23 resultados para Meccano


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The emergence of the mechanical bond during the past 25 years is giving chemistry a fillip in more ways than one. While its arrival on the scene is already impacting materials science and molecular nanotechnology, it is providing a new lease of life to chemical synthesis where mechanical bond formation Occurs as a consequence of the all-important templation Orchestrated by molecular recognition and self-assembly. The way in which covalent bond formation activates noncovalent bonding interactions, switching on molecular recognition that leads to self-assembly, and the template-directed synthesis of mechanically interlocked molecules-of which the so-called catenanes and rotaxanes may be regarded as the prototypes-has introduced a level of integration into chemical synthesis that has not previously been attained jointly at the supramolecular and molecular levels. The challenge now is to carry this I vel of integration during molecular synthesis beyond relatively small molecules into the realms of precisely functionalized extended molecular Structures and superstructures that perform functions in a collective manner as the key sources of instruction, activation, and performance in multi-component integrated Circuits and devices. These forays into organic chemistry by a scientific nomad are traced through thick and thin from the Athens of the North to the Windy City by Lake Michigan with interludes on the edge of the Canadian Shield beside Lake Ontario, in the Socialist Republic of South Yorkshire, on the Plains of Cheshire beside the Wirral, in the Midlands in the Heartland of Albion, and in the City of Angels beside the Peaceful Sea. (C) 2008 Elsevier Ltd. All rights reserved.

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[EN]We present a new method to construct a trivariate T-spline representation of complex solids for the application of isogeometric analysis. We take a genus-zero solid as a basis of our study, but at the end of the work we explain the way to generalize the results to any genus solids. The proposed technique only demands a surface triangulation of the solid as input data. The key of this method lies in obtaining a volumetric parameterization between the solid and the parametric domain, the unitary cube. To do that, an adaptive tetrahedral mesh of the parametric domain is isomorphically transformed onto the solid by applying a mesh untangling and smoothing procedure...

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[EN]The meccano method is a novel and promising mesh generation method for simultaneously creating adaptive tetrahedral meshes and volume parametrizations of a complex solid. We highlight the fact that the method requires minimum user intervention and has a low computational cost. The method builds a 3-D triangulation of the solid as a deformation of an appropriate tetrahedral mesh of the meccano. The new mesh generator combines an automatic parametrization of surface triangulations, a local refinement algorithm for 3-D nested triangulations and a simultaneous untangling and smoothing procedure. At present, the procedure is fully automatic for a genus-zero solid. In this case, the meccano can be a single cube. The efficiency of the proposed technique is shown with several applications...

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[EN]The meccano method is a novel and promising mesh generation technique for simultaneously creating adaptive tetrahedral meshes and volume parameterizations of a complex solid. The method combines several former procedures: a mapping from the meccano boundary to the solid surface, a 3-D local refinement algorithm and a simultaneous mesh untangling and smoothing. In this paper we present the main advantages of our method against other standard mesh generation techniques. We show that our method constructs meshes that can be locally refined by using the Kossaczky bisection rule and maintaining a high mesh quality. Finally, we generate volume T-mesh for isogeometric analysis, based on the volume parameterization obtained by the method…

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[EN]We present a new method to construct a trivariate T-spline representation of complex solids for the application of isogeometric analysis. The proposed technique only demands the surface of the solid as input data. The key of this method lies in obtaining a volumetric parameterization between the solid and a simple parametric domain. To do that, an adaptive tetrahedral mesh of the parametric domain is isomorphically transformed onto the solid by applying the meccano method. The control points of the trivariate T-spline are calculated by imposing the interpolation conditions on points situated both on the inner and on the surface of the solid...

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[EN]In this paper we review the novel meccano method. We summarize the main stages (subdivision, mapping, optimization) of this automatic tetrahedral mesh generation technique and we concentrate the study to complex genus-zero solids. In this case, our procedure only requires a surface triangulation of the solid. A crucial consequence of our method is the volume parametrization of the solid to a cube. We construct volume T-meshes for isogeometric analysis by using this result. The efficiency of the proposed technique is shown with several examples. A comparison between the meccano method and standard mesh generation techniques is introduced.-1…

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Congresos y conferencias

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[EN]We present advances of the meccano method for T-spline modelling and analysis of complex geometries. We consider a planar domain composed by several irregular sub-domains. These sub-regions are defined by their boundaries and can represent different materials. The bivariate T-spline representation of the whole physical domain is constructed from a square. In this procedure, a T-mesh optimization method is crucial. We show results of an elliptic problem by using a quadtree local T-mesh refinement technique…

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[EN]We have recently introduced a new strategy, based on the meccano method [1, 2], to construct a T-spline parameterization of 2D and 3D geometries for the application of iso geometric analysis [3, 4]. The proposed method only demands a boundary representation of the geometry as input data. The algorithm obtains, as a result, high quality parametric transformation between the objects and the parametric domain, i.e. the meccano. The key of the method lies in de_ning an isomorphic transformation between the parametric and physical T-mesh _nding the optimal position of the interior nodes, once the meccano boundary nodes are mapped to the boundary of the physical domain…

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[EN]The authors have recently introduced the meccano method for tetrahedral mesh generation and volume parameterization of solids. In this paper, we present advances of the method for T-spline modelling and analysis of complex geometries. We consider a planar domain composed by several irregular sub-domains. These sub-regions are defined by their boundaries and can represent different materials. The bivariate T-spline representation of the whole physical domain is constructed from a square. In this procedure, a T-mesh optimization method is crucial. We show results of an elliptic problem by using a quadtree local T-mesh refinement technique…

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[EN]We present a new method, based on the idea of the meccano method and a novel T-mesh optimization procedure, to construct a T-spline parameterization of 2D geometries for the application of isogeometric analysis. The proposed method only demands a boundary representation of the geometry as input data. The algorithm obtains, as a result, high quality parametric transformation between 2D objects and the parametric domain, the unit square. First, we define a parametric mapping between the input boundary of the object and the boundary of the parametric domain. Then, we build a T-mesh adapted to the geometric singularities of the domain in order to preserve the features of the object boundary with a desired tolerance…

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[EN]This work presents an innovative method to insert an open surface in a tetrahedral mesh. The insertion of a surface in a mesh can be done with 2 different approaches: introduce the surface to the geometry before generating the mesh, or insert the surface once the mesh is generated. This work uses the second approach. Essentially, the surface is first approximated by a set of faces of the existing mesh. This set is refined to obtain a more accurate approximation. Finally, the set is processed to satisfy some topological properties and projected to the actual surface. The strategy is based on a mesh generated by the Meccano Method…

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[EN]We present a new strategy, based on the idea of the meccano method and a novel T-mesh optimization procedure, to construct a T-spline parameterization of 2D geometries for the application of isogeometric analysis. The proposed method only demands a boundary representation of the geometry as input data. The algorithm obtains, as a result, high quality parametric transformation between 2D objects and the parametric domain, the unit square. First, we define a parametric mapping between the input boundary of the object and the boundary of the parametric domain. Then, we build a T-mesh adapted to the geometric singularities of the domain in order to preserve the features of the object boundary with a desired tolerance...