Search results for "fluids"
showing 10 items of 1936 documents
Collisions moléculaires en phase gazeuse
2019
L’étude théorique des collisions entre atomes et molécules permet, grâce à la résolution d’état à état des simulations numériques basées sur la physique quantique, une description détaillée des mécanismes mis en jeu et contribue grandement à améliorer les modèles atmosphériques et astrophysiques. Dans cet article, après avoir présenté les méthodes de dynamique actuelles, nous donnons des exemples clés d’intérêt pour le milieu interstellaire, l’atmosphère terrestre et les milieux (ultra)froids, et présentons les défis majeurs à relever.
Potentialités des lasers à fibre dans la génération de rayonnement cohérent UV
2006
Le premier laser a fibre dope aux ions de terres rares fonctionna au tout debut des annees 60. Il fournissait quelques milliwatts autour de 1 μm. Les decades suivantes virent tres peu d'ameliorations tant du cote des laboratoires que du point de vue industriel. La derniere decennie (1995/2005) vit se concretiser la seconde revolution des lasers a fibres. Deja kilowatt en continu, ils atteignent desormais les 10 13 watts/cm 2 avec des impulsions de la centaine de femtoseconde. Lors de cette presentation nous passerons en revue les potentialites des lasers a fibre. Nous decrirons les verrous technologiques qui ont ete leves ces dix dernieres annees pour les regimes CW mais aussi femtosecondes…
Analysis of the specific common competences of the Degree Courses in Speech Therapy and on the ability to apply in the didactic systems
2020
Law 11 January 2018 n. 3 places the attention of the Health Professions on the specific common skills, which must be evident in the didactic systems to protect the Profession. The purpose of this work is to identify which skills are always present among the training objectives of the Degree Courses in Speech Therapy, and which instead become "specific" for our profession. The data analysis was conducted on 27 Degree Courses in Speech Therapy present in Italy, using the portal "Universitaly" and evaluating the SUA cards of the various Degree Courses. The analysis of the data revealed that: basic skills were insufficient for the areas of labor law and corporate organization; transversal skill…
Controlled turbulence regime of electron cyclotron resonance ion source for improved multicharged ion performance
2020
Fundamental studies of excitation and non-linear evolution of kinetic instabilities of strongly nonequlibrium hot plasmas confined in open magnetic traps suggest new opportunities for fine-tuning of conventional electron cyclotron resonance (ECR) ion sources. These devices are widely used for the production of particle beams of high charge state ions. Operating the ion source in controlled turbulence regime allows increasing the absorbed power density and therefore the volumetric plasma energy content in the dense part of the discharge surrounded by the ECR surface, which leads to enhanced beam currents of high charge state ions. We report experiments at the ECR ion source at the JYFL accel…
Determining the deformation and resulting coupling efficiency degradation of ultrastable fiber-coupled optical benches under load.
2020
Fiber-coupled optical benches are an integral part of many laser systems. The base of such an optical bench is usually a slab of solid material, onto which optical components are fixed. In many environments, the ability to retain high fiber coupling efficiency under mechanical loads is essential. In this article, we study the fiber-to-fiber coupling efficiency under the application of static mechanical loads experimentally and theoretically: We constructed a simple three-point bending setup to interferometrically measure the deformation of an optical bench under load. Using the same setup, we further recorded the resulting coupling efficiency variations. The examined optical benches are bas…
Partial discharges behavior under different rectified waveforms
2017
In this work, a previous software used to simulate partial discharges (PDs) under Alternating Current (AC) stress has been modified in order to evaluate the PDs behavior under a voltage stress close to the Direct Current (DC) waveform. By using a full-wave and a half-wave rectifier, the specimen with an air void defects has been subjected to a gradual constant stress. Finally, a capacitive filter has been inserted in order to produce a steadier voltage supply. Simulation results show that under an almost DC waveform, the PDs activity become less compared to AC stress.
A study of the optical effect of plasma sheath in a negative ion source using IBSIMU code
2020
A plasma sheath inside an ion source has a strong focusing effect on the formation of an ion beam from the plasma. Properties of the beam depend on the shape and location of the plasma sheath inside the source. The most accessible experimental data dependent on the plasma sheath are the beam phase space distribution. Variation of beam emittance is a reflection of the properties of the plasma sheath, with minimum emittance for the optimal shape of the plasma sheath. The location and shape of the plasma sheath are governed by complex physics and can be understood by simulations using plasma models in particle tracking codes like IBSimu. In the current study, a model of the D-Pace’s TRIUMF lic…
Design and experimental validation of a magnetic device for stem cell culture.
2020
Cell culture of bone and tendon tissues requires mechanical stimulation of the cells in order to mimic their physiological state. In the present work, a device has been conceived and developed to generate a controlled magnetic field with a homogeneous gradient in the working space. The design requirement was to maximize the magnetic flux gradient, assuring a minimum magnetizing value in a 15 mm × 15 mm working area, which highly increases the normal operating range of this sort of devices. The objective is to use the machine for two types of biological tests: magnetic irradiation of biological samples and force generation on paramagnetic particles embedded in scaffolds for cell culture. The…
Modelling of expected B, C, N and O Lyman-α line intensities emitted from W7-X plasmas and measured by means of the W7-X light impurity monitor system
2021
AbstractThe “C/O Monitor” for Wendelstein 7-X (W7-X) is a dedicated light impurity XUV spectrometer intended to measure Lyman-α transitions of hydrogen-like ions of four low-Z impurities—boron (4.9 nm), carbon (3.4 nm), nitrogen (2.5 nm) and oxygen (1.9 nm). Since the discussed diagnostic will deliver continuous information about the line intensities, it is crucial to understand the origin of the obtained signals with respect to the experimental plasma conditions (electron temperature and density). This, however, might be difficult because of the broad acceptance angle of the spectrometer and irregular shape of the plasma edge or SOL where the radiation is expected to mostly come from, depe…
High-Power Multicarrier Generation for RF Breakdown Testing
2017
Testing of satellite components for high RF power breakdown effects, such as multipactor and corona or passive-intermodulation, is a topic of growing interest in the aerospaceindustry. Switching fromthe classical single carrier approach to the more realisticmulticarrier scenario is very challenging from the experimental point of view. Themulticarrier signals, amplifiedby several RF power amplifiers, need to have controlled phase, amplitude, and frequency in each carrier. Fine tuning of the signal generator phases is required in order to compensate the phase drift occurring in the active elements of the test bed. This paper presents an efficient and low-cost technique to generate multicarrie…