363 research outputs found
Contribuição à deteção de defeitos nos rotores de turboalternadores
No full textTese (doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-Graduação em Engenharia Elétrica.Este trabalho tem como objetivo desenvolver métodos de detecção, localização e caracterização de defeitos em um turboalternador em escala reduzida. Os defeitos estudados neste trabalho são o curto-circuito entre espiras do rotor e as excentricidades rotóricas. Os métodos serão, em seguida, adaptados aos estudos das máquinas de 900 e 1300 MW do parque nuclear da empresa EDF (Electricité de France). Para isto, a máquina em escala reduzida, foi simulada com o auxílio de dois modelos, um analítico e um numérico por elementos finitos. Os métodos para detectar e localizar os defeitos rotóricos foram, em seguida, desenvolvidos. Os resultados das simulações utilizando os dois modelos e os testes experimentais foram analisados e comparados entre si. Uma boa concordância foi verificada, o que confirma o bom funcionamento dos métodos propostos para a detecção dessas anomalias. Vários casos de defeitos, associados a diferentes modos de trabalho da máquina, foram estudados, comprovando a confiabilidade dos métodos de detecção desenvolvidos.The aim of this work is to develop methods to detect, locate and recognise faults in a turbogenerator of reduced scale. In the framework of this study, only short-circuit defects in the rotor windings and rotor eccentricities were investigated. The developed methods would be adapted to the machines of EDF nuclear plant of 900 and 1300 MW. First the studied machine was modelled using an analytical approach and a numerical model based on the finite element method. Then, the methods to detect and locate the rotor faults were developed. The results obtained from simulations using both approaches and experimental measurements were analysed and compared. They showed a good agreement and demonstrated a good capacity of the method proposed to detect and locate the faults. Several fault cases, at different operating points of the machine, were studied and they showed the good reliability of the method
AI empowered Auslan learning for parents of deaf children and children of deaf adults
No full textCommunication poses a challenge for the deaf and hearing loss community. This difficulty is even more pronounced in the families of Children of Deaf Adults (CODAs) and Parents of Deaf Children (PODCs). To help these families overcome this challenge, we design an AI-empowered interactive bi-directional Australian Sign Language (i.e., Auslan) dictionary application to facilitate communication within a household. Technically, our APP can not only look up sign gestures for the given English words but also translate isolated Auslan gestures into English. Through an inviting user interface and experience design, we can further improve engagement within the CODA and PODC families while enabling Auslan education at home. The positive user experience underscores the success of our APP not only in leveraging AI to revolutionise Auslan education but also in promoting cross-generational language acquisition and communication.Hongwei Sheng, Xin Shen, Heming Du, Hu Zhang, Zi Huang, Xin Y
Kwaliteit van arbeid, geautomatiseerd... Een studie naar kwaliteit van arbeid en de relatie tussen automatisering, arbeid en organisatie
No full textTechnology, Policy and Managemen
Temporomandibular Joint Pain is Negatively Correlated to TNF Alpha and Osteoprotegrin Content in Synovial Fluid in Patients with Juvenile Idiopathic Arthritis.
No full textObjective: Temporomandibular joint (TMJ) involvement occurs in up to 80% of children with juvenile idiopathic arthritis (JIA). Little is known with regard to the complexity of the protein profile in synovial fluid (SF) from JIA arthritis during growth as compared to both JIA and rheumatoid arthritis (RA) of adults.
Design: Synovial fluid was collected from 54 joints/30 patients with TMJ arthritis (JIA 35 joints/20 patients, JIA adults 9 joints/5 patients, RA 10 joints/5 patients). Three cytokines and seven bone markers were quantified using Luminex multiplex assays and compared to demographic and clinical data of function and pain.
Results: Pain (spontaneous and upon palpation) and duration of pain were all negatively correlated with the TMJ SF content of tumor necrosis factor (TNF)-α. The level of Adrenocorticotropic hormone (ACTH) was negatively correlated to TMJ pain upon palpation and post-treatment pain and function. The concentration of ACTH was significantly lower in SF in JIA (1.4 ± 2.8 pg/ml) compared to adults with JIA (4.7 ± 12.2 pg/ml) and significantly higher compared to adults with RA (0.8 ± 1.5 pg/ml). Osteoprotegerin (OPG) was negatively correlated to spontaneous pain.
Conclusions: Our results indicate that the local concentrations of TNF-α, ACTH and OPG in TMJ fluid may not contribute to TMJ pain and tissue destruction in JIA/RA patients.
© 2014 Olsen-Bergem H, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
The thermal and electrical properties of the promising semiconductor MXene Hf2CO2.
No full textWith the growing interest in low dimensional materials, MXenes have also attracted considerable attention recently. In this work, the thermal and electrical properties of oxygen-functionalized M2CO2 (M=Ti, Zr, Hf) MXenes are investigated using first-principles calculations. Hf2CO2 is determined to exhibit a thermal conductivity better than MoS2 and phosphorene. The room-temperature thermal conductivity along the armchair direction is determined to be 86.25~131.2 Wm(-1)K(-1) with a flake length of 5~100mum. The room temperature thermal expansion coefficient of Hf2CO2 is 6.094*10(-6) K(-1), which is lower than that of most metals. Moreover, Hf2CO2 is determined to be a semiconductor with a band gap of 1.657eV and to have high and anisotropic carrier mobility. At room temperature, the Hf2CO2 hole mobility in the armchair direction (in the zigzag direction) is determined to be as high as 13.5*10(3)cm(2)V(-1)s(-1) (17.6*10(3)cm(2)V(-1)s(-1)). Thus, broader utilization of Hf2CO2, such as the material for nanoelectronics, is likely. The corresponding thermal and electrical properties of Ti2CO2 and Zr2CO2 are also provided. Notably, Ti2CO2 presents relatively lower thermal conductivity but much higher carrier mobility than Hf2CO2. According to the present results, the design and application of MXene based devices are expected to be promising
Exploration de la dynamique non-linéaire et de la compression d'amplitude des lasers à ilots quantiques
No full textLes circuits photoniques intégrés (PIC) utilisant la technologie de la photonique sur silicium présentent un potentiel significatif dans les systèmes de communication à haute vitesse, le calcul optique et la technologie quantique. Les lasers à îlot quantiques (QD), en particulier ceux qui sont cultivés épitaxialement sur silicium, affichent des caractéristiques remarquables telles qu'une forte tolérance aux défauts, un faible courant de seuil et une bonne stabilité thermique. De ce fait, ils émergent progressivement comme des sources laser prometteuses sur puce pour les PIC. Cette thèse vise à explorer la dynamique non linéaire et les propriétés d'état quantique des lasers QD, jetant ainsi les bases de diverses applications potentielles. La première section de la thèse se penche sur le rôle du facteur d'élargissement de la largeur de raie (αH-facteur) dans les lasers QD. J'ai utilisé une technique de modulation de phase optique pour extraire le αH-facteur des lasers QD au-dessus du seuil. Le petit αH-facteur des lasers QD a fortement amélioré la tolérance au feedback optique. Cela facilite le développement de transmissions optiques à haute vitesse sur puce sans isolateur optique et augmente la densité d'intégration. La deuxième section explore les caractéristiques dynamiques des lasers QD sous feedback optoélectronique (OEF). Contrairement au feedback optique, j'ai démontré que les lasers QD présentent une sensibilité accrue à l'OEF, conduisant à diverses dynamiques complexes. Cette sensibilité extrême est cruciale pour l'avancement du calcul optique basé sur le silicium sur puce et des applications des machines d'Ising, un phénomène non observé dans les lasers à puits quantiques (QW). Dans la troisième section, j'ai analysé la dépendance du bruit de fréquence au bruit porteur externe. La recherche a révélé qu'un pompage silencieux est très avantageux pour minimiser le αH-facteur, réduire le bruit de fréquence et, par conséquent, rétrécir la largeur de raie optique des lasers QD. La dernière section met en évidence la génération de lumière comprimée en amplitude directement à partir d'un laser QD à semi-conducteurs entraîné par un courant constant. Avec le pompage silencieux, j'ai atteint une large bande passante de compression de plusieurs gigahertz à température ambiante avec un rapport de compression de 3,5 dB. L'insensibilité extrême à la réflexion du générateur QD comprimé sous feedback optique, en contraste avec un laser de référence utilisant la technologie QW standard, est également démontrée avec un rapport de compression amélioré à 5,7 dB. Trois mesures distinctes, incluant le spectre radiofréquentiel sous le bruit de grenaille, les statistiques photoniques sub-Poissonniennes et la fonction de corrélation d'ordre deux à retard zéro, valident mes conclusions. Cette recherche établit un cadre fondamental pour des circuits quantiques photoniques intégrés compacts et hautement efficaces, démontrant le potentiel d'application immense des lasers QD dans les domaines de la photonique classique et quantique.Photonic integrated circuits (PICs) utilizing silicon photonics technology show significant potential in high-speed communication systems, optical computing, and quantum technology. Quantum dot (QD) lasers, particularly those epitaxially grown on silicon, exhibit notable characteristics such as strong defect tolerance, low threshold current, and good temperature stability. As a result, they are gradually emerging as promising on-chip laser sources for PICs. This thesis aims to explore the nonlinear dynamics and quantum state properties of QD lasers, laying the foundation for various potential applications. The first section of the thesis delves into the role of the linewidth enhancement factor (αH-factor) in QD lasers. I employed an optical phase modulation technique to extract the above-threshold αH-factor of QD lasers. The small αH-factor of QD lasers strongly improved optical feedback tolerance. This facilitates the development of high-speed optical transmission on chips without an optical isolator and increases integration density. The second section explores the dynamic characteristics of QD lasers under optoelectronic feedback (OEF). Unlike optical feedback, I demonstrated that QD lasers exhibit enhanced sensitivity to OEF, leading to various complex dynamics. This extreme sensitivity is crucial for the advancement of on-chip silicon-based optical computing and Ising machine applications, a phenomenon not observed in quantum well (QW) lasers. In the third section, I analyzed the dependency of frequency noise on external carrier noise. The research revealed that quiet pumping is highly advantageous for minimizing the αH-factor, reducing frequency noise, and consequently narrowing the optical linewidth of QD lasers. The last section highlights the generation of amplitude-squeezed light directly from a constant-current-driven semiconductor QD laser. With the quiet pump, I achieved a substantial gigahertz squeezing bandwidth at room temperature with a squeezing ratio of 3.5 dB. The extreme reflection insensitivity of the squeezed QD generator under optical feedback, in contrast to a reference laser using standard QW technology, is also demonstrated with a squeezing ratio further improved to 5.7 dB. Three distinct measurements, including the sub-shot-noise radiofrequency spectrum, sub-Poissonian photon statistics, and second-order correlation function at zero delay, validate my findings. This research establishes a foundational framework for compact and highly efficient photonic quantum integrated circuits, showcasing the immense application potential of QD lasers in both classical and quantum photonics fields
Nonlinéarités optiques dans les lasers à boîtes quantiques pour les communications à haut-débit
No full textThe recent evolution of optical communication systems is such that the transfer of massive amounts of information is no longer limited to long-distance transoceanic links or backbone networks. Numerous short-reach applications requiring high data throughputs are emerging, not only in access networks, where upgrades of the bit rate of fiber-to-the-home systems need to be anticipated, but also in data center networks where huge amounts of information may need to be exchanged between servers, in part triggered by the rise of big data applications. The new requirements in terms of cost and energy consumption set by novel short-reach applications therefore need to be considered in the design and operation of a new generation of semiconductor laser sources. Owing to the tight quantum confinement of carriers, quantum dot lasers constitute a class of oscillators exhibiting superior characteristics such as a lower operating threshold, a better thermal stability as well as larger optical nonlinearities. The investigation of quantum dot lasers operating under external perturbations allows probing such optical nonlinearities in the view of developing all-optical wavelength-converters with improved performance as well as optical feedback-resistant transmitters. This last point iseven more critical since it is expected that short-reach links making use of directly modulated sources will experience massive deployment in the near future, in contrast to conventional backbone links where the number of required optoelectronic interfaces remains relatively modest. In order to do so, the thesis reports on novel findings in GaAs- and InP-based quantum dot lasers such as improved bandwidth and conversion efficiency under optical injection and various complex dynamics with delayed quantum dot oscillators emitting on different lasing states. Last but not the least, the massive deployment of coherent systems as well as the realization of future chip-scale atomic clocks require the implementation of optical sources with narrow spectral linewidth otherwise the sensitivity to the phase noise of both transmitters and local oscillators can strongly affect the bit error rates at the receiver. This is another objective to be addressed in the thesis where the benefits of the quantum dot technology has allowed to reach a spectral linewidth as low as 160 kHz (100 kHz under optical feedback) which is of paramount importance not only regarding the aforementioned applications.L’évolution actuelle des systèmes de communications optiques est telle que la circulation d’information n’est plus exclusivement limitée par les liens longues distances transocéaniques ou par les réseaux cœurs. De nombreuses applications courtes distances comme les réseaux d’accès où les débits des systèmes amenant la fibre chez l’abonné doivent être maximisés et les connexions internes et externes des centres de données transportent un trafic de données important produit en partie par les applications de type « Big Data ». Les critères imposés par ces nouvelles architectures notamment en termes de coût et consommation énergétique doivent être pris en compte en particulier par le déploiement de nouveaux composants d’extrémités. Grâce au très fort confinement des porteurs, les lasers à boites quantiques constituent une classe d’oscillateurs présentant des caractéristiques remarquables notamment en termes de courant de seuil et de stabilité thermique. En particulier, l’application d’une perturbation optique externe permet d’exploiter les nonlinéarités optiques des boîtes quantiques pour la réalisation de convertisseurs en longueur d’onde performants ou de transmetteurs à haut-débit fonctionnant sans isolateur optique. Ce dernier point est particulièrement critique dans les réseaux courtes distances où l’utilisation de sources modulées directement reste une solution technologique importante.Ce travail de thèse réalisé sur des structures lasers à base d’Arséniure de Gallium (GaAs) et de Phosphure d’Indium (InP) montre la possibilité d’améliorer l’efficacité de conversion non-linéaire par injection optique et de générer de nombreuses dynamiques dans des oscillateurs rétroactionnés et émettant sur différents états quantiques. Par ailleurs, le déploiement massif des systèmes cohérents mais également la conception des futures horloges atomiques sur puces nécessite l’utilisation de sources optiques à faible largeur de raie et ce afin de limiter la sensibilité de la réception au bruit de phase du transmetteur et de l’oscillateur local et induire un taux d’erreur binaire important. La conception de laser à faible largeur spectrale constitue un autre objectif de ce travail thèse. Les avantages de la technologie boites quantiques ont été mis à profit pour d’atteindre une largeur spectrale de 160 kHz (100 kHz en présence de rétroaction optique) ce qui est de première importance pour les applications susmentionnées
Damage detection in semiconductor devices by non-linear elastic wave spectroscopy
No full textSemiconductor devices can be found everywhere in our daily lives, for example in self-driving cars, bank cards and personal devices such as smart phones or notebooks. Once part of these personal devices, one does not want them to show failure. Although reliability of such devices is taken into account in the design, the fabrication process might lead to the emergence of small damages in the product. Since these damages or their propagation might cause failure of the device, a series of visual inspections and functional tests is part of the fabrication process. The obtained resolution by optical microscopy, currently the state of the art inspection method, is not sufficient for the detection of small damages such as microcracks or damages located inside a sample. To keep improving the reliability of semiconductor devices, these damages need to be detected in another high speed, low cost way.As semiconductor devices shrink in size, their natural vibration frequencies increase and approach theMHz-range. Vibration based damage detection methods might therefore offer an alternative high speed in-situ inspection method. The main goal of this thesis is to identify and experimentally verify vibration characteristics that indicate the presence of damage, with a focus on microcracks, in semiconductor devices. While linear vibration based damage methods have proven to be insensitive to small damages such as microcracks, non-linear vibration based damage detection methods show much higher sensitivities to this type of damage. The non-linear elastic wave spectroscopy (NEWS) of several damaged materials have shown two characteristic phenomena: amplitude dependent natural frequency shifts and the generation of higher harmonics. Both are explained by a phenomenological non-linear hysteric elastic model. While the applicability of NEWS is proven for several materials, its performance for silicon, in particular at microscale, is still unknown.Mechanical Engineering | Micro and Nano Engineerin
General Analytical Model of Magnet Average Eddy-Current Volume Losses for Comparison of Multi-phase PM Machines with Concentrated Winding
No full textthis paper studies magnet eddy-current losses in permanent magnet (PM) machines with concentrated winding. First of all, space harmonics of magnetomotive force (MMF) and their influence on magnet losses in electrical machines are investigated. Secondly, analytical model of magnet volume losses is developed by studying the interaction between MMF harmonics wavelengths and magnet pole dimensions. Different cases of this interaction are exhibited according to the ratio between each harmonic wavelength and magnet pole width. Then various losses sub-models are deduced. Using this analytical model, magnet volume losses for many Slots/Poles combinations of 3, 5, and 7 phase machines with concentrated winding are compared. This comparison leads to classify combinations into different families depending on their magnet losses level. Finally, in order to verify the theoretical study, Finite Element models are built and simulation results are compared with analytical calculationsProjet MHYGALE/ADEM
- …
