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Thermoelectric devices enable direct conversion between thermal and electrical energy. Recent studies have indicated that the thin film/substrate heterostructure is effective in achieving high thermoelectric performance via decoupling the Seebeck coefficient and electrical conductivity otherwise adversely inter-dependent in homogenous bulk materials. However, the mechanism underlying the thin film/substrate heterostructure thermoelectricity remains unclear. In addition, the power output of the thin film/substrate heterostructure is limited to the nanowatt scale to date, falling short of the practical application requirement. Here, we fabricated the CrN/SrTiO3−x heterostructures with high thermoelectric output power and outstanding thermal stability. By varying the CrN film thickness and the reduction degree of SrTiO3−x substrate, the optimized power output and the power density have respectively reached 276 μW and 108 mW/cm2 for the 30 nm CrN film on a highly reduced surface of SrTiO3−x under a temperature difference of 300 K. The performance enhancement is attributed to the CrN/SrTiO3−x heterointerface, corroborated by the band bending as revealed by the scanning Kelvin probe microscopy. These results will stimulate further research efforts towards interface thermoelectrics.

Lithium (Li) metal is a promising anode for the next generation high-energy–density batteries. However, the growth of Li dendrites, low coulombic efficiency and dramatic volume change limit its development. Here, we report a new synthetic poly-dioxolane (PDOL) approach to constructing an artificial 'elastic' SEI to stabilize the Li/electrolyte interface and the Li deposition/dissolution behavior in a variety of electrolytes. By coating PDOL with optimized molecular weights and synthetic routes on Li metal anode, the 'elastic' SEI layer could be maintained on top of the Li metal anode to accommodate the Li deposition/dissolution. No dendrite formation was observed during the cycling process, and the interfacial side reactions were reduced significantly. Consequently, we successfully achieved 330 cycles with a CE of 98.4% in ether electrolytes and 90 cycles with a CE of 94.3% in carbonate electrolytes. Simultaneously, the Li-metal batteries with LiFePO4 as cathodes also exhibited improved cycling performance. This strategy could promote the development of dendrite-free metal anodes toward high-performance Li-metal batteries.

Among all simple nonbipartite 2-connected graphs, the minimum least Q -eigenvalues are completely determined. As for the nonbipartite θ -graphs known as a special class of 2-connected graphs, the minimum least Q -eigenvalues are also completely determined.

In this study, a novel extraction and safety evaluation method for heavy metals based on different functions of plants was proposed, and an edible plant (pea) was used as the research material to explore the feasibility of the novel method. Pea sprouts were cultured in cadmium (Cd) concentrations of 0, 1.0, 3.0, and 5.0 mg L-1, respectively. The Cd in pea sprouts was continuously extracted with 100 °C distilled water, 60% ethanol, 6% acetic acid, and simulated gastric juice. It was observed that highest amount of Cd (48.65-58.87%) was found in the extraction of roots with 6% acetic acid, followed by 100 °C distilled water (28.68-37.61%). While in stems, most of the Cd (70.73-85.39%) was extracted by 6% acetic acid. The recovery rate of the sequential chemical extraction technique employed in this experiment was between 93 and 106%. Compared with traditional methods, this study has its development potential in two aspects. First, it can determine which steps of sequential extractions of heavy metals in plants are the most harmful to humans. Secondly, corresponding measures can be taken to reduce heavy metals in vegetables used daily, such as soaking edible vegetables in vinegar for a short time. Novelty statement: In this study, a novel extraction and safety evaluation method for heavy metals based on different functions of plants was proposed, and an edible plant (pea) was used as the research material to explore the feasibility of the novel method. Compared with the commonly used extraction methods, the novel method is more reasonable and has greater development potential.

Fine particulate matter with a diameter of less than 2.5 µm ( PM2.5 ) has been used as an important atmospheric environmental parameter mainly because of its impact on human health. PM2.5 is affected by both natural and anthropogenic factors that usually have strong diurnal variations. Such information helps toward understanding the causes of air pollution, as well as our adaptation to it. Most existing PM2.5 products have been derived from polar-orbiting satellites. This study exploits the use of the next-generation geostationary meteorological satellite Himawari-8/AHI (Advanced Himawari Imager) to document the diurnal variation in PM2.5 . Given the huge volume of satellite data, based on the idea of gradient boosting, a highly efficient tree-based Light Gradient Boosting Machine (LightGBM) method by involving the spatiotemporal characteristics of air pollution, namely the space-time LightGBM (STLG) model, is developed. An hourly PM2.5 dataset for China (i.e., ChinaHigh PM2.5 ) at a 5 km spatial resolution is derived based on Himawari-8/AHI aerosol products with additional environmental variables. Hourly PM2.5 estimates (number of data samples = 1 415 188) are well correlated with ground measurements in China (cross-validation coefficient of determination, CV- R2 = 0.85), with a root-mean-square error (RMSE) and mean absolute error (MAE) of 13.62 and 8.49 µg m−3 , respectively. Our model captures well the PM2.5 diurnal variations showing that pollution increases gradually in the morning, reaching a peak at about 10:00 LT (GMT + 8), then decreases steadily until sunset. The proposed approach outperforms most traditional statistical regression and tree-based machine-learning models with a much lower computational burden in terms of speed and memory, making it most suitable for routine pollution monitoring.

Forming robust associative interactions has been an effective strategy for the design of tough hydrogels. However, the role of associative interactions in the dynamics of hydrogels still remains el...

In this work, a hybrid code division multiplexing (CDM) coding and digital filtering method for optical intensity modulation and direct detection (IM-DD) link is investigated to address multipath interference (MPI) and channel bandwidth limitation. CDM signaling already provides robustness to MPI through suppressing the unsynchronized paths by orthogonal (de)coding. As for digital filtering based on square root raised cosine (SRRC) waveforms, its advantage to IM-DD link includes robustness to channel bandwidth limitation due to pulse shaping. Additionally, matching filters achieve the best orthogonality only when they are synchronized well, thus robustness to MPI can be expected on the basis of CDM. We study the performance of such hybrid coding and filtering method over IM-DD link in the presence of MPI and bandwidth limitations through simulation. This is followed by experimental demonstrations of single point-to-point transmission with capacity at 112 Gbps. BER comparison between CDM only and hybrid filtering and coding method is performed by emulating MPI using a Mach-Zehnder interferometer. Furthermore, bidirectional transmission over a single fiber verifies its performance advantage and demonstrates potentials for reducing implementation costs of end-to-end optical communications.

Diabetic nephropathy (DN) is a common microvascular complication of diabetes and one of the leading causes of end-stage renal disease. Tubular damage is an early change and characteristic of DN, and mitochondrial dysfunction plays an important role in the development of DN. Therefore, the timely removal of damaged mitochondria in tubular cells is an effective treatment strategy for DN. Mitophagy is a type of selective autophagy that ensures the timely elimination of damaged mitochondria to protect cells from oxidative stress. In this review, we summarize our understanding of mitochondrial dysfunction and dynamic disorders in tubular cells in DN and the molecular mechanism of mitophagy. Finally, the role of mitophagy in DN and its feasibility as a therapeutic target for DN are discussed.

Due to the advancement of cloud computing, public key encryption with equality test has become a hot topic in the cryptography community. The notion was extended to the identity-based setting to obtain a new primitive, called identity-based encryption with equality test (IBEET). To the best of our knowledge, there are two categories of authorization mechanisms for IBEET: ciphertext-specified authorization and user-specified authorization. However, these authorizations are not applicable for some scenarios. Motivated by this, we propose in this paper a new primitive, called identity-based encryption with equality test and datestamp-based authorization mechanism (IBEET-DBA). In the primitive, the data owner can control the validity of trapdoor by embedding datestamp into it. The cloud server can only obtain the correct equivalence results on the ciphertexts which are generated within the valid period of trapdoor. In this paper, we formally define this primitive and its security notion. Moreover, we propose the first IBEET-DBA scheme and prove its security.

In this article, an analytical equivalent circuit model is established for the piezoelectric micromachined ultrasonic transducer (PMUT) cell and array with a combination of the annular and circular diaphragms used for structural optimization and complex array design. Based on this model, a comprehensive analysis is conducted on the acoustic-structural coupling of an annular and circular diaphragm-coupled PMUT (AC-PMUT) with a new excitation method. The model-derived results are in good agreement with the simulation and experimental results. Then, an optimized design has been presented to achieve high-output pressure and a good array working performance. In summary, a comparison of the array working performance is conducted between the arrays that consist of AC-PMUTs and traditional circular diaphragm PMUTs (C-PMUTs). The results indicate that the AC-PMUT array has a much lower crosstalk effect than that of the traditional C-PMUT array. By this means, the AC-PMUT array can fully use the high vibration amplitude achieved by each AC-PMUT cell to improve its output ability. As a result, the highest ultrasonic output pressure generated by the AC-PMUT array in its resonant condition can achieve an increase of 155%, compared with that generated by the C-PMUT array.

Mitochondria-associated Endoplasmic Reticulum (ER) Membranes (MAMs) are the cellular structures that connect the ER and mitochondria and mediate communication between these two organelles. MAMs have been demonstrated to be involved in calcium signaling, lipid transfer, mitochondrial dynamic change, mitophagy, and the ER stress response. In addition, MAMs are critical for metabolic regulation, and their dysfunction has been reported to be associated with metabolic syndrome, including the downregulation of insulin signaling and the accelerated progression of hyperlipidemia, obesity, and hypertension. This review covers the roles of MAMs in regulating insulin sensitivity and the molecular mechanism underlying MAM-regulated cellular metabolism and reveals the potential of MAMs as a therapeutic target in treating metabolic syndrome.

In this paper, among all k-uniform ( k ≥ 3 ) unicyclic hypergraphs of order n and with matching number at least z (z is an integer satisfying 1 ≤ z ≤ n k − 1 − 1 ), and among all k-uniform ( k ≥ 3 ) unicyclic hypergraphs of order n and with a given matching number, the hypergraphs with the maximum spectral radius are completely determined, respectively.

Summary Perovskite solar cells (PSCs) suffer from significant nonradiative recombination, limiting their power conversion efficiencies. Here, for the first time, we directly observe a complete transformation of perovskite MAPbI3 surface region energetics from p- to n-type during defect passivation caused by natural additive capsaicin, attributed to the spontaneous formation of a p-n homojunction in perovskite active layer. We demonstrate that the p-n homojunction locates at ∼100 nm below perovskite surface. The energetics transformation and defect passivation promote charge transport in bulk perovskite layer and at perovskite/PCBM interface, suppressing both defect-assisted recombination and interface carrier recombination. As a result, an efficiency of 21.88% and a fill factor of 83.81% with excellent device stability are achieved, both values are the highest records for polycrystalline MAPbI3 based p-i-n PSCs reported to date. The proposed new concept of synergetic defect passivation and energetic modification via additive provides a huge potential for further improvement of PSC performance.

Graphene is considered to be a valuable material in the field of photodetection due to its ultra-high electron mobility. However, its weak light absorption, short carrier lifetime and lack of gain mechanism limit the light responsivity of graphene at the magnitude of mA W−1. Herein, based on the oxidation characteristics of eutectic gallium–indium (EGaIn) alloy and the adoption of low-cost physical vapor deposition methods, we develop nanoparticles with gradient changes in elements to solve the drawback of common quantum dots of a narrow response band, fabricating a composite nanostructure of suspended graphene and oxidized EGaIn nanoparticles. The photodetector achieves wide-spectrum and high-performance detection from ultraviolet to near-infrared, with a responsivity enhancement of three order magnitude compared to that of pristine graphene. Then, the enhancement mechanism is analysed through structural characterization and control experiments, proving the dominant effect of oxidized nanoparticles on improving the responsivity and response band. This paper expands the application of EGaIn in the field of photoelectric detection and offers new idea for constructing high-performance quantun-dot based photodetectors.

The ultraviolet to terahertz band forms the main focus of optoelectronics research, while light detection in different bands generally requires the use of different materials and processing methods. However, researchers are aiming to realize multi-band detection simultaneously in the same device in certain specific application scenarios and ultra-wideband photoelectric detectors can also realize multi-function and multi-system integration. Therefore, the research and development work on ultra-wideband photoelectric detectors has important practical application value. Here, we produced self-powered suspended Pd-reduced graphene oxide-Ti (Pd-rGO-Ti) photodetectors. We varied the properties of the rGO films by using different annealing temperatures and achieved p-doping and n-doping of the films by evaporating palladium films and titanium films, respectively, thus enabling preparation of photothermoelectric (PTE) photodetectors based on rGO films. The resulting detectors have excellent photoelectric responses over a wideband illumination wavelength range from 375 nm to 118.8 μm (2.52 THz). At the same time, we determined the best experimental conditions and device structure by varying the channel width, the laser spot irradiation position and the experimental atmospheric pressure. The maximum responsivity obtained from our detectors is 142.08 mV W−1, the response time is approximately 100–200 ms and the devices have high detection sensitivity. Based on this work, we assumed in the subsequent experiments that detectors with higher performance can be obtained by reducing the channel width and atmospheric pressure. With advantages that include simple fabrication, low cost, large-scale production potential and ultra-wideband responses, these Pd-rGO-Ti photodetectors have broad application prospects in high-performance integrated optoelectronics.

Qinshan nuclear power plant is the first large Chinese-designed nuclear power station based on pressurized water reactor, and the second generation main stream active safety injection system is adopted for Qinshan nuclear power plant. In this paper, a novel passive safety injection system (PSIS) has been proposed for ocean-based Qinshan Phase One nuclear power plant to replace the original active one. The PSIS contains high-pressure, medium-pressure, and lower-pressure safety injection systems, and a two-stage automatic depressurization system. To evaluate the system performance, small-break LOCA has been investigated using RELAP5. Various break sizes and locations including 2-inch, 10-inch cold leg break, and double-ended direct vessel injection line break were analyzed. Key safety parameters such as safe injection mass flow rates, coolant level of the core, system pressure, and fuel cladding temperature were monitored during the accident process. The results illustrate that the performance of the safety injection system can guarantee the effective core cooling and submerged under different LOCA even with only half of the safety injection system, which can fulfill the single failure criteria. The thermal-hydraulic analysis for the Qinshan passive safety injection system is significant to master the related technologies for Chinese engineer and develop the Chinese-designed third-generation nuclear power plants, and the PSIS can guarantee the reactor submerged under LOCA even plus the station block out accident.

The optimization of back contact interface is crucial to improve the performance of Cu2ZnSnS4 (CZTS) thin film solar cells. In this paper, we first employ Al-doped ZnO (AZO) as the intermediate layer into the Mo/CZTS interface to improve the quality of back contact region. This AZO intermediate layer, obtained from the sputtering method prior to the CZTS precursor deposition, initially blocks the direct contact of CZTS with the Mo layer and thus indeed suppresses the decomposition reaction between Mo and CZTS. Consequently, the generation of voids at the back contact region is obviously avoided. Besides, the AZO intermediate layer can inhibit the reaction between sulfur (S) and Mo during sulfurization process, and thus significantly reduce the thickness of MoS2. Meanwhile, the AZO intermediate layer with suitable thickness does not affect the crystal quality of CZTS absorber layer. Moreover, the effects of different thicknesses of predeposited AZO on the film morphology, composition, and corresponding device performance were systematically studied. After optimizing the thickness of the AZO layer, the efficiency of the resultant device has increased from 7.1% to 8.4% (the active area efficiency is 9.2%).

The effects of smart-material-based active surface perturbation (i.e. piezo-ceramic actuators) on wall shear stress and noise metric have been investigated by simulations and wind tunnel experiments. A periodic vibration through the application of piezo-ceramic actuators is imposed on the surface of a plate, and the vibration position is located on the upper part of the leading edge of the plate. Both the control results from simulations and experiments are close to each other, when the control parameters are the same. The simulations and wind tunnel experiments show that downstream skin-friction drag and noise metric can be reduced with the active control, and the reductions strongly depend on control parameters. Comparing with the near wall flow structures, the turbulent kinetic energy and characteristic turbulence length scale in the turbulent boundary layer can be controlled with the piezo-ceramic actuator.

Erosive burning refers to the augmentation of propellant burning rate appears when the velocity of combustion gas flowing parallel to the propellant surface is relatively high. Erosive burning can influence the total burning rate of propellant and performance of solid rocket motors dramatically. There have been many different models to evaluate erosive burning rate for now. Yet, due to the complication processes involving in propellant and solid rocket motor combustion, unknown constants often exist in these models. To use these models, trial-and-error procedure must be implemented to determine the unknown constants firstly. This makes many models difficult to estimate erosive burning before plenty of experiments. In this paper, a new erosive burning rate model is proposed based on the assumption that the erosive burning rate is proportional to the heat flux at the propellant surface. With entrance effect, roughness, and transpiration considered, convective heat transfer coefficient correlation proposed in recent years is used to compute the heat flux. This allows the release of unknown constants, making the model universal and easy to implement. The computational data of the model are compared with different experimental and computational data from different models. Results show that good accuracy (10%) with experiments can be achieved by this model. It is concluded that the present model could be used universally for erosive burning rate evaluation of propellant and performance prediction of solid rocket motor as well.

Despite significant improvement in Moderate Resolution Imaging Spectroradiometer (MODIS) aerosol optical depth (AOD) retrieval, high-resolution–high-accuracy AOD retrieval remains a challenging tas...

The pressure-induced densification significantly affects the deformation and damage behavior of fused silica. This paper presents a finite element analysis (FEA) of the densification and its effects on the deformation in fused silica under indentation. An elliptical constitutive model was refined to consider the influence of densification on elastic properties and its saturation with hydrostatic pressure. By matching the simulated indentation hardness to experiments, the plastic properties of fused silica were more accurately identified. FEA shows that the modified elliptical model can improve the prediction accuracy of the load-displacement curve of Berkovich indentation. As a widely-used reference material, the heavy densification in fused silica dose not influence the calibration accuracy of the tip area function in the Oliver-Pharr method, which provides a theoretical foundation for the use of fused silica as a reference material. With the modified elliptical model, the FEA successfully predicted the geometry of plastic zone, and the extent of elastic recovery and densification, which provided input parameters for the analytical embedded center of dilation (ECD) model of indentation stress field. Results show that the stress fields under a conical indenter predicted by the FEA agreed well with the ECD model.

Duzhong Jiangya tablet is a hypotensive drug. In this study, high-performance liquid chromatography-Fourier transform-ion cyclotron resonance-mass spectrometry technology was used to quickly identify its chemical composition. SinoChrom ODS-BP column (250 mm × 4.6 mm, 5 μm) was used. The mobile phase was acetonitrile(A)-0.1% formic acid solution(B). The flow rate was 1 mL/min. Extracted ion chromatogram was used to analyze the samples in positive and negative ion modes. Based on the accurate mass spectrometry information (such as quasi-molecular ions and fragment ions) obtained from the instrument, combined with reference compounds and literature, the chemical composition of Duzhong Jiangya Tablets was identified. A total of 131 compounds were identified, including four types of penylpropanoids, six types of phenylethanoid glycosides, 10 types of organic acids, 14 types of iridoids, 12 types of lignans, 18 types of alkaloids, seven types of coumarins, and 60 kinds of flavonoids. This established method can quickly and efficiently identify chemical constituents in Duzhong Jiangya tablet, lay a foundation for the research on the efficacy and quality of this traditional Chinese medicine, and provide a reference for the characterization of the chemical constituents of other traditional Chinese medicine preparations.

Graphene has excellent electrical, optical, thermal, and mechanical properties that make it an ideal optoelectronic material. However, it still has some problems, such as a very low light absorption rate, which means it cannot meet the application requirements of high-performance optoelectronic devices. Here, we produce a high-responsivity photodetector based on a monolayer graphene/RbAg4I5 composite nanostructure. With the aid of poly(methyl methacrylate), we suspend the monolayer graphene on a hollow carving groove with a width of 100 μm. A RbAg4I5 film evaporated on the back of the graphene causes the composite nanostructure to generate a large photocurrent under periodic illumination. Experimental results show that the dissociation and recombination of ion-electron bound states (IEBSs) are responsible for the excellent photoresponse. The device has very high (>1 A W-1) responsivity in wide-band illumination wavelength from 375 nm to 808 nm, especially at 375 nm, where it shows a responsivity of up to ∼5000 A W-1. We designed the dimensions of the carving groove to allow the light spot to cover the entire groove, and we cut the graphene sheet to match the length of the carving groove. With the structural optimizations, the energy of light can be used more efficiently to dissociate the IEBSs, which greatly improves the photoresponse of optoelectronic devices based on the proposed monolayer graphene/RbAg4I5 composite nanostructure.

It is challenging to explore and prepare polyoxometalates-based nanomaterials (PNMs) with controllable morphologies and diversiform components. Herein, 3d–4f metals are introduced into isopolyoxometalates and Anderson-type polyoxometalates, CeCdW12 nanoflower and EuCrMo6 microflaky have been fabricated respectively. A series of control experiments are carried out to identify the impact factors on the rare morphologies in PNMs. Furthermore, upon excitation at 396 nm, the emission spectrum of EuCrMo6 displays five prominent f − f emitting peaks at 674, 685, 690, 707, and 734 nm that are assigned to Eu3+ 5D0 → 7FJ (J = 0, 1, 2, 3, 4) transitions. Meanwhile, the VSM results show that the Cr+3 ions in EuCrMo6 display anti-ferromagnetic interactions when the temperature is lower than − 17.54 K. After rising temperature, this material exhibits paramagnetic property. This work opens up strategies toward the brand new morphologies and components of PNMs, endowing this kind of material with new functions.

This study evaluated the growth stimulatory effect of low-frequency ultrasound on an ecologically and economically important marine diatom, Skeletonema costatum. To investigate the effect of repeated ultrasonication and the optimum duration of ultrasonication, S. costatum cells were exposed to low-frequency ultrasound (40 kHz) for 0, 2, 30 or 90 s under two sonication conditions: a one-time sonication treatment or a 24-h interval treatment. The cell density and cellular carbohydrate content increased in the ultrasonicated cultures. Similarly, the photosynthetic efficiency, particularly in the exponential growth phase, was enhanced in ultrasonicated cultures, which might account for the enhanced cell growth. At the end of the experiment, compared with the corresponding one-time treatment groups, the cell density in the 30-s sonicated culture and the cellular carbohydrate concentration in the 2-s sonicated culture of the 24-h interval treatment group were increased by 34 ± 4% and 28 ± 3%, respectively. This indicates that, under the same ultrasonic treatment conditions, a higher cellular carbohydrate content can be achieved by repeating the ultrasonication. This study also revealed that, compared with control, the silica/nitrate ratio and silica/phosphate ratio required to produce the same number of S. costatum cells were lower in the sonicated cultures, particularly in the one-time sonicated cultures. This finding indicates that ultrasonic irradiation results in the light silicification of S. costatum cells. This study provides valuable information on the diatom response to low-frequency ultrasonic irradiation and is an important benchmark study for future biotechnological applications of the mass production of S. costatum and other microalgae.

Titanium alloys have high specific strength and excellent high temperature and corrosion resistance but low hardness and poor wear resistance. In this study, TiC-reinforced Ti2Ni/Ti5Si3 eutectic matrix composite coatings were fabricated on TC21 titanium alloy substrates by laser cladding. The phase composition and microstructure of the coating with micro- or nano-sized SiC addition as well as the microhardness and wear resistance of the coatings were evaluated. The analysis showed that the composite coatings were mainly made up of TiC, TiNi, Ti5Si3, and Ti2Ni phases, the TiC phase being distributed on the eutectic Ti2Ni/Ti5Si3 phase. The coatings with nano-SiC addition exhibited better coating quality, and higher microhardness and wear resistance than the coatings with micro-SiC addition. The better properties of the coating with nano-SiC addition were mainly attributed to the larger amount of the TiC hard-reinforcing phase and a more compact microstructure. The predominant wear mechanism of the coating with micro-SiC addition was adhesive wear, while it was abrasive wear for the coating with nano-SiC addition. This study should provide an insight into the development of Ti2Ni/Ti5Si3 eutectic matrix coatings.

Planktonic foraminifera collected from a sediment trap deployed off Hainan in the northwestern South China Sea (SCS-NW) between July 2012 and April 2013 were studied to evaluate their seasonal variability and ecology as well as to infer the factors controlling their shell fluxes. The total planktonic foraminifera flux, as well as the fluxes of the dominant species ( Globigerinoides ruber , Globigerinoides sacculifer and Neogloboquadrina dutertrei ), showed three distinct maxima during SW-monsoon in August 2012, the SW-NE intermonsoon in October 2012 and the NE-monsoon in December 2012–February 2013. These periods were characterized by upwelling, aerosol fallout, and intense wind mixing, respectively, from which the foraminiferal assemblages benefitted, as indicated by the close correlation between wind speed, sea surface temperature (SST), chlorophyll ɑ concentration (Chl- ɑ ), δ 18 O of G . ruber and the shell fluxes. The correlation also suggests that temperature and food availability might have been the primary drivers of the observed changes in foraminiferal abundance. The offset between the SST deduced from flux-weighted of G. ruber δ 18 O and annual mean SST is only ˜0.3 °C, much lower than ˜5.2 °C between the summer and winter temperature, indicating a balanced seasonality bias in the shell flux. The linear regression between the satellite-derived sea surface temperature and G. ruber δ 18 O reveals the strong potential of this species, at least in the studied region, as an ecological indicator for past oceanic environments.

The conversion efficiency of Cu2ZnSn(S,Se)4 (CZTSSe) solar cells is relatively low, due to the complicated intrinsic defects and the unsuitable contact interfaces. In this work, MoO2 thin films prepared by a simple preannealing method are introduced to Mo/CZTSSe back contact interface. For the first time, it is found that MoO2 acts as a sacrificial layer rather than the traditional intermediate layer. Specifically, the MoO2 sacrificial layer will disappear and become a thin MoSe2 layer after it blocks the over-selenization of Mo electrode. In addition, it has a positive effect on the preferred orientation of MoSe2 and the crystallization of CZTSSe layer. Furthermore, the chemical mechanism on MoO2 as sacrificial layer is first investigated, and it can be well described by Van ’t Hoff equation. With the aid of MoO2 sacrificial layer, the performance of CZTSSe device increases from 5.67% to 8.29% (active area efficiency is 9.08%) without the MgF2 antireflection layer.

It is commonly accepted that an estimated soil variogram can be transferred to another similar area for deriving the tolerable spacing of a sampling grid or, more generally, the sample size, given a requirement on the quality of the soil property map of the recipient area. The quality of the derived tolerable grid spacing depends on how similar the population variograms of the donor area and recipient area are. In practice we are uncertain about the variograms of both areas due to sampling errors. Ideally, the uncertainty about the variogram of the donor area is accounted for in deriving the tolerable grid spacing. To assess the transferability, we should also account for uncertainty in the estimated variogram of the recipient area. In this study the transferability of variograms of soil pH, P, Mg and K is analysed for three grassland fields in Ireland, which are similar in soil-forming factors. One field served as donor area, the other two as recipient area. For all three fields and for each soil property, 500 variograms were sampled from the posterior distribution of the variogram parameters. Results showed that the estimated variogram parameters of the recipient fields differed largely from those of the transferred variograms. The ranges of estimated mean kriging variance values for the various grid spacings, as obtained with the two sets of variograms (one set of the donor field, one set of the recipient field), did not overlap. Even after scaling the transferred variogram with an estimate of the variance of the recipient field, the transferred variogram was of no use for determining the tolerable grid spacing. The difference in the variograms can possibly be explained by the difference in historical land use. Highlights: Transferability of variograms to derive tolerable grid spacing for mapping grassland fields is assessed Transferability should be based on the uncertainty distributions of the tolerable grid spacings Due to difference in historical land use, local and transferred variograms differed largely Transferability of a variogram is very poor, even after scaling the transferred variogram.

Novel multi-layer brazed diamond segments were fabricated using NiCr–x(CuCe) composite alloys. Differential scanning calorimetry curves of the composite alloys were measured and analysed. The microstructures of the alloy segments and surface topographies of the brazed diamond segments were characterised. Performance tests of the alloy segments and brazed diamond segments were performed. The undercooling degree of the Ni–Cr alloy in the composite alloy increased with the Cu–Ce alloy addition, which led to coarse NiCu-rich regions and Ni3Si phases. A brazed diamond segment with a 5% Cu–Ce alloy addition exhibited the highest wear resistance and machining performance and the best surface morphology after a wear test. An excessive Cu–Ce alloy addition led to a rapid decrease in wear resistance of the brazed diamond segment owing to the large number of coarse NiCu-rich phases falling off from the composite alloy. The mechanism of the reduction in thermal damage to diamonds by the Cu–Ce alloy is elucidated. Initially the Cu–Ce particles melted and mainly Ni atoms diffused into the Cu–Ce liquid, thereby leading to the formation of NiCu-rich regions and Ce2Ni7 and CeNi2 phases, which in turn promoted the diffusion. The melting temperature of the Ni–Cr composite alloy was significantly reduced by the addition of the Cu–Ce alloy.

Bi2Te3-based materials have been widely utilized for commercial bulk thermoelectric (TE) devices. For the manufacture of miniaturized TE devices, the large-scale deposition of high-performance Bi2Te3-based thin films is crucial. However, it has not yet been effectively resolved. Herein, the Bi0.5Sb1.5Te3 films with different thicknesses were grown on sapphire substrates by controlling the co-sputtering time. We reveal that the film thickness has a significant impact on the electrical transport properties. Due to the mutual influence of electrical conductivity and Seebeck coefficient, there exists an optimal thickness with the maximum power factor is as high as 2900 μW m−1 K−2. Therefore, systematic research on the thickness-dependent TE characteristics of Bi2Te3-based films and the deposition of high-performance films will provide important information for the large-scale development of high-performance micro-TE devices.

Quantum limit is quite easy to achieve once the band crossing exists exactly at the Fermi level ($E_F$) in topological semimetals. In multilayered Dirac fermion system, the density of Dirac fermions on the zeroth Landau levels (LLs) increases in proportion to the magnetic field, resulting in intriguing angle- and field-dependent interlayer tunneling conductivity near the quantum limit. BaGa$_2$ is an example of multilayered Dirac semimetal with anisotropic Dirac cone close to $E_F$, providing a good platform to study its interlayer transport properties. In this paper, we report the negative interlayer magnetoresistance (NIMR, I//c and B//c) induced by the tunneling of Dirac fermions on the zeroth LLs of neighbouring Ga layers in BaGa$_2$. When the field deviates from the c-axis, the interlayer resistivity $\rho_{zz}(\theta)$ increases and finally results in a peak with the field perpendicular to the c-axis. These unusual interlayer transport properties (NIMR and resistivity peak with B$\perp$c) are observed together for the first time in Dirac semimetal under ambient pressure and are well explained by the model of tunneling between Dirac fermions in the quantum limit., Comment: 12 pages, 8 figures, with supplementary materials

A total k -coloring of a graph G is a mapping ϕ : V ( G ) ∪ E ( G ) → { 1 , 2 , … , k } such that no two adjacent or incident elements in V ( G ) ∪ E ( G ) receive the same color. In a total k -coloring of G , let w ( v ) denote the total sum of colors of the edges incident with v and the color of v . If for each edge u v ∈ E ( G ) , w ( u ) ≠ w ( v ) , then we call such a total k -coloring neighbor sum distinguishing. Let χ ∑ ′ ′ ( G ) denote the smallest number k in such a coloring of G . Pilśniak and Woźniak posed the conjecture that χ ∑ ′ ′ ( G ) ≤ Δ ( G ) + 3 for any simple graph G with maximum degree Δ ( G ) . In this paper, we focus on the list version of neighbor sum distinguishing total coloring. Let L z ( z ∈ V ( G ) ∪ E ( G ) ) be a set of lists of integer numbers, each of size k . The smallest k for which for any specified collection of such lists, there exists a neighbor sum distinguishing total coloring using colors from L z for each z ∈ V ( G ) ∪ E ( G ) is called the neighbor sum distinguishing total choosability of G , and denoted by c h ∑ ′ ′ ( G ) . We prove that c h ∑ ′ ′ ( G ) ≤ Δ ( G ) + 3 for planar graphs without adjacent special 5-cycles with Δ ( G ) ≥ 8 .

Elastic recovery of fused silica under scratching has significant effects on its hardness and friction coefficient. However, the effects are seldom considered in previous calculation models causing misestimation of hardness. In this work, scratching on fused silica with a conical indenter and a Berkovich indenter was investigated by finite element analysis (FEA). Meanwhile, analytical models of apparent friction coefficient were built by modeling the geometry of contact regions as a sector and a triangle for the conical and Berkovich indenters, respectively. With the effects of elastic recovery taken into account, the apparent friction coefficient predicted by these analytical models is consistent with FEA. The results provide a reference for calculating hardness of materials with large E/H (Young's modulus/hardness) like fused silica during scratching, which consider elastic recovery. Besides, by analogues to indentation strain, a new parameter, i.e., sliding strain es, is proposed. FEA reveals that es can be used to characterize the effects of indenter geometry and sliding direction on scratching. As demonstrated by the results, the apparent friction coefficient and hardness increase with es, while the elastic recovery ratio decreases with es.

This article presents a resonant cavity-based array design for piezoelectric micromachined ultrasonic transducers (PMUTs). The cavity depth is designed to ensure that its open end achieves a considerably smaller acoustic impedance than the surrounding PMUT cells. The interference acoustic wave generated between every two adjacent PMUT cells at the near surface of the array will take an easy path down to the cavity bottom. As such, the crosstalk effect among different adjacent cells in the array can be largely reduced. An equivalent circuit model of the proposed array is established for its design and optimization. In addition, the solutions for circuit parameters in the electromechanical domain are analytically derived and verified via FEM simulations. Given the low crosstalk effect achieved by the proposed array design, the output sensitivity of the proposed PMUTs can be improved by 259% compared with the traditional PMUTs with a high distribution density of the same size. The cavity-based array design and its model can be used for further advanced PMUT cell structures in other arrays to improve their performance.

Epizoic diatoms on marine copepods are common in nature and may have a special ecological relationship with their hosts. However, this special ecological group is not well known, and it has only rarely been studied in the China seas. To address this knowledge gap, the species diversity and classification of epizoic diatoms on planktonic copepods were studied with samples collected from the East China Sea. In the present study, a marine araphid diatom genus Protoraphis and its type species, Pr. hustedtiana, were observed and identified by light and electron microscopy, thus representing the first record of this genus and its type species in China. This genus is characterized by a median sternum strongly bent to opposite sides and terminate in two transapical grooves at the valve ends. Protoraphis hustedtiana was found to be epizoic on the posterior body appendages and segments of the marine calanoid copepod Candacia bradyi. An internal view shows a complex, ear-shaped process that is close to the apical slit field. The ecological habitats and geographical distributions of Protoraphis were also discussed, and, together with complementary morphological studies, our results have increased the number of records for marine epizoic diatoms to three genera with three species in China, including Pseudohimantidium and Pseudofalcula.

Fine particulate matter with aerodynamic diameters ≤2.5 µm (PM2.5) has adverse effects on human health and the atmospheric environment. The estimation of surface PM2.5 concentrations has made intensive use of satellite-derived aerosol products. However, it has been a great challenge to obtain high-quality and high-resolution PM2.5 data from both ground and satellite observations, which is essential to monitor air pollution over small-scale areas such as metropolitan regions. Here, the space–time extremely randomized trees (STET) model was enhanced by integrating updated spatiotemporal information and additional auxiliary data to improve the spatial resolution and overall accuracy of PM2.5 estimates across China. To this end, the newly released Moderate Resolution Imaging Spectroradiometer Multi-Angle Implementation of Atmospheric Correction AOD product, along with meteorological, topographical and land-use data and pollution emissions, was input to the STET model, and daily 1 km PM2.5 maps for 2018 covering mainland China were produced. The STET model performed well, with a high out-of-sample (out-of-station) cross-validation coefficient of determination (R2) of 0.89 (0.88), a low root-mean-square error of 10.33 (10.93) µg m−3, a small mean absolute error of 6.69 (7.15) µg m−3 and a small mean relative error of 21.28 % (23.69 %). In particular, the model captured well the PM2.5 concentrations at both regional and individual site scales. The North China Plain, the Sichuan Basin and Xinjiang Province always featured high PM2.5 pollution levels, especially in winter. The STET model outperformed most models presented in previous related studies, with a strong predictive power (e.g., monthly R2=0.80), which can be used to estimate historical PM2.5 records. More importantly, this study provides a new approach for obtaining high-resolution and high-quality PM2.5 dataset across mainland China (i.e., ChinaHighPM2.5), important for air pollution studies focused on urban areas.

Daya Bay is facing the influence of human activities and nature changes, which result in phytoplankton adjusting to the changing environment. The data about environmental changes and phytoplankton were obtained from four seasonal cruises in 2013 in the bay. It is helpful to explore seasonal succession of phytoplankton driven by the determining environmental factors in this bay. Temperature is a significant indicator of season change. The limiting factor of phytoplankton growth totally changed from P (PO4-P) limiting during the southwest monsoon to Si (SiO3-Si) limiting during northeast monsoon. The order of diatoms and dinoflagellates was the dominant phytoplankton groups in Daya Bay. The dominant species included chain-forming diatoms (Skeletonema, Pseudo-nitzschia, Thalassionema, Chaetoceros and Rhizosolenia) were found all the year round and filamentous cyanobacteria (Trichodesmium) in spring and autumn. Partial least square regression (PLS) found that salinity, temperature and nutrients were important driving force for phytoplankton seasonal succession.

Ultra-broadband photodetection is crucial for various applications like imaging and sensing and has become a hot research topic in recent years. However, most of the reported ultra-broadband photod...

The proliferation of beach renovation is affecting the change of the landform of the coast and threatening the ecological environment. Therefore, it is necessary to assess the impact on the environment after the beach is transformed. The survey area is located near the Shipu fishing port in the south of Ningbo City, Zhejiang Province. Based on the Delft-3D grid nesting model and wave-fluid coupling model, the astronomical tide and hydrodynamic environment of the 30 days before the construction were simulated. After the beach was rebuilt and sand was added and the spur dike was added, the astronomical tide and hydrodynamic environment were again simulated. Finally, based on the simulated data, the water level, velocity field, effective wave height distribution, and siltation and siltation of Xinhe Beach were obtained. Xinhe Beach's environmental damage risk indicators can be evaluated based on water level, velocity field, effective wave height direction and sediment erosion and deposition. Artificial sanding and construction of spur dikes will change the hydrodynamics and scouring and siltation of Xinhe Beach, but have little effect on the coastal terrain and ecological environment.

Marine picoplankton, including prokaryotic and eukaryotic picoplankton, drive many biogeochemical processes, such as carbon, nitrogen and sulfur cycles, making them crucial to the marine ecosystem. Despite the fact that picoplankton is prevalent, its diversity and spatial distribution from the Straits of Malacca (SM) to the South China Sea (SCS) remain poorly investigated. This work explores the phylogenetic diversity and community structure of picoplankton in relation to environmental factors from the SM to the SCS. To this end, the Illumina MiSeq sequencing technique was applied to 16S and 18S rRNA genes. The results showed significant differences in the dynamics of picoplankton between the open sea and the strait region. Proteobacteria and Cyanobacteria constituted a larger part of the prokaryotic group. Within Cyanobacteria, the abundance of Prochlorococcus in the open sea was significantly higher than that of Synechococcus, while the opposite trend was observed in the strait. Dinoflagellata, Cnidaria, Retaria, Tunicata, and Arthropoda dominated among the eukaryotic taxa. High-throughput sequencing data indicated that salinity, temperature and NO2-N were the key factors determining the prokaryotic community structure, while temperature and dissolved oxygen determined the eukaryotic community structure in the studied region. The network analysis demonstrated that the cooperation and competition were also important factors affecting the picoplankton community.

Blooms caused by microalgae have become a serious threat to public health, fisheries, ecosystems and economies around the world. Recent studies have indicated that some macroalgae have the potential to be used to control bloom-forming microalgae. Here, we report the ability of Pyropia haitanensis, a commercial macroalga cultivated in southeastern China, to inhibit the growth of the common bloom-forming diatom Skeletonema costatum. The results of initial experiments using fresh thalli of P. haitanensis at various temperatures clearly indicated that this macroalga had a high inhibition effect on the growth of S. costatum at 21 °C. Therefore, further treatments with fresh thalli, culture filtrate, dry powder and water-soluble extract were used to determine the dose-dependent inhibition effect on the growth of S. costatum at 21 °C by P. haitanensis. Fresh thalli were potent and significantly inhibited the growth of S. costatum at all concentrations, but the microalga was alive at a very low density. Treatments with culture filtrate, dry powder and water-soluble extract greatly affected the growth of S. costatum at different concentrations, and no living microalgal cells were found after treatment with the water-soluble extract. The present study was carried out under controlled laboratory conditions excluding fluctuations in light and temperature. Therefore, our results, together with the well-known nutrient removal capacity of macroalgae, allows us to conclude that P. haitanensis contains bioactive compounds and allelopathy is the most likely reason for the negative effect on S. costatum.

Land use reflects human activities on land. Urban land use is the highest level human alteration on Earth, and it is rapidly changing due to population increase and urbanization. Urban areas have widespread effects on local hydrology, climate, biodiversity, and food production. However, maps, that contain knowledge on the distribution, pattern and composition of various land use types in urban areas, are limited to city level. The mapping standard on data sources, methods, land use classification schemes varies from city to city, due to differences in financial input and skills of mapping personnel. To address various national and global environmental challenges caused by urbanization, it is important to have urban land uses at the national and global scales that are derived from the same or consistent data sources with the same or compatible classification systems and mapping methods. This is because, only with urban land use maps produced with similar criteria, consistent environmental policies can be made, and action efforts can be compared and assessed for large scale environmental administration. However, despite of the fact that a number of urban-extent maps exist at global scales [3,4], more detailed urban land use maps do not exist at the same scale. Even at big country or regional levels such as for the United States, China and European Union, consistent land use mapping efforts are rare.

Indium tin oxide (ITO) films were deposited on transparent and flexible mica substrates by RF magnetron sputtering at room temperature. The ITO films exhibit atomically flat morphology on the cleaved natural mica surface. Excellent thermal stability of mica allows heat treatment at high temperature up to 500 oC. The electronic and optical characteristics of the ITO films are improved by annealing process, which can be explained by the preferred (2 2 2)-oriented crystallization at temperatures higher than 200 oC. The resistivity of as-deposited amorphous ITO film is ~2.1 × 10−3 Ωcm and remarkably decrease to ~5.0 × 10−4 Ωcm for the annealed samples. Accompanying the rapid increase in the conductivity, the transmittance also increases to more than 90% for the crystallized ITO films. Furthermore, the mechanical tests indicate excellent flexibility and durability of the ITO films on mica. These results demonstrate that the ITO films on mica can endure high temperature process for the applications in flexible electronics.

A comparative analysis of heat transfer characteristic in pulsating flow induced by rolling motion under natural circulation and forced circulation condition was performed. Variation of local and average heat transfer characteristics with rolling motion were also investigated. The results show that the natural circulation time-averaged heat transfer characteristic is enhanced by rolling motion. However, the variation of time-averaged heat transfer characteristic of forced circulation is not significant. In addition, the relationship between the relative pulsation amplitude of Reynolds number and Nusselt number does not present predominant difference in natural and forced circulation conditions.

Recently, Tseng et al. proposed a new notion for identity-based signature (IBS) scheme to resist ephemeral secret leakage (ESL) attacks, called leakage-free identity-based signature (leakage-free IBS), and devised the first secure leakage-free IBS scheme. However, they only considered the situation of the leakage of ephemeral secrets used for generating the signatures. Notice that the private key extraction procedure is probabilistic as well in their scheme, that is, there are ephemeral secrets used by the key generation center to generate the signers’ private keys. It is practical to consider that if the adversary comprises these ephemeral secrets, then he can reveal the master key of the system. Therefore, it is desired to introduce a new security notion for the leakage-free IBS schemes to consider the ESL attacks on both private key extraction and signing procedures. In this paper, we present such security notion. Moreover, we propose two IBS schemes that are proved to be secure under the new security notion.

Rastegari et al. recently proposed a certificateless signcryption (CL-SC) scheme. They claimed that their scheme is the first secure CL-SC scheme, which captures the known session-specific temporary information security (KSSTIS), in the standard model. In this paper, we point out that their scheme is insecure, which implies that how to construct a secure CL-SC scheme with KSSTIS in the standard model is still an open problem.

In this paper, the nonlinear dynamic responses of a piezoelectric cantilever plate near the first-order and second-order natural frequencies under the action of electromechanical coupling are studied by experiments and finite element (FE) methods. The influence of different excitation frequencies on the dynamical characteristics of piezoelectric cantilever plates is analyzed with the fixed excitation amplitude. First, an experimental setup is built, including a carbon fiber cantilever plate attached to a macro fiber composite (MFC) sheet. Then, the electromechanical coupling excitations are subjected to the plate with different frequencies, which are chosen near the first and second-order natural frequencies of the plate. The piezoelectric cantilever plate has periodical motions under a lower frequency excitation, and the motions of the plate become more complex after another high frequency excitation added in the physical field. The experimental results show that the motion of the piezoelectric cantilever plate changes from stable to unstable with high–low coupled resonant frequencies. At last, the FE study is carried out to compare and verify the experimental results and the effects of isotropic and orthotropic materials on the accuracy of natural frequencies results are also compared.

Sb nanosheets, also known as antimonene, have received ever-growing consideration as a promising new type of two-dimensional (2D) material due to their many attractive properties. However, how their nonlinear optical (NLO) properties are affected by their nanosheet structure and measurement conditions remains unclear. Herein, we report a successful size-selective production method for Sb nanosheets, which is based on a combination of lithium ion intercalation, solvent exfoliation and size selection centrifugation. This high-yield and size-selective preparation method enables fundamental investigation on the relation of the intrinsic optical properties of Sb nanosheets. Nanosecond Z-scan measurements revealed a unique size-dependent broadband NLO response. When the average size is reduced from 3 micrometers to 50 nanometers, the Sb nanosheets exhibit a clear transition from saturable absorption to reversed saturable absorption. Ultrafast transient absorption spectroscopic investigation indicated that exciton cooling is significantly faster in a small nanosheet than in large ones, revealing that the different exciton relaxation dynamic plays key roles in the distinct size-tunable nonlinear optical response. This work paves new ways towards the mass production and practical application of antimonene.

Two-dimensional materials have rich physical and chemical properties due to their unique nanostructures and electronic states. Although many two-dimensional materials have been reported in the past decade, they rarely exhibit multiferroic behavior. Herein, we synthesized layered structure NiH2SeO4 single crystals using the hydrothermal method, which can be further exfoliated into nanosheets using the transparent glue method. In addition, we demonstrated using first-principles calculations that the dissociation energy and dissociation strength of NiH2SeO4 crystals are much lower than those of graphite, and the single layer is multiferroic. The monolayer NiH2SeO4 is mainly polarized along the in-plane axis, and the polarization is comparable to the bulk material of BaTiO3. Furthermore, NiH2SeO4 exhibits antiferromagnetic transition at 24 K, and the effective moment of Ni2+ is 3.32 μB. The monolayer NiH2SeO4 is antiferromagnetic and the easy axis is along the in-plane (100) direction. NiH2SeO4 represents one of a few two dimensional multiferroic materials, and this study provides an approach for obtaining two dimensional multiferroic materials by incorporating magnetic ions with ions with lone pairs.