36,765 research outputs found
Carool Kersten, Islam in Indonesia; the Contest for Society, Ideas and Values. London: Hurst & Company, 2015, XX + 373 Pp. ISBN: 9781849044370. Price: GBP 25.00 (Soft Cover).
Probing Unquenching Effects in the Gluon Polarisation in Light Mesons
We introduce an extension to the ladder truncated Bethe-Salpeter equation for
mesons and the rainbow truncated quark Dyson-Schwinger equations which includes
quark-loop corrections to the gluon propagator. This truncation scheme obeys
the axialvector Ward-Takahashi identity relating the quark self-energy and the
Bethe-Salpeter kernel. Two different approximations to the Yang-Mills sector
are used as input: the first is a sophisticated truncation of the full
Yang-Mills Dyson-Schwinger equations, the second is a phenomenologically
motivated form. We find that the spectra and decay constants of pseudoscalar
and vector mesons are overall described well for either approach. Meson mass
results for charge eigenstate vector and pseudoscalar meson masses are compared
to lattice data. The effects of unquenching the system are small but not
negligible.Comment: 26 pages, 13 figure
An analysis of prop-fan/airframe aerodynamic integration
An approach to aerodynamic integration of turboprops and airframes, with emphasis placed upon wing mounted installations is addressed. Potential flow analytical techniques were employed to study aerodynamic integration of the prop fan propulsion concept with advanced, subsonic, commercial transport airframes. Three basic configurations were defined and analyzed: wing mounted prop fan at a cruise Mach number of 0.8, wing mounted prop fan in a low speed configuration, and aft mounted prop fan at a cruise Mach number of 0.8
Solar wind sputtering effects in the Martian atmosphere
A Monte Carlo simulation of the sputtering of the upper atmosphere of Mars by the solar wind was performed. The calculated sputtering yields imply loss rates (molecules/cm square - sec escaping the planet) for carbon dioxide, carbon, and oxygen of R(CO2) = 2.6 X 1000000/cm square - sec, R(C) = 6.6 X 1000000/cm square - sec, and R(O) = 7.7 X 1000000/cm - sec. The total mass loss by sputtering is only about 10% of that due to chemical and photo-chemical processes, but sputtering provides a major exospheric sink for carbon. The erosion process described here preferentially removes the lighter components of the atmosphere. Calculations based on a Monte Carlo simulation suggest that for a model atmosphere, 97% of the N2 and 33% of the CO2 originally present may have been sputtered away over 4.5 X 10 to the 9th power y. In the same length of time the (15)N/(14)N isotopic ratio for the bulk atmosphere would have increased by a factor 1.7
Characterising exo-ringsystems around fast-rotating stars using the Rossiter-McLaughlin effect
Planetary rings produce a distinct shape distortion in transit lightcurves.
However, to accurately model such lightcurves the observations need to cover
the entire transit, especially ingress and egress, as well as an out-of-transit
baseline. Such observations can be challenging for long period planets, where
the transits may last for over a day. Planetary rings will also impact the
shape of absorption lines in the stellar spectrum, as the planet and rings
cover different parts of the rotating star (the Rossiter-McLaughlin effect).
These line-profile distortions depend on the size, structure, opacity,
obliquity and sky projected angle of the ring system. For slow rotating stars,
this mainly impacts the amplitude of the induced velocity shift, however, for
fast rotating stars the large velocity gradient across the star allows the line
distortion to be resolved, enabling direct determination of the ring
parameters. We demonstrate that by modeling these distortions we can recover
ring system parameters (sky-projected angle, obliquity and size) using only a
small part of the transit. Substructure in the rings, e.g. gaps, can be
recovered if the width of the features () relative to the size of the
star is similar to the intrinsic velocity resolution (set by the width of the
local stellar profile, ) relative to the stellar rotation velocity (
sin, i.e. sin/). This opens up a new
way to study the ring systems around planets with long orbital periods, where
observations of the full transit, covering the ingress and egress, are not
always feasible.Comment: Accepted for publication in MNRA
Quark-gluon vertex dressing and meson masses beyond ladder-rainbow truncation
We include a generalized infinite class of quark-gluon vertex dressing
diagrams in a study of how dynamics beyond the ladder-rainbow truncation
influences the Bethe-Salpeter description of light quark pseudoscalar and
vector mesons. The diagrammatic specification of the vertex is mapped into a
corresponding specification of the Bethe-Salpeter kernel, which preserves
chiral symmetry. This study adopts the algebraic format afforded by the simple
interaction kernel used in previous work on this topic. The new feature of the
present work is that in every diagram summed for the vertex and the
corresponding Bethe-Salpeter kernel, each quark-gluon vertex is required to be
the self-consistent vertex solution. We also adopt from previous work the
effective accounting for the role of the explicitly non-Abelian three gluon
coupling in a global manner through one parameter determined from recent
lattice-QCD data for the vertex. With the more consistent vertex used here, the
error in ladder-rainbow truncation for vector mesons is never more than 10% as
the current quark mass is varied from the u/d region to the b region.Comment: 15 pages, 12 figure
Evaluation of wet tantalum capacitors after exposure to extended periods of ripple current, volume 1
The application of tantalum capacitors in the Viking Lander includes both dc voltage and ripple current electrical stress, high temperature during nonoperating times (sterilization), and high vibration and shock loads. The capacitors must survive these severe environments without any degradation if reliable performance is to be achieved. A test program was established to evaluate both wet-slug tantalum and wet-foil capacitors under conditions accurately duplicating actual Viking applications. Test results of the electrical performance characteristics during extended periods of ripple current, the characteristics of the internal silver migration as a function for extended periods of ripple current, and the existence of any memory characteristics are presented
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Kelvin-Helmholtz Instability in a Weakly Ionized Medium
Ambient interstellar material may become entrained in outflows from massive
stars as a result of shear flow instabilities. We study the linear theory of
the Kelvin - Helmholtz instability, the simplest example of shear flow
instability, in a partially ionized medium. We model the interaction as a two
fluid system (charged and neutral) in a planar geometry. Our principal result
is that for much of the relevant parameter space, neutrals and ions are
sufficiently decoupled that the neutrals are unstable while the ions are held
in place by the magnetic field. Thus, we predict that there should be a
detectably narrower line profile in ionized species tracing the outflow
compared with neutral species since ionized species are not participating in
the turbulent interface with the ambient ISM. Since the magnetic field is
frozen to the plasma, it is not tangled by the turbulence in the boundary
layer.Comment: 21 pages, 4 figure
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