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In view of increasing accuracy requirements and difficult machining characteristics of silicon carbide materials, this paper proposes new machining method with ultra-high precision. Based on improvement of ultra-precision machining quality by textured surface, specific nano texture was machined on silicon carbide surface. Effects of different texture parameters on polishing force, polishing temperature, potential energy, dislocation, stress and friction coefficient were analyzed. Two typical textures (grooves and pits) with different sizes were compared. Simulation results show that surface morphology, polishing force and friction coefficient are improved with the increase in groove depth and pit depth. The smaller the groove spacing, the better the polishing quality and polishing behavior. In addition, groove texture can effectively inhibit the growth of dislocations and defect atoms during polishing. Compared with non-textured surface, textured silicon carbide surface can improve polishing conditions. It is found that groove texture has more beneficial effect on polishing quality than pit texture with the same size. [ABSTRACT FROM AUTHOR]

The influence of excess air coefficient, ignition timing, and injection timing were investigated to examine the combustion and emission performance of a hydrogen engine operating at low speed with low loads. Comprehensive experimental research was then undertaken to evaluate the engine performance across a wide range of loads and various combinations of factors. The experimental results show a substantial improvement in brake thermal efficiency (BTE) and a noteworthy reduction in NO X emissions with an increased excess air coefficient. Although the impact of injection timing on BTE is negligible, an appropriate injection timing delay effectively reduces NO X emissions. A lean mixture and a suitable ignition timing delay exhibit high thermal efficiency at a lower engine speed and simultaneously suppress knock. The BTE reaches 33.46% at a mean effective pressure of 10.0 bar. Improving the turbocharging capability under low-speed and high-load conditions is essential for enhancing the performance of hydrogen engines. • EOI has little impact on BTE but is effective in reducing NO X emissions at low load. • Larger excess air ratio can increase BTE and reduce NO X emissions greatly. • Increasing excess air ratio can suppress knock and improve BTE at high load. • Outward-opening injectors are used to decrease hydrogen injection pressure. [ABSTRACT FROM AUTHOR]

Molecular dynamics (MD) simulation was applied to construct the conventional surface, micro textured surface and water lubricated textured surface of cubic silicon carbide (3 C-SiC) workpiece, which were then subjected to grinding by diamond abrasive particles. The results indicated that the textured surface can significantly improve the surface quality and reduce the grinding force, stress, grinding temperature and subsurface structure damage. Moreover, water lubricated textured surface can further reduce grinding temperature and subsurface damage depth, but it increases grinding force and stress. Finally, the increase in grinding depth increases the removal rate of silicon carbide, but the stress, grinding force, grinding temperature, potential energy and subsurface structure damage increase accordingly. The water lubricated textured surface has innovative significance in processing 3 C-SiC. [Display omitted] • MD simulation was applied to construct the conventional surface, micro textured surface and water lubricated textured surface of SiC workpiece. • The textured surface can significantly improve the surface quality and subsurface structure damage. • Water lubricated textured surface can further reduce grinding temperature and subsurface damage depth. • The increase in grinding depth increases the removal rate of silicon carbide. [ABSTRACT FROM AUTHOR]

The pyrite-based autotrophic denitrification usually focused on the anaerobic/anoxic environment with high sulfate production and low denitrification efficiency. In this study, the oxygen limitation was broken and high-rate mixotrophic denitrification was realized via introducing poly-3-hydroxybutyrate-hydroxyvalerate (PHBV) and controlling the pyrite grain sizes compared with PHBV-heterotrophic and pyrite-autotrophic denitrification under natural aerobic conditions. Results showed that the optimal pyrite grain size was 30 meshes (0.45–0.55 mm) with the highest denitrification rate of 0.65 mg NO 3 −−N/(L•h) and sulfate production of <5 mg/L in pyrite-PHBV system. Its removal efficiency of nitrogen and phosphorus was 96% and 25%, respectively. According to functional genes and Raman analysis, the low SO 4 2− production were attributed to the S reduction and polysulfide formation in the mixotrophic systems, which also enhanced denitrification efficiency by improving bioavailability and multi-stage utilization of sulfur matrix (i.e., S2−, poly-S and SO 4 2−) in these mixotrophic systems. Thiobacillus and Acidovorax have been enriched on the pyrite and PHBV surface, respectively, which highlighted that the autotrophic-heterotrophic synergy was achieved via different functional microbes domesticated by substrates. The differential analysis among functional genes suggested that PHBV surface promoted the NO 2 − reduction and S oxidation, and pyrite surface enhanced the N 2 O reduction and S reduction. A closer connection between C degradation and N cycle indicated their copiotrophic nutritional patterns based on the network analysis. The key taxa co-occurrence revealed rare species involved in Fe cycle metabolism were the hidden drivers in the mixotrophic denitrification process. These findings provide an in-depth understanding on the multiple interactions among N, S, and Fe cycling, and improve the practical application of pyrite-PHBV mixotrophic systems. [Display omitted] • Pyrite/PHBV system achieved high-rate denitrification under aerobic condition. • Low SO 4 2− production were attributed to S reduction and polysulfide formation. • Thiobacillus and Acidovorax enriched in pyrite and PHBV surface, respectively. • PHBV promoted the NO 2 − reduction and pyrite enhanced the N 2 O reduction. • Fe-related bacteria were hidden drivers in the pyrite/PHBV mixotrophic system. [ABSTRACT FROM AUTHOR]

The intensive accumulation of di-2-ethylhexyl phthalate (DEHP) in agricultural soils has resulted in severe environmental pollution that endangers ecosystem and human health. Biochar is an eco-friendly material that can help in accelerating organic pollutant degradation; nevertheless, its roles in enhancing DEHP removal in rhizosphere remain unclear. This work investigated the impacts of biochar dosage (0%–2.0%) on DEHP degradation performance in tomato rhizosphere by comprehensively exploring the change in DEHP metabolites, bacterial communities and DEHP-degrading genes. Our results showed a significant increase of rhizosphere pH, organic matter and humus by biochar amendment, which achieved a satisfactorily higher DEHP removal efficiency, maximally 77.53% in treatments with 1.0% of biochar. Biochar addition also remarkably changed rhizosphere bacterial communities by enriching some potential DEHP degraders of Nocardioides , Sphingomonas , Bradyrhizobium and Rhodanobacter. The abundance of genes encoding key enzymes (hydrolase, esterase and cytochrome P450) and DEHP-degrading genes (pht3 , pht4 , pht5 , benC-xylZ and benD-xylL) were increased after biochar amendment, leading to the change in DEHP degradation metabolism, primarily from benzoic acid pathway to protocatechuic acid pathway. Our findings evidenced that biochar amendment could accelerate DEHP degradation by altering rhizosphere soil physicochemical variables, bacterial community composition and metabolic genes, providing clues for the mechanisms of biochar-assisted DEHP degradation in organic contaminated farmland soils. [Display omitted] • The accelerated DEHP degradation in the tomato rhizosphere amended with biochar can be explained by the higher pH and humus levels. • Biochar amendment changed DEHP degradation pathways from benzoic acid to protocatechuic acid. • More genes encoding DEHP-degrading enzymes in biochar treatments. [ABSTRACT FROM AUTHOR]

• FGRA is performed to reveal the individual contribution of the design variables in laminated cooling configuration. • Film hole size is the primary factor on temperature distribution, but insensitive to flow resistance. • The redesigned film holes can obtain high cooling performances at low friction loss. Laminated cooling is a compound system consisting of different cooling units that can provide effective protection to the hot components in next generation gas turbines. In the present work, using validated numerical simulations, the influential levels of geometrical parameters in laminated cooling configuration (film hole diameter, pin-fin diameter, impingement hole diameter and film hole inclined angle) on multi-objective functions (overall cooling effectiveness, friction loss and temperature uniformity) are calculated and ranked by fuzzy grey relational analysis (FGRA). The FGRA results indicate that the film hole diameter is the primary influence factor on the overall cooling effectiveness and temperature uniformity, but insensitive to the friction loss. Based on this finding, two novel laminated cooling configurations with revised film-hole shapes, i.e., fan-shaped film holes and discrete rectangular film slots, are proposed to meet the multi-objective requirement. Through calculations, it is proved that the overall cooling effectiveness of the discrete film slots with a width of 0.5 mm can be increased by approximately 20%, whereas the additional friction loss is negligible (the increase of flow resistance coefficient is only 0.06 at mass flow ratio equals to 1.19%). Meanwhile, the acceptable temperature uniformity along with high overall cooling effectiveness, low friction loss can be obtained with the design of the fan-shaped film holes. The present work provides a novel analytical method for the multi-influence-factor problem and multi-objective design of complex laminated cooling system in gas turbine application. [ABSTRACT FROM AUTHOR]

Abstract: We developed a copolymeric bioadhesive system with the potential to be used as a tissue adhesive based on biopolymer dextran. Copolymeric hydrogels comprising a urethane dextran (Dex-U) and 2-hydroxyethyl methacrylate (HEMA) were prepared and crosslinked under the ultraviolet (UV) irradiation. In this study, the photopolymerization process was monitored by real time infrared spectroscopy (RTIR). The adhesion strength was evaluated by lap-shear-test. The surface tension, viscosity of the solutions and the cytotoxicity assays were investigated. Compared to Dex-U system, the addition of HEMA remarkably improved the properties of Dex-H system especially the adhesion strength and the nontoxicity. And materials variation could be tailored to match the need of tissues. The copolymeric tissue adhesives demonstrated promising adhesion strength and nontoxicity. The maximum adhesion strength reached to 4.33±0.47Mpa which was 86 times higher than that of Tisseel. The obtained products have the potential to serve as tissue adhesive in the future. [Copyright &y& Elsevier]