In order to improve the scalability and reliability of Software Defined Networking(SDN),many studies use multiple controllers to constitute logically centralized control plane to provide load balancing and fail over.I...In order to improve the scalability and reliability of Software Defined Networking(SDN),many studies use multiple controllers to constitute logically centralized control plane to provide load balancing and fail over.In this paper,we develop a flexible dormant multi-controller model based on the centralized multi-controller architecture.The dormant multi-controller model allows part of controllers to enter the dormant state under light traffic condition for saving system cost.Meanwhile,through queueing analysis,various performance measures of the system can be obtained.Moreover,we analyze the real traffic of China Education Network and use the results as the parameters of computer simulation and verify the effects of parameters on the system characteristics.Finally,a total expected cost function is established,and genetic algorithm is employed to find the optimal values of various parameters to minimize system cost for the deployment decision making.展开更多
The effect of kneading clearance on the mixing performance of vertical kneading mixers was investigated by using the CFD methods.Firstly,the mixing field in the kneading tank was simulated numerically after analyzing ...The effect of kneading clearance on the mixing performance of vertical kneading mixers was investigated by using the CFD methods.Firstly,the mixing field in the kneading tank was simulated numerically after analyzing the movement of mixer blade and the rheological properties of the material.Next,some macro mixing performance evaluation indices of the device were proposed.Lastly,the effect of kneading clearance on mixing performance was studied.The results indicated that a small kneading clearance could improve the mixing performance of vertical kneading mixers and better kneading efficiency could be achieved with a uniform kneading clearance.展开更多
Survivability should be considered beyond security for information system. To assess system survivability accurately, for improvement, a formal modeling and analysis method based on stochastic process algebra is propo...Survivability should be considered beyond security for information system. To assess system survivability accurately, for improvement, a formal modeling and analysis method based on stochastic process algebra is proposed in this article. By abstracting the interactive behaviors between intruders and information system, a transferring graph of system state oriented survivability is constructed. On that basis, parameters are defined and system behaviors are characterized precisely with performance evaluation process algebra （PEPA）, simultaneously considering the influence of different attack modes. Ultimately the formal model for survivability is established and quantitative analysis results are obtained by PEPA Workbench tool. Simulation experiments show the effectiveness and feasibility of the developed method, and it can help to direct the designation of survivable system.展开更多
基金the National High-tech R&D Program ("863" Program) of China，the National Science Foundation of China，National Science & Technology Pillar Program of China，the National Science Foundation of China，the Post-Doctoral Funding of China，Tsinghua-Huawei joint research project
文摘In order to improve the scalability and reliability of Software Defined Networking(SDN),many studies use multiple controllers to constitute logically centralized control plane to provide load balancing and fail over.In this paper,we develop a flexible dormant multi-controller model based on the centralized multi-controller architecture.The dormant multi-controller model allows part of controllers to enter the dormant state under light traffic condition for saving system cost.Meanwhile,through queueing analysis,various performance measures of the system can be obtained.Moreover,we analyze the real traffic of China Education Network and use the results as the parameters of computer simulation and verify the effects of parameters on the system characteristics.Finally,a total expected cost function is established,and genetic algorithm is employed to find the optimal values of various parameters to minimize system cost for the deployment decision making.
文摘The effect of kneading clearance on the mixing performance of vertical kneading mixers was investigated by using the CFD methods.Firstly,the mixing field in the kneading tank was simulated numerically after analyzing the movement of mixer blade and the rheological properties of the material.Next,some macro mixing performance evaluation indices of the device were proposed.Lastly,the effect of kneading clearance on mixing performance was studied.The results indicated that a small kneading clearance could improve the mixing performance of vertical kneading mixers and better kneading efficiency could be achieved with a uniform kneading clearance.
基金the National Natural Science Foundation of China (90718003)the Hi-Tech Research and Development Program of China (2007AA01Z401)the Specialized Research Fund for the Doctoral Program of Higher Education (20050217007)
文摘Survivability should be considered beyond security for information system. To assess system survivability accurately, for improvement, a formal modeling and analysis method based on stochastic process algebra is proposed in this article. By abstracting the interactive behaviors between intruders and information system, a transferring graph of system state oriented survivability is constructed. On that basis, parameters are defined and system behaviors are characterized precisely with performance evaluation process algebra （PEPA）, simultaneously considering the influence of different attack modes. Ultimately the formal model for survivability is established and quantitative analysis results are obtained by PEPA Workbench tool. Simulation experiments show the effectiveness and feasibility of the developed method, and it can help to direct the designation of survivable system.
