To analyze and control complex networks effectively, this paper puts forward a new kind of scheme, which takes control separately in each area and can achieve the network’s coordinated optimality. The proposed algori...To analyze and control complex networks effectively, this paper puts forward a new kind of scheme, which takes control separately in each area and can achieve the network’s coordinated optimality. The proposed algorithm is made up of two parts: the first part decomposes the network into several independent areas based on community structure and decouples the information flow and control power among areas; the second part selects the center nodes from each area with the help of the control centrality index. As long as the status of center nodes is kept on a satisfactory level in each area, the whole system is under effective control. Finally, the algorithm is applied to power grids, and the simulations prove its effectiveness.展开更多
In this paper,a series of major policy decisions used to improve the power grid reliability,reduce the risk and losses of major power outages,and realize the modernization of 21st century power grid are discussed. The...In this paper,a series of major policy decisions used to improve the power grid reliability,reduce the risk and losses of major power outages,and realize the modernization of 21st century power grid are discussed. These decisions were adopted by American government and would also be helpful for the strategic development of Chinese power grid. It is proposed that China should take precaution,carry out security research on the overall dynamic behaviour characteristics of the UHV grid using the complexity theory,and finally provide safeguard for the Chinese UHV grid. It is also pointed out that,due to the lack of matured approaches to controll a cascading failure,the primary duty of a system operator is to work as a "watchdog" for the grid operation security,eliminate the cumulative effect and reduce the risk and losses of major cascading outages with the help of EMS and WAMS.展开更多
目前基于正交时频空(orthogonal time frequency space,OTFS)的雷达目标参数估计算法以在网估计为主,但在网估计算法无法有效应对现实应用中的离网现象。同时,现有离网估计算法的目标参数估计性能受建模误差的限制,也难以确保雷达系统...目前基于正交时频空(orthogonal time frequency space,OTFS)的雷达目标参数估计算法以在网估计为主,但在网估计算法无法有效应对现实应用中的离网现象。同时,现有离网估计算法的目标参数估计性能受建模误差的限制,也难以确保雷达系统在复杂环境下的有效应用。针对以上问题,提出了一种基于OTFS调制的动态稀疏贝叶斯(dynamic-sparse Bayesian learning,dynamic-SBL)算法。该算法在稀疏贝叶斯学习框架下引入动态虚拟网格,通过不断更新调整网格参数降低建模误差,提升目标参数估计性能。同时利用OTFS雷达信道特有的稀疏性对网格参数进行选择性局部更新,以降低算法的复杂度。仿真结果表明,所提算法估计的目标归一化时延和多普勒频率的均方误差较小,目标参数的估计性能优于传统离网估计方法的。该算法在实际雷达系统中具有较大应用潜力。展开更多
With urging problem of energy and pollution, smart grid is becoming ever important. By gradually changing the actual power grid system, smart grid may evovle into different systems by means of size, elements and strat...With urging problem of energy and pollution, smart grid is becoming ever important. By gradually changing the actual power grid system, smart grid may evovle into different systems by means of size, elements and strategies, but its fundamental requirements and objectives will not change such as optimizing production, transmission and consumption. Studying the smart grid through modeling and simulation provides us with valuable results which can not be obtained in real world due to time and cost related constraints. However, due to the complexity of the smart grid, achieving optimization is not an easy task, even using computer models. In this paper, we propose an complex system based approach to the smart grid modeling, accentuating on the optimization by combining game theoretical and classical methods in different levels. Thanks to this combination, the optimization can be achieved with flexibility and scalability, while keeping its generality.展开更多
With the characteristics of diversity, randomness, concurrency and decomposability, tasks in manufacturing field are very complicated, and so manufacturing grid (MG) should have considerable flexibility to deal with t...With the characteristics of diversity, randomness, concurrency and decomposability, tasks in manufacturing field are very complicated, and so manufacturing grid (MG) should have considerable flexibility to deal with this problem. With the definition of node and arc, MG structure is converted into a small-world network. Given construction cost constraint, the problem of shortest task waiting time is transformed into the constrained optimization problem, and a corresponding ?exibility analysis model based on average path length (APL) is proposed, and the premise of arc-length and node-distance are defined. The results of application example show that the analysis model is effiective.展开更多
对于高超声速飞行器在临近空间形成的连续与稀薄混合流场,DSMC(direct simulation of Monte Carlo)方法需要消耗巨大的计算资源,CFD(computational fluid dynamics)方法,无法对稀薄效应进行准确模拟。在对连续/稀薄耦合数值方法深入研...对于高超声速飞行器在临近空间形成的连续与稀薄混合流场,DSMC(direct simulation of Monte Carlo)方法需要消耗巨大的计算资源,CFD(computational fluid dynamics)方法,无法对稀薄效应进行准确模拟。在对连续/稀薄耦合数值方法深入研究的基础上,提出了一套非结构网格的CFD/DSMC耦合方法。该方法具有通用强、适应性良好的特点,进行耦合计算时对不规则复杂分界面无需进行光滑处理。对超声速圆柱绕流和钝锥体流场进行了模拟,数值结果表明:该方法对不规则分界面和复杂外形具有高度适用性,通过与重叠网格结果进行比较验证了该方法的有效性和计算效率,相较于传统的DSMC方法,计算效率分别提高了2.3倍和3.16倍,具有高效性。展开更多
基金the National Science Foundation of China (No.50525721, 50595411)the National Basic Research Program of China(No.G2004CB217902)
文摘To analyze and control complex networks effectively, this paper puts forward a new kind of scheme, which takes control separately in each area and can achieve the network’s coordinated optimality. The proposed algorithm is made up of two parts: the first part decomposes the network into several independent areas based on community structure and decouples the information flow and control power among areas; the second part selects the center nodes from each area with the help of the control centrality index. As long as the status of center nodes is kept on a satisfactory level in each area, the whole system is under effective control. Finally, the algorithm is applied to power grids, and the simulations prove its effectiveness.
文摘In this paper,a series of major policy decisions used to improve the power grid reliability,reduce the risk and losses of major power outages,and realize the modernization of 21st century power grid are discussed. These decisions were adopted by American government and would also be helpful for the strategic development of Chinese power grid. It is proposed that China should take precaution,carry out security research on the overall dynamic behaviour characteristics of the UHV grid using the complexity theory,and finally provide safeguard for the Chinese UHV grid. It is also pointed out that,due to the lack of matured approaches to controll a cascading failure,the primary duty of a system operator is to work as a "watchdog" for the grid operation security,eliminate the cumulative effect and reduce the risk and losses of major cascading outages with the help of EMS and WAMS.
文摘目前基于正交时频空(orthogonal time frequency space,OTFS)的雷达目标参数估计算法以在网估计为主,但在网估计算法无法有效应对现实应用中的离网现象。同时,现有离网估计算法的目标参数估计性能受建模误差的限制,也难以确保雷达系统在复杂环境下的有效应用。针对以上问题,提出了一种基于OTFS调制的动态稀疏贝叶斯(dynamic-sparse Bayesian learning,dynamic-SBL)算法。该算法在稀疏贝叶斯学习框架下引入动态虚拟网格,通过不断更新调整网格参数降低建模误差,提升目标参数估计性能。同时利用OTFS雷达信道特有的稀疏性对网格参数进行选择性局部更新,以降低算法的复杂度。仿真结果表明,所提算法估计的目标归一化时延和多普勒频率的均方误差较小,目标参数的估计性能优于传统离网估计方法的。该算法在实际雷达系统中具有较大应用潜力。
文摘With urging problem of energy and pollution, smart grid is becoming ever important. By gradually changing the actual power grid system, smart grid may evovle into different systems by means of size, elements and strategies, but its fundamental requirements and objectives will not change such as optimizing production, transmission and consumption. Studying the smart grid through modeling and simulation provides us with valuable results which can not be obtained in real world due to time and cost related constraints. However, due to the complexity of the smart grid, achieving optimization is not an easy task, even using computer models. In this paper, we propose an complex system based approach to the smart grid modeling, accentuating on the optimization by combining game theoretical and classical methods in different levels. Thanks to this combination, the optimization can be achieved with flexibility and scalability, while keeping its generality.
基金supported by the National Natural Science Foundation of China (Grant No.50805089)the Science Foundation of Science and Technology Commission of Shanghai Municipality (Grant Nos.08DZ1123402,08DZ1124502)
文摘With the characteristics of diversity, randomness, concurrency and decomposability, tasks in manufacturing field are very complicated, and so manufacturing grid (MG) should have considerable flexibility to deal with this problem. With the definition of node and arc, MG structure is converted into a small-world network. Given construction cost constraint, the problem of shortest task waiting time is transformed into the constrained optimization problem, and a corresponding ?exibility analysis model based on average path length (APL) is proposed, and the premise of arc-length and node-distance are defined. The results of application example show that the analysis model is effiective.
文摘对于高超声速飞行器在临近空间形成的连续与稀薄混合流场,DSMC(direct simulation of Monte Carlo)方法需要消耗巨大的计算资源,CFD(computational fluid dynamics)方法,无法对稀薄效应进行准确模拟。在对连续/稀薄耦合数值方法深入研究的基础上,提出了一套非结构网格的CFD/DSMC耦合方法。该方法具有通用强、适应性良好的特点,进行耦合计算时对不规则复杂分界面无需进行光滑处理。对超声速圆柱绕流和钝锥体流场进行了模拟,数值结果表明:该方法对不规则分界面和复杂外形具有高度适用性,通过与重叠网格结果进行比较验证了该方法的有效性和计算效率,相较于传统的DSMC方法,计算效率分别提高了2.3倍和3.16倍,具有高效性。
