Abstract
Quality Infrastructure serves as a crucial foundation for the high-quality development of the equipment manufacturing industry, encompassing numerous factors and constituting a complex systems engineering project. Addressing the current challenges of incomplete elements and insufficient integration in the industry’s quality infrastructure construction, this paper focuses on the construction needs of the equipment manufacturing industry, it clarifies the constituent elements of the industry’s quality infrastructure and constructs an overall framework for capability building based on the “Regulatory System–Management System–Technical System.” To tackle the problems of lacking evaluation indicators and strong subjectivity in evaluating quality infrastructure capability, a quality infrastructure capability evaluation model and indicator system for the equipment manufacturing industry are proposed from the dimensions of industry influence, institutional construction, resource supply, and equipment quality assurance. Based on fuzzy theory and the VIKOR method, a comprehensive evaluation method for quality infrastructure capability in the equipment manufacturing industry is proposed. Ultimately, an application in a specific aviation equipment manufacturing sector is undertaken to validate the effectiveness of the proposed method.
Keywords
Highlights
Build QI framework across regulatory, management, technical systems.
Propose hierarchical model with 4-14-26 indicators.
Integrate fuzzy theory and VIKOR for objective evaluation.
Aviation case (2020–2024): rising index; resources, institutions critical.
Introduction
The equipment manufacturing industry is a vital reflection of economic and social development, national security, and international competitiveness. 1 The level of its quality infrastructure (QI) construction is crucial for ensuring the overall quality equipment. Currently, the industry faces challenges such as an unstable foundation for quality development and difficulties in guaranteeing overall equipment quality, highlighting inadequacies in the construction capability and effectiveness of the industry’s quality infrastructure.2,3 Quality Infrastructure (QI), first proposed by the German Federal Institute of Physics (PTB) in 2002, consists of three elements: metrology, standards, and conformity assessment. It was formally introduced to the public by the UN Trade and Development (UNCTAD) and the World Trade Organization (WTO) in 2005.4,5 In 2017, relevant international organizations jointly recognized QI as “a system comprising public and private institutions, as well as the policies, legal, regulatory frameworks, and practices needed to support and enhance the quality, safety, and health environment of goods, services, and processes.” Its essence is a framework system and practice of institutions, laws, policies, regulations, and practical activities, playing a fundamental and supportive role in industry development and equipment quality improvement. 5
Current research on quality infrastructure capability building and evaluation primarily focuses on the national or regional level. For example: The US government initiated National Quality Infrastructure (NQI) construction as early as the 1980s, issuing a series of policy measures to provide various technical consulting services for enterprise development. 2 The Gesellschaft für Internationale Zusammenarb (GIZ) actively promotes the implementation of NQI. Based on an assessment of Ethiopia’s quality infrastructure construction level, GIZ guided Ethiopia to invest 11.7 million euros over three years in quality infrastructure construction, achieving significant results. 4 Theoretical methods related to quality infrastructure are gradually expanding into industries such as trade, health, and safety.6,7 In terms of evaluation indicators, there is currently a lack of an authoritative international indicator system for measuring the comprehensive level of QI. Various experts, scholars, and research institutions have conducted exploratory work. For instance, the United Nations Industrial Development Organization (UNIDO) developed the Trade Standards Compliance Index (TSSCI), which includes 10 sub-indices and 73 indicators covering standardization, metrology, certification, accreditation, inspection, testing, quality management, technical regulations, etc. 8 Hüseyin Uğur proposed a comprehensive evaluation method for assessing the social and economic impact of NQI, collecting basic data from 15 European and Central Asian countries for evaluation. 9 Jiang et al. 10 analyzed NQI evaluation indicators from capability and effectiveness perspectives, combining them to form an NQI development level index, which mirrors the potential service capability and direct service effectiveness at the national level. In terms of evaluation methods, traditional evaluation methods rely heavily on subjective expert judgment, significantly influenced by the experts’ professional level and cognition. For example, the evaluation of the TSSCI mainly involves distributing questionnaires to relevant institutions for qualitative descriptions from specific aspects of NQI, dividing results into 5 levels to reflect NQI capability.5,10
Regarding the application of quality infrastructure capability building in the equipment manufacturing industry, some enterprises have undertaken exploratory work, effectively supporting equipment manufacturing quality. For example: Boeing emphasizes the application of quality infrastructure elements like standards, metrology, inspection/testing, and certification or accreditation. In product design and manufacturing, 38% of operational data, 39% of engineering data, and 40% of product definition data originate from standards. Siemens’ quality infrastructure construction focuses on digitalization and intelligence as core strategies, supporting quality management, technological innovation, and digital transformation.11,12 However, there are still some issues in quality infrastructure construction and capability evaluation in the equipment manufacturing industry:
The constituent elements of quality infrastructure in the industry are unclear, leading to a lack of a construction model and hindering effective support and guarantee of equipment quality levels.
Current quality infrastructure evaluations mainly target national or regional levels, misaligning with the focus and requirements of industry-level construction, making direct application difficult.
Quality infrastructure capability evaluation relies heavily on qualitative analysis, resulting in strong subjectivity and difficulty in objectively characterizing capability levels. 13
Therefore, building upon national or regional requirements for quality infrastructure construction and evaluation, this paper combines the quality management requirements of the equipment manufacturing industry to construct a quality infrastructure construction model.14,15 Based on fuzzy theory and the VlseKriterijumska Optimizacija I Kompromisno Resenje (VIKOR) method, it proposes a comprehensive evaluation method for assessing the quality infrastructure capability building level within the equipment manufacturing industry, providing methodological support for enhancing its quality infrastructure capability.
To address these issues, this paper makes the following contributions. First, the key elements of quality infrastructure in the equipment manufacturing industry are clarified. Second, a capability-building framework is constructed based on the “Regulatory System–Management System–Technical System.” Third, an evaluation model and indicator system are developed from four dimensions: industry influence, system construction, resource supply, and equipment quality assurance. Finally, a fuzzy theory and VIKOR-based evaluation method is proposed and validated through a case study. These contributions form a complete chain from framework construction to quantitative evaluation.
Quality infrastructure construction model for the equipment manufacturing industry
Constituent elements of quality infrastructure in the equipment manufacturing industry
Based on the quality assurance needs of the equipment manufacturing industry and national quality infrastructure research theory, this paper posits that the industry’s quality infrastructure is a technical system composed of professional elements such as metrology, standards, inspection or testing, certification or accreditation, it includes elements like standardization, metrology, conformity assessment, and general quality characteristics of equipment, as well as regulatory systems, regulatory frameworks, organizational structures, talent teams, and practical activities that support each element4. The capability level of this infrastructure is determined by:
Industry quality infrastructure capability
Industrial quality foundation supply capability
Ancillary quality support capability
General quality characteristics assurance capability
Industry quality supervision capability
Construction model for quality infrastructure in the equipment manufacturing industry
Quality infrastructure construction in the equipment manufacturing industry involves multiple domains such as standards, metrology, inspection or testing, certification or accreditation, industrial data, and general quality characteristics, potentially facing issues of fragmented management and coordination difficulties. Therefore, in order to comprehensively advance this construction, this paper builds upon national quality infrastructure construction requirements and industry characteristics. 11 Focusing on constituent elements like standardization, metrology, conformity assessment (including inspection or testing, certification or accreditation), and equipment general quality characteristics, it proposes a construction model from three dimensions: regulatory system, management system, and technical system. The regulatory system provides the essential basis for equipment quality supervision; the management system is the direct guarantee for standardizing equipment quality; the technical system is the vital foundation for ensuring industry development. The construction model is shown in Figure 1.
(1) Regulatory system

Overall framework of quality infrastructure for the equipment manufacturing industry.
The regulatory system for the equipment manufacturing industry, under the guidance of national laws, consists of industry laws, administrative regulations, departmental rules, normative documents, and management measures for frontline scientific R&D. It ensures the sustainable development of the industry’s quality infrastructure. Relevant administrative regulations mainly include national laws, rules issued by national competent authorities, and industry regulatory requirements.
(2) Management system
Leveraging the existing management systems within the industry, we should further refines the responsibilities for quality infrastructure management and clarifies quality management requirements. It can be divided into four layers according to management hierarchy: governance layer, management layer, support layer, and execution layer.
The governance layer is responsible for organizing the management of industry plans, policies, standards, and regulations, supervising their implementation, proposing overarching governance requirements, defining quality policies and top-level frameworks, and centrally managing the industry’s quality infrastructure. The governance layer primarily refers to industry competent authorities.
The management layer is responsible for implementing governance requirements and leading the construction of industry quality infrastructure. It mainly includes enterprise headquarters’ competent departments and relevant industry associations.
The support layer establishes and improves the industry quality infrastructure management system based on the construction requirements set by the Governance and Management Layers. It primarily consists of industry professional technical institutions and industry management laboratories.
The execution layer includes all units within the industry, serving as the main participants and direct users of quality infrastructure construction.
(3) Technical system
Facing the professional composition of quality infrastructure, the technical system comprises four parts: standardization technical system, metrology technical system, inspection and testing technical system, and equipment general quality characteristics technical system. Among them:
The industry standardization technical system includes standardization fundamental technology, standardization management technology, standard specification development technology, and standard digitalization technology.
The industry metrology technical system scientifically categorizes and delineates metrology technologies based on systems engineering principles, the system covers four fields: scientific theory frontiers, special value transfer, R&D and production support, and professional fundamental sharing.
Inspection and testing are divided into quality testing and technical safety & environmental testing based on different purposes. Quality testing includes non-destructive testing, metrological testing, physical and chemical testing, and product testing, technical safety & environmental testing includes energy conservation and environmental protection testing, vacuum testing, electrostatic protection testing, intelligent video inspection, etc.
The equipment general quality characteristics technical system mainly includes design analysis and test verification technologies for general quality characteristics such as reliability, maintainability, testability, supportability, safety, and environmental adaptability.
This section clarifies the constituent elements of quality infrastructure and establishes an integrated construction framework for the equipment manufacturing industry. The next section further develops a corresponding evaluation model and indicator system based on this framework.
Comprehensive evaluation indicator system for quality infrastructure capability in the equipment manufacturing industry
Comprehensive evaluation model for industry quality infrastructure capability
To enhance the construction level of quality infrastructure in the equipment manufacturing industry, it is necessary to conduct capability evaluations to provide inputs for targeted and continuous improvement. Rooted in the national industrial base, the industry’s quality infrastructure primarily serves the complex equipment construction field, effectively ensuring equipment quality, promoting industrial upgrading, and supporting equipment R&D activities, thereby achieving high-quality development.
This paper focuses on enhancing the quality assurance capability of the equipment manufacturing industry. By integrating the constituent elements and construction model of the quality infrastructure capability in the equipment manufacturing industry, and drawing on the evaluation approach of the National Quality Infrastructure Development Level Index, this paper comprehensively considers the goal of the quality infrastructure in the equipment manufacturing industry serving the quality assurance of equipment development and production. It establishes a comprehensive evaluation model from the dimensions of industry influence, system construction, resource supply, and equipment quality assurance, this model comprises 4 first-level indicators, 15 second-level indicators (see Figure 2), and 26 third-level indicators.
(1) Industry Influence

Comprehensive evaluation model for the equipment manufacturing industry.
Industry influence primarily evaluates the influence of the industry within its technical domain. The evaluation focus is on possessing metrology, standards, accreditation, and conformity assessment systems recognized internally and externally, leading national/industry-related quality infrastructure regulations, and the construction of professional institutions related to quality infrastructure.
(2) System construction
Having a relatively complete regulatory system at the industry level is the foundation for ensuring the sound operation of the quality infrastructure system. When evaluating the regulatory system, it is necessary to build upon national quality infrastructure regulations, while also taking into account the current development status and needs of the specific industry or enterprise, and carrying out targeted evaluations of regulatory construction.
(3) Resource supply
A robust quality infrastructure for the equipment manufacturing industry requires the guarantee capability of relevant resources, serving as a crucial foundation for ensuring its smooth operation. Besides ensuring the supply of resources for metrology, standards, accreditation, and conformity assessment, it is also important to focus on evaluating the supply of human resources, funding, and the construction of technical basic data resource platforms in professional institutions. 16
(4) Equipment quality assurance
During equipment R&D and production, specialized fields such as standardization, metrology, and general quality characteristics are the main quality infrastructure elements ensuring equipment development. Emphasis should be placed on evaluating whether corresponding quality assurance system has been established within the current equipment development process and whether relevant assurance professionals have been appointed.
Evaluation indicator system for quality infrastructure capability in the equipment manufacturing industry
Based on the constructed “Industry Influence–System Construction–Resource Supply–Equipment Assurance” comprehensive evaluation model and its indicator system (4 first-level, 15 second-level, 26 third-level indicators), this paper presents quantitative calculation methods for each third-level indicator to enhance the operability and accuracy of the evaluation index calculations. The comprehensive evaluation indicator system is shown in Table 1.
Evaluation indicator system for quality infrastructure capability in the equipment manufacturing industry.
This section establishes a comprehensive evaluation model and constructs a multi-level indicator system for assessing quality infrastructure capability. Based on these indicators, the next section proposes the evaluation methodology for data processing, weight determination, and capability calculation.
Comprehensive evaluation methodology for quality infrastructure capability in the equipment manufacturing industry
Building upon the established evaluation indicator system for quality infrastructure capability in the equipment manufacturing industry, methods for quantifying evaluation data, determining index weights, and comprehensive evaluation are proposed. 17
Fuzzy theory-based quantitative processing method for evaluation data
Due to variations in personnel knowledge, experience, and engineering backgrounds, expert evaluation information exhibits ambiguity and uncertainty. To improve the accuracy of evaluation results, this paper employs fuzzy theory to quantitatively process subjective evaluation data.18,19
(1) Fuzzy Theory
Fuzzy theory quantifies ambiguous information in natural language, effectively addressing the fuzziness and uncertainty inherent in human judgment. 20
Let
Where,
(2) Fuzzy numbers
Triangular fuzzy numbers are a commonly used method for describing fuzzy sets, let
As shown in Figure 3, when
(3) Linguistic Variables

Triangular fuzzy number.
When evaluating assessment indicators, it is difficult to provide precise descriptions, typically, linguistic variables or interval numbers are employed to characterize evaluation results. Therefore, when analyzing evaluation indicators, it is necessary to construct corresponding linguistic term sets.24,25 Let the term set be denoted as
Ordering:
Maximum property:
Minimum property:
Negation operation:
Triangular fuzzy linguistic variables for evaluation indicators.
After determining the correspondence between the linguistic term set and triangular fuzzy numbers, T experienced experts are invited to evaluate the indicators. The selected experts should have more than 10 years of theoretical foundation and rich practical experience related to quality infrastructure, and be able to transform fuzzy and complex evaluation problems into quantifiable indicators, as well as identify key influencing factors. Let the evaluation information provided by the k-th expert be denoted as equation (4):
Where,
Convert each expert’s evaluation information into a triangular fuzzy number matrix according to Table 2, then aggregate the evaluations from all experts to obtain the comprehensive evaluation index
Where,
During the implementation of indicator evaluation, for objective evaluation data, in order to ensure the accuracy of the evaluation results, relevant business data from the equipment manufacturing industry are collected, including annual reports, quality manuals, capability lists, and other supporting materials, and the statistical analysis requirements for different indicators are clearly specified. Meanwhile, since the indicators differ in dimensions and orders of magnitude, they cannot be directly compared or aggregated through weighted summation. To maintain consistency with the expert evaluation results, the extreme value method is adopted to map the indicator values into a dimensionless interval of [0, 10], where the industry benchmark value is taken as the maximum value and the minimum requirement is taken as the minimum value.
For subjective evaluation indicators, an expert team for quality infrastructure capability evaluation is established. Experts with extensive experience in quality infrastructure management are invited to conduct quantitative assessments of the capability level of each evaluation indicator, based on the constructed fuzzy linguistic evaluation dataset and the corresponding fuzzy numbers.
VIKOR-based evaluation indicator weight calculation
By comprehensively considering the overall impact of the evaluation indicators on equipment operational effectiveness, mission reliability, and equipment quality level (including product physical quality, organizational quality, and process assurance quality), the greater the degree of influence, the larger the weight value of the evaluation indicator. Accordingly, a VIKOR-based method for calculating the weights of evaluation indicators is proposed.
(1) Basic Theory
The VIKOR method is a multi-attribute decision-making algorithm based on the ideal point method. It assumes that multiple attributes of a thing are conflicting and different, making it difficult or impossible to achieve an optimal result satisfying all attributes simultaneously in practical calculations.26,27 The VIKOR method finds a suboptimal solution closest to the ideal solution by comprehensively considering both maximizing group utility and minimizing individual regret, thereby obtaining a compromise ranking for multi-attribute decision-making that makes the ranking results more scientific and accurate.
28
For fuzzy number-based compromise programming, the weighted metric the weighted metric
Where,
(2) Weight Calculation Process
The process for calculating evaluation indicator weights is as follows:
1) Determine the ideal solution and negative-ideal solution for the weight influencing factors.
Calculate the ideal solution
Here,
2) Calculate Group Utility Maximization Ranking and Individual Regret Minimization Ranking
The proximity to the ideal solution is measured by calculating the distance between the analysis results of the weight influencing factors and the ideal solution. A smaller value indicates closer proximity to the ideal solution, meaning the corresponding factor has a greater influence on the weight. Thus, based on Lp, calculate the group utility maximization ranking
Where
3) Calculate the Compromise Ranking for the Quality Influencing Factors as equation (9):
Where,
In order to defuzzify the calculated, Let
A smaller value of x indicates closer proximity to the ideal solution, meaning the influencing factor
4) Calculate Evaluation Indicator Weights
The importance of evaluation indicators is determined by sorting
Step 1: Identify the indicators with the most significant influence on weights based on the following two criteria:
Criterion 1: Acceptable Advantage, whose evaluation method is shown in equation (11).
Where,
Condition 2 (Acceptable stability in decision making): The factor corresponding to
If both conditions are satisfied, the factor corresponding to
The factors corresponding to
Step 2: Remove the most important factor(s) identified in Step 1 from the set, sort the remaining factors in ascending order according to the values of
Step 3: Calculate the weight values of the evaluation indicators by sequentially determining the importance of each indicator and computing their respective contribution degrees, where the contribution rate value of the sorted influencing factors to quality impact is defined as equation (13)
Representing the degree of influence each evaluation indicator has on the comprehensive assessment, thereby serving as the weight value for each respective evaluation indicator.
Comprehensive evaluation of quality infrastructure capability
To conduct a comprehensive evaluation of quality infrastructure capability in the equipment manufacturing industry and enable comparative analysis of results, the comprehensive capability index (QI Index) is calculated based on the constructed evaluation hierarchy and the weights of each indicator. 33 The formula is as equation (14):
Where,
Based on the calculated comprehensive capability index, we can not only conduct comparative analysis on the quality infrastructure capability levels of different enterprises, but also evaluate the quality infrastructure capability construction levels of the same enterprise at different times. This helps understand the enterprise’s quality infrastructure capability building level and provides a decision-making basis for subsequent continuous improvement.34,35
This section proposes a fuzzy theory and VIKOR-based evaluation methodology to quantify indicators and calculate the overall capability index. The following section applies the proposed method to an aviation equipment manufacturing case study for validation.
Case study
This paper selected an aviation equipment manufacturing enterprise for a pilot application, which undertakes the R&D and production of various types of aviation equipment. In terms of quality infrastructure capability building, it has continuously strengthened the construction of the industry’s technical foundation through investments in upgrading its quality management system, intelligent manufacturing transformation, industrial chain collaboration optimization, and talent cultivation, playing a significant role in technological research, service, and supervision for high-quality aviation equipment development.
Evaluation data collection and processing
Following the constructed comprehensive quality infrastructure capability evaluation indicator system, evaluation data was collected for the period 2020–2024. For subjective indicators, to reduce the subjectivity of evaluation data, 3 experienced industry experts were invited to determine evaluation grades based on the enterprise’s quality infrastructure capability construction status and its support for aviation equipment development. These grades were then converted into quantitative evaluation data.
The evaluation data for each indicator of the aviation manufacturing enterprise from 2020 to 2024 is shown in Table 3.
Evaluation data of quality infrastructure capability indicators for an aviation manufacturing enterprise (2020–2024).
Calculation of comprehensive evaluation indicator weights
Considering the impact degree of each quality infrastructure capability evaluation indicator on enterprise organizational quality, process assurance quality, and equipment physical quality, the weights of each indicator were calculated using the VIKOR-based method proposed in this paper.
First, the ideal solution (
The ideal solution and negative-ideal solution.
Then, the group utility maximization ranking and individual regret minimization ranking for each indicator were calculated, the compromise ranking was solved under the principle of balancing approval and rejection (
Ranking based on P, R, and Q.
Finally, determine the importance of each evaluation indicator sequentially and calculate their contribution degrees, which are assigned as the weight values for the respective indicators, the results are shown in Table 6.
Calculation of evaluation indicator weights.
The Figure 4 shows that the trend of the weights calculated by this paper’s method aligns with that calculated by the traditional averaging method, indicating that the proposed method effectively characterizes the relative magnitude of each indicator. Furthermore, since the calculation method considers the comprehensive results of factors influencing the importance of different indicators, the evaluation results show greater differentiation compared to the traditional averaging method, better reflecting the importance of each indicator.

Overall framework of quality infrastructure for the equipment manufacturing industry.
Analysis of comprehensive evaluation results
Based on the evaluation results of each indicator and their weights, the comprehensive quality infrastructure capability evaluation index for the aviation enterprise from 2020 to 2024 was calculated, as shown in Table 7.
Comprehensive evaluation index of quality infrastructure capability for an aviation manufacturing enterprise (2020–2024).
The trend of the enterprise’s comprehensive quality infrastructure capability index is shown in the Figure 5 below. Since 2020, the index has gradually increased, reflecting the steady improvement in the enterprise’s quality infrastructure capability level and the continuous enhancement of equipment quality assurance capability. Furthermore, with the promotion and application of new technologies and methods, the quality infrastructure capability has grown even faster.

Overall framework of quality infrastructure for the equipment manufacturing industry.
From the perspective of first-level evaluation dimensions, the industry influence, system construction level, resource supply capability, and equipment quality assurance capability all showed gradual improvement, the resource supply capability and system construction level increased more significantly and at a faster rate, reflecting the enterprise’s high emphasis on system construction. Additionally, as depicted in Figure 6, since 2023, the quality infrastructure index of the enterprise has grown faster, reflecting a higher emphasis on the level of quality infrastructure capability building. Moving forward, efforts should be intensified to bolster influence and improve equipment quality assurance capabilities.

Overall framework of quality infrastructure for the equipment manufacturing industry.
The case study results demonstrate that the proposed method can effectively reflect the capability level and development trend of quality infrastructure. The final section summarizes the conclusions and discusses future research directions.
Conclusion
This paper addressed the current problems of incomplete elements and insufficient integration in the equipment manufacturing industry’s quality infrastructure construction. It focused on enterprise requirements for quality infrastructure construction, clarified the constituent elements of the industry’s quality infrastructure, and constructed a capability building model based on the dimensions of “regulatory system–management system–technical system.” To enable comparative analysis of quality infrastructure capability levels among equipment manufacturing enterprises and solve problems like missing evaluation indicators and strong subjectivity, an evaluation model and indicator system for quality infrastructure capacity in the equipment manufacturing industry are constructed from four dimensions: industry influence, system construction, resource supply, and equipment quality assurance, and a comprehensive evaluation method based on fuzzy theory and the VIKOR was proposed, it has advantages over traditional methods in quantifying objectivity and accuracy. Validation was conducted through a case study of an aviation equipment manufacturer, where analysis of quality infrastructure development data from 2020 to 2025 calculated the enterprise’’s composite capability index, quantitatively assessed its evolution, revealed 5-year development trends, drove continuous improvement initiatives, and confirmed the methodology’s effectiveness.
In the context of intelligent manufacturing, the evaluation of quality infrastructure capability should evolve from a static measurement of resource supply toward a dynamic, system-level assessment of intelligent operational support capacity. Future research should incorporate industrial Internet security evaluation mechanisms, 36 function–performance coupling analysis, 37 digital twin integration, 38 and “soft quality infrastructure” elements such as adaptive scheduling 39 and intelligent small-shift detection into the framework, thereby enhancing cyber-security resilience, real-time monitoring sensitivity, 40 and decision-support capability. At the methodological level, greater attention should be given to the interrelationships among evaluation indicators, as highly correlated indicators may result in repeated calculations and implicit weight amplification. Therefore, correlation identification methods such as Pearson correlation analysis and causal modeling should be introduced to detect redundancy, merge or eliminate strongly correlated indicators, and improve the robustness and accuracy of the evaluation system, ultimately promoting a more integrated, dynamic, and intelligent quality infrastructure assessment model.
Footnotes
Handling Editor: Aarthy Esakkiappan
Funding
The authors received no financial support for the research, authorship, and/or publication of this article.
Declaration of conflicting interests
The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
