ABSTRACT
Understanding the wider effects of the COVID-19 pandemic on public health is needed to respond sufficiently to the impacts and facilitate recovery. We studied the secondary health impacts of COVID-19 through the changes in transportation using a ripple effect mode. Three ripples are defined to reflect the impacts of COVID-19 on (1) transportation and the systems behind it, (2) transportation-related health risk factors, and (3) public health. COVID-19 impacts on transportation are synthesized through six areas: transportation demand, transportation mode, traffic safety, land use and built environment, transportation jobs, and transportation equity. These changes are further associated with decreased transportation-related air pollution, greenhouse gases, noise, heat, and stress. Higher rates of road casualties were observed in the area of COVID-19. Social exclusion and limitations in accessibility to healthcare and healthy food were identified as negative consequences of changes in transportation. There are uncertainties in the rate of active transportation (i.e., walking and cycling) and related crashes that require further investigation. The findings of this study uncover the complex and relatively unknown impacts of COVID-19 on public health through changes in transportation. © 2023 by the authors.
ABSTRACT
Featured Application: Collapsing cavitation bubbles can be used in material surface cleaning, the medical field, and so on. By adjusting the micro-jet intensity of the collapsing bubbles, the cavitation phenomenon can be employed to clean irregular material surfaces, such as sections, cracks, and vegetable leaves. In the medical field, cavitation bubbles can be used as microbubble contrast agents for ultrasound diagnostic imaging or vehicles for drug or gene delivery. The growth and violent collapse of cavitation bubbles can also be employed in sterilization or killing viruses such as COVID-19. The interaction mechanism between the cavitation bubble and a solid wall is a basic problem in bubble collapse prevention and application. In particular, when bubble collapse occurs near solid walls with arbitrarily complex geometries, it is difficult to efficiently establish a model and quantitatively explore the interaction mechanism between bubbles and solid walls. Based on the advantages of the lattice Boltzmann method, a model for cavitation bubble collapse close to a solid wall was established using the pseudopotential multi-relaxation-time lattice Boltzmann model. Solid walls with arbitrarily complex geometries were introduced in the computational domain, and the fractal dimension was used to quantify the complexity of the solid wall. Furthermore, owing to the lack of periodicity, symmetry, spatial uniformity and obvious correlation in this process, the Minkowski functionals-based morphological analysis method was introduced to quantitatively describe the temporal evolution of collapsing bubble profiles and acquire effective information from the process. The interaction mechanism between the bubble and solid wall was investigated using evolutions of physical fields. In addition, the influences of the solid walls' surface conditions and the position parameter on collapsing bubbles were discussed. These achievements provide an efficient tool for quantifying the morphological changes of the collapsing bubble. © 2023 by the authors.