Transition Between Detonation and Deflagration in a Tube with a Cavity

In this paper, the transition of a detonation from deflagration was investigated numerically while a detonation wave propagates in a tube with a sudden change in cross section, referred to as the expansion cavity. The dispersion-controlled scheme was adopted to solve Euler equations of axis-symmetric flows implemented with detailed chemical reaction kinetics of hydrogen-oxygen (or hydrogen-air) mixture. The fractional step method was applied to treat the stiff problems of chemical reaction flow. It is observed that phenomena of detonation quenching and reigniting appear when the planar detonation front diffracts at the vertex of the expansion cavity entrance. Numerical results show that detonation front in mixture of higher sensitivity keeps its substantial coupled structure when it propagates into the expansion cavity. However, the leading shock wave decouples with the combustion zone if mixture of lower sensitivity was set as the initial gas.

Experimental Observation on Surface Wave Phenomena in Thermal Capillary Convection

An optical diagnostic system consisting of the Michelson interferometer with the image processor has been developed for studying of the surface wave in the thermal capillary convection in a rectangular cavity. In this paper, the capillary convection, surface deformation and surface wave due to the different temperature between the two sidewalls have been investigated. The cavity is 52mm?42mm in horizontal cross section and 4mm in height. The temperature difference is increased gradually and flow in liquid layer will change from steady convection to unstable convection. The optical interference method measures the surface deformation and the surface wave of the convection. The deformation of the interference fringes, which produced by the meeting of the reflected light from the liquid surface and the reference light has been captured, and the surface deformation appears when the steady convection is developed. The surface deformation is enhanced with the increasing of the temperature difference, and then several knaggy peeks in the interference fringes appear and move from the heated side to the cooled side, it demonstrates that the surface wave is existed. The surface deformation, the wavelength, the frequency, and the wave amplitude of the surface wave have been calculated.

Determination of plastic properties by instrumented spherical indentation: Expanding cavity model and similarity solution approach

The present paper aims to develop a robust spherical indentation-based method to extract material plastic properties. For this purpose, a new consideration of-piling-up effect is incorporated into the expanding cavity model; an extensive numerical study on the similarity Solution has also been performed. As a consequence, two semi-theoretical relations between the indentation response and material plastic properties are derived, with which plastic properties of materials can be identified from a single instrumented spherical indentation curve, the advantage being that this approach no longer needs estimations of contact radius with given elastic modulus. Moreover, the inconvenience in using multiple indenters with different tip angles can be avoided. Comprehensive sensitivity analyses show that the present algorithm is reliable. Also, by experimental verification performed oil three typical materials, good agreement of the material properties between those obtained from the reverse algorithm and experimental data is obtained.

Emerging Practice in a Digital Age: A guide to technology-enhanced institutional innovation

Since the launch of the JISC guide Innovative Practice with e-Learning (JISC, 2005), so much has changed. At that time, early adopters were exploring the potential of mobile and wireless learning. Since then, the increased availability of public and institutional wireless networks, the emergence of new and more powerful technologies and an increase in personal ownership of these technologies are changing the way we connect, communicate and collaborate. Emerging Practice in a Digital Age, one of a series of Effective Practice guides, draws on recent JISC reports and case studies and looks at how colleges and universities are continuing to embrace innovation and respond to changes in economic, social and technological circumstances in a fastchanging world.