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Dissolved oxygen (DO) is one of the most important water quality factors. Maintaining the DO concentration at a desired level is of great value to both wastewater treatment plants (WWTPs) and aquaculture. This review covers various DO control strategies proposed by researchers around the world in the past 20 years. The review focuses on published research related to determination and control of DO concentrations in WWTPs in order to improve control accuracy, save aeration energy, improve effluent quality, and achieve nitrogen removal. The strategies used for DO control are categorized and discussed through the following classification: classical control such as proportional-integral-derivative (PID) control, advanced control such as model-based predictive control, intelligent control such as fuzzy and neural networks, and hybrid control. The review also includes the prediction and control strategies of DO concentration in aquaculture. Finally, a critical discussion on DO control is provided. Only a few advanced DO control strategies have achieved successful implementation, while PID controllers are still the most widely used and effective controllers in engineering practice. The challenges and limitations for a broader implementation of the advanced control strategies are analyzed and discussed. HIGHLIGHTS The application of control strategies of dissolved oxygen for water treatment was reviewed.; Systemically summarized the various dissolved oxygen control strategies in wastewater treatment process.; Surveyed the prediction and control methods of dissolved oxygen in aquaculture.; Provided a critical thinking on DO control.;

BackgroundThe repeated outbreaks of COVID-19 and the rapid increase in uncertainty have had many negative effects on the public’s mental health, especially on emotional aspects such as anxiety and depression. However, in previous studies, there are few studies exploring the positive factors between uncertainty and anxiety. The innovation of this study is the first to explore the mechanism of coping style and resilience as people’s psychological protective factors between uncertainty and anxiety caused by the COVID-19 pandemic.MethodsThis study explored the relationship between intolerance of uncertainty and anxiety of freshmen with coping style as mediating variable and resilience as moderating variable. A total of 1049 freshmen participated in the study and completed the Intolerance of Uncertainty Scale (IUS-12), Self-rating Anxiety Scale (SAS), Simplified Coping Style Questionnaire (SCSQ), and Connor-Davidson Resilience Scale (CD-RISC).ResultsSAS score of the surveyed students (39.56 ± 10.195) was significantly higher than that of the Normal Chinese score (29.78 ± 10.07, p < 0.001). Intolerance of uncertainty was significantly positively correlated with anxiety (β = 0.493, p < 0.001). Positive coping style has a significant negative impact on anxiety (β = −0.610, p < 0.001), negative coping style has a significant positive impact on anxiety (β = 0.951, p < 0.001). Resilience moderates the second half of the influence of negative coping style on anxiety (β = 0.011, t = 3.701, p < 0.01).ConclusionThe findings suggest that high levels of intolerance of uncertainty had negative effects mental burden during the COVID-19 pandemic. The knowledge of the mediating role of coping style and the moderating role of resilience may be used by health care workers when consulting freshmen with physical health complaints and psychosomatic disorders.