Experimental Study of Acoustic Noise Correlation Technique for Passive Monitoring of Rails

The work presented in this paper aims at investigating the ability of acoustic noise correlation technique for railway infrastructure health monitoring. The principle of this technique is based on impulse responses reconstruction by correlation of random noise propagated in the medium. Since wheel-rail interaction constitutes a source of such noise, correlation technique could be convenient for detection of rail defects using only passive sensors. Experiments have been carried out on a 2 m-long rail sample. Acoustic noise is generated in the sample at several positions. Direct comparison between an active emission-reception response and the estimated noise correlation function has confirmed the validity of the equivalence relation between them. The quality of the reconstruction is shown to be strongly related to the spatial distribution of the noise sources. High sensitivity of the noise-correlation functions to a local defect on the rail is also demonstrated. However, interpretation of the defect signature is more ambiguous than when using classical active responses. Application of a spatiotemporal Fourier transform on data recorded with variable sensor-defect distances has allowed overcoming this ambiguity.

Passive Samplers Deployment in the Ayapel Swamp for Monitoring Temporal Dynamics of Mercury in the Water Column

Passive sampling is a simple and efficacious sampling technique that guarantees a safe collection and transportation of samples to the analysis site, and obtaining results with more temporal resolution. As a case of study, passive samplers were deployed in the Ayapel Swamp, Colombia, located in the influence zone of open pit gold mines. Mercury, iron and manganese were sampled at two different depths by the Chemcatcher? passive sampler and regular grab sampling. Additionally, dissolved oxygen, oxidation-reduction potential, pH and water temperature were measured. The results showed that depth and time did not have a significant influence (ANOVA, confidence level of 95%) on mercury concentration on both passive samplers and grab sampling. However, concentration of Fe and Hg in passive samplers had a high positive correlation, but it may be because depth increase during sampling period caused the dilution of both analytes. In conclusion, passive samplers proved to be a valuable tool for understanding the response of mercury to the Ayapel Swamp dynamics.

Identification of Antarctic minke and killer whales with passive acoustic monitoring in Prydz Bay, Antarctica

Although four species of odontocete and four species of baleen whale have been recorded in Prydz Bay,their vocalizations have been rarely investigated.Underwater vocalizations were recorded during March 2017 in Prydz Bay,Antarctica.Bio-duck sounds,downsweeps,inverted“u”shape signals,whistles,pulsed sounds,and broadband clicks were recorded.Bio-duck sounds and downsweeps were associated with Antarctic minke whales(Balaenoptera bonaerensis)based on visual observations.Similarities between inverted“u”shape signals,biphonic calls,and clicks with vocalizations previously described for killer whales(Orcinus orca)lead us believe the presence of Antarctic killer whales.According to sound structures,signal characteristics,and recording location,Antarctic type C killer whales were the most probable candidates to produce these detected calls.These represent the fi rst detection of inverted“u”shape signals in Antarctic waters,and the fi rst report of Antarctic killer whale in Prydz Bay based on passive acoustic monitoring.The co-existence of Antarctic minke and killer whales may imply that minke whales can detect diff erences between the sounds of mammal-eating and fi sh-eating killer whales.Our descriptions of these underwater vocalizations contribute to the limited body of information regarding the distribution and acoustic behavior of cetaceans in Prydz Bay.

Passive leg raising as an indicator of fluid responsiveness in patients with severe sepsis

In the management of critically ill patients, the assessment of volume responsiveness and the decision to administer a fluid bolus constitute a common dilemma for physicians. Static indices of cardiac preload are poor predictors of volume responsiveness. Passive leg raising （PLR） mimics an endogenous volume expansion （VE） that can be used to predict fluid responsiveness. This study was to assess the changes in stroke volume index （SVI） induced by PLR as an indicator of fluid responsiveness in mechanically ventilated patients with severe sepsis. This was a prospective study. Thirty-two mechanically ventilated patients with severe sepsis were admitted for VE in ICU of the First Affiliated Hospital, Zhejiang University School of Medicine and Ningbo Medical Treatment Center Lihuili Hospital from May 2010 to December 2011. Patients with non-sinus rhythm or arrhythmia, parturients, and amputation of the lower limbs were excluded. Measurements of SVI were obtained in a semi-recumbent position （baseline） and during PLR by the technique of pulse indicator continuous cardiac output （PiCCO） system prior to VE. Measurements were repeated after VE （500 mL 6% hydroxyethyl starch infusion within 30 minutes） to classify patients as either volume responders or non-responders based on their changes in stroke volume index （ASVI） over 15%. Heart rate （HR）, systolic artery blood pressure （ABPs）, diastolic artery blood pressure （ABPd）, mean arterial blood pressure （ABPm）, mean central venous pressure （CVPm） and cardiac index （CI） were compared between the two groups. The changes ofABPs, ABPm, CVPm, and SVI after PLR and VE were compared with the indices at the baseline. The ROC curve was drawn to evaluate the value of ASVI and the change of CVPm （ACVPm） in predicting volume responsiveness. SPSS 17.0 software was used for statistical analysis. Among the 32 patients, 22 were responders and 10 were non-responders. After PLR among the responders, some hemodynamic variables （including ABPs, ABPd, ABPm and CVPm） were significantly elevated （101.2±17.6 vs. 118.6±23.7, P=0.03; 52.8±10.7 vs. 64.8±10.7, P=0.006; 68.3±11.7 vs. 81.9±14.4, P=0.008; 6.8±3.2 vs. 11.9±4.0, P=0.001）. After PLR, the area under curve （AUC） and the ROC curve of ASVI and ACVPm for predicting the responsiveness after VE were 0.882±0.061 （95%CI 0.759-1.000） and 0.805±0.079 （95%CI 0.650-0.959） when the cut-off levels of ASVI and ACVPm were 8.8% and 12.7%, the sensitivities were 72.7% and 72.7%, and the specificities were 80% and 80%. Changes in ASVI and ACVPm induced by PLR are accurate indices for predicting fluid responsiveness in mechanically ventilated patients with severe sepsis.

Superelastic Radiative Cooling Metafabric for Comfortable Epidermal Electrophysiological Monitoring

Epidermal electronics with superb passive-cooling capabilities are of great value for both daytime outdoor dressing comfort and low-carbon economy. Herein, a multifunctional and skinattachable electronic is rationally developed on a porous all-elastomer metafabric for efficient passive daytime radiative cooling(PDRC) and human electrophysiological monitoring. The cooling characteristics are realized through the homogeneous impregnation of polytetrafluoroethylene microparticles in the styrene–ethylene–butylene–styrene fibers, and the rational regulation of microporosity in SEBS/PTFE metafabrics, thus synergistically backscatter ultraviolet–visible–near-infrared light(maximum reflectance over 98.0%) to minimize heat absorption while efficiently emit human-body midinfrared radiation to the sky. As a result, the developed PDRC metafabric achieves approximately 17℃ cooling effects in an outdoor daytime environment and completely retains its passive cooling performance even under 50% stretching. Further, high-fidelity electrophysiological monitoring capability is also implemented in the breathable and skin-conformal metafabric through liquid metal printing, enabling the accurate acquisition of human electrocardiograph, surface electromyogram, and electroencephalograph signals for comfortable and lengthy health regulation. Hence, the fabricated superelastic PDRC metafabric opens a new avenue for the development of body-comfortable electronics and low-carbon wearing technologies.

Development of piezoelectric-based technology for application in civil structural health monitoring

Piezoelectric material,as one of the great potential materials,had attracted lots of attention all over the world due to its distinguish advantages.In this paper,the development of piezoelectric-based technology for application in the field of civil structural health monitoring(CSHM),was summarized and discussed.Based on the different identification mechanisms,the piezoelectric transducer-based technology can be divided into two main approaches as the active or passive sensing and detection methods.This paper summarized the development of these two approaches and discussed their applications in the area of civil structural health monitoring,such as structural and concrete engineering,bridge engineering,pipeline engineering,protection engineering for geological hazards and earthquake disasters,and so on.In addition,the electrical mechanical impedance(EMI)technique,as one of the active identification methods,was also detailly presented.Finally,its great potential for the piezoelectric-based technique was presented based on the detail discussion,especially in the areas of civil structural health monitoring.

矿井微震与电法耦合监测技术

随着煤炭资源开采区域、深度及强度的增加,矿井工作面采掘扰动极易诱发矿井突水事故,严重威胁我国煤炭资源安全开采。矿井水害事故的发生主要是岩体采动破裂与矿井水渗流共同作用的结果。研究表明,微震信号的纵横波到时、幅值、频率等参量可有效表征岩体破裂位置、强度及其震源机制,地电场信号中的电阻率、激励电流及自然电位等参量可有效表征岩体渗流演化过程。透水通道形成对应微震场特征,地下水渗流对应地电场特征,因此微震电法耦合方法对矿井水害孕育发展过程具有监测预警的功能,可有效对采动破坏过程中形成的突水通道、水源位置及渗流过程等水害三要素进行精准捕捉;减少单一地球物理方法多解性,提高水害监测预警精度,对煤矿防治水意义重大。当前,微震与电法耦合监测技术在煤矿水害实时动态监测中开始得到应用,突破传统微震与电法独立采集的局限,课题组自主研发了国内外首款煤安认证的微震与电法耦合并行监测系统,该系统以微震场与地电场并行采集基站为核心,集被动源微震波场与主被动地电场为一体,通过连接矿井物联网,实现远程数据采集控制、传输及云端存储;其一体化网络服务器主机可连接多个采集基站,并将微震检波器、电法激励电极与电位测量电极进行相互隔离、并行采集,形成微震事件密度与能级分布、电阻率分布、自然电位分布等时空云图来监测预判水害三要素。微震与电法耦合监测技术仍需在微震事件智能识别与定位、地电场的电阻率三维反演以及自然电位渗流反演方面进行专项攻关;结合并行监测的微震电法大数据集,重点在微震电法数据联合反演、智能化监测预警方向开展进一步研究。微震与电法耦合监测技术,作为矿井水害的主动预警监测新方法,可为我国智能化矿井建设发挥重要作用。

基于被动声学的对虾摄食行为研究进展

被动声学监测(Passive acoustic monitoring, PAM)技术可在对水生生物不造成干扰或损害的情况下获取水生生物的声音信息,并利用这些信息进行各种生态研究和养殖活动管理。随着对虾养殖技术的不断提高和进步,对虾的养殖密度持续增加,但是饲料利用率低、水质恶化等问题严重制约对虾养殖的快速发展。利用被动声学监测技术可实现智能化的自动投饲,提高饲料利用率和缓解水质恶化。文章主要阐述了对虾的摄食过程及其影响因素,总结了近年来被动声学监测技术在对虾摄食声信号的研究进展和应用情况,分析了被动声学监测技术的优缺点,并针对存在的问题提出未来的发展趋势,以期为自动投饲系统走向智能化提供参考。

定制化被动式木门窗材柔性分类智能控制系统设计

针对行业内被动式木门窗扇及窗框等集成材根据订单要求完成定长截断、四面刨铣后,需要对尺寸各异的门窗材进行优化分类堆叠的现状设计柔性分类智能远程控制系统。通过Modbus通信协议及多种传感器协同完成现场数据的实时采集,运用消息队列遥测传输(Message Queuing Telemetry Transport,MQTT)协议和通信模块将采集的数据上传至云平台,终端用户通过手机App或Web端实时查看系统运行数据及进行远程操控,实现基于物联网的远程监控与报警。结果显示,设计的控制系统尺寸信息采集系统的鲁棒性较高,系统故障率低,同时提高分类堆叠效率。控制系统的设计实现了门窗材定制化分类堆叠的自动化、数据实时采集与传输以及远程监控,为实木加工的智能化与信息化应用提供了技术支撑。

盾构始发软土深基坑的变形及加固

软土地层具有高灵敏度、高压缩性和承载能力低的特点,在外荷载和震动的作用下容易产生变形和不均匀沉降.依托珠海市杧洲隧道工作井基坑工程,通过现场监测和数值模拟分析地下连续墙墙体水平位移、地表沉降和支撑轴力,研究软土深基坑开挖变形发展规律及被动区加固的影响.结果表明,墙体水平位移曲线图呈现“勺型”,最大值出现在1.4倍基坑开挖深度左右的位置,被动区加固使墙体水平位移最大值降低33%;地表沉降呈现“沉降槽”曲线特征,最大值出现在距离基坑边缘0.3倍开挖深度的位置,被动区加固使地表沉降最大值小于开挖深度的0.1%;开挖土体使支撑轴力迅速增大,下一层支撑的设置可以有效降低上一道支撑的轴力增长,被动区加固使支撑轴力最大值降低25%;被动区加固是软土深基坑控制变形的有效措施.研究结果可为软土深基坑施工和监测提供参考.

基于U形谐振器的无源裂缝传感器

针对传统裂缝传感器需要电源供应才能正常工作的缺陷,本文提出了一种基于无应力组合式贴片天线的无源裂缝传感器设计。利用U形谐振器实现裂缝传感,改变传感器内部谐振单元的谐振频率。通过观测回波信号的幅度和相位提取传感器的谐振频率,进而实现对裂缝的监测。基于天线理论建立了传感器的等效电路模型并推导谐振频率,研究裂缝宽度对传感器谐振频率的影响规律。进一步在三维电磁仿真软件CST中对传感器进行了数值模拟,并且通过试验研究了裂缝拓展对谐振频率的影响。研究表明:随着裂缝的扩展,传感器的谐振频率增加,且裂缝宽度与谐振频率之间具有较好的线性关系。

被动式傅里叶红外光谱遥测技术在炼化企业的应用

在监测石化园区内的危险化学品气体时,常规的气体监测方式存在监测半径小、难以全覆盖、结果不够直观等问题。提出了采用被动式傅里叶红外光谱遥测成像报警系统的气体监测方案,分析了国内大型、特大型石化园区对于危险气体监测的特性需求,介绍了被动式傅里叶红外光谱遥测技术的特点,以及该系统与一体化综合监测平台网络的连接架构。阐述该系统在某炼化企业易燃易爆、有毒有害等气体监测中的应用,并探讨了后续深化应用,以期为石化产业在构建发展危险气体监控体系方面起到借鉴作用。

基于压电超声换能器的被动声学发展及应用综述

深入探讨了微电子机械系统(MEMS)在被动声学领域的应用,特别关注了压电效应、常用压电材料和传感结构设计三方面。阐述了压电效应的基本概念,介绍了石英、PZT(锆钛酸铅)和ZnO(氧化锌)等主要的压电材料,这些材料因其出色的压电特性而被广泛用于MEMS技术。同时详细分析了悬臂梁、薄膜等传感结构,这些结构能够高效地将声波能量转换为电信号。特别介绍了MEMS麦克风、MEMS水听器和MEMS声发射传感器3种具有代表性的MEMS声学器件,并详细说明其工作原理及其在不同领域的应用。最后对MEMS声学器件在消费电子、工业检测、环境监测、军事及医疗等领域的应用进行总结,并对其未来发展趋势进行了展望。

长江江豚对孤立栖息地斑块利用规律研究及潜在因子分析

为研究长江江豚(Neophocaena asiseorientalis asiseorientalis)对人类干扰包围下孤立栖息地斑块的利用规律,采用目视考察和声学监测两种方法研究了不同季节江豚在被航运、航道整治、大型码头等包围的何家洲水域的分布及概率。并与江豚对长江自然岸滩牛屯河边滩的分布及概率做比较,揭示江豚对被高强度人为干扰包围的孤立栖息地斑块利用规律并定性分析潜在影响因子。丰水期和枯水期目视考察平均单次观察到的江豚分别为(10.00±2.35)和(15.60±8.17)头次,主要集中分布在何家洲水域及牛屯河边滩,两个季节平均单次观察到的江豚头次没有显著差异。丰水期和枯水期在何家洲和牛屯河边滩水域几乎每天都能声学监测到江豚分布。丰水期何家洲水域浅滩、汇流区及牛屯河边滩的江豚探测概率分别为0.377±0.074、0.06±0.036和0.140±0.081;枯水期何家洲水域浅滩、汇流区及牛屯河边滩的江豚探测概率分别为0.137±0.102、0.216±0.087和0.495±0.098。江豚在研究水域3个监测点的昼夜分布节律表现出随机性,表明江豚在该水域昼夜活动相当。可见,江豚对何家洲水域仍有较高的利用率,尤其是在丰水期。枯水期江豚对何家洲水域浅滩水域利用率明显降低,低水位导致浅滩萎缩和航运对近岸水域的占据可能是重要的影响因子。鉴于江豚对何家洲水域的高利用率和何家洲外围被较大的人类干扰所包围,研究建议在何家洲水域设置江豚重要栖息地标志及控制何家洲左汊的船只数量和船只间距。

紧邻大直径浅埋原水管深基坑工程设计与实践

以福州江阴电力管廊隧道项目为例,针对长距离紧邻的大直径原水管的保护,介绍深基坑工程的实施方案,重点说明所采取的拉森钢板桩和外侧增加H型钢的围护体结构,竖向设置两道钢管水平支撑和坑底进行旋喷桩被动区加固等关键技术方案。监测结果表明,在基坑开挖和换撑过程中引起的管线位移限值均在可控范围内,采用的设计方案是合理有效的。

无源无线多功能传感器在低压600 V系统中的应用研究

该文提出了一种无源无线多功能传感器,能够利用电缆周围的电磁能量和热能进行供电,同时测量电缆的温度值和电流值,根据电缆的带电状态进行判断和报警。详细介绍该传感器的原理、结构、技术细节和工作流程,并以特高压换流站伴热带为例,展示该传感器的应用方案和效果。实验结果表明,该传感器能够实现对电缆的实时监测和分析,提高电缆运行的安全性和可靠性,节约能源和成本,简化安装和维护,适用于各种环境,具有较高的创新性和实用性。

低压600 V系统中无源无线多功能传感器的设计与实现

该文介绍一种应用于低压600 V系统的无源无线多功能传感器。该传感器能够在线监测电缆的带电状态、电流值和温度值,并通过无线通信上传至采集装置,实现无线电流及温度的监测和分析,捕捉设备运行异常状态。该传感器无需任何外部电源供电,只需要将被测电流线穿入传感器的穿线孔中,通过电缆周围感应电磁能量供电,适用于高电压、大电流、强磁场的特殊环境,保证监测数据的准确性。

矿用无源灰分仪在同忻煤矿井下的应用实践

针对同忻煤矿在线监测井下毛煤灰分的应用需求,基于灰分与煤的天然放射性呈正相关的原理,通过采用高射线透过率材料的隔爆型矿用射线探测器、由隔离变压器供电的光纤通讯分析仪表以及由内外屏蔽实现低本底水平的环境屏蔽体,完成了井下矿用无源灰分仪的设计,并将之应用于同忻煤矿井下毛煤的灰分监测。实践表明:矿用无源灰分仪应用效果良好,测量值与人工化验值的均方根误差低于1.26%;利用灰分监测数据指导井下采煤生产,使毛煤年平均灰分下降了0.76个百分点,达到了从源头加强煤质管控的目的。

Lunar noise correlation,imaging and monitoring

Passive seismic techniques have revolutionarised seismology, leading for example to increased resolution in surface wave tomography, to the possibility to monitor changes in the propagation medium, and to many new processing strategies in seismic exploration. Here we review applications of the new techniques to a very particular dataset, namely data from the Apollo 17 lunar network. The special conditions of the lunar noise environment are investigated, illustrating the interplay between the properties of the noise and the ability to reconstruct Green＇s functions. With a dispersion analysis of reconstructed Rayleigh waves new information about the shallow shear velocity structure of the Moon are obtained. Passive image interferometry is used to study the effect of temperature changes in the subsurface on the seismic velocities providing direct observation of a dynamic process in the lunar environment. These applications highlight the potential of passive techniques for terrestrial and planetary seismology.

ZigBee Sensor Network Platform for Health Monitoring of Rails Using Ambient Noise Correlation

WSNs （wireless sensor networks） can be used for railway infrastructure inspection and vehicle health monitoring. SHM （structural health monitoring） systems have a great potential to improve regular operation, security and maintenance routine of structures with estimating the state of its health and detecting the changes that affect its performance. This is vital for the development, upgrading, and expansion of railway networks. The work presented in this paper aims at the possible use of acoustic sensors coupled with ZigBee modules for health monitoring of rails. The detection principle is based on acoustic noise correlation techniques. Experiments have been performed in a rail sample to confirm the validity of acoustic noise correlation techniques in the rail. A wireless communication platform prototype based on the ZigBee/IEEE 802.15.4 technology has been implemented and deployed on a rail sample. Once the signals from the structure are collected, sensor data are transmitted through a ZigBee solution to the processing unit.