5,236 research outputs found
Needs Assessment: Veterans in the Western United States
In this report, the authors focus on the diverse challenges facing veterans in 12 states and communities that account for nearly one-third of all veterans nationwide. They report on the specific challenges of mental health care, employment, housing, family support, reintegration and legal matters with which veterans in the region are contending and propose steps to address them. Among their recommendations, Mr. Carter and Ms. Kidder urge private philanthropists, as well as public funders, to encourage communities to build collaboration and coordination mechanisms that allocate increasingly scarce resources efficiently an
Needs Assessment: Veterans in Southwest Pennsylvania
This assessment by the Center for a New American Security (CNAS) finds that Southwest Pennsylvania veterans are struggling with issues pertaining to education, access to benefits and economic security immediately after leaving military service. It also finds that the region's 235,000 veterans differ dramatically in how they feel about veterans benefits and their own well-being depending on whether they served before 9/11 or after. This mixed methods study provides a comprehensive portrait of veterans in Southwest Pennsylvania, one of the nation's largest and densest veterans communities. CNAS researchers used cutting-edge analytical tools from the Veterans Data Project to better understand the population, leveraging public data sets made available by DoD, VA, and the Census Bureau to understand macro-level trends in the area. In addition to this data, the CNAS team conducted interviews and working group discussions with individuals representing more than 50 public, private and nonprofit sector organizations serving veterans in the region, and conducted surveys of area veterans as well
On the detectability of post-Newtonian effects in gravitational-wave emission of a coalescing binary
The effect of the recently obtained 2nd post-Newtonian corrections on the
accuracy of estimation of parameters of the gravitational-wave signal from a
coalescing binary is investigated. It is shown that addition of this correction
degrades considerably the accuracy of determination of individual masses of the
members of the binary. However the chirp mass and the time parameter in the
sinal is still determined to a very good accuracy. The performance of the
Newtonian filter is investigated and it is compared with performance of
post-Newtonian search templates introduced recently. It is shown that both
search templates can extract accurately useful information about the binary.Comment: 5 pages (16kb), LATEX, to be published in the proccedings of the 17th
Texas Symposiu
Spectral Methods for Numerical Relativity. The Initial Data Problem
Numerical relativity has traditionally been pursued via finite differencing.
Here we explore pseudospectral collocation (PSC) as an alternative to finite
differencing, focusing particularly on the solution of the Hamiltonian
constraint (an elliptic partial differential equation) for a black hole
spacetime with angular momentum and for a black hole spacetime superposed with
gravitational radiation. In PSC, an approximate solution, generally expressed
as a sum over a set of orthogonal basis functions (e.g., Chebyshev
polynomials), is substituted into the exact system of equations and the
residual minimized. For systems with analytic solutions the approximate
solutions converge upon the exact solution exponentially as the number of basis
functions is increased. Consequently, PSC has a high computational efficiency:
for solutions of even modest accuracy we find that PSC is substantially more
efficient, as measured by either execution time or memory required, than finite
differencing; furthermore, these savings increase rapidly with increasing
accuracy. The solution provided by PSC is an analytic function given
everywhere; consequently, no interpolation operators need to be defined to
determine the function values at intermediate points and no special
arrangements need to be made to evaluate the solution or its derivatives on the
boundaries. Since the practice of numerical relativity by finite differencing
has been, and continues to be, hampered by both high computational resource
demands and the difficulty of formulating acceptable finite difference
alternatives to the analytic boundary conditions, PSC should be further pursued
as an alternative way of formulating the computational problem of finding
numerical solutions to the field equations of general relativity.Comment: 15 pages, 5 figures, revtex, submitted to PR
Tropical cyclone intensities from satellite microwave data
Radial profiles of mean 1000 mb to 250 mb temperature from the Nimbus 6 scanning microwave spectrometer (SCAMS) were constructed around eight intensifying tropical storms in the western Pacific. Seven storms showed distinct inward temperature gradients required for intensification; the eighth displayed no inward gradient and was decaying 24 hours later. The possibility that satellite data might be used to forecast tropical cyclone turning motion was investigated using estimates obtained from Nimbus 6 SCAMS data tapes of the mean 1000 mb to 250 mb temperature field around eleven tropical storms in 1975. Analysis of these data show that for turning storms, in all but one case, the turn was signaled 24 hours in advance by a significant temperature gradient perpendicular to the storm's path, at a distance of 9 deg to 13 deg in front of the storm. A thresholding technique was applied to the North Central U.S. during the summer to estimate precipitation frequency. excep
The Federal Administrative Court Proposal: An Examination of General Principals
Simulations of relativistic hydrodynamics often need both high accuracy and robust shock-handling properties. The discontinuous Galerkin method combines these features—a high order of convergence in regions where the solution is smooth and shock-capturing properties for regions where it is not—with geometric flexibility and is therefore well suited to solve the partial differential equations describing astrophysical scenarios. We present here evolutions of a general-relativistic neutron star with the discontinuous Galerkin method. In these simulations, we simultaneously evolve the spacetime geometry and the matter on the same computational grid, which we conform to the spherical geometry of the problem. To verify the correctness of our implementation, we perform standard convergence and shock tests. We then show results for evolving, in three dimensions, a Kerr black hole; a neutron star in the Cowling approximation (holding the spacetime metric fixed); and, finally, a neutron star where the spacetime and matter are both dynamical. The evolutions show long-term stability, good accuracy, and an improved rate of convergence versus a comparable-resolution finite-volume method
Estimating the final spin of a binary black hole coalescence
We present a straightforward approach for estimating the final black hole
spin of a binary black hole coalescence with arbitrary initial masses and
spins. Making some simple assumptions, we estimate the final angular momentum
to be the sum of the individual spins plus the orbital angular momentum of a
test particle orbiting at the last stable orbit around a Kerr black hole with a
spin parameter of the final black hole. The formula we obtain is able to
reproduce with reasonable accuracy the results from available numerical
simulations, but, more importantly, it can be used to investigate what
configurations might give rise to interesting dynamics. In particular, we
discuss scenarios which might give rise to a ``flip'' in the direction of the
total angular momentum of the system. By studying the dependence of the final
spin upon the mass ratio and initial spins we find that our simple approach
suggests that it is not possible to spin-up a black hole to extremal values
through merger scenarios irrespective of the mass ratio of the objects
involved.Comment: 9 pages, 8 figure
Evolving relativistic fluid spacetimes using pseudospectral methods and finite differencing
We present a new code for solving the coupled Einstein-hydrodynamics
equations to evolve relativistic, self-gravitating fluids. The Einstein field
equations are solved on one grid using pseudospectral methods, while the fluids
are evolved on another grid by finite differencing. We discuss implementation
details, such as the communication between the grids and the treatment of
stellar surfaces, and present code tests.Comment: To appear in the Proceedings of the Eleventh Marcel Grossmann Meetin
- …