Browsing by Subject "Tomography"

Now showing 1 - 3 of 3
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    Evaluation, Development, and Implementation of 3D GPR for Assessment of Minnesota Infrastructure
    (Center for Transportation Studies, University of Minnesota, 2016-12) Hoegh, Kyle; Thompkins, Derek; Khazanovich, Lev
    This research project evaluated the 3D Radar ground penetrating radar (3D GPR) equipment to determine applications and develop software for immediate use. A major focus was the use of 3D GPR to determine asphalt compaction uniformity. Other pavement assessment applications were explored. The research resulted in the development of new software that provides on-site mapping shortly after the last roller pass is completed on new construction. This provides the potential to select validation locations and give feedback to the contractor detailing the as-constructed performance during the paving process. The outputs of the software were also designed to allow for comparison with other technology and as-constructed information. (A user’s guide for the software is included in the project final report.) Overall, the use of 3D GPR with the developed software, combined with as-constructed data such as Intelligent Compaction pass counts, vibration amplitude, and other measures, can lead to better asphalt compaction and longer lasting roads.
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    Magnetoacoustic tomography with magnetic induction for electrical conductivity imaging of biological tissue.
    (2010-09) Li, Xu
    Electrical properties of biological tissue including conductivity and permittivity play important roles in many biomedical and clinical researches such as modeling neural or cardiac electrical activities and management of electromagnetic energy delivery to the body during clinical diagnosis and treatment. More importantly, these electrical properties may serve as an intrinsic contrast for anatomical or functional imaging. It is therefore of great value to noninvasively image the electrical properties of biological tissue with good accuracy and high spatial resolution. This dissertation research aims at developing and evaluating a new modality i.e. magnetoacoustic tomography with magnetic induction (MAT-MI), for imaging electrical conductivity distribution of biological tissue. In MAT-MI, a conductive object is placed in a static magnetic field and a time-varying magnetic stimulation is applied to induce eddy current inside the object volume. Within the static magnetic field, the Lorentz force acting on the induced eddy current causes mechanical movement of those charged particles in the object and leads to detectable ultrasound signals. These ultrasound signals can be acquired by ultrasound probes and used to reconstruct a high spatial resolution image that indicates the object's electrical conductivity contrast. We have proposed and investigated two types of MAT-MI approaches i.e. single-excitation MAT-MI and multi-excitation MAT-MI. The corresponding image reconstruction algorithms, simulation protocols and experiment systems have been developed for feasibility testing and performance evaluation. It is shown in our computer simulation and experiment studies that using the single-excitation MAT-MI we are able to image the conductivity boundaries of the object with several millimeter spatial resolution. In addition, we have also demonstrated that the multi-excitation MAT-MI approach allows us to further extract the internal information and reconstruct more completely the conductivity contrast of the object. For both approaches, two-dimensional (2D) and three-dimensional (3D) images of physical or tissue phantoms have been acquired and showed promising agreement with the target conductivity distribution. All the results we have collected so far from simulations and experiments suggest that the MAT-MI approach is potential to become an important noninvasive modality for electrical conductivity imaging of biological tissue.
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    Portland Cement Concrete Pavement Thickness Variation Versus Observed Pavement Distress
    (Minnesota Department of Transportation, 2016-09) Khazanovich, Lev; Hoegh, Kyle; Barnes, Randal; Conway, Ryan; Salles, Lucio
    Benefits from a potential significant correlation between distresses and slab thickness can be broadly applied in all stages of highway development from design and construction to maintenance decisions. In order to comprehensive explore this possibility, thickness data and existing distresses were related for three highway projects in Minnesota. Thickness was obtained through non-destructive ultrasonic testing, while distresses were recorded for the same location with a distress image software. Significant thickness variation was observed in both longitudinal and transverse directions. The combined results of thickness, shear wave velocity and distresses analysis revealed that an increase in shear wave velocity was coincident with a less damaged pavement area within a section. An in-depth statistical analysis confirmed this observation showing that shear surface velocity variation was better correlated with overall pavement performance than thickness variation. Differences in cracking behavior within a section were traced back to changes in construction and design practices, showing the potential of using shear velocity analysis for pavement maintenance. A survey and analysis procedure for shear wave velocity testing of concrete pavements is proposed.