Stable Recovery from the Magnitude of Symmetrized Fourier Measurements

In this note we show that stable recovery of complex-valued signals $x\in\mathbb{C}^n$ up to global sign can be achieved from the magnitudes of $4n-1$ Fourier measurements when a certain "symmetrization and zero-padding" is performed before measurement ($4n-3$ is possible in certain cases). For real signals, symmetrization itself is linear and therefore our result is in this case a statement on uniform phase retrieval. Since complex conjugation is involved, such measurement procedure is not complex-linear but recovery is still possible from magnitudes of linear measurements on, for example, $(\Re(x),\Im(x))$.Comment: 4 pages, will be submitted to ICASSP1

The dynamics of migration and their impact on the country of origin: A case study of Senegalese labour migrants on the Cape Verdean Island Boa Vista and their relatives at home

As a result of economic growth and the extension of the tourism sector since the beginning of the new millennium, Cape Verde has become a destination for a growing number of migrants from continental West Africa, especially from other ECOWAS member states. After migrants from Guinea-Bissau, Senegalese build the second biggest community of ECOWAS migrants. This thesis addresses migration processes between Senegal and the Cape Verdean Island Boa Vista. The focus lies on migration motives, migration patterns and aspects, which influence the choice of Cape Verde as destination. Furthermore it analyses the flow of remittances and how the situation of the migrants on the island Boa Vista influences this monetary flow. Finally, the influence of these remittances on the lives of the migrants’ families in Senegal and how they are used is examined. Households in Senegal spend a high percentage of their income on food, and they often depend on the support of migrated household members. Families try to minimize risk of food insecurity through the diversification of income resources, and migration is one coping strategy to do so. Empirical data from research in Cape Verde and Senegal are used for the analysis of the above mentioned factors. This thesis seeks to add knowledge about remittances in the environment of intra-continental migration in West Africa, and more specifically about the relatively new and until now barely researched phenomenon of immigration to Cape Verde.O crescimento económico e a extensão do sector do turismo sobretudo nos últimos vinte anos fez de Cabo Verde um destino para um número crescente de migrantes da África Ocidental, especialmente de outros estados membros da CEDEAO, desde o início do nova milénio. Senegaleses formam a segunda maior comunidade de imigrantes da CEDEAO, depois de migrantes da Guiné-Bissau. Esta tese aborda os processos de migração entre o Senegal e a ilha de Boa Vista, Cabo Verde. A tese foca na análise dos motivos da migração, padrões de migração e os aspectos que influenciam a escolha de Cabo Verde como destino. Além disso, o fluxo de remessas e como a situação dos imigrantes na ilha da Boa Vista influencia esse fluxo monetário são analisados. Por fim, examinamos a influência dessas remessas na vida das famílias dos migrantes no Senegal e como elas são gastas. Dados empíricos de pesquisas de campo em Cabo Verde e Senegal são utilizados para a análise dos factores mencionados acima. Esta tese busca agregar conhecimento sobre as remessas de dinheiro no ambiente de migração intracontinental na África Ocidental, e mais especificamente sobre o relativamente novo e até agora pouco pesquisado fenómeno de imigração para Cabo Verde

Multinational Migration in the Global South: Complex and Non-linear Trajectories of Senegalese Migrants in Brazil

A growing number of studies emphasise the non-linearity of migration. Aspirations and capabilities for multinational migration often develop or change during the migration process. These dynamics have mostly been analysed with regards to movements within the European Union or to countries in the so-called ‘Global North’. This chapter aims to broaden this focus by including movements in the context of South-South migration. It discusses multinational migration by Senegalese migrants in Brazil, which is both a destination and an origin of movements that connect a variety of countries and regions. It analyses the complex trajectories of Senegalese migrants from different social and educational backgrounds and focuses on how decisions to move again from one country to another develop and which factors influence the choice of destination. Through a multi-sited qualitative case study using interview and ethnographic methods with Senegalese migrants in four Brazilian cities – São Paulo, Praia Grande, Caxias do Sul and Passo Fundo – the research examines both already-occurred movements from Cape Verde and Argentina to Brazil and aspirations to migrate further to the ‘Global North’. The findings show that these multinational migrations are mostly driven by the desire for self-improvement – financial, professional or educational – and a hierarchy of desired destinations but also a result of suddenly emerging opportunities and mediation. The movements are facilitated through the multiple transnational ties with which Senegalese migrants are connected to different places. Furthermore, the study shows how Senegalese migrants acquire new migratory capital – for example in the form of another nationality, business activities or access to new networks – and how migration experiences influence onward migration aspirations and preparations, hereby drawing attention to the active learning process which migrants experience during their trajectory.info:eu-repo/semantics/publishedVersio

Nonlinear Effects in Superconducting Quantum Interference Meta-Atoms

This thesis deals with the nonlinear aspects of superconducting quantum interference devices (SQUIDs) as magnetic meta-atoms. Such meta-atoms are usually resonant structures that constitute the basic building blocks of a metamaterial with the purpose of giving the material unconventional magnetic properties. Due to their intrinsic nonlinearity, SQUIDs exhibit a number of phenomena such as frequency tunability and multi-stability that make them attractive as controllable meta-atoms

Data Management in Large-Scale Data Collection Scenarios

Despite the progress of digitization and constant innovations in almost all industries, data collection through questionnaires is still often paper-based. The innumerable disadvantages and the unnecessary burden on the environment are obvious. And that is precisely why it is worth asking, why nothing has happened in this sector. This can be due to several reasons, for example, the lack of flexibility compared to paper is one reason why paper questionnaires are often preferred. Also costs are a factor, because especially when flexibility in the execution is required, the implementation of such a questionnaire is often expensive. This is exactly where the QuestionSys framework should help. With its configurator it offers the possibility to create complex questionnaires without previous knowledge. In addition, the web application is a good platform for managing and organizing these. And for the execution of the questionnaires there is the questionnaire application, which has been developed in the context of this bachelor thesis. Concerning this, the focus is especially on the associated data management. Therefore, it is demonstrated how the data flows can be implemented in an application like this, in order to guarantee the full range of functions also on a large scale. This also applies to the storage, management and external communication of data within the application and is always under the condition of cross-platform development and therefore being compatible to the majority of smart mobile devices. The implementation of these requirements is explained by code samples and graphical illustrations

Nonlinear Effects in Superconducting Quantum Interference Meta-Atoms = Nichtlineare Effekte in Supraleitenden Quanten-Interferenz Meta-Atomen

This thesis deals with the nonlinear aspects of superconducting quantum interference devices (SQUIDs) as magnetic meta-atoms. Such meta-atoms are usually resonant structures that constitute the basic building blocks of a metamaterial with the purpose of giving the material unconventional magnetic properties. Due to their intrinsic nonlinearity, SQUIDs exhibit a number of phenomena such as frequency tunability and multi-stability that make them attractive as controllable meta-atoms