Development of a High-Efficiency Inverter with SiC Technology for Photovoltaic Applications

I convertitori elettronici di potenza sono da anni largamente diffusi sul mercato, poiché necessari per pilotare motori elettrici a velocità variabile in ambito industriale e a interfacciare alla rete elettrica i generatori da fonti di energia rinnovabili, in particolare eolica e fotovoltaica. In tutti i casi è richiesto che i convertitori siano efficienti, ovvero che l’energia persa durante la conversione sia minima. Considerando che il cuore di un convertitore è costituito da interruttori statici, è fondamentale una stima accurata dell’efficienza di questi ultimi per definire le prestazioni di un convertitore. Il materiale più diffuso per la realizzazione di questi componenti è il silicio (Si), ma esistono oggi altri semiconduttori che permettono prestazioni migliori, quali il carburo di silicio (SiC) e il nitruro di gallio (GaN). A causa del loro elevato costo di produzione rispetto ai componenti tradizionali, è divenuto sempre più importante stimare l’efficienza dei convertitori che montano queste tecnologie innovative, per trovare una giustificazione al loro impiego. In questa tesi, in particolare, l’efficienza di un convertitore con tecnologia SiC è stata prima calcolata analiticamente e poi testata a banco. Infine, è proposta un’architettura per un inverter trifase che possa essere impiegata per un’applicazione fotovoltaica. Questo lavoro è parte delle attività assegnate a Raw Power S.r.l. nell’ambito del progetto Europeo YesVGaN, il cui scopo ultimo entro i prossimi anni, è la realizzazione di componenti GaN commercialmente appetibili, che necessiteranno di essere testati e confrontati con i dispositivi al silicio e al carburo di silicio.

Benefits of Using Target Activities to Assist in Improvement of Striking in Striking and Fielding Games for Individuals with Autism: A Comparative Case Study

The purpose of the research study was to increase understanding about the potential benefits of combining target activities with striking-fielding games for individuals with high functioning autism spectrum disorder. A comparative case study was conducted to understand if target activities can assist in improving the skills of striking and throwing, aid the learning of tactics and add to current understanding of how certain teaching skills might be linked to the transfer between target and striking-fielding games. Data was collected through observations, student journals and interviews and were analyzed using both inductive and deductive methods. Results show an appearance of improvement in throwing, striking, bowling and badminton for overall skill levels. In regards to teaching skills, appropriate and effective teaching techniques, appropriate and effective equipment, dynamic of participants and student-instructors and consistency of attendance are vital. Future research should further look at the transferability to outdoor settings and interview the participants.

Enhanced shape anisotropy and magneto-optical birefringence by high energy ball milling in NixFe1−xFe2O4 ferrofluids

Ferrofluids belonging to the series NixFe1 xFe2O4 were synthesised by two different procedures—one by standard co-precipitation techniques, the other by co-precipitation for synthesis of particles and dispersion aided by high-energy ball milling with a view to understand the effect of strain and size anisotropy on the magneto-optical properties of ferrofluids. The birefringence measurements were carried out using a standard ellipsometer. The birefringence signal obtained for chemically synthesised samples was satisfactorily fitted to the standard second Langevin function. The ball-milled ferrofluids showed a deviation and their birefringence was enhanced by an order. This large enhancement in the birefringence value cannot be attributed to the increase in grain size of the samples, considering that the grain sizes of sample synthesised by both modes are comparable; instead, it can be attributed to the lattice strain-induced shape anisotropy(oblation) arising from the high-energy ball-milling process. Thus magnetic-optical (MO) signals can be tuned by ball-milling process, which can find potential applications.

Enhanced shape anisotropy and magneto-optical birefringence by high energy ball milling in NixFe1 xFe2O4 ferrofluids

Ferrofluids belonging to the series NixFe1 xFe2O4 were synthesised by two different procedures—one by standard co-precipitation techniques, the other by co-precipitation for synthesis of particles and dispersion aided by high-energy ball milling with a view to understand the effect of strain and size anisotropy on the magneto-optical properties of ferrofluids. The birefringence measurements were carried out using a standard ellipsometer. The birefringence signal obtained for chemically synthesised samples was satisfactorily fitted to the standard second Langevin function. The ball-milled ferrofluids showed a deviation and their birefringence was enhanced by an order. This large enhancement in the birefringence value cannot be attributed to the increase in grain size of the samples, considering that the grain sizes of sample synthesised by both modes are comparable; instead, it can be attributed to the lattice strain-induced shape anisotropy(oblation) arising from the high-energy ball-milling process. Thus magnetic-optical (MO) signals can be tuned by ball-milling process, which can find potential applications

O futebol que se aprende e o futebol que se ensina

Universidade Estadual de Campinas . Faculdade de Educação Física

O futebol e os jogos/brincadeiras de bola com os pes

Universidade Estadual de Campinas. Faculdade de Educação Física

Real-time hand tracking for rehabilitation and character animation

Hand and finger tracking has a major importance in healthcare, for rehabilitation of hand function required due to a neurological disorder, and in virtual environment applications, like characters animation for on-line games or movies. Current solutions consist mostly of motion tracking gloves with embedded resistive bend sensors that most often suffer from signal drift, sensor saturation, sensor displacement and complex calibration procedures. More advanced solutions provide better tracking stability, but at the expense of a higher cost. The proposed solution aims to provide the required precision, stability and feasibility through the combination of eleven inertial measurements units (IMUs). Each unit captures the spatial orientation of the attached body. To fully capture the hand movement, each finger encompasses two units (at the proximal and distal phalanges), plus one unit at the back of the hand. The proposed glove was validated in two distinct steps: a) evaluation of the sensors’ accuracy and stability over time; b) evaluation of the bending trajectories during usual finger flexion tasks based on the intra-class correlation coefficient (ICC). Results revealed that the glove was sensitive mainly to magnetic field distortions and sensors tuning. The inclusion of a hard and soft iron correction algorithm and accelerometer and gyro drift and temperature compensation methods provided increased stability and precision. Finger trajectories evaluation yielded high ICC values with an overall reliability within application’s satisfying limits. The developed low cost system provides a straightforward calibration and usability, qualifying the device for hand and finger tracking in healthcare and animation industries.