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71.
Nicholson JW Bise R Alonzo J Stockert T Trevor DJ Dimarcello F Monberg E Fini JM Westbrook PS Feder K Grüner-Nielsen L 《Optics letters》2008,33(1):28-30
Supercontinuum extending to visible wavelengths is generated in a hybrid silica nonlinear fiber pumped at 1560 nm by a femtosecond, erbium-doped fiber laser. The hybrid nonlinear fiber consists of a short length of highly nonlinear, germano-silicate fiber (HNLF) spliced to a length of photonic crystal fiber (PCF). A 2 cm length of HNLF provides an initial stage of continuum generation due to higher-order soliton compression and dispersive wave generation before launching into the PCF. The visible radiation is generated in the fundamental mode of the PCF. 相似文献
72.
We consider worst case time bounds for certain NP-complete problems. In particular, we consider the (k,2)-satisfiability problem which includes as special cases some canonical problems such as graph coloring and satisfiability. For the (k,2)-satisfiability problem, we present a randomized algorithm that runs in time O*((k!)n/k).2 This bound is equivalent to O((k/ck)n) with ck increasing to the asymptotic limit e. For k11, we improve upon the O((0.4518k)n) randomized bound of Eppstein [Proceedings of the 12th Annual ACM–SIAM Symposium on Discrete Algorithms, pp. 329–337]. A special case of (k,2)-satisfiability is k-colorability; here we achieve the above time bound for a slightly larger ck that has the same asymptotic behavior. 相似文献
73.
To extract information from recent experimental spin-resolved photoemission data from Ni(1 1 0)(2×1)?O, one-step theory calculations were performed for several geometrical and magnetic model structures. The observed strong influence of oxygen chemisorption on the normal photoemission spectra at room temperature is quantitatively reproduced assuming a (2×1) saw-tooth reconstruction with the third and fourth Ni layers magnetically dead, while the magnetization of the topmost two Ni layers is almost irrelevant for the spectra. It is concluded that bulk-like deeper layers are strongly quenched at least with regard to the near-X2 exchange splitting. 相似文献
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Two distinct theories of spin-dependent low energy electron diffraction have been used to calculate scattered intensities and polarizations for the same model of the W(001) surface. The agreement between the results is excellent, demonstrating that calculations using either program should provide a reliable basis for the analysis of experimentally measured intensities and polarizations. The effects of using different surface barriers and of increasing the number of phase shifts and diffracted beams are also examined. 相似文献
76.
A model based on invasion percolation was used to simulate the migration on a non-wetting fluid through a porous medium filled with an immiscible wetting fluid under the influence of a gradient such as that provided by gravity. The migrating fluid clusters undergo both fragmentation and coalescence. The fragment size distribution obtained from two-dimensional simulations in which the gradient g is slowly increased from 0 can be represented by the scaling form Ns(g)s-2ƒ(s|g|-z where z=1+(D−1)ν(ν+1). Here D is the fractal dimensionality of invasion percolation, with trapping, and ν is the ordinary percolation correlation length exponent. 相似文献
77.
Experimental angle-resolved photoemission spectra from Cu(111) and Cu(001) excited by linearly polarized light (21.2 eV) are compared with intensity results calculated by the “one step model” theory. Good overall agreement is obtained both for s- and p-polarized light assuming a classical macroscopic radiation field inside the crystal. 相似文献
78.
R. Feder 《Solid State Communications》1979,31(11):821-823
A theory of elastic scattering of low-energy electrons is outlined, in which the electron-solid interaction contains two spin-dependent contributions: an elastic exchange-correlation part in the real ion-core potential and an inelastic imaginary part describing electron-hole excitation. Numerical calculations for the Fe(110) surface predict, for an unpolarized primary beam, large spin polarization effects (up to 60%), which are highly sensitive to the magnetization of the topmost stomic layer. 相似文献
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