A new efficient numerical method and the dynamic analysis of composite laminates with piezoelectric layers

Firstly, a numerical method for the inversion of Laplace transform is developed and its accuracy is shown through examples. Then, a state-vector equation for the dynamic problems of piezoelectric plates is deduced directly from a modified mixed variational principle for piezoelectric bodies and its exact solution for the dynamic problems of simply supported rectangle piezoelectric plate is simply given. For multilayered hybrid plates, we derive the solution in terms of the propagator matrices. The techniques accounts for the compatibility of generalized displacements and generalized stresses on the interface both the elastic layers and piezoelectric layers, and the transverse shear deformation and the rotary inertia of laminate are also considered in the global algebraic equation of structure. Meanwhile, there is no restriction on the thickness and the number of layers. As an application of the numerical inversion of Laplace transform presented in this paper, typical numerical examples of the harmonic vibration and transient response are proposed and discussed. Since the highly accurate numerical results, they can serve as benchmarks to test various thick plate theories and various numerical methods, such as the finite and boundary element methods for transient response problems.     

Nodally exact Ritz discretizations of 1D diffusion–absorption and Helmholtz equations by variational FIC and modified equation methods

This article presents the first application of the Finite Calculus (FIC) in a Ritz-FEM variational framework. FIC provides a steplength parametrization of mesh dimensions, which is used to modify the shape functions. This approach is applied to the FEM discretization of the steady-state, one-dimensional, diffusion–absorption and Helmholtz equations. Parametrized linear shape functions are directly inserted into a FIC functional. The resulting Ritz-FIC equations are symmetric and carry a element-level free parameter coming from the function modification process. Both constant- and variable-coefficient cases are studied. It is shown that the parameter can be used to produce nodally exact solutions for the constant coefficient case. The optimal value is found by matching the finite-order modified differential equation (FOMoDE) of the Ritz-FIC equations with the original field equation. The inclusion of the Ritz-FIC models in the context of templates is examined. This inclusion shows that there is an infinite number of nodally exact models for the constant coefficient case. The ingredients of these methods (FIC, Ritz, MoDE and templates) can be extended to multiple dimensions     

浅谈2000版IS09000族质量管理体系标准的结构与特点

结合对2000年版ISO9000族质量管理体系标准的理解和分析,对标准的结构和特点进行了探讨。     

尺寸驱动的变参设计系统研究

本研究在简介国际上先进的变参设计几种方法及优点后,叙述了一个国家863/CIMS项目:CAD/CAPP/NCP集成系统中二维尺寸驱动的变参设计子系统的构成与功能;然后着重阐述了本系统采用的尺寸驱动的变参设计思想和几何约束建立的原则,并提供了系统数据结构,最后以几个实例证明了此方法的正确性与工程实用性。     

工业发酵的生物学属性对发酵过程最优控制的制约与对策

从工业发酵过程计算机控制的历史和现状出发，探讨了工业发酵过程的生物学属性对发酵过程最优化控制的制约，以及解决这个难题的对策。在论证了工业发酵具有明显的生物学属性的基础上，阐明了发酵的生物学原理及其在发酵过程最优化控制中应用的重要性。     

复合材料四结点四边形多层退化壳单元

本文提出了一个复合材料四结点四边形多层退化壳单元。单元从修正的Hu-Washizu变分原理导出,独立假设位移场、每层内部应变场和应力场。文中给出了几个复合材料板和壳静力线性问题实例。计算结果表明本文的单元是准确和有效的。     

透明加解密系统原理与实现分析

介绍透明加解密系统产生的背景、原理以及实现技术,同时还对对称加密算法进行简要的介绍,对于加解密系统的使用提出了独特见解。     

避暑山庄的选址

造园首在选址。选址得当,可以事半功倍。计成在《园冶》中指出,只有“相地合宜”,才能“构园得体”。地址要好,清洁卫生,有丘有壑,草地和树林相间”。避暑山庄之所以能够在造园史上独树一帜,选址得当是其中一个重要原因。避暑山庄当时所以选择这块地方建造宫苑,除政治上的原因之外,主要是因为它具有优越的自然条件。避暑山庄的园林艺术成就,已得到世人的公认,造园家相地择址的匠心,也会给我们许多有益的启示。     

不平衡样本下基于变分自编码器预处理深度学习和DGA的变压器故障诊断方法

为提高变压器故障诊断效果,并改善训练样本数量不平衡对故障诊断的不利影响,提出了一种基于变分自编码预处理深度学习和油中溶解气体分析(dissolved gas-in-oil analysis,DGA)的变压器故障诊断方法。该方法以各样本DGA特征量为诊断模型输入,以各故障状态概率分布为诊断模型输出。首先通过变分自编码器对少数类训练样本进行预处理,在学习确定少数类训练样本分布特征的基础上实现训练样本自动生成,进而提高训练样本的均衡性。基于3隐层结构堆栈稀疏自编码器深度学习网络构建变压器故障诊断模型,并以经变分自编码器预处理后的均衡训练样本对诊断模型参数进行更新优化。基于实例验证了所提方法的有效性。实验结果表明,所提方法可改善训练样本不平衡的不利影响,各训练集下,采用所提方法的变压器故障诊断结果准确率均保持在91%以上,且漏报率较低。     

一类负模量Kirchhoff - Carrier方程的解

利用变分方法和反证法研究了一类含有非线性项的Kirchhoff - Carrier方程,证明了当0<λ1时,该方程至少存在一对非平凡解,且当λ≥a λ₁时该方程不存在同号解.