Search results for "OSCILLATOR"

Dynamics of Pattern Formation in Biomimetic Systems

2008

This paper is an attempt to conceptualize pattern formation in self-organizing systems and, in particular, to understand how structures, oscillations or waves arise in a steady and homogenous environment, a phenomenon called symmetry breaking. The route followed to develop these ideas was to couple chemical oscillations produced by Belousov-Zhabotinsky reaction with confined reaction environments, the latter being an essential requirement for any process of Life. Special focus was placed on systems showing organic or lipidic compartments, which represent more reliable biomimetic matrices.

Solving fully randomized first-order linear control systems: Application to study the dynamics of a damped oscillator with parametric noise under sto…

2022

[EN] This paper is devoted to study random linear control systems where the initial condition, the final target, and the elements of matrices defining the coefficients are random variables, while the control is a stochastic process. The so-called Random Variable Transformation technique is adapted to obtain closed-form expressions of the probability density functions of the solution and of the control. The theoretical findings are applied to study the dynamics of a damped oscillator subject to parametric noise.

A simplified analysis for the evaluation of stochastic response of elasto-plastic oscillators

1999

Abstract The paper deals with dynamic hysteretic oscillators without post-yielding hardening, called ideal elasto-plastic oscillators, subjected to white noise. They are characterized by the fact that they do not reach stationarity even though excited by stationary stochastic processes. A simplified solution procedure to capture this behaviour is presented in this paper. It is based on modelling the accumulated plastic deformations as a homogeneous compound Poisson process. In particular, two aspects are addressed in the paper: (1) evaluation of the probabilistic parameters of the accumulated plastic deformation process; and (2) evaluation of the second-order cumulants of the response by me…

Phase-bistable patterns and cavity solitons induced by spatially periodic injection into vertical-cavity surface-emitting lasers

2014

Spatial rocking is a kind of resonant forcing able to convert a self-oscillatory system into a phase-bistable, pattern forming system, whereby the phase of the spatially averaged oscillation field locks to one of two values differing by $\ensuremath{\pi}$. We propose the spatial rocking in an experimentally relevant system---the vertical-cavity surface-emitting laser (VCSEL)---and demonstrate its feasibility through analytical and numerical tools applied to a VCSEL model. We show phase bistability, spatial patterns, such as roll patterns, domain walls, and phase (dark-ring) solitons, which could be useful for optical information storage and processing purposes.

Electroretinographic oscillatory potentials in insulin-dependent diabetes patients: A long-term follow-up.

2002

Purpose: The aim of this research was to study the relevance of long-term follow-up of electroretinographic oscillatory potentials (OPs) in predicting the onset of minimal non-proliferative diabetic retinopathy in insulin-dependent diabetes patients. Methods: A total of 80 insulin-dependent diabetics, with normal fundi and normal OPs at first examination, were followed prospectively for 10 years. Oscillatory potentials were measured and fundus examinations performed once or twice per year. Results: During follow-up, 35% of patients developed diabetic retinopathy after a mean disease duration of 12 ± 2 years. A decrease in OP amplitudes was seen in 46% of this group, but reductions were also…

A Compact SPICE Model for Organic TFTs and Applications to Logic Circuit Design

2016

This work introduces a compact DC model developed for organic thin film transistors (OTFTs) and its SPICE implementation. The model relies on a modified version of the gradual channel approximation that takes into account the contact effects, occurring at nonohmic metal/organic semiconductor junctions, modeling them as reverse biased Schottky diodes. The model also comprises channel length modulation and scalability of drain current with respect to channel length. To show the suitability of the model, we used it to design an inverter and a ring oscillator circuit. Furthermore, an experimental validation of the OTFTs has been done at the level of the single device as well as with a discrete-…

Direct Numerical Simulation of Pulsatile Turbulent Channel Flow

2008

A bounded version of bosonic creation and annihilation operators and their related quasi-coherent states

2007

Coherent states are usually defined as eigenstates of an unbounded operator, the so-called annihilation operator. We propose here possible constructions of {\em quasi-coherent states}, which turn out to be {\em quasi} eigenstate of a \underline{bounded} operator related to an annihilation-like operator. We use this bounded operator to construct a sort of modified harmonic oscillator and we analyze the dynamics of this oscillator from an algebraic point of view.

A theoretical study of the electronic spectrum of thiophene

1993

Abstract The electronic spectrum of thiophene has been studied using multiconfiguration second-order perturbation theory and extended ANO basis sets. The calculations comprise four singlet valence excited states and the 3s3p3rd Rydberg series. The lowest triplet states were included and some n-π* and n-σ* states. The results have been used to assign the experimental spectrum below 8.0 eV, with a maximum deviation of about 0.1 eV for vertical transition energies. The calculations place the 2 1A1 valence state at 5.33 eV, below the 1 1B2 valence state at 5.72 eV, and the most intense valence transitions at 6.69 eV (3 1A1) and 7.32 eV (4 1B2) with oscillator strengths 0.19 and 0.39, respective…

Nonstationary response envelope probability densities of nonlinear oscillators

2006

The nonstationary random response of a class of lightly damped nonlinear oscillators subjected to Gaussian white noise is considered. An approximate analytical method for determining the response envelope statistics is presented. Within the framework of stochastic averaging, the procedure relies on the Markovian modeling of the response envelope process through the definition of an equivalent linear system with response-dependent parameters. An approximate solution of the associated Fokker-Planck equation is derived by resorting to a Galerkin scheme. Specifically, the nonstationary probability density function of the response envelope is expressed as the sum of a time-dependent Rayleigh dis…