Energy-efficient Buffer-aided Optimal Relay Selection Scheme with Power Adaptation and Inter-relay Interference Cancellation

( Xiaorong Xu ),( Liang Li ),( Yingbiao Yao ),( Xianyang Jiang ),( Sanqing Hu ) 한국인터넷정보학회 2016 KSII Transactions on Internet and Information Syst Vol.10 No.11

Considering the tradeoff between energy consumption and outage behavior in buffer-aided relay selection, a novel energy-efficient buffer-aided optimal relay selection scheme with power adaptation and Inter-Relay Interference (IRI) cancellation is proposed. In the proposed scheme, energy consumption minimization is the objective with the consideration of relay buffer state, outage probability and relay power control, in order to eliminate IRI. The proposed scheme selects a pair of optimal relays from multiple candidate relays, denoted as optimal receive relay and optimal transmit relay respectively. Source-relay and relay-destination communications can be performed within a time-slot, which performs as Full-Duplex (FD) relaying. Markov chain model is applied to analyze the evolution of relay buffer states. System steady state outage probability and achievable diversity order are derived respectively. In addition, packet transmission delay and power reduction performance are investigated with a specific analysis. Numerical results show that the proposed scheme outperforms other relay selection schemes in terms of outage behavior with power adaptation and IRI cancellation in the same relay number and buffer size scenario. Compared with Buffer State relay selection method, the proposed scheme reduces transmission delay significantly with the same amount of relays. Average transmit power reduction can be implemented to relays with the increasing of relay number and buffer size, which realizes the tradeoff between energy-efficiency, outage behavior and delay performance in green cooperative communications.

Joint Subcarrier and Bit Allocation for Secondary User with Primary Users` Cooperation

( Xiaorong Xu ),( Yu-dong Yao ),( Sanqing Hu ),( Yingbiao Yao ) 한국인터넷정보학회 2013 KSII Transactions on Internet and Information Syst Vol.7 No.12

Interference between primary user (PU) and secondary user (SU) transceivers should be mitigated in order to implement underlay spectrum sharing in cognitive radio networks (CRN). Considering this scenario, an improved joint subcarrier and bit allocation scheme for cognitive user with primary users` cooperation (PU Coop) in CRN is proposed. In this scheme, the optimization problem is formulated to minimize the average interference power level at the PU receiver via PU Coop, which guarantees a higher primary signal to interference plus noise ratio (SINR) while maintaining the secondary user total rate constraint. The joint optimal scheme is separated into subcarrier allocation and bit assignment in each subcarrier via arith-metric geo-metric (AM-GM) inequality with asymptotical optimization solution. Moreover, the joint subcarrier and bit optimization scheme, which is evaluated by the available SU subcarriers and the allocated bits, is analyzed in the proposed PU Coop model. The performance of cognitive spectral efficiency and the average interference power level are investigated. Numerical analysis indicates that the SU`s spectral efficiency increases significantly compared with the PU non-cooperation scenario. Moreover, the interference power level decreases dramatically for the proposed scheme compared with the traditional Hughes-Hartogs bit allocation scheme.

Joint Beamforming and Power Splitting Design for Physical Layer Security in Cognitive SWIPT Decode-and-Forward Relay Networks

( Xiaorong Xu ),( Andi Hu ),( Yingbiao Yao ),( Wei Feng ) 한국인터넷정보학회 2020 KSII Transactions on Internet and Information Syst Vol.14 No.1

In an underlay cognitive simultaneous wireless information and power transfer (SWIPT) network, communication from secondary user (SU) to secondary destination (SD) is accomplished with decode-and-forward (DF) relays. Multiple energy-constrained relays are assumed to harvest energy from SU via power splitting (PS) protocol and complete SU secure information transmission with beamforming. Hence, physical layer security (PLS) is investigated in cognitive SWIPT network. In order to interfere with eavesdropper and improve relay’s energy efficiency, a destination-assisted jamming scheme is proposed. Namely, SD transmits artificial noise (AN) to interfere with eavesdropping, while jamming signal can also provide harvested energy to relays. Beamforming vector and power splitting ratio are jointly optimized with the objective of SU secrecy capacity maximization. We solve this non-convex optimization problem via a general two-stage procedure. Firstly, we obtain the optimal beamforming vector through semi-definite relaxation (SDR) method with a fixed power splitting ratio. Secondly, the best power splitting ratio can be obtained by one-dimensional search. We provide simulation results to verify the proposed solution. Simulation results show that the scheme achieves the maximum SD secrecy rate with appropriate selection of power splitting ratio, and the proposed scheme guarantees security in cognitive SWIPT networks.

Energy-efficient wing design for flapping wing micro aerial vehicles

Zhonglai Wang,Xiaorong Hu,Yingdong Wu 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.9

Flapping wing micro aerial vehicles (FWMAVs) have attracted more attention during the development of the robotic systems field. The size of the flapping wing plays an important role in the lift force and torque generation based on quasi-steady aerodynamic model. Therefore, it is necessary to study energy-efficient design methods for wings to provide sufficient lift force and torque with minimal energy consumption for hovering flight. In this paper, the sensitive parameters for the lift force and power consumption were first selected based on design of experiment (DOE) and the parameter of the distributed wing stiffness was determined based on experimental data. Design optimization models for three different cases were then built by considering the lift force as one constraint and the energy consumption as the objective function. The combination of subset simulation and the gradient-based optimization was finally used for solving design optimization models, and the corresponding sensitivity analysis was provided.

Effect of Ni2Si Precipitates on Microstructure and Mechanical Properties of Cu–Zn Brasses

Wei Chen,Kai You,Jufang Yin,Ming Chen,Xiaolan Tao,Jiarui Hu,Xiaorong Chen,Qian Lei 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.10

Novel ultrahigh strength Ni2Sistrengthened brasses were fabricated, and microstructure and properties were investigatedusing scanning electron microscopy, optical microscopy, transmission electron microscopy, X-ray diffraction analysis, hardnessmeasurement, and electrical conductivity test. After optimal treatments (solid solution treated at 900 ℃ for 2 h, hotrolledby 80%, cold-rolled by 80%, and ageing treated at 300 ℃ for 8 h), the Cu-20Zn-3Ni-0.68Si alloy’s hardness, tensilestrength, yield strength, and electrical conductivity is 270.6 HV, 964 MPa, 933 MPa, 21.6%IACS, and 3.4%, respectively. δ-Ni2Si precipitates formed during the annealing process, which had a crystal orientation relationship with the matrix: (001)m// (001) δ, and [110]m// [100]δ. Quasi-cleavage fracture surfaces with shallow dimples were presented in both the Cu-20Zn-1.5Ni-0.34Si and the Cu-20Zn-3Ni-0.68Si alloy. These findings give a new method to develop new high strength low-costbrass copper materials.

Prevalence and Prognostic Role of PIK3CA/AKT1 Mutations in Chinese Breast Cancer Patients

Ling Deng,Xuehua Zhu,Yun Sun,Jiemin Wang,Xiaorong Zhong,Jiayuan Li,Min Hu,Hong Zheng 대한암학회 2019 Cancer Research and Treatment Vol.51 No.1

Purpose The prevalence of PIK3CA in Chinese breast cancer patients may be underestimated. Therefore, we investigated the distribution of somatic PIK3CA/AKT1mutations in Chinese breast cancer patients and explored their roles in tumor phenotypes and disease prognosis. Materials and Methods Tumors from 507 breast cancer patients were prospectively collected from the West China Hospital between 2008 and 2013. Whole exons of AKT1 and PIK3CAwere detected in freshfrozen tumors using next-generation sequencing, and correlations between PIK3CA/AKT1 mutations and clinicopathological features were analyzed. Results The AKT1mutation was found in 3.6% (18/507) of patients. Tumors from patients that carried the AKT1mutation were estrogen receptor (ER)+/progesterone receptor (PR)+/human epidermal growth factor receptor 2 (HER2) and were more likely to have high expression levels of Ki67. The prevalence of the PIK3CA mutation was 46.5% (236/507), and 35 patients carried two or three variants of the PIK3CA gene. PIK3CA mutations were associated with ER+/PR+/HER2 status. The prognosis of patients with one mutation in PIK3CA (or PIK3CA/AKT1) was not significantly different than that of patients with wild-type PIK3CA (or PIK3CA/AKT1), while patients with two or three variants in PIK3CA (or PIK3CA/AKT1) exhibited poorer outcomes in the entire group and in all three subgroups (ER+, HER2, Ki67 high), particularly with respect to overall survival. Conclusion A high frequency of somatic PIK3CA mutations was detected in Chinese breast cancer patients. In addition to the mutation frequency, the tumor mutational burden of the PIK3CA and AKT1 genes should also be of concern, as they may be associated with poor prognosis.