宽带波导吸振器吸振性能研究

为了满足对声频振动控制的要求,拓宽动力吸振器的吸振频率范围,本文在对直梁宽频带动力吸振器研究的基础上,研究了螺旋曲梁式动力吸振器.研究表明,该吸振器具有更密集的模态,因而具有宽频带的吸振性能.它的变截面形式使得它具有更强的消耗振动能量的能力,数值分析还表明如果设计合理,在0～1000Hz的频率范围内都可以获得较大的吸振量,有望成为噪声与振动控制新的有效手段.     

可变阻尼对汽车悬架系统振动性能影响分析

通过建立1/4悬架系统的理论数模,分析阻尼系数影响系统的幅频特性.在不同的振动频率范围内,阻尼的相应变化将改善悬架系统的输出性能.     

提高抵御风险能力的思考

提高抵御风险能力是我们党面临的两大历史性课题的重要内容之一，也是加强党的执政能力建设的重大任务之一，我国已进入风险社会，我们必须从战略的高度对待风险问题，深刻认识风险危害，善于区分风险类型，增强全民风险意识，建立风险预警机制，制定风险抵御方案，采取必要保障措施．切实提高抵御风险的能力。     

认知无线电多目标优化算法研究

认知无线电是指能够感知周围频谱环境并动态使用频谱资源的智能无线通信系统。认知无线电的多目标优化问题是一个典型的动态参数优化问题。以传输能量、数据率以及误比特率等多个参数为目标,采用一种基于DNA计算的非支配排序多目标遗传算法(DNA-GA)来对其进行优化。将CR可调参数进行编码作为染色体,产生大小为N的初始化种群,并根据CR目标函数计算个体适应度,再结合克隆操作使算法收敛于全局最优,最终得到CR系统的最优操作参数。仿真结果表明,DNA-GA可以在不同用户需求情况下获得较好的性能优化。     

一维线性系统的无阻尼受迫振动研究

在功率谱分析的基础上,用尝试法得出了一维线性系统仅受简谐强迫力作用时的振动微分方程的解,并据此对无阻尼受迫振动的性质进行了讨论,得到一些有益的结果.     

Robust design and optimization for autonomous PV-wind hybrid power systems

This study presents a robust design method for autonomous photovoltaic （PV）-wind hybrid power systems to obtain an optimum system configuration insensitive to design variable variations. This issue has been formulated as a constraint multi-objective optimization problem, which is solved by a multi-objective genetic algorithm, NSGA-II. Monte Carlo Simulation （MCS） method, combined with Latin Hypercube Sampling （LHS）, is applied to evaluate the stochastic system performance. The potential of the proposed method has been demonstrated by a conceptual system design. A comparative study between the proposed robust method and the deterministic method presented in literature has been conducted, The results indicate that the proposed method can find a large mount of Pareto optimal system configurations with better compromising performance than the deterministic method. The trade-off information may be derived by a systematical comparison of these configurations, The proposed robust design method should be useful for hybrid power systems that require both optimality and robustness.     

Multiple objective particle swarm optimization technique for economic load dispatch

INTRODUCTION The conventional economic load dispatch prob-lem of power generation involves allocation of power generation to different thermal units to minimize the operating cost subject to diverse equality and ine-quality constraints of the power system. This makes the economic load dispatch problem a large-scale highly non-linear constrained optimization problem. However, as a result of public awareness of envi-ronmental protection, diverse emission compliance strategies have emerged (…     

频谱细化技术与功率倒频谱在振动信号分析中的应用

频谱细化技术和功率倒频谱是振动信号分析的两种重要辅助方法.采用细化处理,可以对信号频谱上感兴趣的一段频带进行“局部放大”,从而提高频率分辨率;倒频谱可以识别信号中较弱的周期成分,并对识别调制信号的边频县有特殊的效果.本文在介绍这两种方法基本原理的基础上,运用工程实例说明了其在振动信号分析中的实际应用效果.     

Pareto局部搜索算法的改进

针对一个Pareto局部搜索(PLS)算法在解决多目标组合优化问题中所得到的解集与初始点的选取有关,提出该算法的改进。改进算法从初始解开始进行PLS搜索产生一组改进解集VF,然后对VF中的所有解再进行PLS搜索,如此重复直到满足终止条件。实例计算表明,PLSⅠ算法和算法Ⅱ能得到很好的解且解的质量优于PLS算法。     

载重绳索参数激励横向振动的减振策略

论述了一种抑制载重绳索参数激励横向振动的简便方法. 假设绳索底端的质量受到一个垂直简谐激励并忽略载重绳索高阶振型的影响, 载重绳索的运动方程可以用一个带有立方非线性项的Mathieu方程来描述. 根据Mathieu方程的有关理论, 在载重绳索系统中, 当索端质量垂直振动的频率接近绳索横向振动固有频率2倍时, 一旦索端质量垂直振动的幅度超过某个临界数值时, 绳索将产生参数共振. 为了避免这种现象, 建议在索端质量上加装一个减振器以削减索端质量的垂直振动, 进而抑制绳索的横向振动. 实验验证了该减振方案的有效性.     

Vibration and sound damping in polymers

Excessive vibrations or loud sounds cause deafness or reduced efficiency of people, wastage of energy and fatigue failure of machines/structures. Hence, unwanted vibrations need to be dampened. This article describes the transmission of vibrations/sound through different materials such as metals and polymers. Viscoelasticity and glass transition are two important factors which influence the vibration damping of polymers. Among polymers, rubbers exhibit greater damping capability compared to plastics. Rubbers reduce vibration and sound whereas metals radiate sound. The damping property of rubbers is utilized in products like vibration damper, shock absorber, bridge bearing, seismic absorber, etc.     

基于粒子群算法的太阳能电动汽车复合能源系统优化

太阳能电动汽车的复合能源系统优化匹配问题可以看成一个多目标优化问题,两个相互冲突的目标是极大化系统的峰值功率满足率和极小化系统的成本,前者关系到系统的可靠性后者涉及到样车能否量产,所以两个优化目标都很重要.本文提出了改进的粒子群算法优化配置太阳能电动汽车复合能源系统,这种改进的粒子群算法引进了遗传算法里的变异算子,并且打破常规算法里的加速因子为常数的惯例而使加速因子随时间改变.优化结果显示：改进的粒子群算法也能够很好地解决复合能源系统的多目标优化问题.     

Numerical analysis on aeolian vibration of transmission lines with Stockbridge dampers

We used computational fluid dynamics （CFD） and mode superposition method instead of the energy balance method to compute transmission line aeolian vibrations induced by the Karman vortex. Firstly, we obtained the wind power inputs using CFD theory. The result is effective for aeolian vibration analyses compared with the power which were measured in wind tunnel tests. Then a new aeolian excitation was derived using the wind power equivalent principle, and the aeolian vibration distribution along transmission lines and the wind power input obtained by CFD can be account. Secondly, we formulated the motion equation of a conductor-damper system and derived a semi-analytial solution using the mode superposition method. The Stockbridge-type dampers attached were simplified to the forces transmitted by the clamps. Finally, the semi-analytical solution can be solved by iterative methods. Taking a 1 000 kV Ultra High Voltage transmission line as an example, we analyzed the line with and without dampers by the semi-analytical solution. Compared with the results which were computed by the energy balance method, the semi-analytical solution is precise enogh for aeolian vibration analyses. Besides, we also analyzed the influence of damper position and quantity.     

电源谐波分析及治理

随着非线性负载的逐渐增加,供电电源的谐波越来越严重,对电网、供电设备和用电设备危害也越来越大。引起了供电部门和用户对谐波的抑制和治理的重视,对UPS电源及其他系统谐波治理应选择合理方案才能取得良好的效果。     

本钢发电厂B15-90/39机组的振动与诊断

本钢发电厂B15-90/39机组多次发生在启动过程中跳闸,轴振动超标等故障。通过测试了谱图等分析,调整了汽轮机转速避免其在临界转速附近运行。保证了机组整个安全。     

Joint channel and power allocation scheme for cognitive wireless networks

Cognitive radio (CR) is a promising technology deemed to improve the efficiency of spectrum utilization. This paper considers a spectrum underlay cognitive radio network, in which the cognitive users (CUs) are allowed to use the radio spectrum concurrently with the primary users (PUs) under the interference temperature constraint. We investigate the system performance by using the proposed joint channel and power allocation scheme under two transmit strategies to achieve higher data rates and performance diversity gain respectively. Simulation results show that the proposed scheme provides a significant improvement on the bit error rate (BER) performance and spectrum efficiency of a cognitive wireless network.     

Formation process,key influencing factors,and countermeasures of high-order polygonal wear of locomotive wheels

Two types of high power alternating current(AC) locomotive in China are prone to serious high-order polygonal wear, which has significant negative effects on the operation of locomotives. This study investigates factors influencing polygonal wear in locomotive wheels and determines methods of minimizing operation damage. We designed experiments to analyze the process of polygonization formation of wheels to identify the key influencing factors, finding that natural vibration of wheelsets is the central inherent factor of wheel polygonization and that these vibrations can be easily stimulated by wheel or rail irregularities. We found that poor re-profiling quality is the key external factor in these irregularities. The wheelset bending resonance is activated when the remaining wheel polygonal wear has a wavelength of 200 mm in the 1/3 octave band, in turn leading to significant increases of wheel polygonal wear. In this study, we review a new wheelset design that can mitigate and/or eliminate the polygonal wheel wear due to increased stiffness in wheel bending. We evaluate the potential capacity of the newly designed wheelset and propose two proven effective measures to further improve the wheel re-profiling quality for polygonal wear.     

微机备用电源自动投入装置在电力系统中的应用

微机备用电源自动投入（APD）装置是电力系统的重要组成部分,与传统APD装置相比具有直观简便、可靠性高、智能化程度高、综合功能强等优点和特点。本文以YNT-300系列为例介绍微机APD装置在电力系统中的应用。     

Wind-induced vibration control of long-span power transmission towers

We investigated wind-induced vibration control of long-span power transmission towers based on a case study of the Jingdongnan-Nanyang-Jingmen 1 000 kV transmission line project in P. R. China. The height of the cup tower is 181 m with a ground elevation of 47 m, which makes it a super flexible and wind-sensitive structure. Therefore, we should analyze the wind- resistant capacity of the system. We simulated applicable transverse fluctuating wind velocity field, developed a lead-rubber damper （LRD） for controlling wind-induced vibration of long-span transmission towers, deduced LRD calculation model parameter, and researched the best layout scheme and installation method of LRD. To calculate the wind-induced response of tower-line coupling system in seven layout schemes, we used the time history analysis method, and obtained the efficiencies of wind-induced vibration control. LRD deformation research proved that the damp of all LRDs was efficient under the designed wind velocity when they were laid along the edge of tower heads. We studied the controlling efficiency resulting fTom only applying stiffness to the tower polos where the dampers used to be laid under the designed wind velocity. The results show that the controlling efficiency was not ideal when the stiffness is increased on the poles only. Therefore, LRD should conlxibute to both the stiffness and damp of a structure to effectively reduce the dynamic response of a tower-line coupling system under strong winds. We also discussed the controlling efficiency of LRD under static winds. The results show that there was little difference between displacements derived by the finite clement time history method and those obtained by static wind method conducted by a design institute. This means the simulation on space relevant wind velocity field was accurate and reasonable.     

Reliability based multiobjective optimization for design of structures subject to random vibrations

Based on a multiobjective approach whose objective function （OF） vector collects stochastic reliability performance and structural cost indices, a structural optimization criterion for mechanical systems subject to random vibrations is presented for supporting engineer＇s design. This criterion differs from the most commonly used conventional optimum design criterion for random vibrating structure, which is based on minimizing displacement or acceleration variance of main structure responses, without considering explicitly required performances against failure. The proposed criterion can properly take into account the design-reliability required performances, and it becomes a more efficient support for structural engineering decision making. The multiobjective optimum （MOO） design of a tuned mass damper （TMD） has been developed in a typical seismic design problem, to control structural vibration induced on a multi-storey building structure excited by nonstationary base acceleration random process A numerical example for a three-storey building is developed and a sensitivity analysis is carried out. The results are shown in a useful manner for TMD design decision support.