Preparation and characterization of CuO nanostructures on copper substrate as selective solar absorbers

Selective solar absorber coatings of copper oxide (CuO) on copper substrates are prepared by room temperature oxidation of copper at different alkaline conditions. The surface morphology and structural analyses of the CuO coatings are carried out by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive spectroscopy (EDS) and Raman spectroscopy techniques. XRD and Raman studies indicated the single phase nature and high crystallinity of the prepared CuO nanostructures. Different CuO nanostructures, viz., nanoneedles, nanofibers and nanoparticles are formed at different alkaline conditions. The influence of reaction time on morphology of the CuO nanostructures is also studied. The thermal emittance values of these nanostructured CuO samples are found to be in the range of 6–7% and their solar absorptances are ranged between 84 and 90%. The observed high solar selectivity values (>12.7) suggest that these coatings can be used as selective absorbers in solar thermal gadgets.     

A Feature Identification System for Electron Magnetic Resonance Tomography: Fusion of Principal Components Transform,Color Quantization and Boundary Information

A windows-based, object-oriented, feature identification system for electron magnetic resonance imaging (EMRI) is presented. Identification of region of interest (ROI) is achieved by fusing the standard principal component transform (PCT) and a color quantization method. The performance of the system is evaluated using renal and a series of murine RIF tumor data imaged on different days after the implantation of the tumor. The integrated ROI identification system clearly brings out the capability of EMRI to detect changes in the tumor redox status when thiol levels are lowered. Prior application of PCT reduces the computation load on the color quantization process, enabling the system to be twice faster than an earlier technique reported by the authors. The system is implemented in Visual C++ using Micro Soft Foundation Classes (MFC). Both visual evaluation as well as quantitative metrics shows the performance of the system to be optimal for 8-color quantization.     

Prediction of two‐phase pressure drop and liquid holdup in co‐current gas–liquid downflow of air–Newtonian systems through packed beds

The dependency of pressure drop and liquid holdup on phase velocities, geometry of the column and packing materials as well as on the physical properties have been analyzed. Our experimental data (825 data points obtained using four liquid systems and three different particles) along with those of the available literature (776 data point from five different sources) were used for the analysis. The applicability and the limitations of the literature correlations were evaluated using the available data. Based on the analysis, new correlations for the estimation of pressure drop and liquid holdup, valid for low and high interaction regimes have been developed using the available data, with a wide range of variables. Copyright © 2005 Society of Chemical Industry     

A new correlation for characteristic velocity in rotating disc contactors

On the basis of present experimental results along with those of available literature (1539 experimental results for 12 systems from 13 different sources) with a wide range of variables, a general correlation for the prediction of characteristic velocity, involving phase flow rates, rotor speed (in terms of Froude number), column geometry and also the physical properties, is presented. The present proposed correlations are more accurate than those previously reported.     

Minimum fluidization velocity and gas holdup in gas–liquid–solid fluidized bed reactors

Experiments were performed to study the hydrodynamics of a cocurrent three‐phase fluidized bed with liquid as continuous phase. Based on the 209 experimental data (with four liquid systems and five different particles) along with 115 literature data from six different sources on minimum fluidization velocity, a unique correlation for the estimation of minimum fluidization velocity in two‐phase (u_g = 0) as well as in three‐phase systems is developed. A data bank consisting of 1420 experimental measurements for the fractional gas phase holdup data with a wide range of variables is used for developing empirical correlations. Separate correlations are developed for two flow regimes observed in this present work. The proposed correlations are more accurate and simpler to use. © 2002 Society of Chemical Industry     

A class of rational coefficients biorthogonal Hilbert‐pairs

Two filter banks whose corresponding wavelets are related via the Hilbert transform are said to form a Hilbert‐pair. A simple technique for designing biorthogonal Hilbert‐pairs is the common‐factor technique. The technique yields approximately linear‐phase filters but with irrational coefficients in general. This paper proposes a technique to rationalize the coefficients while preserving the perfect reconstruction and vanishing moment properties of the filters. The rational coefficient filters can be implemented efficiently without any multipliers using simple shifts and adds. The characteristic and analytic qualities of the rationalized filters are comparable with that of the original irrational filters. Copyright © 2014 John Wiley & Sons, Ltd.     

Highly active three-dimensional cage type mesoporous ferrosilicate catalysts for the Friedel–Crafts alkylation

Three-dimensional cage type ferrosilicate catalysts with different n_Si/n_Fe ratios (FeSBA-1(x) where x denotes the n_Si/n_Fe molar ratio) have been prepared at a molar hydrochloric acid to silicon ratio of 10 using cetyltriethylammonium bromide as the template. The obtained materials have been unambiguously characterized by XRD, N₂ adsorption, and ESR spectroscopy, and their catalytic activity in the benzylation of benzene and the substituted benzene has also been investigated. The catalytic results of the FeSBA-1 catalysts with different n_Si/n_Fe ratios have been compared with the uni-dimensional FeSBA-15, AlSBA-15 and FeHMS catalysts. It has been found that the activity of the FeSBA-1 catalysts is much higher as compared to that of the FeSBA-15, FeHMS and AlSBA-15 catalysts. The activity of the catalysts declines in the following order: FeSBA-1(36) > FeSBA-1(90) > FeSBA-1(120) > FeSBA-1(344) > FeSBA-15(152) > FeHMS(50) > AlSBA-15(45). The effect of various reaction parameters such as reaction time, reaction temperature, reactant feed ratio and the various electron donating groups on the benzene ring affecting the activity and selectivity of FeSBA-1(344) have also been studied. The catalysts are highly active and show a complete conversion of benzyl chloride and a clean selectivity to diphenylmethane (DPM) within a short period of time under the optimized reaction conditions. The reaction kinetics of the catalysts has been extensively investigated and the results are presented. The apparent rate constant of the FeSBA-1(344) and the BC conversion sharply increase with increasing the reaction temperature. The activity of the FeSBA-1(344) catalyst for the benzylation of different aromatic compounds is in the following order: benzene > anisole > mesitylene > p-xylene > toluene.     

Peroxomonosulphate, an efficient oxidant for the photocatalysed degradation of a textile dye, acid red 88

Visible light-assisted degradation of a mono azo textile dye acid red 88 (AR88) was carried out in presence of titanium dioxide photocatalyst. Various operational parameters such as variation of the initial dye concentration, photocatalyst and pH on the photocatalytic degradation rate were studied. Effect of the amount of oxidants such as peroxomonosulphate (PMS) and peroxodisulphate (PDS) and the ratio of concentration of oxidant to the concentration of dye (C_oxidant/C_dye) on the photocatalysed degradation rate were also investigated. Though the rate of photodegradation of the dye decreased with increase in dye concentration, the rate increased with C_oxidant/C_dye ratio. Total organic carbon (TOC) analysis revealed a rapid mineralisation of AR88 in the presence of PMS. A suitable mechanism explaining the observed enhanced decolorisation and mineralisation rate of the dye with PMS is presented.     

Evaluation of bio-diesel properties: a statistical approach

In this work, methyl esters of Pungamia (MEOP), ethyl esters of Pungamia (EEOP), and ethyl esters of Neem (EEON) were primarily produced by means of transesterification process using sodium methoxide (mixture of sodium hydroxide and methanol) and potassium methoxide (mixture of potassium hydroxide and methanol). Further, the fuel properties such as calorific value, flash point, density and viscosity of methyl and ethyl esters were determined using ASTM specified equipment. Also, the association between different blend ratios and fuel type with fuel properties was gauged with an assistance of two-way analysis of variance. The experimental outcomes revealed that the maximum ester content of bio-diesel was witnessed for potassium hydroxide catalyst and the quantity of catalyst used was less than that with sodium hydroxide for the same mass of the feedstock oil. Overall, the statistical analysis disclosed that there is a significant difference in the fuel properties of the different combination of fuel type and blend ratios.