1,720,962 research outputs found
Peak-finding methods for improving the resolution of a sonar-based correlation velocity log
No full textProcessing techniques for the recovery of audio from Edison cylinder recordings, via noncontact surface measurement
No full textA non-contact method for the recovery of audio signals from early acoustic cylinder recordings is presented.
The cylinder surface is scanned via optical displacement sensor, capable of submicron axial resolution. Sound recovery
is achieved by estimating the trajectory of a playback stylus over the measured surface. The processing methods
required to extract audio from a discrete height map are described. The signal to noise ratio of the extracted signal as a
function of position across the groove cross-section is examined, for a Blue Amberol cylinder, (circa 1912)
A comparison of optical sensing methods for the high precision 3D surface profile measurement of grooved surfaces
No full textA non-contact method has been shown to be the preferred solution for the scanning of valuable early sound recordings, such as wax cylinders and flat discs for the purpose of cultural preservation [1]. This paper describes the operating principles and compares the performances of four different sensing techniques, including scanning white light interferometer (SWLI), con-focal laser (CL), con-focal white light sensor (WL), and atomic force microscope (AFM), in a range of measurement tasks. The con-focal systems described in this paper are used in a 3 dimensional (3D) cylinder scanning system for the measurement of wax cylinder recordings, where the 3D data is used to create a map of the measured surface. The generation of the map allows the sound recorded on the surface to be decoded without physical contact to the surface. The main advantage of the con-focal system is the scanning speed. Reference samples with sinusoidal and rectangular profiles are used to investigate the effects of surface inclination angle and the interaction between the sensor head and the measured surface. The effects of precision mode, grid spacing and spot size on surface height measurements are investigated
An ultrasonic transducer array for velocity measurement in underwater vehicles
No full textA correlation velocity log (CVL) is an ultrasonic navigation aid for marine applications, in which velocity is estimated using an acoustic transmitter and a receiver array. CVLs offer advantages over Doppler velocity logs (DVLs) in many autonomous underwater vehicle (AUV) applications, since they can achieve high accuracy at low velocities even during hover manoeuvres. DVLs require narrow beam widths, whilst ideal CVL transmitters have wide beam widths. This gives CVLs the potential to use lower frequencies thus permitting operation in deeper water, reducing power requirements for the same depth, or allowing the use of smaller transducers.Moving patterns in the wavefronts across a 2D receiver array are detected by calculating correlation coefficients between bottom reflections from consecutive transmitted pulses, across all combinations of receiver pairings. The position of the peak correlation value, on a surface representing receiver-pairing separations, is proportional to the vessel's displacement between pulses.A CVL aimed primarily for AUVs has been developed. Its acoustical and signal processing design has been optimised through sea trials and computer modelling of the sound field. This computer model is also used to predict how the distribution of the correlation coefficients varies with distance from the peak position.Current work seeks to increase the resolution of the peak estimate using surface fitting methods. Numerical simulations suggest that peak estimation methods significantly improve system precision when compared with simply identifying the position of the maximum correlation coefficient in the dataset. The peak position may be estimated by fitting a quadratic model to the measured data using least squares or maximum likelihood estimation. Alternatively, radial basis functions and Gaussian processes successfully predict the peak position despite variation between individual correlation datasets.This paper summarises the CVL's main acoustical features and signal processing techniques and includes results of sea trials using the device. <br/
Improvement of velocity estimate resolution for a correlation velocity log using surface fitting methods
No full textA Correlation Velocity Log (CVL) is an acoustical navigation aid, consisting of a transmitter and a receiver array. Moving patterns in the wave fronts across the receiver army, indicative of motion, are detected by calculating correlation coefficient between bottom reflections from consecutive transmitted pulses. A velocity vector map is constructed by plotting the correlation coefficient on a grid representing the, velocity vector spacing. The peak position on this map surface provides an estimate of the velocity vector of the vessel.The resolution of the velocity vector map is limited by the minimum diameter of the receiving elements and the maximum size of the array. Current research is focused on exploiting the full potential of the CVL by investigating surface fitting techniques to' interpolate peak position estimates between measurement points.Detailed simulations and sea trials of a prototype CVL have demonstrated that the correlation coefficient surface is subject to high variance at only a modest distance from the peak. This paper presents numerical comparisons between different surface-fitting methods for performing peak finding on the data. Different least squares schemes are investigated, together with a non-liner iterative implementation of Maximum Likelihood Estimation. The performance of these methods is compared both in terms of rms error and mean, error in peak estimation.It is shown that CVL performance can he improved significantly by the use of an appropriate peak finding technique
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
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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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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