A supply chain-oriented perspective to prevent future COVID-19: Mathematical model and experience of guaranteeing quality and safety of fresh agricultural products

: The COVID-19 outbreak has exposed deficiencies in the supply chain of FAPs, which 9 have also increased their vulnerability. As the COVID-19 epidemic continues to develop, the 10 effective supply of FAPs during the epidemic prevention and control period has become a key 11 part of the response to the epidemic in metropolitan areas. Based on the game theory, this study 12 constructed a three-level supply chain consisting of suppliers, TPL service providers and retailers to guarantee the supply of FAPs in metropolises in the context of COVID-19 epidemic. By Stackelberg principle game theory, the optimal epidemic prevention effort level, preservation effort level, wholesale price, retail price and optimal profit result in the supply chain dominated by supplier and retailer are respectively solved. In this study, in addition to the characteristics of FAPs such as easy loss and perishable, COVID-19 epidemic factors such as virus infection coefficient and epidemic prevention efforts were fully integrated into the model to ensure the effective supply of FAPs in metropolitan areas. The main research conclusions are as follows. (i) In the context of COVID-19, compared with the wholesale prices of FAPs, the level of preservation 21 efforts and epidemic prevention efforts will have a greater impact on the retail prices of FAPs in 22 metropolitan areas. (ii) When the supplier is in the dominant position, the sensitivity coefficient of 23 the quality assurance effort level is positively correlated with the optimal profit of the supplier. Compared with other members, they have stronger control ability and decision-making ability, so 25 that their profits are greater than those of other members. (ii) Compared with suppliers who are in the leading position of guarantee and supply, when FAPs retailers are in the leading position of guarantee and supply, TPL service providers have a higher level of epidemic prevention efforts 28 and preservation efforts for FAPs. At the same time, the quality effort level, market demand and 29 retail price are all greater under the retailer-led guarantee. (iv) The profit of FAPs retailers is 30 affected by the sensitivity coefficient of preservation effort level, epidemic prevention effort level 31 and dominant guarantee status. 32


Introduction 36
In 2002, the first case of SARS was found in Guangdong, China. According to a   58 There is no doubt that COVID-19 and SARS have seriously threatened the lives and 59 health of metropolitan residents. In order to prevent the spread of infectious diseases, 60 we must pay attention to this important aspect of urban planning, construction and 61 management. It is necessary to add infectious disease prevention and control planning 62 in the special planning of urban planning, and take measures for infectious disease 63 prevention and control from the perspective of urban planning.

64
Novel Coronavirus nucleic acid positive test was found in seafood products from 4 of 26 the over-dispersed production and consumption markets, the organization of FAPs 115 becomes more difficult, and the multi-level supply chain structure is hard to avoid. In 116 this context, the increasing COVID-19 epidemic has a significant impact on the demand 117 for FAPs among metropolitan residents.

118
It should be emphasized that cold chain FAPs transportation could easily become 119 the carrier of novel Coronavirus due to appropriate temperature. Most viruses can 120 survive for a long time at low temperatures. Both freezing and freezing give the virus a 121 longer survival time. Because the virus has no cellular structure, the ice crystals created 122 when it is frozen cannot kill it. Laboratories that make viruses often freeze them in 123 freezers. After thawing, the virus is still infective. Cold chain is a very complex logistics 124 system, involving a large number of people, as shown in Figure 2. Figure

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The following design structure of this study is as follows. Based on the review of  problems of sowing, production, harvesting, transportation, distribution, inventory, 208 sales and returns in the supply chain through key factors . The aim of these studies 209 is to optimize the operation efficiency of supply chain. Table 2

Manufacturer -Distributor
Productiontransportationsales Quantity and quality loss The design of incentive mechanism can realize the coordination of interests of both sides.

Productiontransportationsales
Quantity and quality loss TPL has a significant impact on supply chain performance.
Cai et al. [5] Producerexport -local market Productiontransportationsales The number of loss Replenishment by order and replenishment by stock will have different effects on product loss.

Cai and
Zhou [6] Producer -seller Production -sales Uncertainty about output, demand and prices To manage uncertainty, vendors need to strike a balance between resource inputs and revenue.
Gokarn et al. [7] Fresh e-commerceoffline physical stores Online -offline sales channels Circulation channel, loss Online and offline dynamic pricing strategies influence each other. He et al. [8] Manufacturerprocessing centerdistributor Harvestprocessingdistribution Seasonality, demand and harvest uncertainty, loss Customization of supply chain around the uncertainty of FAPs can improve the operation performance of supply chain.

Supplytransportationsales
Quantity and quality loss The revenue-sharing contract and the fresh-keeping effort level sharing contract can realize the supply chain coordination and Pareto improvement.
Ma et al. [10] Supplier -Seller Production -sales The cost in quantity and quality The design of revenue-sharing and technology investment contract sharing can achieve coordination.
Mohamma di et al. [11] Manufacturer -Retailer Productiondistributioninventory The quality of whipped consumption A method of building quality loss model for production and distribution decision is proposed.

Productiontransportationsales
Random output and random demand The contract is designed to increase the profit of supply chain members under controllable transport time.
Su et al. [13] Distributorlogistics service provider Transportation -Sales Quantity and quality loss The power structure affects contract design, enterprise decision behavior and system performance.
Wu et al. [14] Manufacturer -Distributor Productiontransportationsales The number of loss Using the pull model can make both parties perform better, and the introduction of FIPF strategy can achieve pareto improvement.

Xiao and
Chen [15] Supplier -TPLretailer Productiontransportationsales The number of loss Cold chain service price and service sensitivity will affect the profit of supply chain members.

Yu and
Xiao [16] Supplier -TPLretailer Supplyproduction -sales Random output and random demand, quality loss The wholesale price and logistics service price clearing contract are introduced in order to realize supply chain coordination.
Feng et al. [17] Supplier -Retailer Supply -Sales Quality loss Purchase price contract and wholesale price -fresh-keeping cost sharing contract can promote the supply chain to improve fresh-keeping.
Wang and Dan, [18] Producerwholesale market Productiontransportationsales The cost in quantity and quality Different business models have a great impact on the decision-making and coordination mechanism of supply chain members.
Xiao et al. [19] Manufacturer -Distributor Production -sales The cost in quantity and quality Adjusting the strategy of freshness preservation effort can affect the benefit of both supply chain members.

Manufacturing -Sales
Strategic consumer behavior Revenue sharing and wholesale price Yan et al. [21] Supplier -Retailer Supply -Sales The value loss of fresh agri-products under different transportation modes Improving the utilization rate of cold chain transportation of fresh agri-products.
Yan et al. [22] Manufacturer -Distributor Production -sales Ultrasound-assisted cleaning Improving food safety for consumers Azam

213
As can be seen from Table 2, the traditional production and marketing supply chain 214 structure composed of "production or supplier -retailer" is still the focus of current 215 research [27]. Therefore, the link involved in most studies is "production or supply -216 sales". E-commerce marketing model is now more and more respected in some research.
These studies involve factors such as live broadcast marketing and promotion. At the    situation and plan, so it must be responded to and adjusted. And the impact that can 256 make such a state appear is called emergency events [33]. Emergencies directly lead to 257 supply chain coordination or the original plan is no longer feasible, and then affect the 258 production decision of the supply chain and affect the supply chain revenue. How to 259 make timely and accurate production decision arrangement in case of emergency is a 260 long-term problem that needs to be solved in the field of emergency management.

261
The concept of emergency management was proposed by Clausen et al [34] in

283
In addition, some scholars also emphasize the importance of quantitative flexible 284 contracts, believing that its main purpose is to reduce the potential risks in the process of 285 product supply. Qi et al [46] took the lead in the systematic study of a supply chain   However, the information about FAPs advertised by e-commerce is difficult to 321 distinguish between true and false, and the quality of FAPs is also uneven.

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To improve the circulation efficiency of FAPs, this paper improves the supply chain 323 model of FAPs based on the intelligent environment of big data, as shown in Figure 3.

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The core values of FAPs supply chain innovation driven by big data technology include digital intelligence of whole-process business processing. Based on the platform support of supply chain, big data intelligent technology can radiate more small platforms and 328 provide entrepreneurial opportunities for more manufacturers and retailers.         Table 3.

550
In formula (5) and substituting formula (6), under the condition that the best FAPs 554 For the first partial derivatives of formula (7) for

570
Since The results of equation (5), equation (8) and equation (10) are substituted into 576 r w p p    . In the case of the optimal fresh agricultural product retailer's increased 577 price, optimal fresh keeping effort level, epidemic prevention effort level and optimal 578 wholesale price, the optimal retail price of the retailer under the fresh agricultural 579 product supplier led supply guarantee can be expressed as follows

596
It can be seen from the above that equations (13), (14) and (15) respectively 597 represent the optimal profits of suppliers, TPL service providers and retailers under the 598 conditions of optimal retailer price increase, optimal preservation effort level, optimal 599 epidemic prevention effort level and optimal wholesale price of suppliers. The solution results of Equations (19) and (20) are substituted into Equation (17). In 646 the case of TPL's optimal quality effort level and optimal retailer markup, the supplier's 647 optimal wholesale price when fresh agricultural product retailer dominates the warranty 648 can be expressed as follows (20) and (21)

661
Equations (19), (21) and (22)  price increase, the optimal freshness preservation effort level, the optimal epidemic 672 prevention effort level and the optimal wholesale price of suppliers.   (13) and (15), it can be known that

824
In this study, a three-level supply chain consisting of a single supplier, a single TPL

833
The main conclusions of this study are as follows.
is negatively correlated with retail prices, and positively correlated with the level of 836 quality control efforts. Compared with the wholesale price of FAPs, the level of preservation efforts and epidemic prevention efforts will have a greater impact on the 838 retail price of FAPs in metropolis.

839
(ii) When the supplier is in the dominant position, the sensitivity coefficient of the 840 quality assurance effort level is positively correlated with the optimal profit of the 841 supplier. Compared with other members, they have stronger control ability and 842 decision-making ability, so that their profits are greater than those of other members.

843
With the improvement of consumers' preference for epidemic prevention efforts and 844 preservation efforts, the profits of the suppliers of FAPs in the supply chain structure 845 under the leading position of supply guarantee will gradually increase.

853
(iv) When FAPs retailers dominate the guarantee, the profit of TPL service provider 854 has nothing to do with the sensitivity coefficient of the quality assurance effort level. The

872
Although this research has achieved the research goal of this paper, there are still 873 some limitations in this paper. Fresh produce suppliers and retailers respectively led the 874 study on fresh produce supply protection in metropolitan areas in the context of 875 COVID-19 outbreak. The guaranteed supply system led by TPL service providers should 876 be studied in the future. In addition, in the context of COVID-19, members of the supply 877 chain for FAPs in metropolitan areas are often one-to-many, many-to-one or 878 many-to-many in reality. In the future, the problem of supply chain game composed of 879 multiple suppliers, multiple TPL service providers and multiple retailers can be 880 considered to ensure the effective supply of FAPs in metropolis.