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981.
Alloyeau D Prévot G Le Bouar Y Oikawa T Langlois C Loiseau A Ricolleau C 《Physical review letters》2010,105(25):255901
Ostwald ripening has been broadly studied because it plays a determinant role in the evolution of cluster size during both chemical and physical synthesis of nanoparticles. This thermoactivated process causes large particles to grow, drawing material from the smaller particles, which shrink. However, this phenomenon becomes more complex when considering the coarsening of metallic alloy clusters. The present experimental and theoretical investigations show that the relative composition of CoPt nanoparticles can be strongly modified during high temperature annealing and displays a size-dependent behavior. This compositional change originates from the higher evaporation rate of Co atoms from the nanoparticles. More importantly, this effect is expected in all alloy clusters containing species with different mobilities. 相似文献
982.
We study a generalization of the Fréchet functional equation, stemming from a characterization of inner product spaces. We show, in particular, that under some weak additional assumptions each solution of such an equation is additive. We also obtain a theorem on the Ulam type stability of the equation. In its proof we use a fixed point result to show the existence of an exact solution of the equation that is close to a given approximate solution. 相似文献
983.
Krzysztof Kurdyka Olivier Le Gal 《Journal of Mathematical Analysis and Applications》2018,457(1):978-990
Let be a connected locally closed set which is definable in an o-minimal structure. We prove that the following three statements are equivalent: (i) X is a manifold, (ii) the tangent cone and the paratangent cone of X coincide at every point in X, (iii) for every , the tangent cone of X at the point x is a k-dimensional linear subspace of (k does not depend on x) varies continuously in x, and the density . 相似文献
984.
Chris Le Sueur 《Annals of Pure and Applied Logic》2018,169(1):83-115
In this paper we develop a technique for proving determinacy of classes of the form (a refinement of the difference hierarchy on lying between and ) from weak principles, establishing upper bounds for the determinacy-strength of the classes for all computable α and of . This bridges the gap between previously known hypotheses implying determinacy in this region. 相似文献
985.
Given X a Hilbert space, ω a modulus of continuity, E an arbitrary subset of X, and functions , , we provide necessary and sufficient conditions for the jet to admit an extension with convex and of class , by means of a simple explicit formula. As a consequence of this result, if ω is linear, we show that a variant of this formula provides explicit extensions of general (not necessarily convex) 1-jets satisfying the usual Whitney extension condition, with best possible Lipschitz constants of the gradients of the extensions. Finally, if X is a superreflexive Banach space, we establish similar results for the classes . 相似文献
986.
Charles Audet Amina Ihaddadene Sébastien Le Digabel Christophe Tribes 《Optimization Letters》2018,12(4):675-689
Blackbox optimization problems are often contaminated with numerical noise, and direct search methods such as the Mesh Adaptive Direct Search (MADS) algorithm may get stuck at solutions artificially created by the noise. We propose a way to smooth out the objective function of an unconstrained problem using previously evaluated function evaluations, rather than resampling points. The new algorithm, called Robust-MADS is applied to a collection of noisy analytical problems from the literature and on an optimization problem to tune the parameters of a trust-region method. 相似文献
987.
In a previous paper a preconditioning strategy based on overlapping domain decomposition was applied to the Galerkin approximation
of elliptic partial differential equations on the sphere. In this paper the methods are extended to more general pseudodifferential
equations on the sphere, using as before spherical radial basis functions for the approximation space, and again preconditioning
the ill-conditioned linear systems of the Galerkin approximation by the additive Schwarz method. Numerical results are presented
for the case of hypersingular and weakly singular integral operators on the sphere
\mathbbS2{\mathbb{S}^2} . 相似文献
988.
This paper deals with the problem of multivariate copula density estimation. Using wavelet methods we provide two shrinkage procedures based on thresholding rules for which knowledge of the regularity of the copula density to be estimated is not necessary. These methods, said to be adaptive, have proved to be very effective when adopting the minimax and the maxiset approaches. Moreover we show that these procedures can be discriminated in the maxiset sense. We provide an estimation algorithm and evaluate its properties using simulation. Finally, we propose a real life application for financial data. 相似文献
989.
Upper semicontinuity result for the solution mapping of a mixed parametric generalized vector quasiequilibrium problem with moving cones 总被引:1,自引:0,他引:1
In this paper, we give sufficient conditions for the upper semicontinuity property of the solution mapping of a parametric
generalized vector quasiequilibrium problem with mixed relations and moving cones. The main result is proven under the assumption
that moving cones have local openness/local closedness properties and set-valued maps are cone-semicontinuous in a sense weaker
than the usual sense of semicontinuity. The nonemptiness and the compactness of the solution set are also investigated. 相似文献
990.
A numerical tool is developed for coupling natural convection in cavities with surface radiation and computations are performed for an air-filled square cavity whose four walls have the same emissivity. Compared to the adiabatic case without radiation, the top wall is cooled, the bottom wall is heated, air flow along the horizontal walls are reinforced and thermal stratification in cavity core is reduced. Detailed analysis shows that net radiative heat flux is linear with ΔT if , which is the case at low Rayleigh number, and that radiative Nusselt number is a linear function of the cavity height. Surface radiation induces an early transition to time-dependent flows: for and a cavity height of 0.335 m the critical Rayleigh number is equal to and the corresponding Hopf bifurcation is supercritical. Furthermore, multiple periodic solutions are observed between and . To cite this article: H. Wang et al., C. R. Mecanique 334 (2006). 相似文献