A Multicriteria Decision Support Methodology for Annual Rehabilitation Programs of Water Networks

Abstract:   This article provides an overview of a multicriteria decision support methodology for annual rehabilitation programs of water networks. A first set of criteria is formulated for the purpose of comparing and ranking rehabilitation projects. Each proposed criterion is a measure of a particular impact of the condition of a pipe. The ELECTRE TRI method is implemented for defining rehabilitation priorities . Two reference profiles are used to define the limits of three categories associated with three increasing priority levels. With these two reference profiles, applying the ELECTRE TRI method to an asset stock ( a set of pipes that are candidates for rehabilitation ) means assigning each pipe to one of six possible priority groups. A second set of criteria, based on the concept of efficiency, is proposed for comparing alternative rehabilitation programs ( subsets of the asset stock ).     

Interpretation of Compositional Patterns Found by Quantitative Energy Dispersive X-ray Analysis for Cement Paste Constituents.

More than 200 individual particles within a portland scement paste were morphologically categorized by backscatter SEM and analyzed systematically by EDXA. Nearly all of the analyses fall either in a dense cluster around a mean C-S-H gel composition or along tie lines connecting this composition to theoretical compositions for calcium hydroxide, monosulfate, ettringite, and ferrite. "Phenograin" C-S-H gel (formed as a direct replacement product within large cement grains) contains small amounts of Al, Fe, and S, but otherwise shows almost negligible compositional variation. In contrast, smaller groundmass particles and shells of gapped phenograins show a slightly differentc S-H gel composition. Some of these, despite being morphologically homogeneous, show compositions falling along tie lines to the other recognized phases. This is attributed to extensive occurrence of intimate mixtures of C-S-H gel with the other components below the scale of SEM observation. Ionic substitutions appear to be minor except for the monosulfate and ettringite components in such mixtures. These show a variable but usually high deficiency in the sulfate content.     

Surface Morphology of Heat-Treated Ceramic Thin Films

The morphology of surfaces of several ceramic materials has been examined using transmission electron microscopy. The approach used was to prepare a sample for examination in the microscope, carefully clean it, and then heat-treat it. In the case of the oxides studied (alumina and spinel) the samples were heated in air; the non-oxides (α-SiC and β -SiC) were annealed under vacuum. The morphology in all but one case was such that the surface faceted parallel to the nearest low-index plane to give well-defined terraces; these were separated by ledges which also tended to facet parallel to the traces of low-index planes. The exception was the {1100} alumina surface, which appears to be unstable in air at temperatures close to 1400°C. A computer program using a multislice approach was used to estimate the height of the steps on the (0001) surface; the step heights appear to be multiples of the c lattice parameter. A reconstruction of this surface as a result of this heat treatment is also proposed.     

High-Temperature Chemical Stability of Plasma-Sprayed Ca05Sr05Zr4P6O24 Coatings on Nicalon/SiC Ceramic Matrix Composite and Ni-Based Superalloy Substrates

The potential application of Ca05Sr05Zr4P6O24 (CS50) as a corrosion-resistant coating material for Si-based ceramics and as a thermal barrier coating material for Ni-based superalloys was explored. A ∼200 (xm thick CS50 coating was prepared by air plasma spray with commercially available powder. A Nicalon/SiC ceramic matrix composite and a Ni-based superalloy coated with a ∼200 (xm thick metallic bond coat layer were used as substrate materials. Both the powder and coating contained ZrP2O7 as an impurity phase, and the coating was highly porous as-deposited. The coating deposited on the Nicalon/SiC substrate was chemically stable upon exposure to air and Na2SO4/O2 atmospheres at 1000°C for 100 h. In contrast, the coating sprayed onto the superalloy substrate significantly reacted with the bond coat surface after similar oxidation in air.     

An analysis of the 1H- and 13C-NMR spectra of poly(6-vinyl-1,4-benzodioxane)

Summary The title monomer was synthesized from the corresponding aldehyde via a Wittig reaction. The monomer was polymerized using free radical initiation and its high field ¹H- and ¹³C-NMR spectra were recorded. When analyzed in terms of stereochemistry the spectra showed poly(6-vinyl-1,4-benzodioxane) is an atactic polymer when synthesized via free radical initiation.