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This chapter covers the basic principles, concepts, and tools governing the operation of the equipment and systems described in Chapter 3. The operation of those systems in off-design conditions, steady as well as unsteady (transient), are described using basic formulae and charts.
In this chapter, we discuss models for the scheduling of continuous processes. We use the sets, subsets, and parameters introduced in Chapter 7 to represent a facility. To simplify the presentation, we consider problems with the following assumptions: (1) dedicated storage vessels; (2) no storage in processing units; (3) instantaneous and resource unconstrained material transfers; (4) no unit deterioration; and (5) demand that can be satisfied (no backlogs). We start, in Section 9.1 with some background and a discussion of the main differences between batch and continuous processing. In Section 9.2, we present the basic, STN-based, model; and we close, in Section 9.3, with numerous extensions including modeling for startups and shutdowns, transitions between tasks, and time delays.
The aim of this study was to investigate the changes in Chinese residents’ psychological state and its influencing factors after the Wuhan shutdown on January 23, 2020.
Methods:
Two surveys were conducted on February 1-5 and February 20-24, separately, using an online self-administrated questionnaire among 3145 and 3814 participants, respectively. Subjective indicators of daily-life changes include level of attention, risk of infection, impact of daily life, self-perceived health status, and mental health help-seeking. Individual scores on changes in anxiety, depression, and stress were generated by 6-item, 4-item, and 3-item questions. A multivariate regression model was fitted in each survey, separately and combined.
Results:
A total of 6959 residents participated in the study, with 32.78% male and 67.22% female, people living in Wuhan and other cities in Hubei Province accounted for 25.22% and 18.85%, respectively. One week after the Wuhan shutdown, their anxiety, depression, and stress had all increased. Compared with the first survey, the changes in the scores of anxiety, depression, and stress in the second survey were decreased (β = −1.220, −0.798, and −0.623, all P < 0.001). The level of attention, risk of infection, and self-perceived health status tended to be positively associated with the changes in the scores of anxiety, depression, and stress.
Conclusions:
The study showed that the lives and psychological conditions of residents had undergone negative changes after the Wuhan shutdown, but the measures taken during this period were effective. These results may provide guidance for public health policies in other countries and regions.
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