Test on Sensor Effect of Cement Matrix Piezoelectric Composite

A novel cement matrix smart piezoelectric composite and its application as sensing element are presented. A cement matrix smart piezoelectric composite piece encapsulated in a cement mortar formed a practical sensor, and it was tested on material test system with cyclic loading. According to the theoretical analysis, the function of the cement matrix piezoelectric sensor output voltage was expressed in terms of the magnitude of the input cyclic loading amplitude and frequency. The curve fitting of gain function that is defined as sensor‘s gain factor under different frequencies of input loading was carried out. From the results of curve fitting, it is found that the cement matrix smart piezoelectric composite has a simple relationship between input loading and output voltage. Therefore the cement matrix piezoelectric composite sensor is suitable to be applied in structural health monitoring.     

辅助性胶凝材料在水泥工业中的应用研究

辅助性胶凝材料是水泥工业应用中的重要组成材料之一。使用辅助性胶凝材料能降低水泥用量,延长水泥基材料的使用寿命,提高水泥应用效率,间接降低生产水泥的能耗、减少CO2排放。本文首先阐述了辅助性胶凝材料的分类和作用及其在水泥中的应用;分别介绍了辅助性胶凝材料对水泥基材料力学性能和体积稳定性的研究进展;最后对辅助性胶凝材料研究趋势进行了展望。     

基于NPSA算法的ZnO镀膜光纤传感器反射系数研究

根据ZnO镀膜光纤传感器的几何结构和等效网络模型,建立了目标函数压电层反射系数模型。提出了一种交叉算子的小生境粒子群算法,优化后的压电层反射系数收敛性较高,入射波的接收效率大大提高。得出了一系列器件参数数据,为ZnO镀膜光纤声光相位传感器的制作提供了理论参考。     

Adaptive Lagrange finite element methods for high precision vibrations and piezoelectric acoustic wave computations in SMT structures and plates with nano interfaces

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基于射频和NB-IoT的危房监测系统设计

为解决危旧房屋状态的实时监测预警问题,设计了基于无线传感网的危房监测系统。利用加速度传感器实时采集房屋状态信息,改进传感器标定算法,采用温度分段式六位置标定法提高精度。数据传输采用射频通信和NB-IoT网络,根据实际房屋结构设计低功耗的路由算法,保证数据可靠传输。最终实现了高精度低功耗的远程监控方案,使决策者通过手机就能实时掌握房屋状态,提高房屋倾角监测精度,误差低于0.1°。     

Adaptive lagrange finite element methods for high precision vibrations and piezoelectric acoustic wave computations in SMT structures and plates with nano interfaces

This paper discusses the validity of (adaptive) Lagrange generalized plain finite element method (FEM) and plate element method for accurate analysis of acoustic waves in multi-layered piezoelectric structures with tiny interfaces between metal electrodes and surface mounted piezoelectric substrates. We have come to conclusion that the quantitative relationships between the acoustic and electric fields in a piezoelectric structure can be accurately determined through the proposed finite element methods. The higher-order Lagrange FEM proposed for dynamic piezoelectric computation is proved to be very accurate (prescribed relative error 0.02%–0.04%) and a great improvement in convergence accuracy over the higher order Mindlin plate element method for piezoelectric structural analysis due to the assumptions and corrections in the plate theories. The converged Lagrange finite element methods are compared with the plate element methods and the computed results are in good agreement with available exact and experimental data. The adaptive Lagrange finite element methods and a new FEA computer program developed for macro- and micro-scale analyses are reviewed, and recently extended with great potential to high-precision nano-scale analysis in this paper and the similarities between piezoelectric and seismic wave propagations in layered structures and plates are stressed. Project supported by SRF for ROCS, SEM of China and partially by Zhejiang Provincial Natural Science Foundation (NSF) of China.     

Evaluation of the pull-out strength of galvanised steel strips in a cement-based material

The study of the interfacial and bond behaviour of reinforced cement-based materials is important for understanding the mechanical behaviour of such composites. This paper presents extensive experimental, theoretical and finite element analyses of pull-out tests of galvanised steel strips with different geometries, in lightweight cement-based material blocks with different densities and mechanical properties. The theoretical model proposed here is capable of determining the pull-out strength and bond stress versus the slip relationship between components of reinforced cement-based materials. This bond-slip relationship is then implemented in finite element simulation through the user-defined subroutine of ABAQUS software. Based on the results, a trilinear bond-slip model is suitable for modelling the interface between a steel strip and a cement-based material interface.     

利用线阵CCD的迈克尔逊干涉仪测量压电材料的压电系数

将压电陶瓷片固定在迈克尔逊干涉仪的移动镜上,当加在压电陶瓷片上的驱动直流电压增加时,引起压电陶瓷的微小伸长进而引起移动镜的移动,引起光屏上干涉条纹环数目的变化;用线阵CCD(charge coupled device)作为光电传感器件捕捉干涉条纹的光强信号,再将电信号进行模数转换,采取USB接口与微机接口,用C++语言编写程序设计了一种新型的条纹自动计数软件,将这种计数方法与压电系数的测量结合起来,可以自动得出其压电系数.     

压电陶瓷材料参数对有限元结果的影响研究

根据压电陶瓷材料的压电效应,改变压电常数,基于阻抗分析法运用有限元分析,结合阻抗实验对比有限元结果,分析了该方法研究的可行性,讨论了各个压电常数对阻抗的影响规律,调整参数并确定了最利于有限元实验的材料参数,总结了有限元分析的研究意义.     

基于改进BESO算法的集材绞盘机卷筒优化设计

通过修正材料插值模型和引入应力均方差作为性能收敛指标,改进了基于von Mises应力的双向渐进结构拓扑优化(Bi-directional Evolutionary Structural Optimization, BESO)方法,并结合Abaqus有限元软件及MATLAB语言编程实现了该算法;在此基础上,优化设计了集材绞盘机摩擦卷筒,得到不同材料体积分数、不同旋转周期数时,摩擦卷筒的最优拓扑结构,在减轻质量的同时,降低了应力集中水平。优化结果对实现集材绞盘机摩擦卷筒轻量化设计具有工程指导意义。     

High-finesse displacement sensor and a theoretical accelerometer model based on a fiber Fabry-Perot interferometer

A displacement sensor based on the fiber Fabry-Perot （F-P） cavity was proposed in this paper. Theoretical and experimental analyses were presented. Displacement resolution was demonstrated by spectrum-domain experiments to obtain the dynamic range of the F-P sensor, and a piezoelectric crystal unit （PZT） was used as the driver. The output signal was modulated by a piezoelectric ceramic ring and demodulated by a phase-locked oscillator. The experimental results show that the displacement resolution of the F-P sensor is less than 5 nm and the dynamic range is more than 100 μm. As acceleration is the second-order differential of displacement, an accelerometer model was proposed using the finite element method （FEM） nd ANSYS software.     

Credibility and Security of Weighing System for Large Structure Object

The weighing system designed for large structure object is mainly composed of three parts. The part of hydraulic system is made up of hydraulic cylinders, high pressure hydraulic hoses and electric pumps; the part of computer controlling system comprises pressure sensors, displacement sensors, data acquisitions, RS 485 network and the computer controlling model; the part of loading system is composed of the fulcrum structure and the concrete girder. The measurement principle and composition of the weighing system are discussed in this paper. Credibility and security of the weighing system are fully considered during the design phase. The hydraulic system is controlled by pilot operated check valves in case of the sudden loss of system pressure. The states of all gauges and RS485 network are monitored by computer controlling system functioning in different modules. When the system is running incorrectly, it will be switched to manual mode and give alarm. The finite element method is employed to analyze fulcrum structure so that the system has enough intensity to be lifted. Hence the reliability of the whole system is enhanced.     

Optimization of threshold for local spectrum sensing with energy detector

Spectrum sensing is the first step of cognitive radio (CR). In this area, previous researches mostly consider distributed local nodes which are under identical channel conditions, hence uniform and fixed detection threshold is set with energy detector. However, the distributions of nodes in real environments are not quite the same. In this paper, the optimal threshold to minimize the total detection error over additive white Gaussion noise (AWGN) channel is derived firstly. Then the dynamic threshold scheme is proposed to reduce the average total detection error. Simulations have shown that, with this scheme, sensing performance is improved.     

Graphene Based Electrochemical Sensor for the Detection of Volatile Organic Compounds

Many household consumables contain volatile organic compounds(VOCs)as the active ingredient.Long term exposure to VOCs could cause various health problems,especially to the respiratory system.Graphene has attracted a lot of attention recently for its potential to be used as sensing material for VOCs.In this project we have constructed graphene/PVA composite based gas sensors for VOC detection.It was perceived that the polymer could introduce better selectivity to the sensor.Results suggest that the proposed sensor is highly sensitive to low molecular weight VOCs and that the manner in which the sensor respond to the vapour depends on the polarity or hydrophobicity of the vapour.     

小板块水泥混凝土路面温度应力影响因素分析

针对近年来农村公路水泥混凝土路面结构中出现的主要病害问题,介绍了小板块水泥混凝土路面温度应力的计算原理,以通用有限元软件ANSYS为基础,采用三维有限元法,对小板块水泥混凝土路面的温度应力进行分析,探讨了小板块水泥混凝土路面结构层参数对其温度应力的影响规律,为目前农村公路小板块水泥混凝土路面结构的设计应用及其后续理论研究提供了有益的参考.     

封闭法测平面度误差时不确定度的计算方法

在精密测量中要求对测量结果的不确定度进行评估 .本文通过实例分析 ,指出用封闭法测平面度误差时 ,测量结果不确定度应该按相关计算法求得 .这一方法大大改善了按独立测量计算不确定度存在的问题 ,提高了测量精度 .该法对平板检定具有一定的参考价值 .     

大体积混凝土施工中裂缝问题的探讨

大体积混凝土结构的裂缝问题是具有普遍性的技术问题。产生裂缝的原因很多，其主要因素是水泥的水化热产生的温度变形和混凝土的收缩变形的共同作用。对如何严格控制混凝土温度，降低内外温差，减小混凝土的收缩，确保大体积混凝土工程施工质量，就材料、配合比及施工方面提出一些技术性措施。     

掺合料和工艺条件对水泥基材料强度的影响

近年来掺粉煤灰水泥基材料的应用越来越广泛。文章主要研究了掺合料和工艺条件对水泥基材料强度的影响。试验结果表明,掺入的粉煤灰品质不同,对水泥基材料强度影响不同;水胶比的大小将会影响到水泥基材料的密实性等;掺粉煤灰水泥基材料前期强度增长慢,而后期较高。在配制上,可适当与减水剂和激发剂共同使用。     

数字式转速传感器的选型及应用研究

随着设备自动化程度的提高及传感检测技术的发展,旋转体的转速测量日益普遍,尤其是旋转体转速的数字化测量尤为重要。目前转速传感器种类很多,如何针对不同场合选择合适的数字式转速仪是很多技术人员关心的问题。电涡流式转速表、霍尔式转速表、光电式转速表、角编码器数字测速等比较常用,通过阐述数字式测速传感器的测速原理、使用特性及选型原则,为技术人员选用转速测量仪器提供一定的理论依据。     

Statistical algorithm for damage detection of concrete beams based on piezoelectric smart aggregate

The functional piezoelectric ceramic smart aggregate(SA) sensors and actuators,based on piezoelectric ceramic materials such as lead zirconium titanate(PZT),were embedded into the reinforced concrete beams with three-point bending under static loading for purposes of damage detection.The SA actuators generated the desired sine sweep excitation signals online and the SA sensors received and detected real-time signals before and after damage.The wavelet analysis and statistical characteristics about damage signals were used as a signal processing and analysis tool to extract the optimal damage information and establish a statistical damage detection algorithm.The damage index-based wavelet analysis and damage probability-based probability and statistics were proposed by PZT wavebased theory and active health monitoring technology.The results showed that the existence of cracks inside largely attenuated the amplitude of active monitoring signal after the damage of beam and the attenuation was related to the severity degree of damage.The innovative statistical algorithm of damage pattern detection based PZT-SA can effectively determine damage probability and damage degree,and provide a prediction for the critical damage location of reinforced concrete structures.The developed method can be utilized for the structural health comprehensive monitoring and damage detection on line of various large-scale concrete structures.