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The onset of Taylor–Görtler vortices in impulsively decelerating swirl flows is analyzed by using the recently developed, relative stability model. This model takes the growth rate of the kinetic energy of the base state and also that of disturbances into consideration. In the present system the primary transient swirl flow is laminar but for the Reynolds number Re>Rec secondary motion sets in at a certain time. The present model yields the critical Reynolds number of Rec=153. This value is larger than that from the strong stability model, but smaller than that from the propagation theory. For Re>Rec the dimensionless critical time to mark the onset of vortex instabilities, τc, is presented as a function of Re. It is found that the predicted τc value is much smaller than experimental detection time of first observable secondary motion. Therefore, it seems evident that small disturbances initiated at τc require some growth period until they are detected experimentally. Since the present system is a rather simple one, the present results will be helpful in comparing available stability models. [ABSTRACT FROM AUTHOR]

A theoretical analysis of convective instability driven by buoyancy forces under the transient concentration fields is conducted in an initially quiescent, liquid-saturated, cylindrical porous layer with gas diffusion from below. Darcy’s law and Boussinesq approximation are used to explain the characteristics of fluid motion, and linear stability theory is employed to predict the onset of buoyancy-driven motion. Under the principle of exchange of stabilities, the stability equations are derived on the basis of the propagation theory and the dominant mode method, which have been developed in a self-similar boundary layer coordinate system. The present predictions suggest the critical Darcy–Rayleigh number RD, which is quite different from the previous ones. The onset time becomes smaller with increasing RD and follows the asymptotic relation derived in the infinite horizontal porous layer. [ABSTRACT FROM AUTHOR]

Spherical thiocyanate-coated Cu@Ag particles were synthesized by a galvanic replacement reaction. These particles were used to fabricate a conductive paste, which was printed on silicon wafers to manufacture inexpensive silicon-wafer-based solar cells. Cells with the thiocyanate-coated Cu@Ag particles showed comparatively favorable solar cell efficiencies because of improved thermal oxidation resistance, resulting from the deposited β-CuSCN layers on the Cu@Ag particles. [ABSTRACT FROM AUTHOR]

New bis-hydrocarbyl complexes of methylene bridged ansa-metallocenes [H2C(C5Me2H2)2]ZrR2 R = Me (1), CH2Ph (2), CH2SiMe3 (3), Ph (4) have been prepared. They form catalytically active intermediates with borane or borate depending on solvent and Zr-R group. Specifically, [H2C(Me2C5H2)2]Zr(CH2Ph)2 (2) produced an ion pair upon treatment with B(C6F5)3 whereas [H2C(Me2C5H2)2]Zr(CH2SiMe3)2 (3) produced a zwitterionic species, identified by 1H, 13C, and 19F NMR spectroscopy. Copolymerization of ethylene and norbornene for the metallocene dichloride/MAO and bis-hydrocarbyl complex/borate systems was compared. [ABSTRACT FROM AUTHOR]