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Geometrical approach to the proton spin decomposition Lorce, Cédric in Physical Review. D, Particles, Fields, Gravitation, and Cosmology (2013), D87 We discuss in detail and from the geometrical point of view the issues of gauge invariance and Lorentz covariance raised by the approach proposed recently by Chen et al. to the proton spin decomposition ... [more ▼] We discuss in detail and from the geometrical point of view the issues of gauge invariance and Lorentz covariance raised by the approach proposed recently by Chen et al. to the proton spin decomposition. We show that the gauge invariance of this approach follows from a mechanism similar to the one used in the famous Stueckelberg trick. Stressing the fact that the Lorentz symmetry does not force the gauge potential to transform as a Lorentz four-vector, we show that the Chen et al. approach is Lorentz covariant provided that one uses the suitable Lorentz transformation law. We also make an attempt to summarize the present situation concerning the proton spin decomposition. We argue that the ongoing debates concern essentially the physical interpretation and are because of the plurality of the adopted pictures. We discuss these different pictures and propose a pragmatic point of view. [less ▲] Detailed reference viewed: 10 (2 ULg)Geometrical considerations for evaluation of reserve design. Bogaert, Jan ; ; et al in Web Ecology (2001), (2), 65-70 Detailed reference viewed: 6 (0 ULg)Geometrical CP violation in the N-Higgs-doublet model Ivanov, Igor ; in European Physical Journal C -- Particles & Fields (2013), 73 Geometrical CP violation is a particular type of spontaneous CP violation in which the vacuum expectation values have phases which are calculable, i.e. stable against the variation of the free parameters ... [more ▼] Geometrical CP violation is a particular type of spontaneous CP violation in which the vacuum expectation values have phases which are calculable, i.e. stable against the variation of the free parameters of the scalar potential. Although originally suggested within a specific version of the three-Higgs-doublet model, it is a generic phenomenon. We investigate its viability and characteristic features in models with several Higgs doublets. Our work contains both general results and illustrative examples. [less ▲] Detailed reference viewed: 19 (0 ULg)Geometrical Effects on the Dynamical Behavior of MEMS structures Pustan, Marius ; Golinval, Jean-Claude ; Rochus, Véronique (2010, May 16) The influence of geometrical dimensions on the dynamical behavior of polysilicon MEMS structures configurations is studied and presented in this paper. Electrostatically actuated MEMS components as ... [more ▼] The influence of geometrical dimensions on the dynamical behavior of polysilicon MEMS structures configurations is studied and presented in this paper. Electrostatically actuated MEMS components as microbridges and microcantilevers are used to investigate the coupled electro-mechanic effect, frequency responses and the dynamic bending stress. The electrostatic principle is common in sensing and acting devices and there are many MEMS structures subjected to electrostatic forces. [less ▲] Detailed reference viewed: 29 (10 ULg)Geometrical guidance and trapping transition of human sperm cells ; ; et al in Physical Review. E : Statistical, Nonlinear, and Soft Matter Physics (2014), 89 The guidance of human sperm cells under con finement in quasi 2D microchambers is investigated using a purely physical method to control their distribution. Transport property measurements and simulations ... [more ▼] The guidance of human sperm cells under con finement in quasi 2D microchambers is investigated using a purely physical method to control their distribution. Transport property measurements and simulations are performed with diluted sperm populations, for which eff ects of geometrical guidance and concentration are studied in detail. In particular, a trapping transition at convex angular wall features is identi ed and analyzed. We also show that highly efficient microratchets can be fabricated by using curved asymmetric obstacles to take advantage of the spermatozoa specifi c swimming strategy. [less ▲] Detailed reference viewed: 50 (13 ULg)Geometrical validity of curvilinear finite elements Johnen, Amaury ; ; Geuzaine, Christophe in William Roshan, Quadros (Ed.) Proceedings of the 20th International Meshing Roundtable (2011, October 25) In this paper, we describe a way to compute accurate bounds on Jacobians of curvilinear finite elements of all kinds. Our condition enables to guarantee that an element is geometrically valid, i.e., that ... [more ▼] In this paper, we describe a way to compute accurate bounds on Jacobians of curvilinear finite elements of all kinds. Our condition enables to guarantee that an element is geometrically valid, i.e., that its Jacobian is strictly positive everywhere in its reference domain. It also provides an efficient way to measure the distortion of curvilinear elements. The key feature of the method is to expand the Jacobian using a polynomial basis, built using Bézier functions, that has both properties of boundedness and positivity. Numerical results show the sharpness of our estimates. [less ▲] Detailed reference viewed: 34 (11 ULg)Geometrical validity of curvilinear finite elements Johnen, Amaury ; ; Geuzaine, Christophe in Journal of Computational Physics (2013), 233 In this paper, we describe a way to compute accurate bounds on Jacobian determinants of curvilinear polynomial finite elements. Our condition enables to guarantee that an element is geometrically valid, i ... [more ▼] In this paper, we describe a way to compute accurate bounds on Jacobian determinants of curvilinear polynomial finite elements. Our condition enables to guarantee that an element is geometrically valid, i.e., that its Jacobian determinant is strictly positive everywhere in its reference domain. It also provides an efficient way to measure the distortion of curvilinear elements. The key feature of the method is to expand the Jacobian determinant using a polynomial basis, built using Bézier functions, that has both properties of boundedness and positivity. Numerical results show the sharpness of our estimates. [less ▲] Detailed reference viewed: 94 (32 ULg)Geometrical validity of curvilinear pyramidal finite elements Johnen, Amaury ; Geuzaine, Christophe in Journal of Computational Physics (2015), 299 Detailed reference viewed: 27 (3 ULg)Geometrical validity of high-order pyramidal finite elements Johnen, Amaury ; Geuzaine, Christophe Conference (2014, July 24) Detailed reference viewed: 38 (15 ULg)Geometrical validity of high-order triangular finite elements Johnen, Amaury ; ; Geuzaine, Christophe in Engineering with Computers (2014), 30(3), 375-382 This paper presents a method to compute accurate bounds on Jacobian determinants of high-order (curvilinear) triangular finite elements. This method can be used to guarantee that a curvilinear triangle is ... [more ▼] This paper presents a method to compute accurate bounds on Jacobian determinants of high-order (curvilinear) triangular finite elements. This method can be used to guarantee that a curvilinear triangle is geometrically valid, i.e., that its Jacobian determinant is strictly positive everywhere in its reference domain. It also provides an efficient way to measure the quality the triangles. The key feature of the method is to expand the Jacobian determinant using a polynomial basis, built using Bézier functions, that has both properties of boundedness and positivity. Numerical results show the sharpness of our estimates. [less ▲] Detailed reference viewed: 110 (30 ULg)Geometrically exact beam finite element formulated on the special Euclidean group SE(3) Sonneville, Valentin ; ; Bruls, Olivier in Computer Methods in Applied Mechanics & Engineering (2014), 268 This paper describes a dynamic formulation of a straight beam finite element in the setting of the special Euclidean group SE(3). First, the static and dynamic equilibrium equations are derived in this ... [more ▼] This paper describes a dynamic formulation of a straight beam finite element in the setting of the special Euclidean group SE(3). First, the static and dynamic equilibrium equations are derived in this framework from variational principles. Then, a non-linear interpolation formula using the exponential map is introduced. It is shown that this framework leads to a natural coupling in the interpolation of the position and rotation variables. Next, the discretized internal and inertia forces are developed. The semi-discrete equations of motion take the form of a second-order ordinary differential equation on a Lie group, which is solved using a Lie group time integration scheme. It is remarkable that no parameterization of the nodal variables needs to be introduced and that the proposed Lie group framework leads to a compact and easy-to-implement formulation. Some important numerical and theoretical aspects leading to a computationally efficient strategy are highlighted and discussed. For instance, the formulation leads to invariant tangent stiffness and mass matrices under rigid body motions and a locking free element. The proposed formulation is successfully tested in several numerical static and dynamic examples. [less ▲] Detailed reference viewed: 82 (26 ULg)A geometrically exact shell finite element with an almost constant tangent stiffness matrix Sonneville, Valentin ; ; Bruls, Olivier Conference (2015, July) Detailed reference viewed: 14 (1 ULg)Geometrically non linear analysis of steel Storage racks submitted to earthquake loading Degée, Hervé ; Rossi, Barbara ; in International Journal of Structural Stability & Dynamics (2011), 11(5), 949-967 Steel storage racks are light and flexible structures. When submitted to earthquake loading, they can exhibit very large transverse displacements and are thus prone to significant consequences of second ... [more ▼] Steel storage racks are light and flexible structures. When submitted to earthquake loading, they can exhibit very large transverse displacements and are thus prone to significant consequences of second-order geometrical effects. In the context of the drafting of European recommendations for the design of steel pallet racks for their seismic resistance, this paper presents a parameter study comparing the various methods commonly used in practice for analyzing the seismic structural behavior of racks (i.e. "modal response spectrum analysis" and "lateral force method analysis") as well as the different ways to account for geometrically nonlinear effects in these conventional methods of analysis in the case of structures designed for low ductility. [less ▲] Detailed reference viewed: 125 (7 ULg)Geometrically non linear dynamic behavior of steel storage racks subjected to earthquake loading Degée, Hervé ; ; in Proceedings of the ESMC 2009 Conference (2009) Detailed reference viewed: 23 (0 ULg)La géométrie de la spatiocarte : corrections et validations, Spatiocartographie ; Billen, Roland in Bulletin de la Société Géographique de Liège (2000), (38(1)), 25-43 Detailed reference viewed: 35 (8 ULg)La géométrie de Lobachevski De Rop, Yves ; E-print/Working paper (2011) Detailed reference viewed: 111 (23 ULg)Géométrie des matrices positives semi-définies de rang fixé : un peu de théorie et beaucoup d’applications Sepulchre, Rodolphe ; ; in Proceedings of Sixième Conférence Internationale Francophone d'Automatique (CIFA 2010) (2010, June) Cet article est une introduction au calcul et `a l’optimisation sur les matrices sym´etriques positives semid ´efinies de rang (faible) fix´e. L’approche propos´ee est bas´ee sur deux g´eom´etries ... [more ▼] Cet article est une introduction au calcul et `a l’optimisation sur les matrices sym´etriques positives semid ´efinies de rang (faible) fix´e. L’approche propos´ee est bas´ee sur deux g´eom´etries riemanniennes quotient, qui permettent de calculer efficacement tout en pr´eservant le rang et le caract` ere positif des matrices consid´er´ees. Le champ d’applications est vaste, et l’article survole quelques d´eveloppements r´ecents qui illustrent l’int´erˆet de l’approche consid´er´ee dans les probl`emes de tr`es grande taille rencontr´es en contrˆole, statistiques, et apprentissage. [less ▲] Detailed reference viewed: 77 (7 ULg)Géométrie en situation (COJEREM), notions pour l'élève ; ; et al Book published by De Boeck (1995) Detailed reference viewed: 36 (0 ULg)Géométrie et géométrie analytique Learning material (2011) L’étudiant préparant l’examen d’admission trouvera dans ces notes des notions qu’il est important de maîtriser pour aborder l’examen de géométrie et géométrie analytique et, plus largement, le cours de ... [more ▼] L’étudiant préparant l’examen d’admission trouvera dans ces notes des notions qu’il est important de maîtriser pour aborder l’examen de géométrie et géométrie analytique et, plus largement, le cours de géométrie de premier bachelier. [less ▲] Detailed reference viewed: 152 (7 ULg)Geometrieoptimierung von gerührten Extraktionskolonnen ; Pfennig, Andreas in Chemie Ingenieur Technik (2012), 84(8), 1274 |
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