Accompagnement de l'élève de 16 à 24 ans en formation générale des adultes du Québec et réussite au sein de l'école

Afin d’enrichir les outils en matière de solution au décrochage scolaire, cette recherche s’intéresse à l’accompagnement de l’élève et à la réussite au sein de l’école. Elle se déroule dans le cadre de la formation générale des adultes (FGA) âgés de 16 à 24 ans et fréquentant les centres d’éducation des adultes du Québec (CÉA). L’objectif général est de décrire ce qui se fait comme pratiques d’accompagnement de l’élève pour la réussite tout en identifiant les caractéristiques et les objectifs de ces pratiques. Pour ce faire, trois questions de recherche ont été étudiées à savoir : 1) que se fait-il comme pratiques d’accompagnement en FGA, 2) quels sont les objectifs poursuivis par ces pratiques et, enfin, 3) quelles sont les caractéristiques de ces pratiques? Cette étude s’appuie sur l’approche de la sociologie de l'éducation de François Dubet (1994) et propose d’examiner trois dimensions (pédagogique, personnelle et sociale) et sept formes de pratiques d’accompagnement de l’élève : le tutorat, le counseling, le compagnonnage, l’entraide par les pairs, le mentorat, le cybermentorat et les pratiques pédagogiques des enseignants. La démarche étant d’établir un ensemble de pratiques d’accompagnement de l’élève comme il se présente dans le milieu, puisque toutes les pratiques d'accompagnement n’avaient pas été, avant notre recherche, répertoriées en tant que telles. Les résultats obtenus permettent de constater la présence d’un déploiement important de plusieurs pratiques d’accompagnement de l’élève en FGA incluant les pratiques pédagogiques des enseignants. En effet, le tutorat et le counseling sont deux pratiques qui obtiennent des scores importants. De plus, il aura été possible de documenter de façon assez complète les pratiques pédagogiques des enseignantes dites « d’accompagnement de l’élève » et de comprendre l’articulation de l’ensemble de ces pratiques avec la réussite de l’élève au sein de l’école. Au terme de cette recherche, deux sources de connaissances ont été mises en évidence. D’abord, la première découle des composantes issues du modèle théorique à l’étude, ensuite, la deuxième concerne l’explicitation des pratiques pédagogiques des enseignants. Dans les deux cas, les résultats, ainsi que les analyses, révèlent le caractère central de la dimension pédagogique dans l’accompagnement de l’élève en FGA, ce qui nous renvoie à l’importante contribution, en matière d’accompagnement de l’élève en FGA, de l’enseignant, puisque ce dernier inclut l’accompagnement de l’élève dans l’acte même d’enseigner.With a view to developing and refining the tools needed to better solve the problem of school drop-out rates, this research interests itself in the accompaniment of the student and the resulting success in the school. It is addressed to the 16 to 24 year old students that are attending Québec’s FGA Education Centres. The general objective is describing what practices are used to accompany the student toward success while also identifying and describing the characteristics and objectives of said practices. In order to achieve this goal, three research questions have been studied, namely: 1) what are the accompaniment methods used in FGA; 2) what are the objectives sought with the use of these methods, and; 3) what are the characteristics of these methods? This research leans on the approach of sociology of education developed by François Dubet (1994), and proposes to examine three dimensions (pedagogical, personal, and social) as well as seven methods of student accompaniment: tutoring, counselling, pair work, assistance between peers, mentoring, cyber-mentoring, and teacher pedagogical methods. The undertaking is aimed at establishing a group of accompaniment practices for the student in his environment. All of these practices, prior to our research, had never been tabulated. The results obtained permit us to observe an important deployment of several accompaniment methods in use in FGA, including the teachers’ own pedagogical methods. In fact, tutoring and counselling are two methods that score high marks. In addition, this research has helped make it possible to document in a rather complete manner the teachers’ pedagogical methods in said student accompaniment, and to understand the dynamics of these methods in student successes at school. Upon the completion of this research, two sources of knowledge stand out. The first one emanates from the components of the theoretical model presently being studied, while the second relates to the specificity of the teachers’ pedagogical methods. In both cases the results, as well as the analyses, reveal the importance of the pedagogical dimension with respect to accompanying the FGA student, which in turn leads us back to the important contribution made by the teacher in student accompaniment in FGA, as in fact the teacher includes student accompaniment in the actual practice of teaching

Ultrasonic characterization of porous silicon using a genetic algorithm to solve the inverse problem

International audienceThis paper presents a method for ultrasonic characterization of porous silicon in which a genetic algorithm based optimization is used to solve the inverse problem. A one dimensional model describing wave propagation through a water immersed sample is used in order to compute transmission spectra. Then, a water immersion wide bandwidth measurement is performed using insertion/substitution method and the spectrum of signals transmitted through the sample is calculated using Fast Fourier Transform. In order to obtain parameters such as thickness, longitudinal wave velocity or density, a genetic algorithm based optimization is used.A validation of the method is performed using aluminum plates with two different thicknesses as references: a good agreement on acoustical parameters can be observed, even in the case where ultrasonic signals overlap.Finally, two samples, i.e. a bulk silicon wafer and a porous silicon layer etched on silicon wafer, are evaluated. A good agreement between retrieved values and theoretical ones is observed. Hypothesis to explain slight discrepancies are proposed

Fabrication and modeling of piezoelectric transducers for High-Frequency medical imaging

International audienceWe have studied the processing of piezoelectric thick films using electrophoretic deposition (EPD) for high-frequency ultrasound applications. Lead-zirconium-titanate (PZT) particles synthetized by solid states synthesis were dispersed in ethanol using ammonium polyacrylate (PAA). The electrophoretic deposition of PZT particles was performed at a constant-current mode. PZT thick-films deposited at 1 mA for 60 seconds were sintered at 900oC for 2 hours in a PbO-controlled atmosphere. The scanning-electron microscopy (SEM) analysis shows that the thickness of PZT layer is uniform and that the pores are homogeneously distributed within the layer. The complex electrical impedance was measured and fitted by KLM scheme in order to deduce the dielectric, mechanical and piezoelectric parameters of the thick-films. The density and thickness of PZT thick films are used as inputs and the thickness coupling factor kt, dielectric constant at constant strain and resonant frequency are deduced. The results show that homogeneous PZT thick-film structures with tailored thickness and density prepared by EPD and sintering having a resonant frequency around 20 MHz can be used for noninvasive medical ultrasound imaging and diagnostics

Ultrasonic transducers based on curved lead-free piezoelectric thick films for high resolution medical imaging

International audienceKNN-based lead free ferroelectric materials are receiving much attention due to their high electromechanical properties that make them promising candidates to replace the lead-based piezoceramics that will eventually be banned by environmental regulations in many countries over the world. Studies include the development of KNN thick films that are particularly well adapted for high frequency applications due to higher wave velocities and a dielectric constant in an acceptable range for single element transducers. Here, a KNN based thick film is deposited on a curved substrate by pad-printing in order to be used in a focused high frequency transducer. This substrate is a porous lead-free KNN cylinder specifically developed to exhibit the required acoustical properties of a backing (acoustical impedance, high attenuation) and is compatible with the high sintering temperature of the KNN thick film. Electromechanical properties of the piezoelectric thick film in thickness mode were deduced (kt over 35%). This structure was used to fabricate a transducer which was characterized (relative bandwidth over 90%). Finally this transducer was integrated in a high frequency imaging system and its performance allowed skin images to be produced. To conclude, the replacement of lead-based high frequency transducers by green devices is a viable option

Non-Planar Pad-Printed Think-Film Focused High-Frequency Ultrasonic Transducers for Imaging and Therapeutic Applications

Pad-printed thick-film transducers have been shown to be an interesting alternative to lapped bulk piezoceramics, because the film is deposited with the required thickness, size, and geometry, thus avoiding any subsequent machining to achieve geometrical focusing. Their electromechanical properties are close to those of bulk ceramics with similar composition despite having a higher porosity. In this paper, padprinted high-frequency transducers based on a low-loss piezoceramic composition are designed and fabricated. High-porosity ceramic cylinders with a spherical top surface are used as the backing substrate. The transducers are characterized in view of imaging applications and their imaging capabilities are evaluated with phantoms containing spherical inclusions and in different biological tissues. In addition, the transducers are evaluated for their capability to produce high-acoustic intensities at frequencies around 20 MHz. High-intensity measurements, obtained with a calibrated hydrophone, show that transducer performance is promising for applications that would require the same device to be used for imaging and for therapy. Nevertheless, the transducer design can be improved, and simulation studies are performed to find a better compromise between low-power and high-power performance. The size, geometry, and constitutive materials of optimized configurations are proposed and their feasibility is discussed

Broadband parametric amplification for multiplexed SiMOS quantum dot signals

Spins in semiconductor quantum dots hold great promise as building blocks of quantum processors. Trapping them in SiMOS transistor-like devices eases future industrial scale fabrication. Among the potentially scalable readout solutions, gate-based dispersive radiofrequency reflectometry only requires the already existing transistor gates to readout a quantum dot state, relieving the need for additional elements. In this effort towards scalability, traveling-wave superconducting parametric amplifiers significantly enhance the readout signal-to-noise ratio (SNR) by reducing the noise below typical cryogenic low-noise amplifiers, while offering a broad amplification band, essential to multiplex the readout of multiple resonators. In this work, we demonstrate a 3GHz gate-based reflectometry readout of electron charge states trapped in quantum dots formed in SiMOS multi-gate devices, with SNR enhanced thanks to a Josephson traveling-wave parametric amplifier (JTWPA). The broad, tunable 2GHz amplification bandwidth combined with more than 10dB ON/OFF SNR improvement of the JTWPA enables frequency and time division multiplexed readout of interdot transitions, and noise performance near the quantum limit. In addition, owing to a design without superconducting loops and with a metallic ground plane, the JTWPA is flux insensitive and shows stable performances up to a magnetic field of 1.2T at the quantum dot device, compatible with standard SiMOS spin qubit experiments

Screen-printed ultrasonic 2-D matrix array transducers for microparticle manipulation

This paper reports the development of a two-dimensional thick film lead zirconate titanate (PZT) ultrasonic transducer array, operating at frequency approximately 7.5 MHz, to demonstrate the potential of this fabrication technique for microparticle manipulation. All layers of the array are screen-printed then sintered on an alumina substrate without any subsequent patterning processes. The thickness of the thick film PZT is 139 ± 2 μm, the element pitch of the array is 2.3 mm, and the dimension of each individual PZT element is 2 × 2 mm2 with top electrode 1.7 × 1.7 mm2. The measured relative dielectric constant of the PZT is 2250 ± 100 and the dielectric loss is 0.09 ± 0.005 at 10 kHz. Finite element analysis was used to predict the behaviour of the array and to optimise its configuration. Electrical impedance spectroscopy and laser vibrometry were used to characterise the array experimentally. The measured surface motion of a single element is on the order of tens of nanometres with a 10 Vpeak continuous sinusoidal excitation. Particle manipulation experiments have been demonstrated with the array by manipulating Ø10 μm polystyrene microspheres in degassed water. The simplified array fabrication process and the bulk production capability of screen-printing suggest potential for the commercialisation of multilayer planar resonant devices for ultrasonic particle manipulation

Etudes électrothermiques de dispositifs électroniques innovants pour les technologies submicroniques

High density integration in advanced CMOS technology, such as STMicroelectronics’ 28 nm UTBB FD-SOI technology, leads to elevated power density. This results in an increase of the local or global temperature which could cause dysfunction of the system, or even lead to its destruction by thermal runaway. In this context, we present innovative solutions for the “ robust integration regarding the electro-thermal activity following different scaling factors within the scope of integrated circuits development ”. Thus, we studied, at first, structures with dual source contact enabling : (i) in-situ heating in MOS transistors (temperature elevation up to hundreds of Kelvin degrees) ; (ii) performance recovery of these transistors by local annealing (MOSFET’s threshold voltage return to its typical value) ; (iii) creation of OTP memory dots (use of an electromigration effect inside the silicide) and (iv) temperature self-regulation of the transistors (utilisation of an integrated temperature sensor). Secondly, we developed a new low power temperature sensor (1 mV.K-1 slope for the output voltage and power of the order of picowatt) and its integration within a circuit using another transistor enabling electro-thermal behavior modification of the circuit. All our electronics structures were fabricated on 28 nm UTBB FD-SOI silicon demonstrators and measured. To carry out our work, we relied on some software for electro-thermal simulations. Their adaptation to our needs has been a third line of work.La haute densité d’intégration dans les technologies CMOS avancées, telle que la technologie 28 nm UTBB FD-SOI de STMicroelectronics, conduit à des densités de puissance élevées. Ceci se traduit par des élévations de température locales ou globales pouvant conduire au dysfonctionnement du système, voire à sa destruction par emballement thermique. Dans ce cadre, nous présentons des solutions innovantes pour « l’intégration robuste vis-à-vis de l’activité électrothermique suivant les différents facteurs d’échelle dans le cadre de développement de circuits intégrés ». Ainsi, nous avons étudié, dans un premier temps, les structures à double contacts de source permettant : (i) le chauffage in-situ dans les transistors MOS (élévation de la température jusqu’à plusieurs centaines de degrés kelvin) ; (ii) le rétablissement des performances desdits transistors par recuit local (retour de la tension de seuil d’un MOSFET vers sa valeur typique) ; (iii) la création de points mémoires OTP compacts (utilisation d’un phénomène d’électromigration dans le siliciure) et (iv) l’autorégulation en température de ces transistors (utilisation d’un capteur de température intégré). Dans un deuxième temps, nous avons développé un nouveau capteur de température basse consommation (pente de 1 mV.K-1 pour la tension de sortie et puissance de l’ordre du picowatt) et son intégration dans un circuit avec un transistor permettant la modification du comportement électrothermique du circuit. Tous nos dispositifs électroniques ont été fabriqués sur des démonstrateurs silicium en 28 nm UTBB FD-SOI et mesurés. Pour réaliser nos travaux, nous avons utilisé plusieurs logiciels de simulations électrothermiques. Leur adaptation à nos besoins a constitué un troisième axe de travail