1,721,102 research outputs found
Failures induced on bipolar operational amplifiers from electromagnetic interferences conducted on the power supply rails
No full textIn this work we will study the effects of electromagnetic interferences conveyed to the supply rails of integrated bipolar operational amplifiers. In particular, with reference to the well known μA741 topology, we will show that amplifiers undergo very strong failures when subjected to EMI conveyed to the negative supply, while they are only moderately sensible to interferences conveyed to the positive supply. Finally, on the basis of detailed circuit analyses and simulations, we will report the physical origin of such failures
The Numerov process over a non-uniform grid
Get PDFThe Numerov process is a solution method applicable to some classes of differential equations, that provides an error term of the fifth order in the grid size with a computational cost comparable to that of the finite-difference scheme. In the original formulation of the method, a uniform grid size is required; the paper shows a procedure for extending its applicability to a non-uniform grid in one dimension. The effectiveness of the procedure is tested on a model problem, and comparisons with other methods are carried out. Finally, it is shown how to extend the applicability of the method to a larger class of equations; among these, the mathematical model of semiconductor devices is important in view of its applications to the integrated-circuit technology
Recursive Least Squares adaptive filters for ultrasonic signal deconvolution
No full textBiomedical ultrasound (US) image quality is limited due to the blurring of tissue reflectivity introduced by the transducer point spread function (PSF). Deconvolution techniques can be used to eliminate this effect and to obtain the pure tissue response. In this paper we propose a new enhancement method based on recursive least squares (RLS) adaptive filtering. The method handles the spatial variability of the PSF by means of blind homomorphic characterization of the transducer. The results show that the RLS adaptation increases contrast and resolution by eliminating the spectral shaping of the backscattered echo and thus enhancing the diagnostic capability of US images
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
High frequency guided waves in a 7 wire strand: Warped Frequency Transform for spectro-temporal characterization
No full textThe aim of this research is to characterize the guided waves behavior in a seven wire strand with particular interest to the dispersive waves attenuation. Here, a pilot study is carried out on a carbon-fiber-reinforced-polymer (CFRP) wire to test a new signal processing procedure aimed at the extraction of the dispersive waves attenuation. The approach uses a novel timefrequency transform (TFR) capable to isolate the dispersive behavior of a single mode from a multimodal and dispersive recorded time-waveform. This TFR, called “Warped Frequency Transform” (WFT), is based on a time-frequency domain tiling chosen to match the spectro-temporal structure of the different propagating guided waves. The WFT is used to highlight the energy content of a guided wave traveling along the wire at different locations from which its dispersive attenuation information can be extracted. Here, the longitudinal L(0,1) wave in a single CFRP wire is studied
Multidimensional complex wavelet transforms for guided waves directional filtering
No full textUltrasonic waves can be used to point out damages and defects in structural components. In fact, a guided wave injected into the specimen under investigation produces a reflected wave when it encounters damage along its propagation path. The analysis of the reflected waves allows determining the existence and localization of damage. This work presents a technique based on the Complex Wavelet Transform for the analysis of full wavefield data, which provides removal of non-informative components (incident wave, contributions from structural features) and exclusive reconstruction of reflected waves relevant to damage detection
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
Expectation Maximization for Joint Deconvolution and Statistics Estimation
No full textBiomedical ultrasound image quality is limited due to the blurring of tissue reflectivity introduced by the transducer Point Spread Function (PSF). Deconvolution techniques can be used to obtain the pure tissue response, otherwise called reflectivity function. Typically deconvolution methods are developed in the only purpose of image visual quality improvement. In this work we present an Expectation Maximization (EM) framework for US images deconvolution in which local statistical description of the tissue reflectivity is restored as well, so that features extracted from the deconvolved frame can theoretically be used for classification purposes
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
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