Detection of Signals in MC–CDMA Using a Novel Iterative Block Decision Feedback Equalizer

This paper presents a technique to mitigate multiple access interference (MAI) in multicarrier code division multiple access (MC-CDMA) wireless communications systems. Although under normal circumstances the MC-CDMA system can achieve high spectral efficiency and resistance towards inter symbol interference (ISI) however when exposed to substantial nonlinear distortion the issue of MAI manifests. Such distortion results when the power amplifiers are driven into saturation or when the transmit signal experiences extreme adverse channel conditions. The proposed technique uses a modified iterative block decision feedback equalizer (IB-DFE) that uses a minimal mean square error (MMSE) receiver in the feed-forward path to nullify the residual interference from the IB-DFE receiver. The received signal is re-filtered in an iterative process to significantly improve the MC-CDMA system’s performance. The effectiveness of the proposed modified IB-DFE technique in MC-CDMA systems has been analysed under various harsh nonlinear conditions, and the results of this analysis presented here confirm the effectiveness of the proposed technique to outperform conventional methodologies in terms of the bit error rate (BER) and lesser computational complexity

Influence of calcination temperature on Cd0.3Co0.7Fe2O4 nanoparticles: Structural, thermal and magnetic properties

Cadmium substituted cobalt ferrite nanoparticles are synthesis using the chemical method. The as-prepared ferrite nanoparticles are calcinated at 300 °C and 600 °C respectively. The samples are studied using; Powder XRD, SEM with EDX, TEM, FT-IR, TG-DTA and vibrating sample magnetometer (VSM) in order to study the calcination temperature effect on structural, morphological and magnetic properties. The magnetic properties, like saturation magnetization and coercivity increases with increasing the calcination temperature. This enhancement is attributed to the transition from amulti-domain to a single-domain nature. The absorption bands observed at 588 cm-1 (ν<inf>1</inf>) and 440 cm-1 (ν<inf>2</inf>) are attributed to the vibrations of tetrahedral and octahedral complexes. The TG-DTA curves reveal the thermal stability of the prepared ferrite nanoparticles. The calcination temperature influences the magnetic properties, surface morphology and crystalline size. © 2015 Elsevier B.V. All rights reserved.

Peak effect in Ca3Rh4Sn13: Vortex phase diagram and evidences for stepwise amorphization of flux line lattice

We elucidate the stepwise amorphization of the ordered flux line lattice and construct the vortex phase diagram in Ca3Rh4Sn13 from the study of characteristics of the peak effect phenomenon in ac and de magnetization measurements

Elucidation of amorphization of flux line lattice in Yb3Rh4Sn13

The characteristic details of die path dependence in the in-phase ac susceptibility data are elucidated via provision of an external stimulus and the process of thermal cyclings across the multiple steps comprising the peak effect (PE) phenomenon in a single crystal of Yb3Rh4Sn13

Stepwise amorphization of the flux-line lattice in Ca3Rh4Sn13: A peak-effect study

The peak effect (PE) region in a single crystal of Ca3Rh4Sn13 is shown to comprise two discontinuous first-order-like transitions located near its onset and peak positions, in accordance with a stepwise fracturing of the flux-line lattice. Magnetization response to thermal cycling across the onset position produces an open hysteresis loop, consistent with the notion of the fracturing. A thermomagnetic history dependence study shows that the critical current density J(c)(H,T) is path dependent over a large part of the (H,T) parameter space. Tills path dependence ceases above the peak position of the peak effect, suggesting a complete amorphization of the flux-line lattice at (T-p,H-p) line. A plausible vortex phase diagram has been constructed for Ca3Rh4Sn13 in which phases like an elastic solid, a plastic solid, and pinned and unpinned amorphous states have been identified

Enhancement of Precise Underwater Object Localization

Underwater communication applications extensively use localization services for object identification. Because of their significant impact on ocean exploration and monitoring, underwater wireless sensor networks (UWSN) are becoming increasingly popular, and acoustic communications have largely overtaken radio frequency (RF) broadcasts as the dominant means of communication. The two localization methods that are most frequently employed are those that estimate the angle of arrival (AOA) and the time difference of arrival (TDoA). The military and civilian sectors rely heavily on UWSN for object identification in the underwater environment. As a result, there is a need in UWSN for an accurate localization technique that accounts for dynamic nature of the underwater environment. Time and position data are the two key parameters to accurately define the position of an object. Moreover, due to climate change there is now a need to constrain energy consumption by UWSN to limit carbon emission to meet net-zero target by 2050. To meet these challenges, we have developed an efficient localization algorithm for determining an object position based on the angle and distance of arrival of beacon signals. We have considered the factors like sensor nodes not being in time sync with each other and the fact that the speed of sound varies in water. Our simulation results show that the proposed approach can achieve great localization accuracy while accounting for temporal synchronization inaccuracies. When compared to existing localization approaches, the mean estimation error (MEE) and energy consumption figures, the proposed approach outperforms them. The MEEs is shown to vary between 84.2154m and 93.8275m for four trials, 61.2256m and 92.7956m for eight trials, and 42.6584m and 119.5228m for twelve trials. Comparatively, the distance-based measurements show higher accuracy than the angle-based measurements

Magnetic phase diagram of weakly pinned type-II superconductors

The phenomenon of superconductivity was discovered in 1911, however, the methodology to classify and distinguish type-IT superconductivity was established only in late fifties after Abrikosov's prediction of a flux line lattice in 1957. The advent of high temperature superconductors (HTSC) in 1986 focused attention onto identifying and classifying other possible phases of vortex matter in all classes of superconductors by a variety of techniques. We have collated evidences in support of a proposal to construct a generic phase diagram for weakly pinned superconducting systems, based on their responses to ac and de magnetic fields. The phase diagram comprises quasi-glassy phases, like, the Bragg glass, a vortex glass and a reentrant glass in addition to the (completely) amorphous phases of pinned and unpinned variety. The characteristic metastability and thermomagnetic history dependent features recognized amongst various glassy vortex phases suggest close connections between vortex matter and other disordered condensed matter systems, like, spin glasses, super cooled liquids/ structural glasses, etc. A novel quenched random disorder driven fracturing transition stands out amongst other noteworthy facets of weakly vortex pinned vortex matter

Enhancement of Precise Underwater Object Localization

Underwater communication applications extensively use localization services for object identification. Because of their significant impact on ocean exploration and monitoring, underwater wireless sensor networks (UWSN) are becoming increasingly popular, and acoustic communications have largely overtaken radio frequency (RF) broadcasts as the dominant means of communication. The two localization methods that are most frequently employed are those that estimate the angle of arrival (AOA) and the time difference of arrival (TDoA). The military and civilian sectors rely heavily on UWSN for object identification in the underwater environment. As a result, there is a need in UWSN for an accurate localization technique that accounts for dynamic nature of the underwater environment. Time and position data are the two key parameters to accurately define the position of an object. Moreover, due to climate change there is now a need to constrain energy consumption by UWSN to limit carbon emission to meet net-zero target by 2050. To meet these challenges, we have developed an efficient localization algorithm for determining an object position based on the angle and distance of arrival of beacon signals. We have considered the factors like sensor nodes not being in time sync with each other and the fact that the speed of sound varies in water. Our simulation results show that the proposed approach can achieve great localization accuracy while accounting for temporal synchronization inaccuracies. When compared to existing localization approaches, the mean estimation error (MEE) and energy consumption figures, the proposed approach outperforms them. The MEEs is shown to vary between 84.2154m and 93.8275m for four trials, 61.2256m and 92.7956m for eight trials, and 42.6584m and 119.5228m for twelve trials. Comparatively, the distance-based measurements show higher accuracy than the angle-based measurements