Virtual Coach Reaches Out To Me

Conference given outside the academic context (2013)

The virtual node polygonal element method for nonlinear thermal analysis with application to hybrid laser welding

in International Journal of Heat and Mass Transfer (2013), 67

The nonlinear heat transfer process occurring during hybrid laser welding was simulated using the Virtual-node Polygonal Element (VPE) method within the framework of the Finite Element Method (FEM). To ... [more ▼]

The nonlinear heat transfer process occurring during hybrid laser welding was simulated using the Virtual-node Polygonal Element (VPE) method within the framework of the Finite Element Method (FEM). To achieve robustness in large-scale welding simulations, a dynamic mesh refinement with quadtree and octree data structures was used in the welding region. Accuracy, convergence and efficiency were verified by solving two and three dimensional problems. It is found that the present VPE can successfully simulate the hybrid laser welding process with good accuracy and convergence. The adaptive refined mesh box can synchronously move with the welding heat source, which dramatically reduces the number of field nodes. Compared with the standard FEM,the VPEM requires only approximately 42% of the total degrees of freedom used in standard FEM for the same accuracy. Furthermore, we compare the computational cost and accuracy of the method to that of the finite element method, the edge based virtual node polygonal element/virtual node method, the edge-based Smoothed Point Interpolation Meshless Method (ES-PIM), the edge-based Element (ES-PIM) the Element Free Galerkin (EFG) method and the Meshless Local Petrove-Galerkin Petrov-Galerkin (MLPG) method. Compared to all those methods, the proposed scheme is found competitive in terms of computational cost versus accuracy, and benefit from a simple implementation. © 2012 Elsevier B.V. All rights reserved. [less ▲]

Virtual-power-based quasicontinuum methods for discrete dissipative materials

Scientific Conference (2016, June)

Viviane Reding on her action in the field of the information society and media (2004-2010)

in Internet Histories: Digital Technology, Culture and Society (2020)

The following pages are taken from a long interview (more than eight hours of footage in total) that Viviane Reding granted us in 2015 in connection with the “Pierre Werner and Europe” research project ... [more ▼]

The following pages are taken from a long interview (more than eight hours of footage in total) that Viviane Reding granted us in 2015 in connection with the “Pierre Werner and Europe” research project. Drawing on more than 40 years’ experience in politics, Viviane Reding spoke about her career, the role of Luxembourg and Luxembourgers in the European integration process, and various key events in which she played a part. In these extracts, she discusses her role as a member of the first and second Barroso Commissions (2004-2009 and 2010-2014) and her efforts to help build an information and knowledge society in Europe, one that serves citizens and protects their rights and fundamental freedoms. Her achievements in this respect include capping mobile phone roaming charges (they were subsequently abolished in 2017), advocating for the introduction of a single emergency number (112) in all EU countries, launching the Europeana digital library, and spearheading a programme to use technological innovation for climate and energy solutions. She also describes the process of developing a Digital Agenda for Europe to improve the continent’s digital competitiveness compared with the United States, China and Japan – a complex and challenging task given the context of globalisation and the divergent interests of the various stakeholders (research, industry, consumers, etc.). Finally, she mentions the reform of personal data protection that she initiated (leading to the GDPR, adopted in April 2016). [less ▲]

Vulnerability Analysis of Cyber Physical Systems under False-Data injection and disturbance attacks

in Vulnerability Analysis of Cyber Physical Systems under False-Data injection and disturbance attacks (2018, September)

In the present paper, the problem of attacks on cyber-physical systems via networked control system (NCS) subject to unmeasured disturbances is considered. The geometric approach is used to evaluate the ... [more ▼]

In the present paper, the problem of attacks on cyber-physical systems via networked control system (NCS) subject to unmeasured disturbances is considered. The geometric approach is used to evaluate the security and vulnerability level of the controlled system. The presented work deals with the so-called false data injection attacks and shows how imperfectly known disturbances can be used to perform undetectable, or at least stealthy, attacks that can make the NCS vulnerable to attacks from malicious outsiders. A numerical example is given to illustrate the approach. [less ▲]

A warmer world

in Pan European Networks (2015), (14), 58-59

Weak and strong from meshless methods for linear elastic problem under fretting contact conditions

in Tribology International (2019), 138

We present numerical computation of stresses under fretting fatigue conditions derived from closed form expressions. The Navier-Cauchy equations, that govern the problem, are solved with strong and weak ... [more ▼]

We present numerical computation of stresses under fretting fatigue conditions derived from closed form expressions. The Navier-Cauchy equations, that govern the problem, are solved with strong and weak form meshless numerical methods. The results are compared to the solution obtained from well-established commercial package ABAQUS, which is based on finite element method (FEM). The results show that the weak form meshless solution exhibits similar behavior as the FEM solution, while, in this particular case, strong form meshless solution performs better in capturing the peak in the surface stress. This is of particular interest in fretting fatigue, since it directly influences crack initiation. The results are presented in terms of von Mises stress contour plots, surface stress profiles, and the convergence plots for all three methods involved in the study. [less ▲]

Weakening the tight coupling between geometry and simulation in isogeometric analysis

Scientific Conference (2016, June 05)

In the standard paradigm of isogeometric analysis, the geometry and the simulation spaces are tightly integrated, i.e. the same non-uniform rational B-splines (NURBS) space, which is used for the geometry ... [more ▼]

In the standard paradigm of isogeometric analysis, the geometry and the simulation spaces are tightly integrated, i.e. the same non-uniform rational B-splines (NURBS) space, which is used for the geometry representation of the domain, is employed for the numerical solution of the problem over the domain. However, there are situations where this tight integration is a bane rather than a boon. Such situations arise where, e.g., (1) the geometry of the domain is simple enough to be represented by low order NURBS, whereas the unknown (exact) solution of the problem is sufficiently regular, and thus, the numerical solution can be obtained with improved accuracy by using NURBS of order higher than that required for the geometry, (2) the constraint of using the same space for the geometry and the numerical solution is particularly undesirable, such as in the shape and topology optimization, and (3) the solution of the problem has low regularity but for the curved boundary of the domain one can employ higher order NURBS. Therefore, we propose to weaken this constraint. An extensive study of patch tests on various combinations of polynomial degree, geometry type, and various cases of varying degrees and control variables between the geometry and the numerical solution will be discussed. It will be shown, with concrete reasoning, that why patch test fails in certain cases, and that those cases should be avoided in practice. Thereafter, selective numerical examples will be presented to address some of the above-mentioned situations, and it will be shown that weakening the tight coupling between geometry and simulation offers more flexibility in choosing the numerical solution spaces, and thus, improved accuracy of the numerical solution. Powered by [less ▲]

A web-based tool for efficient carbon footprint calculations: Lux screen CO2

Scientific Conference (2011, August 30)

Several commercial software tools for Life Cycle Assessment (LCA) are already available on the market and recently included ad-hoc extensions to calculate carbon footprints. Unfortunately, these software ... [more ▼]

Several commercial software tools for Life Cycle Assessment (LCA) are already available on the market and recently included ad-hoc extensions to calculate carbon footprints. Unfortunately, these software tools are often too complex and require too much specific expertise to be used by SMEs, consultants and others. For companies without any experience in the field of environmental assessment, the analysis of company-related CO2 emissions within a regional context is often an impossible task. The presented easy-to-use CO2 screening tool, adapted to their needs, was designed to support these companies. The web-based tool, ‘Lux screen CO2’ is able to assess and report site related direct and indirect greenhouse gas emissions, including the whole supply chain of the company and food-related impacts of the company restaurant. [less ▲]

A well-conditioned and optimally convergent XFEM for 3D linear elastic fracture

in International Journal for Numerical Methods in Engineering (n.d.)

A variation of the extended finite element method for 3D fracture mechanics is proposed. It utilizes global enrichment and point-wise as well as integral matching of displacements of the standard and ... [more ▼]

A variation of the extended finite element method for 3D fracture mechanics is proposed. It utilizes global enrichment and point-wise as well as integral matching of displacements of the standard and enriched elements in order to achieve higher accuracy, optimal convergence rates and improved conditioning for two and three dimensional crack problems. A bespoke benchmark problem is introduced to determine the method's accuracy in the general 3D case where it is demonstrated that the proposed approach improves the accuracy and reduces the number of iterations required for the iterative solution of the resulting system of equations by 40% for moderately refined meshes and topological enrichment. Moreover, when a fixed enrichment volume is used, the number of iterations required grows at a rate which is reduced by a factor of 2 compared to standard XFEM, diminishing the number of iterations by almost one order of magnitude. [less ▲]