DPM model segregation validation and scaling effect in a rotary drum

Discrete phase method (DPM) model was used to analyse rotary drum systems for segregation behavior. DPM simulations were performed for comparison with a dynamic segregation experimental measurement from the literature. This included dynamic segregation and time-averaged particle velocity field, which were validated with experimental data. In addition, a direct DPM and parcel scaled DPM simulation study was performed to analyse the effect of drum and particle parcel size scaling. The segregation dynamics was evaluated using the Lacey mixing index. This work shows segregation dynamics decreases with increasing drum size while keeping the same particle size. It further shows that for a given drum size the segregation dynamics deviate after a certain particle parcel scaling limit. The parcel scaling limit also increases with increasing drum size.

Disproportionate incidence of COVID-19 in African Americans correlates with dynamic segregation

Socio-economic disparities quite often have a central role in the unfolding of large-scale catastrophic events. One of the most concerning aspects of the ongoing COVID-19 pandemics is that it disproportionately affects people from Black and African American backgrounds creating an unexpected infection gap. Interestingly, the abnormal impact on these ethnic groups seem to be almost uncorrelated with other risk factors, including co-morbidity, poverty, level of education, access to healthcare, residential segregation, and response to cures. A proposed explanation for the observed incidence gap is that people from African American backgrounds are more often employed in low-income service jobs, and are thus more exposed to infection through face-to-face contacts, but the lack of direct data has not allowed to draw strong conclusions in this sense so far. Here we introduce the concept of dynamic segregation, that is the extent to which a given group of people is internally clustered or exposed to other groups, as a result of mobility and commuting habits. By analysing census and mobility data on more than 120 major US cities, we found that the dynamic segregation of African American communities is significantly associated with the weekly excess COVID-19 incidence and mortality in those communities. The results confirm that knowing where people commute to, rather than where they live, is much more relevant for disease modelling.

Effect of monotonic lateral load on the performance of reinforced graded concrete column, an experimental study

A gradation pattern in the strength of concrete columns is unavoidable due to the presence of static and dynamic segregation. The effect of concrete uniformity on columns subjected to monotonic lateral load is investigated experimentally in this study. Reinforced concrete columns with cross-sectional dimensions of 150 x 150 mm and a height of 1000 mm are prepared as graded concrete column (GCC) specimens and controlling specimens. The columns are designed with a reinforcement ratio of 1%. Two concrete mixes with a strength of 20 MPa and 30 MPa are cast in moulds using the gradual compaction procedure to create a satisfactory strength transition throughout the specimens’ height. The resulting lateral deformation and resisting load are utilised for further analysis. The analyses show that the GCC exhibits a lower peak load and lateral deformation than the control specimen, and a distinct failure mode is observed. The GCC also shows more brittle behaviour in the post-peak region.