The three-dimensional ionospheric tomography (3DCIT) algorithm based on Global Navigation Satellite System (GNSS) observations have been developed into an effective tool for ionospheric monitoring in recent years. However, because the rays that come into or come out from the side of the inversion region cannot be used, the distribution of the rays in the edge and bottom part of the inversion region is scarce and the electron density cannot be effectively improved in the inversion process. We present a three-dimensional tomography algorithm with side rays (3DCIT-SR) applying the side rays to the inversion. The partial slant total electron content (STEC) of side rays in the inversion region is obtained based on the NeQuick2 model and GNSS-STEC. The simulation experiment results show that the algorithm can effectively improve the distribution of GNSS rays in the inversion region. Meanwhile, the iteration accuracy has also been significantly improved. After the same number of iterations, the iterative results of 3DCIT-SR are closer to the truth than 3DCIT, in particular, the inversion of the edge regions is improved noticeably. The GNSS data of the International GNSS Service (IGS) stations in Europe are used to perform real data experiments, and the inversion results show that the electron density profiles of 3DCIT-SR are closer to the ionosonde measurements. The accuracy improvement of 3DCIT-SR is up to 56.3% while the improvement is more obvious during the magnetic storm compared to the case of a calm ionospheric state . 相似文献
It is universally known that residual soils behave very differently from sedimentary soils. While the latter is widely known as cross-anisotropic, little is known regarding the strength anisotropy of residual soils. This study presents how the inherent anisotropy affects the strength of natural granite residual soils under generalized conditions, where intact specimens were carefully prepared and sheared under triaxial compression, extension, simple shear, and hollow cylinder torsional shear tests. The strength of natural residual soil, in terms of ultimate stress ratio M and undrained shear strength Su, is found to be significantly anisotropic in a different way from normally consolidated clays with the maximum strength obtained under triaxial compression and the minimum under simple shear or at intermediate principal stress direction. As a result, the existing method failed to measure the anisotropy degree of the studied soil. Two parameters were proposed accordingly to quantify the anisotropic strength under general conditions, taking the special strength anisotropy pattern and cohesive-frictional nature of GRS into account. The proposed parameters enable the direct comparison of strength anisotropy among soils. This study serves as a data set to better understand residual soils regarding their anisotropic behaviors under generalized conditions. Although specific to granite residual soils in China, this study is expected to be more widely applicable to other weathered geomaterials.
How supermassive black holes(SMBHs) are spun-up is a key issue in modern astrophysics. As an extension to the study in Wang et al., here we address the issue by comparing the host galaxy properties of nearby(z 0.05) radio-selected Seyfert 2 galaxies. With the two-dimensional bulge+disk decompositions for the SDSS r-band images, we identify a dichotomy in various host galaxy properties for radio-loud SMBHs. By assuming that radio emission from the jet reflects a high SMBH spin, which stems from the well-known Blandford-Znajek mechanism of jet production, high-mass SMBHs(i.e., MBH 107.9 M⊙)have a preference for being spun-up in classical bulges, and low-mass SMBHs(i.e., MBH = 106-107 M⊙)in pseudo-bulges. This dichotomy suggests and confirms that high-mass and low-mass SMBHs are spun-up in different ways, i.e., a major "dry" merger and a secular evolution respectively. 相似文献