Doctor of Philosophy / Department of Mechanical and Nuclear Engineering / Liang-Wu Cai / A computational system is built for conducting deterministic simulations of three-dimensional multiple scattering of elastic waves by spherical inclusions. Based on expansion expression of elastic wave fields in terms of scalar and vector spherical harmonics, analytically exact solutions of single scattering and multiple scattering are obtained, implemented and verified. The verification is done by using continuities of displacement and surface traction at the interface between an inclusion and host medium, energy conservation and published results. The scatterer polymerization methodology is extended to three-dimensional multiple scattering solution. By using this methodology, an assemblage of actual scatterers can be treated as an abstract scatterer. This methodology is verified by using different approaches, with or without scatterer polymerization, to solve a physically the same multiple scattering problem. As an application example, band gap formation process for elastic wave propagation in cubic lattice arrangements of spherical scatterers is observed through a series of numerical simulations. Along the direction of the incident wave, scatterer arrangements are viewed as comprising layers of scatterers, within which scatterers form a square grid. Starting from one layer and by increasing the number of layers, near-field forward wave propagation spectra are computed as the number of layers increases. These simulations also demonstrates that the computational system has the capability to simulate multiple scattering solutions of elastic waves in three-dimension.

Master of Science / Department of Mechanical and Nuclear Engineering / Warren N. White / This thesis describes the process of testing and implementing ultrasonic transducers for ball position feedback on a ball-and-beam apparatus. Also included are specifications for equipment to allow feedback and command signals to be wireless, not hardwired to the control computer. The author presents various ball-and-beam configurations as well as details about the specific configuration used for this work. These details include choices in sensors, materials, hardware, construction, and controller. After the apparatus has been described, the author provides information to support claims about system performance. The conclusions presented specify the necessary hardware to make the system wireless and indicate that acoustic sensors can complete a successful ball-on-beam balancing system.

Doctor of Philosophy / Department of Agronomy / Stephen J. Thien / Range and Training Land Assessment (RTLA) and Land Rehabilitation and Maintenance (LRAM) are key components of The United States Army's Integrated Training Area Management (ITAM) Program, which outlines its commitment to support the sustainable use of military training lands. The primary purpose of the RTLA Program is to provide information and recommendations regarding the condition of training lands to range managers for scheduling of training areas and monitoring the effectiveness of rehabilitation projects. The goal of the LRAM component of ITAM is to reduce the long-term impacts of training on installations through the implementation of improvements to vegetation cover and repairs to landscape damage in disturbed areas. Fort Riley Military Installation, located in the largest remaining expanse of tallgrass prairie in the Flint Hills of northeastern Kansas, is a major training reservation, with seventy percent of its 40,434 ha used for mechanized maneuvers. A randomized complete block design composed of M1A1 tank traffic in a figure-eight pattern during wet and dry soil conditions was established in each of two soil types, a silty clay loam and a silt loam, and recovery of physical, chemical, and biological indicator variables was monitored from 2005 through 2007. In a second study, the effectiveness of LRAM procedures, including leveling, mulching, and reseeding, was evaluated following wheeled vehicle disturbance. The goals of this study were to identify disturbance indicators appropriate for assessing soil quality and, based on the status of these indicators, develop a method for modeling the stage and rate of ecological degradation and potential response to remediation. Disturbance increased significantly during wet compared to dry soil conditions, for increased traffic intensity, and for curve compared to straight-a-way areas in both soil types. The greatest impacts were on above and below ground community structure, providing an effective bioindicator of ecosystem health for military training land managers. Remediation of wheeled vehicle disturbance with leveling and mulching, but not reseeding, increased total vegetation production. The tallgrass prairie typically is considered to be among the most resilient of military training lands, but resiliency is dependent upon soil type and training conditions, and may require longer periods of recovery than previously thought.