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- Type:
- Document
- Date Created:
- 2008 July 20-2008 July 24
- Collection:
- System Dynamic Society Records
- Collecting Area:
- University Archives
- Collection ID:
- ua435
- Parent Record(s):
- 23d738ba88f8333bc39725f9cb5bd0b8, ce498623f0349395d0a141a0525190a0, and 6cbae5a21467df4434abbc87da443217
- Description:
- Due to low immunization coverage, epidemics such as measles still occur in many countries in the world. Various approaches have been applied to understand immunization coverage problems, however, there are still acknowledged deficiencies in these approaches and this has given rise to research efforts for alternative solutions. To better understand immunization health care problems and to generate insights that may increase the immunization coverage effectiveness, the paper applies system dynamics modeling and field study research methods. Causal loop diagram representing the immunization system is presented out of which a model is designed with the intent to show how particular variables influence immunization demand and coverage. The paper builds on earlier papers by the same authors. Model analysis demonstrates the need to upgrade the health system in proportion to the growing population, and how this can lead to improved immunization coverage rates. The paper suggests key leverage points which could substantially improve immunization demand and the effectiveness of the health system as well as vaccine management.
-
- Type:
- Document
- Date Created:
- 2008 July 20-2008 July 24
- Collection:
- System Dynamic Society Records
- Collecting Area:
- University Archives
- Collection ID:
- ua435
- Parent Record(s):
- 23d738ba88f8333bc39725f9cb5bd0b8, ce498623f0349395d0a141a0525190a0, and 6cbae5a21467df4434abbc87da443217
- Description:
- Client involvement in modeling is the hallmark of simulation-based methodologies and applied fields such as information systems development, environmental modeling, and biological systems.
-
- Type:
- Document
- Date Created:
- 2008 July 20-2008 July 24
- Collection:
- System Dynamic Society Records
- Collecting Area:
- University Archives
- Collection ID:
- ua435
- Parent Record(s):
- 23d738ba88f8333bc39725f9cb5bd0b8, ce498623f0349395d0a141a0525190a0, and 6cbae5a21467df4434abbc87da443217
- Description:
- Networks have become the dominant life form in many organizational settings. Most studies of relationships in networks focus on the dyadic interaction between two agents. However, work on enactment, sensemaking, path dependency, and social figuration processes (e.g. by Weick and Elias) suggests complex networks cannot be exclusively understood in terms of dyadic relationships. This paper therefore explores, first, whether emergent processes of enactment and sensemaking in large networks can be represented and simulated in an agent-based model; and second, what can be learned from simulation results obtained with this type of model. We develop an agent-based model of a two-tiered supply network of ten firms with heterogeneous dispositions towards partnership. This model serves to explore the interaction between disposition, sensemaking and behaviour in a network setting. The simulation results exhibit strong path dependency effects and capture, in a highly stylised manner, the emergent process of enactment and retrospective sensemaking. An important finding is that path dependency effects occur in response to life events (e.g. a calamity disrupting the flow of products). Our findings also suggest that inner dispositions may not determine the actual behaviour in complex and turbulent (supply) networks. This raises questions regarding network research that exclusively draws on cross-sectional data.
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- Type:
- Document
- Date Created:
- 2008 July 20-2008 July 24
- Collection:
- System Dynamic Society Records
- Collecting Area:
- University Archives
- Collection ID:
- ua435
- Parent Record(s):
- 23d738ba88f8333bc39725f9cb5bd0b8, ce498623f0349395d0a141a0525190a0, and 6cbae5a21467df4434abbc87da443217
- Description:
- Even the simple run of a medium size system dynamics model can be a cumbersome process, since the uncertainty of the parameters forces the modeller to consider many runs before being confident of how the model behaves. System dynamics simulation packages include some analysis tools, but in many occasions customized tools are desired. For example, one would like to be able to program iterative running of simulations and perform mathematical operations with the results, use analysis techniques such as PPM or screening, or even use fuzzy logic to automate the revision of graphs. In this paper we explore the possibilities of a programming language, Matlab, and its simulation tool, Simulink, for those possibilities mentioned. These languages come from the fields of engineering, but offer many interesting possibilities because of their programming ability. They enable the development of customized analysis tools at a very low programming cost. The World 3 model has been programmed in this languages and some examples of application programming runs, screening and fuzzy logic are given.
-
- Type:
- Document
- Date Created:
- 2008 July 20-2008 July 24
- Collection:
- System Dynamic Society Records
- Collecting Area:
- University Archives
- Collection ID:
- ua435
- Parent Record(s):
- 23d738ba88f8333bc39725f9cb5bd0b8, ce498623f0349395d0a141a0525190a0, and 6cbae5a21467df4434abbc87da443217
- Description:
- In December 2003, a 6.7 earthquake struck the city of Bam in southeastern Iran. The city lost over 45,000 inhabitants and the historic citadel of Arg-e´ Bam was destroyed. High number of casualties in this disaster has encountered it among most recent hazardous natural events in the world. Although the old structure of the city was the main reason for the massive destruction of the city, but the outcome of so many dead people has other important reasons as well. The most important one is that no scientific study has been on dynamical behavior of disaster management in Iran. In this paper a dynamic system is proposed in order to simulate the activities in the zone after the earthquake has shaken the city. Based on that, key parameters are chosen in order to establish some post-disaster policies which are applied on the model and their effects are studied.
-
- Type:
- Document
- Date Created:
- 2008 July 20-2008 July 24
- Collection:
- System Dynamic Society Records
- Collecting Area:
- University Archives
- Collection ID:
- ua435
- Parent Record(s):
- 23d738ba88f8333bc39725f9cb5bd0b8, ce498623f0349395d0a141a0525190a0, and 6cbae5a21467df4434abbc87da443217
- Description:
- Rework cycle is at the heart of modeling projects, one of the major application areas of system dynamics. In this paper we introduce a new formulation for rework cycle in which multiple defects may exist in a task. We compare the performance of this formulation with three others, two adopted from the system dynamics literature and one agent-based formulation. This comparative study illustrates the impact of assumptions about the nature of defects and the homogeneity of tasks on behavior of alternative models and provides information necessary for selecting rework cycle formulations effectively. The new formulation we introduce allows for capturing significant schedule over-runs due to a few tasks, with multiple defects, that may cycle through rework process multiple times. Its perfect mixing assumption, however, over-estimates final project quality. Sensitivity analysis informs the robustness of results to multiple project parameters. We discuss the implications for selecting robust formulations in modeling project dynamics.
-
- Type:
- Document
- Date Created:
- 2008 July 20-2008 July 24
- Collection:
- System Dynamic Society Records
- Collecting Area:
- University Archives
- Collection ID:
- ua435
- Parent Record(s):
- 23d738ba88f8333bc39725f9cb5bd0b8, ce498623f0349395d0a141a0525190a0, and 6cbae5a21467df4434abbc87da443217
- Description:
- Advances in artificial intelligence and optimal control provide increasingly better algorithms for controlling dynamical systems. These algorithms can be applied for policy design in system dynamics models. In this paper we introduce some basic solution concepts and apply the Q-learning algorithm to a simple dynamic model from system dynamics literature to demonstrate potential value of such cross-fertilization. We also extend a state aggregation and partitioning algorithm that may increase the efficiency of basic reinforcement learning models in application to continuous time and space problems. Simulation analysis demonstrates the value of this approach and offers guidelines for future research.
-
- Type:
- Document
- Date Created:
- 2008 July 20-2008 July 24
- Collection:
- System Dynamic Society Records
- Collecting Area:
- University Archives
- Collection ID:
- ua435
- Parent Record(s):
- 23d738ba88f8333bc39725f9cb5bd0b8, ce498623f0349395d0a141a0525190a0, and 6cbae5a21467df4434abbc87da443217
- Description:
- This paper explores the events that engulfed Northern Rock plc, a UK publicly listed company, during the latter part of 2007. The background to those events that took place is illustrated together with their consequences for Northern Rock. A model of the Northern Rock liquidity situation is produced and tested using the System Dynamics paradigm and methodology. The resultant model is verified and validated with reference to known behaviour and data. Hypotheses are constructed resulting in conclusions which centred on the need for co-operation between the Tripartite Authorities and Northern Rock together with a need for active, coordinated management action. Within the limitations of the model different means of coping with banking credit problems are illustrated and remedies postulated. The model presented could be further developed to produce recommendations for automatic triggering of interventions. A variant of the model could be adapted to model contagion risk. These, together with others, are areas for further work. Methodological conclusions are that the model correctly exhibits linear behaviour if not actively managed, that the model contains both continuous and discrete elements, that there is scope within the model to adapt it for use as a teaching/study aid in finance and/or System Dynamics.
-
- Type:
- Document
- Date Created:
- 2008 July 20-2008 July 24
- Collection:
- System Dynamic Society Records
- Collecting Area:
- University Archives
- Collection ID:
- ua435
- Parent Record(s):
- 23d738ba88f8333bc39725f9cb5bd0b8, ce498623f0349395d0a141a0525190a0, and 6cbae5a21467df4434abbc87da443217
- Description:
- Many important dynamically complex issues are also characterized by a large number of stakeholders. Stakeholders often have different (incompatible) world views, value systems, lifestyles, interests, and perspectives. One way to deal with this diversity in System Dynamics modeling is to use different (cultural) profiles. Cultural Theory offers five profiles that could be used to take this diversity explicitly into account in System Dynamics modeling. This will be illustrated with a System Dynamics modeling study concerning the development of a residential district in which cultural profiles are explicitly taken into account.
-
- Type:
- Document
- Date Created:
- 2008 July 20-2008 July 24
- Collection:
- System Dynamic Society Records
- Collecting Area:
- University Archives
- Collection ID:
- ua435
- Parent Record(s):
- 23d738ba88f8333bc39725f9cb5bd0b8, ce498623f0349395d0a141a0525190a0, and 6cbae5a21467df4434abbc87da443217
- Description:
- Bioenergy currently draws worldwide attention and investments. Proponents argue that the large-scale development of bioenergy could be (part of) the solution for diversifying energy sources, enhancing security of energy supply, and meeting environmental and rural development objectives. Opponents argue that it could threaten agricultural food prices/production/security, wildlife areas, and international trade flows. System Dynamics models of the EU27 bioenergy/biofuel