Thesis (Magister Technologiae - Discipline Electrical Engineering, Faculty of Engineering) -- Vaal University of Technology / Discomfort glare is a topic that has been investigated for many years without any reasonable explanation regarding its effect on the human visual system. Results of previous research concluded that established methods have a lot of similarities in implementation; but a number of differences when comparing the results of observer's evaluations with the mathematically calculated glare ratings. Therefore, an alternative method of evaluating the influence of exposure to an unshielded light source was investigated to establish a more reliable and realistic response from observers. In order to address the discrepancies of previous evaluation systems concerning observer's varying opinions regarding the level of discomfort experienced, it was decided to investigate the feasibility of evaluating the brain activity of the observers exposed to an unshielded incandescent lamp. This was done in order to facilitate the differences in each individual observer's sensitivity to bright light sources and the influence of personal taste therefore, eliminating the effect of personal interpretation. The main purpose of this study was to determine whether it would be possible to get any response regarding brain functions when an observer is exposed to a bare light source. In order to determine the pathway of visual stimuli it was necessary to investigate the operating principles of the human eye in detail. Because the eye is only an instrument that makes seeing possible; it was also important to investigate the brain and all its different functions. The part of the brain where visual interpretation takes place was indicated as the occipital lobe. This is the part of the brain monitored for any change of functional status by taking measurements with an electroencephalogram (EEG). Measurements were indeed possible; it was presented as a suppression of the alpha brain activity. During the testing procedure it was observed that the observers were not equally photosensitive. There was also a difference in the amount of alpha suppression with the observer's eyes open and closed respectively. Because the alpha rhythm has a tendency to increase with closed eyes it was much easier to notice the suppression.

Le silicium se présente comme un bon candidat d’électrode négative pour améliorer la densité d’énergie des accumulateurs Li-ion ou rendre les microaccumulateurs compatibles avec le procédé de brasure à refusion qui nécessite un recuit à 260 °C. En effet, il présente une forte capacité spécifique (3759 mAh.g-1) et sa température de fusion est élevée (1410°C). Néanmoins, de fortes variations volumiques se produisent lors du processus de lithiation/délithiation pouvant atteindre 280 %, ce qui constitue un frein majeur à son développement. Ces travaux de thèse se focalisent sur l’étude approfondie du comportement électrochimique du silicium préparé sous forme de couche mince par pulvérisation cathodique. Cette nanostructuration limite la décrépitation de la matière active, et évite l’utilisation de charges et de liants. Ainsi, elle permet d’étudier plus finement le comportement intrinsèque du matériau et révèle des phénomènes en général non détectables avec les électrodes composites. / Silicon which has a theoretical capacity of 3579 mAh.g-1 and low insertion/deinsertion potentials is one of the most promising candidates to replace graphite as a negative electrode in lithium-ion batteries. Moreover, silicon could replace lithium in microbatteries to make them compatible with the solder-reflow. However, this high capacity associated with a dense material leads to high volumetric variations which are a starting point to various issues resulting in poor cycle performances. During this thesis, electrochemical behavior of silicon is evaluated on thin films electrodes. This allows avoiding the use of binder and charges, and it leads to better cycle performances which emphasizes slow phenomenon, not yet measurable on conventional composite electrode.

Le brillant est un attribut de l'apparence visuelle. Il s'agit d'une construction du système visuel, basée sur le signal optique en provenance d’une surface et capté par l'œil. Les développements récents en spectrophotométrie fondamentale ont produit des instruments à même de mesurer la réflexion lumineuse avec une acuité égale à celle du système visuel humain. Une description transverse, visuelle et optique, d'un même ensemble d'échantillons est maintenant possible. Dans ce travail, nous construisons via des procédés sol-gel une échelle de brillant métrologique multivariée en termes de topologie de surface, indice de réfraction, teinte et niveaux de brillant. Cette échelle est caractérisée par la suite en rugosité, en indice de brillant spéculaire et en BRDF. Nous présentons les techniques de mesure et les corrections employées sur ConDOR, notre goniospectrophotomètre dédié à la mesure haute résolution du pic spéculaire. Au terme de cette étude, l'instrument présente une résolution angulaire de 0,014°, la meilleure résolution atteinte à ce jour, deux fois inférieure à celle du système visuel humain. La dynamique est de 6,5 décades. ConDOR est employé pour mesurer les BRDF de plusieurs échantillons brillants issus de différentes échelles. Elles sont étudiées et les discutées. Un premier lien entre rugosité et BRDF est esquissé. Nous étudions finalement en nous basant sur une échelle de référence de brillant deux aspects de sa perception : l’effet d'un changement d'angle solide d'illumination et l’effet du réalisme de l'environnement d'observation. Nos résultats montrent que le système visuel est plus sensible aux variations de brillant dans des conditions d'observations réalistes, tant en matière d'éclairage que d'environnement. L’effet est particulièrement prononcé pour les échantillons mats. Les conditions moins réalistes ou moins naturelles peuvent mener les observateurs à la confusion. / Gloss is a visual appearance attribute. It is a construction from the visual system built on the optical signal from a surface and sensed by the eye. Recent developments in fundamental spectrophotometry lead to instruments able to measure luminous reflection with an acuity equal to the visual system in terms of angular resolution and dynamic. A cross-discipline description between optics and vision is now possible on a same set of samples. In this work, we build through sol-gel process a metrological gloss scale. It is multivariate in terms of surface topology, refractive indices, hue and gloss levels. This scale is then characterized in roughness, specular gloss and BRDF. We expose the measurement techniques and corrections used on our goniospectrophotomer ConDOR. This instrument is dedicated to high resolution measurement of specular peaks. By the end of this study, Condor has reached an angular resolution of 0.014°, the smaller achieved until now, twice better than the human visual system acuity. The dynamic range extends over 6.5 decades. ConDOR is used to measure BRDF of several glossy samples from different scales. These measurements are studied and discussed. A first link between roughness and BRDF is drawn.Using a reference gloss scale, we finally study two aspects of gloss perception: both effects of a change in the solid angle of illumination and in the observation environment realism. Our results indicate that the visual system is more sensitive to gloss variations under realistic conditions as well in lighting as in environment. This effect is particularly noticeable on matt samples. Lesser realistic or lesser natural conditions could lead observers to confusion.