Spiral groove face seal development for SNAP 8 Final report, 31 May 1968 - 7 Aug. 1970

Spiral groove face seal development for SNAP

Multimedia content delivery for emerging satellite networks

Multimedia content delivery over satellite systems is considered as a promising service in the emerging networks. The aim of this work is to design a novel radio resource management (RRM) algorithm for efficiently managing multicast multimedia content transmission over satellite network. The proposed approach performs the spectrum management on a per-group basis, by splitting multicast terminals into different subgroups according to the experienced channel qualities. We demonstrate that subgrouping policy defined by the authors as multicast subgrouping-maximum satisfaction index (MS-MSI), is based on a new metric (i.e., MSI), which overcomes the weakness of the previous techniques proposed in literature and provides the best trade-off between user throughput and fairness. As a further result, we demonstrate that MS-MSI is robust to the long propagation delay of satellite links. An extensive simulation campaign has been conducted by considering several satellite environments

[email protected] Flashover Tests Under Wet Conditions on Full and Sectioned UHV Insulators

(1) CEPEL, (2) FURNAS, (3) ELETROBRÁS BRAZIL SUMMARY This paper aims to be a contribution to the current discussion about dielectric test procedures for full UHV insulators under wet conditions. It presents results of wet power frequency flashover voltage tests performed on 800 kV porcelain multicone type post insulators, composed by two sections with metal fittings between them. UV images were used to observe the differences among the profiles of discharge activities when testing each section at a time in a separated test arrangement and in a full insulator test arrangement with one section short-circuited, compared to the case of testing the complete insulator. It was observed that none of the simplified test arrangement considered was able to represent or to be useful to replace the test on full insulators under artificial rain. It was also verified that the extrapolation of flashover test results on insulator sections may lead to values greater the values obtained for full insulators

Resource Queuing System with Preemptive Priority for Performance Analysis of 5G NR Systems

One of the ways to enable smooth coexistence of ultra reliable low latency communication (URRLC) and enhances mobile broadband (eMBB) services at the air interface of perspective 5G New Radio (NR) technology is to utilize preemptive priority service. In this paper, we provide approximate analysis of the queuing system with random resource requirements, two types of customers and preemptive priority service procedure. The distinctive feature of the systems – the random resource requirements – allows to capture the essentials of 5G NR radio interface but inherently increases the complexity of analysis. We present the main performance metrics of interest including session drop probability and system resource utilization as well as assess their accuracy by comparing with computer simulations. The developed model is not inherently limited to URLLC and eMBB coexistence and can be utilized in performance evaluation of 5G NR systems with priority-based service discipline at the air interface, e.g., in context of network slicing. Among other conclusions we explicitly show that both session drop and interruption probabilities of low priority traffic heavily depend not only on the intensity of high priority traffic but on stochastic characteristics of the resource request distribution.acceptedVersionPeer reviewe

NB-IoT for D2D-enhanced content uploading with social trustworthiness in 5G systems

Future fifth-generation (5G) cellular systems are set to give a strong boost to the large-scale deployment of Internet of things (IoT). In the view of a future converged 5G-IoT infrastructure, cellular IoT solutions such as narrowband IoT (NB-IoT) and device-to-device (D2D) communications are key technologies for supporting IoT scenarios and applications. However, some open issues still need careful investigation. An example is the risk of threats to privacy and security when IoT mobile services rely on D2D communications. To guarantee efficient and secure connections to IoT services involving exchange of sensitive data, reputation-based mechanisms to identify and avoid malicious devices are fast gaining ground. In order to tackle the presence of malicious nodes in the network, this paper introduces reliability and reputation notions to model the level of trust among devices engaged in an opportunistic hop-by-hop D2D-based content uploading scheme. To this end, social awareness of devices is considered as a means to enhance the identification of trustworthy nodes. A performance evaluation study shows that the negative effects due to malicious nodes can be drastically reduced by adopting the proposed solution. The performance metrics that proved to benefit from the proposed solution are data loss, energy consumption, and content uploading time. © 2017 by the authors

NB-IoT for D2D-enhanced content uploading with social trustworthiness in 5G systems

Future fifth-generation (5G) cellular systems are set to give a strong boost to the large-scale deployment of Internet of things (IoT). In the view of a future converged 5G-IoT infrastructure, cellular IoT solutions such as narrowband IoT (NB-IoT) and device-to-device (D2D) communications are key technologies for supporting IoT scenarios and applications. However, some open issues still need careful investigation. An example is the risk of threats to privacy and security when IoT mobile services rely on D2D communications. To guarantee efficient and secure connections to IoT services involving exchange of sensitive data, reputation-based mechanisms to identify and avoid malicious devices are fast gaining ground. In order to tackle the presence of malicious nodes in the network, this paper introduces reliability and reputation notions to model the level of trust among devices engaged in an opportunistic hop-by-hop D2D-based content uploading scheme. To this end, social awareness of devices is considered as a means to enhance the identification of trustworthy nodes. A performance evaluation study shows that the negative effects due to malicious nodes can be drastically reduced by adopting the proposed solution. The performance metrics that proved to benefit from the proposed solution are data loss, energy consumption, and content uploading time. © 2017 by the authors

Federated IoT services leveraging 5G technologies at the edge

The Internet of Things (IoT) ecosystem is evolving towards the deployment of integrated environments, wherein heterogeneous devices pool their capacities together to match wide-ranging user and service requirements. As a consequence, solutions for efficient and synergistic cooperation among objects acquire great relevance. Along this line, this paper focuses on the adoption of the promising MIFaaS (Mobile-IoT-Federation-as-a-Service) paradigm to support delay-sensitive applications for high-end IoT devices in next-to-come fifth generation (5G) environments. MIFaaS fosters the provisioning of IoT services and applications with low-latency requirements by leveraging cooperation among private/public clouds of IoT objects at the edge of the network. A performance assessment of the MIFaaS paradigm in a cellular 5G environment based on both Long Term Evolution (LTE) and the recent Narrowband IoT (NB-IoT) is presented. Obtained results demonstrate that the proposed solution outperforms classic approaches, highlighting significant benefits derived from the joint use of LTE and NB-IoT bandwidths in terms of increased number of successfully delivered IoT services. © 2017 Elsevier B.V

3D Folded Loop UAV Antenna Design

Part 5: Aerial NetworksInternational audienceUtilization of Unmanned Aerial Vehicles (UAVs), also known as “drones”, has a great potential for many emerging applications, such as delivering the connectivity on-demand, providing services for public safety, or recovering after damage to the communication infrastructure. Notably, nearly any application of drones requires a stable link to the ground control center, yet this functionality is commonly added at the last moment in the design, necessitating compact antenna designs. In this work, we propose a novel electrically small antenna element based on the 3D folded loop topology, which could be easily located inside the UAV airframe, yet still delivering good isolation from the drones own noise sources. The complete manufacturing technique along with corresponding simulations/measurements are presented. Measurements and evaluations show that the proposed antenna design is an option to achieve genuinely isotropic radiation in a small size without sacrificing efficiency