Mass transfer from a single fluid sphere to power-law liquids at moderate Reynolds numbers

The steady-state convective inter-phase mass transfer from a single Newtonian fluid sphere (free from surfactants) to a continuous phase with power-law viscosity has been studied at moderate Reynolds and Schmidt numbers under the conditions when the resistance to mass transfer in the dispersed phase is negligible. The species continuity equation, segregated from the momentum equations of both phases, has been numerically solved using a finite difference method. The effects of the Reynolds number (Re_o), power-law index (n_o), internal to external fluid characteristic viscosity ratio (k) and Schmidt number (Sc) on the local and average Sherwood number (Sh) have been analysed over the following ranges of conditions: 5?Re_o?200, 0.6?n_o?1.6, 0.1?k?50 and 1?Sc?1000. It has been observed that irrespective of the values of the Reynolds number and of the power-law index, as the value of k increases the average Sherwood number decreases for intermediate to large values of the Peclet number. As the value of the power-law index increases, the rate of mass transfer decreases for all values of the Reynolds number and the characteristic viscosity ratio thereby suggesting that shear-thinning behaviour facilitates mass transfer, whereas shear-thickening behaviour impedes it. Based on the present numerical results, a simple predictive correlation is proposed which can be used to estimate the rate of inter-phase mass transfer of a fluid sphere sedimenting in power-law liquids.     

Ultrasonic welding of thermoplastics in the near-field

Ultrasonic welding is one of the most popular techniques for joining thermoplastics because it is fast, economical, and easily automated. In near-field ultrasonic welding, the distance between the horn and the joint interface is 6 mm or less. This study investigated the near-field ultrasonic welding of amorphous (acrylonitrile-butadiene-styrene and polystyrene) and semicrystalline (polyethylene and polypropylene) polymers. High frequency ultrasonic wave propagation and attenuation measurements were made in order to estimate the dynamic mechanical moduli of the polymers. The estimated moduli were entered into a lumped parameter model in order to predict heating rates and energy dissipation. Experimental results showed that variations in the welding pressure had little effect on energy dissipation or joint strength; Increasing the amplitude of vibration increased the energy dissipation and the weld strength. For the semicrystalline polymers, increasing the weld time improved strength up to weld times greater than 1.5 s, where strength leveled off. For the amorphous polymers, the weld strength increased with Increasing weld time up to times of 0.8 s; for longer weld times, the power required was too high, causing overloading of the welder. Monitoring of the energy dissipation and static displacement or collapse provided valuable information on weld quality.     

Effect of baffles on a partially filled cubic tank: Numerical simulation and experimental validation

In this paper, sloshing waves have been analyzed for baffled and un-baffled tanks. Numerical simulations were carried out based on volume of fluid (VOF) techniques with arbitrary-Lagrangian–Eulerian (ALE) formulation which adopts the displacement of solid, the pressure and displacement in the fluid as variables to model the coupled system. The response of the coupled system is obtained by using the well-known software ADINA, which offers efficient fully coupled fluid–structure interaction capabilities by finite element method. The results obtained are compared with the available experimental data to demonstrate the reduction of sloshing effects in fluid model.     

Performance Optimization of Video Coding Process on Multi-Core Platform Using Gop Level Parallelism

High definition video applications often require heavy computation, high bandwidth and high memory requirements which make their real-time implementation difficult. Multi-core architecture with parallelism provides new solutions to implementing complex multimedia applications in real-time. It is well-known that the speed of the H.264 encoder can be increased on a multi-core architecture using the parallelism concept. Most of the parallelization methods proposed earlier for these purposes suffer from the drawbacks of limited scalability and data dependency. In this paper, we present a result obtained using data-level parallelism at the Group-Of-Pictures (GOP) level for the video encoder. The proposed technique involves each GOP being encoded independently and implemented on JM 18.0 using advanced data structures and OpenMP programming techniques. The performance of the parallelized video encoder is evaluated for various resolutions based on the parameters such as encoding speed, bit rate, memory requirements and PSNR. The results show that with GOP level parallelism, very high speed up values can be achieved without much degradation in the video quality.     

Partial Agonist Activity of Neonicotinoids on Rat Nicotinic Receptors: Consequences over Epinephrine Secretion and In Vivo Blood Pressure

Neonicotinoid insecticides are nicotine-derived molecules which exert acute neurotoxic effects over the insect central nervous system by activating nicotinic acetylcholine receptors (nAChRs). However, these receptors are also present in the mammalian central and peripheral nervous system, where the effects of neonicotinoids are faintly known. In mammals, cholinergic synapses are crucial for the control of vascular tone, blood pressure and skeletal muscle contraction. We therefore hypothesized that neonicotinoids could affect cholinergic networks in mammals and sought to highlight functional consequences of acute intoxication in rats with sub-lethal concentrations of the highly used acetamiprid (ACE) and clothianidin (CLO). In this view, we characterized their electrophysiological effects on rat α3β4 nAChRs, knowing that it is predominantly expressed in ganglia of the vegetative nervous system and the adrenal medulla, which initiates catecholamine secretion. Both molecules exhibited a weak agonist effect on α3β4 receptors. Accordingly, their influence on epinephrine secretion from rat adrenal glands was also weak at 100 μM, but it was stronger at 500 μM. Challenging ACE or CLO together with nicotine (NIC) ended up with paradoxical effects on secretion. In addition, we measured the rat arterial blood pressure (ABP) in vivo by arterial catheterization. As expected, NIC induced a significant increase in ABP. ACE and CLO did not affect the ABP in the same conditions. However, simultaneous exposure of rats to both NIC and ACE/CLO promoted an increase of ABP and induced a biphasic response. Modeling the interaction of ACE or CLO on α3β4 nAChR is consistent with a binding site located in the agonist pocket of the receptor. We present a transversal experimental approach of mammal intoxication with neonicotinoids at different scales, including in vitro, ex vivo, in vivo and in silico. It paves the way of the acute and chronic toxicity for this class of insecticides on mammalian organisms.     

Vibration analysis of steam turbine discsSchwingungsanalyse von dampfturbinenräder

A knowledge of the vibration characteristics of discs of steam turbines is a prerequisite for a successful design of the turbine. As a matter of fact, considerable research effort, both theoretical and experimental, has been directed towards understanding the dynamic behaviour of blades and discs taken singly and jointly. This paper presents a theoretical analysis of the vibration characteristics of a steam turbine disc. In particular, the Runge—Kutta method has been used to solve the differential equation governing the flexural oscillations of the disc. Numerical results evaluated for a typical disc are presented.     

Steady incompressible fluid flow over a bundle of cylinders at moderate reynolds numbers

The complete Navier-Stokes equations describing the steady flow of incompressible Newtonian fluids normal to an array of long cylinders have been solved numerically using the finite difference method in terms of the stream function and vorticity variables. The inter-cylinder interactions have been mimicked using the well known free surface cell model. Extensive information on the detailed structure of the flow field in terms of the surface vorticity distribution, stagnation pressure, stream line and iso-vorticity line plots, as well as on the values of the integral quantities, such as pressure, friction and total drag coefficients, have been obtained under wide ranges of conditions as follows: 0.3 ≤ ? 0.99 and 0.01 ≤ Re ≤ 100. The numerical results presented herein have been validated using the appropriate theoretical and experimental results available in the literature; the match between the present predictions and the scant experimental results is good.     

Mixed Copper/Copper‐Oxide Anchored Mesoporous Fullerene Nanohybrids as Superior Electrocatalysts toward Oxygen Reduction Reaction

Developing a highly active, stable, and efficient non‐noble metal‐free functional electrocatalyst to supplant the benchmark Pt/C‐based catalysts in practical fuel cell applications remains a stupendous challenge. A rational strategy is developed to directly anchor highly active and dispersed copper (Cu) nanospecies on mesoporous fullerenes (referred to as Cu‐MFC₆₀) toward enhancing oxygen reduction reaction (ORR) electrocatalysis. The preparation of Cu‐MFC₆₀ involves i) the synthesis of ordered MFC₆₀ via the prevalent nanohard templating technique and ii) the postfunctionalization of MFC₆₀ with finely distributed Cu nanospecies through incipient wet impregnation. The concurrence of Cu and cuprous oxide nanoparticles in the as‐developed Cu‐MFC₆₀ samples through relevant material characterizations is affirmed. The optimized ORR catalyst, Cu(15%)‐MFC₆₀, exhibits superior electrocatalytic ORR characteristics with an onset potential of 0.860 vs reversible hydrogen electrode, diffusion‐limiting current density (?5.183 mA cm^?2), improved stability, and tolerance to methanol crossover along with a high selectivity (four‐electron transfer). This enhanced ORR performance can be attributed to the rapid mass transfer and abundant active sites owing to the synergistic coupling effects arising from the mixed copper nanospecies and the fullerene framework.     

An efficient amperometric sensor for chloride ion detection through electroactive e-spun PVA-PANi-g-C3N4 nanofiber

Journal of Materials Science: Materials in Electronics - A novel method for selective and sensitive detection of chloride ion plays a vital role in environmental monitoring, industrial and...     

SPECTRA – a Maple library for solving linear matrix inequalities in exact arithmetic

This document describes our freely distributed Maple library spectra, for Semidefinite Programming solved Exactly with Computational Tools of Real Algebra. It solves linear matrix inequalities with symbolic computation in exact arithmetic and it is targeted to small-size, possibly degenerate problems for which symbolic infeasibility or feasibility certificates are required.