4,053 research outputs found
Elliptical instability of compressible flow in ellipsoids
Elliptical instability is due to a parametric resonance of two inertial modes
in a fluid velocity field with elliptical streamlines. This flow is a simple
model of the motion in a tidally deformed, rotating body. Elliptical
instability typically leads to three-dimensional turbulence. The associated
turbulent dissipation together with the dissipation of the large scale mode may
be important for the synchronization process in stellar and planetary binary
systems. In order to determine the influence of the compressibility on the
stability limits of tidal flows in stars or planets, we calculate the growth
rates of perturbations in flows with elliptical streamlines within ellipsoidal
boundaries of small ellipticity. In addition, the influence of the orbiting
frequency of the tidal perturber and the viscosity of the fluid are
taken into account
High-resolution absorption measurements of NH3 at high temperatures: 2100 - 5500
High-resolution absorption spectra of \NH\ in the region 2100 - 5500 \cm\ at
1027 C and atmospheric pressure (1045 3 mbar) are measured. An
\NH\ concentration of 10\% in volume fraction is used in the measurements.
Spectra are recorded in a high-temperature gas-flow cell using a Fourier
Transform Infrared (FTIR) spectrometer at a nominal resolution of 0.09 \cm. The
spectra are analysed by comparison to a variational line list, BYTe, and
experimental energy levels determined using the MARVEL procedure. 2308 lines
have been assigned to 45 different bands, of which 1755 and 15 have been
assigned or observed for the first time in this work
ExoMol molecular line lists - XVII The rotation-vibration spectrum of hot SO
Sulphur trioxide (SO) is a trace species in the atmospheres of the Earth
and Venus, as well as well as being an industrial product and an environmental
pollutant. A variational line list for SO, named UYT2, is
presented containing 21 billion vibration-rotation transitions. UYT2 can be
used to model infrared spectra of SO at wavelengths longwards of 2 m
( cm) for temperatures up to 800 K. Infrared absorption
cross sections are also recorded at 300 and 500 C are used to validate the UYT2
line list. The intensities in UYT2 are scaled to match the measured cross
sections. The line list is made available in electronic form as supplementary
data to this article and at \url{www.exomol.com}.Comment: 15 pages, 10 figures, 9 tables MNRAS submitte
GPS scintillations associated with cusp dynamics and polar cap patches
This paper investigates the relative scintillation level associated with cusp
dynamics (including precipitation, flow shears, etc.) with and without the
formation of polar cap patches around the cusp inflow region by the EISCAT
Svalbard radar (ESR) and two GPS scintillation receivers. A series of polar cap
patches were observed by the ESR between 8:40 and 10:20 UT on December 3, 2011.
The polar cap patches combined with the auroral dynamics were associated with a
significantly higher GPS phase scintillation level (up to 0.6 rad) than those
observed for the other two alternatives, i.e., cusp dynamics without polar cap
patches, and polar cap patches without cusp aurora. The cusp auroral dynamics
without plasma patches were indeed related to GPS phase scintillations at a
moderate level (up to 0.3 rad). The polar cap patches away from the active cusp
were associated with sporadic and moderate GPS phase scintillations (up to 0.2
rad). The main conclusion is that the worst global navigation satellite system
space weather events on the dayside occur when polar cap patches enter the
polar cap and are subject to particle precipitation and flow shears, which is
analogous to the nightside when polar cap patches exit the polar cap and enter
the auroral oval
Detector imperfections in photon-pair source characterization
We analyze how imperfections in single-photon detectors impact the
characterization of photon-pair sources. We perform exact calculations to
reveal the effects of multi-pair emissions and of noisy, non-unit efficiency,
non photon-number resolving detections on the Cauchy-Schwarz parameter, on the
second order auto-correlation and cross-correlation functions, and on the
visibilities of both Hong-Ou-Mandel and Bell-like interferences. We consider
sources producing either two-mode squeezed states or states with a Poissonian
photon distribution. The proposed formulas are useful in practice to determine
the impacts of multi-pair emissions and dark counts in standard tests used in
quantum optics.Comment: 9 pages, 11 figure
Conditional quantum-state transformation at a beam splitter
Using conditional measurement on a beam splitter, we study the transformation
of the quantum state of the signal mode within the concept of two-port
non-unitary transformation. Allowing for arbitrary quantum states of both the
input reference mode and the output reference mode on which the measurement is
performed, we show that the non-unitary transformation operator can be given as
an -ordered operator product, where the value of is entirely determined
by the absolute value of the beam splitter reflectance (or transmittance). The
formalism generalizes previously obtained results that can be recovered by
simple specification of the non-unitary transformation operator. As an
application, we consider the generation of Schr\"odinger-cat-like states. An
extension to mixed states and imperfect detection is outlined.Comment: 7 Postscript figures, using Late
The use of alkali activated materials in mining Applications
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Ash beneficiation for the enhancement of electrical transmission infrastructure
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