10,951 research outputs found
Development of a Degradation Model for the Collapse Analysis of Composite Aerospace Structures
For stiffened structures in compression the most critical damage mechanism leading to structural collapse is delamination or adhesive disbonding between the skin and stiffener. This paper presents the development of a numerical approach capable of simulating interlaminar crack growth in composite structures as a representation of this damage mecha-nism. A degradation methodology was proposed using shell layers connected at the nodes by user-defined multiple point constraints (MPCs), and then controlling the properties of these MPCs to simulate the initiation and propagation of delamination and disbonding. A fracture mechanics approach based on the Virtual Crack Closure Technique (VCCT) is used to detect growth at the delamination front. Numerical predictions using the degradation methodology were compared to experimental results for double cantilever beam (DCB) specimens to dem-onstrate the effectiveness of the current approach. Future development will focus on address-ing the apparent conservatism of the VCCT approach, and extending the application of the method to other specimen types and stiffened structures representative of composite fuselage designs. This work is part of the European Commission Project COCOMAT (Improved MA-Terial Exploitation at Safe Design of COmposite Airframe Structures by Accurate Simulation of COllapse), an ongoing four-year project that aims to exploit the large strength reserves of composite aerospace structures through more accurate prediction of collapse
Structural, magnetic, and transport properties of CoFeSi Heusler films
We report the deposition of thin CoFeSi films by RF magnetron sputtering.
Epitaxial (100)-oriented and L2 ordered growth is observed for films grown
on MgO(100) substrates. (110)-oriented films on AlO(110) show several
epitaxial domains in the film plane. Investigation of the magnetic properties
reveals a saturation magnetization of 5.0 at low temperatures. The
temperature dependence of the resistivity exhibits a crossover
from a T^3.5 law at T<50K to a T^1.65 behaviour at elevated temperatures.
shows a small anisotropic magnetoresistive effect. A weak
dependence of the normal Hall effect on the external magnetic field indicates
the compensation of electron and hole like contributions at the Fermi surface.Comment: 10 pages, 9 figures to be published in J. Phys. D: Appl. Phy
Charged and Neutral Currents in a 3-3-1 Model with Right-Handed Neutrinos
The charged and the neutral currents are obtained by using a formal
algebraical approach (developed and applied by the author) within the exact
solution of a 3-3-1 gauge model with right-handed neutrinos. The entire
Standard Model phenomenology is recovered without imposing any supplemental
condition, but only by choosing an adecquate set of parameters from the very
beginning of the calculus. A new and rich phenomenology regarding the particles
and their currents occurs as well. The appealing feature of our results resides
in the exact expressions of the currents which need not the adjustment usually
due to the small mixing angle between neutral bosons and
(like in the most of the papers in the literature treating the
same issue). The required mixing was considered and aleready performed as an
intermediate step by the solving method itself, since the physical eigenstates
of those bosons were determined and then identified in the neutral currents.Comment: 14 pages, 1 Table, no figure
No Signalling and Quantum Key Distribution
Standard quantum key distribution protocols are provably secure against
eavesdropping attacks, if quantum theory is correct. It is theoretically
interesting to know if we need to assume the validity of quantum theory to
prove the security of quantum key distribution, or whether its security can be
based on other physical principles. The question would also be of practical
interest if quantum mechanics were ever to fail in some regime, because a
scientifically and technologically advanced eavesdropper could perhaps use
post-quantum physics to extract information from quantum communications without
necessarily causing the quantum state disturbances on which existing security
proofs rely. Here we describe a key distribution scheme provably secure against
general attacks by a post-quantum eavesdropper who is limited only by the
impossibility of superluminal signalling. The security of the scheme stems from
violation of a Bell inequality.Comment: Clarifications and minor revisions in response to comments. Final
version; to appear in Phys. Rev. Let
Quasi-local contribution to the scalar self-force: Geodesic Motion
We consider a scalar charge travelling in a curved background spacetime. We
calculate the quasi-local contribution to the scalar self-force experienced by
such a particle following a geodesic in a general spacetime. We also show that
if we assume a massless field and a vacuum background spacetime, the expression
for the self-force simplifies significantly. We consider some specific cases
whose gravitational analog are of immediate physical interest for the
calculation of radiation reaction corrected orbits of binary black hole
systems. These systems are expected to be detectable by the LISA space based
gravitational wave observatory. We also investigate how alternate techniques
may be employed in some specific cases and use these as a check on our own
results.Comment: Final Phys. Rev. D version. 24 pages, revtex4. Minor typos correcte
Ultraviolet avalanche in anisotropic non-Abelian plasmas
We present solutions of coupled particle-field evolution in classical U(1)
and SU(2) gauge theories in real time on three-dimensional lattices. For
strongly anisotropic particle momentum distributions, we find qualitatively
different behavior for the two theories when the field strength is high enough
that non-Abelian self-interactions matter for SU(2). It appears that the energy
drained by a Weibel-like plasma instability from the particles does not build
up exponentially in transverse magnetic fields but instead returns,
isotropically, to the hard scale via a rapid avalanche into the ultraviolet.Comment: 22 pages, 10 figures; v3: small textual changes; updated to
correspond with version to appear in publicatio
The Effects of Musical Fit on Consumers' Ability to Freely Recall Related Products
Previous studies have claimed that music can prime the selection of
certain products and influence consumers’ propensity to spend because it activates
related knowledge of the world and subsequently raises the salience of certain products
and behaviours associated with that music. The possibility that music can raise the
salience of associated products has not been tested directly, however, and ought to
manifest itself through enhanced ability to recall the products in question when
associated music is played. Accordingly, this study investigated the impact of musical
‘fit’ on product recall. Participants were asked to list as many Malay and Indian food
items as they could while listening to either Malay or Indian music. Among ethnically
Chinese participants, more Malay food items were recalled when Malay music was
played and more Indian food items were recalled when Indian music was played.
Ethnically Malay and Indian participants were more likely to recall food from their
own cultures, irrespective of the music played
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