Recent developments in wireless sensor networks have empowered low-power, intelligent sensor nodes to be distributed over a large area. However, wireless sensor nodes that actively emit electromagnetic waves for energy-hungry communication are limited by the volumes and capacities of batteries, requiring periodic maintenance in widespread applications. To solve this problem, we propose a passive wireless sensor platform, WiSensor, which makes wireless sensor nodes take use of ambient Wi-Fi waves instead of actively emitting electromagnetic waves to transmit sensor data. By affecting the Wi-Fi channels through backscattering, the sensor node modulates the sensor data onto the Wi-Fi channels established by a Wi-Fi transmitting node and a Wi-Fi receiving node. The receiving node acts as the sensor receiver and the sensor data are extracted from the Wi-Fi channel state information. We define the signal-to-noise ratio at the sensor data receiver and analyze the WiSensor performance dependencies, providing guidance for the system design and implementation. A prototype of WiSensor is established, in which sensor data can be transmitted at 200 bps with a bit error rate of 0.01% while the sensor node is placed as far as 5 m from the Wi-Fi transmitting node and 2 m from the Wi-Fi receiving node at 2.37- $\mu \text{W}$ power consumption for the wireless connection. WiSensor is a novel and general wireless sensor platform that embeds the utilization of Wi-Fi channels to practical sensing tasks without the need for wireless sensor nodes to follow Wi-Fi protocols, empowering ubiquitous commodity Wi-Fi devices in our daily life with general sensor connectivity. We believe WiSensor demonstrates promising potential in the field of next-generation smart homes and other applications that urgently require ultralow-power sensor data transmission.

SAW strain sensing element is an important part of SAW strain sensor. It is of great significance to design and analyze it. In this paper, the influence of piezoelectric substrate and electrode structure parameters on the performance of SAW strain sensing element is simulated and analyzed, using ST-quartz as piezoelectric material and aluminum as electrode material, a high-performance surface acoustic wave strain sensing element was designed, fabricated and measured. By analyzing the measured results, the strain sensitivity of frequency ( SSF ), strain coefficient of frequency SCF ) and temperature coefficient of frequency ( TCF ) of the SAW strain sensing element are 550.9Hz/ $\mu \varepsilon $ , 1.26 ppm/ $\mu \varepsilon $ and −1.22 ppm/°C respectively. The experimental results meet the design requirements well. This research provides a good guidance for the application of SAW strain sensor.

The multilayer structure of surface acoustic wave sensor is an important development direction of surface acoustic wave devices in recent years. In this paper, the IDT/AlN/Mo/diamond structure of surface acoustic wave pressure sensing element is modeled and simulated. The influence of the thickness of AlN and IDT on pressure coefficient frequency and K 2 were simulated and analyzed. The performance of surface acoustic wave pressure sensing element is compared when the metal layer is Mo, no metal layer and the metal layer is Pt. Finally, the relationship between frequency variation and pressure of the designed multilayer surface acoustic wave pressure sensing element is obtained. This research provides a good guidance for the design of surface acoustic wave pressure sensor.

Radio-frequency (RF) sensing tags are emerging as the next-generation paradigm toward gathering context-awareness information related to all objects’ physical phenomena for the future Internet of Things (IoT). However, the most attention has been given to realize the sensing functions of a single tag rather than the mutual influences among adjacent tags. It has been found that when multiple RF sensing tags are deployed adjacently, these tags may fail to function properly. Therefore, motivated by the common requirements of deploying multiple RF sensing tags in the IoT, the mutual influences among tags are analyzed. We believe that the mutual impedance of tag antennas, which changes with the antenna separations among adjacent RF sensing tags, affects the wireless links between the tags and reader. The mutual impedance is analyzed using the method of moments and is substituted into forward and backward links. The calculation results show that the influence of the antenna mutual impedance on the RF sensing tag takes the wavelength of RF waves as the period, fluctuates, and gradually diminishes as the separations between antennas increase. To validate the analysis, a sensor array is formed using multiple RF sensing tags integrated with magnetic sensors. The experimental results show that once the antenna separations between the tags exceed 1.5 wavelengths, the backscattering sensing data can be decoded, and the interrogation success rates reach 100%. Numerous sensor arrays can be deployed ubiquitously with convenience, providing a clustered solution toward distributed sensing for the IoT.

The finite element method (FEM) has been applied to extract the coupling-of-modes (COM) parameters of surface acoustic wave (SAW) devices for a long time. It always involves calculating the dispersive curves or harmonic admittance, which makes the extraction process and results sophisticated, time-consuming and inaccurate. Therefore, a simple method is proposed to extract all COM parameters of the SAW devices rapidly and accurately in this paper. It is based on the FEM and combines the stationary analysis with modal analysis. We have described in detail the basic principles and procedures of the proposed method, and made a comprehensive comparison between the proposed method and the other two existing methods. We have also examined the proposed method by extracting COM parameters of some common SAW substrate, and compared our extracted results with those reported in the other literatures. Results show that our proposed method holds higher accuracy and more efficiency (~s order) than the others (~h order). Moreover, our extracted COM parameters are in an excellent agreement with those reported in the other literatures.

断路器的分合闸线圈电流波形是分析断路器机械特性的重要参数之一,文中设计了一套分合闸线圈电流波形采集系统,使用装在分合闸回路引线上的霍尔电流传感器,通过采集系统捕获分合闸线圈的电流信号,并在此基础上应用改进的极值判断法实现了断路器分合闸线圈电流信号特征点的准确提取,证明了该数据处理算法的有效性.现场测试和实际应用结果也表明,该系统可以捕获完整的分合闸线圈电流信号,准确定位特征点的位置,为分析断路器的机械特性提供了重要依据.

卫星在轨工作时因尘埃撞击、作动机构动作引起的颤振的高精度准确测量,对实现振动补偿、图像修正,进而提升遥感卫星的对地分辨率具有重要意义.本文基于FPGA和1553B总线的架构,设计了用于在轨卫星颤振测量的数据采集系统,对系统的多路同步采集、存储、传送以及抗辐射可靠性等关键问题进行了详细分析和设计,并通过硬件设计实现及试验验证了系统的功能.测试结果表明所涉及的数据采集系统样机满足星载测试要求.

The film-based magnetic sensors possess prominent superiorities in miniaturization and integration. Because of the presence of shape demagnetization, the magnetic film effective permeability is dramatically degraded, restricting the performance improvement of planar magnetic sensors. This study reports an efficacious approach to compensate for the shape demagnetization and actively increase effective permeability by introducing grooved grating patterns on a magnetic film surface. The grating patterned films are demonstrated that the maximum values of effective permeability and its variation rate with a magnetic field are increased by 446.03% and 606.77% compared with the same thickness smooth film. It is experimentally demonstrated that the magnetic behavior of the patterned film is modified. The magnetization curves of grooved films exhibit two magnetization rising stages. In addition, the anisotropy of the grooved films can be also tuned through the shape anisotropy of the gratings. Effective permeability and anisotropy field can be enhanced together by grooved grating patterns, which cannot be realized in smooth magnetic films. These results indicate that the surface grating etching strategy provides an effective method to modify the film magnetization behaviors. The grating-patterned films have enormous potential for ultra-sensitive and wide-range micro-magnetic sensors.

Objetivo: Presentar de manera integral las medidas de prevencion y control que podemos adoptar en las consultas dentales durante el periodo pandemico de la enfermedad por el coronavirus 2019 (COVID-19) y aportar alguna experiencia practica para el desarrollo de politicas de enfermeria y sanitarias aplicables al COVID-19. Antecedentes: El brote del COVID-19 ha puesto en peligro el sistema sanitario mundial, lo que influye gravemente en el funcionamiento normal de la sociedad humana. Se deben tomar medidas de enfermeria seguras y efectivas que garanticen el funcionamiento normal de las consultas dentales. Fuentes de evidencia: Buscamos y referenciamos muchas citas de la base de datos PubMed. Mediante la combinacion de la bibliografia relacionada y nuestra experiencia, describimos diversas estrategias, como la gestion de personal, la proteccion personal, la desinfeccion y el aislamiento, adoptadas en la consulta dental de nuestro hospital chino durante la pandemia del COVID-19. Discusion/Conclusiones: Introdujimos estrategias para el personal de enfermeria en las consultas dentales para ayudar a la prevencion y al control del COVID-19. La implementacion satisfactoria de las medidas de proteccion que podian garantizar la seguridad del personal sanitario y de los pacientes, contribuyeron al funcionamiento normal de las consultas dentales durante el periodo pandemico. Conclusiones para la enfermeria y la politica sanitaria: Durante la pandemia, las enfermeras de primera linea se encuentran bajo presion fisica y mental frente a la amenaza de infeccion en el trabajo. Ademas de la prevencion de una pandemia, tambien debemos prestar atencion a las necesidades del personal de enfermeria. Se deberian formular politicas sanitarias y de enfermeria mas razonables y eficaces para garantizar su seguridad y proteger sus derechos e intereses. Esta es la unica forma en que se puede lograr la prevencion y el control del COVID-19 y de que podamos prepararnos para futuros eventos de salud publica.

Bubbles are ubiquitous in water and are unusually energy-rich in the seabed. Harvesting energy from subsea bubbles is a viable solution to supplying energy in situ for underwater equipment, but the existing approaches are unsatisfactory due to low-efficient conversion of bubble potential energy. Here, we propose a novel bubbledriven pipe flow approach for efficient harvesting of bubble energy, which uses the liquid propelled by bubble buoyancy to form a directional pipe flow driving the turbine generator. We perform theoretical analysis of the bubble energy conversion process and the deductions are consistent with the experimental results. The average output power density generated by the new technique reaches 5.84 x 103 times higher than that of the existing bubble energy harvester. This strategy is expected to be a unique in situ power supply technique for underwater Internet of Things application due to its high efficiency and advanced functionality.

Existing piezoelectric energy harvesting circuits consume significant amount of power and have high input power threshold, creating challenges when the ambient input power is limited. This paper proposes a self-powered, ultra-low power control circuit for weak input power and heavy loads, operating intermittently at an extremely low duty cycle while only consuming 0.3 W. By drawing power from the piezoelectric transducer at the maximum power point, the proposed circuit can operate efficiently when cold-starting at an input power threshold of 2 mu W, ideal for harvesting natural vibrational energy which are often interrupted. When using a large 1 F storage capacitor and the DR-DSSH circuit, the proposed circuit can significantly outperform other synchronous circuits, achieving 21.3 % and 897.7 % better than DSSH and SEH, respectively, in terms of final charging voltage. The proposed circuit and control strategy can be applied to similar weak piezoelectric transducers for harvesting ambient energy. (c) 2021 Elsevier B.V. All rights reserved.

The echo signal energy of surface acoustic wave (SAW) strain sensor is weak, resulting in low demodulation accuracy. In order to improve the measurement result, a SAW sensor demodulation method by combining hybrid changing area niche genetic algorithm and MUSIC algorithm was proposed. The proposed method was based on the MUSIC algorithm to construct the power spectrum function of SAW echo signal. A hybrid changing area niche genetic algorithm (CANGA) and particle swarm optimization (PSO) algorithm was developed to improve the spectrum peak search accuracy and reduce the amount calculations of MUSIC algorithm. The power spectrum function of the MUSIC algorithm was used as the fitness function of the hybrid algorithm. The echo frequency was estimated by the variable value corresponding to the optimal solution. The proposed hybrid PSO-CANGA has the characteristics of strong global search ability and fast convergence speed to improve the performance of MUSIC algorithm. The numerical comparisons were performed. The results showed that the hybrid PSO-CANGA gives fastest convergence and the highest estimation accuracy compared to original PSO and NGA. In addition, compared with traditional spectrum estimation algorithms, the proposed algorithm had a minimum estimation error with standard deviation of 0.27KHz. The proposed demodulation method was used to SAW strain system. The nonlinearity of the strain measurement was improved, with a nonlinearity of 0.55%. Simulation and experiment results verified the effectiveness of the proposed algorithm for the demodulation of the SAW strain sensor system. It helps to improve the accuracy of SAW strain measurement.

Compared with apodization, the piston-mode technique is a preferable solution to suppress the spurious transverse modes in surface acoustic wave (SAW) devices. This paper extends the technique to the SAW resonator (SAWR) strain sensors to achieve a high performance, that is, conquer some negative influence in the wireless strain sensing system caused by the spurious modes, such as low signal to noise ratio (SNR), high misreading rate and demodulation difficulty. The principle of piston-mode operation was presented and a modified expression was given for primary design of the piston-mode waveguide, which takes into account the anisotropy difference in different electrode regions. SAWRs based on the Al/ST-quartz with the conventional and two common piston-mode configurations were designed, simulated, fabricated and measured. The experiments to evaluate the wireless performance and strain sensitivity of the SAWR strain sensors with different electrode configurations were performed.

为实现地磁背景下微弱磁异常目标的远距离探测,解决地磁背景信号远大于目标磁异常信号,导致测试系统分辨率和探测能力受限的问题,文中设计了由测量和补偿2个三轴磁通门磁强计构成的实时动态地磁补偿系统.推导了三轴磁通门磁强计非正交、灵敏度和零点误差对测量结果的影响方式,提出了通过电路参数的合理匹配和优化设计实现转向差校正和地磁补偿的硬件技术方案.实验证明该方案有良好的转向差校正和地磁补偿效果,可以为磁异常信号提供更大的增益范围,能够实现对微小磁异常信号的实时提取与动态检测,具有较好的工程应用价值.

Magnetoelectric (ME) composite based on the converse magnetoelectric (CME) effect is promising for the high sensitivity dc and low-frequency magnetic field detection application, however, the performance is restricted by the stress modulation ability of piezoelectric phases and the narrow bandwidth. This work presents a nonlinear equivalent circuit model to design a new ME composite consisting of magnetostrictive layers/radial mode piezoelectric transformer/magnetostrictive layers under dual ac magnetic field and stress modulation. The theoretical model is based on the nonlinear constitutive relationships of magnetostrictive material, motion equation with imperfect interface condition, and improved ME equivalent circuit. This model cannot only predict the resonant ME effects of electrically modulated ME composite under the dual ac stress and magnetic field drive, but can also predict the conventional CME and mutual inductance effects separately. Specifically, the theoretical prediction indicates that with negligible extra power consumption, the dual modulated ME composite provides higher dc and low-frequency magnetic field sensitivity with frequency conversion method and significantly wider bandwidth compared to the conventional CME effect. Such theoretical predictions are further verified by the experimental results of Metglas/piezoelectric transformer/Metglas and Terfenol-D/piezoelectric transformer/Terfenol-D laminate. The theoretical study plays a guiding role in designing the new ME magnetometer with low power consumption, high sensitivity, and wide bandwidth.

Various types of interference signals are available in the working environment of passive wireless surface acoustic wave (SAW) sensors. Among these kinds of interference, co-channel interference is difficult to suppress. To solve this problem, a SAW sensor anti-interference technology was proposed to improve the reliability of the SAW sensor. Wavelet denoising method was used to denoise SAW resonator (SAWR) response, which can maintain the envelope characteristics of the SAW response. The entropy energy model of the SAW response signal was established, and the signal envelope was extracted from the proposed entropy energy function. The waveform envelope and the entropy energy curve were adopted as the signal characteristics to form two-dimensional points. The K-Means algorithm was used to classify the two-dimensional points to distinguish the SAW response from sinusoidal interference. Simulation results showed that the SAW response can be detected with a rate of more than 85% when the signal-to-noise ratio was greater than 4 dB, whereas the false detection rate of the sinusoidal interference signal was less than 8%. Finally, the proposed algorithm was used to detect the actual SAW response and sinusoidal interference signal. The experimental results showed that the proposed method can clearly distinguish the SAW response from the co-channel interference signal. Moreover, the proposed method can be used as the anti-interference technology to improve the stability of the SAW sensor.

Cable current detection plays a vital role in power grids toward improving transmission efficiency, relieving power congestion, and ensuring grid reliability. However, the sensors in existing current detection systems either are wired with measurement instruments or are wireless yet require batteries, which is inconvenient for monitoring overhead powerlines. Inspired by RF sensing tags, which are widely used for applications such as temperature and humidity measurements, in this article, we propose a distinctive cable current detection system that can avoid the constraint of wires and batteries. By detecting the ambient magnetic field produced by ac current flowing through a cable, the proposed system realizes a minimal measurement range of 5–17.5 A at 50/60 Hz with a maximum wireless distance of 5.2 m. This prototype can detect cable current with an extendable measurement range, providing a promising strategy for passive and wireless current detection.

为了解决金属环境条件下的无线供电和信号传输需求,提出了一种基于电容耦合方式的无线能量和信号并行传输方案.通过建立E类放大器的数学模型,分析电容耦合系统的传输特性和阻抗影响机理,设计了适用于E类放大器结构的调制与解调电路,并通过仿真验证了电路的可行性,为CCPT系统从能量传输到信号回传提供了系统性的理论指导.

To improve the dc magnetic field sensitivity of conventional inductor-type (i.e., longitudinally driven giant magnetoimpedance) sensor at the low excitation frequency, a transformer-type laminated magnetic sensor consisting of soft magnetostrictive alloy FeBSiC/piezoelectric ceramics Pb(Zr,Ti)O3/FeBSiC heterostructure wrapped with both the exciting and sensing coils (i.e., FPFCexCse) is proposed. Compared to the inductor-type dc magnetic sensor (i.e., Hac driven FeBSiC ribbons with only exciting coils), on one hand the ac magnetic field (Hac) produced by the exciting coil and the stress produced by electrically driven PZT are synchronously coupled to enhance the magnetic induction variation of FeBSiC and the induced voltage sensitivity of sensing coils. On the other hand the mutual inductance induced voltage eliminates the weak skin effect at the low excitation frequency. When the exciting coil and PZT of FPFCexCse laminate are synchronously excited with 5 mA ac current and 5 V voltage at the mechanical resonance frequency, the maximum magnetic field sensitivity of 21200 V/T is achieved. This is about 4.08 times and 2.98 times as high as that of FeBSiC ribbon with only exciting coils (5190 V/T) and FeBSiC ribbons with both exciting and sensing coils (7120 V/T), respectively. Furthermore the equivalent magnetic noise of $114~{\mathrm {pT}}/\sqrt {{\mathrm {Hz}}} $ (at 1Hz) is achieved by the FPFC exCse laminate, which is obviously lower than that of Hac driven FeBSiC ribbons.

The surface acoustic wave (SAW) sensor has been widely used to measure torque, and the temperature effect on torque sensitivity has been taken into account. However, few studies have been devoted to the influence of electrode on the torque sensitivity. In order to design a SAW torque sensor with high performance, it is necessary to analyze the effect of electrode. We adopt the Mindlin's thin plate equations as a boundary condition due to the electrode, propose a method to evaluate the effect of electrode and make a comparison between our calculation and experimental results. Then, we obtain the frequency shifts with different electrode materials when the applied torque is zero. Finally, we evaluate the torque sensitivity with the effect of electrode and obtain the result with the errors about 1.7 and 7.6% compared with experimental data. The errors have been improved greatly with respect to the calculation ignoring electrode effect, about 30%. However, the analysis is valid only under the condition that the thickness of electrode is relatively small, which is satisfied in the general conditions.