La scoliose idiopathique de l’adolescence (SIA) est une pathologie de cause inconnue impliquant une déformation tridimensionnelle de la colonne vertébrale et de la cage thoracique. Cette pathologie affecte, entre autres, les vertèbres ainsi que les muscles paraspinaux. Ces composantes de la colonne vertébrale jouent un rôle important lors de la marche. Dix sujets témoins et neuf sujets SIA ont effectué dix essais de marche à vitesse normale sur un corridor de marche de dix mètres dans lequel était inséré deux plates-formes de force. De plus, un système de huit caméras (VICON) a permis de calculer les coordonnées tridimensionnelles des 30 marqueurs utilisés afin d’analyser la cinématique des sujets. Les variables faisant l’objet de cette étude sont les amplitudes totales, minimales et maximales des rotations des ceintures pelvienne et scapulaire dans les plans transverse et frontal de même que les coefficients de corrélation et de variation de ces segments. Des tests de Student ont été utilisés pour l’analyse statistique. Malgré le fait qu’aucune différence significative n’a été observée, dans aucun des plans, entre les amplitudes des rotations des ceintures pelvienne et scapulaire entre les groupes témoin et SIA, une différence significative en ce qui a trait aux minimums de rotations pelviennes et scapulaires, dans le plan transverse, a été observée. Cette différence suggère une asymétrie dans les rotations effectuées par ces segments à la marche à vitesse naturelle chez une population atteinte de SIA. / Idiopathic scoliosis is a tridimensional deformation of the spine and of the rib cage. The cause of this pathology is still unknown but its consequences affected different structures including vertebras and spinal muscles. These structures are essential in locomotion activities and this is why it is important to understand well consequences of having a scoliosis on walking. Ten control subjects and nine scoliotic subjects were asked to do ten walking trials at natural speed on a ten-meter walkway with two embedded force-plates. A 3D system (VICON) was also used to record kinematics of 30 body markers. Total, minimal and maximal range of motion (ROM) of pelvic and shoulder rotations, coefficients of variation and correlation were points of interest of this study. Student tests were used to compare groups. No statistically significant difference was observed between group’s total ROM in any planes but some differences were noticed between minimal ROM in coronal plane for pelvis and shoulders. That suggests an asymmetric rotation during natural speed walking in scoliotic group.

In speech communication systems such as voice-controlled systems, hands-free mobile telephones and hearing aids, the received signals are degraded by room reverberation and background noise. This degradation can reduce the perceived quality and intelligibility of the speech, and decrease the performance of speech enhancement and source localization. These problems are difficult to solve due to the colored and nonstationary nature of the speech signals, and features of the Room Impulse Response (RIR) such as its long duration and non-minimum phase. In this dissertation, we focus on two topics of speech enhancement and speaker localization in noisy reverberant environments. A two-stage speech enhancement method is presented to suppress both early and late reverberation in noisy speech using only one microphone. It is shown that this method works well even in highly reverberant rooms. Experiments under different acoustic conditions confirm that the proposed blind method is superior in terms of reducing early and late reverberation effects and noise compared to other well known single-microphone techniques in the literature. Time Difference Of Arrival (TDOA)-based methods usually provide the most accurate source localization in adverse conditions. The key issue for these methods is to accurately estimate the TDOA using the smallest number of microphones. Two robust Time Delay Estimation (TDE) methods are proposed which use the information from only two microphones. One method is based on adaptive inverse filtering which provides superior performance even in highly reverberant and moderately noisy conditions. It also has negligible failure estimation which makes it a reliable method in realistic environments. This method has high computational complexity due to the estimation in the first stage for the first microphone. As a result, it can not be applied in time-varying environments and real-time applications. Our second method improves this problem by introducing two effective preprocessing stages for the conventional Cross Correlation (CC)-based methods. The results obtained in different noisy reverberant conditions including a real and time-varying environment demonstrate that the proposed methods are superior compared to the conventional TDE methods. / Graduate / 0544 / 0984 / saeed.mosayyebpour@gmail.com

In speech communication systems such as voice-controlled systems, hands-free mobile telephones and hearing aids, the received signals are degraded by room reverberation and background noise. This degradation can reduce the perceived quality and intelligibility of the speech, and decrease the performance of speech enhancement and source localization. These problems are difficult to solve due to the colored and nonstationary nature of the speech signals, and features of the Room Impulse Response (RIR) such as its long duration and non-minimum phase. In this dissertation, we focus on two topics of speech enhancement and speaker localization in noisy reverberant environments. A two-stage speech enhancement method is presented to suppress both early and late reverberation in noisy speech using only one microphone. It is shown that this method works well even in highly reverberant rooms. Experiments under different acoustic conditions confirm that the proposed blind method is superior in terms of reducing early and late reverberation effects and noise compared to other well known single-microphone techniques in the literature. Time Difference Of Arrival (TDOA)-based methods usually provide the most accurate source localization in adverse conditions. The key issue for these methods is to accurately estimate the TDOA using the smallest number of microphones. Two robust Time Delay Estimation (TDE) methods are proposed which use the information from only two microphones. One method is based on adaptive inverse filtering which provides superior performance even in highly reverberant and moderately noisy conditions. It also has negligible failure estimation which makes it a reliable method in realistic environments. This method has high computational complexity due to the estimation in the first stage for the first microphone. As a result, it can not be applied in time-varying environments and real-time applications. Our second method improves this problem by introducing two effective preprocessing stages for the conventional Cross Correlation (CC)-based methods. The results obtained in different noisy reverberant conditions including a real and time-varying environment demonstrate that the proposed methods are superior compared to the conventional TDE methods. / Graduate / 2015-04-23 / 0544 / 0984 / saeed.mosayyebpour@gmail.com

With the growth of power system interconnections, the economic drivers encourage the electric companies to load the transmission lines near their limits, therefore it is critical to know those limits well. One important limiting issue is the damping of inter-area oscillation (IAO) between groups of synchronous machines. In this Ph.D. thesis, the contribution of power system components such as load and static var compensators (SVC) that affect the IAO of the power system, are analysed. The original contributions of this thesis are as follows: 1-Identification of eigenvalues and mode shapes of the IAO: In the first contribution of this thesis, the eigenvalues of the IAO are identified using a correlation based method. Then, the mode shape at each identified resonant frequency is determined to show how the synchronous generators swing against each other at the specific resonant frequencies. 2-Load modelling and load contribution to damping: The first part of this contribution lies in identification of the load model using cross-correlation and autocorrelation functions . The second aspect is the quantification of the load contribution to damping and sensitivity of system eigenvalues with respect to the load. 3- SVC contribution to damping: In this contribution the criteria for SVC controller redesign based on complete testing is developed. Then the effect of the SVC reactive power on the measured power is investigated. All of the contributions of this thesis are validated by simulation on test systems. In addition, there are some specific application of the developed methods to real data to find a.) the mode shape of the Australian electricity network, b.) the contribution of the Brisbane feeder load to damping and c.) the effect of the SVC reactive power of the Blackwall substations on the active power supplying Brisbane.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Model predictive control (MPC) strategies have become the standard for advanced control applications in the process industry. Significant benefits are generated from the MPC's capacity to ensure that the plant operates within its constraints more profitably. However, like any controller, after some time under operation, MPCs rarely function as when they were initially designed. A large percentage of performance degradation of MPC is associated with the deterioration of model that controller uses to predict process outputs and calculate inputs. The objective of the present work is implementation of mathematical methods that can be used to detect model-plant mismatch in linear and nonlinear MPC systems. In this work, techniques based on cross correlation, partial correlation and mutual information are implemented and tested by numerical simulation in case studies characteristic of the petrochemical industry, represented by linear and nonlinear models, operating under MPC control. The results obtained through the applying the techniques are analyzed and compared as to their efficiency is not intended to offer their potential for real industrial applications. / Estratégias de controle preditivo (MPC) têm-se tornado o padrão para aplicações de controle avançado na indústria de processos. Os benefícios significativos são gerados a partir da habilidade do controlador MPC de assegurar que a planta opere dentro das restrições de forma mais lucrativa. Porém, como todo controlador, depois de algum tempo em operação, os MPCs raramente funcionam como quando foram inicialmente projetados. Uma grande porcentagem da degradação do desempenho dos controladores MPC está associada à deterioração do modelo que o controlador usa para fazer a predição das saídas do processo e calcular as entradas. O objetivo do presente trabalho é a implementação de métodos matemáticos que possam ser utilizados para a detecção de erros planta-modelo em sistemas de controle MPC lineares e não lineares. Neste trabalho, técnicas baseadas em correlação cruzada, correlação parcial e informação mútua são implementadas e testadas por simulação numérica em estudos de caso característicos da indústria petroquímica, representados por modelos lineares e não lineares, operando sob controle MPC. Os resultados obtidos através da aplicação das técnicas são analisados e comparados quanto à sua eficiência no objetivo proposto avaliando seu potencial para aplicações industriais reais.

Analisamos aproximadamente três anos de dados correntográficos, em toda a coluna d\'água, e de temperatura junto ao fundo, a fim de avaliar o comportamento hidrodinâmico e termal nas proximidades da Quebra da Plataforma Continental (QPC) de Cabo Frio (CF, Rio de Janeiro, Brasil - 23° 20\'S). A Corrente do Brasil (CB) força movimentos apontando para sudoeste, paralelos à isóbata, em todos os níveis verticais, com variação sazonal das intensidades: médias máximas para o verão (58,7 cm/s) e primavera (41,4 cm/s) e mínimas para inverno (31,0 cm/s) e outono (22,8 cm/s). Foram obtidos máximos significativos de correlação entre as correntes paralelas à isóbata, em toda a coluna d\'água, e o vento na mesma direção, com defasagem na resposta das correntes da ordem do período inercial local (31 h). Também foram obtidos máximos significativos de correlação entre as correntes de fundo normais à isóbata, e a componente paralela do vento, concordantes com mecanismos de intrusões de Água Central do Atlântico Sul (ACAS) na plataforma continental, as quais antecedem a conhecida ressurgência costeira de CF. Sazonalmente, os resultados concordaram principalmente com as variações de posicionamento da frente da CB na QPC e, secundariamente, com a variabilidade dos ventos. Os dados de temperatura indicaram presença quase permanente da ACAS no fundo, e os máximos de correlação obtidos com as correntes paralelas à isóbata indicam que águas mais quentes, oriundas do núcleo da CB (Água Tropical), se aproximam do fundo da QPC, principalmente durante o verão. As correntes de maré se mostraram fracas em todo o período avaliado, com importância decrescendo da superfície para o fundo (20 e 10% da variância, respectivamente) / Current data throughout the water column and temperatures at the bottom from about three years have been analyzed in order to evaluate the hydrodynamic and thermal behavior near the Cabo Frio (CF) continental shelf break (23° 20\'S - Rio de Janeiro, Brazil). The Brazil Current (BC) forces movements pointing to SW, isobath-aligned, on all vertical levels. The speed varies seasonally, with surface mean currents maximum on summer (58.7 cm/s) and spring (41.4 cm/s), and minimum on winter (31.0 cm/s) and autumn (22.8 cm/s). Significant maximum correlation was found between subinertial winds and driven-wind currents, both isobath-aligned, with a delay next to the local inertial period (31 hours). Significant maximum correlation were also obtained between bottom cross-isobath currents and the isobath-aligned component of the wind, consistent with the South Atlantic Central Water (SACW) transport towards the continental shelf, which antedates the well-known coastal CF upwelling. Seasonally, the results agreed mainly with the positioning variations of the BC to the shelf break and, secondly, with the local winds variability. The temperature values below the 18ºC (SACW thermohaline index) was almost permanent on the bottom of the shelf break, and the maximum correlation obtained with current along the isobath indicates that the warmer water of the BC nucleus (Tropical Water) approaches to the bottom of the shelf break, especially during the summer. Tidal currents were weak during the entire sampling period, decreasing the relative strength from the surface to the bottom (20% and 10% of the variance, respectively)

Since the mid 1990’s, the wireless communications industry has witnessed explosive growth. The worldwide cellular and personal communication subscriber base surpassed 600 million users by late 2001, and the number of individual subscribers surpassed 2 billion at the end of 2006 [1, 2]. In order to attract and accommodate these subscribers, modern communication systems, like the Third Generation (3G) and Fourth Generation (4G) cellular networks, will have to provide attractive new features such as increased data throughput rates, greater system capacity, and better speech quality. These modern communication systems promise to have advantages such as wireless access in ways that have never been possible before, providing, amongst others services such as live television (TV) broadcasting to Mobile Stations (MS)s, multi-megabit Internet access, communication using Voice over Internet Protocol (VoIP), unparalleled network capacity, seamless accessibility and many more. With specific, but not exclusive reference to the cellular environment, there are numerous ways to increase the data throughput rate and system capacity. From an economical perspective, it would be more efficient to add equipment to the Base Station (BS) rather than the MSs. To achieve these improvements the motivation to utilise transmit diversity’s capabilities have been identified as a key research issue in this study. Alamouti [3] proposed a transmit diversity technique using two transmit antennas and one receive antenna, providing the same diversity order than using one transmit antenna and two receive antennas. Since Alamouti’s publication in 1998, many papers in the field of Space-Time (ST) coding have been published. Current research in the field of ST coding consists of finding methods to extend the number of transmit antennas to more than four, while still achieving full rate, as well as full diversity which is the main motivation for this study. This study proposes a novel idea of breaching the limitations with ST coding theory by combining ST coding with Spread Spectrum (SS) modulation techniques in order to extend the number of transmit antennas to more than four and still achieve full rate as well as full diversity. An advantage of the proposed scheme, called Direct Sequence Space-Time Spreading (DSSTS) has over current Space-Time Spreading (STS) techniques is that it uses 50% less spreading codes. A performance evaluation platform for the DSSTS scheme was developed to simulate the performance of the scheme in a realistic mobile communication environment. A mobile communication channel that has the ability to simulate time-varying multipath fading was developed and used to evaluate the performance of the DSSTS scheme. From the simulation results obtained, it is evident that Walsh sequences that exhibit particularly good cross-correlation characteristics, cannot overcome the effect of the antenna self-noise in order to exploit the diversity gain by adding extra antennas, i.e. diversity extension. The research also showed that an optimal trade-off exists between antenna diversity and antenna created self-noise. Performance results of the DSSTS scheme in slow and fast fading channels for a different number of transmit antennas are also presented in this study. With the capacity analysis of the DSSTS scheme, it was shown that the addition of extra transmit antennas to the system indeed increased the system capacity. A further addition to this study is the investigation into the assumption that the channel should be quasi-static over the frame length of the ST code. A Space Sequence Transmit Diversity (SSTD) technique is consequently proposed that allows the transmission of the Alamouti symbols during one time interval instead of two. This relieves the ST code from the assumption that the channel should be quasi-static, allowing it to be used in a more realistic multi-user environment. A performance evaluation platform for the SSTD scheme was developed and used to obtain simulation results in a multipath fading channel. It was also shown that the proposed SSTD scheme is successful in combating the effects of multipath fading for small Code Division Multiple Access (CDMA) user loads. However, as a rule of thumb, the square root of the spreading sequence length divided by two depicts the user load at which the SSTD scheme was not capable of overcoming the combined effects of Multi-User Interference (MUI) and multipath fading. / Dissertation (MEng)--University of Pretoria, 2008. / Electrical, Electronic and Computer Engineering / unrestricted

Accretion disks are ubiquitous in astrophysics. They are found in active galactic nuclei, around newly formed stars, around compact stellar objects, like black holes, neutron stars etc. When the ambient matter with sufficient initial angular momentum falls towards a central massive object, forming a disk shaped astrophysical structure, it is called an accretion disk. There are both ionized and neutral disks depending on their temperatures. Generally, in accretion disks, Gravitational force is balanced by the centrifugal force (due to the presence of angular momentum of the matter) and the forces due to gas pressure, radiation pressure and advection. Now, the matter to be accreted needs to lose angular momentum. For most of the accretion disks, the mass of the central object is much higher than the mass of the disk, giving rise to a dynamics governed by a central force. Therefore we can neglect the effect of self-gravity of the disk. Balancing the Newtonian gravitational force and centrifugal force leads to a Keplerian rotation profile of the accreting matter with the angular velocity ∼ r−3/2, where r is the distance from the central object. The Keplerian disk model is extremely useful to explain several flow classes (e.g. emission of soft X-ray in disks around stellar mass black holes). Due to the presence of differential rotation and hence shear viscosity, the matter can slowly lose its angular momentum and falls towards the central object. In this way, the accreting matter in the disk releases its gravitational potential energy and gives rise to luminosity that we observe. However, the molecular viscosity originated from the microscopic physics (due to the collisions between molecules) of the disk matter is not sufficient to explain the observed luminosity or accretion rate. For example, it can be shown that the temperature arisen from the dissipation of energy due to molecular viscosity (which is around 50000K for optical depth τ = 100) is much less than the temperature observed in these systems (around 107K). In my thesis, I have addressed the famous problem of infall of matter in astrophysical accretion disks. In general, the emphasis is given on the flows whose angular velocity decreases but specific angular momentum increases with increasing radial coordinate. Such flows, which are extensively seen in astrophysics, are Rayleigh-stable, but must be turbulent in order to explain observed data (observed temperature, as described above). Since the molecular viscosity is negligible in these systems, for a very large astrophysical length scale, Shakura and Sunyaev argued for turbulent viscosity for energy dissipation and hence to explain the infall of matter towards the central object. This idea is particularly attractive because of its high Reynolds number (Re ∼ 1014). However, the Keplerian disks, which are relevant to many astrophysical applications, are remarkably Rayleigh stable. Therefore, linear perturbation apparently cannot induce the onset of turbulence, and consequently cannot provide enough viscosity to transport matter inwards. The primary theme of my thesis is, how these accretion disks can be made turbulent in the first place to give rise to turbulent viscosity. With the application of Magnetorotational Instability (MRI) to Keplerian disks, Balbus and Hawley showed that initial seed, weak magnetic fields can lead to the velocity and magnetic field perturbations growing exponentially. Within a few rotation times, such exponential growth could reveal the onset of turbulence. Since then, MRI has been a widely accepted mechanism to explain origin of instability and hence transport of matter in accretion disks. Note that for flows having strong magnetic fields, where the magnetic field is tightly coupled with the flow, MRI is not expected to work. Hence, it is very clear that the MRI is bounded in a small regime of parameter values when the field is also weak. It has been well established by several works that transient growth (TG) can reveal nonlinearity and transition to turbulence at a sub-critical Re. Such a sub-critical transition to turbulence was invoked to explain colder, purely hydrodynamic accretion flows, e.g. quiescent cataclysmic variables, proto-planetary and star-forming disks, the outer region of the disks in active galactic nuclei etc. Baroclinic instability is another plausible source for vigorous turbulence in colder accretion disks. Note that while hotter flows are expected to be ionized enough to produce weak magnetic fields therein and subsequent MRI, colder flows may remain to be practically neutral in charge and hence any instability and turbulence therein must be hydrodynamic. However, in the absence of magnetic effects, the Coriolis force does not allow any significant TG in accretion disks in three dimensions, independent of Re, while in pure two dimensions, TG could be large at large Re. However, a pure two-dimensional flow is a very idealistic case. Nevertheless, in the presence of magnetic field, even in three dimensions, TG could be very large (Coriolis effects could not suppress the growth). Hence, in a real three-dimensional flow, it is very important to explore magnetic TG. However, as mentioned above, the charge neutral Rayleigh-stable astrophysical flows have hardly any magnetic field (e.g. protoplanetary disks, quiescent cataclysmic variables etc.). Also, the hydrodynamic Rayleigh-stable Taylor-Couette flows and plane Couette flows in the laboratory experiments are seen to be turbulent without the presence of any magnetic field, while they are shown to be stable in linear stability analysis. It is a century old unsolved problem to explain hydrodynamically, the linear instability of Couette flows and other Rayleigh-stable Flows, which are observed to be turbulent, starting from laboratory experiments to astrophysical observations. Therefore, as in one hand, the hydrodynamic instability of the astrophysical accretion flows and laboratory shear flows (e.g. Rayleighstable Taylor-Couette flow, plane Couette flow etc.) has to be understood, on the other hand, the magnetohydrodynamic (MHD) instability of the hotter flows has also to be investigated to understand the nature of MHD instability clearly, whether it arises due to MRI or TG. I have investigated the effect of stochastic noise (which is generated by the shearing motion of the disk layers) on the hydrodynamics and magnetohydrodynamics of accretion disks and explain how stochastic noise can make accretion Disks turbulent. It is found that such stochastically driven flows exhibit large temporal and spatial correlations of perturbations, and hence large energy dissipations of perturbation with time, which presumably generates instability and turbulence. I have also given in my thesis, a plausible resolution of the hydrodynamic turbulence problem of the accretion flows and laboratory shear flows (as discussed above) from pure hydrodynamics, invoking the idea of Brownian motion of particles. I have shown that in any shear flow, very likely, the stochastic noise is generated due to thermal fluctuations. Therefore, the shear flows must be studied including the effect of stochastically driving force and hence the governing equations should not be deterministic. Incorporating the effects of noise in the study of the above mentioned shear flows, I have shown in my thesis that hydrodynamic Rayleigh-stable flows and plane Couette flows can be linearly unstable. I have also investigated the importance of transient growth over magnetorotational instability (MRI) to produce turbulence in accretion disks. Balbus and Hawley asserted that the MRI is the fastest weak field instability in accretion disks. However, they used only the plane wave perturbations to study the instability problem. I have shown that for the flows with high Reynolds number, which are indeed the case for astrophysical accretion disks, transient growth can make the system nonlinear much faster than MRI and can be a plausible primary source of turbulence, using the shearing mode perturbations. Therefore, this thesis provides a plausible resolution of hydrodynamic turbulence observed in astrophysical accretion disks and some laboratory shear flows, such as, Rayleigh-stable Taylor-Couette flows and plane Couette flows. Moreover, this thesis also provides a clear understanding of MHD turbulence for astrophysical accretion disks.

An iterative travel time forecasting scheme, named the Advanced Multilane Prediction based Real-time Fastest Path (AMPRFP) algorithm, is presented in this dissertation. This scheme is derived from the conventional kernel estimator based prediction model by the association of real-time nonlinear impacts that caused by neighboring arcs’ traffic patterns with the historical traffic behaviors. The AMPRFP algorithm is evaluated by prediction of the travel time of congested arcs in the urban area of Jacksonville City. Experiment results illustrate that the proposed scheme is able to significantly reduce both the relative mean error (RME) and the root-mean-squared error (RMSE) of the predicted travel time. To obtain high quality real-time traffic information, which is essential to the performance of the AMPRFP algorithm, a data clean scheme enhanced empirical learning (DCSEEL) algorithm is also introduced. This novel method investigates the correlation between distance and direction in the geometrical map, which is not considered in existing fingerprint localization methods. Specifically, empirical learning methods are applied to minimize the error that exists in the estimated distance. A direction filter is developed to clean joints that have negative influence to the localization accuracy. Synthetic experiments in urban, suburban and rural environments are designed to evaluate the performance of DCSEEL algorithm in determining the cellular probe’s position. The results show that the cellular probe’s localization accuracy can be notably improved by the DCSEEL algorithm. Additionally, a new fast correlation technique for overcoming the time efficiency problem of the existing correlation algorithm based floating car data (FCD) technique is developed. The matching process is transformed into a 1-dimensional (1-D) curve matching problem and the Fast Normalized Cross-Correlation (FNCC) algorithm is introduced to supersede the Pearson product Moment Correlation Co-efficient (PMCC) algorithm in order to achieve the real-time requirement of the FCD method. The fast correlation technique shows a significant improvement in reducing the computational cost without affecting the accuracy of the matching process.

This diploma thesis focuses on a design of camera control system used for detecting defects, appearing during a UV luminescent glue application on the bottom of a paper bag. As a part of this thesis, an application was developed, using Baumer VCXG-53C industrial camera, implementing two dierent control methods - 2D cross correlation image pattern matching based on previously user defined pattern and glue area size measuring based on binary segmented image. The result of this work is a fully developed control system, prepared to be put into operation at the customer’s production line.