Papers by Eduardo Souza de Cursi
WIT transactions on modelling and simulation, 1970
We consider a model for the contact between a homogeneous network of strings and an obstacle. The... more We consider a model for the contact between a homogeneous network of strings and an obstacle. The contact is unilateral with friction. The strings are submitted to gravity-like forces and have a stress-unilateral behaviour : all the internal efforts are traction efforts. In the general case of dry friction , there are situations where infinite solutions do exist. For the situation where friction follows the Coulomb's law , the uniqueness of the tensions and a numerical method are established (Finite Element Approximation of the solution) .
Springer Texts in Business and Economics, 2022
This work presents an application of Uncertainty Quantification (UQ) approaches to a Multiple-Inp... more This work presents an application of Uncertainty Quantification (UQ) approaches to a Multiple-Input Multiple-Output (MIMO) system. The use of UQ techniques in this field is new and is one of the originalities of the paper. A second originality of this work is to furnish an efficient method to deal with non-gaussian noise, with non-zero mean. A third originality is that the method proposed allows the estimation of the noise, of the channel and the decoding of messages the approach makes all the chain: determination of the distribution of the noise, identification of the Channel Matrix and detection of the symbols transmitted. The first step is made by using UQ techniques, which furnish the distribution of the noise, without assumption of Gaussian distribution or a mean equal to zero. A new application of UQ techniques furnishes the channel matrix. Then, the detection of symbols is performed by a method based on the determination of a selection matrix formed by lines of the identity m...
The problem of the dynamics of coupled rotor-blade systems, such as wind turbines, is considered.... more The problem of the dynamics of coupled rotor-blade systems, such as wind turbines, is considered. The blades are modeled as Euler-Bernoulli beams undergoing transverse vibration attached to a rotor in cantilever conditions with the longitudinal axis extending in a radial direction. The rotor is modeled as a lumped mass moving on a plane with different stiffness characteristics in each dimension. Interest is set to the vibration analysis of the ensemble and the interaction of its parts. The study of the evolution of vibration parameters such as critical speeds and resonant frequencies is carried out. The effect of loads acting on the beam are considered, and these are related to the torques generated on the beam and to the stresses that result at the base of the rotor. The model developed has a reduced number of degrees of freedom while preserving the essential dynamical properties. The viability of this model is explored for applications in domains such as fatigue estimation and sto...
International Journal of Applied Mathematics and Computer Science, 2011
Random perturbation of the projected variable metric method for nonsmooth nonconvex optimization ... more Random perturbation of the projected variable metric method for nonsmooth nonconvex optimization problems with linear constraintsWe present a random perturbation of the projected variable metric method for solving linearly constrained nonsmooth (i.e., nondifferentiable) nonconvex optimization problems, and we establish the convergence to a global minimum for a locally Lipschitz continuous objective function which may be nondifferentiable on a countable set of points. Numerical results show the effectiveness of the proposed approach.
Computers & Operations Research, 2006
The objective of districting in logistics distribution problems is to find a near optimal partiti... more The objective of districting in logistics distribution problems is to find a near optimal partition of the served region into delivery zones or districts. This kind of problem has been treated in the literature with geometricshaped districts and continuous approximations. Usually it is assumed an underlying road network equivalent to a Euclidean, rectangular, or ring-radial metric. In most real problems, however, the road network is a coarse combination of metrics. In this context, it is unclear what is the optimal shape of the districts and how one should orientate them. A possibility is to treat the problem with a Voronoi diagram approach. Departing from a previously determined ring-radial districting pattern and relaxing the initial district boundaries, we apply the multiplicativelyweighted Voronoi diagram formulation in order to smooth district contours. The computing process is iterated until the convergence is attained. The model has been applied to solve a parcel delivery problem in the city of São Paulo, Brazil, whose results are presented and discussed in the paper.
Composites Part B: Engineering, 2009
The purpose of the present work is to analyse the influence of the failure criterion on the minim... more The purpose of the present work is to analyse the influence of the failure criterion on the minimum weight and cost of laminated plates subjected to in-plane loads. Three different failure criteria are tested independently: maximum stress, Tsai-Wu and the Puck failure criterion. The optimisation problem is solved by a genetic algorithm.
International Journal of Molecular Sciences, May 1, 2021
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Mecánica Computacional, Nov 28, 2018
This paper aims at presenting an efficient approach for the optimal design of friction tunned mas... more This paper aims at presenting an efficient approach for the optimal design of friction tunned mass damper (FTMD) devices under uncertainties. The objective function of the optimization problem is the maximization of structural reliability, which is approximated here as an out-crossing problem. The solution of the equations of motion of the FTMD system leads to a nonlinear dynamical problem, which coupled with the time dependent reliability problem, requires a substantial computational effort. An additional complexity is that the design of a multiple FTMD system is nonlinear and leads to a multimodal optimization problem. In order to address the issues of computational cost and multi-modality, an Efficient Global Optimization (EGO) method with Expected Improvement as infill criterion is employed. The results showed that the EGO was able to successfully provide the optimum solution of the FTMD design under uncertainty within a reasonable computational effort. For example, using only 80 points, the EGO algorithm was able to consistently find the optimum solution for all the cases analyzed in this paper. One aspect that is worth to be highlighted is that these results were obtained in problems with a relatively high stochastic dimension, e.g. over 30 random variables.
Nanomaterials, Dec 20, 2021
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Lecture notes in mechanical engineering, Aug 20, 2020
This paper presents an approach for the use of stochastic gradient descent methods for the soluti... more This paper presents an approach for the use of stochastic gradient descent methods for the solution of risk optimization problems. The first challenge is to avoid the high-cost evaluation of the failure probability and its gradient at each iteration of the optimization process. We propose here that it is accomplished by employing a stochastic gradient descent algorithm for the minimization of the Chernoff bound of the limit state function associated with the probabilistic constraint. The employed stochastic gradient descent algorithm, the Adam algorithm, is a robust method used in machine learning training. A numerical example is presented to illustrate the advantages and potential drawbacks of the proposed approach.
Cadernos De Saude Publica, Mar 26, 2018
Este é um artigo publicado em acesso aberto (Open Access) sob a licença Creative Commons Attribut... more Este é um artigo publicado em acesso aberto (Open Access) sob a licença Creative Commons Attribution, que permite uso, distribuição e reprodução em qualquer meio, sem restrições, desde que o trabalho original seja corretamente citado.
Applied sciences, Jun 10, 2019
The unavoidable vacancy defects dispersed throughout the entire pristine graphene tailor to the i... more The unavoidable vacancy defects dispersed throughout the entire pristine graphene tailor to the integrity of the lattice structure and thereby have complicated impacts on the mechanical and thermal properties of graphene. In order to analyze the influence of vacancy defects on the extraordinary thermal conductivity of graphene, three typical kinds of vacancy defects-namely center concentrated, periodic, and random distributed vacancy defects-are compared and discussed. In the steady-state thermal conduction, the finite element method (FEM) is performed to calculate the total thermal energy and temperature field. The equivalent coefficient of thermal conductivity is derived from thermal energy, amount of vacancy defects, and boundary condition. The chirality in graphene is discussed by the location of its heat source. Moreover, the Monte Carlo simulation is applied to propagate the uncertainty of random vacancy defects in the finite element model of pristine graphene. In this paper, we provide the robustness to defend the impacts of vacancy defects on thermal conduction and the fluctuation and divergence caused by a certain number of random vacancy defects.
Ocean Engineering, Oct 1, 2022
In this article, we investigate the movement and vibrations of a blade due to the presence of the... more In this article, we investigate the movement and vibrations of a blade due to the presence of the mast. When the blade goes past the mast, a sudden pressure spike induces vibrations in the blade. To study the influence of the stiffness, two different structures have been investigated. We present our numerical methodology concerning solving the flow, the structure behavior and the coupling of the two systems. Then, we validate two methods against an experiment (Bahaj et al., 2007). In a third section, we present fluid-structure interaction cases. Several structures are setup by modifying the stiffness of the material. Their steady open-water (without a mast) behaviors are compared. And finally, two dynamic fluid-structure are performed to compare the behavior of an elastic blade passing next to a mast. For all the cases, we use K-FSI developed by K-Epsilon to solve the fluid-structure interaction (FSI) effects.
Materials, Dec 8, 2018
The beam finite element and molecular dynamics models are two popular methods to represent the re... more The beam finite element and molecular dynamics models are two popular methods to represent the reaction of carbon-carbon bonds in graphene. However, the wrinkles and ripples in geometrical characteristics are difficult take into consideration. The out-planar mechanical properties are neglected in classical models of graphene. This paper proposes a self-adaptive umbrella model for vibration analysis of graphene. The parameters in the umbrella model are flexible to adapting the geometrical and material characteristics of graphene. The umbrella model consists of shell and beam elements. The honeycomb beam and planar shell model of graphene are included in the self-adaptive umbrella model as particular cases. The sensitivity analysis and results confirmed the rationality and feasibility of the self-adaptive umbrella model.
HAL (Le Centre pour la Communication Scientifique Directe), May 25, 2009
Nanomaterials, Jul 2, 2018
The stochastic distributed placement of vacancy defects has evident effects on graphene mechanica... more The stochastic distributed placement of vacancy defects has evident effects on graphene mechanical property, which is a crucial and challenged issue in the field of nanomaterial. Different from the molecular dynamic theory and continuum mechanics theory, the Monte Carlo based finite element method (MC-FEM) was proposed and performed to simulate vibration behavior of vacancy defected graphene. Based on the Monte Carlo simulation, the difficulties in random distributed location of vacancy defects were well overcome. The beam element was chosen to represent the exact atomic lattice of the graphene. The results of MC-FEM have a satisfied agreement with that in the reported references. The natural frequencies in the certain vibration mode were captured to observe the mechanical property of vacancy defected graphene sheets. The discussion about the parameters corresponding with geometry and material property was accomplished by probability theory and mathematical statistics.
Nanomaterials, Apr 27, 2023
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
In this paper, an approach is proposed to conduct reliability analysis on an offshore jacket cons... more In this paper, an approach is proposed to conduct reliability analysis on an offshore jacket considering corrosion degradation under extreme load cases. Corrosion degradation is considered as thickness wastage of the jacket element, which is seen as time-dependent variables. One probabilistic corrosion in literature is adopted by using different distribution models. Also, three different inspection cases (environmental conditions) of the corrosion are studied. The reliability assessment is evaluated by Crude Monte Carlo simulation based on the trained surrogate model. Deep neural networks are used to train the surrogate model, because they are not limited by the distribution and dimension of variables. The results show that using different corrosion distribution model, the probabilities of failure of the jacket are different, even though they have the same mean and standard deviation values. In addition, with same assumption of the distribution model in corrosion, the reliability of the jacket changes a lot concerning different inspection cases. Furthermore, it is noted that the inspection cases have more influences on the reliability analysis of jacket than different corrosion distribution assumptions. At the end, two recommendations are derived from this work.
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Papers by Eduardo Souza de Cursi