平衡硫化体系硫化天然橡胶的平衡硫化性和化学应力松弛行为

<正>WOlff’‘,”采用双（3-三乙氧基甲硅烷基丙基）-四硫化物（St69）与硫黄组成的平衡硫化体系（EC）,既减少了硫化返原的产生,又保留了传统硫黄硫化体系（CV）的优点,同时克服了因采用有效硫化体系（EV）或半有效硫化体系（SEV）所导致的强度等     

磷酸盐玻璃中Mn^2＋离子的发光研究

应用荧光光谱、振动光谱和电子自旋共振波谱等系统研制了掺Ｍｎ＾２＋离子的锌磷酸和铝酸盐系统玻璃的发光行为。结果表明：三元磷酸盐玻璃中Ｍｎ＾２＋用紫外激发，于可见区产生一宽发射带；变换玻璃中的网络外体离子，玻璃网络化学键主振动峰不变，随碱金属或碱土金属子场强减小，Ｍｎ＾２＋离子的＾４ｔ１（Ｇ）－＾６Ａ１（ｓ）发光跃迁的相对强度规律变小，且向长波方向移动，反之亦然，Ｍｎ＾２＋在磷酸盐玻璃中为６配位，发红     

Mn-Nb-Cu-B低碳贝氏体钢的析出动力学

在Gleeble 1500热模拟试验机上,通过应力松弛实验研究了Mn-Nb-Cu-B低碳贝氏体钢在不同工艺条件下析出行为,得到了不同变形量、不同变形速率下的析出动力学曲线。同时,根据实验结果,确定了所研究钢种的析出动力学方程的参数,并计算了析出开始时间。结果表明,在较高温度下,计算值与实验观测值吻合得较好。研究结果对制订合理变形工艺有帮助。     

Interface structure of Ag(111)/SnO_2(200) composite material studied by density functional theory

Electric contact material of Ag/SnO2 was successfully synthesized by in situ process method.The in-terface structure was characterized by high-resolution transmission electron microscopy(HTEM) and simulated at atomic scale on computer.The mean-square displacements of atoms near the interface were calculated,and the results showed that near the interface both Ag side and SnO2 were mis-matched and this effect decays rapidly far from the interface.By inspecting the calculated density of states(DOS),we found th...     

Stress relaxation and estimation of activation volume in a commercial hard PZT piezoelectric ceramic

The stress relaxation of ferroelectric/piezoelectric material was studied using compression testing. The deformation was produced by the switching of ferroelectric domains. The internal stresses were estimated by decremental stress relaxation during unloading. The results were interpreted in terms of reversible and irreversible switching of the domains     

About the activation energies of the main and secondary relaxations in cured styrene butadiene rubber

This article studies the influence of the network structure on the activation energies of the α and β relaxations in vulcanized styrene butadiene rubber, SBR. A cure system based on sulphur and TBBS (N‐t‐butyl‐2‐benzothiazole sulfenamide) was used in the formulation of several compounds cured at 433 K. The activation energies were evaluated from internal friction (loss tangent) data of the compounds using an automated subresonant forced pendulum in a wide frequency range and between 80 K and 273 K. The internal friction data of the samples reveal two transitions, α and β, characterized by the temperatures T_α and T_β, due to the glass transition and the phenyl group rotation of the copolymer, respectively. Although T_α increases at higher crosslink density, it shows also a dependence with the amount of polysulphide and monosulphide linkages present in the samples. The highest activation energy for this process is obtained for the samples with high crosslink density and 30% of monosulphides in this structure. In the case of the β‐relaxation, there is a pronounced change in the activation energy between the uncured and the cured samples. The type of structure formed during vulcanization has an important effect in the activation energy of the segmental mode‐process. In the case of the β‐process, the cis‐trans isomerization that takes place during vulcanization in the butadiene part of the SBR, might be the cause of conformational changes in the surrounding of the phenyl rings that affect the energy barrier associated to the phenyl rotation. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Evaluation of the dielectric parameters from TSDC spectra: application to polymeric systems

The Thermally Stimulated Discharge Current (TSDC) technique is widely used for the study of main and secondary dielectric relaxations in polymers. The TSD current is described by different equations that can be arranged in a unique three-parameters (the activation energy W, A and B) general form. The physical meaning of A and B depends on the origin of the discharge currents. In this paper a method is proposed to obtain these parameters by fitting the experimental data with the analytical expression of the current, in the range around the maximum. Simulations were carried out to underline the relative importance of the parameters. A method is proposed for the decomposition of experimentally determined complex bands into a limited number of elementary peaks, each of them characterized by average values for W and B. The errors resulting from different approximations used in the analytical current expression or by the utilization of various expressions for the relaxation time are analyzed. The method is applied for the analy-sis of the TSDC spectra in the glass-rubber transition temperature regions of PET and PMMA, yielding several peaks characterized by narrow distributions of W (ΔW≈± 0.06 eV). Received: 18 September 2000 / Reviewed and accepted: 20 September 2000     

超松驰方法在正实条件下的收敛性分析

研究使用超松驰（SOR）方法求解正实线性方程组时的收敛性，证明了在适当的选取松驰因子SOR方法是收敛的，进一步丰富了SOR理论，同时给出了SOR方法在对称正交条件下收敛的充要条件的又一新证明。     

Modelling nonlocal processes in semiconductor devices with exponential difference schemes

In this paper nonlocal quasi-hydrodynamic mathematical models describing non-equilibrium physical processes in semiconductor devices are considered. These processes cannot be adequately described with conventional drift-diffusion models. The primary numerical difficulty arises in the energy balance equation. Details of the discretisation for the continuity equations will be described along with a transformation of the energy balance equations to give computationally convenient forms. Effective exponential difference schemes are constructed and applied to modelling transport phenomena in semiconductors. Stability conditions, computational convergence and algorithmic realisations of the proposed schemes are discussed and numerical examples are given.     

Reflection of magneto-thermo-elastic waves from a rotating elastic half-space

Models of generalized magneto-thermo-elasticity based on the Lord-Shulman theory (LS) with one relaxation time, the Green-Lindsay theory (GL) with two relaxation times, as well as the classical dynamic coupled theory (CD), are used to study the electro-magneto-thermo-elastic interactions in a semi-infinite perfectly conducting solid. The elastic medium rotates with uniform angular velocity. The initial magnetic field is parallel to the boundary of the half-space. Reflection of magneto-thermo-elastic waves under generalized thermo-elasticity theory is studied. The reflection coefficients are obtained.