High-order approximations of three-phase-lag heat conduction model: Some qualitative results

This article deals with some high-order approximations of the three-phase-lag heat transfer model aiming, at first, to identify the restrictions that make them well-posed consistence. Consequently, a first result about the uniqueness and continuous dependence of the solutions with respect to the given initial data and to the supply term is established for the related initial boundary value problems. Subsequently, to provide a more comprehensive analysis of the model, some further spatial decay results are established, this time conveniently relaxing the hypotheses about the delay times and the thermal conductivities. More precisely, a theorem of influence domain is proved for the wave propagating models and an exponential decaying estimate of Saint-Venant type is established for the diffusive models.     

Eight-node conforming straight-side quadrilateral element with high-order completeness (QH8-C1)

A new eight-node conforming quadrilateral element with high-order completeness, denoted as QH8-C1, is proposed in this article. First, expressions for the interpolation displacement function satisfying the requirements for high-order completeness in the global coordinate system are constructed. Second, the displacement function expression in global coordinates is transformed into isoparametric coordinates, and the relationships between the two series of coefficients for the two kinds of displacement function expressions are found. Third, the displacement function expression is modified to satisfy the requirements of nodal freedom and interelement boundary continuity. The key to the new element construction is the derivation of the linear relationship expressions among 12 coefficients of element displacement interpolation polynomials in the global and isoparametric coordinate systems. As a result, the relationship between quadratic completeness and interelement continuity is explicitly given, and a proof of the completeness and the continuity was conducted to theoretically guarantee the validity of the derivation results. Furthermore, in order to verify the correctness of the theoretical work, nine numerical examples were performed. The computation results from these examples demonstrate that QH8-C1 exhibited excellent performance, including high simulation accuracy, fast convergence, insensitivity to mesh distortion, and monotonic convergence.     

立式退火炉张力设定模型及应用

带钢在立式退火炉内发生瓢曲、跑偏的临界张力与炉辊凸度、带钢规格都存在一定关系，但缺乏合理的定量分析方法，难以科学制定不同规格、不同钢种带钢的炉内单位张力。通过引入瓢曲风险因子BRI，可以定量地分析炉内板带瓢曲风险，从而确定冷硬板带炉内张力设定上限，即板带发生热瓢曲的临界张力σC，为连退炉加热段和冷却段的张力控制提供依据。采用该方法对连退炉加热、冷却区的张力进行了优化，应用结果表明，优化后的张力值与实测值更加吻合。     

单层球面网壳选型优化设计

采用改进的自适应遗传算法来解决单层球面网壳结构构件截面优化问题，并采用VC＋＋语言编写了相应的自适应遗传算法和有限元计算程序，可以实现单层球面网壳结构的自动优化设计。设计了不同类型、跨度和矢跨比的网壳优化算例；并通过对按照现行相关规范优化设计的单层球面网壳和符合现行相关规范要求但未经优化设计的单层球面网壳用ANSYS软件进行考虑几何非线性的屈曲分析，分别确定其屈曲荷载与设计荷载之比，以比较它们的受力和安全性能。结果表明采用自适应遗传算法进行离散变量的网壳结构截面优化设计容易收敛，优化效果良好。如果综合考虑经济和安全因素，设计网壳时，其矢跨比取1／6～1／5比较合适。     

桩–土–斜拉桥动力相互作用体系振动反应特性试验研究

大跨斜拉桥结构自振频率和阻尼较低,其地震响应可能受桩基础和场地土特性的影响较大,然而目前为止,由于试验条件和技术所限,尚缺乏相关的包括桩基础、场地土和上部结构在内的全模型振动台试验研究。以一座试设计的主跨1400 m超大跨斜拉桥为原型,设计并完成了一座几何相似比为1/70,且包括群桩、人工土和上部结构在内的试验模型,采用多点振动台试验技术,研究了不同加速度峰值和不同频率成分地震作用下桩–土–斜拉桥动力相互作用体系的振动反应特性。试验结果表明:桩–土–结构相互作用对斜拉桥地震响应产生影响,其影响程度与地震输入频谱特性密切相关;在纵向一致激励下,桩–土–结构相互作用受地震动加速度峰值的影响不明显,在横向一致激励下,桩–土–结构相互作用随地震动加速度峰值的增大而减小;主塔高阶振型对其地震响应的贡献明显;地震输入频谱特性影响桩–土–斜拉桥动力相互作用体系的地震响应,特别是在具有丰富长周期成分的Mexico City波作用下主梁竖向地震响应显著增大。     

基于分数阶Fourier变换累积量的目标检测算法

传统的信号检测和噪声分离方法只限于在时域或是频域进行,如果信号和背景噪声有很强的时频耦合,就难以在时频域得到好的检测结果。对此提出了分数阶Fourier变换累积量算法,该算法具有解除时频耦合和抑制噪声的特性,当选择合适的旋转角度使之与处理信号相匹配,就可以在分数阶Fourier域获得较好的检测结果。仿真结果表明,分数阶Fourier累积量算法的检测性能优于分数阶Fourier变换和4阶累积量算法,展现了分数阶Fourier变换累积量算法有优越的信号处理性能。     

苏家浩长江大桥拱箱缆索吊装方案设计与应用

该文根据重庆苏家浩长江大桥拱箱缆索吊装方案的设计及应用,为了优化施工时拱箱吊装的扣挂方式,调整拱上建筑的施工顺序,通过先施工墩上排架,利用墩上排架满足拱箱的扣挂要求,完成拱箱吊装后再施工拱上建筑物。通过该文可为类似工程的缆索吊装设计及施工提供参考。     

基于高阶累积量短波通信电台细微特征提取与分析

首先介绍了高阶统计量基本概念,分析了通信电台的高阶统计量特征,并对几种常见短波通信信号的高阶矩和高阶累积量进行了计算分析;仿真结果表明：高阶统计量可以作为一类有效的特征参数,适用于短波通信信号特征识别研究.     

Thermal buckling and postbuckling analysis of piezoelectric FGM beams based on high-order shear deformation theory

This article deals with the thermal buckling and postbuckling of functionally graded material (FGM) beams with surface-bonded piezoelectric actuators based on physical neutral surface concept and high-order shear deformation theory including von Kármán strain–displacement relationships. The beams are exposed to a uniform temperature field and electric field, the material properties of FGM layers are temperature-dependent and vary in the thickness direction. The approximate solutions of piezoelectric FGM beams for thermal buckling and postbuckling are obtained by a two-step perturbation method, meanwhile, the analytical solutions of Timoshenko beam model and Euler beam model are also presented. The validity of the present work can be confirmed by comparisons with previous results. The effects of the applied actuator voltage, beam geometry as well as volume fraction index of FGM beam on the critical buckling temperature, and postbuckling load–deflection relationships are investigated.