INFLUENCE OF A LEVELNESS DEFECT IN A THRUST BEARING ON THE DYNAMIC BEHAVIOUR OF AN ELASTIC SHAFT

This paper examines the non-linear dynamic behaviour of a flexible shaft. The shaft is mounted on two journal bearings and the axial load is supported by a defective hydrodynamic thrust bearing at one end. The defect is a levelness defect of the rotor. The thrust bearing behaviour must be considered to be non-linear because of the effects of the defect. The shaft is modelled with typical beam finite elements including effects such as the gyroscopic effects. A modal technique is used to reduce the number of degrees of freedom. Results show that the thrust bearing defects introduce supplementary critical speeds. The linear approach is unable to show the supplementary critical speeds which are obtained only by using non-linear analysis.     

Global Analysis of the Flows of Fluids with Pressure-Dependent Viscosities

 To describe the flows of fluids over a wide range of pressures, it is necessary to take into account the fact that the viscosity of the fluid depends on the pressure. That the viscosity depends on the pressure has been verified by numerous careful experiments. While the existence of solutions local-in-time to the equations governing the flows of such fluids are available for small, special data and rather unrealistic dependence of the viscosity on the pressure, no global existence results are in place. Our interest here is to establish the existence of weak solutions for spatially periodic three-dimensional flows that are global in time, for a large class of physically meaningful viscosity-pressure relationships. (Accepted May 1, 2002) Published online November 15, 2002 Communicated by S. S. ANTMAN     

Polyaniline nanofibers: facile synthesis and chemical sensors

Polyaniline nanofibers with uniform diameters between 30 and 50 nm can be made in bulk quantities through a facile aqueous/organic interfacial polymerization method at ambient conditions. The nanofibers have lengths varying from 500 nm to several micrometers and form interconnected networks. Thin films made of the nanofibers have superior performance in both sensitivity and time response to vapors of acid (HCl) and base (NH3).     

Processable stabilizer-free polyaniline nanofiber aqueous colloids

Aqueous polyaniline colloids can be readily prepared by purifying polyaniline nanofibers and controlling the pH and self-stabilized via electrostatic repulsions without the need for any chemical modification or steric stabilizer, thus providing a simple and environmentally friendly way to process the conducting polymer in its conductive state both in bulk and at the nanometre level.     

Syntheses of some mixed AuOs and PtOs clusters and the X-ray structure of [Os4H2(CO)12(AuPPh3)2]

Some reactions of [Os₄H₃(CO)₁₂AuPR₃] (R = Et, Ph) resulting in the formation of [Os₄H₂(CO)₁₂(AuPR₃)₂] are presented. A single-crystal X-ray structure of [Os₄H₂(CO)₁₂(AuPPh₃)₂] is reported and reveals a novel Ph₃PAuAuPPh₃ unit asymmetrically bridging one edge of an Os₄ tetrahedron, the first example of a mixed gold-metal carbonyl cluster with an AuAu bond.