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Inorganic pollution is widespread in groundwater, and sulfate pollution is one of the important types, which has an important impact on the ecological environment and human health. Elevated concentrations of sulfate ion pollutants often come from the sewage discharge of chemical plants. This study takes a sulfate-contaminated site in Dongying City, Shandong Province, China, as the research object. Nine boreholes were arranged along the sewage discharge ditches in the site to collect and analyze soil samples and groundwater samples in layers. The concentration of pollutants and the change with depths were determined; the maximum concentration of sulfate ion was 10,330 mg L−1 in groundwater, and the maximum pollution depth was no more than 8 m. A hydraulic barrier was carried out to cut off the pollution sources. Based on a comprehensive understanding of the hydrogeological conditions and pollution degree of the site, the hydraulic capture technique was used to control the water pumping and injection volume, so that the scope of the pollution plume was gradually reduced. The pumping wells were arranged in the polluted area, and the water injection wells were arranged at the outer edge of the pollution zone. According to the calculation of the single well water inflow and influence radius, 28 pumping wells and 66 water injection wells were needed to be arranged on the site. The treatment process was divided into four stages according to the following steps: water pumping, water injection, stoppage of water injection, stoppage of water pumping, collecting water samples after the water level recovered, and the completion stage of treatment. The above process was repeated twice. Chemical precipitation was employed in the last step. The results of the remediation showed that the sulfate concentrations in 54 percent of the samples decreased significantly to less than 100 mg L−1, and the rest were between 100 and 200 mg L−1 after the treatment process. Two pumping wells with serious pollution were selected as long-term monitoring wells, and two-year continuous monitoring results showed that sulfate concentrations in the monitoring wells ranged from 110 to 220 mg L−1, indicating that integrated groundwater remediation techniques are more effective and more reliable than one single technique.

Earth’s critical zone is defined as a plant–soil–water system, which covers a wide area and has a large vertical thickness, but the soil elemental stoichiometry characteristics of the critical zone at different depths are still unclear. In this study, the spatial distribution of soil carbon (C), nitrogen (N) and phosphorus (P) in the critical zone of a typical wetland in Dongting Lake, China, and their ecological chemometric characteristics were analyzed. The results indicated that: (1) the average C, N and P contents were 18.05, 0.86 and 0.52 g/kg, respectively, with a decreasing trend from the surface to the deeper layers. The soil is relatively rich in C and P, while N is the main element limiting plant growth and development. (2) The mean values of soil C/N, N/P and C/P were 21.1, 1.7 and 35.4 respectively, with the C/N ratio and C/P ratio showing a trend of increasing and then decreasing in the vertical direction and reaching a maximum at a depth of 2–5 m below ground. (3) According to the correlation results, C, N and P in soils are coupled and influenced by each other (p < 0.001), and pH, infiltration coefficient and human activities are closely related to the spatial distribution of C, N and P. (4) Stable Redfield ratios (1:1.6:35.4) may exist in lake wetland soils, and future studies should be conducted for complete systems of the same type of wetlands. The results of the study will provide a theoretical basis for the sustainable development and scientific management of lake wetlands.

This paper presents a novel nested, compliant, constant-force mechanism (CFM) that generates millimeter-scale manipulation stroke. The nested structure is utilized to improve the overall compactness of the CFM. A combination strategy of positive and negative stiffness is induced to generate constant force with a millimeter-level range. In particular, bi-stable beams are used as the negative stiffness part, and V-shaped beams are selected as the positive stiffness part, and they are constructed into the nested structures. With this, a design concept of the CFM is first proposed. From this, an analytical model of the CFM was developed based on the pseudo-rigid body method (PRBM) and chain beam constraint model (CBCM), which was verified by conducting a simulation study with nonlinear finite-element analysis (FEA). Meanwhile, a parametric study was conducted to investigate the influence of the dominant design variable on the CFM performance. To demonstrate the performance of the CFM, a prototype was fabricated by wire cutting. The experimental results revealed that the proposed CFM owns a good constant-force property. This configuration of CFM provides new ideas for the design of millimeter-scale, constant-force, micro/nano, and hard-surface manipulation systems.

Owing to the limited stroke of piezo stacks, compliant amplification mechanisms are widely employed to magnify the displacement of piezoelectric actuators for emerging applications in precision engineering. In this study, a three-dimensional (3D) bridge-type amplification mechanism composed of two serially connected bridge-type amplifiers with a novel constraint form has been developed. The parallel guiding beams mounted at the input and output ends significantly increase the lateral stiffness and minimize parasitic displacements for higher accuracy. Furthermore, a new theoretical model is established to predict the magnification behavior of the 3D amplifier that takes into account the displacement loss caused by the coupling of the two bridge-type amplifiers. The accuracy of this model and the mechanical performance of the developed amplifier are verified by conducting finite element simulations and experimental studies on the manufactured prototypes.

By using the first-principles calculations, the structure, energies and electronic properties of four commonly exposed surfaces for the nesquehonite crystal were investigated. The needle-like nesquehonite whisker is well developed with smooth side faces and irregular hexagonal end faces. Surface energy results indicate that the (1 0 1) surface is the most stable surface and corresponds to the side face. The density of dangling bond has a positive relationship with surface energy and the (1 0 1) surface has the least dangling bonds. In terms of relaxed surface energy, the order of relaxed surfaces is (1 0 1)

In order to build the relationship between inherent crystallographic characteristics and crystal morphology of hydromagnesite, the energies, structures, and growth properties of hydromagnesite surf...

In this article, the ultrahigh-precision planar motion control problem is investigated for a novel long-stroke multileaf spring based microstage, by considering the cross-axial coupling-induced varying stiffness. In particular, a discrete-time dynamical model with the stress stiffening effect is presented in a parameter varying form, where a discrete-time adaptive extended state observer (ESO) with exponential forgetting factor is developed based on Kalman-like observer method, and a synergetic control theory (SCT) approach is further proposed combining the observer structure to achieve microscale multiaxis motion control. The conditions on the convergence of the adaptive ESO and the robust stability of the closed-loop system are also derived with a theoretical analysis. Finally, the proposed control architecture is implemented (in real time) on a designed microstage, demonstrating significant performance improvement over existing results such as proportional-integral-derivative (PID) control and conventional active disturbance rejection controllers control methods.

This paper presents an improved dynamical modeling method for the double parallelogram mechanism (DPM) based motion stage with a large workspace, where the impacts of intermediate stages are considered. According to the mode shape analysis of the DPM by the Euler-Bernoulli beam theory, it is observed that the high order modes induced by the intermediate stages have significant impacts on the dynamical behavior of the DPM. With this in consideration, the matrix displacement method is applied to the modeling of the DPM based compliant stage, where the intermediate stages of DPMs are regarded as nodes with masses. Correspondingly, an improved dynamical model is proposed to better describe the complicated dynamical characteristics of the compliant stage, which is further verified by finite element analysis (FEA) and experiments on a prototype. Compared with existing methods, the proposed dynamical model offers a new look into the kinetostatic analysis and dynamical design of the compliant mechanism-type micro/nanostage.

The interaction effect between feed size distribution (FSD) and underflow orifice diameter (Du) is crucial for the adjustment of the hydrocyclone in plant but not clearly understood. This paper presents a numerical study on effects of FSD on separation performances of hydrocyclones at a wide range of Du. The numerical results show that both small or large Du will cause numerous particles being misplaced to the overflow or underflow products, resulting in poor separation performance. These results can be well explained using the predicted water flow pattern and particle distribution. Moreover, there are intense interaction effects between the Du and the FSD. It is pointed out that for an extremely small Du, the cut size explodes, and the separation efficiency and separation sharpness deteriorate rapidly with the increase of feed median size (d0.5). These behaviors are mainly due to the increase in the coarse particle content as d0.5 increases, resulting in an increase in the extent of particle accumulation near the spigot. Such accumulation causes a decrease in the tangential velocity and a break in the air core, which in turn leads to a decrease in the flow field stability. Thereby, regular distribution of the particle equilibrium radius along the radial direction is destroyed. As Du increases, the separation performance of the hydrocyclone is no longer affected by fluctuations in the FSD. Based on results from this study, it is recommended a moderate increase in Du is competent to mitigate the adverse effects caused by fluctuations in the FSD, to achieve the expected cut size, and relatively high separation precise for particles.

Polysaccharides have been widely investigated in past decades as alternative binders in iron ore pelletization. This study aims to further clarify adsorption mechanisms and binding characteristics of three representative polysaccharides: carboxymethyl starch (CMS), carboxymethyl cellulose (CMC) and guar gum (Guar). FTIR analysis and zeta potential measurements indicate that CMS and CMC can adsorb onto magnetite concentrate via carboxymethyl and hydroxyl groups, while guar gum through the hydroxyl group. Chemical interaction and hydrogen bonding are dominant interactions between binders and magnetite. AFM images show that a continuous thick film is generated after the adsorption of CMS. CMC adsorbs onto magnetite surfaces in the shape of fibrous structure, forming a much thinner layer. The adsorption layer of Guar is the thinnest. Chemical interaction force is the main contribution for adhesive force. Equilibrium adsorption data of these binders can be described by the Freundlich isotherm. Chemical adsorption is the dominant mechanism and adsorption capacity can represent adhesive force. Pelletization results verify that wet strengths of pellets produced with Guar are the largest, followed by CMC and CMS. Viscous force rather than adhesive force is the determining contribution to wet strength. Binder cohesive force and adhesive force are significant contributions to dry strength. Solution viscosity and adsorption capacity are primary criteria to evaluate binders. The combination usage of these binders is recommended to reach the required wet and dry strengths at a lower cost.

Integration of the information from hydrochemical data, statistical analysis and modeling technique is crucial for extending our knowledge of hydrochemistry of karst aquifers. In this paper, conventional graphical methods, statistical analysis and PHREEQC inverse modeling were used to investigate the hydrogeochemical characteristics and evolution processes of karst groundwater in Jinci spring area. The results showed that the dominant hydrochemical types of karst groundwater determined by Piper diagram were Ca·Mg–SO4·HCO3, Ca·Mg–SO4, Ca–SO4, Ca–SO4·HCO3 and Ca–HCO3, and the main components of karst groundwater were dominated by rock–water interactions based on statistical analysis. Ca2+, Mg2+ and HCO3− originated mainly from the dissolution of calcite and dolomite; SO42− came mostly from gypsum dissolution and pyrite oxidation; and the source of Na+ and Cl− could either be major from halite dissolution or cation exchange. Moreover, PHREEQC inverse modeling indicated that calcite, gypsum and CO2 (g) were dissolved, and Ca–Mg exchange prevailed along the flow path (from recharge area to runoff area); the dissolution of gypsum, dolomite and CO2 (g), and halite precipitation, and Na–Mg and Ca–Mg exchange occurred along runoff area to discharge area; and there were the dissolution of carbonate, gypsum, halite and CO2 (g), Na–Mg and Ca–Mg exchange from deep buried area to discharge area.

Interactions between feed size distribution and separation performance for hydrocyclones with different vortex finder diameters (Do) are crucial for hydrocyclone designs but not clearly understood. In this work, the optimum range of Do is numerically confirmed for a 50 mm diameter hydrocyclone using computational fluid dynamics. Furthermore, effects of feed size distribution (FSD) on separation performance for hydrocyclones with different Do are discussed. For a given FSD, the lower limit of Do can be determined from the flow stability characterized by lower turbulence intensity and larger tangential velocity. Below the lower limit, a large proportion of fine particles report to the underflow. The upper limit can be determined from separation performance. Above the upper limit recovery to the underflow for coarse particles decreases drastically, which is caused by an outward shift of the locus of zero vertical velocity (LZVV) and an inward shift of particles equilibrium radius. For a given Do, FSD has no significant effects on partition curves when Do is in the optimum range. When Do is above the optimum range, both recovery to underflow for coarse particles and separation sharpness are decreased as the feed median size increases. In summary, when Do is in the optimum range, the hydrocyclone can adapt to different FSD to obtain the expected cut size by self-adjusting the LZVV and particles equilibrium radius. This method for determining the optimum range of Do is based on flow pattern characteristics and can be used as a universal tool for hydrocyclone design.

In this work, selective surface magnetization technology was employed to separate pentlandite from serpentine by adding fine magnetite coating on pentlandite surfaces, which was different from the conventional flotation. EDLVO (Extended Derjaguin-Landau-Verwey-Overbeek) theory calculations indicate that under a weak external magnetic field of 4.77 kA m − 1 . Interactions between magnetite and pentlandite were obviously stronger than that between magnetite and serpentine. Therefore, fine magnetite fractions selectively adhered to pentlandite surfaces and enhanced its surfaces' magnetism. The above predication was well confirmed by the magnetic coating and magnetic separation tests with adding 3% magnetite fines, at a magnetic field intensity of 200 kA m − 1 . SEM-EDS analyses show that magnetite particles were preferentially adsorbed onto pentlandite instead of serpentine. VSM (vibrating sample magnetometer) measurements further confirm that the magnetism of magnetic products (pentlandite) was strongly enhanced.

CuO-CeO2-ZrO2/cordierite catalysts have been successfully prepared by the impregnation reduction method. The effects of processing parameters such as the condition of reduction process, calcination temperature, the addition of surfactant on the size and shape of catalyst particles were studied by X-ray diffraction (XRD), BET surface area measurements, and scanning electron microscopy (SEM). The catalytic performance of the as-prepared catalysts for CO oxidation were evaluated by using a microreactor-GC system. The results indicate that the processing parameters influence greatly the size and shape of catalyst particles. Fragmental shape catalysts were formed when the impregnated samples were reduced in the thermostat water bath. However, spherical-like particles were obtained by ultrasonic-assisted in the reduction process. Tiny flower-like catalyst particles were found when the surfactant were used. When the calcination temperature decreased, the grain size of catalysts has reduced, and the catalytic activity for CO oxidation has been improved. The introduction of ultrasonic and surfactant resulted in larger specific surface area and better catalytic performance.

Porous cordierite ceramics were synthesised by gel-casting method, using talcum powder, kaolin and alumina as raw materials. Organic monomers and cross-linker were used as additives. The phase comp...

The carboxylmethyl starch modified with nano-CaCO 3 has been identified as an alternative binder in iron ore pelletization. This study aims to further clarify effects of nano-CaCO 3 on the adsorption of carboxymethyl starch (CMS) onto magnetite particles. Variables influencing the adsorption capacity of CMS, such as solution pH, initial concentration, the ratio of nano-CaCO 3 to CMS and adsorption time, were systematically investigated. Zeta potential and solution pH results verify that nano-CaCO 3 can serve as an active site, which reducing the repulsive force between the negatively charged CMS and magnetite surface. Consequently, the adsorption capacity of CMS is promoted by the addition of nano-CaCO 3 . Besides, both the adsorption capacity of CMS and strengths of green pellets with the addition of nano-CaCO 3 decrease by increasing the pH value of binder solution. In other words, there is a positive correction between the adsorption capacity and the strength of green pellet. The equilibrium adsorption data of CMS can be described by the Freundlich isotherm. The addition of nao-CaCO 3 does not change the adsorption type of CMS onto magnetite surface. For the adsorption of CMS with or without the addition of nano-CaCO 3 , the pseudo-second-order kinetics of chemical reaction provides the best correlation. Moreover, the adsorption rate of CMS with nano-CaCO 3 is much larger than that of CMS. SEM results indicate that the cross-linked structure built by CMS + nano-CaCO 3 is unique and different from that of CMS. The nano-CaCO 3 can serve as the active site and skeleton, and promote the cohesion force of neighboring CMS molecules. Consequently, this unique structure gives CMS + nano-CaCO 3 a high binding ability.

This study aimed to identify the carboxymethyl starch modified with nano-CaCO3 (CCMS) as an alternative binder in iron ore pelletization. Pelletization results showed that all wet, dry, preheated and fired pellets produced with CCMS met with the required values of strengths. The total Fe content of pellets also had a 1.04% increase by replacing 2% bentonite with 1% CCMS. FTIR and zeta potential tests verified that CMS interacted with the magnetite mainly through ligand exchange, hydrogen bond and electrostatic interaction. Meanwhile, in addition to above three interactions, CCMS reacted with negative sites of the magnetite by its unique positive charge sites (-Ca(OH)+). CCMS had more active sites and the chemical bonding of CCMS on the magnetite surface was stronger. Besides, nano-CaCO3 interacted strongly with CMS and the cross linked structure between nano-CaCO3 and CMS molecules was built, giving CCMS a higher solution viscosity. Therefore, compared with CMS, the increased strength of green pellets with CCMS was mainly caused by the stronger chemical bonding and higher solution viscosity of CCMS. Porosity and FESEM measurements were also carried out to clarify the developed strengths of preheated and fired pellets with CCMS. In comparison with CMS, the nano-CaCO3 in CCMS resulted in the formation of more melt slags and facilitated the bridging, bonding and recrystallization between hematite particles. Thereby, the developed oxide bonding between hematite grains and the formation of more slags jointly decreased the porosity and improved the compressive strength of heat treated pellets.

With the development of wireless power transfer (WPT) technology, it has become a good method to solve energy problem in wireless sensor networks (WSNs). In this paper, a mobile wireless charging vehicle (WCV) is employed in wireless rechargeable sensor networks (WRSNs) to periodically visit every anchor point and charge multiple nodes within its charging radius simultaneously. Traditional anchor point selection strategies for WRSNs almost focus on the location relationship, which take little consideration of energy consumption of sensor nodes. We propose an energy-aware anchor point selection (EAPS) strategy to minimize overall charging time, which consists of stopping time at anchor points and traveling time. We first group nodes into clusters based on the charging radius, and then apply genetic algorithm (GA) to determine the anchor point in every cluster. The simulation results show that EAPS strategy outperforms several state-of-the-art methods in terms of total traveling length and charging time.

A novel classified gravity system, comprised of a three-product cyclone and a fine high-frequency screen, was developed and tested for recovery of fine coal. The three-product cyclone is characterized by the primary cylinder and a secondary cyclone. The effects of major parameters of the secondary cyclone, such as vortex finder diameter, vortex finder length, and spigot diameter, were investigated by single-factor experiments. Regression models of the yield and ash content of clean coal were developed with statistical design of experiments and showed good correlations of experimental results. The regression models indicated that the spigot diameter had the largest impact on the yield and ash content of clean coal. It also indicated that spigot diameter and vortex finder diameter jointly affect performances of the three-product cyclone. The cylinder played a significant role in desliming of the feed, giving the secondary cyclone a better gravity-separation condition. Ash reductions of +0.150 mm fra...

This paper presents a novel beam flexure-based X-Y-θ micro-stage integrated with a laser interferometric type displacement measurement approach for reducing the measurement error induced by the rotational motion and cross-axis load effect. Aiming at achieving high-precision real-time control of the proposed system, an active disturbance rejection controller is developed such that the inevitable parasitic and coupling errors can be treated as disturbances and actively compensated by using the extended state observer. Finally, the verification experiments are deployed on the fabricated prototype, where the results indicate that the proposed approach achieves excellent performance in terms of motion accuracy and disturbance rejections.

The utilization of long-wave light (1000–2500 nm) in the solar spectrum is a difficulty in photocatalysis. Based on the Arrhenius equation, the activated carbon (AC)/graphitic carbon nitride (CN) composites were designed for photothermal-assisted photocatalytic water treatment. The short-wave solar energy can be converted to chemical energy on CN, and the long-wave solar energy to thermal energy by AC. The energetics and the interfacial charge transfer of activated carbon (AC)/graphitic carbon nitride (CN) composites (ACCN) were improved owing to the π bond between AC and CN. The excellent light absorption capacity (over 80%) led to higher photocatalytic reaction temperature due to the photothermal effect. The higher temperature accelerated the photocatalytic reaction and facilitates the charge transfer on ACCN. Hence, the optimal ACCN sample with good balance between photothermal and photocatalytic property could degrade 98% of sulfamerazine under simulated solar irradiation in 60 min. This work not only developed efficient and low-cost (~$1/kg) carbon-based photocatalysts with ultrahigh solar utilization, but also discussed the mechanism of photothermal effect on photocatalytic reaction.

Composite vascular patches have gained increasingly attention due to the limited availability of autologous patches (vascular graft materials made from the blood vessels of the same recipient), the lack of growth capability of nonautologous patches (vascular graft materials made from the blood vessels of a different donor) and the disadvantages of synthetic patches. In this study, we report a highly biocompatible phosphatidylcholine-polyurethane nanoparticle/polyurethane/decellularized scaffold composite vascular patch (PCVP). It was fabricated by a facile method - cosedimentation. Its in vitro blood and cell compatibility including hemolysis, plasma recalcification time, coagulation time, platelet adhesion and cytotoxicity was evaluated. The surface modified with phosphatidylcholine-polyurethane (PC-PU) nanoparticles exhibited the improved anticoagulation activity. The in vivo performance of the PCVP was investigated in a mouse model. The nanopatterned surface that resembled the concave-convex structure of the luminal surface of native blood vessels enhanced cell attachment, proliferation, migration and differentiation. The decellularized scaffold had the mechanical property similar to that of the targeted blood vessels, which could withstand in vivo dynamic blood pressure. The overall performance of the PCVP was synergistically optimized by each layer of the multilayer design. The patched artery remained patent and the formation of endothelial tissue - endothelialization was achieved 30days after the in vivo implantation in a mouse model.

Bi2O3 samples doped with several transition metal ions (M–Bi2O3, where M = VV, PbII, AgI and CoII) were synthesized using a precipitation method in the presence of sodium dodecyl benzene sulphonate (SDBS). The compounds were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–visible diffuse reflection spectroscopy (UV–vis DRS) and photoluminescence (PL). The monoclinic microcrystal samples displayed different morphology and visible-light harvesting character. The photocatalytic activity of the M–Bi2O3 compounds, evaluated by the extent of decolorization of Rhodamine B under visible light, followed the order: V(V)–Bi2O3 > Pb(II)–Bi2O3 > Ag(I)–Bi2O3 > Co(II)–Bi2O3 > undoped Bi2O3.