Development of novel polymeric flocculant based on grafted sodium alginate for the treatment of coal mine wastewater

Sodium alginate-g-polyacrylamide (SAG) was synthesized by ceric ion induced redox polymerization technique. Six grades of graft copolymers were prepared by varying as well as monomer concentrations. The graft copolymers were characterized by intrinsic viscosity measurements, IR, and ¹³C-NMR spectroscopies. Of the above grades, the graft copolymer of grade six (SAG-VI), which has longer polyacrylamide chains, was used for flocculation study. Two coking and noncoking coal fine suspensions were selected for the flocculation study. The flocculation performance of the graft copolymer was compared with commercial flocculants. In all cases, it was found that the graft copolymer showed better performance than the commercial flocculants. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 375–382, 2001     

Effect of hydroxyl content on the physical properties of calcium metaphosphate glasses

The hydroxyl (OH) content of calcium metaphosphate glasses has been controlled in the range 50–800 ppm by melting calcium dihydrogen phosphate in air, under vacuum and with fluoride addition. Density, refractive index and glass transition temperature of the glasses increase with decrease in OH content while the coefficient of thermal expansion remains almost unchanged. With gradual decrease in OH, the UV cutoff initially shifts towards shorter and finally towards longer wavelengths. IR spectroscopic study shows that the OH groups exist exclusively in the hydrogen bonded states. Correlations of the glass properties with OH content have been explained in terms of structural rearrangement leading to the change in P-O bond length and O-P-O/P-O-P bond angles of the PO₄ tetrahedral units of (PO ₃ ⁻ ) _n chains. These changes are caused due to conversion of non-bridging oxygens (NBOs) of the H-bonded OH groups into bridging oxygens (BOs) during progress of dehydroxylation.     

All-optical Multiplication with the help of Semiconductor Optical Amplifier—assisted Sagnac Switch

An all-optical two 2-bit numbers multiplication with the help of Semiconductor Optical Amplifier (SOA)—assisted Sagnac Switch is proposed and described. The paper describes the multiplication using a set of all-optical half-adder and AND gate. Because of the lack of fast, accurate, and large dynamic range analog-to-digital converter, optical implementation of the digital multiplication through analog convolution algorithm yields a slow digital multiplier. By using a set of optical half-adder and optical AND, a new optical fast digital multiplication method is proposed. The new method promises both higher processing speed and accuracy. Numerical simulation result confirming described methods and conclusion are given in this paper.     

Dumbbell‐shaped defected ground structure

A simplified equivalent circuit model of a dumbbell‐shaped defected ground structure (DGS) is developed. The equivalent circuit model is derived from the equivalent inductance and capacitance, which develop because of the perturbed return current path on the ground and the narrow gap, respectively. The theory is validated against the commercial full‐wave solver CST Microwave Studio. Finally, the calculated results are compared with the measured results. Good agreements between the theory, the commercially available numerical analyses and the experimental results validate the developed model. © 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2007.     

Fabrication of platinum coating on continuous porous SiC–Si3N4 composites by the electroless deposition process

Continuous porous SiC–Si₃N₄ composite fabricated by a multi-pass extrusion process was investigated using SEM, XRD and TEM techniques. In the continuous pore regions, many single crystalline Si₃N₄ whiskers with an average diameter of about 1 μm, which could increase the surface area of the porous composites, were observed. However, to make a platinum coating on the composite, the electroless deposition method was adapted. The spot-type platinum particles, with a diameter of about 50–500 nm, attached to the SiC–Si₃N₄ matrix as well as the surface of the Si₃N₄ whiskers, which can enhance the catalytic activity.     

Kinetics of extraction of Ti(IV) from SO42– medium by Cyanex 301 dissolved in kerosene containing 5% heptan-1-ol

The kinetics of Ti(IV) extraction by Cyanex 301 (HA) were investigated by measuring initial flux of Ti(IV) transfer (F, kmol/m²s), using a Lewis cell, operated at 3 Hz. The empirical flux equation at 298 K is found to be as follows: F (kmol/m²s) = 10^–4.288 [Ti(IV)] (1 + 447 [H⁺])^–1 [HA]_(o) (1 + 1.18[SO₄^2–])^–1. The activation energy, E_a, has been measured to be within 37–60 kJ/mol, depending on experimental parameters and temperature region. The ΔS^± value is always highly negative. Analysis of the flux equation has been done, given various parametric conditions, to elucidate the mechanism of extraction. The rate-determining chemical reaction step, in most parametric conditions, appears to be as follows: TiO²⁺ + A^– → TiOA⁺; and this step occurs via an S_N2 mechanism as suggested by high negative ΔS^± values. However, in certain cases, the extraction process appears as intermediate controlled as supported by E_a value of less than ~48 kJ/mol.     

Knoevenagel condensation reaction over acid–base bifunctional nanocrystalline CexZr1−xO2 solid solutions

Highly thermally stable three-dimensional spongelike mesoporous Ce_xZr_1?xO₂ solid solutions consisting of nanometer size particles with different Ce/Zr compositions were synthesized by a modified sol–gel procedure using a triethanolamine/water mixture as a solvent to be used in liquid Knoevenagel condensation reaction. These materials were investigated in detail by means of X-ray diffraction (XRD), Raman spectroscopy, chemical analysis, X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM), UV–Vis spectroscopy, Fourier transform infrared spectroscopy (FT-IR) and adsorption microcalorimetry. The XRD, HRTEM and XPS studies proved the presence of nanocrystalline Ce_xZr_1?xO₂ solid solutions. These solid solutions showed excellent chemoselectivity in the classical Knoevenagel reaction. The large pore sizes (around 10 nm) highlight the possibility of using Ce_xZr_1?xO₂ as a support material for versatile catalytic systems. The results obtained from NH₃ and SO₂ adsorption microcalorimetry experiments successfully demonstrated the incorporation of ZrO₂ into the CeO₂ lattice resulting in both acidic and basic surface sites in a mixed oxide matrix.     

Infrared Spectroscopic Method for Determination of Thermal Properties of Fluorophosphate Glasses

Fluorophosphate glasses of the Ba(PO₃)₂–MgF₂–CaF₂–AlF₃ system exhibit anomalous behavior, in regard to the glass-transition temperature ( T _g) and the coefficient of thermal expansion (α_CTE), at a fluoride concentration of ∼36 mol%. A similar trend in the infrared band absorption coefficient (α_IR) at 2170 cm⁻¹ of the overtone of 2ν_ss(OPO) and/or a combination of ν_as(OPO)+ν_as(POP) fundamental vibrations of PO₄ tetrahedra also has been observed, relative to changes in the glass composition. Statistical analyses have shown that the T _g and α_CTE values are correlated with α_IR at 2170 cm⁻¹ by linear equations. The thermal properties of some of the glasses have been calculated using these equations, to test their validity and utility. The experimental property values of the glasses present a very good fit of data within a 95% confidence interval of the calculated mean values.     

Measurement of atmospheric water vapour content over a tropical location by dual frequency microwave radiometry

Atmospheric water vapour was measured over a tropical location, Calcutta, by deploying dual frequency microwave radiometers operating at 22.235 and 31.4 GHz. Simultaneous measurements of brightness temperature and hence attenuation in the presence of thin cloud were made for the purpose. An algorithm was developed to exclude the effect of non-precipitating liquid water during the measurement of water vapour. The experimental results are supported by the corresponding radiosonde data analysis. Dual frequency radiometric measurements are shown to improve the rms accuracy, over the single frequency inversion technique, for the measurement of water vapour.     

Fast computation of smallest enclosing circle with center on a query line segment

Here we propose an efficient algorithm for computing the smallest enclosing circle whose center is constrained to lie on a query line segment. Our algorithm preprocesses a given set of n points P={p₁,p₂,…,pn} such that for any query line or line segment L, it efficiently locates a point c on L that minimizes the maximum distance among the points in P from c. Roy et al. [S. Roy, A. Karmakar, S. Das, S.C. Nandy, Constrained minimum enclosing circle with center on a query line segment, in: Proc. of the 31st Mathematical Foundation of Computer Science, 2006, pp. 765-776] have proposed an algorithm that solves the query problem in O(log²n) time using O(nlogn) preprocessing time and O(n) space. Our algorithm improves the query time to O(logn); but the preprocessing time and space complexities are both O(n²).