29,279 research outputs found
Crude oil desulfurization
High sulfur crude oil is desulfurized by a low temperature (25-80 C.) chlorinolysis at ambient pressure in the absence of organic solvent or diluent but in the presence of water (water/oil=0.3) followed by a water and caustic wash to remove sulfur and chlorine containing reaction products. The process described can be practiced at a well site for the recovery of desulfurized oil used to generate steam for injection into the well for enhanced oil recovery
Nonconservative higher-order hydrodynamic modulation instability
The modulation instability (MI) is a universal mechanism that is responsible
for the disintegration of weakly nonlinear narrow-banded wave fields and the
emergence of localized extreme events in dispersive media. The instability
dynamics is naturally triggered, when unstable energy side-bands located around
the main energy peak are excited and then follow an exponential growth law. As
a consequence of four wave mixing effect, these primary side-bands generate an
infinite number of additional side-bands, forming a triangular side-band
cascade. After saturation, it is expected that the system experiences a return
to initial conditions followed by a spectral recurrence dynamics. Much complex
nonlinear wave field motion is expected, when the secondary or successive
side-band pair that are created are also located in the finite instability gain
range around the main carrier frequency peak. This latter process is referred
to as higher-order MI. We report a numerical and experimental study that
confirm observation of higher-order MI dynamics in water waves. Furthermore, we
show that the presence of weak dissipation may counter-intuitively enhance wave
focusing in the second recurrent cycle of wave amplification. The
interdisciplinary weakly nonlinear approach in addressing the evolution of
unstable nonlinear waves dynamics may find significant resonance in other
nonlinear dispersive media in physics, such as optics, solids, superfluids and
plasma
Anisotropic superconducting properties of aligned SmLaFeAsOF microcrystalline powder
The SmLaFeAsOF compound is a quasi-2D
layered superconductor with a superconducting transition temperature T = 52
K. Due to the Fe spin-orbital related anisotropic exchange coupling
(antiferromagnetic or ferromagnetic fluctuation), the tetragonal
microcrystalline powder can be aligned at room temperature using the
field-rotation method where the tetragonal -plane is parallel to the
aligned magnetic field B and -axis along the rotation axis.
Anisotropic superconducting properties with anisotropic diamagnetic ratio
2.4 + 0.6 was observed from low field susceptibility
(T) and magnetization M(B). The anisotropic low-field phase diagram
with the variation of lower critical field gives a zero-temperature penetration
depth (0) = 280 nm and (0) = 120 nm. The magnetic
fluctuation used for powder alignment at 300 K may be related with the pairing
mechanism of superconductivity at lower temperature.Comment: 4 pages, 6 figure
Clustering in Hilbert space of a quantum optimization problem
The solution space of many classical optimization problems breaks up into
clusters which are extensively distant from one another in the Hamming metric.
Here, we show that an analogous quantum clustering phenomenon takes place in
the ground state subspace of a certain quantum optimization problem. This
involves extending the notion of clustering to Hilbert space, where the
classical Hamming distance is not immediately useful. Quantum clusters
correspond to macroscopically distinct subspaces of the full quantum ground
state space which grow with the system size. We explicitly demonstrate that
such clusters arise in the solution space of random quantum satisfiability
(3-QSAT) at its satisfiability transition. We estimate both the number of these
clusters and their internal entropy. The former are given by the number of
hardcore dimer coverings of the core of the interaction graph, while the latter
is related to the underconstrained degrees of freedom not touched by the
dimers. We additionally provide new numerical evidence suggesting that the
3-QSAT satisfiability transition may coincide with the product satisfiability
transition, which would imply the absence of an intermediate entangled
satisfiable phase.Comment: 11 pages, 6 figure
Speed of light as measured by two terrestrial stable clocks
Despite the recent criticism within the special theory of relativity, there exists an arrangement of stable clocks rotating with the earth which predicts diurnal variations of the one-way speed of light, as suggested previously
Approximating random quantum optimization problems
We report a cluster of results regarding the difficulty of finding
approximate ground states to typical instances of the quantum satisfiability
problem -QSAT on large random graphs. As an approximation strategy, we
optimize the solution space over `classical' product states, which in turn
introduces a novel autonomous classical optimization problem, PSAT, over a
space of continuous degrees of freedom rather than discrete bits. Our central
results are: (i) The derivation of a set of bounds and approximations in
various limits of the problem, several of which we believe may be amenable to a
rigorous treatment. (ii) A demonstration that an approximation based on a
greedy algorithm borrowed from the study of frustrated magnetism performs well
over a wide range in parameter space, and its performance reflects structure of
the solution space of random -QSAT. Simulated annealing exhibits
metastability in similar `hard' regions of parameter space. (iii) A
generalization of belief propagation algorithms introduced for classical
problems to the case of continuous spins. This yields both approximate
solutions, as well as insights into the free energy `landscape' of the
approximation problem, including a so-called dynamical transition near the
satisfiability threshold. Taken together, these results allow us to elucidate
the phase diagram of random -QSAT in a two-dimensional
energy-density--clause-density space.Comment: 14 pages, 9 figure
Doping studies of Ga0.5In0.5P organometallic vapor-phase epitaxy
Journal ArticlePresents doping studies of gallium[sub0.5] indium[sub0.5] phosphorus organometallic vapor-phase epitaxy. Distribution coefficient of indium; Description of growth conditions; Case of poor growth morphology for gallium[sub0.5] indium[sub0.5] phosphorus
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