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931.
Amador Menndez‐Velzquez Santiago García‐Granda 《Journal of Applied Crystallography》2003,36(2):193-205
The last step of a crystal structure determination that requires human intervention is the interpretation of Fourier maps, displayed as peaks in a favourable projection. Crystallographers infer bonding by empirically assigning bonds between peaks via purely geometrical criteria. In this paper, a network connecting peaks and passes of the density function is suggested in order to avoid human intervention and bonding inference. A completely automatic algorithm for the full analysis of critical points and recognition of the molecular graph in Fourier maps has been developed and implemented into the package DIRDIF. This procedure has been applied successfully to a wide variety of crystal structures. In most cases, the complete structure is recovered and the connectivity matrix is constructed without any user intervention. 相似文献
932.
Carmelo Giacovazzo Annamaria Mazzone Giuliana Comunale 《Acta Crystallographica. Section A, Foundations and Advances》2011,67(4):368-382
In a recent paper [Giacovazzo & Mazzone (2011). Acta Cryst. A 67 , 210–218] a mathematical expression of the variance at any point of the unit cell has been described. The formulas were derived in P1 for any type of Fourier synthesis (observed, difference and hybrid) under the following hypothesis: the current phases are distributed on the trigonometric circle about the correct values according to von Mises distributions. This general hypothesis allows the variance expressions to be valid at any stage of the phasing process. In this paper the method has been extended to any space group, no matter whether centric or acentric. The properties of the variance generated by space‐group symmetry are described; in particular it is shown that the variance is strictly connected with the implication transformations, which are basic for Patterson deconvolution. General formulas simultaneously taking into account phase uncertainty and measurement errors have been obtained, valid no matter what the quality of the model. 相似文献
933.
J. Heiland V. Mehrmann 《ZAMM - Journal of Applied Mathematics and Mechanics / Zeitschrift für Angewandte Mathematik und Mechanik》2012,92(4):257-274
The construction of reduced order models for flow control via a direct discretization of the input/output behavior of the system is discussed. The spatially discretized equations are linearized such that an explicit formula for the corresponding input/output map can be used to generate a matrix representation of the input/output map. Estimates for the approximation error are derived and the applicability is illustrated via a numerical example for the control of a driven cavity flow. 相似文献
934.
Yuzhen Ge 《Journal of statistical physics》1991,63(1-2):131-140
The topological entropy for some families of one-dimensional unimodal maps is studied. By arranging the windows of constant topological entropy in a binary tree, we have obtained the total measure of these windows. The scaling properties of this measure are studied. 相似文献
935.
T. Wurzbacher 《Journal of Geometry and Physics》1990,7(4):537-552
We study the relation between multiplicity-free symplectic manifolds and the multiplicities of group representations obtained by geometric quantization. With the help of a general equivalence theorem we can prove a conjecture of Guillemin and Sternberg in the compact Kähler case. 相似文献
936.
Introducing the notion of stabilized fundamental group for the complement of a branch curve in , we define effectively computable invariants of symplectic 4-manifolds that generalize those previously introduced by Moishezon and Teicher for complex projective surfaces. Moreover, we study the structure of these invariants and formulate conjectures supported by calculations on new examples. 相似文献
937.
938.
939.
C. B. Garcia 《Journal of Optimization Theory and Applications》1977,21(4):529-530
We show by an example that, in a complementarity problem where the given map is continuous and monotone on the nonnegative orthant, the existence of a feasible solution is not sufficient to guarantee existence of a solution to the complementarity problem.The author thanks Professor S. Karamardian and Dr. J. More for helpful discussions regarding this note. 相似文献
940.
We derive a lower bound for energies of harmonic maps of convex polyhedra in
to the unit sphere S2 with tangent boundary conditions on the faces. We also establish that C maps satisfying tangent boundary conditions are dense with respect to the Sobolev norm in the space of continuous tangent maps of finite energy.This revised version was published online in March 2005 with corrections to the cover date. 相似文献