325 research outputs found
An Offline/Online DDDAS Capability for Self-Aware Aerospace Vehicles
In this paper we develop initial offline and online capabilities for a self-aware aerospace vehicle. Such a vehicle can dynamically adapt the way it performs missions by gathering information about itself and its surroundings via sensors and responding intelligently. The key challenge to enabling such a self-aware aerospace vehicle is to achieve tasks of dynamically and autonomously sensing, planning, and acting in real time. Our first steps towards achieving this goal are presented here, where we consider the execution of online mapping strategies from sensed data to expected vehicle capability while accounting for uncertainty. Libraries of strain, capability, and maneuver loading are generated offline using vehicle and mission modeling capabilities we have developed in this work. These libraries are used dynamically online as part of a Bayesian classification process for estimating the capability state of the vehicle. Failure probabilities are then computed online for specific maneuvers. We demonstrate our models and methodology on decisions surrounding a standard rate turn maneuver
N=2 SYM Action as a BRST Exact Term, Topological Yang Mills and Instantons
By constructing a nilpotent extended BRST operator \bs that involves the
N=2 global supersymmetry transformations of one chirality, we show that the
standard N=2 off-shell Super Yang Mills Action can be represented as an exact
BRST term \bs \Psi, if the gauge fermion is allowed to depend on the
inverse powers of supersymmetry ghosts. By using this nonanalytical structure
of the gauge fermion (via inverse powers of supersymmetry ghosts), we give
field redefinitions in terms of composite fields of supersymmetry ghosts and
N=2 fields and we show that Witten's topological Yang Mills theory can be
obtained from the ordinary Euclidean N=2 Super Yang Mills theory directly by
using such field redefinitions. In other words, TYM theory is obtained as a
change of variables (without twisting). As a consequence it is found that
physical and topological interpretations of N=2 SYM are intertwined together
due to the requirement of analyticity of global SUSY ghosts. Moreover, when
after an instanton inspired truncation of the model is used, we show that the
given field redefinitions yield the Baulieu-Singer formulation of Topological
Yang Mills.Comment: Latex, 1+15 pages. Published versio
Experimental evaluation of impact ionization coefficients in Al xGa1-xN based avalanche photodiodes
The authors report on the metal-organic chemical vapor deposition growth, fabrication, and characterization of high performance solar-blind avalanche photodetectors and the experimental evaluation of the impact ionization coefficients that are obtained from the photomultiplication data. A Schottky barrier, suitable for back and front illuminations, is used to determine the impact ionization coefficients of electrons and holes in an AlGaN based avalanche photodiode. © 2006 American Institute of Physics
Noncommutative gravity coupled to fermions: second order expansion via Seiberg-Witten map
We use the Seiberg-Witten map (SW map) to expand noncommutative gravity
coupled to fermions in terms of ordinary commuting fields. The action is
invariant under general coordinate transformations and local Lorentz rotations,
and has the same degrees of freedom as the commutative gravity action. The
expansion is given up to second order in the noncommutativity parameter
{\theta}. A geometric reformulation and generalization of the SW map is
presented that applies to any abelian twist. Compatibility of the map with
hermiticity and charge conjugation conditions is proven. The action is shown to
be real and invariant under charge conjugation at all orders in {\theta}. This
implies the bosonic part of the action to be even in {\theta}, while the
fermionic part is even in {\theta} for Majorana fermions.Comment: 27 pages, LaTeX. Revised version with proof of charge conjugation
symmetry of the NC action and its parity under theta --> - theta (see new
sect. 2.6, sect. 6 and app. B). References added. arXiv admin note:
substantial text overlap with arXiv:0902.381
The maximally entangled symmetric state in terms of the geometric measure
The geometric measure of entanglement is investigated for permutation
symmetric pure states of multipartite qubit systems, in particular the question
of maximum entanglement. This is done with the help of the Majorana
representation, which maps an n qubit symmetric state to n points on the unit
sphere. It is shown how symmetries of the point distribution can be exploited
to simplify the calculation of entanglement and also help find the maximally
entangled symmetric state. Using a combination of analytical and numerical
results, the most entangled symmetric states for up to 12 qubits are explored
and discussed. The optimization problem on the sphere presented here is then
compared with two classical optimization problems on the S^2 sphere, namely
Toth's problem and Thomson's problem, and it is observed that, in general, they
are different problems.Comment: 18 pages, 15 figures, small corrections and additions to contents and
reference
A hybrid light source with integrated inorganic light-emitting diode and organic polymer distributed feedback grating
We report a compact light source that incorporates a semiconductor light-emitting diode, nanostructured distributed feedback (DFB) Bragg grating and spin-coated thin conjugated polymer film. With this hybrid structure, we transferred electrically generated 390 nm ultraviolet light to an organic polymer via optical pumping and out-couple green luminescence to air through a second-order DFB grating. We demonstrate the feasibility of electrically driven, hybrid, compact light-emitting devices and lasers in the visible range. © IOP Publishing Ltd
Energy utilization and growth performance of chickens fed novel wheat inbred lines selected for different pentosan levels with and without xylanase supplementation
Different F5 recombinant inbred lines
from the cross Yumai 34 × Ukrainka were grown in
replicated trials on a single site in one harvest year at
Rothamsted Research. A total of 10 samples from those
lines were harvested and used in a broiler experiment.
Twenty nutritionally complete meal-form diets that had
630 g/kg of wheat with different amounts of pentosan,
with and without exogenous xylanase supplementation,
were used to compare broiler growth performance and
determine apparent metabolizable energy corrected for
N retention (AMEn). We examined the relationship between the nutritive value of the wheat samples and their
chemical compositions and results of quality tests. The
amounts of total and water soluble pentosans in wheat
samples ranged from 36.7 to 48.0 g/kg DM, and 6.7 to
11.6 g/kg DM, respectively. The mean crude oil and
protein contents of the wheat samples were 10.5 and
143.9 g/kg DM, respectively. The average determined
value for the kinematic viscosity was 0.0018 mPa.s, and
2.1 mPa.s for the dynamic viscosity. The AMEn of the
wheat-based diets had a maximum range of 0.47 MJ/kg
DM within the ten wheat samples that were tested. Xylanase supplementation improved (P < 0.05) dietary
AMEn, dry matter, and fat digestibility coefficients.
There was a positive (P < 0.05) relationship between in
vitro kinematic viscosity of the wheat samples and the
total pentosan content. There was a negative relationship between the total pentosan content in the wheat
and broiler growth performance. An increase by 10 g of
pentosan per kg of wheat reduced (P < 0.001) daily feed
intake and weight gain by 2.9 g and 3.5 g, respectively.
The study shows that the feeding quality of wheat samples can be predicted by their total pentosan content.
Supplementary xylanase improved energy and nutrient
availability of all wheat samples that was independent
of differences in pentosan content
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