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991.
A two-dimensional Total Routhian Surface (TRS) calculation with the fixed hexadecapole deformation ε4 = 0.03 was carried out for several configurations of 174Hf. Results indicate that the shell corrections have an important contribution to the formation of triaxial superdeformation in 174Hf and some possible configuration assignments are made to the 4 TSD bands experimentally found in 174Hf. 相似文献
992.
A new approach is suggested to realize negative magnetic permeability that follows directly from quantum mechanics. It is
shown that a Λ-type three-level atomic system with proper atomic parameters can give rise to striking magnetic responses,
which could exhibit negative permeability in an optical frequency band. Both steady and transient behaviors of the magnetic
permeability in the atomic vapor are studied. The present negative-permeability vapor could be mixed with a quantum coherent
vapor whose electric permittivity is negative. Such a mixed vapor may give an isotropic left-handed vapor medium at the atomic-scale
level.
PACS 32.10.Dk; 42.50.Gy; 78.20.Ci 相似文献
993.
Y.-L. Shen W. Wang J. Zhu C.-D. Lü 《The European Physical Journal C - Particles and Fields》2007,50(4):877-887
We use the decay modes B→K*
0(1430)π and B→a0(980)K to study the scalar mesons K*
0(1430) and a0(980) within the framework of perturbative QCD. For B→K*
0(1430)π, we perform our calculation in two scenarios for the scalar meson spectrum. The results indicate that scenario II
is more favored by the experimental data than scenario I. The important contribution from annihilation diagrams can enhance
the branching ratios by about 50% in scenario I and about 30% in scenario II. The direct CP-asymmetries in B→K*
0(1430)π are small, which is consistent with the present experiments. The predicted branching ratio of B→a0(980)K in scenario I differs from the experiments by a factor of 2, which indicates that a0(980) cannot be interpreted as q̄q. 相似文献
994.
Lu‐Feng Zou Kuang Shen Yao Fu Qing‐Xiang Guo 《Journal of Physical Organic Chemistry》2007,20(10):754-763
Experimental studies showed that sulfur radicals play the vital role in petroleum formation. 1 Sulfur‐ centered radicals also exhibit activities in antioxidant functions. Here we conduct a theoretical investigation of their precursor‐disulfides. By investigation into substituent effect on sulfur? sulfur bond dissociation enthalpies (S? S BDEs), we would like to find the most effective provider for sulfur radicals. In the present work, 50 alpha‐substituted disulfides and 16 para‐substituted aryl disulfides are studied systematically, with the general formula XS‐SX or HS‐SX. The substituent effect on S? S BDEs is found to be very eminent, ranging from 33.2 to 75.0 kcal/mol for alpha‐substituted disulfide, and from 43.7 to 59.7 kcal/mol for para‐substituted phenyl disulfides. We also evaluate the performance of 44 density functional methods to get an accurate prediction. A further study indicates that substituents play a major role in radical energies, instead of molecule energies, which is substantiated by the good linearity between XS‐SX bond dissociation enthalpy (BDE) and HS‐SX BDE. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
995.
Y.M. Zhao J.Y. Zhang K.W. Liu C.X. Shan B. Yao B.H. Li D.Z. Shen 《Applied Surface Science》2007,253(24):9319-9322
We report the growth of cubic MgxZn1−xO alloy thin films on quartz by electron beam evaporation. It can be found that all the samples have sharp absorption edges by the absorption measurements. X-ray diffraction measurements indicate the MgxZn1−xO films are cubic phase with preferred orientation along the (1 1 1) direction. Energy dispersive spectrometry (EDS) demonstrates that the Mg concentration in MgxZn1−xO films is much higher than the ceramic target used, and the composition can be tuned in a small scope by varying the substrate temperature and the beam electric current. The reasons of this phenomenon are also discussed. 相似文献
996.
This Letter presents an adaptive neural network control method for the chaos control problem. Based on a single layer neural network, the dynamic about the unstable fixed period point of the chaotic system can be adaptively identified without detailed information about the chaotic system. And the controlled chaotic system can be stabilized on the unstable fixed period orbit. Simulation results of Henon map and Lorenz system verify the effectiveness of the proposed control method. 相似文献
997.
Shijie Liu Jianyong Ma Zicai Shen Yunxia Jin Zhengxiu Fan 《Applied Surface Science》2007,253(7):3642-3648
Thin-film design used to fabricate multi-layer dielectric (MLD) gratings should provide high transmittance during holography exposure, high reflectance at use wavelength and sufficient manufacturing latitude of the grating design making the MLD grating achieve both high diffraction efficiency and low electric field enhancement. Based on a (HLL)9H design comprising of quarter-waves of high-index material and half-waves of low-index material, we obtain an optimum MLD coating meeting these requirements by inserting a matching layer being half a quarter-wave of Al2O3 between the initial design and an optimized HfO2 top layer. The optimized MLD coatings exhibits a low reflectance of 0.017% under photoresist at the exposure angle of 17.8° for 413 nm light and a high reflectance of 99.61% under air at the use angle of 51.2° for 1053 nm light. Numerical calculation of intensity distribution in the photoresist coated on the MLD film during exposure shows that standing-wave patterns are greatly minimized and thus simulation profile of photoresist gratings after development demonstrates smoother shapes with lower roughness. Furthermore, a MLD gratings with grooves etched into the top layer of this MLD coating provides a high diffraction efficiency of 99.5% and a low electric field enhancement ratio of 1.53. This thin-film design shows perfect performances and can be easily fabricated by e-beam evaporation. 相似文献
998.
Andrew M. Herrero B.P. Gila Hung-Ta Wang T. Anderson B.S. Kang H. Shen Kurt V. Smith 《Applied Surface Science》2007,253(6):3298-3302
The use of cryogenic temperatures (∼77 K) during Au Schottky contact deposition onto n-GaAs produces an increase in barrier height from 0.73 eV for room temperature diodes to 0.82 eV. Not all Schottky metals show this enhancement—for example Pt and Ti do not show any significant change in barrier height whereas Au, Pd and Ni show increases between 7 and 18%. We used X-ray reflectivity to show that the main difference between Au deposited at 77 K and room temperature is a decreased metal roughness while the interfacial roughness between the Au and GaAs is basically the same. As the diodes are annealed to 300 °C both the difference in barrier height and interfacial roughness is lost. This is a simple method with potential for improving the performance of GaAs metal-semiconductor-field-effect-transistors (MESFETs). 相似文献
999.
Based on the paraxial vectorial theory of beams propagating in uniaxially anisotropic media, we have derived the analytical propagation equations of beams generated by Gaussian mirror resonator (GMR) in uniaxial crystals, and given the typical numerical example to illustrate our analytical results. Due to the anisotropy crystals, the ordinary and extraordinary beams originated by incident beams generated by GMR propagate with different diffraction lengths, thus the linear polarization state and axial symmetry of the incident beams generated by GMR do not remain during propagating in crystals. 相似文献
1000.
The carrier localization in InN epilayers grown on Si(111) was studied using time-resolved photoluminescence (PL). The emission energy dependence and temperature dependence of the PL decay times revealed that carrier localization plays an important role in the recombination of this material system. A model based on the transition between free electrons in the conduction band and localized holes in the deeper tail states explains the carrier localization of InN epilayers. We suggest that the carrier localization in InN can be accounted for by the potential fluctuation caused by the random impurities. 相似文献