2011: The UK Chapter has regular meetings in the UK, and annually at the international conference. In February we held the 2011 Annual Gathering, with theme of 'Doing (much) More with Less' - in both public sector and corporate settings. You can see the topics of all the great talks we had at the event at www.systemdynamics.org.uk and also view slide-show videos of them all. Congratulations to Peter Lacey who won the Steer-Davis Gleave prize for the best UK application of system dynamics, and Rhys Lewis who won the UK Chapter Student prize for his work on social housing. Our evening networking events have continued: three in 2010. If you are based in the UK and not already on our membership list (membership is free) then please do join on our website and see what we have to offer. There are between 80 and 100 members active in SD in the UK.
Quality criteria do not only relate to the products mere quality, but to the production and marketing process of the product as well. Customers often express their dissatisfaction with low ethical standards in this area by consumer boycotts. As there are complex relationships between financial aspects and compliance, a system dynamics model is used to unveil causal relationships and explain behavioral patterns. The model highlights the links between a companys dilemma situation and the effectiveness of a boycott for those demanding different corporate conduct. It also demonstrates possible levers for triggering different behavior.
The aim of this paper is to propose an extension of System Dynamics approach for modeling systems to systems described by higher index DAEs (Differential Algebraic Equations). Existing implementations of Forresters methodology are commonly based on fixed step integration methods such as Euler or n-order explicit Runge-Kutta. The main reason for using fixed step integration schemes is their simplicity of imple-mentation as well as the the simplicity of modeling environments based on these integration schemes. On the other hand using fixed step integration can lead to incorrect results especially when equations are stiff. The problems with adequate integration schemes can be overcome by using variable stepsize integration methods such BDF or implicit Runge-Kutta. Since these methods require jacobians of right-hand sides of equations these numerical methods must be supported by procedures for evaluating jacobians either by finite difference, or by automatic differentiation (in order to keep the simplicity of modeling environment). Once we have variable stepsize integration procedure we can attempt to extend Forresters approach to systems described by fully implicit DAEs the paper shows how it can be achieved.
Cigarette smoking presented the most significant public health challenge in the United States in the 20th Century, and remains the single most preventable cause of morbidity and mortality in this country. A number of System Dynamics models exist to inform tobacco control policies. We reviewed them and discuss contributions. We developed a theory of the societal lifecycle of smoking, using a parsimonious set of feedback loops to capture historical trends and explore future scenarios. Previous work did not explain the long-term historical patterns of smoking behaviors. Much of it used stock-and-flow to represent the decline in prevalence in the recent past. With noted exceptions, information feedbacks were not embedded in these models. We present, simulate, and discuss our feedback-rich concept model. A formal analysis shows phenomena composed of different phases of behavior with specific dominant feedbacks associated with each phase. We discuss the implications of our society's current phase. We conclude with simulations of what-if scenarios. We expanded this body of work to provide an endogenous representation of the century-long societal lifecycle of smoking, because System Dynamics models must contain information feedback to be able to anticipate tipping points and to help identify policies that exploit leverage in a complex system.