CsPbX_(3)-based(X=I,Br,Cl)inorganic perovskite solar cells(PSCs)prepared by low-temperature process have attracted much attention because of their low cost and excellent thermal stability.However,the high trap state d...CsPbX_(3)-based(X=I,Br,Cl)inorganic perovskite solar cells(PSCs)prepared by low-temperature process have attracted much attention because of their low cost and excellent thermal stability.However,the high trap state density and serious charge recombination between low-temperature processed TiO_(2)film and inorganic perovskite layer interface seriously restrict the performance of all-inorganic PSCs.Here a thin polyethylene oxide(PEO)layer is employed to modify TiO_(2)film to passivate traps and promote carrier collection.The impacts of PEO layer on microstructure and photoelectric characteristics of TiO_(2)film and related devices are systematically studied.Characterization results suggest that PEO modification can reduce the surface roughness of TiO_(2)film,decrease its average surface potential,and passivate trap states.At optimal conditions,the champion efficiency of CsPbI_(2)Br PSCs with PEO-modified TiO_(2)(PEO-PSCs)has been improved to 11.24%from 9.03%of reference PSCs.Moreover,the hysteresis behavior and charge recombination have been suppressed in PEO-PSCs.展开更多
The size of pores or the grille spacing of water–sediment separation structures directly affects their regulation effect on the debris flow performance.A suitable pore size or grille spacing can effectively improve t...The size of pores or the grille spacing of water–sediment separation structures directly affects their regulation effect on the debris flow performance.A suitable pore size or grille spacing can effectively improve the water–sediment separation ability of the structure.The new funnel-type grating water–sediment separation structure(FGWSS)combines vertical and horizontal structures and provides a satisfactory water–sediment separation effect.However,the regulation effect of the grille spacing of the structure on the debris flow performance has not been studied.The regulation effect of the structure grille spacing on the debris flow performance is studied through a flume test,and the optimal structure grille spacing is obtained.An empirical equation of the relationship between the relative grille spacing of the structure and the sediment separation rate is established.Finally,the influence of the water–sediment separation structure on the regulation effect of debris flows is examined from two aspects:external factors(properties of debris flows)and internal factors(structural factors).The experimental results show that the gradation characteristics of solid particles in debris flows constitute a key factor affecting the regulation effect of the structure on the debris flow performance.The optimum grille spacing of the FGWSS matches the particle size corresponding to the material distribution curves d85~d90 of the debris flow.The total separation rate of debris flow particles is related to the grille spacing of the structure and the content of coarse and fine particles in the debris flow.展开更多
Among the alloying-type anodes,elemental Sb possesses the suitable yet safe plateau,simple lithiation pathway,small voltage polarization,high conductivity,and superior cycle stability.However,challenge is that its int...Among the alloying-type anodes,elemental Sb possesses the suitable yet safe plateau,simple lithiation pathway,small voltage polarization,high conductivity,and superior cycle stability.However,challenge is that its intrinsic capacity is rather low(660 mAh g^(-1)),<1/6 of silicon.Herein,we propose a seamless integration strategy by merging the voltage and capacity of phosphorus and antimony into a solid solution alloy.Interestingly,the enlistment of P is found greatly enlarge the capacity from 660 to 993 mAh g^(-1) for such Sb_(30)P_(30) solid solution,while maintaining a single and stable discharge plateau(~0.79 V)similar to elemental Sb.Various experimental characterizations including XPS,PDF,Raman,and EDS mapping reveal that in such a material the P and Sb atoms have interacted with each other to form a homogenous solid solution alloy,rather than a simple mixing of the two substances.Thus,the Sb_(30)P_(30) exhibits superior rate performances(807 mAh g^(-1) at 5000 mA g^(-1))and cyclability(821 mAh g^(-1) remained after 300 cycles).Furthermore,such Sb_(60-x)P_(x) alloys can even deliver 621 mAh g^(-1) at30℃,which can be served as the alternative anode materials for high-energy and low-temperature batteries.This unique seamless integration strategy based on solid solution chemistry can be easily leveraged to manipulate the capacity of other electrode materials at similar voltage.展开更多
The severe degradation of electrochemical performance for lithium-ion batteries(LIBs)at low temperatures poses a significant challenge to their practical applications.Consequently,extensive efforts have been contribut...The severe degradation of electrochemical performance for lithium-ion batteries(LIBs)at low temperatures poses a significant challenge to their practical applications.Consequently,extensive efforts have been contributed to explore novel anode materials with high electronic conductivity and rapid Li^(+)diffusion kinetics for achieving favorable low-temperature performance of LIBs.Herein,we try to review the recent reports on the synthesis and characterizations of low-temperature anode materials.First,we summarize the underlying mechanisms responsible for the performance degradation of anode materials at subzero temperatures.Second,detailed discussions concerning the key pathways(boosting electronic conductivity,enhancing Li^(+)diffusion kinetics,and inhibiting lithium dendrite)for improving the low-temperature performance of anode materials are presented.Third,several commonly used low-temperature anode materials are briefly introduced.Fourth,recent progress in the engineering of these low-temperature anode materials is summarized in terms of structural design,morphology control,surface&interface modifications,and multiphase materials.Finally,the challenges that remain to be solved in the field of low-temperature anode materials are discussed.This review was organized to offer valuable insights and guidance for next-generation LIBs with excellent low-temperature electrochemical performance.展开更多
During the process of designing the mixed-flow pump impeller, the meridional flow passage shape directly affects the obtained meridional flow field, which then has an influence on the three-dimensional impeller shape....During the process of designing the mixed-flow pump impeller, the meridional flow passage shape directly affects the obtained meridional flow field, which then has an influence on the three-dimensional impeller shape. However, the meridional flow passage shape is too complicated to be described by a simple formula for now. Therefore, reasonable parameter selection for the meridional flow passage is essential to the investigation. In order to explore the effects of the meridional flow passage shape on the impeller design and the hydraulic performance of the mixed-flow pump, the hub and shroud radius ratio (HSRR) of impeller and the outlet diffusion angle (ODA) of outlet zone are selected as the meridional flow passage parameters. 25 mixed-flow pump impellers, with specific speed of 496 under the design condition, are designed with various parameter combinations. Among these impellers, one with HSRR of 1.94 and ODA of 90° is selected to carry out the model test and the obtained experimental results are used to verify accuracies of the head and the hydraulic efficiency predicted by numerical simulation. Based on SIMPLE algorithm and standard k-ε two-equation turbulence model, the three-dimensional steady incompressible Reynolds averaged Navier-Stokes equations are solved and the effects of different parameters on hydraulic performance of mixed-flow pump impellers are analyzed. The analysis results demonstrate that there are optimal values of HSRR and ODA available, so the hydraulic performance and the internal flow of mixed-flow pumps can be improved by selecting appropriate values for the meridional flow passage parameters. The research on these two parameters, HSRR and ODA, has further illustrated influences of the meridional flow passage shape on the hydraulic performance of the mixed-flow pump, and is beneficial to improving the design of the mixed-flow pump impeller.展开更多
The operational performance of a full scale subsurface flow constructed wetland, which treated the mixed industrial and domestic wastewater with BOD 5/COD mean ratio of 0 33 at Shatian, Shenzhen City was studied. ...The operational performance of a full scale subsurface flow constructed wetland, which treated the mixed industrial and domestic wastewater with BOD 5/COD mean ratio of 0 33 at Shatian, Shenzhen City was studied. The constructed wetland system consists of screens, sump, pumping station, and primary settling basin, facultative pond, first stage wetland and secondary stage wetland. The designed treatment capacity is 5000 m 3/d, and the actual influent flow is in the range of <2000 to >10000 m 3/d. Under normal operational conditions, the final effluent quality well met the National Integrated Wastewater Discharge Standard(GB 8978\_1996), with the following parameters(mean values): COD 33 90 mg/L, BOD 5 7.65 mg/L, TSS 7.92 mg/L, TN 9.11 mg/L and TP 0 56 mg/L. Seven species of plants were selected to grow in the wetland: Reed, Sweetcane flower Silvergrass, Great Bulrush, Powdery Thalia and Canna of three colours. The growing season is a whole year round. The seasonal discrepancy could be observed and the plants growing in the wetland are vulnerable to lower temperature in winter. The recycling of the effluent in the first stage of the wetland system is an effective measure to improve the performance of the wetland system. The insufficient DO value in the wetland system not only had significant effect on pollutants removal in the wetland, but also was unfavourable to plant growth. The recycling of effluent to the inlet of wetland system and artificial pond to increase DO value of influent to the wetland is key to operate the subsurface constructed wetland steadily and effectively.展开更多
A subsurface flow wetland(SSFW)was simulated using a commercial computational fluid dynamic(CFD)code.The constructed media was simulated using porous media and the liquid resident time distribution(RTD)in the SSFW was...A subsurface flow wetland(SSFW)was simulated using a commercial computational fluid dynamic(CFD)code.The constructed media was simulated using porous media and the liquid resident time distribution(RTD)in the SSFW was obtained using the particle trajectory model.The effect of wetland configuration and operating conditions on the hydraulic performance of the SSFW were investigated.The results indicated that the hydraulic performance of the SSFW was predominantly affected by the wetland configuration.The hydr...展开更多
In the mixed-flow pump design, the shape of the flow passage can directly affect the flow capacity and the internal flow, thus influencing hydraulic performance, cavitation performance and operation stability of the m...In the mixed-flow pump design, the shape of the flow passage can directly affect the flow capacity and the internal flow, thus influencing hydraulic performance, cavitation performance and operation stability of the mixed-flow pump. However, there is currently a lack of experimental research on the influence mechanism. Therefore, in order to analyze the effects of subtle variations of the flow passage on the mixed-flow pump performance, the frustum cone surface of the end part of inlet contraction flow passage of the mixed-flow pump is processed into a cylindrical surface and a test rig is built to carry out the hydraulic performance experiment. In this experiment, parameters, such as the head, the efficiency, and the shaft power, are measured, and the pressure fluctuation and the noise signal are also collected. The research results suggest that after processing the inlet flow passage, the head of the mixed-flow pump significantly goes down; the best efficiency of the mixed-flow pump drops by approximately 1.5%, the efficiency decreases more significantly under the large flow rate; the shaft power slightly increases under the large flow rate, slightly decreases under the small flow rate. In addition, the pressure fluctuation amplitudes on both the impeller inlet and the diffuser outlet increase significantly with more drastic pressure fluctuations and significantly lower stability of the internal flow of the mixed-flow pump. At the same time, the noise dramatically increases. Overall speaking, the subtle variation of the inlet flow passage leads to a significant change of the mixed-flow pump performance, thus suggesting a special attention to the optimization of flow passage. This paper investigates the influence of the flow passage variation on the mixed-flow pump performance by experiment, which will benefit the optimal design of the flow passage of the mixed-flow pump.展开更多
Carbon cloth modified by hydrothermal treatment in ammonia water is developed as the positive electrode with high electrochemical performance for vanadium redox flow batteries. The SEM shows that the treatment has no ...Carbon cloth modified by hydrothermal treatment in ammonia water is developed as the positive electrode with high electrochemical performance for vanadium redox flow batteries. The SEM shows that the treatment has no obvious influence on the morphology of carbon cloth. XPS measurements indicate that the nitrogenous functional groups can be introduced on the surface of carbon cloth successfully. The electrochemical performance of V(IV)/V(V) redox couple on the prepared electrode is evaluated with cyclic voltammetry and linear sweep voltammetry measurements. The N-doped carbon cloth exhibits outstanding electrochemical activity and reversibility toward V(IV)/V(V) redox couple. The rate constant of V(IV)/V(V) redox reaction on carbon cloth can increase to 2.27 x 10(-4) cm/s from 1.47 x 10(-4) cm/s after nitrogen doping. The cell using N-doped carbon cloth as positive electrode has larger discharge capacity and higher energy efficiency compared with the cell using pristine carbon cloth. The average energy efficiency of the cell using N-doped carbon cloth for 50 cycles at 30 mA/cm(2) is 87.8%, 4.3% larger than that of the cell using pristine carbon cloth. It indicates that the N-doped carbon cloth has a promise application prospect in vanadium redox flow batteries. (C) 2016 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.展开更多
A three-dimensional turbulent flow through an entire centrifugal pump is simulated using k-ε turbulence model modified by rotation and curvature, SIMPLEC method and body-fitted coordinate. The velocity and pressure f...A three-dimensional turbulent flow through an entire centrifugal pump is simulated using k-ε turbulence model modified by rotation and curvature, SIMPLEC method and body-fitted coordinate. The velocity and pressure fields are obtained for the pump under various working conditions, which is used to predict the head and hydraulic efficiency of the pump, and the results correspond well with the measured values. The calculation results indicate that the pressure is higher on the pressure side than that on the suction side of the blade; The relative velocity on the suction side gradually decreases from the impeller inlet to the outlet, while increases on the pressure side, it finally results in the lower relative velocity on the suction side and the higher one on the pressure side at the impeller outlet; The impeller flow field is asymmetric, i.e. the velocity and pressure fields arc totally different among all channels in the impeller; In the volute, the static pressure gradually increases with the flow route, and a large pressure gratitude occurs in the tongue; Secondary flow exists in the rear part of the spiral.展开更多
In this manuscript,the neat epoxy(EP)and functionalized Fe_(3)O_(4)(G-Fe_(3)O_(4))reinforced epoxy(G-Fe_(3)O_(4)/EP)coatings were cured under different temperatures,and the effect of the low curing temperature on the ...In this manuscript,the neat epoxy(EP)and functionalized Fe_(3)O_(4)(G-Fe_(3)O_(4))reinforced epoxy(G-Fe_(3)O_(4)/EP)coatings were cured under different temperatures,and the effect of the low curing temperature on the anticorrosion performance was investigated.The experimental results show that the epoxy-amine ring-open addition reaction mainly exists in the curing process,and the activation energies of the reaction for the two coatings are 55.84 and 53.29 kJ/mol,respectively.For the coatings cured at the low temperature,almost no pores could be detected on the fracture surface,but the presentence of the rough regions reflects the poor curing state.As compared with the samples cured at the high temperature,the anticorrosion performance of the coatings with the low curing temperature is worse,and the decrease rate of the anticorrosion performance is slower,because of the poor curing state and low adhesion obtained at the low temperature.展开更多
For extra-low permeability reservoirs, with a permeability of about 0.3×10?3 μm2, fluid flow and production performance in cores were studied. A long core holder with a multi-location piezometric measurement was...For extra-low permeability reservoirs, with a permeability of about 0.3×10?3 μm2, fluid flow and production performance in cores were studied. A long core holder with a multi-location piezometric measurement was specially designed. An artificial long core, about 700 mm long and with a cross section of 45mm×45mm, was used. In the experiment, pressure distribution along the core can be measured in real time. Single phase flow in the core was investigated. Different modes of production in long cores were also simulated including natural depletion, water flooding, and advanced water flooding. Through physical simulation, flow parameters were collected and production characteristics in extra-low permeability cores were studied. From experimental results, it can be seen that fluid flow in extra-low permeability cores is different from that in high permeability cores. Transmission of pressure in extra-low permeability cores is very slow, and it needs a long time for the pressure to become stable. The distribution curve of pressure along the core is nonlinear and the production rate in extra-low permeability reservoirs decreases sharply. The development effects of different production modes in extra-low permeability cores were compared with one another. Among the production modes, advanced water flooding has much potential for effective development of extra-low permeability reservoirs. Natural depletion and conventional water flooding can also be used in early production periods. In addition, the countermeasures and some ideas especially for the potential development of extra-low permeability reservoirs are suggested.展开更多
It is challenging for aqueous Zn-ion batteries(ZIBs)to achieve comparable low-temperature(low-T)performance due to the easy-frozen electrolyte and severe Zn dendrites.Herein,an aqueous electrolyte with a low freezing ...It is challenging for aqueous Zn-ion batteries(ZIBs)to achieve comparable low-temperature(low-T)performance due to the easy-frozen electrolyte and severe Zn dendrites.Herein,an aqueous electrolyte with a low freezing point and high ionic conductivity is proposed.Combined with molecular dynamics simulation and multi-scale interface analysis(time of flight secondary ion mass spectrometry threedimensional mapping and in-situ electrochemical impedance spectroscopy method),the temperature independence of the V_(2)O_(5)cathode and Zn anode is observed to be opposite.Surprisingly,dominated by the solvent structure of the designed electrolyte at low temperatures,vanadium dissolution/shuttle is significantly inhibited,and the zinc dendrites caused by this electrochemical crosstalk are greatly relieved,thus showing an abnormal temperature inversion effect.Through the disclosure and improvement of the above phenomena,the designed Zn||V_(2)O_(5)full cell delivers superior low-T performance,maintaining almost 99%capacity retention after 9500 cycles(working more than 2500 h)at-20°C.This work proposes a kind of electrolyte suitable for low-T ZIBs and reveals the inverse temperature dependence of the Zn anode,which might offer a novel perspective for the investigation of low-T aqueous battery systems.展开更多
Micromixing efficiency is an important parameter for evaluating the multiphase mass transfer performance and reaction efficiency of microreactors.In this work,the novel curved capillary reactor with different shapes w...Micromixing efficiency is an important parameter for evaluating the multiphase mass transfer performance and reaction efficiency of microreactors.In this work,the novel curved capillary reactor with different shapes was designed to generate Dean flow,which was used to enhance the liquid-liquid micromixing performance.The Villermaux-Dushman probe reaction was employed to characterize the micromixing performance in different curved capillary microreactors.The effects of experiment parameters such as liquid flow rate,inner diameter,tube length,and curve diameter on micromixing performance were systematically investigated.Under the optimal conditions,the minimum value of the segmentation factor XS was 0.008.It was worth noting that at the low Reynolds number(Re<30),the change of curved shape on the capillary microreactor can significantly improve the micromixing performance with XS reduced by 37.5%.Further,the correlations of segment index XS with dimensionless factor such as Reynolds number or Dean number were developed,which can be used to predict the liquid-liquid micromixing performance in capillary microreactors.展开更多
Aqueous zinc-ion batteries are regarded as the promising candidates for large-scale energy storage systems owing to low cost and high safety;however,their applications are restricted by their poor low-temperature perf...Aqueous zinc-ion batteries are regarded as the promising candidates for large-scale energy storage systems owing to low cost and high safety;however,their applications are restricted by their poor low-temperature performance.Herein,a low-temperature electrolyte for low-temperature aqueous zinc-ion batteries is designed by introducing low-polarity diglyme into an aqueous solution of Zn(ClO_(4))_(2).The diglyme disrupts the hydrogenbonding network of water and lowers the freezing point of the electrolyte to-105℃.The designed electrolyte achieves ionic conductivity up to16.18 mS cm^(-1)at-45℃.The diglyme and ClO_(4)^(-)reconfigure the solvated structure of Zn^(2+),which is more favorable for the desolvation of Zn^(2+)at low temperatures.In addition,the diglyme effectively suppresses the dendrites,hydrogen evolution reaction,and by-products of the zinc anode,improving the cycle stability of the battery.At-20℃,a Zn‖Zn symmetrical cell is cycled for 5200 h at 1 mA cm^(-2)and 1 mA h cm^(-2),and a Zn‖polyaniline battery achieves an ultra-long cycle life of 10000 times.This study sheds light on the future design of electrolytes with high ionic conductivity and easy desolvation at low temperatures for rechargeable batteries.展开更多
Contra-rotating axial flow fan is a kind of the vital equipment in coal mines. Their work conditions directly affect the safety of staff and production. In the paper, the performance of the contra-rotating axial flow ...Contra-rotating axial flow fan is a kind of the vital equipment in coal mines. Their work conditions directly affect the safety of staff and production. In the paper, the performance of the contra-rotating axial flow fan is experi- mentally investigated. The study is focused on the fan performance, the shaft power and the match between the motor and fan efficiency at different blade angles. The results show that the blade angle 43°/26° has the best aerodynamic perfor- mance. The first engine has a greater impact on the fan than the second one. The blade angle with the best aerodynamic performance does not necessarily correspond to the one with the best match between the motor and fan efficiency. The blade angle 43°/24° is the best choice for the operation of the fan in the present study.展开更多
Horizontal axis tidal turbines have attracted more and more attentions nowadays, because of their convenience and low expense in construction and high efficiency in extracting tidal energy. The present study numerical...Horizontal axis tidal turbines have attracted more and more attentions nowadays, because of their convenience and low expense in construction and high efficiency in extracting tidal energy. The present study numerically investigates the flow motion and performance of a horizontal axis tidal turbine with a supporting vertical cylinder under steady current. In the numerical model, the continuous equation and incompressible Reynolds-averaged Navier-Stokes equations are solved, and the volume of fluid method is employed to track free surface motion. The RNG k-ε model is adopted to calculate turbulence transport while the fractional area/volume obstacle representation method is used to describe turbine characteristics and movement. The effects of installation elevation of tidal turbine and inlet velocity on the water elevation, and current velocity, rotating speed and resultant force on turbine are discussed. Based on the comparison of the numerical results, a better understanding of flow structure around horizontal axis tidal turbine and turbine performance is achieved.展开更多
It is a challenge to verify integrity of dynamic control flows due to their dynamic and volatile nature. To meet the challenge, existing solutions usually implant an "attachment" in each control transfer. However, t...It is a challenge to verify integrity of dynamic control flows due to their dynamic and volatile nature. To meet the challenge, existing solutions usually implant an "attachment" in each control transfer. However, the attachment introduces additional cost except performance penalty. For example, the attachment must be unique or restrictedly modified. In this paper, we propose a novel approach to detect integrity of dynamic control flows by counting executed branch instructions without involving any attachment. Our solution is based on the following observation. If a control flow is compromised, the number of executed branch instructions will be abnormally increased. The cause is that intruders usually hijack control flows for malicious execution which absolutely introduces additional branch instructions. Inspired by the above observation, in this paper, we devise a novel system named DCFI- Checker, which detect integrity corruption of dynamic control flows with the support of Performance Monitoring Counter (PMC). We have developed a proof-of-concept prototype system of DCFI-Checker on Linux fedora 5. Our experiments with existing kemel rootkits and buffer overflow attack show that DCFI- Checker is effective to detect compromised dynamic control transfer, and performance evaluations indicate that performance penaltyinduced by DCFI-Checker is acceptable.展开更多
Long duration energy storage(LDES)technologies are vital for wide utilization of renewable energy sources and increasing the penetration of these technologies within energy infrastructures.Herein,we propose a low-cost...Long duration energy storage(LDES)technologies are vital for wide utilization of renewable energy sources and increasing the penetration of these technologies within energy infrastructures.Herein,we propose a low-cost alkaline all-iron flow battery by coupling ferri/ferro-cyanide redox couple with ferric/ferrous-gluconate complexes redox couple.The designed all-iron flow battery demonstrates a coulombic efficiency of above 99%and an energy efficiency of~83%at a current density of80 m A cm^(-2),which can continuously run for more than 950 cycles.Most importantly,the battery demonstrates a coulombic efficiency of more than 99.0%and an energy efficiency of~83%for a long duration(~12,16 and 20 h per cycle)charge/discharge process.Benefiting from the low cost of iron electrolytes,the overall cost of the all-iron flow battery system can be reached as low as$76.11 per k Wh based on a10 h system with a power of 9.9 k W.This work provides a new option for next-generation cost-effective flow batteries for long duration large scale energy storage.展开更多
The helico-axial multiphase pump is often used for gas-liquid mixture transportation in offshore oilfields,and slug flow is the main reason for the unstable operation of the pump.Aimed for slug flow condition,a self-d...The helico-axial multiphase pump is often used for gas-liquid mixture transportation in offshore oilfields,and slug flow is the main reason for the unstable operation of the pump.Aimed for slug flow condition,a self-designed three-stage multiphase pump is set to the object to perform unsteady simulations and fluid-structure interaction calculations,and the inlet gas void fraction(IGVF)is set from 20%to 80%.The results show that affected by the flow from the slug,the gas-liquid two-phase flow pattern in the multiphase pump changes sharply,resulting in severe fluctuations in the differential pressure,spindle torque and deformation of the multiphase pump.The gas-phase enters the first-impeller along the suction blade surface when affected by Taylor bubbles,while the second and third-stage impellers gas-phases are in the form of small air masses flow into the impeller along the pressure blade surface.The deformation trend of impeller torque,differential pressure and the main pump spindle is similar to that of trigonometric function,while the fluctuation of torque is more intense,and the shape variable of spindle increases with the inflow of liquid plug,and the maximum deformation amount increases by10.9%at high GVF relative to IGVF.展开更多
基金financially supported by the Guangzhou Basic and Applied Basic Research Foundation,China(No.303523)。
文摘CsPbX_(3)-based(X=I,Br,Cl)inorganic perovskite solar cells(PSCs)prepared by low-temperature process have attracted much attention because of their low cost and excellent thermal stability.However,the high trap state density and serious charge recombination between low-temperature processed TiO_(2)film and inorganic perovskite layer interface seriously restrict the performance of all-inorganic PSCs.Here a thin polyethylene oxide(PEO)layer is employed to modify TiO_(2)film to passivate traps and promote carrier collection.The impacts of PEO layer on microstructure and photoelectric characteristics of TiO_(2)film and related devices are systematically studied.Characterization results suggest that PEO modification can reduce the surface roughness of TiO_(2)film,decrease its average surface potential,and passivate trap states.At optimal conditions,the champion efficiency of CsPbI_(2)Br PSCs with PEO-modified TiO_(2)(PEO-PSCs)has been improved to 11.24%from 9.03%of reference PSCs.Moreover,the hysteresis behavior and charge recombination have been suppressed in PEO-PSCs.
基金supported by the National Natural Science Foundation of China(Grant Nos.42027806 and 42041006)。
文摘The size of pores or the grille spacing of water–sediment separation structures directly affects their regulation effect on the debris flow performance.A suitable pore size or grille spacing can effectively improve the water–sediment separation ability of the structure.The new funnel-type grating water–sediment separation structure(FGWSS)combines vertical and horizontal structures and provides a satisfactory water–sediment separation effect.However,the regulation effect of the grille spacing of the structure on the debris flow performance has not been studied.The regulation effect of the structure grille spacing on the debris flow performance is studied through a flume test,and the optimal structure grille spacing is obtained.An empirical equation of the relationship between the relative grille spacing of the structure and the sediment separation rate is established.Finally,the influence of the water–sediment separation structure on the regulation effect of debris flows is examined from two aspects:external factors(properties of debris flows)and internal factors(structural factors).The experimental results show that the gradation characteristics of solid particles in debris flows constitute a key factor affecting the regulation effect of the structure on the debris flow performance.The optimum grille spacing of the FGWSS matches the particle size corresponding to the material distribution curves d85~d90 of the debris flow.The total separation rate of debris flow particles is related to the grille spacing of the structure and the content of coarse and fine particles in the debris flow.
基金the National Natural Science Foundation of China(Grant No.52072138,21571073,51772115)National Key Research and Development Program of China(Grant No.2018YFE0206900)Hubei Provincial Natural Science Foundation of China(Grant No.2019CFA002)。
文摘Among the alloying-type anodes,elemental Sb possesses the suitable yet safe plateau,simple lithiation pathway,small voltage polarization,high conductivity,and superior cycle stability.However,challenge is that its intrinsic capacity is rather low(660 mAh g^(-1)),<1/6 of silicon.Herein,we propose a seamless integration strategy by merging the voltage and capacity of phosphorus and antimony into a solid solution alloy.Interestingly,the enlistment of P is found greatly enlarge the capacity from 660 to 993 mAh g^(-1) for such Sb_(30)P_(30) solid solution,while maintaining a single and stable discharge plateau(~0.79 V)similar to elemental Sb.Various experimental characterizations including XPS,PDF,Raman,and EDS mapping reveal that in such a material the P and Sb atoms have interacted with each other to form a homogenous solid solution alloy,rather than a simple mixing of the two substances.Thus,the Sb_(30)P_(30) exhibits superior rate performances(807 mAh g^(-1) at 5000 mA g^(-1))and cyclability(821 mAh g^(-1) remained after 300 cycles).Furthermore,such Sb_(60-x)P_(x) alloys can even deliver 621 mAh g^(-1) at30℃,which can be served as the alternative anode materials for high-energy and low-temperature batteries.This unique seamless integration strategy based on solid solution chemistry can be easily leveraged to manipulate the capacity of other electrode materials at similar voltage.
基金supported by the National Key Research and Development Program of China(No.2019YFA0705601)the National Natural Science Foundation of China(No.U23A20122,52101267)the Key Science and Technology Special Project of Henan Province(No.201111311400).
文摘The severe degradation of electrochemical performance for lithium-ion batteries(LIBs)at low temperatures poses a significant challenge to their practical applications.Consequently,extensive efforts have been contributed to explore novel anode materials with high electronic conductivity and rapid Li^(+)diffusion kinetics for achieving favorable low-temperature performance of LIBs.Herein,we try to review the recent reports on the synthesis and characterizations of low-temperature anode materials.First,we summarize the underlying mechanisms responsible for the performance degradation of anode materials at subzero temperatures.Second,detailed discussions concerning the key pathways(boosting electronic conductivity,enhancing Li^(+)diffusion kinetics,and inhibiting lithium dendrite)for improving the low-temperature performance of anode materials are presented.Third,several commonly used low-temperature anode materials are briefly introduced.Fourth,recent progress in the engineering of these low-temperature anode materials is summarized in terms of structural design,morphology control,surface&interface modifications,and multiphase materials.Finally,the challenges that remain to be solved in the field of low-temperature anode materials are discussed.This review was organized to offer valuable insights and guidance for next-generation LIBs with excellent low-temperature electrochemical performance.
基金supported by National Natural Science Foundation of China (Grant No. 51176088)
文摘During the process of designing the mixed-flow pump impeller, the meridional flow passage shape directly affects the obtained meridional flow field, which then has an influence on the three-dimensional impeller shape. However, the meridional flow passage shape is too complicated to be described by a simple formula for now. Therefore, reasonable parameter selection for the meridional flow passage is essential to the investigation. In order to explore the effects of the meridional flow passage shape on the impeller design and the hydraulic performance of the mixed-flow pump, the hub and shroud radius ratio (HSRR) of impeller and the outlet diffusion angle (ODA) of outlet zone are selected as the meridional flow passage parameters. 25 mixed-flow pump impellers, with specific speed of 496 under the design condition, are designed with various parameter combinations. Among these impellers, one with HSRR of 1.94 and ODA of 90° is selected to carry out the model test and the obtained experimental results are used to verify accuracies of the head and the hydraulic efficiency predicted by numerical simulation. Based on SIMPLE algorithm and standard k-ε two-equation turbulence model, the three-dimensional steady incompressible Reynolds averaged Navier-Stokes equations are solved and the effects of different parameters on hydraulic performance of mixed-flow pump impellers are analyzed. The analysis results demonstrate that there are optimal values of HSRR and ODA available, so the hydraulic performance and the internal flow of mixed-flow pumps can be improved by selecting appropriate values for the meridional flow passage parameters. The research on these two parameters, HSRR and ODA, has further illustrated influences of the meridional flow passage shape on the hydraulic performance of the mixed-flow pump, and is beneficial to improving the design of the mixed-flow pump impeller.
文摘The operational performance of a full scale subsurface flow constructed wetland, which treated the mixed industrial and domestic wastewater with BOD 5/COD mean ratio of 0 33 at Shatian, Shenzhen City was studied. The constructed wetland system consists of screens, sump, pumping station, and primary settling basin, facultative pond, first stage wetland and secondary stage wetland. The designed treatment capacity is 5000 m 3/d, and the actual influent flow is in the range of <2000 to >10000 m 3/d. Under normal operational conditions, the final effluent quality well met the National Integrated Wastewater Discharge Standard(GB 8978\_1996), with the following parameters(mean values): COD 33 90 mg/L, BOD 5 7.65 mg/L, TSS 7.92 mg/L, TN 9.11 mg/L and TP 0 56 mg/L. Seven species of plants were selected to grow in the wetland: Reed, Sweetcane flower Silvergrass, Great Bulrush, Powdery Thalia and Canna of three colours. The growing season is a whole year round. The seasonal discrepancy could be observed and the plants growing in the wetland are vulnerable to lower temperature in winter. The recycling of the effluent in the first stage of the wetland system is an effective measure to improve the performance of the wetland system. The insufficient DO value in the wetland system not only had significant effect on pollutants removal in the wetland, but also was unfavourable to plant growth. The recycling of effluent to the inlet of wetland system and artificial pond to increase DO value of influent to the wetland is key to operate the subsurface constructed wetland steadily and effectively.
基金The authors are grateful to"Chemical Grid Project"of Beijing University of Chemical Technology for providingthe computer facilities.
文摘A subsurface flow wetland(SSFW)was simulated using a commercial computational fluid dynamic(CFD)code.The constructed media was simulated using porous media and the liquid resident time distribution(RTD)in the SSFW was obtained using the particle trajectory model.The effect of wetland configuration and operating conditions on the hydraulic performance of the SSFW were investigated.The results indicated that the hydraulic performance of the SSFW was predominantly affected by the wetland configuration.The hydr...
基金Supported by National Natural Science Foundation of China(Grant No.51176088)
文摘In the mixed-flow pump design, the shape of the flow passage can directly affect the flow capacity and the internal flow, thus influencing hydraulic performance, cavitation performance and operation stability of the mixed-flow pump. However, there is currently a lack of experimental research on the influence mechanism. Therefore, in order to analyze the effects of subtle variations of the flow passage on the mixed-flow pump performance, the frustum cone surface of the end part of inlet contraction flow passage of the mixed-flow pump is processed into a cylindrical surface and a test rig is built to carry out the hydraulic performance experiment. In this experiment, parameters, such as the head, the efficiency, and the shaft power, are measured, and the pressure fluctuation and the noise signal are also collected. The research results suggest that after processing the inlet flow passage, the head of the mixed-flow pump significantly goes down; the best efficiency of the mixed-flow pump drops by approximately 1.5%, the efficiency decreases more significantly under the large flow rate; the shaft power slightly increases under the large flow rate, slightly decreases under the small flow rate. In addition, the pressure fluctuation amplitudes on both the impeller inlet and the diffuser outlet increase significantly with more drastic pressure fluctuations and significantly lower stability of the internal flow of the mixed-flow pump. At the same time, the noise dramatically increases. Overall speaking, the subtle variation of the inlet flow passage leads to a significant change of the mixed-flow pump performance, thus suggesting a special attention to the optimization of flow passage. This paper investigates the influence of the flow passage variation on the mixed-flow pump performance by experiment, which will benefit the optimal design of the flow passage of the mixed-flow pump.
基金supported by the Open Project Program of Jiangxi Engineering Research Center of Process and Equipment for New Energy,East China Institute of Technology(No.JXNE2015-14)Youth Foundation of Education Department of Hebei Province(No.QN2016183)the National Natural Science Foundation of China(No.51362002)
文摘Carbon cloth modified by hydrothermal treatment in ammonia water is developed as the positive electrode with high electrochemical performance for vanadium redox flow batteries. The SEM shows that the treatment has no obvious influence on the morphology of carbon cloth. XPS measurements indicate that the nitrogenous functional groups can be introduced on the surface of carbon cloth successfully. The electrochemical performance of V(IV)/V(V) redox couple on the prepared electrode is evaluated with cyclic voltammetry and linear sweep voltammetry measurements. The N-doped carbon cloth exhibits outstanding electrochemical activity and reversibility toward V(IV)/V(V) redox couple. The rate constant of V(IV)/V(V) redox reaction on carbon cloth can increase to 2.27 x 10(-4) cm/s from 1.47 x 10(-4) cm/s after nitrogen doping. The cell using N-doped carbon cloth as positive electrode has larger discharge capacity and higher energy efficiency compared with the cell using pristine carbon cloth. The average energy efficiency of the cell using N-doped carbon cloth for 50 cycles at 30 mA/cm(2) is 87.8%, 4.3% larger than that of the cell using pristine carbon cloth. It indicates that the N-doped carbon cloth has a promise application prospect in vanadium redox flow batteries. (C) 2016 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.
基金This project is supported by Provincial Natural Science Foundation of Jiangsu, China(No.BK2004406)Provincial Innovation Foundation for Graduate Students of Jiangsu, China(No.1223000053
文摘A three-dimensional turbulent flow through an entire centrifugal pump is simulated using k-ε turbulence model modified by rotation and curvature, SIMPLEC method and body-fitted coordinate. The velocity and pressure fields are obtained for the pump under various working conditions, which is used to predict the head and hydraulic efficiency of the pump, and the results correspond well with the measured values. The calculation results indicate that the pressure is higher on the pressure side than that on the suction side of the blade; The relative velocity on the suction side gradually decreases from the impeller inlet to the outlet, while increases on the pressure side, it finally results in the lower relative velocity on the suction side and the higher one on the pressure side at the impeller outlet; The impeller flow field is asymmetric, i.e. the velocity and pressure fields arc totally different among all channels in the impeller; In the volute, the static pressure gradually increases with the flow route, and a large pressure gratitude occurs in the tongue; Secondary flow exists in the rear part of the spiral.
基金Project(U2106216)supported by the National Natural Science Foundation of China。
文摘In this manuscript,the neat epoxy(EP)and functionalized Fe_(3)O_(4)(G-Fe_(3)O_(4))reinforced epoxy(G-Fe_(3)O_(4)/EP)coatings were cured under different temperatures,and the effect of the low curing temperature on the anticorrosion performance was investigated.The experimental results show that the epoxy-amine ring-open addition reaction mainly exists in the curing process,and the activation energies of the reaction for the two coatings are 55.84 and 53.29 kJ/mol,respectively.For the coatings cured at the low temperature,almost no pores could be detected on the fracture surface,but the presentence of the rough regions reflects the poor curing state.As compared with the samples cured at the high temperature,the anticorrosion performance of the coatings with the low curing temperature is worse,and the decrease rate of the anticorrosion performance is slower,because of the poor curing state and low adhesion obtained at the low temperature.
基金supported by China National Program on Key Basic Research Project (973 Program) (Grant No. 2006CB705805)National Key Scientific and Technological Project (Grant No. 2008ZX05009-004)
文摘For extra-low permeability reservoirs, with a permeability of about 0.3×10?3 μm2, fluid flow and production performance in cores were studied. A long core holder with a multi-location piezometric measurement was specially designed. An artificial long core, about 700 mm long and with a cross section of 45mm×45mm, was used. In the experiment, pressure distribution along the core can be measured in real time. Single phase flow in the core was investigated. Different modes of production in long cores were also simulated including natural depletion, water flooding, and advanced water flooding. Through physical simulation, flow parameters were collected and production characteristics in extra-low permeability cores were studied. From experimental results, it can be seen that fluid flow in extra-low permeability cores is different from that in high permeability cores. Transmission of pressure in extra-low permeability cores is very slow, and it needs a long time for the pressure to become stable. The distribution curve of pressure along the core is nonlinear and the production rate in extra-low permeability reservoirs decreases sharply. The development effects of different production modes in extra-low permeability cores were compared with one another. Among the production modes, advanced water flooding has much potential for effective development of extra-low permeability reservoirs. Natural depletion and conventional water flooding can also be used in early production periods. In addition, the countermeasures and some ideas especially for the potential development of extra-low permeability reservoirs are suggested.
基金financially supported by the National Natural Science Foundation of China(52372191)the Natural Science Foundation of Xiamen,China(3502Z202372036)+1 种基金the China Postdoctoral Science Foundation(2022TQ0282)the support of the High-Performance Computing Center(HPCC)at Harbin Institute of Technology on first-principles calculations。
文摘It is challenging for aqueous Zn-ion batteries(ZIBs)to achieve comparable low-temperature(low-T)performance due to the easy-frozen electrolyte and severe Zn dendrites.Herein,an aqueous electrolyte with a low freezing point and high ionic conductivity is proposed.Combined with molecular dynamics simulation and multi-scale interface analysis(time of flight secondary ion mass spectrometry threedimensional mapping and in-situ electrochemical impedance spectroscopy method),the temperature independence of the V_(2)O_(5)cathode and Zn anode is observed to be opposite.Surprisingly,dominated by the solvent structure of the designed electrolyte at low temperatures,vanadium dissolution/shuttle is significantly inhibited,and the zinc dendrites caused by this electrochemical crosstalk are greatly relieved,thus showing an abnormal temperature inversion effect.Through the disclosure and improvement of the above phenomena,the designed Zn||V_(2)O_(5)full cell delivers superior low-T performance,maintaining almost 99%capacity retention after 9500 cycles(working more than 2500 h)at-20°C.This work proposes a kind of electrolyte suitable for low-T ZIBs and reveals the inverse temperature dependence of the Zn anode,which might offer a novel perspective for the investigation of low-T aqueous battery systems.
基金supports of National Natural Science Foundation of China(22308057)Outstanding Talent Introduction Funds from Fuzhou University(0040-511175)Fuzhou University Testing Fund of precious apparatus(2023T003).
文摘Micromixing efficiency is an important parameter for evaluating the multiphase mass transfer performance and reaction efficiency of microreactors.In this work,the novel curved capillary reactor with different shapes was designed to generate Dean flow,which was used to enhance the liquid-liquid micromixing performance.The Villermaux-Dushman probe reaction was employed to characterize the micromixing performance in different curved capillary microreactors.The effects of experiment parameters such as liquid flow rate,inner diameter,tube length,and curve diameter on micromixing performance were systematically investigated.Under the optimal conditions,the minimum value of the segmentation factor XS was 0.008.It was worth noting that at the low Reynolds number(Re<30),the change of curved shape on the capillary microreactor can significantly improve the micromixing performance with XS reduced by 37.5%.Further,the correlations of segment index XS with dimensionless factor such as Reynolds number or Dean number were developed,which can be used to predict the liquid-liquid micromixing performance in capillary microreactors.
文摘Aqueous zinc-ion batteries are regarded as the promising candidates for large-scale energy storage systems owing to low cost and high safety;however,their applications are restricted by their poor low-temperature performance.Herein,a low-temperature electrolyte for low-temperature aqueous zinc-ion batteries is designed by introducing low-polarity diglyme into an aqueous solution of Zn(ClO_(4))_(2).The diglyme disrupts the hydrogenbonding network of water and lowers the freezing point of the electrolyte to-105℃.The designed electrolyte achieves ionic conductivity up to16.18 mS cm^(-1)at-45℃.The diglyme and ClO_(4)^(-)reconfigure the solvated structure of Zn^(2+),which is more favorable for the desolvation of Zn^(2+)at low temperatures.In addition,the diglyme effectively suppresses the dendrites,hydrogen evolution reaction,and by-products of the zinc anode,improving the cycle stability of the battery.At-20℃,a Zn‖Zn symmetrical cell is cycled for 5200 h at 1 mA cm^(-2)and 1 mA h cm^(-2),and a Zn‖polyaniline battery achieves an ultra-long cycle life of 10000 times.This study sheds light on the future design of electrolytes with high ionic conductivity and easy desolvation at low temperatures for rechargeable batteries.
文摘Contra-rotating axial flow fan is a kind of the vital equipment in coal mines. Their work conditions directly affect the safety of staff and production. In the paper, the performance of the contra-rotating axial flow fan is experi- mentally investigated. The study is focused on the fan performance, the shaft power and the match between the motor and fan efficiency at different blade angles. The results show that the blade angle 43°/26° has the best aerodynamic perfor- mance. The first engine has a greater impact on the fan than the second one. The blade angle with the best aerodynamic performance does not necessarily correspond to the one with the best match between the motor and fan efficiency. The blade angle 43°/24° is the best choice for the operation of the fan in the present study.
基金funded by by the National Science Fund for Distinguished Young Scholars(Grant No.51425901)the National Natural Science Foundation of China(Grant Nos.51479053 and 51137002)+4 种基金the Natural Science Foundation of Jiangsu Province(Grant No.BK2011026)the 111 Project(Grant No.B2012032)the Specialized Research Funding for the Doctoral Program of Higher Education(Grant No.20130094110014)the Marine Renewable Energy Research Project of State Oceanic Administration(Grant No.GHME2013GC03)the Fundamental Research Funds for the Central University(Hohai University,Grant Nos.2013B31614 and 2014B04114)
文摘Horizontal axis tidal turbines have attracted more and more attentions nowadays, because of their convenience and low expense in construction and high efficiency in extracting tidal energy. The present study numerically investigates the flow motion and performance of a horizontal axis tidal turbine with a supporting vertical cylinder under steady current. In the numerical model, the continuous equation and incompressible Reynolds-averaged Navier-Stokes equations are solved, and the volume of fluid method is employed to track free surface motion. The RNG k-ε model is adopted to calculate turbulence transport while the fractional area/volume obstacle representation method is used to describe turbine characteristics and movement. The effects of installation elevation of tidal turbine and inlet velocity on the water elevation, and current velocity, rotating speed and resultant force on turbine are discussed. Based on the comparison of the numerical results, a better understanding of flow structure around horizontal axis tidal turbine and turbine performance is achieved.
基金The work is supported in part by the National Natural Science Foundation of China,Natural Science Foundation of Beijing,National 863 High-Tech Research Development Program of China
文摘It is a challenge to verify integrity of dynamic control flows due to their dynamic and volatile nature. To meet the challenge, existing solutions usually implant an "attachment" in each control transfer. However, the attachment introduces additional cost except performance penalty. For example, the attachment must be unique or restrictedly modified. In this paper, we propose a novel approach to detect integrity of dynamic control flows by counting executed branch instructions without involving any attachment. Our solution is based on the following observation. If a control flow is compromised, the number of executed branch instructions will be abnormally increased. The cause is that intruders usually hijack control flows for malicious execution which absolutely introduces additional branch instructions. Inspired by the above observation, in this paper, we devise a novel system named DCFI- Checker, which detect integrity corruption of dynamic control flows with the support of Performance Monitoring Counter (PMC). We have developed a proof-of-concept prototype system of DCFI-Checker on Linux fedora 5. Our experiments with existing kemel rootkits and buffer overflow attack show that DCFI- Checker is effective to detect compromised dynamic control transfer, and performance evaluations indicate that performance penaltyinduced by DCFI-Checker is acceptable.
基金the financial support from National Natural Science Foundation of China(22078313,21908214 and 21925804)the Dalian High Level Talent Innovation support program(2020RD05)+2 种基金the Dalian Young Star of Science and Technology(2021RQ122)the Free exploring basic research project of Liaoning(2022JH6/100100005)the Youth Innovation Promotion Association CAS(2019182)。
文摘Long duration energy storage(LDES)technologies are vital for wide utilization of renewable energy sources and increasing the penetration of these technologies within energy infrastructures.Herein,we propose a low-cost alkaline all-iron flow battery by coupling ferri/ferro-cyanide redox couple with ferric/ferrous-gluconate complexes redox couple.The designed all-iron flow battery demonstrates a coulombic efficiency of above 99%and an energy efficiency of~83%at a current density of80 m A cm^(-2),which can continuously run for more than 950 cycles.Most importantly,the battery demonstrates a coulombic efficiency of more than 99.0%and an energy efficiency of~83%for a long duration(~12,16 and 20 h per cycle)charge/discharge process.Benefiting from the low cost of iron electrolytes,the overall cost of the all-iron flow battery system can be reached as low as$76.11 per k Wh based on a10 h system with a power of 9.9 k W.This work provides a new option for next-generation cost-effective flow batteries for long duration large scale energy storage.
基金the support of the National Key R&D Program of China(Grant No.2020YFB2010002)。
文摘The helico-axial multiphase pump is often used for gas-liquid mixture transportation in offshore oilfields,and slug flow is the main reason for the unstable operation of the pump.Aimed for slug flow condition,a self-designed three-stage multiphase pump is set to the object to perform unsteady simulations and fluid-structure interaction calculations,and the inlet gas void fraction(IGVF)is set from 20%to 80%.The results show that affected by the flow from the slug,the gas-liquid two-phase flow pattern in the multiphase pump changes sharply,resulting in severe fluctuations in the differential pressure,spindle torque and deformation of the multiphase pump.The gas-phase enters the first-impeller along the suction blade surface when affected by Taylor bubbles,while the second and third-stage impellers gas-phases are in the form of small air masses flow into the impeller along the pressure blade surface.The deformation trend of impeller torque,differential pressure and the main pump spindle is similar to that of trigonometric function,while the fluctuation of torque is more intense,and the shape variable of spindle increases with the inflow of liquid plug,and the maximum deformation amount increases by10.9%at high GVF relative to IGVF.