Dissertations / Theses on the topic 'Filtering response'

Auditory brainstem response (ABR) evaluation has been one of the most reliable methods for evaluating hearing loss. Clinically available methods for ABR tests require averaging for a large number of sweeps (~1000-2000) in order to obtain a meaningful ABR signal, which is time consuming.  This study proposes a faster new method for ABR filtering based on wavelet-Kalman filter that is able to produce a meaningful ABR signal with less than 500 sweeps. The method is validated against ABR data acquired from 7 normal hearing subjects with different stimulus intensity levels, the lowest being 30 dB NHL. The proposed method was able to filter and produce a readable ABR signal using 400 sweeps; other ABR signal criteria were also presented to validate the performance of the proposed method.

High-pass filtering that is one of the most efficient methods in removing long-period noise of accelerograms is investigated for its effect on nonlinear oscillator deformation response. Within this context, uncertainty in filter cut-off periods that would significantly modify the low-frequency content of accelerograms come into prominence for obtaining reliable long-period displacement response. Analog and digital ground-motion records from recently compiled Turkish strong-motion database are used and these records are high-pass filtered with a consistent methodology by randomly generated filter cut-offs that represent different filter cut-off decisions of the analysts. The uncertainty in inelastic spectral and residual displacements (SDIE and SDR, respectively) due to variations in filter cut-offs is examined to derive the usable period ranges where the effect of high-pass filtering is tolerable. Non-degrading, stiffness degrading and stiffness and strength degrading oscillator behavior are considered in these analyses. The level of nonlinear behavior in single degree of freedom (SDOF) response is described by varying the yield strength (R, normalized yield strength) and displacement ductility (µ
) levels. The usable period ranges that depend on magnitude, recording quality, level of inelasticity and level of degradation are determined for SDIE through robust probabilistic methodologies.

Ground-motion data processing is a necessity for most earthquake engineering related studies. Important engineering parameters such as the peak values of ground motion and the ordinates of the response spectra are determined from the strong ground-motion data recorded by accelerometers. However, the raw data needs to be processed since the recorded data always contains high- and low-frequency noise from different sources. Low-cut filters are the most popular ground-motion data processing scheme for removing long-period noise. Removing long-period noise from the raw accelogram is important since the displacement spectrum that provides primary information about deformation demands on structural systems is highly sensitive to the long-period noise. The objective of this study is to investigate the effect of low-cut filtering period on linear and nonlinear deformation demands. A large number of strong ground motions from Europe and the Middle East representing different site classes as well as different magnitude and distance ranges are used to conduct statistical analysis. The statistical results are used to investigate the influence of low-cut filter period on spectral displacements. The results of the study are believed to be useful for future generation ground-motion prediction equations on deformation demands that are of great importance in performance-based earthquake engineering.

Thesis (Ph. D.)--Ohio State University, 2005.
Title from first page of PDF file. Document formatted into pages; contains i-xxii, xx-xxi, 183 p.; also includes graphics. Includes bibliographical references (p. 171-183). Available online via OhioLINK's ETD Center

Physiological signals, which are controlled by the autonomic nervous system (ANS), could be used to detect the affective state of computer users and therefore find applications in medicine and engineering. The Pupil Diameter (PD) seems to provide a strong indication of the affective state, as found by previous research, but it has not been investigated fully yet. In this study, new approaches based on monitoring and processing the PD signal for off-line and on-line affective assessment (“relaxation” vs. “stress”) are proposed. Wavelet denoising and Kalman filtering methods are first used to remove abrupt changes in the raw Pupil Diameter (PD) signal. Then three features (PDmean, PDmax and PDWalsh) are extracted from the preprocessed PD signal for the affective state classification. In order to select more relevant and reliable physiological data for further analysis, two types of data selection methods are applied, which are based on the paired t-test and subject self-evaluation, respectively. In addition, five different kinds of the classifiers are implemented on the selected data, which achieve average accuracies up to 86.43% and 87.20%, respectively. Finally, the receiver operating characteristic (ROC) curve is utilized to investigate the discriminating potential of each individual feature by evaluation of the area under the ROC curve, which reaches values above 0.90. For the on-line affective assessment, a hard threshold is implemented first in order to remove the eye blinks from the PD signal and then a moving average window is utilized to obtain the representative value PDr for every one-second time interval of PD. There are three main steps for the on-line affective assessment algorithm, which are preparation, feature-based decision voting and affective determination. The final results show that the accuracies are 72.30% and 73.55% for the data subsets, which were respectively chosen using two types of data selection methods (paired t-test and subject self-evaluation). In order to further analyze the efficiency of affective recognition through the PD signal, the Galvanic Skin Response (GSR) was also monitored and processed. The highest affective assessment classification rate obtained from GSR processing is only 63.57% (based on the off-line processing algorithm). The overall results confirm that the PD signal should be considered as one of the most powerful physiological signals to involve in future automated real-time affective recognition systems, especially for detecting the “relaxation” vs. “stress” states.

The aim of this master’s thesis is to create a multiband stop derived from Lynn filters for suppressing mains hum and baseline variation (drift). The first part of the thesis is focused on brief theoretical introduction to the distortion types affecting ECG signal and twelve lead connection. The following practical part describes free realizations of ECG filter and ECG signal filtration. The filter has been tested both on distorted and on non-distorted signal. Finally filters’ error rate was computed from CSE database signals.

Ce travail presente deux circuits bases sur les memoires de courant. Les applications developpees sont capables de travailler avec des alimentations en tension de 3v et moins. Pour ces realisations, il a ete necessaire de developper a la fois de nouvelles memoires de courants ainsi que des architectures originales pour repondre a tous les criteres des cahiers des charges. La premiere realisation est un fir pour une application video dont la fonction est, en sortie d'un filtre continu, d'y transferer une partie des contraintes de rejection. La phase lineaire que presente ce type de filtre se prete parfaitement bien a cette application tres sensible au delai de groupe. L'architecture developpee utilise un adressage cyclique qui permet de fortement reduire les degradations engendrees par les memoires de courant tout en conservant la dynamique. Le deuxieme circuit est un modulateur sigma-delta d'ordre 2 dont les performances requises sont une resolution superieure a 12 bits dans la bande 300-3400 hz, une surface d'integration reduite et une faible consommation. Pour arriver a obtenir la precision necessaire avec la faible tension d'alimentation, une nouvelle memoire a ete developpee. Sa particularite est d'utiliser un transistor de memorisation en zone triode qui lui confere une grande linearite. Elle laisse esperer des resultats en terme de linearite et de resolution proche de 14 bits.

Dans cette thèse on s'intéresse à deux aspects différents : conceptuel et réalisationel, sur lesquels portent les quatre innovations présentées. Si celles-ci sont illustrées par une application au détecteur de contours de Deriche, elles sont facilement généralisables à d'autres détecteurs qu'ils soient basés sur le calcul de maxima locaux de la dérivée première, ou le calcul des passages par zéro du laplacien. Les filtres à réponse impulsionnelle infinie symétriques ou anti-symétriques peuvent être réalisés sous forme cascade. Le filtre de lissage peut être défini par intégration numérique du filtre dérivateur optimal. Tout filtre détecteur de contours à noyau large peut être considéré comme un filtre de lissage bidimensionnel à noyau large suivi d'un simple filtre Sobel. L’utilisation d'opérateurs blocs série offre le meilleur compromis surface rapidité pour l'intégration en ASICS ou FPGAS. Nous proposons une architecture câblée temps réel optimale en compacité et simplicité de la version récursive du filtre détecteur de contours de Deriche. Nous exposons la méthode qui conduit à notre solution. A travers cette expérience, nous souhaitons transmettre aux concepteurs d'outils de CAO un certain nombre d'idées qui doivent à notre avis être exploitées afin que des outils tels que les graphes flots de données ou les langages synchrones assistent efficacement l'architecte dans les problèmes d'ordonnancement, d'allocation et de repliement temporel du graphe vers l'architecture.

Master’s thesis deals with the issue of electronic filtering circuits with arbitrary frequency characteristics. First part of the thesis describes theoretical basis. Second part explores the possibilities of design procedures for filters with arbitrary frequency characteristics. Design procedures are demonstrated on examples accordingly to the presented methods, including their circuit implementation and computer simulation to verify the correctness of theoretical assumptions. Thesis also explores the possibilities of tuning circuit structures and electronic setting for characteristics using controllable active elements.

碩士
淡江大學
電機工程學系碩士班
100
With developments of IC testing, LFSR and MISR technologies provide very high compression rate. However, unknown (X) states which decrease the reliability are injected into compactor. Many researches added the X-masking logic (XML) which connects between test response and compactor and prevents multiplication of X states due to their simple feedback circuitry. Further, the XML needs to add extra control codes which make it difficult to improve the efficiency. This thesis proposed the method, row-column XML, which is a novel combinational circuit. Our method can block the propagation of X and also use less control codes, but it cannot direct generate control codes as XML. So we also provided the generation algorithm of control code which can mask X efficiently and observe more testing faults. Finally, in best case, our experimental results obtains better compression rate than XML about 6.65%.

碩士
國立臺灣科技大學
資訊工程系
98
Nowadays SMS Spam start becomes a big problem, especially in country such as China, Korea, and Vietnam. Usually the SMS Spam is sent by computer program or bot. Many researchers try to address this problem using Turing test with the conjunction of whitelist and blacklist. They focus on using CAPTCHA as the Turing test. This thesis want to try to address the problem in SMS SPAM by using another type of Turing test called Challenge Response System. The C/R System works as follows; when a message is sent by the sender, it will send to the SMSC first, and the SMSC will send the challenge questions to sender. Sender will reply the answer and SMSC will verify it. If the answer is correct then SMSC will forward the message to destination otherwise if the answer is wrong then SMSC will delete the message. The result from the experimental evaluation is quite good. The successful percentage rate for human user to pass is 94 % as the lowest rate and 100% as the highest rate, while for the machine is 0%. This result indicating that the tests are difficult enough to block automated SMS spammers. We also compare this work with previous work by some researcher in SMS Spam area and this work has some advantages compare to the previous work.

碩士
國立臺灣大學
工程科學及海洋工程學研究所
94
ABSTRACT Upon the digital signal processing and adaptively active control, this study adopts the (IIR) infinite impulse response digital filter as the systematic structure which combines with the (NLMS) normalized least-mean-square algorithm so as to carry on an optimize operation. To set up the acoustic-echo cancellation system for this study, the combination of the LabVIEW program and A/D-D/A converter data acquisitive equipment with personal computer is used as the required platform. For the experiment of the acoustic-echo cancellation, an enclosure with highly reflective walls is used as the experimental site, and the selected input signals both of pure-tones and random. The system performances are identified by comparing the methods to set up the parameter of system, its operation performance and their influence on the effectiveness of echo cancellation for various frequencies. Experimental results show that the ERLE by 20 to 50 decibels for various frequencies form low to high pure-tone sounds are reached. The reductions of echo power spectrum by more than 60 decibels are reached. As regards to the case of randomly acoustic echo, either the ERLE by 2 to 10 dB or the reduction of centre frequency by 3 to 15 dB is achieved. Moreover, for the case of narrow-band acoustic echo, either the ERLE by 13 to 18 dB or the reduction of centre frequency by 10 to 17 dB is achieved.

This thesis begins by applying Lagrange interpolation to linear systems theory. More specifically, a stable, discrete time linear system, with transfer function G(z), is interpolated with an FIR transfer function at n equally spaced points around the unit circle. The L∞ error between the original system and the interpolation is bounded, the bound going to zero exponentially fast as n -> ∞. A similar result applies to unstable systems except that the interpolating function is a non-causal FIR transfer function . The thesis then considers Hilbert transforms from interpolation data. Given the real part of a stable transfer function evaluated at n equally spaced points around the unit circle, the Hilbert transform from interpolation data reconstructs the complete frequency response, real and imaginary parts, at all frequencies, to within a bounded L∞ error. The error bound goes to zero exponentially fast as n -> ∞. Also considered is the gain-phase problem from interpolation data. This is the same as the Hilbert transform from interpolation data, except that magnitude interpolation data instead of real part interpolation data is given. Two constructions for the gain phase problem from interpolation data are given , and L∞ error bounds derived . In both cases, the error bounds go to zero exponentially fast as n -> ∞. Application of Kalman filters to short-time Fourier analysis then follows. This contains a new method in Kalman filtering called covariance setting. The filters derived from covariance setting generalize the discrete Fourier transform. They offer a design trade-off between noise smoothing and transient response time, are recursive, and are of similar computational complexity to the discrete Fourier transform. Combining the Kalman filters for short-time Fourier analysis and Lagrange interpolation gives a new method of adaptive frequency response identification. A feature of this method is the L∞ error bound between the original system and the identified model. Using recent analysis on the inherent frequency weighting in identification algorithms shows the superiority of this new method over previous adaptive frequency response identification schemes. Finally, model reduction for unstable systems is considered. Given an unstable rational function of high McMillan degree, an approximation of lower McMillan degree, but with the same number of unstable poles, is constructed. An L∞ error bound between the original transfer function and approximation is derived. Such an approximation has application to control systems.

碩士
國立臺灣大學
電信工程學研究所
101
This thesis focuses on integrating a 180° hybrid and bandpass filters into a single device, and establishing a general method to achieve an arbitrary filtering response and power division. To begin with, based on the groundwork for the coupled-resonator filter design, it provides an easier way to synthesize the required coupling coefficients, and the external quality factors. Next, in order to verify that this method is flexible and can be extended for different orders, responses and power division ratios, three examples of 180° hybrids using microstrip resonators are presented. In-phase or out-of-phase response of the 180° hybrid is realized by electric coupling, magnetic coupling, or mixed coupling between adjacent resonators. Its physical dimensions should satisfy the calculated coupling coefficients, and external quality factors. Simulated and measured results agree well with the design specification. In comparison to the conventional rat-race coupler, a size reduction of 65% ~ 80% can be achieved. In addition, the circuit size will be further miniaturized if smaller resonators are adopted. As a result, this method has the advantages of not only reducing the circuit size but also ensuring frequency selectivity. By using the proposed method, SIW filtering 180° hybrids can also be implemented in the LTCC technology. The idea is to arrange all cavities in the same plane, so that no additional transition is required for measurement. According to the field pattern of TE101 mode, two types of planar coupling mechanisms are investigated to fulfill the required phase response of the 180° hybrid. Two Ka-band Chebyshev filtering 180° hybrids with different power division ratios are designed to verify the approach.

碩士
國立臺北科技大學
土木與防災研究所
96
There are more than 20 earthfill dams with height over 15 meters in the island of Taiwan for irrigation, industry usages and drinking purposes. According to Central Weather Bureau, every year between 1991 and 2006, there were more than 1000 earthquakes measured, thus it is importance to study of the seismic response of earthfill dams. There are many methods for the purpose of seismic response analysis of earthfill dam. The common methods are the pseudo static analysis, finite element analysis and finite difference analysis. Here, the seismic response of Renyi-Tan earthfill dam has been studied. The study adopted the acceleration records of September 21, 1999, Ji-Ji earthquake, October 22, 1999, Chai-Yi earthquake and ideal sine wave acceleration and observed the effects of these accelerations together with the effects of filtering layer under the downstream slope on the pore-water pressure and settlement of the dam. Hysteretic damping was used to model the changes of shear modulus during shaking.

Pattern diversity is a term used to describe the operation of several antenna elements working together to produce multiple different radiation patterns with the aim of improving the quality and reliability of a communications system. One useful implementation of pattern diversity considers sum and difference radiation patterns which can be exploited to extend high-gain space coverage and tackle multipath fading. The conventional forms of such pattern diversity antennas are generally working at a single or multiple narrowband frequencies and are designed for specific applications. Hence, generating sum and difference pattern diversity in wide range of frequencies requires the development of new pattern diversity antenna designs. Ultrawideband and frequency reconfigurable designs of pattern diversity antennas are desirable to help reduce the cost and increase the flexibility in applications of pattern diversity antennas. These two types of performances constitute the principal parts of this thesis. The first part of this thesis deals with the challenges of designing ultrawideband Vivaldi antennas with sum and difference radiation patterns. When two Vivaldi antennas are placed next to each other, two mutually exclusive phenomena of grating lobe generation at the highest end of frequency and mutual coupling at the lowest end of frequency will define the bandwidth. Hence, to enhance the bandwidth, the separation between the antenna elements is reduced, which delays the grating lobes generation, and the coupling at lower frequencies is mitigated by introducing an asymmetry in the design of each Vivaldi antenna element. It is shown that this method can be extended to multi-element Vivaldi antennas for higher gain. Next, the bandwidth is further enhanced by adding two vertical metal slabs between the antenna elements improving the isolation at lower frequencies. The proposed antennas use commercially available couplers as feeding networks. As a potential replacement for couplers, an out-of-phase power divider with unequal power division is also proposed. In the second part of this thesis, the pattern diversity function is combined with multistate frequency-reconfigurable filtering functions in a series of novel designs. In the first proposed design, two quasi-Yagi-Uda antennas are used for pattern diversity, while two switchable and reconfigurable bandpass-to-bandstop filters are used to excite the antenna elements. The whole system is excited by an external commercially available rat-race coupler. In a next step, this design is modified to attain wideband, tunable bandpass, and tunable bandstop operations while obviating the need for an external coupler by using three antenna elements excited by a switchable power divider. In another implementation, the filtering functions is extended to dual-band independently tunable bandpass and bandstop to excite wideband antennas. While all the former designs featured E-plane pattern diversity, in another design aiming at increasing space coverage, a switchable patch antennas with sum and difference radiation patterns in both E- and H-plane of the antenna is designed.
Thesis (Ph.D.) -- University of Adelaide, School of Electrical and Electronic Engineering, 2020

The study of randomly excited nonlinear dynamical systems forms the focus of this thesis. We discuss two classes of problems: first, the characterization of nonlinear random response of the system before it comes into existence and, the second, assimilation of measured responses into the mathematical model of the system after the system comes into existence. The first class of problems constitutes forward problems while the latter belongs to the class of inverse problems. An outstanding feature of these problems is that they are almost always not amenable for exact solutions. We tackle in the present study these two classes of problems using Monte Carlo simulation tools in conjunction with Markov process theory, Bayesian model updating strategies, and particle filtering based dynamic state estimation methods. It is well recognized in literature that any successful application of Monte Carlo simulation methods to practical problems requires the simulation methods to be reinforced with effective means of controlling sampling variance. This can be achieved by incorporating any problem specific qualitative and (or) quantitative information that one might have about system behavior in formulating estimators for response quantities of interest. In the present thesis we outline two such approaches for variance reduction. The first of these approaches employs a substructuring scheme, which partitions the system states into two sets such that the probability distribution of the states in one of the sets conditioned on the other set become amenable for exact analytical solution. In the second approach, results from data based asymptotic extreme value analysis are employed to tackle problems of time variant reliability analysis and updating of this reliability. We exemplify in this thesis the proposed approaches for response estimation and model updating by considering wide ranging problems of interest in structural engineering, namely, nonlinear response and reliability analyses under stationary and (or) nonstationary random excitations, response sensitivity model updating, force identification, residual displacement analysis in instrumented inelastic structures under transient excitations, problems of dynamic state estimation in systems with local nonlinearities, and time variant reliability analysis and reliability model updating. We have organized the thesis into eight chapters and three appendices. A resume of contents of these chapters and appendices follows. In the first chapter we aim to provide an overview of mathematical tools which form the basis for investigations reported in the thesis. The starting point of the study is taken to be a set of coupled stochastic differential equations, which are obtained after discretizing spatial variables, typically, based on application of finite element methods. Accordingly, we provide a summary of the following topics: (a) Markov vector approach for characterizing time evolution of transition probability density functions, which includes the forward and backward Kolmogorov equations, (b) the equations governing the time evolution of response moments and first passage times, (c) numerical discretization of governing stochastic differential equation using Ito-Taylor’s expansion, (d) the partial differential equation governing the time evolution of transition probability density functions conditioned on measurements for the study of existing instrumented structures, (e) the time evolution of response moments conditioned on measurements based on governing equations in (d), and (f) functional recursions for evolution of multidimensional posterior probability density function and posterior filtering density function, when the time variable is also discretized. The objective of the description here is to provide an outline of the theoretical formulations within which the problems of response estimation and model updating are formulated in the subsequent chapters of the present thesis. We briefly state the class of problems, which are amenable for exact solutions. We also list in this chapter major text books, research monographs, and review papers relevant to the topics of nonlinear random vibration analysis and dynamic state estimation. In Chapter 2 we provide a review of literature on solutions of problems of response analysis and model updating in nonlinear dynamical systems. The main focus of the review is on Monte Carlo simulation based methods for tackling these problems. The review accordingly covers numerical methods for approximate solutions of Kolmogorov equations and associated moment equations, variance reduction in simulation based analysis of Markovian systems, dynamic state estimation methods based on Kalman filter and its variants, particle filtering, and variance reduction based on Rao-Blackwellization. In this review we chiefly cover papers that have contributed to the growth of the methodology. We also cover briefly, the efforts made in applying the ideas to structural engineering problems. Based on this review, we identify the problems of variance reduction using substructuring schemes and data based extreme value analysis and, their incorporation into response estimation and model updating strategies, as problems requiring further research attention. We also identify a range of problems where these tools could be applied. We consider the development of a sequential Monte Carlo scheme, which incorporates a substructuring strategy, for the analysis of nonlinear dynamical systems under random excitations in Chapter 3. The proposed substructuring ensures that a part of the system states conditioned on the remaining states becomes Gaussian distributed and is amenable for an exact analytical solution. The use of Monte Carlo simulations is subsequently limited for the analysis of the remaining system states. This clearly results in reduction in sampling variance since a part of the problem is tackled analytically in an exact manner. The successful performance of the proposed approach is illustrated by considering response analysis of a single degree of freedom nonlinear oscillator under random excitations. Arguments based on variance decomposition result and Rao-Blackwell theorems are presented to demonstrate that the proposed variance reduction indeed is effective. In Chapter 4, we modify the sequential Monte Carlo simulation strategy outlined in the preceding chapter to incorporate questions of dynamic state estimation when data on measured responses become available. Here too, the system states are partitioned into two groups such that the states in one group become Gaussian distributed when conditioned on the states in the other group. The conditioned Gaussian states are subsequently analyzed exactly using the Kalman filter and, this is interfaced with the analysis of the remaining states using sequential importance sampling based filtering strategy. The development of this combined Kalman and sequential importance sampling filtering method constitutes one of the novel elements of this study. The proposed strategy is validated by considering the problem of dynamic state estimation in linear single and multi-degree of freedom systems for which exact analytical solutions exist. In Chapter 5, we consider the application of the tools developed in Chapter 4 for a class of wide ranging problems in nonlinear random vibrations of existing systems. The nonlinear systems considered include single and multi-degree of freedom systems, systems with memoryless and hereditary nonlinearities, and stationary and nonstationary random excitations. The specific applications considered include nonlinear dynamic state estimation in systems with local nonlinearities, estimation of residual displacement in instrumented inelastic dynamical system under transient random excitations, response sensitivity model updating, and identification of transient seismic base motions based on measured responses in inelastic systems. Comparisons of solutions from the proposed substructuring scheme with corresponding results from direct application of particle filtering are made and a satisfactory mutual agreement is demonstrated. We consider next questions on time variant reliability analysis and corresponding model updating in Chapters 6 and 7, respectively. The research effort in these studies is focused on exploring the application of data based asymptotic extreme value analysis for problems on hand. Accordingly, we investigate reliability of nonlinear vibrating systems under stochastic excitations in Chapter 6 using a two-stage Monte Carlo simulation strategy. For systems with white noise excitation, the governing equations of motion are interpreted as a set of Ito stochastic differential equations. It is assumed that the probability distribution of the maximum over a specified time duration in the steady state response belongs to the basin of attraction of one of the classical asymptotic extreme value distributions. The first stage of the solution strategy consists of selection of the form of the extreme value distribution based on hypothesis testing, and, the next stage involves the estimation of parameters of the relevant extreme value distribution. Both these stages are implemented using data from limited Monte Carlo simulations of the system response. The proposed procedure is illustrated with examples of linear/nonlinear systems with single/multiple degrees of freedom driven by random excitations. The predictions from the proposed method are compared with the results from large scale Monte Carlo simulations, and also with the classical analytical results, when available, from the theory of out-crossing statistics. Applications of the proposed method for vibration data obtained from laboratory conditions are also discussed. In Chapter 7 we consider the problem of time variant reliability analysis of existing structures subjected to stationary random dynamic excitations. Here we assume that samples of dynamic response of the structure, under the action of external excitations, have been measured at a set of sparse points on the structure. The utilization of these measurements in updating reliability models, postulated prior to making any measurements, is considered. This is achieved by using dynamic state estimation methods which combine results from Markov process theory and Bayes’ theorem. The uncertainties present in measurements as well as in the postulated model for the structural behaviour are accounted for. The samples of external excitations are taken to emanate from known stochastic models and allowance is made for ability (or lack of it) to measure the applied excitations. The future reliability of the structure is modeled using expected structural response conditioned on all the measurements made. This expected response is shown to have a time varying mean and a random component that can be treated as being weakly stationary. For linear systems, an approximate analytical solution for the problem of reliability model updating is obtained by combining theories of discrete Kalman filter and level crossing statistics. For the case of nonlinear systems, the problem is tackled by combining particle filtering strategies with data based extreme value analysis. The possibility of using conditional simulation strategies, when applied external actions are measured, is also considered. The proposed procedures are exemplified by considering the reliability analysis of a few low dimensional dynamical systems based on synthetically generated measurement data. The performance of the procedures developed is also assessed based on limited amount of pertinent Monte Carlo simulations. A summary of the contributions made and a few suggestions for future work are presented in Chapter 8. The thesis also contains three appendices. Appendix A provides details of the order 1.5 strong Taylor scheme that is extensively employed at several places in the thesis. The formulary pertaining to the bootstrap and sequential importance sampling particle filters is provided in Appendix B. Some of the results on characterizing conditional probability density functions that have been used in the development of the combined Kalman and sequential importance sampling filter in Chapter 4 are elaborated in Appendix C.

碩士
國立交通大學
工學院聲音與音樂創意科技碩士學位學程
107
This thesis focus on the problem in source imaging of auditory steady-state responses in MEG signals. When an audio stimulus is simultaneously presented to the ears of a subject, the brain waves recorded from the subject often have fully correlated sources. Conventional spatial filters cannot accurately estimate correlated sources because it’s assumed that all sources are not cross-correlated. The method in this thesis is dual-core beamformer (DCBF). There are some papers discussing the limitation of DCBF, but the effect of spatial extent on the performance of DCBF remains unknown. The effects of noise types of background sources, and of spatial extents of correlated sources on DCBF localizers are investigated in this thesis. In results, localizer-NAI is better than localizer-K. When the standard deviations of spatial extents of correlated sources are less than 5 mm, localizer-NAI is not affected. But localizer-K only works well when the standard deviations of spatial extents of correlated sources are less than 1 mm. Furthermore, localizer-NAI has much smaller range of artifacts, which means localizer-NAI can suppress the estimation of other source locations than localizer-K.

We develop a theory of vectorial wave coupling in cubic photorefractive crystals placed in an alternating ac-field to enhance the nonlinear response. First we analytically and numerically investigate the dependences of the first Fourier harmonics of the space-charge field, induced in an AC-biased sillenite crystal by a light-interference pattern, on the light contrast m. The data obtained was used to extend the vectorial beam-coupling theory on the whole contrast region. In particular, we proved in the general case that despite of essential differences between thediffusion and AC nonlocal responses the later keeps the light interference fringes straight during the interaction. This fundamental feature allows, under certain restrictions, to reduce the nonlinear problem of vectorial coupling to the known linear problem of vectorial Bragg diffraction from a spatially uniform grating, which admits an exact solution. As a result, the nonlinear vectorial problem can be effectively solved for a number of practically important cases.The developed theory was applied to describe the transformation of a momentary phase changes of one of the input beams into the output intensity modulation (so-called grating translation technique). In contrast to the previous studies, we take into account the change of the space-charge field amplitude across the crystal (the coupling effects). The theory developed is employed to optimize the conditions for the linear signal detection under polarization filtering for the transverse and longitudinal optical configurations. We also analyze the possibility of the linear detection without polarization filtering.Illumination of AC-biased photorefractive BTO crystals with a coherent light beam results in development of strong nonlinear scattering. We investigate the angular and polarization characteristics of the scattered light for the diagonal optical configuration and different polarization states of the pump.

In speech communication systems such as voice-controlled systems, hands-free mobile telephones and hearing aids, the received signals are degraded by room reverberation and background noise. This degradation can reduce the perceived quality and intelligibility of the speech, and decrease the performance of speech enhancement and source localization. These problems are difficult to solve due to the colored and nonstationary nature of the speech signals, and features of the Room Impulse Response (RIR) such as its long duration and non-minimum phase. In this dissertation, we focus on two topics of speech enhancement and speaker localization in noisy reverberant environments. A two-stage speech enhancement method is presented to suppress both early and late reverberation in noisy speech using only one microphone. It is shown that this method works well even in highly reverberant rooms. Experiments under different acoustic conditions confirm that the proposed blind method is superior in terms of reducing early and late reverberation effects and noise compared to other well known single-microphone techniques in the literature. Time Difference Of Arrival (TDOA)-based methods usually provide the most accurate source localization in adverse conditions. The key issue for these methods is to accurately estimate the TDOA using the smallest number of microphones. Two robust Time Delay Estimation (TDE) methods are proposed which use the information from only two microphones. One method is based on adaptive inverse filtering which provides superior performance even in highly reverberant and moderately noisy conditions. It also has negligible failure estimation which makes it a reliable method in realistic environments. This method has high computational complexity due to the estimation in the first stage for the first microphone. As a result, it can not be applied in time-varying environments and real-time applications. Our second method improves this problem by introducing two effective preprocessing stages for the conventional Cross Correlation (CC)-based methods. The results obtained in different noisy reverberant conditions including a real and time-varying environment demonstrate that the proposed methods are superior compared to the conventional TDE methods.
Graduate
2015-04-23
0544
0984
saeed.mosayyebpour@gmail.com

H Διδακτορική Διατριβή μελετά το πρόβλημα της ψηφιακής ισοστάθμισης,σκοπεύοντας στην ανάπτυξη αποτελεσματικών μεθόδων εξάλειψης των ηχητικών παραμορφώσεων, που εισάγονται κατά την ηχητική αναπαραγωγή εξαιτίας της απόκρισης, είτε των ηχείων (ανηχωική ισοστάθμιση), είτε των χώρων ακρόασης (εξάλειψη αντήχησης). Αναπτύσσονται πρωτότυπες μέθοδοι που αφενός εξασφαλίζουν ακριβείς μετρήσεις των ανηχωικών ηλεκτρακουστικών αποκρίσεων μέσα σε μη ανηχωικούς χώρους, αφετέρου πετυχαίνουν κατάλληλη εξομάλυνση των πολύπλοκων αποκρίσεων των ακουστικών συστημάτων για χρήση στην ψηφιακή ισοστάθμιση αλλά και για χρήση σε άλλες εφαρμογές της ακουστικής χώρων που απαιτούν ανάλυση συγκεκριμένων ιδιοτήτων αυτών των συστημάτων. Η συστηματική μελέτη της μεθόδου εξάλειψης αντήχησης που βασίζεται στην ιδανική αντιστροφή των αποκρίσεων χώρων οδηγεί στο πρωτότυπο συμπέρασμα ότι τα ακουστά οφέλη από την εφαρμογή της μεθόδου σε πραγματικό χρόνο είναι σημαντικά υποδεέστερα από τα αναμενόμενα που προκύπτουν από τα αντίστοιχα πειράματα εξομοίωσης αυτής της μεθόδου. Το πρόβλημα της εξάλειψης αντήχησης αντιμετωπίζεται για πρώτη φορά με έναν πρακτικά βιώσιμο τρόπο, με την εισαγωγή πρωτότυπης μεθόδου ισοστάθμισης που βασίζεται στην Μιγαδική Εξομάλυνση των αποκρίσεων χώρων.
The dissertation studies the digital audio equalization problem, in order to develop methods that would effectively eliminate the audio distortions being introduced during the sound reproduction by either the loudspeakers(anechoic equalization) or the room response (dereverberation). Novel methods are introduced that ensure precise measurements of anechoic electracoustic responses inside reverberant enclosures and on the other hand, achieve appropriately smoothed acoustic responses, for use in digital equalization and also in other applications of room acoustics that require analysis of concrete properties of these systems. Novel conclusions have been drawn by the analytic study of the room acoustics dereverberation based on ideal inverse filtering, indicating that the application of such a method in real time yields a significantly degraded performance compared to that achieved by the corresponding simulated dereverberation experiments. The problem of dereverberation is faced with a practically viable solution, with the introduction of a novel method based on the room response Complex Smoothing.

Η σύγχρονη μελέτη της κεντρικής και αυτόνομης δραστηριότητας θεωρούνται χρήσιμες στην ανάδειξη της σχέσης των δύο συστημάτων και της φυγόκεντρου ανατροφοδότησης των περιφερικών αλλαγών. Στην εργασία αυτή διερευνώνται οι πιθανές σχέσεις μεταξύ κεντρικών και αυτόνομων απαντήσεων σε σωματαισθητικούς ερεθισμούς. Η ηλεκτροδερμική δραστηριότητα (ΗΔΑ) είναι δείκτης της αυτόνομης δραστηριότητας. Προκλητά δυναμικά και ΗΔΑ καταγράφονταν ταυτόχρονα έπειτα από μια σειρά ερεθισμών του μέσου νεύρου ,με τρείς διαφορετικές εντάσεις, σε έξι φυσιολογικά άτομα. Η χαμηλότερη ένταση ερεθισμού ρυθμίζονταν έτσι ώστε να μη γίνεται αντιληπτή από το άτομα. Τα επάρματα P40, P100, N200 και P300 των προκλητών δυναμικών εξήχθησαν από το καταγεγραμμένο σήμα. Μελετήσαμε το πλάτος και τον λανθάνοντα χρόνο και διερευνήσαμε την πιθανή συσχέτιση των μεγεθών αυτών της ΗΔΑ. Χρησιμοποιήσαμε την συνηθισμένη μέθοδο της μεσοποίησης (average), καθώς και την προσέγγιση των μοναδιαίων απαντήσεων, εξάγωντας τις απαντήσεις με την χρήση χωρικού φίλτρου. Το συμπαθητικό νευρικό σύστημα φαινόταν να απαντά ακόμα και σε ερεθισμούς μη αντιληπτούς από το υποκείμενο. Η φλοιική επεξεργασία των αντιληπτών και μη ερεθισμάτων όπως αποτυπώνονταν με τα επάρματα των προκλητών δυναμικών, φαίνεται να είναι όμοια και στις δύο περιπτώσεις κατά τη διάρκεια των πρώτων 40ms έπειτα από τον ερεθισμό, ενώ τα μακρά κύματα ήταν απόνατ στους μη αντιληπτούς ερεθισμούς. Τα πλάτη της ΗΔΑ και του P300 με την προσέγγιση των μοναδιαίων απαντήσεων παρουσίαζαν μια σημαντική θετική συσχέτιση.
Concurrent studies of central and autonomic activity are considered useful in elucidating the relationship between the two systems and indicating the centripetal feedback of peripheral changes. The SSR (sympathetic skin response) is one index of autonomic arousal. In our study we examine the possible relationships between central and autonomic responses to somatosensory stimuli. EPs (evoked potentials) and SSRs were simultaneously recorded during a series of electrical stimuli of median nerve in six normal adults using three different intensities of stimuli. The weakest of them was unperceived by subject. The P40, P100, N200 and P300 waves of EPs were extracted and their latencies and amplitudes were analysed in order to find correlations with those of the SSRs. We used the conventional method of signal averaging and the single trial (ST) approach, as the EP waves were subtracted by spatial filtering. Interestingly, sympathetic nervous system seemed to react even to stimuli unperceived by the subject. The cortical processing of consciously perceived and unperceived somatosensory stimuli as it was expressed by the evoked potentials seems to be identical during the first 40ms after the stimulus onset while later waves were absent for unperceived stimuli. SSR and P300 amplitude at the ST level had a positive correlation.