1,394 research outputs found

    Regional variation in diagnosis, prognosis and treatment of Guillain-Barré syndrome

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    Regional variation in diagnosis, prognosis and treatment of Guillain-Barré syndrome

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    Beam scanning by liquid-crystal biasing in a modified SIW structure

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    A fixed-frequency beam-scanning 1D antenna based on Liquid Crystals (LCs) is designed for application in 2D scanning with lateral alignment. The 2D array environment imposes full decoupling of adjacent 1D antennas, which often conflicts with the LC requirement of DC biasing: the proposed design accommodates both. The LC medium is placed inside a Substrate Integrated Waveguide (SIW) modified to work as a Groove Gap Waveguide, with radiating slots etched on the upper broad wall, that radiates as a Leaky-Wave Antenna (LWA). This allows effective application of the DC bias voltage needed for tuning the LCs. At the same time, the RF field remains laterally confined, enabling the possibility to lay several antennas in parallel and achieve 2D beam scanning. The design is validated by simulation employing the actual properties of a commercial LC medium

    Eficiência de acoplamento entre fibras de cristal fotônico e circuitos integrados fotônicos

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    Research interest: In this dissertation, the coupling problem between silicon nanoguides and the "outside world,"namely an optical fiber, was numerically investigated using the FDTD method. The process of guiding light from the fiber into a nanoguide is referred to as optical coupling, and the coupling problem arises from the dimensional incompatibility between the conventional optical fiber core and the cross-sectional area of the integrated nanoguides. Currently, this is one of the most significant challenges faced by researchers in the field of silicon nanophotonics. Although the manufacturing of silicon photonic devices has achieved high quality due to compatibility with CMOS fabrication processes, the transition at the interface between the fiber and the nanoguide is characterized by considerable insertion losses due to the coupling problem. Thus, solving this problem holds great importance for the application of silicon photonic integrated circuits in optical communications.. Objectives: The objective of this work is to address the coupling interface problem between optical fibers and silicon nanoguides, using photonic crystal fibers instead of conventional optical fibers. For this purpose, uniform Bragg gratings are employed as a coupling technique, and the coupling efficiency to the photonic crystal fiber is investigated through numerical simulations, considering the coupling angle, lattice parameters, as well as the physical parameters of the fiber, specifically the air hole diameter. Therefore, this study focuses on the examination, modeling, and optimization of the coupling technique using Bragg gratings to achieve efficient coupling between photonic crystal fibers and silicon nanoguides. Results obtained: The simulations results show that efficient coupling can be achieved between photonic crystal fibers and SOI waveguides. The coupling efficiency was investigated based on two types of uniform Bragg couplers. The first one is a simple grating coupler etched on the surface of a nanoguide integrated in the SOI platform. The second one is a Bragg grating coupler with a bottom metallic reflector. In the latter, a gold reflector was added to maximize the reflection at the oxide/substrate interface of the SOI platform and reuse the radiated energy to the substrate. Efficiency simulations with the standard coupler demonstrate a maximum coupling efficiency of 32.6% at a coupling angle of 10◦. Meanwhile, a maximum coupling efficiency of 70.3% is demonstrated when the reflector is added. Furthermore, an interesting dependence of the coupling efficiency on the air hole diameter of the photonic crystal fibers has also been determined, indicating that this parameter should be appropriately chosen to optimize the coupling efficiency.Interesse de pesquisa: Nesta dissertação, o problema do acoplamento entre nanoguias de silício e o "mundo exterior", ou seja, uma fibra óptica, foi investigado numericamente por meio do método FDTD. O processo de inserção de luz da fibra para um nanoguia é chamado de acoplamento óptico. O problema de acoplamento surge da incompatibilidade dimensional entre o convencional núcleo de fibra óptica e a seção transversal dos nanoguias integrados. Atualmente, este é um dos problemas mais importantes enfrentados pelos pesquisadores na área de nanofotônica de silício. Embora a fabricação de dispositivos fotônicos de silício tenha alcançado alta qualidade devido à compatibilidade com os processos de fabricação CMOS, a transição na interface entre a fibra e o nanoguia é governada por consideráveis perdas de inserção devido ao problema de acoplamento. Portanto, a solução deste problema é de grande importância para a aplicação dos circuitos integrados fotônicos de silício nas comunicações ópticas. Objetivos: O objetivo deste trabalho é abordar o problema de interface de acoplamento entre fibras ópticas e nanoguias de silício, utilizando fibras de cristal fotônico em vez de fibras ópticas convencionais. Para tal, são utilizadas redes de Bragg uniformes como técnica de acoplamento, e a eficiência de acoplamento à fibra de cristal fotónico é investigada através de simulações numéricas, considerando o ângulo de acoplamento, parâmetros de grade, bem como os parâmetros físicos da fibra, nomeadamente o diâmetro dos furos de ar. Portanto, este trabalho foca no estudo, modelagem e otimização da técnica de acoplamento usando grades de Bragg para obter um acoplamento eficiente entre fibras de cristal fotônico e nanoguias de silício. Resultados obtidos: Os resultados das simulações mostram que um acoplamento eficiênte pode ser obtido entre fibras de cristal fotônico e nanoguias SOI. A eficiência de acoplamento foi investigada com base em dois tipos de acopladores de Bragg uniformes. O primeiro é um acoplador de grade simples gravado na superfície de um nanoguia integrado na plataforma SOI. O segundo é um acoplador de grade de Bragg com um refletor metálico inferior. Neste último, um refletor de ouro foi adicionado para maximizar a reflexão na interface óxido/substrato da plataforma SOI e reutilizar a energia irradiada para o substrato. As simulações de eficiência com o acoplador padrão demonstram uma eficiência máxima de acoplamento de 32.6%, em um ângulo de acoplamento de 10◦. Enquanto isso, uma eficiência máxima de acoplamento de 70.3% é demonstrada quando o refletor é adicionado. Além disso, determinou-se também uma interessante dependência da eficiência de acoplamento em função do diâmetro dos furos de ar das fibras de cristal fotônico, de modo que este parâmetro deve ser escolhido adequadamente para otimizar a eficiência de acoplamento

    Resilient and Scalable Forwarding for Software-Defined Networks with P4-Programmable Switches

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    Traditional networking devices support only fixed features and limited configurability. Network softwarization leverages programmable software and hardware platforms to remove those limitations. In this context the concept of programmable data planes allows directly to program the packet processing pipeline of networking devices and create custom control plane algorithms. This flexibility enables the design of novel networking mechanisms where the status quo struggles to meet high demands of next-generation networks like 5G, Internet of Things, cloud computing, and industry 4.0. P4 is the most popular technology to implement programmable data planes. However, programmable data planes, and in particular, the P4 technology, emerged only recently. Thus, P4 support for some well-established networking concepts is still lacking and several issues remain unsolved due to the different characteristics of programmable data planes in comparison to traditional networking. The research of this thesis focuses on two open issues of programmable data planes. First, it develops resilient and efficient forwarding mechanisms for the P4 data plane as there are no satisfying state of the art best practices yet. Second, it enables BIER in high-performance P4 data planes. BIER is a novel, scalable, and efficient transport mechanism for IP multicast traffic which has only very limited support of high-performance forwarding platforms yet. The main results of this thesis are published as 8 peer-reviewed and one post-publication peer-reviewed publication. The results cover the development of suitable resilience mechanisms for P4 data planes, the development and implementation of resilient BIER forwarding in P4, and the extensive evaluations of all developed and implemented mechanisms. Furthermore, the results contain a comprehensive P4 literature study. Two more peer-reviewed papers contain additional content that is not directly related to the main results. They implement congestion avoidance mechanisms in P4 and develop a scheduling concept to find cost-optimized load schedules based on day-ahead forecasts

    Integrated widely tunable laser systems at 1300 and 1550 nm as swept sources for optical coherence tomography

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    Cognitive and Autonomous Software-Defined Open Optical Networks

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    L'abstract è presente nell'allegato / the abstract is in the attachmen

    Challenges and Opportunities in Wireless Fronthaul

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    To date the evolution from traditional distributed radio access networks (D-RAN) towards fronthaul oriented centralized (C-RAN) architectures has imposed significant challenges for the underlying transport network. The processing and coordination benefits anticipated in C-RAN are generally underpinned with the assumption of a full fiber transport network capable of meeting the demanding performance criteria of fronthaul transport. Recent advances in Ethernet based fronthaul interfaces together with exploration of new mmWave and sub-THz spectrum bands present an opportunity for wireless solutions to also realize these fronthaul transport requirements. In this work, the requirements for promising new Ethernet based fronthaul interfaces are explored. These requirements are assessed against the measured capabilities of a state-of-the-art E-band (71-86 GHz) wireless transport solution. The experimental results are then used to forecast the performance expectations of future higher bandwidth systems operating above 100 GHz. A dimensioning and link budget analysis is performed for the various candidate spectrum bands and fronthaul interfaces to highlight the viability of fronthaul delivered over wireless transport. Finding show that transport solutions operating at mmWave and sub-THz frequencies are able to support the performance requirements of newly standardized fronthaul interface splits and as such present an opportunity to utilize wireless fronthaul transport in C-RAN architectures where fiber cannot otherwise be supported. Furthermore, analysis demonstrates that the hop lengths possible for 5G small cell configurations are well aligned with the expected inter-site distances of future dense urban cell deployments making wireless fronthaul a promising concept for realizing future C-RAN based cell densification

    National Conference on ‘Renewable Energy, Smart Grid and Telecommunication-2023

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    Theme of the Conference: “The challenges and opportunities of integrating renewable energy into the grid” The National Conference on Renewable Energy, Smart Grid, and Telecommunication - 2023 is a platform for industry experts, researchers, and policymakers to come together and explore the latest advancements and challenges in the fields of renewable energy, smart grids, and telecommunication. Conference Highlights: In-depth discussions on renewable energy technologies and innovations. Smart grid integration for a sustainable future. The role of telecommunication in advancing renewable energy solutions. Networking opportunities with industry leaders and experts. Presentation of cutting-edge research papers and case studies. Conference topics: Renewable Energy Technologies and Innovations Smart Grid Development and Implementation Telecommunication for Energy Systems Energy Storage and Grid Balancing Policy, Regulation, and Market Dynamics Environmental and Social Impacts of Renewable Energy Energy Transition and Future Outlook Integration of renewable energy into the grid Microgrids and decentralized energy systems Grid cybersecurity and data analytics IoT and sensor technologies for energy monitoring Data management and analytics in energy sector Battery storage technologies and applicationshttps://www.interscience.in/conf_proc_volumes/1087/thumbnail.jp

    Design and Service Provisioning Methods for Optical Networks in 5G and Beyond Scenarios

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    Network operators are deploying 5G while also considering the evolution towards 6G. They consider different enablers and address various challenges. One trend in the 5G deployment is network densification, i.e., deploying many small cell sites close to the users, which need a well-designed transport network (TN). The choice of the TN technology and the location for processing the 5G protocol stack functions are critical to contain capital and operational expenditures. Furthermore, it is crucial to ensure the resiliency of the TN infrastructure in case of a failure in nodes and/or links while the resource efficiency is maximized.Operators are also interested in 5G networks with flexibility and scalability features. In this context, one main question is where to deploy network functions so that the connectivity and compute resources are utilized efficiently while meeting strict service latency and availability requirements. Off-loading compute resources to large and central data centers (DCs) has some advantages, i.e., better utilization of compute resources at a lower cost. A backup path can be added to address service availability requirements when using compute off-loading strategies. This might impact the service blocking ratio and limit operators’ profit. The importance of this trade-off becomes more critical with the emergence of new 6G verticals.This thesis proposes novel methods to address the issues outlined above. To address the challenge of cost-efficient TN deployment, the thesis introduces a framework to study the total cost of ownership (TCO), latency, and reliability performance of a set of TN architectures for high-layer and low-layer functional split options. The architectural options are fiber- or microwave-based. To address the strict availability requirement, the thesis proposes a resource-efficient protection strategy against single node/link failure of the midhaul segment. The method selects primary and backup DCs for each aggregation node (i.e., nodes to which cell sites are connected) while maximizing the sharing of backup resources. Finally, to address the challenge of resource efficiency while provisioning services, the thesis proposes a backup-enhanced compute off-loading strategy (i.e., resource-efficient provisioning (REP)). REP selects a DC, a connectivity path, and (optionally) a backup path for each service request with the aim of minimizing resource usage while the service latency and availability requirements are met.Our results of the techno-economic assessment of the TN options reveal that, in some cases, microwave can be a good substitute for fiber technology. Several factors, including the geo-type, functional split option, and the cost of fiber trenching and microwave equipment, influence the effectiveness of the microwave. The considered architectures show similar latency and reliability performance and meet the 5G service requirements. The thesis also shows that a protection strategy based on shared connectivity and compute resources can lead to significant cost savings compared to benchmarks based on dedicated backup resources. Finally, the thesis shows that the proposed backup-enhanced compute off-loading strategy offers advantages in service blocking ratio and profit gain compared to a conventional off-loading approach that does not add a backup path. Benefits are even more evident considering next-generation services, e.g., expected on the market in 3 to 5 years, as the demand for services with stringent latency and availability will increase
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