Grantee Research Project Results
1999 Progress Report: Geophysical Sensing in Environmental Applications: Efficient Numerical Simulations
EPA Grant Number: R825225Title: Geophysical Sensing in Environmental Applications: Efficient Numerical Simulations
Investigators: Liu, Qing-Huo
Institution: New Mexico State University - Main Campus
EPA Project Officer: Hahn, Intaek
Project Period: November 21, 1996 through September 20, 2001
Project Period Covered by this Report: November 21, 1998 through September 20, 1999
Project Amount: $500,000
RFA: Exploratory Research - Early Career Awards (1996) RFA Text | Recipients Lists
Research Category: Early Career Awards
Objective:
The objective of this research is to develop efficient forward and inverse techniques to model electromagnetic and acoustic problems in environmental geophysical sensing. Specifically, fast forward and inverse computer models will be developed for electrical resistance tomography (ERT), electromagnetic induction (EMI), radio imaging methods (RIM), ground-penetrating radar (GPR), surface seismic reflection, and borehole seismic imaging measurements in three-dimensional inhomogeneous media.Progress Summary:
During the past 12 months, we concentrated on three-dimensional simulations with the numerical mode-matching (NMM) method for electrical resistance measurements, one- and two-dimensional conjugate-gradient fast-Fourier transform (CG-FFT) method for EMI and RIM, three-dimensional finite-difference time-domain (FDTD) and pseudospectral time-domain (PSTD) methods for the GPR, and three-dimensional perfectly matched layer (PML)/FDTD method for elastic wave propagation. Our accomplishments are summarized below.1. Three-Dimensional NMM. The NMM method for the three-dimensional simulations of electrode-type resistivity measurements has been developed. Previously, the NMM method has been demonstrated to be a very efficient numerical method for two-dimensional problems. This is the first NMM method applied to three-dimensional problems where the advantages of the method over the conventional finite-element method is even more profound than the two-dimensional problems. The three-dimensional problem is solved through the eigenmode expansion of a series of two-dimensional problems. The expansion coefficients, expressed in terms of the local and global reflection and transmission matrices, are then efficiently obtained by a recursive scheme. The computer software is already developed and validated. We have confirmed that the three-dimensional NMM method can save a large amount of computer memory and CPU time for borehole measurements. A conference paper on the three-dimensional NMM method has been accepted and a full paper is in preparation.
2. CG-FFT and CG-NUFFT Methods. Traditionally, the integral equations for electromagnetic and acoustic waves have been solved by the method of moment (MOM) via a matrix equation solution. Although flexible and accurate for small-scale problems, the MOM has a high computational complexity and requires a large amount of computer memory and prohibitively large amount of CPU time for large-scale problems. To overcome this limitation, we have developed one- and two-dimensional methods combining the conjugate-gradient procedures and fast Fourier transform. In the CG-FFT method, because there is no need to fill a matrix as in the MOM method, the computer memory requirement is substantially reduced. Furthermore, the matrix inversion is replaced by an iterative conjugate-gradient method. The matrix-vector multiply in the CG iterations is achieved by using the FFT. As a result, the CG-FFT method greatly reduces the computer memory and computation time for integral equations. To further improve the method, we have combined the CG method with our newly developed nonuniform fast-Fourier transform (NUFFT) algorithm. This CG-NUFFT method overcomes the limitation of a uniform grid in the CG-FFT method.
3. New Applications of the PML, FDTD, and PSTD Methods. Based on our previous results on the PML, FDTD, and PSTD methods, new applications have been developed: (a) FDTD and PSTD for ground-penetrating radar in a dispersive earth; (b) electromagnetic waves in a plasma medium; (c) PSTD for electromagnetic waves in anisotropic media; and (d) PML and FDTD for elastic waves in cylindrical and spherical coordinates.
4. NUFFT Algorithms and Other New Fast Transform Algorithms. We have furthered our algorithms for the fast Fourier transform of nonuniformly sampled data NUFFT) and their applications. Conventional FFT algorithms apply only to uniformly sampled data. However, many applications involve nonuniformly sampled data. The NUFFT algorithms have far-reaching applications in computational electromagnetics, acoustics, and signal processing. The new applications of the NUFFT algorithms include the nonuniform fast Hankel transform (NUFHT) and nonuniform fast cosine transform (NUFCT) algorithms. These new applications are important for problems with an axial symmetry and for the Chebyshev PSTD method.
Future Activities:
Continue our research in the validation and improvement of computer programs for the forward modeling ERT, EMI, RIM, and seismic measurements. Develop inverse solvers for these measurements. Compare the simulations with field measurements. Attend conferences to present results from this research project.Journal Articles on this Report : 21 Displayed | Download in RIS Format
| Other project views: | All 54 publications | 24 publications in selected types | All 24 journal articles |
|---|
| Type | Citation | ||
|---|---|---|---|
|
|
Chang C, Liu Q-H. Inversion of source-time functions using borehole array sonic waveforms. Journal of the Acoustical Society of America 1998;103(6):3163-3168. |
R825225 (1997) R825225 (1999) |
Exit |
|
|
Chen Y-H, Chew WC, Liu Q-H. A three-dimensional finite difference code for the modeling of sonic logging tools. Journal of the Acoustical Society of America 1998;103(2):702-712. |
R825225 (1997) R825225 (1999) |
Exit |
|
|
Fan G-X, Liu QH. Pseudospectral time-domain algorithm applied to electromagnetic scattering from electrically large objects. Microwave and Optical Technology Letters 2001;29(2):123-125. |
R825225 (1999) |
Exit |
|
|
Fan G-X, Liu QH, Hutchinson SA. FDTD and PSTD simulations for plasma applications. IEEE Transactions on Plasma Science 2001;29(2):341-348. |
R825225 (1999) |
Exit |
|
|
Fan G-X, Liu QH. Dyadic Green's functions for curved waveguides and cavities and their reformulation. Radio Science 2002;37(5):11-1–11-10. |
R825225 (1999) |
Exit Exit Exit |
|
|
Fan G-X, Liu QH. A PML-FDTD algorithm for simulating plasma-covered cavity-backed slot antennas. Microwave and Optical Technology Letters 1998;19(4):258-262. |
R825225 (1997) R825225 (1999) |
Exit |
|
|
He J-Q, Liu QH. A nonuniform cylindrical FDTD algorithm with improved PML and quasi-PML absorbing boundary conditions. IEEE Transactions on Geoscience and Remote Sensing 1999;37(2):1066-1072. |
R825225 (1999) |
Exit |
|
|
Liu QH. An FDTD algorithm with perfectly matched layers for conductive media. Microwave and Optical Technology Letters 1997;14(2):134-137. |
R825225 (1997) R825225 (1999) |
Exit |
|
|
Liu QH, Nguyen N. An accurate algorithm for nonuniform fast Fourier transforms (NUFFT's). IEEE Microwave and Guided Wave Letters 1998;8(1):18-20. |
R825225 (1997) R825225 (1999) |
Exit |
|
|
Liu QH. The pseudospectral time-domain (PSTD) algorithm for acoustic waves in absorptive media. IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control 1998;45(4):1044-1055. |
R825225 (1997) R825225 (1999) |
Exit |
|
|
Liu QH, He JQ. Quasi-PML for waves in cylindrical coordinates. Microwave and Optical Technology Letters 1998;19(2):107-111. |
R825225 (1997) R825225 (1999) |
Exit |
|
|
Liu QH, Tang XY. Iterative algorithm for nonuniform inverse fast Fourier transform (NU-IFFT). Electronics Letters 1998;34(20):1913-1914. |
R825225 (1997) R825225 (1999) |
Exit |
|
|
Liu QH. Some current trends in numerical methods for transient acoustic and elastic waves in multidimensional inhomogeneous media. Current Topics in Acoustical Research 1998;2:31-42. |
R825225 (1997) R825225 (1999) |
Exit |
|
|
Liu QH. Perfectly matched layers for elastic waves in cylindrical and spherical coordinates. Journal of the Acoustical Society of America 1999;105(4):2075-2084. |
R825225 (1999) |
Exit |
|
|
Liu QH, Fan G-X. A frequency-dependent PSTD algorithm for general dispersive media. IEEE Microwave and Guided Wave Letters 1999;9(2):51-53. |
R825225 (1999) |
Exit |
|
|
Liu QH. PML and PSTD algorithm for arbitrary lossy anisotropic media. IEEE Microwave and Guided Wave Letters 1999;9(2):48-50. |
R825225 (1999) |
Exit |
|
|
Liu QH. Large-scale simulations of electromagnetic and acoustic measurements using the pseudospectral time-domain (PSTD) algorithm. IEEE Transactions on Geoscience and Remote Sensing 1999;37(2):917-926. |
R825225 (1999) |
Exit |
|
|
Liu QH, Zhang ZQ. Nonuniform fast Hankel transform (NUFHT) algorithm. Applied Optics 1999;38(32):6705-6708. |
R825225 (1999) |
Exit |
|
|
Liu QH, Fan G-X. Simulations of GPR in dispersive media using a frequency-dependent PSTD algorithm. IEEE Transactions on Geoscience and Remote Sensing 1999;37(5):2317-2324. |
R825225 (1999) R825216 (2000) |
Exit |
|
|
Liu QH, He JQ. An efficient PSTD algorithm for cylindrical coordinates. IEEE Transactions on Antennas and Propagation 2001;49(9):1349-1351. |
R825225 (1999) |
Exit |
|
|
Liu Q-H, Sinha BK. Multipole acoustic waveforms in fluid-filled boreholes in biaxially stressed formations: a finite-difference method. Geophysics 2000;65(1):190-201. |
R825225 (1999) |
Exit |
Supplemental Keywords:
integrated assessment, remediation, cleanup, restoration, engineering, modeling, monitoring, remote sensing, Scientific Discipline, Waste, Remediation, Physics, Geology, Engineering, Environmental Engineering, nonlinear inverse problems, surface seismic reflection, electromagnetic induction, electromagnetic sensors, acoustic sensors, numerical simulations, electrical resistance tomography, assessment methods, computer modeling programs, ecology assessment models, geophysical sensingProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.