A stochastic method for Bayesian estimation of hidden Markov random field models with application to a color model.

We propose a new stochastic algorithm for computing useful Bayesian estimators of hidden Markov random field (HMRF) models that we call exploration/selection/estimation (ESE) procedure. The algorithm is based on an optimization algorithm of O. Fran?ois, called the exploration/selection (E/S) algorithm. The novelty consists of using the a posteriori distribution of the HMRF, as exploration distribution in the E/S algorithm. The ESE procedure computes the estimation of the likelihood parameters and the optimal number of region classes, according to global constraints, as well as the segmentation of the image. In our formulation, the total number of region classes is fixed, but classes are allowed or disallowed dynamically. This framework replaces the mechanism of the split-and-merge of regions that can be used in the context of image segmentation. The procedure is applied to the estimation of a HMRF color model for images, whose likelihood is based on multivariate distributions, with each component following a Beta distribution. Meanwhile, a method for computing the maximum likelihood estimators of Beta distributions is presented. Experimental results performed on 100 natural images are reported. We also include a proof of convergence of the E/S algorithm in the case of nonsymmetric exploration graphs.     

Calculation of optimal design and ideal productivities of volumetrically lightened photobioreactors using the constructal approach

This article examines the optimal design and ideal kinetic performances of volumetrically lightened photobioreactors (PBR). From knowledge models developed for several years by the author, simple theoretical rules are established at first to define the optimal functioning of solar and artificially lightened PBR. The constructal approach is then used accordingly, which allows the emergence of the optimal design, or the best lighting structures assembly, in Cartesian and curvilinear geometries, with a privileged treatment for the practical case of the 2D-cylindrical geometry. The obtained results confirm the considerable potential of this approach which is applied here for the first time to the case of the radiant light transfer in participating and reactive media. This enables to define clearly, from a theoretical point of view, the concept of ideal PBR (both for solar or artificial illuminations), which is demonstrated to correspond exactly in most cases to volumetrically lightened PBR, mainly for the solar DiCoFluV (Dilution Contrôlée du Flux en Volume) concept developed in this article. For this last case, the results of the calculations allow to announce maximal biomass productivities as thermodynamic limits, what can contribute to clarify a today confused debate on this point. The work proposed in this article finally establishes guidelines to conceive more efficient large-scale PBR of any desired geometry and criteria like volume (for artificial illumination) or surface (for solar illumination) maximum productivities and internal or external irradiation.     

Photodétecteurs en intégration monolithique sur guides optiques : modélisation et vérifications expérimentales

The authors developed a model on optical guided structures with complex refractive indices, on 9 desktop-computer. This model allows to predict the coupling efficiency of photodetectors monolithically integrated with optical waveguides. An oscillatory behaviour of the absorption coefficient versus the absorbing layer thinkness has been pointed out. Comparisons with experimental resuylts obtained with device made in different laboratories show a good agrement     

Signal probability for reliability evaluation of logic circuits

As integrated circuits scale down into nanometer dimensions, a great reduction on the reliability of combinational blocks is expected. This way, the susceptibility of circuits to intermittent and transient faults is becoming a key parameter in the evaluation of logic circuits, and fast and accurate ways of reliability analysis must be developed. This paper presents a reliability analysis methodology based on signal probability, which is of straightforward application and can be easily integrated in the design flow. The proposed methodology computes circuit’s signal reliability as a function of its logical masking capabilities, concerning multiple simultaneous faults occurrence.     

Réutilisation de logiciel: Applications des techniques d’intelligence artificielle

After a brief overview of software reuse techniques and of some applications of artificial intelligence to reusability, two approaches are presented: the Esprit project Knosos to design a knowledge-based environment for software system configuration reusing components, and a study of design reuse. The former is already leading to pre-industrial applications while the latter still involves on-going research.     

Adaptive gain and delay mismatch cancellation for LINC transmitter

Linear amplification with Nonlinear Component (LINC) transmitter architecture is an efficient solution for high efficiency amplification of signals. Nonetheless, this solution suffers both from gain impairment and delay mismatch between the two signal paths. Indeed, a mismatch in propagation time between the paths degrades the quality of the transmit signal but also disrupts the convergence of the gain correction algorithm resulting in a degradation of its performance. In this paper, we present an adaptive algorithm based on a gradient descent formulation for the identification and correction of these delays. We also demonstrate its effectiveness when applied prior to the gain adjustment procedure. The identification approach is preferred here, to ensure monitoring facilities.     

Estimates of fracture density and uncertainties from well data

This paper aims at building a method to estimate the probability law governing the 3D fracture density of a fractured rock conditioned to the number of traces observed on a borehole image when the spatial distribution of fracture centers is assumed to follow a Poisson process. A closed-form expression of this law, allowing to calculate its mean value as well as a confidence interval, is derived in both cases of a lineic well (scanline) and a cylindrical well. The latter is better adapted to the situation of fracture size of the same order of magnitude as the well radius, which enables the presence of partial traces. In particular, the method takes into account the bias in the density estimate due to the fact that a fracture may cut the well along two distinct traces according to the considered fracture size. Monte Carlo simulations finally show a good agreement with the theoretical results of mean density and confidence interval.     

High Yield Conversion of Residual Pentoses into Furfural via Zeolite Catalysis and Catalytic Hydrogenation of Furfural to 2-Methylfuran

Xylose was dehydrated over (H⁺) mordenite, using a continuous two-liquid-phase (aqueous-toluene) plug-flow reactor at 260 °C and 55 atm, with 98% conversion rate, 98% furfural molar yield, and 98% furfural selectivity (results from the first pass). Furfural in toluene was hydrogenated over a Cu/Fe catalyst, at 252 °C (gas-phase), in a 99% conversion rate to give 2-methylfuran in a 98% yield (same activity maintained for a 20-h operation).     

The effect of coupling in a compact handset receiver

This paper deals with the performance of a compact dual diversity receiver. For this study we assume that the channel is characterized by a flat Rayleigh fading and that the incoming waves can be described by a Gaussian angular power distribution. The performance of a maximal-ratio-combiner in a correlated Rayleigh fading is given. These expressions are simplified and studied for the case of a dual diversity receiver. The influence of the mutual coupling between the sensors is taken into account using a simplified model. The results are compared with results obtained from realistic antenna simulations.     

A Decade of Oxothiomolybdenum Wheels: Synthesis,Behavior in Solution,and Electrocatalytic Properties

The last decade has see the development of sulfur-containing polyoxometalates (POTMs) as a subclass of the polyoxometalate family. The structural and physico-chemical properties of this emerging class of compounds is dominating by the striking coordination properties of the [Mo₂O₂S₂(OH₂)₆]²⁺ oxothio cation, used as a building block. The cyclic topology of this arrangement corresponds to the main feature of the {Mo₂O₂S₂}-based compounds, able to develop cycle-based chemistry. The control of the linear oligomerization of the {Mo₂O₂S₂} core is achieved by the presence of the anionic component, which acts as a template. Here, we report on recent examples which illustrate how the use of various template ions such as halide, sulfate, polyphosphate, and polycarboxylate anions allows to tune the nuclearity of the inorganic host from {Mo₈} to {Mo₁₈}. A special focus on behavior in solution is given, highlighting the dynamic and fluxional character of these host–guest systems. The Diffusion Ordered Spectroscopy (DOSY) ¹H NMR, carried out on a large series of cycle-based and capsule-like compounds, demonstrates that such a method can be applied for the speciation of POM anions in solution. Finally, electrocatalytic behavior of the {Mo₂O₂S₂}-based compounds is presented. Preliminary results show that the electrocatalytic reduction of protons into hydrogen (HER) could constitute one of the most relevant applications for this class of molecular compounds.