落球法测液体粘滞系数实验的理论分析

分析了斯托克斯定律及其修正项的适用范围,讨论了落球法测液体粘滞系数实验中液体粘滞系数和落球直径对雷诺数的影响,从理论上给出了实验中落球进入液体后匀速运动的判据.     

The construction of boundary analogues of variational methods to approximate weak solutions of boundary-value problems in the theory of elasticity

Methods of approximating weak solutions of certain boundary-value problems in the theory of elasticity are proposed based on expanding the approximate solution in a finite series in basis functions which identically satisfy a homogeneous differential equation in the domain. The coefficients of the expansion are found by constructing a boundary analogue of the method of least squares (BAMLS). It is proved that the approximate solution thus obtained converges to a weak solution of the problem. Sufficient conditions for the stability of the BAMLS, easily verifiable by computational means, are derived. The construction of a boundary analogue of the collocation method (BACM) is proposed on the basis of the BAMLS, combined with discretization of the scalar product by quadrature formulae. The BACM obtained is convergent and stable and possesses better computational properties than the BAMLS.     

Anisotropic electrical properties of Bi0.5(Na0.75K0.25)0.5TiO3 ceramics fabricated by reactive templated grain growth (RTGG)

We have fabricated lead-free Bi_0.5(Na_0.75K_0.25)_0.5TiO₃ (BNKT) ceramics by a conventional process (CP) and reactive templated grain growth (RTGG) methods. The effect of grain orientation on structure, dielectric, complex impedance and electrical properties was investigated. The phase formation and grain morphology of BNKT ceramics were examined by X-ray diffraction (XRD) and scanning electron microscope (SEM), respectively. High dielectric constant and low dielectric loss was observed for grain oriented (textured) BNKT ceramics. Complex impedance, temperature dependent ac and dc conductivity were performed to explore the conduction behavior of the prepared BNKT ceramics.     

Quantum Fisher Information in the Generalized One-axis Twisting Model

We investigate the quantum Fisher information (QFI) of symmetric states for spin-s particles. We derive the maximal QFI, and find that quantum spin correlations are essential ingredients of the maximal QFI. We make applications to the generalized one-axis twisting model. The results show that the redistributions of uncertainties on the basis of the quantum correlations in the multiqubit system are useful for sub-shot-noise phase sensitivity. Furthermore, for high-spin (s>1/2) composite systems, we find a sufficient criterion for entanglement.     

Structural Equation and Mei Conserved Quantity of Mei Symmetry for Appell Equations in Holonomic Systems with Unilateral Constraints

Structural equation and Mei conserved quantity of Mei symmetry for Appell equations in holonomic systems with unilateral constraints are investigated. Appell equations and differential equations of motion for holonomie mechanic systems with unilateral constraints axe established. The definition and the criterion of Mei symmetry for Appell equations in holonomic systems with unilateral constraints under the infinitesimal transformations of groups axe also given. The expressions of the structural equation and Mei conserved quantity of Mei symmetry for Appell equations in holonomic systems with unilateral constraints expressed by Appell functions are obtained. An example is given to illustrate the application of the results.     

Entanglement dynamics and Bell violation of three-qubit states coupled to an XY spin chain with Dzyaloshinski–Moriya interaction

We investigate the entanglement dynamics and Bell violation of three-qubit quantum states under an environment consisting of an XY spin chain with Dzyaloshinski–Moriya (DM) interaction. From the results, we find that the entanglement dynamics depends not only on the DM interaction, the magnetic field, and the anisotropy parameter but also on the number of the freedom degrees of the environment. The decoherence-free subspaces of our model have been identified and the Bell violation of quantum states is also discussed.     

Inelastic partial cross sections for scattering of HF by neon

An analytic expression of the potential energy surface (PES) of the ground state of the Ne-HF complex is obtained by utilizing nonlinear least square method to fit the intermolecular interaction energies [Zhang Y. Guizhou Science, 2003, 21(3): 9–13 (in Chinese)], which have been computed using the augmented correlation-consistent polarized quadruple zeta basis set aug-cc-pVQZ at the theoretical level of CCSD (T). On the basis of the PES, the partial cross sections (PCSs) at the incident energies of 60, 75, 100 and 150 meV for collisions between Ne atoms and HF molecules are calculated using the quantum close coupling approach. The effects of the long-range attractive and the short-range anisotropic interactions on the inelastic PCSs are discussed in detail. The results show: (1) The long-range attractive well of the EPS makes the significant contribution to the lower excitation PCSs, especially the tail maximum for j = 0→j′ = 1 transitions, whereas no contribution is to the j′⩾3 inelastic transitions. (2) The short-range (the repulsive and attractive) interaction makes the significant contribution to the lower excitation PCSs, especially the main peak for j = 0→j′ = 1, 2. As for the transitions of j′⩾3, the short-range interaction plays a key role in the inelastic excitation. (3) Although the positions of the maximums and minimums of the inelastic PCSs are different at the collision energies, they correspond to almost the same impact parameter. Supported by the National Natural Science Foundation of China (Grant Nos. 10676025 and 10574096)     

Fabrication of regular mesoscopic networks of GaAs wires

A novel and simple approach to nanolithography has been developed as a technique for fabricating two-dimensional periodic mesoscopic (submicrometre) networks of semiconductor wires with a feature size down to about 20 nm. The etching mask is made by coating the material's surface with an initially structured polymer network . This is obtained by self-organized patterning in a complex liquid (nitrocellulose solution). Reactive ion etching is used for GaAs surface patterning. This technique can find potential applications in many areas of science and technology which use low-dimensional and mesoscopic devices.     

锂盐添加剂对润滑油摩擦学性能和导电性的影响

采用MFT-R4000型往复摩擦磨损试验机测试四氟硼酸锂(Li BF4),双三氟甲烷基磺酰亚胺锂(Li NTf2)和六氟磷酸锂(Li PF6)这3种锂盐作为润滑油添加剂时对基础油的摩擦学性能的影响,利用OLS4000型三维形貌测量仪测量钢块的磨损体积,并利用扫描电子显微镜(SEM)观察钢块磨痕的表面形貌.采用DDSJ-308A型电导率测定仪测量不同锂盐含量下,润滑油的盐度和电导率的变化情况,阐述锂盐含量和润滑油电导率之间存在的关系.研究结果表明:锂盐能够降低润滑油的摩擦系数,增强其抗磨性,具有良好的摩擦学性能;同时锂盐的加入使基础油的导电性得到很大提高.     

Quantum Chemical Studies on Structure and Detonation Performance of Bis(2,2-dinitropropyl ethylene)formal

Based on the full optimized molecular geometric structures via B3LYP/6-311+G(2d,p) method, a new gem-dinitro energetic plasticizer, bis(2,2-dinitropropyl ethylene)formal was investigated in order to search for high-performance energetic material. IR spectrum, heat of formation, and detonation performances were predicted. The bond dissociation energies and bond orders for the weakest bonds were analyzed to investigate the thermal stability of the title compound. The results show that the four N-NO₂ BDEs are nearly equal to the values of 164.38 kJ/mol, which shows that the title compound is a stable compound. The detonation velocity and pressure were evaluated by using Kamlet-Jacobs equations basedon the theoretical density and condensed HOF. The crystal structure obtained by molec-ular mechanics belongs to P2₁ space group, with lattice parameters Z=2, a=13.8017 ?, b=13.4072 ?, c=5.5635 ?.