HAL Portal Univ-Côtedazur
Not a member yet
95391 research outputs found
Sort by
Centered colorings in minor-closed graph classes
No full textInternational audienceA vertex coloring of a graph is -centered if for every connected subgraph of , either uses more than colors on , or there is a color that appears exactly once on . We prove that for every fixed positive integer , every -minor-free graph admits a -centered coloring using colors
Language and screen-based multimodal communication
No full textThe main objective of this chapter is to explore how language and languaging are impacted by the mediatization of digital technologies. First we point to the main characteristics of screen-based communication, that is multimodality, interactivity, mobility, relationship to time and technogenres. Then we address three current research issues: multilingualism and translations, discrimination and hate speech, and automatic processing of languages in large language models.Key points•Screen-based communication has evolved according to the technologies available over time.•Screen-based communication has an impact on language in terms of multimodality, interactivity, mobility, temporal plasticity and new genericity.•The presence of natural languages in screen-based communication provides possibilities and constraints for machine translation.•Screen-based communication has shown issues in interactional dynamics for different types of discrimination and hate speech.•Artificial intelligence and large language models for chatbots in screen-based communication open new insights and research questions in linguistics
NURBSFit: Robust Fitting of NURBS Surfaces to Point Clouds
No full textInternational audienceNURBS surfaces are compact parametric representations widely used in Computer-Aided Design (CAD) modeling. Decomposing raw 3D data measurements into a set of such elements is a challenging problem that existing methods approach by learning from CAD databases to both segment synthetic data and fit parametric shapes on each segment. Unfortunately, these methods generalize poorly to raw data measurements, with low robustness to imperfect data and complex objects and low scalability. To address this issue, we propose NURBSFIT, an algorithm that fits NURBS surfaces to unorganized 3D point clouds, such as those generated by laser and photogrammetry acquisition systems. Starting with a fine configuration of planar patches that approximate the object geometry, our algorithm performs merging operations that progressively regroup pairs of adjacent patches into fewer, more expressive NURBS surfaces. This process is designed to be both robust and performant with a series of technical ingredients that include an energy that controls the global quality of a configuration of NURBS surfaces and an efficient ordering of the merging operations based on a cost-efficient quadric surface fitting analysis. We show the potential of our algorithm on both synthetic and real-world data and its efficiency against existing primitive fitting methods with results both simpler and geometrically more accurate. Our implementation is available at: https://github.com/lizOnly/nurbsfit
Algorithms and Lower Bounds for the Maximum Overlap of Two Polygons Under Translation
No full textInternational audienceA fundamental problem in shape matching and geometric similarity is computing the maximum area overlap between two polygons under translation. For general simple polygons, the best-known algorithm runs in time [Mount, Silverman, Wu 96], where and are the complexities of the input polygons. In a recent breakthrough, Chan and Hair gave a linear-time algorithm for the special case when both polygons are convex. A key challenge in computational geometry is to design improved algorithms for other natural classes of polygons. We address this by presenting an -time algorithm for the case when both polygons are orthogonal. This is the first algorithm for polygon overlap on orthogonal polygons that is faster than the almost 30 years old algorithm for simple polygons. Complementing our algorithmic contribution, we provide -SUM lower bounds for problems on simple polygons with only orthogonal and diagonal edges. First, we establish that there is no algorithm for polygon overlap with running time , where , unless the -SUM hypothesis fails. This matches the running time of our algorithm when . We use part of the above construction to also show a lower bound for the polygon containment problem, a popular special case of the overlap problem. Concretely, there is no algorithm for polygon containment with running time under the -SUM hypothesis, even when the polygon to be contained has vertices. Our lower bound shows that polygon containment for these types of polygons (i.e., with diagonal edges) is strictly harder than for orthogonal polygons, and also strengthens the previously known lower bounds for polygon containment. Furthermore, our lower bounds show tightness of the algorithm of [Mount, Silverman, Wu 96] when
The effect of articulatory rehearsal on dual-retrieval processes in semantically related list recall: A comparison between 8- and 10-year-old children and young adults
No full textInternational audienceWhen asked to remember a list of items for later testing, we often repeat earlier items to ourselves as later items are presented. This process, called “rehearsal,” develops during childhood. The present study examined the role of rehearsal in recalling lists of semantically related words and used the dual-retrieval model to pinpoint the retrieval processes modified by rehearsal in children and adults. Thirty-one children (Mage = 8.8 years, SD = 0.5, 12 females and 19 males) and 29 adults (Mage = 20.5 years, SD = 2.7, 23 females and 6 males) performed a complex span task consisting of maintaining words to be recalled later in immediate and delayed tests, while performing a concurrent task. The difficulty of the task was adjusted according to each participant’s abilities. Participants performed the task either silently, which allowed them to use rehearsal, or under articulatory suppression, which reduced rehearsal opportunities. The results showed that, although adults had a higher rate of correct recall, children benefited from rehearsal opportunities for both immediate and delayed correct recall. There were also fewer semantic errors in both age groups when rehearsal could be used. The dual-retrieval model revealed that rehearsal fosters direct access to verbatim memory and reconstruction based on gist memory. Finally, the difference in correct recall and direct access between the two age groups decreased when rehearsal could be used. These findings suggest that, although rehearsal is more effective for adults, children benefit more from it for correct recall and direct access to verbatim traces
Truncated PNA-functionalized porous silicon biosensor for low-cost and early detection of troponin T in myocardial infarction
No full textInternational audienc
Search for Magnetic Monopoles with the Complete ANTARES Dataset
No full textInternational audienceThis study presents a novel search for magnetic monopoles using data collected over a 14 year period (2008-2022) by the ANTARES neutrino telescope. The interaction of magnetic monopoles with matter was modeled according to Kazama, Yang, and Goldhaber cross-section. Upper limits on the flux of magnetic monopoles are obtained for velocities both above and below the Cherenkov threshold. No events consistent with the passage of magnetic monopoles were detected, enabling the setting of an upper flux limit for relativistic magnetic monopoles of the order of
Fast Landmark Reconfiguration for Highway Cover Indexes
No full textInternational audienceThe highway cover labeling (HCL) is an indexing method for weighted digraphs that enables fast queries on important graph properties such as distances and constrained shortest paths. Originally introduced by [Farhan et al., EDBT 2019], the HCL has gained popularity in the field of large-scale graph mining due to its efficiency: in fact, an HCL index can be computed with reasonable preprocessing computational effort, answers queries in near real time, and has low space overhead -even for graphs with tens of millions of arcs. Such a remarkable performance is obtained by carefully selecting, during the preprocessing phase, a subset of the vertices of the input graph, called landmarks, and by computing a suitable collection of paths and distances from/to landmarks to be used to reconstruct graph properties of interest upon query.Recent work has shown how to adapt the HCL method to dynamic graphs, allowing updates to the graph topology without full recomputation, by identifying and updating, efficiently, the portion of the index that is altered by a modification. However, no prior dynamic methods, to efficiently handle changes to the landmark set itself, are known. This paper addresses this limitation by introducing two new dynamic algorithms specifically designed for landmark updates. Our experiments show that these methods can update an HCL index in seconds even in massive graphs -achieving speedups of several orders of magnitude over full reprocessing and enabling the use of HCL indices in fully dynamic settings.</div
Mechanized Dominator Tree Certification
No full textInternational audienceIn modern compilers, many optimizations and analyses, in particular those based on the SSA form, rely on dominance information, so computing dominators efficiently is an important problem. The classic algorithm to compute dominators in a control flow graph is the one designed by Lengauer and Tarjan in 1979. Other efficient algorithms have been proposed since. Previous works formally verified less efficient algorithms, and formally validated parts of the Lengauer-Tarjan algorithm, but there is no complete formal verification or validation of any of the fast algorithms computing dominators so far. In 2016, Georgiadis and Tarjan described a method to tackle these. They defined a certificate with which it becomes easy to validate dominators. Following their method, we successfully implemented and proved correct a validator of dominators in the Rocq Prover, inside the CompCertSSA verified compiler. This is the first complete mechanized certification of a fast algorithm computing dominators
Overview of LifeCLEF 2025: Challenges on Species Presence Prediction and Identification, and Individual Animal Identification
No full textInternational audienceBiodiversity monitoring using AI-powered tools has become vital for tracking species distributions and assessing ecosystem health on a large scale. Automated image- and sound-based species recognition, in particular, continues to accelerate conservation efforts by enabling rapid, low-cost surveys of vulnerable populations. However, the ever-growing variety of algorithms and data sources underscores the need for standardized benchmarks to assess real-world performance. Since 2011, the LifeCLEF lab has filled this role by organizing annual evaluations that promote collaboration among AI experts, citizen science, and ecologists. In this overview, we report on the LifeCLEF 2025 edition, which featured five distinct, data-driven tasks: (i) AnimalCLEF, focusing on open-set individual animal re-identification; (ii) BirdCLEF+, about species recognition in complex acoustic soundscape recordings; (iii) FungiCLEF, addressing few-shot classification of rare fungi species; (iv) GeoLifeCLEF, combining environmental and high-resolution remote sensing with occurrence records to predict plant species presence; and (v) PlantCLEF, aiming to identify multiple co-occurring plant species in vegetation-plot imagery. This paper provides an overview of the motivation, methodology, and main outcomes of the five challenges