Search

The development of the preparation strategy for high-quality and large-size graphene via eco-friendly routes is still a challenging issue. Herein, we have successfully developed a novel route to chemically exfoliate natural graphite into high-quality and large-size graphene in a binary-peroxidant system. This system is composed of urea peroxide (CO(NH2)2⋅H2O2) and hydrogen peroxide (H2O2), where CO(NH2)2⋅H2O2 is used in preparing graphene for the first time. Benefiting from the complete decomposition of CO(NH2)2⋅H2O2 and H2O2 into gaseous species under microwave (MW) irradiation, no water-washing and effluent-treatment are needed in this chemical exfoliation procedure, thus the preparation of graphene in an eco-friendly way is realized. The resultant graphene behaves a large-size, high-quality and few-layer feature with a yield of ~100%. Then 4 μm-thick ultrathin graphene paper fabricated from the as-exfoliated graphene is used as an electromagnetic interference (EMI) shielding material. And its absolute effectiveness of EMI shielding (SSE/t) is up to 34,176.9 dB cm2 g −1, which is, to the best of our knowledge, among the highest values so far reported for typical EMI shielding materials. The EMI shielding performance demonstrates a great application potential of graphene paper in meeting the ever-increasingly EMI shielding demands in miniaturized electronic devices.

To accurately explore the horizontal vibration response and aerodynamic load variation law of high-speed elevator with gas-solid interaction coupling in real environment, a mathematical and a three...

In order to effectively suppress horizontal vibration of the ultra-high-speed elevator car system. Firstly, considering the nonlinearity of guide shoe, parameter uncertainties, and uncertain external disturbances of the elevator car system, a more practical active control model for horizontal vibration of the 4-DOF ultra-high-speed elevator car system is constructed and the rationality of the established model is verified by real elevator experiment. Secondly, a predictive sliding mode controller based on adaptive fuzzy (PSMC-AF) is proposed to reduce the horizontal vibration of the car system, the predictive sliding mode control law is achieved by optimizing the predictive sliding mode performance index. Simultaneously, in order to decrease the influence of uncertainty of the car system, a fuzzy logic system (FLS) is designed to approximate the compound uncertain disturbance term (CUDT) on-line. Furthermore, the continuous smooth hyperbolic tangent function (HTF) is introduced into the sliding mode switching term to compensate the fuzzy approximation error. The adaptive laws are designed to estimate the error gain and slope parameter, so as to increase the robustness of the system. Finally, numerical simulations are conducted on some representative guide rail excitations and the results are compared to the existing solution and passive system. The analysis has confirmed the effectiveness and robustness of the proposed control method.

To effectively suppress the horizontal vibration of a high-speed elevator car caused by uncertainties such as the irregularity of guide rails and the piston wind in the hoistway, this paper proposes a new variable universe fuzzy control method for semi-active guide shoes with magnetorheological (MR) dampers based on the firefly algorithm and backpropagation (FA-BP) algorithm fuzzy neural network (FNN). First, the dynamic model of a car system is constructed, and the FNN system based non-parametric model of the MR damper is established with the original MR damper data collected from experiments. Then, a variable universe fuzzy main controller is presented to control the input current of the MR damper. As for its variable universe contraction-expansion factors, another FNN auxiliary controller is designed to accurately adjust the universe. Furthermore, the FA-BP algorithm is utilized to train the FNN auxiliary controller. Finally, the elevator experiment is carried out to analyze the characteristics of horizontal vibration, and simulation tests are conducted using the measured excitation signal and two kinds of simulated excitation signals, respectively. The results show that the proposed controller has a lower horizontal vibration acceleration, tilt angle acceleration and other index values than the passive controller or the FNN controller, indicating that the proposed control method can effectively suppress the horizontal vibration of a high-speed elevator. This study can provide the technical foundation for intelligent vibration control of high-speed elevators.

Interfacial solar seawater desalination, originating from the driving force of the conversion of sunlight into heat energy, is facing the negative influence of intermittent solar radiation alternat...

The manufacturing of rubber bearing is complicated, the horizontal stiffness of the final product maybe greatly affected by the uncertainties during the processing, thus, it is necessary to study ...

Quasi-static tests were performed for the large-scale precast sandwich wall structures with friction devices. The frictional plates, steel plates, and bolts were used for friction devices to dissipate energy. The structural resilience could be easily realized by the proposed additional dissipated energy system. The results show that the structure with friction devices remained elastic after tests and the friction devices can effectively dissipate energy and protected the concrete structure. The residual displacements of structures with frictional connectors were generally large and additional prestressing force was needed to provide self-centering capability. The finite element analysis was conducted to simulate the experimental structure using the MSC.marc software. Numerical results were in good agreement with the experimental results. Parametric analysis showed that the dissipated energy and lateral load resistance could be improved by increasing the frictional force of vertical or horizontal connectors; however, the residual displacement would also be increased; the self-centering capability could be improved by increasing the posttensioning force. Simplified analysis procedure was also proposed and elaborated. The comparisons between the experimental and analytical results were satisfactory at the whole process of roof drift ratio, especially at 1/150 and 1/50, which were generally used to design the structures.

MgxZn1−xO (x = 0.05, 0.10, 0.15, and 0.20) films prepared on quartz substrates by the sol–gel method were characterized and studied. According to scanning electron microscopy and x-ray diffraction data, the MgxZn1−xO films exhibited a particle-stacking morphology and a hexagonal wurtzite crystal structure. An increase in Mg content led to an obvious increase in particle size. However, a weakening of the hexagonal wurtzite structure was observed and indicated the transition of the MgxZn1−xO crystal structure, which was also confirmed by the Raman spectra results. An increase in bandgap energy from 3.38 eV to 3.55 eV with increased Mg content was determined from the transmittance spectra. Ultraviolet photodetectors based on MgxZn1−xO with interdigital electrodes were then fabricated. Dark current as low as 10 pA (corresponding to 5 nA/cm2) under bias of 10 V was achieved. A blueshift of the peak wavelength and cutoff wavelength was observed with increasing Mg content. Noise equivalent power as low as 2 × 10−15 W was achieved, detectivity was found to be about 1.2 × 1011 cm Hz1/2/W, and quantum efficiency was nearly 100%, which was related to the photoconductive gain.

The specific separation properties of nanofiltration (NF) membranes lead to their application in water treatment, resource recovery, food processing, and chemical and pharmaceutical separations. Nevertheless, the pervasive trade-off effect between the water permeability and salt rejection is one of the main obstacles in further enhancing their performance and fields of application. Numerous studies focusing on this topic report great efforts in attempting to solve this issue over the past decade. In this review, the approach that is followed is that the functional layer of the NF membrane is divided into four different mass transfer regions according to its mass transfer characteristics. The relationship between water permeability and salt rejection has been expounded according to the mass transfer properties of the four regions. On this basis, five technical approaches together with typical examples regarding the coordination of the trade-off between water permeability and salt rejection are proposed. Finally, five aspects that may be instructive to future research are highlighted. Lessons gained from this review are expected to promote the rational design and optimized fabrication of high-performance NF membranes.

Interaction and wear between wheel and rail become increasingly serious with the increase in elevator speed and load. Uneven roller surface, eccentricity of rollers, and the looseness of rail brackets result in serious vibration problems of high-speed and super-high-speed elevators. Therefore, the forced vibration differential equation representing elevator guide rails is established based on Bernoulli–Euler theory, and the vibration equation of the elevator guide shoes and the car is constructed using the Darren Bell principle. Then, the coupled vibration model of guide rail, guide shoes, and car can be obtained using the relationship of force and relative displacement among these components. The roller–rail parameters are introduced into the established coupled vibration model using the model equivalent method. Then, the influence of roller–rail parameters on the horizontal vibration of super-high-speed elevator cars is investigated. Roller eccentricity and the vibration acceleration of the car present a linear correlation, with the amplitude of the car vibration acceleration increasing with the eccentricity of the roller. A nonlinear relationship exists between the surface roughness of the roller and the vibration acceleration of the car. Increased continuous loosening of the guide rail results in severe vibration of the car at the loose position of the support.

Building supercapacitors that can provide high energy density over a wide range of temperatures, where traditional energy storage devices fail to operate, requires tailoring of electrolyte and/or electrode material. Here, we show that record gravimetric capacitances of 164 and 182 F g−1 can be attained at −100 and 60 °C, respectively, nearly equivalent to the room-temperature value of 177 F g−1, when activated carbon-based electrodes with predominantly slit-shaped micropores and a low freezing-point electrolyte are used. Experimental data and density functional theory calculations suggest that electrode material characteristics, such as pore size and shape, matched with the effective size of partially solvated ions of the electrolyte, are the key factors in achieving such performance. This study provides evidence for the effective design of robust supercapacitors with sustained performance at both low and high temperatures.

The seismic performance and damage pattern of the split-foundation frame buildings in across-slope direction are studied. In view of the characteristics of split-foundation structure, the parameter analyses of split-foundation structure with different spans and floors of lower and upper parts are studied, and the main factors affecting the torsional effect of split-foundation structure are also studied theoretically. Finally, the improvements and design procedure of split-foundation structure are put forward to reduce the difference in ductility demands between the upper ground columns and the lower part. Results show that the torsional effect of split-foundation structure is very significant because of the rigidity eccentric. The upper ground columns are the weakest parts of split-foundation structure which are destroyed first under the earthquake action; then, the lower floors are destroyed in succession. Lower ductility demands of the upper ground columns and better seismic performance of the split-foundation structure can be achieved by the designed improvements.

Understanding of cell temperature of Building Integrated Photovoltaics (BIPV) is essential in the calculation of their conversion efficiency, durability and installation costs. Current PV cell temperature models mainly fail to provide accurate predictions in complex arrangement of BIPVs under various climatic conditions. To address this limitation, this paper proposes a new regression model for prediction of the BIPV cell temperature in various climates and design conditions, including the effects of relative PV position to the roof edge, solar radiation intensity, wind speed, and wind direction. To represent the large number of possible climatic and design scenarios, the advanced technique of Latin Hypercube Sampling was firstly utilized to reduce the number of investigated scenarios from 13,338 to 374. Then, a high-resolution validated full-scale 3-dimensional Computational Fluid Dynamics (CFD) microclimate model was developed for modelling of BIPV’s cell temperature, and then was applied to model all the reduced scenarios. A nonlinear multivariable regression model was afterward fit to this population of 374 sets of CFD simulations. Eventually, the developed regression model was evaluated with new sets of unused climatic and design data when a high agreement with a mean discrepancy of 3% between the predicted and simulated BIPV cell temperatures was observed.

An elaborate structural and chemical depth profile of the thin film composite (TFC)-forward osmosis (FO) membrane is indispensable to the complete understanding of how the substrate structures influence the in-situ polyamide (PA) layer formation and ultimately the wastewater concentration performance of the resultant TFC-FO membrane. Herein, the X-ray photoelectron spectroscopy paired with Ar2500+ gas cluster ion beams sputtering is introduced for the first time to conduct the depth profiling analysis of the PA-based TFC-FO membrane. The fine chemical and structural properties of the TFC-FO membranes were successfully reconstructed from the depth profiles, which revealed that the sponge-like substrate with small surface pores favored the formation of a smooth and thin PA layer with a highly cross-linked inner layer, while the macroporous substrate with large surface pores facilitated the development of a rough and defective PA layer with deep formation inside substrate pores. Benefiting from the thin effective thickness and dense inner selective layer, the PA layer formed on sponge-like substrate exhibited superior water permeability and salt selectivity. Besides, even suffered from more serious internal concentration polarization within substrate, the smooth PA layer surface with fewer carboxylic groups endowed the sponge-like substrate supported TFC-FO membrane with much higher anti-fouling capacity and average water flux than its counterpart. However, the TFC-FO membrane with highly cross-linked PA layer still exhibited poor NH4+-N rejections (56.93 ± 0.95%). This work opens up a frontier for depth profiling of the ultrathin PA layer and provides theoretical guidance for the preparation of high-performance and anti-fouling TFC-FO membrane.

Tailoring a compatible membrane with simultaneous resistance to ammonia and fouling is fundamental to the application of forward osmosis (FO)-based technologies in resources recovery from domestic wastewater but challenging. Herein, polyamidoamine dendrimer, with an open interior cavity and abundant terminal primary amines, was grafted on a nascent thin film composite (TFC)-FO membrane surface to provide an energetic barrier for ammonia passage and foulants absorption. Benefiting from the repulsive force imposed by the protonated primary amines, the resultant membrane exhibited superior selectivity towards ammonia (98.81% rejection rate). The hydrophilic dendritic primary amines also generated a protective hydration layer over membrane surface for foulants isolation, thus endowing the grafted membrane with robust fouling resistance and fouling reversibility and further maintaining outstanding average water flux of 29.81 Lh−1m−2 in concentrating domestic wastewater with 80% water reduction. Meanwhile, the grafted membrane possessed a significantly higher ammonia nitrogen rejection of 86.08% than the pristine membrane (40.51%) due to the simultaneously enhanced membrane selectivity to ammonia and anti-fouling capacity. Besides, the robust resistance to organic foulants significantly delayed the initiation of microorganism growth and thus effectively suppressed the formation of biofouling on membrane surface during the long-term domestic wastewater concentration. The developed ammonia-selective and anti-fouling TFC-FO membrane has great potential in facilitating the application of FO-based technologies in resources recovery from domestic wastewater.

The localization and navigation technology are the key factors in the research of mobile robots. With the demand of smart manufacturing industry and the development of robotics technology, the importance of mobile robot has become increasingly prominent. Mobile robot positioning research is mostly based on odometry, however, it has cumulative errors that would affect the accuracy of positioning results. This paper describes an improved measurement model that suitable from 0° to 180° and used this model in the Extended Kalman Filter (EKF) and Unscented Kalman Filter(UKF) time update step respectively, the method can address the interference of kinematics model predicted position and heading angle, both of them are easily disturbed by noises and other factors. Designing a tracked mobile robot as experimental platform to collect the raw data, conducting experimental research including the performance of hardware platform and autonomous obstacle avoidance, the real-time and stability of remote data interaction, and the accuracy of optimal pose estimation. The simulation results have been verified the accuracy of the improved measurement model applied to UKF.

For further enhancing the supercapacitive performances of carbon materials, heteroatoms-doping has proved to be one of the most promising approaches. Up to now, most of the researches focus on the effects of the dopant type and the doping amount. However, it is presently not understood how affects the capacitive performances if the chemical states of the heteroatom doped in carbon materials are further tailored. In this paper, we report for the first time the effect of post-tailoring the chemical states of doped‑sulfur on the supercapacitive performances of a sulfur-doped graphene. In our post-tailoring strategy, the S-doping is firstly realized by thermally treating the H2SO4-GIC compound, and then the chemical states of doped-S are post-tailored by the subsequent Hummers' oxidation. Our work has demonstrated that a unique oxidized-S species ( C S(O)x C ), which is transformed from the thiophene-S species by the Hummers' oxidation, has superior contribution to the supercapacitive performances (e.g., specific capacitance, rate performance and long-term cycling stability). Interestingly, the S-doped graphene sample, which contains the highest content of the unique oxidized-S species, exhibits an outstanding long-term cycling stability, its capacitance retention being up to 100.8% after 10,000 consecutive cycling test, far higher than those previously report for the heteroatom-doped carbon materials. The present work suggests that post-tailoring the chemical states of the doped-heteroatoms can be considered as an effective strategy to obtain the optimal electrochemical performances for the heteroatoms-doped carbon materials.

Interfacial polymerization (IP) has become a dominant technique for preparing thin film composite (TFC) membranes. Deep insight into the IP process is crucial for the design of TFC membranes with optimal performance. According to the conventional mechanism, a PA layer would be formed upon a support membrane during the IP reaction. In order to replenish this mechanism, a phenomenon denoted as “support membrane pore blockage (SMPB)” is explored in this study. Different experiments were designed to show how SMPB affected the membrane performance by regulating the monomer concentration, the pore size of the support membrane, the lag time after aqueous phase coating, and using different IP techniques. Various conceptual models were proposed to expound SMPB. The results indicated that the penetration of polyamide polymer into the support membrane may lead to a dual effect: (i) excessive penetration can cause support membrane pore blockage, and therefore increase the flow resistance and decrease the water permeability; (ii) it can produce a “mechanical interlocking effect”, which can enhance the adhesion between the PA layer and the support membrane, thus improving the TFC membrane stability. The SMPB mechanism can be adopted to elucidate phenomena related to membrane synthesis and to understand the structure-property-performance relationship.

In this study, the kinetic and isothermal behaviors of anion polyacrylamide (APAM) on a polytetrafluoroethylene (PTFE) microfiltration membrane were investigated to better understand the adsorption mechanism. A series of adsorption experiments were conducted to determine the effects of the initial APAM concentration, contact time, solution pH and temperature on the adsorption performance. The results showed that the three isotherm models (Langmuir equation, Freundlich equation and Temkin equation) favorably fit the adsorption process with R2 values of 0.98957, 0.90721 and 0.96321, respectively. The adsorption rate of APAM onto the PTFE membrane increased with increasing temperature, and the adsorption reaction reached equilibrium at 20 h. The values of thermodynamic adsorption parameters ( Δ r G m θ , Δ r H m θ , and Δ r S m θ ) suggested that the adsorption process was not spontaneous but endothermic. In addition, high temperatures favored adsorption, and the adsorption can be categorized as physisorption. Specifically, the main physisorption force was hydrogen bonding. The adsorption process consisted of two phases: rapid adsorption and stable adsorption. The three kinetic equations provided a good fit according to the R2 values and were applicable in the following order: pseudo-first-order > pseudo-second-order > Elovich.

Developing a forward osmosis (FO) membrane with superior ammonia selectivity and robust antifouling performance is important for treating domestic wastewater (DW) but challenging due to the similar polarities and hydraulic radii of NH4+ and water molecules. Herein, we investigated the feasibility of using polyamidoamine (PAMAM) dendrimer to simultaneously enhance the ammonia rejection rate and antifouling capacity of the thin-film composite (TFC) FO membrane. PAMAM dendrimer with abundant, easily-protonated, terminal amine groups was grafted on TFC-FO membrane surface via covalent bonds, which inspired the TFC-FO membrane surface with appreciable Zeta potential (isoelectric point: pH = 5.5) and outstanding hydrophilicity (water contact angle: 39.83 ± 0.57°). Benefiting from the electrostatic repulsion between the protonated amine layer and NH4+-N as well as the concentration-induced diffusion resistance, the introduction of PAMAM dendrimer endowed the grafted membrane with a superior NH4+-N rejection rate of 98.23% and a significantly reduced the reverse solute flux when using NH4Cl solutions as feed solution. Meanwhile, the perfect balance between the electrostatic repulsion to positively-charged micromoleculer ions (metal ions and NH4+-N) and the electrostatic attraction to negatively-charged macromolecular organic foulants together with the hydrophilic nature of amine groups facilitated the enhancement of the grafted membranes in antifouling capacity and hence the NH4+-N selectivity (rejection rate of 91.81%) during the concentration of raw DW. The overall approach of this work opens up a frontier for preparation of ammonia-selective and antifouling TFC-FO membrane.

Elastomeric bearings are widely used in various structures as a type of seismic isolation device, and accurately assessing the state of their stress is an essential step in the design of elastomeri...

Developing a feasible and cost-effective membrane which can remediate highly emulsified oily water, especially those stabilized by surfactants, is of great significance but challenging. In this work, a biomimetic superwetting silica nanofibrous membrane (SNFM) with hierarchical structures, interconnected pores as well as high porosity was developed by the facile combination of electrospinning and a dual-bioinspired method. Bioinspired adhesive (polydopamine/polyethylenimine, PDA/PEI) with positively charged active sites was first linked onto silica nanofiber (SNF) surface via Michael addition reaction and then the membrane roughness was constructed by assembling the negatively charged silica nanoparticles (SNPs) via electrostatic attraction. The resultant membrane exhibits a superwetting performance with a water contact angle of 0° in air and an oil contact angle of 165 ± 3° underwater. Moreover, the hierarchically structured SNFM displays strong acid/alkali resistance, outstanding thermal stability, robust flexibility and high mechanical strength. As a poof-of-concept, the hierarchical SNFM integrated into a wastewater separation tank achieves a high water flux over 7152 and 1120 L m−2 h−1 when treating oil-in-water microemulsion (1000 mg L−1) with and without surfactant, respectively. The dual-bioinspired method can be used as a universal tool to construct material surface roughness for application in other selective separation fields.

Herein we propose a facile and effective method to improve the supercapacitive performance of nano titanium carbide derived carbon (TiC-CDC), which is realized by simply soaking the TiC-CDC sample in the mixed acid solution made by a combination of HF and HNO3 for a designated duration at room temperature. After the acid-soaking, there occurs no significant change in the CDC microstructure, and the specific surface area shows only a little rise (from 958 to 1011 m2 g− 1). However, the specific capacitance of the acid-soaked TiC-CDC increases dramatically from 83 to 304 F g− 1 at the scan rate of 1 A g− 1 in 6 M KOH aqueous electrolyte, showing a more than 3 times improvement in comparison to that of the pristine CDC sample, which is, to the best of our knowledge, among the highest values so far reported for the CDC carbon materials. In addition, the acid-soaked TiC-CDC also exhibits a good rate capability (188 F g− 1 @ 500 mV s− 1) and an excellent cycling stability (no evident performance degradation after 8000 consecutive cycles). The present work may suggest that the mixed acid-soaking treatment at room temperature will be promising for the enhancement of the electrochemical performance for porous carbons.

In this paper, a nanometer-sized spherical carbon black (CB) with an average diameter of 30 nm was utilized to construct the compact carbon structure aiming at the electrode for high volumetric capacitance supercapacitors. The CB surface was modified by oxygen-doping to enhance the reaction with the electrolyte ions. BET result shows that oxygen-doping leads to the significant drop in both the SSA and the total pore volume of CB. Electrochemical measurement demonstrates that the oxygen-doped CB behaves an outstanding capacitive performance, its volumetric capacitance and gravimetric capacitance being up to 253 F cm−3 and 233 F g−1, almost 21.2 times improvement in comparison to those of the pristine CB (12 F cm−3 and 11 F g−1), respectively. Moreover, the oxygen-doped CB also exhibits an excellent cyclic stability, its capacitance remains 91.6% even after 10,000 cycles. Because of its advantages in mass production and low cost, the nano-sized carbon black can be considered as a competitive candidate for the mass production of the electrode materials for high volumetric performance supercapacitors.

Metal–organic frameworks (MOFs) are increasingly utilized for the design of molecular sieve membranes with unprecedented separation performance, mainly attributed to their nanopore structure and superior polymer affinity. Herein, UiO-66-NH2 crystals were synthesized as functional nanofillers to prepare polyamide (PA) composite membranes. The aqueous solution containing piperazine and evenly dispersed UiO-66-NH2 was transferred onto a membrane surface via vacuum filtration, followed by interfacial polymerization (IP) with trimesoyl chloride (TMC). Covalent bonding between the terminal amine groups of Zr-MOFs and TMC enables the stable immobilization of MOF crystals in the formed PA layer. The positioned MOF nanoaggregates that serve as robust nodes connected by the formed continuous striped film after IP reaction facilitate a rough, fishnet-like surface, which has a larger surface area in comparison to the nodular structure. This unique structure is beneficial for the creation of increased water transport channels, while not compromising the salt rejection. The best performing TFN membranes with a loading mass of 20.5 μg cm−2 exhibited a favorable Na2SO4 rejection of 97.5%, and excellent water permeability (30.8 L m−2 h−1 bar−1). This facile, controlled loading of hydrophilic MOFs via vacuum filtration allows fabrication of crumpled PA membranes with outstanding separation performance.

This study presents a non-linear constitutive equation for the rolling guide-shoes associated with a high-speed elevator system. This was done to accurately evaluate the dynamic behavior of a high-speed elevator car and analyze the action mechanism of random factors during manufacturing and installation on the dispersion of vibration acceleration. Through the combination of the Hertz contact theory and the Bouc-Wen hysteretic model, the non-linear vibration model of the elevator car system was founded. This model was equivalent to a linear system by least squares technique, and then the random parameters and the random excitation were converted by random perturbation method and pseudo excitation method. The acceleration response sensitivities of each random parameters, the means and standard deviations of transverse vibration acceleration responses at the observation point were obtained. In the case, the transverse vibration acceleration responses of the car system were calculated. The elevator car’s vibration instance was analyzed under the different degrees of variation of the random parameters and the random excitation. The results showed that the randomness of geometric parameters has the greatest influence on transverse acceleration. The variability of parameters affects the dispersion degree of the transverse vibration responses while the variability of the excitation mainly affects the amplitude of the vibration response. This study provides an effective method for the analysis of non-linear compound random vibration responses of high-speed elevator car system, and provides a reference for the vibration control design and safety assessment.

The development of cost-effective preparation routes for high-quality graphene is important for its large scale application. Here, we propose an one-step scalable preparation method of few-layer graphene (FLG) by the exfoliation of flake graphite in a novel binary-component system comprised of peroxyacetic acid and sulfuric acid. This provides a ∼100% yield of FLGs from the starting graphite in 4 h at room temperature. The as-prepared FLG sheets behave a few-layer feature (average layer number

Due to the influencing factors, such as irregularity of guide, piston wind excitation in the hoistway, and uncertain swinging of hoisting rope during the operation of high-speed traction elevator, car will produce dramatic horizontal vibration. With the purpose of suppressing this vibration effectively, the active car shock absorber is designed with linear motor, and a five-degrees-of-freedom space vibration model of the car is established and, subsequently, its state space equation is derived. For the uncertainty external excitation in the car system, the back propagation neural network proportional–integral–derivative controller with linear prediction model is designed for the intelligent active control of the vibration of the car, and simulation analysis is carried out with MATLAB/Simulink. The result shows that the active shock absorber designed in this study can effectively suppress the horizontal vibration of high-speed elevator car, better than traditional proportional–integral–derivative controller. This study has opened up a new idea of high-speed elevator vibration damping method, and is of important referential significance for the field of active control of car vibration.

Building energy simulation (BES) tools show limitations in calculations of the convective heat transfer exchange with the surrounding urban areas. Therefore, dynamic coupling of BES to computational fluid dynamics (CFD) techniques is a common strategy to improve the simulation performance. Nonetheless, dynamic coupling itself is understood to be computationally intensive and unaffordable even in simplistic neighbourhood-scale scenarios. This paper proposes a novel framework for integration of a high-resolution CFD model (CFDf) into a coupled model of low-resolution CFD (CFDc) and BES. In specific, the CFDf model (fine grids) operates as the off-line component in the whole procedure that provides the boundary conditions, including the flow patterns, to CFDc (coarse grids) at the openings in the form of the mass flow information to BES to start the iterative process. After that, CFDc and BES domains execute a fully dynamic external coupling to deliver an accurate energy simulation. A case study is designed for a simple neighbourhood on a typical hot day for sheltered buildings with night-purge cooling. The results highlight in a significant improvement in results with representing neighbourhood effect and in a substantial reduction of computation cost of the dynamic coupling procedure.

In this paper, for studying the influence of the randomness of structural parameters of high-speed elevator lifting system (HELS) caused by manufacturing error and installation error, a continuous time-varying model of HELS was constructed, considering the compensation rope mass and the tension of the tensioning system. The Galerkin weighted residual method is employed to transform the partial differential equation with infinite degrees of freedom (DOF) into the ordinary differential equation. The five-order polynomial is used to fit the actual operation state curve of elevator, and input as operation parameters. The precise integration method of time-varying model of HELS is proposed. The determination part and the random part response expression of the longitudinal dynamic response of HELS are derived by the random perturbation method. Using the precise integration method, the sensitivity of random parameters is determined by solving the random part response expression of time-varying model of HELS, and the digital characteristics of the acceleration response are analyzed. It is found that the line density of the hoisting wire rope has the maximum sensitivity on longitudinal vibration velocity response, displacement response and acceleration response, and the sensitivity of the elastic modulus of the wire rope is smallest.

Hypothesis Membrane filtration is a promising technology for the treatment of alkali/surfactant/polymer (ASP) flooding oilfield wastewater, which contains high concentration of salt, surfactant, polymer and crude oil. The interactions of key foulants may influence the degree of membrane fouling. By comparing flux decline and interfacial free energies, it should be possible to derive the foulants governing the interactions with the membrane. Experiments Polytetrafluoroethylene microfiltration membrane was employed to treat eleven types of model solutions to understand the effect of the interactions of key foulants on membrane fouling. The extended Derjaguin–Landau–Verwey–Overbeek theory was used to quantify the foulant-membrane and foulant-foulant interaction energies. The cake models were implemented to analyze the fouling form. Fourier transform infrared spectroscopy, atomic force microscopy, and contact angle were used to study the surface properties of various membranes. Findings Microfiltration experiments and thermodynamic analysis revealed that both ions and sodium dodecylbenzenesulfonate could mitigate membrane fouling caused by anionic polyacrylamide (APAM) and crude oil. Moreover, APAM would produce a “shielding effect” on crude oil fouling. In addition, complete pore blocking, which primarily occurred on the membrane surface and formed a fouling layer, was the dominant form of membrane fouling.

Herein, we proposed a novel approach to prepare the graphene with high quality, which was realized by exfoliating the KOH-etched graphite in H2O2 solution under microwave irradiation. The as-prepared graphene exhibits a smooth and transparent feature, and possesses high electrical conductivity of up to 2 × 105 S m−1. Compared with the conventional oxidation-reduction method, the present method is significantly efficient, and, most importantly, does not involve the use of acid and strong oxidizing agent, which will make it more competent in the scalable production of graphene.

In this study, 4-dimethylaminopyridine (DMAP) was firstly used as a catalyst in the interfacial polymerization of pentaerythritol (PE) and trimesoyl chloride (TMC) to enhance membrane performance. A series of nanofiltration membranes were prepared using five different DMAP concentrations of 0%, 10%, 20%, 30% and 40% (mass percentage accounting for PE). The filtration test results demonstrated that the water permeability of the typical PE-4 (40% DMAP addition) was 3.47-fold higher than that of the PE-0 (no DMAP addition) with no significant salt rejection loss, indicating that DMAP could effectively improve the water permeability. Characterization by SEM, AFM, and ATR-FTIR indicated that DMAP facilitated the reaction of PE and TMC, which resulted in polyester forming on the surface of the substrate membrane, rather than blocking the membrane pore. Moreover, the PE-DMAP-TMC TFC membrane displayed excellent dye separation performance and high antifouling ability.

Guide rails are important part of the elevator guide system, which is significant to its dynamic characteristics that influence the vibration of the elevator system. In this study, the researchers set up a guide rail, guide shoe and car coupling system model which is based on the interaction relationship between guide rail, guide shoe and car. The influence of the three parameters such as the length, weight per unit length and the bending stiffness on the dynamic characteristics of the guide rail is analyzed by applying above model, using the step-by-step integration integral method under the discrete variables. The results showed that weight per unit length affects the quiver of the guide rail. The bending stiffness of the guide rail mainly affects the vibration displacement, the length, which has a significant influence on the vibration displacement and the quiver of the guide rail. The results reveal the inherent law between the structural parameters and the dynamic characteristics, which will provide theoretical guidance for the manufacture and selection of the guide rail and the design of the elevator.

Bromate is a highly carcinogenic disinfection by-product in drinking water. Catalytic reduction is an emerging technology that can effectively remove bromate from water without forming additional brines and sludges. In this study, Pd and Pt nanoparticles supported on SBA-15 were prepared for catalytic bromate reduction. The activity investigation results showed that the Pt/SBA-15 catalysts exhibited higher activities than the Pd/SBA-15 catalysts and the commercial 5% Pd/C catalyst, and the highest catalytic activity of 24.72 mg·min−1·gcat−1 was obtained using 4% Pt/SBA-15 as the catalyst. This activity is approximately 2.33- and 6.50-fold higher than the activities of the 4% Pd/SBA-15 and 5% Pd/C catalysts, respectively. Analysis of the intrinsic mechanism revealed that the activation energy of bromate reduction over the 4% Pt/SBA-15 catalyst was 47.31 kJ·mol−1, and the reaction followed the Langmuir-Hinshelwood mechanism, suggesting that the reduction of adsorbed bromate on the Pt surface rather than the diffusion process controlled the overall reaction rate. Catalytic bromate reduction was strongly dependent on the reaction pH, and the catalytic activity increased with decreasing pH. Bromate reduction was suppressed in the presence of coexisting anions, including PO43−, SO42−, and Cl−, and the inhibition effects followed the order of PO43− > SO42− > Cl−. Surprisingly, bromate removal was obviously enhanced when a low concentration (

Herein, we fabricated a nitrogen-doped porous graphene/nanometer-sized carbide-derived carbon (NPG/nCDC) composite. In this architecture, the nCDC with a hierarchical pore structure is used as spacer to inhibit the agglomeration of NPG ensuring the in-plane diffusion paths for electrolyte ions and has contribution to the specific surface area and the pore structure of the composite as well. The nano-sized pores existing on the NPG sheets can provide the cross-plane diffusion paths for electrolyte ions. Furthermore, the nitrogen doping to NPG can further enhance the capacitive performance of the composite. Benefiting from these advantages, the NPG/nCDC composites exhibit outstanding supercapacitive performance. Its specific capacitance is up to 336 F g−1 at 5 mV s−1 in 6 mol L−1 KOH electrolyte, and 99.3% capacitance can be maintained even after 10,000 cycles, demonstrating the great potential as the electrode material for supercapacitors.

Pt nanoparticles supported on SBA-15 and amino-functionalized SBA-15 carriers with different Pt loadings were synthesized and characterized by BET, FTIR, XRD, HR-TEM and zeta potential towards the liquid phase catalytic reduction of bromate by hydrogen. The obtained results indicate that the catalytic reaction performance of Pt@NH2-SBA-15 solids was always significantly higher than that of Pt@SBA-15 for the same Pt loading due to the high zeta potential of NH2-SBA-15, which alludes to the ability of the amino-functionalization of SBA-15 to promote Pt catalyst activity for the reduction of aqueous bromate ions.

Catalytic denitrification is an emerging technology that can remove nitrate and nitrite from water. However, the undesirable formation of ammonia requires further suppression. By preparing three types of Pd-based nanocatalysts with different electronic structures as model catalysts, we demonstrate the interfacial electronic effects induced by ethanol (EtOH) and 1-dodecanethiol (C12T) modifications on the selectivity of nitrite catalytic reduction. XPS and in situ DRIFTS spectral characterization studies illustrate that the electron density of the Pd surface atoms increased with the ethanol modification and decreased with the 1-dodecanethiol modification. The nitrite reduction results show that the Pd–EtOH@MIL-101 catalyst (Pdδ−) exhibited an unexpectedly low ammonia selectivity of 0.31%, while a higher value of 10.18% was obtained for the Pd–C12T@MIL-101 catalyst (Pdδ+), which indicated that the electronic structure of Pd can control the ammonia selectivity during the nitrite reduction. Thermodynamics studies revealed that increasing the electron density of the Pd surface atoms reduced the nitrite reaction activation energy and changed the reaction pathways, which resulted in a significant decrease in the ammonia selectivity. The results in this paper may provide new insight into designing and optimizing Pd-based catalysts with low ammonia selectivity for nitrate and nitrite catalytic reduction.

Large scale application of graphene is still facing a great challenge due to the lack of cost-effective methods for its production. Herein, we report a simple and cost-effective method for scalable production of few-layer graphene (FLG) with high quality and large size in only one step at room temperature. In this method, a novel binary-component system, which is composed of sodium percarbonate (SPC) and concentrated H2SO4, has been developed for the chemical exfoliation of graphite, where sodium percarbonate is used to exfoliate graphite for the first time, furthermore, the amount of the concentrated H2SO4 used as an intercalating agent is reduced dramatically by 83–85% in comparison to those in the other chemical exfoliation methods. It is found that SPC plays a key role in the exfoliation of graphite. Considering the analysis results, a possible mechanism for the exfoliation of graphite to FLG is proposed. The exfoliated graphene sheets exhibit a few-layer feature (average layer number

Various attempts are increasingly being made to decrease the thickness of polyamide (PA) nanofilms, in order to promote water transport. Despite optimization of interfacial polymerization (IP), it is challenging to prepare defect-free, ultrathin nanofilms in situ on top of membrane substrates. This issue is closely linked to the rapid, uncontrolled IP reaction, and the physicochemical properties of support materials. In this study, PA nanofilms less than 12 nm in thickness were fabricated at a free water–hexane interface, followed by directly transferring them onto polydopamine (PDA) coated polymer substrates via vacuum filtration. This method not only efficaciously controls the nanofilm thickness, but also largely reduces the monomer content compared to a traditional IP process. Manipulation of nanofilm thickness and structure through fine-tuning the monomer concentration enables the formation of smooth, ultrathin, and robust PA layers. Composite membranes with polypiperazine amide nanofilms exhibit a high water permeance (25.1 L m−2 h−1 bar−1), and an excellent divalent salt rejection (RNa2SO4 = 99.1%). This more than doubles the permeance of a commercial nanofiltration (NF) membrane, although the Na2SO4 retention is generally below 98.5%. Importantly, the low NaCl retention endows the nanofilm composite membranes with a high mono/divalent salt selectivity (80.6). This facile, one-pot strategy provides a useful guideline for the construction of highly permeable TFC membranes for water purification.

Membrane fouling is a prevalent problem faced by all membrane-based applications, which is affected by membrane features, foulant properties and solution chemistry conditions. Here in this study, we explored the fouling behaviors induced by three typical organic matters (Humic acid (HA), Sodium alginate (SA) and Bovine Serum Albumin (BSA)) during the filtration process of two self-made ceramic hollow fiber MF membranes (denoted as Titania and Alumina, respectively), and compared with that of one commercial PVDF MF membrane. Extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory was employed to investigate the interfacial energy between foulants and different membranes. The results indicated that the anti-fouling ability of the three membranes followed the order: Titania > Alumina > PVDF. Further, it was found that regardless of the membrane features, increase of solution pH improved the interfacial free energy and thus mitigating membrane fouling. The addition of Na+ decreased the fouling tendency of HA and SA, but enhanced the fouling behavior by BSA, while Ca2+ can enhance all the fouling tendency of HA/SA/BSA. Co-existence of different organic matters resulted in a more complex fouling variation, which can not be well described with XDLVO theory. Our research is expected to provide a fundamental reference for MF membrane selection in practical application.

In this paper, we present a strategy to prepare the sulfur and nitrogen co-doped porous graphene electrode, in which, three main procedures—the pore-formation in the natural graphite, the preparation of sulfur doped porous graphite intercalation compounds (S-PGIC) and the construction of the sulfur/nitrogen co-doped porous reduced graphite oxide (SN-PRGO) are included. The as-prepared SN-PRGO sample can behave relatively high specific surface area (SSA) and simultaneously provide through-plane and in-plane diffusion paths for electrolyte ions, thus exhibiting an outstanding capacitive performance. Its specific capacitance at the scan rate of 5 mV s−1 in 6 M KOH aqueous electrolyte can reach up to 438 F g−1, which is, to the best of our knowledge, among the highest values so far reported for heteroatoms doped carbon materials. Besides, SN-PRGO also exhibits an excellent cycling stability with almost 94% of its initial capacitance being retained after the long-term consecutive cycling. This work suggests that constructing the doped graphene-based materials by generating the pores in the graphite sheets and using the intercalated substances among the graphite layers as the dopant sources can be considered as a promising strategy for the development of high performance electrodes in supercapacitors.

In order to integrate the advantages of polyamide thin film composite (TFC) nanofiltration (NF) membranes and that of polyester TFC NF membranes, a novel polyesteramide (PEA) TFC NF membrane was prepared by interfacial polymerization between serinol and trimesoyl chloride (TMC) and catalyzed by 4-dimethylaminopyridine (DMAP) on a flat-sheet polyethersulfone (PES) substrate membrane. The membrane performance was maximized by optimizing different preparation parameters. The reaction process was divided into four basic patterns. X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy confirmed the membrane had a partially cross-linked active layer that contained ester bonds, amide bonds and residual hydroxyl groups. Morphology analysis showed the surface of the PEA-TFC-NF membrane was grainy, which was different from the typical polyamide membranes. The contact angle and zeta potential measurements confirmed the PEA-TFC-NF membrane was highly hydrophilic and negatively charged across the entire pH range tested. The optimized PEA-TFC-NF membrane had a MWCO of 474 Da and water permeability of 6.0 L m −2 h −1 bar −1 at 0.5 MPa and 25 °C. The membrane salt rejections followed the order of Na 2 SO 4 > MgSO 4 > NaCl > MgCl 2 , which were 96.27%, 83.92%, 58.68% and 28.76%, respectively. Moreover, the PEA-TFC-NF membrane displayed good antifouling ability.

Generation of ultrathin polyamide (PA) film has been recognized as an effective strategy for fabricating thin film composite (TFC) NF membranes with ultrahigh water permeance and desirable selectivity. However, direct synthesis of an ultrathin PA film via conventional in-situ interface polymerization (ISIP) on commercial substrate membranes has been widely considered impossible. Here we demonstrated this challenge can be surmounted by simultaneously optimizing the monomer concentration and substrate membrane selection. A defect-free PA film with thickness of 8.5 nm was directly formed on a commercial substrate membrane with smooth and hydrophilic surface, as well as medium pore size, only by using a high trimesoyl chloride (TMC) concentration of 0.1 w/v% and a low piperazine (PIP) concentration of 0.05 w/v %. The optimized TFC NF membrane prepared via this facile strategy exhibited an ultrahigh pure water permeance of 46.6 L m−2 h−1 bar−1 and a desirable Na2SO4 rejection of 98.1%. As far as we know, this performance can exceed all the reported TFC NF membranes fabricated with conventional ISIP technique, and also be comparable to most state-of-the-art TFC NF membranes prepared with other complicated ex-situ interfacial polymerization (ESIP). The novel insight and feasible avenues of this study are expected to pave the way for the practical production and application of TFC NF membranes with ultrahigh water permeance.

How to synthesize nanodiamonds (NDs) under moderate conditions is still a challenging issue. Recently, we have demonstrated that high-stress embedding the Fe catalyst into VC can lead to the catalytic synthesis of NDs by chlorine-etching VC at atmospheric pressure. Herein, we have further probed into the influence of the carbide type on the Fe-catalytic synthesis of NDs, where four carbides - VC, TiC, NbC and β-SiC are used as the precursor to be chlorine-etched in the presence of Fe catalyst, respectively. It has been discovered that various types of NDs, including C type, H type and R type, can be catalytically synthesized. The type of carbide has a decisive influence on the Fe-catalytic synthesis of NDs. Furthermore, the size and type of NDs synthesized are closely related to the number of carbon atoms contained per unit volume in the carbide. This finding may open a new avenue for tailoring the size and type of NDs to satisfy the specified application requirement.

A novel polyester thin film composite nanofiltration (NF) membrane was prepared by interfacial polymerization of pentaerythritol (PE) and trimesoyl chloride (TMC) on polyethersulfone (PES) supporting membrane. The performance of the polyester composite NF membrane was optimized by regulating the preparation parameters, including reaction time, pH of the aqueous phase solution, pentaerythritol concentration and TMC concentration. A series of characterization, including permeation experiments, attenuated total reflectance-fourier transform infrared spectroscopy (ATR-FTIR), scanning electron microscope (SEM), atomic force microscopy (AFM), zeta potential analyzer and chlorine resistance experiments, were employed to study the properties of the optimized membrane. The results showed that the optimized polyester composite NF membrane exhibited very high rejection of Na2SO4 (98.1%), but the water flux is relatively low (6.1 L/m2 h, 0.5 MPa, 25 °C). The order of salt rejections is Na2SO4 > MgSO4 > MgCl2 > NaCl, which indicated the membrane was negatively charged, just consistent with the membrane zeta potential results. After treating by NaClO solutions with different concentrations (100 ppm, 500 ppm, 1000 ppm, 2000 ppm, 3000 ppm) for 48 h, the results demonstrated that the polyester NF membrane had good chlorine resistance. Additionally, the polyester TFC NF membrane exhibits good long-term stability.

Here, we propose a simple, effective method to prepare expanded graphite in which the intercalation and expansion of graphite are realized by only one step under ambient conditions, not involving any heating or any sophisticated devices. We demonstrate that the expanded graphite prepared by such an one-step room-temperature method exhibits an expansion volume of up to 225 times. Most importantly, the used amount of concentrated H2SO4, which acts as the intercalant, can be dramatically decreased by about 85% in comparison to that used in the conventional methods, which will greatly reduces the effluent and alleviate the environmentally detrimental effect caused by the excessive usage of H2SO4.

In this paper, we present an approach to construct the compact carbon structure with high volumetric capacitive performance by means of the porous carbon structural collapse and the introduction of oxygen-containing functional groups, which is exemplarily realized by oxidizing the porous titanium carbide-derived carbon (CDC) via a modified Hummers method. Electrochemical investigations demonstrate that the oxidized CDC exhibits simultaneously outstanding volumetric capacitance (216.6 F cm−3) and high gravimetric capacitance (228 F g−1) in 6 M KOH aqueous electrolyte, almost 23 and 16 times improvement in comparison to those of the pristine CDC (9.4 F cm−3 and 14 F g−1), respectively. Furthermore, the oxidized CDC also exhibits an excellent cycling stability (almost 92% specific capacitance being retained even after 10,000 cycles). The results of this work suggests that the strategy for constructing the compact carbon structure from the porous carbon by means of the structural collapse and the introduction of oxygen-containing functional groups will be promising for the development of the electrode material with high volumetric performance for supercapacitors.

With the purpose of improving the ultrafiltration (UF) efficiency, anionic polyacrylamide (APAM) has been used as a coagulant aid in the flocculation-UF process. In this study, the impact of APAM on UF efficiency has been investigated with regard to membrane fouling, membrane cleaning and effluent quality. The results indicated that the optimal dosage of APAM had positive impacts on membrane fouling control, membrane cleaning and effluent quality. According to the flux decline curve, scanning electron microscopy and contact angle characterization, the optimal dosage of APAM was determined to be 0.1 mg/L coupled with 2 mg/L (as Al3+) poly-aluminium chloride. Under this optimal condition, membrane fouling can be mitigated because of the formation of a porous and hydrophilic fouling layer. APAM in the fouling layer can improve the chemical cleaning efficiency of 0.5% NaOH due to the disintegration of the fouling layer when APAM is dissolved under strong alkaline conditions. Furthermore, with the addition of APAM in the flocculation-UF process, more active adsorption sites can be formed in the flocs as well as the membrane fouling layer, thus more antipyrine molecules in the raw water can be adsorbed and removed in the flocculation-UF process.