A combined r-h adaptive strategy based on material forces and error assessment for plane problems and bimaterial interfaces

An r-h adaptive scheme has been proposed and formulated for analysis of bimaterial interface problems using adaptive finite element method. It involves a combination of the configurational force based r-adaption with weighted laplacian smoothing and mesh enrichment by h-refinement. The Configurational driving force is evaluated by considering the weak form of the material force balance for bimaterial inerface problems. These forces assembled at nodes act as an indicator for r-adaption. A weighted laplacian smoothing is performed for smoothing the mesh. The h-adaptive strategy is based on a modifed weighted energy norm of error evaluated using supercovergent estimators. The proposed method applies specific non sliding interface strain compatibility requirements across inter material boundaries consistent with physical principles to obtain modified error estimators. The best sequence of combining r- and h-adaption has been evolved from numerical study. The study confirms that the proposed combined r-h adaption is more efficient than a purely h-adaptive approach and more flexible than a purely r-adaptive approach with better convergence characteristics and helps in obtaining optimal finite element meshes for a specified accuracy.     

Development of adsorptive removal process for treatment of explosives contaminated wastewater using activated carbon

The adsorption characteristics of nitro-organics such as trinitro-toluene (TNT), dinitro-toluene (DNT) and nitrobenzene (NB) on granular activated carbon (GAC) were studied to understand their dynamic adsorption behaviour for dilute aqueous solutions. A model was developed to predict the dynamics of the adsorption process and the effect of various design and operating parameters on adsorption characteristics. The model predictions would provide inputs to design of bench scale and pilot plant scale experiments.Section 2 of the paper describes the assumptions, predictions, development of the model and its validation with experimental data generated during bench scale and pilot plant trials. Section 3 presents the breakthrough characteristics obtained by conducting experimental runs for GAC of different surface areas from 650 to 1500 m(2)/g, hydraulic loading rates (HLR) ranging between 12 and 24 m(3)/h/m(2), feed concentrations from 50 to 130 mg/l and bed heights between 300 and 1000 mm for TNT, DNT and NB solutions. The effect of these independent parameters on the breakthrough time, adsorption capacity and the minimum concentration achieved in the effluent was studied and the results obtained are presented in this paper. These indicate that the adsorption capacity goes though a maximum when studied as a function of HLR and feed concentration. The adsorption capacity per unit surface area also shows a maximum around 1000 m(2)/g. The minimum bed height required for meeting environmental effluent discharge limit of 1 ppm was experimentally found to be about 800 mm. These results compare well with the predictions based on the model developed for column adsorption process. Data from these experimental runs and the model predictions have been used to optimise various parameters for the design of a pilot plant unit with 200 l per hour capacity.     

Effect of flow fields and humidification of reactant and oxidant on the performance of scaled‐up PEM‐FC using CFD code

The present study focuses on three‐dimensional two‐phase CFD investigation on scaled‐up proton exchange membrane fuel cell (PEM‐FC) for an active area of 100 cm² with different designs of serpentine and parallel flow configuration. The humidification of hydrogen and oxygen is varied from 10% to 100% to study the PEM‐FC performance. The numerical results of polarization curves predicted in this study have been numerically validated with that of the literature for both parallel and counter serpentine flow channels with active area of 24.8‐cm² PEM‐FC. Further upon validation, the numerical study is extended for scaled‐up PEM‐FC with active area of 100 cm² with different flow path designs to study its performance characteristics namely polarization curves, species concentration distribution, water content in the membrane electrolyte, and proton conductivity to evaluate the fuel cell performance. The three‐dimensional CAD models are created in SOLIDWORKS 10.0 and are discretised hexahedrally using finite volume method. The various governing equations namely conservation of mass, momentum, energy, species concentration, and electrochemical equations are solved numerically with the necessary boundary conditions using the CFD code. The novel design of straight zigzag flow path shows the better performance output over the other designs investigated which is having a higher power density of 0.3711 W/cm² for 100% relative humidity of reactant and oxidant.     

Numerical investigation on the effect of flow field and landing to channel ratio on the performance of PEMFC

Three-dimensional numerical investigation of PEMFC with landing to channel ratio (L:C) of 2:2 for 25-cm² serpentine-parallel channel has been simulated, and the obtained results have been validated with the polarization curve obtained through experiments. It is found that the maximum error in the polarization curve is less than 4%, and thus a very good deal exists between the simulation study and experimentation. Upon validation, the study has been extended for various flow path designs with different L:C ratio numerically. The prediction reveals that the L:C ratio of 2:2 exhibits the better performance for all the flow channels considered, and it is found that the straight-zigzag flow field with L:C ratio of 2:2 attributes the maximum power density of 0.3250 W/cm² for an optimum open circuit voltage of 0.4 Volts with minimal pressure drop. Oxygen consumption in the cathode flow channels of serpentine-parallel, serpentine-zigzag, and straight-parallel are 77.08%, 10.41%, and 42.70% lesser than that of straight-zigzag PEMFC, respectively. The pressure drop in the flow channel of serpentine-parallel, serpentine-zigzag, and straight-parallel with landing to channel ratio 2:2 are 78.18%, 95.81%, and 48.33% higher than that of straight-zigzag flow field, respectively. The polarization curve, hydrogen (H₂), oxygen (O₂), water content along the flow channel and the proton conductivity, H₂O content across the membrane electrolyte, and current density contour at the GDL/catalyst interface of the anode side for all flow channel configurations have been presented and discussed.     

Facile microwave synthesis of Sn-doped WO3 for pseudocapacitor applications

In the present work, we have successfully synthesized pure tungsten oxide (WO₃) and Sn (3 and 5 wt%)-doped WO₃ nanoparticles using facile microwave irradiation method and studied about the electrochemical performances for supercapacitor electrode material. Structural and morphological studies of the prepared nanomaterials were investigated systematically. The powder XRD analysis reveals that pure WO₃ and Sn-doped WO₃ have monoclinic crystal structure and also crystallite size of the material decreases from 38 to 30 nm with increasing dopant concentration. Micro-Raman analysis confirms the formation of monoclinic phase with υ(O–W–O) stretching and δ(O–W–O) bending mode of vibration. SEM and micrographs show the elongation of the plate-like nanostructure of WO₃ for the doping of Sn. High-resolution transmission electron microscope images depict the morphological change and increased porosity in doped samples. The supercapacitive performance and the electrochemical conductivity of the samples were analysed using cyclic voltammetry, chronopotentiometry and electrochemical impedance spectroscopy measurements. The results demonstrate that the 5 wt% Sn-doped WO₃ electrode has the enhanced electrochemical performance in 1 M KOH with a maximum specific capacitance of 418 F g^?1 at low current density of 1 A g^?1. Also, it shows the increase in energy density from 4.88 to 11.77 Wh kg^?1 with respect to the Sn concentration at the power density of 225 W kg^?1_.

     

An Improved Efficient Dynamic Load Balancing Scheme Under Heterogeneous Networks in Hybrid Cloud Environment

Wireless Personal Communications - In the rapid development of computer network technology. The cloud computing is a novel technology had become a highly demanded service due to several new...     

Matrix approach for the coefficients of maximally flat FIR filter transfer functions expressed in powers of cos w

A matrix approach is proposed for determining the coefficients of maximally flat FIR filter transfer functions expressed in powers of cos w. It is shown that the transformation matrix is a product of the well known Q-matrix and a diagonal matrix. Also, a property relating two Q-matrices of successive orders, N and N + 1, is pointed out.     

Flow of electro-rheological materials

Summary An electro-rheological fluid is a material in which a particulate solid is suspended in an electrically non-conducting fluid such as oil. On the application of an electric field, the viscosity and other material properties undergo dramatic and significant changes. In this paper, the particulate imbedded fluid is considered as a homogeneous continuum. It is assumed that the Cauchy stress depends on the velocity gradient and the electric field vector. A representation for the constitutive equation is developed using standard methods of continuum mechanics. The stress components are calculated for a shear flow in which the electric field vector, is normal to the velocity vector. The model predicts (i) a viscosity which depends on the shear rate and electric field and (ii) normal stresses due to the interaction between the shear flow and the electric field. These expressions are used to study several fundamental shear flows: the flow between parallel plates, Couette flow, and flow in an eccentric rotating disc device. Detailed solutions are presented when the shear response is that of a Bingham fluid whose yield stress and viscosity depends on the electric field.     

Electrochemical preparation of potassium gold cyanide

The essential requirements for the industrial preparation of potassium gold cyanide (pgc) are: (a) high rate of dissolution and (b) smooth and uniform dissolution. Employing galvanostatic and potentiostatic polarisation data and observations on the surface topography of anodes dissolved by both the techniques, it is shown that potentiostatic dissolution of gold in potassium cyanide at +0·345 V satisfies the above requirements.     

Phosphorylation on histidine is accompanied by localized structural changes in the phosphocarrier protein, HPr from Bacillus subtilis

The histidine-containing protein (HPr) of bacterial phosphoenolpyruvate:sugar phosphotransferase system (PTS) serves a central role in a series of phosphotransfer reactions used for the translocation of sugars across cell membranes. These studies report the high-definition solution structures of both the unphosphorylated and histidine phosphorylated (P-His) forms of HPr from Bacillus subtilis. Consistent with previous NMR studies, local conformational adjustments occur upon phosphorylation of His 15, which positions the phosphate group to serve as a hydrogen bond acceptor for the amide protons of Ala 16 and Arg 17 and to interact favorably with the alpha-helix macrodipole. However, the positively charged side chain of the highly conserved Arg 17 does not appear to interact directly with phospho-His 15, suggesting that Arg 17 plays a role in the recognition of other PTS enzymes or in phosphotransfer reactions directly. Unlike the results reported for Escherichia coli P-His HPr (Van Nuland NA, Boelens R, Scheek RM, Robillard GT, 1995, J Mol Biol 246:180-193), our data indicate that phosphorylation of His 15 is not accompanied by adoption of unfavorable backbone conformations for active site residues in B. subtilis P-Ser HPr.