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When a certain electric vehicle is driving at a constant speed of 40 km/h on the rough asphalt road, the rear passenger can obviously feel the ear pressure, which seriously affects the comfort. Through the analysis of objective data, it was found that the problem was caused by the road excitation, which leads to the coupling between the mode of the backup door and the mode of the acoustic cavity, and causes the resonance of the car cavity, thus causing the ear pressure sensation. To solve this problem, this paper optimizes the backup door by means of experiment and simulation, increases the dynamic vibration absorber, makes its modal frequency avoid the acoustic cavity modal frequency, and achieves the purpose of reducing the interior noise. After optimization, the vehicle noise is reduced by 8 dBA at 42 Hz under 40 km/h working condition of rough road surface, and the ear pressure sensation is reduced at the same time, thus improving the NVH (noise, vibration, and harshness) performance of the vehicle.

The ever-growing demands for energy storage motivate the development of high-performance batteries. Rechargeable alkaline Zn batteries get increasing attractions due to their remarkable performance, high safety, low cost, and environmental friendliness. However, the research is in the early stage with challenges that hinder the road of commercialization, such as the unsatisfactory utilization of active materials and poor stability. Recently, some excellent works are performed to boost the development of alkaline Zn batteries from the electrode optimization to electrolyte exploration and structure design. Herein, this article provides a timely spotlight on the breakthroughs in the performance and structure of well-developed Zn batteries such as Zn–Ag and Zn–Ni batteries, as well as some new types of Zn batteries like Zn–Co, Zn–Cu, and Zn–Bi batteries. The reaction mechanisms of different positive electrodes are first introduced, followed by the summary on positive electrodes, Zn electrodes, and electrolytes. Moreover, current issues and possible strategies are also highlighted.

Strong geometrical confinement and reduced dielectric screening of two-dimensional (2D) materials leads to strong Coulomb interaction and eventually give rise to extraordinary excitonic effects, which dominates the optical and optoelectronic properties. For nonlinear 2D photonic or optoelectronic applications, excitonic effects have been proved effective to tune the light-matter interaction strength. However, the modulation of excitonic effects on the other aspect of nonlinear response, i.e., polarization dependence, has not been fully explored yet. Here we report the first systemic study on the modulation of excitonic effects on the polarization dependence of second and third harmonic generation (SHG and THG) in strained monolayer WS2 by varying excitation wavelength. We demonstrated that polarization-dependent THG patterns undergo a giant evolution near two-photon excitonic resonance, where the long-axis of the parallel component (originally parallel to the strain direction) has a 90° flip when the excitation wavelength increases. In striking contrast, no apparent variation of polarization-dependent SHG patterns occurs at either two- or three-photon excitonic resonance conditions. Our results open a new avenue to modulate the anisotropic nonlinear optical response of 2D materials through effective control of excitonic resonance states, and thus open opportunity for new designs and applications in nonlinear optoelectronic 2D devices.

The integration of photonic crystal fibre (PCF) with various functional materials has greatly expanded the application regimes of optical fibre1–12. The emergence of graphene (Gr) has stimulated new opportunities when combined with PCF, allowing for electrical tunability, a broadband optical response and all-fibre integration ability13–18. However, previous demonstrations have typically been limited to micrometre-sized samples, far behind the requirements of real applications at the metre-scale level. Here, we demonstrate a new hybrid material, Gr–PCF, with length up to half a metre, produced using a chemical vapour deposition method. The Gr–PCF shows a strong light–matter interaction with ~8 dB cm−1 attenuation. In addition, the Gr–PCF-based electro-optic modulator demonstrates a broadband response (1,150–1,600 nm) and large modulation depth (~20 dB cm−1 at 1,550 nm) under a low gate voltage of ~2 V. Our results could enable industrial-level graphene applications based on this Gr–PCF and suggest an attractive platform for two-dimensional material-PCF. A hybrid material based on uniform graphene on both the outer surface and inner hole walls of a photonic crystal fibre offers a strong, tunable light–matter interaction and good broadband electro-optic modulation performance under low gate voltage.

Zn batteries are attractive for energy storage due to their low cost and intrinsic safety. However, the low utilization of active materials results in unsatisfied capacities. Herein, Zn batteries based on nanostructured NiCo2O4 electrodes are developed. Through hydrothermal reactions, porous NiCo2O4 nanosheets, nanowires, and nanoplates are fabricated, which are in-situ grown on the surface of nickel foam substrates, facilitating the electron transport and electrochemical reactions. In particular, the battery with the nanowire electrode exhibits the largest discharge capacity of 230.1 mAh g−1, which accounts for 68.7% of the theoretical capacity of NiCo2O4. Based on the weights of NiCo2O4 and consumed Zn, the energy density of the battery is 301.3 Wh kg−1, higher than most of the reported Zn batteries. At a high current density of 8 A g−1, the capacity is still 164.25 mAh g−1, with the retention of 71.38%, which illustrates the high rate performance. Moreover, after 1000 discharge-charge cycles, the capacity retention is 63.23%, which reveals remarkable cycling stability. The results show that the NiCo2O4 nanowire electrode is attractive for Zn batteries with high capacity, energy density, rate performance, and cycling stability.

To improve the corrosion resistance, bioactivity and bonding strength of magnesium alloys, fluoride doped hydroxyapatite (FHAp) coating was fabricated on micro-arc oxidation (MAO) treated AZ31B magnesium alloy by a simple hydrothermal treatment. The surface morphology, phase composition, electrochemical property, degradation behavior and cytocompatibility of the prepared coatings were investigated in this study. The effect of the doping amount of fluoride ion on the morphology and phase composition of the composited coating was also studied. Through controlling the doping amount of fluoride ions, a uniform and dense FHAp coating composed of many nanorods was successfully prepared on MAO treated AZ31B magnesium alloy. And the the addition of fluoride ions in hydrothermal solution can facilitate the formation of FHAp phase in the coating. The thickness of FHAp/MAO composite coating was about 20 μm and the coating showed good adhesion to the substrate. And the composite coating showed higher corrosion resistance and lower degradation rate than Ca-P/MAO composite coating and the uncoated substrate. Moreover, osteoblasts cellular tests proved that the FHAp/MAO composite coating significantly improved the cell adhesion and spreading, proliferation and expression of alkaline phosphatase due to the doping of fluoride ion.

A novel strategy for constructing sulfur containing bis-S-heterocyclic compounds from oxime esters/vinyl azide, phenylacetylene/aldehydes and elemental sulfur (S8) has been developed. These transformations show good functional group tolerance. Various bis-S-heterocyclic products were efficiently synthesized from easily prepared or widely commercially available starting materials. In this protocol, S8 successfully served as a two-sulfur atom donor for thiophene and thiazole rings, respectively.

High-quality Normalized Difference Vegetation Index (NDVI) time series are essential in studying vegetation phenology, dynamic monitoring, and global change. Gap filling is the most important issue in reconstructing NDVI time series from satellites with high spatial resolution, e.g., the Landsat series and Chinese GaoFen-1/6 series. Due to the sparse revisit frequencies of high-resolution satellites, traditional reconstruction approaches face the challenge of dealing with large gaps in raw NDVI time series data. In this paper, a climate incorporated gap-filling (CGF) method is proposed for the reconstruction of Landsat historical NDVI time series data. The CGF model considers the relationship of the NDVI time series and climate conditions between two adjacent years. Climate variables, including downward solar shortwave radiation, precipitation, and temperature, are used to characterize the constrain factors of vegetation growth. Radial basis function networks (RBFNs) are used to link the NDVI time series between two adjacent years with variabilities in climatic conditions. An RBFN predicted a background NDVI time series in the target year, and the observed NDVI values in this year were used to adjust the predicted NDVI time series. Finally, the NDVI time series were recursively reconstructed from 2018 to 1986. The experiments were performed in a heterogeneous region in the Qilian Mountains. The results demonstrate that the proposed method can accurately reconstruct and generate continuous 30 m 8-day NDVI time series using Landsat observations. The CGF method outperforms traditional time series reconstruction methods (e.g., the harmonic analysis of time series (HANTS) and Savitzky-Golay (SG) filter methods) when the raw time series is contaminated with large gaps, which widely exist in Landsat images.

The release of liquid effluent of nuclear power into aquatic system increases with the rapid development of nuclear facilities in coastal and inland regions. Aquatic model animals are very important for the study of the radiation hazards to non-human biota in water environment and its extrapolation of dose-effect relationship to human models. However, the study of the radiation dose rate calculation model of the aquatic animal zebrafish is still on the homogeneous isotropic model used for the protection of the environment. A series of zebrafish models (including adults, larvae and embryos, named zebrafish-family: ZF-family) with multiple internal organs are established in this study to investigate the mechanism of radiation damage effect in order to protect non-human species. The internal and external dose coefficients (DCs) of the whole body, heart and gonads of zebrafishes are calculated in water environment with the combination of the real experimental culture condition, using Monte Carlo application package GATE (Geant4 Application for Emission Tomography) and eight nuclides, i.e., 3H, 14C, 90Sr, 60Co, 110mAg, 134Cs, 137Cs, 131I, which are commonly found in the liquid effluent of nuclear power plants, as the source items, The results show that the level of nuclide γ energy determines the external DCs (DCext), and 90Sr plays the most important role in internal DCs (DCint). The comparison between the external DCs of the heart and gonad and that of the whole body shows that DCs (DCext) of heart and gonad for females are 80% and 43% lower than that of whole body, respectively, while for males, the DCs (DCext) of heart is 44% lower than that of the whole body, and DCs (DCext) of gonad is slightly higher than that of the whole body for most nuclides (up to 25%).The dose of internal radiation makes greater contribution than that of external radiation to pure beta emitter (3H, 14C, 90Sr). This internal DCs of ZF-family model with complex internal structure turns out to demonstrate more sensitive DCs change trend and higher calculation values compared with the internal DCs of the simple ellipsoid model. In this model, the photon emitter with strong penetrating power has higher internal DCs, while the low-energy pure beta nuclide does not alter much. In conclusion, it is vital to carry out refined systematic modeling for model organisms, and the determination of DCs of model organs can promote the evaluation of the radiation effects on non-human species.

A multicomponent strategy to achieve two different regioselectivities from alkynes, isothiocyanates and H2 O with a proton acid/N-chlorophthalimide (NCPI) system is described to selectively obtain non-aromatic five-membered sulfur heterocycles (1,3-oxathiol-2-imines/thiazol-2(3H)-one derivatives) through multiple bond formations. The process features readily available starting materials, mild reaction conditions, broad substrate scope, good functional-group tolerance, high regio- and chemo- selectivities, gram-scale synthesis and late-stage modifications. Mechanistic studies support the proposal that the transformation process includes a combination of H2 O and isothiocyanate, free-radical formation, carbonation and intramolecular cyclization to give the products. Furthermore, the 1,3-oxathiol-2-imine derivatives possess unique fluorescence characteristics and can be used as Pd2+ sensors with a "turn-off" response, demonstrating potential applications in environmental and biological fields.

Graphene-photonic crystal fibers (PCFs) are obtained by integrating the broadband optical response and electro-optic tunability of graphene with the high-quality waveguide capacity and easy-integrability of the PCF, and this has been proven to be an important step towards multimaterial multifunctional fiber and all-fiber integrated circuits. However, the reported electro-optic modulator based on directly-grown graphene-PCF suffers from very low response speed (below 100 Hz) due to the slow response of ionic liquid. Here, we propose new functional PCFs with a sandwiched graphene/hBN/graphene (Gr/hBN/Gr) film attached to the hole walls of the fibers, and theoretically demonstrate that the in-line modulator based on it can achieve simultaneous single-mode transmission ranging from 1260 nm to 1700 nm (covering all optical communication bands), significant modulation depth (e.g. ∼42 dB mm-1 at 1550 nm) and high modulation speed (up to ∼0.1 GHz). Furthermore, various device functions can be designed by changing the structure of the fiber, including the length, the hole diameter and the layer numbers of graphene and hBN films. This proposed approach directs a viable path to obtain high-performance all-fiber devices based on hybrid two-dimensional material optical fibers.

Benefited from the rapid development of deep learning, object detection in natural image has made great improvements. However, since the size of the optical remote sensing video is very large while the size of airplane is very small, airplane detection in optical remote sensing video still faces a lot of challenges. In this article, we aim at a novel approach for airplane detection in optical remote sensing video. The proposed approach utilizes spatial features from structured forests edge detection and temporal features from neighboring frames. It is capable of circumventing existing challenges and running at a high speed for practical applications. To realize this goal, edge detection results of optical remote sensing video frames are obtained from structured forests edge detection method. Afterwards, improved frames differencing method is utilized to extract temporal features. Finally, airplane detection result is generated by deep neural networks with extracted spatial and temporal features. Our experiments demonstrate that our method has a great breakthrough on the precision and recall of airplane detection in optical remote sensing video.

In this study, a novel micro-nano hierarchically structured fluoridated hydroxyapatite (FHAp) coating on AZ31B substrate was successfully synthesized via a simple one-step electrochemical deposition method. And the formulation of the electrodeposition solution is simple and environment-friendly without any harmful additives. The FHAp coating consists of a large amount of nanorods and some micro-structured spherical aggregates composed of nanorods. Electrochemical tests demonstrated that the FHAp coating exhibited higher anti-corrosion property and lower degradation rate than that of pure HAp coating. Moreover, the FHAp coating with micro-nano hierarchically structured surface displayed good cell biocompatibility. The addition of fluorine ion into HAp coating can further promote the cell adhesion and proliferation. This work provides a simple, environment-friendly, and efficient way to prepare FHAp coating on AZ31B alloy with improved corrosion resistance and biocompatibility.

This study developed a comprehensive system to evaluate the intensity of cropland use and evolution of cropland use in the Huang-Huai-Hai Plain. Delphi-entropy methods were adopted to determine the weight of the index, and the GeoDetector model was established to explore the influencing factors. The results are summarized as follows: (1) The intensity of inputs, degree of utilization, and production increased continuously, but the intensity of continuous conditions experienced an overall decline followed by a rebound towards the end of the study period. The number of counties with high and moderately high intensity increased by 56.8% and 14.6%, respectively, from 1996 to 2011. The number of counties with moderately low and low intensity declined by 35.9 % and 11.9 %, respectively. Areas with significant increases in intensity were mainly distributed in northeast Hebei Province, northwest Shandong Province, and north Jiangsu Province. The intensity is high in northern Jiangsu and Anhui; the output effect remained above moderate intensity mainly near Beijing, Tianjin, Tangshan, and counties in the suburbs of Shijiazhuang. (2) Natural disasters, elevation, slope, and road networks were the main factors influencing the intensity of cropland use in this region, with influence values of 0.158, 0.143, 0.129, and 0.054, respectively. Areas with moderately high and high levels of intensity were distributed in low-lying areas. Uneven distribution of precipitation, seasonal drought, and flood disasters can directly affect the stability index of croplands and reduce the intensity of cropland use. Developed road networks are associated with moderately high intensity. Our results suggest recommendations such as promoting agricultural intensification and large-scale management, promoting the construction of road networks, improving early warning systems for drought and flood disasters, and promoting moderate and intensive use of arable land, and focusing on restoration and sustainable use of cropland.

As one of the most popular Chinese tea products, oolong tea involves the most complicated manufacturing process and the most abundant tea germplasm resources. However, the unclear genetic backgrounds of oolong tea germplasms have been biological limitations for tea breeding and quality control. In this study, high-throughput SNP technology was used to analyze the genetic diversity of 100 oolong tea landraces and cultivars. Ninety-six pairs of primers were selected and validated from the expressed sequence tag (EST) database of Camellia sinensis. The results verified 75 SNP loci that are able to accurately and efficiently determine the genetic relationships among Chinese oolong tea germplasms. The DNA fingerprints of 4 main oolong tea-producing areas were constructed by tracing the information of each site of the SNP. The Guangdong oolong tea germplasms were a relatively distinct group, while the genotypes of Taiwan oolong tea were similar to those of populations in Fujian. The tea germplasms in Southern and Northern Fujian had the largest intersections, and they also showed their own characteristics. Our results provide guidance for the identification, integration, and selection of parents for tea plant germplasms. Moreover, our study provides an effective tool to protect the diversity of tea germplasms and to assist in future breeding work.

A copper-catalyzed aerobic oxidative annulation reaction of 2-aminopyridine/amidine with isothiocyanate has been reported. This strategy involving C-N/N-S bond formations provides various 5-amino/imino-substituted 1,2,4-thiadiazole derivatives under a Cu/O2 catalytic system. This method has demonstrated high reactivity, mild reaction conditions, and a broad substrate scope. Furthermore, the synthetic utilities of the approach are demonstrated by further modifications.

The phase transformation of Al9(Mn, Ni)2 eutectic phase has been observed in the Al-4Ni-2Mn alloy during heat treatment at 350 °C, 400 °C, 450 °C, 500 °C and 550 °C for different times, and investigated by scanning electron microscopy and transmission electron microscopy. It has been found, for the first time, that fibrous Al9(Mn, Ni)2 eutectic phase can transform into a ternary hexagonal κ-phase (κ-Al14.4Cr3.4Nil.1-type, hP227, P63/m) during the heat treatment, and the lattice parameters of Al-Ni-Mn κ-phase have been determined to be a = 1.799 nm, c = 1.295 nm, by measuring the selected area electron diffraction patterns. Furthermore, the experimental results also show that Al-Ni-Mn κ-phase prefers to nucleate at the interface between Al matrix and Al9(Mn, Ni)2 eutectic phase and grows into the parent phase, eventually, resulting in the breakup of the eutectic fiber at the nucleation sites.

This paper investigates the guaranteed cost consensus design problem for generic high-order multi-agent systems subject to control input constraints. Firstly, an intermittent consensus control protocol is constructed with intermittent local information, where the related weighted quadratic cost index is considered to trade off the consensus performance against the energy expenditure while achieving consensus. The guaranteed cost consensus analysis criterion is given by using linear matrix inequality methods. Meanwhile, a guaranteed cost is derived to show the upper bound of the cost index. Then, by the changing variable approach, the guaranteed-cost design criterion is presented. It is proved that multi-agent systems with control input constraints realize guaranteed cost consensus via designing the control gain of the consensus control protocol with the related cost index. Finally, a numerical simulation is provided to verified the effectiveness of the derived theoretical results.

Rugged terrain significantly complicates the land surface albedo modeling and retrievals in remote sensing. Neglecting the topographic effects may lead to large uncertainties when estimating land surface albedo over rugged terrain. In this study’ the sensitivities of snow-free vegetation shortwave albedo to topography are quantitatively investigated and analyzed based on the Moderate Resolution Imaging Spectroradiometer (MODIS) land surface albedo data and the global sensitivity analysis of a mechanistically-based land surface albedo parameterized model over rugged terrain. The results reveal that the topography can account for more than 30% of the total variabilities of the land surface albedo and the topographic effects on land surface albedo cannot be neglected even for the terrain with the mean slope of 10°.

Understory vegetation has largely affected the accuracy of forest leaf area index (LAI) estimation. This study analyzed the components of overstorey and understory based on the forest reflectance and transmittance (FRT) model for six forest types in China: i.e. a planted fir forest, a mixed fir and pine forest, deciduous broad-leaved forest, evergreen broad-leaved forest, broad-leaved pinus koraiensis forest, and seasonal tropical rainforest. The contributions of understory were varied for different forest types within a year. The contributions of understory for the tropical rainforest and the coniferous and broad-leaved mixed forest were low due to the dense canopy with higher LAI of overstorey. The effect of understory was unneglectable for the whole wavelengths.

In natural settings, intermittent dynamics are ubiquitous and often arise from a coupling between external driving and spatial heterogeneities. A well-known example is the generation of transient, turbulent puffs of fluid through a pipe with rough walls. Here we show how similar dynamics can emerge in a discrete, crystalline system of particles driven by noise. Polydispersity in particle masses leads to localized vibrational modes that effectuate a transition to a gas-like phase. A minimal model for the evolution of the system's mechanical energies exhibits quasi-cyclic oscillations, and a single, dimensionless number captures the essential features of the intermittent dynamics, analogous to the Reynolds number for pipe flow.

With the rapid expansion of the electric vehicle market, the demand for advanced energy storage technologies is increasing strongly. An alkaline hybrid zinc battery with cobalt oxide as the positive electrode material combines the advantages of the high working voltage of Zn–Co batteries and the excellent discharge capacity of Zn–air batteries simultaneously. However, the development of hybrid zinc batteries is limited by their low energy efficiency and poor cycling stability. To investigate the charge–discharge behaviors of hybrid zinc batteries, a mathematical model is established, coupling the mass transport inside the porous electrode with energy conversion. Then, the effects of discharge depth, reaction interfaces, and active material degradation on energy efficiency are investigated through numerical analysis. It is found that within a proper region, the higher ratio of two-phase and three-phase interfaces can lead to higher energy efficiency, and the increase of the two-phase interfaces is beneficial for improving energy efficiency. While the effects of active material degradation on energy efficiency are significant, resulting in poor cycling stability. This work is favorable for the design of interfaces and the selection of operating conditions, and guides the performance improvement of hybrid zinc batteries.

The alkaline zinc-iron flow battery is an emerging electrochemical energy storage technology with huge potential, while the theoretical investigations are still absent, limiting performance improvement. A transient and two-dimensional mathematical model of the charge/discharge behaviors of zinc-iron flow batteries is established. After validated by experimental data, numerical analysis is carried out focusing on the influences of electrolyte flow rate and electrode geometry towards the electrochemical performance. The results demonstrate that a high flow rate, high electrode thickness, and porosity are favorable for battery performance. Following this finding, the parameters of a zinc-iron flow battery are optimized by utilizing a high flow rate of 50 mL min−1, an asymmetrical structure with a negative electrode of 7 mm and a positive electrode of 10 mm, and high porosity of 0.98. With the optimal flow rate and geometry, the electrolyte utilization, coulombic efficiency, and energy efficiency attain 98.62%, 99.18%, and 92.84%, respectively, significantly higher than those of the un-optimized design. This work provides a comprehensive strategy allowing for the improvement of the practical design of zinc-iron flow batteries.

The performance of Zn–Co batteries is hindered by some critical issues, such as the low electric conductivity and poor valence-change ability, restricting the utilization of the active material. This study aims at improving the electrochemical performance of the battery via substituting Ni on the Co3O4 electrode. A novel multiple self-assembled nanowire-nanosheet structure is constructed with the substitution of 10% Ni, the high electric conductivity and decent valence change-ability push the electrode to the top-tier among the reported Zn–Co batteries, including the high capacity of 272 mAh g−1, high energy density of 448 Wh kg−1, and excellent rate performance with a capacity retention ratio of 72.5% after even 40-fold increase of the current density. In terms of the cycle stability, it can operate well with a capacity retention ratio of 85.3% before the 1000th cycle, while dramatically decay in the subsequent cycles. More importantly, to illuminate the role of Ni substitution on the capacity decay, a systematic investigation on the Ni substituted Co3O4 electrode is conducted for the first time. The capacity decay mechanism is proposed as the decreased low valence species, microstructure collapse, and irreversible phase transition with an increase of the Ni substitution ratio. This work offers insights to develop high-performance and durable electrodes for Zn–Co batteries.

The temporal characteristic and source apportionment analyses on carbohydrates in this study are useful for understanding PM2.5 sources in Yangtze River Delta (YRD) region. Carbohydrates are important consistent of primary organic aerosol (POA) and some of them are widely used as tracers for source apportionment of fine particle (PM2.5). In this study, ambient concentrations of 10 carbohydrates (levoglucosan, arabitol, mannitol, sucrose, fructose, glucose, inositol, threitol, 2-methyl-threitol, and trehalose) in PM2.5 at a suburb site of Nanjing during 2017–2018 were quantified by a high-performance liquid chromatography tandem mass spectrum/mass spectrum (HPLC-MS/MS). Among all measured carbohydrates, Levoglucosan, with the average concentration of 337.6 ng m−3, was the dominant one, contributing 89% of the total 10 carbohydrates concentration. The concentration of levoglucosan in 2017 was 412.4 ng m−3, higher than that of 2018 (232.5 ng m−3). Similarly, the average concentration for other 9 carbohydrates was 43.6 ng m−3 in 2017, slightly higher than 2018 (38.32 ng m−3). Levoglucosan concentrations presented a similar seasonal variation in both 2017 and 2018, which values were high in winter and autumn, and went down in summer and spring. As for the other 9 carbohydrates, their overall concentrations presented different seasonal variation patterns between 2017 and 2018. During 2017, their concentrations were the highest in summer, followed by spring, autumn, and winter. However, the richest concentrations occurred in spring, followed by autumn, summer and winter during 2018. Positive matrix factorization (PMF) model was then applied for sources apportionment of carbohydrates. Seven sources were identified, including airborne pollen, fungal spores and soil dust, plants debris, biomass burning, biogenic secondary organic aerosol (SOA), threitol-rich source, and inositol-rich source. Biomass burning contributed the most to the measured concentrations of 10 carbohydrates, with relative contribution of 57.9%, followed by airborne pollen (12.9%), 2-methyl-threitol rich source (10.0%), fungal spores and soil dust (9.4%), plant debris (6.3%), threitol-rich source (2.4%), and inositol-rich source (1.1%). Relative contributions of biomass burning showed a significant decrease from 68.8% in 2017 to 50% in 2018, suggesting that biomass burning in YRD region was well controlled in 2018 compared to 2017.

In this work, a sensitive method based on the High Performance Liquid Chromatography-Electrospray Ionization-Mass spectrometry/Mass spectrometry (HPLC-ESI-MS/MS) technique was established and validated, and successfully applied to quantify biomass burning tracer species (in total 20 compounds) in fine aerosol particles (PM2.5) collected during the full year of 2016 in Nanjing, China. The annual levoglucosan concentration was determined to be 328.3 ng m−3, at a similar level as it in other Chinese cities; the concentration peaked in fall, indicating influences of crop/straw burning during harvest periods. Concentrations of other species were a few orders of magnitude lower than that of levoglucosan, with salicylic acid (1.53 ng m−3), cis-pinonic acid (0.60 ng m−3) and vanillic acid (0.51 ng m−3) as the three most abundant ones. Total concentrations of tracers indicative of softwood, hardwood and grass burning were about equal. Seasonal concentrations of these tracers were generally similar, and all peaked in winter, different from that of levolglucosan. Further positive matrix factorization (PMF) identified four types of biomass (cellulose, harwood lignin, softwood lignin and grass). Celluose was dominated in fall, while softwood and hardwood were both dominated in winter, and seasonal contributions (except summer) were relatively even to grass. On an annual basis, softwood, hardwood and grass contributions were almost on par to the selected tracers, in agreement with the results based only on concentrations, but seasonally, grass was the major one in spring, summer and fall, but much less important in winter.

Kompetitive allele-specific PCR (KASP) is a cost-effective single-step SNP genotyping technology, With an objective to enhance the marker repertoire and develop high efficient KASP-SNP markers in Chinese cabbage, we re-sequenced four Chinese cabbage doubled haploid (DH) lines, Y177-47, Y635-10, Y510-1 and Y510-9, and generated a total of more than 38.5 billion clean base pairs. A total of 827,720 SNP loci were identified with an estimated density of 3,217 SNPs/Mb. Further, a total of 387,354 SNPs with at least 30 bp to the next most adjacent SNPs on either side were selected as resource for KASP markers. From this resource, 258 (96.27%) of 268 SNP loci were successfully transformed into KASP-SNP markers using a Roche LightCycler 480-II instrument. Among these markers, 221 (85.66%) were co-dominant markers, 220 (85.27%) were non-synonymous SNPs, and 257 (99.6%) were newly developed markers. In addition, 53 markers were applied for genotyping of 34 Brassica rapa accessions. Cluster analysis separated these 34 accessions into three clusters based on heading types. The millions of SNP loci, a large set of resource for KASP markers, as well as the newly developed KASP markers in this study may facilitate further genetic and molecular breeding studies in Brassica rapa.

Gap probability theory provides a theoretical equation to calculate fractional vegetation cover (FVC). However, the main algorithms used in present FVC products generation are still the linear mixture model and machine learning methods. The reason to limit the gap probability theory applied in the product algorithm is the availability and accuracy of leaf area index (LAI) and clumping index (CI) products. With the improvement of the LAI and CI products, it is necessary to assess whether the algorithm based on gap probability theory using the present products can improve the accuracy of FVC products. In this study, we generated the FVC estimates based on the gap probability theory (FVCgap) with a resolution of 500 m every 8 days for Europe. FVCgap estimates were validated with field FVC measurements of ImagineS from 2013 to 2015 for crop types. Two existing FVC products, Geoland2 Version1 (GEOV1) and Multisource data Synergized Quantitative remote sensing production system (MuSyQ), were used to inter-compare with the FVCgap estimates. FVCgap estimates showed a better agreement with field FVC measurements, with lowest root mean square error (RMSE) (0.1211) and bias (0.0224), than GEOV1 and MuSyQ FVC products. The inter-annual and seasonal variations of FVCgap estimates were also showed the most consistent with field measurements.

Bismuth oxyselenide (Bi2 O2 Se), a new type of 2D material, has recently attracted increased attention due to its robust bandgap, stability under ambient conditions, and ultrahigh electron mobility. In such complex oxides, fine structural distortion tends to play a decisive role in determining the unique physical properties, such as the ferrorotational order, ferroelectricity, and magnetoelasticity. Therefore, an in-depth investigation of the fine structural symmetry of Bi2 O2 Se is necessary to exploit its potential applications. However, conventional techniques are either time consuming or requiring tedious sample treatment. Herein, a noninvasive and high-throughput approach is reported for characterizing the fine structural distortion in 2D centrosymmetric Bi2 O2 Se by polarization-dependent third-harmonic generation (THG). Unprecedentedly, the divergence between the experimental results and the theoretical prediction of the perpendicular component of polarization-dependent THG indicates a fine structural distortion, namely, a

Carbohydrates (such as levoglucosan) are a class of important water-soluble organic compounds in atmosphere. In this study, a high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) was applied to characterize carbohydrates in aerosol particles. Since carbohydrate was a kind of compound with low response in mass spectrometry, the conventional HPLC-MS/MS method was not sensitive enough to determine it. When acetate acid was added into mobile phase as buffer, the transition of [M+CH3COO]−→[M-H]− could be selected as the quantification ions. In the range from 1.0 μg L−1 to 20 μg mL−1, the coefficients of regression (r2) were more than 0.990, and relative standard deviations (RSD) for replicated injections were lower than 2%. The limit of detection (LOD) and quantification (LOQ) were lower than 2.5 ng L−1 and 10 ng L−1, respectively. The precision and accuracy were examined by spiked samples at three different concentration levels (10 μg L−1, 100 μg L−1, and 500 μg L−1) in five replicates. Recovery ratios ranged from 85% to 115% with RSD lower than 16%. Matrix effects of different carbohydrates ranged from 62% to 120%. The most sensitive HPLC-MS/MS method was developed and validated to analyze 40 aerosol samples successfully. The carbohydrates including three sugar alcohols (threitol, arabitol and sorbitol), one monosaccharide sugar (inositol), two disaccharides (sucrose, trehalose), one anhydrosugar (levoglucosan) and one 2-methyltetrols (2-Methylbutane-1,2,3,4-tretraol) were successfully quantified.

Zinc electrode stability is one of the major problems that restrict the wide application of secondary zinc-based batteries. In this work, the impacts of flowing electrolyte on the suppression of zinc dendrite are systematically investigated through experimental and numerical investigations. In a static electrolyte condition, the stability of the zinc electrode increases with an increase of the applied current density. In the presence of flowing electrolyte, the lifespan of the zinc electrode at the current density of 10 mA cm−2 increases dramatically from 900 cycles in the static electrolyte to 2580 cycles with a flow rate of 30 rad min−1, and further increases to 4725 cycles when increasing the flow rate to 50 rad min−1. Moreover, by changing the inlet flow direction from the side to the bottom, a more stable electrode with the lifespan of 18000 cycles (1200 h) is achieved. The numerical calculation illustrates that the distribution of zincate ions is more uniform in the presence of the flowing electrolyte, which is the key to the dendrite suppression. Thus, with the implementation of flowing electrolyte, a stable zinc electrode with an ultralong lifespan is demonstrated, which is promising for practical applications.

Modeling plays an important role to link the land surface physical/chemical properties with remotely sensed data. In the past decade of years, Multi-scale Remote Sensing Models have been developed (Chen, J. M. et. al. 1997, Huang, H. et. al. 2013). In Recent years, remote sensing communities tend to consider the complex terrain scenario more reasonable recently, such as mixed pixel, topography issues and so on.

Spatial heterogeneity is present in the land surface at every scale and is one of the key factors that introduces inherent uncertainty into simulations of land surface processes and parameter retrieval based on remotely sensed data. Because of a lack of understanding of the heterogeneous characteristics of global mixed pixels, few studies have focused on modeling and inversion algorithms in heterogeneous areas. This paper presents a parameterization scheme to describe land cover heterogeneity quantitatively by composition and boundary information based on high-resolution land cover products. Global heterogeneity features at the 1-km scale are extracted from the ‘GlobeLand30’ land cover dataset with a spatial resolution of 30 m. The composition analysis of global mixed pixels shows that only 35% of pixels over the land surface of Earth are covered by a single land cover type, namely, pure pixels, and only 25.8% are located in vegetated areas. Pixels mixed with water are more common than pixels mixed with any other non-vegetation type. The fragmentation analysis of typical biomes based on the boundary length shows that the savanna is the most heterogeneous biome, while the evergreen broadleaf forest is the least heterogeneous. Deciduous needleleaf forests are significantly affected by canopy height differences, while crop and grass biomes are less affected. Lastly, the strengths and limitations of the method and the application of the land cover heterogeneity characteristics extracted in this study are discussed.

Stimulated emission depletion (STED) microscopy has become a powerful imaging and localized excitation method, breaking the diffraction barrier for improved spatial resolution in cellular imaging, lithography, etc. Because of specimen-induced aberrations and scattering distortion, it is a great challenge for STED to maintain consistent lateral resolution deep inside specimens. Here we report on deep imaging STED microscopy using a Gaussian beam for excitation and a hollow Bessel beam for depletion (GB-STED). The proposed scheme shows an improved imaging depth of up to about 155 μm in a solid agarose sample, 115 μm in polydimethylsiloxane, and 100 μm in a phantom of gray matter in brain tissue with consistent super resolution, while standard STED microscopy shows a significantly reduced lateral resolution at the same imaging depth. The results indicate the excellent imaging penetration capability of GB-STED, paving the way for deep tissue super-resolution imaging and three-dimensional precise laser fabrication.

Inspired by the Salvinia effect, we report the fabrication and characterization of a novel "sticky" superhydrophobic surface sustaining a Cassie-Baxter wetting state for water droplets with high contact angles but strong solid-liquid retention. Unlike superhydrophobic surfaces mimicking the lotus or petal effect, whose hydrophobicity and droplet retention are typically regulated by hierarchical micro- and nanostructures made of a homogeneous material with the same surface energy, our superhydrophobic surface merely requires singular microstructures covered with a hydrophobic coating but creatively coupled with hydrophilic tips with different surface energy. Hydrophilic tips are selectively formed by meniscus-confined electrodeposition of a metal (e.g., nickel) layer on top of hydrophobic microstructures. During the electrodeposition process, the superhydrophobic surface retains its plastron so that the electrolyte cannot penetrate into the cavity of hydrophobic microstructures, consequently making the electrochemical reaction between solid and electrolyte occur only on the tip. In contrast to typical superhydrophobic surfaces where droplets are highly mobile, the "sticky" superhydrophobic surface allows a water droplet to have strong local pinning and solid-liquid retention on the hydrophilic tips, which is of great significance in many droplet behaviors such as evaporation.

A copper-catalyzed aerobic oxidative reaction between aromatics or heteroaromatics with KSCN is developed by using O2 as the oxidant. The combination of Cu(OTf)2, N,N,N′,N′-tetramethylethylenediamine (TMEDA) and BF3·Et2O provides an efficient catalytic system, affording substituted thiocyanation products and 2-aminobenzothiazoles in excellent yields. The reaction also possesses a good functional group tolerance for both strong electron-withdrawing and electron-donating groups.

In this paper, a servoing controller composing both homographic relation and direct depth information is designed without decoupling the depth as past contributions have done. The servoing strategy does not need homograghy matrix decomposing to get rotation and displacement, or massive depth data computing, leading to less complex in calculation and faster in operation. The wheeled mobile robot computes the vector normal of and the distance to the feature plane to obtain relative current pose with a fixed RGB-D sensor mounted in direction of the robot linear velocity. Simulation and experiment results are shown for feasibility verification of the RGB-D servoing strategy.

We report a collinear-chiral-SFG microscope for mapping chirality by utilizing longitudinally polarized optical field generated from vectorial beam, diffraction limited spatial resolution is demonstrated which conventional non-collinear chiral SFG imaging could not reach.

Gross primary productivity (GPP) is the most important component of terrestrial carbon flux. Red-edge (680−780 nm) reflectance is sensitive to leaf chlorophyll content, which is directly correlated with photosynthesis as the pigment pool, and it has the potential to improve GPP estimation. The European Space Agency (ESA) Sentinel-2A and B satellites provide red-edge bands at 20-m spatial resolution on a five-day revisit period, which can be used for global estimation of GPP. Previous studies focused mostly on improving cropland GPP estimation using red-edge bands. In this study, we firstly evaluated the relationship between eight vegetation indices (VIs) retrieved from Sentinel-2 imagery in association with incident photosynthetic active radiation (PARin) and carbon flux tower GPP (GPPEC) across three forest and two grassland sites in Australia. We derived a time series of five red-edge VIs and three non-red-edge VIs over the CO2 flux tower footprints at 16-day time intervals and compared both temporal and spatial variations. The results showed that the relationship between the red-edge index (CIr, ρ 783 ρ 705 − 1 ) multiplied by PARin and GPPEC had the highest correlation (R2 = 0.77, root-mean-square error (RMSE) = 0.81 gC∙m−2∙day−1) at the two grassland sites. The CIr also showed consistency (rRMSE defined as RMSE/mean GPP, lower than 0.25) across forest and grassland sites. The high spatial resolution of the Sentinel-2 data provided more detailed information to adequately characterize the GPP variance at spatially heterogeneous areas. The high revisit period of Sentinel-2 exhibited temporal variance in GPP at the grassland sites; however, at forest sites, the flux-tower-based GPP variance could not be fully tracked by the limited satellite images. These results suggest that the high-spatial-resolution red-edge index from Sentinel-2 can improve large-scale spatio-temporal GPP assessments.

The maglev flywheel energy storage system is a kind of high efficiency ways for energy storage and conversion. It has many advantages such as zero-millisecond switching time, high efficiency, high energy storage density, low maintenance costs, long life-time, and no pollution. It has been applied widely. Since the flywheel energy storage characteristics, the moment of inertia ratio between pole and equatorial is large, gyroscopic effect in high speed greatly influence the rigid modes frequencies and stability of the flywheel rotor, the traditional decentralized PID control has been unable to meet the requirements. The cross-feedback algorithm is used to suppress the effect of the gyroscopic effect of magnetic levitation system which simulated by MATLAB. From simulation results, the measurement error of rotor speed, the size of attenuation factor and the delay time of control system will influent the suppression effect of gyroscopic effect with the cross feedback control algorithm, the ranges of influence factors is cleared with simulation to ensure the effectiveness of cross-feedback control algorithm, and laid the foundation for further engineering application.

We report a Gauss-Bessel STED microscope for super-resolution deep imaging. Improved lateral resolution at 95μm-depth in agarose phantom of brain tissue is about 110nm, which is nearly 2-fold improvement on resolution comparing to conventional STED imaging.

In this paper, we report a simple fabrication process of whole Teflon superhydrophobic surfaces, featuring high-aspect-ratio (&gt, 20) nanowire structures, using a hot embossing process. An anodic aluminum oxide (AAO) membrane is used as the embossing mold for the fabrication of high-aspect-ratio nanowires directly on a Teflon substrate. First, high-aspect-ratio nanowire structures of Teflon are formed by pressing a fluorinated ethylene propylene (FEP) sheet onto a heated AAO membrane at 340 &deg, C, which is above the melting point of FEP. Experimental results show that the heating time and aspect ratios of nanopores in the AAO mold are critical to the fidelity of the hot embossed nanowire structures. It has also been found that during the de-molding step, a large adhesive force between the AAO mold and the molded FEP greatly prolongs the length of nanowires. Contact angle measurements indicate that Teflon nanowires make the surface superhydrophobic. The reliability and robustness of superhydrophobicity is verified by a long-term (~6.5 h) underwater turbulent channel flow test. After the first step of hot-embossing the Teflon nanowires, microstructures are further superimposed by repeating the hot embossing process, but this time with microstructured silicon substrates as micromolds and at a temperature lower than the melting temperature of the FEP. The results indicate that the hot embossing process is also an effective way to fabricate hierarchical micro/nanostructures of whole Teflon, which can be useful for applications of Teflon material, such as superhydrophobic surfaces.

An unsteady hypersonic blunt wedge flowfield under freestream slow acoustic wave is solved by direct numerical simulation (DNS), and the receptivity characteristics of the boundary layer under slow acoustic disturbance with different amplitudes are analyzed. Results show that slow acoustic wave in the freestream not only has a significant effect on the aerothermodynamics characteristics of hypersonic flowfield and boundary layer, but also on the bow shock characteristics. It shows that the maximum amplitudes of the disturbance modes in the boundary layer are positively correlated with the disturbance amplitude of the freestream. The bigger the amplitude of the freestream disturbance gets, the earlier the high-frequency disturbance mode exists, and the stronger the high frequency interference is. The larger amplitude of freestream disturbance wave can accelerate the generation of the higher order harmonic modes in boundary layer. Furthermore, the transformation position and the times of the dominant mode in the boundary layer differ under various amplitude of freestream disturbance, and compared with the smaller amplitude’s slow acoustic disturbance in the freestream, the larger amplitude disturbance can accelerate the first transformation of the dominant mode in boundary layer, and also delay its second transformation.

Nonlinear optical fibres have been employed for a vast number of applications, including optical frequency conversion, ultrafast laser and optical communication1–4. In current manufacturing technologies, nonlinearity is realized by the injection of nonlinear materials into fibres5–7 or the fabrication of microstructured fibres8–10. Both strategies, however, suffer from either low optical nonlinearity or poor design flexibility. Here, we report the direct growth of MoS2, a highly nonlinear two-dimensional material11, onto the internal walls of a SiO2 optical fibre. This growth is realized via a two-step chemical vapour deposition method, where a solid precursor is pre-deposited to guarantee a homogeneous feedstock before achieving uniform two-dimensional material growth along the entire fibre walls. By using the as-fabricated 25-cm-long fibre, both second- and third-harmonic generation could be enhanced by ~300 times compared with monolayer MoS2/silica. Propagation losses remain at ~0.1 dB cm–1 for a wide frequency range. In addition, we demonstrate an all-fibre mode-locked laser (~6 mW output, ~500 fs pulse width and ~41 MHz repetition rate) by integrating the two-dimensional-material-embedded optical fibre as a saturable absorber. Initial tests show that our fabrication strategy is amenable to other transition metal dichalcogenides, making these embedded fibres versatile for several all-fibre nonlinear optics and optoelectronics applications. The internal surface of an optical fibre can be covered by uniform two-dimensional-material layers for highly nonlinear and low-loss light propagation.