基于曲线的纹理映射

本文提出一种纹理映射的新方法。二维平面中的一条曲线与三维曲面上的一条曲线相对应，两条曲线上的点再相对应。当对应曲线足够多时，就可获理完成纹理映射所需的足够信息。     

Regular unknown input functional observers for 2-D singular systems

This paper concerns with asymptotic regular unknown input functional observers (UIFOs) for two-dimensional (2-D) acceptable singular systems described by the Fornasini-Marchesini local state-space second model. A sufficient condition for the existence of an asymptotic regular UIFO is first presented in terms of a rank condition on the given system matrices. Based on this, an asymptotic 2-D regular UIFO is constructed using a linear matrix inequality (LMI) technique, while a new method is also given for designing regular functional observers for 2-D acceptable singular systems. Two illustrative examples are provided to demonstrate the feasibility and effectiveness of the proposed method.     

一种新的基于二维云模型不确定性推理的智能控制器

提出一种新型的二维云模型智能控制器结构.这种结构模型是一种本质非线性模型,可以很容易由一组不确定性推理规则构成.分析了一维和二维云模型的非线性映射特性,并给出了基于此结构模型的智能控制器的设计方法及仿真实例.     

改进的最大嫡闭值分割及其快速实现

针对传统二维最大嫡阂值法对二维直方图采用近似处理等的不足,提出了改进的二维最大墒快速阈值分割方法。首先对部域模板进行改进,将改进后的模板用来构建二维直方图,并将最大嫡法用于此直方图上,以便获得最佳阈值;然后,舍弃传统的二维直方图中关于主对角区域的概率近似为1的假设,使阂值选取更准确;最后,分析二维直方图投影,得到其特性,并证明两定理的存在。利用此特性和两定理导出新型、快速的递推算法来降低计算复杂度。仿真实验结果表明,与当前二维最大嫡法相比,提出的方法不仅分割更准确和抗噪性更强,而且占用的存储空间更少,分割速度更快,分割时间少于0.04s。     

空间目标位置误差未知的碰撞概率算法

针对航天器和空间碎片位置误差未知的情况,提出一种空间目标碰撞概率的计算方法。该方法基于正交投影变换将碰撞概率中的三维问题转化到二维进行求解,并利用变量置换的方法计算空间目标碰撞概率。讨论了位置误差椭球形状和大小变化对碰撞概率的影响。根据实际碰撞事例验证了其有效性。     

Determination of camera location from 2-D to 3-D line and pointcorrespondences

A method for the determination of camera location from two-dimensional (2-D) to three-dimensional (3-D) straight line or point correspondences is presented. With this method, the computations of the rotation matrix and the translation vector of the camera are separable. First, the rotation matrix is found by a linear algorithm using eight or more line correspondences, or by a nonlinear algorithm using three or more line correspondences, where the line correspondences are either given or derived from point correspondences. Then, the translation vector is obtained by solving a set of linear equations based on three or more line correspondences, or two or more point correspondences. Eight 2-D to 3-D line correspondences or six 2-D to 3-D point correspondences are needed for the linear approach; three 2-D to 3-D line or point correspondences for the nonlinear approach. Good results can be obtained in the presence of noise if more than the minimum required number of correspondences are used     

基于2_D系统理论的变初始条件线性系统的开闭环学习控制

对于具有重复运动特性的系统,迭代学习控制是一种简便且行之有效的方法.考虑到系统每次运行初始值的不确定性,利用二维系统理论设计了开闭环迭代学习控制器,并给出了控制收敛的充分条件.用仿真试验验证其有效性.     

A new shape decomposition scheme for graph-based representation

Nowadays, the part-based representation of a given shape plays a significant role in shape-related applications, such as those involving content-based retrieval, object recognition, and so on. In this paper, to represent both 2-D and 3-D shapes as a relational structure, i.e. a graph, a new shape decomposition scheme, which recursively performs constrained morphological decomposition (CMD), is proposed. The CMD method adopts the use of the opening operation with the ball-shaped structuring element, and weighted convexity to select the optimal decomposition. For the sake of providing a compact representation, the merging criterion is applied using the weighted convexity difference. Therefore, the proposed scheme uses the split-and-merge approach. Finally, we present experimental results for various, modified 2-D shapes, as well as 3-D shapes represented by triangular meshes. Based on the experimental results, it is believed that the decomposition of a given shape coincides with that based on human insight for both 2-D and 3-D shapes, and also provides robustness to scaling, rotation, noise, shape deformation, and occlusion.     

一种新型2-D模板卷积结构的FPGA实现

在实时图像处理过程中,2-D模板卷积是一种重要的操作,FPGA以其特有的全并行处理机制使得这种操作在硬件设计中得以较好的实现。本文提出了一种基于FPGA的模板卷积运算的新方案,相比传统方案,这种方案在结构上能以较少的硬件资源达到相同的流水深度。为了满足系统对实时性的要求,针对某些特定类型的模板,给出了一种简化的卷积器结构,同时,介绍了一种模板归一化除法运算的硬件实现方法。     

Quantized H∞ control for a class of 2-D systems with missing measurements

In this paper, the problem of quantized H∞ control is investigated for a class of 2-D systems described by Roesser model with missing measurements. The measurement missing of system state is described by a sequence of random variables obeying the Bernoulli distribution. Meanwhile, the state measurements are quantized by logarithmic quantizer before being communicated. By introducing a new 2-D Lyapunov-like function, a sufficient condition is derived to guarantee stochastically stable and H∞ performance of the closed-loop 2-D system, where the method of sector-bounded uncertainties is utilized to deal with quantization error. Based on the condition, the quantized H∞ control can be designed by using linear matrix inequality technique. A simulation example is also given to illustrate the proposed method.

     

基于递归Gabor滤波的指纹图像处理方法的研究

根据一维递归Gabor滤波算法设计了二维RGF(Recursive Gabor Filtering)算法,通过实验论证了RGF不仅与Gabor 滤波等价,而且速度更快.在此基础上提出了RGF方法代替传统的Gabor滤波器方法应用到指纹特征提取,并用实验论证了参数的选择.实验结果显示该方法的有效性,具有很高的实用价值.     

Surface orientation from a projected grid

Two simple methods are given for obtaining the surface shape using a projected grid. After the camera is calibrated to the 3-D workspace, the only input date needed for the computation of surface normals are grid intersect points in a single 2-D image. The first method performs nonlinear computations based on the distortion of the lengths of the grid edges and does not require a full calibration matrix. The second method requires that a full parallel projection model of the imaging is available, which enables it to compute 3-D normals using simple linear computations. The linear method performed better overall in the experiments, but both methods produced normals within 4-8° of known 3-D directions. These methods appear to be superior to methods based on shape-from-shading because the results are comparable, yet the equipment setup is simpler and the processing is not very sensitive to object reflectance     

On a High Order Numerical Method for Solving Partial Differential Equations in Complex Geometries

Initial-boundary value problems for hyperbolic and parabolic partial differential equations with Diriclilet boundary conditions are considered by the method of lines approach in an arbitrarily given domain D in 2-D or 3-D. With D embedded in a rectangular domain, a new high order method for the space discretization problem is constructed in D by employing a Fourier collocation method in a uniform Cartesian system of gridpoints. Singularities are systematically removed by utilizing properties of the Bernoulli polynomials. Theoretical estimates for the accuracy of the method are established. The estimates are confirmed by numerical experiments for simple approximation problems.     

Population density methods for stochastic neurons with realistic synaptic kinetics: firing rate dynamics and fast computational methods

An outstanding problem in computational neuroscience is how to use population density function (PDF) methods to model neural networks with realistic synaptic kinetics in a computationally efficient manner. We explore an application of two-dimensional (2-D) PDF methods to simulating electrical activity in networks of excitatory integrate-and-fire neurons.We formulate a pair of coupled partial differential-integral equations describing the evolution of PDFs for neurons in non-refractory and refractory pools. The population firing rate is given by the total flux of probability across the threshold voltage. We use an operator-splitting method to reduce computation time. We report on speed and accuracy of PDF results and compare them to those from direct, Monte-Carlo simulations.We compute temporal frequency response functions for the transduction from the rate of postsynaptic input to population firing rate, and examine its dependence on background synaptic input rate. The behaviors in the1-D and 2-D cases--corresponding to instantaneous and non-instantaneous synaptic kinetics, respectively--differ markedly from those for a somewhat different transduction: from injected current input to population firing rate output (Brunel et al. 2001; Fourcaud & Brunel 2002).We extend our method by adding inhibitory input, consider a 3-D to 2-D dimension reduction method, demonstrate its limitations, and suggest directions for future study.     

未知摄影参数图象的三维特征逆变换

为了从未知摄影参数的透视图象获得三维几何尺寸，本文导出了实体的特征尺寸与透视图象的几个解析关系式认及曲线，曲面的重建方法，对于只能找出两个正交方向灭点的透视图象，本文提出了用优化方法来求出第三个灭点和其透视参数。文中给出两个实例。     

光照不均匀图像的灰度波动局部阈值分割

针对工业图像经常存在不均匀光照的干扰,提出一种光照不均匀图像的灰度波动局部阈值分割算法。从水平及垂直方向上提取图像的灰度波动曲线,并迭代搜索每条曲线上满足给定波动幅度阈值的较大尺度波峰点和波谷点;在每对交替波峰点或波谷点之间求取浮动阈值来划定目标和背景像素的归属;对两个方向上取得的阈值图像进行相交操作得到最终分割图像。实验结果表明,与二维Otsu法、二维Tsallis熵法、Niblack法等几种算法相比,该算法的分割效果及实时性都具有明显的提升。     

A numerical method for solving a nonlinear 2-D optimal control problem with the classical diffusion equation

This paper presents a numerical solution for solving a nonlinear 2-D optimal control problem (2DOP). The performance index of a nonlinear 2DOP is described with a state and a control function. Furthermore, dynamic constraint of the system is given by a classical diffusion equation. It is preferred to use the Ritz method for finding the numerical solution of the problem. The method is based upon the Legendre polynomial basis. By using this method, the given optimisation nonlinear 2DOP reduces to the problem of solving a system of algebraic equations. The benefit of the method is that it provides greater flexibility in which the given initial and boundary conditions of the problem are imposed. Moreover, compared with the eigenfunction method, the satisfactory results are obtained only in a small number of polynomials order. This numerical approach is applicable and effective for such a kind of nonlinear 2DOP. The convergence of the method is extensively discussed and finally two illustrative examples are included to observe the validity and applicability of the new technique developed in the current work.     

A Lyapunov function of two-dimensional linear systems

In this note a Lyapunov function for a 2-D time invariant discrete linear system is introduced, using the 2-D system model given by Roesser [1]. The Lyapunov function may be used to investigate the asymptotic stability of the 2-D system. Previous work dealing with asymptotic stability of 2-D systems [3]-[5] is based upon the location of roots of the characteristic polynomial in the closed polydiskoverline{U}^{2}.     

Three-dimensional reconstruction of the left ventricle from two angiographic views: an evidence combination approach

Clinical interventional hemodynamic studies quantify the ventricular function from two-dimensional (2-D) X-ray projection images without having enough information of the actual three-dimensional (3-D) shape of this cardiac cavity. This paper reports a left ventricle 3-D reconstruction method from two orthogonal angiographic projections. This investigation is motivated by the lack of information about the actual 3-D shape of the cardiac cavity. The proposed algorithm works in 3-D space and considers the oblique projection geometry associated with the biplane image acquisition equipment. The reconstruction process starts by performing an approximate reconstruction based on the Cylindrical Closure Operation and the Dempster-Shafer theory. This approximate reconstruction is appropriately deformed in order to match the given projections. The deformation procedure is carried out by an iterative process that, by means of the Dempster-Shafer and the fuzzy integral theory, combines the information provided by the projection error and the connectivity between voxels. The performance of the proposed reconstruction method is evaluated by considering first the reconstruction of two 3-D binary databases from two orthogonal synthetized projections, obtaining errors as low as 6.48%. The method is then tested on real data, where two orthogonal preprocessed angiographic images are used for reconstruction. The performance of the technique, in this case, is assessed by means of the projection error, whose average for both views is 7.5%. The reconstruction method is also tested by performing the 3-D reconstruction of a ventriculographic sequence throughout an entire cardiac cycle.