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BACKGROUND: As a special residue containing zinc and manganese, spent Zn-Mn batteries cause a serious concern due to their toxicity, abundance and permanence in the environment, and biotechnological recovery of Zn and Mn is one method of recycling thiswaste. In this study identification of the optimum values of the effective parameters in biotechnological processes was investigated using response surfacemethodology. RESULTS: The released dose of Zn andMnwas highly dependent on many parameters. Non-linear equationswere formulated to describe the relationship between bioleaching efficiency of Zn andMn and four important parameters. The optimum parameter values were determined as follows: dose of mixed energy substrates, exogenous-acid pH adjustment, incubating temperature and pulp density of 28 g L-1, 1.9, 33 °C, 9.7%, respectively, for Zn release and 29 g L-1, 1.8, 36.7 °C, 8%, respectively, for Mn mobilization. Themaximum predictive extraction efficiency of Zn andMn was 52.5% and 52.4%, respectively. CONCLUSION: The maximum efficiency of extraction of both Zn andMn reached 50% under optimum conditions after 9 days of bioleaching. Additionally, XRD analyses suggested that Zn andMn existed mainly as Hetaerolite (ZnMn2O4) in the spent Zn-Mn batteries, which gradually disappeared and released Zn2+ and Mn2+ into solution during bioleaching process. [ABSTRACT FROM AUTHOR]

ABSTRACT In this paper, concerning underwater acoustic (UWA) communications, we propose a wavelet filter bank system as the extension of orthogonal frequency-division multiplexing system. We exploit the convolutional structure of a UWA channel and formulate the pilot-assisted channel estimation as a sparse recovery problem. Then, we investigate the restricted isometry property of the measurement matrix via eigenvalue analysis and Gershgorin circle theorem. The sparse recovery problem is proven to satisfy the restricted isometry property. Moreover, we also propose a low-complexity complex-field homotopy algorithm for sparse channel estimation, regarding the fact that the channel taps of each path are usually complex valued in practice. Simulation results show that the wavelet filter bank system achieves more accurate UWA channel estimation performance than orthogonal frequency-division multiplexing system under the same conditions of bandwidth, duration, data rate and channel profile. The proposed complex homotopy algorithm outperforms orthogonal matching pursuit (OMP) and stagewise OMP in both systems, whereas its computational complexity is similar to OMP. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Pilot power allocation is investigated under the framework of physical layer secure communications in time‐division duplex systems, where the secret keys are generated from the estimates of sparse wireless channels. The joint optimisation of secret key capacity and sparse channel estimation performance based on pilot power allocation is formulated as a convex optimisation problem. Considering the fairness between these two sides, a scaling factor is introduced. Then, a scheme is proposed to fast solve the problem by looking up a table and using existing optimisation solvers. Simulation results show that a proper scaling factor can make a trade‐off between the secret key capacity and sparse channel estimation performance. [ABSTRACT FROM AUTHOR]

The joint sparsity of uplink channels in massive multi‐input–multi‐output (MIMO) systems is explored and a block sparse model is proposed for joint channel estimation. The block coherence of this model is analysed. It is indicated that as the number of antennas at the base station grows to be infinity, the block coherence will be zero. Then a block optimised orthogonal matching pursuit (BOOMP) algorithm is proposed. Simulation results verify the analysis and show that the joint estimation using the BOOMP algorithm can significantly improve the channel estimation performance. [ABSTRACT FROM AUTHOR]