1,721,036 research outputs found
Accurately estimating rigid transformations in registration using a boosting-inspired mechanism
No full textFeature extraction and matching provide the basis of many methods for object registration, modeling, retrieval, and recognition. However, this approach typically introduces false matches, due to lack of features, noise, occlusion, and cluttered backgrounds. In registration, these false matches lead to inaccurate estimation of the underlying transformation that brings the overlapping shapes into best possible alignment. In this paper, we propose a novel boosting-inspired method to tackle this challenging task. It includes three key steps: (i) underlying transformation estimation in the weighted least squares sense, (ii) boosting parameter estimation and regularization via Tsallis entropy, and (iii) weight re-estimation and regularization via Shannon entropy and update with a maximum fusion rule. The process is iterated. The final optimal underlying transformation is estimated as a weighted average of the transformations estimated from the latest iterations, with weights given by the boosting parameters. A comparative study based on real shape data shows that the proposed method outperforms four other state-of-the-art methods for evaluating the established point matches, enabling more accurate and stable estimation of the underlying transformation. © 2016 Elsevier Lt
Regularization based iterative point match weighting for accurate rigid transformation estimation
No full textFeature extraction and matching (FEM) for 3D shapes finds numerous applications in computer graphics and vision for object modeling, retrieval, morphing, and recognition. However, unavoidable incorrect matches lead to inaccurate estimation of the transformation relating different datasets. Inspired by AdaBoost, this paper proposes a novel iterative re-weighting method to tackle the challenging problem of evaluating point matches established by typical FEM methods. Weights are used to indicate the degree of belief that each point match is correct. Our method has three key steps: (i) estimation of the underlying transformation using weighted least squares, (ii) penalty parameter estimation via minimization of the weighted variance of the matching errors, and (iii) weight re-estimation taking into account both matching errors and information learnt in previous iterations. A comparative study, based on real shapes captured by two laser scanners, shows that the proposed method outperforms four other state-of-the-art methods in terms of evaluating point matches between overlapping shapes established by two typical FEM methods, resulting in more accurate estimates of the underlying transformation. This improved transformation can be used to better initialize the iterative closest point algorithm and its variants, making 3D shape registration more likely to succeed. © 1995-2012 IEEE
Underwater 3D vision, ranging and range gating
No full textAn impressive number of laser-based sensors for 3D vision for terrestrial applications have been developed so far, making it a mature and expanding market worth billions of euros. When it comes to the subsea environment the presence of water, combined with the demand to operate at depth, acts as game-changing factors and considerable scientific and technological challenges arise. This chapter concentrates on selected techniques for subsea 3D vision and ranging using laser-based sensors, with priority given to projects where the efforts have been focused on developing devices ready to be deployed in real scenarios. © 2013 Woodhead Publishing Limited. All rights reserved
In-situ and stand-off detection of radionuclides by laser spectroscopy. A feasibility study
Full text linkIl Laboratorio Diagnostiche e Metrologia (FSN-TECFIS-DIM) dell’Agenzia Nazionale per le Nuove Tecnologie, l’Energia e lo Sviluppo Economico Sostenibile (ENEA) ha applicato da anni la spettroscopia laser fotoacustica (LPAS) alla sicurezza alimentare (in situ) e il lidar ad assorbimento differenziale (DIAL) alla rilevazione di esplosivi e al monitoraggio ambientale (a distanza). Tenendo conto del recente rinnovato interesse per l’energia nucleare, da un lato, e della perdurante preoccupazione dell’opinione pubblica sulla sicurezza e protezione nucleare, dall’altro, è stato condotto uno studio di fattibilità preliminare sulla rilevazione di iodio mediante LPAS e DIAL. I suoi risultati sono promettenti per lo ioduro di metile, una forma volatile di radioiodio, e aprono la strada allo sviluppo di sensori laser in situ e a distanza per la sicurezza nucleare. Il Laboratorio di Metodi e Tecniche per la Sicurezza Nucleare, il Monitoraggio e la Tracciabilità (FSN-SICNUC-TNMT) applica la spettroscopia gamma per il monitoraggio di radionuclidi mobili nell’ambiente e potrebbe utilizzare le tecniche LPAS e DIAL per supportare la valutazione e lo studio della concentrazione di radionuclidi rilevanti per la sicurezza e protezione nucleareThe Diagnostics and Metrology Laboratory (FSN-TECFIS-DIM) of the Italian National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA) applied for years laser photoacoustic spectroscopy (LPAS) to food safety (in-situ) and differential absorption lidar (DIAL) to explosive detection and environmental monitoring (stand-off). Taking into account the recent renewed interest in nuclear energy, from one hand, and the long-lasting public concern on nuclear safety and security, from the other one, a preliminary feasibility study on iodine detection by LPAS and DIAL has been carried out. Its results are promising for methyl iodide, a volatile form of radioiodine, and pave the way for the development of in-situ and stand-off laser sensors for nuclear security. The Laboratory for Methods and Techniques for Nuclear Security, Traceability and Monitoring (FSN-SICNUC-TNMT) applies gamma spectroscopy for monitoring mobile radionuclides in the environment and could use the LPAS and DIAL techniques to support the evaluation and the study of the concentration of relevant radionuclides for nuclear safety and security
Why are cities less opposed to European integration than rural areas? Factors affecting the Eurosceptic vote by degree of urbanization
No full textIn recent years, protest voting, voting for populist parties and, specifically for Europe, votes for parties opposed to European integration, have increased substantially. This has focused the attention of researchers and policy makers on the causes behind this trend. Most of the existing research looked at voters' characteristics, mainly values, education and age, or economic insecurity, such as rising unemployment or a declining economy more in general. This paper focuses instead on the urban-rural divide in anti-EU sentiment, and tries to explain why cities – and urban areas in general - in Europe tend to vote less for Eurosceptic parties. Using electoral data for national elections at the electoral district level for the years 2013–2018 and political parties' orientation as assessed by the Chapel Hill Expert Survey, we find robust statistical evidence of a lower anti-EU vote in cities, towns and suburbs than in rural areas. We also find that drivers of voting for anti-EU parties differ significantly between urban and rural areas in the EU and UK, despite some similarities. We show that three factors are associated to a higher anti-EU vote in all areas: growth in unemployment, a low turnout and a higher share of people born outside the EU. A sluggish economy is associated to a higher anti-EU sentiment in rural areas, but not in cities and towns and suburbs. Higher shares of university graduates, people aged 20–64, and of people born in a different EU country reduce anti-EU voting in rural areas and towns and suburbs, but have no impact in cities
The role of spinal magnetic resonance in the diagnosis of 'chronic spinal' type of multiple sclerosis [IL RUOLO DELLA RISONANZA MAGNETICA MIDOLLARE NELLA DIAGNOSI DELLE FORME 'SPINALI CRONICHE' DI SCLEROSI MULTIPLA]
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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
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