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In this article, a new sensor fault estimation algorithm is proposed for industrial processes described by linear discrete-time systems, where the fault dynamics are modeled as a stochastic process. By performing the variational Bayesian inference, the potential sensor fault, as well as the system states, is estimated simultaneously in a probabilistic framework. It is shown that the target fault signal can be satisfactorily estimated through the proposed method, without knowing the statistics of measurement noise and fault coefficient matrix. The efficiency and superiority of the proposed method are demonstrated through numerical simulations and experimental tests performed on a hybrid tank system.

In certain non-stationary processes, the non-stationary dynamics is caused by degradation or wearing of certain process components. Such dynamics can be characterized by a latent monotonic signal. Meanwhile, there also exist stationary dynamics characterizing the regular process variables. It hence becomes pertinent to distinguish these two sets of latent variables for the monitoring of the process from both the stationary and non-stationary aspects. In this regard, we propose a methodology to achieve such a goal by modeling the latent monotonic trend as a closed skew-normal random walk model. The other stationary relations are characterized by a state-space model with Gaussian noises. The problem is solved as a simultaneous state and parameter estimation problem using the expectation–maximization algorithm. As a result of the closed skew-normal random walk model for the monotonic trend, the state estimation problem becomes a skew-normal filtering and smoothing problem. The effectiveness of the proposed method is verified through a numerical simulation, and the algorithm is applied to solve a Hot Lime Softener fouling predictive monitoring problem.

The objective of this paper is to investigate the physical interaction of the cavitation-vortex dynamics around a 3D Delft hydrofoil by large eddy simulations combined with the Zwart–Gerber–Belamri cavitation model. Transient sheet/cloud cavitating flows around the twisted hydrofoil involves the primary and secondary cavity shedding characterized by a U-shape structure, which is consistent with previous experimental data. Different vortex identification methods, namely, the ω criterion, Q criterion, Ω method and Liutex method, are applied to identify and analyze the vortex structure. The Liutex method is further utilized to visualize the detail of vortex structure in the primary and secondary cavity shedding process, especially for formation and development of the U- shape structure. For the primary cavity shedding process, the U- shape structure is the main feature of the shedding process. The primary U- shape vortex structure experiences distortion, and breaks into two parts at the vortex neck. Then, the front part develops into a O-shape structure, whereas the rear part still maintains a U- shape structure. Finally, both parts are dissipative completely in the form of U-shape structures. The shear plays a major role in the primary cavity shedding. For the secondary cavity shedding, U-shape, Ω-shape, O-shape, and hairpin vortexes are observed. The secondary U-shape vortex structure twists and deforms to form a hairpin vortex when the secondary cavity sheds completely, and finally dissipates with a smaller magnitude hairpin vortex. Rotation plays a major role in the secondary cavity shedding.

The electrocatalytic conversion of CO2 into value-added chemicals is a promising approach to realize a carbon-energy balance. However, low current density still limits the application of the CO2 electroreduction reaction (CO2 RR). Metal-organic frameworks (MOFs) are one class of promising alternatives for the CO2 RR due to their periodically arranged isolated metal active sites. However, the poor conductivity of traditional MOFs usually results in a low current density in CO2 RR. We have prepared conductive two-dimensional (2D) phthalocyanine-based MOF (NiPc-NiO4 ) nanosheets linked by nickel-catecholate, which can be employed as highly efficient electrocatalysts for the CO2 RR to CO. The obtained NiPc-NiO4 has a good conductivity and exhibited a very high selectivity of 98.4 % toward CO production and a large CO partial current density of 34.5 mA cm-2 , outperforming the reported MOF catalysts. This work highlights the potential of conductive crystalline frameworks in electrocatalysis.

Data-driven causal modeling approaches find application in process data analysis and control. Process systems can be time-varying in nature; however, the existing literature for data-driven causal modeling hardly accounts for this. In this article, we present a causal modeling approach for the time-varying systems. It relies on the time-varying parameter models (TVPMs), estimated under the variational Bayesian expectation-maximization (VBEM) framework. We incorporate a hypothesis switching procedure followed by the estimation that allows us to infer the time-varying strengths of the causal influence of the inputs on the outputs of the system. We illustrate the proposed approach using the production data from steam-assisted gravity drainage (SAGD) wells. The proposed approach was found to extract consistent causal models across multiple cases of the studied system and outperform the time-invariant models and TVPMs estimated under the maximum likelihood framework.

The vortex-induced vibration may lead to a premature failure of hydraulic mechanical systems, especially under the resonance condition in the torsional mode. To predict the structural fatigue life, a careful consideration of the dynamic response to the hydraulic excitations is essential in the design phase. This study focuses on the numerical investigation of the relationship between the flow velocity, the added mass and the hydrodynamic damping, particularly, with respect to a Donaldson-type hydrofoil, vibrating in the first torsional mode. A two-way fluid-structure interaction (FSI) method is used to predict above two parameters. The flow velocity is in the range of 0 m/s–20m/s. To evaluate the hydrodynamic damping ratio, an identification method is proposed, based on a modified version of the logarithmic decay method. The relative deviations of the simulated natural frequencies and hydrodynamic damping ratios as compared with the experimental data for the first torsional modes, are within 8.1% and 16.6%, respectively. The analysis results show that the added mass coefficient for the first torsional mode is in the range of 1.59–1.86, and is around 44% of that for the first bending mode. The trends of the boundary layer thickness and the wake width against the reduced velocity are found to be opposite to that of the hydrodynamic damping ratio. The theoretical equation for predicting the hydrodynamic damping ratio is modified, which is shown to be more reliable due to its consideration of the velocity independent hydrodynamic damping phase.

Natural cellulose nanocrystals (CNCs) possess outstanding properties, such as biodegradability, hydrophilicity, large specific surface areas, and are low in cost. A highly stable and sensitive humidity sensor based on a quartz crystal microbalance (QCM) was prepared using CNCs as the sensing film. To investigate the impact of CNCs loading on the sensor performance, a series of humidity-sensitive performance tests, including linearity, response and recovery times, repeatability, hysteresis characteristics, selectivity, and long-term stability tests, was conducted. The experimental results indicated that the humidity sensor with CNCs loading of 2 μg (QCM-2) exhibited excellent logarithmic linearity, high sensitivity (32.35 Hz/% relative humidity (RH)), excellent reversible behavior, and long-term stability at a RH of 11–84%. The contact angle of QCM-2 was 12.5°, revealing its suitable hydrophilicity. Thus, we demonstrate that CNCs are great prospects for potential application in humidity sensors with high performance and low cost.

Storm geysers increasingly occur in sewer systems under climate change and rapid urbanization. Mitigation measures are in great demand to avoid safety problems. In this study, three-dimensional computational fluid dynamics models of single-inlet and multi-inlet systems were established to investigate geysering induced by rapid filling and assess the effectiveness of potential mitigation methods. The modeling results suggest that increasing the capacity of the downstream pipe before the inflow front reaches the chamber can effectively reduce the maximum geyser pressure. The peak pressure can be significantly mitigated when the chamber size is designed with care and the drop height between the upstream and downstream pipes is reduced. A diversion deflector with air vents and an orifice plate at the riser top end can alleviate the maximum pressure by about 65% with about 75% of the entrapped air being released. The peak pressure during the geyser event in the multi-inlet model is less than that of a single-inlet model under the same total inflow condition, but more water can be released. HIGHLIGHTS A small drop height between the connecting pipes can effectively reduce the maximum pressure during rapid filling.; Mitigation measures including flow deflectors and orifice plates were studied to alleviate geyser intensity.; Intermittent air–water jets can be generated much more easily in a system with multiple inlets, and the peak pressure is generally small but more water can be released.

Permeable pavement is an effective means for stormwater runoff control and pollutant removal. However, relatively few studies have examined the characteristics of permeable brick and corresponding permeable pavement system (PPS). In this work, the permeable pavement systems consisted of surface permeable brick layer (concrete or ceramic) with structural layer (including a cement mortar layer, a permeable concrete layer, and a gravel layers) were selected as typical cases to assess their permeability and runoff pollutant removal performance by laboratory experiments. The results indicated that PPS had obvious outflow hysteresis effect. The PPS with ceramic brick layer reached the saturation flow rate earlier and showed larger outflow rate than that with concrete brick layer. Both types of PPSs had a relatively high efficiency (83.8-95.2%) in removing suspended solids (SS) in stormwater runoff mainly due to the interception and filtration of the surface brick layer, whereas the structural layer of the PPS played a vital role in the removal of total phosphorus (TP). The percentage of total nitrogen (TN) removal efficiency via ceramic brick layer accounted for via corresponding PPS was obviously larger than that of concrete brick layer. The PPS also displayed a certain chemical oxygen demand (COD) removal ability: around 14.0-27.0% for concrete type and 20.9-28.9% for ceramic type. Subsequently, a multi-objective evaluation model was implemented based on the analytic hierarchy process (AHP) method to identify the optimal scheme in relation to four indices: permeability, environmental benefit, compressive strength, and comprehensive economic cost. The results showed, insofar, the ceramic PPS is preferred with a better economic performance. Our study attempts to select optimal designs of PPS and provides insight into the permeable capacity and the efficiency of pollutant removal in PPS.

Near-infrared (NIR) light-responsive materials had attracted much attention by virtue of their ability to employ abundant light sources to adapt their properties remotely and spatially in which development of novel NIR light-responsive fillers was the key factor. In this work, cellulose nanocrystals (CNCs) were coated with polydopamine (PDA) to endow these plant-derived nanofillers with good light absorption properties. In this work, PDA@CNC was incorporated into the poly(N-isopropylacrylamide) (PNIPAM) matrix to fabricate PDA@CNC/PNIAPM nanocomposite hydrogels with controllable performance in response to NIR stimuli. The PDA@CNC would not only serve as a reinforcement agent to mechanically toughen the hydrogels but also integrate considerable photothermal effect into the same system. As a result of fast NIR responsiveness and easily tailored photothermal properties, the 5-Fluorouracil (5-Fu) release behavior of the nanocomposite hydrogels could be remotely controlled with the assistance of a NIR laser. Besides, the nanocomposite hydrogel with Ag nanoparticles immobilized PDA@CNC (Ag/PDA@CNC) was demonstrated as a novel catalyst to tune the reduction rate of 4-nitrophenol (4-NP) upon NIR irradiation. Taken together, the modified CNCs would be alternative functional nanofillers for the construction of NIR light-responsive materials with controllable performance.

In order to meet the increasing demand for electric energy, it is of great significance to develop high-performance electrochemical energy storage materials. Cobalt/nickel-based tungstates (MWO4, M ​= ​Co, Ni and Co–Ni) show much higher electrical conductivity than pure oxides. However, due to their relatively low capacity and poor cycle stability, their potential as electrode materials for high-performance supercapatteries is limited to a great extent. In this paper, we reported the successful synthesis of bimetallic two-dimensional (2D) Co–Ni tungstates thin sheets assembled by nanosheets through a substrate-free hydrothermal method. The ratio of Co/Ni was optimized to 1:1 and the as-obtained Co0.5Ni0.5WO4 (CNWO) electrode exhibited a high specific capacity of 626.4 ​C ​g−1 ​at 1 ​A ​g−1 and high cyclic stability (105.3% capacity maintained over 10,000 cycles at 10 ​A ​g−1) in a three-electrode system, which is attributed to the synergistic effect of 2D/3D porous architecture and bimetallic composition of CNWO. An alkaline hybrid supercapattery (CNWO//activated carbon(AC)) with CNWO as the positive electrode and AC as the negative one showed the maximum specific energy of 42.2 ​Wh·kg−1 ​at the specific power of 1047.7 ​W ​kg−1 with a long cycle life (93.5% capacity retention after 15,000 cycles at 10 ​A ​g−1). The rational design of CNWO could pave the way for the preparation of bimetallic oxides with significantly improved electrochemical property.

Robust and ultralight biofoams had been successfully prepared using readily available and biocompatible cellulose nanofibrils (CNFs) as the matrix. The γ-glycidoxypropyltrimethoxysilane (GPTMS) was first added into the CNFs suspension to act as a crosslinker to form covalent linkages between cellulose chains. Then the gelatin was incorporated into the networks via reacting with the epoxy groups on GPTMS and forming hydrogen bonding with CNFs. The content of gelatin had a significant influence on the properties of the obtained foams. With the introduction of a small amount of gelatin, the foams exhibited significantly enhanced mechanical properties and stability in water in comparison with the CNF foams without GPTMS and/or gelatin. The foams containing the appropriate ratio of gelatin to CNFs possessed the high porosity (99.16%), ultralow density (0.0077 g/cm3), good mechanical properties, and abundant functional groups (hydroxyl and carboxylate groups). These features made it an ideal adsorbent toward methylene blue (MB) and the maximum adsorption capacity could reach up to 430.33 mg/g. Additionally, the cationic MB could be removed from the mixed cationic/anionic dye solutions with high selectivity, possibly due to the strong electrostatic interactions between MB and the adsorbent. Furthermore, the recycling test demonstrated the good reusability of this biofoam. Therefore, this work provides an environmentally benign method to fabricate robust CNF-based foams, which can be considered as green adsorbents for the treatment of water pollutants.

It is still a great challenge to achieve high selectivity of CH4 in CO2 electroreduction reactions (CO2 RR) because of the similar reduction potentials of possible products and the sluggish kinetics for CO2 activation. Stabilizing key reaction intermediates by single type of active sites supported on porous conductive material is crucial to achieve high selectivity for single product such as CH4 . Here, Cu2 O(111) quantum dots with an average size of 3.5 nm are in situ synthesized on a porous conductive copper-based metal-organic framework (CuHHTP), exhibiting high selectivity of 73 % towards CH4 with partial current density of 10.8 mA cm-2 at -1.4 V vs. RHE (reversible hydrogen electrode) in CO2 RR. Operando infrared spectroscopy and DFT calculations reveal that the key intermediates (such as *CH2 O and *OCH3 ) involved in the pathway of CH4 formation are stabilized by the single active Cu2 O(111) and hydrogen bonding, thus generating CH4 instead of CO.

Monitoring the dynamics of soil salinization is of great importance for agricultural production. This study selected Yucheng County, a typical county on the Huang-Huai-Hai Plain (HHHP) of China, as the study area and evaluated the spatial and temporal variation of soil salinization. Three methods, consisting of principal component analysis (PCA) transformation, tasseled cap (TC) transformation, and optimal band combination (OBC), were used to extract information from an early Landsat multispectral scanner (MSS) image from 1984, and their advantages were compared. In addition, OBC was used on a thematic mapper (TM) image from 2009. An iteratively self-organizing data analysis algorithm was used together with prior knowledge of likely classifications to interpret the MSS and TM images for data classification. Finally, a transfer matrix method was used to assess the spatial and temporal variability of soil salinization and analyze the driving factors of soil salinization. Compared to PCA transformation and OBC, TC transformation was a more effective method for extracting soil salinization information from the MSS sensor. The results indicate that a soil area of approximately 298 km2 was affected by salinity in 1984 in Yucheng County, of which 5.40%, 11.96%, and 12.75% were classified as being subject to slight, moderate, and severe salinization, respectively. In 2009, the saline area was reduced to only 146 km2, of which 10.70% and 3.75% were characterized by slight to moderate salinization and no severe salinization, respectively. The saline land decreased at an average rate of 6 km2 per year. This decrease was probably a result of lower groundwater depth, increased organic fertilizer or crop straw in soil, changed land use type, and increased vegetation coverage.

Three cationic capsule-shaped Zr-based metal-organic polyhedra (MOPs) with different cavity sizes were successfully constructed through the self-assembly of trinuclear zirconocene clusters and imidazolium-functionalized dicarboxylic ligands. Owing to the imidazolium groups in the MOPs, they show good CO2 adsorption uptake. Moreover, the halogen anions of the imidazolium groups and Bronsted acid sites (-OH) in the Zr-based knots are in close proximity, making these MOPs able to catalyze synergistically the cycloaddition reaction of CO2 with epoxides into cyclic carbonates. This is the first report of using MOPs as catalysts for this reaction without the addition of a cocatalyst.

The heterogeneous lamellar structure composed of a mixture of coarse crystal layer and fine crystal layer can improve the mechanical properties and corrosion resistance of the metal. To obtain high-performance aluminum alloy with heterogeneous lamellar structure, high-pressure torsion experiments have been carried out at 360, 380 and 400 °C. The results of tensile test and electrochemical corrosion test show that the strength of the alloy increases from 682.46 to 781.03 MPa and the polarization resistance increases from 42.91 to 81.12 kΩ cm2 with the increase in deformation temperature. It can be inferred from optical microscopy and transmission electron microscope observations that the strength of the alloy increases with increasing temperature. This is because the geometrically necessary dislocations at the interface increase during the stretching process, which in turn increases the back stress. Moreover, the enhancement of chemical corrosion resistance can be attributed to the decreased volume fraction of grain boundaries, which results in an increase in the compactness of the passivation film in the corrosive environment.

Composite electrodes containing both carbon and transition metal oxides have attracted tremendous interest because of their great potential as prominent electrodes for supercapacitors. Herein, direct growth of δ-MnO2 on wheat flour-derived carbon foam (WFCF) with well-developed hierarchical microstructure is readily carried out through an easy, scalable, and reliable two-step synthesis (also referred to as "foaming and cooking" technique), thereby achieving dual goals of environmental sustainability and remarkable electrical energy storage. The unique electrode architecture closely assembled between the prepared sponge-like carbon foam and nanostructured δ-MnO2 affords not only large exposed electroactive surface area but also rapid electrons and ions transport pathway, benefiting from the 3D interconnected hierarchical porous texture as well as considerable open channels between the anchored MnO2 sheets. As a result, the symmetric supercapacitor device based on the WFCF/MnO2-2.0 composite delivers a capacitance of 146 F g−1 and an impressive energy density of 20.3 Wh kg−1 at 1 A g−1 with good cycling stability in 6 M KOH electrolyte. The kinetic analysis indicates a combination of capacitive and battery-like electrochemical response. The proposed "foaming and cooking" strategy renders a prospective way for facile construction of high-performance supercapacitor electrodes with fast kinetics, good reversibility and structure stability.

Lead sulfide (PbS) quantum dots (QDs) are important near infrared (NIR) luminescent materials with tunable and strong emission covering a broad NIR region. However, their optical properties are quite sensitive to air, water, and high temperature due to the surface oxidation, thus limiting their applications in optoelectronic devices and biological imaging. Herein, a cation-doping strategy is presented to make a series of high-quality Zn-doped PbS QDs with strong emission covering whole second near-infrared window (NIR-II, 1,000-1,700 nm). First-principle calculations confirmed that Zn dopants formed dopant states and decreased the recombination energy gap of host PbS. Notably, the Zn dopants significantly improved the quantum yield, photoluminescence lifetime and thermal stability of PbS QDs. Moreover, the PEGylated Zn-doped PbS QDs emitting in the NIR-llb window (1,500-1,700 nm) realized the noninvasive imaging of cerebral vascular of mouse with high resolution, being able to distinguish blood capillary. This material not only provides a new tool for deep tissue fluorescence imaging, but is also promising for the development of other NIR related devices.

As a common environmental problem in China, trace metal accumulation and contamination in soils of greenhouse vegetable production (GVP) may pose significant health risk via oral ingestion, inhalation, and dermal contact to vegetable farmers and children playing in greenhouse fields. Thus, bioaccessibility and health risk of Cr, Ni, Cu, Zn, Cd, and Pb in GVP soils collected from 13 GVP farms or bases near industrial areas of the Yangtze River Delta, China, were investigated as a case study. The results suggested that both GVP and industrial discharges contributed a lot to accumulation or contamination especially of Zn and Cd in soil, which subsequently increased their bioaccessible concentrations. In addition, soil acidification caused by GVP also increased bioaccessible Cr and Ni concentrations in soil of the Anthrosols study area. However, the health risk assessment of metals in GVP soil through inhalation and oral ingestion considering metal bioaccessibility suggested no non-carcinogenic and carcinogenic risks to both farmers and children. In contrast, there was potential carcinogenic risk within acceptable level posed by Cr in GVP soil through dermal contact to farmers and children. This indicates that both GVP and industrial activities had limited effect on health risk of trace metals in GVP soil via ingestion, inhalation, and dermal contact. However, the carcinogenic risk posed by Cr, which mainly originated from natural sources, still cannot be negligible. Overall, the results will provide valuable information for decision-makers to develop reasonable strategies and guidelines for risk management of trace metals in GVP soil.

Aiming at identifying nonlinear systems, one of the most challenging problems in system identification, a class of data-driven recursive least squares algorithms are presented in this work. First, a full form dynamic linearization based linear data model for nonlinear systems is derived. Consequently, a full form dynamic linearization-based data-driven recursive least squares identification method for estimating the unknown parameter of the obtained linear data model is proposed along with convergence analysis and prediction of the outputs subject to stochastic noises. Furthermore, a partial form dynamic linearization-based data-driven recursive least squares identification algorithm is also developed as a special case of the full form dynamic linearization based algorithm. The proposed two identification algorithms for the nonlinear nonaffine discrete-time systems are flexible in applications without relying on any explicit mechanism model information of the systems. Additionally, the number of the parameters in the obtained linear data model can be tuned flexibly to reduce computation complexity. The validity of the two identification algorithms is verified by rigorous theoretical analysis and simulation studies.

Nutrient surplus in intense production system such as plastic greenhouse vegetable production (PGVP) may affects soil degradation and further influences sustainable utilization. In this study, we analyzed nutrient balance of nitrogen (N), phosphorous (P) and potassium (K) in PGVP and measured soil fertility properties, pH and electrical conductivity (EC) in the North, the Middle and the South of Shaanxi Province, northwestern China. Considerable nutrient surplus was found in PGVP systems, and the average nutrient balance of N, P and K were 1407.0, 682.9 and 1169.1 kg ha−1 season−1, respectively. Soil organic matter, total N, total P, total K, available P and available K in PGVP soil were 27%, 49%, 42%, 3%, 200% and 54% greater than those levels in open fields, respectively. Average pH value in greenhouse soil was 0.53 lower than that in open field, and EC value in greenhouse soil (547.11 μS cm−1) was more than triple that in open fields (157.14 μS cm−1). Soil acidification and secondary salinization has occurred in PGVP. Soil P/K ratio in PGVP systems reflected that nutrient surplus in the South (0.080) and the Middle (0.077) were greater than those in the North (0.061). The differences in nutrient accumulation rate and soil pH changes among different regions were the comprehensive results affecting by both fertilization and soil types. We deduced that fertilization in PGVP in Shaanxi Province was excessive, which may further accelerate soil nutrient accumulation, acidification and secondary salinization.

Electroreduction of CO2 (CO2RR) into value-added fuels is of significant importance but remains a big challenge because of poor selectivity, low current density, and large overpotential. Crystallin...

Environmental risk of heavy metals (HMs) in soil is commonly assessed by the different risk screening values of HMs under different pH based on soil environmental quality standards. To explore and establish a reliable, rapid and cost-effective method for detailed soil environmental quality survey with high-density sampling in the large-scale area is of significance for theoretical and practical research. In present study, using data from Yunnan Province, China, rapid analysis of soil HMs were conducted via portable X-ray fluorescence (PXRF) spectrometry, and that of soil pH was estimated by applying PXRF and visible near-infrared reflectance (Vis-NIR) spectroscopy data to partial least-squares regression (PLSR) and support vector machine regression (SVMR). Then we compared soil HM contamination grades calculated by conventional laboratory analysis data with those of rapid analysis data. It was found that soil HMs (i.e., As, Pb, Cu, and Zn) were successfully estimated by PXRF with high coefficient of determination (R2) above 0.97 (P

Monitoring specific immune cells in vivo will provide significant information for improving the therapeutic effect of immunotherapy. Herein, the in vivo two-color fluorescence molecular imaging of an important immune cell, myeloid-derived suppressor cell (MDSC), was realized by using quantum dot (QD)-based nanoprobes with non-overlap emission in the second near-infrared window (NIR-II, 1000-1700 nm). NIR-IIa and NIR-IIb QDs were conjugated with two MDSC-specific antibodies, respectively, and targeted the in vivo MDSCs together. Due to the suppressed photon scattering and diminished autofluorescence in the NIR-II window, the distribution of MDSCs in different organs and tissues was clearly revealed in a non-invasive way by the colocalization of two-color fluorescence from nanoprobes. The high-resolution imaging further confirmed the exact distribution of MDSCs in tumor immune microenvironment (TIME). Our results demonstrated that NIR-II fluorescence nanoprobes with molecular targeting ability provided a powerful tool for monitoring the dynamic change of immune cell populations in TIME in vivo, thus guiding the choice of clinical medicine and evaluating the therapeutic effect.

The photoreduction of toxic Cr(VI) to environmental Cr(III) driven by visible-light is highly desired. Metal-organic frameworks (MOFs), as one class of outstanding porous materials, had been utilized for photoreduction of Cr(VI). Current methods modulated the photoreduction of Cr(VI) mainly by selection of suitable metal ions or organic ligands in single component MOFs. However, most of them still exhibit limited photoreduction performance due to low Cr(VI) adsorption rate/capacity, weak light harvesting efficiency, and/or poor electronic utilization efficiency. Multivariate metal-organic frameworks with highly visible-light photosensitive unit and strong Cr(VI) adsorption strut into one single phase is therefore expected to be an effective strategy to improve the photoreduction of Cr(VI), but remains unexplored. Herein, intense visible-light absorption porphyrin unit and strong toxic anions adsorption strut were integrated into one single MOF simultaneously via a sequential mixed-ligand and ionization method, which strongly improve the photoreduction performance of Cr(VI). The synergistic effect of strong adsorption of Cr2O72− and efficient utilization of light endowed H2TCPP⊂(I-)Meim-UiO-66 with highly efficient photoreduction activity toward toxic Cr2O72− under visible light in a rate of 13.3 mgCr(VI)/gcatalyst/min, much higher than the reported MOF-based photocatalysts including typical NH2-UiO-66 (0.2 mgCr(VI)/gcatalyst/min) and NH2-MIL-125 (1.6 mgCr(VI)/gcatalyst/min). As far as we know, this is the best catalyst among all the reported MOF-based photocatalysts for Cr(VI) photoreduction, in which the I- in our imidazolium functionalized MOF acts as sacrificial agent. Based on the results from time-resolved photoluminescence spectra, electron spin resonance, and theoretical calculation etc., a photoreduction mechanism of Cr2O72- over H2TCPP⊂(I-)Meim-UiO-66 was also well proposed. This general and facial strategy, combining the advantages of adsorption and photosensitivity in a multivariate MOF, paves the way to design of higher efficient photocatalytic materials.

Aerogels that are very porous, mechanically tough, and have low thermal conductivities have attracted significant research interest due to their potential use in engineering applications. Herein, we describe the preparation of biomass-derived composite aerogels containing agar, chitosan (CS), esterified cellulose nanocrystals (ECNCs), and graphene using an environmentally friendly ice-templating method. The prepared composite aerogels have high porosities (> 97%) and low densities (3.1–4.3 kg/m3). FESEM images of these aerogels reveal interconnected honeycomb-like structures several micrometers in size. The thermal conductivity of the ECNCs/CS/agar aerogel was found to be 21 mW/m K, which is close to the thermal conductivity of air under ambient conditions (25.4 mW/m K). The ECNCs/CS/agar aerogel exhibited a stress of 210 kPa, which is about 500% higher than that of the CS/agar aerogel. The compressive strength of the graphene/ECNCs/CS/agar aerogel increased from 210 to 580 kPa (a factor of 2.8) as the graphene content was increased from 0 to 1.3%. Furthermore, the composite aerogels are flexible and compressible, and are candidates for practical applications such as insulating materials.

Two-dimensional (2D) porous materials have been proved to be meritorious for supercapacitors (SCs) due to unique properties of large surface area, superior intrinsic porosity and high electrical conductivity. In this work, we reported for the first synthesis of 2D porous Co3O4 thin sheets assembled by ultrathin nanosheets via direct hydrothermal decomposition of aqueous solution of cobalt nitrate in the presence of benzoic acid (BA) without any template or surfactant. High specific capacity (497, 598.5 and 399 C g−1 at 1.0 A g−1) and remarkable cycling stability (9.8, 6.3 and 13.1% loss over 8000 cycles at 10.0 A g−1) were achieved in a three-electrode system for the Co3O4 thin sheets at 200 °C for 6, 12 and 24 h with different specific surface area of 69.96, 142.15 and 42.07 m2 g−1, which can be attributed to the special structural feature of an open and porous surface layer and the synergistic effect of 2D and 3D structure that significantly facilitates fast electron transport, ion diffusion and intimate electrode/electrolyte contact. Furthermore, an assembled asymmetric supercapacitor (ASC, Co3O4 thin sheets//activated carbon (AC)) can reach a working output potential difference of 0–1.6 V with a maximum energy density of 22.49 Wh·kg−1 at the power density of 800 W kg−1 with excellent cyclic stability (only 8.2% loss of its initial specific capacity value over 10000 cycles). The results show that our synthesis provides a new insight into the fabrication of 2D hierarchical porous Co3O4 thin sheets; in addition, the as-synthesized Co3O4 thin sheets have potential for various applications in SCs, electrochemical sensing, and lithium ion battery.

Slow feature analysis (SFA) is an approach that extracts features from a time series dataset in an unsupervised manner based on the temporal slowness principle. These slow features contain relevant information about the dynamics of the process and hence are useful for developing models. For supervised learning objectives, these slow features need to be relevant to the outputs. Partial least squares (PLS) is a method used to perform supervised feature extraction and build models. For time series datasets this approach cannot be used directly as it assumes each sample to be sequentially independent of each other. We propose an approach to perform feature extraction which combines the temporal slowness element of SFA and the output relevance element of PLS. The proposed approach extracts temporally slow features that are relevant to the outputs, which is an essential aspect of supervised learning. The proposed formulations can be solved using the existing PLS algorithms like NIPALS and SIMPLS with proposed modifications. The proposed methods are applied to three case studies: simulated, industrial and experimental case studies to demonstrate their efficacy.

The use of bamboo for the fabrication of cellulose nanoparticles (CNs) in a facile and mild process is limited because of the existence of strong hydrogen bonding between the cellulose chains. Inspired by the synergistic effects of mechanochemistry, efficient cleavage of the strong hydrogen bonds and green manufacture of CNs with a high yield of 90.8% were realized through a shearing-assisted solvent pretreatment and a subsequent mechanochemical synergy process. In the one-pot tandem reaction, chemical action, thermodynamic interaction, and mechanical force induced by mechanochemistry created synergy to accelerate the dissociation of hydrogen bonds and ultimately regulate the disintegration of cellulose into nanofibers. The CNs showed special granular morphology and cellulose II crystal form. This method of process intensification diminished laborious intermediate purification steps and improved effectively the reaction efficiency. Thus, the study provides a facile and green approach for the large-scale production of CNs, and is expected to carry significant benefits in terms of economy and sustainability.

Although cellulose hydrogels are one of promising biomaterials for drug release carrier, their passive manner of drug release and the absence of remote stimuli response limit their further applications. Herein, we report a simple one-pot method for the synthesis of magnetic β-cyclodextrin (β-CD)/cellulose hydrogel beads, which exhibited rapid swelling–deswelling properties under an external magnetic field (EMF) to remotely control drug release from passive release to stepwise release. The grafted β-CD endows the hydrogel with high drug loading capacity and, simultaneously, the incorporation of Fe3O4 nanoparticles provide the force for stepwise drug release through EMF induced rapid and reversible deformation of 3D network. We demonstrate that the efficiency of the hydrogel in the stepwise drug release dose and rate can be controlled by switching on–off the EMF and adjusting the content of Fe3O4 nanoparticles. Additionally, results from cytotoxicity tests confirmed the excellent biocompatibility of the developed hydrogel, which is promising to be used in the biomedical field.

Cavitation is a complex multiphase flow phenomenon with an abrupt transient phase change between the liquid and the vapor, including multiscale vortical motions. The transient cavitation dynamics is closely associated with the evolution of the cavitation vortex structures. The present paper investigates the cavitation vortex dynamics using different vortex identification methods, including the vorticity method, the Q criterion method, the Omega method (Ω), the λ2 method and the Rortex method. The Q criterion is an eigenvalue-based criterion, and in the Omega method, the parameter is normalized, is independent of the threshold value and in most conditions Ω=0.52. The Rortex method is based on an eigenvector-based criterion. Numerical simulations are conducted using the implemented compressible cavitation solver in the open source software OpenFOAM for the sheet/cloud cavitating flows around a NACA66 (mod) hydrofoil fixed at α=6°, σ=1.25 and Re=7.96×105. The flow is characterized by the alternate interactions of the re-entrant flow and the collapse induced shock wave. Results include the vapor structures and the vortex dynamics in the unsteady sheet/cloud cavitating flows, with emphasis on the vortex structures in the cavitation region, the cavity interface, the cavity closure, the cavity wakes, and the foil wakes with the shedding cavity. The comparisons of the various methods, including that the vorticity method, the Q criterion method, the Omega method, the λ2 method and the Rortex method, show the performances of different methods in identifying the cavitation vortex structures. Generally, during the attached cavity growth stage, the Q criteria can well predict the vortex structures in the cavitation region and at the foil trailing edge in the pure liquid region, while with the Omega method and the Rortex method, the vortex structures outside the attached cavity and on the foil pressure side can also be predicted. The λ2 method can well predict the vortex structures in the cavity closure region. During the re-entrant jet development stage, the vortex structures in the re-entrant jet region is weak. During the cavity cloud shedding stage, the vortex dynamics at the foil leading edge covered by newly grown cavity sheet is different from that during the attached cavity sheet growth stage. During the shock wave formation and propagation stage, strong vortex structures with both the size and the strength are observed owing to the cavity cloud shedding and collapse behavior. The influence of the small parameter e in the Omega method on the cavitation vortex identification is discussed.

The objective of this paper is to investigate the dynamic evolution of unsteady liquid nitrogen cavitating flows in a wide range of free-stream conditions and propose a thermal parameter to evaluate and predict the transition process of two typical cavitation dynamics in liquid nitrogen. The dynamic evolutions of liquid nitrogen cavitating flows in a converging–diverging (C-D) nozzle with a throat height of 2.0 mm under a wide range of free-stream conditions were experimentally investigated. Experiments were carried out in liquid nitrogen with the temperature range from 68 K to 86 K, the pressure in the tanks is within the range of 30–300 kPa. The results show that two typical cavitation dynamics, namely the quasi-isothermal mode and the thermo-sensitive mode were observed under similar cavitation number and Reynolds number with the increasing throat temperature. The cavitation dynamics transits from the quasi-isothermal mode to the thermo-sensitive mode with the increasing throat temperature, and the transition temperature (transition mode) is approximately at 77–78 K. In the quasi-isothermal mode, the shedding cavity with clear interface collapses immediately after shedding. The cavity area increases with the increasing temperature under similar cavitation number and Reynolds number. In the transition mode, the magnitude of cavity area, the time duration of the shedding process, as well as the cavitation aggressiveness reaches the maximum values. In the thermo-sensitive mode, the shedding cavity turns to be mushy and frothy, and the mushy interface collapses slowly after shedding. The cavity area decreases with the increasing temperature under similar cavitation number and Reynolds number. When the thermodynamic effects completely dominate the change of the cavitation dynamics in the thermo-sensitive mode, the cavitation process becomes more stable. The shedding cavity collapses more slowly, while moves more quickly. The thermal parameter C-factor could quantitatively evaluate and predict dynamics transition from the quasi-isothermal mode to the thermo-sensitive mode in liquid nitrogen cavitating flows. The transition mode (transition temperature) should be prevented from causing the maximum cavitation aggressiveness in liquid nitrogen apparatus or system.

Selenium (Se) is an essential trace element for humans and animals. In China, intensive agricultural inputs in greenhouse vegetable production (GVP) have resulted in great changes in Se concentration and bioavailability in soil, which have great influences on Se flux to living organisms through food chains. It is crucial to understand the factors on Se concentration and bioavailability in greenhouse soil. Thus, we chose the east bank of the Dianchi Lake, a typical GVP area covering 177 km2 in Southwest China, as the study area to quantify source contributions to soil Se and estimate relative importance of influence factors on its bioavailability in GVP with a receptor model (absolute principal component scores-multiple linear regression, APCS-MLR) after principal component analysis (PCA). According to the enrichment factor (EF), total Se in greenhouse soil was accumulated at a minor level (1 fertilization > atmospheric deposition. It suggested that fertilization, especially manure, might be an important way to increase total Se in greenhouse soils in Se-deficient areas. The bioavailability of Se was affected by several factors, among of which total Se was the foremost one. In comparison with organic matter and clay, Fe/Al oxides exerted more controls on Se bioavailability, which was dependent on pH. Increasing Olsen P was helpful in improving soil Se bioavailability in greenhouse. More attention should be paid to soil physicochemical characteristics when Se-containing fertilizers are applied to increase Se levels in greenhouse vegetables.

A great amount of insoluble phosphate in agricultural soils is not available for crops. Three strains of bacteria (Bacillus megaterium YLYP1, Pseudomonas prosekii YLYP6 and Pseudomonas sp. YLYP29) isolated from activated sludge and soil could efficiently solubilise tricalcium phosphate. In particular, the novel strain P. prosekii YLYP6 produced 716 mg L−1 of available phosphate within 6 days under the optimal culture conditions [20 °C, pH 7.9, inoculum size of 0.5% (v:v)] determined by response surface methodology. P. prosekii YLYP6 demonstrated efficient phosphate solubilisation in response to broad variations in pH (5–9) and temperature (15–35 °C). The phosphate solubilisation curves of the strains fit well with a first-order kinetic model (R2 > 0.939), with a half-life of 1.51–5.94 d for 5.0 g L−1 calcium phosphate. Continuous culture experiments combined with scanning electron microscopic observations and gas chromatography–mass spectrometry analysis revealed that 2,3-dimethylfumaric acid, gluconic and N-butyl-tert-butylamine that were produced by P. prosekii YLYP6 were responsible for phosphate solubilisation by supplying H+ ions and organic anions. Efficient phosphate solubilisation in actual soil by P. prosekii YLYP6 demonstrated the strong application potential to reduce the use of chemical P fertilisers and the resulting agricultural nonpoint pollution.

Chlorophyll content in lichens is routinely used as an accurate indicator of lichen vigor, interspecific differences, and the effect of site-related environmental parameters. Traditional methods of chlorophyll extraction are destructive, time-consuming, expensive, and inoperable, especially when measuring large quantities of chlorophyll. However, non-destructive methods of measurement using portable chlorophyll meters are rarely used for lichens. Considering the characteristics of lichens such as rough blade surface and absence of chlorophyll b in cyanolichens, we compared the non-destructive methods with traditional methods and evaluated their applicability in studying lichen pigment content. Two instruments, SPAD-502 and CCM-300, were used to measure the pigment content of seven foliose lichen species. These pigment readings were compared with those determined using the dimethyl sulphoxide (DMSO) extraction method. Significant correlations were observed between SPAD/CCM values and pigments (chlorophyll and total carotenoids) extracted from chlorolichens, especially species with a smooth surface. The CCM-300 was more accurate in detecting the pigment content of foliose chlorolichens. However, both instruments showed certain limitations in the determination of pigment content in cyanolichens, especially gelatinous species. For example, CCM-300 often failed to give specific values for some cyanolichen samples, and both instruments showed low measurement accuracy for cyanolichens. Based on the high correlation observed between chlorophyll meter readings and pigments extracted from chlorolichens, equations obtained in this study enabled accurate prediction of pigment content in these lichens.

The rapid development of the Internet of Things (IoT) and the increasing energy crisis call for a new type of energy sources. Triboelectric nanogenerators (TENGs), which can convert mechanical energies to electricity, develop quickly in recent years and catch more and more people's attention all over the world. Meanwhile the importance of the standardization for TENG has been emphasized, thus developing standardized theoretical models and experimental methods to quantitatively evaluate the performance becomes more and more important for the commercialization and industrialization of the TENG technology. This paper systematically reviews the origin of the V-Q plot (the standardized characterization tool) and the figure-of-merits (FOM, the standard for quantitatively charactering the energy output per cycle for TENG). Several essential factors which are going to be potentially involved in the standardization for TENGs will also be discussed in this paper, including the input energy, environmental factors, and life-time assessment. The standardization of TENG will be extremely helpful to understand and improve further applications of this emerging energy harvester. We believe that the standardization of TENG will greatly facilitate the commercialization and industrialization of TENGs in the future.

The FeCrxCoNiB (x values in molar ration, x = 0.5–3) high-entropy alloys coatings were prepared by laser cladding on an AISI 1045 steel substrate. Annealing and high temperature oxidation experiments were performed on the FeCrxCoNiB (x = 0.5–3) coatings at 900 °C. The phase structure, morphology, and composition of the coatings and oxidation layers were analyzed by XRD, TEM, SEM, and EDS. Results demonstrated that the FeCrxCoNiB coatings are composed of simple face-centred cubic (FCC) phase and boride. The hardness value of the coatings is significantly improved due to the boride, which is achieved 860 HV at x = 0.5. Cr is conducive to inhibiting the coarsening of boride and enhancing the resistance of coatings to high-temperature softening. The oxidation kinetics curve of FeCrxCoNiB coatings basically follows oxidation dynamic the parabolic law. The selective oxidation in the FeCrxCoNiB coatings changed from the oxidation of Fe to the oxidation of Cr as an increase in Cr content, and finally formed continuous Cr2O3 film. The high temperature oxidation resistance of the FeCrxCoNiB coatings dropped with adding boron into the coatings, which improved contributing to Cr increasing. FeCrxCoNiB coatings gain a better high temperature oxidation resistance as x ≥ 2 (33.3 at.%).

The effect of industrial activities on trace metals in farmland of rapidly industrializing regions in developing countries has increasingly been a concern to the public. Here, soils were collected from 13 greenhouse vegetable production (GVP) farms or bases near industrial areas in the Yangtze River Delta of China to investigate the occurrence, speciation, and risks of Cr, Cu, Zn, Cd, Ni, and Pb in GVP soil. The results revealed that the main metal elements causing GVP soil pollution were Cd, Zn, Ni, and Cu, of which contamination levels were generally unpolluted to moderately polluted. Zinc pollution was mainly attributed to heavy fertilization, while Cd, Ni, and Cu pollution may be greatly ascribed to industrial effluents and coal combustion. Metal speciation studies showed that most of Cr, Ni, Cu, and Zn was present in residual fraction while more than half of Cd and Pb was present in non-residual fractions. Additionally, pollution of Cd, Cu, Ni, and Zn in GVP soil increased their corresponding mobile fractions. Risk assessment using potential ecological risk index and risk assessment code showed that Cd was the major risk contributor. Specifically, Cd generally posed moderate or considerable ecological risk as well as displayed medium or high mobility risk in GVP soil. Thus, great attention should be paid to the contribution of both industrial discharges and intensive farming to soil pollution by trace metals, especially Cd, because of its high mobility risk.

A combination of conductive polymer with natural biomass is an ideal alternative to the classical conductive materials. In this study, PPy/SA/TOMFC composite hydrogels were fabricated by incorporation of TEMPO-oxidized microfibrillated cellulose (TOMFC) into the alginate-based matrix along with the in situ polymerization of pyrrole monomer. It was found that the mechanical and conductive properties of the composite hydrogels were associated with the concentration of TOMFC, which facilitated the formation of more compact 3D network structures and the growing of PPy conductive network. The mechanical properties of the synthesized hydrogels were significantly enhanced by incorporation of higher amount of TOMFC. In addition, with the introduction of 5.0 wt% TOMFC, the electrical conductivity of composite hydrogels could be ten times higher than that of PPy/SA hydrogels. Moreover, the obtained PPy/SA/TOMFC hydrogels exhibited tunable swelling properties and good biocompatibility, making them promising candidates for the use as biomaterial.

Efficient charge storage media play a pivotal role in transistor‐based memories and thus are under intense research. In this work, the charge storage ability of type‐I InP/ZnS core/shell quantum dots is well revealed through studying a pentacene‐based organic transistor with the quantum dots (QDs) integrated. The quantum well‐like energy band structure enables the QDs to directly confine either holes or electrons in the core, signifying a dielectric layer‐free nonvolatile memory. Especially, the QDs in this device can be charged by electrons using light illumination as the exclusive method. The electron charging process is ascribed to the photoexcitation process in the InP‐core and the hot holes induced. The QDs layer demonstrates an electron storage density of ≈5.0 × 1011 cm−2 and a hole storage density of ≈6.4 × 1011 cm−2. Resultingly, the output device shows a fast response speed to gate voltage (10 µs), large memory window (42 V), good retention (>4.0 × 104 s), and reliable endurance. This work suggests that the core/shell quantum dot as a kind of charge storage medium is of great promise for optoelectronic memories., Type‐I InP/ZnS core/shell quantum dots are implanted into a pentacene organic transistor. The ambipolar charge storage ability and excellent optoelectronic property of the QDs enable the device to be optically programmed and electrically erased, signify a nonvolatile optoelectronic memory. The device demonstrates good retention, endurance, and fast response speed to the electric bias.

Several studies have investigated the associations between diurnal temperature rage (DTR) and mortality, but little evidence has been available regarding the association of DTR with years of life lost (YLL). The aim of this study was to examine the association of DTR with YLL rate, and quantify life loss per death caused by DTR in China. Daily meteorological and death data were collected from 364 locations in China during 2006–2017. First, we calculated daily YLL rate. Then, the distributed lag nonlinear model was applied to estimate the associations of DTR with YLL rate in each location, and multivariable meta-analysis was conducted to pool the location-specific estimates. Finally, we calculated the attributable fractions of DTR on YLL rate and average life loss per death to estimate the mortality burden caused by DTR. Subgroups analyses were conducted by region, age, sex and cause of death. A J-shaped association of DTR with YLL rate was identified in China. The minimum YLL-rate DTR (MYDTR) was 3.7 °C nationwide. The overall AF of DTR in China was 6.40% [95% confidence interval (CI) 3.95–8.86%], and AFs caused by DTR were higher in females, the elderly and south China. An average of 0.96 years (95%CI 0.57–1.35) life loss per death was attributable to DTR nationwide, and life losses per death attributed to DTR were higher in female, young population, and south China. AF and life loss per death caused by DTR were much higher in cold season than that in warm season. Both high DTR and low DTR increased YLL rate in China. Mortality burdens of DTR were much higher in cold season than warm season. The effects of DTR were modified by region, demography and cause of death. Our findings suggest that vulnerable population should be protected when daily temperature change rapidly, especially in cold season.

Microplastics become one of the serious persistent pollutants in terrestrial environments, and thus may represent a threat to the quality of soil and inhabiting organisms. It is imperative to understand occurrence and distribution of microplastics in soils. In this study, a large-scale field survey encompassing 85 locations along the lower reaches of Yangtze River and estuary was performed to investigate the microplastics abundance in agricultural soils. Microplastics were isolated from all the samples and all depths (0–80 cm). The microplastics abundance in soils ranged from 4.94 items/kg to 252.70 items/kg, with an average of 37.32 items/kg. The most common microplastic type detected was Polypropylene (PP) occurring as white fragments with sizes ranging from 0.1 mm to 0.5 mm. Abiotic parameters such as soil pH and texture were the general factors being associated with microplastic abundance. Meantime, traffic was indicated as one important factor to affect the microplastic abundance. Overall, the road input seems to be the main source of microplastic pollution in agricultural areas along the Yangtze River and estuary. Further studies should elucidate the original of the plastic fragments in order to establish a baseline for regulative initiatives securing environmental protection.

A sensitive and robust method has been developed using an ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) assay to quantify Tat-K13, a novel interfering peptide for the treatment of ischemic stroke, in human plasma. Automated solid-phase extraction on a Waters Oasis WCX (30 μm, 10 mg) 96-well plate was used to extract Tat-K13 from human plasma and the extracts were separated on a Waters Acquity CSH column (2.1 × 50 mm i.d., 1.7 μm) with a gradient elution method by mobile phase A (nonafluoropentanoic acid-acetic acid-water, 1:2:1000, v/v/v) and B (nonafluoropentanoic acid-acetic acid-water-acetonitrile, 1:2:100:900, v/v/v/v). The method was fully validated following international bioanalytical guidelines and showed good linearity from 2.10 to 1,050 ng/ml. The method was successfully applied to investigate the clinical pharmacokinetics of Tat-K13 in health volunteers. Rapid elimination of Tat-K13 from the body was observed, with half-life ranging from 0.26 to 0.78 h across different dose levels. The exposure of Tat-K13 was approximately dose-dependent in terms of the area under the concentration-time curve and peak concentration.

The purpose of this study is to investigate the cutting performance of amorphous carbon (a-C) coatings and hydrogenated amorphous carbon (a-C:H) coatings on machining 2A50 aluminum alloy. First-principles molecular dynamics simulation was applied to investigate the effect of hydrogen on the interaction between coatings and workpiece. The cross-section topography and internal structure of a-C and a-C:H films were characterized by field emission scanning electron microscopy and Raman spectroscopy. The surface roughness of the deposited films and processed workpiece were measured using a white light interferometer. The results show that the a-C-coated tool had the highest service life of 121 m and the best workpiece surface quality (Sq parameter of 0.23 &mu, m) while the workpiece surface roughness Sq parameter was 0.35 and 0.52 &mu, m when machined by the a-C:H-coated and the uncoated tool, respectively. Meanwhile, the build-up edge was observed on the a-C:H-coated tool and a layer of aluminum alloy was observed to have adhered to the surface of the uncoated tool at its stable stage. An interface model that examined the interactions between H-terminated diamond (111)/Al(111) surfaces revealed that H atoms would move laterally with the action of cutting heat (549 K) and increase the interaction between a-C:H and Al surfaces, therefore, Al was prone to adhere to the a-C:H-coated tool surface. The a-C coating shows better performance on cutting aluminum alloy than the a-C:H coating.

The objective of this paper is to apply both experimental and numerical methods to investigate acoustic waves induced by the oscillation and collapse of a single bubble. In the experiments, the schlieren technique is used to capture the temporal evolution of the bubble shapes, and the corresponding acoustic waves. The results are presented for the single bubble generated by a low-voltage bubble generator in the free field of water. During the numerical simulations, a three-dimensional (3D) weakly compressible model is introduced to investigate the single bubble dynamics, including the generation and propagation of acoustic waves. The results show that (1) Compression wave, rarefaction wave and shock wave are generated during expansion stage, collapse stage and rebound stage of the bubble respectively. (2) Compression waves are induced by the rapid expansion of the bubble and eventually steepen into one shock wave propagating outward in the liquid, then another strong shock wave is emitted at the final collapse stage. The velocity and pressure of the liquid field increases after the shock wave. (3) Rarefaction waves are generated during the collapse stage due to the contraction of the bubble. The rarefaction wave reduces the liquid pressure and its spatial distribution is dispersive. The pressure of these acoustic waves and their effect on the liquid velocity attenuate with the increase of propagation distance.

Conventional assessment of soil environmental quality commonly focuses on soil heavy metals (HMs), neglecting the HMs in agricultural products. To response this shortcoming, a comprehensive assessment combining both soil environmental quality and agricultural product security for evaluating soil HM impact is urgently required. This comprehensive assessment incorporates not only the HM contents in soil and agricultural product but also soil environmental quality standards, soil elemental background values, and safety standards for HMs in agricultural products. In this study, it was applied to evaluate the potential risk of HMs in soil-crop systems (i.e., soil-vegetable, soil-maize, soil-rice, and soil-wheat systems) along the Yangtze River in Nanjing, Jiangsu Province, Southeast China. Furthermore, 114Cd/110Cd isotope ratio analysis was used to identify the specific contamination sources. The mean concentrations of Cd, As, Hg, Pb, Cu, Zn, and Cr in the surface soils (0–20 cm) were 0.26, 11.07, 0.09, 32.63, 38.57, and 107.92 mg kg−1, respectively, exceeding the corresponding soil background values. Fertilizer and atmospheric deposition were the major anthropogenic sources of HM contamination in crop-growing soils. In addition to the crop type, soil pH and organic matter also influenced the transfer of HMs from soils to the edible parts of crops. Results of comprehensive assessment revealed that approximately 11.1% of paired soil-crop sites were multi-contaminated by HMs, among which paddy soils had the highest potential risk of HMs followed by maize soils, vegetable soils, and wheat soils. To evaluate the potential risk of HMs in arable land, this study provides a novel, scientific and reliable approach via integrating soil environmental quality and agricultural product security.

Identification and quantification of the distribution, ecological risk, and sources of heavy metals in soils are essential for regional pollution control and management. In this study, spatial analysis (SA), GeogDetector model (GDM), and positive matrix factorization (PMF) model were combined to evaluate the status, ecological risk, and sources of heavy metals in soils from a typical coastal economic development area in Southeastern China. The mean contents of Cd, Pb, Cr, Cu, and Zn in the surface soils (0–20 cm) were 0.45, 41.72, 90.50, 47.86, and 145.33 mg/kg, respectively. In accordance, the mean contents of Cd exceeded the risk screening value for contamination of agricultural soil in China. Our results revealed that industrial and residential soils had higher enrichment of heavy metals than agricultural and fallow soils. Industrial production was the major driving factors influencing the spatial distribution of heavy metals. Soil OM and pH were found to be the most important factors affecting the potential ecological risk of heavy metals, followed by distance from the industrial enterprises and roads. Heavy metals in the study area were mainly originated from industrial emissions/atmospheric deposition, agricultural sources, and followed by natural sources. Therefore, regular monitoring and source control for heavy metals, especially for Cd, along with the integrated soil environmental management in the study area are crucial to ensure soil health and ecosystem security.

Rapid filling of a horizontal pipe with an entrapped air pocket has attracted significant attention as overpressurization induced by air compression may cause safety concerns. This study de...

Due to the high cropping index and substantial agricultural inputs in greenhouse vegetable production systems (GVP), the environmental problems caused by heavy metals in GVP are becoming increasingly serious. A systematic investigation of heavy metals accumulation was carried out in GVP located in Jingyang, Shaanxi, China. The accumulation of Cd and Hg was assessed to be more significant than that of other elements in these GVP soils. The pollution load index (PLI) confirmed that 98.9% of the soil samples showed a moderate level of pollution. Additionally, the potential ecological risk index (RI) values indicated that 63.7 and 14.3% of the area was at moderate and high ecological risk, respectively. In assessing the human health risks associated with vegetable consumption, the highest target hazard quotient (THQ) was that for As, followed by Cu > Cd > Zn > Pb > Hg > Cr. Although the hazard index (HI) values were below 1 except for three sample sites in the study area, the 95% quantile of forecasted HI values was 1.22. More attention should be devoted to heavy metal pollution in GVP products. Positive matrix factorization (PMF) was used to identify the sources of the heavy metals. Cu and Zn accumulation were the results of fertilizer overuse; the parent material was the primary source of the As, Pb, and Cr; and the sources of Cd and Hg were inorganic fertilization and industrial emissions, respectively. Effective measures should be implemented to reduce future ecological and health risks in GVP.

High-density samples are usually a prerequisite for obtaining high-precision source apportionment results in large-scale areas. In-situ field portable X-ray fluorescence spectrometry (FPXRF) is a fast and cheap way to increase the sample size of soil heavy metals (HMs). Moreover, categorical land-use types may be closely associated with source contributions. However, the above information has rarely been incorporated into the source apportionment. In this study, robust geographically weighted regression (RGWR) was first used to correct the spatially varying effect of the related soil factors (e.g., soil water and soil organic matter) on in-situ FPXRF in an urban-rural fringe of Wuhan City, China, and the correction accuracy of RGWR was compared with those of the traditionally non-spatial multiple linear regression (MLR) and basic GWR. Then, the effect of land-use types on HM concentrations was partitioned using analysis of variance (ANOVA). Last, based on the robust spatial receptor model (i.e., robust absolute principal component scores/RGWR [RAPCS/RGWR]), this study proposed RAPCS/RGWR with categorical land-use types and RGWR-corrected in-situ FPXRF data (RAPCS/RGWR_LUFPXRF), and its performance was compared with those of RAPCS/RGWR with none or one kind of auxiliary data. Results showed that (i) the performances of the correction models for in-situ FPXRF data were in the order of RGWR GWR MLR, and the relative improvement of RGWR over MLR ranged from 52.6% to 70.71% for each HM; (ii) categorical land-use types significantly affected the concentrations of soil Zn, Cu, As, and Pb; (iii) the highest estimation accuracy for source contributions was obtained by RAPCS/RGWR_LUFPXRF, and the lowest estimation accuracy was obtained by basic RAPCS/RGWR. It is concluded that land-use types and RGWR-corrected in-situ FPXRF data are closely associated with the source contribution, and RAPCS/RGWR_LUFPXRF is a cost-effective source apportionment method for soil HMs in large-scale areas.