In this paper,we propose a Multi-token Sector Antenna Neighbor Discovery(M-SAND)protocol to enhance the efficiency of neighbor discovery in asynchronous directional ad hoc networks.The central concept of our work invo...In this paper,we propose a Multi-token Sector Antenna Neighbor Discovery(M-SAND)protocol to enhance the efficiency of neighbor discovery in asynchronous directional ad hoc networks.The central concept of our work involves maintaining multiple tokens across the network.To prevent mutual interference among multi-token holders,we introduce the time and space non-interference theorems.Furthermore,we propose a master-slave strategy between tokens.When the master token holder(MTH)performs the neighbor discovery,it decides which 1-hop neighbor is the next MTH and which 2-hop neighbors can be the new slave token holders(STHs).Using this approach,the MTH and multiple STHs can simultaneously discover their neighbors without causing interference with each other.Building on this foundation,we provide a comprehensive procedure for the M-SAND protocol.We also conduct theoretical analyses on the maximum number of STHs and the lower bound of multi-token generation probability.Finally,simulation results demonstrate the time efficiency of the M-SAND protocol.When compared to the QSAND protocol,which uses only one token,the total neighbor discovery time is reduced by 28% when 6beams and 112 nodes are employed.展开更多
Investing in projects that support environmental benefits,such as tree harvesting,has the potential to reduce air pollution levels in the atmosphere in the future.However,this kind of investment may increase the curre...Investing in projects that support environmental benefits,such as tree harvesting,has the potential to reduce air pollution levels in the atmosphere in the future.However,this kind of investment may increase the current level of emissions.Therefore,it is necessary to estimate how much the policy affects the current level of CO_(2) emissions.This makes sure the policy doesn’t increase the level of CO_(2) emis-sions.This study aims to analyze the effect of the One Bil-lion Trees program on CO_(2) emissions in New Zealand by employing the 2020 input–output table analysis.This inves-tigation examines the direct and indirect effects of policy on both the demand and supply sides across six regions of New Zealand.The results of this study for the first year of plantation suggest that the policy increases the level of CO_(2) emissions in all regions,especially in the Waikato region.The direct and indirect impact of the policy leads to 64 kt of CO_(2) emissions on the demand side and 270 kt of CO_(2) emis-sions on the supply side.These lead to 0.19 and 0.74%of total CO_(2) emissions being attributed to investment shocks.Continuing the policy is recommended,as it has a low effect on CO_(2) emissions.However,it is crucial to prioritize the use of low-carbon machinery that uses fossil fuels during the plantation process.展开更多
Turkiye maintains its 4th place in the world home textile exports.Home textile manufacturers continue to produce and export despite the negativities such as regional wars,global economic crisis,fluctuations in exchang...Turkiye maintains its 4th place in the world home textile exports.Home textile manufacturers continue to produce and export despite the negativities such as regional wars,global economic crisis,fluctuations in exchange rates and cost increases.In 2024,the home textile sector,whose exports decreased from time to time,started the last quarter of the year with an increase in exports.Turkiye’s home textile exports fell by 8.7%in the JanuaryOctober period of 2024.展开更多
Bangladeshi textile and garment sectors defied the global challenges over the last five years and continued to grow although the growth momentum was not so strong before the COVID-19 pandemic.Before the start of the p...Bangladeshi textile and garment sectors defied the global challenges over the last five years and continued to grow although the growth momentum was not so strong before the COVID-19 pandemic.Before the start of the pandemic,both the textile and garment sectors were growing at a higher rate because of rising demand from the international clothing retailers and brands because of two main reasons including the trade war between USA and China and competitive prices of locally made garment.展开更多
Hainan Island is the biggest supplier of domestic rattan canes in China and is considered the best area to develop rattan plantation in large-scale. This paper discusses the rattan production in Hainan Island on the b...Hainan Island is the biggest supplier of domestic rattan canes in China and is considered the best area to develop rattan plantation in large-scale. This paper discusses the rattan production in Hainan Island on the basis of comprehensively collected information on rattan through interviewing with farmers, middle man, manufacture and official, on-site observation and literatures. The stock of available rattan is more than 25×106kg, but the real production annually is 4×105 kg. The area of rattan plantation established during 2000-2005 was about 10000 hm2, however, they don not produce yet. Four indigenous rattan species （C. Simplicifolius, C. Faberii, C. Tetradactylus, D. margaritae ） and three kinds of exotic canes are mainly utilized in Hainan island. Large quality of canes is treated as timber regulated by government, tax should be paid and a license should be applied from the government if canes are transport out of Hainan Island. The production-to-consumption flow of rattan in Hainan Island was drawn out based on the investigation. Constraints and advantages of the rattan sector in Hainan are identified and recommendations are proposed finally.展开更多
Given the vital importance of global value chains(GVCs)position for a country's international competitiveness,this paper tries to investigate the impacts of environmental regulation on the GVCs position of China&#...Given the vital importance of global value chains(GVCs)position for a country's international competitiveness,this paper tries to investigate the impacts of environmental regulation on the GVCs position of China's industrial sector.Using the latest value-added decomposition method,we first measure the GVCs position of China's industrial sector from 2003 to 2014.Subsequently,both two-stage least squares(2 SLS)method with panel data and mediating effect model are employed to empirically examine the effects of environmental regulation on China's position in GVCs.The results indicate that environmental regulation has significantly upgraded the GVCs position of China's industrial sector,and the effect is more evident for the sub-sectors with originally lower GVCs position.The mediation effect test shows that increasing R&D investment is an important channel through which environmental regulation affects the GVCs position of China's industrial sector,which verifies the existence of the Porter hypothesis.Further analysis finds that the enhancement of GVCs position of China's industrial sector caused by environmental regulation is mainly achieved through reducing the backward GVCs position.展开更多
In this paper, global synchronization is discussed for a general class of delayed neural networks with time-varying and distributed delays. Furthermore, the activation func- tions in the neural networks can be differe...In this paper, global synchronization is discussed for a general class of delayed neural networks with time-varying and distributed delays. Furthermore, the activation func- tions in the neural networks can be different type. Based on the drive-response concept and the Lyapunov stability theorem, some sufficient criteria are obtained to guarantee the global synchronization of the considered models even when input sector nonlinearity caused by physical limitations is presented in response systems. Finally, a typical example is also given to illustrate the effectiveness of the proposed synchronization scheme.展开更多
This paper deals with dynamic airspace sectorization （DAS） problem by an improved genetic algorithm （iGA）. A graph model is first constructed that represents the airspace static structure. Then the DAS problem is ...This paper deals with dynamic airspace sectorization （DAS） problem by an improved genetic algorithm （iGA）. A graph model is first constructed that represents the airspace static structure. Then the DAS problem is formulated as a graph-partitioning problem to balance the sector workload under the premise of ensuring safety. In the iGA, multiple populations and hybrid coding are applied to determine the optimal sector number and airspace sectorization. The sector constraints are well satisfied by the improved genetic operators and protect zones. This method is validated by being applied to the airspace of North China in terms of three indexes, which are sector balancing index, coordination workload index and sector average flight time index. The improvement is obvious, as the sector balancing index is reduced by 16.5 %, the coordination workload index is reduced by 11.2 %, and the sector average flight time index is increased by 11.4 % during the peak-hour traffic.展开更多
Background:Forest based climate mitigation emerged as a key component of the Paris Agreement,and thus re-quires robust science to reduce uncertainties related to such strategies.The aim of this study was to assess and...Background:Forest based climate mitigation emerged as a key component of the Paris Agreement,and thus re-quires robust science to reduce uncertainties related to such strategies.The aim of this study was to assess and compare the cumulative effects on carbon dynamics of forest management and climate change on boreal and northern temperate forest sector in eastern Canada for the 2020–2100 period.Methods:We used the spatially explicit forest landscape model LANDIS-II and its extension Forest Carbon Suc-cession,in conjunction with the Carbon Budget Model for Harvested Wood Products framework.We simulated the dynamics of forest composition and carbon flows from forest ecosystems to wood products and their substitution effect on markets under increasing climate forcing,according to a tonne-year approach.Simulations were con-ducted for a series of forest management scenarios based on realistic practices principally by clearcut in the boreal territory and continuous-cover forestry in the northern temperate one.These scenarios included:i)a business-as-usual scenario(BaU),representing the current management strategy,ii)increased harvesting by 6.3%to 13.9%,iii)increased conservation(i.e.reduced harvesting by 11.1%to 49.8%),iiii)and a scenario representing the natural evolution of the forest landscape(i.e.without any management activity).Results:Our study revealed that increasing harvesting levels had contrasting effects on the mitigation potential in northern temperate(enhance net sequestration)and boreal forest sector(enhance net emissions)in comparison to the BaU from 2040 onwards,regardless of the future climate.Carbon storage in wood products and the substi-tution effect were not sufficient to offset carbon emissions from ecosystems.Moreover,climate change had a strong impact on the capacity of both landscapes to act as carbon sinks.Northern temperate landscapes became a net source of carbon over time due to their greater vulnerability to climate change than boreal landscapes.Conclusions:Our study highlights the need to consider the initial landscape characteristics in simulations to maximize the mitigation potential of alternative forest management strategies.The optimal management solution can be very different according to the characteristics of forest ecosystems.This opens the possibility of optimizing management for specific forest stands,with the objective of maximizing the mitigation potential of a given landscape.展开更多
Capacity enhancement approaches are being intensively studied in the past few years to address the soaring capacity demands. The network densif ication technology is recognized as one promising solution. However,the u...Capacity enhancement approaches are being intensively studied in the past few years to address the soaring capacity demands. The network densif ication technology is recognized as one promising solution. However,the ultra-dense network scheme suffers from severe interference and frequent handovers,which degrade the system performance significantly. In this paper,a virtual sectorization system leveraging a C-plane(control signaling plane) and U-plane(user data plane) split scheme is proposed to overcome these two fundamental problems. Besides,a well-designed fi eld trial is conducted to evaluate its performance. The results show that the interference can be avoided,which leads to a tremendous increase in system capacity. In addition,the number of handovers is also greatly decreased. Thus,the trial results verify the huge potential of the C-plane and U-plane split scheme for system capacity and user experience enhancements.展开更多
Sector capacity estimation plays an important role in applied research of airspace management.Previous researches manifest that sector capacity should be influenced by its standard flow,or routes in that sector.Howeve...Sector capacity estimation plays an important role in applied research of airspace management.Previous researches manifest that sector capacity should be influenced by its standard flow,or routes in that sector.However,if air traffic controller(ATCO)workload busy levels(level of proactivity of an ATCO)are ignored,the estimated sector capacity may not be accurate.There is a need to compare the estimated sector capacity with and without busy levels consideration,both with differentiated routes consideration.This paper proposes a method for sector capacity estimation based on ATCO workload considering differentiated routes and busy levels.Firstly,the main routes in the sector are identified,and for each route,the ATCO workload per flight is determined.Secondly,the workload for each route at three busy levels is determined.Regression analysis is then applied to determine the relationship between workload and the number of flights(with and without considering busy levels)in 15 min and 1h time slices.Sector capacity is then determined on the basis of a specified workload threshold,for the two cases with and without considering busy levels.Comparing the two scenarios and following validation by ATCO survey,it is found that capacity estimation considering busy levels is a more realistic and accurate approach.The validated capacity values for the Zhengzhou approach(ZHCC AP)airspace sector accounting for the busy levels were determined accurately as 10 and 33 flights for the 15 min and 1h slices,respectively.The corresponding results without considering busy levels were 12 and 41 flights for the 15 min and 1h time slices,respectively.展开更多
Terminal airspace(TMA)is the airspace centering several military and civil aviation airports with complex route structure,limited airspace resources,traffic flow,difficult management and considerable airspace complexi...Terminal airspace(TMA)is the airspace centering several military and civil aviation airports with complex route structure,limited airspace resources,traffic flow,difficult management and considerable airspace complexity.A scientific and rational sectorization of TMA can optimize airspace resources,and sufficiently utilize the control of human resources to ensure the safety of TMA.The functional sectorization model was established based on the route structure of arriving and departing aircraft as well as controlling requirements.Based on principles of sectorization and topological relations within a network,the arrival and departure sectorization model was established,using tree based ant colony algorithm(ACO)searching.Shanghai TMA was taken as an example to be sectorizaed,and the result showed that this model was superior to traditional ones when arrival and departure routes were separated at dense airport terminal airspace.展开更多
A method for evaluating instantaneous sector capacity based on the workload of air traffic controller(ATC)is developed.The basic characteristics of the assessed sector is described and a model to correlate the workloa...A method for evaluating instantaneous sector capacity based on the workload of air traffic controller(ATC)is developed.The basic characteristics of the assessed sector is described and a model to correlate the workload with the instantaneous sector capacity is developed using workload data.The correlation between the regional sector/approach sector capacity and the traffic flow organization is analyzed.Experimental results show that the instantaneous sector capacity assessment is reasonable and the instantaneous capacity is strongly correlated with the spatial and temporal distributions of the traffic flow and the sector operation mode.These results can provide an important reference for sector operation safety,capacity prediction,air traffic management,and airspace design.展开更多
The characteristics of traditional acoustic vortices(AVs) were verified by the cross-sectional axisymmetric pressure distributions with perfect phase spirals around the center pressure null. In order to generate a non...The characteristics of traditional acoustic vortices(AVs) were verified by the cross-sectional axisymmetric pressure distributions with perfect phase spirals around the center pressure null. In order to generate a non-axisymmetric pressure distribution, the concept of power-exponent-phase was first introduced into the formation of AV beams, named “powerexponent-phase acoustic vortices(PAVs)” in this paper. Based on a ring-array of sector transducers, the helical distribution of the low-pressure valley in cross-sections of PAVs, which enables particles to move from a distant position to the center low-potential well along a certain spiral passageway, was proved theoretically. The particle manipulation behavior for PAVs with a power order of 2 is numerically modeled and experimentally confirmed. The results show that PAVs with a nonaxisymmetric spiral pressure distribution can be used to realize the directional transport of particles in an enlarged scope,suggesting prospective application potential in biomedical engineering.展开更多
It is known that dynamic channel assignment(D CA ) strategy outperforms the fixed channel assignment(FCA) strategy in omni-direc tional antenna cellular systems. One of the most important methods used in DCA w as chan...It is known that dynamic channel assignment(D CA ) strategy outperforms the fixed channel assignment(FCA) strategy in omni-direc tional antenna cellular systems. One of the most important methods used in DCA w as channel borrowing. But with the emergence of cell sectorization and spatial d ivision multiple access(SDMA) which are used to increase the capacity of cel lular systems, the channel assignment faces a series of new problems. In this pa per, a dynamic channel allocation scheme based on sectored cellular systems is p roposed. By introducing intra-cell channel borrowing (borrowing channels from n eighboring sectors) and inter-cell channel borrowing (borrowing channels from n eighboring cells) methods, previous DCA strategies, including compact pattern ba sed channel borrowing(CPCB) and greedy based dynamic channel assignment(GDCA) schemes proposed by the author, are improved significantly. The computer simu lation shows that either intra-cell borrowing scheme or inter-cell borrowing s cheme is efficient enough to uniform and non-uniform traffic service distributi ons.展开更多
Stability of Volterra systems are discusses by subpositive definite matrix, and some new criterions for Volterra systems on overall situation stability, sector stability and connection stability are acquired. These re...Stability of Volterra systems are discusses by subpositive definite matrix, and some new criterions for Volterra systems on overall situation stability, sector stability and connection stability are acquired. These results expand or improve some existing criterions.展开更多
A new method for sector optimum partition of airspace is proposed by dividing the fright altitude into several layers according to the distribution characteristics of the controller＇s workloads in an airspace. On the...A new method for sector optimum partition of airspace is proposed by dividing the fright altitude into several layers according to the distribution characteristics of the controller＇s workloads in an airspace. On the basis of the original distribution of the waypoints at each level of altitude, the sweel5 line algorithm of Voronoi diagram is used to divide them into certain polygons （ elements）, and the controller＇s workloads are calculated in each Voronoi polygon. Then by the rule about balance of controller＇s workload and by adding conditions of control handover or coordination for the sector, a mathematical model for the controller＇s workload based sector optimization is built. By the model, the Voronoi polygons are optimally partitioned. As a result, a 3D sector optimum partition of the whole airspace is formed by combining the sector optimum partitions at every layer. The actual airspace partition for Xiamen Airport has proved the reasonability and effectiveness of the 3D sector optimum partition of airspace proposed.展开更多
When you look for gas stations to refill yourcar’s tank in China,you will probably find only twobrands:China National Petroleum Corp(CNPC)and China Petroleum and Chemical Corp(SinopecGroup).But there will soon be a n...When you look for gas stations to refill yourcar’s tank in China,you will probably find only twobrands:China National Petroleum Corp(CNPC)and China Petroleum and Chemical Corp(SinopecGroup).But there will soon be a new player in themarket:"Shide."展开更多
基金supported in part by the National Natural Science Foundations of CHINA(Grant No.61771392,No.61771390,No.61871322 and No.61501373)Science and Technology on Avionics Integration Laboratory and the Aeronautical Science Foundation of China(Grant No.201955053002 and No.20185553035)。
文摘In this paper,we propose a Multi-token Sector Antenna Neighbor Discovery(M-SAND)protocol to enhance the efficiency of neighbor discovery in asynchronous directional ad hoc networks.The central concept of our work involves maintaining multiple tokens across the network.To prevent mutual interference among multi-token holders,we introduce the time and space non-interference theorems.Furthermore,we propose a master-slave strategy between tokens.When the master token holder(MTH)performs the neighbor discovery,it decides which 1-hop neighbor is the next MTH and which 2-hop neighbors can be the new slave token holders(STHs).Using this approach,the MTH and multiple STHs can simultaneously discover their neighbors without causing interference with each other.Building on this foundation,we provide a comprehensive procedure for the M-SAND protocol.We also conduct theoretical analyses on the maximum number of STHs and the lower bound of multi-token generation probability.Finally,simulation results demonstrate the time efficiency of the M-SAND protocol.When compared to the QSAND protocol,which uses only one token,the total neighbor discovery time is reduced by 28% when 6beams and 112 nodes are employed.
基金Open Access funding enabled and organized by CAUL and its Member Institutions
文摘Investing in projects that support environmental benefits,such as tree harvesting,has the potential to reduce air pollution levels in the atmosphere in the future.However,this kind of investment may increase the current level of emissions.Therefore,it is necessary to estimate how much the policy affects the current level of CO_(2) emissions.This makes sure the policy doesn’t increase the level of CO_(2) emis-sions.This study aims to analyze the effect of the One Bil-lion Trees program on CO_(2) emissions in New Zealand by employing the 2020 input–output table analysis.This inves-tigation examines the direct and indirect effects of policy on both the demand and supply sides across six regions of New Zealand.The results of this study for the first year of plantation suggest that the policy increases the level of CO_(2) emissions in all regions,especially in the Waikato region.The direct and indirect impact of the policy leads to 64 kt of CO_(2) emissions on the demand side and 270 kt of CO_(2) emis-sions on the supply side.These lead to 0.19 and 0.74%of total CO_(2) emissions being attributed to investment shocks.Continuing the policy is recommended,as it has a low effect on CO_(2) emissions.However,it is crucial to prioritize the use of low-carbon machinery that uses fossil fuels during the plantation process.
文摘Turkiye maintains its 4th place in the world home textile exports.Home textile manufacturers continue to produce and export despite the negativities such as regional wars,global economic crisis,fluctuations in exchange rates and cost increases.In 2024,the home textile sector,whose exports decreased from time to time,started the last quarter of the year with an increase in exports.Turkiye’s home textile exports fell by 8.7%in the JanuaryOctober period of 2024.
文摘Bangladeshi textile and garment sectors defied the global challenges over the last five years and continued to grow although the growth momentum was not so strong before the COVID-19 pandemic.Before the start of the pandemic,both the textile and garment sectors were growing at a higher rate because of rising demand from the international clothing retailers and brands because of two main reasons including the trade war between USA and China and competitive prices of locally made garment.
基金This study is supported jointly by the 15th National Science and Technology Supporting Project Study and Demonstration of Key Technology to Utilize and Cultivate Rattan Resource Effectively (No.2006BAD19B09)the Science and Technology Project of Guangdong, Selection and Propagation of High-yielding Rattan Family (No. 2006B20201026).
文摘Hainan Island is the biggest supplier of domestic rattan canes in China and is considered the best area to develop rattan plantation in large-scale. This paper discusses the rattan production in Hainan Island on the basis of comprehensively collected information on rattan through interviewing with farmers, middle man, manufacture and official, on-site observation and literatures. The stock of available rattan is more than 25×106kg, but the real production annually is 4×105 kg. The area of rattan plantation established during 2000-2005 was about 10000 hm2, however, they don not produce yet. Four indigenous rattan species （C. Simplicifolius, C. Faberii, C. Tetradactylus, D. margaritae ） and three kinds of exotic canes are mainly utilized in Hainan island. Large quality of canes is treated as timber regulated by government, tax should be paid and a license should be applied from the government if canes are transport out of Hainan Island. The production-to-consumption flow of rattan in Hainan Island was drawn out based on the investigation. Constraints and advantages of the rattan sector in Hainan are identified and recommendations are proposed finally.
基金Financial supports from the National Natural Science Foundation of China(under Grants No.72073105,71774122 and 71874064)。
文摘Given the vital importance of global value chains(GVCs)position for a country's international competitiveness,this paper tries to investigate the impacts of environmental regulation on the GVCs position of China's industrial sector.Using the latest value-added decomposition method,we first measure the GVCs position of China's industrial sector from 2003 to 2014.Subsequently,both two-stage least squares(2 SLS)method with panel data and mediating effect model are employed to empirically examine the effects of environmental regulation on China's position in GVCs.The results indicate that environmental regulation has significantly upgraded the GVCs position of China's industrial sector,and the effect is more evident for the sub-sectors with originally lower GVCs position.The mediation effect test shows that increasing R&D investment is an important channel through which environmental regulation affects the GVCs position of China's industrial sector,which verifies the existence of the Porter hypothesis.Further analysis finds that the enhancement of GVCs position of China's industrial sector caused by environmental regulation is mainly achieved through reducing the backward GVCs position.
文摘In this paper, global synchronization is discussed for a general class of delayed neural networks with time-varying and distributed delays. Furthermore, the activation func- tions in the neural networks can be different type. Based on the drive-response concept and the Lyapunov stability theorem, some sufficient criteria are obtained to guarantee the global synchronization of the considered models even when input sector nonlinearity caused by physical limitations is presented in response systems. Finally, a typical example is also given to illustrate the effectiveness of the proposed synchronization scheme.
基金funded by the Joint Funds of the National Natural Science Foundation of China (61079001)
文摘This paper deals with dynamic airspace sectorization （DAS） problem by an improved genetic algorithm （iGA）. A graph model is first constructed that represents the airspace static structure. Then the DAS problem is formulated as a graph-partitioning problem to balance the sector workload under the premise of ensuring safety. In the iGA, multiple populations and hybrid coding are applied to determine the optimal sector number and airspace sectorization. The sector constraints are well satisfied by the improved genetic operators and protect zones. This method is validated by being applied to the airspace of North China in terms of three indexes, which are sector balancing index, coordination workload index and sector average flight time index. The improvement is obvious, as the sector balancing index is reduced by 16.5 %, the coordination workload index is reduced by 11.2 %, and the sector average flight time index is increased by 11.4 % during the peak-hour traffic.
基金This study was funded by the Quebec Ministry of Forests,Wildlife,and Parks(contrats de service de recherche forestier 142332156-2018-A and 142332174-E:PI:E.Thiffault)by the Natural Science and Engineering Research Council through a Discovery Grant to E.Thiffault(grant number RGPIN-2018-05755).
文摘Background:Forest based climate mitigation emerged as a key component of the Paris Agreement,and thus re-quires robust science to reduce uncertainties related to such strategies.The aim of this study was to assess and compare the cumulative effects on carbon dynamics of forest management and climate change on boreal and northern temperate forest sector in eastern Canada for the 2020–2100 period.Methods:We used the spatially explicit forest landscape model LANDIS-II and its extension Forest Carbon Suc-cession,in conjunction with the Carbon Budget Model for Harvested Wood Products framework.We simulated the dynamics of forest composition and carbon flows from forest ecosystems to wood products and their substitution effect on markets under increasing climate forcing,according to a tonne-year approach.Simulations were con-ducted for a series of forest management scenarios based on realistic practices principally by clearcut in the boreal territory and continuous-cover forestry in the northern temperate one.These scenarios included:i)a business-as-usual scenario(BaU),representing the current management strategy,ii)increased harvesting by 6.3%to 13.9%,iii)increased conservation(i.e.reduced harvesting by 11.1%to 49.8%),iiii)and a scenario representing the natural evolution of the forest landscape(i.e.without any management activity).Results:Our study revealed that increasing harvesting levels had contrasting effects on the mitigation potential in northern temperate(enhance net sequestration)and boreal forest sector(enhance net emissions)in comparison to the BaU from 2040 onwards,regardless of the future climate.Carbon storage in wood products and the substi-tution effect were not sufficient to offset carbon emissions from ecosystems.Moreover,climate change had a strong impact on the capacity of both landscapes to act as carbon sinks.Northern temperate landscapes became a net source of carbon over time due to their greater vulnerability to climate change than boreal landscapes.Conclusions:Our study highlights the need to consider the initial landscape characteristics in simulations to maximize the mitigation potential of alternative forest management strategies.The optimal management solution can be very different according to the characteristics of forest ecosystems.This opens the possibility of optimizing management for specific forest stands,with the objective of maximizing the mitigation potential of a given landscape.
基金supported by the National Science and Technology Major Project of China (No. 2013ZX03001018)
文摘Capacity enhancement approaches are being intensively studied in the past few years to address the soaring capacity demands. The network densif ication technology is recognized as one promising solution. However,the ultra-dense network scheme suffers from severe interference and frequent handovers,which degrade the system performance significantly. In this paper,a virtual sectorization system leveraging a C-plane(control signaling plane) and U-plane(user data plane) split scheme is proposed to overcome these two fundamental problems. Besides,a well-designed fi eld trial is conducted to evaluate its performance. The results show that the interference can be avoided,which leads to a tremendous increase in system capacity. In addition,the number of handovers is also greatly decreased. Thus,the trial results verify the huge potential of the C-plane and U-plane split scheme for system capacity and user experience enhancements.
基金partially supported by the National Natural Science Foundation of China(No.61304190)the Fundamental Research Funds for the Central Universities(No.NJ20140018)
文摘Sector capacity estimation plays an important role in applied research of airspace management.Previous researches manifest that sector capacity should be influenced by its standard flow,or routes in that sector.However,if air traffic controller(ATCO)workload busy levels(level of proactivity of an ATCO)are ignored,the estimated sector capacity may not be accurate.There is a need to compare the estimated sector capacity with and without busy levels consideration,both with differentiated routes consideration.This paper proposes a method for sector capacity estimation based on ATCO workload considering differentiated routes and busy levels.Firstly,the main routes in the sector are identified,and for each route,the ATCO workload per flight is determined.Secondly,the workload for each route at three busy levels is determined.Regression analysis is then applied to determine the relationship between workload and the number of flights(with and without considering busy levels)in 15 min and 1h time slices.Sector capacity is then determined on the basis of a specified workload threshold,for the two cases with and without considering busy levels.Comparing the two scenarios and following validation by ATCO survey,it is found that capacity estimation considering busy levels is a more realistic and accurate approach.The validated capacity values for the Zhengzhou approach(ZHCC AP)airspace sector accounting for the busy levels were determined accurately as 10 and 33 flights for the 15 min and 1h slices,respectively.The corresponding results without considering busy levels were 12 and 41 flights for the 15 min and 1h time slices,respectively.
基金supported by the National Natural Science Foundation of China(Nos.U1233101,71271113)the Fundamental Research Funds for the Central Universities(No.NS2016062)
文摘Terminal airspace(TMA)is the airspace centering several military and civil aviation airports with complex route structure,limited airspace resources,traffic flow,difficult management and considerable airspace complexity.A scientific and rational sectorization of TMA can optimize airspace resources,and sufficiently utilize the control of human resources to ensure the safety of TMA.The functional sectorization model was established based on the route structure of arriving and departing aircraft as well as controlling requirements.Based on principles of sectorization and topological relations within a network,the arrival and departure sectorization model was established,using tree based ant colony algorithm(ACO)searching.Shanghai TMA was taken as an example to be sectorizaed,and the result showed that this model was superior to traditional ones when arrival and departure routes were separated at dense airport terminal airspace.
基金supported by the National Key Technology Research and Development Program of the Ministry of Science and Technology of China(No.2011BAH24B08)
文摘A method for evaluating instantaneous sector capacity based on the workload of air traffic controller(ATC)is developed.The basic characteristics of the assessed sector is described and a model to correlate the workload with the instantaneous sector capacity is developed using workload data.The correlation between the regional sector/approach sector capacity and the traffic flow organization is analyzed.Experimental results show that the instantaneous sector capacity assessment is reasonable and the instantaneous capacity is strongly correlated with the spatial and temporal distributions of the traffic flow and the sector operation mode.These results can provide an important reference for sector operation safety,capacity prediction,air traffic management,and airspace design.
基金Project supported by the Natural Science Foundation of Shandong Province, China (Grant Nos. ZR2022MF336 and ZR2022MD036)。
文摘The characteristics of traditional acoustic vortices(AVs) were verified by the cross-sectional axisymmetric pressure distributions with perfect phase spirals around the center pressure null. In order to generate a non-axisymmetric pressure distribution, the concept of power-exponent-phase was first introduced into the formation of AV beams, named “powerexponent-phase acoustic vortices(PAVs)” in this paper. Based on a ring-array of sector transducers, the helical distribution of the low-pressure valley in cross-sections of PAVs, which enables particles to move from a distant position to the center low-potential well along a certain spiral passageway, was proved theoretically. The particle manipulation behavior for PAVs with a power order of 2 is numerically modeled and experimentally confirmed. The results show that PAVs with a nonaxisymmetric spiral pressure distribution can be used to realize the directional transport of particles in an enlarged scope,suggesting prospective application potential in biomedical engineering.
文摘It is known that dynamic channel assignment(D CA ) strategy outperforms the fixed channel assignment(FCA) strategy in omni-direc tional antenna cellular systems. One of the most important methods used in DCA w as channel borrowing. But with the emergence of cell sectorization and spatial d ivision multiple access(SDMA) which are used to increase the capacity of cel lular systems, the channel assignment faces a series of new problems. In this pa per, a dynamic channel allocation scheme based on sectored cellular systems is p roposed. By introducing intra-cell channel borrowing (borrowing channels from n eighboring sectors) and inter-cell channel borrowing (borrowing channels from n eighboring cells) methods, previous DCA strategies, including compact pattern ba sed channel borrowing(CPCB) and greedy based dynamic channel assignment(GDCA) schemes proposed by the author, are improved significantly. The computer simu lation shows that either intra-cell borrowing scheme or inter-cell borrowing s cheme is efficient enough to uniform and non-uniform traffic service distributi ons.
基金Supported by the Natural Sciences Research Foundation of Department of Education of Jiangsu Province(03KJD110088,05KJD110058)
文摘Stability of Volterra systems are discusses by subpositive definite matrix, and some new criterions for Volterra systems on overall situation stability, sector stability and connection stability are acquired. These results expand or improve some existing criterions.
基金The National Natural Science Foundation of China (No.60472117)
文摘A new method for sector optimum partition of airspace is proposed by dividing the fright altitude into several layers according to the distribution characteristics of the controller＇s workloads in an airspace. On the basis of the original distribution of the waypoints at each level of altitude, the sweel5 line algorithm of Voronoi diagram is used to divide them into certain polygons （ elements）, and the controller＇s workloads are calculated in each Voronoi polygon. Then by the rule about balance of controller＇s workload and by adding conditions of control handover or coordination for the sector, a mathematical model for the controller＇s workload based sector optimization is built. By the model, the Voronoi polygons are optimally partitioned. As a result, a 3D sector optimum partition of the whole airspace is formed by combining the sector optimum partitions at every layer. The actual airspace partition for Xiamen Airport has proved the reasonability and effectiveness of the 3D sector optimum partition of airspace proposed.
文摘When you look for gas stations to refill yourcar’s tank in China,you will probably find only twobrands:China National Petroleum Corp(CNPC)and China Petroleum and Chemical Corp(SinopecGroup).But there will soon be a new player in themarket:"Shide."
