Tracking people in video sequences using multiple models

This paper presents a multiple model real-time tracking technique for video sequences, based on the mean-shift algorithm. The proposed approach incorporates spatial information from several connected regions into the histogram-based representation model of the target, and enables multiple models to be used to represent the same object. The use of several regions to capture the color spatial information into a single combined model, allow us to increase the object tracking efficiency. By using multiple models, we can make the tracking scheme more robust in order to work with sequences with illumination and pose changes. We define a model selection function that takes into account both the similarity of the model with the information present in the image, and the target dynamics. In the tracking experiments presented, our method successfully coped with lighting changes, occlusion, and clutter.     

Influence of the B-site ordering on the magnetic properties of the new La3Co2MO9 double perovskites with M = Nb or Ta

Double perovskites La₃Co₂NbO₉ and La₃Co₂TaO₉ have been prepared by both solid state and sol-gel synthesis. The crystal structures have been studied from X-ray and neutron powder diffraction data. Rietveld refinements show that the crystal structure is monoclinic (P2₁/n), with different degrees of ordering of B′ and B″ cations, with octahedra tilted according to the Glazer notation a⁻b⁻c⁺. Occupancy refinements show that the solid state materials are more B-site ordered than the sol-gel ones. Magnetization measurements show that these perovskites show two magnetic contributions, one with spontaneous magnetization and other with linear behaviour with the magnetic field associated to antiferromagnetic correlations. In the samples synthesized by solid state the spontaneous magnetization is more important than those synthesized by the sol-gel and present T_C of 62 K for Nb and 72 K for Ta. On the other hand, materials prepared by sol-gel have T_C 20 K for Nb and 40 K for Ta, respectively and major presence of the antiferromagnetic contribution. The competition between these magnetic behaviours is interpreted, by a microscopic point of view, as to be due to the different degrees of Co²⁺ ions disorder on the B site of the double perovskite structure. This disorder affects the ratio between the antiferromagnetic Co²⁺-O-Co²⁺ and the ferromagnetic Co²⁺-O-M⁵⁺-O-Co²⁺ couplings proposed for the system.     

Accuracy of simplified sampling procedures for estimating milk composition in dairy ewes

Simplified designs of milk-composition recording, based on information from a single monthly milking, adjusted or not for interval between milkings and for milk yield, were simulated and evaluated for 2553 ewe-test-day records belonging to 155 lactations of Churra dairy ewes. Accuracy of simplified methods was evaluated by comparing estimated trait values (fat, protein, casein and total solid yields) with those observed both in a reference plan, where the two daily milkings were recorded at weekly intervals (A1), and in the official A4 milk recording (monthly records of the two daily milkings). Trait yields per lactation were estimated and adjusted to the only milking period (days in milk 30-120). Estimates of milk component traits were less precise when monthly designs, including the A4 design, were compared with a weekly sampling of both a.m. and p.m. milkings, with fat yield being the most difficult trait to estimate. All options with one daily milking every month were more accurate when the corresponding plan was based on, or began with, the a.m. milking. Adjustment for the preceding interval between milkings or milk yield did not improve sampling accuracy. The design alternating a.m. and p.m. milkings every month, without adjustment, is suggested for recoding milk component traits in dairy ewes.     

CuGaxSey chalcopyrite-related thin films grown by chemical close-spaced vapor transport (CCSVT) for photovoltaic application: Surface- and bulk material properties, oxidation and surface Ge-doping

Device-grade ternary Cu-Ga-Se chalcopyrite thin films used for photovoltaic energy conversion have been prepared by a novel chemical close-spaced vapor transport (CCSVT) technique developed for a deposition on areas of up to 10×10 cm². A two-step process has been developed which allows the fine tuning of the film composition and the electronic properties. The extension of deposition times in the two-step process led to final film compositions with [Ga]/[Cu] ratios ranging from 0.9 to 5.7, allowing the study of the structural phase transitions. In this paper the main focus of interest is related to the material properties of the device-grade thin films prepared by CCSVT technique. We present our recent studies on (i) the growth, compositional, structural and electronic structural properties, (ii) the degradation under ambient conditions and (iii) the feasibility of n-type doping this p-type semiconducting material by germanium. Thin films were grown with chalcopyrite (1:1:2) and CuGaSe₂-related defect compound structures (DC) with stoichiometries of CuGa₃Se₅ and CuGa₅Se₈. In order to derive the DC structure, X-ray and neutron powder diffraction investigations have been carried out on powders of these CuGaSe₂-related compounds grown by elemental synthesis (powder) and CCSVT (thin films), respectively. We found no hints for an ordering of defects, as proposed in the past and giving name to the so-called Ordered Defect Compounds (ODC) in this and related structures. From our results a growth model is presented for CuGa₃Se₅ formation in gallium-rich CCSVT-grown CuGa_xSe_y films. The chemical and electronic surface and interface structure of CuGaSe₂ thin films with bulk [Ga]/[Cu] ratios between 0.94 and 1.39 is investigated by X-ray and UV-excited photoelectron spectroscopy (XPS and UPS, respectively). A transition of the Cu:Ga:Se surface composition from 1:1:2 for the Cu-rich bulk sample to 1:3:5 for the sample with the highest bulk [Ga]/[Cu] ratio is observed. Simultaneously, a downward shift of the valence band maximum position with respect to the Fermi energy is found. The comparison of the estimated conduction band minimum with that of CdS reveals the formation of a pronounced “cliff-like” conduction band offset at the respective interface.Furthermore, the CuGaSe₂ thin film degradation under ambient as well as under thermal conditions of CuGaSe₂ thin films has been studied by XPS. During thermal oxidation, the formation of predominantly Ga₂O₃ and some amount of SeO₂ were observed, but no copper oxides could be detected in the near-surface region of the thin films. The same oxides are found after native oxidation in air under ambient conditions. An additional sodium oxide compound formed at the thin film surface, Na_xO and Na₂CO₃ after thermal and native oxidation, respectively.Germanium ion implantation technique of the near-surface region of CuGaSe₂ thin films has been used in order to prove the feasibility of n-type doping. In photoluminescence (PL) studies, the occurrence of a new emission line is identified as Ge related and explained as a donor-acceptor-pair (DAP) recombination. The precise role the Ge is playing in this doping of CuGaSe₂ is revealed by X-ray absorption spectroscopy (XANES and EXAFS) and ab initio calculations based on the density functional theory. The studies indicate that the incorporated Ge atoms preferentially occupy Ga sites when relaxation around the dopant is taken into account. Additionally, our corresponding theoretical band structure model predicts the existence of additional localized electronic acceptor and donor defect bands within the band gap of CuGaSe₂ originating from a strong covalent interaction between Ge 4s and Se 4p states for Ge atoms tetrahedrally surrounded by the Se nearest-neighbor atoms. A theoretically predicted anti-bonding Ge-Se4sp³ defect band appearing well above the Fermi level for the Ge¹⁺_Ga point defect system can be directly linked to a Ge-dopant-related donor-acceptor-pair transition as observed in our photoluminescence spectra.     

Graphitic mesoporous carbons synthesised through mesostructured silica templates

In this paper the fabrication and characterization of graphitizable and graphitized porous carbons with a well-developed mesoporosity is described. The synthetic route used to prepare the graphitizable carbons was: (a) the infiltration of the porosity of mesoporous silica with a solution containing the carbon precursor (i.e. poly-vinyl chloride, PVC), (b) the carbonisation of the silica–PVC composite and (c) the removal of the silica skeletal. Carbons obtained in this way have a certain graphitic order and a good electrical conductivity (0.3 S cm⁻¹), which is two orders larger than that of a non-graphitizable carbon. In addition, these materials have a high BET surface area (>900 m² g⁻¹), a large pore volume (>1 cm³ g⁻¹) and a bimodal porosity made up of mesopores. The pore structure of these carbons can be tailored as a function of the type of silica selected as template. Thus, whereas a graphitizable carbon with a well-ordered porosity is obtained from SBA-15 silica, a carbon with a wormhole pore structure results when MSU-1 silica is used as template. The heat treatment of a graphitizable carbon at a high temperature (2300 °C) allows it to be converted into a graphitized porous carbon with a relatively high BET surface area (260 m² g⁻¹) and a porosity made up of mesopores in the 2–15 nm range.     

Low-temperature SCR of NOx with NH3 over carbon–ceramic cellular monolith-supported manganese oxides

This work describes the development and use of carbon–ceramic cellular monoliths as catalyst supports for the low-temperature selective catalytic reduction (SCR) of NO_x with ammonia. Manganese oxide was selected as catalyst and deposited over the support, which was obtained by coating the cellular ceramics with a polymeric film. The coated material was cured, carbonised and activated prior to impregnation of the active phase. The produced catalysts showed a good NO_x reduction (in the range 34–73%) at 150°C for a space velocity of 4000 h⁻¹. Gasification of the support was negligible at the mentioned conditions.     

Tunable UV/blue luminescence in rare-earth free glass-ceramic phosphor

A novel rare-earth (RE) free feldspar glass-ceramic phosphor has been designed by a fast sintering route, following a conventional ceramic process. In this work, it is studied how subtle chemical modifications of structural elements may affect luminescence behaviour in this novel matrix. These cation additions acting as glass network former and as modifiers, 1 wt % of SiO₂ and CaCO₃ or Na₂CO₃, respectively, produce a photoluminescence enhancement up to 200%. Whereas, addition of Al₂O₃, a glass network former, decreases the photoluminescence emission. Raman spectroscopy evinces a correlation between photoluminescence emission and the Al,Si disorder at microscopic scale. These findings open a new challenge in order to obtain larger structural disorder to make this RE free glass-ceramic much more powerful for future optical applications, highlighting for security markers or light emitting glasses. This new phosphor might be considered as a more sustainable and low-cost alternative to RE phosphors.