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( Jianrong Bao ),( Bin Jiang ),( Chao Liu ),( Xianyang Jiang ),( Minhong Sun ) 한국인터넷정보학회 2017 KSII Transactions on Internet and Information Syst Vol.11 No.7
In a single-source and multi-relay amplify-forward (AF) cooperative network, the outage probability and the power allocation are two key factors to influence the performance of an entire system. In this paper, an optimized AF relay selection by an exclusive method and near optimal power allocation (NOPA) is proposed for both good outage probability and power efficiency. Given the same power at the source and the relay nodes, a threshold for selecting the relay nodes is deduced and employed to minimize the average outage probability. It mainly excludes the relay nodes with much higher thresholds over the aforementioned threshold and thus the remainders of the relay nodes participate in cooperative forwarding efficiently. So the proposed scheme can improve the utility of the resources in the cooperative multi-relay system, as well as reduce the computational complexity. In addition, based on the proposed scheme, a NOPA is also suggested to approach sub-optimal power efficiency with low complexity. Simulation results show that the proposed scheme obtains about 2.1dB and 5.8dB performance gain at outage probability of 10<sup>-4</sup>, when compared with the all-relay-forward (6 participated relays) and the single-relay-forward schemes. Furthermore, it obtains the minimum outage probability among all selective relay schemes with the same number of the relays. Meanwhile, it approaches closely to the optimal exhaustive scheme, thus reduce much complexity. Moreover, the proposed NOPA scheme achieves better outage probability than those of the equal power allocation schemes. Therefore, the proposed scheme can obtain good outage probability, low computational complexity and high power efficiency, which makes it pragmatic efficiently in the single-source and multi-relay AF based cooperative networks.
Static and dynamic characteristics of a novel moving magnet linear compressor
Hong-yue Chen,Zhangquan Lv,Xianyang Liu,Chen Chen 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.1
Linear compressors are popular in the field of household refrigeration due to their high efficiency and excellent capacity modulation capability. In this study, we proposed a novel moving magnet linear compressor and investigated its static and dynamic characteristics. Static performance included static shaft force, force constant, and magnetic spring, which were examined via finite element analysis and verified by conducting specific thrust experiments. For dynamic characteristics, resonance frequency, piston stroke, and piston offset were calculated by considering the magnetic spring effect. Compared with the results that didn’t consider the magnetic spring effect, higher accuracy was achieved under various conditions. In addition, piston offset increased with discharge pressure, but it was insensitive to changes in piston stroke. The motor efficiency of the designed linear compressor prototype can reach 0.92 under no-load condition and 0.80 under a discharge pressure of 0.6 MPa with a stroke of 9 mm under air condition.