一个内生人口生育率可解的C-K模型

得到一个具有可解内生人口出生率的Ｃａｓｓ－Ｋｏｏｐｍａｎｓ经济增长模型．给出此模型在不同劳动和资本的结合方式下存在唯一最优增长轨道和稳态解的条件．最后讨论存在多重最优增长轨道和多重稳态解的可能性态和文中主要结果的经济意义．     

Electronic structures of Fe in La1−x Ba x FeO3−y (0≤x≤0.70)

Mössbauer spectra of La_1–x Ba _x FeO_3–y recorded at room temperature for various values of x show a six-line and/or a single-line subspectrum. The six-line subspectrum with IS=0.41 mm/s and H=52 T results from an orthorhombic perovskite containing only Fe³⁺ ions. The single-line subspectrum at 0.17 mm/s from a cubic perovskite can be assigned to neither Fe³⁺ nor Fe⁴⁺ but to an intermediate valence state, which may be due to electron hopping between the Fe³⁺ and Fe⁴⁺ ions on the identical octahedral sites. The temperature dependence of electron hopping in the compound La_0.40Ba_0.60FeO_3–y is presented.     

一种非连续纳米氧化层自旋阀的显微结构研究

利用高分辨电子显微学方法(HREM)研究了纳米氧化层镜面反射自旋阀多层结构Ta(35nm)Ni80Fe20(2nm)Ir17Mn83(6nm)Co90Fe10(15nm)NOL1Co90Fe10(2nm)Cu(22nm)Co90Fe10(15nm)NOL2Ta(3nm).该自旋阀的巨磁电阻(GMR)效应高达15%,较无此镜面反射纳米氧化层(NOL)的自旋阀提高近1倍,同时交换偏置场亦有所增强.高分辨显微结构分析表明,介于钉扎层与被钉扎层之间的氧化层(NOL1)并未完全氧化,即除氧化过程生成的CoFe氧化物 关键词： 自旋阀 纳米氧化层 高分辨电子显微学 巨磁电阻效应     

A note on the efficiency of the conjugate gradient method for a class of time‐dependent problems

We discuss the efficiency of the conjugate gradient (CG) method for solving a sequence of linear systems; Auⁿ⁺¹ = uⁿ, where A is assumed to be sparse, symmetric, and positive definite. We show that under certain conditions the Krylov subspace, which is generated when solving the first linear system Au¹ = u⁰, contains the solutions {uⁿ} for subsequent time steps. The solutions of these equations can therefore be computed by a straightforward projection of the right‐hand side onto the already computed Krylov subspace. Our theoretical considerations are illustrated by numerical experiments that compare this method with the order‐optimal scheme obtained by applying the multigrid method as a preconditioner for the CG‐method at each time step. Copyright © 2007 John Wiley & Sons, Ltd.     

Theoretical calculation of the shock compression properties of liquid H2 + D2 mixtures

Based on liquid variational perturbation theory with quantum mechanics correction, the effective exp-6 potential is adopted to compute the shock Hugoniot of liquid H₂ + D₂ mixtures at different molar rations. An examination of the confidence of the above computation is performed by comparing experiments and calculations, in which similar calculation procedure used for H₂ + D₂ is adopted for H₂ and D₂ each, since no experimental data are available to conduct this kind of comparison. Good agreement in both comparisons is found. This fact may look as if an indirect positive verification of calculation procedure was used here at least in the pressure and temperature domain covered by the experimental data of H₂ and D₂ used for comparison, numerically nearly up to 20 GPa and 10⁴ K. Project supported by the Science and Technology Foundation of China Academy of Engineering Physics (Grant No. 97Z011).     

概率度量空间中压缩映象的不动点定理

本文通过引入压缩映象集序列的概念,推广并综合了张石生以及V.M.Sehger和A.T.Bharucha-Reid中某些主要定理的结果。     

Photonic band structures of two-dimensional photonic crystals with deformed lattices

Using the plane-wave expansion method, we have calculated and analysed the changes of photonic band structures arising from two kinds of deformed lattices, including the stretching and shrinking of lattices. The square lattice with square air holes and the triangular lattice with circular air holes are both studied. Calculated results show that the change of lattice size in some special ranges can enlarge the band gap, which depends strongly on the filling factor of air holes in photonic crystals; and besides, the asymmetric band edges will appear with the broken symmetry of lattices.     

End‐grafting copolymers of styrene and 4‐vinylpyridine on an interacting solid surface

Copolymers of styrene and 4‐vinylpyridine with a styrene fraction f varying from 1 to 0 were grafted onto a silicon substrate in the melt. The grafting reaction and the stability of the grafted chains were investigated by Fourier transform infrared and X‐ray photoelectron spectroscopy. The thickness and surface morphology of the grafted copolymer layers were characterized with ellipsometry and atomic force microscopy (AFM). The copolymer chains were successfully grafted to the surface of the silicon substrate by a reaction between the hydroxyl groups of the nitroxide moiety at the end of the copolymers and the silanol groups on the surface of the silicon wafer. A measurement of the thickness of the grafted copolymer layers showed that the ratio of grafted‐layer thickness to the unperturbed chain radius of gyration decreased with the increasing fraction of 4‐vinylpyridine in the copolymer; this indicated that the grafted layer was strongly attracted to the substrate. In addition, an accelerated grafting process was observed at grafting times ranging from 48 to 72 h for pure poly(4‐vinylpyridine) and copolymers with f values of 0.3 and 0.5. AFM observation revealed that the grafted layers densely and homogeneously covered the silicon substrate. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1332‐1343, 2005