Generalized M-2M Mapping Scheme for SLM and PTS Based OFDM Systems Without Side-Information

Orthogonal frequency division multiplexing (OFDM) is an attractive multicarrier modulation scheme, but it suffers from the problem of high peak-to-average power ratio (PAPR). Selected mapping (SLM) and partial transmit sequences (PTS) are two well known, distortion-less techniques with good PAPR reduction capabilities. But, both the methods require side information (SI) about the phase rotation factors to recover the original data signal at the receiving end. The transmission of SI not only results in data rate loss but also, in BER performance degradation if SI gets corrupted over the channel. In this paper we have proposed a new mapping scheme, named “ $M\text{- }2M$ Mapping scheme” for SLM and PTS based methods to completely eliminate the requirement of SI at the receiver. In this scheme $M$ data points are mapped to the constellation points of 2M-ary modulation scheme using (1, j) as the phase rotation factors. Some criteria are suggested with which the method is applied for different constellation sizes, $M=4$ to $M=16$ . The method can be easily coupled with conventional SLM and PTS techniques. When compared with the existing methods like multi point square mapping, which do not need SI, our technique is scalable and provides good PAPR reduction capability with consistent BER performance.     

Enhancement of mechanical properties of biocompatible Ti–45Nb alloy by hydrostatic extrusion

β-Type titanium alloys are promising materials for orthopaedic implants due to their relatively low Young’s modulus and excellent biocompatibility. However, their strength is lower than those of α- or α + β-type titanium alloys. Grain refinement by severe plastic deformation (SPD) techniques provides a unique opportunity to enhance mechanical properties to prolong the lifetime of orthopaedic implants without changing their chemical composition. In this study, β-type Ti–45Nb (wt%) biomedical alloy in the form of 30 mm rod was subjected to hydrostatic extrusion (HE) to refine the microstructure and improve its mechanical properties. HE processing was carried out at room temperature without intermediate annealing in a multi-step process, up to an accumulative true strain of 3.5. Significant microstructure refinement from a coarse-grained region to an ultrafine-grained one was observed by optical and transmission electron microscopy. Vickers hardness measurements (HV_0.2) demonstrated that the strength of the alloy increased from about 150 to 210 HV_0.2. Nevertheless, the measurements of Young’s modulus by nanoindentation showed no significant changes. This finding is substantiated by X-ray diffraction analyses which did not exhibit any phase transformation out of the bcc phase being present still before processing by HE. These results thus indicate that HE is a promising SPD method to obtain significant grain refinement and enhance strength of β-type Ti–45Nb alloy without changing its low Young’s modulus, being one prerequisite for biomedical application.     

Ce-doped bismuth ferrite thin films with improved electrical and functional properties

Bi_1?xCe_xFeO₃ (BCFO) thin film capacitors (x = 0 to 0.2) are fabricated on indium tin oxide coated corning glass substrate by chemical solution deposition method. X-ray diffraction results show a partial phase transition from rhombohedral to tetragonal structure induced in BCFO thin film having preferred (110) orientation with increase in Ce dopant concentration. Current density–field (J–E) characteristics indicate that the leakage current density reduces by several orders of magnitude in Ce-doped BFO thin films resulting from smaller grain sizes and smoother surfaces. Space-charge-limited current and Fowler–Nordheim tunneling are identified as dominating leakage behavior in BCFO thin film capacitors at moderate and high field regions, respectively. Enhanced ferroelectric response with well-saturated (P–E) hysteresis loop is observed for Bi_0.88Ce_0.12FeO₃ thin film having high remnant polarization (P _r—127 µC/cm²) at an applied field of 1080 kV/cm. Bi_0.88Ce_0.12FeO₃ thin film exhibiting well-defined capacitance–field (C–E) butterfly loop with dielectric loss (tan δ—0.03) measured at 10 kHz suggested good ferroelectric properties with high tunability of about 88 %.     

ND++ – an extended IPv6 Neighbor Discovery protocol for enhanced stateless address autoconfiguration in MANETs

Recent trends in information and communications technologies are oriented toward the design of the Future Internet and the Internet of Things. While IPv6‐based mobile ad hoc networks (MANETs) are emerging as an important building block of these new technologies, it is necessary to come up with adequate self‐configuration capabilities allowing for seamless and automated configuration of addresses in mobile environment. The mechanisms of stateless address autoconfiguration proposed for IPv6 networks are supposed to automate some configuration steps; however, they would need to be aligned with the requirements imposed by MANET networks. Therefore, in this article, we present Neighbor Discovery ++ – an extended IPv6 Neighbor Discovery protocol for enhanced duplicate address detection in MANETs, which provides increased coverage of network nodes, while minimizing protocol overhead. It exploits efficient flooding mechanism on the basis of the multipoint relay concept, which makes it an interesting approach also for large‐scale networks. Trials performed on the designated real‐world testbed platform indicate that ND++ is a promising solution to support efficient address autoconfiguration in MANETs. Copyright © 2012 John Wiley & Sons, Ltd.     

Behavioural analysis of a hydroelectric production power plant under reworking scheme

By high calibre of the fundamental nature of electric power, both of our economic and personal interests, a system is expected to supply as electrical energy as possible with the highest degree of quality and reliability. This research work aimed to evaluate the reliability measures of a hydroelectric power station. The results of this study are deliberate to provide the improved criteria for upcoming proposals, and serves as a basis for generation expansion planning of hydroelectric power stations. This paper presents a Markov-process based mathematical model for a hydroelectric power plant. The important reliability measures have been derived and discussed with the help of failure and repair rates through the analysis. This research gives a clear view of how the hydropower plants are modelled by defining the states under the failure and repair rates.     

Formation of blisters in kapton polymer by the effect of 1.25 MeV gamma irradiation

The surface morphology, chemical, optical, and structural response of 1.25 MeV gamma rays irradiation at various doses ranging from 16 to 300 kGy on Kapton polymer samples were studied by using scanning electron microscope (SEM), Fourier Transform Infrared (FTIR), ultraviolet/visible absorption (UV/VIS) and X‐ray diffraction (XRD). The morphology study shows the blisters formation on the Kapton polymer surface due to 1.25 MeV gamma rays irradiation at ambient temperature. This observation provides a basis for the quantitative evaluation of FTIR results obtained for thermally stable polymer on the chemical bond deterioration with increasing gamma irradiation. The blistering mechanism is correlated with the internal gases (CO, H₂) released due to gamma radiation induced damages. The recorded UV–VIS spectrum shows a maximum absorption around the wavelength 540 nm. However, the nature of the spectra does not change due to gamma irradiation but a shift in absorption edge towards the higher wavelength side has been observed with increasing dose. The optical data shows an increase in the calculated band gap at the highest dose. The diffraction pattern of virgin sample shows that polymer is semicrystalline, but due to irradiation, a decrease in the peak intensity and FWHM and an increase in the crystallite size at the highest dose level of 300 kGy have been observed. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Fractographic Montage for a Si3N4–SiC Nanocomposite

A silicon nitride–silicon carbide nanocomposite has been prepared by an in situ method that utilizes C+SiO₂ carbo-thermal reduction during the sintering process. The materials consist of a silicon nitride matrix, with an average grain size of 140 nm, and inter- and intragranular SiC particles with sizes of approximately 250 and 45 nm, respectively. The four-point bending strength and its distribution were investigated. The fracture origins were identified and characterized using fractographic methods, and a fractographic montage of the Weibull plot and fracture origins was constructed. The fracture origins were subsurface and volume located processing defects with sizes from 5 to 460 μm, mainly in the form of clusters of pores, together with clusters of large SiC grains.     

Polythiophene gold nanoparticles composite film for application to glucose sensor

Regioregular poly‐3‐hexylthiophene (regP3HT) and dithiobissuccinimidyl propionate (DTSP) have been used to prepare bifunctionalized gold nanoparticles (Bf AuNPs). Processable properties of regP3HT have been used to obtain regP3HT‐AuNPs‐DTSP film on a gold‐coated glass surface and the succinimidyl group of DTSP in this regP3HT‐AuNPs‐DTSP/Au electrode has been utilized for covalent immobilization of glucose oxidase (GOx). The UV‐visible (UV‐vis), scanning electron microscopy (SEM), and Fourier transform infrared (FTIR) spectroscopic studies have been used to characterize regP3HT‐AuNPs‐DTSP/Au and GOx‐regP3HT‐AuNPs‐DTSP/Au electrode, respectively. This GOx‐regP3HT‐AuNPs‐DTSP/Au bioelectrode shows response time of 10 s, linearity from 25 to 300 mg/dL of glucose and the value of Michaelis‐Menten constant as 5.85 mM (105.3 mg/dL). © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008