With the expansion of distributed generation systems and demand response programs, the need to fully utilize distribution system capacity has increased. In addition, the potential bidirectional flow of power on distri...With the expansion of distributed generation systems and demand response programs, the need to fully utilize distribution system capacity has increased. In addition, the potential bidirectional flow of power on distribution networks demands voltage visibility and control at all voltage levels. Distribution system state estimations, however, have traditionally been less prioritized due to the lack of enough measurement points while being the major role player in knowing the real-time system states of active distribution networks. The advent of smart meters at LV loads, on the other hand, is giving relief to this shortcoming. This study explores the potential of bottom up load flow analysis based on customer level Automatic Meter Reading (AMRs) to compute short time forecasts of demands and distribution network system states. A state estimation frame-work, which makes use of available AMR data, is proposed and discussed.展开更多
Load balancing is typically used in the frequency domain of cellular wireless networks to balance paging, access, and traffic load across the available bandwidth. In this paper, we extend load balancing into the spati...Load balancing is typically used in the frequency domain of cellular wireless networks to balance paging, access, and traffic load across the available bandwidth. In this paper, we extend load balancing into the spatial domain, and we develop two approaches--network load balancing and single-carrier multilink--for spatial load balancing. Although these techniques are mostly applied to cellular wireless networks and Wi-Fi networks, we show how they can be applied to EV-DO, a 3G cellular data network. When a device has more than one candidate server, these techniques can be used to determine the quality of the channel between a server and the device and to determine the Ipad on each server. The proposed techniques leverage the advantages of existing EV-DO network architecture and are fully backward compatible. Network operators can substantially increase network capacity and improve user experience by using these techniques. Combining load balancing in the frequency and spatial domains improves connectivity within a network and allows resources to be optimally allocated according to the p-fair criterion. Combined load balancing further improves performance.展开更多
Currently, the article analyzes the CAN bus＇s rule of priority＇s arbitration bit by bit without destroy. It elicits the conclusion that if static priority based on the affirmatory system model is used, the lower pri...Currently, the article analyzes the CAN bus＇s rule of priority＇s arbitration bit by bit without destroy. It elicits the conclusion that if static priority based on the affirmatory system model is used, the lower priority＇s messages will be delayed considerably more, even some data will be lost when the bus＇s bandwidth is widely used. The scheduling cannot be modified neither during the system when static priority is used. The dynamic priority promoting method and the math model of SQSA and SQMA are presented; it analyzes the model＇s rate of taking in and sending out in large quantities, the largest delay, the problems and solutions when using SQMA. In the end, it is confirmed that the method of improving dynamic priority has good performances on the network rate of taking in and sending out in large quantities, the average delay, and the rate of network usage by emulational experiments.展开更多
为提高医院数据中心网络的资源利用率,提出一种基于软件定义网络(Software Defined Network,SDN)的医院数据中心网络负载均衡方法。首先根据SDN架构,搭建医院数据中心网络框架,并以不同类型的医院数据中心网络流量总效用最大为目标函数...为提高医院数据中心网络的资源利用率,提出一种基于软件定义网络(Software Defined Network,SDN)的医院数据中心网络负载均衡方法。首先根据SDN架构,搭建医院数据中心网络框架,并以不同类型的医院数据中心网络流量总效用最大为目标函数,构建基于SDN的医院数据中心网络负载均衡优化模型;然后以近端策略优化(Proximal Policy Optimization,PPO)算法为基础,通过在PPO算法中引入广义优势估计和部分状态局部视图,并改进策略网络结构,提出改进PPO算法;最后利用改进PPO算法对负载均衡优化模型进行求解,并在Mininet仿真平台上对方法进行验证。结果表明,该方法的平均传输时延为28.19 ms,平均吞吐量为82.99 Mbps,链路平均利用率为49.86%。由此说明,该方法可实现高速率、大带宽的医院数据中心网络负载均衡,提高了医院数据中心网络的利用率。通过动态调整医院中心负载分配,实现流量资源的优化利用,同时有利于处理高并发医疗数据。展开更多
为了提高控制器局域网络(controller area network,CAN)通信的实时性,文章基于时间触发CAN(time-triggered CAN,TTCAN)协议,采用verilog硬件描述语言设计实现TTCAN总线控制器。该控制器可在经典CAN模式与TTCAN模式之间进行切换,同时兼...为了提高控制器局域网络(controller area network,CAN)通信的实时性,文章基于时间触发CAN(time-triggered CAN,TTCAN)协议,采用verilog硬件描述语言设计实现TTCAN总线控制器。该控制器可在经典CAN模式与TTCAN模式之间进行切换,同时兼容可变速率CAN(CAN with flexible data rate,CAN FD)协议下的高速通信。实验结果证明,相较于经典CAN总线控制器,该TTCAN总线控制器能够减少在高总线负载率下周期性报文的发送延时,在全波特率范围内且总线负载率大于等于60%的情况下,能够减少75%以上的CAN报文发送延时。展开更多
文摘With the expansion of distributed generation systems and demand response programs, the need to fully utilize distribution system capacity has increased. In addition, the potential bidirectional flow of power on distribution networks demands voltage visibility and control at all voltage levels. Distribution system state estimations, however, have traditionally been less prioritized due to the lack of enough measurement points while being the major role player in knowing the real-time system states of active distribution networks. The advent of smart meters at LV loads, on the other hand, is giving relief to this shortcoming. This study explores the potential of bottom up load flow analysis based on customer level Automatic Meter Reading (AMRs) to compute short time forecasts of demands and distribution network system states. A state estimation frame-work, which makes use of available AMR data, is proposed and discussed.
文摘Load balancing is typically used in the frequency domain of cellular wireless networks to balance paging, access, and traffic load across the available bandwidth. In this paper, we extend load balancing into the spatial domain, and we develop two approaches--network load balancing and single-carrier multilink--for spatial load balancing. Although these techniques are mostly applied to cellular wireless networks and Wi-Fi networks, we show how they can be applied to EV-DO, a 3G cellular data network. When a device has more than one candidate server, these techniques can be used to determine the quality of the channel between a server and the device and to determine the Ipad on each server. The proposed techniques leverage the advantages of existing EV-DO network architecture and are fully backward compatible. Network operators can substantially increase network capacity and improve user experience by using these techniques. Combining load balancing in the frequency and spatial domains improves connectivity within a network and allows resources to be optimally allocated according to the p-fair criterion. Combined load balancing further improves performance.
基金supported by the National Natural Science Foundation of China (50421703)the National Key Laboratory of Electrical Engineering of Naval Engineering University
文摘Currently, the article analyzes the CAN bus＇s rule of priority＇s arbitration bit by bit without destroy. It elicits the conclusion that if static priority based on the affirmatory system model is used, the lower priority＇s messages will be delayed considerably more, even some data will be lost when the bus＇s bandwidth is widely used. The scheduling cannot be modified neither during the system when static priority is used. The dynamic priority promoting method and the math model of SQSA and SQMA are presented; it analyzes the model＇s rate of taking in and sending out in large quantities, the largest delay, the problems and solutions when using SQMA. In the end, it is confirmed that the method of improving dynamic priority has good performances on the network rate of taking in and sending out in large quantities, the average delay, and the rate of network usage by emulational experiments.
文摘为了提高控制器局域网络(controller area network,CAN)通信的实时性,文章基于时间触发CAN(time-triggered CAN,TTCAN)协议,采用verilog硬件描述语言设计实现TTCAN总线控制器。该控制器可在经典CAN模式与TTCAN模式之间进行切换,同时兼容可变速率CAN(CAN with flexible data rate,CAN FD)协议下的高速通信。实验结果证明,相较于经典CAN总线控制器,该TTCAN总线控制器能够减少在高总线负载率下周期性报文的发送延时,在全波特率范围内且总线负载率大于等于60%的情况下,能够减少75%以上的CAN报文发送延时。
