Search results for "signal processing"

Which Reaches the Bottom First?

2008

A well-known classroom demonstration involves the rolling of hollow and solid objects down an incline.1 The fact that the objects roll at different rates can be used as a starting point in introducing students to rotational dynamics and rotational kinetic energy. In this paper we describe a simple quantitative version of the demonstration that is suitable for use as a laboratory experiment.

Aging effects manifested in the potential-energy landscape of a model glass former

2010

We present molecular dynamics simulations of a model glass-forming liquid (the binary Kob-Anderson Lennard-Jones model) and consider the distributions of inherent energies and metabasins during aging. In addition to the typical protocol of performing a temperature jump from a high temperature to a low destination temperature, we consider the temporal evolution of the distributions after an 'up-jump', i.e. from a low to a high temperature. In this case the distribution of megabasin energies exhibits a transient two-peak structure. Our results can qualitatively be rationalized in terms of a trap model with a Gaussian distribution of trap energies. The analysis is performed for different syste…

Nuclear energy and radiochemistry

2007

On the super-energy radiative gravitational fields

2012

We extend our recent analysis (Ferrando J J and S\'aez J A 2012 Class. Quantum Grav. 29 075012) on the Bel radiative gravitational fields to the super-energy radiative gravitational fields defined by Garc\'{\i}a-Parrado (Class. Quantum Grav. 25 015006). We give an intrinsic characterization of the {\it new radiative fields}, and consider some distinguished classes of both radiative and non radiative fields. Several super-energy inequalities are improved.

Algebraic Quantization, Good Operators and Fractional Quantum Numbers

1995

The problems arising when quantizing systems with periodic boundary conditions are analysed, in an algebraic (group-) quantization scheme, and the ``failure" of the Ehrenfest theorem is clarified in terms of the already defined notion of {\it good} (and {\it bad}) operators. The analysis of ``constrained" Heisenberg-Weyl groups according to this quantization scheme reveals the possibility for new quantum (fractional) numbers extending those allowed for Chern classes in traditional Geometric Quantization. This study is illustrated with the examples of the free particle on the circumference and the charged particle in a homogeneous magnetic field on the torus, both examples featuring ``anomal…

Focal-shift formula in apodized nontelecentric focusing systems

2007

A single analytical formulation for evaluating the focal shift in any apodized nontelecentric focusing setup is reported. The formulation is also useful in the case of imaged paraxial beams. We show explicitly that the magnitude of the focal shift is determined by only one parameter that depends on the effective width of the pupil filter and its axial position. To illustrate our approach we examine different focusing setups.

An energy residual-based approach to gradient effects within the mechanics of generalized continua

2012

AbstractGeneralized continua exhibiting gradient effects are addressed through a method grounded on the energy residual (ER)-based gradient theory by the first author and coworkers. A main tool of this theory is the Clausius-Duhem inequality cast in a form differing from the classical one only by a nonstandard extra term, the (nonlocality) ER, required to satisfy the insulation condition (its global value has to vanish or to take a known value). The ER carries in the nonlocality features of the mechanical problem through a strain-like rate field, being the specific nonlocality source, and a concomitant higher-order long-range stress (or microstress) field. The thermodynamic restrictions on …

Stability of the intrinsic energy vanishing in the Schwarzschild metric under a slow rotation

2014

The linearized Kerr metric is considered and put in some Gauss coordinates which are further {\em intrinsic} ones. The linear and angular 4-momenta of this metric are calculated in these coordinates and the resulting value is just zero. Thus, the global vanishing previously found for the Schwarzschild metric remains linearly stable under slow rotational perturbations of this metric.

On the uniqueness of the space-time energy in General Relativity. The illuminating case of the Schwarzschild metric

2013

The case of asymptotic Minkowskian space-times is considered. A special class of asymptotic rectilinear coordinates at the spatial infinity, related to a specific system of free falling observers, is chosen. This choice is applied in particular to the Schwarzschild metric, obtaining a vanishing energy for this space-time. This result is compared with the result of some known theorems on the uniqueness of the energy of any asymptotic Minkowskian space, showing that there is no contradiction between both results, the differences becoming from the use of coordinates with different operational meanings. The suitability of Gauss coordinates when defining an {\em intrinsic} energy is considered a…

"Gravitational waves from newly born, hot neutron stars"

2003

We study the gravitational radiation associated to the non--radial oscillations of newly born, hot neutron stars. The frequencies and damping times of the relevant quasi--normal modes are computed for two different models of proto--neutron stars, at different times of evolution, from its birth until it settles down as a cold neutron star. We find that the oscillation properties of proto--neutron stars are remarkably different from those of their cold, old descendants and that this affects the characteristic features of the gravitational signal emitted during the post-collapse evolution. The consequences on the observability of these signals by resonant--mass and interferometric detectors ar…