This paper deals with the use of âhotâ real-world cases for both testing and teaching purposes such as in the Introductory System Dynamics course at Delft University of Technology in the Netherlands. The paper starts with a brief overview of the System Dynamics curriculum. Then the problem-oriented teaching and testing approach is explained, followed by a presentation and discussion of several examples of âhotâ cases. The main goal of presenting the use of âhotâ testing/teaching cases is to spur other System Dynamics lecturers on to doing the same, and to start up a small network for exchanging the âhottestâ cases.
By the end of December 2008, alarming reports and articles concerning the cholera outbreak in Zimbabwe received plenty of international media coverage. By that time 30000 cases of cholera infections and 1600 cholera deaths had been reported. In the first week of January 2009, a System Dynamics simulation model related to this cholera epidemic was created which was turned into a âhotâ testing/teaching case. Although the model contains some bold assumptions, the dynamics of the model is sufficiently interesting for to be presented. This case is a System Dynamics study under uncertainty focused on exploring the general dynamics over time.
This paper presents a simple experimental System Dynamics model of the underlying value and market values of a bank to analyze the loss of trust in the bank. The System Dynamics model was developed on 28 September 2008 âthe day the governments of the Benelux countries met in a great hurry to rescue the Fortis bankâ in order to gain a better understanding of the potential dynamics of bank crises and to test policies for keeping banks from collapsing. The System Dynamics model âas well as the exam case based on itâ is interesting because of the actuality and importance of the topic, the small size and simplicity of the model, its potential to generate different dynamic behaviors, and its usefulness for policy exploration.
Inventory control is a fundamental activity in closed loop supply chains, particularly for remanufacturing processes. Several models have been developed in the literature where the aim is mostly to optimize cost or profit and to find the optimal order quantity for an integrated production and remanufacturing system. In this study, we explore a System Dynamics approach in order to model an inventory control system for a remanufacturing process in the context of a Closed Loop Supply Chain. Particularly, the return process is modelled through the influences relationships which several factors have on such process. The factors considered are residence time of the product with customer, service agreement with customers and customer behaviour in returning used products. The findings suggest that a reduction of residence time and an increase in the level of service agreement with customers, which in turn increases customer behaviour in returning used product, can lead to efficiency in inventory management for companies involved in remanufacturing process. In addition, we provide two simple case studies in support of these findings.
The aggregate profits of the airline industry have been dominated by a cyclical mode since before deregulation in the 1970s. In this paper we discuss several dynamics that combine to cause profit cycles: The misperception of the delay around capacity acquisition, the pro-cyclical ticket price setting policy and the countercyclical effect of industry congestion on passenger demand. By adding numerous endogenous feedbacks, extensions of previously used standard structures and wholly new structures we quantify the strength of these feedbacks, replicate the past behavior of the industry, and prescribe policies that can help to mitigate the cycle in airline industry earnings.
The Latinamerican Chapter has the mission to help the SD-community grow in the Spanish speaking countries. Founded in 2003, it has Latinamerican members from Mexico to Chile, from Spain and a growing number of Spanish speakers living in other countries. Since 2003, the annual meeting allows practitioners to gather and newcomers to get in to touch; we have been in Mexico, Chile, Colombia and Argentina so far. Since 2005, the Spanish "Revista de Dinámica de Sistemas" publishes two numbers per year. The "sisTEMAS" newsletter and a mail list allow keeping in touch. During October, the 6th Latinamerican Conference took place in Santiago de Chile, organized by University of Talca, Adolfo Ibañez University, Diego Portales University and Andrés Bello University. During the 2008 Annual Meeting we met many Spanish-speaking members living outside the Spanish-speaking countries and the wider group continues to grow. This year's meeting will take place in Santa Marta, Colombia in November 2009 ( http://simon.uis.edu.co/eventosds2009/home/). It is an opportunity to talk about sponsorships and future joint activities and also to welcome new members. If you would like to join us please contact Gloria Perez Salazar ( gloria.perez@itesm.mx), Isaac Dyner ( idyner@unalmed.edu.co) or Martin Schaffernicht ( martin@utalca.cl).
Net migration rate of -3.28 migrants/1000 population ranked Iran 145th in the world. Popular discourse about Iranian immigration focuses on the social and political freedoms associated with relocation. In the current research, the focus is on the authority of the educated people, their impacts on the society, their access to the power and the wealth which seems far negligible. The elites of Iran are no longer the educated people. Based on this assumption, a system dynamics approach is presented to study the long term effects of the emigration on Iranian society. Each emigrant develops themselves in the target country and attracts more emigrants. The success and satisfaction in the target country motivates the young generation to move than to change. The emigrants, when their number increases to millions, form a basement to attract more talented ones from the source country. Emigration of elites is more than a move of people; it has important negative effects on the country to produce wealth, to become industrialized, and to produce more talented
The purpose of this study is to illustrate the similarities and differences between discrete event simulation and continuous simulation modeling. A simple M/M/2 queuing system with crowd-dependent arrival rate is used. In the first part, the arrival rate decreases immediately as the number of customers in the system increases. The system is modeled using discrete event and continuous simulation. The results of two simulations are compared with each other and with their analytical solutions. In the second part, the number of customers in the system affects the arrival rate first with a continuous information delay, then with a discrete delay. Discrete and continuous simulations give very similar results in terms of dynamic behaviors of system variables. There are some minor differences in terms of the steady-state values of the variables, particularly the average time spent in system. Finally, increasing proportionately all parameters of the system (arrival rate and number of servers), reduces the discreteness of the system, bringing the discrete and continuous simulation results much closer.
This article reports on a theoretical simulation model to investigate effects from policy interventions in the adoption of electronic health records among hospitals, physicians, and patients. The project draws on established system dynamics diffusion theories and provides a conceptual framework to develop and test interventions to promote adoption of electronic medical records. Using data from the Greater Capital Region, Northern New York State, the findings from the simulation experiments suggests that there is no single right intervention but a combination of measures to promote the use of electronic health records not only on the provider side but also among patients.
While the System Dynamics modeling process can yield invaluable high level insights, it gives rise to a tremendous amount of detail complexity. In the course of their work, modelers must track successive model versions, the motivation for and assumptions underlying particular what if scenarios, and the implicit relationships between scenarios, model versions and various external artifacts such as spreadsheets, symbolic mathematics calculations, and external documentation. Failure to adequately manage such complexity can reduce the transparency, reliability, and credibility of the modeling process. While adherence to good modeling practices can aid this process, it often falls prey to corner-cutting or human error. This paper describes software that helps manage such complexity, by permitting modelers to easily access and succinctly compare historic versions of a model, by making explicit linkages between scenarios, the model versions and assumptions underlying them, and the motivations for and external files associated with model artifacts.