MATLAB在自动控制系统频域分析中的应用

首先通过对MATLAB语言特点的阐述,指出采用MATLAB进行控制系统频域分析存在的优势,然后以典型二阶系统为例。具体应用此软件完成了控制系统波德图的绘制和相关参数对系统性能影响的分析,最后对此软件在控制系统中广泛应用的前景进行了展望。     

烟酸分子的简正振动与拉曼光谱

利用量子化学软件计算得出了烟酸分子的平衡构形,基于这个构形,理论上计算出了烟酸分子的简正振动光谱,并与实验测得的结果进行了比较,最后对其简正振动模式进行了全面归属.     

钹式水听器的改进及仿真测试研究

钹式水听器体积小,灵敏度高,但是接收的性能不够稳定,接收频带比较窄.为了解决这个问题,文章对钹式水听器结构进行改进,将水听器中单片压电陶瓷晶片改成双片,减小晶片半径,采用并联电路.文中先对水听器进行静态分析,然后用有限元软件对改进前后的水听器进行模拟分析,最后在水池中进行实验.结果都证明了改进后的水听器接收频带变宽,频段内接收性能稳定,灵敏度依然较高.     

高频液压振动锤打桩的可打入性分析模型

分别从力学、运动学、能量守恒方程和运动规律的积分方程等方面进行阐述,总结了国外各种高频液压振动锤打桩的可打入性模型的相应原理、假设条件、判断方法及应注意的问题,最后指出了欲进一步预测高频振动锤打桩的可打入性应考虑的几个问题.     

基于FPGA的一个超混沌Lorenz系统设计与实现

在变形的Lorenz系统的基础上,提出了一个新的四维超混沌系统,并通过理论分析和数值仿真对该系统的基本动力学特性进行了深入研究,得到了该系统的Lyapunov指数谱和Lyapunov维数,还设计了一个数字电路进行实验,从电路实验中观察到了各种超混沌吸引子.     

Preparation of AIN thin films for film bulk acoustic resonator application by radio frequency sputtering

Aluminum nitride (AIN) thin films with high c-axis orientation have been prepared on a glass substrate with an A1bottom electrode by radio frequency (RF) reactive magnetron sputtering. Based on the analysis of Berg's hysteresis model, the improved sputtering system is realized without a hysteresis effect. A new control method for rapidly depositing highly c-axis oriented AIN thin films is proposed. The N2 concentration could be controlled by observing the changes in cathode voltage, to realize the optimum processing condition where the target could be fixed stably in the transition region, and both stoichiometric film composition and a high deposition rate could be obtained. Under a 500 W RF power of a target with a 6 cm diameter, a substrate temperature of 450 ℃, a target-substrate distance of 60 mm and a N2 concentration of 25%, AIN thin film with prefer-ential (002) orientation was deposited at 2.3 μm/h which is a much higher rate than previously achieved. Through X-ray diffraction (XRD) analysis, the full width at half maximum (FWHM) of AIN (002) was shown to be about 0.28°, which shows the good crystallinity and crystal orientation of AIN thin film. With other parameters held constant, any increase or decrease in N2 con-centration results in an increase in the FWHM of AIN.     

Property of critical excitation for moment-resisting frames subjected to horizontal and vertical simultaneous ground motions

It has often been reported that, when building structures are subjected to near-fault earthquake ground motions, horizontal and vertical impulsive inputs may cause critical damage during the first few seconds. In practical design of building structures, however, the safety check, taking into account the effect of multi-component ground motions, is hardly conducted except the design of important structures such as high-rise buildings and nuclear power plants. Ftirthel＇more, it is not clear how the correlation of multi-component ground motions influences the actual safety of structures. In this paper, the detailed property of critical excitation is discussed in association with the relationship between the characteristics of ground motions and those of structures. The properties of various auto power spectral density （PSD） functions of the horizontal and vertical ground motions are investigated, and those of the critical cross PSD function of these two-directional ground motions are found by a devised algorithm in a feasible complex plane. A closed-form expression is derived from the critical relation of the auto PSD functions of the simultaneous inputs. This critical excitation method provides us with a new approach for earthquake-resistant design against the possible future earthquake which causes the critical damages to buildings.     

双模腔中利用循环跃迁的人工原子实现频率转换

在双模腔中,利用循环布局跃迁的人工原子,给出了实现腔模场频率上转换和下转换的方案.其中,腔模和经典场与三能级人工原子的相互作用都是共振耦合.因此,系统的量子动力学操作处于较高的速度进行.从抑制退相干的角度看,这是非常有意义的.结果表明,制备人工原子在某个初态,可以实现腔模频率上转换和下转换操作.最后,简单说明了从腔模场的任意初态可产生双模压缩态.     

一种EPC Gen2 RFID标签时钟校准方法

设计了一种对Gen2 RFID标签的振荡器频率进行校准的方法. 该方法设计了时钟校准命令; 并给出了读写器使用时钟校准命令对标签时钟频率进行逐次逼近的校准过程. 验证结果表明,带有8位校准寄存器的电路可以把时钟偏差从50%校准到0.4%以内.     

g指数在共词分析主题词选取中的应用研究

为了克服共词分析中主题词选取主观性强的缺陷,借鉴g指数的思想,提出一种基于g指数的主题词选取方法——词频g指数。以图书情报学为例,对词频g指数进行了实证分析,并与齐普夫第二定律的选词结果进行比较,得出其选词结果很好的满足二八定律。同时对主题词进行聚类分析得到良好的结果,为共词分析的准确性提供了理论依据。