# Transportation and Reserve of Emergency Medical Supplies during Public Health Events
## 3 Materials and Methods
### Allocation and Storage Model of Emergency Medical Materials
#### 3.3.1 Demand Urgency Function  
The urgency of the demand is the degree to which a certain demand point needs help for public health issues according to its own situation. To design the demand urgency function, it is necessary to first determine the influencing factors and weights. Because there are many factors of public health issues that affect the urgency of demand, to select the main influencing factors and perform quantitative analysis, principal component analysis was used to study the main factors affecting the ability to prevent and control epidemics. According to the requirements of the National Emergency Plan for Public Health Emergencies, the Law of the People's Republic of China on the Prevention and Control of Infectious Diseases, the Emergency Response Law of the People's Republic of China, \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Crowd Category** & **Number of People** & **Demand** & **Total Demand** \\ \hline Susceptible (\(S\)) & \(N-I-R-D\) & \(2\theta\) & \(2\theta(N-I-R-D)\) \\ Infectious (\(I\)) & \(I\) & \(3\theta\) & \(3\theta I\) \\ Recovered (\(R\)) & \(R\) & \(\theta\) & \(\theta R\) \\ Dead (\(D\)) & \(D\) & 0 & 0 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Assumption on the Demands for Emergency Medical Materials. the Novel Coronavirus Diagnosis and Treatment Plan, and related documents [32; 33], combined with the actual situation of countries around the world dealing with SARS-CoV-2, the corresponding evaluation index system is presented [34] in order to facilitate the citation of data and refer to the data format of the statistical yearbook, as shown in Table 2.  
Among them, the strict index of X2 prevention and control policy is calculated from eight indicators: \"whether to close primary and secondary schools and universities\", \"whether to close workplaces\", \"whether to cancel public activities\", \"whether to stop public transportation\", \"order to take refuge on the spot or isolate at home\", \"restriction on internal mobility between cities/regions\", and \"restriction on international travel\". The X11 UHC coverage index refers to the universal health coverage index. In order to establish a scientific and standardized demand urgency function, the evaluation index system needs to be subjected to principal component analysis to extract more effective principal components. Assuming that m principal components are extracted, let the percentage of principal component contribution be \(a_{i}\) and the percentage of principal components accounted for by the 11 indicators in the evaluation index system be \(b_{ij}\). \(X_{ik}(t)\) represents the value of the Xi indicator at demand point \(k\) at moment \(t\). Therefore, based on the weight of classification indicators, this paper designs the urgency function of demand of the prevention and control ability of epidemics. If the urgency of the demand for epidemic prevention and control ability in a certain area is \(Y_{1k}(t)\), the formula of the urgency of the demand for epidemic prevention and control ability in a certain area is obtained:  
\[y_{1k}(t)=\sum\limits_{i=1}^{\text{m}}a_{i}\sum\limits_{j=1}^{11}x_{ik}(t) \times b_{ij} \tag{9}\]  
Finally, normalized treatment is performed and \(Y_{1K}\) represents the urgency of epidemic prevention and control ability in the k-th region among \(n\) regions. \[Y_{1k}=\frac{y_{1k}}{\sum\limits_{i=1}^{n}y_{1i}} \tag{10}\]  
According to the development of an epidemic situation and the need for emergency medical materials, the urgency function of the emergency medical materials demand is designed. In Equation (11), \(N\) denotes the number of the total population at demand point