25 research outputs found
The United States COVID-19 Forecast Hub dataset
Academic researchers, government agencies, industry groups, and individuals have produced forecasts at an unprecedented scale during the COVID-19 pandemic. To leverage these forecasts, the United States Centers for Disease Control and Prevention (CDC) partnered with an academic research lab at the University of Massachusetts Amherst to create the US COVID-19 Forecast Hub. Launched in April 2020, the Forecast Hub is a dataset with point and probabilistic forecasts of incident cases, incident hospitalizations, incident deaths, and cumulative deaths due to COVID-19 at county, state, and national, levels in the United States. Included forecasts represent a variety of modeling approaches, data sources, and assumptions regarding the spread of COVID-19. The goal of this dataset is to establish a standardized and comparable set of short-term forecasts from modeling teams. These data can be used to develop ensemble models, communicate forecasts to the public, create visualizations, compare models, and inform policies regarding COVID-19 mitigation. These open-source data are available via download from GitHub, through an online API, and through R packages
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Experimental analysis of evaporation driven emulsion flow in porous media
textIn some configurations of compact, biofilm based photobioreactors, algae grow on a porous substrate that acts as the support system for the cells providing them with the necessary water and nutrients as well as carrying away their secreted products. The flow in these porous media can be driven by evaporation, mimicking the function of a synthetic leaf. The surface properties of the porous medium as well as the presence of a second immiscible phase in the fluid transported can significantly alter the transport capability and evaporative performance of the porous medium. The focus of this study is to investigate these effects through an experimental study. A dilute, 1% emulsion of lauric acid (chemical formula: CââHââOâ) in water was prepared using TweenÂź 80 surfactant. Evaporation driven flow of deionized water and the emulsion through two porous media, a hydrophilic glass fiber membrane and a less hydrophilic poly(vinylidene) fluoride (PVDF) membrane were studied. Experiments were conducted to determine the effect of porous medium and fluid properties on the rate of evaporation. The parameters investigated were the hydrophilicity of the porous medium and the area of the porous medium available for evaporation for both water and emulsion. During the experiment, the mass flow rate of the fluid as well as the temperature and the relative humidity of the ambient air were monitored. The results showed that for dilute emulsions, the rate of evaporation observed was the same as that for water and was dictated by the governing laws of convection applicable to the situation based on the geometry of the setup and the ambient conditions. The response of the porous medium to flow of dilute emulsion showed that the highly hydrophilic glass fiber porous medium rejected any accumulation of the oil phase in the pores, and ejected it out, whereas the lesser hydrophilic PVDF porous medium allowed the pores to be clogged by the oil phase, resulting in change in the properties of the medium. However, the dependence of this observation solely on surface properties of the medium cannot be ascertained as the glass fiber medium had a larger pore diameter than the PVDF medium, and this factor could be of effect. The relative humidity of ambient air affected the rate of evaporation, which implied that the flow was limited by evaporation rather than by the viscous losses in the porous medium. The response of change in rate of evaporation to change in relative humidity showed a high time lag. Also, it was seen that there was a maximum area over which evaporation occurred which was dictated by the capillary pressure generated by the porous medium and the viscous losses for the fluid flow through the medium. Any excess area available for evaporation did not have any effect on the rate of evaporation. Electrospinning, as a simple and effective process for generating fibrous porous media was presented and a sample porous medium was prepared using this method. A parametric analysis of the effect of the potential difference applied between the syringe tip and the collector electrode, and the distance between the tip and the collector on the diameter of fibers produced, was performed.Mechanical Engineerin