Intelligent Wireless Communications Enabled by Cognitive Radio and Machine Learning

The ability to intelligently utilize resources to meet the need of growing diversity in services and user behavior marks the future of wireless communication systems. Intelligent wireless communications aims at enabling the system to perceive and assess the available resources, to autonomously learn to adapt to the perceived wireless environment, and to reconfigure its operating mode to maximize the utility of the available resources. The perception capability and reconfigurability are the essential features of cognitive radio while modern machine learning techniques project great potential in system adaptation. In this paper, we discuss the development of the cognitive radio technology and machine learning techniques and emphasize their roles in improving spectrum and energy utility of wireless communication systems. We describe the state-of-the-art of relevant techniques, covering spectrum sensing and access approaches and powerful machine learning algorithms that enable spectrum and energy-efficient communications in dynamic wireless environments. We also present practical applications of these techniques and identify further research challenges in cognitive radio and machine learning as applied to the existing and future wireless communication systems.

Recent progress in organic electrodes for zinc-ion batteries

Organic zinc-ion batteries(OZIBs)are emerging rechargeable energy storage devices and have attracted increasing attention as one of the promising alternatives of lithium-ion batteries,benefiting from the Zn metal(low cost,safety and small ionic size)and organic electrodes(flexibility,green and designable molecular structure).Organic electrodes have exhibited fine electrochemical performance in ZIBs,but the research is still in infancy and hampered by some issues.Hence,to provide insight into OZIBs,this review summarizes the progress of organic cathode materials for ZIBs and points out the existing challenges and then addresses potential solutions.It is hoped that this review can stimulate the researchers to further develop high-performance OZIBs.

Asymptotic attenuation of a class of nonlinear systems with unknown sinusoidal disturbances

In this paper,nonlinear observers are incorporated into the adaptive control to synthesize controllers for a class of uncertain nonlinear systems with unknown sinusoidal disturbances which are presented in matched and unmatched forms.In addition to magnitudes and phases,frequencies of the sinusoidal disturbances need not be known as well,so long as the overall order is known.Nonlinear observers are constructed to eliminate the effect of unknown sinusoidal disturbances to improve the steady-state output tracking performance-asymptotic output tracking is achieved.The adaptation law is used to obtain the estimate of all unknown parameters.The presented disturbance decoupling algorithms can deal with matched and unmatched unknown sinusoidal disturbances.

A branched dihydrophenazine-based polymer as a cathode material to achieve dual-ion batteries with high energy and power density

Organic electrode materials have exhibited good electrochemical performance in batteries,but their voltages and rate capabilities still require improvement to meet the increasing demand for batteries with high energy and power density.Herein,we design and synthesize a branched dihydrophenazine-based polymer(p-TPPZ)as a cathode material for dual-ion batteries(DIBs)through delicate molecular design.Compared with the linear dihydrophenazine-based polymer(p-DPPZ,with a theoretical capacity of 209 mAh g^(−1)),p-TPPZ possessed a higher theoretical capacity of 233 mAh g^(−1)and lower highest occupied molecular orbital energy levels,which resulted in a high actual capacity(169.3 mAh g^(−1)at 0.5 C),an average discharge voltage of 3.65 V(vs.Li+/Li)and a high energy density(618.2 Wh kg^(−1),based on the cathode materials).The branched structure of p-TPPZ led to a larger specific surface area than that of p-DPPZ,which was beneficial for the electrolyte infiltration and fast ionic transport,contributing to the high power density.Due to the fast reaction kinetics,even at a power density of 23,725 W kg^(−1)(40 C),the energy density still reached 474.5 Wh kg^(−1).We also made a detailed investigation of the p-TPPZ cathode’s charge storage mechanism.This work will stimulate the further molecular design to develop organic batteries with both high energy and power density.