Biodegradable nanocomposites from toughened polyhydroxybutyrate and titanate-modified montmorillonite clay

Montmorillonite clay treated with neopentyl (diallyl)oxy tri(dioctyl) pyrophosphato titanate was used as a reinforcement for toughened bacterial bioplastic, Polyhydroxybutyrate (PHB) in order to develop novel biodegradable nanocomposites. The modified clay, PHB, toughening partner and specific compatibilizer were processed by extrusion followed by injection molding. Different microscopy and goniometry techniques, rheology analysis, X-ray diffraction and thermo-mechanical testing were used to characterize the nanocomposites. Results showed that the nanocomposites with 5 wt% titanate-modified clay loading exhibited about 400% improvement in impact properties and 40% reduction in modulus in comparison with virgin PHB. The novel aspect of the titanate-based modification was that the nanocomposites still maintained nearly the same impact strength value as that of toughened PHB. The diffraction patterns suggest exfoliation of the organically modified clays and this was further supported by transmission electron microscopy and melt rheological analysis. The mechanical properties of the nanocomposites were correlated with a modified Halpin-Tsai theoretical model and the predictions matched significantly with the experimental results. Toughened and compatibilized PHB showed significantly lower biodegradation rate than virgin PHB and most significantly the addition of the titanate-modified clay in the same formulation enhanced the biodegradation several fold.     

Diamond and Diamond-like-Carbon Growth on Si (100) by Hot Filament-Assisted RF Plasma CVD

Diamond and diamond-like carbon (DLC) crystallites can be grown on a Si (100) substrate by hot filament-assisted RF plasma CVD in a low-vacuum (2-Torr) environment from C₂H₂ without using hydrogen. The deposition was carried out at 900°C onto the precleaned diamond polished Si (100) substrate. XRD and Raman spectra revealed the presence of diamond, graphite, lonsdaleite, and high-order polymeric hydrocarbon phases. The morphology observed by SEM shows typical habit and facets of the diamond crystallites grown on silicon. An attempt was made to explain some discrepancies observed in the XRD and Raman spectra of our multiphasic DLC films.     

Heat and mass transfer flow over a stretching surface with Ohmic heating and chemical reaction

The present study analyzes the effect of chemical reaction on an unsteady magnetohydrodynamic boundary layer viscous fluid over a stretching surface embedded in a porous medium with a uniform transverse magnetic field. A Darcy‐Forchheimer drag force model is employed to simulate the effect of second‐order porous resistance. Dissipative heat energy based on both viscous and Joule dissipation along with a heat source/sink is considered to enhance the energy equation. Similarity analysis is imposed to transform the governing differential equations into a set of nonlinear coupled ordinary differential equations. These sets of equations are solved numerically using the Runge‐Kutta fourth‐order scheme followed by the shooting algorithm. The effects of physical parameters such as magnetic field, Prandtl number, Eckert number, Schmidt number, unsteadiness parameter, and chemical reaction parameters have been discussed on velocity, temperature, and concentration fields. Computation for the coefficient of skin friction, rate of heat and mass transfer is done and presented in a table for validation of the present outcomes.     

Removal of hexavalent chromium by Kendu fruit gum dust

The ability of a low cost adsorbent material, Kendu fruit gum dust (KGD), for removal of hexavalent chromium, Cr(VI), from aqueous solutions of both a synthetic and industrial (effluent) sample is successfully investigated through batch type experiments. The effects of contact time, Cr(VI) concentration, pH, adsorbent amount, and temperature on the extent of Cr(VI) removal are reported. At a lower initial concentration of Cr(VI) and a lower solution pH, the percent removal is found to be increased. A removal efficiency of 100% has been achieved. In the presence of cyanide ion the adsorption efficiency of KGD decreases. Recycling studies suggest that even after the sixth cycle, only ∼ 20% loss of efficiency of KGD occurs. The adsorption process follows the Freundlich adsorption isotherm model. Another important feature of the investigation includes the studies on the characteristics and analysis of various constituents present in the newly developed absorbent material (KGD). From the thermogravimetric analysis curves of the original KGD and Cr(VI) absorbed KGD, it is observed that the thermal stability of KGD increases due to metal ion adsorption. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1485–1494, 1997     

Distribution Network Assessment using EPANET for Intermittent and Continuous Water Supply

Drawbacks of intermittent water supply system and inability to shift to continuous supply mode is the main challenge in developing countries. The suitability of the infrastructure laid over past two to three decades to meet the 24/7 demand of todays population is the issue for many water mangers. The present study addresses this issue using EPANET software for a pilot study area in Nagpur city, India. GIS maps, field survey data, remote sensing data and in-situ measurements of pressure and water quality are used in model simulation study. Total 96 artificial reservoirs are inserted into the network which replicate the end-user practices of excess water withdrawal. Reservoirs are assumed connected to damand nodes with equivalent diameter pipes for intermittent supply simulation. For continuous supply, demand multipliers are derived using Monte Carlo simulation. Bulk decay coefficient 0.17 day^?1 for residual chlorine is used in water quality simulation. Simulation scenario of intermittency indicates existing network is not suitable to maintain desired headloss, and pressure in most of the pipes is very low (<1 m). Water age and water quality problems reveal that rehabilitation of distribution mains and critical pipes in the central part is primarily important before implementing 24/7 water supply scheme in the study area.     

A dual voltage-frequency VLSI chip for image watermarking in DCT domain

In this brief, we present a new VLSI architecture that can insert invisible or visible watermarks in images in the discrete cosine transform domain. The proposed architecture incorporates low-power techniques such as dual voltage, dual frequency, and clock gating to reduce the power consumption and exploits pipelining and parallelism extensively in order to achieve high performance. The supply voltage level and the operating frequency are chosen for each module so as to maintain the required bandwidth and throughput match among the different modules. A prototype VLSI chip was designed and verified using various Cadence and Synopsys tools based on TSMC 0.25-/spl mu/m technology with 1.4 M transistors and 0.3 mW of estimated dynamic power.     

Differential roles of frequency and meaningfulness in free recall.

Performed 2 experiments with 91 experimentally naive high school students to study the comparative influence of frequency and meaningfulness (m) on free recall. In Exp. I, the free-recall scores of 3 lists of words matched for m but varying in frequency levels were compared. In Exp. II, free recall of 3 lists of words matched for their frequency but varying in their m values were compared. Findings reveal that it is the frequency and not m of the words that influences free-recall, and that the influence of frequency is noticeable in the early trials of free-recall learning. Findings are discussed in terms of the existing theories of verbal learning. (French summary) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A particle swarm approach for multi-objective optimization of electrical discharge machining process

This paper proposes an experimental investigation and optimization of various machining parameters for the die-sinking electrical discharge machining (EDM) process using a multi-objective particle swarm (MOPSO) algorithm. A Box–Behnken design of response surface methodology has been adopted to estimate the effect of machining parameters on the responses. The responses used in the analysis are material removal rate, electrode wear ratio, surface roughness and radial overcut. The machining parameters considered in the study are open circuit voltage, discharge current, pulse-on-time, duty factor, flushing pressure and tool material. Fifty four experimental runs are conducted using Inconel 718 super alloy as work piece material and the influence of parameters on each response is analysed. It is observed that tool material, discharge current and pulse-on-time have significant effect on machinability characteristics of Inconel 718. Finally, a novel MOPSO algorithm has been proposed for simultaneous optimization of multiple responses. Mutation operator, predominantly used in genetic algorithm, has been introduced in the MOPSO algorithm to avoid premature convergence. The Pareto-optimal solutions obtained through MOPSO have been ranked by the composite scores obtained through maximum deviation theory to avoid subjectiveness and impreciseness in the decision making. The analysis offers useful information for controlling the machining parameters to improve the accuracy of the EDMed components.