arXiv subjects

David Hébert

Publications and source records attributed to David Hébert.

5 recordsLinked to original sources

arXiv2026

DebrisTracer: Reliable Tracking in Hypervelocity Impact Fast Imaging

This application paper presents DebrisTracer, a framework for the reliable tracking of debris in hypervelocity impact fast imaging. These noisy and highly specific datasets capture the ejection of a large number of debris fragments after the impact of a projectile launched at hypervelocity into a target material. The reliable estimation of debris mass and speed distributions is of major importance in aerospace applications. We document how to extend an off-the-shelf topology tracking framework based on critical point extraction and matching, in order to incorporate domain knowledge and physical assumptions. Our approach automatically produces an accurate and reliable debris tracking, enabling an interpretable visual analysis of this complex space-time phenomenon. Extensive experiments demonstrate the accuracy improvements provided by our approach over established tools used by domain experts in terms of physical validation, specifically via the prediction of the experimental ejected mass and crater depth profiles. We illustrate the utility of our approach across several use cases (with varying impact angles and physics). We show that our statistical summaries enable the visual identification of distinct regimes within the debris population, corroborating and refining prior expectations of domain experts. Our database and our C++ implementation are available at this address: https://github.com/tloloum/DebrisTracer.

cs.LG↗

arXiv2017

Thermo-elasto-plastic simulations of femtosecond laser-induced structural modifications: application to cavity formation in fused silica

The absorbed laser energy of a femtosecond laser pulse in a transparent material induces a warm dense matter region which relaxation may lead to structural modifications in the surrounding cold matter. The modeling of the thermo-elasto-plastic material response is addressed to predict such modifications. It has been developed in a 2D plane geometry and implemented in a hydrodynamic lagrangian code. The particular case of a tightly focused laser beam in the bulk of fused silica is considered as a first application of the proposed general model. It is shown that the warm dense matter relaxation, influenced by the elasto-plastic behavior of the surrounding cold matter, generates both a strong shock and rarefaction waves. Permanent deformations appear in the surrounding solid matter if the induced stress becomes larger than the yield strength. This interaction results in the formation of a sub-micrometric cavity surrounded by an overdense area. This approach also allows one to predict regions where cracks may form. The present modeling can be used to design nano-structures induced by short laser pulses.

physics.app-ph↗

arXiv2012

Logical segmentation for article extraction in digitized old newspapers

Newspapers are documents made of news item and informative articles. They are not meant to be red iteratively: the reader can pick his items in any order he fancies. Ignoring this structural property, most digitized newspaper archives only offer access by issue or at best by page to their content. We have built a digitization workflow that automatically extracts newspaper articles from images, which allows indexing and retrieval of information at the article level. Our back-end system extracts the logical structure of the page to produce the informative units: the articles. Each image is labelled at the pixel level, through a machine learning based method, then the page logical structure is constructed up from there by the detection of structuring entities such as horizontal and vertical separators, titles and text lines. This logical structure is stored in a METS wrapper associated to the ALTO file produced by the system including the OCRed text. Our front-end system provides a web high definition visualisation of images, textual indexing and retrieval facilities, searching and reading at the article level. Articles transcriptions can be collaboratively corrected, which as a consequence allows for better indexing. We are currently testing our system on the archives of the Journal de Rouen, one of France eldest local newspaper. These 250 years of publication amount to 300 000 pages of very variable image quality and layout complexity. Test year 1808 can be consulted at plair.univ-rouen.fr.

cs.IR↗

arXiv2010

Complexe de Poids, Dualité et Motifs de Beilinson

In the article [GS96], Gillet and Soulé define a weight complex on the category of Voevodsky motives over a field of characteristic 0. In [Bon07], Bondarko generalizes this construction for any f-category with a bounded weight structure, as is the case for Beilinson motives (following Cisinski-Déglise ; [CD09]). The first purpose of this note is to generalize [GS96, thm. 2] in the world of Beilinson motives. This done, we will naturally be led to define the motivic Euler characteristic dual to that considered by Bondarko in [Bon10]. This fact will motivate the second line of this note : proving that the duality operation exchanges the weight as is the case for t-structure ([BBD, 5.1.14.(iii)]). ----- Dans l'article [GS96], Gillet et Soulé définissent un complexe de poids sur la catégorie des motifs de Voevodsky définie sur un corps de caractéristique 0. Dans [Bon07], Bondarko généralise cette construction pour toute f-catégorie munie d'une structure de poids bornée, comme c'est le cas pour les motifs de Beilinson (suivant Cisinski-Déglise ; [CD09]). Le premier but de cette note est de généraliser [GS96, thm. 2] dans le monde des motifs de Beilinson. Ceci fait, on sera naturellement amené à définir la caractéristique d'Euler motivique duale à celle considérée par Bondarko dans [Bon10]. Ce fait motivera le second axe de cette note : prouver que l'opération de dualité échange les poids comme c'est le cas pour les t-structures ([BBD, 5.1.14.(iii)]).

math.AG↗

arXiv2010

Structures de poids à la Bondarko sur les motifs de Beilinson

In [Bon07], Bondarko defines and studies the notion of weight structure and he shows that there exist a weight structure over the category of Voevodsky motives with rationals coefficients (over a field of characteristic 0). In this paper we extend this weight structure to the category of Beilinson motives (for any scheme of finite type over a base scheme which is excelent of dimension at most two) introduced and studied by Cisinsky-Déglise. ----- Dans [Bon07], Bondarko définit et étudie la notion de structure de poids et il montre qu'il existe une structure de poids sur la catégorie des motifs de Voevodsky à coefficients rationnels (sur un corps de caractéristique 0). Dans cet article nous étendons cette structure de poids à la catégorie des motifs de Beilinson (pour un schéma de type fini sur un schéma de base qui est excellent de dimension au plus deux) introduite et étudiée par Cisinsky-Déglise ([CD09]).

math.AG↗