Reliable estimation of dense optical flow fields with large displacements

[EN] In this paper we show that a classic optical flow technique by Nagel and Enkelmann can be regarded as an early anisotropic diffusion method with a diffusion tensor. We introduce three improvements into the model formulation that avoid inconsistencies caused by centering the brightness term and the smoothness term in different images use a linear scale-space focusing strategy from coarse to fine scales for avoiding convergence to physically irrelevant local minima, and create an energy functional that is invariant under linear brightness changes.  Applying a gradient descent method to the resulting energy functional leads to a system of diffusion-reaction equations. We prove that this system has a unique solution under realistic assumptions on the initial data, and we present an efficient linear implicit numerical scheme in detail. Our method creates flow fields with 100% density over the entire image domain, it is robust under a large range of parameter variations, and it can recover displacement fields that are far beyond the typical one-pixel limits which are characteristic for many differential methods for determining optical flow. We show that it performs better than the classic optical flow methods with 100%  density that are evaluated by Barron et al. (1994). Our software is available from the Internet.

Reflexiones sobre gobernanza; confianza en las instituciones públicas, densidad asociativa y participación electoral en Europa.

[ES] El presente estudio trata de forma abierta de los cambios que se están produciendo en los métodos de gobernar y en las posibilidades que ofrece la nueva gobernanza a la participación de la ciudadanía para influir en las decisiones que conciernen al territorio y su futuro. También introduce elementos relacionados con el dinamismo que han adquirido los movimientos sociales y la participación política no convencional, precisamente cuando más aumenta la desafección a la política y a los partidos políticos e igualmente se incrementan los índices de abstención electoral.