Non-collinear states in magnetic sensors

Certain materials have an electrical conductivity that is extremely sensitive to an applied magnetic field; this phenomenon, termed 'giant magnetoresistance', can be used in sensor applications. Typically, such a device comprises several ferromagnetic layers, separated by non-magnetic spacer layer(s)--a so-called 'super-lattice' geometry. In the absence of a magnetic field, the ferromagnetic layers may be magnetized in opposite directions by interlayer exchange coupling, while an applied external magnetic field causes the magnetization directions to become parallel. Because the resistivity depends on the magnetization direction, an applied field that changes the magnetic configuration may be detected simply by measuring the change in resistance. In order to detect weak fields, the energy difference between different magnetization directions should be small; this is usually achieved by using many non-magnetic atomic spacer layers. Here we show, using first-principles theory, that materials combinations such as Fe/V/Co multilayers can produce a non-collinear magnetic state in which the magnetization direction between Fe and Co layers differs by about 90 degrees. This state is energetically almost degenerate with the collinear magnetic states, even though the number of non-magnetic vanadium spacer layers is quite small.     

TRP channels as cellular sensors

TRP channels are the vanguard of our sensory systems, responding to temperature, touch, pain, osmolarity, pheromones, taste and other stimuli. But their role is much broader than classical sensory transduction. They are an ancient sensory apparatus for the cell, not just the multicellular organism, and they have been adapted to respond to all manner of stimuli, from both within and outside the cell.     

Stochastic sensors inspired by biology

Sensory systems use a variety of membrane-bound receptors, including responsive ion channels, to discriminate between a multitude of stimuli. Here we describe how engineered membrane pores can be used to make rapid and sensitive biosensors with potential applications that range from the detection of biological warfare agents to pharmaceutical screening. Notably, use of the engineered pores in stochastic sensing, a single-molecule detection technology, reveals the identity of an analyte as well as its concentration.     

CFRP预警传感器的研究

利用碳纤维增强复合材料(CFRP)的导电性和压电效应,根据碳纤维断裂时所形成的电阻阶跃信号,分别采用直接铺层和预先铺层2种方法制成对结构不同状态进行监测的CFRP预警传感器,该预警传感器具有造价低、耐腐蚀、监测信号易于获取等优点,并将此传感器应用于5根钢筋混凝土梁的试验研究.结果表明,CFRP预警传感器对于钢筋混凝土梁宏观行为的预测具有较好的效果,在混凝土开裂、钢筋屈服等关键时刻,其电阻信号发生突变,触发预警信号,该传感器对于钢筋混凝土类构件的监测具有实用性.     

基于自然电场传感器的地下污染监测

垃圾填埋场以及尾砂库废液渗漏监测是预防其周边地下污染等问题的重要手段,本文提出一种利用观测自然电场来实现长期、自动、实时监测的方法。设计了具有无线通信功能的电场传感器作为传感器节点,将这些传感器节点布置到监测区域组成分布式传感器网络。传感器网络按预定程序自动周期性地采集监测区域自然电场数据,并实时发送到远程数据处理端。实验结果表明该方法能自动实时采集自然电场数据,并能及时观测到自然电场随时间的变化情况,从而高效实现废液渗漏等污染的监测。     

热释电红外报警器的设计

设计一种利用热释电红外传感器监测环境变化,进行无线信息传输进而完成报警功能的系统,主要用于家居安全,探测有无外人闯入.该系统方便、稳定,十分适合家庭财产安全的保护.     

用于液相检测的横向场激励模式压电传感器

与传统基于石英晶体微天平的压电传感器相比,横向场激励模式压电传感器具有更优异的性能。该文基于微声波理论,分析了横向场激励模式压电体声波器件的声传播机理,计算了石英晶体在任意切型及横向电场方向上的压电耦合系数,并根据计算结果设计了新型的传感器结构。3种不同浓度的水溶液用于测试传感器对液体粘度、介电常数和电导率等变化的响应。结果表明,横向场激励压电传感器不仅具有较好的质量敏感效应,还对被测液体电特性参数变化具有较高的灵敏度,可用于研制复合型压电生物传感器。     

半导体温度传感器研究进展综述

半导体温度传感器体积小、功耗低,且能与其他外围控制电路集成在同一芯片上,其应用领域广阔。评述了各种半导体温度传感器的基本实现方式、发展现状,总结了现有各种设计方法中的关键技术及其存在的问题和改进方向。     

基于微悬臂梁的谐振式气体传感器

分析了悬臂梁的静态和动态特性,从理论上给出了提高悬臂梁频率分辨率的办法.在此基础上对6对振动激励和检测机制进行了分析与阐述,并对这些激励和检测机制应用于气体传感器的可行性进行了分析.     

锅炉烟气排放监测软件传感器

为监测锅炉烟气排放,采用软件传感器代替实际传感器分析NOx和SO2。根据理论分析和现场试验,选取循环流化床锅炉的有关控制输入和中间变量为输入变量,采用多变量ARX模型(autoregressiveexogenousvariablemodels),设计了全局最优的烟气NOx和SO2排放预测模型,以此作为软件传感器代替实际的烟气分析仪表,具有反应快、维护简单等优点,提高了系统的自动化水平,且降低了成本。现场数据分析表明,软件传感器可用于指导机组优化运行和烟气后处理设备的反馈控制。     

电容式波高传感器采样稳定性实验研究

波高传感器是海工试验中最为重要的检测仪器之一,试验对其精度和稳定性有较高要求,而在实际使用过程中,采样结果会出现较大幅值的波动,且波动频率高,这种现象导致其测量的波高数据不准确,进而对实际的结果造成很大影响,本文通过实验找出采样结果波动的规律,从波高传感器硬件与环境的角度分析产生波动的原因,并且利用数学的方法来减小波动,增加采样稳定性.     

Geometric calibration of high-resolution remote sensing sensors

This paper introduces the applications of high-resolution remote sensing imagery and the necessity of geometric calibration for remote sensing sensors considering assurance of the geometric accuracy of remote sensing imagery. Then the paper analyzes the general methodology of geometric calibration. Taking the DMC sensor geometric calibration as an example, the paper discusses the whole calibration procedure. Finally, it gave some concluding remarks on geometric calibration of high-resolution remote sensing sensors.     

PVDF触觉传感器动态补偿器的设计

为了解决PVDF压电薄膜测量低频信号失真大、泄漏快和阻抗匹配难等问题,首先探讨了 PVDF的工作机理,继而在频域内使用高效的最小二乘算法设计了一款 Hammerstein动态补偿器模型。仿真结果表明,该动态补偿器模型能快速有效地补偿PVDF传感器低频失真,使PVDF压电膜在低频领域的应用成为可能。     

Miniaturized gas ionization sensors using carbon nanotubes

Gas sensors operate by a variety of fundamentally different mechanisms. Ionization sensors work by fingerprinting the ionization characteristics of distinct gases, but they are limited by their huge, bulky architecture, high power consumption and risky high-voltage operation. Here we report the fabrication and successful testing of ionization microsensors featuring the electrical breakdown of a range of gases and gas mixtures at carbon nanotube tips. The sharp tips of nanotubes generate very high electric fields at relatively low voltages, lowering breakdown voltages several-fold in comparison to traditional electrodes, and thereby enabling compact, battery-powered and safe operation of such sensors. The sensors show good sensitivity and selectivity, and are unaffected by extraneous factors such as temperature, humidity, and gas flow. As such, the devices offer several practical advantages over previously reported nanotube sensor systems. The simple, low-cost, sensors described here could be deployed for a variety of applications, such as environmental monitoring, sensing in chemical processing plants, and gas detection for counter-terrorism.     

各向异性磁阻传感器灵敏度在线辨识技术

提出了一种基于灵敏度在线辨识技术的灵敏度变化补偿方法,使用北京科技大学研制的各向异性磁阻传感器BKMC-21进行了实验研究.结果表明:未采用灵敏度变化补偿技术的磁场测量输出结果在磁力计通电后发生剧烈变化;磁力计输出需30min才能趋于稳定,在此期间灵敏度变化超过20%.采用灵敏度变化补偿技术的磁场测量输出结果在磁力计通电后保持平稳,磁力计输出在整个过程中灵敏度变化不超过2%.由以上实验结果可以看出,本文所提出的基于各向异性磁阻传感器灵敏度在线辨识技术的磁力计灵敏度补偿方法能有效地解决磁力计灵敏度变化问题.     

基于主被动传感器融合的车辆检测

为了检测车辆目标,提出了一种基于主被动传感器融合的车辆检测方法.将车辆检测分为假设和验证假设两个步骤,在假设阶段,通过被动传感器——毫米波雷达进行目标的检测与跟踪,在对雷达数据进行最邻近法聚类后,在多假设跟踪模型下,将观测目标集与通过卡尔曼滤波器预测的目标集进行数据关联,得到雷达目标.在验证假设阶段,首先通过新出现的雷达目标找出车辆可能存在的区域,然后通过训练好的分类器对这些区域进行验证得到最终的车辆目标.在实验室的无人自主车平台上,本系统在城市道路和乡村道路环境下进行了大量实验,结果表明本文的方法可以有效地检测并跟踪到车辆目标,得到目标的距离和速度信息,从而帮助自主平台实现更多功能.