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Two types of alumina-based ceramics, pure solid-state sintered (SSS) alumina ceramics, and a liquid phase sintered (LPS) alumina were corrosion tested under both static and quasi—dynamic conditions in 0.5M NaCl solution and in deionized water reference medium at the temperature of 290°C. Static tests were also performed at 150° and 200°C in order to obtain the data for determination of kinetic parameters, and for calculation of the activation energies. The apparent activation energies of dissolution of the LPS alumina in deionized water and in 0.5M NaCl solution were identical and ranged around 49 kJ/mol. The SSS alumina ceramics corroded by grain-boundary attack and slow dissolution of alumina matrix grains, and the corrosion rates were negligible in both corrosion media. The LPS alumina, corroded by preferential attack and dissolution of calcium aluminosilicate grain-boundary glass. The alumina matrix remained relatively intact. The dissolution was markedly faster than in the SSS alumina. The rates of dissolution were found to be temperature dependent, but no influence of the corrosion medium was observed.

The paper deals with sharp embeddings of the spaces B and F into rearrangement-variant spaces and related Hardy inequalities. Here (1/p, s) belongs to the interior of the shaded invariant spaces region in the Figure

The strength of sintered low-temperature co-fired ceramic (LTCC) disks was measured under dry (

The application of the correct industrial thermal pattern for the spheroidization annealing process of steel needs a precise control of the temperature evolution in the furnace environment and in the mass of the treated steel, which was formerly wiredrawn. The aim is to design a thermal evolution that promotes a complete annealed globular structure, the absence of the decarburation and of an excessive grain growth on the surface of the treated material. An experimental procedure that allows building of a reliable simulation model of the heating process, has been based on a precise monitoring of the thermal evolution of the furnace environment and on the microstructural characterisation of the treated steel. The thermal pattern estimated by the simulation model has permitted designing of an optimised industrial thermal cycle to reach a high-quality standard of the production.

Many environmental applications of shallow water flow modelling can be characterized as only slowly varying and everywhere sub-critical. A simplified finite volume model is therefore developed that is capable of describing pertinent shallow water flow processes more efficiently than the usual Godunov/ Riemann characteristics approaches. The model is tested against a number of analytical and numerical solutions to the governing equations. The model reproduces accurately flow round a circular bend, flow over topography, flow up an initially dry beach and floodwave propagation down a meandering river reach, with mass conservative solutions. Copyright © 2004 John Wiley & Sons, Ltd.

Bend strengths of two sizes of specimens of an alumina ceramic were determined under conditions that either enhanced or restricted sub critical crack growth. The specimen sizes differed in each linear dimension by a factor of five and the effective size of small specimens was varied by the use of both 3- and 4-point bending. Strength was dependent on specimen size under both crack-growth conditions, and the dependence was associated with variations in flaws at fracture origins. The experimental data were analyzed for applicability of Weibull's statistical relations and in terms of fractographic examinations of strength-controlling flaws.

The effects of sub-critical crack extension on the fracture properties of ferritic steels after they have been subjected to warm prestressing are investigated. The crack growth is assumed to occur at the temperature of the final loading, after the warm prestressing and the subsequent unloading. Predictions of the fracture behaviour are made using continuum mechanics and a fracture criterion based on a modified J-integral. The results of these calculations are consistent with those of a micromechanistic model of cleavage fracture from a sharp crack. Both the theories predict that the beneficial elevation in fracture load produced by warm prestressing is maintained after sub-critical crack growth provided the latter is not greater than the compressive yielded zone formed on unloading.