Bayesian image reconstruction with space-variant noise suppression

In this paper we present a Bayesian image reconstruction algorithm with entropy prior (FMAPE) that uses a space-variant hyperparameter. The spatial variation of the hyperparameter allows different degrees of resolution in areas of different statistical characteristics, thus avoiding the large residuals resulting from algorithms that use a constant hyperparameter. In the first implementation of the algorithm, we begin by segmenting a Maximum Likelihood Estimator (MLE) reconstruction. The segmentation method is based on using a wavelet decomposition and a self-organizing neural network. The result is a predetermined number of extended regions plus a small region for each star or bright object. To assign a different value of the hyperparameter to each extended region and star, we use either feasibility tests or cross-validation methods. Once the set of hyperparameters is obtained, we carried out the final Bayesian reconstruction, leading to a reconstruction with decreased bias and excellent visual characteristics. The method has been applied to data from the non-refurbished Hubble Space Telescope. The method can be also applied to ground-based images.

Single-trial topographic analysis of human EEG: A new image of event-related potentials

We present a novel approach for analyzing single-trial electroencephalography (EEG) data, using topographic information. The method allows for visualizing event-related potentials using all the electrodes of recordings overcoming the problem of previous approaches that required electrode selection and waveforms filtering. We apply this method to EEG data from an auditory object recognition experiment that we have previously analyzed at an ERP level. Temporally structured periods were statistically identified wherein a given topography predominated without any prior information about the temporal behavior. In addition to providing novel methods for EEG analysis, the data indicate that ERPs are reliably observable at a single-trial level when examined topographically.

Image restoration in astronomy: a Bayesian perspective

When preparing an article on image restoration in astronomy, it is obvious that some topics have to be dropped to keep the work at reasonable length. We have decided to concentrate on image and noise models and on the algorithms to find the restoration. Topics like parameter estimation and stopping rules are also commented on. We start by describing the Bayesian paradigm and then proceed to study the noise and blur models used by the astronomical community. Then the prior models used to restore astronomical images are examined. We describe the algorithms used to find the restoration for the most common combinations of degradation and image models. Then we comment on important issues such as acceleration of algorithms, stopping rules, and parameter estimation. We also comment on the huge amount of information available to, and made available by, the astronomical community.

A wavelet-based method for the determination of the relative resolution between remotely sensed images

Spatial resolution is a key parameter of all remote sensing satellites and platforms. The nominal spatial resolution of satellites is a well-known characteristic because it is directly related to the area in ground that represents a pixel in the detector. Nevertheless, in practice, the actual resolution of a specific image obtained from a satellite is difficult to know precisely because it depends on many other factors such as atmospheric conditions. However, if one has two or more images of the same region, it is possible to compare their relative resolutions. In this paper, a wavelet-decomposition-based method for the determination of the relative resolution between two remotely sensed images of the same area is proposed. The method can be applied to panchromatic, multispectral, and mixed (one panchromatic and one multispectral) images. As an example, the method was applied to compute the relative resolution between SPOT-3, Landsat-5, and Landsat-7 panchromatic and multispectral images taken under similar as well as under very different conditions. On the other hand, if the true absolute resolution of one of the images of the pair is known, the resolution of the other can be computed. Thus, in the last part of this paper, a spatial calibrator that is designed and constructed to help compute the absolute resolution of a single remotely sensed image is described, and an example of its use is presented.

Semi-supervised remote sensing image classification with cluster kernels

A semisupervised support vector machine is presented for the classification of remote sensing images. The method exploits the wealth of unlabeled samples for regularizing the training kernel representation locally by means of cluster kernels. The method learns a suitable kernel directly from the image and thus avoids assuming a priori signal relations by using a predefined kernel structure. Good results are obtained in image classification examples when few labeled samples are available. The method scales almost linearly with the number of unlabeled samples and provides out-of-sample predictions.

Side scan sonar image and geologic interpretation of the Ria de Pontevedra seafloor (Galicia, NW Spain).

High-resolution side scan sonar has been used for mapping the seafloor of the Ría de Pontevedra. Four backscatter patterns have been mapped within the Ría: (1) Pattern with isolated reflections, correlated with granite and metamorphic outcrops and located close to the coastal prominence and Ons and Onza Islands. (2) Pattern of strong reflectivity usually located around the basement outcrops and near the coastline and produced by coarse-grained sediment. (3) Pattern of weak backscatter is correlated with fine sand to mud and comprising large areas in the central and deep part of the Ría, where the bottom currents are weak. It is generally featureless, except where pockmarks and anthropogenic features are present. (4) Patches of strong and weak backscatter are located in the boundary between coarse and fine-grained sediments and they are due to the effect of strong bottom currents. The presence of megaripples associated to both patterns of strong reflectivity and sedimentary patches indicate bedload transport of sediment during high energy conditions (storms). Side scan sonar records and supplementary bathymetry, bottom samples and hydrodynamic data reveal that the distribution of seafloor sediment is strongly related to oceanographic processes and the particular morphology and topography of the Ría.

Comment on the plasmon model for image-potential-induced surface states

Calculations of the binding energy of bound positron states in metal surfaces, with explicit inclusion of plasmon dispersion and single-particle effects, are presented. The binding energy is greatly reduced with respect to the undispersed case.

Semiclassical image potential at a solid surface

A surface dielectric function of a semi-infinite plane-bounded metal is defined in the spirit of the plasmon-pole dielectric function of the bulk. It is modeled in such a way that the surface-plasmon dispersion relation is recovered for small momentum transfer. This function is employed to compute the image potential at all distances outside the surface. Interaction with bulk modes is neglected for simplicity and clarity. The interaction of a massive point charge with a metal surface is also considered in the context of a boson model for surface-plasmon excitation. We present a new definition of the image potential for this case.

Voir le monde comme une image : le schème de l'image mimétique dans la philosophie de Platon (Cratyle, Sophiste, Timée)

Résumé de la thèse Le travail de thèse «VOIR LE MONDE COMME UNE IMAGE. Le schème de l'image mimétique dans la philosophie de Platon (Cratyle, Sophiste, Timée) » d'Alexandre NEVSKY étudie la conception philosophique de l'image chez Platon. En posant la question : qu'est-ce que l'image pour Platon? l'étude se propose, dans un premier temps, d'analyser la manière précise dont l'idée de l'image fonctionne dans l'articulation logique de l'enquête platonicienne, en se basant avant tout sur trois dialogues majeurs où cette idée est explicitement thématisée par Platon lui-même, à savoir le Cratyle, le Sophiste et le Timée. Par une analyse détaillée de ces textes, Alexandre Nevsky essaie de démontrer que l'idée de l'image fonctionne comme un schème euristique dont la logique interne détermine les moments clés dans le déroulement de chaque dialogue examiné, et constitue ainsi une véritable méthode d'investigation philosophique pour Platon. En suivant cette stratégie platonicienne, l'auteur nous montre quel rôle le schème de l'image joue selon Platon d'abord dans la constitution du langage (le Cratyle), puis, dans celle du discours (le Sophiste) et, enfin, dans celle du monde (le Timée). Une telle approche lui permet de revoir l'interprétation traditionnelle de certains passages clés, célèbres pour leurs difficultés, en mettant en évidence la façon dont la nouvelle perspective platonicienne, introduite grâce au schème de l'image, permet de formuler une solution philosophique originale du problème initial. On y trouve ainsi rediscutés, pour ne citer que quelques exemples, la théorie curieuse de l'imitation phonétique et le problème de la justesse propre du nom-image, la définition philosophique de la notion d'image et la distinction platonicienne entre limage-ressemblance et l'image-apparence, la logique paradoxale de l'introduction d'un troisième genre dans la structure ontologique de l'être et la question du sens exact à donner au «discours vraisemblable » de Platon sur la naissance de l'univers. Dans un deuxième temps, cette étude tente de dégager, derrière la méthode heuristique basée sur le schème de l'image, une véritable conception de l'image mimétique chez Platon. L'une des idées principales de la thèse est ici de montrer que cette conception présente une solution philosophique de Platon au problème de l'apparence archaïque. Car, face à la question sophistique : comment une chose - que ce soit le discours ou le monde - peut-elle être une apparence, quelque chose qui n'existe pas? Platon apporte une réponse tout à fait originale elle le peut en tant qu'image. Or, l'image n'est pas une simple apparence illusoire, elle est le reflet d'une autre réalité, indépendante et véritable, que l'on doit supposer, selon Platon, même quand sa nature exacte nous échappe encore. La conception platonicienne de l'image apparaît ainsi comme un pendant indispensable de la théorie des Formes intelligibles et aussi comme son étape préalable au niveau de laquelle l'âme du philosophe, dans son ascension vers la vérité, se retrouve dans un espace intermédiaire, déjà au-delà des illusions du monde phénoménal, mais encore en-deçà des engagements métaphysiques de la théorie des Formes.

Cinema Roads to the Platonic Image of the Cave

The aim of this article is to prove the real possibility of travelling intellectually to the Platonic image of the cave from different films. In this sense, one can speak of explicit references as in The Conformist by B. Bertolucci or in Shadowlands by R. Attenborough -if one bears in mind the Chronicles of Narnia by C. S. Lewis- or The Picture of Dorian Gray ¿if one bears in mind the well-known O. Wilde¿s novel-, but, on other occasions, although the Platonic influence cannot be proved, for instance in The Truman Show, A Room with a View or Brideshead Revisited, one can perfectly think of these films in order to guide the contemporary audiences to that Platonic image, since Plato himself affirms that it deals with an image which can be easily applied and, in first place, to his idealistic philosophy.

Improving Satellite Image Based Forest Inventory by Using A Priori Site Quality Information

Summary