8,147 research outputs found
Some facts about functionals of location and scatter
Assumptions on a likelihood function, including a local Glivenko-Cantelli
condition, imply the existence of M-estimators converging to an M-functional.
Scatter matrix-valued estimators, defined on all empirical measures on
for , and equivariant under all, including singular,
affine transformations, are shown to be constants times the sample covariance
matrix. So, if weakly continuous, they must be identically 0. Results are
stated on existence and differentiability of location and scatter functionals,
defined on a weakly dense, weakly open set of laws, via elliptically symmetric
t distributions on , following up on work of Kent, Tyler, and
D\"{u}mbgen.Comment: Published at http://dx.doi.org/10.1214/074921706000000860 in the IMS
Lecture Notes Monograph Series
(http://www.imstat.org/publications/lecnotes.htm) by the Institute of
Mathematical Statistics (http://www.imstat.org
Turbulence and pressure loss characteristics of the inlet vanes for the 80- by 120-ft wind tunnel
A series of wind tunnel investigations were conducted to determine the flow characteristics downstream of a set of wind tunnel inlet flow conditioning vanes. The purpose was to develop an understanding of the flow mechanisms that contributed to the pressure loss and turbulence generated by the vane set. The near-field characteristics and flow field development were investigated with a 1/3 scale two dimensional model of the vane set at near full-scale Reynolds numbers. In a second series of tests, the global flow field characteristics were investigated by means of a 1/15 scale model of the full vane set and the 5:1 contraction leading to the model's test section. Scale effects due to Reynolds number mismatch were identified and their significance noted and accounted for when possible. Scaling parameters were adopted that allowed predictions to be made of the expected turbulence and pressure distributions in the full-scale wind tunnel test section, based on the small-scale test results. The predictions were found to be in good agreement with actual measurements made in the full-scale facility
Strong Evidence for a Buried AGN in UGC 5101: Implications for LINER-Type Ultra-Luminous Infrared Galaxies
We report on the results of 3--4 m spectroscopy of the ultra-luminous
infrared galaxy (ULIRG) UGC 5101. It has a cool far-infrared color and a
LINER-type optical spectrum, and so, based on a view gaining some currency,
would be regarded as dominated by star formation. However, we find that it has
strong 3.4 m carbonaceous dust absorption, low-equivalent-width 3.3 m
polycyclic aromatic hydrocarbon (PAH) emission, and a small 3.3 m PAH to
far-infrared luminosity ratio. This favors an alternative scenario, in which an
energetically dominant AGN is present behind obscuring dust. The AGN is
plausibly obscured along all lines of sight (a `buried AGN'), rather than
merely obscured along our particular line of sight. Such buried AGNs have
previously been found in thermal infrared studies of the ULIRGs IRAS 08572+3915
and IRAS F001837111, both classified optically as LINERs. We argue that
buried AGNs can produce LINER-type optical spectra, and that at least some
fraction of LINER-type ULIRGs are predominantly powered by buried AGNs.Comment: 11 pages, 1 figure, accepted by ApJ Lette
Bohr's 1913 molecular model revisited
It is generally believed that the old quantum theory, as presented by Niels
Bohr in 1913, fails when applied to few electron systems, such as the H2
molecule. Here we find new solutions within the Bohr theory that describe the
potential energy curve for the lowest singlet and triplet states of H2 about as
well as the early wave mechanical treatment of Heitler and London. We also
develop a new interpolation scheme which substantially improves the agreement
with the exact ground state potential curve of H2 and provides a good
description of more complicated molecules such as LiH, Li2, BeH and He2.Comment: 6 pages, 9 figure
Correlation patterns from massive phonons in 1+1 dimensional acoustic black holes: A toy model
Transverse excitations in analogue black holes induce a mass like term in the
longitudinal mode equation. With a simple toy model we show that correlation
functions display a rather rich structure characterized by groups of parallel
peaks. For the most part the structure is completely different from that found
in the massless case.Comment: 40 pages, 13 figures. Minor changes and corrections Phys. Rev. D
versio
Determination of renewable energy yield from mixed waste material from the use of novel image analysis methods
Two novel techniques are presented in this study which together aim to provide a system able to determine the renewable energy potential of mixed waste materials. An image analysis tool was applied to two waste samples prepared using known quantities of source-segregated recyclable materials. The technique was used to determine the composition of the wastes, where through the use of waste component properties the biogenic content of the samples was calculated. The percentage renewable energy determined by image analysis for each sample was accurate to within 5% of the actual values calculated. Microwave-based multiple-point imaging (AutoHarvest) was used to demonstrate the ability of such a technique to determine the moisture content of mixed samples. This proof-of-concept experiment was shown to produce moisture measurement accurate to within 10%. Overall, the image analysis tool was able to determine the renewable energy potential of the mixed samples, and the AutoHarvest should enable the net calorific value calculations through the provision of moisture content measurements. The proposed system is suitable for combustion facilities, and enables the operator to understand the renewable energy potential of the waste prior to combustion
- âŠ