This paper deals with the representation of mental models of dynamic systems (MMDS). The notion of mental model (MM) has always been fundamental in system dynamics, and 10 years ago, a specific definition was introduced. However, no conceptual model of MMDS content has been offered so far. Two assessment and comparison methods have been borrowed from general MM research:. Are these methods are equivalent in procedure and results, and do they satisfy specific needs of system dynamics? Two exemplary MMDAs are compared with both of the methods, which are found to be different in procedure and in results they produce. In addition, they ignore the feedback loop concept. Based on this finding, we propose a conceptual model for the structure of MMDS, a method for comparing MMDSs and a tentative revised definition of MMDS. The application to the exemplary models shows some alleged advantages. A preliminary conclusion is that more discussion and comparative work are needed.
The integration between health and social care organisations in the UK is an acknowledged public policy problem. Despite government efforts at implementing âjoined up thinkingâ, government have found this area frustratingly âpolicy resistantâ.
Organized crime satisfies a demand for necessary social services in the absence of effective government institutions. This paper examines the rise of the Sicilian mafia. Using system dynamics, we model this system and test various policies to determine what factors have the greatest impact on mafia power. Based on the experiments, the most effective policies for reducing mafia power are those that decrease the demand for private protection services by reducing the threat of banditry in society, and not those policies that act against the mafia directly. We also examine historical examples of other mafia-type organizations and discover that our findings apply not just to Sicily, but also to other societies including present-day Iraq and Afghanistan.
This paper presents preliminary results of a Raytheon project that uses systems dynamics to understand the intricacies of the U.S. educational system and to assist in exploring the effects of policies and programs, with a goal of doubling the numbers of science, technology, engineering and mathematics (STEM) college graduates by 2015. Specifically, a system dynamics model has been developed, the initial version of which targets increasing the number of students both capable and interested in pursuing careers in STEM disciplines. A few scenarios have been analyzed that examine changes for improving student capabilities. Initial results provide insight into the value and viability of a few proposed policies and indicate that with continued research, model development, and analysis it will be possible to further assess proposed improvements in the U.S education system.
Pests and other undesirable populations offer considerable resilience to interventions attempting to limit or eradicate them. These interventions often directly aim at reducing these populations through either by limiting their procreation or accelerating their demise. For example, stray dogs roam the streets of many major Asian cities in spite of the efforts to euthanize or castrate them. Street gangs and the violence associated with them continue in many North American cities in spite of considerable effort on part of law and order institutions to contain them. Suicide attacks menacing public continue in central Asian countries like Pakistan, Iraq and Afghanistan in spite of the concerted military offensives to eradicate their perpetrators. This poster will suggest that a latent capacity enablement structure that maintains the inflow into the undesirable population exists in all such cases. Interventions not cognizant of this structure may only address symptoms and not alleviate the root cause. The capacity enablement process as a generic metaphor may help to bring the latent root cause to fore.
This paper re-defines two hypothetical laws of capital accumulation by including endogenous profit investment share and establishing an explicit inverse relation between this share and capital-output ratio. Other main state variables are labour productivity, employment ratio and unit value of labour force. A comprehensive Phillips equation, governing real labour compensation, is an element of a hypothetical law (HL-IR). Projecting future macroeconomic evolution takes into account structural changes in primary distribution of net value added. After the recent neo-conservative defeat there is no place for stabilising policy with the same or similar aggressiveness as in 2002-2007. Based on the US macroeconomic data mainly for 1969-2007, computer simulation runs for a later period (through 2060) exhibit how a postponed non-aggressive application of CL-IR in 2012 and afterwards could smooth out long waves of capital accumulation and shorten a period of fluctuations from 24-27 to 14-16 years in the restructured US economy compared to evolution based on HL-IR. The present stern crisis of the capital accumulation, probably deepest after the World War II, will last until 2018-2022 when the pre-crisis maximum of net output is restored and 2023-2026 when the pre-crisis maximum of employment is reached again.
The article presents some insights from ongoing research on sustainable organizational change. It focuses on a concept of improvements actions conducted by teams within manufacturing organization. There are considered two types of approaches, namely bottom-up - example of which are empowered, small, cross-functional teams; and top-down - large teams following rigorous problem solving methodologies. In order to investigate impact of small teams and large teams on the organizational system structure a System Dynamics model was developed. The model investigates the effectiveness of both kinds of approaches from the perspective of sustainable organizational change effort. The analysis of the model and simulation results is supported by example of successful organizational change in Lima Refinery. In the conclusion section the implications for sustainable organizational change efforts are presented.
Proper analysis of the financial statements of a company provides valuable insights into financial performance. Financial ratio analysis, a principal tool of financial analysis, determines a company's ability to raise external financing. In the present work, detailed System Dynamics (SD) modeling and analysis of the financial performance of a shore based integrated steel plant is undertaken. The key financial ratios used for simulation and analysis are (i) Liquidity ratios (ii) Turnover ratios and (iii) Profitability ratios over a period of 20 years from 1994. SD model is successfully applied to portray the dynamic behaviour of the financial system of the plant.
In 1973, the first oil crisis leaded most countries to experience economic problems due to sudden unbalance in their trade balance. This leads to reactions, limited at the beginning due to short term inelasticity of petroleum demand, but relevant in long term. Brazil started the Proalcool program, which extended from 1979 to 1990, with the use of ethanol cars (E-100). In 1990 this program was ended, due to economic problems. A decline in international petroleum prices and an increase in international sugar prices, leaded to shortage of ethanol. This shortage made the users confidence to decline. From that point on, ethanol cars acquisitions almost dropped to zero. In 2003 a technological innovation, the flex fuel electronic injection, was launched and was a huge success. In approximately three years, about 85% of all cars sold in Brazil were using this technology. It caused a boom in ethanol industry which competes in terms of resources with sugar industry. This paper presents a framework to simulate the first period of the overall program which lasts from 1970 to 2003.