Analysis of exclusively kinetic two-link underactuated mechanical systems

Analysis of exclusively kinetic two-link underactuated mechanical systems is undertaken in this paper. It is first shown that such systems are not full-state feedback linearizable around any equilibrium point. Also, the equilibrium points for which the system is small-time locally controllable (STLC) is at most a one-dimensional submanifold. A concept less restrictive than STLC, termed the small-time local output controllability (STLOC) is introduced, the satisfaction of which guarantees that a chosen configuration output can be controlled at its desired value. It is shown that the class of systems considered is STLOC, if the inertial coupling between the input and output is nonzero. Also, in such a case, the system is nonminimum phase. An example section illustrates all the results presented.     

A note on stress-constrained truss topology optimization

The purpose of this brief note is to demonstrate that general-purpose optimization methods and codes should not be discarded when dealing with stress-constrained truss topology optimization. By using a disaggregated formulation of the considered problem, such methods may find also “singular optima”, without using perturbation techniques like the ε-relaxed approach. Received February 19, 2002     

局部缺陷对旋转壳内力分布的影响

本文应用有初始几何缺陷的壳体非线性应变分量公式及内时本构理论，对冷却塔在重力作用下的内力进行了弹塑性大变形计算，分析了常见的几种缺陷对冷却塔内力分布的影响。对于工程实际中有缺陷的冷却塔的整体性能分析具有重要意义，可以为工程设计提供理论基础。     

电力变压器局放超声传感器及其应用

作者研制成一种带光纤的电力变压器局放超声PZT传感器.文中分析了它的灵敏度与宽频带特性,介绍了原理、结构设计、实验数据及现场成功实例.理论与实验研究表明:具有这种高灵敏传感器的超声定位系统是确定电力变压器绝缘故障部位的一种方法.     

Application of Wavelet Packet De-noising in Time-Frequency Analysis of the Local Wave Method

The local wave method is a very good time-frequency method for nonstationary vibration signal analysis. But the interfering noise has a big influence on the accuracy of time-frequency analysis. The wavelet packet de-noising method can eliminate the interference of noise and improve the signal-noise-ratio. This paper uses the local wave method to decompose the de-noising signal and perform a time-frequency analysis. We can get better characteristics. Finally, an example of waveletpacket denoising and a local wave time-frequency spectrum application of diesel engine surface vibration signal is put forward.     

测定地下水流向的多计数管探头的研制

多计数管流向探头;;单孔;;总流向;;局部流向;;滤水管 掌握地下水的流动方向,有助于研究地下水的运动规律。利用放射性单孔法可以测定地下水流某一点流动方向。 应用放射性指示剂在单孔中测定地下水流向的方法由奥地利的梅尔霍费于1963年首先提出,1964年波兰的鲍劳斯齐克等把这种方法用于现场测量。放射性单孔流向测量方法有若干种,其原理基本相同,仅测量装置结构有区别,早期有单管旋转式探头。我们从1983年7月     

城市建设的休克疗法——大连现象解说

在启动大规模的现代化建设的进程中，应对发展中听中型城市实施“休克疗法”，强调性终止城市发展的无序而缓慢的自然进程。选择短暂的“回归”或“中断”历史的调整时，应以能否适当地的历史文化特质从而把握当代的发展机遇为依据。     

Effect of heating-rate on failure temperature of pre-loaded brass H62

The response and failure of brass H62 specimens subjected to different levels of pre-loaded stresses and heating rates were investigated using a Gleeble-1500 thermal-mechanical material testing system. The metallographs of the tested material were also observed and analyzed. It is found that the increase of either pre-loaded stress or heating-rate decreases the failure temperature. Metallographic analysis shows that high heating-rate may cause stronger local thermal inconsistency （LTI） and remarkably increase the microdefects in the material, which may markedly degrade the macroscopic mechanical properties of the material.     

一个光纤综合业务环网的故障自动恢复

光纤综合业务区域网是近年来迅速发展的一个领域，环形网是这种网最常用的一种拓扑结构。由于环形网结点串联的特点，网络的可靠性是必须解决的问题。本文针对一个具有３４Ｍｂ／ｓ速率，可以传输计算机数据、话音、传真和会议电视的光纤综合业务环网（ＩＳＲ），研究了其故障的自动隔离。文中分析了ＩＳＲ的故障，讨论了故障的检测、定位和隔离的方法。为了适应综合业务的混合电路交换和分组交换技术，本文提出了采用二分搜索法来定     

水下封底混凝土与钢护筒粘结力试验

针对吊箱围堰施工中，混凝土与钢板间的粘结力无详实数据的现象，介绍了确定数据的实验模型、实验步骤，并分析了实验结果，以方便施工，指导施工。