1,721,015 research outputs found
Analysis of composite beams, plates, and shells using Jacobi polynomials and NDK models
Full text linkFinite elements based on Jacobi shape functions for the free vibration analysis of beams, plates, and shells
Full text linkThis article proposes the use of Jacobi polynomials as shape functions for the free vibration analysis of beam, plate, and shell structures. Jacobi polynomials, indicated as P(γ,θ)p,
belong to the family of classical orthogonal polynomials, and depend on two scalar parameters γ and θ, with p being the polynomial order. The Jacobi-like shape functions are built in the context of the Carrera unified formulation, which permits the expression of displacement kinematics in a hierarchical form. In this manner, it is possible to adopt several classical to complex higher-order theories with ease. Particular attention is focused on the attenuation and the correction of the shear locking. The results have been compared with analytical results from the literature. For the plate benchmark, analytical results are introduced as the reference results in this article for the first time using the closed form of CUF. Beams, plates, and shells with different thicknesses have been considered. It is demonstrated that the parameters γ and θ are not influential for the calculations
Guaranteeing Slice Performance Isolation with SDN
No full textOne of the main concepts recently introduced in communication networks, such as 5G, is network slicing. A slice, as defined by the Third Generation Partnership program (3GPP) for example, is a logical network consisting of network functions and related resources to meet certain requirements. Software Defined Networking (SDN) is the candidate technology for implementing network slicing. However, guaranteeing different and independent QoS to several network slices sharing a single physical infrastructure is not straightforward. In this letter we propose an SDN solution for network slicing in packet-based networks. Deployed slices guarantee effective utilization of the available bandwidth and isolation in terms of both connectivity and performance (i.e., bandwidth and latency). The proposed solution is based on the OpenFlow standard and is validated on an emulated testbed utilizing the ONOS controller
Plate finite elements with arbitrary displacement fields along the thickness
Full text linkThe present paper introduces a methodology for formulating two-dimensional structural theories featuring arbitrary kinematic fields. In the proposed approach, each displacement variable can be examined through an independent expansion function, enabling the integration of both classical and higher-order theories within a unified framework. The Carrera Unified Formulation is used to derive the governing equations in a unified form, independent of the expansion adopted for each displacement component. In this paper, plate structural theories are constructed by using polynomial expansions. The finite element method is used to discretize the structure in the reference plane of the plate, utilizing Lagrange-based elements. The Mixed Interpolation of Tensorial Components is adopted to alleviate the shear locking issues. In this study, isotropic plate structures are investigated under various loadings, boundary conditions, and different length-to-thickness ratios. Whenever possible, the present results are compared with analytical and literature solutions. The accuracy of the presented models is evaluated for both displacements and stress components. The findings indicate that the selection of the most appropriate model is strongly dependent on the specific parameters of the individual problem, however, choosing the right model can significantly enhance the efficiency of the numerical analysis
Shell finite elements with arbitrary displacement fields along the thickness
Full text linkThis paper introduces an innovative approach for developing shell structural theories with an arbitrary kinematic field. In this study, each displacement component may be analysed using an independent expansion function. This method allows for the incorporation of both classical and higher-order theories within a unified framework. The Carrera Unified Formulation is employed to describe the thickness kinematics. In this paper, the structural theories are built by using polynomial terms. The finite element method is employed to discretize the structure in the reference mid-surface of the structure, utilizing Lagrange-based elements. The governing equations for the linear analysis are derived using the principle of virtual displacements. Also, the Mixed Interpolation of Tensorial Components is adopted inside the formulation to limit the locking issues. Cylindrical and spherical shells are studied here. Several radius-to-thickness ratios are taken into account. Both point and distributed loads are considered. Whenever possible, the present results are compared with the existing literature. The accuracy of the models presented is assessed for both displacements and stress outputs. The results illustrate that the selection of the most appropriate model is highly contingent on the specific parameters of the particular problem
Legendre-based node-dependent kinematics shell models for the global–local analysis of homogeneous and layered structures
Full text linkOpenConfig and OpenROADM Automation of Operational Modes in Disaggregated Optical Networks
No full textOpenConfig and Open ROADM are emerging as the most relevant initiatives to support partial disaggregation, in which the optical line system is provided by a single vendor while transponders can be provided, in pairs, by different vendors. This way, vendor lock-in is eliminated at the transponder level, without significantly impacting the transmission performance. Although the above initiatives have defined YANG models reaching a good level of maturity, there are still open issues that prevent the full deployment of vendor-neutral partially disaggregated solutions. Among these, the candidate transmission modes in a transponder, including proprietary solutions, are exposed in the YANG models as opaque attributes called Operational (OP) Modes, thus limiting the awareness and the effectiveness of the SDN controller in the selection of the most appropriate transmission mode. In this work, we focus on the open issues related to the configuration and adaptation of transmission parameters. In particular, we focus on the OpenConfig concept of OP Mode enabling the abstraction of transmission complexity but currently preventing an SDN controller to manage transponders in a fully vendor-neutral way. This work first estimates, through a simulative study, the network performance benefit that is achievable by optimizing the OP mode selection. Then, a telemetry-based automated solution is proposed, designed and implemented to enhance the OP mode concept in case of both provisioning and adaptation scenarios (e.g., upon failure), also considering the impact in the tributary/client network. In particular, the following components have been designed and implemented: (i) software agent for Open Config transponders; (ii) software agent for Open ROADM line systems, (iii) an automatic telemetry-assisted monitoring handler; and (iv)SDN control procedures implemented in the ONOS Controller. The proposed components and comprehensive solution have been evaluated in a network testbed encompassing multi-vendor network elements, successfully demonstrating a full vendor-neutral partially disaggregated provisioning and recovery operations
Operational Mode and Slicing Adaptation in OpenConfig Disaggregated Optical Networks
No full textThis paper proposes and experimentally validates a workflow to handle network failures implying the change of the operational mode on optical OpenConfig transponders. An SDN control plane is considered with a real packet-optical data plane
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