Cereal is an essential source of calories and protein for the global population.Accurately predicting cereal quality before harvest is highly desirable in order to optimise management for farmers,grading harvest and c...Cereal is an essential source of calories and protein for the global population.Accurately predicting cereal quality before harvest is highly desirable in order to optimise management for farmers,grading harvest and categorised storage for enterprises,future trading prices,and policy planning.The use of remote sensing data with extensive spatial coverage demonstrates some potential in predicting crop quality traits.Many studies have also proposed models and methods for predicting such traits based on multiplatform remote sensing data.In this paper,the key quality traits that are of interest to producers and consumers are introduced.The literature related to grain quality prediction was analyzed in detail,and a review was conducted on remote sensing platforms,commonly used methods,potential gaps,and future trends in crop quality prediction.This review recommends new research directions that go beyond the traditional methods and discusses grain quality retrieval and the associated challenges from the perspective of remote sensing data.展开更多
Interferometry Synthetic Aperture Radar(InSAR)provides unique capabilities to map regional/global topography and deformation of the Earth’s surface and has led to a broad spectrum of deformation monitoring applicatio...Interferometry Synthetic Aperture Radar(InSAR)provides unique capabilities to map regional/global topography and deformation of the Earth’s surface and has led to a broad spectrum of deformation monitoring applications.In order to adapt to various challenging monitoring environments,researchers have made tremendous innovations to deal with issues such as atmospheric and ionospheric effects,loss of coherence due to large displacements,geometric distortions and unwrapping errors.Owing to recent technical and methodological advances,the Earth’s surface deformation,ranging from earthquake ruptures,volcanic eruptions,landslides,glaciers,to groundwater storage variations,mining subsidence and infrastructure instability can now be mapped anywhere in the world at high spatial and temporal resolutions.This special issue received a set of contributions highlighting recent advances in methodologies and applications of InSAR to ground deformation monitoring.We aim to present overviews of both the state of the art of SAR/InSAR techniques and the next generation of applications across the broad range of deformation monitoring applications.展开更多
The growth of the wireless and mobile communication data traffic has brought severe challenges to the present telecommunication systems. To meet the ever-increasing mobile traffic demand in the next 5 th generation(5 ...The growth of the wireless and mobile communication data traffic has brought severe challenges to the present telecommunication systems. To meet the ever-increasing mobile traffic demand in the next 5 th generation(5 G) communication systems, deploying 5 G in the unlicensed spectrum(5 G-U), has been regarded as a promising technology. The Third Generation Partnership Project(3 GPP) has specified the standardization of the Licensed Assisted Access(LAA) and its extension enhanced LAA(e LAA), to opportunistically transmit in the unlicensed spectrum. The LAA/e LAA systems share unlicensed spectrum resource with other networks, e.g., the Wi-Fi systems. In this article, we analyze the coexistence between the e LAA and the Wi-Fi systems in the unlicensed spectrum. We firstly establish the system model where the e LAA coexists with the Wi-Fi systems. Then, we theoretically derive and figure out the unfairness in the multi-channel occupancy rate between the e LAA and the Wi-Fi systems. After that, we propose a weight based channel selection method to improve the fairness of the coexistence. The numerical results demonstrate that by avoiding contentions and declining collisions, our method not only enhances the fairness, but also improves the overall unlicensed spectrum usage rate.展开更多
The tremendous development of Synthetic Aperture Radar(SAR)missions in recent years facilitates the study of smaller amplitude ground deformation over greater spatial scales using longer time series.However,this poses...The tremendous development of Synthetic Aperture Radar(SAR)missions in recent years facilitates the study of smaller amplitude ground deformation over greater spatial scales using longer time series.However,this poses greater challenges for correcting atmospheric effects due to the wider coverage of SAR imagery than ever.Previous attempts have used observations from Global Positioning System(GPS)and Numerical Weather Models(NWMs)to separate atmospheric delays,but they are limited by(1)The availability(and distribution)of GPS stations;(2)The low spatial resolution of NWM;And(3)The difficulties in quantifying their performance.To overcome these limitations,we have developed the Generic Atmospheric Correction Online Service for InSAR(GACOS)which utilizes the high-resolution European Centre for Medium-Range Weather Forecasts(ECMWF)products using an Iterative Tropospheric Decomposition(ITD)model.This enables the reduction of the coupling effects of the troposphere turbulence and stratification and hence achieves equivalent performances over flat and mountainous terrains.GACOS comprises a range of notable features:(1)Global coverage;(2)All-weather,all-time usability;(3)Available with a maximum of two-day latency;And(4)Indicators available to assess the model’s performance and feasibility.In this paper,we demonstrate some successful applications of the GACOS online service to a variety of geophysical studies.展开更多
In March 2021,a seismic sequence including three Mw>5.5 events struck northern Thessaly,Greece.Owing to the high temporal resolution of Sentinel-1 images which were sampled every 6 days and recorded the three event...In March 2021,a seismic sequence including three Mw>5.5 events struck northern Thessaly,Greece.Owing to the high temporal resolution of Sentinel-1 images which were sampled every 6 days and recorded the three events separately,we are able to map individually the coseismic deformation fields of the three events.Based on their respective coseismic displacements,we determined the geometry of the fault plane for each earthquake with the method of multipeak particle swarm optimization and inverted the best-fitting slip distribution by linear least squares inversion.Modelling results show that the three events occurred successively on 3,4 and 12 March 2021 were all dominated by normal-slip motions on previously unknown faults within the top 15 km of the Earth’s crust.The 3 March 2021 Mw 6.3 earthquake ruptured a northeast-dipping fault with a strike angle of 301°(clockwise from the North)and a dip angle of 46°,producing the maximum slip of about 2.2 m.The slip motion of the 4 March 2021 Mw 5.9 aftershock shows a similar fault geometry(striking 297°and dipping 42°)to the 3 March mainshock,but with a considerably smaller dip-slip component(~0.8 m).The 12 March 2021 Mw 5.6 aftershock occurred on a southwest-dipping fault(striking 100°and dipping 40°)with a normal fault slip of up to 0.5 m.Static Coulomb stress changes triggered by the earthquake sequence imply a promotion relationship between the first 3 March event and the two subsequent events.Due to the coseismic stress perturbation,more than 70%of aftershocks were distributed in areas with increased Coulomb stress and the northwest segment of the Larissa fault close to the seismic sequence was exposed to a relatively high seismic risk.展开更多
Utilizing the unlicensed spectrum as supplementary is being studied to meet the increasingly growing demand of user equipment for rate,traffic and bandwidth,and thus to mitigate the current spectrum scarcity crisis.In...Utilizing the unlicensed spectrum as supplementary is being studied to meet the increasingly growing demand of user equipment for rate,traffic and bandwidth,and thus to mitigate the current spectrum scarcity crisis.In this paper,we investigate the uplink multi-user multiple-input multiple-output(UL MU-MIMO) technique to achieve multiplexing gain in unlicensed spectrum.We first define a new parameter called channel busy radio(CBR) which is related to the probability of occupying the unlicensed channel,and find that the failure to occupy the unlicensed channel leads to the performance degradation in unlicensed spectrum.Then,according to the user-specific CBR of the unlicensed channel,we propose a flexible scheduling scheme for UL MU-MIMO in unlicensed spectrum,and formulate an optimization problem for the optimal scheduled user number.Furthermore,an adaptive scheduling algorithm is proposed to decide the optimal number of the scheduled users efficiently.The simulation results show that,based on statistical channel condition in unlicensed spectrum,adjusting the number of the scheduled user flexibly can offset the degraded throughput and form an optimal MU-MIMO transmission.展开更多
Synthetic Aperture Radar Interferometry(InSAR)has shown its potential on seismic deformation monitoring since it can achieve the accuracy of centimeter level or even the millimeter level.However,the irregular varietie...Synthetic Aperture Radar Interferometry(InSAR)has shown its potential on seismic deformation monitoring since it can achieve the accuracy of centimeter level or even the millimeter level.However,the irregular varieties of ionosphere can induce the additional phase delay on SAR interferometry,restricting its further application in high-precision deformation monitoring.Although several methods have been proposed to correct the ionospheric phase delay on SAR interferometry,the performances of them haven't been evaluated and compared.In this study,three commonly used methods,including polynomial fitting,azimuth offset and split-spectrum are applied to L'Aquila Earthquake to correct the ionospheric phase delay on two Phased Array type L-band Synthetic Aperture Radar(PALSAR)onboard the Advanced Land Observing Satellite-1(ALOS-1)images.The result indicates that these three methods can effectively correct the ionospheric phase delay error for SAR interferometry,where the standard deviations of the ionosphere-corrected results have decreased by almost a factor of 1.8 times for polynomial fitting method,4.2 times for azimuth offset method and 2.5 times for split-spectrum method,compared to those of the original phase.Furthermore,the result of the sliding distribution inversion of the seismic fault shows the best performance for split-spectrum method.展开更多
Due to high interferometric coherence in the Nevada region,Interferometric Synthetic Aperture Radar(InSAR)phase stacking is capable of mapping coseismic signals from the 27 January 1999,M w 4.8 Frenchman Flat earthqua...Due to high interferometric coherence in the Nevada region,Interferometric Synthetic Aperture Radar(InSAR)phase stacking is capable of mapping coseismic signals from the 27 January 1999,M w 4.8 Frenchman Flat earthquake.This is one of the smallest earthquakes yet studied using InSAR with line-of-sight displacements as small as~1.5 cm.Modelling the event as dislocation in an elastic half space suggests that the fault centroid was located at(115.96°W,36.81°N)with a precision of 0.2~0.3 km(1σ)at a depth of 3.4±0.2 km.Despite the dense local seismic network in southern Nevada,differences as large as 2~5 km were observed between our InSAR earthquake location and those estimated from seismic data.The InSAR-derived magnitude appeared to be greater than that from seismic data,which is consistent with other studies,and believed to be due to the relatively long time interval of InSAR data.展开更多
In 2017,China’s central government approved the national strategy to build Xiong’an New Area(XNA,100 km southwest to Beijing),which was announced as a"millennium strategy"and a"demo area"for a su...In 2017,China’s central government approved the national strategy to build Xiong’an New Area(XNA,100 km southwest to Beijing),which was announced as a"millennium strategy"and a"demo area"for a sustainable,modern,and innovative urban model.Xiong’an will draw in as much as$380 billion investment and is expected to help accelerate the development of the wider Beijing-Tianjin-Hebei(Jingjinji)Area.In this paper,present subsidence in the XNA area is investigated using InSAR observations for the first time.The 24 SAR images acquired by European Space Agency’s Sentinel-1 satellites during the period from June 2017 to July 2018 suggest that in the north of Xiong County,the subsidence rate reaches up to 90 mm/y,which is highly correlated with the exploitation of geothermal drilling.As the construction in the XNA area will significantly accelerate and its high-quality development,the InSAR findings could provide valuable information for future sustainable urban planning and underground infrastructure construction.展开更多
The 2009 M W 7.8 Fiordland (New Zealand) earthquake is the largest to have occurred in New Zealand since the 1931 M W 7.8 Hawke's Bay earthquake, 1 000 km to the northwest. In this paper two tracks of ALOS PALSAR ...The 2009 M W 7.8 Fiordland (New Zealand) earthquake is the largest to have occurred in New Zealand since the 1931 M W 7.8 Hawke's Bay earthquake, 1 000 km to the northwest. In this paper two tracks of ALOS PALSAR interferograms (one ascending and one descending) are used to determine fault geometry and slip distribution of this large earthquake. Modeling the event as dislocation in an elastic half-space suggests that the earthquake resulted from slip on a SSW-NNE orientated thrust fault that is associated with the subduction between the Pacific and Australian Plates, with oblique displacement of up to 6.3 m. This finding is consistent with the preliminary studies undertaken by the USGS using seismic data.展开更多
Rapid socio-economic changes in China,such as land conversion and urbanization,are creating new scopes for the application of precision agriculture(PA).An experiment to assess the economic benefits of two precision ag...Rapid socio-economic changes in China,such as land conversion and urbanization,are creating new scopes for the application of precision agriculture(PA).An experiment to assess the economic benefits of two precision agriculture methods was applied for one year–precision seeding and precision seeding with land leveling.Whilst the results for this were positive,of itself it did not provide evidence of longer terms gains.The costs of land leveling are accrued in a single year but the benefits could carry over into subsequent years.Thus,in this case if the PA method provides carry over benefits to future years,the economic assessment would incorrectly assign all the costs to a single year of benefits i.e.the benefit-cost ratio would be underestimated.To gauge whether there was carry over benefits in future years we looked at NDVI and GUI as proxies for future year benefits.For the single year experiment,our results showed that:(1)Winter wheat yield was increased 23.2%through the integration of precision seeding and laser leveling technologies.(2)Both the single technology and the integrated technologies significant reduced the concentration of soil ammonium nitrogen at the depths of 60 cm;(3)The benefit/cost ratio's of the treatments exceeded that of the baseline by approximately 10%which translated to an increase of several hundred US$per hectare.The NDVI analysis showed that the effect of laser land leveling could last to the next two years.When considering the multi-year impact of land leveling,the benefit/cost ratio of PSLL will increase to 23.5%and 22.9%with and without laser land leveling subsidies.Making clear the eco-nomic benefits of using PA technologies will likely promote application of the technologies in the region.展开更多
Multiple strain sensors are required to identify individual forces/stresses on human joints and recognize how they work together in order to determine the motion’s direction and trajectory.However,current sensors can...Multiple strain sensors are required to identify individual forces/stresses on human joints and recognize how they work together in order to determine the motion’s direction and trajectory.However,current sensors cannot detect and differentiate the individual forces/stresses and their contributions to the motion from the sensors’electrical signals.To address this critical issue,we propose a concept of unimodal tension,bend,shear,and twist strain sensors with piezoelectric poly L-lactic acid films.We then construct an integrated unimodal sensor(i-US)using the unimodal sensors and prove that the i-US can detect and differentiate individual strain modes,such as tensioning,bending,shearing,and twisting in complex motion.To demonstrate the potential impact of unimodal sensors,we design a sleeve and a glove with the i-US that can capture wrist motions and finger movements.Therefore,we expect unimodal strain sensors to provide a turning point in developing motion recognition and control systems.展开更多
Yangbajain contains the largest geothermal energy power station in China.Geothermal explorations in Yangbajain first started in 1976,and two plants were subsequently built in 1981 and 1986.A large amount of geothermal...Yangbajain contains the largest geothermal energy power station in China.Geothermal explorations in Yangbajain first started in 1976,and two plants were subsequently built in 1981 and 1986.A large amount of geothermal fluids have been extracted since then,leading to considerable surface subsidence around the geothermal fields.In this paper,InSAR time series analysis is applied to map the subsidence of the Yangbajain geothermal fields during the period from December 2011 to November 2012 using 16 senses of TerraSAR-X stripmap SAR images.In the case of the TerraSAR-X data,most orbital fringes were removed using precise orbits during the interferometric processing.However,residual orbital ramps remain in some interferograms due to the uncertainties in the TerraSAR-X orbits.To remove the residual orbital ramps,we estimated a best-fit‘twisted plane’for each epoch interferogram using quadratic polynomial models based on a network approach.This method removes most of the long-wavelength signals,including orbit ramps and atmospheric effects.The vertically stratified component(Topography Correlated Atmospheric Delay,TCAD)was also removed using a network approach.If the influence of seasonal frozen ground(SFG)is not taken into consideration,our results show that the subsidence rate around power plant I(the south plant)is approximately 20 mm/yr with a peak of 30 mm/yr.The subsidence rate around power plant II(the north plant)is approximately 10 mm/yr,when accounting for the influence of SFG on the power plant and its surrounding ground surface.Our results show that ground motion is caused by seasonal frozen ground and is strongly related to the temperature change.展开更多
Precision agriculture, and more specifically Site-Specific Crop Management(SSCM), has been implemented in some form across nearly all agricultural production systems over the past 25 years. Adoption has been greatest ...Precision agriculture, and more specifically Site-Specific Crop Management(SSCM), has been implemented in some form across nearly all agricultural production systems over the past 25 years. Adoption has been greatest in developed agricultural countries. In this review article, the current situation of SSCM adoption and application is investigated from the perspective of a developed(UK) and developing(China) agricultural economy. The current state-of-the art is reviewed with an emphasis on developments in position system technology and satellite-based remote sensing. This is augmented with observations on the differences between the use of SSCM technologies and methodologies in the UK and China and discussion of the opportunities for(and limitations to)increasing SSCM adoption in developing agricultural economies. A particular emphasis is given to the role of socio-demographic factors and the application of responsible research and innovation(RRI) in translating agritechnologies into China and other developing agricultural economies. Several key research and development areas are identified that need to be addressed to facilitate the delivery of SSCM as a holistic service into areas with low precision agriculture(PA) adoption. This has implications for developed as well as developing agricultural economies.展开更多
Precision agriculture(PA) technologies have great potential for promoting sustainable intensification of food production, ensuring targeted delivery of agricultural inputs, and hence food security and environmental pr...Precision agriculture(PA) technologies have great potential for promoting sustainable intensification of food production, ensuring targeted delivery of agricultural inputs, and hence food security and environmental protection. The benefits of PA technologies are applicable across a broad range of agronomic, environmental and rural socio-economic contexts globally. However, farmer and land-manager adoption in low to middle income countries has typically been slower than that observed in more affluent countries. China is currently engaged in the process of agricultural modernisation to ensure food security for its 1.4 billion population and has developed a portfolio of policies designed to improve food security,while simultaneously promoting environmental protection.Particular attention has been paid to the reduction of agricultural inputs such as fertilisers and pesticides. The widespread adoption of PA technologies across the Chinese agricultural landscape is central to the success of these policies. However, socio-economic and cultural barriers, farm scale,(in particular the prevalence of smaller family farms) and demographic changes in the rural population,(for example, the movement of younger people to the cities) represent barriers to PA adoption across China. A framework for ensuring an acceptable and accelerated PA technology trajectory is proposed which combines systematic understanding of farmer and end-user priorities and preferences for technology design throughout the technology development process, and subsequent end-user requirements for implementation(including demonstration of economic and agronomic benefits, andknowledge transfer). Future research will validate the framework against qualitative and quantitative socioeconomic, cultural and agronomic indicators of successful,or otherwise, PA implementation. The results will provide the evidence upon which to develop further policies regarding how to secure sustainable food production and how best to implement PA in China, as well as practical recommendations for optimising end-user uptake.展开更多
基金This study was supported by the National Natural Science Foundation of China(42271396)the Natural Science Foundation of Shandong Province(ZR2022MD017)+1 种基金the Key R&D Project of Hebei Province(22326406D)The European Space Agency(ESA)and Ministry of Science and Technology of China(MOST)Dragon(57457).
文摘Cereal is an essential source of calories and protein for the global population.Accurately predicting cereal quality before harvest is highly desirable in order to optimise management for farmers,grading harvest and categorised storage for enterprises,future trading prices,and policy planning.The use of remote sensing data with extensive spatial coverage demonstrates some potential in predicting crop quality traits.Many studies have also proposed models and methods for predicting such traits based on multiplatform remote sensing data.In this paper,the key quality traits that are of interest to producers and consumers are introduced.The literature related to grain quality prediction was analyzed in detail,and a review was conducted on remote sensing platforms,commonly used methods,potential gaps,and future trends in crop quality prediction.This review recommends new research directions that go beyond the traditional methods and discusses grain quality retrieval and the associated challenges from the perspective of remote sensing data.
基金National Natural Science Foundation of China(Nos.41941019,42174018).
文摘Interferometry Synthetic Aperture Radar(InSAR)provides unique capabilities to map regional/global topography and deformation of the Earth’s surface and has led to a broad spectrum of deformation monitoring applications.In order to adapt to various challenging monitoring environments,researchers have made tremendous innovations to deal with issues such as atmospheric and ionospheric effects,loss of coherence due to large displacements,geometric distortions and unwrapping errors.Owing to recent technical and methodological advances,the Earth’s surface deformation,ranging from earthquake ruptures,volcanic eruptions,landslides,glaciers,to groundwater storage variations,mining subsidence and infrastructure instability can now be mapped anywhere in the world at high spatial and temporal resolutions.This special issue received a set of contributions highlighting recent advances in methodologies and applications of InSAR to ground deformation monitoring.We aim to present overviews of both the state of the art of SAR/InSAR techniques and the next generation of applications across the broad range of deformation monitoring applications.
基金partly supported by the National Science and Technology Major Project(grant no.16510711600)the National Natural Science Foundation of China(grant no.61631013)partly supported by the National Natural Science Foundation of China(grant no.61401440)
文摘The growth of the wireless and mobile communication data traffic has brought severe challenges to the present telecommunication systems. To meet the ever-increasing mobile traffic demand in the next 5 th generation(5 G) communication systems, deploying 5 G in the unlicensed spectrum(5 G-U), has been regarded as a promising technology. The Third Generation Partnership Project(3 GPP) has specified the standardization of the Licensed Assisted Access(LAA) and its extension enhanced LAA(e LAA), to opportunistically transmit in the unlicensed spectrum. The LAA/e LAA systems share unlicensed spectrum resource with other networks, e.g., the Wi-Fi systems. In this article, we analyze the coexistence between the e LAA and the Wi-Fi systems in the unlicensed spectrum. We firstly establish the system model where the e LAA coexists with the Wi-Fi systems. Then, we theoretically derive and figure out the unfairness in the multi-channel occupancy rate between the e LAA and the Wi-Fi systems. After that, we propose a weight based channel selection method to improve the fairness of the coexistence. The numerical results demonstrate that by avoiding contentions and declining collisions, our method not only enhances the fairness, but also improves the overall unlicensed spectrum usage rate.
基金National Natural Science Foundation of China(No.41941019)Fundamental Research Funds for the Central Universities(Nos.300102260301/087,300102260404/087)。
文摘The tremendous development of Synthetic Aperture Radar(SAR)missions in recent years facilitates the study of smaller amplitude ground deformation over greater spatial scales using longer time series.However,this poses greater challenges for correcting atmospheric effects due to the wider coverage of SAR imagery than ever.Previous attempts have used observations from Global Positioning System(GPS)and Numerical Weather Models(NWMs)to separate atmospheric delays,but they are limited by(1)The availability(and distribution)of GPS stations;(2)The low spatial resolution of NWM;And(3)The difficulties in quantifying their performance.To overcome these limitations,we have developed the Generic Atmospheric Correction Online Service for InSAR(GACOS)which utilizes the high-resolution European Centre for Medium-Range Weather Forecasts(ECMWF)products using an Iterative Tropospheric Decomposition(ITD)model.This enables the reduction of the coupling effects of the troposphere turbulence and stratification and hence achieves equivalent performances over flat and mountainous terrains.GACOS comprises a range of notable features:(1)Global coverage;(2)All-weather,all-time usability;(3)Available with a maximum of two-day latency;And(4)Indicators available to assess the model’s performance and feasibility.In this paper,we demonstrate some successful applications of the GACOS online service to a variety of geophysical studies.
基金National Key Research and Development Program of China(No.2019YFC1509201)Chinese Scholarship Council Studentship(No.201806270247)+3 种基金Shaanxi Province Science and Technology Innovation Team(No.2021TD-51)UK Natural Environment Research Council through the Centre for the Observation and Modeling of Earthquakes,Volcanoes and Tectonics(No.come30001)LICS Project(No.NE/K010794/1)European Space Agency through the ESA-MOST DRAGON-5 Project(No.59339)。
文摘In March 2021,a seismic sequence including three Mw>5.5 events struck northern Thessaly,Greece.Owing to the high temporal resolution of Sentinel-1 images which were sampled every 6 days and recorded the three events separately,we are able to map individually the coseismic deformation fields of the three events.Based on their respective coseismic displacements,we determined the geometry of the fault plane for each earthquake with the method of multipeak particle swarm optimization and inverted the best-fitting slip distribution by linear least squares inversion.Modelling results show that the three events occurred successively on 3,4 and 12 March 2021 were all dominated by normal-slip motions on previously unknown faults within the top 15 km of the Earth’s crust.The 3 March 2021 Mw 6.3 earthquake ruptured a northeast-dipping fault with a strike angle of 301°(clockwise from the North)and a dip angle of 46°,producing the maximum slip of about 2.2 m.The slip motion of the 4 March 2021 Mw 5.9 aftershock shows a similar fault geometry(striking 297°and dipping 42°)to the 3 March mainshock,but with a considerably smaller dip-slip component(~0.8 m).The 12 March 2021 Mw 5.6 aftershock occurred on a southwest-dipping fault(striking 100°and dipping 40°)with a normal fault slip of up to 0.5 m.Static Coulomb stress changes triggered by the earthquake sequence imply a promotion relationship between the first 3 March event and the two subsequent events.Due to the coseismic stress perturbation,more than 70%of aftershocks were distributed in areas with increased Coulomb stress and the northwest segment of the Larissa fault close to the seismic sequence was exposed to a relatively high seismic risk.
基金partly supported by the NSFC International Cooperation and Exchange Program(Grant No.61461136001)partly supported by the Shanghai Rising-Star Program(grant no.17QA1403800)+2 种基金the NSFC International Cooperation and Exchange Program(Grant No.61461136004)partly supported by the ESEC project of Tekes and the National Natural Science Foundation of China(Grant No.61401440)partly supported by the NSFC International Cooperation and Exchange Program(Grant No.61461136003)
文摘Utilizing the unlicensed spectrum as supplementary is being studied to meet the increasingly growing demand of user equipment for rate,traffic and bandwidth,and thus to mitigate the current spectrum scarcity crisis.In this paper,we investigate the uplink multi-user multiple-input multiple-output(UL MU-MIMO) technique to achieve multiplexing gain in unlicensed spectrum.We first define a new parameter called channel busy radio(CBR) which is related to the probability of occupying the unlicensed channel,and find that the failure to occupy the unlicensed channel leads to the performance degradation in unlicensed spectrum.Then,according to the user-specific CBR of the unlicensed channel,we propose a flexible scheduling scheme for UL MU-MIMO in unlicensed spectrum,and formulate an optimization problem for the optimal scheduled user number.Furthermore,an adaptive scheduling algorithm is proposed to decide the optimal number of the scheduled users efficiently.The simulation results show that,based on statistical channel condition in unlicensed spectrum,adjusting the number of the scheduled user flexibly can offset the degraded throughput and form an optimal MU-MIMO transmission.
基金National Science Foundation of China(Nos.42074040,41941019,41790445)National Key R&D Program of China(Nos.2020YFC1512001,2019YFC1509800)Shenzhen Science and Technology Program(No.KQTD20180410161218820)。
文摘Synthetic Aperture Radar Interferometry(InSAR)has shown its potential on seismic deformation monitoring since it can achieve the accuracy of centimeter level or even the millimeter level.However,the irregular varieties of ionosphere can induce the additional phase delay on SAR interferometry,restricting its further application in high-precision deformation monitoring.Although several methods have been proposed to correct the ionospheric phase delay on SAR interferometry,the performances of them haven't been evaluated and compared.In this study,three commonly used methods,including polynomial fitting,azimuth offset and split-spectrum are applied to L'Aquila Earthquake to correct the ionospheric phase delay on two Phased Array type L-band Synthetic Aperture Radar(PALSAR)onboard the Advanced Land Observing Satellite-1(ALOS-1)images.The result indicates that these three methods can effectively correct the ionospheric phase delay error for SAR interferometry,where the standard deviations of the ionosphere-corrected results have decreased by almost a factor of 1.8 times for polynomial fitting method,4.2 times for azimuth offset method and 2.5 times for split-spectrum method,compared to those of the original phase.Furthermore,the result of the sliding distribution inversion of the seismic fault shows the best performance for split-spectrum method.
基金Shaanxi Province Science and Technology Innovation Team(No.2021TD-51)ESA-MOST DRAGON-5 Project(No.59339)。
文摘Due to high interferometric coherence in the Nevada region,Interferometric Synthetic Aperture Radar(InSAR)phase stacking is capable of mapping coseismic signals from the 27 January 1999,M w 4.8 Frenchman Flat earthquake.This is one of the smallest earthquakes yet studied using InSAR with line-of-sight displacements as small as~1.5 cm.Modelling the event as dislocation in an elastic half space suggests that the fault centroid was located at(115.96°W,36.81°N)with a precision of 0.2~0.3 km(1σ)at a depth of 3.4±0.2 km.Despite the dense local seismic network in southern Nevada,differences as large as 2~5 km were observed between our InSAR earthquake location and those estimated from seismic data.The InSAR-derived magnitude appeared to be greater than that from seismic data,which is consistent with other studies,and believed to be due to the relatively long time interval of InSAR data.
基金National Natural Science Foundation of China(Nos.41941019,41801391)UK NERC through the Centre for the Observation and Modelling of EarthquakesVolcanoes and Tectonics(No.come30001)。
文摘In 2017,China’s central government approved the national strategy to build Xiong’an New Area(XNA,100 km southwest to Beijing),which was announced as a"millennium strategy"and a"demo area"for a sustainable,modern,and innovative urban model.Xiong’an will draw in as much as$380 billion investment and is expected to help accelerate the development of the wider Beijing-Tianjin-Hebei(Jingjinji)Area.In this paper,present subsidence in the XNA area is investigated using InSAR observations for the first time.The 24 SAR images acquired by European Space Agency’s Sentinel-1 satellites during the period from June 2017 to July 2018 suggest that in the north of Xiong County,the subsidence rate reaches up to 90 mm/y,which is highly correlated with the exploitation of geothermal drilling.As the construction in the XNA area will significantly accelerate and its high-quality development,the InSAR findings could provide valuable information for future sustainable urban planning and underground infrastructure construction.
基金supported jointly by the GAS project (Ref: NE/H001085/1)a China 863 Project (No.2009AA12Z317)+2 种基金supported by the Natural Environmental Research Council (NERC) through the National Center of Earth Observation (NCEO) of which the Center for the Observation and Modelling of Earthquakesfunded by a general project of National Natural Science Foundation of China (NS- FC) (No. 40902081)a key project of the Ministry of Land & Resources, China (No. 1212010914015)
文摘The 2009 M W 7.8 Fiordland (New Zealand) earthquake is the largest to have occurred in New Zealand since the 1931 M W 7.8 Hawke's Bay earthquake, 1 000 km to the northwest. In this paper two tracks of ALOS PALSAR interferograms (one ascending and one descending) are used to determine fault geometry and slip distribution of this large earthquake. Modeling the event as dislocation in an elastic half-space suggests that the earthquake resulted from slip on a SSW-NNE orientated thrust fault that is associated with the subduction between the Pacific and Australian Plates, with oblique displacement of up to 6.3 m. This finding is consistent with the preliminary studies undertaken by the USGS using seismic data.
基金funded by the National Key Research and Development Program of China(2017YFE0122500).
文摘Rapid socio-economic changes in China,such as land conversion and urbanization,are creating new scopes for the application of precision agriculture(PA).An experiment to assess the economic benefits of two precision agriculture methods was applied for one year–precision seeding and precision seeding with land leveling.Whilst the results for this were positive,of itself it did not provide evidence of longer terms gains.The costs of land leveling are accrued in a single year but the benefits could carry over into subsequent years.Thus,in this case if the PA method provides carry over benefits to future years,the economic assessment would incorrectly assign all the costs to a single year of benefits i.e.the benefit-cost ratio would be underestimated.To gauge whether there was carry over benefits in future years we looked at NDVI and GUI as proxies for future year benefits.For the single year experiment,our results showed that:(1)Winter wheat yield was increased 23.2%through the integration of precision seeding and laser leveling technologies.(2)Both the single technology and the integrated technologies significant reduced the concentration of soil ammonium nitrogen at the depths of 60 cm;(3)The benefit/cost ratio's of the treatments exceeded that of the baseline by approximately 10%which translated to an increase of several hundred US$per hectare.The NDVI analysis showed that the effect of laser land leveling could last to the next two years.When considering the multi-year impact of land leveling,the benefit/cost ratio of PSLL will increase to 23.5%and 22.9%with and without laser land leveling subsidies.Making clear the eco-nomic benefits of using PA technologies will likely promote application of the technologies in the region.
基金supported by the EU Horizon 2020 through project ETEXWELD-H2020-MSCA-RISE-2014 (Grant No.644268)the University of Manchester through the UMRI project-Graphene-Smart Textiles E-Healthcare Network (Grant No.AA14512)the Engineering and Physical Sciences Research Council (EPSRC)of UK (Grant EP/V057782/1).
文摘Multiple strain sensors are required to identify individual forces/stresses on human joints and recognize how they work together in order to determine the motion’s direction and trajectory.However,current sensors cannot detect and differentiate the individual forces/stresses and their contributions to the motion from the sensors’electrical signals.To address this critical issue,we propose a concept of unimodal tension,bend,shear,and twist strain sensors with piezoelectric poly L-lactic acid films.We then construct an integrated unimodal sensor(i-US)using the unimodal sensors and prove that the i-US can detect and differentiate individual strain modes,such as tensioning,bending,shearing,and twisting in complex motion.To demonstrate the potential impact of unimodal sensors,we design a sleeve and a glove with the i-US that can capture wrist motions and finger movements.Therefore,we expect unimodal strain sensors to provide a turning point in developing motion recognition and control systems.
基金This work was supported by Research grant from Institute of Crustal Dynamics,China Earthquake Administration[grant numbers ZDJ2015-15 and ZDJ2013-22]National Natural Science Foundation of China[grant numbers 41104028 and 41204004]and the TerraSAR-X data we used were provided by the DLR in the frame of the General AO project LAN0208.
文摘Yangbajain contains the largest geothermal energy power station in China.Geothermal explorations in Yangbajain first started in 1976,and two plants were subsequently built in 1981 and 1986.A large amount of geothermal fluids have been extracted since then,leading to considerable surface subsidence around the geothermal fields.In this paper,InSAR time series analysis is applied to map the subsidence of the Yangbajain geothermal fields during the period from December 2011 to November 2012 using 16 senses of TerraSAR-X stripmap SAR images.In the case of the TerraSAR-X data,most orbital fringes were removed using precise orbits during the interferometric processing.However,residual orbital ramps remain in some interferograms due to the uncertainties in the TerraSAR-X orbits.To remove the residual orbital ramps,we estimated a best-fit‘twisted plane’for each epoch interferogram using quadratic polynomial models based on a network approach.This method removes most of the long-wavelength signals,including orbit ramps and atmospheric effects.The vertically stratified component(Topography Correlated Atmospheric Delay,TCAD)was also removed using a network approach.If the influence of seasonal frozen ground(SFG)is not taken into consideration,our results show that the subsidence rate around power plant I(the south plant)is approximately 20 mm/yr with a peak of 30 mm/yr.The subsidence rate around power plant II(the north plant)is approximately 10 mm/yr,when accounting for the influence of SFG on the power plant and its surrounding ground surface.Our results show that ground motion is caused by seasonal frozen ground and is strongly related to the temperature change.
基金supported by the STFC Newton Agri-Tech program through three projects: (1) Exemplar Smart Farming in Newcastle, (2) Exploring the Potential for Precision Nutrient Management in China, and (3) PAFiC: Precision Agriculture for Family-farms in China (ref.: ST/N006801/1)
文摘Precision agriculture, and more specifically Site-Specific Crop Management(SSCM), has been implemented in some form across nearly all agricultural production systems over the past 25 years. Adoption has been greatest in developed agricultural countries. In this review article, the current situation of SSCM adoption and application is investigated from the perspective of a developed(UK) and developing(China) agricultural economy. The current state-of-the art is reviewed with an emphasis on developments in position system technology and satellite-based remote sensing. This is augmented with observations on the differences between the use of SSCM technologies and methodologies in the UK and China and discussion of the opportunities for(and limitations to)increasing SSCM adoption in developing agricultural economies. A particular emphasis is given to the role of socio-demographic factors and the application of responsible research and innovation(RRI) in translating agritechnologies into China and other developing agricultural economies. Several key research and development areas are identified that need to be addressed to facilitate the delivery of SSCM as a holistic service into areas with low precision agriculture(PA) adoption. This has implications for developed as well as developing agricultural economies.
基金conducted as part of the PAFIC-Precision Agriculture for Family-farms in China Project,funded by the UKChina Research and Innovation Partnership Fund(Newton Programme,STFC Ref.:ST/N006801/1NSFC Ref.:61661136003)
文摘Precision agriculture(PA) technologies have great potential for promoting sustainable intensification of food production, ensuring targeted delivery of agricultural inputs, and hence food security and environmental protection. The benefits of PA technologies are applicable across a broad range of agronomic, environmental and rural socio-economic contexts globally. However, farmer and land-manager adoption in low to middle income countries has typically been slower than that observed in more affluent countries. China is currently engaged in the process of agricultural modernisation to ensure food security for its 1.4 billion population and has developed a portfolio of policies designed to improve food security,while simultaneously promoting environmental protection.Particular attention has been paid to the reduction of agricultural inputs such as fertilisers and pesticides. The widespread adoption of PA technologies across the Chinese agricultural landscape is central to the success of these policies. However, socio-economic and cultural barriers, farm scale,(in particular the prevalence of smaller family farms) and demographic changes in the rural population,(for example, the movement of younger people to the cities) represent barriers to PA adoption across China. A framework for ensuring an acceptable and accelerated PA technology trajectory is proposed which combines systematic understanding of farmer and end-user priorities and preferences for technology design throughout the technology development process, and subsequent end-user requirements for implementation(including demonstration of economic and agronomic benefits, andknowledge transfer). Future research will validate the framework against qualitative and quantitative socioeconomic, cultural and agronomic indicators of successful,or otherwise, PA implementation. The results will provide the evidence upon which to develop further policies regarding how to secure sustainable food production and how best to implement PA in China, as well as practical recommendations for optimising end-user uptake.
