卫星中介质深层充电特征研究

介质深层充电效应是诱发地球同步轨道卫星运行故障和异常的重要因素之一.通过数值模拟方法对卫星介质材料中充电所致最大电场与高能电子能谱、介质厚度，及屏蔽厚度等的关系进行了详细研究，给出了介质中最大电场的基本特征. 关键词： 卫星 介质深层充电 高能电子 计算机模拟     

Modeling of radar scattering conditions inside a circular hollow dielectric waveguide

A new ray representation of electromagnetic field inside a quasi — optical structure in the form of a circular hollow dielectric waveguide is suggested and confirms the possibility for the unusual application of such a waveguide as an off-beat microanechoic chamber for electromagnetic modeling in the near millimeter and submillimeter wave regions.     

介质中电位移矢量D=ε_0E_0的充要条件的通俗证明

用电磁学方法通俗地证明电位移矢量Ｄ与介质无关的充要条件．     

Synthesis and characterization of siloxane resins derived from silphenylene‐siloxane copolymers bearing benzocyclobutene pendant groups

Two bis(dimethylamimo)silanes with benzocyclobutene (BCB) groups, bis(dimethylamino)methyl(4′‐benzocyclobutenyl)silane ( 2 ) and bis(dimethylamino)methyl [2′‐(4′‐benzocyclobutenyl)vinyl]silane ( 4 ), were synthesized from different synthetic routes, which were then employed to prepare two novel silphenylene‐siloxane copolymers (SiBu and SiViBu) bearing latent reactive BCB groups by polycondensation procedure with 1,4‐bis(hydroxydimethylsilyl)benzene. At elevated temperatures these copolymers were readily converted to highly crosslinked films and molding disks with network structures by polymer chain crosslinking, which followed the first‐order kinetic reaction model. The final resins of SiBu and SiViBu demonstrated excellent thermal stability with high glass transition temperatures (218 and 256 °C) and high temperatures at 5% weight loss (553 and 526 °C in N₂, 530 and 508 °C in air). After aging at 300 °C in air for 100 h, the cured resins showed weight loss lower than 4%. The films of cured SiBu and SiViBu also exhibited relatively low dielectric constants of 2.66 and 2.64, low dissipation factors of 2.23 and 2.12 × 10^?3, low water absorptions (≤0.28%), and high transparence in the visible region with cutoff wavelengths of 321 and 314 nm. Moreover, the aged films exhibited good dielectric properties and low water absorptions. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7868–7881, 2008     

Plasmon dispersion and linewidth in aluminium

Plasmon dispersion in Al is estimated using the expression for the dynamic structure function,S _pl(K,ω), corresponding to the plasmon excitations in a many-electron system derived earlier. An evaluation of its plasmon linewidth is also presented. It is observed that for Al both the dispersion and linewidth agree fairly well with experiments.     

Transmission Line Model Based CAD of Multilayer Dielectric Filters

A systematical procedure for multilayer dielectric filter design is introduced here based on the transmission line model (TLMBCAD). By this procedure, low-pass, high-pass, and band-pass filters can be designed in the same way. The transmission line model works well and is time efficient not only for normal incidence of linearly polarized wave but also for oblique incidence wave with circular polarization. Design examples are given for low-pass and band-pass filters. Simulation results show that the method developed in this paper is valuable for the engineering design of multilayer dielectric filters.     

A stereochemical microstructure-based attempt to explain the dielectric behavior of poly(vinyl chloride) (PVC)

A poly(vinylchloride) (PVC) obtained by bulk polymerization at 70 °C was modified through substitution reaction with sodium benzenethiolate (NaBT) in cyclohexanone solution at 25 °C, at various conversions up to 15 mol %. According to earlier work, this allows to change, in a controlled way, the stereochemical microstructure in terms of mainly the content of mmr (meso, meso, racemic) tetrad termini of isotactic sequences of at least one heptad in length, and of its likely chain conformations. The samples were all studied by Dielectric Relaxation Spectroscopy, which allows to measure the real and the imaginary parts of the complex dielectrical constant in a frequency range between 1 and 10⁶ Hz, and a temperature range between 100 and 600 K. Most of the changes in the physical quantities that can be analyzed by this technique were found to parallel the changes in stereochemical microstructure with substitution extent. The temperature of the maximum of the dipolar losses, which relates to the temperature range where α relaxation occurs, appeared to increase somewhat up to 0.7% molar conversion. Then the tendency is towards stabilization. The relaxation time τ(T) as deduced from the Havriliak-Negami (NH) function, tends to decrease between 0 and 0.7 substitution percent, and to increase afterwards. The evolution of the Ngai's β parameter with substitution degree is also highly illustrative. It clearly decreases up to 0.7% and then it increases rapidly up to 7% and slowly afterwards. These changes are discussed by taking into account that 0.7 and 7% substitution extents agree with the removal of mmr under GTTG⁻TT conformation and of the same structure under GTGTTT conformation, respectively. From the results, some original correlations between stereochemical microstructure and molecular dynamic behaviors are proposed. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2337–2347, 2004     

Comparison of dielectric theories that explicitly include viscoelastic parameters

In this work we compare four dielectric relaxation models that explicitly include the viscoelastic properties of the environment to define the dielectric relaxation process. These models are the Debye, Gamant, DiMarzio-Bishop, and the Havriliak-Havriliak models. Debye's model assumes a Newtonian viscosity and solves the hydrodynamic problem exactly leading to the venerable Debye function. Gamant's used heuristic arguments to include a time-dependent viscosity. These results lead to a splitting of the relaxation process. DiMarzio-Bishop solved the hydrodynamic equations which included a time-dependent viscosity exactly and applied the results to poly(n-octyl methacrylate). The Havriliak-Havriliak approach is based on statistical mechanics arguments that take into account strain energy which is associated with the polarization process. This model also requires a knowledge of the viscoelastic properties of the system. The results of the four models are compared. © 1995 John Wiley & Sons, Inc.     

Discontinuous fission tracks on the surface of layered dielectrics

The structure of fission fragment tracks on the surface of dielectric layer crystals has been studied by electron microscopy methods. Single crystal of gypsum (CaSO₄·2H₂O), cadmium wolframate (CdWO₄) and muscovite mica (KAl₂(OH)₂Si₃AlO₁₀) have been chosen as objects of investigation. It has been found that a discontinuous change of the surface profile continues at abnormally large (30nm) penetrations of the ion from the surface into the bulk of the crystal. Formation mechanisms of separate segments in the track structure are discussed.     

Polymer matrix effects on the nonlinear optical response of incorporated chromophore: new analytical models.

A new approach aimed at the modeling of the nonlinear optical (NLO) response of a dipole chromophore incorporated into a locally anisotropic, deformable, polarizable polymer matrix is suggested. The general continuum methodology is used with a specific cavity ansatz being employed; the cavity is chosen to be conformal to the characteristic ellipsoid of the generalized permittivity tensor of the polymer medium. The suggested ansatz allows the electrostatic boundary value problem to be solved analytically, and the local field experienced by the chromophore in the polymer electret to be found. Four analytically solvable models, which correspond to two singular and two nonsingular models, are considered; in two of them the chromophore is characterized by singular dipole and quadrupole moments; the other two use the approximation of the electric moment of the chromophore with that of the polarized ellipsoid. The relation between the macroscopic polymer properties and the microscopic characteristics of the NLO chromophore is established. The compliance of the obtained formulas for the local field with those of the classical Onsager approach is analyzed, and their specific features are considered.