Effect of acids and bases on electrophoretic deposition of alumina and zirconia particles in 2-propanol

The effects of acids (monochloroacetic, dichloracetic, trichloroacetic and sulfuric acids) and bases (diethanolamine, triethanolamine, piperidine) on electrophoretic mobility and electrophoretic deposition (EPD) of particles of amphoteric Al₂O₃ and ZrO₂ in anhydrous 2-propanol were studied. It was found that the ζ-potential of Al₂O₃ and ZrO₂ particles had in acidic and alkaline 2-propanol media opposite charge to that in aqueous medium. This phenomenon was explained by the low dissociation constants of acids and bases in 2-propanol. This enables electrosteric stabilization of Al₂O₃ and ZrO₂ particles by acid anions and base cations. Similar electrophoretic behaviour of Al₂O₃ and ZrO₂ particles in 2-propanolic dispersions stabilized by MCAA allowed the preparation of compact, regular layered laminates with high cohesion at the interface of layers.     

Stability and rheology of dilute TiO<Subscript>2</Subscript>-water nanofluids

The apparent wall slip (AWS) effect, accompanying the flow of colloidal dispersions in confined geometries, can be an important factor for the applications of nanofluids in heat transfer and microfluidics. In this study, a series of dilute TiO₂ aqueous dispersions were prepared and tested for the possible presence of the AWS effect by means of a novel viscometric technique. The nanofluids, prepared from TiO₂ rutile or anatase nanopowders by ultrasonic dispersing in water, were stabilized by adjusting the pH to the maximum zeta potential. The resulting stable nanofluid samples were dilute, below 0.7 vol.%. All the samples manifest Newtonian behavior with the fluidities almost unaffected by the presence of the dispersed phase. No case of important slip contribution was detected: the Navier slip coefficient of approximately 2 mm Pa^-1 s^-1 would affect the apparent fluidity data in a 100-μm gap by less than 1%.     

Hydrogenation of phenylacetylene and 3-phenylpropyne using Rh(diene) complexes under homogeneous and heterogeneous conditions

Hydrogenation of phenylacetylene (PA) and 3-phenylpropyne (PP) was carried out using [Rh(diene)Cl]₂ complexes (diene is hexadiene (HD), cycloocta-1,5-diene (COD), norborna-2,5-diene (NBD)) in their immobilized forms and compared with hydrogenation in homogeneous arrangement. Immobilization brings significant increase of the catalytic activity and product selectivity in the step-wise hydrogenation to corresponding vinyl-resp. allyl-benzenes. Diene-ligand effect was apparent in PA hydrogenation; the product selectivity decreased in order Rh(HD) > Rh(NBD) > Rh(COD) and catalytic activity decreased in order Rh(HD) > Rh(COD) > Rh(NBD).     

Polyaniline-coated silver nanowires

Two non-conducting chemicals, aniline and silver nitrate, dissolved in formic acid solutions, yielded a composite of two conducting products, polyaniline and silver. As the concentration of formic acid increased, an alternative reaction, the reduction of silver nitrate with formic acid to silver became dominant, and the content of silver in the composites increased. The formation of polyaniline was confirmed by UV–visible, FTIR, and Raman spectroscopies. The typical conductivity of composites was 43 S cm^?1 at 84 wt.% of silver. Silver nanowires coated with polyaniline nanobrushes are produced at low concentrations of formic acid, the granular silver particles covered with polyaniline dominate at high acid concentrations.     

Efficient Caustic Rendering with Lightweight Photon Mapping

Robust and efficient rendering of complex lighting effects, such as caustics, remains a challenging task. While algorithms like vertex connection and merging can render such effects robustly, their significant overhead over a simple path tracer is not always justified and – as we show in this paper ‐ also not necessary. In current rendering solutions, caustics often require the user to enable a specialized algorithm, usually a photon mapper, and hand‐tune its parameters. But even with carefully chosen parameters, photon mapping may still trace many photons that the path tracer could sample well enough, or, even worse, that are not visible at all. Our goal is robust, yet lightweight, caustics rendering. To that end, we propose a technique to identify and focus computation on the photon paths that offer significant variance reduction over samples from a path tracer. We apply this technique in a rendering solution combining path tracing and photon mapping. The photon emission is automatically guided towards regions where the photons are useful, i.e., provide substantial variance reduction for the currently rendered image. Our method achieves better photon densities with fewer light paths (and thus photons) than emission guiding approaches based on visual importance. In addition, we automatically determine an appropriate number of photons for a given scene, and the algorithm gracefully degenerates to pure path tracing for scenes that do not benefit from photon mapping.     

Proving Resource Consumption of Low-level Programs Using Automated Theorem Provers

In this paper we use a program logic and automatic theorem provers to certify resource usage of low-level bytecode programs equipped with annotations describing resource consumption for methods. We have adapted an existing resource counting logic [Aspinall, D., L. Beringer, M. Hofmann, H.-W. Loidl and A. Momigliano, A program logic for resource verification, in: Proceedings of 17th International Conference on Theorem Proving in Higher Order Logics (TPHOLs2004), Lecture Notes in Computer Science 3223 (2004), pp. 34–49] to fit the first-order setting, implemented a verification condition generator, and tested our approach on programs that contain recursion and deal with recursive data structures. We have successfully applied our framework to programs that did not involve any updates to recursive data structures. But mutation is more tricky because of aliasing of heap. We discuss problems related to this and suggest techniques to solve them.     

Influence of diethylene glycol content on behavior of poly(ethylene terephthalate) fibers

Relationship between structural parameters of poly(ethylene terephthalate) (PET) fibers, their mechanical properties, and nonisothermal sorption of disperse dyes are investigated. Influence of diethylene glycol (DEG) addition and small changes in draw ratio are studied. Mechanical properties are characterized by stress–strain curves at constant deformation rate. The stress–strain relationships are described by means of derivative analysis. For treatment of nonisothermal experiments a simple kinetic model is suggested enabling to determine activation parameters of sorption. Further, the influence of a blank dye bath on the structure and properties of PET fibers is studied.     

The determination of β-ketoamide structures in poly(2-pyrrolidone)

Ketoamide and ketoimide units incorporated in poly(2-pyrrolidone) as a result of side reactions in the anionic polymerization may be quantitatively determined as 1,7-dibenzamido-heptane-4-one (IIa) after the total acid hydrolysis of the polymer and benzoylation of the hydrolyzate. Conditions were found for the quantitative analysis of these structures using liquid chromatography.     

Experimental study of heat transfer in process of rolls cooling in rolling mills by water jets

The paper summarizes results obtained by carrying out a large set of experiments that studied cooling of rolls. The experiments are based on the cooling of a steel plate by a set of flat nozzles from a starting temperature of 615 °C. The temperature histories measured in 39 points of the test plate are the inputs to the evaluation procedure. The sensor distribution covers a surface of a size of 450 × 110 mm. Classical Beck's inverse task was extended for the 3-dimensional area. The inverse task computes the surface distribution of heat transfer coefficient history, heat flux history and surface temperature. The results have pointed out a non-homogeneity in cooling by means of flat jets and provide us with a comparison of the flat and the full cone jets. The possibility of the intensification of the cooling by non-rectangular spray angle is discussed. It is shown that a certain point of saturation exists in the experimental pressure range from 0.4 to 1.2 MPa and increasing the pressure has a negligible influence on the cooling intensity.