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Islami, Kleidi. "System identification and structural health monitoring of bridge structures." Doctoral thesis, Università degli studi di Padova, 2013. http://hdl.handle.net/11577/3423079.
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This research study addresses two issues for the identification of structural characteristics of civil infrastructure systems. The first one is related to the problem of dynamic system identification, by means of experimental and operational modal analysis, applied to a large variety of bridge structures. Based on time and frequency domain techniques and mainly with output-only acceleration, velocity or strain data, modal parameters have been estimated for suspension bridges, masonry arch bridges, concrete arch and continuous bridges, reticular and box girder steel bridges. After giving an in-depth overview of standard and advanced stochastic methods, differences of the existing approaches in their performances are highlighted during system identification on the different kinds of civil infrastructures. The evaluation of their performance is accompanied by easy and hard determinable cases, which gave good results only after performing advanced clustering analysis. Eventually, real-time vibration-based structural health monitoring algorithms are presented during their performance in structural damage detection by statistical models.
The second issue is the noise-free estimation of high order displacements taking place on suspension bridges. Once provided a comprehensive treatment of displacement and acceleration data fusion for dynamic systems by defining the Kalman filter algorithm, the combination of these two kinds of measurements is achieved, improving the deformations observed. Thus, an exhaustive analysis of smoothed displacement data on a suspension bridge is presented. The successful tests were subsequently used to define the non-collocated sensor monitoring problem with the application on simplified modelsQuesto lavoro di ricerca mira a due obiettivi per l'identificazione delle caratteristiche strutturali dei sistemi infrastrutturali civili. Il primo è legato al problema della identificazione del sistema dinamico, mediante analisi modale sperimentale e operativa, applicata ad una grande varietà di strutture da ponte. Basandosi su tecniche nel dominio del tempo e delle frequenze e, soprattutto, su dati di output di accelerazione, velocità o strain, i parametri modali sono stati stimati per ponti sospesi, ponti ad arco in muratura, ponti a travi in calcestruzzo e ad arco, ponti reticolari e ponti in acciaio a cassone. Dopo aver dato una panoramica approfondita dei metodi stocastici standard ed avanzati, sono state evidenziate le differenze degli approcci esistenti nelle loro performance per l'identificazione del sistema sui diversi tipi di infrastrutture civili. La valutazione della loro performance viene accompagnata da casi facilmente e difficilmente determinabili, che hanno dato buoni risultati solo dopo l'esecuzione di analisi avanzate di Clustering. Inoltre, sono stati sviluppati algoritmi di identificazione dinamica automatica in tempo reale basandosi sulle vibrazioni strutturali dei ponti monitorati, a sua volta utilizzati nel rilevamento dei danni strutturali tramite modelli statistici. Il secondo problema studiato riguarda la stima di spostamenti di ordine superiore che si svolgono sui ponti sospesi, eliminando il rumore di misura e di processo. Una volta fornito un trattamento completo della fusione dei dati di spostamento e accelerazione per i sistemi dinamici tramite il filtro di Kalman, la combinazione di questi due tipi di misurazioni ha mostrato un miglioramento nelle deformazioni osservate. Pertanto, è stata presentata un'analisi esauriente di un ponte sospeso e dei sui dati dinamici e di spostamento filtrati. I test positivi sono stati successivamente utilizzati per definire il problema dei sensori non collocati alla stessa locazione ed applicazione su modelli semplificati
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Azevedo, João Henrique Albino de. "Aeroelastic studies using system identification techniques." Instituto Tecnológico de Aeronáutica, 2013. http://www.bd.bibl.ita.br/tde_busca/arquivo.php?codArquivo=2864.
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The present work is concerned with studying techniques which would allow the identification of a multiple degree of freedom aeroelastic system from a single computational fluid dynamics (CFD) unsteady simulation. This data is, then, used to generate the root locus for aeroelastic stability analysis of the dynamic system. The system being considered in the present work is a NACA 0012 airfoil-based typical section in the transonic regime. The CFD calculations are based on the Euler equations and the code uses a finite volume formulation for general unstructured grids. A centered spatial discretization with added artificial dissipation is used, and an explicit Runge-Kutta time marching method is employed. Unsteady calculations are performed for several types of excitation on the plunge and pitch degrees of freedom of the dynamic system. These inputs are mostly based on step and orthogonal Walsh functions. System identification techniques are used to allow the splitting of the aerodynamic coeficient time histories into the contributions of each individual mode to the corresponding aerodynamic transfer functions. Such transfer functions are, then, represented by rational polynomials and used in an aeroelastic stability analysis in the frequency domain. The work compares the results provided for each case and attempts to contribute with guidelines for such analyses.
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Gorti, Bhaskar M. "Techniques for discrete, time domain system identification." Thesis, This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-11242009-020121/.
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Chen, Yi S. M. Massachusetts Institute of Technology. "Nonlinear stochastic system identification techniques for biological tissues/." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/62122.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 205-212).
This research develops a device capable of measuring the nonlinear dynamic mechanical properties of human tissue in vivo. The enabling technology is the use of nonlinear stochastic system identification techniques in conjunction with a high bandwidth actuator to perturb the tissue. The desktop and handheld instruments used for this investigation were custom-built Lorentz force actuators which were able to measure the dynamic compliance between the input force and the output displacement. The actuators have a nominal stroke of 32 mm and were actuated with forces under 15 N. The design includes custom electronics and user software which collects and analyses the information. This research also explores nonlinear stochastic system identification techniques that would be applicable to biological tissues. Several system identification techniques were used including linear, Wiener static nonlinear, Volterra kernel and partitioning techniques. Real time system identification and real time input generation schemes are also implemented. The mathematical formulation and implementation details of these techniques are also discussed. It was found that a simple linear stochastic system identification technique had a variance accounted for (VAF) of 70 to 75 %. More complicated representations using Volterra kernels or partitioning techniques had a VAF of 90 to 97 %. More complex nonlinear system identification techniques can not only capture more of the nonlinear dynamics but also capture those dynamics in an interpretable way. Indentation, extension, and surface mechanics experiments were conducted to investigate the nonlinear mechanical compliance of skin in vivo. The techniques and devices used in this research can be applied directly to consumer product efficacy analysis, medical diagnosis as well as research in biomechanical tissues.
by Yi Chen.
S.M.
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Bihl, Trevor Joseph. "State Variable System Identification through Frequency Domain Techniques." Ohio University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1307128475.
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Shaw, Steven Robert 1973. "System identification techniques and modeling for nonintrusive load diagnostics." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/9119.
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Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2000.Includes bibliographical references (p. 213-219).
This thesis addresses the requirements of a system that can detect on/off transients and identify physical parameters of loads connected to a power distribution network. The thesis emphasizes three areas; a transient classifier that recognizes load transients using a pattern matching scheme, parameter estimation techniques suited for use with this classifier, and case studies of modeling and identification motivated by diagnostics and performance monitoring. Together, these areas support applications that can extract detailed load information from centralized, easily accessible parts of a distribution network. A new approach and implementation of pattern-based nonintrusive transient classification is presented. The classifier is nonintrusive in the sense that it uses aggregated measurements at a central location and does not require instrumentation of individual loads. The classifier implementation includes a framework that integrates preprocessors for AC and DC environments, programs that present results, and load-specific parameter identification modules that are executed as their associated transients are classified. An obstacle for these parameter identification programs is that a good initial guess is needed for the iterative optimization routines typically used to find parameter estimates. Two approaches are given to overcome this problem for certain systems. The first extends conventional optimization methods to identify model parameters given a poor initial guess. The second approach treats the identification as a modeling problem and suggests ways to construct "inverse" models that map observations to parameter estimates without iteration. The techniques presented in the thesis are demonstrated with simulation data and in real world scenarios including a dormitory, an automobile, and an experimental building.
by Steven Robert Shaw.
Ph.D.
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Rocco, Claudio. "Techniques to analyse system performance under uncertainty." Thesis, Robert Gordon University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.313442.
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Rajagopalan, Mohan. "Optimizing System Performance and Dependability Using Compiler Techniques." Diss., Tucson, Arizona : University of Arizona, 2006. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu%5Fetd%5F1439%5F1%5Fm.pdf&type=application/pdf.
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Topor, Zbigniew L. "Investigation of the human respiratory control system by computer modeling and system identification techniques." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape7/PQDD_0020/NQ47917.pdf.
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Emadi, Seyyedbehrad. "Application of observability techniques to structural system identification including shear effects." Doctoral thesis, Universitat Politècnica de Catalunya, 2020. http://hdl.handle.net/10803/670565.
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According to Timoshenko’s beam theory, nodal rotations in beam-like structures are produced by bending and shear effects. On the one hand, bending rotations can be easily calculated by the Euler-Bernoulli stiffness matrix method. On the other hand, shear rotations are traditionally neglected as their effects are practically negligible in most structures. In addition, calculating the shear rotation effects by the stiffness matrix method is not straight forward tasks and it presents practical limitations. Nevertheless, this assumption might lead to significant errors in the simulation of the structural response of some structures (such as deep beams and composite structures). The shear effects are also neglected in the inverse analysis of structures (Structural System Identification) used to calibrate the mechanical properties of the structural elements from the monitoring on-site. Recently, one of the first methods for the inverse analysis of structures including the shear effects (the Observability Method, OM) was presented. This method introduced Timoshenko’s beam theory into the Stiffness Matrix Method (SMM). In this way, the vertical deflections produced by shear effects were included into the simulation while the shear rotations were neglected. In this method, the mechanical properties of the structures could be obtained from the nodal deflections measured on static tests on site. One of the main controversial features of this procedure is the fact that the measurement set must include rotations. This characteristic might be especially problematic in those structures where rotations due to shear are not negligible. In fact, in this case, neglecting the shear rotations might lead to significant errors. This simplification might be especially problematic in those structures where only rotations can be measured. In addition to the OM, some other inverse analysis methods including shear deformation effects have been recently presented in the literature. Nevertheless, all these methods also fail to deal with the shear rotation effects, as they only take into account in the system of equations the vertical deflections produced by shear. Therefore, when actual rotations on site are used estimations with significant errors can be obtained. To fill these gaps, this Ph.D. Thesis deals with the analysis of the effects of the shear deformations in beam-like structures from a direct and inverse approach. First of all, the SMM is updated to enable the calculation of the shear rotations from a direct analysis. This method is used to evaluate the effects of the shear rotations in beam-like structures with different slenderness ratios. In addition, for the first time in the literature, the slenderness ratios where the shear rotation effects can be neglected from a direct analysis are identified. Secondly, the OM is updated to enable the inverse analysis of structures with shear effects from measurement sets with only vertical deflections. This modification is based on the introduction of a numerical optimization method. With this aim, the inverse analysis of several examples of growing complexity are presented to illustrate the validity and potential of the updated method. Finally, the OM is modified to enable the inverse analysis from shear rotations. This modification is based on the introduction of a new iterative process to estimate successively the values of the shear rotations. To illustrate the applicability and potential of the proposed method, the inverse analysis of several examples of growing complexity is presented. A set of calculation recommendations and future researches are also proposed.De acuerdo con la teoría de vigas de Timoshenko, las rotaciones nodales en estructuras tipo viga se producen por efectos de flexión y cortante. Si bien las rotaciones por flexión pueden ser fácilmente calculadas por el método de la matriz de rigidez de Euler-Bernoulli, las rotaciones por cortante no se han tomado en cuenta tradicionalmente ya que sus efectos son prácticamente insignificantes en la mayoría de las estructuras. Así mismo, el cálculo de los efectos de la rotación por cortante mediante el método de la matriz de rigidez no es una tarea sencilla y presenta limitaciones prácticas. Sin embargo, esta omisión podría conducir a errores significativos en la simulación de la respuesta estructural de algunas estructuras (como las vigas de gran canto). De igual forma, los efectos por cortante no han sido tomados en cuenta en el análisis inverso de las estructuras (Identificación del Sistema Estructural) que es utilizado para calibrar las propiedades mecánicas de los elementos estructurales a partir de la monitorización in situ. Recientemente, se presentó uno de los primeros métodos para el análisis inverso de las estructuras, incluidos los efectos por cortante (el método de observación, OM, por sus siglas en inglés). Este método introdujo la teoría de vigas de Timoshenko en el Método de la Matriz de Rigidez (SMM, por sus siglas en inglés). De esta manera, las flechas verticales producidas por los efectos por cortante se incluyeron en la simulación, mientras que las rotaciones por cortante se ignoraron. En este método, las propiedades mecánicas de las estructuras pudieron obtenerse a partir de las flechas nodales medidas en pruebas estáticas in situ. Una de las principales características controvertidas de este procedimiento es el hecho de que en el conjunto de mediciones se deben incluir las rotaciones. Esta característica podría ser especialmente problemática en aquellas estructuras en las que las rotaciones debidas al cortante no son despreciables. De hecho, en este caso, despreciar las rotaciones por cortante podría dar lugar a errores significativos. Además del OM, recientemente se han presentado en la literatura otros métodos de análisis inverso que incluyen los efectos de deformación por cortante. Sin embargo, tampoco ninguno de estos métodos aborda los efectos de rotación por cortante, ya que solo tienen en cuenta en el sistema de ecuaciones las deformaciones verticales producidas por cortante. Por lo tanto, cuando se utilizan las rotaciones reales in situ se pueden obtener estimaciones con errores significativos. Para llenar estos vacíos, esta Tesis Doctoral aborda el análisis de los efectos de las deformaciones por cortante en estructuras tipo viga desde un enfoque directo e inverso. En primer lugar, se actualiza el SMM para permitir el cálculo de las rotaciones por cortante a partir de un análisis directo. Este método se utiliza para evaluar los efectos de las rotaciones por cortante en estructuras tipo viga con diferentes ratios de esbeltez. Además, por primera vez en la literatura, se identifican los ratios de esbeltez en los que los efectos de la rotación por cortante pueden ser despreciados a partir de un análisis directo. En segundo lugar, el OM se ha actualizado para permitir el análisis inverso de estructuras con efectos de cortante a partir de un conjunto de mediciones con solo flechas verticales. Esta modificación se basa en la introducción de un método de optimización numérica. Con este objetivo, se presenta el análisis inverso de varios ejemplos de creciente complejidad para ilustrar la validez y el potencial del método actualizado. Por último, se modifica el OM para permitir el análisis inverso a partir de las rotaciones por cortante. Esta modificación se basa en la introducción de un nuevo proceso iterativo para estimar sucesivamente los valores de las rotaciones por cortante. Para ilustrar la aplicabilidad y el potencial del método propuesto, se presenta el análisis inverso de varios ejemplos de complejidad creciente. Así mismo, se propone un conjunto de recomendaciones de cálculo e investigaciones futuras.
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Halliday, David M. "Application of point-process system identification techniques to complex physiological systems." Thesis, University of Glasgow, 1986. http://theses.gla.ac.uk/2819/.
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This thesis is concerned with the application of system identification techniques to the analysis of complex physiological systems. The techniques are applied to neuronal spike-train data obtained from elements of the neuromuscular system. A brief description of the neuromuscular system is given in chapter 1, along with a more detailed discussion of the muscle spindle, which is the component of the neuromuscular system which this study deals with. In addition, some possibilities for system identification studies of the muscle spindle are discussed. The identification procedure is based on statistical methods for the treatment of point-process data. The point-process representation of a spike-train is introduced in chapter 2 with definitions of time and frequency domain point-process parameters. Estimates for these parameters are given, along with expressions for their asymptotic distributions. The linear point-process system identification model is introduced and estimates are described for the model parameters in terms of the previously defined point-process parameters. These point-process and linear parameter estimates are applied to muscle spindle spike-train data. In the analysis of a single spike-train certain important features only show up in the frequency domain, and for input and output spike-trains a linear transfer function type description is constructed in the frequency domain. The mathematical model of this transfer function is used as the basis for an analogue computer simulation of a subsystem of the muscle spindle. This consists of a linear first order filter followed by an encoder which generates output spikes. Data logged from the simulation is processed in the same manner as experimental data, and the effect of varying the simulation parameters on the linear model estimates is looked at. It is shown that in general the linear model description reflects the properties of the linear filter in the simulation, and varying the simulation parameters can be used to accurately match results from simulated data with those obtained from real data. Chapter 3 compares the point-process approach with a more conventional filtering and sampled data approach to estimate power spectra. The filtering of spike-trains with broad band spectra is investigated, and this shows up a pitfall in the choice of filter cut-off frequency. It is concluded that the point-process approach is preferable due to shorter computational times, and the well documented statistical propeties of the point-process estimates. The application of the point-process techniques described in chapter 2 to the analysis of more general spike-train data is considered in chapter 4. Three techniques for measuring the degree of coupling between two spike-trains are compared, and the point-process frequency domain measure is found to be the most sensitive. This measure is also applied to a data set containing a strong single periodicity, and the ability to detect coupling at a single harmonic is demonstrated. The analysis of coupling between spike-trains in the frequency domain is extended to deal with multiple spike-trains, and the ability to distinguish genuine coupling from the effect of a common input is shown to be a powerful tool which can be used to investigate communications pathways in neural systems. Finally, one special feature of the muscle spindle response to a spike-train input is analysed using the simulation. It is demonstrated that the point-process approach can produce results about a particular phenomenon from a single experiment much more rapidly than using a repetitive trial and error approach. Chapter 5 considers the extension of the linear point-process identification model introduced in chapter 2. Higher order time and frequency domain point-process parameters are defined and estimates given. In the time domain, a new technique for rapidly generating higher order time domain parameters is developed. The quadratic point-process model is introduced and solutions for its parameters given. These estimates are applied to muscle
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Jansson, Daniel. "Identification Techniques for Mathematical Modeling of the Human Smooth Pursuit System." Doctoral thesis, Uppsala universitet, Reglerteknik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-264292.
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This thesis proposes nonlinear system identification techniques for the mathematical modeling of the human smooth pursuit system (SPS) with application to motor symptom quantification in Parkinson's disease (PD). The SPS refers to the complex neuromuscular system in humans that governs the smooth pursuit eye movements (SPEM). Insight into the SPS and its operation is of importance in a wide and steadily expanding array of application areas and research fields. The ultimate purpose of the work in this thesis is to attain a deeper understanding and quantification of the SPS dynamics and thus facilitate the continued development of novel commercial products and medical devices. The main contribution of this thesis is in the derivation and evaluation of several techniques for SPS characterization. While attempts to mathematically model the SPS have been made in the literature before, several key aspects of the problem have been previously overlooked.This work is the first one to devise dynamical models intended for extended-time experiments and also to consider systematic visual stimuli design in the context of SPS modeling. The result is a handful of parametric mathematical models outperforming current State-of-the-Art models in terms of prediction accuracy for rich input signals. As a complement to the parametric dynamical models, a non-parametric technique involving the construction of individual statistical models pertaining to specific gaze trajectories is suggested. Both the parametric and non-parametric models are demonstrated to successfully distinguish between individuals or groups of individuals based on eye movements.Furthermore, a novel approach to Wiener system identification using Volterra series is proposed and analyzed. It is exploited to confirm that the SPS in healthy individuals is indeed nonlinear, but that the nonlinearity of the system is significantly stronger in PD subjects. The nonlinearity in healthy individuals appears to be well-modeled by a static output function, whereas the nonlinear behavior introduced to the SPS by PD is dynamical.
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Wang, Duan. "Element level time domain system identification techniques with unknown input information." Diss., The University of Arizona, 1995. http://hdl.handle.net/10150/187220.
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A finite element based linear time domain system identification algorithm is proposed to estimate the stiffness and damping coefficients of structures at the element level using response data alone without using information of excitation measurements. The unknown input excitation could be applied at any location of the structure including at the ground level representing the seismic excitation. The proposed method is an Iterative Least-Squares with Unknown Input (ILS-UI) procedure. The element-level structural parameters can be identified directly by using proposed ILS-UI procedure. No information of the modal properties is required. The efficiency and robustness of the proposed algorithm is illustrated by numerical examples. For verification purposes, both noise-free and noise-included output responses are considered in numerical examples. The applications of three types of structures, i.e., shear-type buildings, trusses, and frames, are considered in this dissertation. In all examples, the identified results indicate that the proposed ILS-UI method identified the structural parameters very well. For the successful implementation of the proposed method, only a small number of sampling time points are required, and a long time duration of responses is not necessary. For a large system, since it is practically impossible to measure responses at every dynamic degree of freedom, the absence of some observation points of responses and its effect on the proposed system identification technique must be studied. Based on the above ILS-UI procedure, a new technique combined with the Kalman filter technique is developed to identify all element-level structural parameters using measuring responses at several optimal locations only. The optimal numbers and locations of measurement points required to identify uniquely the system using this proposed ILS-EKF-UI technique are determined. Again, numerical examples with two special cases are used to illustrate the applications of this new technique. The results of numerical examples indicate that this new system identification technique is very economical, simple, and robust, since the input is not required to be measured and only several observations are required.
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Carvalho, João Pedro Martins de. "High Performance shallow packet inspection system for traffic identification." Master's thesis, Universidade de Aveiro, 2016. http://hdl.handle.net/10773/18455.
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Mestrado em Engenharia de Computadores e TelemáticaThe evolution and growth of the Internet has led to a growing preoccupation regarding dynamic allocation of resources in large networks, as well as to an unprecedented growing adoption of security policies based on tra c classi cation. This phenomenon triggered the creation of deep inspection mechanisms for packets where we can see a cross-access that is based on the retrieval of speci c strings present in packet's Payload. This event raises a number of technical, ethical, and potentially legal limitations. With the increasing need to develop less invasive and more e cient inspection mechanisms, in terms of processing speed and potentially, memory management, the scienti c community began working in other types of approaches to solve the problem. In this dissertation, we propose a tra c ow classi cation system based on Shallow packet inspection. Given the latest forecasts and current statistical data, which estimates that about 90 % of all tra c will be video in the next few years, we have decided to devote special attention to this speci c type. For this, we proceeded to collect non-sensitive information, with which we perform a statistical study based on low-level statistics. The results obtained from this study were analysed from a behavioural point of view, in order to reach the extraction of coherent rules that allow the di erentiation of independent types of tra c. Finally, we studied, conceived and test an e cient ow organisation paradigm. The system has been tested and evaluated using packet ood tests. Following to the measurement and examination of results in terms of processing times as well as the use of main memory.
A evolução e crescimento da Internet tem levado a uma crescente preocupação tendo em vista a alocação dinâmica de recursos em redes de grande dimensão, assim como uma adopção sem precedente de politicas de segurança baseadas em classi ficação de tráfego. Este fenómeno desencadeou a criação de mecanismos de inspecção profunda de pacotes onde se assiste a um acesso transversal, que assenta na obtenção de sequências de bytes especificas, presentes no Payload de cada pacote, o que levanta uma série de limitações técnicas, éticas e potencialmente legais. Com a crescente necessidade de desenvolvimento de mecanismos de inspecção menos invasivos e mais e cientes em termos de velocidade e potencialmente gestão de memória, a comunidade cientifi ca começou a trabalhar em outros tipos de abordagem ao problema. Nesta dissertação, propomos um sistema de classi cação de fluxos de trafego que assenta em Shallow packet inspection. Tendo em conta as ultimas previsões e dados estatísticos atuais, que estimam que cerca de 90% de todo tráfego na Internet, seja do tipo vídeo nos próximos anos, decidimos dedicar especial atenção sobre esse tipo especifico. Para isso, procedemos a recolha de informação não sensível, com a qual efetuamos um estudo estatístico baseado em estatísticas de baixo nivel. Os resultados obtidos nesse estudo, foram analisados de um ponto de vista comportamental, por forma a alcançar uma prova de conceito na extracção de regras coerentes que permitam diferenciar tipos de tráfego independentes. Por fim, estudamos, concebemos e testamos um paradigma de organizaçao de fluxos de forma e ciente. O sistema foi testado e avaliado recorrendo a testes de inundação por pacotes, seguidos da medição e avaliação dos resultados em termos de tempo de processamento, assim como, ao uso de memoria principal.
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ISLAM, MD JAHERUL. "Performance Analysis of Diversity Techniques for Wireless Communication System." Thesis, Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-1962.
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Different diversity techniques such as Maximal-Ratio Combining (MRC), Equal-Gain Combining (EGC) and Selection Combining (SC) are described and analyzed. Two branches (N=2) diversity systems that are used for pre-detection combining have been investigated and computed. The statistics of carrier to noise ratio (CNR) and carrier to interference ratio (CIR) without diversity assuming Rayleigh fading model have been examined and then measured for diversity systems. The probability of error (p_e) vs CNR and (p_e) versus CIR have also been obtained. The fading dynamic range of the instantaneous CNR and CIR is reduced remarkably when diversity systems are used [1]. For a certain average probability of error, a higher valued average CNR and CIR is in need for non-diversity systems [1]. But a smaller valued of CNR and CIR are compared to diversity systems. The overall conclusion is that maximal-ratio combining (MRC) achieves the best performance improvement compared to other combining methods. Diversity techniques are very useful to improve the performance of high speed wireless channel to transmit data and information. The problems which considered in this thesis are not new but I have tried to organize, prove and analyze in new ways.
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Mauri, Guiseppe. "Integrating safety analysis techniques, supporting identification of common cause failures." Thesis, University of York, 2000. http://etheses.whiterose.ac.uk/10906/.
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Prins, Robert Jack. "System Identification and Calibration Techniques for Force Measurement in Active Magnetic Bearings." Diss., Virginia Tech, 2005. http://hdl.handle.net/10919/30117.
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Many processes involving rotating machinery could benefit from the continuous feedback of force applied to the bearings that support the machinery. Such a system could be used to provide diagnostics for process monitoring in a manufacturing application or to provide information for machine health monitoring. Active Magnetic Bearings (AMBs) have the capability to act concurrently as a shaft force sensor and support bearing. This capability stems from the AMB's control system, which is designed to maintain a specific rotor position, regardless of forces acting on the rotor. Researchers have demonstrated the force sensing ability of AMBs; current state of the art methods typically rely on a direct measurement of magnetic flux density as provided by a Hall probe inserted in the magnetic field. In this work, a system identification approach to force measurement is proposed; the proposed approach is applicable to all active magnetic bearings and does not require Hall probes.
Recent developments in system identification of bearing forces (Kasarda et al., 2000) indicate that a different approach is feasible. In the work of Marshall (Marshall et al., 2001), a variety of perturbations are applied to an AMB while the AMB controller signals are interrogated, no outside instrumentation such as force transducers or Hall probes are required. The work of Kasarda and Marshall is the starting point for the work presented here.
The initial work was expanded to include a general characterization of air gap for any rotor position. Although this characterization relies on static testing to identify system parameters, the identified parameters can then be used in the measurement of dynamic forces. The identification procedure provides a measurement of effective air gap length. Effective gap length is used to infer the effective position of the rotor with respect to the stator. This measurement is made for several specific rotor locations. The relationship between the effective rotor positions provided by the identification and the rotor positions reported by the AMB system sensors establishes a coordinate transformation. The procedure is also applied at different shaft rotation angles. In this way rotor runout can be identified.Ph. D.
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Musa, S. Nurmaya. "Supply Chain Risk Management : Identification, Evaluation and Mitigation Techniques." Doctoral thesis, Linköpings universitet, Produktionsekonomi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-78763.
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Supply chains have expanded rapidly over the decades, with the aim to increase productivity, lower costs and fulfil demands in emerging markets. The increasing complexity in a supply chain hinders visibility and consequently reduces one’s control over the process. Cases of disruption such as the ones faced by Ericsson and Enron, have shown that a risk event occurring at one point of the supply chain can greatly affect other members, when the disruption is not properly controlled. Supply chain management thus faces a pressing need to maintain the expected yields of the system in risk situations. To achieve that, we need to both identify potential risks and evaluate their impacts, and at the same time design risk mitigation policies to locate and relocate resources to deal with risk events. This dissertation aims to analyse how supply chain risks could be effectively managed. This is done firstly by positioning the research agenda in supply chain risk management (SCRM). Then, methods for effective management of supply chain risk are identified and analysed. In order to find these, we develop a research framework in which the supply chain system is divided into subsystems based on the operations of make, source and deliver; as well as on material, financial and information flows. Furthermore, research questions are raised in order to understand the impact of risks on supply chains, to identify the performance measures for monitoring supply chains, and to determine risk mitigation strategies for improving system performances. This dissertation includes a bibliometric analysis of relevant literature of SCRM published in recent years. Based on the co-citation analysis, we identify the changing interest in SCRM, from performance-focused individual issues in the early years to integrated system issues with management perspective in recent years. We also identify the growing importance of information issues in SCRM. However, there is a relative lack of research into risk mitigation focusing on information flows in the literature. This dissertation also develops a conceptual model for analysing supply chain risk. The adoption of tools from the established field of reliability engineering provides a systematic yet robust process for risk analysis in supply chains. We have found that the potential use of a stand-alone tool of Failure Modes and Effect Analysis (FMEA) or a hybrid application of Fault Tree Analysis (FTA) and Analytical Hierarchy Process (AHP), will be most appropriate in SCRM. Apart from above mentioned studies, this dissertation then includes three manuscripts respectively investigating the risk mitigation policies in SCRM. First, we suggest a dynamic pricing policy when facing supply yield risk, such as price postponement, where price is determined only after receiving the delivery information. This postponed pricing, can improve the balance between supply and demand, especially when the delivery quantity is small, demand has a low uncertainty and there is a wide range when demand is sensible to price change. In another paper, a system dynamics model is developed to investigate the dispersion of disruption on the supply chain operation as well as along the network. Based on this simulation model, policies are tested to observe their influence to the performance of the supply chain. The study results support the benefit of a dual-sourcing strategy. Furthermore, information sharing, appropriate order splitting and time to react would further improve the supply chain performance when disruption strikes. In the last paper, we study how capacity should be expanded when a new product is introduced into the market. The major risk here is due to a quick capacity expansion with large investments which could be difficult to recover. Using the Bass diffusion model to describe demand development, we study how capacity expansion, together with sales plan could affect the economics of the system. Using sales information for the forecast, delaying the sales and adding initial inventories, should create a better scheme of cash flows. This dissertation contributes in several ways to the research field of SCRM. It plots research advancements which provide further directions of research in SCRM. In conjunction with the conceptual model, simulations and mathematical modelling, we have also provided suggestions for how a better and more robust supply chain could be designed and managed. The diversified modelling approaches and risk issues should also enrich the literature and stimulate future study in SCRM.
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Chung, Ka Kei. "Interactive visual optimization and analysis for RFID system performance /." View abstract or full-text, 2009. http://library.ust.hk/cgi/db/thesis.pl?CSED%202009%20CHUNG.
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Aburrous, Maher R., M. Alamgir Hossain, F. Thabatah, and Keshav P. Dahal. "Intelligent phishing website detection system using fuzzy techniques." IEEE, 2008. http://hdl.handle.net/10454/2640.
Full textAbstract:
Phishing websites are forged web pages that are created by malicious people to mimic web pages of real websites and it attempts to defraud people of their personal information.
Detecting and identifying Phishing websites is really a complex and dynamic problem involving many factors and criteria, and
because of the subjective considerations and the ambiguities involved in the detection, Fuzzy Logic model can be an effective
tool in assessing and identifying phishing websites than any other
traditional tool since it offers a more natural way of dealing with
quality factors rather than exact values. In this paper, we present
novel approach to overcome the `fuzziness¿ in traditional website phishing risk assessment and propose an intelligent resilient and effective model for detecting phishing websites. The proposed
model is based on FL operators which is used to characterize the
website phishing factors and indicators as fuzzy variables and
produces six measures and criteria¿s of website phishing attack
dimensions with a layer structure. Our experimental results
showed the significance and importance of the phishing website
criteria (URL & Domain Identity) represented by layer one, and
the variety influence of the phishing characteristic layers on the
final phishing website rate.
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Zurek, Eduardo. "System optimization for micron and sub-micron particle identification using spectroscopy-based techniques." [Tampa, Fla] : University of South Florida, 2006. http://purl.fcla.edu/usf/dc/et/SFE0001635.
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Doukoglou, Tilemachos D. "Non-parametric system identification techniques for numerical deconvolution of scanning laser microscope images." Thesis, McGill University, 1988. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=61889.
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Icke, Kyle J. "Determination of the Compressive Response of the Pediatric Thorax Utilizing System Identification Techniques." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1417608406.
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Carrillo, Ramírez Nicolas. "Condition monitoring of complex rotating machines using system identification and speech processing techniques." Berlin Logos, 2008. http://d-nb.info/992155452/04.
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Yu, Xing. "Control aspects of a high performance induction machine drive with parameter identification." Thesis, Heriot-Watt University, 2000. http://hdl.handle.net/10399/1229.
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Ni, Junxiong. "Advanced Modeling Techniques for high performance and human centered LED lighting system." 京都大学 (Kyoto University), 2017. http://hdl.handle.net/2433/225603.
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Wilkinson, Timothy A. H. "Nonlinearities in broadband UHF power amplifiers, linearisation techniques and system performance simulation." Thesis, University of Leeds, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.328941.
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Algreer, Maher Mohammed Fawzi Saber. "Microprocessor based signal processing techniques for system identification and adaptive control of DC-DC converters." Thesis, University of Newcastle Upon Tyne, 2012. http://hdl.handle.net/10443/1554.
Full textAbstract:
Many industrial and consumer devices rely on switch mode power converters (SMPCs) to provide a reliable, well regulated, DC power supply. A poorly performing power supply can potentially compromise the characteristic behaviour, efficiency, and operating range of the device. To ensure accurate regulation of the SMPC, optimal control of the power converter output is required. However, SMPC uncertainties such as component variations and load changes will affect the performance of the controller. To compensate for these time varying problems, there is increasing interest in employing real-time adaptive control techniques in SMPC applications. It is important to note that many adaptive controllers constantly tune and adjust their parameters based upon on-line system identification. In the area of system identification and adaptive control, Recursive Least Square (RLS) method provide promising results in terms of fast convergence rate, small prediction error, accurate parametric estimation, and simple adaptive structure. Despite being popular, RLS methods often have limited application in low cost systems, such as SMPCs, due to the computationally heavy calculations demanding significant hardware resources which, in turn, may require a high specification microprocessor to successfully implement. For this reason, this thesis presents research into lower complexity adaptive signal processing and filtering techniques for on-line system identification and control of SMPCs systems. The thesis presents the novel application of a Dichotomous Coordinate Descent (DCD) algorithm for the system identification of a dc-dc buck converter. Two unique applications of the DCD algorithm are proposed; system identification and self-compensation of a dc-dc SMPC. Firstly, specific attention is given to the parameter estimation of dc-dc buck SMPC. It is computationally efficient, and uses an infinite impulse response (IIR) adaptive filter as a plant model. Importantly, the proposed method is able to identify the parameters quickly and accurately; thus offering an efficient hardware solution which is well suited to real-time applications. Secondly, new alternative adaptive schemes that do not depend entirely on estimating the plant parameters is embedded with DCD algorithm. The proposed technique is based on a simple adaptive filter method and uses a one-tap finite impulse response (FIR) prediction error filter (PEF). Experimental and simulation results clearly show the DCD technique can be optimised to achieve comparable performance to classic RLS algorithms. However, it is computationally superior; thus making it an ideal candidate technique for low cost microprocessor based applications.
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Henriques, Julian F. "Sonic bodies : the skills and performance techniques of the reggae sound system crew." Thesis, Goldsmiths College (University of London), 2008. http://research.gold.ac.uk/22858/.
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This research project describes the performance techniques of the reggae sound system crew in the dancehall session. These are held until dawn every night of the week on the streets of inner city Kingston, Jamaica. The research question asked is: how does a sound system work? The methodology is one of participant observation - what the crew do, with what, and with whom - as well as participant listening. This attunes the research to the auditory qualities of the sounds that the crew describe in recorded interviews, as well as the nuances of the idiomatic expressions they use and their tone of voice. Taking Jamaica's longest running and best-established sound system, Stone Love Movement as a case study, the research concentrates on the roles of three crewmembers in particular. These "sonic bodies" are: the audio engineers who design, build, finetune and maintain the hugely powerful sound system "sets" of equipment; the selectors responsible for the choice of recorded music played to the "crowd" (audience) in the session; and MCs (or DJs) who introduce the music and "build the vibes. " The crew's skilled performance techniques are investigated in relation to the phonographic instrument of the "set" of equipment for making sound, together with the media of sound, music and voice for diffusion of the vibrations to the crowd. These occur at three vibrating frequencies: the material waveband of the mechanics of auditory propagation and hearing itself; the corporeal waveband of the embodied kinetic rhythms of the crowd's dancing and crew's performance; and the ethereal waveband of the "vibes" or social and cultural meaning of the dancehall session and entire scene. Rather than the conventional technological, cultural and social "factors, " it is suggested that the crew's skills and techniques "make sense" of all these frequencies with expert evaluations, as the basis of their connoisseurship (Polanyi) or their logic of practice (Bourdieu). The engineer "just knows" when their fine-tuning is complete; the selector has a "gut feeling" when to repeat a track; and the MC "judges" the exact timing of the punch line. It is concluded that the crew's techniques are best understood as embodying a kind of rationality that pivots on ratio, analogia and proportion, rather than concepts of disembodied logic, representation or calculation. Thus the crew's evaluative techniques provide evidence for understanding the workings of the sound system as an apparatus for the propagation of vibrations.
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Qahwash, Murad M. "High frequency communication system modeling and performance enhancement, employing novel adaptive DSP techniques." Doctoral diss., University of Central Florida, 2002. http://digital.library.ucf.edu/cdm/ref/collection/RTD/id/1383.
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University of Central Florida College of Engineering ThesisHigh Frequency (HF) communication has been shown to be a useful communication technique from the very beginning of World War I and it accelerated during World War 11. This is attributed to its simplicity, ability to provide near globe connectivity at low power without repeaters, moderate cost, and ease of proliferation [I]. In fact, the HF communication system utilizes the ionosphere [2][3][4] to refract the skywave signals to a distant receiver. This ionospheric channel has some disadvantages. First, it is a non-stationary channel as the HF frequency propagation is a function of the sun spot activities, solar winds, and diurnal variations of the ionization level [5]. Second, the channel produces distortion in both signal amplitude and phase. As the different ionospheric layers move up or down, independent Doppler shifts on each propagation mode are introduced. Multipath fading [6] caused by multiple refractions of the signal fiom the ionosphere with or without ground reflection causes performance degradation in the HF system. Some techniques have been developed to improve HF performance [I]. One example is Space-Diversity [7], which uses more than one antenna at distant spaces to combine the received signal. Angle-of-Arrival Diversity that takes advantage of the fact that different modes have different arrival angles at the receiver, and so, highly directional antenna for example, can be used to improve the system performance. Another method of improving HF performance is to use different frequencies to transmit and receive messages. This method is known as Frequency diversity. Using timediversity, one can add a degree of redundancy to the transmitted message through the use of different types of coding, interleaving, etc. In the military standard, MIL-STD- 1 88- 1 1 OA [8], a convolutional encoder [9][10] followed by interleaver [Ill-[14] was used to scramble and transmit the data in different bit rates. In the presence of multipath fading [ 1 51, a training sequence is transmitted in an interleaved fashion with the data symbols with a 50% duty cycle. This has the disadvantage of losing half the bandwidth. At present, the recent advances of the Digital Signal Processing (DSP) [16][17] make it possible to reduce the bit-error-rate BEY and increase the transmission bit rate [18] through the usage of adaptive equalization [ 191-[2 11 which will be the focus of this dissertation. Equalizers such as, Transversal Equalizer [ 1 61, Blind Equalizer [22], Training waveform Equalizer [23], and Minimum Mean Square Error (MMSE) [20] Adaptive Equalizer have been applied into various communication systems. This proposal work will be to initially apply some of the previous developed equalizer to the HF channel specifically. Thereafter, new adaptive channel equalization [24],[25] will be developed to compensate for transmission channel impairments due to bandwidth limitations, multipath propagation, and rayleigh fading [2 11 conditions in mobile environments. A new technique for frequency offset prediction has been developed and finally, a new approach for MIL-STD- 1 88- 1 1 0A high frequency single-tone modem employing orthogonal Walsh-PN codes has been implemented.
Ph.D.
Doctorate;
Department of Electrical and Computer Engineering
Engineering and Computer Science
Electrical Engineering and Computer Science
198 p.
xviii, 198 leaves, bound : ill., (some col.) ; 28 cm.
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Lamprecht, Erwin Cornelius. "Multiple-Input Single-Output system identification techniques using the pebble bed modular reactor data / E.C. Lamprecht." Thesis, North-West University, 2004. http://hdl.handle.net/10394/639.
Full textAbstract:
Models are used to describe the dynamic behaviour of a system, to predict
future outputs of the system and are useful when designing certain control
schemes.
An effective control scheme could be used to influence the dynamic behaviour
of a system in such a way that it exhibits more desirable dynamic behaviour.
A control system could be designed to increase the efficiency of a system.
This makes it obvious that accurate models are very useful.
The focus of this study is to use Multiple-Input Single-Output (MISO) system
identification techniques on data obtained from the Flownex simulation
package. These techniques are used to obtain a (MISO) mathematical model
for the Pebble Bed Modular Reactor (PBMR).
MISO system identification techniques are used in this project to study the
effect that the inputs have on each other. This information helps in the
understanding of processes within the system. The reason for studying the
MIS0 systems and not the Single-Input Single-Output (SISO) systems is
because the field of interest focuses on the effects the inputs have on each
other.Thesis (M.Ing. (Computer and Electronical Engineering))--North-West University, Potchefstroom Campus, 2005.
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Loggins, William Conley 1953. "The development and evaluation of an expert system for identification of variance reduction techniques in simulation." Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/277131.
Full textAbstract:
The subject of this thesis is the development of an expert system to offer advising for variance reduction technique (VRT) selection in simulation. Simulation efficiency is increased by appropriate use of variance reduction techniques. The process of selecting VRTs brings a sharper focus to issues of experimental design and thus to the very purpose and objectives to be attained by the simulation. Students in the University of Arizona Systems and Industrial Engineering Department graduate courses are the intended users of this expert system, with the expectation that their practice of simulation will be facilitated.
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Shuaieb, Wafa S. A. "Radio-Location Techniques for Localization and Monitoring Applications. A study of localisation techniques, using OFDM system under adverse channel conditions and radio frequency identification for object identification and movement tracking." Thesis, University of Bradford, 2018. http://hdl.handle.net/10454/18185.
Full textAbstract:
A wide range of services and applications become possible when accurate position
information for a radio terminal is available. These include: location-based services;
navigation; safety and security applications. The commercial, industrial and military value
of radio-location is such that considerable research effort has been directed towards
developing related technologies, using satellite, cellular or local area network
infrastructures or stand-alone equipment.
This work studies and investigates two location techniques. The first one presents an
implementation scheme for a wideband transmission and direction finding system using
OFDM multi-carrier communications systems. This approach takes advantage of delay
discrimination to improve angle-of-arrival estimation in a multipath channel with high
levels of additive white Gaussian noise. A new methodology is interpreted over the multi carrier modulation scheme in which the simulation results of the estimated channel
improves the performance of OFDM signal by mitigating the effect of frequency offset
synchronization to give error-free data at the receiver, good angle of arrival accuracy and
improved SNR performance. The full system simulation to explore optimum values such
as channel estimation and AoA including the antenna array model and prove the
operational performance of the OFDM system as implemented in MATLAB.
The second technique proposes a low cost-effective method of tracking and monitoring
objects (examples: patient, device, medicine, document) by employing passive radio
frequency identification (RFID) systems. A multi-tag, (totalling fifty-six tags) with known
ID values are attached to the whole patient’s body to achieve better tracking and
monitoring precision and higher accuracy. Several tests with different positions and
movements are implemented on six patients. The aim is to be able to track the patient if
he/she is walking or sitting; therefore, the tests considered six possible movements for
the patient including walking, standing, sitting, resting, laying on the floor and laying on
the bed, these placements are important to monitor the status of the patient like if he
collapsed and fall on the ground so that the help will be quick. The collected data from
the RFID Reader in terms of Time Stamp, RSS, Tag ID, and a number of channels are
processed using the MATLAB code.
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Suleiman, Baha M. "Identification of Finite-Degree-of-Freedom Models for Ship Motions." Diss., Virginia Tech, 2000. http://hdl.handle.net/10919/30069.
Full textAbstract:
Accurate ship-motion prediction is important because it is directly related to the design, control, and economic operation of ships. Many methods are available for studying and predicting ship motions, including time-domain, strip-theory, and system-identification-based predictions. Time-domain and strip-theory predictions suffer from several physical and computational limitations. In this work, we use system-identification techniques to predict ship motions. We establish an identification methodology that can handle general finite-degree-of-freedom (FDOF) models of ship motions.
To establish this methodology, we derive the correct form of the equations of motion. This form contains all relevant linear and nonlinear terms.
Moreover, it explicitly specifies the dependence of the linear and nonlinear parameters on the forward speed. The energy-formulation approach is utilized to obtain full nonlinear ship-motion equations. The advantages of using this formulation are that self-sustained motions are not allowed and the dependence of the parameters on the forward speed is derived explicitly.
The data required for the identification techniques are generated using the Large Amplitude Motions Program (LAMP) developed by the Science Applications International Corporation (SAIC). The ship studied in this work is a Series 60 ship, which is a military cargo ship. LAMP data for different sea states and forward speeds are used to identify and predict the ship motions.
For linear parametric identification, we use the Eigensystem Realization Algorithm (ERA) to determine the coefficients in the linearly coupled equations and the effects of the forward speed on these coefficients.
For linear nonparametric identification, we present a new analysis technique, namely, the circular-hyperbolic decomposition (CHD), which avoids the leakage effects associated with the discrete Fourier transform (DFT). The CHD is then utilized to determine transfer functions and response amplitude operators (RAOs).
For nonlinear parametric identification, we present a methodology that is a combination of perturbation techniques and higher-order spectral moments.
We apply this methodology to identify the nonlinear parameters that cause parametric roll resonance. The level of accuracy of the models and the parameter estimates are determined by validations of the predicted ship motions with the LAMP data.Ph. D.
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CURRERI, Francesco. "Soft Sensor Design, Transferability and Causality through Machine Learning Techniques." Doctoral thesis, Università degli Studi di Palermo, 2023. https://hdl.handle.net/10447/582112.
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Dargel, Michael R. "The influence of physical system parameters on the performance of adaptive filters for system identification of mechanical systems." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1996. http://handle.dtic.mil/100.2/ADA319478.
Full textAbstract:
Thesis (M.S. in Engineering Acoustics) Naval Postgraduate School, September 1996.Thesis advisor(s): Robert Keolian, Roberto Cristi. "September 1996." Includes bibliographical references (p. 75). Also available online.
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劉健強 and Kin-keung Lau. "Preprocessing and postprocessing techniques for improving the performance of a Chinese character recognition system." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1991. http://hub.hku.hk/bib/B31210375.
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Lau, Kin-keung. "Preprocessing and postprocessing techniques for improving the performance of a Chinese character recognition system /." [Hong Kong : University of Hong Kong], 1991. http://sunzi.lib.hku.hk/hkuto/record.jsp?B13154345.
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Karnesis, Nikolaos. "Bayes ian data analys i s for l i sa pathfinder. Techniques applied to system identification experiments." Doctoral thesis, Universitat Autònoma de Barcelona, 2015. http://hdl.handle.net/10803/286039.
Full textAbstract:
Les ones gravitatòries són una predicció de la teoria de la Relativitat General d’Einstein, la detecció i anàlisi de les quals obrirà una nova àrea en el nostre coneixement de l’Univers. En efecte, aquestes ones porten informació de sistemes amb gravetat molt forta i que són molt difícils d’observar amb instruments convencionals, basats en la detecció de llum, per a qual cosa el nostre coneixement actual només en pot ser parcial. Avui en dia tenim evidències experimentals de l’existència de les ones gravitatòries, com la variació del període orbital del pulsar binari PSRB1913+16 (Premi Nobel 1993). Tot i això, encara no se n’ha pogut obtenir una detecció. La comunitat científica té doncs un gran interès en assolir aquesta detecció com es demostra per la quantitat d’observatoris repartits arreu del món: LIGO (Estats Units), VIRGO (Italia, França), GEO600 (Alemanya, Regne Unit), LCGT (Japó), etc.
La missió LISA (Laser Interferomer Space Antenna) és una proposta per posar un d’aquests observatoris en òrbita heliocèntrica mitjançant tres satèl.lits que contindrien masses en caiguda lliure la distància entre les quals es mesuraria mitjançant interferometria laser. El link laser connectaria els diferents satèl.lits que es trobarien separats 1 mil.lió de quilòmetres, conseguint una configuració triangular que seguiria la Terra en la seva òrbita. Aquesta proposta ha estat acceptada per l’Agència Espacia Europea l’any 2013 en el seu pla científic, com el tema d’una missió que seria llançada en la decàda del 2030.
Aquesta tesis s’emmarca dins la missió LISA Pathfinder, que és la missió precursora de LISA i que té data de llançament el 2015. Aquesta missió posarà a proba la tecnologia que requereix la futura missió LISA i per això conté els principals elements (laser, massa de test, etc.) però en una versió reduïda i en un únic satèl.lit. L’objectiu científic principal és aconseguir mesurar l’acceleració relativa entre dues masses en caiguda lliure fins a nivells de 10^(-14) m / s^2 / Hz ^(1/2) en la banda de molt baixa freqüència, és a dir 1mHz.
La tesis desenvolupa els mètodes coneguts com a Markov Chain Monte Carlo (MCMC), els quals s’utilitzen, entre d’altres, per a l’estimació de paràmetres. Aquestes tècniques han estat posades a proba en els darrers anys mitjançant diferents campanyes amb dades simulades i actualment formen part del LTPDA, una toolbox de MATLAB desenvolupada per la col.laboració per a l’anàlisis de les dades de la missió. El treball en aquesta tesis descriu en detall l’aplicació d’aquests tècniques a per a l’estimació dels paràmetres que descriuen la dinàmica de la massa de test a l’interior del satèl.lit.
De la mateixa manera, s’han desenvolupat tècniques estadístiques més enllà de l’estimació de paràmetres per tal d’aplicar-les al que es coneix com a selecció del models, és a dir, l’evaluació estadistíca de diferents models per determinar quin és el que permet una millor descripció de les dades. En aquest aspecte s’han evaluat les diferents opcions existents en la literatura i, en particular, s’ha establert el Reversible Jump Markov Chain Monte Carlo (RJMCMC) com una eina per a poder a duu a terme aquests estudis. Aquesta tècnica permet la comparació de models de diferent dimensionalitat, representat una generalització dels mètodes MCMC.
Les tècniques i resultats obtinguts en aquesta tesis es posaran en pràctica durant les operacions de la missió LISA Pathfinder, la qual obrirà el camí cap a la futura detecció d’ones gravitatòries a l’espai.Gravitational waves are a prediction of Einstein's General Relativity, the detection and analysis of which will open a new area in our understanding of the Universe. Indeed, these waves carry information from systems with strong gravity and are very difficult to observe with conventional instruments, which are based on the detection of light. Today, we have experimental evidence of the existence of gravitational waves, as the variation of the orbital period of the binary pulsar PSRB1913 + 16 (Nobel Prize 1993). However, there has been no detection. The scientific community is pursuing this detection with several observatories spread around the world: LIGO (USA), VIRGO (Italy, France), GEO600 (Germany, UK), LCGT (Japan ), etc. LISA (Laser Interferomer Space Antenna) is a proposal to put one of these observatories in heliocentric orbit using three satellites that contain masses in free fall. A laser interferometer is used to measure the distance between them. The satellites will be separated 1 Mkm, resulting in a triangular configuration that follows the Earth in its orbit. This proposal was accepted by the European Agency Espacia in 2013, as the subject of a mission to be launched in the early 2030's. This thesis is part of the LISA Pathfinder mission, which is the precursor mission of LISA and has a release date in 2015. This mission will test the technology required for the future LISA mission and therefore contains the main elements (laser, test mass, etc.) but in a smaller version and in a single satellite. The main scientific objective is to measure the relative acceleration between two masses in free fall to levels down to 10^(-14) m / s^2 / Hz ^(1/2) in the low frequency band, i.e. 1mHz. This thesis develops the methods known as Markov Chain Monte Carlo (MCMC), which are used, among others, for the estimation of parameters. These techniques have been put to the test in recent years through various campaigns with simulated data and are currently part of the LTPDA, a MATLAB toolbox developed by the collaboration for the analysis of data from the mission. The work in this thesis describes in detail the application of these techniques to estimate the parameters that describe the dynamics of the test mass inside the satellite. Similarly, we have developed statistical techniques beyond the estimation of parameters in order to apply them to what is known as model selection, i.e. the evaluation of different statistical models to determine which one allows a better description of the data. In this respect, we have evaluated the different options available in the literature and, in particular, we have established the Reversible Jump Markov Chain Monte Carlo (RJMCMC) as a tool to carry out these studies during operations. This technique allows the comparison of models of different dimensionality, which represents a generalization of the MCMC methods. The techniques and results obtained in this thesis will be used during the operations of the LISA Pathfinder mission, which will open the way for future detection of gravitational waves in space.
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Sprague, Milo D. "A High Performance DSP Based System Architecture for Motor Drive Control." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-81197-165134/.
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Johansson, Alfred. "Ensemble approach to code smell identification : Evaluating ensemble machine learning techniques to identify code smells within a software system." Thesis, Tekniska Högskolan, Jönköping University, JTH, Datateknik och informatik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-49319.
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The need for automated methods for identifying refactoring items is prelevent in many software projects today. Symptoms of refactoring needs is the concept of code smells within a software system. Recent studies have used single model machine learning to combat this issue. This study aims to test the possibility of improving machine learning code smell detection using ensemble methods. Therefore identifying the strongest ensemble model in the context of code smells and the relative sensitivity of the strongest perfoming ensemble identified. The ensemble models performance was studied by performing experiments using WekaNose to create datasets of code smells and Weka to train and test the models on the dataset. The datasets created was based on Qualitas Corpus curated java project. Each tested ensemble method was then compared to all the other ensembles, using f-measure, accuracy and AUC ROC scores. The tested ensemble methods were stacking, voting, bagging and boosting. The models to implement the ensemble methods with were models that previous studies had identified as strongest performer for code smell identification. The models where Jrip, J48, Naive Bayes and SMO. The findings showed, that compared to previous studies, bagging J48 improved results by 0.5%. And that the nominally implemented baggin of J48 in Weka follows best practices and the model where impacted negatively. However, due to the complexity of stacking and voting ensembles further work is needed regarding stacking and voting ensemble models in the context of code smell identification.
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Zhang, Aijing. "Identification of TEF cofactor(s) in skeletal muscles utilizing yeast two hybrid system." Free to MU Campus, others may purchase, 2004. http://wwwlib.umi.com/cr/mo/fullcit?p1420951.
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Underschultz, James Ross. "Identification of fault and top seal effectiveness through an integration of hydrodynamic and capillary analysis techniques." Thesis, Curtin University, 2009. http://hdl.handle.net/20.500.11937/2371.
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Fault and top seal effectiveness has proved to be a significant risk in exploration success, and creates a large uncertainty in predicting reservoir performance. This is particularly true in the Australian context, but equally applies to exploration provinces worldwide. Seals can be broadly classified into fault, intraformational, and top seal. For geological time-scale processes, intraformational and top seals are typically characterised by their membrane seal capacity and fracture threshold pressure. Fault seals are typically characterised by fault geometry, juxtaposition, membrane seal capacity, and reactivation potential. At the production time scale, subtle variations in the permeability distribution within a reservoir can lead to compartmentalization. These are typically characterised by dynamic reservoir models which assume hydrostatic conditions prior to commencement of production. There are few references in the seals literature concerning the integration of hydrodynamic techniques with the various aspects of seal evaluation. The research for this PhD thesis by published papers includes: Methodology for characterising formation water flow systems in faulted strata at exploration and production time scales; a new theory of hydrodynamics and membrane (capillary) seal capacity; and case study evaluations demonstrating integrated multidisciplinary techniques for the evaluation of seal capacity (fault, intraformational and top seal) that demonstrate the new theory in practice. By incorporating hydrodynamic processes in the evaluation of total seal capacity, the evidence shows that existing shale gouge ratio – across fault pressure difference (SGR-AFPD) calibration plots need adjustment resulting in the calibration envelopes shifting to the centre of the plot.This adjustment sharpens the predictive capacity for membrane seal analysis in the pre-drill scenario. This PhD thesis presents the background and rationale for the thesis topic, presents each published paper to be included as part of the thesis and its contribution to the body of work addressing the thesis topic, and presents related published papers that are not included in the thesis but which support the body of published work on the thesis topic. The result of the thesis is a new theory and approach to characterising membrane seal capacity for the total seal thickness, and has implications for an adjusted SGR-AFPD calibration to be applied in pre-drill evaluations of seal capacity. A large portion of the resources and data required to conduct the research were made available by CSIRO and its associated project sponsors including the CO2CRC.
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Tugsal, Umut. "FAULT DIAGNOSIS OF ELECTRONIC FUEL CONTROL (EFC) VALVES VIA DYNAMIC PERFORMANCE TEST METHOD." ProQuest, 2009. http://hdl.handle.net/1805/2094.
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Indiana University-Purdue University Indianapolis (IUPUI)Electronic Fuel Control (EFC) valve regulates fuel flow to the injector fuel supply line in the Cummins Pressure Time (PT) fuel system. The EFC system controls the fuel flow by means of a variable orifice that is electrically actuated. The supplier of the EFC valves inspects all parts before they are sent out. Their inspection test results provide a characteristic curve which shows the relationship between pressure and current provided to the EFC valve. This curve documents the steady state characteristics of the valve but does not adequately capture its dynamic response. A dynamic test procedure is developed in order to evaluate the performance of the EFC valves. The test itself helps to understand the effects that proposed design changes will have on the stability of the overall engine system. A by product of this test is the ability to evaluate returned EFC valves that have experienced stability issues. The test determines whether an EFC valve is faulted or not before it goes out to prime time use. The characteristics of a good valve and bad valve can be observed after the dynamic test. In this thesis, a mathematical model has been combined with experimental research to investigate and understand the behavior of the characteristics of different types of EFC valves. The model takes into account the dynamics of the electrical and mechanical portions of the EFC valves. System Identification has been addressed to determine the transfer functions of the different types of EFC valves that were experimented. Methods have been used both in frequency domain as well as time domain. Also, based on the characteristic patterns exhibited by the EFC valves, fuzzy logic has been implemented for the use of pattern classification.
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Underschultz, James Ross. "Identification of fault and top seal effectiveness through an integration of hydrodynamic and capillary analysis techniques." Curtin University of Technology, Department of Petroleum Engineering, 2009. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=118307.
Full textAbstract:
Fault and top seal effectiveness has proved to be a significant risk in exploration success, and creates a large uncertainty in predicting reservoir performance. This is particularly true in the Australian context, but equally applies to exploration provinces worldwide. Seals can be broadly classified into fault, intraformational, and top seal. For geological time-scale processes, intraformational and top seals are typically characterised by their membrane seal capacity and fracture threshold pressure. Fault seals are typically characterised by fault geometry, juxtaposition, membrane seal capacity, and reactivation potential. At the production time scale, subtle variations in the permeability distribution within a reservoir can lead to compartmentalization. These are typically characterised by dynamic reservoir models which assume hydrostatic conditions prior to commencement of production. There are few references in the seals literature concerning the integration of hydrodynamic techniques with the various aspects of seal evaluation. The research for this PhD thesis by published papers includes: Methodology for characterising formation water flow systems in faulted strata at exploration and production time scales; a new theory of hydrodynamics and membrane (capillary) seal capacity; and case study evaluations demonstrating integrated multidisciplinary techniques for the evaluation of seal capacity (fault, intraformational and top seal) that demonstrate the new theory in practice. By incorporating hydrodynamic processes in the evaluation of total seal capacity, the evidence shows that existing shale gouge ratio – across fault pressure difference (SGR-AFPD) calibration plots need adjustment resulting in the calibration envelopes shifting to the centre of the plot.This adjustment sharpens the predictive capacity for membrane seal analysis in the pre-drill scenario. This PhD thesis presents the background and rationale for the thesis topic, presents each published paper to be included as part of the thesis and its contribution to the body of work addressing the thesis topic, and presents related published papers that are not included in the thesis but which support the body of published work on the thesis topic. The result of the thesis is a new theory and approach to characterising membrane seal capacity for the total seal thickness, and has implications for an adjusted SGR-AFPD calibration to be applied in pre-drill evaluations of seal capacity. A large portion of the resources and data required to conduct the research were made available by CSIRO and its associated project sponsors including the CO2CRC.
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CONGIU, ANDREA. "Novel load identification techniques and a steady state self-tuning prototype for switching mode power supplies." Doctoral thesis, Università degli Studi di Cagliari, 2014. http://hdl.handle.net/11584/266433.
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Control of Switched Mode Power Supplies (SMPS) has been traditionally achieved through analog means with dedicated integrated circuits (ICs). However, as power systems are becoming increasingly complex, the classical concept of control has gradually evolved into the more general problem of power management, demanding functionalities that are hardly achievable in analog controllers. The high flexibility offered by digital controllers and their
capability to implement sophisticated control strategies, together with the programmability of controller parameters, make digital control very attractive as an option for improving the features of dcdc converters. On the other side, digital controllers find their major weak
point in the achievable dynamic performances of the closed loop system. Indeed, analogto-digital conversion times, computational delays and sampling-related delays strongly limit the small signal closed loop bandwidth of a digitally controlled SMPS. Quantization effects set other severe constraints not known to analog solutions. For these reasons, intensive scientific research activity is addressing the problem of making digital compensator stronger competitors against their analog counterparts in terms of achievable performances.
In a wide range of applications, dcdc converters with high efficiency over the whole range of their load values are required. Integrated digital controllers for Switching Mode Power Supplies are gaining growing interest, since it has been shown the feasibility of digital controller
ICs specifically developed for high frequency switching converters. One very interesting potential
benefit is the use of autotuning of controller parameters (on-line controllers), so that the dynamic response can be set at the software level, independently of output capacitor
filters, component variations and ageing. These kind of algorithms are able to identify the output filter configuration (system identification) and then automatically compute the best compensator gains to adjust system margins and bandwidth. In order to be an interesting
solution, however, the self-tuning should satisfy two important requirements: it should not heavily affect converter operation under nominal condition and it should be based on a simple and robust algorithm whose complexity does not require a significant increase of the
silicon area of the IC controller. The first issue is avoided performing the system identification (SI) with the system open loop configuration, where perturbations can be induced in the system before the start up.
Much more challenging is to satisfy this requirement during steady state operations, where perturbations on the output voltage are limited by the regular operations of the converter.
The main advantage of steady state SI methods, is the detection of possible non-idealities occurring during the converter operations. In this way, the system dynamics can be consequently adjusted with the compensator parameters tuning. The resource saving issue, requires
the development of äd-hocßelf-tuning techniques specifically tailored for integrated digitally controlled converters. Considering the flexibility of digital control, self-tuning algorithms can be studied and easily
integrated at hardware level into closed loop SMPS reducing development time and R & D costs. The work of this dissertation finds its origin in this context. Smart power management is accomplished by tuning the controller parameters accordingly to the identified converter
configuration.
Themain difficult for self-tuning techniques is the identification of the converter output filter
configuration. Two novel system identification techniques have been validated in this dissertation. The open loop SI method is based on the system step response, while dithering
amplification effects are exploited for the steady state SI method. The open loop method can be used as autotunig approach during or before the system start up, a step evolving reference voltage has been used as system perturbation and to obtain the output filter information
with the Power Spectral Density (PSD) computation of the system step response.
The use of ¢§ modulator is largely increasing in digital control feedback. During the steady state, the finite resolution introduces quantization effects on the signal path causing low frequency contributes of the digital control word. Through oversampling-dithering capabilities
of ¢§ modulators, resolution improvements are obtained. The presented steady state identification techniques demonstrates that, amplifying the dithering effects on the signal path, the output filter information can be obtained on the digital side by processing with the PSD computation the perturbed output voltage. The amount of noise added on the output voltage does not affect the converter operations, mathematical considerations have been
addressed and then justified both with a Matlab/Simulink fixed-point and a FPGA-based closed loop system.
The load output filter identification of both algorithms, refer to the frequency domain. When the respective perturbations occurs, the system response is observed on the digital side and processed with the PSD computation. The extracted parameters are the resonant frequency
ans the possible ESR (Effective Series Resistance) contributes,which can be detected as maximumin
the PSD output. The SI methods have been validated for different configurations of buck converters on a fixed-point closed loop model, however, they can be easily applied to further converter configurations. The steady state method has been successfully integrated
into a FPGA-based prototype for digitally controlled buck converters, that integrates a PSD computer needed for the load parameters identification. At this purpose, a novel VHDL-coded full-scalable hybrid processor for Constant Geometry FFT (CG-FFT) computation has been designed and integrated into the PSD computation system. The processor is based on a variation of the conventional algorithm used for FFT, which is the Constant-Geometry FFT (CG-FFT).Hybrid CORDIC-LUT scalable architectures, has been introduced as alternative approach for the twiddle factors (phase factors) computation needed during the FFT algorithms execution. The shared core architecture uses a single
phase rotator to satisfy all TF requests. It can achieve improved logic saving by trading off with computational speed. The pipelined architecture is composed of a number of stages equal to the number of PEs and achieves the highest possible throughput, at the expense of
more hardware usage.
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Hasegawa, Robert Shigehisa. "Using synthetic images to improve iris biometric performance." Scholarly Commons, 2012. https://scholarlycommons.pacific.edu/uop_etds/827.
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Fuggetti, Giuseppe. "Parameter Identification of a QuadPlane VTOL Drone Model by means of Reverse Engineering Techniques for Flight Control System Purposes." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019.
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The aim of this thesis work is to identify the model parameters, both the inertial terms and the aerodynamic ones, of a new drone concept. Based on reverse engineering philosophy, the proposed techniques represents the new way the aerospace industry of drones is going to meet. All over the world the application of drones for the most disparate purposes is advancing exponentially and the need to bring new effective and efficient solutions to the market cannot ignore considering what has been done up to now for the drone industry. In this sense one wants to include reverse engineering in the process of developing new concepts. Working on a purchased commercial drone model in a quad-plane configuration, this work aims to demonstrate how it is possible to obtain models and tools useful for producing a new product optimized for a specific task or mission starting from a fully developed product. Particularly the thesis focuses on the need of a dynamic model for the design of a specific automatic flight control systems for the transition phase of the drone from hovering to level flight because, as from observations and tests, it has been revealed to be the most critic phase of the flight. In order to design such an autopilot the static parameters of the model of the longitudinal dynamics has been identified through CFD simulations and CAD tools. The 3D model of the drone has been obtained using the scan-to-cad technique.
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Shrivastava, Anupam. "Identification and Analysis of Illegal States in the Apoptotic Discrete Transition System Model using ATPG and SAT-based Techniques." Thesis, Virginia Tech, 2008. http://hdl.handle.net/10919/35202.
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Programmed Cell Death, or Apoptosis, plays a critical role in human embryonic development and in adult tissue homeostasis. Recent research efforts in Bioinformatics and Computational Biology focus on gaining deep insight into the Apoptosis process. This allows researchers to clearly study the relation between the dysregulation of apoptosis and the development of cancer. Research in this highly interdisciplinary field of bioinformatics has become much more quantitative, using tools from computational sciences to understand the behavior of Biological systems.
Previously, an abstracted model has been developed to study the Apoptosis process as a Finite State Discrete Transition Model. This model facilitates the reutilization of the digital design verification and testing techniques developed in the Electronic Design Automation domain. These verification and testing techniques for hardware have become robust over the past few decades. Usually simulation is the cornerstone of the Design Verification industry and bulk of states are covered by simulation. Formal verification techniques are then used to analyze the remaining corner case states. Techniques like Genetic Algorithm guided Logic Simulation (GALS) and SAT-based Induction have already been applied to the Apoptosis Discrete Transition Model. However, the Apoptosis model presents some unique problems. The simulation techniques have shown to be unable to cover most of the states of the Apoptosis model. When SAT-based Induction is applied to the Apoptosis model, in particular to find illegal states, very few illegal states are identified. It particularly suffers from the fact that the Apoptosis Model is rather complex and the formulation for testing and verification is hard to tackle at larger bounds greater than 20 or so. Consequently, the state space of the Apoptosis model largely lies in the unknown region, meaning that we are unable to either reach those states or prove that they are illegal. Unless we know whether these states are reachable or illegal, it is not feasible to infer information about the model such as what protein concentrations can be reached under what kind of input stimuli. Questions such as whether certain protein concentrations can be reached or not in this model can only be answered if we have a clear picture of the reachability of state space.
In this thesis, we propose techniques based on ATPG and SAT based image computation of the Apoptosis finite transition model. Our method leverages the results obtained in previous research work. It uses the reachable states obtained from the simulation traces of the previous work as initial states for our technique. This enables us to identify more illegal states in less number of iterations; in other words, we are able to reach the fixed point in image computation faster. Our experimental analysis illustrates that the proposed techniques could prove most of the former unknown states as illegal states. We are able to extend our analysis to obtain clearer picture of the interaction of any two proteins in the system considered together.Master of Science
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Shatnawi, Ibrahem Mahmoud. "Automated Vehicle Delay and Travel Time Estimation Techniques for Improved Performance Measures of Urban Network System." University of Akron / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=akron1446473677.
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