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991.
G. Wang Q. Guo 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,63(2):219-225
Nonlocal effects on the energy conversion efficiency of the second-harmonic generation (SHG) for a p-polarized incident field
in a P?schl-Teller quantum well (PTQW) are investigated in detail. The numerical results show that the spatial distribution
of the second-harmonic field is nonuniform, and that there exist two resonance peaks in the second-harmonic energy reflection
spectra, and their positions have a notable blueshift because of the nonlocal effects. A very important property is that a
maximum blueshift at the second-harmonic resonance can be obtained by adopting a proper quantum-well width and donor concentration,
which may be interesting in future precision experiments. 相似文献
992.
F.A.B.F. de Moura F. Domínguez-Adame 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,66(2):165-169
We study the nature of the vibrational modes in a two-dimensional harmonic
lattice with long-range correlated random masses, with power-law spectral
density S(k)∼1/kα. We obtain numerically the scale invariance of
the fluctuations of the relative participation number and the local density of
states. We find signatures of extended vibrational modes when α>αc
and αc depends on the magnitude of disorder. In order to confirm this
claim, we also study the time evolution of an initially localized perturbation
of the lattice. We show that the second moment of the spatial distribution of
the energy displays a ballistic regime when α>αc, in agreement with
the occurrence of extended vibrational modes. 相似文献
993.
E. Majerníková S. Shpyrko 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,66(2):259-269
The dynamics of excited phonon spectra of the E⊗e
Jahn-Teller (hereafter, JT) model mapped onto the generalized Calogero-Moser (gCM)
gas of pseudoparticles implies a complex interplay between nonlinearity
and fluctuations of quasiparticle trajectories. A
broad crossover appears in a pseudotime (interaction strength) between the
initial oscillator region and the nonlinear region of the
kink-train lattice as a superlattice of the kink-antikink gCM
trajectories. The local nonlinear fluctuations, nuclei (droplets) of
the growing kink phase arise at the crossover, forming a new
intermediate droplet “glassy” phase as a precursor of the kink
phase. The “glassy” phase is related to a broad maximum
in the entropy of the probability distributions of pseudoparticle
accelerations, or level curvatures. The kink-train lattice
phase with multiple kink-antikink collisions is stabilised by
long-range correlations when approaching a semiclassical limit.
A series of bifurcations of nearest-level spacings were recognised as signatures of pre-chaotic behaviour at the quantum level
in the kink phase.
Statistical characteristics can be seen to confirm the coexistence within all of
the spectra of both regularity and chaoticity to a varying extent (nonuniversality).
Regions are observed within which one of the phases is dominant. 相似文献
994.
Exact Solitary Wave Solutions of Nonlinear Evolution Equations with a Positive Fractional Power Term
The bounded and smooth solitary wave solutions of 10 nonlinear evolution equations with a positive fractional power term of dependent variable are successfully obtained by homogeneous balance principle and with the aid of sub-ODEs that admits a solution of sech-power or tanh-power type. In the special cases that the fractional power equals to 1 and 2, the solitary wave solutions of more than 10 important model equations arisen from mathematical physics are easily rediscovered. 相似文献
995.
E.B. Manoukian 《理论物理通讯》2013,60(6):677-686
The paper represents a rigorous treatment of the underlying quantum theory, not just in words but providing the underlying technical details, as to why matter occupies so large a volume and its intimate connection with the Pauli exclusion principle, as more and more matter is put together, as well as of the contraction or shrinkage of "bosonic matter", upon collapse, for which the Pauli exclusion is abolished. From the derived explicit bounds of integrals of powers of the particle number densities, explicit bounds on probabilities of the occurrences of the events just described are extracted. These probabilities lead one to infer the change of the "size" or extension of such matter, upon expansion or contraction, respectively, as their content is increased. 相似文献
996.
Rare backflow (negative wall-shear stress) events have recently been found and quantified in the near-wall region of canonical wall-bounded turbulent flows. Although their existence and correlation with large-scale events have been established beyond numerical and measurement technique uncertainties, their occurrence at numerically high Reynolds numbers is still rare (less than 1 per thousand and 1 per million at the wall and beyond the viscous sublayer, respectively). To better quantify these rare events, the turbulent boundary layer developing over the suction side of a wing section, experiencing an increasing adverse pressure gradient (APG) without separation along its chord c, is considered in the present work. We find that the backflow level of 0.06% documented in turbulent channels and zero-pressure-gradient (ZPG) turbulent boundary layers is already exceeded on the suction side for x/c > 0.3, at friction Reynolds numbers three times lower, while close to the trailing edge the backflow level reaches 30%. Conditional analysis of extreme events indicates that for increasing Clauser pressure-gradient parameters (reaching β ? 35), the flow reaches a state in which the extreme events are more likely aligned with or against the freestream, and that the otherwise strong spanwise component of the wall-shear stress reduces towards the vicinity of the trailing edge. Backflow events subjected to moderate up to strong APG conditions (0.6 < β < 4.1) exhibit an average width of Δz+ ? 20, and an average lifetime of Δt+ ? 2. This directly connects with the findings by Lenaers et al., and implies that there is a connection between high-Re ZPG and strong APG conditions. 相似文献
997.
1.IntroductionWeconsideranextensivesystemofthefamiliarLotka-Volterrasysteminwhichthepopulationshaveself-inhibit(i.e.,withtheadditionofdampingterm)thatcanbemodeledbytheequationswherexandyrepresentthepreydensityandpredatordensityrespectively.Thespecifi... 相似文献
998.
Ahmed Meskini Mustapha Raihane Chady Hakme Isabelle Stevenson Gérard Seytre 《European Polymer Journal》2009,45(3):804-812
In the frame of a research aiming at developing new dielectric polymers containing CCN and CF substituents with strong dipole moment, statistical copolymers based on cyano monomers such as acrylonitrile (AN), methacrylonitrile (MAN), methylvinylidene cyanide (MVCN) and 2,2,2-trifluoroethylmethacrylate (MATRIF), were synthesized and characterized. Elemental analysis has shown that the molar percentages of AN and MAN in the copolymers were 45 mol.%, while only 5 mol.% of MVCN was incorporated in the poly(MVCN-co-MATRIF) copolymer. These copolymers exhibit glass transition temperatures, Tg, in the range of 70-90 °C. The dynamic dielectric analyses and their complex permittivities of these copolymers were studied versus the temperature and the frequency. Evidence of an α-relaxation phenomenon in the glass transition region, which is confirmed by the Vogel-Fulcher-Tammann (VFT) temperature dependence of the relaxation times, was assigned to the cooperative reorientation motions of the cyano groups. The values of dielectric strength (Δε) for the copolymers based on MATRIF were determined by Havriliak-Negami (HN) fitting from the dispersion curves, and can be related to the polarity of the monomer unit and to the packing of the macromolecular chains. These relaxations are sometimes overlapped by conduction phenomena due to ionic impurities at low frequencies and high temperatures dipolar losses. In the glassy state, the permittivity values of AN and MAN copolymers show an increase of polarity which makes them candidates for some applications amongst advanced electrical materials such as dielectric layer for capacitors. 相似文献
999.
N-磷酰化肽酯及小肽与溶菌酶相互作用的ESI-MS研究 总被引:1,自引:0,他引:1
用ESI-MS研究了一系列结构具有可比性的N-磷酰化肽酯及小肽和溶菌酶的非共价相互作用, 比较了磷酰化肽酯及小肽分子中的不同基团对相互作用的影响. 结果表明—OH对其与溶菌酶的相互作用有较大贡献; 芳香环由于位阻原因, 对相互作用有促进和阻碍双重效应; 当—OH与芳香环相连时会发生协同效应, 可使相互作用显著增强. 磷酰化肽酯及小肽的体积大小、空间位阻对相互作用亦有显著影响. 磷酰化二肽中氨基酸残基的构型、顺序、碳链长短的变化(增加1~2个C)对其与蛋白溶菌酶之间的相互作用在质谱中没有表现出影响. 分子结构较为伸展、分子柔顺性好、空间位阻较小的磷酰化小肽更容易使蛋白在溶液中的构象趋于收缩, 而构象较为收缩的蛋白分子更易结合空间位阻较小的磷酰化小肽分子. 相似文献
1000.
Temperature-programmed desorption of NO (TPD) and temperature-programmed reduction of NO by propene and ethanol (TPSR) over the catalyst with redox properties and the structure of spinels - Co3O4 and CoFe2O4 - were investigated.The TPD experiments can determine the temperature range in which the deNOx proceeds and provide information about the heat of adsorption of NO on the surface of catalysts. The values of the adsorption heat are much higher in the case of the catalyst with weaker redox properties (CoFe2O4), because of stronger bonds between the adsorbate and the surface of catalyst. The TPD and TPSR experiments show that ethyl alcohol is a more active reductant in the deNOx process than propene. The maximum of NOx conversion is higher with ethyl alcohol used as a reductant in both cases of investigated catalysts. Moreover, the temperature of the maximum degree of NOx reduction is lower in the case of alcohol used as an reductant. Co3O4 is a more active and suitable catalyst for the deNOx process than CoFe2O4. 相似文献