Wave Propagation in an Elastic Half Space Due to Couples Applied at a Point Beneath the Surface

Office of Naval Research. Department of the Navy: Contract No. N00014-67-A-0305-0010; Project No. NR 064-183U.S. Army Research Office - Durham: Project No. D0161102B33G, Proposal No. D-5

Three-Dimensional Stability of Burgers Vortices: the Low Reynolds Number Case

In this paper we establish rigorously that the family of Burgers vortices of the three-dimensional Navier-Stokes equation is stable for small Reynolds numbers. More precisely, we prove that any solution whose initial condition is a small perturbation of a Burgers vortex will converge toward another Burgers vortex as time goes to infinity, and we give an explicit formula for computing the change in the circulation number (which characterizes the limiting vortex completely.) We also give a rigorous proof of the existence and stability of non-axisymmetric Burgers vortices provided the Reynolds number is sufficiently small, depending on the asymmetry parameter.Comment: 30 pages, no figur

Reproduction of Twentieth Century Intradecadal to Multidecadal Surface Temperature Variability in Radiatively Forced Coupled Climate Models

[1] Coupled Model Intercomparison Project 3 simulations that included time-varying radiative forcings were ranked according to their ability to consistently reproduce twentieth century intradecadal to multidecadal (IMD) surface temperature variability at the 5° by 5° spatial scale. IMD variability was identified using the running Mann-Whitney Z method. Model rankings were given context by comparing the IMD variability in preindustrial control runs to observations and by contrasting the IMD variability among the ensemble members within each model. These experiments confirmed that the inclusion of time-varying external forcings brought simulations into closer agreement with observations. Additionally, they illustrated that the magnitude of unforced variability differed between models. This led to a supplementary metric that assessed model ability to reproduce observations while accounting for each model\u27s own degree of unforced variability. These two metrics revealed that discernable differences in skill exist between models and that none of the models reproduced observations at their theoretical optimum level. Overall, these results demonstrate a methodology for assessing coupled models relative to each other within a multimodel framework

Robinson, Thomas

Co I, 371 Infantryhttps://dh.howard.edu/prom_members/1070/thumbnail.jp

Robinson, Eugene (Mrs.)

https://dh.howard.edu/prom_corres/1124/thumbnail.jp

Robinson, Eugene (Mrs.) (2)

https://dh.howard.edu/prom_corres/1125/thumbnail.jp

Distribution of the Presidential Vote of 1912

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Impact of Optimally Minimizing Delay Times on Safety at Signalized Intersections in Urban Areas, Case Study: The City of Virginia Beach

Optimally minimizing delay times at signalized intersections can significantly improve both traffic flow and safety. However, most traffic flow optimizing tools do not measure the effect on safety. This study uses nonlinear programming (NLP) algorithms to optimally minimize delay times and employs both Safety performance functions (SPFs) and empirical Bayes (EB) before-after methodology to measure the impact on safety presented as a Crash Modification Factor (CMF). A crash modification factor (CMF) is a multiplicative factor used by transportation practitioners to compute the expected number of crashes at specific study site(s) after a countermeasure has been proposed or is implemented. Using 2013 traffic data from seventeen signalized intersections located in Virginia Beach, the results show that optimally minimizing intersection delay times can result in a safety improvement of approximately 26.46% that is a CMF of 0.735. This result is not conclusive, but the significance of the findings shows the need for further investigations and potential inclusion in the future editions of the Highway Safety Manual (HSM)

Innovations for sustainable lifestyles – an agent based model approach

An important aspect of any scientific approach to sustainability must be methods by which the impacts of possible innovations can be assessed. Clearly, we need to make massive changes in our lifestyles if we are to get anywhere near ‘sustainability’. In this paper, an ‘agent-based model’ is developed which for this initial presentation explores probable impacts on household consumption and emissions of possible innovations. The model randomly picks a large number (here 10,000, but it can be much larger) of households from four different countries and calculates the effects resulting from the adoption of specific innovations. The ‘lifestyle’ of the households within the area studied is divided into four different ‘domains’. These are living, food, mobility and energy. Innovations are launched in the four different domains and the model shows the overall effects on the total input requirements (materials, energy, etc.), the household and food wastes and the CO2 emissions, showing how far the system moves towards sustainability. By using the sustainability criteria of 8000 kg ‘input material’ per year per individual developed by the Wuppertal Institute (Lettenmeier et al. in Resources 3:488–515, 2014, https://doi.org/10.3390/resources3030488, http://www.mdpi.com/journal/resources, ISSN 2079-9276), we can calculate how far the nation or region is from sustainability after adopting possible innovations. This is a measure of the total inputs required per individual per year. It allows us to show that for different countries, with widely different climates (e.g. Finland and Spain), different household innovations would have a greater or lesser impact on attaining ‘sustainable lifestyles’. The model does not pretend to develop a full simulation of each system, including the ecosystem, type of economy, etc., but does look at the effect an innovation in one household domain will have on all four domains, thereby providing information that can improve current decisions. It also demonstrates that, although ‘households’ can do much to improve the situation by reducing their demand for energy and materials, some actions at a national/regional level will be required to achieve sustainability. For example, sustainability will require an end to the use of fossil fuels for transportation and a switch to ‘clean’ electrical power generation from renewables and nuclear sources. Without this change, these countries will find it impossible to reach a sustainable lifestyle