A facile ultrasonication method was used to uniformly mix nanospindle-shaped FeOOH (80-100 nm) and a conductive matrix of graphene oxide (GO) to form FeOOH/GO composites. No carbon peak was observed in the X-ray diffraction pattern, indicating that the graphene oxide did not stack together and that the dispersion of graphene was very high. X-ray photoelectron spectroscopy (XPS) tests showed that the formation of Fe-O-C bonds played a positive role in electron transport, revealing that it has a certain impact on the electrochemical performance of FeOOH/GO. The FeOOH/GO was further characterized by TGA, and the content of GO in the synthesized sample was 6.68%. Compared with that of FeOOH, the initial discharge capacity of FeOOH/GO could reach 1437.28 mAh/g. Additionally, compared to that of pure FeOOH, the reversibility of the electrochemical reaction of FeOOH/GO was improved, and the impedance value was reduced. Finally, FeOOH/GO was used directly as a lithium-ion battery (LIB) anode material to improve the kinetics of the Lithium ions insertion/extraction process and improve ionic conductivity.

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In recent years, the access of massive communication devices leads to the insufficient spectrum resources of wireless networks. One of the practical means to resolve the problem is to build cognitive radio networks (CRNs), which can realize the sharing of spectrum resources between primary and secondary users, thereby improving the utilization rate of wireless spectrum resources. To this end, the CRNs are utilized to establish the Wyner’s eavesdropping model over the Beaulieu-Xie fading channels. We mainly deduce the accurate expressions of secrecy outage probability and strictly positive secrecy capacity to explore the performance of physical layer security. Moreover, the better overlap between the statistical simulation and the theoretical results indicates the correctness of the theoretical analysis equation. The interesting results are that both increasing the P max and decreasing the C t h can improve the security performance. This work is a good reference and guidance for modeling CRNs (Internet of Things, fifth generation, cell phone networks, etc.) and security performance evaluation.

In this paper, the statistical characteristics of the multi-cascade κ-μ shadowed fading channels are investigated and analyzed under the classic Wyner’s eavesdropping model. In particular, the general accurate expressions of the probability density function and the cumulative distribution function for amplitude and signal-to-noise ratio (SNR) are derived for the first time. Moreover, we further utilize the two performance evaluation metrics including outage probability and intercept probability to investigate the impacts of cascade number and channel parameters on reliability and security. Finally, the theoretical results are consistent with the simulations, proving the correctness of the derivation. The interesting conclusion is that when the average SNR is greater than 2 dB, the reliability of the multi-cascade model will decrease as the number of cascade increases; on the contrary, more cascading can lead to stronger anti-eavesdropping ability.

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The underwater acoustics is primary and most effective method for underwater object detection and the complex underwater acoustics battlefield environment can be visually described by the three-dimensional (3D) energy field. Through solving the 3D propagation models, the traditional underwater acoustics volume data can be obtained, but it is large amount of calculation. In this paper, a novel modeling approach, which transforms two-dimensional (2D) wave equation into 2D space and optimizes energy loss propagation model, is proposed. In this way, the information for the obtained volume data will not be lost too much. At the same time, it can meet the requirements of data processing for the real-time visualization. In the process of volume rendering, 3D texture mapping methods is used. The experimental results are evaluated on data size and frame rate, showing that our approach outperforms other approaches and the approach can achieve better results in real time and visual effects.

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