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991.
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waveguides with index discontinuity or index slope discontinuity, for the cases when the conventional WKB method is no longer valid.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
992.
Shen Yu-Liang 《Proceedings of the American Mathematical Society》2001,129(1):105-109
F. P. Gardiner gave a sufficient condition for a sequence to be a Hamilton sequence for an extremal Beltrami coefficient. In this note, we shall consider the converse problem, proving that the condition is not necessary.
993.
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
994.
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
995.
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
996.
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
997.
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.
998.
By forming the square root of the Wheeler-DeWitt equation and applying itto a minisuperspace composed of a Kantowski-Sachs universe, we derive acosmological wave function with conserved current and positive-definiteprobability density. 相似文献
999.
Damascelli A Lu DH Shen KM Armitage NP Ronning F Feng DL Kim C Shen ZX Kimura T Tokura Y Mao ZQ Maeno Y 《Physical review letters》2000,85(24):5194-5197
The electronic structure of Sr2RuO4 is investigated by high angular resolution ARPES at several incident photon energies. We address the controversial issues of the Fermi surface (FS) topology and the van Hove singularity at the M point, showing that a surface state and the replica of the primary FS due to sqrt[2]xsqrt[2] surface reconstruction are responsible for previous conflicting interpretations. The FS thus determined by ARPES is consistent with the de Haas-van Alphen results, and it provides additional information on the detailed shape of the alpha, beta, and gamma sheets. 相似文献
1000.
Aspects of ultrasound intensity fluctuations backscattered from additive microstructures in a turbulent flow have been investigated theoretically and experimentally for the conditions of a small insonified volume, a high sound frequency and strong turbulence. These conditions are typically found in high resolution Doppler sonar applications. An easily applicable expression for the auto-correlation of scattering intensity fluctuations is obtained by introducing open-channel turbulence theory, a semi-empirical scalar spectrum (including a Batchelor spectrum) and a Gaussian window function. Experiments carried out in a laboratory-clear water, open-channel flow for different turbulence levels verify the underlying assumptions. A good agreement is found with the predictions made with the above-derived expression. The feasibility of extracting flow information from the backscattered intensity fluctuations is discussed. 相似文献