1,720,992 research outputs found
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
Analysis of EMCCD gain estimation techniques for use in astronomical instruments
No full textElectron-multiplied Charge Coupled Devices (EMCCDs) are used in many astro nomical instruments where they provide much improved signal to noise compared to conventional CCDs. However, the gain provided by electron-multiplication may not be known with precision, leading to errors in the measurements. Several techniques to estimate the gain of EMCCDs are researched and investigated in this work, includ ing some techniques previously only used for microscopy. Investigation and analyses were completed in a simulation environment, in a laboratory environment, and us ing data collected by an astronomical instrument (Galway Astronomical Stokes Polarimeter), where accurate gain estimation of the EMCCD detectors is important for the polarimetry results from the instrument
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
Pre-processing, Registration and Quality Assessment of Adaptive Optics Assisted Retinal Images
No full textIn recent decades, adaptive optics (AO) technology has been embedded into retinal imaging devices, producing a new generation of instrument, which can provide retinal images with cellular resolution. This new technological advancement allows viewing of retinal microscopic structure, which is of great significance for the diagnosis, and subsequent treatment monitoring, of retinal pathologies that can result in visual loss. Developing compact and simplified AO assisted retinal imaging devices with an automated feature analysis is the current focus of interest for transferring AO technology to clinical use. In this study, we present an enhanced processing of sequences of retinal images obtained using an AO flood illumination system. We aim to provide image processing techniques for pre-processing, assessing the quality and image registration of cone photoreceptor and retinal nerve fiber layer (RNFL) images. Our results demonstrate the effectiveness of a wavelet based approach to correcting uneven illumination and automatic evaluation of image quality in terms of the results of image registration. In particular, we present the significance of image quality analysis while selecting a certain percentage of the sharpest images in a sequence for image registration. In order to register the images, we include methods that are specifically developed to measure tiny rotations in addition with correlation based techniques to correct for translational motion. We show that correcting for small rotations exhibits a significant improvement, especially at the edges of the image, which is important for creating larger mosaics. We then present the methods of investigating the characteristics of retinal nerve fiber bundles to discriminate RNFL images with good and poor striation. This enables feature comparison between healthy and glaucoma eyes. Finally, we discuss the implications of our results and possible future studies
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
Visual speech encoding based on facial landmark registration
Full text linkVisual Speech Recognition (VSR) related studies largely ignore the use of state of the art approaches in facial landmark localization, and are also deficit of robust visual features and its temporal encoding. In this work, we propose a visual speech temporal encoding by integrating state of the art fast and accurate facial landmark detection based on ensemble of regression trees learned using gradient boosting. The main contribution of this work is in proposing a fast and simple encoding of visual speech features derived from vertically symmetric point pairs (VeSPP) of facial landmarks corresponding to lip regions, and demonstrating their usefulness in temporal sequence comparisons using Dynamic Time Warping. VSR can be either speaker dependent (SD) or speaker independent (SI), and each of them poses different kind of challenges. In this work, we consider the SD scenario, and obtain 82.65% recognition accuracy on OuluVS database. Unlike recent research in VSR which makes use of auxiliary information such as audio, depth and color channels, our approach does not impose such constraints
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
Using spatial light modulators to investigate the limitations of adaptive optics performance for the European Extremely Large Telescope
No full textThe European Extremely Large Telescope (E-ELT) will be the world’s largest ground based optical / near-infrared telescope ever built. Its primary mirror, M1, will be 39 m in diameter and consist of 798 individual hexagonal segments, each with a diam eter of 1.2 m. The telescope will host various cutting-edge instruments, including a Multi-Conjugate Adaptive Optics (MCAO) instrument, spectrographs, and imagers, all of which are being built alongside the telescope, with some of them planned to be operational for first light. In particular, the Multiconjugate adaptive Optics Relay For ELT Observations (MORFEO) instrument is planned to be one of the first instruments installed, along with the High Angular Resolution Monolithic Optical and Near-infrared Integral field spectrograph (HARMONI), Multi-AO Imaging Camera for Deep Observations (MICADO), and Mid-infrared ELT Imager and Spectrograph (METIS) instruments. This means that MORFEO needs to be calibrated and tested before integration into the ELT infrastructure. For this, the Calibration / Test Unit (CU/TU) is being developed as a method to ensure MORFEO is working as expected before installation. The CU/TU will be required to provide six Laser Guide Star (LGS), three Natural Guide Star (NGS), science sources, emulated turbulence and dynamic aberrations, as well as wavefront correction which emulates the functionality of the M4 mirror, and the segmentation effects of the M1 mirror. This thesis is focused on the Spatial Light Modulator (SLM), a device which consists of an array of Liquid Crystal (LC) pixels which have a controllable index of refraction. This allows for the spatial modification of the phase of any wavefront that passes through the liquid crystals. Here, their ability to emulate atmospheric turbulence and segmented mirrors will be tested, with the intention of using them in a calibration unit for an Adaptive Optics (AO) system. Specifically, this work will use off-the-shelf SLMs for the emulation of atmospheric turbulence with different Fried parameters, and for the emulation of segmented mirrors with different numbers of segments and phase discontinuities. This will test whether they can; i) reproduce the sharp discontinuities one would expect by using small segmented mirrors, and; ii) have these edges detected by a pyramid wavefront sensor and use the measurements to produce a calibration curve which can be used to estimate the phase discontinuity across a misaligned edge. Additionally, the devices will be used to emulate a digital, reconfigurable pyramid wavefront sensor as an alternative method to sensing phase discontinuities. The output of this research will be to determine whether these easily available SLMs could be used to accurately test and calibrate an adaptive optic system, and whether the specific requirements of the MORFEO system could be met by them
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