Traffic engineering such as tunnels in various altitudinal gradient zone are at risk of accidental explosion,which can damage personnel and equipment.Accurate prediction of the distribution pattern of explosive loads ...Traffic engineering such as tunnels in various altitudinal gradient zone are at risk of accidental explosion,which can damage personnel and equipment.Accurate prediction of the distribution pattern of explosive loads and shock wave propagation process in semi-enclosed structures at various altitude environment is key research focus in the fields of explosion shock and fluid dynamics.The effect of altitude on the propagation of shock waves in tunnels was investigated by conducting explosion test and numerical simulation.Based on the experimental and numerical simulation results,a prediction model for the attenuation of the peak overpressure of tunnel shock waves at different altitudes was established.The results showed that the peak overpressure decreased at the same measurement points in the tunnel entrance under the high altitude condition.In contrast,an increase in altitude accelerated the propagation speed of the shock wave in the tunnel.The average error between the peak shock wave overpressure obtained using the overpressure prediction formula and the measured test data was less than15%,the average error between the propagation velocity of shock waves predicted values and the test data is less than 10%.The method can effectively predict the overpressure attenuation of blast wave in tunnel at various altitudes.展开更多
The ability of queens and males of most ant species to disperse by flight has fundamentally contributed to the group’s evolutionary and ecological success and is a determining factor to take into account for biogeogr...The ability of queens and males of most ant species to disperse by flight has fundamentally contributed to the group’s evolutionary and ecological success and is a determining factor to take into account for biogeographic studies(Wagner and Liebherr 1992;Peeters and Ito 2001;Helms 2018).展开更多
Background: Prematurely-born individuals tend to exhibit higher resting oxidative stress, although evidence suggests they may be more resistant to acute hypoxia-induced redox balance alterations. We aimed to investiga...Background: Prematurely-born individuals tend to exhibit higher resting oxidative stress, although evidence suggests they may be more resistant to acute hypoxia-induced redox balance alterations. We aimed to investigate the redox balance changes across a 3-day hypobaric hypoxic exposure at 3375 m in healthy adults born preterm(gestational age ≤ 32 weeks) and their term-born(gestational age ≥ 38 weeks)counterparts.Methods: Resting venous blood was obtained in normoxia(prior to altitude exposure), immediately upon arrival to altitude, and the following 3mornings. Antioxidant(superoxide dismutase(SOD), catalase, glutathione peroxidase(GPx), and ferric reducing antioxidant power(FRAP)),pro-oxidant(xanthine oxidase(XO) and myeloperoxidase(MPO)) enzyme activity, oxidative stress markers(advanced oxidation protein product(AOPP) and malondialdehyde(MDA)), nitric oxide(NO) metabolites(nitrites, nitrates, and total nitrite and nitrate(NOx)), and nitrotyrosine were measured in plasma.Results: SOD increased only in the preterm group(p < 0.05). Catalase increased at arrival in preterm group(p < 0.05). XO activity increased at Day 3 for the preterm group, while it increased acutely(arrival and Day 1) in control group. MPO increased in both groups throughout the3 days(p < 0.05). AOPP only increased at arrival in the preterm(p < 0.05) whereas it decreased at arrival up to Day 3(p < 0.05) for control.MDA decreased in control group from arrival onward. Nitrotyrosine decreased in both groups(p < 0.05). Nitrites increased on Day 3(p < 0.05)in control group and decreased on Day 1(p < 0.05) in preterm group.Conclusion: These data indicate that antioxidant enzymes seem to increase immediately upon hypoxic exposure in preterm adults. Conversely, the blunted pro-oxidant enzyme response to prolonged hypoxia exposure suggests that these enzymes may be less sensitive in preterm individuals.These findings lend further support to the potential hypoxic preconditioning effect of preterm birth.展开更多
[Objectives]To analyze the differences in medicinal component contents of Magnolia officinalis across different altitude gradients and explore their causes.[Methods]In this experiment,M.officinalis trees aged 15-20 ye...[Objectives]To analyze the differences in medicinal component contents of Magnolia officinalis across different altitude gradients and explore their causes.[Methods]In this experiment,M.officinalis trees aged 15-20 years growing at four altitudes(1301,1444,1573,and 1643 m)were selected as experimental materials.Leaf traits,soil physicochemical properties,and medicinal component contents were investigated,and the relationships among leaf traits,soil physicochemical properties,and medicinal components were analyzed.[Results]With increasing altitude,the specific leaf area(SLA)of M.officinalis significantly increased,while stomatal density,vein density,leaf thickness,and mesophyll tissue thickness decreased.Soil total nitrogen(TN),total phosphorus(TP),total potassium(TK),available nitrogen(AN),and organic matter contents(OM)decreased significantly with altitude,whereas available potassium(AK)showed the opposite trend.The contents of medicinal components magnolol and honokiol in M.officinalis also significantly decreased with altitude.Correlation analysis revealed that,in addition to altitude,soil physicochemical properties(pH,TP,OM)and leaf traits(leaf thickness,palisade tissue thickness,SLA)were significantly correlated with magnolol and honokiol contents.[Conclusions]M.officinalis at lower altitudes exhibited better growth and higher magnolol and honokiol contents,which may be attributed to higher soil nutrient availability in low-altitude regions.This study provides guidance for selecting cultivation sites and optimizing planting patterns for M.officinalis.展开更多
1.Opportunities for electric motor drives in the low-altitude economy The implementation plan for the innovative application of general aviation equipment(2024–2030)outlines that by 2027,new general aviation equipmen...1.Opportunities for electric motor drives in the low-altitude economy The implementation plan for the innovative application of general aviation equipment(2024–2030)outlines that by 2027,new general aviation equipment will achieve commercial applications in urban air transport,logistics distribution and emergency rescue.展开更多
Unmanned aerial vehicle light detection and ranging(UAV–LiDAR)is a new method for collecting understory terrain data.The high estimation accuracy of understory terrain is crucial for accurate tree height measurement ...Unmanned aerial vehicle light detection and ranging(UAV–LiDAR)is a new method for collecting understory terrain data.The high estimation accuracy of understory terrain is crucial for accurate tree height measurement and forest resource surveys.The UAV–LiDAR flight altitude and forest canopy cover significantly impact the accuracy of understory terrain estimation.However,since no research examined their combined effects,we aimed to investigate this relationship.This will help optimize UAV–LiDAR flight parameters for understory terrain estimation and forest surveys across various canopy cover.This study analyzed the impacts of three flight altitudes and three canopy cover on the estimation accuracy of understory terrain.The results showed that when canopy cover exceeded a specific value,UAV–LiDAR flight altitudes significantly affected understory terrain estimation.Given a forest canopy cover,the reduction in ground point coverage increased significantly as the flight altitude increased;given a flight altitude,the higher the canopy cover,the more significant the reduction in ground point coverage.In forests with a canopy cover≥0.9,there were substantial differences in the accuracies of understory digital elevation models(DEMs)generated using UAV–LiDAR at different flight altitudes.For forests with a canopy cover<0.9,the mean absolute error(MAE)of understory DEMs from UAV–LiDAR at different flight altitudes was≤0.17 m and the root mean square error(RMSE)was≤0.24 m.However,for forests with a canopy cover≥0.9,the UAV–LiDAR flight altitude significantly affected the accuracy of understory DEMs.At the same flight altitude,the MAE and RMSE of the estimated elevation for forests with a canopy cover≥0.9 were approximately twice those of the estimated elevation for forests with a canopy cover<0.9.In forests with low canopy cover,it is possible to improve data collection efficiency by selecting a higher flight altitude.However,UAV–LiDAR flight altitudes significantly affected understory terrain estimation in forests with high canopy cover,it is essential to adopt terrain-following flight modes,reduce flight altitudes,and maintain a consistent flight altitude during longterm monitoring in high canopy cover forests.展开更多
Ischemic stroke is the leading cause of death in the Chinese population.The incidence of cerebral infarction is higher in high-altitude regions,particularly those above 3,500 m,than in populations residing at lower al...Ischemic stroke is the leading cause of death in the Chinese population.The incidence of cerebral infarction is higher in high-altitude regions,particularly those above 3,500 m,than in populations residing at lower altitudes[1].There are various speculations regarding the mechanisms behind this phenomenon,one of which is that the low oxygen content and cold climate at high altitudes may increase the occurrence of vascular diseases[2].The multifactorial effect of high-altitude environments on residential populations makes it challenging for researchers to determine the specific pathways through which these diseases occur.展开更多
With the theme of“new infrastructure construction in airspace with standards as the foundation-Driving the high-quality development of the low-altitude economy”,a sub-forum brought together representatives from gove...With the theme of“new infrastructure construction in airspace with standards as the foundation-Driving the high-quality development of the low-altitude economy”,a sub-forum brought together representatives from government departments,research institutes,universities,and enterprises to probe into the key role of standardization in the development of the low-altitude economy.展开更多
Low-altitude economy opens up a completely new aerial space for economic growth by enabling brand new services such as fast logistics delivery,timely emergency rescue,and wide-area,high-definition environmental monito...Low-altitude economy opens up a completely new aerial space for economic growth by enabling brand new services such as fast logistics delivery,timely emergency rescue,and wide-area,high-definition environmental monitoring.This new space has many distinct features and therefore faces many new challenges compared with ground-and high-altitude-based information infrastructures.As a result,the rapid and mass development of unmanned aerial vehicles(UAVs)in low-altitude space will inevitably necessitate research on providing ultra-reliable,low-latency,high-capacity.展开更多
As there are numerous challenges to the global industrial and supply chains,the China International Supply Chain Expo(hereinafter referred to as the“CISCE”)hosted by the China Council for the Promotion of Internatio...As there are numerous challenges to the global industrial and supply chains,the China International Supply Chain Expo(hereinafter referred to as the“CISCE”)hosted by the China Council for the Promotion of International Trade(CCPIT),has been playing a unique role as a“stabilizer”for international cooperation,an“accelerator”for economic development,and a“booster”for future transformation.展开更多
With the rapid development of low altitude economic industry,low altitude adhoc network technology has been getting more and more intensive attention.In the adhoc network protocol designed in this paper,the convolutio...With the rapid development of low altitude economic industry,low altitude adhoc network technology has been getting more and more intensive attention.In the adhoc network protocol designed in this paper,the convolutional code used is(3,1,7),and the design of a low power Viterbi decoder adapted to multi-rate variations is proposed.In the traditional Viterbi decoding method,the high complexity of path metric(PM)accumulation and Euclidean distance computation leads to the problems of low efficiency and large storage resources in the decoder.In this paper,an improved add compare select(ACS)algorithm,a generalized formula for branch metric(BM)based on Manhattan distance,and a method to reduce the accumulated PM for different Viterbi decoders are put forward.A simulation environment based on Vivado and Matlab to verify the accuracy and effectiveness of the proposed Viterbi decoder is also established.The experimental results show that the total power consumption is reduced by 15.58%while the decoding accuracy of the Viterbi decoder is guaranteed,which meets the design requirements of a low power Viterbi decoder.展开更多
Propelled by the synergy of policy,technology,and market demand,the low-altitude economy has emerged as a powerful driver of high-quality development in China.This burgeoning sector is reshaping traditional industries...Propelled by the synergy of policy,technology,and market demand,the low-altitude economy has emerged as a powerful driver of high-quality development in China.This burgeoning sector is reshaping traditional industries while forging new strategic pathways for China to excel in the global competitive arena.展开更多
As an emerging industry catering to diverse needs across commercial,industrial,civil,and military fields,the low-altitude economy has the potential to transform industries such as logistics,transportation,tourism,heal...As an emerging industry catering to diverse needs across commercial,industrial,civil,and military fields,the low-altitude economy has the potential to transform industries such as logistics,transportation,tourism,health care,agriculture,and infrastructure.展开更多
Imagine hiring a low-altitude aircraft from your office to the airport to avoid road traffic congestion,flying across the Yangtze River in an air taxi,or sitting by the Great Wall and enjoying a cup of cappuccino deli...Imagine hiring a low-altitude aircraft from your office to the airport to avoid road traffic congestion,flying across the Yangtze River in an air taxi,or sitting by the Great Wall and enjoying a cup of cappuccino delivered by a drone...All these are gradually becoming a reality in China as the low-altitude economy rapidly advances.展开更多
As an economic concept,the low-altitude economy aims to utilise the unique resources of low-altitude airspace in a bid to develop general aviation or civilian non-airline flight,and energise the related industries fro...As an economic concept,the low-altitude economy aims to utilise the unique resources of low-altitude airspace in a bid to develop general aviation or civilian non-airline flight,and energise the related industries from the sky to the ground.展开更多
At Shenzhen’s renowned theme park,Window of the World,drones illuminated the night sky alongside fireworks during the Spring Festival holiday,creating a breathtaking sight.In Longgang District’s central area,citizen...At Shenzhen’s renowned theme park,Window of the World,drones illuminated the night sky alongside fireworks during the Spring Festival holiday,creating a breathtaking sight.In Longgang District’s central area,citizens enjoyed panoramic views of the city from above through helicopter rides.Meanwhile,in Dapeng New District,low-altitude rescue aircraft remained on standby 24/7 to ensure the safety of hikers in the mountains.展开更多
Volocopter,a pioneering German company in the electric vertical take-off and landing(eVTOL)aircraft sector,recently filed for bankruptcy,drawing significant international attention.Founded in 2011,Volocopter was haile...Volocopter,a pioneering German company in the electric vertical take-off and landing(eVTOL)aircraft sector,recently filed for bankruptcy,drawing significant international attention.Founded in 2011,Volocopter was hailed as a leader in the emerging air taxi industry,benefitting from technological breakthroughs and substantial international investment.展开更多
The North China Plain(NCP)frequently experiences ozone pollution events,which are generally related to cross-border transport at multiple scales.However,current methods of calculating ozone transport are insufficient ...The North China Plain(NCP)frequently experiences ozone pollution events,which are generally related to cross-border transport at multiple scales.However,current methods of calculating ozone transport are insufficient to account for ozone transport at different altitudes.To further understand the characteristics of ozone transport,we applied theWeather Research and Forecasting(WRF)model and the Comprehensive Air Quality Model with Extensions(CAMx)based on flux calculation method.The results showed that the simulated flux calculation method was suitable for revealing the evolutionary trend of ozone fluxes.Monthly inflows,outflows,and total net fluxes ranged from-32985.45 to 37361.46 t/d and indicated strong transport and significant spatial and temporal variations of ozone in the urban boundary segments.Vertical distribution analysis of the net ozone fluxes demonstrated that the net fluxes varied with the altitude,and the altitude at which the corresponding peaks were located had a strong correlation with the neighborhood and season.It was noteworthy that there were three main transport directions throughout the year,namely northwest-southeast(NW-SE),southeast-northwest(SE-NW),and southwestnortheast(SW-NE).Additionally,the ozone flux was mainly affected by temperature,wind speed,and ozone concentration,with the correlation coefficient varying by season and altitude,up to 0.78.Moreover,the correlation analysis of ozone flux and wind direction in each city further verified the accuracy of the transport direction.This paper can provide scientific and technological support for the study of ozone generation mechanisms and the solution of urban/interregional ozone pollution problems.展开更多
In this paper,a comprehensive overview of radar detection methods for low-altitude targets in maritime environments is presented,focusing on the challenges posed by sea clutter and multipath scattering.The performance...In this paper,a comprehensive overview of radar detection methods for low-altitude targets in maritime environments is presented,focusing on the challenges posed by sea clutter and multipath scattering.The performance of the radar detection methods under sea clutter,multipath,and combined conditions is categorized and summarized,and future research directions are outlined to enhance radar detection performance for low-altitude targets in maritime environments.展开更多
The corona discharge from transmission lines in high-altitude areas is more severe than at lower altitudes. The radio interference caused thereby is a key factor to be considered when designing transmission lines. To ...The corona discharge from transmission lines in high-altitude areas is more severe than at lower altitudes. The radio interference caused thereby is a key factor to be considered when designing transmission lines. To study the influence of altitude on negative corona characteristics, an experimental platform comprising a movable small corona cage was established: experiments were conducted at four altitudes in the range of 1120-4320 m, and data on the corona current pulse and radio interference level of 0.8-mm diameter fine copper wire under different negative voltages were collected. The experimental results show that the average amplitude, repetition frequency and average current of the corona current pulse increase with increasing altitude. The dispersion of pulse amplitude increases with increase in altitude, while the randomness of the pulse interval decreases continuously. Taking the average current as an intermediate variable,the relationship between radio interference level and altitude is obtained. The result of this research has some significance for understanding the corona discharge characteristics of ultra-highvoltage lines.展开更多
基金financially supported by National Natural Science Foundation of China(Grant Nos.52378401,52278504)the Fundamental Research Funds for the Central Universities(Grant No.30922010918)。
文摘Traffic engineering such as tunnels in various altitudinal gradient zone are at risk of accidental explosion,which can damage personnel and equipment.Accurate prediction of the distribution pattern of explosive loads and shock wave propagation process in semi-enclosed structures at various altitude environment is key research focus in the fields of explosion shock and fluid dynamics.The effect of altitude on the propagation of shock waves in tunnels was investigated by conducting explosion test and numerical simulation.Based on the experimental and numerical simulation results,a prediction model for the attenuation of the peak overpressure of tunnel shock waves at different altitudes was established.The results showed that the peak overpressure decreased at the same measurement points in the tunnel entrance under the high altitude condition.In contrast,an increase in altitude accelerated the propagation speed of the shock wave in the tunnel.The average error between the peak shock wave overpressure obtained using the overpressure prediction formula and the measured test data was less than15%,the average error between the propagation velocity of shock waves predicted values and the test data is less than 10%.The method can effectively predict the overpressure attenuation of blast wave in tunnel at various altitudes.
基金funded by the“Departments of Excellence”program of the Italian Ministry for University and Research(MIUR,2018-2022 and MUR,2023-2027).
文摘The ability of queens and males of most ant species to disperse by flight has fundamentally contributed to the group’s evolutionary and ecological success and is a determining factor to take into account for biogeographic studies(Wagner and Liebherr 1992;Peeters and Ito 2001;Helms 2018).
基金funded by the Swiss National Science Foundation(SNSF Grant No.320030L_192073 to GM)the Slovenian Research Agency(ARRS Grant No.N5-0152 to TD).
文摘Background: Prematurely-born individuals tend to exhibit higher resting oxidative stress, although evidence suggests they may be more resistant to acute hypoxia-induced redox balance alterations. We aimed to investigate the redox balance changes across a 3-day hypobaric hypoxic exposure at 3375 m in healthy adults born preterm(gestational age ≤ 32 weeks) and their term-born(gestational age ≥ 38 weeks)counterparts.Methods: Resting venous blood was obtained in normoxia(prior to altitude exposure), immediately upon arrival to altitude, and the following 3mornings. Antioxidant(superoxide dismutase(SOD), catalase, glutathione peroxidase(GPx), and ferric reducing antioxidant power(FRAP)),pro-oxidant(xanthine oxidase(XO) and myeloperoxidase(MPO)) enzyme activity, oxidative stress markers(advanced oxidation protein product(AOPP) and malondialdehyde(MDA)), nitric oxide(NO) metabolites(nitrites, nitrates, and total nitrite and nitrate(NOx)), and nitrotyrosine were measured in plasma.Results: SOD increased only in the preterm group(p < 0.05). Catalase increased at arrival in preterm group(p < 0.05). XO activity increased at Day 3 for the preterm group, while it increased acutely(arrival and Day 1) in control group. MPO increased in both groups throughout the3 days(p < 0.05). AOPP only increased at arrival in the preterm(p < 0.05) whereas it decreased at arrival up to Day 3(p < 0.05) for control.MDA decreased in control group from arrival onward. Nitrotyrosine decreased in both groups(p < 0.05). Nitrites increased on Day 3(p < 0.05)in control group and decreased on Day 1(p < 0.05) in preterm group.Conclusion: These data indicate that antioxidant enzymes seem to increase immediately upon hypoxic exposure in preterm adults. Conversely, the blunted pro-oxidant enzyme response to prolonged hypoxia exposure suggests that these enzymes may be less sensitive in preterm individuals.These findings lend further support to the potential hypoxic preconditioning effect of preterm birth.
基金Supported by National Key Research and Development Program of China in 2018(2018YFC1708005)the Southwest Minzu University Research Startup Funds(RQD2023020).
文摘[Objectives]To analyze the differences in medicinal component contents of Magnolia officinalis across different altitude gradients and explore their causes.[Methods]In this experiment,M.officinalis trees aged 15-20 years growing at four altitudes(1301,1444,1573,and 1643 m)were selected as experimental materials.Leaf traits,soil physicochemical properties,and medicinal component contents were investigated,and the relationships among leaf traits,soil physicochemical properties,and medicinal components were analyzed.[Results]With increasing altitude,the specific leaf area(SLA)of M.officinalis significantly increased,while stomatal density,vein density,leaf thickness,and mesophyll tissue thickness decreased.Soil total nitrogen(TN),total phosphorus(TP),total potassium(TK),available nitrogen(AN),and organic matter contents(OM)decreased significantly with altitude,whereas available potassium(AK)showed the opposite trend.The contents of medicinal components magnolol and honokiol in M.officinalis also significantly decreased with altitude.Correlation analysis revealed that,in addition to altitude,soil physicochemical properties(pH,TP,OM)and leaf traits(leaf thickness,palisade tissue thickness,SLA)were significantly correlated with magnolol and honokiol contents.[Conclusions]M.officinalis at lower altitudes exhibited better growth and higher magnolol and honokiol contents,which may be attributed to higher soil nutrient availability in low-altitude regions.This study provides guidance for selecting cultivation sites and optimizing planting patterns for M.officinalis.
基金supported by the National Natural Science Foundation of China(No.52407064)。
文摘1.Opportunities for electric motor drives in the low-altitude economy The implementation plan for the innovative application of general aviation equipment(2024–2030)outlines that by 2027,new general aviation equipment will achieve commercial applications in urban air transport,logistics distribution and emergency rescue.
基金supported by the National Natural Science Foundation of China(No.32271876)the Research on Key Technologies of Intelligent Monitoring and Carbon Sink Metering of Forest Resources in Fujian Province(No.2022FKJ03)the Science and Technology Innovation Project of Fujian Agriculture and Forestry University(No.KFB23172A,KFB23173A).
文摘Unmanned aerial vehicle light detection and ranging(UAV–LiDAR)is a new method for collecting understory terrain data.The high estimation accuracy of understory terrain is crucial for accurate tree height measurement and forest resource surveys.The UAV–LiDAR flight altitude and forest canopy cover significantly impact the accuracy of understory terrain estimation.However,since no research examined their combined effects,we aimed to investigate this relationship.This will help optimize UAV–LiDAR flight parameters for understory terrain estimation and forest surveys across various canopy cover.This study analyzed the impacts of three flight altitudes and three canopy cover on the estimation accuracy of understory terrain.The results showed that when canopy cover exceeded a specific value,UAV–LiDAR flight altitudes significantly affected understory terrain estimation.Given a forest canopy cover,the reduction in ground point coverage increased significantly as the flight altitude increased;given a flight altitude,the higher the canopy cover,the more significant the reduction in ground point coverage.In forests with a canopy cover≥0.9,there were substantial differences in the accuracies of understory digital elevation models(DEMs)generated using UAV–LiDAR at different flight altitudes.For forests with a canopy cover<0.9,the mean absolute error(MAE)of understory DEMs from UAV–LiDAR at different flight altitudes was≤0.17 m and the root mean square error(RMSE)was≤0.24 m.However,for forests with a canopy cover≥0.9,the UAV–LiDAR flight altitude significantly affected the accuracy of understory DEMs.At the same flight altitude,the MAE and RMSE of the estimated elevation for forests with a canopy cover≥0.9 were approximately twice those of the estimated elevation for forests with a canopy cover<0.9.In forests with low canopy cover,it is possible to improve data collection efficiency by selecting a higher flight altitude.However,UAV–LiDAR flight altitudes significantly affected understory terrain estimation in forests with high canopy cover,it is essential to adopt terrain-following flight modes,reduce flight altitudes,and maintain a consistent flight altitude during longterm monitoring in high canopy cover forests.
基金supported by the National Natural Science Foundation of Chongqing,China(CSTB2022NSCQ-MSX1100)National Natural Science Foundation of China(grant no.82101499).
文摘Ischemic stroke is the leading cause of death in the Chinese population.The incidence of cerebral infarction is higher in high-altitude regions,particularly those above 3,500 m,than in populations residing at lower altitudes[1].There are various speculations regarding the mechanisms behind this phenomenon,one of which is that the low oxygen content and cold climate at high altitudes may increase the occurrence of vascular diseases[2].The multifactorial effect of high-altitude environments on residential populations makes it challenging for researchers to determine the specific pathways through which these diseases occur.
文摘With the theme of“new infrastructure construction in airspace with standards as the foundation-Driving the high-quality development of the low-altitude economy”,a sub-forum brought together representatives from government departments,research institutes,universities,and enterprises to probe into the key role of standardization in the development of the low-altitude economy.
文摘Low-altitude economy opens up a completely new aerial space for economic growth by enabling brand new services such as fast logistics delivery,timely emergency rescue,and wide-area,high-definition environmental monitoring.This new space has many distinct features and therefore faces many new challenges compared with ground-and high-altitude-based information infrastructures.As a result,the rapid and mass development of unmanned aerial vehicles(UAVs)in low-altitude space will inevitably necessitate research on providing ultra-reliable,low-latency,high-capacity.
文摘As there are numerous challenges to the global industrial and supply chains,the China International Supply Chain Expo(hereinafter referred to as the“CISCE”)hosted by the China Council for the Promotion of International Trade(CCPIT),has been playing a unique role as a“stabilizer”for international cooperation,an“accelerator”for economic development,and a“booster”for future transformation.
基金Supported by the National Natural Science Foundation of China(No.62103257).
文摘With the rapid development of low altitude economic industry,low altitude adhoc network technology has been getting more and more intensive attention.In the adhoc network protocol designed in this paper,the convolutional code used is(3,1,7),and the design of a low power Viterbi decoder adapted to multi-rate variations is proposed.In the traditional Viterbi decoding method,the high complexity of path metric(PM)accumulation and Euclidean distance computation leads to the problems of low efficiency and large storage resources in the decoder.In this paper,an improved add compare select(ACS)algorithm,a generalized formula for branch metric(BM)based on Manhattan distance,and a method to reduce the accumulated PM for different Viterbi decoders are put forward.A simulation environment based on Vivado and Matlab to verify the accuracy and effectiveness of the proposed Viterbi decoder is also established.The experimental results show that the total power consumption is reduced by 15.58%while the decoding accuracy of the Viterbi decoder is guaranteed,which meets the design requirements of a low power Viterbi decoder.
文摘Propelled by the synergy of policy,technology,and market demand,the low-altitude economy has emerged as a powerful driver of high-quality development in China.This burgeoning sector is reshaping traditional industries while forging new strategic pathways for China to excel in the global competitive arena.
文摘As an emerging industry catering to diverse needs across commercial,industrial,civil,and military fields,the low-altitude economy has the potential to transform industries such as logistics,transportation,tourism,health care,agriculture,and infrastructure.
文摘Imagine hiring a low-altitude aircraft from your office to the airport to avoid road traffic congestion,flying across the Yangtze River in an air taxi,or sitting by the Great Wall and enjoying a cup of cappuccino delivered by a drone...All these are gradually becoming a reality in China as the low-altitude economy rapidly advances.
文摘As an economic concept,the low-altitude economy aims to utilise the unique resources of low-altitude airspace in a bid to develop general aviation or civilian non-airline flight,and energise the related industries from the sky to the ground.
文摘At Shenzhen’s renowned theme park,Window of the World,drones illuminated the night sky alongside fireworks during the Spring Festival holiday,creating a breathtaking sight.In Longgang District’s central area,citizens enjoyed panoramic views of the city from above through helicopter rides.Meanwhile,in Dapeng New District,low-altitude rescue aircraft remained on standby 24/7 to ensure the safety of hikers in the mountains.
文摘Volocopter,a pioneering German company in the electric vertical take-off and landing(eVTOL)aircraft sector,recently filed for bankruptcy,drawing significant international attention.Founded in 2011,Volocopter was hailed as a leader in the emerging air taxi industry,benefitting from technological breakthroughs and substantial international investment.
基金supported by the National Natural Science Foundation of China(No.52200120)the R&D Program of Beijing Municipal Education Commission(No.KM202310011003)。
文摘The North China Plain(NCP)frequently experiences ozone pollution events,which are generally related to cross-border transport at multiple scales.However,current methods of calculating ozone transport are insufficient to account for ozone transport at different altitudes.To further understand the characteristics of ozone transport,we applied theWeather Research and Forecasting(WRF)model and the Comprehensive Air Quality Model with Extensions(CAMx)based on flux calculation method.The results showed that the simulated flux calculation method was suitable for revealing the evolutionary trend of ozone fluxes.Monthly inflows,outflows,and total net fluxes ranged from-32985.45 to 37361.46 t/d and indicated strong transport and significant spatial and temporal variations of ozone in the urban boundary segments.Vertical distribution analysis of the net ozone fluxes demonstrated that the net fluxes varied with the altitude,and the altitude at which the corresponding peaks were located had a strong correlation with the neighborhood and season.It was noteworthy that there were three main transport directions throughout the year,namely northwest-southeast(NW-SE),southeast-northwest(SE-NW),and southwestnortheast(SW-NE).Additionally,the ozone flux was mainly affected by temperature,wind speed,and ozone concentration,with the correlation coefficient varying by season and altitude,up to 0.78.Moreover,the correlation analysis of ozone flux and wind direction in each city further verified the accuracy of the transport direction.This paper can provide scientific and technological support for the study of ozone generation mechanisms and the solution of urban/interregional ozone pollution problems.
基金supported by the National Natural Science Foundation of China(62171447)。
文摘In this paper,a comprehensive overview of radar detection methods for low-altitude targets in maritime environments is presented,focusing on the challenges posed by sea clutter and multipath scattering.The performance of the radar detection methods under sea clutter,multipath,and combined conditions is categorized and summarized,and future research directions are outlined to enhance radar detection performance for low-altitude targets in maritime environments.
基金supported by the Science and Technology Project of State Grid Corporation of China (No.5200202155587A-0-5-GC)。
文摘The corona discharge from transmission lines in high-altitude areas is more severe than at lower altitudes. The radio interference caused thereby is a key factor to be considered when designing transmission lines. To study the influence of altitude on negative corona characteristics, an experimental platform comprising a movable small corona cage was established: experiments were conducted at four altitudes in the range of 1120-4320 m, and data on the corona current pulse and radio interference level of 0.8-mm diameter fine copper wire under different negative voltages were collected. The experimental results show that the average amplitude, repetition frequency and average current of the corona current pulse increase with increasing altitude. The dispersion of pulse amplitude increases with increase in altitude, while the randomness of the pulse interval decreases continuously. Taking the average current as an intermediate variable,the relationship between radio interference level and altitude is obtained. The result of this research has some significance for understanding the corona discharge characteristics of ultra-highvoltage lines.
