Stock Flow Diagram Research Articles

Using Generic Structures in System Dynamics Model Building: Reflection from Modeling for Indian Shrimp Industry

The paper focused on how a system dynamics modeler could reduce model development and testing time by using “Generic Structures” as an interim benchmark between causal loop diagram and stock flow diagram. Using generic structures as a benchmark could prevent the modeler from including redundant structures to the model and getting affected by personal biases that in turn could reduce repetitive amendments to the model during model testing. Indian Shrimp Industry, during 1990–2010, sequentially showed an early growth, a hasty decline, a combative rejuvenation, and an inexorable re-decline behavior in terms of the annual shrimp production and production capacity. Average Yield continuously fluctuated throughout the Industry’s life cycle during 1990–2010. Breaking such progressive behavior into temporal units, we found that the unit behaviors resemble with the behaviors of generic structures like, exponential growth, goal-seeking, S-shaped growth, limits to success, and overshoot-and-collapse. We, using the related generic structures as the interim benchmarks, illustrated a step-by-step modeling exercise for studying the dynamic behavior of Indian Shrimp Industry during 1990–2010. The paper concluded that using generic structures as the benchmark during system dynamics modeling improved the efficiency and the effectiveness of model building due to reduction in model building and testing time.

Research on constructing urban green traffic system: the case of Shenzhen City

Traffic jam is a big problem, which influences people's normal travel, and causes environmental pollution. Green traffic can solve traffic problem effectively. By analysing the factors that affect traffic jams, the article builds cause-and-effect relation diagram and then builds stock-flow diagram. Then taking Shenzhen city as an example, make a simulation of the urban green traffic model system. The result shows that the number of private cars ownership and the increase of vehicle exhaust stock are important driving factors of traffic congestion and environmental pollution. By influencing the total of the private cars ownership, auto purchase limit policy, restrictions and congestion pricing policy control motor vehicle trips, reduce vehicle emissions, and balance automobile exhaust gas pollution problem. At the same time, adopt new energy vehicle subsidy policy to advocate the residents to buy new energy vehicles and improve public transport infrastructure to advocate people to take public traffic vehicle.

Research on constructing urban green traffic system: the case of Shenzhen City

Traffic jam is a big problem, which influences people's normal travel, and causes environmental pollution. Green traffic can solve traffic problem effectively. By analysing the factors that affect traffic jams, the article builds cause-and-effect relation diagram and then builds stock-flow diagram. Then taking Shenzhen city as an example, make a simulation of the urban green traffic model system. The result shows that the number of private cars ownership and the increase of vehicle exhaust stock are important driving factors of traffic congestion and environmental pollution. By influencing the total of the private cars ownership, auto purchase limit policy, restrictions and congestion pricing policy control motor vehicle trips, reduce vehicle emissions, and balance automobile exhaust gas pollution problem. At the same time, adopt new energy vehicle subsidy policy to advocate the residents to buy new energy vehicles and improve public transport infrastructure to advocate people to take public traffic vehicle.

A Sustainable Development of the Indian Economy with Special Reference to Jan Dhan Yojana and Pahal Scheme

For the sustainable development of the Indian economy, the Government of India initiated the Jan Dhan Yojana and Pahal scheme. The main objective of the present paper was to study the role of the Jan Dhan Yojana and Pahal Scheme in bringing about sustainable development of the Indian society, develop a causal loop diagram and stock flow diagram of socioeconomic sustainable development, and suggest various measures for the sustainable development of the Indian society. The present study stated that these schemes are playing an important role in creating a universal platform for financial services for every Indian citizen, which is aiding in economic and social capacity building. The causal loop diagram helped to identify various positive and negative relationships between variables of socioeconomic sustainable development through Jan Dhan Yojana and Pahal scheme.

System dynamics analysis on characteristics of iron-flow in sintering process

A system dynamics model for iron-flow in sintering process is built at relatively macroscopic level using the methods of causal loop diagrams and stock-flow diagrams. The simulation results are accurate. The applicability of system dynamics to the study of steel manufacturing process, as well as the validity of the modeling and simulation are verified. The calculations show that the iron-flow of sinter increases rapidly in the initial period and then it tends to steady; the greater the returned iron-flow changes, the longer the time is required to reach steady state for the iron-flow of sinter, the loss iron-flow and the iron-stock in the sintering machine.

Determination of mass, damping coefficient, and stiffness of production system using convolution integral

Discrete event simulation (DES) is most widely used tool for modelling complex production systems. DES model requires skilful mapping of actual production process in a framework used for DES modelling. It also calls for extensive data collection for arriving at probability distributions followed by the time required by various activities involved in production processes and also the probability distribution of various occurrences affecting production process. System dynamics (SD) has also been used to model production system. SD model requires forming causal loop model (stock–flow diagram) showing interrelated influential variables affecting production process, their rates and mathematical relation between cause and effect. Continuous and discrete flow models had also been used for modelling production system. This work proposes a tool for simulating the production output which is simpler as compared to these two techniques. This investigation attempts to establish relationship between inputs to the production system, state of production system and number of units produced. Second-order differential equation analogizing production system with mechanical vibration system is devised and the constants of differential equation are determined. These constants signify mass, damping factor and natural frequency of mechanical vibration system. Differential equation formed for production system helps to simulate the production output in response to forces such as supply order, breakdown and preventive maintenance.

Using System Dynamics Method to Manage Construction and Demolition Waste

During last few decades, construction and demolition waste has attracted great attention from practitioners and researchers, as well as governments in all over the world. It's obvious that construction and demolition waste and its control is very important in many aspects. In other hand, system dynamics is an empirical tool and waste management system is a dynamic system that needs to be studied and analyzed dynamically so that many misconceptions and problems in this area to be avoided. The main question is how we can manage and control waste management system to have a less amount of negative impacts on the environment and society. In order to answer this main question, this paper tries to represent a conceptual model called “cause and effect diagram” to have a general and typical understanding of waste management system especially in Ardabil city. Next, it represents Stock-Flow diagram that has capability of running in computer for further analyzing. Then, it simulates the model by POWERSIM software to analyze and optimize the dynamic model. The study indicated that increasing values of the variables including fines for illegal dumping, unit cost of landfilling, unit cost of collecting, unit cost of transportation and also developing waste management sites has implications of a low illegal waste dumping and a high amount of waste recycling and reuse.

Renewable energy project: Project management, challenges and risk

Renewable energy is one of the most popular topics in utilization of the electric energy resources. There are various types of alternative energy, which can be used as electrical energy. However, the suitableness of the green energy in a certain country is depending on some criteria such as geographical location, the availability of energy and so on. In order to establish the renewable energy, a well-planned strategy and management must be acquired. The main objective of this paper is to analyse the causal relation of some important criteria of project planning and development of a wind energy project in Malaysia. By using a system dynamic approach, it is found that government policies, investment of renewable energy, energy demand, geographical location and fund management are the most important criteria that need to be considered among others. The diagram of causal relationship with reinforcing and balancing loop shows that the application of renewable energy in Malaysia is promising. In addition, the information of the criteria relationship is further investigated by using the stock flow diagram. From the diagram, the factors that affect project’s expenditure could be analysed. This is very important to a developing country where more budgets can be allocated for other facilities, cultures, infrastructure, science, and technology development. By utilise the renewable energy in Malaysia, the carbon dioxide emission can be reduced and contribution to a sustainable and long term alternative energy resources country.

Causal Analysis of Internet Public Opinion Dissemination System Based on the System Dynamics

Internet public opinion reflects the trend of public opinion in all sectors of society directly. It can affect the harmony and stability of society. Therefore reducing the incidence of adverse events and improving the ability to deal with Internet public opinion have become an important issue that the government needs to solve. Based on the existing literature，the paper firstly analyzes the propagation rule of Internet public opinion and its features. Then it uses the system dynamics to have an analysis of the influencing factors of ecological dissemination system about internet public opinion. What’s more, it takes a qualitative analysis to analyze the relationship between the factors through the causal analysis diagrams and it establishes the stock flow diagram of the factors. Lastly, it has a simulation analysis for the model in order to present the suggestions to control the dissemination of Internet public opinion positively..

A system dynamics model for national drug policy

BackgroundData modeling techniques can create a virtual world to analyze decision systems. National drug authorities can use such techniques to take care of their deficiencies in decision making processes. This study was designed to build a system dynamics model to simulate the effects of market mix variables (5 P’s) on the national drug policy (NDP) indicators including availability, affordability, quality, and rationality. This was aimed to investigate how to increase the rationality of decision making, evaluate different alternatives, reduce the costs and identify the system obstacles.System dynamics is a computer-based approach for analyzing and designing complex systems over time. In this study the cognitive casualty map was developed to make a concept about the system then the stock-flow model was set up based on the market demand and supply concept.ResultsThe model demonstrates the interdependencies between the NDP variables through four cognitive maps. Some issues in availability, willingness to pay, rational use and quality of medicines are pointed in the model. The stock-flow diagram shows how the demand for a medicine is formed and how it is responded through NDP objectives. The effects of changing variables on the other NDP variables can be studied after running the stock-flow model.ConclusionThe model can initiate a fundamental structure for analyzing NDP. The conceptual model made a cognitive map to show many causes’ and effects’ trees and reveals some relations between NDP variables that are usually forgotten in the medicines affairs. The model also provides an opportunity to be expanded with more details on a specific disease for better policy making about medication.

A Study on the Dynamic Effect of Sports Promotion Strategy and Effectiveness of NationalHealth Care in Taiwan

Based on system dynamics theory, this study used Vensim software to develop the Stock-Flow Diagram. This study used the Dynamic Situations of system dynamics to perform dynamic simulation on the effect of sports promotion strategy on Taiwan’s national health care and its relevant medical expenditure and future expenditure. Moreover, this study used the simulation results as reference for strategy promotion, which can make it easier to promote strategies, reduce the pressure of increase in national health insurance and increase the success rate of policy implementation. The research results showed that, situational simulation of system dynamics can simulate the effect of development trend of effectiveness of Taiwan’s national health care on the changes in complicated policy promotion system with time. The results of the simulation of policy situation showed that, it is necessary to adopt medium policy promotion and implementation rate of 55% and national physical fitness increase rate of 5% as the best strategy implementation rate in the future two years to obtain the greatest benefit.

Modelling Rural Healthcare Supply Chain in India using System Dynamics

Indian healthcare supply chain seems to be diverse depending upon the healthcare facilities and population. The present work entirely focuses on the supply of Iron Folic Acid tabs in state government owned rural healthcare systems. Brief introduction about system dynamic has been given in this paper. A survey has been conducted related to the supply chain of folic acid tabs from state drug stores to patients via women's hospital, community health centre (CHC), primary health centres, and sub centres in District Haridwar, Uttarakhand, India. Modeling and simulation of entire supply chain has been performed using system dynamics technique. Causal loop diagram (CLD) has been constructed which displays the supply chain process at various stages throughout the entire system. The factors such as frequency of patients, and order frequency has been considered while constructing the causal loop diagram. The CLD has been translated into stock-flow diagram (SFD) for the entire supply chain on Stella® platform and simulation has been run for a period of one year (Jan to Dec). It has been noticed that there is a huge shortage (stock out) of folic acid tabs at women's hospital, CHC, PHCs, and sub centres because of large delivery time. The present research may assist the government policy makers to take necessary decisions for improving the sustainability of the rural healthcare supply chain by reducing stock out of the medicine.

Simulating hedging rules for effective reservoir operation by using system dynamics: a case study of Dez Reservoir, Iran

Some of the most important challenges facing water managers are to increase water supply and reduce its demand. A single systematic method is needed to address both issues, such as the System Dynamics (SD) modeling approach. In this approach all the factors, parameters, and their influences on the problem are considered by causal loops and stock-flow diagrams. The multipurpose Dez Reservoir in southwestern Iran is a good case study for this approach, and we simulated 10 years under differing operation strategies to develop the most appropriate operation policy. A hydrologic time series analysis was conducted to generate simulated inflow to the reservoir, and differing policies, including hedging rules and a “goal-seeking hedge,” were applied. By using performance criteria and a new measure entitled “corrected reliability,”, the most appropriate scenarios were identified. We found that using the goal-seeking hedge in combination with water demand management offers the best chance for effectively meeting demands and minimizing supply shortages.

Profits Management for Reverse Supply Chain with Supply Disruption

In reverse supply chain under our study, there are four supply disruptions. As the source of the reverse supply chain, the supply disruption of used-products between end-consumers and collector will largely affect the profits of the reverse supply chain. In order to manage the profits of the reverse supply chain, we give an expanded stock-flow diagram with this supply disruption of the reverse supply chain by using system dynamics methodology, show the simulation results of collector's profit, disassembly center's profit, remanufacturer's profit and the mean of their profits under different disruption periods. By analyzing the simulation results, we present a strategy to ensure the members positive profits. The strategy is adding another channel of purchasing used-products for the collector. We show the simulation results of the members profits and their mean after using the strategy, and give the suitable range of purchase quantity of used-products for the strategy.

Modelling and Simulation of Power Grid Engineering Project based on System Dynamics on the Background of Smart Grid

Power grid engineering project has the features of dynamics and complexity on the background of smart grid. Firstly, the modelling method based on System Dynamics is proposed. Secondly, on the basis of defined key factors and their mutual relations, a dynamic model with the fundamental structure of casual loop and stock-flow diagrams is built according to complex and dynamic nature of the project. Then this model is used to simulate the management process of the power grid engineering project. The simulation results shows that System Dynamics model can be used efficiently in modelling and optimization of power grid engineering project management for its clear causality, suitable complexity and exact describe characteristics.

A dynamic model for assessing the effects of management strategies on the reduction of construction and demolition waste

During the past few decades, construction and demolition (C&D) waste has received increasing attention from construction practitioners and researchers worldwide. A plethora of research regarding C&D waste management has been published in various academic journals. However, it has been determined that existing studies with respect to C&D waste reduction are mainly carried out from a static perspective, without considering the dynamic and interdependent nature of the whole waste reduction system. This might lead to misunderstanding about the actual effect of implementing any waste reduction strategies. Therefore, this research proposes a model that can serve as a decision support tool for projecting C&D waste reduction in line with the waste management situation of a given construction project, and more importantly, as a platform for simulating effects of various management strategies on C&D waste reduction. The research is conducted using system dynamics methodology, which is a systematic approach that deals with the complexity – interrelationships and dynamics – of any social, economic and managerial system. The dynamic model integrates major variables that affect C&D waste reduction. In this paper, seven causal loop diagrams that can deepen understanding about the feedback relationships underlying C&D waste reduction system are firstly presented. Then a stock-flow diagram is formulated by using software for system dynamics modeling. Finally, a case study is used to illustrate the validation and application of the proposed model. Results of the case study not only built confidence in the model so that it can be used for quantitative analysis, but also assessed and compared the effect of three designed policy scenarios on C&D waste reduction. One major contribution of this study is the development of a dynamic model for evaluating C&D waste reduction strategies under various scenarios, so that best management strategies could be identified before being implemented in practice.

Dynamic cycles of unsold new housing stocks, investment in housing, and housing supply–demand

Unsold new housing stocks may be closely related to housing market fluctuation, especially the difference between housing supply and demand, which is influenced by macroeconomic conditions. These factors simultaneously influence developers’ investment decisions and, thus, housing supply over time. However, previous research on the housing market has focused on explaining the statistical relationships among factors with reduced-form equations rather than analyzing dynamic behavioral changes. Thus, system dynamics should be introduced to analyze the dynamic cycles of unsold new housing stocks, housing investment, and housing supply–demand. This study develops Causal Loop Diagrams (CLDs), in which dynamic relationships are presented, and Stock–Flow Diagrams (SFD) for quantitative simulation by introducing normalized unit modeling by elementary relationship (NUMBER). The simulation results show that system dynamics can explain dynamic relationships in the housing market by focusing on unsold new housing stocks. In terms of the practical use of system dynamics models, governments can establish housing policies and developers can make decisions on investment in housing by considering unsold new housing stocks and their influence on the housing market. However, further consideration should be given to developing a method to reflect unpredictable economic events, such as the global financial crisis, in the system dynamics model.

Toward Endemic Deployment of Educational Simulation Games: A Review of Progress and Future Recommendations

This article presents a conceptual analysis of simulation game adoption and use across university faculty. The metaphor of epidemiology is used to characterize the diffusion of simulation games for teaching and learning. A simple stock-flow diagram is presented to illustrate this dynamic. Future scenarios for simulation game adoption are presented, based on alternative diffusion behaviors. University strategies for increasing simulation game use are explored. It is concluded that while creating endemic use of simulation games by faculty is unlikely, we can employ measures that will significantly expand the stock of faculty acting as simulation game instructors.

The emergence and use of diagramming in system dynamics: a critical account

AbstractThe paper reviews the leading diagramming methods employed in system dynamics to communicate the contents of models. The main ideas and historical development of the field are first outlined. Two diagramming methods—causal loop diagrams (CLDs) and stock/flow diagrams (SFDs)—are then described and their advantages and limitations discussed. A set of broad research directions is then outlined. These concern: the abilities of different diagrams to communicate different ideas, the role that diagrams have in group model building, and the question of whether diagrams can be an adequate substitute for simulation modelling. The paper closes by suggesting that although diagrams alone are insufficient, they have many benefits. However, since these benefits have emerged only as ‘craft wisdom’, a more rigorous programme of research into the diagrams' respective attributes is called for. Copyright © 2008 John Wiley & Sons, Ltd.

Modeling Water Quality Management Alternatives for a Nutrient Impaired Stream Using System Dynamics Simulation

A system dynamics (SD) simulation model is developed using an object-oriented modeling environment to simulate and analyze water quality management strategies for a nutrient impaired stream. An object-oriented simulation environment, STELLA, conceived on the principles of system dynamics (SD) is used for the development of the model. The modeling process consists of developing stock-flow diagrams and carrying out computer simulations using difference equations to integrate stocks and flows. The model structure and behavior of the system is validated using dimensionality, replication and sensitivity tests; and calibration along with validation is carried out using an appropriate model performance measure. The model helps the user to separate policy questions from the data and provides the facility to generate "what-if" scenarios while keeping the modeling process transparent. Case study application of this model is illustrated by developing a total maximum daily load (TMDL) allocation strategy for a nutrient impaired stream in the southeastern region of Kentucky, USA. Results suggest that the fate and transport process of total phosphorus in a river system can be simulated using a conceptually simple object-oriented simulation model.