For repairing concrete transportation infrastructure, such as pavements and bridges, much importance is placed on early-age strength gain as this has a major impact on scheduling and opening to traffic. However, the long-term performance and durability of such repair materials are often not satisfactory, thus resulting in future repairs. This research project focuses on the evaluation of the durability of various rapid-setting cementitious materials. The binders studied in this project include calcium aluminate cement (CAC), calcium sulfoaluminate cement (CSA), Type III portland cement, alkali-activated fly ash (AAFA) , and various prepackaged concrete materials. In addition, selected CAC and CSA mixtures were further modified with the use of a styrene-butadiene latex. The durability aspects studied include freezing-and-thawing damage and the implications of air entrainment in these systems, alkali-silica reaction, sulfate attack, and permeability of the concrete matrix and potential corrosion. / text

Robust speech recognition in acoustic environments that contain multiple speech sources and/or complex non-stationary noise is a difficult problem, but one of great practical interest. The formalism of probabilistic graphical models constitutes a relatively new and very powerful tool for better understanding and extending existing models, learning, and inference algorithms; and a bedrock for the creative, quasi-systematic development of new ones. In this thesis a collection of new graphical models and inference algorithms for robust speech recognition are presented. The problem of speech separation using multiple microphones is first treated. A family of variational algorithms for tractably combining multiple acoustic models of speech with observed sensor likelihoods is presented. The algorithms recover high quality estimates of the speech sources even when there are more sources than microphones, and have improved upon the state-of-the-art in terms of SNR gain by over 10 dB. Next the problem of background compensation in non-stationary acoustic environments is treated. A new dynamic noise adaptation (DNA) algorithm for robust noise compensation is presented, and shown to outperform several existing state-of-the-art front-end denoising systems on the new DNA + Aurora II and Aurora II-M extensions of the Aurora II task. Finally, the problem of speech recognition in speech using a single microphone is treated. The Iroquois system for multi-talker speech separation and recognition is presented. The system won the 2006 Pascal International Speech Separation Challenge, and amazingly, achieved super-human recognition performance on a majority of test cases in the task. The result marks a significant first in automatic speech recognition, and a milestone in computing.

Posttraumatic stress disorder (PTSD) is an anxiety disorder that may follow exposure to severe emotional trauma and presents with various symptoms of anxiety, hyperarousal and cognitive anomalies. Interestingly, only 10-30% of an exposed population will go on to develop full-blown PTSD. Cholinergic neurotransmission is implicated in anxiety as well as other typical manifestations of PTSD, particularly cognitive changes. The frontal cortex and hippocampus regulate and in turn are affected by stress, and have also been implicated in the underlying neuropathology of PTSD. These areas are densely innervated by cholinergic neurons originating from the basal forebrain. In this study, the time dependent sensitization (TDS) model was used to induce symptoms of PTSD in animals. The study was designed to determine the long-term effects of an intense, prolonged aversive procedure on central muscarinic acetylcholine receptor (mAChR) characteristics and the correlation if any of those findings to cognitive aspects and general arousal as characteristics associated with PTSD. In order to achieve this goal, male Sprague-Dawley rats were exposed to the TDS stress paradigm with behavioral/neuro-receptor assessments performed on day 7 post re-stress (duration of each experiment in whole is 14 days). Acoustic startle reflex (ASR) was used to determine emotional state (hyperarousal), while the conditioned taste aversion (CTA) paradigm was implemented in order to assess aversive memory. Muscarinic receptor binding studies were performed in the frontal cortex and hippocampus. Moreover, both the stress-exposed and control animals were pre-tested in the acoustic startle chamber in order to attempt to separate stress sensitive from stress-resilient animals based on predetermined ASR criteria. The ASR niodel was previously validated in our laboratory, while the CTA model was validated in this project before application. In the CTA model, an i.p. injection with lithium chloride (LiCl) (associated with digestive malaise), was used as unconditioned stimulus (US) and was paired with a saccharinlcyclamate drinking solution as conditioned stimulus (CS) to induce aversion to the novel taste (CS) when presented in the absence of the US. Population data of animals tested in the ASR experiment indicated no statistical significant difference between stressed and control animals. However, when each animal was assessed individually, 22.5 % of the exposed population displayed all increase above the predetermined criteria of 35 % in startle response, indicating a state of heightened arousal. In contrast, only 4.2 O h of control animals (no stress) displayed an increase in arousal based on the above mentioned criteria. Muscarinic receptor densities (Bm,) in the total population of animals exposed to stress showed a statistical significant increase in both the hippocampus and frontal cortex when compared to controls, with no changes in & values observed in either one of the areas. In the CTA experiment, TDS stress was implemented as US paired with a saccharinlcyclamate drinking solution as CS. An acute session of prolonged stress (as used in the TDS model) effectively induced aversion to a novel taste and a subsequent reminder of the stress (restress) paired with the CS sustained the acquire adversive memory. Furthermore, LiCl was reintroduced as US in order to assess the effect of prior exposure to two types of stress (acute and TDS) on subsequently acquired CTA memory. Prior exposure to acute stress had no significant effect on subsequently acquired aversive memory when measured either 3- or 7 days post-conditioning (CS-US). Stress-restress (TDS) exposure, however, indicated a significant decrease in aversive memory from 3- to 7 days post-conditioning (CS-US) as well as a significant decrease in aversive memory between the control- and the TDS group 7 days post-conditioning. The mAChR density (B,,) in the frontal cortex; but not in the hippocampus, was elevated at the same point in time (7 days post CS-US pairing) that CTA memory was impaired following TDS stress (stress-restress). Ultimately, these data support an association between altered cholinergic receptors and hyperarousallanxiety in an animal model of PTSD. The data also support the phenomenon of individual susceptibility to stress in animals that parallels that observed in humans exposed to severe trauma. Impaired aversive memory (CTA) is a consequence of prior exposure to TDS stress, but not acute stress, and is likewise mediated by an altered central cholinergic transmission displayed as an increase in mAChRs in the frontal cortex. The lack of studies regarding the influence of the cholinergic system in PTSD related behavior earns ,this project value as inimitable PTSD research. / Thesis (M.Sc. (Pharmacology))--North-West University, Potchefstroom Campus, 2007.

The research work presented in this thesis introduces novel approaches for both visual region of interest extraction and visual feature extraction for use in audio-visual automatic speech recognition. In particular, the speaker‘s movement that occurs during speech is used to isolate the mouth region in video sequences and motionbased features obtained from this region are used to provide new visual features for audio-visual automatic speech recognition. The mouth region extraction approach proposed in this work is shown to give superior performance compared with existing colour-based lip segmentation methods. The new features are obtained from three separate representations of motion in the region of interest, namely the difference in luminance between successive images, block matching based motion vectors and optical flow. The new visual features are found to improve visual-only and audiovisual speech recognition performance when compared with the commonly-used appearance feature-based methods. In addition, a novel approach is proposed for visual feature extraction from either the discrete cosine transform or discrete wavelet transform representations of the mouth region of the speaker. In this work, the image transform is explored from a new viewpoint of data discrimination; in contrast to the more conventional data preservation viewpoint. The main findings of this work are that audio-visual automatic speech recognition systems using the new features extracted from the frequency bands selected according to their discriminatory abilities generally outperform those using features designed for data preservation. To establish the noise robustness of the new features proposed in this work, their performance has been studied in presence of a range of different types of noise and at various signal-to-noise ratios. In these experiments, the audio-visual automatic speech recognition systems based on the new approaches were found to give superior performance both to audio-visual systems using appearance based features and to audio-only speech recognition systems.

Automatic speech recognition (ASR) is one of the most important research areas in the field of speech technology and research. It is also known as the recognition of speech by a machine or, by some artificial intelligence. However, in spite of focused research in this field for the past several decades, robust speech recognition with high reliability has not been achieved as it degrades in presence of speaker variabilities, channel mismatch condi- tions, and in noisy environments. The superb ability of the human auditory system has motivated researchers to include features of human perception in the speech recognition process. This dissertation investigates the roles of perceptual features of human hearing in automatic speech recognition in clean and noisy environments. Methods of simplified synaptic adaptation and two-tone suppression by companding are introduced by temporal processing of speech using a zero-crossing algorithm. It is observed that a high frequency enhancement technique such as synaptic adaptation performs better in stationary Gaussian white noise, whereas a low frequency enhancement technique such as the two-tone sup- pression performs better in non-Gaussian non-stationary noise types. The effects of static compression on ASR parametrization are investigated as observed in the psychoacoustic input/output (I/O) perception curves. A method of frequency dependent asymmetric compression technique, that is, higher compression in the higher frequency regions than the lower frequency regions, is proposed. By asymmetric compression, degradation of the spectral contrast of the low frequency formants due to the added compression is avoided. A novel feature extraction method for ASR based on the auditory processing in the cochlear nucleus is presented. The processings for synchrony detection, average discharge (mean rate) processing and the two tone suppression are segregated and processed separately at the feature extraction level according to the differential processing scheme as observed in the AVCN, PVCN and the DCN, respectively, of the cochlear nucleus. It is further observed that improved ASR performances can be achieved by separating the synchrony detection from the synaptic processing. A time-frequency perceptual spectral subtraction method based on several psychoacoustic properties of human audition is developed and evaluated by an ASR front-end. An auditory masking threshold is determined based on these psychoacoustic e?ects. It is observed that in speech recognition applications, spec- tral subtraction utilizing psychoacoustics may be used for improved performance in noisy conditions. The performance may be further improved if masking of noise by the tonal components is augmented by spectral subtraction in the masked region.

Les alliages ferritiques à base de chrome sont utilisés en tant qu'interconnecteur de pile à combustible à oxyde solide (SOFC). Ces alliages forment à haute température, sous conditions oxydantes, une double couche d'oxydes de MnCr2O4| Cr2O3. L'évaporation des espèces volatiles de chrome provenant de cette double couche d'oxydes peut entraîner l'empoisonnement de la cathode et par conséquent conduire à une dégradation des performances de la cellule SOFC. Une solution pour limiter les pertes de performances du système est d'appliquer une couche barrière contre le chrome sur l'interconnecteur. Le travail de thèse s'intéresse au développement de ces couches de protection pour un alliage ferritique commercial d'ArcelorMittal K41X. Dans un premier temps, une étude sur le comportement en corrosion de l'alliage a été réalisée. Ensuite, l'électrodéposition, de par sa simplicité et sa rapidité de mise en œuvre a permis l'identification des compositions de revêtements les plus prometteurs. Les couches formulées sont des oxydes spinelle à base de métaux de transition (Co, Mn, Cu, Ni, Fe). Enfin, les différentes compositions de couches retenues ont été déposées par in-situ et par ex-situ. En in-situ, les dépôts sont réalisés sous forme métallique, par électrodéposition (dépôt multicouches) et par pulvérisation cathodique (dépôt d'alliage). Un traitement thermique est nécessaire afin d'oxyder le dépôt métallique et de former l'oxyde spinelle jouant le rôle de couche barrière du chrome. En ex-situ la couche de protection est directement déposée sur le substrat par projection atmosphérique plasma. Les différentes couches ont été caractérisées par des analyses MEB, EDX et DRX ainsi que par des mesures de résistances spécifiques de surface ASR. Nous montrons que les couches de protection étudiées réduisent l'ASR (<50 mΩ.cm2) et inhibent la diffusion du chrome. Le travail conclut sur une étude comparative des avantages et des inconvénients des trois procédés industriels utilisés pour le dépôt d'une couche de protection.

<p>In this paper, a navigation support approach for speech-only interaction based on auditory icons for room-based designs is presented, i.e. naturally occurring sounds that have a natural mapping to the system's underlying design metaphor. In contrast to many recent investigations that have focused on multi-modal or augmented reality systems, this paper concerns a unimodal speech and sound-only system. An auditory icon based prototype system for buildings maintenance support using a room-based metaphor was developed. The design was evaluated in a comparison with earcons and no-sound designs. The users’ subjective attitudes toward auditory icons were significantly more positive than to earcons.</p>

Thesis (M.Sc. (Pharmacology))--North-West University, Potchefstroom Campus, 2007.

The speech signal is inherently characterized by its variations in time, which get reflected as variations in frequency. The specto temporal changes are due to changes in vocaltract, intonation, co-articulation and successive articulation of different phonetic sounds. In this thesis we are looking for improving the speech recognition performance through better feature parameters using a non-stationary model of speech. One effective means of modeling a general non-stationary signal is using the AM-FM model. AM-FM model can be extended to speech through a sub-band analysis, which can be mimic the auditory analysis. In this thesis, we explore new methods for estimating AM and FM parameters based on the non-uniform samples of the signal. The non-uniform sample approach along with adaptive window estimation provides for important advantage because of multi-resolution analysis. We develop several new methods based on ZC intervals, local extrema intervals and signal derivative at ZC’s as different sample measures of the signal and explore their effectiveness for instantaneous frequency (IF) and instantaneous envelope (IE) estimation. To deal with speech signal for automatic speech recognition, we explore the use of auditory motivated spectro temporal information through the use of an auditory filter bank and signal parameters (or features) are derived from the instantaneous energy in each band using the non-linear energy operator over a larger window length. The temporal correlation present in the signal is exploited by using DCT and keeping the lower few coefficients of DCT to keep the trend in the energy in each band. The DCT coefficients from different frequency bands are concatenated together, and a further spectral decorrelation is achieved through KLT (Karhunen-Loeve Transform) of the concatenated feature vector. The changes in the vocaltract are well captured by the change in the formant structure and to emphasize these details for ASR we have defined a temporal formant by using the AM-FM decomposition of sub-band speech. A uniform wideband non-overlaping filters are used for sub-band decomposition. The temporal formant is defined using the AM-FM parameters of each subband signal. The temporal evolution of a formant is represented by the lower order DCT coefficients of the temporal formant in each band and its use for ASR is explored. To address the robustness of ASR performance to environmental noisy conditions, we have used a hybrid approach of enhancing the speech signal using statistical models of the speech and noise. Use of GMM for statistical speech enhancement has been shown to be effective. It is found that the spectro-temporal features derived from enhanced speech provide further improvement to ASR performance.

Alkali Silica Reaction in concrete is a chemical deterioration process occurring between alkalis in cement paste and reactive aggregates. ASR increases expansion and cracking as well as other durability problems such as freezing and thawing. It is most probable that concrete structure will collapse unless mechanical, mineral, or chemical preventive measures are taken against ASR or this problem is realized and solved in the design stage of the concrete structure or later on. Rather than ordinary preventive measures in which mineral admixtures are used, mechanical ones were investigated in this study. In the experiment done by using the accelerated mortar bar method, reinforced concrete specimens on which pre-stressing force was applied were examined. The effects of reinforcement ratio and pre-stressing force on ASR based expansion and cracking were studied. Expansion and cracking developments in time were followed, and the connection between these phenomena and the energy produced by ASR was made. By applying the same mechanical preventive measures on the specimens prepared by using different reactive aggregates, the effectiveness of these methods with respect to the degree of v ASR was investigated. Also, the methods in question were compared with traditional preventive measures (fly ash). The investigation results show that reinforcement and pre-stressing force play a significant role in diminishing the effects of ASR.Keywords:Alkali-Silica Reaction, Reinforced Concrete Specimen, Pre-stressed Concrete, Mechanical Preventive Measures, Energy of ASR