压电体椭圆孔边的力学分析

基于复变函数的方法,以PZT-4材料为例,分别采用精确电边界条件和非导通电边界条件进行了远场均匀载荷作用下的横观各向同性压电体椭圆孔的力学分析并与相关结果进行对比。结果表明当椭圆孔退化为圆孔时,无论在远场作用力载荷或电载荷,两种电边界条件下的结果均能完全吻合。随着椭圆孔的愈加尖锐化,非导通电边界条件逐渐不能适用。     

NANOPARTICLE DESIGN AND HANDLING--CHALLENGES FOR ENGINEERS AND PARTICLE TECHNOLOGISTS

In this paper, the opportunities and challenges which future applications based on nanoparticles offer to engineers are described. New high-added value products induce us to rethink ways to control nanoparticle design and handling. Several challenges are described and typical solutions are given: (1) finding relevant engineering tasks outside traditional process industry; (2) the importance of mixing reactants; (3) obtaining monodisperse particles; (4) gaining efficient control via electric forces and (5) developing multi-step processes which allow more control over particle properties.     

Mathematical Modeling,Control, Computer Simulation and Laboratory Experiments of a Spatial Servopneumatic Parallel Robot

In this paper (Part I), the special construction of a controlled parallel structure, called spatial servopneumatic multi-axles test facility (MAP), will be theoretically and numerically investigated and controlled. The investigations include the following steps: (i) design of mathematical models of different complexity of both, the test facility mechanics in terms of DAEs and ODEs (a multi-body system which contains 13 rigid bodies under spatial motion, connected by joints), and the servopneumatic actuators; (ii) construction of different linear and nonlinear (model based) control algorithms; (iii) development of a computer simulation program of the MAP; and (iv) evaluation of various computer simulation runs, obtained by applying different control algorithms and spatial command-input signals. The results show that the efficiency of the control algorithms is closely related to their complexity and cost. In order to check the closeness to reality of the computer simulation results and their benefit for industrial applications, laboratory experiments must be formed with the same MAP, the same control algorithms, and applying the same command-input signals which have been used in the computer simulations. These experimental investigations will be presented in Part II of the paper.     

Influence of the Geometry of a Piezotransformer Transducer on Its Electric Potential During Electroelastic Vibrations of a Piezoceramic Disk

The resonant radial vibrations of a thin piezoceramic disk with solid electrodes and thickness polarization are considered as an example to study the influence of the geometry of piezotransformer transducers on their electric potentials and the mutual influence of neighboring transducers__________Translated from Prikladnaya Mekhanika, Vol. 41, No. 2, pp. 75–80, February 2005.     

Flexoelectric vibration analysis of nanocomposite sandwich plates

Abstract

In the present study, free vibration of sandwich flexoelectric plates resting on Pasternak foundation is investigated. The top and bottom layers are under applied voltage based on flexoelectricity considerations and core is a nanocomposite plate where reinforced by carbon nanotubes. Based on first-order shear deformation theory, flexoelectricity considerations and Hamilton’s principle, the governing equations are derived for the first time. Navier’s method is used to solve the governing equations analytically in the case of simply supported sandwich plate. Finally, the effects of different parameters are discussed in details. It is found when thickness of flexoelectric face sheets increase, the frequency of nano-sandwich plate decrease. The results of this study can be useful in design and manufacturing of flexoelectric systems as sensor and actuator.     

基于近红外频域自适应分析法的电煤发热量模型研究（英文）

目前由于部分电站锅炉所用到的燃煤大多为配煤,在有些情况下,其复杂的物理化学特性导致难以获得高精确度的常规近红外定量分析模型,这给电煤发热量的在线检测带来了一定困难。针对该问题,深入研究了电煤近红外光谱时域和频域特征,提出一种能够通过全局优化策略自动在频域内建立最优近红外定量分析模型的新方法—频域自适应分析法。该方法首先将时域近红外光谱通过快速傅里叶变换转换为频域近红外信号;然后采用有效光谱能量率得到合适的频域信息范围;接着根据近红外光谱频域下的相关系数谱图、方差谱图以及谐波在频域中的坐标合理构建了频域信息量评价参数,利用该参数对模型输入变量的种群位置进行初始化;最后采用频域分区搜索和综合性能评价函数得到最佳建模方案。与此同时,结合电煤煤粉近红外图谱的特性,并以其发热量为待测目标对该方法进行了验证,取得相对较好实验效果,与传统方法主成分回归、偏最小二乘回归、反向传播神经网络以及基于遗传算法的偏最小二乘回归和支持向量机回归相比,该方法预测精度更高,并且有效避免了频域随机搜索潜在的过拟合和虚假有效模型的弊端,具有良好的应用前景。此外,该方法也可推广用于其他类型的光谱定量分析。     

Dipolar response and hydrogen-bond kinetics in liquid water in square-wave time-varying electric fields

Non-equilibrium molecular dynamics simulations of liquid water have been performed at 298 K in the presence of external time-varying electric fields, approximating a square wave, of varying peak intensity (0.005–0.1 V/Å) in the microwave to far-infrared frequency range (20–500 GHz). Significant non-thermal field effects were noted in terms of dipolar response and acceleration of hydrogen-bond kinetics. The coupling between the total dipole moment and the external field has been investigated and autocorrelation functions (ACFs) of both the total dipole moment and the average of the individual molecular dipole moment along the laboratory axis of the applied fields exhibited coupling, with the former showing a stronger coupling and the latter showing coupling to lower magnitude fields. The maximum alignment achieved has been computed as a function of field intensities and frequencies: the lower frequencies show a greater maximum alignment as the system had more time within each field cycle to respond. The normalised probability distribution and the hydrogen-bond ACFs have been computed: the ACF showed a clear effect over shortening the hydrogen-bond relaxation time. The field effects over the molecules’ transitions from four to five hydrogen bonds have been computed. There was an enhancement of fewer molecules undergoing transitions and a dampening for a larger proportion of molecules, depending on the external fields’ periods.     

Contact value relations and density functional theory for the electrical double layer

The recently developed contact-corrected density functional theory is applied to an electric double layer containing a valence and size symmetric electrolyte. The restricted primitive model is used to describe the electrolyte, and a non-polarisable, smooth, planar, uniformly charged hard surface is used to model the electrode. Comparison with Monte Carlo simulation results for this system shows that the theory satisfies the first contact value relation in line with the premise of the approach. Additionally, the theory is found to satisfy the semi-empirical second contact value relation quite closely. This is a welcome result, since no reference is made to this second relation nor is the relation used in the theoretical development. The second contact relation is closely related to the anomalous positive temperature derivative of the double layer capacitance at low temperature, low ion concentration, and low electrode charge, and indeed, the contact-corrected density functional theory predicts this effect.     

Endoscopic optical probe with a PZT actuator and MR tracker

A miniaturized optical probe with a magnetic-resistance (MR) position tracker and piezoelectric-transduce (PZT) mirror system was developed for endoscopic optical imaging. All of the optical components such as collimation and focal lenses, reflection mirror, PZT linear actuator and MR sensor were wholly packaged in a single scanning probe with a volume of 3.57 cm³. This endoscopic probe has the advantages of having a small volume, extended stroke length (4.5 mm), high scanning speed (18.2 mm/s), efficient recoupling ratio (78.3%) and high spatial resolution (11.7 μm) compared to conventional endoscopes. Consequently, it showed the potential for improving the endoscopic imaging system and utilizing the image-guided robotic surgery system.     

线性磁场装置的研制及实验研究

介绍了一种可获取线性磁场的装置。该装置由两匝数及半径相同的环形线圈组成,相向平行同轴放置,两线圈之间的距离等于线圈半径,通以大小相同,方向相反的电流,可获得磁感应强度与其线圈中心轴线位置成线性关系的区域。此装置不仅具有独创性,更有实时性及可调的优点,可将其拓展到实际应用,尤其是传感领域,有重要的应用前景和经济价值。