对“电机及拖动基础“课程教学方法的探讨

针对"电机及拖动基础"课程在教学过程中出现的一些问题,分析了问题出现的原因,并结合多年的教学实践经验,从4个方面提出了解决问题的方法.     

Nanoscale Flexoelectricity

Electromechanical effects are ubiquitous in biological and materials systems. Understanding the fundamentals of these coupling phenomena is critical to devising next‐generation electromechanical transducers. Piezoelectricity has been studied in detail, in both the bulk and at mesoscopic scales. Recently, an increasing amount of attention has been paid to flexoelectricity: electrical polarization induced by a strain gradient. While piezoelectricity requires crystalline structures with no inversion symmetry, flexoelectricity does not carry this requirement, since the effect is caused by inhomogeneous strains. Flexoelectricity explains many interesting electromechanical behaviors in hard crystalline materials and underpins core mechanoelectric transduction phenomena in soft biomaterials. Most excitingly, flexoelectricity is a size‐dependent effect which becomes more significant in nanoscale systems. With increasing interest in nanoscale and nano‐bio hybrid materials, flexoelectricity will continue to gain prominence. This Review summarizes work in this area. First, methods to amplify or manipulate the flexoelectric effect to enhance material properties will be investigated, particularly at nanometer scales. Next, the nature and history of these effects in soft biomaterials will be explored. Finally, some theoretical interpretations for the effect will be presented. Overall, flexoelectricity represents an exciting phenomenon which is expected to become more considerable as materials continue to shrink.     

高职高专《电机学》课程教学改革与实践

分析高职高专《电机学》课程特点及教学中存在问题,提出以培养职业能力为核心的《电机学》课程教学新模式;改革教学手段和方法、制订课程考核标准、改革考核方式,实现课程结构和内容的优化,突显高职教学特色。     

Viscoelectromechanics modeling of intestine wall hyperelasticity

Elastic-electroactive biological media are sensitive to both mechanical and electric forces. Their active behavior is often associated with the presence of reinforcing fibers and their excitation-contraction coupling is due to the interplay between the passive elastic tissue and the active muscular network. In this paper we focus on the theoretical framework of constitutive equations for viscous electroactive media. The approach is based on the additive decomposition of the Helmholtz free energy accompanied to the multiplicative decomposition of the deformation gradient in elastic, viscous and active parts. We describe a thermodynamically sound scenario that accounts for geometric and material nonlinearities.     

Additive Manufacturing of 3D‐Architected Multifunctional Metal Oxides

Additive manufacturing (AM) of complex three‐dimensional (3D) metal oxides at the micro‐ and nanoscales has attracted considerable attention in recent years. State‐of‐the‐art techniques that use slurry‐based or organic–inorganic photoresins are often hampered by challenges in resin preparation and synthesis, and/or by the limited resolution of patterned features. A facile process for fabricating 3D‐architected metal oxides via the use of an aqueous metal‐ion‐containing photoresin is presented. The efficacy of this process, which is termed photopolymer complex synthesis, is demonstrated by creating nanoarchitected zinc oxide (ZnO) architectures with feature sizes of 250 nm, by first patterning a zinc‐ion‐containing aqueous photoresin using two‐photon lithography and subsequently calcining them at 500 ºC. Transmission electron microscopy (TEM) analysis reveals their microstructure to be nanocrystalline ZnO with grain sizes of 5.1 ± 1.6 nm. In situ compression experiments conducted in a scanning electron microscope show an emergent electromechanical response: a 200 nm mechanical compression of an architected ZnO structure results in a voltage drop of 0.52 mV. This photopolymer complex synthesis provides a pathway to easily create arbitrarily shaped 3D metal oxides that could enable previously impossible devices and smart materials.     

单相电动机的无线遥控调速控制器

采用无线模块和嵌入式微控制器STM8S103F6,设计了一种单相电动机的无线遥控调速控制器,完成了控制器各部分功能模块的硬件设计,实现了单相电动机的正反转无线控制和数字PID调速控制。结果表明,该控制器运行平稳,可以满足不同负载的要求。     

直线电机的应用

阐述了在绿色制造理念指导下产生的绿色环保型产品 -直线感应电动机的应用特点及在国内外各行各业的广泛应用 ,说明直线电机是绿色环保型产品 ,具有广阔的应用前景     

Dielectric elastomers – numerical modeling of nonlinear visco‐electroelasticity

Dielectric elastomer actuators that can directly turn electrical energy into mechanical energy belong to the group of electroactive polymers. This type of electroelastic material exhibits large displacement characteristics and is able to change its mechanical behavior in response to the application of an electric field. Dielectric actuators are made out of elastomers which in general show viscoelastic behavior. To take this time dependent effect into account, the deformation gradient is multiplicatively decomposed. The paper is focused on the numerical modeling of soft dielectric elastomers. The theoretical foundation and the consistent finite element implementation is outlined based on the laws of electricity and elasticity. Furthermore, numerical examples of the nonlinear visco‐electroelasticity model are shown. Copyright © 2012 John Wiley & Sons, Ltd.     

Variational‐based modeling of micro‐electro‐elasticity with electric field‐driven and stress‐driven domain evolutions

Recently, increasing interest in so‐called functional or smart materials with electromechanical coupling has been shown such as ferroelectric piezoceramics. These materials are characterized by microstructural properties, which can be changed by external stress and electric field stimuli, and hence find use as the active components in sensors and actuators. The electromechanical coupling effects result from the existence and rearrangement of microstructural domains with uniformly oriented electric polarization. The understanding and efficient simulation of these highly nonlinear and dissipative mechanisms, which occur on the microscale of ferroelectric piezoceramics, are a key challenge of the current research. This paper does not offer a substantially new physical model of these phenomena but a new mathematical modeling approach based on a rigorous exploitation of rate‐type variational principles. This provides a new insight in the structure of the coupled problem, where the governing field equations appear as the Euler equations of a variational statement. We outline a variational‐based micro‐electro‐elastic model for the microstructural evolution of both electrically and mechanically driven electric domains in ferroelectric ceramics, which also incorporates the surrounding free space. To this end, we extend recently developed multifield incremental variational principles of electromechanics from local to gradient‐extended dissipative response and specialize it by a Ginzburg–Landau‐type phase field model, where the thickness of the domain walls enters the formulation as a length scale. This serves as a natural starting point for a canonical compact, symmetric finite element implementation, considering the mechanical displacement, the microscopic polarization, and the electric potential induced by the polarization as the primary fields. The latter is defined on both the solid domain and a surrounding free space. Numerical simulations treat domain wall motions for electric field‐driven and stress‐driven loading processes, including the expansion of the electric potential into the free space. Copyright © 2012 John Wiley & Sons, Ltd.     

点阵式打印机头的机电一体化分析

本文从机电一体化的观点出发,运用机电动力学方法,完成了计算机的点阵针式打印头的建模,并进行了数值模拟分析,且推导出“L”形打印头的磁路、电路和动力学方程,给出了相应的初始条件和边界条件.在此基础上,本文提出了一种解析积分与逐步数值积分相结合的方法,来求解该机电耦合响应的问题,从而导出了非线性联立常微分方程组.文中给出了有关打印头设计的一些有意义的结论,对提高打印速度和印字质量提供了一种计算机辅助设计手段.