Search

La1-xGdxFeO3 (x = 0 to 0.25) nanoparticles are prepared by microwave combustion process (MCP) with L-alanine as a fuel. The synthesized samples were characterized by XRD, TEM, SAED, XPS, FE-SEM, EDX, FTIR, DRS-UV and VSM analysis. XRD and FT-IR confirmed that lanthanum ferrite has an orthorhombic structure with an average crystallite size ranging from 57.8 to 37.9 nm. The energy gap values were estimated using UV–vis spectra and it is in the range between 2.17 and 2.43 eV. The elements Gd, La, Fe and O are present in EDX and XPS analysis. FE-SEM images reveal aggregated spherical morphology. VSM analysis shows strong ferro magnetic behavior of La1-xGdxFeO3 nanoparticles. The Ms and Mr values are in the range between 5.63 to 6.54 and 0.76 to 1.71 emu/g for La1-xGdxFeO3 respectively. The experimental results of this work hold promise for further advancements and novel uses in various fields of technology and industry, include solid oxide fuel cells, oxygen separation membranes, gas sensors, catalysis, magnetic devices, electrochemical devices, and potential use in environmental and thermoelectric applications. [ABSTRACT FROM AUTHOR]

It is crucial to have an effective and efficient humidity sensing material for humidity sensor applications. In this study, Lu3+-doped Zinc ferrites were prepared by chemical synthesis method using urea and glucose as fuels for the first time. The prepared powder samples were subjected to several analyses, including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), and Energy-dispersive X-ray spectroscopy (EDX), to examine the structural and morphological changes in ZnFe2 − xLuxo4 (where x = 0, 0.1, 0.3, 0.5, and 0.7). The XRD results show that a single phase was formed without any impurity peak, as confirmed by XRD. The FTIR spectra exhibited two prominent bands at 532 cm−1 and 360 cm−1, which are characteristic features of spinel ferrite. SEM micrographs revealed that the nanoparticles were almost spherical in shape, porous in nature, and fairly uniform in size. Further analysis of the nanoparticle with EDAX confirmed the elemental composition. The humidity sensing behavior of Lu-doped ZnFe2O4 was tested in the relative humidity range of 11 to 97%. Among the samples, Lu = 0.05 exhibited the highest sensing response of 97% with response and recovery times of 35.6 and 6.5 s, respectively. Hence, our results suggest that the synthesized samples are useful for humidity sensor applications. [ABSTRACT FROM AUTHOR]

Wireless systems and standards are now progressing towards the implementation of fifth generation (5G) to combat with an expected and explosive growth of demands of wireless services in future. Consequently, the orthogonal frequency division multiple access (OFDMA) technology is being utilised for the uplink and downlink transmission to afford the high spectral efficiency in fading environments. However, the 5G implementation requires additional improvements to meet the futuristic stress. This work proposes an innovative solution that combines OFDMA technology with multi-user massive multiple input multiple output (MIMO) technology to meet the required elevated data rates as desired by the growing application needs of 5G. Massive MIMO is capable to fulfil the vision of 5G to realize a huge number of base stations equipped with a large number of terminals to be served in the same time–frequency resource without severe inter-user interference. Furthermore, the proposed system is demonstrated incorporation with discrete wavelet transform, and fractional Fourier transforms. The evaluated outcomes exemplify a considerable improvement in spectral efficiency and BER performance in contrast with the earlier reported work. [ABSTRACT FROM AUTHOR]

Wireless systems and standards are now progressing toward the implementation of fifth generation (5G) to combat with an expected and explosive growth of demands of wireless services in future. Consequently, wireless interoperability for microwave access (WiMAX) with orthogonal frequency division multiplexing (OFDM) technology at its physical layer is being utilized for the uplink and downlink transmission to afford the high spectral efficiency in fading environments. However, the 5G implementation requires additional improvements to meet the futuristic stress. This work proposes an innovative solution that combines WiMAX system with multiple input multiple output (MIMO) technology to meet the required elevated data rates as desired by the growing application needs of 5G. MIMO is capable to fulfil the vision of 5G to realize a huge number of base stations equipped with a large number of terminals to be served in the same time-frequency resource without severe inter-user interference. Furthermore, the proposed system is demonstrated incorporation with discrete wavelet transform (DWT), and fractional Fourier transforms (FrFTs) in the physical layer of the WiMAX system. The evaluated outcomes exemplify a considerable improvement in bit error rate (BER) performance in contrast with the earlier reported work. [ABSTRACT FROM AUTHOR]

Recent advancements in mobile Worldwide Interoperability for Microwave Access (WiMAX) standards have led to the development of more reliable, robust and efficient broadband networks that can provide access for both fixed and mobile users. The physical layer of a WiMAX network is composed of orthogonal frequency-division multiplexing (OFDM) technology, which allows it to provide elevated data rates with minimum distortion in fading environments. However, the presence of interference affects the orthogonality of the OFDM sub-carriers, which increases the probability of network errors. The error probability can be reduced by increasing the output power level at the expense of an elevated peak-to-average power ratio (PAPR). In this work, discrete wavelet transforms (DWTs) and fractional Fourier transforms (FrFTs) are used to augment the reliability and efficiency of an adaptive WiMAX system. The results show considerable improvements in both bit error rate (BER) reduction and spectral efficiency enhancement at a given signal-to-noise ratio (SNR). In addition, a significant PAPR reduction is attained when the DWTs and FrFTs are used in place of fast Fourier transforms. Moreover, the proposed adaptive algorithm realizes a spectral-efficient WiMAX system that enables the system to select the suitable transform strategy (DWT/FrFT) with minimum SNR requirements to achieve the target BER of 10−4. [ABSTRACT FROM AUTHOR]

The full rate can be attained by the conventional Quasi-Orthogonal Space–Time Block Codes (QO-STBC) with the downside of more decoding intricacy and less diversity gain. Grammian matrix of already existing QO-STBC scheme contains non-diagonal elements i.e. interference terms which are responsible for more computational load at the receiver. The non-diagonal elements causing interference while decoding process are eliminated from the grammian matrix by the use of RAR (reflection and rotation) operations on the detection matrix of already existing QO-STBC. Reflection and rotation QO-STBC (RAR-QOSTBC) scheme is proposed in this paper, which results in transformation of the grammian matrix into a diagonal matrix. Corresponding to the diagonal matrix, a new RAR-QOSTBC encoding matrix is generated. RAR-QOSTBC scheme enables to achieve more diversity gain as well as it reduces decoding intricacy at the receiver as comparison to the already existing QO-STBC method. Analysis has been performed for different levels of PSK modulation over two distinct channels (AWGN and Rayleigh) by changing the number of receive antennas. Simulation result shows a significant improvement in the BER performance because of the removal of non-slanting elements from the detection matrix. [ABSTRACT FROM AUTHOR]

Wavelets are brought into the wireless communication field as an orthogonal base of multi-carrier modulation and are now considered as a significant measure. Also, wavelets do contain the capability to improve bandwidth efficiency even more along with lower inter-symbol interference and inter-carrier interference. Appropriately, a BER versus SNR analysis is done for fast Fourier transform (FFT) based OFDM framework and wavelet haar transform (WHT) based OFDM framework in this work. The evaluationis demonstrated over Rayleigh and Rician fading channel utilizing dissimilar M-PSK modulation levels intended for FFT-OFDM and WHT-OFDM. The performance of the simulated test-bed is investigated via BER assessment as a function of SNR. The imitation outcome reports a significant improvement in BER of the simulated system using WHT-OFDM in comparison to FFT-OFDM for both Rayleigh and Rician fading channel. Also, the BER performance of both FFT-OFDM and WHT-OFDM is superior in Rician fading channel in comparison to Rayleigh fading channel. [ABSTRACT FROM AUTHOR]