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Plasma-based microwave power limitation in a printed transmission line: a self-consistent model compared with experimental data
Get PDFPlasma-based microwave power limitation in a suspended microstrip transmission line integrating a micro hollow cathode discharge (MHCD) in its center is experimentally and numerically studied. Transient and steady state microwave power measurements exhibit a limitation threshold of 28 dBm and time responses of 25 microseconds. Intensified charge-coupled device (ICCD) imaging shows that microwave breakdown occurs at the top of the MHCD. The plasma then extends towards the microwave source within the suspended microstrip transmission line. Besides, a self-consistent model is proposed to simulate the non-linear interaction between microwave and plasma. It gives numerical results in agreement with the measurements, and show that the plasma expansion during the transient response is related to a shift between the ionization source term and the electron density maximum. The propagation speed, under the tested conditions, depends mainly on the stepwise ionization from the excited states
Structure-preserving discretization of Allen-Cahn and Cahn-Hilliard equations, as port-Hamiltonian systems
Get PDFWater desalination is a critical process and can be achieved in different ways. One of them is
eutectic freeze crystallisation, this method seems more energy efficient due to the difference
between the latent heat of fusion and the latent heat of vaporisation of water. The question
then arises as to how to model, simulate and control such a system.
Because of the thermodynamic nature of the freezing process, the port-Hamiltonian framework
seems useful for it preserves the structure and extensive variables of the system. Moreover,
the sharp interface between the solid and the liquid makes the modelling more difficult, therefore
one needs to use a phase field method in order to approximate the sharp interface by a
diffuse one.
In this document, the goal is to compute the equations of Allen-Cahn and Cahn-Hilliard using
the pHs formalism by spatially discretizing it using the Partitioned Finite Element Method
Infrasound From Large Earthquakes Recorded on a Network of Balloons in the Stratosphere
Get PDFThe ground movements induced by seismic waves create acoustic waves propagating upward in
the atmosphere, thus providing a practical solution to perform remote sensing of planetary interiors. However, a
terrestrial demonstration of a seismic network based on balloon-carried pressure sensors has not been provided.
Here we present the first detection of seismic infrasound from a large magnitude quake on a balloon network.
We demonstrate that quake's properties and planet's internal structure can be probed from balloon-borne
pressure records alone because these are generated by the ground movements at the planet surface below the
balloon. Various seismic waves are identified, thus allowing us to infer the quake magnitude and location, as
well as planetary internal structure. The mechanical resonances of balloon system are also observed. This study
demonstrates the interest of planetary geophysical mission concepts based on seismic remote sensing with
balloon platforms, and their interest to complement terrestrial seismic networks
Aeroacoustic optimization of MAV rotors
Get PDFThe more restrictive airspace regulations force drone manufacturers to take into account the noise emitted by the drone during the design phase, along with its aerodynamic performance to increase the flight time. A Non-Linear Vortex Lattice Method (NVLM), coupled with the Farassat Formulation-1A of the Ffowcs-Williams and Hawkings acoustic analogy is used to evaluate the aerodynamic and aeroacoustic performance of MAV rotors. Pymoo, a Python-based optimizatio
framework, is employed to modify the geometry, evaluate its performance and extract the set of Pareto optimal solutions.
The two objectives are the aerodynamic Figure-of-Merit and the Sound Pressure Level of the Blade Passing Frequency tone for a microphone located at a far-field distance of 1.62m and 30◦ below the rotor plane. The approach proposed in this paper takes into account up to ten different parameters, ranging from the twist and chord distributions, to the rake
and skew angles
Real-Time Polling Task: Design and Analysis
No full textWhen designing robotic systems, we regularly face the same problem, the systems that we design have to be reactive systems, must be able to react to their environment and, also, to communicate with some other systems. However, the reactive behavior, because of its nondeterministic nature, is difficult to analyze and prevent designers to do real-time analysis, which is needed for critical systems. In this paper, we propose a deterministic task model to handle the reactive behavior as well as the necessary tools to verify the respect of real-time constraints. An implementation of this model, which is used in a ROS2 patch, is also presented
Structure-preserving discretization of a coupled Allen-Cahn and heat equation system
Get PDFEutectic freeze crystallisation is a promising way of purifying water for it may require less energy than other methods. In order to simulate such a process, phase field models such as Allen-Cahn and Cahn-Hilliard can be used. In this paper, a port-Hamiltonian formulation of the Allen-Cahn equations is used and coupled to heat conduction, which allows for a thermodynamically consistent system to be written with the help of the entropy functional. In a
second part, the Partitioned Finite Element Method, a structure-preserving spatial discretization method, is applied to the Allen-Cahn equation; it gives rise to an exact free energy balance at the discrete level. Finally some numerical results are presented
Influence of the transient conditions on release of corrosion products and oxidation of alloy 690 tubes during pressurized water reactor restart after steam generators replacement
Get PDFThe radioactivity of the Reactor Coolant System (RCS) of Pressurized Water Reactors (PWRs) mainly comes from the release of corrosion products of Steam Generator (SG) tubes made of Ni-base alloys. In order to reduce this activity and thus the radiation exposure of PWR operators during maintenance operations, it is necessary to minimize the release. That requires prior understanding of the various mechanisms involved. EDF R&D constructed a loop, BOREAL, to specifically measure rates of release of SG tubes in various conditions of primary environment. Tubes were usually tested at high temperature, under con- stant conditions of primary chemistry. So, it is necessary to carefully investigate the impact of transient conditions during a PWR restart after SG replacement. Tests were performed on the industrial material with curvature, roughness, defects and heterogeneities, regularly observed on this type of component. Characterisations of the inner surface were done on as-received and corroded specimens of SG tubes and were correlated with the obtained release kinetics. The native oxide layer is formed of a very thin layer (1-2 nm) of oxidised matrix, without specific en- richment. During the restart, the most critical step for the release phenomenon is revealed from 170 °C to 297 °C. The majority of the metal is indeed released into the fluid during this step. The characterisa- tions after release tests have made it possible to propose oxidation and release mechanism during a PWR restart after SG replacement. Up to 170 °C, a thin layer of amorphous chromium oxide is formed by selec- tive dissolution of iron and nickel. When the temperature rises, this chromium oxide layer is not stable enough to be protective and the diffusion phenomena are activated. At 325 °C, the oxide does not exhibit any particular enrichment and corresponds to an oxidised metal layer; an equilibrium is established and the rate of release reaches a pseudo-stationary regime
Oxygen-reducing microbial cathodes in hypersaline electrolyte
Get PDFHypersaline electrolytes offer a way to boost the development of microbial fuel cells by overcoming the issue due to the low conductivity of the usual media. Efficient halotolerant bioanodes have already been designed but O2-reducing cathodes remain a strong bottleneck. Here, O2-reducing biocathodes were designed by using salt marsh sediment as the inoculum and a hypersaline media (45 g/L NaCl) of high conductivity (10.4 S m-1). Current density up to 2.2 A m-2 was reached from potential of +0.2 V/SCE. The efficiency of the biocathodes was correlated to the presence of Gammaproteobacteria strain(s) related to Thiohalobacter thiocyanaticus, which were considerably enriched in the best performing biocathodes. This work opens up new perspectives to overcome the O2 reduction issue in hypersaline MFCs by designing efficient halotolerant microbial cathodes and pointing out the strains that should now be focused to improve them
Impact de la sensibilisation des propriétaires de chiens à l'hygiène bucco-dentaire de leur animal sur l'observance des soins dentaires préventifs contre la maladie parodontale
Get PDFLa maladie parodontale est l’un des problèmes de santé le plus courant chez le chien. Elle peut avoir de graves répercussions sur la santé et le bien-être de l’animal. Actuellement, le moyen le plus efficace pour lutter contre cette maladie est la mise en place de moyens préventifs dont le brossage dentaire est la référence. Cette étude a permis de constater l’effet positif de la sensibilisation des propriétaires à cette maladie sur l’observance des soins bucco-dentaires réalisés à la maison. Avant l’entretien de sensibilisation, 38,8% des propriétaires ne savaient pas qu’il était possible de brosser les dents d’un chien et seulement 16,4% avaient déjà essayé. Après avoir été sensibilisés, 63,6% des propriétaires ont essayé de brosser les dents de leur chien. Et plus de 3 mois après l’entretien, 27,3% des propriétaires brossent toujours les dents de leur chien. De plus, après la sensibilisation 81,4% des propriétaires donnent des lamelles ou bâtonnets à mâcher à leur chien contre 53,7% avant sensibilisation
Évaluation expérimentale des effets sédatifs chez la poule d'une administration intranasale de diazépam, seul ou associé à du butorphanol
Get PDFCette étude prospective vise à évaluer la voie intranasale comme alternative à la voie gazeuse dans le cadre d’une sédation légère chez la poule. Deux protocoles à base de diazépam (2 mg/kg) associé ou non à du butorphanol (2mg/kg) ont été expérimentés en cross-over chez 8 poules. La sédation est estimée par la notation de 7 paramètres à 5, 10, 20 et 45 minutes post-administration. Chaque valeur est ensuite comparée à la note basale évaluée avant la sédation. L’administration des protocoles a procuré une sédation satisfaisante en moins de 10 minutes. Elle est notamment suffisante pour placer les animaux en position pour radiographies qui est un examen complémentaire important chez la poule. Cependant aucune différence significative n’a été observée entre les deux protocoles. Quelques effets secondaires indésirables ont été observés tels que de l’épistaxis ou de l’encombrement respiratoire mais sans conséquence sur l’état général des animaux