64 research outputs found

    Development of a Statistical Model to Predict Materialsā€™ Unit Prices for Future Maintenance and Rehabilitation in Highway Life Cycle Cost Analysis

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    The main objectives of this study are to investigate the trends in primary pavement materialsā€™ unit price over time and to develop statistical models and guidelines for using predictive unit prices of pavement materials instead of uniform unit prices in life cycle cost analysis (LCCA) for future maintenance and rehabilitation (M&R) projects. Various socio-economic data were collected for the past 20 years (1997ā€“2018) in California, including oil price, population, government expenditure in transportation, vehicle registration, and other key variables, in order to identify factors affecting pavement materialsā€™ unit price. Additionally, the unit price records of the popular pavement materials were categorized by project size (small, medium, large, and extra-large). The critical variables were chosen after identifying their correlations, and the future values of each variable were predicted through time-series analysis. Multiple regression models using selected socio-economic variables were developed to predict the future values of pavement materialsā€™ unit price. A case study was used to compare the results between the uniform unit prices in the current LCCA procedures and the unit prices predicted in this study. In LCCA, long-term prediction involves uncertainties due to unexpected economic trends and industrial demand and supply conditions. Economic recessions and a global pandemic are examples of unexpected events which can have a significant influence on variations in material unit prices and project costs. Nevertheless, the data-driven scientific approach as described in this research reduces risk caused by such uncertainties and enables reasonable predictions for the future. The statistical models developed to predict the future unit prices of the pavement materials through this research can be implemented to enhance the current LCCA procedure and predict more realistic unit prices and project costs for the future M&R activities, thus promoting the most cost-effective alternative in LCCA

    Greenhouse Gas Reduction Opportunities for Local Governments: A Quantification and Prioritization Framework

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    Caltrans 65A0686, Task Order 010USDOT Grant 69A3551747114Local governments have steadily increased their initiative to address global climate change, and many present their proposed strategies through climate action plans (CAPs). This study conducts a literature review on current local approaches to greenhouse gas (GHG) reduction strategies by assessing CAPs in California and presents common strategies in the transportation sector along with useful tools. One identified limitation of many CAPs is the omission of quantitative economic cost and emissions data for decision-making on the basis of cost-effectiveness. Therefore, this study proposes a framework for comparing strategies based on their life cycle emissions mitigation potential and costs. The results data can be presented in a marginal abatement cost curve (MACC) to allow for side-by-side comparison of considered strategies. Researchers partnered with Yolo and Unincorporated Los Angeles Counties to analyze 7 strategies in the transportation and energy sectors (five and two, respectively). A MACC was subsequently developed for each county. Applying the life cycle approach revealed strategies that had net cost savings over their life cycle, indicating there are opportunities for reducing emissions and costs. The MACC also revealed that some emissions reduction strategies in fact increased emissions on a life cycle basis. Applying the MACC framework to two case study jurisdictions illustrated both the feasibility and challenges of including quantitative analysis in their decision-making process. An additional barrier to using the MACC framework in the context of CAPs, is the mismatch between a life cycle and annual accounting basis for GHG emissions. Future work could explore more efficient data collection, alternative scopes of emissions for reporting, and environmental justice concerns

    Updating Weigh-in-Motion (WIM) Spectra in PaveM

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    Quantum Monte Carlo Study of the Water Dimer Binding Energy and Halogen-?? Interactions

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    Halogen-?? systems are involved with competition between halogen bonding and ??-interaction. Using the diffusion quantum Monte Carlo (DMC) method, we compare the interaction of benzene with diatomic halogens (X2: Cl2/Br2) with the typical hydrogen bonding in the water dimer, taking into account explicit correlations of up to three bodies. The benzene-Cl2/Br2 binding energies (13.07 ?? 0.42/16.62 ?? 0.02 kJ/mol) attributed to both halogen bonding and dispersion are smaller than but comparable to the typical hydrogen bonding in the water dimer binding energy (20.88 ?? 0.27 kJ/mol). All of the above values are in good agreement with those from the coupled-cluster with single, double, and noniterative triple excitations (CCSD(T)) results at the complete basis set limit (benzene-Cl2/Br2: 12.78/16.17 kJ/mol; water dimer: 21.0 kJ/mol)

    Continuous-flow Si-H functionalizations of hydrosilanes via sequential organolithium reactions catalyzed by potassium tert-butoxide

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    We herein report an atom-economic flow approach to the selective and sequential mono-, di-, and tri-functionalizations of unactivated hydrosilanes via serial organolithium reactions catalyzed by earth-abundant metal compounds. Based on the screening of various additives, we found that catalytic potassium tert-butoxide (t-BuOK) facilitates the rapid reaction of organolithiums with hydrosilanes. Using a flow microreactor system, various organolithiums bearing functional groups were efficiently generated in situ under mild conditions and consecutively reacted with hydrosilanes in the presence of t-BuOK within 1 min. We also successfully conducted the di-funtionalizations of dihydrosilane by sequential organolithium reactions, extending to a gram-scale-synthesis. Finally, the combinatorial functionalizations of trihydrosilane were achieved to give every conceivable combination of tetrasubstituted organosilane libraries based on a precise reaction control using an integrated one-flow system.11Nsciescopu
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