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TERENZI, Alessandro. "Innovative Digital Signal Processing Methodologies for Identification and Analysis of Real Audio Systems." Doctoral thesis, Università Politecnica delle Marche, 2021. http://hdl.handle.net/11566/287822.
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Esistono molti sistemi audio reali e ciascuno ha le proprie caratteristiche ma tutti sono accomunati dal fatto che sono sistemi in grado di generare o modificare un suono. Se un sistema naturale o artificiale può essere definito come sistema sonoro, allora è possibile applicare le tecniche del digital signal processing per studiare il sistema ed emularne il comportamento. In questo lavoro di tesi si propone di introdurre delle metodologie innovative di processamento del segnale applicate ad alcuni sistemi sonori reali.
In particolare, vengono studiati e discussi tre diversi sistemi: il mondo dei dispositivi non lineari basati su valvole, con particolare attenzione agli amplificatori per chitarra e hi-fi, l'ambiente acustico di una stanza ed il suo effetto sulla propagazione del suono ed infine il suono emesso dalle api in un alveare.
Per quanto riguarda il primo sistema, vengono proposti dei contributi innovativi per l'identificazione di modelli come la serie di Volterra ed il modello di Hammerstein; in particolare viene discusso un approccio per superare alcune limitazioni dell'identificazione tramite serie di Volterra e l'applicazione di una struttura in sottobande per ridurre il costo computazionale e incrementare la velocità di convergenza di un algoritmo adattativo per l'identificazione del modello di Hammerstein. In ultima analisi, viene proposto un approccio innovativo in grado di stimare con una singola misura vari parametri di distorsione sfruttando un modello di Hammerstein generallizato.
Per quanto riguarda il secondo ambito, vengono proposti i risultati relativi a due applicazioni di equalizzazione multipunto: nel primo caso si mostrerà come l'equalizzazione può essere usata non solo per compensare le anomalie sonore generate all'interno di una stanza, ma anche per migliorare la risposta in frequenza di particolari trasduttori a vibrazione ancorati ad un pannello rigido; nel secondo caso si illustra come un approccio in sottobande può migliorare l'efficienza computazionale e la velocità di un algoritmo di equalizzazione adattativo multipunto e multicanale.
Infine, viene presentato un sistema sonoro naturale, ovvero quello generato da un alveare. In questo caso si illustrerà un sistema di acquisizione innovativo sviluppato per monitorare gli alveari con particolare attenzione al suono; succesivamente si mostrano gli approcci messi a punto per analizzare il suono registrato in due condizioni reali ed infine verranno si illustrano i risultati ottenuti grazie allo studio del suono usando algoritmi di classificazione.
Inoltre, nella parte finale dell'elaborato sono presenti dei contributi secondari ma che hanno comunque come focus principale il signal processing applicato ad ambienti acustici reali, in particolare si discute di un'implementazione di un algoritmo di cancellazione attiva del rumore e di due algoritmi per effetti digitali in cui il primo migliora le performance sonore di altoparlanti compatti, ed il secondo genera un effetto stereofonico per chitarra elettrica.Many real word audio systems exist, each has its own characteristics but almost all of them can be identified from the fact that they are able to generate or modify a sound. If a natural or artificial system can be defined as a sound system, then it is possible to apply the techniques of digital signal processing for the studying and the emulation of the system. In this thesis, innovative methodologies for digital signal processing applied to real audio systems will be discussed. In particular, three different audio systems will be considered: the world of vacuum-based non linear audio devices with particular attention to guitar and hi-fi amplifiers; the room acoustic environment and its effect on the sound propagation; and finally the sound emitted by honey bees in a beehive. Regarding the first system, innovative approaches for the identification of the Volterra series and Hammerstein models will be proposed, in particular an approach to overcome some limitation of Volterra series identification. The application of a sub-band structure to reduce the computational cost and increase the convergence speed of an adaptive Hammerstein model identification will be proposed as well. Finally, an innovative approach for the measurement of several distortion parameters using a single measure, exploiting a generalized Hammerstein model, will be presented. For the second system, the results of the application of a multi-point equalizer to two different situations will be exposed. In particular, in the first case, it will be shown how a multi-point equalization can be used not only to compensate the acoustical anomalies of a room, but also to improve the frequency response of vibrating transducers mounted on a rigid surface. The second contribution will show how a sub-band approach can be used to improve the computational cost and the speed of an adaptive algorithm for a multi-point and multi channel equalizer. At the end, the focus will be on a natural sound system, i.e., a honey bees colony. In this case, an innovative acquisition system for honey bees sound monitoring will be presented. Then, the approaches developed for sound analysis will be exposed and applied to the recorded sounds in two different situations. Finally, the obtained results, achieved with the application of classification algorithms, will be exposed. In the final part of the work some minor contributions still related to signal processing applied to real sound systems are presented. In particular, an implementation of an active noise control system is discussed, and two algorithms for digital effects where the former improves the sound performances of compact loudspeakers and the latter generates a stereophonic effect for electric guitars are exposed.
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DELLA, MARCA ROSSELLA. "Problemi di controllo in epidemiologia matematica e comportamentale." Doctoral thesis, Università degli studi di Modena e Reggio Emilia, 2021. http://hdl.handle.net/11380/1237622.
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Nonostante i progressi nell'eliminazione di infezioni da lungo in circolazione, gli ultimi decenni hanno visto la continua comparsa o ricomparsa di malattie infettive. Esse non solo minacciano la salute globale, ma i costi generati da epidemie nell’uomo e negli animali sono responsabili di significative perdite economiche.
I modelli matematici della diffusione di malattie infettive hanno svolto un ruolo significativo nel controllo delle infezioni. Da un lato, hanno dato un importante contributo alla comprensione epidemiologica degli andamenti di scoppi epidemici; d'altro canto, hanno concorso a determinare come e quando applicare le misure di controllo al fine di contenere rapidamente ed efficacemente le epidemie. Ciononostante, per dare forma alle politiche di sanità pubblica, è essenziale acquisire una migliore e più completa comprensione delle azioni efficaci per controllare le infezioni, impiegando nuovi livelli di complessità. Questo è stato l'obiettivo fondamentale della ricerca che ho svolto durante il dottorato; in questa tesi i prodotti di questa ricerca sono raccolti e interconnessi. Tuttavia, poiché fuori contesto, altri problemi a cui mi sono interessata sono stati esclusi: essi riguardano le malattie autoimmuni e l'ecologia del paesaggio.
Si inizia con un capitolo introduttivo, che ripercorre la storia dei modelli epidemici, le motivazioni e gli incredibili progressi. Sono due gli aspetti su cui ci concentriamo: i) la valutazione qualitativa e quantitativa di strategie di controllo specifiche per il problema in questione (attraverso, ad esempio, il controllo ottimo o le politiche a soglia); ii) l'incorporazione nel modello dei cambiamenti nel comportamento umano in risposta alla dinamica della malattia. In questo quadro si inseriscono e contestualizzano i nostri studi. Di seguito, a ciascuno di essi è dedicato un capitolo specifico.
Le tecniche utilizzate includono la costruzione di modelli appropriati dati da equazioni differenziali ordinarie non lineari, la loro analisi qualitativa (tramite, ad esempio, la teoria della stabilità e delle biforcazioni), la parametrizzazione e la validazione con i dati disponibili. I test numerici sono eseguiti con avanzati metodi di simulazione di sistemi dinamici. Per i problemi di controllo ottimo, la formulazione segue l'approccio classico di Pontryagin, mentre la risoluzione numerica è svolta da metodi di ottimizzazione sia diretta che indiretta.
Nel capitolo 1, utilizzando come base di partenza un modello Suscettibili-Infetti-Rimossi, affrontiamo il problema di minimizzare al contempo la portata e il tempo di eradicazione di un’epidemia tramite strategie di vaccinazione o isolamento ottimali.
Un modello epidemico tra due sottopopolazioni, che descrive la dinamica di Suscettibili e Infetti in malattie della fauna selvatica, è formulato e analizzato nel capitolo 2. Qui, vengono confrontati due tipi di strategie di abbattimento localizzato: proattivo e reattivo.
Il capitolo 3 tratta di un modello per la trasmissione di malattie pediatriche prevenibili con vaccino, dove la vaccinazione dei neonati segue la dinamica del gioco dell’imitazione ed è affetta da campagne di sensibilizzazione da parte del sistema sanitario.
La vaccinazione è anche incorporata nel modello del capitolo 4. Qui, essa è rivolta a individui suscettibili di ogni età ed è funzione dell’informazione e delle voci circolanti sulla malattia. Inoltre, si assume che l'efficacia del vaccino sia parziale ed evanescente col passare del tempo.
L'ultimo capitolo è dedicato alla tuttora in corso pandemia di COVID-19. Si costruisce un modello epidemico con tassi di contatto e di quarantena dipendenti dall’informazione circolante. Il modello è applicato al caso italiano e incorpora le progressive restrizioni durante il lockdown.Despite major achievements in eliminating long-established infections (as in the very well known case of smallpox), recent decades have seen the continual emergence or re-emergence of infectious diseases (last but not least COVID-19). They are not only threats to global health, but direct and indirect costs generated by human and animal epidemics are responsible for significant economic losses worldwide. Mathematical models of infectious diseases spreading have played a significant role in infection control. On the one hand, they have given an important contribution to the biological and epidemiological understanding of disease outbreak patterns; on the other hand, they have helped to determine how and when to apply control measures in order to quickly and most effectively contain epidemics. Nonetheless, in order to shape local and global public health policies, it is essential to gain a better and more comprehensive understanding of effective actions to control diseases, by finding ways to employ new complexity layers. This was the main focus of the research I have carried out during my PhD; the products of this research are collected and connected in this thesis. However, because out of context, other problems I interested in have been excluded from this collection: they rely in the fields of autoimmune diseases and landscape ecology. We start with an Introduction chapter, which traces the history of epidemiological models, the rationales and the breathtaking incremental advances. We focus on two critical aspects: i) the qualitative and quantitative assessment of control strategies specific to the problem at hand (via e.g. optimal control or threshold policies); ii) the incorporation into the model of the human behavioral changes in response to disease dynamics. In this framework, our studies are inserted and contextualized. Hereafter, to each of them a specific chapter is devoted. The techniques used include the construction of appropriate models given by non-linear ordinary differential equations, their qualitative analysis (via e.g. stability and bifurcation theory), the parameterization and validation with available data. Numerical tests are performed with advanced simulation methods of dynamical systems. As far as optimal control problems are concerned, the formulation follows the classical approach by Pontryagin, while both direct and indirect optimization methods are adopted for the numerical resolution. In Chapter 1, within a basic Susceptible-Infected-Removed model framework, we address the problem of minimizing simultaneously the epidemic size and the eradication time via optimal vaccination or isolation strategies. A two-patches metapopulation epidemic model, describing the dynamics of Susceptibles and Infected in wildlife diseases, is formulated and analyzed in Chapter 2. Here, two types of localized culling strategies are considered and compared: proactive and reactive. Chapter 3 concerns a model for vaccine-preventable childhood diseases transmission, where newborns vaccination follows an imitation game dynamics and is affected by awareness campaigns by the public health system. Vaccination is also incorporated in the model of Chapter 4. Here, it addresses susceptible individuals of any age and depends on the information and rumors about the disease. Further, the vaccine effectiveness is assumed to be partial and waning over time. The last Chapter 5 is devoted to the ongoing pandemic of COVID-19. We build an epidemic model with information-dependent contact and quarantine rates. The model is applied to the Italian case and explicitly incorporates the progressive lockdown restrictions.
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Ferrari, Rosalba (ORCID:0000-0002-3989-713X). "An elastoplastic finite element formulation for the structural analysis of Truss frames with application to ha historical iron arch bridge." Doctoral thesis, Università degli studi di Bergamo, 2013. http://hdl.handle.net/10446/28959.
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This doctoral thesis presents a structural analysis of the Paderno d’Adda Bridge, an impressive iron arch viaduct built in 1889 and located in Lombardia region (Italy).
The thesis falls in the context of a research activity started at University of Bergamo since 2005, that is still ongoing and aims to perform an evaluation of the present state of conservation of the bridge. In fact, the bridge is currently still in service and its important position in the context of transport network will soon lead to questions about its future destination, with particular attention to the evaluation of the residual performance capacity.
To this end, an inelastic structural analysis of the Paderno d’Adda bridge has been performed, up to failure. This analysis has been conducted through an autonomous computer code of a 3D frame structure that runs in the MATLAB environment and has been developed within the classical frame of Limit Analysis and Theory of Plasticity.
The algorithm has been developed applying the “exact” and stepwise holonomic step-by-step analysis method. It has shown very much able to track the limit structural behaviour of the bridge, by reaching convergence with smooth runs up to the true limit load and corresponding collapse displacements.
The main characteristic ingredients of its elastoplastic FEM formulation are: beam finite elements; perfectly plastic joints (as an extension of classical plastic hinges); piece-wise linear yield domains; “exact” time integration.
In the algorithm, the following original features have been implemented: treatment of mutual connections by static condensation and Gaussian elimination; determination of the tangent stiffness formulation through Gaussian elimination. These peculiar contributions are presented in detail in this thesis.
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Strandell, Gustaf. "Linear and Non-linear Deformations of Stochastic Processes." Doctoral thesis, Uppsala : Matematiska institutionen, Univ. [distributr], 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-3689.
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Morgenthaler, Michael J. E. "Non-linear optical studies of surfaces." Thesis, Heriot-Watt University, 1993. http://hdl.handle.net/10399/1430.
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Jeang, Fure Lin. "Non-linear analysis of concrete fracture /." Thesis, Connect to this title online; UW restricted, 1985. http://hdl.handle.net/1773/10133.
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Patil, Anupkumar. "Non-linear dynamical analysis of biosignals." Thesis, University of Strathclyde, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.502349.
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Biosignals are physiological signals that are recorded from various parts of the body. Some of the major biosignals are electromyograms (EMG), electroencephalograms (EEG) and electrocardiograms (ECG). These signals are of great clinical and diagnostic importance, and are analysed to understand their behaviour and to extract maximum information from them. However, they tend to be random and unpredictable in nature (non-linear). Conventional linear methods of analysis are insufficient. Hence, analysis using non-linear and dynamical system theory, chaos theory and fractal dimensions, is proving to be very beneficial. In this project, EGG signals are of interest. Changes in the normal rhythm of a human heart may result in different cardiac arrhythmias, which may be fatal or cause irreparable damage to the heart when sustained over long periods of time. Hence the ability to identify arrhythmias from EGG recordings is of importance for clinical diagnosis and treatment and also for understanding the electrophysiological mechanism of arrhythmias.
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Saneinejad, Abolghasem. "Non-linear analysis of infilled frames." Thesis, University of Sheffield, 1990. http://etheses.whiterose.ac.uk/1801/.
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This thesis is concerned with the analysis of building frames acting compositely with infilling wall panels. The significance of the composite action is emphasized and previous work on infilled frames is reviewed. The existing methods of analysis are categorized and their analytical assumptions are highlighted. It is concluded that more accurate results may be obtained from the development of a non-linear finite element analysis. The finite element method is reviewed and new elements for representing beams, interfaces and loading are developed. Failure criteria for concrete under multiaxial stress and also failure criteria for masonry under uniaxial compression are developed. The non-linear elastoplastic behaviour of concrete is modelled using the concept of equivalent uniaxial strain and the model is extended for cracked materials. Elastoplastic models are also developed for ductile materials(steel) for secant and incremental changes of stresses and strains. These models and the newly developed elements are incorporated into the finite element analysis which is numerically implemented by a new computer program, NEPAL. A number of steel frames with concrete inf ills covering the practical range of beam, column and infill strengths and also wall panel aspect ratios, are analysed using this program. The finite element results are compared with the predictions of a range of existing methods of analysis and their limitations are discussed in detail. A new method of hand analysis is developed, based on a rational elastic and plastic analysis allowing for limited ductility of the infill and also limited deflection of the frame at the peak load. The new method is shown to be capable of providing the necessary information for design purposes with reasonable accuracy, taking into account the effects of strength and stiffness of the beams and columns, the aspect ratio for the infill, the semi-rigid joints and the condition of the frame-infill interfaces (co-efficient of friction and lack of fit). It is concluded that simple and economical design approaches can be established for frames with infilling walls.
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Almeida, Ricardo Miguel Moreira de. "Foundations of nonstandard non-linear analysis." Doctoral thesis, Universidade de Aveiro, 2008. http://hdl.handle.net/10773/2937.
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Doutoramento em MatemáticaEsta tese insere-se na área da análise não-standard não linear. São dois os objectivos principais deste trabalho. Um deles envolve diferenciabilidade de funções e o outro geometria diferencial. O nosso trabalho é dividido em três partes. Na primeira apresentamos uma caracterização não-standard de conjuntos compactos conexos em espaços métricos. Na segunda parte exibimos alguns resultados envolvendo o teorema do valor médio para espaços normados. De seguida é apresentado um novo tipo de diferenciabilidade, a mu-diferenciabilidade. Fazemos um estudo exaustivo das propriedades básicas deste tipo de derivada, nomeadamente a regra em cadeia, o teorema do valor médio, o teorema de Taylor e o teorema da função inversa. A última parte é dedicada à geometria diferencial. Primeiro em espaços de dimensão finita, com uma caracterização não-standard de cúspides e de superfícies regulares. Também apresentamos uma construção de uma curva interna que seria uma solução ideal para um problema de máxima resistência. Por último apresentamos um estudo de variedades diferenciáveis em espaços de Banach. O análogo de espaço tangente, derivada de uma função e derivadas direccionais são apresentados.
This thesis presents a study of non-linear nonstandard analysis. There are two main goals of this study. One of them concerns differentiability of functions and the other one is differential geometry. Our study is divided in three parts. The first part contains a nonstandard characterization of connected compact sets in metric spaces. In the second part we give some results related to the mean value theorem in normed spaces. Then we describe a new type of differentiability, the mudifferentiability. We carry out an extensive study of the basic properties of this differentiation, namely the chain rulle, the mean value theorem, Taylor’s theorem and the inverse mapping theorem. The final part is devoted to differential geometry. First in finite dimensional spaces, with nonstandard characterizations of cusps and regular surfaces. We also construct an internal curve which would be an ideal solution for a problem of maximum resistance. Finally we deal with differentiable manifolds modeled on Banach spaces. The analogous of tangent bundle, differential of a function and directional derivatives are given.
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Wilson, Jonathan P. "Non-linear dynamics and power systems." Thesis, University of Bath, 2000. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.341136.
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Moeanaddin, Rahim. "Aspects of non-linear time series analysis." Thesis, University of Kent, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.328463.
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Tomlin, Alison Sarah. "Bifurcation analysis for non-linear chemical kinetics." Thesis, University of Leeds, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.255345.
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NOGUEIRA, CHRISTIANNE DE LYRA. "NON LINEAR ANALYSIS OF EXCAVATIONS AND EMBANKMENTS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1998. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=2136@1.
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CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOO principal objetivo desta tese consiste no desenvolvimento e aplicação de um programa computacional, ANLOG (Análise Não Linear de Obras Geotécnicas), para análises de problemas geotécnicos com acoplamento de fluxo e deformação, e considerando relações constitutivas não lineares na modelagem do solo. A nível global, a solução do sistema de equação não linear originado da formulação via MEF deste problema é feita através do método de Newton-Raphson Modificado com incrementos automáticos de carga e tempo. Enquanto que, a nível local, a equação constitutiva é integrada utilizando-se um algoritmo de integração de tensão explícito com subincrementos. Modelos não lineares elástico (hiperbólico) e elastoplásticos (Camclay Modificado, Lade e Lade-Kim) são utilizados para representar o comportamento tensão-deformação-resistência do solo. As metodologias de ligar a gravidade e a proposta por Brown e Booker (1985) são usadas para simular numericamente, respectivamente, aterros e escavações. Análises preliminares de aterros e escavações são apresentadas nas quais pode-se observar que a resposta é função do tempo e altamente dependente do coeficiente de permeabilidade e da velocidade de solicitação. As situações drenada e não drenada são casos particulares de uma análise acoplada. Com respeito ao emprego da técnica de incremento automático de carga e tempo mostra-se que sua utilização é fundamental para definição do tamanho do incremento mais adequado a ser adotado na solução incremental-iterativa. Quanto ao algoritmo de integração de tensão adotado é mostrado que o erro cometido na verificação da condição de consistência diminui exponencialmente com o aumento do número de subincrementos. Por fim, o programa ANLOG é utilizado para análise da escavação experimental de Camboinhas (Silva, 1979). Comparações entre os deslocamentos numéricos e os de campo apresentam uma razoável concordância. Entretanto, as poro- pressões numéricas variam em torno de 10 por cento a 30 por cento do valor inicial, enquanto que no campo essa variação foi menor que 3 por cento.
The main objective of this thesis consists on the development and application of a computational program, ANLOG (Non Linear Analysis of Geotechnical Constructions), to analyse geotechnical problems coupling flow and deformation, and considering constitutive non-linear relations for the soil modelling.At the global level, the solution of the non linear system of equations, generated by the FEM formulation of this problem, is done using the Newton-Raphson Modified method with automatic load and time increments. On the other hand, at the local level, the constitutive equations are integrated using the explicit algorithm of stress integration with sub steps. Non-linear models, elastic (hyperbolic) and elastoplastic (modified Camclay, Lade and Lade-Kim) are utilised to represent the stress-strain-strength behaviour of the soil. The procedures of turn on gravity and the one proposed by Brown and Booker (1985) are used to simulate numerically, respectively, embankments and excavations.Initial analyses of excavations and embankments are performed in which it can be observed that the response is a function of time and depends strongly on the permeability coefficient and the loading velocity. In particular, drained and undrained situations are special cases of a coupling analysis. With respect to the use of the automatic load and time increment, it is shown that its use is fundamental to define the best increment size to adopt in the incremental iterative solution. About the stress integration algorithm utilised, it is shown that the error in the consistency condition decreases exponentially with the number sub steps. Finally, the ANLOG program is used to analyse the experimental excavation of Camboinhas (Silva, 1979). Comparisons between numerical and field displacements present a reasonable agreement. However, the pore pressure given by the numerical simulation varied between 10 percent to 30 percent in relation to its initial value, whereas in the field this variation was smaller than 3 percent.
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Mallinder, P. A. "The non-linear analysis of masonry arches." Thesis, Sheffield Hallam University, 1988. http://shura.shu.ac.uk/20006/.
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The objective of the research programme has been to investigate the problems besetting the national masonry arch bridge stock and topropose enhanced means of appraisal accordingly. The programme has involved site assessments and limited experimentation together with limit state and serviceability analyses. All theoretical and empirical studies have been mounted as micro-computer software and are supported by computer graphics. Throughout, the accent is on engineering requirements in practice; the almost universal absence of as-built drawings and the involvement of natural materials whose mechanical properties are highly variable are to be noted from the outset. Initial considerations relating to the arch form, its historical context and present masonry arch assessment methods are set out in Chapter 1. Fieldwork studies are presented in Chapter 2. The concept that masonry has finite compressive strength isaccordingly considered in Chapter 3 which includes experimentation establishing the appropriate constitutive properties with respect to natural rock. A general moment-thrust response modelling is established and an original non-linear limit-state moment-thrust interaction diagram is determined. Limit state and serviceability masonry arch bridge models ofinnovatory form are included in Chapter 4. These models follow from the studies of Chapter 3 and are novel in their own right. However, the critical arguments upon which they are based demand that these models be seen as prototypes of enhanced models whose features have now been established. Overall conclusions are discussed in Chapter 5 wherein the practical factors affecting the nature of masonry arch bridges are juxtaposed with the engineering requirements imposed upon them. Modern assessment methods must afford output that is safe without being overconservative. The findings of the research programme are in keeping with this. Supporting documentation is given in the Appendices.
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Wang, Wei. "CAUSAL MEDIATION ANALYSIS FOR NON-LINEAR MODELS." Case Western Reserve University School of Graduate Studies / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=case1332961697.
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Kahraman, Ahmet. "Non-linear dynamic analysis of geared systems /." The Ohio State University, 1990. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487676847117141.
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Cain, Jeffrey S. (Jeffrey Stuart) Carleton University Dissertation Engineering Mechanical and Aerospace. "Non-linear analysis of a gyroscopic rotor." Ottawa, 1996.
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Latini, Corazzini Valentina. "Non-linear dynamic analysis of offshore structures." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2009. http://amslaurea.unibo.it/359/.
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Su, Fei. "Statistical analysis of non-linear diffusion process." Diss., University of Iowa, 2011. https://ir.uiowa.edu/etd/2776.
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In this paper, we study the problem of statistical inference of continuous-time diffusion processes and their higher-order analogues, and develop methods for modeling threshold diffusion processes in particular. The limiting properties of such estimators are also discussed. We also proposed the likelihood ratio test statistics for testing threshold diffusion process against its linear alternative. We begin in Chapter 1 with an introduction of continuous-time non-linear diffusion processes where I summarized the literature on model estimation. The most natural extension from affine to non-linear model would be piecewise linear diffusion process with piecewise constant variance functions. It can also be considered as a continuous-time threshold autoregressive model (CTAR), the continuous-time analogue of AR model for discrete-time time-series data. The order-one CTAR model is discussed in detail. The discussion is directed more toward the estimation techniques other than the mathematical details. Existing inferential methods (estimation and testing) generally assume known functional form of the (instantaneous) variance function. In practice, the functional form of the variance function is hardly known. So, it is important to develop new methods for estimating a diffusion model that does not rely on knowledge on the functional form of the variance function. In the second Chapter, we propose the quasi-likelihood method to estimate the parameters indexing the mean function of a threshold diffusion model without prior knowledge of its instantaneous variance structure. (and apply to other nonlinear diffusion models, which will be further investigated later.) We also explore the limiting properties of the quasi-likelihood estimators. We focus on estimating the mean function, after which the functional form of the instantaneous variance function can be explored and subsequently estimated from quadratic variation considerations. We show that, under mild regularity conditions, the quasi-likelihood estimators of the parameters in the linear mean function of each regime are consistent and are asymptotically normal, whereas the threshold parameter is super consistent and weakly converges to some non-Gaussian continuous distribution. A notable feature is that the limiting distribution of the threshold parameter admits a closed-form probability density function, which enables the construction of its confidence interval; in contrast, for the discrete-time TAR models, the construction of the confidence interval for the threshold parameter has, so far, not been practically solved. A simulation study is provided to illustrate the asymptotic results. We also use the threshold model to estimate the term structure of a long time series of US interest rates. It is also of theoretical and practical interest that whether the observed process indeed satisfy the threshold model. In Chapter 3, we propose a likelihood ratio test scheme to test the existence of thresholds. It can test for non-linearity. Most importantly, we shall study how to price and predict value processes with nonlinear diffusion processes.be shown, under the null hypothesis of no threshold, the test statistics converges to a central Gaussian process asymptotically. Also the test is asymptotically powerful and the asymptotic distribution of the test statistic under the alternative hypothesis converge to a non-central Gaussian distribution. Further, the limiting distribution is the same as that of its discrete analogues for testing TAR(1) model against autoregressive model. Thus the upper percentage points of the asymptotic statistics for the discrete case are immediately applicable for our tests. Simulation studies are also conducted to show the empirical size and power of the tests. The application of our current method leads to more future work briefly discussed in Chapter 4. For example, we would like to extend our estimation methods to higher order and higher dimensional cases, use more general underlying mean processes, and most importantly, we shall study how to price and predict value processes with nonlinear diffusion processes.
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Lee, Chun Hung. "Non-Linear Contact Analysis of Meshing Gears." DigitalCommons@CalPoly, 2009. https://digitalcommons.calpoly.edu/theses/236.
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Gear transmission systems are considered one of the critical aspects of vibration analysis, and it contains various potential faults such as misalignment, cracks, and noise. Therefore, it requires vibration monitoring to ensure the system is operating properly. Case mounted accelerometers are frequently used to monitor frequencies in a system. However, it is not a simple task to identify and interpret the acceleration data since there are many gear mesh frequencies present. One of the approaches utilized by researchers to perform gear diagnostic is Finite Element Modeling. This study focuses on stiffness cycle and meshing stiffness of non-linear quasi-static finite element modeling. The comparisons of meshing stiffness will concentrate on the type of elements, the integration methods, the meshing quality, plane stress and plane strain analysis, sensitivity of model tolerance, and crack modeling. The results show that the FEA approach is extremely sensitive to tolerance, mesh density, and element choice. Also, the results indicate that a complete sensitivity and convergence studies should be carried out for a satisfactory stiffness match.
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Chadwick, Mark Anthony. "Identification and analysis of linear and non-linear fast-sampled systems." Thesis, University of Sheffield, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.489362.
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This thesis presents an investigation into the identification and analysis of and non-linear fast-sampled systems. Traditionally, discrete-time sampled-data systems are represented using shift-operator parameterisations utilising the d-operator. An alternative parameterisation using the q-operator is explored and shown to maintain a close correspondence to the continuous-time. This approach offers the ability to unify discrete and continuous-time theory as each can be considered a special case of the d-operator approach. In addition, these parameterisations possess numerical advantages when compared to the shift-operator representations.
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Frazer, Gordon John. "Aspects of time-varying non Gaussian non-linear signal analysis." Thesis, Queensland University of Technology, 1996. https://eprints.qut.edu.au/105546/1/T%28BE%26E%29%201032%20Aspects%20of%20time-varying%20non-Gaussian%20non-linear%20signal%20analysis.pdf.
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This thesis addresses problems in the field of time-varying, non-Gaussian, non-linear signal processing. It concentrates on developing results in the areas of time-frequency signal analysis and higher-order spectra which are linked by the developing area of time-varying higher-order spectra. Motivation comes from applying procedures developed to underwater acoustic signals. Reviews of time-frequency analysis and higher-order spectra precede the research contributions. Three appendices cover: a review of the
multiple-window spectrum estimation method, an improved procedure for computing analytic signals frequently used in time-frequency signal analysis, and an updated approach for computing Slepian sequences necessary for the multiple-window spectrogram.
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Lüblinghoff, Julia Cordula. "Klinische Charakterisierung von TSH-Rezeptormutationen." Doctoral thesis, Universitätsbibliothek Leipzig, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-96931.
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Diese Dissertation untersucht einen möglichen Zusammenhang zwischen dem beschriebenen klinischen Verlauf bei Patienten mit konstitutiv aktivierenden TSH-Rezeptormutationen und der gemessenen in vitro Aktivität. Konstitutiv aktivierende Mutationen finden sich als somatische Mutationen in autonomen Adenomen und als Keimbahnmutationen bei Patienten mit sporadischer bzw. familiärer nicht-autoimmuner Hyperthyreose. Die in vitro Aktivität der zu Grunde liegenden TSH-Rezeptormutationen wird mit Hilfe der Linearen Regressions-Analyse bestimmt. Dies ist ein Verfahren, welches die basale Produktion des second messenger cAMP (Cyclo-Adenosinmonophosphat) misst, unter Berücksichtigung der Expression des TSH-Rezeptors. Die Analyse der Krankheitsverläufe der sporadischen nicht-autoimmunen Hyperthyreose zeigt keinen eindeutigen Bezug zur gemessenen in vitro Aktivität. Es besteht jedoch eine höhere in vitro Aktivität bei Mutationen, die sowohl bei der nicht-autoimmunen sporadischen Hyperthyreose und in autonomen Adenomen zu finden sind, im Vergleich zu ausschließlich familiären Mutationen. Dies entspricht auch dem klinischen Eindruck. Für die wenigen bekannten Fälle der sporadischen nicht-autoimmunen Hyperthyreose wurden dramatische Verläufe mit häufigen Rückfällen unter medikamentöser Therapie und zahlreichen Komplikationen (z.B. mentale Retardierung, Kraniosynostose, zerebrale Ventrikulomegalie, beschleunigte Knochenreifung) beschrieben.
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Javed, Khalid. "Non linear seismic response of asymmetric buildings." Thesis, University of East London, 1999. http://roar.uel.ac.uk/1260/.
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The study presented in this thesis is an attempt towards a better understanding of the coupled lateral-torsional response of buildings subject to seismic ground motion. Some of the problems identified in the past studies are thoroughly investigated and some new areas of study are explored. Some of these problems encountered in the literature include (a) the existence of several definitions of uncoupled torsional to lateral frequency ratio (b) an arbitrary selection of structural parameters in a parametric analysis resulting in a physically inadmissible structure and (c) the effect of nonlinearity. Because of the simplified models with either eccentricity in one direction or the ground motion applied in only one direction, the effects of a bi-directional loading have not been investigated in detail. These effects may include the relative differences in the amplitude or phase components of the individual accelerograms and their orientation with respect to the building. The phase properties of accelerograms are of particular interest and these have not received much attention in the past. Using analytical methods such as Chasle's[16] and Gerschgorin's[39] theorems, the equation of motion of a bi-eccentric system is derived and all of the existing problems regarding the definition of structural parameters and their bounds are studied in depth. To facilitate nonlinear parametric study, a paraboloid non-linear elastic stiffness model is proposed. Fourier spectral methods are used to study the frequency domain characteristics of the accelerogram pair. The difference in phase and amplitude of the component frequencies in each direction are studied for their effects on the response. For phase difference, cross-correlation function is used as a comparative statistical indicator. USA earthquake records obtained from US National Geophysical Data Centre are grouped into four soil types and the analysis is performed for each group in order to explore the soil-dependency of the aforementioned effects on the response. Computer programs are written in FORTRAN for both parametric and numerical model analyses. The latter can handle any number and orientation of columns with the assumed nonlinear stiffness properties. Newmark's and Runge-Kutta methods of numerical integration with adaptive step size control have been used to calculate parametric and the hysteretic responses of the system. The response to harmonic ground acceleration is used as a preliminary investigation into the response to actual accelerogram frequency components. The study has developed relationships for different definitions of the uncoupled torsional to lateral frequency ratio. Detailed derivation of the Equation of Motion has clarified the confusion that produced different definitions in the past studies. Graphical descriptions of the admissibility bounds on system parameters are produced. The variation in the response quantities is studied for a range of amplitude and phase contents of the applied ground acceleration. The difference in phase and amplitude in x and y ground accelerations have been found to affect the response quite significantly. More generally, the relationship of these differences to the torsional mode amplification has been observed. The effects of structural frequency and eccentricity parameters are also studied. Graphs showing the relationship between, the angle of incidence of the accelerogram with respect to the principal axis of the building, and the phase difference in the accelerogram pair, have been produced. The proposed analysis involving the bi-directional ground acceleration on a bi-eccentric system is an improvement on the current methods employed in design practice. Further work is, however, required before simplified design recommendations can be made and some proposals for future research are given at the end of this thesis.
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PISANO, FABIO. "Analysis and synthesis techniques of nonlinear dynamical systems with applications to diagnostic of controlled thermonuclear fusion reactors." Doctoral thesis, Università degli Studi di Cagliari, 2013. http://hdl.handle.net/11584/266202.
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Nonlinear dynamical systems are of wide interest to engineers, physicists and mathematicians, and this is due to the fact that most of physical systems in nature are inherently non-linear. The nonlinearity of these systems has consequences on their time-evolution, which in some cases can be completely unpredictable, apparently random, although fundamentally deterministic. Chaotic systems are striking examples of this.
In most cases, there are no hard and fast rules to analyse these systems. Often, their solutions cannot be obtained in closed form, and it is necessary to resort to numerical integration techniques, which, in case of high sensitivity to initial conditions, lead to ill-conditioning problems and high computational costs.
The dynamical system theory, the branch of mathematics used to describe the behaviour of these systems, focuses not on finding exact solutions to the equations describing the dynamical system, but rather on knowing if the system stabilises to a steady state in the long term, and what are the possible attractors, e.g. a quasi-periodic or chaotic attractors.
Regarding the synthesis, from both a practical and a theoretical standpoint, it is very desirable to develop methods of synthesizing these systems. Although extensive theory has been developed for linear systems, no complete formulation for nonlinear systems synthesis is present today.
The main topic of this thesis is the solution of engineering problems related to the analysis and synthesis of nonlinear and chaotic systems.
In particular, a new algorithm which optimizes Lyapunov exponents estimation in piecewise linear systems has been applied to PWL and polynomial chaotic systems. In the field of complex systems synthesis, a systematic method to project systems of order 2n characterized by two positive Lyapunov exponents, has been proposed. This procedure couples nth-order chaotic systems with a suitable nonlinear coupling function. Furthermore, a method for the fault detection has been developed. In the field of time series analysis, a new denoising method, based on the wavelet transform of the noisy signal, has been described. The method implements a variable thresholding, whose optimal value is determined by analysing the cross-correlation between the denoised signal and the residuals and by applying different criteria depending on the particular decomposition level. Finally, a study of dynamical behaviour of Type I ELMs has been performed for a future modelization of the phenomenon. In this context, a statistical analysis of time intervals between successive Type I ELMs has been proposed.---------------------------------- Il tema principale di questa tesi è la soluzione di problemi ingegneristici legati all’analisi e alla sintesi di sistemi dinamici non lineari. I sistemi dinamici non lineari sono di largo interesse per ingegneri, fisici e matematici, e questo è dovuto al fatto che la maggior parte dei sistemi fisici in natura è intrinsecamente non lineare.
La non linearità di questi sistemi ha conseguenze sulla loro evoluzione temporale, che in certi casi può rivelarsi del tutto imprevedibile, apparentemente casuale, seppure fondamentalmente deterministica. I sistemi caotici sono un esempio lampante di questo comportamento. Nella maggior parte dei casi non esistono delle regole standard per l’analisi di questi sistemi. Spesso, le soluzioni non possono essere ottenute in forma chiusa, ed è necessario ricorrere a tecniche di integrazione numerica, che, in caso di elevata sensibilità alle condizioni iniziali, portano a problemi di mal condizionamento e di elevato costo computazionale.
La teoria dei sistemi dinamici, la branca della matematica usata per descrivere il comportamento di questi sistemi, non si concentra sulla ricerca di soluzioni esatte per le equazioni che descrivono il sistema dinamico, ma piuttosto sull’analisi del comportamento a lungo termine del sistema, per sapere se questo si stabilizzi in uno stato stabile e per sapere quali siano i possibili attrattori, ad esempio, attrattori quasi-periodici o caotici.
Per quanto riguarda la sintesi, sia da un punto di vista pratico che teorico, è molto importante lo sviluppo di metodi in grado di sintetizzare questi sistemi. Sebbene per i sistemi lineari sia stata sviluppata una teoria ampia e esaustiva, al momento non esiste alcuna formulazione completa per la sintesi di sistemi non lineari.
In questa tesi saranno affrontati problemi di caratterizzazione, analisi e sintesi, legati allo studio di sistemi non lineari e caotici.
La caratterizzazione dinamica di un sistema non lineare permette di individuarne il comportamento qualitativo a lungo termine. Gli esponenti di Lyapunov sono degli strumenti che permettono di determinare il comportamento asintotico di un sistema dinamico. Essi danno informazioni circa il tasso di divergenza di traiettorie vicine, caratteristica chiave delle dinamiche caotiche. Le tecniche esistenti per il calcolo degli esponenti di Lyapunov sono computazionalmente costose, e questo fatto ha in qualche modo precluso l’uso estensivo di questi strumenti in problemi di grandi dimensioni. Inoltre, durante il calcolo degli esponenti sorgono dei problemi di tipo numerico, per ciò il calcolo deve essere affrontato con cautela. L’implementazione di algoritmi veloci e accurati per il calcolo degli esponenti di Lyapunov è un problema di interesse attuale.
In molti casi pratici il vettore di stato del sistema non è disponibile, e una serie temporale rappresenta l’unica informazione a disposizione. L’analisi di serie storiche è un metodo di analisi dei dati provenienti da serie temporali che ha lo scopo di estrarre delle statistiche significative e altre caratteristiche dei dati, e di ottenere una comprensione della struttura e dei fattori fondamentali che hanno prodotto i dati osservati. Per esempio, un problema dei reattori a fusione termonucleare controllata è l’analisi di serie storiche della radiazione Dα, caratteristica del fenomeno chiamato Edge Localized Modes (ELMs). La comprensione e il
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controllo degli ELMs sono problemi cruciali per il funzionamento di ITER, in cui il type-I ELMy H-mode è stato scelto come scenario di funzionamento standard. Determinare se la dinamica degli ELM sia caotica o casuale è cruciale per la corretta descrizione dell’ELM cycle. La caratterizzazione dinamica effettuata sulle serie temporali ricorrendo al cosiddetto spazio di embedding, può essere utilizzata per distinguere serie random da serie caotiche.
Uno dei problemi più frequenti che si incontra nell’analisi di serie storiche sperimentali è la presenza di rumore, che in alcuni casi può raggiungere anche il 10% o il 20% del segnale. È quindi essenziale , prima di ogni analisi, sviluppare una tecnica appropriata e robusta per il denosing.
Quando il modello del sistema è noto, l’analisi di serie storiche può essere applicata al rilevamento di guasti. Questo problema può essere formalizzato come un problema di identificazione dei parametri. In questi casi, la teorie dell’algebra differenziale fornisce utili informazioni circa la natura dei rapporti fra l’osservabile scalare, le variabili di stato e gli altri parametri del sistema.
La sintesi di sistemi caotici è un problema fondamentale e interessante. Questi sistemi non implicano soltanto un metodo di realizzazione di modelli matematici esistenti ma anche di importanti sistemi fisici reali. La maggior parte dei metodi presentati in letteratura dimostra numericamente la presenza di dinamiche caotiche, per mezzo del calcolo degli esponenti di Lyapunov. In particolare, le dinamiche ipercaotiche sono identificate dalla presenza di due esponenti di Lyapunov positivi.
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Harursampath, Dineshkumar. "Non-classical non-linear effects in thin-walled composite beams." Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/12501.
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Nabavian, M. "The linear and non-linear analysis of thin-walled sections in compression and bending." Thesis, Cranfield University, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356202.
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Hata, Misako. "Non linear tolerance analysis by response surface methodology." Ohio : Ohio University, 2001. http://www.ohiolink.edu/etd/view.cgi?ohiou1173897314.
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Morin, Norman J. "Essays in multivariate and non-linear time series analysis /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 1997. http://wwwlib.umi.com/cr/ucsd/fullcit?p9732704.
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Tongal, Hakan Güldal Veysel. "Akarsu akımlarının lineer ve non-lineer parametrik zaman serileriyle modellenmesi /." Isparta : SDÜ Fen Bilimleri Enstitüsü, 2008. http://tez.sdu.edu.tr/Tezler/TF01117.pdf.
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Kang, Lan. "Linear and non-linear free vibration analysis of plates and shallow shells." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0025/MQ30714.pdf.
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Subramaniam, Laxman. "Linear and non-linear free vibration analysis of axisymmetric solids and structures." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0011/MQ30743.pdf.
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Stang, Jorgen. "Iterative methods for linear and geometrically non-linear parallel finite element analysis." Thesis, Heriot-Watt University, 1995. http://hdl.handle.net/10399/743.
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Nemakhavhani, Daniel Phuluwani. "Palatalization and labialization in Tshivenda : a linear and non-linear phonological analysis." Thesis, Stellenbosch : Stellenbosch University, 2002. http://hdl.handle.net/10019.1/52984.
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Thesis (MA)--Stellenbosch University, 2002.ENGLISH ABSTRACT: This study focuses on two phonological processes occurring in Venda, i.e. on palatalization and labialization. Two phonological models are applied to describe these phenomena: a traditional (linear) phonological model, the Transformational Generative model of Chomsky and Halle (1968), and a non-linear Feature Geometry model of Clements (1985). This was done in order to ascertain which model would be more effective in its coverage of these sound changes. The core concepts of each model were described and the sound system of Venda was analysed in terms of distinctive features. The application of the two models led to the conclusion that a linearly structured model seem to be more effective to account for both these phenomena in Venda than its nonlinear counterpart.
AFRIKAANSE OPSOMMING: Hierdie studie fokus op twee fonologiese prosesse in Venda, tewete palatalisasie en labialisasie. Twee fonologie modelle word toegepas om hierdie verskynsels mee te beskryf: 'n tradisionele liniêre model, die sg Transformasioneel Generatiewe model van Chomsky an Halle (1968), en 'n nie-liniêre model van Clements (1985). Die doel hiermee was om te bepaal welke model hierdie verskynsels die beste kan beskryf. Die hoofkomponente van elke model is vireers bespreek waarna die klanke van Venda ontleed is in terme van distinktiewe kenmerke. Uit die toepassing van die twee modelle het dit duidelik geblyk dat die liniêre model "n veel beter beskrywing moontlik maak van die verskynsels as die meer kontemporêre nie-liniêre model.
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Shikongo, Albert. "Numerical Treatment of Non-Linear singular pertubation problems." Thesis, Online access, 2007. http://etd.uwc.ac.za/usrfiles/modules/etd/docs/etd_gen8Srv25Nme4_3831_1257936459.pdf.
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Le, Thanh Nam. "Non-linear Dynamic analysis of corotational beam structures." Thesis, KTH, Bro- och stålbyggnad, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-36799.
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Ntantis, Efstratios. "Capability expansion of non-linear gas path analysis." Thesis, Cranfield University, 2008. http://dspace.lib.cranfield.ac.uk/handle/1826/3790.
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The performance diagnostics of any engine model is accomplished by estimating a set of internal engine health parameters from available sensor measurements. These sensors which comprises of a variety of gas path measurements e.g. pressures, temperatures, fuel flow and spool speeds provide information regarding the health of the engine. No physical measurement, however, elaborate or precise, or how often repeated, can ever completely eliminate the universal presence of measurement uncertainties. Instrument measurements are often distorted by noise and bias, thereby masking the true condition of the engine leads to incorrect estimation results. Measurement uncertainties encourage the inaccurate fault diagnosis, and in order to improve the reliability of diagnostic results, it is important to statistically analyse the data scattering caused by sensor noise. Leakage analysis is a key factor in determining energy losses from a gas turbine. Once the components assembly fails, air leakage through the opening increases resulting in a performance loss. Therefore, the performance efficiency of the engine cannot be reliably determined, without good estimates and analysis of leakage faults. Specifically, for energy calculations it is the air flow leaking around the components at operating conditions that is required. Consequently the implementation of a leakage fault within a gas turbine engine model is necessary for any diagnostic technique that can expand its diagnostics capabilities for more accurate predictions. The simulating methods should either, precisely measure the size of leaks or measure the air flow along gas path with sufficient accuracy. In this research, the diagnostic tool that used to deals with the statistical analysis of measurement noise and leakage fault diagnostics is a model-based method utilizing non-linear GPA. For the purpose of diagnostic, the simulation code used in this study is TURBOMATCH and the engine model Trent 500. TURBOMATCH is the name of a non-linear simulation code created and developed at Cranfield University that represents engine physics and operates for gas turbine performance calculations. Trent 500 is a high by-pass turbofan engine developed by Rolls Royce PLC and used in this research for the construction of a TURBOMATCH model, which assembles the major, gas path components of the real engine. The Trent 500 engine model is therefore, a scaled unclassified representation of the advanced civil three-spool highbypass turbofan engine.
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Kenyon, Jonn Mark. "Non-linear analysis of reinforced concrete plane frames /." Title page, table of contents and abstract only, 1993. http://web4.library.adelaide.edu.au/theses/09PH/09phk368.pdf.
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Elizalde, Siller Hugo Ramon. "Non-linear modal analysis methods for engineering structures." Thesis, Imperial College London, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.419886.
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Chaikittiratana, Arisara. "Non-linear viscoelastic strain analysis for engineering polymers." Thesis, University of Oxford, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342239.
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Afroozi, Milani Mohammad. "Non-linear analysis of optical and microwave sources." Thesis, University of Birmingham, 2016. http://etheses.bham.ac.uk//id/eprint/6675/.
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Due to the ever increasing need for better and more capable communication systems, a large quantity of research is focused on the design and simulation of different sections of communication systems including the communication sources. Due to the massive cost of the fabrication involved in designing new communication sources, the accurate modelling and design of these sources using Computer Aided Design is of great interest. In this thesis fundamentals of laser modelling and nonlinear microwave antenna design; followed by reviewing the most important works carried out by other researchers in these fields. The thesis continues by introducing a proposed, accurate model of the Vertical Cavity Surface Emitting Laser (VCSEL). The proposed model integrates the effects of the matching network as well as the parasitics, due to the VCSEL chip and the packaging mounting and the intrinsic VCSEL noise sources. Further in this thesis, a nonlinear Composite Right/Left Handed frequency doubler Leaky Wave Antenna is designed which is capable of transmitting a signal in a direction that can be varied continuously from backfire to endfire, by varying the input frequency to the structure. The novelty of the proposed design is in the inclusion of nonlinear elements in the CRLH structure and also in the use of a quasi-lumped approach when designing the distributed structure. Finally, in this thesis a novel method of combining harmonic balance and EM analysis for the design and optimisation of nonlinear active antennas is developed. This method responds to the restriction of the CAD software in conveniently combining the analysis of nonlinear active antennas with advanced EM simulations such as radiation patterns. The proposed method enables the advanced EM analysis at the harmonic frequencies, generated within the nonlinear microwave structures when the structure is exited at the fundamental frequency, to be combined with full electromagnetic simulators.
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Hong, Andrew C. (Andrew Choon-Ki). "Non-linear analysis of cello pitch and timbre." Thesis, Massachusetts Institute of Technology, 1992. http://hdl.handle.net/1721.1/67119.
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LADISLAO, Luigi. "Analisi non-lineare di dati posturografici." Doctoral thesis, Università Politecnica delle Marche, 2006. http://hdl.handle.net/11566/242669.
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Blake, Kenneth William. "Moving mesh methods for non-linear parabolic partial differential equations." Thesis, University of Reading, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.369545.
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Madigoe, Mashikane William. "Syllable structure processes in Northern Sotho : a linear and non-linear phonological analysis." Thesis, Stellenbosch : Stellenbosch University, 2003. http://hdl.handle.net/10019.1/53608.
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Thesis (MA)--Stellenbosch University, 2004.ENGLISH ABSTRACT: This study intends to describe and explain syllable structure processes in Northern Sotho. It deals with phonological processes such as vowel deletion, semivocalization and semivowel insertion. The major aim of these processes is to restore the preferred ICVI syllable structure which has been violated by morphological processes such as passive, diminutive, the construction of absolute pronouns, etc. Two phonological models are applied with the intention to determine the one that presents the most credible explanation for the phenomenon at hand. The two models employed are, respectively, the Transformational (TG) and Feature Geometry (FG) models. It appears that Feature Geometry model yields better results in the description of syllable structure processes in Northern Sotho.
AFRIKAANSE OPSOMMING: Hierdie studie beskryf en verklaar sillabestruktuur prosesse in Noord-Sotho. Die tersaaklike fonologiese prosesse is vokaaldelesie, semivokalisasie en semivokaalinvoeging. Die doel van hierdie prosesse is om "n bepaalde voorkeursillabestruktuur IKVI te herstel wat versteur word deur morfologiese prosesse met die vorming van die passief, diminutief, die konstruksie van absolute voornaamwoorde ensovoorts. Twee fonologiese modelle word geïmplementeer ten einde te bepaal welke model die mees geloofwaardige verklarings vir die betrokke verskynsels kan bied. Die Transformasioneel-Generatiewe (TG) en Kenmerk Geometriese(KG) modelle word respektiewelik toegepas. Dit skyn asof die Kenmerk Geometriese model beter resultate lewer in die beskrywing van sillabestruktuurprosesse in Noord-Sotho.
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Djoudi, Mohamed Salah. "Strain based finite elements for linear and geometrically non-linear analysis of structures." Thesis, Cardiff University, 1990. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316332.
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Marangon, Christian. "Linear and non-linear structural analysis of notched components with local energy approaches." Doctoral thesis, Università degli studi di Padova, 2014. http://hdl.handle.net/11577/3423490.
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In engineering practice, mechanical components are weakened by a wide range of sharp or blunt notches and their presence has to be accurately taken into account in the design. In fact near notches a strong stress gradient is always induced when a far field loading is applied.
Aiming to investigate the integrity of notched components subjected to different loading histories, for many years to nowadays a lot of stress and strain based damage criteria have been proposed. However, in the last years, some energy based criteria have been introduced and successfully applied on notched members proving to be powerful damage prediction tools.
In particular the averaged strain energy density criterion (Lazzarin and Zambardi 2001) has been developed and used in order to assess the strength of notched components with various notch geometries subjected to different types of loading.
The aim of this work is to extend the validity of the averaged SED criterion to the three-dimensional effects arising in the vicinity of a notch and to the problems induced by the application of multiaxial static and cyclic loadings.
Taking advantage of some results obtained from multiaxial cyclic analyses, the effect of the phase displacement between the applied loads has been addressed presenting a new proposal based on the maximum tangential stress averaged over an entire loading cycle.
Finally, a dedicated software based on the cyclic plasticity theory has been developed in order to obtain the stress/strain distributions at the tip of a rounded notch subjected to uniaxial and multiaxial low cycle fatigue. A particular link between the plastic hysteresis energy at the notch tip and the averaged SED has been found representing the first potential step for a future extension of the averaged SED criterion to cyclic plasticity.Nella pratica ingegneristica, i componenti meccanici sono sovente indeboliti da discontinuità geometriche di diversa forma e dimensione, i quali devono essere tenuti in considerazione in fase di progettazione al fine di evitare malfunzionamenti o collassi strutturali. Con l’obiettivo di valutare l’integrità strutturale di componenti indeboliti da intagli soggetti a sollecitazioni di diversa natura, numerosi criteri di cedimento sono stati sviluppati considerando lo stato di tensione e/o di deformazione all’apice dell’intaglio o nelle immediate vicinanze di quest’ultimo. Inoltre, negli ultimi anni, sono stati sviluppati approcci di tipo energetico, i quali hanno dimostrato un’ottima attitudine alla previsione del cedimento di componenti intagliati. In particolare, il criterio basato sulla densità di energia di deformazione (SED) mediata all’interno di un volume strutturale è stato presentato da Lazzarin e Zambardi (2001) al fine di valutare la resistenza di componenti intagliati soggetti a diverse sollecitazioni. L’obiettivo del primo filone di ricerca di questa tesi è quello di estendere e validare il criterio SED considerando sia i modi accoppiati che si generano per effetto Poisson in componenti tridimensionali, sia problemi legati all’applicazione di sollecitazioni di modo misto e di fatica multiassiale. Prendendo spunto da alcuni risultati ottenuti nel caso di sollecitazioni cicliche, il secondo filone di ricerca ha riguardato lo studio di una proposta in grado di discriminare l’effetto dello sfasamento tra le sollecitazioni su provini intagliati a spigolo vivo soggetti a fatica multiassiale. Il terzo filone di ricerca ha riguardato l'implementazione di un software in grado di fornire le tensioni e le deformazioni elasto-plastiche all’apice di un intaglio raccordato sottoposto a fatica oligociclica. Infine, è stato possibile trovare un coefficiente di correlazione tra l'area del ciclo di isteresi all'apice dell'intaglio ed il valore della densità di energia di deformazione elasto-plastica all'interno di un volume strutturale.
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Persson, Jonas. "Bandwidth-reduced Linear Models of Non-continuous Power System Components." Doctoral thesis, Stockholm : Electric Power Systems, School of Electrical Engineering, Royal Institute of Technology, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3984.
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Richardson, Thomas Stuart. "Continuation methods applied to non linear flight dynamics and control." Thesis, University of Bristol, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.268783.
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Botero, Alonso. "Sampling weak values : a non-linear Bayesian model for non-ideal quantum measurements /." Digital version accessible at:, 1999. http://wwwlib.umi.com/cr/utexas/main.
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