Volume Registration Using the 3-D Pseudopolar Fourier Transform

This paper introduces an algorithm for the registration of rotated and translated volumes using the three-dimensional (3-D) pseudopolar Fourier transform, which accurately computes the Fourier transform of the registered volumes on a near-spherical 3-D domain without using interpolation. We propose a three-step procedure. The first step estimates the rotation axis. The second step computes the planar rotation relative to the rotation axis. The third step recovers the translational displacement. The rotation estimation is based on Euler's theorem, which allows one to represent a 3-D rotation as a planar rotation around a 3-D rotation axis. This axis is accurately recovered by the 3-D pseudopolar Fourier transform using radial integrations. The residual planar rotation is computed by an extension of the angular difference function to cylindrical motion. Experimental results show that the algorithm is accurate and robust to noise.     

基于改进粒子滤波的鲁棒目标跟踪算法

为了克服样本贫化现象导致的滤波发散,本文对重采样后的粒子进行有方向性的变异操作,在增加样本集的多样性同时使粒子集更集中均匀的分布在目标的邻域.同时把Mean Shift算法引入粒子滤波(PF)框架中,对PF估计结果迭代得到最优的目标状态,并用迭代得到的状态值控制粒子变异的方向.仿真实验表明,本文提出的方法具有更高的估计...     

Componentwise edge detection by Laplacian operator masks

This note introduces componentwise edge detection technique for Laplacian operator masks. Laplacian operator masks are expressed by means of gradient components. The absolute sums of the gradient components at image points form the gradient image, from which the edges are extracted. The results obtained are comparable to those obtained by the gradient sum and max operators or Sobel and Prewitt masks.     

多尺度的灰值形态学在图像边缘检测中的应用

传统的边缘检测算法存在检测边缘不连续、漏检、抗噪性能差等缺点。针对传统方法在边缘检测中遇到的问题,结合数学形态学的方法,介绍一种基于多尺度灰值形态学的边缘检测算子,该算子是在形态学梯度算子的基础上改进之后,结合多尺度的概念,将各种不同尺寸下的边缘图像结合起来,提取出比较理想的边缘图像。采用Visual C++编程实现算法,并与传统边缘检测算子进行比较。实验结果表明本文提到的算子检测边缘效果更好。     

Multiple sclerosis lesion quantification using fuzzy-connectednessprinciples

Multiple sclerosis (MS) is a disease of the white matter. Magnetic resonance imaging (MRI) is proven to be a sensitive method of monitoring the progression of this disease and of its changes due to treatment protocols. Quantification of the severity of the disease through estimation of MS lesion volume via MR imaging is vital for understanding and monitoring the disease and its treatment. This paper presents a novel methodology and a system that can be routinely used for segmenting and estimating the volume of MS lesions via dual-echo fast spin-echo MR imagery. A recently developed concept of fuzzy objects forms the basis of this methodology. An operator indicates a few points in the images by pointing to the white matter, the grey matter, and the cerebrospinal fluid (CSF). Each of these objects is then detected as a fuzzy connected set. The holes in the union of these objects correspond to potential lesion sites which are utilized to detect each potential lesion as a three-dimensional (3-D) fuzzy connected object. These objects are presented to the operator who indicates acceptance/rejection through the click of a mouse button. The number and volume of accepted lesions is then computed and output. Based on several evaluation studies, the authors conclude that the methodology is highly reliable and consistent, with a coefficient of variation (due to subjective operator actions) of 0.9% (based on 20 patient studies, three operators, and two trials) for volume and a mean false-negative volume fraction of 1.3%, with a 95% confidence interval of 0%-2.8% (based on ten patient studies)     

Multiple-parameter quantum estimation and measurement of nonselfadjoint observables

A quantum mechanical form of the Cramér-Rao inequality and a minimum-mcan-square-error quantum estimator for multiple parameters are derived, allowing all possible quantum measurements of the received field. The role of nonselfadjoint operators is emphasized in the formulation. Relations of our results to previous work on quantum estimation are discussed. For the estimation of complex mode amplitudes of coherent signals in Gaussian noise, it is shown that the optimal receiver measures the photon annihilation operator, which corresponds to optical heterodyning. This demonstrates the possible optimality of nonselfadjoint operators and clearly indicates the importance of considering more general quantum measurements in quantum signal detection.     

3D augmented reality teleoperated robot system based on dual vision

A 3D augmented reality navigation system using stereoscopic images is developed for teleoperated robot systems.The accurate matching between the simulated model and the video image of the actual robot can be realized,which helps the operator to accomplish the remote control task correctly and reliably.The system introduces the disparity map translation transformation method to take parallax images for stereoscopic displays,providing the operator an immersive 3D experience.Meanwhile,a fast and accurate registration method of dynamic stereo video is proposed,and effective integration of a virtual robot and the real stereo scene can be achieved.Preliminary experiments show that operation error of the system is maintained at less than 2.2 mm and the average error is 0.854 7,0.909 3 and 0.697 2 mm at x,y,z direction respectively.Lots of experiments such as pressing the button,pulling the drawer and so on are also conducted to evaluate the performance of the system.The feasibility studies show that the depth information of structure can be rapidly and recognized in remote environment site.The augmented reality of the image overlay system could increase the operating accuracy and reduce the procedure time as a result of intuitive 3D viewing.     

一种图像分割的快速不动点算法

该文在去除背景便能获得目标的分割思想之上,提出了一个凸的无约束最小化问题。证明了问题提出过程中添加惩罚项的合理性,并通过实验验证了证明结果。在最小化求解方面,应用次微分和近似算子的相关理论,构造了求解的不动点算子,进而结合Opial -averaged定理,给出了求解所提凸优化问题的不动点算法,并理论推导出了收敛条件,证明了算法的收敛性。与经典文献方法的对比实验表明所提方法分割结果更精确。同时实验显示该文算法比梯度下降法和分裂Bregman方法更快速。另外,所提算法对初始曲线和噪声有较好的鲁棒性。     

基于Legendre正交矩的三维边界检测算子

本文提出了一种新的基于Legendre正交矩的三维边界检测算子。该算子可通过任意大小的窗口自动检测出三维灰度图像中所包含的三维物体边界,具有比一般算子更高的方向灵敏度和表面精度,同时具有明确的几何模型意义。计算量是采用矩运算的一个必须考虑的因素,通过预先计算模板的算法,大大减少了计算量。我们在实验中把该算子和算法结合光线跟踪方法应用于三维医学图像的体绘制当中取得了理想的效果,表明Legendre正交矩三维边界检测算子是一种行之有效的三维边界检测算子。     

基于最优导频的自适应Kalman滤波信道估计方法

针对时变信道中的子载波间干扰(ICI)和噪声的统计模型不准确引起的滤波发散问题,介绍了一种基于最优导频预滤波的自适应Kalman联合算法。该算法通过使用最优导频滤除ICI,获得理想信道初始状态,然后将其作为Kalman滤波初始信息在时域上进行自适应Kalman信道估计。最后仿真实验表明,和传统的基于导频的Kalman滤波(KF)算法相比,该方法能有效抑制KF发散和改善信道估计精度。     

一种空中多目标的定位及识别快速算法

针对空中多个目标进行精确定位及识别的特殊应用场合,该文采用了先进的改进不变矩的算法来进行目标的识别。由于不变矩识别对目标轮廓要求很高,该文提出了一种新的具有方向估计性质的形态学梯度边缘检测算子,弥补了现行的同类算子无法估计边缘方向的缺点;将模糊理论引入该算子,使其更好地抑制噪声,成功分离目标和背景;提出了一种新的断点连接及孤点消除的算法,使目标的轮廓更加清晰平滑,并用跟踪法找到其单像素轮廓线。实验证明,这种新算法极大地提高了对空中多个目标的识别率,并大大加强了系统的可靠性。     

三维旋转激光扫描测量系统的设计

为了实现三维激光扫描仪的旋转扫描测量问题,用于实现形状复杂的三维柱形物体的数字化测量,在普通三维激光扫描仪的基础上,增加了一个可以自动旋转的数控转台,从而实现了旋转测量的目的。通过在转台上安装标定球的方法来实现转台中心轴线的精确标定,获得了新的转台中心轴线的标定方法和后期的拼合和处理方案。     

Operator dependence of 3-D ultrasound-based computational fluid dynamics for the carotid bifurcation

The association between vascular wall shear stress (WSS) and the local development of atherosclerotic plaque makes estimation of in vivo WSS of considerable interest. Three-dimensional ultrasound (3DUS) combined with computational fluid dynamics (CFD) provides a potentially valuable tool for acquiring subject-specific WSS, but the interoperator and intraoperator variability associated with WSS calculations using this method is not known. Here, the accuracy, reproducibility and operator dependence of 3DUS-based computational fluid dynamics were examined through a phantom and in vivo studies. A carotid phantom was scanned and reconstructed by two operators. In the in vivo study, four operators scanned a healthy subject a total of 11 times, and their scan data were processed by three individuals. The study showed that with some basic training, operators could acquire accurate carotid geometry for flow reconstructions. The variability of measured cross-sectional area and predicted shear stress was 8.17% and 0.193 N/m/sup 2/ respectively for the in vivo study. It was shown that the variability of the examined parameters was more dependent on the scan operators than the image processing operator. The range of variability of geometrical and flow parameters reported here can be used as a reference for future in vivo studies using the 3DUS-based CFD approach.     

High-speed digital signal processing and control

An attempt is made to organize and survey recent work, and to present it in a unified and accessible form. The need for a new approach suitable for high-speed processing is discussed in the context of several applications in control and communications, and a historical perspective of the use of difference operators in numerical analysis is presented. The general systems calculus, based on divided-different operators is introduced to unify the continuous-time and discrete-time systems theories. This calculus is then used as a framework to treat the three problems of system state estimation; system identification and time-series modeling; and control system design. Realization aspects of algorithms based on the difference operator representation, including such issues as coefficient rounding and implementation with standard hardware, are also discussed     

国外运营商认证测试要求

介绍了不同层面的终端测试,即强制性测试、终端一致性测试和运营商认证测试。对国外运营商认证测试、运营商认证流程以及欧洲和北美运营商的测试要求和测试内容进行了阐述,并给出了一个运营商定义的测试例。     

真三维旋转显示屏体素分析及均匀化校正研究

基于人眼视觉滞留效应,采用高速旋转的平面显示屏像素瞬间发光,形成圆柱体立体空间中的体素,重建真三维立体图像显示。针对旋转体机械结构造成的体素外疏内密的特点,本文研究了体素均匀化校正处理,得到较为理想的立体三维图像显示。     

基于区域融合的单视点图像深度信息提取

将2D转换为3D是目前3D多媒体成功应用的重要解决方法之一.而在2D至3D转换过程中,单视点图像中深度信息提取是最具挑战的任务.提出一种基于区域融合的单视点图像深度信息提取方法,利用区域融合对单视点图像进行区域融合,用先验假设的深度梯度图对区域进行深度分配,得到基于区域融合的深度图.实验结果表明通过所提方法得到的深度图...     

Fast frequency estimation and tracking using Lagrange interpolation

A computationally efficient and accurate frequency estimation and tracking algorithm is proposed, based on the adaptive frequency estimator (AFE) of Etter and Hush. A Lagrange interpolator (a fractional delay filter) is used to estimate the gradient of the performance surface of the adaptation, which enables highly accurate estimation. The performance of the new algorithm is demonstrated in the context of tracking a chirp signal in noise     

Data Filtering-Based Multi-innovation Stochastic Gradient Algorithm for Nonlinear Output Error Autoregressive Systems

This paper discusses the parameter estimation problems of nonlinear output error autoregressive systems and presents a data filtering-based multi-innovation stochastic gradient algorithm for improving the parameter estimation accuracy of the stochastic gradient algorithm by combining the multi-innovation identification theory and the data filtering technique. The proposed algorithm is effective and can generate highly accurate parameter estimates compared with the multi-innovation stochastic gradient algorithm. The simulation results confirm this conclusion.     

Boundary detection using simulation of particle motion in a vectorimage field

This paper introduces a novel approach in image processing based on a vector image model. A major advantage of the model is that it allows vector operations to be performed on an image. An example of a vector operation is the computation of mechanical moments for detecting inhomogeneities in an object or equivalently edges in an image. A new edge operator derived from a vector image model yields an edge vector field analogous to the Hamiltonian gradient field of the image. The distinct feature of the edge vector field is that edge vectors form current loops encompassing the objects. This feature is exploited to develop a new boundary extraction algorithm based on particle motion in a force field. The edge vector field forces a particle to move along the edges while an orthogonal normalized Laplacian gradient vector field guarantees that the particle will not drift away from the edges. The object boundary can be obtained from the convergent path of the particle trajectory. Using a fine stepping factor, the extracted boundary can achieve subpixel accuracy. The proposed algorithm has major advantages over the conventional edge-detection, edge-thinning, and edge-linking techniques in that it effectively utilizes both direction and magnitude of edges. The algorithm is simple, robust and performs very well even on high curvature objects.