Open Access. Powered by Scholars. Published by Universities.®
Articles 1 - 4 of 4
Full-Text Articles in Mechanical Engineering
Ultrasonic Guided Wave Tomography Of Pipes: A Development Of New Techniques For The Nondestructive Evaluation Of Cylindrical Geometries And Guided Wave Multi-Mode Analysis, Kevin Raymond Leonard
Ultrasonic Guided Wave Tomography Of Pipes: A Development Of New Techniques For The Nondestructive Evaluation Of Cylindrical Geometries And Guided Wave Multi-Mode Analysis, Kevin Raymond Leonard
Dissertations, Theses, and Masters Projects
This dissertation concentrates on the development of two new tomographic techniques that enable wide-area inspection of pipe-like structures. By envisioning a pipe as a plate wrapped around upon itself, the previous Lamb Wave Tomography (LWT) techniques are adapted to cylindrical structures. Helical Ultrasound Tomography (HUT) uses Lamb-like guided wave modes transmitted and received by two circumferential arrays in a single crosshole geometry. Meridional Ultrasound Tomography (MUT) creates the same crosshole geometry with a linear array of transducers along the axis of the cylinder. However, even though these new scanning geometries are similar to plates, additional complexities arise because they are …
A Semi-Empirical Cellular Automata Model For Wildfire Monitoring From A Geosynchronous Space Platform, Brian D. Killough
A Semi-Empirical Cellular Automata Model For Wildfire Monitoring From A Geosynchronous Space Platform, Brian D. Killough
Dissertations, Theses, and Masters Projects
The environmental and human impacts of wildfires have grown considerably in recent years due to an increase in their frequency and coverage. Effective wildfire management and suppression requires real-time data to locate fire fronts, model their propagation and assess the impact of biomass burning. Existing empirical wildfire models are based on fuel properties and meteorological data with inadequate spatial or temporal sampling. A geosynchronous space platform with the proposed set of high resolution infrared detectors provides a unique capability to monitor fires at improved spatial and temporal resolutions. The proposed system is feasible with state-of-the-art hardware and software for high …
Tomography Applied To Lamb Wave Contact Scanning Nondestructive Evaluation, James Christopher P. Mckeon
Tomography Applied To Lamb Wave Contact Scanning Nondestructive Evaluation, James Christopher P. Mckeon
Dissertations, Theses, and Masters Projects
The aging world-wide aviation fleet requires methods for accurately predicting the presence of structural flaws that compromise airworthiness in aircraft structures. Nondestructive Evaluation (NDE) provides the means to assess these structures quickly, quantitatively, and noninvasively. Ultrasonic guided waves, Lamb waves, are useful for evaluating the plate and shell structures common in aerospace applications. The amplitude and time-of-flight of Lamb waves depend on the material properties and thickness of a medium, and so they can be used to detect any areas of differing thickness or material properties which indicate flaws. By scanning sending and receiving transducers over an aircraft, large sections …
On-Line System Identification For Control System Applications In Particle Accelerators, Mahesh Chowdhary
On-Line System Identification For Control System Applications In Particle Accelerators, Mahesh Chowdhary
Dissertations, Theses, and Masters Projects
Particle accelerators require a number of feedback systems in order to stabilize a variety of parameters. The Continuous Electron Beam Accelerator at Thomas Jefferson National Accelerator Facility presents a unique set of control and identification problems. This accelerator produces a continuous electron beam with energies between 0.5 and 4.0 GeV to be delivered to the experimental halls. In order to meet stringent beam quality requirements specified by the experimental halls, the position and the energy of the electron beam needs to stabilized at various locations in the accelerator.;A number of noise measurement tests were conducted at various locations in the …