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3D elastic full-waveform inversion of surface waves in the presence of irregular topography using an envelope-based misfit function

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GEOPHYSICS 2018年第1期83卷 R1-R11页

作者： Borisov, Dmitry Modrak, Ryan Gao, Fuchun Tromp, Jeroen Princeton Univ Dept Geosci Princeton NJ 08544 USA Total E&P Res & Technol Houston TX USA Princeton Univ Program Applied & Computat Math Houston NJ USA

Full-waveform inversion (FWI) is a powerful method for estimating the earth's material properties. We demonstrate that surface-wave-driven FWI is well-suited to recovering near-surface structures and effective at providing S-wave speed starting models for use in conventional body-wave FWI. Using a synthetic example based on the SEG Advanced Modeling phase II foothills model, we started with an envelope-based objective function to invert for shallow large-scale heterogeneities. Then we used a waveform-difference objective function to obtain a higher-resolution model. To accurately model surface waves in the presence of complex tomography, we used a spectral-element wave-propagation solver. Envelope misfit functions are found to be effective at minimizing cycle-skipping issues in surface-wave inversions, and surface waves themselves are found to be useful for constraining complex near-surface features.

关键词： 3D full-waveform inversion surface wave

A proposal for the EI index for fuzzy groups

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Research Square

Research Square 2021年

作者： de Andrade, Ricardo Lopes Rêgo, Leandro Chaves Management Engineering Graduate Program Federal University of Pernambuco Brazil Statistics and Applied Math Department Universidade Federal do Ceará Brazil Statistics Graduate Program Universidade Federal de Pernambuco Brazil

In this paper, it is proposed a measure that quantifies the relational structure within and between groups that comprehend not only the analysis of disjoint groups or non-disjoint groups but also in fuzzy groups. This measure is based on the existing measure known as the EI index. The current EI index is a measure of homophily applied to networks with the presence of disjoint groups, although disjoint groups on a large scale rarely exist in many empirical networks. The new measure permits the expansion of the analysis of social networks, for several types of attributes, and thus generating previously untapped knowledge. Moreover, it is also proposed combining edges’ and nodes’ weights in the evaluation of the EI index. The new measure is tested in two networks in different contexts. The first one is a co-authorship network, where researchers, actors in the network, are divided according to the time of completion of the doctorate. The second network is formed by trade relations between countries of the American continent, where countries are grouped according to the Human Development Index. © 2021, CC BY.

关键词： Fuzzy sets

Cosmological test using the high-redshift detection rate of FSRQs with the square kilometer array

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arXiv 2019年

作者： Leaf, Kyle Melia, Fulvio Department of Physics University of Arizona AZ85721 United States Applied Math Program Department of Physics University of Arizona AZ85721 United States

We present a phenomenological method for predicting the number of Flat Spectrum Radio Quasars (FSRQs) that should be detected by upcoming Square Kilometer Array (SKA) SKA1-MID Wide Band 1 and Medium-Deep band 2 surveys. We use the Fermi Blazar Sequence and mass estimates of Fermi FSRQs, and gamma-ray emitting Narrow Line Seyfert 1 galaxies, to model the radio emission of FSRQs as a function of mass alone, assuming a near-Eddington accretion rate, which is suggested by current quasar surveys at z > 6. This is used to determine the smallest visible black hole mass as a function of redshift in two competing cosmologies we compare in this paper: The standard LCDM model and the R_h=ct universe. We then apply lockstep growth to the observed black-hole mass function at z=6 in order to devolve that population to higher redshifts and determine the number of FSRQs detectable by the SKA surveys as a function of z. We find that at the redshifts for which this method is most valid, LCDM predicts ~30 times more FSRQs than R_h=ct for the Wide survey, and ~100 times more in the Medium-Deep survey. These stark differences will allow the SKA surveys to strongly differentiate between these two models, possibly rejecting one in comparison with the other at a high level of confidence. Copyright © 2019, The Authors. All rights reserved.

关键词： Cosmology

A two-point diagnostic for the hii galaxy hubble diagram

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arXiv 2017年

作者： Leaf, Kyle Melia, Fulvio Department of Physics University of Arizona AZ85721 United States Applied Math Program Department of Physics University of Arizona AZ85721 United States

A previous analysis of starburst-dominated HII Galaxies and HII regions has demonstrated a statistically significant preference for the Friedmann-Robertson-Walker cosmology with zero active mass, known as the Rh = ct universe, over CDM and its related dark-matter parametrizations. In this paper, we employ a 2-point diagnostic with these data to present a complementary statistical comparison of Rh = ct with Planck CDM. Our 2-point diagnostic compares-in a pairwise fashion-the difference between the distance modulus measured at two redshifts with that predicted by each *** results support the conclusion drawn by a previous comparative analysis demonstrating that Rh = ct is statistically preferred over Planck CDM. But we also find that the reported errors in the HII measurements may not be purely Gaussian, perhaps due to a partial contamination by non-Gaussian systematic effects. The use of HII Galaxies and HII regions as standard candles may be improved even further with a better handling of the systematics in these sources. Copyright © 2017, The Authors. All rights reserved.

关键词： Galaxies

Graph Fourier MMD for Signals on Graphs

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Graph Fourier MMD for Signals on Graphs

2023 International Conference on Sampling Theory and Applications, SampTA 2023

作者： Leone, Samuel Venkat, Aarthi Huguet, Guillaume Tong, Alexander Wolf, Guy Krishnaswamy, Smita Applied Math Program New HavenCT United States Yale University Computational Biology & Bioinformatics Program New HavenCT United States Université de Montréal Mila - Quebec Ai Institute Dept. of Math. & Stat Montreal Canada Université de Montréal Mila-Quebec Ai Institute Dept. of Comp. Sci. & Oper. Res. Montreal Canada Yale University Department of Computer Science Department of Genetics New HavenCT United States

ISBN: (纸本)9798350328851

While numerous methods have been proposed for computing distances between probability distributions in Euclidean space, relatively little attention has been given to computing such distances for distributions on graphs. However, there has been a marked increase in data that either lies on graph (such as protein interaction networks) or can be modeled as a graph (single cell data), particularly in the biomedical sciences. Thus, it becomes important to find ways to compare signals defined on such graphs. Here, we propose Graph Fourier MMD (GFMMD), a novel distance between distributions and signals on graphs. GFMMD is defined via an optimal witness function that is both smooth on the graph and maximizes the difference in expectation between the pair of distributions on the graph. We find an analytical solution to this optimization problem as well as an embedding of distributions that results from this method. We also prove several properties of this method including scale invariance and applicability to disconnected graphs. We showcase it on graph benchmark datasets as well on single cell RNA-sequencing data analysis. In the latter, we use the GFMMD-based gene embeddings to find meaningful gene clusters. We also propose a novel type of score for gene selection called gene localization score which helps select genes for cellular state space characterization. © 2023 IEEE.

关键词： Genes

Smooth graph signal interpolation for big data

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arXiv 2018年

作者： Heimowitz, Ayelet Eldar, Yonina C. Program in Applied and Computational Mathematics Princeton University PrincetonNJ United States Faculty of Math and Computer Science Weizmann Institute of Science Rehovot Israel

In this paper we present the Markov variation, a smoothness measure which offers a probabilistic interpretation of graph signal smoothness. This measure is then used to develop an optimization framework for graph signal interpolation. Our approach is based on diffusion embedding vectors and the connection between diffusion maps and signal processing on graphs. As diffusion embedding vectors may be expensive to compute for large graphs, we present a computationally efficient method, based on the Nyström extension, for interpolation of signals over a graph. We demonstrate our approach on the MNIST dataset and a dataset of daily average temperatures around the US. We show that our method outperforms state of the art graph signal interpolation methods on both datasets, and that our computationally efficient reconstruction achieves slightly reduced accuracy with a large speedup. Copyright © 2018, The Authors. All rights reserved.

关键词： Computational efficiency

Integrating engineering concepts under current K-12 state and national standards

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Integrating engineering concepts under current K-12 state an...

2002 ASEE Annual Conference and Exposition: Vive L'ingenieur

作者： Anderson-Rowland, Mary R. Baker, Dale R. Secola, Patricia M. Smiley, Bettie A. Evans, Donovan L. Middleton, James A. Arizona State University CEAS ASU Department of Curriculum ASU WISE Investments Program Coll. of Eng. and Applied Sciences ASU Ctr. Res. Educ. Sci. Math. Eng./T. Mechanical Engineering Department Arizona State University College of Education ASU

Interest in engineering by entering college freshmen is near a 30-year low. Young women especially are not attracted to engineering. Engineering is not featured in popular television programs and usually gets overshadowed in news reporting. Students in middle and high school do not hear about engineering in school since middle school and high school teachers are not well informed about engineering and applied mathematics and science. If engineering is to remain a viable and growing profession, especially among women and minorities, teachers need to be educated so they can present engineering material in a way that meets state/national science curriculum standards. Science standards, inherent in aligning curricula to these science standards, and a partial solution to overcoming these obstacles will be discussed in the paper. In particular, the WISE Investments program, sponsored by the National Science Foundation, introduces teachers and counselors to engineering and helps the teachers develop modules that can be introduced into present mathematics and science high school classes. Examples of these modules, developed to interest young women in middle school and high school, are given. These enriched modules increase curiosity and bring excitement into the classroom for the teachers and their students.

关键词： Engineering education

A cosmological solution to the impossibly early galaxy problem

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arXiv 2018年

作者： Yennapureddy, Manoj K. Melia, Fulvio Department of Physics University of Arizona AZ85721 United States Department of Physics Applied Math Program Department of Astronomy University of Arizona AZ85721 United States

To understand the formation and evolution of galaxies at redshifts 0 z 10, one must invariably introduce specific models (e.g., for the star formation) in order to fully interpret the data. Unfortunately, this tends to render the analysis compliant to the theory and its assumptions, so consensus is still somewhat elusive. Nonetheless, the surprisingly early appearance of massive galaxies challenges the standard model, and the halo mass function estimated from galaxy surveys at z 4 appears to be inconsistent with the predictions of λCDM, giving rise to what has been termed "The Impossibly Early Galaxy Problem" by some workers in the field. A simple resolution to this question may not be forthcoming. The situation with the halos themselves, however, is more straightforward and, in this paper, we use linear perturbation theory to derive the halo mass function over the redshift range 0 z 10 for the Rh = ct universe. We use this predicted halo distribution to demonstrate that both its dependence on mass and its very weak dependence on redshift are compatible with the data. The difficulties with λCDM may eventually be overcome with refinements to the underlying theory of star formation and galaxy evolution within the halos. For now, however, we demonstrate that the unexpected early formation of structure may also simply be due to an incorrect choice of the cosmology, rather than to yet unknown astrophysical issues associated with the condensation of mass fluctuations and subsequent galaxy formation. Copyright © 2018, The Authors. All rights reserved.

关键词： Galaxies

A Truncated Primordial Power Spectrum and Its Impact on B-Mode Polarization

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arXiv 2024年

作者： Liu, Jingwei Melia, Fulvio Department of Physics The University of Arizona AZ85721 United States Department of Physics The Applied Math Program Department of Astronomy The University of Arizona AZ85721 United States

The absence of large-angle correlations in the temperature of the cosmic microwave background (CMB), confirmed by three independent satellite missions, creates significant tension with the standard model of cosmology. Previous work has shown, however, that a truncation, kmin, of the primordial power spectrum comprehensively resolves the anomaly and the missing power at 5 (the low multipoles). Since this cutoff is consistent with the hypothesized delay of inflation well beyond the Planck time, we are strongly motivated to consider its possible impact on other observational signatures. In this Letter, we analyze and predict its influence on the most revealing probe awaiting measurement by upcoming missions—the B-mode polarization of the CMB, whose accurate determination should greatly impact the inflationary picture. We highlight the quantitative power of this discriminant by specifically considering the LiteBIRD mission, predicting the effect of kmin on both the angular power spectrum and the angular correlation function of the B-mode, for a range of tensor-to-scalar ratios, r. While its impact on the latter appears to be negligible, kmin should have a very pronounced effect on the former. We show that for r = 0.036, kmin’s impact on CBB at low ’s should be easily detectable by LiteBIRD, but will be largely hidden by the total uncertainty of the measurement if r 0.02. © 2024, CC BY-NC-ND.

关键词： Cosmology