35,769 research outputs found
Assessment of the risk due to release of carbon fiber in civil aircraft accidents, phase 2
The risk associated with the potential use of carbon fiber composite material in commercial jet aircraft is investigated. A simulation model developed to generate risk profiles for several airports is described. The risk profiles show the probability that the cost due to accidents in any year exceeds a given amount. The computer model simulates aircraft accidents with fire, release of fibers, their downwind transport and infiltration of buildings, equipment failures, and resulting ecomomic impact. The individual airport results were combined to yield the national risk profile
Spacecraft control/flexible structures interaction study
An initial study to begin development of a flight experiment to measure spacecraft control/flexible structure interactions was completed. The approach consisted of developing the equations of motion for a vehicle possessing a flexible solar array, then linearizing about some nominal motion of the craft. A set of solutions is assumed for array deflection using a continuous normal mode method and important parameters are identified. Interrelationships between these parameters, measurement techniques, and input requirements are discussed which assure minimization of special vehicle maneuvers and optimization of data to be obtained during the normal flight sequence. Limited consideration is given to flight data retrieval and processing techniques as correlated with the requirements imposed by the measurement system. Results indicate that inflight measurement of the bending and torsional mode shapes and respective frequencies, and damping ratios, is necessary. Other parameters may be measured from design data
Beyond the First Recurrence in Scar Phenomena
The scarring effect of short unstable periodic orbits up to times of the
order of the first recurrence is well understood. Much less is known, however,
about what happens past this short-time limit. By considering the evolution of
a dynamically averaged wave packet, we show that the dynamics for longer times
is controlled by only a few related short periodic orbits and their interplay.Comment: 4 pages, 4 Postscript figures, submitted to Phys. Rev. Let
Gauge/Anomaly Syzygy and Generalized Brane World Models of Supersymmetry Breaking
In theories in which SUSY is broken on a brane separated from the MSSM matter
fields, supersymmetry breaking is naturally mediated in a variety of ways.
Absent other light fields in the theory, gravity will mediate supersymmetry
breaking through the conformal anomaly. If gauge fields propagate in the extra
dimension they, too, can mediate supersymmetry breaking effects. The presence
of gauge fields in the bulk motivates us to consider the effects of new
messenger fields with holomorphic and non-holomorphic couplings to the
supersymmetry breaking sector. These can lead to contributions to the soft
masses of MSSM fields which dramatically alter the features of brane world
scenarios of supersymmetry breaking. In particular, they can solve the negative
slepton mass squared problem of anomaly mediation and change the predictions of
gaugino mediation.Comment: 4 pages, RevTe
Eigenstate Structure in Graphs and Disordered Lattices
We study wave function structure for quantum graphs in the chaotic and
disordered regime, using measures such as the wave function intensity
distribution and the inverse participation ratio. The result is much less
ergodicity than expected from random matrix theory, even though the spectral
statistics are in agreement with random matrix predictions. Instead, analytical
calculations based on short-time semiclassical behavior correctly describe the
eigenstate structure.Comment: 4 pages, including 2 figure
Localization of Eigenfunctions in the Stadium Billiard
We present a systematic survey of scarring and symmetry effects in the
stadium billiard. The localization of individual eigenfunctions in Husimi phase
space is studied first, and it is demonstrated that on average there is more
localization than can be accounted for on the basis of random-matrix theory,
even after removal of bouncing-ball states and visible scars. A major point of
the paper is that symmetry considerations, including parity and time-reversal
symmetries, enter to influence the total amount of localization. The properties
of the local density of states spectrum are also investigated, as a function of
phase space location. Aside from the bouncing-ball region of phase space,
excess localization of the spectrum is found on short periodic orbits and along
certain symmetry-related lines; the origin of all these sources of localization
is discussed quantitatively and comparison is made with analytical predictions.
Scarring is observed to be present in all the energy ranges considered. In
light of these results the excess localization in individual eigenstates is
interpreted as being primarily due to symmetry effects; another source of
excess localization, scarring by multiple unstable periodic orbits, is smaller
by a factor of .Comment: 31 pages, including 10 figure
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