System Dynamics Modelling Approach Research Articles

An empirical evaluation of policy options for inclusive dairy value chain development in Nicaragua: A system dynamics approach

Achieving inclusive value chain development is a challenging task due to the complex and dynamic nature of interconnected value chains and their social, economic, and ecological dimensions. While many policies and intervention options exist to upgrade value chains, there are fewer methods that can be used to understand and quantify the multidimensional impacts that value chain policies and interventions may have throughout the value chain. This paper addresses this methodological gap by employing a system dynamics (SD) modeling approach. SD models allow us to model and quantify the processes and relationships inherent in the value chain through simulations, serving as a policy laboratory for the empirical assessment of intervention options. An SD model of the Matiguás dairy value chain in Nicaragua was developed and tested through a participatory modeling process. Our research tested and evaluated the short-, medium-, and long-term impacts of specific interventions and policies in the Matiguás dairy value chain with the goal of strengthening the competitiveness and inclusion of small- and medium-scale producers. These interventions centered on improving the feeding system, which was identified by stakeholders as the critical constraint to competitiveness. The policy analysis reveals that both improved pastures and increased use of concentrates raise producer milk productivity by 5% and 11%, respectively in the long run, but are also expensive strategies for smallholder producers, leading to a reduction in profits relative to the baseline by 1% and 3%, respectively. Consequently, policymakers should identify strategies that help to reduce concentrate costs and support producers with investments in improved pasture, while also promoting training in pasture management skills. Indeed, in the long-run, model results reveal that investment and training in pasture management results in a 30% and 35% increase in milk production during the wet and dry season, respectively. Simulation results further highlighted that intensifying the feeding system to improve cow milk yields is mainly profitable in the long term, and thus requires a longer-term perspective by policymakers. The model provides a deeper understanding of the complex and dynamic nature of the Matiguás dairy value chain and the interactions between markets, coordination aspects, biophysical phenomena, and income. The system dynamics approach to value chain analysis further addresses a major analytical shortcoming in value chain analysis and provides decision makers with an improved platform for planning and policy formulation.

Reflections on Teaching System Dynamics Modeling to Secondary School Students for over 20 Years

This paper contains the description of a successful system dynamics (SD) modeling approach used for almost a quarter-century in secondary schools, both in algebra classes and in a year-long SD modeling course. Secondary school students have demonstrated an ability to build original models from the news, write technical papers explaining their models, and present a newfound understanding of dynamic feedback behavior to an audience. The educational learning theory and instructional methods used for both the algebra and modeling courses are detailed, with examples. Successful student SD modeling experiences suggest the SD approach can expand the sophistication of topics that secondary school students can understand.

Forecasting the shortage of neurosurgeons in Iran using a system dynamics model approach.

CONTEXT:Shortage of physicians particularly in specialty levels is considered as an important issue in Iran health system. Thus, in an uncertain environment, long-term planning is required for health professionals as a basic priority on a national scale.AIMS:This study aimed to estimate the number of required neurosurgeons using system dynamic modeling.SETTING AND DESIGN:System dynamic modeling was applied to predict the gap between stock and number of required neurosurgeons in Iran up to 2020.SUBJECTS AND METHODS:A supply and demand simulation model was constructed for neurosurgeons using system dynamic approach. The demand model included epidemiological, demographic, and utilization variables along with supply model-incorporated current stock of neurosurgeons and flow variables such as attrition, migration, and retirement rate.STATISTICAL ANALYSIS USED:Data were obtained from various governmental databases and were analyzed by Vensim PLE Version 3.0 to address the flow of health professionals, clinical infrastructure, population demographics, and disease prevalence during the time.RESULTS:It was forecasted that shortage in number of neurosurgeons would disappear at 2020. The most dominant determinants on predicted number of neurosurgeons were the prevalence of neurosurgical diseases, the rate for service utilization, and medical capacity of the region.CONCLUSIONS:Shortage of neurosurgeons in some areas of the country relates to maldistribution of the specialists. Accordingly, there is a need to reconsider the allocation system for health professionals within the country instead of increasing the overall number of acceptance quota in training positions.

Role of financial mechanisms for accelerating the rate of water and energy efficiency retrofits in Australian public buildings: Hybrid Bayesian Network and System Dynamics modelling approach

In Australia, the government spending on public buildings’ energy and water consumption is considerable; however the building energy and water retrofit market potential has been diminished by a number of barriers, especially financial. In contrast, in other advanced economies there are several reported financing strategies that have been shown to accelerate retrofit projects implementation. In this study, a coupled Bayesian Network – System Dynamics model was developed with the core aim to assess the likely influence of those novel financing options and procurement procedures on public building retrofit outcomes scenarios in the Australian context. A particular case-study focusing on Australian public hospitals was showcased as an example in this paper. Stakeholder engagement was utilised to estimate likely preferences and to conceptualise causal relationships of model parameters. The scenario modelling showed that a revolving loan fund supporting an energy performance contracting procurement procedure was preferred. Subsequently, the specific features of this preferred framework were optimised to yield the greatest number of viable retrofit projects over the long term. The results indicated that such a financing scheme would lead to substantial abatement of energy and water consumption, as well as carbon emissions. The strategic scenario analysis approach developed herein provides evidence-based support to policy-makers advocating novel financing and procurement models for addressing a government’s sustainability agenda in a financially responsible and net-positive manner.

System Dynamics Simulation Model of the Marine Diesel Engine Start up System

System dynamic simulating modelling is one of the most appropriate and successful scientific dynamics modelling methods of the complex, non-linear, natural, technical and organizational systems. Investigation of behavior dynamics of the ship/s propulsion system as one of the complex, dynamic, non-linear technical systems requires application of the most efficient modelling methods. Marine Diesel engine start up system, which it is consisted of ship/s piston compressor and its driving electric motor, i.e. in this case asynchronous motor, shall be presented in the System Dynamics modelling approach in POWERSIM simulation symbolic and language. System dynamic models are essentially continuous models since the realities have been demonstrated by a set of non-linear differential equation, i.e. “equations of conditions”, however they are at the same time discrete ones because their principle time interval calculation i.e. (discretisation) sampling “DT” is determined in full compliance with (Sampling Theorem) by Shannon and Koteljnikov.

Long-term sustainability of cork oak agro-forests in the Iberian Peninsula: A model-based approach aimed at supporting the best management options for the montado conservation

The future of the montado, a human shaped agro-forestry ecosystem of South Western Europe, is questioned due to the observed lack of cork oak health and low natural regeneration. We developed a System Dynamics Modelling approach to predict the long-term sustainability of this agro-forest, by recreating cork-oak population dynamics, management practices and the main environmental and biological constrains associated with this ecosystem. Our results indicate that the leading limitations to cork oak regeneration in montado ecosystems result from the intensity and interaction of land management practices, namely livestock and the use of heavy machinery. The main conclusions indicate that limiting the quantity of livestock up to 0.40 LU.ha−1, and considering soil ploughing with a minimum periodicity of 5 years, are crucial to maintaining sustainable cork oak populations. This study represents a first step to support strategic options for cork oak montado management by providing projections of long-term population trends under realistic social-ecological change scenarios.

An empirical illustration of the transformation process of purchasing

Purpose – The purpose of this paper is to highlight the strategic role of purchasing and model its transformation process based on a case study of a military firm. Design/methodology/approach – The paper reviews the existing literature to highlight the strategic role of purchasing and put forward the transformations the function is undertaking. The model system dynamic approach is then detailed and applied to model the transformation of the purchasing function of a military firm. The modeling software Analytica is then used to run the model and get to results. Findings – The shift of purchasing toward a more strategic function is complex and multidimensional. Implementing these transformations requires flexible designing approaches such as the system dynamic modeling that incorporates both quantitative and qualitative variables to model the function’s changes. The paper details the methodology of applying the system dynamic approach. It recommends a new structure of the purchasing function as well as new and upgraded indicators of purchasing performance and suppliers’ management. Research limitations/implications – A single-case study research. Even though, the objective is not to generalize the findings but to enrich the existing literature as regard the system dynamic modeling in a specific domain, the one-case research setting can be seen as a limitation against generalizeable findings. Practical implications – A clear step-by-step action plan of conducting the transformation of the purchasing function using the system dynamic modeling approach. The paper gives ways to upgrade existing measures of purchasing and policies of suppliers’ management. Originality/value – The application of the system dynamic modeling approach to the specific domain of military purchasing.

System Dynamics Modelling Approach for Managing the Japanese Coastal Squid Jigging Fishery

System Dynamics Modelling Approach for Managing the Japanese Coastal Squid Jigging Fishery

Causality Linkages among Energy Poverty, Income Inequality, Income Poverty and Growth: A System Dynamic Modelling Approach

The energy services stipulation of a country discloses its importance as a decency of course of action necessary for economic prosperity, lessening the poverty and depolarising the social asymmetry [Barnes, et al. (2011)]. The accomplishment of basic needs of energy services that include excess to electricity, commercial use of energy for production process as well as usage of electricity in the residential areas and modern use of energy sources for cooking purposes portraits an image of high-quality living standard of individuals and offers a way forward to economic development.12 The notion of pro-poor growth is well documented in the recent literature for assurance of thinning the poverty that is congregated through translation of growth into the lives of poor by reshaping the income distribution23 for marginalised group of people. Ekouevi and Tuntivate (2012) and studies of international agencies [AGECC (2010); WHO (2006); UNDP and WHO (2009)] have preliminary acknowledged the need of improving the access to reliable and affordable modern energy services in the developing economies for economic prosperity and social welfare of individuals.

Causality Linkages Among Energy Poverty, Income Polarization, Income Poverty and Growth: A System Dynamic Modeling Approach

The study plans to accomplish the efforts in bringing together the new dimensions of poverty dynamics in a system that will probe the causal relationship among the energy poverty, income polarization, growth and income poverty. The study is based on the hypotheses; (I) Does energy poverty cause income polarization? (II) Does energy poverty is a factual impediment to growth? (III) Does the energy poverty spur income poverty? And, whether the alternative also exist against these hypotheses? For this purpose, study efforts an energy poverty measure at national or aggregated macro level defined by International Energy Agency (IEA). For causality analysis, study utilizes annually time series data ranges from 1973 to 2012 and properties of time series data justify the appropriate method for the causality analysis. The present study models the poverty dynamics in Granger non causality context evidenced from augmented VAR system and follows Toda and Yamamoto (1995), TY-procedure for estimation of VARs system at level though seemingly unrelated regression (SUR) using modified Wald-stat (MWald). Whereas the traditional coefficient restriction F-stat does not follow the normal distribution when simple OLS is used for VARs system estimation at level. For a prudent policy formulation, econometrically well-equipped study would provide robustness of the results leaving better understanding for future forethought.

An Economically Sustainable Urban Public Transport Framework: System Dynamics Modelling Approach to Reduce Public Transport Liberalisation Impact in Harare City

Public transportation plays a key role to socio-economic development of any nation. This service enhances people’s livelihood framework by facilitating mobility and accessibility to services. Moreover, there is clear global evidence that a well performing public transport is an important enabler of sustained economic prosperity. Rapid urbanization in developing countries has resulted in transport facilities and infrastructure failing to cope with demand resulting in congestion, movement delays, high travel costs, and construction of holding bays in order to decongest the city, which will contribute to an increased usage of non-renewable energy. This prompts implementation of non-comprehensive strategies such as partial deregulation of transportation systems that caused further deterioration in economic sustainability. An economically sustainable transport system advocates for mobility, resource, and operational efficiency. This research focuses on developing a bus investment conceptual framework of a public transport system that improves mobility, resource, and operational efficiency to aid in sustaining of public transportation system for an unforeseeable future. With this in mind, a Harare bus investment system has been modelled as a policy framework model to evaluate its economic sustainability. This will help develop a long-term economically sustainable public transportation and reduce the overall impact of the earlier liberalisation of the transportation sector

System Dynamic modelling approach for resolving the thermo- chemistry of wood gasification

For Multiphysics problems that require a thorough understanding of multiple, influential, highly transient process parameters, a System Dynamic model can constitute either an alternative option, or a compact prelude to a more expensive 3-D Finite Element or Finite Volume model. As a rather uncommon example for the application of such a modelling method, this work presents a System Dynamic modelling concept, devised for resolving the thermo-chemistry within a wood gasification reactor. It compares the modelling concept as well as its results to a classic, thermo-chemical solution algorithm based on the minimization of LaGrangian Multipliers for resolving the gasification equilibrium equations. In contrast to the latter, the System Dynamic solver can consider the impact of reaction kinetics as well as molecular mass transfer effects on the gasification equilibrium. Thus the transient production rates of methane, hydrogen, carbon (di-) oxide and water, as well as the residual amounts of pyrolysis gas and oxygen, which occur during the gasification of a wood particle, can be predicted.

The Balanced Scorecard and the Strategic Learning Process: A System Dynamics Modeling Approach

The main purpose of this paper is to improve on the conceptual as well as the methodological aspects of BSC as a quantitative model by combining elements from traditional balanced scorecard (BSC) thinking with the Systems Thinking. This is done by combining short and long term aspects of measurements. The result is then used to build and construct a balanced scorecard model for strategic learning with the specific aim to maintain satisfied customers and motivated employees. Strategic planning, operational execution, feedback, and learning are some of the most important key features of any performance measurement model. This paper aims to address not only the conceptual domain related to BSC, that is, learning and system dynamics causality and feedback, but also the methodological domain concept of precision solved by differential equations. Our results show how a potential move from a static strategic vision map to a linked and dynamic understanding may be not fully realistic but very useful for learning purposes. The new knowledge obtained from the learning feedbacks fertilizes both decision discussion and decision-making and what may be required in order to move to the next level of BSC and system dynamics integration.

Holistic modelling for human-autonomous system interaction

For complex systems that embed automation, but also rely on human interaction for guidance and contingency management, holistic models are needed that provide for an understanding of the individual human and computer elements, and address the critical interactions of such complex systems. Discrete event simulation (DES) models and system dynamics (SD) models are two different approaches that can be used to address these requirements. Both modelling approaches can support the designers of future autonomous vehicle (AV) systems by simulating the impact of alternate designs on vehicle, operator, and system performance. However, the DES modelling approach is likely best suited for using probabilistic distributions to accurately model an operator who is a serial processor of discrete tasks, as well as an environment with randomly occurring events. The SD modelling approach is better suited for modelling continuous performance feedback that is temporally dependent and is affected by qualitative variables such as trust.

Contribution to the Development of Simulation Model of Ship Turbine

Simulation modelling, performed by System Dynamics Modelling Approach and intensive use of computers, is one of the most convenient and most successful scientific methods of analysis of performance dynamics of nonlinear and very complex natural technical and organizational systems [1]. The purpose of this work is to demonstrate the successful application of system dynamics simulation modelling at analyzing performance dynamics of a complex system of ship’s propulsion system. Gas turbine is a complex non-linear system, which needs to be systematically investigated as a unit consisting of a number of subsystems and elements, which are linked by cause-effect (UPV) feedback loops (KPD), both within the propulsion system and with the relevant surrounding. In this paper the authors will present an efficient application of scientific methods for the study of complex dynamic systems called qualitative and quantitative simulation System Dynamics Methodology. Gas turbine will be presented by a set of non-linear differential equations, after which mental-verbal structural models and flowcharts in System dynamics symbols will be produced, and the performance dynamics in load condition will be simulated in POWERSIM simulation language.

Modelling the complexity of emergency department operations using hybrid simulation

As a system, the emergency department reveals detailed and dynamic complexity of its interaction between inter-departmental units and intra-departmental elements. Discrete-event simulation (DES) has been recognised for its ability to comprehend operational problems with detailed complexity. Whilst using DES to model the complexities of the integrated emergency department system, we also use system dynamics (SD) to capture the interdependency relationships between the emergency department and other subunits in a hospital. This paper presents the integration of DES and SD modelling approach, hereby named as hybrid simulation, to better understand emergency department operations from a whole system perspective.

Using system dynamics to evaluate renewable electricity development in Malaysia

Purpose – The purpose of this paper is to provide an assessment of Malaysia's renewable capacity target. Malaysia relies heavily on fossil fuels for electricity generation. To diversify the fuel-mix, a technology-specific target has been set by the government in 2010. Considering the complexity in generation expansion, there is a dire need for an assessment model that can evaluate policy in a feedback fashion. The study also aims to expand policy evaluation literature in electricity domain by taking a dynamic systems approach. Design/methodology/approach – System dynamics modelling and simulation approach is used in this study. The model variables, selected from literature, are constituted into casual loop diagram. Later, a stock and flow diagram is developed by integrating planning, construction, operation, and decision making sub-models. The dynamic interactions between the sub-sectors are analysed based on the short-, medium- and long-term policy targets. Findings – Annual capacity constructions fail to achieve short-, medium- and long-term targets. However, the difference in operational capacity and medium- and long-term target are small. In terms of technology, solar photovoltaic (PV) attains the highest level of capacity followed by biomass. Research limitations/implications – While financial calculations are crucial for capacity expansion decisions, currently they are not being modelled; this study primarily focuses on system delays and exogenous components only. Practical implications – A useful model that offers regulators and investors insights on system characteristics and policy targets simultaneously. Originality/value – This paper provides a model for evaluating policy for renewable capacity expansion development in a dynamic context, for Malaysia.

A Decision Support Framework to Assess Grocery Retail Supply Chain Collaboration: A System Dynamics Modelling Approach

 Abstract—Supply chain collaboration contributes to improving overall performance through increasing sales, refining forecasts, reducing inventory costs, and improving customer service. In order to be efficient and cost effective, total costs have to be minimized across the entire supply chain. Collaboration efforts run into many practical challenges, both internal and external among small retailers. This paper proposes a framework of retailer supply chain collaboration to identify better understanding of collaboration benefit. A system dynamics simulation modelling approach is used to represent the collaboration effect on the dynamics of this complex system that helps retailer supply chains to obtain maximum benefit of collaborative relationships and reduce the bullwhip effect. This work helps researchers to use supply chain collaboration dynamic modelling to examine how information sharing across a supply chain can result in the identification and prioritization of better order decisions that can be aligned with the retail supply chain's value proposition for further supply chain integration.

Enhancing the corporate performance through system dynamics modelling

The aim of the current study is to improve the performance of corporate through application of System Dynamics (SD) methodology. The paper discusses the importance of system dynamics modelling in enhancing corporate performance and how it shows the dynamic behaviour of the system. For this purpose a system dynamics model for an Indian Steel company has been prepared. The paper also covers a brief introduction of the system dynamics modelling, a brief narration of Steel Sector and the process adopted in modelling. Some of the important corporate performance parameters such as market share, revenue, employee’s strength, number of shareholders, installed capacity have been taken to reflect corporate behaviour. The behaviour of these performance parameters over time is used for both validation of the model as well as for reflecting their future pattern. The paper concludes that the SD modelling approach has high potential in understanding corporate performance behaviour and their by gaining insight into the corporate functioning and taking appropriate remedial steps for improving its performance.

A System Dynamics Model for Energy Planning in Niger

This paper proposes an energy management model using system dynamics (SD) modeling approach. The time span of the model extends from 2003 to 2030. The Model was calibrated and used for the evaluation of six policy scenarios. Population, per capita electricity consumption, and the industrial sectors were identified as key components and used as inputs to predict future electricity supply and demand needs. Particular attention was paid, in the proposed model, to the individual and total amounts of carbon released into the atmosphere. Finally, to demonstrate the usefulness of the model, it was applied to Niger’s electricity sector. The raw data from the past ten years was used as a benchmark for the study. A key factor in this study was Niger’s fast growing population. The quick increase in population will add uncertainties to both the projections and the accuracy of the results. Model results show that by putting a particular emphasis on the national supply, Niger may be energy self-sufficient from 2018 through 2030. The model also indicates that the bond between Nigeria and Niger must be firmly re-strengthened for the latter to be able to meet its future electricity challenges. The proposed model can be used in guiding public policy in developing regions.