Numerical and experimental study of the flow in an eccentric Couette-Taylor system with small gap

Various papers were dedicated to the technical and industrial aspects of the Taylor–Couette flow, by analyzing the flow structure in dependence of characteristic parameters. Also some studies concerning the influence of an eccentrical position of the rotating inner cylinder relatively to the fixed outer cylinder exist in the case of a large gap width. The principal technical application of such studies is the flow in journal bearings where the gap width is very small, of the order 0.1\% relative to the inner cylinder radius. Analytical and numerical investigations of the flow in journal bearings are generally based on the two–dimensional Reynolds approximation. This investigation in aiming at a validation of the range where the Reynolds equation is applicable in relation to the characteristical parameters: gap width, eccentricity and Reynolds number. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Numerical and Stability Aspects of Non-Newtonian Fluid Flow

This paper is concerned with nonlinear rheological fluids of Oldroyd type. We present a (formal) stability analysis of the corresponding system of equations, showing stability limits on the Weißenberg number in certain cases. Moreover, we introduce a numerical method for solving the full time-dependent Oldroyd system based on the finite element spatial discretization and on the fractional step θ-scheme time approximation. Numerical solutions are presented for two well known benchmark problems: the lid driven cavity and the four-to-one planar contraction. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Tuning a conventional quantum well laser by nonresonant laser field dressing of the active layer

Tunable semiconductor lasers may be considered as a critical technology for optical communications. We investigate the theoretical feasibility of tuning a conventional GaAs/Al_0.2Ga_0.8As quantum well laser emitting at 825 nm by non-resonant laser-dressing of the active layer. Conduction and valence subbands are sensitive to the intense dressing field and this effect can be used to blueshift the active interband transition. The laser-dressed electron and hole states are calculated in the effective mass approximation by using the finite difference method. Emitted wavelength, threshold current and characteristic temperature are discussed as functions of the dressing laser parameter and cavity length.     

Intelligibility of reverberant noisy speech with ideal binary masking

For a mixture of target speech and noise in anechoic conditions, the ideal binary mask is defined as follows: It selects the time-frequency units where target energy exceeds noise energy by a certain local threshold and cancels the other units. In this study, the definition of the ideal binary mask is extended to reverberant conditions. Given the division between early and late reflections in terms of speech intelligibility, three ideal binary masks can be defined: an ideal binary mask that uses the direct path of the target as the desired signal, an ideal binary mask that uses the direct path and early reflections of the target as the desired signal, and an ideal binary mask that uses the reverberant target as the desired signal. The effects of these ideal binary mask definitions on speech intelligibility are compared across two types of interference: speech shaped noise and concurrent female speech. As suggested by psychoacoustical studies, the ideal binary mask based on the direct path and early reflections of target speech outperforms the other masks as reverberation time increases and produces substantial reductions in terms of speech reception threshold for normal hearing listeners.     

Microwave assisted synthesis and magnetic properties of octanuclear and enneanuclear Ni(II) complexes: an unprecedented coordination mode for the NO(2)(-) ligand

Octanuclear and enneanuclear Ni(II) complexes have been synthesized using a microwave reactor. The octanuclear complex Ni(8) presents a new triply bridging coordination mode for the NO(2)(-) ligand.