A simple approach for accurate determination of the resonant frequencies of microstrip antennas of regular geometries is developed and presented. In this approach, a generalised empirical formula for the computation of effective dielectric permittivity is given which takes into account the ratio of the fringing area to the area of the patch. A correction to the equivalent side length of an equilateral triangular patch, previously published, is modified and a new formula is given. A correction to the effective dimensions of an elliptical microstrip antenna is also carried out. Numerical results obtained for the resonant frequencies of elliptical, circular, rectangular and equilateral-triangular microstrip antennas are in good agreement with the available theoretical and experimental results reported by others. The present approach is more efficient, simpler and more accurate.

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In this paper, an improved technique for evolving wavelet coefficients refined for compression and reconstruction of fingerprint images is presented. The FBI fingerprint compression standard [1, 2] uses the cdf 9/7 wavelet filter coefficients. Lifting scheme is an efficient way to represent classical wavelets with fewer filter coefficients [3, 4]. Here Genetic algorithm (GA) is used to evolve better lifting filter coefficients for cdf 9/7 wavelet to compress and reconstruct fingerprint images with better quality. Since the lifting filter coefficients are few in numbers compared to the corresponding classical wavelet filter coefficients, they are evolved at a faster rate using GA. A better reconstructed image quality in terms of Peak-Signal-to-Noise-Ratio (PSNR) is achieved with the best lifting filter coefficients evolved for a compression ratio 16:1. These evolved coefficients perform well for other compression ratios also.

Pure and o-nitroaniline (O-NA) doped benzil single crystals were grown by the slow cooling solution growth method. The doping of O-NA is associated with the strong interaction between the guest and host molecules by the hydrogen bonding. Incorporation of O-NA in the lattice enhances the crystallinity. The nonlinearity increases due to the inductive nitro group added to the benzil. The values of nonlinear absorption coefficient (β) and nonlinear refractive index (n 2 ) of benzil are -78 × 10 -3 cm/W and -22 × 10 -3 cm/W, while the corresponding values for O-NA doped benzil are -9.4 × 10 -9 and -6 × 10 -7 cm 2 /W, respectively. The figure of merit values of benzil and O-NA doped benzil are 2265 and 4990, respectively. The increase in hardness on doping of O-NA to benzil is due to the strong hydrogen bond.

Nucleation parameters such as radius of critical nucleus, critical free energy change and interfacial tension were evaluated for Sulphanilic acid (SAA) single crystals. Metastable zone width and induction period values were determined to optimize the growth parameters. The interfacial tension values estimated using the experimentally determined induction period is found to be comparable with theoretical values. SAA crystals were grown with the optimized growth parameters. The formation of SAA crystals was confirmed by powder X-ray diffraction and FT-IR studies. The density measurements were carried out by both theoretical and experimental methods. The NLO behaviour of SAA crystals was tested by Kurtz-Perry technique. The mechanical hardness was studied by Vickers Microhardness tester. The UV-Vis spectral analysis was carried out on the SAA crystals to study the optical properties. The laser damage threshold values of the SAA crystals are found to be 7.6 and 6.6 GW/cm 2 for single and multiple shots, respectively.