Efficient numerical algorithms for the solution of “good” Boussinesq equation in water wave propagation

This paper proposes three fast and high accuracy numerical methods for solving a nonlinear partial differential equation (PDE) describing water waves and called the Boussinesq (Bq) equation. We numerically solve the Bq equation with fourth-order time-stepping schemes in combination with discrete Fourier transform. We discretize the original PDE with discrete Fourier transform in space and obtain a system of ordinary differential equations (ODEs) which will be solved with fourth-order time-stepping methods. After transforming the equation to a system of ODEs, the linear operator is not diagonal, but we can implement the methods such as diagonal case which reduces the CPU time. Comparing numerical solutions with analytical solutions demonstrates that those methods are accurate and readily implemented. Also we investigate the conservation of mass for Bq equation.     

Enhancement in the Superconductivity of Tl(Ba2−x Mg x )(Ca1Be1)Cu3O10−δ System with the Decreased Thickness of Charge Reservoir Layer

Mg-doped Tl(Ba_2?x Mg _x )(Ca₁Be₁)Cu₃O_10?δ (x=0, 0.25, 0.5, 0.75) superconductors are synthesized at the normal pressure and the possible mechanism of superconductivity in these compounds is studied. Tl(Ba_2?x Mg _x )(Ca₁Be₁)Cu₃O_10?δ samples have shown an orthorhombic crystal structure and their c-axis length decreases with Mg doping. In these studies we have investigated the role of decreased thickness of charge reservoir layer in the mechanism of superconductivity. The T _c(R=0) in as-prepared Tl(Ba_2?x Mg _x )(Ca₁Be₁)Cu₃O_10?δ (x=00, 0.25, 0.5, 0.75) samples was 97, 99, 100, 94 K and in oxygen post-annealed samples the T _c(R=0) is observed at 100, 98, 103, 101 K, respectively. The magnitude of the superconductivity after Mg doping is improved in Tl(Ba_2?x Mg _x )(Ca₁Be₁)Cu₃O_10?δ (x=0, 0.25, 0.5, 0.75) samples. It was observed from the FTIR absorption measurements that the phonon modes related to CuO₂ planar oxygen atoms are hardened with the doping of Mg in the charge reservoir layer. These studies have shown that the thickness of charge reservoir layer decreases with Mg doping which most likely makes charge transfer mechanism more efficient, promoting increase in the magnitude of superconductivity.     

ZnO/WO3 nanostructure as an efficient visible light catalyst

Highly photosensitive ZnO/WO₃ photocatalysts were fabricated by wet impregnation of zinc oxide (ZnO) in different contents. Tungsten trioxide (WO₃) was synthesized by hydrothermal route. The presence of ZnO inhibited the crystallization of WO₃ and caused agglomeration of WO₃ nanoparticles surface. The formation of Zn-O-W linkage was studied by X-ray photoelectron emission (XPS) and Fourier transforms Infra-red spectra (FTIR). These linkages were responsible for red shift of absorption peak of composites as compared to individual ZnO and WO₃. The band gap was decreased due to incorporation of ZnO in WO₃ which promoted the separation of photo-generated carriers. As a result, ZnO/WO₃ composite showed extremely high efficiency for MO degradation in comparison with Degussa P25, pure ZnO and WO₃. 2.0% ZnO/WO₃ composite displayed the highest activity in photocatalytic decomposition of methyl orange (MO) dye.     

Study of the effect of the concentration,size and surface chemistry of zirconia and silica nanoparticle fillers within an epoxy resin on the bulk properties of the resulting nanocomposites

Epoxy resin nanocomposites were prepared by curing bisphenol‐F with an aliphatic amine in the presence of SiO₂ and ZrO₂ nanoparticles as inorganic fillers. Both types of particles were prepared with diameters of around 10 nm and 70 nm to study size effects in the nanocomposites. The nanoparticles showed a different constitution: while silica was amorphous and spherical in nature, zirconia was crystalline and non‐spherical. Both nanoparticles were surface‐functionalized with novel diethylene‐glycol‐based capping agents to increase the compatibility with the epoxy matrix. The organic functionalities were attached to the nanoparticle surface via phosphonic acid (zirconia) and trialkoxysilane (silica) anchor groups. The homogeneity of the distribution of surface‐modified inorganic nano‐sized fillers in the matrix up to 5.8 vol% in case of silica and 2.34 vol% in case of zirconia was determined by small‐angle X‐ray scattering and transmission electron microscopy. Mechanical properties such as hardness and storage modulus were increased with increasing filler content while thermal stability of the obtained materials was nearly unaffected after incorporation of nanoparticles. Copyright © 2011 Society of Chemical Industry     

Fabrication of metallic Cd multifarious prismatic microcrystals (CMPMCs) under NH3 gas ambient

We report here highly dense and pure metallic cadmium (Cd) multifarious prismatic microcrystals (CMPMCs) fabricated by thermal decomposition of cadmium oxide (CdO) powder at 700 °C for 60 min under NH₃ gas ambient inside horizontal tube furnace. CMPMCs were observed to be 1-1.5 μm in size with interesting morphologies of various cross sections such as triangular, trapezoidal, pentagonal and hexagonal etc. having solid, hollow/semi-hollow appearances. The as-synthesized CMPMCS were characterized by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) and selected area electron diffraction (SAED). Room temperature photoluminescence (PL) spectrum for Cd metal microcrystals exhibited a prominent emission band at 365 along with a shoulder peak at 404 nm. The UV main emission band is ascribed to radiative recombination of the electrons in the s, p conduction band near the Fermi surface and holes in the d bands generated under xenon light excitation whereas shoulder peak may be owing to surface oxidation effects or induced defects. This study shows the potential of CMPMCs for applications in optical devices. Based on vapour-solid (VS) process, growth mechanism for the formation of CMPMCs is also proposed and discussed briefly.     

Multi-criteria fuzzy decision support for conceptual evaluation in design of mechatronic systems: a quadrotor design case study

Designing mechatronic systems is known to be a very complex and tedious process due to the high number of system components, their multi-physical aspects, the couplings between the different domains involved in the product, and the interacting design objectives. This inherent complexity calls for the crucial need of a systematic and multi-objective design thinking methodology to replace the often-used sequential design approach that tends to deal with the different domains and their corresponding design objectives separately leading to functional but not necessarily optimal designs. Thus, a new approach based on a multi-criteria profile for mechatronic systems is presented in this paper for the conceptual design stage. Additionally, to facilitate fitting the intuitive requirements for decision-making in the presence of interacting criteria, three different methods are proposed and compared using a case study of designing a vision-guided quadrotor drone system. These methods benefit from three different aggregation techniques such as Choquet integral, Sugeno integral and fuzzy-based neural network. To validate the decision yielded by the results of global concept score for each aggregation methods, a computer simulation of a visual servoing system on all design alternatives for quadrotor drone has been performed. It is shown that although the Sugeno fuzzy can be a useful aggregation function for decisions under uncertainty, but the approaches using Choquet fuzzy and fuzzy integral-based neural network seem to be more precise and reliable in a multi-criteria design problem where interaction between the objectives cannot be overlooked.     

Neighbor Selection Game in Wireless Ad Hoc Networks

In wireless ad hoc networks, there is no infrastructure to enforce cooperation between nodes. As a result, nodes may act selfishly when running network protocols to conserve their energy resources as much as possible. In this paper, we consider the “neighbor selection” game in which each individual node tries to selfishly choose its neighborhood such that its own energy consumption is optimized. We first focus on a simplified version of this game where nodes know their transmission power before participating in the game. After analyzing the problem, we propose a couple of distributed algorithms to find stable topologies using two kinds of global and local connectivity information. We then take into account the general case where the transmission powers are unknown variables and should be determined during the game. Finally, we evaluate the performance of the proposed algorithms through simulations.     

Simulation-based optimization of ecological leasing: a step toward extended producer responsibility (EPR)

In recent years, due to severe environmental legislations and extended producer responsibility, leasing has been recommended as a strategy for increasing resources productivity and minimizing waste generation during consumption and product end-of-life (EOL) phase. Hence, it is essential to develop a model that can help leasing company for achieving sustainable production management. In this paper, a model is developed which optimizes the environmental and economical impact of product during leasing and its EOL phase from customers and leasing company point of view. To solve the problem, simulation-based optimization approach is investigated and the integrated mathematical and simulation model is developed for incorporating uncertainty during leasing period. Finally a case study with data from industry is used to validate the approach and potential applications of the developed model are illustrated.     

Lean blowoff of bluff body stabilized flames: Scaling and dynamics

This paper overviews the dynamics of bluff body stabilized flames and describes the phenomenology of the blowoff process. The first section of the paper provides an overview of the fluid mechanics of the non-reacting and reacting bluff body wake flow. It highlights the key features of the flow (the boundary layer, separated shear layer, and wake), the flow instabilities that influence each of these features, and the influences of the flame on these instabilities. A key point from these studies is the large differences between the non-reacting wake (dominated by an absolutely unstable, sinuous instability associated with vortex shedding from the bluff body) and the reacting wake of high dilatation ratio flames. The latter are dominated by the lower intensity, convective instability of the shear layer. Very low dilatation ratio flames begin to approach the behavior of the non-reacting wake, as might be expected.