Contribution to the determination of vanishing points using Houghtransform

We propose a method to locate three vanishing points on an image, corresponding to three orthogonal directions of the scene. This method is based on two cascaded Hough transforms. We show that, even in the case of synthetic images of high quality, a naive approach may fail, essentially because of the errors due to the limitation of the image size. We take into account these errors as well as errors due to detection inaccuracy of the image segments, and provide a method efficient, even in the case of real complex scenes     

Pose determination of human faces by using vanishing points

A new method for estimating 3D-head pose from a monocular image is proposed in this paper. The approach employs general prior knowledge of face structure and the corresponding geometrical constraints provided by the location of vanishing point to determine pose of human faces. The connection of the two far-eye corners and the two neighboring-eye corners, respectively, form the eye-lines. Connecting the two far-mouth corners forms the mouth-line. The eye-lines and the mouth-line are assumed parallel in 3D space, and their vanishing point on the image plane can be used to infer 3D pose of the human face. Perspective projection imaging model is used and an accurate analytic solution of pose (position and orientation) of human face is deduced. The orientation of the facial plane can be obtained when the ratio of the lengths of the eye-line segment (far-eye corners) and the mouth-line segment (far-mouth corners) is known. Furthermore, if one of the two lengths is known, then the absolute positions of the feature corners can be located. The robustness analysis of the algorithm with synthetic data and the experimental results of real face images are enclosed.     

An error analysis for surface orientation from vanishing points

Given two parallel lines in a plane, their images formed by central projection onto the viewing plane intersect at a vanishing point, which provides a constraint on the orientation of the plane. Two such independent constraints define a vanishing line and thereby determine the orientation of the plane uniquely. In order to effectively use this information, an estimate of its accuracy must be incorporated. In the approach suggested, line directions and surface normal vectors are represented as points on a Gaussian sphere, and the error bounds are computed as regions on the sphere. Information from multiple vanishing points and surfaces is combined by intersecting the corresponding regions. In addition, constraints based on real-world knowledge can be introduced to improve the accuracy. Some experimental results on natural images re presented to illustrate this method     

Generalized gradient method for the determination of (ɛ+μ, ɛ+μ)-saddle points

Cybernetics and Systems Analysis -     

An algorithm for automatic round-off error analysis in discrete linear transforms

The discrete linear transforms implemented on computers require a very great number of computations. The round-off errors inherent in the floating-point arithmetic of the computer generate errors in the results which may be fairly large.

In this paper we propose an algorithm based on the La Porte-Vignes Perturbation Method which is able to automatically analyze the round-off error in any discrete linear transform. Furthermore, this algorithm supplies the local accuracy in any discrete transform in the case of experimental data (data errors and round-off errors).     

词袋模型中梯度方向离散精度阈值经验分析

为避免常规构建词袋模型在选取梯度方向离散精度时存在的盲目性,以及解决不恰当离散精度构造出的词袋模型分类率不高的问题,研究在词袋模型中提取图像特征时梯度方向离散精度是否存在明显的阈值,使选取该阈值时能构造出最佳的词袋模型.基于面向稠密特征提取可快速计算的局部图像特征描述,选择不同的梯度方向离散精度分别进行大量实验,实验结果表明,存在一个明显、统一的阈值24,选择该阈值构造的词袋模型能够得到最高正确分类率.     

Comparison of discrete Hodge star operators for surfaces

We investigate the performance of various discrete Hodge star operators for discrete exterior calculus (DEC) using circumcentric and barycentric dual meshes. The performance is evaluated through the DEC solution of Darcy and incompressible Navier–Stokes flows over surfaces. While the circumcentric Hodge operators may be favorable due to their diagonal structure, the barycentric (geometric) and the Galerkin Hodge operators have the advantage of admitting arbitrary simplicial meshes. Numerical experiments reveal that the barycentric and the Galerkin Hodge operators retain the numerical convergence order attained through the circumcentric (diagonal) Hodge operators. Furthermore, when the barycentric or the Galerkin Hodge operators are employed, a super-convergence behavior is observed for the incompressible flow solution over unstructured simplicial surface meshes generated by successive subdivision of coarser meshes. Insofar as the computational cost is concerned, the Darcy flow solutions exhibit a moderate increase in the solution time when using the barycentric or the Galerkin Hodge operators due to a modest decrease in the linear system sparsity. On the other hand, for the incompressible flow simulations, both the solution time and the linear system sparsity do not change for either the circumcentric or the barycentric and the Galerkin Hodge operators.     

自动确定聚类中心的比较密度峰值聚类算法

针对密度峰值聚类算法(DPC)不能自动确定聚类中心,并且聚类中心点与非聚类中心点在决策图上的显示不够明显的问题,设计了一种自动确定聚类中心的比较密度峰值聚类算法(ACPC).该算法首先利用距离的比较量来代替原距离参数,使潜在的聚类中心在决策图中更加突出;然后通过二维区间估计方法进行对聚类中心的自动选取,从而实现聚类过程...     

On the stable equilibrium points of gradient systems

This paper studies the relations between the local minima of a cost function f and the stable equilibria of the gradient descent flow of f. In particular, it is shown that, under the assumption that f is real analytic, local minimality is necessary and sufficient for stability. Under the weaker assumption that f is indefinitely continuously differentiable, local minimality is neither necessary nor sufficient for stability.     

Simultaneous estimation of vanishing points and their converging lines using the EM algorithm

This paper introduces a new method for the simultaneous computation of sets of lines meeting at multiple vanishing points through the use of the Expectation-Maximisation (EM) algorithm. The proposed method is based on the formulation of novel error functions in the projective plane between lines and points which involve the use of non-linear optimisation procedures that allow to treat equally finite and infinite vanishing points. These functions are included into the EM framework, which handles the multi-modality of the problem naturally with mixture models. Results show that the proposed method of joint computation of vanishing points and lines converging at such points enhances the robustness and the accuracy of locating these points.     

Focus points and convergent process operators: a proof strategy for protocol verification

We present a method for efficiently providing algebraic correctness proofs for communication systems. It is described in the setting of μCRL [J.F. Groote, A. Ponse, The syntax and semantics of μCRL, in: A. Ponse, C. Verhoef, S.F.M. van Vlijmen (Eds.), Algebra of Communicating Processes, Workshops in Computing, Springer, Berlin, 1994, pp. 26–62] which is, roughly, ACP [J.C.M. Baeten, W.P. Weijland, Process Algebra, Cambridge Tracts in Theoretical Computer Science, vol. 18, Cambridge University Press, Cambridge 1990, J.A. Bergstra, J.W. Klop, The algebra of recursively defined processes and the algebra of regular processes, in: Proceedings of the 11th ICALP, Antwerp, Lecture Notes in Computer Science, vol. 172, Springer, Berlin, 1984, pp. 82–95] extended with a formal treatment of the interaction between data and processes. The method incorporates assertional methods, such as invariants and simulations, in an algebraic framework, and centers around the idea that the state spaces of distributed systems are structured as a number of cones with focus points. As a result, it reduces a large part of algebraic protocol verification to the checking of a number of elementary facts concerning data parameters occurring in implementation and specification. The resulting method has been applied to various non-trivial case studies of which a number have been verified mechanically with the theorem checker PVS. In this paper the strategy is illustrated by several small examples and one larger example, the Concurrent Alternating Bit Protocol (CABP).     

FFH100型自动蒸发设备比对分析及使用

为满足水文观测的自动化要求,给水文站自动蒸发设备的推广使用提供依据,通过在安塞水文站安装FFH100型自动蒸发设备,统计自动蒸发设备累积观测的与人工观测的日蒸发量数据（共计82组）,在分析自动蒸发设备构造及计算原理的基础上,对82组日蒸发量数据进行比对分析,分析观测误差及来源。数据定量回归分析及自动蒸发设备使用结果表明：人工和自动蒸发设备观测得到的2个数据变量的相关系数Rp 达到0.988,具备很高的单值对应关系,符合常数要求,能够满足水面蒸发观测规范要求。且自动蒸发设备在降雨期间能对蒸发量进行计量并自动采集与远程发报,实现蒸发观测的自动无人化,可作为北方地区非冰期水面蒸发自动测量设备选择之一。     

A three-dimensional criterion for the determination of optimal grip points

Multifingered grasping has aroused remarkable interest because it makes possible the manipulation of objects of different shapes and sizes. However, manipulating and picking up objects in unstructured environments requires accurate contact-point selection. Generally, such processes are subject to external forces which are difficult to predict and may change during task execution.In this paper, an optimization criterion is proposed which is meant to select the optimal grip points in a three-dimensional problem for any number of contact points. This method may be applied to three-dimensional objects of any shape (curved or polygonal) and does not require that the external forces acting on the object be known. A grasp quality index is presented which has been obtained by minimizing the grasping forces required to balance a generalized external disturbance. The optimization criterion has led to the formulation of a single optimization problem with non-linear constraints. Finally, the paper presents the results obtained in searches for the optimal grip points on some two- and three-dimensional objects.     

Use of an automatic content analysis tool: A technique for seeing both local and global scope

This paper examines what can be learned about bodies of literature using a concept mapping tool, Leximancer. Statistical content analysis and concept mapping were used to analyse bodies of literature from different domains in three case studies. In the first case study, concept maps were generated and analysed for two closely related document sets—a thesis on language games and the background literature for the thesis. The aim for the case study was to show how concept maps might be used to analyse related document collections for coverage. The two maps overlapped on the concept of “language”; however, there was a stronger focus in the thesis on “simulations” and “agents.” Other concepts were not as strong in the thesis map as expected. The study showed how concept maps can help to establish the coverage of the background literature in a thesis. In the second case study, three sets of documents from the domain of conceptual and spatial navigation were collected, each discussing a separate topic: navigational strategies, the brain's role in navigation, and concept mapping. The aim was to explore emergent patterns in a set of related concept maps that may not be apparent from reading the literature alone. Separate concept maps were generated for each topic and also for the combined set of literature. It was expected that each of the topics would be situated in different parts of the combined map, with the concept of “navigation” central to the map. Instead, the concept of “spatial” was centrally situated and the areas of the map for the brain and for navigational strategies overlaid the same region. The unexpected structure provided a new perspective on the coverage of the documents. In the third and final case study, a set of documents on sponges—a domain unfamiliar to the reader—was collected from the Internet and then analysed with a concept map. The aim of this case study was to present how a concept map could aid in quickly understanding a new, technically intensive domain. Using the concept map to identify significant concepts and the Internet to look for their definitions, a basic understanding of key terms in the domain was obtained relatively quickly. It was concluded that using concept maps is effective for identifying trends within documents and document collections, for performing differential analysis on documents, and as an aid for rapidly gaining an understanding in a new domain by exploring the local detail within the global scope of the textual corpus.     

Establishing a balanced neighborhood of discrete points for local quadric surface fitting

This paper presents a novel algorithm to establish a balanced neighborhood of points for reliable local quadric surface fitting, a common task in point cloud data processing. The underlying smooth surface geometry of a point cloud in the vicinity of a point can be locally approximated by the best fitted quadric surface at the point. The quality of the fitted surface considerably depends on what neighboring points are selected for the fitting. Specifically, if the selected neighboring points carry a biased distribution, the fitted geometry becomes biased, resulting in loss of accuracy in the fitting. The presented algorithm in this paper is able to reliably select neighboring points considering measures of both distance and direction. The main feature is the development of a geometric relationship, named as Territory Claiming, between the selected and the candidate neighboring points. The fundamental principle is for the selected point set to cover the whole neighborhood domain without redundancy. The selection procedure starts with a distance-based sequence of neighboring points with the territory claiming relationship functioning as a filter to establish a well-balanced neighborhood. The neighborhood can be expanded to incorporate sufficient number of points for the quadric surface fitting while maintaining the balance of the overall neighborhood. The implementation results have demonstrated that the presented method is robust and selects local neighboring points with superior fitting performance in comparison with the distance-based neighbors, mesh neighbors, and elliptic Gabriel graph neighbors.     

Application of productions for automatic control of logical design of discrete devices

The efficiency of the technique of productions in controlling the processes of logical design in computer aided design systems for discrete devices is demonstrated.     

Modified approach for tooth contact analysis of gear drives and automatic determination of guess values

An approach for the development of a computer program for simulation of meshing and contact of gear tooth surfaces is proposed for the following specific conditions: (i) the basic machine-tool settings applied for generation of meshing gears are given, and (ii) the location of the mean contact point of the contacting surfaces is not known. The contribution of the authors cover: (i) automatic determination of the guess values for derivation of the first contact point of tooth surfaces Σ₁ and Σ₂; (ii) development of a modified computer program for tooth contact analysis (TCA) for the most general case when the tooth surfaces are represented by three related parameters. The determination of guess values is based on the following considerations: (i) the generating surfaces are represented discretely by cells; (ii) the cells for both gears are located on planes of surface parameters that contains n and q cells, respectively; (iii) pairing of cells and their combination is considered in the domains of n × q cells; (iv) determination of a single pair of cells that provides: (a) minimization of deviation of tooth surface normals, (b) minimization of distance between the two cells or (c) an integrated factor m based on conditions (a) and (b). A numerical example for determination of guess values and deciphering of TCA is represented.