• Login
    View Item 
    •   Home
    • UA Graduate and Undergraduate Research
    • UA Theses and Dissertations
    • Dissertations
    • View Item
    •   Home
    • UA Graduate and Undergraduate Research
    • UA Theses and Dissertations
    • Dissertations
    • View Item
    JavaScript is disabled for your browser. Some features of this site may not work without it.

    Browse

    All of UA Campus RepositoryCommunitiesTitleAuthorsIssue DateSubmit DateSubjectsPublisherJournalThis CollectionTitleAuthorsIssue DateSubmit DateSubjectsPublisherJournal

    My Account

    LoginRegister

    About

    AboutUA Faculty PublicationsUA DissertationsUA Master's ThesesUA Honors ThesesUA PressUA YearbooksUA CatalogsUA Libraries

    Statistics

    Most Popular ItemsStatistics by CountryMost Popular Authors

    Spatial sensitivity of low-induction-number frequency-domain electromagnetic-induction instruments

    • CSV
    • RefMan
    • EndNote
    • BibTex
    • RefWorks
    Thumbnail
    Name:
    azu_td_3177545_sip1_m.pdf
    Size:
    2.240Mb
    Format:
    PDF
    Download
    Author
    Callegary, James Briggs
    Issue Date
    2005
    Keywords
    Geophysics.
    Hydrology.
    Agriculture, Soil Science.
    Advisor
    Ferre, Ty P. A.
    
    Metadata
    Show full item record
    Publisher
    The University of Arizona.
    Rights
    Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
    Abstract
    Numerical simulations were used to study spatial averaging in low-induction-number frequency-domain electromagnetic induction (LIN FEM) instruments. Local ( LS) and cumulative (CS) sensitivity were used to analyze three different aspects of LIN FEM spatial sensitivity. LS is the variation in a measured property given a small change at a given location of the property of interest. CS contours are derived from LS and reveal the shape and the fraction of total instrument sensitivity enclosed within the contours. The first study re-evaluated the asymptotic approach to LIN FEM spatial sensitivity. Using this approach, LIN FEM measurements have often been assumed to represent electrical conductivity (sigma) at discreet depths that do not vary with the sigma of the ground. This assumption was tested using simulations of electromagnetic fields in environments with homogeneous and layered sigma distributions. When the induction number was greater than 0.01, the 1-D vertical CS distribution and the depth of investigation varied up to 20% over the range of sigma simulated. As sigma increased, CS contours and depth of investigation decreased in depth. In the second study a small perturbation approach was used to calculate CS distributions so that each distribution is unique to a given LS distribution. CS was summed from regions of high to low LS, and retained information on the magnitude and location of LS. As sigma increased, CS became focused around the highest LS values. The maximum reduction in depth of investigation was about 40% at the highest sigma investigated. In the final study, a series of small, electrically conductive perturbations was simulated in a three-dimensional, homogeneous environment. Three-dimensional LS varied markedly with a large difference between horizontal (HMD) and vertical (VMD) orientations of the transmitter and receiver dipoles. In some regions, the calculated magnetic field intensity with the perturbation was less than that calculated for the host without the perturbation. This occurred for both VMD and HMD orientations of the transmitter. CS contours were highly complex. One dimensional, vertical LS curves extracted from the three-dimensional data were very different from curves from infinite layer simulations.
    Type
    text
    Dissertation-Reproduction (electronic)
    Degree Name
    Ph.D.
    Degree Level
    doctoral
    Degree Program
    Graduate College
    Soil, Water and Environmental Science
    Degree Grantor
    University of Arizona
    Collections
    Dissertations

    entitlement

     
    The University of Arizona Libraries | 1510 E. University Blvd. | Tucson, AZ 85721-0055
    Tel 520-621-6442 | repository@u.library.arizona.edu
    DSpace software copyright © 2002-2017  DuraSpace
    Quick Guide | Contact Us | Send Feedback
    Open Repository is a service operated by 
    Atmire NV
     

    Export search results

    The export option will allow you to export the current search results of the entered query to a file. Different formats are available for download. To export the items, click on the button corresponding with the preferred download format.

    By default, clicking on the export buttons will result in a download of the allowed maximum amount of items.

    To select a subset of the search results, click "Selective Export" button and make a selection of the items you want to export. The amount of items that can be exported at once is similarly restricted as the full export.

    After making a selection, click one of the export format buttons. The amount of items that will be exported is indicated in the bubble next to export format.