3,579 research outputs found
New genus of primitive wombat (Vombatidae, Marsupialia) from Miocene deposits in the Riversleigh World Heritage Area (Queensland, Australia)
Copyright Palaeontological Association, March 2015.
This is an open access article, available to all readers online, published under a creative commons licensing (https://creativecommons.org/licenses/by/4.0/)
On two conjectures concerning convex curves
We recall two basic conjectures on the developables of convex projective
curves, prove one of them and disprove the other in the firdt nontrivial case
of curves in RP^3. Namely, we show that i) the tangent developable surface of
any convex curve in RP^3 has 'degree' 4 and ii) construct an example of 4
tangent lines to a convex curve in RP^3 such that no real line intersects all
four of them.Comment: AMSTEX, 15 pages, 3 eps pictures. to appear in Int. J. Mat
VEGAS: A VST Early-type GAlaxy Survey. II. Photometric study of giant ellipticals and their stellar halos
Observations of diffuse starlight in the outskirts of galaxies are thought to
be a fundamental source of constraints on the cosmological context of galaxy
assembly in the CDM model. Such observations are not trivial because
of the extreme faintness of such regions. In this work, we investigate the
photometric properties of six massive early type galaxies (ETGs) in the VEGAS
sample (NGC 1399, NGC 3923, NGC 4365, NGC 4472, NGC 5044, and NGC 5846) out to
extremely low surface brightness levels, with the goal of characterizing the
global structure of their light profiles for comparison to state-of-the-art
galaxy formation models. We carry out deep and detailed photometric mapping of
our ETG sample taking advantage of deep imaging with VST/OmegaCAM in the g and
i bands. By fitting the light profiles, and comparing the results to
simulations of elliptical galaxy assembly, we identify signatures of a
transition between "relaxed" and "unrelaxed" accreted components and can
constrain the balance between in situ and accreted stars. The very good
agreement of our results with predictions from theoretical simulations
demonstrates that the full VEGAS sample of ETGs will allow us to use
the distribution of diffuse light as a robust statistical probe of the
hierarchical assembly of massive galaxies.Comment: Accepted for publication in Astronomy & Astrophysic
Methods for detection and characterization of signals in noisy data with the Hilbert-Huang Transform
The Hilbert-Huang Transform is a novel, adaptive approach to time series
analysis that does not make assumptions about the data form. Its adaptive,
local character allows the decomposition of non-stationary signals with
hightime-frequency resolution but also renders it susceptible to degradation
from noise. We show that complementing the HHT with techniques such as
zero-phase filtering, kernel density estimation and Fourier analysis allows it
to be used effectively to detect and characterize signals with low signal to
noise ratio.Comment: submitted to PRD, 10 pages, 9 figures in colo
Structural analysis of ultra-high speed aircraft structural components
The buckling characteristics of a hypersonic beaded skin panel were investigated under pure compression with boundary conditions similar to those found in a wing mounted condition. The primary phases of analysis reported include: (1) experimental testing of the panel to failure; (2) finite element structural analysis of the beaded panel with the computer program NASTRAN; and (3) summary of the semiclassical buckling equations for the beaded panel under purely compressive loads. A comparison of each of the analysis methods is also included
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