1,381 research outputs found
Extended frequency turbofan model
The fan model was developed using two dimensional modeling techniques to add dynamic radial coupling between the core stream and the bypass stream of the fan. When incorporated into a complete TF-30 engine simulation, the fan model greatly improved compression system frequency response to planar inlet pressure disturbances up to 100 Hz. The improved simulation also matched engine stability limits at 15 Hz, whereas the one dimensional fan model required twice the inlet pressure amplitude to stall the simulation. With verification of the two dimensional fan model, this program formulated a high frequency F-100(3) engine simulation using row by row compression system characteristics. In addition to the F-100(3) remote splitter fan, the program modified the model fan characteristics to simulate a proximate splitter version of the F-100(3) engine
Flight evaluation of an engine static pressure noseprobe in an F-15 airplane
The flight testing of an inlet static pressure probe and instrumented inlet case produced results consistent with sea-level and altitude stand testing. The F-15 flight test verified the basic relationship of total to static pressure ratio versus corrected airflow and automatic distortion downmatch with the engine pressure ratio control mode. Additionally, the backup control inlet case statics demonstrated sufficient accuracy for backup control fuel flow scheduling, and the station 6 manifolded production probe was in agreement with the flight test station 6 tota pressure probes
Radiation Pressure as a Source of Decoherence
We consider the interaction of an harmonic oscillator with the quantum field
via radiation pressure. We show that a `Schrodinger cat' state decoheres in a
time scale that depends on the degree of `classicality' of the state
components, and which may be much shorter than the relaxation time scale
associated to the dynamical Casimir effect. We also show that decoherence is a
consequence of the entanglement between the quantum states of the oscillator
and field two-photon states. With the help of the fluctuation-dissipation
theorem, we derive a relation between decoherence and damping rates valid for
arbitrary values of the temperature of the field. Coherent states are selected
by the interaction as pointer states.Comment: 14 pages, 3 figures, RevTex fil
Gravitational decoherence of planetary motions
We study the effect of the scattering of gravitational waves on planetary
motions, say the motion of the Moon around the Earth. Though this effect has a
negligible influence on dissipation, it dominates fluctuations and the
associated decoherence mechanism, due to the very high effective temperature of
the background of gravitational waves in our galactic environment.Comment: 6 pages, no figure, to appear in EuroPhysics Letters; needs `epl.cls
Inertial forces in the Casimir effect with two moving plates
We combine linear response theory and dimensional regularization in order to
derive the dynamical Casimir force in the low frequency regime. We consider two
parallel plates moving along the normal direction in dimensional space. We
assume the free-space values for the mass of each plate to be known, and obtain
finite, separation-dependent mass corrections resulting from the combined
effect of the two plates. The global mass correction is proportional to the
static Casimir energy, in agreement with Einstein's law of equivalence between
mass and energy for stressed rigid bodies.Comment: 9 pages, 1 figure; title and abstract changed; to appear in Physical
Review
On the Symmetries of Integrability
We show that the Yang-Baxter equations for two dimensional models admit as a
group of symmetry the infinite discrete group . The existence of
this symmetry explains the presence of a spectral parameter in the solutions of
the equations. We show that similarly, for three-dimensional vertex models and
the associated tetrahedron equations, there also exists an infinite discrete
group of symmetry. Although generalizing naturally the previous one, it is a
much bigger hyperbolic Coxeter group. We indicate how this symmetry can help to
resolve the Yang-Baxter equations and their higher-dimensional generalizations
and initiate the study of three-dimensional vertex models. These symmetries are
naturally represented as birational projective transformations. They may
preserve non trivial algebraic varieties, and lead to proper parametrizations
of the models, be they integrable or not. We mention the relation existing
between spin models and the Bose-Messner algebras of algebraic combinatorics.
Our results also yield the generalization of the condition so often
mentioned in the theory of quantum groups, when no parameter is available.Comment: 23 page
Radioscience simulations in General Relativity and in alternative theories of gravity
In this communication, we focus on the possibility to test GR with
radioscience experiments. We present a new software that in a first step
simulates the Range/Doppler signals directly from the space time metric (thus
in GR and in alternative theories of gravity). In a second step, a
least-squares fit of the involved parameters is performed in GR. This software
allows one to get the order of magnitude and the signature of the modifications
induced by an alternative theory of gravity on radioscience signals. As
examples, we present some simulations for the Cassini mission in
Post-Einsteinian gravity and with the MOND External Field Effect.Comment: 4 pages; Proceedings of "Les Rencontres de Moriond 2011 - Gravitation
session
Movement and Fluctuations of the Vacuum
Quantum fields possess zero-point or vacuum fluctuations which induce
mechanical effects, namely generalised Casimir forces, on any scatterer.
Symmetries of vacuum therefore raise fundamental questions when confronted
with the principle of relativity of motion in vacuum. The specific case of
uniformly accelerated motion is particularly interesting, in connection with
the much debated question of the appearance of vacuum in accelerated frames.
The choice of Rindler representation, commonly used in General Relativity,
transforms vacuum fluctuations into thermal fluctuations, raising difficulties
of interpretation. In contrast, the conformal representation of uniformly
accelerated frames fits the symmetry properties of field propagation and
quantum vacuum and thus leads to extend the principle of relativity of motion
to uniform accelerations.
Mirrors moving in vacuum with a non uniform acceleration are known to
radiate. The associated radiation reaction force is directly connected to
fluctuating forces felt by motionless mirrors through fluctuation-dissipation
relations. Scatterers in vacuum undergo a quantum Brownian motion which
describes irreducible quantum fluctuations. Vacuum fluctuations impose ultimate
limitations on measurements of position in space-time, and thus challenge the
very concept of space-time localisation within a quantum framework.
For test masses greater than Planck mass, the ultimate limit in localisation
is determined by gravitational vacuum fluctuations. Not only positions in
space-time, but also geodesic distances, behave as quantum variables,
reflecting the necessary quantum nature of an underlying geometry.Comment: 17 pages, to appear in Reports on Progress in Physic
Quantum Clock Synchronization Based on Shared Prior Entanglement
We demonstrate that two spatially separated parties (Alice and Bob) can
utilize shared prior quantum entanglement, and classical communications, to
establish a synchronized pair of atomic clocks. In contrast to classical
synchronization schemes, the accuracy of our protocol is independent of Alice
or Bob's knowledge of their relative locations or of the properties of the
intervening medium.Comment: 4 page
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