磁致伸缩液位计信号拾取方法的研究与实现

采用磁致伸缩液位变送器对几种扭转波信号的检测方法进行比较,给出一种简便的信号拾取技术——压电陶瓷法,同时设计自适应电路解决了扭转波衰减的问题.     

基于C8051F410的新型大功率三相逆变器设计

介绍了一种新型大功率三相逆变器的设计方案,该设计以C8051F410单片机为核心,利用其内部资源PCA(可编程计数器阵列)产生SPWM(Sinusoidal PWM)波,输出的SPWM波经脉宽时间调整模块和逻辑处理电路处理后,再由逆变电路和正弦滤波器产生失真度很小的高效三相正弦交流电。并且由频率相位模块和反馈测量模块采集输出波形信号,以此对输出三相正弦交流电波形的频率和幅值进行自适应调节。     

TDLAS甲烷气体检测中驱动信号发生电路的设计

为了满足TDLAS甲烷气体检测要求,以STM32为核心,结合DAC8830、AD9833和OPA188芯片,设计一个驱动信号发生电路。实验数据表明:低频锯齿波信号和正弦波信号噪声小,有效滤除低频噪声干扰;将低频锯齿波信号与10k Hz正弦波叠加,使信号调制到较高频率,通过二倍频正弦波对检测信号进行分析,满足激光器对气体检测驱动信号的要求。     

数字显示式时控装置

该仪器应用数字计数原理,对水泥胶砂搅拌机和振动台等设备,实现精度较高的时间控制,并采用荧光数码管直接显示时间变化,便于操作者正确掌握加水和下料时间,醒目方便。仪器使用国产集成电路,结构简单,稳定可靠。经中国水泥质量监督控制中心、建材院和一些水泥厂试用,效果良好,深受使用者欢迎,评价较高,值得推广。一、仪器工作原理本机采用集成度较高的DC系列集成电路,组成标准信号、计数显示和逻辑控制等单元电路。原理如方框图1。交流电源50HzⅠ频讯号经抗干扰电路输入集成电路,分频而得秒脉冲讯号。仪器的定时精度直接取决于秒脉冲讯号的稳定度。采用市电分频作时间基准,其精度可比一般RC充放     

基于压电陶瓷的地聚合物砂浆强度发展监测研究

将压电陶瓷(PZT)智能骨料成对嵌入地聚合物砂浆试件内部,利用主动感应法监测不同龄期地聚合物砂浆压电应力波信号,将时域信号图分析和小波包能量分析相结合,探讨了压电信号能量变化与地聚合物砂浆强度变化的对应关系。时域信号图分析表明,随着地聚合物砂浆养护龄期的增加,压电陶瓷智能电压幅值逐步增加,反映了地聚合物砂浆抗压强度的变化过程。小波包能量分析表明,随龄期的增加,地聚合物砂浆抗压强度变化过程与压电信号幅值计算总能量具有一致性。基于地聚合物砂浆抗压强度试验结果与压电陶瓷应力波所计算的能量值,拟合出地聚合物砂浆强度与压电应力波信号计算总能量的相关函数关系。     

一种简易信号发生器的设计与仿真

信号发生器是电子实验室最常见仪表之一,在工程和教学中有广泛应用。本信号发生器以差动输入四运算放大器LM324为核心,主要运用模拟运算电路,可以产生正弦波、方波、三角波和单次脉冲信号。设计的创新之处在于增加输出调整电路并整合单脉冲发生功能。在Multisim 14.0环境下进行仿真分析验证了设计方案的可行性。这种信号发生器具有原理易懂、容易调试、成本低廉等优点,可作为高等院校电子技术教学、电子课程设计和电子创新大赛的参考电路。     

基于压电效应的纤维高性能混凝土损伤监测研究

以纤维掺量为变量制作48个混凝土试件,压电陶瓷传感器作为信号激励器和信号接收器置于混凝土试件表面。基于压电效应对玄武岩-聚丙烯纤维增强高性能混凝土(BPHPC)的损伤进行实时监测。通过对单掺、混掺纤维混凝土的压电应力波信号进行分析,得到基于小波包分析法的损伤指数(DI),并拟合出纤维掺量-荷载-DI的函数关系。结果表明:通过外观损伤状态和压电应力波信号变化定性评价试件的健康状态,纤维的掺入能够降低混凝土的外观损伤程度;单掺纤维混凝土的试件应力波信号幅值比混掺纤维混凝土试件大;玄武岩纤维体积掺量为0.15%、聚丙烯纤维体积掺量为0.10%时试件的DI最小,当DI超过0.8时,可以认为试件被完全破坏;试验数据和试验现象吻合良好,通过压电陶瓷实时监测BPHPC损伤有较高的可行性。     

RDX晶体颗粒压制中的声发射现象

在RDX晶体颗粒压制实验中,采用声发射信号检测系统获取压制过程产生的声发射信号.特征参数分析显示,颗粒压制时的声发射信号极为丰富,且信号幅度、波击计数(率)和上升时间随时间的变化曲线均能分成明显的3段,分别与颗粒压制过程的3个阶段,即流动重排、变形破碎和压实阶段相对应.声发射监测结果反映了压制过程中颗粒材料力学行为的变化,为研究颗粒压制过程的行为提供了可行的依据.     

仓式泵输送罐数计数器

水泥生产中用仓式泵输送罐数计算台时产量的做法被普遍使用着。因此输送罐数计数是否准确以及每次输送是否满罐操作就成为计量准确与否的关键。我们设计制作的这套计数装置解决了这一困扰生产的难题。与仓式泵配套的料满检测仪一般采用音叉式料位仪。当音叉探测到物料时,料位仪输出一继电器节点动作信号,我们用它作为计数装置的启动信号。该装置的最大特点是采用了Ｒ１Ｒ２Ｃ１与５５５时基集成电路构成的延时脉冲形成电路。该电路可以将仓式泵音叉料位计在临界仓满状态时可能产生的多次节点动作信号“屏蔽”掉,只在输送操作完成并延时ｔ…     

基于应力波的复合材料圆柱壳结构损伤概率成像研究

本文对复合材料圆柱壳结构健康监测进行了研究,采用应力波技术结合融合损伤概率成像算法,对损伤进行了监测和识别。首先通过在圆柱壳内壁设置压电传感器阵列,使用多通道阵列扫查系统依次在结构中激励和接收应力波信号;然后分别通过相关系数分析和盒维数分形分析方法处理信号,计算出不同传感器路径上的损伤指标;最后利用经过坐标变换以及图像融合方法改进的损伤概率成像算法,实现对复合材料圆柱壳结构中损伤的可视化识别。数值仿真和实验研究结果表明,应力波能够有效地监测和识别出复合材料圆柱壳结构中的损伤,所改进的融合概率成像算法能够提高损伤位置识别的精度。     

改进空分装置开车方案的可行性分析

通过分析原开车方案,依据液态氮气化强吸热制冷的特性,提出了向装置反吹气化氮、反充液氮来改进原开车方案,以求缩短空分装置启动。从安全角度分析论证了反充液氮引起的空分主要设备应力的变化情况,认为依靠现有设备改进空分开车方案的技术上、安全是可行的。实施改进开车方案具有明显的经济效益和社会效益。     

BOUNDARY VALUE PROBLEMS IN ELECTROFLUIDIZED AND MAGNETICALLY STABILIZED BEDS

The stress balance boundary condition at the free surface of a one dimensional electrofluidized or magnetically stabilized bed is reviewed. Conditions for zero interfacial force balance at the top of the bed are investigated. For the case of a uniformly fluidized bed, it is shown that a nonzero particle collision pressure is necessary for a force free bed surface. For the case where the collision pressure is neglected, it is shown that the electrofluidized or magnetically stabilized bed must be nonuniform at equilibrium. Stability criteria for a semi-infinite bed show that a critical field strength is necessary for stabilization. Below this critical condition the bed is convectively unstable. The temporal and spatial responses of a stabilized bed to small signal variations in superficial gas velocity, electrode position, and applied potential are calculated. Specific attention is directed to sinusoidal time variations in superficial gas velocity, where at low frequencies a standing wave character results for the fluidized bed variables.     

Dynamic stress responses at the edges of adhesive layers in lap strap joints of half-infinite length subjected to impact loads

Stress analyses of adhesively bonded lap joints having half-infinite lengths were performed using a half-closed-form approach. To simplify the boundary conditions, the lap strap joint configuration was adopted. The stress variation with respect to time at the edge of the adhesive layer in the joint configuration was investigated. The formulation of the joint kinematics using the dynamic Volkersen model yields simultaneous partial differential equations. The Laplace transforms of the equations yield simultaneous ordinary differential equations that can be solved assuming that the adherends of the joint have the same cross-sectional dimensions and are made of the same material. The transfer function between the stress or stress wave as inputs and shear stress histories at the edges of the adhesive layer as outputs is obtained. The response of the dynamic system can be described by a Bessel function when an impulse stress is applied to the joint. The indicial response of the joint can be calculated by the integration of the impulse response over time. The stress variation with time caused by the variable applied stress can also be calculated by convolution integration of the impulse response and the variable stress in the time domain. The transfer function of the dynamic system is more complex when a stress wave is applied. In this case, the impulse response of the system can be described with a series solution.     

新型高效正反旋转兼上下往复动搅拌器

对开发的正反旋转兼上下往复动搅拌器机械及原理作了简介，并对其宏观混合时间和搅拌功率做了实验考察，同时进行了性能评价。结果表明，该搅拌器适用于中低粘度体系，并对过渡流和湍流区域流体也具有优异的混合性能，但不适用于层流区域流体的混合。     

Digital Signal Processing for Optical Particle Counters in Order to Improve the Signal-to-Noise Ratio

ABSTRACT

Especially In clean technology optical particle counters with high flow rates, low detection limits with respect to particle size and a low false count rate are needed. The lower detection limit and the false count rate can be reduced if the SNR can be increased. In this paper, we present a method to increase the SNR for any given optical particle counter using electronics means. First, the process of signal formation is investigated and the quantities determining the signal are described. The task is then to extract the particle pulses from the mixture of signals. Current methods for signal detection are briefly described. Using the signal theory, a correlation receiver is designed which provides a maximum SNR at the filter exit. This receiver has built-in digital technology. It offers the possibility of on-line filtering of particle signals. The results show a distinct improvement of the SNR. The actual value is different for each individual optical particle counter. In the case of the clean room optical particle counter (TSI LPC 3751), the SNR increased by a factor of 2.06. This means that the lower detection limit can be reduced from 500 to 420 nm or that, without lowering of the detection limit, the security of false counting can be improved to greater than 6σ.     

Water presence detection in a concrete crack using smart aggregates

Liquid migrating into existing concrete cracks is a serious problem for the reliability of concrete structures and can sometimes induce full concrete structural failures. In this paper, the authors present recent research on water presence detection in concrete cracks using piezoceramic-based smart aggregate (SA) transducers. The active sensing approach, in which one piezoceramic transducer is used to generate stress waves and others are used to detect the stress wave responses, is adopted in this research. Cracks formed in concrete structures act as stress reliefs, which attenuate the energy of the signals received by the SAs. In case of a crack being filled with liquid, which changes the wave impedance, the piezoceramic transducers will report higher received energy levels. A wavelet packet-based approach is developed to provide calculated energy values of the received signal. These different values can help detect the liquid presence in a concrete crack. A concrete beam specimen with three embedded SAs was fabricated and tested. Experimental results verified that the SA-based active sensing approach can detect a concrete crack and further detect the liquid presence in the concrete crack.     

波状双螺杆元件混炼性能的数值模拟

借助聚合物流动分析软件Polyflow对半啮合同向/异向波状双螺杆元件和全啮合同向/异向常规双螺杆元件进行流场和混合性能的数值模拟,分析比较两者的剪切速率、混合指数、非弹性应力张量第一特征值、停留时间、时均混合效率、分离尺度等表征混合性能的特征参数,模拟分析结果表明,波状双螺杆元件具有更加优异的混炼性能。