Corrosion fatigue is a common failure mechanism in rock drilling components and many othermechanical parts subjected to cyclic loads in corrosive environments. A crucial part in the design ofsuch components resides in the selection of the right materials for the application, which ideallyinvolves testing and comparison of their performance under working conditions. The present work was performed with the purpose of designing a corrosion-fatigue testing methodthat would allow the designer to compare the performance of different materials exposed to corrosionfatigue, permitting also the comparison with results from dry fatigue testing. The method was designedfor rotating-bending machines. Two different steel grades were used during the work, one throughhardened and one case hardened. The effect of these heat treatments and of shot peening overcorrosion-fatigue behaviour were studied using the proposed method. It was proven that the testing speed has a strong impact on the fatigue life of steel. It was found that,at a fixed stress level, the case hardened and shot peened steel reached 3X10^6 cycles at 2300 rpm,while it failed at only 5X10^5 cycles with a testing speed of 500 rpm. A large beneficial influence of theshot peening was demonstrated. It was also observed that, at fixed testing speed, the shot peening onthe through hardened steel can increase its fatigue strength from 190 MPa to 600 MPa under corrosionfatigue. Many cracks were found at the surface of the shot peened parts, which are arrested near thesurface by the compressive stress layer from the shot peening. It was also found that, for the non-shotpeened parts, case hardening had a slightly higher corrosion-fatigue strength than the throughhardened. This might be a result of the compressive stresses from carburization, or due to the highercore toughness of this steel grade.

High Voltage (HV) rotating machines are widely used in power generation and heavy industry companies. Silicon Carbide (SiC) material is used in the stress grading structure of HV electric machines because of its non-linear characteristic. In this thesis, the resistance characteristics of SiC-based stress grading tape in time domain and the dielectric parameters in frequency domain were measured. The measurement results of samples with axial current-direction in time domain and frequency domain are about ten times that of the samples with radial current-direction, which might be a feature of the tape construction although it also can depend on the measurement method. The finite element method (FEM) simulation of the coil insulation system was carried out by using the experimental parameters, and the results were compared with the actual measurement results. The calculation results show that the non-linearity of SiC-based material does not have much effect on the real part of frequency response of the whole coil. The relative difference of the real part of complex capacitance is less than 5%. However, the influence on the imaginary part is relatively large, the relative difference is about 4% - 60%. / Högspänningsmaskiner används ofta i kraftproduktion och tunga industriella anläggningar. Kiselkarbidmaterial (SiC) används i sådana maskiners potential-styrningssstruktur på grund av dess icke-linjära egenskaper. I denna avhandling mättes ledningsförmågan hos SiC-baserade fältstyrningstejp i tidsdomänen och de dielektriska parametrarna i frekvensdomänen. Resultaten med axiell strömriktning vid tiddomän och frekvensdomänmetoder tyder på omkring tio gånger så stor konduktivitet jämfört med den radiella ström-riktningen, vilken kan bero på tejpkonstruktionen fast även eventuellt på mätmetoden. Simuleringen av en statorhärvas isoleringssystem utfördes med finita element metoden (FEM) med parametrar från materialproven, och resultaten jämfördes med mätresultat från en sådan härva. Beräkningsresultaten visar att det SiC-baserade materialets ickelinjäritet inte har någon större effekt på hela spolens verkliga frekvensrespons. Den relativa skillnaden mellan den verkliga delen av komplex kapacitans är mindre än 5%. Påverkan på den imaginära delen är dock relativt stor, med en relativ skillnad på ca 4% - 60%.

[ES] En la sociedad actual hay cada vez una mayor conciencia de la importancia del calentamiento global. Esta preocupación se ve reflejada por los poderes legislativos de las naciones occidentales en normativas de emisiones cada vez más restrictivas. En este contexto, la industria automovilísitca se ha visto fuertemente incentivada a desarrollar motores térmicos más eficientes e incluso a explorar nuevas soluciones propulsivas, como el motor eléctrico. Para mejorar la eficiencia energética de los motores de combustión interna alternativos se emplea la reducción de los motores. Esto ha obligado a los compresores a trabajar en condiciones, en las que su emisión acústica llega a ser problemática. La revisión bibliográfica llevada a cabo en esta tesis muestra que sigue sin haber consenso acerca de la causa de ciertas componentes del espectro, como los ruidos de banda ancha conocidos cono whoosh y Tip Clearance Noise (TCN). La influencia en el ruido de la geometría de los conductos de entrada al compresor está asimismo poco explorada. Esta tesis presenta una metodología computacional de análisis del campo de flujo que permite la identificación de las estructuras de flujo responsables de las componentes espectrales más relevantes, así como el análisis de la influencia en éstas de las condiciones de operación y las geometrías de entrada. El campo de presión en el interior del compresor se analiza mediante técnicas de descomposición modal. Éstas permiten identificar patrones espaciales y asociarlos a las frecuencias del espectro medido de forma objetiva. Posteriormente se identifica las estructuras de flujo correspondientes a dichos patrones, y su evolución con las condiciones de operación y la geometría de entrada. Mediante la aplicación de la metodología descrita se describe los diferentes mecanismos de generación de los ruidos tonales en el inductor y el borde de fuga del rotor. En cuanto a los ruidos de banda ancha mencionados, los vórtices encontrados aguas arriba del inductor generan oscilaciones en la banda de frecuencias del whoosh, y favorecen el desprendimiento rotativo, que contribuye a dicho ruido en el difusor y la voluta. La carga no estacionaria sobre la superficie de los álabes es identificada como un importante contribuidor al ruido TCN. La influencia de las condiciones de operación en la generación de ruido se manifiesta a través de la intensidad del flujo inverso en el inductor. La aparición de este flujo inverso es característica de los puntos de bajo gasto másico, aunque se sigue apreciando, con menor intensidad, en algunos puntos de alto gasto. El flujo inverso inhibe las condiciones sónicas en el borde de ataque, debilitando el ruido tonal a la frecuencia de paso de álabe. En cuanto a los ruidos de banda ancha, el flujo inverso es la causa de los vórtices en el inductor que producen el ruido whoosh y el despegue rotativo, y además promueve la carga no estacionaria de los álabes, asociada con el TCN. El papel de la geometría del conducto de entrada en el ruido depende de su grado de interacción con los vórtices del inductor. En aquellas geometrías que limitan la extensión aguas arriba de los vórtices del inductor, como los codos con radio de curvatura reducido, tiene lugar una interacción intensa de los vórtices con las paredes del conducto y con otros vórtices. Ello está correlacionado con un aumento del ruido whoosh. Los conductos de entrada que están suficientemente separados de los vórtices, intervienen en el ruido solamente a través de sus propiedades de transmisión de las oscilaciones acústicas generadas en el rotor y el difusor. Al final de la tesis se reflexiona sobre las contribuciones de los resultados expuestos al estado del arte de la investigación en el ruido de compresores. Además, se propone nuevas líneas de investigación para extender la metodología presentada, y completar el conjunto de condiciones de funcionamiento y geometrías de entrada analizadas en este trabajo. / [CA] En la societat actual hi ha cada vegada una major consciència de la importància del calfament global. Aquesta preocupació es veu reflectida pels poders legislatius de les nacions occidentals en normatives d'emissions cada vegada més restrictives. En aquest context, la indústria de l'automòbil s'ha vist fortament incentivada a desenvolupar motors tèrmics més eficients i fins i tot a explorar noves solucions propulsives, com el motor elèctric. La tendència adoptada per a millorar l'eficiència energètica dels motors de combustió interna alternatius és la reducció de la grandària dels motors. Això ha obligat els compressors a treballar en condicions més extremes, en les quals la seua emissió acústica arriba a ser problemàtica. La revisió bibliogràfica duta a terme en aquesta tesi mostra que segueix sense haver-hi consens sobre la causa d'unes certes components de l'espectre, com els sorolls de banda ampla coneguts con whoosh i Tip Clearance Noise (TCN). La influència en el soroll de la geometria dels conductes d'entrada al compressor està així mateix poc explorada. Aquesta tesi presenta una metodologia computacional d'anàlisi del camp de flux que permet la identificació de les estructures de flux responsables de les components espectrals més rellevants, així com l'anàlisi de la influència en aquestes de les condicions d'operació i les geometries d'entrada. El camp de pressió a l'interior del compressor s'analitza mitjançant tècniques de descomposició modal. Aquestes permeten identificar patrons espacials i associar-los a les freqüències de l'espectre mesurat de manera objectiva. Posteriorment s'identifica les estructures de flux corresponents a aquests patrons, i la seua evolució amb les condicions d'operació i la geometria d'entrada. Mitjançant l'aplicació de la metodologia descrita es descriu els diferents mecanismes de generació dels sorolls tonals en l'inductor i la vora de fugida del rotor. Quant als sorolls de banda ampla esmentats, els vòrtexs trobats aigües amunt de l'inductor generen oscil·lacions en la banda de freqüències del whoosh, i afavoreixen el despreniment rotatiu, que contribueix a aquest soroll en el difusor i la voluta. La càrrega no estacionària sobre la superfície dels àleps és identificada com un important contribuïdor al soroll TCN. La influència de les condicions d'operació en la generació de soroll es manifesta a través de la intensitat del flux invers en l'inductor. L'aparició d'aquest flux invers és característica dels punts de baixa despesa màssica, encara que es continua apreciant, amb menor intensitat, en alguns punts d'alta despesa. El flux invers inhibeix les condicions sòniques en la vora d'atac, afeblint el soroll tonal a la freqüència de pas d'àlep. Quant als sorolls de banda ampla, el flux invers és la causa dels vòrtexs en l'inductor que produeixen el soroll whoosh i el despreniment rotatiu, i a més promou la càrrega no estacionària dels àleps, associada amb el TCN. El paper de la geometria del conducte d'entrada en el soroll depén del seu grau d'interacció amb els vòrtexs de l'inductor. En aquelles geometries que limiten l'extensió aigües amunt dels vòrtexs de l'inductor, com els colzes amb radi de curvatura reduït, té lloc una interacció intensa dels vòrtexs amb les parets del conducte i amb altres vòrtexs. Això està correlacionat amb un augment del soroll whoosh. Els conductes d'entrada que estan prou separats dels vòrtexs, intervenen en el soroll solament a través de les seues propietats de transmissió de les oscil·lacions acústiques generades en el rotor i el difusor. Al final de la tesi es reflexiona sobre les contribucions dels resultats exposats a l'estat de l'art de la investigació en el soroll de compressors. A més, es proposa noves línies d'investigació per a estendre la metodologia presentada, i completar el conjunt de condicions de funcionament i geometries d'entrada analitzades en aquest treball. / [EN] In today's society, there is a growing awareness of the importance of global warming. This concern is reflected by the legislative powers of Western nations in increasingly restrictive emissions regulations. In this context, the automotive industry has been strongly encouraged to develop more efficient thermal engines and even to explore new propulsion solutions, such as the electric motor. The trend adopted to improve the energy efficiency of reciprocating internal combustion engines is the reduction of engine size. This has forced compressors to work in more extreme conditions, where their acoustic emission becomes troublesome. The literature review carried out in this thesis shows that in the last two decades, there has been a great boom of research in the acoustics of radial turbocharger compressors. Despite the progress made, there is still no consensus about the cause of specific spectrum components, such as the broadband noises known as whoosh and Tip Clearance Noise (TCN). The influence of compressor inlet duct geometry on noise is also scarcely explored. This thesis presents a computational methodology of flow field analysis that allows the identification of the flow structures responsible for the most relevant spectral components and the analysis of the influence of operating conditions and inlet geometries on them. The pressure field inside the compressor is analyzed through modal decomposition techniques. These allow identifying spatial patterns and associating them to the frequencies of the measured spectrum in an objective manner. Subsequently, the flow structures corresponding to these patterns are identified, and their evolution with the operating conditions and the inlet geometry is analyzed. Through the application of the described methodology, the different mechanisms of generation of the tonal noises in the inducer and the impeller trailing edge are identified. While the former is related to the sonic conditions at the leading edge, the latter is excited by the asymmetric pressure field in the diffuser. As for the aforementioned broadband noises, the vortices encountered upstream of the inducer generate oscillations in the whoosh frequency band and favor rotating stall, contributing to such noise in the diffuser and volute. Unsteady blade surface loading is identified as an important contributor to TCN noise. The influence of operating conditions on noise generation manifests through the intensity of the backflow in the inducer. The occurrence of backflow is characteristic of low mass flow points, although it is also found, with less intensity, at some higher mass flow points. The backflow inhibits the sonic conditions at the leading edge, weakening the tonal noise at the blade passing frequency. As for broadband noise, reverse flow is the cause of vortices in the inducer that produce whoosh noise and rotating stall. It also promotes the unsteady blade loading associated with TCN. The role of the inlet duct geometry in the noise depends on its degree of interaction with the inducer vortices. In geometries that limit the upstream extent of these vortices, such as low curvature radii elbows, intense interaction of the vortices with the duct walls and other vortices occurs. This is correlated with an increase in whoosh noise. Inlet ducts that are sufficiently separated from the vortices only affect noise through their transmission properties regarding acoustic oscillations generated in the impeller and diffuser. At the end of the thesis, reflections are offered on the contributions of the results to the current knowledge on compressor noise. In addition, new lines of research are proposed to extend the methodology presented and to complete the set of operating conditions and inlet geometries analyzed in this work. / Roig Villanueva, F. (2023). On the Influence of Inlet Geometry on Turbocharger Compressor Noise [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/192264

La cinétique lente de la réduction de l’oxygène (ORR) est en grande partie responsable de la perte d’énergie de nombreux systèmes de conversion tels que les piles à combustible. Parmi les possibles catalyseurs de l’ORR, les oxydes de type pérovskite sont des candidats prometteurs en milieu alcalin. La présente thèse est consacrée à l’étude de l’activité, du mécanisme et de la stabilité de pérovskites à base de Co et Mn pour l’ORR. Grâce aux techniques d’électrode tournante à disque et disque-anneau (R(R)DE), les études de l’ORR et des transformations d’HO2- sur les couches minces de pérovskite/carbone dans une solution de NaOH ont montré qu’O2 est réduit en OH- via un mécanisme « en série » avec formation d’HO2- intermédiaire. Pour des quantités d’oxyde suffisantes, HO2- est ensuite réduit, ce qui résulte en un mécanisme apparent de 4 électrons. Dans ces électrodes, le carbone joue un double rôle. Il augmente l’activité électrocatalytique en améliorant le contact électrique et il est impliqué dans le mécanisme de l’ORR en catalysant la réduction d’O2 en HO2-, surtout pour les pérovskites à base de cobalt qui sont considérablement moins actives que celles à base de Mn. Néanmoins, l’électrocatalyse de l’ORR semble dégrader les sites actifs des pérovskites. / The sluggish kinetics of the oxygen reduction reaction (ORR) is largely responsible for the energy losses in energy conversion systems such as fuel cells. Among possible inexpensive catalysts for the ORR, perovskite oxides are promising electrocatalysts in alkaline media. The present thesis is devoted to the investigation of the ORR activity, mechanism and stability of some Co and Mn-based perovskites. The rotating (ring) disk electrode (R(R)DE) studies of the ORR and the HO2- transformations on perovskite/carbon thin layers in NaOH electrolyte prove that O2 is reduced to OH- via a “series” pathway with the HO2- intermediate. For high oxide loadings, the formed HO2- species are further reduced to give a global 4 electron pathway. In these electrodes, carbon plays a dual role. It increases the electrocatalytic activity by improving the electrical contact and it is involved in the ORR mechanism by catalyzing the reduction of O2 into HO2-, especially for Co-based perovskites which display lower reaction rates than Mn-based perovskites.

Breast cancer poses a serious public health concern. This case-control study describes the relationship of night-shift working on the development of breast cancer in 57 women diagnosed with breast cancer compared to 49 women with other types of cancer in the Vaal Triangle area (selected through non-probability purposive sampling from CANSA). The study revealed that women who work night-shift developed breast cancer 1.24 times more often than women who do not work nightshift (OR=1.24 [95% CI 0.52 to 2.89]). The odds ratio was further increased in women who worked rotating-shift (OR=1.44 [95% CI 0.58 to 3.59]). Night-shift work exposure was not statistically related to the development of breast cancer. It is recommended that the relationship between night-shift exposure and breast cancer risk be further explored through cross-sectional and cohort studies, and other breast cancer pathways. / Health Studies / M.A. (Public Health)

In More Electric Aircraft, different power system activities are attributed to electrical means such as the start-up of the main engine. In this context, the study of the sensorless control of the Brushless Synchronous Starter Generator (BSSG) that is used to electrically start the main engine is revealed to be a very interesting issue. For long time, the elimination of the mechanical sensor was highly recommended for reliability, cost, weight, integration issues.Hence, this work aims to transpose the results obtained in the research area to an avionic testbench. It presents an adaptive sensorless technique to use when electrically starting the main engine of the aircraft. This is achieved by elaborating three different methods selected depending on the speed of the machine and based on the :- injection of a high frequency signal- use of the back-emf of the Permanent Magnet Generator (PMG)- use of the extended Kalman Filter EKFIn this work, it is shown that the …first method gives good position estimation results from standstill up to 8% of the rated speed. Then, the back-emfs of the PMG are used to detect the position of the BSSG when the speed exceeds the 8% of the rated speed. Good results are observed with this method at medium and high speed.For redundancy reasons, the EKF was also used in this work. Thus, the estimated position can be delivered via two different estimation algorithms in medium and high speed region.The implementation of the algorithm was achieved on an FPGA board since the latter can ensure a very tiny execution time. The fastness of the treatment ensures quasi-instantaneous position estimation and does not practically introduce any phase lag in the position estimation. / Aujourd'hui, l'aviation est en train de vivre des évolutions technologiques concernant surtout l'attribution de différentes fonctionnalités aux équipements électriques et ceci au détriment d'équipements hydrauliques et mécaniques assurant les mêmes fonctionnalités.Dans le cadre de l'avion plus électrique, le démarrage électrique sans capteurs mécaniques de la turbine de l'avion préoccupe les avionneurs de nos jours. Les problèmes introduits par ce capteur ont été identifiés : problèmes de coût et de poids, problèmes de fiabilité et d'intégration.Ce travail présente alors une commande sans capteurs pour la machine synchrone à trois étages à utiliser durant le démarrage électrique de l'avion. Ceci est réalisé avec trois méthodes de détection de la position selon la vitesse de rotation, basées sur :- l'injection d'un signal à haute fréquence- l'utilisation d'un filtre de Kalman étendu FKE- les fém. du PMG (Permanent Magnet Generator) La première méthode donne de bons résultats d'estimation depuis l'arrêt jusqu'à 8% de la vitesse nominale de la machine. Au-delà de cette vitesse, es valeurs des fém. du PMG deviennent assez élevées pour être utilisées dans l'estimation de la position. De bons résultats sont obtenus à moyenne et haute vitesse.Pour des questions de redondance, le FKE est aussi utilisé. Ainsi, la position estimée peut être fournie par l'un des deux algorithmes à moyenne et haute vitesse.L'implémentation de ces algorithmes est réalisée via une carte FPGA étant donné que celui-ci garantit un temps d'exécution. La rapidité de traitement garantit une estimation de la position quasi-instantanée et donc n'introduit pratiquement pas des retards dans l'estimation.

The thermally-driven rotating annulus is a laboratory experiment used to study the dynamics of planetary atmospheres under controlled and reproducible conditions. The predictability of this experiment is studied by applying the same principles used to predict the atmosphere. A forecasting system for the annulus is built using the analysis correction method for data assimilation and the breeding method for ensemble generation. The results show that a range of flow regimes with varying complexity can be accurately assimilated, predicted, and studied in this experiment. This framework is also intended to demonstrate a proof-of-concept: that the annulus could be used as a testbed for meteorological techniques under laboratory conditions. First, a regime diagram is created using numerical simulations in order to select points in parameter space to forecast, and a new chaotic flow regime is discovered within it. The two components of the framework are then used as standalone algorithms to measure predictability in the perfect model scenario and to demonstrate data assimilation. With a perfect model, regular flow regimes are found to be predictable until the end of the forecasts, and chaotic regimes are predictable over hundreds of seconds. There is a difference in the way predictability is lost between low-order chaotic regimes and high-order chaos. Analysis correction is shown to be accurate in both regular and chaotic regimes, with residual velocity errors about 3-8 times the observational error. Specific assimilation scenarios studied include information propagation from data-rich to data-poor areas, assimilation of vortex shedding observations, and assimilation over regime and rotation rate transitions. The full framework is used to predict regular and chaotic flow, verifying the forecasts against laboratory data. The steady wave forecasts perform well, and are predictable until the end of the available data. The amplitude and structural vacillation forecasts lose quality and skill by a combination of wave drift and wavenumber transition. Amplitude vacillation is predictable up to several hundred seconds ahead, and structural vacillation is predictable for a few hundred seconds.

Breast cancer poses a serious public health concern. This case-control study describes the relationship of night-shift working on the development of breast cancer in 57 women diagnosed with breast cancer compared to 49 women with other types of cancer in the Vaal Triangle area (selected through non-probability purposive sampling from CANSA). The study revealed that women who work night-shift developed breast cancer 1.24 times more often than women who do not work nightshift (OR=1.24 [95% CI 0.52 to 2.89]). The odds ratio was further increased in women who worked rotating-shift (OR=1.44 [95% CI 0.58 to 3.59]). Night-shift work exposure was not statistically related to the development of breast cancer. It is recommended that the relationship between night-shift exposure and breast cancer risk be further explored through cross-sectional and cohort studies, and other breast cancer pathways. / Health Studies / M. A. (Public Health)

The Counter-Rotating Open Rotors (CROR) are identified as a possible alternative to turbofan engines for middle-range aircrafts. Providing significant fuel savings and reducing the green-house gas emissions, they may lead however to an increased noise radiation due to the absence of nacelle shielding. To properly predict the acoustic radiation of such systems is then mandatory both to reduce the source mechanisms of the isolated engine and to offer an optimal noise installation solution. Such an objective is tackled in the present thesis in two steps. In a first part, the research aims at predicting the tonal noise radiated from the first propeller of CROR mounted on the rear fuselage by means of a pylon (pusher configuration), considering both the pylon-wake and the uniform ow effects. From the Ffowcs Williams & Hawkings' formalism, three noise sources are identified. First the unsteady loading is computed using a similar procedure to the one used for the rotor-rotor wake interaction noise prediction. The velocity deficit in the pylon wake is locally expanded in two-dimensional Fourier gusts in a reference frame attached to the front rotor. The unsteady lift induced by each gust on a blade segment is calculated using a linearized analytical response function that accounts for a realistic geometry. The steady loading is the second source contribution and is evaluated using both a software based on the lifting-line theory and some numerical simulations for different reference source surfaces. Finally the thickness noise due to the blade volume displacement is included in the analysis using Isom's formulation. From the linear acoustic assumptions, all these sources modelled as equivalent acoustic dipoles rotating in a uniformly moving atmosphere are then summed to calculate the far-field noise. The whole methodology is assessed against wind-tunnel test data and reference software predictions. A parametric study considering several pylon positionings and pylon-wake configurations with blowing is performed in order to emphasize the relative contribution of the three noise sources. Secondly, the rotor- rotor wake interaction noise being recognized as the most significant contribution in isolated configuration, its modelling is completed by introducing the dynamics of the vortex occurring near the rear-rotor leading edge. A semi-analytical methodology is developed to determine a vortex attached over a at plate embedded in a uniform ow with incidence. Applied to the case of a rear blade going through a front-rotor wake, it provides a first estimate of the noise contribution of the vortex. / Les hélices contrarotatives constituent une alternative possible aux turboréacteurs pour les avions moyens- courriers. Réduisant significativement la consommation de carburant et les émissions de gaz à effet de serre, ils peuvent néanmoins conduire à un rayonnement sonore accru de par l'absence de carénage. Prédire correctement le rayonnement sonore de telles motorisations est donc indispensable pour réduire les mécanismes sources propres au moteur isolé ou assurer une solution d'installation acoustique optimale. Un tel objectif est abordé dans cette thèse en deux temps. Dans un premier temps, l’étude vise à prédire le bruit tonal rayonné par la première hélice d'un moteur monté à l'arrière du fuselage (configuration dite en pousseur), en considérant les effets du sillage du pylône supportant le moteur et de l'écoulement moyen. Partant du formalisme de Ffowcs Williams & Hawkings, trois sources sonores sont identifiées à cet effet. La charge instationnaire, tout d'abord, est calculée en s'appuyant sur une méthodologie similaire à celle utilisée pour la prédiction du bruit d'interaction de sillages entre les deux rotors. Le déficit de vitesse dans le sillage du mât est décomposé localement en rafales bidimensionnelles dans un repère attaché au rotor amont. La portance instationnaire induite par chaque rafale sur un segment de pale est calculée en utilisant une fonction de réponse analytique linéarisée considérant une géométrie réaliste. Deuxième contribution, la charge stationnaire est évaluée au moyen d'un logiciel s'appuyant sur la théorie de la ligne portante mais également via des simulations numériques pour différentes surfaces sources de référence. Enfin, le bruit d'épaisseur associé au déplacement du volume de la pale est inclus dans l'analyse à partir de la formulation d'Isom. D'après les hypothèses de l'acoustique linéaire, toutes ces sources modélisées comme des dipôles acoustiques tournant dans une atmosphère uniforme en mouvement sont ensuite sommées pour calculer le bruit en champ lointain. L'ensemble de la méthodologie est comparé à des données d'essai et des prédictions d'un logiciel de référence. Une étude paramétrique considérant plusieurs positionnements du pylône et des configurations avec soufflage est effectuée afin de bien mettre en évidence les contributions relatives des trois sources sonores. Dans un deuxième temps, le bruit d'interaction de sillages étant reconnu comme la contribution majoritaire en configuration isolée, sa modélisation est complétée en introduisant la dynamique du tourbillon se développant au voisinage du bord d'attaque du rotor aval. Une méthodologie semi-analytique est développée pour déterminer un tourbillon attaché au-dessus d'une plaque plane plongée dans un écoulement uniforme avec incidence. Appliquée au cas d'une pale aval traversant le sillage du rotor amont, elle fournit une première estimation de la contribution sonore du tourbillon.

Text in English with abstracts in English, isiZulu, Northern Sotho and Tshivenda / This study explores the phenomenon of stokvels − membership-based savings schemes providing for the social and financial wellbeing of their members as well as entertainment (Lukhele, 1990). The purpose of the study is to identify the existence of a different kind of economy that is not informed by the capitalist logic. The study aims to examine the values that underpin stokvels and to locate them within a particular socio-cultural and historical context. This is a qualitative research study and my research approach included fieldwork, participant observation, in-depth interviews and the procedure of genealogy. The study, employing these methods, has enabled me to draw a connection between the Khumalo clan - the generation of Mzilikazi Khumalo who was a friend to King Shaka and is argued to have played a pivotal role in building what is known as the Zulu nation today – and my uncles. In the six months I spent at Esihlengeni, a small village in Vryheid, KwaZulu-Natal, I interviewed 27 people, attended two funerals, one family ritual and conducted two focus group discussions with stokvel women. I found that stokvels are not centred on an African epistemic framework as anticipated in the problem statement but are still within the capitalist logic of profit and thus do not draw from the community’s traditional values. While stokvels are informed by the dominant capitalist logic, the community of Esihlengeni still draws from their cosmological worldview that provides them with a different understanding of the economy that is centred on cattle – the means that allow them to perform rituals that guarantee protection and continuity of life - to make sense of their world. Their insistence on the importance of cattle in this community is their cry to be allowed to exist and be recognised as humans that can think for themselves. I conclude by arguing that to understand this community correctly, we need to take the ontological difference seriously that we cannot possibly have only one way of existing. The community of Esihlengeni thus provides us with the economic theory that is centred on life in its totality – that takes both the physical and metaphysical into consideration to ensure the continuity of life. As such, the community of Esihlengeni should be regarded as a gift to be appreciated. / Lolucwaningo luhlaziya isimo sezitokofela – uhlelo lokonga olunika abayingxenye yalo ukweseka kwezomphakathi, ezomnotho nezokuzijabulisa (Lukhele 1990). Ingqikimba yokwenza lolucwaningo ukubonisa ubukhona bomnnotho ohlukile, ongatshelwa wumnotho ogxile kwinzuzo, phecelezi ikhephithalizimu. Injongo yalolucwaningo ukuhlolisisa izimiso ezisekela amastokofela nokuwabeka endaweni ethize yezinhlalo zomphakathi-namasiko kanye nomlando. Lolucwaningo lugxile kwizizathu zokuba yingxenye kuloluhlelo, indlela yokuthola imininingwane ixhumanisa ukuchitha isikhathi nabantu, ukubamba ingxenye kwizinto abazenzayo, ukubabuza imibuzo ejulile, nokudweba imvelaphi yabo. Kulolucwaningo, ngokusebenzisa lezizindlela zokucwaninga, ngakwazi ukuxhumanisa isizwe sakwaKhumalo – inzalo yenkosi uMzilikazi Khumalo owaye umngani wenkosi uShaka futhi kuthiwa wabamba iqhaza eliqavile ekwakheni isizwe esaziwa njengamaZulu namhlanje – nomalume bami. Ezinyangeni eziyisithupha engazicitha eSihlengeni - isigodi esiseFilidili KwaZulu-Natali, ngaba nendabangxoxiswano nabantu amangamashumi amabili nesikhombisa, ngaya emingcwabeni emibili nasembenzini owodwa womndeni, ngase ngikhulumisana namaqoqo amabili omama besitokofela. Ngathola ukuthi izitokofela azizinzile kwinqubomigomo yesintu njengoba ngangisola esitatimendeni socwaningo, kodwa angaphakathi komnotho ogxile kwinzuzo, ikhephithalizimi, ngakhoke awasebenzisi imikhuba yesintu yalomphakathi. Noma amastokofela egxile kumnotho oqgamile ogxile kwinzuzo, lomphakathi waseSihlengeni usasebenzisa indlela yawo yokuphila eveza inqubomgomo ehlukile yomnotho ogxile ezinkomeni - eziyisisekelo sokwenza amasiko aqinekisa ukuvikeleka nenqubekela phambili yempilo – ukuqondisisa imvelo. Ukuphikelela kokubaluleka kwezinkomo kulomphakathi isikhalo sokuthi uvumeleke ukuba aphile futhi ubonwe njengabantu abakwaziyo ukuzicabangela. Ngiphetha ngokuthi ukuqondisisa lomphakathi kahle, kumele sithathe ukuhlukana kwezizwe okuyimvelo yempilo ngokuzimisela, ukuthi kungenzeke kube nendlela eyodwa yokuphila. Umphakathi waseSihlengeni ngakhoke usinika inqubomugomo yomnotho egxile empilweni ngokuphelela kwayo – uthatha okubonakalayo nokungabonakali ukuqiniseka kokuqhubekela phambili kwempilo. Kanjaloke, umphakathi waseSihlengeni kumele ubonakale njengesipho okumelwe sibungazwe. / Nyakišišo ye e bolela ka ditokofele – dikema tša polokelo tša go thewa godimo ga boleloko go dira gore maloko a tšona a be le boiketlo go tša leago, matlotlo le boithabišo (Lukhele, 1990). Morero wa nyakišišo ye ke go hlaola go ba gona ga mehuta ya go fapana ya ekonomi yeo e sa huetšwego ke lotšiki ya bokepitale. Maikemišetšo a nyakišišo ke go lekola melawana yeo e thekgago ditokofele le go di bea ka gare ga maemo a itšeng a histori, a leago le a setšo. Ye ke nyakišišo ya khwalithethifi gomme sebopego sa nyakišišo ya ka se akaretša tlhohlomišo, temošo ya bakgathatema, dipoledišano tša go tsenelela le tshepedišo ya tšinealotši. Nyakišišo, ya go šomiša mekgwa ye, e nkgontšhitše go laetša kamano gare ga lešika la ga Khumalo ‒ moloko wa Mzilikazi Khumalo yoo a bego e le mogwera wa Kgošikgolo Shaka gape o dumelwa go ba a bapetše karolo ye bohlokwa kagong ya seo lehono se tsebjago bjalo ka setšhaba sa Mazulu ‒ le bomalome ba ka. Mo dikgweding tše tshela tše ke di feditšego Esihlengeni, motse wo monyane go la Vryheid, KwaZulu-Natal, ke boledišane le batho ba 27, ke tsenetše ditirelo tše pedi tša poloko, moetlo o tee wa lapa le go swara dipoledišano tše pedi tša go lebantšha sehlopha gotee le basadi ba setokofele. Ke hweditše gore ditokofele ga di latele foreimiweke ya epistemiki ya Afrika bjalo ka ge go letetšwe ka gare ga tlhalošo ya taba eupša di sa le ka gare ga lotšiki ya bokepitale ya poelo gomme ka go realo ga di latele ditumelo tša setšo tša setšhaba. Mola ditokofele di latela lotšiki ya bokepitale ye e bušago, setšhaba sa Esihlengeni se sa ntše se latela pono ya sona ya kosmolotši ya lefase yeo e ba fago kwešišo ye e fapanego ya ekonomi ya go thewa godimo ga dikgomo – mokgwa wo o ba dumelelago go phetha moetlo wa go tiišetša tšhireletšo le tšwelopele ya bophelo – go kwešiša lefase la bona. Phegelelo ya bona go bohlokwa bja dikgomo ka setšhabeng se ke sello sa bona sa gore ba dumelelwe go ba gona le go amogelwa bjalo ka batho bao ba kago inaganela. Ke fetša ka gore go kwešiša setšhaba se e le ka nnete, re nyaka go tšea kgopolo ya ontolotši bjalo ka ye bohlokwa ya gore re ka se kgonego ba fela le tsela e tee ya go phela. Setšhaba sa Esihlengeni ka go realo se re fa teori ya ekonomi yeo e theilwego godimo ga bophelo ka moka ga bjona – seo se akaretša bobedi fisikale le metafisikale go kgonthišiša tšwelopele ya bophelo. Bjalo, setšhaba sa Esihlengeni se swanela go tšewa bjalo ka mpho ye e amogelwago. / Ngudo iyi i tandula tshibveleli tsha zwiṱokofela − vhuraḓo ho ḓisendekaho nga zwikimu zwa u vhulunga u itela u dzudzanyea nga tshitshavha na lwa masheleni kha miraḓo khathihi na vhuḓimvumvusi (Lukhele, 1990). Ndivho ya ngudo ndi u topola u vha hone ha tshaka dzo fhambanaho dza ikonomi dzine dza sa ḓivhadzwe nga thevhekano ya pfuma. Ngudo yo pika u ṱola zwithu zwa ndeme zwo tikaho zwiṱokofela na u u wana vhukati hazwo nyimele ya matshilisano na mvelelo kathihi na ḓivhazwakale. Hei ndi ngudo ya ṱhoḓisiso ya ndeme na nyolo ya ṱhoḓisiso yanga yo katela mushumo wa nnḓa, u sedza vhadzheneli, inthaviwu dzo dzhenelelaho na kuitele kwa vhutumbukwa. Ngudo dzi shumisaho ngona idzi, dzo nkonisa u vhona vhuṱumani vhukati ha lushaka lwa ha Khumalo ‒ murafho wa ha Mzilikazi Khumalo we wa vha u khonani dza Khosi Shaka nahone hu pfi wo shela mulenzhe zwihulwane kha u fhaṱa zwi vhidzwaho uri lushaka lwa ha Zulu ṋamusi ‒ na vhomalume anga. Kha miṅwedzi ya rathi ye nda I fhedza ngei Esihlengeni, kuḓana ku re kha ḽa Vryheid, KwaZulu-Natal, ndo inthaviwa vhathu vha 27, nda dzhenela mbulungo mbili, nyitelatherelo nthihi ya muṱa na tshimbidza nyambedzano dza zwigwada zwo sedzaho mbili na vhafumakadzi vha zwiṱokofela. Ndo wana uri zwiṱokofela a zwo ngo ḓisendeka nga muhanga wa nḓivho ya Afrika sa zwe zwa lavhelelwa kha tshitatamende tsha thaidzo fhedzi hu kha ḓi vha nga ngomu ha thevhekano ya pfuma ya u bindula zwenezwo a zwo bvi kha zwithu zwa ndeme zwa sialala zwa tshitshavha. Musi zwiṱokofela zwi tshi ḓivhadzwa nga thevhekano thakhulwa ya pfuma, tshitshavha tsha Esihlengeni tshi kha ḓi dzhia u bva kha kuvhonele kwa mvelo kwa ḽifhasi ku vha ṋekedzaho kupfesesele kwo fhambanaho lwa ikonomi yo ḓisendekaho nga kholomo – nḓila ine ya vha tendela u shuma nyitelatherelo dzavho zwi themendelaho tsireledzo na u bvelaphanḓa ha vhutshilo – u itela u pfesesa ḽifhasi ḽavho. U omelela kha ndeme ya kholomo kha tshitshavha itshi sa tshililo tshavho tsha u tendelwa u vha hone na u dzhielwa nṱha sa vhathu vhane vha kona u ḓihumbulela. Ndi pendela nga u amba uri u itela u pfesesa tshoṱhe tshitshavha itshi ri tea u dzhia kuvhonele kwa zwa mvumbo ro khwaṱhisa uri ri sa tou vha na nḓila nthihi fhedzi ya u vha hone. Tshitshavha tsha Esihlengeni zwenezwo tshi ri fha thyori ya ikonomi yo ḓisendekaho nga vhutshilo ho fhelelaho – hezwo zwi dzhiela nṱha zwa muvhili na zwa khumbulelwa u khwaṱhisedza u bvelaphanḓa ha vhutshilo. Zwenezwo, tshitshavha tsha Esihlengeni tshi tea u dzhiiwa sa tshifhiwa tsho tewaho nga dzindivhuwo. / Anthropology and Archaeology / D. Phil. (Anthropology)