For rigid-flexible coupling multi-body with variable topology,such as the system of internally carried air-launched or heavy cargo airdrop,in order to construct a dynamic model with unified form,avoid redundancy in th...For rigid-flexible coupling multi-body with variable topology,such as the system of internally carried air-launched or heavy cargo airdrop,in order to construct a dynamic model with unified form,avoid redundancy in the modeling process and make the solution independent,a method based on the equivalent rigidization model was proposed.It divides a system into independent subsystems by cutting off the joints,of which types are changed with the operation process of the system.And models of different subsystems can be constructed via selecting suitable modeling methods.Subsystem models with flexible bodies are on the basis of the equivalent rigidization model which replaces the flexible bodies with the virtual rigid bodies.And the solution for sanction,which is based on the constraints force algorithm(CFA)and vector mechanics,can be independent on the state equations.The internally carried air-launched system was taken as an example for verifying validity and feasibility of the method and theory.The dynamic model of aircraft-rocket-parachute system in the entire phase was constructed.Comparing the modeling method with the others,the modeling process was programmed;and form of the model is unified and simple.The model,method and theory can be used to analyze other similar systems such as heavy cargo airdrop system and capsule parachute recovery system.展开更多
The Xinjiang Production andConstruction Corps (XPCC) was foundedin October 1954. Since 1990, its plan hasbeen listed directly under the state councilof PRC.After 50 years of arduouspioneering and development, the XPCC...The Xinjiang Production andConstruction Corps (XPCC) was foundedin October 1954. Since 1990, its plan hasbeen listed directly under the state councilof PRC.After 50 years of arduouspioneering and development, the XPCChas now developed to be a specialorganization with a solid economicstrength and enterprise group superiority,which is based on the large-scale andmodernized agriculture, and guided展开更多
Although composting is a very effective way to dispose agricultural wastes,its development is greatly limited by the low compost quality and greenhouse gas emissions.At present,there is a lack of effective means to so...Although composting is a very effective way to dispose agricultural wastes,its development is greatly limited by the low compost quality and greenhouse gas emissions.At present,there is a lack of effective means to solve these two problems simultaneously.Here,the effects of three additives of compound microbial agent,biochar and biochar carried microbial agent on the composting performance,nitrogen transformation,greenhouse gas and ammonia emissions,and bacterial communities were investigated in sheep manure composting during 28 days.Results showed that biochar carried microbial agent prolonged the thermophilic stage and promoted compost maturity.At the same time,it was confirmed by the increase of the decomposition of organic nitrogen and the transformation of NH_(4)^(+)-N to NO_(3)^(−)-N.Besides,adding biochar carried microbial agent decreased CH_(4),NH_(3) and N_(2)O emissions by 65.23%,42.05%and 68.64%,respectively.The gas emissions were mainly correlated to Chloroflexi,Myxococcota,Acidobacteriota,Firmicutes,and Gemmatimonadota.Redundancy analysis showed that EC and TKN were closely related to bacterial community.Therefore,biochar carried microbial agent is recommended as an effective additive to enhance compost quality and reduce gas emissions during sheep manure composting.展开更多
Carried-Heat Partial Gasification Combined cycle is a novel combined cycle which was proposed by Thermal Engineering Department of Tsinghua University in 1992. The idea of the system comes from the situation that the ...Carried-Heat Partial Gasification Combined cycle is a novel combined cycle which was proposed by Thermal Engineering Department of Tsinghua University in 1992. The idea of the system comes from the situation that the efficiency of the power plants in China is much lower than that of the advanced countries, but the coal consumption is much higher, which brings about the waste of primary energy resources and the pollution of the environment. With the deep study of the gasification technology, Coke Carried-Heat Gasification Coal-Fired Combined Cycle, as the improved system, came into birth in 1996 based on the partial gasification one. At the end of 1997, a new cycle scheme similar to IGCC was created. This paper focuses on several classes combined cycle put forward by Tsinghua University, depending on the plant configuration and carbon conversion, making the solution a viable and attractive option for efficient coal utilization.展开更多
The Selenge River Basin(SRB)in Mongolia has faced ecosystem degradation because of climate change and overloading.The dynamics of the pastoral system and the extent of overload under future scenarios have not been doc...The Selenge River Basin(SRB)in Mongolia has faced ecosystem degradation because of climate change and overloading.The dynamics of the pastoral system and the extent of overload under future scenarios have not been documented.This study aims to answer the following questions:Will the typical soums in the SRB become more overgrazed in the future?What optimal strategy should be implemented?Multisource data were integrated and utilized to model the pastoral system of typical soums using a system dynamics approach.Future scenarios under three SSP-RCPs were projected using the model.The conclusions are as follows:(1)From upstream to downstream,rational scenarios for pastoral system transferred from SSP1-RCP2.6 to SSP2-RCP4.5,which reflect improved productivity at the expense of ecosystem stability.(2)Compared with that during the historical period of 2000-2020,the projected carrying capacity of the soums decreases by 15.2%-37.3%,whereas the number of livestock continues to increase.Consequently,the stocking rate is expected to increase from 0.32-1.16 during 2000-2020 to 1.26-2.02 during 2021-2050,indicating that rangeland will become more overloaded.(3)A livestock reduction strategy based on future livestock stock and grassland carrying capacity scenarios was proposed to maintain a dynamic forage-livestock equilibrium.It is suggested that reducing livestock is a practical option for harmonizing grassland conservation with livestock husbandry development.展开更多
Research on grassland carrying capacity(GCC)and forage-livestock balance is of great significance for promoting the harmonious development of human and grassland.However,the lack of understanding of GCC and forage-liv...Research on grassland carrying capacity(GCC)and forage-livestock balance is of great significance for promoting the harmonious development of human and grassland.However,the lack of understanding of GCC and forage-livestock balance in the agro-pastoral transition zone of northern China has limited the grassland sustainable development.Here,the spatial and temporal characteristics of GCC and forage-livestock balance in the grassland of agro-pastoral transition zone of northern China from 2000 to 2022 were analyzed using meteorological data and remote sensing data.Geographical detectors and geographically weighted regression were also used to identify the driving factors and their interactions with GCC changes.Moreover,future GCC trends were predicted using the Coupled Model Intercomparison Project Phase 6 dataset.Results revealed that:(1)GCC showed an overall upward trend from 2000 to 2022 but with significant inter-annual fluctuations.Its spatial distribution decreased gradually from north to south and from east to west.Precipitation,temperature,and cumulative solar radiation were the main drivers of the inter-annual variation of GCC,and the interaction between precipitation and temperature was the main influencing factor of the spatial distribution of GCC;(2)the forage-livestock balance was in an overloaded state in most years,but its index remained basically stable.Spatially,grazing overloading was mainly distributed in northeastern area and the severe overloading was mainly distributed in northwestern area;and(3)future projections indicated a downward trend in potential GCC.Under shared socioeconomic pathway(SSP)2-4.5 scenario,the potential GCC had a ranged of 1.38×10^(7)-1.86×10^(7)standard sheep unit(SHU)and a mean of 1.60×10^(7)SHU.Meanwhile,the potential GCC under SSP5-8.5 scenario had a range of 1.18×10^(7)-1.69×10^(7)SHU and a mean of 1.49×10^(7)SHU.These results indicated that although GCC of the agro-pastoral transition zone of northern China showed an overall increasing trend from 2000 to 2022,the forage-livestock balance index remained basically stable.The GCC was predicted to show a decreasing trend in the future.The findings provide a scientific basis for the sustainable development of grassland and the optimization of grazing management policies in this area.展开更多
U.S.president-elect Donald Trump made tariff threats again in late 2024,declaring that if BRICS countries undermined the U.S.dollar,he would impose a 100 percent tariff on them.Prior to this,he had claimed that he wou...U.S.president-elect Donald Trump made tariff threats again in late 2024,declaring that if BRICS countries undermined the U.S.dollar,he would impose a 100 percent tariff on them.Prior to this,he had claimed that he would impose a 25 percent tariff on all goods from Mexico and Canada and an extra 10 percent on Chinese products.These tariff threats again upset the world.This time,the United States will treat its strategic ally and neighbor alike.Japan,which maintains a huge trade surplus with the United States,is also worried.Facing the huge uncertainty Trump’s second term will bring to the world economy,China and Japan are grappling with the appropriate response.The situation was heatedly discussed at the recent 2024 Beijing-Tokyo Forum.展开更多
Bangladesh has a denser population in comparison with many other countries. Though the rate of population increase has been regarded as a concerning issue, estimation of the population instability in the upcoming year...Bangladesh has a denser population in comparison with many other countries. Though the rate of population increase has been regarded as a concerning issue, estimation of the population instability in the upcoming years may be useful for national planning. To predict Bangladesh’s future population, this study compares the estimated populations of two popular population models, the Malthusian and the logistic population models, with the country’s census population published by BBS. We also tried to find out which model gives a better approximation for forecasting the past, present, and future population between these two models.展开更多
National e-commerce demonstration city(NEDC)pilots play a crucial role in transforming urban e-commerce and significantly affect urban land resource carrying capacity(LRCC).Using panel data from prefecture-level citie...National e-commerce demonstration city(NEDC)pilots play a crucial role in transforming urban e-commerce and significantly affect urban land resource carrying capacity(LRCC).Using panel data from prefecture-level cities in China spanning 2006 to 2020,this study treats the NEDC pilot program as a quasi-natural experiment.A theoretical mechanism analysis was conducted to explore the implications of the NEDC pilot program on urban LRCC,and the propensity score matching double-difference method was used to estimate its effects.The findings show that the NEDC pilot program significantly inhibits the enhancement of urban LRCC,a conclusion that remains robust after multiple validity tests.Moreover,as the level of green development in urban land increases,the impact of the NEDC pilot program on urban LRCC shifts from positive to negative.This negative effect is especially pronounced in regions with lower levels of urban informatization,as well as in central and western areas and large cities.Furthermore,the mechanism analysis indicates that the NEDC pilot program exerts a significant negative influence on urban LRCC through three main channels:technological innovation,industrial structure,and economic correlation.展开更多
Recently,a roundtable on carrying forward the Bandung Spirit,co-hosted by the Chinese People’s Institute of Foreign Affairs(CPIFA)and the Embassy of the Republic of Indonesia in China,took place in Beijing.Wang Yi,me...Recently,a roundtable on carrying forward the Bandung Spirit,co-hosted by the Chinese People’s Institute of Foreign Affairs(CPIFA)and the Embassy of the Republic of Indonesia in China,took place in Beijing.Wang Yi,member of the Political Bureau of the Communist Party of China Central Committee and Minister of Foreign Affairs,delivered a written speech.Indonesian Deputy Foreign Minister Siti Nugraha Mauludiah delivered a keynote speech.CPIFA President Wang Chao,Indonesian Ambassador to Bandung Spirit Driving Modernization of the Global South China Djauhari Oratmangun,former Pakistani Foreign Minister Khurshid Mahmud Kasuri,former Deputy Foreign Minister of Myanmar U Thant Kyaw,and former Under-Secretary-General of the UN Wu Hongbo attended the roundtable and delivered speeches.Also attending were more than 60 Chinese and Indonesian experts and scholars,representatives from countries that participated in the Bandung Conference,and heads of UN agencies in China.Chinese and foreign vips carried out in-depth exchange and discussion on the theme“The Global South:Carrying Forward the Bandung Spirit and Marching Together toward Modernization.”展开更多
In ultra-deep and large well sections,high collapse stresses and diminished annular return velocity present significant challenges to wellbore cleaning.With increasing depth,rising temperature and pressure constrain t...In ultra-deep and large well sections,high collapse stresses and diminished annular return velocity present significant challenges to wellbore cleaning.With increasing depth,rising temperature and pressure constrain the regulation of displacement and drilling fluid rheology,impairing the fluid’s capacity to transport cuttings effectively.A precise understanding of cuttings settlement behavior and terminal velocity is therefore essential for optimizing their removal.This study accounts for variations in wellbore temperature and pressure,incorporates non-spherical cuttings and wellbore diameter parameters,and develops accordingly a simplified model to predict terminal settlement velocity.Thecuttings carrying ratio is introduced as a metric for evaluatingwellbore cleanliness.Findings reveal that temperature and pressure fluctuations can alter terminal velocity by up to 3.4%.Cuttings shape plays a crucial role,with block-shaped cuttings requiring higher annular return velocity than flake-shaped ones at the same carrying ratio.As wellbore size increases,the minimum required carrying flow rate rises nonlinearly,though the rate of increase gradually declines.For a Φ444.5mmwellbore,a carrying ratio of at least 0.6 is recommended.Terminal velocity decreases with increasing consistency coefficient,particularly in high-viscosity regimes.The proposed carrying ratio offers a more accurate and practical assessment of wellbore cleanliness.展开更多
On the morning of May 31st,the parallel forum"Ecological Actions to Carry Forward the Shared Values of Mankind,"as part of the 4th Dialogue on Exchanges and Mutual Learning among Civilisations,was held in Du...On the morning of May 31st,the parallel forum"Ecological Actions to Carry Forward the Shared Values of Mankind,"as part of the 4th Dialogue on Exchanges and Mutual Learning among Civilisations,was held in Dunhuang.More than 50 experts and scholars from different countries,including China,Kenya and Japan,engaged in indepth discussions on the theme.展开更多
Water scarcity and environment deterioration have become main constraints to sustainable economic and social development.Scientifically assessing Water Resources Carrying Capacity(WRCC)is essential for the optimal all...Water scarcity and environment deterioration have become main constraints to sustainable economic and social development.Scientifically assessing Water Resources Carrying Capacity(WRCC)is essential for the optimal allocation of regional water resources.The hilly area at the northern foot of Yanshan Mountains is a key water conservation zone and an important water source for Beijing,Tianjin and Hebei.Grasping the current status and temporal trends of water quality and WRCC in representative small watersheds within this region is crucial for supporting rational water resources allocation and environment protection efforts.This study focuses on Pingquan City,a typical watershed in northern Hebei Province.Firstly,evaluation index systems for surface water quality,groundwater quality and WRCC were estab-lished based on the Pressure-State-Response(PSR)framework.Then,comprehensive evaluations of water quality and WRCC at the sub-watershed scale were conducted using the Varying Fuzzy Pattern Recogni-tion(VFPR)model.Finally,the rationality of the evaluation results was verified,and future scenarios were projected.Results showed that:(1)The average comprehensive evaluation scores for surface water and groundwater quality in the sub-watersheds were 1.44 and 1.46,respectively,indicating that both met the national Class II water quality standard and reflected a high-quality water environment.(2)From 2010 to 2020,the region's WRCC steadily improved,with scores rising from 2.99 to 2.83 and an average of 2.90,suggesting effective water resources management in Pingquan City.(3)According to scenario-based predic-tion,WRCC may slightly decline between 2025 and 2030,reaching 2.92 and 2.94,respectively,relative to 2020 levels.Therefore,future efforts should focus on strengthening scientific management and promoting the efficient use of water resources.Proactive measures are necessary to mitigate emerging contradiction and ensure the long-term stability and sustainability of the water resources system in the region.The evalua-tion system and spatiotemporal evolution patterns proposed in this study can provide a scientific basis for refined water resource management and ecological conservation in similar hilly areas.展开更多
In recent years,the rapid advancement of artificial intelligence(AI)has fostered deep integration between large AI models and robotic technology.Robots such as robotic dogs capable of carrying heavy loads on mountaino...In recent years,the rapid advancement of artificial intelligence(AI)has fostered deep integration between large AI models and robotic technology.Robots such as robotic dogs capable of carrying heavy loads on mountainous terrain or performing waste disposal tasks and humanoid robots that can execute high-precision component installations have gradually reached the public eye,raising expectations for embodied intelligent robots.展开更多
The unique wave-manipulation capabilities of zero-index metamaterials(ZIMs)offer a new opportunity for realizing bound states in the continuum(BICs).However,the relationship between anomalous scattering and BICs remai...The unique wave-manipulation capabilities of zero-index metamaterials(ZIMs)offer a new opportunity for realizing bound states in the continuum(BICs).However,the relationship between anomalous scattering and BICs remains underexplored when parity–time(PT)symmetry is introduced.In this work,we demonstrate that a BIC splits into a pair of lasing modes carrying opposite topological charges by introducing PT symmetry through gain-loss cylinders embedded in ZIM layers.Theoretical analysis and numerical simulations reveal that lasing and unidirectional transparency phenomena result from the singularities and exceptional points of the scattering matrix.Moreover,exceptional points can be tuned via propagation phase modulation in the air gap,and their coalescence produces quasi-BICs with symmetric responses.This work provides a framework for manipulating BICs and topological lasing modes in non-Hermitian systems,offering new insights for designing non-Hermitian photonic devices.展开更多
文摘For rigid-flexible coupling multi-body with variable topology,such as the system of internally carried air-launched or heavy cargo airdrop,in order to construct a dynamic model with unified form,avoid redundancy in the modeling process and make the solution independent,a method based on the equivalent rigidization model was proposed.It divides a system into independent subsystems by cutting off the joints,of which types are changed with the operation process of the system.And models of different subsystems can be constructed via selecting suitable modeling methods.Subsystem models with flexible bodies are on the basis of the equivalent rigidization model which replaces the flexible bodies with the virtual rigid bodies.And the solution for sanction,which is based on the constraints force algorithm(CFA)and vector mechanics,can be independent on the state equations.The internally carried air-launched system was taken as an example for verifying validity and feasibility of the method and theory.The dynamic model of aircraft-rocket-parachute system in the entire phase was constructed.Comparing the modeling method with the others,the modeling process was programmed;and form of the model is unified and simple.The model,method and theory can be used to analyze other similar systems such as heavy cargo airdrop system and capsule parachute recovery system.
文摘The Xinjiang Production andConstruction Corps (XPCC) was foundedin October 1954. Since 1990, its plan hasbeen listed directly under the state councilof PRC.After 50 years of arduouspioneering and development, the XPCChas now developed to be a specialorganization with a solid economicstrength and enterprise group superiority,which is based on the large-scale andmodernized agriculture, and guided
基金National Key Research and Development Program of China(2018YFC1802904)National Science Foundation of China(52264013 and 41867061)+2 种基金Inner Mongolia Science&Technology Plan Program(2019 and 2020)National Science Foundation of Inner Mongolia(2020MS02005)Inner Mongolia Engineering Research Center of Evaluation and Restoration in the Mining Ecological Environment and the Special Fund for the Transformation of Scientific and Technological Achievements in Inner Mongolia(2019CG062).
文摘Although composting is a very effective way to dispose agricultural wastes,its development is greatly limited by the low compost quality and greenhouse gas emissions.At present,there is a lack of effective means to solve these two problems simultaneously.Here,the effects of three additives of compound microbial agent,biochar and biochar carried microbial agent on the composting performance,nitrogen transformation,greenhouse gas and ammonia emissions,and bacterial communities were investigated in sheep manure composting during 28 days.Results showed that biochar carried microbial agent prolonged the thermophilic stage and promoted compost maturity.At the same time,it was confirmed by the increase of the decomposition of organic nitrogen and the transformation of NH_(4)^(+)-N to NO_(3)^(−)-N.Besides,adding biochar carried microbial agent decreased CH_(4),NH_(3) and N_(2)O emissions by 65.23%,42.05%and 68.64%,respectively.The gas emissions were mainly correlated to Chloroflexi,Myxococcota,Acidobacteriota,Firmicutes,and Gemmatimonadota.Redundancy analysis showed that EC and TKN were closely related to bacterial community.Therefore,biochar carried microbial agent is recommended as an effective additive to enhance compost quality and reduce gas emissions during sheep manure composting.
文摘Carried-Heat Partial Gasification Combined cycle is a novel combined cycle which was proposed by Thermal Engineering Department of Tsinghua University in 1992. The idea of the system comes from the situation that the efficiency of the power plants in China is much lower than that of the advanced countries, but the coal consumption is much higher, which brings about the waste of primary energy resources and the pollution of the environment. With the deep study of the gasification technology, Coke Carried-Heat Gasification Coal-Fired Combined Cycle, as the improved system, came into birth in 1996 based on the partial gasification one. At the end of 1997, a new cycle scheme similar to IGCC was created. This paper focuses on several classes combined cycle put forward by Tsinghua University, depending on the plant configuration and carbon conversion, making the solution a viable and attractive option for efficient coal utilization.
基金National Natural Science Foundation of China,No.32161143025,No.42371283,No.W2412155National Key R&D Program of China,No.2022YFE0119200。
文摘The Selenge River Basin(SRB)in Mongolia has faced ecosystem degradation because of climate change and overloading.The dynamics of the pastoral system and the extent of overload under future scenarios have not been documented.This study aims to answer the following questions:Will the typical soums in the SRB become more overgrazed in the future?What optimal strategy should be implemented?Multisource data were integrated and utilized to model the pastoral system of typical soums using a system dynamics approach.Future scenarios under three SSP-RCPs were projected using the model.The conclusions are as follows:(1)From upstream to downstream,rational scenarios for pastoral system transferred from SSP1-RCP2.6 to SSP2-RCP4.5,which reflect improved productivity at the expense of ecosystem stability.(2)Compared with that during the historical period of 2000-2020,the projected carrying capacity of the soums decreases by 15.2%-37.3%,whereas the number of livestock continues to increase.Consequently,the stocking rate is expected to increase from 0.32-1.16 during 2000-2020 to 1.26-2.02 during 2021-2050,indicating that rangeland will become more overloaded.(3)A livestock reduction strategy based on future livestock stock and grassland carrying capacity scenarios was proposed to maintain a dynamic forage-livestock equilibrium.It is suggested that reducing livestock is a practical option for harmonizing grassland conservation with livestock husbandry development.
基金supported by the National Natural Science Foundation of China(42271309)the Natural Science Foundation of Shaanxi Province(2024JC-YBMS-194).
文摘Research on grassland carrying capacity(GCC)and forage-livestock balance is of great significance for promoting the harmonious development of human and grassland.However,the lack of understanding of GCC and forage-livestock balance in the agro-pastoral transition zone of northern China has limited the grassland sustainable development.Here,the spatial and temporal characteristics of GCC and forage-livestock balance in the grassland of agro-pastoral transition zone of northern China from 2000 to 2022 were analyzed using meteorological data and remote sensing data.Geographical detectors and geographically weighted regression were also used to identify the driving factors and their interactions with GCC changes.Moreover,future GCC trends were predicted using the Coupled Model Intercomparison Project Phase 6 dataset.Results revealed that:(1)GCC showed an overall upward trend from 2000 to 2022 but with significant inter-annual fluctuations.Its spatial distribution decreased gradually from north to south and from east to west.Precipitation,temperature,and cumulative solar radiation were the main drivers of the inter-annual variation of GCC,and the interaction between precipitation and temperature was the main influencing factor of the spatial distribution of GCC;(2)the forage-livestock balance was in an overloaded state in most years,but its index remained basically stable.Spatially,grazing overloading was mainly distributed in northeastern area and the severe overloading was mainly distributed in northwestern area;and(3)future projections indicated a downward trend in potential GCC.Under shared socioeconomic pathway(SSP)2-4.5 scenario,the potential GCC had a ranged of 1.38×10^(7)-1.86×10^(7)standard sheep unit(SHU)and a mean of 1.60×10^(7)SHU.Meanwhile,the potential GCC under SSP5-8.5 scenario had a range of 1.18×10^(7)-1.69×10^(7)SHU and a mean of 1.49×10^(7)SHU.These results indicated that although GCC of the agro-pastoral transition zone of northern China showed an overall increasing trend from 2000 to 2022,the forage-livestock balance index remained basically stable.The GCC was predicted to show a decreasing trend in the future.The findings provide a scientific basis for the sustainable development of grassland and the optimization of grazing management policies in this area.
文摘U.S.president-elect Donald Trump made tariff threats again in late 2024,declaring that if BRICS countries undermined the U.S.dollar,he would impose a 100 percent tariff on them.Prior to this,he had claimed that he would impose a 25 percent tariff on all goods from Mexico and Canada and an extra 10 percent on Chinese products.These tariff threats again upset the world.This time,the United States will treat its strategic ally and neighbor alike.Japan,which maintains a huge trade surplus with the United States,is also worried.Facing the huge uncertainty Trump’s second term will bring to the world economy,China and Japan are grappling with the appropriate response.The situation was heatedly discussed at the recent 2024 Beijing-Tokyo Forum.
文摘Bangladesh has a denser population in comparison with many other countries. Though the rate of population increase has been regarded as a concerning issue, estimation of the population instability in the upcoming years may be useful for national planning. To predict Bangladesh’s future population, this study compares the estimated populations of two popular population models, the Malthusian and the logistic population models, with the country’s census population published by BBS. We also tried to find out which model gives a better approximation for forecasting the past, present, and future population between these two models.
基金funded by the National Social Science Foundation of China(later funded)[Grant No.23FJYA005].
文摘National e-commerce demonstration city(NEDC)pilots play a crucial role in transforming urban e-commerce and significantly affect urban land resource carrying capacity(LRCC).Using panel data from prefecture-level cities in China spanning 2006 to 2020,this study treats the NEDC pilot program as a quasi-natural experiment.A theoretical mechanism analysis was conducted to explore the implications of the NEDC pilot program on urban LRCC,and the propensity score matching double-difference method was used to estimate its effects.The findings show that the NEDC pilot program significantly inhibits the enhancement of urban LRCC,a conclusion that remains robust after multiple validity tests.Moreover,as the level of green development in urban land increases,the impact of the NEDC pilot program on urban LRCC shifts from positive to negative.This negative effect is especially pronounced in regions with lower levels of urban informatization,as well as in central and western areas and large cities.Furthermore,the mechanism analysis indicates that the NEDC pilot program exerts a significant negative influence on urban LRCC through three main channels:technological innovation,industrial structure,and economic correlation.
文摘Recently,a roundtable on carrying forward the Bandung Spirit,co-hosted by the Chinese People’s Institute of Foreign Affairs(CPIFA)and the Embassy of the Republic of Indonesia in China,took place in Beijing.Wang Yi,member of the Political Bureau of the Communist Party of China Central Committee and Minister of Foreign Affairs,delivered a written speech.Indonesian Deputy Foreign Minister Siti Nugraha Mauludiah delivered a keynote speech.CPIFA President Wang Chao,Indonesian Ambassador to Bandung Spirit Driving Modernization of the Global South China Djauhari Oratmangun,former Pakistani Foreign Minister Khurshid Mahmud Kasuri,former Deputy Foreign Minister of Myanmar U Thant Kyaw,and former Under-Secretary-General of the UN Wu Hongbo attended the roundtable and delivered speeches.Also attending were more than 60 Chinese and Indonesian experts and scholars,representatives from countries that participated in the Bandung Conference,and heads of UN agencies in China.Chinese and foreign vips carried out in-depth exchange and discussion on the theme“The Global South:Carrying Forward the Bandung Spirit and Marching Together toward Modernization.”
基金partly supported by the National Natural Science Foundation of China(52304045)the Open Fund(PLN2023-40)of the National Key Laboratory of Oil and Gas Reservoir Geology and Exploitation(Southwest Petroleum University)the Open Fund(2024-KFKT-08)of China National Petroleum Corporation Science and Technology Research Institute.
文摘In ultra-deep and large well sections,high collapse stresses and diminished annular return velocity present significant challenges to wellbore cleaning.With increasing depth,rising temperature and pressure constrain the regulation of displacement and drilling fluid rheology,impairing the fluid’s capacity to transport cuttings effectively.A precise understanding of cuttings settlement behavior and terminal velocity is therefore essential for optimizing their removal.This study accounts for variations in wellbore temperature and pressure,incorporates non-spherical cuttings and wellbore diameter parameters,and develops accordingly a simplified model to predict terminal settlement velocity.Thecuttings carrying ratio is introduced as a metric for evaluatingwellbore cleanliness.Findings reveal that temperature and pressure fluctuations can alter terminal velocity by up to 3.4%.Cuttings shape plays a crucial role,with block-shaped cuttings requiring higher annular return velocity than flake-shaped ones at the same carrying ratio.As wellbore size increases,the minimum required carrying flow rate rises nonlinearly,though the rate of increase gradually declines.For a Φ444.5mmwellbore,a carrying ratio of at least 0.6 is recommended.Terminal velocity decreases with increasing consistency coefficient,particularly in high-viscosity regimes.The proposed carrying ratio offers a more accurate and practical assessment of wellbore cleanliness.
文摘On the morning of May 31st,the parallel forum"Ecological Actions to Carry Forward the Shared Values of Mankind,"as part of the 4th Dialogue on Exchanges and Mutual Learning among Civilisations,was held in Dunhuang.More than 50 experts and scholars from different countries,including China,Kenya and Japan,engaged in indepth discussions on the theme.
基金financially supported by China Geological Survey Project(No.DD20220954)Open Funding Project of the Key Laboratory of Groundwater Sciences and Engineering,Ministry of Natural Resources(No.SK202301-4)+2 种基金Science and Technology Innovation Foundation of Comprehensive Survey&Command Center for Natural Resources(No.KC20240003)Yanzhao Shanshui Science and Innovation Fund of Langfang Integrated Natural Resources Survey Center,China Geological Survey(No.YZSSJJ202401-001)Open Foundation of the Key Laboratory of Coupling Process and Effect of Natural Resources Elements(No.2022KFKTC009).
文摘Water scarcity and environment deterioration have become main constraints to sustainable economic and social development.Scientifically assessing Water Resources Carrying Capacity(WRCC)is essential for the optimal allocation of regional water resources.The hilly area at the northern foot of Yanshan Mountains is a key water conservation zone and an important water source for Beijing,Tianjin and Hebei.Grasping the current status and temporal trends of water quality and WRCC in representative small watersheds within this region is crucial for supporting rational water resources allocation and environment protection efforts.This study focuses on Pingquan City,a typical watershed in northern Hebei Province.Firstly,evaluation index systems for surface water quality,groundwater quality and WRCC were estab-lished based on the Pressure-State-Response(PSR)framework.Then,comprehensive evaluations of water quality and WRCC at the sub-watershed scale were conducted using the Varying Fuzzy Pattern Recogni-tion(VFPR)model.Finally,the rationality of the evaluation results was verified,and future scenarios were projected.Results showed that:(1)The average comprehensive evaluation scores for surface water and groundwater quality in the sub-watersheds were 1.44 and 1.46,respectively,indicating that both met the national Class II water quality standard and reflected a high-quality water environment.(2)From 2010 to 2020,the region's WRCC steadily improved,with scores rising from 2.99 to 2.83 and an average of 2.90,suggesting effective water resources management in Pingquan City.(3)According to scenario-based predic-tion,WRCC may slightly decline between 2025 and 2030,reaching 2.92 and 2.94,respectively,relative to 2020 levels.Therefore,future efforts should focus on strengthening scientific management and promoting the efficient use of water resources.Proactive measures are necessary to mitigate emerging contradiction and ensure the long-term stability and sustainability of the water resources system in the region.The evalua-tion system and spatiotemporal evolution patterns proposed in this study can provide a scientific basis for refined water resource management and ecological conservation in similar hilly areas.
文摘In recent years,the rapid advancement of artificial intelligence(AI)has fostered deep integration between large AI models and robotic technology.Robots such as robotic dogs capable of carrying heavy loads on mountainous terrain or performing waste disposal tasks and humanoid robots that can execute high-precision component installations have gradually reached the public eye,raising expectations for embodied intelligent robots.
基金supported by the National Natural Science Foundation of China(Grant Nos.12504361,12274313,and 62465005)the Natural Science Foundation of Guangxi(Grant No.2025GXNSFBA069179)the Guangxi Colleges and Universities Young and Middle-aged Teachers’Basic Scientific Research Ability Enhancement Project(Grant No.2025KY0093)。
文摘The unique wave-manipulation capabilities of zero-index metamaterials(ZIMs)offer a new opportunity for realizing bound states in the continuum(BICs).However,the relationship between anomalous scattering and BICs remains underexplored when parity–time(PT)symmetry is introduced.In this work,we demonstrate that a BIC splits into a pair of lasing modes carrying opposite topological charges by introducing PT symmetry through gain-loss cylinders embedded in ZIM layers.Theoretical analysis and numerical simulations reveal that lasing and unidirectional transparency phenomena result from the singularities and exceptional points of the scattering matrix.Moreover,exceptional points can be tuned via propagation phase modulation in the air gap,and their coalescence produces quasi-BICs with symmetric responses.This work provides a framework for manipulating BICs and topological lasing modes in non-Hermitian systems,offering new insights for designing non-Hermitian photonic devices.
