正压给水的主排水泵启动特性仿真分析研究

峰峰集团某矿排水系统在采用正压给水方式后主排水泵泵效明显提高,为了研究排水系统的启动特性,利用Flowmaster软件建立了离心泵串联系统模型。根据水力机械试验室的设备参数进行了仿真,分析了正压给水条件下主泵定量启动前由单泵和双泵组成的排水系统特性。在此基础上,得到了离心泵瞬时启动转速和功率的特性曲线。结果表明,在正压给水条件下,主泵启动功率的影响基本消除,主泵功率达到稳定值的时间缩短。提高了主排水泵的效率,提高了排水系统的综合效率。     

双机器人系统运动协调仿真与实验研究

针对具有重量大、形状不规则特征的物品,采用双机器人协同作业是该技术领域的研究热点问题之一。运用ADAMS软件对双机器人虚拟样机进行运动学仿真分析,模拟空间搬运轨迹,对DREE末端点的运动轨迹曲线进行同步误差分析。搭建了实验平台,对双机器人同步搬运箱体进行实验验证。实验结果表明:双机器人协作搬运箱体时,在水平方向和垂直方向的轨迹误差均小于±2.8mm,较好地满足同步搬运作业工艺要求。     

屏边苗式建筑风格及建设初探

考察屏边建筑特色风貌,总结了屏边在打造特色风貌县城建设方面的成功经验,对县城风貌建设提出合理化建议。     

焊点对于传动滚筒强度特性的影响分析

以带式输送机传动滚筒为研究对象,运用ANSYS Workbench有限元软件,对有无焊点时的传动滚筒进行强度分析,在软件中模拟给定载荷的工况环境,探究有无焊点时滚筒的强度变化情况。模拟结果表明,考虑焊点时传动滚筒的变形分布变化不明显,最大变形位置并没有变化,均在滚筒筒壳中间部分;而考虑焊点时传动滚筒的应力分布变化明显,最大应力位置从外短轴变为外长轴,为带式输送机传动滚筒参数优化提供了有利依据。     

基于Romax行星齿轮传动振动特性仿真分析

以某行星齿轮传动为研究对象,分析行星齿轮传动原理;建立行星齿轮三维模型,导入仿真软件Romax对行星齿轮传动模态、固定内齿圈振动加速度、振动速度等振动特性进行仿真分析。仿真结果表明:行星齿轮传动不同阶数下的振动频率、振型和振动总位移不同;行星齿轮传动固定内齿圈的振动加速度、振动速度都呈现在某一均值波动的情况。该研究为避免行星齿轮传动发生共振、减小振动噪声及增加疲劳寿命提供理论依据。     

355 MPa级转向架构架用钢连续冷却转变行为

高速动车组转向架构架对高速动车组的运行品质、行车安全起到至关重要的作用。为向355 MPa级转向架构架用钢的工业试制提供指导，在Gleeble-3800热模拟试验机上进行了热模拟试验，结合热膨胀法和金相-硬度法，绘制了355 MPa级转向架构架用钢动态连续冷却转变曲线，研究了试验钢在连续冷却条件下的显微组织演变规律。结果表明，冷速小于1 ℃/s时，其组织主要为多边形铁素体和珠光体；冷速大于5 ℃/s时，贝氏体类组织快速增加；冷速达到50 ℃/s时，为板条贝氏体组织。因此，对于355 MPa级转向架构架用钢，冷速控制在1~5 ℃/s较为适宜，其组织主要由比例适中软硬性相结合的铁素体、珠光体和贝氏体构成，可以获得优良的强韧性匹配。     

Experimental investigation on the self-acceleration of 10%H2/90%CO/air turbulent expanding premixed flame

The self-acceleration characteristics of a syngas/air mixture turbulent premixed flame were experimentally evaluated using a 10% H₂/90% CO/air mixture turbulent premixed flame by varying the turbulence intensity and equivalence ratio at atmospheric pressure and temperature. The propagation characteristics of the turbulent premixed flame including the variation in the flame propagation speed and turbulent burning velocity of the syngas/air mixture turbulent premixed flame were evaluated. In addition, the effect of the self-acceleration characteristics of the turbulent premixed flame was also evaluated. The results show that turbulence gradually changes the radius of the premixed flame from linear growth to nonlinear growth. With the increase of turbulence intensity, the formation of a cellular structure of the flame front accelerated, increasing the flame propagation speed and burning speed. In the transition stage, the acceleration exponent and fractal excess of the turbulent premixed flame decreased with increasing equivalence ratio and increased with increasing turbulence intensity at an equivalence ratio of 0.6. The acceleration exponent was always greater than 1.5.     

减少手术创伤始终是妇科肿瘤手术快速康复的决定性因素

减少手术创伤始终是快速康复的决定性因素,这一点在目前的加速康复外科研究尤其是复杂手术,如妇科肿瘤手术中尚未得到充分重视。尊重学习曲线、全面规划手术方案、总结失利经验、开展前瞻性研究是解决此问题的主要方案。本文着重讨论妇科肿瘤手术创伤对术后加速康复的影响及可能的改进措施。     

Study of equivalent efficiency calibration method for radioactive gas source measured on HPGe detectors

ABSTRACT

In view of the complexity of current detection efficiency calibration of radioactive gas sources, a method using solid planar sources to be equivalent to gas sources was studied. For the 50 mL gas source box, an optimal equivalent scheme was selected by Monte Carlo Simulations. Then, the full-energy-peak efficiency curve of gas sources at the measurement position of 25 cm, with source-to-detector distance of 25 cm, was fitted by measuring solid planar sources with known activity. To verify the accuracy of the efficiency curve, ⁴¹Ar, ¹³³Xe and ⁸⁷Kr gases were produced and determined by length-compensated method. Then, their full-energy-peak efficiencies at 25 cm position away from the detector were directly calibrated. The percentage efficiency deviations between interpolation from the efficiency curve and direct calibration are all less than 2.5%, which proves the accuracy of the equivalent method. This calibration method is a general one and can be also used for some other radioactive sample measurements, such as non-destructive analysis of gaseous fission product samples with a suitable source-to-detector distance.     

A review on ultrasonic spot welding of copper alloys

As a solid state joining process, ultrasonic spot welding has been proven to be a promising technique for joining copper alloys. However, challenges still remain in employing ultrasonic spot welding to join copper alloys. This article comprehensively reviews the current state of ultrasonic spot welding of copper alloys with a number of critical issues including materials flow, plastic deformation, temperature distribution, vibration, relative motion, vertical displacement, interface friction coefficient, online monitoring technique, coupled with the macrostructure and microstructure, the mechanical properties and electrical conductivity. In addition, the future trends in this field are provided.