基于桥梁动力响应的车-桥接触力识别方法

将桥梁划分为欧拉梁单元建立桥梁的振动方程,基于拉格拉日原理建立汽车的振动方程,根据接触点处的接触力将汽车和桥梁系统耦合在一起。求解汽车-桥梁系统耦合方程得到桥梁节点动力响应,由广义正交函数和模态叠加原理确定模态响应及其导数,用正则化方法得到稳定的识别结果。数值模拟结果表明,该方法用于识别车桥接触力是有效的、可行的。     

基于差分模型的无控制DEM差异探测方法

为了提高现有方法的性能，提出了基于差分模型的无控制数字高程模型（DEM）差异探测的新方法，并成功地用于普歪沟泥石流地区地表变形探测（该区变形面积超过50％）．该方法在LZD算法（最小高差法）的基础上引入差分模型，兼顾了观测值的数值及其相互关系的影响，显著提了高算法的差异探测性能．结果表明，新方法的匹配精度比目前代表性的采用肌估计的LZD算法（M-LZD）和采用最小平方中位数的LZD算法（LMSLZD）的精度高．     

仿紧集上新型抽象广义双拟变分不等式

笔者在本文应用文献[1]中得到的极大极小不等式研究了仿紧集上新型抽象广义双拟变分不等式解的存在性问题.     

BP神经网络在土工合成材料蠕变预测中的应用研究

通过对目前广泛应用于加筋土工程的土工合成材料-CE131土工网、SDL25土工格栅进行不同应力水平作用下的长期荷载蠕变试验，获得大量的实验数据。在此基础上，运用最小二乘和BP神经网络对其蠕变量进行预测。最小二乘原理是在曲线族中寻找一曲线去拟合实验数据，从得到的误差平方和σ=0．00116来看，其拟合精度较高。BP神经网络具有白适应学习和记忆能力，尤其是三层BP神经网络模型，所得预测值与实际值误差最大为0．91％，较最小二乘3．4％的误差改善了许多，该法为蠕变预测找到了一条新的途径。     

海港工程设计潮位计算方法

针对G um be l分布,考虑了连续样本及非连续样本两种情况,采用M on te-C arlo模拟分析技术,对海港工程设计潮位计算中的矩法(M OM)、最小二乘法(L-S)以及目前流行的线性矩法(L-M)进行了比较研究,同时采用沿海9个潮位站的资料进行了验证计算。结果表明,与M OM法和L-S法相比,L-M法具有最优的统计性能,建议为工程设计所采用;现有规范推荐的最小二乘法偏于安全,但对不连续系列或当总体分布参数Cv较小时,亦能提供较合理的设计成果。     

Existence of simultaneous route and departure choice dynamic user equilibrium

This paper is concerned with the existence of the simultaneous route-and-departure choice dynamic user equilibrium (SRDC-DUE) in continuous time, first formulated as an infinite-dimensional variational inequality in Friesz et al. (1993). In deriving our existence result, we employ the generalized Vickrey model (GVM) introduced in Han et al., 2013a, Han et al., 2013b to formulate the underlying network loading problem. As we explain, the GVM corresponds to a path delay operator that is provably strongly continuous on the Hilbert space of interest. Finally, we provide the desired SRDC-DUE existence result for general constraints relating path flows to a table of fixed trip volumes without invocation of a priori bounds on the path flows.     

Are there bubbles in the shipping freight market?

ABSTRACT

This paper addresses the reconsideration of price bubbles specific to the shipping freight market based on the method of the Generalized Supremum Augmented Dickey–Fuller (GSADF). This approach offers the opportunity to recognize multiple bubbles and set their corresponding original and final dates. Empirical results reveal that four bubbles existed in the shipping freight market between October 1988 and February 2018 in which freight deviated from fundamental values. Strong demand (especially in China), the supply capacity, crude oil prices and U.S. dollar fluctuations are potential explanations for the first three bubbles. The global financial crisis that burst in 2008 is the major factor results in the last bubble. Hence, we must distinguish the potential reasons of bubbles in different periods and take measures such as promoting economic multipolarization, strengthening the bargaining power of China, building an effective information transfer system, employing financial derivatives and accelerating the consolidation of the shipping industry to alleviate the negative influences on global seaborne trade.     

Scattering of surface water waves involving semi-infinite floating elastic plates on water of finite depth

Two problems of scattering of surface water waves involving a semi-infinite elastic plate and a pair of semi-infinite elastic plates,separated by a gap of finite width,floating horizontally on water of finite depth,are investigated in the present work for a two-dimensional time-harmonic case.Within the frame of linear water wave theory,the solutions of the two boundary value problems under consideration have been represented in the forms of eigenfunction expansions.Approximate values of the reflection and transmission coefficients are obtained by solving an over-determined system of linear algebraic equations in each problem.In both the problems,the method of least squares as well as the singular value decomposition have been employed and tables of numerical values of the reflection and transmission coefficients are presented for specific choices of the parameters for modelling the elastic plates.Our main aim is to check the energy balance relation in each problem which plays a very important role in the present approach of solutions of mixed boundary value problems involving Laplace equations.The main advantage of the present approach of solutions is that the results for the values of reflection and transmission coefficients obtained by using both the methods are found to satisfy the energy-balance relations associated with the respective scattering problems under consideration.The absolute values of the reflection and transmission coefficients are presented graphically against different values of the wave numbers.     

基于广义回归神经网络的磁流变减振器模型辨识

根据磁流变减振器的非线性特性,提出磁流变减振器广义回归神经网络(GRNN)模型辨识方法,利用台架试验获取的力学特性数据,建立磁流变减振器广义回归神经网络正、逆模型,并与反向传播神经网络(BPNN)模型进行比较.结果表明:通过合理选取网络变量并优化光滑因子,GRNN模型能准确预测磁流变减振器的阻尼力和控制电流,其正、逆模型辨识精度优于BPNN模型.此外,GRNN还具有结构简单、快速收敛等特点,为磁流变减振器的准确建模与控制提供了重要手段.     

运输速度技术对未来客运业发展的影响研究

以技术提升促速度提高为背景,研究运输速度对客运业的影响.首先,系统回顾了历史上航空运输、铁路运输和公路运输速度的进步,以及助推速度提高的技术支撑;其次,以运输速度丰富内涵为切入点,从运输速度可靠性和快速性两个维度分别探讨了未来客运市场的基本特征;第三,在未来不同运输方式提速的背景下,明确各运输方式在不同客运市场的功能定位,并分别构建不同出行方式的效用函数和乘客广义出行成本函数,进一步运用演化博弈理论和Logit分担率模型研究未来速度提升对不同客运市场交通结构的影响.研究结果表明：首先,影响乘客方式选择的主要因素是全过程“门到门”速度,全过程“门到门”出行时间包含在车时间和节点时间.其次,不同运输方式速度提升,换乘效率提高和节点时间压缩均可能影响不同客运市场的交通结构;在短距离客运市场,压缩端点时间对交通结构影响更为显著;在中长距离客运市场,提升运输速度可以显著改变交通结构.设计速度250 km/h的高速铁路与民航竞争的临界距离不到800 km,但高铁设计时速提高到350 km/h时临界点可望推至1 200 km.第 三,在城市内,运输速度的可靠性对于通勤通学客流影响显著.第四,科技是速度提升的重要支撑,但也应关注技术实现背后的经济性和市场购买力.第五,研究与速度相关产品的差异化定价是助推企业提供高质量出行产品的关键.