To improve the comprehensive mechanical properties of Al-Si-Cu alloy,it was treated by a high-pressure torsion process,and the effect of the deformation degree on the microstructure and properties of the Al-Si-Cu allo...To improve the comprehensive mechanical properties of Al-Si-Cu alloy,it was treated by a high-pressure torsion process,and the effect of the deformation degree on the microstructure and properties of the Al-Si-Cu alloy was studied.The results show that the reinforcements(β-Si andθ-CuAl_(2)phases)of the Al-Si-Cu alloy are dispersed in theα-Al matrix phase with finer phase size after the treatment.The processed samples exhibit grain sizes in the submicron or even nanometer range,which effectively improves the mechanical properties of the material.The hardness and strength of the deformed alloy are both significantly raised to 268 HV and 390.04 MPa by 10 turns HPT process,and the fracture morphology shows that the material gradually transits from brittle to plastic before and after deformation.The elements interdiffusion at the interface between the phases has also been effectively enhanced.In addition,it is found that the severe plastic deformation at room temperature induces a ternary eutectic reaction,resulting in the formation of ternary Al+Si+CuAl_(2)eutectic.展开更多
宽带电力线载波通信采用自适应正交频分复用(orthogonal frequency division multiplexing,OFDM)技术有效提升了通信速率,为实现电力多业务应用提供了丰富的通信资源保证。现有研究多是基于单一层级的网络状态进行资源划分,各业务所需...宽带电力线载波通信采用自适应正交频分复用(orthogonal frequency division multiplexing,OFDM)技术有效提升了通信速率,为实现电力多业务应用提供了丰富的通信资源保证。现有研究多是基于单一层级的网络状态进行资源划分,各业务所需速率多为静态预先设定且为固定值,因此会导致各子载波信噪比存在明显差异性的情况下,系统无法根据业务的不同QoS需求及网络中实时队列长度对所需资源进行自适应调整。抑或缺乏依据当前网络状态的动态调配灵活性,导致通信资源的浪费或通信需求无法满足。文章针对并发多业务的资源分配问题,通过应用层、数据链路层、物理层间的数据映射,建立了跨层资源分配模型。根据应用层电力多业务的QoS需求、数据链路层缓存区内队列长度以及底层物理层子载波和系统功率,将数据分组等待时延以及分组损耗映射为实时/非实时类用户的最低传输速率,进而提出基于效用函数的MAC层用户调度和物理层资源分配算法。最后通过典型电力线信道环境仿真实验发现:所提算法比现有2个电力线载波资源分配算法在多业务并发场景下单用户的吞吐量最高可提升47.62%,分组等待时延缩短37.25%,分组损耗降低72.04%。更好的资源分配使得文章所提算法能够在保证QoS需求情况下,允许更多的用户同时接入系统,有效提升了基于OFDM的宽带电力线载波通信资源利用率。展开更多
基金Funded by the National Natural Science Foundation of China(No.51905215)Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.SJCX23_1233)+1 种基金Major Scientific and Technological Innovation Project of Shandong Province of China(No.2019JZZY020111)the National College Students Innovation and Entrepreneurship Training Program of China(No.CX2022415)。
文摘To improve the comprehensive mechanical properties of Al-Si-Cu alloy,it was treated by a high-pressure torsion process,and the effect of the deformation degree on the microstructure and properties of the Al-Si-Cu alloy was studied.The results show that the reinforcements(β-Si andθ-CuAl_(2)phases)of the Al-Si-Cu alloy are dispersed in theα-Al matrix phase with finer phase size after the treatment.The processed samples exhibit grain sizes in the submicron or even nanometer range,which effectively improves the mechanical properties of the material.The hardness and strength of the deformed alloy are both significantly raised to 268 HV and 390.04 MPa by 10 turns HPT process,and the fracture morphology shows that the material gradually transits from brittle to plastic before and after deformation.The elements interdiffusion at the interface between the phases has also been effectively enhanced.In addition,it is found that the severe plastic deformation at room temperature induces a ternary eutectic reaction,resulting in the formation of ternary Al+Si+CuAl_(2)eutectic.
文摘宽带电力线载波通信采用自适应正交频分复用(orthogonal frequency division multiplexing,OFDM)技术有效提升了通信速率,为实现电力多业务应用提供了丰富的通信资源保证。现有研究多是基于单一层级的网络状态进行资源划分,各业务所需速率多为静态预先设定且为固定值,因此会导致各子载波信噪比存在明显差异性的情况下,系统无法根据业务的不同QoS需求及网络中实时队列长度对所需资源进行自适应调整。抑或缺乏依据当前网络状态的动态调配灵活性,导致通信资源的浪费或通信需求无法满足。文章针对并发多业务的资源分配问题,通过应用层、数据链路层、物理层间的数据映射,建立了跨层资源分配模型。根据应用层电力多业务的QoS需求、数据链路层缓存区内队列长度以及底层物理层子载波和系统功率,将数据分组等待时延以及分组损耗映射为实时/非实时类用户的最低传输速率,进而提出基于效用函数的MAC层用户调度和物理层资源分配算法。最后通过典型电力线信道环境仿真实验发现:所提算法比现有2个电力线载波资源分配算法在多业务并发场景下单用户的吞吐量最高可提升47.62%,分组等待时延缩短37.25%,分组损耗降低72.04%。更好的资源分配使得文章所提算法能够在保证QoS需求情况下,允许更多的用户同时接入系统,有效提升了基于OFDM的宽带电力线载波通信资源利用率。
