Interfacial fracture analysis of bonded dissimilar strips with a functionally graded interlayer under antiplane deformation

This paper provides the solution to the problem of dissimilar, homogeneous semi-infinite strips bonded through a functionally graded interlayer and weakened by an embedded or edge interfacial crack. The bonded system is assumed to be under antiplane deformation, subjected to either traction-free or clamped boundary conditions along its bounding planes. Based on the Fourier integral transform, the problem is formulated in terms of a singular integral equation which has a simple Cauchy kernel for the embedded crack and a generalized Cauchy kernel for the edge crack. In the numerical results, the effects of geometric and material parameters of the bonded system on the crack-tip stress intensity factors are presented in order to quantify the interfacial fracture behavior in the presence of the graded interlayer.     

新型路基同心筒热冲击机理与热环境影响因子

针对新型同心筒自力发射高速热冲击载荷下热环境评估与影响因子决策问题,结合弹性变形和域动分层结合的动网格技术,求解了二维轴对称Navier-Stokes方程,分析了新型路基同心筒流场机理与热冲击特性,并确定了热环境评价指标;通过建立以优化拉丁超立方试验设计和径向基神经网络为理论基础的近似数学模型,解决了CFD自动建模困难、计算量大的难点;结合径向基神经网络训练方法,对导弹热环境的影响因子进行了智能决策研究。分析表明:倒吸进入新型同心筒内筒的低温气体有力改善了同心筒热环境;建立的近似模型精度较高,满足工程需求;对导弹热环境的影响因子从大到小依次为筒底导流板直径、筒底导流板长度、导流器高度;为导弹热环境多学科优化设计提供参考。     

Cylindrical interface crack in a hollow layered functionally graded cylinder under static torsion

A hollow functionally graded composite cylinder under static torsion, which consists of an inner and outer elastic circular tube with a cylindrical interface crack, is studied in this work. By utilizing Fourier integral transform method, the mixed boundary value problem is reduced to a Cauchy singular integral equation, from which the numerical results of the stress intensity factor are obtained by the Lobatto–Chebyshev quadrature technique. Numerical results demonstrate the coupled effects of geometrical, physical, and functionally graded parameters on the interfacial fracture behavior.     

Thermoelastic analysis of multiple defects with the extended finite element method

In this paper, the extended finite element method (XFEM) is adopted to analyze the interaction between a sin-gle macroscopic inclusion and a single macroscopic crack as well as that between multiple macroscopic or micro-scopic defects under thermal/mechanical load. The effects of different shapes of multiple inclusions on the material thermomechanical response are investigated, and the level set method is coupled with XFEM to analyze the interaction of multiple defects. Further, the discretized extended finite element approximations in relation to thermoelastic prob-lems of multiple defects under displacement or temperature field are given. Also, the interfaces of cracks or materials are represented by level set functions, which allow the mesh assignment not to conform to crack or material interfaces. Moreover, stress intensity factors of cracks are obtained by the interaction integral method or the M-integral method, and the stress/strain/stiffness fields are simulated in the case of multiple cracks or multiple inclusions. Finally, some numer-ical examples are provided to demonstrate the accuracy of our proposed method.     

装备制造业环境技术创新效率及其影响因素研究——基于DEA-Malmquist和Tobit的实证分析

运用2005~2011年中国装备制造业的面板数据,采用熵值法测度中国装备制造业的环境污染指数,应用DEA-Malmquist方法在考虑环境污染和能源消耗问题的基础上测度中国各类装备制造业环境技术创新效率,应用Tobit回归分析法对影响中国装备制造业环境技术创新效率的因素进行分析。研究结果表明:中国装备制造业的环境污染指数呈现下降—上升—下降的趋势;中国装备制造业的总体环境技术创新效率呈现先上升再下降的趋势,技术效率持续上升,技术退步是导致环境技术创新效率后期下降的原因;市场竞争、资本深化和外资引进对环境技术创新效率的提升具有显著的推动作用。     

XPS-AES联用技术对Pt-Co，Cu-Au和Cu-Ag合金薄膜的定量表征方法研究

俄歇电子能谱(AES)在表面微区元素分析方面优势明显,但是受基体效应的影响,其定量分析,特别是非单质材料表面元素含量分析的准确度差,X射线光电子能谱(XPS)的定量分析准确度较高。为了降低AES定量分析的误差,将XPS和AES两种分析技术联用,选择Pt-Co,Cu-Au和Cu-Ag三种二元合金样品进行了研究,利用样品的XPS定量分析结果对AES的定量分析所用相对灵敏度因子进行修正,将修正后的相对灵敏度因子用于其他不同组分比的样品的定量分析,以验证其分析准确性。结果表明,修正后的灵敏度因子在用于AES定量分析时相对误差明显降低,分析相对误差小于10%。为了解决AES定量分析在积分谱处理形式下选峰困难的问题,将积分谱进行微分化处理,并修正了微分谱的处理形式下的相对灵敏度因子,AES的定量分析相对误差降低到小于9%,表明在两种处理形式下都能得到较为准确的定量结果。修正后的相对灵敏度因子包含了基体效应尤其是背散射效应的影响,从而有助于降低AES定量分析的误差。说明借助XPS提高AES定量分析准确度的研究方法具有一定的可行性。     

Cluster preformation in heavy nuclei and radioactivity half-lives

Various cluster radioactivities of heavy nuclei have been investigated by using the unified fission model (UFM). The cluster preformation factors have been extracted by employing the UFM connected with the experimental half-lives, and the relationship of preformation probability between the cluster and -particle has been discussed in detail. In addition, the cluster preformation probability has been studied in the framework of statistical physics. Some useful predictions on the cluster emission half-lives are provided for future experiments.     

Electromagnetic form factor via Bethe-Salpeter amplitude in Minkowski space

For a relativistic system of two scalar particles, we find the Bethe-Salpeter amplitude in Minkowski space and use it to compute the electromagnetic form factor. The comparison with Euclidean space calculation shows that the Wick rotation in the form factor integral induces errors which increase with the momentum transfer Q². At JLab domain (Q ² = 10 GeV^2/c²), they are about 30%. Static approximation results in an additional and more significant error. On the contrary, the form factor calculated in light-front dynamics is almost indistinguishable from the Minkowski space one.     

When VSEPR Fails: Experimental and Theoretical Investigations of the Behavior of Alkaline‐Earth‐Metal Acetylides

The synthesis, structural, and spectral characterization as well as a theoretical study of a family of alkaline‐earth‐metal acetylides provides insights into synthetic access and the structural and bonding characteristics of this group of highly reactive compounds. Based on our earlier communication that reported unusual geometry for a family of triphenylsilyl‐substituted alkaline‐earth‐metal acetylides, we herein present our studies on an expanded family of target derivatives, providing experimental and theoretical data to offer new insights into the intensively debated theme of structural chemistry in heavy alkaline‐earth‐metal chemistry.     

The membranes (Nafion and LDPE) in binary liquid mixtures benzene + methanol - sorption and swelling

Sorption studies provide valuable information about the interactions of the components of the liquid mixture with the polymer. In the present paper, the behaviour of Nafion and low-density polyethylene membranes in binary mixtures benzene + methanol was examined with respect to their application in separation processes. The individual sorption isotherms, the separation factors, and the composition of the swollen membranes were derived from the experimental data. The results confirm that Nafion as a polar material sorbs the more polar component of the mixture (methanol) preferentially to the less polar component (benzene) whereas non-polar polyethylene prefers non-polar benzene in the whole concentration range. Volume measurements of the swollen membranes indicate that the ideal sorption behaviour cannot be considered for the selected systems.