3.1. Descriptive Analysis
The analysis of the scientific publications in
Mathematics that address the studied topics reveals a preponderance of concerns for environmental (738), followed by economic (472), and then ecological (47) issues. Regarding the type of document, most are articles (1228), noting the existence of a number of 25 review articles and 4 editorial materials. On the structure of the topic, they are presented in
Table 1.
The most relevant papers concerning economic issues are those of Santos-Jaen et al. (2022), Owolabi et al. (2022), Shu et al. (2022), Shinkevich et al. (2022), Ayuda et al. (2022), Guo et al. (2022), Balash et al. (2021), Kovacs et al. (2021), Huang et al. (2021), and Cai et al. (2021), these addressing various topics (performance, industrial zones, export, business market profitability, economic risk, patent commercialization performance, and finance), in specific contexts (hotel, chemical industries, agriculture, COVID-19, etc.). Papers such as those of Arav et al. (2022), Ramirez-Carrasco et al. (2022), Trivedi et al. (2022), Qian and Cui (2022), Khan et al. (2022), Liu et al. (2022), Shinkevich et al. (2022), Gocheva-Ilieva et al. (2022), Riou et al. (2022), and Ainapure et al. (2022) are relevant in terms of environmental issues. Targeting ecological issues, the most relevant articles are those of Shinkevich et al. (2022), Carletti and Banerjee (2019), Gutierrez et al. (2022), Vakulenko and Grigoriev (2021), Uso-Domenech et al. (2019), Mondal et al. (2022), Oborny (2018), Yilanci et al. (2022), Abbas and Naji (2022), and Dyvak et al. (2020).
Research productivity, estimated through the number of scientific publications in
Mathematics,
per year per topic, is shown in
Table 2. The trend line has been plotted in
Figure 1, allowing the referral of the issues of interest and providing useful results for both researchers and decision-makers. It can be observed that there is an upward trend in publications, with most papers published in 2022. While the environmental topic is a growing concern in the authors’ approaches, the economic topic has decreased as a research objective. The ecological topic is kept at a low level in the research priorities.
Author productivity, calculated as number of articles per author, is relatively similar, with a higher value in the economic concerns: a total of 1467 authors presented a 0.3217 average productivity, contributing 472 scientific publications in the economic field over the period under study; 2495 authors conducted 738 studies concerning environmental topics, presenting an average productivity of 0.2958; 156 authors wrote 47 articles on ecological topics, with an average productivity of 0.3013. The authors with the most scientific publications on these topics in
Mathematics, are presented in
Table 3. Wang Chia-Nan (n = 20) and Sarkar Biswajit (n = 19) are the most prolific authors, addressing both economic and environmental issues. The authors’ focus is on the use of mathematical tools for solving economic and environmental problems, providing relevant benchmarks for decision-makers in the matter. The development of approaches by publishing several articles in the field ensures a superior quality of the research and a greater pertinence of the results.
Regarding economic topics, Sarkar’s main concerns have targeted the efficiency of production processes. On this subject, a smart production process where the autonomation policy allows the system to manufacture a defect-free product was developed, determining the maximum profit and the optimal values for buffer inventory, production rate, selling price, and investment for autonomation [
26,
27]. Furthermore, a single-stage manufacturing method to make a perfect production system without defective items was formulated [
28]. With reference to the perishable products with a maximum life span and price-dependent demand and trade credit, in order to maximize the vendor’s net profit, the optimum investment under preservation, sales price, and cycle time were calculated using the classical optimization algorithm [
29]. Furthermore, a multi-product production process was introduced, based on the advertising- and price-dependent demands of products, in order to reduce the failure rate of the production system under the optimum energy consumption [
30]. An important production factor is human capital. Sarkar identified worker’s cost of stress by developing a link between economic efficiency and working conditions enhancement, using a sequential quadratic programming to optimize the given nonlinear model for production planning [
31]. Addressing the issue of credit policies under an imperfect quality environment, Sarkar and co-authors proposed a supply chain with customer-based two-level credit policies, demonstrating the benefit of shorter contracts, particularly with new retailers, over the expected total profit per unit time [
32].
Correlating the economic issue with that of environmental protection, Sarkar analyzed the effects of preservation technology investment on waste generation in a two-echelon supply chain model. A model is proposed to optimize the preservation investment, the number of shipments, and the shipment quantity so that the total cost per unit time of the supply chain is minimized. At the same time, by increasing the lot size, the order cost is also reduced. Complementary to economic benefits, preservation leads to a reduction of solid waste from damaged products, with effects on environmental protection [
33]. Furthermore, to address the negative environmental effects of corporate activities, joint inventory and pricing decisions were studied in a multi-echelon CLSC model that considered online to offline (O2O) business strategy. For an imperfect production process, the highest profit is generated when the defect rate follows a uniform distribution [
34]. Furthermore, an imperfect manufacturing process produces defective products at an uncertain rate and is reworked to transform them into perfect quality products and reduce losses. Using the interactive Weighted Fuzzy Goal Programming (WFGP) approach can determine a sustainable lot size, reducing the conflict between economic performance and environmental protection [
35].
The studies carried out by Wang Chia-Nan focus on economic and environmental issues. Using DEA Malmquist model, an analysis of the organizational performance measurement of the automakers was conducted, considering the relevant technical efficiency, technological progress, total factor productivity of global automobile manufacturers, and financial indicators (total assets, shareholder’s equity, cost of revenue, operating expenses, revenue, and net income) [
36]. He assessed the operational efficiency of airport runway configurations considering specific input factors (number of runways, dimension of runways, and airport area) and output factors (annual number of flights and annual number of passengers), using the data envelopment analysis models Charnes, Cooper, and Rhodes (CCR), Banker, Charnes, and Cooper (BCC), Slacks-Based Measure (SBM), and Epsilon-Based Measure (EBM) [
37]. Furthermore, he developed a two-stage data envelopment analysis model for measuring the performance efficiency, forecasting, and improving future performance for port industry, indicating that the determinants of growing productivity are the technical efficiency change indexes [
38]. The performance of the bank sector was analyzed by a dynamic Slacks-Based Measure model in data envelopment analysis, considering assets, capitalization, and liabilities as inputs, revenue as output, and net interest income as a good link [
39]. Regarding the supply chain network design problem, he developed a multi-objective mathematical model to design four-echelon intermodal multi-product perishable supply chain configuration, defining the optimization objective functions as minimizing costs, delivery time, emissions, and the supply-demand mismatch in time. The decisions are approached from a strategic perspective (the location, size of facilities, product flows, and workforce level), and from a tactical perspective (harvest time, delivery time, the delivery route, and mode of transport) [
40]. Exploiting a hybrid multi-criteria method, which is fuzzy analytic hierarchy process (FAHP) and fuzzy vlsekriterijumska optimizacija i kompromisno resenje (FVIKOR), he proposed a model for evaluating and selecting the most efficient third-party logistics [
41].
In the context of the industrial and manufacturing sector development, which involves high energy consumption, Wang Chia-Nan presented a multi-criterion decision-making model (MCDM) that implemented the grey analytic hierarchy process (G-AHP) method and the weighted aggregates sum product assessment (WASPAS) method for the selection of optimal renewable energy sources for the energy sector in Vietnam [
42]. Considering the geographical conditions and that wind energy is a viable option, the author studying the selection of wind turbine suppliers as a complex and multi-criteria decision-making process in uncertain environmental conditions with incidents on the cost reduction of equipment safety and delivery to term, is proposing a fuzzy MCDM model [
43]. Under the constraints imposed by sustainable development, companies must focus on issues related to the reduction of CO
2 and toxic emissions, energy use and efficiency, waste generation, and worker health and safety. In this context, Wang Chia-Nan proposed a supplier selection model based on a hybrid multi-criterion decision-making model (MCDM) using a fuzzy analytic hierarchy process (FAHP) and green data envelopment analysis (GDEA) [
44]. Furthermore, a stochastic multi-objective optimization model is proposed that aims both at production efficiency under uncertain conditions through the objective function that optimizes the amount of pending orders, machine operation time, and customer satisfaction, as well as ensuring sustainable development, through the correlation of three functions related to optimizing profits, emissions, and changing jobs [
45].
The main concern of Tarasov VE is memory in economics, using fractional calculus, which is a theory of integrals, derivatives, sums, and differences of non-integer orders, to cure amnesia in economics [
46]. Reviewing the problems and difficulties arising in the construction of fractional-dynamic analogs of standard models by using fractional calculus, Tarasov analyzed the effects of memory and non-locality, distributed lag, and scaling, and formulating rules (principles) for constructing fractional generalizations of standard models, which were described by differential equations of integer order, highlighting the importance of the derivability principle, the multiplicity principle, the solvability and correspondence principles, and the interpretability principle [
47]. Generalizing the standard continuous-time model of Solow and Lucas, he proposed two non-linear models to study the influence of memory effects on the rate of economic growth when other parameters of the model are unchanged [
48]. Furthermore, by a generalization of the standard Keynesian macroeconomic model, a mathematical model of economic growth with fading memory and continuous distribution of delay time was proposed [
49]. In another study, he analyzed depreciation of a non-exponential type and simultaneously considered memory effects in economics by using the Prabhakar fractional derivatives and integrals [
50].
Ref. [
51] performed an analytical study of a system with multiple time scales to reveal a sequence of bifurcations that are responsible for the change in the system dynamics from a simple steady state and/or a limit cycle to canards and relaxation oscillations, considering it a more realistic description of ecological dynamics. Furthermore, given that demographic noise is simply the biological or ecological counterpart of intrinsic noise in genetic regulation, [
52] proposed a technique to model and simulate demographic noise going backward from a deterministic continuous differential system to its underlying discrete stochastic process, based on the framework of chemical kinetics. Petrovskii Sergei and co-authors studied the movement pattern in the context of trapping, based on the Brownian motion and Levy walks, showing that this controversy can be more superficial than real if the problem is considered in the context of traps and that the whole “Levy or diffusion” debate is rather meaningless unless placed in a specific ecological context [
53].
The first ten meso-topics with the most citations are presented in
Table 4. The artificial intelligence and machine learning topic is the most cited meso-topic, highlighting its relevance in the study of economic, environmental, and ecological phenomena to identify real-world problems, measure and improve predictive performance, devise innovative solutions, and refine strategies through algorithmic decision-making. Furthermore, considering the approach to multidimensional problems, the numerical methods topic is one of the most cited meso-topics in this research context. Understanding the general trends and patterns requires the use of statistical methods. Regarding the content of the issue, the most cited meso-topics are economics, supply chain logistics, management, power systems electric vehicles and security systems.
The countries that have devoted most effort to publish in
Mathematics are the People’s Republic of China, followed by Spain, Taiwan, Russia and South Korea (
Table 5). China’s leading position in scientific production is not surprising. Previous studies have already shown that scientific production in China is growing impressively, and in 2018 the country was the largest producer of SCI-indexed original research articles [
54]. However, what is particularly notable is the great effort made by Spain in this area.
The first five most cited articles in
Mathematics, are presented by topic in
Table 6,
Table 7 and
Table 8.
3.2. Term Co-occurrence
In order to identify the frequently used and highly connected terms in Mathematics related to these three fields of research, we carried out a term co-occurrence analysis.
Economic*
Of the 12540 terms, 236 meet the threshold, and the first 10 most relevant are presented in
Table 9.
It was found that the predominant use of mathematical tools in optimization processes was in areas with increased volatility, such as the stock market, in order to rigorously substantiate the decisions of investors and policymakers. Data envelopment analysis (DEA) represents the most relevant method in operations research and economics, allowing the identification of the best-practice frontier.
We used co-occurrence networks to extract and visualize the relationships between terms in
Mathematics scientific publications (
Figure 2).
Four clusters were identified: red (country, market, period, index, dynamic, sector, risk, uncertainty, gdp, investor, volatility, and stock market), green (problem, solution, algorithm, cost, function, parameter, management, state, optimization, control, and energy), blue (economic, population, tool, prediction, technology, and sustainability), and yellow (efficiency, evaluation, assessment, decision making, case study, and alternative).
Environment*
Of the 19,717 terms, 344 meet the threshold, and the first 10 most relevant are presented in
Table 10.
The terms with the highest co-occurrence reveal the importance of mathematics, technology, and education in solving environmental problems. The convolutional neural network (CNN) is the learning algorithm used in the environmental issues’ recognition, classification, segmentation, and identification of specific patterns.
In the co-occurrence network (
Figure 3), four clusters were identified: red (algorithm, network, accuracy, field, state, feature, and limitation), green (decision, evaluation, set, criterium, property, case study, and decision making), blue (impact, cost, product, management, industry, emission, and supply chain), and yellow (learning, knowledge, student, and education).
Ecologic*
Of the 1643 terms, 3 meet the threshold (
Table 11).
With the exception of economic, the first terms according to relevance are not specific to the topic, which reveals the existence of a diversity of addressed issues without explicitly identifying a focus on specific themes.
3.3. Keywords Co-occurrence
To assess the presence, frequency of occurrence, and proximity of keywords across the papers in the fields of economy, environment, and ecology, in Mathematics, a co-occurrence analysis was conducted. Understanding the knowledge structure of these scientific fields required the achievement of a keyword co-occurrence network, which ensured the examination of the links between keywords, the mapping of the dynamics of the subject, and the identification of the core research topics.
Economic*
Considering the minimum number of occurrences for a keyword 5 among the 3302 keywords, 109 met the threshold, and the first 10 keywords with the greatest total link strength of the co-occurrence are presented in
Table 12.
Based on the pattern of co-occurrence of pairs of keywords, six clusters were identified, the most relevant keywords being (
Figure 4) red (optimization, system, impact, dynamics, stability, prediction, innovation, economic-growth, regression, algorithm, and entropy), green (policy, quality, demand, supply chain, eoq model, and time), blue (machine learning, design, economics, finance, big data, data science, hybrid, network), yellow (performance, efficiency, growth, models, models, forecasting, data envelopment analysis, behavior, and dea), lilac (risk, cointegration, volatility, investment, economic policy uncertainty, sustainable development, CO
2 emissions, return, and liquidity), and turquoise (model, management, selection, sustainability, framework, decision making, ahp, mcdm, performance evaluation).
Environment*
Of the 4920 keywords, 135 met the threshold for a minimum number of occurrences for a keyword 5. The first ten keywords with the greatest total strength of the co-occurrence links with other keywords are presented in
Table 13.
The most relevant keywords in the network, structured in seven clusters (
Figure 5), are optimization, uncertainty, system, machine learning, prediction, neural network, classification, regression, convergence, and decomposition (red); system, performance, model, efficiency, risk, and network (green); decision making, selection, aggregation-operators, framework, topsis, and entropy (blue); dynamics, design, stability, environment, and simulation (yellow); model, management, impact, behavior, innovation, competitiveness, and determinants (lilac); quality, strategies, supply chain, indicators, eoq model, logistics, and internet (turquoise); and education, students, higher-education, augmented reality, and mathematics (orange). Model, performance, and management represent the common keywords in the economic and environmental topics.
Ecologic*
Of the 431 keywords, 5 recorded a minimum of 3 occurrences (
Table 14). Selection and optimization are the common keywords for environmental and ecological issues. Three clusters were delimited in the network: bifurcation and stability; multicriteria decision making and selection; and optimization.
3.6. Co-citation
The structure of scientific knowledge is investigated using a co-citation analysis. The co-citation network explored the links between citations in order to detect the relationships between authors and construct a knowledge structure.
Economic*
Of the 17424 authors, 21 met the threshold for a minimum number of 20 citations, and the first 10 authors with the greatest total strength of the co-citation links with other authors were selected (
Table 27).
The visualization of the scientific publications based on the authors’ co-citation patterns, considering the largest set of connected items in the network, highlighted three clusters (
Figure 16): Charnes A, Diebold FX., Fama EF. Hair JF., Saaty TL., Shaheen AM., Wang CN., Wang Y., Zadeh LA., and Zavadskas E.; Granger CWJ., Machado JAT., Tarasov VE., Tarasova VE., and Tejado I.; Cardenas-Barron LE., Chung KJ., Sarkar B., and Taleizadeh AA., with relevant nodes. An intellectual structure of specific disciplines is created.
Environment*
Of the 24,507 authors, 40 meet the threshold for a minimum number of 20 citations. The first ten authors with the greatest total strength of the co-citation links with other authors are presented in
Table 28.
The largest set of connected items in the network consists of 38 items, in 5 clusters (
Figure 17): red (Hair JF., Li J., Li X., Liu Y., Mirjalili S., Sarkar B., Taleizadeh AA., Wang J., Wang L., Wang Y., Yang XS., Zhang J., and Zhang Y.), green (Buyukozkan G., Govindan K., Keshavaz Ghorabaee M., Liu HC., Rezaei J., Saaty TL., Salabun W., Wang CN., and Zavadskas EK.), blue (Garg H., Li L., Liu PD., Peng XD., Wei GW., Xu ZS., and Yager RR.), yellow (Akram M., Atanassov KT., Zadeh LA., and Zimmermann HJ.) and lilac (Pramanik S., Smarandache F., Wang H., and Ye J.).
Ecologic*
There is no co-citation between the authors of the articles on ecological issues.