Documents published in Scipedia

• Feedback reconstruction techniques for optimal control problems on a tree structure

  A. Alla, L. Saluzzi

  eccomas2022.

  
  

  Abstract

  The computation of feedback control using Dynamic Programming equation is a difficult task due the curse of dimensionality. The tree structure algorithm is one the methods introduced recently that mitigate this problem. The method computes the value function avoiding the construction of a space grid and the need for interpolation techniques using a discrete set of controls. However, the computation of the control is strictly linked to control set chosen in the computation of the tree. Here, we extend and complete the method selecting a finer control set in the computation of the feedback. This requires to use an interpolation method for scattered data which allows us to reconstruct the value function for nodes not belonging to the tree. The effectiveness of the method is shown via a numerical example.

  Abstract
  The computation of feedback control using Dynamic Programming equation is a difficult task due the curse of dimensionality. The tree structure algorithm is one the methods [...]

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• Structure-Preserving Neural Networks for the N-body Problem

  P. Horn, B. Koren, S. Portegies Zwart

  eccomas2022.

  
  

  Abstract

  In order to understand when it is useful to build physics constraints into neural networks, we investigate different neural network topologies to solve the N -body problem. Solving the chaotic N -body problem with high accuracy is a challenging task, requiring special numerical integrators that are able to approximate the trajectories with extreme precision. In [1] it is shown that a neural network can be a viable alternative, offering solutions many orders of magnitude faster. Specialized neural network topologies for applications in scientific computing are still rare compared to specialized neural networks for more classical machine learning applications. However, the number of specialized neural networks for Hamiltonian systems has been growing significantly during the last years [3, 5]. We analyze the performance of SympNets introduced in [5], preserving the symplectic structure of the phase space flow map, for the prediction of trajectories in N -body systems. In particular, we compare the accuracy of SympNets against standard multilayer perceptrons, both inside and outside the range of training data. We analyze our findings using a novel view on the topology of SympNets. Additionally, we also compare SympNets against classical symplectic numerical integrators. While the benefits of symplectic integrators for Hamiltonian systems are well understood, this is not the case for SympNets.

  Abstract
  In order to understand when it is useful to build physics constraints into neural networks, we investigate different neural network topologies to solve the N -body problem. [...]

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• An accelerated deflation preconditioner for parametric systems based on subspace recycling

  D. Panagiotopoulos, W. Desmet, E. Deckers

  eccomas2022.

  
  

  Abstract

  Krylov subspace recycling [1] is often deployed to accelerate the iterative solution of sequences of linear systems. Such approaches reuse a continuously updated deflation subspace to reach a converged solution within a low number of iterations. This procedure is justified for problems that describe gradually evolving phenomena, such as crack propagation, and thus involve a sequence of systems that are not simultaneously available. However considering parametric systems, these techniques might induce an unnecessary overhead cost. Specifically, by constantly updating the recycled subspace a new projection on the newly constructed subspace needs to be operated for each new system, inducing a cost that scales with O( × N2) for dense systems, where N is the size of the system and is the size of the employed recycled basis. In that context, this work proposes an accelerated recycling procedure for parametric systems that is inspired by the Galerkin Model Order Reduction strategy and employs an offline ­ online operation splitting. In the offline part, the subspace to be recycled is constructed via an Automatic Krylov subspaces Recycling algorithm (AKR) [2] and the parametric system is projected on the subspace to yield a Reduced Order Model (ROM). Then, in the online part the construction of the deflation preconditioner only requires employing the ROM and as a result the cost of constructing the preconditioner is reduced to O(2). The proposed procedure is tested on a randomly parametrized linear system and is compared the non-deflated GMRES algorithm and a conventional recycling strategy presented in [11].

  Abstract
  Krylov subspace recycling [1] is often deployed to accelerate the iterative solution of sequences of linear systems. Such approaches reuse a continuously updated deflation [...]

  • 8
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• Mixed finite element formulations and energy-momentum time integrators for thermo-viscoelastic gradient-based fiber-reinforced continua

  J. Dietzsch, M. Groß, I. Kalaimani

  eccomas2022.

  
  

  Abstract

  Nowadays, fibre-reinforced materials and their accurate dynamic simulation play a significant role in the construction of lightweight structures. On the one hand, we are dealing with locking of the matrix material as well as the fibres, thermal expansion, the directed heat conduction through the fibres and viscoelastic behaviour in such materials. The material reinforcement is performed by fiber rovings with a separate bending stiffness, which can be modelled by second order gradients. On the other hand, we also want to perform accurate long-term simulations. In this presentation, we focus on numerically stable dynamic long-time simulations with locking free meshes, and thus use higherorder accurate energy-momentum schemes emanating from mixed finite element methods. We adapt the variational-based space-time finite element method in Reference [1] to the material formulation, and additionally include independent fields to obtain well-known mixed finite elements [2, 3].

  Abstract
  Nowadays, fibre-reinforced materials and their accurate dynamic simulation play a significant role in the construction of lightweight structures. On the one hand, we are dealing [...]

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• A tensor-product finite element cochain complex with arbitrary continuity

  F. Bonizzoni, G. Kanschat

  eccomas2022.

  
  

  Abstract

  We develop tensor product finite element cochain complexes of arbitrary smoothness on Cartesian meshes of arbitrary dimension. The first step is the construction of a onedimensional Cm-conforming finite element cochain complex based on a modified Hermite interpolation operator, which is proved to commute with the exterior derivative by means of a general commutation lemma. Adhering to a strict tensor product construction we then derive finite element complexes in higher dimensions.

  Abstract
  We develop tensor product finite element cochain complexes of arbitrary smoothness on Cartesian meshes of arbitrary dimension. The first step is the construction of a onedimensional [...]

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• Least-Squares and DPG approximation of eigenvalue associated to coupled problems

  F. Bertrand

  eccomas2022.

  
  

  Abstract

  The Arts and Science Contest of the ECCOMAS Young Investigators Committee (EYIC) aims to show science in all its beauty and elegance, by visualizing scientific works with an artistic point of view. The competition was open to every participant with an accepted the visuals were uploaded in 4 groups on the ECCOMAS Facebook page, one group per week. The visual with the most likes of each group was put in the finalists short-list, and a jury chose the final winners of the contest. The starry night of reaction diffusion won this competition and the present contribution presents the numerical method behind the picture.

  Abstract
  The Arts and Science Contest of the ECCOMAS Young Investigators Committee (EYIC) aims to show science in all its beauty and elegance, by visualizing scientific works with [...]

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• Comparative mechanical assessment of the common structural joining techniques implemented in the marine industries

  F. Portugal), R. Pereira, D. Cardoso, R. Carbas, A. Barbosa, L. Silva

  This presentation was made at 4th International Conference on Materials Design and Applications on 7-8 July 2022.

  
  

  Abstract

  The main objective of FIBRE4YARDS project is to maintain European global leadership in ship building and ship maintenance, through implementation of the Shipyard 4.0 concept in which advanced and innovative FRP manufacturing technologies are successfully introduced. This project has received funding from European Union's Horizon 2020 research and innovation programme under grant agreement n°101006860.

  Abstract
  The main objective of FIBRE4YARDS project is to maintain European global leadership in ship building and ship maintenance, through implementation of the Shipyard 4.0 concept [...]

  • 3
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• Parametric optimization of ultrasonic welding on thermoplastic fibre-reinforced composites by the implementation of statistical analysis of variance method (ANOVA)

  F. Portugal), R. Pereira, D. Cardoso, A. Barbosa, L. Silva

  This poster was presented at 4th International Conference on Materials Design and Applications on 7-8 July 2022.

  
  

  Abstract

  The main objective of FIBRE4YARDS project is to maintain European global leadership in ship building and ship maintenance, through implementation of the Shipyard 4.0 concept in which advanced and innovative FRP manufacturing technologies are successfully introduced. This project has received funding from European Union's Horizon 2020 research and innovation programme under grant agreement n°101006860.

  Abstract
  The main objective of FIBRE4YARDS project is to maintain European global leadership in ship building and ship maintenance, through implementation of the Shipyard 4.0 concept [...]

  • 1
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• Modular construction design of a composite catamaran based on FIBRE4YARDS technologies

  P. Guijarro

  This presentation was made at the E-LASS event on 13-15 September 2022.

  
  

  Abstract

  The main objective of FIBRE4YARDS project is to maintain European global leadership in ship building and ship maintenance, through implementation of the Shipyard 4.0 concept in which advanced and innovative FRP manufacturing technologies are successfully introduced. This project has received funding from European Union's Horizon 2020 research and innovation programme under grant agreement n°101006860.

  Abstract
  The main objective of FIBRE4YARDS project is to maintain European global leadership in ship building and ship maintenance, through implementation of the Shipyard 4.0 concept [...]

  • 1
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• FIBREGY & FIBRE4YARDS 2nd INFORMATION DAY

  D. Sá

  This presentation was made at the 2nd Information Day of FIBRE4YARDS and FIBREGY projects on 13 September 2022.

  
  

  Abstract

  The main objective of FIBRE4YARDS project is to maintain European global leadership in ship building and ship maintenance, through implementation of the Shipyard 4.0 concept in which advanced and innovative FRP manufacturing technologies are successfully introduced. This project has received funding from European Union's Horizon 2020 research and innovation programme under grant agreement n°101006860.

  Abstract
  The main objective of FIBRE4YARDS project is to maintain European global leadership in ship building and ship maintenance, through implementation of the Shipyard 4.0 concept [...]

  • 1
  •  read