329,819 research outputs found
Flammability control for electrical cables and connectors
Technique of covering fire-hazardous sections of electrical wiring with fireproof materials prevents fires from spreading in oxygen-enriched atmospheres and eliminates use of heavy metal enclosures. Materials used to cover potting on connectors and ground terminals are made from Teflon-coated Beta cloth and Fluorel, a nonflammable fully-saturated polymer
Radium single-ion optical clock
We explore the potential of the electric quadrupole transitions
7s\,^2S_{1/2} - 6d\,^2D_{3/2}, 6d\,^2D_{5/2} in radium isotopes as
single-ion optical frequency standards. The frequency shifts of the clock
transitions due to external fields and the corresponding uncertainties are
calculated. Several competitive Ra candidates with 223 - 229 are
identified. In particular, we show that the transition
7s\,^2S_{1/2}\,(F=2,m_F=0) - 6d\,^2D_{3/2}\,(F=0,m_F=0) at 828 nm in
Ra, with no linear Zeeman and electric quadrupole shifts, stands
out as a relatively simple case, which could be exploited as a compact, robust,
and low-cost atomic clock operating at a fractional frequency uncertainty of
. With more experimental effort, the Ra clocks
could be pushed to a projected performance reaching the level.Comment: 20 pages, 1 figur
Dilepton radiation by vector mesons and off-shell partons in the hot and dense medium
According to the dynamical quasiparticle model (DQPM) - matched to reproduce
lattice QCD results in thermodynamic limit, - the constituents of the strongly
interacting quark-gluon plasma (sQGP) are massive and off-shell quasi-particles
(quarks and gluons) with broad spectral functions. In order to address the
electromagnetic radiation of the sQGP, we derive off-shell cross sections of
q+qbar->gamma*, q+qbar->gamma*+glue and q+glue->gamma*+q(qbar+glue->gamma*qbar)
reactions taking into account the effective propagators for quarks and gluons
from the DQPM. Dilepton production in In+In collisions at 158 AGeV is studied
by implementing these processes into the parton-hadron-string dynamics (PHSD)
transport approach. The microscopic PHSD transport approach describes the full
evolution of the heavy-ion collision: from the dynamics of quasi-particles in
the sQGP phase (when the local energy density is above ~1 GeV/fm^3) through
hadronization and to the following hadron interactions and off-shell
propagation after the hadronization. A comparison to the data of the NA60
Collaboration shows that the low mass dilepton spectra are well described by
including a collisional broadening of vector mesons, while the spectra in the
intermediate mass range are dominated by off-shell quark-antiquark
annihilation, quark Bremsstrahlung and gluon-Compton scattering in the
nonperturbative QGP. In particular, the observed softening of the mT spectra at
intermediate masses (1 GeV < M < 3 GeV) is approximately reproduced.Comment: Talk given at the XIII International Conference on Hadron
Spectroscopy (HADRON 09), November 29 - December 4, 2009, Tallahassee,
Florida; two references added in version
Electromagnetic probes of the QGP
We investigate the properties of the QCD matter across the deconfinement
phase transition in the scope of the parton-hadron string dynamics (PHSD)
transport approach. We present here in particular the results on the
electromagnetic radiation, i.e. photon and dilepton production, in relativistic
heavy-ion collisions. By comparing our calculations for the heavy-ion
collisions to the available data, we determine the relative importance of the
various production sources and address the possible origin of the observed
strong elliptic flow of direct photons. We argue that the different
centrality dependence of the hadronic and partonic sources for direct photon
production in nucleus-nucleus collisions can be employed to shed some more
light on the origin of the photon "puzzle". While the dilepton spectra at
low invariant mass show in-medium effects like an enhancement from multiple
baryonic resonance formation or a collisional broadening of the vector meson
spectral functions, the dilepton yield at high invariant masses (above 1.1 GeV)
is dominated by QGP contributions for central heavy-ion collisions at
ultra-relativistic energies. This allows to have an independent view on the
parton dynamics via their electromagnetic massive radiation.Comment: 12 pages, Proceedings of the 3rd International Conference on 'New
Frontiers in Physics 2014', Kolymbari, Cret
Study, selection, and preparation of solid cationic conductors
Crystal chemical principles and transport theory have been used to predict structures and specific compounds which might find application as solid electrolytes in rechargeable high energy and high power density batteries operating at temperatures less than 200 C. Structures with 1-, 2-, and 3-dimensional channels were synthesized and screened by nuclear magnetic resonance, dielectric loss, and conductivity. There is significant conductivity at room temperature in some of the materials but none attain a level that is comparable to beta-alumina. Microwave and fast pulse methods were developed to measure conductivity in powders and in small crystals
Digital image correlation techniques applied to LANDSAT multispectral imagery
The author has identified the following significant results. Automatic image registration and resampling techniques applied to LANDSAT data achieved accuracies, resulting in mean radial displacement errors of less than 0.2 pixel. The process method utilized recursive computational techniques and line-by-line updating on the basis of feedback error signals. Goodness of local feature matching was evaluated through the implementation of a correlation algorithm. An automatic restart allowed the system to derive control point coordinates over a portion of the image and to restart the process, utilizing this new control point information as initial estimates
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