Minimização de perdas em redes veiculares com multihoming

The growing interest in Vehicular Ad-hoc NETworks (VANETs) is encouraging its deployment in new environments, allowing the development of safety and entertainment applications. Vehicles can connect to other vehicles or to the infrastructure, providing an Internet connection. The communication equipment placed inside the vehicles may have multiple network interfaces of diverse technologies, such as IEEE 802.11p/WAVE, IEEE 802.11a/g/n (Wi- Fi) and cellular. This diversity enables the exploration of Multihoming (MH) and Network Coding (NC) mechanisms which can be used to provide higher bandwidth and reliability to these services, reducing packet losses due to poor wireless signal quality, therefore improving the final Quality-of-Service (QoS). This dissertation enhances the communication quality of a MH vehicular network by improving its mobility protocol and the NC mechanisms. Specifically, changes were performed to ensure the reliability of control mobility messages to help the infrastructure to react faster to the wireless communication conditions of a mobile node. On a different perspective, it has been provided a mechanism to enable NC through different technologies being used in MH, and making use of all technologies simultaneously to code and recover the packets. Both approaches were evaluated with real systems in a laboratory scenario. The obtained results on the reliability of the control messages show that the new approach is able to provide higher communication reliability, reducing the packet losses presented in case of an abrupt disconnection, and when in presence of other connections. For the multi-technology architecture proposed for the NC, the experimental tests evaluated its impact on the effective delivery ratio and the delay. The comparative results show that the multi-technology approach integrated with MH has a better delivery ratio when compared to the single-technology, despite the small impact on the packet delay.O interesse crescente em Redes Veiculares está a encorajar a sua implementação em novos ambientes, permitindo o desenvolvimento de aplicações de segurança e de entretenimento. Os veículos podem-se ligar a outros veículos ou à infraestrutura, tendo assim uma ligação à Internet. O equipamento de comunicação colocado nos veículos poderá ter múltiplas interfaces de rede de tecnologias diferentes, como por exemplo, IEEE 802.11p/WAVE, IEEE 802.11a/g/n (Wi-Fi) e celular. Esta diversidade permite a exploração e utilização de mecanismos de Multihoming e de Network Coding, os quais podem ser usados para oferecer maior largura de banda e maior fiabilidade a este tipo de aplicações, reduzindo as perdas de pacotes na presença de um sinal sem fios de fraca qualidade, melhorando assim a qualidade de serviço. Esta dissertação tem como objetivo melhorar a qualidade de comunicação de uma rede veicular que suporta Multihoming, assim como melhorar os seus mecanismos de Network Coding e do protocolo de mobilidade. Mais especificamente, foram feitas alterações a nível do processo de handover entre redes, para ajudar a infraestrutura a reagir mais rapidamente às condições de comunicação de um nó móvel na rede. Numa perspetiva diferente, foi desenvolvido um mecanismo que permite a aplicação de Network Coding através de diferentes tecnologias em Multihoming, o qual faz uso das diferentes tecnologias simultaneamente para codificar e recuperar os pacotes. Ambos os mecanismos foram avaliados em cenários de laboratório com sistemas reais. Os resultados obtidos relativos ao envio das mensagens de controlo mostram que esta nova abordagem é capaz de fornecer uma comunicação com maior fiabilidade, reduzindo as perdas de pacotes no caso de uma desconexão abrupta, e quando na presença de outras tecnologias e ligações. Quanto à proposta de muti-tecnologia para o Network Coding, os testes experimentais avaliaram o seu impacto na taxa de entrega de pacotes efetiva e no atraso de transmissão. Os resultados comparativos evidenciam que, apesar de ter um pequeno impacto no atraso dos pacotes em comparação com a abordagem que considera o Network Coding em cada tecnologia de forma independente, a abordagem de multi-tecnologia apresenta uma melhor taxa de entrega.CMUP-ERI/TIC/0010/2014Mestrado em Engenharia Eletrónica e Telecomunicaçõe

The Long-Baseline Neutrino Experiment: Exploring Fundamental Symmetries of the Universe

The preponderance of matter over antimatter in the early Universe, the dynamics of the supernova bursts that produced the heavy elements necessary for life and whether protons eventually decay --- these mysteries at the forefront of particle physics and astrophysics are key to understanding the early evolution of our Universe, its current state and its eventual fate. The Long-Baseline Neutrino Experiment (LBNE) represents an extensively developed plan for a world-class experiment dedicated to addressing these questions. LBNE is conceived around three central components: (1) a new, high-intensity neutrino source generated from a megawatt-class proton accelerator at Fermi National Accelerator Laboratory, (2) a near neutrino detector just downstream of the source, and (3) a massive liquid argon time-projection chamber deployed as a far detector deep underground at the Sanford Underground Research Facility. This facility, located at the site of the former Homestake Mine in Lead, South Dakota, is approximately 1,300 km from the neutrino source at Fermilab -- a distance (baseline) that delivers optimal sensitivity to neutrino charge-parity symmetry violation and mass ordering effects. This ambitious yet cost-effective design incorporates scalability and flexibility and can accommodate a variety of upgrades and contributions. With its exceptional combination of experimental configuration, technical capabilities, and potential for transformative discoveries, LBNE promises to be a vital facility for the field of particle physics worldwide, providing physicists from around the globe with opportunities to collaborate in a twenty to thirty year program of exciting science. In this document we provide a comprehensive overview of LBNE's scientific objectives, its place in the landscape of neutrino physics worldwide, the technologies it will incorporate and the capabilities it will possess.Comment: Major update of previous version. This is the reference document for LBNE science program and current status. Chapters 1, 3, and 9 provide a comprehensive overview of LBNE's scientific objectives, its place in the landscape of neutrino physics worldwide, the technologies it will incorporate and the capabilities it will possess. 288 pages, 116 figure

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

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements

The DUNE Far Detector Interim Design Report, Volume 3: Dual-Phase Module

The DUNE IDR describes the proposed physics program and technical designs of the DUNE far detector modules in preparation for the full TDR to be published in 2019. It is intended as an intermediate milestone on the path to a full TDR, justifying the technical choices that flow down from the high-level physics goals through requirements at all levels of the Project. These design choices will enable the DUNE experiment to make the ground-breaking discoveries that will help to answer fundamental physics questions. Volume 3 describes the dual-phase module's subsystems, the technical coordination required for its design, construction, installation, and integration, and its organizational structure

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