Objectives: To improve ambulance response time, matching ambulance availability with the emergency demand is crucial. To maintain the standard of 90% of response times within 9 minutes, the authors introduce a discrete-event simulation method to estimate the threshold for expanding the ambulance fleet when demand increases and to find the optimal dispatching strategies when provisional events create temporary decreases in ambulance availability.Methods: The simulation model was developed with information from the literature. Although the development was theoretical, the model was validated on the emergency medical services (EMS) system of Tainan City. The data are divided: one part is for model development, and the other for validation. For increasing demand, the effect was modeled on response time when call arrival rates increased. For temporary availability decreases, the authors simulated all possible alternatives of ambulance deployment in accordance with the number of out-of-routine-duty ambulances and the durations of three types of mass gatherings: marathon races (06:00-10:00 hr), rock concerts (18:00-22:00 hr), and New Year's Eve parties (20:00-01:00 hr).Results: Statistical analysis confirmed that the model reasonably represented the actual Tainan EMS system. The response-time standard could not be reached when the incremental ratio of call arrivals exceeded 56%, which is the threshold for the Tainan EMS system to expand its ambulance fleet. When provisional events created temporary availability decreases, the Tainan EMS system could spare at most two ambulances from the standard configuration, except between 20:00 and 01:00, when it could spare three. The model also demonstrated that the current Tainan EMS has two excess ambulances that could be dropped. The authors suggest dispatching strategies to minimize the response times in routine daily emergencies.Conclusions: Strategies of capacity management based on this model improved response times. The more ambulances that are out of routine duty, the better the performance of the optimal strategies that are based on this model.
A method is developed for growing three-dimensional hierarchic structures of porous graphenic carbon film/ hollow carbon nanorods where porous graphenic carbon film is first synthesized followed by, growth of carbon nanorods. By annealing an amorphous carbon layer deposited underneath a nickel thin film at elevated temperatures, the porous graphenic carbon film forms on top via carbon diffusion and precipitation from the grain boundaries of the nickel film. The porosity of the graphenic carbon film is determined by the surface voids of the nickel film resulting from grain coalescence during annealing. Hollow carbon nanorods can then be grown on the pore edges of the porous graphenic carbon film by chemical vapor deposition without catalysts. It is speculated that the dangling bonds of the carbon atoms on the pore edges of the graphene layers might be responsible for the nucleation of the hollow carbon nanorods. The microstructures and growth mechanisms of both porous graphenic carbon film and hollow carbon nanorods are characterized and discussed in detail.
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