49,040 research outputs found
Stability and control of the Gossamer human powered aircraft by analysis and flight test
The slow flight speed, very light wing loading, and neutral stability of the Gossamer Condor and the Gossamer Albatross emphasized apparent-mass aerodynamic effects and unusual modes of motion response. These are analyzed, approximated, and discussed, and the resulting transfer functions and dynamic properties are summarized and compared. To verify these analytical models, flight tests were conducted with and electrically powered Gossamer Albatross II. Sensors were installed and their outputs were telemetered to records on the ground. Frequency sweeps of the various controls were made and the data were reduced to frequency domain measures. Results are given for the response of: pitch rate, airspeed and normal acceleration from canard-elevator deflection; roll rate and yaw rate from canard-rudder tilt; and roll rate and yaw rate from wing warp. The reliable data are compared with the analytical predictions
Detection of structural deterioration and associated airline maintenance problems
Airline operations involving the detection of structural deterioration and associated maintenance problems are discussed. The standard approach to the maintenance and inspection of aircraft components and systems is described. The frequency of inspections and the application of preventive maintenance practices are examined. The types of failure which airline transport aircraft encounter and the steps taken to prevent catastrophic failure are reported
Two-channel Kondo physics in odd impurity chains
We study odd-membered chains of spin-(1/2) impurities, with each end
connected to its own metallic lead. For antiferromagnetic exchange coupling,
universal two-channel Kondo (2CK) physics is shown to arise at low energies.
Two overscreening mechanisms are found to occur depending on coupling strength,
with distinct signatures in physical properties. For strong inter-impurity
coupling, a residual chain spin-(1/2) moment experiences a renormalized
effective coupling to the leads; while in the weak-coupling regime, Kondo
coupling is mediated via incipient single-channel Kondo singlet formation. We
also investigate models where the leads are tunnel-coupled to the impurity
chain, permitting variable dot filling under applied gate voltages. Effective
low-energy models for each regime of filling are derived, and for even-fillings
where the chain ground state is a spin singlet, an orbital 2CK effect is found
to be operative. Provided mirror symmetry is preserved, 2CK physics is shown to
be wholly robust to variable dot filling; in particular the single-particle
spectrum at the Fermi level, and hence the low-temperature zero-bias
conductance, is always pinned to half-unitarity. We derive a Friedel-Luttinger
sum rule and from it show that, in contrast to a Fermi liquid, the Luttinger
integral is non-zero and determined solely by the `excess' dot charge as
controlled by gate voltage. The relevance of the work to real quantum dot
devices, where inter-lead charge-transfer processes fatal to 2CK physics are
present, is also discussed. Physical arguments and numerical renormalization
group techniques are used to obtain a detailed understanding of these problems.Comment: 21 pages, 19 figure
Seasonal Occurrence of the White Shark, Carcharodon carcharias, in Waters off the Florida West Coast, with Notes on its Life History
The white shark, Carcharodon carcharias, is considered rare in the Gulf of Mexico; however, recent longline captures coupled with historical landings information suggest that the species occurs seasonally (winter-spring) within this region. We examined a total of seven adult and juvenile white sharks (185-472 em total length) captured in waters off the west coast of Florida. Commercial longline fisheries were monitored for white sharks during all months (1981-94), but this species was captured only from January to April. All white sharks were captured in continental shelf waters from 37 to 222 km off the west coast of Florida when sea surface temperatures ranged from 18.7° to 21.6°C. Depths at capture locations ranged from 20 to 164 m. Fishing gear typically used in Gulf of Mexico offshore fisheries may not be effective at capturing this species, and the apparent rarity of white sharks in this area may be, in part, a function of gear bias
Ultraviolet degradation of thin films of zinc oxide
Ultraviolet degradation of zinc oxide thin film
Attitude control for spacecraft Patent
Attitude control device for space vehicle
Conductivity phenomena in polycrystalline zinc oxide films
Photoconductivity and electric conductivity of polycrystalline zinc oxide thin film under low intensity irradiatio
Midcourse maneuver operations program
Midcourse Maneuver Operations Program /MMOP/ computes the required velocity change to correct a spacecraft trajectory. The program establishes the existence of maneuvers which satisfy spacecraft constraints, explores alternate trajectories in the event that some out-of-tolerance condition forces a change in plans, and codes the maneuvers into commands
Potential for measuring the longitudinal and lateral profile of muons in TeV air showers with IACTs
Muons are copiously produced within hadronic extensive air showers (EAS)
occurring in the Earth's atmosphere, and are used by particle air shower
detectors as a means of identifying the primary cosmic ray which initiated the
EAS. Imaging Atmospheric Cherenkov Telescopes (IACTs), designed for the
detection of gamma-ray initiated EAS for the purposes of Very High Energy (VHE)
gamma-ray astronomy, are subject to a considerable background signal due to
hadronic EAS. Although hadronic EAS are typically rejected for gamma-ray
analysis purposes, single muons produced within such showers generate clearly
identifiable signals in IACTs and muon images are routinely retained and used
for calibration purposes. For IACT arrays operating with a stereoscopic
trigger, when a muon triggers one telescope, other telescopes in IACT arrays
usually detect the associated hadronic EAS. We demonstrate for the first time
the potential of IACT arrays for competitive measurements of the muon content
of air showers, their lateral distribution and longitudinal profile of
production slant heights in the TeV energy range. Such information can provide
useful input to hadronic interaction models.Comment: 15 pages, 11 figures, 2 tables, accepted for publication in
Astroparticle Physic
Racial and Ethnic Health Disparities in Incarcerated Populations
Alarming disparities in population health and wellness in the United States have led to multi-disciplinary research efforts to create health equity. Identifying disparities, elucidating the etiological bases of disparities, and implementing solutions to eliminate disparities are part of the U.S. national health agenda. Racial and ethnic disparities have been identified throughout the cancer control continuum, in cardiovascular disease, diabetes and a multitude of other conditions. The causes of disparities are complex, condition specific, and conjectured to result from combinations of biological and socio-behavioral factors. Racial and ethnic health disparities within the vast incarcerated communities have been excluded from most studies, yet are of significant ethical and fiscal concern to inmates, governing bodies, and non-incarcerated communities into which inmates return. Importantly, research on racial and ethnic disparities in this unique population may shed light on the relative etiologies of health disparities and solutions for creating health equity throughout the general population in the United States
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