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[en] This book presents the papers given at a conference on free convection in porous materials. Topics considered at the conference included heat transfer, nonlinear temperature profiles and magnetic fields, boundary conditions, concentrated heat sources in stratified porous media, free convective flow in a cavity, heat flux, laminar mixed convection flow, and the onset of convection in a porous medium with internal heat generation and downward flow

[en] RAMONA-4B code is currently under development for simulating thermal hydraulic instabilities that can occur in Boiling Water Reactors (BWRs) and the Simplified Boiling Water Reactor (SBWR). As one of the missions of RAMONA-4B is to simulate SBWR startup transients, where geysering or condensation-induced instability may be encountered, the code needs to be assessed for this application. This paper outlines the results of the assessments of the current version of RAMONA-4B and the modifications necessary for simulating the geysering or condensation-induced instability. The test selected for assessment are the geysering tests performed by Prof Aritomi (1993)

[en] A dimensional analysis of the Brinkman-extended Darcy formulation which includes the transport and viscous terms, leads to four governing parameters for the steady state natural convection in a vertical porous cavity. The problem becomes ill-formulated at high values of these parameters and may require the consideration of Forchheimer modifications

[en] The effect of uniform transverse magnetic field is investigated on the flow formed, when a straight channel formed by two parallel porous walls through which liquid is flowing under a constant pressure gradient, is rotated about an axis perpendicular to the walls. The flow depends on the Taylor's number α, pressure gradient P, the suction Reynolds number β and the Hartmann number M. When α→infinity such that P is finite, thin boundary layers are formed in the vicinity of the porous walls and the effect of the magnetic field is to reduce the thickness of the boundary layers. A method for setting up an experiment to test the theoretical conclusions of the paper has been suggested. (author)

[en] Numerical analysis and experimental measurements of the flattening degree of plasma sprayed molybdenum and zirconia droplets deposited on different substrate materials are presented. Investigation is focused on the influence of rate of solidification and wetting angle on droplet spreading. In the numerical analysis, the Madejski-Zhang model with one-dimensional treatment of solidification as well as heat transfer in the melt, solidified splat and substrate is employed. A parametric study is conducted to examine the effect of droplet size, impact velocity, superheating of droplets, substrate temperature, thermal contact resistance, and wetting angle on the spreading of droplet and flattening degree. Results show that the time scale for solidification can be as small as that for spreading and rate of solidification can greatly influence the flattening degree. A guideline for when the effect of wetting angle and surface tension on droplet deformation can be neglected is derived. A correlation for the relationship between the flattening degree and Reynolds number with the consideration of solidification is deduced, and a criterion for the effect of droplet solidification on impact dynamics to be negligible is given. The limitation of the assumption of isothermal substrate is discussed. The numerical predictions statistically agree well with the experimental data

[en] Survey and alignment activities at CAT (Centre for Advanced Technology - India) are related to two accelerator projects called INDUS-1 and INDUS -2. Former is a 450 MeV SRS and latter is a 2.5 GeV SRS. Both the machines use a 450/700 MeV booster synchrotron and 20 MeV pre-injector microtron for injection. Indus-1 was commissioned with 100 mA stored beam current in May 1999. Indus-2 is under construction and expected to be commissioned within next 4 years. Survey and alignment work of booster synchrotron and Indus-1 (storage ring) was accomplished using optical surveying techniques with software ECDS-2 of Kern. That was possible due to small size of machines of Indus-1. For Indus-2 with circumference of 172.47 m, the network surveying and alignment scheme has been planned. Indus-2 is a high brilliance machine and this puts more stringent requirements on alignment. This paper describes methodology and performance results of Indus-1 alignment and strategy for Indus-2. (authors)

[en] A general theory of excitation of a diatomic molecule due to collision with an atom (or a molecule), for example the He-CO system, in the presence of an infra-red laser beam is presented. A non-perturbative quasi-energy method is used to describe the quantum dynamics of excitation of a diatomic molecule due to a laser field. The dressed states of the molecule are obtained by solving the equation of motion of an explicitly time-dependent Hamiltonian. The effect of collision on the radiative excitation process is investigated by changing the various collision parameters, for example, the impact parameter, collision velocity etc, with different values of molecule-field detunings. (orig.)

[en] The high T_c superconductor of nominal composition Bisub(1.5)-Pbsub(0.5)-Ca₂-Sr₂-Cu₃-O_x was prepared by solid-state reaction method. The upper critical field Hsub(c2) of the material with a zero-resistance transition at 110 K was investigated by observing variations in resistance with temperature down to 90 K and with a magnetic field up to 7T. The slope of Hsub(c2) with temperature was about -0.41T/K for zero resistance transition and -6.86 T/K for onset of superconductivity. Hsub(c2) values of 0K were estimated to be 31.3 T and 563 T for zero-resistance transition and onset of superconductivity respectively. (author). 6 refs., 2 figs

[en] A theory of collisional excitation transfer between atoms in the presence of a laser field is presented. The cross-section for the process is obtained and its variation with the laser frequency, intensity and collision velocity is shown. (orig.)