18,941 research outputs found
On the determination of the earthquake slip distribution via linear programming techniques
The description that one can have of the seismic source is the mani-
festation of an imagined model, obviously outlined from Physic Theories
and supported by mathematical methods. In that context, the modelling
of earthquake rupture consists in finding values of the parameters of the
selected physics-mathematical model, through which it becomes possible
to reproduce numerically the records of earthquake effects on the Earths
surface. We present and test a Linear Programming (LP) inversion in dual
form, for reconstructing the kinematics of the rupture of large earthquakes
through space-time seismic slip distribution on finite faults planes
Extended Seismic Source Characterisation using Linear Programming Inversion in a Dual Formulation
A linear programming (LP) inversion method in a dual formulation was applied to reconstruct the kinematics of
finite seismic ruptures. In a general setting, this approach can yield results from several data sets: strong ground
motion, teleseismic waveforms or/and geodesic data (static deformation). The dual formulation involves the
transformation of a normal solution space into an equivalent but reduced space: the dual space. The practical
result of this transformation is a simpler inversion problem that is therefore faster to resolve, more stable and
more robust. The developed algorithm includes a forward problem that calculates Green’s functions using a
finite differences method with a 3D structure model. To evaluate the performance of this algorithm, we applied it
to the reconstitution of a realistic slip distribution model from a data set synthesised using this model, i.e., the
solution of the forward problem. Several other standard inversion approaches were applied to the same synthetic
data for comparison
On the Resolution of Singularities of Multiple Mellin-Barnes Integrals
One of the two existing strategies of resolving singularities of multifold
Mellin-Barnes integrals in the dimensional regularization parameter, or a
parameter of the analytic regularization, is formulated in a modified form. The
corresponding algorithm is implemented as a Mathematica code MBresolve.mComment: LaTeX, 10 page
Asymptotic Bound-state Model for Feshbach Resonances
We present an Asymptotic Bound-state Model which can be used to accurately
describe all Feshbach resonance positions and widths in a two-body system. With
this model we determine the coupled bound states of a particular two-body
system. The model is based on analytic properties of the two-body Hamiltonian,
and on asymptotic properties of uncoupled bound states in the interaction
potentials. In its most simple version, the only necessary parameters are the
least bound state energies and actual potentials are not used. The complexity
of the model can be stepwise increased by introducing threshold effects,
multiple vibrational levels and additional potential parameters. The model is
extensively tested on the 6Li-40K system and additional calculations on the
40K-87Rb system are presented.Comment: 13 pages, 8 figure
On the Finite Temperature Formalism in Integrable Quantum Field Theories
Two different theoretical formulations of the finite temperature effects have
been recently proposed for integrable field theories. In order to decide which
of them is the correct one, we perform for a particular model an explicit check
of their predictions for the one-point function of the trace of the
stress-energy tensor, a quantity which can be independently determined by the
Thermodynamical Bethe Ansatz.Comment: 12 pages, corrected some typos and an equatio
Ways of improvement of technological equipment performance
Increasing of production performance of production systems and equipment in the meat-processing industry is integrally linked to maintenance activities. The article analyzes the influence of technological effectiveness, level of hygiene, reliability and simplicity of equipment design on the main parameters of meat products quality. Here it is shown that the strategy of Total Productive Maintenance (TRM) and Lean production is important tool for assessment of parameter of the Overall Equipment Effectiveness (OEE), which is used to assess the main types of losses that reduce the equipment productivity. The link of influence between the structural and mechanical properties of food masses, the moisture content of the initial food raw material, the temperature and viscosity, the processing pressure, and the density for the optimal operating terms of the equipment are analyzed in this research. With the help of OEE concept, the time losses related to the features of the equipment functioning are determined. The types of losses are classified as follows: downtime and readjustment (availability or readiness for operation) of equipment, short-term shutdown of equipment and a decrease in processing speed (productivity or performance rate of the equipment), product rejects and product losses (quality losses) during startup of equipment. While analyzing of the operation of vacuum filler for sausages production, the values of parameters of equipment availability, it productivity and product quality are calculated. The availability index is 0.79, the productivity index is 0.76, and the product quality index is 0.95. Taking into account the obtained data on equipment availability, productivity and product quality, it is determined that the overall equipment effectiveness (OEE) accounts for 57%. The application of this method for studying the overall equipment effectiveness operation can be applied to any technological equipment used in the meat-processing industry and allows eliminating many problems that arise during the operation of technological equipment, improving its technical and economic parameters, and developing a system of measures for improvement of its maintenance and repair
Predicting scattering properties of ultracold atoms: adiabatic accumulated phase method and mass scaling
Ultracold atoms are increasingly used for high precision experiments that can
be utilized to extract accurate scattering properties. This calls for a
stronger need to improve on the accuracy of interatomic potentials, and in
particular the usually rather inaccurate inner-range potentials. A boundary
condition for this inner range can be conveniently given via the accumulated
phase method. However, in this approach one should satisfy two conditions,
which are in principle conflicting, and the validity of these approximations
comes under stress when higher precision is required. We show that a better
compromise between the two is possible by allowing for an adiabatic change of
the hyperfine mixing of singlet and triplet states for interatomic distances
smaller than the separation radius. A mass scaling approach to relate
accumulated phase parameters in a combined analysis of isotopically related
atom pairs is described in detail and its accuracy is estimated, taking into
account both Born-Oppenheimer and WKB breakdown. We demonstrate how numbers of
singlet and triplet bound states follow from the mass scaling.Comment: 14 pages, 9 figure
Sympathetic cooling route to Bose-Einstein condensate and Fermi-liquid mixtures
We discuss a sympathetic cooling strategy that can successfully mitigate
fermion-hole heating in a dilute atomic Fermi-Bose mixture and access the
temperature regime in which the fermions behave as a Fermi liquid. We introduce
an energy-based formalism to describe the temperature dynamics with which we
study a specific and promising mixture composed of 6Li and 87Rb. Analyzing the
harmonically trapped mixture, we find that the favourable features of this
mixture are further enhanced by using different trapping frequencies for the
two species.Comment: 4 pages, 2 figure
Proton transport and torque generation in rotary biomotors
We analyze the dynamics of rotary biomotors within a simple
nano-electromechanical model, consisting of a stator part and a ring-shaped
rotor having twelve proton-binding sites. This model is closely related to the
membrane-embedded F motor of adenosine triphosphate (ATP) synthase, which
converts the energy of the transmembrane electrochemical gradient of protons
into mechanical motion of the rotor. It is shown that the Coulomb coupling
between the negative charge of the empty rotor site and the positive stator
charge, located near the periplasmic proton-conducting channel (proton source),
plays a dominant role in the torque-generating process. When approaching the
source outlet, the rotor site has a proton energy level higher than the energy
level of the site, located near the cytoplasmic channel (proton drain). In the
first stage of this torque-generating process, the energy of the
electrochemical potential is converted into potential energy of the
proton-binding sites on the rotor. Afterwards, the tangential component of the
Coulomb force produces a mechanical torque. We demonstrate that, at low
temperatures, the loaded motor works in the shuttling regime where the energy
of the electrochemical potential is consumed without producing any
unidirectional rotation. The motor switches to the torque-generating regime at
high temperatures, when the Brownian ratchet mechanism turns on. In the
presence of a significant external torque, created by ATP hydrolysis, the
system operates as a proton pump, which translocates protons against the
transmembrane potential gradient. Here we focus on the F motor, even though
our analysis is applicable to the bacterial flagellar motor.Comment: 24 pages, 5 figure
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