Approaching the Outage Probability of the Amplify-and-Forward Relay Fading Channel

We study coding techniques for the single-relay non-orthogonal amplify-and-forward half-duplex relay fading channel. Unlike the multiple-antenna case, we show that 2times2 rotations induce large gains in outage probability with no increase in decoding complexity under iterative probabilistic decoding. We compare rotated and unrotated turbo-coded schemes and show that they both perform close to their corresponding outage limits.     

Impact of signal constellation expansion on the achievable diversity of pragmatic bit-interleaved space-time codes

This letter studies the effect of signal constellation expansion on the achievable diversity of pragmatic bit-interleaved space-time codes in quasistatic multiple antenna channels. Signal constellation expansion can be obtained either by increasing the size of the constellation in the complex plane or by using multidimensional linear mappings. By means of two simple constructions, we provide a comparison of the two options with message passing decoding. We show that multidimensional expansion achieves some performance advantage over complex-plane expansion at the cost of significantly higher decoding complexity and larger peak-to-average power ratio of the transmitted signals     

Error probability analysis of bit-interleaved coded modulation

This correspondence presents a simple method to accurately compute the error probability of bit-interleaved coded modulation (BICM). Thanks to the binary-input output-symmetric (BIOS) nature of the channel, the pairwise error probability (PEP) is equal to the tail probability of a sum of random variables with a particular distribution. This probability is in turn computed with a saddlepoint approximation. Its precision is numerically validated for coded transmission over standard Gaussian noise and fully interleaved fading channels for both convolutional and turbo-like codes.     

On the electrical anisotropy of conducting polypyrrole

The electrical properties of polypyrrole films prepared by electrochemical polymerization have been studied. The films were electrochemically and optically characterized. A very high anisotropy of the resistivities and mobilities, both parallel and perpendicular to the substrate, has been found. The results obtained are consistent with a hopping model for the conduction mechanism, with the interchain hopping much lower than the intrachain hopping, if it is assumed that the chains are oriented preferentially parallel to the substrate.     

Energy transfer from Eu2+ to trivalent rare earth ions in BaY2F8

An efficient energy transfer from divalent europium to trivalent rare earth ions appears in the luminescence spectrum of BaY₂F₈ when it is simultaneously doped with Eu²⁺ and Ln³⁺ ions (Ln = Tb, Ho, Er) as a consequence of a f-f emission of Eu²⁺.     

Relationship between the passivation of TiO2 particles and LLDPE photodegradation: a comparison between bulk and surface impacts

The effect of the concentration of alumina (Al₂O₃) and silica (SiO₂) used to passivate titanium dioxide (TiO₂) particles on the photodegradation of plastic films containing these particles was investigated. The films were made of linear low-density polyethylene (LLDPE) containing four different types of passivated TiO₂ particles. The UV degradation of the films was evaluated for the surface and the bulk by measuring the physical and chemical changes as a function of time. The surface chemical and physical degradation effects were measured by ATR-FTIR and AFM, respectively. A statistical Gaussian adjustment was proposed to correlate the AFM depth profiles of the eroded surfaces of the films after the photodegradation process. The bulk physical effect was evidenced by the loss of mechanical properties in the films. The results showed that the higher the concentrations of Al₂O₃ are, the better the inhibition of the photodegradation of the LLDPE films. In this study, it was confirmed that the observed UV degradation effect correlated at both the surface and bulk levels. The results showed not only the reduction of the photodegradative effect as the passivation of the TiO₂ particles increased but also the possibility of using these particles as UV stabilizers of LLDPE films. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47026.     

Crystallization behavior of iron- and boron-containing nepheline (Na2O·Al2O3·2SiO2) based model high-level nuclear waste glasses

This study focuses on understanding the relationship between iron redox, composition, and heat-treatment atmosphere in nepheline-based model high-level nuclear waste glasses. Glasses in the Na₂O–Al₂O₃–B₂O₃–Fe₂O₃–SiO₂ system with varying Al₂O₃/Fe₂O₃ and Na₂O/Fe₂O₃ ratios have been synthesized by melt-quench technique and studied for their crystallization behavior in different heating atmospheres—air, inert (N₂), and reducing (96%N₂–4%H₂). The compositional dependence of iron redox chemistry in glasses and the impact of heating environment and crystallization on iron coordination in glass-ceramics have been investigated by Mössbauer spectroscopy and vibrating sample magnetometry. While iron coordination in glasses and glass-ceramics changed as a function of glass chemistry, the heating atmosphere during crystallization exhibited minimal effect on iron redox. The change in heating atmosphere did not affect the phase assemblage but did affect the microstructural evolution. While glass-ceramics produced as a result of heat treatment in air and N₂ atmospheres developed a golden/brown colored iron-rich layer on their surface, those produced in a reducing atmosphere did not exhibit any such phenomenon. Furthermore, while this iron-rich layer was observed in glass-ceramics with varying Al₂O₃/Fe₂O₃ ratio, it was absent from glass-ceramics with varying Na₂O/Fe₂O₃ ratio. An explanation of these results has been provided on the basis of kinetics of diffusion of oxygen and network modifiers in the glasses under different thermodynamic conditions. The plausible implications of the formation of iron-rich layer on the surface of glass-ceramics on the chemical durability of high-level nuclear waste glasses have been discussed.     

Investigation of Performance Enhancements for Air Brayton/ORC Combined Cycles for Small (~ 2 MWe) Power Systems and a Moderate Heat Source Temperature

JOM - Attractive power generation cycles from economic and sustainability considerations are highly efficient and require minimal cooling water. Air Brayton cycles (ABCs) require no cooling water;...