Upgrading models, evolutionary mechanisms and vertical cases of service-oriented manufacturing in SVC leading enterprises: Product-development and service-innovation for industry 4.0

Table of Contents

Research methodology

This paper uses a longitudinal case study to analyze the upgrade model and evolutionary mechanism of the SVC leading enterprise SOM for the following reasons: (1) to provide a scientific analysis of how and why a SOM was upgraded; and (2) to reveal the dynamic process of SOM the evolution of a vertical case.

Subjects of study

Based on typicality, illumination, and completeness principles, we take AVIC Hi-Tech (AVIC), a well-known and listed Chinese company, as the subject of our research.

(1)

The typicality of SOM: AVIC, as the domestic LE in new materials and equipment manufacturing, has nearly 40 years of manufacturing history that span the development of China’s manufacturing industry. In terms of manufacturing categories, AVIC and its predecessor (Nantong Machine Tools) and subsidiaries cover cutting-edge manufacturing, such as new materials for aviation and technology development for high-end intelligent equipment, as well as R&D and manufacturing of products related to primary manufacturing fields, such as aviation, rail transportation, automotive, medical devices and equipment manufacturing. Moreover, AVIC has formed a complete product service system in its long-term development, forming a complete service organization of sales and technical services, real estate development, innovation, and entrepreneurial investment.
(2)

Case inspiration: AVIC has gone through various development, acquisition, and redevelopment stages and has changed from a laggard to a leader in terms of product services. Moreover, it is an SVC-leading enterprise that has moved through several service manufacturing upgrading models and evolutionary cycles.
(3)

Evolutionary integrity: The complete evolution of AVIC spans the various types of SOM models illustrated in Fig. 6. Therefore, an analysis of PD and SI regarding AVIC facilitates analysis of the dynamic trends and critical initiatives of SOM. The path to the scientific development of SOM enterprises is thus summarized, laying the foundation for latecomers to become SVC-leading enterprises.

Data collection

AVIC is a listed company, and its official website is open and interactive; this provides a reasonable basis for compiling the following data in this study: (1) The content of AVIC’s PD and SI was compiled via official website reports, executive statements, and WeChat publicity platform content, whereby the interview questions were extracted. (1) We obtained first-hand data through interview conversations and expert consultations with AVIC’s senior and middle leaders. (3) The results of these interviews were grouped and coded from the PD and SI perspectives while taking into account the Self-dominance and Other-dominance of the service track and the product track. The theoretical analysis model was collated through the coding structure and the design of these constructs. All the primary data sources and classifications are shown in Table 2.

Table 2 Information on data.

During data collection, we first used text analysis software, UCINET, to collect information on service-oriented manufacturing enterprises. Through social semantic network analysis, we found that a large number of service-oriented manufacturing keywords pointed to “AVIC” enterprises. Therefore, we preliminarily set this as the research object of our case analysis. Second, we held two expert meetings in March 2022 and June 2022. The March 2022 conference was held online. We invited members of the expert service manufacturing committee, personnel from the Ministry of Industry and Information Technology, etc., to select suitable service manufacturing demonstration enterprises. This meeting was held at AVIC in June 2022. AVIC has been recognized as a service manufacturing model in China. We invited 2 academicians from the Chinese Academy of Sciences, 3 provincial and ministerial leaders, and more than 20 university professors. All the participants acknowledged the service-oriented manufacturing model of AVIC, ensuring the objectivity and validity of our research while strengthening the research value of the case.

In this study, the acquisition of all qualitative data followed the principle of calibration sampling. In the design of case information quality control standards, we set standards that met the specific content of service manufacturing product development and service innovation. The design of the targeted basic conditions thus includes (1) distinct service-oriented manufacturing activity attributes; (2) flexible production or service activities; and (3) work in accordance with the provisions of the Identification Rules of China Service Manufacturing enterprises. After controlling for the samples, we coded our case information using the root method and then verified our coding via survey sampling to demonstrate that the information met the sample selection standard, guaranteeing our sampling quality.

AVIC SOM upgrade mode scenario

Combining Fig. 5 with the case’s facts, we summarize the performance and coding of the elements and supplement these with empirical examples.

SOM upgrade basis

As a sizeable state-controlled enterprise, AVIC’s abundant capital reserves have enabled it to take the lead in completing its information transformation. In 1956, AVIC’s predecessor, Nantong Machine Tools, was established. In 1993, Nantong Machine Tools was officially launched. As one of the first machine tool companies in China, AVIC represents the nation’s traditional manufacturing industry. Its resource-intensive advantage allows it to hold nearly 10% of China’s primary manufacturing industry, and it has rapidly expanded its foreign trade in machine tools since China acceded to the WTO. Since 2010, AVIC has been promoting the intelligent transformation of the manufacturing chain in the context of information technology reform as follows: (1) In terms of technical architecture, the transformation from information technology (IT) to digital technology (DT) is achieved. The information transformation is based on the traditional architecture + desktop side. AVIC has introduced a complete technical information support system and a technology cluster for machine tool manufacturing using technologies such as cloud network segments. (2) Among the demand characteristics, machine tools, aerospace compound materials, intelligent equipment, and other products are used to achieve any change, from facing deterministic demand to uncertain demand. With the help of enterprise resource planning (ERP) and customer relationship management (CRM), AVIC meets its scale-oriented deterministic demand. Furthermore, intelligent customer platforms are used with the aid of digital technology to customize and differentiate product requirements and meet uncertainty in its customer market. (3) In terms of its core requirements, AVIC establishes information stations to shift from improving efficiency to supporting innovation, which enables it to support business innovation, management innovation, and organizational innovation in the face of uncertain demands.

With its information technology transformation, AVIC is gradually building an open technology innovation platform. In the past, AVIC was more oriented toward internal resource optimization, resulting in a closed technology system. Today, AVIC is thinking about transforming service manufacturing to build an open technology system based on global optimization and achieve data integration with its suppliers, their suppliers, its agents, and its customers. Via this participation of multiple parties, AVIC’s technological innovation is optimized in the same direction: on the service side. Hence, AVIC not only provides hardware + software + solutions but also, more importantly, a set of consumer-focused operation solutions, where the technical demands made by customers become an essential basis guiding service innovation. AVIC further optimizes existing technologies to achieve rapid growth in technical specifications on the product side.

In terms of its institutional innovation and organizational restructuring, AVIC has performed even better. On the one hand, changes in AVIC’s structure were inevitable due to its military-industrial properties. The military is the end user of the military industry’s products, and today’s establishment system changes will directly impact future military equipment procurement needs. Moreover, reform is bound to co-occur with user demand changes, and the supply side—the military industry/defense industry drives such changes. Since the adoption of the Decision of the Central Committee of the Communist Party of China on Several Major Issues of Comprehensively Deepening Reform at the Third Plenary Session of the 18th Central Committee in 2013, the reform of state-owned enterprises has entered a new phase, with a substantial increase in the top-level design, depth of reform, areas involved and their quantity, and the implementation of pilot reform measures, resulting in the upgrading and overall deepening of the reform of state-owned enterprises. In AVIC, such reform has formed a “1 + N” top-level framework system, involving the implementation of its four actions, ten actions, “double hundred actions,” and other pilot reforms. Specific examples of such actions include revising the business performance assessment standards to guide AVICs’ high-quality development and stimulate internal vitality; focusing on the development of the primary industry; divesting the “three supply and one industry” to streamline the organization and strengthen the technological breakthroughs in the primary industry while avoiding any duplication of investment and waste of resources; moving from “managing assets” to “managing capital” while promoting the internal vitality of the enterprise through equity incentives and other means; and, finally, improving the level of asset-backed securities of central military enterprises through measures such as the restructuring of research institutes and mixed ownership reform. AVIC has therefore expanded its corporate structure and organizational volume through the internal restructuring of research institutes and matching asset structure with organizational structure, with core assets leading the SOM infrastructure.

The core architecture of the SOM

As a leading SVC company, AVIC has implemented a convergence framework between PD and SI. At the product development end, the company is in the prepreg stage, a critical link in the composite material industry chain with obvious advantages in terms of positioning. Prepregs are made from reinforcing materials impregnated with resin and are an essential intermediate substrate for the preparation of composite materials; they are irreplaceable in the production and development of composite materials. Around this core function, AVIC has implemented prepreg materials into its functional modules of Machine Tools–Smart Manufacturing using its manufacturing platforms (Airwise Equipment and Nantong Machine Tools). Through the linkage and synergy of the functional modules of several subsidiaries, domestic resin and T300 grade carbon fiber prepreg are formed. Furthermore, through vertical cooperation and internal operations, the company has made composite parts (prepreg and honeycomb) into full-size large wall panels, automated assembly products for aircraft wall panels, etc. AVIC thus leads the entire spectrum of basic–high-end manufacturing at the service innovation end. In turn, a complete customer base and service marketing system have been built. At the same time, through the merger and acquisition of several subsidiaries, the systematic management of capital and intellectual property has been developed. For example, AVIC’s machine tool manufacturing technology is constantly being adapted by drawing on the individual input of external customers, which has been consolidated into a permanent innovation that is applied to its products. This complete docking–marketing–information extraction–concept customization–tracking–application–feedback upgrade path thus forms the basis of AVIC’s services. Finally, AVIC fulfills more than 50% of the effective orders for carbon fibers worldwide through its product–service fusion. The company’s technology accumulation in the vital process of prepreg preparation and perfect resin system reserves, and military aviation’s prepreg need to participate in the preresearch stage of military aircraft research and development to confirm the completion of technical indicators further strengthen the company’s leading position in this field; thus, its first-mover advantage is obvious. In addition, the company’s main downstream customers are concentrated in its controlling shareholder, the Aviation Industry Group, a professional development, and production unit for military aircraft in China. Covering all critical models in China’s military aviation field, the company relies on the Group’s significant downstream channel advantages. Hence, it has a solid leading position in the field of military aviation prepreg.

Theoretical model construction

Based on the previous analysis and the coding of our cases, we compiled our coding results. These are shown in Table 3.

Table 3 AVIC SOM upgrade mode codes.

Building on Table 3, we have developed a logical evolutionary framework of resource–capability–superiority–development from a strategic management perspective. AVIC’s SOM upgrade model shows that the core requirement for companies to achieve the SVC faucet goal is the multidimensional integration of their supply chain, value chain, and innovation chain and that their integration must follow this logic. In conjunction with our previous overview of the SOM upgrade model, we specify the mechanistic model of the SOM upgrade in Fig. 8.

**Fig. 8: Mechanistic model of the SOM upgrading model (Figures source: self-made by the author).**

Subsequent scholars can use the findings in Fig. 8 in empirical analysis. In conjunction with Fig. 8, the logical framework of resource–capacity–advantage development better reveals the case mechanism. Leaving aside the dynamic perspective, the SOM enterprise is represented within each evolutionary stage, as shown in Fig. 8. Figure 8 can therefore be further summarized as a static upgrade process for a SOM enterprise.

At the resource end, SOM enterprises should combine the background of Industry 4.0 and rely on the industrial internet and digital intelligence technology. They should begin by building on their established manufacturing foundation, breaking the traditional manufacturing shackles to extend and penetrate their service field, and then promote the integration of manufacturing and services to achieve SOM transformation. Technological, institutional, and organizational innovations require a sound public service system with the following resources: (1) SOM major research and development program—to break the static bottleneck of the SOM upgrading model, on the one hand, a company needs to systematically launch scientific and technological research, use critical technologies and information platforms, and set up joint research institutions with key enterprises and universities. On the other hand, it must strengthen the support of essential critical standard technologies and research and distinguish the technologies that restrict the development of its SOM, forming a list of standard technology catalogs. This development of the innovation background drives the overall atmosphere of resource sharing. (2) Precise policy toolkit—i.e., strengthen policy guidance and support, formulate comprehensive policies to promote the development of SOM, and increase support in terms of financial resources and other aspects. Here, the government appropriately relaxes market access, breaks down barriers to the expansion of manufacturing enterprises into the service sector, and supports the service business of manufacturing enterprises at the same price as the general industry in terms of preferential policies and resource use. (3) SOM enterprises receive adequate resources from the service industry, i.e., comprehensive and professional services such as strategic research, planning, enterprise diagnosis, and solutions for manufacturing enterprises via resources, intermediary service agency development, and business model innovation. Manufacturing companies thus draw on relatively favorable information technology to form industry-wide service transformation solutions by addressing fundamental issues such as talent development, basic R&D, joint standards development, intellectual property protection, and service value measurement.

At the competence end, the effective combination of SVC is used to expand the SOM enterprise division of the labor system. The company expands the two-way access to SOM through the convergence of PD and SI, reducing information silos and encouraging manufacturing enterprises to work with upstream and downstream enterprises and third-party service enterprises to achieve risk sharing and information sharing in multiple scenarios and channels. Throughout the life cycle, it works with industry associations, research institutions, and industrial parks to facilitate new industry alliances across regions, industries, and fields, giving full play to the demonstrative role of leading enterprises. Finally, it forms a new pattern of SOM development for SMEs from point to point. Based on the excellence of SOM’s capabilities, a national brand image of manufacturing can be formed with the ultimate goal of enhancing the competitiveness and capabilities of basic manufacturing.

On the advantage end, SOM gradually demonstrates the model’s superiority by integrating products and services. A product–service system spans the entire product lifecycle, forming a comprehensive, whole-chain system-based service and providing customers with product service packages comprising integrated products and services. Based on SOM experiences, industry understandings, and technical potentials, pain points and difficulties in the market can be resolved. By establishing the industry base, connecting and improving the supply chain, and exporting business models and other enabling services, the quality of market SOM output increases, culminating in the upgrade of multidimensional indicators, such as profit and performance.

Finally, as its resources, capabilities, and strengths continue to be strengthened, the SOM entity builds sufficient strength to begin upgrading from static to dynamic, and thus it eventually repeats the accumulation of resources, capabilities, and strengths in each stage of the model’s performance. By accumulating quantitative changes, qualitative leaps can be achieved, ultimately allowing it to reach the target development state of SOM breakthrough evolution.

Evolution of the AVIC SOM

This paper has outlined the complete evolution of AVIC SOM based on the case discussions. Due to its long history and continuous progress, AVIC encapsulates the primary stages of traditional manufacturing and the three evolutionary models of SOM. Its specific evolutionary process is shown in Fig. 9.

**Fig. 9: AVIC SOM evolution process (Figures source: self-made by the author).**

(1)

Traditional manufacturing (1956–1989): AVIC’s predecessor, Nantong Machine Tool, was established in 1956 as one of the first machine tool companies to have absolute industrial leadership and a voice in China’s heavy industry construction strategy. Over nearly 30 years of development, AVIC has become a large backbone enterprise in the Ministry of Machinery Industry, the first of the machine tool export base enterprises in China. Moreover, in 1989, Nantong Machine Tool became the new centerpiece of the capital market as the second listed company in the machine tool industry in China.

AVIC went through a problematic product development cycle in the Traditional Manufacturing stage. Initially, due to capital constraints, a lack of technology, and the institutional constraints of the planned economy, AVIC was only able to produce loose parts for machine tools independently. The product platform and the complete production chain had not been formed. The organizational structure was ancient, resulting in AVIC’s participation in only a few simple links in the supply chain, with low bargaining power for its products. Following China’s reforms and opening up, which introduced some foreign investment and advanced technology, AVIC seized the opportunity to become one of the first Chinese machine tool enterprises to export to foreign markets. It thus formed the framework of its VMC and VMCL product platforms, which can manufacture, produce and repair all kinds of machine tools that were compatible with a single product type. Its main products included ten categories, thirteen series, and more than seventy variations. These included a rocker universal milling machine, CNC milling machine, vertical milling machine, CNC lathe, vertical machining center, horizontal machining center, and gantry machining center. Its large manufacturing scale and production capacity made it the leading traditional manufacturing industry in China. When upgrading in the manufacturing phase, AVIC continued to develop its product tracks. It took advantage of the scale effect to establish functional modules and aggregation systems for its complementary products, resulting in a significant increase in production efficiency. In addition, the streamlining of personnel and the organization’s restructuring ensured that AVIC remained flexible and could better position itself in changing times. Relaxations and changes in the institutional context also provided the impetus for AVIC’s development. However, in this stage, AVIC did not develop any service-oriented activities. The target audience for the marketing and sales departments remained secondary companies or distributors; there was no direct targeting of market customer groups. In addition, the feedback capability for operation and maintenance was poor, and some of the machines purchased by customers would not even be returned to the factory for a warranty repair. Overall, AVIC’s product track development in this stage was excellent, but its service track construction was unimpressive.
(2)

SOM progressive upgrading (1990–2009): With AVIC’s manufacturing upgrades, its product development capabilities were significantly enhanced, culminating in its qualification for market launch in 1989. The rapid entry of financial capital offered AVIC access to more comprehensive market information, and the service track entered an accelerated phase of development. In the 1990s, AVIC built a series of marketing platforms around its core machine tool products and introduced service packages for machine tools through partnerships with the government, companies, and universities, combining machine tool products and service innovation to enter the ‘soft product’ market. After 2000, with its accession to the WTO and expansion into the foreign trade market, AVIC began to expand its marketing and knowledge management, designing integrated support services around large units, including customized machine tools, customized adaptations, and complete solutions model designs. In the process, however, the rapid escalation of AVIC’s service track was divorced from the effective renewal of its product track. Its product side did not change but instead exacerbated the serviceable change in costs (Fig. 7). In addition, due to a decline in technological competitiveness, many homogeneous latecomers entered the market; AVIC’s earnings from manufacturing could not cover its costs of service, and the company’s profitability began to decline; thus, it entered a restructuring phase in 2010.
(3)

SOM Breakthrough Upgrading I (2010–2020): With the restructuring of AVIC and the rapid importation of state-owned assets, AVIC began to enter the Breakthrough Upgrading I stage. First, AVIC started the construction of the autonomy of its product track, the iteration of its traditional machine tool products, the formation of an intelligent machine tool manufacturing chain for 4.0, and the generation of new intelligent machine tool products. Second, AVIC entered the high-end manufacturing market through mergers and acquisitions and by introducing novel product chains, such as carbon fiber (as shown in Fig. 10). The broadening of the market for high-end products significantly increased the company’s manufacturing earnings. Then, AVIC established a sales network under its control and entered the service industry to support the stable sales of high-end products through a superimposed balance of service tracks. In this stage, AVIC achieved massive profitability through revenue servitization and cost manufacturing (reduction), and the enterprise’s SOM entered a breakthrough development, allowing it to become a leading demonstration of China’s manufacturing transformation.

Fig. 10: Self-dominated upgrade of the AVIC product track (Figures source: self-made by the author).

AVIC has formed an innovative and advantageous carbon fiber preparation mode. The advantages of production are realized through the optimization of the PE film.
(4)

SOM Breakthrough Upgrading II (2020–): This phase has seen a whole new development of AVIC due to its upgrade of PD and SI, combined with its SOM upgrade base’s renewal in Industry 4.0. The supporting resources of the enterprise have become broader and broader, forming a complete SVC via the interweaving of its supply chain, innovation chain, and value chain. AVIC has mastered the ability to extract new materials and resources for high-end manufacturing, to offer new top products, and to dominate the controllable and adjustable ability of service channels; hence, finally, it has formed a substantial soft power of service. AVIC’s SVC industrial network is shown in Fig. 11.

Fig. 11: AVIC complete SVC enterprise network (Figures source: self-made by the author).

Through the development of a service-oriented manufacturing model, AVIC has spanned multiple industries and formed a development framework with comprehensive strength.

However, the autonomous extension of AVIC’s service track in this phase has exacerbated its cost pressures. The simultaneous juxtaposition of revenue and cost servitization reduces profit margins from SOM Breakthrough Upgrading I. Based on its annual report, AVIC’s net profit has decreased at an average annual scale of 3%, compressing its profit margin. However, in the long run, the increased autonomy of AVIC High Tech’s services gives it a better voice in its competitive market. With the enhancement of its service capacity, AVIC has transformed this from a service production activity to a production service activity. The supply capacity and quality of the supply of its services have been significantly improved, providing access to capital and new technological elements and allowing AVIC to become an active leader in Industry 4.0. With the stabilization of its service supply, AVIC will continue to optimize cost space, improve the quality and efficiency of its service supply, reduce consumption, and further grasp the leading position in the SVC.

Contribution refinement

Based on the real-life case of AVIC High Tech, this study has corroborated the specific upgrading process of service-oriented manufacturing, unifying and coordinating the strategies of product development and service innovation in specific activities. The service targets in this study include responsible governmental industrial sector agencies, traditional manufacturing companies, model companies with leading positions, and service-oriented companies seeking to form manufacturing activities. For each of these service recipients, the study provides the following respective contributions:

(1)

Government industrial sector: Both service and product activities depend on the information platform in Industry 4.0. Therefore, government departments should vigorously promote infrastructure construction concerning the hardware foundation of service-oriented manufacturing, i.e., the deep integration of manufacturing and service industries and the comprehensive utilization of factor resources across industries. Efforts should be made to break through existing institutional and mechanical barriers, change traditional thinking patterns, and increase policy support and guidance for the integrated development of the manufacturing and service industries; manufacturing enterprises should improve their level of the industrial division of labor and collaboration while promoting the optimal integration of factor resources into different business sectors.
(2)

Traditional manufacturing enterprises: Service and product tracks need to be integrated to achieve the advancements of the service-oriented manufacturing model. Based on the case of AVIC High Tech and the process of service-oriented manufacturing evolution discussed in this paper, manufacturing enterprises should design innovation and model upgrades to cultivate, create and guide consumer demand. Through a scientific service and product tracking, they should predict and explore market demand to develop new products based on digital intelligence drives, creating a closed-loop model of the whole chain of “design–production–consumption–design” to promote the precise matching of enterprise production capacity and market demand while driving consumption upgrading. The operation of the four stages of service-oriented manufacturing should impel thinking guidance under the HFJZ matrix. Enterprises should foster the development of new industrial design industries and new models, which encourage industrial design enterprises to give full play to their design advantages and vertically incubate their own product brands. They should avoid the negative transformation path of the high service cost and low-cost value.
(3)

Leading enterprises: Our results highlight the role of the service-based manufacturing upgrade model. The key to becoming a leading enterprise via SVC is the deep application of modern technology in both management and model. The coordination of the innovation chain, value chain, and supply chain is driven by technological progress, market opening, and institutional innovation. In the crossover of the product track and service track, the original industrial boundary is broken through technology penetration, industry linkage, chain extension, and internal reorganization. These eventually promote industrial cross-fertilization and breed new business models. The dynamic process of mutual support, efficient synergy, integration, and interaction between service and manufacturing is thus a process of intermingling multiple value chains.
(4)

Service companies that expand their manufacturing activities: We have proposed a progression model of service innovation that circumvents the trend of industrial hollowing out. The phenomenon of a service industry’s detachment from the real economy still exists, and one of the more prominent examples is the internal circulation of funds in the financial service industry, where some funds are detached from the real economy. The HFJZ and service-oriented manufacturing evolution mechanism proposed in this paper highlight the construction strategy of service enterprises when integrating manufacturing activities to accelerate the construction of an industrial system with the synergistic development of the real economy, science and technology innovations, modern finances, and human resources.

This paper thus completely explains the meaning and mechanism of service-oriented manufacturing and describes the upgrading characteristics and evolutionary direction in each stage. Through our use of case summary and induction, the research system of service-oriented manufacturing has been enriched. At the theoretical level, this study focuses on the practice of SOM at the product-service level. Through the intersection of product and service activities, the specific practice strategy of service-oriented manufacturing is clarified. On the application side, through the design framework of resource–capability–advantage development, the specific practices of enterprises are revealed, and the transformation path ordinary enterprises can follow in service-oriented manufacturing to become leading enterprises is designed and formed. Our global study of service-oriented manufacturing is further enriched by the focal Chinese cases. Compared with similar case studies, we are the first to use a review case study the unity of our review, framework construction, and case study. Similar to other research, we have applied a combination of qualitative and objective analysis. First, we use “soft” methods, such as expert surveys and Delphi, to narrow the scope of case collection. Second, using objective methods such as social semantic networks and grounded theory, we determined our specific case of AVIC. Then, based on the theoretical guidance and logical framework we obtained, this case was analyzed, and the dynamic and static evolution process at each stage was considered. Finally, the reasonableness and correctness of our theory and framework were demonstrated by a case study. In addition, we have promoted a particular research system in this paper. In contrast to similar studies, (1) we have used longitudinal cases to achieve static and dynamic analysis in our research. Thus, the service and product track change course of service manufacturing have been better described. The key strategies to control the service-oriented manufacturing model are extracted from our conclusions. (2) We have used cases to prove the scientificity of and support our theory. The “demonstration” of our qualitative research is thus realized. Through the comprehensive application of cases, our research, and our literature review, a new direction of qualitative research has been integrated. (3) At the content and contribution level, the HFJZ matrix and other theories are proposed. These effectively support the development idea of service manufacturing. Expanding the depth for subsequent research, our variable–model relationship also contributes to better applications of the quantitative method.

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