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Advanced Backscattering Simulation Methods for the Design of Spaceborne Radar SoundersGerekos, Christopher 23 April 2020 (has links)
Spaceborne radar sounders are an important class of remote sensing instruments which operate by recording backscattered electromagnetic waves in the vicinity of a solid planetary body. The incoming waves are generally transmitted by the radar itself (active sounding), although external signals of opportunity can also be used (passive sounding). There are currently two major planetary radar sounders under development, both headed to the Jovian icy moons (Europa, Ganymede and Callisto). Designing a radar sounder is a very challenging process involving careful leveraging of heritage and predictive tools, and in which backscattering simulators play a central role. This is especially true for coherent simulators, due to their higher accuracy and the possibility they offer to apply advanced processing techniques on the resulting simulated data, such as synthetic aperture radar focusing, or any other operation which requires field amplitude, phase and polarisation. For this reason, designing computationally-efficient coherent simulators is an important and active research area. The first contribution of this thesis is a novel multilayer coherent simulator based on the Stratton-Chu equation and the linear phase approximation, which can generate realistic simulated radar data on a wide range of surface and subsurface digital elevation models (DEM), using only a fraction of the computational resources that a finite-difference time-domain method would need. Thorough validation was conducted against both theoretical formulations and real data, which confirmed the accuracy of the method. The method was then generalised to noisy active and passive sounding, which is an important capability in the context of the proposed use of passive sounding on the Jovian icy moons. Provided that representative information about the surface and this external field exists, the simulator could compare the relative scientific value of active and passive sounding of a given target under given conditions. However, quality DEMs of the Jovian icy moons are scarce. For this reason we also present a comparative study of the fractal roughness of Europa and Mars (a much better studied body), where we derive fractal analogue maps of twelve types of Europan terrains on Mars. These maps could be used to guide the choice of Martian DEMs on which to perform representative backscattering simulations for future radar missions on Europa. Finally, we explore the possibility of entirely new radar architectures with the novel concept of the distributed radar. In a distributed sounder, very large across-track antennas can be synthesised from smallsats flying on selected orbits, providing a way to obtain a highly-directive antenna without the need to deploy large and complex structures in space. We develop an analytical formulation to treat the problem of beamforming with an array affected by perturbations on the positions of its array elements, and propose a set of Keplerian parameters that enable the concept.
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”De otroliga åren” - behandlares erfarenhet av Webster-Strattons manualbaserade föräldraträningStiernborg, Anneli January 2008 (has links)
<p>Aggressivitet och utagerande beteenden hos barn är ett växande problem med konsekvenser både på individ och på samhällsnivå. Det finns idag evidensbaserade behandlingsmetoder som förebygger och behandlar barns utagerande beteendeproblem men forskningen visar att få barn får tillgång till dem. Föräldraträning är den metod som har starkast forskningsstöd. Studiens syfte är att med hjälp av kvalitativa intervjuer ge en bild av behandlares erfarenhet och upplevelse av ”De otroliga åren”, ett manualbaserat föräldraträningsprogram inom Barn och ungdomspsykiatrin samt att beskriva hur det tillämpats. Resultatet visar att 7 av 9 mottagningar som använder metoden arbetar manualtroget dvs. får med kärnkomponenterna i programmet. Detta innebär en positiv förändring jämfört med tidigare utvärderingar. Faktorer som motiverar behandlarna att följa manualen är metodens effektivitet, tillgång till handledning, tillräckligt med tid, kollegor som arbetar med metoden, tillit till forskningsbaserade metoder samt stöd från chefen.</p>
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”De otroliga åren” - behandlares erfarenhet av Webster-Strattons manualbaserade föräldraträningStiernborg, Anneli January 2008 (has links)
Aggressivitet och utagerande beteenden hos barn är ett växande problem med konsekvenser både på individ och på samhällsnivå. Det finns idag evidensbaserade behandlingsmetoder som förebygger och behandlar barns utagerande beteendeproblem men forskningen visar att få barn får tillgång till dem. Föräldraträning är den metod som har starkast forskningsstöd. Studiens syfte är att med hjälp av kvalitativa intervjuer ge en bild av behandlares erfarenhet och upplevelse av ”De otroliga åren”, ett manualbaserat föräldraträningsprogram inom Barn och ungdomspsykiatrin samt att beskriva hur det tillämpats. Resultatet visar att 7 av 9 mottagningar som använder metoden arbetar manualtroget dvs. får med kärnkomponenterna i programmet. Detta innebär en positiv förändring jämfört med tidigare utvärderingar. Faktorer som motiverar behandlarna att följa manualen är metodens effektivitet, tillgång till handledning, tillräckligt med tid, kollegor som arbetar med metoden, tillit till forskningsbaserade metoder samt stöd från chefen.
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[en] DIFFRACTION OF ELECTROMAGNETIC WAVES BY IRREGULAR SURFACES / [pt] DIFRAÇÃO POR SUPERFÍCIES IRREGULARESCARLOS GUSTAVO MIGLIORA 12 February 2008 (has links)
[pt] Este trabalho trata do problema da difração das ondas
eletromagnéticas por obstáculos do tipo gume de faca com
perfil transversal qualquer. A partir da integral de
Huygens-Fresnel (formulação escalar) e da integral de
Stratton-Chu (formulação vetorial) é estabelecida uma
solução em forma fechada para o problema, cujas
interpretação física e aplicações práticas são bastante
simples. Os resultados teóricos são verificados por
comparação com medidas experimentais para três tipos de
perfil transversal: semi-circular, triangular e rampa.
Através da mesma formulação é investigado o
comportamento
do campo atrás do obstáculo, onde existe uma região de
interferência formada pelas diversas contribuições
independentes do campo difratado. Procurou-se ainda, nos
casos dos obstáculos triangular e rampa, interpretar os
resultados finais em termos do raio da 1(primeira) zona
de Fresnel.
Embora o modelo utilizado seja limitado por não
considerar
a dimensão do obstáculo no sentido de propagação
(longitudinal), as conclusões obtidas são de grande
importância para os enlaces radioelétricos que operam
por
difração. / [en] The present work deals with the problem of the diffraction
of electromagnetic waves by knife-edge obstacles with
arbitrary transverse profile. From the Huygens-Fresnel
(acalar formulation) and the Stratton-Chu ( vectorial
formulation) integrals, a closed-form solution for the
problem is establications. The theoretical results are
verified by comparison with experimental measurements fot
three kinds od profiles: semi-circular, triangular and
ramp. Using this same formulation, the behavior of the
field behind the obstacle is investigated, where a region
of interference exists caused by the several independet
contributions of the diffracted field. An attempt was made
to interpret the final results in terms of the first
Fresnel zone radius in cases of triangular and ramp
obstacles. Although the model used here is limited for not
taking into account the longitudinal dimension of the
obstacles, the obtained conclusions have major importance
to radio links operating in diffraction.
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The Bird Woman Takes Her Stand : Gene Stratton Porter's Conservancy as seen in "A Girl of the Limberlost" and "The Harvester"Knight, Elisabeth D. January 2019 (has links)
No description available.
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