Made available in DSpace on 2016-08-17T14:53:10Z (GMT). No. of bitstreams: 1 Bernardo Nogueira Neto.pdf: 936161 bytes, checksum: 8cae25f84e9e07f78244f10040d97213 (MD5) Previous issue date: 2010-06-04 / In this dissertation, we explore the application of the Theory of System Identification to develop a mathematical model that represents the behavior of the electrical current rectifier used to power the traction motors of a locomotive diesel-electric, based on mathematical manipulation of its temperature data. It was developed an ARX model and, using the aid of the computational system identification toolbox of MATLAB ®, simulations were made for estimation and validation of the order of the model that best describes the dynamic response of the physical system. The input and output data of the rectifier are obtained from the direct measurement of the output current of main generator, which is the input, and from the measurement of the temperature on the rectifier, which corresponds to the output. These data are used in developing the mathematical model of the system under study. The goal is to obtain a model that best represents the behavior of the main engine rectifier, allowing control actions to optimize the relation between supplied and required power of locomotive, so that downtime events resulting from self-protection mechanisms against high temperatures during operation of the rectifier in severe operations are minimized. As a result, we have a more advanced and efficient model that allows a strategy to monitoring the equipment at the various points of operation, considering their variation and ensuring a stable and safety locomotive's operation. / Nesta dissertação, aborda-se a aplicação da Teoria de Identificação de Sistemas para escolha de um modelo polinomial, que represente o comportamento do retificador de corrente elétrica, utilizado para suprimento dos motores de tração de uma locomotiva dieselelétrica, a partir da manipulação matemática de seus dados de temperatura. Desenvolve-se um modelo ARX e, com auxílio da ferramenta computacional do toolbox de identificação do MATLAB®, são feitas simulações para estimação e validação da ordem do modelo que melhor descreva a resposta dinâmica do sistema físico. Os dados de entrada e saída do retificador são obtidos a partir da medição direta da corrente de saída do gerador principal, que corresponde à entrada, e da medição da temperatura na bancada retificadora, que corresponde à saída. Estes dados são utilizados na elaboração do modelo matemático do sistema em estudo. Busca-se obter um modelo matemático que represente o comportamento do retificador principal da locomotiva, possibilitando ações de controle para uma melhor otimização entre a potência fornecida e a requerida para tração, de tal forma que os eventos de downtime, decorrentes da atuação da proteção contra altas temperaturas do retificador durante operações em regimes severos, sejam minimizados. Como resultado, tem-se um método mais avançado, eficaz e que possibilita uma estratégia de monitoramento nos diversos pontos de operação do equipamento, considerando suas variações e garantindo uma operação estável e segura do sistema.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

This thesis presents performance evaluation and a field validation study of a time and temperature indexed autoregressive with exogenous (4-3-5 ARX) building thermal load prediction model with an aim to integrate the model with actual predictive control systems. The 4-3-5 ARX model is very simple and computationally efficient with relatively high prediction accuracy compared to the existing sophisticated prediction models, such as artificial neural network prediction models. However, performance evaluation and field validation of the model are essential steps before implementing the model in actual practice. The performance of the model was evaluated under different climate conditions as well as under modeling uncertainty. A field validation study was carried out for three buildings at Mississippi State University. The results demonstrate that the 4-3-5 ARX model can predict building thermal loads in an accurate manner most of the times, indicating that the model can be readily implemented in predictive control systems.

<p>This master thesis has been performed at Sectra Communications AB in Linköping where they manufacture electronic encryption devices. In cryptology it is essential that an eavesdropper cannot find the plain text. To assure that a system is safe, all devices are thoroughly examined so that they don’t emit any secret information, so called Compromising Emanations (CE). This is done by comparing the secret signal with measured signals on the screen of an oscilloscope, a process that is very time consuming and furthermore, the risk of missing compromising emanations is high. The purpose of this thesis is to investigate the possibilities to let a computer do this job. Two methods for comparing the signals have been suggested and implemented; cross covariance and model estimation. In the cross covariance method, the cross covariance is calculated and its highest value determine how well the signals match. In the model estimation method, a number of ARX models are estimated, and if the best model is successful in explaining the output signal, it is assumed that there exists CE. </p><p>The work shows that both these methods are functional for solving the task, yet with a few limitations. Both methods announce CE for clock signals, which really aren’t compromising. The cross covariance method is limited only to find compromising emanations that look like the secret signal or certain frequently occurring non-linearities of it. The model estimation method is more general and detects CE for all linear systems, along with the known non-linearities. However, this method has a flaw: the time delay in the system must be known approximately. Further, the results show that the model estimation method is considerably more time consuming than the cross covariance method. The measurement is carried out with a computer communicating with oscilloscope and spectrum analyzer via the GPIB interface. The implementation has been done in LabView with calculation modules coded in C++.</p>

This master thesis has been performed at Sectra Communications AB in Linköping where they manufacture electronic encryption devices. In cryptology it is essential that an eavesdropper cannot find the plain text. To assure that a system is safe, all devices are thoroughly examined so that they don’t emit any secret information, so called Compromising Emanations (CE). This is done by comparing the secret signal with measured signals on the screen of an oscilloscope, a process that is very time consuming and furthermore, the risk of missing compromising emanations is high. The purpose of this thesis is to investigate the possibilities to let a computer do this job. Two methods for comparing the signals have been suggested and implemented; cross covariance and model estimation. In the cross covariance method, the cross covariance is calculated and its highest value determine how well the signals match. In the model estimation method, a number of ARX models are estimated, and if the best model is successful in explaining the output signal, it is assumed that there exists CE. The work shows that both these methods are functional for solving the task, yet with a few limitations. Both methods announce CE for clock signals, which really aren’t compromising. The cross covariance method is limited only to find compromising emanations that look like the secret signal or certain frequently occurring non-linearities of it. The model estimation method is more general and detects CE for all linear systems, along with the known non-linearities. However, this method has a flaw: the time delay in the system must be known approximately. Further, the results show that the model estimation method is considerably more time consuming than the cross covariance method. The measurement is carried out with a computer communicating with oscilloscope and spectrum analyzer via the GPIB interface. The implementation has been done in LabView with calculation modules coded in C++.

Commercial Aircraft Corporation of China, Ltd (COMAC)and Chinese Scholarship Council. / The aim of this thesis is to develop a real time PIO detection and mitigation system that consists of a detector based on short time Fourier transform(STFT) and autoregressive model(ARX) with exogenous inputs, together with an adaptive controller based mitigation system. The system not only detects the traditional PIO characteristics but also focuses on the trend of pilot behaviour by calculating the rate of change in the open loop crossover frequency. In the detection system, a sliding windowed STFT method was applied to identify the frequency and phase characteristics of the system via processing the signal of pilot input and aircraft state. An ARX model was also applied to get the rate of change of the crossover frequency. After detection, a PIO cue was shown on the primary flight display. A scheduled gain controller was coupled to provide PIO mitigation by varying stick input gain. Compensatory and tracking tests for the evaluation of this system were performed using a quasi-linear Boeing-747 aircraft model including nonlinear command gearing and actuator rate-limiting. Bandwidth and Gibson criteria were used to design PIO prone control laws for system evaluation experiments. Results from PIO tests conducted on desktop PCs were presented. These were analyzed and compared with those obtained from implementing the Real-time Oscillation Verifier module available in literature.

This study models the energy used for heating in buildings by applying system identification methodology. The model development is grounded in physics to provide guidance and interpretability when evaluated. Time-series of heating demand, outdoor temperature, indoor temperature and solar irradiation are considered for the modelling purpose. Evaluation is done through simulation and relies on quantitative measures, residual analysis and visual inspection of model output. Through model development, the study seeks to extrapolate information of physical properties that drives heating demand in buildings. Seven buildings located in the same geographic area are studied. It is found that linear ARX-models can simulate heating demand with high precision but at times low accuracy. A common system model structure can be identified between buildings, indicating that physical properties shared between buildings can be identified through this methodology. A sensitivity analysis is conducted to derive the contributions from model constituents to simulation results. Two buildings were also modelled as OE-models. These models performed better than the respective ARX-models but were deemed more difficult to use for the purpose of this study. The study finds difficulties in implementing aggregated time-series of indoor temperature, which could be explored further in future studies for more detailed interpretations.

This project aimed to evaluate the effectiveness of the Auto Regressive Exogenous(ARX) model in forecasting stock prices and contribute to research on statisticalmodels in predicting stock prices. An ARX model is a type of linear regression modelused in time series analysis to forecast future values based on past values and externalinput signals. In this study, the ARX model was used to forecast the closing pricesof stocks listed on the OMX Stockholm 30 (OMXS30*) excluding Essity, Evolution,and Sinch, using historical data from 2016-01-01 to 2020-01-01 obtained from YahooFinance. The model was trained using the least squares approach with a control signal that filtersoutliers in the data. This was done by modeling the ARX model using optimizationtheory and then solving that optimization problem using Gurobi OptimizationSoftware. Subsequently, the accuracy of the model was tested by predicting prices in aperiod based on past values and the exogenous input variable. The results indicated that the ARX model was not suitable for predicting stock priceswhile considering short time periods.

Grâce aux progrès de la génétique moléculaire qui ont permis d’identifier de nouveaux gènes de déficience intellectuelle liée à l’X, il nous a été possible de travailler sur des groupes homogènes de malades présentant une mutation dans le même gène. Nous avons d’une part, pu mettre en évidence un dysfonctionnement du circuit cérébello-thalamo-préfrontal grâce à une étude en IRM morphométrique réalisée chez des patients ayant une mutation dans le gène Rab-GDI. D’autre part, nous avons identifié un phénotype tout à fait spécifique lié aux mutations du gène ARX, tant clinique que neuropsychologique, et cinématique, associant une atteinte très particulière de la motricité distale des membres supérieurs et du langage. La préhension des patients est pathognomonique, avec une préférence pour la pince pouce-majeur, une difficulté accrue pour l’utilisation du bord cubital de la main, et un trouble de la pronosupination. Sur le plan neuroanatomique, il existe une diminution de volume des noyaux gris centraux et des épaisseurs corticales des régions contrôlant la motricité, bien corrélées au paramètres de cinématique. Enfin, nous avons exploré les stratégies de raisonnement des patients déficients intellectuels atteints du syndrome de l’X fragile, d’une mutation du gène ARX ou de trisomie 21 en élaborant un paradigme de raisonnement visuel analogique issu des matrices de Raven. Nous en avons établi la trajectoire développementale. Les stratégies utilisées par les patients (étude en eyetracking) sont différentes de celles des contrôles y compris de même âge mental, avec un défaut d’inhibition majeur, encore plus franc chez les patients X fragiles que ceux porteurs de trisomie 21 / Thanks to progress in molecular genetics, that allowed identification of new genes responsible for X linked intellectual disability, we studied on homogeneous groups of patients presenting with a mutation in one or the other gene. In the first section, we showed dysfunction of cerebello-thalamo-prefrontal networks, thanks to morphological MRI study performed on patients with a mutation in the Rab-GDI gene. In the second section, we highlighted a very specific phenotype related to ARX gene mutations, clinically, neuropsychologically, and kinematically, with a very peculiar impairment of upper limbs distal motricity, and language disorder. Patients hand-grip is pathognomonic, with a preference for the middle finger instead of the index for the grip of object, major impairment of fourth finger use, and lack of pronation movements. Neuroimaging study showed decreased volume of basal ganglia, and cortical thickness of motor regions, well correlated to kinematic parameters. In the third section, we explored reasoning strategies in three groups of patients with intellectual deficiency: fragile X, ARX mutated and Down syndrome patients and controls (both chronological and mental age-matched subjects). We notably elaborated a visual analogical reasoning paradigm, inspired from Raven’s matrices. We established a developmental trajectory of this paradigm. The strategy used by patients (eyetracking study) was different from the one used by controls, with a huge lack of inhibition, even greater for fragile X patients than for Down syndrome patients

Submitted by Maria Aparecida (cidazen@gmail.com) on 2017-09-06T13:31:47Z No. of bitstreams: 1 Antonio_José_da_Silva2.pdf: 2564341 bytes, checksum: ff7454362aecf3bf6afd177edfd5c821 (MD5) / Made available in DSpace on 2017-09-06T13:31:47Z (GMT). No. of bitstreams: 1 Antonio_José_da_Silva2.pdf: 2564341 bytes, checksum: ff7454362aecf3bf6afd177edfd5c821 (MD5) Previous issue date: 2009-06-05 / FAPEMA / The Anode effect that occurs in electrolytic smelter pot is responsible for gases such as PFC s. These gases contribute to the greenhouse effect, and in addition jeopardizes its productive capacity. From the voltage (output) and current (input) are estimate ARX and OE models of the electrolytic smelter pot using the Systems Identification Theory, the ARX and OE models of the electrolytic smelter pot are built to represent the steady state operation and the anode effect occurrence. After the simulation are chosen the models with better adjustment to the measure exit. For the selection are used established criteria along the research, the ARX and OE models of electrolytic smelter pot, are built to represent the full state operation of the electrolytic smelter pot. Based on real data and via algebraic properties, the models generate the functions of specific transfer of each model that are validated with real data obtained in the industry, the answer in time, in the convergence frequency and speed are analyzed. From the transfer function is made the representation of the normal stage of operation of the electrolytic smelter pot, and by the properties of the estimate model is made the prediction the anode effect identifying the increase of the voltage in the validation stage. Therefore, this work introduces the investigation of ARX and OE parametric models how better represent the operation of the electrolytic smelter pot to can enable the prediction of the anode effect in the productive process of the aluminum. In this dissertation, we propose the models development in the domain of the continuous and discreet time with a study of her transitory answers and of steady state as well as your answer in frequency of your normal operation and in the phase that precedes the anode effect. / O efeito anódico que ocorre nas cubas eletrolíticas é responsável pela emissão de gases como os PFC s, gases esses, que contribuem para o efeito estufa, além de comprometer sua capacidade produtiva. A partir dos sinais de tensão (saída) e corrente (entrada) são estimados modelos ARX e OE da cuba eletrolítica utilizando a Teoria de Identificação de Sistemas. Após a simulação são escolhidos os modelos com melhor ajuste à saída medida. Para a seleção são utilizados critérios estabelecidos ao longo da pesquisa. Os modelos ARX e OE das cubas eletrolítica, são construídos para representar o pleno estado de funcionamento da cuba. Baseados em dados reais e via propriedades algébricas, os modelos geram as funções de transferência específicas de cada modelo que são validadas com dados reais obtidos na indústria, a resposta no tempo, na freqüência e velocidade de convergência são analisadas. A partir da função de transferência é feita a representação da fase normal de funcionamento da cuba eletrolítica, e pelas propriedades do modelo é feita a predição do efeito anódico identificando o aumento da tensão na fase de validação. Portanto, este trabalho apresenta a investigação de modelos paramétricos ARX e OE que melhor representam o funcionamento da cuba eletrolítica para possibilitar a predição do efeito anódico no processo produtivo do alumínio. Nesta dissertação propomos o desenvolvimento de modelos no domínio do tempo contínuo e discreto com um estudo das suas respostas transitória e de regime permanente assim como sua resposta em freqüência de seu funcionamento normal e na fase que antecede o efeito anódico.