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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Advanced Methods for Generating and Processing Simulated Radar Sounder Data for Planetary Missions

Sbalchiero, Elisa 17 October 2022 (has links)
Radar sounders (RS) are active instruments that have proved to be able to profile the subsurface of planetary bodies. The design of RS instruments, as well as the interpretation of the acquired data, is a non-trivial task due to the complexity of the scenario of acquisition and the limited amount of information on the targets (especially in planetary exploration). In this context, data simulations are necessary to support the design of the radar, the development of the related processing chain, and the definition of algorithms for the automatic analysis of data. However, state-of-the-art RS simulation methods are characterized by different trade-offs between simulation accuracy and computational costs. On the one hand, numerical methods, such as the Finite-Difference Time-Domain (FDTD) technique, allow to accurately model the wave-target interaction by exactly solving Maxwell's equations at the cost of very high computational requirements. On the other hand, optical methods, such as the ray-tracing based Multi-layer Coherent Simulator (MCS), rely on approximated solution of Maxwell's equations that allow for a better usage of computational resources at the cost of a less accurate modeling. Moreover, simulators produce raw or range-compressed only data, making it difficult to interpret and analyze them via direct comparison with the real data, which are typically processed also for azimuth compression. In this thesis, we present four main contributions related to the simulation of RS data to address the above-mentioned limitations. The first and second contributions thus present 3D simulations of selected targets of two new RS instruments, i.e., the Radar for Icy Moon Exploration (RIME) and the EnVision Subsurface Radar Sounder (SRS). The simulations are performed with the FDTD and MCS simulators. Despite producing good results in terms of detection probability of the selected targets, these two contributions highlight the above-mentioned gaps in the literature of simulation of RS data. The first main limitation is the lack of methods that can accurately model both large and small-scale scattering phenomena at relatively low computational costs. This problem is addressed by the third contribution of this thesis, which presents a novel integrated simulation technique that models both large and small-scale surface scattering phenomena by combining the advantages of the FDTD and MCS techniques, in an accurate and computationally efficient way. The second problem identified is the lack of SAR processing techniques to be applied to the simulated radargrams. This is addressed in the fourth contribution which presents a range-Doppler method for focusing raw radar sounder data simulated with 3D coherent electromagnetic simulators. The method is general and can be applied to any electromagnetic simulator, and is demonstrated for both the FDTD and MCS methods. The results presented throughout the thesis indicate that the proposed methods advance the state-of-the-art of techniques for both generating and processing simulated RS data.
2

CSR, Glocalisation and Football

Rosell, Nathanael Tim January 2015 (has links)
AbstraktNyckelord: Globalisering, Amerikanisering, Europanisering, Glokaliseringoch CSRFörfattare: Tim Nathanael RosellHandledare: Bo Carlsson och Gun NormarkTitel: CSR, Glokalisering och Fotboll – En jämförelse mellan amerikanskoch svensk fotboll.Problem: I den begränsade svenska sport modellen söker klubbar attattrahera sponsorer, skapa intäkter och vinna fördelar översina konkurrenter. Problemet är att hitta en ekonomistyrningsmetodkompatibel med det interna regelverket.Syfte: Syftet är att belysa gloaliseringsprocesser inom fotboll ochundersöka CSR konceptet i kontexten av Seattle Soundersoch Djurgården IF.Metod: Den här uppsatsen antar en hermeneutisk ansats via en deduktivtillvägagångssätt. Således ger litteraturgenomgångenen grundläggande förståelse för ämnet, där två fallstudierbehandlar det teoretiska ramverket. Fallstudierna med DjurgårdenIF och Seattle Sounders kontextualiserar och behandlarde diverse begrepp som presenteras.Slutsats: Även fast Djurgården IF och Seattle Sounders har olika utmaningargällande regelverk, organisatoriska strukturer ochkapital medger de vikten av CSR. Vidare visar fallstudiernaatt CSR är glokaliserat och att amerikanisering inte är en envägsprocess. / AbstractKeywords: Globalisation, Americanisation, Europeanisation, Glocalisationand CSRAuthor: Tim Nathanael RosellSupervisors: Bo Carlsson and Gun NormarkTitle: CSR, Glocalisation and Football - A comparison betweenAmerican and Swedish footballProblem: In the restricted Swedish Sports model, clubs in Swedenaims attract sponsors, create revenue and gain an advantageover their competitors. The problem is finding an economicgovernance method compatible with the internal legislativesystem.Purpose: The purpose is to illuminate globalisation processes in footballand investigate the concept of CSR in the context of SeattleSounders and Djurgården IF.Method: This thesis adopts a hermeneutical shoulder via a deductiveapproach. Thus, a literature review provides the basal understandingof the subject and two case studies treat the theoreticalframework. The two case studies, Djurgården IF and SeattleSounders, contextualise and treat the various conceptspresented.Conclusion: Although Djurgården IF and Seattle Sounders have differentchallenges regarding legislations, organisational structuresand capital, they recognise the importance of CSR. Furthermore,the case studies showed that the notion of CSR is glocalisedand that Americanisation is not a one-way process
3

Observations of the South Atlantic Subtropical Mode Water using PIES data / Observações da Água Modal Subtropical Sul utilizando dados PIES

Matheus Vasconcellos Cortezi 18 August 2017 (has links)
Subtropical mode water is a voluminous body of water in the ocean whose main feature is the homogeneity in both vertical structure and horizontal extension. The subtropical mode water (STMW) of the southwest Atlantic is formed between the months of July and October near the Brazil-Malvinas confluence and along the Brazil Current recirculation gyre. The formation region extends on the order of 3000 km zonally, from 20°W to 50°W, and 1000 km meridionally, from 30°S to 40°S, and it is typically about 170 m thick. In situ data from pressure-equipped inverted echo sounders (PIES) installed in the western portion of the basin, along 34.5°S, are available from 2009 to the present. These data after processed and calibrated can provide an unprecedented description of the STMW involving processes since its formation at the surface until the final stage of its residence in the interior of the ocean. Temperature and salinity data estimated by the PIES are based on empirical look-up tables that relate the acoustic travel time with the baroclinic structure of the ocean. This technique is known as the Gravest Empirical Mode (GEM), and here it is used to detect profiles containing homogeneous segments of temperature and salinity that characterize the mode water. The GEM method was seasonally corrected to reconstruct surface variability necessary for STMW formation. The interannual covariance between STMW layer thickness and the Brazil Current was calculated, but no significant correlation at that time scale was observed. The mode water layer detected was about 220 m ± 55 m thick on all sites, agreeing with previous studies. / A água modal subtropical é um grande volume de água no oceano cuja característica principal é a homogeneidade nas estruturas vertical e horizontal. A água modal subtropical do sudoeste do Atlântico é formada entre os meses de julho e outubro perto da confluência Brasil-Malvinas e ao longo da recirculação da Corrente do Brasil. A região de formação se estende na ordem de 3000 km zonalmente, de 20°W a 50°W e 1000 km meridionalmente, de 30°S a 40°S, e tipicamente tem cerca de 170 m de espessura. Dados in situ de ecossondas invertidas com sensor de pressão (PIES) instaladas na porção ocidental da bacia, ao longo de 34,5°S, estão disponíveis a partir de 2009 até o presente. Estes dados após o processamento e calibração podem fornecer uma descrição sem precedentes da Água Modal Subtropical do Atlântico Sul envolvendo processos desde sua formação na superfície até o estágio final de sua permanência no interior do oceano. Os dados de temperatura e salinidade estimados pelos PIES são baseados em tabelas de referência (look-up tables) que relacionam o tempo de retorno do sinal acústico com a estrutura baroclínica do oceano. Esta técnica é conhecida como o Gravest Empirical Mode (GEM),e aqui é usado para detectar perfis contendo segmentos homogêneos de temperatura e salinidade que caracterizam a água modal. Foi aplicada uma correção sazonal ao método GEM para reconstruir a variabilidade da superfície necessária para a formação STMW. A covariância interanual entre a espessura da camada STMW e a corrente do Brasil foi calculada, mas não foi observada correlação significativa naquela escala de tempo. A camada de água em modo detectada foi de cerca de 220 m ± 55 m de espessura em todos os sites, concordando com estudos prévios.
4

Observations of the South Atlantic Subtropical Mode Water using PIES data / Observações da Água Modal Subtropical Sul utilizando dados PIES

Cortezi, Matheus Vasconcellos 18 August 2017 (has links)
Subtropical mode water is a voluminous body of water in the ocean whose main feature is the homogeneity in both vertical structure and horizontal extension. The subtropical mode water (STMW) of the southwest Atlantic is formed between the months of July and October near the Brazil-Malvinas confluence and along the Brazil Current recirculation gyre. The formation region extends on the order of 3000 km zonally, from 20°W to 50°W, and 1000 km meridionally, from 30°S to 40°S, and it is typically about 170 m thick. In situ data from pressure-equipped inverted echo sounders (PIES) installed in the western portion of the basin, along 34.5°S, are available from 2009 to the present. These data after processed and calibrated can provide an unprecedented description of the STMW involving processes since its formation at the surface until the final stage of its residence in the interior of the ocean. Temperature and salinity data estimated by the PIES are based on empirical look-up tables that relate the acoustic travel time with the baroclinic structure of the ocean. This technique is known as the Gravest Empirical Mode (GEM), and here it is used to detect profiles containing homogeneous segments of temperature and salinity that characterize the mode water. The GEM method was seasonally corrected to reconstruct surface variability necessary for STMW formation. The interannual covariance between STMW layer thickness and the Brazil Current was calculated, but no significant correlation at that time scale was observed. The mode water layer detected was about 220 m ± 55 m thick on all sites, agreeing with previous studies. / A água modal subtropical é um grande volume de água no oceano cuja característica principal é a homogeneidade nas estruturas vertical e horizontal. A água modal subtropical do sudoeste do Atlântico é formada entre os meses de julho e outubro perto da confluência Brasil-Malvinas e ao longo da recirculação da Corrente do Brasil. A região de formação se estende na ordem de 3000 km zonalmente, de 20°W a 50°W e 1000 km meridionalmente, de 30°S a 40°S, e tipicamente tem cerca de 170 m de espessura. Dados in situ de ecossondas invertidas com sensor de pressão (PIES) instaladas na porção ocidental da bacia, ao longo de 34,5°S, estão disponíveis a partir de 2009 até o presente. Estes dados após o processamento e calibração podem fornecer uma descrição sem precedentes da Água Modal Subtropical do Atlântico Sul envolvendo processos desde sua formação na superfície até o estágio final de sua permanência no interior do oceano. Os dados de temperatura e salinidade estimados pelos PIES são baseados em tabelas de referência (look-up tables) que relacionam o tempo de retorno do sinal acústico com a estrutura baroclínica do oceano. Esta técnica é conhecida como o Gravest Empirical Mode (GEM),e aqui é usado para detectar perfis contendo segmentos homogêneos de temperatura e salinidade que caracterizam a água modal. Foi aplicada uma correção sazonal ao método GEM para reconstruir a variabilidade da superfície necessária para a formação STMW. A covariância interanual entre a espessura da camada STMW e a corrente do Brasil foi calculada, mas não foi observada correlação significativa naquela escala de tempo. A camada de água em modo detectada foi de cerca de 220 m ± 55 m de espessura em todos os sites, concordando com estudos prévios.
5

Progress in space weather modeling in an operational environment

Tsagouri, I., Belehaki, A., Bergeot, N., Cid, C., Delouille, V., Egorova, T., Jakowski, N., Kutiev, I., Mikhailov, A., Nunez, M., Pietrella, M., Potapov, A., Qahwaji, Rami S.R., Tulunay, Y., Velinov, P., Viljanen, A. January 2013 (has links)
Yes / This paper aims at providing an overview of latest advances in space weather modeling in an operational environment in Europe, including both the introduction of new models and improvements to existing codes and algorithms that address the broad range of space weather's prediction requirements from the Sun to the Earth. For each case, we consider the model's input data, the output parameters, products or services, its operational status, and whether it is supported by validation results, in order to build a solid basis for future developments. This work is the output of the Sub Group 1.3 "Improvement of operational models'' of the European Cooperation in Science and Technology (COST) Action ES0803 "Developing Space Weather Products and services in Europe'' and therefore this review focuses on the progress achieved by European research teams involved in the action.

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