49,912 research outputs found
TriCCo v1.1.0 – a cubulation-based method for computing connected components on triangular grids
We present a new method to identify connected components on triangular grids used in atmosphere and climate models to discretize the horizontal dimension. In contrast to structured latitude–longitude grids, triangular grids are unstructured and the neighbors of a grid cell do not simply follow from the grid cell index. This complicates the identification of connected components compared to structured grids. Here, we show that this complication can be addressed by involving the mathematical tool of cubulation, which allows one to map the 2-D cells of the triangular grid onto the vertices of the 3-D cells of a cubical grid. Because the latter is structured, connected components can be readily identified by previously developed software packages for cubical grids. Computing the cubulation can be expensive, but, importantly, needs to be done only once for a given grid. We implement our method in a Python package that we name TriCCo and make available via pypi, gitlab, and zenodo. We document the package and demonstrate its application using simulation output from the ICON atmosphere model. Finally, we characterize its computational performance and compare it to graph-based identifications of connected components using breadth-first search. The latter shows that TriCCo is ready for triangular grids with up to 500 000 cells, but that its speed and memory requirement should be improved for its application to larger grids
Addition of higher order plate elements to NASTRAN
Two plate elements, the linear strain triangular membrane element CTRIM6 and the higher order plate bending element CTRPLT1, were added to NASTRAN Level 16.0. The theoretical formulation, programming details, and bulk data information pertaining to the addition of these elements are discussed. Sample problems illustrating the use of these elements are presented
Demodulation of Spatial Carrier Images: Performance Analysis of Several Algorithms Using a Single Image
http://link.springer.com/article/10.1007%2Fs11340-013-9741-6#Optical full-field techniques have a great importance in modern experimental mechanics. Even if they are reasonably spread among the university laboratories, their diffusion in industrial companies remains very narrow for several reasons, especially a lack of metrological performance assessment. A full-field measurement can be characterized by its resolution, bias, measuring range, and by a specific quantity, the spatial resolution. The present paper proposes an original procedure to estimate in one single step the resolution, bias and spatial resolution for a given operator (decoding algorithms such as image correlation, low-pass filters, derivation tools ...). This procedure is based on the construction of a particular multi-frequential field, and a Bode diagram representation of the results. This analysis is applied to various phase demodulating algorithms suited to estimate in-plane displacements.GDR CNRS 2519 “Mesures de Champs et Identification en Mécanique des Solide
Vortex arrays in neutral trapped Fermi gases through the BCS–BEC crossover
Vortex arrays in type-II superconductors reflect the translational symmetry of an infinite system. There are cases, however, such as ultracold trapped Fermi gases and the crust of neutron stars, where finite-size effects make it complex to account for the geometrical arrangement of vortices. Here, we self-consistently generate these arrays of vortices at zero and finite temperature through a microscopic description of the non-homogeneous superfluid based on a differential equation for the local order parameter, obtained by coarse graining the Bogoliubov–de Gennes (BdG) equations. In this way, the strength of the inter-particle interaction is varied along the BCS–BEC crossover, from largely overlapping Cooper pairs in the Bardeen–Cooper–Schrieffer (BCS) limit to dilute composite bosons in the Bose–Einstein condensed (BEC) limit. Detailed comparison with two landmark experiments on ultracold Fermi gases, aimed at revealing the presence of the superfluid phase, brings out several features that make them relevant for other systems in nature as well
Addition of higher order plate and shell elements into NASTRAN computer program
Two higher order plate elements, the linear strain triangular membrane element and the quintic bending element, along with a shallow shell element, suitable for inclusion into the NASTRAN (NASA Structural Analysis) program are described. Additions to the NASTRAN Theoretical Manual, Users' Manual, Programmers' Manual and the NASTRAN Demonstration Problem Manual, for inclusion of these elements into the NASTRAN program are also presented
Semiparametric Estimation of Structural Functions in Nonseparable Triangular Models
Triangular systems with nonadditively separable unobserved heterogeneity
provide a theoretically appealing framework for the modelling of complex
structural relationships. However, they are not commonly used in practice due
to the need for exogenous variables with large support for identification, the
curse of dimensionality in estimation, and the lack of inferential tools. This
paper introduces two classes of semiparametric nonseparable triangular models
that address these limitations. They are based on distribution and quantile
regression modelling of the reduced form conditional distributions of the
endogenous variables. We show that average, distribution and quantile
structural functions are identified in these systems through a control function
approach that does not require a large support condition. We propose a
computationally attractive three-stage procedure to estimate the structural
functions where the first two stages consist of quantile or distribution
regressions. We provide asymptotic theory and uniform inference methods for
each stage. In particular, we derive functional central limit theorems and
bootstrap functional central limit theorems for the distribution regression
estimators of the structural functions. These results establish the validity of
the bootstrap for three-stage estimators of structural functions, and lead to
simple inference algorithms. We illustrate the implementation and applicability
of all our methods with numerical simulations and an empirical application to
demand analysis.Comment: 45 pages, 4 figures, 1 table, we have added grant funding
acknowledgement to v
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