The synthesis and characterization of novel complexes of silver supported by sterically demanding, highly electrophilic N-heterocyclic carbene (NHC) ancillary ligands, is described. Stable hydride, fluoride, alkoxide, alkyl, aryl, and alkynyl complexes are characterized by NMR spectroscopy and X-ray diffraction crystallography, and their reactivity is investigated. The interaction of silver centers in dinuclear complexes is probed by 109Ag NMR spectroscopy. Relevance to renewable fuel technology is demonstrated through the mediation of fundamental chemical transformations, including the heterolysis of hydrogen, the transfer of hydride to carbon dioxide, and the formation of carbon-carbon bonds. Kinetic studies shed light on the mechanism of hydrogen activation by hard-soft mismatched complexes of silver, and a formal catalytic cycle for the hydrogenation of carbon dioxide to formate derivatives is reported.

Roundabout installations are becoming common practice among DOTs and other local governments due to their superior safety attributes compared to other conventional at-grade intersections, especially stop-control and uncontrolled intersections. Current U.S. national guidelines for roundabout illumination recommend systematic illumination for all roundabouts. This recommendation might become a potential hindrance to desired widespread installations due to implied financial costs, especially in rural areas because the competing stop-control and uncontrolled intersections can be kept unlit. Interestingly rural roundabouts in most countries around the world are not illuminated as indicated by a recent survey of international roundabout illumination policies and standards from 45 countries. Also, review of intersection safety literature does not identify any publication that supports a systematic illumination policy of U.S. roundabouts. In fact, despite this recommendation there is no quantitative research on influence of illumination levels on nighttime safety at roundabouts and little on conventional intersections. Conversely, the literature shows a significant number of published studies which have indicated that currently recommended illumination levels on roadways can be reduced without compromising nighttime safety. This dissertation evaluates the link between roundabout crashes and different illumination levels. At the beginning of this dissertation research, there was no available repository of quantitative intersection illumination levels which could be used in highway safety research. Also, existing protocols for measurement require expensive light meters and are extremely time consuming to follow, making them impractical to use to study a large number of intersections. Consequently, this dissertation first evaluates the relationship with the best available data. The best available intersection illumination data was obtained from the Minnesota data contained in the Highway Safety Information System (HSIS). Minnesota crash and illumination data from 2003 to 2010 were analyzed. This illumination data was a qualitative description of intersection illuminating schemes and/or luminaire arrangement. Therefore, this dissertation also developed a cost-effective, accurate, and rapid method for measurement of quantitative intersection illumination data, and applied the developed protocol to a case study in Georgia. The measured intersection illumination was analyzed together with crash data obtained from GDOT for 2009 to 2014. The results of a naive analysis on the best available data indicated among other findings that the presence of lighting can provide approximately 61 percent lower total nighttime crash rate compared to the unlit condition. Also, providing illumination to the roundabout circle alone can yield about 80 percent of the benefits (55 percent reduction from unlit condition) of illuminating both the roundabout circle and approaches (66 percent reduction from unlit condition). Field test results for the camera calibration indicate that the average intersection illuminance derived from the protocol is within 4 percent difference of the actual average intersection illumination estimated from following the existing protocols. Next, despite limited roundabout data and potential issues of selection bias which could not be addressed in this dissertation, a cautious roundabout illumination specific crash modification factor was estimated with a negative binomial regression model. The model results showed that an increase of 1 lux in average roundabout illuminance will result in a 4.72 percent reduction in expected number nighttime crashes. The results of this work are useful in creating a sound framework for DOTs and other transportation agencies to determine the most appropriate level of illumination for roundabouts. This study also makes a number of significant contributions to highway safety research. First, this work is the first quantitative study on the impact of illumination on safety at roundabouts. The status-quo for highway safety research regarding the impacts of illumination had been to treat road lighting as a binary (Lit/Unlit) variable. However, even in most places without purposely-built road lighting there is usually ambient lighting from abutting facilities such as a gas stations or a store. Second, this dissertation is the first documented application of the photographic method to roundabouts. It is also the first documented application of the photographic method’s camera specific constant calibration approach to transportation field measurements. Previous documented application of the photographic method to transportation field measurements used an exposure specific calibration approach. Unlike the camera specific constant calibration approach, the exposure specific approach is rigid and field measurements must always be done at the exposure settings used in calibrating the camera. Thirdly, this work demonstrates the first developed procedure to developing uniformity (contour) plots from the photographic method. Next, this work can serve as the basis for initial efforts to create an illumination specific quantitative crash modification factor. Currently, the Highway Safety Manual is lacking in this important safety parameter. Last, but not the least this work offers procedures for collecting luminance data from the field and also documents a database of intersection illumination levels and intersection characteristics which can be used by future research.

Energy demand is projected to increase by 56% before 2040 and this will lead to the fast depletion of fossil fuels. Currently, biomass is the only sustainable source of organic carbon and liquid fuels. One major method of converting biomass involves the utilization of heterogeneous catalysts. However, there is still a lack of understanding in the reaction mechanisms and surface interactions between biomass-derived oxygenates and catalysts. Specifically, three important reactions are investigated: i) dehydration of glycerol, ii) hydrolysis of cellulose and cellobiose, and iii) hydrodeoxygenation of bio-oil. Some important concepts are gathered and provide insight into the most attractive conversion strategies. These concepts include the role of Lewis and Brønsted acid sites, synergistic effect between defect sites and functional groups, the advantage of weak acid sites, steric effect imposed by aromatic substituents, and the evolution of surface species in catalyst deactivation. These studies show that a deep understanding of surface chemistry can help to elucidate elementary reaction steps, and there is great potential in using heterogeneous catalysts for the conversion of biomass into targeted fuels and chemicals.

Erosion of a river bed has important implications with respect to scour around river structures such as bridges, transport of contaminants attached to the sediment, and disruption or destruction of aquatic habitats. Erosion occurs when the resistive strength of the sediment is overcome by the hydrodynamic forces produced by the flow of water. This resistance to erosion in a sediment originates from gravity or interparticle forces for coarse sediment (sand and gravel) and fine sediment (silt and clay), respectively. Since the erosion of fine sediment depends on the combination of many interparticle forces, and this combination fluctuates widely amongst different fine sediments, past studies have had difficulty finding a consistent method to estimate fine sediment erosion. This study analyzes sediments that fall in the transition size range between fine and coarse sediments and compares the findings with those from fine sediments (Wang 2013) and sandy coarse sediments (Navarro 2004, Hobson 2008), in order to correlate the erosion rates of both sediment types to their physical characteristics. In this study, kaolin-sand mixtures were prepared by mixing various percentages of Georgia kaolin by weight ranging from 30% to 100% with industrial fine sand and tap water. Geotechnical and other tests of sediment properties were performed to measure water content, bulk density, grain size distribution, temperature, pH, and conductivity of these mixtures. Hydraulic flume experiments measured the erosion rates of each sediment and these rates were used to estimate the critical shear stress correlating to that mixture. Relationships between the physical properties of the sediment and critical shear stress were developed by multiple regression analysis. An alternative option of estimating the critical shear stress by a weighted equation, which uses the combination of fine sediment erosion and coarse sediment erosion equations separately, was explored and found to be a viable and accurate option to estimating both coarse and fine sediment erosion from the same parameters and equation. The results from this study can be used to estimate sediment erodibility and thus river bed stability based on simple tests of physical properties of the river bed sediment and will help predict scour around bridges and other flow obstructions.

Level of Traffic Stress (LTS) is a bicycle quality of service measure originally developed by the Mineta Transportation Institute (MTI) that categorizes road infrastructure into four levels based on amount of traffic stress perceived by a bicyclist. The concept builds on research indicating that bicyclists can be grouped based on their comfort level. Riders identifying as strong and fearless as well as enthused and confident bicyclists represent most of the current users of the bicycle network across the US. However, there is a large group of cautious and concerned bicyclists that might be more likely to bike if the bicycle infrastructure were less stressful. This research applies the LTS methodology to quantify low stress bicycle access around the West End, Oakland City, and Lakewood/Ft. McPherson (Metropolitan Atlanta Rapid Transit Authority) MARTA rail stations. The Equitable Transit Oriented Development (TOD) typology analysis conducted by Reconnecting America identified these station areas as highly vulnerable with lagging markets. Additional analysis compares the existing low stress network, improved low stress networks, and the entire (low and high stress) bike network. Ultimately this work can serve as a model for both transportation planners interested in improving bike access both in general and specifically to transit.

This thesis examines the use of nonlinear ultrasound to evaluate sensitization, a precursor to stress corrosion cracking in austenitic stainless steel. Ultrasonic Rayleigh surface waves are generated on a specimen; as these waves pass through sensitized material, second harmonic generation (SHG) increases. In austenitic stainless steel with oven-induced sensitization, this increase is due only to the formation of chromium carbide precipitates, key products of the sensitization process. Weld-induced sensitization specimens demonstrate additional increases in SHG, likely caused by increased residual stress and dislocation density as a result of uneven heating. Experimental data are used to calculate the acoustic nonlinearity parameter, which provides a single value directly related to the quantity of micro- and nano-scale damage present within any given sample. Using this procedure, the effects of weld- and oven-induced sensitization are compared. Results demonstrate the feasibility of using nonlinear Rayleigh waves to detect and monitor stress corrosion susceptibility of welded material.

The Metropolitan Atlanta Rapid Transit Authority (MARTA) Transit Oriented Development (TOD) program has been expanding the number of stations being considered for development of surface parking lots and into the air rights over certain rail stations. As of 2015, MARTA has six rail stations in various stages of TOD development, which will increase multi-modal options for metro Atlanta residents. The overarching goal of TOD development is to increase transit ridership and reduce auto-dependency; hence quantifying the potential benefits of TOD development in terms of ridership is paramount. Despite several drawbacks, travel demand models have historically been utilized to forecast ridership for land use changes and transit improvements. Direct ridership models (DRMs) are transit demand forecasting methods that can be applied to land development in cases where traditional travel demand models (TDMs) are not well suited. DRMs leverage geographic tools commonly used by planners to take advantage of small scale pedestrian environment factors immediately surrounding transit stations. Although DRM data and methods can achieve greater precision in predicting local walk-access transit trips, the lack of regional and large-scale datasets reduces the ability to model ridership generated from riders outside the immediate vicinity of the rail stations. Stations that have high multi-modal access trips, particularly via personal vehicle and connecting buses, are not typically accounted for by DRMs. Hence, this study focuses on pedestrian-based rail boardings only, a metric that also allows the use of a large scale onboard survey distributed by the Atlanta Regional Commission (ARC) in late 2009 and early 2010 in Atlanta, Georgia. Analysis of the large scale on-board ridership survey also reveals variables that may be useful in forecasting ridership at the station level when coupled with available census data. Comparison of variables such as income, age, gender, ethnicity, and race from census data with the large scale survey guided the selection of candidate variables to be included in a DRM for MARTA rail stations. Results from the comparison showed that using census data in DRMs does not always accurately reflect the ridership demographics. Notable differences in pedestrian-based ridership and transit catchments appear to occur in populations making less than $40,000, African American populations, and the young and elderly populations. Large differences in the survey and census data reported around the stations raise questions about the usability of census data in predicting ridership at rail stations. Despite the shortcomings of using census data to directly predict walk access transit ridership, an ordinary least squared (OLS) regression model predicts a high proportion of variance of pedestrian-based ridership in Atlanta, Georgia. A small number of variables were incorporated into a DRM to show the strong relationship of employment density with pedestrian based ridership. The number of low income residents was also influential in increasing ridership via walk access.

Reflective roof coatings keep the roof cooler by minimizing solar absorption and maximizing thermal emission. Keeping the surface of the roof cooler allows less heat to be conducted into the interior of the building which reduces the cooling load in air-conditioned buildings and improve comfort conditions in non-air conditioned buildings. A number of cool white materials, compatible with most roofing products, are available on the market. To appeal to homeowners, special cool “color” products have been developed to match the dark colors of conventional residential roofs but are highly reflective in the invisible near-infrared (NIR) spectrum. Although many studies highlight the benefits of cool white coatings on roof membranes of low-slope roofs, knowledge of NIR reflective coatings on asphalt shingles of steep slope roofs remains limited. The intent of this exploratory study is to present a process that can be used to evaluate the perceived and actual benefits of NIR coatings field-applied to asphalt shingles on single-family houses. The proposed process can be applied to a large sample of homes and occupants in a future study. A questionnaire was designed to attempt to evaluate occupants’ perceived benefits in regards to their indoor environment and occupant satisfaction following applications of NIR coatings. Along with subjective data collection, a field-experiment was developed to objectively compare the thermal performance of an NIR reflective field-coated asphalt shingle roof system with that of a conventional asphalt shingle roof system. Questionnaire results indicated that occupants did not perceive any significant changes to their indoor environment but were satisfied overall with the application and appearance of the roof coating. Additionally, 50% of occupants stated that their monthly energy costs somewhat decreased after the application. Interestingly, 63% of respondents experienced some form of roof leak following the coating application. Among those who experienced roof leaks, 100% of the roofs were 10 years or older. Field results showed that the coated roof surface was 2 to 5℉ cooler than the uncoated roof surface at midafternoon. Statistical testing for correlation between coated roof surface temperature and external conditions revealed that relative humidity was negatively correlated with coated roof temperature, while solar altitude angle was positively correlated with coated roof temperature. Multiple linear regression analysis was used to develop a model for predicting the surface temperature of the coated asphalt shingle roofs from the ambient temperature, sky conditions, dew point temperature, relative humidity, solar altitude and azimuth angle.

The main objective of idle reduction devices is to reduce the amount of energy wasted by idling trucks, decrease exhaust emissions and save in fuel use and maintenance costs and vehicle life extension. To achieve reductions emissions from vehicle idling in heavy-duty trucks, strategies and actions have been employed through the use of various technologies, namely auxiliary power units (APUs), direct-fire heaters (DFHs), truck stop electrification (TSE) and advanced truck stop electrification (ATSE). Little quantitative data exists on the amount of emissions that are emitted by heavy-duty trucks during idling. In general, diesel engines emit less CO and hydrocarbons (HC) when compared to gasoline engines since fuel-lean mixtures tend to reduce CO and HC emissions. The purpose of this study is to conduct a systematic review that illustrates the status of data present in literature for costs and emissions reduced for APUs, DFHs, TSEs and ATSEs. From the review process, a cost calculator was devised from the synthesis of literature data to measure cost-effectiveness of these technologies in dollars per year per ton per year of emissions reduced over a 30 year investment period. Data on capital costs, maintenance and operational costs, and fuel costs were reported in order to calculate net present values, payback periods and fuel savings from each technology. Given the relevant data available from various studies that compute the efficiency of competing technologies, TSEs were the most cost-effective for the investor and the truck owner in regards to NOx emissions reduction. Cost-effectiveness measured for investors at $1,707.57 and $1,473.27 per ton of NOx reduced, and $16,799.91, $22,261.44, and $20,583.79 per ton of NOx reduced for truck owners. The calculator also served as a tool to illustrate insufficient data currently present in the body of literature. Limited quantitative data and unknown variability of costs as a function of time over the 30-year investment period was used to assess best practices. Thus, policymakers and other stakeholders can benefit from this review in order to conduct future studies that would enlighten greater understanding of data points from specifications of the operating context and devise more robust models for the sake of comparing these technologies based on impact and risk

<p> Clinical utility has been offered by numerous researchers as a criterion for understanding the value of diagnostic constructs, but it does not yet have a standard operational definition or recommended forms of measurement. The construct has significant overlap with diagnostic validity and it is possible that sub-domains of clinical utility may emerge that would contribute to development of a scale which could assess for improvements and degradations following nosological revisions, and also provide opportunity for cross-analysis with alternative systems of mental health diagnosis. Therefore, the present study collected survey data from psychologists about the clinical utility of the <i>DSM-5,</i> using online data collection and quantitative methods. Seven questions of clinical utility were rated using a 5 point likert scale for each of the <i>DSM-5</i>'s diagnostic categories and for the <i>DSM-5</i> as an overall nosology. Descriptive data, internal consistency and inter-item correlations were analyzed so that results could help address research questions posed about the clinical utility of the <i> DSM-5</i>'s diagnostic categories, the merits of <i>DSM-5</i> when compared to <i>DSM-IV,</i> and additional recommendations regarding optimal measurement of the clinical utility of diagnostic constructs.</p>