Leveraging blur information for plenoptic camera calibration

This paper presents a novel calibration algorithm for plenoptic cameras, especially the multi-focus configuration, where several types of micro-lenses are used, using raw images only. Current calibration methods rely on simplified projection models, use features from reconstructed images, or require separated calibrations for each type of micro-lens. In the multi-focus configuration, the same part of a scene will demonstrate different amounts of blur according to the micro-lens focal length. Usually, only micro-images with the smallest amount of blur are used. In order to exploit all available data, we propose to explicitly model the defocus blur in a new camera model with the help of our newly introduced Blur Aware Plenoptic (BAP) feature. First, it is used in a pre-calibration step that retrieves initial camera parameters, and second, to express a new cost function to be minimized in our single optimization process. Third, it is exploited to calibrate the relative blur between micro-images. It links the geometric blur, i.e., the blur circle, to the physical blur, i.e., the point spread function. Finally, we use the resulting blur profile to characterize the camera's depth of field. Quantitative evaluations in controlled environment on real-world data demonstrate the effectiveness of our calibrations.Comment: arXiv admin note: text overlap with arXiv:2004.0774

Stochastic Downscaling Method: Application to Wind Refinement

International audienceIn this article, we propose a new stochastic downscaling method: provided a numerical prediction of wind at large scale, we aim to improve the approximation at small scales thanks to a local stochastic model. We first recall the framework of a Lagrangian stochastic model borrowed from S.B. Pope. Then, we adapt it to our meteorological framework, both from the theoretical and numerical viewpoints. Finally, we present some promising numerical results corresponding to the simulation of wind over the Mediterranean Sea

On mean discounted numbers of passage times in small balls of Ito processes observed at discrete times

International audienceThe aim of this note is to prove estimates on mean values of the number of times that Itô processes observed at discrete times visit small balls in \er^d. Our technique, in the infinite horizon case, is inspired by Krylov's arguments in~\cite[Chap.2]{kry80}. In the finite horizon case, motivated by an application in stochastic numerics, we discount the number of visits by a locally exploding coefficient, and our proof involves accurate properties of last passage times at 0 of one dimensional semimartingales

On mean numbers of passage times in small balls of discretized Itô processes

International audienceThe aim of this note is to prove estimates on mean values of the number of times that Itô pro- cesses observed at discrete times visit small balls in Rd. Our technique, in the infinite horizon case, is inspired by Krylov's arguments in [2, Chap.2]. In the finite horizon case, motivated by an application in stochastic numerics, we discount the number of visits by a locally exploding coef- ficient, and our proof involves accurate properties of last passage times at 0 of one dimensional semimartingales

MULTI-STAKEHOLDER VARIETAL INNOVATION PLATFORMS. A SOCIOTECHNICAL PARTNERSHIP RESEARCH SCHEME ASSESSED IN BENIN

International audienceParticipatory plant breeding research may be hampered by the fact that results that have been obtained in very specific localized settings cannot be disseminated and scaled. Varietal innovation platforms aim to overcome this problem by ensuring that the viewpoints of people involved in assessments are representative of broad interest groups and that assessment results will be validated and disseminated by an organization. Each platform is designed as a sociotechnical scheme consisting of a five-member steering committee (SC), a club with a membership of 25 local users and experts (CLUE), a common varietal test plot and a network of around 15-20 on-farm plots. The aim is to describe, evaluate and disseminate improved varieties to target groups of stakeholders faced with the same environmental, agricultural and socioeconomic constraints. Partnerships between all of these stakeholders are set up, organized and managed according to six principles outlined in a charter—legitimacy, competence, efficiency, democracy, solidarity and transparency. Two experimental platforms were set up in the villages of Zé and Tori-Bossito, in southern Benin, to assess plantain varieties released by the Centre africain de recherche sur le bananier et le plantain (CARBAP). These platforms were monitored 20 months following their creation. The survey showed that the two platforms had successfully carried out all of their initially planned activities. The CLUEs identified four interesting varieties. The survey focused on the future plans made by SC and CLUE members to tap the benefits of knowledge acquired during 18 months. It showed that: (i) their plans provided conditions favorable for varietal dissemination and scaling, (ii) SC plans were based on transfer of the platform scheme whereas the CLUE plans were based on varietal dissemination, and (iii) the Tori plan was collective while the Zé plan was more individually focused. Our analysis highlighted that the respect of the legitimacy, skill and solidarity principles was most required to expect successful dissemination of the results obtained on the platforms

Stochastic Particle Method Applied to Local Wind Simulation

International audienceA Lagrangian stochastic model is introduced in order to describe the local behavior of the wind. Based on some MM5 data, and thanks to particles driven by stochastic differential equations, we propose a numerical method allowing to improve the MM5 simulations at small scales, without requiring too much additional computational cost

Modélisation stochastique et approche fiabiliste pour la sécurité routière des poids lourds articulés

L'objectif de cet article est le développement d'une stratégie fiabiliste pour la prévention des risques de renversement et de mise en portefeuille des véhicules, de type poids lourd (tracteur et semi-remorque), en zone accidentogène. Le caractère aléatoire du triplet conducteur-véhicule-infrastructure est intégré à l'aide de variables et processus aléatoires dans un modèle dynamique spécifiquement développé. Une analyse de sensibilité globale ainsi qu'une analyse de fiabilité, par des méthode de type FORM/SORM, permettent la détection de situations à risque

Thermal conductivity of the Toda lattice with conservative noise

We study the thermal conductivity of the one dimensional Toda lattice perturbed by a stochastic dynamics preserving energy and momentum. The strength of the stochastic noise is controlled by a parameter $\gamma$. We show that heat transport is anomalous, and that the thermal conductivity diverges with the length $n$ of the chain according to $\kappa(n) \sim n^\alpha$, with $0 < \alpha \leq 1/2$. In particular, the ballistic heat conduction of the unperturbed Toda chain is destroyed. Besides, the exponent $\alpha$ of the divergence depends on $\gamma$