Generating dynamically feasible trajectory for fixed-wing Unmanned Aerial Vehicles(UAVs)in dense obstacle environments remains computationally intractable.This paper proposes a Safe Flight Corridor constrained Sequent...Generating dynamically feasible trajectory for fixed-wing Unmanned Aerial Vehicles(UAVs)in dense obstacle environments remains computationally intractable.This paper proposes a Safe Flight Corridor constrained Sequential Convex Programming(SFC-SCP)to improve the computation efficiency and reliability of trajectory generation.SFC-SCP combines the front-end convex polyhedron SFC construction and back-end SCP-based trajectory optimization.A Sparse A^(*)Search(SAS)driven SFC construction method is designed to efficiently generate polyhedron SFC according to the geometric relation among obstacles and collision-free waypoints.Via transforming the nonconvex obstacle-avoidance constraints to linear inequality constraints,SFC can mitigate infeasibility of trajectory planning and reduce computation complexity.Then,SCP casts the nonlinear trajectory optimization subject to SFC into convex programming subproblems to decrease the problem complexity.In addition,a convex optimizer based on interior point method is customized,where the search direction is calculated via successive elimination to further improve efficiency.Simulation experiments on dense obstacle scenarios show that SFC-SCP can generate dynamically feasible safe trajectory rapidly.Comparative studies with state-of-the-art SCP-based methods demonstrate the efficiency and reliability merits of SFC-SCP.Besides,the customized convex optimizer outperforms off-the-shelf optimizers in terms of computation time.展开更多
Global climate warming has placed immense pressure on the ecological environment worldwide,and the ecological issues affecting the quality of the living environment have garnered widespread attention.In this context,t...Global climate warming has placed immense pressure on the ecological environment worldwide,and the ecological issues affecting the quality of the living environment have garnered widespread attention.In this context,the question of“how to effectively optimize regional ecological network patterns”has become one of the critical issues that urban and rural planning and ecological geography need to address.This study takes Huzhou,Zhejiang Province,China,as the research area,and uses a combination of landscape type transition matrices and landscape pattern indices to analyze the evolution characteristics of green space landscape patterns from 2017 to 2022.Through geographical detectors and GBDT(Gradient Boosting Decision Tree)algorithms,the study explores the driving factors behind the changes in green space landscape patterns.Based on MSPA(Morphological Spatial Pattern Analysis),key ecological sources in Huzhou are extracted.Using a combination of resistance surfaces and gravity models,ecological corridors and networks are constructed.The study also provides suggestions for the evaluation and optimization of ecological network patterns.The aim is to summarize generalizable patterns of green space landscape evolution and methods for constructing and optimizing regional ecological corridor networks,offering insights and references for the improvement of the living environment and the construction of ecological civilization.展开更多
The Inner Asian Mountain Corridor(IAMC)acted as a crossroads of trans-Eurasian exchange since approximately 6000 cal.yr BP.The history of the introduction and utilization of crops and livestock in the area has been in...The Inner Asian Mountain Corridor(IAMC)acted as a crossroads of trans-Eurasian exchange since approximately 6000 cal.yr BP.The history of the introduction and utilization of crops and livestock in the area has been intensively discussed,while geographical-temporal variations of human activities and subsistence strategies remain unclear.Here we report new zooarchaeological data and radiocarbon dates from the Naba Cemeteries,revealing herbivorous livestock were predominant animal resource during both the Bronze and Early Iron Ages,and sheep/goat and horse were paramount sacrificial animals in these two periods,respectively.In tandem with published radiocarbon dates,zooarchaeological and archaeobotanical data from IAMC's prehistoric sites,we detect humans mainly engaged in hunting-gathering games in the IAMC during 8000-5000 cal.yr BP.During 5000-4000 cal.yr BP,the territory of agro-pastoral groups evidently expanded in the IAMC with a hotspot in the Altai Region,and wheat and barley were introduced into the area.In the following two millennia,herding became an economic mainstay,and cultivations of crops were ubiquitous in the IAMC's oases.We argue that prehistoric human activities in the IAMC were mainly affected by agro-pastoral expansions associated with exchanges across the Eurasia,which was likely promoted by climate change.展开更多
Carbon fluxes are essential indicators assessing vegetation carbon cycle functions.However,the extent and mechanisms by which climate change and human activities influence the spatiotemporal dynamics of carbon fluxes ...Carbon fluxes are essential indicators assessing vegetation carbon cycle functions.However,the extent and mechanisms by which climate change and human activities influence the spatiotemporal dynamics of carbon fluxes in arid oasis and non-oasis area remains unclear.Here,we assessed and predicted the future effects of climate change and human activities on carbon fluxes in the Hexi Corridor.The results showed that the annual average gross primary productivity(GPP),net ecosystem productivity(NEP),and ecosystem respiration(Reco)in the Hexi Corridor oasis increased by 263.91 g C·m^(-2)·yr^(-1),118.45 g C·m^(-2)·yr^(-1)and 122.46 g C·m^(-2)·yr^(-1),respectively,due to the expansion of the oasis area by 3424.84 km^(2) caused by human activities from 2000 to 2022.Both oasis and non-oasis arid ecosystems in the Hexi Corridor acted as carbon sinks.Compared to the non-oasis area,the carbon fluxes contributions of oasis area increased,ranging from 10.21%to 13.99%for GPP,8.50%to11.68%for NEP,and 13.34%to 17.13%for Reco.The contribution of the carbon flux from the oasis expansion area to the total carbon flux change in the Hexi Corridor was 30.96%(7.09 Tg C yr^(-1))for GPP,29.57%(3.39 Tg C yr^(-1))for NEP and 32.40%(3.58 Tg C yr^(-1))for Reco.The changes in carbon fluxes in the oasis area were mainly attributed to human activities(oasis expansion)and temperature,whereas non-oasis area was mainly due to climate factors.Moreover,the future increasing trends were observed for GPP(64.99%),NEP(66.29%)and Reco(82.08%)in the Hexi Corridor.This study provides new insights into the regulatory mechanisms of carbon cycle in the arid oasis and non-oasis area.展开更多
Urban traffic congestion is a significant challenge that contributes to high-density environments in urban areas,adversely impacting the living conditions of urban residents.The concept of urban renewal introduces new...Urban traffic congestion is a significant challenge that contributes to high-density environments in urban areas,adversely impacting the living conditions of urban residents.The concept of urban renewal introduces new requirements and challenges pertaining to urban transportation issues.To mitigate urban traffic congestion,enhance the greening rate of the city,and improve the urban environment,the concept of developing urban aerial ecological corridors is proposed.An analysis of the current state of various urban aerial corridors in different cities indicates that aerial ecological corridors effectively enhance connectivity and accessibility between different spaces,representing a significant strategy for addressing the issue of urban traffic congestion.Aerial ecological corridors have the potential to enhance the vertical space within urban environments,increase the greening rate of cities,and promote the physical and mental health of urban residents.Additionally,these corridors can improve the connectivity of habitat patches and address the developmental needs of biodiversity.Consequently,they serve as a crucial foundation for guiding the future transformation of urban development towards a healthier and greener direction.展开更多
Most of the existing non-line-of-sight(NLOS)localization methods depend on the layout information of the scene which is difficult to be obtained in advance in the practical application scenarios.To solve the problem,a...Most of the existing non-line-of-sight(NLOS)localization methods depend on the layout information of the scene which is difficult to be obtained in advance in the practical application scenarios.To solve the problem,an NLOS target localization method in unknown L-shaped corridor based ultra-wideband(UWB)multiple-input multiple-output(MIMO)radar is proposed in this paper.Firstly,the multipath propagation model of Lshaped corridor is established.Then,the localization process is analyzed by the propagation characteristics of diffraction and reflection.Specifically,two different back-projection imaging processes are performed on the radar echo,and the positions of focus regions in the two images are extracted to generate candidate targets.Furthermore,the distances of propagation paths corresponding to each candidate target are calculated,and then the similarity between each candidate target and the target is evaluated by employing two matching factors.The locations of the targets and the width of the corridor are determined based on the matching rules.Finally,two experiments are carried out to demonstrate that the method can effectively obtain the target positions and unknown scene information even when partial paths are lost.展开更多
Using fog meteorological data of five stations of Wuwei in east of Hexi Corridor from 1961 to 2008,geography distribution and climate characteristic of fog were analyzed with statistical method.The results showed that...Using fog meteorological data of five stations of Wuwei in east of Hexi Corridor from 1961 to 2008,geography distribution and climate characteristic of fog were analyzed with statistical method.The results showed that fog had the obvious region characteristic,fog days were more in mountainous area than Sichuan area and were more in south than north.Fog assumed reducing tendency year by year.Fog occurring frequency was the highest from July to October in one year.Fog occurring centralized time was form 20:00 to next day 08:00 in one day.Selecting of ECMWF numerical forecast grid field,factor was initially elected with Press criterion,factor was selected with stepwise regression forecast method.The fog forecasting equation was built with optimal subset regression.The overall situation and the most superior significance equations of fog forecasting were ascertained finally for spring,summer and autumn.Fitting rate three seasonal forecasting equation were 85.5%,82.1% and 81.2% respectively,which would provide objective and effective instruction products for forecasting service.展开更多
The general situation of planning and construction project for Agroecological parks in ecological corridor was introduced and its planning orientation or guiding ideology was also analyzed.Furthermore,countermeasures ...The general situation of planning and construction project for Agroecological parks in ecological corridor was introduced and its planning orientation or guiding ideology was also analyzed.Furthermore,countermeasures and suggestions for planning and construction of Agroecological parks in ecological corridor were proposed.展开更多
[Objective] The aim was to explore the spatial and temporal distribution characteristics of wind energy resource and preservation in central and west area of Hexi Corridor. [Method] By dint of the wind speed data from...[Objective] The aim was to explore the spatial and temporal distribution characteristics of wind energy resource and preservation in central and west area of Hexi Corridor. [Method] By dint of the wind speed data from 1955 to 2007 in ten meteorological observation station in central and west area of Hexi Corridor,and special wind tower fine data from January to December in 2007,the distribution and reserves of the region＇s wind energy resources were studied. [Result] The results showed that environmental wind speed was relatively stable in central and west Hexi Corridor. There were no distinct changes in climate characteristics distribution. There were regional differences in the distribution of wind energy,and there was a large numerical area of wind energy in Gazhou County and Yumen City; Wind energy in the region generally was higher. The wind energy density was above 100 w/m2 in the 10 m layer,around 140 w/m2 in most places,and was more than 200 w/m2 in the large number area. The wind grew in vertical direction along with the linear growth of height. Each 10 m high wind increased to 15 w/m2 averagely,50m layer wind energy was greater than the general 240 w/m2 and there were obvious changes on daily and annual with wind energy in central and west area of Hexi Corridor. The duration from March to May was a wind energy-intensive stage,10m height from the ground in the wind around 10：00 in low-value. After growing from 11：00,it met the day largest number at 18：00,and then reduced gradually. Effective wind speed hours in the region in general were more than 6 200 h,and the value in the large areas was close to 7 600 h. [Conclusion] The study laid basis for the development and application of wind energy in central and west area of Hexi Corridor.展开更多
Cultural heritage of emperor's tomb of Wulingyuan Mausoleum lies in Xianyang which is located at north-central of Guanzhong Plain and which is the central area of Guanzhong-Tianshui economic development zone.With ...Cultural heritage of emperor's tomb of Wulingyuan Mausoleum lies in Xianyang which is located at north-central of Guanzhong Plain and which is the central area of Guanzhong-Tianshui economic development zone.With special geographical position and excellent location condition,it is the important tourism resource and archaeological remains in Shaanxi Province.By using relevant knowledge on tourism,in the perspective of development principle,necessity,feasibility,construction strategy and thought of top-quality tourism corridor with cultural heritage of emperor's tomb of Wulingyuan Mausoleum as theme experience,the author systematically explained the mode elements and value of experiential tourism products,and publicized the tourism resources to a certain extent.On the basis of publicity,the author strived to provide reference for the sustainable development of economy and ecology in this region.展开更多
[Objective] The research aimed to provide the certain theory basis for the accurate forecast and early warning of high and low temperature in the east of Hexi Corridor.[Method] Based on the high(the daily highest temp...[Objective] The research aimed to provide the certain theory basis for the accurate forecast and early warning of high and low temperature in the east of Hexi Corridor.[Method] Based on the high(the daily highest temperature ≥35 ℃) and low(the daily lowest temperature ≤-20 ℃) temperature data in five observatories in the east of Hexi Corridor during 1960-2009,the temporal and spatial distribution,intensity,continuity and circulation situation of high and low temperature were analyzed in detail by using the statistical method.[Result] The high temperature weather in the east of Hexi Corridor mainly happened in the edge of northeast desert,and the low temperature mainly happened in the mountain zone where the altitude was higher and the edge of north desert.As the climate became warm,the high temperature days showed the weak increase trend,and the intensity strengthened.The low temperature days showed the obvious decrease trend,and the intensity weakened.The high temperature weather mainly occurred in June,August,and the low temperature mainly occurred in January,February,December.The high and low temperature weather had the durative characteristic.The strong high and low temperature mainly occurred in the durative time of high and low temperature.The high temperature weather appeared in the zone where was controlled and affected by the subtropical high.The low temperature weather appeared in the zone where the strong cold air accumulated and invaded.[Conclusion] The research had the extremely important significance on servicing for the agriculture,preventing and reducing the natural disasters,promoting the local economic development.展开更多
Soil water content(SWC) is a key factor limiting ecosystem sustainability in arid and semi-arid areas of the Hexi Corridor of China, which is characterized by an ecological environment that is vulnerable to climate ch...Soil water content(SWC) is a key factor limiting ecosystem sustainability in arid and semi-arid areas of the Hexi Corridor of China, which is characterized by an ecological environment that is vulnerable to climate change. However, there is a knowledge gap regarding the large-scale spatial distribution of SWC in this region. The specific objectives of this study were to determine the spatial distribution patterns of SWC across the Hexi Corridor and identify the factors responsible for spatial variation of SWC at a regional scale. This study collected and analyzed SWC in the 0–100 cm soil profile from 109 field sampling sites(farmland, grassland and forestland) across the Hexi Corridor in 2017. We selected 17 factors, including land use, topography(latitude, longitude, elevation, slope gradient, and slope aspect), soil properties(soil clay content, soil silt content, soil bulk density, saturated hydraulic conductivity, field capacity, and soil organic carbon content), climate factors(mean annual precipitation, potential evaporation, and aridity index), plant characteristic(vegetation coverage) and planting pattern(irrigation or rain-fed), as possible environmental variables to analyze their effects on SWC. The results showed that SWC was 0.083(±0.067) g/g in the 0–100 cm soil profile and decreased in the order of farmland, grassland and forestland. The SWC in the upper soil layers(0–20, 20–40 and 40–60 cm) had obvious difference when the mean annual precipitation differed by 200 mm. The SWC decreased from southeast to northwest following the same pattern as precipitation, and had a moderate to strong spatial dependence in a large effective range(75–378 km). The SWC showed a similar distribution and had no significant difference between soil layers in the 0–100 cm soil profile. The principal component analysis showed that the mean annual precipitation, geographical position(longitude and latitude) and soil properties(soil bulk density and soil clay content) were the main factors dominating the variance of environmental variables. A stepwise linear regression equation showed that plant characteristic(vegetation coverage) and soil properties(soil organic carbon content, field capacity and soil clay content) were the optimal factors to predict the variation of SWC. Soil clay content could be better to explain the SWC variation in the deeper soil layers compared with the other factors.展开更多
The apatite fission track（AFT） ages and thermal modeling of the Longshoushan and deformation along the northern Hexi Corridor on the northern side of the Qinghai-Tibetan Plateau show that the Longshoushan along the ...The apatite fission track（AFT） ages and thermal modeling of the Longshoushan and deformation along the northern Hexi Corridor on the northern side of the Qinghai-Tibetan Plateau show that the Longshoushan along the northern corridor had experienced important multi-stage exhumations during the Late Mesozoic and Cenozoic. The AFT ages of 7 samples range from 31.9 Ma to 111.8 Ma.Thermal modeling of the AFT ages of the samples shows that the Longshoushan experienced significant exhumation during the Late Cretaceous to the Early Cenozoic（-130-25 Ma）. The Late Cretaceous exhumation of the Longshoushan may have resulted from the continuous compression between the Lhasa and Qiangtang blocks and the flat slab subduction of the Neo-Tethys oceanic plate, which affected wide regions across the Qinghai-Tibetan Plateau. During the Early Cenozoic, the Longshoushan still experienced exhumation, but this process was caused by the Indian-Eurasian collision. Since this time,the Longshoushan was in a stable stage for approximately 20 Ma and experienced erosion. Since -5 Ma,obvious tectonic deformation occurred along the entire northern Hexi Corridor, which has also been reported from the peripheral regions of the Qinghai-Tibetan Plateau, especially in the Qilianshan and northeastern margin of the plateau. The AFT ages and the Late Cenozoic deformation of the northern Hexi Corridor all indicate that the present northern boundary of the Qinghai-Tibetan Plateau is situated along the northern Hexi Corridor.展开更多
The composition and stability of soil aggregate are closely related to soil quality, soil erosion, and agricultural sustainability. In this study, 49 soil samples at the 0-10 cm surface layer were collected from four ...The composition and stability of soil aggregate are closely related to soil quality, soil erosion, and agricultural sustainability. In this study, 49 soil samples at the 0-10 cm surface layer were collected from four soil types （i.e., Ari-Sandic Primosols, Calci-Orthic Aridosols, Siltigi-Otrthic Anthrosols, and Ustic Cambosols） in the marginal farmland in the oasis of the middle Hexi Corridor region and was used to determine the characteristics of soil aggregates. The composition of dry- and wet- sieved aggregates and the physical and chemical properties （including soil particle distribution, soil organic carbon （SOC）, calcium carbonate （CaCO3）, and oxides of Fe^3＋ and Al^3＋） of the selected soils were analyzed. The results show that soil particle size distribution is dominated by fine sand fraction in most of soils except Ustic Cambosols. Soil organic carbon concentration is 5.88 ± 2.52 g kg^-1 on average, ranging from 4.75 g kg^-1 in Ari-Sandic Primosols to 10.51 g kg^-1 in Ustic Cambosols. The soils have high calcium carbonate （CaCO3） concentration, ranging from 84.7 to 164.8 g kg^-1, which is increased with soil fine particle and organic carbon content. The percentage of 〉0.25 mm dry aggregates ranges from 65.2% in Ari-Sandic Primosols to 94.6% in Ustic Cambosols, and large dry blocky aggregates （〉5 mm） is dominant in all soils. The mean weight diameter of dry aggregates （DMWD） ranges from 3.2 mm to 5.5 mm. The percentage of 〉0.25 mm water-stable aggregate is from 23.8% to 45.4%. The percentage of aggregate destruction （PAD） is from 52.4% to 66.8%, which shows a weak aggregate stability. Ari-Sandic Primosols has the highest PAD. The distribution and characteristics of soil aggregates are in favor of controlling soil wind erosion. However, the stability of aggregate of all soils is weak and soils are prone to disperse and harden after irrigation. The mass of macro-aggregates and DMWD are positively significantly correlated with the contents of soil clay and silt, soil organic carbon （SOC）, CaCO3, and oxides of Fe^3＋ and Al^3＋. Soil fine silt and clay, SOC and CaCO3 are important agents of aggregation in this region, and the effect of SOC and CaCO3 on aggregate stability is more significant than that of soil silt and clay. Converting cropland to alfalfa forage land can increase SOC concentration, and in turn, enhance the formation of aggregates and stability. For the marginal farmlands in this fragile ecological area, converting cropland to alfalfa grassland or performing crop-grass rotation is an effective and basic strategy to improve soil structure and quality, to mitigate soil wind erosion, and to enhance oasis agricultural sustainability.展开更多
This paper, taking Hexi Corridor as an example, analyzes the altemating intimidation and the dynamic evolving relation between urbanization and eco-environment in arid area of West China. We argue that the harmonious ...This paper, taking Hexi Corridor as an example, analyzes the altemating intimidation and the dynamic evolving relation between urbanization and eco-environment in arid area of West China. We argue that the harmonious development system of the urbanization and eco-environment would go through four phases： rudimentary symbiotic phase, harmonious developmental phase, utmost increasing phase and spiral type rising phase. Throughout the four phases, the elements of the system would influence each other, coerce each other, and complete the spiral type rising process from low-grade symbiosis to high-grade harmony together. The study on Hexi Corridor shows that the urbanization level in Hexi Corridor has increased gradually from 1985 to 2003 accompanied with the fluctuations of eco-environment state. The response of eco-environment to urbanization has been evident, but lagged behind the urbanization course. At present, the harmonious development system in Hexi Corridor was in its harmonious developmental phase. However, the coupling degree has increased quickly and approached 90 yet, which is signaling that the system is about to enter the utmost increasing phase, and the ecological crisis will enter the latent period. We have found that the coupling degree can well reflect the interactive coercing and dynamic evolving situation between urbanization and eco-environment in Hexi Corridor. From the temporal change of the coupling degree, it can be concluded that urbanization sometimes needs to pay a certain cost for the damage of the eco-environment in its initial stages, but as the urbanization continues, the state of the eco-environment would be meliorated.展开更多
This study is focused on the northwestern part of Gansu Province, namely the Hexi Corridor. The aim is to address the question of whether any trend in the annual and monthly series of temperature and precipitation dur...This study is focused on the northwestern part of Gansu Province, namely the Hexi Corridor. The aim is to address the question of whether any trend in the annual and monthly series of temperature and precipitation during the period 1955-2011 appears at the scale of this region. The temperature and precipitation variation and abrupt change were examined by means of linear regression, five-year moving average, non-parameter Mann-Kendall test, accumulated variance analysis and Pettitt test method. Conclusions provide evidence of warming and wetting across the Hexi Corridor. The mean annual temperature in Hexi Corridor increased significantly in recent 57 years, and the increasing rate was 0.27℃/10a. The abrupt change phenomenon of the annual temperature was detected mainly in 1986. The seasonal average temperature in this region exhibited an evident upward trend and the uptrend rate for the standard value of winter temperature indicated the largerst of four seasons. The annual precipitation in the Hexi Corridor area displayed an obviously increasing trend and the uptrend rate was 3.95 mm/10a. However, the annual precipitation in each basin of the Hexi Corridor area did not passed the significance test. The rainy season precipitation fluctuating as same as the annual one presented insignificant uptrend. No consistent abrupt change was detected in precipitation in this study area, but the rainy season precipitation abrupt change was mainly observed in 1968.展开更多
The eastern Hexi Corridor Belt（HCB） is located in the transitional belt among the Alxa Block,the Qilian Orogenic Belt and the North China Block. Because of its unique tectonic location, the tectonic setting, provena...The eastern Hexi Corridor Belt（HCB） is located in the transitional belt among the Alxa Block,the Qilian Orogenic Belt and the North China Block. Because of its unique tectonic location, the tectonic setting, provenance, and even the age of the sedimentary strata in the eastern HCB during the Early Paleozoic remain controversial. This study analyzes the provenance of the poorly studied Xiangshan Group, discusses its age of development and tectonic setting in the eastern HCB using a combination of petrological, geochemical and LA-ICP-MS U-Pb zircon dating methods. Based on the youngest age peaks and the fossil evidence, we suggest that the Xiangshan Group is Middle Cambrian to Late Ordovician in age. The complexity of the geochemical characteristics and associated diagrams suggests that the early stage of the Xiangshan Group developed in a passive continental margin environment, late in the backarc basin of the eastern HCB. Based on the sandstone detrital composition, whole-rock geochemistry and detrital zircon ages, we conclude that the Xiangshan Group had an early provenance that was mainly from the Qilian Block and a late provenance from the Qilian Block and the western Alxa Block. The eastern HCB and its northern and southern blocks have similar palaeontology, lithology and basement age characteristics to the South China Block. This indicates that the eastern HCB might not have formed in the intra-continental aulacogen of the North China Block during the Early Paleozoic but has a close affinity to eastern Gondwana.展开更多
Because of the existence of gradient field of the urban center and the corridor effect. underthe drive of going merely after economic benefit, the city intrinsically has the trend of massive growth, and this will se...Because of the existence of gradient field of the urban center and the corridor effect. underthe drive of going merely after economic benefit, the city intrinsically has the trend of massive growth, and this will seriously destroy the urban reasonable landscape structure and the ecological equilibrium.By applying the theory of corridor effect. this paper studies the interactive process between artificialcorridors and natural corridors. At the same time, by studying the Beijing's spatial extension pattern in central urban area during different periods. this paper analyses the corridors extension volume.extension velocity and variant tendency of urban landscape on & directions. Moreover. this paperbrings forward the idea of incorporating the systen of natural corridors into the Beijing'smetropolitan planning, namely to form a star-shaped scattering-group pattern in which artificialcorridors and natural corridors are alternately distributed in order to effectively prevent built-up areafrom massive growth .展开更多
The Hexi Corridor is an important base of agriculture development inNorthwest China. According to recent statistics, there are 65. 94 x 10~8m^3 of water resourcesavailable in the Hexi Corridor. At present, net consump...The Hexi Corridor is an important base of agriculture development inNorthwest China. According to recent statistics, there are 65. 94 x 10~8m^3 of water resourcesavailable in the Hexi Corridor. At present, net consumption in development and utilization is 43. 33x 10~8m^3. Water supply and demand reach a balance on the recent level of production, but loss ofevaporation and evapotranspiration is as much as 25. 69 x 1010~8m^3. So net use efficiency of waterresources is 59% Based on analyzing balance between water and land considering ecologicalenvironment at present, there exists the serious water shortage in the Shiyang River system whereirrigation lands have overloaded. There is a comparative balance between supply and demand of waterresource in the Heihe River system; and the Sule River system has some surplus water to extendirrigation land. Use of agriculture water accounts for 83. 3% and ecological forest and grass for 6.9% . The Hexi Corridor still has a great potential for water saving in agriculture production.Water-saving efficiency of irrigation is about 10% by using such traditional technologies as furrowand border-dike irrigation and small check irrigation, and water-saving with plastic film cover andtechniques of advanced sprinkler and drip/micro irrigation etc. can save more than 60% of irrigatedwater. Incremental irrigation area for water-saving potential in the Hexi Corridor has beenestimated as 56% - 197% to original irrigation area. So the second water sources can be developedfrom water saving agriculture in the Hexi Corridor under Development of the Western Part of China inlarge scale. This potential can be realized step by step through developing the water-savingmeasures, improving the ecological condition of oasis agriculture, and optimizing allocation ofwater resources in three river systems.展开更多
基金supported by the National Natural Science Foundation of China(No.62203256)。
文摘Generating dynamically feasible trajectory for fixed-wing Unmanned Aerial Vehicles(UAVs)in dense obstacle environments remains computationally intractable.This paper proposes a Safe Flight Corridor constrained Sequential Convex Programming(SFC-SCP)to improve the computation efficiency and reliability of trajectory generation.SFC-SCP combines the front-end convex polyhedron SFC construction and back-end SCP-based trajectory optimization.A Sparse A^(*)Search(SAS)driven SFC construction method is designed to efficiently generate polyhedron SFC according to the geometric relation among obstacles and collision-free waypoints.Via transforming the nonconvex obstacle-avoidance constraints to linear inequality constraints,SFC can mitigate infeasibility of trajectory planning and reduce computation complexity.Then,SCP casts the nonlinear trajectory optimization subject to SFC into convex programming subproblems to decrease the problem complexity.In addition,a convex optimizer based on interior point method is customized,where the search direction is calculated via successive elimination to further improve efficiency.Simulation experiments on dense obstacle scenarios show that SFC-SCP can generate dynamically feasible safe trajectory rapidly.Comparative studies with state-of-the-art SCP-based methods demonstrate the efficiency and reliability merits of SFC-SCP.Besides,the customized convex optimizer outperforms off-the-shelf optimizers in terms of computation time.
基金Major Program of National Fund of Philosophy and Social Science of China(24&ZD148).
文摘Global climate warming has placed immense pressure on the ecological environment worldwide,and the ecological issues affecting the quality of the living environment have garnered widespread attention.In this context,the question of“how to effectively optimize regional ecological network patterns”has become one of the critical issues that urban and rural planning and ecological geography need to address.This study takes Huzhou,Zhejiang Province,China,as the research area,and uses a combination of landscape type transition matrices and landscape pattern indices to analyze the evolution characteristics of green space landscape patterns from 2017 to 2022.Through geographical detectors and GBDT(Gradient Boosting Decision Tree)algorithms,the study explores the driving factors behind the changes in green space landscape patterns.Based on MSPA(Morphological Spatial Pattern Analysis),key ecological sources in Huzhou are extracted.Using a combination of resistance surfaces and gravity models,ecological corridors and networks are constructed.The study also provides suggestions for the evaluation and optimization of ecological network patterns.The aim is to summarize generalizable patterns of green space landscape evolution and methods for constructing and optimizing regional ecological corridor networks,offering insights and references for the improvement of the living environment and the construction of ecological civilization.
基金The NSFC-INSF Joint Research Project,No.42261144670The Second Tibetan Plateau Scientific Expedition and Research Program,No.2019QZKK0601。
文摘The Inner Asian Mountain Corridor(IAMC)acted as a crossroads of trans-Eurasian exchange since approximately 6000 cal.yr BP.The history of the introduction and utilization of crops and livestock in the area has been intensively discussed,while geographical-temporal variations of human activities and subsistence strategies remain unclear.Here we report new zooarchaeological data and radiocarbon dates from the Naba Cemeteries,revealing herbivorous livestock were predominant animal resource during both the Bronze and Early Iron Ages,and sheep/goat and horse were paramount sacrificial animals in these two periods,respectively.In tandem with published radiocarbon dates,zooarchaeological and archaeobotanical data from IAMC's prehistoric sites,we detect humans mainly engaged in hunting-gathering games in the IAMC during 8000-5000 cal.yr BP.During 5000-4000 cal.yr BP,the territory of agro-pastoral groups evidently expanded in the IAMC with a hotspot in the Altai Region,and wheat and barley were introduced into the area.In the following two millennia,herding became an economic mainstay,and cultivations of crops were ubiquitous in the IAMC's oases.We argue that prehistoric human activities in the IAMC were mainly affected by agro-pastoral expansions associated with exchanges across the Eurasia,which was likely promoted by climate change.
基金The Foundation for Distinguished Young Scholars of Gansu Province,No.22JR5RA046Key Research Program of Gansu Province,No.23ZDKA0004+2 种基金The Joint Funds of the National Natural Science Foundation of China,No.U22A202690Interdisciplinary Youth Team Project from the Key Laboratory of Cryospheric Science and Frozen Soil Engineering,No.CSFSE-ZQ-2408The Youth Innovation Promotion Association CAS to X.W.,No.2020422。
文摘Carbon fluxes are essential indicators assessing vegetation carbon cycle functions.However,the extent and mechanisms by which climate change and human activities influence the spatiotemporal dynamics of carbon fluxes in arid oasis and non-oasis area remains unclear.Here,we assessed and predicted the future effects of climate change and human activities on carbon fluxes in the Hexi Corridor.The results showed that the annual average gross primary productivity(GPP),net ecosystem productivity(NEP),and ecosystem respiration(Reco)in the Hexi Corridor oasis increased by 263.91 g C·m^(-2)·yr^(-1),118.45 g C·m^(-2)·yr^(-1)and 122.46 g C·m^(-2)·yr^(-1),respectively,due to the expansion of the oasis area by 3424.84 km^(2) caused by human activities from 2000 to 2022.Both oasis and non-oasis arid ecosystems in the Hexi Corridor acted as carbon sinks.Compared to the non-oasis area,the carbon fluxes contributions of oasis area increased,ranging from 10.21%to 13.99%for GPP,8.50%to11.68%for NEP,and 13.34%to 17.13%for Reco.The contribution of the carbon flux from the oasis expansion area to the total carbon flux change in the Hexi Corridor was 30.96%(7.09 Tg C yr^(-1))for GPP,29.57%(3.39 Tg C yr^(-1))for NEP and 32.40%(3.58 Tg C yr^(-1))for Reco.The changes in carbon fluxes in the oasis area were mainly attributed to human activities(oasis expansion)and temperature,whereas non-oasis area was mainly due to climate factors.Moreover,the future increasing trends were observed for GPP(64.99%),NEP(66.29%)and Reco(82.08%)in the Hexi Corridor.This study provides new insights into the regulatory mechanisms of carbon cycle in the arid oasis and non-oasis area.
基金Sponsored by Research Team Project of Anhui Xinhua University(kytd202202)Anhui Provincial Undergraduate Innovation Training Program(S202212216146,S202212216133,S202212216138,AH202112216114)Key Project of Anhui Provincial Higher Education Scientific Research Project(Natural Science)(2022AH051861,2024AH050601).
文摘Urban traffic congestion is a significant challenge that contributes to high-density environments in urban areas,adversely impacting the living conditions of urban residents.The concept of urban renewal introduces new requirements and challenges pertaining to urban transportation issues.To mitigate urban traffic congestion,enhance the greening rate of the city,and improve the urban environment,the concept of developing urban aerial ecological corridors is proposed.An analysis of the current state of various urban aerial corridors in different cities indicates that aerial ecological corridors effectively enhance connectivity and accessibility between different spaces,representing a significant strategy for addressing the issue of urban traffic congestion.Aerial ecological corridors have the potential to enhance the vertical space within urban environments,increase the greening rate of cities,and promote the physical and mental health of urban residents.Additionally,these corridors can improve the connectivity of habitat patches and address the developmental needs of biodiversity.Consequently,they serve as a crucial foundation for guiding the future transformation of urban development towards a healthier and greener direction.
基金supported by National Natural Science Foundation of China(U20B2070,62001091)Sichuan Science and Technology Program(2022YFS0531).
文摘Most of the existing non-line-of-sight(NLOS)localization methods depend on the layout information of the scene which is difficult to be obtained in advance in the practical application scenarios.To solve the problem,an NLOS target localization method in unknown L-shaped corridor based ultra-wideband(UWB)multiple-input multiple-output(MIMO)radar is proposed in this paper.Firstly,the multipath propagation model of Lshaped corridor is established.Then,the localization process is analyzed by the propagation characteristics of diffraction and reflection.Specifically,two different back-projection imaging processes are performed on the radar echo,and the positions of focus regions in the two images are extracted to generate candidate targets.Furthermore,the distances of propagation paths corresponding to each candidate target are calculated,and then the similarity between each candidate target and the target is evaluated by employing two matching factors.The locations of the targets and the width of the corridor are determined based on the matching rules.Finally,two experiments are carried out to demonstrate that the method can effectively obtain the target positions and unknown scene information even when partial paths are lost.
基金Supported by Key Research Project of Gansu Meteorological Bureau in 2007
文摘Using fog meteorological data of five stations of Wuwei in east of Hexi Corridor from 1961 to 2008,geography distribution and climate characteristic of fog were analyzed with statistical method.The results showed that fog had the obvious region characteristic,fog days were more in mountainous area than Sichuan area and were more in south than north.Fog assumed reducing tendency year by year.Fog occurring frequency was the highest from July to October in one year.Fog occurring centralized time was form 20:00 to next day 08:00 in one day.Selecting of ECMWF numerical forecast grid field,factor was initially elected with Press criterion,factor was selected with stepwise regression forecast method.The fog forecasting equation was built with optimal subset regression.The overall situation and the most superior significance equations of fog forecasting were ascertained finally for spring,summer and autumn.Fitting rate three seasonal forecasting equation were 85.5%,82.1% and 81.2% respectively,which would provide objective and effective instruction products for forecasting service.
文摘The general situation of planning and construction project for Agroecological parks in ecological corridor was introduced and its planning orientation or guiding ideology was also analyzed.Furthermore,countermeasures and suggestions for planning and construction of Agroecological parks in ecological corridor were proposed.
基金Supported by National Natural Science Fund (41075008)Chinese Meteorological Climate Changes Program (280200S011000)Gansu Meteorological Bureau Climate Science and Research Program(2011-09)~~
文摘[Objective] The aim was to explore the spatial and temporal distribution characteristics of wind energy resource and preservation in central and west area of Hexi Corridor. [Method] By dint of the wind speed data from 1955 to 2007 in ten meteorological observation station in central and west area of Hexi Corridor,and special wind tower fine data from January to December in 2007,the distribution and reserves of the region＇s wind energy resources were studied. [Result] The results showed that environmental wind speed was relatively stable in central and west Hexi Corridor. There were no distinct changes in climate characteristics distribution. There were regional differences in the distribution of wind energy,and there was a large numerical area of wind energy in Gazhou County and Yumen City; Wind energy in the region generally was higher. The wind energy density was above 100 w/m2 in the 10 m layer,around 140 w/m2 in most places,and was more than 200 w/m2 in the large number area. The wind grew in vertical direction along with the linear growth of height. Each 10 m high wind increased to 15 w/m2 averagely,50m layer wind energy was greater than the general 240 w/m2 and there were obvious changes on daily and annual with wind energy in central and west area of Hexi Corridor. The duration from March to May was a wind energy-intensive stage,10m height from the ground in the wind around 10：00 in low-value. After growing from 11：00,it met the day largest number at 18：00,and then reduced gradually. Effective wind speed hours in the region in general were more than 6 200 h,and the value in the large areas was close to 7 600 h. [Conclusion] The study laid basis for the development and application of wind energy in central and west area of Hexi Corridor.
基金Supported by Financial Project of Shaanxi Province Key Disciplines:Key Supported Discipline of History and Geography (Landscape Lay-out and Cultural Tourism Development of Wulingyuan Mausoleum)the Financial Project of Shaanxi (College) Philosophy and Social Key Research Base Science -Guanzhong Ancient Mausoleum Culture Research Center~~
文摘Cultural heritage of emperor's tomb of Wulingyuan Mausoleum lies in Xianyang which is located at north-central of Guanzhong Plain and which is the central area of Guanzhong-Tianshui economic development zone.With special geographical position and excellent location condition,it is the important tourism resource and archaeological remains in Shaanxi Province.By using relevant knowledge on tourism,in the perspective of development principle,necessity,feasibility,construction strategy and thought of top-quality tourism corridor with cultural heritage of emperor's tomb of Wulingyuan Mausoleum as theme experience,the author systematically explained the mode elements and value of experiential tourism products,and publicized the tourism resources to a certain extent.On the basis of publicity,the author strived to provide reference for the sustainable development of economy and ecology in this region.
基金Supported by Gansu Province the Fifth Installment "Ten Plan"~~
文摘[Objective] The research aimed to provide the certain theory basis for the accurate forecast and early warning of high and low temperature in the east of Hexi Corridor.[Method] Based on the high(the daily highest temperature ≥35 ℃) and low(the daily lowest temperature ≤-20 ℃) temperature data in five observatories in the east of Hexi Corridor during 1960-2009,the temporal and spatial distribution,intensity,continuity and circulation situation of high and low temperature were analyzed in detail by using the statistical method.[Result] The high temperature weather in the east of Hexi Corridor mainly happened in the edge of northeast desert,and the low temperature mainly happened in the mountain zone where the altitude was higher and the edge of north desert.As the climate became warm,the high temperature days showed the weak increase trend,and the intensity strengthened.The low temperature days showed the obvious decrease trend,and the intensity weakened.The high temperature weather mainly occurred in June,August,and the low temperature mainly occurred in January,February,December.The high and low temperature weather had the durative characteristic.The strong high and low temperature mainly occurred in the durative time of high and low temperature.The high temperature weather appeared in the zone where was controlled and affected by the subtropical high.The low temperature weather appeared in the zone where the strong cold air accumulated and invaded.[Conclusion] The research had the extremely important significance on servicing for the agriculture,preventing and reducing the natural disasters,promoting the local economic development.
基金sponsored by the National Natural Science Foundation of China (41530854, 41571130081)
文摘Soil water content(SWC) is a key factor limiting ecosystem sustainability in arid and semi-arid areas of the Hexi Corridor of China, which is characterized by an ecological environment that is vulnerable to climate change. However, there is a knowledge gap regarding the large-scale spatial distribution of SWC in this region. The specific objectives of this study were to determine the spatial distribution patterns of SWC across the Hexi Corridor and identify the factors responsible for spatial variation of SWC at a regional scale. This study collected and analyzed SWC in the 0–100 cm soil profile from 109 field sampling sites(farmland, grassland and forestland) across the Hexi Corridor in 2017. We selected 17 factors, including land use, topography(latitude, longitude, elevation, slope gradient, and slope aspect), soil properties(soil clay content, soil silt content, soil bulk density, saturated hydraulic conductivity, field capacity, and soil organic carbon content), climate factors(mean annual precipitation, potential evaporation, and aridity index), plant characteristic(vegetation coverage) and planting pattern(irrigation or rain-fed), as possible environmental variables to analyze their effects on SWC. The results showed that SWC was 0.083(±0.067) g/g in the 0–100 cm soil profile and decreased in the order of farmland, grassland and forestland. The SWC in the upper soil layers(0–20, 20–40 and 40–60 cm) had obvious difference when the mean annual precipitation differed by 200 mm. The SWC decreased from southeast to northwest following the same pattern as precipitation, and had a moderate to strong spatial dependence in a large effective range(75–378 km). The SWC showed a similar distribution and had no significant difference between soil layers in the 0–100 cm soil profile. The principal component analysis showed that the mean annual precipitation, geographical position(longitude and latitude) and soil properties(soil bulk density and soil clay content) were the main factors dominating the variance of environmental variables. A stepwise linear regression equation showed that plant characteristic(vegetation coverage) and soil properties(soil organic carbon content, field capacity and soil clay content) were the optimal factors to predict the variation of SWC. Soil clay content could be better to explain the SWC variation in the deeper soil layers compared with the other factors.
基金funded by the National Natural Science Foundation of China(No.41572190)the National Program on Key Basic Research Project from the Ministry of Science and Technology of China(No.2015CB453002)the China Geological Survey(Nos.12120115070101,1212010611806,1212010611817)
文摘The apatite fission track（AFT） ages and thermal modeling of the Longshoushan and deformation along the northern Hexi Corridor on the northern side of the Qinghai-Tibetan Plateau show that the Longshoushan along the northern corridor had experienced important multi-stage exhumations during the Late Mesozoic and Cenozoic. The AFT ages of 7 samples range from 31.9 Ma to 111.8 Ma.Thermal modeling of the AFT ages of the samples shows that the Longshoushan experienced significant exhumation during the Late Cretaceous to the Early Cenozoic（-130-25 Ma）. The Late Cretaceous exhumation of the Longshoushan may have resulted from the continuous compression between the Lhasa and Qiangtang blocks and the flat slab subduction of the Neo-Tethys oceanic plate, which affected wide regions across the Qinghai-Tibetan Plateau. During the Early Cenozoic, the Longshoushan still experienced exhumation, but this process was caused by the Indian-Eurasian collision. Since this time,the Longshoushan was in a stable stage for approximately 20 Ma and experienced erosion. Since -5 Ma,obvious tectonic deformation occurred along the entire northern Hexi Corridor, which has also been reported from the peripheral regions of the Qinghai-Tibetan Plateau, especially in the Qilianshan and northeastern margin of the plateau. The AFT ages and the Late Cenozoic deformation of the northern Hexi Corridor all indicate that the present northern boundary of the Qinghai-Tibetan Plateau is situated along the northern Hexi Corridor.
文摘The composition and stability of soil aggregate are closely related to soil quality, soil erosion, and agricultural sustainability. In this study, 49 soil samples at the 0-10 cm surface layer were collected from four soil types （i.e., Ari-Sandic Primosols, Calci-Orthic Aridosols, Siltigi-Otrthic Anthrosols, and Ustic Cambosols） in the marginal farmland in the oasis of the middle Hexi Corridor region and was used to determine the characteristics of soil aggregates. The composition of dry- and wet- sieved aggregates and the physical and chemical properties （including soil particle distribution, soil organic carbon （SOC）, calcium carbonate （CaCO3）, and oxides of Fe^3＋ and Al^3＋） of the selected soils were analyzed. The results show that soil particle size distribution is dominated by fine sand fraction in most of soils except Ustic Cambosols. Soil organic carbon concentration is 5.88 ± 2.52 g kg^-1 on average, ranging from 4.75 g kg^-1 in Ari-Sandic Primosols to 10.51 g kg^-1 in Ustic Cambosols. The soils have high calcium carbonate （CaCO3） concentration, ranging from 84.7 to 164.8 g kg^-1, which is increased with soil fine particle and organic carbon content. The percentage of 〉0.25 mm dry aggregates ranges from 65.2% in Ari-Sandic Primosols to 94.6% in Ustic Cambosols, and large dry blocky aggregates （〉5 mm） is dominant in all soils. The mean weight diameter of dry aggregates （DMWD） ranges from 3.2 mm to 5.5 mm. The percentage of 〉0.25 mm water-stable aggregate is from 23.8% to 45.4%. The percentage of aggregate destruction （PAD） is from 52.4% to 66.8%, which shows a weak aggregate stability. Ari-Sandic Primosols has the highest PAD. The distribution and characteristics of soil aggregates are in favor of controlling soil wind erosion. However, the stability of aggregate of all soils is weak and soils are prone to disperse and harden after irrigation. The mass of macro-aggregates and DMWD are positively significantly correlated with the contents of soil clay and silt, soil organic carbon （SOC）, CaCO3, and oxides of Fe^3＋ and Al^3＋. Soil fine silt and clay, SOC and CaCO3 are important agents of aggregation in this region, and the effect of SOC and CaCO3 on aggregate stability is more significant than that of soil silt and clay. Converting cropland to alfalfa forage land can increase SOC concentration, and in turn, enhance the formation of aggregates and stability. For the marginal farmlands in this fragile ecological area, converting cropland to alfalfa grassland or performing crop-grass rotation is an effective and basic strategy to improve soil structure and quality, to mitigate soil wind erosion, and to enhance oasis agricultural sustainability.
基金NationalNaturalScience Emphases Foundation ofChina,No.40335049NationalNaturalScience Foundation ofChina,No.40471059
文摘This paper, taking Hexi Corridor as an example, analyzes the altemating intimidation and the dynamic evolving relation between urbanization and eco-environment in arid area of West China. We argue that the harmonious development system of the urbanization and eco-environment would go through four phases： rudimentary symbiotic phase, harmonious developmental phase, utmost increasing phase and spiral type rising phase. Throughout the four phases, the elements of the system would influence each other, coerce each other, and complete the spiral type rising process from low-grade symbiosis to high-grade harmony together. The study on Hexi Corridor shows that the urbanization level in Hexi Corridor has increased gradually from 1985 to 2003 accompanied with the fluctuations of eco-environment state. The response of eco-environment to urbanization has been evident, but lagged behind the urbanization course. At present, the harmonious development system in Hexi Corridor was in its harmonious developmental phase. However, the coupling degree has increased quickly and approached 90 yet, which is signaling that the system is about to enter the utmost increasing phase, and the ecological crisis will enter the latent period. We have found that the coupling degree can well reflect the interactive coercing and dynamic evolving situation between urbanization and eco-environment in Hexi Corridor. From the temporal change of the coupling degree, it can be concluded that urbanization sometimes needs to pay a certain cost for the damage of the eco-environment in its initial stages, but as the urbanization continues, the state of the eco-environment would be meliorated.
基金National Key Technology R&D Programme of China,No.2012CB955304
文摘This study is focused on the northwestern part of Gansu Province, namely the Hexi Corridor. The aim is to address the question of whether any trend in the annual and monthly series of temperature and precipitation during the period 1955-2011 appears at the scale of this region. The temperature and precipitation variation and abrupt change were examined by means of linear regression, five-year moving average, non-parameter Mann-Kendall test, accumulated variance analysis and Pettitt test method. Conclusions provide evidence of warming and wetting across the Hexi Corridor. The mean annual temperature in Hexi Corridor increased significantly in recent 57 years, and the increasing rate was 0.27℃/10a. The abrupt change phenomenon of the annual temperature was detected mainly in 1986. The seasonal average temperature in this region exhibited an evident upward trend and the uptrend rate for the standard value of winter temperature indicated the largerst of four seasons. The annual precipitation in the Hexi Corridor area displayed an obviously increasing trend and the uptrend rate was 3.95 mm/10a. However, the annual precipitation in each basin of the Hexi Corridor area did not passed the significance test. The rainy season precipitation fluctuating as same as the annual one presented insignificant uptrend. No consistent abrupt change was detected in precipitation in this study area, but the rainy season precipitation abrupt change was mainly observed in 1968.
基金financially supported by the Natural Science Foundation of China(Grant No.41330315,91214301)the Program of China Geological Survey(Grant No.12120113039900)MOST Special Funds from the State Key Laboratory of Continental Dynamics,Northwest University
文摘The eastern Hexi Corridor Belt（HCB） is located in the transitional belt among the Alxa Block,the Qilian Orogenic Belt and the North China Block. Because of its unique tectonic location, the tectonic setting, provenance, and even the age of the sedimentary strata in the eastern HCB during the Early Paleozoic remain controversial. This study analyzes the provenance of the poorly studied Xiangshan Group, discusses its age of development and tectonic setting in the eastern HCB using a combination of petrological, geochemical and LA-ICP-MS U-Pb zircon dating methods. Based on the youngest age peaks and the fossil evidence, we suggest that the Xiangshan Group is Middle Cambrian to Late Ordovician in age. The complexity of the geochemical characteristics and associated diagrams suggests that the early stage of the Xiangshan Group developed in a passive continental margin environment, late in the backarc basin of the eastern HCB. Based on the sandstone detrital composition, whole-rock geochemistry and detrital zircon ages, we conclude that the Xiangshan Group had an early provenance that was mainly from the Qilian Block and a late provenance from the Qilian Block and the western Alxa Block. The eastern HCB and its northern and southern blocks have similar palaeontology, lithology and basement age characteristics to the South China Block. This indicates that the eastern HCB might not have formed in the intra-continental aulacogen of the North China Block during the Early Paleozoic but has a close affinity to eastern Gondwana.
文摘Because of the existence of gradient field of the urban center and the corridor effect. underthe drive of going merely after economic benefit, the city intrinsically has the trend of massive growth, and this will seriously destroy the urban reasonable landscape structure and the ecological equilibrium.By applying the theory of corridor effect. this paper studies the interactive process between artificialcorridors and natural corridors. At the same time, by studying the Beijing's spatial extension pattern in central urban area during different periods. this paper analyses the corridors extension volume.extension velocity and variant tendency of urban landscape on & directions. Moreover. this paperbrings forward the idea of incorporating the systen of natural corridors into the Beijing'smetropolitan planning, namely to form a star-shaped scattering-group pattern in which artificialcorridors and natural corridors are alternately distributed in order to effectively prevent built-up areafrom massive growth .
文摘The Hexi Corridor is an important base of agriculture development inNorthwest China. According to recent statistics, there are 65. 94 x 10~8m^3 of water resourcesavailable in the Hexi Corridor. At present, net consumption in development and utilization is 43. 33x 10~8m^3. Water supply and demand reach a balance on the recent level of production, but loss ofevaporation and evapotranspiration is as much as 25. 69 x 1010~8m^3. So net use efficiency of waterresources is 59% Based on analyzing balance between water and land considering ecologicalenvironment at present, there exists the serious water shortage in the Shiyang River system whereirrigation lands have overloaded. There is a comparative balance between supply and demand of waterresource in the Heihe River system; and the Sule River system has some surplus water to extendirrigation land. Use of agriculture water accounts for 83. 3% and ecological forest and grass for 6.9% . The Hexi Corridor still has a great potential for water saving in agriculture production.Water-saving efficiency of irrigation is about 10% by using such traditional technologies as furrowand border-dike irrigation and small check irrigation, and water-saving with plastic film cover andtechniques of advanced sprinkler and drip/micro irrigation etc. can save more than 60% of irrigatedwater. Incremental irrigation area for water-saving potential in the Hexi Corridor has beenestimated as 56% - 197% to original irrigation area. So the second water sources can be developedfrom water saving agriculture in the Hexi Corridor under Development of the Western Part of China inlarge scale. This potential can be realized step by step through developing the water-savingmeasures, improving the ecological condition of oasis agriculture, and optimizing allocation ofwater resources in three river systems.
