James C. Austin

Defect Detection in Reinforced Concrete Using Random Neural Architectures

This article discusses how detecting defects within reinforced concrete is vital to the safety and durability of infrastructure. A non-invasive technique, ElectroMagnetic Anomaly Detection (EMAD) is used in this article to provide information into the electromagnetic properties of reinforcing steel for which data analysis is currently performed visually. The first use of two neural network approaches to automate the analysis of this data is investigated in this article. These approaches are called Echo State Networks (ESNs) and Extreme Learning Machines (ELMs) where fast and efficient training procedures allow networks to be trained and evaluated in less time than traditional neural network approaches. Data collected from real-world concrete structures are analyzed in this article using these two approaches as well as using a simple threshold measure and a standard recurrent neural network. Two ESN architectures provided the best performance for a mesh-reinforced concrete structure, while the ELM approach offers a large improvement in the performance of a single tendon-reinforced structure.

Ultrasonic wave propagation in colloid suspensions and emulsions: recent experimental results

Early theories of acoustic propagation such as those by Urick, and Urick and Ament, are attractive because of their computational simplicity, but limited in application. The more complex models of Allegra and Hawley, and Harker and Temple, have since gained application. A wideband ultrasonic attenuation and phase velocity spectrometer have been used to determine the validity of these models for a range of colloidal materials. Measurements taken validate the Allegra and Hawley model for colloids with spherical base particles. The Harker and Temple model is used to infer changes in the flocculation state of kaolin slurries which result from chemical intervention.

Ultrasonic propagation through aqueous kaolin suspensions during degassing

A degassing procedure is necessary prior to taking ultrasonic measurements in aqueous kaolin suspensions as well as many other liquid based colloids. In this work we compare two degassing methods and show that subjecting a sample to a power ultrasound field is easier and less time consuming than exposing it to a vacuum. We also combine degassing and deflocculation procedures to show that air bubbles are trapped in cage-like kaolin flocs and are released when such flocs break up.