Polarization and morphological characteristics of thin ZnO films deposited on tin-coated glass electrodes are presented. The films were obtained at a low temperature by an electrolytic process, where the cathode potential is an important control variable. The process is also promising as an electrochemical doping technique.

The structure of Taylor vortices in the annulus of coaxial horizontal rotating cylinders with and without axial flow was studied by a flow visualization technique based on the colour change of analytical indicators. Flow interaction effects can be characterized by three parameters whose numerical values are obtained from photographs and super 8 mm film strips.

This step is slow and irreversible. The thus formed lrO26 is stable under the experimental conditions. The catalytic activity for ethylene combustion on lrO2 is higher than on lr02 and this causes the observed catalytic rate enhancement after electrochemical pretreatment. The assumption for the formation of lrO2 is strongly supported since the catalyst work function after current application is higher than the initial value, since oxygen adsorbates cause increase in work function of clean surfaces.6The 1r02 catalyst can restore its initial activity only after treatment with excess ethylene in absence of oxygen or after cathodic polarization.4

The sequential form of the axial displacement of inclined Taylor vortices and their progressive degeneration to horizontal streaks due to the increasing dominance of axial flow is demonstrated via an analytical indicator-based direct flow visualization technique applied to a concentric cylinder cell with the inner cylinder rotating.Cette communication d6crit le decalage s6quentiel axial des tourbillons de Taylor inclinks, ces derniers se d6sa-gr6geant h la fin en de striures horizontales h la mesure de la domination du debit axial. Le ph6nomtne est manifest6 au moyen de visualisation bade sur les indicateurs color6s dans une cellule B cylindres coaxiaux, le cylindre int6rieur 6tant tournt. n recent years, there has been an increasing theoretical I and experimental interest in Taylor-Couette flow (Di Prima and Swinney, 1981;Park et al. 1983; Marcus, 1984a,b). A particularly interesting case is axial flow passing through the annulus between two concentric cylinders with one or both cylinders rotating. The onset of Taylor vortex formation in the presence of axial flow has been extensively studied (Chung and Astill, 1977;Takeuchi and Jankowski, 1981), but the structure of combined flow resulting at rotation rates of the inner-cylinder much larger than the critical rotation rate has not been thoroughly examined. Such a flow structure is expected to be highly complicated due to strong interaction between axial and rotating flow. Simmers and Coney (1979a) measured the velocity distribution in combined flow via hot wire anemometry. Based on the measurement of electric conductivity, Kataoka et al. (1975) described the axial movement of the Taylor vortices as an ideal plug flow without intermixing between adjacent Taylor cells in the range of 5 1.4 < Ta < 640 and 0 < Re < 90. Kataoka et al. (1977) also observed indirectly Taylor vortices distorted by the small imposed axial flow by means of a micro-electrode technique. Using the same technique, Coeuret et al. (Coeuret and Legrand, 1983;Legrand et al., 1983) attributed the disappearance of sharp frequency peaks in the associated density spectra to the deformation of Taylor vortices caused by the increasing axial flow. However, the entire process of propagation and deformation of the Taylor vortices induced by the imposed axial flow has not been studied in a systematic manner and current knowledge about the process mechanism is very limited. Classical visualization approaches (e.g., dye or smoke injection) cannot follow continuously the axial displacement of Taylor vortices, since the accumulation of the dye causes a rapid fading of colour and the suspended solid-particle technique fails to indicate a detailed flow structure in the intercylinder gap. The crucial experimental requirement is that the visualization technique must closely follow both convective propagation of Taylor vortices and their fine structure. The analytical-indicator technique (Quraishi and Fahidy , 1983a) is especially attractive for meeting this challenge. Because of its complete reversibility , the t...

In the anodie dissolution of copper into aqueous NaCI/KSCN electrolytes, the interaction of externally imposed magnetic fields with the anode potential determines the domain of oscillations. The oscillation patterns are analyzed in terms of power spectra and the theory of fractional Brownian motion.