Fluxing of a 359/SiC/10p composite with alkali chlorides: effect of inclusions

The effect of salt addition, in the form of a fluxing agent containing equivalent amounts of NaCl and KCl, on the microstructure and mechanical properties of 359/SiC/10p composite has been investigated. Both microstructure and properties are affected, with the removal of magnesium and strontium and the introduction of sodium and potassium being responsible for the degradation in properties. Thermodynamic calculations have been carried out to account for the effect of salt addition in terms of the surface adsorption of sodium and potassium impurities and the consequent changes in the surface-interface tension of their binary alloys. Mechanisms for the degradation of properties have been discussed.     

Density functional theory studies of Cu-zeolite de-NOx catalysts

Summary Recent progress in the modelling of exchanged Cu sites and their interactions with small molecules, based on DFT cluster calculations, is briefly reviewed.     

On the path and efficiency of two micromachines with rigid tails

This paper reports on the results of investigation of the swimming of two different micro-machines. Mechanically each of these micro-machines consists of a head (containing an electromechanical power source) and a tail which moves relative to the head as a rigid body. The problem is approached theoretically by considering the types of movement which can occur for these micro-machines immersed in a viscous medium. The first micro-machine has a tail which oscillates in vertical plane, therefore the trajectory of this machine is in that plane too. The tail of the second micro-machine roates conically, so it produces a three dimensional helical path in space with its axis approximately along the direction of tail centreline.Using the boundary element method for solving the traction equations on the surface of the tail, and a time-dependent Euler kinematic scheme to plot the path, the net propulsive force and torque, the translational velocity, angular velocity and the trajectory of each machine are calculated. Evaluation of the path and the direction of motion for each micro-machine using different dimensional parameters can give an idea of the efficiency for such machines with rigid tails.     

Acoustic resonance spectroscopy (ARS)

The basics of acoustic resonance spectroscopy (ARS), which provides data about an object's physical structure and composition, are explained. In ARS, one actively excites a large number of resonances (normal modes) in an object that has no internal vibrations by slowly sweeping the excitation frequency to obtain an acoustic spectrum of the object. The instrumentation for this nondestructive evaluation technique is described, and some applications are briefly discussed