Complex Geometrical Features Research Articles

Time‐implicit fixed and deforming grid solutions for compression mold filling

AbstractA general governing equation for tracking the filling free surface during compression molding is derived. From this equation, with appropriate choice of parameters, a time‐implicit fixed grid solution and a time‐implicit deforming grid solution are obtained. Numerical results of several test problems reveal that both solutions reach the same level of accuracy. The fixed grid scheme, however, is more robust and can solve problem with complex geometrical features.

A model for representing topological relationships between complex geometric features in spatial databases

Various models for the representation of topological relationships have been developed. The aim of this paper is to show that the set of relationships proposed in [7] (the CBM), for describing topological relationships among two-dimensional simple features, is applicable with few modifications to the case of complex features (that is, areas made up of several components possibly containing holes, lines with self-intersections, and/or more than two endpoints, and so on). The CBM offers a small set of topological relationships with high expressiveness which is proven to be mutually exclusive and complete, and therefore suitable to be embedded in a spatial query language.

Finite Element Modelling of the Plasma Edge

AbstractAnalysis of particle‐ and energy‐transport in tokamak plasmas shows the importance of the scrape‐off layer (SOL) to achieve satisfying conditions for a burning plasma in a fusion reactor. To take into account the influence of complex geometrical features on transport, we developed a 2D‐fluid‐code based on a Finite Element Method (FEM). Because this numerical scheme needs no regular grid structure, one can deal much more accurately with the plasma flow in non simply connected domains and near limiter‐ or divertor‐plates, where the magnetic field is inclined to the target. This permits a geometrically and physically more realistic description of the interaction of plasma‐ and neutral‐particles. Results from a coupled calculation between the FEM‐code and a neutral‐gas Monte‐Carlo‐code (EIRENE) are discussed for the SOL of TEXTOR.

A class of hybrid finite element methods for electromagnetics: a review

Integral equation methods have generally been the workhorse for antenna and scattering computations. In the case of antennas, they continue to be the prominent computational approach, but for scattering applications the requirement for large-scale computations has turned researchers' attention to near neighbor methods such as the finite element method, which has low O(N) storage requirements and is readily adaptable in modeling complex geometrical features and material inhomogeneities. In this paper, we review three hybrid finite element methods for simulating composite scatterers, conformal microstrip antennas, and finite periodic arrays. Specifically, we discuss the finite element method and its application to electromagnetic problems when combined with the boundary integral, absorbing boundary conditions, and artificial absorbers for terminating the mesh. Particular attention is given to large-scale simulations, methods, and solvers for achieving low memory requirements and code performance on parallel computing architectures.

Floral morphogenesis in Anagallis: Scanning-electron-micrograph sequences from individual growing meristems before, during, and after the transition to flowering

Non-destructive scanning electron microscopy allows one to visualize changing patterns of individual cells during epidermal development in single meristems. Cell growth and division can be followed in parallel with morphogenesis. The method is applied here to the shoot apex of Anagallis arvensis L. before, during, and after floral transition. Phyllotaxis is decussate; photoperiodic induction of the plant leads to the production of a flower in the axil of each leaf. As seen from above, the recently formed oval vegetative dome is bounded on its slightly longer sides by creases of adjacent leaf bases. The rounded ends of the dome are bounded by connecting tissue, horizontal bands of node cells between the opposed leaf bases. The major growth axis runs parallel to the leaf bases. While slow-growing at the dome center, this axis extends at its periphery to form a new leaf above each band of connecting tissue. Connecting tissue then forms between the new leaves and a new dome is defined at 90° to the former. The growth axis then changes by 90°. This is the vegetative cycle. The first observed departure from vegetative growth is that the connecting tissue becomes longer relative to the leaf creases. Presumably because of this, the major growth axis does not change in the usual way. Extension on the dome continues between the older leaves until the axis typically buckles a second time, on each side, to form a second crease parallel to the new leaf-base crease. The tissue between these two creases becomes the flower primordium. The second crease also delimits the side of a new apical dome with the major axis and growth direction altered by 90°. During this inflorescence cycle the connecting tissue is relatively longer than before. Much activity is common to both cycles. It is concluded that the complex geometrical features of the inflorescence cycle may result from a change in a biophysical boundary condition involving dome geometry, rather than a comprehensive revision of apical morphogenesis.

The integrity of geometrical boundaries in the two‐dimensional delaunay triangulation

AbstractThe Delaunay triangulation has recently received attention as a viable method for construction computational meshes. However, an arbitrary boundary definition which must be preserved in the triangulation process will not, in general, satisfy the geometrical definition on which the Delaunay construction is founded. The effect of this is that the integrity of the given boundary edges will be violated and the computational mesh will not conform to the applied geometrical shape. A method is proposed whereby boundary data are supplemented with points to ensure that imposed boundary edges are preserved during the Delaunay triangulation. The method is illustrated on a geometry of an estuary which exhibits highly complex geometrical features.

Growth twins and development of polycrystallinity in electrodeposits

Twins in nickel electrodeposits have been characterized by transmission electron microscopy. A diffraction-contrast analysis of twin structure and its associated dislocation substructure have led us to conclude that all of the observed cases are growth twins. Their complex geometrical features primarily originate from the accidental agglomerations of individual small twins which are nucleated close to each other. A probable mechanism for the formation of such growth twins, consistent with our observations, was found to be best described by a twinning model based on a two-dimensional nucleation on {111} growth planes with a stacking fault. Furthermore, it has been demonstrated that the addition of an organic impurity to the nickel electrolyte not only increases the twinning probability considerably by inducing a high density of {111} microfacets, but also refines the sizes by inhibiting their growth. The structure of growth twins formed on {001} and {110} growth planes is discussed with a special emphasis on the probability for forming polycrystalline films.