We test the controversial ideas about the role of corridors in fragmented animal habitats. Using simulation studies we analyze how fragmentation affects a simple prey-predator system and how the introduction of openings that connect the habitats changes the situation. Our individual based model consists of 3 levels: renewable prey food, as well as prey and predators that both have a simple economy. We find, in line with intuition, that the fragmentation of a habitat has a strong negative effect especially on the predator population. Connecting the fragmented habitats facilitates predator (and hence prey) survival, but also leads to an important counterintuitive effect: in the presence of a high quality predator, connected fragmented systems fare better in terms of coexistence than do unfragmented systems. Using a frequency domain analysis we explain how corridors between sub-habitats serve as "wave breakers" in the population flow, thus preventing deadly density waves to occur.

abstract: Neural interfacing applications have advanced in complexity, with needs for increasingly high degrees of freedom in prosthetic device control, sharper discrimination in sensory percepts in bidirectional interfaces, and more precise localization of functional connectivity in the brain. As such, there is a growing need for reliable neurophysiological recordings at a fine spatial scale matching that of cortical columnar processing. Penetrating microelectrodes provide localization sufficient to isolate action potential (AP) waveforms, but often suffer from recorded signal deterioration linked to foreign body response. Micro-Electrocorticography (μECoG) surface electrodes elicit lower foreign body response and show greater chronic stability of recorded signals, though they typically lack the signal localization necessary to isolate individual APs. This dissertation validates the recording capacity of a novel, flexible, large area μECoG array with bilayer routing in a feline implant, and explores the ability of conventional μECoG arrays to detect features of neuronal activity in a very high frequency band associated with AP waveforms. Recordings from both layers of the flexible μECoG array showed frequency features typical of cortical local field potentials (LFP) and were shown to be stable in amplitude over time. Recordings from both layers also showed consistent, frequency-dependent modulation after induction of general anesthesia, with large increases in beta and gamma band and decreases in theta band observed over three experiments. Recordings from conventional μECoG arrays over human cortex showed robust modulation in a high frequency (250-2000 Hz) band upon production of spoken words. Modulation in this band was used to predict spoken words with over 90% accuracy. Basal Ganglia neuronal AP firing was also shown to significantly correlate with various cortical μECoG recordings in this frequency band. Results indicate that μECoG surface electrodes may detect high frequency neuronal activity potentially associated with AP firing, a source of information previously unutilized by these devices. / Dissertation/Thesis / Doctoral Dissertation Biomedical Engineering 2018

The thesis treats model reduction for linear time-varying systems. Time-varying models appear in many fields, including power systems, chemical engineering, aeronautics, and computational science. They can also be used for approximation of time-invariant nonlinear models. Model reduction is a topic that deals with simplification of complex models. This is important since it facilitates analysis and synthesis of controllers. The thesis consists of two parts. The first part provides an introduction to the topics of time-varying systems and model reduction. Here, notation, standard results, examples, and some results from the second part of the thesis are presented. The second part of the thesis consists of four papers. In the first paper, we study the balanced truncation method for linear time-varying state-space models. We derive error bounds for the simplified models. These bounds are generalizations of well-known time-invariant results, derived with other methods. In the second paper, we apply balanced truncation to a high-order model of a diesel exhaust catalyst. Furthermore, we discuss practical issues of balanced truncation and approximative discretization. In the third paper, we look at frequency-domain analysis of linear time-periodic impulse-response models. By decomposing the models into Taylor and Fourier series, we can analyze convergence properties of different truncated representations. In the fourth paper, we use the frequency-domain representation developed in the third paper, the harmonic transfer function, to generalize Bode's sensitivity integral. This result quantifies limitations for feedback control of linear time-periodic systems. / QC 20120206

This diploma thesis deals with the algorithms for signal processing in a field of a low-coherence interferometry. The introductory part is devoted to the basic principle of the low-coherence interferometry and to presenting its field of applications. The second part contains a list of selected algorithms supplemented by a description of their functionality. The procedure of experimental measurement of known surface with Michelson interferometer is described in the third part and the results obtained for particular algorithms are presented. Finally, algorithms are compared on the basis of measurement results.

Des systèmes avec des coefficients dépendant du retard ont été rencontrés dans diverses applications de la science et de l'ingénierie. Malgré la littérature abondante sur les systèmes de temporisation, il y a peu de résultats concernant l'analyse de stabilité des systèmes avec des coefficients dépendant du retard. Cette thèse est consacrée à l'analyse de stabilité de cette classe de systèmes.Les méthodes d'analyse de la stabilité sont développées à partir de l'équation caractéristique correspondante suivant une approche généralisée tau-décomposition. Étant donné un intervalle d'intérêt de retard, nous sommes capables d'identifier toutes les valeurs de retard critique contenues dans cet intervalle pour lesquelles l'équation caractéristique admet des racines sur l'axe imaginaire du plan complexe. Le critère de direction de croisement des racines sont proposées pour déterminer si ces racines caractéristique se déplacent vers le plan complexe demi-gauche ou demi-droite lorsque le paramètre de retard passe par ces valeurs de retard critique. Le nombre de racines caractéristiques instables pour un retard donné peut ainsi être déterminé. Notre analyse comprend les systèmes avec un seul retard ou des retards proportionnés sous certaines hypothèses. Le critère de direction de croisement des racines développés dans cette thèse peut être appliqués aux multiple racines caractéristiques, ou aux racines caractéristiques dont la position paramétrée par le retard est tangent à l'axe imaginaire. En tant qu'application, il est démontré que les systèmes avec des coefficients dépendant du retard peuvent provenir de schémas de contrôle qui utilisent une sortie retardée pour approcher ses dérivés pour la stabilisation. Les méthodes d'analyse de stabilité développées dans cette thèse sont adaptées et appliquées pour trouver les intervalles de retard qui atteignent un taux de convergence demandé du système en boucle fermée. / Systems with delay-dependent coefficients have been encountered in various applications of science and engineering. However, general and systematic stability analysis is rarely reported in the rich literature on time-delay systems. This thesis is committed to the stability analysis of such class of systems.Stability analysis methods are developed based on the corresponding characteristic equation following a generalized tau-decomposition approach. Given a delay interval of interest, we are able to identify all the critical delay values contained in this interval for which the characteristic equation admits roots on the imaginary axis of the complex plane. Various root crossing direction criteria are proposed to determine whether these characteristic roots move toward the left or the right half complex plane as the delay parameter sweeps through these critical delay values. The number of unstable characteristic roots for any given delay can thus be determined. Our analysis covers systems with a single delay or commensurate delays under certain assumptions. The root crossing direction criteria developed in this thesis can be applied to characteristic roots with multiplicity, or characteristic roots whose locus parametrized by the delay is tangent to the imaginary axis. As an application, it is demonstrated that systems with delay-dependent coefficients can arise from control schemes that use delayed output to approximate its derivatives for stabilization. The stability analysis methods developed in this thesis are tailored and applied to find the delay intervals that achieve a demanded convergence rate of the closed-loop system.

<p>This thesis proposes a new analytical self-adjoint sensitivity analysis to calculate the Jacobian of the <em>S</em>-parameters for metallic shape parameters. This method is independent of the full-wave numerical analysis and the respective system matrix. The theory works for both volumetric and infinitesimally thin metallic shapes. It exploits the computational efficiency of the self-adjoint sensitivity analysis (SASA) approach where only one EM simulation suffices to obtain both the responses and their gradients in the designable parameter space.</p> <p>There are three major advantages to this development: (1) the Jacobian computation for metallic structures is completely analytical and there is no approximation involved in the sensitivity analysis of shape parameters; (2) the implementation is straightforward and in the form of a post-processing algorithm operating on the exported field solutions on the surface or around the edge of the metallic structure; and (3) it provides the possibility for exact sensitivity analysis with all electromagnetic high-frequency simulators whose system matrices are not available to export or are not differentiable with respect to shape parameters, e.g., simulators based on the FDTD method and the MoM.</p> <p>The method was verified in a number of examples using a commercial finite-element solver. The agreement between the results calculated with the proposed method and the reference self-adjoint sensitivity curves provided with the simulator are very promising.</p> <p>Suggestions for future work are provided.</p> / Master of Applied Science (MASc)

Various methods of DNA sequences modifications for frequency analysis and basic characteristics of DNA are described in the theoretical part of this thesis. Tricolor spectrograms, created by short time Fourier transform help us to recognize some characteristic patterns in DNA sequences. Practical part of this work deals with developed programme which generates spectrograms and analyse them. Last part deals with the analysis of selected sequences of C. elegans genome. Some patterns are related to data of public databases such as NCBI. Various patterns are explained from the biological nature, which relates to chromosome structure and protein coding regions. Another well recognised patterns, tandem repetitions composed of satellites, microsatellites and minisatelites are described by spectrograms as well.

Em projetos de veículos, prever adequadamente a durabilidade de um componente estrutural é vital para a redução de custos assim como para se estipular prazos de garantia e de manutenção. Por outro lado, em diversas situações, tal previsão é difícil, pois inúmeros parâmetros não estão sob controle preciso do projetista, dentre eles os mais relevantes são: o carregamento ao qual o componente será submetido e as propriedades de vida em fadiga do material. Desta forma, pode-se aplicar, em conjunto com o MEF, tratamento probabilístico do cálculo da vida em fadiga,resultando em um valor de confiabilidade, a ser usado como esteio do critério de projeto, no intuito de conferir maior significado prático à análise e aos resultados obtidos. Assim sendo, o presente trabalho descreve e relaciona os principais aspectos de um tratamento probabilístico para cálculo de vida em fadiga, configurando-se um procedimento completo subdividido nas seguintes etapas: 1. Modelagem do carregamento sobre o veículo, visando análise espectral em MEF no domínio da freqüência; 2. Cálculo da densidade de probabilidade das amplitudes cíclicas de Rainflow para as tensões atuantes na estrutura, a partir dos resultados da análise espectral em MEF no domínio da freqüência; 3. Tratamento probabilístico das propriedades características de vida em fadiga do material; 4. Cálculo da confiabilidade estrutural de vida em fadiga, tomando os resultados prévios dos tratamentos probabilísticos de tensões e de vida em fadiga do material; 5. Demonstração da viabilidade e aplicação prática de tal procedimento, implementando-o para o caso de um semi-reboque tanque autoportante. As conclusões finais obtidas confirmam o fato de haver mais falhas estruturais em veículos no Brasil do que em países do primeiro mundo, pois se evidenciou que a pior qualidade das vias trafegáveis brasileiras exacerba a probabilidade de falha por fadiga. Por fim, a metodologia proposta na presente tese, quando implementada em um programa computacional pós-processador de MEF, que automaticamente transforme os desvios padrão das tensões, resultantes da análise espectral, em probabilidades de falha, pode, mais adequadamente, subsidiar critério de projeto fundamentado na avaliação probabilística de durabilidade de um veículo através de preceitos bem definidos de confiabilidade estrutural. / In structural design, forecast correctly the part’s lifetime is vital to reduce costs and to estimate the periods of warranty and of maintenance. On the other hand, in many situations, this forecast is difficult because many parameters are not under the engineers control, some examples of this kind of parameters are: the loads acting in the part and the fatigue properties of the material. Therefore, it is possible to apply finite element analysis with a probabilistic approach in fatigue lifetime calculation, what results in reliability values that can be used as design criterion in order to give a broader meaning to the analyses and its results. Hence, this text describes and establishes the relationship between the main aspects of the probabilistic approach in fatigue lifetime calculation, resulting in the definition of a complete procedure that is divided in the following steps: 1. Modeling of the vehicle’s load aiming spectral analysis in the frequency domain; 2. Calculation procedure of the probability density function of Rainflow stress amplitudes applied in the structure upon using the spectral analysis in frequency domain results; 3. Probabilistic approach of fatigue properties of the material; 4. Fatigue reliability calculation through the use of the previous results provided by the probabilistic approach of stresses and of fatigue properties of the material; 5. Implementation of the proposed methodology for fatigue lifetime prediction of a semi-trailer tank. The conclusion confirms the fact of having much more structural failures in Brazilian vehicles than in European ones. This can be said because the results show that the worsening of the roads quality increases the fatigue failure probability. Finally, when implemented in a post-processing software for finite element programs that automatically transforms the stresses standard deviation, obtained by spectral analysis, in the fatigue failure probability, the proposed methodology in the present thesis may, more adequately, work as design criterion based on the probabilistic evaluation of the vehicles durability, upon applying well established structural reliability theory.

In this thesis, the conventional low voltage power line communication methods is investigated in the axis of automated meter reading applications and the classification and experimental verification of common noise types for low voltage power line communication network. The investigated system provides the real time transmission of electricity consumption data recorded by electricity meters, initially to a local computer via a low voltage line through a low speed PLC (Power Line Carrier) environment and subsequently to a corporate network through a high speed data transmission medium. The automated meter system provides a more effective tracking and data acquisition, a more detailed and vigorous knowledge about consumer behavior for subscriber assessment in electricity distribution in association with a brand new management and system supervision concept in electricity distribution control and management technology. The theoretical studies are experimentally verified for the Turkish low voltage power infrastructure through laboratory experiments performed in METU Electrical and Electronics Engineering Department, Electrical Machines and Drives Laboratory and R&amp / D Laboratories of MAKEL facilities in Hadimk&ouml / y. The single phase voltage of the mains line between the phase and neutral is monitored to exhibit the disturbing effects of various noise sources. The resulting voltage spectrum is logged by using digital data acquisition devices in time and frequency domain. The waveforms are converted to frequency domain using the Fast Fourier Transform (FFT) functions of the MATLAB. The experimental results are compared to the theoretical findings obtained through literature survey.

Em projetos de veículos, prever adequadamente a durabilidade de um componente estrutural é vital para a redução de custos assim como para se estipular prazos de garantia e de manutenção. Por outro lado, em diversas situações, tal previsão é difícil, pois inúmeros parâmetros não estão sob controle preciso do projetista, dentre eles os mais relevantes são: o carregamento ao qual o componente será submetido e as propriedades de vida em fadiga do material. Desta forma, pode-se aplicar, em conjunto com o MEF, tratamento probabilístico do cálculo da vida em fadiga,resultando em um valor de confiabilidade, a ser usado como esteio do critério de projeto, no intuito de conferir maior significado prático à análise e aos resultados obtidos. Assim sendo, o presente trabalho descreve e relaciona os principais aspectos de um tratamento probabilístico para cálculo de vida em fadiga, configurando-se um procedimento completo subdividido nas seguintes etapas: 1. Modelagem do carregamento sobre o veículo, visando análise espectral em MEF no domínio da freqüência; 2. Cálculo da densidade de probabilidade das amplitudes cíclicas de Rainflow para as tensões atuantes na estrutura, a partir dos resultados da análise espectral em MEF no domínio da freqüência; 3. Tratamento probabilístico das propriedades características de vida em fadiga do material; 4. Cálculo da confiabilidade estrutural de vida em fadiga, tomando os resultados prévios dos tratamentos probabilísticos de tensões e de vida em fadiga do material; 5. Demonstração da viabilidade e aplicação prática de tal procedimento, implementando-o para o caso de um semi-reboque tanque autoportante. As conclusões finais obtidas confirmam o fato de haver mais falhas estruturais em veículos no Brasil do que em países do primeiro mundo, pois se evidenciou que a pior qualidade das vias trafegáveis brasileiras exacerba a probabilidade de falha por fadiga. Por fim, a metodologia proposta na presente tese, quando implementada em um programa computacional pós-processador de MEF, que automaticamente transforme os desvios padrão das tensões, resultantes da análise espectral, em probabilidades de falha, pode, mais adequadamente, subsidiar critério de projeto fundamentado na avaliação probabilística de durabilidade de um veículo através de preceitos bem definidos de confiabilidade estrutural. / In structural design, forecast correctly the part’s lifetime is vital to reduce costs and to estimate the periods of warranty and of maintenance. On the other hand, in many situations, this forecast is difficult because many parameters are not under the engineers control, some examples of this kind of parameters are: the loads acting in the part and the fatigue properties of the material. Therefore, it is possible to apply finite element analysis with a probabilistic approach in fatigue lifetime calculation, what results in reliability values that can be used as design criterion in order to give a broader meaning to the analyses and its results. Hence, this text describes and establishes the relationship between the main aspects of the probabilistic approach in fatigue lifetime calculation, resulting in the definition of a complete procedure that is divided in the following steps: 1. Modeling of the vehicle’s load aiming spectral analysis in the frequency domain; 2. Calculation procedure of the probability density function of Rainflow stress amplitudes applied in the structure upon using the spectral analysis in frequency domain results; 3. Probabilistic approach of fatigue properties of the material; 4. Fatigue reliability calculation through the use of the previous results provided by the probabilistic approach of stresses and of fatigue properties of the material; 5. Implementation of the proposed methodology for fatigue lifetime prediction of a semi-trailer tank. The conclusion confirms the fact of having much more structural failures in Brazilian vehicles than in European ones. This can be said because the results show that the worsening of the roads quality increases the fatigue failure probability. Finally, when implemented in a post-processing software for finite element programs that automatically transforms the stresses standard deviation, obtained by spectral analysis, in the fatigue failure probability, the proposed methodology in the present thesis may, more adequately, work as design criterion based on the probabilistic evaluation of the vehicles durability, upon applying well established structural reliability theory.