Showing papers by "All Saints' College published in 2014"

Synthesis and characterization of strontium and barium bismuth borate glass-ceramics

Abstract: Glass ceramics in the 20MO.55Bi2O3.25B2O3 (M = Sr, Ba) system were prepared by conventional melt quenching method, followed by heat treatment. XRD patterns show that the crystalline phase boron sillenite (Bi24B2O39) was formed on thermal treatment. The variation in the microstructure of the sample as a function of crystallization temperature was studied using scanning electron microscopy. The structural changes due to heat-treatment of the glasses have been explained on the basis of the changes in FT-IR and FT-Raman spectra. The glass ceramics in the present study have relatively high dielectric constant and low dielectric loss.

Influence of Fe dopant concentration and annealing temperature on the structural and optical properties of ZnO thin films deposited by sol–gel method

Abstract: Nanostructured Fe doped ZnO thin films were deposited onto glass substrates by sol–gel spin coating method. Influence of Fe doping concentration and annealing temperature on the structural, compositional, morphological and optical properties were investigated using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), UV–Vis spectroscopy and photoluminescence (PL) measurements. XRD analysis showed that all the films prepared in this work possessed a hexagonal wurtzite structure and were preferentially oriented along the c-axis. Pure ZnO thin films possessed extensive strain, whereas Fe doped films possessed compressive strain. In the doped films, least value of stress and strain was observed in the 0.5 at.% Fe doped thin film, annealed at 873 K. Average crystallite size was not significantly affected by Fe doping, but it increased from 15.57 to 17.79 nm with increase in annealing temperature from 673 to 873 K. Fe ions are present in +3 oxidation state as revealed by XPS analysis of the 0.5 at.% Fe doped film. Surface morphology is greatly affected by changes in Fe doping concentration and annealing temperature which is evident in the SEM images. The increase in optical band gap from 3.21 to 3.25 eV, with increase in dopant concentration was attributed to Moss–Burstein shift. But increase in annealing temperature from 673 to 873 K caused a decrease in band gap from 3.22 to 3.20 eV. PL spectra showed emissions due to excitonic combinations in the UV region and defect related emissions in the visible region in all the investigated films.

(2E)-2-Benzyl-idene-N-phenyl-hydrazinecarboxamide.

Abstract: The mol­ecule of the title compound, C14H13N3O, adopts an E conformation with respect to the azomethine C=N bond, and is roughly planar, with an r.m.s. deviation of the non-H atoms from the least-squares plane of 0.100 (2) A and a dihedral angle between the terminal benzene rings of 5.74 (12)°. An intramolecular N—H⋯N hydrogen bond closes an S(6) ring. In the crystal, mol­ecules are linked by the pairs of N—H⋯O hydrogen bonds into centrosymmetric dimers. Dimers related by translation along [010] form slanted stacks, the shortest C⋯C inter­molecular distance within the stack being 3.283 (3) A. Weak C—H⋯π inter­actions link the stacks into a three-dimensional structure.

BER and SER Based Performance Analysis of BPSK and QPSK Modulation Schemes with OFDM in Rayleigh Fading Channel

Abstract: BER is a key property of the digital communication system Various types of modulation methods are used in the digital information transmission system BER can be demarcated as the number of received bits of a data stream over a communication channel that can be affected due to noise, interference and distortion or bit synchronization errors OFDM can be seen as either a modulation technique or a multiplexing technique One of the main reasons to use OFDM is to increase the robustness against frequency selective fading or narrowband interference In a single carrier system, a single fade or interferer can cause the entire link to fail, but in a multicarrier system, only a small percentage of the subcarriers will be affected The BPSK digital modulation technique for OFDM system over AWGN and Rayleigh fading channels From comparison we can observe that the OFDM- BPSK modulation has no any specific advantage over a conventional BPSK modulation scheme in AWGN channel but OFDM-BPSK modulation in AWGN channel has great advantage over OFDM-BPSK modulation in Rayleigh fading channel The performance of BER of BPSK over AWGN and Rayleigh channel is compared Simulation of BPSK signals is carried with both AWGN and Rayleigh channel The work provides link level performance analysis of non-line of sight QPSK-OFDM data transmission over Rayleigh fading channels Two scenarios have been considered in this thesis Firstly, the performance of BPSK-OFDM and QPSK-OFDM over the AWGN and Rayleigh channel was obtained Keywords: OFDM,QPSK,BPSK,AWGN,RAYLEIGH CHANNEL