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.     

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.     

Efficient privacy-preserving similar document detection

Similar document detection plays important roles in many applications, such as file management, copyright protection, plagiarism prevention, and duplicate submission detection. The state of the art protocols assume that the contents of files stored on a server (or multiple servers) are directly accessible. However, this makes such protocols unsuitable for any environment where the documents themselves are sensitive and cannot be openly read. Essentially, this assumption limits more practical applications, e.g., detecting plagiarized documents between two conferences, where submissions are confidential. We propose novel protocols to detect similar documents between two entities where documents cannot be openly shared with each other. The similarity measure used can be a simple cosine similarity on entire documents or on document fragments, enabling detection of partial copying. We conduct extensive experiments to show the practical value of the proposed protocols. While the proposed base protocols are much more efficient than the general secure multiparty computation based solutions, they are still slow for large document sets. We then investigate a clustering based approach that significantly reduces the running time and achieves over 90% of accuracy in our experiments. This makes secure similar document detection both practical and feasible.     

Fusion zone grain refinement in aluminum alloy welds through magnetic arc oscillation and its effect on tensile behavior

Grain size reduction in weld fusion zones confers the advantages of an increased resistance to solidification cracking and an improvement in mechanical properties. Oscillation of the welding arc through an imposed alternating magnetic field is one of several approaches to modify weld solidification structures. In this study, gas tungsten arc welds were produced in two high strength, age hardenable aluminum alloys with and without an external magnetic field. Metallographic characterization revealed the degree of structural refinement produced by magnetic arc oscillation. The decrease in grain size was found to increase tensile elongation, while the effect on strength and age hardening response was only meager. The improvement in ductility was partially maintained in the peak aged condition also.     

A Study on the Effect of Thermal Ageing on the Specific-Heat Characteristics of 9Cr–1Mo–0.1C (mass%) Steel

The effect of thermal ageing on the heat-capacity behavior of 9Cr–1Mo–0.1C (mass%) ferritic/martensitic steel has been studied using differential scanning calorimetry (DSC) in the temperature range from 473 K to 1,273 K. The DSC results in the case of slow cooled, normalized and tempered, and subsequently thermally aged samples (500 h to 5,000 h at 823 K (550 °C) and 923 K (650 °C), clearly marked the presence of both magnetic and α-ferrite + carbide → γ-austenite phase transformations that take place successively upon heating. Furthermore, for the case of fully martensitic microstructure, an additional exothermic transformation at about 920 K(647 °C), arising from carbide precipitation is noticed. This event is characterized by a sharp drop in C _P . It is found that the α-ferrite + carbide → γ-austenite phase transformation temperature is only mildly sensitive to microstructural details, but the enthalpy change associated with this phase transformation, and especially the change in specific heat around the transformation regime, are found to be dependent on the starting microstructure generated by thermal ageing treatment. Prolonged ageing for about 500 h to 5,000 h in the temperature range from 823 K to 923 K (550 °C to 650 °C) contributed to a decrease in heat capacity, as compared to the normalized and tempered sample. This is due to the increase in carbide volume fraction. The martensitic microstructure is found to possess the lowest room-temperature C _P among different microstructures.     

In-Situ Catalyst Generation and Controlled Hydrolysis in the Sol–Gel Precipitation of Zirconia and Titania Particles in Poly(dimethylsiloxane)

The usual sol–gel hydrolysis-condensation technique for the in-situ generation of reinforcing silica particles within an elastomer was recently modified by (i) controlling the required water of hydrolysis by simply absorbing it from the air, and (ii) generating the required catalyst in-situ from a tin salt. In the case of the silica, which is generated in poly(dimethylsiloxane) (PDMS), the technique had the advantages of producing well dispersed, highly reinforcing particles that did not significantly reduce the transparency of the composite. Applying the new technique to the in-situ generation of zirconia and titania in the same polymer also gave small well-dispersed particles, good reinforcement, and improved thermal stability. Although transparency was not maintained as well as in the case of the controlled hydrolysis producing silica, it was definitely better than that of composites prepared by the usual excess water method.     

HOLDUP, INTERFACIAL AREA AND POWER REQUIREMENTS IN TURBINE AGITATED GAS-LIQUID CONTACTORS

This paper reports a detailed study of the hydrodynamic variables involved in the operation of 6-blade (flat) turbine agitated gas-liquid contractors. New information is presented regarding the characteristic velocity of the dispersed gas bubbles. Generalized correlations for prediction of power consumption of impellers under aeration conditions, gas phase holdup, characteristic velocity, mean residence time of gas bubbles, interfacial area of contact and mean bubble size are proposed in terms of system variables.     

Synthesis, characterization and fabrication of solar cells making use of [Ru(dcbpy)(tptz)X]X (where X = Cl, SCN, CN) complexes

Dye-sensitized TiO₂ solar cells were fabricated using tridentate ligand ruthenium(II) complexes, [Ru(dcbpy)(tptz)X]X (where dcbpy = 4,4′-dicarboxy-2,2′-bipyridine, tptz = 2,4,6-Tris(2-pyridyl)-s-triazine and X = Cl⁻, SCN⁻, CN⁻) attached to sol–gel processed TiO₂ electrodes. The ligand tptz functions as spectator ligand and dcbpy functions as the anchoring ligand with sufficient visible light absorption. The synthesized complexes were characterized before using them in solar cells. The functioning of the solar cells fabricated using different conducting glasses was monitored and the current–voltage characteristics were measured. The efficiencies of different cells were calculated and compared.