1,720,964 research outputs found
Polynomial interpolation for inversion-based control
Full text linkTo help to achieve high performances in the regulation of linear scalar (SISO) nonminimum-phase systems, an inversion-based (feedforward) control method is proposed. The aim is designing an inverse input to smoothly switch from a current, arbitrary, steady-state regime to a new, future, desired steady-state output. A new-found polynomial basis solves the related interpolation problem to join the current output to the future one while ensuring the necessary or desired smoothness. The (interpolation) transition time can be minimized in order to optimally reduce the delay with which the desired output occurs. By applying a behavioral stable inversion formula to the overall smoothed output, detailed expressions of the inverse input are finally derived. A simulation of a flexible arm rotating in the horizontal plane exemplifies the presented method
Pressure matching with optimized target phase for personal sound zone systems
No full textPressure matching (PM) is an advanced digital signal processing technique aimed at designing loudspeaker filters to achieve a target acoustic field in a desired sound region. This enables to establish personal sound zones (PSZs) in a desired environment. The target sound field is chosen during the design stage and influences the performance of the system in terms of acoustic contrast (AC) between bright and dark zones, as well as fidelity of the reproduced audio. The sound regions are represented by groups of control points (microphones) properly placed in the considered environment. With more than one control point in the bright region, the same target sound field is usually considered for all the microphones. This paper investigates the optimization of the phase of the target acoustic field required by the PM algorithm in terms of AC. The achievable performance is analyzed in a realistic automotive environment with two sound zones and two control points per zone. The numerical results show a potential improvement of the achievable AC at the cost of some spatial effects and possibly non constant group delay in the reproduced sound, which should nonetheless be tolerable in voice applications
Experimental Analysis and Design Guidelines for Microphone Virtualization in Automotive Scenarios
Full text linkIn this article, a performance analysis on the estimation of the so-called observation filter for the Virtual Microphone Technique (VMT) in a realistic automotive environment is presented. A performance comparison between adaptive and fixed observation filter estimation methods, namely Least Mean Square (LMS) and Minimum Mean Square Error (MMSE), respectively, was carried on. Two different experimental setups were implemented on a popular B-segment car. Eight microphones were placed at the monitoring and virtual positions in order to sense environmental acoustic noise propagating within the cabin of the car running at variable speed on a smooth asphalt. Our experimental results show that a large spectral coherence between monitoring and virtual microphone signals indicates a potentially effective and relatively wide-band virtual microphone signal reconstruction. The fixed observation filter estimation method achieves better performance than the adaptive one, guaranteeing remarkable broadband estimation accuracy. Moreover, for each considered setup, design guidelines are proposed to obtain a good trade-off between estimation accuracy and material costs
Heuristic Design of Feedback Active Noise Control for Automotive Applications
No full textIn this paper, a performance analysis of FeedBack (FB) Active Noise Control (ANC) systems for automotive applications is presented. Noise cancellation is obtained from a fixed controller, heuristically designed using concepts from control theory. An experimental setup, representative of a headrest of a car seat with loudspeaker-microphone distance on the order of a few centimeters, has been developed to limit the system delay. The experimental band-limited noise source has been obtained from an idling car. Our results show that the proposed system guarantees appreciable peak noise cancellation and simultaneously avoids noise amplification outside the band of interest
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
Performance Analysis of Feedback MIMO ANC in Experimental Automotive Environment
No full textIn this paper, a performance analysis of FeedBack (FB) Active Noise Cancellation (ANC) systems for automotive applications is presented. Since the performance of FB ANC systems is strongly impaired by the delay induced by the physical distance between microphones and loudspeakers, an experimental setup representative of a car seat headrest has been developed. In this setup, the loudspeaker-microphone distance is on the order of few centimeters. An experimentally acquired band-limited noise source is obtained from an idling car. Noise reduction is performed by using a Filtered-x Least Mean Square (FxLMS) algorithm. Two 2×2 Multiple Input - Multiple Output (MIMO) schemes are considered - standard one and Filtered-Error (FE) based. Our experimental results show that the proposed MIMO systems enable improved performance and are able to control the perceived noise at two listening positions in a realistic automotive application
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
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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