Ultrasonic surface rolling (USR) is a surface modification method to generate a nanostructured surface layer with highly improved mechanical behaviors. In this paper, the USR technology was used to ...improve the surface performance of 17-4PH stainless steel and the microstructure and mechanical properties of USR-treated17-4PH stainless steel were investigated in detail. The microstructural features were investigated by X-ray diffraction and scanning electron microscopy. A certain thickness deformation layer consisted of the nanoscaled metal grains was obtained on the surface of 17-4PH stainless steel by the USR technology. And the surface properties of USR-treated 17-4PH stainless steel were improved significantly, such as the surface roughness, microhardness and the residual compressive stress. In addition, the friction-wear performance test and potentiodynamic polarization experiment were conducted for USR-treated 17-4PH steel. Based on the experimental results, the wear and corrosion resistance of the USR-treated specimens were both improved markedly.
•Ultrafine grains surface layer with strong (110) and (211) texture is produced by ultrasonic surface rolling.•Surface roughness is reduced drastically and surface microhardness is improved by 20%.•Friction coefficient and wear rate are decreased up to 10–14.3% and 25% respectively.•The corrosion resistance is enhanced by ultrafine grains surface layer.
In order to solve the problem of coordinated development among mining economy, social governance and environmental conservation in global resource-based cities, we choose Guangxi Zhuang Autonomous ...Region as the research area. The advantage of resource endowment and resource industry was measured by location quotient and input-output method. The panel data related to mining governance from 2010 to 2021 were selected to build the evaluation and coupling analysis model between mining economic, social governance and environmental conservation, and the spatial-temporal heterogeneity and coupling effect of them were analyzed by comprehensive empowerment evaluation, spatial autocorrelation analysis and barrier degree methods. The results show that: (1) Except for the overall upward trend of social governance, the development level of mining economy and environmental conservation are basically stable; (2) The resource-rich areas have obvious mining economic advantages, and the central cities have good social governance capabilities, and the environmental conservation effectiveness is uncertain; (3) The coupling effect between mining economy and social governance is stronger than that between mining economy and environment conservation, and the synergistic coupling effect of the three is relatively random. Finally, we put forward some policy response strategies to Guangxi, and theoretical and practical reference would be provided for resource-based cities around the world.
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•An integrated vulnerability assessment approach is proposed.•Improved MSW method is developed to address the local spatial dependence.•The uncertainties of damage curve shapes and ...risky assets are considered.•The proposed approach can provide more reliable for vulnerability results.
Vulnerability assessment is an essential step for urban flood risk management. Due to the objective existence of statistical errors in the variables and spatial heterogeneity, as well as the similarity of flood experience, precautionary status and environments for neighbouring areas, an urban flood vulnerability assessment essentially entails a multi-factor decision-making process that accounts for uncertainties and the local spatial dependence of neighbourhoods. To address these issues, an uncertainty-based vulnerability assessment approach embedded with an improved moving split-window (IMSW) analysis and probabilistic method is proposed. To develop an integrated urban flood vulnerability assessment model, three technical issues need to be resolved: (1) the development of damage curves of land-use types, (2) an uncertainty model and spatial dependence model of damages based on an IMSW analysis, and (3) an uncertainty-based framework to quantify vulnerability considering the uncertainties and local spatial dependence of the damage curves as well as the spatial heterogeneity of risky assets simultaneously. The proposed method is applied to an urban area in China and provides an integrated vulnerability assessment for different land-use types. Moreover, uncertainty and sensitivity analyses were performed to analyse the spatial differentiation and the dominant parameters of vulnerability. Compared with two other commonly used methods, the proposed local-correlated method (LCM) is more in line with reality, and provides more reasonable information for making a better-informed decision.
Powering marine distributed buoys sustainably and cost-efficiently has always been challenging in the ocean environment. Triboelectric nanogenerators (TENG), thanks to their robustness, high ...efficiency and low cost in energy harvesting, has provided a novel solution to the long-term electrical power supply for a series of distributed systems (including buoys). In this study, a wave energy harvesting sandwich-like TENG (S-TENG) has been proposed. In the on-land forced motion experiments, the S-TENG yields much superior performances compared to previous tower-like TENG in terms of the power density. The studies also reveal that the electrical output increases linearly even with larger number of parallel connected S-TENG layers. Consequently, a buoy integrated with 7 parallel connected S-TENGs is studied through systematic wave basin experiments and the relevance of most hydrodynamic parameters (including wave height, frequency, direction as well as mooring system) have been revealed. The presented wave basin experiments are original in wave energy harvesting TENG research practice and prove to be very helpful in that they simulate the most close-to-real ocean environments in the lab. The studies are concluded with a 12 W high-brightness LED lit up on a navigation supporting buoy. This study has set a benchmark of achieving self-powered buoy with TENG, which can be extended to other marine distributed systems such as sensors and small robotics.
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•Sandwich structure boosting output power density of triboelectric nanogenerators.•Accessible power promotion through parallel nanogenerators in layers.•First time triboelectric nanogenerator tested in an advanced wave basin.•Self-powered navigation buoy achieved by triboelectric nanogenerator integration.
Polyamines are small amines that accumulate during stress and contribute to disease resistance through as yet unknown signaling pathways. Using a comprehensive RNA‐sequencing analysis, we show that ...early transcriptional responses triggered by each of the most abundant polyamines (putrescine, spermidine, spermine, thermospermine and cadaverine) exhibit specific quantitative differences, suggesting that polyamines (rather than downstream metabolites) elicit defense responses. Signaling by putrescine, which accumulates in response to bacteria that trigger effector triggered immunity (ETI) and systemic acquired resistance (SAR), is largely dependent on the accumulation of hydrogen peroxide, and is partly dependent on salicylic acid (SA), the expression of ENHANCED DISEASE SUSCEPTIBILITY (EDS1) and NONEXPRESSOR of PR GENES1 (NPR1). Putrescine elicits local SA accumulation as well as local and systemic transcriptional reprogramming that overlaps with SAR. Loss‐of‐function mutations in arginine decarboxylase 2 (ADC2), which is required for putrescine synthesis and copper amine oxidase (CuAO), which is involved in putrescine oxidation, compromise basal defenses, as well as putrescine and pathogen‐triggered systemic resistance. These findings confirm that putrescine elicits ROS‐dependent SA pathways in the activation of plant defenses.
Polyamines trigger stress signaling that involves defense sectors. Putrescine, which accumulates during ETI, contributes to defense through activation of a ROS, EDS1, SA and NPR1 ‐ dependent pathway which leads to local SA accumulation and the establishment of systemic responses overlapping with SAR.
The multi-layer indices decision-making of complex industrial processes is the key to reducing costs and improving production efficiency. With the development of the Industrial Internet, a large ...number of industrial streaming data and intelligent algorithms have brought opportunities for optimizing plant-wide production indices. However, due to the strong dynamic and coupling of the production process, the intelligent system based only on the optimization algorithm cannot give practical data analysis suggestions and decision results, so a human–computer interactive visual analysis and index decision system are urgently needed. This paper combines multi-layer indices decision-making algorithms with 3D digital twin visual analysis technology to propose an intelligent decision-making system for mineral processing production indices based on 3D digital twin interactive visualization (DTIV). The DTIV system provides users a 3D digital twin modeling view from the production park, workshop, and equipment scenes. It adopts visualization technology that seamlessly integrates 3D and 2D to help users obtain indices decision input information and hidden data features from real-time stream data with different spatiotemporal data characteristics. In addition, the DTIV system also combines a multi-layer indices optimization decision-making algorithms engine and designs a human–machine interaction indices decision interface and indices decision execution visual analysis interface to improve users’ production perception and decision-making ability. Through our collaboration with domain experts, carefully designed interviews, and prototype system evaluation in a beneficiation plant, the effectiveness and usability of the system have been proven.
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Under the condition of constant external stress, the displacement and stress of the joint will be adjusted continuously with time, resulting in the creep phenomenon, that is, the continuous increase ...of the strain with time, which further causes the damage of the jointed rock mass. In order to study the size effect of joint shear rheological mechanical properties, this paper conducted shear rheological numerical simulations on nonpenetrating and penetrating joint models established in Particle Flow Code (PFC) and analyzed the effect of specimen size on the rheological and shear mechanical behavior of the model. The results show the following: (1) For the rheological direct shear test, the instantaneous shear displacement of the joint increases continuously as the size increases, showing a significant positive size effect. (2) For through-type joints, only the cohesion shows a certain size effect, and the shear strength and friction angle have a nonobvious relation with specimen size. (3) For anchored through-type joints, the increase of the model size leads to a decrease in shear strength, while the friction angle-size effect of joints is not remarkable.
This paper studies the tracking problem of nonholonomic wheeled robots subject to control input constraints. In order to take optimality considerations into account while designing saturated tracking ...controllers, a Lyapunov-based predictive tracking controller is developed, in which the contractive constraint is characterized by a backup global saturated tracking controller. Theoretical results on ensuring global feasibility and closed-loop stability of the controller are provided. In addition, the proposed methodology admits suboptimal solutions. Finally, numerical simulations are performed to verify the effectiveness of the proposed control strategy.
The swaging quality of self-lubricating spherical plain bearings (SSPBs) has an important influence on the safety of the aircraft. The roller swaging process has an edge on other swaging processes in ...low swaging load and high swaging quality. The 3D elastic–plastic finite element model of roller swaging and push-out test were developed, and the influence of the roller swaging process loading parameters, such as the swaging time, the swaging load and the rotation speed of the roller tool on the push-out load, the gap between the flanging lip of the V-groove and the housing chamfer, and the radial displacement (the inner surface of the outer ring) after roller swaging were studied. Finally, the roller swaging test was conducted, and the test results were compared with the simulation results. The research shows that the test results are consistent with the results of the simulation model, and with the increase of the swaging time, swaging load, and rotation speed of the roller tool, the gap will be increased as well, resulting in an increase in the push-out load. However, the excessive swaging load and rotation speed of the roller tool will increase the radial displacement, which will result in a reduction in the rotation flexibility of the bearing. Under the conditions of reasonable swaging time and swaging load, a good swaging quality can be obtained by controlling reasonable rotation speed of the roller tool.
CO2 emissions caused by household consumption have become one of the main sources of greenhouse gas emissions. Studying household CO2 emissions (HCEs) is of great significance to energy conservation ...and emissions reduction. In this study, we quantitatively analyzed the direct and indirect CO2 emissions by urban and rural households in Beijing, Tianjin, Shanghai, and Chongqing. The results show that urban total HCEs are larger than rural total HCEs for the four megacities. Urban total per capita household CO2 emissions (PHCEs) are larger than rural total PHCEs in Beijing, Tianjin, and Chongqing, while rural total PHCEs in Shanghai are larger than urban total PHCEs. Electricity and hot water production and supply was the largest contributor of indirect HCEs for both rural and urban households. Beijing, Tianjin, Shanghai, and Chongqing outsourced a large amount of indirect CO2 emissions to their neighboring provinces.
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