<p>Many flow cases in fluid dynamics face undesirable flow separation due torising static pressure on wall boundaries. This occurs e.g. due to geometry as ina highly curved turbine inlet duct or e.g. on flow control surfaces such as wingtrailing edge flaps within a certain angle of attack range. Here, flow controldevices are often used in order to enhance the flow and delay or even totallyeliminate flow separation. Flow control can e.g. be achieved by using passiveor active vortex generators (VG) that enable momentum mixing in such flows.This thesis focusses on passive VGs, represented by VG vanes that are mountedupright on the surface in wall-bounded flows. They typically have an angle ofincidence to the mean flow and, by that, generate vortex structures that in turnallow for the desired momentum mixing in order to prevent flow separation.A statistical VG model approach, developed by KTH Stockholm and FOI,the Swedish Defence Research Agency, has been evaluated computationally.Such a statistical VG model approach removes the need to build fully resolvedthree-dimensional geometries of VGs in a computational fluid dynamics mesh.Usually, the generation of these fully resolved geometries is rather costly interms of preprocessing and computations. By applying this VG model, thecosts reduce to computations without VG effects included. Nevertheless, theVG model needs to be set up in order to define the modelled VG geometry inan easy and fast preprocessing step. The presented model has shown sensitivityfor parameter variations such as the modelled VG geometry and the VG modellocation in wall-bounded zero pressure gradient and adverse pressure gradientflows on a flat plate, in a diffuser, and on an airfoil with its high-lift systemextracted. It could be proven that the VG model qualitatively describes correcttrends and tendencies for these different applications.</p>

A flutuação na abundância de estoques pesqueiros é tema de investigação científica desde o final do século XIX. A ciência pesqueira se estabeleceu para que se pudesse compreender os impactos da exploração da pesca em recursos naturais renováveis, e, principalmente, para evitar colapsos e preservar as populações exploradas. A principal fonte de dados para investigações pesqueiras são provenientes da própria pesca. Um dos problemas associados à esse fato, é que os pescadores procuram sempre por áreas de alto rendimento, o que faz com que os dados de captura analisados sejam de uma amostra não aleatória. Além disso, entre as diversas espécies que são capturadas, algumas poucas são consideradas alvo da pescaria, enquanto que as demais são chamadas de capturas incidentais. Tudo isso faz com que dados pesqueiros possuam características particulares, como assimetria, excesso de zeros e sobredispersão. Tradicionalmente, estes dados são analisados ignorando-se a estrutura de dependência espacial e temporal, reconhecidamente importante devido a natureza das informações. O objetivo deste trabalho foi então utilizar abordagens estatísticas recentes, que são capazes de lidar com as características desafiadoras de dados pesqueiros. Inicialmente, foram utilizados modelos hierárquicos bayesianos para a modelagem da estrutura temporal da captura de uma espécie. Para esta modelagem, foi utilizado a aproximação de Laplace encaixada e integrada (INLA), um método recente na literatura para realizar inferência no contexto bayesiano através de aproximação, ao contrário dos tradicionais métodos por amostragem. Esta alternativa é computacionalmente mais eficiente, e se mostrou extremamente viável para a análise de dados pesqueiros. Ao final, pode-se concluir que a dependência temporal é de fato importante, e não pode ser ignorada nesse tipo de dado. Seguindo a mesma ideia, foi também desenvolvido um método de estimação em dois estágios para a obtenção dos parâmetros de modelos dinâmicos de biomassa. A estimação em dois estágios permite a consideração de toda a estrutura de dependência espaço-temporal presente nos dados pesqueiros. De fato, os resultados mostraram que quando estas estruturas são levadas em consideração, as estimativas dos parâmetros de interesse são não viesadas e consistentes. Abordagens multivariadas seriam escolhas naturais para a análise da captura de diversas espécies. No entanto, a maioria destas técnicas envolve a suposição de normalidade, o que praticamente torna inviável seu uso em dados de captura. Os Modelos Multivariados de Covariância Linear Generalizada (McGLM) são uma alternativa recente, pois permitem considerar que as respostas possam assumir qualquer distribuição da família exponencial de dispersão. Isso faz com que dados que possuem dependência, excesso de zeros e sobredispersão possam ser considerados de maneira natural. Neste trabalho, os McGLMs foram utilizados para se verificar a influência de um dispositivo que evita a captura incidental de aves, na captura de duas espécies consideradas alvo da pescaria. Com isso, pôde-se concluir que o artefato, comprovadamente eficiente na redução da captura de aves, não diminui a captura das espécies desejadas. / Fluctuation in abundance of fish stocks is scientifically studied since the end of the 19th century. Fisheries science was established to understand impacts of fisheries in renewable natural resources, and mainly to avoid overfishing and to preserve explored populations. The primary data source for fisheries investigation is from fisheries itself. One of the problems associated with this fact is that fishermen are always looking for high productivity areas, which makes catch data a non-random sample. In addition, among many species captured, only a few are considered targets, while the rest are called bycatch. As a consequence, fisheries data presents particular features, such as asymmetry, excess zeros, and overdispersion. It is well known that catches are highly dependent in time and space, however, this spatiotemporal structure is traditionally ignored when analyzing catch data. The aim of this work was then to apply newly developed statistical approaches, capable of handling the challenging features of fisheries data. Initially, the temporal structure of a bycatch species was modeled through Bayesian hierarchical models. The Integrated Nested Laplace Approximation (INLA), a recent method that uses approximation rather than sampling, in the Bayesian framework, was used. This approach is computationally more efficient and turned out to be a quite viable method to analyze fisheries data. As a conclusion, we showed that the temporal dependence is indeed important, and cannot be ignored when analyzing this kind of data. Following the same reasoning, a two-stage approach was developed for the estimation of parameters from biomass dyna- mic models. This two-stage approach allows the inclusion of spatial and temporal effects, inherently present in fisheries data. Results showed that when this structures are considered, parameter estimates are unbiased and consistent. Multivariate statistical methods should be the default approach when analyzing catch data from several species. However, most of this techniques are based on the normality assumption, which makes it of little use for catch data. The recently developed Multivariate Covariance Generalized Linear Models (McGLM) assumes that response variables could follow any distribution from the exponential dispersion family. This flexibility allows that data with both overdispersion and excess zeros may be modeled in a natural way. In this work, McGLMs were used to assess the influence of a device used to prevent seabird bycatch, in two target species captures. As a conclusion, we showed that the device does not interfere in the catch of targeted species.

Die Blockgletscher der trockenen Anden sind weitverbreitete Oberflächenformen sowie bedeutende Bodeneisvorkommen. In der vorliegenden Arbeit werden statistische Modellierungen und geomorphologische Kartierungen durchgeführt, um die Verbreitung dieser Formen in den Anden von Zentralchile (27-36° s.Br.) in ihrem Bezug zu Klima und Topographie zu quantifizieren und analysieren. Eine stichprobenbasierte statistische Erhebung und eine logistische Regressionsmodellierung wurden durchgeführt, um in den Anden von Santiago (33-34,5° s.Br.) Verbreitungsmuster quantitativ zu schätzen und die geomorphologische Nische von Blockgletschern unter Verwendung von digitalen Geländemodellen zu charakterisieren. Das in Blockgletschern der Anden von Santiago gespeicherte Wasseräquivalent von 0,7-1,1 km³ je 1000 km² Gebirgsfläche ist um eine Größenordnung größer als in den Schweizer Alpen. Mindestens ein Fünftel der Hochgebirgsfläche der Anden von Santiago wird durch Blockgletscher hindurch entwässert. Dies unterstreicht die Bedeutung von Blockgletschern im andinen hydrologischen System und Schutttransportsystem. Die optimale Blockgletschernische der Anden von Santiago besitzt ein konvergierendes Einzugsgebiet von etwa 0,5-1 km² Fläche sowie rezente mittlere Jahrestemperaturen von +1 bis -1°C in 3500-3800 m Höhe. Unter günstigen morphographischen und topoklimatischen Bedingungen reichen intakte Blockgletscher bis 3000 m Höhe hinab. Das überregionale Verbreitungsmuster wird gesteuert durch Niederschlag, Vergletscherung, Topographie und Vulkanismus. Diese Faktoren wirken in Kombination auch an der nördlichen und südlichen Verbreitungsgrenze der Blockgletscher des Winterregengebiets bei 27° bzw. 35° s.Br. Die Verwendung der Blockgletscher-Sedimentbilanzen zur Abschätzung von holozänen Denudationsraten sowie von Blockgletschern als Permafrostindikatoren vermittelt weitere Einblicke in die Umweltverhältnisse der zentralchilenischen Anden. / Rock glaciers are ubiquitous landforms in the dry Andes, and significant, but unheralded stores of frozen water. In this study, statistical modelling techniques and geomorphological mapping are applied to quantify and analyze the distribution of rock glaciers in the Andes of Central Chile (27-35°S) as related to climate and topography. A statistical sample survey and a logistic regression model were designed to quantitatively estimate distribution patterns and characterize the geomorphological niche of rock glaciers in the Andes of Santiago (33-34.5°S) based upon digital elevation models. The amount of water stored within rock glaciers of the Andes of Santiago per unit area is by one order of magnitude higher than in the Swiss Alps, reaching an average 0.7-1.1 km³ of water equivalent per 1000 km² in the Andes. At least one fifth of the high-mountain area of the Andes of Santiago drains through intact rock glaciers. This underlines the importance of rock glaciers within the Andean hydrological and debris-transport system. The optimal rock glacier niche in the Andes of Santiago has a convergent contributing area of 0.5-1 km² and modern mean annual air temperatures of +1 to -1°C, corresponding to 3500-3800 m a.s.l. Intact rock glaciers reach down to 3000 m a.s.l. under favorable topographic and topoclimatic conditions. The supra-regional distribution pattern is influenced by precipitation, glaciation, topography and volcanism. These act as combined controls at the northern (27°S) and southern (35°S) limit of rock glacier occurrence in the Chilean area of winter precipitation. Rock glacier sediment budgets revealing Holocene denudation rates, and the use of rock glaciers as permafrost indicators give further insight into the periglacial environment of the Andes of Central Chile.

Idéalement située à la confluence entre climat tropical et climat tempéré, l'Afrique australe est une zone très sensible aux variations des conditions climatiques. Cette région fait cependant preuve d'un manque de données paléoclimatiques important, et les méthodes de reconstruction traditionnelles trouvent rapidement leurs limites face aux conditions particulières qui y sévissent. Les méthodes de reconstruction quantitatives communément employées se révèlent inutilisables face aux conditions d'aridité extrêmes qui ne permettent que très rarement l'accumulation et la préservation de pollen moderne et fossile et se confrontent également aux particularités de la végétation abritée par cette région. L'objectif de ces travaux de thèse vise à développer une méthode de reconstruction quantitative basée sur des données polliniques fossiles, à partir de la relation entre la distribution actuelle des taxons polliniques et le climat en Afrique australe. Nous avons développé une fonction de transfert utilisant les propriétés des fonctions de densité de probabilité (pdfs), permettant de transformer l'information contenue dans un assemblage pollinique en estimation quantitative du climat. En parallèle, cette étude a permis de développer une méthode permettant de sélectionner les espèces les plus probables à inclure dans chaque type pollinique qui compose un assemblage. Cette méthode de sélection des espèces (SSM) a permis de pallier la faible résolution taxonomique des données polliniques de cette région caractérisée par une biodiversité élevée et d'affiner la méthode des espèces indicatrices, afin de la rendre utilisable en Afrique australe. Cette méthodologie a été appliquée aux données polliniques du site de Wonderkrater (Afrique du Sud). Les résultats observés et leur comparaison avec ceux provenant de sites régionaux ont permis de déterminer que les températures estivales et hivernales étaient 6±2°C inférieure au cours du LGM et du Younger Dryas et que les précipitations au cours de la saison humide étaient 50% moins importantes qu'actuellement. Ces résultats montrent que les SST enregistrées dans le canal du Mozambique régissent les conditions hydrologiques du continent adjacent, en opposition avec la possible implication de l'ITCZ sous ces latitudes. Les résultats indiquent également que les deux tropiques montrent des tendances climatiques similaires au cours des derniers 20 000 ans. La méthode a ensuite été appliquée à un enregistrement pollinique provenant de la région du fynbos (Afrique du Sud). Les résultats ont montré les limites de la méthode au vu de la faible amplitude de reconstruction obtenue pour les températures entre le LGM et l'Holocène (~2°C). Les résultats ont néanmoins permis de mettre en évidence que les températures montraient un pattern similaire à celui observé en Antarctique. Nous avons également pu montrer que les périodes glaciaires coïncidaient avec les périodes les plus humides, en accord avec le modèle de Cockroft (1987). Ce modèle dérive du mécanisme de migration des « westerlies » vers l'équateur au cours des périodes glaciaires, en réponse au déplacement du vortex circcum polaire. Les travaux issus de cette thèse ont montré qu'il était possible d'utiliser la distribution actuelle des plantes pour estimer les variations quantitatives des changements climatiques passés, dans la plupart des configurations botaniques et climatiques rencontrées en Afrique australe. La méthode de sélection des espèces se révèle être un outil indispensable dans cette région de haute biodiversité. Ces travaux offrent des perspectives intéressantes dans cette zone actuellement dépourvue de reconstructions climatiques quantitatives. Cependant, les résultats émanant des deux cas d'études ont mis en évidence des faiblesses et des limites méthodologiques qui devront faire l'objet d'études supplémentaires afin d'en améliorer les performances. / Located at the interface between tropical and temperate climate systems, southern Africa is a particularly sensitive region in terms of long-term climate change. However, few reliable paleoclimatic records exist from the region – largely as a result of the arid climate with precludes the preservation of wetland sequences - , and virtually no quantitative reconstructions are available.The aim of this thesis is to develop quantitative palaeoclimate reconstruction method based the relation between modern plant distributions and climate in southern Africa. We develop botanical-climatological transfer functions derived from probability density functions (pdfs), allowing for quantitative estimates of the palaeoclimatic variables to be calculated from fossil pollen assemblages. In addition, a species-selection method (SSM) based on Bayesian statistics is outlined, which provides a parsimonious choice of most likely plant species from what are otherwise taxonomically broad pollen-types. This method addresses limitations imposed by the low taxonomic resolution of pollen identification, which is particularly problematic in areas of high biodiversity such as many regions of southern Africa.This methodology has been applied to pollen record from Wonderkrater (South Africa). Results indicate that temperatures during both the warm and cold season were 6±2°C colder during the Last Glacial Maximum and Younger Dryas, and that rainy season precipitation during the Last Glacial Maximum was ~50% of that during the mid-Holocene. Our results also imply that changes in precipitation at Wonderkrater generally track changes in Mozambique Channel sea-surface temperatures, with a steady increase following the Younger Dryas to a period of maximum water availability at Wonderkrater ~3-7 ka. These findings indicate that the northern and southern tropics experienced similar climatic trends during the last 20 kyr, and highlight the role of variations in sea-surface temperatures over the more popularly perceived role of a shifting Intertropical Convergence Zone in determining long-term environmental trends.This method has also been applied to a pollen record from Pakhuis Pass, in the Fynbos Biome (South Africa). Results show the limitations of quantitative methods, with only unrealistically low amplitude being reconstructed between the Last Glacial Maximum and Holocene (~2°C). However, results indicate that the reconstructed temperature trends, if not amplitudes, are similar to trends observed in Antarctic ice core records. Further, in reconstructing past humidity, we show that over the last 18 kyr, cooler conditions appear to be generally wetter at the site. These results are consistent with Cockcroft model (1987), derived from equatorward shift of the westerlies resulting from expansions of the circum-polar vortex.This study shows the potential of using modern plant distributions to estimates past climate parameters in southern Africa, and the species selection method proves to be a useful tool in region with high biodiversity. This work provides a novel perspective in the region, where no quantitative paleoclimatic reconstructions have been available. However, results from Pakhuis Pass highlight some of the limitations of this methodology, which will be subject of future work in this promising field of inquiry.

Le multiparasitisme et surtout les associations qui en découlent, ont une grande influence sur l’écologie des parasites concernés. Elle est d’autant plus grande que les parasites peuvent interagir et ainsi modifier leurs effets sur les hôtes. Cependant, l’identification des associations et interactions de parasites est complexe au niveau populationnel. Notre objectif était de modéliser les associations et les interactions multiparasitaires, notamment dans le cadre des parasites d’importance médicale, vétérinaire ou agronomique. Nous avons tout d’abord réalisé une revue bibliographique sur les différentes causes et conséquences du multiparasitisme ainsi que sur les méthodes et outils disponibles pour comprendre les phénomènes qui le génèrent. Dans un second temps, nous nous sommes intéressés tout particulièrement à la détection des associations multiparasitaires. Nous avons développé une nouvelle méthode « de screening des associations » pour tester statistiquement la présence d’associations de parasites à une échelle globale. Nous avons utilisé cette méthode pour identifier les associations et pour révéler précisément les parasites associés au sein de diverses populations d’hôtes. Puis, nous avons étudié les interactions entre les parasites. Nous avons développé un modèle pour identifier les interactions entre deux parasites vectorisés et persistants chez un hôte, à partir de données issues d’études transversales. L’une des voies de progression de la connaissance sur les interactions est la prise en compte des facteurs de risque communs. La prise en compte des interactions contribue à améliorer le diagnostic, les traitements et la prévention des maladies infectieuses. / Multiparasitism and specifically statistical associations among parasites, have a strong influence on the ecology of parasites. This influence reinforced when parasites interact and thus modify their effect on hosts. However, the identification of associations and interactions between parasites is complex at the population level. Our aim was to model multi-parasite associations and interactions, in particular for parasites of medical, veterinary or agricultural importance. We first present a review of the literature on the different causes and consequences of multiparasitism and the methods and tools available to better understand the phenomena that generate them. In a second step we worked on the detection of multi-parasite associations. We developed a new approach « association screening » to statistically test the presence of multi-parasite associations on a global scale. We used this method to identify associations and to reveal precisely associated parasites in different host populations. Then, we focused on the study of interactions between parasites. We developed a model to identify the interactions between two vector-borne and persistent parasites in a host, using data from cross-sectional studies. One way to increase our capacity to detect parasite interactions in populations is the taking into account common risk factors. Taking into account interactions increases diagnosis, treatments and prevention of infectious diseases.

Vehicles being driven for work purposes represent a large proportion of road collision and deaths in the workplace. These observations mean that people driving for work can impose a large burden on organisations and on society. In addition, previous studies identified a fleet driver effect for which there was greater collision risk for those who drive for work compared to the general driving population, even after controlling for exposure. This accentuates the need for both organisational and government policy makers to take steps to reduce the impact of these collisions. No single intervention has been found to solve issues around work-related road safety therefore a range of initiatives have been directed towards the risks associated with drivers, vehicles, journeys and organisations. Many of the interventions, however, lack robust evidence to support their use. The aim of this thesis is to assess organisational interventions to improve work-related road safety by using econometric models on real-world data. The data represents driving claims made between 2005 and 2012 by employees of a large UK company, with a fleet of approximately 35,000 vehicles. The drivers were employed in a variety of roles such as working in technical positions at customer sites or making sales visits. The company has applied a range of strategies to road safety resulting in annual claim reductions of 7.7% compared to only a 4.5% reduction in collisions nationally. The company s data are used to undertake three studies which focused on driver training, manager training and claim segmentation. Statistical models were employed to investigate the effect of two different driver training courses on the frequency of claims while controlling for other factors. The results indicated that driver training courses significantly reduced both the total number of claims and the claim types targeted by the training. The impacts of the interventions were also adjusted for the effects of non-random driver selection and other safety improvements initiated by the company or other agencies. An important finding of this work was that randomly inflated pre-training events accounted for between a third and a quarter of the observed reduction in claims following training. The second study evaluated the impact of management training on claims using multilevel models which allowed for correlation between observations. The study could not confirm that this training was an effective safety intervention. This null result provides an incentive to re-evaluate the implementation of the scheme. The final study identified homogeneous claim segments using statistical models and the impact of training was evaluated on these segments. Such claims were estimated to be reduced by between 32% to 55% following existing driver training courses. This thesis has helped close important gaps and contributed to knowledge in terms of both intervention methodology and the understanding of the effectiveness of work-related road safety interventions. The results, which are already being applied in the case study organisation, demonstrated that training employees in either safe and fuel efficient driving, or low speed manoeuvring, reduced vehicle insurance claims. Further work is necessary to verify the safety value of manager training including gathering detailed information on interactions between managers and drivers.

In geosciences modelling is rather quickly developing discipline. Statistical modelling of landslide susceptibility is relatively more traditional approach. Nevertheless, more complicated statistical methods are being developed and applied on larger areas. This development is caused especially by increasing computational capacity and software. This diploma thesis summarises existing statistical landslide susceptibility modelling approaches. In the following part, several landslide susceptibility models were created for the area of Czechia. These models were created using logistic regression, naive Bayes and artificial neural network (ANN). Additionally, two more models were created using expert driven approach. All models were made using thirteen conditioning factors, i.e.elevation, slope, engineering geological regions, climatic areas, mean annual precipitation, topographic wetness index (TWI), aspect, orogenetic class, distance from confirmed fault, distance from watercourse, internal relief, land cover and slope shape. Models driven by statistical approach were created using Orange software. Landslide inventories that were used for construction of all models are based on two databases: "Registr svahových nestabilit" and "Registr sesuvů-Geofond". Using validation by SRC, PRC and ROC curves...

With code division multiple access (CDMA) systems being the prominent multiple access scheme for the air interface for 3G cellular systems, most standardisation bodies have based their terrestrial cellular systems on DS-CDMA (W-CDMA, UMTS, cdma2000). With 4G systems fast approaching, bringing with them improved services and quality of service standards, there is growing interest in further investigating and developing more efficient multiple access techniques such as multicarrier CDMA (MC-CDMA) systems. MC-CDMA combines multicarrier modulation (MCM), namely OFDM, with CDMA profiting from the benefits of both multiplexing techniques; as such, MC-CDMA is emerging as a possible candidate for the air interface multiple access scheme for 4G cellular systems. Multiple access interference (MAI) is a limiting factor of CDMA systems in terms of system capacity as orthogonally designed spreading sequences lose their orthogonality in the presence of timing misalignments amongst mobile subscribers in a cell; such is the case over the uplink channel. Ensuring orthogonal code properties minimises the MAI over synchronous environments, however, it is when the users are allowed to transmit asynchronously, as is the case over the uplink channel, that MAI inflicts significant performance degradation. In CDMA systems, all subscribers are active on the same frequency band simultaneously and signal separation is facilitated upon reception via the properties of the assigned spreading codes. Under asynchronous conditions the code properties alone do not provide the necessary separation and an additive MAI term remains in the detection process. In addition to the separation abilities of the spreading codes, a further method of deciphering the desired subscriber signal from the interfering subscriber signals is sought. In this thesis we propose a statistical model for both the probability density function (pdf) of the total MAI power and the corresponding bit-error rate (BER) observed during asynchronous CDMA transmission. The modelling offers the full statistic the MAI power and resulting BER, not just the first and second order statistics. In addition to statistically quantifying the MAI power, the thesis also proposes a technique for the successful reduction of MAI caused by asynchronous transmission. This interference reduction technique is derived from an ambiguity domain analysis of the asynchronous CDMA detection problem and its application to both the DS-CDMA and MC-CDMA multiplexing techniques is presented and the results show significant MAI reduction, and thus an improved the BER. A methodology for the approximation of the total MAI power pdf and the resulting BER pdf is proposed for the asynchronous DS-CDMA and MC-CDMA techniques. This methodology is derived for the use of Walsh-Hadamard (WH) and Gold spreading sequences, however, it is applicable to any given set of deterministic spreading sequences. The total MAI power pdfs of both systems are statistically modelled as being Nakagamim distributed and the corresponding BER modelling is derived from the Nakagami-m formulation offering the full statistic of both the incurred MAI power and the achievable BER. The proposed pdf acquisition methodology and statistical models can be used as analysis tools to assess the relative performances of the DS-CDMA and MC-CDMA techniques for a variety of communications environments. Here the asynchronous uplink channel is considered in the absence of fading and the results show a clear distinction between the BER performances of the MC-CDMA and DS-CDMA systems, for which the MC-CDMA system offers a superior performance for the purely asynchronous channel considered. The results suggest a higher resistance to MAI in the MC-CDMA technique in comparison to the DS-CDMA system for the considered transmission scenario. Following ambiguity function analysis of the asynchronous CDMA detection problem, the concept of dual-frequency switching is introduced to the existing DS-CDMA and MC-CDMA techniques giving rise to the proposed dual-frequency DS-CDMA (DF/DSCDMA) and dual-frequency MC-CDMA (DF/MC-CDMA) schemes. Periodically switching the carrier frequency between dual frequency bands at consecutive symbol boundaries facilitates partial CDMA signal separation upon asynchronous reception. Such switching of the carrier frequency induces a separation in frequency between offset interference signals and the reference signal; this is equivalent to shifting the energy concentration of the interference signals away form the ambiguity domain origin (representing the decision variable of the matched filter). Further MAI reduction is demonstrated through careful design of the dual carrier frequencies. The newly proposed DF systems clearly outperform the standard DS-CDMA and MC-CDMA systems when adopting equivalent spreading factors. The DF/DS-CDMA technique in particular achieves the most MAI reduction and in doing so, surpasses all other considered techniques to offer the best BER performance for the purely asynchronous channel considered. In terms of bandwidth usage, the DF/DS-CDMA band width is 1.5 times that of the DF/MC-CDMA system and from the BER results presented, one may argue that DF/MC-CDMA offers the better BER given the bandwidth usage. The multicarrier systems presented, MC-CDMA and DF/MC-CDMA, offer attractive BER performances for the bandwidth used and it is concluded that MC-CDMA is a genuine candidate for the uplink air interface multiple access scheme for future mobile cellular technologies.

Ce travail de thèse concerne le développement d'une méthode de pronostic de défaillance des systèmes de production en série. Une méthode de génération d'un indice de santé brut à partir d'un tenseur de données, appelée Méthode des Points Significatifs a été développée puis validée sur un exemple d'illustration. L'indice généré est ensuite traité par une nouvelle méthode appelée méthode des percentiles, qui permet de générer des profils monotones à partir d'un indice de santé brut. Les profils générés sont ensuite modélisés par un processus Gamma, et la fonction de densité de probabilité agrégée introduite dans ce travail a permis d'estimer le temps de vie résiduel (Remaining Useful Life (RUL)) dans un intervalle de confiance qui assure une marge de sécurité à l'utilisateur industriel. La méthode proposée est appliquée avec succès sur des données expérimentales issues des équipements de production industrielle. / This thesis develops a fault prognosis approach for Discrete Manufacturing Processes. A method of raw health index extraction from a data tensor, called Significant Points was developped and validated on an illustrative example. The generated index is later processed by a new method, called Percentile Method, which allows to generate the monotonic profiles from the raw health index. These profiles are then modelled by a Gamma process, and the aggregate probability density function introduced in this work allowed to estimate the Remaining Useful Life (RUL) in a confidence interval that ensures a safety margin for industrial users. The proposed method is applied successfully on the experimental data of industrial production machines.

Many flow cases in fluid dynamics face undesirable flow separation due torising static pressure on wall boundaries. This occurs e.g. due to geometry as ina highly curved turbine inlet duct or e.g. on flow control surfaces such as wingtrailing edge flaps within a certain angle of attack range. Here, flow controldevices are often used in order to enhance the flow and delay or even totallyeliminate flow separation. Flow control can e.g. be achieved by using passiveor active vortex generators (VG) that enable momentum mixing in such flows.This thesis focusses on passive VGs, represented by VG vanes that are mountedupright on the surface in wall-bounded flows. They typically have an angle ofincidence to the mean flow and, by that, generate vortex structures that in turnallow for the desired momentum mixing in order to prevent flow separation.A statistical VG model approach, developed by KTH Stockholm and FOI,the Swedish Defence Research Agency, has been evaluated computationally.Such a statistical VG model approach removes the need to build fully resolvedthree-dimensional geometries of VGs in a computational fluid dynamics mesh.Usually, the generation of these fully resolved geometries is rather costly interms of preprocessing and computations. By applying this VG model, thecosts reduce to computations without VG effects included. Nevertheless, theVG model needs to be set up in order to define the modelled VG geometry inan easy and fast preprocessing step. The presented model has shown sensitivityfor parameter variations such as the modelled VG geometry and the VG modellocation in wall-bounded zero pressure gradient and adverse pressure gradientflows on a flat plate, in a diffuser, and on an airfoil with its high-lift systemextracted. It could be proven that the VG model qualitatively describes correcttrends and tendencies for these different applications.