The virial theorem in refined Thomas－Fermi－Dirac theory for the interior of atoms in a solid

The virial theorem in refined Thomas－Fermi－Dirac theory for the interior of atoms in a solid is given and proven.     

New periodic solutions to a generalized Hirota－Satsuma coupled KdV system

Using expansions in terms of the Jacobi elliptic cosine function and third Jacobi elliptic function, some new periodic solutions to the generalized Hirota－Satsuma coupled KdV system are obtained with the help of the algorithm Mathematica. These periodic solutions are also reduced to the bell-shaped solitary wave solutions and kink-shape solitary solutions. As special cases, we obtain new periodic solution, bell-shaped and kink-shaped solitary solutions to the well-known Hirota－Satsuma equations.     

NMR analogue of the generalized Grover‘s algorithm of multiple marked states and its application

The generalized Grover's algorithm for the case in which there are multiple marked states is demonstrated on a nuclear magnetic resonance (NMR) quantum computer. The Walsh－Hadamard transform and the phase inversion are all replaced. NMR analogues of Einstein－Podolsky－Rosen states (pseudo-EPR states) are synthesized using the above algorithm.     

A method of detecting capture γ-rays in a strong pulsed radiation field

We present a technology for diagnosing the D－T fusion process by detecting capture γ-rays. This technology provides an alternative route to diagnosing the D－T reaction process when a great deal of heavy Z materials surrounds the D－T region. A very important aspect of this paper is to focus on the methods of shielding low-energy γ-rays whose radiation intensity is 10⁶ times higher than that of the capture γ-rays. Another aspect is about how to distinguish signal from noise. The result of a 50/1 signal-to-noise ratio indicates that the designed double-magnetic spectrograph is very successful for diagnosing the D－T fusion reaction process.     

Nonlinear current－voltage characteristics of sintered tungsten－vanadium oxide

We have studied the densification behaviour, microstructure and electrical properties of WO_3 ceramics with V_2O_5 as the additive ranging from 0.5 to 15mol%. Scanning electron microscopic photos indicated that the grain size of WO_3－V_2O_5 specimens is smaller than that of pure WO_3. The addition of V_2O_5 to WO_3 showed a tendency to enhance the densification rate and to restrict the grain growth. Electrical properties of all specimens were measured for different electrodes at different temperatures. The formation of the grain boundary barrier layer was confirmed by the non-ohmic I－V behaviour. The nonlinear coefficient was obtained at the current density J=0.01, 0.1 and 1mA/cm^2 for a series of WO_3－V_2O_5 samples. The V0.5mol% specimen showed an abnormal phenomenon that the nonlinear characteristics appeared at 350℃ and disappeared at lower and higher temperatures. This implies that it could be applied as a high-temperature varistor. The double Schottky barrier model was adopted to explain the phenomena for the WO_3-V_2O_5 varistors.     

Vacuum polarization of scalar electrodynamics in flat space－time with nontrivial topology

The one-loop vacuum polarization is calculated for scalar electrodynamics in a flat space－time with the topology S¹×R³. The effect of vacuum polarization upon photon propagation is considered. It is found that photon propagation becomes anisotropic with some photon modes acquiring a positive topological mass and thus travelling at a subluminal speed.     

Characteristics of critical amplitude of a sinusoidal stimulus in a model neuron

The characteristics of the critical amplitude of a sinusoidal stimulus in a model neuron, Morris－Lecar model, are investigated numerically. It is important in the study of stochastic resonance to determine whether a periodic stimulus is subthreshold or not. The critical amplitude as a function of the stimulus frequency is not a constant, but a curve, which is the boundary between subthreshold and suprathreshold stimulation. It has been considered that this curve is U-shaped in the previous investigations, and this has been accepted as a universal phenomenon. Nevertheless, we think that it is only true for a type of neuron: namely, resonators. Actually, there exists another type of neuron, integrators, which can undergo a saddle-node on invariant circle bifurcation from the rest state to the firing state. For the latter we find that the critical amplitude increases monotonically as the frequency of sinusoidal stimulus is increased. This is shown by way of the Morris－Lecar model. As a consequence, the critical amplitude curve is studied further, and the dynamical mechanisms underlying the change in critical amplitude curve are uncovered. The results of this paper can provide a reference to choose the subthreshold periodic stimulus.     

针状纳米NixZn1-xFe2O4的制备及磁性能

以FeCl₂, Zn(NO₃)₂, Ni(NO₃)₂为原料, 利用化学沉淀法制得了针状纳米α-FeOOH, 并借助针状α-FeOOH做为中间体, 采用柠檬酸法在针状纳米α-FeOOH表面包裹镍和锌的柠檬酸络合物后, 于不同温度煅烧后制得了针状纳米Ni_xZn_1－xFe₂O₄. 利用红外光谱仪(IR)、X射线衍射技术(XRD)、透射电子显微镜(TEM)对样品的物相﹑晶格常数、形貌和粒径进行表征, 并利用振动样品磁强计(VSM)对样品进行磁性能研究. 结果表明: 利用化学沉淀-柠檬酸法制得的Ni-Zn铁氧体样品保持了中间体α-FeOOH的针状形貌, 所得样品的直径在40 nm左右, 长度约600 nm, 长径比大于15. 随着煅烧温度的升高样品直径有所增加, 长径比下降, 随着x值的增加, Ni_xZn_1－xFe₂O₄样品的晶格常数a从0.8442 (x＝0)逐步减少到0.8353 (x＝1.00), 矫顽力(Hc)从63.5 Oe (x＝0)逐步增加到358.7 Oe (x＝1), 饱和磁化强度(M_s)先增加后减小, 当x＝0.6时达到最大为58.9 emu/g. 与相似条件时制备的不定型Ni_xZn_1－xFe₂O₄相比, 由于针状Ni_xZn_1－xFe₂O₄的各向异性增大, 而表现出明显的硬磁性.     

BaCe0.5Zr0.4La0.1O3－α陶瓷的制备及其电性能

以高温固相反应法合成了BaCe0.5Zr0.4La0.1O3－α陶瓷. 粉末XRD结果表明, 该陶瓷材料为单一钙钛矿型BaCeO3斜方晶结构, 在高温下、CO2或水蒸气气氛中具有较高的稳定性. 以陶瓷材料为固体电解质、多孔性铂为电极, 用交流阻抗谱技术测定了材料在500～900 ℃下, 不同气体气氛中的电导率; 用气体浓差电池方法测定了材料在干燥空气、湿润空气和湿润氢气气氛中的离子迁移数, 研究了材料的离子导电特性. 结果表明, 在500～900 ℃下, 干燥或湿润的气体气氛中, 随着温度升高和氧分压增大, 材料的电导率均增大. 在干燥空气中, 陶瓷材料的氧离子迁移数为0.685～0.147, 是一个氧离子与电子空穴的混合导体. 在湿润空气中, 陶瓷材料的质子迁移数为0.001～0.006, 氧离子迁移数为0.618～0.164, 是一个质子、氧离子和电子空穴的混合导体. 在湿润氢气中, 500～700 ℃温度范围内, 陶瓷材料的质子迁移数为1, 是一个纯的质子导体; 而在800～900 ℃温度范围内, 陶瓷材料的质子迁移数为0.957～0.954, 是一个质子与电子的混合导体, 质子电导占主导.     

在(TPA)2O-Na2O-SiO2-H2O体系中MFI型硅沸石的结晶行为(Ⅱ)──硅沸石微细晶粒的低温合成及其结构和性质表征

以白炭黑和硅溶胶为桂源, 在(TPA)₂O-Na₂O-SiO₂－H₂O体系60℃下合成了高结晶度纯相硅佛石.由SEM测得其晶粒尺寸为0.2μm和0.45μm, 用XRD线宽法测得的为0.02μm.与180℃时合成的硅沸石样品相比, 低温合成的细晶粒硅沸石已具备纳米级材料的若干特性.其正乙烷吸附量反常增大;XRD、FTIR、²⁹SiMASNMR和TG／DTG／DTA的研究证明, 其结构破坏温度和单斜／正交对称性相转变温度明显下降, 桂羟基缺陷明显增加.