Real-time chloride diffusion coefficient in concrete using embedded resistivity sensors

Service life of concrete infrastructure is severely compromised because of chloride-induced corrosion and measuring the chloride content is crucial to determine the remaining service life. DuraCrete provides a chloride ingress model based on Fick’s 2nd law. Although the diffusion coefficient is modelled as a time-dependent variable, the DuraCrete solution averages it to a constant value. This simplification leads to inaccurate estimation of the chloride content. A new analytical solution that addresses the underlying mathematical discrepancy has been proposed. However, the time-dependent diffusion coefficient is still based on an empirical factor. In this study, a real-time durability monitoring system has been developed using remotely operated resistivity sensors. Such a system is able to monitor the time dependent diffusion coefficient without the need to incorporate empirical factors. Additionally, a numerical technique to find an approximation of the proposed improved analytical solution is presented using real-time resistivity measurements from laboratory and real structures. The results show that the discrete sensor data measurements over time provide a good approximation of the proposed analytical solution. The system developed in this study is used as a data-driven input parameter to supplement the existing chloride models.Concrete Structure

Stopping Voltage-Dependent PCM and RRAM-Based Neuromorphic Characteristics of Germanium Telluride

Recently, phase change chalcogenides, such as monochalcogenides, are reported as switching materials for conduction-bridge-based memristors. However, the switching mechanism focused on the formation and rupture of an Ag filament during the SET and RESET, neglecting the contributions of the phase change phenomenon and the distribution and re-distribution of germanium vacancies defects. The different thicknesses of germanium telluride (GeTe)-based Ag/GeTe/Pt devices are investigated and the effectiveness of phase loops and defect loops future application in neuromorphic computing are explored. GeTe-based devices with thicknesses of 70, 100, and 200 nm, are fabricated and their electrical characteristics are investigated. Highly reproducible phase change and defect-based characteristics for a 100 nm-thick GeTe device are obtained. However, 70 and 200 nm-thick devices are unfavorable for the reliable memory characteristics. Upon further analysis of the Ag/GeTe/Pt device with 100 nm of GeTe, it is discovered that a state-of-the-art dependency of phase loops and defect loops exists on the starting and stopping voltage sweeps applied on the top Ag electrode. These findings allow for a deeper understanding of the switching mechanism of monochalcogenide-based conduction-bridge memristors.Computer Engineerin