This paper focuses on optimally determining the existence of connected paths between some given nodes in random ring-based graphs.Serving as a fundamental underlying structure in network modeling,ring topology appears...This paper focuses on optimally determining the existence of connected paths between some given nodes in random ring-based graphs.Serving as a fundamental underlying structure in network modeling,ring topology appears as commonplace in many realistic scenarios.Regarding this,we consider graphs composed of rings,with some possible connected paths between them.Without prior knowledge of the exact node permutations on rings,the existence of each edge can be unraveled through edge testing at a unit cost in one step.The problem examined is that of determining whether the given nodes are connected by a path or separated by a cut,with the minimum expected costs involved.Dividing the problem into different cases based on different topologies of the ring-based networks,we propose the corresponding policies that aim to quickly seek the paths between nodes.A common feature shared by all those policies is that we stick to going in the same direction during edge searching,with edge testing in each step only involving the test between the source and the node that has been tested most.The simple searching rule,interestingly,can be interpreted as a delightful property stemming from the neat structure of ring-based networks,which makes the searching process not rely on any sophisticated behaviors.We prove the optimality of the proposed policies by calculating the expected cost incurred and making a comparison with the other class of strategies.The effectiveness of the proposed policies is also verified through extensive simulations,from which we even disclose three extra intriguing findings:i)in a onering network,the cost will grow drastically with the number of designated nodes when the number is small and will grow slightly when that number is large;ii)in ring-based network,Depth First is optimal in detecting the connectivity between designated nodes;iii)the problem of multi-ring networks shares large similarity with that of two-ring networks,and a larger number of ties between rings will not influence the expected cost.展开更多
文章首先采用溶剂热法合成了系列LiMn1-xFexPO4(x=0.15、0.25、0.35、0.45)微纳颗粒,随后采用热分解的方法对微纳颗粒进行碳包覆处理。采用X射线衍射仪(X-ray diffraction,XRD)和扫描电子显微镜(scanning electron microscope,SEM)对微...文章首先采用溶剂热法合成了系列LiMn1-xFexPO4(x=0.15、0.25、0.35、0.45)微纳颗粒,随后采用热分解的方法对微纳颗粒进行碳包覆处理。采用X射线衍射仪(X-ray diffraction,XRD)和扫描电子显微镜(scanning electron microscope,SEM)对微纳颗粒进行表征,结果可知所获微纳颗粒均为橄榄石结构,而LiMn0.75Fe0.25PO4/C分散性较好,颗粒大小较均匀。与LiFePO4/C正极材料相比,LiMn0.75Fe0.25PO4/C的导电性、放电电压、循环稳定性和储锂性能均有明显提高。LiMn0.75Fe0.25PO4/C充放电电压平台为4.1V;在0.5C的电流密度下,首次放电比容量为160mA·h/g,在100圈循环后容量依然保持在140mA·h/g;在10C的电流密度下,保持了60mA·h/g的容量。该文对于研究和发展新型可替代LiFePO4的锂离子电池正极材料具有重要的意义。展开更多
With difficulties in maintaining multicomponent systems of wind turbines and formulating economical and reasonable maintenance strategies,a dynamic opportunistic maintenance strategy of multicomponent systems is appli...With difficulties in maintaining multicomponent systems of wind turbines and formulating economical and reasonable maintenance strategies,a dynamic opportunistic maintenance strategy of multicomponent systems is applied in terms of economic relevance and opportunistic maintenance among various components.A preventive maintenance model based on cost-effectiveness is proposed by incorporating cost-effectiveness analysis into the multicomponent preventive maintenance strategy.The failure rate recovery degree is used to describe the effects of imperfect maintenance and replacement.When the reliability of the component reaches the threshold of preventive or opportunistic maintenance,a reasonable maintenance method is selected on the basis of the cost-effectiveness ratio of the failure rate.A case study is conducted by taking four components of a wind turbine as the research object and comparing them with the opportunistic maintenance model without considering cost-effectiveness.Results show that the total maintenance cost is reduced by 373600 yuan,indicating that the preventive opportunistic maintenance based on cost-effectiveness is more economical and can provide a theoretical basis for formulating a preventive maintenance plan.展开更多
基金supported by NSF China(No.61960206002,62020106005,42050105,62061146002)Shanghai Pilot Program for Basic Research-Shanghai Jiao Tong University。
文摘This paper focuses on optimally determining the existence of connected paths between some given nodes in random ring-based graphs.Serving as a fundamental underlying structure in network modeling,ring topology appears as commonplace in many realistic scenarios.Regarding this,we consider graphs composed of rings,with some possible connected paths between them.Without prior knowledge of the exact node permutations on rings,the existence of each edge can be unraveled through edge testing at a unit cost in one step.The problem examined is that of determining whether the given nodes are connected by a path or separated by a cut,with the minimum expected costs involved.Dividing the problem into different cases based on different topologies of the ring-based networks,we propose the corresponding policies that aim to quickly seek the paths between nodes.A common feature shared by all those policies is that we stick to going in the same direction during edge searching,with edge testing in each step only involving the test between the source and the node that has been tested most.The simple searching rule,interestingly,can be interpreted as a delightful property stemming from the neat structure of ring-based networks,which makes the searching process not rely on any sophisticated behaviors.We prove the optimality of the proposed policies by calculating the expected cost incurred and making a comparison with the other class of strategies.The effectiveness of the proposed policies is also verified through extensive simulations,from which we even disclose three extra intriguing findings:i)in a onering network,the cost will grow drastically with the number of designated nodes when the number is small and will grow slightly when that number is large;ii)in ring-based network,Depth First is optimal in detecting the connectivity between designated nodes;iii)the problem of multi-ring networks shares large similarity with that of two-ring networks,and a larger number of ties between rings will not influence the expected cost.
文摘文章首先采用溶剂热法合成了系列LiMn1-xFexPO4(x=0.15、0.25、0.35、0.45)微纳颗粒,随后采用热分解的方法对微纳颗粒进行碳包覆处理。采用X射线衍射仪(X-ray diffraction,XRD)和扫描电子显微镜(scanning electron microscope,SEM)对微纳颗粒进行表征,结果可知所获微纳颗粒均为橄榄石结构,而LiMn0.75Fe0.25PO4/C分散性较好,颗粒大小较均匀。与LiFePO4/C正极材料相比,LiMn0.75Fe0.25PO4/C的导电性、放电电压、循环稳定性和储锂性能均有明显提高。LiMn0.75Fe0.25PO4/C充放电电压平台为4.1V;在0.5C的电流密度下,首次放电比容量为160mA·h/g,在100圈循环后容量依然保持在140mA·h/g;在10C的电流密度下,保持了60mA·h/g的容量。该文对于研究和发展新型可替代LiFePO4的锂离子电池正极材料具有重要的意义。
基金The National Key Research and Development Program of China(No.2019YFB1707300).
文摘With difficulties in maintaining multicomponent systems of wind turbines and formulating economical and reasonable maintenance strategies,a dynamic opportunistic maintenance strategy of multicomponent systems is applied in terms of economic relevance and opportunistic maintenance among various components.A preventive maintenance model based on cost-effectiveness is proposed by incorporating cost-effectiveness analysis into the multicomponent preventive maintenance strategy.The failure rate recovery degree is used to describe the effects of imperfect maintenance and replacement.When the reliability of the component reaches the threshold of preventive or opportunistic maintenance,a reasonable maintenance method is selected on the basis of the cost-effectiveness ratio of the failure rate.A case study is conducted by taking four components of a wind turbine as the research object and comparing them with the opportunistic maintenance model without considering cost-effectiveness.Results show that the total maintenance cost is reduced by 373600 yuan,indicating that the preventive opportunistic maintenance based on cost-effectiveness is more economical and can provide a theoretical basis for formulating a preventive maintenance plan.
