1,721,059 research outputs found
Influence of processing conditions on rheology of tyre rubber modified bitumens
No full textTyre Rubber Modified Binders (TR-MBs), produced through McDonald wet process and used worldwide (e.g. asphalt rubber), have been demonstrated to provide various benefits to pavements and, moreover, they represent a good opportunity for recycling tyre rubber. However this technology is still struggling to be fully adopted in Europe, mainly because of their poor stability during high temperatures storage, which leads to high initial costs in modifying existing asphalt plants. NO-agitation TR-MBs (also known as terminal blends) is proving to be a great option and its development could also be the key to spreading the recycling of tyre rubber in paving applications in Europe. This paper aims to enrich this field of research by presenting the results of a study focused on the optimisation of laboratory procedures to better understand the effect of varying processing conditions on the rheology TR-MBs. The experimental programme has been carried out by a preliminary selection of materials, followed by the production of the TR-MBs, via practical laboratory protocols. A continuous comparison between two commercially used SBS-MBs, with high and medium levels of modification, and the produced TR-MBs, helped to understand the effect of varying the selected processing conditions on binder properties. Results have shown that TR-MBs are a very effective alternative to commercially used SBS-MB. Although the rheology of TR-MBs is very sensitive to the varying of processing conditions, therefore an appropriate selection of materials and a superior binder design are mandatory to optimise the modification process to achieve the desired level of modification
Comparison between bitumen modified with crumb tyre rubber and styrene butadiene styrene
No full textThe improvements in terms of mechanical properties due to the use of polymers
to modify bitumens in road paving applications have already been widely demonstrated. The
aim of this paper is to show how the rheology and the performance of a bituminous binder
mixed with crumb rubber recycled from used tyres (CR-MB), could be comparable with a
styrene butadiene styrene (SBS-MB) created with the same base binder and currently used for
road applications. Physical, chemical and performance characterization followed by rheological
and storage stability analyses have been undertaken as the basis for the comparison. The results
of the investigation indicate that the blended CR-MB shows large improvements with respect to
the base bitumen, comparable with the SBS-MB under almost all the conditions. However, in
order to use this binder for practical purposes, major work regarding the improvement of the
storage stability of the CR-MB still needs to be done
Dictionary Attacks on Speaker Verification
No full textIn this paper, we propose dictionary attacks against speaker verification - a novel attack vector that aims to match a large fraction of speaker population by chance. We introduce a generic formulation of the attack that can be used with various speech representations and threat models. The attacker uses adversarial optimization to maximize raw similarity of speaker embeddings between a seed speech sample and a proxy population. The resulting master voice successfully matches a non-trivial fraction of people in an unknown population. Adversarial waveforms obtained with our approach can match on average 69% of females and 38% of males enrolled in the target system at a strict decision threshold calibrated to yield false alarm rate of 1%. By using the attack with a black-box voice cloning system, we obtain master voices that are effective in the most challenging conditions and transferable between speaker encoders. We also show that, combined with multiple attempts, this attack opens even more to serious issues on the security of these systems
Adversarial optimization for dictionary attacks on speaker verification
No full textIn this paper, we assess vulnerability of speaker verification systems to dictionary attacks. We seek master voices, i.e., adversarial utterances optimized to match against a large number of users by pure chance. First, we perform menagerie analysis to identify utterances which intrinsically hold this property. Then, we propose an adversarial optimization approach for generating master voices synthetically. Our experiments show that, even in the most secure configuration, on average, a master voice can match approx. 20% of females and 10% of males without any knowledge about the population. We demonstrate that dictionary attacks should be considered as a feasible threat model for sensitive and high-stakes deployments of speaker verification
Comparison between various bituminous binders modified with crumb tyre rubber
No full textThe aim of this paper is to show how the rheology, the performance and the storage
stability of different bituminous binders, obtained from two bitumens with different
asphaltenes content, change their properties when they are modified with recycled tyre crumb
rubber. Physical, chemical and performance characterisation followed by rheological and
storage stability analyses have been undertaken as the basis for the comparison. The results
of the investigation indicate that bitumen with lower asphaltenes content is more influenced
by the modification with the rubber. However, the modification of the bitumen with the higher
asphaltenes content gives a binder with better performance and storage stability. Moreover,
results shows that the addition of a certain amount of oil extender to the bitumens reduces the
effect of the modification and has no positive effect on storage stability
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
No full text“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
No full textWe 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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