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Experimental analysis of the effects of wrinkles in the radius of curvature of L-shaped carbon-epoxy specimens on unfolding failure
Full text linkAn experimental study has been carried out to describe the evolution of the failure load relative to the maximum
misalignment angle of curved carbon–epoxy laminates with out-of-plane wrinkle defects for a large range of
misalignments. L-angle specimens with different levels of fibre wrinkling were manufactured and tested in fourpoint
bending tests. Digital Image Correlation (DIC) and infrared thermography were used to monitor the tests.
They allowed the stress concentrations induced by the wrinkles to be identified, together with their influences on
the failure load of the sample. In most cases, increases in wrinkling levels led to decreases in failure loads
Specification of Incremental Requirements Upstream of System Design
No full textDrones and autonomous robots have started to be widely used in various application domains like military and real-life operations such as transportation, logistics, infrastructure
inspection, disaster relief, rescue operation, etc. Therefore, industries have started designing and modeling these drones and autonomous robots to address general operations such as surveillance and infrastructure inspection of inaccessible environments. Though, these drones are still quite limited to relatively simple operations due to its immature level of missions. However, an extension of the drone operation generally leads to equip the drone with additional components such as camera, storage device, lidar, sonar, sensors, etc. In this article, a focus is placed on the deployment of a pre-requirements and post-requirements specification approach while dealing with requirements and constraints of the designed system. This is done in order to maintain control over the overall stakeholder needs and mitigates the risk of an useless system. More precisely, a high attention must be paid to the payload of the drone, the volume and the dimension dedicated to the payload
Analyse combinée de l'optimisation des procédés et de l'évaluation environnementale pour l'écoconception de voies de synthèse. : Application à une voie de synthèse alternative du carbonate de diméthyle.
Full text linkCette thèse a été développée par la nécessité du laboratoire de concevoir une méthodologie multicritère pour le choix de voies de synthèse d’une molécule chimique d’intérêt en incluant des aspects environnementaux, économiques et énergétiques. Pour répondre à cette demande, les principes de la chimie verte sont classiquement utilisés depuis les années 80. Néanmoins, un des problèmes identifiés est le manque de résultats quantitatifs apportés par ces principes. En parallèle, la méthodologie d’analyse de cycle de vie (ACV) est déjà reconnue comme une solution efficace pour l’analyse environnementale. Pour notre étude, nous avons sélectionné comme cas d’étude le carbonate de diméthyle (DMC) car sa production mondiale est en constante augmentation (multiplié par 4 entre 2007 et 2015). En effet le DMC est considéré comme une molécule verte avec des applications très variées. Il est utilisé en tant qu’électrolyte de batterie et pour la production de polycarbonates. Dans un premier temps, trois voies de synthèses pour la production de DMC (2 industrielles et la méthanolyse de l’urée) ont été comparées d’un point de vue environnemental en utilisant l’ACV via les recommandations de la base de donnée ECOINVENT (classiquement utilisée en ACV pour fournir des données d’arrière-plan) et les principes de la chimie verte. Il apparait que les résultats des deux méthodes sont complémentaires mais ne permettent pas une étude approfondie en particulier sur des éléments comme la consommation énergétique. Dans un second temps, l’utilisation combinée de la modélisation-simulation des procédés et de l’analyse de cycle de vie a été appliquée à notre cas d’étude : la production de DMC via la méthanolyse de l’urée. Une étude bibliographique a été réalisée sur les alternatives technologiques pour produire le DMC par la méthanolyse de l’urée afin d’identifier les déficiences des modèles utilisés dans la simulation de la voie de synthèse et les procédés de séparations de mélanges. L’objectif principal de notre étude est l’éco-conception d’un nouveau procédé technologique en considérant les phénomènes réactionnels et l’équilibre de phases réel par l’exclusion des hypothèses effectuées dans les travaux consultés. La modélisation-optimisation de la voie de synthèse du DMC a été réalisée autour de trois scénarios incluant des modèles thermodynamiques de réaction de degrés de complexité différents en utilisant une colonne de distillation réactive. Cette étude cherche à montrer les différences dans l’évaluation environnementale du procédé en considérant un modèle « taux de conversion », un modèle « équilibre chimique » et un modèle « cinétique de réactions consécutives et concurrentes ». Dans un troisième temps, une analyse du procédé du berceau à la porte indique que le train de colonnes interconnectées pour la séparation des mélanges issues de la réaction a des impacts environnementaux importants parmi lesquels la chauffe apparait comme un élément plus important. Ensuite, trois scénarios de séparation ont été étudiés (distillation à haute pression, distillation avec deux colonnes à différentes pressions et distillation extractive avec un nouveau solvant vert, l’ethyl lactate) afin d’optimiser la purification de DMC à partir de son azéotrope avec le méthanolLes différentes études effectuées tout au long de la thèse ont permis de développer les différentes solutions applicables à l’échelle du laboratoire selon l’avancement de la recherche dans la phase de conception d’une nouvelle voie de synthèse. Les avantages et les inconvénients de l’étude à chaque étape de la conception sont listés afin de permettre un usage facile par les différents intervenants de l’équipe de recherche du laboratoire
Worst-Case Delay Bounds in Time-Sensitive Networks With Packet Replication and Elimination
Full text linkPacket replication and elimination functions are used by time-sensitive networks (as in the context of IEEE TSN and IETF DetNet) to increase the reliability of the network. Packets are replicated onto redundant paths by a replication function. Later the paths merge again and an elimination function removes the duplicates. This redundancy scheme has an effect on the timing behavior of time-sensitive networks and many challenges arise from conducting timing analyses. The replication can induce a burstiness increase along the paths of replicates, as well as packet mis-ordering that could increase the delays in the crossed bridges or routers. The induced packet mis-ordering could also negatively affect the interactions between the redundancy and scheduling mechanisms such as traffic regulators (as with per-flow regulator and interleaved regulator, implemented by TSN asynchronous traffic shaping). Using the network calculus framework, we provide a method of worst-case timing analysis for time-sensitive networks that implement redundancy mechanisms in the general use case, i.e., at end-devices and/or intermediate nodes. We first provide a network calculus toolbox for bounding the burstiness increase and the amount of reordering caused by the elimination function of duplicate packets. We then analyze the interactions with traffic regulators and show that their shaping-for-free property does not hold when placed after a packet elimination function. We provide a bound for the delay penalty when using per-flow regulators and prove that the penalty is not bounded with interleaved regulators. Finally, we use an industrial use-case to show the applicability and the benefits of our findings
A Multipath and Thermal noise joint error characterization and exploitation for low-cost GNSS PVT estimators in urban environment
Full text linkAchieving an accurate localization is a significant challenge for low-cost GNSS devices in dense urban areas. The main limitations are encountered in the urban canyons, consisting in a reduced satellite signal availability and a positioning estimation error due to the impact of Line-of-Sight and Non Line-of-Sight multipath phenomenon. This PhD study allows to understand the impact of the multipath phenomenon on the low-cost GNSS receivers and to prove the need of accurate assessment of the multipath error model affecting the GNSS measurements, especially in urban environment. It consists in the investigation, characterization, and finally, exploitation of the multipath error components affecting the pseudorange and pseudorange-rate measurements, of a single frequency, dual constellation GNSS receiver in the urban environment, operating with GPS L1 C/A and Galileo E1 OS signals. The first goal consists in providing a set of methodologies able to identify, isolate and characterize the multipath error components from the measurements under test. However, considering that the isolation of the multipath error is a complex operation due to the superimposed effects of multipath and thermal noise, the final method consists of isolating the joint contribution of multipath and thermal noise components. The isolated multipath and thermal noise error components are firstly classified depending the corresponding received signal /0 values, and, secondly, statistically characterized by means of Probability Density Function, sample mean and sample variance. Also, the temporal and spatial correlation properties of the isolated error components are calculated by means of a methodology which estimates the temporal correlations as a function of the receiver speed. In addition, an image processing methodology based on the application of a sky-facing fish-eye camera provides the determination of an empirical /0 threshold equal to 35 dB-Hz used to qualitatively identify the Non Line- Of-Sight and Line-Of-Sight received signal reception states. The resulting errors are characterized by a nonsymmetrical, positive biased PDF for a /0 lower than 35 dBHz, while they are characterized by a symmetrical and zero-centred PDF for a /0 higher than 35 dB-Hz. Correlation times for pseudoranges are ranged from around 5s for static and very low speed dynamics to around 1s for high-speed dynamics. Correlation times for pseudorange-rates ranged from around 0.5s for static and very low speed dynamics to around 0.2s for high-speed dynamics, due to the data-rate limitations. The second goal consists in exploiting the multipath and thermal noise error models and the LOS/NLOS received signal reception state estimation in a low-complex EKF-based architecture to improve the accuracy of the PVT estimates. This is obtained by implementing some techniques based on the measurement weighting approach to take into account the statistical properties of the error under exam and by the application of a time differenced architecture design to exploit the temporal correlation properties. Positioning performance of the tested solutions surpassed the performances of a simple EKF architecture and are comparable to the performances of a uBlox M8T receiver
zkBeacon: Proven Randomness Beacon Based on Zero-Knowledge Verifiable Computation
Full text linkThe generation of random numbers by a trusted third-party is essential to many cryptographic protocols.
Recently, the NIST proposed the standardization of randomness beacons, which are hash-based chains of
pulses. Each pulse contains a random number and is generated at regular time intervals. However, if the
owner of the beacon generator is untrusted, several attacks allow the manipulation of the provided random
numbers. In this paper, we firstly suggest protecting the first hash functions of the NIST scheme by adding
a verifiable argument of knowledge. More precisely, we propose furnishing a zk-SNARK or a zk-STARK
with the hash to make the system more transparent and resistant to randomness manipulation. Secondly, we
propose a verifiable computation-based interactive protocol to allow a client, with the help of the beacon, to
generate proven randomness. Then, we show that connecting this system to a blockchain could have several
benefits. We provide a security analysis with a model allowing a malicious beacon generator. We prove that
our first application improves the resilience of the system against randomness manipulation attacks and that
the interactive protocol rules out timing attacks for the client and ensures the non-predictability of the random
numbers. Finally, we evaluated the computation cost with zk-SNARKs
Benchmarking cEEGrid and Solid Gel-Based Electrodes to Classify Inattentional Deafness in a Flight Simulator
Full text linkTransfer from experiments in the laboratory to real-life tasks is challenging due notably to the inability to reproduce the complexity of multitasking dynamic everyday life situations in a standardized lab condition and to the bulkiness and invasiveness of recording systems preventing participants from moving freely and disturbing the environment. In this study, we used a motion flight simulator to induce inattentional deafness to auditory alarms, a cognitive difficulty arising in complex environments. In addition, we assessed the possibility of two low-density EEG systems a solid gel-based electrode Enobio (Neuroelectrics, Barcelona, Spain) and a gel-based cEEGrid (TMSi, Oldenzaal, Netherlands) to record and classify brain activity associated with inattentional deafness (misses vs. hits to odd sounds) with a small pool of expert participants. In addition to inducing inattentional deafness (missing auditory alarms) at much higher rates than with usual lab tasks (34.7% compared to the usual 5%), we observed typical inattentional deafness-related activity in the time domain but also in the frequency and time-frequency domains with both systems. Finally, a classifier based on Riemannian Geometry principles allowed us to obtain more than 70% of single-trial classification accuracy for both mobile EEG, and up to 71.5% for the cEEGrid (TMSi, Oldenzaal, Netherlands). These results open promising avenues toward detecting cognitive failures in real-life situations, such as real flight
Metalorganic chemical vapor deposition of aluminum oxides: A paradigm on the process structure- properties relationship
No full textThis chapter introduces the complex relationships existing among the process conditions, the microstructure and the functional properties for metal oxide films processed by metalorganic chemical vapor deposition. Amorphous aluminum oxide films are considered as a model material due to their promising barrier properties for various applications including non-volatile memories and to the extended investigation of the process and the material. The first part of the chapter considers modeling and simulation aspects of the metal-organic chemical vapor deposition (MOCVD) process with the aim to conformally cover non line of sight surfaces. The second part establishes the relationship between short range order in the films and their barrier properties
A Taxonomy of MBSE Approaches by Languages, Tools and Methods
Full text linkSystems engineering has gained in maturity over the last decades and started a transition from document-centric approaches to Model-Based Systems Engineering (MBSE). Several papers have discussed the benefits and potential, but also the limitations, of using MBSE, based on literature surveys and analyze feedback from academia and industry. The current paper explores a complementary avenue and aims at
giving students and industry practitioners a set of keys and decision criteria to select MBSE languages, tools and methods. Languages, tools and methods are categorised and selection criteria are proposed for a panorama of languages that goes beyond SysML and other techniques commonly associated with MBSE. In addition, research avenues for the future of MBSE are identified. The discussion relies on the authors’ experience in teaching and using system engineering and MBSE in both academia and industry, as well as on the experience shared within the framework of Concorde, a French project dedicated to drone systems design methodologies
CO2 Footprint minimization for AFP bio-composites thin structures
Full text linkThe development of the aeronautical industry has brought about certain demands like the reduction of fuel consumption and, consequently, the weight of used structures. Therefore, topology analysis of aircraft components has played an important role in meeting these demands. Another factor widely studied in this context is the type of materials used in the manufacture of such components, hence, by presenting lower densities, composites have gained ground in this industry sector.
Besides, an increasingly sought-after characteristic is the sustainability associated with the entire life cycle of any system or part, from its design, through the production phase, to its end of life. The assessment of such sustainability is often carried out by analysing the life cycle’s CO2 footprint, which tends to decrease when the raw materials used are less processed. Materials of natural origin, also known as "bio-materials", have therefore been the target of study, being the basis of the concept of eco-design.
The accelerated development of 3D printing technologies has allowed the evolution of structural design methods. Additive manufacturing emerged in the 1980s and has since been expanding in the aerospace field. One of its great advantages is that it can be combined with the use of bio-composites, such as flax or hemp.
The topology optimisation of any given structure brings great benefits in terms of the mitigation of the CO2 impact of a given part, as it translates into a reduction of its mass and fuel consumption. However, the combination of this method with the optimisation of the fibre path, in the 3D printing process, and the CO2 footprint of the part’s life cycle simultaneously can bring even more evident benefits.
In this paper modifications to existing methods are proposed. In MATLAB, strategies are developed to study the topology and fibre orientation of potentially 3D printed thin structures