The anodic oxidation of thiocyanate ion dissolved as KSCN in dimethylsulphoxide

The anodic oxidation of SCN⁻ ion dissolved as KSCN in dimethylsulphoxide, on platinum electrodes, was investigated at ca 25, 60 and 160°C by means of various non-stationary electrochemical techniques. At low temperatures one anodic and two main cathodic processes were found. The anodic oxidation of SCN⁻ ion yields as primary product the SCN radical, which readily produces (SCN)₂. The latter can be in part reduced back to SCN⁻ ion, because it reacts in part yielding solvated hydrogen ions which cause the second cathodic reaction. In the region of 60°C, no (SCN)₂ cathodic current is observed. In the region of 160°C the only reaction is SCN⁻ ion oxidation and the primary product polymerizes to (SCN)_x, which forms a film on the electrode, causing passivation.

On the basis of kinetic data obtained for the different reactions, a mechanism for the anodic oxidation of the SCN⁻ ion and for the passivating film formation is suggested. The second process only partly fits the Müller model for the electrochemical growth of insoluble layers.     

Sets of Globally Optimal Stream Surfaces for Flow Visualization

Stream surfaces are a well‐studied and widely used tool for the visualization of 3D flow fields. Usually, stream surface seeding is carried out manually in time‐consuming trial and error procedures. Only recently automatic selection methods were proposed. Local methods support the selection of a set of stream surfaces, but, contrary to global selection methods, they evaluate only the quality of the seeding lines but not the quality of the whole stream surfaces. Global methods, on the other hand, only support the selection of a single optimal stream surface until now. However, for certain flow fields a single stream surface is not sufficient to represent all flow features. In our work, we overcome this limitation by introducing a global selection technique for a set of stream surfaces. All selected surfaces optimize global stream surface quality measures and are guaranteed to be mutually distant, such that they can convey different flow features. Our approach is an efficient extension of the most recent global selection method for single stream surfaces. We illustrate its effectiveness on a number of analytical and simulated flow fields and analyze the quality of the results in a user study.     

Geochemical implications of trace elements and sulfur in the saturate, aromatic and resin fractions of crude oil from the Mara and Mara Oeste fields, Venezuela

Ten trace elements (Cr, Zn, Fe, Mn, Cu, Co, Ni, Mo, V and Sr) and sulfur were determined in the saturate, aromatic and resin fractions of 15 crude oils from Mara (DM) and Mara Oeste (DMO) fields of the Maracaibo Basin, Venezuela. The oils studied are classified as unaltered or altered by biodegradation. In the altered oil, the depletion of n-alkanes, the absence of isoprenoids and the presence of steranes and hopanes unaltered by biodegradation are indicative of moderate biodegradation. The elements Zn, Fe, Mn, Cu, Ni, and Sr were detected in the saturated hydrocarbon fraction; Cr and V were detected in the aromatic fraction in addition to the above elements; whereas the elements detected for the resin fraction were Cr, Zn, Fe, Cu, Ni, Mo, V, and Sr. Co was not detected in any fractions of the oils analyzed. Sulfur was found in all fractions of the oils studied. It was proposed that Fe, Zn, Sr, and Mn could have entered the oil during migration or Fe, Zn and Mn as pollutants during oil extraction. Cr and Cu may be of biological origin and Mo could be incorporated into the reservoir through bacteria. Only S, V, and Ni in the resin fractions can be used as indicators of the origin and correlation of Mara and Mara Oeste oils. Based on the results obtained in this work, it can be established that the V/(V+Ni) ratio in the resin fraction can be used as a correlation parameter, for these oils.     

HumanTop: a multi-object tracking tabletop

In this paper, a computer vision based interactive multi-touch tabletop system called HumanTop is introduced. HumanTop implements a stereo camera vision subsystem which allows not only an accurate fingertip tracking algorithm but also a precise touch-over-the-working surface detection method. Based on a pair of visible spectra cameras, a novel synchronization circuit makes the camera caption and the image projection independent from each other, providing the minimum basis for the development of computer vision analysis based on visible spectrum cameras without any interference coming from the projector. The assembly of both cameras and the synchronization circuit is not only capable of performing an ad-hoc version of a depth camera, but it also introduces the recognition and tracking of textured planar objects, even when contents are projected over them. On the other hand HumanTop supports the tracking of sheets of paper and ID-code markers. This set of features makes the HumanTop a comprehensive, intuitive and versatile augmented tabletop that provides multitouch interaction with projective augmented reality on any flat surface. As an example to exploit all the capabilities of HumanTop, an educational application has been developed using an augmented book as a launcher to different didactic contents. A pilot study in which 28 fifth graders participated is presented. Results about efficiency, usability/satisfaction and motivation are provided. These results suggest that HumanTop is an interesting platform for the development of educational contents.     

Synthesis of UHMW-PE by a Highly Active Homogeneous System: η5-(C5H5)2Ti(η1-OC(O)C6H5)2/MAO

Summary The complex ⁵-(C₅H₅)₂Ti (¹-OC(O)C₆H₅)₂ was synthesized and activated with MA0 for ethylene polymerization. The resultant polymer is UHMW-PE with a viscosimetric molecular weight of Mv = 6.8 x 10⁶ to 0.7 x 10⁶ g/mol dependent on the temperature of the reaction. The effects of the Al/Ti molar ratio and temperature of the reaction on the catalytic activity and polymer properties were studied.     

A quantitative feedback solution to the multivariable tracking error problem

This paper introduces a novel solution for the multi‐input multi‐output (MIMO) quantitative feedback theory control design problem with tracking error specifications. Looking for a minimum controller overdesign, the technique finds new controller quantitative feedback theory bounds based on necessary and sufficient conditions for the existence of suitable associated prefilter matrix elements. It improves previous approaches to the subject and includes (i) the possibility of a free selection of the nominal plant, (ii) a less conservative application of the Schwartz inequality to decisively reduce the potential controller overdesign, (iii) a methodology to design independently the elements of the prefilter matrix, and (iv) a scope of application to both sequential and nonsequential MIMO controller design methods. The benefits of the new control design technique are illustrated by means of two examples. The first one, a standard 2 × 2 MIMO problem, is provided for comparison purposes with previous approaches. The second example, included as a major control challenge, deals with a well‐known demanding distillation column benchmark problem. Copyright © 2013 John Wiley & Sons, Ltd.     

Catalytic combustion of trichloroethene over Ru/Al2O3: Reaction mechanism and kinetic study

The performance of 0.5% Ru/Al₂O₃ for the deep oxidation of trichloroethene (1000–2500 ppmV, WHSV = 55 h⁻¹) in air was studied in this work. Experiments were carried out both at dry and wet (20,000 ppmV of H₂O) conditions. Catalytic performance was studied in terms of activity and selectivity for the different reaction products (CO₂, HCl, Cl₂, C₂Cl₄, CCl₄ and CHCl₃). Both the activity and the selectivity for total combustion are higher than other catalysts suggested in the literature for this process (especially Pd and Pt).The main organic by-products are CCl₄ and CHCl₃, whereas in all the other catalysts tested in the literature, tetrachloroethene is the main organic by-product. This fact suggests that the mechanism of the combustion reaction, involving a double-bond scission, is essentially specific for this catalyst.Kinetic data was fit to a pseudo-first order kinetic expression, providing fairly good fit.     

Factors affecting the mechanical properties of mica-filled polypropylenes

Water-ground Phlogopite mica (Kemira Siilinjarvi phlogopite) has been evaluated as a reinforcing filler in polypropylene. The major factors which influence the composite strength and modulus include the size, aspect ratio, and uniformity of the mica flakes. Aqueous delamination permits the production of very small flakes (less than 44 microns diameter) with aspect ratios near 50. Such small flakes impart greater tensile and modulus values to polypropylene than larger flakes and the former can also be reprocessed many times without any deterioration of properties. Surface treatment is necessary for adequate dispersion and coupling, particularly with the finely divided mica fillers. Other properties such as the heat-distortion temperature, fracture toughness, and gas permeability are also influenced by the mean size and aspect ratio of the mica filler. Guidelines are presented to indicate the preferred characteristics of mica fillers for optimum performance.     

Preparation of silica by acid dissolution of sepiolite and study of its reinforcing effect in elastomers

The preparation of amorphous silica by acid treatment of a natural magnesium silicate and its use as reinforcing filler for NR and SBR compounds are studied. Limited to the treatment with nitric acid, the rate constants at different temperatures and acid concentrations and the activation energy are calculated, as a function of percentage of extracted magnesium. The resulting material is basically an amorphous silica (92.5% SiO₂), as shown by X-ray analysis, that keeps the fibrous morphology of the original mineral. According to a preliminary technological study the resulting silica is a suitable reinforcing filler for general purpose rubbers; a comparison between the experimental results and those obtained with a commercial fine particle precipitated silica was made. Using a SBR compound the effect of silane coupling agents on the new silica was studied.     

Time-Temperature-Transformation Curves for Kaolinite-α-Alumina

The C-shaped time-temperature-transformation curves (T-T-T curves) of cristobalite formation and the L-shaped T-T-T curves of α-alumina reaction were established for a high-purity kaolinite-α-alumina mixture during heating. The results revealed that cristobalite formation in kaolinite was retarded by the presence of α-alumina between 1250° and 1350°C and was totally prohibited above 1380°C due to the reaction of kaolinite with α-alumina to form secondary mullite. The reaction of α-alumina with kaolinite was initiated at about 1250°C. It became quite extensive above 1380°C and was extremely fast at 1600°C and above, indicating the strong effect of the eutectic liquid formation at ∼1587°C in silica-alumina. The effectiveness of the established T-T-T curves was demonstrated and discussed.