Performance Evaluation of Low Complexity Massive MIMO Techniques for SC-FDE Schemes

Massive-MIMO technology has emerged as a means to achieve 5G's ambitious goals; mainly to obtain higher capacities and excellent performances without requiring the use of more spectrum. In this thesis, focused on the uplink direction, we make a study of performance of low complexity equalization techniques as well as we also approach the impact of the non-linear elements located on the receivers of a system of this type. For that purpose, we consider a multi-user uplink scenario through the Single Carrier with Frequency Domain Equalization (SC-FDE) scheme. This seems to be the most appropriate due to the low energy consumption that it implies, as well as being less favorable to the detrimental effects of high envelope fluctuations, that is, by have a low Peak to Average Power Ratio (PAPR) comparing to other similar modulations, such as the Orthogonal Frequency Division Multiplexing (OFDM). Due to the greater number of antennas and consequent implementation complexity, the equalization processes for Massive- MIMO schemes are aspects that should be simplified, that is, they should avoid the inversion of matrices, contrary to common 4G, with the Zero Forcing (ZF) and Minimum Mean Square Error (MMSE) techniques. To this end, we use low-complexity techniques, such as the Equal Gain Combining (EGC) and the Maximum Ratio Combining (MRC). Since these algorithms are not sufficiently capable of removing the entire Inter-Symbol Interference (ISI) and Inter-User Interference (IUI), we combine them with iterative techniques, namely with the Iterative Block with Decision Feedback Equalizer (IB-DFE) to completely remove the residual ISI and IUI. We also take into account the hardware used in the receivers, since the effects of non-linear distortion can impact negatively the performance of the system. It is expected a strong performance degradation associated to the high quantization noise levels when implementing low-resolution Analog to Digital Converters (ADCs). However, despite these elements with these configurations become harmful to the performance of the majority of the systems, they are considered a desirable solution for Massive-MIMO scenarios, because they make their implementation cheaper and more energy efficient. In this way, we made a study of the impact in the performance by the low-resolution ADCs. In this thesis we suggest that it is possible to bypass these negative effects by implementing a number of receiving antennas far superior to the number of transmitting antennas

Strain partitioning and westwards migration of deformation in NW Gulf of Cadiz (Africa-Iberia plate boundary)

European Geosciences Union General Assembly 2007 (EGU 2007), Vienna, Austria, 15-20 April 200

Deep Submarine Giant Scours in northern Gulf of Cadiz (offshore SW Iberia) : a singular case of sedimentary and tectonic coupling

European Geosciences Union General Assembly 2007 (EGU 2007), Vienna, Austria, 15-20 April 200

Para o estudo da evolução do ensino e da formação em administração educacional em Portugal

Estudos sobre a evolução do ensino de disciplinas, na formação de professores em Portugal, são recentes. O controle burocrático centralizado reteve as dimensões do controle político-administrativo. De certo modo, protegeu a esfera educativa das influências modernizantes, do capitalismo industrial e das lógicas mercantis e gerencialistas. Defendeu a educação do domínio político, da intervenção de movimentos sociais, das propagandas de ideais democráticos e da cidadania. A utilização da designação "Administração educacional" ilustra as dificuldades sentidas, ao longo dos últimos anos, em termos da construção acadêmica de uma área, seja pela falta de tradição, seja pelos antecedentes históricos.In Portugal, studies about the evolution of disciplines teaching in the teachers formation are recent. The centralized bureaucratic control has held back the dimensions of politic administrative control. In a certain way, it has protected the education against the new-fashioned influences, manufacturing capitalism, and mercantile and managerial logics. This centralized bureaucratic control has also profected the education against the politic dominion, the intervention of social movements, the advertising of democratic ideals, and against the citizenship. The use of the term "Educational administration" shows the difficulties met by the searchers along the latest years, since there is no tradiction nor historic antecedence

O que as revisões sistemáticas dizem sobre o impacto da cirurgia robótica na neurocirurgia?

Introduction: Neurosurgery, with its intricate complexities and demands for extreme precision, has been shaped and transformed over the years by the constant evolution of medical technology. Methodology: The methodology adopted for this work involved a systematic literature review focused on specific MESH descriptors, conducted in the PUBMED database. The period considered for article searches spanned from 2017 to 2023, aiming to capture the latest contributions to the topic. The selected MESH descriptors to outline the research were "Robotic Surgical Procedures," "Neurosurgery," and "Minimally Invasive Surgical Procedures." Results: Systematic reviews present a comprehensive overview of recent advances in robotic surgery and its applications in various areas. The promising landscape outlined by these analyses not only validates the progress made but also underscores the ongoing need for research and development to further enhance surgical practices. Conclusion: The learning curve, the need for specialized training, and economic considerations are crucial aspects shaping the practical implementation of robotic surgery in the neurosurgical scenario.Introdução: A neurocirurgia, com suas complexidades intricadas e demandas por precisão extrema, tem sido moldada e transformada ao longo dos anos pela constante evolução da tecnologia médica. Metodologia: A metodologia adotada para este trabalho compreendeu uma revisão sistemática de literatura, focada em descritores MESH específicos, realizada no banco de dados PUBMED. O período considerado para a busca de artigos abrangeu de 2017 a 2023, visando capturar as mais recentes contribuições à temática. Os descritores MESH selecionados para delinear a pesquisa foram "Robotic Surgical Procedures", "Neurosurgery" e "Minimally Invasive Surgical Procedures". Resultado: As revisões sistemáticas apresentam um panorama abrangente dos avanços recentes na cirurgia robótica e suas aplicações em diversas áreas. O cenário promissor delineado por essas análises não apenas valida os progressos alcançados, mas também ressalta a necessidade contínua de pesquisa e desenvolvimento para aprimorar ainda mais as práticas cirúrgicas. Conclusão: A curva de aprendizado, a necessidade de treinamento especializado e as considerações econômicas são aspectos cruciais que moldam a implementação prática da cirurgia robótica no cenário neurocirúrgico

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear un derstanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5–7 vast areas of the tropics remain understudied.8–11 In the American tropics, Amazonia stands out as the world’s most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepre sented in biodiversity databases.13–15 To worsen this situation, human-induced modifications16,17 may elim inate pieces of the Amazon’s biodiversity puzzle before we can use them to understand how ecological com munities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple or ganism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region’s vulnerability to environmental change. 15%–18% of the most ne glected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lostinfo:eu-repo/semantics/publishedVersio

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear understanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5,6,7 vast areas of the tropics remain understudied.8,9,10,11 In the American tropics, Amazonia stands out as the world's most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepresented in biodiversity databases.13,14,15 To worsen this situation, human-induced modifications16,17 may eliminate pieces of the Amazon's biodiversity puzzle before we can use them to understand how ecological communities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple organism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region's vulnerability to environmental change. 15%–18% of the most neglected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lost