快速划线仪的制作和应用

根据斜截正圆柱(锥)截面形状为椭圆,制作一种零件结构简单、加工容易、组装快捷、携带方便的快速划线仪。该划线仪具有三个特点,即一、容易操作;二、适用范围广,配备规格齐全的模板,可在多种规格正圆柱(锥)形状材料表面由正截至斜截45°范围内任何角度划截面线;三、效率高。     

Equations for heating and cooling of bodies of various shapes

Equations for predicting temperatures in solids of various shapes undergoing heating or cooling are presented. The derived equations are compared with the available numerical values obtained for plates, cylinders and spheres. The centre and surface temperatures and the heat transferred can be described with a maximum deviation of −4.3/3.9%, even though the temperature profiles in these bodies are described with a maximum deviation of −6.8/7.6%.     

Two- and three-dimensional equilibrium morphology of a misfitting particle and the Gibbs–Thomson effect

The equilibrium shapes of misfitting precipitates in elastically anisotropic systems are obtained in both two and three dimensions, and the corresponding Gibbs–Thomson equation is derived as a function of the characteristic ratio between elastic and interfacial energies, L′. The effect of elastic inhomogeneity is investigated systematically. For soft or moderately hard particles, the stable equilibrium shape bifurcates from a fourfold symmetric shape to a twofold symmetric one in 2D and from a cubic symmetric shape to a plate-like one in 3D. For a very hard particle, the shape bifurcation is not observed in 2D for the range of L′ investigated, but both plate-like and rod-like shapes are found in 3D. The computed Gibbs–Thomson equation is well approximated by a piecewise linear function of L′. Predictions are made for coarsening of many-particle systems based on an established mean-field theory. The results predict that the elastic stress has no effect on coarsening kinetics where most particles are highly symmetric (fourfold in 2D and cubic in 3D), and the exponent remains 1/3 but the rate constant increases if stress is sufficient to induce symmetry-breaking bifurcation on most particles.     

采用分析边界形状法对激振器骨架进行形状优化

采用分析边界形状法来描述激振器骨架的边界形状,以骨架一阶固有频率满足期望值为目标建立数学模型,对骨架进行了形状优化。结果表明此法实际可行,具有较高的效率,避免了结构大变形时网格产生畸变;同时采用优化后骨架的激振器,不仅拓宽了使用频宽的上限,而且减小了对被测试件附加质量的影响。     

Probabilistic stability of uncertain composite plates and stochastic irregularity in their buckling mode shapes: A semi-analytical non-intrusive approach

In this study, the mechanical properties of the composite plate were considered Gaussian random fields and their effects on the buckling load and corresponding mode shapes were studied by developing a semi-analytical non-intrusive approach. The random fields were decomposed by the Karhunen−Loève method. The strains were defined based on the assumptions of the first-order and higher-order shear-deformation theories. Stochastic equations of motion were extracted using Euler–Lagrange equations. The probabilistic response space was obtained by employing the non-intrusive polynomial chaos method. Finally, the effect of spatially varying stochastic properties on the critical load of the plate and the irregularity of buckling mode shapes and their sequences were studied for the first time. Our findings showed that different shear deformation plate theories could significantly influence the reliability of thicker plates under compressive loading. It is suggested that a linear relationship exists between the mechanical properties’ variation coefficient and critical loads’ variation coefficient. Also, in modeling the plate properties as random fields, a significant stochastic irregularity is obtained in buckling mode shapes, which is crucial in practical applications.     

基于先验信息的供水管网阻力系数识别

供水管网阻力系数识别是指通过调整管网水力模型中管道阻力系数,使模型计算值与监测值相符的过程。由于实际中监测点数量有限,管网阻力系数识别为欠定的优化问题。现行方法通常采用管道分组这一参数化方法将欠定问题转换为超定,应用遗传算法或其它随机搜索算法求解。提出了基于先验信息的供水管网阻力系数识别算法,所提出算法根据管道管材、管龄等先验信息对管道阻力系数进行估计,并将估计值作为伪观测值引入目标函数将欠定优化问题转换为超定,采用高斯-牛顿算法进行求解。与现有方法相比,所提出算法避免了管道分组不唯一的问题;再者,推导了供水管网阻力系数雅克比矩阵解析式用于搜索向量构造,提高了参数识别计算效率。采用小型管网阐明了雅克比矩阵计算及搜索向量构造,利用大型管网验证了算法的实用性。     

短码元长度长波PSK 信号的一种混沌检测方法

为解决对潜通信中部分带宽相移键控信号(phase shift keying,PSK)无法被检测的问题,从混沌振子检测 PSK 信号的原理出发,提出一种短码元长度PSK 信号的混沌检测方法。利用PSK 信号载波间相关系数的特点提取 先验相位信息,结合固有载波信息生成待测序列,构造新的判别依据进行相位判别,并以8PSK 信号为例进行仿真 实验。仿真实验表明：该方法能够检测该类信号且保持较传统的相干检测、非相干检测更优良的检测性能,并降低 了传统的混沌检测方法的运算量。     

联合低秩与稀疏先验的高光谱图像压缩感知重建

本文建立了一种新的高光谱图像压缩感知重建模型,编码端采用块对角的Noiselet测量矩阵对每一谱带进行独立采样,解码端首先建立高光谱图像低秩稀疏表示模型,分解为低秩与稀疏成分,并对低秩成分在空间维进行稀疏分解,进而构建联合谱间低秩性先验与谱内空间稀疏性先验的凸优化重建模型,并提出模型求解的增广拉格朗日乘子迭代算法,通过引入辅助变量与线性化技巧,使得每一子问题均存在解析解,降低了模型求解的复杂度。实验结果验证了本文模型及其算法的有效性。     

FGH97合金的显微组织

结合FGH97合金的制备工艺,采用显微组织观察等手段,对合金的显微组织进行了分析研究与讨论,结果表明,直接热等静压成形的FGH97合金的晶粒组织均匀,晶粒度为6～7级;合金中的Hf元素对减少合金中的原始颗粒边界(PPB)有着显著作用,同时,Hf元素会进入γ'相和碳化物,提高γ'相的强度和碳化物的稳定性;合金的显微组织具有弯晶特点,这对合金的塑性和韧性非常重要.     

基于Bayes Monte Carlo方法的复杂系统平均剩余寿命评估方法

讨论了复杂系统平均剩余寿命评估的问题,首先基于先验信息和试验样本数据利用Bayes Monte Carlo方法给出了单个设备可靠性参数,然后结合系统的组成结构,求出系统可靠度函数,接着根据可靠度和平均剩余寿命之间的关系,建立复杂系统平均剩余寿命评估模型并给出具体的评估算法,最后,通过实例验证,表明本文的方法较为精确,能够满足工程的实际需求。