6,619 research outputs found
Econometrics
Since the last decade we live in a digitalized world where many actions in human and economic life are monitored. This produces a continuous stream of new, rich and high quality data in the form of panels, repeated cross-sections and long time series . These data resources are available to many researchers at a low cost. This new erais fascinating for econometricians who can adress many open economic questions. To do so, new models are developed that call for elaborate estimation techniques. Fast personal computers play an integral part in making it possible to deal with this increased complexity. --
Hysteresis and avalanches in the T=0 random-field Ising model with 2-spin-flip dynamics
We study the non-equilibrium behavior of the three-dimensional Gaussian
random-field Ising model at T=0 in the presence of a uniform external field
using a 2-spin-flip dynamics. The deterministic, history-dependent evolution of
the system is compared with the one obtained with the standard 1-spin-flip
dynamics used in previous studies of the model. The change in the dynamics
yields a significant suppression of coercivity, but the distribution of
avalanches (in number and size) stays remarkably similar, except for the
largest ones that are responsible for the jump in the saturation magnetization
curve at low disorder in the thermodynamic limit. By performing a finite-size
scaling study, we find strong evidence that the change in the dynamics does not
modify the universality class of the disorder-induced phase transition.Comment: 9 pages, 10 figure
Near-BPS Skyrmions: Non-shell configurations and Coulomb effects
The relatively small binding energy in nuclei suggests that they may be well
represented by near-BPS Skyrmions since their mass is roughly proportional to
the baryon number For that purpose, we propose a generalization of the
Skyrme model with terms up to order six in derivatives of the pion fields and
treat the nonlinear and Skyrme terms as small perturbations. For our
special choice of mass term (or potential) , we obtain well-behaved
analytical BPS-type solutions with non-shell configurations for the baryon
density, as opposed to the more complex shell-like configurations found in most
extensions of the Skyrme model . Along with static and (iso)rotational
energies, we add to the mass of the nuclei the often neglected Coulomb energy
and isospin breaking term. Fitting the four model parameters, we find a
remarkable agreement for the binding energy per nucleon with respect to
experimental data. These results support the idea that nuclei could be near-BPS
Skyrmions.Comment: Correction of minors errors, references adde
Optimizing wireless access networks towards power consumption : influence of the optimization algorithm
Radiation reaction in the 2.5PN waveform from inspiralling binaries in circular orbits
In this Comment we compute the contributions of the radiation reaction force
in the 2.5 post-Newtonian (PN) gravitational wave polarizations for compact
binaries in circular orbits. (i) We point out and correct an inconsistency in
the derivation of Arun, Blanchet, Iyer, and Qusailah. (ii) We prove that all
contributions from radiation reaction in the 2.5PN waveform are actually
negligible since they can be absorbed into a modification of the orbital phase
at the 5PN order.Comment: 7 pages, no figures, submitted to CQ
Experimental Investigation of Nozzle/Plume Aerodynamics at Hypersonic Speeds
The work performed by D. W. Bogdanoff and J.-L. Cambier during the period of 1 Feb. - 31 Oct. 1992 is presented. The following topics are discussed: (1) improvement in the operation of the facility; (2) the wedge model; (3) calibration of the new test section; (4) combustor model; (5) hydrogen fuel system for combustor model; (6) three inch calibration/development tunnel; (7) shock tunnel unsteady flow; (8) pulse detonation wave engine; (9) DCAF flow simulation; (10) high temperature shock layer simulation; and (11) the one dimensional Godunov CFD code
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