang; Pompoš, Arnold; Hrycushko, Brian; Albuquerque, Kevin; Zhen, Xin; Zhou, Linghong; Gu, Xuejun
2016-02-07
GEC-ESTRO guidelines for high dose rate cervical brachytherapy advocate the reporting of the D2cc (the minimum dose received by the maximally exposed 2cc volume) to organs at risk. Due to large interfractional organ motion, reporting of accurate cumulative D2cc over a multifractional course is a non-trivial task requiring deformable image registration and deformable dose summation. To efficiently and accurately describe the point-to-point correspondence of the bladder wall over all treatment fractions while preserving local topologies, we propose a novel graphic processing unit (GPU)-based non-rigid point matching algorithm. This is achieved by introducing local anatomic information into the iterative update of correspondence matrix computation in the 'thin plate splines-robust point matching' (TPS-RPM) scheme. The performance of the GPU-based TPS-RPM with local topology preservation algorithm (TPS-RPM-LTP) was evaluated using four numerically simulated synthetic bladders having known deformations, a custom-made porcine bladder phantom embedded with twenty one fiducial markers, and 29 fractional computed tomography (CT) images from seven cervical cancer patients. Results show that TPS-RPM-LTP achieved excellent geometric accuracy with landmark residual distance error (RDE) of 0.7 ± 0.3 mm for the numerical synthetic data with different scales of bladder deformation and structure complexity, and 3.7 ± 1.8 mm and 1.6 ± 0.8 mm for the porcine bladder phantom with large and small deformation, respectively. The RDE accuracy of the urethral orifice landmarks in patient bladders was 3.7 ± 2.1 mm. When compared to the original TPS-RPM, the TPS-RPM-LTP improved landmark matching by reducing landmark RDE by 50 ± 19%, 37 ± 11% and 28 ± 11% for the synthetic, porcine phantom and the patient bladders, respectively. This was achieved with a computational time of less than 15 s in all cases
Directory of Open Access Journals (Sweden)
Giyasov Botir Iminzhonovich
2015-03-01
Full Text Available The construction quality of road surface of non-rigid type essentially depend on providing the temperature regimes in the process of laying and packing of hot asphalt concrete mixtures. In order to provide the required characteristics of asphalt concrete due to the surface width it is necessary to provide the temperature regimes of hot asphalt concrete mixture in the zones of lane connection. The hot mixture is promptly cooling right after laying within several minutes, which results, according to the construction technology and the specific conditions of work production, in temperature abuse of the mixture at joints of the lanes at packing. The authors present the analysis of the technology of arranging multilane road surface by one paver with the possibility of heating the surface lane edge with the temperature of the adjacent lane. The results of the studies of the production conditions effect on the temperature of edge heating of the previously laid lanes, and the time required to achieve the maximum heating temperature depending on the relative thickness of coating layers.
Rupnik, Ewelina; Jansa, Josef
2013-04-01
Central to our investigation is determination of dynamic behaviour of a highly reflective platform floating on water, as well as derivation of parameters defining instantaneous water state. The employed imaging setup consists of three off-the-shelf dSLR cameras capable of video recording at a 30Hz frame rate. In order to observe a change, the non-rigid and non-diffuse bodies impose the adoption of artificial targetting and custom measurement algorithms. Attention will be given to an in-house software tool implemented to carry out point measurement, correspondence search, tracking and outlier detection methods in the presence of specular reflections and a multimedia scene. A methodology for retrieval of wave parameters in regular wave conditions is also automatically handled by the software and will be discussed. In the context of performed measurements and achieved results, we will point out the extent to which consumer grade camera can fulfil automation and accuracy demands of industrial applications and the pitfalls entailed. Lastly, we will elaborate on visual representation of computed motion and deformations.
Marreiros, Filipe M. M.; Wang, Chunliang; Rossitti, Sandro; Smedby, Örjan
2016-03-01
In this study we present a non-rigid point set registration for 3D curves (composed by 3D set of points). The method was evaluated in the task of registration of 3D superficial vessels of the brain where it was used to match vessel centerline points. It consists of a combination of the Coherent Point Drift (CPD) and the Thin-Plate Spline (TPS) semilandmarks. The CPD is used to perform the initial matching of centerline 3D points, while the semilandmark method iteratively relaxes/slides the points. For the evaluation, a Magnetic Resonance Angiography (MRA) dataset was used. Deformations were applied to the extracted vessels centerlines to simulate brain bulging and sinking, using a TPS deformation where a few control points were manipulated to obtain the desired transformation (T1). Once the correspondences are known, the corresponding points are used to define a new TPS deformation(T2). The errors are measured in the deformed space, by transforming the original points using T1 and T2 and measuring the distance between them. To simulate cases where the deformed vessel data is incomplete, parts of the reference vessels were cut and then deformed. Furthermore, anisotropic normally distributed noise was added. The results show that the error estimates (root mean square error and mean error) are below 1 mm, even in the presence of noise and incomplete data.
Multi-objective optimization of a 3D vaneless diffuser based on fuzzy theory
Institute of Scientific and Technical Information of China (English)
Chuang GAO; Chuangang GU; Tong WANG; Xinwei SHU
2008-01-01
An optimization model based on fuzzy theory was set up and the corresponding Interactive modified simplex (IMS) method was developed to solve it. Both static pressure recovery and total pressure loss were considered in the model. Computational fluid dynamics (CFD) method was applied to solve the Reynolds-Averaged Navier-Stokes equation (RANS) and to find flow field distribution to get the value of the object function. After receiving the new shroud curve, grid movement and redrawing technology were adopted to avoid grid-line crossing and negative cells. The shroud curve was fitted with B-spline. The optimized results concur with the results reported in references.
窗口自适应更新的柔性目标视频跟踪%Visual Tracking with Window Updating of Non-rigid Object
Institute of Scientific and Technical Information of China (English)
李翠君; 王成儒
2012-01-01
运动人体目标的跟踪一直是视频监控中研究的重点.本文主要侧重柔性目标变形的方面,以HSI颜色模型进行模板的学习,在当前帧中得到模板,并且统计每一帧图像的信息量,然后在一下帧中进行Kalman预测.将预测到的区域与模板比较判断之后再决定是否更新模板,减少了一定的计算量,为了约束窗口的变化,引入信息量的概念,信息量由HSI颜色空间的I的特征点计算得到.这样,一直更新模板和窗口直至准确有效地跟踪人体目标.实验表明,在人体发生较大形变的过程中,会持续的跟踪人体,不会发生跟踪丢失的问题.%The human tracking is the key in the video surveillance. This text focuses on non-rigid objects, learning based on the HSI color model template. Each pixel of the template is modeled using two components with H and S. Get template from the current frame, statistic the information of every frame, and predict in the next frame using Kalman filter. Decide whether to update the template after comparing the forecast region and the template, reducing the amount of calculation. And for restraining the tracking window, information which is calculated from the color I is introduced. After that, the template and the window will be updated. The experimental results show that the proposed method achieves continuously tracking, and resolve the problem with the object disappeared.
Energy Technology Data Exchange (ETDEWEB)
Tatsugami, Fuminari; Higaki, Toru; Nakamura, Yuko; Yamagami, Takuji; Date, Shuji; Awai, Kazuo [Hiroshima University, Department of Diagnostic Radiology, Minami-ku, Hiroshima (Japan); Fujioka, Chikako; Kiguchi, Masao [Hiroshima University, Department of Radiology, Minami-ku, Hiroshima (Japan); Kihara, Yasuki [Hiroshima University, Department of Cardiovascular Medicine, Minami-ku, Hiroshima (Japan)
2015-01-15
To investigate the feasibility of a newly developed noise reduction technique at coronary CT angiography (CTA) that uses multi-phase data-averaging and non-rigid image registration. Sixty-five patients underwent coronary CTA with prospective ECG-triggering. The range of the phase window was set at 70-80 % of the R-R interval. First, three sets of consecutive volume data at 70 %, 75 % and 80 % of the R-R interval were prepared. Second, we applied non-rigid registration to align the 70 % and 80 % images to the 75 % image. Finally, we performed weighted averaging of the three images and generated a de-noised image. The image noise and contrast-to-noise ratio (CNR) in the proximal coronary arteries between the conventional 75 % and the de-noised images were compared. Two radiologists evaluated the image quality using a 5-point scale (1, poor; 5, excellent). On de-noised images, mean image noise was significantly lower than on conventional 75 % images (18.3 HU ± 2.6 vs. 23.0 HU ± 3.3, P < 0.01) and the CNR was significantly higher (P < 0.01). The mean image quality score for conventional 75 % and de-noised images was 3.9 and 4.4, respectively (P < 0.01). Our method reduces image noise and improves image quality at coronary CTA. (orig.)
Application of Aerodynamic Shape Deformation based on NURBS Surface%NURBS曲面在气动外形变形中的应用
Institute of Scientific and Technical Information of China (English)
马晓永; 张彦军; 雷武涛
2014-01-01
针对翼吊布局飞机复杂气动外形，建立了基于样条（NURBS，非均匀有理B样条）曲面和曲面叠加技术的曲面变形方法。在对样条曲线性质分析的基础上，以DLR-F6飞机为实例，对其机翼翼根、短舱挂架局部进行曲面网格变形，结果表明该方法能有效表述其复杂几何外形及型面变化特性，并且具有较好的局域性、可控性和光滑性。该方法可有效应用于吊舱挂架等复杂气动外形的建模、表面网格变形及气动外形优化设计等。%A free deformation method based on the B-Spline (NURBS, Non-Uniform Rational B-Spline) and surface superposition technique was presented for complex aerodynamic shape such as wing mounted nacelle-pylon conifguration. The characteristic of parameters were analyzed with B-Spline curves case, and the application instances of surface grids deformation on wing and pylon of DLR-F6 plane shows that the method could describe complex surfaces and its deformation characteristic effectively, the control parameter only change its local surface, and it is easy to carry out. The method is feasible and applicable to model representation, surface grids deformation and aerodynamic shape optimization etc.
Institute of Scientific and Technical Information of China (English)
李继云; 耿兆丰
2003-01-01
主要研究在给定误差的情况下,如何求得具有最少数据点的B样条拟合曲线.算法包括遗传算法的算子设计的基本实现细节,并通过实例证明了该算法的有效性.
Institute of Scientific and Technical Information of China (English)
邱绵浩; 刘箐; 丛华
2007-01-01
经典的经验模式分解(EMD)方法通过求解信号的上下2条三次样条包络曲线的均值曲线,实现对原始信号的分解.但是对于非平稳、非线性信号,包络平均无法代替真正的局部平均.另外,基于包络平均的分解方法还会引入极值过冲和欠冲问题.利用B样条的良好局部性质直接计算信号的局部均值插值曲线,克服了三次样条包络方法在EMD分解中的不足.通过对旋转机械故障振动信号的分解处理,表明基于B样条局部均值插值曲线的经验模式分解方法得到的固有模式函数更符合信号的真实物理意义,分解结果更好.
Evaluation of skin and muscular deformations in a non-rigid motion analysis
Goffredo, Michela; Carli, Marco; Conforto, Silvia; Bibbo, Daniele; Neri, Alessandro; D'Alessio, Tommaso
2005-04-01
During contraction and stretching, muscles change shape and size, and produce a deformation of skin tissues and a modification of the body segment shape. In human motion analysis, it is indispensable to take into account this phenomenon and thus approximating body limbs to rigid structures appears as restrictive. The present work aims at evaluating skin and muscular deformation, and at modeling body segment elastic behavior by analysing video sequences that capture a sport gesture. The soft tissue modeling is accomplished by using triangular meshes that automatically adapt to the body segment during the execution of a static muscle contraction. The adaptive triangular mesh is built on reference points whose motion is estimated by using the technique based on Gauss Laguerre Expansion. Promising results have been obtained by applying the proposed method to a video sequence, where an upper arm isometric contraction was present.
Wavelet-based multiresolution with n-th-root-of-2 Subdivision
Energy Technology Data Exchange (ETDEWEB)
Linsen, L; Pascucci, V; Duchaineau, M A; Hamann, B; Joy, K I
2004-12-16
Multiresolution methods are a common technique used for dealing with large-scale data and representing it at multiple levels of detail. The authors present a multiresolution hierarchy construction based on n{radical}2 subdivision, which has all the advantages of a regular data organization scheme while reducing the drawback of coarse granularity. The n{radical}2-subdivision scheme only doubles the number of vertices in each subdivision step regardless of dimension n. They describe the construction of 2D, 3D, and 4D hierarchies representing surfaces, volume data, and time-varying volume data, respectively. The 4D approach supports spatial and temporal scalability. For high-quality data approximation on each level of detail, they use downsampling filters based on n-variate B-spline wavelets. They present a B-spline wavelet lifting scheme for n{radical}2-subdivision steps to obtain small or narrow filters. Narrow filters support adaptive refinement and out-of-core data exploration techniques.
Approximate Bayesian methods for kernel-based object tracking
Zivkovic, Z.; Cemgil, A.T.; Kröse, B.
2009-01-01
A framework for real-time tracking of complex non-rigid objects is presented. The object shape is approximated by an ellipse and its appearance by histogram based features derived from local image properties. An efficient search procedure is used to find the image region with a histogram most simila
Cage-based performance capture
Savoye, Yann
2014-01-01
Nowadays, highly-detailed animations of live-actor performances are increasingly easier to acquire and 3D Video has reached considerable attentions in visual media production. In this book, we address the problem of extracting or acquiring and then reusing non-rigid parametrization for video-based animations. At first sight, a crucial challenge is to reproduce plausible boneless deformations while preserving global and local captured properties of dynamic surfaces with a limited number of controllable, flexible and reusable parameters. To solve this challenge, we directly rely on a skin-detached dimension reduction thanks to the well-known cage-based paradigm. First, we achieve Scalable Inverse Cage-based Modeling by transposing the inverse kinematics paradigm on surfaces. Thus, we introduce a cage inversion process with user-specified screen-space constraints. Secondly, we convert non-rigid animated surfaces into a sequence of optimal cage parameters via Cage-based Animation Conversion. Building upon this re...
A RAISED PANEL METHOD BASED ON NURBS FOR FREE-SURFACE POTENTIAL FLOWS WITH FORWARD SPEED
Institute of Scientific and Technical Information of China (English)
Gao Gao; Ma Ling
2003-01-01
A raised panel method based on NURBS (Non-Uniform Rational B-Splines) for free-surface flows with forward speed is presented. In this generalized panel method, NURBS are employed to represent the body geometry, disturbed free surface, and to express the unknown source strength distribution, on the body surface and above the free surface. Compared with common higher-order panel methods, it has no need of adopting local coordinates. NURBS make the geometry representation of the body shape and the wave pattern more precise. Raised panels above the free surface produce less numerical dispersion error, need less CPU consumption and are helpful and combined with collocation-point shifting up-stream, can satisfy the radiation condition numerically. By using continuous and discrete Fourier analysis, numerical errors of this method are discussed and a general expression for the errors of numerical damping and dispersion, including the effects of the vertical distance of singularities to the free surface, the order of singularity distribution represented by B-splines in panels, and collocation-point shifting is derived.
Sensitivity analysis based preform die shape design using the finite element method
Zhao, G. Q.; Hufi, R.; Hutter, A.; Grandhi, R. V.
1997-06-01
This paper uses a finite element-based sensitivity analysis method to design the preform die shape for metal forming processes. The sensitivity analysis was developed using the rigid visco-plastic finite element method. The preform die shapes are represented by cubic B-spline curves. The control points or coefficients of the B-spline are used as the design variables. The optimization problem is to minimize the difference between the realized and the desired final forging shapes. The sensitivity analysis includes the sensitivities of the objective function, nodal coordinates, and nodal velocities with respect to the design variables. The remeshing procedure and the interpolation/transfer of the history/dependent parameters are considered. An adjustment of the volume loss resulting from the finite element analysis is used to make the workpiece volume consistent in each optimization iteration and improve the optimization convergence. In addition, a technique for dealing with fold-over defects during the forming simulation is employed in order to continue the optimization procedures of the preform die shape design. The method developed in this paper is used to design the preform die shape for both plane strain and axisymmetric deformations with shaped cavities. The analysis shows that satisfactory final forging shapes are obtained using the optimized preform die shapes.
Image-based temporal alignment of echocardiographic sequences
Danudibroto, Adriyana; Bersvendsen, Jørn; Mirea, Oana; Gerard, Olivier; D'hooge, Jan; Samset, Eigil
2016-04-01
Temporal alignment of echocardiographic sequences enables fair comparisons of multiple cardiac sequences by showing corresponding frames at given time points in the cardiac cycle. It is also essential for spatial registration of echo volumes where several acquisitions are combined for enhancement of image quality or forming larger field of view. In this study, three different image-based temporal alignment methods were investigated. First, a method based on dynamic time warping (DTW). Second, a spline-based method that optimized the similarity between temporal characteristic curves of the cardiac cycle using 1D cubic B-spline interpolation. Third, a method based on the spline-based method with piecewise modification. These methods were tested on in-vivo data sets of 19 echo sequences. For each sequence, the mitral valve opening (MVO) time was manually annotated. The results showed that the average MVO timing error for all methods are well under the time resolution of the sequences.
Directory of Open Access Journals (Sweden)
Amir Pasha Mahmoudzadeh
2013-01-01
Full Text Available Interpolation has become a default operation in image processing and medical imaging and is one of the important factors in the success of an intensity-based registration method. Interpolation is needed if the fractional unit of motion is not matched and located on the high resolution (HR grid. The purpose of this work is to present a systematic evaluation of eight standard interpolation techniques (trilinear, nearest neighbor, cubic Lagrangian, quintic Lagrangian, hepatic Lagrangian, windowed Sinc, B-spline 3rd order, and B-spline 4th order and to compare the effect of cost functions (least squares (LS, normalized mutual information (NMI, normalized cross correlation (NCC, and correlation ratio (CR for optimized automatic image registration (OAIR on 3D spoiled gradient recalled (SPGR magnetic resonance images (MRI of the brain acquired using a 3T GE MR scanner. Subsampling was performed in the axial, sagittal, and coronal directions to emulate three low resolution datasets. Afterwards, the low resolution datasets were upsampled using different interpolation methods, and they were then compared to the high resolution data. The mean squared error, peak signal to noise, joint entropy, and cost functions were computed for quantitative assessment of the method. Magnetic resonance image scans and joint histogram were used for qualitative assessment of the method.
Mahmoudzadeh, Amir Pasha; Kashou, Nasser H
2013-01-01
Interpolation has become a default operation in image processing and medical imaging and is one of the important factors in the success of an intensity-based registration method. Interpolation is needed if the fractional unit of motion is not matched and located on the high resolution (HR) grid. The purpose of this work is to present a systematic evaluation of eight standard interpolation techniques (trilinear, nearest neighbor, cubic Lagrangian, quintic Lagrangian, hepatic Lagrangian, windowed Sinc, B-spline 3rd order, and B-spline 4th order) and to compare the effect of cost functions (least squares (LS), normalized mutual information (NMI), normalized cross correlation (NCC), and correlation ratio (CR)) for optimized automatic image registration (OAIR) on 3D spoiled gradient recalled (SPGR) magnetic resonance images (MRI) of the brain acquired using a 3T GE MR scanner. Subsampling was performed in the axial, sagittal, and coronal directions to emulate three low resolution datasets. Afterwards, the low resolution datasets were upsampled using different interpolation methods, and they were then compared to the high resolution data. The mean squared error, peak signal to noise, joint entropy, and cost functions were computed for quantitative assessment of the method. Magnetic resonance image scans and joint histogram were used for qualitative assessment of the method.
Kuźnik, Krzysztof
2013-06-01
This paper introduces a grammar-based model for developing a multi-thread multi-frontal parallel direct solver for one- dimensional isogeometric finite element method. The model includes the integration of B-splines for construction of the element local matrices and the multi-frontal solver algorithm. The integration and the solver algorithm are partitioned into basic indivisible tasks, namely the grammar productions, that can be executed squentially. The partial order of execution of the basic tasks is analyzed to provide the scheduling for the execution of the concurrent integration and multi-frontal solver algo- rithm. This graph grammar analysis allows for optimal concurrent execution of all tasks. The model has been implemented and tested on NVIDIA CUDA GPU, delivering logarithmic execution time for linear, quadratic, cubic and higher order B-splines. Thus, the CUDA implementation delivers the optimal performance predicted by our graph grammar analysis. We utilize the solver for multiple right hand sides related to the solution of non-stationary or inverse problems.
Scattered Data Processing Approach Based on Optical Facial Motion Capture
Directory of Open Access Journals (Sweden)
Qiang Zhang
2013-01-01
Full Text Available In recent years, animation reconstruction of facial expressions has become a popular research field in computer science and motion capture-based facial expression reconstruction is now emerging in this field. Based on the facial motion data obtained using a passive optical motion capture system, we propose a scattered data processing approach, which aims to solve the common problems of missing data and noise. To recover missing data, given the nonlinear relationships among neighbors with the current missing marker, we propose an improved version of a previous method, where we use the motion of three muscles rather than one to recover the missing data. To reduce the noise, we initially apply preprocessing to eliminate impulsive noise, before our proposed three-order quasi-uniform B-spline-based fitting method is used to reduce the remaining noise. Our experiments showed that the principles that underlie this method are simple and straightforward, and it delivered acceptable precision during reconstruction.
Contour Propagation With Riemannian Elasticity Regularization
DEFF Research Database (Denmark)
Bjerre, Troels; Hansen, Mads Fogtmann; Sapru, W.;
2011-01-01
the planning CT onto the rescans and correcting to reflect actual anatomical changes. For deformable registration, a free-form, multi-level, B-spline deformation model with Riemannian elasticity, penalizing non-rigid local deformations, and volumetric changes, was used. Regularization parameters was defined...
Towards Better Retrievals in Content -Based Image Retrieval System
Directory of Open Access Journals (Sweden)
Kumar Vaibhava
2014-04-01
Full Text Available -This paper presents a Content-Based Image Retrieval (CBIR System called DEICBIR-2. The system retrieves images similar to a given query image by searching in the provided image database.Standard MPEG-7 image descriptors are used to find the relevant images which are similar to thegiven query image. Direct use of the MPEG-7 descriptors for creating the image database and retrieval on the basis of nearest neighbor does not yield accurate retrievals. To further improve the retrieval results, B-splines are used for ensuring smooth and continuous edges of the images in the edge-based descriptors. Relevance feedback is also implemented with user intervention. These additional features improve the retrieval performance of DEICBIR-2 significantly. Computational performance on a set of query images is presented and the performance of the proposed system is much superior to the performance of DEICBIR[9] on the same database and on the same set of query images.
B-spline goal-oriented error estimators for geometrically nonlinear rods
2011-04-01
approximation space is the same as the one used to represent the geometry and which can be represented by B–splines, NURBS (Non–Uniform Rational B... NURBS basis) and the related advantages in the context of analysis, we refer the reader to [7] and [15] (and to the references therein indicated). We...Publications, 2000. [26] T.J.R. Hughes, J.A. Cottrell, and Y. Bazilevs. Isogeometric analysis: Cad, finite el- ements, nurbs , exact geometry and mesh
A sparse collocation method for solving time-dependent HJB equations using multivariate B-splines
Govindarajan, N.; De Visser, C.C.; Krishnakumar, K.
2014-01-01
This paper presents a sparse collocation method for solving the time-dependent Hamilton–Jacobi–Bellman (HJB) equation associated with the continuous-time optimal control problem on a fixed, finite timehorizon with integral cost functional. Through casting the problem in a recursive framework using t
P wave onset time picking with the B-spline biorthogonal wavelet
Institute of Scientific and Technical Information of China (English)
TENG Yun-tian; WANG Xi-zhen; WANG Xiao-mei; MA Jie-mei; XU Jian-hua
2006-01-01
@@ The seismic wave consists of many seismic phases, which contain rich geophysical information from the hypocenter, medium of seismic wave passing through and so on. It is very important to detect and pick these seismic phases for understanding the mechanism of earthquake, the Earth structure and property of seismic waves. In order to reduce or avoid the loss resulted from the earthquake, one of the important goals of seismic event detecting is to obtain its related information before and after it occurs. Because of the particularity of P wave and S wave,the seismic event detecting focuses on distinguishing P and S waves and picking their onset time, it has been becoming one of the research hotspots for many geophysicists to pick the P and S wave arrival accurately and effectively.
Isogeometric Divergence-conforming B-splines for the Unsteady Navier-Stokes Equations
2012-04-01
remark on the role of helicity. Comptes Rendus Mathematique , 347:613–618, 2009. [9] M E Brachet. Small-scale structure of the Taylor-Green vortex...suitable. Journal de Mathematiques Pures et Appliquees, 88:87–106, 2007. [25] J-L Guermond. On the use of the notion of suitable weak solutions in CFD
Adaptive Hierarchical B-spline Surface Representation of Large-Scale Scattered Data
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
The representation of large scale scattered data is a difficult problem, especially when various features of the representation, such as C2-continuity, are required. This paper describes a fast algorithm for large scale scattered data approximation and interpolation. The interpolation algorithm uses a coarse-to-fine hierarchical control lattice to fit the scattered data. The refinement process is only used in the regions where the error between the scattered data and the result in a surface is greater than a specified tolerance. A method to ensure C2-continuity is introduced to calculate the control lattice under constrained conditions. Experimental results show that this method can quickly represent large scale scattered data set.
B-splines on 3-D tetrahedron partition in four-directional mesh
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
It is more difficult to construct 3-D splines than in 2-D case. Some results in the three directional meshes of bivariate case have been e xtended to 3-D case and corresponding tetrahedron partition has been constructed. The support of related Bsplines and their recurrent formulas on integration and differentiationdifference are obtained. The results of this paper can be extended into higher dimension spaces, and can be also used in wavelet analysis, because of the relationship between spline and wavelets.
Li, Zili; Xia, Xuezhi; Zhu, Guangxi; Zhu, Yaoting
2004-03-01
The principle to construct G&IBMR virtual scene based on stereo panorama with binocular stereovision was put forward. Closed cubic B-splines have been used for content-based segmentation to virtual objects of stereo panorama and all objects in current viewing frustum would be ordered in current object linked list (COLL) by their depth information. The formula has been educed to calculate the depth information of a point in virtual scene by the parallax based on a parallel binocular vision model. A bilinear interpolation algorithm has been submitted to deform the segmentation template and take image splicing between three key positions. We also use the positional and directional transformation of binocular virtual camera bound to user avatar to drive the transformation of stereo panorama so as to achieve real-time consistency about perspective relationship and image masking. The experimental result has shown that the algorithm in this paper is effective and feasible.
Real Time Animation of Trees Based on BBSC in Computer Games
Directory of Open Access Journals (Sweden)
Xuefeng Ao
2009-01-01
Full Text Available That researchers in the field of computer games usually find it is difficult to simulate the motion of actual 3D model trees lies in the fact that the tree model itself has very complicated structure, and many sophisticated factors need to be considered during the simulation. Though there are some works on simulating 3D tree and its motion, few of them are used in computer games due to the high demand for real-time in computer games. In this paper, an approach of animating trees in computer games based on a novel tree model representation—Ball B-Spline Curves (BBSCs are proposed. By taking advantage of the good features of the BBSC-based model, physical simulation of the motion of leafless trees with wind blowing becomes easier and more efficient. The method can generate realistic 3D tree animation in real-time, which meets the high requirement for real time in computer games.
Creating analytically divergence-free velocity fields from grid-based data
Ravu, Bharath; Rudman, Murray; Metcalfe, Guy; Lester, Daniel R.; Khakhar, Devang V.
2016-10-01
We present a method, based on B-splines, to calculate a C2 continuous analytic vector potential from discrete 3D velocity data on a regular grid. A continuous analytically divergence-free velocity field can then be obtained from the curl of the potential. This field can be used to robustly and accurately integrate particle trajectories in incompressible flow fields. Based on the method of Finn and Chacon (2005) [10] this new method ensures that the analytic velocity field matches the grid values almost everywhere, with errors that are two to four orders of magnitude lower than those of existing methods. We demonstrate its application to three different problems (each in a different coordinate system) and provide details of the specifics required in each case. We show how the additional accuracy of the method results in qualitatively and quantitatively superior trajectories that results in more accurate identification of Lagrangian coherent structures.
HIGH RESOLUTION RANGE PROFILE FORMATION BASED ON LFM SIGNAL FUSION OF MULTIPLE RADARS
Institute of Scientific and Technical Information of China (English)
Wang Cheng; Hu Weidong; Du Xiaoyong; Yu Wenxian
2007-01-01
This paper presents a new method of High Resolution Range (HRR) profile formation based on Linear Frequency Modulation (LFM) signal fusion of multiple radars with multiple frequency bands.The principle of the multiple radars signal fusion improving the range resolution is analyzed. With the analysis of return signals received by two radars, it is derived that the phase difference between the echoes varies almost linearly with respect to the frequency if the distance between two radars is negligible compared with the radar observation distance. To compensate the phase difference, an entropy-minimization principle based compensation algorithm is proposed. During the fusion process, the B-splines interpolation method is applied to resample the signals for Fourier transform imaging. The theoretical analysis and simulations results show the proposed method can effectively increase signal bandwidth and provide a high resolution range profile.
Optimal Trajectory Planning for Glass-Handing Robot Based on Execution Time Acceleration and Jerk
Directory of Open Access Journals (Sweden)
Honggang Duan
2016-01-01
Full Text Available This study describes a trajectory planning method based on execution time, acceleration, and jerk to ensure that a glass-handing robot runs smoothly at execution time. The minimised objective function consists of the weighted sum of the square of the integral of the execution time, the integral of the acceleration, and the integral of the jerk, all of which are obtained through the weighted coefficient method. A three-dimensional kinematics model of the glass-handing robot is then established and nonuniform fifth-order B-splines are used to interpolate its path points. The acceleration and jerk are expressed as functions of time through mathematical simulation. Simulation results show that the designed method for robot trajectory planning not only improves the working efficiency of the glass-handing robot but also ensures that it runs smoothly.
Institute of Scientific and Technical Information of China (English)
季学武; 王健; 赵又群; 刘亚辉; 臧利国; 李波
2015-01-01
In order to diminish the impacts of external disturbance such as parking speed fluctuation and model un-certainty existing in steering kinematics, this paper presents a parallel path tracking method for vehicle based on pre-view back propagation (BP) neural network PID controller. The forward BP neural network can adjust the parameters of PID controller in real time. The preview time is optimized by considering path curvature, change in curvature and road boundaries. A fuzzy controller considering barriers and different road conditions is built to select the starting po-sition. In addition, a kind of path planning technology satisfying the requirement of obstacle avoidance is introduced. In order to solve the problem of discontinuous curvature, cubic B spline curve is used for curve fitting. The simulation results and real vehicle tests validate the effectiveness of the proposed path planning and tracking methods.
Optimization of the Upper Surface of Hypersonic Vehicle Based on CFD Analysis
Gao, T. Y.; Cui, K.; Hu, S. C.; Wang, X. P.; Yang, G. W.
2011-09-01
For the hypersonic vehicle, the aerodynamic performance becomes more intensive. Therefore, it is a significant event to optimize the shape of the hypersonic vehicle to achieve the project demands. It is a key technology to promote the performance of the hypersonic vehicle with the method of shape optimization. Based on the existing vehicle, the optimization to the upper surface of the Simplified hypersonic vehicle was done to obtain a shape which suits the project demand. At the cruising condition, the upper surface was parameterized with the B-Spline curve method. The incremental parametric method and the reconstruction technology of the local mesh were applied here. The whole flow field was been calculated and the aerodynamic performance of the craft were obtained by the computational fluid dynamic (CFD) technology. Then the vehicle shape was optimized to achieve the maximum lift-drag ratio at attack angle 3°, 4° and 5°. The results will provide the reference for the practical design.
RESEARCH ON ED-MILLING TO COMPLEX CAVITY BASED ON LAMINATION MACHINING
Institute of Scientific and Technical Information of China (English)
无
2003-01-01
Based on the principle of laminated machining, the method of auto-programming in the electro discharge milling (ED-milling) process is drawn out.With the help of IGES formatted files, the process slicing and the machining locus can be programmed well.The program adopts three-parameter convergence as the basic way to slice the geometry mold and divide the non-uniform rational B-spline curve (NURBS) surface.With the great mount of discrete points, a given arithmetic is drawn out to order them, and then is carried out the interpolation of bi-arc.In the process, according to the character of the EDM process, the zigzag track of machining is accepted to remove the volume of work piece and shape the contour along the contour line of the slicing segments, including multi-connection.As a result, some correlative experiments are accomplished.
Human Body Modeling and Posture Simulating Based on 3D Surface Scan Data
Institute of Scientific and Technical Information of China (English)
马永有; 张辉; 任少云; 蒋寿伟
2003-01-01
This paper presents a new approach for modeling the human body by considering the motion state and the shape of whole body. The body model consists of a skeleton kinematic model and a surface model. The former is used to determine the posture of the body,and the latter is used to generate the body shape according to the given posture. The body surface is reconstructed with multi-segment B-spline surfaces based on the 3D scan data from a real human body.Using only a few joints parameters and the original surface scan data, the various body postures and the shape can be generated easily. The model has a strong potential of being used for ergonomic design,garment design, virtual reality environment, as well as creating human animation, etc.
Spline model of the high latitude scintillation based on in situ satellite data
Priyadarshi, S.; Wernik, A. W.
2013-12-01
We present a spline model for the high latitude ionospheric scintillation using satellite in situ measurements made by the Dynamic Explorer 2 (DE 2) satellite. DE 2 satellite measurements give observations only along satellite orbit but our interpolation model fills the gaps between the satellite orbits. This analytical model is based on products of cubic B-splines and coefficients determined by least squares fit to the binned data and constrained to make the fit periodic in 24 hours of geomagnetic local time, periodic in 360 degrees of invariant longitude, in geomagnetic indices and solar radio flux. Discussion of our results clearly shows the seasonal and diurnal behavior of ionospheric parameters important in scintillation modeling for different geophysical and solar activity conditions. We also show that results obtained from our analytical model match observations obtained from in situ measurements. Shishir Priyadarshi Space Research Centre, Poland
An Optimized Spline-Based Registration of a 3D CT to a Set of C-Arm Images.
Jonić, S; Thévenaz, P; Zheng, G; Nolte, L-P; Unser, M
2006-01-01
We have developed an algorithm for the rigid-body registration of a CT volume to a set of C-arm images. The algorithm uses a gradient-based iterative minimization of a least-squares measure of dissimilarity between the C-arm images and projections of the CT volume. To compute projections, we use a novel method for fast integration of the volume along rays. To improve robustness and speed, we take advantage of a coarse-to-fine processing of the volume/image pyramids. To compute the projections of the volume, the gradient of the dissimilarity measure, and the multiresolution data pyramids, we use a continuous image/volume model based on cubic B-splines, which ensures a high interpolation accuracy and a gradient of the dissimilarity measure that is well defined everywhere. We show the performance of our algorithm on a human spine phantom, where the true alignment is determined using a set of fiducial markers.
Brandes, Susanne; Mokhtari, Zeinab; Essig, Fabian; Hünniger, Kerstin; Kurzai, Oliver; Figge, Marc Thilo
2015-02-01
Time-lapse microscopy is an important technique to study the dynamics of various biological processes. The labor-intensive manual analysis of microscopy videos is increasingly replaced by automated segmentation and tracking methods. These methods are often limited to certain cell morphologies and/or cell stainings. In this paper, we present an automated segmentation and tracking framework that does not have these restrictions. In particular, our framework handles highly variable cell shapes and does not rely on any cell stainings. Our segmentation approach is based on a combination of spatial and temporal image variations to detect moving cells in microscopy videos. This method yields a sensitivity of 99% and a precision of 95% in object detection. The tracking of cells consists of different steps, starting from single-cell tracking based on a nearest-neighbor-approach, detection of cell-cell interactions and splitting of cell clusters, and finally combining tracklets using methods from graph theory. The segmentation and tracking framework was applied to synthetic as well as experimental datasets with varying cell densities implying different numbers of cell-cell interactions. We established a validation framework to measure the performance of our tracking technique. The cell tracking accuracy was found to be >99% for all datasets indicating a high accuracy for connecting the detected cells between different time points.
Sacharow, Alexei
2011-12-01
The unprecedented success of the iterative closest point (ICP) method for registration in geometry processing and related fields can be attributed to its efficiency, robustness, and wide spectrum of applications. Its use is however quite limited as soon as the objects to be registered arise from each other by a transformation significantly different from a Euclidean motion. We present a novel variant of ICP, tailored for the specific needs of production engineering, which registers a triangle mesh with a second surface model of arbitrary digital representation. Our method inherits most of ICP\\'s practical advantages but is capable of detecting medium-strength bendings i.e. isometric deformations. Initially, the algorithm assigns to all vertices in the source their closest point on the target mesh and then iteratively establishes isometry, a process which, very similar to ICP, requires intermediate re-projections. A NURBS-based technique for applying the resulting deformation to arbitrary instances of the source geometry, other than the very mesh used for correspondence estimation, is described before we present numerical results on synthetic and real data to underline the viability of our approach in comparison with others. © 2011 Elsevier Ltd. All rights reserved.
Shape modification of NURBS curves based on weight%基于权值的NURBS曲线形状修改
Institute of Scientific and Technical Information of China (English)
陈军; 崔汉国
2012-01-01
This paper deals with the deficiency in NURBS curve's shape modification based on control points and the way to perform the prescribed shape modification of NURBS curves merely by the modification of the weight of some of their control points.As is known,NURBS curves can be considered as central projections of infinite number of non-rational B-spline curve's,whose control points are the original NURBS curve's control points with weight.Thus,a weight-based shape modification method is proposed through the examples in which B-spline curves are determined by definite free parameter.The method can not only determine the new position of an arbitrary chosen point of plane NURBS curve,but also prescribe the tangent direction well.%针对基于控制顶点的NURBS曲线形状修改的不足,讨论了如何通过修改控制顶点的权值进行NURBS曲线的形状修改问题.NURBS曲线可以看作是高一堆空间非有理B样条曲线的中心投影,该B样条的控制顶点为原NURBS曲线的带权控制顶点,并且这样的B样条曲线有无数多条.根据这个性质,以实例的方式通过特定自由参数确定B样条曲线,实现了基于权值的NURBS曲线形状修改.该方法不仅能够较好地确定新的带权控制顶点,还解决了修改后曲线在给定点的切矢问题,具有更好的灵活性.
Institute of Scientific and Technical Information of China (English)
金鑫; 孙刚
2012-01-01
Aerodynamic drag reduction design is the key to the design of civil aircraft. To solve the drag reduction problem of wing a new method was proposed based on non-uniform B-spline modeling technology and an improved particle swarm optimization(PSO) algorithm. The former was used to describe the wing shapes with small amount of calculation: it not only had good local control of shape, but also ensured the overall appearance of smoothness; the latter, as a new intelligent optimization method, had fast convergence ability and global search ability for multi-objective optimization problems. The results showed that cubic non-uniform B-spline curves and bi-cubic non-uniform B-spline surface could describe the airfoil and wing shapes more accurately with fewer control points, and the efficiency of multi-objective aerodynamic optimization had been improved. Even for the airfoil and wing with high efficiency factor, aerodynamic performance also made a further increase.%机翼减阻设计是民用客机气动设计的关键,本文提出了一种基于非均匀B样条曲线曲面造型技术和改进的粒子群算法的新型优化方法.前者用来描述机翼的外形,具有计算量小的优点,在优化过程中不仅具有良好的局部操控性,又能保证整体外形的光顺性；后者作为一种新兴的智能化优化方法,具有简单易行、收敛速度快、全局搜索能力强等优点,同时又适用于多目标优化问题.研究结果表明:三次非均匀B样条曲线曲面能够方便地使用较少的控制顶点较为精确地描述翼型及机翼的外形,在此基础上利用改进的粒子群算法进行的多目标气动优化设计,优化效率得到了提升.在效率因子本身较高的初始外形基础上,最终外形的气动性能也取得了较大幅度的提高.
Castro-Mateos, Isaac; Pozo, Jose M.; Lazary, Aron; Frangi, Alejandro F.
2016-03-01
Computational medicine aims at developing patient-specific models to help physicians in the diagnosis and treatment selection for patients. The spine, and other skeletal structures, is an articulated object, composed of rigid bones (vertebrae) and non-rigid parts (intervertebral discs (IVD), ligaments and muscles). These components are usually extracted from different image modalities, involving patient repositioning. In the case of the spine, these models require the segmentation of IVDs from MR and vertebrae from CT. In the literature, there exists a vast selection of segmentations methods, but there is a lack of approaches to align the vertebrae and IVDs. This paper presents a method to create patient-specific finite element meshes for biomechanical simulations, integrating rigid and non-rigid parts of articulated objects. First, the different parts are aligned in a complete surface model. Vertebrae extracted from CT are rigidly repositioned in between the IVDs, initially using the IVDs location and then refining the alignment using the MR image with a rigid active shape model algorithm. Finally, a mesh morphing algorithm, based on B-splines, is employed to map a template finite-element (volumetric) mesh to the patient-specific surface mesh. This morphing reduces possible misalignments and guarantees the convexity of the model elements. Results show that the accuracy of the method to align vertebrae into MR, together with IVDs, is similar to that of the human observers. Thus, this method is a step forward towards the automation of patient-specific finite element models for biomechanical simulations.
Petibon, Y.; Ouyang, J.; Zhu, X.; Huang, C.; Reese, T. G.; Chun, S. Y.; Li, Q.; El Fakhri, G.
2013-04-01
Cardiac motion and partial volume effects (PVE) are two of the main causes of image degradation in cardiac PET. Motion generates artifacts and blurring while PVE lead to erroneous myocardial activity measurements. Newly available simultaneous PET-MR scanners offer new possibilities in cardiac imaging as MRI can assess wall contractility while collecting PET perfusion data. In this perspective, we develop a list-mode iterative reconstruction framework incorporating both tagged-MR derived non-rigid myocardial wall motion and position dependent detector point spread function (PSF) directly into the PET system matrix. In this manner, our algorithm performs both motion ‘deblurring’ and PSF deconvolution while reconstructing images with all available PET counts. The proposed methods are evaluated in a beating non-rigid cardiac phantom whose hot myocardial compartment contains small transmural and non-transmural cold defects. In order to accelerate imaging time, we investigate collecting full and half k-space tagged MR data to obtain tagged volumes that are registered using non-rigid B-spline registration to yield wall motion information. Our experimental results show that tagged-MR based motion correction yielded an improvement in defect/myocardium contrast recovery of 34-206% as compared to motion uncorrected studies. Likewise, lesion detectability improved by respectively 115-136% and 62-235% with MR-based motion compensation as compared to gating and no motion correction and made it possible to distinguish non-transmural from transmural defects, which has clinical significance given the inherent limitations of current single modality imaging in identifying the amount of residual ischemia. The incorporation of PSF modeling within the framework of MR-based motion compensation significantly improved defect/myocardium contrast recovery (5.1-8.5%, p defect detectability (39-56%, p < 0.01). No statistical difference was found in PET contrast and lesion detectability
Medical image collection indexing: shape-based retrieval using KD-trees.
Robinson, G P; Tagare, H D; Duncan, J S; Jaffe, C C
1996-01-01
The capacity to retrieve images containing objects with shapes similar to a query shape is desirable in medical image databases. We propose a similarity measure and an indexing mechanism for non-rigid comparison of shape which adds this capability to image databases. The (dis-)similarity measure is based on the observations that: (1) the geometry of the same organ in different subjects is not related by a strictly rigid transformation; and (2) the orientation of the organ plays a key role in comparing shape. We propose a similarity measure that computes a non-rigid mapping between curves and uses this mapping to compare oriented shape. We also show how KD-trees can index curves so that retrieval with our similarity measure is efficient. Experiments with real-world data from a database of magnetic resonance images are provided.
基于嵌入式系统的机器人关节空间轨迹规划%Robot trajectory planning based on embedded system in joint space
Institute of Scientific and Technical Information of China (English)
王宪; 王伟; 张方生; 张宏
2011-01-01
Aiming at the appearance of dithering caused by the discontinuous of the speed or acceleration of industrial robot during operating,a kind of trajectory planning algorithm based on B-spline curve is put forward, which use cubic B-spline curve to plan the joint space of robot with six degrees of freedom. According to the request of processing real-time interpolation points, a cohesive interpolation algorithm based on ARM9 is used to solve this problem, which eventually used in the embedded system. It is proved by experiment that this algorithm can not only reduce computation but also shorten processing time, and of course can guarantee the smooth of curve,eventually reducing the continuous mechanical wobble.%针对工业机器人运行过程经常出现的因速度或加速度不连续从而导致抖动等问题,提出了一种基于B样条曲线的轨迹规划算法,该算法使用三次B样条曲线来对六自由度机器人的关节空间进行插值,并根据实时性的要求运用一种控制点衔接插补算法进行分段插补,最终应用于基于ARM9的嵌入式系统中.实验证明:该算法不仅计算量小、处理时间短,而且能保证速度曲线的连续平滑,减少了机械抖动.
Uniform B-Spline with Shape Parameter%带形状参数的均匀B样条
Institute of Scientific and Technical Information of China (English)
王文涛; 汪国昭
2004-01-01
n阶均匀B样条基函数是n阶带形状参数的均匀B样条基函数的一个特例 .由带形状参数的均匀B样条基组成的样条曲线可通过改变形状参数的取值而调整曲线的形状 .随着阶数的升高,形状参数的取值范围将扩大.
DEFF Research Database (Denmark)
Christensen, Ole; Sun, Wenchang
2008-01-01
We consider systems of functions appearing by letting a class of modulations act on a countable collection of functions. These systems correspond to shift-invariant systems, considered on the Fourier side. We provide sufficient conditions for the system to be a frame, as well as an explicit const...
A cubic interpolation pipeline for fast computation of 3D deformation fields modeled using B-splines
Castro-Pareja, Carlos R.; Shekhar, Raj
2006-02-01
Fast computation of 3D deformation fields is critical to bringing the application of automated elastic image registration algorithms to routine clinical practice. However, it lies beyond the computational power of current microprocessors; therefore requiring implementations using either massively parallel computers or application-specific hardware accelerators. The use of massively parallel computers in a clinical setting is not practical or cost-effective, therefore making the use of hardware accelerators necessary. We present a hardware pipeline that allows accelerating the computation of 3D deformation fields to speeds up to two orders of magnitude faster than software implementations on current workstations and about 64 times faster than other previously reported architectures. The pipeline implements a version of the free-form deformation calculation algorithm, which is optimized to minimize the number of arithmetic operations required to calculate the transformation of a given set of neighboring voxels, thereby achieving an efficient and compact implementation in hardware which allows its use as part of a larger system.
Institute of Scientific and Technical Information of China (English)
Hong WANG; Hong YUE
2003-01-01
This paper presents a novel approach to detect and diagnose faults in the dynanmic part of a chis of stochastic sys-tems. the Such a group of systems are subjected to a set of crisp inputs but the outputs considered are the measurable probability density functions (PDFs) of the system output, rather than thie system output alone. A new approximation model is developed for the output probability density functions so that the dynamic part of the system is decoupled fron the output probability density functions. A nonlinear adaptive observer is constructed to detect and diagnose the fault in the dynamic part of the system. Convergency analysis is perfomed for the error dynamics raised from the fault detection and diagnosis phase and an applicability study on the detection and diagnosis of the unexpected changes in the 2D grmmage distributions in a paper forming process is included.
Energy Technology Data Exchange (ETDEWEB)
Sanchez Castro, F.J.; Cuisenaire, O.; Thiran, J.P. [Ecole Polytechnique Federale de Lausanne (EPFL) (Switzerland). Signal Processing Inst.; Pollo, C. [Ecole Polytechnique Federale de Lausanne (EPFL) (Switzerland). Signal Processing Inst.; Centre Hospitalier Universitaire Vaudois (CHUV), Lausanne (Switzerland). Dept. of Neurosurgery; Villemure, J.G. [Centre Hospitalier Universitaire Vaudois (CHUV), Lausanne (Switzerland). Dept. of Neurosurgery
2006-03-15
Objects: In functional stereotactic neurosurgery, one of the cornerstones upon which the success and the operating time depends is an accurate targeting. The subthalamic nucleus (STN) is the usual target involved when applying deep brain stimulation for Parkinson's disease (PD). Unfortunately, STN is usually not clearly visible in common medical imaging modalities, which justifies the use of atlas-based segmentation techniques to infer the STN location. Materials and methods: Eight bilaterally implanted PD patients were included in this study. A three-dimensional T1-weighted sequence and inversion recovery T2-weighted coronal slices were acquired pre-operatively. We propose a methodology for the construction of a ground truth of the STN location and a scheme that allows both, to perform a comparison between different non-rigid registration algorithms and to evaluate their usability to locate the STN automatically. Results: The intra-expert variability in identifying the STN location is 1.06{+-}0.61 mm while the best non-rigid registration method gives an error of 1.80{+-}0.62 mm. On the other hand, statistical tests show that an affine registration with only 12 degrees of freedom is not enough for this application. Conclusions: Using our validation-evaluation scheme, we demonstrate that automatic STN localization is possible and accurate with non-rigid registration algorithms. (orig.)
Atlas Based Automatic Liver 3D CT Image Segmentation%基于图谱的肝脏CT三维自动分割研究
Institute of Scientific and Technical Information of China (English)
刘伟; 贾富仓; 胡庆茂; 王俊
2011-01-01
目的 在肝脏外科手术或肝脏病理研究中,计算肝脏体积是重要步骤.由于肝脏外形复杂、临近组织灰度值与之接近等特点,肝脏的自动医学图像分割仍是医学图像处理中的难点之一.方法 本文采用图谱结合3D非刚性配准的方法,同时加入肝脏区域搜索算法,实现了鲁棒性较高的肝脏自动分割程序.首先,利用20套训练图像创建图谱,然后程序自动搜索肝脏区域,最后将图谱与待分割CT图像依次进行仿射配准和B样条配准.配准以后的图谱肝脏轮廓即可表示为目标肝脏分割轮廓,进而计算出肝脏体积.结果 评估结果显示,上述方法在肝脏体积误差方面表现出色,达到77分,但在局部(主要在肝脏尖端)出现较大的误差.结论 该方法分割临床肝脏CT图像具有可行性.%Objective Liver segmentation is an important step for the planning and navigation in liver surgery. Accurate, fast and robust automatic segmentation methods for clinical routine data are urgently needed. Because of the liver- s characteristics, such as the complexity of the external form, the similarity between the intensities of the liver and the tissues around it, automatic segmentation of the liver is one of the difficulties in medical image processing. Methods In this paper, 3D non-rigid registration from a refined atlas to liver CT images is used for segmentation. Firstly, twenty sets of training images are utilized to create an atlas. Then the liver initial region is searched and located automatically. After that threshold filtering is used to enhance the robustness of segmentation. Finally, this atlas is non-rigidly registered to the liver in CT images with affine and B-spline in succession. The registered segmentation of liver- s atlas represented the segmentation of the target liver, and then the liver volume was calculated. Results The evaluation show that the proposed method works well in liver volume error, with the 77 score
ASM Based Synthesis of Handwritten Arabic Text Pages.
Dinges, Laslo; Al-Hamadi, Ayoub; Elzobi, Moftah; El-Etriby, Sherif; Ghoneim, Ahmed
2015-01-01
Document analysis tasks, as text recognition, word spotting, or segmentation, are highly dependent on comprehensive and suitable databases for training and validation. However their generation is expensive in sense of labor and time. As a matter of fact, there is a lack of such databases, which complicates research and development. This is especially true for the case of Arabic handwriting recognition, that involves different preprocessing, segmentation, and recognition methods, which have individual demands on samples and ground truth. To bypass this problem, we present an efficient system that automatically turns Arabic Unicode text into synthetic images of handwritten documents and detailed ground truth. Active Shape Models (ASMs) based on 28046 online samples were used for character synthesis and statistical properties were extracted from the IESK-arDB database to simulate baselines and word slant or skew. In the synthesis step ASM based representations are composed to words and text pages, smoothed by B-Spline interpolation and rendered considering writing speed and pen characteristics. Finally, we use the synthetic data to validate a segmentation method. An experimental comparison with the IESK-arDB database encourages to train and test document analysis related methods on synthetic samples, whenever no sufficient natural ground truthed data is available.
Adaptive Surface Reconstruction Based on Tensor Product Algebraic Splines
Institute of Scientific and Technical Information of China (English)
Xinghua Song; Falai Chen
2009-01-01
Surface reconstruction from unorganized data points is a challenging problem in Computer Aided Design and Geometric Modeling. In this paper, we extend the mathematical model proposed by Juttler and Felis (Adv. Comput. Math., 17 (2002), pp. 135-152) based on tensor product algebraic spline surfaces from fixed meshes to adaptive meshes. We start with a tensor product algebraic B-spline surface defined on an initial mesh to fit the given data based on an optimization approach. By measuring the fitting errors over each cell of the mesh, we recursively insert new knots in cells over which the errors are larger than some given threshold, and construct a new algebraic spline surface to better fit the given data locally. The algorithm terminates when the error over each cell is less than the threshold. We provide some examples to demonstrate our algorithm and compare it with Jiittler's method. Examples suggest that our method is effective and is able to produce reconstruction surfaces of high quality.AMS subject classifications: 65D17
Parameter tuning for the NFFT based fast Ewald summation
Directory of Open Access Journals (Sweden)
Franziska Nestler
2016-07-01
Full Text Available The computation of the Coulomb potentials and forces in charged particle systems under 3d-periodic boundary conditionsis possible in an efficient way by utilizing the Ewald summation formulas and applying the fast Fourier transform (FFT. In this paper we consider the particle-particle NFFT (P$^2$NFFT approach, which is based on the fast Fourier transform for nonequispaced data (NFFT and compare the error behaviors regarding different window functions, which are used in order to approximate the given continuous charge distribution by a mesh based charge density. Typically B-splines are applied in the scope of particle mesh methods, as for instance within the well known particle-particle particle-mesh (P$^3$M algorithm. The publicly available P$^2$NFFT algorithm allows the application of an oversampled FFT as well as the usage of different window functions. We consider for the first time also an approximation by Bessel functions and show how the resulting root mean square errors in the forces can be predicted precisely and efficiently. The results show that, if the parameters are tuned appropriately, the Bessel window function is in many cases even the better choice in terms of computational costs. Moreover, the results indicate that it is often advantageous in terms of efficiency to spend some oversampling within the NFFT while using a window function with a smaller support.
Construction of Hilbert Transform Pairs of Wavelet Bases and Gabor-like Transforms
Chaudhury, Kunal Narayan
2009-01-01
We propose a novel method for constructing Hilbert transform (HT) pairs of wavelet bases based on a fundamental approximation-theoretic characterization of scaling functions--the B-spline factorization theorem. In particular, starting from well-localized scaling functions, we construct HT pairs of biorthogonal wavelet bases of L^2(R) by relating the corresponding wavelet filters via a discrete form of the continuous HT filter. As a concrete application of this methodology, we identify HT pairs of spline wavelets of a specific flavor, which are then combined to realize a family of complex wavelets that resemble the optimally-localized Gabor function for sufficiently large orders. Analytic wavelets, derived from the complexification of HT wavelet pairs, exhibit a one-sided spectrum. Based on the tensor-product of such analytic wavelets, and, in effect, by appropriately combining four separable biorthogonal wavelet bases of L^2(R^2), we then discuss a methodology for constructing 2D directional-selective complex...
AN AERIAL-IMAGE DENSE MATCHING APPROACH BASED ON OPTICAL FLOW FIELD
Directory of Open Access Journals (Sweden)
W. Yuan
2016-06-01
Full Text Available Dense matching plays an important role in many fields, such as DEM (digital evaluation model producing, robot navigation and 3D environment reconstruction. Traditional approaches may meet the demand of accuracy. But the calculation time and out puts density is hardly be accepted. Focus on the matching efficiency and complex terrain surface matching feasibility an aerial image dense matching method based on optical flow field is proposed in this paper. First, some high accurate and uniformed control points are extracted by using the feature based matching method. Then the optical flow is calculated by using these control points, so as to determine the similar region between two images. Second, the optical flow field is interpolated by using the multi-level B-spline interpolation in the similar region and accomplished the pixel by pixel coarse matching. Final, the results related to the coarse matching refinement based on the combined constraint, which recognizes the same points between images. The experimental results have shown that our method can achieve per-pixel dense matching points, the matching accuracy achieves sub-pixel level, and fully meet the three-dimensional reconstruction and automatic generation of DSM-intensive matching’s requirements. The comparison experiments demonstrated that our approach’s matching efficiency is higher than semi-global matching (SGM and Patch-based multi-view stereo matching (PMVS which verifies the feasibility and effectiveness of the algorithm.
An Aerial-Image Dense Matching Approach Based on Optical Flow Field
Yuan, Wei; Chen, Shiyu; Zhang, Yong; Gong, Jianya; Shibasaki, Ryosuke
2016-06-01
Dense matching plays an important role in many fields, such as DEM (digital evaluation model) producing, robot navigation and 3D environment reconstruction. Traditional approaches may meet the demand of accuracy. But the calculation time and out puts density is hardly be accepted. Focus on the matching efficiency and complex terrain surface matching feasibility an aerial image dense matching method based on optical flow field is proposed in this paper. First, some high accurate and uniformed control points are extracted by using the feature based matching method. Then the optical flow is calculated by using these control points, so as to determine the similar region between two images. Second, the optical flow field is interpolated by using the multi-level B-spline interpolation in the similar region and accomplished the pixel by pixel coarse matching. Final, the results related to the coarse matching refinement based on the combined constraint, which recognizes the same points between images. The experimental results have shown that our method can achieve per-pixel dense matching points, the matching accuracy achieves sub-pixel level, and fully meet the three-dimensional reconstruction and automatic generation of DSM-intensive matching's requirements. The comparison experiments demonstrated that our approach's matching efficiency is higher than semi-global matching (SGM) and Patch-based multi-view stereo matching (PMVS) which verifies the feasibility and effectiveness of the algorithm.
Energy Technology Data Exchange (ETDEWEB)
Kumarasiri, Akila, E-mail: akumara1@hfhs.org; Siddiqui, Farzan; Liu, Chang; Yechieli, Raphael; Shah, Mira; Pradhan, Deepak; Zhong, Hualiang; Chetty, Indrin J.; Kim, Jinkoo [Department of Radiation Oncology, Henry Ford Health System, Detroit, Michigan 48202 (United States)
2014-12-15
Purpose: To evaluate the clinical potential of deformable image registration (DIR)-based automatic propagation of physician-drawn contours from a planning CT to midtreatment CT images for head and neck (H and N) adaptive radiotherapy. Methods: Ten H and N patients, each with a planning CT (CT1) and a subsequent CT (CT2) taken approximately 3–4 week into treatment, were considered retrospectively. Clinically relevant organs and targets were manually delineated by a radiation oncologist on both sets of images. Four commercial DIR algorithms, two B-spline-based and two Demons-based, were used to deform CT1 and the relevant contour sets onto corresponding CT2 images. Agreement of the propagated contours with manually drawn contours on CT2 was visually rated by four radiation oncologists in a scale from 1 to 5, the volume overlap was quantified using Dice coefficients, and a distance analysis was done using center of mass (CoM) displacements and Hausdorff distances (HDs). Performance of these four commercial algorithms was validated using a parameter-optimized Elastix DIR algorithm. Results: All algorithms attained Dice coefficients of >0.85 for organs with clear boundaries and those with volumes >9 cm{sup 3}. Organs with volumes <3 cm{sup 3} and/or those with poorly defined boundaries showed Dice coefficients of ∼0.5–0.6. For the propagation of small organs (<3 cm{sup 3}), the B-spline-based algorithms showed higher mean Dice values (Dice = 0.60) than the Demons-based algorithms (Dice = 0.54). For the gross and planning target volumes, the respective mean Dice coefficients were 0.8 and 0.9. There was no statistically significant difference in the Dice coefficients, CoM, or HD among investigated DIR algorithms. The mean radiation oncologist visual scores of the four algorithms ranged from 3.2 to 3.8, which indicated that the quality of transferred contours was “clinically acceptable with minor modification or major modification in a small number of contours
Non-Fourier based thermal-mechanical tissue damage prediction for thermal ablation.
Li, Xin; Zhong, Yongmin; Smith, Julian; Gu, Chengfan
2017-01-02
Prediction of tissue damage under thermal loads plays important role for thermal ablation planning. A new methodology is presented in this paper by combing non-Fourier bio-heat transfer, constitutive elastic mechanics as well as non-rigid motion of dynamics to predict and analyze thermal distribution, thermal-induced mechanical deformation and thermal-mechanical damage of soft tissues under thermal loads. Simulations and comparison analysis demonstrate that the proposed methodology based on the non-Fourier bio-heat transfer can account for the thermal-induced mechanical behaviors of soft tissues and predict tissue thermal damage more accurately than classical Fourier bio-heat transfer based model.
Preform design optimization for forging process based on the topological approach
Shao, Yong; Lu, Bin; Ou, Hengan; Cui, Zhenshan
2013-05-01
Preform design plays an important role in forging design especially for parts with complex shapes. In this paper, an attempt was made to develop a topological approach in the preform design of bulk metal forming processes based on the Bi-direction evolutionary structural optimization (BESO) strategy. In this approach, a new element addition and removal criteria based on the equivalent strain have been proposed for evaluating and optimizing the material flow in the forging process. To obtain a smooth preform boundary, a closed B-spline curve based on the least square approximation algorithm is employed to approximate the uneven surface of updated preform. An inhouse developed C♯ program has been employed to integrate the FE simluation, shape optimsation and surface approximation process. A 2D blade forging perform design problem are evaluate using the developed method. The results suggest that the optimized preform has shown better performance in improving the material flow and deformation uniformity during the forging. The results also demonstrate the robustness and efficiency of the developed preform design optimization method.
Tracking facial features in video sequences using a deformable-model-based approach
Malciu, Marius; Preteux, Francoise J.
2000-10-01
This paper addresses the issue of computer vision-based face motion capture as an alternative to physical sensor-based technologies. The proposed method combines a deformable template-based tracking of mouth and eyes in arbitrary video sequences with a single speaking person with a global 3D head pose estimation procedure yielding robust initializations. Mathematical principles underlying deformable template matching together with definition and extraction of salient image features are presented. Specifically, interpolating cubic B-splines between the MPEG-4 Face Animation Parameters (FAPs) associated with the mouth and eyes are used as template parameterization. Modeling the template a network of springs interconnecting with the mouth and eyes FAPs, the internal energy is expressed as a combination of elastic and symmetry local constraints. The external energy function, which allows to enforce interactions with image data, involves contour, texture and topography properties properly combined within robust potential functions. Template matching is achieved by applying the downhill simplex method for minimizing the global energy cost. Stability and accuracy of the results are discussed on a set of 2000 frames corresponding to 5 video sequences of speaking people.
Institute of Scientific and Technical Information of China (English)
王力平; 罗晓兰; 高强; 段梦兰; 徐健; 脱浩虎
2016-01-01
The ship’s anchor impact is easy to make submarine cable breakage and damage.It is very meaningful to carry out the research on the impact damage of submarine cable structure, which is very important for ensuring the safety of communication,power and production.Aiming at admiral anchor on the non-rigid bottom,a finite element model of drop anchor impacting photo-electric composite cable is created,and the plastic strain and sectional deformation of photoelectric composite cable are analyzed and calculated when admiral anchor dropped the cable.To find the strain and deformation trend of photoelectric composite cable structure of each layer are basic con-sistency,so the damage the internal structure from outer injury can be determined.Meanwhile,the comparative calculation and test results show that the light unit is more likely to suffer extrusion deformation than the electric unit.When the cross-sectional deformation of the photoelectric com-posite cable reaches 9%,the light unit of cable is damaged.%船锚撞击容易使海底电缆断裂、破损，为此，开展海底电缆结构的撞击损伤研究，对保障海底通讯通电生产安全具有非常重要的意义。针对非刚性底及质海军锚，建立落锚冲击光电复合缆的有限元计算模型，通过对落锚冲击时光电复合缆结构的等效塑性应变和截面变形量的计算分析，发现光电缆各层结构的应变和变形趋势基本一致，从而可以从外层铠装的损伤来判断内部结构的损伤情况。计算结果对比试验结果表明，光单元比电单元更容易遭受挤压变形，当光电缆的截面变形量达到9％，电缆中光单元受损。
Gordon, R. G.; Kreemer, C.
2015-12-01
Plate rigidity is the central tenet of plate tectonics. Mounting evidence suggests, however, that significant intraplate deformation occurs in oceanic lithosphere due to horizontal thermal contraction, the rate of which decreases as ≈ 1/age [Kumar & Gordon 2009]. Support for this hypothesis comes from the azimuths of submarine transform faults, which are fit significantly better assuming shrinking plates than by assuming rigid plates [Mishra & Gordon 2015]. Previously we estimated the intraplate velocity field of the Pacific plate accounting for horizontal thermal contraction. The ≈2 mm/yr southeastward motion predicted for the northeastern part of the plate relative to the Pacific-Antarctic Rise may contribute to the non-closure of the Pacific-North America plate motion circuit. In a reference frame in which fix the oldest portion of the Pacific plate, some sites on the plate move up to ≈2 mm/yr [Kreemer & Gordon 2014]. Here we present intraplate velocity fields of the Cocos and Nazca plates and discuss their implications for the non-rigidity of plates and the non-closure of the Pacific-Cocos-Nazca plate circuit, which fails closure by a stunning 14 ±5 mm/yr [DeMets et al. 2010]. If we fix the oldest part of the Cocos plate, intraplate velocities of up to ≈2 mm/yr are estimated, with the fastest motion occurring at the northern end of the plate. If we fix the oldest part of the Nazca plate, displacement rates up to 2 mm/yr are estimated, with the fastest motion occurring in the northeasternmost portion of the plate. In the velocity fields for both plates, the lithosphere adjacent to transform faults along the East Pacific Rise tends to move to the south, which would skew the azimuths of the transform faults clockwise of the values expected for rigid plates, which is the same as the sense of misfit between observed azimuths of transform faults and the azimuths calculated from the MORVEL global set of relative angular velocities [DeMets et al. 2010]. Direct
2012-11-01
first instantiations of isogeometric analysis were based on Non-Uniform Rational B-Splines ( NURBS ), and to date, NURBS -based isogeometric analysis has...compressible flow simulation technologies. In this work, we restrict ourselves to the NURBS -based isogeometric analysis approach, but we would like to...We utilize Non-Uniform Rational B-Splines ( NURBS ) basis functions to de- fine the discrete spaces. Making use of NURBS basis functions and the
Espath, L. F R
2015-02-03
A numerical model to deal with nonlinear elastodynamics involving large rotations within the framework of the finite element based on NURBS (Non-Uniform Rational B-Spline) basis is presented. A comprehensive kinematical description using a corotational approach and an orthogonal tensor given by the exact polar decomposition is adopted. The state equation is written in terms of corotational variables according to the hypoelastic theory, relating the Jaumann derivative of the Cauchy stress to the Eulerian strain rate.The generalized-α method (Gα) method and Generalized Energy-Momentum Method with an additional parameter (GEMM+ξ) are employed in order to obtain a stable and controllable dissipative time-stepping scheme with algorithmic conservative properties for nonlinear dynamic analyses.The main contribution is to show that the energy-momentum conservation properties and numerical stability may be improved once a NURBS-based FEM in the spatial discretization is used. Also it is shown that high continuity can postpone the numerical instability when GEMM+ξ with consistent mass is employed; likewise, increasing the continuity class yields a decrease in the numerical dissipation. A parametric study is carried out in order to show the stability and energy budget in terms of several properties such as continuity class, spectral radius and lumped as well as consistent mass matrices.
Path planning based on sliding window and variant A*algorithm for quadruped robot
Institute of Scientific and Technical Information of China (English)
张慧
2016-01-01
In order to improve the adaptability of the quadruped robot in complex environments , a path planning method based on sliding window and variant A * algorithm for quadruped robot is presen-ted .To improve the path planning efficiency and robot security , an incremental A*search algorithm ( IA*) and the A*algorithm having obstacle grids extending ( EA*) are proposed respectively .The IA* algorithm firstly searches an optimal path based on A * algorithm, then a new route from the current path to the new goal projection is added to generate a suboptimum route incrementally .In comparison with traditional method solving path planning problem from scratch , the IA* enables the robot to plan path more efficiently .EA* extends the obstacle by means of increasing grid g-value, which makes the route far away from the obstacle and avoids blocking the narrow passage .To navi-gate the robot running smoothly , a quadratic B-spline interpolation is applied to smooth the path . Simulation results illustrate that the IA* algorithm can increase the re-planning efficiency more than 5 times and demonstrate the effectiveness of the EA * algorithm.
Pérez, E A Coello
2015-01-01
We present a model-independent approach to electric quadrupole transitions of deformed nuclei. Based on an effective theory for axially symmetric systems, the leading interactions with electromagnetic fields enter as minimal couplings to gauge potentials, while subleading corrections employ gauge-invariant non-minimal couplings. This approach yields transition operators that are consistent with the Hamiltonian, and the power counting of the effective theory provides us with theoretical uncertainty estimates. We successfully test the effective theory in homonuclear molecules that exhibit a large separation of scales. For ground-state band transitions of rotational nuclei, the effective theory describes data well within theoretical uncertainties at leading order. In order to probe the theory at subleading order, data with higher precision would be valuable. For transitional nuclei, next-to-leading order calculations and the high-precision data are consistent within the theoretical uncertainty estimates. We also...
Campuzano, Saioa A.; Gómez-Paccard, Miriam; Pavón-Carrasco, Francisco Javier; Osete, María Luisa
2016-04-01
The knowledge of the ancient Earth's magnetic field is crucial to understand its origin and future evolution. In this context, the palaeomagnetic studies provide useful information about the past geomagnetic field registered in rocks, lava flows, sediments or archaeological materials. The continuous upgrade of the palaeomagnetic database during the last decade has allowed the generation of global geomagnetic field models based on different palaeomagnetic data and techniques (such as the SHA.DIF.14K, ARCH3K.1, CALS3K.4b, pfm9k.1a models, among others). Some recent studies have pointed out that the archaeointensity database might not be reliable enough, by observing high scatter in the records. Here, we present a new global geomagnetic model for the last 2000 years, SHAQ2K, based on high quality archaeomagnetic and volcanic intensity data. For this purpose we classify the palaeointensity data in two quality categories following widely accepted palaeomagnetic criteria based on the methodology used during the laboratory treatment of the samples and on the number of specimens finally used to calculate the mean intensities. Respect to the modelling process, we use the spherical harmonic analysis in space and cubic b-splines in time, also applying a spatial and temporal regularization which minimizes the energy of the geomagnetic field at the core-mantle boundary. The implications of the differences between this new model and other previously published global geomagnetic models are discussed.
Jin, BoCheng
2011-12-01
Organic and inorganic fiber reinforced composites with innumerable fiber orientation distributions and fiber geometries are abundantly available in several natural and synthetic structures. Inorganic glass fiber composites have been introduced to numerous applications due to their economical fabrication and tailored structural properties. Numerical characterization of such composite material systems is necessitated due to their intrinsic statistical nature, which renders extensive experimentation prohibitively time consuming and costly. To predict various mechanical behavior and characterizations of Uni-Directional Fiber Composites (UDFC) and Random Fiber Composites (RaFC), we numerically developed Representative Volume Elements (RVE) with high accuracy and efficiency and with complex fiber geometric representations encountered in uni-directional and random fiber networks. In this thesis, the numerical simulations of unidirectional RaFC fiber strand RVE models (VF>70%) are first presented by programming in ABAQUS PYTHON. Secondly, when the cross sectional aspect ratios (AR) of the second phase fiber inclusions are not necessarily one, various types of RVE models with different cross sectional shape fibers are simulated and discussed. A modified random sequential absorption algorithm is applied to enhance the volume fraction number (VF) of the RVE, which the mechanical properties represents the composite material. Thirdly, based on a Spatial Segment Shortest Distance (SSSD) algorithm, a 3-Dimentional RaFC material RVE model is simulated in ABAQUS PYTHON with randomly oriented and distributed straight fibers of high fiber aspect ratio (AR=100:1) and volume fraction (VF=31.8%). Fourthly, the piecewise multi-segments fiber geometry is obtained in MATLAB environment by a modified SSSD algorithm. Finally, numerical methods including the polynomial curve fitting and piecewise quadratic and cubic B-spline interpolation are applied to optimize the RaFC fiber geometries
Alternative 3D Modeling Approaches Based on Complex Multi-Source Geological Data Interpretation
Institute of Scientific and Technical Information of China (English)
李明超; 韩彦青; 缪正建; 高伟
2014-01-01
Due to the complex nature of multi-source geological data, it is difficult to rebuild every geological struc-ture through a single 3D modeling method. The multi-source data interpretation method put forward in this analysis is based on a database-driven pattern and focuses on the discrete and irregular features of geological data. The geological data from a variety of sources covering a range of accuracy, resolution, quantity and quality are classified and inte-grated according to their reliability and consistency for 3D modeling. The new interpolation-approximation fitting construction algorithm of geological surfaces with the non-uniform rational B-spline (NURBS) technique is then pre-sented. The NURBS technique can retain the balance among the requirements for accuracy, surface continuity and data storage of geological structures. Finally, four alternative 3D modeling approaches are demonstrated with reference to some examples, which are selected according to the data quantity and accuracy specification. The proposed approaches offer flexible modeling patterns for different practical engineering demands.
Sun, Wenjuan; Jia, Xianghong; Xie, Tianwu; Xu, Feng; Liu, Qian
2013-03-01
With the rapid development of China's space industry, the importance of radiation protection is increasingly prominent. To provide relevant dose data, we first developed the Visible Chinese Human adult Female (VCH-F) phantom, and performed further modifications to generate the VCH-F Astronaut (VCH-FA) phantom, incorporating statistical body characteristics data from the first batch of Chinese female astronauts as well as reference organ mass data from the International Commission on Radiological Protection (ICRP; both within 1% relative error). Based on cryosection images, the original phantom was constructed via Non-Uniform Rational B-Spline (NURBS) boundary surfaces to strengthen the deformability for fitting the body parameters of Chinese female astronauts. The VCH-FA phantom was voxelized at a resolution of 2 × 2 × 4 mm(3)for radioactive particle transport simulations from isotropic protons with energies of 5000-10 000 MeV in Monte Carlo N-Particle eXtended (MCNPX) code. To investigate discrepancies caused by anatomical variations and other factors, the obtained doses were compared with corresponding values from other phantoms and sex-averaged doses. Dose differences were observed among phantom calculation results, especially for effective dose with low-energy protons. Local skin thickness shifts the breast dose curve toward high energy, but has little impact on inner organs. Under a shielding layer, organ dose reduction is greater for skin than for other organs. The calculated skin dose per day closely approximates measurement data obtained in low-Earth orbit (LEO).
Adaptive statistic tracking control based on two-step neural networks with time delays.
Yi, Yang; Guo, Lei; Wang, Hong
2009-03-01
This paper presents a new type of control framework for dynamical stochastic systems, called statistic tracking control (STC). The system considered is general and non-Gaussian and the tracking objective is the statistical information of a given target probability density function (pdf), rather than a deterministic signal. The control aims at making the statistical information of the output pdfs to follow those of a target pdf. For such a control framework, a variable structure adaptive tracking control strategy is first established using two-step neural network models. Following the B-spline neural network approximation to the integrated performance function, the concerned problem is transferred into the tracking of given weights. The dynamic neural network (DNN) is employed to identify the unknown nonlinear dynamics between the control input and the weights related to the integrated function. To achieve the required control objective, an adaptive controller based on the proposed DNN is developed so as to track a reference trajectory. Stability analysis for both the identification and tracking errors is developed via the use of Lyapunov stability criterion. Simulations are given to demonstrate the efficiency of the proposed approach.
A NURBS-based generalized finite element scheme for 3D simulation of heterogeneous materials
Safdari, Masoud; Najafi, Ahmad R.; Sottos, Nancy R.; Geubelle, Philippe H.
2016-08-01
A 3D NURBS-based interface-enriched generalized finite element method (NIGFEM) is introduced to solve problems with complex discontinuous gradient fields observed in the analysis of heterogeneous materials. The method utilizes simple structured meshes of hexahedral elements that do not necessarily conform to the material interfaces in heterogeneous materials. By avoiding the creation of conforming meshes used in conventional FEM, the NIGFEM leads to significant simplification of the mesh generation process. To achieve an accurate solution in elements that are crossed by material interfaces, the NIGFEM utilizes Non-Uniform Rational B-Splines (NURBS) to enrich the solution field locally. The accuracy and convergence of the NIGFEM are tested by solving a benchmark problem. We observe that the NIGFEM preserves an optimal rate of convergence, and provides additional advantages including the accurate capture of the solution fields in the vicinity of material interfaces and the built-in capability for hierarchical mesh refinement. Finally, the use of the NIGFEM in the computational analysis of heterogeneous materials is discussed.
Thueler, Philippe; Charvet, Igor; Bevilacqua, Frederic; St Ghislain, M; Ory, G; Marquet, Pierre; Meda, Paolo; Vermeulen, Ben; Depeursinge, Christian
2003-07-01
A fast spectroscopic system for superficial and local determination of the absorption and scattering properties of tissue (480 to 950 nm) is described. The probe can be used in the working channel of an endoscope. The scattering properties include the reduced scattering coefficient and a parameter of the phase function called gamma, which depends on its first two moments. The inverse problem algorithm is based on the fit of absolute reflectance measurements to cubic B-spline functions derived from the interpolation of a set of Monte Carlo simulations. The algorithm's robustness was tested with simulations altered with various amounts of noise. The method was also assessed on tissue phantoms of known optical properties. Finally, clinical measurements performed endoscopically in vivo in the stomach of human subjects are presented. The absorption and scattering properties were found to be significantly different in the antrum and in the fundus and are correlated with histopathologic observations. The method and the instrument show promise for noninvasive tissue diagnostics of various epithelia.
A fault diagnosis approach for diesel engine valve train based on improved ITD and SDAG-RVM
Yu, Liu; Junhong, Zhang; Fengrong, Bi; Jiewei, Lin; Wenpeng, Ma
2015-02-01
Targeting the non-stationary characteristics of the vibration signals of a diesel engine valve train, and the limitation of the autoregressive (AR) model, a novel approach based on the improved intrinsic time-scale decomposition (ITD) and relevance vector machine (RVM) is proposed in this paper for the identification of diesel engine valve train faults. The approach mainly consists of three stages: First, prior to the feature extraction, non-uniform B-spline interpolation is introduced to the ITD method for the fitting of baseline signal, then the improved ITD is used to decompose the non-stationary signals into a set of stationary proper rotation components (PRCs). Second, the AR model is established for each PRC, and the first several AR coefficients together with the remnant variance of all PRCs are regarded as the fault feature vectors. Finally, a new separability based directed acyclic graph (SDAG) method is proposed to determine the structure of multi-class RVM, and the fault feature vectors are classified using the SDAG-RVM classifier to recognize the fault of the diesel engine valve train. The experimental results demonstrate that the proposed fault diagnosis approach can effectively extract the fault features and accurately identify the fault patterns.
Zhang, Dong; Zhang, Ting-Ting; Zhang, Xiao-Lei; Yang, Yan; Hu, Ying; Qin, Qian-Qing
2013-05-01
We present a new method of three-dimensional (3-D) seismic ray tracing, based on an improvement to the linear traveltime interpolation (LTI) ray tracing algorithm. This new technique involves two separate steps. The first involves a forward calculation based on the LTI method and the dynamic successive partitioning scheme, which is applied to calculate traveltimes on cell boundaries and assumes a wavefront that expands from the source to all grid nodes in the computational domain. We locate several dynamic successive partition points on a cell's surface, the traveltimes of which can be calculated by linear interpolation between the vertices of the cell's boundary. The second is a backward step that uses Fermat's principle and the fact that the ray path is always perpendicular to the wavefront and follows the negative traveltime gradient. In this process, the first-arriving ray path can be traced from the receiver to the source along the negative traveltime gradient, which can be calculated by reconstructing the continuous traveltime field with cubic B-spline interpolation. This new 3-D ray tracing method is compared with the LTI method and the shortest path method (SPM) through a number of numerical experiments. These comparisons show obvious improvements to computed traveltimes and ray paths, both in precision and computational efficiency.
An Optimized Spline-Based Registration of a 3D CT to a Set of C-Arm Images
Directory of Open Access Journals (Sweden)
2006-01-01
Full Text Available We have developed an algorithm for the rigid-body registration of a CT volume to a set of C-arm images. The algorithm uses a gradient-based iterative minimization of a least-squares measure of dissimilarity between the C-arm images and projections of the CT volume. To compute projections, we use a novel method for fast integration of the volume along rays. To improve robustness and speed, we take advantage of a coarse-to-fine processing of the volume/image pyramids. To compute the projections of the volume, the gradient of the dissimilarity measure, and the multiresolution data pyramids, we use a continuous image/volume model based on cubic B-splines, which ensures a high interpolation accuracy and a gradient of the dissimilarity measure that is well defined everywhere. We show the performance of our algorithm on a human spine phantom, where the true alignment is determined using a set of fiducial markers.
Neural Network Methods for NURBS Curve and Surface Interpolation
Institute of Scientific and Technical Information of China (English)
秦开怀
1997-01-01
New algorithms based on artificial neural network models are presented for cubic NURBS curve and surface interpolation.When all th knot spans are identical,the NURBS curve interpolation procedure degenerates into that of uniform rational B-spline curves.If all the weights of data points are identical,then the NURBS curve interpolation procedure degenerates into the integral B-spline curve interpolation.
Wavelet subdivision methods gems for rendering curves and surfaces
Chui, Charles
2010-01-01
OVERVIEW Curve representation and drawing Free-form parametric curves From subdivision to basis functions Wavelet subdivision and editing Surface subdivision BASIS FUNCTIONS FOR CURVE REPRESENTATION Refinability and scaling functions Generation of smooth basis functions Cardinal B-splines Stable bases for integer-shift spaces Splines and polynomial reproduction CURVE SUBDIVISION SCHEMES Subdivision matrices and stencils B-spline subdivision schemes Closed curve rendering Open curve rendering BASIS FUNCTIONS GENERATED BY SUBDIVISION MATRICES Subdivision operators The up-sampling convolution ope
Brownian Warps for Non-Rigid Registration
DEFF Research Database (Denmark)
Nielsen, Mads; Johansen, Peter; Jackson, Andrew D.;
2008-01-01
prior, we formulate a Partial Differential Equation for obtaining the maximally likely warp given matching constraints derived from the images. We solve for the free boundary conditions, and the bias toward smaller areas in the finite domain setting. Furthermore, we demonstrate the technique on 2D...
Non-rigid precession of magnetic stars
Lander, S K
2016-01-01
Stars are, generically, rotating and magnetised objects with a misalignment between their magnetic and rotation axes. Since a magnetic field induces a permanent distortion to its host, it provides effective rigidity even to a fluid star, leading to bulk stellar motion which resembles free precession. This bulk motion is however accompanied by induced interior velocity and magnetic field perturbations, which are oscillatory on the precession timescale. Extending previous work, we show that these quantities are described by a set of second-order perturbation equations featuring cross-terms scaling with the product of the magnetic and centrifugal distortions to the star. For the case of a background toroidal field, we reduce these to a set of differential equations in radial functions, and find a method for their solution. The resulting magnetic-field and velocity perturbations show complex multipolar structure and are strongest towards the centre of the star.
Nonrigid registration of myocardial perfusion MRI
DEFF Research Database (Denmark)
Ólafsdóttir, Hildur
2005-01-01
This paper describes a fully automatic registration of 10 multi-slice myocardial perfusion magnetic resonance image sequences. The registration of these sequences is crucial for the clinical interpretation, which currently is subjected to manual labour. The approach used in this study is a nonrig...
Automatic detection of diabetic foot complications with infrared thermography by asymmetric analysis
Liu, Chanjuan; van Netten, Jaap J.; van Baal, Jeff G.; Bus, Sicco A.; van der Heijden, Ferdi
2015-02-01
Early identification of diabetic foot complications and their precursors is essential in preventing their devastating consequences, such as foot infection and amputation. Frequent, automatic risk assessment by an intelligent telemedicine system might be feasible and cost effective. Infrared thermography is a promising modality for such a system. The temperature differences between corresponding areas on contralateral feet are the clinically significant parameters. This asymmetric analysis is hindered by (1) foot segmentation errors, especially when the foot temperature and the ambient temperature are comparable, and by (2) different shapes and sizes between contralateral feet due to deformities or minor amputations. To circumvent the first problem, we used a color image and a thermal image acquired synchronously. Foot regions, detected in the color image, were rigidly registered to the thermal image. This resulted in 97.8%±1.1% sensitivity and 98.4%±0.5% specificity over 76 high-risk diabetic patients with manual annotation as a reference. Nonrigid landmark-based registration with B-splines solved the second problem. Corresponding points in the two feet could be found regardless of the shapes and sizes of the feet. With that, the temperature difference of the left and right feet could be obtained.
Energy Technology Data Exchange (ETDEWEB)
Hogrebe, Luke; Paiva, Antonio R.; Jurrus, Elizabeth R.; Christensen, Cameron; Bridge, Michael; Dai, Li; Pfeiffer, Rebecca; Hof, Patrick; Roysam, Badrinath; Korenberg, Julie; Tasdizen, Tolga
2012-06-15
In the context of long-range digital neural circuit reconstruction, this paper investigates an approach for registering axons across histological serial sections. Tracing distinctly labeled axons over large distances allows neuroscientists to study very explicit relationships between the brain's complex interconnects and, for example, diseases or aberrant development. Large scale histological analysis requires, however, that the tissue be cut into sections. In immunohistochemical studies thin sections are easily distorted due to the cutting, preparation, and slide mounting processes. In this work we target the registration of thin serial sections containing axons. Sections are first traced to extract axon centerlines, and these traces are used to define registration landmarks where they intersect section boundaries. The trace data also provides distinguishing information regarding an axon's size and orientation within a section. We propose the use of these features when pairing axons across sections in addition to utilizing the spatial relationships amongst the landmarks. The global rotation and translation of an unregistered section are accounted for using a random sample consensus (RANSAC) based technique. An iterative nonrigid refinement process using B-spline warping is then used to reconnect axons and produce the sought after connectivity information.
DEFF Research Database (Denmark)
Carvalho, Diego D. B.; Arias Lorza, Andres Mauricio; Niessen, Wiro J.;
2017-01-01
An automated method for registering B-mode ultrasound (US) and magnetic resonance imaging (MRI) of the carotid arteries is proposed. The registration uses geometric features, namely, lumen centerlines and lumen segmentations, which are extracted fully automatically from the images after manual...... annotation of three seed points in US and MRI. The registration procedure starts with alignment of the lumen centerlines using a point-based registration algorithm. The resulting rigid transformation is used to initialize a rigid and subsequent non-rigid registration procedure that jointly aligns centerlines...
DEFF Research Database (Denmark)
Jubeli, Emile; Maginty, A. B.; Khalique, N. A.;
2016-01-01
a dimethylamine or trimethylamine headgroup, and a macrocyclic or an acyclic hydrophobic domain composed of, or derived from two 16-atom, succinic-based acyl chains. The synthesized lipids and a co-lipid of neutral charge, either cholesterol or 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE), were formulated...... within the hydrophobic domain of the cationic lipids was found to improve lipid hydration. The transfection assays revealed a general trend in which mismatched formulations that employed a rigid lipid combined with a non-rigid (or flexible) lipid, outperformed the matched formulations. The results from...
NURBS Interpolation Technology in CNC System Based on STEP-NC%基于STEP-NC的CNC系统中NURBS插补技术研究
Institute of Scientific and Technical Information of China (English)
杜娟; 田锡天; 张振明; 朱名铨; 李建克
2007-01-01
STEP-NC is a new interface standard for data exchanging and sharing between CAD/CAM and CNC, and the CNC based on STEP-NC will be the next generation of CNC controller, which not only holds linear and circular interpolation but also possesses the capability of spline interpolation. A universal NURBS ( non-uniform rational B-spline) based interpolator was designed and the interpolation technique based on constant arc increment and interpolation algorithm were inverstigated arc increment. The validity and reliability of algorithm was tested by an instance simulation and machining.%STEP-NC是一个用来实现CAD/CAM与CNC系统间数据交换的接口标准,基于STEP-NC的CNC系统是未来数控技术发展方向之一,该系统不但具有直线和圆弧插补功能,而且还具有样条曲线插补功能.为此设计了一个统一的基于NURBS样条曲线插补的通用插补器,并开发了一种基于等弧长的插补技术和插补算法.最后通过仿真和实例加工验证了该算法的有效性和可靠性.
Hybrid Modeling of CMM Dynamic Error Based on Improved Partial Least Squares%基于改进偏最小二乘的CMM动态误差混合建模分析
Institute of Scientific and Technical Information of China (English)
张梅; 费业泰
2012-01-01
三坐标测量机(CMM)动态误差源错综复杂,并且相互影响,因此很难建立一个通过误差源分析误差的准确预测模型.本文以空间测量位置的三维坐标值和测量机测量时的计算机直接控制(DCC)参数,包括移动速度、逼近距离和触测速度作为CMM动态测量误差模型的原始自变量,并通过3B样条变换获得各原始自变量与动态测量误差的非线性关系函数,再利用正交投影法把解释矩阵中与因变量无关的成分扣除掉,得到新的解释矩阵后再用偏最小二乘(PLS)回归进行降维和参数估计,从而得到CMM动态测量误差模型,即基于3B样条-正交投影偏最小二乘(3BSOPPLS)模型.这样既避免了分析错综复杂的误差源及其相互影响,又能够捕捉各自变量对动态测量误差的非线性影响,并能克服因解释变量过多而产生的多重共线性问题.实验结果表明建立的3BS-OPPLS模型的预测效果优于未经正交投影的3B样条-偏最小二乘(3BS-PLS)模型,模型的预测精度得到显著提高.%The error sources and their mutual influences on the dynamic measurement errors of coordinate measurement machine (CMM) are complicated, and it is hard to build an accurate model to forecast the dynamic measurement errors by analyzing error sources. A dynamic measurement error model was built based on 3B spline-orthogonal projection partial least squares(3BS-OPPLS) model, which took three-dimensional coordinates and direct computer control (DCC) parameters including positioning velocity, approximate distance and contact velocity as the original independent variables of the model, and obtained the nonlinear function between the original independent variables and the CMM dynamic measurement errors by the 3B spline transform. Then the method of orthogonal projection was used to deduct the components which are unrelated to the dependent variable in the explanatory matrix and a new explanatory matrix was achieved
Koo, Seungbum; Giori, Nicholas J; Gold, Garry E; Dyrby, Chris O; Andriacchi, Thomas P
2009-12-01
Cartilage morphology change is an important biomarker for the progression of osteoarthritis. The purpose of this study was to assess the accuracy of in vivo cartilage thickness measurements from MR image-based 3D cartilage models using a laser scanning method and to test if the accuracy changes with cartilage thickness. Three-dimensional tibial cartilage models were created from MR images (in-plane resolution of 0.55 mm and thickness of 1.5 mm) of osteoarthritic knees of ten patients prior to total knee replacement surgery using a semi-automated B-spline segmentation algorithm. Following surgery, the resected tibial plateaus were laser scanned and made into 3D models. The MR image and laser-scan based models were registered to each other using a shape matching technique. The thicknesses were compared point wise for the overall surface. The linear mixed-effects model was used for statistical test. On average, taking account of individual variations, the thickness measurements in MRI were overestimated in thinner (<2.5 mm) regions. The cartilage thicker than 2.5 mm was accurately predicted in MRI, though the thick cartilage in the central regions was underestimated. The accuracy of thickness measurements in the MRI-derived cartilage models systemically varied according to native cartilage thickness.
S, Kyriacou; E, Kontoleontos; S, Weissenberger; L, Mangani; E, Casartelli; I, Skouteropoulou; M, Gattringer; A, Gehrer; M, Buchmayr
2014-03-01
An efficient hydraulic optimization procedure, suitable for industrial use, requires an advanced optimization tool (EASY software), a fast solver (block coupled CFD) and a flexible geometry generation tool. EASY optimization software is a PCA-driven metamodel-assisted Evolutionary Algorithm (MAEA (PCA)) that can be used in both single- (SOO) and multiobjective optimization (MOO) problems. In MAEAs, low cost surrogate evaluation models are used to screen out non-promising individuals during the evolution and exclude them from the expensive, problem specific evaluation, here the solution of Navier-Stokes equations. For additional reduction of the optimization CPU cost, the PCA technique is used to identify dependences among the design variables and to exploit them in order to efficiently drive the application of the evolution operators. To further enhance the hydraulic optimization procedure, a very robust and fast Navier-Stokes solver has been developed. This incompressible CFD solver employs a pressure-based block-coupled approach, solving the governing equations simultaneously. This method, apart from being robust and fast, also provides a big gain in terms of computational cost. In order to optimize the geometry of hydraulic machines, an automatic geometry and mesh generation tool is necessary. The geometry generation tool used in this work is entirely based on b-spline curves and surfaces. In what follows, the components of the tool chain are outlined in some detail and the optimization results of hydraulic machine components are shown in order to demonstrate the performance of the presented optimization procedure.
Jurcak, V; Fripp, J; Engstrom, C; Walker, D; Salvado, O; Ourselin, S; Crozier, S
2008-01-01
This study presents a novel method for the automatic segmentation of the quadratus lumborum (QL) muscle from axial magnetic resonance (MR) images using a hybrid scheme incorporating the use of non-rigid registration with probabilistic atlases (PAs) and geodesic active contours (GACs). The scheme was evaluated on an MR database of 7mm axial images of the lumbar spine from 20 subjects (fast bowlers and athletic controls). This scheme involved several steps, including (i) image pre-processing, (ii) generation of PAs for the QL, psoas (PS) and erector spinae+multifidus (ES+MT) muscles and (iii) segmentation, using 3D GACs initialized and constrained by the propagation of the PAs using non-rigid registration. Pre-processing of the images involved bias field correction based on local entropy minimization with a bicubic spline model and a reverse diffusion interpolation algorithm to increase the slice resolution to 0.98 x 0.98 x 1.75mm. The processed images were then registered (affine and non-rigid) and used to generate an average atlas. The PAs for the QL, PS and ES+MT were then generated by propagation of manual segmentations. These atlases were further analysed with specialised filtering to constrain the QL segmentation from adjacent non-muscle tissues (kidney, fat). This information was then used in 3D GACs to obtain the final segmentation of the QL. The automatic segmentation results were compared with the manual segmentations using the Dice similarity metric (DSC), with a median DSC for the right and left QL muscles of 0.78 (mean = 0.77, sd=0.07) and 0.75 (mean =0.74, sd=0.07), respectively.
Institute of Scientific and Technical Information of China (English)
李桂清; 李华
2001-01-01
顶点位置和法向插值是参数曲面造型的重要内容．文中基于混合子分方法生成三次B样条控制网格，使得相应的三次B样条曲面插值初始网格中指定的顶点，并通过引入插值模板的概念，把法向的插值转化为对模板的旋转变换，使得曲面在不改变插值顶点的情况下插值法向，最后得到一张C2连续的插值指定顶点和法向的曲面．与传统的逐片Bézier或Coons曲面片构造方法相比，此方法更为简洁且具有更高的连续阶，而且易于推广到高阶B样条和任意拓扑情形，具有较强的实用性．%Interpolation to vertex positions and normals is one of important contents in parametric surface modeling. This paper presents an approach based on Catmull-Clark and Doo-Sabin subdivision schemes to generate the control net of bi-cubic B-spline surface interpolating the given vertices of initial net. The notion of stencils is introduced such that the normal interpolation is converted into the rotation transformation of stencils without influencing the effects of vertex interpolation, thus a C2-continuous surface interpolating given vertices and normals is obtained. Compared to traditional methods through stitching patches piece by piece, our method is more compact and has smoothness of higher degree. In addition, the method can be easily extended to high degree B-spline surfaces with arbitrary topology nets and it is also fairly useful for practical applications.
DBSC-Based Grayscale Line Image Vectorization
Institute of Scientific and Technical Information of China (English)
Konstantin Melikhov; Feng Tian; Jie Qiu; Quan Chen; Hock Soon Seah
2006-01-01
Vector graphics plays an important role in computer animation and imaging technologies. However present techniques and tools cannot fully replace traditional pencil and paper. Additionally, vector representation of an image is not always available. There is not yet a good solution for vectorizing a picture drawn on a paper. This work attempts to solve the problem of vectorizing grayscale line drawings. The solution proposed uses Disk B-Spline curves to represent strokes of an image in vector form. The algorithm builds a vector representation from a grayscale raster image, which can be a scanned picture for instance. The proposed method uses a Gaussian sliding window to calculate skeleton and perceptive width of a stroke. As a result of vectorization, the given image is represented by a set of Disk B-Spline curves.
Image Registration of Cochlear µCT Data Using Heat Distribution Similarity
DEFF Research Database (Denmark)
Kjer, Hans Martin; Vera, Sergio; Fagertun, Jens;
2015-01-01
Better understanding of the anatomical variability of the human cochlear is important for the design and function of Cochlear Implants. Good non-rigid alignment of high-resolution cochlear μCT data is a challenging task. In this paper we study the use of heat distribution similarity between sampl...... as an anatomical registration prior. We set-up and present our heat distribution model for the cochlea and utilize it in a typical cubic B-spline registration model. Evaluation and comparison is done against a corresponding normal registration of binary segmentations....
The role of continuity in residual-based variational multiscale modeling of turbulence
Akkerman, I.; Bazilevs, Y.; Calo, V.M.; Hughes, T.J.R.; Hulshoff, S.
2007-01-01
This paper examines the role of continuity of the basis in the computation of turbulent flows. We compare standard finite elements and non-uniform rational B-splines (NURBS) discretizations that are employed in Isogeometric Analysis (Hughes et al. in Comput Methods Appl Mech Eng, 194:4135–4195, 2005
Directory of Open Access Journals (Sweden)
Mehdi Rahnama
2014-11-01
Full Text Available Extraction and interpretation of tectonic lineaments is one of the routines for mapping large areas using remote sensing data. However, this is a subjective and time-consuming process. It is difficult to choose an optimal lineament extraction method in order to reduce subjectivity and obtain vectors similar to what an analyst would manually extract. The objective of this study is the implementation, evaluation and comparison of Hough transform, segment merging and polynomial fitting methods towards automated tectonic lineament mapping. For this purpose we developed a new MATLAB-based toolbox (TecLines. The proposed toolbox capabilities were validated using a synthetic Digital Elevation Model (DEM and tested along in the Andarab fault zone (Afghanistan where specific fault structures are known. In this study, we used filters in both frequency and spatial domains and the tensor voting framework to produce binary edge maps. We used the Hough transform to extract linear image discontinuities. We used B-spline as a polynomial curve fitting method to eliminate artificial line segments that are out of interest and to link discontinuous segments with similar trends. We performed statistical analyses in order to compare the final image discontinuities maps with existing references map.
Bazilevs, Y.; Kamran, K.; Moutsanidis, G.; Benson, D. J.; Oñate, E.
2017-03-01
In this two-part paper we begin the development of a new class of methods for modeling fluid-structure interaction (FSI) phenomena for air blast. We aim to develop accurate, robust, and practical computational methodology, which is capable of modeling the dynamics of air blast coupled with the structure response, where the latter involves large, inelastic deformations and disintegration into fragments. An immersed approach is adopted, which leads to an a-priori monolithic FSI formulation with intrinsic contact detection between solid objects, and without formal restrictions on the solid motions. In Part I of this paper, the core air-blast FSI methodology suitable for a variety of discretizations is presented and tested using standard finite elements. Part II of this paper focuses on a particular instantiation of the proposed framework, which couples isogeometric analysis (IGA) based on non-uniform rational B-splines and a reproducing-kernel particle method (RKPM), which is a Meshfree technique. The combination of IGA and RKPM is felt to be particularly attractive for the problem class of interest due to the higher-order accuracy and smoothness of both discretizations, and relative simplicity of RKPM in handling fragmentation scenarios. A collection of mostly 2D numerical examples is presented in each of the parts to illustrate the good performance of the proposed air-blast FSI framework.
Surface Reconstruction Based on Points Cloud Data from CMM%基于三坐标测量数据的点云曲面重构
Institute of Scientific and Technical Information of China (English)
吴雪梅; 文珈; 于广滨; 李瑰贤; 单德彬
2011-01-01
基于CMM测量数据,针对鼠标数据的特点,进行了边界拟合、特征识别、分片重建、光滑拼接等技术的研究.利用三次B样条拟合边界曲线,利用微分几何方法进行曲面特征的识别与分割,利用拉伸及放样法进行曲面片重构,最后进行曲面片相交、剪裁、过渡完成最终的鼠标模型.%Based on CMM data, the some critical techniques has been researched: boundary fitting, characteristic identifying, surface patch reconstructing, smooth matching considering the feature of mouse data. By employing cubic B-spline curves to fit boundary curves, differential coefficient geometry method to do surface characteristic identifying and division, and pulling and molding methods to accomplish surface patch reconstruction, the mouse model is finally fulfilled through surface patch intersecting, cutting out and transition.
Physics-based shape matching for intraoperative image guidance
Energy Technology Data Exchange (ETDEWEB)
Suwelack, Stefan, E-mail: suwelack@kit.edu; Röhl, Sebastian; Bodenstedt, Sebastian; Reichard, Daniel; Dillmann, Rüdiger; Speidel, Stefanie [Institute for Anthropomatics and Robotics, Karlsruhe Institute of Technology, Adenauerring 2, Karlsruhe 76131 (Germany); Santos, Thiago dos; Maier-Hein, Lena [Computer-assisted Interventions, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, Heidelberg 69120 (Germany); Wagner, Martin; Wünscher, Josephine; Kenngott, Hannes; Müller, Beat P. [General, Visceral and Transplantation Surgery, Heidelberg University Hospital, Im Neuenheimer Feld 110, Heidelberg 69120 (Germany)
2014-11-01
Purpose: Soft-tissue deformations can severely degrade the validity of preoperative planning data during computer assisted interventions. Intraoperative imaging such as stereo endoscopic, time-of-flight or, laser range scanner data can be used to compensate these movements. In this context, the intraoperative surface has to be matched to the preoperative model. The shape matching is especially challenging in the intraoperative setting due to noisy sensor data, only partially visible surfaces, ambiguous shape descriptors, and real-time requirements. Methods: A novel physics-based shape matching (PBSM) approach to register intraoperatively acquired surface meshes to preoperative planning data is proposed. The key idea of the method is to describe the nonrigid registration process as an electrostatic–elastic problem, where an elastic body (preoperative model) that is electrically charged slides into an oppositely charged rigid shape (intraoperative surface). It is shown that the corresponding energy functional can be efficiently solved using the finite element (FE) method. It is also demonstrated how PBSM can be combined with rigid registration schemes for robust nonrigid registration of arbitrarily aligned surfaces. Furthermore, it is shown how the approach can be combined with landmark based methods and outline its application to image guidance in laparoscopic interventions. Results: A profound analysis of the PBSM scheme based on in silico and phantom data is presented. Simulation studies on several liver models show that the approach is robust to the initial rigid registration and to parameter variations. The studies also reveal that the method achieves submillimeter registration accuracy (mean error between 0.32 and 0.46 mm). An unoptimized, single core implementation of the approach achieves near real-time performance (2 TPS, 7–19 s total registration time). It outperforms established methods in terms of speed and accuracy. Furthermore, it is shown that the
Institute of Scientific and Technical Information of China (English)
黄海峤; 王英男
2011-01-01
A new systematic approach is proposed based on three dimensional (3D) human body data to establish a developable 3D prototype garment, and two dimensional (2D) patterns are generated. Firstly, body features and landmarks are defined to develop a basic wireframe by piecewise horizontal B-spline curve (PHBC) model. Then, ease are distributed into the basic wireframe in order to guarantee appropriate fit, and a new algorithm called developable boundary triangulation (DBT) is implemented to generate 3D developable garment based on the fit wireframe. Finally, 2D patterns are obtained by flattening the 3D garment.%基于3D人体数据,提出一种新的3D服装原型建模方式,并通过展开得到2D服装样板.首先利用分段水平B样条曲线(PHBC)建立参数化人台,识别人体标记点和服装结构线框架模型,然后分布适当松量在框架模型之中,同时实现基于框架模型的可展曲面构造方法——DBT算法,最后通过整合带有松量的框架和DBT算法,构建出可展3D服装原型,并生成服装样板.
Accurate alignment of functional EPI data to anatomical MRI using a physics-based distortion model.
Studholme, C; Constable, R T; Duncan, J S
2000-11-01
Mapping of functional magnetic resonance imaging (fMRI) to conventional anatomical MRI is a valuable step in the interpretation of fMRI activations. One of the main limits on the accuracy of this alignment arises from differences in the geometric distortion induced by magnetic field inhomogeneity. This paper describes an approach to the registration of echo planar image (EPI) data to conventional anatomical images which takes into account this difference in geometric distortion. We make use of an additional spin echo EPI image and use the known signal conservation in spin echo distortion to derive a specialized multimodality nonrigid registration algorithm. We also examine a plausible modification using log-intensity evaluation of the criterion to provide increased sensitivity in areas of low EPI signal. A phantom-based imaging experiment is used to evaluate the behavior of the different criteria, comparing nonrigid displacement estimates to those provided by a imagnetic field mapping acquisition. The algorithm is then applied to a range of nine brain imaging studies illustrating global and local improvement in the anatomical alignment and localization of fMRI activations.
Institute of Scientific and Technical Information of China (English)
吴泽福
2012-01-01
Based on the comparision of basic static estimate methods of term structure of interest rate (TSIR), we improved B-spline function estimate method, which involved optimization on estimation programmes, node numbers choice, and node placement design. To overcome the subjective effect of B-spline node distribution and C2 smoothness condition of discount function, we introduced negative exponential smoothness cubic Li-spline optimization technology with minimum constraint function of estimation error from quadratic sum to absolute value and minimum volatility of discount function, to increase the estimation reliability and prediction ability of short-term interest rate's volatility structure mutation, improve the advantage on depicting the long-term interest rate volatility trend, and reduce the excessive volatility of discount function.%通过对比国内外利率期限结构静态估计模型的优劣,分析节点数目变化和定位改进B样条函数对利率期限结构静态估计的误差,构建最小化定价误差的节点组合布局搜索程序,并引入负指数平滑立方L1样条优化模型,将误差函数最小化结构从平方和最小化转化为误差距离最小化,权衡拟合误差绝对距离最小化与贴现函数波动性约束,克服B样条函数对节点数目与定位的人工干预和放宽对贴现函数的二阶平滑要求,保留B样条函数刻画中长期利率波动趋势的优势,增强对短期利率波动结构突变的估计和预测能力,提高定价精确度和缓解利率期限结构曲线的过度波动问题.
Research on Intensity and Shape Based Non-rigid Image Registration%基于灰度和形状的非刚性图像配准算法的研究
Institute of Scientific and Technical Information of China (English)
林相波; 邱天爽; RUAN Su; Frédéric Morain-Nicolier
2009-01-01
提出一种新的灰度和形状信息相结合的全自动同模态医学图像非刚性配准-分割算法,将欧氏距离表示的形状信息融入基于灰度的配准算法中,构造出新的代价函数.该算法在医学图像多目标分割的应用中,能够较好地完成灰度相近、边缘模糊、间距较小的不同结构的分割.对5组真实脑部MRI图像进行分割脑深层灰质结构的实验,结果表明,本算法优于基于灰度信息的图像配准算法.
Non-Rigid Medical Image Registration Based on the Thin-Plate Spline%基于薄板样条的非刚体医学图像配准
Institute of Scientific and Technical Information of China (English)
方柏林; 唐慧慧
2010-01-01
非刚体图象配准是非线性的图像配准方法,它能够实现图像之间的配准,为提高医学图像配准精度,对于形变较大的多模图像的配准等都有着重要的作用.提出了一种基于薄板样条的3D/2D非刚体医学图象配准算法,算法首先提出一个混合能量公式,在配准的过程中,用薄板样条法实现全局配准,并通过仿真退火算法进行迭代,以缩小并确定变形的待配准区域.在局部的待配准区域,采用互信息的方法进行配准.解决了因特征点不足引起的不完整匹配问题,使得图像连续平滑,以得到较优的配准效果.
Mutual Information Based Registration for 3D Non-Rigid Medical Images%基于互信息非刚性医学图像配准的方法
Institute of Scientific and Technical Information of China (English)
陈昱; 庄天戈
1999-01-01
提出了一种基于互信息的对非刚性三维医学图像进行弹性配准的方法.用2D联合直方图法计算两幅图像重叠部分的图像灰度之间的互信息,使之最大化,从而实现两图像之间的全局仿射配准.然后将两幅图像的重叠部分均分成互为重叠的体积子块,再最大化每对对应体积子块图像灰度之间的互信息,实现每对对应子决的局部刚体配准,并将每个子块的中心作为一一对应的控制点.利用这些均匀分布的控制点对结合薄平板样条插值法实现图像的全局非刚性弹性配准.实验结果表明,该算法可以有效地实现三维图像全局弹性配准,但计算时间较长.
ON NATURAL CHARACTERISTICS OF A RIGID MOTOR FLEXIBLE BASE DYNAMIC COUPLED SYSTEM
Institute of Scientific and Technical Information of China (English)
Sun Yuguo; Song Kongjie
2004-01-01
In shipping and aircraft engineering,the vibrating motor or instrumentation is usually mounted on a non-rigid base.To apply isolation design effectively,it is necessary to investigate the nature vibration characteristics of the rigid motor,flexible base coupled system.A universal dynamic express for the coupled system is derived.A PC-based measurement solution is presented.And the system's dynamic behavior is then investigated numerically and experimentally.The results show that a strong interaction will exist between the motor's rigid mode and the flexible base's mode when the motor's mounting frequency is close to the flexible base's first natural frequency.The first natural frequency of the coupled system is generally lower than the motor's rigid mode frequency.At high frequency,the flexible base's modes are the dominant modes of the coupled system.
有理B样条曲面的区间隐式化%Interval Implicitization of Rational B-Spline Surfaces
Institute of Scientific and Technical Information of China (English)
陈越强; 冯玉瑜; 邓建松
2007-01-01
提出有理B样条曲面的区间隐式化方法,即对一个有理B样条曲面,寻求包含给定的曲面的区间隐式B样条曲面,使得区间隐式B样条曲面的"厚度"尽量小,同时尽量避免出现多余分支.该问题等价于求区间隐式B样条曲面的2个边界曲面.针对该问题建立一个最优化模型并求解.
Convolution Surface Modeling for Cubic B-Spline Skeletons%三次B样条曲线骨架卷积曲面造型
Institute of Scientific and Technical Information of China (English)
张海林; 金小刚; 冯结青
2006-01-01
提出一种基于B样条曲线降阶的三次B样条曲线骨架卷积曲面造型方法.首先通过顶点扰动降阶方法把三次B样条曲线骨架(C1连续)降阶为C1连续的二次B样条,然后应用二次B样条曲线骨架的卷积曲面势函数计算方法得到三次B样条曲线骨架的势函数.
双三次B样条曲面的G1连续条件%G1 Continuity Conditions of Bicubic B-Spline Surfaces
Institute of Scientific and Technical Information of China (English)
施锡泉; 赵岩
2002-01-01
讨论并得到关于两个双三次非均匀内部单节点B样条曲面片G1连续的充分必要条件,以及在公共边界线上控制向量的本征条件.这些条件直接由两个非均匀B样条曲面的控制向量表示.并证明了用单节点双三次非均匀B样条不能构造出具有局部性质的曲面模型.
Offset Algorithm and Its Applications of B-Spline Curves%B样条曲线的等距算法及应用
Institute of Scientific and Technical Information of China (English)
朱朝艳; 陈小雕
2010-01-01
等距曲线的拓扑结构是等距算法中的核心因素之一.该文以B样条曲线为例,给出了一种基于关键点的等距算法.它应用了自适应离散等手段并给出了关键点的求解方法,同时利用关键点确定等距线各个分段的取舍,从而有效地去除自交的情况,使得计算出的等距曲线有着正确的拓扑结构.该文的算法已应用于商业软件OpenCAD中.
有理三次均匀B样条曲线的形状控制%Shape Control for Rational Cubic Uniform B-Spline Curves
Institute of Scientific and Technical Information of China (English)
雷开彬
2000-01-01
采用建立局部仿射坐标系的方法,研究了有理三次均匀B样条的几何结构及端点性质.给出了有理三次均匀B样条曲线的几何形状修改法,使对该样条曲线的修改更加灵活、方便.
双五次B-样条曲面的G2连续条件%G2 CONTINUOS CONDITIONS OF BIQUINTIC B-SPLINE SURFACES
Institute of Scientific and Technical Information of China (English)
赵岩; 施锡泉
2004-01-01
Some practical problems in designing the outline of hidden airplane require to construct high-order surfaces with at least second order continuity. The high-order smooth surfaces'construction has been always a difficuit problem in CAGD. In this paper, G2 smoothness between two biquintic surface patches is discussed, and the intrinsic conditions of the control vectors of the common boundary curve are presented.
Bejancu, Aurelian
2006-12-01
This paper considers the problem of interpolation on a semi-plane grid from a space of box-splines on the three-direction mesh. Building on a new treatment of univariate semi-cardinal interpolation for natural cubic splines, the solution is obtained as a Lagrange series with suitable localization and polynomial reproduction properties. It is proved that the extension of the natural boundary conditions to box-spline semi-cardinal interpolation attains half of the approximation order of the cardinal case.
Cubic B-spline interpolation for one-dimensional search method%一维搜索问题的三次B样条插值法
Institute of Scientific and Technical Information of China (English)
罗煦琼
2008-01-01
基于一元三次B样条函数插值, 给出了一种求解一维搜索问题的新算法和数值实验结果. 结果表明,新算法能很快地求出全局最优解, 且剖分数越大, 精度越高.
带法向约束的3次均匀B样条曲线插值%Cubic uniform B-spline curves interpolation with normal constrains
Institute of Scientific and Technical Information of China (English)
胡巧莉; 寿华好
2014-01-01
基于3次均匀B样条曲线段的端点性质,及其与控制顶点构成的三角形的几何关系,提出了一种插值给定顶点与法向约束的3次均匀B样条曲线构造算法.与以往B样条曲线的顶点法向插值算法不同的是,本算法结合由控制顶点构成的三角形的几何性质求解新添加的控制顶点,可生成严格插值型值点并且在型值点处法向与给定法向无偏移的B样条曲线.
Planning and Simulation of Wafer-handling Robot Trajectories Based on ADAMS%基于ADAMS的硅片传输机器人轨迹规划及仿真
Institute of Scientific and Technical Information of China (English)
张昊; 孙强; 李龙晶; 丛明
2013-01-01
为了提高硅片传输机器人运动的平滑性,采用5次均匀B样条插值方法进行轨迹规划,并利用两种遗传算法对轨迹进行优化.以硅片传输机器人为研究对象,基于ADAMS软件对机器人进行轨迹仿真分析.结果表明,自适应混合遗传算法与自适应遗传算法相比,具有较好的局部搜索能力,能够得到性能更好的解.获得的轨迹具有脉动连续的特点,有利于提高机器人在运动过程中的轨迹跟踪精度.%In order to improve running smoothness of wafer-handling robot, uniform B-splines of five degree is exploited in order to get joint trajectories. Two kinds of genetic algorithm are proposed to solve the optimization problem. Simulation analysis is implemented based on ADAMS. The results show that the algorithm above used can improve the solution quality. The trajectories generated by the proposed planner have the advantage of continuous jerk, can improve the trajectory tracking accuracy in the moving process.
基于暗原色先验的雾天图像车牌定位%License Plate Location Based on Dark Channel Prior in Fog-degraded Images
Institute of Scientific and Technical Information of China (English)
鞠丽丽; 王英
2016-01-01
在雾天条件下，会影响到基于传统车牌识别方法的车牌识别系统的车牌识别准确率。首先根据He提出的暗原色先验原理应用IMF算法对图像去雾处理；然后进行小波边缘检测，定位车牌候选区域；最后根据车牌先验知识定位车牌区域。实验表明，该方法对雾天条件下车牌定位有良好的效果。%Fog weather conditions affect the license plate recognition system accuracy,which based on traditional license plate recognition method.Firstly,this paper employs Dark Channel Prior principle proposed by He to eliminate the influence of fog weather.Secondly uses b-spline wavelet edge detection to position license plate candidate area of restored images,final-ly locates the license plate according to the the candidate area.
SU-E-J-209: Verification of 3D Surface Registration Between Stereograms and CT Images
Energy Technology Data Exchange (ETDEWEB)
Han, T; Gifford, K [UT MD Anderson Cancer Center, Houston, TX (United States); Smith, B [MD Anderson Cancer Center, Houston, TX (United States); Salehpour, M [M.D. Anderson Cancer Center, Houston, TX (United States)
2014-06-01
Purpose: Stereography can provide a visualization of the skin surface for radiation therapy patients. The aim of this study was to verify the registration algorithm in a commercial image analysis software, 3dMDVultus, for the fusion of stereograms and CT images. Methods: CT and stereographic scans were acquired of a head phantom and a deformable phantom. CT images were imported in 3dMDVultus and the surface contours were generated by threshold segmentation. Stereograms were reconstructed in 3dMDVultus. The resulting surfaces were registered with Vultus algorithm and then exported to in-house registration software and compared with four algorithms: rigid, affine, non-rigid iterative closest point (ICP) and b-spline algorithm. RMS (root-mean-square residuals of the surface point distances) error between the registered CT and stereogram surfaces was calculated and analyzed. Results: For the head phantom, the maximum RMS error between registered CT surfaces to stereogram was 6.6 mm for Vultus algorithm, whereas the mean RMS error was 0.7 mm. For the deformable phantom, the maximum RMS error was 16.2 mm for Vultus algorithm, whereas the mean RMS error was 4.4 mm. Non-rigid ICP demonstrated the best registration accuracy, as the mean of RMS errors were both within 1 mm. Conclusion: The accuracy of registration algorithm in 3dMDVultus was verified and exceeded RMS of 2 mm for deformable cases. Non-rigid ICP and b-spline algorithms improve the registration accuracy for both phantoms, especially in deformable one. For those patients whose body habitus deforms during radiation therapy, more advanced nonrigid algorithms need to be used.
Curve interpolation based on Catmull-Clark subdivision scheme
Institute of Scientific and Technical Information of China (English)
无
2003-01-01
An efficient algorithm for curve interpolation is proposed. The algorithm can produce a subdivision surface that can interpolate the predefined cubic B-spline curves by applying the Catmull-Clark scheme to a polygonal mesh containing "symmetric zonal meshes", which possesses some special properties. Many kinds of curve interpolation problems can be dealt with by this algorithm, such as interpolating single open curve or closed curve, a mesh of nonintersecting or intersecting curve. The interpolating surface is C2 everywhere excepting at a finite number of points. At the same time, sharp creases can also be modeled on the limit subdivision surface by duplicating the vertices of the tagged edges of initial mesh, i.e. the surface is only C0 along the cubic B-spline curve that is defined by the tagged edges. Because of being simple and easy to implement, this method can be used for product shape design and graphic software development.
Institute of Scientific and Technical Information of China (English)
姜慧; 谭京; 王新知
2012-01-01
目的:评价带有非刚性连接体与刚性连接体后牙四单位金属翼板粘结桥在模拟口腔功能状态下抗疲劳寿命的差别.方法:选择新鲜完整的离体人第一前磨牙和第二磨牙作为基牙包埋于自凝树脂中,模拟第二前磨牙和第一磨牙的连续缺失,制作10个模型试块,随机均分为两组,实验组在第一前磨牙的远中设计栓体栓道式非刚性连接体,在第二磨牙的近中设计刚性连接体；对照组制作双端刚性连接的四单位金属翼板粘结桥,将试块置于冷热循环机械载荷咀嚼模拟疲劳试验机上进行加载,记录粘结桥发生破坏时的循环加载次数.结果:实验组与对照组初次粘结后发生破坏时的平均循环加载次数分别为(134.34±8.17)万次和(92.58±19.73)万次,经过独立样本t检验(双侧,α =0.05),差异具有统计学意义(P＜0.05),即一端带有非刚性连接体的后牙四单位金属翼板粘结桥比双端均为刚性连接的后牙四单位金属翼板粘结桥的抗疲劳寿命长.结论:在体外模拟使用一端为非刚性连接体的长跨度金属翼板粘接桥的寿命要长于两端均为刚性连接体的传统粘接桥,结果需临床进一步验证.%Objective: The aim of this study was to test the difference of fatigue longevity between the 4-unit posterior resin-bonded fixed partial dentures (RBFPD)with non-rigid connector and rigid connector, a wear test to stimulate masticatary function was used. Methods; Extracted intact human teeth were used to prepare specimens, a first premolar and a second molar as the abutment teeth with a space equivalent to a second premolar and a first molar. Ten specimens were seperated into two groups randomly. The control group was prepared to receive conventional RBFPDs; in the test group a non-rigid connector was used on the distal side of the first premolar. The specimens were put on the thermocycling and mechanical loading (TCML) chewing simulator until the
NURBS reconstruction of digital terrain for hydropower engineering based on TIN model
Institute of Scientific and Technical Information of China (English)
Denghua Zhong; Jie Liu; Mingchao Li; Caiwei Hao
2008-01-01
Digital terrain model (DTM) has played an important role in 3D designing, visual analysis and 3D geological modeling in large-scale hydropower engineering. As the pivotal base of 3D visualization and modeling, DTM should be characterized by high precision, less storage and well interactivity during graphic operation. Considering the diversity of data source and taking advantage of two data structures, triangulated irregular network (TIN) and non-uniform rational B-splines (NURBS), a novel methodology is presented for reconstructing engineering terrain of hydropower project. With integration of multi-source data, enhanced Delaunay algorithm is introduced to rebuild the TI NDTM, which is a terrain surface in TIN and a faithful depiction of complex topography but in low-memory efficiency. Based on the TIN model, applying section scanning sampling and linear interpolation, the transformation from discrete, irregular and diverse data to continuous and regular sampling cross-sectional curve sequence, is realized. The appropriate compression of the sampling data is also imposed to be performed for guaranteeing the following reconstruction work. Eventually, employing the NURBS technique and skinning method, the NURBS-DTM, which represents a NURBS surface and satisfies the requirement after precision assess with weighted errors, is reconstructed with the intermediate data. Meanwhile, there is another achievement that two databases of terrain data, one from initial data and the other from sampling data, are established for repeatable reconstruction with different demands. With the successful application of the presented method, a stable foundation is laid for 3D engineering geological modeling, visual designing and analysis of the hydropower projects.
Pectus excavatum postsurgical outcome based on preoperative soft body dynamics simulation
Moreira, Antonio H. J.; Rodrigues, Pedro L.; Fonseca, Jaime; Pinho, A. C. M.; Rodrigues, Nuno F.; Correia-Pinto, Jorge; Vilaça, João L.
2012-02-01
Pectus excavatum is the most common congenital deformity of the anterior chest wall, in which an abnormal formation of the rib cage gives the chest a caved-in or sunken appearance. Today, the surgical correction of this deformity is carried out in children and adults through Nuss technic, which consists in the placement of a prosthetic bar under the sternum and over the ribs. Although this technique has been shown to be safe and reliable, not all patients have achieved adequate cosmetic outcome. This often leads to psychological problems and social stress, before and after the surgical correction. This paper targets this particular problem by presenting a method to predict the patient surgical outcome based on pre-surgical imagiologic information and chest skin dynamic modulation. The proposed approach uses the patient pre-surgical thoracic CT scan and anatomical-surgical references to perform a 3D segmentation of the left ribs, right ribs, sternum and skin. The technique encompasses three steps: a) approximation of the cartilages, between the ribs and the sternum, trough b-spline interpolation; b) a volumetric mass spring model that connects two layers - inner skin layer based on the outer pleura contour and the outer surface skin; and c) displacement of the sternum according to the prosthetic bar position. A dynamic model of the skin around the chest wall region was generated, capable of simulating the effect of the movement of the prosthetic bar along the sternum. The results were compared and validated with patient postsurgical skin surface acquired with Polhemus FastSCAN system.
Reconstruction of large, irregularly sampled multidimensional images. A tensor-based approach.
Morozov, Oleksii Vyacheslav; Unser, Michael; Hunziker, Patrick
2011-02-01
Many practical applications require the reconstruction of images from irregularly sampled data. The spline formalism offers an attractive framework for solving this problem; the currently available methods, however, are hard to deploy for large-scale interpolation problems in dimensions greater than two (3-D, 3-D+time) because of an exponential increase of their computational cost (curse of dimensionality). Here, we revisit the standard regularized least-squares formulation of the interpolation problem, and propose to perform the reconstruction in a uniform tensor-product B-spline basis as an alternative to the classical solution involving radial basis functions. Our analysis reveals that the underlying multilinear system of equations admits a tensor decomposition with an extreme sparsity of its one dimensional components. We exploit this property for implementing a parallel, memory-efficient system solver. We show that the computational complexity of the proposed algorithm is essentially linear in the number of measurements and that its dependency on the number of dimensions is significantly less than that of the original sparse matrix-based implementation. The net benefit is a substantial reduction in memory requirement and operation count when compared to standard matrix-based algorithms, so that even 4-D problems with millions of samples become computationally feasible on desktop PCs in reasonable time. After validating the proposed algorithm in 3-D and 4-D, we apply it to a concrete imaging problem: the reconstruction of medical ultrasound images (3-D+time) from a large set of irregularly sampled measurements, acquired by a fast rotating ultrasound transducer.
Gonizzi Barsanti, S.; Guidi, G.
2017-02-01
Conservation of Cultural Heritage is a key issue and structural changes and damages can influence the mechanical behaviour of artefacts and buildings. The use of Finite Elements Methods (FEM) for mechanical analysis is largely used in modelling stress behaviour. The typical workflow involves the use of CAD 3D models made by Non-Uniform Rational B-splines (NURBS) surfaces, representing the ideal shape of the object to be simulated. Nowadays, 3D documentation of CH has been widely developed through reality-based approaches, but the models are not suitable for a direct use in FEA: the mesh has in fact to be converted to volumetric, and the density has to be reduced since the computational complexity of a FEA grows exponentially with the number of nodes. The focus of this paper is to present a new method aiming at generate the most accurate 3D representation of a real artefact from highly accurate 3D digital models derived from reality-based techniques, maintaining the accuracy of the high-resolution polygonal models in the solid ones. The approach proposed is based on a wise use of retopology procedures and a transformation of this model to a mathematical one made by NURBS surfaces suitable for being processed by volumetric meshers typically embedded in standard FEM packages. The strong simplification with little loss of consistency possible with the retopology step is used for maintaining as much coherence as possible between the original acquired mesh and the simplified model, creating in the meantime a topology that is more favourable for the automatic NURBS conversion.
Digitalized accurate modeling of SPCB with multi-spiral surface based on CPC algorithm
Huang, Yanhua; Gu, Lizhi
2015-09-01
The main methods of the existing multi-spiral surface geometry modeling include spatial analytic geometry algorithms, graphical method, interpolation and approximation algorithms. However, there are some shortcomings in these modeling methods, such as large amount of calculation, complex process, visible errors, and so on. The above methods have, to some extent, restricted the design and manufacture of the premium and high-precision products with spiral surface considerably. This paper introduces the concepts of the spatially parallel coupling with multi-spiral surface and spatially parallel coupling body. The typical geometry and topological features of each spiral surface forming the multi-spiral surface body are determined, by using the extraction principle of datum point cluster, the algorithm of coupling point cluster by removing singular point, and the "spatially parallel coupling" principle based on the non-uniform B-spline for each spiral surface. The orientation and quantitative relationships of datum point cluster and coupling point cluster in Euclidean space are determined accurately and in digital description and expression, coupling coalescence of the surfaces with multi-coupling point clusters under the Pro/E environment. The digitally accurate modeling of spatially parallel coupling body with multi-spiral surface is realized. The smooth and fairing processing is done to the three-blade end-milling cutter's end section area by applying the principle of spatially parallel coupling with multi-spiral surface, and the alternative entity model is processed in the four axis machining center after the end mill is disposed. And the algorithm is verified and then applied effectively to the transition area among the multi-spiral surface. The proposed model and algorithms may be used in design and manufacture of the multi-spiral surface body products, as well as in solving essentially the problems of considerable modeling errors in computer graphics and
Optimization of wavelet- and curvelet-based denoising algorithms by multivariate SURE and GCV
Mortezanejad, R.; Gholami, A.
2016-06-01
One of the most crucial challenges in seismic data processing is the reduction of noise in the data or improving the signal-to-noise ratio (SNR). Wavelet- and curvelet-based denoising algorithms have become popular to address random noise attenuation for seismic sections. Wavelet basis, thresholding function, and threshold value are three key factors of such algorithms, having a profound effect on the quality of the denoised section. Therefore, given a signal, it is necessary to optimize the denoising operator over these factors to achieve the best performance. In this paper a general denoising algorithm is developed as a multi-variant (variable) filter which performs in multi-scale transform domains (e.g. wavelet and curvelet). In the wavelet domain this general filter is a function of the type of wavelet, characterized by its smoothness, thresholding rule, and threshold value, while in the curvelet domain it is only a function of thresholding rule and threshold value. Also, two methods, Stein’s unbiased risk estimate (SURE) and generalized cross validation (GCV), evaluated using a Monte Carlo technique, are utilized to optimize the algorithm in both wavelet and curvelet domains for a given seismic signal. The best wavelet function is selected from a family of fractional B-spline wavelets. The optimum thresholding rule is selected from general thresholding functions which contain the most well known thresholding functions, and the threshold value is chosen from a set of possible values. The results obtained from numerical tests show high performance of the proposed method in both wavelet and curvelet domains in comparison to conventional methods when denoising seismic data.
Lagrangian and Eulerian biventricular strains from anatomical NURBS models using tagged MRI
Tustison, Nicholas J.; Amini, Amir A.
2005-04-01
We present current research in which both left and right ventricular deformation is estimated from tagged cardiac magnetic resonance imaging using volumetric deformable models constructed from nonuniform rational B-splines (NURBS). The four model types considered include Cartesian-based NURBS models with both a cylindrical and prolate-spheroidal parameterization, prolate spheroidal-based NURBS models with a prolate-spheroidal parameterization, and cylindrical-based NURBS models with a cylindrical parameterization. For each frame subsequent to end-diastole, a NURBS model is constructed by fitting two surfaces with the same parameterization to the corresponding set of epicardial and endocardial contours from which a volumetric model is created. Using normal displacements of the three sets of orthogonal tag planes as well as displacements of contour/tag line intersection points and tag plane intersection points, one can solve for the optimal homogeneous coordinates, in a weighted least squares sense, of the control points of the deformed NURBS model at end-diastole using quadratic programming. This allows for subsequent forward displacement fitting from end-diastole to all later time frames. After fitting to all time points of data, lofting the NURBS model at each time point creates a comprehensive 4-D NURBS model. From this model, we can extract 3-D myocardial deformation fields and corresponding strain maps which are local measures of non-rigid deformation. The results show that, in the case of simulated data, the quadratic Cartesian-based NURBS model outperformed its counterparts in predicting normal strain. This model was used to then calculate normal Lagrangian and Eulerian strains in canine data.
Atlas-based segmentation for globus pallidus internus targeting on low-resolution MRI.
Iacono, Maria I; Makris, Nikos; Mainardi, Luca; Gale, John; van der Kouwe, Andre; Mareyam, Azma; Polimeni, Jonathan R; Wald, Lawrence L; Fischl, Bruce; Eskandar, Emad N; Bonmassar, Giorgio
2011-01-01
In this paper we report a method to automatically segment the internal part of globus pallidus (GPi) on the pre-operative low-resolution magnetic resonance images (MRIs) of patients affected by Parkinson's disease. Herein we used an ultra-high resolution human brain dataset as electronic atlas of reference on which we segmented the GPi. First, we registered the ultra-high resolution dataset on the low-resolution dataset using a landmarks-based rigid registration. Then an affine and a non-rigid surface-based registration guided by the structures that surround the target was applied in order to propagate the labels of the GPi on the low-resolution un-segmented dataset and to accurately outline the target. The mapping of the atlas on the low-resolution MRI provided a highly accurate anatomical detail that can be useful for localizing the target.
A Method for Calculation of Low-Frequency Slow Drift Motions Based on NURBS for Floating Bodies
Institute of Scientific and Technical Information of China (English)
LIU Wen-xi; REN Hui-long
2009-01-01
Through a higher-order boundary element method based on NURBS (Non-uniform Rational B-splines), the calcula-tion of second-order low-frequency forces and slow drift motions is conducted for floating bodies. In the floating body's in-ner domain, an auxiliary equation is obtained by applying a Green function which satisfies the solid surface condition. Then, the auxiliary equation and the velocity potential equation are combined in the fluid domain to remove the solid an-gle coefficient and the singularity of the double layer potentials in the integral equation. Thus, a new velocity potential in-tegral equation is obtained. The new equation is extended to the inner domain to relieve the irregular frequency effects; on the basis of the order analysis, the comparison is made about the contribution of all integral terms with the result in the second-order low-frequency problem; the higher-order boundary element method based on NURBS is applied to calculate the geometric position and velocity potentials; the slow drift motions are calculated by the spectrum analysis method. Re-moving the solid angle coefficient can apply NURBS technology to the hydrodyynaic calculation of floating bodies with complex surfaces, and the extended boundary integral method can reduce the irregular frequency effects. Order analysis shows that free surface integral can be neglected, and the numerical results can also prove the correctness of order analy-sis. The results of second-order low-frequency forces and slow drift motions and the comparison with the results from ref-erences show that the application of the NURBS technology to the second-order low-frequeney problem is of high efficiency and credible results.
Deformable image registration for cone-beam CT guided transoral robotic base-of-tongue surgery
Reaungamornrat, S.; Liu, W. P.; Wang, A. S.; Otake, Y.; Nithiananthan, S.; Uneri, A.; Schafer, S.; Tryggestad, E.; Richmon, J.; Sorger, J. M.; Siewerdsen, J. H.; Taylor, R. H.
2013-07-01
Transoral robotic surgery (TORS) offers a minimally invasive approach to resection of base-of-tongue tumors. However, precise localization of the surgical target and adjacent critical structures can be challenged by the highly deformed intraoperative setup. We propose a deformable registration method using intraoperative cone-beam computed tomography (CBCT) to accurately align preoperative CT or MR images with the intraoperative scene. The registration method combines a Gaussian mixture (GM) model followed by a variation of the Demons algorithm. First, following segmentation of the volume of interest (i.e. volume of the tongue extending to the hyoid), a GM model is applied to surface point clouds for rigid initialization (GM rigid) followed by nonrigid deformation (GM nonrigid). Second, the registration is refined using the Demons algorithm applied to distance map transforms of the (GM-registered) preoperative image and intraoperative CBCT. Performance was evaluated in repeat cadaver studies (25 image pairs) in terms of target registration error (TRE), entropy correlation coefficient (ECC) and normalized pointwise mutual information (NPMI). Retraction of the tongue in the TORS operative setup induced gross deformation >30 mm. The mean TRE following the GM rigid, GM nonrigid and Demons steps was 4.6, 2.1 and 1.7 mm, respectively. The respective ECC was 0.57, 0.70 and 0.73, and NPMI was 0.46, 0.57 and 0.60. Registration accuracy was best across the superior aspect of the tongue and in proximity to the hyoid (by virtue of GM registration of surface points on these structures). The Demons step refined registration primarily in deeper portions of the tongue further from the surface and hyoid bone. Since the method does not use image intensities directly, it is suitable to multi-modality registration of preoperative CT or MR with intraoperative CBCT. Extending the 3D image registration to the fusion of image and planning data in stereo-endoscopic video is anticipated to
Energy Technology Data Exchange (ETDEWEB)
Park, P; Schreibmann, E; Fox, T; Roper, J; Elder, E; Tejani, M; Crocker, I; Curran, W; Dhabaan, A [Department of Radiation Oncology and Winship Cancer Institute, Emory University, Atlanta, GA (United States)
2014-06-15
Purpose: Severe CT artifacts can impair our ability to accurately calculate proton range thereby resulting in a clinically unacceptable treatment plan. In this work, we investigated a novel CT artifact correction method based on a coregistered MRI and investigated its ability to estimate CT HU and proton range in the presence of severe CT artifacts. Methods: The proposed method corrects corrupted CT data using a coregistered MRI to guide the mapping of CT values from a nearby artifact-free region. First patient MRI and CT images were registered using 3D deformable image registration software based on B-spline and mutual information. The CT slice with severe artifacts was selected as well as a nearby slice free of artifacts (e.g. 1cm away from the artifact). The two sets of paired MRI and CT images at different slice locations were further registered by applying 2D deformable image registration. Based on the artifact free paired MRI and CT images, a comprehensive geospatial analysis was performed to predict the correct CT HU of the CT image with severe artifact. For a proof of concept, a known artifact was introduced that changed the ground truth CT HU value up to 30% and up to 5cm error in proton range. The ability of the proposed method to recover the ground truth was quantified using a selected head and neck case. Results: A significant improvement in image quality was observed visually. Our proof of concept study showed that 90% of area that had 30% errors in CT HU was corrected to 3% of its ground truth value. Furthermore, the maximum proton range error up to 5cm was reduced to 4mm error. Conclusion: MRI based CT artifact correction method can improve CT image quality and proton range calculation for patients with severe CT artifacts.
Lee, Ho; Fahimian, Benjamin P.; Xing, Lei
2017-03-01
This paper proposes a binary moving-blocker (BMB)-based technique for scatter correction in cone-beam computed tomography (CBCT). In concept, a beam blocker consisting of lead strips, mounted in front of the x-ray tube, moves rapidly in and out of the beam during a single gantry rotation. The projections are acquired in alternating phases of blocked and unblocked cone beams, where the blocked phase results in a stripe pattern in the width direction. To derive the scatter map from the blocked projections, 1D B-Spline interpolation/extrapolation is applied by using the detected information in the shaded regions. The scatter map of the unblocked projections is corrected by averaging two scatter maps that correspond to their adjacent blocked projections. The scatter-corrected projections are obtained by subtracting the corresponding scatter maps from the projection data and are utilized to generate the CBCT image by a compressed-sensing (CS)-based iterative reconstruction algorithm. Catphan504 and pelvis phantoms were used to evaluate the method’s performance. The proposed BMB-based technique provided an effective method to enhance the image quality by suppressing scatter-induced artifacts, such as ring artifacts around the bowtie area. Compared to CBCT without a blocker, the spatial nonuniformity was reduced from 9.1% to 3.1%. The root-mean-square error of the CT numbers in the regions of interest (ROIs) was reduced from 30.2 HU to 3.8 HU. In addition to high resolution, comparable to that of the benchmark image, the CS-based reconstruction also led to a better contrast-to-noise ratio in seven ROIs. The proposed technique enables complete scatter-corrected CBCT imaging with width-truncated projections and allows reducing the acquisition time to approximately half. This work may have significant implications for image-guided or adaptive radiation therapy, where CBCT is often used.
Fourier-based linear systems description of free-breathing pulmonary magnetic resonance imaging
Capaldi, D. P. I.; Svenningsen, S.; Cunningham, I. A.; Parraga, G.
2015-03-01
Fourier-decomposition of free-breathing pulmonary magnetic resonance imaging (FDMRI) was recently piloted as a way to provide rapid quantitative pulmonary maps of ventilation and perfusion without the use of exogenous contrast agents. This method exploits fast pulmonary MRI acquisition of free-breathing proton (1H) pulmonary images and non-rigid registration to compensate for changes in position and shape of the thorax associated with breathing. In this way, ventilation imaging using conventional MRI systems can be undertaken but there has been no systematic evaluation of fundamental image quality measurements based on linear systems theory. We investigated the performance of free-breathing pulmonary ventilation imaging using a Fourier-based linear system description of each operation required to generate FDMRI ventilation maps. Twelve subjects with chronic obstructive pulmonary disease (COPD) or bronchiectasis underwent pulmonary function tests and MRI. Non-rigid registration was used to co-register the temporal series of pulmonary images. Pulmonary voxel intensities were aligned along a time axis and discrete Fourier transforms were performed on the periodic signal intensity pattern to generate frequency spectra. We determined the signal-to-noise ratio (SNR) of the FDMRI ventilation maps using a conventional approach (SNRC) and using the Fourier-based description (SNRF). Mean SNR was 4.7 ± 1.3 for subjects with bronchiectasis and 3.4 ± 1.8, for COPD subjects (p>.05). SNRF was significantly different than SNRC (p<.01). SNRF was approximately 50% of SNRC suggesting that the linear system model well-estimates the current approach.
Automatic recognition of intersecting features of freeform sheet metal parts
Institute of Scientific and Technical Information of China (English)
Chun-jie ZHANG; Xiong-hui ZHOU; Cong-xin LI
2009-01-01
This paper presents an approach for recognizing both isolated and intersecting geometric features of freeform surface models of parts, for the purpose of automating the process planning of sheet metal forming. The developed methodology has three major steps: subdivision of B-spline surfaces, detection of protrusions and depressions, and recognition of geometric features for sheet metal forming domain. The input geometry data format of the part is based on an IGES CAD surface model represented in the form of trimmed B-spline surfaces. Each surface is classified or subdivided into different curvature regions with the aid of curvature property surfaces obtained by using symbolic computation of B-spline surfaces. Those regions satisfying a particular geometry and topology relation are recognized as protrusion and depression (DP) shapes. The DP shapes are then classified into different geometric features using a rule-based approach. A verified feasibility study of the developed method is also presented.
Sensitivity Analysis Based Multiple Objective Preform Die Shape Optimal Design in Metal Forging
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
The multiple objective preform design optimization was put forward. The final forging's shape and deformation uniformity were considered in the multiple objective. The objective is to optimize the shape and the deformation uniformity of the final forging at the same time so that a more high integrate quality of the final forging can be obtained. The total objective was assembled by the shape and uniformity objective using the weight adding method. The preform die shape is presented by cubic B-spline curves. The control points of B-spline curves are used as the design variables. The forms of the total objective function, shape and uniformity sub-objective function are given. The sensitivities of the total objective function and the sub-objective functions with respect to the design variables are developed. Using this method, the preform die shape of an H-shaped forging process is optimally designed. The optimization results are very satisfactory.
Olkhov, A. A.; Karpova, S. G.; Staroverova, O. V.; Krutikova, A. A.; Orlov, N. A.; Kucherenko, E. L.; Iordanskii, A. L.
2016-11-01
The fibrous materials (the mats) based on poly-3-hydroxybutyrate (PHB) containing the drug, dipiridomole (DPD) were produced by electrospinning (ES). Thermophysical and dynamical properties of the single filaments and the mats were studied by scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and probe electron paramagnetic resonance spectroscopy (EPR). The effect of annealing temperature on the structure and crystallinity of the fibers was examined. It was shown that the loading of DPD influences on both the melting enthalpy and the morphology of the fibers. Besides the analysis of EPR spectra revealed that there are two populations of spin-probes distributed in the rigid and nonrigid amorphous regions of the PHB fibers respectively. For all fibrous materials with different content of DPD (0-5%) the correlation between thermophysical (DSC) and dynamic data (EPR) was observed.
基于神经网络的数控插补容错技术%ANN-based Fault Tolerance of CNC Interpolation
Institute of Scientific and Technical Information of China (English)
王义强; 袁修华; 马明阳; 胡艳娟
2011-01-01
Artificial neural network (ANN) and fuzzy math were introduced to the design filed of CNC software for realizing the fault tolerance of CNC interpolation and improving the reliability of software. In addition, function aspects ( velocity, acceleration, chord error, prediction accuracy, fault tolerance, real time ) from the experiment on non-uniform rational B-spline ( NURBS) interpolator based on ANN were evaluated in detail. The experimental results show that the NURBS interpolation based on ANN can not only meet the requirements of the function aspects, but also realize the fault tolerance of CNC interpolation, which may provide a new strategy in the improvement of the reliability of CNC software.%提出将神经网络和模糊数学应用到数控系统软件设计领域,以实现数控插补容错技术,提高软件可靠性.为了验证该方法的可行性,对基于神经网络的NURBS插补模块进行了实验研究,并对速度、加速度、插补精度、神经网络预测精度、容错和实时性等方面进行了分析.实验结果表明,基于神经网络的插补模块在保证加工要求的前提下实现了数控插补软件容错技术,为提高数控系统软件的可靠性提供了新的途径.
An Irregular-gridded Stable Potential-field Downward Continuation Method
Wang, B.
2004-12-01
Potential-fields downward continuation can increase the resolution, while it is an inherent ill-posed inverse problem. We advance a fast algorithm to solve the interpolation coefficients of arbitrary-spaced four variable cubic B-spline. The downward continuation, both 2D and 3D, is accomplished by solving integral equations using B-spline bases in space domain. In contrast to FFT method, our method can be irregular spacing, and the number of knots need not to be a power of 2. Through comparison with FFT method using synthetic examples, including noise-contaminated data continuation, it is found that our method is more accurate and more stable. Real data applications of B-spline method downward continuation provide very useful information for further interpretation.
Image registration using stationary velocity fields parameterized by norm-minimizing Wendland kernel
DEFF Research Database (Denmark)
Pai, Akshay Sadananda Uppinakudru; Sommer, Stefan Horst; Sørensen, Lauge;
by the regularization term. In a variational formulation, this term is traditionally expressed as a squared norm which is a scalar inner product of the interpolating kernels parameterizing the velocity fields. The minimization of this term using the standard spline interpolation kernels (linear or cubic) is only...... approximative because of the lack of a compatible norm. In this paper, we propose to replace such interpolants with a norm-minimizing interpolant - the Wendland kernel which has the same computational simplicity like B-Splines. An application on the Alzheimer's disease neuroimaging initiative showed...... that Wendland SVF based measures separate (Alzheimer's disease v/s normal controls) better than both B-Spline SVFs (pB-Spline freeform deformation (p
An adaptive MR-CT registration method for MRI-guided prostate cancer radiotherapy
Zhong, Hualiang; Wen, Ning; Gordon, James J.; Elshaikh, Mohamed A.; Movsas, Benjamin; Chetty, Indrin J.
2015-04-01
Magnetic Resonance images (MRI) have superior soft tissue contrast compared with CT images. Therefore, MRI might be a better imaging modality to differentiate the prostate from surrounding normal organs. Methods to accurately register MRI to simulation CT images are essential, as we transition the use of MRI into the routine clinic setting. In this study, we present a finite element method (FEM) to improve the performance of a commercially available, B-spline-based registration algorithm in the prostate region. Specifically, prostate contours were delineated independently on ten MRI and CT images using the Eclipse treatment planning system. Each pair of MRI and CT images was registered with the B-spline-based algorithm implemented in the VelocityAI system. A bounding box that contains the prostate volume in the CT image was selected and partitioned into a tetrahedral mesh. An adaptive finite element method was then developed to adjust the displacement vector fields (DVFs) of the B-spline-based registrations within the box. The B-spline and FEM-based registrations were evaluated based on the variations of prostate volume and tumor centroid, the unbalanced energy of the generated DVFs, and the clarity of the reconstructed anatomical structures. The results showed that the volumes of the prostate contours warped with the B-spline-based DVFs changed 10.2% on average, relative to the volumes of the prostate contours on the original MR images. This discrepancy was reduced to 1.5% for the FEM-based DVFs. The average unbalanced energy was 2.65 and 0.38 mJ cm-3, and the prostate centroid deviation was 0.37 and 0.28 cm, for the B-spline and FEM-based registrations, respectively. Different from the B-spline-warped MR images, the FEM-warped MR images have clear boundaries between prostates and bladders, and their internal prostatic structures are consistent with those of the original MR images. In summary, the developed adaptive FEM method preserves the prostate volume
A hybrid biomechanical intensity based deformable image registration of lung 4DCT
Samavati, Navid; Velec, Michael; Brock, Kristy
2015-04-01
Deformable image registration (DIR) has been extensively studied over the past two decades due to its essential role in many image-guided interventions (IGI). IGI demands a highly accurate registration that maintains its accuracy across the entire region of interest. This work evaluates the improvement in accuracy and consistency by refining the results of Morfeus, a biomechanical model-based DIR algorithm. A hybrid DIR algorithm is proposed based on, a biomechanical model-based DIR algorithm and a refinement step based on a B-spline intensity-based algorithm. Inhale and exhale reconstructions of four-dimensional computed tomography (4DCT) lung images from 31 patients were initially registered using the biomechanical DIR by modeling contact surface between the lungs and the chest cavity. The resulting deformations were then refined using the intensity-based algorithm to reduce any residual uncertainties. Important parameters in the intensity-based algorithm, including grid spacing, number of pyramids, and regularization coefficient, were optimized on 10 randomly-chosen patients (out of 31). Target registration error (TRE) was calculated by measuring the Euclidean distance of common anatomical points on both images after registration. For each patient a minimum of 30 points/lung were used. Grid spacing of 8 mm, 5 levels of grid pyramids, and regularization coefficient of 3.0 were found to provide optimal results on 10 randomly chosen patients. Overall the entire patient population (n = 31), the hybrid method resulted in mean ± SD (90th%) TRE of 1.5 ± 1.4 (2.9) mm compared to 3.1 ± 1.9 (5.6) using biomechanical DIR and 2.6 ± 2.5 (6.1) using intensity-based DIR alone. The proposed hybrid biomechanical modeling intensity based algorithm is a promising DIR technique which could be used in various IGI procedures. The current investigation shows the efficacy of this approach for the registration of 4DCT images of the lungs with average accuracy of 1.5 mm.
基于亚像素的埋弧焊焊缝图像处理%SAW edge detection of image based on sub-pixel
Institute of Scientific and Technical Information of China (English)
张姝; 张文明; 王滨
2011-01-01
Submerged arc welding is one of the widespread welding technology.It has high efficiency,good weld quality.no arc radiation, etc.It is more and more important/To improve the submerged arc welding process automatic and intelligent, increasing demands for precision tracking technology.In order to improve the accuracy of submerged arc welding, a sub-pixel location based on B Spline transform was put forward for welding line and dibided edge.The algorithm is conducting a Marr-Hildreth edge detection and a sub-pixel location.Field tests,achieved standard error less than 255.The traditional edge detection was low in precision,but the problem is constraining by using the transform.%埋弧焊是普遍使用的熔焊方法之一,具有生产效率高、焊缝成形好、没有弧光辐射等诸多优点,应用前景广阔.为了提高埋弧焊焊接过程的自动化和智能化,对埋弧焊精密跟踪技术的要求不断提高,需对焊缝间隙和坡口边缘进行精密检测.在此提出了一种基于B样条变换的亚像素定位算法,该算法是在对图像进行一次Marr-Hildreth边缘检测后再进行亚像素二次提取.通过现场试验,实现了检测标准误差小于255E/μm,克服了传统边缘检测精度低的问题.
Two different methods for numerical solution of the modified Burgers' equation.
Karakoç, Seydi Battal Gazi; Başhan, Ali; Geyikli, Turabi
2014-01-01
A numerical solution of the modified Burgers' equation (MBE) is obtained by using quartic B-spline subdomain finite element method (SFEM) over which the nonlinear term is locally linearized and using quartic B-spline differential quadrature (QBDQM) method. The accuracy and efficiency of the methods are discussed by computing L 2 and L ∞ error norms. Comparisons are made with those of some earlier papers. The obtained numerical results show that the methods are effective numerical schemes to solve the MBE. A linear stability analysis, based on the von Neumann scheme, shows the SFEM is unconditionally stable. A rate of convergence analysis is also given for the DQM.
Hiemstra, R R; Gerritsma, M I
2012-01-01
Conservation laws, in for example, electromagnetism, solid and fluid mechanics, allow an exact discrete representation in terms of line, surface and volume integrals. We develop high order interpolants, from any basis that is a partition of unity, that satisfy these integral relations exactly, at cell level. The resulting gradient, curl and divergence conforming spaces have the property that the conservation laws become completely independent of the basis functions. This means that the conservation laws are exactly satisfied even on curved meshes. As an example, we develop high order gradient, curl and divergence conforming spaces from NURBS - non uniform rational B-splines - and thereby generalize the compatible spaces of B-splines developed by Buffa et al.[1]. We give several examples of 2D Stokes flow calculations which result, amongst others, in a point wise divergence free velocity field.
Institute of Scientific and Technical Information of China (English)
李增彦; 李小民
2012-01-01
在传统无人侦察机模拟训练方法中,视景仿真环境逼真度不足,三维地形容易忽视动态目标.为此,提出一种基于谷歌地球(GE)和SketchUp(SU)模型的动态侦察环境模拟方法.通过GE场景建立三维仿真环境,利用SU制作三维模型,采用三次B样条插值方法对路径进行平滑处理,计算模型的姿态角,使用Keyhole标记语言和GE COM API,完成飞行视景仿真.实验结果表明,该方法能生成逼真的动态三维场景,减少建模工作和开发周期.%In order to solve the difficulties of traditional simulation training method on unmanned reconnaissance aircraft, such as the low environment fidelity, ignoring dynamic target in 3D terrain, this paper proposes a simulation method of dynamic reconnaissance environment based on Google Earth(GE) and SketchUp(SU) model. It produces the 3D simulation environment based on GE and the 3D model through the SU, adopts cubic B-spline interpolation method to smooth the path, and calculates models' attitude data as well, completes flight visual simulation through the method of Keyhole Markup Language(KML) and GE COM API. Experimental results show that this method can generate a realistic dynamic 3D scene, and reduce the amount of modeling work and the development cycle.
Institute of Scientific and Technical Information of China (English)
周胜德; 梁宏斌; 乔宇
2011-01-01
A new ACCeleration-DECeleration method (ACC-DEC) was put forward, which aimed at the shortages of S-curve ACC-DEC.The proposed approach was designed to satisfy the requirements of nonuniform rational B-spline (NURBS) interpolation with high-speed and high-accuracy.Based on the impacts which used conventional linear ACC-DEC, the complex algorithm of the seven phased S-curve, the five phased S-curve was adopted, taking chord error and maximal centripetal acceleration into consideration,solving rationally difficulty in the predetermination deceleration point.The simulation results showed that the method can make sure the acceleration was continuous, the speed changed smoothly, the flexibility was improved, the algorithm was easy to implement.%为满足非均匀有理B样条曲线高速高精度插补加工的需要,针对目前参数曲线插补加减速控制方法的不足,常规直线加减速方法存在冲击,七段S曲线加减速方法算法复杂等问题,提出了基于NURBS曲线插补的五段S曲线加减速控制方法.该方法将高速加工中容易超限的弓高误差和机床所能承受的法向加速度等参数均考虑在内,而且合理地解决了插补前加减速控制中的减速点预测困难的问题.仿真结果表明,该方法能够保证加速度的连续,速度的平滑过渡,有效提高了系统的柔性,简化了算法.
基于曲线插补的多轴联动交叉耦合控制方法%Multi-axis cross-coupled control approach based on curve interpolation
Institute of Scientific and Technical Information of China (English)
赵国勇; 赵玉刚
2011-01-01
针对高精度轮廓跟踪需要,将曲线插补和交叉耦合控制器结合起来进行研究。在每个采样周期根据各轴反馈的实际刀具位置与插补缓冲区中存储的一定数量的插补点,研究了一种＂三点圆弧法＂轮廓误差计算模型,并研究了轮廓误差补偿修正量计算及分配方法。在数控试验台上跟踪一段三次非均匀有理B样条轮廓曲线,对比试验表明,所提出的基于曲线插补的轮廓误差交叉耦合控制方法能够有效减小轮廓误差,获得更高轮廓精度。%Aiming at the tracking demand of high precision contour,the cross-coupled controller integrated with curve interpolation was studied.According to the real cutter positions from each axis feedback and the interpolation dots stored in the interpolation buffer in every sampling period,a ＂three-point arc approach＂ contour error computing model was developed.Moreover,the contour error compensated correction quantity computation and distribution approach was put forward.A cubic Non-Uniform Rational B-Spline Curve（NURBS） profile curve on the numerial control experiment table was tracked.The experiment results showed that the developed contour error cross-coupled control approach based on curve interpolation could effectively reduce contour error and obtain satisfactory contour precision.
Interactive Perception of Rigid and Non-Rigid Objects
Directory of Open Access Journals (Sweden)
Bryan Willimon
2012-12-01
Full Text Available This paper explores the concept of interactive perception, in which sensing guides manipulation, in the context of extracting and classifying unknown objects within a cluttered environment. In the proposed approach, a pile of objects lies on a flat background, and the goal of the robot is to isolate, interact with, and classify each object so that its properties can be obtained. The algorithm considers each object to be classified using color, shape, and flexibility. The approach works with a variety of objects relevant to service robot applications, including both rigid objects such as bottles, cans, and pliers as well as non‐rigid objects such as soft toy animals, socks, and shoes. Experiments on a number of different piles of objects demonstrate the ability of efficiently isolating and classifying each item through interaction.
The freedom to heal: nonrigid immobilization by a halo orthosis.
Genin, Guy M; Rosenberg, Stuart P; Seger, Laura M; Tran, Elizabeth L; Rivet, Dennis J; Leuthardt, Eric C
2014-11-01
Halo orthoses present a paradox. On the one hand, the nominally rigid immobilization they provide to the head aims to remove loads on the cervical spine following injury or surgery, and the devices are retightened routinely to maintain this. On the other hand, bone growth and remodeling are well known to require mechanical stressing. How are these competing needs balanced? To understand this trade-off in an effective, commercial halo orthosis, the authors quantified the response of a commercial halo orthosis to physiological loading levels, applied symmetrically about the sagittal plane. They showed for the first time that after a few cycles of loading analogous to a few steps taken by a patient, the support presented by a standard commercial halo orthosis becomes nonlinear. When analyzed through straightforward structural modeling, these data revealed that the nonlinearity permits mild head motion while severely restricting larger motion. These observations are useful because they open the possibility that halo orthosis installation could be optimized to transfer mild spinal loads that support healing while blocking pathological loads.
Torsional and rotational coupling in non-rigid molecules
Omiste, Juan J
2016-01-01
We analyze theoretically the interplay between the torsional and the rotational motion of an aligned biphenyl-like molecule. To do so, we consider a transition between two electronic states with different internal torsional potentials, induced by means of a resonant laser pulse. The change in the internal torsional potential provokes the motion of the torsional wavepacket in the excited electronic state, modifying the structure of the molecule, and hence, its inertia tensor. We find that this process has a strong impact on the rotational wave function, displaying different behavior depending on the electronic states involved and their associated torsional potentials. We describe the dynamics of the system by considering the degree of alignment and the expectations values of the angular momentum operators for the overall rotation of the molecule.
Large-deformation modal coordinates for nonrigid vehicle dynamics
Likins, P. W.; Fleischer, G. E.
1972-01-01
The derivation of minimum-dimension sets of discrete-coordinate and hybrid-coordinate equations of motion of a system consisting of an arbitrary number of hinge-connected rigid bodies assembled in tree topology is presented. These equations are useful for the simulation of dynamical systems that can be idealized as tree-like arrangements of substructures, with each substructure consisting of either a rigid body or a collection of elastically interconnected rigid bodies restricted to small relative rotations at each connection. Thus, some of the substructures represent elastic bodies subjected to small strains or local deformations, but possibly large gross deformations, in the hybrid formulation, distributed coordinates referred to herein as large-deformation modal coordinates, are used for the deformations of these substructures. The equations are in a form suitable for incorporation into one or more computer programs to be used as multipurpose tools in the simulation of spacecraft and other complex electromechanical systems.