Research on Dynamic Measurement and Early Warning of Systemic Financial Risk in China Based on TVP-FAVAR and Deep Learning Model
Abstract
1. Introduction
2. Model Construction
2.1. Construction of the Systemic Financial Risk Index (SFRI)
2.1.1. State Space Model Setting
2.1.2. Parameter Evolution Process
2.1.3. Dynamic Weighting Process
2.2. Construction of the Network Public Opinion Index (NPOI)
2.2.1. Calculation of the Sentiment Score for a Single Comment
2.2.2. Standardization of Interactive Data
2.2.3. Interaction Weight Distribution
2.2.4. Comprehensive Calculation of the Public Opinion Index
2.3. Construction of a Systemic Financial Risk Early Warning System
3. Measuring China’s Systemic Financial Risk
3.1. Data Description
3.2. Time-Varying Analysis of Systemic Financial Risk
3.2.1. Trends in Systemic Financial Risks
3.2.2. Comparative Analysis of Systemic Financial Risks in Various Markets
3.2.3. Identification of Risk Status and Inflection Points
4. Research on Early Warning of Systemic Financial Risks in China
4.1. Network Public Opinion Index
4.2. Financial Risk Early Warning Indicators
4.3. Construction of Financial Risk Early Warning System
5. Conclusions and Suggestions
5.1. Research Conclusions
5.2. Policy Recommendations
Author Contributions
Funding
Data Availability Statement
Conflicts of Interest
References
- Yang, Z.; Chen, Y.; Lin, S. A Literature Review of Systemic Risk: Status, Development and Prospect. J. Financ. Res. 2022, 1, 185–206. [Google Scholar]
- Tobias, A.; Brunnermeier, M.K. CoVaR. Am. Econ. Rev. 2016, 106, 1705. [Google Scholar] [CrossRef]
- Ismal, R. Volatility of the Returns and Expected Losses of Islamic Bank Financing. Int. J. Islam. Middle East. Financ. Manag. 2010, 3, 267–279. [Google Scholar] [CrossRef]
- Yamai, Y.; Yoshiba, T. Value-at-Risk versus Expected Shortfall: A Practical Perspective. J. Bank. Financ. 2005, 29, 997–1015. [Google Scholar] [CrossRef]
- Wang, Z.; Liu, Y. Nonlinear Relationship between Physical Environment Risks, Investor Attentions, and Financial Systemic Risks: Evidence from MLSTM-CoVaR Networks. J. Environ. Manag. 2025, 374, 124065. [Google Scholar] [CrossRef] [PubMed]
- Acerbi, C.; Tasche, D. On the Coherence of Expected Shortfall. J. Bank. Financ. 2002, 26, 1487–1503. [Google Scholar] [CrossRef]
- Chen, A.; Nguyen, T. Risk Management under Weighted Limited Expected Loss. Quant. Financ. 2024, 24, 593–612. [Google Scholar] [CrossRef]
- Acharya, V.V.; Pedersen, L.H.; Philippon, T.; Richardson, M. Measuring Systemic Risk. Rev. Financ. Stud. 2017, 30, 2–47. [Google Scholar] [CrossRef]
- DeYoung, R.; Huang, M. The External Effects of Bank Executive Pay: Liquidity Creation and Systemic Risk. J. Financ. Intermediat. 2021, 47, 100920. [Google Scholar] [CrossRef]
- Dalla Valle, L.; Giudici, P. A Bayesian Approach to Estimate the Marginal Loss Distributions in Operational Risk Management. Comput. Stat. Data Anal. 2008, 52, 3107–3127. [Google Scholar] [CrossRef]
- Gadanecz, B.; Jayaram, K. Measures of Financial Stability-a Review. Irving Fish. Comm. Bull. 2008, 31, 365–383. [Google Scholar]
- Bisias, D.; Flood, M.; Lo, A.W.; Valavanis, S. A Survey of Systemic Risk Analytics. Annu. Rev. Financ. Econ. 2012, 4, 255–296. [Google Scholar] [CrossRef]
- Dumičić, M. Financial Stability Indicators—The Case of Croatia. J. Cent. Bank. Theory Pract. 2016, 5, 113–140. [Google Scholar] [CrossRef]
- Giglio, S.; Kelly, B.; Pruitt, S. Systemic Risk and the Macroeconomy: An Empirical Evaluation. J. Financ. Econ. 2016, 119, 457–471. [Google Scholar] [CrossRef]
- Tian, S.; Li, S.; Gu, Q. Measurement and Contagion Modelling of Systemic Risk in China’s Financial Sectors: Evidence for Functional Data Analysis and Complex Network. Int. Rev. Financ. Anal. 2023, 90, 102913. [Google Scholar] [CrossRef]
- Benoit, S.; Colliard, J.E.; Hurlin, C.; Pérignon, C. Where the Risks Lie: A Survey on Systemic Risk. Rev. Financ. 2017, 21, 109–152. [Google Scholar] [CrossRef]
- Yu, B.; Ouyang, H.; Guan, C.; Lin, B. Network Measurement and Influence Mechanism of Dynamic Risk Contagion among Global Stock Markets: Based on Time-Varying Spillover Index and Complex Network Method. N. Am. J. Econ. Financ. 2024, 74, 102258. [Google Scholar] [CrossRef]
- Wang, Y.; Zhao, X.; Shang, J. Dynamic Risk Spillover in Green Financial Markets: A Wavelet Frequency Analysis from China. Energy Econ. 2025, 143, 108301. [Google Scholar] [CrossRef]
- Huang, A.; Qiu, L.; Li, Z. Applying Deep Learning Method in TVP-VAR Model under Systematic Financial Risk Monitoring and Early Warning. J. Comput. Appl. Math. 2021, 382, 113065. [Google Scholar] [CrossRef]
- Li, H. Research on Financial Risk Early Warning System Model Based on Second-Order Blockchain Differential Equation. Intell. Decis. Technol. 2024, 18, 327–342. [Google Scholar] [CrossRef]
- Zhu, K.; Liu, D.; Wu, J.; Sun, L. The Research of the Regional Financial Risk Early-Warning Model Integrating the Regression of Lagging Factors. AASRI Procedia 2012, 1, 428–434. [Google Scholar] [CrossRef]
- Wei, L.; Yu, H.; Li, B. Energy Financial Risk Early Warning Model Based on Bayesian Network. Energy Rep. 2023, 9, 2300–2309. [Google Scholar] [CrossRef]
- Owoo, N.; Odei-Mensah, J. Hierarchical Clustering-Based Early Warning Model for Predicting Bank Failures: Insights from Ghana’s Financial Sector Reforms (2017–2019). Res. Int. Bus. Financ. 2025, 77, 102944. [Google Scholar] [CrossRef]
- Wang, Y.; Xi, W. Measurement and Early Warning of Systemic Financial Risk in China: Markov Switching Models. Comput. Econ. 2025, 65, 1–29. [Google Scholar] [CrossRef]
- Bu, Y.; Du, X.; Li, H.; Yu, X.; Wang, Y. Research on the FinTech Risk Early Warning Based on the MS-VAR Model: An Empirical Analysis in China. Glob. Financ. J. 2023, 58, 100898. [Google Scholar] [CrossRef]
- Zhang, W. Dynamic Monitoring of Financial Security Risks: A Novel China Financial Risk Index and an Early Warning System. Econ. Lett. 2024, 234, 111445. [Google Scholar] [CrossRef]
- Ristolainen, K. Predicting Banking Crises with Artificial Neural Networks: The Role of Nonlinearity and Heterogeneity. Scand. J. Econ. 2018, 120, 31–62. [Google Scholar] [CrossRef]
- Bluwstein, K.; Buckmann, M.; Joseph, A.; Kapadia, S.; Şimşek, Ö. Credit Growth, the Yield Curve and Financial Crisis Prediction: Evidence from a Machine Learning Approach. J. Int. Econ. 2023, 145, 103773. [Google Scholar] [CrossRef]
- Chen, P.; Ji, M. Deep Learning-Based Financial Risk Early Warning Model for Listed Companies: A Multi-Dimensional Analysis Approach. Expert Syst. Appl. 2025, 283, 127746. [Google Scholar] [CrossRef]
- Ouyang, Z.; Yang, X.; Lai, Y. Systemic Financial Risk Early Warning of Financial Market in China Using Attention-LSTM Model. N. Am. J. Econ. Financ. 2021, 56, 101383. [Google Scholar] [CrossRef]
- Tang, P.; Xu, W.; Wang, H. Network-Based Prediction of Financial Cross-Sector Risk Spillover in China: A Deep Learning Approach. N. Am. J. Econ. Financ. 2024, 72, 102151. [Google Scholar] [CrossRef]
- Vaswani, A.; Shazeer, N.; Parmar, N.; Uszkoreit, J.; Jones, L.; Gomez, A.N.; Kaiser, Ł.; Polosukhin, I. Attention Is All You Need. Adv. Neural Inf. Process. Syst. 2017, 30, 1–8. [Google Scholar]
- Bernanke, B.S.; Boivin, J.; Eliasz, P. Measuring the Effects of Monetary Policy: A Factor-Augmented Vector Autoregressive (FAVAR) Approach. Q. J. Econ. 2005, 120, 387–422. [Google Scholar]
- Agrrawal, P.; Clark, J.M. A multivariate liquidity score and ranking device for ETFs. In Proceedings of the Academy of Financial Services Annual Conference, Boca Raton, FL, USA, 2009; Available online: https://www.researchgate.net/publication/257890697_A_Multivariate_Liquidity_Score_and_Ranking_Device_for_ETFs (accessed on 2 February 2025).
- Waggle, D.; Agrrawal, P.; Johnson, D. Interaction between Value Line’s timeliness and safety ranks. J. Investig. 2001, 10, 53–62. [Google Scholar] [CrossRef]
- Valadkhani, A. Inflation-driven instability in US sectoral betas. J. Asset Manag. 2025, 1–8. [Google Scholar] [CrossRef]
- Huang, W.; Nakamori, Y.; Wang, S.Y. Forecasting stock market movement direction with support vector machine. Comput. Oper. Res. 2005, 32, 2513–2522. [Google Scholar] [CrossRef]
- Hochreiter, S.; Schmidhuber, J. Long short-term memory. Neural Comput. 1997, 9, 1735–1780. [Google Scholar] [CrossRef]
- Pfreundschuh, S.; Eriksson, P.; Duncan, D.; Rydberg, B.; Håkansson, N.; Thoss, A. A neural network approach to estimating a posteriori distributions of Bayesian retrieval problems. Atmos. Meas. Technol. 2018, 11, 4627–4643. [Google Scholar] [CrossRef]
- Wang, J.; Xu, Y.; Liu, L.; Wu, W.; Shen, C.; Huang, H.; Zhen, Z.; Meng, J.; Li, C.; Qu, Z.; et al. Comparison of LASSO and random forest models for predicting the risk of premature coronary artery disease. BMC Med. Inform. Decis. Mak. 2023, 23, 297. [Google Scholar] [CrossRef]
- Coelho e Silva, L.; Fonseca, G.F.; Castro, P.A.L. Transformers and attention-based networks in quantitative trading: A comprehensive survey. In Proceedings of the 5th ACM International Conference on AI in Finance, New York, NY, USA, 14–17 November 2024; pp. 822–830. [Google Scholar]
- Chefer, H.; Gur, S.; Wolf, L. Transformer interpretability beyond attention visualization. In Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition, Nashville, TN, USA, 20–25 June 2021; pp. 782–791. [Google Scholar]
- Kim, Y.S.; Kwon, O. Central Bank Digital Currency and Financial Stability. Bank of Korea WP 2019-6. Available online: https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3330914 (accessed on 8 February 2019).
Indicator | Equation | Indicator | Equation |
---|---|---|---|
MAE | IA | ||
RMSE | VAR | ||
TIC |
Dimensions | Indicator | Indicator Name | Abbr. | Meaning and Nature of Indicators |
---|---|---|---|---|
Financial institutions | Adequate capital | Financial institutions’ loan-to-deposit ratio | X1 | The percentage of total loans to total deposits. When the growth rate of loans of financial institutions exceeds the growth rate of deposits, the risk increases (+). |
Capital adequacy ratio | X2 | The core indicator for measuring the capital buffer capacity of banks. The higher the value, the stronger the risk resistance capacity (−). | ||
Capital quality | Non-performing loan ratio | X3 | Directly reflects the deterioration of bank asset quality and is positively correlated with credit risk (+). | |
Liquidity risk | Ratio of medium- and long-term loans to total loans | X4 | Reflects medium- and long-term loans as a proportion of total loans. If the proportion of medium- and long-term loans is too high, this will reduce the liquidity of bank assets (+). | |
Money creation | M2 year-on-year growth rate/GDP year-on-year growth rate | X5 | Reflects the efficiency of economic operation. If the growth rate of M2 is greater than the growth rate of GDP, this reflects that the amount of money invested is large, but the GDP output is small, which may cause asset bubbles or inflationary pressure (+). | |
Stock market | Market prosperity | Year-on-year growth rate of the total market value of listed companies—excluding finance | X6 | Reflects changes in capital market valuations of the real economy sector (+). |
Shanghai Composite Index—excluding finance | X7 | Represents the comprehensive trend of non-financial enterprise stock prices (+). | ||
CSI 300 Index—excluding finance | X8 | Reflects the price fluctuations of large-cap blue-chip stocks (+). | ||
Market volatility risk | Stock market volatility | X9 | The return rate of the CSI 300 Index (excluding finance) is calculated using the GARCH model to measure market uncertainty (+). | |
Bond market | Sovereign credit risk | Sovereign bond spreads | X10 | The 10-year Chinese government bond yield minus the 10-year US government bond yield is an indicator of a debt crisis. The widening of the interest rate gap between China and foreign countries reflects an increase in the sovereign credit risk premium (+). |
Liquidity risk | Yield spread between 5-year and 3-month treasury bonds | X11 | Reflects the interest rate differential between long-term assets and short-term assets. A narrowing interest rate differential indicates expectations of an economic recession (−). | |
Market volatility risk | Bond market volatility | X12 | Calculated based on the 10-year Chinese government bond yield using the GARCH model, this reflects the interest rate risk (+). | |
Money market | Liquidity risk | SHIBOR term spread (7 days–1 year) | X13 | An indicator of liquidity pressure in the money market. When short-term funding demand increases, the interest rate spread widens. It is highly correlated with the interbank funding pressure index (+). |
Domestic and foreign interest rate differential (SHIBOR 3 months–LIBOR 3 months) | X14 | A cross-border carry trade attractiveness indicator: a widening interest rate spread attracts hot money inflows, thereby easing liquidity pressure (−). | ||
Interbank pledged repo term spread (7 days–1 year) | X15 | The term premium in the pledged repo market reflects the short-term liquidity preference of financial institutions (+). | ||
Market volatility risk | Currency market volatility | X16 | The GARCH model is used to calculate the SHIBOR 7-day interest rate, reflecting the liquidity risk premium of the interbank market (+). | |
Foreign exchange market | Foreign exchange reserves | Month-on-month growth rate of foreign exchange reserves | X17 | The core indicator for measuring the buffer capacity of cross-border capital flows. The decline in growth rate indicates external repayment pressure (−). |
Effective exchange rate of local currency | RMB real effective exchange rate | X18 | The trade-weighted and inflation-adjusted composite exchange rate index continues to depreciate, reflecting weakening confidence in the currency (−). | |
Local currency exchange rate volatility | RMB exchange rate volatility | X19 | The nominal effective exchange rate index yield is calculated using the GARCH model, and it increases significantly when market uncertainty increases (+). | |
Real estate market | Economic prosperity | Cumulative year-on-year growth rate of completed real estate development investment | X20 | Reflecting developers’ expectations of the market outlook, a slowdown in growth indicates industry contraction (−). |
Cumulative year-on-year growth rate of commercial housing sales | X21 | A demand prosperity index. Continued negative growth indicates that the market has entered a downward cycle (−). | ||
Real estate climate index | X22 | If the composite index of the real estate industry’s overall prosperity continues to decline, it reflects systemic risks (−). | ||
Market volatility | Real estate market volatility | X23 | Calculated using the real estate climate index yield based on the GARCH model. This reflects industry risk fluctuations (+). | |
Government departments | Economic growth | GDP growth rate | X24 | The core observation indicator of macroeconomic fundamentals. The lower the overall macroeconomic growth rate, the higher the risk (−). |
Investment | China’s cumulative year-on-year growth rate of fixed asset investment completion | X25 | A capital formation activity index. The higher the investment, the more prosperous the economy (−). | |
Inflation | CPI month-on-month | X26 | A price stability monitoring indicator, reflecting the inflation level. Generally speaking, a high CPI is one of the manifestations of a crisis (+). |
Variables | Sample Size | Mean | Min. | Max. |
---|---|---|---|---|
X1 | 180 | −1.11 × 10−9 | −1.352 | 1.627 |
X2 | 180 | 5.56 × 10−10 | −1.791 | 2.122 |
X3 | 180 | 5.56 × 10−9 | −1.706 | 1.353 |
X4 | 180 | −8.33 × 10−9 | −1.404 | 1.419 |
X5 | 180 | 3.33 × 10−9 | −5.106 | 4.212 |
X6 | 180 | −1.89 × 10−8 | −2.937 | 2.873 |
X7 | 180 | 4.44 × 10−9 | −1.755 | 2.396 |
X8 | 180 | −3.33 × 10−9 | −1.884 | 3.117 |
X9 | 180 | 1.39 × 10−8 | −1.630 | 1.770 |
X10 | 180 | 8.89 × 10−9 | −2.713 | 1.407 |
X11 | 180 | 6.67 × 10−9 | −2.450 | 3.049 |
X12 | 180 | −1.00 × 10−8 | −1.385 | 3.416 |
X13 | 180 | 3.33 × 10−9 | −2.087 | 4.630 |
X14 | 180 | −1.28 × 10−8 | −1.520 | 2.146 |
X15 | 180 | 5.56 × 10−9 | −5.825 | 2.412 |
X16 | 180 | −8.89 × 10−9 | −0.976 | 3.280 |
X17 | 180 | −3.89 × 10−9 | −2.941 | 2.458 |
X18 | 180 | −1.22 × 10−8 | −1.318 | 1.897 |
X19 | 180 | −6.67 × 10−9 | −0.822 | 4.428 |
X20 | 180 | 5.56 × 10−9 | −3.719 | 7.889 |
X21 | 180 | −2.78 × 10−9 | −3.955 | 5.586 |
X22 | 180 | −2.11 × 10−8 | −1.988 | 1.717 |
X23 | 180 | −1.17 × 10−8 | −0.357 | 6.276 |
X24 | 180 | −6.11 × 10−9 | −3.301 | 3.924 |
X25 | 180 | 3.33 × 10−9 | −4.228 | 7.232 |
X26 | 180 | 4.44 × 10−9 | −1.816 | 2.923 |
Financial institutions | Stock market | Bond market | Money market |
0.348 | 0.248 | 0.634 | 0.522 |
Foreign exchange market | Real estate market | Government departments | |
0.251 | 0.156 | 0.285 |
Regime | Transition Probability (Regime 1) | Transition Probability (Regime 2) | State Probability | Average Duration | AR (1) 1 | Sigma |
---|---|---|---|---|---|---|
Regime 1 | 0.9231 | 0.0769 | 62.6% | 12.99 | 0.9601 *** (146.756) | 0.0011 |
Regime 2 | 0.1213 | 0.8787 | 36.9% | 8.22 | 0.9601 *** (146.756) | 0.0102 |
Indicators | Meaning |
---|---|
SFRI | A comprehensive early-warning indicator based on a dynamic systemic risk model |
NPOI | The network public opinion index monitors risk sentiment on social media |
R007 | The 7-day interbank pledged repo rate, reflecting real-time liquidity stress in the money market |
PPI | Producer Price Index year-on-year, reflecting inflationary/deflationary pressures in the industrial sector |
INV | Finished goods inventory of industrial enterprises above a designated size, indicating demand contraction risks if persistently high |
AR | Accounts receivable of industrial enterprises above a designated size; excessive YoY growth signals credit risk |
MAR | An indicator of leveraged capital market activity, reflecting stock market volatility |
Name | Value | Name | Value | |
---|---|---|---|---|
Parameters | Time Step | 6 | Loss Function | Mean Squared Error |
Prediction Step | 1 | Learning Rate Scheduler | Cosine Annealing | |
Iterations | 200 | Batch Size | 32 | |
Optimizer | Adam | Model Architecture Parameters | Model Dimension = 64 Number of Attention Heads = 4 Encoder Layers = 2 | |
Dropout | 0.05 | Test Set Ratio | 0.2 | |
Structure | Input → Linear Projection Layer → Positional Encoding → Transformer Encoder Layers → Fully Connected Output |
Variables | BDS Statistic 1 |
---|---|
SFRI | 2.431 *** |
NPOI | 3.872 *** |
R007 | 4.115 *** |
PPI | 3.958 *** |
INV | 4.226 *** |
AR | 3.205 *** |
MAR | 4.178 *** |
Transmission Direction | R007 1 | PPI | INV | AR | MAR | NPOI |
---|---|---|---|---|---|---|
SFRI ← X | 0.593 *** | 0.487 *** | 0.602 *** | 0.620 *** | 0.569 *** | 0.552 *** |
X ← SFRI | 0.399 ** | 0.573 *** | 0.473 *** | 0.355 * | 0.540 *** | 0.582 *** |
p-value | 0.001/0.013 | 0.001/0.001 | 0.001/0.001 | 0.001/0.099 | 0.001/0.001 | 0.001/0.001 |
Confidence interval (95%) | [0.2088, 0.3922]/[0.2088, 0.3894] | [0.2045, 0.3824]/[0.2131, 0.3879] | [0.2088, 0.3851]/[0.2131, 0.4007] | [0.2103, 0.3851]/[0.2131, 0.3866] | [0.2131, 0.3922]/[0.2088, 0.3980] | [0.2174, 0.3894]/[0.2174, 0.3894] |
Standard error (SFRI ← X) | 0.0456 | 0.0458 | 0.0459 | 0.0457 | 0.0450 | 0.0449 |
Standard error (X ← SFRI) | 0.0458 | 0.0464 | 0.0467 | 0.0437 | 0.0474 | 0.0450 |
Training Set | Testing Set | |||||||
---|---|---|---|---|---|---|---|---|
Transformer | BP | RF | SVM | Transformer | BP | RF | SVM | |
RMSE | 0.0714 | 0.1936 | 0.0937 | 0.1351 | 0.1088 | 0.1985 | 0.2034 | 0.1772 |
MAE | 0.0612 | 0.1599 | 0.0776 | 0.1208 | 0.0831 | 0.1555 | 0.1599 | 0.1499 |
IA | 0.9281 | 0.6646 | 0.8638 | 0.6191 | 0.8553 | 0.7843 | 0.5909 | 0.6790 |
TIC | 0.1694 | 0.3419 | 0.2222 | 0.3265 | 0.3468 | 0.4310 | 0.6495 | 0.5497 |
VAR | 0.0033 | 0.0312 | 0.0077 | 0.0175 | 0.0122 | 0.0404 | 0.0207 | 0.0151 |
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content. |
© 2025 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).
Share and Cite
Yang, H.; Liu, L.; Cui, J.; Wu, W.; Gao, Y. Research on Dynamic Measurement and Early Warning of Systemic Financial Risk in China Based on TVP-FAVAR and Deep Learning Model. Systems 2025, 13, 720. https://doi.org/10.3390/systems13080720
Yang H, Liu L, Cui J, Wu W, Gao Y. Research on Dynamic Measurement and Early Warning of Systemic Financial Risk in China Based on TVP-FAVAR and Deep Learning Model. Systems. 2025; 13(8):720. https://doi.org/10.3390/systems13080720
Chicago/Turabian StyleYang, Hufang, Luyi Liu, Jieyang Cui, Wenbin Wu, and Yuyang Gao. 2025. "Research on Dynamic Measurement and Early Warning of Systemic Financial Risk in China Based on TVP-FAVAR and Deep Learning Model" Systems 13, no. 8: 720. https://doi.org/10.3390/systems13080720
APA StyleYang, H., Liu, L., Cui, J., Wu, W., & Gao, Y. (2025). Research on Dynamic Measurement and Early Warning of Systemic Financial Risk in China Based on TVP-FAVAR and Deep Learning Model. Systems, 13(8), 720. https://doi.org/10.3390/systems13080720