36,952 research outputs found
Residual-strength tests of L-1011 vertical fin components after 10 and 20 years of simulated flight service
Part of the NASA/ACEE Program was to determine the effect of long-term durability testing on the residual strength of graphite-epoxy cover panel and spar components of the Lockheed L-1011 aircraft vertical stabilizer. The results of these residual strength tests are presented herein. The structural behavior and failure mode of both cover panel and spar components were addressed, and the test results obtained were compared with the static test results generated by Lockheed. The effect of damage on one of the spar specimens was described
Diffusion and Contagion in Networks with Heterogeneous Agents and Homophily
We study how a behavior (an idea, buying a product, having a disease,
adopting a cultural fad or a technology) spreads among agents in an a social
network that exhibits segregation or homophily (the tendency of agents to
associate with others similar to themselves). Individuals are distinguished by
their types (e.g., race, gender, age, wealth, religion, profession, etc.)
which, together with biased interaction patterns, induce heterogeneous rates of
adoption. We identify the conditions under which a behavior diffuses and
becomes persistent in the population. These conditions relate to the level of
homophily in a society, the underlying proclivities of various types for
adoption or infection, as well as how each type interacts with its own type. In
particular, we show that homophily can facilitate diffusion from a small
initial seed of adopters.Comment: 18 pages, 1 figur
A study of stopping power in nuclear reactions at intermediate energies
We show a systematic experimental study based on INDRA data of the stopping
power in central symmetric nuclear reactions. Total mass of the systems goes
from 80 to 400 nucleons while the incident energy range is from 12 AMeV to 100
AMeV. The role of isospin diffusion at 32 and 45 MeV/nucleon with 124,136Xe
projectiles on 112,124Sn targets performed at GANIL is also discussed. Results
suggest a strong memory of the entrance channel above 20 AMeV/A (nuclear
transparency) and, as such, constitute valuable tests of the microscopic
transport models.Comment: 7 pages, 3 figures, Proceedings of International Workshop on
Multifragmentation and Related Topics (IWM 2009), Catania, Italy, 4 Nov-7 Nov
200
Modeling Electronic Quantum Transport with Machine Learning
We present a Machine Learning approach to solve electronic quantum transport
equations of one-dimensional nanostructures. The transmission coefficients of
disordered systems were computed to provide training and test datasets to the
machine. The system's representation encodes energetic as well as geometrical
information to characterize similarities between disordered configurations,
while the Euclidean norm is used as a measure of similarity. Errors for
out-of-sample predictions systematically decrease with training set size,
enabling the accurate and fast prediction of new transmission coefficients. The
remarkable performance of our model to capture the complexity of interference
phenomena lends further support to its viability in dealing with transport
problems of undulatory nature.Comment: 5 pages, 4 figure
Symmetry algebra of a generalized anisotropic harmonic oscillator
It is shown that the symmetry Lie algebra of a quantum system with accidental degeneracy can be obtained by means of the Noether's theorem. The procedure is illustrated by considering a generalized anisotropic two dimensional harmonic oscillator, which can have an infinite set of states with the same energy characterized by an u(1,1) Lie algebra
Conductance through atomic point contacts between fcc(100) electrodes of gold
Electrical conductance through various nanocontacts between gold electrodes
is studied by using the density functional theory, scalar-relativistic
pseudopotentials, generalized gradient approximation for the
exchange-correlation energy and the recursion-transfer-matrix method along with
channel decomposition. The nanocontact is modeled with pyramidal fcc(100) tips
and 1 to 5 gold atoms between the tips. Upon elongation of the contact by
adding gold atoms between the tips, the conductance at Fermi energy E_F evolves
from G ~ 3 G_0 to G ~ 1 G_0 (G_0 = 2e/h^2). Formation of a true one-atom point
contact, with G ~ 1 G_0 and only one open channel, requires at least one atom
with coordination number 2 in the wire. Tips that share a common vertex atom or
tips with touching vertex atoms have three partially open conductance channels
at E_F, and the symmetries of the channels are governed by the wave functions
of the tips. The long 5-atom contact develops conductance oscillations and
conductance gaps in the studied energy range -3 < E-E_F < 5 eV, which reflects
oscillations in the local density of electron states in the 5-atom linear "gold
molecule" between the electrodes, and a weak coupling of this "molecule" to the
tips
Isoscaling as a measure of Symmetry Energy in the Lattice Gas Model
The energetic properties of nuclear clusters inside a low-density,
finite-temperature medium are studied with a Lattice Gas Model including
isospin dependence and Coulomb forces. Important deviations are observed
respect to the Fisher approximation of an ideal gas of non-interacting
clusters, but the global energetics can still be approximately expressed in
terms of a simple modified energy-density functional. The multi-fragmentation
regime appears dominated by combinatorial effects in this model, but the
isoscaling of the largest fragment in low energy collisions appears a promising
observable for the experimental measurement of the symmetry energy.Comment: 4 pages, 3 figure, submitted to PR
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