Sudden Blocking of a Supercritical Open‐Channel Flow

This paper reports results of experiments in which a steadystate nonuniform supercritical openchannel flow was suddenly blocked by a rapidly falling gate at a downstream distance of about one hundred critical depths. This results in a hydraulic jump propagating upstream. Experimental data on the shape, height, and propagation speed of its leading front are given. It is shown that the parameters of the jump differ significantly from the values found using a quasistationary approach.     

缺口疲劳门槛值的实验研究

本文报告了对常用高强材料３０ＣｒＭｎＳｉＡ的双边Ｖ型缺口疲劳门槛值进行的实验测量。通过测试结果分析，证实了对不同缺口半径的试样（△Ｋ１／√Ｐ）ｔｈ基本一致的结论。     

超高效液相色谱-串联质谱法测定人参、黄芪中多种除草剂残留量

建立了人参和黄芪中55种除草剂残留量的超高效液相色谱-串联质谱检测方法.样品中残留的药物经乙腈提取,石墨化碳黑固相萃取柱净化,甲醇-二氯甲烷洗脱,最后采用电喷雾串联质谱在正离子多反应监测模式下进行测定.55种农药的检测限和定量限分别为0.4 ～20 μg/kg和2～100 μg/kg.在各自的浓度范围内,55种药剂的线...     

基于广义动态因子模型的中国出口周期分析与预测

研究出口周期的景气循环对于进一步扩大出口及推动整个国民经济的发展具有重要的意义.基于传统的先行指标体系和SW景气指数方法能够为出口周期的监测和预警提供参考,而近年来逐渐完善的广义动态因子模型基于频域分析方法,在处理高维数据方面比前两种方法更具有优势,同时该方法在拐点的探测方面也具有重要的作用.作者首先对三种指数构建方法进行了理论上的介绍;其次,分别运用三种方法构建了中国出口增长循环的一致及先行指数;最后,对三种方法在中国出口周期分析上的表现进行了比较与评价,得出了一些重要的结论.     

中美燃料油期货价格引导研究

本文利用ADF单整检验、EG协整检验、误差修正模型、引导关系检验等方法研究中美燃料油期货价格之间的互动关系,结果表明:我国燃料油期货在价格和价格收益方面均与国际燃料油市场存在明显的即时引导关系;国际燃料油期货市场上的价格变动对国内燃料油期货价格以及价格收益的变动具有单向的滞后引导作用;我国燃料油期货市场的价格和收益方面的信息对于国际市场几乎不产生影响,我国尚不具备制定价格的话语权。     

根值判别法的两个推广

讨论正项级数的根值判别法．若将判别极限lim↓n→∞ n√an更改为lim↓n→∞或lim↓n→∞^n√am^n＋i,则相应结果在一定条件下将比原判别方法更为精细,且应用范围也有所推广．     

Using a pseudo-functionally graded interlayer in order to improve the static and dynamic behavior of wind turbine blade T-bolt root joints

The large wind turbines blades with multi-ton composite structures are mostly connected to the peach-bearings flanges using T-bolt joints which induce shear and bearing stress fields around the cross bolts. The significant differences between the modulus of elasticity of metallic bolts and composite surrounding materials cause stress concentration around interfaced zones and, also, limit the load capacity of the joints. In the present research, a pseudo functionally graded material (PFGM) as an interlayer is used around the cross bolts to examine the reduction of the stress concentration. Some radial variation of the mechanical properties would be considered for this interlayer. The finite element method is used to analyze the structures. Loadings are applied to the center of the cross bolts analogous to the real cases. Both the static and dynamic loadings are studied. For the finite element of the functionally graded material interlayer, a multilayer alternative material with constant properties in each layer is used. The results show that using an isotropic single layer with an average modulus of elasticity and specific thickness decreases the stress concentration of the composite part up to 47%. The various property models for the interlayer also show that an appropriated model can decrease the stress concentration up to 55%. Dynamic transient analyses would be implemented over the joint structure and improved considering to the practical cases. Using the PFGM interlayer decreases the constant and variable parts of the stresses up to 55% and also causes significant increasing of the joint fatigue life.     

A one parameter method for the matrix inverse square root

This paper is motivated by the paper [3], where an iterative method for the computation of a matrix inverse square root was considered. We suggest a generalization of the method in [3]. We give some sufficient conditions for the convergence of this method, and its numerical stabillity property is investigated. Numerical examples showing that sometimes our generalization converges faster than the methods in [3] are presented.     

具有多重解的非线性Robin问题的奇摄动[英文]

本文利用边界层法，研究了具有多重解的非线性Robin问题εx″ f(t,x)x′ g(t,x)=0,0≤t≤1,x′(0,ε）-ax(0,ε)=A,x′(1,ε） bx(1,ε）=B其中ε为正的小参数。在适当的假设下，我们通过给出外部解展开式系数的一般表达式，得到了退化问题的边值为某方程的多重根时的渐近解，推广了有关结果。     

Root Systems and Length Functions

We introduce root systems for those imprimitive complex reflection groups which are generated by involutory reflections, and study the associated length functions. These have many properties in common with the usual length functions for finite Weyl groups.