@article{heidari_guddati_2007, title={Novel finite-element-based subsurface imaging algorithms}, volume={43}, ISSN={["1872-6925"]}, DOI={10.1016/j.finel.2006.11.007}, abstractNote={Through an unconventional use of the finite-element method, we have developed a new class of wave equation-based subsurface imaging algorithms. These methods, which are based on the recently developed arbitrarily wide-angle wave equations (AWWE) [M.N. Guddati, Arbitrarily wide-angle wave equations for complex media, Comput. Methods Appl. Mech. Eng. 195(1–3), 63–93], employ the finite-element concepts not just to solve, but to derive the governing equations of the imaging problem. The authors have successfully applied the AWWE imaging algorithms to both acoustic and elastic media. These implementations of AWWE imaging algorithms are discussed here, and the role of finite elements in their derivation is depicted. The stability of the AWWE imaging methods is analytically studied, and their accuracy is shown through numerical impulse responses. Finally, the effectiveness of the methods is illustrated using various synthetic problems for both acoustic and elastic media.}, number={5}, journal={FINITE ELEMENTS IN ANALYSIS AND DESIGN}, author={Heidari, A. H. and Guddati, M. N.}, year={2007}, month={Mar}, pages={411–422} }
 @article{guddati_heidari_2007, title={Subsurface imaging via fully coupled elastic wavefield extrapolation}, volume={23}, ISSN={["1361-6420"]}, DOI={10.1088/0266-5611/23/1/004}, abstractNote={We develop a new space-domain wavefield extrapolation technique for subsurface imaging in heterogeneous elastic media. Unlike the existing space-domain techniques, which separately propagate pressure and shear waves, the proposed method simulates one-way propagation with strong coupling between the pressure and shear waves, thus resulting in more accurate images. This is achieved by combining downward continuation ideas with the concepts of the recently developed arbitrarily wide-angle wave equations (Guddati M N 2006 Comput. Methods Appl. Mech. Eng. 195 63–93). In this method, one-way propagation is modelled by attaching a virtual halfspace to each depth step, which is represented by special complex-length finite elements. The parameters of the method, namely the lengths of the special finite elements, are chosen such that the wavefield extrapolation is stable and accurate. The accuracy of the proposed method is illustrated by its impulse response, which accurately captures the pressure, shear and head wave fronts. Application to various synthetic imaging problems, in both homogeneous and heterogeneous domains, further confirms the effectiveness of the method.}, number={1}, journal={INVERSE PROBLEMS}, author={Guddati, Murthy N. and Heidari, A. Homayoun}, year={2007}, month={Feb}, pages={73–98} }
 @article{underwood_heidari_guddati_kim_2005, title={Experimental Investigation of Anisotropy in Asphalt Concrete}, volume={1929}, ISBN={["0-309-09403-8"]}, ISSN={0361-1981 2169-4052}, url={http://dx.doi.org/10.1177/0361198105192900128}, DOI={10.3141/1929-28}, abstractNote={Accurate multiaxial characterization of asphalt concrete requires a thorough understanding of its anisotropic behavior. For that purpose a study has been conducted to examine the anisotropic properties of asphalt concrete in the linear viscoelastic range, with growing damage, and during volumetric deformation. Tests were conducted on specimens cored in the vertical and horizontal directions from gyratory-compacted specimens. Anisotropy was found to have no effect on the linear viscoelastic properties of the material. This finding is supported by subsequent results from monotonic constant crosshead rate uniaxial tension and uniaxial compression tests. It was also found that anisotropy contributes greatly to the behavior of asphalt concrete in compression, but shows little, if any, effect on tensile properties. In addition, the strong dependence of anisotropy on temperature and strain rate is presented. Finally, promising results from a simplified method of extracting the anisotropic behavior of asphalt concrete with the use of the hydrostatic test are also introduced.}, number={1}, journal={Transportation Research Record: Journal of the Transportation Research Board}, publisher={SAGE Publications}, author={Underwood, Shane and Heidari, A. Homayoun and Guddati, Murthy and Kim, Y. Richard}, year={2005}, month={Jan}, pages={238–247} }
 @article{guddati_heidari_2005, title={Migration with arbitrarily wide-angle wave equations}, volume={70}, ISSN={["1942-2156"]}, DOI={10.1190/1.1925747}, abstractNote={We develop a new scalar migration technique that is highly accurate for imaging steep dips in heterogeneous media. This method is based on arbitrarily wide-angle wave equations (AWWEs) that are highly accurate space-domain one-way wave equations and have a form similar to the 15° equation. The accuracy of the proposed method is increased by introducing auxiliary variables, as well as adjusting the parameters of the approximation. Poststack migration is carried out by downward continuation using the AWWE, for which we have developed a stable, explicit, double-marching scheme. Up to 80° accuracy is achieved by second-order AWWE migration with only 2.3 times the computational effort of the 15° equation and requiring almost the same storage. We illustrate the performance of AWWE migration using impulse-response graphs, a single-dipping reflector, and a slice of the SEG/EAGE salt model.}, number={3}, journal={GEOPHYSICS}, author={Guddati, MN and Heidari, AH}, year={2005}, pages={S61–S70} }