Automated fusion welding processes play a fundamental role in modern manufacturing industries. The proliferation of joint geometries together with the large permutation of associated process variable configurations has given rise to research into complex system modelling and control strategies. Many of these techniques have involved monitoring of not only the electrical characteristics of the process but visual and acoustic information. Acoustic information derived from certain welding processes is well documented as it is an established fact that skilled manual welders utilise such information as an aid to creating an optimum weld. The experimental investigation presented in this thesis is dedicated to the feasibility of monitoring airborne acoustic emissions of Submerged Arc Welding (SAW) for diagnostic and real time control purposes. The experimental method adopted for this research takes a cybernetic approach to data processing and interpretation in an attempt to replicate the robustness of human biological functions. A custom designed audio hardware system was used to analyse signals obtained from bead on mild steel plate fusion welds. Time and frequency domains were used in an attempt to establish salient characteristics or identify the signatures associated with changes of the process variables. The featured parameters were voltage / current and weld travel speed, due to their ease of validation. However, consideration has also been given to weld defect prediction due to process instabilities. As the data proved to be highly correlated and erratic when subjected to off line statistical analysis, extensive investigation was given to the application of artificial neural networks to signal processing and real time control scenarios. As a consequence, a dedicated neural based software system was developed, utilising supervised and unsupervised neural techniques to monitor the process. The research was aimed at proving the feasibility of monitoring the electrical process parameters and stability of the welding process in real time. It was shown to be possible, by the exploitation of artificial neural networks, to generate a number of monitoring parameters indicative of the welding process state. The limitations of the present neural method and proposed developments are discussed, together with an overview of applied neural network technology and its impact on artificial intelligence and robotic control. Further developments are considered together with recommendations for future areas of research.

Thesis (MMus) -- University of Stellenbosch, 2015. / This study details the design of an audible QR Code. The audible QRCode seeks to increase the rate of information exchanged in a human interaction and increase the quality of communication by altering the delivery medium of a QRCode. The delivery medium is changed from a two dimensional bar code to a audio signal. The design is discussed in detail grounded on telecommunication theory including signal modulation, packet construction and error correction. Three techniques were tested in order to reduce the possible intrusive characteristics of the audible QR Code on media content. The commercial uses of the audible QR Code is discussed as well as possible competitions and the advantages it has over the traditional visual QR Code. / Hierdie studie verduidelik die ontwerp van ’n hoorbare QR-Kode. Die hoorbare QR-Kode se doel is om die hoeveelheid inligting wat verruil word gedurende menslike interaksies te verhoog en ook om die kwaliteit van die kommunikasie te verbeter deur die afleweringsmedium van ’n QR-kode te verander. Die medium word verander van n visuele tweedimensionele streepkode na ’n klanksein. Die ontwerp word in diepte bespreek gegrond op die telekommunikasie teorie wat seinmodulasie, datapakkonstruksie en foutkorreksie insluit. Daar word drie tegnieke getoets wat ontwerp is om die indringende eienskappe van die Hoorbare QR-Kode te verminder. Die kommersi¨ele gebruike van die Hoorbare QR-Kode word bespreek, so ook moontlike kompetisie en die voordele wat die Hoorbare QR-kode besit bo die tradisionele visuele QR-kode.

This thesis presents audible vibratory mode data obtained by mechanically exciting acoustic modes in mc-Si wafers grown by EFG technique with various levels and distributions of residual stress. Stress maps obtained using scanning infrared polariscopy are presented, illustrating the variation of residual stress.Modal analyses of the wafers are performed using the finite element method and are in remarkably good agreement with the measured frequency response data. The calculated mode shapes were further validated through classic Chladni type patterns.The vibratory data is found to correlate with the residual stress measurements. The data is fit with both linear and quadratic models with correlation coefficients of 0.8. The results reveal a dependence of wafer audible mode frequencies on residual stress level that may be useful for solar cell mechanical quality control and breakage inspection.

Objective: The purpose of this study is to determine whether a novel, user-friendly rating system, visual sort and rate (VSR) provides comparable ratings to the currently used direct magnitude estimation (DME) rating system for rating perceptions of audible nasal emission (ANE) and hypernasality in cleft palate speakers. Methods: Twelve naïve listeners rated 152 speech samples of speakers with cleft palate across four conditions: rating hypernasality and ANE using either a VSR or DME rating scale. Raters were provided with a short training session, prior to rating each day. Inter- and intra-rater reliabilities, as well the line of best fit between scores using VSR and scores using DME was calculated to determine usability of VSR as a novel rating system. Results: Direct magnitude estimation resulted in the highest levels of inter-rater reliability, when rating hypernasality (DME r= .48; VSR r=.14), as well as ANE (DME r= .27; VSR r=.15). Most raters demonstrated high intra-rater reliabilities across conditions. A curvilinear line of best fit most accurately captured the relationship between DME and VSR scores when rating hypernasality (r=.64) and ANE (r=.66). Conclusions: A curvilinear relationship between ratings suggests that both variables are prothetic, and therefore, best captured using a DME rating scale (Eadie & Doyle, 2002). The use of DME is supported for continued use rating hypernasality, even amongst naïve listeners given a training session. Rating ANE was difficult, as ratings yielded low inter-rater reliabilities, regardless of the scale used. Further research regarding perceptions of audible nasal emission is warranted.

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Made available in DSpace on 2016-04-27T17:27:06Z (GMT). No. of bitstreams: 1 Fabiano Incerti.pdf: 1157907 bytes, checksum: 59797543fc6157fd37405ab6cea01af2 (MD5) Previous issue date: 2013-12-16 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The goal of this paper is to analyze, from the interpretations made by Michel Foucault, how visual and sound are crucial for the discovery of truth (manifestation de la vérité) tragedy Oedipus the King by Sophocles. These elements are problematized, first of all, on what the French thinker understands, it is one of the central themes of the play: the plot involving Oedipus develops in terms of a legal process. In this sense, looking and listening become key elements of the outcome of the issues involving the play: the investigation and discovery of the perpetrator of a crime and the punishment of the criminal. There is no revelation of truth in the story of the hero of the Greek poet despite the different and complementary ways of seeing and listening. And second, with regards to the figure of Oedipus. For Foucault, it is the subject of power-knowledge, over knowledge and over power. And it is precisely for this Power-Knowledge in excess, for that rude awakening and denial to hear the truth that is presented before him, he falls into the trap of his own destiny. Oedipus, the subject of knowledge and power, but also the subject of looking and listening / O objetivo deste trabalho de pesquisa é analisar, a partir das interpretações realizadas por Michel Foucault, de que forma o visual e o sonoro são decisivos para a descoberta da verdade (manifestation de vérité) na tragédia Édipo-Rei de Sófocles. Esses elementos são problematizados, em primeiro lugar, no que o pensador francês compreende ser um dos eixos centrais da peça: a trama que envolve Édipo se desenvolve em termos de um processo jurídico. Nesse sentido, olhar e escuta se tornam elementos primordiais para o desfecho dos pontos que envolvem a peça: a investigação e a descoberta do autor de um crime e a punição do criminoso. Não há revelação da verdade, na história do herói do poeta grego, que não esteja atravessada por maneiras diferentes e complementares de ver e de escutar. E, num segundo momento, no que diz respeito à própria figura de Édipo. Para Foucault, ele é o sujeito do saber-poder; do saber em excesso e do poder em excesso. E é precisamente por esse saber-poder em demasia, por esse abrir os olhos ao que está acontecendo e se recusar a escutar a verdade que se apresenta a sua frente, que ele cai na armadilha de seu próprio destino. Édipo, sujeito do saber e do poder, mas também sujeito do olhar e da escuta

The objective of this work is to optimize high-power low-frequency sonication (US) pretreatment of sludge, and especially to investigate for the first time possible improvements by higher pressure and audible frequency. After a preliminary examination of regular process conditions (sludge conditioning, sludge type, prior alkalization, temperature control, etc), effects of US parameters (power -PUS, intensity -IUS, specific energy input -ES, frequency -FS, etc.) and of hydrostatic pressure (Ph) were specifically looked into, separately and in combination, first under cooling at constant temperature (28°C), then under the progressive temperature rise provoked by sonication. First, it was confirmed that specific energy input (ES) plays a key role in sludge US disintegration (i.e. solubilisation of organic matter) and that temperature rise during adiabatic-like sonication is beneficial through additional effects of thermal hydrolysis and cavitation. At a given ES value, low FS (12 kHz vs. 20 kHz) and high PUS enhance soluble chemical oxygen demand (SCOD) due to more violent cavitation, while hydrostatic pressure gives rise to an optimum value due to its opposite effects on cavitation threshold and intensity. One major result is that optimal pressure depends on IUS (P¬US) as well as temperature profile, but not on ES, FS, nor sludge type. Setting the other parameters at the most favorable conditions expected, i.e. 12 kHz, 360 W , 28 gTS/L, and adiabatic conditions, final optimization was achieved by searching for this pressure optimum and examining sequential procedure to avoid too high temperature dampening cavitation intensity and damaging the transducer. Such conditions with sequential mode and Ph of 3.25 bar being selected succeeded in achieving very high SCOD, but only marginally improved subsequent methanization yield.

The dynamic behaviour in the audible frequency range of magneto-sensitive (MS) rubber is the focus of this thesis consisting of five papers A-E. Paper A presents results drawn from experiments on samples subjected to different constant shear strains over varying frequencies and magnetic fields. Main features observed are the existence of an amplitude dependence of the shear modulus referred to as the Fletcher-Gent effect for even small displacements, and the appearance of large MS effects. These results are subsequently used in Paper B and C to model two magneto-sensitive rubber isolators, serving to demonstrate how, effectively, by means of MS rubber, these can be readily improved. The first model calculates the transfer stiffness of a torsionally excited isolator, and the second one, the energy flow into the foundation for a bushing inserted between a vibrating mass and an infinite plate. In both examples, notable improvements in isolation are obtainable. Paper D presents a non-linear constitutive model of MS rubber in the audible frequency range. Characteristics inherent to magneto-sensitive rubber within this dynamic regime are defined: magnetic sensitivity, amplitude dependence, elasticity and viscoelasticity. A very good agreement with experimental values is obtained. In Paper E, the magneto-sensitive rubber bushing stiffness for varying degrees of magnetization is predicted by incorporating the non-linear magneto-sensitive audio frequency rubber model developed in Paper D, into an effective engineering formula for the torsional stiffness of a rubber bushing. The results predict, and clearly display, the possibility of controlling over a large range through the application of a magnetic field, the magneto-sensitive rubber bushing stiffness. / QC 20100816

This thesis is about detection of cracks in single-crystalline silicon wafers by using a vibration method in the form of an impact test. The goal to detect cracks from vibration measurements introduced by striking the silicon wafer with an impact hammer. Such a method would reduce costs in the production of solar cells. It is an inexpensive, relatively simple method which if commercialized could be used as an efficient in-line production quality test. A hammer is used as the actuator and a microphone as the response sensor. A signal analyzer is used to collect the data and to compute frequency response. Parameters of interest are audible natural frequencies, peak magnitudes, damping ratio and coherence. The data reveals that there are differences in frequency between the cracked silicon wafers and the non-cracked silicon wafers. The resonant peaks in the defective wafers were not as sharp (i.e., lightly damped) and occurred at lower frequencies (i.e., lower stiffness) with a lower magnitude and a higher damping ratio. These differences could be used to detect damaged product in a solar cell production line.

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Power utilities are expected to keep the cost of electricity as low as possible. They are also expected to be environmentally friendly and, amongst other things, not to produce unacceptable audible noise. When the electric field on a conductor is high enough corona is produced and this is accompanied by audible noise. Air pressure, which is directly related to altitude, has an effect on the voltage at which corona will start. It is more difficult to ionise the air at sea level (high air pressure) than at high altitude (low air pressure). Altitude does not only affect the corona inception voltage, but also the intensity of the audible noise. A thorough scan of literature revealed that there is very little evidence of prior research work on the effect of air density on corona under fair weather (dry) conditions. In South Africa, transmission lines are built at altitudes higher than 1800 m above sea level. The cost of a 400 kV line is in the region of R2M per km. It is important to predict the noise levels under a proposed line accurately, before it is energised. This research indicated that the altitude correction for conductor corona audible noise, under dry conditions, might be steeper than the general accepted correction of 1 dB/300m. This correction, however, appears to be valid for heavy rain conditions. Under heavy rain conditions the corona is mainly determined by the water droplets, whereas under dry conditions the condition of the conductor plays the biggest role. The air density therefore has a bigger effect on the corona performance under dry conditions. The implication of a steeper altitude correction for dry conditions is that too low noise levels will be predicted for a higher altitude, which could lead to complaints. On the other hand, predictions for lower altitudes will be too conservative. / AFRIKAANSE OPSOMMING: Daar word van kragvoorsieners verwag om die koste van elektrisiteit so laag as moontlik te hou. Hulle is verder onder druk om omgewingsvriendelik te wees en om onder andere nie onaanvaarbare hoorbare geraas te veroorsaak nie. Wanneer die elektriese veld op ‘n geleier hoog genoeg is, kan korona ontstaan wat dan hoorbare geraas veroorsaak. Die lugdruk, en daarom die hoogte bo seevlak, beïnvloed die spanning waarby ‘n geleier in korona sal gaan. Dit is moeiliker om die lug te ioniseer by seevlak (hoë lugdruk) as hoog bo seevlak (lae lugdruk). Die hoogte bo seevlak beïnvloed daarom nie net die spanning waarby korona sal begin nie maar ook die intensiteit van die hoorbare geraas. Dit wil voorkom of die effek van hoogte bo seevlak, op hoorbare geraas, a.g.v. geleier korona tot op datum baie skraps nagevors is. Baie min kon in die literatuur gevind word op die effek onder droë toestande. In Suid-Afrika is dit nodig om transmissielyne op hoogtes van 1800 m en hoër te bou. So ‘n lyn (400 kV) kos in die omgewing van R2M per km. Dit is daarom van uiterste belang om die geraasvlakke wat ‘n beplande lyn sal veroorsaak, akkuraat te bepaal, voordat so ‘n lyn aangeskakel word. Hierdie navorsing het gewys dat die effek van hoogte bo seespieël op hoorbare korona geraas onder droë toestande groter kan wees as wat algemene aanvaar word. Die helling van die korreksiefaktor vir hoogte bo seevlak blyk steiler as 1 dB/300 m te wees vir droë toestande. Die implikasie hiervan is dat geraas voorspellings vir hoër hoogtes bo seespieël te laag sal wees en die vir lae hoogtes te konserwatief kan wees. Die navorsing stem egter saam met die korreksiefaktor van 1 dB/300 m onder swaar reën toestande. Dit wil voorkom of die invloed van die waterdruppels op geleier korona groter is as lugdruk. Onder droë toestande speel die toestand van die geleier 'n groter rol en is die effek van lugdruk groter.