The objective of this workshop is to provide participants an introduction to agent-based modeling of
crowd dynamics. A summary of pedestrian socio-psychological egress behavior will be presented
together with an outline of existing modeling techniques and software tools. A detailed description of a
simple crowd model that can be implemented using MATLAB will be presented. Participants will learn
how to develop a simple yet fully functional simulation and visualization of crowd dynamics. Skeleton
Matlab scripts will be available for download from www.sanithw.org starting July 1st, 2005 but will also
be available via PC/MAC compatible USB drives during the workshop.
In a constantly changing environment, a Computer Security Incident Response Team (CSIRT) has to evolve over time in order to sustain or improve its effectiveness. The main task of a CSIRT is to help victims mitigate the effects of computer security incidents. A frequently identified problem for a CSIRT is that they are overworked, understaffed and under funded. In this paper, we present a conceptual model of such conditions based on a case study. The model is a first attempt to understand the main factors influencing a CSIRTs ability to handle computer security incidents effectively, and to identify ways to improve their overall effectiveness. Based on theory from process improvement and information from the case study, we have identified that short-term pressure from a growing incident workload prevents any attempts for developing more response capability long-term. Fundamental solutions to solve this problem will typically involve a worse-before-better trade-off for management.
Information revolutions change the world by taping into a positive feedback loop. If we can identify the loops we can understand where they might be going and what their limits might be. We need to know the difference between a short-term trend and a long term dynamic. We need to know where this information might be pushing us so we can know if it is where we want to go.
Trying to look at a category, as broad as information revolutions, to identify patterns requires an approach that will give a broad but well specified picture a way to understand the positive feedback loops that create the growth and also to understand the countervailing loops that come into play in various ways. I believe that causal loop diagrams can give us a clearer picture of this kind of broad, messy problem
This paper describes transform approaches to control Vendor-Managed Inventory (VMI). The effect of different modelling techniques and their significance is examined. Modelling was achieved with the Simulink package using the equations developed by Disney and Towill for a VMI system model. Analysis of several types of delay representation were compared to illustrate how the results depend on their formulation. The effect of using a discrete model is to deepen the stock-out and increase the required order rate. Analysis of the stability of the different models are discussed and evaluated. It is shown that the continuous model with an exponential delay is always stable and with a fixed delay can be made stable. The requirement for the system is also computed for a discrete model with exponential delay. Reduced inventory stock-out and a smaller WIP peak are achieved with different order smoothing function. This has special significance for e-manufacture.
An interactive learning environment (ILE) appropriate for intermediate macroeconomics students has
been simplified for students in introductory college and high school courses. Without changing the
underlying model or the simulation options, the simplified instructional approach relies on feedback
loop diagramming more than stock-and-flow diagramming. Interactive Vensim causal loop diagrams
are embedded in a STELLA interface, using slide show and video software. In addition, students appear
to learn more as model-users if they engage in preliminary model-building activities using simple
word-and-arrow diagrams.
Diffusion models of radical technologies are often based on an epidemic structure developed on the Bass principles of generic external and internal communications. However, in most cases such processes involve more complex communication and decision mechanisms. The diffusion processes should account for interdependences with other innovations and also the substitution mechanisms with regard to the technology in place. Substitution must be understood with a much broader scope than the analytical view of the Fisher and Pry model. As many diffusion authors have acknowledged (but partially excluded from their models), diffusion is a social process with innovation moving through interpersonal networks. We propose a model that accounts for the dynamics of social factors in technological substitution. Based on the System Dynamics methodology, our model disaggregates most of the communication structure and individuals characteristics that are implicitly embedded in traditional diffusion models. Our discussion starts with the characteristics of radical technological innovations. We then proceed with the theoretical basis of our social aggregation approach by presenting Kellys personal constructs system theory, outlines of social psychology, decision making under uncertainty, and the interdependences between innovations characteristics and human behavior. We also make an attempt at considering both sides (consumers adoption / competitors imitation) of a substitutive diffusion. Brice Dattée's research is funded by the National Institute of Technology Management in Ireland.
This work captures and analyzes the fundamental dynamics of innovative industries with a System Dynamics model. We selectively reviewed the innovation literature, identified the dynamics to be modelled, formulated a conceptual model of these dynamics, and then developed the initial simulation model. By design the conceptual model is simple and generic. It is intended to apply to a broad range of products and services assembled and process-based, complex and simple, physical and digital, business and consumer, early stage and mature, 19th century and 21st century. That is what we mean by the fundamental dynamics of innovative industries. In many variations and combinations they can explain the evolution of most markets. The initial simulation model was developed from the conceptual model. It represents products based on two generations of technology. At this stage the simulation model does not represent a specific market or industry. It is quantified with hypothetical inputs, parameters, and cause/effect relationships. The simulation model recreates well-documented reference modes of market evolution. We currently are building the information base which will enable the initial model to be applied to the photography and display markets.
The, for economists well-known Goodwin model was one of the first models which tried to combine cyclical behavior and economic growth. The basis for this is the predator-prey model a basic structure for every System Dynamicists. The economic literature about the Goodwin model is enormous, but so far, it was mostly concentrate on the mathematical behavior or on some extensions that could be implemented. In addition, there are only two papers from R. Solow and D. Harvie about an econometrical verification of the model and none from a System Dynamics perspective. This article provides therefore two System Dynamics models of Goodwins theory and tests the enhanced one on the German economic situation and on the data provide by Harvie 2000. Additionally there are some suggested modifications of the Goodwin model, tested from different authors, which reveal surprising outcomes for the understanding of Goodwins theory.
In this paper, I will present relatively simple system dynamics models which capture some of the insights of a key critic of the U.S. policy for defending the country, Stephen Flynn. Flynn is especially concerned with the over-reaction to the attacks of September 11, 2001. He warns of the dangers of shutting down legitimate commerce and investing in overseas offensive measures as a knee-jerk reaction to the attacks. It is not that he is advocating a lax approach to security. Rather he is advocating a measured look at the implications of a draconian defense policy which may cause much more damage to our societal infrastructures than the attacks that triggered it. He also presents recommended solutions.