# Relief Aircraft Dispatch Strategies Based on Different Levels of Information Sharing Systems
## 5 Simulation  
In this study, we compared different strategies by utilizing an agent-based simulation framework. In agent-based modeling, we can identify individual active components of a system, define their behaviors, and establish connections between them. The global dynamics of the system can emerge from the interactions of the many individual behaviors. Besides, it is also convenient to obtain various indicators for analysis.  
Therefore, we adopted an agent-based simulation tool to model the dynamic system of relief aircraft, rescue shelters, and dispatchment centers. The different strategies are embedded in the simulation to compare the effect of the relief activities using different indexes.  
This simulation has several components, as shown in Figure 7: injury data, airport operation, and dispatch strategies. The injury data are the input requests from the shelter, which are introduced in the numerical section. The dispatch strategies, which were embedded in this simulation, have been explained in the previous section. This section focuses on the aircraft operation process.  
In this simulation, each aircraft has four states: take-off, updating the injuries, landing, and dispatching. Hence, we set four corresponding aircraft groups and place the aircraft with similar states in the same group. This simulation determines the state of the aircraft in each group and updates these groups every minute. The following is a description of the different aircraft groups:  
Takeoff group:  
Figure 7: Framework of simulation.  
The simulation first updates the takeoff group. In this group, the aircraft have been assigned both the planned flight routing and time from the dispatch group (which is explained later). Each minute, the simulation simultaneously checks the planned takeoff time and the runway slot. If the aircraft's planned takeoff time is appropriate with any vacant runway slot, then the aircraft enters the next aircraft group, collecting group, and is removed from the takeoff group. If the aircraft's planned takeoff time is not appropriate in the runway slot, its planned time could be delayed to wait for the next check.  
Collecting group:  
In this group, each aircraft takes off and travels to the planned rescue center according to the planned routing. Upon arrival at a rescue shelter, the aircraft collects the injured. When it completes the various planned destinations, it enters the landing group and is removed from the collecting group.  
Landing group:  
The simulation checks the planned landing time and runway slot. If the planned landing time is suitable in the runway slot, the aircraft is removed from the landing group and enters the dispatching group. If there is no suitable runway slot for the landing time, it is delayed until the next check.  
Dispatching group:  
This part embeds different modules according to the different strategies. Each aircraft in this group is waiting to be assigned a planned routing and flight time. When a new injury request comes into the simulation system, the system checks the available aircraft and then employs different strategies to arrange a planned routing and flight time to the aircraft. After this, the aircraft is removed from this group into the takeoff group.