月尘静电浮扬现象的理论模拟

对月球上的月尘静电浮扬现象进行了理论研究,对比分析了影响月球表面静电浮扬强弱的主要因素．研究过程分为两个步骤:首先采用一维PIC（particle in cell）模拟计算了月尘和月球表面的充电过程,然后基于这一结果引进试验粒子,对月尘的静电浮扬现象进行了分析研究．结果表明月尘的静电浮扬主要受两个因素的影响:太阳角和月尘颗粒的大小．月尘静电浮扬现象在日出日落时分更容易发生,即太阳角越小越容易引起剧烈的月尘浮扬现象;并且月尘粒径越小,其浮扬高度越高．     

静电电子回旋脉塞的动力学理论

本文从线性Vlasov-Maxwell方程出发,利用沿未扰轨道积分的方法,建立了同轴波导TE模、圆未扰平衡轨道静电电子回旋脉塞的动力学理论。研究表明:在静电电子回旋脉塞中,非相对论性回旋脉塞不稳定性与相对论性回旋脉塞不稳定性不仅可以同时存在,而且两者相互加强。文中给出了非相对论性静电电子回旋脉塞不稳定性发生的阈值条件以及不稳定性增长率公式。文中还对静电电子回旋脉塞和静磁电子回旋脉塞在群聚、负质量不稳定性等方面作了比较,阐明了这两种脉塞之间的异同之处。     

微加工静电超声传感器的动力学机制及其建模 *

通过对微加工静电超声传感器的动力学机制的深入研究发展了一个空气弹簧支撑的张力板模型 (tensile-plate-on-air-spring,简称为TDK模型 ) .该模型全面计及了气隙空气弹簧的刚度 ,膜片的弯曲刚度和平面张力这三个机械刚度及一个静电负刚度的影响 .根据这个模型通过适当选用传感器的几何结构 ,尺寸和材料 ,便可获得所需要的基频和带宽 ,从而为微加工超声传感器的研究和优化设计提供了一个可靠的理论基础 .     

静电MEMS开关的数学分析(英文)

本文研究在电压阶梯函数的驱动下,微电子机械系统含有阻尼项与不含阻尼项时的动态响应.对于受非线性弹性力作用的无阻尼静电开关系统,证明当电压低于临界值时,系统存在停滞时间、停滞位移;当电压高于临界值时,开关系统将在有限时间发生短路.对于含阻尼项的系统,稳定的开关电压是有限值,此时系统的位移将接近初始驱动差距的1/3.进一步估计静电开关短路发生的时间.     

静电电子迴旋脉塞

本文提出并研究一类新的不稳定性的概念,即静电电子迥旋脉塞不稳定性。文中求解了静电离心系统中电子的相对论运动方程,在此基础上,求得了静电电子迴旋脉塞的色散方程,并进行了详细的讨论。文中指出,在静电电子迥旋脉塞系统中,存在有两种不稳定性机理:一种是以Q=ω-k_∥v_∥一-mω₀=0为基础的不稳定性,它类似于静磁电子遇旋脉塞不稳定性。另一种是以Q₁²=(2-β_⊥0²)ω₀²-Q²=0为基础的,不稳定性,是本文首次提出的。     

拟弧长延拓法在静电激励MEMS吸合特性研究中的应用

在静电激励微机电系统MEMS(micro-electro-mechanical systems)吸合特性研究中,基于应变梯度理论的微梁结构的控制方程是非线性高阶微分方程,给方程的求解带来了困难.由于该问题的数学模型本质上是分叉问题,方程的解支上出现奇异点,而运用局部延拓法无法通过奇异点.因此,通过运用广义微分求积法将控制方程降阶离散,结合拟弧长延拓法使迭代顺利通过奇异点,求出了整个解曲线.结果表明,拟弧长延拓法能有效并准确地求解具有分叉现象的高阶微分方程问题,为精确预测静电激励MEMS的吸合电压提供有力帮助.     

非均匀介质中Zakharov系统的位力奇性解

研究非均匀介质中Zakharov系统的位力奇性解.该系统描述了静电势与等离子密度在静电极限意义下的相互作用.一方面,利用位力恒等式,在c₀=+∞时证明了所研究的Zakharov系统的有限时间爆破结果.另一方面,通过建立局部的位力恒等式并利用关于时间的Lyapunov函数的存在性,在00<+∞时得到了所研究的Zakharov系统具负能量的径向对称解的爆破结果.     

各向异性静态电磁场的本征理论

在物理表象的规范空间下研究了静电磁场方程,推导出了一阶模态形式的各向异性介质静电磁场的基本求解方程,从而得到了如下的理论结论:各向同性介质电或磁场为标量场;各向异性介质电或磁场则为失量场,其大小和方向与介质的异性子空间有关.以电各向异性介质为例,具体讨论了各向异性电场的规律.     

接地平面上突起一个部分多层介质柱的静电问题

本文应用双极坐标系求解了在垂直均匀电场中,置于接地平面上的部分多层电介质柱的静电问题,并由此给出了作为特殊情形时的部分导体柱的结果。最后,应用退化的双极坐标系求解了多层介质柱与接地平面相切时的场问题。     

KT-5C托卡马克等离子体中边缘扰动的传输特性

在KT-5C托卡马克上,利用外加驱动的静电探针调制等离子体边缘湍动的实验研究,不仅验证TEXT装置上的结果:外部激发的扰动能沿着磁场长距离传播,而横向传播尺度很短。并且还通过新的实验,观察到扰动传播的方向性和粒子种类相关性,显示了这种扰动沿着磁力线方向的长程传播实际上是由于对电子运动的调制而发生,是一种粒子模式。由动力学分析表明,在托卡马克等离子体中传播的这种模式可以用弹道模理论给出与实验结果完全一致的解释。     

Adomian decomposition method used for solving nonlinear pull-in behavior in electrostatic micro-actuators

Nonlinear pull-in behavior for different electrostatic micro-actuators were simulated in this study. The Adomian decomposition method was employed to overcome the difficulty in the nonlinear equation of motion. Because no iteration is required in solving the nonlinear deformation, the decomposition method is one of the most efficient methods for evaluating the unstable pull-in behavior of an electrostatic micro-actuator. To investigate the feasibility of applying the Adomian decomposition method in dealing with the nonlinear deflection equation in the micro-actuator problem, different types of micro-actuators, e.g., fixed-fixed beam actuator and cantilever beam actuator were studied and analyzed. The calculated results agreed well with those from the literature.     

Numerical Model for Electro-Mechanical Analysis Based on Finite Element Method

In this paper, we present a numerical procedure that can be used to model the electro-mechanical coupled behavior of the dielectric actuator domain. The equation describing the electrostatical part is given by the reduced form of the Maxwell equation and the electrostatic potential [1]. The mechanical problem is described by the constitutive equations and equilibrium equations. Using the finite element method, this technique is to divide a whole problem into sub-problems. The complexity of the original problem is therefore reduced by focusing only on the most relevant areas. A finite element analysis is then performed by applying the electrostatic Maxwell pressure as Neumann boundary conditions to compute the displacements. Once the displacement is computed, the electrostatic domain or the conductor is updated. Electrostatic analysis is performed on the updated geometry and the finite element method is then used to determine the change in potential due to geometric perturbations. Once the surface charge densities are known, the new electrostatic Maxwell pressure is computed. The mechanical and electrostatic analysis is repeated until an equilibrium state is computed. The procedure is demonstrated in the paper by the solution of some two-dimensional and three-dimensional problems. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Detection,isolation and identification of multiple actuator and sensor faults in nonlinear dynamic systems: Application to a waste water treatment process

The goal in many fault detection and isolation schemes is to increase the isolation and identification speed. This paper, presents a new approach of a nonlinear model based adaptive observer method, for detection, isolation and identification of actuator and sensor faults. Firstly, we will design a new method for the actuator fault problem where, after the fault detection and before the fault isolation, we will try to estimate the output of the instrument. The method is based on the formation of nonlinear observer banks where each bank isolates each actuator fault. Secondly, for the sensor problem we will reformulate the system by introducing a new state variable, so that an augmented system can be constructed to treat sensor faults as actuator faults. A method based on the design of an adaptive observers’ bank will be used for the fault treatment. These approaches use the system model and the outputs of the adaptive observers to generate residues. Residuals are defined in such way to isolate the faulty instrument after detecting the fault occurrence. The advantages of these methods are that we can treat not only single actuator and sensor faults but also multiple faults, more over the isolation time has been decreased. In this study, we consider that only abrupt faults in the system can occur. The validity of the methods will be tested firstly in simulation by using a nonlinear model of waste water treatment process with and without measurement noise and secondly with the same nonlinear model but by using this time real data.     

Proposing a Pretwisted Bimorph Actuator

Though only small strains are available in piezoceramic materials, bending actuators provide reasonable deflections. Due to beam kinematics bending actuators usually are slender beams having flat cross-sections. This feature allows for maximum deflection in one direction. However, the axis orthogonal to it usually is not actuated. Instead of combining two straight bending actuators to overcome this problem we propose a bending actuator which is pretwisted. Controlling the pretwisted actuator segment-wise provides bending in several independent directions as well. Investigated is a pretwisted bimorph, similar to a helicoid. The active elements along the beam axis are subdivided and controlled separately, hence allowing independent control of the curvature of each section. Herein we give a first characterization of the pretwisted bimorph actuator. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Empirical Modeling of a Hydraulic Actuator in a Vehicle Control System

The pressure information of a hydraulic actuator plays a key role in modern vehicle control and fault diagnosis. The difficulty in measuring pressure directly naturally motivates such an indirect approach as an observer whose accuracy depends heavily upon the availability of a high fidelity model of a hydraulic actuator. Notwithstanding its success in understanding the dynamics of the first principle model of a hydraulic actuator, it is not suited to controller/observer design due to its complexity. This paper presents an alternative to the first principle modeling methodology: an empirical approach to hydraulic actuator modeling. Linear and nonlinear system identification techniques are applied to obtain low-order models of a hydraulic actuator. Experimental results show how the empirical models reproduce the key features of a hydraulic actuator with sufficient accuracy.     

Complete solution of the electrostatic equilibrium problem for classical weights

In this paper we complete the solution of the electrostatic equilibrium problem for all classical weight functions. In particular we solve this problem for classical generalized Bessel, Jacobi on (0, +∞) and pseudo-Jacobi weights. In addition we present an elementary unified way of dealing with the electrostatic equilibrium problem, which depends on the weights satisfying the Pearson differential equation.     

On the flow around Glauert-Goldschmied body in the narrow channel and separation control strategy

Previously, there was tested a wire dielectric barrier discharge (DBD) plasma actuator to generate sufficiently strong ionic wind to affect freely developed boundary layer in the narrow channel. This paper will report about next step – to installation of actuator inside a streamlined body. The experiment will take place inside perspex rectangular (250 × 100 mm) channel and main task is to find the appropriate place for actuator fitting for three different flow regimes. Hence, the separation point and recirculation area will be investigated via PIV anemometry for base case and for active flow control methods (e.g. plasma actuator) as well as frequency spectrum of the flow will be evaluated to describe the nature of the flow. The measurement plane will be perpendicular to the bottom of the channel and in longitudinal level. These essential information will be used for actuator design, actuator embedding and to tune actuator frequency in order to suppress the recirculation area as much as possible. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Actuator fault detection and estimation for the Lur’e differential inclusion system

This paper deals with actuator fault detection and estimation for the Lur’e differential inclusion system. An adaptive full-order observer is used to detect the occurrence of the actuator fault. Then, based on a reduced-order observer, an approach to estimate the actuator fault is presented. A simulation of rotor system is given to illustrate the effectiveness of the proposed method.