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Erasmo Carrera - One of the best experts on this subject based on the ideXlab platform.
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finite beam elements based on legendre polynomial expansions and node dependent kinematics for the global Local Analysis of composite structures
European Journal of Mechanics A-solids, 2019Co-Authors: A G De Miguel, Alfonso Pagani, Enrico Zappino, Erasmo CarreraAbstract:This work introduces an innovative type of FEM beam models with node-dependent kinematics. A variety of global-Local approaches have been proposed to reduce the consumption of computational resources in FEM Analysis, in which mostly the main idea is to couple the elements in the Locally refined region (with either refined mesh or higher-order theories) and those in the less refined area. As a new method to build FEM models in a global-Local Analysis, node-dependent kinematics makes it possible to construct elements with different kinematic theories on different nodes and implement a kinematic variation conveniently within an element to bridge a Local model to a global one. With the help of the introduced cross-section functions, CUF allows the definition of different kinematics on each node and their interpolation over the axial domain of the beam element. Without using any ad hoc coupling method, beam elements with node-dependent kinematics have very compact and coherent formulations through the Fundamental Nucleus (FN). Corresponding FEM governing equation is derived from the Principle of Virtual Displacements (PVD), and the expressions of FNs of the stiffness matrix and load vector are given. Both ESL (Equivalent Single-layer) and LW (Layer-wise) models are addressed. In fact, in this work, Legendre polynomials are used to construct refined beam models, obtaining cross- section functions (nodal kinematics) with Hierarchical Legendre Expansions (HLE) and, eventually, LW accuracy. In the numerical examples, refined models with HLE are employed in the Local area with a higher stress gradient, and in the less critical regions ESL models are adopted; meanwhile, in the kinematic transition zone, a beam element with node-dependent kinematics are used to connect these two domains. By comparing the numerical results with those in literature and from 3D FEM modeling, it is demonstrated that when used in the Analysis of composite beams with Local effects to be considered, node-dependent kinematic beam elements can reduce the computational costs significantly without losing numerical accuracy.
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a global Local approach for the elastoplastic Analysis of compact and thin walled structures via refined models
Computers & Structures, 2018Co-Authors: Marco Petrolo, M H Nagaraj, Ibrahim Kaleel, Erasmo CarreraAbstract:Abstract A computationally efficient framework has been developed for the elastoplastic Analysis of compact and thin-walled structures using a combination of global-Local techniques and refined beam models. The theory of the Carrera Unified Formulation (CUF) and its application to physically nonlinear problems are discussed. Higher-order models derived using Taylor and Lagrange expansions have been used to model the structure, and the elastoplastic behavior is described by a von Mises constitutive model with isotropic work hardening. Comparisons are made between classical and higher-order models regarding the deformations in the nonlinear regime, which highlight the capabilities of the latter in accurately predicting the elastoplastic behavior. The concept of global-Local Analysis is introduced, and two versions are presented - the first where physical nonlinearity is considered for both the global and Local analyses, and the second where nonlinearity is considered only for the Local Analysis. The second version results in reasonably accurate results compared to a full 3D finite element Analysis, with a twofold reduction in the number of degrees of freedom.
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global Local Analysis of laminated plates by node dependent kinematic finite elements with variable esl lw capabilities
Composite Structures, 2017Co-Authors: Enrico Zappino, Alfonso Pagani, Erasmo CarreraAbstract:Abstract This work presents a class of plate finite elements (FEs) formulated with node-dependent kinematics, which can be used to construct global-Local models with high numerical efficiency. Taking advantage of Carrera Unified Formulation (CUF), plate theory kinematics can be individually defined on each FE node, realizing a variation of refinement levels within the in-plane domain of one element. When used in the bridging zone between a global model and a Locally refined one, an efficient global-Local model can be constructed. Elements with variable ESL/LW kinematics from node to node are developed and applied in the global-Local Analysis of laminated structures. This work includes numerical examples in which LW models with refined kinematics are employed in Local regions while ESL models are adopted in the less critical area, and modeling domains are connected by transition zone composed of elements with node-dependent kinematics. The obtained results are compared with solutions from literature and 3D FE modeling. For laminated plates with Local effects to be considered, the proposed plate models can reduce the computational costs significantly while guaranteeing numerical accuracy without using special global-Local coupling methods.
O Breitenstein - One of the best experts on this subject based on the ideXlab platform.
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nondestructive Local Analysis of current voltage characteristics of solar cells by lock in thermography
Solar Energy Materials and Solar Cells, 2011Co-Authors: O BreitensteinAbstract:By evaluating dark lock-in thermography images taken at one reverse and three forward biases, images of all two-diode-parameters J01, J02, n (ideality factor of J02), and Gp (the parallel Ohmic conductivity) of the dark current–voltage characteristic are obtained. A Local series resistance is explicitly considered and may be provided as a series resistance image, e.g. resulting from luminescence imaging. The results enable a separate investigation of factors influencing the depletion region recombination current and the diffusion current, which is governed by the bulk lifetime. Local I–V characteristics of special sites may be simulated.
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nondestructive Local Analysis of current voltage characteristics of solar cells by lock in thermography
Photovoltaic Specialists Conference, 2011Co-Authors: O BreitensteinAbstract:By evaluating dark lock-in thermography images taken at one reverse and three forward biases, images of all two-diode-parameters J 01 , J 02 , n 2 (ideality factor of J 02 ), and G p (the parallel ohmic conductivity) are obtained. A Local series resistance is explicitly considered and may be provided as a series resistance image, e.g. resulting from luminescence imaging. The results allow a separate investigation of factors influencing the depletion region recombination current and the bulk lifetime-governed diffusion current.
A W Roscoe - One of the best experts on this subject based on the ideXlab platform.
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efficient deadlock freedom checking using Local Analysis and sat solving
Integrated Formal Methods, 2016Co-Authors: Pedro Antonino, Thomas Gibsonrobinson, A W RoscoeAbstract:We build upon established techniques of deadlock Analysis by formulating a new sound but incomplete framework for deadlock freedom Analysis that tackles some sources of imprecision of current incomplete techniques. Our new deadlock candidate criterion is based on constraints derived from the Analysis of the state space of pairs of components. This new characterisation represents an improvement in the accuracy of current incomplete techniques; in particular, the so-called non-hereditary deadlock-free systems i.e. deadlock-free systems that have a deadlocking subsystem, which are neglected by most incomplete techniques, are tackled by our framework. Furthermore, we demonstrate how SAT checkers can be used to efficiently implement our framework in a way that, typically, scales better than current techniques for deadlock Analysis. This is demonstrated by a series of practical experiments.
David E Crawford - One of the best experts on this subject based on the ideXlab platform.
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predominant treatment failure in postprostatectomy patients is Local Analysis of patterns of treatment failure in swog 8794
Journal of Clinical Oncology, 2007Co-Authors: Gregory P Swanson, Michael A Hussey, Catherine M Tangen, Joseph L Chin, Edward M Messing, Edith D Canbyhagino, Jeffrey D Forman, Ian M Thompson, David E CrawfordAbstract:Purpose Southwest Oncology Group (SWOG) trial 8794 demonstrated that adjuvant radiation reduces the risk of biochemical (prostate-specific antigen [PSA]) treatment failure by 50% over radical prostatectomy alone. In this Analysis, we stratified patients as to their preradiation PSA levels and correlated it with outcomes such as PSA treatment failure, Local recurrence, and distant failure, to serve as guidelines for future research. Patients and Methods Four hundred thirty-one subjects with pathologically advanced prostate cancer (extraprostatic extension, positive surgical margins, or seminal vesicle invasion) were randomly assigned to adjuvant radiotherapy or observation. Results Three hundred seventy-four eligible patients had immediate postprostatectomy and follow-up PSA data. Median follow-up was 10.2 years. For patients with a postsurgical PSA of 0.2 ng/mL, radiation was associated with reductions in the 10-year risk of biochemical treatment failure (72% to 42%), Local failures (20% to 7%), and distant failures (12% to 4%). For patients with a postsurgical PSA between higher than 0.2 and 1.0 ng/mL, reductions in the 10-year risk of biochemical failure (80% to 73%), Local failures (25% to 9%), and distant failures (16% to 12%) were realized. In patients with postsurgical PSA higher than 1.0, the respective findings were 94% versus 100%, 28% versus 9%, and 44% versus 18%. Conclusion The pattern of treatment failure in high-risk patients is predominantly Local with a surprisingly low incidence of metastatic failure. Adjuvant radiation to the prostate bed reduces the risk of metastatic disease and biochemical failure at all postsurgical PSA levels. Further improvement in reducing Local treatment failure is likely to have the greatest impact on outcome in high-risk patients after prostatectomy. J Clin Oncol 25:2225-2229. © 2007 by American Society of Clinical Oncology
Pedro Antonino - One of the best experts on this subject based on the ideXlab platform.
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efficient deadlock freedom checking using Local Analysis and sat solving
Integrated Formal Methods, 2016Co-Authors: Pedro Antonino, Thomas Gibsonrobinson, A W RoscoeAbstract:We build upon established techniques of deadlock Analysis by formulating a new sound but incomplete framework for deadlock freedom Analysis that tackles some sources of imprecision of current incomplete techniques. Our new deadlock candidate criterion is based on constraints derived from the Analysis of the state space of pairs of components. This new characterisation represents an improvement in the accuracy of current incomplete techniques; in particular, the so-called non-hereditary deadlock-free systems i.e. deadlock-free systems that have a deadlocking subsystem, which are neglected by most incomplete techniques, are tackled by our framework. Furthermore, we demonstrate how SAT checkers can be used to efficiently implement our framework in a way that, typically, scales better than current techniques for deadlock Analysis. This is demonstrated by a series of practical experiments.