Text embedded in images is one of many important cues for indexing and retrieval of images and videos. In the paper, we present a novel method of detecting text aligned either horizontally or vertically, in which a py...Text embedded in images is one of many important cues for indexing and retrieval of images and videos. In the paper, we present a novel method of detecting text aligned either horizontally or vertically, in which a pyramid structure is used to represent an image and the features of the text are extracted using SUSAN edge detector. Text regions at each level of the pyramid are identified according to the autocorrelation analysis. New techniques are introduced to split the text regions into basic ones and merge them into text lines. By evaluating the method on a set of images, we obtain a very good performance of text detection.展开更多
Multiple complex networks, each with different properties and mutually fused, have the problems that the evolving process is time varying and non-equilibrium, network structures are layered and interlacing, and evolvi...Multiple complex networks, each with different properties and mutually fused, have the problems that the evolving process is time varying and non-equilibrium, network structures are layered and interlacing, and evolving characteristics are difficult to be measured. On that account, a dynamic evolving model of complex network with fusion nodes and overlap edges（CNFNOEs） is proposed. Firstly, we define some related concepts of CNFNOEs, and analyze the conversion process of fusion relationship and hierarchy relationship. According to the property difference of various nodes and edges, fusion nodes and overlap edges are subsequently split, and then the CNFNOEs is transformed to interlacing layered complex networks（ILCN）. Secondly,the node degree saturation and attraction factors are defined. On that basis, the evolution algorithm and the local world evolution model for ILCN are put forward. Moreover, four typical situations of nodes evolution are discussed, and the degree distribution law during evolution is analyzed by means of the mean field method.Numerical simulation results show that nodes unreached degree saturation follow the exponential distribution with an error of no more than 6%; nodes reached degree saturation follow the distribution of their connection capacities with an error of no more than 3%; network weaving coefficients have a positive correlation with the highest probability of new node and initial number of connected edges. The results have verified the feasibility and effectiveness of the model, which provides a new idea and method for exploring CNFNOE＇s evolving process and law. Also, the model has good application prospects in structure and dynamics research of transportation network, communication network, social contact network,etc.展开更多
Unmanned Aerial Vehicle(UAV)has emerged as a promising technology for the support of human activities,such as target tracking,disaster rescue,and surveillance.However,these tasks require a large computation load of im...Unmanned Aerial Vehicle(UAV)has emerged as a promising technology for the support of human activities,such as target tracking,disaster rescue,and surveillance.However,these tasks require a large computation load of image or video processing,which imposes enormous pressure on the UAV computation platform.To solve this issue,in this work,we propose an intelligent Task Offloading Algorithm(iTOA)for UAV edge computing network.Compared with existing methods,iTOA is able to perceive the network’s environment intelligently to decide the offloading action based on deep Monte Calor Tree Search(MCTS),the core algorithm of Alpha Go.MCTS will simulate the offloading decision trajectories to acquire the best decision by maximizing the reward,such as lowest latency or power consumption.To accelerate the search convergence of MCTS,we also proposed a splitting Deep Neural Network(sDNN)to supply the prior probability for MCTS.The sDNN is trained by a self-supervised learning manager.Here,the training data set is obtained from iTOA itself as its own teacher.Compared with game theory and greedy search-based methods,the proposed iTOA improves service latency performance by 33%and 60%,respectively.展开更多
Three types of landscape boundary (forest/pepper field, forest/cabbage field,and forest/grassland) were selected in the arid valley of upper reaches of Minjiang River,southwestern China. On the basis of vegetation div...Three types of landscape boundary (forest/pepper field, forest/cabbage field,and forest/grassland) were selected in the arid valley of upper reaches of Minjiang River,southwestern China. On the basis of vegetation diversity, the depth of edge influence (DEI) ondifferent types of landscape boundaries was estimated using principal components analysis (PCA)method and moving split-window techniques (MSWT). The results showed that in the 5 transects, PCAmethod was able to detect the edge influence depth with 3 transects, while MSWT could explain 4transects. It is concluded that PCA and MSWT both can be used to detect the depth of edge influencewithin 50 m from the edge to the interior. Similar conclusions were drawn in the forest of eachtransect with the two methods, but no similar conclusions were drawn in the pepper field of eachtransect. Although the two methods have advantages and disadvantages respectively, they are usefultools for characterizing edge dynamics. Comparing the two methods, MSWT is more successful.展开更多
As a clean and renewable future energy source, hydrogen fuel can be produced via solar water splitting. Two-dimensional (2D) black phosphorene (black-P) can harvest visible light due to the desirable band gap, which p...As a clean and renewable future energy source, hydrogen fuel can be produced via solar water splitting. Two-dimensional (2D) black phosphorene (black-P) can harvest visible light due to the desirable band gap, which promises it as a metal-free photocatalyst. However, black-P can be only used to produce hydrogen since the oxidation potential of water locates lower than the position of the valence band maximum. To improve the photocatalytic performance of black-P, here, using black-P and blue phosphorene (blue-P) monolayers, we propose a 2D van der Waals (vdW) heterojunction. Theoretical results, including the band structures, density of states, Bader charge population, charge density di erence, and optical absorption spectra, clearly reveal that the visible light absorption ability is obviously improved, and the band edge alignment of the proposed vdW heterojunction displays a typical type-II feature to effectively separate the photogenerated carriers. At the same time, the built-in interfacial electric field prevents the electron-hole recombination. These predictions suggest that the examined phosphorene-based vdW heterojunction is an efficient photocatalyst for solar water splitting.展开更多
Antichiral gyromagnetic photonic crystal(GPC)in a honeycomb lattice with the two interpenetrating triangular sublattices A and B magnetically biased in opposite directions can realize antichiral one-way edge states pr...Antichiral gyromagnetic photonic crystal(GPC)in a honeycomb lattice with the two interpenetrating triangular sublattices A and B magnetically biased in opposite directions can realize antichiral one-way edge states propagating along the same direction at its two parallel edges.Here,we report the construction and observation of topological beam splitting with the easily adjustable right-to-left ratio in an antichiral GPC.The splitter is compact and configurable,has high trans-mission efficiency,and allows for multi-channel utilization,crosstalk-proof,and robust against defects and obstacles.This magnificent performance is attributed to the peculiar property that antichiral one-way edge states exist only at zigzag edge but not at armchair edge of antichiral GPC.When we combine two rectangular antichiral GPCs holding left-and right-propagating antichiral one-way edge states respectively,bidirectionally radiating one-way edge states at two paral-lel zigzag edges can be achieved.Our observations can enrich the understanding of fundamental physics and expand to-pological photonic applications.展开更多
After a necessary condition is given, 3-rainbow coloring of split graphs with time complexity O(m) is obtained by constructive method. The number of corresponding colors is at most 2 or 3 more than the minimum number ...After a necessary condition is given, 3-rainbow coloring of split graphs with time complexity O(m) is obtained by constructive method. The number of corresponding colors is at most 2 or 3 more than the minimum number of colors needed in a 3-rainbow coloring.展开更多
Graphite-like carbon nitride （g-C3N4） based heterostrutures has attracted intensive attention due to their prominent photocatalytic performance. Here, we explore the g-CaN4/SnS2 coupling effect on the electronic str...Graphite-like carbon nitride （g-C3N4） based heterostrutures has attracted intensive attention due to their prominent photocatalytic performance. Here, we explore the g-CaN4/SnS2 coupling effect on the electronic structures and optical absorption of the proposed g-CaN4/SnS2 heterostructure through performing extensive hybrid functional calculations. The obtained geometric structure, band structures, band edge positions and optical absorptions clearly reveal that the g-C3N4 monolayer weakly couples to SnS2 sheet, and forms a typical van der Waals heterojunction. The g-C3N4/SnS2 heterostructure can effectively harvest visible light, and its valence band maximum and conduction band minimum locate in energetically favorable positions for both water oxidation and reduction reactions. Remarkably, the charge transfer from the g-C3N4 monolayer to SnS2 sheet leads to the built-in interface polarized electric field, which is desirable for the photogenerated carrier separation. The built-in interface polarized electric field as well as the nice band edge alignment implys that the g-CaN4/SnS2 heterostructure is a promising g-CaN4 based water splitting photocatalyst with good performance.展开更多
Among various photocatalytic materials,Z-scheme photocatalysts have drawn tremendous research interest due to high photocatalytic performance in solar water splitting.Here,we perform extensive hybrid density functiona...Among various photocatalytic materials,Z-scheme photocatalysts have drawn tremendous research interest due to high photocatalytic performance in solar water splitting.Here,we perform extensive hybrid density functional theory calculations to explore electronic structures,interfacial charge transfer,electrostatic potential profile,optical absorption properties,and photocatalytic properties of a proposed two-dimensional(2D)small-lattice-mismatched GaTe/Bi2Se3 heterostructure.Theoretical results clearly reveal that the examined heterostructure with a small direct band gap can effectively harvest the broad spectrum of the incoming sunlight.Due to the relative strong interfacial built-in electric field in the heterostructure and the small band gap between the valence band maximum of Ga Te monolayer and the conduction band minimum of Bi2Se3 nanosheet with slight band edge bending,these photogenerated carriers transfer via Z-scheme pathway,which results in the photogenerated electrons and holes effectively separating into the Ga Te monolayer and the Bi2Se3 nanosheet for the hydrogen and oxygen evolution reactions,respectively.Our results imply that the artificial 2D GaTe/Bi2Se3 is a promising Z-scheme photocatalyst for overall solar water splitting.展开更多
基于网络功能虚拟化(Network Function Virtualization,NFV)软硬件解耦的网络架构,运营商通过部署多个端到端逻辑网络为垂直行业提供多样化服务.然而,面对时延敏感型服务,需要将部分虚拟网络功能(Virtual Network Function,VNF)下沉到...基于网络功能虚拟化(Network Function Virtualization,NFV)软硬件解耦的网络架构,运营商通过部署多个端到端逻辑网络为垂直行业提供多样化服务.然而,面对时延敏感型服务,需要将部分虚拟网络功能(Virtual Network Function,VNF)下沉到网络边缘.基于此,多接入边缘计算(Multi-Access Edge Computing,MEC)技术应运而生.但是,与核心云相比,边缘云的资源容量和计算能力有限,因此,在部署网络服务时既要考虑云边协同下的资源分配问题,还要考虑如何进行流量调度以提升边缘云的资源利用率并解决底层网络中的负载均衡问题.鉴于此,本文提出了一种基于动态流量拆分的VNF部署和流量调度方法.通过动态流量拆分将流量请求分配到多条路径和多个节点,从而使全局流量分布的更加均衡,根据流量拆分结果进行VNF部署,进而减少发生网络拥塞和流量请求超时的概率.其中,每条流量请求的拆分条数与拆分比例可以根据底层网络的资源状态和流量的特性灵活调整.因此,整个过程包括有效的流量拆分策略、VNF部署策略和流量调度策略.本文将云边协同下的虚拟网络功能部署和流量调度问题描述为混合整数线性规划(Mixed Integer Linear Programming,MILP)问题,并提出了一种基于禁忌搜索算法和遗传算法的联合优化(TSGA)算法.仿真结果表明,TSGA算法相比于TS算法和RB算法可以分别提高7.7%和12.9%的流量请求接受率,并分别减少5.4%和7.8%的流量平均开销.展开更多
文摘Text embedded in images is one of many important cues for indexing and retrieval of images and videos. In the paper, we present a novel method of detecting text aligned either horizontally or vertically, in which a pyramid structure is used to represent an image and the features of the text are extracted using SUSAN edge detector. Text regions at each level of the pyramid are identified according to the autocorrelation analysis. New techniques are introduced to split the text regions into basic ones and merge them into text lines. By evaluating the method on a set of images, we obtain a very good performance of text detection.
基金supported by the National Natural Science Foundation of China(615730176140149961174162)
文摘Multiple complex networks, each with different properties and mutually fused, have the problems that the evolving process is time varying and non-equilibrium, network structures are layered and interlacing, and evolving characteristics are difficult to be measured. On that account, a dynamic evolving model of complex network with fusion nodes and overlap edges（CNFNOEs） is proposed. Firstly, we define some related concepts of CNFNOEs, and analyze the conversion process of fusion relationship and hierarchy relationship. According to the property difference of various nodes and edges, fusion nodes and overlap edges are subsequently split, and then the CNFNOEs is transformed to interlacing layered complex networks（ILCN）. Secondly,the node degree saturation and attraction factors are defined. On that basis, the evolution algorithm and the local world evolution model for ILCN are put forward. Moreover, four typical situations of nodes evolution are discussed, and the degree distribution law during evolution is analyzed by means of the mean field method.Numerical simulation results show that nodes unreached degree saturation follow the exponential distribution with an error of no more than 6%; nodes reached degree saturation follow the distribution of their connection capacities with an error of no more than 3%; network weaving coefficients have a positive correlation with the highest probability of new node and initial number of connected edges. The results have verified the feasibility and effectiveness of the model, which provides a new idea and method for exploring CNFNOE＇s evolving process and law. Also, the model has good application prospects in structure and dynamics research of transportation network, communication network, social contact network,etc.
基金the Artificial Intelligence Key Laboratory of Sichuan Province(Nos.2019RYJ05)National Natural Science Foundation of China(Nos.61971107).
文摘Unmanned Aerial Vehicle(UAV)has emerged as a promising technology for the support of human activities,such as target tracking,disaster rescue,and surveillance.However,these tasks require a large computation load of image or video processing,which imposes enormous pressure on the UAV computation platform.To solve this issue,in this work,we propose an intelligent Task Offloading Algorithm(iTOA)for UAV edge computing network.Compared with existing methods,iTOA is able to perceive the network’s environment intelligently to decide the offloading action based on deep Monte Calor Tree Search(MCTS),the core algorithm of Alpha Go.MCTS will simulate the offloading decision trajectories to acquire the best decision by maximizing the reward,such as lowest latency or power consumption.To accelerate the search convergence of MCTS,we also proposed a splitting Deep Neural Network(sDNN)to supply the prior probability for MCTS.The sDNN is trained by a self-supervised learning manager.Here,the training data set is obtained from iTOA itself as its own teacher.Compared with game theory and greedy search-based methods,the proposed iTOA improves service latency performance by 33%and 60%,respectively.
基金This work was financially supported by the Major State Basic Research Program of China (973 Program: 2002CB111506).
文摘Three types of landscape boundary (forest/pepper field, forest/cabbage field,and forest/grassland) were selected in the arid valley of upper reaches of Minjiang River,southwestern China. On the basis of vegetation diversity, the depth of edge influence (DEI) ondifferent types of landscape boundaries was estimated using principal components analysis (PCA)method and moving split-window techniques (MSWT). The results showed that in the 5 transects, PCAmethod was able to detect the edge influence depth with 3 transects, while MSWT could explain 4transects. It is concluded that PCA and MSWT both can be used to detect the depth of edge influencewithin 50 m from the edge to the interior. Similar conclusions were drawn in the forest of eachtransect with the two methods, but no similar conclusions were drawn in the pepper field of eachtransect. Although the two methods have advantages and disadvantages respectively, they are usefultools for characterizing edge dynamics. Comparing the two methods, MSWT is more successful.
基金supported by the National Natural Science Foundation of China (No.21473168 and No.21873088)the Natural Science Foundation of the Anhui Higher Education Institutions (No.KJ2016A144)
文摘As a clean and renewable future energy source, hydrogen fuel can be produced via solar water splitting. Two-dimensional (2D) black phosphorene (black-P) can harvest visible light due to the desirable band gap, which promises it as a metal-free photocatalyst. However, black-P can be only used to produce hydrogen since the oxidation potential of water locates lower than the position of the valence band maximum. To improve the photocatalytic performance of black-P, here, using black-P and blue phosphorene (blue-P) monolayers, we propose a 2D van der Waals (vdW) heterojunction. Theoretical results, including the band structures, density of states, Bader charge population, charge density di erence, and optical absorption spectra, clearly reveal that the visible light absorption ability is obviously improved, and the band edge alignment of the proposed vdW heterojunction displays a typical type-II feature to effectively separate the photogenerated carriers. At the same time, the built-in interfacial electric field prevents the electron-hole recombination. These predictions suggest that the examined phosphorene-based vdW heterojunction is an efficient photocatalyst for solar water splitting.
基金the National Natural Science Foundation of China(11974119)Science and Technology Project of Guangdong(2020B010190001)+1 种基金Guangdong Innovative and Entrepreneurial Research Team Program(2016ZT06C594)National Key R&D Program of China(2018YFA 0306200).
文摘Antichiral gyromagnetic photonic crystal(GPC)in a honeycomb lattice with the two interpenetrating triangular sublattices A and B magnetically biased in opposite directions can realize antichiral one-way edge states propagating along the same direction at its two parallel edges.Here,we report the construction and observation of topological beam splitting with the easily adjustable right-to-left ratio in an antichiral GPC.The splitter is compact and configurable,has high trans-mission efficiency,and allows for multi-channel utilization,crosstalk-proof,and robust against defects and obstacles.This magnificent performance is attributed to the peculiar property that antichiral one-way edge states exist only at zigzag edge but not at armchair edge of antichiral GPC.When we combine two rectangular antichiral GPCs holding left-and right-propagating antichiral one-way edge states respectively,bidirectionally radiating one-way edge states at two paral-lel zigzag edges can be achieved.Our observations can enrich the understanding of fundamental physics and expand to-pological photonic applications.
基金Supported by the National Natural Science Foundation of China(No.11001196)
文摘After a necessary condition is given, 3-rainbow coloring of split graphs with time complexity O(m) is obtained by constructive method. The number of corresponding colors is at most 2 or 3 more than the minimum number of colors needed in a 3-rainbow coloring.
基金This work is supported by the National Key Basic Research Program （No.2014CB921101）, the National Natural Science Foundation of China （No.21503149, No.21273208, and No.21473168）, the PhD foundation of Tianjin Normal University （No.52XBI408）, and the Innovative Program of Development Foundation of Hefei Center for Physical Science and Technology. Jing Huang thanks the Natural Science Foundation of the Anhui Higher Education Institutions （No.KJ2016A144） and the Natural Science Foundation of Anhui Province （No.1408085QB26）. Computational resources have been provided by CAS, Shanghai and USTC Supercomputer Centers.
文摘Graphite-like carbon nitride （g-C3N4） based heterostrutures has attracted intensive attention due to their prominent photocatalytic performance. Here, we explore the g-CaN4/SnS2 coupling effect on the electronic structures and optical absorption of the proposed g-CaN4/SnS2 heterostructure through performing extensive hybrid functional calculations. The obtained geometric structure, band structures, band edge positions and optical absorptions clearly reveal that the g-C3N4 monolayer weakly couples to SnS2 sheet, and forms a typical van der Waals heterojunction. The g-C3N4/SnS2 heterostructure can effectively harvest visible light, and its valence band maximum and conduction band minimum locate in energetically favorable positions for both water oxidation and reduction reactions. Remarkably, the charge transfer from the g-C3N4 monolayer to SnS2 sheet leads to the built-in interface polarized electric field, which is desirable for the photogenerated carrier separation. The built-in interface polarized electric field as well as the nice band edge alignment implys that the g-CaN4/SnS2 heterostructure is a promising g-CaN4 based water splitting photocatalyst with good performance.
基金the National Natural Science Foundation of China(No.21873088 and NO.11634011)。
文摘Among various photocatalytic materials,Z-scheme photocatalysts have drawn tremendous research interest due to high photocatalytic performance in solar water splitting.Here,we perform extensive hybrid density functional theory calculations to explore electronic structures,interfacial charge transfer,electrostatic potential profile,optical absorption properties,and photocatalytic properties of a proposed two-dimensional(2D)small-lattice-mismatched GaTe/Bi2Se3 heterostructure.Theoretical results clearly reveal that the examined heterostructure with a small direct band gap can effectively harvest the broad spectrum of the incoming sunlight.Due to the relative strong interfacial built-in electric field in the heterostructure and the small band gap between the valence band maximum of Ga Te monolayer and the conduction band minimum of Bi2Se3 nanosheet with slight band edge bending,these photogenerated carriers transfer via Z-scheme pathway,which results in the photogenerated electrons and holes effectively separating into the Ga Te monolayer and the Bi2Se3 nanosheet for the hydrogen and oxygen evolution reactions,respectively.Our results imply that the artificial 2D GaTe/Bi2Se3 is a promising Z-scheme photocatalyst for overall solar water splitting.
文摘基于网络功能虚拟化(Network Function Virtualization,NFV)软硬件解耦的网络架构,运营商通过部署多个端到端逻辑网络为垂直行业提供多样化服务.然而,面对时延敏感型服务,需要将部分虚拟网络功能(Virtual Network Function,VNF)下沉到网络边缘.基于此,多接入边缘计算(Multi-Access Edge Computing,MEC)技术应运而生.但是,与核心云相比,边缘云的资源容量和计算能力有限,因此,在部署网络服务时既要考虑云边协同下的资源分配问题,还要考虑如何进行流量调度以提升边缘云的资源利用率并解决底层网络中的负载均衡问题.鉴于此,本文提出了一种基于动态流量拆分的VNF部署和流量调度方法.通过动态流量拆分将流量请求分配到多条路径和多个节点,从而使全局流量分布的更加均衡,根据流量拆分结果进行VNF部署,进而减少发生网络拥塞和流量请求超时的概率.其中,每条流量请求的拆分条数与拆分比例可以根据底层网络的资源状态和流量的特性灵活调整.因此,整个过程包括有效的流量拆分策略、VNF部署策略和流量调度策略.本文将云边协同下的虚拟网络功能部署和流量调度问题描述为混合整数线性规划(Mixed Integer Linear Programming,MILP)问题,并提出了一种基于禁忌搜索算法和遗传算法的联合优化(TSGA)算法.仿真结果表明,TSGA算法相比于TS算法和RB算法可以分别提高7.7%和12.9%的流量请求接受率,并分别减少5.4%和7.8%的流量平均开销.
