The outbreak of the novel coronavirus disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been continuously affecting human lives and communities around the world in many ways, from cities under lockdown to new social experiences. Although in most cases COVID-19 results in mild illness, it has drawn global attention due to the extremely contagious nature of SARS-CoV-2. Governments and healthcare professionals, along with people and society as a whole, have taken any measures to break the chain of transition and flatten the epidemic curve. In this study, we used multiple data sources, i.e., PubMed and ArXiv, and built several machine learning models to characterize the landscape of current COVID-19 research by identifying the latent topics and analyzing the temporal evolution of the extracted research themes, publications similarity, and sentiments, within the time-frame of January-May 2020. Our findings confirm the types of research available in PubMed and ArXiv differ significantly, with the former exhibiting greater diversity in terms of COVID-19 related issues and the latter focusing more on intelligent systems/tools to predict/diagnose COVID-19. The special attention of the research community to the high-risk groups and people with complications was also confirmed.
The CH149 Cormorant is the Canadian Forces (CF) designation for the AgustaWestland EH101, the Canadian Air Force's only dedicated search and rescue (SAR) helicopter. Since its procurement, the availability for operations of the CH149 fleet has been less than what was initially predicted. This study was undertaken to determine if the low serviceability of the fleet was due to its maintenance programme. A discrete-event simulation model was created to determine the number of aircraft available at any given time during a simulation run, assuming an ideal sparing situation. Analysis indicates that the current fleet cannot operate from four (or even three) Main Operating Bases (MOBs) in an ideal sparing situation, implying that the fleet's availability problem cannot theoretically be solved simply by addressing the logistical problem of the spares.
Pure CCl3F (Freon-11) vapor, initially below its room-temperature saturated vapor pressure, was compressed behind weak incident shock waves. The initial pressure was varied from 26 to 747 mm Hg, and the shock speed was varied from 141 to 321 m/s. The equilibrium cluster-size distribution was thus perturbed to varying degrees. Under the present experimental conditions cluster-forming processes en route to homonuclear condensation were set into motion. The exothermic redistribution of cluster sizes at the new temperature and pressure was monitored using the laser-schlieren technique over a time period of 10–300 μs. A characteristic redistribution time scale was measured as a function of temperature and pressure. The measured temperature and pressure dependence of the redistribution times are different than the classical temperature and pressure dependence of lag times in supersaturated vapors. A negative activation energy is observed, indicative of a strong competition between cluster formation, redissociation, and stabilization. A stability analysis of the nonlinear kinetic mechanism leads to a criterion for the onset of oscillations, and provides a basis for extracting elementary rate constants from the observations.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.