1,720,961 research outputs found
Nonlinear Inductors in Power Electronics: Modeling, Design, and Control
No full textInductors that operate in partial magnetic saturation are increasingly attracting the interest
of the scientific community in the attempt of enhancing the power density of switched-mode
power supplies. Designing and simulating converters that use nonlinear magnetic components
need accurate models capable of predicting their voltage and current characteristics, as well as
power losses under various operating conditions.
Typically, inductor datasheets do not provide comprehensive information regarding inductance and losses related to partial magnetic saturation. Furthermore, the data usually applies
only to sinusoidal excitation waveforms. However, the voltage across inductors is often nonsinusoidal. In the case of DC-DC converters, the inductor voltage typically resembles a square
wave, with varying frequency, amplitude, and duty cycle. The inductor current is approximately
a biased triangular wave, which can become significantly distorted as magnetic saturation
occurs.
This thesis is focused on circuit models for inductors that account for partial magnetic
saturation and power losses. These models are validated using inductors with cores made of
ferrite – the most widely used core material – and amorphous alloys. The models operate across
various frequencies with sinusoidal, square, and triangular waveforms, while also considering
the influence of inductor design parameters such as the number of turns and any air gaps in the
core. Temperature effects are accounted for as well.
One of the developed circuit models is exploited for an embedded control based on model
predictive control of a boost converter. With an accurate model, the predictive control enables
the control of converters while enforcing constraints, even when the inductors operate under
conditions of partial magnetic saturation.
An analysis of the effects of magnetic saturation in the inductor of a buck converter is
carried out using a circuit model validated against experimental measurements. This study
provides a proof of concept for switching converters that exploit saturable inductors. In the
test case, using inductors that operate in partial magnetic saturation can lead to an increase in
power density, with only a slight reduction in efficiency
A nonlinear behavioral model of a ferrite-core inductor with fixed-frequency sinusoidal voltage input
No full textEmbedded Linear Model Predictive Control Through Mesh Adaptive Direct Search Algorithm
No full textIn this paper we apply the derivative-free mesh adaptive direct search (MADS) algorithm to find the minimum of a constrained optimization problem, resulting from model predictive control (MPC). MPC requires indeed to solve an optimization problem online, at each sampling time of the system to regulate. A progressive barrier approach is used in MADS, in order to cope with the possibly infeasible initial point for the algorithm. Hardware-in-the-loop simulations are performed where the MADS-based MPC regulator is implemented on a microcontroller and a double integrator system is simulated on a PC. Control performances and circuit latency are assessed with respect to the number of MADS iterations
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
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe 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
Narrativa italiana: note critiche sull’annata letteraria 2023-2024
No full textRassegna critica sull'annata 2023-2024 di narrativa italiana. Tra gli autori presi in considerazione, Vitaliano Trevisan, Janek Gorczyca, Nicola Lecca, Aldo Nove, Lidia Ravera, Alessandro Piperno, Alfredo Palomba, Marco Erba, Isacco Turina, Silvia Avallone, Ezio Sinigaglia, Valerio Varesi, Marco Balzano, Francesca Melandri, Hans Tuzzi, Silvia Cassioli, Sandro Veronesi, Giovanni D'Alessandro, Piergiorgio Paterlini, Angelo Ferracuti, Antonio Prete, Carmine Abate, Marilù Oliva, Furio Bordon
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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