聚合物-金属界面相形貌的研究

环氧树脂在 Al 合金表面生成纤维状的界面相结构,其形成、发展和特征与树脂的体系、交联反应条件以及 Al 合金的表面状态有关。环氧树脂的基础相为颗粒状的超结构组织。聚合物界面相的力学破坏表现为纤维体的拉伸、变形和断裂,而基础相在纯剪切受力时出现在45°方向的裂纹,并发展导致连接层的破坏。     

Formation of layered structure on bismuth-borate glass surface

X-ray diffraction analysis shows that the transformation during heat treatment from amorphous to crystalline phases of bismuth-borate glass samples takes place in sequences. After a short heat treatment, 5 min at 550 °C, a layered structure with a preferred orientation of crystallites on the surface is observed. After a long heat treatment, 8 h at the same temperature, normal polycrystalline bulk samples are obtained.     

浅析异步电机电子软起动器的现状和展望

本文在分析异步电机电子软起动器的现状和展望的基础上，以一个当前正在设计完善的电子软起动器为例，基本说明新型电子软起动器的特点和结构功能。     

A new iterative order reduction (IOR) method for eigensolutions of large structures

Order reduction is a computationally efficient method to estimate some lowest eigenvalues and the corresponding eigenvectors of large structural systems by reducing the order of the original model to a smaller one. But its accuracy is limited to a small range of frequencies that depends on the selection of the retained degrees of freedom. This paper proposes a new iterative order reduction (IOR) technique to obtain accurately the eigensolutions of large structural systems. The technique retains all the inertia terms associated with the removed degrees of freedom. This hence leads to the reduced mass matrix being in an iterated form and the reduced stiffness matrix constant. From these mass and stiffness matrices, the eigensolutions of the reduced system can be obtained iteratively. On convergence the reduced system reproduces the eigensolutions of the original structure. A proof of the convergence property is also presented. Applications of the method to a practical GARTEUR structure as well as a plate have demonstrated that the proposed method is comparable to the commonly used Subspace Iteration method in terms of numerical accuracy. Moreover, it has been found that the proposed method is computationally more efficient than the Subspace Iteration method. Copyright © 2003 John Wiley & Sons, Ltd.     

真空制盐蒸发结晶器的设计与实践

真空蒸发制盐外热式强制逆循环轴向出料蒸发结晶器，经多个厂家生产应用实践证明是成功的，具有生命力的。这种新型结构，作为一项新技术新设备应加强研究，总结提高，推广应用。不断完善。文章从流体力学、结晶机理角度要求，到具体工程设计参数和材质选用。论述了该罐的特点。     

复杂结构高耸建筑物爆破拆除切口研究

针对壁体材料多样、结构复杂的高耸建筑物的爆破拆除,通过实验研究确定了爆破切口形式,运用力学理论推导了余留支撑体所对应的圆心角和爆破切口高度计算公式,并在工程实践中得到验证.对爆破拆除类似建筑物具有较大的实用价值.     

Disorder effects on the strain response of model polymer networks

Molecular dynamics simulations are used to investigate polymer networks made by either end-linking or randomly crosslinking a melt of linear precursor chains. The resulting network structures are very different, since end-linking leads to nearly ideal monodisperse networks, while random crosslinking leads to polydisperse networks, characterized by an exponential strand length distribution. Networks with average strand length 20 and 100 were generated. These networks were used to study the effects of disorder in the network connectivity on observables averaged either over the entire network or selected sub-structures. Heterogeneities in the randomly crosslinked networks cause significant differences in the localization of monomers, however, neither the localization of crosslinks nor the microscopic strain response are significantly affected. Compared to end-linked networks, randomly crosslinked networks have a slightly increased tube diameter, and as a result a slightly decreased shear modulus, but otherwise identical stress-strain behavior. For the investigated systems, we conclude that the microscopic strain response, tube diameter, and stress-strain relation are all insensitive to the heterogeneities due to the linking process by which the network were made.     

A Bayesian propensity score adjustment for latent variable modeling and MCMC algorithm

The estimation of the differences among groups in observational studies is frequently inaccurate owing to a bias caused by differences in the distributions of covariates. In order to estimate the average treatment effects when the treatment variable is binary, Rosenbaum and Rubin [1983. The central role of the propensity score in observational studies for causal effects. Biometrika 70, 41-55] proposed an adjustment method for pre-treatment variables using propensity scores. Imbens [2000. The role of the propensity score in estimating dose-response functions. Biometrika 87, 706-710] extended the propensity score methodology for estimation of average treatment effects with multivalued treatments.However, these studies focused only on estimating the marginal mean structure. In many substantive sciences such as the biological and social sciences, a general estimation method is required to deal with more complex analyses other than regression, such as testing group differences on latent variables. For latent variable models, the EM algorithm or the traditional Monte Carlo methods are necessary. However, in propensity score adjustment, these methods cannot be used because the full distribution is not specified.In this paper, we propose a quasi-Bayesian estimation method for general parametric models that integrate out the distributions of covariates using propensity scores. Although the proposed Bayes estimates are shown to be consistent, they can be calculated by existing Markov chain Monte Carlo methods such as Gibbs sampler. The proposed method is useful to estimate parameters in latent variable models, while the previous methods were unable to provide valid estimates for complex models such as latent variable models.We also illustrated the procedure using the data obtained from the US National Longitudinal Survey of Children and Youth (NLSY1979-2002) for estimating the effect of maternal smoking during pregnancy on the development of the child's cognitive functioning.     

混凝土结构的质量通病——裂缝

从材料、结构构造、施工工艺、地基变形、温湿度变形等方面论述了混凝土裂缝产生的原因 ,提出只有真正了解裂缝产生的原因 ,才能有针对性地采取有效措施 ,确保工程质量