Utilisation d'un capteur à courant de Foucault pour prévenir la fissuration dans des structures métalliques: travail de bachelor : diplôme 2016

Sensima Inspection Sàrl. a développé un capteur à courant de Foucault flexible et peu intrusif qui permet de surveiller la propagation de fissures dans des éléments métalliques. Il est actuellement testé in-situ sur des ponts. Le but de ce projet est de démontrer que ce capteur peut être utilisé dans le cadre du suivi conditionnel d’installations hydroélectriques et en particulier des machines tournantes. Il devrait, à terme, permettre d’arrêter certains organes dans le cas où les fissures suivies dépasseraient une taille critique déterminée à partir de la mécanique de la rupture. Les jalons de ce projet sont de démontrer que le capteur permet de suivre l’évolution de fissures dans des tôles minces lors d’essais de traction en déchirement et en fatigue, et de valider expérimentalement s’il est possible de corréler le signal obtenu par le capteur en pointe de fissure avec d’autres mesures expérimentales comme des tests de dureté et des observations métallographiques

The bivalency effect: adjustment of cognitive control without response set priming

The occasional occurrence of bivalent stimuli, that is, stimuli with features relevant to two tasks, slows performance on subsequent tasks with univalent stimuli, including those which have no common features with bivalent stimuli (i.e., the "bivalency effect”). We have suggested that the bivalency effect might stem from an episodic context binding arising from the occasional occurrence of bivalent stimuli. However, as the same response set is used usually for univalent and bivalent stimuli, bivalent stimulus features may be negatively primed via response features. We investigated this possibility in two experiments, in which one group of participants used the same response keys for all tasks and another group used separate response keys. The results showed a comparable bivalency effect in both groups. Thus, it rather results from episodic context binding than from response set primin

Paternité au sein d'une maternité

Tout au long de ce travail, je recherche comment le père est réellement intégré au sein d'un service de post-partum et plus particulièrement dans les soins de son nouveau-né par le personnel soignant d'un tel service. Je m'attarde uniquement sur la situation d'un couple ayant mené une grossesse physiologique et un accouchement eutocique afin de découvrir quelle place reste véritablement au père lorsque sa compagne est pleinement capable d'effectuer elle-même tous les soins à prodiguer à l'enfant. Pour ce faire, je procède à des entretiens dirigés auprès d'infirmières, d'infirmières sages-femmes et de sages-femmes. Suite à cette collecte de données, je procède à une analyse de type qualitative et thématique afin de mettre en évidence les points forts et d'établir des liens entre le corpus de réponse et mes cadres de référence préalablement construits. Entre autres, j'ai pu observer que c'est principalement sur le support des soins aux corps qu'une intégration des pères est possible dans un tel service. C'est tout simplement en leur proposant et en les faisant participer à ces soins que les soignantes permettent aux pères de s'impliquer dans leur paternité, favorisant ainsi la construction d'un lien d'attachement particulier entre l'enfant et son parent

Microfabricated solid oxide fuel cells

Micro-fabricated solid oxide fuel cells (µSOFCs) are finding an increasing interest as potential power sources for portable devices such as MP3 players or laptops. The aim of this work was to fabricate a µSOFC demonstrator that works at 500°C and is fuelled by hydrogen. This thesis was divided into two parts. The first one was devoted to the development of an electrolyte and electrodes in form of sputtered thin films with electrical and mechanical properties suitable for the implementation in a real cell. YSZ and CGO electrolyte have been reactively sputtered from metallic targets. Both films are dense and have a columnar microstructure. The ionic conductivity of these films was of 0.5 S/m at 550°C for the CGO and of 5.5 x 10-3 S/m at 500°C for the yttria stabilized zirconia (YSZ) . Albeit the ceria doped gadolinia (CGO) was a better ionic conductor at low temperature, it was not possible to obtain an open circuit voltage (OCV) with a CGO electrolyte film. Most likely, the reduction of the Ce+4 ion into Ce+3 in a hydrogen atmosphere creates an electrical leakage. Better results were obtained with YSZ layers. Single, (111) textured columnar films showed OCV's of 200 mV. Best results were obtained with a double layer of two different microstructures. The first one exhibited a dense, columnar microstructure with (111) texture. The second layer was porous with nanocrystalline grains and preferential (200) orientation. The improved properties are ascribed to the absence of film crossing grain boundaries. Of special interest is the mechanical stress behaviour upon heating to the operation temperature. The stress was investigated as a function of temperature up to 700°C. An anomalous, hysteretic behaviour was found during the first heating cycle in YSZ as well as CGO thin films. This phenomenon could be modelled as an oxygen uptake to fill up excess oxygen vacancies created during the sputtering process. The model allowed to derive a diffusion activation energy of 0.6 eV for these excess vacancies in YSZ. Annealing in air at 700 °C permits to reduce stress and to stabilize the YSZ membrane. As electrode materials, sputter deposited, porous platinum, porous Ni-CGO composites and dense LaxSr1-xCoO3-y (LSCO) thin films were developed and characterized. The PEN (Positive electrode-Electrolyte-Negative electrode) layer processes were combined with Micro Electro Mechanical System (MEMS) process technology to fabricate µSOFC test devices. The PEN membranes were liberated by deep silicon dry etching. The cell diameter was varied between 0.5 and 5 mm, the electrolyte thickness between 500 and 700 nm. A nickel grid grown by electroplating was used to support the electrolyte layer and to serves as current collector for the anode. The cell with a 5 mm diameter shows a very good mechanical stability up to 600°C in SOFC operating conditions and for several heating cycles. The functionality of the fuel cell with two 20 nm thick porous platinum electrodes and a YSZ bilayer electrolyte (500 nm) has been demonstrated. An OCV of 850 mV was measured at 500°C with hydrogen fuel. Unfortunately, a too high cathode contact resistance reduced the current to very low values. The achieved maximal power density was only 19 µW/cm2. A simple design change should remedy the problem

Oxygen reduction at thin dense La0.52Sr0.48Co0.18Fe0.82O3- δ electrodes: Part II: Experimental assessment of the reaction kinetics

The mechanism and kinetics of oxygen reduction at thin dense two-dimensional $${\text{La}}_{{0.52}} {\text{Sr}}_{{0.48}} {\text{Co}}_{{0.18}} {\text{Fe}}_{{0.82}} {\text{O}}_{{3 - \delta }}$$ (LSCF) electrodes have been investigated in air between 500 and 700 °C with electrochemical impedance spectroscopy and steady-state voltammetry. Dense and geometrically well-defined LSCF films with various thicknesses ranging between 16 and 766nm have been prepared on cerium gadolinium oxide substrates by pulsed laser deposition and structured with photolithography. The current collection was ensured by a porous LSCF layer. A good agreement was found between the experimental data and the impedance of the reaction model calculated with state-space modelling for various electrode potentials and thicknesses. It was evidenced that oxygen adsorption, incorporation into the LSCF and bulk diffusion are rate-determining while charge transfer at the electrode/electrolyte interface remains at quasi-equilibrium. The 16 and 60nm thin dense LSCF electrodes appear to be more active towards oxygen reduction than thicker layers and porous films at 600 and 700°

The bivalency effect represents an interference-triggered adjustment of cognitive control: An ERP study

When bivalent stimuli (i.e., stimuli with relevant features for two different tasks) occur occasionally among univalent stimuli, performance is slowed on subsequent univalent stimuli even if they have no overlapping stimulus features. This finding has been labeled the bivalency effect. It indexes an adjustment of cognitive control, but the underlying mechanism is not well understood yet. The purpose of the present study was to shed light on this question, using event-related potentials. We used a paradigm requiring predictable alternations between three tasks, with bivalent stimuli occasionally occurring on one task. The results revealed that the bivalency effect elicited a sustained parietal positivity and a frontal negativity, a neural signature that is typical for control processes implemented to resolve interference. We suggest that the bivalency effect reflects interference, which may be caused by episodic context bindin

Is executive control related to working memory capacity and fluid intelligence?

In the last two decades, individual-differences research has put forward 3 cognitive psychometric constructs: executive control (i.e., the ability to monitor and control ongoing thoughts and actions), working memory capacity (WMC, i.e., the ability to retain access to a limited amount of information in the service of complex tasks), and fluid intelligence (gF, i.e., the ability to reason with novel information). These constructs have been proposed to be closely related, but previous research failed to substantiate a strong correlation between executive control and the other two constructs. This might arise from the difficulty in establishing executive control as a latent variable and from differences in the way the 3 constructs are measured (i.e., executive control is typically measured through reaction times, whereas WMC and gF are measured through accuracy). The purpose of the present study was to overcome these difficulties by measuring executive control through accuracy. Despite good reliabilities of all measures, structural equation modeling identified no coherent factor of executive control. Furthermore, WMC and gF—modeled as distinct but correlated factors—were unrelated to the individual measures of executive control. Hence, measuring executive control through accuracy did not overcome the difficulties of establishing executive control as a latent variable. These findings call into question the existence of executive control as a psychometric construct and the assumption that WMC and gF are closely related to the ability to control ongoing thoughts and actions

The pressure to communicate efficiently continues to shape language use later in life

Language use is shaped by a pressure to communicate efficiently, yet the tendency towards redundancy is said to increase in older age. The longstanding assumption is that saying more than is necessary is inefficient and may be driven by age-related decline in inhibition (i.e. the ability to filter out irrelevant information). However, recent work proposes an alternative account of efficiency: In certain contexts, redundancy facilitates communication (e.g., when the colour or size of an object is perceptually salient and its mention aids the listener’s search). A critical question follows: Are older adults indiscriminately redundant, or do they modulate their use of redundant information to facilitate communication? We tested efficiency and cognitive capacities in 200 adults aged 19–82. Irrespective of age, adults with better attention switching skills were redundant in efficient ways, demonstrating that the pressure to communicate efficiently continues to shape language use later in life