525 research outputs found
Remote control of an impact demonstration vehicle
Uplink and downlink telemetry systems were installed in a Boeing 720 aircraft that was remotely flown from Rogers Dry Lake at Edwards Air Force Base and impacted into a designated crash site on the lake bed. The controlled impact demonstration (CID) program was a joint venture by the National Aeronautics and Space Administration (NASA) and the Federal Aviation Administration (FAA) to test passenger survivability using antimisting kerosene (AMK) to inhibit postcrash fires, improve passenger seats and restraints, and improve fire-retardent materials. The uplink telemetry system was used to remotely control the aircraft and activate onboard systems from takeoff until after impact. Aircraft systems for remote control, aircraft structural response, passenger seat and restraint systems, and anthropomorphic dummy responses were recorded and displayed by the downlink stems. The instrumentation uplink and downlink systems are described
Longshoreman-Shipowner-Stevedore: The Circle of Liability
It is universally recognized that in the past two decades the United States Supreme Court has substantially revised the law under which seamen, longshoremen and harbor workers (or their survivors) may recover damages for personal injury and death. One of the more recent and most authoritative texts in the field of admiralty and maritime law devotes an entire chapter, 147 pages in length, to the subject of the rights of seamen and maritime workers (or their survivors) of recovery for injury and death. The introduction to that chapter likens the Court\u27s rewriting of the law in this field to a volcano and states that as long as it continues in eruption, no charts can be guaranteed reliable as to its future course. It must be conceded that one of the more recent, major and most astounding eruptions is that pertaining to the rights of longshoremen to recover damages for personal injuries sustained in the course of their employment aboard vessels. Since World War II the spotlight of judicial decision and review in maritime cases has been focused upon this one narrow field until it has become one of the most litigious in this country. It is the purpose of this article to review the background and history of events within that field, set forth clearly and concisely the status of the law and note some changes which may be forthcoming
Cross-Section Fluctuations in Chaotic Scattering
For the theoretical prediction of cross-section fluctuations in chaotic
scattering, the cross-section autocorrelation function is needed. That function
is not known analytically. Using experimental data and numerical simulations,
we show that an analytical approximation to the cross-section autocorrelation
function can be obtained with the help of expressions first derived by Davis
and Boose. Given the values of the average S-matrix elements and the mean level
density of the scattering system, one can then reliably predict cross-section
fluctuations
Scattering Experiments with Microwave Billiards at an Exceptional Point under Broken Time Reversal Invariance
Scattering experiments with microwave cavities were performed and the effects
of broken time-reversal invariance (TRI), induced by means of a magnetized
ferrite placed inside the cavity, on an isolated doublet of nearly degenerate
resonances were investigated. All elements of the effective Hamiltonian of this
two-level system were extracted. As a function of two experimental parameters,
the doublet and also the associated eigenvectors could be tuned to coalesce at
a so-called exceptional point (EP). The behavior of the eigenvalues and
eigenvectors when encircling the EP in parameter space was studied, including
the geometric amplitude that builds up in the case of broken TRI. A
one-dimensional subspace of parameters was found where the differences of the
eigenvalues are either real or purely imaginary. There, the Hamiltonians were
found PT-invariant under the combined operation of parity (P) and time reversal
(T) in a generalized sense. The EP is the point of transition between both
regions. There a spontaneous breaking of PT occurs
Exceptional Points in a Microwave Billiard with Time-Reversal Invariance Violation
We report on the experimental study of an exceptional point (EP) in a
dissipative microwave billiard with induced time-reversal invariance (T)
violation. The associated two-state Hamiltonian is non-Hermitian and
non-symmetric. It is determined experimentally on a narrow grid in a parameter
plane around the EP. At the EP the size of T violation is given by the relative
phase of the eigenvector components. The eigenvectors are adiabatically
transported around the EP, whereupon they gather geometric phases and in
addition geometric amplitudes different from unity
Chaotic Scattering in the Regime of Weakly Overlapping Resonances
We measure the transmission and reflection amplitudes of microwaves in a
resonator coupled to two antennas at room temperature in the regime of weakly
overlapping resonances and in a frequency range of 3 to 16 GHz. Below 10.1 GHz
the resonator simulates a chaotic quantum system. The distribution of the
elements of the scattering matrix S is not Gaussian. The Fourier coefficients
of S are used for a best fit of the autocorrelation function if S to a
theoretical expression based on random--matrix theory. We find very good
agreement below but not above 10.1 GHz
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