Continuous monitoring of the health status of cement-based structures: electrical impedance measurements and remote monitoring solutions

<p class="Abstract">The continuous monitoring of cement-based structures and infrastructures is fundamental to optimize their service life and reduce maintenance costs. In the framework of the EnDurCrete project (GA no. 760639), a remote monitoring system based on electrical impedance measurements was developed. Electrical impedance is measured according to the Wenner’s method, using 4-electrode arrays embedded in concrete during casting, selecting alternating current as excitation, to avoid the polarization of both electrode/material interface and of material itself. With this measurement, it is possible to promptly identify events related to contaminants ingress or damages (e.g. cracks formation). Conductive additions are included in some elements to enhance signal-to-noise ratio, as well as the self-sensing properties of concrete. Specifically, a distributed sensor network was implemented<span style="text-decoration: line-through;">,</span> consisting of measurement nodes installed in the elements to be monitored, then connected to a central hub (RS-232 protocol). Nodes are realized with an embedded unit for electrical impedance measurements (EVAL-AD5940BIOZ board with AD5940 chip, by Analog Device) and a digital thermometer (DS18B20 by Maxim Integrated), enclosed in cabinets filled with an IP68 gel against moist-related problems. Data are available on a Cloud through Wi-Fi network or LTE modem, hence can be accessed remotely via a use-friendly multi-platform interface.</p>

The Effects of Symmetry Breaking Perturbation on the Dynamics of a Novel Chaotic System with Cyclic Symmetry: Theoretical Analysis and Circuit Realization

Symmetry is an important property shared by a large number of nonlinear dynamical systems. Although the study of nonlinear systems with a symmetry property is very well documented, the literature has no sufficient investigation on the important issues concerning the behavior of such systems when their symmetry is broken or altered. In this work, we introduce a novel autonomous 3D system with cyclic symmetry having a piecewise quadratic nonlinearity [Formula: see text] where parameter [Formula: see text] is fixed and parameter [Formula: see text] controls the symmetry and the nonlinearity of the model. Obviously, for [Formula: see text] the system presents both cyclic and inversion symmetries while the inversion symmetry is explicitly broken for [Formula: see text]. We consider in detail the dynamics of the new system for both two regimes of operation by using classical nonlinear analysis tools (e.g. bifurcation diagrams, plots of largest Lyapunov exponents, phase space trajectory plots, etc.). Several nonlinear patterns are reported such as period doubling, periodic windows, parallel bifurcation branches, hysteresis, transient chaos, and the coexistence of multiple attractors of different topologies as well. One of the most gratifying features of the new system introduced in this work is the existence of several parameter ranges for which up to twelve disconnected periodic and chaotic attractors coexist. This latter feature is rarely reported, at least for a simple system like the one discussed in this work. An electronic analog device of the new cyclic system is designed and implemented in PSpice. A very good agreement is observed between PSpice simulation and the theoretical results.

A Reconstruction Filter for Saturated Accelerometer Signals Due to Insufficient FSR in Foot-mounted Inertial Navigation System

In pedestrian inertial navigation, one possible placement of Inertial Measurement Units (IMUs) is on a footwear. This placement allows to limit the accumulation of navigation errors due to the bias drift of inertial sensors and is generally a preferable placement of sensors to achieve the highest precision of pedestrian inertial navigation. However, inertial sensors mounted on footwear experience significantly higher accelerations and angular velocities during regular pedestrian activities than during more conventional navigation tasks, which could exceed Full Scale Range (FSR) of many commercial-off-the-shelf IMUs, therefore degrading accuracy of pedestrian navigation systems. This paper proposes a reconstruction filter to mitigate localization error in pedestrian navigation due to insufficient FSR of inertial sensors. The proposed reconstruction filter approximates immeasurable accelerometer's signals with a triangular function and estimates the size of the triangles using a Gaussian Process regression. To evaluate performance of the proposed reconstruction filter, we conducted two series of indoor pedestrian navigation experiments with a VectorNav VN-200 IMU and an Analog Device ADIS16497-3 IMU. In the first series of experiments, forces experienced by the IMUs did not exceed the FSRs of the sensors, while in the second series, the forces surpassed the FSR of the VN-200 IMU and saturated the accelerometer's readings. The saturated readings reduced the accuracy of estimated positions using the VN-200 by 1.34× and 3.37× along horizontal and vertical directions. When applying our proposed reconstruction filter to the saturated measurements, the navigation accuracy was increased by 5% horizontally and 50% vertically, as compared to using unreconstructed signals.

A Reconstruction Filter for Saturated Accelerometer Signals Due to Insufficient FSR in Foot-mounted Inertial Navigation System

In pedestrian inertial navigation, one possible placement of Inertial Measurement Units (IMUs) is on a footwear. This placement allows to limit the accumulation of navigation errors due to the bias drift of inertial sensors and is generally a preferable placement of sensors to achieve the highest precision of pedestrian inertial navigation. However, inertial sensors mounted on footwear experience significantly higher accelerations and angular velocities during regular pedestrian activities than during more conventional navigation tasks, which could exceed Full Scale Range (FSR) of many commercial-off-the-shelf IMUs, therefore degrading accuracy of pedestrian navigation systems. This paper proposes a reconstruction filter to mitigate localization error in pedestrian navigation due to insufficient FSR of inertial sensors. The proposed reconstruction filter approximates immeasurable accelerometer's signals with a triangular function and estimates the size of the triangles using a Gaussian Process regression. To evaluate performance of the proposed reconstruction filter, we conducted two series of indoor pedestrian navigation experiments with a VectorNav VN-200 IMU and an Analog Device ADIS16497-3 IMU. In the first series of experiments, forces experienced by the IMUs did not exceed the FSRs of the sensors, while in the second series, the forces surpassed the FSR of the VN-200 IMU and saturated the accelerometer's readings. The saturated readings reduced the accuracy of estimated positions using the VN-200 by 1.34× and 3.37× along horizontal and vertical directions. When applying our proposed reconstruction filter to the saturated measurements, the navigation accuracy was increased by 5% horizontally and 50% vertically, as compared to using unreconstructed signals.

Realization of fractional band pass filter on reconfigurable analog device

This paper presents a realization of fractional-order Band pass-filter (FOBF) based on the concepts of fractional order inductors and fractional order capacitors. The FOBF is designed and implemented using both simulation and hardware approaches. The proposed filter order is considered up to second order or less with any real positive number. One of the cases is considered when α ≤ 1 and β ≥ 1. In the second case, the filter is designed when β ≤ 1 and α ≥ 1. In order to calculate the optimal filter parameters, the modified Particle Swarm Optimization (mPSO) algorithm has been utilized for coefficient tuning. Also, a generalized approach to design any second order FOBF is discussed in this work. The realization and performance assessment have been carried out in simulation environment as well as in lab experiment with field programmable analog array (FPAA) development board. The experimental results indicate the value of efforts to realize the fractional filter.

Effect of CNTs Parameter Variation on the Performance of Analog Device

Carbon nanotubes (CNTs) have emerged as a prominent material for present day nano-scale systems design. In spite of their widespread use in biology, and nano-electro mechanical systems (NEMS, CNTs have encroached upon conventional MOSFETs for the design of low power and high speed circuits. Because CNT possesses higher current carrying capability, higher transconductance and near ballistic transport of charge carriers. The diameter of the CNTs laid from the Source to the Drain in a CNFET has the significant influence on the characteristics of the device itself as well as on the features of circuits implemented using the said CNFET. Such variations in circuit parameters with CNT diameter can be shown to be more pronounced in analog circuits as compared to digital CNFET-based designs. The present work attempts to investigate the effect of diameter variation on a versatile analog building block (ABB) viz. the inverting current conveyor. It is demonstrated that various parameters of the ICC-II under scrutiny, like voltage bandwidth, current bandwidth, average power dissipation, etc. depend on the diameter of CNT(s) used in the CNFETs. HSPICE simulations performed on a 0.9V; 32nm CNFET-based ICC-II are included to exemplify the dependencies studied.

Floating-Gate MOS Transistor with Dynamic Biasing as a Radiation Sensor

This paper describes the possibility of using an Electrically Programmable Analog Device (EPAD) as a gamma radiation sensor. Zero-biased EPAD has the lowest fading and the highest sensitivity in the 300 Gy dose range. Dynamic bias of the control gate during irradiation was presented for the first time; this method achieved higher sensitivity compared to static-biased EPADs and better linear dependence. Due to the degradation of the transfer characteristics of EPAD during irradiation, a function of the safe operation area has been found that determines the maximum voltage at the control gate for the desired dose, which will not lead to degradation of the transistor. Using an energy band diagram, it was explained why the zero-biased EPAD has higher sensitivity than the static-biased EPAD.

Modernized Solar Radio Spectrograph in the L Band Based on Software Defined Radio

The paper presents the concept, implementation, and test operation of a modernized solar radio spectrograph for an investigation of the solar emission and solar bursts in radio frequency bands. Besides having a strong diagnostic significance for studying the flare energy release, the solar radio bursts can also cause strong interference for radio communication and navigation systems. The current spectrograph for the Ondrejov observatory (Astronomical Institute of Czech Academy of Sciences) was modernized by using a direct-conversion receiver connected to a field-programmable gate array (FPGA) for the fast Fourier transform (FFT) spectrum estimation and put into the test operation. The higher time and frequency resolution and lower noise in comparison with the existing analog instrument were reached by the implementation of the latest optimal signal processing methods. To reduce the costs for such modernization, the operating frequency range was divided into four sub-bands of bandwidth 250 MHz, which brings another benefit of greater scalability. The first observations obtained by the new spectrograph and their comparison with the analog device are presented in the paper with future steps to put the spectrograph into the regular operation.