## 2 Methods
### Experimental Design  
In this study, a tower air traffic control simulator was used to provide an air traffic control environment to collect data. The simulator provided a virtual take-off, landing, and taxi scenario of an airport. The simulator and the layout of the simulated airport are shown in Figures 1 and 2, respectively. In the simulator, nine network computers were used to simulate the control system, approach radar, airport surveillance radar, and scenarios. Two radio communication devices were used to provide communication between the controller and pilot. The airport scenario was shown on five large displays, providing a 120\({}^{\circ}\) field of view. Flights were simulated in the control system during the experiment. The ATCOs provided instructions to the virtual pilots through the radio according to the radar and airport view and the virtual pilots executed the instructions to operate all the virtual planes. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Characteristics** & **Equipment** & **Measurement Methods** & **Parameters** \\ \hline Perception and decision-making & Detector for spatial configuration test & Four rectangles randomly numbered 1 to 4 from left to right were displayed on a screen, and there were four corresponding buttons. One of the rectangles was highlighted, and the subject had to press one of the buttons; an indicator light changed to green once the subject had pressed the correct button. The test was repeated 20 times. & LSPWB ART \\ \hline Perception and decision-making & Detector for spatial configuration test & The subject was required to determine the sequence of numbers for the four rectangles according to the previous tests and press the correct buttons in the subsequent tests as quickly as possible. At the end of the test, the last sequence of pressing the wrong button (LSPWB) and the average reaction time (ART) for the test sequences with the correct response were determined. & \\ \hline Dynamic physical state & Two heart rate monitors & The heart rate of the ATCO was monitored during the experiments. & Dynamic heart rate (DHR) (interval of 1 min) \\ \hline Comprehensive performance & Voice recorder & The speech of the ATCO and pilot were recorded during the experiments. & Speech recording \\ \hline \hline \end{tabular}
\end{table} 
Table 1: _Cont._The simulator has been used in ATCO training and license assessment for many years, which was helpful to make the ATCOs immerse in the simulated environment of air traffic control under a similar psychological state to their actual work. The primary objective of the experimental design was to induce fatigue and tense states and support data collection. The FA state was designed through the experiment time on the basis of the ATCOs' circadian rhythm in sleep and the TE state, by performing complex tasks according to the relation between tension and tasks. The recruitment survey of the ATCOs indicated that they generally slept from 11 pm to 7 am, had a noon break between 11:30 am and 1:00 pm, and began working again at 1:30 pm. It was also found that fatigue or sleepiness was especially common in connection with early morning and night shifts, and fatigue levels were highest during the night shift [7; 12; 60]. Therefore, the AL and TE state experiments were completed at 9-11 am or 3-5 pm, and the subjects were asked to sleep well more than three days before each visit to reduce the effects of fatigue. The FA and FT state experiments were conducted between 1 am and 3 am to make the participants become fatigued easily. Meanwhile, they were required to sleep for less than 6 h, get up before 8 am on the previous day, and not sleep before the FA and FT state experiments. ATCOs are more likely to become tense when control task demands exceed their abilities. It was also reported that most ATCOs felt nervous or tense in challenging situations [52]. The TE state was designed through complex control tasks.