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971.
: Multiple electron transfer processes are studied for Arq+n- Ne (q= 8, 9, 11, 12) collisions by using multi-parameter coincidence techniques. Various electron transfer processes are identified experimentally and the related cross-sections are measured. The dependence of transfer ionization cross-sections on the recoil charge states is compared with the results from the modified molecular classical overbarrier model. It is found that the modified model described the experimental results reasonably. 相似文献
972.
Although the classical Fractional Brownian Motion is often used to describe porosity,
it is not adapted to anisotropic situations. In the present work, we study a class of Gaussian
fields with stationary increments and spectral density. They present asymptotic self-similarity
properties and are good candidates to model a homogeneous anisotropic material, or its radiographic
images. Unfortunately, the paths of all Gaussian fields with stationary increments have the
same apparent regularity in all directions (except at most one). Hence we propose here a procedure
to recover anisotropy from one realization: computing averages over all the hyperplanes which
are orthogonal to a fixed direction, we get a process whose Hölder regularity depends explicitly on
the asymptotic behavior of the spectral density in this direction. 相似文献
973.
The Spherical Code (SC) problem has many important applications in such fields as physics, molecular biology, signal transmission, chemistry, engineering and mathematics. This paper presents a bilevel optimization formulation of the SC problem. Based on this formulation, the concept of balanced spherical code is introduced and a new approach, the Point Balance Algorithm (PBA), is presented to search for a 1-balanced spherical code. Since an optimal solution of the SC problem (an extremal spherical code) must be a 1-balanced spherical code, PBA can be applied easily to search for an extremal spherical code. In addition, given a certain criterion, PBA can generate efficiently an approximate optimal spherical code on a sphere in the n-dimensional space
n. Some implementation issues of PBA are discussed and putative global optimal solutions of the Fekete problem in 3, 4 and 5-dimensional space are also reported. Finally, an open question about the geometry of Fekete points on the unit sphere in the 3-dimensional space is posed. 相似文献
974.
Collection-mode near-field scanning optical microscopy (NSOM) is used to map nanoscopic second-harmonic generation (SHG) in N -(4-nitrophenyl)- (L) -prolinol crystals. A spatial resolution of 98 nm is achieved. Near-field polarization-dependent SHG measurement is performed, and a local effective SHG susceptibility of 224+/-18 pm/V is obtained. 相似文献
975.
Liu Qing Cao Zhuang Qi Shen Qishun Dou Xiaoming Chen Yingli 《Optical and Quantum Electronics》2001,33(6):675-683
In this paper, we propose a novel analytic transfer matrix method (ATMM) to the analysis of planar waveguides with index discontinuity or index slope discontinuity, for the cases when the conventional WKB method is no longer valid. We also analyze the physical insight of the approximations in WKB theory, and according to our research, the phase shift at the turning point is not /2, but exactly . Test calculations are done for an index profile with a known solution and the comparison shows that our method gives extremely accurate propagation constant. 相似文献
976.
Armitage NP Lu DH Feng DL Kim C Damascelli A Shen KM Ronning F Shen ZX Onose Y Taguchi Y Tokura Y 《Physical review letters》2001,86(6):1126-1129
We have performed angle resolved photoelectron spectroscopy on the electron doped cuprate superconductor Nd1.85Ce0.15CuO4. A comparison of the leading edge midpoints between the superconducting and normal states reveals a small, but finite shift of 1.5-2 meV near the ( pi,0) position, but no observable shift along the zone diagonal near ( pi/2, pi/2). This is interpreted as evidence for an anisotropic superconducting gap in the electron doped materials, which is consistent with the presence of d-wave superconducting order in this cuprate superconductor. 相似文献
977.
Fast orientational motion of molecules at a surface can affect the sum-frequency vibrational spectra of the surface. Calculation shows that the effect is significant if the molecular orientation varies over a broad range within the vibrational relaxation time. The stretch vibration of the free OH bonds at the vapor/water interface is used to illustrate the importance of the effect. 相似文献
978.
Highly emissive Re(I) complexes, hydrophobic cis-Re(CO)2(c-dppene)(dpphen) and water-soluble cis-Re(CO)2(c-dppene)(SO3-dpphen) with a negative charge, were synthesized [where c-dppene is cis-(bis(diphenylphosphino)ethylene, dpphen is 4,7-diphenyl-1,10-phenanthroline, and SO3-dpphen is its disulfonate derivative]. These Re(I) complexes have significantly higher molar absorption in the 350- to 490-nm region compared to their tricarbonyl Re(I) counterparts and their emission spectra are similar to those of Ru(II) polypyridyl complexes. The luminescence lifetimes of these Re(I) complexes approach 10 s in the absence of oxygen in both aqueous and less polar solvents. The complexes have limiting anisotropy values exceeding 0.3. As both ligands, the diimine and the bidentate phosphine, can be modified by adding different substituents, it should be possible to make cis-Re(CO)2(diimine)(P-P) derivatives which are capable of labeling biomacromolecules for biochemical and biophysical studies. 相似文献
979.
Shen J 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2001,149(2):234-238
Unlike prefocused pulses and shaped pulses based on the linear response theory, delayed-focus pulses (X.-L. Wu et al., 1991, Magn. Reson. Med. 20, 165--170) produce a selective spin echo after a predefined short delay without using a pi refocusing pulse. In this paper, a series of delayed-focus pulses of different flip angles are proposed based on optimization using Fourier series representation and simulated annealing. The resistance of these delayed-focus pulses to T(2) relaxation is also demonstrated using numerical simulation of Bloch equations. 相似文献
980.
Shen Yu-Liang 《Proceedings of the American Mathematical Society》2000,128(1):135-139
Given a family of quasiconformal deformations such that has a uniform bound , the solution of the Löwner-type differential equation
is an -quasiconformal mapping. An open question is to determine, for each fixed , whether the extremality of is equivalent to that of . The note gives this a negative approach in both directions.