École Européenne Supérieure de l'Image

This paper presents a number of new methods for visual tracking using the output of an event-based asynchronous neuromorphic dynamic vision sensor. It allows the tracking of multiple visual features in real time, achieving an update rate of several hundred kilohertz on a standard desktop PC. The approach has been specially adapted to take advantage of the event-driven properties of these sensors by combining both spatial and temporal correlations of events in an asynchronous iterative framework. Various kernels, such as Gaussian, Gabor, combinations of Gabor functions, and arbitrary user-defined kernels, are used to track features from incoming events. The trackers described in this paper are capable of handling variations in position, scale, and orientation through the use of multiple pools of trackers. This approach avoids the N(2) operations per event associated with conventional kernel-based convolution operations with N × N kernels. The tracking performance was evaluated experimentally for each type of kernel in order to demonstrate the robustness of the proposed solution.

The efficiency of electrostatic separation processes depends on a multitude of factors, including the characteristics of the granular mixtures to be sorted, the feed rate, the configuration of the electrode system, the applied high voltage, and the environmental conditions. The possibility of optimizing the operation of industrial electrostatic separators using rather simple computed-assisted experimental design techniques has already been demonstrated. The aim of the present work is to analyze the peculiarities of application of a more sophisticated group of response surface experimental design techniques that make use of quadratic functions for modeling the electrostatic separation process. One unique contribution to this work is to consider the economic value of the process in addition to the technical result. The 11 electrostatic separation tests, corresponding to a central composite design, were carried out on samples of chopped electric wire wastes. The CARPCO laboratory roll-type electrostatic separator employed for this study enabled a rigorous control of two factors: the applied high-voltage level and the speed of the rotating roll electrode. The objective was to maximize the benefits from the recycling of both constituents of the binary copper-polyvinyl chloride granular mixture. The optimum operating conditions computed with the quadratic model derived from the experimental results were in good agreement with the data of pilot-plant tests. Thus, the highest extraction of useful materials was obtained at high voltage and low speed, while the optimum conditions for greatest economic value were found to be high voltage and high speed. The response surface methodology can be easily applied to most of the industrial applications of electrostatic separation technologies.

The output of any electrostatic separation process is strongly dependent on the effectiveness of particle charging. A novel laboratory-scale fluidized-bed tribocharging device has been described in a previous paper. The aim of this paper is to assess the effectiveness of two materials, aluminum and polypropylene (PP), that could be employed in the tribocharging chamber of that device. The electrostatic separation experiments designed for this purpose were carried out on three samples of a granular polyethylene/polyvinyl chloride mixture, characterized by different compositions. Aluminum and PP were found to be equally effective for the triboelectrostatic separation of the 50% PVC 50% PE sample. For the other two samples (10% PVC 90% PE, 90% PVC 10% PE), the best results were obtained with the PP tribocharging chamber.

Abstract Electrostatic separation is extensively used for the selective sorting of granular mixtures, by means of the electric forces which act on charged or polarized bodies. The roll-type separator with combined corona-electrostatic field has been proved to be the most advantageous solution when the purpose is to isolate conductive particles from non-conductive ones. The paper presents the contributions of the High Intensity Electric Fields Laboratory of the Technical University of Cluj-Napoca to the development of this solution for various industrial applications. The first chapter is devoted to the theoretical analysis of the phenomena and points out the multitude of factors which influence the efficiency of the separation process. A special attention is paid to the study of the corona charging conditions of insulating particles. In the second and third cahpters, the authors show how the results of numerical modeling guided the design of new equipment and the optimization of their operating conditions. Laboratory and pilot plant tests described in the forth chapter brought evidence of the effectiveness of the proposed technologies. The presentation of several applications in the recycling industry concludes the paper.

A 5-GHz fully integrated, full PMOS, low-phase-noise and low-power differential voltage-controlled oscillator (VCO) is presented. This circuit is implemented in a 0.35-/spl mu/m four-metal BiCMOS SiGe process. At 2.7-V power supply voltage and a total power dissipation of only 13.5 mW, the proposed VCO features a worst case phase noise of -97 dBc/Hz and -117 dBc/Hz at 100 kHz and 1 MHz frequency offset, respectively. The oscillator is tuned from 5.13 to 5.68 GHz with a tuning voltage varying from 0 to 2.7 V.

The surface-potential-decay measurement techniques are commonly employed for the adjustment of Xerox photography processes, development of electrets, and assessment of polyethylene films for cable insulation. In all these situations, it is important to evaluate the surface charge density and compare it to the limit imposed by the dielectric rigidity of atmospheric air. The aim of the experiments reported in this paper is to enhance the efficiency of the corona charging of nonwoven filter media for heat, ventilation, and air-conditioning applications. Samples of nonwoven polypropylene fibrous media were exposed to positive corona discharges from a wire electrode, as the efficiency of the filter can be enhanced when the insulating fibers are electrically charged. The observed surface potential levels and the potential decay characteristics indicate that the charge of the filter is limited by the local discharges that occur inside the fibrous dielectric. The performance of the filter can be further improved by using a triode-type electrode system that assures a uniform distribution of the electric charge at the surface of the filtering media.

Taxonomic over-splitting of extinct or endangered taxa, due to an incomplete knowledge of both skeletal morphological variability and the geographical ranges of past populations, continues to confuse the link between isolated extant populations and their ancestors. This is particularly problematic with the genus Equus. To more reliably determine the evolution and phylogeographic history of the endangered Asiatic wild ass, we studied the genetic diversity and inter-relationships of both extinct and extant populations over the last 100,000 years, including samples throughout its previous range from Western Europe to Southwest and East Asia. Using 229 bp of the mitochondrial hypervariable region, an approach which allowed the inclusion of information from extremely poorly preserved ancient samples, we classify all non-African wild asses into eleven clades that show a clear phylogeographic structure revealing their phylogenetic history. This study places the extinct European wild ass, E. hydruntinus, the phylogeny of which has been debated since the end of the 19th century, into its phylogenetic context within the Asiatic wild asses and reveals recent mitochondrial introgression between populations currently regarded as separate species. The phylogeographic organization of clades resulting from these efforts can be used not only to improve future taxonomic determination of a poorly characterized group of equids, but also to identify historic ranges, interbreeding events between various populations, and the impact of ancient climatic changes. In addition, appropriately placing extant relict populations into a broader phylogeographic and genetic context can better inform ongoing conservation strategies for this highly-endangered species.

The aim of this paper is to analyze the robustness of the electrostatic separation process control. The objective was to reduce variation in the process outcome by finding operating conditions (high-voltage level, roll speed), under which uncontrollable variation in the noise factors (granule size, composition of the material to be separated) has minimal impact on the quantity (and the quality) of the recovered products. The experiments were carried out on a laboratory roll-type electrostatic separator, provided with a corona electrode and a tubular electrode, both connected to a dc high-voltage supply. The samples of processed material were prepared from genuine chopped electric wire wastes (granule size >1 mm and <5 mm) containing various proportions of copper and PVC. The design and noise factors were combined into one single experimental design, based on Taguchi's approach, and a regression model of the process was fitted. The impact of the noise factors could be estimated, as well as the interactions between the design and noise factors. The conditions of industry application of Taguchi's methodology are discussed, as well as the possibility of adapting it to other electrostatic processes.

The dual corona-electrostatic electrodes consist of one or several ionizing elements (wires, needles, and blades) attached to a metallic support. This paper analyzes the characteristic features of a particular type of such electrodes and formulates recommendations on their design and utilization. The experiments focused on several models of dual corona-electrostatic electrodes, the ionizing element being the edge of a thin metallic blade. The tested devices had similar cylindrical metallic supports but blades of different sizes. Thus, it was possible to investigate the influence of electrode geometry on corona onset voltage and spark-over threshold in configurations that are specific to industrial electrostatic processes. Most of the experiments were performed by using roll-type electrostatic separators. A special experimental setup was employed for the study of the distribution of corona current density at the surface of a plate collecting electrode. For the model having the blade edge closer to the metallic support, the corona onset voltage was higher, and the corona discharge affected a smaller area at the surface of the collector. These experiments are discussed in relation with the results of the numerical analysis of the electric field generated by the different electrode configurations. At a given voltage and distance between the ionizing element and the collector, the presence of the cylindrical support diminishes the electric field at the edge of the blade and distorts the field lines. These effects were exploited in the design of the electrode system of an electrostatic separator for the recycling industry.

Early Cretaceous ornithomimosaurian theropod dinosaurs have been reported from various localities in Asia, whereas they remain poorly represented and extremely rare in North America, Africa and Europe. So far, the only known European ornithomimosaur is Pelecanimimus from the Barremian of Spain. The recent discovery in southwestern France of a lignitic bone bed in Angeac, which has yielded several hundred ornithomimosaur bones, sheds new light on the ornithomimosaurian fossil record. Based on this new material, we re-evaluate here the systematic position of various isolated theropod bones from the Wealden of England, including historical taxa of uncertain affinities. Based on a unique combination of derived characters, Thecocoelurus and Valdoraptor are linked to the Angeac taxon but are considered to be nomina dubia. Valdoraptor from the Valanginian of West Sussex appears to be the oldest known ornithomimosaur together with the contemporaneous Nqwebasaurus from South Africa. Ornithomimosaurs were a common component of the Early Cretaceous European dinosaur fauna. Their presence in Spain, France and England further strengthens the palaeobiogeographic affinities of the European fossil biota with that of Asia during this period.

Electrostatic separation is a typical multifactorial process. Its efficiency depends on the characteristics of the granular mixtures to be sorted, the feed rate, the configuration of the electrode system, the applied high voltage, the environmental conditions, and so on. The aim of this paper is to demonstrate the usefulness of computer-assisted experimental design in the optimization of such a process. The example analyzed in the paper was suggested by a typical application of electrostatic separation technique in the recycling industry: the selective sorting of metals and insulating materials from chopped wire and cable waste. The objective was to maximize the benefits from the recycling of both constituents of a binary copper-polyvinyl chloride granular mixture. A preliminary set of electrostatic separation tests, performed on a custom-designed laboratory unit, guided the choice of the starting values of the parameters considered in the computer-assisted experimental procedure of process optimization. The results of a first experiment, carried out in conformity with a fractional factorial scheme, were used for the computation of the coefficients of a linear mathematical model of the electrostatic process. The model was then employed to predict the values of the operating variables for which the optimum of the process is attained. A second experiment was performed in order to confirm the accuracy of the prediction. The procedure presented in this paper and the accompanying computer programs can be easily adapted to other electrostatic process applications.

Electric charging of the non-woven electret filter media leads to increased particle collection efficiency. Estimation of the charge state of the media can be done by measuring its surface potential. The aim of this paper is to evaluate the effects of the factors that influence the surface potential decay characteristics of these media: the grid potential of the triode-type corona electrode system employed for the electric charging, the active carbon, the ambient relative humidity and the temperature at which the media are thermally pre-conditioned. The experiments were carried out on two types of samples, one of which includes an active carbon layer between two 400 μm thick layers of non - woven polypropylene fibers, the diameter of each fiber being approximately 20 μm. The results show that the surface potential values increase with the increasing of the electric potential of the grid. Thus, if the grid potential Vg increases from 3 to 10 kV, the surface potential value increases over 3 times. A 20% increase of the surface potential values is also recorded in the case of thermally conditioned samples. The surface potential decreases by roughly 10% in the case of the samples with carbon layer, and by about 20%, and in the case of relative humidity increase from 21% to 80%.

Nous décrivons une portion de diaphyse fémorale humaine découverte lors de l&rsquo;exploration spéléologique de la &laquo; grotte de la Tour &raquo;, près du site préhistorique de La Chaise-de-Vouthon (Charente, France). Le contexte de découverte est compatible avec un dépôt de tanière de hyène ; l&rsquo;assemblage des restes mammifères associés suggère une attribution chronologique au MIS 3. La morphologie externe, les propriétés géométriques des sections et l&rsquo;analyse quantitative tridimensionnelle à haute résolution de la structure interne montrent que ce spécimen (CDV-Tour 1) appartient à un individu néandertalien adulte, vraisemblablement de sexe masculin.

This article aims at demonstrating the interest the design of experiment methodology might present for modeling and optimization of a typical electrostatic separation process. A classical 23 full-factorial design followed by a composite design were employed for carrying out experiments on the selective sorting of conductive and nonconductive particles contained in a granular mixture. The study was performed on a roll-type corona-electrostatic separator, with samples prepared from genuine electric cable wastes, composed of 5% copper and 95% PVC. The response function was the mass of the middling fraction collected after separation, the factors under investigation being the high-voltage level, the speed of the rotating roll electrode, and the angular position of the splitter between the copper and middling compartments of the collector. By using commercial design of experiments software, it was possible to estimate the effects of these factors and then derive the model of the process as a quadratic polynomial function. This model served at predicting the optimal set point of the process. The results reported support design of experiments methodology as an efficient tool for the optimization of industrial electrostatic separation processes.

Development of new applications of plate-type electrostatic separators need increased controllability of particle trajectories. The aim of this paper is to model the particle behavior after lift-off from the plate electrode. A superficial charge simulation program was employed for the computation of the electric field in the active zone of the separator. This enabled the evaluation of the charge acquired by a conducting particle in contact with the plate electrode and the electric force exerted on it before and after detachment. Based on a previously derived mathematical model, the particle trajectories were calculated for various electrode configurations. The data of such numerical simulations can guide the experimental studies needed for the assessment of new industry applications of electrostatic sorting or classifying techniques.

Among the separation techniques used in industry, the triboelectric separation of insulating particles using rotary tube is an efficient technology employed in waste recovery and mineral industries. This process, also called free-fall triboelectric separation, is widely used for the sorting and the purification of granular materials resulting from industrial plastic wastes. This paper aims to achieve a comprehensive description of the laboratory triboelectric separator built up by the authors, and its utilisation for an experimental study carried out on granular samples containing particles of polyvinyl chloride and polyethylene. Thus, among the variable factors of the process, we analysed the influence of the most important ones, i.e. the rotational speed of the cylinder n (rpm), the applied high voltage U (kV), the charging time of the particles t (s), the mass of the sample m (g) and the composition percentage of the sample C p (%). Furthermore, the output process was optimised using the methodology of experimental designs. The obtained results are very instructive and confirmed the efficiency of this separation method for the processing of industrial plastic wastes.

Plate-type electrostatic separators are commonly used for the selective sorting of conductive from nonconductive constituents of a granular mixture. This paper addresses the more delicate issue of granular materials that are characterized by finite nonzero resistivities. The study was conducted with three materials having similar granule size range and specific weight but slightly different electrical properties. Two sets of experiments were performed for evaluating the effect of electrode geometry on the behavior of each of the materials. These results were then employed for predicting the outcome of the electrostatic separation of binary mixtures of good and poor conductors. A third set of experiments validated the predictions and pointed out a couple of nonelectric factors that might deteriorate the performance of a plate-type electrostatic separator in an industrial environment.

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Industry application of electrostatic separation technologies still faces a major difficulty: good results can be obtained only by adequate control of a multitude of operating parameters. The aim of the present paper is to analyze a key factor of electrostatic separation efficiency: the position of the high-voltage electrodes. Experiments were performed with two types of granular materials: chopped electric wire wastes and foundry sands. The electrostatic separator employed for the tests was provided with a wire-type corona electrode, associated - in some experiments - with a tubular-type electrostatic electrode, at various angular and radial positions, with respect to a rotating roll electrode connected to the ground. The experimental data are discussed in relation to the results of the numerical analysis of the electric field, carried out with a charge simulation program. They show that the outcome of the separation process (i.e., the weight percentage of the conductor and nonconductor fractions, as well as the purity of the recovered materials) depends on the configuration of the electrode system. The position of the electrodes affects both the particles charging conditions on the surface of the roll electrode, and the trajectories of the charged particles in the high-intensity electric field of the separator. Some recommendations could be formulated for the industrial application of the electrostatic separation technology.

Purpose A current trend is to use waste and by‐products in concrete to replace binders and aggregates. This trend reduces the impact on the environment and the use of finite natural resources. This paper aims to investigate whether concrete which includes crushed, graded and washed recycled construction demolition waste, used as a coarse aggregate, can be manufactured to a comparable strength as concrete manufactured from virgin aggregates. Design/methodology/approach Laboratory testing investigated the strength development of concrete manufactured with varying degrees of coarse aggregate replacement. All of the concrete samples were tested at five, seven, 14 and 21 days and the concrete with the recycled aggregate was compared to a plain control sample manufactured with virgin aggregates. The mixes tested against the control sample were: 100 per cent gravel replacement with recycled aggregate, and the same mix with a viscosity modifying agent. A 50 per cent partial coarse aggregate replacement was used in one batch to compare against the control and the 100 per cent recycled aggregate concrete. Compressive strength was used to compare the different concrete batch performance. Density was used to indicate the degree of particle packing and void content which was measured across the range of samples to evaluate the relationship between the different concrete mixes. Findings The optimum concrete mix design using recycled construction waste was obtained by using a 50‐50 per cent mix of virgin gravel and recycled aggregates. Using recycled construction waste as a 100 per cent coarse aggregate replacement produces concrete with a lower compressive strength when compared to concrete made with virgin aggregates. Originality/value The paper investigates ways of incorporating construction demolition waste as recycled aggregate to reduce the environmental impact of the production of concrete.