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De Bruijn sequences in spread spectrum systems: problems and performance in vehicular applications
No full textQuesta tesi affronta l’analisi circa il possibile utilizzo di un particolare set
di sequenze, le cosiddette sequenze de Bruijn, in un sistema radar veicolare di
tipo Direct Sequence Spread Spectrum (DSSS). Rispetto ad altri codici di espansione
adottati nei sistemi DSSS, maggiore è la lunghezza delle sequenze del
set, più la numerosità delle sequenze di de Bruijn aumenta in modo esponenziale
e permette teoricamente di assegnare ad ogni radar una diversa sequenza
generata, che funge da specifica chiave personale. In questo modo è possibile
sviluppare un sistema radar autoconsistente in grado di lavorare senza
alcuna infrastruttura necessaria all’assegnazione delle sequenze, come accade
per i convenzionali codici di espansione tipo i codici Gold o i codici di Kasami.
Grazie alle loro favorevoli proprietà di auto- e cross-correlazione, sono particolarmente
indicati per sistemi automotive dove è molto importante rilevare con
precisione un bersaglio in un contesto di radar multi-utente. Considerando le
loro buone proprietà di correlazione e la loro elevata numerosità, le sequenze
di de Bruijn possono essere utilizzate non solo nei sistemi radar veicolari ma
anche in altri scenari di tipo Spread Spectrum, come il canale di downlink
e uplink di sistemi DS-CDMA. Infatti, le sequenze di de Bruijn, nella versione
standard, se selezionate accuratamente hanno proprietà di ortogonalità
e quindi particolarmente vantaggioso è il loro utilizzo nel canale di downlink
di un sistema DS-CDMA. Inoltre, dal set di sequenze di de Bruijn è possibile
derivare un altro particolare insieme di sequenze, le cosiddette sequenze di de
Bruijn modificate. Queste sequenze mostrano prestazioni migliori in termini di
cross-correlazione e potrebbero essere utilizzate nel canale uplink di un sistema
DS-CDMA. Al fine di verificare le prestazioni in un vero e proprio banco di
prova, è stata sviluppata anche una preliminare implementazione di un radar
DSSS su Software Defined Radio. Infine è stato sviluppato un simulatore per
sistemi radar veicolari DSSS su scenari multi-utente. L’analisi effettuata ed
i risultati sulle prestazioni ottenuti suggeriscono di evolvere questa soluzione
verso le recenti tecniche di radar cognitivo tramite l’ausiliodi tecniche di visione
computazionale.This thesis deals with the analysis about a possible utilization of a particular set
of sequences, the so-called de Bruijn sequences, in a Direct Sequence Spread
Spectrum (DSSS) vehicular radar system. Compared with other spreading
codes adopted in DSSS systems, the greater the span of the set is, the more the
number of de Bruijn sequences exponentially increases and theoretically permits
to assign each radar a different generated sequence, as a specific key. By
this way it is possible to develop a self-consistent radar system, which is able
to work without any infrastructure required to assign sequences, as it happens
in the case conventional spreading codes, like Gold codes or Kasami codes, are
adopted. Due to their both favourable auto- and cross-correlation properties
they are particularly indicated for automotive systems in which there are the
needs of detecting accurately a target and performing in a multi-user radar environment.
Considering their good correlation properties and their huge number,
de Bruijn sequences could be used not only in vehicular radar systems but
also in other Spread Spectrum and so, they are evaluated in various scenarios
like downlink and uplink channel of DS-CDMA systems. In fact, in standard
version de Bruijn sequences, if accurately selected, have the property of orthogonality
and so they are tested in a downlink channel of a DS-CDMA system.
In addition, from de Bruijn sequences another particular set of sequences, the
so-called modified de Bruijn sequences, can be derived. These sequences show
better performance in terms of cross-correlation properties and could be used
in uplink channel of DS-CDMA system. In order to verify the performance in
a real test-bed, a preliminary implementation on Software Defined Radios is
also developed. Finally they are adopted and compared in simulated multiuser
DSSS radar scenarios. The analysis done and the performance results
obtained suggest to evolve this radar solution to a cognitive radar approach
using computer vision systems as external aid sensor which can outperform
actual solutions
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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