Mutual information optimization based dynamic log-polar image registration

Log-polar transformation(LPT)is widely used in image registration due to its scale and rotation invariant properties.Through LPT,rotation and scale transformation can be made into translation displacement in log-polar coordinates,and phase correlation technique can be used to get the displacement.In LPT based image registration,constant samples in digitalization processing produce less precise and effective results.Thus,dynamic log-polar transformation(DLPT)is used in this paper.DLPT is a method that generates several sample sets in axes to produce several results and only the effective results are used to get the final results by using statistical approach.Therefore,DLPT can get more precise and effective transformation results than the conventional LPT.Mutual information(MI)is a similarity measure to align two images and has been used in image registration for a long time.An optimal transform for image registration can be obtained by maximizing MI between the two images.Image registration based on MI is robust in noisy,occlusion and illumination changing circumstance.In this paper,we study image registration using MI and DLPT.Experiments with digitalizing images and with real image datasets are performed,and the experimental results show that the combination of MI with DLPT is an effective and precise method for image registration.     

一种基于稀疏表达和光流的目标跟踪方法

提出一种将稀疏表达技术融入到传统光流算法的目标跟踪方法.首先使用FAST和Harris算法在视频序列的每一帧中为光流算法采集运动目标的特征点,之后光流算法基于后向跟踪-形心配准的方法对跟踪目标完成粗略定位.在当前帧的粗略定位处应用仿射变换产生N个候选区域.最后应用稀疏表达技术判断出与原始目标匹配率最高的仿射变换区域做为最终目标跟踪区域.实验结果表明,该算法既能较好地适应目标的外观变化,又具有较强的抗遮挡能力,鲁棒性强.     

基于互信息快速算法的多模医学图像配准

互信息作为相似性测度在多模医学图像配准领域得到了广泛应用,具有高精度和稳健的特点.但频繁的互信息计算降低了配准效率,同时对两幅图像重叠区域比较敏感.采用归一化互信息为测度,降低互信息计算中灰度级的快速算法,通过多模CT/MRI配准实验证明,可以在确保配准精度的同时缩短时间提高配准效率.     

基于点特征和边缘特征的无人机影像配准方法

为解决变形较大的无人机影像配准问题,提出了点特征和边缘特征相结合的配准方法.用尺度不变特征变换(SIFT)算法提取点特征,完成影像的初步配准,并通过多项式函数对影像进行粗校正.在此基础上提取影像的边缘特征信息,根据距离相似性对边缘特征信息进行配准;依据色彩能量差筛选点特征信息配准结果和边缘特征信息配准结果,采用小面元微分校正的方法对变形影像进行校正.实验结果表明:提出的配准方法能够弥补点特征配准方法和边缘特征配准方法的不足,其配准的鲁棒性提高10%左右,可以较好地完成变形较大的无人机影像配准.      

点云数据配准算法的研究

点云配准是点云数据处理的关键,直接影响最后合成结果和模型精度。目前,点云配准方法普遍存在对配准数据初始位姿要求高的缺点。将点云配准分为两个阶段：第一阶段是基于同名点配准,即粗配准,采用人机交互式,配准过程耗时短,节约时间;第二阶段是精配准,在粗配准后,依据最小二乘原理,用间接平差思想,通过最近点迭代算法对点云数据快速配准,并采用目标点集中、目标点坐标与转入目标点集中的点坐标中误差为指标,评价配准精度。进行粗配准的精配准不仅速度快、耗时短,并且可以避免因局部收敛而带来的局部最小问题。试验表明该方法有效可行。     

Modified gray level difference-based thresholding segmentation and its application in X-Ray welding image

Thresholding is a popular image segmentation method that often requires as a preliminary and indispensable stage in the computer aided image process, particularly in the analysis of X-ray welding images. In this paper, a modified gray level difference-based transition region extraction and thresholding algorithm is presented for segmentation of the images that have been corrupted by intensity inhomogeneities or noise. Classical gray level difference algorithm is improved by selective output of the result of the maximum or the minimum of the gray level with the pixels in the surrounding, and multi-structuring of neighborhood window is used to represent the essence of transition region. The proposed algorithm could robustly measure the gray level changes, and accurately extract transition region of an image. Comparisons with other approaches demonstrate the superior performance of the proposed algorithm.     

Mean shift registration algorithm for dissimilar sensors

The mean shift registration (MSR) algorithm is proposed to accurately estimate the biases for multiple dissimilar sensors. The new algorithm is a batch optimization procedure. The maximum likelihood estimator is used to estimate the target states, and then the mean shift algorithm is implemented to estimate the sensor biases. Monte Carlo simulations show that the MSR algorithm has significant improvement in performance with reducing the standard deviation and mean of sensor biased estimation error compared with the maximum likelihood registration algorithm. The quantitative analysis and the qualitative analysis show that the MSR algorithm has less computation than the maximum likelihood registration method.     

桥梁下部结构裂缝提取的改进C-V模型算法(英文)

应用改进C-V模型,进行桥梁下部结构裂缝图像分割,通过裂缝截取、图像填充和旋转变换精确提取裂缝宽度。对不同光照条件下拍摄的在役混凝土桥梁结构裂缝图像,分别利用改进C-V模型算法、自适应阈值法、形态学算法、C-V模型以及Canny算法进行试验对比。分析结果表明:改进C-V模型算法误分率和运算时间最小,分别为3.02%与89ms;1 000幅桥梁结构裂缝图像试验对比显示裂缝检测准确率大于90.8%,裂缝宽度平均误差小于0.03mm。可见,改进算法可有效提高检测准确率,减少运算时间。     

基于一面两孔特征的点云配准方法

为了提高零件在扫描检测过程中点云与设计模型的配准精度,提出了一种基于一面两孔特征的点云配准方法.该方法粗配准以零件的平面/圆柱孔特征为对象,使设计模型和点云的局部坐标系重合,并通过改进ICP算法求解点云与设计模型最近点的距离最小平方和实现精配准.由于配准区域和最近点的计算方法不同,精配准进一步分为全域和特征域配准两种类型.全域精配准以距点云最近的设计模型三角网格点或投影点为最近点,适合于毛坯件;特征域精配准则通过求解点云在平面/圆柱孔特征上的投影点为最近点,适合于成品件.试验及计算结果表明:全域配准的配准精度随表面离散点距离的减小而提高, 当离散点距离达到1.50 mm时,其配准精度已经达到0.15 mm,基本满足工程应用要求.当配准精度相同时,配准效率较其它方法提高10%~20%.      

RC矩形空心墩的新型滞回模型及参数识别方法

为了准确模拟RC （reinforced concrete）矩形空心桥墩的刚度退化特性,为桥梁震后可恢复性能研究提供理论基础,进行了不同设计参数的14个RC矩形空心墩模型拟静力试验. 通过引入峰值位移影响系数体现刚度退化与峰值位移的关联,建立修正的Bouc-Wen-Baber-Noori （BWBN）滞回模型;基于粒子群-引力搜索混合智能优化算法（combination of particle swarm optimization and gravitational search algorithm,PSOGSA）识别实测滞回曲线对应的滞回参数,并建立桥墩设计参数与滞回参数间的对应关系,进而总结滞回参数的经验预测方法. 研究结果表明:修正的BWBN滞回模型曲线与实测滞回曲线吻合程度高,相关性系数在0.98以上,且新型滞回模型能准确地反映出桥墩侧向刚度随墩顶位移退化的特性;PSOGSA算法能精确地识别实测滞回曲线的模型参数;采用经验预测方法得到的模型曲线与实测滞回曲线的相关性系数为0.83,该方法适用于缺乏实测滞回曲线的桥墩.      

基于共轭梯度的大尺度医学图像非刚性配准算法

人体胸腹腔中大量非刚性软组织器官由于呼吸、脏器蠕动和体位变动等会产生大尺度非线性形变,粘性流体配准将图像的形变模拟为流体的流动过程而适宜于大的形变.针对粘性流体配准算法应用超松驰迭代求解离散化偏微分方程组耗时量大,且其最优松驰参数难以获得的问题,使用基于不需要预先估计参数的共轭梯度迭代求解形变参数,实现粘性流体配准.该方法所需存储量小,且具有步收敛性、稳定性高的优点,实验证明该方法在不损失配准精度的前提下提高了配准速度.     

Measuring System Regularity Using Fuzzy Similarity-based Approximate Entropy

Approximate entropy (ApEn), a measure quantifying regularity and complexity, is believed to be an effective analyzing method of diverse settings that include both deterministic chaotic and stochastic processes, particularly operative in the analysis of physiological signals that involve relatively small amount of data. However, the similarity definition of vectors based on Heaviside function, of which the boundary is discontinuous and hard, may cause some problems in the validity and accuracy of ApEn. To overcome these problems, a modified ApEn based on fuzzy similarity (mApEn) was proposed. The performance on the MIX stochastic model, as well as those on the Logistic map and the Hennon map with noise, shows that the fuzzy similarity-based ApEn gets more satisfying results than the standard ApEn when characterizing systems with different regularities.     

Renyi信息熵指导下的聚合层次化聚类

聚合层次化聚类是聚类分析中发现数据集潜在结构的一类重要方法．在这类方法中,影响聚类质量的一个关键问题是如何度量子类之间的距离．作为子类间的相似性度量,不但可以通过非参数估计的方式进行计算,还可有效地利用子类数据集中所有样本提供的信息,对子类中数据分布的描述更加充分．实验结果显示,在两种具有代表性的人造数据集上,基于Renyi熵的类间距离度量比3种传统度量方法有更好的层次化聚类效果．并且,在图像过分割的情况下,通过Renyi熵距离对子分割区域进行合并可以找到合理的分割目标．     

碳纤维双向加固RC板抗弯承载力计算模型研究

对配筋相同的9块碳纤维布加固的RC双向板和1块同规格的对比板进行了抗弯试验，试验板采用四点加载、简支支承。依据试验板的实际破坏形态模拟出三种塑性铰线破坏模式并提出相应的实用计算公式，计算结果与试验结果较吻合，且偏于安全，可供工程设计参考。     

Kinect-based automatic spatial registration framework for neurosurgical navigation

As image-guided navigation plays an important the pre-operative images with the intra-operative patient role in neurosurgery, the spatial registration mapping position becomes crucial for a high accurate surgi- cal output. Conventional landmark-based registration requires expensive and time-consuming logistic support. Surface-based registration is a plausible alternative due to its simplicity and efficacy. In this paper, we propose a comprehensive framework for surface-based registration in neurosurgical navigation, where Kinect is used to auto- matically acquire patient＇s facial surface in a real time manner. Coherent point drift （CPD） algorithm is employed to register the facial surface with pre-operative images （e.g., computed tomography （CT） or magnetic resonance imaging （MRI）） using a coarse-to-fine scheme. The spatial registration results of 6 volunteers demonstrate that the proposed framework has potential for clinical use.     

基于高斯混合部件模型的铁路扣件检测

针对采集图像中铁路扣件存在形状的变化、扣件图像的光照差异较大和扣件被异物局部遮挡的问题,根据对可变形部件模型算法和高斯混合模型的研究,提出了高斯混合部件模型算法. 结合扣件图像边缘特性及改进的Roberts算子计算图像梯度,将归一化后的方向梯度直方图特征作为高斯混合部件模型算法的底层特征,根据扣件形状划分部件,部件之间的相对位置采用星型连接方式度量,运用余弦相似性度量部件中方向梯度直方图特征的相似度,部件模型使用高斯混合模型并采用期望最大化算法迭代求解. 将高斯混合部件模型算法应用于扣件检测中,最终平均检测效果为漏检率3.16%、误检率9.80%、正确率90.27%.      

基于灰关联测度的分裂式层次聚类算法

为估计数据集的聚类数目及获得较好的聚类性能,提出了一种基于灰关联测度的分裂式层次聚类算法.该算法用灰关联测度衡量数据对象之间的相似程度,以基于密度扩展的方式自顶向下分裂成不同层次的数据集划分;然后,根据灰关联测度定义聚类有效性指标;最后将有效性指标曲线极值点对应的聚类划分用于估计最佳聚类数目.实际数据和合成数据集的实验表明,与FCM聚类相比,该算法的聚类正确率平均提高3.7%,并且能够识别任意形状的簇.     

基于三维模型重构技术的公路预制构件尺寸检验评价方法

为使公路工程异形混凝土预制构件的制造尺寸检验评价适应工业化建造要求,应用三维模型重构技术检验评价了异形混凝土预制构件尺寸,提出了高精度、自动化异形混凝土预制构件尺寸检验评价方法,包括三维模型重构、点云数据处理和检验评价体系3个环节;总结了基于三维摄影的点云模型重构技术的原理和关键环节,研究了基于坐标转换和包围盒的无关点...     

Optimization of CMOS repeater driven interconnect RC line using genetic algorithm

In this work, optimization of complementary metal oxide semiconductor (CMOS) repeater driven interconnect resistive-capacitive (RC) line is carried out using genetic algorithm (GA). This work is aimed at powerdelay- product (PDP) minimization of RC interconnect at 180 nm technology node. The algorithm simultaneously optimizes the values of supply voltage, number of repeaters and repeater width for delay and PDP minimization. The accuracy of results obtained is verified by simulations from Cadence virtuoso tool. For delay minimization, comparison of GA results with previous results of the literature shows an improvement of 44.4% in the value of the optimal number of repeaters required. This improvement is obtained by increasing the repeater size, which also increases power dissipation, so a tradeoff has also been achieved in terms of PDP minimization. The comparison of PDP results obtained in this work, with the results at 70, 100, and 130 nm technologies from literature shows improvement in optimal number of repeaters required. The results of algorithm and simulations are in good agreement and demonstrate the validity of proposed algorithm.