As the scale of power networks has expanded,the demand for multi-service transmission has gradually increased.The emergence of WiFi6 has improved the transmission efficiency and resource utilization of wireless networ...As the scale of power networks has expanded,the demand for multi-service transmission has gradually increased.The emergence of WiFi6 has improved the transmission efficiency and resource utilization of wireless networks.However,it still cannot cope with situations such as wireless access point(AP)failure.To solve this problem,this paper combines orthogonal fre-quency division multiple access(OFDMA)technology and dynamic channel optimization technology to design a fault-tolerant WiFi6 dynamic resource optimization method for achieving high quality wireless services in a wirelessly covered network even when an AP fails.First,under the premise of AP layout with strong coverage over the whole area,a faulty AP determination method based on beacon frames(BF)is designed.Then,the maximum signal-to-interference ratio(SINR)is used as the principle to select AP reconnection for the affected users.Finally,this paper designs a dynamic access selection model(DASM)for service frames of power Internet of Things(IoTs)and a schedul-ing access optimization model(SAO-MF)based on multi-frame transmission,which enables access optimization for differentiated services.For the above mechanisms,a heuristic resource allocation algorithm is proposed in SAO-MF.Simulation results show that the method can reduce the delay by 15%and improve the throughput by 55%,ensuring high-quality communication in power wireless networks.展开更多
The dynamic fracture behaviors of Ti-6Al-4V alloy at high strain rate loading were investigated systemically through Taylor impact test, over the range of impact velocities from 145 m/s to 306 m/s. The critical impact...The dynamic fracture behaviors of Ti-6Al-4V alloy at high strain rate loading were investigated systemically through Taylor impact test, over the range of impact velocities from 145 m/s to 306 m/s. The critical impact velocity of fracture ranges from 217 m/s to 236 m/s. Smooth surfaces and ductile dimple areas were observed on the fracture surfaces. As the impact velocity reached 260 m/s, the serious melting regions were also observed on the fracture surfaces. Self-organization of cracks emerges when the impact velocity reaches 260 m/s, while some special cracks whose ＂tips＂ are not sharp but arc and smooth, and without any evidence of deformation or adiabatic shear band were also observed on the impact end surfaces. Examination of the sections of these special cracks reveals that the cracks expand along the two maximum shear stress directions respectively, and finally intersect as a tridimensional ＂stagger ridge＂ structure.展开更多
The dynamic recrystallization（DRX） behavior of Ti-6Al-2Zr-1Mo-1V alloy was investigated at deformation temperature of 1000-1100 °C and strain rate of 10-3-1.0 s-1 by using compression test.The results show that...The dynamic recrystallization（DRX） behavior of Ti-6Al-2Zr-1Mo-1V alloy was investigated at deformation temperature of 1000-1100 °C and strain rate of 10-3-1.0 s-1 by using compression test.The results show that discontinuous dynamic recrystallization（DDRX） is the predominant recrystallization mechanism at temperature higher than 1050 °C and strain rate lower than 0.01 s-1.Meanwhile,continuous dynamic recrystallization is the main mechanism observed at temperature below 1050 °C and strain rate above 0.01 s-1,mixed with a few DDRX grains.In addition,decreasing strain rate and increasing deformation temperature are found to facilitate the progress of DRX and refinement of grains in the Ti alloy in β forging process.展开更多
基金supported by State Grid Jiangsu Electric Power Co.,Ltd.Science and Technology Project“Research on Low-Cost Wireless Coverage and Trusted Access Technologies for Underground Pipe Gallery Digital Network”(J2021081).
文摘As the scale of power networks has expanded,the demand for multi-service transmission has gradually increased.The emergence of WiFi6 has improved the transmission efficiency and resource utilization of wireless networks.However,it still cannot cope with situations such as wireless access point(AP)failure.To solve this problem,this paper combines orthogonal fre-quency division multiple access(OFDMA)technology and dynamic channel optimization technology to design a fault-tolerant WiFi6 dynamic resource optimization method for achieving high quality wireless services in a wirelessly covered network even when an AP fails.First,under the premise of AP layout with strong coverage over the whole area,a faulty AP determination method based on beacon frames(BF)is designed.Then,the maximum signal-to-interference ratio(SINR)is used as the principle to select AP reconnection for the affected users.Finally,this paper designs a dynamic access selection model(DASM)for service frames of power Internet of Things(IoTs)and a schedul-ing access optimization model(SAO-MF)based on multi-frame transmission,which enables access optimization for differentiated services.For the above mechanisms,a heuristic resource allocation algorithm is proposed in SAO-MF.Simulation results show that the method can reduce the delay by 15%and improve the throughput by 55%,ensuring high-quality communication in power wireless networks.
基金Project (51001014) supported by the Young Scientists Fund of the National Natural Science Foundation of China
文摘The dynamic fracture behaviors of Ti-6Al-4V alloy at high strain rate loading were investigated systemically through Taylor impact test, over the range of impact velocities from 145 m/s to 306 m/s. The critical impact velocity of fracture ranges from 217 m/s to 236 m/s. Smooth surfaces and ductile dimple areas were observed on the fracture surfaces. As the impact velocity reached 260 m/s, the serious melting regions were also observed on the fracture surfaces. Self-organization of cracks emerges when the impact velocity reaches 260 m/s, while some special cracks whose ＂tips＂ are not sharp but arc and smooth, and without any evidence of deformation or adiabatic shear band were also observed on the impact end surfaces. Examination of the sections of these special cracks reveals that the cracks expand along the two maximum shear stress directions respectively, and finally intersect as a tridimensional ＂stagger ridge＂ structure.
基金Project (2007CB613803) supported by the National Basic Research Program of ChinaProject (2010GQC0170) supported by the Natural Science Foundation of Jiangxi Province,ChinaProject (GJJ11159) supported by the Educational Committee of Jiangxi Province,China
文摘The dynamic recrystallization（DRX） behavior of Ti-6Al-2Zr-1Mo-1V alloy was investigated at deformation temperature of 1000-1100 °C and strain rate of 10-3-1.0 s-1 by using compression test.The results show that discontinuous dynamic recrystallization（DDRX） is the predominant recrystallization mechanism at temperature higher than 1050 °C and strain rate lower than 0.01 s-1.Meanwhile,continuous dynamic recrystallization is the main mechanism observed at temperature below 1050 °C and strain rate above 0.01 s-1,mixed with a few DDRX grains.In addition,decreasing strain rate and increasing deformation temperature are found to facilitate the progress of DRX and refinement of grains in the Ti alloy in β forging process.
