1,721,263 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
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
Efficient trellis search techniques for adaptive MLSE on fast Rayleigh fading channels
No full textWe analyze trellis search algorithms for joint sequence estimation and channel tracking, assuming rapidly varying frequency-selective Rayleigh fading. The Generalized Viterbi Algorithm (GVA) and the M-Algorithm (MA) are considered for approximately searching the maximum likelihood path in the trellis diagram and compared with the Viterbi Algorithm (VA). All algorithms perform channel tracking utilizing Per-Survivor Processing (PSP) techniques by associating a channel estimate
to each hypothetical trellis path, according to the Least Mean Square (LMS) or Recursive Least Square (RLS) algorithm.
To reproduce a typical mobile digital communication system,
a Time-Division Multiple Access (TDMA) data frame
is assumed, where each user transmits a block of information
symbols with known preamble and tail. For Doppler bands up to one hundredth the symbol frequency and a three path delay profile, the MA is shown to exhibit a slightly better performance than the GVA for an equal number of survivors, and outperform the VA
A Recursive Formulation for Quadratic Detection on Rayleigh Fading Channels
No full textWe address the problem of optimal detection of a random signal transmitted over a time-varying frequency-selective correlated Rayleigh fading channel. We present a general recursive solution which may be operated at full complexity to provide optimal detection or at reduced complexity, using per-survivor processing (PSP) techniques, to yield a suboptimal receiver
On the Use of Oversampling in Adaptive Receivers for Frequency-Selective Rayleigh Fading Channels
No full textIn this work, we investigate Maximum Likelihood Sequence Estimation (MLSE) of data sequences transmitted over time-varying frequency-selective Rayleigh fading channels and consider adaptive receivers which realize joint data estimation and channel tracking utilizing Per-Survivor Processing (PSP) techniques. In order to obtain a sufficient statistics for data detection, the received signal is oversampled with respect to the symbol rate. Accordingly, a time-discrete channel model with fractional spacing, with respect to the symbol interval, is assumed and an algorithm which performs fractionally-spaced
PSP-based channel tracking is analyzed. We show that receivers which employ this algorithm outperform traditional adaptive receivers based on one sample per symbol interval. Two samples per symbol interval are shown to be sufficient to attain the optimal performance for these receivers
On the Performance of the Quadratic Receiver for Rayleigh Fading Channels
No full textWe investigate maximum likelihood sequence estimation (MLSE) of data sequences transmitted over time-varying frequency-selective Rayleigh fading channels. We present the optimal receiver designed to exploit perfect channel state information (CSI) at the beginning of the data sequence and the optimal receiver which does not use this information. For any given data sequence length, a performance range for the optimal detection can be identified: this range is lower bounded by the optimal receiver with perfect CSI and upper bounded by that without CSI. Furthermore, this range narrows for increasing data sequence lengths. The performance of these optimal receivers is compared to that of some suboptimal receivers based on per-survivor processing (PSP) which perform joint sequence detection and channel tracking using the least mean square (LMS) algorithm. In terms of performance, these suboptimal receivers are shown to be intermediate between the optimal receivers with and without initial CSI. In addition, we show that the performance of both optimal receivers degrades significantly if they are provided with imperfect information about the signal-to-noise ratio or channel delay profile-information which is not necessary to the suboptimal PSP-based receivers
Phenolic acids composition, total polyphenols content and antioxidant activity of Triticum monococcum, Triticum turgidum and Triticum aestivum : a two-years evaluation
No full textWheat is a good source of polyphenols, plant metabolytes with beneficial effects on human health.
However, little information is available on phenolic acid composition and concentration in different Triticum species, as well as on possible environmental effects. To shed some light on this issue, thirtynine wheat accessions cropped for two years and belonging to different Triticum species (Triticum monococcum, Triticum turgidum ssp. dicoccum, turanicum and durum, Triticum aestivum ssp. spelta and aestivum) were assessed for phenolic acids (ferulic, p-coumaric, vanillic, syringic, p-hydroxybenzoic, caffeic acids and syringaldehyde), total polyphenols and antioxidant activity in soluble conjugated and insoluble bound extracts. Ferulic acid was the most abundant compound in both extracts. Insoluble
bound phenolic acids represented >90% of total phenolic acids. Einkorn showed the maximum concentration of conjugated phenolic acids (50.5 mg/kg DM), while durum and bread wheats presented the
highest content of bound phenolic acids (651.8 and 629.2 mg/kg DM, respectively). Cropping year influenced the concentration of conjugated but not of bound phenolic acids. A survey of phenolic acid distribution in the kernel showed that they are rare in endosperm, but abundant in germ and bran. Total polyphenols and antioxidant activity were highly correlated to phenolic acid content
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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