A new analytical-numerical method for calculating interacting stresses of a multi-hole problem under both remote and arbitrary surface stresses

Based on the elementary solutions and new integral equations,a new analytical-numerical method is proposed to calculate the interacting stresses of multiple circular holes in an infinite elastic plate under both remote stresses and arbitrarily distributed stresses applied to the circular boundaries.The validity of this new analytical-numerical method is verified by the analytical solution of the bi-harmonic stress function method,the numerical solution of the finite element method,and the analytical-numerical solutions of the series expansion and Laurent series methods.Some numerical examples are presented to investigate the effects of the hole geometry parameters(radii and relative positions)and loading conditions(remote stresses and surface stresses)on the interacting tangential stresses and interacting stress concentration factors(SCFs).The results show that whether the interference effect is shielding(k<1)or amplifying(k>1)depends on the relative orientation of holes(α)and remote stresses(σ^∞x,σ^∞y).When the maximum principal stress is aligned with the connecting line of two-hole centers andσ^∞y<0.5σ^∞x,the plate containing two circular holes has greater stability than that containing one circular hole,and the smaller circular hole has greater stability than the bigger one.This new method not only has a simple formulation and high accuracy,but also has an advantage of wide applications over common analytical methods and analytical-numerical methods in calculating the interacting stresses of a multi-hole problem under both remote and arbitrary surface stresses.

基于原子范数最小化的通信感知一体化目标参数估计方法

为解决传统算法对信噪比和快拍数要求较高的问题,提出了一种基于原子范数最小化的通信感知一体化目标参数估计方法。首先,基于正交频分复用波形设计了通信感知一体化接收信号模型。在此基础上,挖掘接收信号在目标时延与多普勒在时频域的稀疏性,在快拍数有限情形下,利用原子范数最小化理论实现二维时频多普勒和时延参数联合估计。此外,利用奇异值分解提取接收信号的主要成分,设计了基于交替方向乘子法的快速求解算法,以降低算法的计算量。仿真结果表明:所提算法实现了通信感知一体化系统在有限快拍下的高估计精度,并显著提升了运算效率。

Prediction of Velocity and Deformation Fields During Multipass Plate Hot Rolling by Novel Mixed Analytical-Numerical Method

An integrated mathematical model is proposed to predict the velocity field and strain distribution during multi-pass plate hot rolling. This model is a part of the mixed analytical-numerical method （ANM） aiming at predic- tion of deformation variables, temperature and microstructure evolution for plate hot rolling. First a velocity field with undetermined coefficients is developed according to the principle of volume constancy and characteristics of metal flow during rolling, and then it is solved by minimizing the total energy consumption rate. Meanwhile a thermal model coupling with the plastic deformation is exploited through series function solution to determine temperature distribution and calculate the flow stress. After that, strain rate field is calculated through geometric equations and strain field is derived by means of difference method. This model is employed in simulation of an industrial seven pass plate hot rolling process. The velocity field result and strain field result are in good agreement with that from FEM simulation. Furthermore, the rolling force and temperature agree well with the measured ones. The compari- sons verify the validity of the presented method. The calculation of temperature, strain and strain rate are helpful in predicting microstructure. Above all, the greatest advantage of the presented method is the high efficiency, it only takes 12 s to simulate a seven-pass schedule, so it is more efficient than other numerical methods such as FEM.

可重构智能表面辅助的毫米波信道估计算法

针对可重构智能表面(RIS)辅助的毫米波通信中信道状态信息难以获取问题,该文给RIS的部分器件配备射频链,以分开估计基站(BS)/用户(UE)到RIS之间的信道。根据该结构,提出一种低复杂度的信道估计算法。该算法首先采用解耦原子范数最小化(ANM)方法将信道的离开角和到达角的2维角度估计问题转化为两个1维的角度估计的半正定规划(SDP)问题;其次,利用交替方向乘子算法(ADMM)对该SDP问题进行求解,采用动量梯度下降法对信道矩阵参数进行更新以避免矩阵求逆运算,并通过对迭代步长和信道矩阵参数的联合优化以获得更加精准的信道估计值;最后利用信号的2维角度和信道矩阵参数得到路径增益估计。仿真结果表明,该算法达到了优良的信道估计性能,且在确保信道估计性能的系统参数设置下,该算法的复杂度较低。

电力系统分析综合程序连续潮流算法的改进

连续潮流计算是电力系统静态电压稳定分析的基本工具,目前国内多数连续潮流程序仍存在计算可靠性不高和计算效率低等问题。对电力系统分析综合程序(PSASP)中的连续潮流程序在提高计算可靠性和计算效率等方面进行了改进,使之能够适应大型电力系统的电压稳定性分析。改进后的PSASP连续潮流算法包含基本的拟弧长和局部参数化方法以及渐近数值方法(asymptotic numerical method,ANM)。ANM实质是一种采用高阶泰勒展开进行预测的连续方法,是一种半解析计算方法。ANM计算步长能够根据解曲线的形状自适应控制,因而是一种快速的连续潮流计算方法。实际电力系统的计算表明,修改后的连续潮流算法在计算可靠性和计算效率方面相比原来的程序有了很大程度提高,能够满足大型电力系统工程计算的需要。所做的研究对其他连续潮流的计算软件也会有一定的借鉴作用。

潮流方程鞍结分岔点计算的块消去算法

潮流方程鞍结分岔点(saddle-node bifurcation point,SNBP)的计算是静态电压稳定分析中比较关键的问题。在电力系统中,Moore-Spence方程被常用来确定潮流方程的鞍结分岔点,其阶数约为一般潮流方程的2倍。采用在非线性分歧计算中常使用的块消去(block elimination,BE)算法来求解Moore-Spence方程。利用块消去算法,在Moore-Spence方程的每一步牛顿迭代过程中,只需求解潮流雅可比矩阵或其转置作为系数矩阵的线性方程组,可充分利用潮流雅可比矩阵的稀疏特点来提高计算效率。采用渐进数值方法(asymptotic numerical method,ANM)快速确定牛顿迭代的初值。国内几个电力系统的计算实例验证了该方法的有效性。

利用混合块消去算法的电压稳定负荷裕度灵敏度计算

电力系统中目前多采用潮流雅可比矩阵在鞍结分歧点(saddle-node bifurcation point,SNBP)零特征值对应的左特征向量计算负荷裕度对参数变化的灵敏度,存在零特征值左特征向量和负荷裕度高阶灵敏度不容易计算等难题。与传统方法不同,给出了一种直角坐标中通过递归求解系列线性方程组计算任意阶负荷裕度灵敏度的方法。线性方程组的右端向量通过双线性函数计算,采用W.Govaerts提出的数值向后稳定(backward stable)的混合块消去(mixed block elimination,BEM)算法求解线性方程组。在计算各阶灵敏度时,只需一次潮流雅可比矩阵三角分解。以实际电网为背景研究了网络参数、负荷变化、支路开断等对负荷裕度的影响。计算结果表明,当参数变化范围较大或系统非线性程度较强时,高阶灵敏度的计算精度要远高于1阶灵敏度,且不需要附加太多计算量。

高维潮流方程功率注入空间中最近鞍-结分歧点的计算

电力系统中一般采用临界点边界的法向量迭代计算潮流方程的局部最近鞍–结分歧点(closest saddle-node bifurcation point,CSNBP)。对于高维非线性系统来说,计算量将非常大。利用渐近数值方法(asymptotic numerical method,ANM)和确定鞍–结分歧点的扩张系统,给出了一种快速计算潮流方程CSNBP的系统化方法。采用步长自适应计算的ANM快速逼近指定发电、负荷变化方向对应的鞍–结分歧点,并利用扩张系统确定临界点边界的法向量。核心计算只需求解潮流雅可比矩阵或其转置作为系数矩阵的线性方程组,线性方程组右端向量中潮流方程的二阶导数项通过双线性函数方便确定。2 383节点系统和我国实际电网的计算验证了所提方法的有效性和可行性。

一测多评法结合面积归一化法测定西红花中西红花苷类成分

目的:采用一测多评法结合面积归一化法,对西红花药材中西红花总苷进行质量控制,解决HPLC法测定含量时对照品不易获得的问题。方法:以西红花苷-Ⅰ为内参物,建立西红花苷-Ⅰ对西红花苷-Ⅱ的相对校正因子,利用相对校正因子计算西红花苷-Ⅱ的含量,实现一测多评;并与中国药典采用的外标法测定的32批西红花中西红花苷-Ⅰ和苷-Ⅱ含量进行比较,以验证一测多评法的可行性。同时以西红花苷-Ⅰ为对照,面积归一化法检测西红花中总西红花苷的含量。结果:西红花苷-Ⅰ相对西红花苷-Ⅱ的相对校正因子重复性好,一测多评法测定的32批西红花中西红花苷-Ⅱ的含量范围为1.2%~8.2%,与外标法测定的结果基本一致。面积归一化法测定的总西红花苷含量范围为7.1%~28.7%,与UV法测定的总西红花苷含量无显著性差异。结论:一测多评法结合面积归一化法测定西红花苷含量,该方法准确可靠,简便可行,能更合理地反映西红花的内在质量,可用于西红花中西红花苷类成分的质量控制。