Synthesis of Filtering Structures for Microstrip Active Antennas Using Orlov's Formula

In this paper, a synthesis technique for nonuniform filtering structures to be employed in active integrated antenna layouts is presented. The idea is to suppress the higher harmonic contribution due to the presence of nonlinear components through a nonuniform transmission line properly designed via Orlov's synthesis formula. The theory presented is applied here to synthesize an amplifier‐based active antenna layout for wireless local area network (WLAN) purposes working at 2.4 GHz. The numerical results presented show the capabilities of the proposed approach.     

Combined Space Diversity Reception and Trellis Coding for Rayleigh Fading Channels

Space diversity reception, in which several signals received at different antennas are combined, is a well known method that can be used to combat the effects of fading in wireless systems. Also, trellis coded modulation (TCM), when combined with interleaving of sufficient depth, is known to provide some form of time diversity that allows the achievement of good error performance in fading environments. In this paper we consider the analysis of the error performance of reference-based Maximal Ratio Combining (MRC) systems when used in conjunction with trellis-coded MPSK modulation techniques over a Rayleigh fading channel. We also consider the analysis of MRC trellis-coded MPSK systems with conventional differential detection. The results are obtained by using a combination of theoretical analysis and simulation. Exact and near-exact expressions for the pairwise error-event probability in Rayleigh fading are derived. Monte-Carlo simulation results, which are more indicative of the exact system performance, are also given.     

Purification and characterization of cellulases from Clostridium papyrosolvens

The extracellular cellulolytic enzyme complex from Clostridium papyrosolvens was isolated from a culture of this organism grown on filter paper. The complex showed xylanase, carboxymethyl cellulase (CMCase) and Avicelase (but not β-glucosidase) activities. Non-denaturing polyacrylamide gel electrophoresis (PAGE) revealed two dominant bands, sited at the origin (corresponding to a fraction of high molecular weight) and at 280 kDa, and eight other very weak bands in the 20–180 kDa MW range. Gel overlay techniques showed strong CMCase activity in the region comprised between the origin and 320 kDa and in three distinct sites in the 40–230 kDa region. Xylanase activities were detected as a continuous band almost covering all the track. SDS—PAGE gave a multiplicity of different intensity bands in the 20–130 kDa range. Cellulolytic activities (CMCase in the 85–90 kDa range) and hemicellulolytic activities (xylanase at approximately 95, 60, 42 and 32 kDa) were detected through application of the corresponding CMC and xylan overlay techniques. Though anion-exchange chromatography (DEAE-Sephadex A-50) and gel filtration (Biogel P-100) techniques did not permit a good separation of the different cellulolytic activities, an 11.3-fold increase of the Avicelase specific activity was achieved in a fraction containing 38.5% of the original total activity. Maximum enzymatic activities in crude preparations were observed at pH 5.4 and 50°C for xylanase and at pH 4.8 and 45°C for CMCase. The Michaelis constants for CMCase and xylanase were respectively: V_max = 9.1 μg glucose equivalents min^? ml^?, Km=3.3 g CMcellulose liter^? and V_max=44.5 μg xylose equiuulents min^? ml^? and K_m=2.7 g xylun liter^?. Both enzymes were inhibited by a competitive mechanism.     

Understanding trust in privacy-aware video surveillance systems

Recent advances in pervasive video surveillance systems pave the way for a comprehensive surveillance of every aspect of our lives, hence, leading us to a state of dataveillance. Computerized and interconnected systems of cameras could be used to profile, track and monitor individuals for the sake of security. Notwithstanding, these systems clearly interfere with the fundamental right of the individuals to privacy. Most literature on privacy in video surveillance systems concentrates on the goal of detecting faces and other regions of interest and in proposing different methods to protect them. However, the trustworthiness of those systems and, by extension, of the privacy they provide are mostly neglected. In this article, we define the concept of trustworthy privacy-aware video surveillance system. Moreover, we assess the techniques proposed in the literature according to their suitability for such a video surveillance system. Finally, we describe the properties that a deployment of a trustworthy video surveillance system must fulfill.     

Étude du comportement d’une boucle de Costas en modulation MAQ 16 en présence d’évanouissements sélectifs

This paper gives the variance of the phase recovered by a conventional quadriphase Costas loop in 16 Qam modulation in the presence of a selective fading, represented as a three rays simplified model. The power spectral density of the phase error is computed using a spectral estimation technique. The phase error variance is evaluated for different values of the fade depth, the location of the maximum attenuation in the frequency band and the delay of the reflected ray. Finally the relation between the performance degradation and phase noise is given, assuming a gaussian p.d.f. of the phase error.     

Unsupervised colour image segmentation by low-level perceptual grouping

This paper proposes a new unsupervised approach for colour image segmentation. A hierarchy of image partitions is created on the basis of a function that merges spatially connected regions according to primary perceptual criteria. Likewise, a global function that measures the goodness of each defined partition is used to choose the best low-level perceptual grouping in the hierarchy. Contributions also include a comparative study with five unsupervised colour image segmentation techniques. These techniques have been frequently used as a reference in other comparisons. The results obtained by each method have been systematically evaluated using four well-known unsupervised measures for judging the segmentation quality. Our methodology has globally shown the best performance, obtaining better results in three out of four of these segmentation quality measures. Experiments will also show that our proposal finds low-level perceptual solutions that are highly correlated with the ones provided by humans.     

Matching Feature Points in Image Sequences through a Region-Based Method

In order to achieve reliable matching in image sequences, a hierarchical approach is proposed. First, matching is established between regions of consecutive segmented images. In a second step, feature point matching between features of matched regions is performed. Regions provide a structural representation for features in the same region. To establish matching between features of two corresponding regions, a relational graph is built. Matching features is based on three principles: exclusion, proximity, and rigidity. The use of subgraph matching techniques through maximal clique detection provides a method to cope with partial occlusion and missing features between frames.     

Synthetic content generation for auto-stereoscopic displays

Due to the appearance of auto-stereoscopic visualization as one of the most emerging tendencies used in displays, new content generation techniques for this kind of visualization are required. In this paper we present a study for the generation of multi-view synthetic content, studying several camera setups (planar, cylindrical and hyperbolic) and their configurations. We discuss the different effects obtained varying the parameters of these setups. A study with several users was made to analyze visual perceptions, asking them for their optimal visualization. To create the virtual content, a multi-view system has been integrated in a powerful game engine, which allows us to use the latest graphics hardware advances. This integration is detailed and several demos and videos are attached with this paper, which represent a virtual world for auto-stereoscopic displays and the same scenario in a two-view anaglyph representation for being visualized in any conventional display. In all these demos, the parameters studied can be modified offering the possibility of easily appreciate their effects in a virtual scene.