11,755 research outputs found
Recent developments in classical density functional theory: Internal energy functional and diagrammatic structure of fundamental measure theory
An overview of several recent developments in density functional theory for
classical inhomogeneous liquids is given. We show how Levy's constrained search
method can be used to derive the variational principle that underlies density
functional theory. An advantage of the method is that the Helmholtz free energy
as a functional of a trial one-body density is given as an explicit expression,
without reference to an external potential as is the case in the standard
Mermin-Evans proof by reductio ad absurdum. We show how to generalize the
approach in order to express the internal energy as a functional of the
one-body density distribution and of the local entropy distribution. Here the
local chemical potential and the bulk temperature play the role of Lagrange
multipliers in the Euler-Lagrange equations for minimiziation of the
functional. As an explicit approximation for the free-energy functional for
hard sphere mixtures, the diagrammatic structure of Rosenfeld's fundamental
measure density unctional is laid out. Recent extensions, based on the
Kierlik-Rosinberg scalar weight functions, to binary and ternary non-additive
hard sphere mixtures are described.Comment: 15 pages, 6 figure
Multiscale probability mapping: groups, clusters and an algorithmic search for filaments in SDSS
We have developed a multiscale structure identification algorithm for the
detection of overdensities in galaxy data that identifies structures having
radii within a user-defined range. Our "multiscale probability mapping"
technique combines density estimation with a shape statistic to identify local
peaks in the density field. This technique takes advantage of a user-defined
range of scale sizes, which are used in constructing a coarse-grained map of
the underlying fine-grained galaxy distribution, from which overdense
structures are then identified. In this study we have compiled a catalogue of
groups and clusters at 0.025 < z < 0.24 based on the Sloan Digital Sky Survey,
Data Release 7, quantifying their significance and comparing with other
catalogues. Most measured velocity dispersions for these structures lie between
50 and 400 km/s. A clear trend of increasing velocity dispersion with radius
from 0.2 to 1 Mpc/h is detected, confirming the lack of a sharp division
between groups and clusters. A method for quantifying elongation is also
developed to measure the elongation of group and cluster environments. By using
our group and cluster catalogue as a coarse-grained representation of the
galaxy distribution for structure sizes of <~ 1 Mpc/h, we identify 53 filaments
(from an algorithmically-derived set of 100 candidates) as elongated unions of
groups and clusters at 0.025 < z < 0.13. These filaments have morphologies that
are consistent with previous samples studied.Comment: 22 pages, 14 figures and 6 tables. Accepted for publication in MNRAS.
Data products, three-dimensional visualisations and further information about
MSPM can be found at http://www.physics.usyd.edu.au/sifa/Main/MSPM/ . v2
contains two additional references. v3 has a slightly altered title and
updated reference
Assessing the variation in the load that produces maximal upper-body power
Substantial variation in the load that produces maximal power has been reported. It has been suggested that the variation observed may be due to differences in subject physical characteristics. Therefore the aim of this study was to determine the extent in which anthropometric measures correlate to the load that produces maximal power. Anthropometric measures (upper-arm length, forearm length, total arm length, upper-arm girth) and bench press strength were assessed in 26 professional rugby union players. Peak power was then determined in the bench press throw exercise using loads of 20 to 60% of one repetition maximum (1RM) in the bench press exercise. Maximal power occurred at 30 +/- 14 %1RM (mean +/- SD). Upper-arm length had the highest correlation with the load maximizing power: -0.61 (90% confidence limits -0.35 to -0.78), implying loads of 22 vs. 38 %1RM maximize power for players with typically long vs. short upper-arm length. Correlations for forearm length, total arm length and upper-arm girth to the load that maximized power were -0.29 (0.04 to -0.57), -0.56 (-0.28 to -0.75), and -0.29 (0.04 to -0.57), respectively. The relationship between 1RM and the load that produced maximal power was r = -0.23 (0.10 to -0.52). The between-subject variation in the load that maximised power observed (SD= +/- 14 %1RM) may have been due to differences in anthropometric characteristics, and absolute strength and power outputs. Indeed, athletes with longer limbs and larger girths, and greater maximal strength and power outputs utilised a lower percentage of 1RM loads to achieve maximum power. Therefore, we recommend individual assessment of the load that maximizes power output
THE MARKET FOR E-COMMERCE SERVICES IN AGRICULTURE
We report results of a survey of 608 Ohio agribusinesses in 1999 and show them to be divided in their attitudes and acceptance of e-commerce. Half of the respondents report that their business has a web site, although many had taken a negative stance toward such a move. Nearly all say that the internet will significantly change their sector, and the majority of managers report that e-commerce has significantly affected the way they view their business.Marketing,
Furnace and support equipment for space processing
A core facility capable of performing a majority of materials processing experiments is discussed. Experiment classes are described, the needs peculiar to each experiment type are outlined, and projected facility requirements to perform the experiments are treated. Control equipment (automatic control) and variations of the Czochralski method for use in space are discussed
Optimization of Picosecond Laser Parameters for Surface Treatment of Composites Using a Design of Experiments (DOE) Approach
Based on guidelines from the Federal Aviation Administration, research supported by the NASA Advanced Composites Project is investigating methods to improve process control for surface preparation and pre-bond surface characterization on aerospace composite structures. The overall goal is to identify high fidelity, rapid, and reproducible surface treatments and surface characterization methods to reduce the uncertainty associated with the bonding process. The desired outcome is a more reliable bonded airframe structure, and to reduce time to achieve certification. In this work, a design of experiments (DoE) approach was conducted to determine optimum laser ablation conditions using a pulsed laser source with a nominal pulse width of 10 picoseconds. The laser power, frequency, scan speed, and number of passes (1 or 2) were varied within the laser system operating boundaries. Aerospace structural carbon fiber reinforced composites (Torayca 3900-2/T800H) were laser treated, then characterized for contamination, and finally bonded for mechanical testing. Pre-bond characterization included water contact angle (WCA) using a handheld device, ablation depth measurement using scanning electron microscopy (SEM), and silicone contamination measurement using laser induced breakdown spectroscopy (LIBS). In order to accommodate the large number of specimens in the DoE, a rapid-screening, double cantilever beam (DCB) test specimen configuration was devised based on modifications to ASTM D5528. Specimens were tested to assess the failure modes observed under the various laser surface treatment parameters. The models obtained from this DoE indicated that results were most sensitive to variation in the average laser power. Excellent bond performance was observed with nearly 100% cohesive failure for a wide range of laser parameters. Below about 200 mW, adhesive failure was observed because contamination was left on the surface. For laser powers greater than about 600 mW, large amounts of fiber were exposed, and the failure mode was predominately fiber tear
The Phoenix Deep Survey: Extremely Red Galaxies and Cluster Candidates
We present the results of a study of a sample of 375 Extremely Red Galaxies
(ERGs) in the Phoenix Deep Survey, 273 of which constitute a subsample which is
80% complete to K_s = 18.5 over an area of 1160 arcmin^2. The angular
correlation function for ERGs is estimated, and the association of ERGs with
faint radio sources explored. We find tentative evidence that ERGs and faint
radio sources are associated at z > 0.5. A new overdensity-mapping algorithm
has been used to characterize the ERG distribution, and identify a number of
cluster candidates, including a likely cluster containing ERGs at 0.5 < z < 1.
Our algorithm is also used in an attempt to probe the environments in which
faint radio sources and ERGs are associated. We find limited evidence that the
I - K_s > 4 criterion is more efficient than R - K_s > 5 at selecting dusty
star-forming galaxies, rather than passively evolving ERGs.Comment: 14 emulateapj pages, 15 figures, 1 table, accepted for publication in
Astronomical Journal. A version with full resolution figures is available at
http://www.physics.usyd.edu.au/~asmith/research/ERGpaper.pd
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