Extension to the analytical model of the interdigital electrodes capacitance for a multi-layered structure

Interdigital electrodes (IE) are one of the most used transducers in different technical and analytical applications with the particular importance in the field of chemical and biological sensors. With the recent demand for lab-on-a-chip devices and the need for sensors miniaturization it becomes common the use of such transducers in structures with several dielectric layers (either substrates or superstrates). In a previous a work we proposed a model for the computation of the capacitance of these multi-layered structures using the techniques of conformal mapping and partial capacitance. Until now, that model has been used in applications where the permittivity of consecutive layers monotonically decreases from layer to layer (as we move away from the electrodes plane) giving excellent results. New applications, such as the use of Si/SiO₂ substrates (to promote very smooth surfaces for electrodes deposition) or the use of passivation layers for the protection of electrodes (e.g. from liquids), among others, represent a new challenge for the computation of the overall capacitance since in these devices the permittivity can decrease from layer to layer. Under these conditions the original partial capacitance technique needs to be modified to include these new configurations. In this work we will discuss a new approach, splitting the concept of partial capacitance in parallel partial capacitance and serial partial capacitance where new conformal mapping transformations are proposed for the latter case. Hence this novel approach will extend our previous analytical model in order to account for the cases where there is a decrease in the permittivity from layer to layer. The results are compared with finite element simulation and experimental results.     

Water activated ionic conduction in cross-linked polyelectrolytes

The electrical properties of polyelectrolytes depend on the water concentration of the environment. The behaviour of both conductance and capacitance caused by variations in relative humidity and temperature was investigated by impedance spectroscopy for humidity sensors based on an interpenetrated network of a polymer and a polyelectrolyte. The results were interpreted on the base of the Langmuir and Kelvin equations and two different sensing mechanisms were highlighted for low and high water content.     

汽车尾气用NO_x传感器

汽车尾气中的有害物主要有CO,HC,NOx,SOx以及一些微粒物质,给人类赖以生存的大气环境带来了严重的危害。汽车尾气用NOx传感器开发主要是为了解决NOx(包括NO,NO2)的排放问题,能够实现准确、快速地测定NOx含量,从而满足大气质量检测和环境保护的要求。目前,NOx气体传感器主要有半导体型、电位型和电流型。主要介绍了这3种汽车用NOx传感器的原理、结构及应用,并简要分析了其向微型化、集成化和智能化等方向发展的趋势。     

Fluctuation-enhanced scent sensing using a single gas sensor

Scent or aroma sensing during aromatherapy can be carried out by applying only a single resistance gas sensor (TGS - Taguchi Gas Sensors). This paper considers the efficiency of detection of essential oils by DC resistance and its fluctuations observed in TGS sensors. A detailed study has been conducted for scents emitted by five popular essential oils using three sensor types (TGS 2600, TGS 2602, TGS 823). The research was focused on the practical use in aromatherapy to assure the same intensity of scents which are sprayed by a glass nebulizer. The prepared system for scent emission and control of its intensity was presented as well.     

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.     

移动传感器栅栏覆盖研究

栅栏覆盖保证当某个移动目标沿任意路径穿越监控区域时都能被检测到,适合于移动监测和边界保护等应用.随机部署静止传感器时,为保证栅栏覆盖需要大量节点,造成了不必要的浪费.本文利用可移动传感器进行栅栏覆盖,移动传感器随机部署后能够自动再部署,可以利用少得多的节点保证栅栏覆盖.本文研究了能量有效的栅栏覆盖再部署问题,并设计了一个集中式再部署算法,为所有节点计算最优的再部署位置.     

Viscosity virtual sensor to control combustion in fossil fuel power plants

Thermo-electrical power plants utilize fossil fuel oil to transform the calorific power of fuel into electric power. An optimal combustion in the boiler requires the fuel oil to be in its best conditions. One of fuel's most important properties to consider is viscosity. Viscosity has influence on the optimal combustion between fuel and air. Hardware viscosity meters for fuel oils are expensive and unreliable to operate in power plant conditions. Chemical laboratory measures viscosity accurately with special apparatus, but they cannot be used in a real time process. This paper describes the development of a virtual sensor that estimates fuel oil viscosity in the combustion process of a power plant. A virtual sensor or soft sensor is a computer program that estimates the value of a certain variable based on related measurements and a model of the process where the variable participates. In this project, a probabilistic model is constructed using automatic learning algorithms with historical data and experts' advice. The learning and validation experiments are described and discussed. The virtual sensor is installed in the Tuxpan Power Plant in Veracruz, Mexico.     

基于优化深度置信网络的多传感器水质监测研究

为了满足多种水环境的大范围、精准监测需求,提出了基于优化深度置信网络的多传感器水质监测方法。设置水质监测标准,作为水质等级的判定条件。优化设计水体温度、PH值、溶解氧、浊度等传感器设备,利用优化深度置信网络选择多传感器的安装位置。利用多传感器采集水环境数据并完成融合处理,通过多个水质监测指标的计算以及与设置标准的比对,得出多传感器水质监测的可视化输出结果。通过性能测试实验得出结论：优化设计方法的水质监测范围为2041.79平方千米,浊度、pH值、溶解氧和氨氮浓度指标的监测误差分别为0.005FTU、0.07、0.05mg/L和0.007mg/L,均低于传统方法,且满足预设条件。     

A sensor array based on mass and capacitance transducers for the detection of adulterated gasolines

The simultaneous use of different sensors technologies is an efficient method to increase the performance of chemical sensors systems. Among the available technologies, mass and capacitance transducers are particularly interesting because they can take advantage also from non-conductive sensing layers, such as most of the more interesting molecular recognition systems. In this paper, an array of quartz microbalance sensors is complemented by an array of capacitors obtained from a commercial biometrics fingerprints detector. The two sets of transducers, properly functionalized by sensitive molecular and polymeric films, are utilized for the estimation of adulteration in gasolines, and in particular to quantify the content of ethanol in gasolines, an application of importance for Brazilian market. Results indicate that the hybrid system outperforms the individual sensor arrays even if the quantification of ethanol in gasoline, due to the variability of gasolines formulation, is affected by a barely acceptable error.     

Thin polymer film based rapid surface acoustic wave humidity sensors

Polyvinyl alcohol (PVA) and polyvinyl pyrrolidone (PVP) thin films, deposited on the surface of glass slides, were studied using transmission FTIR spectroscopy upon varying relative humidity (RH) from 2 to 70%. The obtained data revealed fast dynamics of water vapor adsorption-desorption with responses on the order of several seconds. Based on the fast FTIR signal intensity changes versus RH, it was proposed that a similar rapid response can be achieved for PVA and PVP coated SAW devices due to changes in mass-loading and film viscoelastic properties upon absorption of water vapor in the films. Sub-micron thickness films were spin-coated onto the surface of LiNbO₃ SAW substrates. Both PVA and PVP based humidity sensors revealed prompt reversible response to variations in humidity, although PVP-based device demonstrated better sensor parameters with total insertion loss variation of about 50 dB over the studied RH range and response time 1.5 s for the humidity step 5-95% (recovery time - 2.5 s), representing one of the fastest SAW-based humidity sensors reported to date.     

水质检测传感器研究的新进展

水质检测传感器主要包括化学水质检测传感器、生物学水质检测传感器、光学水质检测传感器和谐振式水质检测传感器四类。综述了水质传感器的原理、应用、研究现状和各自的特点,对水质检测传感器现存的问题进行了阐述。对我国生活饮用水卫生标准的主要常规指标进行了介绍,并与其它国家的几种主要用水标准进行了对比。     

Analysis of optochemical absorbance sensors based on bidimensional planar ARROW microoptics

A new approach for developing absorbance optochemical sensors is presented in this paper. It is based on a planar microoptic circuit where an optochemically active membrane, which responds selectively to a compound, is deposited in the device, yielding a part of the guiding planar structure. Light is propagated through the membrane, which changes its spectral absorption properties and controls the selectivity of the measurements by means of several immobilised compounds. This way, high sensitivity of the device can be easily obtained due to relatively long light paths through the membrane, and low response times can be achieved as the analyte diffusion occurs perpendicularly to the light path and through a thin membrane. Experimental results on measurements of the concentration of a specific ion in solution using the fabricated sensors are also presented.     

Fiber optic humidity sensors for high-energy physics applications at CERN

This work is devoted to a feasibility analysis for the development of novel fiber optic humidity sensors to be applied in high-energy physics (HEP) applications and in particular in experiments actually running at the European Organization for Nuclear Research (CERN). On this line of argument and due to the wide investigations carried out in the last years aimed to assess the radiation hardness capability of fiber optic technology in high energy physics environments, our multidisciplinary research group has been recently engaged in the development of near-field fiber optic sensors based on particle layers of tin dioxide to perform the monitoring of low values of relative humidity RH even at low temperatures.While this sensor type has been successfully employed for ppm and sub-ppm chemical detection in air and water environments, it is the first reported use for relative humidity measurements.The RH sensing performance of fabricated probes was analyzed during a deep experimental campaign carried out in the laboratories of CERN, in Genève. A very good agreement was observed between humidity measurements provided by the optical fiber sensors and commercial polymer-based hygrometers at 20 °C and 0 °C, with limits of detection for low RH regimes below 0.1%.     

Lateral field excited Y-cut langasite bulk acoustic wave sensor

Previous studies have shown that lateral field excited (LFE) devices on AT-cut quartz are sensitive to liquid electrical property changes. AT-cut quartz LFE devices have low piezoelectric coupling factors. To further improve electrical sensitivities of LFE sensors, it is necessary to study LFE sensors based on other piezoelectric materials with higher coupling factors. In this paper, LFE sensors on Y-cut langasite, which has twice the higher piezoelectric coupling factor of AT-cut quartz, are investigated. Several Y-cut langasite LFE sensors are designed, fabricated, and tested. The experimental results show that the devices are over 6 times more sensitive to liquid conductivity changes and about 2.5 times more sensitive to liquid permittivity changes compared to AT-cut quartz LFE devices. It was also found that the Y-cut langasite LFE devices are about 1.3 times more sensitive to changes in liquid acoustic viscosity compared to the AT-cut quartz LFE devices.     

Low-Cost IMU Sensors for Satellite Maturity Improvement

The satellite technology proves its impact in the modern era with its wide benefits and applications. However, the cost of the development in this field presents gaps in many countries, almost the developed countries. Therefore, this paper provides a rich platform around low-cost sensors in order to improve maturity in space technology, mostly the system of attitude determination and control. The development of this knowledge turns out to be very interesting in order to achieve a space mission which leads to the progression of the spatial technology readiness level (TRL) defined by the international measurement scale which is able to estimate the technological maturity. Thus, the idea is carried out for the development of low-cost sensors’ system for attitude determination around an Arduino board. A sensor fusion method was applied on three types of sensors: accelerometer, magnetometer, and gyroscope in order to detect the reliable orientation. It is aimed to apply quaternion based Kalman filter on different platform than previous systems. It is succeeded therefore to improve measurement accuracy around low-cost sensor to achieve the main goal of this paper.     

Biodiesel production control using PNN and Coriolis flowmeter

In order to complete the transesterification process, online result verification is applied to the traditional offline verification process based on chromatographic methods. There is a quick analytical method for assessing the biodiesel content of transesterification reaction by applying a correlation with viscosity. The results can substitute chromatographic verifications when recognizing and selecting the specified biodiesel quality. This type of verification could save hours of biodiesel process production per day. The proposed work designs a control solution for online biodiesel production verification using an online application based on the PNN technology and Coriolis viscosity sensors.     

Calibration of a TDR probe for low soil water content measurements

Time domain reflectometry (TDR) probes are increasingly used for field and laboratory estimation of soil water content. Usual calibration of TDR probes for the determination of soil water content uses two media: air for low and water for high values of dielectric permittivity, although the measured range of dielectric permittivity in soil is much smaller as compared to the range implied by the calibration media. The use of air for calibration of short TDR probes gives calibration errors due to overlapping incident and reflected pulses in the reflectogram, which result in their relative shift in time. This phenomenon, named the convolution effect, can be avoided by the application of selected calibration media. The presented approach minimizes of dielectric permittivity measurement errors by choosing the calibration media with dielectric permittivity values close to the limits of the measurement range and the possibility to use TDR probes of various lengths. The comparison of errors of TDR apparent dielectric permittivity measurement in three sandy soils, based on the probe calibrations in various media, is also presented.     

基于K-最近邻算法的管道系统传感器数据有效性分析研究

在管道运输中传感器的正常使用至关重要,为了防止因传感器故障而导致的数据采集失效,造成误报警和漏报警,对传感器本身的故障诊断和失效分析已经成为当前研究的重要方向.通过对各传感器采集数据进行组合分析,以各传感器之间的数据关联特性作为研究内容,运用K-最近邻算法对管道上传感器所采集数据进行相似性拟合,提出采用C4.5算法定义各传感器所采集数据对目标传感器的支持度以决定目标传感器数据的有效性,对故障传感器运行状态进行分析与定位,进而判断传感器的数据可靠性和输差出现位置.实验结合西南某管道流量传感器数据进行分析,结果表明,该算法能够准确判断目标传感器数据的有效性和故障传感器在时域中发生的位置.     

基于移动传感器的大规模复杂供水管网监测研究进展

采用移动传感器监测供水管网的目标是,在一定成本内,获取管网数据、发现管网内的泄漏与污染等问题,对节约水资源和保障居民健康具有重要的意义。然而,相关研究尚处于起步阶段。虽然在管网结构探测、移动传感器移动建模、移动传感器投放决策变量的选择等方面取得了一定成果。但是,管网水流情况多变、优化计算复杂等问题依然对该领域形成挑战。为了更好地推进该领域的研究,论文对相关工作进行了归纳、分析和对比,了解当前工作的优缺点,并对未来研究方向进行了展望。