Kinetics and Mechanisms of Phosphorus Adsorption in Soils from Diverse Ecological Zones in the Source Area of a Drinking-Water Reservoir.

On-site soils are increasingly used in the treatment and restoration of ecosystems to harmonize with the local landscape and minimize costs. Eight natural soils from diverse ecological zones in the source area of a drinking-water reservoir in central China are used as adsorbents for the uptake of phosphorus from aqueous solutions. The X-ray fluorescence (XRF) spectrometric and BET (Brunauer-Emmett-Teller) tests and the Scanning Electron Microscopy (SEM) and Fourier Transform Infrared (FTIR) spectral analyses are carried out to investigate the soils' chemical properties and their potential changes with adsorbed phosphorous from aqueous solutions. The intra-particle diffusion, pseudo-first-order, and pseudo-second-order kinetic models describe the adsorption kinetic processes. Our results indicate that the adsorption processes of phosphorus in soils occurred in three stages and that the rate-controlling steps are not solely dependent on intra-particle diffusion. A quantitative comparison of two kinetics models based on their linear and non-linear representations, and using the chi-square (χ2) test and the coefficient of determination (r2), indicates that the adsorptive properties of the soils are best described by the non-linear pseudo-second-order kinetic model. The adsorption characteristics of aqueous phosphorous are determined along with the essential kinetic parameters

Transmit Diversity Assisted Space Shift Keying for Colocated and Distributed/Cooperative MIMO Elements

Space Shift Keying (SSK) modulation is a recently proposed MIMO technique, which activates only a single transmit antenna during each time slot and uses the specific index of the activated transmit antenna to implicitly convey information. Activating a single antenna is beneficial in terms of eliminating the inter-channel interference, and mitigates the peak-to-mean power ratio, while avoiding the need for synchronisation among transmit antennas. However, this benefit is achieved at a sacrifice, since the transmit diversity gain potential of the multiple transmit antennas is not fully exploited in existing SSK assisted systems. Furthermore, a high SSK throughput requires the transmitter to employ a high number of transmit antennas, which is not always practical. Hence, we propose four algorithms, namely open-loop Space Time Space Shift Keying (ST-SSK), closed-loop feedback-aided phase rotation, feedback-aided power allocation, and cooperative ST-SSK, for the sake of achieving a diversity gain. The performance improvements of the proposed schemes are demonstrated by Monte-Carlo simulations for spatially independent Rayleigh fading channels. Their robustness against channel estimation errors is also considered. We advocate the proposed ST-SSK techniques, which are capable of achieving a transmit diversity gain of about 10 dB at a BER of 10-5, at a cost of imposing a moderate throughput loss dedicated to a modest feedback overhead. Furthermore, our proposed ST-SSK scheme lends itself to efficient communication, because the deleterious effects of deep shadow fading no longer impose spatial correlation on the signals received by the antennas, which cannot be readily avoided by co-located antenna elements