Based on the compressive sensing,a novel algorithm is proposed to solve reconstruction problem under sparsity assumptions.Instead of estimating the reconstructed data through minimizing the objective function,the auth...Based on the compressive sensing,a novel algorithm is proposed to solve reconstruction problem under sparsity assumptions.Instead of estimating the reconstructed data through minimizing the objective function,the authors parameterize the problem as a linear combination of few elementary thresholding functions,which can be solved by calculating the linear weighting coefficients.It is to update the thresholding functions during the process of iteration.The advantage of this method is that the optimization problem only needs to be solved by calculating linear coefficients for each time.With the elementary thresholding functions satisfying certain constraints,a global convergence of the iterative algorithm is guaranteed.The synthetic and the field data results prove the effectiveness of the proposed algorithm.展开更多
Road geometric design data are a vital input for diverse transportation studies. This information is usually obtained from the road design project. However, these are not always available and the as-built course of th...Road geometric design data are a vital input for diverse transportation studies. This information is usually obtained from the road design project. However, these are not always available and the as-built course of the road may diverge considerably from its projected one, rendering subsequent studies inaccurate or impossible. Moreover, the systematic acquisition of this data for the entire road network of a country or even a state represents a very challenging and laborious task. This study＇s goal was the extraction of geometric design data for the paved segments of the Brazilian federal highway network, containing more than 47,000 km of highways. It presents the details of the method＇s adoption process, the particularities of its application to the dataset and the obtained geometric design information. Additionally, it provides a first overview of the Brazilian federal highway network composition （curves and tangents） and geometry.展开更多
Land use generalization indices are critical for producing normative multi-scale land use databases and maps,but there is still not a national criterion for these indices in China.Previous studies on land use data gen...Land use generalization indices are critical for producing normative multi-scale land use databases and maps,but there is still not a national criterion for these indices in China.Previous studies on land use data generalization indices often neglect macroindices such as area proportion of land use types and map load,and also ignore landscape effects on land use generalization indices.Here we constructed an index system of land use data generalization from macro-and micro-perspectives,and examined scale and landscape effects on land use data generalization indices based on the countrywide multi-scale land use data samples.We formulated relationships between land use data generalization indices and both scale and land use pattern metrics.We defined thresholds of land use data generalization indices on scales of 1:50000,1:100000,1:250000,and 1:500000.We verified our methodology and index thresholds through generalizing a county land use database.展开更多
The Hadley circulation is one of the most important atmospheric circulations.Widening of the Hadley circulation has drawn extensive studies in the past decade.The key concern is that widening of the Hadley circulation...The Hadley circulation is one of the most important atmospheric circulations.Widening of the Hadley circulation has drawn extensive studies in the past decade.The key concern is that widening of the Hadley circulation would cause poleward shift of the subtropical dry zone.Various metrics have been applied to measure the widening of the tropics.What are responsible for the observed widening trends of the Hadley circulation? How anthropogenic and natural forcings caused the widening? How the widening results in regional climatic effects? These are the major questions in studing the widening of the Hadley circulation.While both observations and simulations all show widening of the Hadley circulation in the past few decades,there are no general agreements of changes in the strength of the Hadley circulation.Although some reanalysis datasets show strengthening of the Hadley circulation,it was shown that the strengthening trend could be artificial,and simulations show weakening of the Hadley circulation for global greenhouse warming.In the present paper,we shall briefly review the major progresses of studies in trends in width and strength of the Hadley circulation.We address answers to these questions,clarify inconsistent results,and propose ideas for future studies.展开更多
文摘Based on the compressive sensing,a novel algorithm is proposed to solve reconstruction problem under sparsity assumptions.Instead of estimating the reconstructed data through minimizing the objective function,the authors parameterize the problem as a linear combination of few elementary thresholding functions,which can be solved by calculating the linear weighting coefficients.It is to update the thresholding functions during the process of iteration.The advantage of this method is that the optimization problem only needs to be solved by calculating linear coefficients for each time.With the elementary thresholding functions satisfying certain constraints,a global convergence of the iterative algorithm is guaranteed.The synthetic and the field data results prove the effectiveness of the proposed algorithm.
文摘Road geometric design data are a vital input for diverse transportation studies. This information is usually obtained from the road design project. However, these are not always available and the as-built course of the road may diverge considerably from its projected one, rendering subsequent studies inaccurate or impossible. Moreover, the systematic acquisition of this data for the entire road network of a country or even a state represents a very challenging and laborious task. This study＇s goal was the extraction of geometric design data for the paved segments of the Brazilian federal highway network, containing more than 47,000 km of highways. It presents the details of the method＇s adoption process, the particularities of its application to the dataset and the obtained geometric design information. Additionally, it provides a first overview of the Brazilian federal highway network composition （curves and tangents） and geometry.
基金supported by National Basic Research Program of China (Grant No. 2006CB701303)National High Technology Research and Development Program of China (Grant No. 2007AA12Z225)+2 种基金National Natural Science Foundation of China (Grant Nos. 40771168, 40901188)Key Laboratory of Geo-informatics of State Bureau of Surveying and Mapping (Grant No. 200906)Fundamental Research Funds for the Central Universities (Grant No. 4082002)
文摘Land use generalization indices are critical for producing normative multi-scale land use databases and maps,but there is still not a national criterion for these indices in China.Previous studies on land use data generalization indices often neglect macroindices such as area proportion of land use types and map load,and also ignore landscape effects on land use generalization indices.Here we constructed an index system of land use data generalization from macro-and micro-perspectives,and examined scale and landscape effects on land use data generalization indices based on the countrywide multi-scale land use data samples.We formulated relationships between land use data generalization indices and both scale and land use pattern metrics.We defined thresholds of land use data generalization indices on scales of 1:50000,1:100000,1:250000,and 1:500000.We verified our methodology and index thresholds through generalizing a county land use database.
基金supported by the National Natural Science Foundation of China(41530423,and 41761144072)
文摘The Hadley circulation is one of the most important atmospheric circulations.Widening of the Hadley circulation has drawn extensive studies in the past decade.The key concern is that widening of the Hadley circulation would cause poleward shift of the subtropical dry zone.Various metrics have been applied to measure the widening of the tropics.What are responsible for the observed widening trends of the Hadley circulation? How anthropogenic and natural forcings caused the widening? How the widening results in regional climatic effects? These are the major questions in studing the widening of the Hadley circulation.While both observations and simulations all show widening of the Hadley circulation in the past few decades,there are no general agreements of changes in the strength of the Hadley circulation.Although some reanalysis datasets show strengthening of the Hadley circulation,it was shown that the strengthening trend could be artificial,and simulations show weakening of the Hadley circulation for global greenhouse warming.In the present paper,we shall briefly review the major progresses of studies in trends in width and strength of the Hadley circulation.We address answers to these questions,clarify inconsistent results,and propose ideas for future studies.
