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• Machine learning techniques are applied to predict long-term prestress loss of prestressed reinforced concrete cylinder structures. • Explicit functions of concrete shrinkage and creep are proposed by using genetic programming (GP). • Finite element analysis model considers the long-term prestress loss under multi-factor coupling is established to expand the experimental database. • The prediction models of the long-term prestress loss based on GP, ANN and CNN are validated to be accurate and efficient by practical engineering. The long-term prestress loss caused by shrinkage and creep of concrete and stress relaxation of prestressed tendons has significant effects on the sealability and safety of prestressed concrete cylinder structures such as nuclear reactor containments and liquified natural gas (LNG) tanks. By utilizing machine learning (ML) techniques, this study aims to establish an intelligent approach for the long-term prestress loss prediction of concrete cylinder structures. Firstly, based on the Infrastructure Technology Institute of Northwestern University (NU-ITI) database of concrete shrinkage and creep performance, the explicit expressions are presented for concrete shrinkage and creep function using genetic programming (GP); Moreover, the concrete constitutive model is incorporated into a general finite-element software package based on the ABAQUS UMAT platform. Then finite element analysis (FEA) models are established and calibrated based on the existing long-term prestress loss tests of prestressed concrete beams. In addition to the experimental results in the literature, the numerical results of the FEA model are also used to form the database of the long-term prestress losses for concrete cylinder structures. Finally, three prediction models of long-term prestress loss are proposed by utilizing the artificial neural network (ANN), one-dimensional convolutional neural network (1D CNN) and genetic programming (GP). Compared with the measured results of nuclear containments in practical engineering, the ML based prediction models are demonstrated to be accurate and efficient in evaluating the long-term prestress loss for prestressed concrete cylinder structures. [ABSTRACT FROM AUTHOR]

• FE model for PC slab subjected to hard missile impact is established and verified. • Prestress in concrete is the main reason for the ballistic resistance increase. • Contribution of prestressing bars to ballistic resistance increase is moderate. • Semi-empirical formula for crucial perforation velocity of PC slabs is proposed. Prestressed concrete (PC) structure has been extensively used in civil engineering like nuclear and protective structures. But systematic studies on its ballistic performance are still inadequate, hindering its ballistic design and applications. In this paper, the ballistic performance of PC slabs subjected to hard missile impact is numerically investigated through finite element (FE) modeling. The method to introduce prestressing force is specially investigated and the feasibility of the established models is verified against existing experimental results. The models are then employed to conduct a comparative study between PC and reinforced concrete (RC) slabs, in which the influences of the prestress and prestressing bars are decoupled. The variations of concrete tensile strain and energy dissipation capacities of PC slabs with different failure modes are analyzed to understand the mechanism of the ballistic resistance. It is revealed that the prestress is the main reason for the enhancement of ballistic resistance of PC slabs, while the increase of reinforcement ratio due to prestressing bars is the secondary reason. It is also proved that the confinement effect applied to the concrete is the major reason for the increase in ballistic resistance. Based on the mechanism, by using mechanical and regression analysis, a semi-empirical formula for the critical perforation velocity of the PC slabs is proposed, which gives better predictions compared to existing formulas. The proposed formula also allows a straightforward parametric study, the results of which could be used for simplified estimations in the ballistic design of PC slabs. [ABSTRACT FROM AUTHOR]

Multicopters have been attracting increasing attention in recent years, while it is significant to consider the flight safety of multicopters in the presence of propulsor faults or failures. Therefore, this paper presents a methodology to analyze the controllable probability of a multicopter with arbitrary configurations based on controllability theory and an available control authority index. The methodology is then used to analyze the controllable probability of multicopters with different propulsor numbers and configurations to show its effectiveness. Based on the controllable probability results, an optimal configuration method is given. [ABSTRACT FROM AUTHOR]

The emergence of drug-resistant bacterial strains has challenged the use of traditional antibiotic therapies. Therefore, there is an urgent need to develop novel antibacterial materials or methods to effectively eradicate bacteria. Herein, we demonstrated a novel antibacterial system consisting of cupric oxide nanoparticles combined with ascorbic acid (CuO NPs/AA), which could act as a potent nanoantibiotic targeting both Escherichia coli (gram-negative) and Staphylococcus aureus (gram-positive) in vivo and in vitro , without noticeable cytotoxicity to mammalian tissue. The CuO NP/AA antibacterial system killed these microbes through a combined mechanism involving biofilm inhibition, cell membrane destruction, DNA damage, and enzyme inactivation. The antibacterial properties of CuO NPs/AA were mainly attributed to the generation of reactive oxygen species (e.g., ·OH) produced through the intrinsic ascorbate oxidase- and peroxidase-like activities of CuO NPs, highlighting their use as antibacterial nanozymes to treat bacterial infections. • CuO NPs/AA was demonstrated as a novel antibacterial system. • CuO NPs/AA has potent nanoantibiotics targeting both E. coli and S. aureus in vivo and in vitro. • CuO NPs/AA killed microbes through a combined mechanism. • CuO NPs/AA generated ·OH through the CuO NPs' intrinsic ascorbate oxidase- and peroxidase-like activities. • The biological applications of bifunctional CuO NPs can be extended. [ABSTRACT FROM AUTHOR]

The rapid urbanization and frequent occurrence of extreme weather have made flooding more frequent; tide-sensitive areas are more prone to flooding due to tide level. However, the extent of their respective impacts on flood variability in the context of the combined effects remains to be explored. Therefore, analysis of the driveability of the water level is important for regional flood control. Land use data from 1985 to 2015 was used in this study to analyze the characteristics of the changes. General trends, abrupt variability, and persistence of rainfall, tide, and water level data from 1957 to 2018 were analyzed. The influence of rainfall, tide level factors and underlying surface on water level variation was analyzed qualitatively and the contribution of the three factors to water level variation was quantified. The results indicate that the most important directions of land-type transformation were the construction land and arable land. Within the rainfall sequence, only the 3d rainfall sequence exhibited a significant increasing trend, while both tide level and water levels showed significant increasing trends. The 3d rainfall sequence and tide level sequence are significantly positively correlated with water level sequences, whereas among the underlying surface factors, only construction land and unused land are significantly positively correlated with water levels. Furthermore, the contribution rates of driving factors vary across different regions. In the Changzhou region, the underlying surface factors dominated with a relative influence of 62%., whereas for other regions, the combined relative influences of rainfall and tide level are 57.2%, 52.8%, 60.4%, and 66.9%, The methods and results of this study contribute to regional flood regulation. • The main directions of conversion of land type are construction land and arable land. • Rainfall and tide level are positively correlated with water level in an upward trend. • The rainfall and tide level factors are the dominant factors influencing the rise in water level. • The net effect of human activities on changes in water level is actually not very strong. [ABSTRACT FROM AUTHOR]

• Ecosystem service supply is related to regional natural conditions. • Ecosystem service demand is related to regional socio-economic development. • Land-use change was intense and urban expansion was noticeable from 2000 to 2020. • Ecosystem service supply and demand show significant spatial correlation. • Study scale has impacts on coupled matching of ecosystem service supply and demand. Ecosystem services are the environmental basis of human living and sustainable development, and the coupled matching of ecosystem service supply and demand (ESSD) plays an important role in socioeconomic and eco-environmental development. As one of the major regions supplying ecological products in China, the Shandong Peninsula urban agglomeration (SPUA) has unique geographical advantages and a strategic position. Based on high-resolution land-use and regional socioeconomic development data in SPUA, this study used value quantity assessment and an ecosystem service demand model to quantify ecosystem service supply (ESS) and ecosystem service demand (ESD) at both the city and county scale in 2000, 2010 and 2020. Meanwhile, the CA-Markov model was used to predict the potential land-use, the Moran index and Getis-Ord Gi* index were used to analyze spatial clusters of ESS and ESD, and a coupling coordination degree model and matching index were used to analyze the relationship between ESS and ESD. The results show that: (1) The most prominent land-use change in SPUA from 2000 to 2020 was the conversion of cropland to other land-use types; the process of land-use change was more intense from 2010 to 2020 than from 2000 to 2010; and the center of city activities might expand by 2030, which is related to the regional development plan. (2) The ESS was related to the regional natural conditions. Coastal regions or regions with abundant natural resources in SPUA had higher ESS, and the southwest region had lower ESS in SPUA. The ESS presented high–high clusters, low–low clusters and hot spots, and the cluster phenomena gradually diminished from 2000 to 2020. (3) The ESD was related to the regional location and economic development, with the southwest region of SPUA having a higher ESD than the northeast. The ESD presented low–low clusters, and Jinan and Qingdao had hot spots, which are the most developed cities in SPUA. (4) The study scale had impacts on coupled matching of ESSD. Coupled matching of ESSD was found to be unbalanced at the county scale from 2000 to 2020, but tended to be balanced at the city scale, which was related to resource management at different spatial scales. This study reveals the evolution and coupled matching of ESSD at different scales, which has important implications for the sustainable development of regional urban agglomerations. [ABSTRACT FROM AUTHOR]

Continuously encircling and monitoring an individual static target is an important application scenario for a multi-UAV system. In this paper, to address the problem of multi-UAV encircling the target arbitrarily, evenly and densely in 3D space, a distributed vector field control method with an annular virtual tube is proposed. Some Lyapunov-like functions are designed elaborately, and a formal analysis based on the invariant set theorem is made to show that all UAVs can complete the encirclement task successfully. Simulations and experiments are carried out to show the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]