4,745 research outputs found
Mechanical and analytical screening of braided composites for transport fuselage applications
The mechanics of materials progress in support of the goal of understanding the application of braided composites in a transport aircraft fuselage are summarized. Composites consisting of both 2-D and 3-D braid patterns are investigated. Both consolidation of commingled graphite/PEEK and resin transfer molding of graphite-epoxy braided composite processes are studied. Mechanical tests were used to examine unnotched tension, open hole tension, compression, compression after impact, in-plane shear, out-of-plane tension, bearing, and crippling. Analytical methods are also developed and applied to predict the stiffness and strengths of test specimens. A preliminary study using the test data and analytical results is performed to assess the applicability of braided composites to a commercial aircraft fuselage
Towards the QCD phase diagram from analytical continuation
We calculate the QCD cross-over temperature, the equation of state and
fluctuations of conserved charges at finite density by analytical continuation
from imaginary to real chemical potentials. Our calculations are based on new
continuum extrapolated lattice simulations using the 4stout staggered actions
with a lattice resolution up to . The simulation parameters are tuned
such that the strangeness neutrality is maintained, as it is in heavy ion
collisions.Comment: 4 pages, 2 figures, Proceedings of the Quark Matter 2015 conference,
Kobe, Japa
Test methods for textile composites
Various test methods commonly used for measuring properties of tape laminate composites were evaluated to determine their suitability for the testing of textile composites. Three different types of textile composites were utilized in this investigation: two-dimensional (2-D) triaxial braids, stitched uniweave fabric, and three-dimensional (3-D) interlock woven fabric. Four 2-D braid architectures, five stitched laminates, and six 3-D woven architectures were tested. All preforms used AS4 fibers and were resin-transfer-molded with Shell RSL-1895 epoxy resin. Ten categories of material properties were investigated: tension, open-hole tension, compression, open-hole compression, in-plane shear, filled-hole tension, bolt bearing, interlaminar tension, interlaminar shear, and interlaminar fracture toughness. Different test methods and specimen sizes were considered for each category of test. Strength and stiffness properties obtained with each of these methods are documented in this report for all the material systems mentioned above
A hybrid parametrical wave prediction model
The development of a numerical wave prediction model incorporating a parametrical wind-sea model and a characteristic swell model is described. The parametrical model is an extension of an earlier two-parameter model to the full five Jonswap spectral parameters. An application is presented in which the model is used to hindcast severe wave conditions in the North Sea as part of an engineering study to define long-term extreme wave statistics for the area. The limitations of the model and the needs for future research are discussed
Macroscopic Quantum Phase Interference in Antiferromagnetic Particles
The tunnel splitting in biaxial antiferromagnetic particles is studied with a
magnetic field applied along the hard anisotropy axis. We observe the
oscillation of tunnel splitting as a function of the magnetic field due to the
quantum phase interference of two tunneling paths of opposite windings. The
oscillation is similar to the recent experimental result with Fe}\textrm{\
molecular clusters.}Comment: 8 pages, 2 postscript figures, to appear in J. Phys.: Condes. Matte
Thermoacoustic tomography with variable sound speed
We study the mathematical model of thermoacoustic tomography in media with a
variable speed for a fixed time interval, greater than the diameter of the
domain. In case of measurements on the whole boundary, we give an explicit
solution in terms of a Neumann series expansion. We give necessary and
sufficient conditions for uniqueness and stability when the measurements are
taken on a part of the boundary
Spin relaxation in Mn12-acetate
We present a comprehensive derivation of the magnetization relaxation in a
Mn12-acetate crystal based on thermally assisted spin tunneling induced by
quartic anisotropy and weak transverse magnetic fields. The overall relaxation
rate as function of the magnetic field is calculated and shown to agree well
with data including all resonance peaks. The Lorentzian shape of the resonances
is also in good agreement with recent data. A generalized master equation
including resonances is derived and solved exactly. It is shown that many
transition paths with comparable weight exist that contribute to the relaxation
process. Previously unknown spin-phonon coupling constants are calculated
explicitly.Comment: 4 pages,4 EPS figures,LaTeX(europhys.sty);final version accepted for
EP
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