1,720,960 research outputs found
Hysteresis and creep: Comparison between a power-law model and Kuhnen's model
No full textIn this paper we analyze some properties of a recently proposed model of hysteresis and creep (related to a circuit model, whose only nonlinear element is based on a power law) and compare it with the well-known Kuhnen's model. A first qualitative comparison relies on the analysis of the behavior of the elementary cell of each model. Their responses to step inputs (which allow to better evidence the creep effect) are analyzed and compared. Then, a quantitative comparison is proposed, based on the fitting performances of the two models on experimental data measured from a commercial piezoelectric actuator
A circuit model of hysteresis and creep
No full textA circuit architecture that models hysteretic phenomena is proposed. The model is flexible enough to reproduce both rate-independent hysteresis and thermal relaxation effects (creep), commonly observed in many real-world physical systems such as piezoelectric actuators. By suitably tuning the nonlinear characteristics of the resistive elements of the network, the well-known log(t) time dependence of the creep relaxation dynamics can be accurately reproduced. An identification procedure is proposed, and two test cases are discussed
Open-Loop Compensation of Hysteresis and Creep Through a Power-Law Circuit Model
No full textThe inverse of a recently proposed hysteresis and creep circuit model is proposed and discussed. The model is particularly suitable for piezoelectric actuators and its inverse can be used for open-loop compensation of the undesired nonlinearities in high-precision applications. The inversemodel is defined, analyzed in terms of conditions ensuring a correct compensation, and discretized to provide a digital compensation algorithm suitable for implementation in low-cost programmable devices. Quantitative results on experimental data are provided and discussed, including the compensation on an atomic force microscope
Phase analysis method for burst onset prediction
No full textThe response of bursting neurons to fluctuating inputs is usually hard to predict, due to their strong nonlinearity. For the same reason, decoding the injected stimulus from the activity of a bursting neuron is generally difficult. In this paper we propose a method describing (for neuron models) a mechanism of phase coding relating the burst onsets with the phase profile of the input current. This relation suggests that burst onset may provide a way for postsynaptic neurons to track the input phase. Moreover, we define a method of phase decoding to solve the inverse problem and estimate the likelihood of burst onset given the input state. Both methods are presented here in a unified framework, describing a complete coding-decoding procedure. This procedure is tested by using different neuron models, stimulated with different inputs (stochastic, sinusoidal, up, and down states). The results obtained show the efficacy and broad range of application of the proposed methods. Possible applications range from the study of sensory information processing, in which phase-of-firing codes are known to play a crucial role, to clinical applications such as deep brain stimulation, helping to design stimuli in order to trigger or prevent neural bursting
Modeling and compensation of hysteresis and creep: The HysTool toolbox
No full textThis paper describes the MATLAB toolbox HysTool for the identification from experimental measurements and the simulation of four different hysteresis and creep models (Preisach, Prandtl-Ishlinskii, Kuhnen and power-law). The toolbox can automatically generate the inverse models (compensators) and also provide (for three out of four models) the C files for their microcontroller implementation. Tests on two different datasets are provided
A circuit model for open-loop compensation of hysteresis
No full textHysteresis is a nonlinear phenomenon useful whenever memory is required, but that can become annoying in applications where linearity is desired. In these cases, a possible way to reduce the inconvenience is to compensate the undesired memory effect by pre-processing the input signal through the
hysteresis inverse model. In this paper, the inverse of a recently proposed circuit modeling rate-independent hysteretic phenomena is presented and discussed. The inverse circuit model is tested through experimental data measured from a commercial piezoelectric actuator. The obtained results are compared with those obtained by resorting to the well-known Preisach model. All the circuit simulations are performed by using PSPICE
A low-complexity circuit model of hysteresis
No full textA circuit architecture modelling rate-independenthysteretic phenomena is presented and discussed. The core ofthe circuit is a ladder structure with longitudinal nonlinearresistors and transverse linear capacitors. In a separate loop, alinear combination of input and capacitor voltages provides thedriving voltage for a resistor with monotonic, piecewise-lineardriving-point characteristic. The resistor current represents theoutput variable. The circuit parameters can be found fromexperimental data through a standard quadratic programmingoptimization procedure. The model fitting features are tested byusing two experimental data sets. One is theB(H)function of amagnetic material; the other is the deformation of a piezoelectricactuator as a function of the applied voltage. In this last case,an accurate comparison with the predictions of the well-knownPreisach model evidences that the circuit model achieves the sameaccuracy with a much smaller number of parameters. All thecircuit simulations are performed by using PSPICE
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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