The problem of binarization of gray level images acquired under nonuniform illumination is reconsidered. Yanowitz and Bruckstein proposed to use for image binarization an adaptive threshold surface, determined by interpolation of the image gray levels at points where the image gradient is high. The rationale is that high image gradient indicates probable object edges, and there the image values...

We propound a systematic and formal method to compute the Galois group of a non-necessarily irreducible polynomial: we proceed by successive inclusions, using mostly computations on scalars (and very few on polynomials). It is based on a formal method of specialization of relative resolvents: it consists in expressing the generic coeecients of the resolvent using the powers of a primitive eleme...

The goal of this paper is to bring to the attention of the computational community a long overlooked, very simple, acceleration method that impressively speeds up explicit time-stepping schemes, at essentially no extra cost. We explain the basis of the method, namely stabilization via wisely chosen inner steps (stages), justify it for linear problems, and spell out how simple it is to incorpora...

The vast majority of recent advances in the field of numerical radiative transfer relies on approximate operator methods better known in astrophysics as Accelerated Lambda-Iteration (ALI). A superior class of iterative schemes, in term of rates of convergence, such as Gauss-Seidel and Successive Overrelaxation methods were therefore quite naturally introduced in the field of radiative transfer ...

In non-cooperative scenarios, the estimation of direct sequence spread spectrum (DS-SS) signals has to be done in a blind manner. In this letter, we consider the spreading sequence estimation problem for DS-SS signals. First, the maximum likelihood estimate (MLE) of spreading sequence is derived, then a semidefinite relaxation (SDR) approach is proposed to cope with the exponential complexity o...

To find an optimum accelerating parameter of the SOR method is important and a difficult part of the problem. It is more difficult to estimate many optimum parameters of the GSOR method. In this talk, we propose a new algorithm to estimate the optimum parameters of the GSOR method. The key point to estimate these parameters is using a preconditioned matrix constructed by a part of the coefficie...

In this paper we propose and analyze a new parallel SOR method, the PSOR method, formulated by using domain partitioning and interprocessor data communication techniques. We prove that the PSOR method has the same asymptotic rate of convergence as the Red/Black (R/B) SOR method for the five-point stencil on both strip and block partitions, and as the four-color (R/B/G/O) SOR method for the nine...

The convergence rates of the explicit group methods derived from the standard and skewed (rotated) finite difference operators depend on the spectral properties of the coefficient matrices resulted from these group discretization formulas. By applying appropriate preconditioner, we may transform the resulting linear system into another equivalent system that has the same solution, but has a bet...

The numerical solutions of 2-D steady incompressible flow in a driven cavity are presented. The Navier-Stokes equations in streamfunction and vorticity variables are solved simply with Successive Over Relaxation (SOR) method. Using a very fine grid mesh with 1025 × 1025 points, the steady driven cavity flow is solved for Re ≤ 20,000. For accuracy, the iterations are carried out on the streamfun...

This work integrates two distinct research areas of parallel and distributed computing, (1) automatic loop parallelization, and (2) component-based Grid programming. The latter includes technologies developed within CoreGRID for simplifying Grid programming: the Grid Component Model (GCM) and HigherOrder Components (HOCs). Components support developing applications on the Grid without taking al...