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Proactive Risk-Based Integrity Assessment of Water Distribution Networks

Sustainable management of urban water distribution networks should include not only new methods for monitoring, repairing or replacing aging infrastructure, but also (and more importantly) expanded methods for modelling deteriorating infrastructure, for pro-actively assessing the risk of failure and for devising replace or repair strategies. The study presented herein describes a framework for proactive risk-based integrity monitoring of urban water distribution networks and the results obtained from a case-study based on a 5-year data sample. A combination of artificial neural network and statistical modelling techniques stemming from parametric and nonparametric survival analysis (Kaplan–Meier survival curves with Epanechnikov’s kernel) are utilized in the investigation of identified risk factors and for estimation of the forecasted time to failure metric. The data is stratified for different pipe groups for a more targeted analysis.     

The role of non-covalent interactions and matrix viscosity on the dispersion and properties of LLDPE/MWCNT nanocomposites

Linear low density polyethylene (LLDPE)/multi-walled carbon nanotube (MWCNT) composites were prepared by melt compounding, following two different compatibilization strategies that involved non-covalent interactions between the matrix and the filler. The first approach involved grafting pyridine aromatic moieties on the maleated polyolefin backbone, which are able to interact by π–π stacking with the surface of the nanotubes. The second method implemented non-covalent/non-specific surface functionalization of the MWCNTs with a hyperbranched polyethylene (HBPE). The enhanced interfacial interactions established in the composites containing LLDPE functionalized with pyridine grafts improved the dispersion of the nanotubes within the polymer matrix. Dispersion was also favoured by higher matrix viscosity. Composites containing finely dispersed MWCNTs exhibited an increase in the rheological and electrical percolation thresholds, and a significant improvement in mechanical properties. On the contrary the composites based on the low viscosity matrix contained large amounts of aggregates, which promoted lower percolation thresholds. Manipulation of matrix viscosity and compatibilization resulted in composites with good mechanical properties, and low percolation thresholds.     

Polyurethanes from 4,4′‐diphenylmethane diisocyanate and poly(ethylene glycol)s. II. Crystallographic data,heats of melting and crystallization,thermal stability,crystallinity and density

Wide‐angle X‐ray scattering analysis, heats of melting, crystallization and re‐melting, thermogravimetric analysis and density measurements have been used to study the crystallographic data and degree of crystallinity of linear polyurethanes (PUs) prepared by the polymerization of 4,4′‐diphenylmethane diisocyanate (MDI) with poly(ethylene glycol)s (PEGs) of various number‐average molecular weights (M_ns) (106, 200, 400, 1000, 2000 and 4000 g mol^?1) in equivalent molar ratios. The crystallinities of polyurethanes PU1000 to PU4000 are shown to be due to the polyoxyethylene segments of the PEGs, while PU400 and PU200 appeared to be amorphous. However, PU106, similarly prepared from diethylene glycol (PEG106), is highly crystalline with a different crystal structure. Thermogravimetric analysis of PU106, PU400 and PU1000 exhibited high thermal stabilities up to 260 °C for these materials under the conditions of measurement (10 °C min^?1). The heat of melting for the 100 % crystalline structure of PU106 has been indirectly obtained. Copyright © 2004 Society of Chemical Industry     

Sol—Gel Synthesis of Strontium-Doped Lanthanum Manganite

Strontium-doped lanthanum manganite powders were prepared using a peroxide acetate salt based solution. The stable sol was peptized by reacting ammonium hydroxide with the precursor solution. The amorphous dried gel powders exhibit a high energy level, due to their high cations coordination and small particles, to develop the perovskite phase. This crystalline phase development from powders containing monocarboxylate ligands was characterized by thermal analysis (TG, DTG, DTA), X-ray diffraction, and IR spectroscopy. The transformation from amorphous powders into a crystallized homogeneous oxycarbonate phase in a first stage corresponds to an exothermal DTA peak at 270°C. X-ray diffraction patterns and IR spectra showed similar behavior of the powders after complete organic removal, during the conversion into perovskite phase starting at approximately 630°C and achieved about 700°C and achieved about 700°C, as well as during the sintering process.     

High‐Performance Supercapacitors Based on a Zwitterionic Network of Covalently Functionalized Graphene with Iron Tetraaminophthalocyanine

Graphene derivatives are promising candidates as electrode materials in supercapacitor cells, therefore, functionalization strategies are pursued to improve their performance. A scalable approach is reported for preparing a covalently and homogenously functionalized graphene with iron tetraaminophthalocyanine (FePc‐NH₂) with a high degree of functionalization. This is achieved by exploiting fluorographene's reactivity with the diethyl bromomalonate, producing graphene‐dicarboxylic acid after hydrolysis, which is conjugated with FePc‐NH₂. The material exhibits an ultrahigh gravimetric specific capacitance of 960 F g^?1 at 1 A g^?1 and zero losses upon charging–discharging cycling. The energy density of 59 Wh kg^?1 is eminent among supercapacitors operating in aqueous electrolytes with graphene‐based electrode materials. This is attributed to the structural and functional synergy of the covalently bound components, giving rise to a zwitterionic surface with extensive π–π stacking, but not graphene restacking, all being very beneficial for charge and ionic transport. The safety of the proposed system, owing to the benign Na₂SO₄ aqueous electrolyte, the high capacitance, energy density, and potential of preparing the electrode material on a large‐scale and at low cost make the reported strategy very attractive for development of supercapacitors based on the covalent attachment of suitable molecules onto graphene toward high‐synergy hybrids.