AD GALERKIN ANALYSIS FOR NONLINEAR PSEUDO—HYPERBOLIC EQUATIONS

AD(Alternating direction)Galerkin schemes for d-dimensional nonlinear pseudo-hyperbolic equations are studied.By using patch approximation technique,AD procedure is realized,and calculation,work is simplified.By using Galerkin approach,highly computational accuracy is kept.By using various priori estimate techniques for differential equations,difficulty coming form non-linearity is treated,and optimal H^1 and L^2 convergence prop-erties are demonstrated.Moreover,although all the existed AD Galerkin schemes using patch approximation are limited to have only one order accuracy in time increment,yet the schemes formulated in this paper have second order accuracy in it.This implies an essential advancement in AD Galerkin aualysis.     

计算机上的抽象算符演算系统

本文在REDUCE语言环境下,利用公理化方法建立了一个“抽象算符演算”系统.使REDUCE系统可用于抽象的算符演算,逆演算;用于Laplace变换,逆变换及解微分方程,推导公式,以及验证有关定理等.     

Phase formation and magnetic properties of Nd2Fe14B-type Nd16Co76B8−xCx alloys and their hydrides

An attempt is made to synthesize Nd₂Co₁₄C compound by mechanical alloying Nd₁₆Co₇₆B_8−xC_x (0x8) alloys and subsequent annealing. Phase formation and magnetic properties of Nd₂Fe₁₄B-type Nd₁₆Co₇₆B_8−xC_x alloys and their hydrides are investigated. The Nd₂Co₁₄(B,C) phase with Nd₂Fe₁₄B-type structure is formed for Nd₁₆Co₇₆B_8−xC_x (0x7) alloys, while NdCo₇C_δ phase with TbCu₇-type structure is observed in Nd₁₆Co₇₆C₈ alloy. The lattice parameter c of the Nd₂Co₁₄(B,C) phase decreases with increasing the carbon content. A limit volume of the unit cell to form the Nd₂Fe₁₄B-type structure is estimated to be 0.870 nm³. The spin-reorientation temperature T_SR increases with increasing the carbon content, due to an enhancement of magnetocrystalline anisotropy caused by carbon substitution for boron. After hydrogenation, the lattice expansion is observed for Nd₁₆Co₇₆B_8−xC_x (0x7) alloys. The spin-reorientation temperature of Nd₁₆Co₇₆B_8−xC_xH_y (0x7) is much lower than that of the host alloys. Some structural and magnetic properties of hypothetic Nd₂Co₁₄C and Nd₂Co₁₄CH_y compounds are estimated by extrapolation.     

The structure-tunable synthesis and magnetic properties of Fe3O4 nanocrystals

Magnetite nanocrystals with tunable crystalline structures (orthorhombic and cubic) were synthesized via a simple oxidation-coprecipitation approach basing on the reaction of FeSO₄·7H₂O with C₆H₁₂N₄. The average diameter of prepared orthorhombic Fe₃O₄ nanorods were 15 nm while their lengths were approximately 150~200 nm. As-prepared cubic counterparts were composed of 10 nm sized nanoparticles. XRD, FESEM, TEM, SAED and HRTEM were then used to characterize our samples. In addition, magnetic measurements showed the saturation magnetization of orthorhombic magnetite was lower than that of cubic ones. Mössbauer spectroscopy verified the samples possessed the nature of cubic magnetite. Finally, a possible growth mechanism for orthorhombic nanorods and cubic nanoparticles was also discussed.     

Immunoassays Based on Surface-Enhanced Fluorescence using Gap-Plasmon-Tunable Ag Bilayer Nanoparticle Films

A novel gap-plasmon-tunable Ag bilayer nanoparticle film for immunoassays is demonstrated. Different from a traditional Ag monolayer nanoparticle film, a desired number of polyelectrolyte (PEL) layers are deposited on the nanoparticles before the self-assembly of a second Ag nanoparticle layer. Interestingly, by controlling the number of the PEL interlayers, the gap plasmon between the two Ag nanoparticle layers can be tuned across the visible spectral range. The ability of the presented Ag bilayer nanoparticle films in fluorescence enhancement has been examined experimentally. A maximal enhancement of around 15.4 fold was achieved when 7 layers of polyelectrolyte were used. When this optimal Ag bilayer nanoparticle film was applied to fluorescence immunoassay, a performance with approximately 3.3-fold enhancement was obtained compared with that performed on a traditional glass substrate. The experimental results suggest that the presented gap-plasmon tunable Ag bilayer nanoparticle films have great potential in fluorescence-based immunoassays. The method of the bilayer-film construction presented here also provides new insights into the rational design of the plasmonic substrates.     

有ITO透明导电膜的平面分层介质系统的电磁波性能理论研究

理论研究了有ITO(indium tin oxide)透明导电膜的多层平面分层介质系统的电磁性能，给出的理论曲线和实测曲线符合很好.多层平面分层介质系统的电磁性能与ITO膜(方块电阻为8Ω)所在界面位置和平面分层介质系统层数及各层厚度等有关.优化设计了一种含有ITO透明导电膜的厚度仅7.35mm的四层平面分层介质系统，其在8—18GHz频段内电磁波反射性能很好.作为多层平面分层系统中的ITO导电膜，其方块电阻应低于30Ω，并且越小，其反射性能越好. 关键词： 多层平面介质系统 电磁性能 ITO透明导电膜     

超相对论强度激光与薄膜靶作用中0.4 nm以下X射线阿秒脉冲的产生

用一维粒子模拟程序对功率密度在10²² W/cm²以上的超强激光驱动薄膜靶产生的相对论电子层及其经过汤姆孙散射产生的阿秒X射线进行了研究. 结果表明, 在超相对论强度范围下增大驱动激光强度, 相应减小等离子体密度及厚度可使电子层获得更高纵向动量, 使汤姆孙散射光明显向更短波长移动. 优化相关参数得到了波长为 1.168 nm的阿秒脉冲. 经过对倍频探测光方案与驱动光以及薄膜靶参数进行综合考虑和优化, 得到的X射线相干辐射波长有效减小到0.4 nm以下, 产生的光子能量达到2 keV以上. 关键词： 超相对论强度激光 阿秒X射线 相对论电子层 汤姆孙后向散射     

Impurity effects of the Λhyperon in the hypernuclear systems ${}_{{\rm{\Lambda }}}^{25}\mathrm{Mg}$ and ${}_{{\rm{\Lambda }}}^{29}\mathrm{Si}$

Based on the beyond-mean-field Skyrme–Hartree–Fock model, impurity effects of the Λhyperon in the hypernuclear systems ${}_{\,{\rm{\Lambda }}}^{25}$ Mg and ${}_{\,{\rm{\Lambda }}}^{29}$ Si are investigated, respectively. Four cases, in which the Λhyperon occupies the single-particle orbitals ${\rm{\Lambda }}$[000]${\tfrac{1}{2}}^{+}$, ${\rm{\Lambda }}$[110]${\tfrac{1}{2}}^{-}$, ${\rm{\Lambda }}$[101]${\tfrac{3}{2}}^{-}$ and ${\rm{\Lambda }}$[101]${\tfrac{1}{2}}^{-}$, are focused. In each case, the potential energy surface and the energy curves projected on certain angular momenta are employed to show the influence of the Λhyperon on the nuclear core. Beside the shrinkage effect that is induced by the Λhyperon occupying the s_Λ orbital, it is found that the Λhyperon on the p_Λ orbital, ${\rm{\Lambda }}$[110]${\tfrac{1}{2}}^{-}$, drives the nuclear core toward a prolate shape, while the ones on the other two p_Λ orbitals, ${\rm{\Lambda }}$[101]${\tfrac{3}{2}}^{-}$ and ${\rm{\Lambda }}$[101]${\tfrac{1}{2}}^{-}$, drive the nuclear core toward an oblate shape. The energy spectra and the corresponding intra-band E2 transition rates for the rotational bands are given as a prediction for future experiments.     

In-medium pion dispersion relation and medium correction of Nπ■Δ near the threshold energy of pion production

Transport models cannot simultaneously explain very recent data on pion multiplicities and pion charged ratios from central collision of Sn+Sn at 0.27 A GeV.This stimulates further investigations on the pion dispersion relation,in-medium Nπ→Δ cross sections,and Δ→Nπ decay widths near the threshold energy or at subthreshold energy of pion production in isospin asymmetric nuclear matter.In this study,the pion dispersion relation,in-medium Nπ→Δ cross section,and Δ→Nπ decay width near the threshold energy are investigated in isospin asymmetric nuclear matter by using the one-boson-exchange model.With the consideration of the energy conservation effect,the in-medium Nπ→Δ cross sections are enhanced at s1/2 <1.11 GeV in a nuclear medium.The prediction of pion multiplicity and π-/π+ ratios near the threshold energy could be modified if this effect is considered in transport model simulations.