13,367 research outputs found
Microwave Electronics
Contains a report on a research project.Lincoln Laboratory (Purchase Order DDL B-00283)United States ArmyUnited States Air Force (Contract AF19(604)-5200)United States Navy, Office of Naval Research (Nonr-1841(49)
A Hybrid Observer for a Distributed Linear System with a Changing Neighbor Graph
A hybrid observer is described for estimating the state of an channel,
-dimensional, continuous-time, distributed linear system of the form
. The system's state is
simultaneously estimated by agents assuming each agent senses and
receives appropriately defined data from each of its current neighbors.
Neighbor relations are characterized by a time-varying directed graph
whose vertices correspond to agents and whose arcs depict
neighbor relations. Agent updates its estimate of at "event
times" using a local observer and a local parameter
estimator. The local observer is a continuous time linear system whose input is
and whose output is an asymptotically correct estimate of
where a matrix with kernel equaling the unobservable space of .
The local parameter estimator is a recursive algorithm designed to estimate,
prior to each event time , a constant parameter which satisfies the
linear equations , where is a small
positive constant and is the state estimation error of local observer
. Agent accomplishes this by iterating its parameter estimator state
, times within the interval , and by making use of
the state of each of its neighbors' parameter estimators at each iteration. The
updated value of at event time is then . Subject to the assumptions that (i) the neighbor graph
is strongly connected for all time, (ii) the system whose state
is to be estimated is jointly observable, (iii) is sufficiently large, it
is shown that each estimate converges to exponentially fast as
at a rate which can be controlled.Comment: 7 pages, the 56th IEEE Conference on Decision and Contro
Piezoconductivity of gated suspended graphene
We investigate the conductivity of graphene sheet deformed over a gate. The
effect of the deformation on the conductivity is twofold: The lattice
distortion can be represented as pseudovector potential in the Dirac equation
formalism, whereas the gate causes inhomogeneous density redistribution. We use
the elasticity theory to find the profile of the graphene sheet and then
evaluate the conductivity by means of the transfer matrix approach. We find
that the two effects provide functionally different contributions to the
conductivity. For small deformations and not too high residual stress the
correction due to the charge redistribution dominates and leads to the
enhancement of the conductivity. For stronger deformations, the effect of the
lattice distortion becomes more important and eventually leads to the
suppression of the conductivity. We consider homogeneous as well as local
deformation. We also suggest that the effect of the charge redistribution can
be best measured in a setup containing two gates, one fixing the overall charge
density and another one deforming graphene locally
Shock propagation and stability in causal dissipative hydrodynamics
We studied the shock propagation and its stability with the causal
dissipative hydrodynamics in 1+1 dimensional systems. We show that the presence
of the usual viscosity is not enough to stabilize the solution. This problem is
solved by introducing an additional viscosity which is related to the
coarse-graining scale of the theory.Comment: 14 pages, 16 figure
Magnetovac Cylinder to Magnetovac Torus
A method for mapping known cylindrical magnetovac solutions to solutions in
torus coordinates is developed. Identification of the cylinder ends changes
topology from R1 x S1 to S1 x S1. An analytic Einstein-Maxwell solution for a
toroidal magnetic field in tori is presented. The toroidal interior is matched
to an asymptotically flat vacuum exterior, connected by an Israel boundary
layer.Comment: to appear in Class. Quant. Gra
Two-dimensional shear modulus of a Langmuir foam
We deform a two-dimensional (2D) foam, created in a Langmuir monolayer, by
applying a mechanical perturbation, and simultaneously image it by Brewster
angle microscopy. We determine the foam stress tensor (through a determination
of the 2D gas-liquid line tension, 2.35 0.4 pJm) and the
statistical strain tensor, by analyzing the images of the deformed structure.
We deduce the 2D shear modulus of the foam, .
The foam effective rigidity is predicted to be , which agrees with the value obtained in an independent mechanical measurement.Comment: submitted May 12, 2003 ; resubmitted Sept 9, 200
Factors Influencing Collegiate Athletic Department Revenues
One of the primary challenges of Division I Football Bowl Subdivision (FBS) collegiate athletic programs is revenue generation, particularly in light of increasing costs and competition. Surprisingly, a limited number of studies have investigated factors related to athletic department-generated revenues. A statistically significant multiple regression model was created, explaining 76.7 percent of the variance in annual generated revenues among FBS programs. Factors such as conference affiliation, success in football and men’s basketball, enrollment, and time were identified as important in predicting revenue generation. The Revenue Theory of Costs was put forth as a framework for better understanding the financial behavior of intercollegiate athletic programs
On Gravitational Radiation in Quadratic Gravity
We investigate the gravitational radiation emitted by an isolated system for
gravity theories with Lagrange density . As a formal result we
obtain leading order corrections to the quadrupole formula in General
Relativity. We make use of the analogy of theories with scalar--tensor
theories, which in contrast to General Relativity feature an additional scalar
degree of freedom. Unlike General Relativity, where the leading order
gravitational radiation is produced by quadrupole moments, the additional
degree of freedom predicts gravitational radiation of all multipoles, in
particular monopoles and dipoles, as this is the case for the most alternative
gravity theories known today. An application to a hypothetical binary pulsar
moving in a circular orbit yields the rough limit by constraining the dipole power to account at
most for 1% of the quadrupole power as predicted by General Relativity.Comment: 14 Pages, 1 Figur
Four-body Efimov effect
We study three same spin state fermions of mass M interacting with a
distinguishable particle of mass m in the unitary limit where the interaction
has a zero range and an infinite s-wave scattering length. We predict an
interval of mass ratio 13.384 < M/m < 13.607 where there exists a purely
four-body Efimov effect, leading to the occurrence of weakly bound tetramers
without Efimov trimers.Comment: 4 pages, 2 figure
Polynomial Solutions of Shcrodinger Equation with the Generalized Woods Saxon Potential
The bound state energy eigenvalues and the corresponding eigenfunctions of
the generalized Woods Saxon potential are obtained in terms of the Jacobi
polynomials. Nikiforov Uvarov method is used in the calculations. It is shown
that the results are in a good agreement with the ones obtained before.Comment: 14 pages, 2 figures, submitted to Physical Review
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