We investigate the use of non-linear constraints for geophysical inverse problems, with specific examples applied to source inversion of self-potential data. Typical regularization methods often produce smooth solutions by introducing a quadratic term in the objective function that minimizes the L2 norm of a low-order differential operator applied to the model. In some cases, however, the prope...

Surface-wave methods are widely used in earth sciences and engineering for the geometric characterization of geological bodies and tectonic structures of the subsurface. These techniques exploit the dispersive nature of Rayleigh waves to indirectly estimate shear wave velocity profiles from surface-wave measurements; however, they are limited to parallel-layered geometries. To overcome such lim...

We show that inversion symmetry breaking together with spin-orbit coupling leads to coupled spin and valley physics in monolayers of MoS2 and other group-VI dichalcogenides, making possible controls of spin and valley in these 2D materials. The spin-valley coupling at the valence-band edges suppresses spin and valley relaxation, as flip of each index alone is forbidden by the valley-contrasting...

INTRODUCTION To compare the diagnostic accuracy of contrast-enhanced 3D(dimensional) T1-weighted sampling perfection with application-optimized contrasts by using different flip angle evolutions (T1-SPACE), 2D fluid attenuated inversion recovery (FLAIR) images and 2D contrast-enhanced T1-weighted image in detection of leptomeningeal metastasis except for invasive procedures such as a CSF tappin...

We introduce 2D potential field migration for the interpretation of gravity gradiometry data. This method is based on a direct integral transformation of the observed gravity gradients into subsurface density distributions which can be used for realtime imaging or as an a priori model for subsequent 3D regularized inversion. Potential field migration is very fast and stable with respect to nois...

s, 28, 719–722. Commer, M., and G. Newman, 2008a, New advances in three-dimensional controlled source electromagnetic inversion: Geophysical Journal International, 172, no. 2, 513–535, doi:10.1111/j.1365-246X.2007.03663.x. ———, 2008b, Optimal conductivity reconstruction using three-dimensional joint and model-based inversion for controlled-source and magnetotelluric data: 78th Annual Internatio...

Given a rather general weight function n0, we derive a new cone beam transform inversion formula. The derivation is explicitly based on Grangeat’s formula (1990) and the classical 3D Radon transform inversion. The new formula is theoretically exact and is represented by a 2D integral. We show that if the source trajectory C is complete in the sense of Tuy (1983) (and satisfies two other very mi...

We describe the successful application of a new method to estimate permeability and permeability anisotropy from transient measurements of pressure acquired with a wireline straddle-packer formation tester. Unlike standard algorithms used for the interpretation of formation-tester measurements, the method developed in this paper incorporates the physics of two-phase immiscible flow as well as t...

Fluid flow in the vadose zone is governed by Richards equation; it is parameterized by hydraulic conductivity, which is a nonlinear function of pressure head. Investigations in the vadose zone typically require characterizing distributed hydraulic properties. Saturation or pressure head data may include direct measurements made from boreholes. Increasingly, proxy measurements from hydrogeophysi...

In this article we study the fan-beam Radon transform Dm of symmetrical solenoidal 2D tensor fields of arbitrary rank m in a unit disc D as the operator, acting from the object space L2(D;Sm) to the data space L2([0, 2π) × [0, 2π)). The orthogonal polynomial basis s (±m) n,k of solenoidal tensor fields on the disc D was built with the help of Zernike polynomials and then a singular value decomp...