A parameter inversion for sea bridge based on high-resolution polarimetric synthetic aperture radar

Each reflection return of a bridge over water is displayed as wide stripe in a high-resolution synthetic aperture radar （SAR） image, which lead to difficulties in a parameter inversion. Therefore, a method of bridge parameter inversion is proposed for high-resolution full polarimetric SAR （PolSAR）. First, the single, double and triple- bounce returns from each component of the bridge are distinguished by the polarization scattering features. Then the reasons which lead to the backscatter echoes oft_he bridge over water being displayed as stripes are analyzed, using a principle of microwave reflection, as well as an extraction method for each reflection return, and a parameter retrieval method is obtained. Finally, the parameters of the bridge, including the height （top and bottom surfaces of the sea bridge）, width, thickness, span, and height of the bridge tower, are retrieved using full polarimetric AIRSAR data. When a comparison of the measured data is completed, the results indicate that the proposed method can invert the parameters with a high accuracy, and that the inversion error of the bridge height （bottom surface） is only 1.3%. Moreover, the results also show that for the high-resolution SAR, the C and L-band images have the same ability in regards to parameter retrieval.

Research on Risk Management of Cross-Sea Bridges Based on Analytic Hierarchy Process—Taking Hangzhou Bay Bridge as an Example

Today, as the process of urbanization is accelerating, the country builds an extensive transportation network through bridges and roads, which facilitates the daily travel of the people and greatly promotes the development of the national economy. However, due to the cross-sea bridge spanning the bay, the overall scale, the complex construction environment, and the high technology content, the objective existence of risk factors in the construction process cannot be completely avoided. In the construction of cross-sea bridges, once a construction safety accident occurs, it will cause irreparable losses to the construction of the project. Taking Hangzhou Bay Bridge as an actual case, using the Analytic Hierarchy Process to identify possible risk factors during the life cycle of Hangzhou Bay Bridge, establish a corresponding risk evaluation system to evaluate the importance and probability of risk, and to rank the importance of risks, and control the corresponding construction risks by adopting measures such as risk transfer and risk retention. The research example shows that the project risk of the cross-sea bridge project can be combined with the analytic hierarchy process to identify, analyze and evaluate the importance of the various risks faced by the project, so as to adopt corresponding avoidance methods to reduce the project risk loss and achieve the project construction expectations Target.

Phylogenetic relationship,biogeography,and conservation genetics of endangered Fraxinus chiisanensis(Oleaceae),endemic to South Korea

Endemic plants are important for understanding phylogenetic relationships,biogeographical history,and genetic variation because of their restricted distribution and their role in conserving biodiversity.Here,we investigated the phylogenetic relationships of the Korean endemic Fraxinus chiisanensis by reconstructing the molecular phylogeny of Fraxinus based on two nuclear DNA(nrITS and phantastica)and two chloroplast DNA(psbA-trnH and rp132-trnL)regions.Within our fossil-calibrated phylogenetic framework,we also inferred the biogeographical history of F.chiisanensis.To provide a scientific basis for the conservation of F.chiisanensis,we determined the levels of genetic diversity and genetic differentiation in this species.Combining information from nuclear and chloroplast DNA sequence data,our molecular phylogenetic analyses identified F.chiisanensis as a genetically distinct unit from its sister group,Fraxinus platypoda from Japan.Our molecular dating analyses using nuclear and chloroplast DNA data sets show F.chiisanensis diverged from its sister F.platypoda in the Early or Middle Miocene and differentiated in the Late Miocene on the Korean Peninsula.Our results suggest that the divergence of F.chiisanensis was associated with the submergence of the East China Sea land bridge and enhanced monsoons in East Asia.When compared to F.platypoda,F.chiisanensis exhibits low genetic diversity within populations and high genetic differentiation among populations.These results help us to understand the evolutionary history of F.chiisanensis and to develop a conservation strategy for this species.