1,466 research outputs found
On the Identification of Agents in the Design of Production Control Systems
This paper describes a methodology that is being developed for designing and building agent-based systems for the domain of production control. In particular, this paper deals with the steps that are involved in identifying the agents and in specifying their responsibilities. The methodology aims to be usable by engineers who have a background in production control but who have no prior experience in agent technology. For this reason, the methodology needs to be very prescriptive with respect to the agent-related aspects of design
Magnetic field enhanced structural instability in EuTiO_{3}
EuTiO_{3} undergoes a structural phase transition from cubic to tetragonal at
T_S = 282 K which is not accompanied by any long range magnetic order. However,
it is related to the oxygen ocathedra rotation driven by a zone boundary
acoustic mode softening. Here we show that this displacive second order
structural phase transition can be shifted to higher temperatures by the
application of an external magnetic field (increased by 4 K for mu_{0}H = 9 T).
This observed field dependence is in agreement with theoretical predictions
based on a coupled spin-anharmonic-phonon interaction model.Comment: 4 pages, 4 figure
Oxygen-isotope effect on the superconducting gap in the cuprate superconductor Y_{1-x}Pr_xBa_2Cu_3O_{7-\delta}
The oxygen-isotope (^{16}O/^{18}O) effect (OIE) on the zero-temperature
superconducting energy gap \Delta_0 was studied for a series of
Y_{1-x}Pr_xBa_2Cu_3O_{7-\delta} samples (0.0\leq x\leq0.45). The OIE on
\Delta_0 was found to scale with the one on the superconducting transition
temperature. These experimental results are in quantitative agreement with
predictions from a polaronic model for cuprate high-temperature superconductors
and rule out approaches based on purely electronic mechanisms.Comment: 5 pages, 3 figure
Theory of Dynamic Stripe Induced Superconductivity
Since the recently reported giant isotope effect on T* [1] could be
consistently explained within an anharmonic spin-charge-phonon interaction
model, we consider here the role played by stripe formation on the
superconducting properties within the same model. This is a two-component
scenario and we recast its basic elements into a BCS effective Hamiltonian. We
find that the stripe formation is vital to high-Tc superconductivity since it
provides the glue between the two components to enhance Tc to the unexpectedly
large values observed experimentally.Comment: 7 pages, 2 figure
Lattice and polarizability mediated spin activity in EuTiO_3
EuTiO_3 is shown to exhibit novel strong spin-charge-lattice coupling deep in
the paramagnetic phase. Its existence is evidenced by an, until now, unknown
response of the paramagnetic susceptibility at temperatures exceeding the
structural phase transition temperature T_S = 282K. The "extra" features in the
susceptibility follow the rotational soft zone boundary mode temperature
dependence above and below T_S. The theoretical modeling consistently
reproduces this behavior and provides reasoning for the stabilization of the
soft optic mode other than quantum fluctuations.Comment: 8 pages, 4 figure
Hybrid paramagnon phonon modes at elevated temperatures in EuTiO3
EuTiO3 (ETO) has recently experienced an enormous revival of interest because
of its possible multiferroic properties which are currently in the focus of
research. Unfortunately ETO is an unlikely candidate for enlarged
multifunctionality since the mode softening - typical for ferroelectrics -
remains incomplete, and the antiferromagnetic properties appear at 5.5K only.
However, a strong coupling between lattice and Eu spins exists and leads to the
appearance of a magnon-phonon-hybrid mode at elevated temperatures as evidenced
by electron paramagnetic resonance (EPR), muon spin rotation ({\mu}SR)
experiments and model predictions based on a coupled spin-polarizability
Hamiltonian. This novel finding supports the notion of strong
magneto-dielectric (MD) effects being realized in ETO and opens new strategies
in material design and technological applications.Comment: 9 pages, 4 figure
The Spectral Energy Distributions and Infrared Luminosities of z \approx 2 Dust Obscured Galaxies from Herschel and Spitzer
Dust-obscured galaxies (DOGs) are a subset of high-redshift (z \approx 2)
optically-faint ultra-luminous infrared galaxies (ULIRGs, e.g. L_{IR} > 10^{12}
Lsun). We present new far-infrared photometry, at 250, 350, and 500 um
(observed-frame), from the Herschel Space Telescope for a large sample of 113
DOGs with spectroscopically measured redshifts. Approximately 60% of the sample
are detected in the far-IR, confirming their high IR luminosities, which range
from 10^{11.6} Lsun < L_{IR} (8-1000 um) <10^{13.6} Lsun. 90% of the Herschel
detected DOGs in this sample are ULIRGs and 30% have L_{IR} > 10^{13} Lsun. The
rest-frame near-IR (1 - 3 um) SEDs of the Herschel detected DOGs are predictors
of their SEDs at longer wavelengths. DOGs with "power-law" SEDs in the
rest-frame near-IR show observed-frame 250/24 um flux density ratios similar to
the QSO-like local ULIRG, Mrk 231. DOGs with a stellar "bump" in their
rest-frame near-IR show observed-frame 250/24 um flux density ratios similar to
local star-bursting ULIRGs like NGC 6240. For the Herschel detected DOGs,
accurate estimates (within \approx 25%) of total IR luminosity can be predicted
from their rest-frame mid-IR data alone (e.g. from Spitzer observed-frame 24 um
luminosities). Herschel detected DOGs tend to have a high ratio of infrared
luminosity to rest-frame 8 um luminosity (the IR8= L_{IR}(8-1000 um)/v L_{v}(8
um) parameter of Elbaz et al. 2011). Instead of lying on the z=1-2 "infrared
main-sequence" of star forming galaxies (like typical LIRGs and ULIRGs at those
epochs) the DOGs, especially large fractions of the bump sources, tend to lie
in the starburst sequence. While, Herschel detected DOGs are similar to scaled
up versions of local ULIRGs in terms of 250/24 um flux density ratio, and IR8,
they tend to have cooler far-IR dust temperatures (20-40 K for DOGs vs. 40-50 K
for local ULIRGs). Abridged.Comment: 24 pages, 14 figures, 3 tables, accepted for publication in the
Astronomical Journa
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