Effect of different atmospheres on dry friction behavior of steel sliding against brass at high speed

The atmosphere components have an influence on tribological behaviors of tribo-pairs. Through changing the atmosphere component, the effect of atmosphere component on the tribological behaviors of CrNiMo steel against brass at high sliding velocity was investigated. The wear test was carried out on a high-speed friction and wear test rig whose test atmosphere could be controlled. The tests were performed at four sliding velocities （30, 40, 50, 60 m/s）, one contact pressure （1.33 MPa） and two atmosphere components （N2 or O2）. The morphologies of the worn surfaces of various pins were observed with a scanning electron microscope. The chemical compositions of the surfaces and subsurfaces for steels were determined with an energy dispersion spectroscopy. The results showed that the wear rate of the steel pins were low all the time with the sliding velocity increasing in oxygen atmosphere, and that the wear rate of the steel pin in nitrogen atmosphere was higher than that of the steel pin in oxygen atmosphere. It was found that the thin and compact oxidation layer formed on the worn surface of the steel in oxygen atmosphere played a key role in wear resistance. However, the wear rate of the steel pin increased rapidly with the sliding velocity increasing in nitrogen atmosphere, which was attributed to the thick and loose surface layer formed on the worn surface of the steel.     

宽板坯结晶器流场和温度场数值模拟优化分析

以某钢厂宽板坯连铸结晶器为研究对象,通过FLUENT商业软件模拟结晶器内温度和速度场分布,证明原有水口存在上循环弱,热交换慢,保护渣熔化不均匀等缺点是铸坯出现表面纵裂纹的主要原因.针对原水口的缺点,设计出满足现场生产工艺条件的水口形状为扁形、侧孔倾角-15°、底部形状为凸底的新结晶器浸入式水口,并运用数值模拟手段对新水口形成的钢液流动形式进行了分析.结果表明,新水口各项参数均明显优于原有水口,现场实验证明新水口使用效果良好.     

带落角约束的再入机动弹头的变结构导引律

针对再入机动弹头垂直打击目标的要求,研究了具有末端落角约束的变结构导引律.该导引律包括俯冲平面内的制导方程和转弯平面内的制导方程,通过采用准滑动模态控制削弱抖振的影响.通过数学仿真,分析了四个制导参数对制导效果的影响,探讨了利用遗传算法离线优化制导参数的可行性,检验了最优制导参数的制导效果对不同初始状态偏差的敏感性.仿真结果表明,与最优导引律相比,变结构导引律具有较强的鲁棒性,在干扰影响下仍能保持较高的制导精度.     

灰色-马尔科夫链在年降水量预测中的应用

首先用三点滑动法优化原始数据,并在此基础上建立了灰色-马尔科夫链预测模型,然后利用湖北省恩施市1985年至2002年的年降水量历史资料,分别用此模型、无偏GM(1,1)及滑动无偏GM(1,1)模型预测了该市2003年至2008年的年降水量.结果表明;新模型预测精度明显提高,该模型应用于年降水量预测切实可行.最后,还结合预测数据给恩施市提供了政策建议.     

Improved hybrid position/force controller design of a flexible robot manipulator using a sliding observer

An improved hybrid position/force controller design of a flexible robot manipulator is presented using a sliding observer. The friction between the end effector and the environment is considered and compensated. For systematic reasons the controller is designed taking into consideration the rigid link subsystems and the flexible joints. The proposed control system satisfies the stability of the two subsystems and copes with the uncertainty of robot dynamics. A sliding observer is designed to estimate the time derivative of the torque applied as input to the rigid part of the robot. For the stability of the observer, it is assumed that the uncertainty of the observed system is bounded. A MRAC algorithm is used for the estimation of the friction forces at the contact point between the end effector and the environment. Finally simulation and experimental results are given, to demonstrate the effectiveness of the proposed controller.     

一种基于密度的数据流检测算法SWKLOF

总结目前数据流在线检测算法的优缺点,提出了一种新的数据流在线检测算法—SWKLOF。该算法采用滑动时间窗口对数据流进行封装,用k-距离进行剪枝,剔除大部分正常数据,对剩余疑似异常数据采用局部离群因子LOF(local outlier factor)进一步精确筛选。理论分析和实验结果表明该算法降低了时间复杂度,提高了检测准确性。     

水口大坝监控系统的测值疑点成因分析研究

对疑点测值进行快速、准确的物理成因分析,是水口水电站在线监控及反馈分析系统的关键,基于水口水电站工程监测项目繁多,信息量大,涉及的知识面广以及重力坝的自身工作特点,系统遵循突出重点,兼顾全面,以坝段为单元,以变形异常为重点,水平位移异常为核心,融汇渗流和应力应变,实时在线地分析测值疑点的物理成因。     

不确定系统的滑动模态最优控制

本提出了利用滑模渐近特性和滑模渐近到达条件设计变结构新思路,理论分析表明设计的ＶＳＣ系统有良好的动态特性。     

水口水电厂年内首末两场洪水的长期预报

根据流域气候特征及年内首末两场洪水的来水规律,挑选出与预报对象关系最密切的气象因子作为预报因子,首先研究趋势预报,然后应用逐步判别法筛选因子,最后建立预报模型。研究发现,前期的月平均降水、月平均气温,月平均北太平洋海温因子是影响水口流域首末两场洪水的主要气象因子。     

Φ40自由浮球式疏水阀工况分析

对自由浮球式疏水阀内浮球在开启过程中的受力情况进行了全面的分析,首次提出疏水阀开启疏水的两种不同方式,即滑动开启和滚动开启方式,并分别给出了两种不同开启方式所对应的压差合力和关闭力矩的计算公式,确定了保证此类疏水阀可靠工作的许用最高工作压力,可供此类疏水阀设计和开发参考.