2,219,257 research outputs found
Application of quasi-homogeneous anisotropic laminates in grid-stiffened panel design
Composite laminates are derived for standard configurations with quasi-homogeneous anisotropic properties, whereby in-plane and out-of-plane stiffness properties are concomitant. Dimensionless parameters, and their relationship to the well-known ply- orientation-dependent lamination parameters, are also developed from which the elements of the extensional and bending stiffness matrices are readily calculated for any fiber/resin properties. The definitive list of laminate configurations for up to 21 plies is presented, together with graphical representations of the lamination parameter design space for standard ply orientations +45, -45, 0 and 90 degrees. Finally, the potential of quasi-homogeneous anisotropic laminates as an optimum design solution for anisogid structures is explored for cases where buckling and strength constraints are both active
Energy and Momentum of Oscillating Neutrinos
It is shown that Lorentz invariance implies that in general flavor neutrinos
in oscillation experiments are superpositions of massive neutrinos with
different energies and different momenta. It is also shown that for each
process in which neutrinos are produced there is either a Lorentz frame in
which all massive neutrinos have the same energy or a Lorentz frame in which
all massive neutrinos have the same momentum. In the case of neutrinos produced
in two-body decay processes, there is a Lorentz frame in which all massive
neutrinos have the same energy.Comment: 6 pages, no figure
Global Seismic Oscillations in Soft Gamma Repeaters
There is evidence that soft gamma repeaters (SGRs) are neutron stars which
experience frequent starquakes, possibly driven by an evolving, ultra-strong
magnetic field. The empirical power-law distribution of SGR burst energies,
analogous to the Gutenberg-Richter law for earthquakes, exhibits a turn-over at
high energies consistent with a global limit on the crust fracture size. With
such large starquakes occurring, the significant excitation of global seismic
oscillations (GSOs) seems likely. Moreover, GSOs may be self-exciting in a
stellar crust that is strained by many, randomly-oriented stresses. We explain
why low-order toroidal modes, which preserve the shape of the star and have
observable frequencies as low as ~ 30 Hz, may be especially susceptible to
excitation. We estimate the eigenfrequencies as a function of stellar mass and
radius, and their magnetic and rotational shiftings/splittings. We also
describes ways in which these modes might be detected and damped. There is
marginal evidence for 23 ms oscillations in the hard initial pulse of the 1979
March 5th event. This could be due to the mode in a neutron star with B
~ 10^{14} G or less; or it could be the fundamental toroidal mode if the field
in the deep crust of SGR 0526-66 is ~ 4 X 10^{15} G, in agreement with other
evidence. If confirmed, GSOs would give corroborating evidence for
crust-fracturing magnetic fields in SGRs: B >~ 10^{14} G.Comment: 12 pages, AASTeX, no figures. Accepted for Astrophysical Journal
Letter
Compensation of pulse-rebalanced inertial instruments
Study explains the basic concept of pulse-rebalanced inertial instruments in terms of an idealized model which performs the processes of integration, prediction and quantization. An analytical model of an actual pulse-rebalanced instrument was derived in a form comparable to the idealized system
Elements of orbit-determination theory - Textbook
Text applies to solution of various optimization problems. Concepts are logically introduced and refinements and complexities for computerized numerical solutions are avoided. Specific topics and essential equivalence of several different approaches to various aspects of the problem are given
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