水轮机轴系支承刚度识别

本文用时间序列分析的方法,在不测量输入信号的前提下,利用ARMA模型拟合测量响应信号,对运行中的水轮转子在转轴接近为刚性的情况下,求得水轮机系统的轴系特征值与特征向量,进而求出其支承刚度.并用一仿真模型作了检验,结果证明本方法具有较好的在线识别应用价值.     

塑性成形中的切向加载及其功率计算

论述了塑性成形时，作为切向载荷的摩擦力对坯料变形所作功率的计算方法。明确指出摩擦力提供给坯料的功率只与坯料接触表面的切向速度有关，与坯料和工、模具之间的相对速度无关。     

高聚物银纹断裂的研究现状

银纹化是高聚物的一种非线性变形方式，对高聚物的增韧设计十分重要。考虑银纹细观结构特征的银纹生长和断裂规律是研究银纹增韧机制的核心内容。结合国内外最新的研究进展，对承载高聚物中的银纹断裂及其与裂纹扩展的相互作用等问题作了较全面的总结和分析，并对今后的研究重点和趋势作了简要展望。     

小波分析在调制信号自动识别中的应用

自动调制识别是非合作通信系统接受机设计中的重要研究课题。本文着重讨论了在软件无线电中所有基本调制制式(DSB．FM．PM,2ASK,2FSK．2PSK)的识别问题．对高斯白噪声中的通信信号的自动识别进行了计算机仿真．实验结果表明．此种识别算法具有较为理想的识别效果。     

A new method of choosing scales in wavelet transform for damping identification

A systematic study of the method of selecting scales in wavelet transform for damping identification in frequency domain was carried out. A method to select the scale with the modUlus at the maximum was developed by extending the range of scales. It is proved that using this method in small damping ratio and linear system, we can achieve better results in identification of the closely-spaced model.     

Effects of stress and physical ageing on nonlinear creep behavior of poly(methyl methacrylate)

The effects of stress,ageing time and ageing temperature on creep behavior of poly(methyl methacrylate) were studied.After annealing above its glass transition temperature for a period of time to eliminate the stress and thermal history,the specimens were quenched and aged at various ageing temperatures for different ageing time,and then the short-term creep tests under different stress levels were carried out at room temperature.The creep strains were modeled by means of time-ageing time equivalence and ti...     

Effects of gamma irradiation and moisture absorption on mechanical properties of PA6/PTFE blends

PA6/PTFE blends with varying polytetrafluoroethylene content from 3% to 15%(mass fraction) were irradiated by 60Co gamma-ray with various doses(20,50 and 100 kGy) under ambient conditions.Moisture absorption test,U-notched Charpy impact test and quasi-static tension and bending were conducted to investigate the effect of irradiation on moisture absorption and mechanical properties of the blends.It is shown that the exposure of the blend to 60Co irradiation improves the tensile modulus,tensile strength and f...     

涪陵页岩气田上部气层高效降本压裂工艺探讨

涪陵页岩气田上部气层资源量大,前期试验井压后取得较好的试气效果,表明上部气层开采潜力大。剖析试验井平面上试气效果差异大的原因,针对上部气层粘土含量增加、地应力值相对较低、层理缝较发育等特点,形成了"减阻水+中途胶液转向"的压裂思路,进一步优化压裂施工参数,采取少段多簇工艺、低成本压裂液材料、"电动泵+压裂车"组合等措施在保证压裂效果的情况下有效降低施工成本,为涪陵页岩气田上部气层资源的后期开发提供技术支撑。     

Mises准则的圆形屈服轨迹及其在板料成形中的应用

按Ｍｉｓｅｓ屈服准则求解板料成形问题,理论严密,结果准确。本文提出了一种Ｍｉｅｓ准则的圆形屈服轨迹图。利用这种圆形屈服轨迹图求解轴对称板料成形问题,可使求解过程简化,使求解结果更加清晰,直观。与传统的椭圆屈服轨迹比较,有明显的改进。     

塑性有限元网格重分系统基于AutoCAD的二次

阐述了基于ＡｕｔｏＣＡＤ ｆｏｒ Ｗｉｎｄｏｗｓ平台开发研制塑性有限元的人机交互式二维网格重分系统的网络畸变判据、新网格的再定义、新旧网格场变量信息传递的技术原理和ｖｉｓｕａｌ Ｂａｓｉｃ程序实现的方法,同针网格重分与ＡｕｔｏＣＡＤ有效结合。最后给出实例验证系统的正确性。