Dissertations / Theses on the topic 'Frequency domain'
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Johnson, Richard. "Frequency domain structural identification." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1996. http://handle.dtic.mil/100.2/ADA312408.
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Chen, Shuming. "Filtering in the frequency domain." Thesis, University of Sheffield, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.434612.
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Ye, Lei. "Adaptive frequency-domain access techniques." Thesis, University of York, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.479512.
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Dickerson, Jeffrey Crawford. "Frequency domain secondary pulse estimation." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/36983.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1995.Includes bibliographical references (leaves 44-45).
by Jeffrey Crawford Dickerson.
M.Eng.
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Wang, Yong. "Frequency domain coupled circuit-electromagnetic simulation /." Thesis, Connect to this title online; UW restricted, 2004. http://hdl.handle.net/1773/6071.
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Kalyoncu, Ozden. "Noise Reduction In Time-frequency Domain." Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12608768/index.pdf.
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In this thesis work, time-frequency filtering of nonstationary signals in noise using Wigner-Ville Distribution is investigated. Continuous-time, discrete-time and discrete Wigner Ville Distribution definitions, their relations, and properties are given.
Time-Frequency Peak Filtering Method is presented. The effects of different parameters on the performance of the method are investigated, and the results are presented.
Time-Varying Wiener Filter is presented. Using simulations it is shown that the performance of the filter is good at SNR levels down to -5 dB. It is proposed and shown that the performance of the filter improves by using Support Vector Machines.
The presented time-frequency filtering techniques are applied on test signals and on a real world signal. The results obtained by the two methods and also by classical zero-phase low-pass filtering are compared. It is observed that for low sampling rates Time-Varying Wiener Filter, and for high sampling rates Time-Frequency Peak Filter performs better.
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Anyaegbu, Esther Olulu. "Frequency Domain Processing of GNSS Signals." Thesis, University of Leeds, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.486155.
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Mousavi, Amir Mehdi. "Frequency-domain equivalents for passive networks." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0017/NQ45692.pdf.
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Afran, Md Shah. "Frequency Domain Equalizer for Aeronautical Telemetry." International Foundation for Telemetering, 2015. http://hdl.handle.net/10150/596444.
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ITC/USA 2015 Conference Proceedings / The Fifty-First Annual International Telemetering Conference and Technical Exhibition / October 26-29, 2015 / Bally's Hotel & Convention Center, Las Vegas, NVThis paper presents a frequency domain equalization (FDE) technique for aeronautical telemetry channels. The FDE has significantly lower computational complexity compared to its time-domain counterpart, however both are found to exhibit almost identical performance. A cyclic prefix is generally needed to implement the FDE. In this paper, we exploit the repetition of iNET preamble and ASM bits in place of cyclic prefix.
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Zhong, Shiyin. "Electricity Load Modeling in Frequency Domain." Diss., Virginia Tech, 2017. http://hdl.handle.net/10919/75109.
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In today's highly competitive and deregulated electricity market, companies in the generation, transmission and distribution sectors can all benefit from collecting, analyzing and deep-understanding their customers' load profiles. This strategic information is vital in load forecasting, demand-side management planning and long-term resource and capital planning.
With the proliferation of Advanced Metering Infrastructure (AMI) in recent years, the amount of load profile data collected by utilities has grown exponentially. Such high-resolution datasets are difficult to model and analyze due to the large size, diverse usage patterns, and the embedded noisy or erroneous data points. In order to overcome these challenges and to make the load data useful in system analysis, this dissertation introduces a frequency domain load profile modeling framework. This framework can be used a complementary technology alongside of the conventional time domain load profile modeling techniques.
There are three main components in this framework: 1) the frequency domain load profile descriptor, which is a compact, modular and extendable representation of the original load profile. A methodology was introduced to demonstrate the construction of the frequency domain load profile descriptor. 2) The load profile Characteristic Attributes in the Frequency Domain (CAFD). Which is developed for load profile characterization and classification. 3) The frequency domain load profile statistics and forecasting models. Two different models were introduced in this dissertation: the first one is the wavelet load forecast model and the other one is a stochastic model that incorporates local weather condition and frequency domain load profile statistics to perform medium term load profile forecast.
7 different utilities load profile data were used in this research to demonstrate the viability of modeling load in the frequency domain. The data comes from various customer classes and geographical regions. The results have shown that the proposed framework is capable to model the load efficiently and accurately.Ph. D.
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Tiran, Sébastien. "Side Channels in the Frequency Domain." Thesis, Montpellier 2, 2013. http://www.theses.fr/2013MON20164/document.
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De nos jours, l'emploi de la cryptographie est largement répandu et les circuits intègrent des primitives cryptographiques pour répondre à des besoins d'identification, de confidentialité, ... dans de nombreux domaines comme la communication, la PayTV, ...La sécurisation de ces circuits est donc un enjeu majeur. Les attaques par canaux cachés consistent à espionner ces circuits par différents biais comme le temps de calcul, la consommation en courant ou les émanations électromagnétiques pour obtenir des informations sur les calculs effectués et retrouver des secrets comme les clefs de chiffrement. Ces attaques ont l'avantage d'être indétectables, peu couteuses et ont fait l'objet des nombreuses études. Dans le cadre des attaques par analyse de la consommation en courant ou des émanations électromagnétiques l'acquisition de bonnes courbes est un point crucial. Malgré la forte utilisation de techniques de prétraitement dans la littérature, personne n'a tenté d'établir un modèle de fuite dans le domaine fréquentiel. Les travaux effectués durant cette thèse se concentrent donc sur cet aspect avec pour intérêt d'améliorer l'efficacité des attaques. De plus, de nouvelles attaques dans le domaine fréquentiel sont proposées, sujet peu étudié malgré l'intérêt de pouvoir exploiter plus efficacement la fuite éparpillée dans le tempsNowadays, the use of cryptography is widely spread, and a lot of devices provide cryptographic functions to satisfy needs such as identification, confidentiality, ... in several fields like communication, PayTV, ...Security of these devices is thus a major issue.Side Channel Attacks consist in spying a circuit through different means like the computation time, power consumption or electromagnetic emissions to get information on the performed calculus and discover secrets such as the cipher keys.These attacks have the advantage to be cheap and undetectable, and have been studied a lot.In the context of attacks analysing the power consumption or the electromagnetic emissions, the acquisition of good traces is a crucial point.Despite the high use of preprocessing techniques in the literature, nobody has attempted to model the leakage in the frequency domain.The works performed during this thesis are focusing on this topic with the motivation of improving the efficiency of attacks.What's more, new frequency domain attacks are proposed, subject poorly studied despite the advantage of better exploiting the leakage spread in time
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Zhou, Tingdong. "Electromagnetic system frequency-domain reduced-order modeling and time-domain simulation." Diss., The University of Arizona, 2002. http://hdl.handle.net/10150/279965.
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Model order reduction methodologies are presented for semi-discrete electromagnetic systems obtained from the spatial discretization of the hyperbolic system of Maxwell's equations. Different reduced-order modeling algorithms, i.e., Pade via Lanczos (PVL), multiple point PVL, Krylov, rational Krylov, PVL with expansion at infinity, are presented and applied for model order reduction and the properties of these algorithms are discussed. The implementation of the model order reduction methodologies to a full-wave frequency domain electromagnetic system simulator (ROMES) is discussed in detail. Scattering parameters are calculated for several electromagnetic systems with discontinuities. A time domain simulation framework is also introduced for transmission line embedded systems described by the Telegrapher's equations. The time domain convolution approach is selected to perform the transmission line embedded circuit simulations. Derivations for Closed-form triangle impulse responses (TIR) are discussed and numerical examples are presented. The developed triangle impulse responses are used to perform time-domain circuit simulations. The effects of frequency-dependent lossy transmission lines on signal integrity and causality issues associated with the transmission line parameters ( R, L, C, and G) in Telegrapher's equation are discussed. The presented research provides an accurate and efficient way to characterize electromagnetic systems for high-speed circuit applications in the frequency domain and methods to simulate these circuits in the time domain.
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Elayouty, Amira Sherif Mohamed. "Time and frequency domain statistical methods for high-frequency time series." Thesis, University of Glasgow, 2017. http://theses.gla.ac.uk/8061/.
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Advances in sensor technology enable environmental monitoring programmes to record and store measurements at high-temporal resolution over long time periods. These large volumes of high-frequency data promote an increasingly comprehensive picture of many environmental processes that would not have been accessible in the past with monthly, fortnightly or even daily sampling. However, benefiting from these increasing amounts of high-frequency data presents various challenges in terms of data processing and statistical modeling using standard methods and software tools. These challenges are attributed to the large volumes of data, the persistent and long memory serial correlation in the data, the signal to noise ratio, and the complex and time-varying dynamics and inter-relationships between the different drivers of the process at different timescales. This thesis aims at using and developing a variety of statistical methods in both the time and frequency domains to effectively explore and analyze high-frequency time series data as well as to reduce their dimensionality, with specific application to a 3 year hydrological time series. Firstly, the thesis investigates the statistical challenges of exploring, modeling and analyzing these large volumes of high-frequency time series. Thereafter, it uses and develops more advanced statistical techniques to: (i) better visualize and identify the different modes of variability and common patterns in such data, and (ii) provide a more adequate dimension reduction representation to the data, which takes into account the persistent serial dependence structure and non-stationarity in the series. Throughout the thesis, a 15-minute resolution time series of excess partial pressure of carbon dioxide (EpCO2) obtained for a small catchment in the River Dee in Scotland has been used as an illustrative data set. Understanding the bio-geochemical and hydrological drivers of EpCO 2 is very important to the assessment of the global carbon budget. Specifically, Chapters 1 and 2 present a range of advanced statistical approaches in both the time and frequency domains, including wavelet analysis and additive models, to visualize and explore temporal variations and relationships between variables for the River Dee data across the different timescales to investigate the statistical challenges posed by such data. In Chapter 3, a functional data analysis approach is employed to identify the common daily patterns of EpCO2 by means of functional principal component analysis and functional cluster analysis. The techniques used in this chapter assume independent functional data. However, in numerous applications, functional observations are serially correlated over time, e.g. where each curve represents a segment of the whole time interval. In this situation, ignoring the temporal dependence may result in an inappropriate dimension reduction of the data and inefficient inference procedures. Subsequently, the dynamic functional principal components, recently developed by Hor mann et al. (2014), are considered in Chapter 4 to account for the temporal correlation using a frequency domain approach. A specific contribution of this thesis is the extension of the methodology of dynamic functional principal components to temporally dependent functional data estimated using any type of basis functions, not only orthogonal basis functions. Based on the scores of the proposed general version of dynamic functional principal components, a novel clustering approach is proposed and used to cluster the daily curves of EpCO2 taking into account the dependence structure in the data. The dynamic functional principal components depend in their construction on the assumption of second-order stationarity, which is not a realistic assumption in most environmental applications. Therefore, in Chapter 5, a second specific contribution of this thesis is the development of a time-varying dynamic functional principal components which allows the components to vary smoothly over time. The performance of these smooth dynamic functional principal components is evaluated empirically using the EpCO2 data and using a simulation study. The simulation study compares the performance of smooth and original dynamic functional principal components under both stationary and non-stationary conditions. The smooth dynamic functional principal components have shown considerable improvement in representing non-stationary dependent functional data in smaller dimensions. Using a bootstrap inference procedure, the smooth dynamic functional principal components have been subsequently employed to investigate whether or not the spectral density and covariance structure of the functional time series under study change over time. To account for the possible changes in the covariance structure, a clustering approach based on the proposed smooth dynamic functional principal components is suggested and the results of application are discussed. Finally, Chapter 6 provides a summary of the work presented within this thesis, discusses the limitations and implications and proposes areas for future research.
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Mui, Chi Seong. "Frequency domain approach to time series analysis." Thesis, University of Macau, 2000. http://umaclib3.umac.mo/record=b1446676.
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Lupton, Richard. "Frequency-domain modelling of floating wind turbines." Thesis, University of Cambridge, 2015. https://www.repository.cam.ac.uk/handle/1810/252880.
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The development of new types of offshore wind turbine on floating platforms requires the development of new approaches to modelling the combined platform-turbine system. In this thesis a linearised frequency-domain approach is developed which gives fast but approximate results: linearised models of the structural dynamics, hydrodynamics, aerodynamics and control system dynamics are brought together to find the overall response of the floating wind turbine to harmonic wind and wave loading. Initially, a nonlinear flexible multibody dynamics code is developed and verified, which is then used to provide reference nonlinear simulation results. The structural dynamics of a wind turbine on a moving platform are shown to be nonlinear, but for realistic conditions the effects are small. An approximate analysis of the second-order response of floating cylinders to hydrodynamic loads suggests slow drift motion may be relatively small for floating wind turbines, compared to other floating offshore structures. The aerodynamic loads are linearised using both harmonic and tangent linearisation approaches; the harmonic linearisation gives improved results when stall occurs. The wake dynamics can also be included. The control system behaviour is linearised using the same method, which works well when the wind speed is far from the rated wind speed; close to the rated wind speed the nonlinearity is stronger, but further improvement should be possible. These sub-models are combined to give a simple but complete model of a floating wind turbine, with flexible blades and a flexible tower, but neglecting the control system behaviour, wake dynamics and nonlinear hydrodynamic loads. For the OC3-Hywind turbine, the accuracy of the results is assessed by comparison to nonlinear time-domain simulations using the commercial code Bladed. Peak-peak errors of less than 5 % are achievable for many harmonic wind and wave inputs, but certain conditions lead to larger errors. The effect of including linearised control system behaviour is demonstrated for a subset of conditions. Overall, the results are promising but more work is needed for practical application.
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Carnovale, Christina. "Purchasing power parity and frequency domain filtering." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/MQ65028.pdf.
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Wernholt, Erik. "Multivariable Frequency-Domain Identification of Industrial Robots." Doctoral thesis, Linköping : Department of Electrical Engineering, Linköping University, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-10149.
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Monfet, Frederic. "Turbo equalization using frequency-domain shortening filter." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=99527.
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Turbo equalization provides excellent performance but the complexity associated with this technique prohibits its use in application with severe inter-symbol interference (ISI) channel; the turbo equalizer complexity increases exponentially with the length of the channel impulse response (CIR) and the modulation level used for data transmission. In this work, a combined frequency-domain pre-equalizer with a turbo equalizer is proposed in an attempt to reduce the length of the CIR used by the turbo equalizer and hence the complexity of the receiver. The optimum selection of coefficients of the frequency-domain pre-equalizer and desired channel impulse response is discussed. With the proposed receiver, the complexity of the turbo equalizer can be controlled by pre-selecting the length of the desired channel impulse response. This complexity reduction is achieved at the cost of an increase in the noise level, which degrades the performance. The effect on the performance of such pre-equalizer is studied analytically. The overall performance of the proposed receiver for different length of the desired channel impulse response is studied via analytical comparison and simulation. Simulation results on performance in various frequency-selective fading channels indicate a substantial performance gain when compared to a conventional feed-forward equalizer (FFE) plus decision-feedback equalizer (DFE) receiver. Finally, in cases where a large alphabet is used for modulation, the reduced-search BCJR (Bahl, Cocke, Jelinek, and Raviv) [1] algorithm is utilized in the proposed receiver to further reduce the complexity of the receiver.
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Sendashonga, Mireille. "Image quality assessment using frequency domain transforms." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=99537.
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Measurement of image quality plays a central role in optimization and evaluation of imaging systems. The most straight-forward way to assess image quality is subjective evaluations by human observers, where the mean value of their scores is used as the quality measure. However, objective (quantitative) measures are needed because subjective evaluations are impractical and expensive. The aim of this thesis is to develop simple and low-complexity metrics for quality assessment of digital images.Traditionally, the most widely used quantitative measures are the mean squared error and measures that model the human visual system. The proposed method uses the Discrete Cosine Transform and the Discrete Wavelet Transform to divide images into four frequency bands and relates the visual quality of the distorted images to the weighted average of the mean squared error between original and distorted images within each band.
The performance of the metrics presented in this thesis is tested and validated on a large database of subjective quality ratings. Simulations show that the proposed metrics accurately predict visual quality and outperform current state-of-the-art methods with simple and easily implemented processing steps.
Extensions of the proposed image quality metrics are investigated. More particularly, this thesis explores image quality assessment when the reference image is only partially available (reduced reference settings), and presents a method for successfully quantifying the quality of distorted images in such settings.
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Saleem, Sajid. "Frequency-domain equalization for continuous phase modulation." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/50391.
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Continuous phase modulation~(CPM) is a non-linear, constant-envelope modulation scheme with memory, known for its bandwidth and power efficiency. Multi-h CPM uses multiple modulation indices in successive symbol intervals to improve the error performance as compared to single-h CPM~(basic CPM that utilizes only a single modulation index). One of the major applications of multi-h CPM is in aeronautical telemetry systems. Modern aeronautical devices host an increasing number of sensors, which can transmit flight testing data to the ground station. However, this excess data transfer increases the intersymbol interference, and thus channel equalization is required at the receiver. The objective of our research is to propose low-complexity frqeuency-domain equalization~(FDE) techniques for multi-h CPM waveforms. For a modulation scheme with memory, such as CPM, the cyclic constraint on the FDE block necessitates the use of an extra segment of symbols, called intrafix or tail segment. We have used very simple geometric arguments to derive upper and lower bounds on the length of the intrafix in terms of the parameters of the modulation scheme and the Frobenius number. It is concluded that the length of the intrafix for multi-h CPM schemes is typically shorter than those required for single-h modulation schemes. We propose two receiver architectures; one uses a matched filter front end, while the other utilizes a fractional sampling front end. Various simplifications are proposed for each architecture, and the trade-off between receiver complexity and performance is analyzed and verified through detailed simulation studies.
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Abdnoor, Al-zurfi Huda Kadhem. "Optimizing frequency domain contention in wireless network." Thesis, The University of North Carolina at Greensboro, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=1558125.
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Wireless communication became popular in the last decades, giving the mobility to the users. However with increased number of users and contention, network efficiency can hardly keep up with user needs. This thesis focuses on a new frequency domain contention technique called FICA. In FICA, the channel is assumed to be using Orthogonal Frequency Division Multiplex (OFDM) with multiple sub-carriers. We investigated the use of multiple channels and multiple access points (APs) in the design. First we investigated having one channel that is divided into number of sub-carriers, it shows good result, but only for limited number of users. Therefore we worked on the second scenario of having several sub-channels and each sub-channel is divided into a number of sub-carriers to communicate through one AP. And for efficient result nodes contend on the contention band and winner nodes will have the chance to send their data through the transmission band. In real world, networks have more than one AP, for that reason we investigate the third scenario, which is having more than one AP. In this setup, the result showed significant outcome, that we can divide the channel into several sub-channels to serve more than one AP and hash an ID for each AP. We further investigated optimal number of ID bits that are used to represent the hashed receiver IDs. We summarize the results as following: 1) it is possible to divide the channel bandwidth into several sub-channels that is divided into several sub-carriers to serve large number of users. 2) node contention should be partitioned into contention band and transmission band to reduce the overhead that the contending node cause when contending on the whole channel. 3) AP ID is required when the network has more than one AP. 4) number of sub-carriers in the contention band has to increase at least to the double for higher efficiency, since more AP on the network would make the channel more loaded. 5) AP ID can be anything between 20-40 bits. Decreasing the ID to less than 40bits did not affect the throughput and efficiency of the channel.
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Giakas, Giannis K. "Time and frequency domain applications in biomechanics." Thesis, Manchester Metropolitan University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389498.
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Ho, C. "Nonlinear vibration control : a frequency domain approach." Thesis, University of Sheffield, 2014. http://etheses.whiterose.ac.uk/5157/.
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A vibration isolator, sometimes called an isolating mount, is the device situating between the vibration source and the sensitive system preventing the transmission of undesired disturbances. The performance is measured by the force or the displacement transmissibility, both functions of frequency. A good vibration isolation system has three main properties - a low resonant peak, a large isolation range and low transmissibility at non-resonant regions. Unfortunately, these characteristics cannot be achieved simultaneously by a simple linear vibration isolation system. The thesis addresses this problem for single-degree-of-freedom (sdof) vibration isolation systems by introducing nonlinear damping and stiffness devices into the system. First, theoretical studies were carried out to rigorously reveal the benefits of the proposed nonlinear vibration isolation systems over linear ones. Next, the performance of these nonlinear systems were analysed by simulations. Then, experimental studies were conducted to verify the theoretical and simulations results. Finally, a systematic approach was developed to design the parameters of the nonlinear damping and stiffness devices in order to satisfy specific vibration isolation requirements. Many vibration isolators can be modelled as a single-degree-of-freedom mass-spring-damper system. Many researchers have attempted to enhance the vibration isolation performance by designing springs with nonlinear stiffness. Others have focused on different types of damping nonlinearities. The new vibration isolation system proposed in the thesis combines both spring and damping nonlinearities in one system to exploit the advantages of both components while avoiding their undesirable effects. The theoretical properties of this proposed nonlinear vibration isolation system were analysed rigorously using the output frequency response function (OFRF) approach, a novel and unique method recently proposed at Sheeld. The stiffness nonlinearity is already a well researched area and can readily be realised in practice. Therefore, the implementation of the proposed nonlinear vibration suppression system focused on the realisation of the nonlinear damping component using commercially available magneto-rheological (MR) dampers which provide a damping force that is dependent on a control current. With feedback control, the force-velocity relationship of an MR damper can be shaped into a designed function. This implementation has been incorporated first in a vibration isolation system by simulation, then in a physical experimental rig which has a moving mass. The simulation and experimental data not only showed the successful realisation of a damping device with a particular nonlinear damping characteristic, but also confirmed the theoretical findings on the beneficial effects of nonlinear damping on a vibration isolation application. The final part of the thesis is devoted to the practical design of the proposed vibration isolation system. Given specific transmissibility requirements at certain critical frequencies, the values of the linear parameters are first designed, then the OFRF approach is applied to determine the nonlinear parameters. This pragmatic method simplifies the design of a complicated nonlinear system, which was traditionally difficult to work with, into a step-by-step guide and, therefore, has significant potential of industrial applications. The thesis has exploited the special effects of two nonlinear components on the performance of a passive sdof vibration isolation system. With the support of theoretical, simulation and experimental studies, the newly proposed configuration has shown substantial benefits to many vibration isolation problems. The simple yet effective design and implementation has significant implications for a wide range of engineering applications such as car suspension designs and building protection against earthquakes.
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Hwang, Irena T. (Irena Tammy). "Frequency domain model-based intracranial pressure estimation." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/77016.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 73-75).
Elevation of intracranial pressure (ICP), the pressure of the fluid surrounding the brain, can require urgent medical attention. Current methods for determining ICP are invasive, require neurosurgical expertise, and can lead to infection. ICP measurement is therefore limited to the sickest patients, though many others could potentially benefit from availability of this vital sign. We present a frequency-domain approach to ICP estimation using a simple lumped, linear time-invariant model of cerebrovascular dynamics. Preliminary results from 28 records of patients with severe traumatic brain injury are presented and discussed. Suggestions for future work to improve the estimation algorithm are proposed.
by Irena T. Hwang.
M.Eng.
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Spear, Steven J. "Frequency domain quantification of manufacturing process resolution." Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/80915.
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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1993, and Thesis (M.S.)--Sloan School of Management, 1993.Vita.
Includes bibliographical references (leaves 117-136).
by Steven J. Spear.
M.S.
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Wang, Dexin. "Structural damage identification in the frequency domain." Diss., The University of Arizona, 1999. http://hdl.handle.net/10150/284350.
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This study presents novel approaches for direct damage identification of structures in the frequency domain. Relations between structural stiffness variations and measured system responses are formulated, thus opening the possibility of locating structural damage in terms of the reduction in the local stiffness when analytical baseline models are not available. After this, the related identifiability is discussed under the noise-free condition. In identifying damage in structural points, generic joint elements with only translational degrees of freedom are defined to parameterize the stiffness variations in the joints. Since ill-conditioning is a common problem in system identification and damage detection, a solution regularization based on parameter subset selection is proposed and used with least squares methods. A substructure-based parameter-recursive algorithm is developed for selecting parameter subsets to make use of the fact that the damage is local in structures. The proposed methods are verified by various simulated examples in which systematic modeling errors are present. Finally, the methods are also applied to the degradation identification of a vehicle structure.
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Law, Eugene L. "FREQUENCY DOMAIN EFFECTS OF LOW RESOLUTION DIGITIZATION." International Foundation for Telemetering, 1991. http://hdl.handle.net/10150/612909.
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International Telemetering Conference Proceedings / November 04-07, 1991 / Riviera Hotel and Convention Center, Las Vegas, NevadaThere is a requirement to digitize certain wide-band analog signals in telemetry applications. Typically, an analog-to-digital converter (ADC) with eight or more bits of resolution is used. The resulting signal requires a much larger transmission bandwidth than the original analog signal. The frequency domain information is of primary interest for many applications. In these cases, there are several methods for minimizing the transmitted bandwidth. One method is to perform fast fourier transforms (FFTs) on the signals and only transmit information about the largest signals. The disadvantages of this approach include: relatively long time delay before transmission, resolution bandwidth fixed when FFT performed (unless phase information is also transmitted), and extra complexity in the telemeter. This paper will discuss some effects of minimizing the transmitted bandwidth by quantizing to a small number of bits. The performance will also be compared with analog frequency modulation (FM). Measured performance will be presented for four different input signals and one-, three-, and eight-bit quantization. These signals are amplitude modulation, angle modulation, sum of sine waves, and frequency sweep. The test setup is shown in figure 1. The analyses presented in this paper were performed using either fast fourier transforms (FFTs) or a Kay DSP Sonagraph. The FFT length was 1024 points and a Hann (cosine) window was used. The analysis hardware used for these tests has an analog input, therefore, all digitized signals were converted to analog signals before analysis. The signals were low pass filtered before analysis to minimize aliasing in the analysis and display process.
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Vundavalli, Suveen Kumar, and Sri Rama Srinivasa Varma Danthuluri. "Bird Chirps Annotation UsingTime-Frequency Domain Analysis." Thesis, Blekinge Tekniska Högskola, Institutionen för tillämpad signalbehandling, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-13624.
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There are around 10,426 bird species around the world. Recognizing the bird species for an untrained person is almost impossible either by watching or listening them. In order to identify the bird species from their sounds, there is a need for an application that can detect the bird species from its sound. Time-frequency domain analysis techniques are used to implement the application. We implemented two time-frequency domain feature extraction methods. In feature extraction, a signature matrix which consist of extracted features is created for bird sound signals. A database of signature matrix is created with bird chirps extracted features. We implemented two feature classification methods. They are auto-correlation feature classification method and reference difference feature classification method. An unknown bird chirp is compared with the database to detect the species name. The main aim of the research is to implement the time-frequency domain feature extraction method, create a signature matrix database, implement two feature classification methods and compare them. At last, bird species were identified in the research and the auto-correlation classification method detects the bird species better than the reference difference classification method.
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Warburton, Niels Jamie. "Frequency domain approach to self-force calculations." Thesis, University of Southampton, 2012. https://eprints.soton.ac.uk/167481/.
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In this thesis, the problem of computing the back-reaction, or self-force, caused by a point particle interacting with its own field is studied. In particular, motivated by the prospect of detecting gravitational waves from extreme mass ratio inspiral systems, we consider the motion of the particle in black hole spacetimes. As a toy model for the most astrophysically relevant scenario of orbits about a rotating black hole we first study the scalar-field self-force (SSF)experienced by a scalar charge moving on a fixed geodesic in Kerr spacetime for a variety of orbits. Our approach is to work in the frequency domain, fully decomposing the scalar field into spheroidal harmonic and frequency modes and numerically solving for the retarded field mode-by-mode. Regularization of the retarded field is performed using the standard mode-sum technique which requires spherical harmonic modes as input, which we obtain by projecting the spheroidal harmonic modes on to a basis of spherical harmonics. We find for circular, equatorial orbits that the black hole spin can have a pronounced effect on the conservative piece of the SSF, causing it to (with respect to the Schwarzschild scalar-field self-force) change sign for certain spins and orbital radii. For eccentric orbits in the equatorial plane, we make use of the recently introduced method of extended homogeneous solutions to overcome the Gibbs phenomenon associated with a naive approach. As an application of our work we compute the shift to the innermost stable circular orbit due to the conservative piece of the scalar-field self-force for a variety of black hole spins. We also present some preliminary results for the SSF along circular, inclined geodesics. As well as studying the toy model SSF, we also consider the gravitational self-force (GSF) problem in the context of orbits around a Schwarzschild black hole. Our approach is again to work in the frequency domain, and we perform a complete decomposition of the metric perturbation in tensor spherical harmonics and frequency modes. The ten metric perturbation fields decouple with respect to the multipole indices but remain coupled within each spherical harmonic mode. We solve the resulting coupled sets numerically with a code set up to run on a computer cluster. Regularization is again performed using the mode-sum technique. Our resulting code is extremely efficient for low eccentricity orbits, and using it we compute the GSF for a great many points in the orbital parameter space. With these results we fit an analytic model to our numerical data and then use a relativistic osculating elements scheme to evolve the orbital inspiral. This allows us, for the first time, to assess the contribution to a complete inspiral from the conservative piece of the gravitational self-force. Finally, as an aside, we investigate the recently discovered phenomenon of isofrequency orbits, whereby it is possible to have pairs of physically distinct bound geodesics about a Kerr black hole that share the same three orbital frequencies.
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Kriel, Thomas Edwin Slaughter. "Assessment of frequency domain force identification procedures." Diss., Pretoria : [s.n.], 2000. http://upetd.up.ac.za/thesis/available/etd-01122007-131828/.
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Papagni, Francesca <1993>. "Frequency domain analysis of stationary time series." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amsdottorato.unibo.it/9850/1/Papagni_Francesca_tesi.pdf.
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This thesis provides a necessary and sufficient condition for asymptotic efficiency of a nonparametric estimator of the generalised autocovariance function of a Gaussian stationary random process. The generalised autocovariance function is the inverse Fourier transform of a power transformation of the spectral density, and encompasses the traditional and inverse autocovariance functions. Its nonparametric estimator is based on the inverse discrete Fourier transform of the same power transformation of the pooled periodogram. The general result is then applied to the class of Gaussian stationary ARMA processes and its implications are discussed.
We illustrate that for a class of contrast functionals and spectral densities, the minimum contrast estimator of the spectral density satisfies a Yule-Walker system of equations in the generalised autocovariance estimator. Selection of the pooling parameter, which characterizes the nonparametric estimator of the generalised autocovariance, controlling its resolution, is addressed by using a multiplicative periodogram bootstrap to estimate the finite-sample distribution of the estimator. A multivariate extension of recently introduced spectral models for univariate time series is considered, and an algorithm for the coefficients of a power transformation of matrix polynomials is derived, which allows to obtain the Wold coefficients from the matrix coefficients characterizing the generalised matrix cepstral models. This algorithm also allows the definition of the matrix variance profile, providing important quantities for vector time series analysis. A nonparametric estimator based on a transformation of the smoothed periodogram is proposed for estimation of the matrix variance profile.
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Williams, N. G. "Frequency domain parameter identification and the statistical properties of frequency response estimates." Thesis, Loughborough University, 1993. https://dspace.lboro.ac.uk/2134/25141.
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Frequency domain techniques in systems theory have their origins in Heavyside's operational calculus (Heavyside, 1889). Such work was later developed by Foster and Campbell (1931), Brune (1931), Nyquist (1932), Black (1934), Darlington (1939) and subsequently Bode (1948). This interest in the frequency domain was due to its appeal to the intuition of the engineer. The dominance of frequency domain techniques was subsequently eroded from the late 1950s through the 1960s by the influence of the space programmes. The space systems being analysed were based on strong theoretical foundations with well-defined sets of differential equations. The analysis led to the development of the state-space methods which were able to cope with the multivariable problems and were amenable to numerical solution. As a result of these developments, control engineering was largely dominated by the state-space approach and the associated areas of LQG optimal control, Kaiman-Bucy filters, observability and controllability. Two factors led to a resurgence of interest amongst academics in the development of frequency domain techniques in the 1970s and 1980s. The first was the development of the Fast Fourier Transform (FFT) (Cooley & Tookey, 1965). This provided an efficient method of analysing the Fourier transforms of signals and allowed the development of spectral methods of obtaining frequency response estimates. The collection of data was greatly speeded up and this enabled frequency domain methods to be increasingly applied to on-line control problems. The second factor was that the developments in the time domain were never fully embraced by practicing engineers in traditional control environments.
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Campbell, Marvin G. "Structural damage detection using frequency domain error localization." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1994. http://handle.dtic.mil/100.2/ADA289932.
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Li, Ran. "Signal peptide prediction in the space-frequency domain." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file 0.44 Mb., 68 p, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:1432421.
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Ulusoy, Yavuz Barbaros. "Frequency Domain Computation Of Turbofan Exhaust Noise Radiation." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12607234/index.pdf.
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In this study, acoustic noise radiation through a duct in frequency domain is analyzed. Frequency domain linearized Euler equations are solved for turbofan exhaust noise propagation and radiation. The geometry in studied cases is assumed as axisymmetric. The acoustic waves are decomposed into periodic azimuthal modes. Characteristic boundary conditions, and buffer zone boundary conditions are employed. Iterative type pseudo time integration is employed. Nonuniform background flow effect on the radiation pattern is experienced. All computations are performed in parallel using MPI library routines in computer cluster. Results proved that the one with the buffer zone has a better radiation characteristic than the characteristic one because of absorbtion of spurious waves. It is seen that the efficiency of the buffer zone is frequency dependent.
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Routh, Partha Sarathi. "Electromagnetic coupling in frequency domain induced polarisation data." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0015/NQ48704.pdf.
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Hagdahl, Stefan. "Hybrid Methods for Computational Electromagnetics in Frequency Domain." Doctoral thesis, Stockholm : Numerisk analys och datalogi (NADA) ; Tekniska högsk, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-400.
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Haywood, John. "A frequency domain investigation of model based prediction." Thesis, Lancaster University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386424.
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Iyengar, S. G. "Resolving multiple amperometric signals in the frequency domain." Thesis, University of Cambridge, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.604976.
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This thesis applies immittance spectroscopy (IS) to resolve a "mixed" amperometric signal from two chemical species undergoing electro-oxidation at a single electrode, separating and quantifying the contribution of one or both of these species to the total measured signal. Traditional amperometric sensors base their mode of selectivity on the redox potential of the analyte and so are limited to samples where no other sample species is electroactive at the measuring potential. IS offers increased selectivity by utilising the kinetic and mechanistic information contained in the frequency domain. The methodology of IS is developed for the simultaneous detection of hydrogen peroxide and ascorbic acid because hydrogen peroxide cannot normally be oxidised without Faradaic interference from ascorbic acid in samples containing both. The theoretical basis for the origin of the ac response is considered and ac measurements are used to select information about one species or to determine individual signal fingerprints which identify those species that simultaneously contribute to the amperometric signal. The experimental parameters which may be altered to yield a desired spectrum are identified and selective detection of hydrogen peroxide are demonstrated. To determine both species simultaneously, the phase angles of their respective ac responses, given in terms of admittance, are used as fingerprints to quantify the amperometric signal from each; a matrix transformation is used to resolve the signal into its respective components to determine the concentration of each species. Finally, the phase angle detection method is extended to the case of the glucose biosensor, which uses the enzyme glucose oxidase to convert glucose to the amperometrically detectable hydrogen peroxide. This method allows for simultaneous measurement of glucose and ascorbic acid, overcoming transducer non-specificity and extending biosensor performance.
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Wang, Ruhuai. "Frequency domain fatigue analysis of dynamically sensitive structures." Thesis, University College London (University of London), 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.264193.
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Molnos, Michael Robert Leopold. "Supplementing frequency domain interpolation methods for character animation." Thesis, University of East Anglia, 2012. https://ueaeprints.uea.ac.uk/42364/.
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The animation of human characters entails di�culties exceeding those met simulating objects, machines or plants. A person's gait is a product of nature a�ected by mood and physical condition. Small deviations from natural movement are perceived with ease by an unforgiving audience. Motion capture technology is frequently employed to record human movement. Subsequent playback on a skeleton underlying the character being animated conveys many of the subtleties of the original motion. Played-back recordings are of limited value, however, when integration in a virtual environment requires movements beyond those in the motion library, creating a need for the synthesis of new motion from pre-recorded sequences. An existing approach involves interpolation between motions in the frequency domain, with a blending space de�ned by a triangle network whose vertices represent input motions. It is this branch of character animation which is supplemented by the methods presented in this thesis, with work undertaken in three distinct areas. The �rst is a streamlined approach to previous work. It provides bene�ts including an e�ciency gain in certain contexts, and a very di�erent perspective on triangle network construction in which they become adjustable and intuitive user-interface devices with an increased exibility allowing a greater range of motions to be blended than was possible with previous networks. Interpolation-based synthesis can never exhibit the same motion variety as can animation methods based on the playback of rearranged frame sequences. Limitations such as this were addressed by the second phase of work, with the creation of hybrid networks. These novel structures use properties of frequency domain triangle blending networks to seamlessly integrate playback-based animation within them. The third area focussed on was distortion found in both frequency- and timedomain blending. A new technique, single-source harmonic switching, was devised which greatly reduces it, and adds to the bene�ts of blending in the frequency domain.
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Tant, Katherine M. M. "Time-frequency domain modelling for ultrasonic nondestructive testing." Thesis, University of Strathclyde, 2014. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=24448.
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This thesis endeavours to develop and implement new and improved methods for the characterisation of defects embedded in steel welds through the analysis of data collected by ultrasonic phased array inspections. A factor common to the existing imaging techniques used for flaw characterisation is the subjective thresholding required to estimate the size of the flaw. The work contained in this thesis uses the mathematics of inverse problems and scattering theory to extract information about such defects and puts forward an objective approach which employs a mathematical model. A relationship between the pulse-echo response curve of a scattering matrix and the size and orientation of a flaw is derived analytically via the Born approximation and results in a completely objective approach to crack sizing. Further expansion of these relationships allows for expressions to be formulated concerning the minimum resolvable crack length and the effects of array pitch and flaw depth on the accuracy of the algorithm. The methodology is then extended and tested on experimental data collected from welded austenitic steel plates containing a lack of fusion crack. In the latter part of this thesis, work focusses on the exploration of the fractional Fourier transform and coded excitations. The fractional Fourier transform allows for retention of both time and frequency domain information simultaneously and permits the in homogeneous wave equation (with a forcing function prescribed as a linear chirp modulated by a Gaussian envelope) to be solved in time-frequency space. This in turn facilitates a comparison between a gated continuous wave excitation and a Gaussian modulated linear chirp. It is observed that the Gaussian modulated linear chirp results in a marked increase in the scattering amplitude.
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Weiss, Michael. "Frequency domain identification of block-oriented nonlinear systems." Thesis, University of South Wales, 2003. https://pure.southwales.ac.uk/en/studentthesis/frequency-domain-identification-of-blockoriented-nonlinear-systems(314dc35f-b29a-4ac9-825f-9a0281d5e2e2).html.
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The science of modelling the behaviour of natural phenomena and physical systems has grown significantly in importance in the last century. It helps us to understand and predict natural phenomena or improve and control all types of industrial processes. There are basically two approaches to system modelling: a model can be derived from physical knowledge of the system or by systematically testing it and estimating the model structure and parameters based on the test data. The method of system testing has gained importance due to the increasing complexity of modern industrial systems and processes. It also serves as a verification tool to the physical model. It has led to a rapid advance of a particular discipline within science generally referred to as system identification. This thesis deals with a frequency domain approach to identifying a particular class of nonlinear systems which can be modelled by the Volterra series. The methodology is based on the application of specially designed multisine test signals which allow second and third order terms of the Volterra series, so-called Volterra kernels, to be measured directly and the structure of the nonlinear system to be identified. In the first part of this thesis an introduction is given to system identification in the frequency domain and the analysis of a particular class of nonlinear systems using the Volterra series. Particular attention is given to the design of multisine signals and the development of a comprehensive software tool to aid with the identification task. The second part examines Volterra kernels and the application of block-oriented models to Volterra systems. A method is proposed for identifying the structure of such models based on Volterra kernels and in particular for the de-composition of a cascade structure into its linear dynamic components. The contributions made in this work include the development of a software tool for system identification, the measurement and representation of frequency domain Volterra kernels, as well as the classification and decomposition of block-oriented models by applying specially designed multisine signals.
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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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Nilsson, Martin. "Iterative solution of Maxwell's equations in frequency domain." Licentiate thesis, Uppsala universitet, Avdelningen för teknisk databehandling, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-86390.
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We have developed an iterative solver for the Moment Method. It computes a matrix–vector product with the multilevel Fast Multipole Method, which makes the method scale with the number of unknowns. The iterative solver is of Block Quasi-Minimum Residual type and can handle several right-hand sides at once. The linear system is preconditioned with a Sparse Approximate Inverse, which is modified to handle dense matrices. The solver is parallelized on shared memory machines using OpenMP. To verify the method some tests are conducted on varying geometries. We use simple geometries to show that the method works. We show that the method scales on several processors of a shared memory machine. To prove that the method works for real life problems, we do some tests on large scale aircrafts. The largest test is a one million unknown simulation on a full scale model of a fighter aircraft.
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Gokten, Mesut. "New frequency domain electromagnetic solvers based on multiresolution." Related electronic resource: Current Research at SU : database of SU dissertations, recent titles available full text, 2007. http://wwwlib.umi.com/cr/syr/main.
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Kumar, Manish. "Application of frequency-domain-method to rotorcraft aerodynamics." Related electronic resource: Current Research at SU : database of SU dissertations, recent titles available full text, 2008. http://wwwlib.umi.com/cr/syr/main.
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Chen, Yen-shuo, and 陳延碩. "Development of frequency-domain holography." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/77075747711629226170.
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碩士國立中正大學
物理所
96
Recently using ultra-short and high power laser systems to study laser plasma interaction has reached a new milestone. Significant achievements such as productions of GeV monoenergetic electron beams, generations of high-efficiency soft x-ray lasers, and attosecond pulse productions with high harmonic generation etc. have been reported. These results will soon inspire more scientific researches and novel applications. In the past, the study of the temporal evolution of electron densities in laser-plasma interactions were all based on computer simulations. Due to rapid progresses on the development of the detection technique both in spectral and temporal domains, direct measurements of the spatiotemporal profile of plasma waves have become possible now. The new technique will give us an insight into the laser-plasma interactions and thus help us to obtain a full physical picture of the phenomenal. Frequency domain holography is known as one of the best tool to diagnose the temporal evolution of electron density profile in laser-produced plasmas. In this work, we have designed and constructed a similar system which can measure the nonlinear temporal phase variation in a glass induced by a laser pulse. This system will later be applied to measure the amplitude and period of plasma waves as the phase variation in plasmas depends on the electron density profile. In this thesis, the progress of frequency domain interferometer and frequency domain holography is reviewed and a brief introduction of the laser system is also given in chapter 1. The theory of frequency domain holography and simulation work is discussed in Chapter 2. In Chapter 3, the parameter design and setup of the experiment are presented. The analysis and discussion of the experimental data is shown in Chapter 4. Finally, the application and future work of this detection system are given in Chapter 5, followed by the conclusion of this thesis.
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Shi, Wendong. "Frequency domain aspects of aggregation." Thesis, 2013. https://hdl.handle.net/2144/13140.
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In this dissertation, I focus on various issues related to aggregation in the frequency domain. The problems tackled include the effects of skip sampling and temporal aggregation on the long memory property, the choice of the sampling frequency, and the asymptotic properties of the discrete Fourier transform (dft).
The first chapter considers the effects of temporal aggregation for stochastic volatility model. I provide the link between the spectral density function of the squared low and high-frequency returns. I also analyze the properties of the spectral density function of realized volatility series constructed from squared returns with different frequencies under temporal aggregation. The theoretical results allow explaining many findings reported and uncover new features about volatility in financial market indices.
The second chapter deals with the dft of generalized fractional processes, including the case where a singularity in the spectrum can occur at any frequency. This work extends Philips' (1999) results about the dft of a fractional process for which the spectrum is unbounded only at frequency zero. I study the asymptotic properties of the dft and their asymptotic distributions. Applications to semi-parametric estimation methods of the long-memory parameter are also presented.
The third chapter studies aggregation pertaining to skip sampling of stock variables as well as temporal aggregation of flow variables. I derive the dft and the periodogram of the aggregated series in terms of the original dft. I further analyze the limit of the expectation of the periodogram of aggregated series in the nonstationary case for a generalized fractional process. I show that for skip sampling a long memory feature at the zero frequency can arise from the aggregation of a generalized fractional series, while temporal aggregation does not induce such an effect. Simulation results pertaining to the estimates of the memory parameter are included to demonstrate the practical relevance of my theoretical results.
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Wei-nanLiao and 廖偉男. "Memristor Based Control System Analysis：Time Domain and Frequency Domain." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/00919396787597799153.
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碩士逢甲大學
電子工程學系
101
Memristor predicted and described by L. O. Chua is a new electrical element. Memristor with variable resistance which changes automatically as its voltage changing can be used as a tunable parameter in control systems. Phase-lead, phase-lag and phase-lag-lead (or phase-lead-lag) controllers are widely used in industrial process control applications. The traditional method for adjusting phase-lead, phase-lag and phase-lead-lag controller parameters is based on the “trial and error” procedure which leads to an inconvenient and approximated design. In the meantime, once the parameters are adjusted, they are fixed during the control system operation. In this thesis, based on memristor time domain and frequency domain control system analysis is proposed. In time domain, both rise time and maximum overshoot can be made smaller simultaneously by suitably choosing memristor and voltage polarity. In frequency domain, M-phase-lead, M-phase-lag and M-phase-lag-lead controllers give an adaptable specification band and it is more flexible during the design process.