Given a vector eld X on the real plane, we study the innuence of the curvature of the orbits of _ x = X ? (x) in the stability of those of the system _ x = X(x). We pay special attention to the case in which this curvature is negative in the whole plane. Under this assumption, we classify the possible critical points and give a criterion for a point to be globally asymptotically stable. In the ...

A temporal reasoning problem can often be naturally characterized as a collection of constraints with associated local preferences for times that make up the admissible values for those constraints. Globally preferred solutions to such problems emerge as a result of well-defined operations that compose and order temporal assignments. The overall objective of this work is a characterization of d...

In this paper we study the survival probability of the followed ray in random walk global illumination algorithms. When the ray hits a surface, the survival probability is responsible for the dying of the ray, thus for finishing the walk. We examine the variance of the Russian roulette random walk estimator of gathering type, give an explanation of the formula and show visually the behavior of ...

The “well-balanced” distribution of points over the surface of a sphere is of significant interest in various fields of science. The quality of point configurations is typically expressed by criterion functions that have many local optima. A general global optimization framework is suggested to solve such problems. To illustrate the viability of this approach, the model development and solver s...

we study local stability of self-gravitating fluid and stellar disk in the context of modified gravity theories which predict a yukawa-like term in the gravitational potential of a point mass. we investigate the effect of such a yukawa-like term on the dynamics of self-gravitating disks. more specifically, we investigate the consequences of the presence of this term for the local stability of t...

To obtain consistency and asymptotic normality, a generalized method of moments (GMM) estimator typically is defined to be an approximate global minimizer of a GMM criterion function. To compute such an estimator, however, can be problematic because of the difficulty of global optimization. In consequence, practitioners usually ignore the problem and take the GMM estimator to be the result of a...

OBJECTIVE Remission criteria for schizophrenia have been proposed, consisting of a time criterion and a symptomatic remission criterion. With longitudinal data of a representative patient group (N=317; median follow-up: 1,132 days), validity of the symptomatic remission criterion was investigated. METHOD In a group of 145 patients meeting the symptomatic remission criterion at baseline and a ...

Iterative data-based controller tuning consists of iterative adjustment of the controller parameters towards the parameter values which minimize an H2 performance criterion. The convergence to the global minimum of the performance criterion depends on the initial controller parameters and on the step size of each iteration. This paper presents convergence properties of iterative algorithms when...

The success of kernel-based learning methods is heavily dependent on the choice of a kernel function and proper setting of its parameters. In this paper, we optimize the Gaussian kernel for binary-class problems by using centered kernel polarization criterion. This criterion is an extension of kernel polarization and a simplified style of centered kernel alignment. Compared with formulated kern...

We consider acyclic directed mixed graphs, in which directed edges (x → y) and bi-directed edges (x ↔ y) may occur. A simple extension of Pearl’s d-separation criterion, called m-separation, is applied to these graphs. We introduce a local Markov property which is equivalent to the global property resulting from the m-separation criterion.