Solar energy is a pivotal clean energy source in the transition to carbon neutrality from fossil fuels.However,the intermittent and stochastic characteristics of solar radiation pose challenges for accurate simulation...Solar energy is a pivotal clean energy source in the transition to carbon neutrality from fossil fuels.However,the intermittent and stochastic characteristics of solar radiation pose challenges for accurate simulation and prediction.Accurately simulating and predicting solar radiation and its variability are crucial for optimizing solar energy utilization.This study conducted simulation experiments using the WRF-Solar model from 25 June to 25 July 2022,to evaluate the accuracy and performance of the simulated solar radiation across China.The simulations covered the whole country with a grid spacing of 27 km and were compared with ground observation network data from the Chinese Ecosystem Research Network.The results indicated that WRF-Solar can accurately capture the spatiotemporal patterns of global horizontal irradiance over China,but there is still an overestimation of solar radiation,and the model underestimates the total cloud cover.The root-mean-square error ranged from 92.83 to 188.13 W m^(-2) and the mean bias(MB)ranged from 21.05 to 56.22 W m^(-2).The simulation showed the smallest MB at Lhasa on the Qinghai–Tibet Plateau,while the largest MB was observed in Southeast China.To enhance the accuracy of solar radiation simulation,the authors compared the Fast All-sky Radiation Model for Solar with the Rapid Radiative Transfer Model for General Circulation Models and found that the former provides better simulation.展开更多
In recent years,intensified environmental pollution and climate change have increasingly exposed the world to natural disasters such as earthquakes and floods,resulting in substantial economic losses[1].These disaster...In recent years,intensified environmental pollution and climate change have increasingly exposed the world to natural disasters such as earthquakes and floods,resulting in substantial economic losses[1].These disasters frequently damage terrestrial communication infrastructures,making the rapid deployment of emergency communication networks in affected areas critical in increasing rescue efficiency[2].展开更多
This paper presents an efficient algorithm for reducing RLC power/ground network complexities by exploitation of the regularities in the power/ground networks. The new method first builds the equivalent models for man...This paper presents an efficient algorithm for reducing RLC power/ground network complexities by exploitation of the regularities in the power/ground networks. The new method first builds the equivalent models for many series RLC-current chains based on their Norton＇s form companion models in the original networks,and then the precondition conjugate gradient based iterative method is used to solve the reduced networks,which are symmetric positive definite. The solutions of the original networks are then back solved from those of the reduced networks.Experimental results show that the complexities of reduced networks are typically significantly smaller than those of the original circuits, which makes the new algorithm extremely fast. For instance, power/ground networks with more than one million branches can be solved in a few minutes on modern Sun workstations.展开更多
A CAD tool based on a group of efficient algorithms to verify,design,and optimize power/ground networks for standard cell model is presented.Nonlinear programming techniques,branch and bound algorithms and incomplete ...A CAD tool based on a group of efficient algorithms to verify,design,and optimize power/ground networks for standard cell model is presented.Nonlinear programming techniques,branch and bound algorithms and incomplete Cholesky decomposition conjugate gradient method (ICCG) are the three main parts of our work.Users can choose nonlinear programming method or branch and bound algorithm to satisfy their different requirements of precision and speed.The experimental results prove that the algorithms can run very fast with lower wiring resources consumption.As a result,the CAD tool based on these algorithms is able to cope with large-scale circuits.展开更多
A new form of producing and sharing knowledge has emerged as an international(United States of America,Asia,and Europe) research collaboration,known as the Long-Term Ecological Research(LTER) Network.Although Africa b...A new form of producing and sharing knowledge has emerged as an international(United States of America,Asia,and Europe) research collaboration,known as the Long-Term Ecological Research(LTER) Network.Although Africa boasts rich biodiversity,including endemic species,it lacks the long-term initiatives to underpin sustainable biodiversity managements.At present,climate change may exacerbate hunger and poverty concerns in addition to resulting in ecosystem degradation,land use change,and other threats in Africa.Therefore,ecosystem monitoring was suggested to understanding the effects of climate change and setting strategies to mitigate these changes.This paper aimed to investigate ecosystem monitoring ground sites and address their coverage gaps in Africa to provide a foundation for optimizing the African Ecosystem Research Network(AERN) ground sites.The geographic coordinates and characteristics of ground sites-based ecosystem monitoring were collected from various networks aligned with the LTER implementation in Africa.Additionally,climatic data and biodiversity distribution maps were retrieved from various sources.These data were used to assess the size of existing ground sites and the gaps in description,ecosystems and biomes.The results reveal that there were 1089 sites established by various networks.Among these sites,30.5%,27.5%,and 28.8% had no information of area,year of establishment,current status,respectively.However,68.0% of them had an area equal to or greater than 1 km2.Sites were created progressively over the course of the years,with 68.9% being created from 2000 to 2005.To date,only 41.5% of the sites were operational.The sites were scattered across Africa,but they were concentrated in Eastern and Southern Africa.The unbalanced distribution pattern of the sites left Central and Northern Africa hardly covered,and many unique ecosystems in Central Africa were not included.To sustain these sites,the AERN should be based on operational sites,seeking secure funding by establishing multiple partnerships.展开更多
In this paper,a layer-constrained triangulated irregular network（ LC-TIN） algorithm is proposed for three-dimensional（ 3 D） modelling,and applied to construct a 3 D model for geological disease information based o...In this paper,a layer-constrained triangulated irregular network（ LC-TIN） algorithm is proposed for three-dimensional（ 3 D） modelling,and applied to construct a 3 D model for geological disease information based on ground penetrating radar（ GPR） data. Compared with the traditional TIN algorithm,the LCTIN algorithm introduced a layer constraint to the discrete data points during the 3 D modelling process,and it can dynamically construct networks from layer to layer and implement 3 D modelling for arbitrary shapes with high precision. The experimental results validated this method,the proposed algorithm not only can maintain the rationality of triangulation network,but also can obtain a good generation speed. In addition,the algorithm is also introduced to our self-developed 3 D visualization platform,which utilized GPR data to model geological diseases. Therefore the feasibility of the algorithm is verified in the practical application.展开更多
As an emerging vertical heterogeneous network architecture that integrates the satellite-based space networks,air networks,and traditional ground networks,space–air–ground integrated network(SAGIN)is developed to re...As an emerging vertical heterogeneous network architecture that integrates the satellite-based space networks,air networks,and traditional ground networks,space–air–ground integrated network(SAGIN)is developed to realize the Internet of everything,global coverage,and ubiquitous intelligent communications.However,SAGIN also faces quite a few challenges due to its unique characteristics,such as highly complex network architecture,highly dynamic node topology,time-varying communication channels,and restricted resources.In this paper,we first introduce the architecture and benefits of SAGIN,and then present the faced challenges.Next,we discuss some key technologies in SAGIN.In particular,we discuss the flexible access in the realization of a dynamic communication architecture,explore some efficient resource scheduling methods to avoid wastage of resources,and investigate the secure communications,such as covert communications,physical layer security,and anti-jamming communications,in SAGIN.Finally,the potential future directions are discussed.展开更多
The space–air–ground information network(SAGIN)has been widely used due to its excellent performances including wide coverage and high flexibility.However,the dynamic network topology of SAGIN presents challenges fo...The space–air–ground information network(SAGIN)has been widely used due to its excellent performances including wide coverage and high flexibility.However,the dynamic network topology of SAGIN presents challenges for traditional protocols.The statistical priority-based multiple access(SPMA)control protocol has received widespread attention because it effectively allocates resources in networks with heterogeneous terminals and dynamic topology.However,the existing SPMA protocols suffer from issues like large errors and low prediction accuracy in channel load statistics.Therefore,this paper proposes an improved SPMA based on the bi-directional long short-term memory(BiLSTM)neural network.First,we analyze and correct errors in channel load statistics at the physical layer,then develop a BiLSTM-based channel load prediction model,and finally simulated the improved SPMA using Matlab.Experimental results show that the proposed channel load prediction model achieves good prediction accuracy,and the improved SPMA protocol markedly improves channel utilization,providing differentiated services for multi-priority businesses.展开更多
Space–air–ground integrated networks(SAGINs)have been considered to be the trend of future 6G network development.In the presence of hostile interferers/attackers especially under military application scenarios,the ...Space–air–ground integrated networks(SAGINs)have been considered to be the trend of future 6G network development.In the presence of hostile interferers/attackers especially under military application scenarios,the resilience of the SAGIN to various threats such as physical,electronic,and cyberattacks can be crucial to guarantee desirable networking performance.This motivates advanced enhancement and evaluation schemes for the resilience of SAGIN.In this paper,the SAGIN resilience enhancement process is divided into 4 resilience enhancement phases,namely,resistance,absorption,recovery,and reconfiguration.Then,different resilience enhancement methods are discussed and analyzed within each phase,respectively.Further,considering that SAGIN is coupled by several cross-domain subsystems,the indicator system for resilience capabilities evaluation and evaluation methods of SAGIN are given.Firstly,the resilience capability of each subsystem is evaluated based on 4 indicators,namely,resistance,absorption,recovery,and reconfiguration capability.Then,by combining the resilience capability of the space-based,air-based,and ground-based communication subnetworks,the overall resilience enhancement capability of SAGIN is evaluated.展开更多
Electrically conductive coatings are required for static charge dissipation in power ground network. In the present investigation electrically conductive nanocoatings were prepared by the incorporation of graphite, na...Electrically conductive coatings are required for static charge dissipation in power ground network. In the present investigation electrically conductive nanocoatings were prepared by the incorporation of graphite, nano-SiO2 concentrate, acrylic nanoemulsion and fluorocarbon emulsion onto the waterborne epoxy polymer. The nanosize distribution of nano-SiO2 concentrate and nanoemulsion was characterized with laser diffraction analyzer and scanning electron microscopy （SEM）. From the results of SEM image, the graphite particles were well distributed in conductive coating. The corrosion resistance and thermal stability of nanocoatings were comparatively studied by SEM and thermogravimetry （TG）. The corrosion-inhibiting properties of the conductive nanocoatings were investigated by salt immersion test. The measurements of contact angle, bonding strength and heat-freeze charge demonstrated that 1.5-2.0 wt% nanoparticles improve the resistance to pollution, adherence and resistance to heat-freeze charge of conductive nanocoatings. The measured results of surface electric resistance of nanocoatings demonstrated that a small amount of nano- SiO2 particles could enhance the conductivity in the corrosive environment.展开更多
The existing current break protection cannot achieve full-line current protection and may lose its protection capability. Therefore, a self-adjusted full-line current protection strategy based on a double-layer criter...The existing current break protection cannot achieve full-line current protection and may lose its protection capability. Therefore, a self-adjusted full-line current protection strategy based on a double-layer criterion is proposed. The first layer of the criterion adopts the adaptive adjustment threshold as the setting value to realize full-line fault monitoring, which is not affected by the system operation mode and fault type. The second layer is used to locate the fault section of the line and improve the selectivity of the protection strategy. Considering the difficulty in accurately identifying high-resistance ground faults using current protection, an identification method based on compound power is proposed by analyzing the zero-sequence network of the system. Simulation results show that the proposed protection strategy can realize full-length line protection and the effective identification of high-resistance ground faults and is not affected by the system load variation and fault type.展开更多
The rapid expansion of satellite Internet deployments,driven by the rise of Space-Ground Integration Network (SGIN) construction,has led to a significant increase in satellite numbers.To address the challenge of effic...The rapid expansion of satellite Internet deployments,driven by the rise of Space-Ground Integration Network (SGIN) construction,has led to a significant increase in satellite numbers.To address the challenge of efficient networking between large-scale satellites and limited ground station resources,this paper presents a hybrid learning-assisted multi-parallel algorithm (HLMP).The HLMP features a multi-parallel solving and deconflicting framework,a learning-assisted metaheuristic (LM) algorithm combining reinforcement learning (RL) and Tabu simulated annealing (TSA),and a linear programming (LP) exact-solving algorithm.The framework first divides the problem into parallel sub-problems based on the time domain,then applies LM and LP to solve each sub-problem in parallel.LM uses LP-generated scheduling results to improve its own accuracy.The deconflicting strategy integrates and refines the planning results from all sub-problems,ensuring an optimized outcome.HLMP advances beyond traditional task-driven satellite scheduling methods by offering a novel approach for optimizing large-scale satellite-ground networks under the new macro paradigm of "maximizing linkage to the greatest extent feasible." Experimental cases involving up to 1,000 satellites and 100 ground stations highlight HLMP’s efficiency.Comparative experiments with other metaheuristic algorithms and the CPLEX solver further demonstrate HLMP’s ability to generate high-quality solutions more quickly.展开更多
Secondary earth faults occur frequently in power distribution networks under harsh weather conditions.Owing to its characteristics,a secondary earth fault is typically hidden within the transient of the first fault.Th...Secondary earth faults occur frequently in power distribution networks under harsh weather conditions.Owing to its characteristics,a secondary earth fault is typically hidden within the transient of the first fault.Therefore,most researchers tend to focus on a feeder with single fault while disregarding secondary faults.This paper presents a fault feeder identification method that considers secondary earth faults in a non-effectively grounded distribution network.First,the wavelet singular entropy method is used to detect a secondary fault event.This method can identify the moment at which a secondary fault occurs.The zero-sequence current data can be categorized into two fault stages.The first and second fault stages correspond to the first and secondary faults,respectively.Subsequently,a similarity matrix containing the time-frequency transient information of the zero-sequence current at the two fault stages is defined to identify the fault feeders.Finally,to confirm the effectiveness and reliability of the proposed method,we conduct simulation experiments and an adaptability analysis based on an electromagnetic transient program.展开更多
This paper proposes a novel algorithm, which can be used to model and analyzemesh tree hybrid power/ground distribution networks with multiple voltage supply in time domain.Not only this algorithm enhances common meth...This paper proposes a novel algorithm, which can be used to model and analyzemesh tree hybrid power/ground distribution networks with multiple voltage supply in time domain.Not only this algorithm enhances common method''s ability on analysis of power/ground network withirregular topology, but also very high accuracy it keeps. The accuracy and stability of thisalgorithm is proved using strict math method in this paper. Also, the usage of both preconditiontechnique based on Incomplete Choleskey Decomposition and fast variable elimination technique hasimproved the algorithm''s efficiency a lot. Experimental results show that it can finish the analysisof power/ground network with enormous, size within very short time. Also, this algorithm can beapplied to analyze the clock network, bus network, and signal network without buffer under highworking frequency because of the independence of the topology.展开更多
This article presents a comprehensive study on the emerging near-space communications (NS-COM) within the context of space–air–ground–sea integrated network (SAGSIN). Specifically, we firstly explore the recent tec...This article presents a comprehensive study on the emerging near-space communications (NS-COM) within the context of space–air–ground–sea integrated network (SAGSIN). Specifically, we firstly explore the recent technical developments of NS-COM, followed by the discussions about motivations behind integrating NS-COM into SAGSIN. To further demonstrate the necessity of NS-COM, a comparative analysis between the NS-COM network and other counterparts in SAGSIN is conducted, covering aspects of deployment, coverage, channel characteristics, and unique problems of NS-COM network. Afterward, the technical aspects of NS-COM, including channel modeling, random access, channel estimation, array-based beam management, and joint network optimization, are examined in detail. Furthermore, we explore the potential applications of NS-COM, such as structural expansion in SAGSIN communication, civil aviation communication, remote and urgent communication, weather monitoring, and carbon neutrality. Finally, some promising research avenues are identified, including stratospheric satellite-to-ground direct links for mobile terminals, reconfigurable multiple-input multiple-output and holographic multiple-input multiple-output, federated learning in NS-COM networks, maritime communication, electromagnetic spectrum sensing and adversarial game, integrated sensing and communications, stratospheric-satellite-based radar detection and imaging, NS-COM-assisted enhanced global navigation system, NS-COM-assisted intelligent unmanned system, and free-space optical communication. Overall, this paper highlights that the NS-COM plays an indispensable role in the SAGSIN puzzle, providing substantial performance and coverage enhancement to the traditional SAGSIN architecture.展开更多
The rational design of a grounding grid is a crucial prerequisite for ensuring the safe and reliable operation of mobile substations.This paper discusses the design of the grounding grid for mobile substations from th...The rational design of a grounding grid is a crucial prerequisite for ensuring the safe and reliable operation of mobile substations.This paper discusses the design of the grounding grid for mobile substations from the perspective of standardized design,aiming to minimize on-site construction and enable rapid deployment.It introduces a type of grounding ring network design that can ensure the entire equipment forms a reliable equipotential grounding,thereby enhancing the operational reliability of mobile substations.展开更多
Near-space communication network(NS-ComNet),as an indispensable component of sixth-generation(6G)and beyond mobile communication systems and the space–air–ground–sea integrated network(SAGSIN),demonstrates unique a...Near-space communication network(NS-ComNet),as an indispensable component of sixth-generation(6G)and beyond mobile communication systems and the space–air–ground–sea integrated network(SAGSIN),demonstrates unique advantages in wide-area coverage,long-endurance high-altitude operation,and highly flexible deployment.This paper presents a comprehensive review of NS-ComNet for 6G and beyond era.Specifically,by contrasting satellite,low-altitude unmanned aerial vehicle(UAV),and terrestrial communications,we first elucidate the background and motivation for integrating NSComNet into 6G network architectures.Subsequently,we review the developmental status of nearspace platforms,including high-altitude balloons,solar-powered UAVs,and stratospheric airships,and analyze critical challenges faced by NS-ComNet.To address these challenges,the research focuses on key enabling technologies such as topology design,resource and handover management,and multiobjective joint optimization,with particular emphasis on artificial intelligence techniques for NS-ComNet.Finally,envisioning future intelligent collaborative networks that integrate NS-ComNet with satellite–UAV–terrestrial systems,we explore promising directions.This paper aims to provide technical insights and research foundations for the systematic construction of NS-ComNet and its deep deployment in the 6G and beyond era.展开更多
基金supported by the National Natural Science Foundation of China[grant number 42175132]the National Key R&D Program[grant number 2020YFA0607802]the CAS Information Technology Program[grant number CAS-WX2021SF-0107-02]。
文摘Solar energy is a pivotal clean energy source in the transition to carbon neutrality from fossil fuels.However,the intermittent and stochastic characteristics of solar radiation pose challenges for accurate simulation and prediction.Accurately simulating and predicting solar radiation and its variability are crucial for optimizing solar energy utilization.This study conducted simulation experiments using the WRF-Solar model from 25 June to 25 July 2022,to evaluate the accuracy and performance of the simulated solar radiation across China.The simulations covered the whole country with a grid spacing of 27 km and were compared with ground observation network data from the Chinese Ecosystem Research Network.The results indicated that WRF-Solar can accurately capture the spatiotemporal patterns of global horizontal irradiance over China,but there is still an overestimation of solar radiation,and the model underestimates the total cloud cover.The root-mean-square error ranged from 92.83 to 188.13 W m^(-2) and the mean bias(MB)ranged from 21.05 to 56.22 W m^(-2).The simulation showed the smallest MB at Lhasa on the Qinghai–Tibet Plateau,while the largest MB was observed in Southeast China.To enhance the accuracy of solar radiation simulation,the authors compared the Fast All-sky Radiation Model for Solar with the Rapid Radiative Transfer Model for General Circulation Models and found that the former provides better simulation.
基金supported in part by the National Natural Science Foundation of China(U2441226).
文摘In recent years,intensified environmental pollution and climate change have increasingly exposed the world to natural disasters such as earthquakes and floods,resulting in substantial economic losses[1].These disasters frequently damage terrestrial communication infrastructures,making the rapid deployment of emergency communication networks in affected areas critical in increasing rescue efficiency[2].
文摘This paper presents an efficient algorithm for reducing RLC power/ground network complexities by exploitation of the regularities in the power/ground networks. The new method first builds the equivalent models for many series RLC-current chains based on their Norton＇s form companion models in the original networks,and then the precondition conjugate gradient based iterative method is used to solve the reduced networks,which are symmetric positive definite. The solutions of the original networks are then back solved from those of the reduced networks.Experimental results show that the complexities of reduced networks are typically significantly smaller than those of the original circuits, which makes the new algorithm extremely fast. For instance, power/ground networks with more than one million branches can be solved in a few minutes on modern Sun workstations.
文摘A CAD tool based on a group of efficient algorithms to verify,design,and optimize power/ground networks for standard cell model is presented.Nonlinear programming techniques,branch and bound algorithms and incomplete Cholesky decomposition conjugate gradient method (ICCG) are the three main parts of our work.Users can choose nonlinear programming method or branch and bound algorithm to satisfy their different requirements of precision and speed.The experimental results prove that the algorithms can run very fast with lower wiring resources consumption.As a result,the CAD tool based on these algorithms is able to cope with large-scale circuits.
基金Under the auspices of National Natural Science Foundation of China(No.31161140355)
文摘A new form of producing and sharing knowledge has emerged as an international(United States of America,Asia,and Europe) research collaboration,known as the Long-Term Ecological Research(LTER) Network.Although Africa boasts rich biodiversity,including endemic species,it lacks the long-term initiatives to underpin sustainable biodiversity managements.At present,climate change may exacerbate hunger and poverty concerns in addition to resulting in ecosystem degradation,land use change,and other threats in Africa.Therefore,ecosystem monitoring was suggested to understanding the effects of climate change and setting strategies to mitigate these changes.This paper aimed to investigate ecosystem monitoring ground sites and address their coverage gaps in Africa to provide a foundation for optimizing the African Ecosystem Research Network(AERN) ground sites.The geographic coordinates and characteristics of ground sites-based ecosystem monitoring were collected from various networks aligned with the LTER implementation in Africa.Additionally,climatic data and biodiversity distribution maps were retrieved from various sources.These data were used to assess the size of existing ground sites and the gaps in description,ecosystems and biomes.The results reveal that there were 1089 sites established by various networks.Among these sites,30.5%,27.5%,and 28.8% had no information of area,year of establishment,current status,respectively.However,68.0% of them had an area equal to or greater than 1 km2.Sites were created progressively over the course of the years,with 68.9% being created from 2000 to 2005.To date,only 41.5% of the sites were operational.The sites were scattered across Africa,but they were concentrated in Eastern and Southern Africa.The unbalanced distribution pattern of the sites left Central and Northern Africa hardly covered,and many unique ecosystems in Central Africa were not included.To sustain these sites,the AERN should be based on operational sites,seeking secure funding by establishing multiple partnerships.
基金Supported by the National Science Foundation of China(61302157)the National High Technology Research and Development Program of China(863 Program)(2012AA12A308)the Yue Qi Young Scholars Project of China University of Mining&Technology(Beijing)(800015Z1117)
文摘In this paper,a layer-constrained triangulated irregular network（ LC-TIN） algorithm is proposed for three-dimensional（ 3 D） modelling,and applied to construct a 3 D model for geological disease information based on ground penetrating radar（ GPR） data. Compared with the traditional TIN algorithm,the LCTIN algorithm introduced a layer constraint to the discrete data points during the 3 D modelling process,and it can dynamically construct networks from layer to layer and implement 3 D modelling for arbitrary shapes with high precision. The experimental results validated this method,the proposed algorithm not only can maintain the rationality of triangulation network,but also can obtain a good generation speed. In addition,the algorithm is also introduced to our self-developed 3 D visualization platform,which utilized GPR data to model geological diseases. Therefore the feasibility of the algorithm is verified in the practical application.
基金supported by the National Natural Science Foundation of China under grants U23B2005,62201054,62201055,62371047Beijing Natural Science Foundation under grant JQ23015Beijing Nova Program under grant Z211100002121161.
文摘As an emerging vertical heterogeneous network architecture that integrates the satellite-based space networks,air networks,and traditional ground networks,space–air–ground integrated network(SAGIN)is developed to realize the Internet of everything,global coverage,and ubiquitous intelligent communications.However,SAGIN also faces quite a few challenges due to its unique characteristics,such as highly complex network architecture,highly dynamic node topology,time-varying communication channels,and restricted resources.In this paper,we first introduce the architecture and benefits of SAGIN,and then present the faced challenges.Next,we discuss some key technologies in SAGIN.In particular,we discuss the flexible access in the realization of a dynamic communication architecture,explore some efficient resource scheduling methods to avoid wastage of resources,and investigate the secure communications,such as covert communications,physical layer security,and anti-jamming communications,in SAGIN.Finally,the potential future directions are discussed.
基金funded by the National Natural Science Foundation of China Youth Fund(grant no.62203048)the National Natural Science Foundation of China(grant nos.62073039 and 62073040).
文摘The space–air–ground information network(SAGIN)has been widely used due to its excellent performances including wide coverage and high flexibility.However,the dynamic network topology of SAGIN presents challenges for traditional protocols.The statistical priority-based multiple access(SPMA)control protocol has received widespread attention because it effectively allocates resources in networks with heterogeneous terminals and dynamic topology.However,the existing SPMA protocols suffer from issues like large errors and low prediction accuracy in channel load statistics.Therefore,this paper proposes an improved SPMA based on the bi-directional long short-term memory(BiLSTM)neural network.First,we analyze and correct errors in channel load statistics at the physical layer,then develop a BiLSTM-based channel load prediction model,and finally simulated the improved SPMA using Matlab.Experimental results show that the proposed channel load prediction model achieves good prediction accuracy,and the improved SPMA protocol markedly improves channel utilization,providing differentiated services for multi-priority businesses.
基金supported by the National Natural Science Foundation of China(nos.U22A2007 and 62171010).
文摘Space–air–ground integrated networks(SAGINs)have been considered to be the trend of future 6G network development.In the presence of hostile interferers/attackers especially under military application scenarios,the resilience of the SAGIN to various threats such as physical,electronic,and cyberattacks can be crucial to guarantee desirable networking performance.This motivates advanced enhancement and evaluation schemes for the resilience of SAGIN.In this paper,the SAGIN resilience enhancement process is divided into 4 resilience enhancement phases,namely,resistance,absorption,recovery,and reconfiguration.Then,different resilience enhancement methods are discussed and analyzed within each phase,respectively.Further,considering that SAGIN is coupled by several cross-domain subsystems,the indicator system for resilience capabilities evaluation and evaluation methods of SAGIN are given.Firstly,the resilience capability of each subsystem is evaluated based on 4 indicators,namely,resistance,absorption,recovery,and reconfiguration capability.Then,by combining the resilience capability of the space-based,air-based,and ground-based communication subnetworks,the overall resilience enhancement capability of SAGIN is evaluated.
基金Financial supports of this research by State Grid Program (Research and Demonstration in Corrosion and Protection of Transmission Line Tower and Power Ground Network at the Heavy Industrial Pollution Area)State Key Laboratory for Corrosion and Protection Program(Grant No.JO8F161PP61)
文摘Electrically conductive coatings are required for static charge dissipation in power ground network. In the present investigation electrically conductive nanocoatings were prepared by the incorporation of graphite, nano-SiO2 concentrate, acrylic nanoemulsion and fluorocarbon emulsion onto the waterborne epoxy polymer. The nanosize distribution of nano-SiO2 concentrate and nanoemulsion was characterized with laser diffraction analyzer and scanning electron microscopy （SEM）. From the results of SEM image, the graphite particles were well distributed in conductive coating. The corrosion resistance and thermal stability of nanocoatings were comparatively studied by SEM and thermogravimetry （TG）. The corrosion-inhibiting properties of the conductive nanocoatings were investigated by salt immersion test. The measurements of contact angle, bonding strength and heat-freeze charge demonstrated that 1.5-2.0 wt% nanoparticles improve the resistance to pollution, adherence and resistance to heat-freeze charge of conductive nanocoatings. The measured results of surface electric resistance of nanocoatings demonstrated that a small amount of nano- SiO2 particles could enhance the conductivity in the corrosive environment.
基金Supported by the National Natural Science Foundation of China(U22B20106)the State Grid Power Company of Hunan Province Science and Technology Project(5216A5220022).
文摘The existing current break protection cannot achieve full-line current protection and may lose its protection capability. Therefore, a self-adjusted full-line current protection strategy based on a double-layer criterion is proposed. The first layer of the criterion adopts the adaptive adjustment threshold as the setting value to realize full-line fault monitoring, which is not affected by the system operation mode and fault type. The second layer is used to locate the fault section of the line and improve the selectivity of the protection strategy. Considering the difficulty in accurately identifying high-resistance ground faults using current protection, an identification method based on compound power is proposed by analyzing the zero-sequence network of the system. Simulation results show that the proposed protection strategy can realize full-length line protection and the effective identification of high-resistance ground faults and is not affected by the system load variation and fault type.
基金supported by the National Natural Science Foundation of China(Grant Nos.72201272 and U23B2039)the National Fundamental Research Project,China(Grant No.2023-JCJQ-QT-042)the Science Foundation of National University of Defense Technology,China(Grant No.ZK22-48).
文摘The rapid expansion of satellite Internet deployments,driven by the rise of Space-Ground Integration Network (SGIN) construction,has led to a significant increase in satellite numbers.To address the challenge of efficient networking between large-scale satellites and limited ground station resources,this paper presents a hybrid learning-assisted multi-parallel algorithm (HLMP).The HLMP features a multi-parallel solving and deconflicting framework,a learning-assisted metaheuristic (LM) algorithm combining reinforcement learning (RL) and Tabu simulated annealing (TSA),and a linear programming (LP) exact-solving algorithm.The framework first divides the problem into parallel sub-problems based on the time domain,then applies LM and LP to solve each sub-problem in parallel.LM uses LP-generated scheduling results to improve its own accuracy.The deconflicting strategy integrates and refines the planning results from all sub-problems,ensuring an optimized outcome.HLMP advances beyond traditional task-driven satellite scheduling methods by offering a novel approach for optimizing large-scale satellite-ground networks under the new macro paradigm of "maximizing linkage to the greatest extent feasible." Experimental cases involving up to 1,000 satellites and 100 ground stations highlight HLMP’s efficiency.Comparative experiments with other metaheuristic algorithms and the CPLEX solver further demonstrate HLMP’s ability to generate high-quality solutions more quickly.
基金This work was supported in part by National Science Foundation of China(No.51907097)National Key R&D Program of China(No.2020YFF0305800)+1 种基金the Full-time Postdoc Research and Development Fund of Sichuan University in China(No.2019SCU12003)the Applied Basic Research of Sichuan Province(No.2020YJ0012).
文摘Secondary earth faults occur frequently in power distribution networks under harsh weather conditions.Owing to its characteristics,a secondary earth fault is typically hidden within the transient of the first fault.Therefore,most researchers tend to focus on a feeder with single fault while disregarding secondary faults.This paper presents a fault feeder identification method that considers secondary earth faults in a non-effectively grounded distribution network.First,the wavelet singular entropy method is used to detect a secondary fault event.This method can identify the moment at which a secondary fault occurs.The zero-sequence current data can be categorized into two fault stages.The first and second fault stages correspond to the first and secondary faults,respectively.Subsequently,a similarity matrix containing the time-frequency transient information of the zero-sequence current at the two fault stages is defined to identify the fault feeders.Finally,to confirm the effectiveness and reliability of the proposed method,we conduct simulation experiments and an adaptability analysis based on an electromagnetic transient program.
文摘This paper proposes a novel algorithm, which can be used to model and analyzemesh tree hybrid power/ground distribution networks with multiple voltage supply in time domain.Not only this algorithm enhances common method''s ability on analysis of power/ground network withirregular topology, but also very high accuracy it keeps. The accuracy and stability of thisalgorithm is proved using strict math method in this paper. Also, the usage of both preconditiontechnique based on Incomplete Choleskey Decomposition and fast variable elimination technique hasimproved the algorithm''s efficiency a lot. Experimental results show that it can finish the analysisof power/ground network with enormous, size within very short time. Also, this algorithm can beapplied to analyze the clock network, bus network, and signal network without buffer under highworking frequency because of the independence of the topology.
基金supported in part by the Beijing Nova Program,the Shandong Province Natural Science Foundation under grant ZR2022YQ62the Natural Science Foundation of China(NSFC)under grants 62071044 and U2233216.
文摘This article presents a comprehensive study on the emerging near-space communications (NS-COM) within the context of space–air–ground–sea integrated network (SAGSIN). Specifically, we firstly explore the recent technical developments of NS-COM, followed by the discussions about motivations behind integrating NS-COM into SAGSIN. To further demonstrate the necessity of NS-COM, a comparative analysis between the NS-COM network and other counterparts in SAGSIN is conducted, covering aspects of deployment, coverage, channel characteristics, and unique problems of NS-COM network. Afterward, the technical aspects of NS-COM, including channel modeling, random access, channel estimation, array-based beam management, and joint network optimization, are examined in detail. Furthermore, we explore the potential applications of NS-COM, such as structural expansion in SAGSIN communication, civil aviation communication, remote and urgent communication, weather monitoring, and carbon neutrality. Finally, some promising research avenues are identified, including stratospheric satellite-to-ground direct links for mobile terminals, reconfigurable multiple-input multiple-output and holographic multiple-input multiple-output, federated learning in NS-COM networks, maritime communication, electromagnetic spectrum sensing and adversarial game, integrated sensing and communications, stratospheric-satellite-based radar detection and imaging, NS-COM-assisted enhanced global navigation system, NS-COM-assisted intelligent unmanned system, and free-space optical communication. Overall, this paper highlights that the NS-COM plays an indispensable role in the SAGSIN puzzle, providing substantial performance and coverage enhancement to the traditional SAGSIN architecture.
文摘The rational design of a grounding grid is a crucial prerequisite for ensuring the safe and reliable operation of mobile substations.This paper discusses the design of the grounding grid for mobile substations from the perspective of standardized design,aiming to minimize on-site construction and enable rapid deployment.It introduces a type of grounding ring network design that can ensure the entire equipment forms a reliable equipotential grounding,thereby enhancing the operational reliability of mobile substations.
基金supported in part by the Natural Science Foundation of China(NSFC)under Grant U2233216 and Grant 62471036in part by the Beijing Natural Science Foundation under Grant L242011+1 种基金in part by the Shandong Province Natural Science Foundation under Grant ZR2025QA30 and Grant ZR2022YQ62in part by the Beijing Nova Program.
文摘Near-space communication network(NS-ComNet),as an indispensable component of sixth-generation(6G)and beyond mobile communication systems and the space–air–ground–sea integrated network(SAGSIN),demonstrates unique advantages in wide-area coverage,long-endurance high-altitude operation,and highly flexible deployment.This paper presents a comprehensive review of NS-ComNet for 6G and beyond era.Specifically,by contrasting satellite,low-altitude unmanned aerial vehicle(UAV),and terrestrial communications,we first elucidate the background and motivation for integrating NSComNet into 6G network architectures.Subsequently,we review the developmental status of nearspace platforms,including high-altitude balloons,solar-powered UAVs,and stratospheric airships,and analyze critical challenges faced by NS-ComNet.To address these challenges,the research focuses on key enabling technologies such as topology design,resource and handover management,and multiobjective joint optimization,with particular emphasis on artificial intelligence techniques for NS-ComNet.Finally,envisioning future intelligent collaborative networks that integrate NS-ComNet with satellite–UAV–terrestrial systems,we explore promising directions.This paper aims to provide technical insights and research foundations for the systematic construction of NS-ComNet and its deep deployment in the 6G and beyond era.
