Finite difference discretization of the extended Fisher-Kolmogorov equation in two dimensions

Approximate solutions are considered for the extended Fisher-Kolmogorov (EFK) equation in two space dimension with Dirichlet boundary conditions by a Crank-Nicolson type finite difference scheme. A priori bounds are proved using Lyapunov functional. Further, existence, uniqueness and convergence of difference solutions with order O(h²+k²) in the L^∞-norm are proved. Numerical results are also given in order to check the properties of analytical solutions.     

Development of an odor wheel classification scheme for wastewater.

Overall, in the air pollution control field, odor concentration and intensity as well as hedonic rating have been well studied to the point where some level of standardization is being developed or is already in place. However, there has been no standardization with respect to odor quality characterization. There is now sufficient understanding of the types of odorous compounds that can arise from wastewater treatment processes to develop an odor classification scheme. This article presents the first wastewater odor wheel or classification scheme that should form the foundation for the evolution of odor quality data reporting with links to chemical causes.     

Modelling of heat and mass transfer in a tunnel dryer

This work presents a numerical model for heat and mass transfer of granular products in a fixed-bed tunnel dryer. The drying process is simulated under real operating conditions based on a thin layer model and experimental drying kinetics. A simplified heat and mass transfer numerical model is developed based on the governing equations and the drying rate of a thin layer bed of granular products.The obtained system of non-linear partial differential equations is numerically solved by a finite volume method. The turbulent airflow and granular bed convection coefficient as well as the effective conductivity are estimated using the turbulent airflow over flat-plate correlations. Simulations are compared with experimental data from drying of grapes in a thin layer model.In order to study the effects of the air inlet conditions on the relative moisture content and the drying time and therefore to optimise the tunnel dryer operation, the influences of different parameters essentially the air flow characteristics and the fixed-bed dryer length are examined. The numerical code allows establishing the drying front propagation for several operating conditions.     

Optimization of Stirling engine performance based on an experimental design approach

The Stirling engine performances depend on several physicals characteristics and functioning parameters. The influence of each parameter and of their interactions is difficult to achieve with classical univariate studies. The experimental design is an alternative to identify the parameters sets allowing optimal Stirling engine performances. Hence, a four factor Central Composite Rotatable Design was used to observe the effect of cooling water flowrate, initial charge pressure, heating temperature, and operation time on a Stirling engine brake power. The influence of each parameter and the effect of the interaction between two or three parameters on the engine performances are presented and discussed. Using the surface response method, it appears that initial charge pressure and heating temperature are the more influencing parameters on the Stirling engine performances. With modeling, optimal conditions for the Stirling engine functioning are the following: charge pressure of 8 bar, heating temperature of 500 °C, and cooling water flow rates of 7.34 l/min, independent of the engine operation time. Copyright © 2012 John Wiley & Sons, Ltd.     

New lignocellulosic fibres-reinforced composite materials: A stepforward in the valorisation of the Posidonia oceanica balls

In this work, new lignocellulosic particles obtained from Posidonia oceanica were studied to reinforce a commercial biodegradable thermoplastic matrix. First, these reinforcing fillers were characterised by Fourier-transform infrared (FT-IR) and X-ray photoelectron (XPS) spectroscopies. Then, they were used to prepare several composite films using BIOPLAST GF 106 matrix. Different P. oceanica fragment loadings, namely 0%, 10%, 20% and 30% (w/w with respect to the matrix) were investigated. The morphology of the ensuing materials was assessed by scanning electron microscopy (SEM), whereas their thermal and mechanical properties were studied by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and tensile tests. The obtained results showed that P. oceanica-based particles enhanced the thermo-mechanical properties of the thermoplastic matrix.     

Occurrence and removal of chloro-s-triazines in water treatment plants

Atrazine, simazine, and propazine and their major chlorinated degradates (deethylatrazine, deisopropylatrazine, and didealkylatrazine) are considered as a group to be endocrine-disrupting chemicals by the U.S. Environmental Protection Agency. On this basis, regulatory action levels are currently under consideration for the total chloro-s-triazine (TCT) levels in drinking waters. To assess the concentrations of each of these species in drinking water and their treatability in conventional water treatment, a comprehensive, full-scale studywas conducted that included frequent monitoring at 33 and 47 water utilities during 2003 and 2004, respectively. Approximately 900 paired raw and treated water samples were analyzed using a gas chromatography/mass spectrometry method with preconcentration using a mixed-mode, solid-phase extraction that allowed quantitation of each species including didealkylatrazine. The results showed that atrazine concentrations were generally well within the 3 microg/L maximum contaminant level (MCL) and that simazine and propazine concentrations were generally negligible. Ninety-fifth-percentile values for the ratio of TCT/atrazine were 4.8 and 4.7, respectively. Effectiveness of conventional treatment technologies, including carbon, was observed to vary significantly. Concerns that didealkyatrazine concentrations may be high and significantly elevate the TCT appear to be unfounded. In general, the results suggest that potential treatment requirements for TCT are not likely to be any more difficult for utilities to meet than the current requirements for atrazine.     

Study of the regenerator constituting material influence on a gamma type Stirling engine

A gamma Stirling engine with compressed air as working fluid was investigated. This engine operates at a maximum charge pressure of 10 bar, runs at a maximum rotation speed of 600 rpm and can provide 500 W of brake power on the shaft. The engine is equipped with several pressure sensors and thermocouples. This experimental study concentrates on the regenerator constituting material (porous medium). Four different materials were investigated: stainless steel, copper, aluminum and Monel 400. The obtained experimental results provide guidance to Stirling engine enhancement and selection of the appropriate regenerator material. As a conclusion, the regenerator has an important role to enhance the heat exchange and to improve Stirling engine performance, which closely depends on its constituting material.