26,674 research outputs found
Testing procedures for carbon fiber reinforced plastic components
Tests for studying the basic material are considered and quality control investigations involving preimpregnated materials (prepreg) are discussed. Attention is given to the prepreg area weight, the fiber area weight of prepregs, the resin content, volatile components, the effective thickness, resin flow, the resistance to bending strain, tensile strength, and shear strength. A description of tests conducted during the manufacturing process is also presented, taking into account X-ray methods, approaches of neutron radiography, ultrasonic procedures, resonance methods and impedance studies
Ab Initio Calculations of Even Oxygen Isotopes with Chiral Two- Plus Three-Nucleon Interactions
We formulate the In-Medium Similarity Renormalization Group (IM-SRG) for
open-shell nuclei using a multi-reference formalism based on a generalized Wick
theorem introduced in quantum chemistry. The resulting multi-reference IM-SRG
(MR-IM-SRG) is used to perform the first ab initio study of even oxygen
isotopes with chiral NN and 3N Hamiltonians, from the proton to the neutron
drip lines. We obtain an excellent reproduction of experimental ground-state
energies with quantified uncertainties, which is validated by results from the
Importance-Truncated No-Core Shell Model and the Coupled Cluster method. The
agreement between conceptually different many-body approaches and experiment
highlights the predictive power of current chiral two- and three-nucleon
interactions, and establishes the MR-IM-SRG as a promising new tool for ab
initio calculations of medium-mass nuclei far from shell closures.Comment: 5 pages, 4 figures, v2 corresponding to published versio
Density functional theory for hard-sphere mixtures: the White-Bear version Mark II
In the spirit of the White-Bear version of fundamental measure theory we
derive a new density functional for hard-sphere mixtures which is based on a
recent mixture extension of the Carnahan-Starling equation of state. In
addition to the capability to predict inhomogeneous density distributions very
accurately, like the original White-Bear version, the new functional improves
upon consistency with an exact scaled-particle theory relation in the case of
the pure fluid. We examine consistency in detail within the context of
morphological thermodynamics. Interestingly, for the pure fluid the degree of
consistency of the new version is not only higher than for the original
White-Bear version but also higher than for Rosenfeld's original fundamental
measure theory.Comment: 16 pages, 3 figures; minor changes; J. Phys.: Condens. Matter,
accepte
Dynamic fracture of icosahedral model quasicrystals: A molecular dynamics study
Ebert et al. [Phys. Rev. Lett. 77, 3827 (1996)] have fractured icosahedral
Al-Mn-Pd single crystals in ultrahigh vacuum and have investigated the cleavage
planes in-situ by scanning tunneling microscopy (STM). Globular patterns in the
STM-images were interpreted as clusters of atoms. These are significant
structural units of quasicrystals. The experiments of Ebert et al. imply that
they are also stable physical entities, a property controversially discussed
currently. For a clarification we performed the first large scale fracture
simulations on three-dimensional complex binary systems. We studied the
propagation of mode I cracks in an icosahedral model quasicrystal by molecular
dynamics techniques at low temperature. In particular we examined how the shape
of the cleavage plane is influenced by the clusters inherent in the model and
how it depends on the plane structure. Brittle fracture with no indication of
dislocation activity is observed. The crack surfaces are rough on the scale of
the clusters, but exhibit constant average heights for orientations
perpendicular to high symmetry axes. From detailed analyses of the fractured
samples we conclude that both, the plane structure and the clusters, strongly
influence dynamic fracture in quasicrystals and that the clusters therefore
have to be regarded as physical entities.Comment: 10 pages, 12 figures, for associated avi files, see
http://www.itap.physik.uni-stuttgart.de/~frohmut/MOVIES/emitted_soundwaves.avi
and
http://www.itap.physik.uni-stuttgart.de/~frohmut/MOVIES/dynamic_fracture.av
Spinorial Characterizations of Surfaces into 3-dimensional pseudo-Riemannian Space Forms
We give a spinorial characterization of isometrically immersed surfaces of
arbitrary signature into 3-dimensional pseudo-Riemannian space forms. For
Lorentzian surfaces, this generalizes a recent work of the first author in
to other Lorentzian space forms. We also characterize
immersions of Riemannian surfaces in these spaces. From this we can deduce
analogous results for timelike immersions of Lorentzian surfaces in space forms
of corresponding signature, as well as for spacelike and timelike immersions of
surfaces of signature (0,2), hence achieving a complete spinorial description
for this class of pseudo-Riemannian immersions.Comment: 9 page
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