Based on the analysis of the existing classic clustering routing algorithm HEED, this paper proposes an efficient dynamic clustering routing algorithm ED-HEED. In the cluster selection process, in order to optimize th...Based on the analysis of the existing classic clustering routing algorithm HEED, this paper proposes an efficient dynamic clustering routing algorithm ED-HEED. In the cluster selection process, in order to optimize the network topology and select more proper nodes as the cluster head, the proposed clustering algorithm considers the shortest path prediction of the node to the destination sink and the congestion situation. In the data transmission procedure, the high-efficiency CEDOR opportunistic routing algorithm is applied into the ED-HEED as the data transmission mode between cluster headers. A novel adaptive dynamic clustering mechanism is also considered into the algorithm, as well as the data redundancy and security control. Our Simulation demonstrates that the ED-HEED algorithm can reduce the energy consumption, prolong the network life and keep the security and availability of the network compared with the HEED algorithm.展开更多
The distribution and concentration of dissolved oxygen(DO)play important roles in aerobic heterotroph activities and some slow chemical reactions,and can affect the water quality,biological communities,and ecosystem f...The distribution and concentration of dissolved oxygen(DO)play important roles in aerobic heterotroph activities and some slow chemical reactions,and can affect the water quality,biological communities,and ecosystem functions of rivers and lakes.In this work,the transport of high Schmidt number DO at the sediment-water interface of spanwise oscillating flow is investigated.The volume-averaged Navier-Stokes(VANS)equations and Monod equation are used to describe the flow in the sediment layer and the sediment oxygen demand of microorganisms.The phase-averaged velocities and concentrations of different amplitudes and periods are studied.The dependence of DO transfer on the amplitude and period is analyzed by means of phase-average statistical quantities.It is shown that the concentration in the sediment layer is positively correlated with the turbulence intensity,and the DO concentration and penetration depth in the sediment layer increases when the period and amplitude of the oscillating flow increase.Moreover,in the presence of oscillating flow,a specific scaling relationship exists between the Sherwood number/oxygen consumption of aerobic heterotrophs and the Reynolds number.展开更多
A helical wire is a critical component of an unbounded flexible riser prone to fatigue failure. The helical wire has been the focus of much research work in recent years because of the complex multilayer construction ...A helical wire is a critical component of an unbounded flexible riser prone to fatigue failure. The helical wire has been the focus of much research work in recent years because of the complex multilayer construction of the flexible riser. The present study establishes an analytical model for the axisymmetric and bending analyses of an unbonded flexible riser. The interlayer contact under axisymmetric loads in this model is modeled by setting radial dummy springs between adjacent layers. The contact pressure is constant during the bending response and applied to determine the slipping friction force per unit helical wire. The model tracks the axial stress around the angular position at each time step to calculate the axial force gradient, then compares the axial force gradient with the slipping friction force to judge the helical wire slipping region, which would be applied to determine the bending stiffness for the next time step. The proposed model is verified against the experimental data in the literature. The bending moment-curvature relationship under irregular response is also qualitatively discussed. The stress at the critical point of the helical wire is investigated based on the model by considering the local flexure. The results indicate that the present model can well simulate the bending stiffness variation during irregular response, which has significant effect on the stress of helical wire.展开更多
Pulse signal recovery is to extract useful amplitude and time information from the pulse signal contaminated by noise. It is a great challenge to precisely recover the pulse signal in loud background noise. The conven...Pulse signal recovery is to extract useful amplitude and time information from the pulse signal contaminated by noise. It is a great challenge to precisely recover the pulse signal in loud background noise. The conventional approaches,which are mostly based on the distribution of the pulse energy spectrum,do not well determine the locations and shapes of the pulses. In this paper,we propose a time domain method to reconstruct pulse signals. In the proposed approach,a sparse representation model is established to deal with the issue of the pulse signal recovery under noise conditions. The corresponding problem based on the sparse optimization model is solved by a matching pursuit algorithm. Simulations and experiments validate the effectiveness of the proposed approach on pulse signal recovery.展开更多
The laser host crystals of KLu(WO4)2(KLuW) with large sizes up to 43 × 35 × 16 mm3 have been grown along, [110], b, and c crystallographic directions, respectively, by the top-seeded solution growth (TSSG) s...The laser host crystals of KLu(WO4)2(KLuW) with large sizes up to 43 × 35 × 16 mm3 have been grown along, [110], b, and c crystallographic directions, respectively, by the top-seeded solution growth (TSSG) slow-cooling method. The macro defects are observed using optical microscopy. The main defects found were cracks, inclusions, growth striations, sector boundaries and twin boundaries. The formation mechanism and approaches to reduce or eliminate the defects have been analyzed.展开更多
Membrane distillation(MD)is a promising alternative desalination technology,but the hydrophobic membrane cannot intercept volatile organic compounds(VOCs),resulting in aggravation in the quality of permeate.In term of...Membrane distillation(MD)is a promising alternative desalination technology,but the hydrophobic membrane cannot intercept volatile organic compounds(VOCs),resulting in aggravation in the quality of permeate.In term of this,electro-Fenton(EF)was coupled with sweeping gas membrane distillation(SGMD)in a more efficient way to construct an advanced oxidation barrier at the gas-liquid interface,so that the VOCs could be trapped in this layer to guarantee the water quality of the distillate.During the so-called EF-MD process,an interfacial interception barrier containing hydroxyl radical formed on the hydrophobic membrane surface.It contributed to the high phenol rejection of 90.2% with the permeate phenol concentration lower than 1.50 mg/L.Effective interceptions can be achieved in a wide temperature range,even though the permeate flux of phenol was also intensified.The EF-MD system was robust to high salinity and could electrochemically regenerate ferrous ions,which endowed the long-term stability of the system.This novel EF-MD configuration proposed a valuable strategy to intercept VOCs in MD and will broaden the application of MD in hypersaline wastewater treatment.展开更多
Electron energy dissipation is an important energy dissipation pathway that cannot be ignored in friction process.Two-dimensional zeolite imidazole frameworks(2D ZIFs)and fluorine doping strategies give 2D Zn-ZIF and ...Electron energy dissipation is an important energy dissipation pathway that cannot be ignored in friction process.Two-dimensional zeolite imidazole frameworks(2D ZIFs)and fluorine doping strategies give 2D Zn-ZIF and 2D Co-ZIF unique electrical properties,making them ideal materials for studying electron energy dissipation mechanism.In this paper,based on the superlubricity modulation of 2D fluoridated ZIFs,the optimal tribological properties are obtained on the 2D F-Co-ZIF surface,with the friction coefficient as low as 0.0010.Electrical experiments,density functional theory(DFT)simulation,and fluorescence detection are used to explain the mechanism of fluorine doping regulation of tribological properties from the two stages,namely energy transfer and energy release.Specifically,the energy will transfer into the friction system through the generation of electron–hole pairs under an external excitation,and release by radiation and non-radiation energy dissipation channels.Fluorination reduces energy transfer by altering the electronic properties and band structures of ZIFs,and slows down the charge transfer by enhancing the shielding efficiency,thus slowing the non-radiative energy dissipation rate during the energy release stage.Our insights not only help us better understand the role of fluorine doping in improving tribological properties,but also provide a new way to further explore the electron energy dissipation pathway during friction.展开更多
Ferrograph-based wear debris analysis(WDA)provides significant information for wear fault analysis of mechanical equipment.After decades of offline application,this conventional technology is being driven by the onlin...Ferrograph-based wear debris analysis(WDA)provides significant information for wear fault analysis of mechanical equipment.After decades of offline application,this conventional technology is being driven by the online ferrograph sensor for real-time wear state monitoring.However,online ferrography has been greatly limited by the low imaging quality and segmentation accuracy of particle chains when analyzing degraded lubricant oils in practical applications.To address this issue,an integrated optimization method is developed that focuses on two aspects:the structural re-design of the online ferrograph sensor and the intelligent segmentation of particle chains.For enhancing the imaging quality of wear particles,the magnetic pole of the online ferrograph sensor is optimized to enable the imaging system directly observe wear particles without penetrating oils.Furthermore,a light source simulation model is established based on the light intensity distribution theory,and the LED installation parameters are determined for particle illumination uniformity in the online ferrograph sensor.On this basis,a Mask-RCNN-based segmentation model of particle chains is constructed by specifically establishing the region of interest(ROI)generation layer and the ROI align layer for the irregular particle morphology.With these measures,a new online ferrograph sensor is designed to enhance the image acquisition and information extraction of wear particles.For verification,the developed sensor is tested to collect particle images from different degraded oils,and the images are further handled with the Mask-RCNN-based model for particle feature extraction.Experimental results reveal that the optimized online ferrography can capture clear particle images even in highly-degraded lubricant oils,and the illumination uniformity reaches 90%in its imaging field.Most importantly,the statistical accuracy of wear particles has been improved from 67.2%to 94.1%.展开更多
The Learning With Errors(LWE)problem is widely used in lattice-based cryptography,which is the most promising post-quantum cryptography direction.There are a variety of LWE-solving methods,which can be classified into...The Learning With Errors(LWE)problem is widely used in lattice-based cryptography,which is the most promising post-quantum cryptography direction.There are a variety of LWE-solving methods,which can be classified into four groups:lattice methods,algebraic methods,combinatorial methods,and exhaustive searching.The Blum–Kalai–Wasserman(BKW)algorithm is an important variety of combinatorial algorithms,which was first presented for solving the Learning Parity With Noise(LPN)problem and then extended to solve LWE.In this paper,we give an overview of BKW algorithms for solving LWE.We introduce the framework and key techniques of BKW algorithms and make comparisons between different BKW algorithms and also with lattice methods by estimating concrete security of specific LWE instances.We also briefly discuss the current problems and potential future directions of BKW algorithms.展开更多
Controlling friction by the electric field is a promising way to improve the tribological performance of a variety of movable mechanical systems.In this work,the assembly structure and microscale superlubricity of a h...Controlling friction by the electric field is a promising way to improve the tribological performance of a variety of movable mechanical systems.In this work,the assembly structure and microscale superlubricity of a host–guest assembly are effectively controlled by the electric field.With the help of the scanning tunneling microscopy(STM)technique,the host–guest assembly structures constructed by the co-assembly of fullerene derivative(Fluorene-C60)with macrocycles(4B2A and 3B2A)are explicitly characterized.Combined with density functional theory(DFT),the distinct different assembly behaviors of fullerene derivatives are revealed at different probe biases,which is attributed to the molecular polarity of the fullerene derivative.Through the control on the adsorption behavior,the friction coefficient of host–guest assembly is demonstrated to be controllable in the electric field by using atomic force microscopy(AFM).At positive probe bias,the friction coefficient of the host–guest assembly is significantly reduced and achieves superlubricity(μmin=0.0049).The efforts not only help us gain insight into the host–guest assembly mechanism controlled by the electric field,but also promote the further application of fullerene in micro-electro-mechanical systems(MEMS).展开更多
Layered double hydroxides(LDHs)have the potential to be superlubricated materials due to their strong adsorption effect and weak internal interaction.However,obtaining stable superlubricity during the ultrafast time(&...Layered double hydroxides(LDHs)have the potential to be superlubricated materials due to their strong adsorption effect and weak internal interaction.However,obtaining stable superlubricity during the ultrafast time(<10 s)is still a challenge.Here,we demonstrated macroscale superlubricity based on LDHs of multiple metal ions at high surface roughness,achieving superlow friction coefficients(0.006)and ultrafast wearing-in time(<7 s),which mainly originated from tribochemical reactions and the formation of nanostructured adsorption layers.Through cross-sectional analysis and density functional theory,we revealed the properties of the protective tribofilm to achieve ultrafast superlubricity.LDHs strongly adsorbed on the surface of the bearing steel,the sliding interface transformed into a heterogeneous interface between the polytetrafluoroethylene and LDH,leading to macroscale superlubricity.These findings demonstrate that tribochemical treatment of surfaces produces tribofilm that effectively reduces wearing-in time and promotes ultralow friction.展开更多
Layered palygorskite(PAL),commonly called attapulgite,is a natural inorganic clay mineral composed of magnesium silicate.In this study,an aqueous miscible organic solvent treatment method is adopted to prepare molybde...Layered palygorskite(PAL),commonly called attapulgite,is a natural inorganic clay mineral composed of magnesium silicate.In this study,an aqueous miscible organic solvent treatment method is adopted to prepare molybdenum-dotted palygorskite(Amo-PMo)nanoplatelets,which greatly improved the specific surface area of PAL and the dispersion effect in an oil-based lubricant system.Their layered structure and size were confirmed using transmission electron microscopy(TEM)and atomic force microscopy.Following a tribological test lubricated with three additives(PAL,organic molybdenum(SN-Mo),and Amo-PMo),it was found that the sample of 0.5 wt%Amo-PMo exhibited the best tribological properties with a coefficient of friction of 0.09.Moreover,the resulting wear scar diameter and wear volume of the sliding ball surface were 63%and 49.6%of those lubricated with base oil,respectively.Its excellent lubricating performance and self-repairing ability were mainly attributed to the generated MoS2 adsorbed on the contact surfaces during the tribochemical reaction,thereby effectively preventing the direct collision between asperities on sliding solid surfaces.Thus,as-prepared Amo-PMo nanoplatelets show great potential as oil-based lubricant additives,and this study enriches the existing application of PAL in industry.展开更多
A large amount of solid waste has been produced by the antimony smelting process in the"World Capital of Antimony", Xikuangshan area in China. This study comprehensively investigated the physical and chemical charac...A large amount of solid waste has been produced by the antimony smelting process in the"World Capital of Antimony", Xikuangshan area in China. This study comprehensively investigated the physical and chemical characteristics of the various solid wastes, as well as the leaching behavior of the solid wastes, which included water-quenched slag,arsenic-alkali residue, desulfurized slag and blast furnace dust. These four types of waste were enriched in a variety of heavy metals and metalloids and more specifically with As and Sb levels up to 8.6 × 104 and 3.16 × 105mg/kg, respectively, in arsenic-alkali residue. For desulfurized slag and water-quenched slag, the leaching concentration of Sb significantly exceeded the acceptable limits during the leaching tests using the toxicity characteristic leaching procedure and the synthetic precipitation leaching procedure. In addition, As leaching in arsenic-alkali residue was extraordinarily hazardous, being three orders of magnitude higher than the regulatory level of As. According to the results of the extraction tests, all the tested wastes were classified as hazardous waste.展开更多
A sensitive atomic spectrometric method for the redox speciation analysis of Sb in water is described. The proposed method is based on the selective generation of stibine from Sb(III) in a continuous flow system usi...A sensitive atomic spectrometric method for the redox speciation analysis of Sb in water is described. The proposed method is based on the selective generation of stibine from Sb(III) in a continuous flow system using non-dispersive atomic fluorescence spectrometry for detection. The effects of the HCI concentration on the fluorescence intensities of Sb(III) and Sb(V) were investigated. The results indicated that atomic fluorescence emission due to Sb(V) can constructively interfere with the determination of Sb(III). For the determination of Sb(III), four compounds were tested as masking agents to inhibit the generation of stibine from Sb(V). The effects of the concentrations of the masking agents and of HC1 on the fluorescence signals from Sb(III) and Sb(V) were studied. The results indicated that citric acid and NaF can successfully suppress hydride generation from Sb(V). To evaluate the developed methodology and the influence of the matrix, the recovery of Sb(III) from natural water that was spiked with different Sb(III) and Sb(V) concentrations was tested.展开更多
The current development toward quantum attack has shocked our confidence on classical digital signature schemes.As one of the mainstreams of post quantum cryptography primitives,hash-based signature has attracted more...The current development toward quantum attack has shocked our confidence on classical digital signature schemes.As one of the mainstreams of post quantum cryptography primitives,hash-based signature has attracted more and more concern in both cryptographic research and application in recent years.The goal of this paper is to present,classify and discuss different solutions for hash-based signature.Firstly,this paper discusses the research progress in the component of hash-based signature,i.e.,one-time signature and few-time signature;then classifies the tree-based public key authentication schemes of hash-based signature into limited number and stateful schemes,unlimited number and stateful schemes and unlimited number and stateless schemes.The above discussion aims to analyze the overall design idea of different categories of hash-based signatures,as well as the construction,security reduction and performance efficiency of specific schemes.Finally,the perspectives and possible development directions of hash-based signature are briefly discussed.展开更多
It is difficult to achieve macroscale superlubricity under high contact pressures and high normal loads.Layered double hydroxide(LDH)nanoadditives were introduced into an ionic liquid alcohol solution(IL(as))with cont...It is difficult to achieve macroscale superlubricity under high contact pressures and high normal loads.Layered double hydroxide(LDH)nanoadditives were introduced into an ionic liquid alcohol solution(IL(as))with contact pressures up to 1.044 GPa,which resulted in a friction coefficient(COF)of 0.004 and a robust superlubricity state lasting for 2 h.Compared with the LDH particles(LDH-Ps)with ca.90-nm widths and 18-nm thickness,micron-scale LDH nanosheet(LDH-N)additives with ca.1.5-pm width and 6-nm thickness increased the load-bearing capacity by approximately three times during superlubricity.The lubricant film thickness and the ultrathin longitudinal dimension of the LDH-N additives did not influence the continuity of the fluid film on the contact surface.These improvements resulted from the protective adsorption layer and ion distribution formed on the contact interface,as revealed by detailed surface analyses and simulation studies.In particular,the sliding energy barrier and Bader charge calculation revealed that weak shear sliding between the nanosheet and the solid surface formed easily and the anions in the liquid adsorbed on the solid surface exhibited electrostatic repulsion forces,which generated stable tribological properties synergistically.This research provides a novel method for obtaining macroscale superlubricity for practical industrial applications.展开更多
Impact and torsion pendulums are applied in impulse coupling experiments of high-energy laser irradiation of space debris. It is difficult to achieve a multi-pulse experiment and thus hard to analyze the multi-pulse i...Impact and torsion pendulums are applied in impulse coupling experiments of high-energy laser irradiation of space debris. It is difficult to achieve a multi-pulse experiment and thus hard to analyze the multi-pulse impulse coupling effect. Here, we designed a new recoil impulse experimental measurement system of non-contact, multidegrees of freedom, and multi-pulse irradiation. The system used a low-pressure and low-temperature vacuum chamber to simulate the space environment, the pinning effect of magnetic levitation to achieve aluminum target suspension, and high-speed cameras to record the displacement over time to calculate the impulse of the target.Then the impulse coupling experiment of multi-pulse laser irradiation on the aluminum target was performed.The result shows that the multi-pulse impulse coupling effect is not the linear accumulation of coupling results by every single-pulse and multi-pulse coefficient that decreases with the increase of the number of pulses, and eventually stabilizes as the decrease gets smaller.展开更多
文摘Based on the analysis of the existing classic clustering routing algorithm HEED, this paper proposes an efficient dynamic clustering routing algorithm ED-HEED. In the cluster selection process, in order to optimize the network topology and select more proper nodes as the cluster head, the proposed clustering algorithm considers the shortest path prediction of the node to the destination sink and the congestion situation. In the data transmission procedure, the high-efficiency CEDOR opportunistic routing algorithm is applied into the ED-HEED as the data transmission mode between cluster headers. A novel adaptive dynamic clustering mechanism is also considered into the algorithm, as well as the data redundancy and security control. Our Simulation demonstrates that the ED-HEED algorithm can reduce the energy consumption, prolong the network life and keep the security and availability of the network compared with the HEED algorithm.
基金Project supported by the National Natural Science Foundation of China(Nos.91852111 and 92052201)and the Program of the Shanghai Municipal Education Commission(No.2019-01-07-00-09-E00018)。
文摘The distribution and concentration of dissolved oxygen(DO)play important roles in aerobic heterotroph activities and some slow chemical reactions,and can affect the water quality,biological communities,and ecosystem functions of rivers and lakes.In this work,the transport of high Schmidt number DO at the sediment-water interface of spanwise oscillating flow is investigated.The volume-averaged Navier-Stokes(VANS)equations and Monod equation are used to describe the flow in the sediment layer and the sediment oxygen demand of microorganisms.The phase-averaged velocities and concentrations of different amplitudes and periods are studied.The dependence of DO transfer on the amplitude and period is analyzed by means of phase-average statistical quantities.It is shown that the concentration in the sediment layer is positively correlated with the turbulence intensity,and the DO concentration and penetration depth in the sediment layer increases when the period and amplitude of the oscillating flow increase.Moreover,in the presence of oscillating flow,a specific scaling relationship exists between the Sherwood number/oxygen consumption of aerobic heterotrophs and the Reynolds number.
基金Supported by the Natural Science Foundation of Jiangsu Province under Grant No. BK20160557, and the General Program for Colleges and Universities in Jiangsu Province under Grant No. 16KJD570001
文摘A helical wire is a critical component of an unbounded flexible riser prone to fatigue failure. The helical wire has been the focus of much research work in recent years because of the complex multilayer construction of the flexible riser. The present study establishes an analytical model for the axisymmetric and bending analyses of an unbonded flexible riser. The interlayer contact under axisymmetric loads in this model is modeled by setting radial dummy springs between adjacent layers. The contact pressure is constant during the bending response and applied to determine the slipping friction force per unit helical wire. The model tracks the axial stress around the angular position at each time step to calculate the axial force gradient, then compares the axial force gradient with the slipping friction force to judge the helical wire slipping region, which would be applied to determine the bending stiffness for the next time step. The proposed model is verified against the experimental data in the literature. The bending moment-curvature relationship under irregular response is also qualitatively discussed. The stress at the critical point of the helical wire is investigated based on the model by considering the local flexure. The results indicate that the present model can well simulate the bending stiffness variation during irregular response, which has significant effect on the stress of helical wire.
基金Supported by the National Natural Science Foundation of China(61501385)Science and Technology Planning Project of Sichuan Province,China(2016JY0242,2016GZ0210)Foundation of Southwest University of Science and Technology(15kftk02,15kffk01)
文摘Pulse signal recovery is to extract useful amplitude and time information from the pulse signal contaminated by noise. It is a great challenge to precisely recover the pulse signal in loud background noise. The conventional approaches,which are mostly based on the distribution of the pulse energy spectrum,do not well determine the locations and shapes of the pulses. In this paper,we propose a time domain method to reconstruct pulse signals. In the proposed approach,a sparse representation model is established to deal with the issue of the pulse signal recovery under noise conditions. The corresponding problem based on the sparse optimization model is solved by a matching pursuit algorithm. Simulations and experiments validate the effectiveness of the proposed approach on pulse signal recovery.
文摘The laser host crystals of KLu(WO4)2(KLuW) with large sizes up to 43 × 35 × 16 mm3 have been grown along, [110], b, and c crystallographic directions, respectively, by the top-seeded solution growth (TSSG) slow-cooling method. The macro defects are observed using optical microscopy. The main defects found were cracks, inclusions, growth striations, sector boundaries and twin boundaries. The formation mechanism and approaches to reduce or eliminate the defects have been analyzed.
基金supported by the National Natural Science Foundation of China(Nos.52200111,51978651,and 51878049)the China Postdoctoral Science Foundation(No.2021M703407)the special fund from the State Key Joint Laboratory of Environment Simulation and Pollution Control(Research Center for Eco-Environmental Sciences,Chinese Academy of Sciences(No.21Z01ESPCR)。
文摘Membrane distillation(MD)is a promising alternative desalination technology,but the hydrophobic membrane cannot intercept volatile organic compounds(VOCs),resulting in aggravation in the quality of permeate.In term of this,electro-Fenton(EF)was coupled with sweeping gas membrane distillation(SGMD)in a more efficient way to construct an advanced oxidation barrier at the gas-liquid interface,so that the VOCs could be trapped in this layer to guarantee the water quality of the distillate.During the so-called EF-MD process,an interfacial interception barrier containing hydroxyl radical formed on the hydrophobic membrane surface.It contributed to the high phenol rejection of 90.2% with the permeate phenol concentration lower than 1.50 mg/L.Effective interceptions can be achieved in a wide temperature range,even though the permeate flux of phenol was also intensified.The EF-MD system was robust to high salinity and could electrochemically regenerate ferrous ions,which endowed the long-term stability of the system.This novel EF-MD configuration proposed a valuable strategy to intercept VOCs in MD and will broaden the application of MD in hypersaline wastewater treatment.
基金supported by the National Natural Science Foundation of China(Nos.52350323 and 52105194)the National Postdoctoral Fellowship Program of China(No.GZB20230340)the Project was funded by the China Postdoctoral Science Foundation(Nos.2023TQ0184 and 2023M731941).
文摘Electron energy dissipation is an important energy dissipation pathway that cannot be ignored in friction process.Two-dimensional zeolite imidazole frameworks(2D ZIFs)and fluorine doping strategies give 2D Zn-ZIF and 2D Co-ZIF unique electrical properties,making them ideal materials for studying electron energy dissipation mechanism.In this paper,based on the superlubricity modulation of 2D fluoridated ZIFs,the optimal tribological properties are obtained on the 2D F-Co-ZIF surface,with the friction coefficient as low as 0.0010.Electrical experiments,density functional theory(DFT)simulation,and fluorescence detection are used to explain the mechanism of fluorine doping regulation of tribological properties from the two stages,namely energy transfer and energy release.Specifically,the energy will transfer into the friction system through the generation of electron–hole pairs under an external excitation,and release by radiation and non-radiation energy dissipation channels.Fluorination reduces energy transfer by altering the electronic properties and band structures of ZIFs,and slows down the charge transfer by enhancing the shielding efficiency,thus slowing the non-radiative energy dissipation rate during the energy release stage.Our insights not only help us better understand the role of fluorine doping in improving tribological properties,but also provide a new way to further explore the electron energy dissipation pathway during friction.
基金the National Natural Science Foundation of China(Nos.51975455,52105159 and 52275126)the China Postdoctoral Science Foundation(No.2021M702594)the Open Foundation of State Key Laboratory of Compressor Technology(Compressor Technology Laboratory of Anhui Province),No.SKL-YSJ202102.
文摘Ferrograph-based wear debris analysis(WDA)provides significant information for wear fault analysis of mechanical equipment.After decades of offline application,this conventional technology is being driven by the online ferrograph sensor for real-time wear state monitoring.However,online ferrography has been greatly limited by the low imaging quality and segmentation accuracy of particle chains when analyzing degraded lubricant oils in practical applications.To address this issue,an integrated optimization method is developed that focuses on two aspects:the structural re-design of the online ferrograph sensor and the intelligent segmentation of particle chains.For enhancing the imaging quality of wear particles,the magnetic pole of the online ferrograph sensor is optimized to enable the imaging system directly observe wear particles without penetrating oils.Furthermore,a light source simulation model is established based on the light intensity distribution theory,and the LED installation parameters are determined for particle illumination uniformity in the online ferrograph sensor.On this basis,a Mask-RCNN-based segmentation model of particle chains is constructed by specifically establishing the region of interest(ROI)generation layer and the ROI align layer for the irregular particle morphology.With these measures,a new online ferrograph sensor is designed to enhance the image acquisition and information extraction of wear particles.For verification,the developed sensor is tested to collect particle images from different degraded oils,and the images are further handled with the Mask-RCNN-based model for particle feature extraction.Experimental results reveal that the optimized online ferrography can capture clear particle images even in highly-degraded lubricant oils,and the illumination uniformity reaches 90%in its imaging field.Most importantly,the statistical accuracy of wear particles has been improved from 67.2%to 94.1%.
基金supported by National Natural Science Foundation of China(No.U1936209).
文摘The Learning With Errors(LWE)problem is widely used in lattice-based cryptography,which is the most promising post-quantum cryptography direction.There are a variety of LWE-solving methods,which can be classified into four groups:lattice methods,algebraic methods,combinatorial methods,and exhaustive searching.The Blum–Kalai–Wasserman(BKW)algorithm is an important variety of combinatorial algorithms,which was first presented for solving the Learning Parity With Noise(LPN)problem and then extended to solve LWE.In this paper,we give an overview of BKW algorithms for solving LWE.We introduce the framework and key techniques of BKW algorithms and make comparisons between different BKW algorithms and also with lattice methods by estimating concrete security of specific LWE instances.We also briefly discuss the current problems and potential future directions of BKW algorithms.
基金This work was financially supported by the National Basic Research Program of China(No.2017YFA0205000)the National Natural Science Foundation of China(Nos.51875303 and 21972031)the Strategic Priority Research Program of Chinese Academy of Sciences(No.XDB36000000).
文摘Controlling friction by the electric field is a promising way to improve the tribological performance of a variety of movable mechanical systems.In this work,the assembly structure and microscale superlubricity of a host–guest assembly are effectively controlled by the electric field.With the help of the scanning tunneling microscopy(STM)technique,the host–guest assembly structures constructed by the co-assembly of fullerene derivative(Fluorene-C60)with macrocycles(4B2A and 3B2A)are explicitly characterized.Combined with density functional theory(DFT),the distinct different assembly behaviors of fullerene derivatives are revealed at different probe biases,which is attributed to the molecular polarity of the fullerene derivative.Through the control on the adsorption behavior,the friction coefficient of host–guest assembly is demonstrated to be controllable in the electric field by using atomic force microscopy(AFM).At positive probe bias,the friction coefficient of the host–guest assembly is significantly reduced and achieves superlubricity(μmin=0.0049).The efforts not only help us gain insight into the host–guest assembly mechanism controlled by the electric field,but also promote the further application of fullerene in micro-electro-mechanical systems(MEMS).
基金the National Natural Science Foundation of China(Nos.52105194,52275203,51875303,and 51905294)the China Postdoctoral Science Special Funding Project(No.2022T150353)the Tribology Science Fund of State Key Laboratory of Tribology in Advanced Equipment(No.SKLTKF20A01).
文摘Layered double hydroxides(LDHs)have the potential to be superlubricated materials due to their strong adsorption effect and weak internal interaction.However,obtaining stable superlubricity during the ultrafast time(<10 s)is still a challenge.Here,we demonstrated macroscale superlubricity based on LDHs of multiple metal ions at high surface roughness,achieving superlow friction coefficients(0.006)and ultrafast wearing-in time(<7 s),which mainly originated from tribochemical reactions and the formation of nanostructured adsorption layers.Through cross-sectional analysis and density functional theory,we revealed the properties of the protective tribofilm to achieve ultrafast superlubricity.LDHs strongly adsorbed on the surface of the bearing steel,the sliding interface transformed into a heterogeneous interface between the polytetrafluoroethylene and LDH,leading to macroscale superlubricity.These findings demonstrate that tribochemical treatment of surfaces produces tribofilm that effectively reduces wearing-in time and promotes ultralow friction.
基金This project was supported by Major Science and Technology Project in Guizhou Province(Grant No.Q.K.H.Z.D.Z.X.Z[2019]3016),National Natural Science Foundation of China(Grant Nos.51527901,51875303,51905294,and 51465008),Science and Technology Innovation Team Project in Guizhou Province(Grant No.Q.K.H.P.T.R.C[2020]5020),Preferred Project of Scientific and Technological Activities for Personnel Studying Abroad in Guizhou Province(Grant No.Q.R.X.M.Z.Z.H.T(2018XXX)1),Science and Technology Planning Project in Guizhou Province(Grant No.Q.K.H.P.T.R.C[2017]5788),and Training Plan for High-level Innovative Talent in Guizhou Province(Grant No.Q.K.H.P.T.R.C[2016]5659).
文摘Layered palygorskite(PAL),commonly called attapulgite,is a natural inorganic clay mineral composed of magnesium silicate.In this study,an aqueous miscible organic solvent treatment method is adopted to prepare molybdenum-dotted palygorskite(Amo-PMo)nanoplatelets,which greatly improved the specific surface area of PAL and the dispersion effect in an oil-based lubricant system.Their layered structure and size were confirmed using transmission electron microscopy(TEM)and atomic force microscopy.Following a tribological test lubricated with three additives(PAL,organic molybdenum(SN-Mo),and Amo-PMo),it was found that the sample of 0.5 wt%Amo-PMo exhibited the best tribological properties with a coefficient of friction of 0.09.Moreover,the resulting wear scar diameter and wear volume of the sliding ball surface were 63%and 49.6%of those lubricated with base oil,respectively.Its excellent lubricating performance and self-repairing ability were mainly attributed to the generated MoS2 adsorbed on the contact surfaces during the tribochemical reaction,thereby effectively preventing the direct collision between asperities on sliding solid surfaces.Thus,as-prepared Amo-PMo nanoplatelets show great potential as oil-based lubricant additives,and this study enriches the existing application of PAL in industry.
基金supported by the Environment Protection Specific Project (Nos. 201409096, 201009037-06)the National Natural Science Foundation of China (Nos. 41273105, 41371440)
文摘A large amount of solid waste has been produced by the antimony smelting process in the"World Capital of Antimony", Xikuangshan area in China. This study comprehensively investigated the physical and chemical characteristics of the various solid wastes, as well as the leaching behavior of the solid wastes, which included water-quenched slag,arsenic-alkali residue, desulfurized slag and blast furnace dust. These four types of waste were enriched in a variety of heavy metals and metalloids and more specifically with As and Sb levels up to 8.6 × 104 and 3.16 × 105mg/kg, respectively, in arsenic-alkali residue. For desulfurized slag and water-quenched slag, the leaching concentration of Sb significantly exceeded the acceptable limits during the leaching tests using the toxicity characteristic leaching procedure and the synthetic precipitation leaching procedure. In addition, As leaching in arsenic-alkali residue was extraordinarily hazardous, being three orders of magnitude higher than the regulatory level of As. According to the results of the extraction tests, all the tested wastes were classified as hazardous waste.
文摘A sensitive atomic spectrometric method for the redox speciation analysis of Sb in water is described. The proposed method is based on the selective generation of stibine from Sb(III) in a continuous flow system using non-dispersive atomic fluorescence spectrometry for detection. The effects of the HCI concentration on the fluorescence intensities of Sb(III) and Sb(V) were investigated. The results indicated that atomic fluorescence emission due to Sb(V) can constructively interfere with the determination of Sb(III). For the determination of Sb(III), four compounds were tested as masking agents to inhibit the generation of stibine from Sb(V). The effects of the concentrations of the masking agents and of HC1 on the fluorescence signals from Sb(III) and Sb(V) were studied. The results indicated that citric acid and NaF can successfully suppress hydride generation from Sb(V). To evaluate the developed methodology and the influence of the matrix, the recovery of Sb(III) from natural water that was spiked with different Sb(III) and Sb(V) concentrations was tested.
基金National Natural Science Foundation of China(No.61972391).
文摘The current development toward quantum attack has shocked our confidence on classical digital signature schemes.As one of the mainstreams of post quantum cryptography primitives,hash-based signature has attracted more and more concern in both cryptographic research and application in recent years.The goal of this paper is to present,classify and discuss different solutions for hash-based signature.Firstly,this paper discusses the research progress in the component of hash-based signature,i.e.,one-time signature and few-time signature;then classifies the tree-based public key authentication schemes of hash-based signature into limited number and stateful schemes,unlimited number and stateful schemes and unlimited number and stateless schemes.The above discussion aims to analyze the overall design idea of different categories of hash-based signatures,as well as the construction,security reduction and performance efficiency of specific schemes.Finally,the perspectives and possible development directions of hash-based signature are briefly discussed.
基金This project was supported by the National Natural Science Foundation of China(Nos.51875303,51905294,and 52105194)the Tribology Science Fund of the State Key Laboratory of Tribology(No.SKLTKF20A01).
文摘It is difficult to achieve macroscale superlubricity under high contact pressures and high normal loads.Layered double hydroxide(LDH)nanoadditives were introduced into an ionic liquid alcohol solution(IL(as))with contact pressures up to 1.044 GPa,which resulted in a friction coefficient(COF)of 0.004 and a robust superlubricity state lasting for 2 h.Compared with the LDH particles(LDH-Ps)with ca.90-nm widths and 18-nm thickness,micron-scale LDH nanosheet(LDH-N)additives with ca.1.5-pm width and 6-nm thickness increased the load-bearing capacity by approximately three times during superlubricity.The lubricant film thickness and the ultrathin longitudinal dimension of the LDH-N additives did not influence the continuity of the fluid film on the contact surface.These improvements resulted from the protective adsorption layer and ion distribution formed on the contact interface,as revealed by detailed surface analyses and simulation studies.In particular,the sliding energy barrier and Bader charge calculation revealed that weak shear sliding between the nanosheet and the solid surface formed easily and the anions in the liquid adsorbed on the solid surface exhibited electrostatic repulsion forces,which generated stable tribological properties synergistically.This research provides a novel method for obtaining macroscale superlubricity for practical industrial applications.
文摘Impact and torsion pendulums are applied in impulse coupling experiments of high-energy laser irradiation of space debris. It is difficult to achieve a multi-pulse experiment and thus hard to analyze the multi-pulse impulse coupling effect. Here, we designed a new recoil impulse experimental measurement system of non-contact, multidegrees of freedom, and multi-pulse irradiation. The system used a low-pressure and low-temperature vacuum chamber to simulate the space environment, the pinning effect of magnetic levitation to achieve aluminum target suspension, and high-speed cameras to record the displacement over time to calculate the impulse of the target.Then the impulse coupling experiment of multi-pulse laser irradiation on the aluminum target was performed.The result shows that the multi-pulse impulse coupling effect is not the linear accumulation of coupling results by every single-pulse and multi-pulse coefficient that decreases with the increase of the number of pulses, and eventually stabilizes as the decrease gets smaller.