Extreme winter weather events in North America have become more frequent and increasingly destructive. This phenomenon was linked to a jet stream pattern that generates abnormally warm conditions in the west and cold conditions in the east, referred to as the North American Winter Dipole. Studies have shown that the Dipole may have amplified and this amplification could be linked to global warming. By analyzing the atmospheric and oceanic data worldwide, the wintertime circulation in the Northern Hemisphere shows signs of a persistent change after the 1980s. In the first part of this study, we examine how the ocean has changed in correspondence to the Dipole and the evolution of the pattern change. In the second part of this study, we use multiple global reanalysis datasets to construct the Dipole index. The result validates the reported Dipole variation during the modern period. We also use the Dipole variance to investigate the Dipole’s behavior in the paleoclimate and future warming conditions. Overall, we sought to better understand how the Dipole pattern evolves and how it may link to the different forcing, as a way to anticipate future change in North America’s winter.

A thesis submitted to the Faculty of Engineering,University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree or Doctor of Philosophy. / The aim of the thesis is to develop techniques for the analysis of antennas composed of dipoles and folded dipoles,that are efficient relative to the method-of-moments. (Abbreviation abstract) / AC2017

<p> The relative acidities of some aryl germanes have been measured in liquid ammonia.</p> <p> The NMR spectra of phenyl silane and phenyl germane have been completely analysed and the chemical shifts shown to arise from the presence of an electric dipole in the molecule. The NMR spectrum of phenyl germyl anion was unambiguously assigned and partially analysed. The results are consistent with little delocalization of the negative charge from the Ge onto the ring.</p> <p> The vibrational spectra of the germyl anion have been observed and the geometry of the molecule estimated from a normal coordinate analysis of the data.</p> <p> The Raman spectrum of liquid ammonia-D3 has been measured and two bands in the Raman spectrum of liquid ammonia have been reassigned.</p> / Thesis / Doctor of Philosophy (PhD)

We formulate a variational method to obtain the binding energies of a charged particle in presence of an electric dipole and a magnetic field aligned along the dipole. First, we test the method by obtaining the critical dipole moment for a point dipole, as well as a finite dipole in the absence of a magnetic field. A few larger dipole moments supporting a zero energy bound state are also obtained. Adding a magnetic field of ~ 20 - 100 T, we show that for a rigid and stationary dipole of moment 2.54 D, the electron binding energy increases by 15% - 66%. Our approach also shows the absence of a critical dipole moment in presence of an aligned magnetic field. / Thesis / Master of Science (MSc)

Yes / A printed dipole antenna integrated with a duplex RF switch used for mobile base station antenna beam steering is presented. A coplanar waveguide to coplanar strip transition was adopted to feed the printed dipole. A novel RF switch circuit, used to control the RF signal fed to the dipole antenna and placed directly before the dipole, was proposed. Simulated and measured data for the CWP-to-CPS balun as well as the measured performance of the RF switch are shown. It has demonstrated the switch capability to control the beam in the design of beam steering antenna array for mobile base station applications.

Os métodos geoelétricos, principalmente a eletrorresistividade, estão sendo cada vez mais requisitados na área da mineração, indicando espessura de capeamento de solo, zonas fraturadas e heterogeneidades do material, viabilizando economicamente, ou não, um projeto minerário. Este trabalho, realizado no município do Cabo de Santo Agostinho -PE, apresenta e discute resultados de aplicações do método geofísico, da eletrorresistividade, como instrumento de auxílio na abertura de uma nova frente de lavra para extração de blocos graníticos de grande porte. Foi investigada a espessura do capeamento de solo, bem como as principais zonas locais de falhas e fraturas. Para isso foram realizadas 32 SEVs (03 SEVs por perfil, à exceção da Linha 11, com 02) com arranjo Schlumberger de AB/2 máximo de 60metros, e 11 caminhamentos elétricos com arranjo dipolo-dipolo de AB=MN=20 metros,com aproximadamente 1000m de extensão cada perfil. As SEVs foram dispostas nas linhas de modo a cobrir adequadamente a área do terreno, possibilitando a confecção de um mapa de contorno da profundidade do topo rochoso e a caracterização do perfil de alteração pedológico. Os caminhamentos elétricos foram dispostos paralelamente entre si e espaçados de 60 metros, podendo ser observadas as possíveis configurações do topo rochoso, como rocha não fraturada e zonas fraturadas. A partir dos dados dos caminhamentos elétricos foram elaboradas simulações 3D de resistividade e para a estimativa de volume de rocha não fraturada na área de estudo (com base nas resistividades mais elevadas).Os resultados obtidos mostraram a eficiência da eletrorresistividade na determinação do topo da rocha sã e detecção das zonas fraturadas no maciço granítico. / The geoeletric methods, especially electroresistivity, are being progressively more required on mining, for identifying soil thickness, fractured zones and geological heterogeneities, to check economical viability of mining projects. This work, held in Cabo de Santo Agostinho-PE city, presents and discusses geophysics application results of electroresistivity as a tool for helping the opening of a new granitic blocks exploitation front. The soil thickness was investigated, as well as the main local fault zones and fractures. A total of 32 VESs (03 VESs per section, exception made to line 11, with 02 VESs) using Schlumberger array with AB/2 maximum of 60 m, and 11 geoelectrical profilings using dipole-dipole array (AB=MN=20 m), with section lengths close to 1000 m. The VESs lines were organized in order to cover the studied area properly, allowing mapping the top of the rock massif and characterizing the soil profile. The geoelectrical profilings were disposed parallel with 60 m gap among each other, enabling the observation of the massif top configurations, such as fractured and non fractured zones. 3D resistivity simulations were performed using the geoelectrical profilings data in order to estimate the total volume of non fractured rock in the studied area (based on the highest resistivities). The obtained data showed the efficiency of electroresistivity for fractured zones detection and for mapping the top of the fresh rock massif.

A blue sky, a white cloud or a red sunset are explained by classical multiple scattering theory of light. However, these phenomena neglect interference occurrence. Once it is taken into account, interference in a disordered medium may actually put a halt to the propagation of light, an effect known as Anderson Localization. Until now, experimental reports of Anderson Localization of light in 3D systems have not been conclusive. Our goal is to understand what are the underlying obstacles, and look for new insights from a theoretical point of view. In this dissertation, the properties of a cloud of two-level atoms scattering light are investigated. The dipole-dipole interaction generates collective modes, some of them, being localized. We found that finite-size effects dominate the lifetime of the localized modes, specifically by the ratio of localization length to their distance to the system boundaries. Localized modes saturates at maximum of 20% even above phase transition. Studying the steady-state regime, the coupling between localized modes and light is weak. Both results agrees with the difficulty of experimental evidence of light localization and promote the link of experiments and theory. / Um céu azul, uma nuvem branca ou um por do sol vermelho são explicados pela teoria clássica de espalhamento múltiplo da luz. No entanto, esses fenômenos negligenciam a ocorrência de interferências. Uma vez levada em conta, a interferência em um meio desordenado pode interromper a propagação da luz, um efeito conhecido como Localização de Anderson. Até agora, relatos experimentais de Anderson Localização de luz em sistemas 3D não foram conclusivos. Nosso objetivo é entender quais são os obstáculos fundamentais, e buscar novos insights do ponto de vista teórico. Nesta dissertação, as propriedades de uma nuvem de átomos de dois níveis espalhando luz de é investigado. A interação dipolo-dipolo gera modos coletivos, alguns deles, sendo localizados. Descobrimos que os efeitos de tamanho finito dominam o tempo de vida dos modos localizados, especificamente pela razão entre o comprimento da localização e sua distância até os limites do sistema. Os modos localizados saturam no máximo 20%, mesmo acima da transição de fase. Estudando o regime de estado estacionário, o acoplamento entre modos localizados e luz é fraco. Ambos os resultados concordam com a dificuldade da evidência experimental da localização da luz e promovem a ligação entre experimentos e teoria.

The effective and efficient remediation of contaminated groundwater sites requires site specific information regarding the physical, chemical and biological properties of the aquifer. Building on the dipole flow test (DFT) and the dipole flow and tracer test (DFTT), the dipole flow and reactive tracer test (DFRTT) has been proposed as an alternative to current aquifer parameter estimation methods. A steady-state dipole flow field is created by circulating groundwater between chambers isolated by the dipole tool. A tracer is released into the injection chamber and the breakthrough curve at the extraction chamber is interpreted with the DFRTT specific model. The overall goal of this thesis was to demonstrate the ability of a prototype dipole system to produce tracer BTCs in conventional wells installed in an unconfined sandy aquifer. The Waterloo dipole probe was constructed and field tested at CFB Borden. DFTs conducted along the length of the screen of non-filter packed monitoring wells provided similar estimates of radial hydraulic conductivity (Kr) to slug tests and literature values. The geometric mean Kr estimated in the filter packed wells was approximately an order of magnitude greater than the mean Kr estimate for the non-filter packed wells due to short-circuiting through the filter pack. A total of 46 DFTTs were completed in the monitoring wells at CFB Borden to investigate the properties of the BTCs. The shape of the BTC for a conservative tracer is affected by test set up parameters, well construction, and aquifer formation properties. The BTCs from the DFTTs completed in the non-filter pack monitoring wells were categorized into four “type curves” based on the BTC properties. The differences between the type curves were largely defined by the ratio of K between the skin zone and the aquifer (Ks/Kr). Now that a series of DFTT BTCs have been generated, the DFRTT model will be used to estimate the aquifer parameters. To continue the work outlined in this thesis, DFRTTs are planned for well-documented contaminated sites.

The effective and efficient remediation of contaminated groundwater sites requires site specific information regarding the physical, chemical and biological properties of the aquifer. Building on the dipole flow test (DFT) and the dipole flow and tracer test (DFTT), the dipole flow and reactive tracer test (DFRTT) has been proposed as an alternative to current aquifer parameter estimation methods. A steady-state dipole flow field is created by circulating groundwater between chambers isolated by the dipole tool. A tracer is released into the injection chamber and the breakthrough curve at the extraction chamber is interpreted with the DFRTT specific model. The overall goal of this thesis was to demonstrate the ability of a prototype dipole system to produce tracer BTCs in conventional wells installed in an unconfined sandy aquifer. The Waterloo dipole probe was constructed and field tested at CFB Borden. DFTs conducted along the length of the screen of non-filter packed monitoring wells provided similar estimates of radial hydraulic conductivity (Kr) to slug tests and literature values. The geometric mean Kr estimated in the filter packed wells was approximately an order of magnitude greater than the mean Kr estimate for the non-filter packed wells due to short-circuiting through the filter pack. A total of 46 DFTTs were completed in the monitoring wells at CFB Borden to investigate the properties of the BTCs. The shape of the BTC for a conservative tracer is affected by test set up parameters, well construction, and aquifer formation properties. The BTCs from the DFTTs completed in the non-filter pack monitoring wells were categorized into four “type curves” based on the BTC properties. The differences between the type curves were largely defined by the ratio of K between the skin zone and the aquifer (Ks/Kr). Now that a series of DFTT BTCs have been generated, the DFRTT model will be used to estimate the aquifer parameters. To continue the work outlined in this thesis, DFRTTs are planned for well-documented contaminated sites.

The purpose of this research is to find ways to create an omnidirectional antenna with high directivity in the vertical plane. The investigation is based on computer simulation using the program CST 2011. The objective is a narrow-band antenna that is omnidirectional in the horizontal plane and has maximum achievable directivity for a fixed size. Three of the most promising antenna designs are selected based on the current state of antenna technology. Their maximum directivities are estimated by means of well known relations in antenna theory. It is shown that the most suitable design is an omnidirectional antenna in the form of a cylindrical dipole antenna array with an active central dipole. For this antenna, excitation by means of a radial traveling wave, with a phase velocity smaller than speed of the light, is possible. It is found that for a certain value of a moderating factor it is possible to obtain a directivity that is 2.5 – 3 dB larger than that of a dipole or a linear antenna with uniform excitation. The antenna structures are modeled to determine the number of dipoles, their dimensions and the spacing between them that maximizes the directivity.