Electromagnetic silicon MEMS resonator

We have fabricated a silicon MEMS resonator aiming at multimodal sensors, and evaluated vibration characteristics by electromagnetic drive and induced electromotive force detection. The resonance frequency of the driving voltage of 0.6 Vpp shows torsional vibration of approximately 87 kHz, and the resonance frequency is shifted toward the low‐frequency side as the driving voltage increases. Resonance characteristics due to temperature change and film stress were evaluated.     

Applying silicon micromachining to cellular metabolism: measuringthe rate of acidification induced in the extracellular environment

Describes how a microphysiometer works and shows how silicon micromachining can be used to provide a multichannel capability. The authors consider extracellular acidification, metabolic rate detection, LAPS pH sensors, wells for the capture of nonadherent cells, and a multichannel flow-through microphysiometer chip     

Mathematical model of sapphire micromachining by CVD diamond coating tool

Abstract

A CVD diamond coating tool with prismatic crystal structure was prepared by hot filament chemical vapor deposition (HFCVD) method to improve sapphire’s lapping efficiency. The full plastic removal model of Sapphire (0001) plane is established based on the extended domain removal theory of hard and brittle materials such as sapphires. This model is used to analyze the effect of parameters such as prismatic particle’s size of the CVD diamond coating, lapping rate, lapping pressure, and material properties on the removal rate during the lapping process, and to predict the material removal rate, which lays the foundation for the high-efficiency micromachining of sapphire.     

Surface micromachined segmented mirrors for adaptive optics

This paper presents recent results for aberration correction and beam steering experiments using polysilicon surface micromachined piston micromirror arrays. Microfabricated deformable mirrors offer a substantial cost reduction for adaptive optic systems. In addition to the reduced mirror cost, microfabricated mirrors typically require low control voltages (less than 30 V), thus eliminating high-voltage amplifiers. The greatly reduced cost per channel of adaptive optic systems employing microfabricated deformable mirrors promise high-order aberration correction at low cost. Arrays of piston micromirrors with 128 active elements were tested. Mirror elements are on a 203-μm 12×12 square grid (with 16 inactive elements, four in each corner of the array). The overall array size is 2.4 mm square. The arrays were fabricated in a commercially available surface micromachining process. The cost per mirror array in this prototyping process is less than $200. Experimental results are presented for a hybrid correcting element comprised of a lenslet array and piston micromirror array, and for a piston micromirror array only. Also presented is a novel digital deflection micromirror that requires no digital to analog converters, further reducing the cost of adaptive optics systems     

基于BLT方程的电磁干扰建模

为了解决场线耦合下传输线负载端响应问题,基于BLT方程建模思想,利用电磁拓扑概念中的管道和节点概念构建了计算的物理模型;利用场线耦合、传输线理论结合叠加原理推导了线上负载干扰的计算方法;利用辐射场空间传播、传输线散射理论结合叠加原理推导了空间场的计算方法;对节点处的电压方程进行合并、整理得到了类似BLT方程的矩阵方程。计算结果表明,该分析方法不仅可计算传输线负载响应,还可计算空间电磁场。与其它论文计算结果的比较证实其模型、推导、计算的正确性。     

A 5-V operated MEMS variable optical attenuator by SOI bulk micromachining

We report the design, fabrication, and successful demonstration of microelectromechanical variable optical attenuator (VOA) using an electrostatic microtorsion mirror (0.6 mm in diameter) combined with a fiber-optic collimator. The VOA operates at low voltages (dc 5 V or less) for large optical attenuation (40 dB, corresponding to mirror angle of 0.3/spl deg/) and a fast response time (5 ms or faster). The mirror made of a bulk-micromachined silicon-on-insulator wafer has been designed to be shock resistant up to 500 G without any mechanical failure. We also have suppressed temperature dependence of optical performance to be less than /spl plusmn/0.5 dB at 10-dB attenuation in the range of -5/spl deg/C-70/spl deg/C by mechanically decoupling the parasitic bimorph effect from the electrostatic operation.     

Spot optical measurements on micromachined mirrors for photonic switching

This paper describes and compares three optical methods for performing spot measurements on micromachined mirrors, designed for photonic switching in fiberoptic networks. For static characterization, two spot-position detection systems, one based on a vidicon camera and the other based on a bidimensional silicon position sensitive detector (PSD), are illustrated, tested, and compared. Moreover, the dynamic behavior has been monitored with the PSD-based detection arrangement and with a semiconductor laser feedback interferometer. Advantages and drawbacks of these methods are highlighted. Testing is reported on torsional, silicon micromachined mirrors, with a single degree of freedom. High dc voltage for static measurements, and sinusoidal or white-noise or step excitation for dynamic characterization, have been used for mirror driving.     

基于辅助槽的汽车爪极发电机电磁振动削弱方法

探讨了在汽车发电机爪极上开辅助槽对其电磁振动的影响,采用机械阻抗法分析汽车发电机的空载电磁振动,研究了通过开辅助槽来削弱汽车发电机电磁激振力,从而降低电机的电磁振动。对一台36槽12极汽车发电机进行电磁和结构有限元仿真,利用麦克斯韦张量法分析了有无辅助槽时发电机的转矩脉动以及2阶激振力波的对比。理论分析和仿真结果表明选择合适的辅助槽能够有效的降低汽车发电机的电磁振动。     

无刷电磁弹射器中电磁力的仿真计算

设计了一个基于无刷直流直线电机的电磁弹射器模型，采用二维场仿真方法计算了模型的电磁力静态特性曲线，分析了结构参数如气隙长度，磁钢厚度，铁磁材料特性等对电磁力特性的影响，该分析对模型的设计具有重要的指导意义。     

Large deflection micromechanical scanning mirrors for linear scansand pattern generation

An electrostatically driven silicon micro scanning mirror (MSM) for one-dimensional (1-D) and two-dimensional (2-D) deflection of light is presented. A special configuration of the driving electrodes allows the use of small electrode gaps without restricting the deflection of the plate geometrically. In this paper, the starting of the oscillation and the operation of the scanner is discussed. Experimental results show that scan angles of up to 60° can be achieved at a driving voltage of only 20 V. The 2-D deflection of a laser beam is obtained by a gimbal mounting of the mirror plate. For the fabrication of the devices, SOI-wafers are used as the base material. The mechanical structures are defined by a deep silicon etch. For the electrical isolation of areas on the movable frame, polysilicon-filled trenches are used. The mechanical stability of the scanners is tested. The devices resist shocks of more than 1000 g and show no change of the resonance frequency even after long run tests of 7×10⁹ periods     

利用频谱分析仪进行电磁干扰预测试

电子产品的电磁干扰经常在屏蔽暗室进行测量甚至调试,往往带来高昂的费用,而在测量前利用频谱分析仪来进行预测试,可以有效的缩短暗室的调试测量时间,从而降低成本。RIGOL的DSA815频谱分析仪具有准峰值检波和EMI测量功能,用近场探头或天线探测被测设备,可以快捷的对被测设备的电磁干扰情况进行预测试。     

Electromagnetic effects excited by magnetic loops

Contents An analysis is made of the electromagnetic effects in the space around magnetic loops moving in inertial systems. The methods of the relativistic electrodynamics, a four-dimensional potential, and the concepts of a model of a magnetic charge have been used. The obtained results allow to correct certain inaccuracies connected with the application of the magnetic loops theory. Conclusions are made about the applicability and the perspectives concerning the development of the magnetic loops theory.

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Elektromagnetische Effekte die durch magnetische Kreise angeregt werden

Übersicht Es werden elektromagnetische Effekte von sich in Inertialsystemen bewegenden magnetischen Kreisen analysiert. Man wendet Methoden der Relativitätselektrodynamik, das vierdimensionale Potential, die Darstellungsmodelle der magnetischen Ladung und die entsprechenden Tensoren des Elektromagnetischen Feldes an. Die gewonnenen Ergebnisse gestatten es bestimmte Ungenauigkeiten in den existierenden Anwendungen der Theorie der magnetischen Kreise zu korrigieren. Es werden Schlußfolgerungen bezüglich der Praxis und der Perspektiven der Entwicklung und Anwendung der Theorie magnetischer Anregungskreise gemacht.

     

Modeling of Cu-linked rectification devices by varying torsion angles

Using the nonequilibrium Green’s function (NEGF) method in combination with the density functional theory (DFT), we have analyzed the rectifying performance in Cu-linked molecular devices by varying torsion angles (φ=0^°–90^°). The linking effect of Cu atom has been investigated by calculating current-voltage (I-V) characteristics, rectification performance, transmission functions, projected density of states (PDOS), and molecular projected self-consistent Hamiltonian (MPSH). Present calculations revealed that linking of Cu in combination with conjugated dithiocarboxylate (-CS₂) and standard thiol linkers significantly affects the metal-molecule coupling asymmetry, and thus the rectifying behavior in molecular devices. Further, the subsequent studies show that the left-right combination of -CS₂ linker and Cu atom displays higher rectification ratio at various torsion angles in gold–biphenyl–gold junctions than thiol and Cu linkers. The calculated results are helpful not only in predicting an optimal combination of linking groups for realistic applications but also provide the way for better control of rectification effects in molecular devices.     

电磁脉冲环境下电磁继电器温度场仿真

对电磁脉冲（EMP）环境下的电磁继电器温度场分布进行了三维有限元热电耦合仿真。在建立热分析模型时对热源进行了等效处理,通过电路仿真得到了电磁脉冲在电磁继电器接触系统回路中引入的干扰电流。在仿真中基于热相似理论计算了电磁继电器各向表面的对流散热系数,考虑了连接导线对散热的影响,得到电磁继电器的温度场分布。     

电磁元件的误差补偿

提出了电磁元件的多种误差补偿法，这些补偿法可显著提高电磁元件的精度和性能，提高产品成品率。     

Double antireflection coating layer with silicon nitride and silicon oxide for crystalline silicon solar cell

Anti-reflection coating (ARC) film effectively reduces the reflection of sunlight on the silicon wafer surface and then increases substantially the solar cell conversion efficiency. In this work, we carried out experiments to lessen the reflectance and thus improve the conversion efficiency with double AR coating layer with silicon nitride and silicon oxide by plasma enhanced chemical vapor deposition (PECVD) for the silicon solar cells. The optimized thicknesses and refractive indices of each ARC layer were calculated with Essential Macleod program and the theoretical method. The single antireflection layer of silicon nitride was applied with 800 Å thickness and its cell showed the conversion efficiency as 17.45 %. For the double layer AR coating (DLARC), silicon nitride layer was deposited first using SiH₄ and NH₃, and then, silicon oxide was deposited with SiH₄ and N₂O. The thicknesses of SiN_x and SiO₂ were 800 Å and 1400 Å for DLARC-1 and 500 Å and 1000 Å for DLARC-2, respectively. As a result, the reflectance of DLARCs was lower than single SiN_x and then yielded increase of short-circuit current and conversion efficiency. The completed solar cell with DLARCs showed conversion efficiencies of 17.57 % for DLARC-1 and 17.76 % for DLARC-2. This indicates that the double AR coating layer is effective to obtain the high efficiency solar cell with PECVD.     

利用定子槽口宽度削弱永磁电机电磁噪声研究

着重研究了永磁电机定子槽口宽度对电磁噪声的影响。通过电磁力解析计算得出电磁力与定子槽口宽度的计算关系。利用Ansoft软件对1台电动汽车用永磁电机进行电磁场计算,求解改变定子槽口宽度对电磁力波的影响,并用ANSYS软件对该永磁电机进行不同定子槽口宽度的2D声场计算。进行了试验验证,仿真计算与试验结果基本一致,可为该类电机削弱噪声设计计算提供参考。     

电磁超声检测系统中消除电磁干扰电路的设计

电磁超声技术作为一种非接触式探伤技术在恶劣工况条件下具有广泛的应用前景,然而其发射电路产生的以共模噪声为主的脉冲电磁干扰会影响检测电路的接收效果进而产生误检。针对该问题,设计了消除电磁干扰的硬件电路,构建了具有高速、高共模抑制比、高输入阻抗以及低噪等特点的复合仪表放大器。电路用高速低噪双通道ADA4817-2作为输入增益级放大器,后接高共模抑制性能的AD8429仪表运放,提高了电路对噪声的抑制能力。在工况下进行测试,结果表明该电路能够实现共模噪声的有效消除。     

Force Distributions Produced by an Electromagnetic Mold

The electromagnetic force and consequent fluid flow patterns that can occur in a conventional electromagnetic mold for continuous casting of aluminum are described. The role of system geometry, specifically the placement of the confinement coil and shield, is examined in detail. The distribution of electromagnetic pressure as well as the curl of the lorentz force are presented. The effect of frequency is also considered. The coupled circuit method is used to predict the current density distribution for a specific mold geometry. The induced currents are then used to predict the pressures and forces. Nonlinear stream function/vorticity equations are solved under the assumption of constant turbulent viscosity to obtain the flow patterns. The role of the screen in shaping the force patterns is critically examined.     

无单元法在电磁场数值计算中的应用研究

无单元法的突出特点是可以求解复杂边界条件的边值问题 ,它可以根据场函数的特性布置随机节点 ,只需节点信息 ,无需单元信息 ,解决了有限元方法中前处理困难的问题 ,它的理论基础是滑动最小二乘法。其基本思想是将计算场域离散成若干节点 ,由滑动最小二乘法来拟合场函数 ,从而摆脱了单元的限制 ,具有精度高、计算速度快的特点 ,是解决工程电磁场问题的又一新的有效方法