Software Defined Networking(SDN) provides flexible network management by decoupling control plane from data plane. And multiple controllers are deployed to improve the scalability and reliability of the control plane,...Software Defined Networking(SDN) provides flexible network management by decoupling control plane from data plane. And multiple controllers are deployed to improve the scalability and reliability of the control plane, which could divide the network into several subdomains with separate controllers. However, such deployment introduces a new problem of controller load imbalance due to the dynamic traffic and the static configuration between switches and controllers. To address this issue, this paper proposes a Distribution Decision Mechanism(DDM) based on switch migration in the multiple subdomains SDN network. Firstly, through collecting network information, it constructs distributed migration decision fields based on the controller load condition. Then we choose the migrating switches according to the selection probability, and the target controllers are determined by integrating three network costs, including data collection, switch migration and controller state synchronization. Finally, we set the migrating countdown to achieve the ordered switch migration. Through verifying several evaluation indexes, results show that the proposed mechanism can achieve controller load balancing with better performance.展开更多
This paper proposes a simple and efficient distributed algorithm for calculating minimal dominating set in wireless sensor network. This method can avoid maintaining the connectivities between backbone hosts. Consider...This paper proposes a simple and efficient distributed algorithm for calculating minimal dominating set in wireless sensor network. This method can avoid maintaining the connectivities between backbone hosts. Considering that the hosts in mobile networks have different characteristics, this paper proposes a method of calculating minimal dominating set with weight. The nodes can be chosen to form a minimal dominating set when the network topology changes. For the host switch on/off operation, the updating algorithm was provided. The change in the status of a hostaffects only the status of hosts in the restricted vicinity. Simulation results show that the proposed method can ensure fewer dominators but with higher weight to form the minimal dominating set and the nodes can be adaptive to the changes of network topology.展开更多
Magnetic nanoscale systems,including nanodots,nanofibers,nanowires and nanoparticles,are currently attracting great interest due to their interesting physical and promising applications in various fields,such as magne...Magnetic nanoscale systems,including nanodots,nanofibers,nanowires and nanoparticles,are currently attracting great interest due to their interesting physical and promising applications in various fields,such as magnetic recording,sensors,target drugs and catalysts,as well as others.To achieve ultrahigh recording density,the method of heat assisted magnetic recording(HAMR) has been introduced.In this work,with the help of a Monte Carlo method,the mechanisms of thermally assisted magnetization switching in FePt single-domain particles driven by an external magnetic field are investigated,where the temperature in the particles is assumed to follow a Gaussian distribution.Two nucleation modes are observed for different distributions of temperature.One is initiated by many droplets,which join each other at the boundary of the system;the other is ini-tiated by many droplets at the boundary,but in growth tending toward the inner part of the system.An inverse proportional relationship between the metastable lifetime and the distribution is also found.展开更多
Partial shading and mismatch conditions among the series-connected modules/sub-modules suffer from a nonconvex power curve with multiple local maxima and decreased peak power for the whole string. Energy transfer betw...Partial shading and mismatch conditions among the series-connected modules/sub-modules suffer from a nonconvex power curve with multiple local maxima and decreased peak power for the whole string. Energy transfer between the sub-modules brings them to the same operating voltage, and this collective operation produces a convex power curve, which results in increased peak power for the string. The proposed topology benefits from the switched-capacitor （SC） converter concept and is an application for sub-module-level power balancing with some novelties, including stopping the switching in absence of shading, string-level extension, and a reduced number of power electronics components as compared to those in the literature. Reduction in the number of power electronics components is realized by the fact that two sub-modules share one SC converter. This leads to reduced power electronics losses as well as less cost and volume of the converter circuit. Insertion loss analysis of the topology is presented. The proposed topology is simulated in the PSpice environment, and a prototype is built for experimental verification. Both simulation and experimental results confirm the loss analysis. This proves that with the proposed topology it is possible to extract almost all the power available on the partially shaded string and transfer it to the load side.展开更多
基金supported in part by This work is supported by the Project of National Network Cyberspace Security(Grant No.2017YFB0803204)the National High-Tech Research and Development Program of China(863 Program)(Grant No.2015AA016102)+1 种基金Foundation for Innovative Research Group of the National Natural Science Foundation of China(Grant No.61521003)Foundation for the National Natural Science Foundation of China(Grant No.61502530)
文摘Software Defined Networking(SDN) provides flexible network management by decoupling control plane from data plane. And multiple controllers are deployed to improve the scalability and reliability of the control plane, which could divide the network into several subdomains with separate controllers. However, such deployment introduces a new problem of controller load imbalance due to the dynamic traffic and the static configuration between switches and controllers. To address this issue, this paper proposes a Distribution Decision Mechanism(DDM) based on switch migration in the multiple subdomains SDN network. Firstly, through collecting network information, it constructs distributed migration decision fields based on the controller load condition. Then we choose the migrating switches according to the selection probability, and the target controllers are determined by integrating three network costs, including data collection, switch migration and controller state synchronization. Finally, we set the migrating countdown to achieve the ordered switch migration. Through verifying several evaluation indexes, results show that the proposed mechanism can achieve controller load balancing with better performance.
基金Supported by National Natural Science Foundation of China (No.60973141)Natural Science Foundation of Tianjin (No.09JCYBJC00300)
文摘This paper proposes a simple and efficient distributed algorithm for calculating minimal dominating set in wireless sensor network. This method can avoid maintaining the connectivities between backbone hosts. Considering that the hosts in mobile networks have different characteristics, this paper proposes a method of calculating minimal dominating set with weight. The nodes can be chosen to form a minimal dominating set when the network topology changes. For the host switch on/off operation, the updating algorithm was provided. The change in the status of a hostaffects only the status of hosts in the restricted vicinity. Simulation results show that the proposed method can ensure fewer dominators but with higher weight to form the minimal dominating set and the nodes can be adaptive to the changes of network topology.
基金support by the Fund for Talents Introduction of Chongqing University of Arts and Sciences (Grant No. Z2011RCYJ03)
文摘Magnetic nanoscale systems,including nanodots,nanofibers,nanowires and nanoparticles,are currently attracting great interest due to their interesting physical and promising applications in various fields,such as magnetic recording,sensors,target drugs and catalysts,as well as others.To achieve ultrahigh recording density,the method of heat assisted magnetic recording(HAMR) has been introduced.In this work,with the help of a Monte Carlo method,the mechanisms of thermally assisted magnetization switching in FePt single-domain particles driven by an external magnetic field are investigated,where the temperature in the particles is assumed to follow a Gaussian distribution.Two nucleation modes are observed for different distributions of temperature.One is initiated by many droplets,which join each other at the boundary of the system;the other is ini-tiated by many droplets at the boundary,but in growth tending toward the inner part of the system.An inverse proportional relationship between the metastable lifetime and the distribution is also found.
基金Project supported by the BAP Department of Karabuk University,Turkey(No.KBU-BAP-13/2-DR-010)
文摘Partial shading and mismatch conditions among the series-connected modules/sub-modules suffer from a nonconvex power curve with multiple local maxima and decreased peak power for the whole string. Energy transfer between the sub-modules brings them to the same operating voltage, and this collective operation produces a convex power curve, which results in increased peak power for the string. The proposed topology benefits from the switched-capacitor （SC） converter concept and is an application for sub-module-level power balancing with some novelties, including stopping the switching in absence of shading, string-level extension, and a reduced number of power electronics components as compared to those in the literature. Reduction in the number of power electronics components is realized by the fact that two sub-modules share one SC converter. This leads to reduced power electronics losses as well as less cost and volume of the converter circuit. Insertion loss analysis of the topology is presented. The proposed topology is simulated in the PSpice environment, and a prototype is built for experimental verification. Both simulation and experimental results confirm the loss analysis. This proves that with the proposed topology it is possible to extract almost all the power available on the partially shaded string and transfer it to the load side.
