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
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
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
Traditional small current grounding system has many advantages. Pilot operation shows that optimized one has even better operation characteristics. It has proven to be a geenrallly properand relatively perfect neutyal...Traditional small current grounding system has many advantages. Pilot operation shows that optimized one has even better operation characteristics. It has proven to be a geenrallly properand relatively perfect neutyal grounding method in urban MV network.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
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
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
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.
文摘Traditional small current grounding system has many advantages. Pilot operation shows that optimized one has even better operation characteristics. It has proven to be a geenrallly properand relatively perfect neutyal grounding method in urban MV network.
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(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.
