冲击作用下七元石英传感器动态性能研究

石英传感器已被广泛应用于冲击波剖面应力的测量。通过1.16 GPa冲击作用下七元石英传感器与分流型、短路型单元石英传感器的对比实验研究表明:七元石英传感器测量单元的压电电流特征与短路型单元石英传感器基本相同;中心测量单元受边缘效应等因素的影响较小,压电电流斜升幅度相对最小,其性质类似于分流型单元石英传感器,可特别应用于空间非均匀冲击作用分布等的测量。     

压电传感器冲击滞后响应时间测量与分析

压电传感器作为机电换能器使用时响应迅速,使用冲击设备和测量系统对其进行了瞬态冲击滞后响应时间测量和分析.从传感器二阶系统的动态响应、应力波的传播角度出发,通过对滞后响应时间建模和分析,得到了影响该时间的因素,与传感器的结构参数、冲击激励的脉宽、是否有转接结构及安装力矩的大小有关.当传感器固有频率高、阻尼比小、激励脉宽窄、无转接结构和使用较大的安装力矩时,传感器具有更快的响应速度.     

一种采用压电矩形鼓和永磁铁的小型电流传感器研究

提出了一种采用压电矩形鼓和永磁铁的小型电流传感器。基于安培定律,永磁铁感受电流变化并驱动压电矩形鼓振动,压电矩形鼓因压电效应将振动转化为电信号输出,从而实现电流传感。利用有限元分析方法研究了电流传感器的一阶振动模态及其应力分布,并计算了电流传感器的灵敏度频率响应特性,其与实验结果较吻合。实验结果表明,该电流传感器在一阶谐振频率204 Hz处具有较高的灵敏度(0.95 V/A),在动态范围0.005 A～30 A内具有良好的线性度(0.3%);与采用压电悬臂梁结构的电流传感器相比,具有更好的稳定性。文中提出的传感器结构还可以应用于振动信号、磁场的长期不间断测量或监测。     

一种基于压电石英晶体的高g_n值加速度传感器

高gn值加速度传感器广泛地用于冲击加速度的测量。概述了对高gn值加速度传感器的需求;简述了压电式高gn值加速度传感器的结构原理;介绍了高gn值压电加速度传感器的设计方案;开发了一种压缩、双屏蔽套筒式、用压电石英材料进行能量转换的高gn值加速度传感器;用马希特锤击机和霍普金森杆进行了试验;试验表明:该加速度传感器动态范围和工作频段分别可以达到0~150 000gn和0~20 kHz,幅值线性度小于10%,满足弹上要求。     

一种采用压电复合音叉的电流传感器研究

针对当前非接触电流测量方式存在的灵敏度低、结构复杂等问题,本文提出了一种采用压电复合音叉的电流传感器用于非接触低频微弱电流测量,其结构由永磁体、弹性音叉、压电片及底座组成.当该传感器处于电线周围交变磁场中时,永磁体在磁场作用下产生扭矩并驱动弹性音叉臂及压电片产生形变;因压电效应,形变的压电片两端电极之间输出交变电压信号,从而实现电流的测量.由于磁扭矩效应,这种传感器具有较高的谐振灵敏度,大约是压电悬臂梁式电流传感器的4.0倍;在负载电阻为10 MΩ、频率为41.7 Hz时,灵敏度可达1.393 V/A,线性度约为0.57%.这种压电复合音叉式电流传感器模型还可以应用于微弱振动、磁场信号探测等.     

利用Msc.dytran优化高冲击压电式加速度传感器设计

为优化压电式加速度传感器设计,提高其量程,用瞬态动力学仿真软件Msc.dytran对中心压缩型压电式加速度传感器在导弹碰靶过程中的加速度和动态应力进行模拟仿真。结果表明：对于结构一定的传感器,压电片厚度存在一个最佳值,可以通过仿真选择较好的材料组合（如,基座选铝、压电材料选石英）来减小透射到压电片中的应力波强度,以提高传感器的量程。     

控制电位型水中臭氧电化学传感器的试验研究

阐述了控制电位型水中臭氧电化学传感器的结构及其原理,通过对循环伏安曲线、极化曲线和不同电位时的电流响应对比曲线的综合分析,得出控制电位为0.50 V时传感器电流响应线性度好、灵敏度高。此外,设计并应用了电位控制和测量电路,实现了对传感器的电位控制以及输出信号的处理。     

光纤Bragg光栅传感器高速冲击试验研究

光纤Bragg光栅是一种性能优良的敏感元件,光纤Bragg光栅传感器在很多领域得到了应用.通过霍普金森压杆上的冲击试验研究了光纤光栅的动态响应能力.试验表明Bragg光栅能够正确响应不同频率的冲击信号,解调仪能够正确并快速解调出高速动态激励信号,同时Bragg光栅在受拉和受压时以及动态和静态灵敏度基本一致.光纤光栅传感器能够应用于武器侵彻爆炸等强冲击、恶劣环境下动态应力应变的测试.     

瞬态冲击电流测量传感系统的研究

本文根据瞬态冲击电流的特点 ,探讨了符合国际电工委员会标准要求的测量系统 ,并以对雷电浪涌发生器短路电流波形为例 ,提出了用罗柯夫斯基线圈作为测量传感器的测量系统设计方案 ,该测量系统可用于静电放电电流、雷电电流等瞬态电流的测量。     

压电石英在岩土压力测量中的应用前景

木文把压电石英传感器的固有特点与岩土介质压力测量的特殊要求有机地联系起来,论述了压电石英及传感器在岩土压力测量中,具有匹配件性能稳定、宽量程范围内线性好、频响特性好、稳定性好等待。同时,介绍了几种传感器的综合性能和现场应用简况,从而展示了压电石英压力传感器在岩土工程中的应用前景。     

超导磁共振主磁体励磁测控系统设计与开发

医用超导磁共振主磁体在励磁过程中出现的交流损耗和传导漏热等情况,是超导磁体失超的根本原因;为了控制和保证励磁过程的稳定性、可靠性和安全性,开发和完善励磁的测控系统就显得格外重要;设计并开发了基于LabVIEW平台的超导磁共振主磁体励磁测控系统;系统数据通过在虚拟仪器平台上调用动态链接库文件(DLL),控制泰克公司KE2700系列集成式采集卡采集得到;传感器选择根据相应功能需要配置;操作台仪器控制、数据采集程序和人机界面由LabVIEW编写;搭配保护电路,保护超导线圈,降低失超损失;实现数据采集、参数控制、失超保护、匀场测试等功能。系统满足设计开发目的,平台搭建稳定可靠;功能相对完善,具体操作简易,交互界面友好,后期修改和功能扩展灵活;经工程实际运行测试验证,提高了研究和工作效率,达到设计要求,有实际应用价值。     

Control of serial microfluidic droplet size gradient by step-wise ramping of flow rates

This paper describes a method to control and detect droplet size gradient by step-wise flow rate ramping of water-in-oil droplets in a microfluidic device. The droplets are generated in a cross channel device with two oil inlets and a water inlet. The droplet images are captured and analyzed in a time sequence in order to quantify the droplet generation frequency. It is demonstrated that by controlling the ramping of the oil flow rates it is possible to manipulate the ramping of droplet sizes. Increasing or decreasing of droplet sizes is achieved for a step-wise triangular ramping profile of the oil flow rate. The dynamic behavior of droplets due to the step-wise flow pulses is investigated. Uniform linear size ramping of water-in-oil droplets from 73 to 83 μm in diameter is generated with an oil flow ramping range from 1 to 11 μL/min in a minimum of five steps while water flow rate is held constant at 2 μL/min.     

石英晶体压电式力传感器的 单晶【djm】转换及晶组的排列与组合

本文深入研究了石英晶体的[d_(jm)]较换,晶组的排列与组合,从压电原理与工艺理论方面给出了单元与复合晶组的构成形式。对一些新形式的传感器在理论与实践方面给以明确的阐述。 本文不仅对压电式传感器研制与使用有重要的意义,而且对新型传感器的开拓具有重要的参考价值。     

A contact-type piezoresistive micro-shear stress sensor forabove-knee prosthesis application

A prototype contact-type micro piezoresistive shear-stress sensor that can be utilized to measure the shear stress between skin of stump and socket of above-knee (AK) prosthesis was designed, fabricated and tested. Micro-electro-mechanical system (MEMS) technology has been chosen for the design because of the low cost, small size and adaptability to this application. In this paper, the finite element method (FEM) package ANSYS has been employed for the stress analysis of the micro shear-stress sensors. The sensors contain two transducers that will transform the stresses into an output voltage. In the developed sensor, a 3000×3000×300 μm³ square membrane is formed by bulk micromachining of an n-type (100) monolithic silicon. The piezoresistive strain gauges were implanted with boron ions with a dose of 10¹⁵ atoms/cm². Static characteristics of the shear sensor were determined through a series of calibration tests. The fabricated sensor exhibits a sensitivity of 0.13 mV/mA-MPa for a 1.4 N full scales shear force range and the overall mean hysteresis error is than 3.5%. In addition, the results simulated by FEM are validated by comparison with experimental investigations     

The Generating Power of Total Deterministic Tree Transducers

Attributed tree transducers are abstract models used to study properties of attribute grammars. One abstraction which occurs when modeling attribute grammars by attributed tree transducers is that arbitrary trees over a ranked alphabet are taken as input, instead of derivation trees of a context-free grammar. In this paper we show that with respect to the generating power this isnotan abstraction; i.e., we show that attributed tree transducers and attribute grammars generate the same class of term (or tree) languages. To prove this, a number of results concerning the generating power of top-down tree transducers are established, which are interesting in their own. We also show that the classes of output languages of attributed tree transducers form a hierarchy with respect to the number of attributes. The latter result is achieved by proving a hierarchy of classes of tree languages generated by context-free hypergraph grammars with respect to their rank.     

Very‐sensitive direct measurement of plasma‐display exoemission

Abstract— The exoemission of electrons from the MgO cathode surface has a great impact on many properties of plasma displays and needs to be carefully engineered for successful display products. A method for direct measurement of this exoemission current using an ultra‐high‐impedance amplifier, which detects the integrated exoemission charge collected by a capacitance, is presented. The large discharge and displacement currents initiated by the changing sustain waveform, which could overload and saturate the sensitive amplifier, are shorted by a very low impedance switch in the form of a common reed relay. The exoemission current from the MgO cathode is significantly amplified by avalanches in the gas, and thus methods for directly measuring the avalanche amplification factor so as to correct the measured current and obtain the true exoemission current from the cathode are described. This highly variable avalanche amplification factor is measured and estimated to be as large as 500 when the voltage across the gas is just below breakdown. Methods are covered to correct for the small ion currents that flow in the plasma‐panel soda glass substrates and that add an unwanted error signal. Practical circuit techniques for measuring the very small exoemission currents are presented.     

基于EDEM的高压熔断器填料密实度研究

高压熔断器是一种用在高压线路和配电系统中的保护装置,可对故障电路予以安全保护。其结构中石英砂填料的密实度对熔断器的安全性能至关重要,为此本文探究了一种径向冲击旋转熔管的方式来解决熔断器中填料的密实度问题。石英砂颗粒在冲击作用下进行位置的重新排列来降低孔隙率,进而提高填充密实度。本文采用离散元素法,建立了颗粒接触过程的动力学方程,应用EDEM软件模拟了石英砂的振动过程,并通过石英砂填料的填充实验进行了验证。结果证明:径向冲击旋转熔管方式可以使熔管填料的平均密实度达到1.65 g/cm3的密实度要求,同时随着振动时间的增加填充密实度表现出先增加后稳定的规律。     

加权数据融合方法在多声道超声波流量计测量中的应用

针对多声道超声波流量计在流体流速测量时由于单个或多个换能器不能正常工作而导致测量存在误差的问题。提出在多传感器数据融合理论的基础上对其进行改进,使其适用于多声道超声波流量计的数据融合计算,同时改进后的最优加权数据融合方法能够在每次测量后自适应的计算最优权重系数。通过实验表明当流量计各声道均能正常工作时,该方法与Gauss-Jacobi积分法计算得到的流速值基本一致,当流量计单个声道不能正常工作时,应用该方法可以得到比Gauss-Jacobi积分法更加稳定的流速值,能够减小测量误差对计算结果的影响。     

石英挠性加速度计表头力矩器噪声模型研究

石英挠性加速度计的内部力矩器噪声对于高精度的加速度计应用系统的影响是不可忽视的,但很少引起高度重视.针对高精度加速度计电路应用需要,研究了力矩器机械热噪声和力矩器线圈谐振的影响,建立了表头内部力矩器噪声电路模型,设计了测试电路,并对噪声电路模型进行了测试与验证.理论和实验结果均表明:机械热噪声产生的等效加速度对系统影响较小,力矩器线圈影响的谐振与驱动方式及驱动频率有关,脉宽调制(PWM)波驱动方式较正弦波驱动方式产生的谐振影响更大,当驱动频率靠近谐振点时,产生毫安(mA)级的谐振电流.模型的建立对石英挠性加速度计应用具有较好的参考价值.