Electrodeposition of polypyrrole on aluminium in aqueous tartaric solution

The electrosynthesis of polypyrrole (PPy) has been achieved on aluminium in aqueous medium of tartaric acid by means of cyclic voltammetry, potentiostatic and galvanostatic techniques. Scanning electron microscopy (SEM) and X-ray microanalysis by energy spectroscopy dispersion (EDS) applying on surfaces show that the PPy coating is developed from the metal surface through the cracks of the initial Al₂O₃ layer.A mechanism involving the participation of the supporting electrolyte and the pyrrole (Py) in distinct active sites was proposed based on the linear sweep voltammetry. It is observed for all applied electrochemical techniques that the pyrrole concentration has to be higher than 0.1 M to allow the polypyrrole electrodeposition in acid medium.Scanning electron microscopy, secondary electrons (SE) and backscattering electrons (BE), shows that the PPy coating obtained in galvanostatic and potentiostatic modes starts with small islands at weak applied potentials or current densities. Moreover, EDS reveals a good homogeneity and compactness of the film achieved in galvanostatic method. The corrosion results in 3% NaCl medium show that the PPy coating decreases the corrosion behaviour of the aluminium. The bilayer Al₂O₃/PPy shows a capacitor with future applications.     

Prediction of mean square radius of gyration of tree-like polymers by a general kinetic approach

This paper describes a kinetic method to predict the z-average molecular mean square radius of gyration of tree-like polymers formed by irreversible reactions, assuming Gaussian chains. It is based on the population balance equations for the two-sided molecular distributions of pendant chains associated with every chemically distinguishable kind of bonds. An automated method for the solution of those equations is valid both before as well as after gelation for complex kinetic schemes. Examples of its use are presented with polycondensation systems leading to hyperbranched polymers, the anionic polymerization of mono- and divinyl monomers and a radical polymerization with terminal branching and transfer to polymer.     

A web-based platform for biosignal visualization and annotation

With the advent of wearable sensing and mobile technologies, biosignals have seen an increasingly growing number of application areas, leading to the collection of large volumes of data. One of the difficulties in dealing with these data sets, and in the development of automated machine learning systems which use them as input, is the lack of reliable ground truth information. In this paper we present a new web-based platform for visualization, retrieval and annotation of biosignals by non-technical users, aimed at improving the process of ground truth collection for biomedical applications. Moreover, a novel extendable and scalable data representation model and persistency framework is presented. The results of the experimental evaluation with possible users has further confirmed the potential of the presented framework.     

Catkin liked nano-Co3O4 catalyst built-in organic microreactor by PEMOCVD method for trace CO oxidation at room temperature

In this paper, tricobalt tetraoxide (Co₃O₄) catalyst was coated on the polydimethylsiloxane microchannel by the plasma-enhanced metal-organic chemical vapor deposition technology. The obtained Co₃O₄ film was characterized by SEM, XRD, XPS, and TEM, and the results show that the as-deposited Co₃O₄ film was initially composed of many cauliflowers-shaped microclusters. Also, the microcauliflower was transformed from an amorphous phase to a crystal phase when the Co₃O₄ film was treated by Ar and O₂ plasma for more than 20 min, and the crystal lattice line occurred on the surface of nano-sized-Co₃O₄ particles. Meanwhile, the interface of Co₃O₄ particles with diameter between 3 and 12 nm became obvious and some nano-catkin structures were also formed on the Co₃O₄ film. The ratio of Co³⁺/Co²⁺ in the spinel-type Co₃O₄ was nearly 2, and the nano-particles predominantly expose their {311}, {111}, and {220} planes. These morphologies and structure characteristics were found to be ideal for increasing the catalytic activity efficiency of Co₃O₄ for CO oxidation, and the catalytic stability of Co₃O₄ coated on the organic microreactor lasted nearly 85 h for trace CO oxidation at room temperature.     

A comparative study on the effect of promoter content of hydrodesulfurization catalysts at different evaluation scales

CoMo and NiMo supported Al₂O₃ catalysts have been investigated for hydrotreating of model molecule as well as industrial feedstock. Activity studies were carried out for thiophene and SRGO hydrodesulfurization (HDS) in an atmospheric pressure and batch reactor respectively. These activities on sulfided catalysts were evaluated as a function of promoter content [M/(M + Mo) = 0.30, 0.34, 0.39; M = Co or Ni] using fixed (ca. 8 wt.%) molybdenum content. The promoted catalysts were characterized by textural properties, XRD, and temperature programmed reduction (TPR). TPR spectra of the Co and Ni promoter catalysts showed that Ni promotes the easy reduction of Mo species compared with Co. With the variation of promoter content NiMo catalyst was found to be superior to CoMo catalyst for gas oil HDS, while at low-promoter content the opposite trend was observed for HDS of thiophene. The behavior was attributed to the several reaction mechanisms involved for gas oil HDS. A nice relationship was obtained for hydrodesulfurized gas oil refractive index (RI) and aromatic content, which corresponds to the Ni hydrogenation property.     

Assessment of weld line performance of PP/Talc moldings produced in hot runner injection molds

Weld lines are weak regions in thermoplastic injection moldings caused by low molecular entanglement and unfavorable orientation. Their occurrence may lead to a significantly reduced mechanical performance of the products. Therefore, when weld lines are likely to occur in molded products, they must be taken into account during the mechanical and technological design processes. The weld lines become more critical when particulate fillers are compounded with the polymer. The performance of weld lines in talc‐filled polypropylene box moldings produced with a double‐gated hot runner mold is assessed in this work. The processing conditions were varied in order to cause morphology and tensile‐impact resistance changes. The weld performance at room temperature was assessed in terms of the energy absorbed in the impact tests. It was found that the performance depends on the injection temperature, the injection rate, and the orientation of the talc particles in the weld‐line plane. J. VINYL ADDIT. TECHNOL., 13:159–165, 2007. © 2007 Society of Plastics Engineers     

On Hypotheses Testing for the Selection of Spatio‐Temporal Models

Abstract. Several models have been proposed in recent years for analysing spatial data and also, to some extent, spatio‐temporal data. One of the important problems, namely the choice of an appropriate model for describing real data sets, remains unsolved. Here we consider the analysis of spatio‐temporal processes from which observations over space and time are available. We propose statistical tests for discriminating between space–time autoregressive processes and multivariate autoregressive processes. The sampling properties of the proposed tests are considered. We illustrate the methods with a real example. We use the above tests to find the best model to describe spatio‐temporal variations of hourly carbon monoxide measurements at four locations in London in January 2004.     

Chemical Composition Determination at the Bottom Region of a Recovery Boiler Furnace by Direct Minimization of Gibbs Free Energy

An optimization strategy has been applied to describe the chemical composition at the furnace bottom in the Kraft recovery boiler of a pulp production process. The concentrations of each involved chemical species were calculated through an optimization approach, minimizing the Gibbs free energy of the system. Various systems were proposed and tested, assuming different chemical species and phases number. Because serious initialization problems were found at this stage for some of the proposed systems, an optimization heuristic method (PSO) was used for the first approach to the problem. Once the appropriate phases number and chemical species in the system were determined, the initialization problems disappeared and the use of a deterministic optimization method (SQP) became viable. The proposed approach has shown to be satisfactory to reproduce industrial data and also data reported in the open scientific literature.     

Capture device identification from digital images using Kullback-Leibler divergence

Multimedia Tools and Applications - It is proposed a forensic method for the capture device identification from digital images, which requires two elements: i) a digital image subject to...