《1 Engineering research fronts》

1 Engineering research fronts

《1.1 Trends in Top 10 engineering research fronts》

1.1 Trends in Top 10 engineering research fronts

The Top 10 engineering research fronts in the field of civil, hydraulic, and architectural engineering are summarized in Table 1.1.1. These fronts cover a variety of disciplines, including hydraulic engineering, transportation engineering, construction materials, architectural design and theory, municipal engineering, urban planning and landscaping, structural engineering, engineering mechanics, surveying and mapping engineering, and bridge engineering. The following research fronts from expert nomination: “the eco- environmental effects of interbasin water transfer”, “resilience improvement of transportation infrastructure”, “water pollution control and remediation in drinking water source areas”, and “perception methods of spatiotemporal big data towards smart sustainable cities”. The other six fronts were identified using the co-citation clustering method applied to the top 10% of highly cited papers, and they were confirmed in expert panel meetings. Table 1.1.2 presents annusl statisticals on the core papers published between 2015 and 2020 that are relevant to these Top 10 research fronts.

(1)  The eco-environmental effects of interbasin water transfer

Interbasin water transfer shows promising potential and advantages in resolving the contradiction between water demand and supply through optimizing water resources allocation. Interbasin water transfer changes the temporal and spatial distribution of water resources and hydrological conditions of affected areas, and may cause complex and long-term eco-environmental effects. Different from other types of water conservancy projects, interbasin water transfer work normally involves two or more basins and has diverse ecological and environmental impacts on the basins. Regarding water donating basins, the related research is concentrated on the effect of water variation on the fluvial morphology and aquatic habitat in the downstream reach. Regarding transfer lines, the related research focuses on model-based analyses of water quality evolving along the lines. Regarding water receiving basins, the related research focuses on the effect of water variation on the structure and

《Table 1.1.1》

Table 1.1.1 Top 10 engineering research fronts in civil, hydraulic, and architectural engineering

No. Engineering research front Core papers Citations Citations per paper Mean year
1 The eco-environmental effects of interbasin water transfer 26 842 32.38 2018.2
2 Resilience improvement of transportation infrastructure 29 646 22.28 2017.8
3 Low-carbon long-life cement-based materials 84 8 648 102.95 2017.4
4 The development path of green building underthe background of carbon neutrality 135 5 496 40.71 2017.7
5 Water pollution control and remediation in drinking water source areas 46 1828 39.74 2016.5
6 Perception methods of spatiotemporal big data towards smart sustain able cities 22 987 44.86 2018.3
7 Earthquake-resilient structural system 24 1437 59.88 2018.1
8 Flow-induced vibration of flexible structures and anti-vibration measures 22 567 25.77 2019.1
9 Geographic big-data knowledge graph construction 15 414 27.6 2018.1
10 Disaster monitoring and mechanism analysis of bridge structure dynamic multi load coupled action 71 1634 23.01 2018

《Table 1.1.2》

Table 1.1.2 Annual number of core papers published for the Top 10 engineering research fronts in civil, hydraulic, and architectural

No. Engineering research front 2015 2016 2017 2018 2019 2020
1 The eco-environmental effects of interbasin water transfer 3 4 1 4 5 9
2 Resilience improvement of transportation infrastructure 3 3 4 7 10 2
3 Low-carbon long-life cement-based materials 13 19 11 18 10 13
4 The development path of green building underthe background of carbon neutrality 20 14 28 21 30 22
5 Water pollution control and remediation in drinking water source areas 16 10 7 7 5 1
6 Perception methods of spatiotemporal big data towards smart sustainable cities 1 2 2 6 8 3
7 Earthquake-resilient structural system 0 5 3 5 7 4
8 Flow-induced vibration of flexible structures and anti­vibration measures 1 0 1 3 6 11
9 Geographic big-data knowledge graph construction 1 1 5 1 3 4
10 Disaster monitoring and mechanism analysis of bridge structure dynamic multi load coupled action 6 8 12 15 16 14

the function of the local ecosystem, and on the temporal and spatial distribution of groundwater. Most of current studies on the eco-environmental effects of interbasin water transfer are limited to the regional scale, while systematic assessments at the basin scale with comprehensive consideration of water resources management and preservation of ecological environment deserve further attentions in the future. Between 2015 and 2020, 26 core papers relevant to this research front were published. These papers received 842 citations, with an average of 32.38 citations of per paper.

(2)  Resilience improvement of transportation infrastructure

The resilience of transportation infrastructure refers to the ability of transportation infrastructure to adapt to an ever- changing environment, continuously self-sense and self- adapt, withstand various hazards, and quickly recover to normal service conditions. Enhancing the resilience of transportation infrastructure is one of the critical solutions to deal with severe climate change. Improving the resilience of transportation infrastructure and reducing the impact of natural hazards and other emergencies has become a significant issue in the field of transportation engineering. The main topics include: ① theoretical frameworks for resilience improvement of transportation infrastructure under extreme climates; ② theories for assessing transportation infrastructure network elasticity and key nodes; ③ emergency management strategies of resilient transportation infrastructure under new disaster modes; and ④ technologies of low-impact construction and intelligent maintenance for resilient transportation infrastructure.

Developed countries have considered resilience improvement as an essential part of the next-generation transportation system that faces the challenge of climate change, and attention has been paid to the key features of the systems such as being intelligent, low-carbon, networked, shock resisting, and rapidly recoverable. Between 2015 and 2020, 29 core papers relevant to this research front were published. These papers received 646 citations, with an average of 22.28 citations per paper.

(3)  Low-carbon long-life cement-based materials

Cement contributes 10% to tatal carbon dioxide (CO2) emissions in China. Reducing the CO2 emission during cement production and application is an effective approach for realization of the CO2 emission peak in 2030, and carbon neutrality in 2060. Low-carbon long-life cement-based materials are designed to achieve low CO2 emission and to meet the requirement of long service life. The research focuses on: ① life-cycle assessment of carbon footprint and real-time monitor of CO2 emission during production and application of cement-based materials; ② reduction in carbon footprint by reducing the content of clinker in cements, increasing the substitution level of supplementary cementitious materials, and applying recycled aggregates in concretes; ③ development and application of novel low carbon binding materials; ④ extending the service life of cement-based materials by durability improvement, surface protection and repair technologies; and ⑤ utilization of CO2 such as recarbonation of existing concrete structures. The research trends include: ① development of methods and systems for life-cycle evaluation of carbon footprint of cement-based materials; ② development of efficient technologies of carbon capture, utilization and storage inside or around cement plants; ③ development of novel low carbon binding materials mainly from industrial solid waste and recycled materials, and to apply them in concretes; and ④ development of durability improving technologies for low carbon cement-based materials for extending the service life of concrete structures. Between 2015 and 2020, 84 core papers relevant to this research front were published. These papers received 8 648 citations, with an average of 102.95 citations per paper.

(4)    The development path of green building under the background of carbon neutrality

Green building is high-quality building that is able to save resources, protect environment and reduce pollution during its whole life cycle while providing people with a healthy, applicable and efficient space and maximally realizing harmonious coexistence with nature. Driven by the goal of carbon peak and carbon neutrality, building sectors of urban and rural development are undergoing a green and low- carbon transformation, and the main research directions include: ① principles and methods of green building design under the guidance of dual carbon goals; ② zero energy and zero carbon building technologies and basic design parameters; ③ principles and methods of low-carbon urban and rural planning and design; ④ green transformation technologies of existing buildings; ⑤ durable, reliable and high-performance anti-seismic structural systems; ⑥ new green building materials and structural systems; ⑦ intelligent control technologies of indoor and outdoor air quality and physical environment; and ⑧ green building decarbonization energy systems. The development trend is to implement design, construction and operation of green building in new constructions, to transform existing buildings to green ones with nearly zero or zero energy consumption, and to increase substantially the energy efficiency and the usage of renewable energy in buildings in order to make an early approach to the dual carbon goals. Between 2015 and 2020, 135 core papers relevant to this research front were published. These papers received 5 496 citations, with an average of 40.71 citations per paper.

(5)  Water pollution control and remediation in drinking water source areas

Water pollution control and remediation in water source areas mainly focuses on the in-situ control and remediation at drinking water source areas such as reservoirs and lakes. The quality of water sources presents seasonal fluctuation, as well as interannual periodicity and variability due to global climate change, the increased occurrence of extreme weather, and the change of hydrodynamic conditions. The effective control of runoff, eutrophication, algal growth and endogenous pollution has become a challenge for global water quality security. The main research directions include: ① the impact of climate change and greenhouse effects on the migration and transformation of pollutants in the complex air-soil-water environment, and to develop the hydrodynamic regulation techniques for reducing the pollution load of rainstorm runoff; ② the mixing and oxygenation coupled with aerobic denitrification technique to remove nitrogen and phosphorus, reducing organic matter and inhibiting algae reproduction, and employing the mechanism of aerobic denitrification bacteria driven by inorganic electron donor processes; ③ the mechanism of mixing and oxygenation induced continuous natural mixing of water bodies, which improves water quality and restores the ecological purification function, and olfactory mechanism and odor control technology of actinomycetes; and ④ the mechanism and the technology for controlling endogenous pollution and remediating continuously contaminated sediments by increasing both water temperature and dissolved oxygen concentration. The future trend is to systematically explore the causes and evolution patterns of water pollution in drinking water source areas with multi-disciplinary knowledge from climatology, hydrology, watershed runoff pollution, aquatic biology and ecology, sedimentology, geochemistry, and environmental hydraulics, and to develop the integrated key technologies based on physics–biology–ecology–hydrodynamics (PBEH). Between 2015 and 2020, 46 core papers relevant to this research front were published. These papers received 1 828 citations, with an average of 39.74 citations per paper.

(6)   Perception methods of spatiotemporal big data towards smart sustainable cities

Smart city has surpassed the concept of technology and starts to target a sustainable social and economic growth, forming the concept of smart sustainable city. The spatiotemporal big data perception methods for smart sustainable cities is to acquire the spatiotemporal big data through information and communication technology (ICT), and achieve comprehensive perception of city operation for supporting urban planning, construction, operation and service. The current research directions include: ① enhancing disaster mitigation and prevention capabilities of smart sustainable cities, by using social media as real-time sensors of the impact of hazards such as floods and hurricanes for effective hazard management; ② enhancing public participation in smart sustainable cities by using spatiotemporal big data perception methods to realize digital public participation, and to promote the sustainability of social development; and ③ applying of artificial intelligence technologies such as deep learning to spatiotemporal big data perception, which involves multiple dimensions of economy, society, environment, and governance with a focus on multiple fields including energy, environment, health, land use, safety, transportation, and urban management. The spatiotemporal big data perception method combined with artificial intelligence directed at the goal of smart sustainable cities is still an emerging subject, which has potential value for improving livability, productivity, and innovation of smart sustainable cities, and supporting the improvement in urban planning and governance. Between 2015 and 2020, 22 core papers relevant to this research front were published. These papers received 987 citations, with an average of 44.86 citations per paper.

(7)  Earthquake-resilient structural system

The traditional structural seismic design method is based on the ductility design concept, and commonly employs damage of structural members and connections to achieve good structural ductility. The resulting structures often suffer excessive post-earthquake damages and residual deformations, and it is difficult to restore their normal functions quickly. With the development of seismic technologies, the aim of structural seismic fortification is gradually upgraded from anti-collapse to indude rapid recovery of service functions after strong earthquakes. Resilient structures are able to maintain an acceptable functional level when subjected to frequent and rare earthquakes by using technologies such as rocking systems, base isolation systems, and structural systems with replaceable energy dissipation devices. They can restore their service functions without post-earthquake retrofitting or with slight repairing in some service states. The resilient structures feature easy construction and maintenance at low life-cycle cost. The research directions include: ① low damage design theory of new structural systems such as rocking systems and structural systems with replaceable members/components; ② energy dissipation mechanisms of new high- performance dampers; and ③ post-earthquake resilience evaluation methods of structural members, connections and systems. The main development trends in the future include: ① design and resilience evaluation of the whole building system including non-structural and structural systems  such as ceilings, internal partition walls, curtain walls and contents; ② resilience of communities, cities and even regions; and ③ multi-disciplinary research on resilient structural systems based on artificial intelligence. Between 2015 and 2020, 24 core papers relevant to this research front were published. These papers received 1 437 citations, with an average of 59.88 citations per paper.

(8)   Flow-induced vibration of flexible structures and anti- vibration measures

Flexible structures are widely used in engineering practice mostly in slender forms with circular, wing, or blunt sections. The examples of flexible structures are the submarine pipelines, offshore platform risers, power transmission lines, high-rise structures, and main girders and cables of large-span bridges. Under the action of wind/water flows, flexible structures are susceptible to different forms of flow- induced vibrations, including the vortex-induced vibration, buffeting, fluttering, and galloping. Flow-induced vibrations of these structures exhibit highly complicated non-linearity, being affected by the properties of the fluids (e.g., laminar/ turbulent flow characteristics, boundary layer separation, vortex shedding, and shear layer effects), the properties of the structures (e.g., mass, damping, stiffness, and boundary conditions), and the fluid-structure interaction. Additionally, the wake caused by an upstream structure affects the flow field in the downstream, making the dynamics design and vibration control of flexible structures even more complicated.

The research topics include: ① the theory of flow vibration of flexible structures with circular/non-circular cross- sections; ② the fluid-structure interaction analysis based on computational fluid dynamics and structural dynamics; and ③ active/passive control of flow-induced vibration of flexible structures. The future research trends are: ① the mechanism of vortex-induced vibration and galloping of flexible structures and energy harvesting of non-linear vibrations; ② the flow- induced vibration of multiple tandem flexible structures and vibration reduction; ③ multi-scale computational fluid dynamics methods for flexible structures in a high-Reynolds-number flow; and ④ data-driven methods for extracting flow field features and analyzing fluid-structure interaction.

Between 2015 and 2020, 22 core papers relevant to this research front were published. These papers received 567 citations, with an average of 25.77 citations per paper.

(9)  Geographic big-data knowledge graph construction

The geographic big-data knowledge graph is a knowledge- based system that uses a semantic network to describe geographic concepts, entities, and their relations. It provides systematic and deep structured geographic knowledge, and is the key to upgrade geographic information service to geographic knowledge service. The geographic big-data knowledge graph has application prospects in geographic knowledge understanding, geological problem solution, and spatiotemporal prediction and decision-making.

The research directions may involve: ① the geographic knowledge expression model, which is constructed across spatiotemporal dimensions based on the general graph model of knowledge expression by integrating the complex spatiotemporal characteristics, calculation attributes, relation and rules in geoscience knowledge; ② the construction of a geoscience knowledge graph, including the  crowd-based cooperative construction method and the multi-modal dynamic construction method based on depth analysis; and ③ geographic knowledge reasoning, which attempts to establish new associations between geographical entities, understand the evolution characteristics of geoscience knowledge systems, and find new geoscience knowledge by using the relationship between entity concepts in the geographical knowledge graph and by computer reasoning. Between 2015 and 2020, 15 core papers relevant to this research front were published. These papers received 414 citations, with an average of 27.60 citations per paper.

(10)   Disaster monitoring and mechanism analysis of bridge structure dynamic multi load coupled action

Bridges in operation receive various loads caused by wind, ground motion, traffic flow, ship collision, scouring, debris flow, and temperature change. The combined action of the loads leads to rich dynamic disaster behaviors of the bridges. Observing and understanding these catastrophes has practical guiding significance and scientific value. In recent years, relevant research has developed to analyze the process considering the interaction from single load to combined loads. The research directions include: ① analysis and observation of coupled vibration response of long-span bridges considering vehicle-wind-bridge interaction; ② seismic and ship collision safety analysis of arch bridges and beam bridges considering pier scouring; ③ analysis and monitoring of derailment safety and driving comfort of high-speed railway bridges under a sudden earthquake; ④ seismic risk analysis of tropical and subtropical rigid frame bridges considering temperature load; and ⑤ seismic dynamic safety analysis of mountain bridges under flood and debris flow. The future trend is to monitor the emergence of dynamic disasters in the system of in-service bridges, to understand the onset, the phase transition and the inducing factors of structural dynamic disaster behavior, and to provide theoretical guidance for the life-cycle performance regulation, management and maintenance of bridges. Between 2015 and 2020, 71 core papers relevant to this research front were published. These papers received 1 634 citations, with an average of 23.01 citations per paper.

《1.2 Interpretations for three key engineering research fronts》

1.2 Interpretations for three key engineering research fronts

1.2.1 The eco-environmental effects of interbasin water transfer

The global climate change increases the uncertainties of temporal and spatial distribution of water resource. Interbasin water transfer projects effectively relieve the contradiction between water supply and demand of different regions by diverting water within and between river basins, which optimizes the allocation of water resources. Therefore, the interbasin water transfer projects play an increasingly important role in global water supply systems, which normally have long distance transfer lines and divert large volumes of water. Meanwhile, they significantly affect the ecological environment of water donating and receiving basins as well as the areas along transfer routes, and the resulting eco- environmental effects are complex, comprehensive, and hysteretic.

Currently, the major topics of this research front include:

1)   The response of hydrological regimes in water transfer affected areas to the re-allocation of water resources, which covers: ① the change of fluvial morphology and the impact on aquatic habitat in concerned areas caused by water division; ② the influence of water reduction in the donating basin on the water regime in a downstream reach; and ③ the influence of re-allocation of water resources on spatiotemporal distribution and physic-chemical characteristics of underground water in affected basins.

2)  The influence of water diversion on biodiversity of aquatic ecosystem of affected basins, which covers: ① the evolution of ecosystem structure and function in affected areas caused by change of water quantity and aquatic habitat; and ② the species migration and invasion phenomenon breaking biogeographic barriers triggered by water transfer.

3)   The trend and characteristics analysis of source water quality change in the water transfer process, which covers: ① simulation and prediction of source water quality during long-distance transfer based on water quality-quantity models; ② migration and transformation of key pollutants in transferred water; and ③ the effects and particularly the ecological impact of the water transfer on nutrient structure of water body in receiving basins.

As shown in Table 1.1.1, 26 core papers concerning “the eco- environmental effects of interbasin water transfer” were published between 2015 and 2020, with each paper being cited 32.38 times on average. The top five countries in terms of output of core papers on this topic are China, the USA, the UK, Australia, and Iran (Table 1.2.1). China is one of the most active countries, having published 42.31% of the core papers.

The five countries with the highest average citations were Laos, New Zealand, Singapore, Thailand, and the USA. The papers published by Chinese authors were cited 33.55 times on average, which is slightly above the overall average. As illustrated by the international collaborative network depicted in Figure 1.2.1, close cooperation was observed among the most productive Top 10 countries.

The five institutions that published the most core papers were Chinese Academy of Sciences, Wuhan University, China Institute of Water Resources and Hydropower Research, University of Oxford, and Xi’an University of Technology (Table 1.2.2). Chinese Academy of Sciences focuses on the investigation of migration and transformation characteristics of key pollutants; Wuhan University focuses on the analysis and modelling of water quality and quantity trends during water transfer; and China Institute of Water Resources and Hydropower Research focuses on the investigation of the conflict and balance between water supply and riverine ecosystem protection. As illustrated in Figure 1.2.2, the ten most productive institutions have conducted collaborative studies in this regard.

As shown in Table 1.2.3, the five most active countries in terms of paper citations were China, the USA, India, the UK, and Australia. The top five institutions in terms of citations of core papers were Chinese Academy of Sciences, Chang’an University, Hohai University, Wuhan University, and China Institute of Water Resources and Hydropower Research (Table 1.2.4). China ranked first in terms of the quantity of core papers produced and the number of citations of core papers, indicating that Chinese

《Table 1.2.1》

Table 1.2.1 Countries with the greatest output of core papers on “the eco-environmental effects of interbasin water transfer”

No. Country Core papers Percentage of core papers Citations Citations per paper Mean year
1 China 11 42.31% 369 33.55 2018.5
2 USA 8 30.77% 327 40.88 2017.9
3 UK 4 15.38% 91 22.75 2018.5
4 Australia 3 11.54% 117 39 2017.3
5 Iran 2 7.69% 63 31.5 2017.5
6 Canada 2 7.69% 21 10.5 2020
1 Laos 1 3.85% 95 95 2019
8 New Zealand 1 3.85% 95 95 2019
9 Singapore 1 3.85% 95 95 2019
10 Thailand 1 3.85% 95 95 2019

《Table 1.2.2》

Table 1.2.2 Institutions with the greatest output of core papers on “the eco-environmental effects of interbasin water transfer”

No. Institution Core papers Percentage of core papers Citations Citations per paper Mean year
1 Chinese Academy of Sciences 4 15.38% 94 23.5 2019.2
2 Wuhan University 3 11.54% 87 29 2016.3
3 China Institute of Water Resources and Hydropower Research 3 11.54% 65 21.67 2019.3
4 University of Oxford 2 7.69% 55 27.5 2018
5 Xi'an University of Technology 2 7.69% 46 23 2019.5
6 Chang'an University 1 3.85% 111 111 2019
7 International Water Management Institute 1 3.85% 95 95 2019
8 Singapore University of Technology and Design 1 3.85% 95 95 2019
9 Stockholm Environment Institute 1 3.85% 95 95 2019
10 Thuyloi University 1 3.85% 95 95 2019

《Figure 1.2.1》

Figure 1.2.1 Collaboration network among major countries in the engineering research front of “the eco-environmental effects of

《Figure 1.2.2》

Figure 1.2.2 Collaboration network among major institutions in the engineering research front of “the eco-environmental effects of interbasin water transfer”

researchers pay close attention to this front.

Summarizing the above statistics, Chinese scholars have performed well and gradually leads the research of “the eco- environmental effects of interbasin water transfer”.

1.2.2 Resilience improvement of transportation infrastructure

Transportation infrastructure is a basis of cities. Improving the resilience of transportation infrastructure can avoid high maintenance costs and significantly reduce the impact of natural hazards on mankind. At present, transportation resilience has become an essential part of urban resilience, and resilient transportation infrastructure is characterized by four primary features: robustness, reliability, redundancy, and recoverability. The relevant research has gradually expanded from single-facility resilience design to the network resilience assessment and system analysis.

The research topics of this front include:

1)   Theoretical frameworks for improving the resilience of transportation infrastructure under extreme climatic conditions, which covers: ① quantitatively assessing the impact of climate change and natural hazards on transportation infrastructure in different regions; ② developing hazard warning systems for transportation infrastructure; and ③ establishing evacuation models and economic loss prediction models under natural hazards.

《Table 1.2.3》

Table 1.2.3 Countries with the greatest output of citing papers on “the eco-environmental effects of interbasin water transfer”

No. Country Citing papers Percentage of citing papers Mean year
1 China 377 38.59% 2019.6
2 USA 174 17.81% 2019.4
3 India 84 8.60% 2019.8
4 UK 75 7.68% 2019.8
5 Australia 65 6.65% 2019.1
6 Iran 48 4.91% 2019.6
7 Germany 35 3.58% 2019.2
8 Brazil 33 3.38% 2019.6
9 Netherlands 31 3.17% 2020
10 Spain 29 2.97% 2019.6

《Table 1.2.4》

Table 1.2.4 Institutions with the greatest output of citing papers on “the eco-environmental effects of interbasin water transfer”

No. Institution Citing papers Percentage of citing papers Mean year
1 Chinese Academy of Sciences 85 23.48% 2019.6
2 Chang^n University 54 14.92% 2019.7
3 Hohai University 32 8.84% 2019.7
4 Wuhan University 28 7.73% 2019.3
5 China Institute of Water Resources and Hydropower Research 28 7.73% 2019.5
6 Xi'an University of Technology 25 6.91% 2019.8
7 Michigan State University 25 6.91% 2018.8
8 U n iversity of Oxfo rd 25 6.91% 2019.4
9 Beijing Normal University 23 6.35% 2018.9
10 The University of Melbourne 21 5.80% 2018.7

2)   Evaluation and node analysis theory of transportation infrastructure network. The transportation infrastructure network is interconnected, and thus a single transportation asset cannot maintain resilience to all risks. The following issues receive research interests: ① developing an assessment model of the criticality and complexity of the transportation infrastructure network; ② optimizing the network recovery strategy under emergency conditions; and ③ proposing a multi-objective network decision support system.

3)   Resilience improvement of transportation infrastructure under new disaster modes. With the widespread application of intelligent transportation system (ITS) and the increasing urban network connection, new disaster modes such as cyber attacks, terrorist attacks, and the spread of infectious diseases cannot be ignored. With the multi-integrated data fusion technology, the following issues are of interest: ① developing the multi-level resilience analysis of the information layer of transportation infrastructure; and ② application of ITS in pre-disaster prediction, disaster response, and post-disaster rescue.

4)   User resilience of transportation infrastructure, which covers: ① from the perspective of policy, establishing a pre- and post-disaster risk management decision support framework, and developing a pre-disaster investment decision model for transportation infrastructure; and ② from the perspective of users, building adaptive and self-healing transportation infrastructure with low-impact intelligent construction technology and intelligent maintenance technology.

As listed in Table 1.1.1, 29 core papers concerning “resilience improvement of transportation infrastructure” were published between 2015 and 2020, with each paper being cited an average 22.28 times. The top five countries in terms of core-paper output were the USA, China, the UK, Colombia, and Greece (Table 1.2.5). China was one of the most active countries on this front, producing 20.69% of the core papers. The top five countries in terms of the average number of citations were the Saudi Arabia, the USA, the UK, Malaysia, and China. In terms of core-paper citations, papers published by Chinese authors were cited 16.00 times on average, indicating that researchers in China are gradually gaining attention. As illustrated by the international collaborative network depicted in Figure 1.2.3, relatively close cooperation was observed between the USA and China.

As listed in Table 1.2.6, the five institutions publishing the highest number of core papers were University of Illinois, Shanghai Jiao Tong University, the University of Oklahoma, University of Maryland, and the Hong Kong Polytechnic University. In recent years, the top two institutions on this research front are Shanghai Jiao Tong University and University of Illinois. These two institutions focused on the assessment of the vulnerability and resilience of transportation infrastructure. As illustrated in Figure 1.2.4, the ten most productive institutions have conducted collaborative studies.

The five countries with the most citations of core papers were the USA, China, the UK, Iran, and Canada (Table 1.2.7). The five institutions with the most citations of core papers were

《Table 1.2.5》

Table 1.2.5 Countries with the greatest output of core papers on “resilience improvement of transportation infrastructure”

No. Country Core papers Percentage of core papers Citations Citations per paper Mean year
1 USA 16 55.17% 489 30.56 2017.5
2 China 6 20.69% 96 16 2017.2
3 UK 2 6.90% 37 18.5 2017
4 Colombia 2 6.90% 24 12 2019
5 Greece 2 6.90% 17 8.5 2017
6 Saudi Arabia 1 3.45% 32 32 2015
7 Malaysia 1 3.45% 18 18 2019
8 France 1 3.45% 11 11 2019
9 Netherlands 1 3.45% 11 11 2019
10 Norway 1 3.45% 11 11 2019

《Table 1.2.6》

Table 1.2.6 Institutions with the greatest output of core papers on “resilience improvement of transportation infrastructure”

No. Institution Core papers Percentage of core papers Citations Citations per paper Mean year
1 University of Illinois 2 6.90% 101 50.5 2017.5
2 Shanghai Jiao Tong University 2 6.90% 34 17 2017
3 The University of Oklahoma 1 3.45% 123 123 2016
4 University of Maryland 1 3.45% 117 117 2015
5 The Hong Kong Polytechnic University 1 3.45% 32 32 2015
6 King Saud University 1 3.45% 32 32 2015
7 Missouri University of Science and Technology 1 3.45% 32 32 2015
8 The University of Kansas 1 3.45% 32 32 2015
9 Lancaster University 1 3.45% 32 32 2015
10 University of Washington 1 3.45% 24 24 2015

《Figure 1.2.3》

Figure 1.2.3 Collaboration network among major countries in the engineering research front of “resilience improvement of transportation

《Figure 1.2.4》

Figure 1.2.4 Collaboration network among major institutions in the engineering research front of “resilience improvement of transportation infrastructure”

Delft University of Technology, the Hong Kong Polytechnic University, University of Illinois, Tsinghua University, and University of Tehran (Table 1.2.8).

Based on the above statistics, China ranked second in terms of both the number of published core papers and the number of citations of core papers. Chinese scholars have paid close attention to this research front; however, Chinese scholars rarely conducted international collaboration.

1.2.3 Low-carbon long-life cement-based materials

Cement and concrete are the largest manufactured products on Earth by mass. China consumes about 60% of the global production of cement, which contributes about 10% to total CO2 emissions in the country. Therefore, reducing the CO2 emission during cement production and application is likely to be important in achieving CO2 emission peak in 2030, and carbon neutrality in 2060. The CO2 emission arises from fossil fuel combustion and limestone decomposition during calcination. Nowadays, technologies including furnace heat preservation, waste heat recovery and utilization, co- processing of waste, renewable fuels and energy have been widely used in cement manufacture to minimize the energy consumption and CO2 emission. It is difficult to further reduce the CO2 emission relying solely on the upgrading of calcination process and equipment. Therefore, it is crucial to develop low-carbon long-life cement-based materials with the concept

《Table 1.2.7》

Table 1.2.7 Countries with the greatest output of citing papers on “resilience improvement of transportation infrastructure”

No. Country Citing papers Percentage of citing papers Mean year
1 USA 210 32.71% 2019.3
2 China 187 29.13% 2019.5
3 UK 51 7.94% 2019.3
4 Iran 31 4.83% 2019
5 Canada 30 4.67% 2019.7
6 Australia 24 3.74% 2019.4
7 France 23 3.58% 2019.2
8 Italy 23 3.58% 2019.2
9 India 22 3.43% 2019.3
10 South Korea 22 3.43% 2019.7

《Table 1.2.8》

Table 1.2.8 Institutions with the greatest output of citing papers on “resilience improvement of transportation infrastructure”

No. Institution Citing papers Percentage of citing papers Mean year
1 Delft University of Technology 14 12.50% 2019.7
2 The Hong Kong Polytechnic University 14 12.50% 2019.6
3 University of Illinois 11 9.82% 2019.6
4 Tsinghua University 10 8.93% 2020.1
5 University of Tehran 10 8.93% 2019.4
6 Tongji University 10 8.93% 2020.3
7 Dalian Maritime University 9 8.04% 2020.8
8 Huazhong University of Science and Technology 9 8.04% 2019.4
9 Beijing Jiaotong University 9 8.04% 2020.7
10 Zhejiang University 8 7.14% 2020

of low CO2 emission by widening the range of raw material sources in order to meet the requirement of long service life and environmental protection.

The research directions of this front are as follows:

1)  Life-cycle assessment of carbon footprint of cement-based materials, which aims at comprehensive analytical models considering multiple factors (e.g., environment protection, energy saving, carbon footprint reduction, and cost reduction) for quantifying CO2 emission during the production and application of cement-based materials.

2)   Low-carbon transformation of cement-based materials, which covers: ① reducing clinker by increasing the use of supplementary cementitious materials; ② use of recycled aggregates; and ③ improvement in the mechanical properties of cement-based materials to satisfy the performance requirement of structures with reduced component sizes and concrete usage.

3)  Development and application of novel low-carbon binding materials. New binding materials with low CO2 emission, such as limestone calcined clay cement, alkali activated materials, can be designed and developed by using tailings, industrial waste and construction waste, with various activation technologies.

4)  Service life extension of cement-based materials. Durability improvement, surface protection and repair technologies of low carbon cement-based materials can be developed to extend the life of concrete structures, thereby reducing the amount of cement usage in their life cycle.

5)   Recarbonation of existing concrete structures, and new technologies for carbon capture, utilization and storage. The following issues are of interest: ① enhancing the level of CO2 uptake by concrete through recarbonation; ② capturing CO2 generated from cement calcination by oxy-fuel combustion, and physical and chemical adsorption; ③ storing carbon in geological or ocean reservoirs; and ④ recycling captured carbon in the manufacture and curing of concrete products containing carbonation-hardening materials.

As listed in Table 1.1.1, 84 core papers concerning “low-carbon long-life cement-based materials” were published between 2015 and 2020, and on average each paper was cited 102.95 times. The top five countries in terms of core-paper output were China, the UK, Australia, India, and the USA (Table 1.2.9). As one of the leading research countries, China published 35.71% of the core papers on this research front. The top five countries in terms of the average number of citations were the UK, India, the USA, Brazil, and China. On average, the papers published by Chinese authors received 99.10 citations, which indicates that there is a room for improvement by Chinese scholars on this front. From the perspective of cooperation networks between countries (Figure 1.2.5), close cooperation was observed among the most productive ten countries particularly between China and Australia.

The five institutions producing the most core papers on this front are Hunan University, the Hong Kong Polytechnic University, Tongji University, Universiti Teknologi Malaysia, and The University of Sheffield (Table 1.2.10). Hunan University is leading in the development and application of novel low-carbon cement-based materials, especially alkali activated materials. Both Hong Kong Polytechnic University and Tongji University are leaders in the area of recycled aggregates in concrete, and the life-cycle assessment of the carbon footprint of concrete. From the perspective of cooperation networks among the leading institutions (Figure 1.2.6), collaborative studies have been conducted by the Top 10 most productive institutions on this front, except for Universiti Teknologi Malaysia, University of Lisbon, and Western Sydney University.

The top five countries in terms of citations of core papers are China, the USA, Australia, India, and the UK (Table 1.2.11). The top five institutions in terms of citations of core papers are Tongji University, Wuhan University of Technology, the Hong Kong Polytechnic University, Hunan University, and Shenzhen University (Table 1.2.12). China ranked first in terms of the number of published core papers and citations of core papers, indicating that Chinese researchers have paid close attention to research performed on this front.

Summarizing the above statistics, Chinese scholars are gradually becoming leaders on this research front.

《Table 1.2.9》

Table 1.2.9 Countries with the greatest output of core papers on “low-carbon long-life cement-based materials”

No. Country Core papers Percentage of core papers Citations Citations per paper Mean year
1 China 30 35.71% 2 973 99.1 2017.5
2 UK 12 14.29% 2130 177.5 2017.2
3 Australia 11 13.10% 1073 97.55 2016.5
4 India 7 8.33% 1159 165.57 2017.3
5 USA 7 8.33% 1120 160 2016.7
6 Canada 6 7.14% 425 70.83 2017.5
7 Malaysia 6 7.14% 291 48.5 2018.5
8 Brazil 5 5.95% 749 149.8 2017.4
9 South Korea 4 4.76% 383 95.75 2016.5
10 Portugal 4 4.76% 382 95.5 2016.8

《Table 1.2.10》

Table 1.2.10 Institutions with the greatest output of core papers on “low-carbon long-life cement-based materials”

No. Institution Core papers Percentage of core papers Citations Citations per paper Mean year
1 Hunan University 9 10.71% 1339 148.78 2016.8
2 The Hong Kong Polytechnic University 6 7.14% 573 95.5 2015.8
3 Tongji University 5 5.95% 269 53.8 2018.2
4 Universiti Teknologi Malaysia 5 5.95% 259 51.8 2018.4
5 The University of Sheffield 4 4.76% 941 235.25 2017.2
6 University of Lisbon 4 4.76% 382 95.5 2016.8
7 Central South University of Forestry and Technology 3 3.57% 473 157.67 2015.3
8 WOWA International Engineering & Consulting Co., Ltd. 3 3.57% 473 157.67 2015.3
9 Western Sydney University 3 3.57% 285 95 2017.7
10 The Hong Kong University of Science and Technology 3 3.57% 259 86.33 2017

《Figure 1.2.5》

Figure 1.2.5 Collaboration network among major countries in the engineering research front of “low-carbon long-life cement-based materials”

《Figure 1.2.6》

Figure 1.2.6 Collaboration network among major institutions in the engineering research front of “low-carbon long-life cement-based materials”

《Table 1.2.11》

Table 1.2.11 Countries with the greatest output of citing papers on “low-carbon long-life cement-based materials”

No. Country Citing papers Percentage of citing papers Mean year
1 China 1896 37.23% 2019.5
2 USA 564 11.08% 2019.4
3 Australia 468 9.19% 2019.3
4 India 431 8.46% 2019.5
5 UK 327 6.42% 2019.2
6 Spain 284 5.58% 2019.3
7 Malaysia 252 4.95% 2019.2
8 Brazil 250 4.91% 2019.4
9 South Korea 209 4.10% 2019.2
10 Italy 206 4.05% 2019.2

《Table 1.2.12》

Table 1.2.12 Institutions with the greatest output of citing papers on “low-carbon long-life cement-based materials”

No. Institution Citing papers Percentage of citing papers Mean year
1 Tongji University 141 13.61% 2019.7
2 Wuhan University of Technology 120 11.58% 2019.3
3 The Hong Kong Polytechnic University 114 11.00% 2019.3
4 Hunan University 106 10.23% 2019.1
5 Shenzhen University 103 9.94% 2019.8
6 Southeast University 96 9.27% 2019.1
7 University of Lisbon 91 8.78% 2019.2
8 Harbin Institute of Technology 77 7.43% 2019.6
9 Universiti Teknologi Malaysia 65 6.27% 2019.2
10 Xi'an University of Architecture and Technology 62 5.98% 2019.6

《2 Engineering development fronts》

2 Engineering development fronts

《2.1 Trends in Top 10 engineering development fronts》

2.1 Trends in Top 10 engineering development fronts

The Top 10 engineering development fronts in the field of civil, hydraulic, and architectural engineering are summarized in Table 2.1.1. These fronts cover a variety of disciplines, including structural engineering, municipal engineering, surveying and mapping engineering, transportation planning, construction materials, geotechnical and underground engineering, urban planning and landscaping, and hydraulic engineering. The following development fronts were from expert nomination: “intelligent and integrated sewage treatment device for village and town”, “infrastructure construction technology of the high-speed maglev over 600 km/h”, “technology for safety of hydraulic structures under multiple hazards”, and “monitoring, evaluation, and optimization technology of complex transportation network resilience”. The remaining topics were identified from patent maps and confirmed in expert panel meetings. Table 2.1.2 presents annual statistics on patents published between 2015 and 2020 related to these Top 10 development fronts.

(1)    Intelligent construction technology for building engineering

The intelligent construction technology for building engineering arises from the integration of the new-generation information technology and building engineering. The new- generation information technology featurs digitalization, networking, and intelligence, and it is enhanced in calculations, algorithms, computing power. Based on digitization of engineering construction element resources, technologies including standardized modeling, networked interaction, visual cognition, high-performance computation, and intelligent decision support are developed. The integrated and high-efficiency coordination of building engineering project planning, design, construction production, operation and maintenance services, and circular consumption are driven by the digital chain. The technologies are adopted to continuously expand the construction value chain of building engineering, and transform the ecological chain of industrial structures. The goal is to deliver people-oriented, green and sustainable intelligent building engineering products and services. The technical directions include: ① building engineering digital modeling and interactive simulation; ② building engineering ubiquitous perception and broadband Internet of Things; ③ building engineering

《Table 2.1.1》

Table 2.1.1 Top 10 engineering development fronts in civil, hydraulic, and architectural engineering

No. Engineering development front Published patents Citations Citations per patent Mean year
1 Intelligent construction technology for building engineering 107 625 5.84 2018
2 Intelligent and integrated sewage treatment devices for village and town 82 106 1.29 2017.7
3 Indoorand outdoor integrated high-precision positioning and navigation system 85 425 5 2017.8
4 Infrastructure construction technology of the high-speed maglev over 600 km/h 54 17 0.31 2019.4
5 Efficient resource utilization technology of solid waste in civil engineering 339 598 1.76 2018.2
6 Industrialized construction of underground space 132 234 1.77 2017.4
7 Multi-scale and multi-element digital twin city perception and simulation technology 137 371 2.71 2018.8
8 Technology for safety of hydraulic structures under multiple hazards 24 75 3.13 2017.3
9 Monitoring, evaluation, and optimization technology of complex transportation network resilience 274 1599 5.84 2017.3
10 Technology on bio-inspired crack sensing and self-healing of concrete 88 1419 16.13 2016.6

《Table 2.1.2》

Table 2.1.2 Annual number of core patents published for the Top 10 engineering development fronts in civil, hydraulic, and architectural engineering

No. Engineering development front 2015 2016 2017 2018 2019 2020
1 Intelligent construction technology for building engineering 12 7 15 23 32 18
2 Intelligent and integrated sewage treatment devices for village and town 3 7 21 28 14 8
3 Indoorand outdoor integrated high-precision positioning and navigation system 11 8 15 14 15 20
4 Infrastructure construction technology of the high-speed maglev over 600 km/h 0 0 3 3 17 31
5 Efficient resource utilization technology of solid waste in civil engineering 20 34 34 54 79 107
6 Industrialized construction of underground space 9 23 35 28 14 17
7 Multi-scale and multi-element digital twin city perception and simulation technology 3 5 8 24 44 52
8 Technology for safety of hydraulic structures under multiple hazards 7 0 0 5 8 2
9 Monitoring, evaluation, and optimization technology of complex transportation network resilience 25 32 35 35 58 53
10 Technology on bio-inspired crack sensing and self-healing of concrete 24 23 14 19 8 0

factory manufacturing and machine construction; ④ building engineering artificial intelligence and auxiliary decision- making; and ⑤ key technologies for green, low-carbon and eco-friendly construction. The intelligent construction technology has become the main developing trend of building engineering technology. The focus of this development front is to promote the transformation of traditional building construction to intelligent construction by fully exploring and applying artificial intelligence technologies (represented by big data intelligence, human-machine hybrid enhanced intelligence, and brain-like intelligence), and taking advantage of the unique value of the technologies in active perception, autonomous learning, analysis and knowledge application. Between 2015 and 2020, 107 patents relevant to this research front were published. These patents received 625 citations, with an average of 5.84 citations per patent.

(2)  Intelligent and integrated sewage treatment devices for village and town

The intelligent and integrated sewage treatment devices for village and town refer to integrated devices that can be monitored and controlled intelligently and are suitable for small-scale and decentralized sewage treatment in villages and towns. Such devices provide an effective way to achieve the extensive collection, efficient treatment and centralized management of discharged wastewater. The technical directions include: ① integrated sewage treatment devices driven by gravitational potential energy, wind energy and solar energy, and purification and reuse technology using biotechnology and ecological technology; ② low-cost and high-reliability online intelligent sensors of water quality based on optical and electronic methods, and remote data transmission and control system; ③ predictive and early- warning models of sewage plant operation states based on the activated sludge model coupled with artificial intelligence deep learning algorithm; and ④ a new intelligent maintenance mode of sewage treatment devices featuring “unattended– cloud diagnosis–cloud early warning–mobile maintenance”. The main development trend of this front is to integrate multi-disciplinary knowledge, such as water pollution control engineering, microbiology, instrument science, artificial intelligence and internet of things, for developing intelligent integrated sewage treatment devices and their operation and cloud management modes with low consumption, high efficiency and easy maintenance. Between 2015 and 2020, 82 patents relevant to this research front were published. These patents received 106 citations, with an average of 1.29 citations per patent.

(3)  Indoor and outdoor integrated high-precision positioning and navigation system

The indoor and outdoor integrated high-precision positioning and navigation system integrates the technology of outdoor and indoor systems in a common terminal to provide users with indoor and outdoor location information services. It has wide application in scenarios such as warehousing and logistics, smart elderly care, special hospitals, smart factories, community correction, and mall management.

The development trends of this front include: ① indoor and outdoor combination positioning technology for integrated seamless and high-precision positioning under different spatial scenes; ② multi-sensor information fusion technology, which improves indoor and outdoor positioning accuracy by fusing multi-sensor positioning information from such as inertial measurement equipment, satellite navigation equipment, magnetic sensors and vision equipment; and ③ the low-power positioning signal transmitting and receiving device, which enables low-power transmission of positioning and communication signals through low-power wide-area network (LPWAN), and therefore improves the endurance and standby time of positioning and navigation systems. Between 2015 and 2020, 85 patents relevant to this research front were published. These patents received 425 citations, with an average of 5.00 citations per patent.

(4)  Infrastructure construction technology of the high-speed maglev over 600 km/h

The infrastructure construction technology of the high-speed maglev over 600 km/h involves the design, construction, and maintenance of the infrastructure for ensuring the safe and stable operation of the maglev system. At present, the high- speed maglev over 600 km/h has been off the production line, but the infrastructure construction technology of medium- long-distance lines that meet the engineering requirements is not mature and restricts the further application of high-speed maglevs. Systematic research is desired for fundamental theory and experimental verification. The coupling of high-speed maglev vehicles and infrastructure is the basic theoretical support of infrastructure construction technology, involving many disciplines such as structural dynamics, electromagnetic control theory, and superconducting electrokinetics. In addition, high-speed maglev infrastructure faces severe challenges such as complex health monitoring, maintenance environment, and high safety risks, while the corresponding comprehensive technology of the traditional wheel/rail transport infrastructure presents difficulty in satisfying  the aforementioned requirements. The development directions include: ① the theory of high-speed maglev vehicle- infrastructure coupling dynamics; ② comprehensive test platforms for high-speed maglev infrastructure; ③ the evolution mechanism and countermeasures of high-speed maglev infrastructure structures and material performance under complex service environments; and ④ the intelligent dynamic detection method and the maintenance technology of high-speed maglev infrastructure. The main development trends in the future are as follows: ① engineering verification of key technologies of infrastructure construction in the  medium-long-distance lines; ② the long-term service performance and the evolution mechanism of high-speed maglev infrastructure; and ③ the intelligent detection and monitoring technology of infrastructure. Between 2015 and 2020, 54 patents were published on this topic with 17 patent citations and an average of 0.31 citations per patent.

(5)  Efficient resource utilization technology of solid waste in civil engineering

Solid waste refers to any solid garbage, refuse, or discards that are produced from human activities. As a way of turning waste into resources, solid waste obtained from the steel industry, the coal industry, the non-ferrous metals industry, the chemical engineering industry, the architecture industry, the mining industry, the agriculture industry, and the waste management industry can all be utilized to produce building materials and products. These techniques reduce the cost of waste disposal and mitigate the depletion of natural resources by the construction industry. They are considered important tools in circular economy and sustainable development. Solid waste can be reused to produce building materials by different means. Depending on the physical and chemical properties of wastes, the approaches include: ① waste consist of siliceous-aluminous glasses can be used as supplementary cementitious materials for concrete production, mineral additives for cement production, alternative raw materials for cement clinkering, or raw materials for preparing alternative binders, e.g., alkali activated materials; ② waste consist mainly of calcium sulfate can be used in cement manufacture, dry-mix mortar manufacture, or for producing gypsum board; ③ waste with low calcium content and chemical reactivity, e.g., river sludge, excavated soil, and tailings, can be used for road backfill or for manufacturing building masonries; ④ waste concrete and other bulky wastes can be used as aggregates for concrete manufacture; and ⑤ fibrous bio- wastes can be used for manufacturing board and batten.

Stakeholders from the waste management industry are interested in new techniques aiming to increase the reuse of wastes and enhance the safety of the products. Their concerns may include: ① improvement of the chemical reactivity of waste materials; ② development of new approaches for waste treatment and reuse; and ③ minimization of the potential hazards relating to certain wastes. Stakeholders from the cement, concrete, and construction industry, however, will be interested in: ① establishing new theories to improve the performance of materials prepared from waste materials; and ② optimizing the allocation of high-quality resources within the industry. Between 2015 and 2020, 339 patents relevant to this research front were published. These patents received 598 citations, with an average of 1.76 citations per patent.

(6)  Industrialized construction of underground  space

Building industrialization features pre-manufactured structural elements and prefabricated construction. With design procedure standardized, structural elements componentized, construction mechanized, and management informationized, building industrialization develops a new sustainable mode of building production that aims at creating energy-saving, environmentally friendly, and life-cycle value maximized building products. With the increasing demand for underground space usage and the development of prefabricated construction technology, the industrialization of underground space construction has become an important part of building industrialization, and the application extends from traditional shield tunnels to more complicated multi- functional ones such as prefabricated subway stations, pipe galleries, and shaft garages. The technical directions include: ① standardization and serialization of the components forming complex underground structure systems; ② prefabricated construction technology and intelligent equipment that  adapt to complex underground construction conditions; ③ resilience improvement of prefabricated underground structural systems that resist extreme disasters; ④ research and development of new waterproof and seismic materials suitable for prefabricated underground structures; and ⑤ information technology supporting the industrialization of underground space construction. The technologies for industrialized construction of underground space are progressing towards increasingly complex and large-space underground projects. Between 2015 and 2020, 132 patents relevant to this research front were published. These patents received 234 citations, with an average of 1.77 citations per patent.

(7)  Multi-scale and multi-element digital twin city perception and simulation technology

The urban digital twin city built with the complex and comprehensive technology is a future form of cities where virtual and physical realities co-exist and co-evolve. It operates with advanced intelligence in a data-driven mode that combines online and offline approaches. Its main features include digitization and virtualization of all urban elements, real-time visualization of all statuses, synergy among various sectors for the city’s intelligent operation, full coverage, and a smart decision-making process from sensing, detecting, warning, simulation, computation to assessment. From a space perspective, the development of digital twin city technologies should cover various scales including national, regional, city, neighborhood, and building scales. In terms of elements, the requirement is for urban sensing to extend from the physical aspects to the natural, economic, and ecological ones. To shape urban digital twinning for all scales and all elements requires the key technologies of smart cities, city information model, the smart systems for cities and neighborhoods with the help of the internet of things, edge computing, deep learning, and active perception. The key directions of these technologies include: ① serving a people-oriented city, by accurately predicting population and activity characteristics with multi-source big data, creating an intelligent and convenient digital public service system, and building a vibrant digital life service ecosystem; ② serving modern governance, by promoting the development of urban delicacy, intelligent and high-quality management via data empowerment; and ③ maintaining urban resilience and safety, by studying global perception and transparency of three-dimensional topology and physical information of each element with integrated multi-source sensors, and constructing distributed multi-level digital twinning to facilitate life-cycle digitization and to improve the safety of disaster prevention and mitigation. Between 2015 and 2020, 137 patents relevant to this research front were published. These patents received 371 citations, with an average of 2.71 citations per patent.

(8)   Technology for safety of hydraulic structures under multiple hazards

Hydraulic structures may encounter a variety of severe natural hazards during operation, such as extreme rainfall and strong earthquakes. These hazards could subsequently trigger secondary geological disasters such as large- scale river landslides and mudslides, which cause further failure such as swells in reservoir areas, dam breaks, and floods. A combination of multiple disastrous factors could catastrophically impact the safety of the hydraulic structures within the affected areas, pose system risks to the entire watershed, and damage the cascade reservoir group. The technology for safety of hydraulic structures under multiple hazards aims to improve the structures’ resistance to multiple hazards and to reduce system risks, especially in seismically active areas threatened by frequent geological and meteorological disasters. The technical directions include: ① spatiotemporal characteristics of the chain effect of earthquake-geology-flood disasters and the relevant evaluation methods; ② technologies and measures for assessing, preventing, and controlling catastrophic  risk; ③ numerical simulations and risk deduction of extreme scenarios considering over-standard floods, strong earthquakes, and superposed effect of extraordinarily large geological disasters; and ④ multi-dimensional safety control and risk management system for water engineering at the watershed scale. Between 2015 and 2020, 24 patents relevant to this research front were published. These patents received 75 citations, with an average of 3.13 citations per patent.

(9)   Monitoring, evaluation, and optimization technology of complex transportation network resilience

Resilience characterizes a system’s ability to resist, absorb, adapt and recover from internal and external risks throughout the life cycle of the system. Transportation systems are core parts of a city’s operation systems. Transportation network is loaded with city’s travel demand and also performs as an important lifeline system. The Outline Development Plan for Building China’s Strength in Transportation suggests “improving the multi-level network layout, optimizing the allocation of stock resources, and enhancing the resilience of transportation system.” Cities are characterized by high- density travel demand and strong coupling of multi-mode networks. Disturbances and disruptions occur frequently inside and outside the transportation system. Due to the spreading effect of large-scale, strongly-correlated, and multi- mode network, regional or network-wide failures become possible. Disturbances and disruptions have a global impact on the network, while existing responses are post-event and localized. Therefore, considering the entire-cycle impact of disturbances and disruptions on the network, developing a resilient transportation network has become the state-of-art in the fields of transportation engineering and urban science. The core purpose of developing a resilient transportation network is to achieve synoptic monitoring, precise assessment, and collaborative optimization of the network. The directions of development include: ① strategies and methods for network resilience monitoring of massive elements, in order to accurately and rapidly identify abnormal network conditions and triggering dynamic control mechanisms; ② advanced technologies for precise assessment of network resilience and self-recoverability prediction, in order to enable sensitive, diagnostic, and predictive response to abnormal events; and ③ life-cycle optimization of multi-mode network resilience, which requires a robust transportation network designed beforehand and an optimized time-spatial allocation of multi- stakeholder recovery resources afterwards. To overcome the difficulties in failure prevention, system evolution prediction, and rapid post-recovery, it is necessary to develop the resilience analysis and optimization technology on complex transportation network with a full use of big data, artificial intelligence, Internet of Things and other emerging technologies, and eventually to build a platform of scenario simulations and decision-making for transportation system resilience. Between 2015 and 2020, 274 patents relevant to this research front were published. These patents received 1 599 citations, with an average of 5.84 citations per patent.

(10)  Technology on bio-inspired crack sensing and self-healing of concrete

With the help of the technology on bio-inspired crack sensing and self-healing of concrete, concrete cracks can be intelligently self-sensed and be automatically healed without extra human interference. Upon cracking, the pre-embedded self-healing functional unit is immediately triggered by the crack or environmental activators in the crack such as water, dissolved oxygen, CO2, and chloride. Subsequently, the self- healing functional unit release/generate healing agents to heal the crack or repair the concrete environment. By means of the research on the key technologies of the functional unit, of the trigger release and of healing mechanism, the impermeability and mechanical properties of self-healing concrete can be increased, so as to improve the durability and safety of the concrete structure. Main research topics include: ① the crack responsive triggering mechanism; ② the design of self-healing functional units and their merging technologies with concrete; ③ the simulating and monitoring techniques of responding and self-healing processes; ④ the multiscale evaluation of self-healing properties; and ⑤ the technological exploration of concrete crack self-healing in realistic service conditions. At present, it is of importance to optimize the compatibility between self-healing functional units and concrete, improve the stability and durability of self-healing functional units in concrete, explore the structure of self-healing functional units and responsive mechanism for achieving high healing efficiency, and develop the bio- inspired self-healing concrete in realistic service conditions. Such conditions include those of the marine environment, the underground water environment, and the regions with large temperature difference. Between 2015 and 2020, 88 patents relevant to this research front were published. These patents received 1 419 citations, with an average of 16.13 citations per patent.

《2.2 Interpretations for three key engineering development fronts》

2.2 Interpretations for three key engineering development fronts

2.2.1 Intelligent construction technology for building engineering

Traditional construction projects have problems such as low labor efficiency and extensive resource consumption. At present, a new generation of information technology represented by the internet of things, big data, cloud computing, artificial intelligence, and blockchain is promoting the development of various industries, and is profoundly changing the development of science and technology of building engineering. The era of future building engineering represented by “intelligent construction” is approaching.

The core of intelligent construction technology for building engineering is the information interconnection technology of the entire industrial chain of building engineering, i.e., creation, integration, management, display and service of basic information, which are provided through building information modeling (BIM) technology. The information perception, collection, transmission and feedback in the process of production, logistics, construction and service are provided through the Internet of Things technology. The information processing, decision-making and operation in all links of the whole life cycle are provided through artificial intelligence technology. The aforementioned technologies are adopted to realize the standardized design, industrial production, mechanized construction, and integration of construction projects decoration, information management, intelligent application and green consumption.

The current research and development directions include:

1)   Intelligent design of building engineering, including theoretical methods, key technologies, and the digital-twins- based intelligent design.

2)  Intelligent construction of building engineering, including sustainable and green construction technology, modular and fine construction technology, artificial intelligence and decision-making technology, robotic system and automation technology, technology integration and information modeling.

3)   Intelligent operation and maintenance of building engineering, including intelligent perception and data acquisition technology, environmentally-friendly structural maintenance technology, precise structural reinforcement and maintenance technology, large-scale engineering transformation and collaboration technology.

4)  Intelligent consumption of building engineering, including intelligent classification and recycling technology, clean value- added utilization, efficient and safe conversion and intensive processing technology, precise control and decision-making technology.

As listed in Table 2.1.1, 107 patents related to this topic were published between 2015 and 2020, and the citations per patent was 5.84. The three countries that published the most patents were China, Japan, and the USA (Table 2.2.1), with China contributing 75.70% of the patents. The average citations of Chinese patents was 5.17, demonstrating increased attention being paid to Chinese patents.

The five organizations that produced the most patents were China State Construction Engineering Corporation, China Metallurgical Group Corporation, Xiamen Huaway IoT Technology Co., Ltd., Fastbrick IP Pty. Ltd., and China Communications Construction Company Limited (Table 2.2.2).

《Table 2.2.1》

Table 2.2.1 Countries with the greatest output of core patents on “intelligent construction technology for building engineering”

No. Country Published patents Percentage of published patents Citations Percentage of citations Citations per patent
1 China 81 75.70% 419 67.04% 5.17
2 Jan 8 7.48% 26 4.16% 3.25
3 USA 6 5.61% 102 16.32% 17
4 Germany 3 2.80% 38 6.08% 12.67
5 Australia 3 2.80% 25 4.00% 8.33
6 South Korea 2 1.87% 0 0.00% 0
7 Canada 1 0.93% 15 2.40% 15
8 Russia 1 0.93% 0 0.00% 0

《Table 2.2.2》

Table 2.2.2 Institutions with the greatest output of core patents on “intelligent construction technology for building engineering”

No. Institution Country Published patents Percentage of published patents Citations Percentage ( of citations Citations per patent
1 China State Construction Engineering Corporation China 8 7.48% 67 10.72% 8.38
2 China Metallurgical Group Corporation China 3 2.80% 33 5.28% 11
3 Xiamen Huaway loT Technology Co., Ltd. China 3 2.80% 33 5.28% 11
4 Fastbrick IP Pty. Ltd. Australia 3 2.80% 25 4.00% 8.33
5 China Communications Construction Company Limited China 3 2.80% 14 2.24% 4.67
6 SLM Solutions Group AG Germany 2 1.87% 18 2.88% 9
7 Power Construction Corporation of China China 2 1.87% 12 1.92% 6
8 Changzhou Well-Tech Technology Co., Ltd. China 2 1.87% 8 1.28% 4
9 China Railway Group Limited China 2 1.87% 4 0.64% 2
10 Armatron Systems LLC USA 1 0.93% 36 5.76% 36

2.2.2 Intelligent and integrated sewage treatment devices for village and town

Intelligent and integrated sewage treatment devices for village and town refers to the integrated devices that can be monitored and controlled intelligently and that are suitable for small-scale and decentralized sewage treatment in villages and towns. Their treatment capacity is about 5–500 m3/d. In the countryside of many developing countries including China, all-over-the-place discharge of wastewater, low laying rate of pipe network and low centralized processing rate are widespread issues because of the decentralized living pattern and the limitation of economic and technical conditions. Conventional sewage treatment plants suffer common problems such as low operation rate, high operation cost, high failure rate and difficult maintenance. To achieve the extensive collection, efficient treatment and centralized management of discharged wastewater is challenging, and intelligent and integrated sewage treatment devices provide a possible solution to the challenge.

The technical directions of research include:

1)  To develop integrated sewage treatment devices driven by gravitational potential energy, wind energy and solar energy according to local conditions, and to improve purification and reuse technology and to employ combined processes using biotechnology and ecological technology.

2)   To develop low-cost and high-reliability online intelligent sensors for water quality based on optics and electronic methods, and to construct remote data transmission and control system.

3)  To develop predictive and early-warning models of sewage plant operation states based on the activated sludge model coupled with artificial intelligence deep learning algorithm, and to establish intelligent fault diagnosis models for sewage treatment devices.

4)   To build a cloud management platform and a regional center of decentralized sewage treatment plants, and to establish a new intelligent maintenance mode of sewage treatment devices featuring “unattended–cloud diagnosis– cloud early warning–mobile maintenance”.

The main development trend of this front is to integrate multi-disciplinary knowledge, such as water pollution control engineering, microbiology, instrument science, artificial intelligence and internet of things, for developing intelligent integrated sewage treatment devices and their operation and cloud management modes with low consumption, high efficiency and easy maintenance.

As listed in Table 2.1.1, 82 patents related to this topic were published between 2015 and 2020. The three countries that published the most patents were China, South Korea, and Russia (Table 2.2.3). China contributed 92.68% of the patents. The average citation frequency of Chinese patents was 1.12.

The five organizations that produced the most patents were Hunan Zihong Ecological Technology Co., Ltd., Chuzhou Youlin Technology Development Co., Ltd., Fujian Zhiqing Ecological Environment Protection Co., Ltd., Doosan Heavy Industries & Construction Co., Ltd., and Wuhan Yijinxiang Biological Environmental Protection Co., Ltd. (Table 2.2.4). The patents owned by Hunan Zihong Ecological Technology Co., Ltd. involve a novel activated sludge process combined with a filtration process. The novelty of the patents lies in the use of the invented three-phase separation zone to achieve a stable and efficient separation of sludge from wastewater so as to realize an automatic reflux of sludge without extra energy consumption. The patents owned by Chuzhou Youlin Science and Technology Development Co., Ltd. involve an integration of activated sludge with biofilm, and an integration of oxidation process with a flocculation process. The activated flocculant component of a combination of porous perlite micro-powder, fly ash micro-powder, and bentonite powder has also been invented to realize an advanced treatment of wastewater in terms of an efficient phosphorus removal and decolorization. The patents owned by Fujian Zhiqing Ecological Environmental Protection Co., Ltd. involve an integrated device for a high-strength wastewater treatment. The device combines an upflow anaerobic sludge blanket reactor (UASB) and a membrane bio-reactor (MBR) into an anaerobic/aerobic (A/O) process and integrates with photocatalytic oxidation to improve effluent quality. An anaerobic sludge digestion and biogas production is processed automatically, and self-energy of the device is realized through the electricity generation from biogas.

The trend of the patent disclosure shows that the research in this field started in 1989. The number of the patents increased rapidly from 2015, and reached a peak in 2018, and then decreased gradually.

2.2.3 Indoor and outdoor integrated high-precision positioning and navigation system

The indoor and outdoor integrated high-precision positioning and navigation system integrates the technology of outdoor and indoor systems in a common terminal to provide users with indoor and outdoor location information services. It has a wide range of application needs in scenarios such as warehousing and logistics, smart elderly care, special hospitals, smart factories, community correction, and mall management.

Development trends in this research front include:

1)  Indoor and outdoor combination positioning technology,

《Table 2.2.3》

Table 2.2.3 Countries with the greatest output of core patents on “intelligent and integrated sewage treatment devices for village and town”

No. Country Published patents Percentage of published patents Citations Percentage of citations Citations per patent
1 China 76 92.68% 85 80.19% 1.12
2 South Korea 4 4.88% 10 9.43% 2.5
3 Russia 1 1.22% 7 6.60% 7
4 USA 1 1.22% 4 3.77% 4

《Table 2.2.4》

Table 2.2.4 Institutions with the greatest output of core patents on “intelligent and integrated sewage treatment devices for village and town”

No. Institution Country Published patents Percentage of published patents Citations Percentage of citations Citations per patent
1 Hunan Zihong Ecological Technology Co., Ltd. China 2 2.44% 1 0.94% 0.5
2 Chuzhou Youlin Technology Development Co., Ltd. China 1 1.22% 15 14.15% 15
3 Fujian Zhiqing Ecological Environment Protection Co., Ltd. China 1 1.22% 8 7.55% 8
4 Doosan Heavy Industries & Construction Co., Ltd. South Korea 1 1.22% 7 6.60% 7
5 Wuhan Yijinxiang Biological Environmental Protection Co., Ltd. China 1 1.22% 5 4.72% 5
6 China Aerospace Academy of Systems Science and Engineering China 1 1.22% 4 3.77% 4
7 Presby Patent Trust USA 1 1.22% 4 3.77% 4
8 Ruisheng Environmental Co., Ltd. China 1 1.22% 4 3.77% 4
9 Shenzhen Biyuan Environmental Protection Technology Co., Ltd. China 1 1.22% 4 3.77% 4
10 Beijing Huaqing Boya Environmental Protection Engineering Co., Ltd. China 1 1.22% 3 2.83% 3

including the integrated positioning system of Global Navigation Satellite System (GNSS) and Ultra Wide Band (UWB), Global Positioning System (GPS) and Geomagnetic integrated positioning system, GNSS and Inertial Measurement Unit (IMU) integrated positioning system, GNSS and Cellular integrated positioning system.

2)  Multi sensor information fusion technology, which improves indoor and outdoor positioning accuracy by fusing multi- sensor information such as GNSS, inertial measurement equipment, magnetic sensors and vision equipment and multi-source positioning information such as pseudosatellite signals and map constraints.

3)    The low-power positioning signal transmitting and receiving device, which realizes the low-power transmission of positioning and communication signals through Low-Power Wide-Area Network (LPWAN), and improves the endurance and standby time of positioning and navigation system.

As listed in Table 2.1.1, 85 patents related to this topic were published between 2015 and 2020. The three countries that published the most patents were China, the UK, and South Korea (Table 2.2.5). Among these countries, China was at the forefront of development, contributing 91.76% of the patents. The average citation frequency of Chinese patents was 5.12, demonstrating that Chinese patents are receiving increasing attention.

The five organizations that produced the most patents were China Electronic Technology Group Corporation, China Aerospace Academy of Systems Science and Engineering, Alibaba Group, Guilin University of Electronic Technology, and Shenzhen Czhou Technology Co., Ltd. (Table 2.2.6). China Electronics Technology Corporation focuses on indoor and outdoor combined positioning technology and multi- source integrated positioning technology; China Aerospace Academy of Systems Science and Engineering focuses on the research and development of satellite positioning signal transmitting and receiving devices to provide transmitted satellite positioning signals for indoor test tasks of whole aircraft systems; Alibaba Group focuses on the research and development of vehicle indoor and outdoor integrated high- precision positioning and navigation system. Cooperation among these organizations is rare (Figure 2.2.1).

《Table 2.2.5》

Table 2.2.5 Countries with the greatest output of core patents on “indoor and outdoor integrated high-precision positioning and navigation system”

No. Country Published patents Percentage of published patents Citations Percentage of citations Citations per patent
1 China 78 91.76% 399 93.88% 5.12
2 UK 2 2.35% 10 2.35% 5
3 South Korea 2 2.35% 0 0.00% 0
4 Cayman Islands 1 1.18% 12 2.82% 12
5 USA 1 1.18% 4 0.94% 4
6 Austria 1 1.18% 0 0.00% 0

《Table 2.2.6》

Table 2.2.6 Institutions with the greatest output of core patents on “indoor and outdoor integrated high-precision positioning and navigation system”

No. Institution Country Published patents Percentage of published patents Citations Percentage of citations Citations per patent
1 China Electronic Technology Group Corporation China 3 3.53% 12 2.82% 4
2 China Aerospace Academy of Systems Science and Engineering China 3 3.53% 1 0.24% 0.33
3 Alibaba Group China 2 2.35% 27 6.35% 13.5
4 Guilin University of Electronic Technology China 2 2.35% 15 3.53% 7.5
5 Shenzhen Czhou Technology Co., Ltd. China 2 2.35% 13 3.06% 6.5
6 Guangdong University of Technology China 2 2.35% 13 3.06% 6.5
7 Hangzhou Dianzi University China 2 2.35% 7 1.65% 3.5
8 Changsha Haige Beidou Information Technology Co., Ltd. China 2 2.35% 6 1.41% 3
9 Shenzhen Urban Traffic Planning and Design Research Center Co., Ltd. China 2 2.35% 4 0.94% 2
10 Beijing Aerospace Changzheng Aircraft Institute China 2 2.35% 1 0.24% 0.5

《Figure 2.2.1》

Figure 2.2.1 Collaboration network among major institutions in the engineering development front of “indoor and outdoor integrated high-precision positioning and navigation system”

 

 

 

Participants of the Field Group

Leaders

CUI Junzhi, ZHANG Jianyun, GU Xianglin

Members of the expert group

Academicians

JIANG Yi, OU Jinping, YANG Yongbin, ZHANG Jianyun, LIU Jiaping①, MIAO Changwen, DU Yanliang, NIU Xinqiang,

PENG Yongzhen, ZHENG Jianlong, WANG Fuming, ZHANG Jianmin, WU Zhiqiang, YUE Qingrui, LV Xilin, MA Jun,

FENG Xiating, ZHU Hehua, HU Yaan, TANG Hongwu, LIU Jiaping②

Experts

AI Jianliang, CAI Chunsheng, CAI Yi, CHEN Peng, CHEN Qing, CHEN Qiuwen, CHEN Xianhua, CHEN Xin, CHEN Yiyi,

CHEN Zhiguang, DA Liangjun, DAI Xiaohu, DONG Biqin, FAN Jiansheng, GAO Jun, GAO Liang, GE Yaojun, GU Chongshi,

GUO Jinsong, HAN Jie, HUANG Tinglin, HUANG Zishuo, JIA Liangjiu, JIANG Jinyang, JIANG Ping, JIANG Zhengwu,

JIAO Wenling, JIN Junliang, LI Angui, LI Chen, LI Jianbin, LI Yinong, LI Zhengrong, LIN Borong, LING Jianming, LIU Chao,

LIU Fang, LIU Jing, LIU Shuguang, LIU Yanling, MA Teng, NIU Xinyi, PAN Haixiao, REN Weixin, SHAO Yisheng, SHEN Di,

SHEN Yao, SHI Caijun, SHI Liangsheng, SHU Zhangkang, SUN Jian, SUN Zhi, TAN Guangming, TAN Yiqiu, TAN Zheng,

TONG Xiaohua, WANG Jieqiong, WANG Shuangjie, WANG Benjin, WANG Guoqing, WANG Jianhua, WANG Wei, WANG Yayi,

WANG YUANZhan, XIA Shengji, XIAO Feipeng, XIAO Yang, XIAO Zhong, XU Junzeng, YAN Jinxiu, YANG Min, YANG Qingshan,

YANG Zhongxuan, YAO Junlan, YE Wei, YU Zhongbo, YUAN Feng, ZHANG Chen, ZHANG Feng, ZHANG Song, ZHANG Xu,

ZHANG Yunsheng, ZHENG Bailin, ZHENG Gang, ZHONG Zheng, ZHOU Weiguo, ZHOU Xiang, ZHU Neng, ZHU Xingyi,

ZHUANG Xiaoying

Report writers

LIU Jiaping②, CHEN Peng, CHEN Qiuwen, DONG Biqin, GAO Liang, GUO Jinsong, HUANG Tinglin, JIA Liangjiu, JIANG Zhengwu,

LIU Chao, LIU Fang, LIU Jiaping, NIU Xinyi, SHEN Yao, SUN Jian, SUN Zhi, WANG Benjin, WANG Wei, XIANG Yan, XIAO Feipeng,

YANG Liu, YAO Junlan, ZHOU Xingang

 

① Xi’an University of Architecture and Technology.

② Southeast University.