测量地表声阻抗率的实验研究

建立一个声波能量从空气中耦合到地下的实验系统模型。采用音响作为能量源发射扫频的正弦波声信号穿透到地下土壤;用声级计和地震检波器串分别测得地表的声压级和震动速度,画出二者比值即地面声阻抗率的变化曲线,以此分析声/地震波耦合的效率及其影响因素。在给定音响喇叭相对被测地面高度的情况下,地表声阻抗率在73到90Hz这个范围附近出现了极小值。现场实验证明,该系统能有效完成测量任务,可用于地下浅层埋藏物探测的实验室研究。     

基于FPGA的光栅地震检波器信号处理研究

光栅地震检波器是基于光栅检测技术设计的一种新型数字传感器,基于单片机的光栅地震检波器信号处理速度较慢,现场可编程门阵列FPGA时钟频率高,内部延时小,硬件资源丰富,在控制数据采集、转换等方面有着单片机和DSP所无法比拟的优势。为了提高光栅地震检波器的测量精度和分辨力,该文进行了基于FPGA的光栅地震检波器信号处理研究,并将软件细分原则应用于信号处理系统中。该系统基于硬件描述语言Verilog和PicoBlaze软核进行设计,在有效地减小电路板面积的同时,可实现数据的快速采集和高精度测量。     

井下声波遥测地面定频信号采集装置设计

采用定频声波脉冲作为信号传输手段的特点,利用共振原理设计了一种地面定频信号采集装置。采用Abaqus有限元法进行模态分析设计和谐响应分析,证明了定频信号采集装置具有良好的选频性;通过与动圈式地震检波器LGT—20D40和压电式加速度传感器INV9828的对比试验,验证了其在灵敏度、抗干扰能力方面的优势;现场应用试验证明其能够大幅提高地面解码成功率,具有实用价值。设计的定频信号采集装置为解决井下无线声波遥测系统(ATS)地面解码困难的问题提供了一种新的手段,同时还可推广应用到类似场合。     

一种压电加速度地震检波器的设计与研究

研究和讨论了一种陆用压电加速度地震检波器,并从理论上对其幅频、相频特性进行推导,得出影响频响宽度的主要因素,并在压电晶体的选择及检波器的结构上予以改进。通过对传统速度地震检波器和压电加速度地震检波器主要指标测试和理论及现场试验结果表明:此压电加速度检波器具有较好的低频和高频响应特性以及较高的灵敏度,是一种较好的检波方法。     

提高光栅数字地震检波器精度的方法研究

在地震勘探系统中,随着数据记录系统动态范围的突破,地震检波器的动态范围已不能满足系统的要求,提高检波器的精度和动态范围变成地震勘探技术研究的关键.光栅数字地震检波器的研制成功,提高了检波器的精度和动态范围.通过对光栅传感器机理的深入分析,采用5细分专用芯片为核心的细分电路,成功实现了光栅脉冲信号的20倍细分技术.在采用100线计量光栅的情况下,使检波器分辨率达到0.000 5 mm,动态范围达到75dB.并采用PIC单片机系统完成了振动信号的再现.该方法将有助于光栅数字地震检波器的性能完善,为实现高精度地震勘探技术奠定基础.     

加速度过阻尼地震检波器测量的研究

研究恒加速度过阻尼动圈式地震检波器参数的测量方法。通过对这种地震检波器的工作原理分析,给出了参数定义,推导了它在直流阶跃电流激励下的响应函数,明确了加速度过阻尼地震检波器实质是一个带通系统。基于对响应函数的分析,介绍了经典的参数辨识法测量,并提出了一种新的测量方法。该方法通过简单的测量、查表和数值计算便可获得加速度过阻尼地震检波器的阻尼、自然频率和灵敏度3个参数。     

新型MEMS地震检波器的研究

以MEMS加速度传感器为基础的新型地震检波器大幅度提高了地震检波器的各项性能指标.介绍了一种新型的石油勘探MEMS地震检波器的设计及其主要技术参数,并通过微传感器结构的力学性能仿真,得出其具体的结构尺寸.经采用表面工艺和体工艺相结合的方法,利用磁控溅射、光刻、化学蚀刻及等离子体蚀刻等工艺,在高阻硅上制备出检波器样品.     

差分式地震检波器测试仪的失真度测试研究

失真度作为地震检波器的一项重要参数,其测试方法直接决定测试结果的精确度。现有检波器测试仪在失真度测试过程中受电路本身产生的噪声干扰较大,测试精度不能满足高精度地震检波器的测试要求。采用差分输入法进行失真度参数的测试,差分信号由高性能数模转换芯片内部的正弦信号发生器产生。信号处理部分采用二阶有源低通滤波器,使截止频率限定在100 Hz,实现低通效果。通过全差分的设计方式,减小了电路中的共模干扰,使通过地震检波器的正弦信号极大限度地接近标准正弦信号。信号采集部分选用24位模数转换芯片,达到高采集精度测试的要求。试验结果表明,失真度测试系统满足地震检波器测试仪器误差标准,精确度达到10-5数量级。全差分方法设计的测试电路在一定程度上提高了测试精度;同时,高性能芯片的选取对系统的测试结果也具有重要作用。     

地震检波器技术浅析

地震检波器是地震勘探必不可少的地震波传感部件,其性能直接关系到地震勘探信号采集的质量。本文通过对地震检波器技术及各种检波器性进行对比分析,对地震检波器的综合技术进行了探讨和研究,并在此基础上就地震检波器提出了自己的认识与建议。     

基于DSP技术的微震实时监测系统

一种基于DSP技术的井下微地震实时监测系统的设计,并对实现这种技术的几个重要环节进行了详细阐述。介绍了地震波的特性并对地震检波器的选择与安装进行了讨论和设计,包括系统前向通道的前置放大、低通滤波环节的设计,系统核心数据采集部分VC5402与A/D转换接口以及与PC机串行通信的设计;DSP系统抗干扰的一些措施及系统在其他方面的应用。     

声表面波气体传感器振荡电路设计

基于反馈振荡器的工作原理,采用对振荡电路的开环增益和相位进行检测和调节的方法,设计制作了用于声表面波(SAW)气体传感器的振荡电路。根据开环测量的结果,通过改变匹配电感值来使得0°相位在增益峰值附近,以获得稳定的振荡和提高振荡器可承受的最大传感器插损。在印制电路板(PCB)版图设计中,采用50Ω特性阻抗和保证最短RF回流电流路径等措施以实现稳定的振荡。基于上述方法,分别制作了频率为315,433.92 MHz的振荡电路。后者的噪声幅度在20 Hz以内,标准方差约为3.92。该实验结果表明:此设计方法具有快速、便捷、可靠的优点,设计的振荡电路具有较高的稳定性,可广泛用于SAW传感器设计。     

Mechanical impedance of the human hand-arm system

The mechanical impedance of the human hand-arm system was measured within the frequency range of 20–1500 Hz. A handle, specially designed for such measurements, was used. The studies were carried out on eight healthy male subjects during different experimental conditions defined by three different hard-arm postures, hand grip forces (25–75 N) adopted by the subjects, the amplitude (27–53 mm/ s_rms; 1.4–2.8 g at 80 Hz) and direction of the vibration stimuli. The outcome shows that the mechanical impedance of the hand-arm system depends on the frequency of the vibration stimuli. Above 200 Hz, the impedance, in general, increases quite rapidly, from about 150 Ns/m up to about 500 Ns/m at 1500 Hz, with the frequency. At lower frequencies, however, various shapes of the impedance curves were found which were most pronounced between different hand-arm postures. For the transverse direction, the impedance increased from about 50 Ns/m at 20 Hz to maximum about 100 Hz followed by a slight decrease. For the proximal-distal direction the impedance decreased from about 150 Ns/m at 20 Hz to minimum at about 100 Hz. More firm hand grips, as well, as higher vibration levels, resulted in higher impedance magnitudes for frequencies above about 100 Hz. Remarkably enough, for lower frequencies an almost opposite relationship was found. Furthermore, the results indicate a non-linear relationship between mechanical impedence and the studied experimental variables. Therefore, prior to setting up future standards, the mechanical properties of the hand-arm system should be taken into careful consideration.     

The impact of false alarm mitigation on surface landmine detection in MWIR imagery

Surface landmine and minefield detection from airborne imagery is a difficult problem. As part of the minefield detection process, anomaly detection is performed to identify potential landmines in individual airborne images. Post-processing is performed on the initial landmines identified to reduce the number of false alarms, referred to as false alarm mitigation. In this research, a circular harmonics transform image processing approach (the CHT method) and a constant false alarm rate technique (the RX approach) are investigated for surface landmine detection and false alarm mitigation in medium wave infrared (MWIR) image data. The false alarm mitigation approach integrates the CHT and RX methods to identify candidate landmine locations with one technique at a given false alarm rate and applies the other technique to confirm landmine locations and eliminate potential false alarms. Individual detector and false alarm mitigation experimental results are presented for 31 daytime and 43 nighttime MWIR images containing 76 and 142 landmines, respectively. At a 0.9 desired probability of landmine detection, experimental results show that false alarm mitigation reduces the false alarm rate by as much as 84.3% and 13.7% for daytime and nighttime images, respectively, maintaining the probability of detection at 0.85 and 0.90, respectively.     

Mechanical impedance of the human body in vertical direction

The mechanical impedance of the human body in sitting posture and vertical direction was measured during different experimental conditions, such as vibration level (0.5-1.4 m/s2), frequency (2-100 Hz), body weight (57-92 kg), relaxed and erect upper body posture. The outcome shows that impedance increases with frequency up to a peak at about 5 Hz after which it decreases in a complex manner which includes two additional peaks. The frequency at which the first and second impedance peak occurs decreases with higher vibration level. Erect, compared with relaxed body posture resulted in higher impedance magnitudes and with peaks located at somewhat higher frequencies. Heavy persons show higher impedance magnitudes and peaks at lower frequencies.     

Strength of landmine signatures under different soil conditions: implications for sensor fusion

Most sensors for the detection of buried landmines are influenced by the properties of the soil that surrounds the mine. The temporal and spatial variability in soil properties accounts for a significant part of the detection uncertainty that is associated with most sensors. In particular, most sensor types (e.g. ground-penetrating radar, thermal infrared cameras, and chemical sniffers) are affected by the water content of the soil. However, each sensor type reacts in its own way to variations in soil water content and other soil properties. The resulting variation in sensor performance has serious implications for sensor fusion operations. We show how knowledge of soil physics can contribute to a better understanding of sensor performance and can lead to improved data fusion.     

基于仿真与实测的列车远场气动噪声分析

随着高速列车气动噪声诱发的铁路沿线噪声污染问题变得日益明显,需对高速铁路诱发的远场噪声特性进行研究。基于Lighthill声学理论,应用LES大涡模拟和FW-H声学模型对高速列车整车的气动噪声进行数值模拟,实测高速列车以300 km/h运行时的通过噪声,将仿真与实测进行对比分析。高速列车诱发的远场气动噪声是宽频带噪声,能量主要集中在200~1500 Hz的中低频带范围内。实测与仿真的噪声声压级频谱分析具有相似的变化趋势,但声压级数值不同;由于实测噪声数据不仅包括气动噪声,还包括轮轨、集电系统噪声等,所以实测数据普遍大于仿真结果。通过对比分析验证了仿真结果的科学性,为数值模拟方法研究高速列车气动噪声问题提供了科学依据。     

食物致病菌快速检测系统的设计与实现

设计了食物致病菌快速检测一体化系统。基于抗原-抗体特异性结合的原理,采用TiO2纳米线束为敏感元件设计微生物免疫传感器,以高集成度芯片AD5933设计阻抗检测电路来通过电化学阻抗谱法测量该传感器中TiO2纳米线束的阻抗变化量,实现了致病菌数量的快速检测。以大肠杆菌为例作为实验样本对检测一体化系统的性能进行测试,实验结果表明该检测一体化系统可以快速检测出食物中存在的大肠杆菌,检测周期约为1 h,系统的检测下限为4.5×102cfu/mL,传感器在扫描频率为1 000 Hz～10 000 Hz之间表现出来的重复性较好。     

基于声发射的地震、山体滑坡监测诊断系统的应用研究

阐述了采用声发射技术对矿山、岩石、水土、水工、建筑结构等行业进行监测。岩体工程如矿山边坡、山体边坡,因内外力作用以及外界环境因素影响,易发生滑坡蹋陷,在滑坡蹋陷之前都会有声发射现象发生,如何检测到这些声发射信号,是研究的重点内容。如何根据检测到的声发射信号进行危险预报,确定声发射源,是基于声发射的地震、山体滑坡监测诊断系统的主要研究任务。     

基于电路仿真技术异型声表面波器件特性分析

为了能够采用EDA工具设计含声表面波器件的电子系统,本文研究了应用EDA工具仿真声表面波器件特性的方法.它以叉指换能器一个周期段的Mason等效电路模型为基础,根据电网络理论将Mason等效电路模型中的复阻抗采用LC串并联网络来等效,LC网络中的各L、C值采用进化方法确定,使得串并联网络的等效阻抗和Mason等效电路中的阻抗特性误差最小,并以子电路的形式由自行研制的异型声表面波器件各叉指换能器的等效电路调用,异型声表面波器件幅度特性仿真结果与实测结果在中心频率处插入损耗基本相符.