Science & Mathematics

We consider the active learning problem of inferring the transition model of a Markov Decision Process by acting and observ- ing transitions. This is particularly useful when no reward function is a priori defined. Our proposal is to cast the active learning task as a utility maximization problem using Bayesian reinforcement learning with belief-dependent rewards. After presenting three possible performance criteria, we derive from them the belief-dependent rewards to be used in the decision-making process. As computing the optimal Bayesian value function is intractable for large horizons, we use a simple algorithm to approximately solve this optimization problem. Despite the sub-optimality of this technique, we show experimentally that our proposal is efficient in a number of domains.

The aim of the present paper is to introduce new mathematical tools for the analysis and control of nonlinear time-delay systems (NLTDS). An Extended Lie bracket operation equivalent to the Lie bracket operation for system without delays is introduced. It will be shown that this operation helps to characterize certain properties of a given submodule, such as nilpotency. This basic property is then used to define the conditions under which a given unimodular matrix represents a bicausal change of coordinates. The effectiveness of the proposed approach will be shown by solving an important basic problem: to characterize if a NLTDS is equivalent or not, to a Linear Time-Delay System by bicausal change of coordinates.

Le traitement de poudres en four tournant met en oeuvre des phénomènes chimiques et mécaniques qui se caractérisent par une grande diversité d'échelles spatiales et temporelles dont la simulation est rendue délicate par la nécessité de concilier consistance du modèle et temps de calcul. Pour la modélisation du mouvement nous avons développé une méthode des éléments discrets fondée sur le modèle de Cundall et couplée à une représentation géométrique du four par éléments finis. La recherche des contacts est optimisée par l'emploi d'une triangulation de Delaunay ou d'un système de casiers.

Industry 4.0 proposes the inclusion of IoT components in industrial contexts to have a better control on production and logistic processes. Unfortunately, growing connectivity in a formerly isolated world induces major security risks which are especially critical in an industrial context. Furthermore, the highly fragmented nature of the industrial IoT market imposes interoperability management. Interoperability and heterogeneity generally poses security challenges, exacerbating these risks. oneM2M is a promising standard that can enable interoperability and ensure communication with various tier protocols. The interface between oneM2M and tiers protocols has however to be trusted, which is undesirable. In this paper, we focus on the first phase of an approach to enable end-to-end encryption between oneM2M and Zigbee devices: secure key exchange. We fully define an exchange protocol taking place during the enrolment of a Zigbee device within oneM2M. We provide and discuss an implementation of this protocol, demonstrating its technical feasibility.

Ce travail vise à étudier l'interaction entre un écoulement de couche limite instable et une structure déformable dans le but d'évaluer le bruit hydrodynamique qui peut en résulter. Des simulations numériques directes de l'évolution de la couche limite totale sur une plaque mince élastique encastrée sont effectuées, la dynamique du couplage fort entre le déplacement de la paroi et la pression dans l'écoulement étant notamment prise en compte par une méthode de pas fractionnaire. Ces simulations, complétées par des analyses spectrales en espace et en temps, mettent en évidence des phénomènes de résonances et de masse ajoutée au niveau de la paroi et montrent que les vibrations propres de la paroi peuvent générer des oscillations supplémentaires de pression le long de la paroi à relativement hautes fréquences et petites échelles spatiales, sources potentielles de bruit hydrodynamique. Ce travail est effectué dans le cadre d'une bourse de thèse Cifre avec Thales Underwater Systems.

La mise en oeuvre de la Directive Cadre Européenne sur l’eau (DCE) et les approches centrées sur la biodiversité nécessitent, en particulier, des méthodes d’évaluation et de suivi des sources de pressions. L’occupation du sol dans les corridors rivulaires a un rôle significatif sur la qualité écologique des cours d’eau. Cet espace est donc un facteur de gestion privilégié pour les différents niveaux d’acteurs. Cette communication relate les expériences croisées de développement d’un outil opérationnel de gestion : la production d’indicateurs normatifs et descriptifs d’occupation du sol. Nous présentons les dimensions des besoins de chaque partenaire. Nous montrons ensuite, au travers de la production coordonnée d’indicateurs, les apports réciproques. De la concomitance de besoins est né un véritable travail d’équipe, de co-construction à même d’asseoir la légitimité des indicateurs des différents partenaires. / Water Framework Directive implementation and biodiversity centered approaches require pressure assessment and monitoring methods. Riparian corridors have a significant role on the river ecological quality. So, they are key space of management for stakeholders whatever their working scales. This paper describes the experiences of a cross-development for an operational tool management. The aim is the production of normative and descriptive land use indicators. The objective is to respond to each partner needs. We demonstrate the part brought by reciprocal contributions through coordinated production of indicators. A true project team is born from concomitant needs. This co-construction work permits partners to establish indicators legitimacy.

The tumor microenvironment is crucial for the growth of cancer cells, triggering particular biochemical and physiological changes, which frequently influence the outcome of anticancer therapies. The biochemical rationale behind many of these phenomena resides in the activation of transcription factors such as hypoxia-inducible factor 1 and 2 (HIF-1/2). In turn, the HIF pathway activates a number of genes including those involved in glucose metabolism, angiogenesis, and pH regulation. Several carbonic anhydrase (CA, EC 4.2.1.1) isoforms, such as CA IX and XII, actively participate in these processes and were validated as antitumor/antimetastatic drug targets. Here, we review the field of CA inhibitors (CAIs), which selectively inhibit the cancer-associated CA isoforms. Particular focus was on the identification of lead compounds and various inhibitor classes, and the measurement of CA inhibitory on-/off-target effects. In addition, the preclinical data that resulted in the identification of SLC-0111, a sulfonamide in Phase Ib/II clinical trials for the treatment of hypoxic, advanced solid tumors, are detailed.

We investigate a multi-household DSGE model in which past aggregate consumption impacts the confidence, and therefore consumption propensity, of individual households. We find that such a minimal setup is extremely rich, and leads to a variety of realistic output dynamics: high output with no crises; high output with increased volatility and deep, short lived recessions; alternation of high and low output states where relatively mild drop in economic conditions can lead to a temporary confidence collapse and steep decline in economic activity. The crisis probability depends exponentially on the parameters of the model, which means that markets cannot efficiently price the associated risk premium. We conclude by stressing that within our framework, narratives become an important monetary policy tool, that can help steering the economy back on track.

There exists a special kind of perfection-in symmetry, simplicity, and stability-attainable for structures generated from precisely 60 ligands (all of a single type) that protect 145 metal-atom sites. The symmetry in question is icosahedral ( Ih), generally, and chiral icosahedral ( I) in particular. A 60-fold equivalence of the ligands is the smallest number to allow this kind of perfection. Known cluster compounds that approximate this structural ideal include palladium-carbonyls, Ih-Pd145(CO)60; gold-thiolates, I-Au144(SR)60; and gold-alkynyls, I-Au144(C2R)60. Many other variants are suspected. The Pd145 compound established the basic achiral structure-type. However, the Au144-thiolate archetype is prominent, historically in its abundance and ease of preparation and handling, in its proliferation in many laboratories and application areas, and ultimately in the intrinsic chirality of its geometrical structure and organization of its bonding network or connectivity. As discovered by mass spectrometry (the "30-k anomaly") in 1995, it appeared as a broad single peak, as solitary and symmetrical as Mount Fuji, centered near 30 kDa (∼150 Au atoms), provoking these thoughts: Surely this phenomenon requires a unique explanation. It appears to be the Buckminsterfullerene (carbon-60) of gold-cluster chemistry. Herein we provide an elementary account of the unexpected discovery, in which the Pd145-structure played a critical role, that led to the identification and prediction, in 2008, of a fascinating new molecular structure-type, evidently the first one of chiral icosahedral symmetry. Rigorous confirmation of this prediction occurred in early spring 2018, when two single-crystal X-ray crystallography reports were submitted, each one distinguishing both enantiomeric structures and noting profound chirality for the surface (ligand) layer. The emphasis here is on the structure and bonding principles and how these have been elucidated. Our aim has been to present this story in simplest terms, consistent with the radical simplicity of the structure itself. Because it combines intrinsic profound chirality, at several levels, with the highest possible symmetry-type (icosahedral), the structure may attract broader interest also from educators, especially if studied in tandem with the analysis of hollow (shell) metallic systems that exhibit the same chirality and symmetry. Because the shortest (stiffest) bonds follow the chiral 3-way weave pattern of the traditional South-Asian reed football, this cultural artifact may be used to introduce chiral-icosahedral symmetry in a pleasant and memorable way. One may also appreciate easily the bonding and excitations in I-symmetry metallic nanostructures via the golden fullerenes, that is, the proposed hollow Au60,72 spheres. Beyond any aesthetic or pedagogical value, we aim that our Account may provide a firm foundation upon which others may address open questions and the opportunities they present. This Account can scarcely hint at the prospects for further fundamental understanding of these compounds, as well as a widening sphere of applications (chemical, electronic, imaging). The compounds remain crucial to a wider field presently under intense development.

Nous proposons une méthode de calibration en énergie entre 0 et 14 MeV, d'un dispositif de spectrométrie γ utilisant un détecteur Ge(Li). Nous exposons ensuite le principe d'une mesure de la variation de son efficacité de détection avec l'énergie, à l'aide de trois résonances de la réaction 27Al(p, γ)28Si, pour des protons de 655, 992 et 2 489 keV.

In recent years, major progress has been made in measuring weakly absorbing atmospheric trace gases from high spectral resolution space observations. In this paper, we apply the so‐called whitening transformation on spectra of the Infrared Atmospheric Sounding Interferometer (IASI), and show that it allows removing most of the climatological background from spectra, leaving a residual that contains those spectral signatures that depart from normality. These can subsequently be attributed to changes in the abundance of trace species. This is illustrated for two diverging cases: (1) a biomass burning plume from the 2019/2020 Australian bushfires, leading to the unambiguous identification of nine reactive trace gases, including a first observation of glycolaldehyde; (2) spectra observed a decade apart, from which changes in eight long‐lived halogenated substances are identified; three of them never observed before by a nadir sounder.

During the life time of Concentrated Solar Power (CSP) plants, optical performance of solar mirrors is affected by soiling phenomena and surface degradation. It is imperative to dissociate soiling that requires cleaning from irreversible degradations which affect the plant performance. In both cases, small degradations or dust deposition cause an optical reflectance loss. In order to provide an adequate cleaning strategy, operators need to determine soiling-induced performance loss. Several commercial instruments already exist to measure optical reflectance, but they are dedicated to a single wavelength range or angle, punctual measurements or to laboratory analyses. CEA has developed a new kind of laboratory sensor to measure separately the loss of reflectance due to the degradation and soiling, thanks to a CCD camera and photodiodes. This equipment allows addressing variable wavelength, incidence and acceptance angles, to compare specular and hemispherical reflectance from other devices. The analysis of the images will quantify the soiling rate in order to optimize the frequency of cleaning water operations. The aim of the present contribution is to distinguish soiling from degradations (abrasion or corrosion of the reflective layer). This paper reviews the different current research works on prototype instruments and a comparison of this new alternative instrument with available commercial ones.

In this paper, we explore the use of an adaptive electrical calibration strategy in the context of design-for-manufacturing for MEMS convective accelerometers. The calibration principle relies on the adjustment of the heater power level such that sensitivity is set to a given target value. The idea is to define multiple sensitivity targets in order to improve production yield and to insert a criterion on power consumption. Different device binning can then be achieved depending on test limit settings. Results obtained from Monte-Carlo simulation are presented to demonstrate potentialities of the technique.

This article examines the way in which the South and the West intersect in Garth Ennnis and Steve Dillon's comic book series, Preacher (DC/Vertigo, 1995-2000). Preacher attempts to chart the ground for a renovated hybrid fiction which would blend the iconography of the South and the West in order to redefine both the limitations and the possibilities of southern identity, offering a version of the South that is self-consciously in dialogue with its popular representations and with the real histories those representations both reveal and conceal. From this dialogue comes the possibility for a new, more complex South, one that acknowledges its histories and representations without being constrained by familiar narratives.