The wear condition of the piston/cylinder pair is crucial to the performance and reliability of the axial piston pump.The hard piston surface,the soft cylinder bore surface,and the interface oil film affects each othe...The wear condition of the piston/cylinder pair is crucial to the performance and reliability of the axial piston pump.The hard piston surface,the soft cylinder bore surface,and the interface oil film affects each other during the wear process.Specifically,in the mixed lubrication region,the geometry of the hard piston surface asperity directly affects the wear of soft cylinder bore surface,while the asperities may deform or even degrade when penetrating and sliding against the cylinder bore.So far,there is no suitable method to simulate their coupled evolution.This paper proposed a wear process simulation model considering the real-time interaction between the elasto-plastic deformation of the piston surface asperity,the wear contour of the cylinder bore,and the lubrication condition of the interface.An offline library of the elasto-plastic constitutive behavior of the asperity based on the finite element method(FEM)is established as a part of the simulation model to precisely analyze the deformation and degradation of the asperity and quickly invoke them in the numerical wear process simulation.The simulation and experimental results show that the piston asperity and the cylinder bore contour converge to a steady state after running-in for about 0.5 h.The distribution of the simulated asperity degradation and wear depth is also verified by the experiment.展开更多
The Chang-63 reservoir in the Huaqing area has widely developed tight sandstone ＂thick sand layers, but not reservoirs characterized by rich in oil＂, and it is thus necessary to further study its oil and gas enrichm...The Chang-63 reservoir in the Huaqing area has widely developed tight sandstone ＂thick sand layers, but not reservoirs characterized by rich in oil＂, and it is thus necessary to further study its oil and gas enrichment law. This study builds porosity and fracture development and evolution models in different deposition environments, through core observation, casting thin section, SEM, porosity and permeability analysis, burial history analysis, and ＂four-property-relationships＂ analysis.展开更多
Developing highly active and robust oxygen evolution reaction(OER)electrocatalysts is still a critical challenge for water electrolyzers and metal-air batteries.Realizing the dynamic evolution of the intermediate and ...Developing highly active and robust oxygen evolution reaction(OER)electrocatalysts is still a critical challenge for water electrolyzers and metal-air batteries.Realizing the dynamic evolution of the intermediate and charge transfer during OER and developing a clear OER mechanism is crucial to design high-performance OER catalysts.Recently in Nature,Xue and colleagues revealed a new OER mechanism,coupled oxygen evolution mechanism(COM),which involves a switchable metal and oxygen redox under light irradiation in nickel oxyhydroxide-based materials.This newly developed mechanism requires a reversible geometric conversion between octahedron(NiO_(6))and square planar(NiO_(4))to achieve electronic states with both“metal redox”and“oxygen redox”during OER.The asymmetric structure endows NR-NiOOH with a nonoverlapping region between the dz^(2) orbitals and a_(1g)^(*)bands,which facilitate the geometric conversion and enact the COM pathway.As a result,NR-NiOOH exhibited better OER activity and stability than the traditional NiOOH.展开更多
The prediction of the wheel wear is a fundamental problem in heavy haul railway. A numerical methodology is introduced to simulate the wheel wear evolution of heavy haul freight car. The methodology includes the spati...The prediction of the wheel wear is a fundamental problem in heavy haul railway. A numerical methodology is introduced to simulate the wheel wear evolution of heavy haul freight car. The methodology includes the spatial coupling dynamics of vehicle and track, the three-dimensional rolling contact analysis of wheel-rail, the Specht's material wear model, and the strategy for reproducing the actual operation conditions of railway. The freight vehicle is treated as a full 3D rigid multi-body model. Every component is built detailedly and various contact interactions between parts are accurately simulated, taking into account the real clearances. The wheel-rail rolling contact calculation is carried out based on Hertz's theory and Kalker's FASTSIM algorithm. The track model is built based on field measurements. The material loss due to wear is evaluated according to the Specht's model in which the wear coefficient varies with the wear intensity. In order to exactly reproduce the actual operating conditions of railway,dynamic simulations are performed separately for all possible track conditions and running velocities in each iterative step.Dimensionless weight coefficients are introduced that determine the ratios of different cases and are obtained through site survey. For the wheel profile updating, an adaptive step strategy based on the wear depth is introduced, which can effectively improve the reliability and stability of numerical calculation. At last, the wear evolution laws are studied by the numerical model for different wheels of heavy haul freight vehicle running in curves. The results show that the wear of the front wheelset is more serious than that of the rear wheelset for one bogie, and the difference is more obvious for the outer wheels. The wear of the outer wheels is severer than that of the inner wheels. The wear of outer wheels mainly distributes near the flange and the root; while the wear of inner wheels mainly distributes around the nominal rolling circle. For the outer wheel of front wheelset of each bogie, the development of wear is gradually concentrated on the flange and the developing speed increases continually with the increase of traveled distance.展开更多
The intraplate uplift of the Qinghai-Tibet Plateau took place on the basis of breakup and assembly of the Precambrian supercontinent, and southward ocean-continent transition of the Proto-, Paleo-, Meso- and Neo-Tethy...The intraplate uplift of the Qinghai-Tibet Plateau took place on the basis of breakup and assembly of the Precambrian supercontinent, and southward ocean-continent transition of the Proto-, Paleo-, Meso- and Neo-Tethys during the Caledonian, Indosinian, Yanshanian and Early Himalayan movements. The intraplate tectonic evolution of the Qinghai-Tibet Plateau underwent the early stage of intraplate orogeny characterized by migrational tectonic uplift, horizontal movement and geological processes during 180-7 Ma, and the late stage of isostatic mountain building characterized by pulsative rapid uplift, vertical movement and geographical processes since 3.6 Ma. The spatial-temporal evolution of the intraplate orogeny within the Qinghai-Tibet Plateau shows a regular transition from the northern part through the central part to the southern part during 180-120 Ma, 65-35 Ma, and 25-7 Ma respectively, with extensive intraplate faulting, folding, block movement, magmatism and metallogenesis. Simultaneous intraplate orogeny and basin formation resulted from crustal rheological stratification and basin-orogen coupling that was induced by lateral viscous flow in the lower crust. This continental dynamic process was controlled by lateral flow of hot and soft materials within the lower crust because of slab dehydration and melted mantle upwelling above the subducted plates during the southward Tethyan ocean-continent transition processes or asthenosphere diapirism. Intraplate orogeny and basin formation were irrelevant to plate collision. The Qinghai-Tibet Plateau as a whole was actually formed by the isostatic mountain building processes since 3.6 Ma that were characterized by crust-scale vertical movement, and integral rapid uplift of the plateau, accompanied by isostatic subsidence of peripheral basins and depressions, and great changes in topography and environment. A series of pulsative mountain building events, associated with gravity equilibrium and isostatic adjustment of crustal materials, at 3.6 Ma, 2.5 Ma, 1.8-1.2 Ma, 0.9-0.8 Ma and 0.15-0.12 Ma led to the formation of a composite orogenic belt by unifying the originally relatively independent Himalayas, Gangdise, Tanghla, Longmenshan, Kunlun, Altyn Tagh, and Qilian mountains, and the formation of the complete Qinghai-Tibet Plateau with a unified mountain root after Miocene uplift of the plateau as a whole.展开更多
The sluggish electron transfer process in the oxygen evolution reaction(OER)greatly restrict the large-scale application of water electrolysis for hydrogen generation.The modification of the electronic states around t...The sluggish electron transfer process in the oxygen evolution reaction(OER)greatly restrict the large-scale application of water electrolysis for hydrogen generation.The modification of the electronic states around the Fermi level of the electrocatalysts is significant for accelerating the sluggish OER kinetics.So far,the OER kinetics solely involve either an adsorbate evolution mechanism(AEM),or a lattice oxygen oxidation mechanism(LOM).In a paper recently published in Nature,Xue and coworkers report an electron transfer mechanism that involves a switchable AEM and LOM in nickel-oxyhydroxide-based materials triggered by the light[1].In contrast with previously reported electrocatalysts,the electrocatalyst proceeding through this mechanism shows a better OER activity.Hence,the reported light-triggered mechanism that couples AEM and LOM pioneers an innovative pathway towards the exploration of OER kinetics.展开更多
Replacing the challenging water oxidation with thermodynamically favorable organic oxidation presents a promising strategy for the efficient simultaneous production of hydrogen and value-added chemicals.However,photoc...Replacing the challenging water oxidation with thermodynamically favorable organic oxidation presents a promising strategy for the efficient simultaneous production of hydrogen and value-added chemicals.However,photocatalytic activity is hindered by inefficient separation of photogenerated electron-hole pairs and limited redox active sites.Herein,Fe/ZnIn_(2)S_(4)/Ni(Fe/ZIS/Ni)micro heterojunctions were rationally engineered for synergistically photocatalytic hydrogen evolution and selective oxidation of benzylamine.Using Fe-based metal-organic frameworks(MIL-88A)as the self-etching morphology template and iron source,ZIS was grown in situ to obtain Fe-doped ZIS(Fe/ZIS).Then nickel was introduced into Fe/ZIS to locally construct Ni-doped ZIS(ZIS/Ni)microregion,thereby forming numerous microscopic heterojunctions(Fe/ZIS/Ni).The introduction of Fe effectively lowers the energy band(EB)position of Fe/ZIS,while the introduction of Ni elevates the EB position of ZIS/Ni microregion.Such difference in the EB structures of Fe/ZIS and ZIS/Ni promote the formation of local electric field,effectively suppresses the recombination of photogenerated carriers and enhances their efficient separation and migration.Moreover,the nanosheet assembly structure increases the availability of active sites and enhances the uptake of reactants.The optimized Fe/ZIS/Ni catalyst achieves remarkable hydrogen evolution and N-benzylidenebenzylamine(NBI)production rates of 7.9 and 6.8 mmol·g^(-1)·h^(-1),respectively.Additionally,the selectivity for the oxidation of benzylamine to NBI exceeds 95%.This work establishes a novel design paradigm for developing high-performance photocatalytic systems that integrate renewable H2 production with selective organic transformations.展开更多
Photocatalytic hydrogen evolution coupled with organic oxidation holds great promise for converting solar energy into high-valueadded chemicals,but it is hampered by sluggish charge dynamics and limited redox potentia...Photocatalytic hydrogen evolution coupled with organic oxidation holds great promise for converting solar energy into high-valueadded chemicals,but it is hampered by sluggish charge dynamics and limited redox potential.Herein,a porous S-doped carbon nitride(S-C_(3)N_(4−y))foam assembled from ultrathin nanosheets with rich nitrogen vacancies was synthesized using a molecular selfassembly strategy.The S dopants and N vacancies synergistically adjusted the band structure,facilitating light absorption and enhancing the oxidation ability.Moreover,the ultrathin nanosheets and porous structure provided more exposed active sites and facilitated mass and charge transfer.Consequently,S-C_(3)N_(4−y)foam exhibited enhanced photocatalytic activities for synchronous hydrogen evolution(4960μmol/(h·g))and benzylamine oxidation to N-benzylidenebenzylamine(4885μmol/(h·g))with high selectivity of>99%,which were approximately 17.6 and 72.9 times higher than those of bulk CN,respectively.The photocatalytic coupling pairing reaction promotes the water splitting by consuming H2O2,thereby improving the hydrogen evolution efficiency and achieving the production of high value-added imines.This study provides an effective route for regulating the morphology and band structure of carbon nitride for synthesizing highly valuable chemicals.展开更多
基金financially supported by the National Key Research and Development Program of China(No.2018YFB2001101)the National Outstanding Youth Science Foundation of China(No.51922093)the National Natural Science Foundation of China(No.51890882).
文摘The wear condition of the piston/cylinder pair is crucial to the performance and reliability of the axial piston pump.The hard piston surface,the soft cylinder bore surface,and the interface oil film affects each other during the wear process.Specifically,in the mixed lubrication region,the geometry of the hard piston surface asperity directly affects the wear of soft cylinder bore surface,while the asperities may deform or even degrade when penetrating and sliding against the cylinder bore.So far,there is no suitable method to simulate their coupled evolution.This paper proposed a wear process simulation model considering the real-time interaction between the elasto-plastic deformation of the piston surface asperity,the wear contour of the cylinder bore,and the lubrication condition of the interface.An offline library of the elasto-plastic constitutive behavior of the asperity based on the finite element method(FEM)is established as a part of the simulation model to precisely analyze the deformation and degradation of the asperity and quickly invoke them in the numerical wear process simulation.The simulation and experimental results show that the piston asperity and the cylinder bore contour converge to a steady state after running-in for about 0.5 h.The distribution of the simulated asperity degradation and wear depth is also verified by the experiment.
文摘The Chang-63 reservoir in the Huaqing area has widely developed tight sandstone ＂thick sand layers, but not reservoirs characterized by rich in oil＂, and it is thus necessary to further study its oil and gas enrichment law. This study builds porosity and fracture development and evolution models in different deposition environments, through core observation, casting thin section, SEM, porosity and permeability analysis, burial history analysis, and ＂four-property-relationships＂ analysis.
基金supported by the National Natural Science Foundation of China(52122308,21905253,51973200).
文摘Developing highly active and robust oxygen evolution reaction(OER)electrocatalysts is still a critical challenge for water electrolyzers and metal-air batteries.Realizing the dynamic evolution of the intermediate and charge transfer during OER and developing a clear OER mechanism is crucial to design high-performance OER catalysts.Recently in Nature,Xue and colleagues revealed a new OER mechanism,coupled oxygen evolution mechanism(COM),which involves a switchable metal and oxygen redox under light irradiation in nickel oxyhydroxide-based materials.This newly developed mechanism requires a reversible geometric conversion between octahedron(NiO_(6))and square planar(NiO_(4))to achieve electronic states with both“metal redox”and“oxygen redox”during OER.The asymmetric structure endows NR-NiOOH with a nonoverlapping region between the dz^(2) orbitals and a_(1g)^(*)bands,which facilitate the geometric conversion and enact the COM pathway.As a result,NR-NiOOH exhibited better OER activity and stability than the traditional NiOOH.
基金Project(U1234211)supported of the National Natural Science Foundation of ChinaProject(20120009110020)supported by the Specialized Research Fund for Ph.D. Programs of Foundation of Ministry of Education of ChinaProject(SHGF-11-32)supported the Scientific and Technological Innovation Project of China Shenhua Energy Company Limited
文摘The prediction of the wheel wear is a fundamental problem in heavy haul railway. A numerical methodology is introduced to simulate the wheel wear evolution of heavy haul freight car. The methodology includes the spatial coupling dynamics of vehicle and track, the three-dimensional rolling contact analysis of wheel-rail, the Specht's material wear model, and the strategy for reproducing the actual operation conditions of railway. The freight vehicle is treated as a full 3D rigid multi-body model. Every component is built detailedly and various contact interactions between parts are accurately simulated, taking into account the real clearances. The wheel-rail rolling contact calculation is carried out based on Hertz's theory and Kalker's FASTSIM algorithm. The track model is built based on field measurements. The material loss due to wear is evaluated according to the Specht's model in which the wear coefficient varies with the wear intensity. In order to exactly reproduce the actual operating conditions of railway,dynamic simulations are performed separately for all possible track conditions and running velocities in each iterative step.Dimensionless weight coefficients are introduced that determine the ratios of different cases and are obtained through site survey. For the wheel profile updating, an adaptive step strategy based on the wear depth is introduced, which can effectively improve the reliability and stability of numerical calculation. At last, the wear evolution laws are studied by the numerical model for different wheels of heavy haul freight vehicle running in curves. The results show that the wear of the front wheelset is more serious than that of the rear wheelset for one bogie, and the difference is more obvious for the outer wheels. The wear of the outer wheels is severer than that of the inner wheels. The wear of outer wheels mainly distributes near the flange and the root; while the wear of inner wheels mainly distributes around the nominal rolling circle. For the outer wheel of front wheelset of each bogie, the development of wear is gradually concentrated on the flange and the developing speed increases continually with the increase of traveled distance.
基金supported by the China National Science Foundation (Grant No: 40572113)China national key basic research program for earlier stage study (Grant No: 2005CCA05600)
文摘The intraplate uplift of the Qinghai-Tibet Plateau took place on the basis of breakup and assembly of the Precambrian supercontinent, and southward ocean-continent transition of the Proto-, Paleo-, Meso- and Neo-Tethys during the Caledonian, Indosinian, Yanshanian and Early Himalayan movements. The intraplate tectonic evolution of the Qinghai-Tibet Plateau underwent the early stage of intraplate orogeny characterized by migrational tectonic uplift, horizontal movement and geological processes during 180-7 Ma, and the late stage of isostatic mountain building characterized by pulsative rapid uplift, vertical movement and geographical processes since 3.6 Ma. The spatial-temporal evolution of the intraplate orogeny within the Qinghai-Tibet Plateau shows a regular transition from the northern part through the central part to the southern part during 180-120 Ma, 65-35 Ma, and 25-7 Ma respectively, with extensive intraplate faulting, folding, block movement, magmatism and metallogenesis. Simultaneous intraplate orogeny and basin formation resulted from crustal rheological stratification and basin-orogen coupling that was induced by lateral viscous flow in the lower crust. This continental dynamic process was controlled by lateral flow of hot and soft materials within the lower crust because of slab dehydration and melted mantle upwelling above the subducted plates during the southward Tethyan ocean-continent transition processes or asthenosphere diapirism. Intraplate orogeny and basin formation were irrelevant to plate collision. The Qinghai-Tibet Plateau as a whole was actually formed by the isostatic mountain building processes since 3.6 Ma that were characterized by crust-scale vertical movement, and integral rapid uplift of the plateau, accompanied by isostatic subsidence of peripheral basins and depressions, and great changes in topography and environment. A series of pulsative mountain building events, associated with gravity equilibrium and isostatic adjustment of crustal materials, at 3.6 Ma, 2.5 Ma, 1.8-1.2 Ma, 0.9-0.8 Ma and 0.15-0.12 Ma led to the formation of a composite orogenic belt by unifying the originally relatively independent Himalayas, Gangdise, Tanghla, Longmenshan, Kunlun, Altyn Tagh, and Qilian mountains, and the formation of the complete Qinghai-Tibet Plateau with a unified mountain root after Miocene uplift of the plateau as a whole.
基金National Natural Science Foundation of China(No.61705063 and No.51974113)Natural Science Foundation of Heilongjiang Province(No.LH2022F051)Basic Scientific Research Fund of Provincial Universities of Heilongjiang(No.2021KYYWF1466).
文摘The sluggish electron transfer process in the oxygen evolution reaction(OER)greatly restrict the large-scale application of water electrolysis for hydrogen generation.The modification of the electronic states around the Fermi level of the electrocatalysts is significant for accelerating the sluggish OER kinetics.So far,the OER kinetics solely involve either an adsorbate evolution mechanism(AEM),or a lattice oxygen oxidation mechanism(LOM).In a paper recently published in Nature,Xue and coworkers report an electron transfer mechanism that involves a switchable AEM and LOM in nickel-oxyhydroxide-based materials triggered by the light[1].In contrast with previously reported electrocatalysts,the electrocatalyst proceeding through this mechanism shows a better OER activity.Hence,the reported light-triggered mechanism that couples AEM and LOM pioneers an innovative pathway towards the exploration of OER kinetics.
基金supported by the National Key R&D Program of China(No.2022YFA1503003)the National Natural Science Foundation of China(No.22271081)+2 种基金the Postdoctoral Science Foundation of Heilongjiang Province(No.LBH-Z22240)the Basic Research Fund of Heilongjiang University in Heilongjiang Province(No.2022-KYYWF-1060)the Heilongjiang University Excellent Youth Foundation.
文摘Replacing the challenging water oxidation with thermodynamically favorable organic oxidation presents a promising strategy for the efficient simultaneous production of hydrogen and value-added chemicals.However,photocatalytic activity is hindered by inefficient separation of photogenerated electron-hole pairs and limited redox active sites.Herein,Fe/ZnIn_(2)S_(4)/Ni(Fe/ZIS/Ni)micro heterojunctions were rationally engineered for synergistically photocatalytic hydrogen evolution and selective oxidation of benzylamine.Using Fe-based metal-organic frameworks(MIL-88A)as the self-etching morphology template and iron source,ZIS was grown in situ to obtain Fe-doped ZIS(Fe/ZIS).Then nickel was introduced into Fe/ZIS to locally construct Ni-doped ZIS(ZIS/Ni)microregion,thereby forming numerous microscopic heterojunctions(Fe/ZIS/Ni).The introduction of Fe effectively lowers the energy band(EB)position of Fe/ZIS,while the introduction of Ni elevates the EB position of ZIS/Ni microregion.Such difference in the EB structures of Fe/ZIS and ZIS/Ni promote the formation of local electric field,effectively suppresses the recombination of photogenerated carriers and enhances their efficient separation and migration.Moreover,the nanosheet assembly structure increases the availability of active sites and enhances the uptake of reactants.The optimized Fe/ZIS/Ni catalyst achieves remarkable hydrogen evolution and N-benzylidenebenzylamine(NBI)production rates of 7.9 and 6.8 mmol·g^(-1)·h^(-1),respectively.Additionally,the selectivity for the oxidation of benzylamine to NBI exceeds 95%.This work establishes a novel design paradigm for developing high-performance photocatalytic systems that integrate renewable H2 production with selective organic transformations.
基金the National Key Research and Development Program of China(No.2022YFA1503003)the National Natural Science Foundation of China(Nos.U20A20250 and 22271081)+1 种基金the Natural Science Foundation of Heilongjiang Province(No.ZD2021B003)the University Nursing Program for Young Scholars with Creative Talents in Heilongjiang Province(No.UNPYSCT-2020004).
文摘Photocatalytic hydrogen evolution coupled with organic oxidation holds great promise for converting solar energy into high-valueadded chemicals,but it is hampered by sluggish charge dynamics and limited redox potential.Herein,a porous S-doped carbon nitride(S-C_(3)N_(4−y))foam assembled from ultrathin nanosheets with rich nitrogen vacancies was synthesized using a molecular selfassembly strategy.The S dopants and N vacancies synergistically adjusted the band structure,facilitating light absorption and enhancing the oxidation ability.Moreover,the ultrathin nanosheets and porous structure provided more exposed active sites and facilitated mass and charge transfer.Consequently,S-C_(3)N_(4−y)foam exhibited enhanced photocatalytic activities for synchronous hydrogen evolution(4960μmol/(h·g))and benzylamine oxidation to N-benzylidenebenzylamine(4885μmol/(h·g))with high selectivity of>99%,which were approximately 17.6 and 72.9 times higher than those of bulk CN,respectively.The photocatalytic coupling pairing reaction promotes the water splitting by consuming H2O2,thereby improving the hydrogen evolution efficiency and achieving the production of high value-added imines.This study provides an effective route for regulating the morphology and band structure of carbon nitride for synthesizing highly valuable chemicals.
