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To improve the corrosion inhibition of zinc-rich epoxy (ZRE) composite coatings and shed light on the influence of the spatial structure of graphene fillers on the coatings' performance, three-dimensional graphene (3DG) and a conventional graphene sheet (G) were used to modify the ZRE composite paint, respectively. The effect of introducing the 2D G fillers on the anti-corrosion behavior of ZRE was studied comprehensively, and its optimal content was determined to be 0.5 wt%. Interestingly, it was found that, comparing with 2D graphene sheets, the corrosion resistance of the ZRE coating could be enhanced more significantly with incorporating even less 3DG. With introducing only 0.1 wt% 3DG, the corrosion current intensity of the resulting 3DG/ZRE coating was reduced to be about 1/10 that of the G/ZRE coating with the same graphene content and 27% of that of the optimized G/ZRE. The corrosion products of the coating were analyzed with the XRD technique. The results indicated that, in contrast to neat ZRE coating, Zn5(CO3)2(OH)6 was absent from the corroded 3DG/ZRE coating, confirming its improved long-term anti-corrosion performance. The porous interconnected framework and high crystallinity of 3DG could contribute to not only its facilely mixing with epoxy resin, but also its effective incorporation into the conductive network of zinc micro-flakes, thus enhancing the corrosion resistance of its ZRE coating at a lower content. The innovative technology to improve the anti-corrosion performance of the ZRE coatings via using the 3D graphene fillers should be capable to be extended to other 2D fillers, such as MXenes. [ABSTRACT FROM AUTHOR]

Approximate nearest neighbor (ANN) search has become an essential paradigm for large-scale image retrieval. Conventional ANN search requires the categories of query images to been seen in the training set. However, facing the rapid evolution of newly-emerging concepts on the web, it is too expensive to retrain the model via collecting labeled data with the new (unseen) concepts. Existing zero-shot hashing methods choose the semantic space or intermediate space as the embedding space, which ignore the inconsistency of visual space and semantic space and suffer from the hubness problem on the zero-shot image retrieval task. In this paper, we present an novel deep quantization network with visual-semantic alignment for efficient zero-shot image retrieval. Specifically, we adopt a multi-task architecture that is capable of 1) learning discriminative and polymeric image representations for facilitating the visual-semantic alignment; 2) learning discriminative semantic embeddings for knowledge transfer; and 3) learning compact binary codes for aligning the visual space and the semantic space. We compare the proposed method with several state-of-the-art methods on several benchmark datasets, and the experimental results validate the superiority of the proposed method. [ABSTRACT FROM AUTHOR]

To solve the problem of thermal deformation during the cut-off process of polylactic acid (PLA) filter rods for heated tobacco products (HTPs), a vortex tube was added to the cut-off unit of filter rod maker to cool the cut-off knife. By numerical simulation, the preferable parameters of the vortex tube were determined: inlet pressure Pin 0.5 MPa, inlet air temperature Tin 26.85 °C, the air flow leaving the vortex tube is divided into hot and cold streams. When the hot end air pressure Phot is fixed at 0.07 MPa, the maximum cooling effect can be achieved. The vortex tube cooling was tested on an AF-KDF2 filter rod maker. The results showed that the temperature of the cut-off knife was lowered from 57.8 °C to 13.1 °C, the fibrous tail at filter's cut end was avoided, meantime, the running speed of the maker was increased from 50 m/min to 150 m/min. The roundness and circumference of the filter rods were stably within the specified limits. This technology supports the improvement of HTP quality. [ABSTRACT FROM AUTHOR]

Some sensitive data in the network will be leaked due to the loopholes or weaknesses of the web system itself, which will bring potential harm to the society or the public. Aiming at this, this study carries out the design of web security penetration test system. A test scheme comparing single method with an automatic comprehensive test method is designed. Based on this scheme, an automatic penetration test system script used under the terminal operation page is tested and designed. A security evaluation algorithm based on the prediction results of the game between attack and defense is proposed. Through this algorithm, different website systems are evaluated and scored, and the test results are compared through scoring. The automatic penetration test integration system designed and implemented in this study can meet the main objectives of web security and the protection requirements of websites against general, routine, and universal security attacks. The proposed evaluation algorithm is more detailed, accurate, and reference in scoring. [ABSTRACT FROM AUTHOR]

Dense medium component (DMC) is a group component of coal, which is composed of macromolecular skeleton aggregate embedded by small molecules. Previously, the dense medium component skeleton (DMC-S) aggregate model was established. In this paper, the DMC-S aggregate model was characterised and the behaviour of small organic molecules filling the DMC-S aggregate was investigated by Molecular dynamics (MD) method. The energy change was the largest when olefins were filled into the DMC-S aggregate, followed by alkanes and aromatics, because most of the small olefin molecules were embedded into the DMC-S aggregate in a network-embedded state that depends on intermolecular hydrogen bonds and π-σ hyperconjugation. In contrast, aromatic molecules were relatively incompatibility with the DMC-S aggregate and primarily presented in a free state on the surface of the macromolecular network. The simulation results are in good agreement with the studies on the leaching behaviour of olefins, aromatics, and alkanes in the coal extraction process, indicating that the molecular dynamics simulation technique is a useful method in the field of coal structure. [ABSTRACT FROM AUTHOR]

The protective layer mining method of the traditional deep coal seam in has been confronted with great challenges, and it is difficult for coal and gas to be extracted together. Taking the occurrence conditions of III1 mining area of Luling Coal Mine located at Huaibei, China, as engineering background, the influence law of the lithology on stress environment in front of the stope was analyzed by theoretical analysis and numerical simulations. The mining-induced mechanical effect of coal-rock mass was studied under different protective layer mining modes. The results showed that the peak value of the advanced abutment pressure decreased with the decrease of lithologic strength under the same mining conditions. For simulated geological conditions, the stress concentration coefficient of soft rock and coal seam protective layer mining modes was 1.9 and 1.7, respectively. Under the mining stress path of different protective layers, the ratio of axial stress increase and confining pressure unloading in secondary unloading phase were 2 : 1 and 1.5 : 1, respectively. The axial stress-strain curves of different protective layer mining modes had similar trends, and they had a volume expansion at the end of unloading (failure stage). In addition, it revealed the pressure-relief antireflection mechanism of the protective layer mining. Under the same confining pressure condition, the peak stress and peak strain increased with the increase of loading and unloading velocity ratio. The reduced value of the confining pressure increased, while the volume expansion decreased at failure. The results were applied to III1 mining area in soft rock protective layer mining, which created the mining way of traditional coal seam protective layer. Furthermore, the gas control technology of soft rock protective layer working face was put forward for deep coal seam with low permeability and high gas, enriching the pressure-relief mining theory of protective layer. [ABSTRACT FROM AUTHOR]

Summary: We develop a unique self‐template method to synthesize hierarchical porous carbons (HPCs) by co‐activation of heavy component (HC) and dense medium component (DMC) separated from bituminous coal. HC and DMC are obtained by employing the mixture solvent (CS2/N‐methyl‐2‐pyrrolidone) and deionized water as extractant and back extractant to separate bituminous coal. The plentiful kaolinite [Al2(Si2O5) (OH)4] in the HC produce Natrolite (K) (K2Al2Si3O10•2H2O) during the activation process, which can serve as self‐template to prepare HPCs. Moreover, the addition of asphalt‐like DMC allows the templates to be better utilized. Effect of the remixture ratio of DMC/HC on HPCs' porous structures and electrochemical properties are studied in detail. The optimal sample (HPC‐0.4) displays an ultrahigh surface area (3851 m2 g−1), appropriate hierarchically system and excellent conductivity. When applied to supercapacitors, HPC‐0.4 delivers a large capacity of 436 F g−1 at 0.1 A g−1 in alkaline electrolyte, and maintains 212 F g−1 at 10 A g−1. This self‐template strategy paves a practical route to construct applicable porous carbons for supercapacitors from low‐cost high‐minerals coal. [ABSTRACT FROM AUTHOR]

A natural hydrogen donor, i.e., a subfraction of the coker gas oil, was used in thermal upgrading of the Venezuela extra-heavy oil. The role of hydrogen donor was quantitatively studied by a combination of thermogravimetric analysis and differential scanning calorimetry. The hydrogen donation was clearly evidenced and reliably evaluated by comparing the experimental and calculated thermal parameters. The mutual interactions between the heavy oil and the hydrogen donor extended the coke induction period (from 19 to 25 min), inhibited the thermal evaporation of the hydrogen donor, and resulted in a stronger endothermic effect in the pyrolysis stage. [ABSTRACT FROM AUTHOR]

Driven by the association of chemical weak forces and solvent effects, zero- to two-dimensional nanostructures of thiophene-substituted perylene bisimide such as spheres and blocky structures were obtained. Light-controlled intramolecular charge transfer from the trithiophene unit to the perylene bisimide in the solid state can induce a hypochromatic shift and enhanced fluorescent emission. [ABSTRACT FROM AUTHOR]

Two kinds of D–A molecular of (4-(4-(9H-carbazol-9-yl)phenyl))-7-nitrobenzothiadiazole (BSC) and 4-((4-(9H-carbazol-9-yl)phenyl)ethynyl)-7-nitrobenzothiadiazole (BEC) containing carbazole moieties as the donor were synthesized. X-ray crystal data elucidated the multiple intermolecular interactions. They exhibit distinctly different self-assembly behaviours. The nonlinear optical properties were studied using the top-hat Z-scan technique at 532 nm with a 21 ps pulse. The results indicate that they exhibit large third-order nonlinear absorption effects. The nonlinear absorption coefficients α2 fitting the experimental data are 6.3 × 10−12 m W−1 for BSC and 3.6 × 10−11 m W−1 for BEC. The time-resolved pump–probe results show that both nonlinear absorption and nonlinear refraction of BEC in CH2Cl2 solution have rapid optical responses, which indicate the nonlinear absorption and nonlinear refraction mechanism are excited-state nonlinear. Moreover, both of these two compounds are observed to be aggregation-induced emission (AIE) active. The aggregates of the well-formed one-dimensional microrods of BEC and BSC endow the material with potential applications in the field of optical devices. [ABSTRACT FROM AUTHOR]

A perylenetetracarboxdiimide derivative containing an anthraquinone unit has been synthesized by the phototriggered intramolecular cyclization of 2-anthraquinone-substituted perylenetetracarboxdiimide. The anthraquinone-substituted perylenetetracarboxdiimide dyes showed excellent electron-accepting abilities with four reversible reduction potentials. Photovoltaic devices of ITO/PEDOT:PSS/P3HT:PDIs/Ca/Al were fabricated and power conversion efficiencies of 0.16 and 0.39 were obtained for 1 and 2, respectively. [ABSTRACT FROM AUTHOR]

A new supramolecular species of naphthalene-diimide cyclophane containing triazole units was synthesized, and its fluorescent responses to metal ions were investigated in dichloromethane (DCM). The fluorescence emission of NDI was quenched by intramolecular electron transfer, whereas the appearance of dimer emission of the naphthalene-diimide in the presence of Mg2+, Ba2+, Hg2+, Ca2+, Zn2+ and Pb2+ was observed. [ABSTRACT FROM AUTHOR]

Previewing plays a crucial role in formal learning. This paper reports a study intended to investigate the picture of English text previewing by non-English majors. Think-aloud, observation and interview were employed. The results indicate that non-English majors exercised learner autonomy in their previewing by setting objectives and selecting materials for their previewing, selecting previewing approaches, monitoring and evaluating their previewing. Although both groups in the study attached great importance to previewing and exercised autonomy in previewing, differences existed between successful and unsuccessful English learners, with the former group taking more effective control of this autonomous learning activity than the latter. Based on the findings, some suggestions concerning English teaching and textbook compiling are made. [ABSTRACT FROM AUTHOR]

A smooth and defectless carbon sheet with thickness of 1–2 μm was prepared by loose medium component from coal. Then, porous carbon sheet materials were prepared by activation of the carbon sheet using KCl and KOH under 750 °C and N 2 atmosphere. Such materials have lattice defect and porous structure which were verified by emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman and N 2 adsorption-desorption. Their electrochemical performances were studied by cyclic voltammetry curves and constant current charge-discharge curves. The results showed that varing the content of KCl could control the distribution of the mesopore so as to change the specific capacitance. When carbon/KCl/KOH was at a mass ratio of 1:3:4, the specific capacitance reached up to 346 F g−1 at the current density of 0.1 A g −1 with high energy density and power density of 12 Wh kg−1 and 25 W kg−1, respectively. The high specific capacitance of this material was corresponded to its porous structure with high specific surface area of 3627 m2 g−1. Based on the above structure features and performance results, this paper supplies a brand new and promising way for synthesis of supercapacitor materials. • Coal was used to form smooth carbon sheets that are etched into pores. • KCl did not act as a pore-creating agent on the carbon sheets, but act as an adjuvant when added with KOH. • The specific surface area of the porous activated carbon sheet was up to 3627 m2 g−1. • The electrochemical properties were up to 346 F g−1 at 0.1 A g −1. [ABSTRACT FROM AUTHOR]

Abstract: The Fe-doping LiMnPO4 (LiMn1−x Fe x PO4, x ≤ 0.5) nanomaterials are solvothermally synthesized in a mixed solvent of water and polyethylene glycol (PEG). The particle morphology can be controlled simply by adjusting the pH values of precursor suspensions. Electrochemical test shows that LiMn0.9Fe0.1PO4 nanoplates with a thickness of 20–30 nm could deliver the largest discharge capacity, which is attributed to the fast Li+ diffusion in the diffusion path of [010] crystallographic axis along the short radial direction of the nanoplates. It is demonstrated that Fe doping could significantly increase the initial reversible capacity, cycle performance and rate capability. The first discharge capacities of Fe-doped LiMnPO4 are all above 150 mAh g−1 at the discharge rate of 0.05 C. Especially, LiMn0.5Fe0.5PO4 delivers 100% capacity retention with the reversible capacity of 147 mAh g−1 at the discharge rate of 1 C, and losses only about 23.4% capacity with the discharge rate varying from 0.1 C to 5 C. The variation of energy density predicts that LiMn0.5Fe0.5PO4 shows the potential application for high-power devices. [Copyright &y& Elsevier]

Coal as an important fossil energy has been comprehensively studied in terms of its structure, reactivity, and application. However, there are few publications reported about the formation mechanism of coal. In order to explore the molecular mechanism of the formation of the dense medium component (DMC) aggregate, which is extracted from coal, the molecular model of the DMC scaffold (DMC-S) was constructed based on a number of X-ray photoelectron spectroscopy, 13 C NMR, and ultimate analysis. Then, DMC-S was further optimized, and the periodic boundary condition was added for molecular mechanics and molecular dynamics simulation. The DMC-S molecule model with a density of 1.05 g/cm 3 and a different number of unit cells was obtained after the aforementioned experiments and simulations. When the unit cell contained 12 DMC-S molecules, the absolute value of electrostatic energy significantly increased and the peripheral branch chains in DMC-S interlaced with each other, forming a compact aggregate. The density and macrosize calculated values are all slightly lower than the true relative values because the presence of minerals or small molecules was not included in the model construction. Despite some unavoidable defects, the comparison between the simulated and experimental results validates the DMC-S aggregate model and lays a solid foundation for an in-depth study of DMC and its reactivity., Competing Interests: The authors declare no competing financial interest., (Copyright © 2020 American Chemical Society.)

This study was aimed to assess the potential of Dioscorea (yam) leaves as a source of antioxidants. Microwave-assisted extraction (MAE) process was used to prepare the extracts. The phenolic compounds in Dioscorea leaves extracts were analyzed by HPLC-DAD-ESI-MS/MS method and the contents of major compounds were determined. Results indicated that a total of 17 phenolic compounds were separated identified by means of UV and mass spectra compared with authentic reference substances and/or reported values in the literature. The main phenolic compound was rosmarinic acid and its highest amount was found in Dioscorea glabra Roxb. leaves (22.31±1.33 mg/g DW). Rutin was the dominant flavonoid followed by quercetin which highest amount was found in Dioscorea alata leaves (8.66±0.29 mg/g DW). Antioxidant activity of the extracts was estimated by the use of DPPH and ABTS assays. Both kinds of leaves exhibited satisfied antioxidant capacity which was correlated with phenolic contents. In the cytoprotective effect on HUVECs viability assay, Dioscorea glabra Roxb. leaves extract was found to be more active than that of Dioscorea alata against H 2 O 2 -induced oxidative stress. Our findings support the promising role of Dioscorea leaves that can be used as an interesting source of phenolic antioxidants.

s-Tetrazine and their derivatives are found to be a class of selective and colorimetric chemosensors for fluoride anions. The supramolecular interaction (anion-π and charge/electron transfer) between fluoride ion and π-electron deficient tetrazines receptor could facilitate the F(-)-tetrazines electron transfer (ET) event that generates tetrazine˙(-) radical anion. Accordingly, the color of its solution changed from red to green. Furthermore, the recognition of F(-) in DMSO is tolerant to water (DMSO-H(2)O = 9:1, v/v) and shows excellent selectivity towards other anions, especially H(2)PO(4)(-) and OAc(-).