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To guide a robotic swarm in a cluttered environment, a curve virtual tube is designed in this paper. There is no obstacle within the curve virtual tube, and the area inside can be seen as a safety zone. Then, a distributed swarm controller is proposed with three elaborate control terms. Formal analyses and proofs show that the curve virtual tube passing-through control problem can be solved in a finite time. For convenience in practical use, a modified controller with an approximate control performance is put forward. Some control laws for different types of robots to track their vector fields are also presented. The effectiveness of the proposed method is validated by numerical simulations and real experiments. To show the advantages of the proposed method, the comparisons between our method and other methods are also presented. [ABSTRACT FROM AUTHOR]

• 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]

A promising bio-based and biodegradable polybutyrolactam (PBY) fiber with health care function was prepared for the first time by dry-jet-wet spinning. As-prepared PBY fibers possesses the degree of crystallization upto 45.61%, appreciable thermal stability, excellent strength upto 2.1 cN•dtex−1, as well as good resistance to alkalis based on the results of X-ray diffraction, thermal and physical properties. The bio-degradability of PBY fibers were evaluated by the degraded behavior in soil, UV aging irradiation and seawater, showing commendable bio-degradation within 100 days. The analysis of the degradation based on TGA demonstrates that the removal of oligomers preferentially occurs, and then PBY macromolecules are broken. More interestingly, pharmaceutical γ -aminobutyric acid (GABA) is released during the degradation process, and it is beneficial to health care. As a biomass-derived and bio-degradable fiber, the sustainable PBY fiber exhibits an impressively competitive tensile strength among the existing degradable man-made fibers, showing great potential in bio-based fiber materials and health care textiles. [Display omitted] • Polybutyrolactam fiber was prepared for the first time by dry-jet-wet spinning. • The tensile strength of fiber reaches to 2.1 cN.•dtex−1. • Showing a commend bio-degradation performance within 100 days. • Pharmaceutical GABA is released during the degradation process. [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]

Rational design of bifunctional two-dimensional (2D) heterostructures with excellent activity and durability remains a great challenge for electrocatalytic water splitting. Herein, we propose a topochemical domain engineering to realize 2D mosaic heterostructures with ultrafine phosphide nanodomains highly dispersed on the surface of Ru doped CoMoO 4 nanosheets (denoted as Ru-CMOP), which are vertically interconnected on the conductive skeleton assembling a 3D array structure. The as-prepared Ru-CMOP electrocatalyst exhibits excellent activity and long-term stability with the overpotentials of 114 and 286 mV at 100 mA cm−2 for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in 1.0 M KOH solution, respectively, outperforming most reported metal phosphide-based bifunctional heterostructures. Moreover, an assembled electrolyzer using the Ru-CMOP as anode and cathode simultaneously delivers cell voltages of 1.697 V and 1.828 V to achieve 100 mA cm−2 and 500 mA cm−2, respectively, with outstanding durability at 250 mA cm−2 for 120 h. Density functional theory calculations and experimental results indicate that the strongly coupled heterointerfaces with built-in electric field can facilitate electron transfer while multi-porous nanosheet arrays contribute to active sites exposure and mass/gas transport, thereby synergistically accelerating the reaction kinetics. Additionally, combining with a commercial silicon photovoltaic solar cell, the electrolyzer can be efficiently and robustly established, demonstrating the great potential for practical photovoltaic-electrolysis applications. [Display omitted] • 2D mosaic heterostructures are prepared by topochemical domain engineering. • The Ru-CMOP exhibits outstanding activity and stability for HER and OER in alkaline media. • The rich heterointerfaces optimize the electronic configuration, indicated by DFT calculations. • A solar-cell-driven overall water-splitting device is efficiently constructed. [ABSTRACT FROM AUTHOR]

Electrochemical conversion of nitrate to ammonia is widely considered a "two birds with one stone" approach to alleviate the nitrate pollution in water and simultaneously to generate the valuable green NH 3 fuels. However, it remains challenging due to the lack of efficient electrocatalysts for practical utilization. Herein, we investigate the synergistic effect between asymmetric Cu-O v -W sites (O v represents oxygen vacancy) and adjacent Mo clusters in tuning the local electronic environment around active sites of catalysts for substantially enhanced nitrate reduction. The dynamic balance between the adsorption and desorption of O in NO 3 - caused by asymmetric O v and the promoted protonation process due to Mo clusters are responsible for boosting the entire process. Such synergistic effect modulates the local electronic environment for binding the reaction intermediates and dramatically facilitates the intermediate formation in rate-determining steps (*NO→*NOH and *NOH→*N), leading to the high NH 3 Faradaic efficiency and yield rate of 94.60% and 5.84 mg h−1 mg cat. −1 at − 0.7 V vs. RHE, respectively. [Display omitted] • Plasma method was applied to control the concentration of oxygen vacancies. • Oxygen vacancies act as active sites for the adsorption and activation of NO 3-. • Asymmetric vacancies balance the adsorption and desorption of O in NO 3- , facilitating the formation of *N intermediate. • Mo clusters accelerate the protonation process, leading to a relatively lower energy in the rate-determining step (*NO→*NOH). • The synergistic effect of asymmetric Cu-Ov-W and adjacent Mo clusters modulates the local electronic environment. [ABSTRACT FROM AUTHOR]

• A total-sliding-mode-control (TSMC)-based distributed secondary control (TSMC-DSC) scheme is designed. • Using an adaptive fuzzy-neural-network (FNN) to mimic the TSMC-DSC law. • A model-free control structure with favorable convergence speed, no chattering phenomenon, and strong robustness. • Training AFNN-DSC parameters online adaptively. • The network convergence as well as the Lyapunov stability. In this study, an adaptive fuzzy-neural-network (FNN) control scheme is proposed for an islanded micro-grid (MG) as a distributed secondary controller (DSC) to achieve the aims of voltage and frequency restoration and the optimal power sharing. Firstly, the dynamic model of an islanded MG is built, which consists of an inverter-interfaced distributed generation (DG) model and a MG architecture model. The DG model can be represented by considering the dynamics of a primary controller with an optimal active power sharing scheme. The MG architecture model is composed of power flow dynamics and loads. Then, a consensus-algorithm-based error function is defined, and a model-dependent total sliding-mode control (TSMC) technique is presented for dealing with synchronization and tracking problems. Moreover, an adaptive FNN (AFNN) scheme is designed to mimic the TSMC law to inherit its fast dynamic response with robust properties. Meanwhile, the requirement of precise information of the MG dynamic model in the TSMC law can be relaxed by the AFNN scheme. Adaptive tuning algorithms for FNN network parameters of the AFNN-based DSC (AFNN-DSC) strategy are derived by using the projection algorithm and the Lyapunov stability theorem, which can guarantee the stability of the AFNN-DSC-controlled system. The effectiveness of the proposed control method is verified by numerical simulations for real scenarios. © 2017 Elsevier Inc. All rights reserved. [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]

The photocatalysis for environment purification and clean energy production has attracted widespread attention, however, traditional powder-form photocatalysts cannot meet the practical application due to their poor recyclability, especially in slurry system. Here, polypyrrole/cadmium sulfide/nickel (PPy/CdS/Ni) multi-layer hollow fibrous photocatalyst with favorable photocatalytic activity for pollutants removal and hydrogen (H 2) evolution was successfully fabricated, which possesses a narrow band gap of ∼1.87 eV and enhanced visible-light photocatalytic activity. The removal efficiency of methylene blue (MB) and tetracycline can reach up to ∼94.76% and ∼76.1%, respectively. Simultaneously, the TOC removal efficiency with regard to MB can reach up to 78.1% and Cd2+ leakage is extremely low (<3 mg⋅L−1). More interestingly, H 2 evolution rate of PPy/CdS/Ni hollow fiber is up to as high as 665.7 μmol⋅g−1⋅h−1, which is about 1.43 and 1.86 folds higher than the PPy/CdS/Ni/PET fiber (466.3 μmol⋅g−1⋅h−1) and CdS/Ni/PET fiber (357.1 μmol⋅g−1⋅h−1), respectively. As a fiber-form intrinsic photocatalyst, our catalytic fiber shows great promise for pollutants removal and hydrogen energy production due to its easy-handling and recyclement. [Display omitted] • A novel PPy/CdS/Ni hollow fiber with photocatalytic activity was synthesized. • Pollutant removal efficiency and H 2 evolution rate are appreciable. • Possible photocatalytic mechanism was proposed. • PPy/CdS/Ni hollow fiber shows good photocatalytic stability and recyclability. [ABSTRACT FROM AUTHOR]

Low-altitude aircraft is being developed as a new mode of urban transport; consequently, the penetration of low-altitude aircraft into the urban airspace is inevitable in the near future. This will give rise to new urban air transport systems, called low-altitude air city transport (LAAT) systems. Such systems will include aircraft operated with or without pilots, transferring passengers and goods in urban areas using low-altitude levels of urban airspace. This paper investigates the collective and aggregate aircraft traffic flow diagrams, i.e. Macroscopic Fundamental Diagrams (MFDs), for LAAT systems. A LAAT plant model that captures the microscopic and macroscopic levels is established to construct the MFD curve, which links flow, density, and speed. The MFD allows us to identify the airspace traffic conditions, and to detect congested regimes. Different case study examples were simulated to analyze the full shape of MFD curves for LAAT systems, considering different algorithms (waypoints and destination plane), aircraft, and airspace settings. In this paper, a unique modeling framework for LAAT operation and a real-time synchronized implementation of large-scale LAAT simulation were developed. The findings of the current paper, the development of LAAT simulation environment, and the identification of airspace traffic conditions, can lead to the development of aggregate models and new control strategies to minimize congestion in futuristic urban airspace. • Investigating the collective and aggregate aircraft traffic flow diagrams. • Developing a LAAT plant model that captures the microscopic and macroscopic levels. • Developing a real-time synchronized implementation of large-scale LAAT simulation. [ABSTRACT FROM AUTHOR]

Sesamol (SEM), a lignan from sesame oil, exhibited potential benefits on obesity treatment by promoting browning of adipocytes, and the current study is aimed to explore the molecular mechanisms of SEM from the aspect of systemic liver-adipose crosstalk that mediated by hepatic fibroblast growth factor 21 (FGF21). Our in vivo data showed that SEM induced energy expenditure and white adipose tissue (WAT) browning by increasing the expression level of uncoupling protein-1 in high fat diet induced obese C57BL/6J mice. Elevated levels of circulating FGF21 associated with the increased expression of hepatic FGF21 were observed after SEM intervention. Simultaneously, the increased adipose fibroblast growth factor tyrosine kinase receptor 1/beta-klotho indicated that FGF21 sensitivity was enhanced by SEM in WAT. Furthermore, our in vitro results from HepG2 and 3T3-L1 cell lines confirmed the effects and revealed the mechanism of SEM on the white adipocytes browning. We found that with the specific inhibitors of PPARα, the SEM-mediated hepatic FGF21 expression was decreased, and with the specific inhibitors of PPARγ, the browning effect of adipocytes by SEM combining with FGF21 was significantly suppressed. Taken together, the mechanism of SEM for inducing the WAT browning might be the modulation of SEM on liver-adipose crosstalk mediated by FGF21, and the PPARs family might be the targets of SEM. The novel findings from the present study provided evidence that SEM could be a potent obesity-treating compound. [Display omitted] [ABSTRACT FROM AUTHOR]

• The process of making sea-slurry ice with specific ultrasonic wave can reduce the subcooling degree during seawater crystallization. • When the experimental working condition is 33 kHz and 600 W, its overall performance is the best. • The subcooling degree is effectively reduced by 8.6 °C, the preparation process time is shortened by 90 s, the average crystal size of sea-slurry ice is refine to 20 µm. • The actual energy consumption rate is effectively reduced by 40%, and the evaporator temperature is risen 10 °C. In order to reduce the energy consumption in the process of making sea-slurry ice, this research is based on the related theory of the promotion of solution crystallization by ultrasonic wave, and conducts an experimental study on the energy-saving effect of the process of making sea-slurry ice from seawater under the action of ultrasonic wave. The orthogonal experimental study was carried out on the production of sea-slurry ice from seawater solution by using ultrasonic waves of different frequencies under a specific power. The results show that the process of making sea-slurry ice with specific parameters (power/frequency) can increase the seawater crystallization speed and reduce the subcooling degree during seawater crystallization. When the experimental working condition is 33 kHz and 600 W, its overall performance is the best. Compared with the no ultrasonic condition its subcooling degree is effectively reduced by 8.6 °C, the preparation process time is shortened by 90 s, the average crystal size of sea-slurry ice is refine to 20 µm, the actual energy consumption rate is effectively reduced by 40%, and the evaporator temperature is risen to −5 °C. [ABSTRACT FROM AUTHOR]

To navigate and control a single mobile robot or a robotic swarm with higher efficiency, a novel non-potential orthogonal vector field method is proposed in this paper, which is modified from the traditional artificial potential field method. The improvement strategy aims at making the overall repulsive vector field orthogonal to the attractive vector field in some conditions. And the same potential field function is still applied to the Lyapunov-based stability analysis. In short, such an improvement strategy combines the advantages of the artificial potential field method with the non-potential vector field method, namely a combination of theoretical completeness and control efficiency. Finally, the effectiveness of the proposed method is validated both by numerical simulations with statistical significance and real experiments. The comparisons between our method and other methods are also presented. [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]