基于ZigBee的煤矿井下甲烷浓度检测系统设计

针对传统煤矿井下甲烷浓度采用工业总线检测方法的不灵活和存在盲点等问题,本文提出了一种基于ZigBee的煤矿井下甲烷浓度检测系统。系统采用ZigBee协议栈构建无线传感器通讯网络,该网络的终端节点感知和采集矿井甲烷的浓度,并将浓度数据通过无线传输至协调器,协调器再经过串口传输到地面的监控中心。详细介绍了检测系统的软硬件设计,并对系统进行了测试验证。     

基于无线传感器网络及GPRS的水质监测系统设计

提出了一种基于ZigBee无线传感器网络和GPRS技术的多参数远程实时水质监测系统。无线传感器网络以CC2430通信模块为核心。传感器节点采集到的数据经路由节点汇总至协调器节点,通过GPRS模块及时远传至监控中心。设计信号调理电路,将传感器电极输出的微弱电信号进行放大、滤波。采用时间同步机制实现网络节点的同步唤醒,大幅提高网络的稳定性。对系统进行了多天连续测试。通信距离为100米时,网络的平均丢包率低于1%。pH值、溶氧度的平均相对偏差低于1%。测试结果表明,系统具有灵活、实时性好、准确性高、稳定可靠等优点,具有很强的实用价值。     

基于ZigBee的环境参数远程无线监控系统设计

针对室内环境参数的远程监控问题,提出一种基于ZigBee技术与手机进行实时数据交换的远程无线监控系统。传感器节点采集环境中的温湿度、光强和烟雾浓度数据,通过ZigBee无线网络将数据传输到中心协调器;协调器与WIFI模块通过串口连接,将数据发送到互联网;另外,设计Android手机软件对监测数据进行获取,并发出对参数进行调节的指令,从而完成远程的无线监控任务。经过测试,通过手机可以在任何有网络的地方实时对环境参数进行采集和控制,且各节点性能稳定,满足长期监测的需求。     

基于ZigBee的矿井环境监测系统设计

针对矿井环境恶劣、干扰严重和传统信号有线传输的现状,设计了基于ZigBee无线传感器网络的矿井环境监测系统;系统由井下ZigBee传感器终端节点、路由器、协调器和井上监测上位机构成,其中传感器终端节点对井下瓦斯、一氧化碳、温度等信号进行采集,利用ZigBee无线组网技术将信号送给井上PC机,井上管理人员通过PC机能够随时掌握井下设备和环境的状况;与传统的信号有线传输监测方法相比,该系统低功耗、低成本、抗干扰;实验结果表明,该系统运行稳定可靠,精度高,具有一定的实用性和推广价值。     

基于ZigBee的大型公共建筑能耗采集器设计

针对大型公共建筑能耗实时采集系统中存在的布线复杂、通信成本高、安全性低等问题,提出一种基于ZigBee技术的能耗数据采集器设计方案。该方案采用STM32做主控制器, ZigBee采集单元通过RS485接口实现与基于Modbus协议的智能电表之间的数据通信,并采用ZigBee无线网络将数据发送至协调器,协调器通过USART方式与主控制器进行通信;主控制器利用以太网将数据发送至上位机。通过软硬件设计,以XY194E智能电表为例,对其电能参数进行测试采集,结果表明该方案克服了传统人工采集传输的不足,提高了数据采集传输的实时性、准确性,能够满足能耗采集系统的要求。     

闸机人体步态测量与识别算法研究

针对轨道交通闸机检票中存在的尾随逃票现象,研究了基于多红外传感器的闸机人体识别技术;该技术采用多个红外传感器采集乘客通行信息,在对闸机系统分析的基础上,设计了红外传感器的结构布局;将传感器区域分析和事件识别标志分析相结合,提取人体特征识别乘客通行事件;研制了闸机门人体识别实验系统,对4种常见的闸机通行事件进行了分析,并开展了实验研究;实验结果表明,实验系统能够有效识别闸机通行的多种事件,实时性好,具有较好的工程应用前景。     

基于多传感器数据融合的人体运动模式识别研究

针对单一传感器在人体运动姿态监测中误差较大的问题,提出了一种基于加速度传感器和陀螺仪数据融合的人体运动模式识别方法。该方法使用陀螺仪输出的人体运动信息对加速度传感器采集到的姿态角信息进行修正,采用卡尔曼滤波算法实现多传感器信息的融合,有效提高了姿态角度测量的准确度。根据人体日常的活动状态构建了基于人体姿态角度特征的隐马尔可夫模型实现人体运动模式的识别。实验表明,该方法比采用单一传感器方法识别的准确率高,可以有效区分不同的日常活动行为。     

基于时空双流卷积神经网络的红外行为识别

针对红外视频人体行为识别问题,提出了一种基于时空双流卷积神经网络的红外人体行为识别方法。通过将整个红外视频进行平均分段,然后将每一段视频中随机抽取的红外图像和对应的光流图像输入空间卷积神经网络,空间卷积神经网络通过融合光流信息可以有效地学习到红外图像中真正发生运动的空间信息,再将每一小段的识别结果进行融合得到空间网络结果。同时将每一段视频中随机抽取的光流图像序列输入时间卷积神经网络,融合每一小段的结果后得到时间网络结果。最后再将空间网络结果和时间网络结果进行加权求和,从而得到最终的视频分类结果。实验中,采用此方法对包含23种红外行为动作类别的红外视频数据集上的动作进行识别,正确识别率为92.0%。结果表明,该算法可以有效地对红外视频行为进行准确识别。     

基于ZigBee的艇载无线传感器网络设计与实现

为减少飞艇上部署的线缆数量,提高飞艇的载荷能力,增加飞艇上数据传输的灵活性。对基于ZigBee的短距离无线通信技术进行研究,提出了在大型飞艇中运用ZigBee技术组成无线传感器网络,对分布在飞艇上的传感器采集到的数据进行无线传输。设计适合飞艇使用的ZigBee硬件电路,并通过软件仿真和实际侧量,验证网络链路的通畅,保证数据的可靠传输。从而验证了在飞艇上运用Zigbee无线传感器网络采集并传输数据具有可行性。为飞艇上数据的传输提供了新的方法和思路。     

基于机器鱼的内陆湖泊水质在线监测系统设计

仅依赖无线传感器网络在线实测是利用多跳式通信实现远程发送与存储数据丢包率高,实验阶段设计的二维结构仿真机器鱼巡游避障性能差,GPRS全天候数据采集与传送所需的流量费用高,针对以上这些问题,设计了一套可进行实测的机器鱼自动巡游避障、水质环境实时监测系统平台;该系统通过移动终端程序设计、利用三维采集路径跟踪算法及WSNs与Wifi热点技术对机器鱼群实现远程精准控制,按照设定深度、路径规划的采集点进行水温水位、PH值、溶解氧、电导率、浊度等常五类水质环境数据实时采集、处理、远程存储、显示、分析及预警,给出了系统的总体设计、机器鱼的结构与控制系统设计、终端节点与协调器的硬件系统及上下位机软件系统设计;利用这套系统对巢湖5个取样点实测,水温、溶解氧、PH值平均误差率分别为0.18%、0.5%及0.01%,远高于其他水质在线监测的精度要求,达到了预期成果;同时对水库及精细水产养殖业等水质在线监测与预警具有很高的推广价值。     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Femtosecond Transform-Limited Pulse Generation by Compensating for the Linear Chirp of SPM Spectra in Dispersion Shifted Fibers

A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output.     

Sorting of bending magnets for the SSRF booster

The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper.     

Measurement of nonlinear coefficient of optical fiber based on small chirped soliton transmission

We measure the waveform and phase curves of short optical pulses before and after transmission over different lengths of fibers by use of the pulse analyzer with the frequency-resolved optical gating (FROG),and numerically simulate pulse evolution under the experimental conditions.The nonlinear coefficient of the fiber is given by comparing the experimental results with the numerical ones.Difference between the experiment and numerical simulation is analyzed.     

Resonance scattering of canonical elastic shells in absorbing fluid medium

Resonance scattering of elastic spherical shell and cylindrical shell while the surrounding fluid medium has absorption is studied. The normal mode solution derived using exact elastic theory and the separation of variables is still applicable. However, the scattering form function has to be modified for the absorbing medium, otherwise the unreasonable result would be obtained. The backscattering form function in the absorbing medium is redefined, and the form function of elastic spherical and cylindrical shell with vacuum or solid matter filled is calculated in various absorption conditions. The results show that the absorption of surrounding fluid leads to notable attenuation of the coincidence resonances in the mid-frequency, but it has a little influence on the low-frequency resonance scattering induced by the filler inside the shell.     

Single-beam self-referenced phase-sensitive surface plasmon resonance sensor with high detection resolution

A versatile and low-cost single-beam self-referenced phase-sensitive surface plasmon resonance(SPR)sensing system with ultra-high resolution performance is presented.The system exhibits a root-mean-square phase fluctuation of ±0.0028.over a period of 45 min.i.e.a resolution of±5.2×10-9 refractive index units.The enhanced performance has been achieved through the incorporation of three design elements:a true single-beam configuration enabling complete self-referencing so that only the phase change associated with SPR gets detected,a differential measurement scheme to eliminate spurious signals not related to the sensor response,and the elimination of retardation drifts by incorporating temperature stabilization in the liquid crystal phase modulato .Our design should bring the detection sensitivity of non-labeling SPR biosensing closer to that achievable by conventional fluorescence-based techniques.     

Influences of SiO2 protective layers and annealing on the laser-induced damage threshold of Ta2O5 films

Ta2O5 films are prepared on BK7 substrates with conventional electron beam evaporation deposition.The effects of SiO2 protective layers and annealing on the laser-induced damage threshold (LIDT) of the films are investigated.The results show that SiO2 protective layers exert little influence on the electric field intensity(EFI)distribution,microstructure and microdefect density but increase the absorption slightly.Annealing iS effective on decreasing the microdefect density and the absorption of the films.Both SiO2 protective layers and annealing are beneficial to the damage resistance of the films and the latter is more effective to improve the LIDT.Moreover,the maximal LIDT of Ta2O5 films is achieved by the combination of SiO2 protective layers and annealing.     

A stereo matching algorithm using multi-peak candidate matches and geometric constraints

Gray cross correlation matching technique is adopted to extract candidate matches with gray cross correla- tion coefficients less than some certain range of maximal correlation coefficient called multi-peak candidate matches. Multi-peak candidates are extracted corresponding to three closest feature points at first. The corresponding multi-peak candidate matches are used to construct the model polygon. Correspondence is determined based on the local geometric relations between the three feature points and the multi-peak candidates. The disparity test and the global consistency checkout are applied to eliminate the remaining ambiguous matches that are not removed by the local geometric relational test. Experimental results show that the proposed algorithm is feasible and accurate.