•MAO + EPS composite coatings were prepared on magensium alloy.•Composite coatings had good binding force with substrates.•Composite coatings had excellent scratch resistance and acid corrosion ...resistance.
Based on the morphological characteristics of the microporous micro arc oxidation (MAO) ceramic coating, a double layer composite coating system was applied on the surface of AZ31 magnesium alloy by MAO plus electrostatic powder spraying (EPS) technique. The Mg sample coated with MAO plus EPS (MAO + EPS) was compared with Mg sample coated by MAO coating or EPS monolayer. The results indicated that the corrosion resistance of AZ31 Mg alloy was significantly improved by MAO + EPS composite coating with the exellent binding force. Furthermore, the corrosion mechanism of three coated Mg alloy was discussed.
A novel hollow ZnS–CdS nanocage-based molecularly imprinted photoelectrochemical (ZnS–CdS/rMIP PEC) sensor was designed for sensitive detection of oxytetracycline (OTC). O-phenylenediamine was ...electropolymerized onto hollow ZnS–CdS nanocages to form a polymer film, and then OTC molecules were imprinted on the polymer film through hydrogen bonding. When OTC was eluted, many specific recognition sites were formed on the polymer membrane for detecting OTC in samples. It is worth noting that the rhombohedral dodecahedral structure of hollow ZnS–CdS nanocage can provide large specific surface area, allowing more OTC molecules to be imprinted into the polymer film. Moreover, the unique hollow structure and the heterojunction formed by ZnS and CdS can significantly enhance the photocurrent response. Furthermore, molecular imprint polymer (MIP) technology greatly improves the selectivity and sensitivity of the constructed PEC sensor for detection of OTC. Under optimal conditions, the ZnS–CdS/rMIP PEC sensor has prominent linear relationship in the range of OTC concentration from 1 nmol L−1 to 3 μmol L−1, and the detection limit is 0.10 nmol L−1 (S/N = 3). It is gratifying that the fabricated ZnS–CdS/rMIP PEC sensor displays excellent selectivity for OTC detection when interferences with similar structure exist. It also exhibits superior reproducibility and stability as well as high recovery in the investigation of actual water samples. The combination of PEC and MIP technology will provide significant reference value for effective and rapid detection of other pollutants in the environment.
•A PEC sensor based on hollow ZnS–CdS/rMIP is used for detection of OTC.•Heterojunction and hollow structure enhance photoelectric response of the material.•Molecular imprinting improves the selectivity of the PEC sensor.•This PEC platform could detect OTC with high sensitivity.
Recently, stereoscopic image quality assessment has attracted a lot attention. However, compared with 2D image quality assessment, it is much more difficult to assess the quality of stereoscopic ...images due to the lack of understanding of 3D visual perception. This paper proposes a novel no-reference quality assessment metric for stereoscopic images using natural scene statistics with consideration of both the quality of the cyclopean image and 3D visual perceptual information (binocular fusion and binocular rivalry). In the proposed method, not only is the quality of the cyclopean image considered, but binocular rivalry and other 3D visual intrinsic properties are also exploited. Specifically, in order to improve the objective quality of the cyclopean image, features of the cyclopean images in both the spatial domain and transformed domain are extracted based on the natural scene statistics (NSS) model. Furthermore, to better comprehend intrinsic properties of the stereoscopic image, in our method, the binocular rivalry effect and other 3D visual properties are also considered in the process of feature extraction. Following adaptive feature pruning using principle component analysis, improved metric accuracy can be found in our proposed method. The experimental results show that the proposed metric can achieve a good and consistent alignment with subjective assessment of stereoscopic images in comparison with existing methods, with the highest SROCC (0.952) and PLCC (0.962) scores being acquired on the LIVE 3D database Phase I.
The performance of perovskite solar cells (PSCs) relies on the synthesis method and chemical composition of the perovskite materials. So far, PSCs that have adopted two‐step sequential deposited ...perovskite with the state‐of‐art composition (FAPbI3)1−x(MAPbBr3)x (x < 0.05) have achieved record power conversion efficiency (PCE), while their one‐step antisolvent dripping counterparts with typical composition Cs0.05FA0.81MA0.14Pb(I0.85Br0.15)3 with more bromine have exhibited much better long‐term operational stability. Thus, halogen engineering that aims to elevate bromine content in sequential deposited perovskite film would push operational stability of PSCs toward that of antisolvent dripping deposited perovskite materials. Here, a Br‐rich seeding growth method is devised and perovskite seed solution with high bromine content is introduced into a PbI2 precursor, leading to bromine incorporation in the resulting perovskite film. Photovoltaic devices fabricated by Br‐rich seeding growth method exhibit a PCE of 21.5%, similar to 21.6% for PSCs having lower bromine content. Whereas, the operational stability of PSCs with higher bromine content is significantly enhanced, with over 80% of initial PCE retained after 500 h tracking at maximum power point under 1‐sun illumination. This work highlights the vital importance of halogen composition for the operational stability of PSCs, and introduces an effective way to incorporate bromine into mixed‐cation‐halide perovskite film via sequential deposition method.
Operationally stable mixed‐cation‐halide perovskite solar cells are fabricated by halogen‐engineering concept via a Br‐rich seeding growth method. Bromine anions are effectively incorporated into the final perovskite film with larger grains and better vertical columnar alignment. Photovoltaic devices based on the film show a power conversion efficiency (PCE) of 21.5% and significantly enhanced operational stability for over 500 h.
Graphene has been extensively investigated as anode material for Li and Na ion batteries due to its excellent physical and chemical performance. Herein, we report a new member of ‘graphene family’, a ...reduced graphene nanowire on three-dimensional graphene foam (3DGNW). The novel graphene nanowires were synthesized via a template strategy involving reduction and assembly process of nanosized graphene oxides (nGO), pyrolysis of polystyrene spheres (PS) template and catalytic reaction between GO and PS decomposition products. When evaluated as anodes material for Li and Na ion batteries, the 3DGNW exhibits relatively low discharge-voltage plateau, excellent reversible capacity, rate capability, and durable tolerance. For anode of Na ion batteries, a reversible capacity of more than 301mAhg−1 without capacity fading after 1000 cycles at rate of 1C were achieved. Even at rate of 20C, a high reversible capacity of 200mAhg−1 can be retained. The superior electrochemical performance is ascribed to hierarchical multidimensional graphene architecture, high graphene crystallinity, expansile graphene interlayer distance, and extensively lateral exposed edges/pores, which can promote the electron and ion transport. The realization of assembling reduced graphene sheets to graphene nanowire offers new opportunities for energy storage application of graphene based assembly in future.
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•The novel graphene nanowires anchored to 3D graphene foam were synthesized via a template strategy.•The all graphene anode exhibits relatively low discharge plateau, excellent rate capability, and durable tolerance.•The assembling of reduced graphene to graphene nanowire offers new opportunities for energy storage application.
The ever-growing demand for electrical energy of sensing devices in the Internet of Things (IoT) has led to generating large amounts of electricity consumption data. Electricity service providers ...often use wireless sensor networks to collect sensing devices' electricity consumption data for statistical analysis, so as to provide sensing devices with improved electrical services. As an important data mining technique, while data clustering excels in dealing with such massive data, it imposes the risk of privacy disclosure in the process of data clustering. In an effort of solving this problem, Blum et al. proposed a differential privacy <inline-formula> <tex-math notation="LaTeX"> {k} </tex-math></inline-formula>-means algorithm, effectively preventing privacy disclosure. However, the availability of data clustering results is reduced due to the data distortion in Blum's algorithm. In this paper, we propose a privacy and availability data clustering (PADC) scheme based on <inline-formula> <tex-math notation="LaTeX"> {k} </tex-math></inline-formula>-means algorithm and differential privacy, which enhances the selection of the initial center points and the distance calculation method from other points to center point. Moreover, PADC attempts to reduce the outlier effect through detecting outliers during the clustering process. Security analysis indicates that our scheme satisfies the goal of differential privacy and prevents privacy information disclosure. Meanwhile, performance evaluation shows that our scheme, at the same privacy level, improves the availability of clustering results compared to the existing differential privacy <inline-formula> <tex-math notation="LaTeX"> {k} </tex-math></inline-formula>-means algorithms, suggesting that our proposed PADC scheme outperforms others for intelligent electrical service in IoT.
One of the characteristics of topological materials is their nontrivial Berry phase. Experimental determination of this phase largely relies on a phase analysis of quantum oscillations. We study the ...angular dependence of the oscillations in a Dirac material Formula: see text and observe a striking spin-zero effect (i.e., vanishing oscillations accompanied with a phase inversion). This indicates that the Berry phase in Formula: see text remains nontrivial for arbitrary field direction, in contrast with previous reports. The Zeeman splitting is found to be proportional to the magnetic field based on the condition for the spin-zero effect in a Dirac band. Moreover, it is suggested that the Dirac band in Formula: see text is likely transformed into a line node other than Weyl points for the field directions at which the spin zero occurs. The results underline a largely overlooked spin factor when determining the Berry phase from quantum oscillations.
It has been proposed that dehydration embrittlement of hydrous materials can trigger intermediate-depth earthquakes and form a double seismic zone in a subducting slab. Seismic anisotropy may provide ...a possible insight into intermediate-depth intraslab seismicity, because anisotropic properties of minerals change with varying water distribution, temperature and pressure. Here we present a high-resolution model of P-wave radial anisotropy tomography of the Japan subduction zone down to ~400 km depth, which is obtained using a large number of arrival-time data of local earthquakes and teleseismic events. Our results reveal a close correlation between the pattern of intermediate-depth seismicity and anisotropic structures. The seismicity occurs in portions of the Pacific and Philippine Sea slabs where positive radial anisotropy (i.e., horizontal velocity being faster than vertical one) dominates due to dehydration, whereas the inferred anhydrous parts of the slabs are found to be aseismic where negative radial anisotropy (i.e., vertical velocity being faster than horizontal one) dominates. Our anisotropic results suggest that intermediate-depth earthquakes in Japan could be triggered by dehydration embrittlement of hydrous minerals in the subducting slabs.
One of the characteristics of topological materials is their nontrivial Berry phase. Experimental determination of this phase largely relies on a phase analysis of quantum oscillations. We study the ...angular dependence of the oscillations in a Dirac material Formula: see text and observe a striking spin-zero effect (i.e., vanishing oscillations accompanied with a phase inversion). This indicates that the Berry phase in Formula: see text remains nontrivial for arbitrary field direction, in contrast with previous reports. The Zeeman splitting is found to be proportional to the magnetic field based on the condition for the spin-zero effect in a Dirac band. Moreover, it is suggested that the Dirac band in Formula: see text is likely transformed into a line node other than Weyl points for the field directions at which the spin zero occurs. The results underline a largely overlooked spin factor when determining the Berry phase from quantum oscillations.
Intensification of short‐duration rainfall extremes contributes to increased urban flood risk. Yet, it remains unclear how upper‐tail rainfall statistics could change with regional warming. Here, we ...characterize the non‐stationarity of rainfall extremes over durations of 1–24 hr for the rapidly developing coastal megalopolis of the Greater Bay Area, China. Using high‐resolution, multi‐source, merged and gridded data we observe greater increases in rainfall intensities over the north‐central part of the region compared with the southern coastal region. Our results show, for the first time, that urbanization nonlinearly increases rainfall intensities at different durations and return periods. Over short durations (≤3‐hr) and short return periods (2‐yr), urban areas have the greatest scaling rates (≥19.9%/°C). However, over longer durations (≥9‐hr) rural areas have greater scaling rates, with a lower degree of dependency on both durations and return periods.
Plain Language Summary
Short‐duration (sub‐daily) rainfall extremes are major drivers of flash floods and hence significant disruptions to society. Previous modeling and statistical studies show that urbanization intensifies short‐duration rainfall extremes. However, there has been less attention to regional variations in rates of rainfall intensification under a warming climate, particularly for extreme events with return periods that are comparable to or longer than the years of record. In this study, we investigate changes in rainfall extremes over the Greater Bay Area, China using long records of high‐resolution data merged from gauge networks, satellite observations, and reanalysis products. This enables us to evaluate changes in low‐frequency rainfall extremes (2‐ to 100‐yr return periods) over different land surfaces, under a warming climate. We find that increases in rainfall extremes significantly depend on the duration and return period of events, with the largest scaling occurring for short‐duration “nuisance” rainfall intensities over urban areas.
Key Points
Non‐stationarities of sub‐daily rainfall extremes over a coastal megalopolis exhibit marked land cover and duration dependencies
Urban areas show more prominent intensification of events over short durations and short return periods compared with rural areas
Rural areas show smaller nonstationary variabilities across durations and return periods and a lower peak scaling rate than urban areas
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