54,674 research outputs found
Apparatus for measuring an aircraft's speed and height
An apparatus for measuring aircraft horizontal speed and height above ground without the need for airborne cooperative devices is presented. Two ground level TV cameras separated by a measured distance and pointed at zenith are placed in line with the projection of the expected path of the aircraft. Speed is determined by measuring the time that it takes the aircraft to travel between the fields of view of the two TV cameras using zenith crossings as the reference points. Height is determined by correlating the speed with the time required to cross the field of view of either of the two cameras
Evaluation of dry lubricants and bearings for spacecraft applications
Performance of dry film lubricated ball bearings in high vacuum environmen
NASTRAN analysis of an air storage piping system
The application of NASTRAN to a complex piping design evaluation problem is summarized. Emphasis is placed on structural modeling aspects, problems encountered in modeling and analyzing curved pipe sections, principal results, and relative merits of using NASTRAN as a pipe analysis and design tool. In addition, the piping and manifolding system was analyzed with SNAP (Structural Network Analysis Program). The parallel SNAP study provides a basis for limited comparisons between NASTRAN and SNAP as to solution agreement and computer execution time and costs
The gravity of magnetic stresses and energy
In the framework of designing laboratory tests of relativistic gravity, we
investigate the gravitational field produced by the magnetic field of a
solenoid. Observing this field might provide a mean of testing whether stresses
gravitate as predicted by Einstein's theory. A previous study of this problem
by Braginsky, Caves and Thorne predicted that the contribution to the
gravitational field resulting from the stresses of the magnetic field and of
the solenoid walls would cancel the gravitational field produced by the
mass-energy of the magnetic field, resulting in a null magnetically-generated
gravitational force outside the solenoid. They claim that this null result,
once proved experimentally, would demonstrate the stress contribution to
gravity. We show that this result is incorrect, as it arises from an incomplete
analysis of the stresses, which neglects the axial stresses in the walls. Once
the stresses are properly evaluated, we find that the gravitational field
outside a long solenoid is in fact independent of Maxwell and material
stresses, and it coincides with the newtonian field produced by the linear mass
distribution equivalent to the density of magnetic energy stored in a unit
length of the solenoid. We argue that the gravity of Maxwell stress can be
directly measured in the vacuum region inside the solenoid, where the newtonian
noise is absent in principle, and the gravity generated by Maxwell stresses is
not screened by the negative gravity of magnetic-induced stresses in the
solenoid walls.Comment: 10 pages, final version accepted for publication in PR
Fabrication of transparent conducting amorphous Zn–Sn–In–O thin films by direct current magnetron sputtering
Amorphous ZnO–SnO2–In2O3 films were grown by direct current magnetron sputtering from vacuum hot pressed ceramic oxide targets of Zn:In:Sn cation ratios 1:2:1 and 1:2:1.5 onto glass substrates. X-ray diffraction analysis showed that the microstructure remained amorphous during annealing at 200 °C for up to 5 hours. By monitoring the electrical resistivity, oxygen content and substrate temperature were optimized during deposition. The optimal films were characterized by Hall Effect, work function and optical spectroscopy measurements. Films of 1:2:1 composition showed the lowest resistivity (7.6×10−4 Ω-cm), when deposited onto substrates preheated to 300 °C. Transmissivity of all films exceeded 80% in the visible spectral region. The energy gap was 3.52–3.74 eV, and the work function ranged 5.08–5.22 eV, suitable for cathode applications in organic light emitting diodes. Overall, the film characteristics were comparable or superior to those of amorphous tin-doped indium oxide and zinc-doped indium oxide films and may serve as viable, lower-cost alternatives
Intercomparisons of GOES-derived cloud parameters and surface observations over San Nicolas Island
The spatial sampling limitations of surface measurement systems necessitate the use of satellite data for the investigation of large-scale cloud processes. Understanding the information contained in the satellite-observed radiances, however, requires a connection between the remotely sensed cloud properties and those more directly observed within the troposphere. Surface measurements taken during the First ISCCP Regional Experiment (FIRE) Marine Stratocumulus Intensive Field Observations (IFO) are compared here to cloud properties determined from Geostationary Operational Environmental Satellite (GOES) data in order to determine how well the island measurements represent larger areas and to verify some of the satellite-measured parameters
A South African investigation into the meaning of work within the context of caring for children with HIV/AIDS
Bibliography: leaves 128-144
Chiral and Continuum Extrapolation of Partially-Quenched Lattice Results
The vector meson mass is extracted from a large sample of partially quenched,
two-flavor lattice QCD simulations. For the first time, discretisation,
finite-volume and partial quenching artefacts are treated in a unified
framework which is consistent with the low-energy behaviour of QCD. This
analysis incorporates the leading infrared behaviour dictated by chiral
effective field theory. As the two-pion decay channel cannot be described by a
low-energy expansion alone, a highly-constrained model for the decay channel of
the rho-meson is introduced. The latter is essential for extrapolating lattice
results from the quark-mass regime where the rho is observed to be a physical
bound state.Comment: 9 pages, 3 figures; revised version appearing in PL
Chiral and Continuum Extrapolation of Partially-Quenched Hadron Masses
Using the finite-range regularisation (FRR) of chiral effective field theory,
the chiral extrapolation formula for the vector meson mass is derived for the
case of partially-quenched QCD. We re-analyse the dynamical fermion QCD data
for the vector meson mass from the CP-PACS collaboration. A global fit,
including finite lattice spacing effects, of all 16 of their ensembles is
performed. We study the FRR method together with a naive polynomial approach
and find excellent agreement ~1% with the experimental value of M_rho from the
former approach. These results are extended to the case of the nucleon mass.Comment: 6 pages, Contribution to Lattice2005, PoS styl
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