Homotopy perturbation method for motion of a spherical solid particle in plane couette fluid flow

He’s homotopy perturbation method is applied to obtain exact analytical solutions for the motion of a spherical particle in a plane couette flow. It is demonstrated that the applied analytical method is very straightforward in comparison with existing techniques. Furthermore, it is decidedly effectual in terms of accuracy and rapid convergence. The formulation of the problem is presented in the text as well as the analytical and numerical procedures. The current results can be used in different areas of particulate flows.     

An investigation on the behavior of electrospun ZnO nanofibers under the application of low frequency AC electric fields

In present study, the behavior of electrospun ZnO nanofibers under the application of low frequency alternating (AC) electric fields within the range of 1 Hz–20 kHz was investigated using planar parallel electrodes. In the first stage, ZnO nanofibers with diameters up to 100 nm were prepared by electrospinning. At 1 Hz, the strong electric field-induced fluid flow due to charge redistribution around the electrode swept the fibers on the electrode surface farther from the edges. As the frequency was increased to 1 kHz, most depositing fibers accumulated on the electrode edges and in the meantime, a small fraction of them was pushed into the surface as a result of AC electroosmosis effect. Above 1 kHz, the fibers were assembled within the electrode gap bridging the interelectrode space. The dielectrophoresis force was considered responsible for the assembly and relative alignment of ZnO nanofibers above 1 kHz.     

Effect of inulin and galactooligosaccharides on particle size distribution and rheological properties of prebiotic ketchup

The aim of this study was to evaluate the effects of different combinations of long-chain inulin and short-chain galactooligosaccharides mixed with different hydrocolloids on the physical/rheological attributes of prebiotic ketchup. Novel prebiotic ketchup was produced in which modified starch, xanthan, and guar gum was incorporated. Results showed that modified starch negatively influenced the physical properties of prebiotic samples and the optimum condition was 7.5% long-chain inulin and 2.5% galactooligosaccharides along with 0.4 % xanthan and 0.18% guar gum. Under these conditions, smaller hysteresis loop area, higher values of the linear viscoelastic region, larger G₀, η₀ in the creep test, and smaller sized suspended particles as compared to the other prebiotic samples were observed. In addition, galactooligosaccharides may interfere with the elastic behavior due to its high water solubility. Therefore, an appropriate amount (2.5%) of this ingredient may be used to produce a nutritive prebiotic ketchup with desirable textural properties. Environmental scanning electron microscopic images confirmed larger and inter-connected air bubbles entrapped into the semi-solid matrix of prebiotic sample produced under optimum condition.     

Reducing Dangerous Effects of Unsymmetrical Dimethylhydrazine as a Liquid Propellant by Addition of Hydroxyethylhydrazine—Part I: Physical Properties

In this work, the effect of low volatile hydroxyethylhydrazine (HEH) as a solute on unsymmetrical dimethylhydrazine (UDMH) has been studied in order to reduce harmful effects of UDMH vapors. Desirable physical properties of binary mixtures UDMH/HEH have been measured and compared to pure UDMH. These properties include boiling point, viscosity, density, and vapor pressure that are important for using binary mixtures of UDMH/HEH as less dangerous liquid propellants. Due to the formation of strong hydrogen bonding between UDMH and HEH, the volatility of UDMH has been reduced appreciably upon the addition of HEH. It is indicated that the measured physical properties may deviate significantly compared to corresponding predicted values. Binary mixtures of UDMH/HEH can also react spontaneously in contact with nitrogen tetroxide (NTO) and red fuming nitric acid (RFNA), so they can be called hypergolic propellants.     

Comparison between the effect of nanoglass flake and montmorillonite organoclay on corrosion performance of epoxy coating

Montmorillonite organoclay (OMMT) and nanoglass flake (GF) were incorporated into epoxy resin by mechanical agitation and sonication process. Optical microscopy was used to analyse the optical homogeneity of dispersions. To investigate anticorrosive properties of nanocomposite organic coatings, salt fog test, electrochemical impedance spectroscopy (EIS), polarization measurement, pull-off adhesion and water absorption tests have been employed. The time course of impedance parameters and polarization studies show that coating corrosion resistance is improved as the amounts of OMMT and GF are increased to 3 wt%. The results indicated that nano-GF filled specimens display better corrosion performance than the OMMT filled ones.