The effects of inclining angle of the coaxial nozzle in the longitudinal section of deposited bead on the molten pool geometry and the corresponding crystal growth in laser powder deposition of ...single-crystal superalloy are studied through the coupling of a numerical FLUENT program and a three-dimensional transient transport phenomena mathematical model. Systematical experiments with single-crystal nickel-based superalloy were conducted to verify the computational results. The results show that the inclination angle of the coaxial nozzle in the longitudinal section of deposited bead has a predominant effect on the molten pool geometry and the solidified microstructure. The inclination of coaxial nozzle reduces the height of the molten pool while increases the melting depth compared to the normal-direction deposition. The epitaxial grain growth in the deposited bead is enhanced when the coaxial nozzle inclines toward the laser scanning direction, while it is restrained as the nozzle inclines toward the opposite direction. When the coaxial nozzle inclines to a +45°, the ratio of melting depth to the height of equiaxied stray grain on the top of the previous layer of deposited bead exceeds 1.0, which implies that the deposited layer can completely remelt the stray grains in the previous layer. The capacity of continuous-epitaxial grain growth can be therefore achieved through the nozzle inclination effectively. This method can be used to optimize and control the processing parameters and broaden the processing window for a single-crystal turbine blade tip repair.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Chlorinated polyfluoroalkyl ether sulfonates (trade name F-53B) has been detected in various environmental matrices, and reported to be equally or more toxic than perfluorooctane sulfonate. Efficient ...sorptive removal of F-53B from water by two types of layered double hydroxides (LDHs), NO3−-LDH and sodium dodecyl sulfate modified NO3−-LDH (SDS-LDH), was demonstrated in this study. Both LDHs removed F-53B in several minutes and had sorption capacities of over 860 mg/g. SDS-LDH exhibited a greater F-53B uptake than NO3−-LDH under the influence of different solution chemistry, including pH 3-11, or in the presence of competing anions or co-contaminants, primarily due to the higher surface areas and the presence of SDS for SDS-LDH. Batch experiments, structural characterization, molecular dynamics simulations, and density functional theory calculations were combined to explore the sorption mechanisms, which mainly include ion exchange (specifically, O-H⋯O/F hydrogen bond), C-F/Cl⋯H hydrogen bond, and micellar sorption (occurring at high initial F-53B concentrations). Accordingly, we propose to improve the sorption performance of LDHs by increasing their surface areas and modifying LDHs to produce more hydrogen bond sites, as well as exfoliating LDHs into two dimensional nanosheets to eliminate the steric hindrance for the micellar formation of F-53B or other per- and polyfluoroalkyl substances.
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•NO3−-LDH and SDS-LDH showed fast and effective removal of F-53B from water.•Increasing the SBET of LDHs and introducing SDS onto LDHs improved F-53B uptake.•The sorption mechanisms mainly included hydrogen bond and micellar sorption.•The design strategies for future LDHs preparation were proposed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
China's iron and steel sector is faced with increasing pressure to control both local air pollutants and CO2 simultaneously. Additional policy instruments are needed to co-control these emissions in ...this sector. This study quantitatively evaluates and compares two categories of emission reduction instruments, namely the economic-incentive (EI) instrument of a carbon tax, and the command-and-control (CAC) instrument of mandatory application of end-of-pipe emission control measures for CO2, SO2 and NOx. The comparative evaluation tool is an integrated assessment model, which combines a top-down computable general equilibrium sub-model and a bottom-up technology-based sub-model through a soft-linkage. The simulation results indicate that the carbon tax can co-control multiple pollutants, but the emission reduction rates are limited under the tax rates examined in this study. In comparison, the CAC instruments are found to have excellent effects on controlling different pollutants separately, but not jointly. Such results indicate that no single EI or CAC instrument is overwhelmingly superior. The environmental and economic effectiveness of an instrument highly depends on its specific attributes, and cannot be predicted by the general policy category. These findings highlight the necessity of clearer identification of policy target priorities, and detail-oriented and integrated policy-making among different governmental departments.
•A carbon tax and command-and-control (CAC) instruments are evaluated and compared.•The carbon tax co-controls multiple pollutants by limited rates.•The CAC instruments control pollutant separately, but not jointly.•No single category of instruments is superior on all the criteria.•Policy-making for CO2 and local air pollution control should be integrated.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Recent academic endeavours have questioned whether the rapidly unfolding Payments for Environmental Services (PES) may have profound influence on land tenure which would in turn impact the ...conservation efficacy of PES. This paper developed a game-theory model in the context of rural China, which describes the endogenous formation of land rights as a bargaining process between ordinary villagers and village leaders. This model gave rise to theoretical predictions pertaining to the implications of two PES schemes in China for land tenure, namely the Sloping Land Conversion Programme (SLCP) and the Ecological Public-Benefit Forest Compensation Programme (EPBFCP). The theoretical predictions were tested using primary data collected through large-scale field surveys. These data were analysed using the Propensity Score Matching method and panel data models. Both the theoretical analysis and the empirical results find that the SLCP has likely enhanced land tenure security by increasing the bargaining costs of village leaders' attempts to reallocate SLCP lands to other households. On the other hand, villagers tend to have less motivation to de-collectivise those forest lands enrolled in the EPBFCP, which somewhat stands in the way of the country's agenda to further de-collectivise communal forests and allocate them to individual households.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
The scalable fabrication of flexible membranes for efficient oil/water separation is in high demand but still significantly underdeveloped. Here, we present a flexible membrane using Ti3C2Tx (MXene) ...as the functional layer on conventional print paper as the substrate. With a simple coating process using MXene ink, we developed a highly hydrophilic and oleophobic membrane with an underwater oil contact angle of 137°. Such a simple membrane shows outstanding flexibility and robustness, and demonstrates a facile approach for membrane scale-up using MXene ink on low-cost print paper. The membrane shows high separation efficiency for oil/water emulsions, of over 99%, and a high water permeation flux of over 450 L per m2 per h per bar. We demonstrate the excellent anti-fouling property of this membrane by cleaning the membranes without chemicals. These low-cost, highly efficient, anti-fouling membranes can provide new opportunities for industrial oil/water separation applications.
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IJS, KILJ, NUK, UL, UM, UPUK
The controlled functionalization of semiconducting 2D materials (2DMs) with photoresponsive molecules enables the generation of novel hybrid structures as active components for the fabrication of ...high‐performance multifunctional field‐effect transistors (FETs) and memories. This study reports the realization of optically switchable FETs by decorating the surface of the semiconducting 2DMs such as WSe2 and black phosphorus with suitably designed diarylethene (DAE) molecules to modulate their electron and hole transport, respectively, without sacrificing their pristine electrical performance. The efficient and reversible photochemical isomerization of the DAEs between the open and the closed isomer, featuring different energy levels, makes it possible to generate photoswitchable charge trapping levels, resulting in the tuning of charge transport through the 2DMs by alternating illumination with UV and visible light. The device reveals excellent data‐retention capacity combined with multiple and well‐distinguished accessible current levels, paving the way for its use as an active element in multilevel memories.
Optically switchable field‐effect transistors (FETs) are realized by decorating the surface of 2D WSe2 and black phosphorene with photochromic diarylethenes. Both electron and hole transport can be efficiently and reversibly modulated as a result of light irradiation at different wavelengths. These FETs also show five distinguishable output current levels with high‐accuracy readout, demonstrating their huge potential for multilevel memories.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
•PFAA can be found in all the vegetables from the largest vegetable production base.•PFBA was the predominant PFAA in vegetables from the largest vegetable production base.•Cabbage had higher ...bioaccumulation of PFBA (log BAF 1.24) than other vegetables.•Daily exposure to PFOA was highly likely to exceed health guideline value.•Consumption of cabbage contributed most to EDIs of PFBA, PFOA and PFOS.
This study investigated perfluoroalkyl acids (PFAAs) in edible parts of vegetables, soils, and irrigation water in greenhouse and open filed, for the first time, in Shouguang city, the largest vegetable production base in China, which is located nearby a fluorochemical industrial park (FIP). The bioaccumulation factors (BAFs) were calculated, and the human exposures of PFAAs via consumption of the vegetables for different age groups assuming the maximum levels detected in each vegetable and average consumption rates were also estimated. The ΣPFAA levels ranged from 1.67 to 33.5 ng/g dry weight (dw) in the edible parts of all the vegetables, with perfluorobutanoic acid (PFBA) being the dominant compound with an average contribution of 49% to the ΣPFAA level. The leafy vegetables showed higher ΣPFAA levels (average 8.76 ng/g dw) than the fruit and root vegetables. For all the vegetables, the log10 BAF values of perfluorinated carboxylic acids showed a decreasing trend with increasing chain length, with PFBA having the highest log10 BAF values (average 0.98). Cabbage had higher bioaccumulation of PFBA (log10 BAF 1.24) than other vegetables. For the greenhouse soils and vegetables, the average contribution of perfluorooctanoic acid (PFOA) to ΣPFAA was lower than that in the open field samples, while the contributions of PFBA, PFHxA, PFPeA to ΣPFAA were higher. Irrigation water may be an important source of PFAAs in greenhouse, while for open field vegetables and soils, atmospheric deposition may be an additional contamination pathway. The estimated maximum exposure to PFOA through vegetable consumption for urban preschool children (aged 2–5 years) was 63% of the reference dose set by the European Food Safety Authority. Suggestions are also provided for mitigating the health risks of human exposure to PFAAs.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Artificial intelligence (AI) could automatedly detect abnormalities in digital cytological images, however, the effect in cervical cancer screening is inconclusive. We aim to evaluate the performance ...of AI-assisted cytology for the detection of histologically cervical intraepithelial lesions (CIN) or cancer.
We trained a supervised deep learning algorithm based on 188,542 digital cytological images. Between Mar 13, 2017, and Oct 20, 2018, 2145 referral women from organized screening were enrolled in a multicenter, clinical-based, observational study. Cervical specimen was sampled to generate two liquid-based slides: one random slide was allocated to AI-assisted reading, and the other to manual reading conducted by skilled cytologists from senior hospital and cytology doctors from primary hospitals. HPV testing and colposcopy-directed biopsy was performed, and histological result was regarded as reference. We calculated the relative sensitivity and relative specificity of AI-assisted reading compared to manual reading for CIN2+. This trial was registered, number ChiCTR2000034131.
In the referral population, AI-assisted reading detected 92.6% of CIN 2 and 96.1% of CIN 3+, significantly higher than or similar to manual reading. AI-assisted reading had equivalent sensitivity (relative sensitivity 1.01, 95%CI, 0.97–1.05) and higher specificity (relative specificity 1.26, 1.20–1.32) compared to skilled cytologists; whereas higher sensitivity (1.12, 1.05–1.20) and specificity (1.36, 1.25–1.48) compared to cytology doctors. In HPV-positive women, AI-assisted reading improved specificity for CIN1 or less at no expense of reduction of sensitivity compared to manual reading.
AI-assisted cytology may contribute to the primary cytology screening or triage. Further studies are needed in general population.
•AI based on deep learning could generated severity scores of abnomal cytology associating with histological lesions.•AI-assisted cytology show comparable performance for the detection of CIN2+ relative to skilled cytologist in referral women.•AI-assisted cytology would improve specificity at no expense of sensitivity in HPV-positive triage.•AI-assisted cytology may contribute to the primary cytology screening or HPV-positive triage.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The feasibility of producing high-density sintered magnesia with a one-step sintering method was investigated by utilizing finely ground magnesite as raw materials for direct flotation. The mechanism ...of flotation desilication of microfine grain magnesite was investigated by combining microstructure and chemical properties. The results showed that dodecylamine (DDA) has a sorting effect on magnesite reverse flotation desilication. Under the premise of 150 mg/L sodium polyacrylate (PAANa) as an inhibitor and 300 mg/L DDA as a collector, the content and recovery rate of MgO can reach 83.91% and 78.78%, respectively. When sodium oleate (NaOL) was used as a collector, the recovery rate of MgO was only 49.22%; therefore, it is unsuitable for magnesite purification. The flotation effect was affected because MgO particles and SiO2 particles agglomerated in the flotation process. The flotation agent cannot work for a single element but works for the mineral agglomerate. While collecting Si elements, the agglomerated MgO was also brought into the froth layer, making flotation impossible.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
The dextran coated Fe₃O₄ magnetic nanoparticles (MNPs) have been successfully synthesized and used for brackish water desalination for the first time. The dextran coated Fe₃O₄ MNPs well meets the ...stringent criteria for draw solutes of forward osmosis (FO) process via technologically integrating the good solubility of dextran and strong magnetism of Fe₃O₄ nanoparticles. Our experimental results demonstrated that the dextran coated Fe₃O₄ MNPs are not only able to produce high osmotic pressure to draw clean water across FO membranes from brackish water, but also can be easily recovered from the diluted draw solution by an external magnet. Based on our currently conducted works, it is believed that the dextran coated Fe₃O₄ MNPs can be an ideal draw solute for brackish water desalination by using FO process in an environmental-friendly and energy-saving manner.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
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