Submitted by Rafael Santana (rafael.silvasantana@ufpe.br) on 2018-02-01T19:25:01Z No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Dissertação Mestrado - Lorenna Santos.pdf: 3570385 bytes, checksum: af7a221e2cdc99daa203b7c07de4c948 (MD5) / Made available in DSpace on 2018-02-01T19:25:01Z (GMT). No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Dissertação Mestrado - Lorenna Santos.pdf: 3570385 bytes, checksum: af7a221e2cdc99daa203b7c07de4c948 (MD5) Previous issue date: 2016-08-23 / FACEPE / O câncer de mama é um grande problema da saúde pública mundial. No Brasil, ele é responsável por cerca de 25% de novos casos de câncer a cada ano. Em 2016, espera-se aproximadamente 57.960 novos casos de câncer de mama no país. A principal ferramenta na redução da taxa de mortalidade por essa doença é o diagnóstico precoce. Apesar do uso bastante difundido da mamografia, ela apresenta algumas desvantagens em sua utilização como a exposição direta do paciente à radiação ionizante; a semelhança de densidade entre tecidos tumoral e normal; e a baixa reprodutibilidade em mamas de alta densidade. A tomografia por micro-ondas da mama é uma alternativa bastante promissora no auxílio ao diagnóstico de mama. Essa técnica de tomografia traz como vantagens, uma maior facilidade em diagnóstico precoce e de difícil localização, menor exposição da paciente; menor custo; e maior conforto à paciente. Faz-se necessário à produção de phantoms com características semelhantes ao tecido humano real, para o uso da tomografia por micro-ondas em mamas. O presente trabalho tem como objetivo principal a elaboração de um phantom de mama específico para tomografia em micro-ondas e sua caracterização através de simulações e medidas em sonda coaxial aberta. A metodologia e os materiais de escolha utilizados na confecção dos phantoms de estudo, foram retirados de pesquisas posteriores de autores reconhecidos na área. O HFSS foi o software de escolha para realização das simulações. Os resultados da simulação e as medidas experimentais dos phantoms na sonda coaxial foram compatíveis com os da literatura. Diante dos resultados, esperase que a caracterização dos phantoms da pesquisa contribua de forma positiva para a consolidação da técnica de tomografia por microondas e que a partir dessa pesquisa seja possível a elaboração de protocolos que facilitem a produção de phantoms para pesquisas posteriores. / Breast cancer is a major problem of public health worldwide. In Brazil, it is responsible for about 25% of new cases of cancer each year. In 2016, it is expected about 57,960 new cases of breast cancer in the country. The main tool in reducing the death rate from this disease is early diagnosis. Despite the widespread use of mammography, it has some disadvantages in its use as direct patient exposure to ionizing radiation; the similarity in density between tumor and the normal tissues; and low reproducibility in high-density breasts. The positron breast microwave is a very promising alternative to help diagnose breast cancer. This tomography technique has some advantages, greater ease in early diagnosis and difficult location, less exposure of the patient; lower cost; and greater comfort to the patient. It is necessary for the production of phantoms with similar characteristics to the actual human tissue, for the use of microwave tomography in breasts. This work has as main objective the development of a specific breast phantom tomography in microwave and characterization through simulations and measurements in open coaxial probe. The methodology and the choice of materials used in the manufacture of phantoms study were drawn from further research of authors recognized in the area. The HFSS was the software of choice to perform the simulations. The simulation results and experimental measurements of phantoms in coaxial probe were consistent with the literature. Given the results, it is expected that the characterization of the research phantoms contribute positively to the consolidation of microwave tomography technique and that from this research is the possible development of protocols that facilitate the production of phantoms for further research.

Wakefields and the corresponding frequency-domain phenomenon beam coupling impedance have been well studied for a number of years as a source of beam instabilities within particle accelerators. With the development of the Large Hadron Collider (LHC) and the large beam currents stored in the LHC during fills for physics production, wakefield driven instabilities and strong beam induced heating have become a limiting factors in luminosity production due to both instantaneous luminousity and the available time for collisions.In this thesis is presented an in depth study of the beam coupling impedance of two important (from an impedance and operational point of view) devices in the LHC; the collimation system and the injection kicker magnets (MKIs). These systems have both been sources of concern for the beam impedance of the LHC, the collimators due to their large transverse impedance and the MKIs due to the strong heating observed during the increased of beam current during operation in 2011 and 2012. The source of the heating for the MKIs is studied in depth, found to be power lost by the beam to wakefields in the MKIs. Simulations and measurements are used to characterise the impedance and localise the areas responsible for the high impedance, here the beam screen and ferrite yoke of the magnet; improvements are proposed to better screen the ferrite yoke and verified. A new RF damping system using ferrite for the collimation system is studied and compared to the existing RF damping system, focusing on the heating of the damping system. Highlights include a new method for measuring the quadrupolar and constant transverse impedances of an asymmetric structure using a coaxial wire technique is proposed and verified using computational simulations, and a study of the heat loss in a ferrite damped cavity, focusing on the location of the power loss for cavities being damped to varying degrees.

Conventional rectangular waveguides are commonly used for high power and millimetre wave microwave applications. However their use at lower frequencies has been limited by their bulky nature at these frequencies. A new type of compact waveguide called a partial H-plane waveguide has previously been proposed that has only one quarter of the cross sectional area of a conventional waveguide. However, only limited information relating to the feeding of such waveguides is available. This study focuses on the development of a practical end-launched coaxial and a microstrip to partial H-plane waveguide adapters with similar or larger achievable bandwidths compared to conventional waveguide probe feed adapters. The two proposed waveguide transition geometries are investigated to determine which parameters can be used to optimise the insertion and return losses. The prototype waveguide transitions were optimised using numerous simulations and fabricated in the back-to-back configuration. Simulated single ended and back-to-back S-parameters yield good performance over the entire H-band (3.95 to 5.85 GHz, also known as G-Band). De-embedding techniques are used to measure the approximate single ended response of the two waveguide adapters based on the back-to-back measurements. The measurement and simulation results compare favourably and validate the designs. / Dissertation (MEng)--University of Pretoria, 2014. / tm2015 / Electrical, Electronic and Computer Engineering / MEng / Unrestricted

With global warming on the rise and the urge for conserving our natural resources, it becomes very important that proper steps are taken to protect our natural resources and utilize them efficiently. Forest fires are one of the many issues on the charts towards protection of natural resources. The catastrophic aftermaths caused by forest fires are known to all. The causes for these fires could be known/unknown natural causes or human intervention. Remote sensing techniques use the electromagnetic radiation in the RF/Microwave region, emitted from an object. The amount of energy emitted from an object depends on its present conditions, primarily its temperature and its emissivity. The sensing devices used in such measurements are classified into active and passive sensors. Herein, passive radiometry is used to investigate a model for the propagation of subsurface radiation from underground forest fires through upper ground layers of soil till the land-air interface. Passive radiometry involves capturing the radiation incident on a radiometer antenna aperture directly or deflected from several objects. The energy emitted from sources above 0K is collected and is compared with the calibration standards to estimate the physical quantity under test. Detecting forest fires is one of the potential applications of passive radiometry investigated here.

The main target of this master’s thesis is to introduce the reader with the spectrum analyzer, Agilent N1996A CSA. This work explains all the functions of this measuring instrument, control elements and presents some technical parameters. The next part of this thesis deals with the measurement of coaxial cables, so that is why a whole chapter is devoted to coaxial cables and conductors in general. The rest of this thesis deals with issues of measurement uncertainties. This part contains the general procedure for the evaluation of uncertainty, followed by a practical part. The practical part contains measurement of distance to fault and return loss. Measurements were made on 4 samples of coaxial cable. At the end of the practical parts the measured values including the uncertainties and results are summarized in the final paragraph.

Philosophiae Doctor - PhD / The application of porous materials into industrial hydrogen (H2) storage systems is based on their use in combination with high-pressure cylinders. The processing of metal-organic frameworks (MOF) powders into shaped forms is therefore imperative in order to counteract the adverse effects of poor packing of powders in cylinders. The fabrication of shaped MOFs has, however, been shown to be accompanied by compromised properties such as surface areas, gravimetric and volumetric H2 capacities, and also the working/deliverable H2 capacities in comparison to MOF powders.

The use of electromagnetic waves as a nondestructive evaluation technique to evaluate Portland cement concrete (PCC) structures is based on the principle that a change in the structure, composition, or properties of PCC results in a change in its dielectric properties. The coaxial transmission line is one of the few devices that can measure the dielectric properties of PCC at a frequency range of 100-1000 MHz. A coaxial transmission line developed at Virginia Tech was used to study the effect of moisture, type of aggregate, water/cement ratio, curing period, admixture type (microsilica, superplasticizer, and shrinkage admixture), and chloride content on the dielectric properties of PCC. Measurements were conducted in the time domain and converted to the frequency domain using Fast Fourier Transform. The research found that an increase in the moisture content of PCC resulted in an increase in the dielectric constant. Mixes containing limestone aggregate had a greater dielectric constant than those containing granite. The dielectric constant decreased with curing period due to the reduction in free water availability. Mixes containing higher water/cement ratios exhibited a higher dielectric constant, especially in the initial curing period. The admixtures did not significantly affect the dielectric constant after one day of curing. After 28 days of curing, however, all three admixtures had an effect on the measured dielectric constant as compared to control mixes. Chloride content had a significant effect on the loss part of the dielectric constant especially during early curing. A relationship was also established between the chloride permeability (based on conductance measurements) of PCC and its dielectric constant after 75 days of moist curing. / Master of Science

No description available.

A new approach of making ion trap mass analyzers was developed in which trapping fields are created in the space between two ceramic plates. Based on microfabrication technology, a series of independently-adjustable electrode rings is lithographically patterned on the facing surfaces of each ceramic plate. The trapping field can be modified or fine-tuned simply by changing the RF amplitude applied to each electrode ring. By adjusting the potential function applied to the plates, arbitrary trapping fields can be created using the same set of ceramic plates. Unlike conventional ion traps, the electrodes of planar ion traps have a non-equipotential surface, thus the electric field is independent of electrode geometry and can be optimized electronically. The simple geometry and open structure of planar ion traps address obstacles to miniaturization, such as fabrication tolerances, surface smoothness, electrode alignment, limited access for ionization or ion injection, and small trapping volume, thereby offering a great opportunity for a portable mass spectrometer device. Planar ion traps including the planar quadrupole ion trap and the coaxial ion trap have been designed and tested using this novel method. The planar quadrupole trap has demonstrated a mass range up to 180 Da (Th), with mass resolution typically between 400-700. We have also developed a novel ion trap in which both toroidal and quadrupolar trapping regions are created simultaneously between a set of plates. This "Coaxial Trap" allows trapping and mass analysis of ions in two different regions: ions can be trapped and mass analyzed in either the toroidal or quadrupolar regions, and transferred between these regions. Some simulation work based on the ion motion between two different trapping regions in the coaxial ion trap has been performed. Using a one-dimensional simulation method, ion motion was investigated to transfer ions between these two regions. The effect of the mutipole components in the radial field and axial field, amplitude and frequency of the primary RF and supplementary AC signal were studied to obtain high mass resolution in the axial direction and high transfer efficiency in the radial direction. In all these devices, the independent control of each patterned electrode element allows independent control of higher-order multipole fields. Fields can be optimized and changed electronically instead of physically as is done in conventional traps.

The Yorkshire Dales National Park contains some of the UK’s most extensive and well-preserved prehistoric landscapes. Of particular interest are a number of coaxial field systems, which cover hundreds of hectares and exhibit significant time-depth, yet remain little studied and poorly understood in relation to comparable resources elsewhere in Britain and north western Europe. This research aims to address this situation, bringing together existing disparate source materials for the first time, alongside supplementary field observation, to develop a detailed record of the coaxial landscapes. Using a Geographic Information System to manage, interpret and interrogate the combined datasets, analysis focuses on form and character, and explores prehistoric use of the iconic landscape. The study seeks to enhance our knowledge and understanding of the landscapes’ place in space and time, setting them against the backdrop of systems elsewhere, and attempts to place them within the context of later prehistoric society. The research, conducted in association with the Yorkshire Dales National Park Authority, also informs the management and public understanding of the archaeological resource of the Dales via the Historic Environment Record. / Arts and Humanities Research Council Collaborative Doctoral Award.