Given the growing concern over climate change, air pollution, rising energy prices, and the uncertain reliability of conventional fuel sources, solar power has become more popular in a variety of applications. Solar power is free, safe, abundant, renewable, and has few negative impacts on the environment. The photovoltaic array is substantially influenced with unpredictable environmental conditions (sun illumination and array temperature), which in turn, results in nonlinear Voltage-Current (or Power-Voltage, Power-Current) characteristics. These characteristics make it difficult to estimate the maximum power operating point. To extract the maximum power available from photovoltaic (PV) arrays on a continuous basis, a device called the Maximum Power Point Tracker (MPPT) is needed to continuously deliver the highest possible power to the load given unpredictable variations in environmental conditions. The PV system used in our experiment has a maximum 300W capability. Two sets of PV arrays are used in parallel to demonstrate the scalability of the system; each branch consists of three series-connected PV modules that are individually rated at 50W. Two DC-DC buck-type converters are implemented. A 24V battery bank is used as a power storage unit and is also connected to the load. An MC-based 56F8013 and its demonstration board from Freescale are employed to implement different MPPT control schemes, with multiple-PWM channels. The design can therefore adequately handle two main independent switches for each power converter. Several MPPT control algorithms are validated and comparatively analyzed in both indoor and outdoor experiments in real time. A new control strategy (called Adaptive Hill-Climbing) is proposed as a modified version of the conventional Hill-Climbing method using an optimally adaptive power window. Other methods including dp/dv method and IncCond method are also implemented in the PV system. The experimental investigation is conducted using these control topologies to seek continuously varying Maximum Power Point (MPP) from solar arrays. The experimental results show that the new proposed control method strongly outperforms the other methods. This thesis shows that the proposed MPPT can increase the power generated by PV arrays by up to at least 30% more than a PV system without an MPPT. The proposed MPPT system is adaptive to environmental disturbances; it is flexible and can be expanded to an N-parallel PV system. / Thesis / Master of Applied Science (MASc)

Data from an airborne laser scanner, a dual-band interferometric synthetic aperture radar (DBInSAR), and Landsat were evaluated for estimating ages of even-aged loblolly pine stands in Appomattox-Buckingham State Forest, Virginia, U.S.A. The DBInSAR data were acquired using the GeoSAR sensor in summer, 2008 in both the P- and X-bands. The LiDAR data were acquired in the same summer using a small-footprint laser scanner. Loblolly pine stand ages were assigned using the establishment year of loblolly pine stands provided by the Virginia Department of Forestry. Random circular plots were established in stands which varied in age from 5 to 71 years and in site index from 21 to 29 meters (base age 25 years). LiDAR- and GeoSAR-derived independent variables were calculated. The final selected LiDAR model used common logarithm of age as the dependent variable and the 99.5th percentile of height above ground as the independent variable (R2adj = 90.2%, RMSE = 4.4 years, n=45). The final selected GeoSAR models used the reciprocal of age as the dependent variable and had three independent variables: the sum of the X-band magnitude, the 25th percentile of X/P-band magnitudes, and the 90th percentile of the X-band height above ground (R2adj = 84.1%, RMSE = 7.9 years, n=46). The Vegetation Change Tracker (VCT) algorithm was run using a digital elevation layer, a land cover map, and a series of Landsat (5 and 7) images. A comparison was made between the loblolly pine stand ages obtained using the three methods and the reference data. The results show that: (1) although most of the time VCT and reference data ages were different, the differences were normally small, (2) all three remote sensing methods produced reliable age estimates, and (3) the Landsat-VCT algorithm produced the best estimates for younger stands (5 to 22 years old, RMSEVCT=2.2 years, RMSEGeoSAR=2.6 years, RMSELiDAR=2.6 years, n=35) and the model that used LiDAR-derived variables was better for older stands. Remote sensing can be used to estimate loblolly pine stand age, though prior knowledge of site index is required for active sensors that rely primarily on the relationship between age and height. / Ph. D.

L’agrivoltaïque, combinaison de panneaux photovoltaïques et d’une culture sur le même sol, a été proposé en 1982 comme solution au conflit d’usage des sols. Lancé en 2010 à Montpellier, le concept associant panneaux fixes et diverses cultures a fait la preuve d’une productivité combinée de la parcelle améliorée grâce, notamment, à l’acclimatation de la culture à l’ombre. Dans cette thèse, les panneaux fixes ont été échangés par des panneaux orientables au cours de la journée. L’objectif était d’optimiser l’orientation des panneaux pour maximiser la productivité combinée de la parcelle sans pénaliser la culture. Pour cela, la croissance et le développement de laitues ont été analysés en conditions contrôlées et en plein champ sous différentes modalités d’ombrage par panneaux fixes ou mobiles. Les panneaux mobiles ont permis d’améliorer la productivité combinée de la parcelle par rapport à des panneaux fixes, avec un maintien de la production agricole dans certaines conditions. Une approche écophysiologique basée sur le développement de la plante, sa capacité à intercepter et convertir le rayonnement en biomasse, a révélé que les modalités d’ombrage avaient peu d’impact sur la mise en place de la surface foliaire malgré des différences de biomasse accumulée en rapport avec le rayonnement transmis à la plante. Des modifications du développement foliaire ont conduit à une meilleure utilisation du rayonnement transmis lorsque celui-ci était réduit. Ce travail a débouché sur une modélisation de l’impact de l’orientation des panneaux sur la biomasse des laitues permettant d’optimiser le pilotage des panneaux en fonction du scénario climatique et des objectifs de productions. / Agrivoltaic systems, combining solar panels and crops on the same land were proposed in the early 1980’s as a solution to solve land use conflict. Introduced in 2010 in Montpellier, the concept has proven itself associating fixed panels to multiple food crops. Total land productivity was improved, thanks to plant acclimation to shade. In this thesis, fixed panels were replaced with mobile panels, adjustable along the day. The aim of this work was to optimize solar panel orientations to maximise total land productivity without threatening the crop culture. Growth and development of lettuces were analysed in controlled conditions and in the field under several shading conditions by fixed or mobile panels. Total land productivity was improved with mobile panels in comparison with fixed panels, maintaining lettuce yield under certain conditions. Through an ecophysiological approach based on plant development and its ability to intercept and convert light into biomass, the different shading conditions were shown to have a small impact in the plant leaf area dynamic despite large differences in accumulated dry mass associated with transmitted radiation at the plant level. This was due to differences in leaf development resulted in higher use of the transmitted radiation when it was reduced. This study proposed a modelling approach of the incidence of panel orientations on lettuce dry mass at harvest. The model allows an optimisation of solar panels controlling as a function of climate scenario and crop and electricity production objectives.

L'objectif de ce travail est de montrer que l’'expertise peut-être une solution aux baisses de performances observées dans un paradigme de multitâche. Beaucoup d'expériences sur l'expertise expliquent que les experts vont mobiliser leurs connaissances antérieurement acquises afin de réaliser une tâche (stratégie top-down). Au contraire des novices, qui vont explorer le matériel de manière plus exhaustive en partant uniquement de l’objectif de la tâche à réaliser (stratégie bottom-up). Nous avons réalisé trois études. La première porte sur les patterns visuels des experts du jeu WoW. Alors que les experts devaient mémoriser des éléments d’une vidéo (simple vs complexe) tout en écoutant une histoire, on observe que lorsque le matériel est simple, les experts mettent en place une stratégie top-down, au contraire lorsque la tâche est plus complexe ils vont retourner progressivement à une stratégie bottom-up. Les novices, quant à eux suivront une stratégie bottom-up tout le long de l’expérience. La saillance capturerait le regard des novices, au contraire des experts qui arriveraient à l'inhiber. Grâce à ces résultats, nous avons mis à jour une grille d’heuristiques ergonomique. Enfin, nous avons étudié les patterns visuels dans un environnement plus écologique comme la réservation de billets d’avion en ligne. Les résultats, tout comme ceux de la première expérience, montrent le même type de pattern visuel trouvé dans les recherches n’impliquant que l’expertise. Les experts dans un domaine seraient aussi experts en multitâche dans ce domaine. De plus, la dernière expérience montre que les experts, quelques soient la charge de travail, mettent en place des stratégies top-down. / The aim of this project is to show how expertise can be a solution to the decrease of the performance in a multitasking paradigm. A lot of experience on the expertise explain that these experts will use their knowledge previously learned to explore an interface (top-down strategy). Unlike novices, who will explore the material in a more exhaustive way based on the objective of the task to be achieved (bottom-up strategy).We have carried out three studies to answer this problem. We studied the visual patterns of the WoW game experts, while asking them to memorize elements of a video (simple vs complex) and listening a story . We observe ambivalence in the strategy of exploration. Effectively, when the material is simple, experts will use a top-down strategy, and progressively with the complexity of the task, they will return to a bottom-up strategy. The novices, meanwhile, will follow a bottom-up strategy throughout the experience. The study of the map of salience shows that the attention of the novices will be captured by this one. This is not the case for experts who will inhibit it and explore the most important information for the task. From these results, we have updated an usability heuristic grid. Finally, we have completed this research by studying visual patterns in a more ecological context as booking airline tickets online. The results, like those of the first experiment, show the same type of visual pattern found in research involving only expertise. Experts in one field would also be experts in multitasking in this field. Moreover, in the last research, we found experts use all long these top-down’ strategy even on the more complex condition.

The purpose of this dissertation is to design the dual-axis solar tracker carrying the concentrator photovoltaic panels. The preamble of the dissertation shortly examines a photovoltaic cells development up to concentrators and the common support structures of solar power plants. The second part focuses on the engineering process itself. It includes the choice of the variant that suits best the requirements, the calculations of wind load and design of the various joints. The conclusion part is devoted to the evaluation, economy analysis of the construction and proposals for improvements.

Många undersökningar har gjorts inom marknadsföringsområdet med hjälp av eye-tracker. Gemensamt för majoriteten av dessa undersökningar är att de har gjorts på statisk reklam såsom reklam i tidningar och reklambanderoller på hemsidor. Relativt få undersökningar har gjorts där reklamen är integrerad i den rörliga bilden. I denna rapport undersöks logotyper i rörlig bild med hjälp av en eye-tracker där syftet var att undersöka relationen mellan fixering av blick på, tidigare kännedom om och hågkomst av logotyper. En studie genomfördes på 12 testpersoner som fick titta på ett filmklipp medan en eye-tracker registrerade deras ögonrörelser. De fick därefter svara på en enkät som handlade om logotyperna som presenterats i klippet. Resultatet visar att personer kommer ihåg logotyper som de har fixerat blicken på och samtidigt har tidigare kännedom om i större utsträckning än logotyper som de inte har någon tidigare kännedom om. En säker relation mellan tidigare kännedom och benägenhet att fixera blick har inte kunnat hittas. Fler studier bör därför göras med fler filmklipp, logotyper och testpersoner för att uppnå ett säkrare resultat. Vid studier av objekt i rörlig bild med eye-tracker, där intresse av att undersöka om objektet uppfattats eller ej finns, bör en studie av den minsta fixeringstid som krävs för att uppfatta objektet först göras. Det bör även göras fler studier på hur graden av hågkomst, tidigare kännedom och egenskaper hos fixeringar påverkar resultatet. / Many studies have been done in the field of marketing with the help of an eye-tracker. The common element in the majority of these studies is that they have been done on static advertising such as advertisements in magazines and web banners. Relatively few studies have been done when the advertisements are integrated in the moving picture. In this report logotypes that are integrated in the moving picture are investigated. The purpose of this report is to investigate the relationship between fixation of gaze on, prior knowledge of and the ability to recall logotypes. A study was done on 12 test subjects. The given task was to watch a film clip while their eye movements were registered with an eye-tracker. After the test they filled out a questionnarie about the presented logotypes in the clip. The result tells us that people are better at remembering logotypes that they have fixated on and simultaneously had prior knowledge of than logotypes that they fixated on but had no prior knowledge of. No certain relation was found between prior knowledge and the tendancy of fixating ones gaze was found. More studies have to be done with more clips, logotypes and test subjects in order to obtain a certain result. When investigating objects in moving picture with the help of an eye-tracker, when you are interested in investigating whether the object are resigistred or not, a study about the shortest required fixation duration for registration of the object should be done in advance. More studies has to be done on how properties of fixations, the degree of recollection and prior knowledge affects the result.

BACKGROUND: Physical activity for the majority of individuals is below recommended levels despite strong evidence of its significant health benefits. Activity tracker devices present as a promising and affordable tool to help promote physical activity and active choices. Additionally, young adults present as an ideal age group to implement behavior change interventions. OBJECTIVE: To determine what features of activity tracker hardware and software are helpful in motivating active choices. METHODS: This cross-sectional study included 149 participants ranging in age from 18-29 years old who wore an ActiGraph GT3X+ accelerometer for one week. They then continued to wear the accelerometer in addition to a randomly assigned activity tracker (Apple Watch, Fitbit Surge, Basis Peak, or Microsoft Band 2) for an additional week. They also used the corresponding app for their activity tracker. Participants filled out a survey about their experience at the end of the study RESULTS: Overall hardware rating (p = 0.162) and overall software rating (p = 0.125) did not differ between the four devices. Degree of motivation of the hardware (p = 0.177) and software (p = 0.120) was also similar for all the activity trackers. There were 625 positive comments made about tracker hardware with the majority of these comments concerning mode options (n = 149), other (n = 94), and battery (n = 79). There were 287 positive software comments with the majority in the categories of other (n = 78) and information (n = 68). CONCLUSIONS: The analyses of our data did not show a significant difference between devices in any category. Furthermore, results indicated a high number of positive comments for both hardware and software overall. Users also reported device hardware and software to be personally motivating.

Physical activities like walking have proven health benefits. People are adopting fitness trackers to track physical activity, but they often stop using them after a relatively short time. Many apps and games exist in the app markets that use gamification to tackle this problem of motivation. In this thesis, we examined these existing gamified fitness tracker apps from app markets and looked at the usage of different game elements within these apps. We conducted a systematic review of existing fitness Tracker Apps from Google Play Store and Apple App Store and used a mixed-method approach to identify apps, categorize them by different game elements used and found gaps in the design space using basic statistics, group clustering algorithms, and network analysis using NodeXL. We also developed a mobile game that combines step tracker data, a compelling narrative, and a strategic resource management mechanic with social cooperative-collaborative gameplay to encourage users to keep using fitness trackers and exercise more. It utilizes game elements and mechanics that haven't been explored by previous research or games as validated by our results from the systematic review of gamified fitness tracker apps.

La fonction d’équilibration est une fonction complexe qui implique une interaction entre les systèmes somatosensoriel, vestibulaire et visuelle qui en assurent la régulation. En pathologie, le contrôle de la posture et de l’équilibre peut être atteint comme dans le cas de neuropathies périphériques qui se caractérisent par une atteinte des fibres sensitives et motrices de niveau variable. Les neuropathies à prédominance sensitive sont dénommées neuropathies ataxiantes ; elles se caractérisent au niveau des membres inférieurs par l’atteinte proprioceptive qui peut entraîner des troubles de la posture et de l’équilibre en condition statique, dynamique ou encore lors de la marche. Ce travail rapporte trois méthodes d’évaluation élaborées dans les trois conditions d’équilibration afin de mieux caractériser les troubles de l’équilibre de cette population. L’évaluation de l’équilibre en condition statique sur une plateforme de force nous a permis de caractériser le poids des atteintes sensorielles et motrices dans les neuropathies à condition d’y inclure la mesure du paramètre de limite de l’équilibre qui dissocie le plus ces deux composantes. En condition dynamique, l’analyse de l’équilibre sur une plateforme de force motorisée « IsiMove » nous a permis de créer un score composé qui discrimine les troubles de l’équilibre d’une population de sujets ataxiques caractérisé par une instabilité majeure en conditions quasi statique (basse fréquence de déstabilisation) et une instabilité moins marquée en conditions plus dynamiques (hautes fréquences). Au cours de la marche, les lunettes eye-tracker se sont avérées constituer un outil pertinent pour l’analyse de la compensation visuelle, à la fois reproductible et sensible à la pathologie. Cette technologie nous a aidés à caractériser quantitativement une stratégie visuelle mise en place par les patients ataxiques lors de la locomotion. Les résultats de ce travail de thèse ouvrent différentes perspectives en ce qui concerne l’élaboration de programmes de rééducation plus spécifiques pour cette population, et la caractérisation instrumentale de nouveaux profils de troubles de l’équilibre des patients présentant une instabilité d’origine neurologique. / The balance function is a complex function that involves interaction between the somatosensory, the vestibular and the visual systems, the latter ensuring the equilibrium function regulation. In pathology, the control of posture and balance can be impaired as in the case of peripheral neuropathies, characterized by the impairment of sensory and motor fibers of variable level. Predominantly sensory neuropathies are called ataxic neuropathies; they are characterized by proprioceptive impairment in the lower limbs that can lead to disorders of posture and balance in static or dynamic condition, or even during gait. This study reports three assessment methods developed under the three balance conditions to better characterize balance disorders concerning this population. Balance assessment under static condition on a force platform has enabled us to characterize the weight of the sensory and motor impairments in neuropathies, provided that by the inclusion of measuring the limits of equilibrium balance parameter, which separates the most these two components. Under dynamic conditions, the analysis of balance on the motorized force platform "IsiMove" allowed us to create a composed score that distinguishes balance disorders in a population of ataxic subjects, which is characterized by major instability in quasi-static conditions (low frequency instability) and a less marked instability in more dynamic conditions (high frequencies). During gait, the eye tracker glasses have proven to be a relevant tool for the analysis of visual compensation, both reproducible and sensitive to the pathology. This technology has helped us to quantitatively characterize the visual strategy implemented by ataxic patients during locomotion. The results of this thesis open different perspectives regarding the development of more specific rehabilitation programs for this population. It also opens different perspectives on the instrumental characterization of new profiles of balance disorders in patients with instability of neurological origin.

Feedback plays a vital role in learning. With online learning on the rise, feedback can be given directly to each student in a way that can not be achieved in a traditional classroom with one teacher. But while the importance of feedback is well-known, little is known about how students interact with feedback. This study was conducted to find out how students interact with feedback from a question-based learning platform in terms of their eye movement patterns. Using an eye tracker and a multiple choice quiz, data of gaze duration in each quiz segment and gaze transactions in between segments was extracted and analyzed. The results show that students fall into three groups: 1) those who spend most time on feedback and less on the question, 2) those who spend most time on questions and less on the feedback 3) those who use a mixed approach. Students in group 1) and 3) had few gaze transactions between the questions and feedback, indicating that the feedback was used as intended. Having discovered the presence of distinct patterns of feedback interaction, the next steps will be to investigate how these impact the use and utility of the feedback by students. / Feedback spelar en avgörande roll för inlärning. Med e-learning kan feedback ges individuellt till varje elev på ett sätt som inte är möjligt i ett traditionellt klassrum med endast en lärare. Men medan vikten av feedback är välkänd, är det mindre känt hur studenter interagerar med feedback. Denna studie utfördes med syftet att ta reda på hur studenter interagerar med feedback i en frågebaserad lärplattform, när det gäller deras ögonrörelsemönster. Med hjälp av en eye tracker och ett quiz med flervalsfrågor, kunde data om deltagarnas ögonrörelser – hur länge de tittade i olika segment och vilka övergångar deras ögon gjorde mellan segment – samlas in och sedan analyseras. Resultaten visade att deltagarna hamnar i tre kategorier: 1) de som spenderar mycket tid på att läsa feedback och mindre på att läsa frågan 2) de som spenderar mycket tid på att läsa frågan och mindre på att läsa feedback och 3) de som hade ett blandat angreppssätt. Deltagare i grupperna 1) och 3) hade få blickövergångar mellan frågor och feedback, vilket indikerar att feedbacken användes som avsett av dessa deltagare. Upptäckten av distinkta mönster av interaktion med feedback öppnar upp för framtida studier att undersöka hur dessa påverkar användning och användbarheten av feedback hos studenter.