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941.
942.
Based on the research in Ref. [5][Materials Science and Engineering, 1989; A122： 57 63], an improved model of heat source is set up, the different modes of Lamb wave in an isotropic sample generated by a chopped electron beam at frequency f are obtained with integral transform and normal function expansion method, and the output signal of PZT coupled at the back surface of the sample is found out. The generation mechanism of SEAM （Scanning Electron Acoustic Microscopy） signal is discussed. It shows that the SEAM is a near field imaging technique with high spatial resolution and its best lateral spatial resolution is about 2√2α （α is the radius of the focused electron beam）. Some of experimental results of SEAM images are presented in the paper and it shows that the spatial resolution of SEAM is better than 0.5 μm and smaller than the thermal diffusion length of the sample. Therefore the character of near field imaging in SEAM is also proved experimentally. 相似文献
943.
研究了Kerr介质中对相干态光场与V型三能级原子依赖强度耦合相互作用的量子统计性质.对Cauchy-Schwartz不等式的研究表明:失谐量不为零(Ω1=Ω2≠0)时两模间的非经典相关程度有所增强,当初始场强ξ一定而两模场光子数差q增大时,场的非经典相关程度加强;q一定而ξ增大时,场的非经典相关程度减弱,Kerr效应使两模场的非经典相关性有所减弱.对二阶相干度的研究表明,第一模总呈现反聚束效应且Kerr效应对其影响相对较小,而第二模则聚束与反聚束效应交替出现,Kerr效应对g(222)的振荡幅度影响与q的 相似文献
944.
邹艳 《原子与分子物理学报》2008,25(5):1079-1085
运用量子约化熵研究了Kerr介质中V型三能级原子与双模奇偶纠缠相干光场相互作用系统中场熵的演化特性.分析了Kerr介质、失谐量和光场的初始平均光子数对场熵的影响.结果表明:Kerr介质与光场的耦合系数对场熵的振荡特性有调制作用,增大失谐量,场熵的最大值减小,振荡频率增大,由初始时刻的零值增大到最大值所需的时间也增大;光场的平均光子数太大或太小都不利于原子与光场之间的纠缠. 相似文献
945.
Jan Petzelt Dmitry Nuzhnyy Viktor Bovtun Maxim Savinov Martin Kempa Ivan Rychetsky 《physica status solidi (a)》2013,210(11):2259-2271
946.
J.Q. Shen 《Annalen der Physik》2010,522(7):524-531
An isotropic electromagnetic medium becomes gyrotropically anisotropic when it moves, and an anisotropic electromagnetic environment can then be created in this motion‐induced anisotropic medium. One of the most remarkable features is that the quantum vacuum in the anisotropic electromagnetic environment exhibits a nonzero electromagnetic momentum density, since the universal symmetry of the vacuum fluctuation field is broken, and the anisotropic quantum vacuum mode structure is produced because of the symmetry breaking. This would give rise to a noncompensation effect among the four vacuum eigenmodes (i.e., the forward and backward propagating modes as well as their respective mutually perpendicular polarized components), and leads to an anisotropic correction to the vacuum momentum in the moving medium. The physical significance and the potential applications of the anisotropic quantum vacuum are discussed. This quantum‐vacuum effect may be used to develop sensitive sensor techniques and to design new quantum optical and photonic devices. 相似文献
947.
Tomi Nath Das 《Journal of Physical Organic Chemistry》2009,22(9):872-882
A novel hidden reaction of the phenoxyl radical (C6H5O•) with a specific daughter is found to significantly alter its hitherto accepted coupling reactions' scheme. Transient characterizations and mechanistic evaluations in highly acidic to strongly alkaline aqueous medium reveal this concurrent reaction competing favorably in nanosecond–microsecond time‐scale with the five distinct C6H5O• + C6H5O• reactions, which produce various phenolic end‐products as reported earlier (M. Ye and R. H. Schuler, J. Phys. Chem. 1989, 93, 1898). Presently, only the symmetric 4,4′‐dioxo transient precursor, OC6H5 H5C6O that leads to the stable 4,4′‐biphenol product, gets partially oxidized by a fraction of remaining C6H5O•. The resulting secondary transient •C12H9O2 radical is generated at diffusion‐controlled rate, k > 5.0 × 109 M−1 s−1, and follows an independent chemistry. Consequently, when the previously reported five coupled end product distribution ratios were appropriately updated, the respective fractional values revealed a closer match for the symmetric 2,2′‐ and 4,4′‐biphenols with their suggested coupling reaction branching probabilities based on the atomic spin‐density distributions in the C6H5O• radical (P. Neta, R. W. Fessenden, J. Phys. Chem., 1974, 78, 523). Results also suggest that in the remaining fraction, differential solvation in aqueous medium of various orientation‐related encounter complexes (C6H5O…C6H5O) formed during coupling favors rearrangement only toward 2,4′‐biphenolic product, at the cost of 2‐ and 4‐phenoxyphenolic species. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
948.
S.V. Novikov 《Annalen der Physik》2009,18(12):949-953
An appropriate model for the random energy landscape in organic glasses is a spatially correlated Gaussian field. We calculated the distribution of the average value of a Gaussian random field in a finite domain. The results of the calculation demonstrate a strong dependence of the width of the distribution on the spatial correlations of the field. Comparison with the simulation results for the distribution of the size of the cluster indicates that the distribution of an average field could serve as a useful tool for the estimation of the asymptotic behavior of the distribution of the size of the clusters for “deep” clusters where value of the field on each site is much greater than the rms disorder. We also demonstrate significant modification of the properties of energetic disorder in organic glasses at the vicinity of the electrode. 相似文献
949.
Using the concept of optical transformation, we report on an amplifying device, which can make an arbitrary object enlarged. Its potential application to small object identification and detection is foreseeable. The cylindrical anisotropic amplifying shell could be mimicked by radially symmetrical ＂sectors＂ alternating in composition between two profiles of isotropic dielectrics; the permittivity and permeability in each ＂sector＂ can be properly determined by the effective medium theory. Both the magnetic and nonmagnetic amplifying devices are validated by full-wave finite element simulations. Good amplifying performance is observed. 相似文献
950.
E. Vahedi H. Tajalli A. Ghanadzadeh Gilani J. Parka H. Nasirzadeh Milani 《Phase Transitions》2013,86(6):432-439
We have experimentally studied for the first time the electro-optical Kerr effect and the pre-transitional behavior in the isotropic phase of two antiferroelectric liquid crystal mixtures, W-232 and W-204D, composed of rod-like ester molecules exhibiting the direct smectic-A to isotropic (SmA-I) phase transition. The Kerr law has been confirmed for the two compounds and the variation of inverse Kerr constant with temperature above the smectic–isotropic transition temperatures were determined. Both the mixtures with very broad antiferroelectric phase around room temperature have similar sequence of the phases (i.e., Cr-SmC*A-SmC*-SmA-I). Although, the pre-transitional behavior is usually complex in the isotropic phase of the chiral smectic liquid crystal compounds, the investigated compounds showed a similar behavior compared to that of nematic–isotropic behavior. 相似文献