Neighborhood Of Edges Research Articles

Novel peer group filtering method based on the CIELab color space for impulse noise reduction

This paper presents a novel peer group filtering method for impulsive noise reduction. The main contributions of the proposed method are twofold. First, noise detection is performed in the CIELab, instead of the RGB, color space to enhance the noise detection effect. Secondly, two different-sized windows are used to determine the peer group for deducing more accurate status of each pixel, alleviating the problem of deducing non-corrupted pixels as corrupted in the neighborhood of edges in the textural regions. Based on five typical test color images, experimental results demonstrate that the proposed method achieves better performance in noise detection and hence noise reduction when compared to five existing competitive methods.

Stability of a rectangular plate axially compressed on its two opposite free edges

AbstractThe stability of a rectangular plate under two different compressive loading scenarios applied to the free edges of the plate has been investigated. It is assumed that under the applied load the edges have translational and rotational degrees of freedom. In the first case, a conservative external force, that is assumed to have a fixed direction with respect to the deforming body, is applied while in the second case the load is directed to be tangential to the deflected middle surface, the follower force. It is found that for a sufficiently narrow plate the buckling is localized in the neighborhood of free edges as the conservative load is applied. A similar phenomenon is known for the case when a plate is uniformly compressed along hinged edges. In the case of a follower force, the static formulation of the problem leads to the conclusion that localized buckling does not exist. However, depending on the parameters of the problem, the usual (global) buckling is predicted.

LASER STRAIGHT CUTTING BRONZE SHEETS: THERMAL STRESS ANALYSIS AND EXPERIMENT

Laser straight cutting of bronze sheet is carried out. Temperature and stress fields in the cutting section are simulated using the finite element method. Temperature predictions are validated with the thermocouple measurements. The kerf surfaces are examined using optical and scanning electron microscopes. To prevent the oxidation reactions taking place during the cutting process, nitrogen at high pressure is used as the assisting gas. It is found that high stress levels are generated in the neighborhood of the cut edges due to the high temperature gradients formed in this region. Two stress peaks are observed along the cutting direction: i) one is in the re-cast layer and ii) the other is in the frontal region of the laser beam. The striations formed at the kerf surface have shallow depths and the dross attachment is observed at the edges of the kerf exit, which is associated with the low viscosity of the molten flow and the momentum loss of the assisting gas towards the kerf exit.

Cliques with maximum/minimum edge neighborhood and neighborhood density

Given a graph G=(V,E) and a clique C of G, the edge neighborhood of C can be defined as the total number of edges running between C and V⧹C, being denoted by N(C). The density of the edge neighborhood N(C) can be set as the ratio (|N(C)|/(|C|·|V⧹C|)).This paper addresses maximum/minimum edge neighborhood and neighborhood density cliques in G. Two versions will be undertaken, by fixing, or not, the size of the cliques.From an optimization point of view these problems do not bring much novelty, as they can be seen as particular or special versions of weighted clique problems. However, from a practical point of view, they concentrate on certain kinds of properties of cliques, rather than their size, revealing clique's engagement in the graph. In fact, a maximum edge neighborhood clique should be strongly embraced in the graph, while a minimum edge neighborhood clique should reveal an almost isolated strong component. In particular, special versions of the new problems allow to distinguish among cliques of the same size, namely among possible tied maximum cliques in the graph.We propose node based formulations for these edge based clique related problems. Using these models, we present computational results and suggest applications where the new problems can bring additional insights.

Apply GPCA to Motion Segmentation

In this paper, we present a motion segmentation approach based on the subspace segmentation technique, the genera-lized PCA. By incorporating the cues from the neighborhood of intensity edges of images, motion segmentation is solved under an algebra framework. Our main contribution is to propose a post-processing procedure, which can detect the boundaries of motion layers and further determine the layer ordering. Test results on real imagery have confirmed the validity of our method.

Partial differential equation–based approach for removal of chromatic aberration with local characteristics

We propose a chromatic aberration (CA) reduction technique that removes artifacts caused by lateral CA and longitudinal CA, simultaneously. In general, most visible CA-related artifacts appear locally in the neighborhoods of strong edges. Because these artifacts usually have local characteristics, they cannot be removed well by regular global warping methods. Therefore, we designed a nonlinear partial differential equation (PDE) in which the local characteristics of the CA are taken into account. The proposed algorithm estimates the regions with apparent CA artifacts and the ratios of the magnitudes between the color channels. Using this information, the proposed PDE matches the gradients of the edges in the red and blue channels to the gradient in the green channel, which results in an alignment of the positions of the edges while simultaneously performing a deblurring process on the edges. Experimental results show that the proposed method can effectively remove even significant CA artifacts, such as purple fringing as identified by the image sensor. The experimental results show that the proposed algorithm achieves better performance than existing algorithms.

Efficient and reliable Monte Carlo localization with thinning edges

The global convergence of MCL is time-consuming because of a large number of random samples. Moreover, its success is not guaranteed at all times. This paper presents a novel approach to reduce the number of samples of MCL and one heuristic approach to detect localization failure using thinning edges extracted in real time. Random samples are drawn only around the neighborhood of the thinning edges rather than over the entire free space and localization quality is estimated through the probabilistic analysis of samples added around the thinning edges. A series of experiments verified the performance of the proposed scheme.

Local Computations on Triangular Graphs

The paper deals with the class of finite triangular graphs. It turns out that this class enjoys regular properties similar to those of trees and complete graphs. The main objective of the paper is to lift algorithms for some typical local computations, known for other classes of graphs, to the class of triangular graphs. Local algorithms on graphs, according to [8, 9], are defined as local rules for relabeling graph nodes. Rules are local, if they are defined only for a class of subgraphs of processed graph (as neighborhoods of nodes or edges) and neither their results nor their applicability do not depend upon the knowledge of the whole graph labeling. While designing local algorithm for triangular graphs one needs to use some intrinsic properties of such graphs; it puts some additional light on their inherent structure. To illustrate essential features of local computations on triangular graphs, local algorithms for three typical issues of local computations are discussed: leader election, spanning tree construction, and nodes ordering. Correctness of these algorithms, as deadlock freeness, proper termination, and impartiality, are proved.

Diffraction of paraxial partially coherent fields by planar obstacles in the Wigner representation

The free-space propagation of paraxial, partially coherent stationary fields can be described in a simple and intuitive way through the use of the Wigner function. In this context, this function plays the role of a generalized radiance that is constant along straight lines or rays. The effect of diffraction by transverse planar opaque obstacles or apertures is considered here for this representation, and a simple analytic approximate formula is given for the case when the incident field is quasi-homogeneous, at least in the neighborhood of the obstacle's edges. In this result, diffraction is accounted for by including rays emanating from the obstacle's edges.

Enhancement of nonlinear effects at the degenerate band edge of two-dimensional photonic crystals

The ability of two-dimensional (2D) photonic crystals (PC) for high enhancements of nonlinear processes is analyzed in the case of a degenerate band edge when two symmetrical diffracted beams are generated by Bragg diffraction in the 2D-PC. Calculations are performed using the very simple Bragg-coupled wave theory which only involves three coupled waves (the incident wave and the two diffracted waves) for the linear interaction. The validity of the approximation is proved for wavelengths lying at the neighborhood of the band edges of 2D-PC. Very large local-field intensities are predicted around the band-edge wavelengths, in particular for the upper band edge. Nonlinear propagation is studied through the analysis of degenerate four-wave mixing. For counterpropagating pump beams orthogonally sent onto the 2D-PC huge improvement of the phase conjugate reflectivity are predicted at least for small incidence angles of the signal beam. These results represent an improvement by a factor of 20 when compared to the case of a one-dimensional PC of the same thickness made of the same materials. As three intense phase conjugate beams are generated in the four-wave mixing interaction, the 2D-PC could be very interesting for the purpose of dense parallel optical signal processing. Moreover, the simple theoretical analysis developed in the paper can be used for any kind of 2D-PC.

Methods to Automate Print Quality Assessment

This paper demonstrates how image processing techniques can be combined to automate print quality assessment and reduce the time to market. Typically, significant engineering resource is required to evaluate and optimize print quality over a range of environmental conditions. This method is not only tedious, but its subjective nature induces error. An automated process has been developed to quantify print quality for a variety of digitized print samples. The process uses neighborhood analysis and edge detection to automatically align the digitized image. Techniques such as gradient-based edge detection, neighborhood analysis, and thresholding are used to quantify print quality for each region of interest. Calibration curves are used to relate manually graded images to computationally graded images. Finally, a weighted normalized least-squares fitting routine transforms print quality metrics for each environmental condition into a table of optimized electrophotographic voltage settings.

Adaptive remeshing based on a posteriori error estimation for forging simulation

This paper presents a fully automatic 3D adaptive remeshing procedure and its application to non-steady metal forming simulation. Remeshing, here, is considered as the improvement of an existing mesh rather than a complete rebuilding process. The mesh optimization technique is described. It is based on the combination of local improvement of the neighbourhood of nodes and edges. The surface and the volume remeshing are coupled by using a layer of virtual boundary elements. The mesh adaptation is performed by the optimization of the shape factor. The mesh size map enforcement is accounted for working in a locally transformed space. The size map is provided by a Zienkiewicz–Zhu type error estimator. Its accuracy is evaluated in the frame of a velocity/pressure formulation, viscoplastic constitutive equation and 3D linear tetrahedral elements, by numerical experiments. The adaptive remeshing procedure is applied to non-steady forging. Several complex 3D examples show the reliability of the proposed approach to automatically produce optimal meshes at a prescribed computational cost.

Optimal filter and mollifier for piecewise smooth spectral data

We discuss the reconstruction of piecewise smooth data from its (pseudo-) spectral information. Spectral projections enjoy superior resolution provided the function is globally smooth, while the presence of jump discontinuities is responsible for spurious O ( 1 ) {\mathcal O}(1) Gibbs’ oscillations in the neighborhood of edges and an overall deterioration of the convergence rate to the unacceptable first order. Classical filters and mollifiers are constructed to have compact support in the Fourier (frequency) and physical (time) spaces respectively, and are dilated by the projection order or the width of the smooth region to maintain this compact support in the appropriate region. Here we construct a noncompactly supported filter and mollifier with optimal joint time-frequency localization for a given number of vanishing moments, resulting in a new fundamental dilation relationship that adaptively links the time and frequency domains. Not giving preference to either space allows for a more balanced error decomposition, which when minimized yields an optimal filter and mollifier that retain the robustness of classical filters, yet obtain true exponential accuracy.

Modeling nematic liquid crystals in the neighborhood of edges

We present a method to simplify simulation techniques for determining liquid-crystal director orientation in geometries with sharply defined edges and for surfaces with strong anchoring without preferred direction. We show analytically that close to such edges, the liquid crystal can be described by just a few parameters. After examining the solutions, it is explained how these results can avoid the numerical problems that arise when simulating such configurations.

Impurity mode techniques applied to the study of light sources

The dispersion relation, density of states, wave-functions and single site impurity bound and resonant modes of a photonic crystal slab are computed. The photonic crystal slab is formed by embedding a hexagonal lattice array of dielectric cylinders in a background dielectric. Outside the photonic crystal slab is a uniform, isotropic dielectric medium. The solution of Maxwell's equations for the modes of a free-standing photonic crystal slab are obtained by treating a self-consistent matrix eigenvalue problem that is solved iteratively using a fast computer routine. The properties of single site impurities in photonic crystal slabs are determined using both Green's function methods and effective mass equations based on a Wannier function representation. The impurity dielectric constant supporting an impurity bound state is shown to be a multiple valued function of the frequency of the impurity mode. Asymptotic forms are obtained for the behaviour of impurity bound states at frequencies in the neighbourhood of the band edges. Resonant modes at pass band frequencies are computed for the impurities formed by replacing a single dielectric cylinder of the photonic crystal slab with background dielectric media. Comparison of the theoretical results is made with experiments on an electrically injected photonic crystal microcavity light source.

Branched quantum wave guides with Dirichlet boundary conditions: the decoupling case

We consider a family of open sets $M_\epsilon$ which shrinks with respect to an appropriate parameter $\epsilon$ to a graph. Under the additional assumption that the vertex neighbourhoods are small we show that the appropriately shifted Dirichlet spectrum of $M_\epsilon$ converges to the spectrum of the (differential) Laplacian on the graph with Dirichlet boundary conditions at the vertices, i.e., a graph operator without coupling between different edges. The smallness is expressed by a lower bound on the first eigenvalue of a mixed eigenvalue problem on the vertex neighbourhood. The lower bound is given by the first transversal mode of the edge neighbourhood. We also allow curved edges and show that all bounded eigenvalues converge to the spectrum of a Laplacian acting on the edge with an additional potential coming from the curvature.

Adaptive Mollifiers for High Resolution Recovery of Piecewise Smooth Data from its Spectral Information

We discuss the reconstruction of piecewise smooth data from its (pseudo-) spectral information. Spectral projections enjoy superior resolution provided the data is globally smooth, while the presence of jump discontinuities is responsible for spurious O (1) Gibbs oscillations in the neighborhood of edges and an overall deterioration of the unacceptable first-order convergence in rate. The purpose is to regain the superior accuracy in the piecewise smooth case, and this is achieved by mollification. Here we utilize a modified version of the two-parameter family of spectral mollifiers introduced by Gottlieb and Tadmor [GoTa85]. The ubiquitous one-parameter, finite-order mollifiers are based on dilation . In contrast, our mollifiers achieve their high resolution by an intricate process of high-order cancellation . To this end, we first implement a localization step using an edge detection procedure [GeTa00a, b]. The accurate recovery of piecewise smooth data is then carried out in the direction of smoothness away from the edges, and adaptivity is responsible for the high resolution. The resulting adaptive mollifier greatly accelerates the convergence rate, recovering piecewise analytic data within exponential accuracy while removing the spurious oscillations that remained in [GoTa85]. Thus, these adaptive mollifiers offer a robust, general-purpose ``black box'' procedure for accurate post-processing of piecewise smooth data.

Verifying edges for visual inspection purposes

In this paper we develop a method for verifying edges for visual inspection purposes. This method characterizes and examines a candidate edge against a given condition which can be designed and modified according to the required specifications of an application. A criterion is established using the edge strength, edge length and the distributions of grey level values of the pixels located in an edge neighbourhood. In consideration of computational speed and the accuracy of the locations of the edges, we first convolve the image with a Gaussian impulse response with a single small smoothing scale factor σ to generate candidate edges. The candidate edges are verified against the criterion and an edge is then retained or discarded on the basis of its local characteristics.

Vortex damping of sloshing in tanks with baffles

The problem of damping the sloshing in tanks with sharp-edged baffles (thin inserts which partially span a longitudinal or transverse cross-section) is considered. Separation of the boundary layer and the formation of vortices occur at these sharp edges. It is assumed that the domains where there is significant vortex motion of the fluid are localized in small neighbourhoods of the sharp edges of the baffles. The non-linear vortex damping is determined from the distribution of the velocity intensity factors at these sharp edges in the same way as the linear damping, caused by the dissipation of energy in a boundary layer close to a wall, is determined from the fluid velocity distribution on the walls of a cavity. Both of the above-mentioned distributions are calculated by solving the same boundary-value problem on the oscillations of an ideal fluid. The second of the distributions characterizes the singular properties of the solutions of this problem on particular lines. A method based on the variation of the area of the baffles, which simplifies the calculation of the velocity intensity factors is described. The distinctive features arising when the method of finite elements is used are considered. The results of numerical calculations of the damping of sloshing in a cylindrical tank with a ring baffle are compared with experimental data.

New edge neighborhood graphs

Let G be an undirected simple connected graph, and e = uv be an edge of G. Let NG(e) be the subgraph of G induced by the set of all vertices of G which are not incident to e but are adjacent to u or v. Let Ne be the class of all graphs H such that, for some graph G,NG (e) ≅ H for every edge e of G. Zelinka [3] studied edge neighborhood graphs and obtained some special graphs in Ne. Balasubramanian and Alsardary [1] obtained some other graphs in Ne. In this paper we given some new graphs in Ne.