Nonlinear flexural vibrations of laminated orthotropic plates

Large amplitude free flexural vibrations of laminated orthotropic plates are studied using C⁰ shear flexible QUAD-8 plate element. The nonlinear governing equations are solved using the direct iteration technique. Numerical results are obtained for isotropic, orthotropic and cross-ply laminated plates with simply-supported boundary conditions on immovable edges. It is observed that hardening behaviour is increased for thick plates and orthotropic plates.     

A new shear flexible cubic spline plate element for vibration analysis

Here, a new cubic B‐spline plate element is developed using field consistency principle, for vibration analysis. The formulation includes anisotropy, transverse shear deformation, in‐plane and rotary inertia effects. The element is based on a laminated refined plate theory, which satisfies the interface transverse shear stress and displacement continuity, and has a vanishing shear stress on the top and bottom surfaces of the plates. The lack of consistency in the shear strain field interpolations in its constrained physical limits produces poor convergence and results in unacceptable solutions due to locking phenomenon. Hence, numerical experimentation for the evaluation of natural frequencies of plates is carried out to check this deficiency with a series of assumed shear strain functions, redistributed in a field consistent manner. Copyright © 2002 John Wiley & Sons, Ltd.     

Growth and characterization of laser-deposited Ag-doped YBa2Cu3O7−x thin films on bare sapphire

Microstructural and superconducting properties of YBa₂Cu₃O_7−x thin films grownin situ on bare sapphire by pulsed laser deposition using YBa₂Cu₃O_7−x targets doped with 7 and 10 wt% Ag have been studied. Ag-doped films grown at 730°C on sapphire have shown very significant improvement over the undoped YBa₂Cu₃O_7−x films grown under identical condition. A zero resistance temperature of 90 K and a critical current density of 1·2×10⁶ A/cm² at 77 K have been achieved on bare sapphire for the first time. Improved connectivity among grains and reduced reaction rate between the substrate and the film caused due to Ag in the film are suggested to be responsible for this greatly improved transport properties.     

LaNiO3: A promising material for contact with YBa2Cu3O7− δ thin films

Epitaxial LaNiO₃ metallic oxide thin films have been grown onc-axis oriented YBa₂Cu₃O_7?δ thin films on 〈100〉 LaAlO₃ substrates by pulsed laser deposition technique and the interface formed between the two films has been exmained by measuring the contact conductance of the same. The high value of specific contact conductance indicates the existence of a clean interface at the LaNiO₃?YBaO₂CuO₃OO_7?δ thin film contact.     

On the error probability of coded frequency-hopped spread-spectrummultiple-access systems

A simple, exact calculation is presented of the probability distribution of the number of hits in a block of n symbols in a frequency-hopped, spread-spectrum, multiple-access communication system. While the sequence of hits is not Markovian, there is an underlying Markovian structure that allows the probability distribution of the number of hits to be calculated in a recursive fashion. Knowing the probability distribution of the number of hits makes it possible to calculate the probability of error for a system employing error correcting codes for several different types of receivers, including receivers with both errors and erasures. The numerical results show that both the approximation obtained by assuming the actual sequence of hits is Markovian and the approximation obtained by assuming the hits are independent are very good. When the number of frequency slots is not too small (less than five), calculations show that assuming the independence of hits gives an error probability accurate to within 1% of the actual error probability. Assuming the hits are Markovian gives error probabilities which are accurate to within 0.001%     

Assessment of radiological significance of naturally occurring radionuclides in soil and rock matrices around Kakrapar environment

The activity and gamma-absorbed dose rate due to the naturally occurring radionuclides in the terrestrial environment such as (238)U, (232)Th and (40)K were determined in soil and rock samples collected around Kakrapar Atomic Power Plant site, using gamma-ray spectrometry. The mean concentration levels measured in Kakrapar soil from naturally occurring radioisotopes such as (238)U, (232)Th and (40)K are lower than the corresponding global average values obtained in worldwide soil. The external hazard index (H(ex)) and absorbed gamma dose rate in air outdoors is observed to be 0.04-0.18 and 3.1-14.1 nGy h(-1), respectively.     

A non-parametric statistical analysis in the measurement of outdoor gamma exposure to the residents around Trombay

During this study, non-parametric statistical methods were used to validate the measured gamma dose rate with the calculated one, around Trombay. Portable dose rate digital gamma spectrometry system (target fieldSPEC) was used for in situ measurement of external gamma (gamma) dose rate (measured) with the range of 1 nSv/h-10 Sv/h. The activity concentration of U-238, Th-232, K-40 and Cs-137 in the soil and their respective external dose-conversion factor (nSv/h/Bq/kg) was used to evaluate the gamma dose rate (calculated). Non-parametric statistical tool like Box- and -Whisker Plot, Spearman's (rho) rank Correlation coefficient, the Wilcoxon/Mann-Whitney test and chi(2) distribution test have been applied for validation. The randomness or discrete behaviour of measured and calculated dose rate was obvious from the Box- and -Whisker Plot as mean and median of the two are not equal. The inter quartile range (Q3-Q1), which explains about the dispersion of measured and calculated dose rate were also evaluated and found to be 10 and 16 microSv/y, respectively. The linear association between the order of ranks of the two dose rates was established by using Spearman's (rho) rank correlation that showed a coefficient of R = +0.90 with the intercept +1.9, whereas Pearson's correlation was observed with a coefficient of R = +0.93 with the intercept -25.6. Wilcoxon/Mann-Whitney test shows that, medians of the calculated and the measured dose rate as significantly different under the assumption of null hypothesis and measured dose rate was made to the normal distribution by applying Z-statistics. Value of chi(2) was calculated and found to be 284.95, which was very much greater than the critical value of chi(2)(0.05) = 43.77 at a degree of freedom 30, concluding that there is a highly significant difference between the measured and calculated dose rate at 5% significance level.     

Nanofabricated multilayer coatings of Zn-Ni alloy for better corrosion protection

As an effort to increase the corrosion resistance of conventional monolayer Zn-Ni alloy coating, the multilayer Zn-Ni alloy coating have been done electrolytically on mild steel (MS), using gelatin and glycerol as additives. Multilayered, or more correctly composition modulated multilayer alloy (CMMA) coatings have been developed using square current pulse. Successive layers of alloys, in nanometric scale having alternately changing composition were fabricated by making the cathode current to cycle between two values, called cyclic cathode current densities (CCCD’s). The coatings having different configuration, in terms of composition and thicknesses of individual layers were developed and their corrosion performances were evaluated by electrochemical methods. The corrosion rate (CR)’s were found to decrease drastically with progressive increase in number of layers (up to 300 layers), and then increased. The coating configurations have been optimized for best protection against corrosion. The CMMA Zn-Ni coating having 300 layers was found to be about 37 times more corrosion resistant than corresponding monolayer alloy, developed from same bath for same time. High protection efficacy of the coatings were attributed to alternate layers of alloys having different surface structure and composition, supported by Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD) study, respectively. Optimization procedure has been explained, and results are discussed.     

Authentication using Finger Knuckle Prints

Automated security is one of the major concerns of modern times. Secure and reliable authentication systems are in great demand. A biometric trait like the finger knuckle print (FKP) of a person is unique and secure. Finger knuckle print is a novel biometric trait and is not explored much for real-time implementation. In this paper, three different algorithms have been proposed based on this trait. The first approach uses Radon transform for feature extraction. Two levels of security are provided here and are based on eigenvalues and the peak points of the Radon graph. In the second approach, Gabor wavelet transform is used for extracting the features. Again, two levels of security are provided based on magnitude values of Gabor wavelet and the peak points of Gabor wavelet graph. The third approach is intended to authenticate a person even if there is a damage in finger knuckle position due to injury. The FKP image is divided into modules and module-wise feature matching is done for authentication. Performance of these algorithms was found to be much better than very few existing works. Moreover, the algorithms are designed so as to implement in real-time system with minimal changes.     

Catalysis for NOx abatement

Research in the field of NO_x abatement has grown significantly in the past two decades. The general trend has been to develop new catalysts with complex materials in order to meet the stringent environmental regulations. This review discusses briefly about the different sources of NO_x and its adverse effect on the ecosystem. The main portion of the review discusses the progress and development of various catalysts for NO_x removal from exhaust by NO decomposition, NO reduction by CO or H₂ or NH₃ or hydrocarbons. The importance of understanding the mechanism of NO decomposition and reduction in presence of metal ion substituted catalysts is emphasized. Some conclusions are made on the various catalytic approaches to NO_x abatement.