An-Najah Staff

Present methods of analysis and mathematical modeling contain so many assumptions that separate them from reality and thus represent a defect in design which makes it difficult to analyze reasons of failure. Three dimensional (3D) modeling is so superior to 1D or 2D modeling, static analysis deviates from the true nature of earthquake load which is “a dynamic punch”, and conflicting assumptions exist between structural engineers (who assume flexible structures on rigid block foundations) and geotechnical engineers (who assume flexible foundations supporting rigid structures). Thus a 3D dynamic soil‐structure interaction is a step that removes many of the assumptions and thus clears reality to a greater extent. However such a model cannot be analytically analyzed. We need to anatomize and analogize it. The paper will represent a conceptual (analogical) 1D model for soil structure interaction and clarifies it by comparing its outcome with 3D dynamic soil‐structure finite element analysis of two structures. The aim is to focus on how to calculate the period of the structure and to investigate effect of variation of stiffness on soil‐structure interaction.

Ultradispersed metal oxide nanoparticles have applications as heterogeneous catalysts for organic reactions. Their catalytic activity depends primarily on their surface area, which in turn, is dictated by their size, colloidal concentration and stability. This work presents a microemulsion approach for in situ preparation of ultradispersed copper oxide nanoparticles and discusses the effect of different microemulsion variables on their stability and highest possible time-invariant colloidal concentration (nanoparticle uptake). In addition, a model which describes the effect of the relevant variables on the nanoparticle uptake is evaluated. The preparation technique involved solubilizing CuCl2 in single microemulsions followed by direct addition of NaOH. Upon addition of NaOH, copper hydroxide nanoparticles stabilized in the water pools formed in addition to a bulk copper hydroxide precipitate at the bottom. The copper hydroxide nanoparticles transformed with time into copper oxide. After reaching a time-independent concentration, mixing had limited effect on the nanoparticle uptake and particle size. Particle size increased with increasing the surfactant concentration, concentration of the precursor salt, and water to surfactant mol ratio; while the nanoparticle uptake increased linearly with the surfactant concentration, displayed an optimum with R and a power function with the concentration of the precursor salt. Surface areas per gram of nanoparticles were much higher than literature values. Even though lower area per gram of nanoparticles was obtained at higher uptake, higher surface area per unit volume of the reverse micellar system was attained. A model based on water uptake by Wisor type II microemulsions, and previously used to describe iron oxide nanoparticle uptake by the same microemulsions, agreed well with the experimental results.

Water-in-oil (w/o) microemulsions are very appealing reaction media due to their ability to provide huge surface of contact between water-soluble and oil-soluble reactants. Their application as reaction media, including the preparation of nanoparticles, is, however, limited to water soluble precursors. In this study, we present a first step scheme in a two-step process for the preparation of metal oxide nanoparticles starting from their water-insoluble metal oxide bulk powder. This step involves solubilizing the metal oxide in the water pools of the microemulsion with the aid of a solubilizing agent. The variables affecting the solubilizing capacity of iron and copper oxides,as examples of important metal oxides, in single HCl-containing AOT/water/isooctane microemulsions were investigated. The effect of the following variables on the solubilization capacity is reported, namely, mixing time, surfactant concentration, water to surfactant mole ratio (R),and the nominal concentration of HCl in the water pool. At 300-rpm, time-invariant concentration of the metals in the microemulsions was achieved in about 6 hours. These values were quoted as the solubilization capacity of the metal oxide at the corresponding conditions.Solubilization capacity increased linearly with the surfactant concentration and R, and portrait a power function with the nominal concentration of HCl in the water pool. A mathematical model previously derived to describe nanoparticle uptake by single microemulsion accurately accounted for the effect of the aforementioned variables on the solubilization capacity.