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A segmented estimation method of roughness based on the variation of hydraulic radius and estimation accuracy is proposed in order to realize the real- time and high- fidelity roughness estimation of hydrodynamic digital twin (DT) models. This method considers the spatial variability of the roughness value in the longitudinal direction of canals. Based on canal segmentation, two different estimation frameworks, the independent estimation method and joint estimation method, are proposed. The ensemble Kalman filter algorithm is applied to estimate the roughness of each canal segment online based on the limited observed water levels. The results show that the two estimation methods can improve the accuracy of the model by 20% —50% . In addition, the independent estimation method is suitable for a complex canal system with a small error accumulation, while the joint estimation method is suitable for simple canals with unavailable observations. The proposed method can be used for parameter estimation and variable updating of hydrodynamic DT models, and provide a reference for the construction of DT water networks. [ABSTRACT FROM AUTHOR]

Objectives: Complex construction organization strategies such as parallel same direction and reverse boring for long railroad tunnel projects lead to sparse spatiotemporal distribution and large spatiotemporal overlap in the digital twin three-dimensional model. The existing spatiotemporal indexes for the continuous uniform spatiotemporal distribution characteristics can not satisfy the needs of efficient retrieval of time, mileage, and semantics in multi-dimensions, and they also restrict the efficiency of the digital twin application in real-time virtual and real mutual feeds. Methods: This paper proposes a multi-dimensional efficient spatiotemporal indexing method applicable to the digital twin model of railroad tunnels. First, a 3D tile data structure of railroad tunnels associated with time, mileage, and semantic multi-dimensions is designed. Second, an oriented bounding box corrective mechanism constrained by the global optimal solution is established, and then a multi-granular spatiotemporal index of railroad tunnel lines-tiles-components is realized. Finally, the effectiveness of the method is verified using typical long railroad tunnel twin model data. Results: The results show that the average value of the proposed method in the mixed retrieval time of time, mileage and semantic multi-dimensions is 135.44 ms, which improves the retrieval efficiency of the 3D spatial single dimension and the time-mileage mixed dimension comparing with the existing typical spatial and temporal index. Conclusions: The proposed method can effectively support the efficient spatial and temporal retrieval of the digital twin 3D model of railroad tunnels, and the application of high-performance visualization and analysis. [ABSTRACT FROM AUTHOR]

Aiming at the complex and changeable flight operation environment, a dynamic prediction model of flight chain delay based on digital twin is proposed to improve the accuracy and adaptability of the traditional prediction methods. The model is constructed based on the digital twin flight chain system. Through the model, the unit-level delay prediction is accomplished by the multi-channel feature modeling method under the sliding windows, and the parameter optimization is completed by a hybrid optimization strategy. Moreover, the whole chain’s delays are analyzed and corrected with the help of the twin data-driven strategy. Flight data in China are used to conduct the study. The mean absolute error (MAE) of flight delay prediction is 11.79 min, which is lower than those of other baseline models or static models, and the forecast error of subsequent flight delay can be reduced by 6.44% after twin data-driven analysis is implemented. The results show that the model is beneficial for the digital twin system to realize the virtual reality interaction, and has excellent prediction accuracy and adaptability. [ABSTRACT FROM AUTHOR]

Mining robots are a component of mining production, concerning multiple stages such as mining, transportation, production, maintenance, safety control, and rescue, The degree of production automation directly affects the production safety, economic and social benefits of enterprises, With the rapid development and popularization of artificial intelligence in China, mine intelligence has become an important research field, Especially with the promulgation of some policies and regulations in China, intelligent unmanned mining technology has become a key part of mining production in the field of gold mining, To understand the connotation, status, and development trend of intelligent mining robots, this article reviews the underground intelligent robot technologies matching mining operations, including neural networks, binocular vision, and digital twins, from the perspective of the relationship between key technologies and practical engineering applications of intelligent mining robots in China, From the 4 perspectives of basic theories, critical technologies, engineering applications, and overall design system theories, this article reviews the relevant research, On this basis, the current development trend of domestic intelligent mining robots and the future development trend of smart mining models are summarized, [ABSTRACT FROM AUTHOR]

After completing the technical integration of beneficiation equipment, processes, automation, and IT, the Sanshandao gold mine has significantly improved the reliability of its beneficiation equipment and processes, and achieved a higher level of intelligence in gold beneficiation through the upgrades in data acquisition platforms, intelligent operation of the beneficiation plant, and VR beneficocetoon plant. The mine has achieved stable and optimized production processes, leading to reduced manpower and increased efficiency. This has resulted in improved technical indicators and economic benefits, establishing it as one of the world’s advanced gold beneficiation plants. [ABSTRACT FROM AUTHOR]

Coiled tubing is an important tool in the oil and gas industry, the existence of the actual operation of the running process differs greatly from the results of transmission theory analysis, and in turn, the field operation faces multiple running, causing the safety hazard of coiled tubing. The digital model of coiled tubing was proposed for its running problem, and the contact state algorithm and load analysis physical model of the running process were established, and the synchronous twinning of the whole process of running was carried out to realize the load-bearing state and strength calibration of the tubing column calculated in real time for running coiled tubing, as well as the whole process analysis of the running of coiled tubing. The results show that the contact state of coiled tubing varies with the running depth in real time, and the pipe diameter ratio and friction coefficient are significant factors affecting the self-locking judgment during running. The analysis method proposed in this study can effectively serve for coiled tubing field operations and real-time operational safety assessment, and provide an important basis for coiled tubing service life analysis. [ABSTRACT FROM AUTHOR]

Coiled tubing is an important tool in the oil and gas industry, the existence of the actual operation of the running process differs greatly from the results of transmission theory analysis, and in turn, the field operation faces multiple running, causing the safety hazard of coiled tubing. The digital model of coiled tubing was proposed for its running problem, and the contact state algorithm and load analysis physical model of the running process were established, and the synchronous twinning of the whole process of running was carried out to realize the load-bearing state and strength calibration of the tubing column calculated in real time for running coiled tubing, as well as the whole process analysis of the running of coiled tubing. The results show that the contact state of coiled tubing varies with the running depth in real time, and the pipe diameter ratio and friction coefficient are significant factors affecting the self-locking judgment during running. The analysis method proposed in this study can effectively serve for coiled tubing field operations and real- time operational safety assessment, and provide an important basis for coiled tubing service life analysis. [ABSTRACT FROM AUTHOR]

A digital twin construction method based on the reduced order model library and machine learning was proposed for structures under dynamic loads. Firstly, the high-fidelity finite element models were established according to the possible damage states occurring during the service of the physical structures. Secondly, the Krylov subspace order reduction method was used to reduce the orders of the models and the reduced order models were assembled to a library. Finally, the random forest machine learning algorithm was used to train the model selector, infer the current state of the physical structure through the sensor data from the structure, and then drive the digital twin to evolve with the physical structure. A physical frame structure was designed and manufactured to simulate the damages of different degrees at different points, and verify the proposed digital twin construction method for dynamic structures. [ABSTRACT FROM AUTHOR]

The construction digital measurement and control system for self-propelled harge for immersed tube section transportation and installation is the key technology to ensure the long-distance safe transportation and high-precision docking uf immersed tube sections. The system realizes the functions of construction parameter setting, construction and design document management, construction process automatic control, horizontal height orientation and display, construction data storage, construction state playback and restoration, and preparation of construction reports, etc., thus realizing full-time on- line tracking and monitoring of equipment operation, quality of communication and signal, and safety waming of harge and immersed tube positions during the whole construction process. A test and control operation mode of integrating undocking, Boating transportation, mooring and installation of an immersed tube section is systematically constructed, and a data acquisition mode that multiple GNSS signal sources based mainly on BDS data sources are synchronously and independently operated and signal sources can be intelligently switched is adopted to obtain a large number of high-precision data which are fed back in time to the floating transportation and docking control system to realize the visual interface between multi-source data, such as navigation information and meteorological information, and the digital twin of the real construction state, provideing guarantee for rapid, accurate and safe transportation and installation of immersed tubes. [ABSTRACT FROM AUTHOR]

Positioning navigation and timing (PNT) is the nation's critical infrastructure. At present, China has established the relatively complete ground-based augmentation systems, satellite-based augmentation systems and low earth orbit(LEO) satellite-based augmentation system for comprehensive PNT. Although indoor positioning on a contemporary smartphone is booming, including Wi-Fi, bluetooth, magnetic field fingerprinting, and so on, these existing methods still cannot provide high quality PNT services for the whole area, such as underground, indoor space, and underwater. Recently, the key technologies of real three-dimensional model and digital twin model received more and more attention. The information of geographic scene presents unrecalled opportunities to improve the robust availability, continuity, high accuracy and reliability of comprehensive PNT system. First, we introduce the state-of-the-art of related studies of scene-based augmentation systems, including scene-based PNT systems augmentation. Second, we summarize the challenges and present the definition and basic concept of the scene-based augmentation systems for comprehensive PNT. Next, the system architecture, construction units and hierarchical service mechanism of scene-based augmentation systems is proposed. Finally, we forecast the development trend of scene-based augmentation systems for comprehensive PNT. The China comprehensive PNT system should be BeiDou-centered and include ground-based augmentation systems, satellite-based augmentation systems (SBAS), LEO SBAS and scene-based augmentation systems for comprehensive PNT as auxiliary augmentation systems. It has the ability to provide intelligent PNT services in whole area. [ABSTRACT FROM AUTHOR]

The digital twin city seeks to restore virtually the geographic scene that is close to reality and provide the audience an immersive experience. Three dimensional (3D) real urban scene is one of the key technologies to achieve the goal. Nowadays, the combination of geographic information system and game engine becomes an industrial trend and provides new opportunities for 3D real urban scene. Oblique photogrammetric data, as being a fundamental data source for 3D urban modeling, is able to represent large-scale and high-precision scene. The game engine plays an excellent role in offering realistic effects and post-production systems that are greatly useful for geospatial data visualization. However, the diversity of specifications and formats of oblique photogrammetric data has caused many different data loading and transformation methods, resulting in a problem to be solved in 3D real urban scene. Methods: This paper aims to propose a data transformation approach from oblique photogrammetric data to rendering resources in game engine. To stress, the proposed approach can allow us to load instantly massive amount of oblique photogrammetric data in Unreal Engine, which is one of the most popular game engines. We further compared oblique photogrammetric data with rendering resources in game engine and discussed the significance of such a data transformation. The approach reorganizes the original structure of the data by parsing data into a tree structure that better suits transformation purposes. Also, the proposed approach transforms respectively the geometry and texture data when iterating tree nodes, as well as considers the essential physical properties of rendering assets. All these features are combined into a package data format. Results: In the case study of Futian district, Shenzhen, the results show that the proposed approach successfully converts oblique photogrammetric data to rendering resources in Unreal Engine 4. In the transformation process, the geometrical structure and collision properties of triangular mesh are guaranteed, and color, bump and other visual elements of original data are kept in materials. The rendering resources are loaded to simulate the real urban scenarios at different time periods of a day in Unreal Engine 4. Conclusions: This paper devises a novel approach which can convert the oblique photogrammetric data into rendering resource for a game engine to load and render, and meantime maintain the consistency of data's geometry and texture. For its scalability, it also supports parallel processing of large-scale data transformation when data is organized in the same directory. The proposed approach may be of great theoretical and practical value for other related 3D model data transformation problems. [ABSTRACT FROM AUTHOR]

As an emerging concept, metaverse has attracted extensive attention from industry, academia and scientific research field. The combination of agriculture and metaverse will greatly promote the development of agricultural informatization and agricultural intelligence, provide new impetus for the transformation and upgrading of agricultural intelligence. Firstly, to expound feasibility of the application research of metaverse in agriculture, the basic principle and key technologies of agriculture metaverse were briefly described, such as blockchain, non-fungible token, 5G/6G, artificial intelligence, Internet of Things, 3D reconstruction, cloud computing, edge computing, augmented reality, virtual reality, mixed reality, brain computer interface, digital twins and parallel system. Then, the main scenarios of three agricultural applications of metaverse in the fields of virtual farm, agricultural teaching system and agricultural product traceability system were discussed. Among them, virtual farm is one of the most important applications of agricultural metaverse. Agricultural metaverse can help the growth of crops and the raising of livestock and poultry in the field of agricultural production, provide a three-dimensional and visual virtual leisure agricultural experience, provide virtual characters in the field of agricultural product promotion. The agricultural metaverse teaching system can provide virtual agricultural teaching similar to natural scenes, save training time and improve training efficiency by means of fragmentation. Traceability of agricultural products can let consumers know the production information of agricultural products and feel more confident about enterprises and products. Finally, the challenges in the development of agricultural metaverse were summarized in the aspects of difficulties in establishing agricultural metaverse system, weak communication foundation of agricultural metaverse, immature agricultural metaverse hardware equipment and uncertain agricultural meta universe operation, and the future development directions of agricultural metaverse were prospected. In the future, researches on the application of metaverse, agricultural growth mechanism, and low power wireless communication technologies are suggested to be carried out. A rural broadband network covering households can be established. The industrialization application of agricultural meta universe can be promoted. This review can provide theoretical references and technical supports for the development of metaverse in the field of agriculture. [ABSTRACT FROM AUTHOR]

The prevention and control of the disaster of water-sand mixture inrush caused by mining is becoming one of important bottlenecks, which restricts mining safety. The state-of-the-art and trend of water-sand mixture inrush from seam roof were reviewed, including the catastrophic mechanism, movement law and risk evaluation. The engineering geological models of disaster formation are divided into four categories, including water-sand mixture inrush by direct or indirect exposure of unconsolidated aquifers, by seepage failure due to water-conducting fractured zone connecting, by man-made borehole drilling through unconsolidated aquifers, and by softened overburden with deterioration of water and inrush under the combined action of water pressure and mining pressure. In view of the seepage failure of water-sand mixture inrush, combined with the model test and theoretical derivation results, the basic movement law of the water-sand mixture flow through the orifice, single fracture, fracture network and caving zone was obtained, which lays the foundation for the establishment of a unified equation of the movement of water-sand mixture flow. An expression of critical hydraulic gradient from top to bottom seepage was derived, and the concept and calculation method of safe water head against water-sand mixture inrush were proposed. A qualitative and quantitative evaluation method for water-sand mixture was established, and a dynamically quantitative evaluation method for water-sand mixture inrush was realized. The successful application of active prevention and control measures was introduced by grouting to transform the properties of unconsolidated aquifers and backfill mining, in order to reduce overburden failure and prevent water-sand mixture inrush failure. Finally, the scientific problems of the mechanism of water-sand mixture inrush from seam roof and key technical issues, which should be solved in the next step of prevention and control, were proposed. The main scientific issues include that establishment of a digital twin model of the geological geology of water-sand mixture inrush from seam roof, revealing the formation mechanism of the water-sand mixture inrush pathway, the interaction between the water-sand mixture and the surrounding rocks, constructing the motion equation reflecting the whole process of water-sand mixture inrush, obtaining the grout propagation and solidification characteristics in the advanced area of preventing water-sand mixture inrush, etc. Research and development of key technologies include monitoring and early warning technology, actual environment modeling technology, and equipment for high-efficiency grouting. [ABSTRACT FROM AUTHOR]

As Software Defined Network（SDN） is increasingly widely used in various scenarios, a new challenge for SDN to support dynamic requirements of various applications begin to emerge. Digital Twin（DT） can enhance the capabilities of SDN in aspects of real-time analysis, deduction, and network control, and consequently satisfy the dynamic requirements of various applications. Whereas, current DT constructing schemes for SDN usually suffer from the challenges of strict delay constraint, heavy computing overhead, and low cooperating efficiency. To address the above issue, this paper proposes a novel Variable Granularity-Digital Twin（VGDT） according to the application requirement and available computing resource. Based on the distribution characteristic of the computing resource in the network, VGDT builds a cooperatively optimizing model to ensure the delay and effectiveness of the DT for SDN. Then, this paper proposes a hybrid coding genetic algorithm to solve this model, which can achieve the best granularity and the DT placement policy. The simulation results show the performance of VGDT. Compared with current DT, VGDT has higher integrity and validity of digital twin model under limited computing resource. [ABSTRACT FROM AUTHOR]

The optimal allocation of land‐use is an important technical means to solve the contradiction be‐ tween supply and demand of land resources and to coordinate social and economic development with eco‐ logical protection, and it is also one of the key issues that need to be solved for the sustainable use of land resources. With the development of spatial simulation and intelligent optimization technology, the theoretical basis and methodological system of land‐use optimization are constantly updated. Based on bibliometrics analysis, this paper systematically summarized the driving theories and methodology of land‐use optimal al‐ location at home and abroad, focused on the application of spatial simulation models and intelligent optimization models in land‐use optimization problems, discussed and prospected the challenges and the future development of optimal land‐use allocation, and put forward that: The coupling drive of natural and human processes, spatial collaboration of multiple models, embedding big data knowledge mining methods, and the support of digital twin technology, should be the research direction of the next stage in the field of optimal land‐use allocation. [ABSTRACT FROM AUTHOR]

The digital twin watershed is an important part of the digital twin earth. Clarifying the theoretical definition and connotation of the digital twin watershed is the premise and foundation for the research and construction of the digital twin watershed, and it is of great significance for the intelligent management of the watershed. Based on the digital twin theory and technology, the following research has been carried out in this paper. ① The definition of a digital twin watershed is given, and it is considered that a digital twin watershed is a new infrastructure and new paradigm serving the entire life- cycle management of the watershed, which is the interactive mapping, co- intelligence evolution, and virtual reality integration between physical and virtual watersheds driven by the full amount of data and domain knowledge, and the differences between a digital twin watershed and traditional modeling and simulation are analyzed. ② The connotation of a digital twin watershed is to realize the full life- cycle control of physical watershed objects by loading the physical watershed into the virtual watershed, mapping the physical watershed with the virtual watershed, and then managing and controlling the physical watershed using the virtual watershed. Its characteristics include high fidelity, evolution autonomy, real-time synchronization, closed- loop interaction, and symbiotic evolution. ③ The basic model of a digital twin watershed is composed of a physical watershed, a virtual watershed, the real-time connection and interaction, the digital enabling service, the twin watershed data, and the twin watershed knowledge. Its core capabilities include physical watershed perception and control, digital expression of all of the water-related elements, visual dynamic presentation of real scene, watershed data fusion supply, watershed knowledge fusion supply, watershed simulation and deduction, and self- learning and optimization of digital twin watershed. ④ This paper puts forward the key scientific problems and key technical systems to be solved in the digital twin watershed, and looks forward to the development direction of the digital twin watershed from the perspective of a perception network, data network, knowledge network, model network, and service network, and expounds the enabling field of the digital twin watershed. This paper aims to provide theoretical guidance for the application of digital twin watershed technology through the new research paradigm of digital twin watershed theory and to provide useful inspiration and reference for future smart watershed research and the application of digital technology in watershed governance and management. [ABSTRACT FROM AUTHOR]

Objectives: The complex and dangerous mountainous environment, uncertain geographical and geological conditions are the key factors affecting the safety, quality and schedule of railway tunnel construction. Methods: Orient to intelligent and precise construction management, this paper proposes a top-down and bottom-up combination of railway tunnel drill safety-quality-schedule knowledge graph construction method, clarifies the conceptual connotation and semantic relationship for the five key elements of man-machine-material-method-environment(4M1E) related to safety-quality-schedule during the construction of railway tunnels, and designs a two-way collaborative construction method of mode layer from top to bottom and data layer from bottom to top, then introduces key technologies such as data acquisition and knowledge extraction. Results: Taking the construction event of the Kangding No. 2 railway tunnel exit work area as an example, we construct a case knowledge graph. The results show that the knowledge graph constructed by the method in this paper finely depicts the key element attributes that affect safety‐quality‐schedule, the semantic relationship between the elements, and the mutual feedback relationship, etc. Conclusions: Our proposed method provides key support for the overall systemic intelligent management of safety-quality-schedule in the whole process of railway tunnel drilling and blasting construction, and also lays the foundation for the digital twin of railway tunnel engineering. [ABSTRACT FROM AUTHOR]

Digital twin technology has the characteristic of virtual real fusion. The digital twin for intelligent factories can make the production process more transparent, and the production can be effectively guided with the real-time data in the workshop. In order to realize the visual control of production process based on the digital twin, a method of digital twin modeling for intelligent factories oriented to the production process is proposed. First, the framework of the digital twin system for intelligent factories is constructed. Second, the key technologies are elaborated, including the method of 3D geometric modeling based on the point cloud fitting, the method of object linking and embedding for process control unified architecture (OPC UA) information modeling for data interaction, multi-source heterogeneous data integration and fast matching of virtual-real mapping data. Finally, the digital twin system for an engine manufacturing workshop is realized. This demonstrates the correctness and effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

At present, the megacity of Shanghai has made remarkable achievements in the construction and development of the international economic centre, international financial centre, international trade centre, international shipping centre science and technology innovation center. However, it still faces many criminal risks that threaten economic security, and presents criminal mainstreaming, risk — based, cross — border, capital channelization and digital twinning development trends. It is easy to induce systematic risks of Shanghai' s economy and finance, thus affecting its high — quality financial development. It is found that the risk of economic crime exists in the interweaving and interaction of multiple factors such as institutional supply, regulatory operation mode, techno-logical development and change, law enforcement ability, corporate governance mode, and investment group weak-nesses. In the future, Shanghai' s "Five Centers" construction should build a overall system constitute institutional governance, system governance, technology governance, corporate governance and source governance so as to establish and maintain a prevention and control barrier for high level, high efficiency and high quality construction and development of the economic and financial security in megacities. [ABSTRACT FROM AUTHOR]

Objectives: Nowadays, a vast number of sensors and observation platforms bring a significant challenge for city perception. In the study, we focus on developing of a smart city tempo‑spatial perception system. The concept of smart city awareness base station (SCABS) is proposed in this study, and the SCABS architecture considers the above problems. Methods: Firstly, we systematically reviewed the requirements and the complexity of smart city perception and summarized the development process and network architecture of smart city perception technology systems. On this basis, the challenges of ubiquitous access, trusted perception and intelligent management in future smart city perception are addressed. Then, this paper sorted out the demand for future city perception services and constructed the architecture of SCABS. Finally, we standardized the technical indicators and service capabilities of SCABS. Results: We constructed the prototype of SCABS. According to the qualitative analysis and experiments based on real environment, we found that SCABS with unified access, integrated management, and edge intelligence can meet the access and management ability of multi‑platform and high‑density sensing resources. Conclusions: SCABS would act an essential role in the smart city perception in the future. As a cyber‑physical infrastructure, it expects to cover various scenarios in the city with multiple heterogeneous perception access and hybrid access of multi‑protocols, and to automatically support the multi‑platform coordinated control. The SCABS meets global, accurate, heterogeneous, and multiple sensory perception. The SCABS is expected to be one of the critical infrastructures of the future smart city. [ABSTRACT FROM AUTHOR]

Based on the intelligent factory assembly line experimental device, a digital twin experiment system for intelligent assembly manipulator is constructed, including manipulator ' s physical device, virtual entity, virtual-real mapping module, digital twin database and experimental teaching software. Aiming at the difficulties of heterogeneous model integration encountered during the construction process, a digital twin model integration method based on multimodel fusion is proposed. The method can be applied to the experimental teaching of intelligent manufacturing related undergraduate majors, and several experimental teaching cases indicate the effectiveness of the experimental digital twin system. [ABSTRACT FROM AUTHOR]