61,834 research outputs found
Engine Data Interpretation System (EDIS), phase 2
A prototype of an expert system was developed which applies qualitative constraint-based reasoning to the task of post-test analysis of data resulting from a rocket engine firing. Data anomalies are detected and corresponding faults are diagnosed. Engine behavior is reconstructed using measured data and knowledge about engine behavior. Knowledge about common faults guides but does not restrict the search for the best explanation in terms of hypothesized faults. The system contains domain knowledge about the behavior of common rocket engine components and was configured for use with the Space Shuttle Main Engine (SSME). A graphical user interface allows an expert user to intimately interact with the system during diagnosis. The system was applied to data taken during actual SSME tests where data anomalies were observed
Energy spectrum, dissipation and spatial structures in reduced Hall magnetohydrodynamic
We analyze the effect of the Hall term in the magnetohydrodynamic turbulence
under a strong externally supported magnetic field, seeing how this changes the
energy cascade, the characteristic scales of the flow and the dynamics of
global magnitudes, with particular interest in the dissipation.
Numerical simulations of freely evolving three-dimensional reduced
magnetohydrodynamics (RHMHD) are performed, for different values of the Hall
parameter (the ratio of the ion skin depth to the macroscopic scale of the
turbulence) controlling the impact of the Hall term. The Hall effect modifies
the transfer of energy across scales, slowing down the transfer of energy from
the large scales up to the Hall scale (ion skin depth) and carrying faster the
energy from the Hall scale to smaller scales. The final outcome is an effective
shift of the dissipation scale to larger scales but also a development of
smaller scales. Current sheets (fundamental structures for energy dissipation)
are affected in two ways by increasing the Hall effect, with a widening but at
the same time generating an internal structure within them. In the case where
the Hall term is sufficiently intense, the current sheet is fully delocalized.
The effect appears to reduce impulsive effects in the flow, making it less
intermittent.Comment: 17 pages, 10 figure
Pseudodeterminants and perfect square spanning tree counts
The pseudodeterminant of a square matrix is the last
nonzero coefficient in its characteristic polynomial; for a nonsingular matrix,
this is just the determinant. If is a symmetric or skew-symmetric
matrix then .
Whenever is the boundary map of a self-dual CW-complex ,
this linear-algebraic identity implies that the torsion-weighted generating
function for cellular -trees in is a perfect square. In the case that
is an \emph{antipodally} self-dual CW-sphere of odd dimension, the
pseudodeterminant of its th cellular boundary map can be interpreted
directly as a torsion-weighted generating function both for -trees and for
-trees, complementing the analogous result for even-dimensional spheres
given by the second author. The argument relies on the topological fact that
any self-dual even-dimensional CW-ball can be oriented so that its middle
boundary map is skew-symmetric.Comment: Final version; minor revisions. To appear in Journal of Combinatoric
Multiwavelength analysis of the young open cluster NGC 2362
We present a multiwavelength analysis of the young open cluster NGC 2362.
UBVRcIc CCD photometric observations, together with available data in the
Chandra data base, near infrared data from the Two Micron All Sky Survey
(2MASS), and recently published Halpha spectroscopy were used to get
information about the evolutionary stage of the cluster and the main physical
properties of its stellar content. Cluster membership is estimated for every
individual star by means of ZAMS and isochrone fitting. The cluster is
confirmed to host a richly populated pre-main sequence (PMS), and to contain a
large amount of X-ray emitting stars, which reach from the PMS members of GK
spectral type, up to the most luminous OB type main sequence (MS) members. The
PMS cluster members show no significant age spread, and the comparison to both
PMS and post-MS isochrones suggests a younger age for the more massive MS than
for lower mass PMS members. The analysis allows to asses the validity of
currently used pre-main sequence evolutionary models, and supports the
suggestion of a well defined positive correlation of the X-ray emission from
PMS stars with their bolometric luminosity. Clear differences are found on the
other hand, between the X-ray activity properties of MS and PMS cluster
members, both in the relation between X-ray luminosity and bolometric
luminosity, and in spectral properties as well.Comment: 1 gzipped file: 1 tex file with 9 pages text. 5 ps files with
figures. Submitted to Astrophysical Journa
Entanglement of localized states
We derive exact expressions for the mean value of Meyer-Wallach entanglement
Q for localized random vectors drawn from various ensembles corresponding to
different physical situations. For vectors localized on a randomly chosen
subset of the basis, tends for large system sizes to a constant which
depends on the participation ratio, whereas for vectors localized on adjacent
basis states it goes to zero as a constant over the number of qubits.
Applications to many-body systems and Anderson localization are discussed.Comment: 6 pages, 4 figure
Oyster Demand Adjustments to Counter-Information and Source Treatments in Response to Vibrio vulnificus
A web-based contingent behavior analysis is developed to quantity the effect of both negative and positive information treatments and post harvest processes (PHP) on demand for oysters. Results from a panel model indicate that consumers of raw and cooked oysters behave differently after news of an oyster-related human mortality. While cooked oyster consumers take precautionary measures against risk, raw oyster consumers exhibit optimistic bias and increase their consumption level. Further, by varying the source of a counter-information treatment, we find that source credibility impacts behavior. Oyster consumers, and in particular, raw oyster consumers, are most responsive to information provided by a not-for-profit, non-governmental organization. Finally, post harvest processing of oysters has no impact on demand. Key Words: Oyster demand; consumer behavior; non-market valuation; Vibrio vulnificus; information treatments; source credibility; optimistic bias
Oyster Demand Adjustments to Counter-Information and Source Treatments in Response to Vibrio vulnificus
A web-based contingent behavior analysis was developed to quantify the effect of both negative and positive information treatments and post harvest processes on demand for oysters. Results from a panel model indicate that consumers of raw and cooked oysters behave differently after news of an oyster-related human mortality. While cooked oyster consumers take precautionary measures against risk, raw oyster consumers exhibit optimistic bias and increase their consumption level. Further, by varying the source of a counter-information treatment, we find that source credibility impacts behavior. Oyster consumers, and in particular, raw oyster consumers, are most responsive to information provided by a not-for- profit, nongovernmental organization. Finally, post harvest processing of oysters has no impact on demand.consumer behavior, information treatments, non-market valuation, optimistic bias, Oyster demand, source credibility, Vibrio vulnificus, Agribusiness, Demand and Price Analysis, Food Consumption/Nutrition/Food Safety, Institutional and Behavioral Economics, Q18, Q13, Q58,
Effects of the Generalized Uncertainty Principle on the Inflation Parameters
We investigate the effects of the generalized uncertainty principle on the
inflationary dynamics of the early universe in both standard and braneworld
viewpoint. We choose the Randall-Sundrum II model as our underlying braneworld
scenario. We find that the quantum gravitational effects lead to a spectral
index which is not scale invariant. Also, the amplitude of density fluctuations
is reduced by increasing the strength of quantum gravitational corrections.
However, the tensor-to-scalar ratio increases by incorporation of these quantum
gravity effects. We outline possible manifestations of these quantum gravity
effects in the recent and future observations.Comment: 11 pages, revised version with new references, Accepted for
publication in IJMP
Vehicle Searches – The Automobile Exception: The Constitutional Ride From Carroll v. United States to Wyoming v. Houghton
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