Surface acoustic wave (SAW) sensors detect chemical and biological species by monitoring the shifts in frequency of surface acoustic waves generated on piezoelectric substrates. Incorporation of nanomaterials having increased surface area as sensing layer have been effective in improving the sensitivity as well as miniaturization of SAW sensors. Selectivity, sensitivity and speed of response are the three primary aspects for any type of sensor. This dissertation focuses on design and development of SAW devices with novel transducer configurations employing nanomaterial sensing layers for enhanced sensing, improved selectivity, and speed of response. The sensing mechanism in these SAW sensors is a complex phenomenon involving interactions across several different length and time scales. Surface acoustic wave propagation at the macro-scale is influenced by several kinetic phenomena occurring at the molecular scale such as adsorption, diffusion, reaction, and desorption which in turn depend on the properties of nanomaterials. This suggests the requirement of a multi-scale model to effectively understand and manipulate the interactions occurring at different length scales, thereby improving sensor design. Sensor response modeling at multiple time and length scales forms part of this research, which includes perturbation theories, and simulation techniques from finite element methods to molecular-level simulations for interpreting the response of these surface acoustic wave chemical and biosensors utilizing alloy nanostructures as sensing layers. Molecular modeling of sensing layers such as transition metal alloy nanoclusters and nanowires is carried out to gain insights into their thermodynamic, structural, mechanical and dynamic properties. Finite element technique is used to understand the acoustic wave propagation at the macroscale for sensing devices operating at MHz frequencies and with novel transducer designs. The findings of this research provide insights into the design of efficient surface acoustic wave sensors. It is expected that this work will lead to a better understanding of surface acoustic wave devices with novel transducer configurations and employing nanomaterial sensing layers.

Darbo tikslas - aptarti akustinės taršos problemas ir ištirti triukšmo sulaikančių užtvarų saugos zonose aplinką psichologinio ir garso energijos ¬¬ sklaidos požiūriu. Akustinė aplinka triukšmą sulaikančių užtvarų saugos zonose apibūdinančios garso lauko amplitudinės dažninės charakteristikos kinta dėl garso bangų difrakcijos. Jos laipsni apibudinanti Fresnelio skaičių lemią užtvaros geometrinių dydžių ir atstumo iki šaltinio bei stebėjimo taškų santykis. Tyrimų rezultatų analizė rodo jog dėl garso bangų difrakcijos akustinio šešėlio zonoje 7-15 m nuotolyje nuo triukšmo sulaikančios užtvaros garso lygis sumažėja atitinkamai 11-9 dBA, o nuo želdinių 8-5 dBA. Dėl atstumo padidėjimo garso lygis už 7-15 m nuo triukšmą sulaikančių sienelių sumažėja 6-8 dBA ,o už želdinių 6-9 dBA. Dėl garso bangų difrakcijos už akustinio šešėlio zonos ribų 50 m nuotolyje nuo sienelės garso lygis sumažėja 5 dBA, o nuo kelio iškasos sumažėja 3 dBA, tuo tarpu dėl atstumo padidėjimo garso lygis sumažėja 14-15 dBA . Taip pat nustatyta, jog kokybės vertinimo požiūriu ir prieš ir už triukšmą sulaikančių užtvarų aplinka palankiai nepriskirtina, nes ženkliai viršijamas kokybės vertinimo indeksas 22-10>5 dBA. Pastebima neženkli akustinės aplinkos pagerėjimo tendencija už akustinio šešėlio ribų. Taigi galima teigti, kad aplinkosauginis triukšmą sulaikančių užtvarų efektyvumas didžiausias, kai jos įrengiamos atstume ne toliau kaip trigubas sienelės aukštis iki apsaugomo objekto. / Purpose of this workwas to research the acoustic climate in the safety zones of lightweight noise barriers from energy’s dissipation and psychological point of view. Acousticenvironment behind the noise barriers is usually described by amplitude frequency characteristic of sound fields at different distances which are caused mainly due to diffraction of sound waves. Diffraction effects are characterized by the Fresnel’s number, calculation of which includes the shape of the barrier, its dimensions, position of noise source and the listening point. Research results showed that diffraction effects were most significant up to 30 m radius from the noise barrier in its acousticshadow zone. Sound pressure level ∆L_pAat 10-15 m distance from noise barrier reduced 9…11 dBA while behind plantings ∆L_pAwas 5…8 dBA. Effect of increasing distance decreased the sound pressure level ∆L_pA6…8 dBA for noise barriers and 6…9 dBA for plantings respectively. At the non-acoustic shadow zone (50 maway from noise barrier) diffraction level was reduced by some 4…5 dBA and more noticeably from the excavation. At the distance of 10 meters from the edge of the excavation the reduction of 7 dBA in sound pressure level was found, and the decrement because of increased distance for noise barrier was 15 dBA and excavation 11 dBA respectively. It was also ascertained that acoustic environment in the shadow zones of noise barrier is not attributed to favourable. Calculated quality assessment index (QAI) was... [to full text]

With increased exposure to transportation noise, there have been continued efforts to help insulate homes from aircraft noise. Current aircraft noise guidelines are based primarily on outdoor sound levels. As people spend the majority of their time indoors, however, human perception is evidently more related to indoor sound levels. Investigations are being made to provide further insight into how typical residential constructions affect indoor response. A pilot study has built a single-room "test house", according to typical construction for mixed-humid climate regions, and has directly measured outdoor-to-indoor transmission of sound - with specific focus on continuous commercial aircraft signatures. The results of this study are being used to validate and improve modelling software that simulates a wide range of construction types and configurations for other US climate regions. The improved models will allow for increased flexibility in simulating the impacts of acoustic and energy retrofits. Overall, the project intends to improve the ability to predict acoustic performance for typical US construction types as well as for any possible design alterations for sound insulation.

The languages spoken in developing countries are diverse and most are currently under-resourced from an automatic speech recognition (ASR) perspective. In South Africa alone, 10 of the 11 official languages belong to this category. Given the potential for future applications of speech-based information systems such as spoken dialog system (SDSs) in these countries, the design of minimal ASR audio corpora is an important research area. Specifically, current ASR systems utilise acoustic models to represent acoustic variability, and effective ASR corpus design aims to optimise the amount of relevant variation within training data while minimising the size of the corpus. Therefore an investigation of the effect that different amounts and types of training data have on these models is needed. With this dissertation specific consideration is given to the data sufficiency principals that apply to the training of acoustic models. The investigation of this task lead to the following main achievements: 1) We define a new stability measurement protocol that provides the capability to view the variability of ASR training data. 2) This protocol allows for the investigation of the effect that various acoustic model complexities and ASR normalisation techniques have on ASR training data requirements. Specific trends with regard to the data requirements for different phone categories and how these are affected by various modelling strategies are observed. 3) Based on this analysis acoustic distances between phones are estimated across language borders, paving the way for further research in cross-language data sharing. Finally the knowledge obtained from these experiments is applied to perform a data sufficiency analysis of a new speech recognition corpus of South African languages: The Lwazi ASR corpus. The findings correlate well with initial phone recognition results and yield insight into the sufficient number of speakers required for the development of minimal telephone ASR corpora. / Thesis (M. Ing. (Computer and Electronical Engineering))--North-West University, Potchefstroom Campus, 2009.

The languages spoken in developing countries are diverse and most are currently under-resourced from an automatic speech recognition (ASR) perspective. In South Africa alone, 10 of the 11 official languages belong to this category. Given the potential for future applications of speech-based information systems such as spoken dialog system (SDSs) in these countries, the design of minimal ASR audio corpora is an important research area. Specifically, current ASR systems utilise acoustic models to represent acoustic variability, and effective ASR corpus design aims to optimise the amount of relevant variation within training data while minimising the size of the corpus. Therefore an investigation of the effect that different amounts and types of training data have on these models is needed. With this dissertation specific consideration is given to the data sufficiency principals that apply to the training of acoustic models. The investigation of this task lead to the following main achievements: 1) We define a new stability measurement protocol that provides the capability to view the variability of ASR training data. 2) This protocol allows for the investigation of the effect that various acoustic model complexities and ASR normalisation techniques have on ASR training data requirements. Specific trends with regard to the data requirements for different phone categories and how these are affected by various modelling strategies are observed. 3) Based on this analysis acoustic distances between phones are estimated across language borders, paving the way for further research in cross-language data sharing. Finally the knowledge obtained from these experiments is applied to perform a data sufficiency analysis of a new speech recognition corpus of South African languages: The Lwazi ASR corpus. The findings correlate well with initial phone recognition results and yield insight into the sufficient number of speakers required for the development of minimal telephone ASR corpora. / Thesis (M. Ing. (Computer and Electronical Engineering))--North-West University, Potchefstroom Campus, 2009.

During the lift-off of a launch vehicle, the acoustic pressure fluctuations caused by the engine exhaust gases produce high noise levels inside the cavity of the fairing and can damage the payload inside the fairing. Hence reducing the noise transmitted into the payload bay is an important area of research. Work presented in this thesis investigates the external acoustic pressure excitations on the fairing of a launch vehicle during the lift-off acoustic environment. In particular, it investigates the external sound pressure levels in the low frequency range from 50Hz to 400Hz, on the fairing during the lift-off of a launch vehicle. This study establishes theoretical and numerical models for the prediction of external sound pressure loading on composite structures representing launch vehicles, such as a large composite cylinder referred to as a Boeing cylinder and a Representative Small Launch Vehicle Fairing (RSLVF). To predict the external sound pressure loading, various incident wave conditions were investigated, including incident plane waves, oblique plane waves and oblique plane waves with random phases that strike the circumference of the composite structures. For the theoretical model, both the incident and scattered sound pressure fields due to incident plane waves; perpendicular to an idealised long cylinder were investigated. The results show that the scattered sound pressure field plays a major role in determining the total circumferential sound pressure field at the surface of the cylinder and cannot be ignored for the launch case. The theoretical model was developed further for a point source, line source and oblique incident waves, and modified to determine the incident, scattered and total sound pressure fields away from the cylinder. The approach developed overcomes some limitations of previous analytical derivations. An experiment was undertaken to determine the sound pressure patterns at the surface of a cylinder at various frequencies due to a point source positioned at a finite distance from the cylinder surface. The experimental work confirmed the accuracy of the theoretical model for a point source at a finite distance from the cylinder. The Boundary Element Method (BEM), approach was used for the numerical investigation of the acoustic loadings. The numerical analysis was developed for various acoustic loading conditions and verified with the theoretical results, which showed that the numerical and theoretical models agree well. Both models were extended to a Boeing composite cylinder and an RSLVF for various acoustic loading conditions. The complex acoustic environment generated during the lift-off of a launch vehicle was investigated and used as a basis for the acoustic loading on an RSLVF. To predict the acoustic excitations on an RSLVF, two different source allocation techniques were investigated, which considered acoustic sources along the rocket engine exhaust flow. The investigations were conducted both numerically and analytically. Both results agree well and show that it is possible to predict the acoustic loads on the fairing numerically and analytically. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1347443 / Thesis (Ph.D.) -- University of Adelaide, School of Mechanical Engineering, 2008

Thesis (M.S.) -- University of Maryland, College Park, 1999. / Thesis research directed by Institute for Systems Research. "M.S. 99-6." Includes bibliographical references (leaves 75-78). Available also online as a PDF file via the World Wide Web.

Η παρούσα διπλωματική εργασία αφορά τη σχεδίαση της εσωτερικής ηλεκτρολογικής εγκατάστασης στα αρχιτεκτονικά σχέδια μουσείου και στην ακουστική μελέτη αμφιθεάτρου εντός του μουσείου. Για την σχεδίαση της ηλεκτρολογικής εσωτερικής εγκατάστασης χρησιμοποιήθηκαν τα σύμβολα και οι κανονισμοί από τον ΕΛΛΟΤ HD 384. Για την κατασκευή των ηλεκτρολογικών σχεδίων χρησιμοποιήθηκε το λογισμικό Autocad 2008 και για την ακουστική μελέτη το λογισμικό CATT-Acoustic v7.2l, το οποίο είναι ένας προσομοιωτής μοντέλου ακουστικής χώρου. Η διπλωματική εργασία χωρίζεται σε 4 κεφάλαια όπου στο πρώτο κεφάλαιο γίνεται μια γενική περιγραφή για την Ε.Η.Ε., γενικές οδηγίες-κανονισμοί και αναφορά στα διάφορα καλώδια και αγωγούς που χρησιμοποιούνται. Στο 2ο κεφάλαιο, εξετάζονται στοιχεία φωτοτεχνίας και εξηγείται αναλυτικά η σημαντικότητα της χρήσης του σωστού είδους τεχνητού φωτισμού στα μουσεία και στις προθήκες τους. Στην συνέχεια, στο 3ο κεφάλαιο γίνεται η παρουσίαση του κάθε ηλεκτρικού κυκλώματος που σχεδιάστηκε και τί αγωγοί, ασφάλειες και συσκευές προτείνονται για την υλοποίηση του. Στο 4ο κεφάλαιο, παρουσιάζεται θεωρία ακουστικής και στο 5ο κεφάλαιο παρουσιάζεται η μεθοδολογία που ακολουθήθηκε, με τη χρήση του λογισμικού CATT- Acoustic, για τη διεξαγωγή της ακουστική μελέτης. Τέλος στο 6ο κεφάλαιο, παρουσιάζονται τα αποτελέσματα και τα συμπεράσματα της ακουστικής προσομοίωσης. / The present dissertation's subject is the design of internal electrical installation for the architectural plans of a museum, as well as the acoustic study of an amphitheatre inside the museum premises. For the design of this internal electrical installation symbols and regulations from ELOT HD 384 were used. The construction of the electrical plans was done on the software AUTOCAD 2008 and the acoustic study was done using the CATT-acoustic v.32, which is a software for simulating room acoustic. The dissertation is divided in 4 chapters, where in the first chapter a general description of the internal electrical installation is given, general instructions and regulations and reference to cables and wires that are used. In the 2nd chapter, elements of light are examined and the importance of using the correct kind of technical light in museums and their show-cases is explained thoroughly. Next, in the 3rd chapter, every electrical circuit that is designed is presented with the appropriate cables fuses and appliances for its implementation. In the 4th chapter, the acoustic theory is explained and in the 5th chapter the methodology followed for the acoustic simulation, with the use of the logismic CATT-Acoustic, is presented. Finally, in the 6th chapter the results of the acoustic simulation are presented and analyzed.

A highly successful architecture for the exchange of single quanta between coupled quantum systems is circuit quantum electrodynamics (QED), in which the electrical interaction between a qubit and a high-quality microwave resonator offers the possibility to reliably control, store, and read out quantum bits of information on a chip. This architecture has also been implemented with mechanical resonators, showing that a vibrational mode can in principle be manipulated via a coupled qubit. The work presented in this thesis consists of realising an acoustic version of circuit QED that we call circuit quantum acoustodynamics (QAD), in which a superconducting qubit is piezoelectrically coupled to an acoustic cavity based on surface acoustic waves (SAWs). Designing and building this novel platform involved the following main accomplishments: a systematic characterisation of SAW resonators at low temperatures; successfully developing a recipe for the fabrication of Josephson junction on quartz and diamond; measuring the coherence time of superconducting 3D transmon qubits on these substrates and demonstrating the dispersive coupling between a SAW cavity and a qubit on a planar geometry. This thesis presents evidence of the coherent interaction between a SAW cavity and a superconducting qubit in several ways. First of all, a frequency shift of the mechanical mode as a function of qubit frequency is observed. We also measure the acoustic Stark shift of the qubit due to the population of the SAW cavity. The extracted coupling is in agreement with theoretical expectations. A time delayed acoustic Stark shift serves to further demonstrate that the Stark shifts that we observe are indeed due to the acoustic field of the SAW mode. The dispersive coupling between these two quantum systems offers the possibility to perform qubit spectroscopy using the SAW resonator as readout component, indicating that these acoustic resonators can, in principle, be adopted as an alternative qubit readout scheme in quantum information processors. We finally present preliminary measurements of the direct coupling between a SAW resonator and a transmon on diamond, suggesting that strong coupling can in principle be obtained.

L'oxydation thermique est souvent étudiée par les méthodes classiques : mesure thermogravimétrie et observations MEB. L'utilisation de l'EA n'a pas encore été largement développée dans le domaine de l'oxydation thermique. Le présent travail vise à utiliser l'EA pour suivre in-situ l'oxydation et détecter les phénomènes physiques se produisant à haute température. Il porte sur deux groupes de matériaux : sensibles à l'oxydation catastrophique (Ti, Zy-4) et passifs (Cr, Ni). Ce travail présente tout d'abord l'oxydation du Ti pur à 900°C sous 150 mbar d'O2, en tant que matériau modèle. Il aborde également l'influence de la température, de l'atmosphère et de l'état de surface sur le comportement d'EA. L'oxydation du Zy-4, du Cr pur et du Ni pur sous oxygène et/ou sous vapeur d'eau est ensuite étudiée. Les ondes élastiques issues de l'oxydation sont converties en signaux d'EA via un capteur, lequel est collé au côté froid d'un guide d'onde en alumine. Une corrélation entre les mesures d'EA et les résultats classiques a été mise en évidence. La technique d'EA est capable de détecter l'oxydation catastrophique et d'identifier le mode de rupture de l'oxyde. Au-delà des paramètres discriminants d'EA, nous observons deux populations distinctes : la population dite normale est attribuée au bruit de fond et aux relaxations des contraintes dans l'oxyde associées à des phénomènes de fluage micro-mécanique, probablement situé aux joints de grains. La vitesse d'EA peut alors dépendre du niveau de ces contraintes et/ou de leurs relaxations. La population post-transitoire est associée à l'endommagement de l'oxyde conduisant à l'oxydation catastrophique. Selon le niveau d'énergie de transition, le mode de rupture de l'oxyde pourra être identifié. En revanche, l'EA n'a pas donné de résultats probants sur les matériaux passifs. Des signaux enregistrés ont pour principale origine le bruit de fond. / Thermal oxidation was often studied by conventional methods: thermogravimetric measurement and SEM observations. The use of AE has not yet been widely developed in the field of thermal oxidation. The present work aims to use AE to monitor on-line oxidation and detect physical phenomena occurring at high temperature. It focuses on two groups of materials: susceptible to catastrophic oxidation (Ti, Zy-4) and passive (Cr, Ni). This work first presents the oxidation of pure Ti at 900°C under 150 mbar of O2, as a model material. It also discusses the influence of temperature, atmosphere and surface condition on acoustic behaviour. Oxidation of Zy-4, pure Cr and Ni in pure oxygen and/or under water vapour is then studied. Elastic waves from oxidation are converted into AE signals via a sensor, which is placed outside the furnace by an alumina wave guide. A correlation between AE measures and classical results was highlighted. AE technique was able to detect catastrophic oxidation and identify failure modes of the oxide. Beyond the AE discriminated parameters, we observed two distinct populations: the so-called normal population is attributed to background noise and relaxation of stresses in the oxide associated with micro-mechanic creep, probably located at grain boundaries. AE velocity may then depend on stress level and/or their relaxation. Post-transition population is associated to oxide failure leading to breakaway oxidation. According to the transition energy level, the oxide failure modes could be identified. However, AE did not give conclusive results on passive materials. Recorded signals are mainly caused by background noise.