Fast motion estimation using bidirectional gradient methdos

Gradient based motion estimation techniques (GM) are considered to be in the heart of state-of-the-art registration algorithms [3], being able to account for both pixel and subpixel registration and to handle various motion models (translation, rotation, affine, projective). These methods estimate the motion between two images based on the local changes in the image intensities while assuming image smoothness. This paper offers two main contributions: (i) Enhancement of the GM technique by introducing two new bidirectional formulations of the GM. This improves the convergence properties for large motions. (ii) We present an analytical convergence analysis of the GM and its properties. Experimental results demonstrate the applicability of these algorithms to real images

Level Set Modeling of Transient Electromigration Grooving

A numerical investigation of grain-boundary (GB) grooving by means of the Level Set (LS) method is carried out. GB grooving is emerging as a key element of electromigration drift in polycrystalline microelectronic interconnects, as evidenced by a number of recent studies. The purpose of the present study is to provide an efficient numerical simulation, allowing a parametric study of the effect of key physical parameters (GB and surface diffusivities, grain size, current density, etc) on the electromigration drift velocity as well as on the morphology of the affected regions. An idealized polycrystalline interconnect which consists of grains separated by parallel GBs aligned normal to the average orientation of interconnect's surface is considered. Surface and grain-boundary diffusion are the only diffusion mechanisms assumed. The diffusion is driven by surface curvature gradients and by an externally applied electric field. The corresponding mathematical system is an initial boundary value problem for a two-dimensional Hamilton-Jacobi type equation. To solve for the electrostatic problem at a given time step, a full model based on the solution of Laplace's equation for the electric potential is employed. The resulting set of linear algebraic equations (from the finite difference discretization of the equation) is solved with an effective multigrid iterative procedure. The details of transient slit and ridge formation processes are presented and compared with theoretical predictions on steady-state grooving.Comment: 19 pages, 9 PS figures; submitted to Computational Materials Scienc

Segmentation of Moving Objects Based on Connectivity Analysis of Weighted Region Adjacency Graph

The paper suggests a novel segmentation algorithm for separating moving objects from the background in video sequences without any prior information. The problem is formulated as a connectivity analysis of region adjacency graph (RAG) (see [1]) that is based on temporal information. By applying a watershed based algorithm, the video frame is segmented into a semantic homogeneous region. The boundary pixels in each region are compared with a series of consecutive frames in order to generate temporal information. The edges of the RAG represent temporal information. Each node represents a different homogeneous region. Analysis of the RAG’s connectivity is achieved by modifying the breadth-first-search (BFS) algorithm. After a sufficient number of comparisons, each of the object’s components is merged into a single segment which represents the moving object in the frame. The accuracy of the algorithm is proportional to the number of allowed comparisons

Compact XML grammar based compression ∗

Extensible Markup Language (XML) is the standard format for content representation and sharing on the Web. XML is a highly verbose language, especially regarding the duplication of meta-data in the form of elements and attributes. As XML content is becoming more widespread so is the demand to compress XML data volume. This paper presents a new grammar, called D-grammar, which defines XML structure for a specific DTD. DTD is chosen as an explanatory example. The grammar can be extended to define other deterministic XML scheme languages such as XML Scheme. It also presents a parser generator which generates a D-grammar parser. DPDT is an efficient and compact XML validator for the DTD which the D-grammar reflects. The presented compression technique encodes the DPDT validation choices during the XML structure parsing instead of the textual tags that compose the XML structure. This enhances the XML text compression twofold: first, there are less symbols to encode and second, the encoded structure symbols can predict the preceding text better than the textual structure tags. A unique advantage of the presented technique is that it combines the validation phase with the compression phase and thus saves processing time. This XML validation/compression fits streaming technologies and can be used in a wide variety of XML network applications such as gateways, routers, etc. The DPDT validation choices are encoded by a partial prediction matching (PPM) codec, which is considered to be the state-of-the-art for text encoding. We compare the performance of the presented algorithm, also called DPDT-L, with other existing XML compression techniques. The proposed compression algorithm achieves, on average, better compression ratio. The superiority of our compression technique is more evident when it is tested on XML medium size (∼10MB) dataset

Performance of MIMO Schemes with Partial Channel Knowledge

Multiple antenna techniques are used to enhance wireless links and therefore have been studied extensively. Many practical systems differ from the ideal schemes discussed in the literature. One example is the lack of precise channel information at the transmitter. We evaluate analytically the performance of several multiple input multiple output (MIMO) techniques that use partial channel knowledge. Specifically, we analyze schemes which are used in Worldwide Inter-operability for Microwave Access (WiMAX) and are also supported by Long Term Evolution (LTE) systems. All the results are supported by simulations

Image denoising using regularized Butterworth wavelet frames

We present an efficient algorithm for image restoration from highly noised originals. The algorithm is based on diverse library of tight and semi-tight wavelet frames. Unlike majority of current denoising methods, which threshold the transform coefficients, our algorithm performs direct and inverse multiscale transforms using properly modified frame filters. No thresholding is applied. The processing is linear. The algorithm is fast and can be implemented in real time. It depends on one numerical parameter, which is estimated from the noise level.

their

of moving objects in video through invariant features i

A Hierarchical 3-D Direct Helmholtz Solver by Domain Decomposition and Modified Fourier Method

The paper contains a non-iterative solver for the Helmholtz and the modified Helmholtz equations in a hexahedron. The solver is based on domain decomposition. The solution domain is divided into mostly parallelepiped subdomains. In each subdomain a particular solution of the non-homogeneous Helmholtz equation is first computed by a fast spectral 3-D method which was developed in our earlier papers (see, for example, SIAM J. Sci. Comput. 20 (1999), 2237-2260). This method is based on the application of the discrete Fourier transform accompanied by a subtraction technique. For high accuracy the subdomain boundary conditions must be compatible with the specified inhomogeneous right hand side at the edges of all the interfaces. In the following steps the partial solutions are hierarchically matched. At each step pairs of adjacent subdomains are merged into larger units. The paper describes in detail the matching algorithm for two boxes which is a basis of the domain decomposition scheme. The hierarchical approach is convenient for parallelization and can minimize the global communication. The algorithm requires O(N 3 log N) operations, where N is the number of grid points in each direction.

Interpolatory frames in signal space

We present a new family of frames, which are generated by perfect reconstruction filter banks consisting of linear phase filters. The filter banks are designed on the base of the discrete interpolatory splines and are related to the Butterworth filters. Each filter bank comprises one interpolatory symmetric low-pass filter and two high-pass filters, one of which is also interpolatory and symmetric. The second high-pass filter may be symmetric or antisymmetric. These filter banks generate the analysis and synthesis scaling functions and pairs of framelets. We introduced the concept of semi-tight frame. While in the tight frame all the analysis waveforms coincide with their synthesis counterparts, in the semi-tight frame we can vary the second framelets making them different for the synthesis and the analysis cases. By this means we can switch the vanishing moments from the synthesis to the analysis framelets or to add smoothness to the synthesis framelet. We constructed dual pairs of frames, where all the waveforms are symmetric and all the framelets have the same number of vanishing moments. Although most of the designed filters are IIR, they allow fast implementation via recursive procedures. The waveforms are well localized in the time domain despite their infinite support. The frequency response of the designed filters are flat