A posteriori finite element bounds for linear-functional outputs of elliptic partial differential equations

We present a domain decomposition finite element technique for efficiently generating lower and upper bounds to outputs which are linear functionals of the solutions to symmetric or nonsymmetric second-order coercive linear partial differential equations in two space dimensions. The method is based upon the construction of an augmented Lagrangian, in which the objective is a quadratic ‘energy’ reformulation of the desired output, and the constraints are the finite element equilibrium equations and intersubdomain continuity requirements. The bounds on the output for a suitably fine ‘truth-mesh’ discretization are then derived by appealing to a dual max min relaxation evaluated for optimally chosen adjoint and hybrid-flux candidate Lagrange multipliers generated by a K-element coarser ‘working-mesh’ approximation. Independent of the form of the original partial differential equation, the computation on the truth mesh is reduced to K decoupled subdomain-local, symmetric Neumann problems. The technique is illustrated for the convection-diffusion and linear elasticity equations.     

MeshVision: an adaptive wireless mesh network video surveillance system

The major surveillance camera manufacturers have begun incorporating wireless networking functionality into their products to enable wireless access. However, the video feeds from such cameras can only be accessed within the transmission range of the cameras. These cameras must be connected to backbone infrastructure in order to access them from more than one hop away. This network infrastructure is both time-consuming and expensive to install, making it impractical in many rapid deployment situations (e.g., to provide temporary surveillance at a crime scene). To overcome this problem, we propose the MeshVision system that incorporates wireless mesh network functionality directly into the cameras. Video streams can be pulled from any camera within a network of MeshVision cameras, irrespective of how many hops away that camera is. To manage the trade-off between video stream quality and the number of video streams that could be concurrently accessed over the network, MeshVision uses a bandwidth adaptation mechanism. This mechanism monitors the wireless network looking for drops in link quality or signs of congestion and adjusts the quality of existing video streams in order to reduce that congestion. A significant benefit of the approach is that it is of low cost, requiring only a software upgrade of the cameras.     

Synthesis and adsorption properties of nanocrystalline ferrites for kinetic modeling development

Nanocrystalline ferrites are known to be used in different applications, including industrial wastewater management. For environmental water issues, one of the most widely applied techniques is the adsorption of pollutants. The adsorption capacity of Congo red (CR) dye on different MFe₂O₄ (M = Co²⁺, Mg²⁺, Mn²⁺, Ni²⁺, and Zn²⁺) ferrites, synthesized by coprecipitation method, was determined. Specific isotherms and kinetic models were used to characterize the adsorption process. Interesting results were obtained for MgFe₂O₄ with adsorption capacity ranging from 39% up to 70% dependent on the initial dye concentration. Furthermore, an artificial intelligence model based on neural network was developed in order to model the adsorption rates followed by the generation of 3D adsorption rate models for each type of synthesized ferrite. These models were obtained in order to provide information about the particle-dye system`s kinetics at various initial CR concentration. Specific techniques were used to characterize the functionalized magnetic particles.     

Heat treatment influence on the structural properties of supported Ni nanoclusters

Ni nanoclusters supported on Al₂O₃ were prepared using a coprecipitation method. A heat treatment at different temperatures was applied. The obtained samples were analyzed by X-ray diffraction (XRD), X-ray absorption spectroscopy and X-ray photoelectron spectroscopy in order to determine their global, local and electronic structures. The average particle size, the mean squares of the microstrain, the particle size and microstrain distribution functions of the supported Ni nanoclusters were determined by the XRD method using a generalized Fermi function for the approximation of the X-ray line. The recrystallization induced during the heat treatment process was analyzed. The present study indicated strong deformation of the local structure of the active metal in all of the samples investigated due to the metal-support interaction and the effects of the small particle size. Electronic structural investigations showed the presence of Ni in a metallic state as well as Ni²⁺ on the cluster surfaces.     

Improving the Surface Electric Potential Measurement Capability for Textile Materials

The system currently employed for measuring the electric potential of the surface of textile fabrics consists in an electrostatic probe connected to an electrostatic voltmeter. The primary aim of the present work is to improve the capability of this measurement system, as evaluated by gauge repeatability and reproducibility studies. The experiments were conducted on samples of polypropylene non‐woven fabrics, electrostatically charged by exposing them to a negative corona discharge from a custom‐designed electrode system. A first series of fully operator‐controlled measurements pointed out the need to automatically control the relative position between the sample and probe, so that to eliminate the variability due to the non‐uniform structure of the non‐woven fabrics. The following series of partly automated experiments revealed that the repeatability and the reproducibility of the measurements are negatively affected by the decay of the electric potential at the surface of the samples. The best gauge capability is obtained when the measurements are delayed with respect to the moment of corona charging, in order to reduce the variability due to the fact that the samples characteristics change in time. Copyright © 2013 John Wiley & Sons, Ltd.