PERIDYNAMIC UNIT CELL ENABLED FINITE ELEMENT MODELING OF FIBER STEERED COMPOSITES

This study presents an approach based on traditional finite elements and peridynamic unit cell (PDUC) to perform structural analysis of fiber steered composite laminates. Effective material property matrix for each ply in the plate element is computed by employing the PDUC based on the orientation of the fiber path and orthotropic ply properties. Each element defines the unit cell domain if the element shape is rectangular. Otherwise, the rectangle that circumscribes the element defines the domain of the unit cell. The element stiffness matrix is constructed through a traditional finite element implementation. This approach provides an accurate and simple modeling of variable angle tow laminates. It can be readily integrated in commercially available finite element programs.

Flowering in bursting bubbles with viscoelastic interfaces

The lifetime of bubbles, from formation to rupture, attracts attention because bubbles are often present in natural and industrial processes, and their geometry, drainage, coarsening, and rupture strongly affect those operations. Bubble rupture happens rapidly, and it may generate a cascade of small droplets or bubbles. Once a hole is nucleated within a bubble, it opens up with a variety of shapes and velocities depending on the liquid properties. A range of bubble rupture modes are reported in literature in which the reduction of a surface energy drives the rupture against inertial and viscous forces. The role of surface viscoelasticity of the liquid film in this colorful scenario is, however, still unknown. We found that the presence of interfacial viscoelasticity has a profound effect in the bubble bursting dynamics. Indeed, we observed different bubble bursting mechanisms upon the transition from viscous-controlled to surface viscoelasticity-controlled rupture. When this transition occurs, a bursting bubble resembling the blooming of a flower is observed. A simple modeling argument is proposed, leading to the prediction of the characteristic length scales and the number and shape of the bubble flower petals, thus paving the way for the control of liquid formulations with surface viscoelasticity as a key ingredient. These findings can have important implications in the study of bubble dynamics, with consequences for the numerous processes involving bubble rupture. Bubble flowering can indeed impact phenomena such as the spreading of nutrients in nature or the life of cells in bioreactors.

The majority of the variation in COVID-19 rates between nations is explained by median age, obesity rate, and island status

Since the World Health Organization declared SARS-CoV-2 to be a global pandemic on March 11, 2020, nearly every nation on earth has reported infections. Incidence and prevalence of COVID-19 case rates have demonstrated extreme geospatial and temporal variability across the globe. The outbreaks in some countries are extreme and devastating, while other countries face outbreaks that are relatively minor. The causes of these differences between nations remain poorly understood, and identifying the factors that underlie this variation is critical to understand the dynamics of this disease in order to better respond to this and future pandemics. Here, we examine four factors that we anticipated would explain much of the variation in COVID-19 rates between nations: median age, obesity rate, island status, and strength of border closure measures. Clinical evidence suggests that age and obesity increase both the likelihood of infection and transmission in individual patients, which make them plausible demographic factors. The third factor, whether or not each country is an island nation, was selected because the geographical isolation of islands is expected to influence COVID-19 transmission. The fourth factor of border closure was selected because of its anticipated interaction with island nation status. Together, these four variables are able to explain a majority of the international variance in COVID-19 case rates. Using a dataset of 190 countries, simple modeling based on these four factors and their interactions explains more than 70% of the total variance between countries. With additional covariates, more complex modeling and higher-order interactions explains more than 80% of the variance. These novel findings offer a solution to explain the unusual global variation of COVID-19 that has remained largely elusive throughout the pandemic.

Simple Modeling of Crystal Structure of Carbon Tetrachloride, Diamond, and Fullerene using Molymods

This research aims to make simple modeling of the crystal structure of carbon tetrachloride, diamond, and fullerenes using molymod. The method used is a descriptive quantitative with the research stages including the selection, making, and testing the feasibility of crystal structure. The feasibility of the crystal structure was assessed using a product feasibility test sheet and analyzed using the ideal standard mean equation. The development of a crystal structure model was carried out using a simple and easy method to obtain equipment in the form of molymod. The results of this research indicate that the crystal structure of carbon tetrachloride, diamond, and fullerenes can be interpreted significantly and easily with the help of molymod. The simple model of the crystal structure is also suitable for use as a physics learning medium that can help students understand abstract crystal structure material.

An analysis of the WTC fires using CIB correlations and simple modeling

CIB correlations for compartment burning rates and average gas temperatures are examined for accuracy, utility, and generality. The results are applied to modeling the fire on 9/11 in WTC 1. Specific information is used from the NIST investigation. It is demonstrated that simple heat transfer modeling can predict the truss steel rod temperatures for the E119 tests of WTC done by NIST. The CIB temperature correlation and steel truss modeling are used to predict burning conditions for the WTC 1 96th floor fire and compared to the NIST results. Here a consideration of fuel loads from 20 to 40 kg/m2 was considered compared to just 20 used by NIST. The results suggest that the fully insulated truss bar temperatures would achieve higher values for higher fuel loads. A critical steel truss temperature of 650°C could support failure of the trusses as a theory for the collapse of the towers.

Modelling the probability of detecting mass mortality events

While reports of mass mortality events (MMEs) are increasing in the literature, comparing the incidence of MMEs through time, among locations, or taxa is problematic without accounting for detection probabilities. MMEs involving small, cryptic species can be difficult to detect even during the event, and degradation and scavenging of carcasses can make the window for detection very short. As such, the number or occurrence rate of MMEs may often be severely underestimated, especially with infrequent observations. We develop a simple modeling framework to quantify the probability of detecting an MME as a function of the observation frequency relative to the rate at which MMEs become undetectable. This framework facilitates the design of surveillance programs and may be extended to correct estimates of the incidence of MMEs from actual surveillance data for more appropriate analyses of trends through time and among taxa.