Experimental studies on air-assisted impinging jet atomization

In the present study, a novel air-assisted impinging jet atomization is demonstrated. A configuration in which a gas jet is directed on to the impinging point of two liquid jets is used to improve the atomization. The effect of liquid properties such as viscosity and surface tension, angle between liquid jets and gas injection orifice diameter on spray characteristics has been experimentally studied. Backlit imaging and particle/droplet imaging and analysis techniques are utilized to characterize the sprays. The experimental results indicate that the effect of liquid viscosity is significant on the liquid sheet break up formed by the impinging jets. However, surface tension does not affect the spray structure significantly in this mode of atomization. At low liquid jet velocity, the prompt mode of atomization is observed where as atomization occurs in classical mode at higher liquid jet velocity. Results showed that variation in the angle between liquid jets do not affect the breakup phenomenon significantly. The spray angle is computed by finding the angle between the lines joining the impinging point and spray edge at an axial distance of 15 mm downstream of the impinging point from the ensemble-averaged data over 100 spray images. It was observed that effect of liquid jets impinging angle on the spray angle is higher at higher liquid velocity. Higher viscosity liquids exhibit lower spray angles. Droplet size measurements indicate a radial variation in the spray. An overall Sauter Mean Diameter (SMD) value is obtained by combining the droplet statistics at all radial locations at a fixed axial location. A very interesting trend is that the SMD is constant beyond a critical Gas to Liquid Ratio (GLR) and momentum ratio for a large variation in liquid viscosity and surface tension. This observation has important ramifications for fuel flexible systems. (C) 2013 Elsevier Ltd. All rights reserved.

Influence of binder solvent on carbon-layer structure in electrical-double-layer capacitors

Porous activated-carbons with a large surface-area have been the most common materials for electrical-double-layer capacitors (EDLCs). These carbons having a wide pore distribution ranges from micropores to macropores in conjunction with a random pore connection that facilitates the high specific-capacitance values. Pore distribution plays a central role in controlling the capacitance value of EDLCs, since electrolyte distribution inside the active material mainly depends on the pore distribution. This has a direct influence on the distribution of resistance and capacitance values within the electrode. As a result, preparation of electrodes remains a vital issue in realising high-performance EDLCs. Generally, carbon materials along with some binders are dispersed into a solvent and coated onto the current collectors. This study examines the role of binder solvents used for the carbon-ink preparation on the microstructure of the electrodes and the consequent performance of the EDLCs. It is observed that the physical properties of the binder solvent namely its dielectric constant, viscosity and boiling point have important role in determining the pore-size distribution as well as the microstructure of electrodes which influence their specific capacitance values.

Evaluation of document binarization using eigen value decomposition

A necessary step for the recognition of scanned documents is binarization, which is essentially the segmentation of the document. In order to binarize a scanned document, we can find several algorithms in the literature. What is the best binarization result for a given document image? To answer this question, a user needs to check different binarization algorithms for suitability, since different algorithms may work better for different type of documents. Manually choosing the best from a set of binarized documents is time consuming. To automate the selection of the best segmented document, either we need to use ground-truth of the document or propose an evaluation metric. If ground-truth is available, then precision and recall can be used to choose the best binarized document. What is the case, when ground-truth is not available? Can we come up with a metric which evaluates these binarized documents? Hence, we propose a metric to evaluate binarized document images using eigen value decomposition. We have evaluated this measure on DIBCO and H-DIBCO datasets. The proposed method chooses the best binarized document that is close to the ground-truth of the document.

Effect of fluid medium on mechanical behavior of carbon nanotube foam

This study reports the constitutive response and energy absorption capabilities of fluid-impregnated carbon nanotube (CNT) foams under compressive loading as a function of fluid viscosity and loading rates. At all strain rates tested, we observe two characteristic regimes: below a critical value, increasing fluid viscosity increases the load bearing and energy absorption capacities; after a critical value of the fluid's viscosity, we observe a rapid decrease in the systems' mechanical performance. For a given fluid viscosity, the load bearing capacity of the structure slightly decreases with strain rate. A phenomenological model, accounting for fluid-CNT interaction, is developed to explain the observed mechanical behavior. (C) 2014 AIP Publishing LLC.

Hall viscosity to entropy ratio in higher derivative theories

In this paper based on the basic principles of gauge/gravity duality we compute the hall viscosity to entropy ratio in the presence of various higher derivative corrections to the dual gravitational description embedded in an asymptotically AdS(4) space time. As the first step of our analysis, considering the back reaction we impose higher derivative corrections to the abelian gauge sector of the theory where we notice that the ratio indeed gets corrected at the leading order in the coupling. Considering the probe limit as a special case we compute this leading order correction over the fixed background of the charged black brane solution. Finally we consider higher derivative (R-2) correction to the gravity sector of the theory where we notice that the above ratio might get corrected at the sixth derivative level.

A detailed numerical study of NOx kinetics in low calorific value H-2/CO syngas flames

The present study provides an extensive and detailed numerical analysis of NO chemical kinetics in low calorific value H-2/CO syngas flames utilizing predictions by five chemical kinetic mechanisms available out of which four deal with H-2/CO while the fifth mechanism (GRI 3.0) additionally accounts for hydrocarbon chemistry. Comparison of predicted axial NO profiles in premixed flat flames with measurements at 1 bar, 3.05 bar and 9.15 bar shows considerably large quantitative differences among the various mechanisms. However, at each pressure, the quantitative reaction path diagrams show similar NO formation pathways for most of the mechanisms. Interestingly, in counterflow diffusion flames, the quantitative reaction path diagrams and sensitivity analyses using the various mechanisms reveal major differences in the NO formation pathways and reaction rates of important reactions. The NNH and N2O intermediate pathways are found to be the major contributors for NO formation in all the reaction mechanisms except GRI 3.0 in syngas diffusion flames. The GRI 3.0 mechanism is observed to predict prompt NO pathway as the major contributing pathway to NO formation. This is attributed to prediction of a large concentration of CH radical by the GRI 3.0 as opposed to a relatively negligible value predicted by all other mechanisms. Also, the back-conversion of NNH into N2O at lower pressures (2-4 bar) was uniquely observed for one of the five mechanisms. The net reaction rates and peak flame temperatures are used to correlate and explain the differences observed in the peak NO] at different pressures. This study identifies key reactions needing assessment and also highlights the need for experimental data in syngas diffusion flames in order to assess and optimize H-2/CO and nitrogen chemistry. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Phenyl carbohydrazone conjugated 2-oxoindoline as a new scaffold that augments the DNA and BSA binding affinity and anti-proliferative activity of a 1,10-phenanthroline based copper(II) complex

A new type of copper(II) complex, CuL(phen)(2)](NO3) (CuIP), where L ((E)-N'-(2-oxoindolin-3-ylidene) benzohydrazide) is a N donor ligand and phen is the N, N-donor heterocyclic 1,10-phenanthroline, has been synthesized. The phenyl carbohydrazone conjugated isatin-based ligand L and CuIP were characterized by elemental analysis, infrared, UV-Vis, H-1 and C-13 NMR and ESI-mass spectral data, as well as single-crystal X-ray diffraction. The interaction of calf thymus DNA (CT DNA) with L and CuIP has been investigated by absorption, fluorescence and viscosity titration methods. The complex CuIP displays better binding affinity than the ligand L. The observed DNA binding constant (K-b = 4.15(+/- 0.18) x 10(5) M-1) and binding site size (s = 0.19), viscosity data together with molecular docking studies of CuIP suggest groove binding and/or a partial intercalative mode of binding to CT DNA. In addition, CuIP shows good binding propensity to the bovine serum albumin (BSA) protein, giving a K-BSA value of 1.25(+/- 0.24) x 10(6) M-1. In addition, the docking studies on DNA and human serum albumin (HSA) CuIP interactions are consistent with the consequence of binding experiments. The in vitro anti-proliferative study establishes the anticancer potency of the CuIP against the human cervical (HeLa) and breast (MCF7) cancer cells; noncancer breast epithelial (MCF10a) cells have also been investigated. CuIP shows better cytotoxicity and sensitivity towards cancer cells over noncancer ones than L under identical conditions, with the appearance of apoptotic bodies. (C) 2014 Elsevier B.V. All rights reserved.

Optimal error estimate using mesh equidistribution technique for singularly perturbed system of reaction-diffusion boundary-value problems

In this article, we study the problem of determining an appropriate grading of meshes for a system of coupled singularly perturbed reaction-diffusion problems having diffusion parameters with different magnitudes. The central difference scheme is used to discretize the problem on adaptively generated mesh where the mesh equation is derived using an equidistribution principle. An a priori monitor function is obtained from the error estimate. A suitable a posteriori analogue of this monitor function is also derived for the mesh construction which will lead to an optimal second-order parameter uniform convergence. We present the results of numerical experiments for linear and semilinear reaction-diffusion systems to support the effectiveness of our preferred monitor function obtained from theoretical analysis. (C) 2014 Elsevier Inc. All rights reserved.

High Value of Proton Relaxivity Achieved by Graphene Oxide-Cobalt Ferrite Nanoparticle Composite: A Potential Contrast Agent in Magnetic Resonance Imaging

This work investigates the potential of graphene oxide-cobalt ferrite nanoparticle (GO-CoFe2O4) composite as image contrast enhancing material in Magnetic Resonance Imaging (MRI). In the preset work, GO-CoFe2O4 composites were produced by a two-step synthesis process. In the first step, graphene oxide (GO) was synthesized, and in the second step CoFe2O4 nanoparticles were synthesized in a reaction mixture containing GO to yield graphene GO-CoFe2O4 composite. Proton relaxivity value obtained from the composite was 361 mM(-1)s(-1). This value of proton relaxivity is higher than a majority of reported relaxivity values obtained using several ferrite based contrast agents.

Fragility correlates thermodynamic and kinetic properties of glass forming liquids

In our earlier communication we proposed a simple fragility determining function, (NBO]/(VmTg)-T-3), which we have now used to analyze several glass systems using available thermal data. A comparison with similar fragility determining function, Delta C-p/C-p(1), introduced by Chryssikos et al. in their investigation of lithium borate glasses has also been performed and found to be more convenient quantity for discussing fragilities. We now propose a new function which uses both Delta C-p and Delta T and which gives a numerical fragility parameter, F whose value lies between 0 and 1 for glass forming liquids. F can be calculated through the use of measured thermal parameters Delta C-p, C-p(1), T-g and T-m. Use of the new fragility values in reduced viscosity equation reproduces the whole range of viscosity curves of the Angell plot. The reduced viscosity equation can be directly compared with the Adam-Gibbs viscosity equation and a heat capacity function can be formulated which reproduces satisfactorily the Delta C-p versus In(T-r) curves and hence the configurational entropy. (C) 2014 Elsevier Ltd. All rights reserved.

Fragility correlates thermodynamic and kinetic properties of glass forming liquids

In our earlier communication we proposed a simple fragility determining function, (NBO]/(VmTg)-T-3), which we have now used to analyze several glass systems using available thermal data. A comparison with similar fragility determining function, Delta C-p/C-p(1), introduced by Chryssikos et al. in their investigation of lithium borate glasses has also been performed and found to be more convenient quantity for discussing fragilities. We now propose a new function which uses both Delta C-p and Delta T and which gives a numerical fragility parameter, F whose value lies between 0 and 1 for glass forming liquids. F can be calculated through the use of measured thermal parameters Delta C-p, C-p(1), T-g and T-m. Use of the new fragility values in reduced viscosity equation reproduces the whole range of viscosity curves of the Angell plot. The reduced viscosity equation can be directly compared with the Adam-Gibbs viscosity equation and a heat capacity function can be formulated which reproduces satisfactorily the Delta C-p versus In(T-r) curves and hence the configurational entropy. (C) 2014 Elsevier Ltd. All rights reserved.

Wall-mode instability in plane shear flow of viscoelastic fluid over a deformable solid

The linear stability analysis of a plane Couette flow of an Oldroyd-B viscoelastic fluid past a flexible solid medium is carried out to investigate the role of polymer addition in the stability behavior. The system consists of a viscoelastic fluid layer of thickness R, density rho, viscosity eta, relaxation time lambda, and retardation time beta lambda flowing past a linear elastic solid medium of thickness HR, density rho, and shear modulus G. The emphasis is on the high-Reynolds-number wall-mode instability, which has recently been shown in experiments to destabilize the laminar flow of Newtonian fluids in soft-walled tubes and channels at a significantly lower Reynolds number than that for flows in rigid conduits. For Newtonian fluids, the linear stability studies have shown that the wall modes become unstable when flow Reynolds number exceeds a certain critical value Re c which scales as Sigma(3/4), where Reynolds number Re = rho VR/eta, V is the top-plate velocity, and dimensionless parameter Sigma = rho GR(2)/eta(2) characterizes the fluid-solid system. For high-Reynolds-number flow, the addition of polymer tends to decrease the critical Reynolds number in comparison to that for the Newtonian fluid, indicating a destabilizing role for fluid viscoelasticity. Numerical calculations show that the critical Reynolds number could be decreased by up to a factor of 10 by the addition of small amount of polymer. The critical Reynolds number follows the same scaling Re-c similar to Sigma(3/4) as the wall modes for a Newtonian fluid for very high Reynolds number. However, for moderate Reynolds number, there exists a narrow region in beta-H parametric space, corresponding to very dilute polymer solution (0.9 less than or similar to beta < 1) and thin solids (H less than or similar to 1.1), in which the addition of polymer tends to increase the critical Reynolds number in comparison to the Newtonian fluid. Thus, Reynolds number and polymer properties can be tailored to either increase or decrease the critical Reynolds number for unstable modes, thus providing an additional degree of control over the laminar-turbulent transition.

Viscosity bound for anisotropic superfluids in higher derivative gravity

In the present paper, based on the principles of gauge/gravity duality we analytically compute the shear viscosity to entropy (eta/s) ratio corresponding to the super fluid phase in Einstein Gauss-Bonnet gravity. From our analysis we note that the ratio indeed receives a finite temperature correction below certain critical temperature (T < T-c). This proves the non universality of eta/s ratio in higher derivative theories of gravity. We also compute the upper bound for the Gauss-Bonnet coupling (lambda) corresponding to the symmetry broken phase and note that the upper bound on the coupling does not seem to change as long as we are close to the critical point of the phase diagram. However the corresponding lower bound of the eta/s ratio seems to get modified due to the finite temperature effects.

Graphene oxide-Fe3O4 nanoparticle composite with high transverse proton relaxivity value for magnetic resonance imaging

The potential of graphene oxide-Fe3O4 nanoparticle (GO-Fe3O4) composite as an image contrast enhancing material in magnetic resonance imaging has been investigated. Proton relaxivity values were obtained in three different homogeneous dispersions of GO-Fe3O4 composites synthesized by precipitating Fe3O4 nanoparticles in three different reaction mixtures containing 0.01 g, 0.1 g, and 0.2 g of graphene oxide. A noticeable difference in proton relaxivity values was observed between the three cases. A comprehensive structural and magnetic characterization revealed discrete differences in the extent of reduction of the graphene oxide and spacing between the graphene oxide sheets in the three composites. The GO-Fe3O4 composite framework that contained graphene oxide with least extent of reduction of the carboxyl groups and largest spacing between the graphene oxide sheets provided the optimum structure for yielding a very high transverse proton relaxivity value. It was found that the GO-Fe3O4 composites possessed good biocompatibility with normal cell lines, whereas they exhibited considerable toxicity towards breast cancer cells. (C) 2015 AIP Publishing LLC.