Results 1 - 10 of 585
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[en] 1 - Description of program or function: SLAROM solves the neutron integral transport equations to determine flux distribution and spectra in a lattice and calculates cell averaged effective cross sections. 2 - Method of solution: Collision probability method for cell calculation and 1D diffusion for core calculation. 3 - Restrictions on the complexity of the problem: Variable dimensions are used throughout the program so that computer core requirements depend on a variety of program parameters
[en] A conforming representation composed of 2D finite elements and finite Fourier series is applied to 3D nonlinear non-ideal magnetohydrodynamics using a semi-implicit time-advance. The self-adjoint semi-implicit operator and variational approach to spatial discretization are synergistic and enable simulation in the extremely stiff conditions found in high temperature plasmas without sacrificing the geometric flexibility needed for modeling laboratory experiments. Growth rates for resistive tearing modes with experimentally relevant Lundquist number are computed accurately with time-steps that are large with respect to the global Alfven time and moderate spatial resolution when the finite elements have basis functions of polynomial degree (p) two or larger. An error diffusion method controls the generation of magnetic divergence error. Convergence studies show that this approach is effective for continuous basis functions with p (ge) 2, where the number of test functions for the divergence control terms is less than the number of degrees of freedom in the expansion for vector fields. Anisotropic thermal conduction at realistic ratios of parallel to perpendicular conductivity (x(parallel)/x(perpendicular)) is computed accurately with p (ge) 3 without mesh alignment. A simulation of tearing-mode evolution for a shaped toroidal tokamak equilibrium demonstrates the effectiveness of the algorithm in nonlinear conditions, and its results are used to verify the accuracy of the numerical anisotropic thermal conduction in 3D magnetic topologies.
[en] Description of program or function: The use of electromagnetic radiation cross-sections in radiation shielding calculations and more generally in transport theory applications actually requires an interpolation between values which are tabulated for certain values of the energy. In order to facilitate this process and to reduce the computer memory requirements, we have developed, by a least squares method, a set of functions which represents the cross-sections for the photoelectric absorption, the coherent (Rayleigh) and the incoherent (Compton) scattering (1). For this purpose we have accepted as true values the ones tabulated by Storm and Israel (2) for the photoeffect, by Hubbell et Al. (3) for the incoherent scattering and by Hubbell and Overbo (4) for the coherent scattering
[en] 1 - Description of program or function: The asymmetry factor S of Mott's differential cross section for the scattering of electrons and positrons by point nuclei without screening is calculated for any energy, atomic number and angle of scattering. 2 - Method of solution: We have summed the conditionally convergent series, F and G, appearing in the asymmetry factor using two consecutive transformations: The one of Yennie, Ravenhall and Wilson and that of Euler till we have seven times six significant figures repeated in the factor S. 3 - Restrictions on the complexity of the problem: Those appearing in the use of Mott's cross section for unscreened point nuclei
[en] In the preceding paper of the author parametrizing functions Fi, Th, Ro were introduced depending on word variables, positive-integer variables, and variables whose values are finite sequences of positive-integer variables. With the help of the parametrizing functions Fi, Th, Ro finite formulae are written out for the family of solutions of every equation of the form φ(x1,x2,x3) x4=ψ(x1,x2,x3) x5, where φ(x1,x2,x3) and ψ(x1,x2,x3) are arbitrary words in the alphabet x1, x2, x3 in a free monoid.
[en] In 1983 Knudsen proved that the triple-canonical map of a pointed Deligne-Mumford stable curve is an embedding, and the double-canonical map has no base points. The same question is discussed here for the canonical map. The answer can be stated virtually purely topologically in terms of the dual graph, with the exception of the case of hyperelliptic curves.
[en] A simple proof of the well-known approximation theorem for the homogeneous convolution equation is presented. The method used in the proof makes it possible to extend this result to the more general case of vector convolution.
[en] Systems generalizing Lorenz's are considered in a bounded subdomain of R3. It is shown that under certain conditions of uniform hyperbolicity small non-autonomous perturbations do not lead to the formation of stable trajectories.
[en] Results on the convergence of solutions of variational inequalities for obstacle problems are proved. The variational inequalities are defined by a non-linear monotone operator of the second order with periodic rapidly oscillating coefficients and a sequence of functions characterizing the obstacles. Two-scale and macroscale (homogenized) limiting variational inequalities are obtained. Derivation methods for such inequalities are presented. Connections between the limiting variational inequalities and two-scale and macroscale minimization problems are established in the case of potential operators.
[en] 1 - Description of program or function: SONATINA is used for predicting the behaviour of a prismatic high-temperature gas-cooled reactor (HTGR) core under seismic excitation. The SONATINA code system contains three computer programs, which are SONATINA-1, SONATINA-2H and SONATINA-2V. SONATINA-1: one column model SONATINA-2H: Horizontal two-dimensional slice core model SONATINA-2V: vertical two-dimensional slice core model 2 - Methods: Runge-Kutta integration method. 3 - Restrictions on the complexity of the problem: None