An improved cuckoo search algorithm and its application in vibration fault diagnosis for a hydroelectric generating unit

This article presents an improved cuckoo search (ICS) algorithm based on the parametric adaptation mechanism and non-uniform mutation. In the ICS algorithm, the biased random walk operator is modified to take advantage of the neighbourhood information of the current solution, and then the control parameters of step size, discovery probability and scaling factor are directly integrated into the optimized problems. Meanwhile, the non-uniform mutation operation is used to adaptively tune the search step of the current optimal solution. To evaluate the feasibility and efficiency of the presented algorithm, three groups of benchmark test functions are employed to perform the validation analysis. Subsequently, to diagnose the vibration fault of a hydroelectric generating unit, a combinational model is built, which combines ICS with a back-propagation neural network (ICSBP). The experimental results indicate that ICS is competitive on the optimization problems, and the ICSBP approach can effectively improve the accuracy of vibration fault diagnosis for a hydroelectric generating unit.     

粗化床面非均匀沙推移质运动扩散特性研究

对泥沙颗粒运动规律的把握是准确估算推移质输沙率的基础。本文开展了粗化床面条件下的水槽试验，分析了非均匀沙颗粒的均方位移和速度自相关系数变化，并与已有均匀沙试验进行了对比。结果表明，粗化床面存在着由单个或多个粗颗粒组成的粗化结构体，形成比平整床面更复杂的底部边界，粗化结构体对泥沙颗粒运动造成较大影响，颗粒在运动过程中与水流动量交换强度大，泥沙颗粒运动与均匀沙试验“类弹道扩散”存在一定差异；受床面结构影响，部分颗粒表现出较强的横向运动，颗粒的横向扩散特性与流向扩散特性类似。与均匀沙平整床面不同，粗化床面上颗粒运动可能会相应改变床面结构，从而改变水流底部边界条件，进而对泥沙颗粒运动造成影响，泥沙颗粒运动存在较明显的记忆效应和反常扩散现象。     

Recursive least squares estimation methods for a class of nonlinear systems based on non-uniform sampling

Many dynamic processes in practice have nonlinear characteristics and must be described by using nonlinear models. It remains to be a challenging problem to build the models of such nonlinear systems and to estimate their parameters. This article studies the parameter estimation problem for a class of Hammerstein-Wiener nonlinear systems based on non-uniform sampling. By means of the auxiliary model identification idea, an auxiliary model-based recursive least squares algorithm is derived for the systems. In order to enhance the computational efficiency, an auxiliary model-based hierarchical least squares algorithm is proposed by utilizing the hierarchical identification principle. The simulation results confirm the effectiveness of the proposed algorithms.     

Stress distribution in thick-walled cylinder due to non-uniform radial pressure on the example of reinforcement corrosion in concrete

This paper presents an analytical solution to the non-uniform pressure on thick-walled cylinder. The formulation is based on the linear elasticity theory (plain strain) and stress function method. As an example, the proposed solution is used to model the stress distribution due to non-uniform steel reinforcement corrosion in concrete. The model is formulated considering different scenarios of corrosion pressure distribution. It is validated against the finite element model for different cases of non-uniform pressure distributions. The results show that the corrosion-induced cracks are likely to start just beyond the anodic zone. This is confirmed by the experimental tests on concrete cylinder exposed to non-uniform accelerated corrosion of steel reinforcement. The model can be effectively used to calculate the distribution of corrosion-induced stresses in concrete.     

采动敏感型底板巷道支护技术研究

某煤矿底板巷道受上覆煤层开采影响时,变形失稳严重,支护困难。在矿区地应力场、围岩力学性能测试的基础上,对巷道失稳状况进行了调查,实测了巷道围岩变形的基本规律,分析了巷道失稳的机制,提出了基于采动敏感型巷道的控制围岩稳定的支护机理;同时针对工程实践,提出高强度预应力锚杆为基础,巷道关键部位加强支护及二次注浆加固技术方案,并在现场进行了工业性试验。实践表明,提出的支护对策可有效的控制巷道围岩稳定,具有广阔的推广应用前景。     

阳泉矿区部分建（构）筑物破坏的原因分析和对策

本文介绍了阳泉矿区部分建(构)筑物由于受地基不均匀沉降、湿陷、潜蚀、管涌、地面塌陷等影响,导致建(构)筑物破坏的情况,在分析破坏原因的基础上,提出了相应的对策。     

结构跨度对非一致输入下大跨空间网格结构地震响应的影响

以非一致输入法对不同跨度的大跨空间网格结构进行竖向和水平地震计算,综合分析不同跨度下杆件内力、危险杆件的数量以及不同非一致输入方法引起的结构响应差异,最终分别推断出在竖向与水平地震作用下可以不考虑空间相关性的结构最小跨度.     

铁摩辛柯梁弯曲问题的精细积分法

Timoshenko梁弯曲问题的哈密顿对偶方程,是关于梁截面上的广义力和广义位移的一阶常微分方程组,可与现代控制理论的一些问题相比拟。由于系统矩阵具有辛矩阵的特性,数值计算具有良好的稳定性,可将Timoshenko梁弯曲问题的两端边值问题转化成初值问题,用精细积分法求得高精度的数值解。算例计算结果表明,本方法具有较高的精度和适用性,并可方便地用于变截面梁的计算。     

矩形变截面单跨梁的内力计算公式和图表

本文推导了矩形变截面单跨梁的内力计算公式,并制成图表,便于结构计算中应用。     

地基沉降引起墙体开裂的成因和预防措施

分析了由于地基不均匀沉降引起墙体开裂的原因，并分别从勘查、设计和施工三方面提出了一些预防不均匀沉降的措施，介绍了墙体开裂的防治措施，以保证建筑物的结构质量。