Thesis (doctoral)--Universität Bern.

Multiple-InputMultiple-Output (MIMO) systems promise higher data rates and better quality of service for wireless communications, by using multiple antennas at both the transmitter and receiver. However, applying MIMO technology at small portable wireless devices is faced with the problem of mutual coupling between antenna elements due to the limited space to put multiple antennas. It is shown in the literature that the mutual coupling degrades the MIMO performance. For a given channel matrix and a known mutual coupling model, using antenna impedance matching network(s) between the coupled antenna array and its load or source network is proposed by recent studies to counteract the mutual coupling effects and maximise the MIMO performance. There are two issues with the existing matching techniques. First, they employ a model based on open-circuit voltages that separates the channel matrix and the mutual coupling model. This model is not valid except for a limited types of antennas (e.g. half-wavelength dipoles). Secondly, there is no solution among existing approaches that are capable of adapting to variations of the channel matrix. This thesis focuses on the mutual coupling problem at the receiver. We first examine the most common approaches to model the mutual coupling. For instance, we compare various definitions of coupling matrix available in the literature, analyse their relationship and clarify when we can use them. The mutual coupling effects on MIMO performance metrics and impedance matching are also investigated using the conventional open-circuit voltage based model and a new method called receiving mutual impedances. Then we propose the idea of having an adaptive uncoupled impedance matching technique which tunes the antenna impedance loads to compensate the effects of the propagation channel and mutual coupling together by directly dealing with the received signals. The mutual coupling model is unknown, but it is included implicitly by using the voltages across the real parts of the antenna load impedances to estimate the total effects. Assuming identical impedance loads for all receive antennas, several optimisation techniques such as Gradient-based, Newton-Raphson, and random search methods are investigated to implement such an adaptive impedance match. We found the random search method to be a simple and robust solution in comparison to other approaches. Finally, we extend this adaptive matching technique to non-identical termination case, in which all load impedances are tuned individually. The performance of the adaptive matching networks are compared with the conventional termination scenarios such as: characteristic impedance match, and self-impedance conjugate match. Simulation results for a 3 × 3 MIMO system under different propagation scenarios show that both identical and non-identical adaptive impedance matching networks are capable of optimising the performance in the presence of strong mutual coupling and time variations of the channel. The adaptive non-identical match gives a significant improvement in the mean capacity (more than 20% compared to conventional terminations for 0.05λ element separation) at the expense of a longer convergence time compared to the identical match.

Recently, schema matching has found considerable interest in both research and practice. Determining matching components of database or XML schemas is needed in many applications, e.g. for E-business and data integration. Various schema matching systems have been developed to solve the problem semi-automatically. While there have been some evaluations, the overall effectiveness of currently available automatic schema matching systems is largely unclear. This is because the evaluations were conducted in diverse ways making it difficult to assess the effectiveness of each single system, let alone to compare their effectiveness. In this paper we survey recently published schema matching evaluations. For this purpose, we introduce the major criteria that influence the effectiveness of a schema matching approach and use these criteria to compare the various systems. Based on our observations, we discuss the requirements for future match implementations and evaluations.

Lorsque les joueurs de football réalisent plus d’un match par semaine, la durée de récupération entre deux rencontres successives pourrait être insuffisante, ce qui entraînerait une augmentation du nombre de blessures et/ou une diminution de la performance en match. L’objectif principal de cette thèse était d’identifier les facteurs (environnementaux, intrinsèques, position sur le terrain) susceptibles d’influencer la fatigue et les cinétiques de récupération de joueurs de football professionnels après un match. La présente thèse comprenait quatre études ayant pour objectifs d’analyser l’influence des courses et actions de jeu réalisées au cours d’un match (duel, saut, frappe/centre, tacle, changement de direction) ainsi que la surface de jeu (herbe naturelle contre surface synthétique) sur les cinétiques de récupération de marqueurs de performance physique, cognitive, subjectifs et biochimiques. Nos résultats ont montré que les courses réalisées au cours d’un match de football ne sont pas la cause principale de la fatigue générée par le match. Cette fatigue est également fonction des actions de jeu (duel, saut, frappe et changement de direction) réalisées au cours du match. La fatigue générée par le match est fonction de la position occupée sur le terrain (gardiens de but contre joueurs de champ). La surface de jeu n’influence pas les cinétiques de récupération de joueurs habitués à la surface synthétique. Ces résultats devraient permettre d’optimiser dans le futur les stratégies de récupération réalisées après le match. / During periods when the schedule is particularly congested (i.e. two matches per week over several weeks), the recovery time allowed between two successive matches may be insufficient. As a result, players may experience underperformance and/or injury. The overall aim of the present thesis was to identify underlying factors (environmental and intrinsic factors, playing position) that contribute to fatigue and recovery time of professional soccer players after a match. Four experimental studies were conducted to investigate the influence of soccer running activity profile, playing actions performed during a match (i.e. contact, jump, shot/long pass, tackle, change of direction) and playing surface (natural grass versus artificial turf) on the recovery kinetics of physical performance, cognitive performance, subjective ratings and biochemical parameters. Results showed that soccer running performance does not appear to be the main cause for post soccer match-induced fatigue. Post-match fatigue and recovery time depend on playing actions performed during the match (contact, jump, shot/long pass and change of direction). Post-match fatigue depends on playing position (goalkeepers versus outfield players). Playing surface does not impact recovery kinetics among regular artificial turf players. Present results may promote the prescription of more efficient and individualized recovery practices after soccer match.

This chapter presents the generic schema match system, COmbination MAtch (COMA), which provides an extensible library of simple and hybrid match algorithms and supports a powerful framework for combining match results. The user can tailor match strategies by selecting the marchers and their combination for a given match problem. Hybrid matchers can also be configured easily by combining existing matchers using the provided combination strategies. Schema matching is the task of finding semantic correspondences between elements of two schemas. It is needed in many database applications, such as integration of web data sources, data warehouse loading, and XML message mapping. To reduce the amount of user effort as much as possible, automatic approaches combining several match techniques are required. While such match approaches have found considerable interest recently, the problem of how to best combine different match algorithms still requires further work.

In this study, we apply the streamline-based production data integration method to condition a multimillion cell geologic model to historical production response for a giant Saudi Arabian reservoir. The field has been under peripheral water injection with 16 injectors and 70 producers. There is also a strong aquifer influx into the field. A total of 30 years of production history with detailed rate, infill well and re-perforation schedule were incorporated via multiple pressure updates during streamline simulation. Also, gravity and compressibility effects were included to account for water slumping and aquifer support. To our knowledge, this is the first and the largest such application of production data integration to geologic models accounting for realistic field conditions. We have developed novel techniques to analytically compute the sensitivities of the production response in the presence of gravity and changing field conditions. This makes our method computationally extremely efficient. The field application takes less than 6 hours to run on a PC. The geologic model derived after conditioning to production response was validated using field surveillance data. In particular, the flood front movement, the aquifer encroachment and bypassed oil locations obtained from the geologic model was found to be consistent with field observations. Finally, an examination of the permeability changes during production data integration revealed that most of these changes were aligned along the facies distribution, particularly the 'good' facies distribution with no resulting loss in geologic realism. We also propose a novel assisted history matching procedure for finite difference simulators using streamline derived sensitivity calculations. Unlike existing assisted history matching techniques where the user is required to manually adjust the parameters, this procedure combines the rigor of finite difference models and efficiencies of streamline simulators to perform history matching. Finite difference simulator is used to solve for pressure, flux and saturations which, in turn, are used as input for the streamline simulator for estimating the parameter sensitivities analytically. The streamline derived sensitivities are then used to update the reservoir model. The updated model is then used in the finite difference simulator in an iterative mode until a significant satisfactory history match is obtained. The assisted history matching procedure has been tested for both synthetic and field examples. The results show a significant speed-up in history matching using conventional finite difference simulators.

A Thesis submitted to The University of Arizona College of Medicine - Phoenix in partial fulfillment of the requirements for the Degree of Doctor of Medicine.

No description available.

Cette thèse s’intéresse à l’histoire des allumettières de la E.B. Eddy Match de Hull des années 1850 jusqu’au déménagement de l’entreprise, en 1928. Pendant plus de sept décennies, des centaines de femmes s’affairent à la confection d’allumettes, ce bien nécessaire à tous quotidiennement. L’expérience des ouvrières employées par le plus grand producteur de cette industrie au Canada se définit par leurs conditions de vie et de travail difficiles. Bien que des améliorations s’observent au fil des ans, particulièrement à l’intérieur de la fabrique, la pauvreté de la classe ouvrière et les dangers de l’emploi restent une réalité bien présente. Pour mener à bien cette recherche, nous proposons dans un premier temps un examen de celles qui composent cette main-d’œuvre. En nous appuyant principalement sur les données du recensement canadien, nous examinons le portrait démographique et la situation socio-économique des allumettières, en plus de leur apport à la survie familiale. De ce fait, nous soulevons pourquoi le poids économique des jeunes filles et des femmes s’avère non négligeable pour de nombreux ménages dans un contexte de précarité qui touche l’ensemble de la classe populaire. Dans un deuxième temps, les conditions de travail sont observées. En utilisant l’exemple de l’emploi du phosphore blanc dans la confection d’allumettes, nous abordons les risques du métier présents au cours du 19e siècle jusqu’au début des années 1910. Alors que la substance est retirée du processus de production, d’autres dangers subsistent. Les conditions de travail dans les années 1920 subissent certaines avancées, mais restent généralement précaires. Les heures de travail sont réduites, mais les salaires n’augmentent pas nécessairement. La syndicalisation des travailleuses amène quelques progrès et laisse voir la volonté d’implication des allumettières dans le mouvement ouvrier catholique. Toutefois, l’expérience se termine par un échec et cause fort probablement le départ de la compagnie en 1928.

Spatial data occurs in several important and diverse applications in P2P systems, for example, P2P virtual cities, GIS, development planning, etc. For the problem of answering exact queries for spatial region data in the P2P environment, an R¡Vtree based structure probably is a good choice. However, since a peer system is dynamic, the global update characteristics of data insertion/deletion in an R¡Vtree can not work well in a P2P system. Moreover, the problem of overlaps in an R¡Vtree results in large number of the disk accesses (which will be considered as large number of messages in P2P systems). Therefore, a P2PR¡Vtree based indexing method for P2P systems has been proposed which has only local update to the proposed index structure when data insertion/deletion occurs. Although the P2PR¡Vtree can achieve the goal of the local update for data insertion/deletion, the overlapping phenomenon is still hard to solve. Recently, for region data access, an NA¡Vtree has been proposed which outperforms R¡Vtree¡Vlike data structures. Moreover, it does not have the problem of overlaps which may occur in an R¡Vtree. Basically, an NA¡Vtree does not split the spatial space, but it just classifies the spatial data objects by some rules. On the other hand, the Chord system is a well¡Vknown structured P2P system in which the data search is performed by a hash function, instead of flooding used in most of the unstructured P2P system. Since the Chord system is a hash approach, it is easy to deal with data insertion/deletion with only local update. However, the current Chord system can not work well with the region data, since it only works well with a single key value. Therefore, in this thesis, we propose to apply an NA-tree in the Chord system to encode spatial region data in the data key part used in the hash function to data search. That is, we still use one hash function of Chord to assign nodes to peers, and use another hash function to do data assignment by applying an NA¡Vtree to encode the spatial region data to data keys. First, we use three bits to present the first eight children in the NA¡Vtree. Next, we propose two methods to generate the key value of the remaining bits. For our first proposed method, it generates the remaining bits by adding 0¡¦s. This method is simple and applicable to the case that there are few objects in P2P systems. To avoid the case that a peer may own too many objects, the second method takes the central points of regions into consideration. This method is applicable to the case that there are too many objects in the P2P system. Finally, we concatenate the first three and the remaining bits to get the key values of objects. Thus, we combine the NA¡Vtree with the Chord system to solve the overlapping problem which the P2PR¡Vtree can not deal with. In our simulation study, we use six different data distributions to compare our method with the P2PR¡Vtree. From our simulation results, we show that the number of visited peers in our approach is less than that in the P2PR¡Vtree.