1,720,956 research outputs found
Space-frequency bit-interleaved convolutional and turbo coded OFDM systems with simplified iterative approaches
No full textIn this paper, space–time bit–interleaved coded OFDM (orthogonal frequency division multiplexing) modulated systems are studied. Using multiple antennas at transmitter and receiver side, spatial diversity can be exploited with ordinary channel codes followed by an interleaver. Moreover, the combined use with OFDM modulation enable effective frequency selectivity exploitation in multipath channels. High spectral efficiency can be achieved using high modulation orders and increasing the number of transmitting antennas.
Asymptotical performances are analyzed using pairwise error probability evaluation. It is shown as transmission parameters and radio channel characteristics impact on achievable diversity order and coding gain.
Different channel codes are taken into account. Convolutional codes with several constraint lengths are simulated and results are compared with those of turbo coded solution.
The iterative receiver complexity grows at the increase of modulation order, subcarriers and number of antennas. Simplified detection criterions can be used for signals separation at receiver side. Turbo coded system allows for iterative approaches with reduced complexity when some turbo
decoding iterations are performed between successive detection steps
Frequency-domain multi-user access interference cancellation and nonlinear equalization in CDMA receivers
No full textA wireless CDMA communication system receiver receives a stream of chips generated by spreading data symbols formed by grouping bits of information at a wireless CDMA communication transmitter which are broadcast at a certain chip-rate. The received chips are de-spread and symbols pertaining to respective users are reconstructed. The stream of chips are formatted into blocks of chips, and an iterative block decision feedback equalization is performed in a frequency domain at the chip-rate of the broadcast stream of chips to remove inter-symbol interference by defining a transfer function. The chips generated are interleaved by spreading each data symbol being transmitted before broadcasting the stream of interleaved chips in distinct blocks of chip
Investigating maintenance operations in Industry 5.0: a cognitive-oriented tasks framework
No full textThe Industry 5.0 paradigm aims to improve, through a human-centric approach, the performance of cyber-physical production systems promoted by the fourth industrial revolution. If, on the one hand, the digitisation promoted by the Industry 4.0 paradigm provides many opportunities for improving the performance of production systems, on the other hand, it introduces a high level of complexity for operators in the execution of ordinary activities mainly from a cognitive point of view. The complexity of tasks and the increasing use of innovative technologies could overload the operator with numerous options and efforts to be made in a limited time, requiring decisions that lead to an excessive cognitive workload and reduce human well-being in work environments. In this context, maintenance activities are of utmost relevance; their inherent complexity and the direct dependence of the production performance on their proper and timely execution led to the development of dedicated support technologies and techniques known as Maintenance 4.0 (M4.0). Notably, M4.0 activities are strongly characterised by the above-outlined complexities, especially from a cognitive point of view. To this concern, the present research work consists of developing, through a literature search, a framework of the main M4.0 tasks aiming to identify the perceived cognitive workload according to the operator's profile (i.e., competencies, hard skills, age, etc.). This framework, as mentioned, represents the starting point for more in-depth analyses that will allow the identification of the proper operator to accomplish a high-cognitive M4.0 task by ensuring operator well-being and industrial performance
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
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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