12,870 research outputs found
System remotely inspects, measures, and records internal irregularities in piping
Video electromechanical probe visually inspects and measures internal offset and peaking of welds in relatively large piping. Irregularity dimensions are recorded on peripheral equipment consisting of video tape and X-Y plotter. The probe is used for inspection of vacuum-jacketed liquid lines that cannot be inspected externally
Effect of training and familiarity on responsiveness to human cues in domestic dogs (<i>Canis familiaris</i>)
Domestic dogs (Canis familiaris) seem to possess an evolved competency to follow human-given cues, often out-performing their wild progenitor the wolf (Canis lupus) on cue-following tasks. However, domestication may not be solely responsible for the socio-cognitive skills of dogs, with ontogenetic experience also playing a role. This research evaluated the effects of intensive training on cue-following behaviour using an unreinforced object-choice paradigm. The responses of dogs that were trained to competitive levels were compared to those of pet dogs with only basic training, and dogs living in an animal shelter that demonstrated no or only rudimentary following of basic commands. Using a cue-following task where three types of cues were presented by familiar and unfamiliar human partners, the number of cues followed by each training group were recorded. All dogs found cues where gesture was combined with a congruent head and eye movement easier to follow than either gesture or eye gaze alone. Whether the cue-giver was familiar or not had a significant effect on number of cues followed in homed dogs, and the performance of shelter dogs was comparable to the other groups when faced with an unfamiliar cue-giver. Contrary to predictions, level of training did not improve performance on the cue-following task. This work does provide support for the presence of an evolved adaptation to exploit social cues provided by humans that can be augmented by familiarity with the cue giver. However, additional joint activity as experienced in an intensive training regime does not seem to increase accuracy in following human-given cues
A Simulation Model of Primary Production and Carbon Allocation in the Creosotebush, Larrrea Tridentata (DC) Cav.
Strategic Network Formation with Attack and Immunization
Strategic network formation arises where agents receive benefit from
connections to other agents, but also incur costs for forming links. We
consider a new network formation game that incorporates an adversarial attack,
as well as immunization against attack. An agent's benefit is the expected size
of her connected component post-attack, and agents may also choose to immunize
themselves from attack at some additional cost. Our framework is a stylized
model of settings where reachability rather than centrality is the primary
concern and vertices vulnerable to attacks may reduce risk via costly measures.
In the reachability benefit model without attack or immunization, the set of
equilibria is the empty graph and any tree. The introduction of attack and
immunization changes the game dramatically; new equilibrium topologies emerge,
some more sparse and some more dense than trees. We show that, under a mild
assumption on the adversary, every equilibrium network with agents contains
at most edges for . So despite permitting topologies denser
than trees, the amount of overbuilding is limited. We also show that attack and
immunization don't significantly erode social welfare: every non-trivial
equilibrium with respect to several adversaries has welfare at least as that of
any equilibrium in the attack-free model.
We complement our theory with simulations demonstrating fast convergence of a
new bounded rationality dynamic which generalizes linkstable best response but
is considerably more powerful in our game. The simulations further elucidate
the wide variety of asymmetric equilibria and demonstrate topological
consequences of the dynamics e.g. heavy-tailed degree distributions. Finally,
we report on a behavioral experiment on our game with over 100 participants,
where despite the complexity of the game, the resulting network was
surprisingly close to equilibrium.Comment: The short version of this paper appears in the proceedings of WINE-1
NLC-2 graph recognition and isomorphism
NLC-width is a variant of clique-width with many application in graph
algorithmic. This paper is devoted to graphs of NLC-width two. After giving new
structural properties of the class, we propose a -time algorithm,
improving Johansson's algorithm \cite{Johansson00}. Moreover, our alogrithm is
simple to understand. The above properties and algorithm allow us to propose a
robust -time isomorphism algorithm for NLC-2 graphs. As far as we
know, it is the first polynomial-time algorithm.Comment: soumis \`{a} WG 2007; 12
Shrinkage of Inland Silverside Larvae Preserved in Ethanol and Formalin
Length measurements of preserved larval fish are necessary in many types of larval fish surveys. If the fixative causes significant shrinkage, then the preserved lengths cannot be used to indicate accurate live lengths. The objective of this study was to determine how preservation in two different concentrations of formalin and ethanol affects the total length of larval inland silversides Menidia beryllina. Larvae were measured (nearest 0.1 mm) and individually fixed in one of four fixative treatments (80% ethanol, 100% ethanol, 5% buffered formalin, and 10% buffered formalin). Fish were remeasured (nearest 0.1 mm) at 15 min; 4 h; and 1, 7, 14, and 21 d after preservation. Most shrinkage occurred within the first day after preservation in all four fixatives. Initial length was positively correlated with absolute shrinkage, but percent shrinkage was not affected by initial length. We found no difference in percent shrinkage between the 80% and 100% ethanol concentrations. The 10% buffered formalin caused more percent shrinkage than 5% buffered formalin. Furthermore, ethanol (80% and 100% combined) caused greater percent shrinkage than either 5% or 10% buffered formalin
Applying black hole perturbation theory to numerically generated spacetimes
Nonspherical perturbation theory has been necessary to understand the meaning
of radiation in spacetimes generated through fully nonlinear numerical
relativity. Recently, perturbation techniques have been found to be successful
for the time evolution of initial data found by nonlinear methods. Anticipating
that such an approach will prove useful in a variety of problems, we give here
both the practical steps, and a discussion of the underlying theory, for taking
numerically generated data on an initial hypersurface as initial value data and
extracting data that can be considered to be nonspherical perturbations.Comment: 14 pages, revtex3.0, 5 figure
No evidence for feedback: Unexceptional Low-ionization winds in Host galaxies of Low Luminosity Active Galactic Nuclei at Redshift z ~1
We study winds in 12 X-ray AGN host galaxies at z ~ 1. We find, using the
low-ionization Fe II 2586 absorption in the stacked spectra, that the
probability distribution function (PDF) of the centroid velocity shift in AGN
has a median, 16th and 84th percentiles of (-87, -251, +86) km/s respectively.
The PDF of the velocity dispersion in AGN has a median, 84th and 16th
percentile of (139, 253, 52) km/s respectively. The centroid velocity and the
velocity dispersions are obtained from a two component (ISM+wind) absorption
line model. The equivalent width PDF of the outflow in AGN has median, 84th and
16th percentiles of (0.4, 0.8, 0.1) Angstrom. There is a strong ISM component
in Fe II 2586 absorption with (1.2, 1.5, 0.8) Angstrom, implying presence of
substantial amount cold gas in the host galaxies. For comparison, star-forming
and X-ray undetected galaxies at a similar redshift, matched roughly in stellar
mass and galaxy inclination, have a centroid velocity PDF with percentiles of
(-74, -258, +90) km/s, and a velocity dispersion PDF percentiles of (150, 259,
57) km/s. Thus, winds in the AGN are similar to star-formation-driven winds,
and are too weak to escape and expel substantial cool gas from galaxies. Our
sample doubles the previous sample of AGN studied at z ~ 0.5 and extends the
analysis to z ~ 1. A joint reanalysis of the z ~ 0.5 AGN sample and our sample
yields consistent results to the measurements above.Comment: 24 pages, 11 figures, accepted in Ap
Brewster-angle measurements of sea-surface reflectance using a high resolution spectroradiometer
This paper describes the design, construction and testing of a ship-borne spectroradiometer based on an imaging spectrograph and cooled CCD array with a wavelength range of 350-800 nm and 4 nm spectral sampling. The instrument had a minimum spectral acquisition time of 0.1 s, but in practice data were collected over periods of 10 s to allow averaging of wave effects. It was mounted on a ship's superstructure so that it viewed the sea surface from a height of several metres at the Brewster angle (53 degrees) through a linear polarizing filter. Comparison of sea-leaving spectra acquired with the polarizer oriented horizontally and vertically enabled estimation of the spectral composition of sky light reflected directly from the sea surface. A semi-empirical correction procedure was devised for retrieving water-leaving radiance spectra from these measurements while minimizing the influence of reflected sky light. Sea trials indicated that reflectance spectra obtained by this method were consistent with the results of radiance transfer modelling of case 2 waters with similar concentrations of chlorophyll and coloured dissolved organic matter. Surface reflectance signatures measured at three locations containing blooms of different phytoplankton species were easily discriminated and the instrument was sufficiently sensitive to detect solar-stimulated fluorescence from surface chlorophyll concentrations down to 1 mg m−3
Head-on collisions of black holes: the particle limit
We compute gravitational radiation waveforms, spectra and energies for a
point particle of mass falling from rest at radius into a
Schwarzschild hole of mass . This radiation is found to lowest order in
with the use of a Laplace transform. In contrast with numerical
relativity results for head-on collisions of equal-mass holes, the radiated
energy is found not to be a monotonically increasing function of initial
separation; there is a local radiated-energy maximum at . The
present results, along with results for infall from infinity, provide a
complete catalog of waveforms and spectra for particle infall. We give a
representative sample from that catalog and an interesting observation: Unlike
the simple spectra for other head-on collisions (either of particle and hole,
or of equal mass holes) the spectra for show a series of
evenly spaced bumps. A simple explanation is given for this. Lastly, our energy
vs. results are compared with approximation methods used elsewhere, for
small and for large initial separation.Comment: 15 pages, REVTeX, 25 figure
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