1,720,972 research outputs found
Spice e PSpice esercitazioni di elettrotecnica
Get PDFQuesto testo si propone di introdurre lo studente all'apprendimento dell'Elettrotecnica, avvalendosi di una serie di esercizi da risolvere usando un moderno programma di analisi circuitale. Contemporaneamente, oltre alle soluzioni, per cosi' dire sperimentali, sono presentate le soluzioni analitiche ottenute per via teorica, applicando le leggi e i metodi dell'Elettrotecnica. Come dice il titolo stesso, il programma prescelto e' il ben noto Spice, sviluppato all'Universita' di Berkeley. Esso ha segnato l'inizio di un'epoca nel campo della simulazione dei circuiti ed e' stato universalmente adottato, nelle sue innumerevoli versioni commerciali, per la sua riconosciuta efficienza. PSpice, usato nello svolgere gli esercizi qui proposti, ne rappresenta una delle prime evoluzioni commerciali ed e' distribuito gratuitamente in una versione dimostrativa per PC, rendendo possibile una piu' ampia diffusione delle tecniche di simulazione. Il presente testo cerca anche di colmare, almeno in parte, la grave lacuna nella formazione universitaria degli studenti della Laurea triennale, rappresentata dalla difficolta' ad accedere a laboratori sperimentali, a causa dell'elevata numerosita' dei corsi di base, quali l'Elettrotecnica. Grazie agli esercizi proposti e all'uso di PSpice, gli studenti potranno compiere esperimenti come se avessero costruito un circuito reale in laboratorio, anche se e' opportuno ricordare che una reale verifica sperimentale rimane insostituibile per una buona formazione scientifica. Il libro e' diviso in due parti: la prima presenta i testi degli esercizi, con un breve richiamo, ove necessario, ai fondamenti utili per la loro soluzione; la seconda mostra le soluzioni dei problemi ricavate con PSpice e le verifiche analitiche effettuate analizzando i circuiti proposti. Gli argomenti trattati riguardano: l'analisi di circuiti resistivi lineari, contenenti resistori, generatori indipendenti e dipendenti e amplificatori operazionali ideali; l'analisi nel dominio del tempo di circuiti dinamici; l'analisi di circuiti in regime sinusoidale; l'analisi di circuiti resistivi non lineari, contenenti diodi. Infine, un grazie molto sentito all'Editore, per aver seguito con la consueta cura l'edizione del presente volume
Complex behavior in memristor circuits based on static nonlinear two-ports and dynamic bipole
No full textSince memristors are widely studied and the range
of applications developed for these devices are becoming increasingly
broad, circuital implementations exhibiting fingerprints of
memristive behavior have become highly relevant. A class of
memristor circuits was recently obtained by cascading a static
nonlinear two-port with a dynamical one-port. In general, these
circuits are classifiable as extended memristors and may be
controlled either in current or in voltage. This paper has the aim
of presenting a novel element from this class which experiences
various complex behaviors, including periodic oscillations and
chaos. This thorough investigation of the rich nonlinear dynamics
emerging in the proposed circuit may shed light on interesting
engineering applications that memristors may be suited for
Complex dynamics in circuits with memristors
No full textInnovative memristor-centered strategies to sense,
store, and process information may be tested inexpensively and
reliably exploiting the nonlinear dynamics of simple emulators
based upon standard two-terminal devices from electrical circuit
theory. Should a promising outcome emerge from the emulatorbased
tests, the novel strategies would be later implemented with
memristor nanodevices. A wide variety of dynamic phenomena
may emerge in oscillators employing these kinds of emulator.
Here we first design a fourth-order memristor chaotic oscillator,
and then simplify it to obtain a simpler third-order circuit
with complex dynamics. The application of techniques from the
theory of nonlinear dynamics to the mathematical description
of the oscillators allows to gain a deeper insight into their
rich dynamic behaviour, revealing the potential of arrays of
circuits of this kind to support the appearance of a wide set of
spatio-temporal patterns enabling the implementation of novel
computing paradigms
Synchronization properties in networks of Hindmarsh-Rose neurons and their PWL approximations with linear symmetric coupling
No full text
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Synchronization properties in networks of Hindmarsh-Rose neurons and their PWL approximations with linear symmetric coupling
No full textIn this paper we analyze the collective behaviors of networks of Hindmarsh-Rose (HR) neurons and compare them with the behaviors of networks of piecewise-linear (PWL) approximations of the HR neurons. In all cases, the neurons are assumed to be symmetrically and diffusively coupled, with different topologies. The analysis is based on the Master Stability Function (MSF) approach. The obtained results are verified by numerical time domain simulations of networks of 100 neurons. The synchronization properties of the PWL networks turn out to be very similar to those of the HR networks, as well as the dynamical properties of the single neurons (analyzed elsewhere)
Variations on the Author
Get PDF“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
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Memristor and Memristor Circuit Modelling Based on Methods of Nonlinear System Theory
No full textTremendous efforts are made towards the development and realization
of memristors for memory technology. Furthermore, memristor-based neuron and
synapse models are considered in several investigations on neuromorphic systems.
Some work is devoted to take advantage of peculiar nonlinear dynamics emerging
in memristors to extend or improve the functionalities of state-of-the-art circuits and
systems, both in the digital domain, where their use has been proposed in logic gate
design, and in the analog domain, where volatile memristors with negative differential
resistance effect, capable to amplify infinitesimal fluctuations of energy, have
been adopted to design interesting transistor-less circuits. While in an increasingly
number of cases, memristor models based on charge transport phenomena can be
verified through measurements to a high degree of accuracy, the systematic design
of circuits exploiting the rich dynamical behavior of memristors is still restricted to
certain cases. For some memristors, even circuits with a few number of elements
may exhibit different nonlinear phenomena, which can be only described by results
obtained in numerical simulations. In this manuscript a nonlinear system theorybased
approach will be introduced and discussed in detail. It is based on the determination
of nonlinear characteristic functions allowing the characterization of circuit
properties to a high degree of accuracy. These real-valued functions represent circuit
elements or sub-circuits, and may be used in an automated circuit design approach.
Results showing the performance of the proposed method will be given and discussed
in this contribution
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