A novel microwave method for measuring the complex dielectric constant of polymer thin sheets

A new method of measuring the complex dielectric constant of a thin sheet of polymer samples at microwave frequency is presented. In order to obtain the complex dielectric constant in terms of reflection coefficient, a higher order power series solution has been introduced. Application of lower order power series solution to the greater thickness of the sample requires a frequency of less than 1.5 GHz. To overcome this constraint and to extend the range of working frequency, the higher order power series solution is used to obtain the complex dielectric constant. This method is used to measure the complex dielectric constant of poly(ethylene vinyl acetate), polyurethane, polyvinyl acetate, and polystyrene. The results obtained are in good agreement with literature. Electronic Publication     

A comparative study on chitosan nanoparticle synthesis methodologies for application in aquaculture through toxicity studies

Chitosan nanoparticles (CSNPs) have been recently used for various applications in aquaculture, especially as drug carriers. The aim of this study was to synthesise and investigate a superlative method of CSNP synthesis for application in aquaculture through aquaculture‐based toxicology screening methods. Two different methods were analysed: the first a direct ionic gelation method (A) and the other involving a low‐molecular‐weight chitosan microparticle intermediate method (B). Dynamic light scattering characterisation revealed that the CSNP particle sizes were 192.7 ± 11.8 and 22.9 nm from methods A and B, respectively. The LC₅₀ values for brine shrimp toxicity were found to be 1.51 and 0.02 ppt in 24 h for methods A and B, respectively. Acute toxicity studies in Litopenaeus vannamei rendered LC₅₀ values of 3235.94 and 2884.03 ppt in 24 h for methods A and B, respectively. Zebrafish toxicity studies revealed mortality rates of 21.67% and 55% at 20 mg/L concentration for methods A and B, respectively, with an increased expression of intracellular reactive oxygen species in method B. From these findings, it can be concluded that a comparatively reduced toxicity of CSNPs derived from ionic gelation method makes it more appropriate for application in aquaculture.     

Secure Distance Based Improved Leach Routing to Prevent Puea in Cognitive Radio Network

Wireless Personal Communications - Routing in cognitive radio networks (CRNs) faces numerous limitations in misbehaving activities and secure the routing requests and reply messages. In this...     

Performance Analysis of Robust GRCR Based Spectrum Detector Using Compressed Sensing with Non-reconstruction Model

Wireless Personal Communications - In cognitive radio applications, a robust detector is essentially required for the determination of spectrum sensing. Gerschgorin radii and centers ratio (GRCR)...     

Efficient reordering algorithm for color palette image using adaptive particle swarm technique

Palette re-ordering is a class of pre-processing methods aiming at finding a permutation of color palette such that the resulting image of indexes is more amenable for compression. The objective is to manipulate the palette index such that the adjacent symbols are assigned close indices in the symbol space, thus enhancing the compressibility of the image with many lossless compressors. Finding an exact reordered palette would certainly be exhaustive and computationally complex. To address this issue, a heuristic approach based on Traveling Salesman Problem formulation (NP hard) is sought. In this paper, the solution to this NP hard problem is presented by using an Adaptive Particle Swarm Optimization to achieve fast global convergence by maximizing the co-occurrences.     

Enhanced Dielectric Properties in Spark Plasma Sintered Zinc Titanate Ceramics

The ever increasing application of zinc titanate ceramics as a dielectric material in microwave devices and low temperature co-fired ceramics calls for the improvement in their dielectric properties. In this paper, the effect of different sintering techniques on the dielectric properties of zinc titanate have been discussed. Zinc titanate was prepared by ball milling 1:1 molar ratio of ZnO and TiO₂ for 12 h and calcined at 800 °C for 2 h. The presence of ZnTiO₃ and Zn₂TiO₄ phases were confirmed by X-ray diffraction and the dielectric properties of the sintered samples were studied using LCR meter. Samples consolidated by spark plasma sintering (SPS) showed highest densification (13% increase), higher dielectric permittivity (?_r = 25.17) and Q factor (Q factor = 162.78) with lower loss tangent values (tanδ = 0.00614) than that of microwave sintered samples (?_r = 21.86, Q factor = 99.08, tanδ = 0.01009) and conventionally sintered samples (?_r = 20.54, Q factor = 60.07, tanδ = 0.01665). The fabrication time was considerably reduced for the materials prepared via SPS than that prepared by conventional route with improved properties and also the dependence of dielectric properties on density was confirmed in this research work.     

Nonlinear spectral-estimation methods for ground clutter analysis

A simple ground clutter model has been analysed using nonlinear methods of power spectral estimation and the performance of these methods has been studied. The methods considered are the maximum entropy method (MEM), the maximum likelihood method (MLM), the least-squares method (LSM), the autoregressive moving average (ARMA) method and Prony's energy spectral-density estimation (PESD). The performance of these power spectral-estimation methods has been studied for different data lengths and different model orders