A Modelling Study of Evolving Particle-laden Turbulent Pipe-flow

An Eulerian turbulent two phase flow model using kinetic theory of granular flows for the particle phase was developed in order to study evolving upward turbulent gas particle flows in a pipe. The model takes the feedback of the particles into account and its results agree well with experiments. Simulations show that the pipe length required for particle laden turbulent flow to become fully developed is up to five times longer than an unladen flow. To increase the understanding of the dependence of the development length on particle diameter a simple model for the expected development length was derived. It shows that the development length becomes shorter for increasing particle diameters, which agrees with simulations up to a particle diameter of 100 ??m. Thereafter the development length becomes longer again for increasing particle diameters because larger particles need a longer time to adjust to the velocity of the carrier phase.     

Hermitian <Emphasis Type="Italic">K</Emphasis>-theory and 2-regularity for totally real number fields

We completely determine the 2-primary torsion subgroups of the hermitian K-groups of rings of 2-integers in totally real 2-regular number fields. The result is almost periodic with period 8. Moreover, the 2-regular case is precisely the class of totally real number fields that have homotopy cartesian “Bökstedt square”, relating the K-theory of the 2-integers to that of the fields of real and complex numbers and finite fields. We also identify the homotopy fibers of the forgetful and hyperbolic maps relating hermitian and algebraic K-theory. The result is then exactly periodic of period 8 in the orthogonal case. In both the orthogonal and symplectic cases, we prove a 2-primary hermitian homotopy limit conjecture for these rings.     

Reaction mechanism of aerobic oxidation of alcohols conducted on activated-carbon-supported cobalt oxide catalysts

Catalytic performances and the reaction mechanism of Co(3)O(4)/AC (AC=activated carbon) for aerobic oxidation of alcohols carried out in the liquid phase were investigated. Co(3)O(4)/AC shows a high activity for aerobic oxidation of benzyl alcohol, comparable to noble metal catalysts (e.g., Au/AC) even in the absence of additives or promoters (e.g., NaOH). Changing preparation conditions, such as treatment temperature and/or time, can affect the catalytic performances of Co(3)O(4)/AC, due to decomposition of surface groups of the carbon support. Careful studies show that low alcohol conversions are obtained with either Co(3)O(4) or AC alone, which indicates that the high conversion observed over the Co(3)O(4)/AC is due to a synergistic effect between Co(3)O(4) and AC. Parallel experiments using a high-surface-area covalent triazine framework or oxygen-inert carbon nitride as support for the Co(3)O(4) catalyst also show lower conversions, which suggest that the ability of AC (in Co(3)O(4)/AC) to activate molecular oxygen is essential for the reaction. FTIR and XPS spectra taken from catalysts before and after the reaction confirm that oxygen activation proceeds mainly on the carbon support. As a result, it can be assumed that the alcohol dehydrogenation step proceeds on the metal oxide, whereas the oxygen activation step occurs mainly on the carbon support.     

Taming functionality: easy-to-handle chiral phosphiranes

Enantiopure chiral phosphiranes possessing a binaphthyl backbone demonstrate remarkable thermal stability, are highly resistant to air-oxidation and are effective ligands in catalytic asymmetric hydrosilylations.     

Assessment of the change in similarity judgements of auralized engine sounds caused by changes in frequency resolution of transfer functions

Auralization facilitates aural examination of contributions from different sound sources, individually and as parts of a context. Auralizations can be created by filtering sounds of the perceptually most salient sources through binaural transfer functions (BTFs) from source positions to a listening position. When psychoacoustic analysis is based on auralizations, the auralizations need to give the same impression as real sounds. The objective of this study was to determine the frequency resolution required for auralizations to be perceptually equivalent to recordings made with an artificial head. Auralizations of the contribution of engine sounds to interior sounds of a truck were examined. In listening tests auralizations based on simplified BTFs were compared to artificial head recordings. The BTFs were simplified by lowering the frequency resolution and by smoothing in the frequency domain. Auralizations made through BTFs with a resolution of 4 Hz or higher or smoothed with maximum 1/96 octave moving average filters were perceived as similar to artificial head recordings.     

Mechanisms of Non-Newtonian Polymer Flow Through Porous Media Using Navier–Stokes Approach

This study includes solving non-Newtonian Navier–Stokes equation in three-dimensions (real rock images) and two-dimensions (simplified pore geometries) using the finite-difference method. The purpose of this study is to improve understanding of local phenomena leading to the mobilization of residual oil. This involves local pressure variations for non-Newtonian polymers and compares it with Newtonian fluid behavior. When a higher degree of shear thickening is induced, more flow diversion to side channels perpendicular to the main flow path and larger drag on fluids inside side channels will occur. This is consistent with oil mobilization and lowering of residual oil saturation.     

Selenium speciation in anaerobic granular sludge

Chromatographic (IC-CD, GC-FID) and spectroscopic (XRD) techniques that allow the specific determination of several selenium species present or formed during bioremediation processes of selenate contaminated drinking, ground, or wastewaters have been established. The developed techniques are shown to be applicable in determining selenium species in the range of target concentrations for emissions and are thus appropriate to characterize bioremediation processes. The applied techniques offer advantages regarding short analytical times without loss of satisfactory accurateness towards more sophisticated methods. By means of IC-CD, selenate and selenite can be detected specifically to concentrations far below allowance levels for metal finishing industries (20?µg?L^?1 selenate, 40?µg?L^?1 selenite) within 16.0?min. Thus, the removal of selenate from the liquid phase by anaerobic granular sludge was quantified by IC-CD, and the concomitantly formed red precipitates were analysed by XRD. Hexagonal elemental selenium was found to be present in the XRD analysis. Even if the precipitate contained iron and zinc, as shown by ICP-OES, no iron- or zinc-containing selenium minerals were detected by XRD. The GC-FID method described determines dimethylselenide and dimethyldiselenide at a detection limit of 1?ng and 2?ng, respectively, without further chemical derivatization within 7.4?min. Thus, the GC-FID offers adequate detection of two major volatile organic selenium species potentially formed during bioremediation of selenium contaminated waters.     

A Cryptic Polyene Biosynthetic Gene Cluster in Streptomyces calvus Is Expressed upon Complementation with a Functional bldA Gene

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