Soil salinization or alkalization is a form of soil desertification. Coastal saline-alkali soil represents a type of desert and a key system in the network of ecosystems at the continent-ocean interface. Tamarix chine...Soil salinization or alkalization is a form of soil desertification. Coastal saline-alkali soil represents a type of desert and a key system in the network of ecosystems at the continent-ocean interface. Tamarix chinensis is a drought-tolerant plant that is widely distributed in the coastal saline-alkali soil of Bohai Bay, China. In this study, we used 454 pyrosequencing techniques to investigate the characteristics and distribution of the microbial diversity in coastal saline-alkali soil of the T. chinensis woodland at Bohai Bay. A total of 20,315 sequences were obtained, representing 19 known bacterial phyla and a large proportion of unclassified bacteria at the phylum level. Proteobacteria, Acidobacteria and Actinobacteria were the predominant phyla. The coverage of T. chinensis affected the microbial composition. At the phylum level, the relative abundance of y-Proteobacteria and Bacteroidetes decreased whereas Actinobacteria increased with the increasing coverage of T. chinensis. At the genus level, the proportions of Steroidobacter, Lechevalieria, Gp3 and Gp4 decreased with the increase of the vegetation coverage whereas the proportion of Nocardioides increased. A cluster analysis showed that the existing T. chinensis changed the niches for the microorganisms in the coastal saline-alkali soil, which caused changes in the microbial community. The analysis also distinguished the microbial community structure of the marginal area from those of the dense area and sparse area. Furthermore, the results also indicated that the distance to the seashore line could also affect certain groups of soil bacteria in this coastal saline-alkali soil, such as the family Cryomorphaceae and class Flavobacteria, whose population decreased as the distance increased. In addition, the seawater and temperature could be the driving factors that affected the changes.展开更多
The health conditions of highway bridges is critical for sustained transportation operations.US federal government mandates that all bridges built with public funds are to be inspected visually every two years. There ...The health conditions of highway bridges is critical for sustained transportation operations.US federal government mandates that all bridges built with public funds are to be inspected visually every two years. There is a growing consensus that additional rapid and non-intrusive methods for bridge damage evaluation are needed.This paper explores the potential of applying ground-based laser scanners for bridge damage evaluation. LiDAR has the potential of providing high-density,full-field surface static imaging.Hence,it can generate volumetric quantification of concrete corrosion or steel erosion.By recording object surface topology,LiDAR can detect different damages on the bridge structure and differentiate damage types according to the surface flatness and smoothness.To determine the effectiveness of LiDAR damage detection,two damage detection algorithms are presented and compared using scans on actual bridge damages.The results demonstrate and validate LiDAR damage quantification,which can be a powerful tool for bridge condition evaluation.展开更多
基金funded by the National Natural Science Foundation of China(31470544,41271265)a special financial grant from the China Postdoctoral Science Foundation(2013T60900)the Science and Technology Projects in Gansu Province(1304NKCA135)
文摘Soil salinization or alkalization is a form of soil desertification. Coastal saline-alkali soil represents a type of desert and a key system in the network of ecosystems at the continent-ocean interface. Tamarix chinensis is a drought-tolerant plant that is widely distributed in the coastal saline-alkali soil of Bohai Bay, China. In this study, we used 454 pyrosequencing techniques to investigate the characteristics and distribution of the microbial diversity in coastal saline-alkali soil of the T. chinensis woodland at Bohai Bay. A total of 20,315 sequences were obtained, representing 19 known bacterial phyla and a large proportion of unclassified bacteria at the phylum level. Proteobacteria, Acidobacteria and Actinobacteria were the predominant phyla. The coverage of T. chinensis affected the microbial composition. At the phylum level, the relative abundance of y-Proteobacteria and Bacteroidetes decreased whereas Actinobacteria increased with the increasing coverage of T. chinensis. At the genus level, the proportions of Steroidobacter, Lechevalieria, Gp3 and Gp4 decreased with the increase of the vegetation coverage whereas the proportion of Nocardioides increased. A cluster analysis showed that the existing T. chinensis changed the niches for the microorganisms in the coastal saline-alkali soil, which caused changes in the microbial community. The analysis also distinguished the microbial community structure of the marginal area from those of the dense area and sparse area. Furthermore, the results also indicated that the distance to the seashore line could also affect certain groups of soil bacteria in this coastal saline-alkali soil, such as the family Cryomorphaceae and class Flavobacteria, whose population decreased as the distance increased. In addition, the seawater and temperature could be the driving factors that affected the changes.
基金supported by grant number DTOS59-07-H-0005 from the United States Department of Transportation(USDOT), Research and Innovative Technology Administration (RITA)
文摘The health conditions of highway bridges is critical for sustained transportation operations.US federal government mandates that all bridges built with public funds are to be inspected visually every two years. There is a growing consensus that additional rapid and non-intrusive methods for bridge damage evaluation are needed.This paper explores the potential of applying ground-based laser scanners for bridge damage evaluation. LiDAR has the potential of providing high-density,full-field surface static imaging.Hence,it can generate volumetric quantification of concrete corrosion or steel erosion.By recording object surface topology,LiDAR can detect different damages on the bridge structure and differentiate damage types according to the surface flatness and smoothness.To determine the effectiveness of LiDAR damage detection,two damage detection algorithms are presented and compared using scans on actual bridge damages.The results demonstrate and validate LiDAR damage quantification,which can be a powerful tool for bridge condition evaluation.
