Cultural relics line graphic serves as a crucial form of traditional artifact information documentation,which is a simple and intuitive product with low cost of displaying compared with 3D models.Dimensionality reduct...Cultural relics line graphic serves as a crucial form of traditional artifact information documentation,which is a simple and intuitive product with low cost of displaying compared with 3D models.Dimensionality reduction is undoubtedly necessary for line drawings.However,most existing methods for artifact drawing rely on the principles of orthographic projection that always cannot avoid angle occlusion and data overlapping while the surface of cultural relics is complex.Therefore,conformal mapping was introduced as a dimensionality reduction way to compensate for the limitation of orthographic projection.Based on the given criteria for assessing surface complexity,this paper proposed a three-dimensional feature guideline extraction method for complex cultural relic surfaces.A 2D and 3D combined factor that measured the importance of points on describing surface features,vertex weight,was designed.Then the selection threshold for feature guideline extraction was determined based on the differences between vertex weight and shape index distributions.The feasibility and stability were verified through experiments conducted on real cultural relic surface data.Results demonstrated the ability of the method to address the challenges associated with the automatic generation of line drawings for complex surfaces.The extraction method and the obtained results will be useful for line graphic drawing,displaying and propaganda of cultural relics.展开更多
Research on climate changes between the last interglacial period and Holocene renders a speculation on the tendency of present climate. Fully understanding the nature of the changes will play a significant role in a b...Research on climate changes between the last interglacial period and Holocene renders a speculation on the tendency of present climate. Fully understanding the nature of the changes will play a significant role in a better understanding of global climate change. This work discussed the climate change of the last interglacial period and Holocene in Beijing area to discover the mechanism of local palaeo-climate change. The palaeo-vegetation of the last interglacial period in Xishan Mountain of Beijing was reconstructed by pollen analysis and thermo-luminescence dating to represent the change of palaeo-climate and palaeo-environment. Palaeo-vegetation indicators demonstrated that the climate change of the last interglacial period included 6 stages and was homologous to that reflected by the records from deep sea depositions and polar ice cores, respectively corresponding to Marine Isotope Stage (MIS) 5e, 5d, 5c, 5b, 5a and the interim from MIS5 to MIS4 from the early to the late. Millennial climate abrupt events occurred in MIS 5e, which had an agreement with the records of GRIP. In addition, a climate warming event appeared in the interim from MIS5 to MIS4 and it also was found in other regions of the world. Compared with the vegetation and environment indicators of Holocene in Beijing area, it was found that the vegetation, climate and environment of the last glacial period were better than those of Holocene. The climate abrupt events not only appeared in the last interglacial period and MIS 5e, but also occurred in Holocene, whose mechanism and pattern were analogical. After analyzing the records of millennial climate abrupt change events from this work, Ice Cores and others, it was concluded that climate was instability in the interglacial period.展开更多
Based on multi-source data,this paper evaluated the economic value of ecological services in the Yeyahu Wetland Nature Reserve,Beijing,China.The ecological services of wetland included gas regulation,water quality im-...Based on multi-source data,this paper evaluated the economic value of ecological services in the Yeyahu Wetland Nature Reserve,Beijing,China.The ecological services of wetland included gas regulation,water quality im-provement,biodiversity maintenance,erosion control,water supply,recreational opportunity,raw material supply and existence value.Multiple conventional evaluation methods were used to calculate the value of eight wetland services.The results showed that significant values came from biodiversity maintenance and recreational opportunity.The main reasons were as follows.Firstly,Yeyahu Wetland Nature Reserve was the habitat for migrant birds,and government had payed more efforts to protect precious birds.Secondly,the population is large in Beijing.People enjoyed going outside and enjoyed the natural and artificial wetland scenes.At the same time,most people were prepared to pay for wetland conservation.The decline of vegetation cover made the economic value of erosion control the lowest.While the shrink of water resource and the deteriorative water quality caused the economic value of water supply lower.The evaluation results could help decision-makers understand the present status of the Yeyahu Wetland Nature Reserve and provide a scientific basis for strategic decision.展开更多
Mechanism and modeling of the land subsidence are complex because of the complicate geological background in Beijing, China. This paper analyzed the spatial relationship between land subsidence and three factors, incl...Mechanism and modeling of the land subsidence are complex because of the complicate geological background in Beijing, China. This paper analyzed the spatial relationship between land subsidence and three factors, including the change of groundwater level, the thickness of compressible sediments and the building area by using remote sensing and GIS tools in the upper-middle part of alluvial-proluvial plain fan of the Chaobai River in Beijing. Based on the spatial analysis of the land subsidence and three factors, there exist significant non-linear relationship between the vertical displacement and three factors. The Back Propagation Neural Network (BPN) model combined with Genetic Algorithm (GA) was used to simulate regional distribution of the land subsidence. Results showed that at field scale, the groundwater level and land subsidence showed a significant linear relationship. However, at regional scale, the spatial distribution of groundwater depletion funnel did not overlap with the land subsidence funnel. As to the factor of compressible strata, the places with the biggest compressible strata thickness did not have the largest vertical displacement. The distributions of building area and land subsidence have no obvious spatial relationships. The BPN-GA model simulation results illustrated that the accuracy of the trained model during fifty years is acceptable with an error of 51% of verification data less than 20 mm and the average of the absolute error about 32 mm. The BPN model could be utilized to simulate the general distribution of land subsidence in the study area. Overall, this work contributes to better understand the complex relationship between the land subsidence and three influencing factors. And the distribution of the land subsidence can be simulated by the trained BPN-GA model with the limited available dada and acceptable accuracy.展开更多
The five central cities-Beijing,Tianjin,Shanghai,Guangzhou and Shenzhen-of the three most important strategic regions in China,namely Beijing-Tianjin-Hebei metropolitan region,the Yangtze River Delta and the Pearl Riv...The five central cities-Beijing,Tianjin,Shanghai,Guangzhou and Shenzhen-of the three most important strategic regions in China,namely Beijing-Tianjin-Hebei metropolitan region,the Yangtze River Delta and the Pearl River Delta,are taken as a comparative analysis on urban producer services' competitiveness,especially focusing on the comparative advantages and disadvantages of producer services in Beijing.Firstly,based on an integrated indicator system including one objective hierarchy,four standard hierarchies and 35 indicator hierarchies,the study applies factor analysis model and analytic hierarchy process model reformed by entropy technology to measure the comprehensive competitiveness of producer services in the above five cities.Secondly,Beijing has comparative advantages of capital resource,industrial base,scientific research resource and market scale,since it takes the first place of the five cities in the comprehensive competitiveness of producer services,the competitiveness of industrial development,business environment and living environment,only inferior to Shanghai in the competitiveness of talent capital.Thirdly,Beijing has comparative disadvantages in the level of producer services development,urban innovation capability and living environment.Finally,five proposals are put forth to enhance the competitiveness of producer services in Beijing,namely perfecting the system of laws and statutes,supporting the development of industry association,implementing scientific development planning,introducing preferential fiscal and taxation policies and strengthening human capital reserve.展开更多
Taking 140 administrative villages for tourism expert diagnostic training as the object, using the minimum variance method and spatial analysis method, this paper studied leading types of rural tourism industry in Bei...Taking 140 administrative villages for tourism expert diagnostic training as the object, using the minimum variance method and spatial analysis method, this paper studied leading types of rural tourism industry in Beijing based on a comprehensive analysis of the tourism business types in the villages. The results showed that rural tourism businesses are mostly the combination of many types, dominated by picking gardens and leisure farms, and the second dominant type is the combination of leisure farm and natural village household, with the clear regional distribution. The combined-business structure and its distribution is influenced by geographical location, natural conditions and industrial investment and many other factors. Water element is an important symbol of rural tourism in the suburbs of Beijing. The newly-emerging operation modes should be concluded in the scope of new format.展开更多
The precipitation recharge coefficient(PRC), representing the amount of groundwater recharge from precipitation, is an important parameter for groundwater resources evaluation and numerical simulation. It was usually ...The precipitation recharge coefficient(PRC), representing the amount of groundwater recharge from precipitation, is an important parameter for groundwater resources evaluation and numerical simulation. It was usually obtained from empirical knowledge and site experiments in the 1980 s. However, the environmental settings have been greatly modified from that time due to land use change and groundwater over-pumping, especially in the Beijing plain area(BPA). This paper aims to estimate and analyze PRC of BPA with the distributed hydrological model and GIS for the year 2011 with similar annual precipitation as long-term mean. It is found that the recharge from vertical(precipitation + irrigation) and precipitation is 291.0 mm/yr and 233.7 mm/yr, respectively, which accounts for 38.6% and 36.6% of corresponding input water. The regional mean PRC is 0.366, which is a little different from the traditional map. However, it has a spatial variation ranging from –7.0% to 17.5% for various sub-regions. Since the vadose zone is now much thicker than the evaporation extinction depth, the land cover is regarded as the major dynamic factor that causes the variation of PRC in this area due to the difference of evapotranspiration rates. It is suggested that the negative impact of reforestation on groundwater quantity within BPA should be well investigated, because the PRC beneath forestland is the smallest among all land cover types.展开更多
The scientific evaluation of arable land remediation potential can be used to formulate remediation policies based on local conditions. This study took arable land resources in Tongxu County, China as the research obj...The scientific evaluation of arable land remediation potential can be used to formulate remediation policies based on local conditions. This study took arable land resources in Tongxu County, China as the research object and administrative villages as the evaluation unit, constructed an evaluation index system by integrating three aspects—quantity, quality and ecology. Based on the evaluation of arable land remediation potential, the K-means++ spatial clustering algorithm combined with elbow method is used to divide the remediation partition and give the remediation strategy. The results showed that: 1) the evaluation index system of arable land improvement potential, which integrated “quantity-quality-ecology”, was more systematic in analyzing the potential of arable land improvement than the previous single target evaluation index, and explored its internal linkage. 2) There are some spatial differences in the quantitative, qualitative and ecological potentials in Tongxu County, with the quantitative potential being higher in Changzhi Township, the intersection of Lizhuang Township and the southern part of Yuhuangmiao Township, the qualitative potential being more evenly distributed, and the ecological potential being higher around Chengguan Township. 3) Through K-means++ clustering algorithm combined with elbow method, Tongxu County was divided into five subzones: quality improvement zone, intensive improvement zone, quantity improvement zone, comprehensive improvement zone and health improvement zone, among which the highest percentage of quality improvement zone and the lowest percentage of comprehensive improvement zone were 49.2% and 1.5% respectively, and differentiated remediation strategies were provided by research for each sub-district to promote high quality of arable land.展开更多
Land urbanization plays an important supporting and restriction role in the rapid and sustainable development of urbanization in China, and it shows distinctive spatial heteroge- neity. Applying urban area as the basi...Land urbanization plays an important supporting and restriction role in the rapid and sustainable development of urbanization in China, and it shows distinctive spatial heteroge- neity. Applying urban area as the basic research unit and urban construction land area as the core indicator, this paper establishes the conceptual framework and calculation method for the quantity and rate of land urbanization process. The study evaluates the spatial differen- tiation pattern of absolute and relative process of land urbanization in 658 cities in China from 2000 to 2010. The spatial distribution of cities with rapid land urbanization process is dis- cussed, and the contribution rate and its spatial heterogeneity of major land use types are examined with the aid of GIS. The main conclusions are as follows： （1） Land urbanization in China shows a clear spatial difference. The greater the city scale, the faster its land urbani- zation. The cities with rapid land urbanization show a significant pattern of central distribution in coastal regions and a scattered distribution in the inland regions. （2） Over the last 10 years, the average quantity of land urbanization in the 656 cities was 3.82 km2, the quantity of land urbanization is differentiated by administrative grade. The average rate of land urbanization was 6.89%, obviously faster than the speed of population urbanization. The rate of land ur- banization reveals a pattern of differentiation between coastal and other cities. （3） In the past 10 years, the two primary land use types associated with land urbanization in China are residential and industrial, with a combined contribution rate of 52.49%. The greater the scale of the city, the more significant the driving effect of industrial land. In small- and medium-scale cities of the western and central regions, the growth of residential land is the primary driver of land urbanization, while in coastal urban agglomerations and cities on important communica- tion axes, the growth of industrial land is the main driver. （4） Overall, urban population ag- glomeration, industrial growth and investment are the three drivers of land urbanization in China, but cities of different scales have different drivers.展开更多
Air pollution is a serious problem brought by the rapid urbanization and economic development in China, imposing great challenges and threats to population health and the sustainability of the society. Based on the re...Air pollution is a serious problem brought by the rapid urbanization and economic development in China, imposing great challenges and threats to population health and the sustainability of the society. Based on the real-time air quality monitoring data obtained for each Chinese city from 2013 to 2014, the spatiotemporal characteristics of air pollution are analyzed using various exploratory spatial data analysis tools. With spatial econometric models, this paper further quantifies the influences of socioeconomic factors on air quality at both the national and regional scales. The results are as follows： （1） From 2013 to 2014, the percentage of days compliance of urban air quality increased but air pollution deteriorated and the worsening situation in regions with poor air quality became more obvious. （2） Changes of air quality show a clear temporal coupling with regional socioeconomic activities, basically ＂relatively poor at daytime and relatively good at night＂. （3） Urban air pollution shows a spatial pattern of ＂heavy in the east and light in the west, and heavy in the north and light in the south＂. （4） The overall extent and distribution of regional urban air pollution have clearly different characteristics. The formation and evolution of regional air pollution can be basically induced as ＂the pollution of key cities is aggravated--pollution of those cities spreads-- regional overall pollution is aggravated--the key cities lead in pollution governance--regional pollution joint prevention and control is implemented--regional overall pollution is reduced＂. （5） At the national level, energy consumption, industrialization and technological progress are the major factors in the worsening of urban air quality, economic development is a significant driver for the improvement of that quality. （6） Influenced by resources, environment and the development stage, the socioeconomic factors had strongly variable impacts on air quality, in both direction and intensity in different regions. Based on the conclusion, the regional differ- entiation and development idea of the relationship between economic development and en- vironmental changes in China are discussed.展开更多
Structural characteristics and proton binding properties of sub-fractions（FA3–FA13） of fulvic acid（FA）, eluted stepwise by pyrophosphate buffer were examined by use of fluorescence titration combined with fluores...Structural characteristics and proton binding properties of sub-fractions（FA3–FA13） of fulvic acid（FA）, eluted stepwise by pyrophosphate buffer were examined by use of fluorescence titration combined with fluorescence regional integration（FRI） and differential fluorescence spectroscopy（DFS）. Humic-like（H-L） and fulvic-like（F-L） materials, which accounted for more than 80% of fluorescence response, were dominant in five sub-fractions of FA. Based on FRI analysis, except the response of F-L materials in FA9 and FA13, maximum changes in percent fluorescence response were less than 10% as pH was increased from 2.5 to 11.5.Contents of carboxylic and phenolic groups were compared for fluorescence peaks of FA sub-fractions based on pH-dependent fluorescence derived from DFS. Static quenching was the dominant mechanism for binding of protons by FA sub-fractions. Dissociation constants（p Ka） were calculated by use of results of DFS and the modified Stern-Volmer relationship. The p Kaof H-L, F-L, tryptophan-like and tyrosine-like materials of FA subfractions exhibited ranges of 3.17–4.06, 3.12–3.97, 4.14–4.45 and 4.25–4.76, respectively, for acidic pHs. At basic pHs, values of p Ka for corresponding materials were in ranges of 9.71–10.24, 9.62–10.99, 9.67–10.31 and 9.33–10.28, respectively. At acidic pH, protein-like（P-L）materials had greater affinities for protons than did either H-L or F-L materials. The dicarboxylic and phenolic groups were likely predominant sites of protonation for both H-L and F-L materials at both acidic and basic pHs. Amino acid groups were significant factors during proton binding to protein-like materials of FA sub-fractions at basic pH.展开更多
In order to evaluate the impact of reclaimed water on the ecology of bacterial communities in the Typha angustifolia L. rhizosphere soil, bacterial community structure was investigated using a combination of terminal ...In order to evaluate the impact of reclaimed water on the ecology of bacterial communities in the Typha angustifolia L. rhizosphere soil, bacterial community structure was investigated using a combination of terminal restriction fragment length polymorphism and 16S rRNA gene clone library. The results revealed significant spatial variation of bacterial communities along the river from upstream and downstream. For example, a higher relative abundance of γ-Proteobacteria, Firmicutes, Chloroflexi and a lower proportion of β-Proteobacteria and ε-Proteobacteria was detected at the downstream site compared to the upstream site. Additionally, with an increase of the reclaimed water interference intensity, the rhizosphere bacterial community showed a decrease in taxon richness, evenness and diversity. The relative abundance of bacteria closely related to the resistant of heavy-metal was markedly increased, while the bacteria related for carbon/nitrogen/phosphorus/sulfur cycling wasn＇t strikingly changed. Besides that, the pathogenic bacteria markedly increased in the downstream rhizosphere soil since reclaimed water supplement, while the possible plant growth-promoting rhizobacteria obviously reduced in the downstream sediment. Together these data suggest cause and effect between reclaimed water input into the wetland, shift in bacterial communities through habitat change, and alteration of capacity for biogeochemical cycling of contaminants.展开更多
Volatile organic compounds(VOCs)play an important role in the formation of ground-level ozone and secondary organic aerosol(SOA),and they have been key issues in current air pollution prevention and control in China.C...Volatile organic compounds(VOCs)play an important role in the formation of ground-level ozone and secondary organic aerosol(SOA),and they have been key issues in current air pollution prevention and control in China.Considerable attention has been paid to industrial activities due to their large and relatively complex VOCs emissions.The present research aims to provide a comprehensive review on whole-process control of industrial VOCs,which mainly includes source reduction,collection enhancement and end-pipe treatments.Lower VOCs materials including water-borne ones are the keys to source substitution in industries related to coating and solvent usage,leak detection and repair(LDAR)should be regarded as an efficient means of source reduction in refining,petrochemical and other chemical industries.Several types of VOCs collection methods such as gas-collecting hoods,airtight partitions and others are discussed,and airtight collection at negative pressure yields the best collection efficiency.Current end-pipe treatments like UV oxidation,low-temperature plasma,activated carbon adsorption,combustion,biodegradation,and adsorption-combustion are discussed in detail.Finally,several recommendations are made for future advanced treatment and policy development in industrial VOCs emission control.展开更多
Tracing erosion flux within a single catchment is one of the major targets for the Earth's Critical Zone science. The sedimentary succession in landslide-dammed reservoirs within the Chinese Loess Plateau(CLP) ser...Tracing erosion flux within a single catchment is one of the major targets for the Earth's Critical Zone science. The sedimentary succession in landslide-dammed reservoirs within the Chinese Loess Plateau(CLP) serves as a valuable archive of past erosion history. Deposition couplets and annual freeze–thaw layers were firstly identified for the sedimentary succession of the Jingbian reservoir on the northern CLP with high-resolution XRF core scanning. The deposition couplets in the reservoir since 1963 A.D. were further dated with ^(137) Cs activity. We found consistent one-to-one correspondence between couplet specific sediment yield and storm intensity. The reconstructed soil erosion history highlights the control of storm intensity and frequency on loess erosion on the northern CLP in the past hundreds of years.展开更多
Spatiotemporal residual noise in terrestrial earth observation products,often caused by unfavorable atmospheric conditions,impedes their broad applications.Most users prefer to use gap-filled remote sensing products w...Spatiotemporal residual noise in terrestrial earth observation products,often caused by unfavorable atmospheric conditions,impedes their broad applications.Most users prefer to use gap-filled remote sensing products with time series reconstruction(TSR)algorithms.Applying currently available implementations of TSR to large-volume datasets is time-consuming and challenging for non-professional users with limited computation or storage resources.This study introduces a new open-source software package entitled‘HANTS-GEE’that implements a well-known and robust TSR algorithm,i.e.Harmonic ANalysis of Time Series(HANTS),on the Google Earth Engine(GEE)platform for scalable reconstruction of terrestrial earth observation data.Reconstruction tasks can be conducted on user-defined spatiotemporal extents when raw datasets are available on GEE.According to site-based and regional-based case evaluation,the new tool can effectively eliminate cloud contamination in the time series of earth observation data.Compared with traditional PC-based HANTS implementation,the HANTS-GEE provides quite consistent reconstruction results for most terrestrial vegetated sites.The HANTS-GEE can provide scalable reconstruction services with accelerated processing speed and reduced internet data transmission volume,promoting algorithm usage by much broader user communities.To our knowledge,the software package is thefirst tool to support full-stack TSR processing for popular open-access satellite sensors on cloud platforms.展开更多
Alpine timberline, as the ＂ecologica tion of scientists in many fields, especially in transition zone,＂ has long attracted the atten- recent years. Many unitary and dibasic fitting models have been developed to expl...Alpine timberline, as the ＂ecologica tion of scientists in many fields, especially in transition zone,＂ has long attracted the atten- recent years. Many unitary and dibasic fitting models have been developed to explore the relationship between timberline elevation and latitude or temperature. However, these models are usually on regional scale and could not be applied to other regions; on the other hand, hemispherical-scale and continental-scale models are usually based on about 100 timberline data and are necessarily low in precision. The present article collects 516 data sites of timberline, and takes latitude, continentality and mass elevation effect （MEE） as independent variables and timberline elevation as dependent variable to develop a ternary linear regression meteorological data released by WorldClim and model. Continentality is calculated using the mountain base elevation （as a proxy of mass elevation effect） is extracted on the basis of SRTM 90-meter resolution elevation data. The results show that the coefficient of determination （R2） of the linear model is as high as 0.904, and that the contribution rate of latitude, continentality and MEE to timberline elevation is 45.02% （p=0.000）, 6.04% （p=0.000） and 48.94% （p=0.000）, respectively. This means that MEE is simply the primary factor contributing to the elevation distribution of timberline on the continental and hemispherical scales. The contribution rate of MEE to timberline altitude dif- fers in different regions, e.g., 50.49% （p=0.000） in North America, 48.73% （p=0.000） in the eastern Eurasia, and 43.6% （p=0.000） in the western Eurasia, but it is usually very high.展开更多
Well-preserved Late Glacial moraines in the Barenduo and Yuqiongqu valleys on the eastern slope of the Samdainkangsang Peak present an opportunity to reconstruct glacier extents and examine the character of the climat...Well-preserved Late Glacial moraines in the Barenduo and Yuqiongqu valleys on the eastern slope of the Samdainkangsang Peak present an opportunity to reconstruct glacier extents and examine the character of the climate during the Late Glacial stage in the Nyaiqentanggulha Mountains. This study employs a coupled mass-balance and ice-flow model to reconstruct the glacier extents in the two valleys and assess the magnitudes of temperature and precipitation change during the Late Glacial period. Model results indicate that during the Late Glacial, the Barenduo valley contained an ice volume of 1.67x 108 m3, with the equilibrium-line altitude （ELA） being -5500 m asl; and the Yuqiongqu valley had an ice volume of 5.56x 108 m3, with the ELA being -5470 m asl. A climate scenario, temperature depression of 2.6-2.8°C and 60-70%, percent of modern （1981-2010） precipitation, can sustain both of the Late Glacial glacier extents in the two valleys. A 50% increase or decrease from modern precipitation would have been coupled with the respective Late Glacial temperature depressions of 1.6 and 3.0°C in the Barenduo valley, and 2.1 and 2.8°C in the Yuqiongqu valley.展开更多
In forest ecosystem studies,tree stem structure variables(SSVs)proved to be an essential kind of parameters,and now simultaneously deriving SSVs of as many kinds as possible at large scales is preferred for enhancing ...In forest ecosystem studies,tree stem structure variables(SSVs)proved to be an essential kind of parameters,and now simultaneously deriving SSVs of as many kinds as possible at large scales is preferred for enhancing the frontier studies on marcoecosystem ecology and global carbon cycle.For this newly emerging task,satellite imagery such as WorldView-2 panchromatic images(WPIs)is used as a potential solution for co-prediction of tree-level multifarious SSVs,with static terrestrial laser scanning(TLS)assumed as a‘bridge’.The specific operation is to pursue the allometric relationships between TLS-derived SSVs and WPI-derived feature parameters,and regression analyses with one or multiple explanatory variables are applied to deduce the prediction models(termed as Model1s and Model2s).In the case of Picea abies,Pinus sylvestris,Populus tremul and Quercus robur in a boreal forest,tests showed that Model1s and Model2s for different tree species can be derived(e.g.the maximum R^(2)=0.574 for Q.robur).Overall,this study basically validated the algorithm proposed for co-prediction of multifarious SSVs,and the contribution is equivalent to developing a viable solution for SSV-estimation upscaling,which is useful for large-scale investigations of forest understory,macroecosystem ecology,global vegetation dynamics and global carbon cycle.展开更多
Land subsidence is a geohazard phenomenon caused by the lowering of land elevation due to the compression of the sinking land soil body,thus creating an excessive constraint on the safe construction and sustainable de...Land subsidence is a geohazard phenomenon caused by the lowering of land elevation due to the compression of the sinking land soil body,thus creating an excessive constraint on the safe construction and sustainable development of cities.The use of accurate and efficient means for land subsidence prediction is of remarkable importance for preventing land subsidence and ensuring urban safety.Although the current time-series prediction method can accomplish relatively high accuracy,the predicted settlement points are independent of each other,and the existence of spatial dependence in the data itself is lost.In order to unlock this problem,a spatial convolutional long short-term memory neural network(ConvLSTM)based on the spatio-temporal prediction method for land subsidence is constructed.To this end,a cloud platform is employed to obtain a long time series deformation dataset from May 2017 to November 2021 in the understudied area.A convolutional structure to extract spatial features is utilized in the proposed model,and an LSTM structure is linked to the model for time-series prediction to achieve unified modeling of temporal and spatial correlation,thereby rationally predicting the land subsidence progress trend and distribution.The experimental results reveal that the prediction results of the ConvLSTM model are more accurate than those of the LSTM in about 62%of the understudied area,and the overall mean absolute error(MAE)is reduced by about 7%.The achieved results exhibit better prediction in the subsidence center region,and the spatial distribution characteristics of the subsidence data are effectively captured.The present prediction results are more consistent with the distribution of real subsidence and could provide more accurate and reasonable scientific references for subsidence prevention and control in the Beijing-Tianjin-Hebei region.展开更多
Matching multi-scale road networks in the same area is the first step in merging two road networks or updating one based upon the other.The quality of the merge or update depends greatly on the matching accuracy of th...Matching multi-scale road networks in the same area is the first step in merging two road networks or updating one based upon the other.The quality of the merge or update depends greatly on the matching accuracy of the two road networks.We propose an improved probabilistic relaxation method,considering both local and global optimizations for matching multi-scale of road networks.The aim is to achieve local optimization,as well as to address the identification of the M:N matching pattern by means of inserting virtual nodes to achieve global optimization effects.Then,by adding two attribute-related evaluation indicators,we developed four evaluation indicators to evaluate the matching accuracy,considering both geographic and attribute information.This paper also provides instructions on how to identify the proper buffer threshold during matching procedures.Extensive experiments were conducted to compare the proposed method with the traditional approach.The results indicate that:(1)the overall matching accuracy of each evaluation indicator exceeds 90%;(2)the overall matching accuracy increases by 6–12%after an M:N matching pattern is added,and by 4–6%following the addition of topology indicators;and(3)the proper buffer threshold is about twice the average value of the closest distance from all nodes.展开更多
基金National Natural Science Foundation of China(Nos.42071444,42101444)。
文摘Cultural relics line graphic serves as a crucial form of traditional artifact information documentation,which is a simple and intuitive product with low cost of displaying compared with 3D models.Dimensionality reduction is undoubtedly necessary for line drawings.However,most existing methods for artifact drawing rely on the principles of orthographic projection that always cannot avoid angle occlusion and data overlapping while the surface of cultural relics is complex.Therefore,conformal mapping was introduced as a dimensionality reduction way to compensate for the limitation of orthographic projection.Based on the given criteria for assessing surface complexity,this paper proposed a three-dimensional feature guideline extraction method for complex cultural relic surfaces.A 2D and 3D combined factor that measured the importance of points on describing surface features,vertex weight,was designed.Then the selection threshold for feature guideline extraction was determined based on the differences between vertex weight and shape index distributions.The feasibility and stability were verified through experiments conducted on real cultural relic surface data.Results demonstrated the ability of the method to address the challenges associated with the automatic generation of line drawings for complex surfaces.The extraction method and the obtained results will be useful for line graphic drawing,displaying and propaganda of cultural relics.
文摘Research on climate changes between the last interglacial period and Holocene renders a speculation on the tendency of present climate. Fully understanding the nature of the changes will play a significant role in a better understanding of global climate change. This work discussed the climate change of the last interglacial period and Holocene in Beijing area to discover the mechanism of local palaeo-climate change. The palaeo-vegetation of the last interglacial period in Xishan Mountain of Beijing was reconstructed by pollen analysis and thermo-luminescence dating to represent the change of palaeo-climate and palaeo-environment. Palaeo-vegetation indicators demonstrated that the climate change of the last interglacial period included 6 stages and was homologous to that reflected by the records from deep sea depositions and polar ice cores, respectively corresponding to Marine Isotope Stage (MIS) 5e, 5d, 5c, 5b, 5a and the interim from MIS5 to MIS4 from the early to the late. Millennial climate abrupt events occurred in MIS 5e, which had an agreement with the records of GRIP. In addition, a climate warming event appeared in the interim from MIS5 to MIS4 and it also was found in other regions of the world. Compared with the vegetation and environment indicators of Holocene in Beijing area, it was found that the vegetation, climate and environment of the last glacial period were better than those of Holocene. The climate abrupt events not only appeared in the last interglacial period and MIS 5e, but also occurred in Holocene, whose mechanism and pattern were analogical. After analyzing the records of millennial climate abrupt change events from this work, Ice Cores and others, it was concluded that climate was instability in the interglacial period.
基金Under the auspices of National Natural Science Foundation of China (No. 40771170)Beijing Municipal Natural Science Foundation (No. 8082010)
文摘Based on multi-source data,this paper evaluated the economic value of ecological services in the Yeyahu Wetland Nature Reserve,Beijing,China.The ecological services of wetland included gas regulation,water quality im-provement,biodiversity maintenance,erosion control,water supply,recreational opportunity,raw material supply and existence value.Multiple conventional evaluation methods were used to calculate the value of eight wetland services.The results showed that significant values came from biodiversity maintenance and recreational opportunity.The main reasons were as follows.Firstly,Yeyahu Wetland Nature Reserve was the habitat for migrant birds,and government had payed more efforts to protect precious birds.Secondly,the population is large in Beijing.People enjoyed going outside and enjoyed the natural and artificial wetland scenes.At the same time,most people were prepared to pay for wetland conservation.The decline of vegetation cover made the economic value of erosion control the lowest.While the shrink of water resource and the deteriorative water quality caused the economic value of water supply lower.The evaluation results could help decision-makers understand the present status of the Yeyahu Wetland Nature Reserve and provide a scientific basis for strategic decision.
基金Under the auspices of National Natural Science Foundation of China(No.41201420,41130744)Beijing Nova Program(No.Z111106054511097)Foundation of Beijing Municipal Commission of Education(No.KM201110028016)
文摘Mechanism and modeling of the land subsidence are complex because of the complicate geological background in Beijing, China. This paper analyzed the spatial relationship between land subsidence and three factors, including the change of groundwater level, the thickness of compressible sediments and the building area by using remote sensing and GIS tools in the upper-middle part of alluvial-proluvial plain fan of the Chaobai River in Beijing. Based on the spatial analysis of the land subsidence and three factors, there exist significant non-linear relationship between the vertical displacement and three factors. The Back Propagation Neural Network (BPN) model combined with Genetic Algorithm (GA) was used to simulate regional distribution of the land subsidence. Results showed that at field scale, the groundwater level and land subsidence showed a significant linear relationship. However, at regional scale, the spatial distribution of groundwater depletion funnel did not overlap with the land subsidence funnel. As to the factor of compressible strata, the places with the biggest compressible strata thickness did not have the largest vertical displacement. The distributions of building area and land subsidence have no obvious spatial relationships. The BPN-GA model simulation results illustrated that the accuracy of the trained model during fifty years is acceptable with an error of 51% of verification data less than 20 mm and the average of the absolute error about 32 mm. The BPN model could be utilized to simulate the general distribution of land subsidence in the study area. Overall, this work contributes to better understand the complex relationship between the land subsidence and three influencing factors. And the distribution of the land subsidence can be simulated by the trained BPN-GA model with the limited available dada and acceptable accuracy.
基金supported by National Natural Science Foundation of China (Crant No. 40971101Grant No.40871069)+1 种基金Mega-project of Science and Technology Research for the 11th Five Year Plan of China (Crant No.2006BAJ05A06No.2006BAJ14B02)
文摘The five central cities-Beijing,Tianjin,Shanghai,Guangzhou and Shenzhen-of the three most important strategic regions in China,namely Beijing-Tianjin-Hebei metropolitan region,the Yangtze River Delta and the Pearl River Delta,are taken as a comparative analysis on urban producer services' competitiveness,especially focusing on the comparative advantages and disadvantages of producer services in Beijing.Firstly,based on an integrated indicator system including one objective hierarchy,four standard hierarchies and 35 indicator hierarchies,the study applies factor analysis model and analytic hierarchy process model reformed by entropy technology to measure the comprehensive competitiveness of producer services in the above five cities.Secondly,Beijing has comparative advantages of capital resource,industrial base,scientific research resource and market scale,since it takes the first place of the five cities in the comprehensive competitiveness of producer services,the competitiveness of industrial development,business environment and living environment,only inferior to Shanghai in the competitiveness of talent capital.Thirdly,Beijing has comparative disadvantages in the level of producer services development,urban innovation capability and living environment.Finally,five proposals are put forth to enhance the competitiveness of producer services in Beijing,namely perfecting the system of laws and statutes,supporting the development of industry association,implementing scientific development planning,introducing preferential fiscal and taxation policies and strengthening human capital reserve.
基金Sponsored by Beijing Outstanding Talents Training Program “Background Value and Assessment System of Natural Tourism Resources in Beijing(20071E0501600216)”
文摘Taking 140 administrative villages for tourism expert diagnostic training as the object, using the minimum variance method and spatial analysis method, this paper studied leading types of rural tourism industry in Beijing based on a comprehensive analysis of the tourism business types in the villages. The results showed that rural tourism businesses are mostly the combination of many types, dominated by picking gardens and leisure farms, and the second dominant type is the combination of leisure farm and natural village household, with the clear regional distribution. The combined-business structure and its distribution is influenced by geographical location, natural conditions and industrial investment and many other factors. Water element is an important symbol of rural tourism in the suburbs of Beijing. The newly-emerging operation modes should be concluded in the scope of new format.
基金Under the auspices of Beijing Natural Science Foundation(No.8152012)National Natural Science Foundation of China(No.41101033,41130744,41171335)
文摘The precipitation recharge coefficient(PRC), representing the amount of groundwater recharge from precipitation, is an important parameter for groundwater resources evaluation and numerical simulation. It was usually obtained from empirical knowledge and site experiments in the 1980 s. However, the environmental settings have been greatly modified from that time due to land use change and groundwater over-pumping, especially in the Beijing plain area(BPA). This paper aims to estimate and analyze PRC of BPA with the distributed hydrological model and GIS for the year 2011 with similar annual precipitation as long-term mean. It is found that the recharge from vertical(precipitation + irrigation) and precipitation is 291.0 mm/yr and 233.7 mm/yr, respectively, which accounts for 38.6% and 36.6% of corresponding input water. The regional mean PRC is 0.366, which is a little different from the traditional map. However, it has a spatial variation ranging from –7.0% to 17.5% for various sub-regions. Since the vadose zone is now much thicker than the evaporation extinction depth, the land cover is regarded as the major dynamic factor that causes the variation of PRC in this area due to the difference of evapotranspiration rates. It is suggested that the negative impact of reforestation on groundwater quantity within BPA should be well investigated, because the PRC beneath forestland is the smallest among all land cover types.
文摘The scientific evaluation of arable land remediation potential can be used to formulate remediation policies based on local conditions. This study took arable land resources in Tongxu County, China as the research object and administrative villages as the evaluation unit, constructed an evaluation index system by integrating three aspects—quantity, quality and ecology. Based on the evaluation of arable land remediation potential, the K-means++ spatial clustering algorithm combined with elbow method is used to divide the remediation partition and give the remediation strategy. The results showed that: 1) the evaluation index system of arable land improvement potential, which integrated “quantity-quality-ecology”, was more systematic in analyzing the potential of arable land improvement than the previous single target evaluation index, and explored its internal linkage. 2) There are some spatial differences in the quantitative, qualitative and ecological potentials in Tongxu County, with the quantitative potential being higher in Changzhi Township, the intersection of Lizhuang Township and the southern part of Yuhuangmiao Township, the qualitative potential being more evenly distributed, and the ecological potential being higher around Chengguan Township. 3) Through K-means++ clustering algorithm combined with elbow method, Tongxu County was divided into five subzones: quality improvement zone, intensive improvement zone, quantity improvement zone, comprehensive improvement zone and health improvement zone, among which the highest percentage of quality improvement zone and the lowest percentage of comprehensive improvement zone were 49.2% and 1.5% respectively, and differentiated remediation strategies were provided by research for each sub-district to promote high quality of arable land.
基金National Natural Science Foundation of China, No.41401164, No.41430636 The Key Research Program of the Chinese Academy of Sciences, No.KZZD-EW-06.
文摘Land urbanization plays an important supporting and restriction role in the rapid and sustainable development of urbanization in China, and it shows distinctive spatial heteroge- neity. Applying urban area as the basic research unit and urban construction land area as the core indicator, this paper establishes the conceptual framework and calculation method for the quantity and rate of land urbanization process. The study evaluates the spatial differen- tiation pattern of absolute and relative process of land urbanization in 658 cities in China from 2000 to 2010. The spatial distribution of cities with rapid land urbanization process is dis- cussed, and the contribution rate and its spatial heterogeneity of major land use types are examined with the aid of GIS. The main conclusions are as follows： （1） Land urbanization in China shows a clear spatial difference. The greater the city scale, the faster its land urbani- zation. The cities with rapid land urbanization show a significant pattern of central distribution in coastal regions and a scattered distribution in the inland regions. （2） Over the last 10 years, the average quantity of land urbanization in the 656 cities was 3.82 km2, the quantity of land urbanization is differentiated by administrative grade. The average rate of land urbanization was 6.89%, obviously faster than the speed of population urbanization. The rate of land ur- banization reveals a pattern of differentiation between coastal and other cities. （3） In the past 10 years, the two primary land use types associated with land urbanization in China are residential and industrial, with a combined contribution rate of 52.49%. The greater the scale of the city, the more significant the driving effect of industrial land. In small- and medium-scale cities of the western and central regions, the growth of residential land is the primary driver of land urbanization, while in coastal urban agglomerations and cities on important communica- tion axes, the growth of industrial land is the main driver. （4） Overall, urban population ag- glomeration, industrial growth and investment are the three drivers of land urbanization in China, but cities of different scales have different drivers.
基金Key Program of National Natural Science Foundation of China,No.41430636Youth Program of the Humanities and Social Science Research of Ministry of Education,No.16YJC790056
文摘Air pollution is a serious problem brought by the rapid urbanization and economic development in China, imposing great challenges and threats to population health and the sustainability of the society. Based on the real-time air quality monitoring data obtained for each Chinese city from 2013 to 2014, the spatiotemporal characteristics of air pollution are analyzed using various exploratory spatial data analysis tools. With spatial econometric models, this paper further quantifies the influences of socioeconomic factors on air quality at both the national and regional scales. The results are as follows： （1） From 2013 to 2014, the percentage of days compliance of urban air quality increased but air pollution deteriorated and the worsening situation in regions with poor air quality became more obvious. （2） Changes of air quality show a clear temporal coupling with regional socioeconomic activities, basically ＂relatively poor at daytime and relatively good at night＂. （3） Urban air pollution shows a spatial pattern of ＂heavy in the east and light in the west, and heavy in the north and light in the south＂. （4） The overall extent and distribution of regional urban air pollution have clearly different characteristics. The formation and evolution of regional air pollution can be basically induced as ＂the pollution of key cities is aggravated--pollution of those cities spreads-- regional overall pollution is aggravated--the key cities lead in pollution governance--regional pollution joint prevention and control is implemented--regional overall pollution is reduced＂. （5） At the national level, energy consumption, industrialization and technological progress are the major factors in the worsening of urban air quality, economic development is a significant driver for the improvement of that quality. （6） Influenced by resources, environment and the development stage, the socioeconomic factors had strongly variable impacts on air quality, in both direction and intensity in different regions. Based on the conclusion, the regional differ- entiation and development idea of the relationship between economic development and en- vironmental changes in China are discussed.
基金supported by the National Natural Science Foundation of China(Nos.41173084,41521003,41573130,41630645,41703115 and 41503104)the Beijing Natural Science Foundation(No.8162044)the Canada Research Chair program,Einstein Professor Program of the Chinese Academy of Sciences,and the High Level Foreign Experts Program(#GDT20143200016)
文摘Structural characteristics and proton binding properties of sub-fractions（FA3–FA13） of fulvic acid（FA）, eluted stepwise by pyrophosphate buffer were examined by use of fluorescence titration combined with fluorescence regional integration（FRI） and differential fluorescence spectroscopy（DFS）. Humic-like（H-L） and fulvic-like（F-L） materials, which accounted for more than 80% of fluorescence response, were dominant in five sub-fractions of FA. Based on FRI analysis, except the response of F-L materials in FA9 and FA13, maximum changes in percent fluorescence response were less than 10% as pH was increased from 2.5 to 11.5.Contents of carboxylic and phenolic groups were compared for fluorescence peaks of FA sub-fractions based on pH-dependent fluorescence derived from DFS. Static quenching was the dominant mechanism for binding of protons by FA sub-fractions. Dissociation constants（p Ka） were calculated by use of results of DFS and the modified Stern-Volmer relationship. The p Kaof H-L, F-L, tryptophan-like and tyrosine-like materials of FA subfractions exhibited ranges of 3.17–4.06, 3.12–3.97, 4.14–4.45 and 4.25–4.76, respectively, for acidic pHs. At basic pHs, values of p Ka for corresponding materials were in ranges of 9.71–10.24, 9.62–10.99, 9.67–10.31 and 9.33–10.28, respectively. At acidic pH, protein-like（P-L）materials had greater affinities for protons than did either H-L or F-L materials. The dicarboxylic and phenolic groups were likely predominant sites of protonation for both H-L and F-L materials at both acidic and basic pHs. Amino acid groups were significant factors during proton binding to protein-like materials of FA sub-fractions at basic pH.
基金supported by the National Natural Science Foundation of China(No.40901281)the Beijing of Education Science and Technology Program(No.KM201310028012)the International S&T Cooperation Program of China(No.2014DFA21620)
文摘In order to evaluate the impact of reclaimed water on the ecology of bacterial communities in the Typha angustifolia L. rhizosphere soil, bacterial community structure was investigated using a combination of terminal restriction fragment length polymorphism and 16S rRNA gene clone library. The results revealed significant spatial variation of bacterial communities along the river from upstream and downstream. For example, a higher relative abundance of γ-Proteobacteria, Firmicutes, Chloroflexi and a lower proportion of β-Proteobacteria and ε-Proteobacteria was detected at the downstream site compared to the upstream site. Additionally, with an increase of the reclaimed water interference intensity, the rhizosphere bacterial community showed a decrease in taxon richness, evenness and diversity. The relative abundance of bacteria closely related to the resistant of heavy-metal was markedly increased, while the bacteria related for carbon/nitrogen/phosphorus/sulfur cycling wasn＇t strikingly changed. Besides that, the pathogenic bacteria markedly increased in the downstream rhizosphere soil since reclaimed water supplement, while the possible plant growth-promoting rhizobacteria obviously reduced in the downstream sediment. Together these data suggest cause and effect between reclaimed water input into the wetland, shift in bacterial communities through habitat change, and alteration of capacity for biogeochemical cycling of contaminants.
基金supported by the R&D Program of Beijing Municipal Education Commission(No.KJZD20191443001)the Project of Beijing Municipal Science&Technology Commission(No.Z181100000118003)the Foundation of Beijing Municipal Research Institute of Environmental Protection(No.Y2020-011)。
文摘Volatile organic compounds(VOCs)play an important role in the formation of ground-level ozone and secondary organic aerosol(SOA),and they have been key issues in current air pollution prevention and control in China.Considerable attention has been paid to industrial activities due to their large and relatively complex VOCs emissions.The present research aims to provide a comprehensive review on whole-process control of industrial VOCs,which mainly includes source reduction,collection enhancement and end-pipe treatments.Lower VOCs materials including water-borne ones are the keys to source substitution in industries related to coating and solvent usage,leak detection and repair(LDAR)should be regarded as an efficient means of source reduction in refining,petrochemical and other chemical industries.Several types of VOCs collection methods such as gas-collecting hoods,airtight partitions and others are discussed,and airtight collection at negative pressure yields the best collection efficiency.Current end-pipe treatments like UV oxidation,low-temperature plasma,activated carbon adsorption,combustion,biodegradation,and adsorption-combustion are discussed in detail.Finally,several recommendations are made for future advanced treatment and policy development in industrial VOCs emission control.
基金financially supported by the 973Program(No.2013CB956402)National Natural Science Foundation of China(No.41225015)
文摘Tracing erosion flux within a single catchment is one of the major targets for the Earth's Critical Zone science. The sedimentary succession in landslide-dammed reservoirs within the Chinese Loess Plateau(CLP) serves as a valuable archive of past erosion history. Deposition couplets and annual freeze–thaw layers were firstly identified for the sedimentary succession of the Jingbian reservoir on the northern CLP with high-resolution XRF core scanning. The deposition couplets in the reservoir since 1963 A.D. were further dated with ^(137) Cs activity. We found consistent one-to-one correspondence between couplet specific sediment yield and storm intensity. The reconstructed soil erosion history highlights the control of storm intensity and frequency on loess erosion on the northern CLP in the past hundreds of years.
基金supported by the National Natural Science Foundation of China(grant number 42171371 and No.41701492)Massimo Menenti acknowledges the support of the MOST High Level Foreign Expert program(grant number G2022055010L)the Chinese Academy of Sciences President s International Fellowship Initiative(grant number 2020VTA0001).
文摘Spatiotemporal residual noise in terrestrial earth observation products,often caused by unfavorable atmospheric conditions,impedes their broad applications.Most users prefer to use gap-filled remote sensing products with time series reconstruction(TSR)algorithms.Applying currently available implementations of TSR to large-volume datasets is time-consuming and challenging for non-professional users with limited computation or storage resources.This study introduces a new open-source software package entitled‘HANTS-GEE’that implements a well-known and robust TSR algorithm,i.e.Harmonic ANalysis of Time Series(HANTS),on the Google Earth Engine(GEE)platform for scalable reconstruction of terrestrial earth observation data.Reconstruction tasks can be conducted on user-defined spatiotemporal extents when raw datasets are available on GEE.According to site-based and regional-based case evaluation,the new tool can effectively eliminate cloud contamination in the time series of earth observation data.Compared with traditional PC-based HANTS implementation,the HANTS-GEE provides quite consistent reconstruction results for most terrestrial vegetated sites.The HANTS-GEE can provide scalable reconstruction services with accelerated processing speed and reduced internet data transmission volume,promoting algorithm usage by much broader user communities.To our knowledge,the software package is thefirst tool to support full-stack TSR processing for popular open-access satellite sensors on cloud platforms.
基金National Natural Science Foundation of China,No.41030528No.40971064
文摘Alpine timberline, as the ＂ecologica tion of scientists in many fields, especially in transition zone,＂ has long attracted the atten- recent years. Many unitary and dibasic fitting models have been developed to explore the relationship between timberline elevation and latitude or temperature. However, these models are usually on regional scale and could not be applied to other regions; on the other hand, hemispherical-scale and continental-scale models are usually based on about 100 timberline data and are necessarily low in precision. The present article collects 516 data sites of timberline, and takes latitude, continentality and mass elevation effect （MEE） as independent variables and timberline elevation as dependent variable to develop a ternary linear regression meteorological data released by WorldClim and model. Continentality is calculated using the mountain base elevation （as a proxy of mass elevation effect） is extracted on the basis of SRTM 90-meter resolution elevation data. The results show that the coefficient of determination （R2） of the linear model is as high as 0.904, and that the contribution rate of latitude, continentality and MEE to timberline elevation is 45.02% （p=0.000）, 6.04% （p=0.000） and 48.94% （p=0.000）, respectively. This means that MEE is simply the primary factor contributing to the elevation distribution of timberline on the continental and hemispherical scales. The contribution rate of MEE to timberline altitude dif- fers in different regions, e.g., 50.49% （p=0.000） in North America, 48.73% （p=0.000） in the eastern Eurasia, and 43.6% （p=0.000） in the western Eurasia, but it is usually very high.
基金supported by the National Natural Science Foundation of China(Grant Nos.41471006,41101004 & 41301006)Strategic Priority Research Program(B) of the Chinese Academy of Sciences(Grant No.XDB01020300)State Key Laboratory of Cryospheric Sciences(Grant No.SKLCS-OP-2016-08)
文摘Well-preserved Late Glacial moraines in the Barenduo and Yuqiongqu valleys on the eastern slope of the Samdainkangsang Peak present an opportunity to reconstruct glacier extents and examine the character of the climate during the Late Glacial stage in the Nyaiqentanggulha Mountains. This study employs a coupled mass-balance and ice-flow model to reconstruct the glacier extents in the two valleys and assess the magnitudes of temperature and precipitation change during the Late Glacial period. Model results indicate that during the Late Glacial, the Barenduo valley contained an ice volume of 1.67x 108 m3, with the equilibrium-line altitude （ELA） being -5500 m asl; and the Yuqiongqu valley had an ice volume of 5.56x 108 m3, with the ELA being -5470 m asl. A climate scenario, temperature depression of 2.6-2.8°C and 60-70%, percent of modern （1981-2010） precipitation, can sustain both of the Late Glacial glacier extents in the two valleys. A 50% increase or decrease from modern precipitation would have been coupled with the respective Late Glacial temperature depressions of 1.6 and 3.0°C in the Barenduo valley, and 2.1 and 2.8°C in the Yuqiongqu valley.
基金This work was financially supported in part by the National Natural Science Foundation of China[grant numbers 41471281 and 31670718]in part by the SRF for ROCS,SEM,China.
文摘In forest ecosystem studies,tree stem structure variables(SSVs)proved to be an essential kind of parameters,and now simultaneously deriving SSVs of as many kinds as possible at large scales is preferred for enhancing the frontier studies on marcoecosystem ecology and global carbon cycle.For this newly emerging task,satellite imagery such as WorldView-2 panchromatic images(WPIs)is used as a potential solution for co-prediction of tree-level multifarious SSVs,with static terrestrial laser scanning(TLS)assumed as a‘bridge’.The specific operation is to pursue the allometric relationships between TLS-derived SSVs and WPI-derived feature parameters,and regression analyses with one or multiple explanatory variables are applied to deduce the prediction models(termed as Model1s and Model2s).In the case of Picea abies,Pinus sylvestris,Populus tremul and Quercus robur in a boreal forest,tests showed that Model1s and Model2s for different tree species can be derived(e.g.the maximum R^(2)=0.574 for Q.robur).Overall,this study basically validated the algorithm proposed for co-prediction of multifarious SSVs,and the contribution is equivalent to developing a viable solution for SSV-estimation upscaling,which is useful for large-scale investigations of forest understory,macroecosystem ecology,global vegetation dynamics and global carbon cycle.
基金National Natural Science Foundation of China,No.41930109/D010702Beijing Outstanding Young Scientist Program,No.BJJWZYJH01201910028032R&D Program of Beijing Municipal Education Commission,No.KM202210028009。
文摘Land subsidence is a geohazard phenomenon caused by the lowering of land elevation due to the compression of the sinking land soil body,thus creating an excessive constraint on the safe construction and sustainable development of cities.The use of accurate and efficient means for land subsidence prediction is of remarkable importance for preventing land subsidence and ensuring urban safety.Although the current time-series prediction method can accomplish relatively high accuracy,the predicted settlement points are independent of each other,and the existence of spatial dependence in the data itself is lost.In order to unlock this problem,a spatial convolutional long short-term memory neural network(ConvLSTM)based on the spatio-temporal prediction method for land subsidence is constructed.To this end,a cloud platform is employed to obtain a long time series deformation dataset from May 2017 to November 2021 in the understudied area.A convolutional structure to extract spatial features is utilized in the proposed model,and an LSTM structure is linked to the model for time-series prediction to achieve unified modeling of temporal and spatial correlation,thereby rationally predicting the land subsidence progress trend and distribution.The experimental results reveal that the prediction results of the ConvLSTM model are more accurate than those of the LSTM in about 62%of the understudied area,and the overall mean absolute error(MAE)is reduced by about 7%.The achieved results exhibit better prediction in the subsidence center region,and the spatial distribution characteristics of the subsidence data are effectively captured.The present prediction results are more consistent with the distribution of real subsidence and could provide more accurate and reasonable scientific references for subsidence prevention and control in the Beijing-Tianjin-Hebei region.
基金This work was supported by the National Natural Science Foundation of China[grant number 41371375]the Natural Science Foundation of Beijing Municipality[grant number 8132018]International Exchange and Joint Training Program of Graduate School of Capital Normal University.
文摘Matching multi-scale road networks in the same area is the first step in merging two road networks or updating one based upon the other.The quality of the merge or update depends greatly on the matching accuracy of the two road networks.We propose an improved probabilistic relaxation method,considering both local and global optimizations for matching multi-scale of road networks.The aim is to achieve local optimization,as well as to address the identification of the M:N matching pattern by means of inserting virtual nodes to achieve global optimization effects.Then,by adding two attribute-related evaluation indicators,we developed four evaluation indicators to evaluate the matching accuracy,considering both geographic and attribute information.This paper also provides instructions on how to identify the proper buffer threshold during matching procedures.Extensive experiments were conducted to compare the proposed method with the traditional approach.The results indicate that:(1)the overall matching accuracy of each evaluation indicator exceeds 90%;(2)the overall matching accuracy increases by 6–12%after an M:N matching pattern is added,and by 4–6%following the addition of topology indicators;and(3)the proper buffer threshold is about twice the average value of the closest distance from all nodes.
