水流对浮体作用的SPH方法模拟

水流与浮体相互作用时,运动情况十分复杂,目前很难准确有效地模拟。而SPH作为一种纯拉格朗日方法,无需构建网格,用核函数近似粒子进行离散,能较好地解决一些自由面大变形问题。文章利用SPH法对溃坝时引起的高速水流冲击浮体以及水体晃动时破损浮体的运动过程进行模拟。模拟结果表明,SPH法能有效地进行水流对浮体作用的研究。     

面向目标跟踪的传感器调度方法

针对传感器网络对目标的跟踪问题,提出一种传感器优化调度方法。该方法以传感器使用成本和允许激活的最大传感器数量为约束条件,把最小化目标位置误差作为优化目标,运用二进制凸规划技术对优化调度问题进行建模,采取逼近算法迭代求解规划模型。蒙特卡罗实验表明,对于节点数目小于70的传感器网络,优化调度方案可以获得高精度的目标跟踪结果。     

Network-based real option models

Building on earlier work to incorporate real option methodologies into network modeling, two models are proposed. The first is the network option design problem, which maximizes the expanded net present value of a network investment as a function of network design variables with the option to defer the committed design investment. The problem is shown to be a generalized version of the network design problem and the multi-period network design problem. A heuristic based on radial basis functions is used to solve the problem for continuous link expansion with congestion effects. The second model is a link investment deferral option set, which decomposes the network investment deferral option into individual, interacting link or project investments. This model is a project selection problem under uncertainty, where each link or project can be deferred such that the expanded net present value is maximized. The option is defined in such a way that a lower bound can be solved using an exact method based on multi-option least squares Monte Carlo simulation. Numerical tests are conducted with the classical Sioux Falls network and compared to earlier published results.     

Walking frequency, cars, dogs, and the built environment

To explain walking propensity or frequency, empirical studies have generally used two sets of explanatory variables, namely, socio-demographic variables and built environment variables. They have generally shown that both socio-demographic characteristics and built environment characteristics are associated with walking propensity. We examine the traditional walkability variables that encompass density, mix of uses, and network connectivity in New Jersey, using a statewide sample including an oversample of Jersey City. We estimate a two-stage least squares model using a conditional mixed process that combines an ordered probit model of walking frequency in the second stage based on a truncated regression of car ownership in the first stage. Our results show that built environment variables have some small effects, mainly from better network connectivity associated with increased walking frequency. One of our key findings is that built environment features also work indirectly via how they influence car ownership. In general, we find sufficient evidence that suggests fewer cars are owned in areas with more walkable built environment features. The other key variable that we control for is whether a household owns a dog. This also proved to be strongly associated with walking suggesting that dog ownership is a necessary control variable to understand the frequency of walking.     

杂交边界点法在沥青路面裂纹分析中的应用

杂交边界点法在积分和插值时都不需要网格,它是将移动最小二乘近似与修正位移变分原理结合起来,不但不需要划分网格,而且具有边界点法降维和高精度的优点。应用杂交边界点法对沥青路面表面裂纹扩展中强度应力因子变化规律和裂纹扩展路径进行研究,并对面层、基层设计参数对裂纹扩展影响规律进行分析,探讨沥青路面的裂纹扩展机理,具有一定的工程实用价值。     

基于LLE和LS_SVM的胃粘膜肿瘤细胞图像分类

胃粘膜肿瘤细胞图像的复杂性,组织器官形状的不规则性以及不同细胞的差异性,使得采用一般的线性分类方法对其进行分类很困难,结合局部线性嵌入（LLE）在处理非线性数据及最小二乘支持向量机（LS_SVM）在处理小样本、高维数及泛化问题方面的优势,文章提出一种基于LLE＋LS_SVM的胃粘膜肿瘤细胞图像分类方法,并采用LS_SVM的线性拟合误差来判断实验效果,最后比较本文方法与其他分类方法的优越性。实验结果表明,该方法在分类准确率和运行时间方面都有很大的优势。     

最小一乘法与最小二乘法的差异及其实证分析

从算术平均数分析入手,探讨了算术平均数与中位数的内涵,给出了用最小一乘法估计两变数线性回归模型中的参数的计算方法。论述了最小一乘法与最小二乘法的历史及其在解的多重性、突出点对回归线影响等方面的差异。     

桥梁动位移测试的数字处理方法研究

提出了采用MEMS加速度传感器进行动位移测试整体算法框架,即对测量的加速度信号进行板上软件滤波和积分处理进而得到桥梁的动位移.设计了各环节的算法并分析其性能,进行了实际测试的对比研究,成功地处理了天津汉沽蓟运桥现场试验数据.研究表明:采用该传感器进行桥梁动位移测试稳定性好,可靠性高.该研究时桥梁动态监测工作有重要的实用...     

基于压电薄膜的车辆动态称重系统数据采集及处理

介绍了基于压电薄膜的车辆动态称重系统数据采集前端的信号调理电路,针对传感器信号进行了处理及分析,着重介绍数据滤波以及系统试验方案,并给出了整个系统的程序流程图。     

基于二次响应面的震区边坡稳定性可靠度分析

本文在考虑边坡岩体参数非确定的基础上,基于二次响应面的边坡稳定可靠度分析方法,采用快速拉格朗日方法建立了震区岩质边坡稳定性可靠指标计算模型。结合湖南省对口支援四川理县灾后重建项目——理县至小金公路（理县段）路堑边坡,开展了震区边坡稳定性可靠度分析,计算结果表明：二次响应面计算次数远远少于传统蒙特卡洛方法,计算结果满足精度要求;通过对依托工程边坡动力数值模拟的可靠度分析表明,采用二次响应面法计算的可靠度指标Pf=6.861%,采用传统蒙特卡洛方法计算的可靠度指标Pf=5.117×10-2,计算精度较好;最大剪应变增量出现在坡体表面坡腰处,故选择该坡腰处作为边坡安全的控制点,其可靠度最小值为3.1左右,时间出现在16.5 s,可靠度满足设计要求,表明该处边坡整体稳定性较好。