USING SYSTEM DYNAMICS MODELING TO ASSESS THE IMPACT OF CONNECTICUT GOOD SAMARITAN LAWS: A PROTOCOL PAPER

Background We applied a participatory system dynamics (SD) modeling approach to evaluate the effectiveness and impact of Connecticut Good Samaritan Laws (GSLs) that are designed to promote bystander intervention during an opioid overdose event and reduce opioid overdose-related adverse outcomes. Our SD model can be used to predict whether additional revisions of the statutes might make GSLs more effective. SD modeling is a novel approach for assessing the impact of GSLs; and, in this protocol paper, we describe its applicability to our policy question, as well as expected outcomes of this approach. Methods This project began in February 2021 and is expected to conclude by March 2022. During this time, a total of six group model-building (GMB) sessions will have been held with key stakeholders to elicit feedback that will, in turn, contribute to the development of a more robust SD model. Session participants include bystanders who witness an overdose, law enforcement personnel, first responders, pharmacists, physicians, and other health care professionals who work in at least two major metropolitan areas of Connecticut (New Haven and Hartford). Due to the restrictions imposed by the COVID-19 pandemic, the sessions are being held virtually via Zoom. The information obtained during these sessions will be integrated with a draft SD model that has already been developed by the modeling team as part of a previous CDC-funded project. Model calibration and policy simulations will then be performed to assess the impact of the current GSLs and to make recommendations for future public policy changes. Discussion An SD modeling approach enables capture of complex interrelationships among multiple health outcomes to better assess the drivers of the opioid epidemic in Connecticut. The model simulation results are expected not only to align with current real-world data but also to recreate historical trends and infer future trends in a situationally relevant fashion. This will facilitate the work of policy makers who are devising and implementing time-sensitive changes to address opioid overdose-related deaths at the state level. Replicating our approach as described can be applied to make similar improvements in other jurisdictions. CONTRIBUTIONS TO THE LITERATURE - System dynamics (SD) modeling and group model-building (GMB) approaches enable the group to start with a simple concept model and apply the collective knowledge of the group to finish the session with a much more developed model that can produce impressively accurate simulation results. - The model will be used to understand the impact of Connecticut Good Samaritan Laws (GSLs), as well as their limitations, and to deduce factors to further improve public health laws to counter opioid overdose-related deaths. - The approach can be applied to other jurisdictions, taking into account local conditions and existing Good Samaritan legislation. KEYWORDS: System dynamics modeling, group model building, opioid overdose deaths, opioid use disorder, Good Samaritan laws

A SYSTEM DYNAMICS MODEL FOR URBAN TAXI PRICE SIMULATION

Urban taxi services have been developing year on year, playing an increasingly important role in the economy and the transportation markets of each city. This increases interest in measuring their performance. This paper analysed the relationship among the four stakeholders (including administrative department, operational companies, taxi drivers and customers) for urban taxi passenger transport system in China, and applied System Dynamics (SD) model to explore the dynamic characteristics of urban taxi price system. The main achievements of this paper are as follows, firstly, this paper adopted stakeholder mapping to describe the relationships among the four stakeholders. Then analysed the causal flow diagrams and the different variables of urban taxi passenger transport system operation, and presented the SD model, which considers factors that affect the taxi operation. With the combination of taxi operation data of Harbin city, we simulated eleven urban taxi operation scenarios and proposed kinds of suggestions to improve urban taxi passenger transport system operation, which can provide a good basis for recommending policy decisions for urban taxi market.

Identifying the dynamic evolution and feedback process of water resources nexus system considering socioeconomic development, ecological protection, and food security: A practical tool for sustainable water use

The accelerated consumption of water resources caused by the rapid increase in population and urbanization is intensifying the complex interactions across water resources, socioeconomic development, ecological protection, and food security (WSEF), which causes not only the imbalance between water supply and demand but also the vulnerability of both food and ecological systems. Therefore, identifying the dynamic coevolution and feedback process is one of the most crucial ways of achieving the goal of sustainable water use. In this study, we developed an integrated modeling framework to better identify the dynamic interaction and coevolution process of the nexus across WSEF systems in the context of sustainable water uses by coupling system dynamic (SD) model and multi-objective optimization model. The SD model is used to simulate both the dynamic interaction of each agent and the coevolution process of the whole nexus system by positive/negative feedback loops. The multi-objective optimization model is used to quantify the negative feedback loops of the SD model by generating the optimal scheme of different water users. Finally, the model uncertainty considering different weighting factors is analyzed. The framework is applied to the upper reaches of the Guijiang River basin, China. Results show that (i) the rapid economic growth increases the conflict between the water uses for socioeconomic development and ecological protection, intensifying the ecological awareness and resulting in more water shortages of socioeconomic and food agents, which is unable to support such rapid development. (ii) Once the economic growth rate decreases, water resources are able to support economic development with a decreased overload index and stable crop yield, which further contributes to water sustainability. (iii) The river ecological agent is the critical factor that affects the robustness of the model. (iv) The equal consideration of each water usage is the most beneficial to sustainable development. These results highlight the importance of water resources management, considering the tradeoffs across multiple stakeholders, and give a strong reference to policymakers for comprehensive urban planning.

A System Dynamics Prediction Model of Airport Environmental Carrying Capacity: Airport Development Mode Planning and Case Study

Airport environmental carrying capacity (AECC) provides the fundamental conditions for airport development and operation activities. The prediction of AECC is a necessary condition for planning an appropriate development mode for the airport. This paper studies the dynamic prediction method of the AECC to explore the development characteristics of AECC in different airports. Based on the driving force-pressure-state-response (DPSR) framework, the method selects 17 main variables from economic, social, environmental and operational dimensions, and then combines the drawing of causal loop diagrams and the establishment of system flow diagrams to construct the system dynamics (SD) model of AECC. The predicted values of AECC are obtained through SD model simulation and accelerated genetic algorithm projection pursuit (AGA-PP) model calculation. Considering sustainable development needs, different scenarios are set to analyze the appropriate development mode of the airport. The case study of the Pearl River Delta airports resulted in two main conclusions. First, in the same economic zone, different airports with similar aircraft movements have similar development characteristics of AECC. Second, the appropriate development modes for different airports are different, and the appropriate development modes for the airport in different periods are also different. The case study also proves that the AECC prediction based on SD model and AGA-PP model can realize short-term policy formulation and long-term planning for the airport development mode, and provide decision-making support for relevant departments of airport.

Performance Assessment of BDS-2/BDS-3/GPS/Galileo Attitude Determination Based on the Single-Differenced Model with Common-Clock Receivers

Global navigation satellite system (GNSS)-based attitude determination has been widely applied in a variety of fields due to its high precision, no error accumulation, low power consumption, and low cost. Recently, the emergence of common-clock receivers and construction of GNSS systems have brought new opportunities for high-precision GNSS-based attitude determination. In this contribution, we focus on evaluating the performance of the BeiDou regional navigation satellite system (BDS-2)/BeiDou global navigation satellite system (BDS-3)/Global Positioning System (GPS)/Galileo navigation satellite system (Galileo) attitude determination based on the single-differenced (SD) model with a common-clock receiver. We first investigate the time-varying characteristics of BDS-2/BDS-3/GPS/Galileo line bias (LB) with two different types of common-clock receivers. The results have confirmed that both the phase and code LBs are relatively stable in the time domain once the receivers have started. However, the phase LB is expected to change to an arbitrary value after each restart of the common-clock receivers. For the first time, it is also found that the phase LBs of overlapping frequencies shared by different GNSS systems are identical. Then, we primarily evaluated the performance of BDS-2/BDS-3/GPS/Galileo precise relative positioning and attitude determination based on the SD model with a common-clock receiver, using a static dataset collected at Wuhan. Experimental results demonstrated that, compared with the double-differenced (DD) model, the SD model can deliver a comparable root–mean–square (RMS) error of yaw but a significantly smaller RMS error of pitch, whether for BDS-2, BDS-3, GPS, or Galileo alone or a combination of them. The improvements of pitch accuracy are approximately 20.8–47.5% and 40.7–57.5% with single- and dual-frequency observations, respectively. Additionally, BDS-3 can deliver relatively superior positioning and attitude accuracy with respect to GPS and Galileo, due to its better geometry. The three-dimensional positioning and attitude (including yaw and pitch) accuracy for both the DD and SD models can be remarkably improved by the BDS-2, BDS-3, GPS, and Galileo combination with respect to a single system alone.

A predictive framework for sustainable youth skills development

PurposeThe purpose of this research is to investigate sustainable strategies for skills development that is specific to the youth of South Africa. International and South African data are statistically analysed and quantified to provide inputs for the systems dynamics (SD)-based predictive skills model. The skills model simulates the impact of barriers and drivers on youth skills development towards identification of focus areas for improvement.Design/methodology/approachThe research adopts a mixed-methods approach. The study begins with an explorative literature study on skills development, with the findings applied in developing (1) South African specific research instruments for small, medium and micro enterprises (SMMEs) and skills programme grant recipients and (2) a conceptual framework of the SD predictive skills model. The responses to the South African specific instruments are analysed via confirmatory factor analysis (CFA), which quantifies the input coefficients to the system dynamics model. To quantify the global inputs for the SD model, an in-depth literature review of the global skills development initiatives is conducted. The SD model output on skills, for the South African inputs, is comparatively evaluated against global inputs.FindingsThe paper details the results of the literature analysis, instrument analyses, CFA and SD model. The instrument results rank experience, skills and interactions with experts and work-based learning as most important. South African and global learners identify networking as the primary medium for identifying training and employment opportunities. South African and global learners also identify qualifications and work-based experience as key to finding employment. The quantified results of the SA and global analysis are used as inputs in the SD model to deliver a forecasting tool. The SD model finds that the global data provide for better development of the skills base than the South African inputs. The key focus areas identified for improvement in South Africa include networking, work-based experience and a reduction in administrative requirements.Originality/valueThe research's originality resides in the ability to predict the impact of drivers and barriers on skills development. This research sought to transform qualitative global and South African inputs into a consolidated, predictive systems-based model. The SD model can be adopted as an indicator of drivers and barriers focused towards the optimisation of skills development.

Estimating the value-at-risk of JSE indices and South African exchange rate with Generalized Pareto and stable distributions

South Africa’s economy has faced many downturns in the previous decade, and to curb the spread of the novel SARS-CoV-2, the lockdown brought South African financial markets to an abrupt halt. Therefore, the implementation of risk mitigation approaches is becoming a matter of urgency in volatile markets in these unprecedented times. In this study, a hybrid generalized autoregressive conditional heteroscedasticity (GARCH)-type model combined with heavy-tailed distributions, namely the Generalized Pareto Distribution (GPD) and the Nolan’s S0-parameterization stable distribution (SD), were fitted to the returns of three FTSE/JSE indices, namely All Share Index (ALSI), Banks Index and Mining Index, as well as the daily closing prices of the US dollar against the South African rand exchange rate (USD/ZAR exchange rate). VaR values were estimated and back-tested using the Kupiec likelihood ratio test. The results of this study show that for FTSE/JSE ALSI returns, the hybrid exponential GARCH (1,1) model with SD model (EGARCH(1,1)-SD) outperforms the GARCH-GPD model at the 2.5% VaR level. At VaR levels of 95% and 97.5%, the fitted GARCH (1,1)-SD model for FTSE/JSE Banks Index returns performs better than the GARCH (1,1)-GPD. The fitted GARCH (1,1)-SD model for FTSE/JSE Mining Index returns is better than the GARCH (1,1)-GPD at 5% and 97.5% VaR levels. Thus, this study suggests that the GARCH (1,1)-SD model is a good alternative to the VaR robust model for modeling financial returns. This study provides salient results for persons interested in reducing losses or obtaining a better understanding of the South African financial industry.

PENGEMBANGAN MEDIA PERMAINAN MONOPOLI PEMBELAJARAN MATEMATIKA

Berdasarkan hasil penelitian di SD Negeri Sukorejo 2 Lamongan pembelajaran pada mata pelajaran Matematika guru masih menggunakan metode ceramah dan tugas sehingga proses belajar mengajar di dalam kelas monoton. Pengembang membuat media alternatif yang dapat memberikan daya tarik sehingga dapat meningkatkan hasil belajar dan mempermudah guru dalam menyampaikan materi pembelajaran. Tujuan Penelitian pengembangan ini adalah untuk merancang dan menguji kelayakan media permainan monopoli pembelajaran untuk digunakan sebagai pendukung pembelajaran Matematika materi Unsur dan Sifat-sifat bangung Datar Sederhana bagi siswa kelas 3 SD. Model Pengembangan yang digunakan adalah model Borg and Gall, media monopoli pembelajaran ini diujicobakan kepada siswa kelas 3 SD Negeri Sukorejo 2 Lamongan mata pelajaran Matematika. Hasil yang diperoleh nilai uji kelayakan media permainan monopoli pembelajaran yang dikembangkan menurut ahli desain pembelajaran memperoleh hasil sebesar 86.53%, ahli media pembelajaran memperoleh hasil sebesar 93,33%, dan ahli materi memperoleh hasil sebesar 87,50%. Berdasarkan hasil uji kelayakan tersebut dapat diinterpretasikan bahwa media permainan monopoli pembelajaran yang dikembangkan menurut para ahli validasi termasuk pada kriteria sangat layak, serta bisa digunakan untuk mendukung pembelajaran Matematika materi Unsur dan Sifat-sifat Bangun Datar Sederhana bagi siswa kelas 3 SD Negeri Sukorejo 2 Lamongan

Enhancing sustainability of Indian PPP procurement process using system dynamics model

Purpose Increasingly adopted by various governments for infrastructure development, public-private partnerships (PPPs) have become a popular procurement delivery system, outperforming other systems. However, PPPs have been especially criticised due to the lack of sustainability aspect during the development and implementation of the projects. In India, similar critiques have been raised, as these qualities have inhibited the development of society and increased the time and cost overrun in the development of PPP projects. This paper, therefore, aims to address the sustainability issues in PPPs and systematically analyses from the perspective of the principles of sustainable development. Design/methodology/approach Based on literature review and focussed interviews with stakeholders in India, a qualitative system dynamics (SD) model using causal loop diagramming is developed to propose the inclusion of various strategies in the PPP procurement process, which can enhance the sustainability of the PPP process. Finally, the integration of these strategies in the current PPP procurement process has been highlighted in the form of the introduction of new mechanisms and policies and modification of the existing mechanism and procurement policies. Findings The paper first highlights key sustainability issues in the PPP procurement process and suggests 34 strategies to address the issues. The modelling approaches and the proposed strategies, along with their interrelationships, could help the PPP decision makers in implementing responsive policies in bringing sustainable development in the PPP procurement process. Research limitations/implications The SD model developed is based on limited data, primarily focussed on PPP procurement practices in the context of infrastructure development in India. Developing the model with the analysis of a wider range of data and constructing a customised model can take broader perspectives into account. Social implications Adoption of the identified strategies can facilitate the inclusion of sustainability practices in the development of infrastructure projects, which are even procured using private finance. Originality/value Studies on how to promote sustainable infrastructure development when procured through the PPP route are in the nascent stage. This study, therefore, extends the current body of knowledge on infrastructure projects implementation through PPPs from financial engineering and risk management to a sustainability perspective.