In the area of Discrete Event Systems (DES), formal verification techniques are important in examining a variety of system properties including controllability and nonblocking. Nonetheless, in reality, most software and hardware practitioners are not proficient in formal methods which holds them back from the formal representation and verification of their systems. Alternatively, it is a common observation that control engineers are typically familiar with Moore synchronous Finite State Machines (FSM) and use them to express their controllers’ behaviour. Taking this into consideration, we devise a generic and structured approach to automatically translate Moore synchronous FSM into timed DES (TDES) supervisors. In this thesis, we describe our FSM-TDES translation method, present a set of algorithms to realize the translation steps and rules, and demonstrate the application and correctness of our translation approach with the help of an example. In order to develop our automatic FSM-TDES translation approach, we exploit the structural similarity created by the sampled-data (SD) supervisory control theory between the two models. To build upon the SD framework, first we address a related issue of disabling the tick event in order to force an eligible prohibitable event in the SD framework. To do this, we introduce a new synchronization operator called the SD synchronous product (||SD), adapt the existing TDES and SD properties, and devise our ||SD setting. We formally verify the controllability and nonblocking properties of our ||SD setting by establishing logical equivalence between the existing SD setting and our ||SD setting. We present algorithms to implement our ||SD setting in the DES research tool, DESpot. The formulation of the ||SD operator provides twofold benefits. First, it simplifies the design logic of the TDES supervisors that are modelled in the SD framework. This results in improving the ease of manually designing SD controllable TDES supervisors, and reduced verification time of the closed-loop system. We demonstrate these benefits by applying our ||SD setting to an example system. Second, it bridges the gap between theoretical supervisors and physical controllers with respect to event forcing. This makes our FSM-TDES translation approach relatively uncomplicated. Our automatic FSM-TDES translation approach enables the designers to obtain a formal representation of their controllers without designing TDES supervisors by hand and without requiring formal methods expertise. Overall, this work should increase the adoption of the SD supervisory control theory in particular, and formal methods in general, in the industry by facilitating software and hardware practitioners in the formal representation and verification of their control systems. / Dissertation / Doctor of Philosophy (PhD)

No / Study is presented into the performance of Fast Fourier Transform (FFT) and Discrete Wavelet Transform (DWT) and MIMO-DWT with transmit beamforming. Feedback loop has been used between the equalizer at the transmitter to the receiver which provided the channel state information which was then used to construct a steering matrix for the transmission sequence such that the received signals at the transmitter can be combined constructively in order to provide a reliable and improved system for next generation wireless systems. As convolution in time domain equals multiplication in frequency domain no such counterpart exist for the symbols in space, means linear convolution and Intersymbol Interference (ISI) generation so both zero forcing (ZF) and minimum mean squared error (MMSE) equalizations have been employed. The results show superior performance improvement and in addition allow keeping the processing, power and implementation cost at the transmitter which has less constraints and the results also show that both equalization algorithms perform alike in wavelets and the ISI is spread equally between different wavelet domains.

Este trabalho tem dois objetivos principais. Primeiramente, analisamos a preservação de conexidade na extensão de espaços compactos por funções contínuas, técnica utilizada por Koszmider para obter $C(K)$ indecomponível com poucos operadores. Mostramos que para todo compacto metrizável $K$ existe um desconexo $L$ que é obtido a partir de $K$ por uma quantidade finita de extensões por funções contínuas. Em seguida, enfatizamos a construção de espaços de Banach da forma $C(K)$ com poucos operadores, com a propriedade de que $C(L)$ tem poucos operadores, para todo fechado $L \\subseteq K$. Assumindo o princípio diamante construímos uma família $(K_\\xi)_{\\xi < 2^{(2^\\omega)}}$ de espaços conexos e hereditariamente Koszmider tais que todo operador de $C(K_\\xi)$ em $C(K_\\eta)$ é fracamente compacto, para $\\xi$ diferente de $\\eta$. Em particular, $(C(K_\\xi))_{\\xi < 2^{(2^\\omega)}}$ é uma família de espaços de Banach indecomponíveis e dois a dois essencialmente incomparáveis, e cada espaço $K_\\xi$ responde positivamente ao problema de Efimov. Apresentamos também um método de construção via forcing de um espaço compacto e conexo $K$ hereditariamente fracamente Koszmider. / This work has two main objectives. First, we analyze the preservation of connectedness in the extension of compact spaces by continuous functions, a technique used by Koszmider to obtain an indecomposable Banach space $C(K)$ with few operators. We show that for any metrizable compactum $K$ there exists a disconnected $L$ which is obtained from $K$ by finitely many extensions by continuous functions. Next, we emphasize the construction of Banach spaces of the form $C(K)$ with the property that $C(L)$ has few operators, for every closed $L \\subseteq K$. Assuming the diamond principle we construct a family $(K_\\xi)_{\\xi < 2^{(2^\\omega)}}$ of connected and hereditarily Koszmider spaces such that every operator from $C(K_\\xi)$ into $C(K_\\eta)$ is weakly compact, for $\\xi$ different from $\\eta$. In particular, $(C(K_\\xi))_{\\xi < 2^{(2^\\omega)}}$ is a family of indecomposable and pairwise essentially incomparable Banach spaces, and each space $K_\\xi$ responds positively to the Efimov\'s problem. We also present a method of construction using forcing of a compact and connected hereditarily weakly Koszmider space $K$.

Este trabalho tem dois objetivos principais. Primeiramente, analisamos a preservação de conexidade na extensão de espaços compactos por funções contínuas, técnica utilizada por Koszmider para obter $C(K)$ indecomponível com poucos operadores. Mostramos que para todo compacto metrizável $K$ existe um desconexo $L$ que é obtido a partir de $K$ por uma quantidade finita de extensões por funções contínuas. Em seguida, enfatizamos a construção de espaços de Banach da forma $C(K)$ com poucos operadores, com a propriedade de que $C(L)$ tem poucos operadores, para todo fechado $L \\subseteq K$. Assumindo o princípio diamante construímos uma família $(K_\\xi)_{\\xi < 2^{(2^\\omega)}}$ de espaços conexos e hereditariamente Koszmider tais que todo operador de $C(K_\\xi)$ em $C(K_\\eta)$ é fracamente compacto, para $\\xi$ diferente de $\\eta$. Em particular, $(C(K_\\xi))_{\\xi < 2^{(2^\\omega)}}$ é uma família de espaços de Banach indecomponíveis e dois a dois essencialmente incomparáveis, e cada espaço $K_\\xi$ responde positivamente ao problema de Efimov. Apresentamos também um método de construção via forcing de um espaço compacto e conexo $K$ hereditariamente fracamente Koszmider. / This work has two main objectives. First, we analyze the preservation of connectedness in the extension of compact spaces by continuous functions, a technique used by Koszmider to obtain an indecomposable Banach space $C(K)$ with few operators. We show that for any metrizable compactum $K$ there exists a disconnected $L$ which is obtained from $K$ by finitely many extensions by continuous functions. Next, we emphasize the construction of Banach spaces of the form $C(K)$ with the property that $C(L)$ has few operators, for every closed $L \\subseteq K$. Assuming the diamond principle we construct a family $(K_\\xi)_{\\xi < 2^{(2^\\omega)}}$ of connected and hereditarily Koszmider spaces such that every operator from $C(K_\\xi)$ into $C(K_\\eta)$ is weakly compact, for $\\xi$ different from $\\eta$. In particular, $(C(K_\\xi))_{\\xi < 2^{(2^\\omega)}}$ is a family of indecomposable and pairwise essentially incomparable Banach spaces, and each space $K_\\xi$ responds positively to the Efimov\'s problem. We also present a method of construction using forcing of a compact and connected hereditarily weakly Koszmider space $K$.

Space-Time Block Coding is an efficient communication technique used in multiple-input multiple-output wireless systems. The complexity with which a Space-Time Block Code (STBC) can be decoded is important from an implementation point of view since it directly affects the receiver complexity and speed. In this thesis, we address the problem of designing low complexity decoding techniques for STBCs, and constructing STBCs that achieve high rate and full-diversity with these decoders. This thesis is divided into two parts; the first is concerned with the optimal decoder, viz. the maximum-likelihood (ML) decoder, and the second with non-ML decoders. An STBC is said to be multigroup ML decodable if the information symbols encoded by it can be partitioned into several groups such that each symbol group can be ML decoded independently of the others, and thereby admitting low complexity ML decoding. In this thesis, we first give a new framework for constructing low ML decoding complexity STBCs using codes over the Klein group, and show that almost all known low ML decoding complexity STBCs can be obtained by this method. Using this framework we then construct new full-diversity STBCs that have the least known ML decoding complexity for a large set of choices of number of transmit antennas and rate. We then introduce the notion of Asymptotically-Good (AG) multigroup ML decodable codes, which are families of multigroup ML decodable codes whose rate increases linearly with the number of transmit antennas. We give constructions for full-diversity AG multigroup ML decodable codes for each number of groups g > 1. For g > 2, these are the first instances of g-group ML decodable codes that are AG or have rate more than 1. For g = 2 and identical delay, the new codes match the known families of AG codes in terms of rate. In the final section of the first part we show that the upper triangular matrix R encountered during the sphere-decoding of STBCs can be rank-deficient, thus leading to higher sphere-decoding complexity, even when the rate is less than the minimum of the number of transmit antennas and the number receive antennas. We show that all known AG multigroup ML decodable codes suffer from such rank-deficiency, and we explicitly derive the sphere-decoding complexities of most known AG multigroup ML decodable codes. In the second part of this thesis we first study a low complexity non-ML decoder introduced by Guo and Xia called Partial Interference Cancellation (PIC) decoder. We give a new full-diversity criterion for PIC decoding of STBCs which is equivalent to the criterion of Guo and Xia, and is easier to check. We then show that Distributed STBCs (DSTBCs) used in wireless relay networks can be full-diversity PIC decoded, and we give a full-diversity criterion for the same. We then construct full-diversity PIC decodable STBCs and DSTBCs which give higher rate and better error performance than known multigroup ML decodable codes for similar decoding complexity, and which include other known full-diversity PIC decodable codes as special cases. Finally, inspired by a low complexity essentially-ML decoder given by Sirianunpiboon et al. for the two and three antenna Perfect codes, we introduce a new non-ML decoder called Adaptive Conditional Zero-Forcing (ACZF) decoder which includes the technique of Sirianunpiboon et al. as a special case. We give a full-diversity criterion for ACZF decoding, and show that the Perfect codes for two, three and four antennas, the Threaded Algebraic Space-Time code, and the 4 antenna rate 2 code of Srinath and Rajan satisfy this criterion. Simulation results show that the proposed decoder performs identical to ML decoding for these five codes. These STBCs along with ACZF decoding have the best error performance with least complexity among all known STBCs for four or less transmit antennas.

Une grande quantité d'énergie est présente dans les mouvements de rotations propre et orbitale des planètes. Des forçages harmoniques tels que les déformations de marées, la précession ou la libration peuvent en convertir une partie pour générer des écoulements dans les couches fluides d'une planète. Ces écoulements restent largement méconnus même s'ils sont importants pour contraindre des modèles d'intérieur planétaire ou expliquer la présence de champs magnétiques dans certains astres.Dans cette thèse, nous étudions les mécanismes engendrés par ces forçages en combinant une approche théorique, expérimentale et numérique et soulignons la généricité des phénomènes observés. L'étude d'un forçage de libration longitudinale, i.e. des oscillations de la vitesse de rotation d'un astre, montre la présence d'un écoulement zonal généré par des interactions non-linéaires dans les couches visqueuses. Nous étudions ensuite l'instabilité qui apparaît à la paroi pour des amplitudes de libration suffisantes et qui peut transférer de l'énergie vers le volume du fluide. Finalement, une étude expérimentale de forçage de marées dans une sphère met en évidence que l'excitation directe d'ondes inertielles induit un écoulement zonal intense et localisé. Cet écoulement peut se déstabiliser par une instabilité de cisaillement et générer un écoulement turbulent dans tout le volume.Pour finir, nous considérons la pertinence de ces résultats pour des applications géo-/astrophysiques, telles que l'étude des océans internes sous la surface de glace des satellites joviens Ganymède, Encelade et Europe. / A huge amount of energy is stored in the spin and orbital motions of any planet. Harmonic forcings such as libration, precession and tides are capable of conveying a portion of this energy to drive intense three-dimensional flows in liquid layers of planetary bodies. The generated flows remain largely unknown even if they are important to constraint model of planetary interior or to explain the presence of magnetic fields in some astrophysical bodies.In this thesis, we study the mechanisms induced by these forcings by combining theoretical, experimental and numerical approaches and we highlight the genericity of the observed phenomena. The study of a longitudinal libration forcing, corresponding to oscillations of the rotation rate of a planet, shows the presence of a mean zonal flow generated by non-linear interactions in the viscous layers. We then study the instability which appears at the outer boundary at sufficiently large libration amplitude or small Ekman number and which can transfer energy to the bulk of the fluid. Finally, an experimental study of tidal forcing in a sphere shows that the nonlinear self-interaction of excited inertial waves may drive an intense and localised axisymmetric jet, which becomes unstable at low Ekman number following a shear instability, generating space-filling turbulence.To conclude, we consider the relevance of these results to geo-/astrophysical applications, such as the subsurface oceans of the icy satellites Ganymede, Enceladus or Europa.

The Late Cretaceous–early Paleogene is the most recent period of Earth history with a dynamic carbon cycle that experienced sustained global greenhouse warmth and can offer a valuable insight into our anthropogenically-warmer future world. Yet, knowledge of ambient climate conditions and evolution of the carbon cycle at this time, along with their relation to forcing mechanisms, are still poorly constrained. In this thesis, I examine marine sediments recovered from the South Atlantic Walvis Ridge (ODP Site 1262) and Indian Ocean Ninetyeast Ridge (IODP Site U1443 and ODP Site 758), to shed new light on the evolution of the climate and carbon cycle from the Late Maastrichtian through to the Early Eocene (~67.10–52.35 Ma). The overarching aims of this thesis are: 1) to identify the long-term trends and principle forcing mechanisms driving the climate and carbon cycle during this time period, through construction of 14.75 million-year-long, orbital-resolution (~1.5–4 kyr), stratigraphically complete, benthic stable carbon (δ13Cbenthic) and oxygen (δ18Obenthic) isotope records; 2) to investigate in more detail the climatic and carbon-cycle perturbations of the Early–Middle Paleocene (e.g., the Dan-C2 event, Latest Danian Event and the Danian/Selandian Transition Event) and place these in their proper (orbital) temporal context; 3) to investigate the Late Maastrichtian warming event and its relationship to the eruption of the Deccan Traps Large Igneous Province, as well as its role (if any) in the subsequent Cretaceous/Paleogene (K/Pg) mass extinction; 4) to provide the first orbital-resolution estimates of temperature and carbonate chemistry variability from the low latitude Indian Ocean spanning the Late Paleocene–Early Eocene, through analysis of trace element and stable isotope data from multiple foraminiferal species. Taken together, the results presented in this thesis provide a critical new insight into the dynamic evolution of the climate and carbon cycle during the greenhouse world of the early Paleogene, and shed light on the potential forcing mechanisms driving the climate and carbon cycle during this time.

The way people view development is changing. The world now advocates for a development that also considers future generations. There is a paradigm shift towards sustainable development - a development in today's lifestyle without destroying the resources for tomorrow generations. Sustainable development is a broad concept that addresses how human activities impact on the economic, environmental and social well-being of an ecosystem; however, practical application of the sustainability concept is complex because its objective assessment is elusive. It is often said that the effect of technology on society has never been more profound than today. As mankind develops in science and technology to improve on his well-being, certain impacts are made on the systems that support human existence. Liquefied natural gas (LNG) technology, like gas-to-liquid (GTL) technology, is a latest innovation conceived to 'fight' the problem of gas flaring, and help contribute to the social and economic growth of the people; but it is necessary for man to know if these contemporary technologies are sustainable. This dissertation critically appraises the impact of the LNG project on the community of Bonny Island in Nigeria from a holistic perspective. The approach to the research work is three-fold: an appropriate sustainability framework is selected based on certain criteria; sustainability indicators are developed from the chosen framework; and the sustainability indicators are used to assess the impact of the project on the flora and fauna of the community. To have a clear picture of the impact of Nigeria LNG on its host community, Epe-Waterside is chosen as a control community because of its similar socio-geographical outlook to Bonny Island community. The control community is then subjected to the same set of sustainability indicators for a comparative analysis. The outcome of the research work shows that, though the economic and social conditions of Bonny Island seem much better, its environmental status remains a challenge. In other words, it can be concluded that the present approach to the operation of the LNG technology is not sustainable. / Thesis (M.Ing. (Development and Management))--North-West University, Potchefstroom Campus, 2009.

The way people view development is changing. The world now advocates for a development that also considers future generations. There is a paradigm shift towards sustainable development - a development in today's lifestyle without destroying the resources for tomorrow generations. Sustainable development is a broad concept that addresses how human activities impact on the economic, environmental and social well-being of an ecosystem; however, practical application of the sustainability concept is complex because its objective assessment is elusive. It is often said that the effect of technology on society has never been more profound than today. As mankind develops in science and technology to improve on his well-being, certain impacts are made on the systems that support human existence. Liquefied natural gas (LNG) technology, like gas-to-liquid (GTL) technology, is a latest innovation conceived to 'fight' the problem of gas flaring, and help contribute to the social and economic growth of the people; but it is necessary for man to know if these contemporary technologies are sustainable. This dissertation critically appraises the impact of the LNG project on the community of Bonny Island in Nigeria from a holistic perspective. The approach to the research work is three-fold: an appropriate sustainability framework is selected based on certain criteria; sustainability indicators are developed from the chosen framework; and the sustainability indicators are used to assess the impact of the project on the flora and fauna of the community. To have a clear picture of the impact of Nigeria LNG on its host community, Epe-Waterside is chosen as a control community because of its similar socio-geographical outlook to Bonny Island community. The control community is then subjected to the same set of sustainability indicators for a comparative analysis. The outcome of the research work shows that, though the economic and social conditions of Bonny Island seem much better, its environmental status remains a challenge. In other words, it can be concluded that the present approach to the operation of the LNG technology is not sustainable. / Thesis (M.Ing. (Development and Management))--North-West University, Potchefstroom Campus, 2009.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / In this work, the combined multi-direct forcing and immersed boundary method (IBM) were presented to simulate uid-structure interaction problems. The multi-direct forcing is used aim at satisfying the no-slip condition in the immersed boundary. For the numerical simulations was used a multi-purpose computer code that is being developed in the MFlab - Fluid Mechanics Laboratory of Federal University of Uberl^andia. Tests are made to validate the numerical schemes and routines were implemented to simulate uid-structures interaction problems. Furthermore, computational tools are developed to construct and manage and optimize the use of a Beowulf cluster where all the parallel simulations presented in this work were done. The Method of Manufactured Solutions has been used for order-of-accuracy verication in the computational uid dynamics code. Two uid-structure interaction problems were studied using this methodology. The rst is a ow over a sphere for some Reynolds numbers. The results were compared to empirical results, obtaining satisfactory approximations. The second one is a immersed simple pendulum. For this problem the results are in agreement with physics. Indeed, these are preliminar results. New tests must be done to make progress in the methodology. Improvements are proposed in the IBM, in the uid-structure model, in the turbulence model, in the method used to discretize the uid domain. It is also proposed to apply the methodology to real problems as risers and valves. / O presente trabalho tem como principal objetivo a aplicação do método multifoçagem (MMF) para solução numérica tridimensional de problemas de interação uidoestrutura, buscando-se garantir a condição de não-escorregamento na região da fronteira imersa. Para as simulações numéricas foi utilizado um código computacional multipropósito em desenvolvimento no MFlab - Laboratório de Mecânica dos Fluidos da Universidade Federal de Uberlândia. Foram feitas modificações nesse código para que se pudesse validá-lo para solução de problemas com fronteira imersa e foi implementada uma rotina para solução de um problema de interação uido-estrutura total. Além disso, foi desenvolvido um pacote de ferramentas computacionais que possibilitou instalar e melhorar o desempenho de um cluster do tipo Beowulf utilizado para o desenvolvimento das simulações num eriças em paralelo do presente trabalho. Utilizando o Método das Soluções Manufaturadas foram obtidas soluções sintetizadas para as equações de Navier-Stokes, o que possibilitou obter a ordem de convergência numérica do código computacional para problemas contínuos e a validação deste código para problemas envolvendo corpos imersos ao combinar a o método das soluções manufaturadas com a metodologia de fronteira imersa. Na sequência foi solucionado o problema de escoamento ao redor de uma esfera parada, cujos resultados foram comparados com referencias empíricas, obtendo-se boa aproximação. Ainda para esse caso foi feita a avalição da norma L2 para as soluções num eriças obtidas nos pontos lagrangianos verificando a garantia da condição de não-escorregamento e feita uma análise da inuência dos número de ciclos utilizados no método multi-forçagem. Foi vericado que a solução numérica obtida depende do número de ciclos o que faz com que seja necessário se estabelecer um critério de convergência para este método. Um segundo problema de interação uido-estrutura total foi estudado. Consiste em um pêndulo simples imerso em um uido que parte de uma dada posição angular inicial e oscila em torno da sua posição de equilíbrio, até parar. Para esse caso foram feitas análises quantitativas. Os resultados são preliminares mas coerentes com a física do problema, indicando que a metodologia é adequada para solução deste tipo de problema. / Mestre em Engenharia Mecânica