Water pipe network reliability assessment using the DAC method

The Discriminant Analysis and Classification (DAC) method has offered remarkable results regarding the prediction of failures in an oil or a gas pipe network, based on the network characteristics. The DAC method also proved its ability to identify the most crucial network parameters affecting its behavior. The present study attempts to check whether the DAC method can provide safe results regarding the reliability assessment of urban water networks too. The DAC method aims at classifying the network pipes in two groups (failures/successes), based on simple or/and dimensionless joint variables. Serious problems related to the quality, reliability and compatibility of the data provided by the Water Utilities were tackled using dummy variables based on field data. The distinction between the meanings of 'failure' and 'success', for a water pipe network, was also crucial. For the case study water pipe network of Larisa city, in Greece, the criterion used to define the meanings of 'failure' and 'success' was "the total water volume being lost" through a leak or a break in a pipe. The available pipe failure data records for Larisa city were poor and not fully compatible to the DAC method demands. The results showed that discrimination is good enough and would be even better if additional data (in line with the DAC standards) was available. Thus, overall, the DAC method proved to be a useful tool for pipe reliability prediction in urban water pipe networks

Achieving 21.4% efficient CdSeTe/CdTe solar cells using highly resistive intrinsic ZnO buffer layers

In this study, the use of intrinsic and highly insulating ZnO buffer layers to achieve high conversion efficiencies in CdSeTe/CdTe solar cells is reported. The buffer layers are deposited on commercial SnO2:F coated soda‐lime glass substrates and then fabricated into arsenic‐doped CdSeTe/CdTe devices using an absorber and back contact deposited by First Solar. The ZnO thickness is varied from 30 to 200 nm. The devices incorporating a 50 nm ZnO buffer layer achieved an efficiency of 21.23% without an anti‐reflection coating. An improved efficiency of 21.44% is obtained on a substrate with a multilayer anti‐reflection coating deposited prior to device fabrication. The highly efficient ZnO based devices are stable and do not develop anomalous J‐V behavior following environmental tests. High resolution microstructural analysis reveals the formation of a high‐quality ZnO/CdSeTe interface. Unusually, chlorine is not detected as a discrete layer at the interface, these observations point to a high‐quality interface. The extrapolation of Voc to 0 K indicates that interface recombination dominates, suggesting that further improvement is possible. Using device modeling, an attempt is made to understand how this type of device performs so well.</p