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11.
12.
F. Rubio F. García H. D. Burrows A. A. C. C. Pais A. J. M. Valente M. J. Tapia J. M. García 《Journal of polymer science. Part A, Polymer chemistry》2007,45(9):1788-1799
The interaction between trivalent lanthanide ions and poly(1,4,7,10,13‐pentaoxacyclopentadecan‐2‐yl‐methyl methacrylate), PCR5, in aqueous solution and in the solid state have been studied. In aqueous solution, evidence of a weak interaction between the lanthanides and PCR5 comes from the small red shift of the Ce(III) emission spectra and the slight broadening of the Gd(III) EPR spectra. From the Tb(III) lifetimes in the presence of H2O and D2O the loss of one or two water coordinated molecules is confirmed when Tb(III) is bound to PCR5. An association constant of the order of 200 M?1 was obtained for a 1:1 (lanthanide:15‐crown‐5) complex from the shift of the polymer NMR signals induced by Tb(III). A similar association constant is obtained from the differences of the molar conductivity of Ce(III) solution at various concentrations in presence and absence of PCR5. When Tb(III) is adsorbed on PCR5 membranes, lifetime experiments in H2O and D2O confirm the loss of 5 or 6 water coordinated molecules indicating that in solid state the lanthanide(III)‐PCR5 interaction is stronger than in solution. The adsorption of Ce(III) in PCR5 membranes shows a Langmuir type isotherm, from which an equilibrium constant of 39 M?1 has been calculated. SEM shows that the membrane morphology is not much affected by lanthanide adsorption. Support for lanthanide ion–crown interactions comes from ab initio calculations on 15‐crown‐5/La(III) complex. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1788–1799, 2007 相似文献
13.
Juan Pablo Vielma 《Operations Research Letters》2007,35(1):29-35
Two independent proofs of the polyhedrality of the split closure of mixed integer linear program have been previously presented. Unfortunately neither of these proofs is constructive. In this paper, we present a constructive version of this proof. We also show that split cuts dominate a family of inequalities introduced by Köppe and Weismantel. 相似文献
14.
In this paper, we apply a three-stage-DEA model to the Spanish Professional Football League, which means separating the teams’
economic behaviour into three components: operating efficiency—of the offence and defence—athletic or operating effectiveness,
and social effectiveness. The results showed that the technical inefficiency of the defence is greater than that of the offence,
both being caused by aspects linked to the poor management of players’ abilities and by the football team’s size. Teams showed
a favourable evolution of their offensive and defensive efficiency during the 2004/2005 season and to a lesser extent in the
season before. The point system assigned by the professional football league regulations evaluates the teams’ athletic effectiveness,
but we detected that the teams with the most experience perform athletically in a more effective manner. Their social effectiveness
is strongly related to the level of play in itself and to factors linked to their PFL ranking: participation in international
competitions for important football teams; or the struggle of minor football teams to stay in the first division. 相似文献
15.
L.G. Casado I. García T. Csendes V.G. Ruíz 《Journal of Optimization Theory and Applications》2003,118(1):27-43
Based on the investigation carried out in Ref. 1, this paper incorporates new studies about the properties of inclusion functions on subintervals while a branch-and-bound algorithm is solving global optimization problems. It is found that the relative place of the global minimum value within the inclusion function value of the objective function at the current interval indicates mostly whether the given interval is close to a minimizer point. This information is used in a heuristic interval rejection rule that can save a considerable amount of computation. Illustrative examples are discussed and an extended numerical study shows the advantages of the new approach. 相似文献
16.
E. García-Matres N. Stüßer M. Hofmann M. Reehuis 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,32(1):35-42
The magnetic structures of Mn1-xFexWO4 with x
= 0.0, 0.16, 0.21, 0.225, 0.232, 0.24, 0.27, 0.29, and 1.0 were refined from neutron powder diffraction data. The magnetic phase
diagram could be completed in the coexistence range of different magnetic structures up to x
= 0.29. For the magnetic state at 1.5 K a commensurate antiferromagnetic structure with a propagation vector
= (±1/4, 1/2, 1/2) was found for x
⩽ 0.22 while the magnetic spins order with
= (1/2, 0, 0) for x
≥ 0.22. In the latter phase, additionally, weak magnetic reflections indexed to an incommensurate ordering with
= (- 0.214, 1/2, 0.457) occur in the diffraction pattern up to x
= 0.29 indicating the occurence of a reentrant phase. For 0.12 ⩽
x
⩽ 0.29 the low temperature phases are separated from a magnetic high temperature phase showing only magnetic reflections indexed
to a spin arrangement with
= (1/2, 0, 0). The magnetic phase diagram is discussed qualitatively considering random superexchange between the statistically distributed
Mn2+- and Fe2+-ions in the coexistence range 0.12 ⩽
x
⩽ 0.29 of different magnetic structures related to those of pure MnWO4 and FeWO4.
Received 9 October 2002 Published online 14 March 2003 相似文献
17.
René Meziat Diego Patiño Pablo Pedregal 《Computational Optimization and Applications》2007,38(1):147-171
We propose an alternative method for computing effectively the solution of non-linear, fixed-terminal-time, optimal control
problems when they are given in Lagrange, Bolza or Mayer forms. This method works well when the nonlinearities in the control
variable can be expressed as polynomials. The essential of this proposal is the transformation of a non-linear, non-convex
optimal control problem into an equivalent optimal control problem with linear and convex structure. The method is based on
global optimization of polynomials by the method of moments. With this method we can determine either the existence or lacking
of minimizers. In addition, we can calculate generalized solutions when the original problem lacks of minimizers. We also
present the numerical schemes to solve several examples arising in science and technology. 相似文献
18.
Bosco García-Archilla 《Numerische Mathematik》1992,61(1):291-310
Summary A finite-difference method for the integration of the Korteweg-de Vries equation on irregular grids is analyzed. Under periodic boundary conditions, the method is shown to be supraconvergent in the sense that, though being inconsistent, it is second order convergent. However, such a convergence only takes place on grids with an odd number of points per period. When a grid with an even number of points is used, the inconsistency of the method leads to divergence. Numerical results backing the analysis are presented. 相似文献
19.
Inmaculada García Cuesta José Sánchez-Marín Alfredo M J Sánchez de Merás 《Chemphyschem》2006,7(2):508-513
Investigations into the charge-separated states and electron-transfer transitions in tetracyanoethylene (TCNE) complexes have recently generated much interest. In this work we present theoretical calculations showing that the most stable structure of the dianion TCNE2- has D2d symmetry in vacuum as well as in the solvents dichloromethane and acetonitrile. By means of the coupled cluster linear response, we compute the vertical electronic spectrum in both the gas phase and solution. The theoretical results are compared to the experimental data and good agreement is achieved. 相似文献
20.
Ignacio Moreno Pablo Velásquez Daniel Puerto Asticio Vargas 《Optics Communications》2006,260(1):12-18
In this work, we show a very simple birefringent filter useful to modulate a broadband light spectrum. We first show the generation of various oscillating spectra using two identical multiple-order waveplates. In particular a sinusoidal broadband spectrum with a rapid oscillation is obtained. This spectrum is amplitude modulated by adding another waveplate to the system. This waveplate has a small phase shift, and with the proper orientation generates amplitude beats on the broadband spectrum. Finally, we show how this system can be voltage controlled by means of a ferroelectric liquid crystal modulator. We experimentally demonstrate this behavior with the aid of a portable spectrophotometer, and we provide a theoretical explanation on the basis of the Jones matrix formalism. 相似文献