Effect of silica nanopowder on the properties of wood flour/polymer composite

Low‐density polyethylene (LDPE), high‐density polyethylene (HDPE), polypropylene (PP), and polyvinyl chloride (PVC) (1:1:1:0.5) were solution blended by using a mixture of solvents consisting of xylene and tetrahydrofuran (THF) (70:30). SiO₂ nanoparticles were modified by cetyl trimethyl ammonium bromide (CTAB). Wood polymer composites (WPC) were prepared by using polymer mixture, polyethylene‐co‐glycidyl methacrylate (PE‐co‐GMA), wood flour, and modified SiO₂. X‐ray diffraction (XRD) studies showed that the intensity of the peaks of polymer mixture decreased due to incorporation of SiO₂. The dispersion of SiO₂ nanoparticles and morphological characteristics were examined by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The interaction between SiO₂ nanoparticles, PE‐co‐GMA, polymer mixture, and wood was studied by Fourier transform infrared spectroscopy (FTIR). Tensile and flexural properties of the composites improved significantly due to the incorporation of SiO₂ nanoparticles. Thermal stability, hardness, flame retardancy, and water resistance capacity were also found to enhance. Maximum improvement in properties was observed by the inclusion of 3 phr modified SiO₂ in WPC. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers     

Field operation of a robotic small waterplane area twin hull boat for shallow‐water bathymetric characterization

An innovative robotic boat has been developed for performing bathymetric mapping of very shallow coastal, estuarine, and inland waters. The boat uses a small waterplane area twin hull design to provide natural platform stability for a multibeam sonar payload, and a navigation system automatically guides the boat in a “lawn‐mowing” pattern to map a region of interest. Developed in stages over five years as part of a low‐cost student design program, the boat is now operational and is being used to generate science‐quality maps for scientific and civil use; it is also being used as a testbed for evaluating the platform for other types of scientific missions and for demonstrating advanced control techniques. This paper reviews the student‐based development process, describes the design of the boat, presents results from field operations, and reviews plans for future extensions to the system. © 2012 Wiley Periodicals, Inc.     

A Possible Scaling-up Technique for Dense Phase Pneumatic Conveying

In this article experimental findings have been presented to show that the pressure drop coefficient (K) for vertical and horizontal pneumatic conveying for a given bulk material follows a certain pattern. The pressure drop coefficient for vertical pneumatic conveying for a given material has been found to be independent of any variation of particle size distribution, within experimental limits. The pressure drop prediction technique proposed by the authors previously has been validated with the test results of alumina and bentonite.     

Relationship between size of oil droplet generated during chemical dispersion of crude oil and energy dissipation rate: Dimensionless,scaling, and experimental analysis

Droplet formation mechanisms during the chemical dispersion of crude oil were investigated using both theoretical and experimental approaches. Dimensionless and force balance analysis identified four distinct regimes of droplet formations. For d>η, d scales either with (ε^?2/5) or (ε^?1/4) or and for d<η, d scales either with (ε^?1/2) or (ε^?1/4) depending on whether the main restoring force against droplet breakage is provided by surface tension or oil viscosity. The symbols d, η, and ε represent the droplet diameter, the Kolmogorov length scale, and energy dissipation rate, respectively. For d>η and <η, the external force, which tries to deform and break the droplet is provided by the pressure difference across the droplet diameter and viscous shear, respectively. Identification of the relationship d～(ε^?1/4) for d<η is a new contribution of this present study. The validity of this relationship was also proven by our experimental observations over a range of physical properties (dynamic viscosity 0.015–8.6 Pa s; oil–water interfacial tension 0.0001–0.015 N/m) and mixing energies (0.00075–0.16 W/kg), similar to those in real environmental settings (e.g., estuary, surface layer of oceans). All these above findings and observations are vital from the stand point of appropriately scaling droplet formation process, during chemical dispersion of crude oil, and in the development of reliable predictive models.     

Fuzzy Genetic Algorithm Approach for the Optimal Placement of Flexible AC Transmission Systems Devices in a Power System

Abstract—This article presents a novel approach for optimal flexible AC transmission systems devices planning in an interconnected power system under different loading conditions. The static VAR compensator and thyristor-controlled series capacitor are two types of flexible AC transmission systems devices considered for optimal power system operation. In the proposed approach, a fuzzy membership function is used to determine weak nodes in the power system for the placement of static VAR compensators as a flexible AC transmission systems device. The thyristor-controlled series capacitor is the other type of flexible AC transmission systems devices for which its positions are determined by the reactive power flow in lines. The genetic algorithm is used for the optimal setting of the power system variables, including flexible AC transmission systems devices. The proposed technique is compared with other optimization methods using different globally accepted evolutionary algorithms where the nodes or point of VAR compensation is determined by eigenvalue analysis, and the amount of flexible AC transmission systems devices is determined by evolutionary techniques, such as the genetic algorithm, differential evolution, and particle swarm optimization. The superiority of the proposed fuzzy-based optimization approach is established by the results and comparative analysis with other methods.     

Dielectric switching above a critical frequency occured in iron mullite composites used as an electronic substrate

Highly crystallized mullite is synthesized via sol–gel technique in presence of iron of different concentrations at different temperature. FTIR spectroscopy, XRD and FESEM characterization showed prominent mullite phase which is found to depend on the concentrations of Fe²⁺ ions. The phase evolution and electrical properties like dielectric constant, tangent loss, a.c. conductivity and resistivity of the composites with increasing concentration of the doped metal at different temperature have been studied. The results showed a decrease in mullite phase up to 1.2 (M) which is mainly responsible for the increasing dielectric behavior with respect to undoped mullite. The hematite phase continued to increase with increasing doping concentration. The dielectric constant decreased with frequency for all the samples attaining constancy at higher frequency, which is normal behavior for dielectric ceramics. A.c. conductivity increased with frequency following Jonscher’s power law and was found to depend on the amount of glassy phase and concentration of mobile ions present in the composites. The composite showed a minimum dielectric constant of 33.69 at 1.2 (M) concentration of iron at 2 MHz. Thus due to their good dielectric response the composite may widely be used use as electronic substrates like packaging materials for integrated high speed circuits, multilayer capacitors, high voltage insulators etc.     

EFFECTS OF VISCOSITY VARIATIONS IN STEADY AND OSCILLATORY COUETTE FLOW

A Newtonian fluid with small variations in the viscosity in the primary flow direction of steady and oscillatory Couette flow is studied. These variations in viscosity create a coupling of the components of the momentum equations between the flow-direction component and the gradient-direction component. The coupling leads to secondary flows even in planar Couette flow where a rectilinear flow may be expected for a purely viscous fluid under creeping flow conditions. A perturbation solution has been applied for small-amplitude oscillations in the viscosity in both steady and oscillatory Couette flow. Because many rheological measurements are made assuming rectilinear flow, these results may have important consequences and may allow error caused by heterogeneity to be estimated. Finally, the relation between the momentum and the assumption of a symmetric stress tensor is discussed by introducing an alternative constitutive equation that is linear in the velocity gradient tensor and objective, but gives an asymmetric stress tensor. By adjusting the degree of asymmetry for the stress tensor, the secondary flows can be altered or eliminated.     

A Simple Technique for Scaling Up Pneumatic Conveying Systems

A brief survey has shown that although scaling-up techniques in pneumatic conveying systems have generally been based on laboratory-scale test data, there still exists a divergence of opinions about the right choice of certain basic parameters such as solids friction factor and air friction factor. In this article, a simple model for pressure drop calculation has been proposed based on the classical Darcy's equation with some modifications. A parameter K, called pressure drop coefficient, has been shown to be independent of pipe diameter and hence suitable for scaling up to pipe sizes different from those used in laboratory-scale tests. For each of the bulk material and pipe size combinations used in this study, we calculated the standard deviation of predicted pressure values from the experimental values along the central 45° line passing through the origin; it varied from±165 mbar to a maximum±285 mbar. It has been shown that the model can be used for both horizontal and vertical pneumatic conveying.     

In situ fabrication of polyaniline‐silver nanocomposites using soft template of sodium alginate

Polyaniline (PANI)‐Ag nanocomposites were synthesized by in situ chemical polymerization approach using ammonium persulfate and silver nitrate as oxidant. Characterizations of nanocomposites were done by ultraviolet–visible ( UV–vis), Fourier transform infrared (FTIR), X‐ray diffraction (XRD), scanning electron microscopy, and transmission electron microscopy (TEM). UV–vis, XRD and FTIR analysis established the formation of PANI/Ag nanocomposites and face‐centered‐cubic phase of silver. PANInanofibers were of average diameter ～ 30 nm and several micrometers in length. Morphological analysis showed that the spherical‐shaped silver nanoparticles decorate the surface of PANI nanofibers. Silver nanoparticles of average diameter ～ 5–10 nm were observed on the TEM images for the PANI‐Ag nanocomposites. Such type of PANI‐Ag nanocomposites can be used as bistable switches as well as memory devices. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effect of SiO2 and nanoclay on the properties of wood polymer nanocomposite

Wood polymer composite (WPC) were developed by using solution blended high density polyethylene, low density polyethylene, polypropylene, poly(vinyl chloride), Phragmites karka wood flour and polyethylene-co-glycidyl methacrylate. The effect of addition of nanoclay and SiO₂ on the properties of the composite was examined. X-ray diffractrometry and transmission electron microscopy were used to study the distribution of silicate layers and SiO₂ nanopowder in the composite. The improvement in miscibility among the polymers and WPC was studied by scanning electron microscopy. Fourier transform infrared spectroscopy study revealed the interaction between polymer, wood, clay and SiO₂. WPC treated with 3 wt% each of clay and SiO₂ showed an excellent improvement in mechanical properties, thermal and flame retarding properties. Water uptake of WPC was found to decrease on incorporation of nanoclay and SiO₂ in WPC.