2d gauge theories and generalized geometry

in Journal of High Energy Physics [=JHEP] (2014)

We show that in the context of two-dimensional sigma models minimal coupling of an ordinary rigid symmetry Lie algebra g leads naturally to the appearance of the “generalized tangent bundle” TM ≡ T M ⊕ T ... [more ▼]

We show that in the context of two-dimensional sigma models minimal coupling of an ordinary rigid symmetry Lie algebra g leads naturally to the appearance of the “generalized tangent bundle” TM ≡ T M ⊕ T ∗ M by means of composite fields. Gauge transformations of the composite fields follow the Courant bracket, closing upon the choice of a Dirac structure D ⊂ TM (or, more generally, the choide of a “small Dirac-Rinehart sheaf” D), in which the fields as well as the symmetry parameters are to take values. In these new variables, the gauge theory takes the form of a (non-topological) Dirac sigma model, which is applicable in a more general context and proves to be universal in two space-time dimensions: a gauging of g of a standard sigma model with Wess-Zumino term exists, iff there is a prolongation of the rigid symmetry to a Lie algebroid morphism from the action Lie algebroid M × g → M into D → M (or the algebraic analogue of the morphism in the case of D). The gauged sigma model results from a pullback by this morphism from the Dirac sigma model, which proves to be universal in two-spacetime dimensions in this sense. [less ▲]

2D Tool-Path Generation Method for Multi-Axis Milling Machine using ToF camera

Scientific Conference (2014, September 12)

Multi-axis machines are known for their precise production of complex parts, where multi-tool are working in the same area or static workpiece support or clamping parts, may cause collision problems. It ... [more ▼]

Multi-axis machines are known for their precise production of complex parts, where multi-tool are working in the same area or static workpiece support or clamping parts, may cause collision problems. It is therefore necessary to identify potential collision risks and avoid them in an efficient way, which may cause production stops and machinery damage. This research study has been focusing on safe non-functional (rapid) tool-path generation for multi-axis milling machine, where no efficient automatic collision avoidance solution exists (in the literature). A 3D Time of Flight (TOF) camera attached into the machine will be able to sense any unwanted situation in the manufacturing environment and provide rapid and automatic solution to detect and avoid collisions for safe tool movements during production. In the presence of obstacles, the proposed approach will provide decisions regarding tool-path correction and improvement automatically. The proposed algorithm based on 3D vision concept is also able to take into account unknown obstacle shape, size during production but dynamic aspects of the scene will be treated in future. The concept presented take into account the 3D information from the scene for traversal safe tool-paths generation for a static environment as an initial application, which will be adapted to more complex real machining scenarios by integrating it with STEP-NC technology in future. [less ▲]

3 Fragen an 4 Luxemburger Theatermacher

Speeches/Talks (2018)

A 3.2% efficient Kesterite device from electrodeposited stacked elemental layers

in Journal of Electroanalytical Chemistry (2010), 646(1-2), 52-59

30. Symposium Klinische Psychologie und Psychotherapie, Abstractband

Book published by University of Luxembourg (2012)

§§ 325 bis 329 HGB zur Publizität der Rechnungslegung

in Hachmeister et al., Bilanzrecht (2018)

§ 338 KAGB und die EuSEF-VO

in Kapitalanlagegesetzbuch, Kommentar (2019)

§ 36. Die Pädagogik

in Holzhey, Helmut; Mudroch, Vilem (Eds.) Die Philosophie des 18. Jahrhunderts 5/1+2: Heiliges Römische Reich Deutscher Nation. Schweiz. Nord- und Osteuropa (2014)

3D Crack Detection Using an XFEM Variant and Global Optimization Algorithms

Scientific Conference (2016, May)

3D DEM – FEM Coupling to Analyse the Tractive Performance of Different Tire Treads in Soil

in Idelsohn, S; Papadrakakis, M; Schrefler, B (Eds.) Computational Methods for Coupled Problems in Science and Engineering V (2013, June)

This contribution investigates the tractive performance of different tire treads on granular terrain by an efficient combination of the Discrete Element Method (DEM) and the Finite Element Method (FEM ... [more ▼]

This contribution investigates the tractive performance of different tire treads on granular terrain by an efficient combination of the Discrete Element Method (DEM) and the Finite Element Method (FEM). The proposed coupling method has been shown to be a sufficient technique when resolving the different length scales involved in engineering problems dealing with granular assemblies in contact with deformable bodies [1][2]. Herein, the extended discrete element method (XDEM) is used to describe the dynamics of the granular assembly. Thereby the discrete approach accounts for the motion and forces of each grain individually. On the other hand, the finite element method accurately predicts the deformations and stresses acting within the tire tread. Hence, the simulation domain occupied by the tire is efficiently described as a continuous entity. The coupling of both method is based on the interface shared by the two spatially separated domains. The interface coupling enables to apply a contact model fitting the particular contact behaviour between the grains and the tread surface. Thus, contact forces develop at the interface and propagate into each domain. The coupling method enables to capture both responses simultaneously. Each grain in contact with the tread surface generates a contact force which it reacts on repulsively. The contact forces sum up over the surface and cause the tire tread to deform. The resultant stresses are then again recognised by the granular assembly. The coupling method compensates quite naturally the shortages of both numerical methods. It further employs a fast contact detection algorithm to spare valuable computation time [1]. The proposed DEM-FEM Coupling technique was employed to study the tractive performance of four different tire treads on a soil layer of the material sand. The simulations were conducted in accordance to the experimental measurements undertaken by Shinone et al. [3]. The contact forces at the surface of smooth, lug, rib and block tread patterns are captured by 3D simulations of different slip values of each tire tread. The simulation results are used to analyse the gross tractive effort, running resistance and drawbar pull of the different tread patterns in sand. [less ▲]