交流电量采集技术在LF炉的应用

介绍交流电量采集系统的设计,及其在LF精炼炉中的应用.     

Experimental study on temperature stress calculation and temperature control optimization of concrete based on early age parameters

Temperature control curve is the key to achieving temperature control and crack prevention of high concrete dam during construction,and its rationality depends on the accurate measurement of temperature stress.With the simulation testing machine for the temperature stress,in the present study,we carried out the deformation process tests of concrete under three temperature curves：convex,straight and concave.Besides,we not only measured the early-age elastic modulus,creep parameters and stress process,but also proposed the preferred type.The results show that at early age,higher temperature always leads to greater elastic modulus and smaller creep.However,the traditional indoor experiments have underestimated the elastic modulus and creep development at early age,which makes the calculated value of temperature stress too small,thus increasing the cracking risk.In this study,the stress values of the three curves calculated based on the strain and early-age parameters are in good agreement with the temperature stress measured by the temperature stress testing machine,which verifies the method accuracy.When the temperature changes along the concave curve,the law of stress development is in consistent with that of strength.Under this condition,the stress fluctuation is small and the crack prevention safety of the concave type is higher,so the concave type is better.The test results provide a reliable basis and support for temperature control curve design and optimization of concrete dams.     

基于不同线路条件下的车辆动力学性能分析

随着我国在既有线上的线路改造和载运量的不断增加,对线路参数的设计要求也随之提高。应用动力学方法建立车辆-轨道系统动力学模型,研究不同曲线半径和线路激励对车辆动力学性能的影响。研究结果表明：增加曲线半径有利于增加车辆曲线通过安全性,车辆经过曲线线路连接处时脱轨概率变大,驶入曲线时的脱轨系数明显高于驶出曲线,重点考虑曲线线路连接位置处的车辆通过速度以及车辆运行状态;适当增加曲线半径可以减少轮轨间磨耗,有效降低磨耗速度;轨道激励变化对车辆临界速度的影响较大,应根据实际运行工况模拟得出最佳临界速度范围。     

Influence of Structural Parameters of Turbocharger Floating Bearing on Its Dynamic Characteristic Coefficients

The structure parameters in an actual industrial production have a great influence on the coefficient of supercharger floating bearing dynamic characteristics,but there has been little systematic study so far. In this paper, the influence of structural parameters of the turbocharger floating bearing on its dynamic characteristic coefficientsis systematically investigated based on the theories of hydrodynamic lubrication and tribology. The influence of clearance ratio on eccentricity and the influence of internal to external radius ratios, and Sommerfeld number were analyzed.A new formula of responding characteristics of the oil film force caused by the displacement or velocity disturbance was deduced near an equilibrium in the steady state. Applying the newly developed formula, the dynamic characteristic was studied for floating bearings. Regularity for change of oil film stiffness and damping was analyzed with the structural parameters of floating bearing such as radius ratios and eccentricity.It has been found that the clearance ratio increases with eccentricity when the radius ratio is unchanged.The eccentricity decreases with the internal to external radius ratio of floating rings when the clearance ratio is constant.The absolute value of total principal stiffness and total main damping decrease with the clearance ratio and radius ratio of floating rings when the total cross damping is stable. The results and findings in this paper can contribute to nonlinear dynamics designs of turbocharger rotor-bearing systems.     

Analysis on the gear-shifting schedule of hydraulic automatic transmission

With an advanced foreign hydraulic automatic transmission as the objective, an analytical method for the gear-shifting schedule is proposed. First the demanded maximum gradient of test is estimated. Then a test scheme and analytical procedure is formulated by initial test and hypothetical shift parameters. Finally through gear-shifting tests under different road conditions, load, accelerator pedal position limitation, throttle opening and output shaft speed are found to be the gear-shifting parameters. Under a common road condition, the gear-shifting schedule is a double-parameter schedule. Based on the driver''s demands on braking and dynamic performance, different shift schedules are made under downhill, uphill and quick releasing acceleration pedal conditions. The operation criteria of down-shift schedule on abrupt grade are proposed.     

基于漂木分离效果的鱼脊型水石分离结构参数优化

山洪、泥石流中往往携带有大量漂木,漂木的堵塞作用和冲击作用往往会加剧灾害,并对山洪、泥石流防治工程造成影响。鱼脊型泥石流水石分离结构是一种新型的水石分离结构,对泥石流中粗大颗粒具有良好的分离作用,但该结构对漂木的分离作用和漂木对结构的影响尚未进行研究。本文通过模型实验,研究了引流口的漂木过流能力和水石分离格栅对漂木的分离效果,探讨了该结构对漂木的减灾效果及相关影响因素。实验结果表明水石分离格栅结构参数以及流速对漂木的分离效果有重要影响。根据实验结果提出了基于漂木分离效果的鱼脊型水石分离结构主要参数的优化方法。     

平面铰链四杆机构的轨迹综合方法

为提高平面铰链四杆机构轨迹综合的速度与精度,提出基于B样条曲线的综合方法.采用三次非均匀B样条曲线对连杆曲线进行拟合,将B样条曲线控制多边形各相邻两边的夹角作为连杆曲线的特征参数,将大量连杆曲线特征参数和对应的机构尺寸参数存入计算机以建立电子图谱库;当输入一定数目的有序离散数据点时,通过B样条曲线拟合得到期望曲线,提取期望曲线的特征参数;再利用神经网络将期望曲线的特征参数与电子图谱库中特征参数进行匹配,从而找到满足要求的机构,最终达到轨迹综合的目的.设计实例表明,该方法可快速实现四杆机构的轨迹综合,综合的精度高且所提取的特征参数与连杆曲线方位、缩放比例无关,减少了图谱库的数据冗余.     

切削参数对锯片铣刀切削振动特性的影响研究

锯片铣刀切削加工过程中,普遍存在严重的振动问题.为研究锯片铣刀的切削振动特性,设计了多种切削条件下的锯片铣刀切削实验.在理论计算锯片铣刀固有频率的基础上,对实验结果进行了分析和讨论.结果表明:锯片铣刀切削系统的频率仅仅取决于系统的固有频率,基本不受切削参数的影响.因此,通过增加刀具系统的刚度或改变切削速度,使激振频率远离刀具系统的固有频率可有效降低和控制切削系统的振动.     

并联混合有源电力滤波器的参数设计与仿真

针对有源滤波器技术的实际工程需要,探讨了并联混合型有源电力滤波器的参数设计,主要包括无源滤波器的参数设计和IGBT模块的组合分析,并根据一个变电站实测的电流数据,建立了仿真研究模型,仿真结果验证了设计的正确性和可行性.     

四川省大瑞乡泥石流灾害特征及减灾对策

在地质勘查的基础上,分析了大瑞乡泥石流形成条件、基本特征,并计算了泥石流的容重、流量、流速、冲出量等动力学参数,计算证明大瑞乡泥石流属于中频暴雨沟谷型泥石流。根据泥石流的具体情况和当地经济、社会、生态建设的需要,以及被保护对象的重要性,提出了"拦防结合"的防治对策。