Immobilized Fe(III)-HY: an efficient and stable photo-Fenton catalyst

This article presents preparation, characterization and evaluation of an efficient heterogeneous Fe(III)-HY catalyst for photo-assisted Fenton reaction. Fe(III) ions are immobilized on HY zeolite using different loadings by impregnation, calcination and the activity of the catalyst is evaluated by the degradation of phenol. To initiate a photo-Fenton reaction, suspended Fe(III)-HY in solution is irradiated using UV light to form Fe(II)-HY necessary for the reaction to go. The effect of Fe loadings, H₂O₂ concentration, pH and quenching on photo-Fenton reaction are studied. The results obtained clearly show that 0.25 wt.% Fe(III)-HY is efficient in the degradation of phenol at pH = 6. Further the efficiency of Fe(III)-HY is compared with that of a homogeneous photo-Fenton reaction and the increased rate of reaction on Fe(III)-HY highlights the synergistic role of zeolite. Heterogeneous Fe(III)-HY in photo-Fenton reaction allows a wide range of pH for reaction against the narrow pH range in homogeneous system. The system is further subjected to evaluate its stability in solid state. Firstly the reaction solution containing Fe(III)-HY catalyst on irradiation is analyzed for Fe ions with atomic absorption spectroscopy (AAS) and also by calorimetry using 1,10-phenanthroline (o-phen) to find out any Fe leaching from the catalyst and the results show insignificant leaching of Fe (<0.3 ppm) at maximum loading of Fe under experimental conditions. Secondly, the irradiated Fe(III)-HY is complexed with o-phen and it is subjected to Fourier transform infrared spectroscopy (FT-IR), diffuse reflectance spectroscopy (DRS) and electron spectroscopy for chemical analysis (ESCA) studies to detect and confirm the oxidation state of Fe in solid state. Critical analysis of these studies clearly show that Fe(III)-HY on irradiation changed to Fe(II)-HY and it is intact with the surface during the course of the reaction. The DRS spectra further evidences complexation of Fe(II) with o-phen. The stability of the catalyst is established by recycling studies.     

Compressive property of liquid silicon (infiltrated) boron carbide

Compressive deformation of reaction bonded boron carbide has been carried out over a strain rate range 10⁻⁴ to 10⁻² s⁻¹. The maximum compressive strength of reaction bonded boron carbide at strain rate of 10⁻⁴ s⁻¹ is 370 MPa and 470 MPa at strain rate of 10⁻² s⁻¹. It is not possible to carryout quasi-static compression test at very higher strain rates (≥ 10² s⁻¹). However, the data generated at low strain rates can be extrapolated to higher strain rates and this data correlate well with the experimental compressive strength values generated by dynamic compression tests.     

Analysis of Commutation of a Current Inverter Feeding an Induction Motor Load

A method for analyzing the performance of an induction motor fed from a current source inverter and especially for computing the currents during commutation of the inverter is presented. A mathematical model of an inverter-fed induction motor is given in terms of Park's vector. Based on this model a closed form time domain expression is developed for the current during commutation. The stator voltage of a current-controlled inverter-fed induction motor is shown to be almost sinusoidal with superimposed spikes during commutation of current. The computed performance of the machine is verified experimentally, and there is a very close agreement between the computed and test results. The method presented also provides information regarding the voltages across the commutating capacitors and thyristors based on which proper selection of the thyristors and commutating capacitors can be made.     

Detection of Rossby waves in multi-parameters in multi-mission satellite observations and HYCOM simulations in the Indian Ocean

Rossby waves are difficult to detect with in situ methods. However, as we show in this paper, they can be clearly identified in multi-parameters in multi-mission satellite observations of sea surface height (SSH), sea surface temperature (SST) and ocean color observations of chlorophyll-a (chl-a), as well as 1/12° global HYbrid Coordinate Ocean Model (HYCOM) simulations of SSH, SST and sea surface salinity (SSS) in the Indian Ocean. While the surface structure of Rossby waves can be elucidated from comparisons of the signal in different sea surface parameters, models are needed to gain direct information about how these waves affect the ocean at depth. The first three baroclinic modes of the Rossby waves are inferred from the Fast Fourier Transform (FFT), and two-dimensional Radon Transform (2D RT). At many latitudes the first and second baroclinic mode Rossby wave phase speeds from satellite observations and model parameters are identified. Wavelet transforms of these multi-parameters from satellite observations and model simulations help to discriminate between the annual and semi-annual signal of these Rossby waves. This comprehensive study reveals that the surface signature of Rossby waves in SSS anomalies is likely to be between 0.05 and 0.3 psu in the South Indian Ocean.     

Estimation of the sharma constant and thermoacoustic properties of vegetable oils

The density and volume of four Indian edible vegetable oils, sunflower, rice bran, groundnut and coconut, and one Indian nonedible oil, castor oil, have been experimentally determined. The values obtained were used to estimate the volume expansivity α, hence the thermoacoustic parameters, such as the Sharma constantS ₀, the isochoric temperature coefficient of internal pressure , the isochoric temperature coefficient of volume expansion , reduced volume , reduced compressibility and the Huggins parameter F. The results obtained show that the Sharma constantS ₀ has the same characteristic value of 1.11±0.01 for the five oils, thus establishing the constancy of the Sharma parameter. All the other parameters are of the expected order of magnitude; however, in all cases there is a uniform deviation at 293°K, which can be attributed to the behavior of density and volume at this temperature.     

Expert system design using wavelet and color vocabulary trees for image retrieval

A new image indexing and retrieval system for content based image retrieval (CBIR) is proposed in this paper. The characteristics (vector points) of image are computed using color (color histogram) and SOT (spatial orientation tree). The SOT defines the spatial parent-child relationship among wavelet coefficients in multi-resolution wavelet sub-bands. First the image is divided into sub-blocks and then constructed the SOT for each low pass wavelet coefficient is considered as a vector point of that particular image. Similarly the color histogram features are collected from the each sub-block. The vector points of each image are indexed using vocabulary tree. The retrieval results of the proposed method are tested on different image databases, i.e., natural image database consists of Corel 1000 (DB1), Brodatz texture image database (DB2) and MIT VisTex database (DB3). The results after being investigated show a significant improvement in terms of average precision, average recall and average retrieval rate on DB1 database and average retrieval rate on texture databases (DB2 and DB3) as compared with most of existing techniques on respective databases.     

Non-linear flap-lag-extensional vibrations of rotating, pretwisted, preconed beams including Coriolis effects

The effects of pretwist, precone, setting angle, Coriolis forces and second degree geometric non-linearities on the steady state deflections, coupled frequencies and mode shapes of rotating, torsionally rigid, cantilevered beams are studied in this investigation. The equations governing flap-lag-extensional motion are derived including the effects of large precone (a component of sweep) and retaining geometric non-linearities up to second degree. The Galerkin method, with non-rotating normal modes, is used for the solution of both steady state non-linear equations and linear perturbation equations. The results indicate that the second degree geometric non-linear terms, which vanish for zero precone, can produce frequency changes of engineering significance (of the order of 20% on the fundamental mode, and about ±4% on the second mode). The results further indicate that the linear and non-linear Coriolis effects must be included in analyzing thick blades while these effects can be neglected in analyzing thin blades, typical of advanced turboprop blade configurations. For those cases where the effect is significant, the linear and non-linear Coriolis effects oppose one another, the non-linear effects generally being stronger.     

Synthesis of nanocrystalline molybdenum carbide (Mo2C) by solution route

Nanocrystalline molybdenum carbide (Mo₂C) of less than 10 nm size was synthesized by solution route. The process temperature and composition of raw materials were optimized by thermodynamic equilibrium calculation. The raw materials as well as synthesized nanocrystalline molybdenum carbide were characterized by X-ray diffraction (XRD) and thermogravimetric analysis/differential thermal analysis (TGA/DTA).     

A Recursive Filter for Despeckling SAR Images

This correspondence proposes a recursive algorithm for noise reduction in synthetic aperture radar imagery. Excellent despeckling in conjunction with feature preservation is achieved by incorporating a discontinuity-adaptive Markov random field prior within the unscented Kalman filter framework through importance sampling. The performance of this method is demonstrated on both synthetic and real examples.