According to a 2012 American Coal Ash Association Coal production Survey Report, US coal fired power plants produced more than 109 million tons of waste that year. Approximately half of this waste is the valuable by-product fly ash. There are three classes of fly ash: cementitious class C and non-cementitious classes F and N. Over half of the fly ash produced is used in the geotechnical/construction industries. Most geotechnical soil stabilization studies using fly ash are focused on controlling shrink-swell potential of clays. This study utilized the less desirable class F fly ash to assess the improvement of shear strength parameters of granular soils. Two mix designs were developed and tested using consolidated undrained, unconfined compression, and triaxial testing. Mix designs consisted of 15% fly ash with 0.5 or 1% cement, and poorly graded Ottawa sand compacted using a standard effort at 10 percent moisture content. Consolidated undrained testing on Mix 1, which included flushing and saturating the specimens, produced higher shear strength parameters than for the sand alone. However, the results were inconsistent with respect to the increase in shear strength parameters with time. Unconfined compression testing was then conducted on both Mix 1 and Mix 2 to assess strength gain with time. Results showed both mixes gained appreciable strength with time but doubling the cement did not double the unconfined compressive strength. Triaxial testing was then conducted on Mix 1 using specimens that were not flushed or saturated. This testing was used to determine if flushing destroyed the specimen soil fabric. The shear strength parameters from the triaxial testing were very similar to those determined from consolidated undrained testing. This demonstrated that flushing did not affect the shear strength parameters. Inconsistent triaxial test results from fly ash-cement-sand mixes have been previously reported in the literature.

Weathering has a negative effect on both physical and engineering properties of rock specimens and rock masses. When rock masses are weathered it is often difficult to obtain core segments that are the correct size for unconfined compressive strength testing. Thus engineers must use index testing to estimate the strength of specimens for design purposes. This thesis relates the unconfined compressive strength to index strength tests of Ocala limestone. The relationships developed include weathering states of the specimens and proximity of unconfined compressive strength specimens to index specimens. One hundred and ninety five specimens were classified using International Society for Rock Mechanics (ISRM) weathering designations, had their unit weight determined, and were tested under unconfined compression, point load, or indirect tensile conditions. Qualitative results show the average unit weight decreases with an increase in weathering state and the range of index strength values decreases with an increase in weathering state. The data also shows low index strength test results across a wide range of unit weights. Quantitative relationships were also developed with the strength data. All of the developed relationships were linear. Point load strengths have better correlations with unit weight than indirect tensile strengths. Unconfined compressive strength was correlated to index strength and weathering using three different approaches. For all approaches, indirect tensile strength has a better correlation with unconfined compressive strength than point load strength. Specimen pairs from the same weathering state also have a better correlation than specimen pairs from different weathering states. Unconfined compressive strength was also correlated to index strength results by incorporating specimen proximity. Once again, indirect tensile strength is a better predictor of unconfined compressive strength than point load strength. Specimen pairs, consisting of unconfined compressive strength and index strength test specimens, had better correlations when the two specimens are located close together.

While extensive mathematical and numerical work has been done in terms of modeling the mainstream flow in a tube with porous walls, very little has been done experimentally to confirm these various solutions, and what has been done has focused on large sintered metal tubes used in nuclear power applications. Furthermore, these solutions are quite mathematically complex and arduous to implement. In this work, the mainstream flow through a porous polymer membrane tube is examined and a method for calculating the through-membrane flow rate and axial pressure drop is presented. Two membrane tubes are tested experimentally, and a simple set of modeling equations that are physically intuitive are presented which fit the data. A characterization test is described which can be used to determine the permeability coefficient, kD, for a membrane sample, which can in turn be used to calculate the through-membrane flow rate and axial pressure drop. The models are then evaluated by performing flow-through experiments and measuring the pressures and flows within the membrane. For both membranes tested, the permeability coefficient is determined to be kD = 5.9394 × 10−14 m2 . For the tube diameters (2 mm and 8 mm) and flow rates (100-500 sccm) tested, it is shown that for dimensionless tube lengths bL = L/(dReD) ≥ 0.3, a model that assumes fully developed flow through the entire tube accurately describes the through-membrane flow rate data. The fully-developed model consistently under-predicts the experimental data for axial pressure drop, therefore it is assumed that the discrepancy is due to an additional pressure loss from the developing region. This loss is determined empirically using the data. The model’s validity is examined and compared to that of other authors for the range of flow rates tested.

The present work details the creation and analysis of a finite element model of the foot, wherein the plantar fascia was modeled as a viscohyperelastic solid. The objective of this work was to develop a fully functional CAD and Finite Element Model of the foot and plantar fascia for analysis by examining the transient stresses on the plantar fascia through the use of a viscohyperelastic material model. The model’s geometry was developed through the use of image processing techniques with anatomical images provided by the National Institutes of Health. The finite element method was used to analyze the transient response of the plantar fascia during loading. As a first step towards modeling the transient response of the mechanical behavior of the plantar fascia under dynamic loadings, standing conditions were used to analyze the relaxation of the plantar fascia over a time period of 120 seconds (which is the steady-state relaxation time of the plantar fascia). This study resulted in a fully functional model with transient stress data on the behavior of the plantar fascia during loading, along with stress and deformation data for the bones and soft tissue of the foot. The results obtained were similar to that recorded in literature. This model is the first step towards fully characterizing the mechanics of the plantar fascia so as to develop novel treatment methods for plantar fasciitis, and can be applied to future studies to develop novel orthotic devices and surgical techniques for the treatment of and prevention of plantar fasciitis.

Merging from on-ramps to mainline traffic is one of the most challenging driving maneuvers on freeways. The challenges are further heightened for older drivers, as they are known to have longer perception-reaction times, larger acceptance gaps, and slower acceleration rates. In this research, VISSIM, a microscopic traffic simulation software, was used to evaluate the influence of the aging drivers on the operations of a typical diamond interchange. First, drivers were recorded on video cameras as they negotiated joining the mainline traffic from an on-ramp acceleration lane at two sites along I-75 in Southwest Florida. Several measures of effectiveness were collected including speeds, gaps, and location of entry to the mainline lanes. This information was used as either model input or for verification purposes. Two VISSIM models were developed for each site – one for the existing conditions and verification, and another for a sensitivity analysis, varying the percentage of older drivers and Level of Service (from A to E), to determine their influence on ramp operational characteristics. According to the results, there was a significant difference in driving behavior between older, middle-aged, and younger drivers, based on the measures of effectiveness analyzed in this study. Additionally, as the level of service and percentage of older adult motorists increased, longer queues were observed with slower speeds on the acceleration lanes and the right-most travel lane of the mainline traffic.

Aluminum alloy castings are being integrated increasingly into automotive and aerospace assemblies due to their extraordinary properties, especially high strength-to-density ratio. To produce high quality castings, it is necessary to understand the mechanisms of the formation of defects, specifically pores and inclusion, in aluminum. There have been numerous studies on pore formation during solidification which lead to hot tearing and/or reduction in mechanical properties. However, a comprehensive study that correlates pore formation theory with in situ observations and modeling assumptions from the literature as well as experimental observations in not available. The present study is motivated to fill this gap. An in-depth discussion of pore formation is presented in this study by first reinterpreting in situ observations reported in the literature as well as assumptions commonly made to model pore formation in aluminum castings. The physics of pore formation is reviewed through theoretical fracture pressure calculations based on classical nucleation theory (i) for homogeneous and heterogeneous nucleation, and (ii) with and without dissolved gas, i.e., hydrogen. Based on the fracture pressure for aluminum, critical pore size and corresponding probability of vacancies clustering to form the critical-size pore have been calculated by using thermodynamic data reported in the literature. Calculations show that it is impossible for a pore to nucleate either homogeneously or heterogeneously in aluminum, even with dissolved hydrogen. The formation of pores in aluminum castings can only be explained by inflation of entrained surface oxide films entrained during prior damage to liquid aluminum (bifilms) under reduced pressure and/or with dissolved gas, which involves only growth, avoiding any nucleation problem. This mechanism is consistent with reinterpretations of in situ observations as well as assumptions made in the literature to model pore formation. To determine whether damage to liquid aluminum by entrainment of surface oxides can be observed and measured, Reduced Pressure Tests (RPT) have been conducted by using high quality, continuously cast A356.0 aluminum alloys ingots. Analyses of RPT samples via micro-computer tomography (μ-CT) scanning have demonstrated that number of pores and volume fraction of pore in aluminum casting increased by raising the pouring height (i.e., velocity of the liquid). Moreover, pore size distributions were observed to be lognormal, consistent with the literature. Cross-sections of RPT samples have been investigated via scanning electron microscopy. In all cases, the presence of oxygen was detected inside, around and between the pores. The existence of oxide films inside all pores indicates that oxide films act as initiation sites for pores and hydrogen only assist to growth of pores. For the first time, the pore formation is reconciled with physical metallurgy principles, supported by observations of oxide films in aluminum castings. Results clearly indicate that pores are extrinsic defects and can be eliminated by careful design of the entire melting and casting process.

Tomography is an imaging technique to develop a representation of the internal features of material using a penetrating wave, such as an electromagnetic wave. The calculation method used is an example of an inverse problem, which is a system where the input and the output are known but the internal parameters are not. These parameters can be estimated by understanding the responses of a penetrating wave as it passes through the unknown media. A forward problem is just the opposite; the internal structure and input penetrating wave is known and the output is determined. For both forward and inverse problems, raytracing is needed to define the raypath through the medium and inversion techniques are used to minimize the error for a discretized matrix of material properties. To assess various inversion techniques for use in shallow karst conditions, three synthetic karst geology models, each with increasing complexity, were generated. Each model was analyzed using forward modeling techniques to compare the calculated tomograms from known geometry and material properties. Gaussian Raytracing with LSQR inversion technique performed the best. This technique, Gaussian Raytracing with LSQR, was then applied to an inversion problem; cross-borehole ground penetrating radar data was collected at a karst geology field site and tomograms were produced. The resulting tomography confirmed information detailed in the driller's logs and features between boreholes were identified. This confirmed that cross-borehole ground penetrating radar is an applicable technique for use in geotechnical site characterization activities in karst areas.

Renewable energy sources are essential to our future, not only because they generally minimize harm to our environment but are also a relatively free source of energy that are available for generations to come. Wind and solar energy are proven sources of renewable energy, but both are highly variable. On the other hand, water wave energy is relatively persistent in locations around the world. Many researchers have tried to capture the energy of ocean waves, some were successful, but most were not. Harnessing wave energy is not a simple matter. One must design systems that can withstand the extreme forces of waves, the corrosive nature of salt water, and biofouling effects that can impact the system, while safely extracting energy from waves. This thesis presents the process followed in developing a new system to capture wave energy that has the potential to overcome many of the problems faced by other wave energy convertors (WEC). The concept of the design consists of a floating compliant structure that utilizes a mechanical system to harness water wave energy. The floating system can house several mechanical systems within the same structure, improving its power production and utilizing a greater area on the sea surface. The methodology uses linear wave theory to simulate different wave conditions to calculate the available energy to the system. This model provides estimates of the orbital motion of water particles which can be used to quantify the motions that such a system will undergo. The model can also be used to calculate the forces acting on the structure assuming rigid conditions. As with wind and solar power the wave energy greatly varies depending on the wave conditions, making the design of the structure much more difficult. The designed system must be capable of generating energy at low and high wave conditions and surviving extreme wave events.

Every year in the United States, an estimated 1.6 to 3.8 million people sustain sports-related traumatic brain injuries (TBIs), with an appreciable number of these injuries coming from the sport of softball. Several studies have analyzed the impact performance of catcher’s masks within the context of baseball; however, virtually no studies have been performed on fielder’s masks within the context of softball. Thus, the main objective of the present work was to evaluate the protective capabilities of softball fielder’s masks. To better understand the injury mechanisms and frequency associated with softball head/facial injuries, epidemiological data from a national database was reviewed first. Results displayed “struck-by-ball” as the most frequent injury mechanism (74.3%) for all head/facial injuries with a large majority occurring to defensive players (83.7%). With further motivation, the present work focused on testing the impact attenuation and facial protection capabilities of fielder’s masks from softball impacts. Testing with an instrumented Hybrid III headform was conducted at two speeds and four impact locations for several protective conditions: six fielder’s masks, one catcher’s mask, and unprotected (no mask). The results showed that most fielder’s masks reduced head accelerations, but not to the standard of catcher’s masks. On average, they reduced peak linear and angular acceleration from 40-mph impacts by 36-49% and 14-45%, respectively, while for 60-mph impacts they were reduced by 25-42% and 13-46%, respectively. Plastic-frame fielder’s masks were observed to allow facial contact when struck at the nose region at high speed. Observed differences in impact attenuation across fielder’s mask designs further suggested influence from specific design features such as foam padding and frame properties. Overall, the results clearly demonstrate that head/facial injuries may be mitigated through the broader use of masks, while further optimization of impact attenuation for fielder’s masks is pursued.

Rainfall affects the performance of traffic operations and endangers safety. A common and conventional method (rain gauges) for rainfall measurements mostly provide precipitation records in hourly and 15-minute intervals. However, reliability, continuity, and wide area coverage pose challenges with this data collection method. There is also a greater likelihood for data misrepresentation in areas where short duration rainfall is predominant, i.e., reported values may not reflect the actual equivalent rainfall intensity during subintervals over the entire reporting period. With recent weather and climate patterns increasing in severity, there is a need for a more effective and reliable way of measuring rainfall data used for traffic analyses. This study deployed the use of precipitation radar data to investigate the spatiotemporal effect of rainfall on freeways in Jacksonville, Florida. The linear regression analysis suggests a speed reduction of 0.75%, 1.54%, and 2.25% for light, moderate, and heavy rainfall, respectively. Additionally, headways were observed to increase by 0.26%, 0.54%, and 0.79% for light, moderate, and heavy rainfall, respectively. Measuring precipitation from radar data in lieu of using rain gauges has potential for improving the quality of weather data used for transportation engineering purposes. This approach addresses limitations experienced with conventional rain data, especially since conventional collection methods generally do not reflect the spatiotemporal distribution of rainfall.