Construction of XVCS for (k,n,t)∗ access structure

XOR-based Visual Cryptography System (XVCS) is developed to achieve high contrast and good resolution of the recovered secret image. In general (k,n) VCS, the secret image can be visualized only if k or more than k shares are stacked together. In (k,n,t)^? access structure, t number of participants are considered as the essential participants(t ≤ k ≤ n) whose shares are absolutely necessary to reconstruct the secret image. Several methods have been already proposed for the construction of (k,n)^? VCS for black and white images. The major focus of this work is to design an XVCS for (k,n,t)^? access structure for both black and white images and color images with maximum contrast. The experimental outcome shows that the proposed method has better results than other techniques proposed so far. Also, numerical examples are provided for (k,n,t)^? XVCS for t =?1 and 2. The XVCS designed for (k,n,t)^? access structure can be used for any real time application and is demonstrated with an example of user authentication in banking system.

     

Slot line fed dual‐band dipole antenna for 2.4/5.2 GHz WLAN applications

A printed slot line fed dual‐band coplanar dipole antenna having a dimension of 0.40λ_g × 0.20λ_g suitable for both 2.4 and 5.2 GHz (IEEE 802.11 b/g and 802.11 a) WLAN application is presented. The structure comprises of a slot line fed symmetrical L strips to achieve dual‐band operation. Design equations of the antenna are developed and validated on different substrates. The simulation and experimental results show that the proposed antenna exhibits good impedance match, gain, and stable radiation patterns in both the frequency bands. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE , 2012.     

Planar UWB antenna with modified slotted ground plane

A compact coplanar waveguide‐fed (CPW) monopole antenna for ultra‐wideband wireless communication is presented. The proposed antenna comprises of a CPW‐fed beveled rectangular patch with a modified slotted ground. The overall size of the antenna is 30 mm × 27 mm × 1.6 mm. The lower edge of the band is attained by properly decoupling the resonant frequencies due to the extended ground plane and the beveled rectangular patch of the antenna. The upper edge of the radiating band is enhanced by beveling the ground plane corners near the feed point. Experimental results show that the designed antenna operates in the 2.7–12 GHz band, for S₁₁ ≤ ?10 dB with a gain of 2.7–5 dBi. Both the frequency domain and time domain characteristics of the antenna are investigated using antenna transfer function. It is observed that the antenna exhibits identical radiation patterns and reasonable transient characteristics over the entire operating band. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2012.     

Facile fabrication and structural elucidation of lignin based macromolecular green composites for multifunctional applications

The present work deals with the preparation and characterization of lignin based macromolecular polymeric composites and applications thereof. Here lignin is complexed with pectin and/ or gellan gum, to form two different macromolecular green composites LP and LPG. The best ratios screened out through evaluation of nanoparticle characterization and rheology, then confirmed by surface morphology. The superior thermal stability is proved by DSC analysis. The reaction groups involving in complexation are confirmed by FT-IR spectroscopic evaluation where the methoxy or methyl group of lignin interacts with the hydroxyl group of pectin and gellan gum to form nanocomposites. The reduced particle size and surface charge confirm the complexation due to interaction between ionizable functional groups. The applications of these composites are validated by their dye adsorption capacity and anti-microbial properties (after loading of green silver nanoparticles) which proves the multifunctional properties of novel composites. The maximum dye removal efficiency of both composites is independent of initial dye concentration. Dye adsorption capacity is best fitted by Freundlich adsorption isotherms that follow pseudo-second-order adsorption kinetics. The antibacterial study of developed silver nanoparticle loaded and unloaded composites shows wide spectrum activity against E. coli and S. aureus, with higher inhibition efficiency against gram-negative organism.     

Analytical equations for compact dual frequency microstrip antenna

Design equations are presented for calculating the resonance frequencies for a compact dual frequency arrow‐shaped microstrip antenna. This provides a fast and simple way to predict the resonant frequencies of the antenna. The antenna is also analyzed using the IE3D simulation package. The theoretical predictions are found to be very close to the IE3D results and thus establish the validity of the design formulae. © 2002 Wiley Periodicals, Inc. Int J RF and Microwave CAE 12, 477–482, 2002. Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mmce.10048     

C-shaped slot loaded reconfigurable microstrip antenna

A new electronically reconfigurable dual frequency microstrip patch antenna with highly simplified varactor tuning circuitry is presented. The proposed design allows relatively independent selection of the two operating frequencies. Tuning ranges of 7.1 and 4.1% are realised for the two resonant frequencies without the use of any matching circuits.     

Effect of silane coupling agent on the dielectric and thermal properties of DGEBA-forsterite composites

Diglycidyl ether of bisphenol A (DGEBA) -forsterite composites have been prepared through mechanical mixing process and the influence of silane coupling agent on the microstructure, dielectric and thermal properties were studied. Phase pure forsterite (Mg₂SiO₄) powder was prepared through solid state ceramic route. Filling fraction of forsterite in DGEBA matrix was varied from 10 to 40 vol%. The morphology and filler distribution of filled composite were studied by Scanning Electron Microscopy. Waveguide cavity perturbation technique was employed to measure the dielectric properties of composites. It is found that aminosilane treatment increased the dielectric constant and dielectric loss of the composites in both microwave and radio frequency ranges compared to composites prepared using untreated powders. Coefficient of thermal expansion of composites decreased with the forsterite addition and attains a relatively low value of 45 ppm/°C for composite containing 40 vol% surface treated filler.     

Microwave dielectric properties of LaMgAl11O19

The suitable choice of a substrate material is one of the aims to be fulfilled in high speed microwave technology. LaMgAl₁₁O₁₉ oxide ceramic material, which belongs to the magnetoplumbite family, has been reported earlier as a potential candidate for such applications. This material has been prepared by conventional solid-state ceramic route. The structure has been studied by X-ray diffraction and characterized at microwave frequencies. The effect of dopant and glass addition on the microwave dielectric properties of this material has also been investigated. LaMgAl₁₁O₁₉ has relatively low dielectric constant (ε_r=14), low dielectric loss or high quality factor (Q_u×f>28,000 GHz at 7 GHz) and small temperature variation of resonant frequency (τ_f=−12 ppm/°C) at room temperature (300 K). These properties make LaMgAl₁₁O₁₉ as a good substrate material and as a dielectric resonator to be used in microwave devices operating at relatively high frequencies.