## 3 The Main Content and Key Technologies of SC Supported by DTs
### Features of DTs in Realizing SC  
Since 2020, the outbreak of the novel coronavirus globally has also demonstrated deficiencies in the current urban management and operation of population flow and information connectivity [77, 78, 79]. Traditionally, city management is passive. Visualization technology is managed by collecting and processing the events that have occurred in DTs SC entities. With the progression of a new generation of science and technology, such as the fifth generation of communication technology, cloud computing, and edge computing, the progression of informational has also started a new process [80]. The development of visualization technology has also brought new approaches, and proactive management of cities has become possible [81]. As a visualization technology, according to NASA's authoritative definition, digital town pairing refers to making full use of the physical model, sensor, tag, and other data to integrate the multidisciplinary, multifaceted simulation. In short, DTs is copied in the real world of the physical body, systems, and processes in the network space to form a \"clone\". The two eventually form a \"DTs body\".  
[PERSON] et al. [82] believed that an important application value of DTs SCs is the interaction and feedback of digital and physical systems in the virtual world and the real world to ensure the coordination and adaptation of physical and digital systems in the whole process of information resource collection. DTs play a crucial role in the field of intelligent manufacturing and effectively promote the effective cooperation between production and design. Some researchers extend the adoption of digital technology from products to workshops and whole enterprises, realizing integration and replication of the total factor, whole process, whole business data, factor management, and production plan [83; 84; 85]. These dual digital applications provide valuable inspiration and references for DTs SCs. Through the construction of urban DTs bodies, the interactive operation of the weather environment, infrastructure, population and land, industrial transportation, and other elements can be deduced in the digital world in the form of quantitative and qualitative combinations to draw an \"urban portrait\". This supports decision-makers in the physical world to achieve the optimal layout of comprehensive benefits of \"a map\" of urban planning and \"a chess game\" of urban governance. The DTs+ urban operation management architecture is shown in Figure 5.  
DTs urban construction is divided into four stages, namely vision first, IoT perception, application upgrade, and simulation [86; 87]. In the first stage, a visual city model is established, which presents static information such as urban infrastructure, buildings, and geographic information in the way of 3D rendering. In the second stage, the hardware devices are gradually increased, such as sensors, cameras, and intelligent terminals, to collect dynamic urban data. In the third stage, technical means are utilized to conduct a basic analysis of the urban operation and make decisions under the DTs urban model platform. The fourth stage is the high-level form of DTs' urban progression. In the case of a comprehensive grasp of the past and present operation data information of the city, the possible state of urban operation is deduced through deep learning and calculation, the solution is designed in advance, and a decision-making simulation is carried out to propose the best solution.