基于Metaball的曲面约束变形模型及应用

结合曲面变形技术和Metaball原理,提出了基于Metaball的曲面约束变形模型,将Metaball的势函数表达曲面变形的约束,用它去作用于待变形曲面,通过调整Metaball势函数的约束中心、作用半径、偏移等参数控制曲面的预期变形效果,利用骨架卷积获得平坦光滑的曲面.讨论了约束关系、单个约束的影响、控制约束的相互影响等问题,并举例说明了这个模型的机理和应用.     

一种基于Walsh变换的立体匹配基元

提出了一种以Walsh变换系数作为匹配基元的双目立体匹配方法。通过Walsh正交变换核对图像，变换得到Walsh系数，图像的特征被嵌入到该系数中，费用函数采用了Walsh变换系数作为匹配基元，而不是采用传统的像素灰度值。该文给出了算法的费用函数、匹配过程中相关的数据和最后的视差图。试验结果表明，将Walsh 系数作为一种匹配基元的方法是可行和有效的。     

Constrained Ordinal Optimization—A Feasibility Model Based Approach

Ordinal Optimization (OO) is a useful simulation-based approach for stochastic optimization problems such as the problems in Discrete Event Dynamic Systems (DEDS). However, OO cannot be applied directly for the problem since many infeasible decisions cannot be excluded from ordinal comparison without extensive computation involving the expectation operation. In this paper, a new approach for solving constrained ordinal optimization (COO) problems is presented. The key idea of our method for constrained OO problems is to estimate the feasibility of decisions and to choose selected subset based on the estimated feasibility. Any crude method such as the one based on rough set theory developed in our previous work can be applied to determine the decision feasibility efficiently. The algorithm for subset selection and the procedure of Blind Picking with Feasibility Model (BPFM) for COO are derived in the paper. The infeasible decisions are excluded by an imperfect feasibility model in the procedure of subset selection. The performance of the new method is evaluated and compared with the regular OO method. Numerical testing with two examples including the planning problem of a practical remanufacturing system shows that to meet the same required alignment probability, BPFM is more efficient than pure Blind Picking in regular OO. The research presented in this paper is supported in part by the National Outstanding Young Investigator Grant (6970025), National Science Foundation (60243001, 60274011, 60574067) and 863 High Tech Development Plan (2001AA413910) of China. The research effort of Ho is supported in part by U.S. Army Research Office (contract DAAD19-01-1-0610), U.S. Air Force Office of Scientific Research (contract F49620-01-1-0288).     

Constrained Hough Transforms for Curve Detection

This paper describes techniques to perform fast and accurate curve detection using constrained Hough transforms, in which localization error can be propagated efficiently into the parameter space. We first review a formal definition of Hough transform and modify it to allow the formal treatment localization error. We then analyze current Hough transform techniques with respect to this definition. It is shown that the Hough transform can be subdivided into many small subproblems without a decrease in performance, where each subproblem is constrained to consider only those curves that pass through some subset of the edge pixels up to the localization error. This property allows us to accurately and efficiently propagate localization error into the parameter space such that curves are detected robustly without finding false positives. The use of randomization techniques yields an algorithm with a worst-case complexity ofO(n), wherenis the number of edge pixels in the image, if we are only required to find curves that are significant with respect to the complexity of the image. Experiments are discussed that indicate that this method is superior to previous techniques for performing curve detection and results are given showing the detection of lines and circles in real images.     

基于Zernike矩的区域匹配方法

在基于区域的立体匹配中,由于遮掩、区域变形及光照条件会对匹配算法造成很大的影响,而传统的顺序性约束、唯一性约束、外极线约束和邻域约束并不能很好地解决这些问题,而近几年提出的相对位置约束虽能解决其中大部分问题,但对于区域的遮掩情况依然效果不佳。为此提出了一种新的基于Zernike矩的区域匹配算法,该算法在相对位置约束的基础上,采用中心距离和Zernike矩构造了新的费用函数,并提出根据匹配区域之间中心距离的大小来动态评判费用函数的权重系数值,从而提高了算法的性能。实验结果表明,该算法优于原方法,且对于区域的遮掩和变形情况都具备更好的识别性能,是一种行之有效的区域匹配算法。     

一种基于结构索引的XML模式匹配方法

XML文档采用了树型的数据模型,对其查询通常是用带有选择谓词的模式树在XML数据中进行匹配.因此,找出XML文档中所有符合模式树结构的元素集,是XML查询处理的核心操作.本文提出了结构索引JoinGuide,并在此基础上提出了一种新的XML模式匹配方法.它使用JoinGuide来对模式树进行预匹配,这样在XML文档上查询时可以利用索引上的匹配结果来忽略部分连接谓词和不必要的候选XML元素序列.本文还提出了三种具体算法来利用索引匹配结果进行进一步的查询.实验结果表明本文中的模式树匹配方法优于以往的匹配方法,并且索引所需的空间很小.     

A Formal Logic Approach to Constrained Combinatorial Testing

Combinatorial testing is as an effective testing technique to reveal failures in a given system, based on input combinations coverage and combinatorial optimization. Combinatorial testing of strength t (t ≥ 2) requires that each t-wise tuple of values of the different system input parameters is covered by at least one test case. Combinatorial test suite generation algorithms aim at producing a test suite covering all the required tuples in a small (possibly minimal) number of test cases, in order to reduce the cost of testing. The most used combinatorial technique is the pairwise testing (t = 2) which requires coverage of all pairs of input values. Constrained combinatorial testing takes also into account constraints over the system parameters, for instance forbidden tuples of inputs, modeling invalid or not realizable input values combinations. In this paper a new approach to combinatorial testing, tightly integrated with formal logic, is presented. In this approach, test predicates are used to formalize combinatorial testing as a logical problem, and an external formal logic tool is applied to solve it. Constraints over the input domain are expressed as logical predicates too, and effectively handled by the same tool. Moreover, inclusion or exclusion of select tuples is supported, allowing the user to customize the test suite layout. The proposed approach is supported by a prototype tool implementation and results of experimental assessment are also presented.     

一种整体的视频匹配方法

给出一种视频时空配准的整体方法,提出一种视频内匹配与视频间匹配相结合的空间配准策略,改进动态时间扭曲方法以用于时间维的对齐.视频内匹配跟踪视频内各帧图像的特征点并记录其轨迹,视频间匹配配准不同视频的帧图像,使用轨迹对应提供图像配准所需的初始特征点对应,根据图像配准得到的特征点对应建立和更新轨迹对应.该匹配策略充分利用了视频的连贯性提高了匹配的稳定性和效率,同时提高了配准视频的连贯性.改进的动态时间扭曲方法通过极小化两段视频的整体距离建立视频之间的帧对应关系,保持视频内部各帧之间的时序关系并能处理非线性偏移     

基于梯度的受限空间安全定位方法

现有的无线传感器网络定位技术消耗了大量的计算和处理资源,并且受到了环境因素以及对手攻击等干扰,在受限空间中定位精度较低,无法满足定位需求。为了提高受限空间中的定位精度,提出了一种基于梯度的安全定位算法,算法在双曲线定位模型基础上,引入梯度的概念,降低了算法的计算复杂度,使算法能够适应受限空间的环境要求,实现高效高精度的定位;为了提高算法的安全性,增加了对不一致性测量的选择性剪枝过程,增强了算法对恶意攻击的抵抗能力。最后,以室内走廊为实验环境进行了仿真验证,通过主频计时策略,提高了算法的定位精度。分析结果表明,在室内受限空间中,提出的算法在定位精度、能量消耗和抗干扰能力上优于现有算法。     

A Wikipedia Matching Approach to Contextual Advertising

Contextual advertising is an important part of today’s Web. It provides benefits to all parties: Web site owners and an advertising platform share the revenue, advertisers receive new customers, and Web site visitors get useful reference links. The relevance of selected ads for a Web page is essential for the whole system to work. Problems such as homonymy and polysemy, low intersection of keywords and context mismatch can lead to the selection of irrelevant ads. Therefore, a simple keyword matching technique gives a poor accuracy. In this paper, we propose a method for improving the relevance of contextual ads. We propose a novel “Wikipedia matching” technique that uses Wikipedia articles as “reference points” for ads selection. We show how to combine our new method with existing solutions in order to increase the overall performance. An experimental evaluation based on a set of real ads and a set of pages from news Web sites is conducted. Test results show that our proposed method performs better than existing matching strategies and using the Wikipedia matching in combination with existing approaches provides up to 50% lift in the average precision. TREC standard measure bpref-10 also confirms the positive effect of using Wikipedia matching for the effective ads selection.     

A Flexible Classifier Based on Optimum Curve Fitting Approach

ABSTRACT

This study proposes a curve fitting approach for classification problems. The different classification data sets are utilized to test and evaluate the suggested method. For tested classification problems, the Gaussian curve fitting models are used. In the curve fitting stage, the number of curves equals the number of attributes in the related classification problem. For example, there are 4 attributes for iris dataset, thus four Gaussian curves are fitted for this problem. Then, output values of these fitted curves are calculated to average values, and this average value is rounded to the nearest integers. The same procedure is applied to the other dataset with having different number of features. In optimization stage, for each of classification application, the optimum values of constants of Gaussian function are determined by using genetic algorithm. For all used classification dataset, a part of the set is used during the optimization phase, and then the proposed model is validated with the remainder of the dataset. Furthermore, the optimal valuesof each of the attributes in tested classification application are determined by optimization algorithm. It is a valuable property of the proposed method that the accuracy of high classification can be achieved with a low number of reference data by the stage of determination of optimal feature set. Simulation results show that proposed classification approach with optimum values of constants and optimal feature set based on curve fitting has high accuracy rate. The proposed approach can be used for different classification problems.     

二维模式近似匹配的快速算法

给定一个大小为ｎ×ｎ的文本Ｔ和一个大小为ｍ×ｍ的模板Ｐ，如果文本Ｔ中存在一个ｍ×ｍ的子块与模板Ｐ能够逐点匹配，称为精确匹配。如果最多有ｋ个元素不同，称为带有最多ｋ个误差的近似匹配。对于精确匹配，本文给出了一个时间复杂性为Ｏ（ｎ２ｌｏｇ｜∑｜）的算法，∑＝｛ａ１，２，…，ａ｜∑｜｝，是模板的字符集。对于近似匹配，快速算法分为两步：（１）预选。利用精确匹配算法找出能精确匹配的ｓ×ｓ（０≤ｓ≤ｍ）子块，得到ｈ个候选的对准点；（２）验证。把模板对准候选点，逐点比较，以确定不相同的元素是否不超过ｋ个。近似匹配的时间复杂性为Ｏ（ｎ２ｌｏｇ｜∑｜＋ｈｍ２）。     

保测地曲率的曲面曲线设计

给出一种在给定光滑曲面上进行曲线设计的算法．由于曲面上曲线的曲率向量可分解为测地曲率向量与法曲率向量的和,故可以通过设计平面源曲线,并将这条源曲线保测地曲率对应到给定曲面上,得到一条测地曲率和平面源曲线的曲率相同的目标曲线．取给定曲面上一点为初始点,逐次迭代跟踪得到整条目标曲线．该算法既可以用来进行曲面上的图案设计,也可用于求解光滑曲面上的测地线。     

一种基于Hopfield网络的立体匹配方法

立体匹配是计算机视觉研究的经典难题，其算法的复杂度和精度直接影响了视觉系统对外部景物的重建性能。为此提出了一种新的基于神经网络的立体匹配方法，其基本思想是：在实现核线重排的前提下，利用唯一性、相容性以及相似性等匹配约束条件，建立反映对应极线间所有匹配点约束关系的能量函数，将其映射到二维Hopfield网络进行极小化求解，网络最后的稳态表示匹配点的对应关系；通过对图中所有极线进行上述操作，可以得到所求的视差图。与传统方法相比，本算法具有两个明显的特点：(1)匹配基元采用了普通的图像点，可以直接获得稠密的深度图；(2)Hopfield网的外部输入不再为常数，而是一个反映对应点灰度相似性关系的值。通过对合成图以及真实图景进行测试，验证了该方法的有效性。     

A Flexible Approach to Bayesian Multiple Curve Fitting

We model sparse functional data from multiple subjects with a mixed-effects regression spline. In this model, the expected values for any subject (conditioned on the random effects) can be written as the sum of a population curve and a subject-specific deviate from this population curve. The population curve and the subject-specific deviates are both modeled as free-knot b-splines with k and k^′ knots located at and , respectively. To identify the number and location of the “free” knots, we sample from the posterior using reversible jump MCMC methods. Sampling from this posterior distribution is complicated, however, by the flexibility we allow for the model’s covariance structure. No restrictions (other than positive definiteness) are placed on the covariance parameters ψ and σ² and, as a result, no analytical form for the likelihood exists. In this paper, we consider two approximations to and then sample from the corresponding approximations to . We also sample from which has a likelihood that is available in closed form. While sampling from this larger posterior is less efficient, the resulting marginal distribution of knots is exact and allows us to evaluate the accuracy of each approximation. We then consider a real data set and explore the difference between and the more accurate approximation to .     

A Nonparametric Approach to Design Fixed-order Controllers for Systems with Constrained Input

International Journal of Control, Automation and Systems - This paper presents an approach for designing fixed-structure controllers for input-constrained linear systems using frequency domain...     

Improved Algorithms for Partial Curve Matching

We revisit the problem of deciding whether a given curve resembles some part of a larger curve under a fixed Fréchet distance, achieving a running time of O(nm), for n and m being the number of segments in the two curves. This improves the long-standing result of Alt and Godau by an O(log(nm)) factor. Our solution is based on constructing a simple data structure which we call free-space map. Using this data structure, we obtain improved algorithms for several variants of the Fréchet distance problem, including the Fréchet distance between two closed curves, and the so-called minimum/maximum walk problems. We also improve the map matching algorithm of Alt et al. for the particular case in which the map is a directed acyclic graph.     

一种实用的基于证据积累的图像曲线粗匹配方法

该文提出了一种基于证据积累的图像曲线粗匹配方法,比较有效地解决了将图像中提取的一条曲线(较短)与一条参考曲线(较长)相匹配的问题．该方法具有如下特点：(1)通过实验发现曲线上两点之间的直线距离较它们之间的曲线距离对噪声等误差更鲁棒;基于此,在参考曲线上选取可能的匹配曲线段时,利用首尾点的直线距离作为主要匹配标准,大大提高了算法的鲁棒性;(2)将证据积累的思想应用到控制点的匹配上,有效地去除了错误的控制点和不必要进行匹配的曲线段,在提高算法鲁棒性的同时极大地降低了算法的计算复杂度;(3)在传统的Hausdorff距离计算中引入高斯概率统计模型,使其更适合作为实际应用中评价两条曲线匹配程度优劣的一种度量．大量卫星影像及数码相机照片实验证明了该匹配方法的有效性和实用性．     

基于Bézier曲线的碰撞角约束多项式制导方法

研究了一种基于Bézier曲线的碰撞角约束的制导律.通过模型转化将制导指令设计的问题转化为二次Bézier曲线形式的航迹角设计问题.首先,利用Bézier曲线的性质设计了导弹速度大小不变的制导律;然后进一步对导弹速度时变的末端角度约束的制导律进行了研究,同时对导弹速度时变情形下的剩余飞行时间进行了估计;最后通过不同情况下的数值仿真,验证了所提出的制导律的有效性.     

基于视觉约束能量最小化的特征点匹配算法

为了解决海上目标航空遥感图像重复特征较多导致的匹配不一致问题,并简化匹配过程,文中提出了基于SIFT视觉约束能量最小化的匹配算法(CEM-SIFT)。该算法将约束能量最小化模型应用于特征点的匹配,通过构造有限脉冲响应线性滤波器,采用视觉信息计算其能量值,使得待匹配的点集经过滤波之后的平均输出能量在一定约束下达到最小值,最终实现含重复信息的特征精确匹配。采用10组航空遥感海冰图像对算法进行测试,结果表明,相对于采用SIFT欧氏距离(ED-SIFT),在匹配重复特征比较多、点集规模比较大的图像时,CEM-SIFT算法的匹配精度更高,能够达到100%。