Prediction of leak flow rate in plastic water distribution pipes using vibro-acoustic measurements

Leakage from water distribution systems is a worldwide issue with consequences including loss of revenue, health and environmental concerns. Leaks have typically been found through leak noise correlation by placing sensors either side of the leak and recording and analysing its vibro-acoustic emission. While this method is widely used to identify the location of the leak, the sensors also record data that could be related to the leak’s flow rate, yet no reliable method exists to predict leak flow rate in water distribution pipes using vibro-acoustic emission. The aim of this research is to predict leak flow rate in medium-density polyethylene pipe using vibro-acoustic emission signals. A novel experimental methodology is presented whereby circular holes of four sizes are tested at several leak flow rates. Following the derivation of a number of features, least squares support vector machines are used in order to predict leak flow rate. The results show a strong correlation highlighting the potential of this technique as a rapid and practical tool for water companies to assess and prioritise leak repair

Real-Time Structural Damage Assessment Using Artificial Neural Networks and Antiresonant Frequencies

The main problem in damage assessment is the determination of how to ascertain the presence, location, and severity of structural damage given the structure's dynamic characteristics. The most successful applications of vibration-based damage assessment are model updating methods based on global optimization algorithms. However, these algorithms run quite slowly, and the damage assessment process is achieved via a costly and time-consuming inverse process, which presents an obstacle for real-time health monitoring applications. Artificial neural networks (ANN) have recently been introduced as an alternative to model updating methods. Once a neural network has been properly trained, it can potentially detect, locate, and quantify structural damage in a short period of time and can therefore be applied for real-time damage assessment. The primary contribution of this research is the development of a real-time damage assessment algorithm using ANN and antiresonant frequencies. Antiresonant frequencies can be identified more easily and more accurately than mode shapes, and they provide the same information. This research addresses the setup of the neural network parameters and provides guidelines for the selection of these parameters in similar damage assessment problems. Two experimental cases validate this approach: an 8-DOF mass-spring system and a beam with multiple damage scenarios

Spectral intensities in cubic systems. I. Progressions based upon parity vibrational modes

The well-resolved emission and absorption spectra of centrosymmetric coordination compounds of the transition metal ions have been used widely to provide the experimental data against which to test theoretical models of vibronic intensities. With reference to the 2Eg → 4A2g luminescence transition, at a perfect octahedral site in Cs2SiF6, over than one hundred vibronic lines are observed with line widths of a few wavenumber spread over some 3000 cm-1. This paper reports a thorough examination of both the electronic and vibrational factors, which influences the observed vibronic intensities of the various assigned and identified lines in the spectra of the MnF62- complex ion in the Cs2SiF6 cubic lattice. The origin and nature of higher order vibronic interactions are analysed on the basis of a symmetrized vibronic crystal field-ligand polarization model

Spectral intensities in cubic systems. III. The Cs2NaEuCl6 system

The optical properties of Cs2NaEuCl6 system are reinvestigated on the basis of new and updated experimental data from Raman, electronic Raman, Infrared absorption and visible luminescence. These experimental studies have enable scientist to identify and assign all of the energy levels and corresponding electronic transitions up to 21 500 cm-1. Futhermore, the crystal field level identification from absorption spectroscopy has been confirmed from the additional emission and electronic Raman studies. We decided to study the most likely intensify mechanisms for this system, based upon these new experimental data and a modified version of a combined vibronic formalism, which takes into account the closure procedure for the intermediate electronic states. The total and relative vibronic intensity distributions are calculated and compared with the experimental data, when available. It is shown that the present calculation model although complex uses a minimum set of adjustable parameters fr

Effect of Sr2+ and Ba2+ doping on structural stability and mechanical properties of La2NiO4+delta

Structural and mechanical Characterizations of La1.8M0.2NiO4+delta (M: Sr and Ba) prepared by low frequency ultrasound assisted synthesis technique and sintered at different temperatures were studied. HRTEM and XRD analyses showed the uniform shape of calcined nanocrystalline powders with the particle size of less than 100 nm with mixed phases, which were refined by Rietveld method using orthorhombic (Fmmm) and tetragonal (F4/mmm) structures. Sintering La1.8M0.2NiO4+delta and La1.8M0.2NiO4+delta compacted discs at temperatures higher than 1300 degrees C and 1250 degrees C, respectively, resulted in appearance of extra peaks close to a monoclinic phase. Doping La2NiO4+delta with Sr2+ and Ba2+ did not affect its sinterability and average grain size significantly, however, Ba2+ improved the elastic modulus and microhardness, while Sr2+ improved the fracture toughness.FONDECYT, Government of Chile 1116020