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891.
Meshfree Thinning of 3D Point Clouds 总被引:1,自引:0,他引:1
An efficient data reduction scheme for the simplification of a surface given by a large set X of 3D point-samples is proposed. The data reduction relies on a recursive point removal algorithm, termed thinning, which
outputs a data hierarchy of point-samples for multiresolution surface approximation. The thinning algorithm works with a point
removal criterion, which measures the significances of the points in their local neighbourhoods, and which removes a least
significant point at each step. For any point x in the current point set Y⊂X, its significance reflects the approximation quality of a local surface reconstructed from neighbouring points in Y. The local surface reconstruction is done over an estimated tangent plane at x by using radial basis functions. The approximation quality of the surface reconstruction around x is measured by using its maximal deviation from the given point-samples X in a local neighbourhood of x. The resulting thinning algorithm is meshfree, i.e., its performance is solely based upon the geometry of the input 3D surface
point-samples, and so it does not require any further topological information, such as point connectivities. Computational
details of the thinning algorithm and the required data structures for efficient implementation are explained and its complexity
is discussed. Two examples are presented for illustration.
This paper is dedicated to Arieh Iserles on the occasion of his 60th anniversary. 相似文献
892.
Graph Coloring with Adaptive Evolutionary Algorithms 总被引:4,自引:0,他引:4
This paper presents the results of an experimental investigation on solving graph coloring problems with Evolutionary Algorithms (EAs). After testing different algorithm variants we conclude that the best option is an asexual EA using order-based representation and an adaptation mechanism that periodically changes the fitness function during the evolution. This adaptive EA is general, using no domain specific knowledge, except, of course, from the decoder (fitness function). We compare this adaptive EA to a powerful traditional graph coloring technique DSatur and the Grouping Genetic Algorithm (GGA) on a wide range of problem instances with different size, topology and edge density. The results show that the adaptive EA is superior to the Grouping (GA) and outperforms DSatur on the hardest problem instances. Furthermore, it scales up better with the problem size than the other two algorithms and indicates a linear computational complexity. 相似文献
893.
András Krámli 《Journal of statistical physics》1996,83(1-2):167-191
An exposition of some methods of proving exponential (stretched exponential) decay of correlations is given. One-dimensional strictly hyperbolic and quadratic maps and two-dimensional piecewise smooth, uniformly hyperbolic maps are considered. The emphasis is on the fundamental constructions of the Markov sieve method due to Bunimovich-Chernov-Sinai and those of Liverani's Hilbert metric method. 相似文献
894.
Nazakat Ullah 《Pramana》1993,41(2):171-174
A formulation is developed to derive exact analytic expressions for electron-electron correlation and density of electrons
in momentum space using hydrogenic wave functions. It is shown that for large atoms the expression for density of electrons
has a simple form. 相似文献
895.
896.
Vijay GUPTA 《数学学报(英文版)》2007,23(8):1457-1462
In this paper, we study the rate of convergence for functions of bounded variation for the recently introduced Bzier variant of the Meyer-Knig-Zeller-Durrmeyer operators. 相似文献
897.
A two-dimensional linearized problem on plane buckling modes (BMs) of a rectangular plate with free edges, made of an elastic
orthotropic material, underbiaxial tension-compression is considered. With the use of double trigonometric basis functions,
displacement functions exactly satisfying all static boundary condition on plate edges are constructed. It is shown that the
exact analytic solutions found describe only the pure shear BMs, and if the normal stress in one direction is assumed equal
to zero, an analog of the solution given by the kinematic Timoshenko model can be obtained. Upon performing the limit passage
to the zero harmonic in the displacement functions of one of the directions, the solution to the problem of biaxial compression
can be obtained by equating the Poisson ratio to zero; in the case of uniaxial compression, this solution exactly agrees with
that following from the classical Bernoulli-Euler model.
__________
Translated from Mekhanika Kompozitnykh Materialov, Vol. 43, No. 2, pp. 149–170, March–April, 2007. 相似文献
898.
We study the contractibility of the efficient solution set of strictly quasiconcave vector maximization problems on (possibly) noncompact feasible domains. It is proved that the efficient solution set is contractible if at least one of the objective functions is strongly quasiconcave and any intersection of level sets of the objective functions is a compact (possibly empty) set. This theorem generalizes the main result of Benoist (Ref.1), which was established for problems on compact feasible domains.The authors thank Dr. T. D. Phuong, Dr. T. X. D. Ha, and the referees for helpful comments and suggestions. 相似文献
899.
In this paper we give new and purely analytical proofs of a number of classical results on the asymptotic behavior of large random matrices of complex Wigner type (the GUE-case) or of complex Wishart type: Wigner's semi-circle law, the Harer-Zagier recursion formula, the Marchenko-Pastur law, the Geman-Silverstein results on the largest and smallest eigenvalues and other related results. Our approach is based on the derivation of explicit formulae for the moment generating functions for random matrices of the two considered types. 相似文献
900.
In this paper we consider a collocation method for solving Fredholm integral equations of the first kind, which is known to be an ill-posed problem. An “unregularized” use of this method can give reliable results in the case when the rate at which smallest singular values of the collocation matrices decrease is known a priori. In this case the number of collocation points plays the role of a regularization parameter. If the a priori information mentioned above is not available, then a combination of collocation with Tikhonov regularization can be the method of choice. We analyze such regularized collocation in a rather general setting, when a solution smoothness is given as a source condition with an operator monotone index function. This setting covers all types of smoothness studied so far in the theory of Tikhonov regularization. One more issue discussed in this paper is an a posteriori choice of the regularization parameter, which allows us to reach an optimal order of accuracy for deterministic noise model without any knowledge of solution smoothness. 相似文献