One Class Splitting Criteria for Random Forests

Random Forests (RFs) are strong machine learning tools for classification and regression. However, they remain supervised algorithms, and no extension of RFs to the one-class setting has been proposed, except for techniques based on second-class sampling. This work fills this gap by proposing a natural methodology to extend standard splitting criteria to the one-class setting, structurally generalizing RFs to one-class classification. An extensive benchmark of seven state-of-the-art anomaly detection algorithms is also presented. This empirically demonstrates the relevance of our approach

Implementation strategies for hyperspectral unmixing using Bayesian source separation

Bayesian Positive Source Separation (BPSS) is a useful unsupervised approach for hyperspectral data unmixing, where numerical non-negativity of spectra and abundances has to be ensured, such in remote sensing. Moreover, it is sensible to impose a sum-to-one (full additivity) constraint to the estimated source abundances in each pixel. Even though non-negativity and full additivity are two necessary properties to get physically interpretable results, the use of BPSS algorithms has been so far limited by high computation time and large memory requirements due to the Markov chain Monte Carlo calculations. An implementation strategy which allows one to apply these algorithms on a full hyperspectral image, as typical in Earth and Planetary Science, is introduced. Effects of pixel selection, the impact of such sampling on the relevance of the estimated component spectra and abundance maps, as well as on the computation times, are discussed. For that purpose, two different dataset have been used: a synthetic one and a real hyperspectral image from Mars.Comment: 10 pages, 6 figures, submitted to IEEE Transactions on Geoscience and Remote Sensing in the special issue on Hyperspectral Image and Signal Processing (WHISPERS

Mutualistic interactions shape global spatial congruence and climatic niche evolution in Neotropical mimetic butterflies

Understanding the mechanisms underlying species distributions and coexistence is both a priority and a challenge for biodiversity hotspots such as the Neotropics. Here, we highlight that Mullerian mimicry, where defended prey species display similar warning signals, is key to the maintenance of biodiversity in the c. 400 species of the Neotropical butterfly tribe Ithomiini (Nymphalidae: Danainae). We show that mimicry drives large-scale spatial association among phenotypically similar species, providing new empirical evidence for the validity of Muller's model at a macroecological scale. Additionally, we show that mimetic interactions drive the evolutionary convergence of species climatic niche, thereby strengthening the co-occurrence of co-mimetic species. This study provides new insights into the importance of mutualistic interactions in shaping both niche evolution and species assemblages at large spatial scales. Critically, in the context of climate change, our results highlight the vulnerability to extinction cascades of such adaptively assembled communities tied by positive interactions

Mesure et prédiction des déformations et contraintes résiduelles lors du refroidissement d’un stratifié composite thermoplastique

International audienceCooling of thermoplastic composite parts inevitably leads to the development of residual stresses, which may have negative consequences on the final part health. Modelling their development during cooling therefore appears as an interesting solution to optimize the process parameters and limit the stresses intensity. This study proposes a coupled model accounting for heat transfer, crystallization kinetics and mechanical behavior of thermoplastic composite laminate. This latter is treated according to the modified lamination theory, which is for the first time adapted to the study of a thermoplastic composite during cooling, with temperature dependent properties. This is made possible by the use of an incremental linear elastic law, which also accounts for the crystallization shrinkage and thermal expansion of the material. The model is applied to the study of an unsymmetric laminate, which leads to estimated stress and strain states. These latter are compared with experimentally measured strains, highlighting an excellent agreement which validates the proposed moLe refroidissement des pièces composites thermoplastiques durant leur mise en oeuvre mène inexorablement au développement de contraintes résiduelles. Ces contraintes peuvent être néfastes pour la santé finale de la pièce et il convient de prédire leur développement au cours du procédé afin d'optimiser celui-ci et ainsi limiter l'impact des contraintes sur le matériau. Cette étude propose un modèle de prédiction du développement des contraintes résiduelles au cours du refroidissement d'un composite thermoplastique à fibres continues de verre et matrice PA66. Celui-ci prend en compte les transferts thermiques, la cinétique de cristallisation ainsi que le comportement mécanique du composite au cours de son refroidissement. Ce dernier est traité à l'aide de la théorie modifiée des stratifiés qui est adaptée pour la première fois au refroidissement d'un composite thermoplastique dont les propriétés thermomécaniques varient avec la température. Ceci est rendu possible à l'aide d'une formulation incrémentale de la loi de comportement linéaire élastique, prenant en compte les retraits d'origine thermique et de cristallisation. Appliqué au cas d'un empilement asymétrique, le modèle permet de prédire contraintes et déformations résiduelles. Ces dernières sont comparées à des mesures expérimentales pour évaluer la fiabilité du modèle développédel

Stable isotopes show Homo sapiens dispersed into cold steppes ~45,000 years ago at Ilsenhöhle in Ranis, Germany

The spread of Homo sapiens into new habitats across Eurasia ~45,000 years ago and the concurrent disappearance of Neanderthals represents a critical evolutionary turnover in our species' history. 'Transitional' technocomplexes, such as the Lincombian-Ranisian-Jerzmanowician (LRJ), characterize the European record during this period but their makers and evolutionary significance have long remained unclear. New evidence from Ilsenhöhle in Ranis, Germany, now provides a secure connection of the LRJ to H. sapiens remains dated to ~45,000 years ago, making it one of the earliest forays of our species to central Europe. Using many stable isotope records of climate produced from 16 serially sampled equid teeth spanning ~12,500 years of LRJ and Upper Palaeolithic human occupation at Ranis, we review the ability of early humans to adapt to different climate and habitat conditions. Results show that cold climates prevailed across LRJ occupations, with a temperature decrease culminating in a pronounced cold excursion at ~45,000-43,000 cal BP. Directly dated H. sapiens remains confirm that humans used the site even during this very cold phase. Together with recent evidence from the Initial Upper Palaeolithic, this demonstrates that humans operated in severe cold conditions during many distinct early dispersals into Europe and suggests pronounced adaptability. [Abstract copyright: © 2024. The Author(s).

NOUVEAUX RECEPTEURS ELECTROACTIFS SUBSTITUES PAR DES ACIDES OU ESTERS BORONIQUES. RECONNAISSANCE ANIONIQUE ET MOLECULAIRE EN PHASES HOMOGENE ET HETEROGENE

LA FONCTIONNALISATION DE MOLECULES ELECTROACTIVES PAR DES ACIDES OU ESTERS BORONIQUES A ETE REALISEE EN VUE DE CREER DE NOUVEAUX SYSTEMES DE RECONNAISSANCE ELECTROCHIMIQUE MOLECULAIRE OU ANIONIQUE. L'UTILISATION DE TELS GROUPEMENTS PRESENTE UN INTERET DOUBLE : D'UNE PART, LE CARACTERE ACIDE DUR DE LEWIS DE L'ATOME DE BORE LUI CONFERE UNE AFFINITE PARTICULIERE VIS-A-VIS DE CERTAINES BASES DURES COMME LES IONS FLUORURE ; D'AUTRE PART, LES GROUPEMENTS HYDROXYLES DE L'ACIDE BORONIQUE PERMETTENT EGALEMENT LA COMPLEXATION DE CERTAINES STRUCTURES POLYHYDROXYLEES TELLES QUE LES SUCRES. TOUT D'ABORD, L'ELECTROPOLYMERISATION DE COMPOSES AROMATIQUES (THIOPHENE, PYRROLE, ANILINE) PREFONCTIONNALISES PAR UN ACIDE OU UN ESTER BORONIQUE A ABOUTI A LA FORMATION DE FILMS DE POLYMERES ELECTROACTIFS EN MILIEUX AQUEUX ET ORGANIQUE. EN PHASE IMMOBILISEE, L'INTERACTION ENTRE LE BORE ET LE SUBSTRAT ETUDIE VA INDUIRE, DANS CERTAINS CAS, UNE MODIFICATION DU SIGNAL ELECTROCHIMIQUE CAUSEE PAR LA PERTURBATION DES PROPRIETES ELECTRONIQUES OU CONFORMATIONNELLES DU POLYMERE. L'ETUDE ELECTROCHIMIQUE DE CES POLYMERES CONDUCTEURS ELECTRONIQUES (EN PARTICULIER LE POLYPYRROLE SUBSTITUE EN POSITION 3 PAR UN ESTER BORONIQUE) A FINALEMENT RENDU COMPTE D'UNE BONNE SELECTIVITE VIS-A-VIS DES IONS FLUORURE ET, DANS UNE MOINDRE MESURE, DES IONS CHLORURE. L'ETUDE EN PRESENCE DE SUCRES N'A PU ETRE APPROFONDIE A CAUSE DE LA FAIBLE ELECTROACTIVITE DES DEPOTS ELECTROFORMES DANS L'EAU. LA SYNTHESE D'AUTRES RECEPTEURS DERIVES DES TRIPHENYLAMINES DANS LESQUELS LA DELOCALISATION ELECTRONIQUE S'ETEND DU CENTRE REDOX A L'ATOME DE BORE A ENSUITE ETE DECRITE. DES MODIFICATIONS VOLTAMPEROMETRIQUES REMARQUABLES SONT OBSERVEES AVEC CES COMPOSES EN SOLUTION SUITE A L'AJOUT DE F ALORS QU'AUCUN EFFET N'EST REMARQUE AVEC CL OU BR . ENFIN, LES ESSAIS REALISES AVEC LE COMPLEXE FERREUX DE L'ACIDE 4-2,2-BIPYRIDINE BORONIQUE ONT ELARGI LE DOMAINE D'INVESTIGATION AU MILIEU AQUEUX. LES MODIFICATIONS DE LA REPONSE ELECTROCHIMIQUE DU COUPLE REDOX FE(II)/FE(III) SUITE A L'AJOUT D'HALOGENURES ONT MIS EN AVANT UNE SELECTIVITE IDENTIQUE DU BORE VIS-A-VIS DES IONS FLUORURE. L'INTERET D'UTILISER DE TELLES STRUCTURES DANS L'EAU RESIDE DANS LA POSSIBILITE DE DETECTER D'AUTRES MOLECULES DE TYPE POLYOL. L'ETUDE ELECTROCHIMIQUE A DEMONTRE UNE AFFINITE PARTICULIERE VIS-A-VIS DU D-FRUCTOSE PARMI D'AUTRES SUCRES.RENNES1-BU Sciences Philo (352382102) / SudocSudocFranceF

Variable-Length Coding for Zero-Error Channel Capacity

International audienceThe zero-error channel capacity is the maximum asymptotic rate that can be reached with error probability exactly zero, instead of a vanishing error probability. The nature of this problem, essentially combinatorial rather than probabilistic, has led to various researches both in Information Theory and Combinatorics. However, the zero-error capacity is still an open problem, for example the capacity of the noisy-typewriter channel with 7 letters is unknown. In this article, we propose a new approach to construct optimal zero-error codes, based on the concatenation of words of variable-length, taken from a generator set. Three zero-error variable-length coding schemes, referred to as "variable-length coding", "intermingled coding" and "automata-based coding", are under study. We characterize their asymptotic performances via linear difference equations, in terms of simple properties of the generator set, e.g. the roots of the characteristic polynomial, the spectral radius of an adjacency matrix, the inverse of the convergence radius of a generator series. For a specific example, we construct an "intermingled" coding scheme that achieves asymptotically the zero-error capacity

Variable-Length Coding for Zero-Error Channel Capacity

International audienceThe zero-error channel capacity is the maximum asymptotic rate that can be reached with error probability exactly zero, instead of a vanishing error probability. The nature of this problem, essentially combinatorial rather than probabilistic, has led to various researches both in Information Theory and Combinatorics. However, the zero-error capacity is still an open problem, for example the capacity of the noisy-typewriter channel with 7 letters is unknown. In this article, we propose a new approach to construct optimal zero-error codes, based on the concatenation of words of variable-length, taken from a generator set. Three zero-error variable-length coding schemes, referred to as "variable-length coding", "intermingled coding" and "automata-based coding", are under study. We characterize their asymptotic performances via linear difference equations, in terms of simple properties of the generator set, e.g. the roots of the characteristic polynomial, the spectral radius of an adjacency matrix, the inverse of the convergence radius of a generator series. For a specific example, we construct an "intermingled" coding scheme that achieves asymptotically the zero-error capacity