المؤلفون: Morgenstern, Charles O.

المساهمون: Ganesh, Mahadevan, Tilton, Nils, Tenorio, Luis, Porter, Aaron T.

مصطلحات موضوعية: boundary element method, finite element method, high-order, indefinite systems, iterative methods, wave propagation

الوصف: Includes bibliographical references. ; 2016 Summer. ; Understanding the propagation of waves using computer models is important for several applications. Major challenges for developing efficient wave propagation computer models include incorporating heterogeneous and unbounded wave propagation media, and high-frequency data. Such models lead to very large and poorly conditioned indefinite linear systems. The main focus of this thesis is to address these challenges through several mathematical and high-performance computing techniques. Our novel algorithms include developing and implementing unbounded heterogeneous media models using a hybrid of finite element and boundary element methods (FEM/BEMs). For incorporating heterogeneous media, high-frequency input data, and hybrid models, large scale simulations are needed in conjunction with iterative methods for indefinite systems. We develop efficient computer models through innovative preconditioned iterative high-order FEMs. Our implementation includes multigrid and domain decomposition algorithms, and multiple- and high-frequency simulations in two- and three-dimensional heterogeneous media with non-smooth and curved boundaries. Indefiniteness is a major computational bottleneck for wave propagation models that have been investigated for several decades. In addition to our efficient methods for the standard indefinite systems, we develop, analyze, and implement a new class of sign-definite high-order preconditioned wave propagation computer models. Our sign-definite iterative models require a small number of iterations which is independent of the frequency of the wave propagation. We demonstrate our many novel algorithms developed in this thesis using high-performance parallel computing implementations.

وصف الملف: born digital; doctoral dissertations; application/pdf

العلاقة: 2016 - Mines Theses & Dissertations; T 8089; http://hdl.handle.net/11124/170316Test

الإتاحة: http://hdl.handle.net/11124/170316Test

المؤلفون: Dworzak, Bradley

المساهمون: Ganesh, Mahadevan, Porter, Aaron T., Ahrens, Cory

مصطلحات موضوعية: computer model, inverse, wave propagation, far-field, acoustics, location

الوصف: 2015 Fall. ; Includes illustrations (some color). ; Includes bibliographical references. ; This research is centered around improving and developing forward and inverse models to characterize a class of wave scattering configurations. The improvement is based on a project suggested by a group (P-23) at the Los Alamos National Laboratory (LANL). The scattering configuration is determined by a set of parameters. The main aim of the project is to develop data oriented forward and associated efficient inverse wave configuration parameter estimation algorithms. A key constraint associated with the project is that the input data is from a single incident wave impinging on the configuration. Based on a set of LANL experiments, the LANL group developed a preliminary configuration parameter estimation model by making strong assumptions about the experimentally determined configurations. The initial LANL model is based on the assumption that all particles in a dynamic blast configuration have the same simple (spherical) shape and also that the wave interaction between particles is weak. Such assumptions are not practical for the experimental data, leading to the research project investigated in this report. The main components of this research comprise the following: (i) Develop a forward computer model for multiple particle wave propagation that allow various shapes and material properties to facilitate collection of synthetic data from general configurations. (ii) Using the synthetic data, quantify the validity of the preliminary LANL inversion model. (iii) Develop an efficient inversion model to characterize an associated class of configurations. We achieve the objectives in our research by first implementing a high-order algorithm and developing a high performance computing (HPC) code for generating synthetic data for various configurations. The forward algorithm is based on an efficient non-polynomial finite element method that facilitates data generation from configurations with smooth and non-smooth particles. Then ...

وصف الملف: born digital; masters theses; application/pdf

العلاقة: 2015 - Mines Theses & Dissertations; T 7883; http://hdl.handle.net/11124/20324Test

الإتاحة: http://hdl.handle.net/11124/20324Test

المؤلفون: Lee, En Jui, Chen, Po, Jordan, Thomas H., Wang, L.

المصدر: Geology and Geophysics Faculty Publications

مصطلحات موضوعية: Computational seismology, Early warning, Earthquake ground motions, Earthquake source observations, Probability distributions, Wave propagation

الوصف: ©2011 The Authors. Geophysical Journal International ©2011 RAS. ; A central problem of seismology is the inversion of regional waveform data for models of earthquake sources. In regions such as Southern California, preliminary 3-D earth structure models are already available, and efficient numerical methods have been developed for 3-D anelastic wave-propagation simulations. We describe an automated procedure that utilizes these capabilities to derive centroid moment tensors (CMTs). The procedure relies on the use of receiver-side Green's tensors (RGTs), which comprise the spatial-temporal displacements produced by the three orthogonal unit impulsive point forces acting at the receivers. We have constructed a RGT database for 219 broad-band stations in Southern California using a tomographically improved version of the 3-D SCEC Community Velocity Model Version 4.0 (CVM4) and a staggered-grid finite-difference code. Finite-difference synthetic seismograms for any earthquake in our modelling volume can be simply calculated by extracting a small, source-centred volume from the RGT database and applying the reciprocity principle. The partial derivatives needed for the CMT inversion can be generated in the same way. We have developed an automated algorithm that combines a grid-search for suitable focal mechanisms and hypocentre locations with a Gauss-Newton optimization that further refines the grid-search results. Using this algorithm, we have determined CMT solutions for 165 small to medium-sized earthquakes in Southern California. Preliminary comparison with the CMT solutions provided by the Southern California Seismic Network (SCSN) shows that our solutions generally provide better fit to the observed waveforms. When applied to a large number of earthquakes, our algorithm may provide a more robust CMT catalogue for earthquakes in Southern California.

وصف الملف: application/pdf

العلاقة: Faculty Publication - Geology & Geophysics; https://hdl.handle.net/20.500.11919/1177Test

الإتاحة: https://doi.org/20.500.11919/1177Test
https://doi.org/10.1111/j.1365-246X.2011.05031.xTest
https://hdl.handle.net/20.500.11919/1177Test

المؤلفون: Van Avendonk, Harm J. A., Holbrook, W. Steven, Lizarralde, Daniel, Mora, Mauricio M., Harder, Steven H., Bullock, Andrew D., Alvarado, Guillermo E., Ramírez, Carlos J.

المصدر: Geology and Geophysics Faculty Publications

مصطلحات موضوعية: Body waves, Continental margins: convergent, Controlled source seismology, Subduction zone processes, Wave propagation

الوصف: ©2010 The Authors Journal compilation ©2010 RAS. ; In the 2005 TICOCAVA explosion seismology study in Costa Rica, we observed crustal turning waves with a dominant frequency of ~10 Hz on a linear array of short-period seismometers from the Pacific Ocean to the Caribbean Sea. On one of the shot records, from Shot 21 in the backarc of the Cordillera Central, we also observed two seismic phases with an unusually high dominant frequency (~20 Hz). These two phases were recorded in the forearc region of central Costa Rica and arrived ~7 s apart and 30-40 s after the detonation of Shot 21. We considered the possibility that these secondary arrivals were produced by a local earthquake that may have happened during the active-source seismic experiment. Such high-frequency phases following Shot 21 were not recorded after Shots 22, 23 and 24, all in the backarc of Costa Rica, which might suggest that they were produced by some other source. However, earthquake dislocation models cannot produce seismic waves of such high frequency with significant amplitude. In addition, we would have expected to see more arrivals from such an earthquake on other seismic stations in central Costa Rica. We therefore investigate whether the high-frequency arrivals may be the result of a deep seismic reflection from the subducting Cocos Plate. The timing of these phases is consistent with a shear wave from Shot 21 that was reflected as a compressional (S×P) and a shear (S×S) wave at the top of the subducting Cocos slab between 35 and 55 km depth. The shift in dominant frequency from ~10 Hz in the downgoing seismic wave to ~20 Hz in the reflected waves requires a particular seismic structure at the interface between the subducting slab and the forearc mantle to produce a substantial increase in reflection coefficients with frequency. The spectral amplitude characteristics of the S×P and S×S phases from Shot 21 are consistent with a very high Vp/Vs ratio of 6 in ~5 m thick, slab-parallel layers. This result suggests that a system of thin shear ...

وصف الملف: application/pdf

العلاقة: Faculty Publication - Geology & Geophysics; https://hdl.handle.net/20.500.11919/1187Test

الإتاحة: https://doi.org/20.500.11919/1187Test
https://doi.org/10.1111/j.1365-246X.2010.04552.xTest
https://hdl.handle.net/20.500.11919/1187Test

المؤلفون: Meischner, Peter F., author, Hagen, Martin, author, Bringi, V. N., author, Vivekanandan, J., author, IEEE, publisher

مصطلحات موضوعية: remote sensing by radar, tropospheric electromagnetic wave propagation, clouds, polarimetry, storms, radiowave propagation, remote sensing

الوصف: Single scattering properties of ice crystals are described at microwave frequencies using discrete dipole approximations and Rayleigh scattering techniques. For a given shape, the average bulk densities of ice crystals can be estimated using the ratio of the copolarized radar signal in a linear (horizontal, vertical) polarization basis. Reflectivity depends on the ice content (g • m-3), and also on both size distribution parameters and average bulk density of the scatterers. Differential propagation phase is primarily a function of shape, ice water content, and is independent of size distribution parameters. Thus, by using a combination of polarimetric radar measurements, average ice content, bulk density, and shape of distributed scatterers can be inferred. These techniques become quite complex in the case of a winter storm where scatterers can exist with varying shape and bulk densities. Polarimetric radar properties of such complex distributed scatterers are modeled. Physical variations in the relation among ice water content, reflectivity, and differential propagation phase are considered with respect to change in the shape of size distribution, bulk density, and average shape of the scatterers. Also, simultaneous polarimetric radar observations and in situ aircraft measurements are shown to demonstrate practical applicability of the techniques. ; This work was supported under FAA Contract DTFA01-90-Z-02005. The work of J. Vivekanandan and V. N. Bringi was supported by the National Science Foundation under Grants ATM-8915141 and ATM-9214864.

وصف الملف: born digital; articles; application/pdf

العلاقة: Faculty Publications; Vivekanandan, J., et al., Polarimetric Radar Studies of Atmospheric Ice Particles, IEEE Transactions on Geoscience and Remote Sensing 32, no. 1 (January 1994): 1-10.; http://hdl.handle.net/10217/1546Test

الإتاحة: http://hdl.handle.net/10217/1546Test

المؤلفون: Deng Yi, author, Ebert-Uphoff, Imme, author

مصطلحات موضوعية: large-scale atmospheric waves, graph of information flow, wave source, wave propagation, causal discovery, spatial, climate

الوصف: September 3, 2014. ; Causal discovery algorithms have recently been applied to several climate applications. In particular, in prior work we have developed methods to recover pathways of interaction in the global climate system, using the classic PC algorithm. However, standard implementations of the PC algorithm cannot handle the large number of variables and temporal models required for this application. This technical report shows that a more efficient implementation of the PC algorithm can provide speed gains of a factor of 1,000 or more. This in turn enables us to calculate graphs of information flow with much higher resolution grids. Furthermore, we can now - for the first time ever - calculate information flow graphs that extend over three dimensions, i.e. rather than just including one layer of the planet's atmosphere we can now capture interactions across several height layers.

وصف الملف: born digital; reports; application/pdf

العلاقة: Faculty Publications; Technical report (Colorado State University. Department of Electrical and Computer Engineering), Report Nr. CSU-ECE-2014-1; http://hdl.handle.net/10217/83709Test

الإتاحة: http://hdl.handle.net/10217/83709Test

المؤلفون: Steinecker, Simone

المساهمون: Eustes, Alfred William, Miller, Mark G., Tutuncu, Azra, Bratton, Tom

مصطلحات موضوعية: Shale gas, Boring, Gas wells, Regression analysis, Elastic wave propagation

الوصف: 2014 Spring. ; Includes illustrations (some color), color maps. ; Includes bibliographical references (pages 98-101). ; Recent economic developments of the US gas market and enhanced technological improvements lead towards an increase of future operations in the sector of shale gas plays. The Eagle Ford field in Texas, being amongst the youngest US shale plays, serves as a good example of how correlating recorded real-time surface drilling parameters and well log data can be used to improve reservoir characterization. Variations of properties occurring horizontally and vertically, across the entire play or even along the wellbore are regarded as a major challenge directly affecting the economic development of shale gas reservoirs. An enormous amount of data is collected at present but not analyzed and evaluated in detail. Instead the trend is evolving that more data is generated, resulting in the incapability to integrate the data. Regression analysis is used to determine quantitative relationships between a real-time surface drilling parameter and petrophysical logging data for wells located in the same geographic and geologic area. This research describes how the rate of penetration correlates with the gamma and acoustic log (slowness of elastic waves) for the predominant shale section of each well and how the regression outputs contribute to optimize reservoir characterization. Within the shale formation, the gamma log (GR) shows a good correlation with the rate of penetration. Information from mudlogs and daily drilling reports is used to identify possible reasons for misfits between the actual and the calculated rate of penetration. Studying a defined set of data in depth has proven to be a reliable indicator for comparing and categorizing wells. The results depict similarities and differences amongst the wells based on the properties of the formation they were drilled in. It is expected that additional real-time surface drilling parameters besides the rate of penetration are useful to obtain improved ...

وصف الملف: born digital; masters theses; application/pdf

العلاقة: 2014 - Mines Theses & Dissertations; T 7433; http://hdl.handle.net/11124/355Test

الإتاحة: http://hdl.handle.net/11124/355Test

المؤلفون: Adam, Mohammed Mustafa

المساهمون: Berger, John R., Mustoe, Graham G. W., Martin, P. A., Reimanis, Ivar E. (Ivar Edmund), Griffiths, D. V.

مصطلحات موضوعية: waves in layered media, singularities in bimaterials, auxetic material, elastic wave propagation, crack propagation, Composite materials, Composite materials -- Cracking, Strains and stresses, Boundary element methods

الوصف: 2014 Fall. ; Includes illustrations (some color). ; Includes bibliographical references (pages 90-97). ; An auxetic material is a material which has a negative Poisson's ratio, so they exhibit lateral expansion upon longitudinal tensile loading, or undergo lateral contraction under longitudinal compression. Such materials can exist in cellular form, or along specific axes in certain crystals. The singularity order in a half plane consisting of two quarter dissimilar materials and the singularity at the tip of interfacial crack have been studied where the bi-material contains an auxetic material. The main goal was to investigate the effects of the auxetic behavior on the singularities. We have determined that the auxetic material has a significant effect on the singularity order. For example, the free-edge singularity can be removed for certain combinations of elastic moduli and auxetic Poisson's ratios. In general, the effects of the mismatch of elastic constants between the two materials on the singularity have been investigated and all these results will be shown in this dissertation. The effect of a single particle or inclusion on crack propagation has been studied effectively using symmetric Galerkin boundary elements and a modified quarter-point crack tip element. Typical results show that an inclusion can decrease the crack-tip stress intensity as the crack approaches an inclusion, followed by deflection of the crack. Interestingly, as the crack extends beyond the inclusion there can also be an amplification of stress intensity. These previous results have shown the great influence the presence of an inclusion may have on a crack extension behavior. Here, we examine the influence of an auxetic particle on crack growth behavior. The objective of the present study is to understand the crack extension behavior and predict the crack growth direction in materials reinforced with auxetic particles. We will show the dramatic difference in crack path as compared to particles with positive Poisson's ratio. The ...

وصف الملف: born digital; doctoral dissertations; application/pdf

العلاقة: 2014 - Mines Theses & Dissertations; T 7664; http://hdl.handle.net/11124/17018Test

الإتاحة: http://hdl.handle.net/11124/17018Test

المؤلفون: Rodrigues, Patricia Evelyn

المساهمون: Batzle, Michael L., Prasad, Manika, Li, Yaoguo, Sava, Paul C., Yang, Yuan, Merkel, Richard

مصطلحات موضوعية: confinement, heavy oils, amplitude dependence, shear modulus, Heavy oil -- Elastic properties -- Measurement, Shear waves, Elastic wave propagation, Rheometers, Viscoelasticity

الوصف: 2014 Spring. ; Includes illustrations (some color), maps. ; Includes bibliographical references (pages 94-99). ; The success of seismic and other acoustic monitoring techniques is based on the ability of geophysicists to accurately model acoustic waves propagation. True "fluids" are not capable of supporting shear stress; however, heavy oils are viscoelastic and allow the transmission of shear waves. The shear modulus of heavy oils is highly dependent on frequency which adds a major difficulty since the data we study are obtained at different frequencies. Measuring elastic properties at high frequencies has been done for many years and it is much simpler than low frequencies measurements; specifically in bulk heavy oils. The equipment deforms the sample at frequencies from 3 to 3000 Hz and it works well for solid-like samples but cannot be used for liquid-like samples. An alternative method to measure the shear modulus of heavy oils at low frequencies is the rheometer which measures the shear modulus at frequencies from 0.01 to 100 Hz with strains amplitudes in the order of 10-4, two or three orders of magnitude larger than tension/compression. Linear viscoelasticity theory indicates that measurements done in the linear viscoelastic regime should be consistent between techniques as elastic properties are independent of amplitude. My research is focused on understanding rheometer measurements, and validating them against the tension/compression technique. However, in this work I identified two aspects of the rheometer that make their measurements not consistent with tension/compression results. The first is the presence of the two solid-liquid interfaces provided by the parallel plates; and the second is the increased strains amplitudes in the rheometer. The solid-liquid interfaces cause reorientation of the surface active components of the heavy oils, increasing the shear modulus near the interface in a scale that can be measured by the rheometer. This was evidenced by an increased of the shear modulus when ...

وصف الملف: born digital; doctoral dissertations; application/pdf

العلاقة: 2014 - Mines Theses & Dissertations; T 7448; http://hdl.handle.net/11124/413Test

الإتاحة: http://hdl.handle.net/11124/413Test