Pattern phase diagram for 2D arrays of coupled limit-cycle oscillators

Arrays of coupled limit-cycle oscillators represent a paradigmatic example for studying synchronization and pattern formation. They are also of direct relevance in the context of currently emerging experiments on nano- and optomechanical oscillator arrays. We find that the full dynamical equations for the phase dynamics of such an array go beyond previously studied Kuramoto-type equations. We analyze the evolution of the phase field in a two-dimensional array and obtain a "phase diagram" for the resulting stationary and non-stationary patterns. The possible observation in optomechanical arrays is discussed briefly

Bauschinger effect in thin metallic films by fem simulations

Unpassivated free-standing gold and aluminum thin films (thickness ~ 200-400 nm, mean grain size dm,Au≈ 70-80nm, dm,Al≈ 120-200nm), subjected to tensile tests show Bauschinger effect (BE) during unloading [1, 2]. The focus of this work is to investigate the effect of microstructural heterogeneity such as grain sizes on the BE and the macroscopic deformation behavior in thin metallic films. The finite element code LAGAMINE is used to model the response of films involving sets of grains with different strengths. The numerical results are compared with experimental results from tensile tests on aluminum thin films from the work of Rajagopalan, et al. [2]

Resonances in dissipative optomechanics with nanoparticles: Sorting, speed rectification and transverse cooling

The interaction between dielectric particles and a laser-driven optical cavity gives rise to both conservative and dissipative dynamics, which can be used to levitate, trap and cool nanoparticles. We analytically and numerically study a two-mode setup in which the optical potentials along the cavity axis cancel, so that the resulting dynamics is almost purely dissipative. For appropriate detunings of the laser-drives, this dissipative optomechanical dynamics can be used to sort particles according to their size, to rectify their velocities and to enhance transverse cooling

Entanglement Rate for Gaussian Continuous Variable Beams

We derive a general expression that quantifies the total entanglement production rate in continuous variable systems, where a source emits two entangled Gaussian beams with arbitrary correlators.This expression is especially useful for situations where the source emits an arbitrary frequency spectrum,e.g. when cavities are involved. To exemplify its meaning and potential, we apply it to a four-mode optomechanical setup that enables the simultaneous up- and down-conversion of photons from a drive laser into entangled photon pairs. This setup is efficient in that both the drive and the optomechanical up- and down-conversion can be fully resonant.Comment: 18 pages, 6 figure

Modes of a rotating astigmatic optical cavity

Nuevamente sacado à luz, y de muchos errores purgadoMarca tip. en port.Texto a dos columnasDatos de ed. preceden a "segunda parte

Geometric phases in astigmatic optical modes of arbitrary order

The transverse spatial structure of a paraxial beam of light is fully characterized by a set of parameters that vary only slowly under free propagation. They specify bosonic ladder operators that connect modes of different order, in analogy to the ladder operators connecting harmonic-oscillator wave functions. The parameter spaces underlying sets of higher-order modes are isomorphic to the parameter space of the ladder operators. We study the geometry of this space and the geometric phase that arises from it. This phase constitutes the ultimate generalization of the Gouy phase in paraxial wave optics. It reduces to the ordinary Gouy phase and the geometric phase of non-astigmatic optical modes with orbital angular momentum states in limiting cases. We briefly discuss the well-known analogy between geometric phases and the Aharonov-Bohm effect, which provides some complementary insights in the geometric nature and origin of the generalized Gouy phase shift. Our method also applies to the quantum-mechanical description of wave packets. It allows for obtaining complete sets of normalized solutions of the Schr\"odinger equation. Cyclic transformations of such wave packets give rise to a phase shift, which has a geometric interpretation in terms of the other degrees of freedom involved.Comment: final versio

On Damage Characterization of a Steel Sheet

Ductile damage is a physical phenomena which involves progressive deterioration of mechanical properties of metals, when undergoing high deformations. Compared to plasticity, the physical mechanisms behind damage are more complex and the microscale is not longer negligible. In mathematical damage models, founding an optimal set of material parameters can be a hard task due to the strong coupling and non-linearity of the equations. An identification strategy is then crucial to arrive to a general set of parameters. Therefore, we address the fully characterization of a ferritic steel sheet, involving the elasto-plastic and damage parameters. This poster presents an hybrid experimental-numerical procedure, coupling numerical simulations, optimization algorithms and digital image correlation measurements, over a set of representative experimental and numerical results of tensile, shear and plane strain tests in different material directions. Due to the small thickness of the sheet, the constitutive model is very prone to localization into a shear band difficulting the damage parameters identification. It is found that a porosity induced inhomogeneity plus a mixed hardening can delay localization and represent the entire deformation range of the tests, leading to acceptable results. Different set of parameters are also obtained and then validated with experimental results. This localization phenomena should be carefully considered in applications involving complex strain paths

Reference Architecture for e-Learning Solutions

In deze scriptie worden de volgende drie modellen en raamwerken voor e-Learning besproken: het e-Learning raamwerk ontwikkeld voor de UKeU, het model voor Web-based Instructional Systems ontwikkeld door Retalis en Avgeriou en het LTSA ontwikkeld door het IEEE. Deze drie modellen vormen de theoretische basis voor een Managed Learning Environment die als domeinmodel dienen voor e-Learning oplossingen