Experimental Study of the Loosening Phenomenon of an Assembly with Multi Fixations Under Vibration in the Transversal Direction

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Multicast Tree Construction with QoS Guaranties

Multimedia applications, such as videoconferences, require an efficient management of the Quality of Service (QoS) and consist of a great number of participants which requires the use of multicast routing protocol. Unlike unicast protocol, multicast protocol handles a great number of users while minimizing both network overhead and bandwidth consumption. However, combining multicast routing and QoS guarantee is a hard challenging task, known as the delay and delay variation multicast problem. This problem is considered as an NP-complete problem, and is resolved only by heuristic solutions. In this paper, we propose a scalable multicast algorithm that tackle the delay and delay variation by exploiting the Hierarchic Tree construction concepts. In fact, the proposal algorithm guarantees QoS by: (i) reducing the network charge; (ii) decreasing the multicast delay variation. We compare the performance of our algorithm against the DDVCA (Delay and Delay Variation Constraint Algorithm) scheme and demonstrate lower multicast delay variation and efficient bandwidth utilization while maintaining lower time complexity

Behavior of single-lap bolted joint subjected to dynamic transverse load

International audienceBolted joints used in aeronautical structures are subject to vibrations, which can result in critical damage either from self-loosening or from fatigue. This study examines the dynamic behavior of a simple bolted joint assembly subjected to a rapidly varying transverse load, which induces bending of the jointed plates. The approach adopted is based on a finite element method, with a coupled bolt model and a penalty friction model, and implicit time simulation. Numerical result sets are presented and discussed

On supporting UAV based services in 5G and beyond mobile systems

Abstract While Unmanned Aerial Vehicles (UAVs) are expected to introduce disruptive innovations in our society, it is foreseen that the used communication technology is the key factor that can unlock their potential. To this end, the upcoming generation of mobile networks, 5G-and-beyond, are envisioned to be the communication standards to support diverse UAV applications. This will also enable UAVs to benefit from the limitless progress achieved in mobile systems. To facilitate the support of UAV services in 5G-and-beyond networks, this article introduces a framework that links the mobile telecommunication domain to the UAV domain. The proposed framework reflects an operational view enabling UAV operators to prepare and deploy their applications over different 5G mobile telecommunication networks. Moreover, the framework allows UAV operators to customize mobile systems in accordance with the specifications of their target services and to constantly receive analytical and statistical data on their running applications. Furthermore, in order to ensure network services (dedicated to UAV applications) over heterogeneous mobile systems, this article also discusses the federation of 5G networks

A survey and comparison of several friction force models for dynamic analysis of multibody mechanical systems

This study is aimed at examining and comparing several friction force models dealing with different friction phenomena in the context of multibody system dynamics. For this purpose, a comprehensive review of present literature in this field of investigation is first presented. In this process, the main aspects related to friction are discussed, with particular emphasis on the pure dry sliding friction, stick–slip effect, viscous friction and Stribeck effect. In a simple and general way, the friction force models can be classified into two main groups, namely the static friction approaches and the dynamic friction models. The former group mainly describes the steady-state behavior of friction force, while the latter allows capturing more properties by using extra state variables. In the present study, a total of 21 different friction force models are described and their fundamental physical and computational characteristics are discussed and compared in details. The application of those friction models in multibody system dynamic modeling and simulation is then investigated. Two multibody mechanical systems are utilized as demonstrative application examples with the purpose of illustrating the influence of the various frictional approaches on the dynamic response of the systems. From the results obtained, it can be stated that both the choice of the friction force model and friction parameters involved can significantly affect the simulated/ modeled dynamic response of mechanical systems with friction.The first author expresses his gratitude to the Portuguese Foundation for Science and Technology through the PhD grant (PD/BD/114154/2016). This work has been supported by the Portuguese Foundation for Science and Technology with the reference project UID/EEA/04436/2013, by FEDER funds through the COMPETE 2020—Programa Operacional Competitividade e Internacionalização (POCI) with the reference project POCI-01-0145-FEDER-006941.info:eu-repo/semantics/publishedVersio