3,451 research outputs found
Numerical relativity simulations of binary neutron stars
We present a new numerical relativity code designed for simulations of
compact binaries involving matter. The code is an upgrade of the BAM code to
include general relativistic hydrodynamics and implements state-of-the-art
high-resolution-shock-capturing schemes on a hierarchy of mesh refined
Cartesian grids with moving boxes. We test and validate the code in a series of
standard experiments involving single neutron star spacetimes. We present test
evolutions of quasi-equilibrium equal-mass irrotational binary neutron star
configurations in quasi-circular orbits which describe the late inspiral to
merger phases. Neutron star matter is modeled as a zero-temperature fluid;
thermal effects can be included by means of a simple ideal-gas prescription. We
analyze the impact that the use of different values of damping parameter in the
Gamma-driver shift condition has on the dynamics of the system. The use of
different reconstruction schemes and their impact in the post-merger dynamics
is investigated. We compute and characterize the gravitational radiation
emitted by the system. Self-convergence of the waves is tested, and we
consistently estimate error-bars on the numerically generated waveforms in the
inspiral phase
Isogeometric Analysis for Electromagnetism
The combination of numerical analysis with the scanning technology has been seeing increased use in many research areas. There is an emerging need for high-fidelity geometric modeling and meshing for practical applications. The Isogeometric Analysis (IGA) is a comprehensive computational framework, which integrates geometric modeling and meshing with analysis. Different from other existing numerical methods, the IGA can generate analysis ready models without loss of geometrical accuracy. In IGA, the continuity and the quality of a solution can be conveniently controlled and refined. These features enable IGA to integrate modeling, analysis, and design in a unified framework, the root idea of IGA. The IGA for electromagmetics is studied here for steady and transient electromagnetics as well as electromagnetic scattering. The solution procedure and the associated Matlab codes are developed to simulate the electromagnetic radiation on a biological tissues. The scattered and the total electrical fields are computed over the complex geometry of a brain section with realistic material properties. A perfectly matched layer (PML) is developed to model the far field boundary condition. The IGA platform developed here offers a reliable simulation within an accurate representation of the geometry. The results of this research can be used both in evaluating the potential health and safety risks of electromagnetic radiations and in optimizing the design of radiating devices used in non-invasive diagnostics and therapies
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