67,287 research outputs found
Computation of three-dimensional nozzle-exhaust flow fields with the GIM code
A methodology is introduced for constructing numerical analogs of the partial differential equations of continuum mechanics. A general formulation is provided which permits classical finite element and many of the finite difference methods to be derived directly. The approach, termed the General Interpolants Method (GIM), can combined the best features of finite element and finite difference methods. A quasi-variational procedure is used to formulate the element equations, to introduce boundary conditions into the method and to provide a natural assembly sequence. A derivation is given in terms of general interpolation functions from this procedure. Example computations for transonic and supersonic flows in two and three dimensions are given to illustrate the utility of GIM. A three-dimensional nozzle-exhaust flow field is solved including interaction with the freestream and a coupled treatment of the shear layer. Potential applications of the GIM code to a variety of computational fluid dynamics problems is then discussed in terms of existing capability or by extension of the methodology
Power filters for gravitational wave bursts: network operation for source position estimation
A method is presented to generalize the power detectors for short bursts of
gravitational waves that have been developed for single interferometers so that
they can optimally process data from a network of interferometers. The
performances of this method for the estimation of the position of the source
are studied using numerical simulations.Comment: To appear in the proceedings of GWDAW 2002 (Classical and Quantum
Gravity, Special issue
The root of the problems of the British banks is the same as that of American banks: shaky mortgage-backed securities
Banks and banking - Great Britain ; Great Britain
Vacuum Polarisation and the Black Hole Singularity
In order to investigate the effects of vacuum polarisation on mass inflation
singularities, we study a simple toy model of a charged black hole with cross
flowing radial null dust which is homogeneous in the black hole interior. In
the region we find an approximate analytic solution to the
classical field equations. The renormalized stress-energy tensor is evaluated
on this background and we find the vacuum polarisation backreaction corrections
to the mass function . Asymptotic analysis of the semiclassical mass
function shows that the mass inflation singularity is much stronger in the
presence of vacuum polarisation than in the classical case.Comment: 12 pages, RevTe
Edge coating of flat wires
An apparatus and technique is described for the coating of the edge surfaces of flat ribbon conductors with an adherent coating of a dielectric insulating material. Means for passing the ribbon conductors between a pair of generally axially aligned rollers is provided. The edge surfaces of the conductor are disposed adjacent to and generally tangentially to the confronting surfaces of the roller so as to form a fillet of dielectric material along the edge surface of the conductor
What is moving in silica at 1 K? A computer study of the low-temperature anomalies
Though the existence of two-level systems (TLS) is widely accepted to explain
low temperature anomalies in many physical observables, knowledge about their
properties is very rare. For silica which is one of the prototype glass-forming
systems we elucidate the properties of the TLS via computer simulations by
applying a systematic search algorithm. We get specific information in the
configuration space, i.e. about relevant energy scales, the absolute number of
TLS and electric dipole moments. Furthermore important insight about the
real-space realization of the TLS can be obtained. Comparison with experimental
observations is included
Large- limit of a Hubbard model in a magnetic field: chiral spin interactions and paramagnetism
We consider the large- limit of the one-band Hubbard model at half-filling
on a non-bipartite two-dimensional lattice. An external magnetic field can
induce a three-spin chiral interaction at order . We discuss
situations in which, at low temperatures, the chiral term may have a larger
effect than the Pauli coupling of electron spins to a magnetic field. We
present a model which explicitly demonstrates this. The ground state is a
singlet with a gap; hence the spin susceptibility is zero while the chiral
susceptibility is finite and paramagnetic.Comment: 12 pages, plain TeX, one figure available on request, to appear in
Phys. Rev.
c-axis transport and phenomenology of the pseudo-gap state in
We measure and analyze the resistivity of
crystals for different doping . We obtain the fraction of carrier
that do not participate to the c-axis
conductivity. All the curves collapse onto a universal curve
when plotted against a reduced temperature
. We find that at the superconducting
transition is doping independent. We also show that a magnetic field up
to 14 T does not affect the degree of localization in the (a,b) planes but
widens the temperature range of the x-scaling by suppressing the
superconducting phase coherence.Comment: 11 pages, 5 figures, submitted to Phys.Rev.
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