9,782 research outputs found
Bayesian Model Selection with Future 21cm Observations of The Epoch of Reionisation
We apply Bayesian statistics to perform model selection on different
reionisation scenarios via the Multinest algorithm. Initially, we recover the
results shown by 21CMMC for the parameter estimation of 21cmFAST models. We
proceed to test several toy models of the Epoch of Reionisation (EoR) defined
in contrasting morphology and scale. We find that LOFAR observations are
unlikely to allow model selection even with long integration times. HERA would
require 61 dipoles to perform the same analysis in 1080 hours, and becomes
comparable to the SKA with 217 dipoles. We find the SKA requires only 324 hours
of observation to conclusively distinguish between our models. Once model
selection is achievable, an analysis of observational priors is performed
finding that neutral fraction checks at specific redshifts add little to no
inference. We show the difficulties in model selection at the level of
distinguishing fiducial parameters within a model or distinguishing galaxies
with a constant versus power law mass-to-light ratio. Finally, we explore the
use of the Savage-Dickey density ratio to show the redundancy of the parameter
Rmfp within 21cmFAST.Comment: 20 pages, 16 figures - Accepted for publication by MNRA
Senstitivty analysis and optimization of nodal point placement for vibration reduction
A method is developed for sensitivity analysis and optimization of nodal point locations in connection with vibration reduction. A straightforward derivation of the expression for the derivative of nodal locations is given, and the role of the derivative in assessing design trends is demonstrated. An optimization process is developed which uses added lumped masses on the structure as design variables to move the node to a preselected location - for example, where low response amplitude is required or to a point which makes the mode shape nearly orthogonal to the force distribution, thereby minimizing the generalized force. The optimization formulation leads to values for added masses that adjust a nodal location while minimizing the total amount of added mass required to do so. As an example, the node of the second mode of a cantilever box beam is relocated to coincide with the centroid of a prescribed force distribution, thereby reducing the generalized force substantially without adding excessive mass. A comparison with an optimization formulation that directly minimizes the generalized force indicates that nodal placement gives essentially a minimum generalized force when the node is appropriately placed
BRAVO economic study of LANDSAT follow-on
The LANDSAT Follow-On satellite consists of two major systems: the instrument module and the Multi-Mission Modular Spacecraft (MMS). The instrument module contains the thematic mapper and the five-band multispectral scanner instruments. The instrument module also includes the solar array, the tracking and data relay satellite (TDRS) antenna, and the wideband data module. The MMS contains the modularized and standardized power, propulsion, attitude control, and command and data handling subsystems. The Shuttle will be supporting the LANDSAT Follow-On system. The LANDSAT Follow-On Project plans two Delta 3910 launches. The first is scheduled for 1981; the second Delta launch will occur as needed to keep one satellite operational on orbit. The second satellite will be ready six months after the first. It could be launched any time after that. Shuttle support of the system could begin in early 1983 but would be scheduled to start after the second Delta launch
Bolometric and UV Light Curves of Core-Collapse Supernovae
The Swift UV-Optical Telescope (UVOT) has been observing Core-Collapse
Supernovae (CCSNe) of all subtypes in the UV and optical since 2005. We present
here 50 CCSNe observed with the Swift UVOT, analyzing their UV properties and
behavior. Where we have multiple UV detections in all three UV filters (\lambda
c = 1928 - 2600 \AA), we generate early time bolometric light curves, analyze
the properties of these light curves, the UV contribution to them, and derive
empirical corrections for the UV-flux contribution to optical-IR based
bolometric light curves
Optimized Coplanar Waveguide Resonators for a Superconductor-Atom Interface
We describe the design and characterization of superconducting coplanar
waveguide cavities tailored to facilitate strong coupling between
superconducting quantum circuits and single trapped Rydberg atoms. For initial
superconductor-atom experiments at 4.2 K, we show that resonator quality
factors above can be readily achieved. Furthermore, we demonstrate that
the incorporation of thick-film copper electrodes at a voltage antinode of the
resonator provides a route to enhance the zero-point electric fields of the
resonator in a trapping region that is 40 m above the chip surface,
thereby minimizing chip heating from scattered trap light. The combination of
high resonator quality factor and strong electric dipole coupling between the
resonator and the atom should make it possible to achieve the strong coupling
limit of cavity quantum electrodynamics with this system.Comment: 4 pages, 4 figure
Safety, the Preface Paradox and Possible Worlds Semantics
This paper contains an argument to the effect that possible worlds semantics renders
semantic knowledge impossible, no matter what ontological interpretation is given
to possible worlds. The essential contention made is that possible worlds semantic
knowledge is unsafe and this is shown by a parallel with the preface paradox
Comparing cancer mortality and GDP health expenditure in England and Wales with other major developed countries from 1979 to 2006
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