Two-dimensional homogeneous isotropic fluid turbulence with polymer additives

We carry out an extensive and high-resolution direct numerical simulation of homogeneous, isotropic turbulence in two-dimensional fluid films with air-drag-induced friction and with polymer additives. Our study reveals that the polymers (a) reduce the total fluid energy, enstrophy, and palinstrophy; (b) modify the fluid energy spectrum in both inverse-and forward-cascade regimes; (c) reduce small-scale intermittency; (d) suppress regions of high vorticity and strain rate; and (e) stretch in strain-dominated regions. We compare our results with earlier experimental studies and propose new experiments.

Studies on NOX Removal From Diesel Engine Exhaust Using Duct-Type DBD Reactor

With ever more stringent NOX emissions, it is necessary to examine removal of nitrogen oxide from diesel engine exhaust. This paper describes the study of NOX reduction from 5.9-kW stationary diesel engine exhaust under nanosecond pulse energization. Two plasma reactors characterized by dielectric barrier discharge has been designed, built, and evaluated. One of the reactor designs include nine numbers of electrodes kept in parallel, and the exhaust was allowed to pass axially, whereas the second reactor consists of nine parallel electrodes and the exhaust was allowed to pass radially. The reactors were individually tested for the treatment of nitrogen oxides for gas flow rate of 2, 5, and 10 L/min. Both the reactors have been individually tested, and results show an appreciable removal of NOX with equal discharge volume. From the results, it was found that both the reactors were an efficient NOX removal. With consumption of only 36 J/L, the reactors had shown a considerable 45% DeNO(X) efficiency.

Discharge Plasma Combined With Bauxite Residue for Biodiesel Exhaust Cleaning: A Case Study on NOx Removal

Experiments were conducted at laboratory level to treat the oxides of nitrogen (NOx) present in raw and dry biodiesel exhaust utilizing a combination of electric discharge plasma and bauxite residue, i. e., red mud, an industrial waste byproduct from the aluminum industry. In this paper, the adsorption and a possible catalytic property of bauxite residue are discussed. Nonthermal plasma was generated using dielectric barrier discharges initiated by ac/repetitive pulse energization. The effect of corona electrodes on the plasma generation was qualitatively studied through NOx cleaning. The plasma reactor and adsorbent reactors were connected in cascade while treating the exhaust. The diesel generator, running on biodiesel fuel, was electrically loaded to study the effectiveness of the cascade system in cleaning the exhaust. Interestingly, under the laboratory conditions studied, plasma-bauxite residue combination has shown good synergistic properties and enhanced the NOx removal up to about 90%. With proper scaling up, the suggested cascade system may become an economically feasible option to treat the exhaust in larger installations. The results were discussed emphasizing the role of bauxite residue as an adsorbent and as a room temperature catalyst.

HYDROMAGNETICS OF ADVECTIVE ACCRETION FLOWS AROUND BLACK HOLES: REMOVAL OF ANGULAR MOMENTUM BY LARGE-SCALE MAGNETIC STRESSES

We show that the removal of angular momentum is possible in the presence of large-scale magnetic stresses in geometrically thick, advective, sub-Keplerian accretion flows around black holes in steady state, in the complete absence of alpha-viscosity. The efficiency of such an angular momentum transfer could be equivalent to that of alpha-viscosity with alpha = 0.01-0.08. Nevertheless, the required field is well below its equipartition value, leading to a magnetically stable disk flow. This is essentially important in order to describe the hard spectral state of the sources when the flow is non/sub-Keplerian. We show in our simpler 1.5 dimensional, vertically averaged disk model that the larger the vertical-gradient of the azimuthal component of the magnetic field is, the stronger the rate of angular momentum transfer becomes, which in turn may lead to a faster rate of outflowing matter. Finding efficient angular momentum transfer in black hole disks via magnetic stresses alone, is very interesting when the generic origin of alpha-viscosity is still being explored.

Ag-doped hydroxyapatite as efficient adsorbent for removal of Congo red dye from aqueous solution: Synthesis, kinetic and equilibrium adsorption isotherm analysis

In the present study a versatile and efficient adsorbent with high adsorption capacity for adsorption of Congo red dye in aqueous solution at ambient temperature without adjusting any pH is presented over the Ag modified calcium hydroxyapatite (CaHAp). CaHAp and Ag-doped CaHAp materials were synthesized using facile aqueous precipitation method. The physico-chemical properties of the materials were determined by powder X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, Transmission electron microscopy (TEM), UV-Visible spectroscopy, N-2 physisorption and acidity was determined by n-butylamine titration and pyridine adsorption methods. XRD analysis confirmed all adsorbents exhibit hexagonal CaHAp structure with P6(3)/m space group. TEM analysis confirms the rod like morphology of the adsorbents and the average length of the rods were in the range of 40-45 nm. Pyridine adsorption results indicate increase in number of Lewis acid sites with Ag doping in CaHAp. Adsorption capacity of CaHAp was found increased with Ag content in the adsorbents. Ag (10): CaHAp adsorbent showed superior adsorption performance among all the adsorbents for various concentrations of Congo red (CR) dye in aqueous solutions. The amount of CR dye adsorbed on Ag (10): CaHAp was found to be 49.89-267.81 mg g(-1) for 50-300 ppm in aqueous solution. A good correlation between adsorption capacity and acidity of the adsorbents was observed. The adsorption kinetic data of adsorbents fitted well with pseudo second-order kinetic model with correlation coefficients ranged from 0.998 to 0.999. The equilibrium adsorption data was found to best fit to the Langmuir adsorption isotherm model. (C) 2015 Elsevier Inc. All rights reserved.

In Situ Crystallographic Probing on Ameliorating Effect of Sulfide Additives and Carbon Grafting in Iron Electrodes

Beneficial effects of carbon grafting into the iron active material for rechargeable alkaline-iron-electrodes with and without Bi2S3 additive is probed by in situ X-ray diffraction in conjunction with Extended X-ray Absorption Fine Structure (EXAFS) and electrochemistry. EXAFS data unravel that the composition of pristine active material (PAM) for iron electrodes comprises 87% of magnetite and 13% of alpha-iron while carbon-grafted active material comprises 60% of magnetite and 40% of alpha-iron. In situ XRD patterns are recorded using a specially designed electrochemical cell. XRD data reflect that magnetite present in PAM iron electrode, without bismuth sulfide additive, is not reduced during charging while PAM iron electrode with bismuth sulfide additive is partially reduced to alpha-Fe/Fe(OH)(2). Interestingly, carbon-grafted-iron electrodes with bismuth sulfide exhibit complete conversion of active material to alpha-Fe/Fe(OH)2. The ameliorating effect of carbon grafting is substantiated by kinetic parameters obtained from steady-state potentiostatic polarization and Tafel plots. The mechanism for iron-electrode charge - discharge reactions are discussed in the light of the potential - pH diagrams for Fe - H2O, S - H2O and FeSads - H2O systems and it is surmised that carbon grafting into iron active material promotes its electrochemical utilization. (C) The Author(s) 2015. Published by ECS. All rights reserved.

Isolation and characterization of a bioflocculant from Bacillus megaterium for turbidity and arsenic removal

A biodegradable flocculant was produced during growth of Bacillus megaterium. The major component of the bioflocculant was found to be a polysaccharide composed of some proteins. Fourier transform infrared (FTIR) spectra analysis revealed the presence of carboxyl and hydroxyl groups in the bioflocculant, and thermal characterization by differential scanning calorimetly (DSC) showed the transition and crystalline melting point at 90-105 degrees C. The effects of bioflocculant dosage and pH on the flocculation of mineral suspensions were evaluated. The bioflocculant exhibited good flocculating capability on mineral suspensions and achieved flocculating efficiencies of 90 percent for k-aolinite and 85 percent for hematite suspensions at a dosage of only 5 mL/L. The maximum arsenite removal was found to be 90 percent at a bioflocculant dosage of 2 g/L, which is better than traditional chemicalflocculants. This study demonstrates that microbial bioflocculants have potential for application in environmental cleanup, such as in the flocculation of mineral fines and in the remediation of solutions that contain toxic heavy metals.

No More HF: Teflon-Assisted Ultrafast Removal of Silica to Generate High-Surface-Area Mesostructured Carbon for Enhanced CO2 Capture and Supercapacitor Performance

An innovative technique to obtain high-surface-area mesostructured carbon (2545m(2)g(-1)) with significant microporosity uses Teflon as the silica template removal agent. This method not only shortens synthesis time by combining silica removal and carbonization in a single step, but also assists in ultrafast removal of the template (in 10min) with complete elimination of toxic HF usage. The obtained carbon material (JNC-1) displays excellent CO2 capture ability (ca. 26.2wt% at 0 degrees C under 0.88bar CO2 pressure), which is twice that of CMK-3 obtained by the HF etching method (13.0wt%). JNC-1 demonstrated higher H-2 adsorption capacity (2.8wt%) compared to CMK-3 (1.2wt%) at -196 degrees C under 1.0bar H-2 pressure. The bimodal pore architecture of JNC-1 led to superior supercapacitor performance, with a specific capacitance of 292Fg(-1) and 182Fg(-1) at a drain rate of 1Ag(-1) and 50Ag(-1), respectively, in 1m H2SO4 compared to CMK-3 and activated carbon.

No More HF: Teflon-Assisted Ultrafast Removal of Silica to Generate High-Surface-Area Mesostructured Carbon for Enhanced CO2 Capture and Supercapacitor Performance

An innovative technique to obtain high-surface-area mesostructured carbon (2545m(2)g(-1)) with significant microporosity uses Teflon as the silica template removal agent. This method not only shortens synthesis time by combining silica removal and carbonization in a single step, but also assists in ultrafast removal of the template (in 10min) with complete elimination of toxic HF usage. The obtained carbon material (JNC-1) displays excellent CO2 capture ability (ca. 26.2wt% at 0 degrees C under 0.88bar CO2 pressure), which is twice that of CMK-3 obtained by the HF etching method (13.0wt%). JNC-1 demonstrated higher H-2 adsorption capacity (2.8wt%) compared to CMK-3 (1.2wt%) at -196 degrees C under 1.0bar H-2 pressure. The bimodal pore architecture of JNC-1 led to superior supercapacitor performance, with a specific capacitance of 292Fg(-1) and 182Fg(-1) at a drain rate of 1Ag(-1) and 50Ag(-1), respectively, in 1m H2SO4 compared to CMK-3 and activated carbon.

Effect of current density on the microstructure and corrosion properties of plasma electrolytic oxidation (PEO) coatings on AM50 Mg alloy produced in an electrolyte containing clay additives

Plasma electrolytic oxidation coatings were produced on AM50 Mg alloy in alkaline phosphate based electrolyte with montmorillonite clay additives employing current densities of 30, 60, and 120 mA/cm(2). The effect of current density on the microstructure and corrosion properties of the coating was investigated. The clay additives got melted and reactively incorporated into the coating forming an amorphous phase, at all the current densities. However, the coating was predominantly amorphous only at 30 mA/cm(2) and with increasing current density, increasing fractions of crystalline phases were formed. Higher current densities resulted in increased thickness of the coating, but reduced the compactness of the coatings. Electrochemical impedance spectroscopy tests in 0.5 wt.% (0.08 M) and 3.5 wt.% (0.6 M) NaCl solution revealed that the coatings processed at 30 mA/cm(2) exhibited a relatively better initial corrosion resistance owing to its relatively defect-free barrier layer and compactness of the coating. However, the presence of amorphous phases in significant amounts and lack of MgO in the coating resulted in increased rate of dissolution of the coatings and degradation of corrosion resistance. Coatings produced at higher current densities exhibited initial inferior corrosion resistance due to a more defective barrier layer and increased porosity in pore band and outer porous layer. However, the increased amount of crystalline phases and an increased amount of MgO, which resisted dissolution, counterbalanced the negative effects of defective barrier and increased porosity resulting in a relatively lower rate of the degradation of the corrosion resistance. Thus, the corrosion resistance of all the coatings continuously decreased with time and became similar after prolonged immersion in NaCl solution. Increasing current density, therefore, did not prove to be beneficial for the improvement of the corrosion performance of the PEO coatings. (C) 2016 Elsevier B.V. All rights reserved.

Interactions of CO, HCl, and Sox in Pulverised Coal Flames

The effect of HCl and SO_2 on CO oxidation in pulverised coal flames was investigated experimentally and kinetically in an entrained flow combustion reactor. Two bituminous coals (German 'Goettelborn' and a Polish coal) were used as fuels with a feeding rate of 1 or 1.5 kg/h. HCl or SO_2 is introduced into the reactor premixed with the primary air. Experimental results indicate that HCl addition may inhibit CO oxidation in coal flames and increases CO emission. Reducing temperature in the reactor will enhance the inhibitory effect of HCl on CO oxidation. The measured CO profiles along the reactor height clearly show that the addition of HCl may inhibit CO oxidation. In the experimental range of SO_2 addition. The inhibiting effect of SO_2 on CO oxidation is less significant than HCl. A detailed kinetic mechanism is used to model the reactions. And the controlling reactions are analysed.

Characterisation of cell adhesion to substrate materials and the resistance to enzymatic and mechanical cell-removal

Cell-implant adhesive strength is important for prostheses. In this paper, an investigation is described into the adhesion of bovine chondrocytes to Ti6Al4V-based substrates with different surface roughnesses and compositions. Cells were cultured for 2 or 5 days, to promote adhesion. The ease of cell removal was characterised, using both biochemical (trypsin) and mechanical (accelerated buoyancy and liquid flow) methods. Computational fluid dynamics (CFD) modelling has been used to estimate the shear forces applied to the cells by the liquid flow. A comparison is presented between the ease of cell detachment indicated using these methods, for the three surfaces investigated. © 2008 Materials Research Society.