959 research outputs found
Three-Body Dynamics and Self-Powering of an Electrodynamic Tether in a Plasmasphere
The dynamics of an electrodynamic tether in a three-body gravitational environment are investigated. In the classical two-body scenario the extraction of power is at the expense of orbital kinetic energy. As a result of power extraction, an electrodynamic tether satellite system loses altitude and deorbits. This concept has been proposed and well investigated in the past, for example for orbital debris mitigation and spent stages reentry. On the other hand, in the three-body scenario an electrodynamic tether can be placed in an equilibrium position fixed with respect to the two primary bodies without deorbiting, and at the same time generate power for onboard use. The appearance of new equilibrium positions in the perturbed three-body problem allow this to happen as the electrical power is extracted at the expenses of the plasma corotating with the primary body. Fundamental differences between the classical twobody dynamics and the new phenomena appearing in the circular restricted three-body problem perturbed by the electrodynamic force of the electrodynamic tether are shown in the paper. An interesting application of an electrodynamic tether placed in the Jupiter plasma torus is then considered, in which the electrodynamic tether generates useful electrical power of about 1 kW with a 20-km-long electrodynamic tether from the environmental plasma without losing orbital energy
Evaluation of the changes in working limits in an automobile assembly line using simulation
The aim of the work presented in this paper consists of the development of a decision-making support system, based on discrete-event simulation models, of an automobile assembly line which was implemented within an Arena simulation environment and focused at a very specific class of production lines with a four closed-loop network configuration. This layout system reflects one of the most common configurations of automobile assembly and preassembly lines formed by conveyors. The sum of the number of pallets on the intermediate buffers, remains constant, except for the fourth closed-loop, which depends on the four-door car ratio (x) implemented between the door disassembly and assembly stations of the car body. Some governing equations of the four closed-loops are not compatible with the capacities of several intermediate buffers for certain values of variable x. This incompatibility shows how the assembly line cannot operate in practice for x0,97 in a stationary regime, due to the starvation phenomenon or the failure of supply to the machines on the production line. We have evaluated the impact of the pallet numbers circulating on the first closed-loop on the performance of the production line, translated into the number of cars produced/hour, in order to improve the availability of the entire manufacturing system for any value of x. Until the present date, these facts have not been presented in specialized literature. © 2012 American Institute of Physics
On the radicality property for spaces of symbols of bounded Volterra operators
In a recent paper of the authors together with A. Aleman, it is shown that
the Bloch space in the unit disc has the following radicality
property: if an analytic function satisfies that , then
, for all . Since coincides with the
space of analytic symbols such that the
Volterra-type operator is bounded
on the classical weighted Bergman space , the radicality property
was used to study the composition of paraproducts and on
. Motivated by this fact, we prove that
also has the radicality property, for any radial weight . Unlike the
classical case, the lack of a precise description of
for a general radial weight, induces us to prove the radicality property for
from precise norm-operator results for compositions of analytic
paraproducts
Quark mass dependence of the rho and sigma from dispersion relations and Chiral Perturbation Theory
We use the one-loop Chiral Perturbation
Theory pion-pion scattering amplitude and dispersion theory in the form of
the inverse amplitude method, to study the quark mass dependence of the two
lightest resonances of the strong interactions, the f_0(600) (sigma) and the
rho-meson. As main results we find that the rho-pion-pion coupling constant is
almost quark mass independent and that the rho mass shows a smooth quark mass
dependence while that of the sigma shows a strong non-analyticity. These
findings are important for studies of the meson spectrum on the lattice.Comment: Final version to appear in Phys. Rev. Lett. References added and
typos corrected. 4 pages, three figure
Variability in disease phenotypes within a single PRNP genotype suggests the existence of multiple natural sheep scarpie strains within Europe
Variability of pathological phenotypes within classical sheep scrapie cases has been reported for some time, but in many instances it has been attributed to differences in the PRNP genotype of the host. To address this issue we have examined by immunohistochemistry (IHC) and Western blotting (WB) for the disease-associated form of the prion protein (PrPd), the brains of 23 sheep from five European countries, all of which were of the same ARQ/ARQ genotype. As a result of IHC examinations, sheep were distributed into five groups with different phenotypes and the groups were the same regardless of the scoring method used, ‘long’ or ‘short’ PrPd profiling. The groups made did not respond to the geographical origin of the cases and did not correlate with the vacuolar lesion profiles, which showed a high individual variability. Discriminatory IHC and WB methods coincided to detect a ‘CH1641-like’ case but otherwise correlated poorly in the classification of disease phenotypes. No other polymorphisms of the PRNP gene were found that could account for the pathological differences, except perhaps for a sheep from Spain with a mutation at codon 103 and a unique pathological phenotype. Preliminary evidence indicates that those different IHC phenotypes correlate with distinct biological properties on bioassay, suggesting that they are indicative of strain diversity. We therefore conclude that natural scrapie strains exist and that they can be revealed by detailed pathological examinations, which can be harmonized between laboratories to produce comparable results
Light propagation through optical media using metric contact geometry
In this work, we show that the orthogonality between rays and fronts of light
propagation in a medium is expressed in terms of a suitable metric contact
structure of the optical medium without boundaries. Moreover, we show that
considering interfaces (modeled as boundaries) orthogonality is no longer
fulfilled, leading to optical aberrations and in some cases total internal
reflection. We present some illustrative examples of this latter point.Comment: 8 pages, 7 figure
Dispersive amplitude and giant CP violation in B to three light-meson decays at LHCb
The LHCb collaboration has recently reported the largest CP violation effect
from a single amplitude, as well as other giant CP asymmetries in several
-meson decays into three charmless light mesons. It is also claimed that
this is predominantly due to rescattering in the
final state, particularly in the 1 to 1.5 GeV region. In these analyses the
amplitude is by default estimated from the
elastic scattering amplitude and does not describe the existing
scattering data. Here we show how the recent
model-independent dispersive analysis of data can
be easily implemented in the LHCb formalism. This leads to a more accurate
description of the asymmetry, while being consistent with the measured
scattering amplitude and confirming the prominent role of hadronic final state
interactions, paving the way for more elaborated analyses.Comment: 9 pages, 6 figures. Minor corrections and discussions were added.
Extended appendix with an additional improved model of the S-wave. Final
version to appear in Phys.Rev.Let
A Variational Method for the Propagation of Spacecraft Relative Motion.
A new formulation of the spacecraft relative motion for a generic orbit is presented based on the orbital propagation method proposed by Peláez et al. in 2006 [1]. Two models have been developed. In the first model the method is applied to each spacecraft using a time synchronization of the system dynamical states. In the second model we employ a local orbital reference frame with a linearization of gravitational terms, apply the method to the formation center of mass and propagate the relative dynamics with respect to the center of mass reference orbit. The models are compared in terms of computational speed for the case of a bounded triangular formatio
Perturbative QCD relations inspired by hypothetical tau leptons
We review our recent works on tests of perturbative QCD, inspired by the
relation between the hadronic decay of the tau lepton and the e+ e-
annihilation into hadrons. First, we present a set of commensurate scale
relations that probe the self-consistency of leading-twist QCD predictions for
any observable which defines an effective charge. These tests are independent
of the renormalization scheme and scale, and are applicable over wide data
ranges. As an example we apply this approach to R_{e+ e-}. Second, using a
differential form of these conmensurate scale relations, we present a method to
measure the QCD Gell-Mann--Low Psi function.Comment: To appear in the proceedings of the QCD 99 Euroconference, 7-13th
July 1999 Montpellier, France 4 pages, uses espcrc2.sty (included
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