1,721,147 research outputs found
Positioning with GNSS and 5G: Analysis of Geometric Accuracy in Urban Scenarios
Full text linkGNSS positioning in urban scenarios suffers for the scarce visibility of satellites. Integration with 5G services for positioning could improve this situation. In this paper, the digital surface models (DSMs) relevant to different urban scenarios, namely residential streets and urban canyons, are simulated around one observer in northern Italy (Milano) for one day of the year chosen as an example. The time series of the number of in-view GNSS satellites, their geometry and the derived quality indexes (position dilution of precision (PDOP)) are computed and analyzed. As expected, in urban canyons, a significant number of epochs does not provide four satellites within view, and many more epochs present really mediocre PDOPs. In residential streets, the situation is always quite fair. Different geometric configurations of 5G base stations are simulated around the observer. The availability of 5G times of arrival (ToAs) and their differences (TDoAs) is hypothesized, and the integration of these observations with GNSS pseudoranges is analyzed, again in terms of the PDOPs. In residential streets, 5G availability improves the positioning. In urban canyons, the optimal configuration of 5G base stations (five base stations around the observer) completely solves the positioning problem for all the epochs of the day. Less favorable configurations (four and three base stations) improve epochs with poor PDOPs in a GNSS-only configuration. They allow the positioning of epochs with few satellites but cannot completely replace the GNSS
A view into the brain of female children with autism pectrum disorder: Morphometric regional alterations detected by structural MRI mass-univariate and pattern classification analisys
No full textFemale children with autism spectrum disorder: An insight from mass-univariate
and pattern classification analyses.
Calderoni S, Retico A, Biagi L, Tancredi R, Muratori F, Tosetti M.
IRCCS Stella Maris Foundation, Viale del Tirreno 331, 56018 Calambrone, Pisa,
Italy; Division of Child Neurology and Psychiatry, University of Pisa, Pisa,
Italy.
Several studies on structural MRI in children with autism spectrum disorders
(ASD) have mainly focused on samples prevailingly consisting of males. Sex
differences in brain structure are observable since infancy and therefore caution
is required in transferring to females the results obtained for males. The
neuroanatomical phenotype of female children with ASD (ASDf) represents indeed a
neglected area of research. In this study, we investigated for the first time the
anatomic brain structures of a sample entirely composed of ASDf (n=38; 2-7years
of age; mean=53months; SD=18) with respect to 38 female age and non verbal IQ
matched controls, using both mass-univariate and pattern classification
approaches. The whole brain volumes of each group were compared using voxel-based
morphometry (VBM) with diffeomorphic anatomical registration through
exponentiated lie algebra (DARTEL) procedure, allowing us to build a
study-specific template. Significantly more gray matter (GM) was found in the
left superior frontal gyrus (SFG) in ASDf subjects compared to controls. The GM
segments obtained in the VBM-DARTEL preprocessing are also classified with a
support vector machine (SVM), using the leave-pair-out cross-validation protocol.
Then, the recursive feature elimination (SVM-RFE) approach allows for the
identification of the most discriminating voxels in the GM segments and these
prove extremely consistent with the SFG region identified by the VBM analysis.
Furthermore, the SVM-RFE map obtained with the most discriminating set of voxels
corresponding to the maximum Area Under the Receiver Operating Characteristic
Curve (AUC(max)=0.80) highlighted a more complex circuitry of increased cortical
volume in ASDf, involving bilaterally the SFG and the right temporo-parietal
junction (TPJ). The SFG and TPJ abnormalities may be relevant to the
pathophysiology of ASDf, since these structures participate in some core atypical
features of autism
5G Positioning: An Analysis of Early Datasets
Full text link: Global Navigation Satellite Systems (GNSSs) are nowadays the prevailing technology for positioning and navigation. However, with the roll-out of 5G technology, there is a shift towards 'hybrid positioning': indeed, 5G time-of-arrival (ToA) measurements can provide additional ranging for positioning, especially in environments where few GNSS satellites are visible. This work reports a preliminary analysis, the processing, and the results of field measurements collected as part of the GINTO5G project funded by ESA's EGEP programme. The data used in this project were shared by the European Space Agency (ESA) with the DICA of Politecnico di Milano as part of a collaboration within the ESALab@PoliMi research framework established in 2022 between the two organizations. The ToA data were collected during a real-world measurement campaign and they cover a wide range of user environments, such as indoor areas, outdoor open sky, and outdoor obstructed scenarios. Within the test area, eleven self-made replica 5G base stations were set up. A trolley, carrying a self-made 5G receiver and a data storage unit, was moved along predefined trajectories; the trolley's accurate trajectories were determined by a total station, which provided benchmark positions. In the present work, the 5G data are processed using the least squares method, testing and comparing different strategies. Therefore, the primary goal is to evaluate algorithms for position determination of a user based on 5G observations, and to empirically assess their accuracy. The results obtained are promising, with positional accuracy ranging from decimeters to a few meters in the worst cases
MAPPING THE ACCESSIBILITY IN OPENSTREETMAP: A COMPARISON OF DIFFERENT TECHNIQUES
Full text linkArchitectural barriers are physical elements that limit the freedom of movement and use of services of a person. The lack of accessibility is one of the physical barriers that most limit people with motor disabilities, as recognised by the World Health Organization. The work aims to identify the optimal methodology to map accessible ways and critical barriers, in order to produce cartographic support for people with motor disabilities. It should also be a tool that allows citizens to report barriers to public authority. The work is part of the ViaLibera?! project, which aims to apply the methodology in the Municipality 9 of the city of Milan. The project is founded by Fondazione di Comunit`a Milano; Politecnico di Milano is the scientific partner, while the other partners are associations that represent people with disabilities: Spazio Vita Niguarda Onlus, Ledha Milano and AUS Niguarda Onlus. The mapping elements of interest for the project were identified in collaboration with the other partners, also studying the state of the art. In the framework of Open Street Map, a comparison between different existing mapping techniques was done to select the optimal compromise between rigour and simplicity. In addition, the different techniques must be suitable for the chosen tagging scheme to map accessibility elements. The techniques analysed involve the use of paper maps, Field Papers, and street-level images or applications for smartphones. They are compared to identify the best one
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
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