108,862 research outputs found
Multiple Q-Adapted Integrals and Ito Formula of Noncommutative Stochastic Calculus in Fock Space
We study the continuity property of multiple Q-adapted quantum stochastic
integrals with respect to noncommuting integrands given by the non-adapted
multiple integral kernels in Fock scale. The noncommutative algebra of
relatively (exponentially) bounded nonadapted quantum stochastic processes is
studied in the kernel form as introduced by Belavkin in 1991. The differential
Q-adapted formula generalizing Ito product formula for adapted integrals is
presented in both strong and weak sense as a particular case of the quantum
stochastic nonadapted Ito formula.Comment: Due to appear in communications on stochastic analysis journal (KRP
volume). 21 page
Molecular simulations of entangled defect structures around nanoparticles in nematic liquid crystals
We investigate the defect structures forming around two nanoparticles in a
Gay-Berne nematic liquid crystal using molecular simulations. For small
separations, disclinations entangle both particles forming the figure of eight,
the figure of omega and the figure of theta. These defect structures are
similar in shape and occur with a comparable frequency to micron-sized
particles studied in experiments. The simulations reveal fast transitions from
one defect structure to another suggesting that particles of nanometre size
cannot be bound together effectively. We identify the 'three-ring' structure
observed in previous molecular simulations as a superposition of the different
entangled and non-entangled states over time and conclude that it is not itself
a stable defect structure.Comment: keywords: molecular-simulation, defects, nematic, disclination,
algorithmic classification ; 8 pages, 7 figures, 1 tabl
An analytical and experimental assessment of flexible road ironwork support structures
This paper describes work undertaken to investigate the mechanical performance of road ironwork installations in highways, concentrating on the chamber construction. The principal aim was to provide the background research which would allow improved designs to be developed to reduce the incidence of failures through improvements to the structural continuity between the installation and the surrounding pavement. In doing this, recycled polymeric construction materials (Jig Brix) were studied with a view to including them in future designs and specifications. This paper concentrates on the Finite Element (FE) analysis of traditional (masonry) and flexible road ironwork structures incorporating Jig Brix. The global and local buckling capacity of the Jig Brix elements was investigated and results compared well with laboratory measurements. FE models have also been developed for full-scale traditional (masonry) and flexible installations in a surrounding flexible (asphalt) pavement structure. Predictions of response to wheel loading were compared with full-scale laboratory measurements. Good agreement was achieved with the traditional (masonry) construction but poorer agreement for the flexible construction. Predictions from the FE model indicated that the use of flexible elements significantly reduces the tensile horizontal strain on the surface of the surrounding asphaltic material which is likely to reduce the incidence of surface cracking
Monogroove heat pipe design: Insulated liquid channel with bridging wick
A screen mesh artery supported concentrically within the evaporator section of a heat pipe liquid channel retains liquid in the channel. Continued and uniform liquid feed to the heat pipe evaporation section (20) during periods of excessive heat transfer is assured. The overall design provides high evaporation and condensation film coefficients for the working fluid by means of the circumferential grooves in the walls of the vapor channel, while not interfering with the overall heat transport capability of the axial groove. The design has particular utility in zero-g environments
Comparison of Models of Critical Opacity in the Quark-Gluon Plasma
In this work we discuss two methods of calculation of quark propagation in
the quark-gluon plasma. Both methods make use of the Nambu-Jona-Lasinio model.
The essential difference of these calculations is the treatment of
deconfinement. A model of confinement is not included in the work of Gastineau,
Blanquier and Aichelin [hep-ph/0404207], however, the meson states they
consider are still bound for temperatures greater than the deconfinement
temperature T_c. On the other hand, our model deals with unconfined quarks and
includes a description of the q(bar)q resonances found in lattice QCD studies
that make use of the maximum entropy method (MEM). We compare the q{bar)q cross
sections calculated in these models.Comment: 7 pages and 4 figures RevTe
Polarimetric variations of binary stars. II. Numerical simulations for circular and eccentric binaries in Mie scattering envelopes
We present numerical simulations of the periodic polarimetric variations
produced by a binary star placed at the center of an empty spherical cavity
inside a circumbinary ellipsoidal and optically thin envelope made of dust
grains. Mie single-scattering is considered along with pre- and post-scattering
extinction factors which produce a time-varying optical depth and affect the
morphology of the periodic variations. We are interested in the effects that
various parameters will have on the average polarization, the amplitude of the
polarimetric variations, and the morphology of the variability. We show that
the absolute amplitudes of the variations are smaller for Mie scattering than
for Thomson scattering. Among the four grain types that we have studied, the
highest polarizations are produced by grains with sizes in the range 0.1-0.2
micron. In general, the variations are seen twice per orbit. In some cases,
because spherical dust grains have an asymmetric scattering function, the
polarimetric curves produced also show variations seen once per orbit.
Circumstellar disks produce polarimetric variations of greater amplitude than
circumbinary envelopes.
Another goal of these simulations is to see if the 1978 BME (Brown, McLean, &
Emslie, ApJ, 68, 415) formalism, which uses a Fourier analysis of the
polarimetric variations to find the orbital inclination for Thomson-scattering
envelopes, can still be used for Mie scattering. We find that this is the case,
if the amplitude of the variations is sufficient and the true inclinations is
i_true > 45 deg. For eccentric orbits, the first-order coefficients of the
Fourier fit, instead of second-order ones, can be used to find almost all
inclinations.Comment: 23 pages, 5 figures, to be published in Astronomical Journa
Lifting classes for the fixed point theory of -valued maps
The theory of lifting classes and the Reidemeister number of single-valued
maps of a finite polyhedron is extended to -valued maps by replacing
liftings to universal covering spaces by liftings with codomain an orbit
configuration space, a structure recently introduced by Xicot\'encatl. The
liftings of an -valued map split into self-maps of the universal
covering space of that we call lift-factors. An equivalence relation is
defined on the lift-factors of and the number of equivalence classes is the
Reidemeister number of . The fixed point classes of are the projections
of the fixed point sets of the lift-factors and are the same as those of
Schirmer. An equivalence relation is defined on the fundamental group of
such that the number of equivalence classes equals the Reidemeister number. We
prove that if is a manifold of dimension at least three, then algebraically
the orbit configuration space approach is the same as one utilizing the
universal covering space. The Jiang subgroup is extended to -valued maps as
a subgroup of the group of covering transformations of the orbit configuration
space and used to find conditions under which the Nielsen number of an
-valued map equals its Reidemeister number. If an -valued map splits into
single-valued maps, then its -valued Reidemeister number is the sum of
their Reidemeister numbers.Comment: near complete rewrite from previous versio
Bounds on thickness and loading noise of rotating blades and the favorable effect of blade sweep on noise reduction
The maxima of amplitudes of thickness and loading noise harmonics are established when the radial distribution of blade chord, thickness ratio, and lift coefficient is specified. It is first shown that only airfoils with thickness distribution and chordwise loading distributions which are symmetric with respect to midchord need be considered for finding the absolute maxima of thickness and loading noise. The resulting chordwise thickness and load distributions for these maximum noise conditions require infinite slope at some points along the chord but otherwise are uniform. It is shown that sweeping the blades reduces the thickness and loading noise, but there is no optimum sweep which generates the lowest noise
Reversal Modes of Simulated Iron Nanopillars in an Obliquely Oriented Field
Stochastic micromagnetic simulations are employed to study switching in
three-dimensional magnetic nanopillars exposed to highly misaligned fields. The
switching appears to proceed through two different decay modes, characterized
by very different average lifetimes and different average values of the
transverse magnetization components.Comment: 3 pages, 4 figure
Short distance physics with heavy quark potentials
We present lattice studies of heavy quark potentials in the quenched
approximation of QCD at finite temperatures. Both, the color singlet and color
averaged potentials are calculated. While the potentials are well known at
large distances, we give a detailed analysis of their short distance behavior
(from 0.015 fm to 1 fm) near the critical temperature. At these distances we
expect that the T-dependent potentials go over into the zero temperature
potential. Indeed, we find evidences that the temperature influence gets
suppressed and the potentials starts to become a unique function of the
underlying distance scale. We use this feature to normalize the heavy quark
potentials at short distances and extract the free energy of the quark system
in a gluonic heat bath.Comment: Lattice2001(hightemp), 3 pages, 2 figure
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