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Discrete-event Simulation (discrete-event + simulation)

Distribution by Scientific Domains

Engineering	50%

Selected Abstracts

Using a Discrete-event Simulation to Balance Ambulance Availability and Demand in Static Deployment Systems

ACADEMIC EMERGENCY MEDICINE, Issue 12 2009
Ching-Han Wu EMT-P
Abstract 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. [source]

Scene Graph and Frame Update Algorithms for Smooth and Scalable 3D Visualization of Simulated Construction Operations

COMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 4 2002
Vineet R. Kamat
One of the prime reasons inhibiting the widespread use of discrete-event simulation in construction planning is the absence of appropriate visual communication tools. Visualizing modeled operations in 3D is arguably the best form of communicating the logic and the inner working of simulation models and can be of immense help in establishing the credibility of analyses. New software development technologies emerge at incredible rates that allow engineers and scientists to create novel, domain-specific applications. The authors capitalized on a computer graphics technology based on the concept of the scene graph to design and implement a general-purpose 3D visualization system that is simulation and CAD-software independent. This system, the Dynamic Construction Visualizer, enables realistic visualization of modeled construction operations and the resulting products and can be used in conjunction with a wide variety of simulation tools. This paper describes the scene graph architecture and the frame updating algorithms used in designing the Dynamic Construction Visualizer. [source]

Quantitative analysis of passenger and baggage security screening at airports

JOURNAL OF ADVANCED TRANSPORTATION, Issue 2 2007
Alexandre G. de Barros
The terrorist attacks in the United States in 2001 opened a new era in air transportation. The realization that civil aircraft can be used as powerful weapons of mass destruction by a small group of people has drastically increased the need for security screening procedures to protect civil flights. Serving as the interface between the air and land transportation modes, airports have become the main focus in the implementation of those procedures. The need to more thoroughly screen passengers and baggage, and the consequent increase in processing time, has created the need for more space for security checkpoints and baggage screening inside passenger terminal buildings,space that is costly and very difficult to find in existing buildings. This paper evaluates the impact those measures have had on the planning and operation of airport passenger terminals. Quantification of those impacts is performed with the use of discrete-event simulation and spreadsheet models. [source]

A hybrid method for simulation factor screening

NAVAL RESEARCH LOGISTICS: AN INTERNATIONAL JOURNAL, Issue 1 2010
Hua Shen
Abstract Factor screening is performed to eliminate unimportant factors so that the remaining important factors can be more thoroughly studied in later experiments. Controlled sequential bifurcation (CSB) and controlled sequential factorial design (CSFD) are two new screening methods for discrete-event simulations. Both methods use hypothesis testing procedures to control the Type I Error and power of the screening results. The scenarios for which each method is most efficient are complementary. This study proposes a two-stage hybrid approach that combines CSFD and an improved CSB called CSB-X. In Phase 1, a prescreening procedure will estimate each effect and determine whether CSB-X or CSFD will be used for further screening. In Phase 2, CSB-X and CSFD are performed separately based on the assignment of Phase 1. The new method usually has the same error control as CSB-X and CSFD. The efficiency, on the other hand, is usually much better than either component method. © 2009 Wiley Periodicals, Inc. Naval Research Logistics, 2010 [source]