1,720,969 research outputs found
Depositional dynamic of glaucony-rich deposits in the Lower Cretaceous of the Nice arc (Southeast France).
No full textA sedimentological and stratigraphical analysis has been applied to the Early Cretaceous glaucony-rich deposits of the southeastern margin of the Vocontian Basin. Thin sections, X-ray diffraction on random powders analyses, and data from geochemical analyses, performed on pure disaggregated glauconite grains by wavelength dispersion spectroscopy (WDS), allow the distinction of two populations of highly evolved glauconite grains. The first population is interpreted to be autochthonous (i.e., grains that have not experienced any transport from their place of origin). The second is interpreted to be parautochthonous (i.e., grains that have been removed from their place of origin and concentrated landward and seaward within nearly coeval deposits). Palaeoenvironmental information has been deduced mainly from (1) the characteristics of glauconitic grains, (2) meso- and microscopic analyses performed on the named lithozones, and (3) their lateral changes on a kilometre scale. Basin palaeogeography implies a southern area belonging to an outer platform and a northern zone with the characteristics of a distal ramp (Hauterivian). This depositional setting changed during the Barremian–Aptian owing to tectonics; fault systems led to a drowning of the western segment, but the previous environmental pattern presented again during Albian–Early Cenomanian times. Four different depositional events have been distinguished in the Early Cretaceous, and the relative sea-level changes have been reconstructed. We have traced relative sea-level fall during the Late Valanginian, the Early Barremian and the Albian (the second and third of these corresponding to the tectonic uplift outlined by Wilpshaar et al. (Cretac. Res. 18 (1997) 457)), while the general subsidence is confirmed by the transgression that led to the formation of glauconitic minerals. During the Lower Cretaceous, two second-order cycles have been recognized; although of the second order, the first sequence (Late Valanginian–Barremian) is made up like a third-order depositional sequence where different system-tracts are enhanced. The compared relative sea-level change corresponds to the curve of the second-order cycles of Haq et al. (1988, SEPM Spec. Publ. 42, 71–108)
DivNoise: A Data Collection for Source Identification on Diverse Camera Sensors
No full textIdentifying the acquisition source of media data is one of the most widely studied problems in multimedia forensics. A crucial aspect in this field is the availability of representative, diverse and up-to-date data corpora, so that the potential of existing and newly proposed techniques can be assessed in a reliable and reproducible manner. In this light, we present a novel dataset, named DivNoise, which encompasses both image and video data from a wide range of device cameras and collected in different environmental conditions. In particular, differently from existing databases, the dataset also includes data acquired from frontal cameras of mobile devices (smartphones and tablets) and from webcams, which are increasingly used tools to enable remote video communications in many application scenarios. The dataset is made publicly available to the research community, with the goal of supporting the development of novel source identification techniques. We perform an experimental evaluation on the DivNoise dataset through state-of-the-art algorithms, thus exposing preliminary yet intriguing empirical insights
Beyond Screens: Investigating Identity Proofing for the Metaverse Through Cross-Device Flows
No full textThis paper presents a secure identity proofing flow for metaverse-based applications, enabling the validation of authoritative identity evidence (such as electronic passports and identity cards) to support sensitive or legally binding operations performed through virtual reality (VR) headsets. These use cases, common in business environments, require users' credentials to be strongly linked to verified real-world identities, ensuring compliance with regulatory standards. The solution involves a cross-device flow where users first verify their identity on a mobile device by presenting valid identity evidence. This verified identity is then transferred to the VR headset, where users can register and activate credentials for future authentication. Beyond providing key security considerations and defining a taxonomy of possible attacks, we discuss how our design choices enhance the security of the flow
Towards a Fine-Grained Threat Model for Video-Based Remote Identity Proofing
No full textThe attack landscape against video-based face verification is rapidly evolving, thus leading to increased opportunities of impersonation and identity theft within remote identity proofing processes. To support reliable security and risk analyses, we provide an extended threat model composed of threats and security controls for the face acquisition phase. Special emphasis is devoted to recent advancements in video synthesis and physical rendering, as well as diversified approaches for liveness detection
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
Adversarial mimicry attacks against image splicing forensics: An approach for jointly hiding manipulations and creating false detections
Full text linkThe term “mimicry attack” has been coined in computer security and used in adversarial machine learning: an attacker observes what a machine-learning system has learned and adjusts the malicious input so that it mimics a benign input. In this paper we extend this concept to image forensics, to allow an attacker modifying a manipulated image so that it appears pristine when analyzed by a target forensic detector. Recent work has shown that such attacks can be executed against detectors based on deep networks for hiding image tampering. We do more than that: our mimicry attack can force the target detector to identify arbitrary fictitious manipulations, while hiding the true ones. Accordingly, the user of the forensic detector is completely misled. From a methodological viewpoint, the proposed attack artificially alters the detector-specific intermediate representations according to the pixel distribution in the manipulated image, by applying a gradient-based optimization process. Experimental tests on different data sets and detectors demonstrate that our approach succeeds in jointly hiding manipulated areas and arbitrarily adding new ones, favorably comparing with the state-of-the-art in the first task
Verbesserung der Syndrome-Trellis-Kodierung zur Erhöhung der Unvorhersagbarkeit von Einbettpositionen in steganographischen Systemen
No full textBeim Einbetten einer versteckten Nachricht in ein Trägermedium wählen adaptive steganographische Systeme die Einbettpositionen abhängig von der erwarteten Auffälligkeit der Änderungen. Die optimale Auswahl kann statistisch modelliert werden. Wir präsentieren Ergebnisse einer Reihe von Experimenten, in denen untersucht wird, inwiefern die Auswahl durch Syndrome-Trellis-Kodierung dem Modell unabhängiger Bernoulli-verteilter Zufallsvariablen entspricht. Wir beobachten im Allgemeinen kleine Näherungsfehler sowie Ausreißer an Randpositionen. Bivariate Abhängigkeiten zwischen Einbettpositionen ermöglichen zudem Rückschlüsse auf den verwendeten Kode und seine Parameter. In Anwendungen, welche die Ausreißer nicht mithilfe zufälliger Permutationen verstecken können, kann die hier vorgeschlagene „outlier corrected“-Variante verwendet werden um die steganographische Sicherheit zu verbessern. Die aggregierten bivariaten Statistiken sind dahingegen invariant unter Permutationen und stellen, unter der Annahme mächtiger Angreifer, ein bisher nicht erforschtes Sicherheitsrisiko dar
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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