Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 269 for “"Time-frequency"”.
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Statistical time-frequency analysis
Time-frequency representations (TFRs), such as the short-time Fourier transform, the wavelet transform, and the Wigner distribution, represent signal characteristics jointly in time and frequency and provide a versatile set of tools for the analysis and processing of nonstationary signals. Recent …
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Strategies for Sparsity-based Time-Frequency Analyses
… acoustics, and vibration applications. Joint time-frequency (TF) domain representations provide a time-varying spectrum for their analyses, discrimination, and classifications. Nonstationary signals commonly exhibit sparse occupancy in the TF domain. In this dissertation, we incorporate such …
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Frequency Estimation Using Time-Frequency Based Methods
… of spectral parameters such as its amplitude, frequency, phase, and the variability of its instantaneous spectral components. The accuracy of these parameters depends on several processing variables such as resolution, noise level, and bias of the algorithm used. This thesis presents some …
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Analyzing lakes in the time frequency domain
… is to demonstrate the benefits of innovative frequency-based methods to better explain the variability observed in lake ecosystems. Freshwater ecosystems may be the most threatened part of the hydrosphere. Lake ecosystems are particularly sensitive to changes in climate and land use because …
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Space/time/frequency methods in adaptive radar
… systems may be processed with various space, time and frequency techniques. Advanced radar systems are required to detect targets in the presence of jamming and clutter. This work studies the application of two types of radar systems. It is well known that targets moving along-track within a …
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Bayesian approaches to time-frequency inverse problems
… the way their spectral composition evolves over time. Characterising the dynamics of these hidden spectral components—rather than their raw waveform—is crucial in a wide range of practical applications involving sound. However, the mathematical description of auditory phenomena possesses a high …
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Transfer function estimation using time-frequency analysis
… transfer function estimate despite noisy data, a time-frequency analysis approach to system identification has been developed. The method is based on the observation that for a linear system, an input at a given frequency should result in a response at the same frequency, and a time localized …
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Time frequency analysis techniques in terahertz pulsed imaging
… imaging data are unusual in that an entire time series is `behind' every pixel of the image. While resulting in rich data sets, this high dimensionality necessitates some form of distillation or extraction of pertinent features before images can be formed. Within this thesis the technology …
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Time-frequency domain modelling for ultrasonic nondestructive testing
… 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 …
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Design and Computation of Warped Time-Frequency Transforms
… work we introduce an analytical approach for the frequency warping transform. Criteria for the design of operators based on arbitrary warping maps are provided and an algorithm carrying out a fast computation is defined. Such operators can be used to shape the tiling of time-frequency plane in a …
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Implicit neural representations for time-frequency signal processing
Submission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2025-10-20 without embargo terms
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Time-frequency analysis techniques for non-intrusive load monitoring
The work in this thesis examines time-frequency analysis techniques and in particular the wavelet transform to extract the features contained within the electrical load signals. A novel approach that is based on wavelet design was utilized to generate a wavelet library which was used to match each …
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Shear Madness: Signal-Dependent and Metaplectic Time-Frequency Representations
Time-frequency representations are multidimensional transformations that indicate the joint time-frequency content of a signal. Representations such as the wavelet transform, the short-time Fourier transform, and the Wigner distribution have proven to be powerful tools for signal analysis and …
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Speech enhancement by modeling of stationary time-frequency regions
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1999.
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DISCRETE TRANSFORMS WITH GOOD TIME-FREQUENCY AND SPATIAL-FREQUENCY LOCALIZATION
<p>Discrete orthonormal time-frequency basis functions are described and used for both analysis and synthesis of complex-valued signals. We derive expressions for complex-valued expansion coefficients in time-frequency lattices in the discrete one dimensional case. This derivation is based on …
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Time-Frequency Localisation of Distributed Brillouin Optical Time Domain Reflectometry
… (SHM) of strain changes induced during the lifetime of a structure. Among different DFOS systems, the Brillouin Optical Time Domain Reflectometry (BOTDR) takes the advantages of obtaining full frequency spectrum to provide strain and temperature information along the optic fibre. The key …
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