High-sensitivity fibre-optic strain sensors for measuring structural distortion

A high sensitivity fibre-optic microbend strain sensor for detecting bending of large mechanical structures has been constructed; experimental data on transmission modulation against structural strain are presented. Optical time domain reflectometry for detecting strains at several structural points simultaneously by placing many sensors in tandem along a single fibre is described. Structural bend radii of greater than 5 km have been measured.     

Resonant mechanical magnetic sensor in standard CMOS

A novel micromechanical magnetic sensor has been built and tested. The field is detected by measuring the vibration amplitude of a mechanical Lorentz force oscillator. This device is made from a standard 2-μm CMOS fabrication process with a post-processing etch step to undercut and release the sensor. When operated at the resonant frequency of the mechanical system, a sensitivity of 20 μV/G was measured     

High Sensitivity FBG Pressure Sensor Based on Mechanical Amplifier and Interrogation Using Tunable FBG Filter

A high sensitivity fiber Bragg grating pressure sensor by using mechanical amplifier is demonstrated. The measured pressure sensitivity is -1.80×10 -4 /MPa, which is about two orders of magnitude better than a simple monomode fiber with an in-fiber grating. The resolution of pressure measurement is 0.015 MPa based on interrogation using tunable fiber grating filter.     

Measurement of high electrical current density effects in solder joints

Measuring mechanical implications of high current densities in microelectronic packaging interconnects has always been a challenging goal. Due to small interconnect size this task has typically been accomplished by measuring the change in electrical resistance of the joint. This measurement parameter is global and does not give local mechanical state information. Also, understanding strain evolution in the solder over time is an important step toward developing a damage mechanics model.The real-time, full-field, strain displacement in a eutectic Sn/Pb solder joint during electrical current stressing was measured with Moiré interferometry (Post et al., High sensitivity Moire, Springer, New York, 1994) under in situ conditions. A finite element model simulation for thermal stressing was performed and compared with measured strain. The initial results show that the measured strain was largely due to thermal stressing versus the current density of 1.8 × 10² A/cm². A second Moiré interferometry experiment with thermal control distinguishes deformation of solder joint due to pure current stressing above 5000 A/cm².     

一种新型光纤Bragg光栅振动传感器的设计

为满足各种工程结构和机械系统的低频测试需求,设计并研制了一种特殊三脚支架和等强度悬臂梁结构的可放大振动信号、增加灵敏度和有较宽工作频带的光纤Bragg光栅(FBG)振动传感器,建立了传感器的数学模型,测试了传感器固有频率、灵敏度、失真系数和横向抗干扰能力等参数.实验表明,研制的FBG振动传感器,其同有频率约为100 H...     

电容式微传声器的性能模拟与优化设计

针对所研制的电容式微传声器在理想模式下的工作原理,建立了有限元分析模型和声电模型,从理论上分析了器件的机械性能、灵敏度以及频响特性,得出了结构优化的设计原则,即要想得到高灵敏度的微传声器器件,必须考虑采用尽可能小的空气隙厚度和声学孔尺寸以及具有较小内应力的声学振膜.为采用MEMS技术制备出高性能的电容式微传声器提供了理论基础.     

Mobile Ferroelastic Domain Walls in Nanocrystalline PZT Films: the Direct Piezoelectric Effect

Ferroelastic (90°) domain wall motion occurs readily in bulk samples of displacive ferroelectrics such as Pb(Zr,Ti)O₃ (PZT), dictating critical piezoelectric, dielectric, and polarization switching properties. Many prior studies have used converse piezoelectric measurements to probe the dynamics of ferroelastic domains in thin films; however, such experiments are strongly influenced by the mechanical clamping effect of the substrate, which inhibits electric field‐induced 90° domain wall motion. Nevertheless, these observations raise a tantalizing question: Does the application of mechanical stress, rather than electric field, result in an entirely different response in thin films? Here we report biaxial stress‐driven crystallographic reorientation of (100)/(001) textured, 70 nm thick Pb(Zr_0.25Ti_0.75)O₃ films via 90° domain wall motion, measured in situ by both x‐ray diffraction and piezoforce microscopy. Visual evidence of nanoscale mechanisms that underlie the direct piezoelectric effect is shown. Mobile 90° domain walls effect complete orientation switching in the grains in which they operate, without apparent wall pinning, indicating that bulk‐like ferroelastic behavior can extend to nanocrystalline films in the absence of substrate clamping.     

Analysis of a Microwave FET Oscillator Using an Efficient Computer Model for the Device

This paper presents a time domain analysis of a microwave 10-GHz FET oscillator, which employs a practical and efficient computer model for the FET. Good agreement is demonstrated between the predicted and measured performance. A sensitivity analysis of the circuit is performed with respect to some of the FET parameters. This is useful information to estimate variation in production.     

Electrooptic wafer beam deflector in LiTaO/sub 3/

A novel electrooptic beam deflector is reported based on ferroelectric domain inversion extending through the thickness of a Z-cut LiTaO/sub 3/ wafer. The selective domain inversion is achieved by electric-field poling assisted by proton exchange, rather than proton exchange followed by rapid thermal annealing. The deflection sensitivity of the device was measured to be 5.0 mrad/KV. This is 93% of the theoretical value for this geometry, and a significant improvement over the value of 80% of theoretical previously reported for a waveguide deflector. This improvement is attributed to the new domain inversion process. No degradation of deflection sensitivity is observed up to the frequency of 300 KHz, which is then limited by the response time of detectors.     

SnAgCu体钎料及BGA焊球焊点纳米级力学性能

为了研究低银Sn-0.3Ag-0.7Cu无铅体钎料、BGA焊料小球和BGA焊点的力学行为,基于物理反分析的方法采用纳米压痕仪对其进行实验。从压痕载荷–深度曲线提取出弹性模量、硬度和蠕变速率敏感指数。结果表明:体钎料的杨氏模量和蠕变速率敏感指数大约是BGA焊料小球和BGA焊点的2.5倍,验证了尺寸效应理论。采用纳米压痕仪测出的体钎料维氏硬度(15.101HV)小于显微硬度计的测量结果(20.660HV)。     

扭杆弹簧倾斜仪相关性能的实验研究

扭杆弹簧倾斜仪是一种结构简单的小型化倾斜仪,在工农业生产、地球物理和科学实验等方面有着广泛的应用.描述了扭杆弹簧倾斜仪的机械结构及工作原理,构建了扭杆弹簧倾斜仪原型,测定了扭杆弹簧倾斜仪的灵敏度和机械振子的本征频率,并对其温度特性和长期工作性能进行了实验研究.实验结果表明扭杆弹簧倾斜仪能实现对地面倾斜的精密测量.     

Optical time domain reflectometer using a photon-counting InGaAs/InP avalanche photodiode at 1.3 ?m

We report the first photon-counting optical time domain reflectometer using an InGaAsInP avalanche photodiode. The measured sensitivity at a temperature of ?40°C is comparable to that of the best present conventional PINFET receiver results.     

Crosstalk investigation of laser-diode pairs

The crosstalk between the lasers of different laser-diode pairs has been investigated experimentally in the frequency domain. The mutual crosstalk of two lasers diodes monolithically integrated on a single transmitter chip and separated by 100 μm was measured to be about -50 dB up to a modulation frequency of 100 MHz. At higher frequencies, it rises linearly with the frequency to -40 dB at 1 GHz. Measurements and calculations indicate that the origin of this crosstalk is the leakage current in the chip and inductive coupling of the bond wires. With these crosstalk values, digital data transmission at high bit rates is possible without significantly reducing the receiver sensitivity     

Mechanical signature analysis using time-frequency signalprocessing: application to internal combustion engine knock detection

Signature analysis consists of the extraction of information from measured signal patterns. The work presented in this paper illustrates the use of time-frequency (TF) analysis methods for the purpose of mechanical signature analysis. Mechanical signature analysis is a mature and developed field; however, TF analysis methods are relatively new to the field of mechanical signal processing, having mostly been developed in the present decade, and have not yet been applied to their full potential in this field of engineering applications. Some of the ongoing efforts are briefly reviewed in this paper. One important application of TF mechanical signature analysis is the diagnosis of faults in mechanical systems. In this paper we illustrate how the use of joint TF signal representations can result in tangible benefits when analyzing signatures generated by transient phenomena in mechanical systems, such as might be caused by faults or otherwise abnormal operation. This paper also explores signal detection concepts in the joint TF domain and presents their application to the detection of internal combustion engine knock     

Analysis and measurement of a broadband spiral antenna

A broadband spiral antenna (2 to 18 GHz) is modeled using the FDTD method. The inner turn of the antenna is an Archimedean spiral, while the outer turn is an Archimedean spiral with a zigzag shape. The current-density distribution along the spiral arms is first presented in the time domain, interestingly manifesting the impulse current propagation from the feed point to the outer end of the spiral arms. The performance of the broadband spiral antenna is also measured in an anechoic chamber. The simulated and measured results showed the sensitivity of the axial ratio and radiation pattern to the current distribution. The simulated linear gain, radiation patterns, and axial ratios agree well with the measured data over all of the frequency range from 2 to 18 GHz.     

电容式微波功率检测系统的灵敏度特性研究

为了提高电容式微波功率检测系统的综合性能,首先建立了MEMS悬臂梁的力学解析模型,研究了MEMS悬臂梁在静电力与弹性力综合作用下的运动规律,并建立了灵敏度的解析模型。研究结果表明,灵敏度主要受悬臂梁至下拉极板的初始间距、梁板长度影响。其中,灵敏度与间距成反相关关系,与梁板长度成正相关关系。在34~36 GHz的Ka波段内,根据力学解析模型和灵敏度模型,灵敏度的仿真结果分别为4.4 fF/W @34 GHz、4.1 fF/W @35 GHz、3.7 fF/W @36 GHz,实验测试结果分别为5.0 fF/W @34 GHz、4.5 fF/W @35 GHz、4.0 fF/W @36 GHz。灵敏度的仿真结果与测试结果比较吻合,这对改善电容式微波功率检测系统的综合性能具有一定的指导意义。     

Guided-wave electro-optic beam deflector using domain reversal inLiTaO3

We have fabricated and demonstrated the operation of electro-optic beam deflectors using domain reversal in planar waveguides fabricated on LiTaO₃ substrates. The planar waveguides were made using proton exchange on z-cut substrates, and proton exchange with subsequent rapid thermal annealing was used to form the inverted domains. The deflection sensitivity of the device was measured to be about 6.7 mrad/kV. Calculations indicate that the deflection sensitivity should be increased by a factor of 25 to 30 with improvements in device geometry     

盘形谐振陀螺的机械灵敏度仿真优化

针对盘形谐振陀螺的机械灵敏度这一关键性能,采用结构优化法对盘形谐振陀螺的谐振环壁厚分布进行了优化。首先基于COMSOL with MATALB实现了盘形谐振陀螺品质因数Q、谐振频率f0、等效质量meff和角度增益Ag的有效计算,估算出了盘形谐振陀螺的机械灵敏度;然后以机械灵敏度为优化目标,采用移动渐近线法对盘形谐振子的谐振环壁厚分布进行了优化。壁厚分布优化使陀螺的机械灵敏度提升了20%。     

Nanocomposite Microcontainers with High Ultrasound Sensitivity

A water suspension of nanocomposite microcapsules with embedded ZnO nanoparticles in the capsule shell is reported. The microcapsule morphology is characterized by confocal microscopy, TEM, SEM, and AFM before and after ultrasound treatment. A remarkably high capsule sensitivity to ultrasound is evidenced, and it is observed to grow with increasing number of ZnO nanoparticle layers in the nanocomposite shell. This effect is correlated with the mechanical properties of microcapsules measured with AFM.     

基于相关系数的雷达高分辨距离像分帧方法

高分辨距离像(HRRP)的方位敏感性造成HRRP数据是很长的统计特性连续变化的序列。从HRRP序列的统计特性出发,提出一种基于相关系数的HRRP分帧方法。外场实测数据的分帧结果表明,该方法可准确划分HRRP统计特性的变化,分帧结果与实际飞行轨迹符合;且采用时域模板匹配法(TMM)、谱域最短距离分类器和支撑向量机(SVM)分类器的识别结果均表明,相比目前基于散射点模型的均匀分帧方法,本文方法可有效提高识别率。