四瓦可倾瓦径向滑动轴承动力特性的实验研究

采用在线分析方法考察了300MW汽轮发电机可倾瓦轴承的静、动力特性,探讨了载荷、轴颈转速以及动态激振力频率等参数变化对可倾瓦轴承的静、动态性能的影响,比较试验结果与理论计算结果发现,在不同频率激振力作用下,理论计算所得到的可倾瓦轴承动特性参数与试验结果有较大的差异。     

开放型物理实验教学研究

本文介绍了全开放型物理实验教学方法。讨论了物理实验教学方法实行开放的意义,以及在人才培养方面的作用。     

氟代吡啶甲酸解离的环金属铱配合物及其电致化学发光性能

以2-苯基吡啶为主配体、以氟修饰的吡啶-2-甲酸为辅助配体合成出一系列环金属中性铱配合物。产物结构通过核磁及质谱进行了确认,对其光物理性能研究表明,这些配合物的发光波长在498～516 nm之间,属于绿光发射。没有氟取代的配合物Ir1量子效率最高,达到32%,而由于2位氟取代的位阻影响Ir4的量子效率最低只有6%,其他氟取代配合物的量子效率在13%～16%之间。引入氟原子后配合物的氧化电位都有所增加,氧化电位由511 mV增加到547～574 mV之间。热稳定性也在氟取代后增加,由142℃提高到187～380℃之间,Ir4提高的最少,为187℃。应用于电致化学发光时,除Ir4外,氟取代都能增加其电致化学发光强度,由332增加到333～370之间。而配合物Ir4的发光强度只有203。以上结果表明氟取代的效果跟位置有很大关系,2位氟取代由于位阻效应,使配合物的量子效率及稳定性都有不利影响,而其他位置的取代则能提高配合物的这些性能。该研究结果对设计开发综合性能优异的发光材料具有借鉴意义。     

Thorpe尺度估算库尔勒、茂名、拉萨大气光学湍流廓线

在新疆库尔勒、广东茂名海边、西藏拉萨三个地区释放的探空气球, 实现了温度、气压、风速等常规气象参数以及大气折射率结构常数的廓线测量。基于Tatarski湍流参数化方案以及以上地区探空数据, 利用Thorpe尺度估算了新疆库尔勒、广东茂名海边、西藏拉萨三个地区的高空大气光学湍流廓线, 并将这三个地区实测的廓线与其对应的估算结果做了对比, 结果表明: 估算值与实测值在量级和变化趋势上表现出较好的一致性, 相关性分别为69%, 60%, 68%;Thorpe尺度相较于其他估算湍流廓线的参数化方法输入参数少、更简便。     

扭转塑性变形对6063铝合金拉伸力学性能的影响机理研究

扭转是一种常用的冷作硬化方法。本文通过实心圆轴扭转实验和预扭试件的单向拉伸实验,研究了扭转塑性变形程度对6063铝合金拉伸力学性能的影响。通过理论研究和硬度分析探究了造成这一影响的内在机理。结果表明,试件扭转后其内部形成的以屈服强度为特征参数的梯度结构,是造成预扭试件力学性能得到改善的根本原因。并且,扭转不同的角度,材料内部产生的梯度结构也是不同的。而不同的梯度结构对试件力学性能的影响则表现为后继拉伸屈服强度随预扭角度的增大而增大。为了预测预扭试件的后继拉伸力学行为,验证前述结论的正确性,建立了由内到外屈服强度逐渐变化的有限元模型。此模型代表了预扭转变形试件,对其施加位移载荷,模拟后继单向拉伸加载过程。模拟所得材料力学性能随扭转角的变化趋势与实验结果基本吻合,从而验证了扭转冷作硬化后,圆轴试件内部产生了以屈服强度为特征参数的梯度结构这一结论。同时,也提供了一种有效的预测材料扭转后拉伸力学性能的数值模拟方法。     

一种微型矢量水听器姿态测量系统

矢量水听器姿态校正的通常做法是将姿态测量系统捷联安装在声纳平台上,这种方案无法准确测量矢量水听器的姿态变化。针对这个问题,设计了一种微型姿态测量系统,并将其捷联封装在矢量水听器内部。系统采用MEMS陀螺测量角速度,用毕卡迭代算法解四元数姿态更新方程。用MEMS加速度计和磁力计分别测量重力方向和磁北方向,再使用扩展卡尔曼滤波对解算姿态角进行实时校正。经测试,该系统横滚角和俯仰角的静态误差小于0.2°,航向角的静态误差小于0.8°。摇摆实验中,横滚角和俯仰角的动态相对误差小于2.9%,航向角的动态相对误差小于3.6%。海上试验结果证明该姿态测量系统应用于矢量水听器可明显提高目标方位估计的精度。     

基于NURBS插值的三维渐进结构优化方法

提出一种基于等几何控制点密度变量的三维双向渐进结构拓扑优化方法。在当前列式下,高阶NURBS基函数被同时用于CAD模型中NURBS实体片的几何场、位移场和温度场以及密度场插值,实现了几何模型、分析模型和优化模型的有效统一,确保了位移场、温度场及密度场的高阶连续性;详细推导了基于等几何控制点密度变量的三维渐进结构法模型及其灵敏度分析列式;最后几个典型的数值算例,包括最小柔顺性、热传导优化问题及三维结构自由振动的基频最大化问题,验证了本文方法的有效性。     

Emission spectrum from an Al/Mg tracer in the blow-off region of a radiatively ablated capsule

A study of X-ray emissions from Al/Mg tracers buried at two different depths in a plastic shell is presented. The X-rays originating from the K-shell transitions of the Al/Mg ions begin to irradiate after the ablative heating wave has passed through the trace layer and are recorded with a streaked crystal spectrometer. Only emissions from the capsule with the trace layer buried at a smaller depth are observed. Hydrodynamic simulations and a collisional—radiative model including detailed atomic physics are used to investigate the measured spectrum. It is found that the effects of the radiative heating play important roles in the formation of the K-shell emission. The time correlation between the simulations and the measurements is obtained by comparing the measured time profile of the He α emission with the calculated one. The line ratio of Ly α to He α is also calculated and is found to be in fairly good agreement with the experimental data. Finally, the relation between the time profile of the He α emission and the ablation velocity is also discussed.     

Global exponential synchronization between Lü system and Chen system with unknown parameters and channel time-delay

This paper proposes a nonlinear feedback control method to realize global exponential synchronization with channel time-delay between the Lü system and Chen system,which are regarded as the drive system and the response system respectively.Some effective observers are produced to identify the unknown parameters of the Lü system.Based on the Lyapunov stability theory and linear matrix inequality technique,some sufficient conditions of global exponential synchronization of the two chaotic systems are derived.Simulation results show the effectiveness and feasibility of the proposed controller.     

Modified impulsive synchronization of fractional order hyperchaotic systems

In this paper, a modified impulsive control scheme is proposed to realize the complete synchronization of fractional order hyperchaotic systems. By constructing a suitable response system, an integral order synchronization error system is obtained. Based on the theory of Lyapunov stability and the impulsive differential equations, some effective sufficient conditions are derived to guarantee the asymptotical stability of the synchronization error system. In particular, some simpler and more convenient conditions are derived by taking the fixed impulsive distances and control gains. Compared with the existing results, the main results in this paper are practical and rigorous. Simulation results show the effectiveness and the feasibility of the proposed impulsive control method.