Dissertations / Theses on the topic 'Self-flux'

Self-excited oscillations in a collapsible-tube flow driven by fixed upstream flux have been observed by numerical and laboratory experiments. In this thesis we attempt to understand the mechanism of onset of these oscillations by focusing on a reduced physical model. We consider flow in a finite-length planar channel, where a segment of one wall is replaced by a membrane under longitudinal tension. The upstream flux and downstream pressure are prescribed and an external linear pressure distribution is applied to the membrane such that the system admits uniform Poiseuille flow as a steady solution. We describe the system using a one-dimensional model that accounts for viscous and fluid inertial effects. We perform linear stability analysis and weakly nonlinear analysis on the one-dimensional model, the resulting predictions are tested against two-dimensional Navier–Stokes numerical simulation. When the membrane has similar length to the rigid segment of channel downstream of the membrane, we find that in a narrow parameter regime we consider “mode-2” oscillations (i.e. membrane displacements with two extrema) are largely independent of the downstream segment but are driven by divergent instabilities of two non-uniform steady configurations of the membrane. When the downstream segment is much longer than the membrane, our analysis reveals how instability is promoted by a 1:1 resonant interaction between two modes, with the resulting oscillations described by a fourth-order amplitude equation. This predicts the existence of saturated sawtooth oscillations, which we reproduce in full Navier–Stokes simulations of the same system. In this case, our analysis shows some agreements with experimental observations, namely that increasing the length of the downstream tube reduces the frequency of oscillations but has little effect on the conditions for onset. We also use linear stability analysis to show that steady highly-collapsed solutions, constructed by utilizing matched asymptotic expansions, are very unstable, which allows the possibility that they are a precursor to slamming motion whereby the membrane becomes transiently constricted very close to the opposite rigid wall before rapidly recovering.

We used the self-organizing maps (SOMs) method on eight models that participated in the Coupled model intercomparison project phase 5 (CMIP5) and two different greenhouse gases (GHG) concentration experiments. The SOMs were created from the winter 500 hPa horizontal temperature flux for each model. The clustering by the SOM revealed that in addition to the three flux pathways found in reanalyses (Pacific, Atlantic and Siberian/continental pathway), superpositions of these occur for the free running climate models, which develop their dynamic more freely than the reanalyses. It was found that the general structure of fluxes is indirectly dependent on the GHG concentrations, as the derived results from SOM patterns are different between the two GHG concentrations. It is suggested that flux patterns change from stable cyclonic motion over the north pole to flux pathways that feature more meridional fluxes through the North Atlantic and North Pacific into the Arctic.
Die Methode der Self-Organizing Maps (SOMs) wurde auf acht CMIP5-Modelle mit jeweils zwei verschiedenen Treibhausgasszenarien angwendet. Die SOMs wurden für jedes Modell und jede der beiden Modelläufe für den horizontalen Temperaturfluss in 500 hPa im Winter erstellt. Zusätzlich zu den aus der Analyse von Reanalyse-Daten erwarteten drei Transportwegen (pazifisch, atlantisch und sibirisch/kontinental) wurden Überlagerungen dieser gefunden. Es konnte gezeigt werden, dass die grundsätzliche Struktur der Transporte indirekt abhängig von der Treibhausgaskonzentration ist. Die Ergebnisse deuten darauf hin, dass sich die generelle Struktur des atmosphärischen Transports von einer stabilen zyklonalen Bewegung über dem Nordpol sich zu Transporten verschiebt, welche meridionale Transporte über den Nortdatlantik und den Nordpazifik in die Arktis führen.

Thesis (M.S.) -- University of Maryland, College Park, 2007.
Thesis research directed by: Dept. of Mechanical Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.

Barrières de transport (TB) sont un élément clé dans le contrôle de transport turbulent et atteindre la haute performance des ‘plasmas brûlants’. Les études théoriques abordent l’autorégulation de la turbulence comme une explication possible pour la formation de TB, mais une compréhension complète de ces dynamiques complexes est toujours manquante. Dans ce contexte, nous abordons l’auto-organisation dans le transport turbulent dans les plasmas de fusion dans le but de présenter une nouvelle compréhension de la dynamique des TB. Les outils numériques que nous utilisons des simulations de portée de la turbulence gyrocinétique plus complexe à simple turbulence des fluides 2D et prédateur-proie comme modèles.Deux principales caractéristiques de l'auto-organisation, les avalanches et les flux zonal (ZF), semblent contrôler transport à grande échelle. Dans la région de SOL (Scrape Off layer), événements avalancheux intermittents ne permettent pas séparation d'échelle dans le temps ou l'espace entre champs moyens et les modalités de fluctuation. Dans le bord (edge), la génération des doubles couches de cisaillement dans les profils de vitesse réduit le transport turbulent. Un modèle turbulent 2D pour la génération de ‘piedestal’, qui est non spécifique des plasmas de tokamak, a été mis au point, le piedestal étant localisée à l'interface entre les régions a différent amortissement d'écoulement zonal: edge et SOL. Les événements de relaxation quasi-périodiques sont étudiés réduisent le modèle à trois couplage des modes pour identifier l'interaction entre les streamers et les ZF et le rôle du Reynolds stress dans la génération et la saturation du TBs
Transport barriers (TB) are a key element in controlling turbulent transport and achieving high performance burning plasmas. Theoretical studies are addressing the turbulence self-regulation as a possible explanation for transport barrier formation but a complete understanding of such complex dynamics is still missing. In this context, we address self-organized turbulent transport in fusion plasmas with the aim of presenting a novel understanding of transport barriers dynamics. The numerical tools we use span simulations from the most complex gyrokinetic turbulence to simpler 2D fluid turbulence and predator-prey like models.Two features of self-organizations, avalanches and zonal flows (ZFs), appear to control large scale transport. In the SOL (Scrape Off Layer) , intermittent avalanche events do not allow for time or space scale separation between mean fields and fluctuation terms. In the edge, the generation of long living double shear layers in the profiles of the velocity reduces radial turbulent transport. Such radially distributed barriers govern profile corrugations. A 2D turbulent model for pedestal generation, which is not specific of Tokamak plasmas, has been developed, the pedestal being localized at the interface between regions with different zonal flow damping: the edge region, where zonal flows are weakly damped by collisions, and the SOL region characterized by zonal flow damping due to boundary conditions. Quasi-periodic relaxation events are studied reducing the model to three modes coupling to identify the interplay between streamers and ZFs and the role of Reynolds stress in the generation and saturation of TBs

Dans cette thèse nous ajustons la phase d’isolant de Mott du BaCoS2, un modèle multiorbital pour l’étude des corrélations électroniques. Nous avons développer une nouvelle technique de self-flux afin de produire des cristaux de qualité et de taille supérieures. Puis nous avons confirmé une phase stable orthorhombique Cmma à l’ambiante où la distorsion orthorhombique est concomitante à l’établissement d’un ordre AFM de longue portée. Ensuite, nous avons exploré la possibilité d’induire un état métallique dans du BaCoS2 via pression chimique et dopage électronique comme paramètres de contrôle. Pour cela, nous avons appliqué des techniques HP pour synthétiser des échantillons de Ba1−xSrxCoS2 et Ba1−xKxCoS2 avec x allant jusqu’à 0,07. On s’attend à ce que la substitution partielle du Ba par du Sr ou du K induise de la pression chimique ou du dopage de trous respectivement, favorisant ainsi une phase métallique dans les deux cas
In this thesis we tune the Mott insulating phase of BaCoS2, a playground for the study of electronic correlations in a multiorbital system. We first developed a novel self-flux technique to grow single crystals of improved quality and size. We then confirmed a stable orthorhombic Cmma phase at ambient conditions where the orthorhombic distortion is concomitant to a long-range AFM order, suggesting a scenario of orbital ordering that stabilises this order. Next, we explored the possibility of inducing a metallic state in BaCoS2 using chemical pressure and electronic doping as control parameters. For this goal, we successfully applied HP technique to the synthesis of Ba1−xSrxCoS2 and Ba1−xKxCoS2 samples with x up to 0.07. The partial substitution of Ba for Sr or K is expected to produce chemical pressure or hole-doping, respectively, thus favouring a metallic phase in both cases. We find that both substitutions induce similar structural changes, and a full suppression of the orthorhombic distortion and of the AFM order. However, no indication of metallic properties is found in the Ba1−xSrxCoS2 samples. However, a sizeable value of Sommerfeld coefficient,γ= 5.7mJ mol−1K−2 is found at 7% of K-substitution suggesting a metallic state induced by hole doping

This thesis summarizes a senior project on the Active Galactic Nucleus (AGN) Markarian 421 (Mrk 421). Observations of Gev and TeV flux with Fermi Large Area Telescope (LAT) and High Energy Stereoscopic System (H.E.S.S.) were compared with previous reports and publications of flux analyses of the gamma-ray emission from Mrk 421. Power laws with exponential cutoffs made consistent fits to most SEDs in the GeV and TeV bands.

L'objectif principal de cette thèse est de mettre en évidence le rôle de la direction et du mouvement de la tête et des yeux dans la perception et le contrôle de trajectoires courbes, en référence aux propriétés des flux optiques générés par notre déplacement dans un environnement stable. Nous utilisons deux méthodes expérimentales : une approche comportementale sur simulateur de conduite et une approche psychophysique permettant d'évaluer les capacités d'observateurs humains à percevoir la direction du mouvement propre. Ces méthodes combinées visent à mettre en évidence les effets comportementaux d'une perception active de la direction du mouvement propre. L'introduction dresse l'état de la recherche sur les informations disponibles et les stratégies perceptives impliquées dans la prise de virage en conduite automobile. Ainsi, l'accent est à la fois mis sur le rôle du point de corde (dans le cas étudié d'un déplacement sur une route délimitée) et plus généralement sur le rôle du flux optique (description de la transformation apparente de l'environnement visuel lors du déplacement), soulignant notre capacité à interpréter spatialement le mouvement, mais aussi le caractère indissociable de la motricité et de la perception. Nous abordons ensuite le rôle des mouvements combinés des yeux et de la tête, dans une perspective fonctionnelle du contrôle du mouvement.Dans un premier chapitre expérimental, nous analysons les mouvements d'orientation de la tête lors de la prise de virage en conduite simulée. Nous montrons que les mouvements de la tête sont indépendants de la manipulation du volant et qu'ils participent activement à l'orientation du regard vers le point de corde. Dans un second chapitre expérimental, nous nous attachons à décrire les mouvements combinés des yeux et de la tête, en lien avec la géométrie de l'environnement routier. Dans une troisième partie, nous analysons plus finement le comportement du regard en lien avec la direction du point de corde et la vitesse locale du flux optique. Nous montrons à la fois que le point de corde correspond à un minimum local de vitesse optique et que la composante globale du flux optique induit un nystagmus optocinétique systématique. Enfin, lors d'une quatrième étude psychophysique, nous nous attachons à décrire finement l'effet de la variation de la direction du regard sur la discrimination de la direction du mouvement propre. Nous montrons que les seuils de discrimination de trajectoire sont minimaux lorsque le regard est orienté vers une zone de vitesse de flux minimal. Nous proposons finalement un modèle de détection de la trajectoire, basé sur une fraction de Weber des vitesses de flux fovéales, qui prédit très précisément les seuils expérimentaux. Les stratégies observées d'orientation du regard (combinaison des mouvements des yeux et de la tête) vers le point de corde sont compatibles avec une sélection optimale de l'information présente dans le flux optique
The main purpose of this dissertation is to determine the role of the direction and movement of the eyes and the head in the perception and control of self-motion in curved trajectories, with respect to the properties of the optical flows generated in a stable environment. To do so, we used two experimental methods: a psychophysical approach which allows to assess human observers' ability to perceive the direction of self-motion; and a behavior-based approach on a driving simulator. The two methods combined should help to highlight active perception of self-motion.The introduction reviews the current knowledge of perceptuo-motor strategies during curve driving. In this context, we put a stress on both (1.) the particular role of the tangent point -- in the driving situation on a delimited road, and on the role of the optic flow in general (apparent transformation of the optic array during self-motion), emphasizing the capability of humans to spatially interpret the movement; and (2.) on the duality between movement and perception. We then address the role of head-and-eye combined movements, in a functional perspective of the control of self-motion. In a first experimental section, we analyze the oriented movements of the head in simulated curve driving. We demonstrate that head movements are independent from the handling of the steering wheel, and that they actively participate in the gaze orientation toward the tangent point.In a second experimental section, we set out to describe the combined movements of head and eyes, with respect to the geometry of the road environment. In a third section, we analyze in more details gaze behavior as a function of the tangent point direction and of the local speed of optical flow. We demonstrate that the tangent point corresponds to a local minimum of optic flow speed and that the global component of the optic flow induces a systematic optokinetic nystagmus. In a fourth section involving a psychophysical study, we scrutinize the effect of varying gaze direction on the discrimination of the direction of self-motion. We show that the trajectory discrimination thresholds are minimal when the gaze is oriented toward an area of minimum flow speed. We finally propose a model of trajectory change detection, relying on a Weber fraction of foveal flow speeds, predicting the experimental thresholds very precisely. The gaze orientation strategies we have observed (combination of head and eye movements) toward the tangent point are compatible with this model and with the hypothesis of an active an optimal selection of the information contained in the optical flow

L'indagine ha riguardato il profilo del vento nei primi 30 metri dello strato limite atmosferico stabile nell'ambito della teoria di similarità locale. Ad oggi, diversi esperimenti hanno confermato la validità della teoria per strati-limite su terreni livellati e superfici omogenee. Tali condizioni ideali sono però infrequenti nella realtà ed è perciò importante capire quali siano i limiti della similarità locale per strati-limite su terreni complessi e superfici disomogenee. Entrambe le condizioni sono presenti a Ny-Alesund (Svalbard, Norvegia) dove il Consiglio Nazionale delle Ricerche (CNR), nel 2009, ha installato una torre di 30 m, la Amudsen-Nobile Climate Change Tower (CCT), per lo studio dello strato-limite artico. Il lavoro di tesi ha riguardato misure di vento e turbolenza acquisite sulla CCT da maggio 2012 a maggio 2014. Il confronto tra le velocità del vento misurate dagli anemometri installati sulla CCT, ha rivelato criticità nel dato sonico manifestatesi con sovrastime sistematiche e maggiore erraticità rispetto alle misure provenienti dagli anemometri a elica. Un test condotto fra diversi metodi per il calcolo dei gradienti verticali della velocità del vento ha rivelato scarsa sensibilità dei risultati ottenuti al particolare metodo utilizzato. Lo studio ha riguardato i gradienti verticali adimensionali della velocità del vento nei primi 30-m dello strato limite stabile. Deviazioni significative tra i tra le osservazioni e i valori predetti dalla similarità locale sono state osservate in particolare per i livelli più distanti dal suolo e per valori crescenti del parametro di stabilità z/L (L, lunghezza di Obukhov locale). In particolare, si sono osservati gradienti adimensionali inferiori a quelli predetti dalle più usate relazioni di flusso-gradiente. Tali deviazioni, presenti perlopiù per z/L>0.1, sono state associate ad un effetto di accentuazione della turbolenza da parte delle irregolarità del terreno. Per condizioni meno stabili, z/L<0.1, scarti positivi tra i gradienti osservati e quelli attesi sono stati attribuiti alla formazione di strati limite interni in condizioni di vento dal mare verso la costa. Sono stati proposti diversi metodi per la stima dell'effetto della self-correlazione nella derivazione delle relazioni di flusso-gradiente, dovuta alla condivisione della variabile u*. La formula per il coefficiente lineare di self correlazione e le sue distribuzioni di probabilità empiriche sono state derivate e hanno permesso di stimare il livello di self-correlazione presente nel dataset considerato.

Lorsqu’ils explorent leur environnement, les humains comme les autres animaux ont la capacité d’utiliser de nombreuses sources d’information afin d’estimer la distance qu’ils parcourent. Le flux optique est un indice important dans la perception de la distance parcourue. De plus, il a été montré que l’ajout d’un point de vue oscillant à une simulation visuelle de mouvement propre vers l’avant modulait cette perception. A travers ce travail, nous nous sommes intéressés à tester si la perception de la distance parcourue était également affectée par un point de vue oscillant, mimant de manière plus ou moins fidèle les mouvements de la tête lors de la marche. Dans six premières expériences, il était demandé aux participants stationnaires, confrontés à un flux optique simulant leur propre mouvement vers l’avant, d’indiquer quand ils pensaient avoir atteint la position d’une cible distante initialement perçue. Une expérience subséquentes s'est intéressée à déterminer si l’absence de ces oscillations jouait un rôle important dans l’estimation de la distance parcourue lorsqu’ils marchaient sur un tapis roulant. Enfin, dans une dernière expérience nous avons développé une mesure dynamique de la distance parcourue à travers l’utilisation d’une tâche demandant aux participants de pointer continuellement la position d’une cible distante initialement perçue. Dans l’ensemble, nos résultats montrent qu’un point de vue oscillant joue un rôle important dans la perception visuelle du mouvement propre et que de nombreux paramètres semblent être impliqués dans ce processus, incluant les informations visuelles et proprioceptives mais également l’aspect écologique de la marche naturelle
When exploring their environment, humans and other animals have the ability to use many sources of information to estimate the distance they travel. Several studies have shown that optic flow is a significant cue to perceive distance travelled. Furthermore, it was found that adding various viewpoint oscillations to a purely translational optic flow, simulating forward self-motion, modulated this perception. In a series of experiments, we tested whether the perception of distance travelled was also affected by viewpoint oscillation, similar to head motion during natural walking. A first series of experiments, participants were exposed to an immersive optic flow simulating forward self-motion and they were asked to indicate when they thought they had reached the remembered position of a previously seen target. Two further experiments aimed to test whether the idiosyncrasy of viewpoint oscillations affects the perception of distance travelled in stationary observers and whether the absence of their own viewpoint oscillation played an important role in subjects’ estimates, while they were walking on a treadmill. And finally, in a last experiment we tried to develop a dynamic measure of distance travelled to a previously seen target, with a continuous pointing task method. Overall, our results show that viewpoint oscillations play an important role in visual self-motion perception and that several parameters (including visual information, proprioceptive information and ecological aspects of natural walking) seem to be involved in this process

Made available in DSpace on 2014-10-09T12:42:41Z (GMT). No. of bitstreams: 0
Made available in DSpace on 2014-10-09T13:57:18Z (GMT). No. of bitstreams: 1 05028.pdf: 9521463 bytes, checksum: 8a386f78270b1c225d259433bbd3167d (MD5)
Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

As one of the oldest machine topologies, the concept of synchronous reluctance (REL) machine can be traced back as early as 1900s. In the last 20 years, particularly, the REL machines have attracted more and more attention in both academic and industrial fields. Without permanent magnets and rotor bars, the rotor construction of the REL machine is more robust than either permanent magnet (PM) machines or induction machines (IMs). In addition, it achieves the merits of low cost, low maintenance, and high reliability. All these features reveal the REL machine to be an attractive alternative to the widely used machine topologies. Therefore, the investigation of REL machines is essential, and specific applications will be of great interest. In this thesis, the design and analysis of high performance REL machines are developed and discussed. Furthermore, two particular applications are investigated: REL motors for electric vehicle (EV) applications and self-excited reluctance generators (SERG) for isolated wind applications. To start with, the transversely-laminated anisotropy rotor type with multiple flux-barriers is chosen to be designed and analyzed. More specifically, a detailed parametric analysis of this kind of rotor geometry is carried out, which aims to suggest an automatic drawing and simulating procedure. The shape of flux-barriers is selected to achieve both high d-axis inductance and low q-axis inductance. Methods to properly design the geometry of barrier ends and PMs are adopted. Some tuning steps are suggested in order to achieve the high performance design. Such a procedure is then used to rapidly analyze the impact of some rotor parameters on the machine performance, in order to provide a guideline for the preliminary design of the REL machine. After that, as a practical example, a REL motor according to the dimension of a commercial motor is designed. Certain design procedures are followed, and optimization is also carried out. The performance comparisons between the optimized REL motor and the commercial product are given. Merits and defects of the REL machine for EV application are highlighted. The study on SERG starts with the recognition of the steady-state performance, both analytically and experimentally. The conditions related to successful self-excitation in SERG, such as required capacitance, rotor residual magnetism, rotor acceleration and pre-charging capacitors, are investigated. The possibility to adopt self-excited PM-assisted reluctance generator is also dealt with, and the performance comparison with SERG is made. The effect of some design parameters on the performance of the PMAREL generator is analyzed. Referring to wind applications, the method to maintain the generated voltage constant at variable speeds is proposed. Finally, the prediction of the "optimal capacitor and resistor combination" that achieves the maximum utilization of the mechanical power produced by the wind turbine will be presented.
L’idea di macchina sincrona a riluttanza (REL) può essere rintracciato già a partire dal 1900. Negli ultimi 20 anni, in particolare, le macchine REL hanno attirato sempre più attenzione sia nel settore accademico che in quello industriale. Senza magneti permanenti e barre del rotore, la costruzione del rotore della macchina REL è più robusta delle macchine a magneti permanenti (PM) o delle macchine a induzione (IM). Inoltre, ha un basso costo, necessita di poca manutenzione e è altamente affidabile. Tutte queste caratteristiche fanno della macchina REL è un'alternativa interessante alle topologie di macchine ampiamente utilizzate come macchine a magneti permanenti o ad induzione. Pertanto, lo studio delle macchine REL è di grande interesse. In questa tesi la progettazione e l'analisi di macchine REL ad alte prestazioni vengono sviluppate e discusse. Inoltre, vengono studiate due applicazioni particolari: motori REL per veicoli elettrici (EV) e generatori a riluttanza autoeccitati (SERG) per applicazioni con vento isolato. Per iniziare, il tipo di rotore anisotropo laminato trasversalmente con più barriere di flusso viene scelto per essere progettato e analizzato. Nello specifico, viene eseguita un'analisi parametrica dettagliata di questo tipo di geometria del rotore, che mira a suggerire una procedura di disegno e simulazione automatica. La forma delle barriere di flusso viene selezionata per raggiungere un valore di induttanza alto sull’asse d e basso sull’asse q. Metodi specifici per progettare correttamente la geometria delle estremità di barriera e dei PM vengono utilizzati e descritti. Particolari procedure per evitare errori nella geometria vengono applicate. Tali procedure sono utilizzate per analizzare rapidamente l'impatto di alcuni parametri del rotore sulle prestazioni della macchina, al fine di fornire linee guida per la progettazione preliminare della macchina REL. Successivamente, come esempio pratico, viene progettato un motore REL con le dimensioni di un motore commerciale. Alcune procedure di progettazione sono eseguite insieme all'ottimizzazione. Vengono forniti i confronti delle prestazioni tra il motore REL ottimizzato e il prodotto commerciale. Meriti e difetti della macchina REL per l'applicazione EV vengono evidenziati. Lo studio su SERG inizia con il riconoscimento delle prestazioni allo stato stazionario, sia analiticamente che sperimentalmente. Vengono esaminate le condizioni relative all'autoeccitazione del SERG, quali capacità richiesta, magnetismo residuo del rotore, accelerazione del rotore e condensatori di precarica. Viene inoltre trattata la possibilità di adottare un generatore di riluttanza assistito da PM autoeccitato e viene eseguito il confronto delle prestazioni con SERG. Viene analizzato l'effetto di alcuni parametri di progettazione sulle prestazioni del generatore PMAREL. Riferendosi alle applicazioni eoliche, viene proposto un metodo per mantenere costante la tensione generata a velocità variabile. Infine, verrà presentata la previsione della "combinazione ottimale di condensatore e resistore" che raggiunge il massimo sfruttamento della potenza meccanica prodotta dalla turbina eolica.

La matière organique dissoute (MOD) est constituée d’un mélange hétérogène et complexe de molécules. Elle intervient dans de nombreux processus physiques, biologiques et chimiques dans les milieux aquatiques, et notamment dans les grands cycles biogéochimiques ou le transport et la biodisponibilité des contaminants.Ainsi un des enjeux actuels de nombreux domaines de recherche (chimie, écologie, océanographie) est de mieux comprendre et caractériser la MOD dans l’environnement. Dans ce contexte-là, l’objectif de ces travaux a été le développement d’une méthodologie analytique pour l’analyse et la séparation, en fonction de la taille, par fractionnement par couplage flux-force avec flux asymétrique (AF4) de la MOD. Le développement a principalement porté sur la phase mobile, le flux croisé, le temps de focus et l’utilisation d’étalons organiques proches de la MOD, permettant de calculer sa masse moléculaire moyenne.Cette méthode optimisée, couplée à un détecteur UV/Vis, équipée d’une membrane de 1kDa, d’un espaceur de 490μm et d’une phase mobile de 5mM en tampon phosphate a permis l’étude de la dynamique de la MOD.L’application de cette méthode couplée aux techniques de spectroscopie optique (absorbance et fluorescence) a permis l’étude de la MOD dans les estuaires de Seine et de Gironde mettant en avant les effets de la marée et des saisons sur la taille et le type de MOD.De plus, différentes approches statistiques ont été développées afin de mieux appréhender les multiples variables (analytiques ou environnementales) et notamment les modèles de régression linéaire ou les cartes auto-organisatrices de Kohonen
Dissolved organic matter (DOM) is a heterogeneous and complex mixture of molecules. It is involved in many physical, biological and chemical processes in aquatic ecosystems, especially in the major biogeochemical cycles or transport and bioavailability of contaminants.Thus one of the current issues in many areas of research (chemistry, ecology, oceanography) is to better understand and characterize DOM in the environment. In this context, the aim of this work was the development of an analytical methodology for DOM analysis and separation, depending on its size, by asymmetrical flow field-flow fractionation (AF4). The development focused on the mobile phase, the cross-flow, the focus time and the use of organic macromolecules standards close to DOM, in order to calculate its molecular weight.This optimized method, coupled with a UV/Vis detector, equipped with a 1kDa membrane, a 490μm spacer and a mobile phase of 5 mM phosphate buffer allowed us to study the MOD dynamics in estuarine environments.The application of this method coupled to optical spectroscopy techniques (absorbance and fluorescence) permitted the study of MOD in the Seine and Gironde estuaries and to highlight the tidal and the seasonal effects on the size and type of DOM.Furthermore, different statistical approaches have been developed to better understand the multiple variables (analytical or environmental), especially linear regression models or self-organizing maps (Kohonen)

The betavoltaic battery is a type of micro nuclear battery that harvests beta emitting radioactive decay energy using semiconductors. The literature results suggest that a better model is needed to design a betavoltaic battery. This dissertation creates a comprehensive model that includes all of the important factors that impact betavoltaic battery output and efficiency. Recent advancements in micro electro mechanical systems (MEMS) necessitate an onboard miniaturized power source. As these devices are highly functional, longevity of the power source is also preferred. Betavoltaic batteries are a very promising power source that can fulfill these requirements. They can be miniaturized to the size of a human hair. On the other hand, miniaturization of chemical batteries is restricted by low energy density. That is why betavoltaics are a viable option as a power source for sophisticated MEMS devices. They can also be used for implantable medical devices such as pacemakers; for remote applications such as spacecraft, undersea exploration, polar regions, mountains; military equipment; for sensor networks for environmental monitoring; and for sensors embedded in bridges due to their high energy density and long lifetime (up to 100 years). A betavoltaic battery simulation model was developed using Monte Carlo particle transport codes such as MCNP and PENELOPE whereas many researchers used simple empirical equations. These particle transport codes consider the comprehensive physics theory for electron transport in materials. They are used to estimate the energy deposition and the penetration depth of beta particles in the semiconductors. A full energy spectrum was used in the model to take into account the actual radioactive decay energy of the beta particles. These results were compared to the traditional betavoltaic battery design method of estimating energy deposition and penetration depth using monoenergetic beta average energy. Significant differences in results were observed that have a major impact on betavoltaic battery design. Furthermore, the angular distribution of the beta particles was incorporated in the model in order to take into account the effect of isotropic emission of beta decay. The backscattering of beta particles and loss of energy with angular dependence were analyzed. Then, the drift-diffusion semiconductor model was applied in order to estimate the power outputs for the battery, whereas many researchers used the simple collection probability model neglecting many design parameters. The results showed that an optimum junction depth can maximize the power output. The short circuit current and open circuit voltage of the battery varied with the semiconductor junction depth, angular distribution, and different activities. However, the analysis showed that the analytical results overpredicted the experimental results when self-absorption was not considered. Therefore, the percentage of self-absorption and the source thickness were estimated using a radioisotope source model. It was then validated with the thickness calculated from the specific activity of the radioisotope. As a result, the battery model was improved significantly. Furthermore, different tritiated metal sources were analyzed and the beta fluxes were compared. The optimum source thicknesses were designed to increase the source efficiencies. Both narrow and wide band gap semiconductors for beryllium tritide were analyzed.
PHD

Le déplacement collectif est l'un des phénomènes les plus remarquables de la nature. Il a été observé pour de nombreuses espèces animales, comme les essaims de bactéries, l'agrégation des fourmis, les bancs de poissons, les nuées d'oiseaux ou encore les foules d'humains. Ces comportements collectifs d'animaux ne sont pas seulement des scènes spectaculaires mais sont aussi une source d'intérêt pour explorer les mécanismes sous-jacents dans le but de comprendre les lois et l'évolution des groups biologiques ou même de nous aider à élaborer des essaims auto-organisés de robots.Nous avons étudié différents systèmes de déplacements collectifs, incluant des systèmes avec une seule espèce, comme les bancs de poissons et les foules d'humains et d'autres à plusieurs espèces, comme les systèmes de fuite et poursuite en groupe. Parmi lesquels, nous nous concentrons sur les mécanismes et les rôles du traitement de l'information sur les motifs macroscopiques. De plus, pour palier à la difficulté d'extraire des trajectoires depuis des vidéos expérimentales de qualité médiocre, nous proposons un outil rapide et robuste de suivi du déplacement. Notre contenu de recherche détaillé est le suivant : 1. Nous avons étudié les mécanismes de traitement de l'information dans les déplacements du Nez-rouge dans un dispositive annulaire. Pour la première fois, nous avons définis un comportement particulier aux bancs de poissons : des évènements de demi-tour. En introduisant un délai entre l'interaction entre les poissons, nous avons trouvé qu'à un poisson d'intérêt correspondent seulement un ou deux poissons qui ne sont pas nécessairement les plus proches. De plus, nous avons montré que l'information de tourner pendant un évènement de demi-tour collectif se propage comme des dominos. Enfin, nous avons utilisé le transfert d'entropie pour quantifier les flux d'information dans l'espace et le temps durant les évènements de demi-tour. 2. Nous avons étudié le rôle d'une perturbation dans un système de foule humaine en plaçant des obstacles (les perturbations) dans un flux de fuite de panique. Nous avons trouvé une façon simple et efficace d'augmenter le flux de fuite dans le but de sauver plus de vies dans des situations dangereuses. Nous avons appliqué des algorithmes génétiques pour optimiser l'agencement des piliers dans les simulations puis nous avons testé la qualité de ces résultats contre des expériences avec de vrais humains. Les résultats suggèrent que placer deux piliers le long des deux côtés d'une sortie peut maximiser la vitesse de sortie. 3. Nous avons étudié le rôle des mécanismes de traitement de l'information dans les déplacements collectifs multi-espèces en introduisant différentes strategies pour les proies dans un modèle de poursuite en groupe. Nous proposons trois stratégies d'agrégation : se déplacer vers le centre de masse de toutes les proies (MC), se déplacer vers la proie la plus proche (NN) et minimiser la distance totale entre toutes les proies (MD). Les résultats montrent que l'agrégation augmente grandement la durée de survie du groupe, et ceci même en autorisant les proies à être immortelles. Il y a une transition de phase de t (la durée de survie moyenne) en fonction de M (le nombre de prédateurs). 4. Nous avons développé un nouvel outil de suivi de déplacement pour améliorer les algorithmes de reconnaissance d'image et de suivi actuels afin d'extraire des trajectoires depuis des vidéos de qualité médiocre. Notre outil intègre un filtre de moyenne glissante, la soustraction du bruit de fond, des réseaux de neurones artificiels, du partitionnement en k-moyennes et une fonction d'erreur définie minutieusement. L'outil peut extraire une trajectoire depuis une video de basse qualité qui ne peut être fait que très difficilement par d'autres outils. Il peut suivre plusieurs animaux comme des poissons, des drosophiles, des fourmis, etc. Les performances de notre outil sont meilleures que idTracker et Ctrax
Collective motion is one of the most striking phenomena in nature. It has been observed in a lot of animal species, such as bacteria, ants, fish, flocks of birds and crowds of human. These collective animal behaviors not only show us spectacular scenes, but also attract us to explore the underlying mechanisms in order to understand the laws and evolution of biological groups and even help us design smarter self-organizing robots. We study different collective motion systems including single species systems such as fish school and human crowd; and multi-species group chase and escape system. Among which, we focus on the mechanisms and roles of information processing on macro patterns. Moreover, regarding to the fact that it's very difficult to extract trajectory data from low quality experiment videos, we propose a fast and robust tracking tool. Details are as follows: 1. We study the mechanisms of information processing in the movements of Hemigrammus rhodostomus in a ring-shaped tank. For the first time, we define a special behavior of fish school: U-turn event. By introducing time delay between fish interaction, we find that a focal fish usually corresponds to only 1 or 2 fish which is not necessarily the nearest one. Moreover, we find the turning information during a group U-turn event propagates like domino. In addition, we use transfer entropy to quantify dynamic information flows in space and time across the U-turn events. 2. We study the role of perturbation information in human crowd system by introducing obstacles as perturbation information into a panic escaping flow. We find a useful and simple way to increase the panic flow in order to save more lives under dangerous situation. We apply genetic algorithms to optimize the layout of pillars in the simulations and then test the results with real human experiments. Results show that putting two pillars along the two sides of the exit can maximize the escape velocity. In the end, a tangential momentum theory is proposed to explain the role of the perturbation information. 3. We study the role of information processing mechanisms in multi-species collective motion by introducing different strateg?ies for the prey in a group chase model. We propose three aggregation strategies: moving to mass center of all preys, moving to the nearest prey and minimising the total distance to all preys. Results show that aggregation increase the group survival time greatly, even allowing immortal prey. There is a phase transition of t (average survival time) against M (number of predator). 4. We developed a new tracking tool to improve the current image recognizing and video tracking algorithms so as to extract trajectories from low quality videos. Our tool integrates mean-value filter, background substraction, artificial neural network, K-means clustering and a well defined cost function. It can track low quality videos which can be hardly tracked by other tools. And it can track different animals such as fish, drosophila, ants and so on. The overall tracking performance is better than idTracker and Ctrax

Percevoir son espace d’évolution est une activité déterminante dans l’élaboration des relations spatiales que nous tissons avec notre environnement. En neurosciences comportementales, l’étude de ces relations a généralement été abordée selon deux perspectives théoriques. L’une d’elle s’attache à décrire les relations au monde au travers des processus de perception directe impliquant notamment la notion d’affordances (i.e. de possibilités d’actions naturellement offertes par l’environnement) ; tandis que d’autres s’intéressent d’avantage aux aspects cognitifs de la perception avec la mise en place de processus de représentation spatiale. Cette dernière reflète notamment l’existence d’état(s) représenté(s) qu’il est possible de décrire à travers de la combinaison d’espaces stables appelés référentiels spatiaux. L’objectif de ce travail de thèse vise à mieux comprendre la contribution du référentiel égocentré (i.e. corporel) dans la perception de l’espace géocentré (i.e. gravitaire). La question a notamment été abordée autour de deux axes de recherche interrogeant d’une part (i) l’origine de l’influence égocentrée préalablement observée dans le noir sur la perception géocentrée, et d’autre part (ii) la présence du phénomène égocentré dans un contexte visuel plus enrichi suite à l’ajout d’un flux optique. Pour ce faire quatre études centrées autour d’un paradigme d’estimation des possibilités de franchissement d’obstacles hauts ont été réalisées. Pris dans leur ensemble, les résultats expérimentaux soulignent le caractère particulièrement puissant et complexe du phénomène égocentré corporel observé sur la perception de l’espace gravitaire. Ces résultats, discutés en termes d’interpénétrabilité entre référentiels spatiaux offrent un support d’étude intéressant sur la manière dont les référentiels sont utilisés dans les processus de représentation spatiale
Perceiving space is a relevant task in determining our relationships with the environment. In behavioral neuroscience, investigating this spatial relationship can classically be explored with two theoretical approaches. The first one uses direct perception to describe the spatial relationships, involving affordances (i.e. the action ability naturally offer by the environment). The other one investigates the cognitive aspect of perception implying the use of spatial representation process. The later one traduces the existence of represented states which can be described through the interaction of different stable states called spatial reference frames. The present work investigates the contribution of the egocentric reference frame (body-related) on the perception of the geocentric space (earth-based). This was questioned through two research lines, (i) the origin of egocentric influence previously observed in darkness upon geocentric perception, (ii) the existence of the egocentric phenomenon in an enriched visual scene. To answer these questions, four experiments were conducted where the paradigm of passing under high obstacles was used. Overall, these results stress the powerful and complex aspect of the egocentric phenomenon observed upon geocentric perception. This work, discussed in term of interpenetrability between reference frames, provide an interesting support on the way how spatial reference frames are used in perceiving space

Safety and reliability are one of the key objectives for future Generation IV nuclear energy systems. The neutron flux monitoring system forms an integral part of the safety design of a nuclear reactor and must be able to detect any irregularities during all states of reactor operation. The work in this thesis mainly concerns the detection of in-core perturbations arising from unwanted movements of control rods with in-vessel neutron detectors in a sodium-cooled fast reactor. Feasibility study of self-powered neutron detectors (SPNDs) with platinum emitters as in-core power profile monitors for SFRs at full power is performed. The study shows that an SPND with a platinum emitter generates a prompt current signal induced by neutrons and gammas of the order of 600 nA/m, which is large enough to be measurable. Therefore, it is possible for the SPND to follow local power fluctuations at full power operation. Ex-core and in-core detector locations are investigated with two types of detectors, fission chambers and self-powered neutron detectors (SPNDs) respectively, to study the possibility of detection of the spatial changes in the power profile during two different transient conditions, i.e. inadvertent withdrawal of control rods (IRW) and one stuck rod during reactor shutdown (OSR). It is shown that it is possible to detect the two simulated transients with this set of ex-core and in-core detectors before any melting of the fuel takes place. The detector signal can tolerate a noise level up to 5% during an IRW and up to 1% during an OSR.

L’objectif de cette thèse était de mettre au point une analyse critique de vecteurs polymères utilisés pour la thérapie photodynamique (PDT) et de faire le lien avec l’efficacité thérapeutique observée. Pour cela, une analyse complète des vecteurs a été réalisée par des techniques classiques comme la diffusion dynamique de la lumière ou la microscopie électronique, mais aussi grâce au fractionnement flux-force, technique peu utilisée jusqu’à présent dans le domaine des auto-assemblages polymères. Dans un deuxième temps, les auto-assemblages ont été utilisés comme vecteurs d’un photosensibilisateur, le Phéophorbide a, et l’efficacité thérapeutique évaluée en travaillant sur culture cellulaire 2D et 3D de lignées HCT116 (cancer du colon) ou FaDu (cancer tête et cou). Différents vecteurs polymères simples ont tout d’abord été examinés, à savoir des micelles ou des polymersomes à base de copolymères diblocs amphiphiles comme le poly(oxyde d’éthylène-b--caprolactone), le poly(oxyde d’éthylène-b-lactide) ou le poly(oxyde d’éthylène-b-styrène). Ceci a permis d’obtenir des vecteurs présentant des tailles et des morphologies variables. Les résultats en PDT ont montré des comportements différents et une meilleure efficacité en 3D pour les systèmes à base de PEO-PDLLA. La technique de fractionnement flux-force asymétrique (AsFlFFF) a particulièrement été utilisée pour ces vecteurs afin de démontrer la pureté des auto-assemblages. Les connaissances acquises dans cette première partie ont permis de caractériser des vecteurs faits à base de mélanges d’auto-assemblages micelles/vésicules. Ceux-ci ont révélé des phénomènes d’antagonisme ou de synergie dans l’efficacité en PDT, démontrant l’existence de processus complexes au niveau de la réponse cellulaire.Des auto-assemblages figés par réticulation ont aussi été développés, caractérisés et examinés en PDT. Ils se sont avérés extrêmement intéressants pour la PDT sur les cultures cellulaires en 3D, démontrant une efficacité accrue comparée aux systèmes simples. La comparaison de ces résultats avec ceux obtenus en culture 2D pour les mêmes objets a de plus permis de mettre en évidence la différence entre ces deux modèles biologiques. Enfin, des auto-assemblages à base de complexes poly-ioniques ont aussi été formés et caractérisés. Le fractionnement flux-force s’est là encore avéré efficace, mais a nécessité l’utilisation d’une injection spéciale par Frit-inlet. Leur efficacité en PDT s’est avérée faible
The objective of this study was to critically analyze different polymer self-assemblies used for photodynamic therapy (PDT) and to link this analysis to their therapeutic efficiency. To do that, a thorough characterization of the vectors has been performed by classical techniques such as Dynamic Light Scattering or electron Microscopy, but also using flow fractionation, which has been seldomly used so far for polymeric self-assemblies. In a second step, these have been used as vectors of a photosensitizer, namely Phéophorbide a, and the therapeutic efficiency assessed on both 2D and 3D cell cultures of HCT 116 (colon cancer) and FaDu (head and neck cancer) cells. Different simple polymer vectors have first been evaluated, namely micelles and polymersomes based on diblock amphiphilic copolymers such as poly(ethylene-oxide-b--caprolactone), poly(ethylene-oxide-b-lactide) or poly(ethylene-oxide-b-styrene). This enabled obtaining vectors exhibiting various sizes and morphologies. Results in PDT showed different behaviours and a better efficiency in 3D for PEO-PDLLA. The Asymmetric Flow Field Flow Fractionation was particularly used for these systems to demonstrate their purity. The acquired expertise on this part enabled us to also characterize vectors made of known mixtures of micelles and polymersomes. These revealed antagonism and synergy effects in PDT, demonstrating the presence of complex processes for the cell response. Other self-assemblies consisting of crosslinked systems have also been developed and characterized. These were observed to be particularly efficient for PDT on 3D cell cultures. The comparison of these results with those for the 2D cell culture enabled to highlight the difference between those two biological systems. Finally, self-assemblies based on Polyion Complexes were also formed and characterized. Field Flow Fractionation was once again used as a powerful technique for this, although this implied the use of a special injection device called Frit Inlet. Their PDT efficiency however proved to be low

Identity always presupposes a sense of location and a relationship with others and the representation of identity most often occurs precisely at the point when there has been a displacement (Bhabha cited in Papastergiadis 1995:17, emphasis added). In this study I focus on the condition of displacement, placing emphasis on the disjunctures of identity arising from temporal and physical dislocations and relocations in historical and postapartheid South African contexts. Displacement, and the attendant senses of dislocation and alienation it may evoke, is explored with reference to three selected female personae. For each persona, displacement is shown to provoke transmutations in subjectivity and identity, resulting in disjunctive identities and relationships with place. Their individual narratives raise questions around the consequences of displacement for a sense of (un)belonging and the (re)making of identities across geographical, cultural, temporal, ethnic and environmental borders. The pivotal role displacement plays in the processes of formation and transformation of subjectivity and identity is foregrounded. Familial histories of diasporic displacement, together with colonial legacies that have shaped my subject position as a white, middle-class, female South African woman, are interlaced with a recounting of personal experience of displacement in postapartheid South Africa. This personal sense of displacement, experienced between the years 2000 to 2006, is extended to a discussion on what is argued to be collective forms of white, English-speaking South Africans’ dislocation during the same time period. I suggest that their sense of displacement was experienced in relation to the uncertainty of their subject positions in postapartheid South Africa. In the practical and theoretical components of the degree, I consider how the three personae’s subjectivities are practiced and lived from their different space-time continuums. This exploration prompts further questions around how the effects of displacement on subjectivity and new identity formations are contingent upon each persona’s relation to the Other of colonial discourse, or the other-strangerforeigner within. Although there are marked differences between their colonial, diasporic and postcolonial contexts, a central theme that underpins the study is that the three conditions of displacement are linked by disjunctures arising from processes of dislocation, alienation, relocation and adaptation. Each persona’s epistemological reality is shown to comprise multiple ambivalences and ambiguities, and is marked by processes of cultural contestation and inner conflict. Their ambivalences and ambiguities encompass slippages between positions of inclusion and exclusion; insider and outsider; inhabitant and immigrant; alienation and belonging; placelessness and locatedness; homely and unhomely that the experience of uprooting and relocating foregrounds. While displacement is understood in terms of trauma and conflict, this condition is also regarded as a generative space of possibility for the emergence of new identity formations. Using my experiences of self-transformation and renegotiation of my identity through processes of cultural contact and exchange as a departure point, I consider ways in which collective white, English-speaking South Africans’ cultural identities are being reformulated, renegotiated or ‘hybridised’ in postapartheid South Africa as a transforming, postcolonial society.
Thesis (DPhil)--University of Pretoria, 2012.
Visual Arts
unrestricted

Le thème principal de cette thèse est d’étudier la détection d’anomalies dans des flux de données de grande dimension avec une application spécifique au Health Monitoring des moteurs d’avion. Dans ce travail, on considère que le problème de la détection d’anomalies est un problème d’apprentissage non supervisée. Les données modernes, notamment celles issues de la surveillance des systèmes industriels sont souvent des flux d’observations de grande dimension, puisque plusieurs mesures sont prises à de hautes fréquences et à un horizon de temps qui peut être infini. De plus, les données peuvent contenir des anomalies (pannes) du système surveillé. La plupart des algorithmes existants ne peuvent pas traiter des données qui ont ces caractéristiques. Nous introduisons d’abord un algorithme de clustering probabiliste offline dans des sous-espaces pour des données de grande dimension qui repose sur l’algorithme d’espérance-maximisation (EM) et qui est, en plus, robuste aux anomalies grâce à la technique du trimming. Ensuite, nous nous intéressons à la question du clustering probabiliste online de flux de données de grande dimension en développant l’inférence online du modèle de mélange d’analyse en composantes principales probabiliste. Pour les deux méthodes proposées, nous montrons leur efficacité sur des données simulées et réelles, issues par exemple des moteurs d’avion. Enfin, nous développons une application intégrée pour le Health Monitoring des moteurs d’avion dans le but de détecter des anomalies de façon dynamique. Le système proposé introduit des techniques originales de détection et de visualisation d’anomalies reposant sur les cartes auto-organisatrices. Des résultats de détection sont présentés et la question de l’identification des anomalies est aussi discutée
The subject of this Thesis is to study anomaly detection in high-dimensional data streams with a specific application to aircraft engine Health Monitoring. In this work, we consider the problem of anomaly detection as an unsupervised learning problem. Modern data, especially those is-sued from industrial systems, are often streams of high-dimensional data samples, since multiple measurements can be taken at a high frequency and at a possibly infinite time horizon. More-over, data can contain anomalies (malfunctions, failures) of the system being monitored. Most existing unsupervised learning methods cannot handle data which possess these features. We first introduce an offline subspace clustering algorithm for high-dimensional data based on the expectation-maximization (EM) algorithm, which is also robust to anomalies through the use of the trimming technique. We then address the problem of online clustering of high-dimensional data streams by developing an online inference algorithm for the popular mixture of probabilistic principal component analyzers (MPPCA) model. We show the efficiency of both methods on synthetic and real datasets, including aircraft engine data with anomalies. Finally, we develop a comprehensive application for the aircraft engine Health Monitoring domain, which aims at detecting anomalies in aircraft engine data in a dynamic manner and introduces novel anomaly detection visualization techniques based on Self-Organizing Maps. Detection results are presented and anomaly identification is also discussed

Crystals of the overdoped cuprate superconductor TI₂Ba₂CuO₆[sub ±δ], with T[sub c]'s ranging from 5K to 90K, have been grown by a copper-rich self-flux method and characterized by X-ray Diffraction and with a SQUID magnetometer. The as-grown T[sub c]’s were several Kelvin wide, the crystals studied were found to be multi-domain, and the c-axis lattice parameter was found to be 23.143(2) Å for a T[sub c] = 5K crystal. The successful growth of TI₂Ba₂CuO₆[sub ±δ] hinged on the ability to exclude carbon while containing the thallium oxides. This study of TI₂Ba₂CuO₆[sub ±δ], while still in its infancy, has the potential to reveal a great deal about the cuprate superconductors.

碩士
國立雲林科技大學
機械工程系
106
The objective of this thesis was to use polymer material and an annular support to form the bearing body for constructing an aerostatic guideway, where the annular support could improve the rigidity and load force of the bearing and such bearing body of polymer material would form a concave surface under air pressure. With the attachment of a metal membrane on the surface, the air pressure could be maintained to increase the load force. The membrane not only provided a uniform surface roughness and flatness, but also protected the surface of the polymer body when the air film was collapsed. The above advantages were applied in the hollow rectangular aerostatic guideway to provide a better static and dynamic properties. The experiment involved a “static” discussion and a “dynamic” measurement. In the static experiment, when the bearing body of the guideway was switched to polymer material with annular support, its load capacity, aerodynamics and rigidity, either with or without a metal membrane, would be discussed; And, for the dynamic experiment, its performances were measured to investigate any instability in absorption of vibration when the re-designed hollow rectangular aerostatic guideway was placed under different loads. Under pressure of 0.5 MPa (5 bar), in the static experiment, results showed that the body exhibited better load capacity (an increase of 18%) and average rigidity (an increase of 24%) when it was changed to polymer material with an annular support and metal membrane at a lower air flow (approximately 30%) than the original guideway. In the dynamic experiment, results showed that the change to polymer material and annular support with a metal membrane could achieve the maximum capillary acceleration of 0.069 m/s^2, in contrast with the maximum acceleration of the guideway at 0.116 m/s^2, indicating better stability of polymer body of annular support and metal membrane than the original guideway. Keywords: Aerostatic guideway; Rectangular bearing; Polymer; Rigidity; Air flow; Vibration

碩士
修平科技大學
電機工程碩士班
104
This paper proposes a Fuzzy System Constructed by Self-Splitting Rule generation and Iterative Linear Support Vector Regression (FS-RGLSVR) for Laboratory Light Flux Estimation. For structure learning, a Self-splitting K-means algorithm clusters the input training data and determines the rule number. For parameter learning, a linear support vector regression (SVR) algorithm is proposed to tune free parameters in the consequent part. The motivation for using SVR for parameter learning is to improve the FS-RGLSVR generalization ability. This paper demonstrates the capabilities of FS-RGLSVR by conducting simulations in Laboratory Light Flux Estimation. These simulations show the performance of FS-RGLSVR using different values of with different insensitive values ( =0.07, and 0.02). This paper also compares simulation results from the FS-RGLSVR with SSKNFS-SVR.

GeV electron bunches accelerated on a centimeter scale device exemplify the extraordinary advances of laser-plasma acceleration. The combination of high charges from optimized injection schemes and intrinsic femtosecond short bunch duration yields kiloampere peak currents. Further enhancing the current while reducing the energy spread will pave the way for future application, e.g. the driver for compact secondary radiation sources such as high-field THz, high-brightness x-ray or gamma-ray sources. One essential key for beam transport to a specific application is an electron bunch with high quality beam parameters such as low energy spread as well as small divergence and spot size. The inherent micrometer size at the plasma exit is typically sufficient for an efficient coupling into a conventional beamline. However, energy spread and beam divergence require optimization before the beam can be transported efficiently. Induced by the high peak current, the beam loading regime can be used in order to achieve optimized beam parameters for beam transport.
In this thesis, the impact of beam loading on the transverse electron dynamic is systematically studied by investigating betatron radiation and electron beam divergence. For this reason, the bubble regime with self-truncated ionization injection (STII) is applied to set up a nanocoulomb-class laser wakefield accelerator. The accelerator is driven by 150TW laser pulses from the DRACO high power laser system. A supersonic gas jet provides a 3mm long acceleration medium with electron densities from 3 × 10^18 cm^−3 to 5 × 10^18 cm^−3. The STII scheme together with the employed setup yields highly reproducible injections with bunch charges of up to 0.5 nC. The recorded betatron radius at the accelerator exit is about one micron and reveals that the beam size stays at the same value. The optimal beam loading, which is observed at around 250 pC to 300 pC, leads to the minimum energy spread of ~40MeV and a 20% smaller divergence. It is demonstrated that an incomplete betatron phase mixing due to the small energy spread can explain the experimentally observed minimum beam divergence.