23,004 research outputs found
A failsafe analysis using NASTRAN's piecewise linear analysis and a nine node linear crack element
A two-dimensional crack element was implemented into NASTRAN as a user dummy element and used to study failsafe characteristics of the C5A fuselage. The element is formulated from Reitsner's functional requiring that it satisfy compatability with the linear boundary displacement elements in NASTRAN. Its accuracy is demonstrated by analyzing for the stress intensity factors of two simple crack configurations for which there are classic solutions
NASTRAN used in a production environment
A finite element analysis procedure built around the NASTRAN system is assessed. A number of support programs that were either written or modified to interface with NASTRAN and some improvements that were made to NASTRAN itself are noted. Some typical models are analyzed and an actual schedule is followed for constructing and analyzing the models to support a large design program
Synchrotron Polarization at High Galactic Latitude
We present preliminary results from mapping the high-latitude Galactic
polarization with the Effelsberg Telescope at 21 cm. Structures on the
resulting maps are mostly on the scale of several degrees. The results show
detection of polarization over most of the field, at the level of tens of
percent of the synchrotron emission. The evidence of more structure in Stokes Q
and U rather than in suggests the existence of Faraday
rotation.Comment: To be published in the proceedings of "The Cosmic Microwave
Background and its Polarization", New Astronomy Reviews, (eds. S. Hanany and
K.A. Olive
The tidal stripping of satellites
We present an improved analytic calculation for the tidal radius of
satellites and test our results against N-body simulations.
The tidal radius in general depends upon four factors: the potential of the
host galaxy, the potential of the satellite, the orbit of the satellite and
{\it the orbit of the star within the satellite}. We demonstrate that this last
point is critical and suggest using {\it three tidal radii} to cover the range
of orbits of stars within the satellite. In this way we show explicitly that
prograde star orbits will be more easily stripped than radial orbits; while
radial orbits are more easily stripped than retrograde ones. This result has
previously been established by several authors numerically, but can now be
understood analytically. For point mass, power-law (which includes the
isothermal sphere), and a restricted class of split power law potentials our
solution is fully analytic. For more general potentials, we provide an equation
which may be rapidly solved numerically. Over short times (\simlt 1-2 Gyrs
satellite orbit), we find excellent agreement between our analytic and
numerical models. Over longer times, star orbits within the satellite are
transformed by the tidal field of the host galaxy. In a Hubble time, this
causes a convergence of the three limiting tidal radii towards the prograde
stripping radius. Beyond the prograde stripping radius, the velocity dispersion
will be tangentially anisotropic.Comment: 10 pages, 5 figures. Final version accepted for publication in MNRAS.
Some new fully analytic tidal radii have been added for power law density
profiles (including the isothermal sphere) and some split power law
A quantum Peierls-Nabarro barrier
Kink dynamics in spatially discrete nonlinear Klein-Gordon systems is
considered. For special choices of the substrate potential, such systems
support continuous translation orbits of static kinks with no (classical)
Peierls-Nabarro barrier. It is shown that these kinks experience, nevertheless,
a lattice-periodic confining potential, due to purely quantum effects anaolgous
to the Casimir effect of quantum field theory. The resulting ``quantum
Peierls-Nabarro potential'' may be calculated in the weak coupling
approximation by a simple and computationally cheap numerical algorithm, which
is applied, for purposes of illustration, to a certain two-parameter family of
substrates.Comment: 13 pages LaTeX, 7 figure
Gegenbauer-solvable quantum chain model
In an innovative inverse-problem construction the measured, experimental
energies , , ... of a quantum bound-state system are assumed
fitted by an N-plet of zeros of a classical orthogonal polynomial . We
reconstruct the underlying Hamiltonian (in the most elementary
nearest-neighbor-interaction form) and the underlying Hilbert space
of states (the rich menu of non-equivalent inner products is offered). The
Gegenbauer's ultraspherical polynomials are chosen for
the detailed illustration of technicalities.Comment: 29 pp., 1 fi
The Dielectric Constant and Specific Conductance of Liquid Hydrogen Sulphide at 194.5° K
The following values have been reported for the specific conductance of liquid hydrogen sulphide.
0.1x10-6 ohm-1 cm3 - a-c method - Steel, Mcintosh & Archibald;
less than 4x10-7 ohm-1 cm3 - d.c. method - Magri;
1x10-11 ohm-1 cm3 - d.c. method - Quam & Wilkinson;
3.7x10-11 ohm-1 cm3 - d.c. method - Satwaleker, Butler & Wilkinson
The unfamiliar face effect on forensic craniofacial reconstruction and recognition.
Previous research into the reliability of forensic craniofacial reconstruction (CFR) has focused primarily on the accuracy of reconstructed faces from European or African ancestry skulls. Moreover, the recognition of CFR in relation to the experience and ancestry of the practitioners and the assessors has not been previously considered. The cross-race effect is a recognised phenomenon in psychology studies, where familiar ancestry faces are recognised more readily than unfamiliar ancestry faces, but there is a paucity of research addressing the relationship between the accuracy of reconstructed faces and the familiarity with this ancestry by the practitioners/assessors. The aims of this research were to investigate whether 'unfamiliar-race effect' has any influence on the accuracy of CFR and to evaluate how much the correct recognition rate of CFR is affected by the cross-race effect. Eight CFRs from three ancestry groups were produced by experienced practitioners in order to explore the aims. The results demonstrated that practitioners produced more recognisable CFRs using skulls from a familiar ancestry than skulls from unfamiliar ancestries
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