含甲缩醛柴油喷雾和燃烧排放特性的试验研究

应用激光相位多普勒技术测量了含甲缩醛柴油喷雾的速度场和粒径场,在直喷式柴油机上研究了该含氧混合燃油的燃烧排放特性。结果表明,添加甲缩醛可改善柴油的雾化,增加喷雾轴线上的粒子速度,但减小喷雾锥角;同时以远大于其加入的比例降低柴油机排气烟度,但对氮氧化物的排放影响不大。柴油机采用甲缩醛作燃油添加剂时,需改造燃油系统。     

Aberration correction and its automatic control in scanning electron microscopes

An automatic aberration correction method has been implemented in scanning electron microscopes (SEM). Necessity of the automatic aberration correction is discussed. The procedure of the automatic aberration correction is explained in detail, where deconvolution techniques are used in order to extract probe information from SEM images. Due to the precise digitization and the usage of proper combinations of correction fields, linearity has been found between the amplitude of each aberration and the corresponding field strength. Experimental results are shown which demonstrate that the aberrations are corrected automatically by a linear feedback control method. After the automatic aberration correction, the image quality has been improved drastically.     

基于物联网的智能化条纹相机控制系统的研制

为满足条纹相机便携化、智能化的发展需要,研制了一种高适用性的分布式智能控制系统,实现了对条纹相机工作参量的监测,对电极电压、扫描工作模式的精确控制以及对图像的采集与处理.基于物联网技术框架与客户端-服务器的结构模式,实现了有线及无线设备扩展的多机协作功能与移动监控功能.并针对该控制系统,设计了具有自保护功能的自激型反激式可调高压电源模块,基于自激式拓扑的简单结构,实现了电源的小型化,且线性调整准确度可达1%.采用Nd∶YLF脉冲激光器(脉宽8ps,波长526.5nm)对应用该控制系统的可见光皮秒条纹相机进行标定,测试得到动态分辨率为12.75Lp/mm(CTF=14%),动态范围为234∶1,时间分辨率达到14ps.     

Generation of minimally persistent circle formation for a multi-agent system

In this paper, two methods of generating minimally persistent circle formation are presented. The proposed methods adopt a leader-follower strategy and all followers are firstly motivated to move into the leader＇s interaction range. Based on the information about relative angle and relative distance, two numbering schemes are proposed to generate minimally persistent circle formation. Distributed control laws are also designed to maintain the desired relative distance between agents. The distinctive features of the proposed methods are as follows. First, only 2n - 3 unilateral communication links for n agents are needed during the circle formation process and thus the communication complexity can be reduced. In addition, the formation topology is kept fixed for the whole motion and achieves a self-stability property. Finally, each follower keeps a regualr interval with its neighbors and the formation converges to a uniform circle formation. Simulation results are also provided to demonstrate the effectiveness of the proposed methods.     

激光诱导击穿光谱脉冲激光功率锁定的研究

激光诱导击穿光谱(laser-induced breakdown spectroscopy,LIBS)在煤质在线监测方面展现了突出的应用前景和研究价值。针对该技术在实际应用中会由于脉冲激光功率起伏导致的长期测量稳定性差的问题,建立了闭环负反馈式脉冲激光功率锁定装置,采用激光功率负反馈信号控制和锁定Nd∶YAG激光器输出功率。实验研究了不同分光比例脉冲激光器锁定在设定输出功率,同一分光比例激光器锁定在不同输出功率以及长时间运行时的功率锁定。结果表明,不同的分光比例对激光输出功率的锁定效果影响不大,分光比例越小,稳定速度越快;同一分光比例实现激光脉冲功率不同预设值的锁定以及在长时间运行时,采用此装置进行功率锁定后,激光输出功率处于预设区间内,RSD值由自由运行时的2.4%降低至1.1%。     

State-dependent event-triggered control of multi-agent systems

Event-triggered control has been recent/y proposed as an effective strategy for the consensus of multi-agent systems. We present an improved distributed event-triggered control scheme that remedies a shortcoming of some previous event- triggered control schemes in the literature. This improved distributed event-triggered method has no need for continuously monitoring each agent＇ neighbors. Moreover, each agent in the multi-agent systems will not exhibit the Zeno behavior. Numerical simulation results show the effectiveness of the proposed consensus control.     

ZnO一维纳米结构的形貌调控与亲疏水性研究

分别使用金属、半导体等类型的基片作沉积衬底,采用气相沉积的方法合成了多种ZnO一维纳米结构,如塔状结构、锥状结构、蘑菇状结构、环状结构等等.用扫描电镜,透射电镜等对合成产物的形貌和结构进行了研究,结果发现沉积衬底对合成产物形貌和结构有着重要的影响.同时对合成塔状纳米结构的生长机理做了系统地分析,并研究了其相应的亲疏水性能. 关键词： 纳米结构 气相沉积 形貌调控 结构表征     

Admissible consensus and consensualization of high-order linear time-invariant singular swarm systems

Admissible consensus analysis and consensualizing controller design problems for high-order linear time-invariant singular swarm systems are investigated. Firstly, by projecting the state of a singular swarm system onto a consensus subspace and a complement consensus subspace, a necessary and sufficient condition for admissible consensus is presented in terms of linear matrix inequalities (LMIs). An approach to decrease the calculation complexity is proposed, by which only three LMIs independent of the number of agents need to be checked. Then, by using the changing variable method, sufficient conditions for admissible consensualization are shown. An explicit expression of the consensus function is given, and it is shown that the modes of the consensus function can be arbitrarily placed if each agent is R$R$-controllable and impulse controllable and the interaction topology has a spanning tree. Finally, theoretical results are applied to deal with cooperative control problems of multi-agent supporting systems.     

Accuracy analysis and stabilization design of the Fabry–Perot frequency discriminator in double-edge wind lidars

The measurement error of a double-edge wind lidar caused by a disturbed Fabry–Perot interferometer (FPI) is analyzed. Several error sources such as air pressure variations, temperature changes, and mechanical vibrations are considered in the measurement-error model. The simulation results show that a double-edge wind lidar is so sensitive to environmental variations that the measurement error reaches ±60 m/s if the FPI is not stabilized. In order to compensate the external disturbance acting on the FPI, a nonlinear proportional–integral–derivative (PID) control scheme is designed based on the transmission measurement of the calibration channel. An arc tangent function is used to improve the feedback gain of the usual PID control design. The results show that with the new controller the measurement accuracy of the wind lidar can be improved 4–5 times in comparison with the usual control design, and the range of the measurement error is only ±3 m/s.     

基于多项式模型的混沌系统平方和算法脉冲控制

针对一大类混沌系统,提出一种新颖的基于多项式模型的脉冲控制方法.首先,建立系统的多项式模型.其状态方程由系统状态的多项式矩阵与其单项式组成列向量构成.与其他建模方法相比,该方法不必使用任何预制的假设.其次,提出基于平方和优化算法的脉冲控制方法,使得混沌系统的状态能够实现渐近稳定.基于该算法的脉冲控制与基于线性矩阵不等式凸优化算法的结果相比,能得到更大的脉冲间距,从而可以使用较少的控制能量实现同样的控制效果.最后,仿真实验结果验证了本方法的有效性.