Time-resolved spectroscopy of infrared active vibrations in 2,5-dioctyloxy poly(phenylene vinylene) films

We report on picosecond time resolved spectroscopy of photogenerated infrared active vibrations in thin films of 2,5-dioctyloxy poly(phenylene vinylene). We excited the films by ?4 ps long pulses of 565 nm laser light with 2×10¹³ photons/cm² per pulse and repetition rate of 76 MHz. We then followed the temporal evolution of the infrared active vibrational (IRAV) spectrum using a subsequent, variably delayed, weak tunable IR probe pulses of similar temporal duration. Under these conditions, we show clear spectroscopic evidence for photogenerated infrared active vibrations at times which are shorter than our temporal resolution (<4 ps). We suggest that the transient IRAV absorption is due to secondary polarons formation following exciton dissociation.     

A p‐version,first order shear deformation,finite element for geometrically non‐linear vibration of curved beams

A p‐version, hierarchical finite element for curved, moderately thick, elastic and isotropic beams is introduced. The convergence properties of the element are analysed and some results are compared with results published elsewhere or calculated using a commercial finite element package. It is verified that, with the proposed element, shear locking does not affect the computation of the natural frequencies and that low dimensional, accurate models are obtainable. Geometrically non‐linear vibrations due to finite deformations, which occur for harmonic excitations with frequencies close to the first three natural frequencies of vibration, are investigated using Newmark's method. The influence of the thickness, longitudinal inertia and curvature radius on the dynamic behaviour of curved beams are studied. Copyright © 2004 John Wiley & Sons, Ltd.     

重油催化裂化装置轴流风机的损坏与修复

广州分公司炼油厂重油催化裂化装置四机组轴流风机在 1998年 9月由于入口消音器故障引发重大事故 ,严重影响了装置生产。该文主要针对其损坏的原因、情况和修复方法作了探讨和论述     

一种直流力矩电机跑合防堵转控制电路

本文介绍了一种力矩电机跑合防堵转控制电路。作者对该电路的原理、使用和调试以及实验结果进行了描述。     

Vibrations of stretched damped beams under non-ideal boundary conditions

A simply supported damped Euler-Bernoulli beam with immovable end conditions are considered. The concept of non-ideal boundary conditions is applied to the beam problem. In accordance, the boundaries are assumed to allow small deflections and moments. Approximate analytical solution of the problem is found using the method of multiple scales, a perturbation technique.     

参数强迫激励下非线性振子尖点型奇点的分叉

本文首先研究了不具有Z_2—对称性时的规范形理论和退化向量场的普适开折理论。然后利用这些理论研究了参数激励与强迫激励联合作用下非线性振动系统的尖点型奇点的余维2退化分叉。     

自适应比例因子模糊控制器在异步电动机调速系统中的应用

为了降低转子电阻变化对异步电动机矢量控制系统性能的影响，本文把自适应比例因子模糊控制器应用到了矢量控制系统中。介绍了自适应比例因子模糊控制方法的綦本原理，给出了使用自适应比例因子模糊控制器的异步电动机矢量控制系统的结构框图，对主模糊控制器和辅助模糊控制器进行了设计。仿真实验结果表明，采用这种控制方法的调速系统不仅具有优良的动态性能，而且对转子电阻变化具有很强的鲁棒性。     

铝合金熔体旋转喷吹除气净化过程模拟

采用计算机模拟方法对铝合金熔体旋转喷吹除气净化过程的温度场以及流场进行分析。结果表明,在转杆内部放置一个导气管,可以显著降低气体温度,从而可以有效地解决旋转喷头由于熔剂因高温变软而堵塞的问题;旋转速度和进气流量对铝合金熔体旋转喷吹除气净化效果具有重要影响,应该根据具体情况选择合适的工艺参数。熔池为方形结构时,气体主要从对角处出去,而远离对角处的体积分数却显著降低,甚至可能发生吸气。     

双金属盘式制动器的试制与研究

汽车工业的发展对刹车系统的关键零部件——刹车盘的抗冲击韧性提出了更高的要求。研究结果表明，把灰铸铁(HT250)与用优质碳素结构钢25Mn预先冲压成型的钢件镶铸在一起制成的1种新型刹车盘，既具有灰铸铁良好的抗磨、减震、尺寸稳定等性能，又具有较高的抗冲击韧性，能够满足汽车工业高速化、轻量化对刹车盘的综合要求。     

带轴涡轮转子在立式超速试验台上的超速试验

对带轴涡轮转子提供了可行的试验处理方法 ,并成功地进行了超速试验