3R02型减速器箱体振动特性的数值模拟分析

为研究3R02型减速器工作振动特性,利用ANSYS软件对减速器箱体进行有限元建模,并对其进行静力学计算和模态分析。结果表明:工作过程中最大变形出现在最大轴承孔与中间轴承孔的连接处。在箱体x方向,箱体的振动产生的位移从两侧端向最大轴承孔表现出由小到大的趋势。从第六阶模态开始,箱体不易产生共振;而在低频区,当外界的激励频率与其自然频率一致时,箱体会承受较大的应力。箱体在X、Z方向存在振动,在优化设计过程中应适当增加刚度和阻尼来抑制此类振动的影响。     

细长油缸孔在卧式床上的加工

液压缸的基本零件是油缸,对于细长油缸孔的加工应采用拉削加工的方法。刀杆在工作时不是悬伸的,而是两头有支撑,从而改变了其切削条件。切削刚度的加强,消除了振动,保证了加工精度,提高了生产率。     

椭圆半带滤波器及其在小波包谐波分析中的应用

小波包分解因为具有较高频谱分析的精度，在电力系统谐波检测中得到了广泛的应用．但其复杂的计算使它在实时的测量中受到了限制．现提出了将IIR椭圆半带滤波器应用于小波包谐波分析中的新方法，通过研究表明，该算法可以将复杂的计算减少到与快速傅立叶变换（FFT）同等数量级上．仿真和实验结果进一步表明了该算法的有效性．     

缸套激光淬火的网格化效应

研究了缸套材料激光淬火的网格化效应，分析了不同淬火道方向对材料副耐磨性的影响，提出了一种适用的表面硬化模型。     

高速铁路40m箱梁现浇碗扣式支架施工技术及承载力检算

文章结合南广高速铁路右线贵港特大桥的具体施工实例,从支架基底处理、碗扣式支架搭设、通车门洞设置方面详细介绍了高速铁路现浇箱梁施工方案,并通过支架承载力检算,验证了方案的可行性,为今后类似工程的施工提供参考。     

浅析华南快速三期春岗立交钢箱梁吊装施工

文章通过对华南快速三期春岗立交钢箱梁现场吊装施工进行分析和总结，特别是对临时支撑的稳定性和安全性进行了受力计算和分析，并结合实际施工过程提出了一些应注意的问题。     

桥梁钢箱梁顶推施工技术探索和构建

在我国基础交通设施建设的过程中,桥梁建设是其中的重点内容,也是整个交通设施的生命线。在道路桥梁施工中,顶推施工技术是重要的施工技术之一,在各类道路桥梁工程施工中具有重要的主体性地位。在开展桥梁钢箱梁顶推施工过程中,要严格遵照相关施工工艺标准和施工流程,并且科学、专业地进行施工指导,保障施工质量和施工安全。本文对于桥梁钢箱梁顶推施工技术的相关问题进行了分析与探索。     

Realizing stock market crashes: stochastic cusp catastrophe model of returns under time-varying volatility

This paper develops a two-step estimation methodology that allows us to apply catastrophe theory to stock market returns with time-varying volatility and to model stock market crashes. In the first step, we utilize high-frequency data to estimate daily realized volatility from returns. Then, we use stochastic cusp catastrophe theory on data normalized by the estimated volatility in the second step to study possible discontinuities in the markets. We support our methodology through simulations in which we discuss the importance of stochastic noise and volatility in a deterministic cusp catastrophe model. The methodology is empirically tested on nearly 27 years of US stock market returns covering several important recessions and crisis periods. While we find that the stock markets showed signs of bifurcation in the first half of the period, catastrophe theory was not able to confirm this behaviour in the second half. Translating the results, we find that the US stock market’s downturns were more likely to be driven by the endogenous market forces during the first half of the studied period, while during the second half of the period, exogenous forces seem to be driving the market’s instability. The results suggest that the proposed methodology provides an important shift in the application of catastrophe theory to stock markets.     

Risk-type density diagrams by crash type on two-lane rural roads

The research presented here aims to plot density diagrams per road crash risk type to identify all possible scenarios where driving is less than safe. The starting point was the prediction of injury crash rate on horizontal homogeneous segments of two-lane rural roads for three main injurious crash types (head-on/side collisions, rear-end crashes, and single-vehicle run-off-road crashes) as observed on the network. A careful analysis of the database shows that a wide variety of factors appear to be influenced or associated with the crash dynamic, as follows: the road scenario (combination of infrastructure and environmental conditions found at the site at the time of the crash), mean lane width, the horizontal curvature indicator (measurement of the curvature change rate), and mean speed. Crashes recorded from 2003 to 2010, of which 1597 were injurious, and 645 resulted only in damage to property, were analyzed on more than 3700?km of road network in Southern Italy. Generalized estimating equations with a negative binomial distribution were implemented. Risk-type density charts were plotted to thoroughly identify all possible combinations of existing explicative variables producing hazardous conditions on the road. The different shades in the diagrams represent different ranges of injurious crash rates: the white band shows low levels, while a black band shows high values. It is not possible to consider working on an explanatory variable to reduce hazardous conditions on the road network without also considering how this variation might affect the influence of the remaining explanatory variables on crash phenomena and, consequently, on the predictive model. The risk maps make it possible to keep under control in a simple and immediate approach the way each variable as a result of variations of a part or of all.     

怀远龙江特大桥深水高桩承台施工技术

黔桂铁路怀远龙江特大桥(8#～15#)主桥墩基础承台为深水高桩大体积混凝土承台施工,此项施工技术已在深水桥承台施工中多次使用。结合黔桂线的现场施工特点及工期紧迫的要求,固采用钢吊箱围堰进行设计施工,速度快,质量优,效益好。