No description available.

It is a common belief that there are invariant acoustic patterns in speech signals, which can be related to their phonetic description. These patterns are expected to remain invariant, independent of the language, speaker, phonetic context, etc. Although many investigations based on short-time spectral analysis have established the feasibility of extracting invariant cues in certain contexts, they could not provide a set of invariant cues in any given phonetic context. In this thesis, the Wigner distribution (WD) was used to analyze speech signals for the first time, to investigate acoustic invariance. The WD, like the spectrogram, provides a time-frequency description of the signal. Unlike the spectrogram, it provides correct marginals in the time and frequency domains, but it is not a positive distribution. It is demonstrated here that the partially smoothed WD, in which both the properties of positivity and correct marginals are sacrificed to some extent, provides a better time-frequency resolution than short-time spectral analyses methods. An implementation and an interpretation of the partially smoothed WD are presented. The choice of smoothing parameters and the nature of cross-term suppression in a partially smoothed WD are discussed in detail. It is shown that the cross-terms in a partially smoothed WD do not mask the underlying nature of a signal in the time-frequency plane. A partially smoothed WD was used to investigate acoustic invariance in voiceless, unaspirated stop consonants spoken by native speakers of English, Telugu and French. Contrary to reports in the literature, it was shown that the features "diffuse-rising" and "compact" spectral shapes were not unique to alveolar and velar places of articulation, respectively, but depended on the vowel context. The resulting ambiguities when specifying the place of articulation were resolved using Formant Onset Duration (time taken for the steady state formants to occur in the vocal tract after the consonantal release) and F₂ of the following vowel. The place of articulation was specified correctly for 86% of the tokens. Unlike in other investigations, the errors in specifying the place of articulation were uniformly distributed over all vowel contexts. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

No description available.

A new method for the general application of quadratic spatial/spatial frequency domain filtering to imagery is presented in this dissertation. The major contribution of this research is the development of an original algorithm for approximating the inverse psuedo Wigner distribution through synthesis of an image in the spatial domain which approximates the result of filtering an original image in the DPWD domain.

To track evolution of autonomic responses during orthostasis in men and women, we used discrete pseudo-Wigner distribution based time-frequency analysis to compute dominant frequencies and spectral powers in RR intervals and Systolic Blood Pressure (SBP). Data were collected from 38 healthy volunteers (22 men, 16 women) during 10 min supine posture followed by 30 min of 700 head up tilt. The RR intervals were computed from ECG and systolic blood pressure was and spectral amplitudes of RR intervals were integrated in two regions viz., Low Frequency (LF) region defined between 0.05-0.15 Hz and High Frequency region (HF), sometimes referred to as respiratory frequency region, defined as mean breathing frequency of the individual +/- one standard deviation. Dominant frequencies of RR intervals in the LF region decreased in both men and women. There were no significant differences between men and women as far as the SBP data were concerned for the dominant frequencies, however women had higher values than men. Dominant frequencies of RR intervals in the HF region increased both in men and women from supine to tilt. No significant differences in dominant frequencies were found between men and women. Also there were no significant differences even for the SBP data, however men had higher values than women Integrated powers within the auto spectra of RR showed that in the HF region, power decreased significantly for both men (pandlt;0.005), and women (pandlt;0.001) during tilt compared to supine. However, the HF power in women was significantly higher for men during both supine (pandlt;0.001), and tilt (pandlt;0.005). In LF region integrated power spectrum showed no significant difference between men and women although women showed a slight increase from supine to tilt. These results suggest that men have a higher sympathetic control while women have greater para-sympathetic influence.

Wigner distribution is considered to be one of the most powerful tools for time-frequency analysis of rumvstationary signals. Wigner distribution is a bilinear signal transformation which provides two dimensional time-frequency characterization of one dimensional signals. Although much work has been done recently in signal analysis and applications using Wigner distribution, not many synthesis methods for Wigner distribution have been reported in the literature. This thesis is concerned with signal synthesis from discrete-time Wigner distribution and from discrete-time pseudo-Wigner distribution and their applications in noise filtering and signal separation. Various algorithms are developed to reconstruct signals from the modified or specified Wigner distribution and pseudo-Wigner distribution which generally do not have a valid Wigner distributions or valid pseudo-Wigner distribution structures. These algorithms are successfully applied to the noise filtering and signal separation problems. / Master of Science

Reproduction de : Thèse de doctorat : Génie électrique : Toulouse, INPT : 2006. / Titre provenant de l'écran-titre. Bibliogr. 110 réf.

La théorie de la dynamique des processus chimiques élementaires cherche à décrire quantitativement les collisions réactives à l'échelle atomique. Les mouvements des noyaux étant extrêmement difficiles à traiter dans le formalisme quantique, les tomes sont souvent considérés comme des objets classiques. Cepandant, les effets purement quantiques jouent un rôle majeur dans certaines situations, alors que la description classique les néglige. Cette thèse apporte de nouvelles perspectives sur l'inclusion, dans le formalisme clasique, de forts effets quantiques, à savoir la quantification des mouvements internes des réactifs et produits. / The goal of chemical reaction dynamics theory is the quantitative description of reactive molecular collistions at the atomic scale. Since nuclear motions are difficult to study quantum mechanically, nuclei are often considered as classical object. However, quantum effects may play a major role in some situation, and the standard classical description does not take them into account. This thesis brings new perspectives on the inclusion into the classical treatment of one of the strongest qunatum effects, the quantization of reagents and products.

This thesis deals with the topic of high resolution spectral analysis. In the first part, selected methods are presented and afterwards compared based on the Matlab implementations. The problematics of reduction of crossterms in quadratic time–frequency distributions is also covered. The second part is focused on the implementation and optimization of the algorithm for real-time computation of smoothed Wigner distribution function.

Brushless Direct Current (BLDC) motors are one of the motor types rapidly gaining popularity. BLDC motors are being increasingly used in critical high performance industries such as appliances, automotive, aerospace, consumer, medical, industrial automation equipment and instrumentation. Fault detection and condition monitoring of BLDC machines is therefore assuming a new importance. The objective of this research is to advance the field of rotor and load fault diagnosis in BLDC machines operating in a variety of operating conditions ranging from constant speed to continuous transient operation. This objective is addressed as three parts in this research. The first part experimentally characterizes the effects of rotor faults in the stator current and voltage of the BLDC motor. This helps in better understanding the behavior of rotor defects in BLDC motors. The second part develops methods to detect faults in loads coupled to BLDC motors by monitoring the stator current. As most BLDC applications involve non-stationary operating conditions, the diagnosis of rotor faults in non-stationary conditions forms the third and most important part of this research. Several signal processing techniques are reviewed to analyze non-stationary signals. Three new algorithms are proposed that can track and detect rotor faults in non-stationary or transient current signals.