Sparse flight spotlight mode 3-D imaging of spaceborne SAR based on sparse spectrum and principal component analysis

The spaceborne synthetic aperture radar(SAR)sparse flight 3-D imaging technology through multiple observations of the cross-track direction is designed to form the cross-track equivalent aperture,and achieve the third dimensionality recognition.In this paper,combined with the actual triple star orbits,a sparse flight spaceborne SAR 3-D imaging method based on the sparse spectrum of interferometry and the principal component analysis(PCA)is presented.Firstly,interferometric processing is utilized to reach an effective sparse representation of radar images in the frequency domain.Secondly,as a method with simple principle and fast calculation,the PCA is introduced to extract the main features of the image spectrum according to its principal characteristics.Finally,the 3-D image can be obtained by inverse transformation of the reconstructed spectrum by the PCA.The simulation results of 4.84 km equivalent cross-track aperture and corresponding 1.78 m cross-track resolution verify the effective suppression of this method on high-frequency sidelobe noise introduced by sparse flight with a sparsity of 49%and random noise introduced by the receiver.Meanwhile,due to the influence of orbit distribution of the actual triple star orbits,the simulation results of the sparse flight with the 7-bit Barker code orbits are given as a comparison and reference to illuminate the significance of orbit distribution for this reconstruction results.This method has prospects for sparse flight 3-D imaging in high latitude areas for its short revisit period.

A TENSOR ANALYSIS METHOD FOR ESTIMATING 3-D MOTION PARAMETERS

By using the center projection image sequence to estimate 3-D motion parameters,one needs to know the corresponding relationship between the feature of motion object in spaceand the projection coordinate on image plane.In order to avoid using the relationship of featurecorrespondence,the tensor analysis method in the affine transformation system is presented,andthe simulation data of experimental results are given.

SAR tomography imaging via higher-order spectrum analysis

To deal with the non-Caussian noise in standard 2-D SAR images, the deramped signal in imaging plane, and the possible symmetric distribution of complex noise, the fourth-order cumulant of complex process is introduced into SAR tomography. With the estimated AR parameters of ARMA model of noise through Yule-Walker equation, the signal series of height is pre-filtered. Then, through ESPRIT, the spectrum is obtained and the aperture in height direction is synthesized. Finally, the SAR tomography imaging of scene is achieved. The results of processing on signal with non-Gaussian noise demonstrate the robustness of the proposed method. The tomography imaging of the scenes shows that the higher-order spectrum analysis is feasible in the application.

3-D Modelling of the Confederation Bridge Using Data of Full Scale Tests

Long-span bridges are special structures that require advanced analysis techniques to examine their performance. This paper presents a procedure developed to model the Confederation Bridge using 3-D beam elements. The model was validated using the data collected before the opening of the bridge to the public. The bridge was instrumented to conduct fullscale static and dynamic tests. The static tests were to measure the deflection of the bridge pier while the dynamic tests to measure the free vibrations of the pier due to a sudden release of the static load. Confederation Bridge is one of the longest reinforced concrete bridges in the world. It connects the province of Prince Edward Island and the province of New Brunswick in Canada. Due to its strategic location and vital role as a transportation link between these two provinces, it was designed using higher safety factors than those for typical highway bridges. After validating the present numerical model, a procedure was developed to evaluate the performance of similar bridges subjected to traffic and seismic loads. It is of interest to note that the foundation stiffness and the modulus of elasticity of the concrete have significant effects on the structural responses of the Confederation Bridge.

基于动力沟道追踪的地下流体运移预测方法初步研究

地下流体的分布运移预测既是重要的科学问题,又是重要的应用技术问题。作者提出并发展了基于地震图像分析与动力沟道追踪的地下流体运移预测方法。该方法包括两个主要的步骤:(1)由三维地震振幅数据进行岩石裂缝预测,然后据此构造岩石的视渗透率模型;(2)假设地下流体在压力的驱使下主要沿连通的裂缝系统迁移,通过引入假想的源(与汇),以总阻力最小为准则进行流体迁移路径的动力沟道追踪。该文介绍了所提方法的思路与步骤,给出了流体迁移动力沟道追踪的离散格式、追踪准则及数值实验结果。

Tomographic determination of the upper crustal structure in the Jiashi strong earthquake swarm region

A three-dimensional temporary seismic transmission array was arranged in a 50x60 km2 region around Jiashi strong earthquake swarm to receive seismic waves generated by 8 fires from different azimuths. With the inversion method without model blocks and using P and S reflections from Moho at critical distances, the 3-D images of P, S velocity perturbation and ratio vP/vS perturbation of the upper crust under the seismic array were reconstructed. Meanwhile, the seismicity of the Jiashi earthquake swarm was taken into consideration in the analysis of the seismogenesis. The results indicate that the upper crustal structure under the Jiashi strong earthquake swarm region is characterized by significant inhomogeneity both laterally and vertically. From 12 km depth, it is clear that there is an NNW-oriented high P-wave velocity anomalous body corresponding to the epicenter of the swarm with low-velocity anomaly around it, which is the direct cause of the strong earthquakes. High vP/vS is distributed in the same location, which may indicate the decline of shear strength of the source region owing to relative softness of the medium, this can be accounted as an explanation for the seismicity feature of the Jiashi strong earthquake swarm.