Recovering pointwise values of discontinuous data within spectral accuracy

The pointwise values of a function, f(x), can be accurately recovered either from its spectral or pseudospectral approximations, so that the accuracy solely depends on the local smoothness of f in the neighborhood of the point x. Most notably, given the equidistant function grid values, its intermediate point values are recovered within spectral accuracy, despite the possible presence of discontinuities scattered in the domain. (Recall that the usual spectral convergence rate decelerates otherwise to first order, throughout). To this end, a highly oscillatory smoothing kernel is employed in contrast to the more standard positive unit-mass mollifiers. In particular, post-processing of a stable Fourier method applied to hyperbolic equations with discontinuous data, recovers the exact solution modulo a spectrally small error. Numerical examples are presented

Stability analysis of spectral methods for hyperbolic initial-boundary value systems

A constant coefficient hyperbolic system in one space variable, with zero initial data is discussed. Dissipative boundary conditions are imposed at the two points x = + or - 1. This problem is discretized by a spectral approximation in space. Sufficient conditions under which the spectral numerical solution is stable are demonstrated - moreover, these conditions have to be checked only for scalar equations. The stability theorems take the form of explicit bounds for the norm of the solution in terms of the boundary data. The dependence of these bounds on N, the number of points in the domain (or equivalently the degree of the polynomials involved), is investigated for a class of standard spectral methods, including Chebyshev and Legendre collocations

Convergence of spectral methods for hyperbolic initial-boundary value systems

A convergence proof for spectral approximations is presented for hyperbolic systems with initial and boundary conditions. The Chebyshev collocation is treated in detail, but the final result is readily applicable to other spectral methods, such as Legendre collocation or tau-methods

Spectral methods for discontinuous problems

Spectral methods yield high-order accuracy even when applied to problems with discontinuities, though not in the sense of pointwise accuracy. Two different procedures are presented which recover pointwise accurate approximations from the spectral calculations

Solar flux and its variations

Data are presented on the solar irradiance as derived from a number of sources. An attempt was made to bring these data onto a uniform scale. Summation of fluxes at all wavelengths yields a figure of 1357.826 for the solar constant. Estimates are made of the solar flux variations due to flares, active regions (slowly varying component), 27-day period, and the 11-yr cycle. Solar activity does not produce a significant variation in the value of the solar constant. Variations in the X-ray and EUV portions of the solar flux may be several orders of magnitude during solar activity, especially at times of major flares. It is established that these short wavelength flux enhancements cause significant changes in the terrestrial ionosphere

Computerized Physician Order Entery (CPOE) at Thomas Jefferson University Hospital

No abstract available

Rolling John Bingham in His Grave: The Rehnquist Court makes Sport With the 14th Amendment

The Warren Court organized the concept of strict scrutiny in Shelton v. Tucker. Where the defendant was obligated to treat people without regard to membership in a suspect class and failed to do that, the Court would hold them liable for their behavior unless it was done for a compelling public reason and there was no less damaging alternative. The concept of strict scrutiny had nothing to do with intentions. The issue for the Warren Court was whether one party had injured another because of a forbidden reason. That concept of causation was understood broadly. The Court was not looking into people’s minds, rather it looked at their behavior. If the behavior was tied to race, religion or other “suspect” categories it was not permissible. The Court drove this point home in Palmer v. Thompson, holding that the closing of a swimming pool applied to everyone, not just blacks, and that the Court was uninterested in the actors’ motivations

The A-B variable and nursing staff-patient relationships.

PsychologyDoctor of Philosophy (PhD