73,106 research outputs found
Relativistic r-modes in Slowly Rotating Neutron Stars: Numerical Analysis in the Cowling Approximation
We investigate the properties of relativistic -modes of slowly rotating
neutron stars by using a relativistic version of the Cowling approximation. In
our formalism, we take into account the influence of the Coriolis like force on
the stellar oscillations, but ignore the effects of the centrifugal like force.
For three neutron star models, we calculated the fundamental -modes with
and 3. We found that the oscillation frequency of the
fundamental -mode is in a good approximation given by , where is defined in the corotating frame at the
spatial infinity, and is the angular frequency of rotation of the
star. The proportional coefficient is only weakly dependent on
, but it strongly depends on the relativistic parameter ,
where and are the mass and the radius of the star. All the fundamental
-modes with computed in this study are discrete modes with distinct
regular eigenfunctions, and they all fall in the continuous part of the
frequency spectrum associated with Kojima's equation (Kojima 1998). These
relativistic -modes are obtained by including the effects of rotation higher
than the first order of so that the buoyant force plays a role, the
situation of which is quite similar to that for the Newtonian -modes.Comment: 22 pages, 8 figures, accepted for publication in Ap
Formulation and characterization of polyimide resilient foams of various densities for aircraft seating applications
Light weight, heat and fire resistant low smoke generating polyimide foams are developed for aircraft seating applications. The material is upgraded and classified into groups for fabrication of cushions possessing acceptable comfort properties. Refinement and selection of foaming processes using a variety of previously developd foaming techniques and definition of property relationships to arrive at the selection and classfication of polyimide foams into five groups in accordance with predetermined ILD values are emphasized
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Generalised additive dependency inflated models including aggregated covariates
Let us assume that X, Y and U are observed and that the conditional mean of U given X and Y can be expressed via an additive dependency of X, λ(X)Y and X + Y for some unspecified function . This structured regression model can be transferred to a hazard model or a density model when applied on some appropriate grid, and has important forecasting applications via structured marker dependent hazards models or structured density models including age-period-cohort relationships. The structured regression model is also important when the severity of the dependent variable has a complicated dependency on waiting times X, Y and the total waiting time X+Y . In case the conditional mean of U approximates a density, the regression model can be used to analyse the age-period-cohort model, also when exposure data are not available. In case the conditional mean of U approximates a marker dependent hazard, the regression model introduces new relevant age-period-cohort time scale interdependencies in understanding longevity. A direct use of the regression relationship introduced in this paper is the estimation of the severity of outstanding liabilities in non-life insurance companies. The technical approach taken is to use B-splines to capture the underlying one-dimensional unspecified functions. It is shown via finite sample simulation studies and an application for forecasting future asbestos related deaths in the UK that the B-spline approach works well in practice. Special consideration has been given to ensure identifiability of all models considered
R-modes of neutron stars with a solid crust
We investigate the properties of -mode oscillations of a slowly rotating
neutron star with a solid crust, by taking account of the effects of the
Coriolis force. For the modal analysis we employ three-component neutron star
models that are composed of a fluid core, a solid crust and a surface fluid
ocean. For the three-component models, we find that there exist two kinds of
-modes, that is, those confined in the surface fluid ocean and those
confined in the fluid core, which are most important for the -mode
instability. The -modes do not have any appreciable amplitudes in the solid
crust if rotation rate of the star is sufficiently small. We find that the core
-modes are strongly affected by mode coupling with the crustal torsional
(toroidal) modes and lose their simple properties of the eigenfunction and
eigenfrequency as functions of the angular rotation velocity . This
indicates that the extrapolation formula, which is obtained in the limit of
, cannot be used to examine the -mode instability of rapidly
rotating neutron stars with a solid crust unless the effects of mode coupling
with the crustal torsional modes are correctly taken into account.Comment: 10 pages, 3 figures, revised version accepted for publication in the
Ap
High-dimensional Bell test for a continuous variable state in phase space and its robustness to detection inefficiency
We propose a scheme for testing high-dimensional Bell inequalities in phase
space. High-dimensional Bell inequalities can be recast into the forms of a
phase-space version using quasiprobability functions with the complex-valued
order parameter. We investigate their violations for two-mode squeezed states
while increasing the dimension of measurement outcomes, and finally show the
robustness of high-dimensional tests to detection inefficiency.Comment: 8 pages, 2 figures; title and abstract changed, published versio
Development of fire-resistant, low smoke generating, thermally stable end items for commercial aircraft and spacecraft using a basic polyimide resin
A terpolyimide precursor was developed which can be foamed by microwave methods and yields foams possessing the best seating properties. A continuous process, based on spray drying techniques, permits production of polyimide powder precursors in large quantities. The constrained rise foaming process permits fabrication of rigid foam panels with improved mechanical properties and almost unlimited density characteristics. Polyimide foam core rigid panels were produced by this technique with woven fiberglass fabric bonded to each side of the panel in a one step microwave process. The fire resistance of polyimide foams was significantly improved by the addition of ceramic fibers to the powder precursors. Foams produced from these compositions are flexible, possess good acoustical attenuation and meet the minimum burnthrough requirements when impinged by high flux flame sources
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