Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.

Thesis (MEng)--University of Stellenbosch, 2000. / ENGLISH ABSTRACT: Handwritten signature verification (HSV) is the process through which handwritten signatures are analysed in an attempt to determine whether the person who made the signature is who he claims to be. Banks and other financial institutions lose billions of rands annually to cheque fraud and other crimes that are preventable with the aid of good signature verification techniques. Unfortunately, the volume of cheques that are processed precludes a thorough HSV process done in the traditional manner by human operators. It is the aim of this research to investigate new methods to compare signatures automatically, to eventually speed up the HSV process and improve on the accuracy of existing systems. The new technology that is investigated is the use of the so-called hidden Markov models (HMMs). It is only quite recently that the computing power has become commonly available to make the real-time use of HMMs in pattern recognition a possibility. Two demonstration programs, SigGrab and Securitlheque, have been developed that make use of this technology, and show excellent improvements over other techniques and competing products. HSV accuracies in excess of99% can be attained. / AFRIKAANSE OPSOMMING: Handgeskrewe handtekening verifikasie (HHV) is die proses waardeur handgeskrewe handtekeninge ondersoek word in 'n poging om te bevestig of die persoon wat die handtekening gemaak het werklik is wie hy voorgee om te wees. Banke en ander finansiele instansies verloor jaarliks biljoene rande aan tjekbedrog en ander misdrywe wat voorkom sou kon word indien goeie metodes van handtekening verifikasie daargestel kon word. Ongelukkig is die volume van tjeks wat hanteer word so groot, dat tradisionele HHV deur menslike operateurs 'n onbegonne taak is. Dit is die doel van hierdie navorsmg om nuwe metodes te ondersoek om handtekeninge outomaties te kan vergelyk en so die HHV proses te bespoedig en ook te verbeter op die akkuraatheid van bestaande stelsels. Die nuwe tegnologie wat ondersoek is is die gebruik van die sogenaamde verskuilde Markov modelle (VMMs). Dit is eers redelik onlangs dat die rekenaar verwerkingskrag algemeen beskikbaar geraak het om die intydse gebruik van VMMs in patroonherkenning prakties moontlik te maak. Twee demonstrasieprogramme, SigGrab en SecuriCheque, is ontwikkel wat gebruik maak van hierdie tegnologie en toon uitstekende verbeterings teenoor ander tegnieke en kompeterende produkte. 'n Akkuraatheid van 99% of hoer word tipies verkry.

Thesis (MSc (Geography and Environmental Studies))--University of Stellenbosch, 2005. / 81 Leaves printed on single pages i-xi, preliminary pages and numbered pages 1- 70. Includes bibliography, list of tables and list of figures. / Digitized at 300 dpi color PDF format (OCR), using KODAK i 1220 PLUS scanner. / ENGLISH ABSTRACT: Geological field mapping is often limited by logistical and cost constraints as well as the scope and extent of observations possible using ground-based mapping. Remote sensing offers, among others, the advantages of an increased spectral range for observations and a regional perspective of areas under observation. This study aimed to determine the accuracy of a collection of image classification techniques when applied to ASTER reflectance data. Band rationing, the Crosta Technique, Constrained Energy Minimization, Spectral Correlation Mapping and the Maximum Likelihood Classifier were evaluated for their efficiency in detecting and discriminating between greenstone and granitoid material. The study area was the Archaean Barberton Greenstone Belt in the eastern Mpumalanga Province, South Africa. ASTER reflectance imagery was acquired and pre-processed. Training and reference data was extracted from the image through visual inspection and expert knowledge. The training data was used in conjunction with USGS mineral spectra to train the five classification algorithms using the ERDAS's software package. This resulted in abundance images for the target materials specified by the training data. The Maximum Likelihood Classifier produced a classified thematic map. The reference data was used to perform a rigorous classification accuracy assessment procedure. All abundance images were thresholded to varying levels, obtaining accuracy statistics at every level. In so doing, threshold levels could be defined for every abundance image in such a way that the reliability of the classification was optimized. For each abundance image, as well as for the output map of the Maximum Likelihood Classifier, user's- and producer's accuracies as well as kappa statistics were derived and used as comparative measures of efficiency between the five techniques. This information was also used to assess the spectral separability of the target materials. The Maximum Likelihood Classifier outperformed the other techniques significantly, achieving an overall classification accuracy of 81.1% and an overall kappa value of 0.748. Greenstone rocks were accurately discriminated from granitoid rocks with accuracies between 72.9% and 98.5%, while granitoid rocks showed very poor ability to be accurately distinguished from each other. The main recommendations from this study are that thermal infrared and gamma-ray data be considered, together with better vegetation masking and an investigation into object orientated techniques. / AFRIKAANSE OPSOMMING: Geologiese veldkartering word algemeen beperk deur logistiese en koste-verwante faktore, sowel as die beperkte bestek waartoe waarnemings met veld-gebasseerde tegnieke gemaak kan word. Afstandswaarneming bied, onder andere, 'n vergrote spekrale omvang vir waarnemings en 'n regionale perspektief van die area wat bestudeer word. Hierdie studie was gemik daarop om die akkuraatheid van 'n versameling beeld-klassifikasie tegnieke, toegepas op ASTER data, te bepaal. Bandverhoudings, die Crosta Tegniek, "Constrained Energy Minimization", Spektrale Korrellasie Kartering, en Maksimum Waarskynlikheid Klassifikasie is evalueer op grond van hul vermoë om groensteen en granitoied-rotse op te spoor en tussen hulle te onderskei. Die studiegebied was die Argalese Barberton Groensteengordel in die oostelike Mpumalanga Provinsie in Suid Afrika. 'n ASTER refleksie beeld is verkry, waarop voorverwerking uitgevoer is. Opleidings- en verwysingsdata is van die beeld verkry deur visuele inspeksie en vakkundige kennis. Die opleidingsdata is saam met VSGO mineraalspektra gebruik om die vyf klassifikasie algoritmes met behulp van die ERDAS sagteware pakket op te lei. Die resultaat was volopheidsbeelde vir die teikenmateriale gespesifiseer in die opleidingsdata. Die Maksimum Waarskynlikheid algoritme het 'n geklassifiseerde tematiese beeld gelewer. Met behulp van die verwysingsdata is 'n streng akkuraatheidstoetsing prosedure uitgevoer. Vir alle volopheidsbeelde is 'n reeks drempelwaardes gestel, en by elke drempelwaarde is akkuraatheidsstatistieke afgelei. Op hierdie manier kon 'n drempelwaarde vir elke volopheidsbeeld vasgestel word sodat die drempelwaarde die betroubaarheid van die klassifikasie optimeer. Vir elke volopheidsbeeld, asook vir die tematiese kaart verkry van die Maksimum Waarskynlikheid klassifikasie, is gebruikers- en produsent-akkuraathede en kappa statistieke bereken. Hierdie waardes is gebruik as vergelykende maatstawwe van akkuraatheid tussen die vyf tegnieke, asook van die spektrale skeibaarheid van die onderskeie teikenmateriale. Die Maksimum Waarskynlikheid klassifikasie het die beste resultate gelewer, met 'n algehele klassifikasie akkuraatheid van 81.1%, en 'n gemiddelde kappa waarde van 0.748. Groensteenrotse kon met hoë akkuraathede van tussen 72.9% en 98.5% van granitoiedrotse onderskei word, terwyl granitoiedrotse 'n swak vermoë getoon het om van mekaar onderskei te word. Die belangrikste aanbevelings vanuit hierdie studie is dat termiese uitstralingdata asook gamma-straal data geimplimenteer word. Beter verwydering van plantegroei en 'n studie na die lewensvatbaarheid van objekgeorienteerde metodes word ook aanbeveel.

abstract: The objective of this work is to design a low-profile compact Terahertz (THz) imaging system that can be installed in portable devices, unmanned aerial vehicles (UAVs), or CubeSats. Taking advantage of the rotational motion of these platforms, one can use linear antennas, such as leaky-wave antennas or linear phased arrays, to achieve fast image acquisition using simple RF front-end topologies. The proposed system relies on a novel image reconstructing technique that uses the principles of computerized tomography (Fourier-slice theorem). It can be implemented using a rotating antenna that produces a highly astigmatic fan-beam. In this work, the imaging system is composed of a linear phased antenna array with a highly directive beam pattern in the E-plane allowing for high spatial resolution imaging. However, the pattern is almost omnidirectional in the H-plane and extends beyond the required field-of-view (FOV). This is a major drawback as the scattered signals from any interferer outside the FOV will still be received by the imaging aperture and cause distortion in the reconstructed image. Also, fan beams exhibit significant distortion (curvature) when tilted at large angles, thus introducing errors in the final image due to its failure to achieve the assumed reconstructing algorithm. Therefore, a new design is proposed to alleviate these disadvantages. A 14×64 elements non-uniform array with an optimal flat-top pattern is designed with an iterative process using linear perturbation of a close starting pattern until the desired pattern is acquired. The principal advantage of this design is that it restricts the radiated/received power into the required FOV. As a result, a significant enhancement in the quality of images is achieved especially in the mitigation of the effect of any interferer outside the FOV. In this report, these two designs are presented and compared in terms of their imaging efficiency along with a series of numerical results verifying the proof of concept. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2018

Thesis (MTech (Electrical Engineering))--Cape Peninsula University of Technology, 2016. / Ultrasound is widely used in most medical clinics, especially obstetrical clinics. It is a way of imaging methods that has important diagnostic value. Although useful in many different applications, diagnostic ultrasound is especially useful in antenatal (before delivery) diagnosis. The use of two-dimensional ultrasound (2DUS) in obstetrics has been established. However, there are many disadvantages of 2DUS imaging. Several researchers have published information on the significance of patients being shown the ultrasound screen during examination, especially during three- and four-dimensional (3D/4D) scanning. In addition, a form of ultrasound, called keepsake or entertainment ultrasound, has boomed, particularly in the United States. However, long-term epidemiological studies have failed to show the adverse effects of ultrasound in human tissues. Until now, there is no proof that diagnostic ultrasound causes harm in a human body or the developing foetus when used correctly. While ultrasound is supposed to be absolutely safe, it is a form of energy and, as such, has effects on tissues it traverses (bio-effects). The two most important mechanisms for effects are thermal and non-thermal. These two mechanisms are indicated on the screen of ultrasound devices by two indices: The thermal index (TI) and the mechanical index (MI). These are the purposes of this thesis: • evaluate end-users’ knowledge regarding the safety of ultrasound; • evaluate and make a comparison between acoustic output indices (AOI) in B-mode (2D) and three-dimensional (3D) ultrasound – those measured by thermal (TI) and mechanical (MI) indices; • assess the acoustic output indices (AOI) to benchmark current practice with a survey conducted by the British Medical Ultrasound Society (BMUS); and • review how to design 2D and 3D arrays for medical ultrasound imaging

Orientador: Jose Joaquin Lunazzi / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-08-04T02:40:53Z (GMT). No. of bitstreams: 1 Magalhaes_DanielSouzaFerreira_M.pdf: 2786566 bytes, checksum: d02ed179060d33a6a269a495bcb6a2bb (MD5) Previous issue date: 2005 / Resumo: Neste trabalho analisamos a formação de imagens por elementos difrativos com luz branca fazendo o traçado de raios pelas direções principais e explorando as possibilidades que a simetria de um conjunto de dois elementos definidos bidimensionalmente e intermediados por um pequeno orifício oferece. A mais interessante delas é a de termos uma imagem convergente, que pode ser vista projetando sobre uma tela, por exemplo / Abstract: We perform ray tracing analysis on the imaging of white light objects by diffractive elements by means of the main direction of the rays. We explore the possibilities that the symmetry of a set of two bidimensionally acting diffracting elements intermediated for a pinhole offers. The most interesting of them is that we have a convergent image, that can be seen projecting on a screen, for example / Mestrado / Ótica / Mestre em Física

M.A. / This dissertation comprises an in-depth investigation into the domain of computer vision, with specific reference to the textile industry. The study consists of three main sections. In the first section, the computer-vision process is scrutinised in its entirety. Attention is given in this regard to what computer vision is, where it originated from, how it compares with human vision and what the motivations are for its implementation. Following, the computer-vision process is divided into four main components, namely image acquisition, image processing, image analysis and image interpretation. Subsequently, each component is discussed in greater detail, as well as aspects such as the hardware used in the course of the process, the algorithms that are implemented and the specific applications used for the process of analysis. In the second section, the focus is shifted to the textile industry, where our main focus lies. In this regard, examples are examined of the successful implementation of computer-vision technologies in the textile industry. In the third section, an investigation is launched into the specific problem for which a solution needs to be found in the present study, namely to determine whether computer vision constitutes a cost-effective way in which to locate broken thread during the spinning process. A wide range of algorithms has been applied for this purpose, whereafter the results of these experiments are announced.

The inadequacies of the current generation of deconvolution algorithms are rapidly becoming apparent as new, more sensitive radio interferometers are constructed. In light of these inadequacies, there is renewed interest in the field of deconvolution. Many new algorithms are being developed using the mathematical framework of compressed sensing. One such technique, MORESANE, has recently been shown to be a powerful tool for the recovery of faint difuse emission from synthetic and simulated data. However, the original implementation is not well-suited to large problem sizes due to its computational complexity. Additionally, its use of proprietary software prevents it from being freely distributed and used. This has motivated the development of a freely available Python implementation, PyMORESANE. This thesis describes the implementation of PyMORESANE as well as its subsequent augmentation with MPU and GPGPU code. These additions accelerate the algorithm and thus make it competitive with its legacy counterparts. The acceleration of the algorithm is verified by means of benchmarking tests for varying image size and complexity. Additionally, PyMORESANE is shown to work not only on synthetic data, but on real observational data. This verification means that the MORESANE algorithm, and consequently the PyMORESANE implementation, can be added to the current arsenal of deconvolution tools.

The crustal structure of a young (<10 My) ocean basin is imaged by two multichannel seismic reflection lines comprising 230 km recorded over the central part of the northern Juan de Fuca plate off western Canada. The more northerly line ties previously interpreted deep seismic reflection lines across the Juan de Fuca ridge and the Cascadia subduction zone; the southern line ties with another interpreted line across the subduction zone. Both lines trend obliquely to the spreading direction. A marine refraction profile crossing the eastern end of the lines provides velocity constraints. The processing sequence applied to the data includes a prestack inside-trace mute of CMP gathers to reduce noise levels on the deep data, CMP stack, post-stack dip filtering, f-k migration and bandpass. Coherency-filtered stacks are helpful in tracing weaker reflectors. The stacked sections reveal a horizontally layered sedimentary sequence overlying a rugged and prominent basement reflector dipping slightly landward. A strong, fairly continuous reflection from the base of the crust at about 2 s two-way-time below the basement surface generally mimics the basement topography and shows the characteristic doubling and tripling of reflections seen in other similar surveys. Although in general the crust appears acoustically transparent, weaker, discontinuous intracrustal reflectors are observed over 40 km at the eastern end of the northern line, and are interpreted to arise from the oceanic Layer 3A/3B and Layer 2/3 boundaries. The im-persistence of these reflectors is an indication of the complexity of the processes producing intracrustal reflectivity, and an indication of the lateral variability of crustal formation. Pseudofault traces of propagating rifts are crossed at three different locations on the two lines, the first MCS crossings of such structures. Crust associated with the pseudofault traces is related to both subhorizontal and dipping subcrustal events which are interpreted as zones of crustal thickening or underplating. Although the crustal thickness elsewhere on the lines varies by only about 10%, crust associated with the pseudofaults is as much as about 25% thicker than average, suggesting that magma supply at transform-type offsets may at times be large. A small seamount discovered on the southern line may result from the excessive magma production at the ridge postulated at propagating rift zones. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

M.Ing. / Globally, hazardous weather phenomena such as violent storms, oods, cyclones, tornadoes, snow and hail contribute to signi cant annual xed property damages, loss of movable property and loss of life. The majority of global natural disasters are related to hydro-meteorological events. Hazardous storms are destructive and pose a threat to life and property. Forecasting, monitoring and detecting hazardous storms are complex and demanding tasks, that are however essential. In this study automatic hazardous weather detection utilizing remotely sensed meteorological data has been investigated. Image processing techniques have been analyzed and applied to multispectral meteorological satellite image data obtained from the Spinning Enhanced Visible and Infrared Imager (SEVIRI) instruments on-board the Meteosat Second Generation (MSG) geostationary meteorological satellites Meteosat-8 and Meteosat-9. The primary focus of this study is the detection of potentially hazardous hydrometeorological phenomena in South Africa. A methodology for detecting potentially hazardous storms over South Africa using meteorological satellite imagery from MSG/SEVIRI is presented. An index indicative of the hazardous potential of a storm is de ned to aid in the identi cation of a ected geographical areas and to quantify the destructive potential of the detected storm. The Hazardous Potential Index (HPI) is generated through the use of image processing techniques such as cloud masking, cloud tracking and an image-based analysis of the constituent elements of a severe convective storm. A retrospective review was performed with respect to 20 case studies of documented storms which had adversely a ected areas of South Africa. A red-green-blue (RGB) composite image analysis technique, that may be utilized in the identi cation of severe convective storms using SEVIRI image data, was also applied to these case studies.