The transformation of 1,2,4-trimethylbenzene A probe reaction to monitor external surface modifications of HZSM-5?

The transformation of 1,2,4-trimethylbenzene is proposed as a new probe reaction to monitor the catalytic effects of inertisation of the external surface of HZSM-5. The external surface has been modified by coating ZSM-5 crystallites with an inert silicalite shell. At 723 K and a WHSV of 0.6 h−1 it has been shown that the isomerisation products 1,2,3-trimethylbenzene and 1,3,5-trimethylbenzene reflect changes in external activity. The disproportionation products, 1,2,4,5-tetramethylbenzene and 1,2,3,5-tetramethylbenzene together are shown to indicate changes in overall activity and shape selective properties of the catalyst sample. The results correlate with those observed for the reaction of 1,3,5-triisopropylbenzene and n-hexane cracking

Orthogonality conditions and asymptotic stability in the Stefan problem with surface tension

We prove nonlinear asymptotic stability of steady spheres in the two-phase Stefan problem with surface tension. Our method relies on the introduction of appropriate orthogonality conditions in conjunction with a high-order energy method.Comment: 25 pages, important references added, two remarks added, typos correcte

Qualitative behavior of solutions for thermodynamically consistent Stefan problems with surface tension

The qualitative behavior of a thermodynamically consistent two-phase Stefan problem with surface tension and with or without kinetic undercooling is studied. It is shown that these problems generate local semiflows in well-defined state manifolds. If a solution does not exhibit singularities in a sense made precise below, it is proved that it exists globally in time and its orbit is relatively compact. In addition, stability and instability of equilibria is studied. In particular, it is shown that multiple spheres of the same radius are unstable, reminiscent of the onset of Ostwald ripening.Comment: 56 pages. Expanded introduction, added references. This revised version is published in Arch. Ration. Mech. Anal. (207) (2013), 611-66

Objektivierung der Einstellung der Verstärkungsfunktion von CI - Sprachprozessoren

Der Hörerfolg von Patienten mit Cochlea - Implantaten hängt neben einem guten Implantationsergebnis nicht allein von der korrekten Ermittlung der Schwellen und der C - Werte (MCL - Werte) ab. Auch die Einstellung der Verstärkungskurve kann eine wichtige Rolle spielen. Die Verstärkungskurve sollte an die Wachstumsfunktion der elektrisch evozierten Potenziale des Hörnervs angepasst werden. Gründe hierfür sind die Forderung nach einer möglichst guten Wahrnehmung akustischer Signale zwischen den beiden Grenzwerten Schwelle und C - level sowie eine ungenügende Kenntnis über die dem CI - Träger täglich applizierte Schalldosis (insbesondere von Hintergrundgeräuschen, die ständig präsent sind). Diese Schalldosis kann minimiert werden, wenn die Verstärkungskurve optimal angepasst wird. Bisher war eine kategoriale Lautheitsskalierung das Mittel der Wahl bei der Festlegung der Verstärkungskurve. Deren Ergebnis ist aber sehr stark von der Kooperationsbereitschaft und -fähigkeit der Patienten abhängig und dauert sehr lange. Es wird gezeigt, ob mit Hilfe der NRT - Methode (neural response telemetry) die aufwendige kategoriale Lautheitsskalierung umgangen werden kann

Progress in heliostat development

Abstract not availableAndreas Pfahl, Joe Coventry, Marc Röger, Fabian Wolfertstetter, Juan Felipe Vásquez-Arango, Fabian Gross, Maziar Arjomandi, Peter Schwarzbözl, Mark Geiger, Phillip Liedk

CFD Simulation and Performance Analysis of Alternative Designs for High-Temperature Solid Particle Receivers

Direct-absorption solid particle receivers are theoretically capable of yielding temperatures in excess of 1000°C, which enables higher efficiency power cycles and lower thermal storage costs. This paper presents rigorous CFD simulations of alternative solid particle receiver designs with recirculation to help identify optimal configurations that maximize the receiver thermal efficiency. The alternative receiver designs considered are a north-facing cavity receiver and a face-down surround-field cavity receiver. The CFD simulations model incident solar radiation from a heliostat field as a boundary condition on the model domain. The CFD simulations also couple convective flow with the thermal and discrete-phase (particle) solutions, which in turn affects absorption of incident solar radiation and thermal re-radiation within the receiver. The receivers are optimized to yield comparable particle temperatures at the outlets of 750-850°C, heated from an injection temperature of 300°C, and are compared on the basis of thermal efficiency. The CFD simulations yielded thermal efficiencies of the north-facing receiver at 72.3% (losses were 6.5% radiative and 20.9% convective) and the face-down receiver at 78.9% (losses were 11.4% radiative and 9.6% convective) at solar noon on March 22. Ongoing efforts are focused on reducing convective and radiative losses from both receiver configurations