Stochastic Behavior Analysis of the Gaussian Kernel Least-Mean-Square Algorithm

The kernel least-mean-square (KLMS) algorithm is a popular algorithm in nonlinear adaptive filtering due to its simplicity and robustness. In kernel adaptive filters, the statistics of the input to the linear filter depends on the parameters of the kernel employed. Moreover, practical implementations require a finite nonlinearity model order. A Gaussian KLMS has two design parameters, the step size and the Gaussian kernel bandwidth. Thus, its design requires analytical models for the algorithm behavior as a function of these two parameters. This paper studies the steady-state behavior and the transient behavior of the Gaussian KLMS algorithm for Gaussian inputs and a finite order nonlinearity model. In particular, we derive recursive expressions for the mean-weight-error vector and the mean-square-error. The model predictions show excellent agreement with Monte Carlo simulations in transient and steady state. This allows the explicit analytical determination of stability limits, and gives opportunity to choose the algorithm parameters a priori in order to achieve prescribed convergence speed and quality of the estimate. Design examples are presented which validate the theoretical analysis and illustrates its application

New information from fish diets on the importance of glassy flying squid (Hyaloteuthis pelagica) (Teuthoidea: Ommastrephidae) in the epipelagic cephalopod community of the tropical Atlantic Ocean

Squids of the family Ommastrephidae are a vital part of marine food webs and support major fisheries around the world. They are widely distributed in the open ocean, where they are among the most abundant in number and biomass of nektonic epipelagic organisms. In turn, seven of the 11 genera of this family (Dosidicus, Illex, Martialia, Nototodarus, Ommastrephes, Sthenoteuthis, and Todarodes) are heavily preyed upon by top marine predators, i.e., birds, mammals, and fish, and currently support fisheries in both neritic and oceanic waters (Roper and Sweeney, 1984; Rodhouse, 1997). Their commercial importance has made the large ommastrephids the target of many scientific investigations and their biology is consequently reasonably well-known (Nigmatullin et al., 2001; Zuyev et al., 2002; Bower and Ichii, 2005). In contrast, much less information is available on the biology and ecological role of the smaller, unexploited species of ommastrephids (e.g., Eucleoteuthis, Hyaloteuthis, Ornithoteuthis, and Todaropsis)

Système d'information multimédia de la région amazonienne : un projet - une démarche

Le projet SIMBIOSEA (Système d'information Multimédia sur la liaison BIO-diversité et Socio-Econonomie en Amazonie) s'inscrit dans les enjeux du TCA (Traité de Coopération Amazonienne) et répond à une demande concrète du SURAPA (Sous-Réseau des Aires Protégées Amazoniennes) au CIRAD. Son objectif est de favoriser les articulations entre développement et conservation pour une gestion durable de la bio-diversité. Il constitue un renforcement des capacités de recherche et d'action dans les pays amazoniens et a pour ambition de donner une information pertinente aux principaux acteurs pour la mise en place de politiques de développement durable. Le projet s'organise autour de trois axes pour produire une information systémique - la connaissance des dynamiques des espaces protégés, - la synthèse des données scientifiques, - la représentation de l'information. En se référant à des exemples concrets, il s'appuie sur des méthodes, des outils et des concepts prenant en compte trois types d'espaces : - les espaces de compréhension (ensemble de l'Amazonie), - les espaces de planification (les Aires Protégées), - les espaces d'exécution (correspondant au territoire d'une communauté). L'élaboration du système d'information est prévue en six étapes - rédaction d'une charte de programme, - conception d'un cadre d'information, - élaboration d'outils de gestion de l'information, - validation du prototype, - développement du produit, - formation et valorisation du produit. Enfin, il est proposé la création de différents comités nécessaires à la coordination des activités des très nombreux partenaires potentiels. (Résumé d'auteur

Cygnus A super-resolved via convex optimisation from VLA data

We leverage the Sparsity Averaging Reweighted Analysis (SARA) approach for interferometric imaging, that is based on convex optimisation, for the super-resolution of Cyg A from observations at the frequencies 8.422GHz and 6.678GHz with the Karl G. Jansky Very Large Array (VLA). The associated average sparsity and positivity priors enable image reconstruction beyond instrumental resolution. An adaptive Preconditioned Primal-Dual algorithmic structure is developed for imaging in the presence of unknown noise levels and calibration errors. We demonstrate the superior performance of the algorithm with respect to the conventional CLEAN-based methods, reflected in super-resolved images with high fidelity. The high resolution features of the recovered images are validated by referring to maps of Cyg A at higher frequencies, more precisely 17.324GHz and 14.252GHz. We also confirm the recent discovery of a radio transient in Cyg A, revealed in the recovered images of the investigated data sets. Our matlab code is available online on GitHub.Comment: 14 pages, 7 figures (3/7 animated figures), accepted for publication in MNRA

EUR-ASSESS Project Subgroup Report on Coverage

The issue of health benefits coverage—and its relation to health technology assessment (HTA)—has gained increasing attention in recent years. Economic constraints on health care, as well as the rapid pace of technological change, have forced European countries to face difficult choices in providing such care. The active use of coverage decision making has been proposed as a tool to help rationalize health care, and HTA has been advocated as a necessary activity to improve coverage decision

Real-time, in situ monitoring of surface reactions during plasma passivation of GaAs

Real-time, in situ observations of surface chemistry during the remote plasma passivation of GaAs is reported herein. Using attenuated total reflection Fourier transform infrared spectroscopy, the relative concentrations of -As-O, -As-H, -H2O, and -CH2 bonds are measured as a function of exposure to the effluent from a microwave discharge through NH3, ND3, H2, and D2. The photoluminescence intensity (PL) from the GaAs substrate is monitored simultaneously and used qualitatively to estimate the extent of surface state reduction. It was found that, while the -CHx(x = 2,3) and -As-O concentrations are reduced rapidly, the rates at which the -As-H concentration and the PL intensity increase are relatively slow. The concentration of -H2O on the GaAs surface increases throughout the process as surface arsenic oxides and the silica reactor walls are reduced by atomic hydrogen. These observations suggest that removal of elemental As by reaction with H at the GaAs–oxide interface limits the passivation rate

Nonlinear unmixing of hyperspectral images: Models and algorithms

When considering the problem of unmixing hyperspectral images, most of the literature in the geoscience and image processing areas relies on the widely used linear mixing model (LMM). However, the LMM may be not valid, and other nonlinear models need to be considered, for instance, when there are multiscattering effects or intimate interactions. Consequently, over the last few years, several significant contributions have been proposed to overcome the limitations inherent in the LMM. In this article, we present an overview of recent advances in nonlinear unmixing modeling