ABSTRACT
In this study, a numerical investigation based on the CFD method is carried out to study the unsteady laminar flow of Newtonian fluid with a high viscosity in a three-dimensional simulation of a twisted double planetary mixer, which is composed of two agitating rods inside a moving tank. The considered stirring protocol is a "Continuous sine squared motion" by using the dynamic mesh model and user-defined functions (UDFs)to define the velocity profiles. The chaotic advection is obtained in our active mixers by the temporal modulation of rotational velocities of the moving walls in order to enhance the mixing of the fluid for a low Reynolds number and a high Peclet number. For this goal, we applied the Poincaré section and Lyapunov exponent as reliable mathematic tools for checking mixing quality by tracking a number of massless particles inside the fluid domain. Additionally, we investigated the development of fluid kinematics proprieties, such as vorticity, helicity, strain rate and elongation rate, at various time periods in order to view the impact of temporal modulation on the flow properties. The results of the mentioned simulation showed that it is possible to obtain a chaotic advection after a relatively short time, which can deeply enhance mixing fluid efficiency.
ABSTRACT
Background: The COVID-19 pandemic has caused overwhelming changes in individual and community daily-life, resulting from the public health measures implemented to contain it, and also from its psychological and socio-economic consequences. These shifts and consequences impacted the entire population, but some groups are more likely to be affected by these changes, including higher education students. Objectives: a) to investigate mental health status and its determinants among higher-education students in Portugal and Switzerland; and b) to explore adjustment patterns used by these students to overcome the impact of the COVID-19 pandemic. Methods: A cross-sectional study with a mixed-methods sequential explanatory design was conducted in two phases. First, an online survey was conducted among higher education students in Portugal and Switzerland, in Portuguese and French respectively. A convenience sampling method was used. Second, some participants from the first phase were invited to participate in four online focus group discussions (two in each country) using a maximum variation sampling method. Results: The survey was answered by 1,880 students. Portuguese students revealed higher levels of stress and anxiety, but lower depression symptoms and less resilient coping compared to Swiss respondents. Hope was identified as an explanatory variable for mental health symptoms in students from both countries. In the focus groups (n = 27), 13 adjustment strategies were found, which were subdivided into three spheres: personal, social, and contextual. Conclusions: The results suggest that the COVID-19 pandemic had a mild to moderate impact on most of the evaluated mental health variables. Nevertheless, the students reacted and mobilized positive short-term strategies, which need to be reinforced in order to prevent long-term psychological harm. In addition, our results can inform psychosocial interventions to minimize psychological impact, anxiety, depression, and stress due to sanitary crises or other population-wide problems or disasters.
ABSTRACT
BACKGROUND: Higher-education students are particularly vulnerable to both everyday stressors and mental health problems. Public health emergencies may generate a range of unforeseen potential stressors for vulnerable individuals and communities. The current pandemic has apparently led to an increase in psychiatric symptoms among these students. OBJECTIVE: The goal of this study is to characterize the psychological impact of the COVID-19 pandemic among Portuguese and Swiss higher-education students. METHODS: This project will use a mixed methods sequential explanatory design in Portugal and Switzerland, with two consecutive phases. During Phase I, a quantitative study will assess the psychological responses of higher-education students during the COVID-19 pandemic. A convenience sampling method will be used for collecting information from students. The association between variables will be determined with univariable and multivariable analyses. During Phase II, qualitative data will be collected in order to understand the determinants of psychological stress and the strategies adopted by students as a result of the COVID-19 pandemic, as well as to identify their opinions and feelings about the teaching-learning process during quarantine. In this phase, participants will be selected using a maximum-variation sampling method. Data from focus group discussions will be coded and inductively analyzed using a thematic analysis approach. Finally, quantitative and qualitative results will be merged during interpretation to provide complementary perspectives. RESULTS: This paper describes and discusses the protocol for this mixed methods study, which will be completed in December 2021. This study was formally approved by the local ethics committee (CE/IPLEIRIA/22/2020) in Portugal and authorized by the Swiss Association of Research Ethics Committees, swissethics (CER-VD-2020-02889). CONCLUSIONS: This research can contribute to the development of teaching tools and methods that reinforce positive mental health strategies, hope, and adaptive coping among students, and to the development of a class on mental health interventions in the context of catastrophic and traumatic events. This project will also help government stakeholders as well as health and education professionals safeguard the psychological well-being of students facing an expanding COVID-19 pandemic. INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): PRR1-10.2196/28757.
