28,459 research outputs found
Numerical studies of interacting vortices
To get a basic understanding of the physics of flowfields modeled by vortex filaments with finite vortical cores, systematic numerical studies of the interactions of two dimensional vortices and pairs of coaxial axisymmetric circular vortex rings were made. Finite difference solutions of the unsteady incompressible Navier-Stokes equations were carried out using vorticity and stream function as primary variables. Special emphasis was placed on the formulation of appropriate boundary conditions necessary for the calculations in a finite computational domain. Numerical results illustrate the interaction of vortex filaments, demonstrate when and how they merge with each other, and establish the region of validity for an asymptotic analysis
Coal desulfurization process
A method for chlorinolysis of coal is an organic solvent at a moderate temperautre and atmospheric pressure has been proven to be effective in removing sulfur, particularly the organic sulfur, from coal. Chlorine gas is bubbled through a slurry of moist coal in chlorinated solvent. The chlorinated coal is separated, hydrolyzed and the dechlorinated. Preliminary results of treating a high sulfutr (4.77%S) bituminous coal show that up to 70% organic sulfur, 90% hyritic sulfur and 76% total sulfur can be removed. The treated coal is dechlorinated by heating at 500 C. The presence of moisture helps to remove organic sulfur
Invisible Higgs boson, continuous mass fields and unHiggs mechanism
We explore the consequences of an electroweak symmetry breaking sector which
exhibits approximately scale invariant dynamics -- i.e., nontrivial fixed point
behavior, as in unparticle models. One can think of an unHiggs as a composite
Higgs boson with a continuous mass distribution. We find it convenient to
represent the unHiggs in terms of a Kallen-Lehmann spectral function, from
which it is simple to verify the generation of gauge boson and fermion masses,
and unitarization of WW scattering. We show that a spectral function with broad
support, which corresponds to approximate fixed point behavior over an extended
range of energy, can lead to an effectively invisible Higgs particle, whose
decays at LEP or LHC could be obscured by background.Comment: 8 page
New urea-absorbing polymers for artificial kidney machines
Etherified polymer is made from modified cellulose derivative which is reacted with periodate. It will absorb 2 grams of urea per 100 grams of polymer. Indications are that polymers could be used to help remove uremic wastes in artificial kidneys, or they could be administered orally as therapy for uremia
Aldehyde-containing urea-absorbing polysaccharides
A novel aldehyde containing polymer (ACP) is prepared by reaction of a polysaccharide with periodate to introduce aldehyde groups onto the C2 - C3 carbon atoms. By introduction of ether and ester groups onto the pendant primary hydroxyl solubility characteristics are modified. The ACP is utilized to absorb nitrogen bases such as urea in vitro or in vivo
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
Effective interactions between star polymers
We study numerically the effective pair potential between star polymers with
equal arm lengths and equal number of arms. The simulations were done for
the soft core Domb-Joyce model on the simple cubic lattice, to minimize
corrections to scaling and to allow for an unlimited number of arms. For the
sampling, we used the pruned-enriched Rosenbluth method (PERM). We find that
the potential is much less soft than claimed in previous papers, in particular
for . While we verify the logarithmic divergence of , with
being the distance between the two cores, predicted by Witten and Pincus, we
find for that the Mayer function is hardly distinguishable from that for
a Gaussian potential.Comment: 5 pages, 5 figure
Grand unification through gravitational effects
We systematically study the unification of gauge couplings in the presence of
(one or more) effective dimension-5 operators cHGG/4MPl, induced into the grand
unified theory by gravitational interactions at the Planck scale MPl. These
operators alter the usual condition for gauge coupling unification, which can,
depending on the Higgs content H and vacuum expectation value, result in
unification at scales MX significantly different than naively expected. We find
non-supersymmetric models of SU(5) and SO(10) unification, with natural Wilson
coefficients c, that easily satisfy the constraints from proton decay.
Furthermore, gauge coupling unification at scales as high as the Planck scale
seems feasible, possibly hinting at simultaneous unification of gauge and
gravitational interactions. In the Appendix we work out the group theoretical
aspects of this scenario for SU(5) and SO(10) unified groups in detail; this
material is also relevant in the analysis of non-universal gaugino masses
obtained from supergravity.Comment: 27 pages, 5 figures, 8 tables, 1 appendix, revtex; v2: introduction
and conclusion expanded, references added, minor changes, version published
in PR
Trellis phase codes for power-bandwith efficient satellite communications
Support work on improved power and spectrum utilization on digital satellite channels was performed. Specific attention is given to the class of signalling schemes known as continuous phase modulation (CPM). The specific work described in this report addresses: analytical bounds on error probability for multi-h phase codes, power and bandwidth characterization of 4-ary multi-h codes, and initial results of channel simulation to assess the impact of band limiting filters and nonlinear amplifiers on CPM performance
Experimental study of ion heating and acceleration during magnetic reconnection
Ion heating and acceleration has been studied in the well-characterized reconnection layer of the Magnetic Reconnection Experiment [M. Yamada , Phys. Plasmas 4, 1936 (1997)]. Ion temperature in the layer rises substantially during null-helicity reconnection in which reconnecting field lines are anti-parallel. The plasma outflow is sub-Alfvenic due to a downstream back pressure. An ion energy balance calculation based on the data and including classical viscous heating indicates that ions are heated largely via nonclassical mechanisms. The T-i rise is much smaller during co-helicity reconnection in which field lines reconnect obliquely. This is consistent with a slower reconnection rate and a smaller resistivity enhancement over the Spitzer value. These observations show that nonclassical dissipation mechanisms can play an important role both in heating the ions and in facilitating the reconnection process
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