25 research outputs found

    Modeling of fatigue crack in particle reinforced composites with Voronoi cell finite element method

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    AbstractThe modeling of fatigue crack initiation and propagation for particulate reinforced composites is facilitated with new Voronoi cell finite element method (VCFEM), considering the matrix-inclusion interfacial fatigue crack and matrix fatigue crack. In the new element, all possible contacts on the crack edge are considered by remeshing method, when the crack is closing under all possible changing loads. The fatigue crack initiates when the fatigue damage exceeds certain critical damage value, and fatigue crack propagation are simulated by gradual seeking crack propagating directions and new crack tips, using a remeshing method that a damaged node at the crack tip is replaced by a pair of nodes, a new crack tip node is assigned at the crack propagating directions and a more pair of nodes are needed to be added on the crack edge near the crack tip in order to better facilitate the free-traction boundary condition. The comparison of the results of proposed VCFEM and commercial finite element packages MARC. An example has been given for Particle-reinforced metal-matrix composites with 20 elliptical inclusions to simulate the fatigue crack initiation and propagation under plane stress conditions. It appears that this method is a more efficient way to deal with the interfacial damage of composite materials

    Design of Ultra-compact Graphene-based Superscatterers

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    The energy-momentum dispersion relation is a fundamental property of plasmonic systems. In this paper, we show that the method of dispersion engineering can be used for the design of ultra-compact graphene-based superscatterers. Based on the Bohr model, the dispersion relation of the equivalent planar waveguide is engineered to enhance the scattering cross section of a dielectric cylinder. Bohr conditions with different orders are fulfilled in multiple dispersion curves at the same resonant frequency. Thus the resonance peaks from the first and second order scattering terms are overlapped in the deepsubwavelength scale by delicately tuning the gap thickness between two graphene layers. Using this ultra-compact graphene-based superscatterer, the scattering cross section of the dielectric cylinder can be enhanced by five orders of magnitude.Comment: This paper has been accepted by IEEE Journal of Selected topics in Quantum Electronic

    Design and implementation of quantitative remote sensing monitoring and intelligent analysis system for mine ecological environment

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    Mine ecological environment monitoring and governance is a critical requirement for national ecological civilization construction and the dual carbon goal. The informatization and intelligent construction of the mine ecological environment have become an important part of Digital China driven by the new generation of information technology, and it is also an inevitable trend in the development of the current era. However, existing mine ecological environment monitoring systems are still in the primary stage with a single theme, incomplete elements, basic measurement, and local management, and they cannot meet the demand for multi-element, long-term, high-frequency monitoring and analysis of the mine ecological environment. To address this problem, the quantitative remote sensing monitoring and intelligent analysis system for the mine ecological environment under B/S architecture is proposed, called Mine Ecology Remote Eyes. The development requirements, technical framework, key technologies, and core functions of the system are further described in detail. The system utilizes satellite remote sensing technology and other monitoring methods to obtain and aggregate mine ecological big data from different sources, forming a map of mine distribution and data resource services. Using quantitative remote sensing to invert ecological parameters of mine environments, a set of long-term and multi-element monitoring products can be generated. These products cover various ecological elements such as human activities, natural geographical conditions, and “vegetation-soil-water-atmosphere” parameters. The system provides a range of tools for GIS spatial and temporal analysis, statistical analysis, and comprehensive quantitative evaluation. With these tools, users can monitor spatial changes in ecological parameters such as land use and normalized difference vegetation index (NDVI) in mining areas along with mining activities, as well as query and visualize historical statistical values of ecological elements such as soil water content and suspended solids concentration in water under different spatiotemporal locations or regions. Additionally, the system enables comprehensive quantitative evaluation of the quality of the mine ecological environment taking into account multiple ecological elements. Finally, the system generates a monitoring report on ecological disturbance and governance of the mine. The application of Mine Ecology Remote Eyes will facilitate the change monitoring, data management, intelligent analysis, and decision-making applications of the mine ecological environment. This system has the potential to improve the efficiency and intelligence level of monitoring and governance of the mine ecological environment, and provides a reference for promoting the informatization of ecological civilization

    How Does Parental Involvement Affect Children's Academic Development from A Core Literacy Perspective?

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    This study explores the influence of parental involvement on children's academic development, and comprehensively defines the indicators of children's academic development from the perspective of core literacy. Based on urban and rural household registration status and regional migration, children in China are divided into four categories. Three main findings are as follows. First, parents' direct learning participation can hardly benefit children's academic development, regardless of what type of children. Specifically, this type of parental participation has a significant negative impact not only on academic test score of all children, but also on all academic development dimensions of   children who have rural to urban migrant experience. Second, parents' emotional participation behavior can effectively promote the academic development of children, regardless of migration type. Third, parents’ cultural participation has a positive effect on local urban children’s academic development, while it has a negative effect on the learning willpower and curiosity of urban–urban migrant children who move from one urban area to another in different provinces/districts. Under the background of mass internal migration and rapid urbanization, our findings provide implications for parents to better participate in their children's education in the context of rapid population movements and urbanization

    New Strain of <i>Bacillus amyloliquefaciens</i> G1 as a Potential Downy Mildew Biocontrol Agent for Grape

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    To obtain effective biocontrol strains for downy mildew of grape, 38 endophytic bacteria were isolated from fruits, seeds, and old stems of six grape varieties. Using spot inoculation mixtures of sporangial suspensions of Plasmopara viticola and biocontrol bacterial suspension, this screen yielded three strains (G1, G5, and G9) with good antagonistic effects against P. viticola. The growth inhibition rate was 100%, which was comparable to the effect of the positive control Bacillus subtilis strain CN181. The enzyme activity and the metabolites of strain G1 were examined on casein hydrolysate medium, sodium carboxymethyl cellulose agar plates, and chrome azurol sulfonate (CAS) agar plates. The antifungal protein component was identified by liquid chromatography–mass spectrometry (LC–MS). The results showed that strain G1 was more effective against Plasmopara viticola after two field trials, and the inhibition rates of strain G1 on the seventh day of the two field trials were 47.5% and 36.9%, respectively. Strain G1 was identified as Bacillus amyloliquefaciens based on morphological examination and 16S rDNA sequence analysis. It produced proteases, cellulases, and siderophores. Crude protein of the strain mainly included the putative segregation protein SpoVG, which inhibited P. viticola

    Investigation of Low-Calcium Circulating Fluidized Bed Fly Ash on the Mechanical Strength and Microstructure of Cement-Based Material

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    This present study mainly focuses on the influence of low-calcium circulating fluidized bed fly ash (LCFA) on the mechanical property and microstructure of cement-based materials under different curing conditions. The mechanical properties test was conducted by changing variable parameters, such as LCFA content, the internal mixing ratio of LCFA and fly ash (FA), and dry and water curing conditions. Further, the hydration products and pore structure were analyzed using XRD, FT-IR, TG-DTG, NI, SEM, and BET micro-testing technology. The strength development law of LCFA on cement-based materials is discussed. The research results show that LCFA has a certain degree of self-hardening and can be used as a cementitious material in cement-based materials. Still, the loose and porous microstructure of LCFA leads to higher water requirements, which reduces the fluidity of cement-based pastes. Water curing is favorable for promoting the development of LCFA on the long-term compressive strength of cement-based materials. When the LCFA was added to the cement, the optimal substitution ratio was 20%, and the compressive strength at 91 days reached 101 MPa. In the case of compounding LCFA and FA, when the internal mixing ratio of LCFA/FA was 3 and the total content was 20%, the mechanical properties were the highest, and the compressive strength at 91 days was 92 MPa. The microscopic analysis result shows that the cumulative hydration heat of the samples decreased significantly with the increase of dosage of LCFA. The main hydration products of cement-based materials mixed with LCFA were AFt, C-S-H gel, and Ca(OH)2. AFt and C-S-H gels are critical to the strength development of OPC-LCFA samples. The active Al2O3 and active SiO2 in LCFA were involved in hydration reactions to promote the formation of C-A-H and C-S-H gel and effectively promote the development of the mechanical properties. Overdosages of LCFA would reduce the ettringite formation rate. FA is not conducive to AFt formation in the hydration process of OPC-FA samples

    Assessing the effect, attribution, and potential of vegetation restoration in open-pit coal mines’ dumping sites during 2003–2020 utilizing remote sensing

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    Ecological restoration in open-pit coal mines faces significant challenges, particularly regarding vegetation restoration in dumping sites, which often experience unstable vegetation status after restoration. Hence, monitoring the vegetation restoration process and evaluating restoration effect in dumping sites are crucial. In this study, the restoration process in dumping sites was rebuilt based on the Fractional Vegetation Cover (FVC), and the restoration effect was evaluated with reference to the FVC before destruction. Considering the topographic factors in dumping sites, the relative contributions of climate change and human activities was quantified. The future restoration potential of dumping sites was explored using the constructed FVC Restoration Potential Index (FRPI). The results show that: (1) This study can accurately identify the actions and characteristics of vegetation destruction and restoration of open-pit coal mines’ dumping sites based on FVC time-series curves. (2) The vegetation restoration effect in dumping sites can be accurately evaluated based on the constructed “difference-value” indicator. Additionally, the FRPI enabled the assessment of dumping sites’ future FVC restoration potential, providing valuable guidance for future restoration projects. (3) The correlation between topographic factors and FVC in dumping sites was slightly weak, with climate change and human activities serving as the main driving forces. Climate change was key in outer dumping sites, whereas human activities had a greater influence in Inner dumping site. This study provided a valuable approach for assessing the restoration effect, potential, and attribution, facilitating the optimization of future restoration projects
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