Numerical modeling of MHD stability in a cylindrical configuration

A numerical modeling of natural convection under the influence of either axial (B_z) or radial (B_r) magnetic field in a cylindrical configuration filled with a low-Prandtl number electrically conducting fluid, is studied. The finite volume method is used to discretize the equations of continuity, Navier Stokes and energy. A computer program based on the SIMPLER algorithm is developed. The flow and temperature fields are presented by stream function and isotherms, respectively. Stability diagrams are established according to the numerical results of this investigation. These diagrams put in evidence the dependence of the critical Grashof number, Gr_cr with the increase of the Hartmann number, Ha. The strongest stabilization of the convective flows occurs when the magnetic field is applied in the radial direction. This study confirms the possibility of stabilization of a liquid metal flow in natural convection by application of a radial magnetic field.     

Extensive reading as a means of input to L2 learning

A group of ESL learners (n = 16) in the UK were given a 3-month extensive reading programme involving graded readers to test the hypothesis that input of this nature could effect an improvement in their L2 competence. Comparison of pre-and post-treatment tests in reading and writing indicated that subjects had improved significantly in both skills, though particularly in writing. A subsequent more detailed analysis of one of the writing tests (an essay) showed post-treatment gains in number of words written and accuracy of expression. However, subjects' vocabulary base remained relatively unchanged and they used a generally more simple syntax. The experimental treatment thus appears to have encouraged a simpler but more correct form of expression in the L2. These results may relate to the linguistic models provided by the simplified language used in the graded readers. Extensive reading is suggested to have a potential in L2 development terms, teough the effect obtained from any given reading programme may be significantly related to the linguistic form of the material used.