A two-stage algorithm for identification of nonlinear dynamic systems

This paper investigates the two-stage stepwise identification for a class of nonlinear dynamic systems that can be described by linear-in-the-parameters models, and the model has to be built from a very large pool of basis functions or model terms. The main objective is to improve the compactness of the model that is obtained by the forward stepwise methods, while retaining the computational efficiency. The proposed algorithm first generates an initial model using a forward stepwise procedure. The significance of each selected term is then reviewed at the second stage and all insignificant ones are replaced, resulting in an optimised compact model with significantly improved performance. The main contribution of this paper is that these two stages are performed within a well-defined regression context, leading to significantly reduced computational complexity. The efficiency of the algorithm is confirmed by the computational complexity analysis, and its effectiveness is demonstrated by the simulation results.     

一类非线性脉冲发展方程的最优反馈控制

本文考虑受控系统为Banach空间中一类G0紧半群的非线性脉冲积微分方程的最优反馈控制问题。首先证明容许控制对的存在性,进一步对Lagrange问题给出了一个新的存在性定理。     

根据波速计算多相土石地基压实度的理论模型

本文基于多相复合介质的波动传播特性，导出介质内纵、横波速的理论计算公式。通过对影响因素分析，建立了横波波速与土石复合介质的干密度之间的近似理论关系。在此基础上，推导出土石地基压实度的波速计算理论模型的近似表达式。最后进行了现场地基的波速测试和灌砂法测试，通过理论计算和灌砂法测试结果的对比分析，表明该近似模型是可行的，并且其在对非均匀土石复合地基的压实质量评价中优越于传统的密度法。     

浅析水利工程中混凝土检测试验及其质量控制措施

现阶段,混凝土技术在水利工程中的应用越来越广,而水利工程的建设质量关系着人民群众的生命财产安全,因此,混凝土的质量控制对水利工程整体质量的控制具有重要意义。从混凝土检测试验的角度出发,结合水利工程施工的实际,对水利工程中混凝土检测试验及其质量控制措施进行深入的研究。     

具有某种特性的向量优化问题的解的刻画

在有限维空间中,当目标函数凸下半连续时,向量优化问题一定有弱有效解,并且解集是紧的,但当目标函数非凸时,这不一定成立,文章讨论了把目标函数的凸性减弱之后,向量优化问题的解集是非空并且紧的,另外还得到一些等价的刻画。     

从Zygmund空间到Bloch-type空间的加权复合算子

令φ,u分别是复平面C上的单位开圆盘D中的解析自映射和解析函数.加权复合算子定义为（uCφ）（f）（z）=u（z）f（φ（z））,z∈D,f∈H（D）.主要讨论了从Zygmund空间到Bloch-type空间的加权复合算子的有界性和紧性.     

基于压实度保证率的砾石土压实度快速检测法优化

砾石土心墙料压实度指标是砾石土心墙大坝工程质量控制的一个关键指标,常借助核子密度仪进行快速检测。鉴于砾石土的非均质特性,常规方法利用最大干密度均值求取的压实度为近似值,当实际最大干密度大于最大干密度均值时,压实度计算值偏大,易引起误判,影响工程质量。提出了压实度保证率概念,通过压实度及压实度保证率双控指标,对常规方法进行优化,明确了优化方法的评定流程及判定准则。并结合两河口水电站工程实例,论证了常规方法仅为优化方法的一种特殊表现形式。通过两河口水电站工程2019年3月份实测数据对比分析发现：采用常规方法检测的压实度均一次检验合格,而采用优化方法检测时,存在个别不合格点,需进一步复测。优化方法较常规方法更为严格,提高了工程安全裕度,保障了工程质量。     

软土地区旧桩拔除技术和新建桩基础调整方案及施工措施

结合天津南开区某地块定向经济适用房项目,介绍其在基础施工中遇到旧预制方桩时,采用全套管高压喷气、射水振动沉管施工工艺清孔拔桩,并对该工艺进行分析得出:该拔桩施工工艺适用于软土地区旧桩拔除项目;并针对旧桩孔无法回填压实、部分新建桩基础与拔除旧桩孔距离较近等原因导致钻孔倾斜、串孔等问题,提出远离旧桩位置或调整至旧桩桩心位置等方法调整桩位,并采用加大桩径、增设承台等调整方案承担因调整桩位而产生的上部偏心荷载;采用拌和白灰、分层压实、回填静置等措施提高回填土的密实度,采用保证垂直度和调节泥浆配合比等措施,以改善不良施工条件,得出适当增加混凝土充盈系数保证成桩质量等施工经验,为后续类似工程提供借鉴。     

改进的粒子群模糊聚类算法

针对传统的模糊C-均值聚类算法对初始聚类中心较敏感、易陷入局部最优的缺点,将粒子群优化算法和FCM算法相结合,提出一种改进的模糊聚类算法。该算法利用粒子群算法的全局搜索能力代替FCM算法寻找初始聚类中心,使其跳出局部最优,实现模糊聚类。主要从反映数据集分类的类内紧致性程度和类间分离性程度的角度考虑,重新设计适应度函数。实验结果表明,提出的算法在聚类正确率和有效性指标上有更好的效果。     

A unique property of single-link distance and its application in data clustering

We prove a unique property of single-link distance, based on which an algorithm is designed for data clustering. The property states that a single-link cluster is a subset with inter-subset distance greater than intra-subset distance, and vice versa. Among the major linkages (single, complete, average, centroid, median, and Ward's), only single-link distance has this property. Based on this property we introduce monotonic sequences of iclusters (i.e., single-link clusters) to model the phenomenon that a natural cluster has a dense kernel and the density decreases as we move from the kernel to the boundary. A monotonic sequence of iclusters is a sequence of nested iclusters such that an icluster in the sequence is a dominant child (in terms of size) of the icluster before it. Our data clustering algorithm is monotonic sequence based. We classify a dataset of one monotonic sequence into to two classes by splitting the sequence into two parts: the kernel part and the surrounding part. For a data set of multiple monotonic sequences, each leaf monotonic sequence represents the kernel of a class, which then “grows” by absorbing nearby non-kernel points. This algorithm, proved by experiments, compares favorable in effectiveness to other clustering algorithms.