Online Content
Number of results to display per page
Search Results
-
- Type:
- Document
- Date Created:
- 2009 July 26-2009 July 30
- Collection:
- System Dynamic Society Records
- Collecting Area:
- University Archives
- Collection ID:
- ua435
- Parent Record(s):
- 23d738ba88f8333bc39725f9cb5bd0b8, b3584c6b53c3f58e0202549d7d851f84, and 4818cb531cdd68d6ec6af3f291216fc7
- Description:
- Recent oil prices escalations, current production of biofuels from food, and rising food prices have caused an awareness of a potential conflict between biofuel production and food availability. Biofuels could help countries reduce their dependence on imported oil and biofuels could lead to some reductions in CO2 emissions. For such reasons governments have stimulated research and development and subsidized biofuel production. In this study we use a simulation model to study how markets for oil, biofuel, and food may interact and develop in the long run as world oil production peaks and starts to decline due to resource depletion. We hypothesize that a shortage of oil will make biofuels highly profitable, lead to a take-off for the biofuel industry, and lead to food shortages and starvation. We do not reject this hypothesis. A number of policies all tend to delay rather than cure the problem of food shortage. Therefore it seems urgent to start discussing and building support for a ban on biofuel production from food.
-
- Type:
- Document
- Date Created:
- 2009 July 26-2009 July 30
- Collection:
- System Dynamic Society Records
- Collecting Area:
- University Archives
- Collection ID:
- ua435
- Parent Record(s):
- 23d738ba88f8333bc39725f9cb5bd0b8, b3584c6b53c3f58e0202549d7d851f84, and 4818cb531cdd68d6ec6af3f291216fc7
- Description:
- People have difficulties making good decisions in the presence of uncertainty and in nonlinear dynamic systems. When these challenges are combined, decision problems get even worse. The workshop gives an introduction to optimization under uncertainty in such systems. This is normally a very complex undertaking. However, it has been greatly simplified by the new software SOPS from Powersim Software. After the introduction, participants get hands-on experience with SOPS.
-
- Type:
- Document
- Date Created:
- 2009 July 26-2009 July 30
- Collection:
- System Dynamic Society Records
- Collecting Area:
- University Archives
- Collection ID:
- ua435
- Parent Record(s):
- 23d738ba88f8333bc39725f9cb5bd0b8, b3584c6b53c3f58e0202549d7d851f84, and 4818cb531cdd68d6ec6af3f291216fc7
- Description:
- Resource shortages are a fact of life in most organizations and in the currently challenging economic climate will be even more common. There is little doubt that resource shortages are widespread and that they lead to undesirable outcomes, yet there has been surprisingly little attention to questions about why they occur and even more insidiously why they persist despite the apparently clear adverse consequences. This paper develops a grounded theory that helps to understand chronic resource shortages, drawing on data from field work at a manufacturing firm adopting lean manufacturing. The paper examines how the actions of various groups (e.g., managers, production workers, and other shop floor workers) interact with each other and with the physical characteristics of the workplace to sustain problematic resource shortages. The paper uses a causal loop diagram and a stylized system dynamics model to highlight some important features of the dynamics.
-
- Type:
- Document
- Date Created:
- 2009 July 26-2009 July 30
- Collection:
- System Dynamic Society Records
- Collecting Area:
- University Archives
- Collection ID:
- ua435
- Parent Record(s):
- 23d738ba88f8333bc39725f9cb5bd0b8, b3584c6b53c3f58e0202549d7d851f84, and 4818cb531cdd68d6ec6af3f291216fc7
- Description:
- Agriculture is an important economic sector and a strategic component for the rural development in Iran. However, the sector has been beset by a labour surplus situation. This situation, together with inappropriate combination of labour with other factors of production, has caused a low growth rate in the agricultural production. The main objective of this study was to determine the optimal employment and production policies in the Iranian agricultural sector. Then, production, export-import, demand for labour and agricultural products, as well as the wage functions were estimated using the data collected during 35 years, and substituted in the economic component of the System Dynamics (SD) model to simulate the outcomes. The results indicate that a downward turn for the labour surplus problem will happen in 2008. Afterwards, the agricultural employment will gradually decline. Consequently, the cityward migration will increase, and the unemployment problem shifts from the rural to the urban areas. The average annual production growth rate in the 2007-2021 period is estimated at 1.8%. Furthermore, higher production is commensurate needed with substantial investment and adoption of appropriate technology. This study further demonstrates that combination of the SD approach and econometrics methods is highly effective in arriving at logical answer.
-
- Type:
- Document
- Date Created:
- 2009 July 26-2009 July 30
- Collection:
- System Dynamic Society Records
- Collecting Area:
- University Archives
- Collection ID:
- ua435
- Parent Record(s):
- 23d738ba88f8333bc39725f9cb5bd0b8, b3584c6b53c3f58e0202549d7d851f84, and 4818cb531cdd68d6ec6af3f291216fc7
- Description:
- Real-world concepts can be operationalized into variety of feedback structures which may be mathematically identical but diverse in the number of feedback loops. Factors including model purpose, the modelers perspective and the intended audience all influence the final layout of a feedback rich model. One challenge in the analysis of model behavior is to account for the variations in the appearance of its structure and the feedback loops. This paper focuses on consistency in explaining model behavior illustrates some of the issues related to the cancellation problem and figure-8 loops. Both conditions can potentially lead to poor and even contradictory explanations of model behavior based on its idiosyncratic feedback structure. The paper concludes by illustrating how the pathway participation approach addresses these two issues and calls for comparative studies to using alternative approaches to model analysis to better understand the general principles and subtleties in connecting the structure to the behavior and explaining observed dynamics. Different methods in formal analysis can learn from one another and expedite the development of user-friendly tools to aid model analysis that serve a wider audience.
-
- Type:
- Document
- Date Created:
- 2009 July 26-2009 July 30
- Collection:
- System Dynamic Society Records
- Collecting Area:
- University Archives
- Collection ID:
- ua435
- Parent Record(s):
- 23d738ba88f8333bc39725f9cb5bd0b8, b3584c6b53c3f58e0202549d7d851f84, and 4818cb531cdd68d6ec6af3f291216fc7
- Description:
- With support from the U.S. Centers for Disease Control and Prevention, we developed the HealthBound policy simulation game for those wanting to experience the possibility of transforming our troubled health system. The game's simulator tracks movement of the U.S. population among states of health, risk behavior, environmental exposures, and socioeconomic status. The model is quantified based on publicly available data from the early 2000s as well as studies from the professional literature on health care utilization and programmatic impact. Players try to steer the country's health system toward greater levels of health, equity, and cost-effectiveness. The goals are difficult to achieve, in part, because the game includes resource constraints, time delays, and side effects of intervention similar to those of the actual health system. The game allows tests of many types of interventions, individually or in combination, and at different points in time over a 25-year time horizon. Various types of output screens allow players to trace the precise reasons for their successes or failures. Those who aspire to lead change on a national scale, or in their own sphere of influence, may benefit by first testing and refining their ideas in this realistic, but simplified version of the U.S. health system, and learning its core lessons.
-
- Type:
- Document
- Date Created:
- 2009 July 26-2009 July 30
- Collection:
- System Dynamic Society Records
- Collecting Area:
- University Archives
- Collection ID:
- ua435
- Parent Record(s):
- 23d738ba88f8333bc39725f9cb5bd0b8, b3584c6b53c3f58e0202549d7d851f84, and 4818cb531cdd68d6ec6af3f291216fc7
- Description:
- Air strategy planners have the difficult task of providing commanders with campaign plans prior to commencing operations, and recommending options during the campaign. BAE Systems has developed the Commanderâs Model Integration and Simulation Toolkit (CMIST), a tool for creating and using simulation models appropriate for high-level strategic decision-making. CMIST provides a unified graphical interface for a variety of methodologies appropriate for systems modeling, including System Dynamics, Bayesian cause-effect, individual agents, Coloured Petri Nets, and other families. Recent development on CMIST enables an agent to run an embedded simulation model representing its own internal, usually simplified, model of the outside world. This proactive intent model allows the agent to project the future state of the world in order to make decisions and take appropriate preventative measures before those future states occur. We discuss comparative results using reactive vs. proactive intent models in the context of our notional Insurgent Growth model.
-
- Type:
- Document
- Date Created:
- 2009 July 26-2009 July 30
- Collection:
- System Dynamic Society Records
- Collecting Area:
- University Archives
- Collection ID:
- ua435
- Parent Record(s):
- 23d738ba88f8333bc39725f9cb5bd0b8, b3584c6b53c3f58e0202549d7d851f84, and 4818cb531cdd68d6ec6af3f291216fc7
- Description:
- Determining in advance emergency supplies and personnel required for a disaster relief operation is crucial for mitigating the societal impacts of such events. Prompt and effective response to either natural or man-made emergencies requires the analysis of key information where the role of disaster relief organizations is multiple. DROs approve the assistance requested by victims and coordinate supplies and personnel collected and transported to the disaster site. They provide mental health services and shelter while more long-term government aid is decided. The dynamic framework presented here was formulated to understand the complex multi-factor dynamic processes evolving over time during a hurricane emergency. It maps the process of interdependence between resource availability and satisfaction with human services and the influence of the media reacting to victims' complaints. It hypothesizes key mechanisms governing these relationships. Exogenous factors such as customer reactions to the category event; training level of response personnel; race, social stratum, home/pet ownership and education are all taken into account. The model was built with the analysis of data collected from victims of the 2005 Katrina Hurricane and paired with real operational data provided by the American Red Cross and then calibrated/validated by real data from the 2005 Rita Hurricane.
-
- Type:
- Document
- Date Created:
- 2009 July 26-2009 July 30
- Collection:
- System Dynamic Society Records
- Collecting Area:
- University Archives
- Collection ID:
- ua435
- Parent Record(s):
- 23d738ba88f8333bc39725f9cb5bd0b8, b3584c6b53c3f58e0202549d7d851f84, and 4818cb531cdd68d6ec6af3f291216fc7
- Description:
- Many field studies are available that describe successful applications of model-driven group decision support methodologies. However, these studies might suffer from a potential bias of contextual factors. Recently, there has been a call for a more rigorous testing of the effectiveness of model-driven methodologies. The purpose of our research is to determine the effectiveness of a particular model-driven approach, Group Model Building (GMB), on decision-making in a controlled research situation. In this paper, we first clarify 'effectiveness' as a construct. Then, we describe the present study. We compared groups supported by GMB (13 groups) and not being supported (13 groups) on perceptions of the quality of decision-making and on the quality of their decisions. Preliminary results show that there are no winners. However, some differences in the perceptions of the members of decision-making groups call for further testing in the future.
-
- Type:
- Document
- Date Created:
- 2009 July 26-2009 July 30
- Collection:
- System Dynamic Society Records
- Collecting Area:
- University Archives
- Collection ID:
- ua435
- Parent Record(s):
- 23d738ba88f8333bc39725f9cb5bd0b8, b3584c6b53c3f58e0202549d7d851f84, and 4818cb531cdd68d6ec6af3f291216fc7
- Description:
- This paper presents the attempt to set up the dynamic land-use transport interaction (LUTI) model MARS (Metropolitan Activity Relocation Simulator) for a nation wide case study of Austria. To this end we adapted the existing urban MARS model. The purpose of the model is to capture the most important interactions and feedback mechanisms between the land-use- and the transport system. Particular attention was paid to the structural changes of the model and the estimation of the transport model parameters as well as the land-use model parameters, which are modelled with a gravity model approach. For this purpose we used the build-in optimizer of the modelling software Vensim by minimizing the sum of squared deviations between observed and predicted data. We present the model fit, estimated parameters and results of a first model run (30 years)