A new technique to de-Dopplerize microphone signals from moving sources of sound is derived. Currently available time domain de-Dopplerization techniques require oversampling and interpolation of the microphone time data. In contrast, the technique presented in this dissertation performs the de-Dopplerization entirely in the frequency domain eliminating the need for oversampling and interpolation of the microphone data. As a consequence, the new de-Dopplerization technique is computationally more efficient. The new de-Dopplerization technique is then implemented into a frequency domain beamforming algorithm to locate moving sources of sound. The mathematical formulation for the implementation of the new de-Dopplerization technique is presented for sources moving along a linear trajectory and for sources moving along a circular trajectory, i.e. rotating sources. The resulting frequency domain beamforming method to locate moving sound sources is then validated using numerical simulations for various source configurations (e.g. emission angle, emission frequency, and source velocity), and different processing parameters (e.g. time window length). Numerical datasets for sources with linear motion as well as for rotating sources were simulated. For comparison purposes, selected datasets were also processed using traditional time domain beamforming. The results from the numerical simulations show that the frequency domain beamforming method is at least 10 times faster than the traditional time domain beamforming method with the same performance. Furthermore, the results show that as the number of microphones and/or grid points increase, the processing time for the traditional time domain beamforming method increases at a rate 20 times larger than the rate of increase in processing time of the new frequency domain beamforming method. / Ph. D.

Most drill wear monitoring research found in the literature is based on conventional vibration technologies. However, these conventional approaches still have not attracted real interest from manufacturers for multiples of reasons: some of these techniques are not practical and use complicated Tool Condition Monitoring (TCM) systems with less value in industry. In addition, they are also prone to give spurious drill deterioration warnings in industrial environments. Therefore, drills are normally replaced at estimated preset intervals, sometimes long before they are worn or by expertise judgment. Two of the great problems in the implementation of these systems in drilling are: the poor signal-to-noise ratio and the lack of system-made sensors for drilling, as is prevalent in machining operations with straight edge cutters. In order to overcome the noise problems, many researchers recommend advanced and sophisticated signal processing while the work of Rehorn et al. (2005) advises the following possibilities to deal with the lack of commercial system-made sensors:  Some research should be directed towards developing some form of instrumented tool for drill operations.  Since the use of custom-made sensors is being ignored in drilling operations, effort should be focused on intelligent or innovative use of available sensor technology. It is expected that the latter could minimize implementation problems and allows an optimal drill utilization rate by means of modern and smart sensors. In addition to the accelerometer sensor commonly used in conventional methods, this work has considered two other sensor-based methods to monitor the drill wear indirectly. These methods entail the use of an instrumented drill with strain gauges to measure the torque and the use of an encoder to measure the Instantaneous Angular Speed (IAS). The signals from these sensors were analyzed using signal processing techniques such as, statistical parameters, Fast Fourier Transform (FFT), and a ii preliminary Time-Frequency (TF) analysis. A preliminary investigation has revealed that the use of a Regression Analysis (RA) based on a higher order polynomial function can very well follow and give prognosis of the development of the monitored parameters. The experimental investigation has revealed that all the above monitoring systems are sensitive to the deterioration of the drill condition. This work is however particularly concerned with the use of IAS on the spindle of the drill, compared to conventional monitoring systems for drill condition monitoring. This comparison reveals that the IAS approach can generate diagnostic information similar to vibration and torque measurements, without some of the instrumentation complications. This similitude seems to be logical, as it is well known that the increase of friction between the drill and workpiece due to wear increase the torque and consequently it should reduce or at least affect the spindle rotational speed. However, the use of a drill instrumented with a strain gauge is not practical, because of the inconvenience it causes on production machines. By contrast, the IAS could be measured quite easily by means of an encoder, a tachometer or some other smart rotational speed sensors. Thus, one could take advantage of advanced techniques in digital time interval analysis applied to a carrier signal from a multiple pulse per revolution encoder on the rotating shaft, to improve the analysis of chain pulses. As it will be shown in this dissertation, the encoder resolution does not sensibly affect the analysis. Therefore, one can easily replace encoders by any smart transducers that have become more popular in rotating machinery. Consequently, a non-contact transducer for example could effectively be used in on-line drill condition monitoring such as the use of lasers or time passage encoder-based systems. This work has gained from previous research performed in Tool Condition Monitoring TCM, and presents a sensor that is already available in the arsenal of sensors and could be an open door for a practical and reliable sensor in automated drilling. iii In conclusion, this dissertation strives to answer the following question: Which one of these methods could challenge the need from manufacturers by monitoring and diagnosing drill condition in a practical and reliable manner? Past research has sufficiently proved the weakness of conventional technologies in industry despite good results in the laboratory. In addition, delayed diagnosis due to time-consuming data processing is not beneficial for automated drilling, especially when the drill wears rapidly at the end of its life. No advanced signal processing is required for the proposed technique, as satisfactory results are obtained using common time domain signal processing methods. The recommended monitoring choice will definitely depend on the sensor that is practical and reliable in industry. / Dissertation (MEng)--University of Pretoria, 2012. / gm2013 / Mechanical and Aeronautical Engineering / MEng / Unrestricted

International Telemetering Conference Proceedings / October 25-28, 1999 / Riviera Hotel and Convention Center, Las Vegas, Nevada / An all-digital high data rate parallel receiver architecture developed jointly by Goddard Space Flight Center and the Jet Propulsion Laboratory is pre- sented. This receiver utilizes only a small number of high speed components along with a majority of lower speed components operating in a parallel fre- quency domain structure implementable in CMOS, and can process over 600 Mbps with numerous varieties of QPSK modulation, including those incorpo- rating precise pulse shaping for bandwidth eÆcient modulation. Performance results for this receiver for bandwidth eÆcient QPSK modulation schemes such as square-root raised cosine pulse shaped QPSK and Feher’s patented QPSK are presented, demonstrating the great degree of exibility and high performance of the receiver architecture.

Parameterised analytical models that describe the trimmed inflight behaviour of classical aircraft have been studied and are widely accepted by the flight dynamics community. Therefore, the primary role of aircraft parameter estimation is to quantify the parameter values which make up the models and define the physical relationship of the air vehicle with respect to its local environment. Nevertheless, a priori empirical predictions dependent on aircraft design parameters also exist, and these provide a useful means of generating preliminary values predicting the aircraft behaviour at the design stage. However, at present the only feasible means that exist to actually prove and validate these parameter values remains to extract them through physical experimentation either in a wind-tunnel or from a flight test. With the advancement of UAVs, and in particular smaller UAVs (less than 1m span) the ability to fly the full scale vehicle and generate flight test data presents an exciting opportunity. Furthermore, UAV testing lends itself well to the ability to perform rapid prototyping with the use of COTS equipment. Real-time system identification was first used to monitor highly unstable aircraft behaviour in non-linear flight regimes, while expanding the operational flight envelope. Recent development has focused on creating self-healing control systems, such as adaptive re-configurable control laws to provide robustness against airframe damage, control surface failures or inflight icing. In the case of UAVs real-time identification, would facilitate rapid prototyping especially in low-cost projects with their constrained development time. In a small UAV scenario, flight trials could potentialy be focused towards dynamic model validation, with the prior verification step done using the simulation environment. Furthermore, the ability to check the estimated derivatives while the aircraft is flying would enable detection of poor data readings due to deficient excitation manoeuvres or atmospheric turbulence. Subsequently, appropriate action could then be taken while all the equipment and personnel are in place. This thesis describes the development of algorithms in order to perform online system identification for UAVs which require minimal analyst intervention. Issues pertinent to UAV applications were: the type of excitation manoeuvers needed and the necessary instrumentation required to record air-data. Throughout the research, algorithm development was undertaken using an in-house Simulink© model of the Aerosonde UAV which provided a rapid and flexible means of generating simulated data for analysis. In addition, the algorithms were further tested with real flight test data that was acquired from the Cranfield University Jestream-31 aircraft G-NFLA during its routine operation as a flying classroom. Two estimation methods were principally considered, the maximum likelihood and least squares estimators, with the aforementioned found to be best suited to the proposed requirements. In time-domain analysis reconstruction of the velocity state derivatives ˙W and ˙V needed for the SPPO and DR modes respectively, provided more statistically reliable parameter estimates without the need of a α- or β- vane. By formulating the least squares method in the frequency domain, data issues regarding the removal of bias and trim offsets could be more easily addressed while obtaining timely and reliable parameter estimates. Finally, the importance of using an appropriate input to excite the UAV dynamics allowing the vehicle to show its characteristics must be stressed.

Approved for public release; distribution is unlimited / Computer simulation studies of a frequency domain adaptive beamforming algorithm are presented. These simulation studies were conducted to determine the multiple broadband target localization capability and the full angular coverage capability of the algorithm. The algorithm was evaluated at several signal-to-noise ratios with varying sampling rates. The number of iterations that the adaptive algorithm took to reach a minimum estimation error was determined. Results of the simulation studies indicate that the algorithm can localize multiple broadband targets and has full angular coverage capability. / http://archive.org/details/computersimulati00behr / Lieutenant, United States Navy

Tradicionalmente, o processo de análise para obtenção da vida à fadiga em sistemas estruturais ou componentes mecânicos sujeitos a carregamentos dinâmicos é realizado no domínio do tempo, procedimento que, mesmo sendo amplamente conhecido, demanda maior tempo e esforço computacional. Nas últimas décadas, tem se aperfeiçoado métodos de solução no domínio da frequência que vêm apresentando maior eficiência e mostrando-se competitivos, além de um campo com promissor potencial de desenvolvimento. Assim, neste trabalho será desenvolvida uma abordagem visando reduzir os recursos computacionais consumidos numa análise de vida à fadiga, utilizando para isso métodos no domínio da frequência, onde excitação e resposta são representadas por PSD, e também uma abordagem de análise Global-Local. Para isso, será realizada uma sequência de etapas que de forma resumida são: geração do modelo Global, análise modal, geração do modelo Local e matriz de compatibilidade, cálculo da PSD a partir do carregamento, transformação do sistema para o domínio da frequência, montagem da Função de Resposta em Frequência, e por fim, utilizando dados da curva S-N do material será realizada a aplicação do modelo de Dirlik para prever a vida em fadiga. Todas estas etapas foram implementadas em programa numérico, e seus resultados testados com exemplos da literatura, gerando assim, um conjunto de ferramentas para pesquisa da fadiga no domínio da frequência. O estudo desenvolvido utiliza como hipóteses que a resposta do sistema estrutural seja linear, o carregamento seja randômico, estocástico e ergódico, a distribuição de picos siga uma distribuição gaussiana, e o método probabilístico para previsão da vida a fadiga se baseie nos parâmetros espectrais. / Traditionally the analysis process to obtain the fatigue life of structural systems or mechanical components subjected to dynamic loading is performed in the time domain, a procedure which, although widely known, requires more time and computational effort. In the last decades it has been optimized solution methods in the frequency domain that has shown greater efficiency and proving to be competitive, besides a field with promising potential development. Thus, this work will be developed an approach aimed at reducing the computational resources consumed in an analysis of fatigue life, using for this frequency domain method, where excitement and response are represented by PSD, and also a global-local analysis approach. Thereunto, there will be a sequence of steps that briefly are: Global model generation, modal analysis, generation of local model and compatibility matrix, calculation of the PDS from the load, system transformation to the frequency domain, assembly frequency response function and finally, using data from the SN curve of the material will be realized the application of Dirlik model to predict the fatigue life. All these steps were implemented in numerical software and their results were tested with literature examples, generating a set of search tools to fatigue in the frequency domain. The study was developed using hypotheses that the structural system response is linear, the loading is random, stochastic and ergodic, the peaks distribution follow a Gaussian distribution, and the probabilistic method to prediction of life for the fatigue is based on the spectral parameters.

Orientador: João Antonio Pereira / Banca: Gilberto Pechoto de Melo / Banca: Sérgio Sartori / Resumo: O presente trabalho propõe o estudo e implementação de uma metodologia para a estimação dos parâmetros modais de estruturas utilizando uma técnica de identificação baseada apenas na resposta do modelo, denominada Decomposição no Domínio da Freqüência (DDF). Para tal são abordados os conceitos básicos envolvidos na análise modal, análise modal baseada apenas na resposta e métodos de identificação. A formulação do algoritmo é baseada na decomposição da matriz densidade espectral de potência utilizando a técnica da decomposição em valores singulares (SVD). A decomposição da matriz densidade espectral nas linhas de freqüências correspondentes aos picos de amplitude, permite a estimativa dos modos de vibrar do sistema. Tem-se ainda que, o primeiro vetor singular obtido com a decomposição da matriz densidade espectral, para cada linha de freqüência, na região em torno do modo, contém as respectivas informações daquele modo e o correspondente valor singular leva a uma estimativa da função densidade espectral de um sistema de um grau de liberdade (1GL) equivalente. Neste caso, a matriz densidade espectral de saída é decomposta em um conjunto de sistemas de 1 grau de liberdade. Posteriormente, esses dados são transformados para o domínio do tempo, utilizando a transformada inversa de Fourier, e as razões de amortecimento são estimadas utilizando o conceito de decremento logaritmo. A metodologia é avaliada, numa primeira etapa, utilizando dados simulados e posteriormente utilizando dados experimentais. / Abstract: The present work proposes the study and implementation of a methodology for the estimating of the modal parameters of structures by using the output-only data. The technique called Frequency Domain Decomposition (DDF) identifies the modal parameters without knowing the input. For that, it is discussed the basic concepts involved in identification, modal analysis and output-only modal analysis. The formulation of the algorithm is based on the decomposition of the power spectral density matrix by using the singular values decomposition technique (SVD). The decomposition of the spectral density matrix for the lines of frequency corresponding to the amplitude peaks, allows the estimating of the modes shape of the system. Additionally, the first singular vector obtained with the decomposition of the spectral density matrix, for each line of frequency, in the area around of the peak, contains the respective information of that mode. The corresponding singular value leads to an estimating of the spectral density function of an equivalent system of one degree of freedom. Therefore, the output spectral density matrix is decomposed in a set of one degree of freedom system. Later on, those data are transformed for the time domain by using the inverse Fourier transform and the damping ratios estimated from the crossing times and the logarithm decrement of the corresponding single degree of freedom system correlation function. The methodology is evaluated using simulated and experimental data. / Mestre

Master of Science / Department of Civil Engineering / Hani G. Melhem / This study reports the results of an analytical, experimental and a numerical study (proof of concept study) on a proposed method for extracting the pseudo-free-vibration response of a structure using ambient vibration, usually of a random nature, as a source of excitation to detect any change in the dynamic properties of a structure that may be caused by damage. The structural response contains not only a random component but also a component reflecting the dynamic properties of the structure, comparable to the free vibration for a given initial condition. Structural response to the arbitrary excitation is recorded by one or several accelerometers with a desired data-collection frequency and resolution. The free-vibration response of the structure is then extracted from this data by removing the random component of the response by the method proposed in this study. The features of the free-vibration response of the structure extracted by a suitable method, namely Fast Fourier Transform (FFT) in this study, can be used for change detection. Possible change of the pattern of these features is dominantly linked to the change in dynamic properties of the system, caused by possible damage. To show the applicability of the concept, besides an analytical verification using Newmark’s linear acceleration method, two steel portal frames with different flexural stiffness were made in the steel workshop of the structural laboratory for an experimental study. These structures were also numerically modeled using a finite element software. A wireless accelerometer with a sampling frequency rate of 2046 Hz was affixed on the top of the physical structure, at the same location where the acceleration was recorded for the corresponding numerical model. The physical structure was excited manually by an arbitrary hit and the response of the structure to this excitation, in terms of the acceleration on the top of the structure, was recorded. The pseudo-free-vibration response was extracted and transferred into frequency domain using FFT. The frequency with the largest magnitude which is the fundamental frequency of the structure was traced. This was repeated for several independent excitations and the fundamental frequencies were observed to be the same, showing that the process can correctly identify the natural frequencies of the structure. Similarly, the numerical model was excited and for several base excitation cases, the fundamental frequencies were found to be the same. Considering the acceptable accuracy of the results from the two numerical models in simulating the response of their corresponding physical models, additional numerical models were analyzed to show the consistency and applicability of the proposed method for a range of flexural stiffness and damping ratio. The results confirm that the proposed method can precisely extract the pseudo-free-vibration response of the structures and detect the structural frequencies regardless of the excitation. The fundamental frequency is tied to the stiffness and a larger stiffness leads to a higher frequency, as expected, regardless of the simulated ambient excitation.

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

Despite significant advances in medical imaging technologies, there currently exist no tools to effectively assist healthcare professionals during surgical procedures. In turn, procedures remain subjective and dependent on experience, resulting in avoidable failure and significant quality of care disparities across hospitals. Optical techniques are gaining popularity in clinical research because they are low cost, non-invasive, portable, and can retrieve both fluorescence and endogenous contrast information, providing physiological information relative to perfusion, oxygenation, metabolism, hydration, and sub-cellular content. Near-infrared (NIR) light is especially well suited for biological tissue and does not cause tissue damage from ionizing radiation or heat. My dissertation has been focused on developing rapid imaging techniques for mapping endogenous tissue constituents to aid surgical guidance. These techniques allow, for the first time, video-rate quantitative acquisition over a large field of view (> 100 cm2) in widefield and endoscopic implementations. The optical system analysis has been focused on the spatial-frequency domain for its ease of quantitative measurements over large fields of view and for its recent development in real-time acquisition, single snapshot of optical properties (SSOP) imaging. Using these methods, this dissertation provides novel improvements and implementations to SSOP, including both widefield and endoscopic instrumentations capable of video-rate acquisition of optical properties and sample surface profile maps. In turn, these measures generate profile-corrected maps of hemoglobin concentration that are highly beneficial for perfusion and overall tissue viability. Also utilizing optical property maps, a novel technique for quantitative fluorescence imaging was also demonstrated, showing large improvement over standard and ratiometric methods. To enable real-time feedback, rapid processing algorithms were designed using lookup tables that provide a 100x improvement in processing speed. Finally, these techniques were demonstrated in vivo to investigate their ability for early detection of tissue failure due to ischemia. Both pre-clinical studies show endogenous contrast imaging can provide early measures of future tissue viability. The goal of this work has been to provide the foundation for real-time imaging systems that provide tissue constituent quantification for tissue viability assessments. / 2018-01-09T00:00:00Z