306 research outputs found
Comments on the articles "Hyperbolic thermoelasticity: A review of recent literature" (Chandrasekharaiah DS, 1998, appl mech rev 51(12), 705-729) and "Thermoelasticity with second sound: a review" (Chandrasekharaiah DS, 1986, appl mech rev 39(3), 355-376)
This review article is a continuation of a previous article by the author, Thermoelasticity with second sound: A review, which appeared in this journal in March, 1986 (Appl Mech Rev39 (3) 355-376). Here, attention is focused on papers published during the past 10-12 years. Contributions to the theory of thermoelasticity with thermal relaxation and the temperature-rate dependent thermoelasticity theory are reviewed. The recently developed theory of thermoelasticity without energy dissipation is described, and its characteristic features highlighted. A glance is made at the new thermoelasticity theory which includes the so-called dual-phase-lag effects. There are 338 references
The Coral reef fishes of Broward County Florida, species and abundance: a work in progress
The inshore environment of Broward County, FL consists of three coral reef/hard bottom reef tracts, separated by sand substrate, running parallel to the coast in sequentially deeper water. At quarter nautical mile intervals, for a five mile coastline section, fishes were censused at western, eastern and crest sites of each of the three reef tracts. On SCUBA and using the Bohnsack/Bannerot point-count method, we recorded: fish abundance, species richness, size, and general habitat of an imaginary cylinder 15 m in diameter. The position of each site was recorded by DGPS after census. One hundred and eighty-one sites were censused during a 10 month period (August 1998 to May 1999). A total of 16,746 fish belonging to 139 species of 39 families were recorded. There were significant differences (p \u3c 0.05, ANOVA) in the species richness and the total abundance of fishes among the three reef tracts. There were significantly fewer total fish (p \u3c 0.001) and fewer fish species (p \u3c 0.001) on the inshore reef tract as compared to either the middle or offshore reef tracts. The middle and offshore reefs tracts did not differ (p \u3e 0.05, SNK). Differences were also found based on the location (edges or crest) on the reef. With all data from the three reef tracts combined, the eastern edge showed significantly fewer total fish (p \u3c 0.001) than either the crest of the reef or the western edge, which did not differ significantly (p\u3e 0.05). Species richness also varied with the western edges of the tracts having significantly more species (p \u3c 0.01) than the crests or the eastern edges, again there was no significant difference between these two (p \u3e 0.05). Statistical analysis of a subjective complexity rating taken at each site mirrored the results of fish abundance and species richness. This supports the hypothesis that topographical complexity is, at least in part, a determinant in the differences in fish assemblages among the three reef tracts
Phase-fitted Discrete Lagrangian Integrators
Phase fitting has been extensively used during the last years to improve the
behaviour of numerical integrators on oscillatory problems. In this work, the
benefits of the phase fitting technique are embedded in discrete Lagrangian
integrators. The results show improved accuracy and total energy behaviour in
Hamiltonian systems. Numerical tests on the long term integration (100000
periods) of the 2-body problem with eccentricity even up to 0.95 show the
efficiency of the proposed approach. Finally, based on a geometrical evaluation
of the frequency of the problem, a new technique for adaptive error control is
presented
Efficient Algorithms for Universal Quantum Simulation
A universal quantum simulator would enable efficient simulation of quantum
dynamics by implementing quantum-simulation algorithms on a quantum computer.
Specifically the quantum simulator would efficiently generate qubit-string
states that closely approximate physical states obtained from a broad class of
dynamical evolutions. I provide an overview of theoretical research into
universal quantum simulators and the strategies for minimizing computational
space and time costs. Applications to simulating many-body quantum simulation
and solving linear equations are discussed
Efficiency of free energy calculations of spin lattices by spectral quantum algorithms
Quantum algorithms are well-suited to calculate estimates of the energy
spectra for spin lattice systems. These algorithms are based on the efficient
calculation of the discrete Fourier components of the density of states. The
efficiency of these algorithms in calculating the free energy per spin of
general spin lattices to bounded error is examined. We find that the number of
Fourier components required to bound the error in the free energy due to the
broadening of the density of states scales polynomially with the number of
spins in the lattice. However, the precision with which the Fourier components
must be calculated is found to be an exponential function of the system size.Comment: 9 pages, 4 figures; corrected typographical and minor mathematical
error
Simulating Physical Phenomena by Quantum Networks
Physical systems, characterized by an ensemble of interacting elementary
constituents, can be represented and studied by different algebras of
observables or operators. For example, a fully polarized electronic system can
be investigated by means of the algebra generated by the usual fermionic
creation and annihilation operators, or by using the algebra of Pauli
(spin-1/2) operators. The correspondence between the two algebras is given by
the Jordan-Wigner isomorphism. As we previously noted similar one-to-one
mappings enable one to represent any physical system in a quantum computer. In
this paper we evolve and exploit this fundamental concept in quantum
information processing to simulate generic physical phenomena by quantum
networks. We give quantum circuits useful for the efficient evaluation of the
physical properties (e.g, spectrum of observables or relevant correlation
functions) of an arbitrary system with Hamiltonian .Comment: 44 pages, 15 psfigur
The power of quantum systems on a line
We study the computational strength of quantum particles (each of finite
dimensionality) arranged on a line. First, we prove that it is possible to
perform universal adiabatic quantum computation using a one-dimensional quantum
system (with 9 states per particle). This might have practical implications for
experimentalists interested in constructing an adiabatic quantum computer.
Building on the same construction, but with some additional technical effort
and 12 states per particle, we show that the problem of approximating the
ground state energy of a system composed of a line of quantum particles is
QMA-complete; QMA is a quantum analogue of NP. This is in striking contrast to
the fact that the analogous classical problem, namely, one-dimensional
MAX-2-SAT with nearest neighbor constraints, is in P. The proof of the
QMA-completeness result requires an additional idea beyond the usual techniques
in the area: Not all illegal configurations can be ruled out by local checks,
so instead we rule out such illegal configurations because they would, in the
future, evolve into a state which can be seen locally to be illegal. Our
construction implies (assuming the quantum Church-Turing thesis and that
quantum computers cannot efficiently solve QMA-complete problems) that there
are one-dimensional systems which take an exponential time to relax to their
ground states at any temperature, making them candidates for being
one-dimensional spin glasses.Comment: 21 pages. v2 has numerous corrections and clarifications, and most
importantly a new author, merged from arXiv:0705.4067. v3 is the published
version, with additional clarifications, publisher's version available at
http://www.springerlink.co
Tensor-scalar gravity and binary-pulsar experiments
Some recently discovered nonperturbative strong-field effects in
tensor-scalar theories of gravitation are interpreted as a scalar analog of
ferromagnetism: "spontaneous scalarization". This phenomenon leads to very
significant deviations from general relativity in conditions involving strong
gravitational fields, notably binary-pulsar experiments. Contrary to
solar-system experiments, these deviations do not necessarily vanish when the
weak-field scalar coupling tends to zero. We compute the scalar "form factors"
measuring these deviations, and notably a parameter entering the pulsar timing
observable gamma through scalar-field-induced variations of the inertia moment
of the pulsar. An exploratory investigation of the confrontation between
tensor-scalar theories and binary-pulsar experiments shows that nonperturbative
scalar field effects are already very tightly constrained by published data on
three binary-pulsar systems. We contrast the probing power of pulsar
experiments with that of solar-system ones by plotting the regions they exclude
in a generic two-dimensional plane of tensor-scalar theories.Comment: 35 pages, REVTeX 3.0, uses epsf.tex to include 9 Postscript figure
On the Detection of a Scalar Stochastic Background of Gravitational Waves
In the near future we will witness the coming to a full operational regime of
laser interferometers and resonant mass detectors of spherical shape. In this
work we study the sensitivity of pairs of such gravitational wave detectors to
a scalar stochastic background of gravitational waves. Our computations are
carried out both for minimal and non minimal coupling of the scalar fields.Comment: 25 pages, 3 figure
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