匝间短路是无刷直流电机(brushless DC motor,BLDCM)的常见故障之一,因此开展短路下电机在线检测非常关键。目前,关于BLDCM匝间短路在线检测的研究鲜见报道,同时BLDCM的机械结构、驱动方式与其他类型电机差异明显,现有的研究成果无法直...匝间短路是无刷直流电机(brushless DC motor,BLDCM)的常见故障之一,因此开展短路下电机在线检测非常关键。目前,关于BLDCM匝间短路在线检测的研究鲜见报道,同时BLDCM的机械结构、驱动方式与其他类型电机差异明显,现有的研究成果无法直接适用。为此,该文提出基于零序电压特性的无刷直流电机匝间短路在线检测法,构建新的特征参数指标。首先,建立匝间短路下绕组解析模型,理论推导故障下零序电压基频分量的演变特性;其次,联合三相电流与零序电压基频分量,提出全新的故障相定位参数与故障程度评估参数;最后,为了验证所提方法的有效性,联合Simulink仿真模型与实验平台开展研究,结果表明该方法能有效实现匝间短路的故障检测、故障相定位及故障程度评估。另外,该方法对电机瞬时状态具有鲁棒性,能够实现BLDCM匝间短路的实时检测。展开更多
Network function virtualization is a new network concept that moves network functions from dedicated hardware to software-defined applications running on standard high volume severs. In order to accomplish network ser...Network function virtualization is a new network concept that moves network functions from dedicated hardware to software-defined applications running on standard high volume severs. In order to accomplish network services, traffic flows are usually processed by a list of network functions in sequence which is defined by service function chain. By incorporating network function virtualization in inter-data center(DC) network, we can use the network resources intelligently and deploy network services faster. However, orchestrating service function chains across multiple data centers will incur high deployment cost, including the inter-data center bandwidth cost, virtual network function cost and the intra-data center bandwidth cost. In this paper, we orchestrate SFCs across multiple data centers, with a goal to minimize the overall cost. An integer linear programming(ILP) model is formulated and we provide a meta-heuristic algorithm named GBAO which contains three modules to solve it. We implemented our algorithm in Python and performed side-by-side comparison with prior algorithms. Simulation results show that our proposed algorithm reduces the overall cost by at least 21.4% over the existing algorithms for accommodating the same service function chain requests.展开更多
针对差分混沌-相关延时移位键控(DC-CDSK)存在的码间干扰而造成的比特误码率较高问题,提出了一种无码间干扰DC-CDSK混沌通信方案。通过改变混沌信号发生器的结构,确保发送的两路混沌信号严格正交,彻底解决了判决变量中码间干扰问题。推...针对差分混沌-相关延时移位键控(DC-CDSK)存在的码间干扰而造成的比特误码率较高问题,提出了一种无码间干扰DC-CDSK混沌通信方案。通过改变混沌信号发生器的结构,确保发送的两路混沌信号严格正交,彻底解决了判决变量中码间干扰问题。推导了在高斯白噪声信道中的比特误码率公式并完成仿真,结果表明,在一定信噪比和扩频因子条件下无码间干扰DC-CDSK比特误码率比原系统提高了2~3 d B。展开更多
文摘匝间短路是无刷直流电机(brushless DC motor,BLDCM)的常见故障之一,因此开展短路下电机在线检测非常关键。目前,关于BLDCM匝间短路在线检测的研究鲜见报道,同时BLDCM的机械结构、驱动方式与其他类型电机差异明显,现有的研究成果无法直接适用。为此,该文提出基于零序电压特性的无刷直流电机匝间短路在线检测法,构建新的特征参数指标。首先,建立匝间短路下绕组解析模型,理论推导故障下零序电压基频分量的演变特性;其次,联合三相电流与零序电压基频分量,提出全新的故障相定位参数与故障程度评估参数;最后,为了验证所提方法的有效性,联合Simulink仿真模型与实验平台开展研究,结果表明该方法能有效实现匝间短路的故障检测、故障相定位及故障程度评估。另外,该方法对电机瞬时状态具有鲁棒性,能够实现BLDCM匝间短路的实时检测。
基金supported by the National Natural Science Foundation of China(61501044)
文摘Network function virtualization is a new network concept that moves network functions from dedicated hardware to software-defined applications running on standard high volume severs. In order to accomplish network services, traffic flows are usually processed by a list of network functions in sequence which is defined by service function chain. By incorporating network function virtualization in inter-data center(DC) network, we can use the network resources intelligently and deploy network services faster. However, orchestrating service function chains across multiple data centers will incur high deployment cost, including the inter-data center bandwidth cost, virtual network function cost and the intra-data center bandwidth cost. In this paper, we orchestrate SFCs across multiple data centers, with a goal to minimize the overall cost. An integer linear programming(ILP) model is formulated and we provide a meta-heuristic algorithm named GBAO which contains three modules to solve it. We implemented our algorithm in Python and performed side-by-side comparison with prior algorithms. Simulation results show that our proposed algorithm reduces the overall cost by at least 21.4% over the existing algorithms for accommodating the same service function chain requests.
文摘针对差分混沌-相关延时移位键控(DC-CDSK)存在的码间干扰而造成的比特误码率较高问题,提出了一种无码间干扰DC-CDSK混沌通信方案。通过改变混沌信号发生器的结构,确保发送的两路混沌信号严格正交,彻底解决了判决变量中码间干扰问题。推导了在高斯白噪声信道中的比特误码率公式并完成仿真,结果表明,在一定信噪比和扩频因子条件下无码间干扰DC-CDSK比特误码率比原系统提高了2~3 d B。
