Three-dimensional magnetotelluric modeling in the spherical and Cartesian coordinate systems:A comparative study

With the increase in the coverage area of magnetotelluric data,three-dimensional magnetotelluric modeling in spherical coordinates and its differences with respect to traditional Cartesian modeling have gradually attracted attention.To fully understand the influence of the Earth’s curvature and map projection deformations on Cartesian modeling,qualitative and quantitative analyses based on realistic three-dimensional models need to be examined.Combined with five representative map projections,a type of model conversion method that transforms the original spherical electrical conductivity model to Cartesian coordinates is described in this study.The apparent resistivity differences between the spherical western United States electrical conductivity model and the corresponding five Cartesian models are then compared.The results show that the cylindrical equal distance map projection has the smallest error.A meridian convergence correction resulting from the deformation of the map projection is introduced to rotate the Cartesian impedance tensor from grid north to geographic north,which reduces differences from the spherical results.On the basis of the magnetotelluric field data,the applicability of the Cartesian coordinate system to western and contiguous United States models is quantitatively evaluated.Precise interpretations of the contiguous United States model were found to require spherical coordinates.

Guest Editorial:Special Issue on Intelligent Interpretation of Remote Sensing Images: Theory, Methods and Applications

This special edition of the Journal of Geodesy and Geoinformation Science(JGGS)presents a curated selection of papers that offer novel techniques in the realm of intelligent interpretation of remote sensing images.In recent years,tremendous efforts have been made across a wide spectrum including theory,models,algorithms,applications and datasets,etc.Such advancements have demonstrated their stunning performance in a variety of remote sensing topics spanning from general challenges like remote image classification and object detection,to highly specialized tasks such as autonomous situation awareness and disaster response.Moreover,such achievements have redefined disciplinary boundaries and also reshaped our education.

Effects of Addition of Amino Acids or Soybean Phospholipid in Diet on Slaughter Performance and Meat Quality of Pigs

[Objectives]The study aims to discuss the effects of addition of arginine and glutamic acid or soybean phospholipid,vitamin E and yeast selenium in diet on the slaughter performance and meat quality of long(white)×large(York)binary hybrid pigs.[Methods]27 long×large castrated hybrid boars with the body weight of(54.4±0.15)kg were randomly divided into 3 groups,with 3 replicates per group and 3 pigs per replicate.Group A was the control group,in which the pigs were fed basal diet;in group B,0.8%arginine and 0.60%glutamate were added to the basal diet;in group C,75 g of soybean phospholipid,20 g of vitamin E and 8 g of yeast selenium were added to every 100 kg of the basal diet.The trial period was 60 d.After the experiment was ended,one test pig with similar body weight was selected from each replicate for slaughter and meat determination.[Results]The average weight gain and eye muscle area of the pigs in group B were significantly higher than those in group C(P<0.05),and also showed an increasing trend compared with group A,but there was no statistically significant difference(P>0.05);there was no significant difference between group B or C and group A in the average weight gain and eye muscle area(P>0.05).There was no significant difference in other slaughter performance between the three groups(P>0.05).Besides,there was also no significant difference in the content of various amino acids,total amino acids and total umami amino acids between the three groups(P>0.05).The inosine content in the longissimus dorsi muscle and muscle cooking loss of binary hybrid pigs in group C were significantly better than those in group B(P<0.05),and also had a tendency to be better than those in group A,but there was no significant difference(P>0.05);there was no significant difference between group B or C and group A in the inosine content and muscle cooking loss of the pigs(P>0.05).In addition,there was no significant difference in other meat traits and chemical composition of the longissimus dorsi muscle between group B or C and group A(P>0.05).[Conclusions]The addition of arginine and glutamic acid or soybean phospholipid,vitamin E and yeast selenium in diet had no significant effect on the growth rate,slaughter performance and meat traits of long×large binary hybrid pigs.

Multiscale anisotropic diffusion for ringing artifact suppression in geophysical deconvolution data

Ringing artifact degradations always appear in the deconvolution of geophysical data. To address this problem, we propose a postprocessing approach to suppress ringing artifacts that uses a novel anisotropic diffusion based on a stationary wavelet transform （SWT） algorithm. In this paper, we discuss the ringing artifact suppression problem and analyze the characteristics of the deconvolu- tion ringing artifact. The deconvolution data containing ringing artifacts are decomposed into different SWT sub- bands for analysis, and a new multiscale adaptive aniso- tropic filter is developed to suppress these degradations. Finally, we demonstrate the performance of the proposed method and describe the experiments in detail.

A regularized magnetotelluric inversion with a minimum support gradient constraint

Magnetotelluric(MT)inversion is an illposed problem and the standard way to address it is through regularization,by adding a stabilizing functional to the data objective functional in order to obtain a stable solution.The traditional stabilizing functionals,in which a low-order differential operator is used,yield a smooth solution that may not be appropriate when anomalies occur in block patterns.In some cases the focused imaging of a sharp electrical boundary is necessary.Even though various experiments have used stabilizing functionals that are suitable to obtain a clear and sharp boundary,such as the minimum support(MS)and the minimum gradient support(MGS)functionals,there are still some limitations in practice.In this paper,the minimum support gradient(MSG)is proposed as the stabilizing functional.Under the uniform regularization framework,a regularized inversion with a variety of stabilizing functionals is performed and the inversion results are compared.This study shows that MSG inversion can not only obtain a clearly focused inversion but also a quite stable and robust one.

酸性土壤下缓解大豆铝胁迫的研究进展

大豆是我国重要的油料作物,具有独特的营养成分,在我国各地区被广泛种植.铝毒是植物在酸性土壤环境中的重要胁迫因子,影响植物生长发育,具体表现为阻碍营养物质交换、引起细胞DNA损伤等.近年来,随着工业发展,我国土壤酸性不断增强,植物受铝胁迫影响日益加剧,大豆作为铝毒敏感作物,其生长、产量乃至品质受到极大的限制.因此,揭示铝离子对大豆生长发育的影响及大豆对铝胁迫的防御机制,对了解大豆耐铝性和治理大豆铝毒害具有重要意义.本文基于铝毒对大豆作用及大豆对铝胁迫的抗性机制两方面进行探究,综合分析酸性土壤下大豆根际的环境变化,列举缓解铝毒害的主要措施,并提出需要从分子生物学角度更进一步深入构建铝胁迫分子调控机制,为推进大豆耐铝性研究而努力,以期为该领域更深入的探索提供参考.

How to Effectively Prevent and Mitigate Geomagnetic Hazard?

Compared to well-known geological hazards such as earthquakes, volcanic eruptions, landslides, and mudslides, the concept of “geomagnetic hazards” is much less familiar to people. Geomagnetic hazards are intense disturbances in the Earth’ s magnetic field caused by solar flares, which can lead to geomagnetic storms. These storms ignite large geomagnetic induction currents and disrupt the global upper atmospheric and ionospheric environment.

A Goal-Oriented Adaptive Finite Element Method for 3D Resistivity Modeling Using Dual-Error Weighting Approach

A goal-oriented adaptive finite element（FE） method for solving 3D direct current（DC） resistivity modeling problem is presented. The model domain is subdivided into unstructured tetrahedral elements that allow for efficient local mesh refinement and flexible description of complex models. The elements that affect the solution at each receiver location are adaptively refined according to a goal-oriented posteriori error estimator using dual-error weighting approach. The FE method with adapting mesh can easily handle such structures at almost any level of complexity. The method is demonstrated on two synthetic resistivity models with analytical solutions and available results from integral equation method, so the errors can be quantified. The applicability of the numerical method is illustrated on a resistivity model with a topographic ridge. Numerical examples show that this method is flexible and accurate for geometrically complex situations.

A review on developments in the electrical structure of craton lithosphere

Cratons have a long history of evolution.In this paper,applications of the magnetotelluric method used in the study of craton lithosphere over the past 30 years were reviewed,examining case studies of cratons in North America,South America,Asia,Australia,and Africa.The nuclei of the Archean cratons,for example the Kalahari Craton and Rae Craton,are usually characterized by thick and highly resistive lithospheric roots.During or after the formation of the cratons,tectonothermal events,such as collision,mantle plume,and asthenosphere upwelling led to the formation of high-conductivity zones in the craton lithosphere,which could be attributed to the increased hydrogen content(of nominally anhydrous minerals),higher iron content,and formation of graphite films or sulfides along the grain boundary of minerals.These conductive zones are characterized by resistivity discontinuities in craton lithosphere.In particular,the conductive zones include(1)large-scale lithospheric mantle conductors beneath the Slave Craton,Gawler Craton,and central part of North China Craton(Trans-North China Orogen);(2)near-vertical high-conductivity zone associated with the fossil subduction zone beneath the Dharwar Craton and Slave Craton;and(3)regional lateral electrical discontinuities,such as a conductive anomaly under the Bushveld Complex of the Kaapvaal Craton.The eMoho refers to the electrical discontinuity in the crust-mantle boundary.In existing research,this has been detected under the condition of extremely high lithospheric resistivity with only a slight decrease in the lower crust,and in the case of a very thin conductive lower crust or the lack thereof.In the resistivity model,the unique"mushroom-like"lower crust-lithosphere mantle conductor and very thin lower crust layer of the North China Craton may represent lithosphere destruction and/or thinning.We also find that some of the cratons are still not well understood.Therefore,extensive three-dimensional inversion and joint interpretation of geochemical,geophysical,and geologic data are necessary to understand the tectonic evolutionary history of craton lithosphere.

3D finite-element modeling of Earth induced electromagnetic field and its potential applications for geomagnetic satellites

The accumulated large amount of satellite magnetic data strengthens our capability of resolving the electrical conductivity of Earth’s mantle.To invert these satellite magnetic data,accurate and efficient forward modeling solvers are needed.In this study,a new finite-element based forward modeling solver is developed to accurately and efficiently compute the induced electromagnetic field for a realistic 3D Earth.Firstly,the nodal-based finite element method with linear shape function on tetrahedral grid is used to assemble the final system of linear equations for the magnetic vector potential and electric scalar potential.The FGMRES solver with algebraic multigrid(AMG)preconditioner is used to quickly solve the final system of linear equations.The weighted moving least-square method is employed to accurately recover the electromagnetic field from the numerical solutions of magnetic vector and electric scalar potentials.Furthermore,a local mesh refinement technique is employed to improve the accuracy of the estimated electromagnetic field.At the end,two synthetic models are used to verify the accuracy and efficiency of our newly developed forward modeling solver.A realistic 3D Earth model is used to simulate the induced magnetic field at 450 and 200 km altitudes which are the planned flying altitudes of Macao’s geomagnetic satellites.The simulation indicates that(1)the amplitude of the mantle-induced magnetic field can reach 10–30 nT at 450 km altitude,which is 10–30%of the primary magnetic field.The induced magnetic field at 200 km altitude has larger amplitudes.These mantleinduced magnetic fields can be measured by Macao geomagnetic satellites;(2)the amplitude of the ocean-induced magnetic field can reach 5–30 nT at satellite altitudes,which needs to be carefully considered in the interpretation of satellite magnetic data.We are confident that our newly developed forward modeling solver will become a key tool for interpreting satellite magnetic data.