Design Analysis of Broadband Stacked Microstrip Patch Antenna for WLAN Applications

Wireless Personal Communications - A novel configuration of stacked microstrip patch antenna is designed, simulated and fabricated for WLAN applications. Return loss is calculated below...     

Enhanced mandrel design for electrospinning aligned fiber mats from low volatility solvents

A cylindrical mandrel with axially aligned rods was designed and tested for the collection of electrospun fibers. Blended polyaniline/polyethylene oxide fibers were electrospun from a solution containing a nonvolatile solvent, m-cresol. Camphorsulfonic acid served as the primary dopant and m-cresol were used as the secondary dopant to enhance fiber conductivity. A smooth, rotating cylindrical mandrel collector failed to collect and align fibers and instead afforded a wet, sticky film. An eight-rod, rotating cylindrical mandrel resulted in a dry, aligned fiber mat composed of 7–10 μm diameter fibers. Alignment was maintained for at least 18 h of continuous spinning and the resulting mat could be easily recovered from the mandrel. A simulation of the rotating system indicated that the efficient formation of dry, nonsticky, aligned fiber mat was facilitated by the high mass transfer coefficient associated with the use of corrugated rods. Experiments indicated that 6–10 rods were optimal avoiding sagging of the fibers at the low end and increased mas transfer resistance at the high end.     

Polar Cation Ordering: A Route to Introducing >10% Bond Strain Into Layered Oxide Films

The 3d transition metal (M) perovskite oxides exhibit a remarkable array of properties, including novel forms of superconductivity, magnetism and multiferroicity. Strain can have a profound effect on many of these properties. This is due to the localized nature of the M 3d orbitals, where even small changes in the M–O bond lengths and M–O–M bond angles produced by strain can be used to tune the 3d– O 2p hybridization, creating large changes in electronic structure. A new route is presented to strain the M–O bonds in epitaxial two‐dimensional perovskite films by tailoring local electrostatic dipolar interactions within every formula unit via atomic layer‐by‐layer synthesis. The response of the O anions to the resulting dipole electric fields distorts the M–O bonds by more than 10%, without changing substrate strain or chemical composition. This distortion is largest for the apical oxygen atoms (O_ap), and alters the transition metal valence state via self‐doping without chemical substitution.     

Radiometric calibration stability assessment for the RISAT-1 SAR sensor using a deployed point target array at the Desalpar site,Rann of Kutch,India

Synthetic aperture radar (SAR) data used for quantitative temporal and/or spatial analysis requires calibration to ensure that observed pixel values of amplitude and phase can be related to the geophysical parameters of interest. The process of radiometric calibration of SAR images involves comparison of the backscattered radar reflectivity signal from a ground resolution element containing a calibration target of known signal response, such as a corner reflector. In this study, absolute radiometric calibration of RISAT-1 intensity data of fine resolution stripmap-1 (FRS-1) and medium resolution ScanSAR (MRS) mode was carried out by utilizing array of standard point targets of various types (triangular trihedral, square trihedral, and dihedral) with known radar cross-section deployed prior to satellite overpass with precise azimuth and elevation angles in Desalpar, Rann of Kutch in western India. The derived calibration constants using the integral method were then compared with the values provided in the header file. Deviations in the results are reported in this article. The results obtained show that the difference between the estimated average calibration constants for FRS-1 and MRS mode data with the provided value was found to be within the absolute radiometric accuracy specification of Radar Imaging SATellite (RISAT-1). Near-range to far-range difference of 0.1–0.2 dB for HH (Horizontal transmit, Horizontal receive) polarization and 0.1–0.3 dB for HV (Horizontal transmit, Vertical receive) polarization was estimated for the same scene using distributed target analysis indicating the stability of calibration for the same scene. This study also concluded that Desalpar site in Rann of Kutch has the potential of being an operational SAR calibration site.     

Off-grid energy services for the poor: Introducing LED lighting in the Millennium Villages Project in Malawi

Lanterns that use light-emitting diodes (LEDs) powered by batteries, which are in turn charged by grid electricity or small solar panels, have emerged as a cost-competitive alternative to kerosene and other fuel-based lighting technologies, offering brighter light for longer duration at equal or lower cost over time. This paper presents lessons learned from the introduction of solar LED lanterns in rural Malawi. We discuss a market-based program using new and existing local commercial structures such as vendors and cooperatives to sell lanterns to village households without subsidy. The paper addresses issues of enterprise development, community interactions, and survey data on lighting use and expenditure patterns before and after LED lantern introduction. Households that purchased a lantern reported high levels of satisfaction with the LED lanterns as well as savings in annual kerosene expenditure comparable to the price of the lantern. These households also reported monthly incomes comparable to the price of the LED lanterns whereas non-adopters surveyed reported monthly incomes about half this level, suggesting a need for financing options to maximize adoption among poorer populations in rural areas. These results suggest that similar market based models of LED lighting technology dissemination have the potential to be replicated and scaled up in other off-grid regions in developing countries. However, viability of local cooperatives and supply chains for lantern products over the medium-to-long term remain to be assessed.     

Media optimisation for production of lactic acid by lactobacillus plantarum NCIM 2084 using response surface methodology

Abstract

For the production of lactic acid by Lactobacillus plantarum NCIM 2084, response surface methodology (RSM) using central composite rotatable design (CCRD) was adopted for optimising the media composition with respect to liquefied starch, wheat bran extract, ammonium nitrate and sodium acetate. A set of 28 experiments were carried out and cannonical analysis was employed. Significant (p ≤ 0.25) effects were observed for the first three variables. Quadratic and interaction effects of the variables were more prominent than the linear effects. The respective optimum concentrations obtained were 9.99, 0.05, 2.48 and 0.08% giving a substrate conversion of 92% and a lactic acid concentration of 72.9 g/L in 24 h. It has been possible to replace the expensive yeast extract by. a combination of wheat bran extract and ammonium nitrate.