System Dynamics Model Research Articles

Simulation and Prediction of Land Use Change and Carbon Emission under Multiple Development Scenarios at the City Level: A Case Study of Xi’an, China

Studying urban land use and its impact on carbon emissions is crucial for achieving China’s dual carbon goals. This research utilized the Shared Socio-economic Pathways (SSPs) scenarios 126, 245, and 585 from the Sixth International Coupled Model Intercomparison Project (CMIP6), along with a coupled System Dynamics (SD) and Patch-generating Land Use Simulation (PLUS) model and a carbon emission coefficient method to simulate and predict Xi’an’s land use carbon emissions from 2020 to 2040. The results indicate the following: (1) Cultivated and forest lands are the predominant land use types in Xi’an, with cultivated and grassland areas projected to decline under all three SSP scenarios by 2040. The most significant expansion of construction land, primarily at the expense of farmland, is projected under the SSP585 scenario, with an increase of 515.92 km2 by 2040. (2) Land use carbon emissions increased from 414.15 × 104 t in 2000 to 2376.10 × 104 t in 2020, with construction land being the primary source of emissions and forest land serving as the main carbon sink. However, the carbon sink capacity remained low at only 21.38 × 104 t in 2020. (3) Carbon emissions are expected to continue increasing under all scenarios through 2030 and 2040, though at a decreasing rate. The SSP126 scenario predicts the lowest emissions, reaching 9186.00 × 104 t by 2040, while SSP585 predicts the highest at 14,935.00 × 104 t. The findings of this study provide theoretical support for future low-carbon and high-quality urban development strategies.

Shifting wood between material and energy use: Modeling the effects of substitution

AbstractWood as a renewable material is relevant for climate change mitigation: Carbon sequestration in forests and carbon storage in harvested wood products (HWPs) contribute to carbon reduction in the atmosphere, and the substitution of carbon‐intensive products with wood products can reduce greenhouse gas (GHG) emissions. Since wood is a limited resource, it must be used efficiently and sustainably. Shifting wood from one application to another might result in decreased GHG emissions due to substitution effects. However, which wood application will lead to a GHG emission reduction is currently unknown. This study investigates the effects of shifting wood between applications and the resulting substitution effects from a system perspective. A system dynamics model describes the wood utilization system of Austria, including the value chains from the forest to wood‐processing industries and the substitution that takes place in these industries. These value chains are associated with the global warming potential. Seven wood utilization scenarios shifting between material use and use for energy are simulated. The results show that wood shifts lead to both a substitution effect (emission reduction) in industries where wood utilization is increased and a counter effect (emission increase) where wood is replaced. The two effects potentially outweigh each other partly, leading to comparatively small net effects. However, carbon sequestration in HWPs and future changes in substitution effects might lead to additional effects. To substantially contribute to climate change mitigation, alternatives other than shifting wood between material and energy value chains need to be found within the wood utilization system.

Circular battery production in the EU: Insights from integrating life cycle assessment into system dynamics modeling on recycled content and environmental impacts

AbstractThe European Union (EU) Battery Regulation aims to establish a circular battery production and sets minimum battery material recycled targets for new batteries from post‐production and post‐consumer waste batteries. However, it is uncertain whether these targets can be met due to dynamic market developments and if their compliance results in environmental benefits. Therefore, this study examines the circular battery production in the EU and its impact on material flows and the environment from a market perspective. We combined a system dynamic market model with process models for battery production and recycling, using prospective life cycle assessment. According to our analysis, the projected amount of post‐consumer waste alone may not meet the specified levels of recycled materials due to long battery lifetimes. Thereby, the targets for cobalt are particularly ambitious, with a gap of between 9.8 and 14.6 percentage points for most scenarios. In the case of reduced battery lifetimes, the achievable recycled content across all materials increases by more than 75% in 2032 and by more than 85% in 2037. The avoidance of post‐production waste leads to 9% lower greenhouse gas (GHG) emissions compared to recycling with 100% recycling efficiency. Thus, attributable amounts of post‐production waste and unfavorable prolonged use of batteries create misguided incentives to meet legal targets. Additionally, the delay between production and recycling limits the potential for circular production as this depends significantly on market conditions. Our study highlights, that besides recycling, the industry should especially advance production processes including upstream material extraction and refinement to reduce environmental impacts.

Research on Coupling Effect Measurement and Coupling Risk Simulation of Green Building Construction Safety Risk Factors

The construction of green buildings is an important direction for the transformation and development of the construction industry, but it is beset with problems such as a lack of construction experience, immature new technologies, and unstable material properties; these issues bring risks to the construction stage of green buildings, and the coupling of uncertain risk factors in the construction process of green buildings may lead to unfavorable results. The purpose of this study is to explore the coupling degree of green building construction safety risk factors and the changing trend in their coupling combinations at the system risk level. First, the risk factor index system was defined by reading the literature and gathering expert opinions, and the coupling degree between risk factors was measured using an improved coupling degree model. Then, a system dynamics model was established to simulate and analyze the coupling effects among the risk factors and determine the combinations with the greatest influence. The results show that the risk probability is proportional to the risk coupling value, the human–environment coupling value is the largest, and the material equipment–management coupling value is the smallest. The human–environment system simulation shows that reducing the coupling value of system factors will promote a decrease in the total level of system risk. According to the research conclusions, measures to prevent risk coupling are proposed, which offer theoretical references for green building practitioners carrying out risk management; these measures hold a certain guiding significance for the risk control and future development of green buildings.

Tracking and managing the water-food-environment-ecosystem (WFEE) nexus in groundwater irrigation districts using system dynamics modelling

Groundwater irrigation districts, which play a crucial role in the Earth's critical zone, are confronted with numerous challenges, including water scarcity, pollution, and ecological degradation. These issues come from multiple systems and are linked to a groundwater-dominated water-food-environment-ecosystem nexus problem related to agricultural activities (WFEE). There is a pressing need for the scientific characterization and evaluation of the WFEE nexus in groundwater irrigation districts to assure high-quality, sustainable development. Furthermore, it is critical to provide practical and efficient regulations at the farmer level to uphold the health of this nexus. This paper presents a mapping network that focuses on groundwater irrigation districts. The network aims to convert the restriction indicators utilized to maintain the health of the WFEE nexus (at the irrigation district scale) into the targets employed to manage farmers' living and agricultural activities (at the farmer scale). Additionally, a system dynamics model is created to track and manage the interacting relationships between the WFEE nexus and farmers' living and agricultural activities. This proposed model employs a structured parameter system comprising targets, state parameters, regulatory parameters, and evaluation parameters. This system can get insight into the status of the WFEE nexus at the farmer level using state parameters, induce tailored management and regulation measures using regulatory parameters, assess the effectiveness of various measures using the evaluation parameters, and finally provide decision support to enhance the health of the WFEE nexus. The findings from the research conducted in the Yong'an groundwater irrigation district demonstrated that the model accurately described the relationship between the WFEE nexus and farmers' activities in groundwater irrigation districts. Furthermore, the model responded strongly to a variety of improvement strategies, including adjustments in planting area, optimization of planting pattern, improvement of irrigation method, and implementation of agronomic measures. As a result, it provided farmers with decision support for applying agricultural management methods and addressing the WFEE nexus problem in groundwater irrigation areas.

Signal enhancement method for gearboxes fault diagnosis in robotic flexible joint

Abstract Motor Current Signal Analysis (MCSA) provides a non-intrusive approach to fault diagnosis. However, the fault impact reacting in the current is reduced due to the presence of flexible structures in the transmission path from the fault source to the motor. Therefore, this paper proposes a method to enhance the frequency domain of the current signal of a single mechanical fault through a transfer model between motor torque and link vibration. First, the joint system dynamics model was developed based on a three-inertia simplified model. The transfer model of motor torque and link vibration was defined based on the system dynamics. The link vibration is then estimated based on the transfer model and electromagnetic torque. Link vibration signal is considered as an enhancement of the torque signal. Finally, the link vibration signature analysis is performed instead of MCSA. The experimental results show that the method is effective in enhancing the features of individual mechanical faults and improving the fault diagnosis performance.

A complete shortest independent loop set algorithm for model structure analysis

AbstractThis article looks at the well‐known shortest independent loop set algorithm, which is used to identify an independent loop set in system dynamics models. It addresses the cases where the algorithm fails to find a complete set due to its limitation to geodetic cycles and introduces a modification that has the potential to identify a complete independent loop set in every case while maintaining the efficiency of the original algorithm. The modified algorithm uses second‐shortest paths to complete the loop set. Special attention is given to the creation of the second‐shortest path matrix required for the modified algorithm, and to the application of the algorithm to a model where the independent loop set created by the shortest independent loop set algorithm was previously shown to be incomplete. © 2024 System Dynamics Society.

Dynamic evaluation of distribution channels in a fresh food supply chain from a sustainability and resilience approach

Research on agrifood supply chains has grown in recent years; however, little attention has been given to the effect of the choice of distribution channel on the sustainable and resilient performance of the network. This research proposes a system dynamics model to evaluate different distribution channels for a fresh food supply chain in a developing country. Among the main results is that the use of food hubs in a channel distribution produces long-term environmental, social and resilience benefits for the entire network, while short supply chains are the most economically viable alternative.

Exploring the Nexus between Food Systems and the Global Syndemic among Children under Five Years of Age through the Complex Systems Approach.

The intricate relationship between food systems and health outcomes, known as the food-nutrition-health nexus, intersects with environmental concerns. However, there's still a literature gap in evaluating food systems alongside the global syndemic using the complex systems theory, especially concerning vulnerable populations like children. This research aimed to design a system dynamics model to advance a theoretical understanding of the connections between food systems and the global syndemic, particularly focusing on their impacts on children under five years of age. The framework was developed through a literature review and authors' insights into the relationships between the food, health, and environmental components of the global syndemic among children. The conceptual model presented 17 factors, with 26 connections and 6 feedback loops, categorized into the following 5 groups: environmental, economic, school-related, family-related, and child-related. It delineated and elucidated mechanisms among the components of the global syndemic encompassing being overweight, suffering from undernutrition, and climate change. The findings unveiled potential interactions within food systems and health outcomes. Furthermore, the model integrated elements of the socio-ecological model by incorporating an external layer representing the environment and its natural resources. Consequently, the development of public policies and interventions should encompass environmental considerations to effectively tackle the complex challenges posed by the global syndemic.

Dual-Mode Square Root Cubature Kalman Filter for Miniaturized Underwater Profiler Dead Reckoning

Miniaturized underwater profilers have the advantages of small size, low cost, and flexible deployment, which play together an important role in the persistent monitoring of a designated ocean area. Based on the demand for ocean observation, the system design, dynamic modeling, and dead reckoning algorithm of a miniaturized underwater profiler are carried out. The process of the persistent monitoring of designated area with a miniaturized underwater profiler is analyzed, and the overall structure of the miniaturized underwater profiler was designed. Additionally, the kinematic and dynamic model of the miniaturized underwater profiler is given based on the inertial and body coordinate systems. Then, according to the state equation and the observation equation of the miniaturized underwater profiler, a dual-mode square root cubature Kalman filter (DSRCKF) algorithm, combining standard SRCKF and adaptive SRCKF, is proposed for the dead reckoning of the miniaturized underwater profiler. Finally, a comprehensive comparison of EKF, UKF, CKF, SRCKF, and DSRCKF and the associated simulations and experiments are conducted to verify the performance of the underwater dead reckoning algorithm for the miniaturized underwater profiler. The results show that the DSRCKF algorithm has a certain role in the dead reckoning of the miniaturized underwater profiler, particularly in the z direction and attitude. In future, a real underwater dead reckoning test using miniaturized underwater profiler will be carried out.

Climate and geopolitical risk correlations and response decisions for semiconductor global supply chains

Threats from climate risk (CR) and geopolitical risk (GR) undermine the resilience of the Semiconductor Global Supply Chain (SGSC). Plenty of company profit has plummeted due to the chip supply disruptions and delays. Particularly, the complex risk correlations (RCs) in a multi-project environment, and the inter-entity relationships, render the risk analysis and risk response decisions (RRDs) within CR and GR challenging. To address the problem, this study proposes a novel three-stage approach to explore the impact of CR and GR and obtain RRDs. First, based on the actual operation of SGSC, a system dynamics model of the RCs is conducted to analyze the effects of CR and GR. Second, a Stackelberg game model is formed based on the project interdependencies to find the optimal response resources and profit considering the inter-entity relationships. Third, a binary optimization model constrained in the optimal response resources is developed to determine RRDs. From the simulation results and the numerical example, the proposed approach is a powerful tool for risk managers of SGSCs. The actionable recommendations on managing and responding to CR and GR are summarized. This study provides theoretical and managerial insights for resilient supply chain management.

Leveraging Life Cycle Assessment and System Dynamics Model Analysis for an Integrated Household E-Waste Management System in Yaoundé, Cameroon

Electronic waste (E-waste) is a global environmental issue and a contemporary challenge in developing countries, where implementing sustainable E-waste management policies is required to mitigate the adverse impacts of inappropriate treatment and disposal. This study assesses the environmental and human health impacts of the current E-waste management system in Yaoundé. The study then proposes an integrated E-waste management system (IEMS) with policy instruments for increased formal E-waste collection and reduced environmental impacts from informal E-waste treatment. Life cycle assessment (LCA) was utilized to identify high-impact contributing processes within the current E-waste management system (EMS) and to determine the optimum scenario for an integrated system. The system dynamics model (SDM) analysis ascertained the efficiency of the E-waste policy under the IEMS. Results show that the IEMS can reduce global warming potential, fine particulate matter formation, and human carcinogenic toxicity from one ton of E-waste treatment by 27%, 16.3%, and 34%, respectively. Regarding the policy efficiency simulation for the IEMS, the policy instrument (Policy 1), with levies on electronic appliance producers, proved environmentally efficient in reducing the quantity of informal recycling. It was also more economically viable for the recycling fund to increase formal E-waste collection and subsidize formal treatment within the context of the IEMS. The study outcome is informative for E-waste management policy planning in developing economies.

Estimated attribution of the RFS program on soybean biodiesel in the U.S. using the bioenergy scenario model

Biofuels are supported by various governmental policies in the U.S. and globally as an alternative transportation fuel for environmental, geopolitical, and economic reasons. Much debate surrounds the effectiveness of these policies as well as the overall net environmental effect of increased biofuels use. In the U.S., recent studies have shown that the Renewable Fuels Standard (RFS) Program, overall, may not have been the leading driver of the ethanol industry from 2005 to 2020, contrary to common perception. Similar scrutiny has not been applied to biodiesel. This study uses the Bioenergy Scenario Model, a well-vetted system dynamics model, to retrospectively apportion historical biodiesel production between the RFS Program and other potentially influential drivers, such as the economics of biodiesel vs. diesel, the Biodiesel Tax Credit (BTC), California's Low Carbon Fuel Standard, and other factors. From 2002 to 2020 about 36% of biodiesel production can be attributed to the RFS Program, 35% to the BTC, and the rest to other factors. Thus, the overall effect of the RFS Program appears much larger on biodiesel than on corn ethanol. The finding that the same policy may have very disparate effects on different biofuels helps inform the design of future policies on biofuels.

A piezoelectric cantilever-beam-spring-pendulum oscillator for multi-directional vibration energy harvesting

Harvesting energy from environmental vibrations holds significance for powering wireless sensors and transducers. However, the current vibration energy harvesting methods still have room for improvement, especially in the field of low-frequency vibration, where the performance of output voltage is relatively insufficient. This paper proposes a novel piezoelectric energy harvester consisting of a piezoelectric cantilever beam and a spring pendulum in order to address this challenge. Under external excitation, energy exchange is generated between the internal parts of the system, so that the swinging of the pendulum is interchanged with the extension and contraction motion of the spring and the bending motion of the cantilever beam to realize multidirectional energy harvesting. Firstly, the energy equation of system is obtained and the dynamics model of system is derived based on Lagrange's theorem. In addition, the response characteristics of system under harmonic excitation and the effects of different parameters on the system performance are investigated by simulation. With proper parameter selection, the system can produce higher output voltages. Compared to a piezoelectric cantilever-single-pendulum, the proposed structure demonstrates superior performance, especially in low-frequency vibration. The maximum voltage amplitudes in the x- and z-directions were 106.6% and 187.3% of those of the piezoelectric cantilever-single-pendulum, respectively. This paper proves the superior energy harvesting performance of the proposed structure.

A purely centered and non-redundant piezoelectric stick-slip rotary stage with force amplification

This paper proposes a purely center-rotation and non-redundant piezoelectric stick–slip rotary stage with force magnification. A bridge driving mechanism with centrosymmetric actuation feet is proposed, and its tilt angle can be adjusted to regulate the clamping force amplification characteristics, thus improving load capacities. Meanwhile, only a single piezoelectric actuator is used, and the driving mechanism is built in the circular slider, hence achieving non-redundant, purely centered rotation and improving the structural compactness. Theoretical calculations and simulation analyses of single-step rotation angles and force amplification of the rotary stage are carried out. In addition, a system dynamics model with electromechanical, rigid-flexible, and friction coupling properties is established. Finally, a prototype is fabricated, and various experiments are conducted. The designed bridge driving mechanism amplifies the piezoelectric actuation force by 2.8 times, and the stick–slip rotary stage has a maximum load of up to 9 kg. Also, the stage can rotate more than 360°, and the angular resolution is 0.1265 μrad, demonstrating superior performances of the non-redundant center-rotation stage.

A System Dynamics Model of Organizational Resilience

AbstractResilience is the ability to avoid, withstand, and recover from adversity. In this paper, we examine organizational resilience using a case study of an organization that suffers from a series of scandals that lead to problems with its reputation as an inclusive organization, which results in difficulties in recruiting and retaining employees. We suggest some policies involving leadership efforts to change the culture in the organization and thereby restore its reputation. Based on the results of a System Dynamics Model that mixes quantitative and qualitative measures, we find that changing organizational culture is difficult. There can be inertia and long delays before the leadership sees results in improved recruiting and retention statistics.

From text to map: a system dynamics bot for constructing causal loop diagrams

AbstractWe introduce and test the System Dynamics Bot, a computer program leveraging a large language model to automate the creation of causal loop diagrams from textual data. To evaluate its performance, we ensembled two distinct databases. The first dataset includes 20 causal loop diagrams and associated texts sourced from the system dynamics literature. The second dataset comprises responses from 30 participants to a vignette, along with causal loop diagrams coded by three system dynamics modelers. The bot uses textual data and successfully identifies approximately 60% of the links between variables and feedback loops in both datasets. This article outlines our approach, provides examples, and presents evaluation results. We discuss encountered challenges and implemented solutions in developing the System Dynamics Bot. The bot can facilitate extracting mental models from textual data and improve model‐building processes. Moreover, the two datasets can serve as a test‐bed for similar programs. © 2024 The Author(s). System Dynamics Review published by John Wiley & Sons Ltd on behalf of System Dynamics Society.

Unraveling the Complexity of Food and Nutrition Security for College Students in the United States: A Qualitative Community-Based System Dynamics Modeling Protocol

Unraveling the Complexity of Food and Nutrition Security for College Students in the United States: A Qualitative Community-Based System Dynamics Modeling Protocol

Can China's energy quota trading impact the market performance and policy effects of carbon emissions trading?

With the gradual shift from dual control of energy consumption to dual control of carbon emissions, energy quota trading (EQT) and carbon emissions trading (CET) policies will be implemented in parallel in China. EQT policy will significantly affect the market performance and policy effects of CET, which consequently affects the dual control of carbon emissions. Therefore, constructing a system dynamics model coupling the national CET, EQT, and electricity markets, this paper researches the impact of EQT policy and its parameter design on the market performance and policy effects of CET through scenario analysis. The results show that: (1) Implementing EQT policy will reduce CET price and trading volume, negatively affecting CET market performance. This indicates that there is a certain substitution between EQT and CET. (2) EQT policy can enhance the emission reduction and decarbonization effects of CET policy. By curbing thermal power investment and generation and promoting green power, the EQT policy reduces carbon emissions by about 4.87% and optimizes the power supply structure. (3) To scientifically design the EQT policy parameters, lower energy saving targets and energy quota benchmark prices can alleviate the negative impact on CET market performance, but are not conducive to improving CET policy effects.

Utilizing System Dynamics for Border Area Development in Napan Village, North Bikomi, East Nusa Tenggara

Napan Village, North Bikomi District - North Central Timor Regency - East Nusa Tenggara is some of the areas that border Indonesia on land with neighboring countries. Napan Village shares a land border with Timor Leste. Various issues regarding security, prosperity and the environment in development often arise. This research was conducted to develop models dynamically in three development scenarios using these three approaches. The research sample was obtained using a questionnaire distributed to 78 respondents consisting of village soldiers and police, Napan village officials, the North Bikomi sub-district head, and border officers in Napan village. From the results of the questionnaire, descriptive analysis and multiple regression analysis were carried out to obtain a regression model of the influence of security, prosperity, and environmental approach variables on border area development. Next, the analysis results are used to develop a system dynamics model with three simulation scenarios. The reference used in this simulation is the average data value for each variable minus and adding one standard deviation and the equation resulting from multiple regression analysis. The simulation results show that the target for achieving development in border areas will reach 73% within 5 years if input from security, prosperity, and environmental factors is increased from the current condition of 8% for security, 6% for prosperity, and 9% for the environment. Furthermore, it is recommended to increase development on factors in security, prosperity, and environmental approaches according to these results so that in the next five years significant progress can be achieved, which reaches almost double the current conditions.