Download or read book Electromagnetic Subsurface Imaging at VLF Using Distributed Optimization written by David Strauss and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The purpose of radio remote sensing is to learn more about the environment by observing how the environment interacts with radio waves. Radio remote sensing can be seen as three generic steps: measurement, processing, and interpretation. In this thesis, we discuss methods to address the latter components of radio remote sensing as they pertain to electromagnetic subsurface imaging. We describe a signal processing technique, known as sparse separation, that allows us to decompose the observed data into components that are of scientific value and those that are considered interference. We formulate electromagnetic subsurface imaging as an optimization problem constrained by a set of partial differential equations (PDEs), specifically Maxwell's equations, which govern electromagnetic wave propagation. Algorithms for approximating the solution to these optimization problems are presented and tested numerically. We image conductivities underground with natural sources of electromagnetic radio waves. In the VLF (Very Low Frequency, 3-30kHz) band there are many types of naturally occurring electromagnetic waves. We are primarily interested in a class of electromagnetic waves known as radio atmospherics, or sferics for short. Sferics are short-duration, broadband radio bursts produced by lightning discharges worldwide. Sferics provide three basic advantages for electromagnetic subsurface imaging. First sferics are plentiful; lightning occurs at a rate of 45 discharges per second. Second, because of the global distribution of lightning discharges, we are able to observe sferics incident from multiple different directions of arrival. Each independent incident direction provides more information about the subsurface conductivities. Third, sferics are broadband in nature. Each sferic contains information at multiple frequencies, further augmenting the information we have collected about the subsurface area of interest. The techniques developed in this thesis are designed to take advantage of these three basic properties. To better understand the data, we introduce and develop the technique of sparse separation in an overcomplete dictionary. By solving for a sparse, higher dimensional representation of our data we are able to partition the data into components that are scientifically valuable and components that are considered interference. We develop methods based on soft thresholding, the proximal operator for the sparsity promoting l1 bound. These first order methods scale well, thus permitting the processing of large datasets. Electromagnetic subsurface imaging is formulated as a nonlinear, non-convex, PDE-constrained optimization problem. Using the finite difference frequency domain (FDFD) method for modeling Maxwell's equations on a discrete grid, we can predict the electromagnetic fields everywhere within a computational domain for any wave illumination and any set of scattering conductivities underground. The goal of electromagnetic subsurface imaging is to find an optimal set of conductivities within our model of Maxwell's equations that predict electromagnetic fields that closely match a set of electromagnetic field observations. Many techniques exist for approximating the solution to non-convex optimization problems including sequential linear approximation, alternating projections, and semidefinite relaxations and embeddings. Adaptations of the alternating directions method of multipliers (ADMM) to this non-convex problem have shown the best performance for obtaining the best accuracy and incorporating the multiple frequency and multiple direction of arrival information from sferics in a distributed and scalable manner. Development of these algorithms leads to computational experiments to discover the real-world performance bounds. Adding more information to the problem increases estimation accuracy of subsurface conductivities. We investigate performance as a function of background conductivity and sensor noise. Varying these parameters allows us to predict the influence of basic physics principles and test the algorithms in a variety of possible real-world scenarios. Furthermore, we explore the relationship between the number of sensor measurements necessary and the accuracy we can obtain for determining the subsurface conductivity parameters. Numerical testing leads to a subsampling principle which gives a relationship between accuracy and the number of radio observations.
Download or read book Introduction to Subsurface Imaging written by Bahaa Saleh and published by Cambridge University Press. This book was released on 2011-03-17 with total page 455 pages. Available in PDF, EPUB and Kindle. Book excerpt: Describing and evaluating the basic principles and methods of subsurface sensing and imaging, Introduction to Subsurface Imaging is a clear and comprehensive treatment that links theory to a wide range of real-world applications in medicine, biology, security and geophysical/environmental exploration. It integrates the different sensing techniques (acoustic, electric, electromagnetic, optical, x-ray or particle beams) by unifying the underlying physical and mathematical similarities, and computational and algorithmic methods. Time-domain, spectral and multisensor methods are also covered, whilst all the necessary mathematical, statistical and linear systems tools are given in useful appendices to make the book self-contained. Featuring a logical blend of theory and applications, a wealth of color illustrations, homework problems and numerous case studies, this is suitable for use as both a course text and as a professional reference.
Download or read book The LASI High frequency Electromagnetic Subsurface imaging System written by and published by . This book was released on 1996 with total page 17 pages. Available in PDF, EPUB and Kindle. Book excerpt: A high-frequency, high-resolution, electromagnetic imaging system has been developed for environmental geophysics surveys. Some key features include: (1) rapid surveying to allow dense spatial sampling over a large area, (2) high-accuracy measurements which are used to produce a high-resolution image of the subsurface, (3) measurements which have excellent signal-to-noise ratio over a wide bandwidth (31 kHz to 32 MHz), (4) large-scale physical modeling to produce accurate theoretical responses over targets of interest in environmental geophysics surveys, (5) rapid neural network interpretation at the field site, and (6) visualization of complex structures during the survey. A field survey was conducted at INEL, Nov. 28-Dec. 1, 1995, over the Cold Test Pit, which simulates waste pits at INEL and other DOE sites.
Download or read book Subsurface Imaging Using Measured Antenna Foot prints written by K. W. A. van Dongen and published by . This book was released on 2003 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Introduction to Subsurface Imaging written by Bahaa Saleh and published by Cambridge University Press. This book was released on 2011-03-17 with total page 456 pages. Available in PDF, EPUB and Kindle. Book excerpt: Describing and evaluating the basic principles and methods of subsurface sensing and imaging, Introduction to Subsurface Imaging is a clear and comprehensive treatment that links theory to a wide range of real-world applications in medicine, biology, security and geophysical/environmental exploration. It integrates the different sensing techniques (acoustic, electric, electromagnetic, optical, x-ray or particle beams) by unifying the underlying physical and mathematical similarities, and computational and algorithmic methods. Time-domain, spectral and multisensor methods are also covered, whilst all the necessary mathematical, statistical and linear systems tools are given in useful appendices to make the book self-contained. Featuring a logical blend of theory and applications, a wealth of color illustrations, homework problems and numerous case studies, this is suitable for use as both a course text and as a professional reference.
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1994 with total page 836 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Petroleum Abstracts written by and published by . This book was released on 1993 with total page 1752 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Geotechnical and Environmental Geophysics Environmental and groundwater written by Stanley H. Ward and published by . This book was released on with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Electromagnetic Methods in Applied Geophysics written by Misac N. Nabighian and published by SEG Books. This book was released on 1988 with total page 989 pages. Available in PDF, EPUB and Kindle. Book excerpt: As a slag heap, the result of strip mining, creeps closer to his house in the Ohio hills, fifteen-year-old M. C. is torn between trying to get his family away and fighting for the home they love.
Download or read book Advances in Modeling and Interpretation in Near Surface Geophysics written by Arkoprovo Biswas and published by Springer Nature. This book was released on 2020-01-01 with total page 414 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book deals primarily with the aspects of advances in near surface geophysical data modeling, different interpretation techniques, new ideas and an integrated study to delineate the subsurface structures. It also involves the practical application of different geophysical methods to delineate the subsurface structures associated with mineral, groundwater exploration, subsurface contamination, hot springs, coal fire etc. This book is specifically aimed with the state-of-art information regarding research advances and new developments in these areas of study, coupled to extensive modeling and field investigations obtained from around the world. It is extremely enlightening for the research workers, scientists, faculty members and students, in Applied Geophysics, Near Surface Geophysics, Potential Field, Electrical and Electromagnetic Methods, Mathematical Modeling Techniques in Earth Sciences, as well as Environmental Geophysics.
Download or read book Circuit and Layout Techniques for Soft error resilient Digital CMOS Circuits written by Hsiao-Heng Kelin Lee and published by Stanford University. This book was released on 2011 with total page 156 pages. Available in PDF, EPUB and Kindle. Book excerpt: Radiation-induced soft errors are a major concern for modern digital circuits, especially memory elements. Unlike large Random Access Memories that can be protected using error-correcting codes and bit interleaving, soft error protection of sequential elements, i.e. latches and flip-flops, is challenging. Traditional techniques for designing soft-error-resilient sequential elements generally address single node errors, or Single Event Upsets (SEUs). However, with technology scaling, the charge deposited by a single particle strike can be simultaneously collected and shared by multiple circuit nodes, resulting in Single Event Multiple Upsets (SEMUs). In this work, we target SEMUs by presenting a design framework for soft-error-resilient sequential cell design with an overview of existing circuit and layout techniques for soft error mitigation, and introducing a new soft error resilience layout design principle called LEAP, or Layout Design through Error-Aware Transistor Positioning. We then discuss our application of LEAP to the SEU-immune Dual Interlocked Storage Cell (DICE) by implementing a new sequential element layout called LEAP-DICE, retaining the original DICE circuit topology. We compare the soft error performance of SEU-immune flip-flops with the LEAP-DICE flip-flop using a test chip in 180nm CMOS under 200-MeV proton radiation and conclude that 1) our LEAP-DICE flip-flop encounters on average 2,000X and 5X fewer errors compared to a conventional D flip-flop and our reference DICE flip-flop, respectively; 2) our LEAP-DICE flip-flop has the best soft error performance among all existing SEU-immune flip-flops; 3) In the evaluation of our design framework, we also discovered new soft error effects related to operating conditions such as voltage scaling, clock frequency setting and radiation dose.
Download or read book Source Variation and Ground Accessibility of Magnetospheric Mid latitude ELF VLF Chorus and Hiss written by Daniel Irving Golden and published by Stanford University. This book was released on 2011 with total page 192 pages. Available in PDF, EPUB and Kindle. Book excerpt: The distribution of relativistic electrons that form the Earth's radiation belts is extremely variable, with the trapped flux changing by several orders of magnitude on timescales of a few hours to days. These energetic particles pose a significant hazard to satellites and astronauts in the near-Earth space environment. The dynamic evolution of the radiation belts is believed to be controlled in large part by two separate but related classes of naturally occurring plasma waves: extremely low frequency/very low frequency (ELF/VLF) chorus and hiss. This dissertation explores characteristics of chorus and hiss observed at Palmer Station, Antarctica with the goal of improving our ability to differentiate between variations in emission generation and the effects of emissions' propagation to the ground. Results are presented from a two-part study, consisting of both observations and modeling, which explores the manner in which the plasmapause affects the propagation of chorus from its magnetospheric source to the ground. Results indicate that the observed chorus propagates in a non-ducted mode, which is contrary to a long-standing belief that guiding structures are necessary for chorus to propagate to the ground. This newly-explored mode of ground propagation indicates that ground stations may be able to observe a larger portion of waves than previously thought and provides for a more accurate interpretation of ground-observed waves and their influence on energetic particle distributions. Following this, an automated system of detecting chorus and hiss in broadband ELF/VLF data using neural networks is discussed. Results of running the automated detector on ten years of data are discussed including diurnal, seasonal and solar cyclical variations of emissions.
Download or read book Subsampling GPS Receiver Front end written by Carsten Barth and published by Stanford University. This book was released on 2011 with total page 122 pages. Available in PDF, EPUB and Kindle. Book excerpt: Research in RFIC design has recently shifted towards direct conversion and subsampling architectures as an alternative to the conventional super-heterodyne architectures. Bandpass sampling architectures, also called subsampling architectures, exhibit several advantages over super-heterodyne architectures, notably, the complexity of subsampling architectures is significantly lower since no phase-locked loop is required. A direct consequence is that downconversion from RF to IF can be achieved with significant power savings as compared to the super-heterodyne architecture. Another significant benefit of such architectures is the capability for processing multiple signals in parallel. The ability to simultaneously handle multiple carriers makes subsampling architectures particularly well suited for GNSS applications, as downconversion of multiple frequency bands is required in GNSS environments. With the advent of the new civilian GPS signals, L2C and L5, and the onset of the new Galileo signal, a receiver that can process multiple signals without adding complexity, is highly desired. An integrated proof-of-concept subsampling GPS receiver front-end in 130 nm BiCMOS is presented in this dissertation. The receiver achieves a noise figure of less than 3.8 dB, the lowest ever recorded noise figure of a subsampling based receiver.
Download or read book Near Surface Applied Geophysics written by Mark E. Everett and published by Cambridge University Press. This book was released on 2013-04-25 with total page 419 pages. Available in PDF, EPUB and Kindle. Book excerpt: Just a few meters below the Earth's surface lie features of great importance, from geological faults which can produce devastating earthquakes, to lost archaeological treasures. This refreshing, up-to-date book explores the foundations of interpretation theory and the latest developments in near-surface techniques, used to complement traditional geophysical methods for deep-exploration targets. Clear but rigorous, the book explains theory and practice in simple physical terms, supported by intermediate-level mathematics. Techniques covered include magnetics, resistivity, seismic reflection and refraction, surface waves, induced polarization, self-potential, electromagnetic induction, ground-penetrating radar, magnetic resonance, interferometry, seismoelectric and more. Sections on data analysis and inverse theory are provided and chapters are illustrated by case studies, giving students and professionals the tools to plan, conduct and analyze a near-surface geophysical survey. This is an important textbook for advanced-undergraduate and graduate students in geophysics and a valuable reference for practising geophysicists, geologists, hydrologists, archaeologists, and civil and geotechnical engineers.
Download or read book The Magnetotelluric Method written by Alan D. Chave and published by Cambridge University Press. This book was released on 2012-04-26 with total page 571 pages. Available in PDF, EPUB and Kindle. Book excerpt: The magnetotelluric method is a technique for imaging the electrical conductivity and structure of the Earth, from the near surface down to the 410 km transition zone and beyond. This book forms the first comprehensive overview of magnetotellurics, from the salient physics and its mathematical representation to practical implementation in the field, data processing, modeling and geological interpretation. Electromagnetic induction in 1-D, 2-D and 3-D media is explored, building from first principles, and with thorough coverage of the practical techniques of time series processing, distortion, numerical modeling and inversion. The fundamental principles are illustrated with a series of case histories describing geological applications. Technical issues, instrumentation and field practices are described for both land and marine surveys. This book provides a rigorous introduction to magnetotellurics for academic researchers and advanced students, and will be of interest to industrial practitioners and geoscientists wanting to incorporate rock conductivity into their interpretations.
Download or read book Precambrian Geology of Nigeria written by Geological Survey of Nigeria and published by . This book was released on 1988 with total page 338 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Earth Resources written by and published by . This book was released on 1977 with total page 852 pages. Available in PDF, EPUB and Kindle. Book excerpt:
