22 research outputs found
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Bipole-dipole interpretation with three-dimensional models (including a field study of Las Alturas, New Mexico)
The bipole-dipole responses of three-dimensional (3D) prisms were studied using an integral equation numerical solution. Although response patterns are quite complex, the bipole-dipole method appears to be a useful, efficient means of mapping the areal distribution of resistivity. However, 3D modeling is required for quantitative interpretation. Computer time for our solution varies from negligible for small bodies to 6 minutes on a UNIVAC 1108 for the largest possible body (85 cubes). Bipole-dipole response varies significantly with bipole orientation and position, but simply changing the distance between the bipole and the body does not greatly affect the response. However, the response is complex and interpretation ambiguous if both transmitter electrodes are located directly over a body. Boundaries of shallow bodies are much better resolved than those of deep bodies. Conductive bodies produce false polarization highs that can confuse interpretation. It is difficult to distinguish the effects of depth and resistivity contrast, and, as with all electrical methods, depth extent is difficult to resolve. Interactive interpretation of bipole-dipole field results from a geothermal prospect in New Mexico illustrates the value of the 3D modeling technique
Theoretical Development of the Differential Scattering Decomposition for the 3D Resistivity Experiment
In any numerical solution of the DC resistivity experiment, care must be taken to deal with strong heterogeneity of electrical conductivity. In order to examine the importance of conductivity contrasts, we develop a scattering decomposition of the DC resistivity equation in the sparse differential domain as opposed to the traditional dense integral formulation of scattering-type equations. We remove the singularity in the differential scattered series via separation of primary and secondary conductivity, thereby avoiding the need to address the singularity in a Green\u27s function. The differential scattering series is observed to diverge for large conductivity contrasts and to converge for small contrasts. We derive a convergence criterion, in terms of matrix norms for the weak-form finite-volume equations, that accounts for both the magnitude and distribution of heterogeneity of electrical conductivity. We demonstrate the relationship between the differential scattering series and the Fréchet derivative of the electrical potential with respect to electrical conductivity, and we show how the development may be applied to the inverse problem. For linearization associated with the Fréchet derivative to be valid, the perturbation in electrical conductivity must be small as defined by the convergence of the scattered series. The differential scattering formulation also provides an efficient tool for gaining insight into charge accumulation across contrasts in electrical conductivity, and we present a derivation that equates accumulated surface charge density to the source of scattered potential
Theoretical development of the differential scattering decomposition for the 3D resistivity experiment
THREE-DIMENSIONAL INTERPRETATION OF MULTIPLE-SOURCE BIPOLE-DIPOLE RESISTIVITY DATA USING THE APPARENT RESISTIVITY TENSOR1
Emergency Bleeding Control Interventions After Immediate Total-Body CT Scans in Trauma Patients
Contains fulltext :
201035.pdf (publisher's version ) (Open Access
APPLICATION OF THE MULTIFREQUENCY HORIZONTAL-LOOP EM METHOD IN OVERBURDEN INVESTIGATIONS1
Refining the criteria for immediate total-body CT after severe trauma
Contains fulltext :
218590.pdf (publisher's version ) (Open Access