Solubilization of multi walled carbon nanotubes under a facile and mild condition

Multi-walled carbon nanotubes (MWCNTs) functionalized with amino groups was prepared via chemical modification of carboxyl groups introduced on the carbon nanotube surfaces. Oxidation of MWCNTs was performed with ozone in aqueous phase and amidation of generated carboxylic groups, was occurred with amines in the presence of HATU as a coupling agent. Obtained functionalized MWCNTs are soluble in many common organic solvents. The functionalized MWCNTs were characterized in detail using FTIR-ATR, Raman CHN and SEM methods.     

Kinetic modeling and half life study on bioremediation of crude oil dispersed by Corexit 9500

Hydrocarbon pollution in marine ecosystems occurs mainly by accidental oil spills, deliberate discharge of ballast waters from oil tankers and bilge waste discharges; causing site pollution and serious adverse effects on aquatic environments as well as human health. A large number of petroleum hydrocarbons are biodegradable, thus bioremediation has become an important method for the restoration of oil polluted areas. In this research, a series of natural attenuation, crude oil (CO) and dispersed crude oil (DCO) bioremediation experiments of artificially crude oil contaminated seawater was carried out. Bacterial consortiums were identified as Acinetobacter, Alcaligenes, Bacillus, Pseudomonas and Vibrio. First order kinetics described the biodegradation of crude oil. Under abiotic conditions, oil removal was 19.9% while a maximum of 31.8% total petroleum hydrocarbons (TPH) removal was obtained in natural attenuation experiment. All DCO bioreactors demonstrated higher and faster removal than CO bioreactors. Half life times were 28, 32, 38 and 58 days for DCO and 31, 40, 50 and 75 days for CO with oil concentrations of 100, 500, 1000 and 2000 mg/L, respectively. The effectiveness of Corexit 9500 dispersant was monitored in the 45 day study; the results indicated that it improved the crude oil biodegradation rate.     

Use of clay-anchored reactive modifier for the synthesis of poly (styrene-co-butyl acrylate)/clay nanocomposite via in situ AGET ATRP

Atom transfer radical polymerization using activators generated by electron transfer (AGET ATRP) was employed to synthesize well-defined poly (styrene-co-butyl acrylate)/clay nanocomposites. Dodecyltrimethylammonium bromide (DDTMAB) and Vinylbenzyltrimethylammonium chloride (VBTMAC) surfactants were used as clay modifier. The classical surfactant is used to expand the interlayer gallery of montmorillonite; however, double bond of reactive modifier participates in chain propagation process and forms clay-attached polymer chains. Subsequently synthesis of attached and free poly (styrene-co-butyl acrylate) chains and their composition was confirmed by Fourier-transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance spectroscopy (¹H NMR). Narrow distribution of nanocomposites molecular weight was confirmed by gel permeation chromatography (GPC). Partially exfoliated clay layers in the copolymer matrix were revealed by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Thermal properties of the nanocomposites were evaluated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Thermal decomposition of the nanocomposites was hindered in the presence of nanoclay. Dynamic mechanical thermal analysis (DMTA) results show that addition of nanoclay was also resulted in enhanced storage modulus (E′) in comparison with the neat copolymer. Lower glass transition temperature of nanocomposites was displayed by DSC.     

Three-dimensional optimal multi-level Monte–Carlo approximation of the stochastic drift–diffusion–Poisson system in nanoscale devices

The three-dimensional stochastic drift–diffusion–Poisson system is used to model charge transport through nanoscale devices in a random environment. Applications include nanoscale transistors and sensors such as nanowire field-effect bio- and gas sensors. Variations between the devices and uncertainty in the response of the devices arise from the random distributions of dopant atoms, from the diffusion of target molecules near the sensor surface, and from the stochastic association and dissociation processes at the sensor surface. Furthermore, we couple the system of stochastic partial differential equations to a random-walk-based model for the association and dissociation of target molecules. In order to make the computational effort tractable, an optimal multi-level Monte–Carlo method is applied to three-dimensional solutions of the deterministic system. The whole algorithm is optimal in the sense that the total computational cost is minimized for prescribed total errors. This comprehensive and efficient model makes it possible to study the effect of design parameters such as applied voltages and the geometry of the devices on the expected value of the current.     

Using Evolutionary Optimization Techniques for Scheduling Water Pipe Renewal Considering a Short Planning Horizon

Abstract: The maintenance and management of underground infrastructures is a growing problem for a majority of municipalities. The maintenance costs are increasing while the financial resources of municipalities remain limited. Water distribution system (WDS) managers therefore need tools to assist them in the elaboration of pipe renewal management plans. In this article, results of a newly developed strategy for pipe renewal based on a cost function are presented. The strategy allows the minimization of a cost function while also considering hydraulic criterion. This strategy was tested on a short planning horizon of five years. The pipe number to be replaced and the optimal moment for renewal are identified using three different optimization techniques: IGA (Island Genetic Algorithm), NPGA‐2 (Niched Pareto Genetic Algorithm 2), and NSGA‐II (Non‐dominated Sorting Genetic Algorithm‐II). The proposed approach has five distinctive features: (1) it is coupled with a flexible evolutionary framework that allows the user to select any type of operator for IGA or any kind of multiobjective genetic algorithm; (2) it uses the hydraulic simulator Epanet2.0 which allows steady state or dynamic simulations; (3) it considers a probabilistic break model to evaluate the structural deterioration of pipes; (4) it integrates a Bayesian approach for the estimation of the pipe break model parameters that take into account the influence of inherent uncertainties related to the quality of data during the decision‐making process; and (5) it simulates the variation of the pipe's roughness over the years. The developed strategy/model is explained using an example that allows us to elucidate its most important components. Simulation experiments on a small network (100 pipes) are presented. A comparison of three evolutionary algorithm results is provided. Tests showed that IGA performs well, but for networks of larger sizes, we recommend increasing the number of demes to reach better solutions. Higher quality results were achieved with NSGA‐II than NPGA‐2 on differently sized networks. We recommend the use the NSGA‐II to optimize large WDS. Future developments for this strategy are also discussed.     

Microtexture of chloride treated CdTe thin films deposited by CSS technique

This work investigates the microstructural changes—especially in grain boundary structure and grain orientation distribution—in CdTe thin films deposited by close spaced sublimation at low (LT) and high temperatures (HT) and submitted to a CdCl₂ heat treatment. These changes are quantitatively described by microtexture analysis, a spatial distribution of the orientation of the grains. The analysis is performed in a scanning electron microscope by means of identification of the electron back-scattered diffraction patterns from individual grains. The texture of each grain, the misorientation between grains, and coincident site lattice boundary maps are obtained. The results show that the CdCl₂ treatment did not promote significant microstructural changes in HT-CdTe films, which grow with large and randomly oriented grains, and with a predominance of high-angle boundaries. On the other hand, for LT-CdTe films, this treatment promotes a substantial increase in grain size, a decreasing of preferential orientation, and an increase in the number of CSL and high-angle boundaries. These changes are considered to be a strong evidence for recrystallization.     

Integrated Decision Support System for Optimal Renewal Planning of Sewer Networks

Municipalities are under increasing pressure to adopt proactive and optimized renewal strategies to reduce the risks, life-cycle costs, and resources needed to maintain acceptable performance and service levels of their infrastructure assets. A new integrated approach for optimal renewal planning of municipal infrastructure systems has been developed. This paper discusses the application of the proposed approach to implement a GIS-based decision support system (DSS) to support the renewal planning of sewer networks. Condition rating, risk assessment, and prioritization techniques are described. A procedure for identifying and selecting the most suitable renewal technologies is also presented. A genetic algorithm-based multiobjective optimization technique is used to find a Pareto front of feasible solutions, each comprising a set of sewers to be renewed each year, along with the associated costs and expected benefits in terms of condition improvement and risk reduction. The paper also presents an example application of the prototype DSS on the sewer network in Regina, Canada.     

The behavior of dithiocarbimate derivative as safety accelerator of natural rubber compounds

A conventional vulcanization system containing tetrabutylammonium bis(4‐methylphenyldithiocarbimato)zincate(II) (ZNIBU) was used for curing of natural rubber (NR) compounds. Rheometric (t_s1, t₉₀, and CRI) and mechanical properties, such as tensile and tear strengths and modulus at 300%, were measured to evaluate the acceleration potential of ZNIBU. Commercial accelerators (TMTD, MBTS, and CBS) and a binary system CBS/ZNIBU were also tested for comparison purposes. It was observed that ZNIBU alone does not give either safe scorch time or cure rates appropriate for industrial applications. Nevertheless, mechanical properties are comparable to those given by the other accelerators used. As for the binary system, positive synergistic effects can be found in tear strength and modulus of NR vulcanizates. Besides, ZNIBU does not contribute for the formation of nitrosamines in the vulcanization process. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Using computational fluid dynamics modeling to study the mixing of pseudoplastic fluids with a Scaba 6SRGT impeller

The 3D flow field generated by a Scaba 6SRGT impeller in the agitation of xanthan gum, a pseudoplastic fluid with yield stress, was simulated using the commercial CFD package. The flow was modeled as laminar and a multiple reference frame (MRF) approach was used to solve the discretized equations of motion. The velocity profiles predicted by the simulation agreed well with those measured using ultrasonic Doppler velocimetry, a non-invasive fluid flow measurement technique for opaque systems. Using computed velocity profiles across the impeller, the effect of fluid rheology on the impeller flow number was investigated. The validated CFD model provided useful information regarding the formation of cavern around the impeller in the mixing of yield stress fluids and the size of cavern predicted by the CFD model was in good agreement with that calculated using Elson's model.