15,156 research outputs found
Tracking analysis of a first order phase- locked loop with two sinewaves modulation
Phase locked-loop tracking with sine wave modulation in Apollo communication system
Clearigate ® Treatments for Control of Giant Salvinia
Results of recent field trials using the chelated copper formulation
Clearigate®
4
showed that applying a 20% solution
by volume was effective for controlling populations of giant
salvinia in irrigation canals.
5
Lower rates may be efficacious,
thereby reducing chemical use and cost; however, little is
known about the dose-response effects of Clearigate®
against giant salvinia. The objective of this study was to determine
the effective rate range of chelated copper applied as
Clearigate® for control of giant salvinia
Exploration and exploitation in the presence of network externalities
This paper examines the conditions under which exploration of a new, incompatible technologyis
conducive to firm growth in the presence of network externalities. In particular,
this studyis motivated bythe divergent evolutions of the PC and the workstation markets in
response to a new technology: reduced instruction set computing (RISC). In the PC market,
Intel has developed new microprocessors bymaintaining compatibilitywith the established
architecture, whereas it was radicallyr eplaced byRISC in the workstation market. History
indicates that unlike the PC market, the workstation market consisted of a large number
of power users, who are less sensitive to compatibilitythan ordinaryusers. Our numerical
analysis indicates that the exploration of a new, incompatible technologyis more likelyto
increase the chance of firm growth when there are a substantial number of power users or
when a new technologyis introduced before an established technologytakes off.
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Extended BRST invariance in topological Yang Mills theory revisited
Extended BRST invariance (BRST plus anti-BRST invariances) provides in
principle a natural way of introducing the complete gauge fixing structure
associated to a gauge field theory in the minimum representation of the
algebra. However, as it happens in topological Yang Mills theory, not all gauge
fixings can be obtained from a symmetrical extended BRST algebra, where
antighosts belong to the same representation of the Lorentz group of the
corresponding ghosts. We show here that, at non interacting level, a simple
field redefinition makes it possible to start with an extended BRST algebra
with symmetric ghost antighost spectrum and arrive at the gauge fixing action
of topological Yang Mills theory.Comment: Interaction terms heve been included in all the calculations. Two
references added. Version to be published in Phys. Rev. D. 7 pages, Latex, no
figure
Kink pairs unbinding on domain walls and the sequence of phase transitions in fully frustrated XY models
The unbinding of kink pairs on domain walls in the fully frustrated XY model
(on square or triangular lattices) is shown to induce the vanishing of phase
coupling across the walls. This forces the phase transition, associated with
unbinding of vortex pairs to take place at a lower temperature than the other
phase transition, associated with proliferation of the Ising-type domain walls.
The results are applicable for a description of superconducting junction arrays
and wire networks in perpendicular magnetic field (corresponding to
half-integer number of flux quanta per each lattice plaquette), as well as of
planar antiferromagnets with a triangular lattice.Comment: 4 pages, ReVTeX, the final versio
Towards a Tetravalent Chemistry of Colloids
We propose coating spherical particles or droplets with anisotropic
nano-sized objects to allow micron-scale colloids to link or functionalize with
a four-fold valence, similar to the sp3 hybridized chemical bonds associated
with, e.g., carbon, silicon and germanium. Candidates for such coatings include
triblock copolymers, gemini lipids, metallic or semiconducting nanorods and
conventional liquid crystal compounds. We estimate the size of the relevant
nematic Frank constants, discuss how to obtain other valences and analyze the
thermal distortions of ground state configurations of defects on the sphere.Comment: Replaced to improve figures. 4 figures Nano Letter
Phase transitions in the antiferromagnetic XY model with a kagome lattice
The ground state of the antiferromagnetic XY model with a kagome lattice is
characterized by a well developed accidental degeneracy. As a consequence the
phase transition in this system consists in unbinding of pairs of fractional
vortices. Addition of the next-to-nearest neighbors (NNN) interaction leads to
stabilization of the long-range order in chirality (staggered chirality). We
show that the phase transition, related with destruction of this long-range
order, can happen as a separate phase transition below the temperature of the
fractional vortex pairs unbinding only if the NNN coupling is extremely weak,
and find how the temperature of this transition depends on coupling constants.
We also demonstarte that the antiferromagnetic ordering of chiralities and,
accordingly, the presence of the second phase transition are induced by the
free energy of spin wave fluctuations even in absence of the NNN coupling.Comment: 10 pages (Revtex) + 8 figures (in 2 postscript files
Evidence for a Two-stage Melting Transition of the Vortex Matter in Bi2Sr2Ca1Cu2O8+d Single Crystals obtained by Muon Spin Rotation
From muon spin rotation measurements on under- to overdoped Bi-2212 crystals
we obtain evidence for a two-stage transition of the vortex matter as a
function of temperature. The first transition is well known and related to the
irreversibility line (IL). The second one is located below the IL and has not
been previously observed. It occurs for all three sets of crystals and is
unrelated to the vortex mobility. Our data are consistent with a two-stage
melting scenario where the intra-planar melting of the vortex lattice and the
inter-planar decoupling of the vortex lines occur independently.Comment: 9 pages and 3 figure
Macroscopic traffic models from microscopic car-following models
We present a method to derive macroscopic fluid-dynamic models from
microscopic car-following models via a coarse-graining procedure. The method is
first demonstrated for the optimal velocity model. The derived macroscopic
model consists of a conservation equation and a momentum equation, and the
latter contains a relaxation term, an anticipation term, and a diffusion term.
Properties of the resulting macroscopic model are compared with those of the
optimal velocity model through numerical simulations, and reasonable agreement
is found although there are deviations in the quantitative level. The
derivation is also extended to general car-following models.Comment: 12 pages, 4 figures; to appear in Phys. Rev.
Vortex lattce melting in 2D superconductors and Josephson arrays
Monte Carlo simulations of 2D vortex lattice melting in a thin
superconducting film (or alternatively an array of Josephson junctions) are
performed in the London limit. Finite size scaling analyses are used to make a
detailed test of the dislocation mediated melting theory of KTNHY. We find that
the melting transition is weakly first order, with a jump in the shear modulus
very close to that predicted by the KTNHY theory. No hexatic liquid phase is
found.Comment: 12 pages, 4 figures (available on request from
[email protected]), REVTEX [we revise our conclusion on the order of the
melting transition from second to first order - new figure 4 added
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