Influence of temperature on the impact behavior and damage tolerance of hybrid woven-ply thermoplastic laminates for aeronautical applications

Impact damage tolerance of hybrid carbon and glass fibers woven-ply reinforced PolyEther Ether Ketone(PEEK) thermoplastic (TP) laminates obtained by consolidation process is investigated. Service temperature being one of the most important parameters to screen TP or thermosetting matrix for aeronautical purposes, impact testing at room temperature (RT) and near the glass transition temperature (Tg) has been conducted. From the results, it turns out that temperature has little influence on the impact behavior in terms of maximum force developed or maximum deflection, though it reduces the dissipated energy especially at lower impact energy. However, temperature has a strong effect on the internal and external damages caused to the plate, as it increases the permanent indentation and it limits the projected delaminated area. As for the influence of temperature on the compressive residual strength of the laminates, it also appears that the classical experimental set-up for CAI tests is not completely appropriate to draw a clear cut conclusion. At last the obtained results show that the considered TP-based laminates are characterized by a very good impact behavior and a high-degree of damage tolerance

Statistical Characterization of Bare Soil Surface Microrelief

Because the soil surface occurs at the boundary between the atmosphere and the pedosphere, it plays an important role for geomorphologic processes. Roughness of soil surface is a key parameter to understand soil properties and physical processes related to substrate movement, water infiltration or runoff, and soil erosion. It has been noted by many authors that most of the soil surface and water interaction processes have characteristic lengths in millimeter scales. Soil irregularities at small scale, such as aggregates, clods and interrill depressions, influence water outflow and infiltration rate. They undergo rapid changes caused by farming imple‐ ments, followed by a slow evolution due to rainfall events. Another objective of soil surface roughness study is investigating the effects of different tillage implements on soil physical properties (friability, compaction, fragmentation and water content) to obtain an optimal crop emergence. Seedbed preparation focuses on the creation of fine aggregates and the size distribution of aggregates and clods produced by tillage operations is frequently measured. Active microwave remote sensing allows potential monitoring of soil surface roughness or moisture retrieving at field scale using space-based Synthetic Aperture Radars (SAR) with high spatial resolution (metric or decametric). The scattering of microwaves depends on several surface characteristics as well as on imagery configuration. The SAR signal is very sensitive to soil surface irregularities and structures (clod arrangement, furrows) and moisture content in the first few centimeters of soil (depending on the radar wavelength). In order to link the remote sensing observations to scattering physical models as well as for modelling purpose, key features of the soil microtopography should be characterized. However, this characteri‐ zation is not fully understood and some dispersion of roughness parameters can be observed in the same field according to the methodology used. It seems also, that when describing surface roughness as a whole, some information related to structured elements of the micro‐ topography is lost

Dripping dynamics and transitions at high Bond numbers

We report experiments on the dripping dynamics and jetting transitions that take place when a liquid is injected vertically downwards at a constant flow rate, for wide ranges of the liquid viscosity and injector radius. We explore values of the Bond number significantly larger than in previous works, revealing the existence of period-2 dripping regimes with satellite formation that do not exist at small Bond numbers. In addition, we quantify the influence of liquid viscosity on the hysteresis associated with the dripping-jetting transition, that had previously been studied only for the particular case of water.The authors thank the financial support of the Spanish MINECO through projects nos. DPI2014-59292-C03-01-P, DPI2014-59292-C03-03-P, DPI2015-71901-REDT, DPI2017-88201-C3-2-R and DPI2017-88201-C3-3-R. These research projects have been partly financed through European funds.Publicad

Parents’ Perceptions of the College Experiences of Twice-Exceptional Students with Autism Spectrum Disorder

Students with Autism Spectrum Disorder are accessing college in increasing numbers, and within this group, there is a cohort of academically talented students who can be considered twice-exceptional, or 2e-ASD. While research about college students with ASD is increasing, there is a relative dearth of literature about 2e-ASD college students, and their secondary transition and college experiences. The current study presents the results of individual interviews that were conducted with 10 parents of 2e-ASD college students to explore their perceptions of their children’s experiences, including what things went well and what were problematic areas. Parents described clear and early expectations that the student would attend college and that college provided the student with independence and the chance to be with people who shared similar interests. They described factors that were considered during the college search including the size of the campus and distance from home, and the importance of letting the student take increased responsibility, and if necessary, make and learn from mistakes. The need to focus on executive functioning and social skills was also noted. Implications for families, secondary transition personnel, and vocational rehabilitation counselors are presented

Vers un environnement pour le déploiement logiciel autonomique

Le déploiement de logiciels répartis dans des environnements à grande échelle et ouverts (tels les systèmes ubiquitaires, les systèmes mobiles et les systèmes P2P) est une problématique actuelle ouverte. Ces environnements sont distribués, hétérogènes et peuvent être de nature instable (dotés d une topologie dynamique du réseau). Le déploiement dans ces environnements met en jeu un très grand nombre de machines, de liens réseau ainsi qu un ensemble de contraintes de déploiement. Quelques solutions de déploiement existent aujourd hui, mais ne sont exploitables que dans le cadre d architectures figées et fiables. Dans la plupart des solutions, une personne en charge du déploiement doit décrire plus ou moins manuellement la topologie. En outre, la majorité de ces outils ne prennent pas en compte les problèmes dûs à la variabilité de la qualité de service du réseau, aux pannes des hôtes, aux défaillances des liens du réseau ou encore aux changements dynamiques de topologie, qui caractérisent les environnements ouverts. Dans ce mémoire, nous présentons les motivations de la réalisation d'une infrastructure de déploiement logiciel autonomique et les exigences sous-jacentes d'une telle plate-forme. Nous présentons un état de l art du déploiement logiciel que nous analysons au regard du contexte visé. Ensuite, nous présentons notre contribution pour le déploiement autonomique. Notre proposition s'appuie sur une combinaison de technologies (composants logiciels, agents mobiles adaptables, intergiciel, langage dédié). Nous proposons j-ASD, un intergiciel qui exploite la complémentarité de ces technologies pour réaliser un déploiement logiciel autonomique. Le processus de déploiement contient trois étapes : description des contraintes de déploiement, résolution, et déploiement autonomique. Pour la première étape, nous avons défini un langage dédié (DSL) comme langage de haut niveau pour exprimer des contraintes de déploiement. Pour la deuxième, nous avons conçu une infrastructure répartie pour collecter les propriétés des sites cibles, ce qui permet de résoudre les contraintes de déploiement. Pour la troisième étape, nous proposons un intergiciel à base d agents mobiles pour la réalisation et la supervision du déploiement autonomique. Enfin, nous donnons les éléments de conception du prototype que nous avons implémenté, ainsi que les résultats de certaines expérimentations pour montrer la validité de notre approcheSoftware deployment in large-scale and open distributed systems (such as ubiquitous systems, mobile systems and P2P systems) is still an open issue. These environments are distributed, heterogeneous and can be naturally unstable (fitted with a dynamic network topology). Deployment in such environments require the management of a large number of hosts, network links and deployment constraints. Existing distributed deployment solutions are usable only within static and reliable topologies of hosts, where a man in charge of the deployment has to describe more or less manually the topology. Moreover, majority of these tools do not take into account network and computer QoS variabilities, hosts crashes, network link failures and network topology changes, which characterize open and mobile environments. In this thesis, we discuss the motivations for an autonomic software deployment and the requirements underlying for such a platform. We carefully study and compare the existing work about software deployment. Then, we propose a middleware framework, designed to reduce the human cost for setting up software deployment and to deal with failure-prone and change-prone environments. We also propose an autonomic deployment process in three steps : deployment constraints description step, constraints resolution step and the autonomic deployment step. For the first step, we defined a high-level constraint-based dedicated language (DSL) as support for expressing deployment constraints. In the second step, we have designed a distributed infrastructure to collect target hosts properties used to solve deployment constraints. For the third step, we propose an agent-based system for establishing and maintaining software deployment. At last, we give an overview of our working prototype with some details on some experimental resultsEVRY-INT (912282302) / SudocSudocFranceF

Mastering interactions with Internet of Things platforms through the IoTVar middleware

International audienceThe rising popularity of the Internet of Things (IoT) has led to a plethora of highly heterogeneous, geographically dispersed devices. In recent years, IoT platforms have been used to provide a variety of services to applications such as device discovery, context management, and data analysis. However, the lack of standardization currently means that each IoT platform comes with its own abstractions, APIs, and interactions. As a consequence, programming the interactions between an application and an IoT platform is often time consuming, error prone, and depends on the developers' level of knowledge about the IoT platform. To address these issues, we propose offering to application developers on the client side the possibility to declare variables that are automatically mapped to sensors and whose values are transparently updated with sensor observations. For this purpose, we introduce IoTVar, a middleware between IoT applications and platforms. In IoTVar, all the necessary interactions with IoT platforms are managed by proxies. This paper presents IoTVar integrated with the FIWARE platform, which is used for developing IoT Future Internet applications. We also report results of some experiments performed to evaluate IoTVar, showing IoTVar reduces the effort required to declare and manage IoT variables and its impact in terms of CPU, memory, and energy

Apprentissage dynamique du nombre d'états d'un modèle de markov caché à observations continues : Application au tri de formulaires

Dans le cadre de la reconnaissance automatique de types de formulaires avec champs manuscrits et sans aucun signe de référence, basée sur une description de la structure physique du formulaire, nous sommes amenés à représenter un formulaire par un modèle de Markov caché pseudo-2D (PHMM). Ce modèle est constitué d'un graphe de super-états. A chaque super-état on associe un modèle de Markov caché secondaire (HMM) dont les observations sont continues. Nous exposons pourquoi la méthode classique des k-moyennes est mal adaptée à notre problème, puis nous détaillons une nouvelle méthode générale qui prend mieux en compte la réalité physique des états, en les situant dans l'espace de représentation des caractéristiques, et en les construisant dynamiquement par agrégation progressive des séquences d'observations. Ce n'est qu'à la fin du processus d'agrégation que le nombre d'états du modèle stochastique initial est connu

Marge de stabilité des systèmes linéaires : une extension du critère de Routh-Hurwitz

Nous exposons une condition nécessaire et suffisante, portant sur les coefficients d'un polynôme, qui permet de localiser les racines de celui-ci relativement à un secteur angulaire du plan complexe, ce qui généralise le champ de validité du théorème de Routh-Hürwitz qui est limité au cas du demi-plan gauche. Ce résultat théorique permet d'étendre le critère de stabilité absolue de Routh-Hürwitz, utilisé notamment pour le réglage du gain des systèmes asservis linéaires, au cas où l'on souhaite préserver une marge de stabilité réglable, les pôles de la fonction de transfert étant alors situés à l'intérieur du secteur angulaire qui définit la zone de stabilité

Synergy between optical and microwave remote sensing to derive soil and vegetation parameters from MAC Europe 1991 Experiment

The ability of remote sensing for monitoring vegetation density and soil moisture for agricultural applications is extensively studied. In optical bands, vegetation indices (NDVI, WDVI) in visible and near infrared reflectances are related to biophysical quantities as the leaf area index, the biomass. In active microwave bands, the quantitative assessment of crop parameters and soil moisture over agricultural areas by radar multiconfiguration algorithms remains prospective. Furthermore the main results are mostly validated on small test sites, but have still to be demonstrated in an operational way at a regional scale. In this study, a large data set of radar backscattering has been achieved at a regional scale on a French pilot watershed, the Orgeval, along two growing seasons in 1988 and 1989 (mainly wheat and corn). The radar backscattering was provided by the airborne scatterometer ERASME, designed at CRPE, (C and X bands and HH and VV polarizations). Empirical relationships to estimate water crop and soil moisture over wheat in CHH band under actual field conditions and at a watershed scale are investigated. Therefore, the algorithms developed in CHH band are applied for mapping the surface conditions over wheat fields using the AIRSAR and TMS images collected during the MAC EUROPE 1991 experiment. The synergy between optical and microwave bands is analyzed