The objective of this paper is to propose and illustrate feasibility, approach, validation as per prevailing codes and design standards, specification to rehabilitate bridge pier cap by using Ultra-High Performance Co...The objective of this paper is to propose and illustrate feasibility, approach, validation as per prevailing codes and design standards, specification to rehabilitate bridge pier cap by using Ultra-High Performance Concrete (UHPC). The evaluation of existing pier caps and bearings indicates that the complete removal of existing bearing is undesirable due to 1) massive size of bearing 2) difficulty in cutting through the thick components of existing bearing 3) deeply anchored lower shoe of existing bearings 4) huge cost and time required to erect temporary support system for superstructure to facilitate the construction of new piers. To overcome these difficulties, UHPC could be cast around the lower shoe up to the existing bearing pin. This UHPC cast could be used to support jacks and temporary bearings. The new low height permanent bearing could then be installed after removing the upper shoe of the existing bearing. In the present research, first properties of UHPC are summarized followed by evaluation of case studies to check feasibility of the solution to rehabilitate pier cap by using UHPC. The complex load paths in pier cap are idealized by using validated strut and tie model as per prevailing AASHTO LRFD Bridge Design Specification.展开更多
We developed ultra-high performance concrete(UHPC)incorporating mullite sand and brown corundum sand(BCS),and the quartz sand UHPC was utilized to prepare for comparison.The properties of compressive strength,elastic ...We developed ultra-high performance concrete(UHPC)incorporating mullite sand and brown corundum sand(BCS),and the quartz sand UHPC was utilized to prepare for comparison.The properties of compressive strength,elastic modulus,ultrasonic pulse velocity,flexural strength,and toughness were investigated.Scanning electron microscopy and nanoindentation were also conducted to reveal the underlying mechanisms affecting macroscopic performance.Due to the superior interface bonding properties between mullite sand and matrix,the compressive strength and flexural toughness of UHPC have been significantly improved.Mullite sand and BCS aggregates have higher stiffness than quartz sand,contributing to the excellent elastic modulus exhibited by UHPC.The stiffness and volume of aggregates have a more significant impact on the elastic modulus of UHPC than interface performance,and the latter contributes more to the strength of UHPC.This study will provide a reference for developing UHPC with superior elastic modulus for structural engineering.展开更多
Interactive holography offers unmatched levels of immersion and user engagement in the field of future display.Despite of the substantial progress has been made in dynamic meta-holography,the realization of real-time,...Interactive holography offers unmatched levels of immersion and user engagement in the field of future display.Despite of the substantial progress has been made in dynamic meta-holography,the realization of real-time,highly smooth interactive holography remains a significant challenge due to the computational and display frame rate limitations.In this study,we introduced a dynamic interactive bitwise meta-holography with ultra-high computational and display frame rates.To our knowledge,this is the first reported practical dynamic interactive metasurface holographic system.We spa-tially divided the metasurface device into multiple distinct channels,each projecting a reconstructed sub-pattern.The switching states of these channels were mapped to bitwise operations on a set of bit values,which avoids complex holo-gram computations,enabling an ultra-high computational frame rate.Our approach achieves a computational frame rate of 800 kHz and a display frame rate of 23 kHz on a low-power Raspberry Pi computational platform.According to this methodology,we demonstrated an interactive dynamic holographic Tetris game system that allows interactive gameplay,color display,and on-the-fly hologram creation.Our technology presents an inspiration for advanced dynamic meta-holography,which is promising for a broad range of applications including advanced human-computer interaction,real-time 3D visualization,and next-generation virtual and augmented reality systems.展开更多
Reinforcement corrosion is the main cause of performance deterioration of reinforced concrete(RC)structures.Limited research has been performed to investigate the life-cycle cost(LCC)of coastal bridge piers with nonun...Reinforcement corrosion is the main cause of performance deterioration of reinforced concrete(RC)structures.Limited research has been performed to investigate the life-cycle cost(LCC)of coastal bridge piers with nonuniform corrosion using different materials.In this study,a reliability-based design optimization(RBDO)procedure is improved for the design of coastal bridge piers using six groups of commonly used materials,i.e.,normal performance concrete(NPC)with black steel(BS)rebar,high strength steel(HSS)rebar,epoxy coated(EC)rebar,and stainless steel(SS)rebar(named NPC-BS,NPC-HSS,NPC-EC,and NPC-SS,respectively),NPC with BS with silane soakage on the pier surface(named NPC-Silane),and high-performance concrete(HPC)with BS rebar(named HPC-BS).First,the RBDO procedure is improved for the design optimization of coastal bridge piers,and a bridge is selected to illustrate the procedure.Then,reliability analysis of the pier designed with each group of materials is carried out to obtain the time-dependent reliability in terms of the ultimate and serviceability performances.Next,the repair time of the pier is predicted based on the time-dependent reliability indices.Finally,the time-dependent LCCs for the pier are obtained for the selection of the optimal design.展开更多
An accurate mapping and understanding of remaining oil distribution is very important for water control and stabilize oil production of mature oilfields in ultra-high water-cut stage.Currently,the Tuo-21 Fault Block o...An accurate mapping and understanding of remaining oil distribution is very important for water control and stabilize oil production of mature oilfields in ultra-high water-cut stage.Currently,the Tuo-21 Fault Block of the Shengtuo Oilfield has entered the stage of ultra-high water cut(97.2%).Poor adaptability of the well pattern,ineffective water injection cycle and low efficiency of engineering measures(such as workover,re-perforation and utilization of high-capacity pumps)are the significant problems in the ultra-high water-cut reservoir.In order to accurately describe the oil and water flow characteristics,relative permeability curves at high water injection multiple(injected pore volume)and a semiquantitative method is applied to perform fine reservoir simulation of the Sand group 3e7 in the Block.An accurate reservoir model is built and history matching is performed.The distribution characteristics of remaining oil in lateral and vertical directions are quantitatively simulated and analyzed.The results show that the numerical simulation considering relative permeability at high injection multiple can reflect truly the remaining oil distribution characteristics after water flooding in an ultrahigh water-cut stage.The distribution of remaining oil saturation can be mapped more accurately and quantitatively by using the‘four-points and five-types’classification method,providing a basis for potential tapping of various remaining oil types of oil reservoirs in late-stage of development with high water-cut.展开更多
Ultra-high nickel cobalt-free lithium layered oxides are promising cathode material for lithium-ion batteries(LIBs)because of their relatively high capacity and low cost.Nevertheless,the high nickel content would indu...Ultra-high nickel cobalt-free lithium layered oxides are promising cathode material for lithium-ion batteries(LIBs)because of their relatively high capacity and low cost.Nevertheless,the high nickel content would induce bulk structure degradation and interfacial environment deterioration,and the absence of Co element reduces the lithium diffusion kinetics,severely limiting the performance liberation of this kind of cathodes.Herein,a multifunctional Ti/Zr dual cation co-doping strategy has been employed to improve the lithium storage performance of LiNi_(0.9)Mn_(0.1)O_(2)(NM91)cathode.On the one hand,the Ti/Zr co-doping weakens the Li^(+)/Ni^(2+)mixing through magnetic interactions due to the inexistence of unpaired electrons for Ti^(4+)and Zr^(4+),increasing the lithium diffusion rate and suppressing the harmful coexistence of H1 and H2 phases.On the other hand,they enhance the lattice oxygen stability because of the strong Ti-O and Zr-O bonds,inhibiting the undesired H3 phase transition and lattice oxygen loss,improving the bulk structure and cathode-electrolyte interface stability.As a result,the Ti/Zr co-doped NM91(NMTZ)exhibits a 91.2%capacity retention rate after 100 cycles,while that of NM91 is only82.9%.Also,the NMTZ displays better rate performance than NM91 with output capacities of 115 and93 mA h g^(-1)at a high current density of 5 C,respectively.Moreover,the designed NMTZ could enable the full battery to deliver an energy density up to 263 W h kg^(-1),making the ultra-high nickel cobaltfree lithium layered oxide cathode closer to practical applications.展开更多
Local scour around bridge piers and abutments is one of the most significant causes of bridge failure.Despite a plethora of studies on scour around individual bridge piers or abutments,few studies have focused on the ...Local scour around bridge piers and abutments is one of the most significant causes of bridge failure.Despite a plethora of studies on scour around individual bridge piers or abutments,few studies have focused on the joint impact of a pier and an abutment in proximity to one another on scour.This study conducted laboratory experiments and flow analyses to examine the interaction of piers and abutments and their effect on clear-water scour.The experiments were conducted in a rectangular laboratory flume.They included 18 main tests(with a combination of different types of piers and abutments)and five control tests(with individual piers or abutments).Three pier types(a rectangular pier with a rounded edge,a group of three cylindrical piers,and a single cylindrical pier)and two abutment types(a wingewall abutment and a semicircular abutment)were used.An acoustic Doppler velocimeter was used to measure the three-dimensional flow velocity for analyses of streamline,velocity magnitude,vertical velocity,and bed shear stress.The results showed that the velocity near the pier and abutment increased by up to 80%.The maximum scour depth around the abutment increased by up to 19%.In contrast,the maximum scour depth around the pier increased significantly by up to l71%.The presence of the pier in the vicinity of the abutment led to an increase in the scour hole volume by up to 87%relative to the case with a solitary abutment.Empirical equations were also derived to accurately estimate the maximum scour depth at the pier adjacent to the abutment.展开更多
The seismic behavior of horizontally curved bridges,particularly with unequal height piers,is more complicated than that of straight bridges due to their geometric properties.In this study,the seismic responses of sev...The seismic behavior of horizontally curved bridges,particularly with unequal height piers,is more complicated than that of straight bridges due to their geometric properties.In this study,the seismic responses of several horizontally curved single-column-bent viaducts with various degrees of curvature and different pier heights have been investigated,employing three different analysis approaches:namely,modal pushover analysis,uniform load method,and nonlinear time history analysis.Considering the investigated bridge configurations and utilizing the most common regularity indices,the results indicate that viaducts with 45-degree and 90-degree deck subtended angles can be categorized as regular and moderately irregular,respectively,while the bridges with 180-degree deck subtended angle are found to be highly irregular.Furthermore,the viaducts whose pier heights are asymmetric may be considered as irregular for almost all ranges of the deck subtended angles.The effects of higher transverse and longitudinal modes are discussed and the minimum analysis requirements are identified to assess the seismic response of such bridge configurations for design purposes.Although the Regularity Indices used here are useful tools to distinguish between regular and irregular bridges,further studies are needed to improve their reliability.展开更多
The deterioration of the performance of offshore bridges is particularly prominent due to the complex natural environment,including the coupling effects of earthquake and seawater erosion.In particular,bridge piers ar...The deterioration of the performance of offshore bridges is particularly prominent due to the complex natural environment,including the coupling effects of earthquake and seawater erosion.In particular,bridge piers are the main energy-consuming and load-bearing components,so that excellent seismic capacity of bridge piers is the key to avoiding bridge damage.Although earthquake resistant behavior of ordinary reinforced concrete bridge piers(ordinary pier)can be improved by increasing the section size and reinforcement ratio of piers,the improvement of the earthquake resistant behavior is limited.To further improve the earthquake resistant behavior of bridge piers,high-tensile reinforcement engineered cementitious composite(ECC)bridge piers are utilized and time-varying seismic fragility analysis are conducted in this study.The refined model of a bridge pier is built by OpenSees.First,the influence of ECC replacement height on pier curvature is analyzed to determine the reasonable ECC height.Then,the time-varying fragility analysis of high-tensile reinforcement ECC piers(ECC composite piers)with durability damage are evaluated considering the time-varying law of materials.Four damage states,slight damage,moderate damage,extensive damage and complete collapse,are utilized in the study.These fragility curves indicate the durability damage can debase the earthquake resistant behavior of piers continually,the exceedance probability of the same state of destruction increases with the increase of peak ground acceleration(PGA)and service time of pier.The results also indicate that the corrosion level of chloride ion to pier is small during the early service period,and the bridge pier vulnerable curve is similar to that of the new bridge pier.As the level of chlorine ion corrosion deepens,transcendental probability is increased.Compared with the ordinary pier,the exceedance probability in each limit state of ECC composite piers is significantly reduced.The proposed ECC composite pies leads to better realistic time-varying earthquake resistant behavior.展开更多
Conventional reinforced concrete piers are vulnerable to severe compressive damage under strong earthquake conditions and are difficult to quickly rehabilitate.This paper develops a new type of composite pier,consisti...Conventional reinforced concrete piers are vulnerable to severe compressive damage under strong earthquake conditions and are difficult to quickly rehabilitate.This paper develops a new type of composite pier,consisting of ultra-high-performance concrete(UHPC)and reinforced concrete(RC).This UHPC-RC composite pier uses a UHPC cover outside of an RC core to achieve a high load-carrying capacity and mitigate compressive damage.An experiment is performed to evaluate the performance of the UHPC-RC composite pier under cyclic deformation.The crack development,ultimate failure modes,and load-carrying capacities of the pier are observed.Because of the extraordinary compressive strength of UHPC,the composite pier suffers little compressive damage under large lateral deformations.The composite pier fails as a result of fracturing of the reinforcement.A numerical model is developed to reproduce the cyclic behavior of the composite pier.On the basis of the verified numerical model,a parametric analysis is used to investigate the influence of the thickness of the UHPC cover and the axial load ratio.Finally,an approach is recommended for designing composite piers.展开更多
Various regions are becoming increasingly vulnerable to the increased frequency of floods due to the recent changes in climate and precipitation patterns throughout the world.As a result,specific infrastructures,notab...Various regions are becoming increasingly vulnerable to the increased frequency of floods due to the recent changes in climate and precipitation patterns throughout the world.As a result,specific infrastructures,notably bridges,would experience significant flooding for which they were not intended and would be submerged.The flow field and shear stress distribution around tandem bridge piers under pressurized flow conditions for various bridge deck widths are examined using a series of three-dimensional(3D)simulations.It is indicated that scenarios with a deck width to pier diameter(Ld/p)ratio of 3 experience the highest levels of turbulent disturbance.In addition,maximum velocity and shear stresses occur in cases with Ld/p equal to 6.Results indicate that increasing the number of piers from 1 to 2 and 3 results in the increase of bed shear stress by 24%and 20%respectively.Finally,five machine learning algorithms,including Decision Trees(DT),Feed Forward Neural Networks(FFNN),and three Ensemble models,are implemented to estimate the flow field and the turbulent structure.Results indicated that the highest accuracy for estimation of U,and W,were obtained using AdaBoost ensemble with R2=0.946 and 0.951,respectively.Besides,the Random Forest algorithm outperformed AdaBoost slightly in the estimation of V and turbulent kinetic energy(TKE)with R2=0.894 and 0.951,respectively.展开更多
Polymer gels have been accepted as a useful tool to address many sealing operations such as drilling and completion,well stimulation,wellbore integrity,water and gas shutoff,etc.Previously,we developed an ultra-high s...Polymer gels have been accepted as a useful tool to address many sealing operations such as drilling and completion,well stimulation,wellbore integrity,water and gas shutoff,etc.Previously,we developed an ultra-high strength gel(USGel)for medium to ultra-low temperature reservoirs.However,the removal of USGel is a difficult problem for most temporary plugging operations.This paper first provides new insights into the mechanism of USGel,where multistage network structure and physical entanglement are the main reasons for USGel possessing ultra-high strength.Then the effects of acid breakers,encapsulated breakers,and oxidation breakers(including H_(2)O_(2),Na_(2)S_(2)O_(8),Ca(ClO)_(2),H_(2)O_(2)+NaOH,Na_(2)S_(2)O_(8)+NaOH,and Ca(ClO)_(2)+NaOH)were evaluated.The effects of component concentration and temperature on the breaking solution were studied,and the corrosion performance,physical simulation and formation damage tests of the breaking solution were carried out.The final formulation of 2%-4%NaOH+4.5%-6%H_(2)O_(2) breaking solution was determined,which can make USGel completely turn into water at 35e105C.The combinations of“acid t breaking solution”,“acid+encapsulated breaker”and“encapsulated breaker+breaking solution”were evaluated for breaking effect.The acid gradually reduced the volume of USGel,which increased the contact area between breaking solution and USGel,and the effect of“4%acid+breaking solution”was 23 times higher than that of breaking solution alone at 35C.However,the acid significantly reduced the strength of USGel.This paper provides new insights into the breaking of high-strength gels with complex network structures.展开更多
Considering the desirable behavior of concrete filled steel tube(CFT)columns and the complicated behavior of segmental double-column piers under cyclic loads,three post-tensioned precast segmental CFT double-column pi...Considering the desirable behavior of concrete filled steel tube(CFT)columns and the complicated behavior of segmental double-column piers under cyclic loads,three post-tensioned precast segmental CFT double-column pier specimens were tested to extend their application in moderate and high seismicity areas.The effects of the number of CFT segments and the steel endplates as energy dissipaters on the seismic behavior of the piers were evaluated.The experimental results show that the segmental piers exhibited stable hysteretic behavior with small residual displacements under cyclic loads.All the tested specimens achieved a drift ratio no less than 13%without significant damage and strength deterioration due to the desirable behavior of CFT columns.Since the deformation of segmental columns was mainly concentrated at the column-footing interfaces,the increase of the segment numbers for each column had no obvious effects on the loading capacity but reduced the initial stiffness of the specimens.The use of steel endplates improved the bearing capacity,stiffness and energy dissipation of segmental piers,but weakened their self-centering capacity.Fiber models were also proposed to simulate the hysteretic behavior of the tested specimens,and the influences of segment numbers and prestress levels on seismic behavior were further studied.展开更多
An in-depth understanding of the structure-activity relationship between the surface structure,chemical composition,adsorption and desorption of molecules,and their reaction activity and selectivity is necessary for t...An in-depth understanding of the structure-activity relationship between the surface structure,chemical composition,adsorption and desorption of molecules,and their reaction activity and selectivity is necessary for the rational design of high-performance catalysts.Herein,we present a method for studying catalytic mechanisms using a combination of in situ reaction cells and surface science techniques.The proposed system consists of four parts:preparation chamber,temperatureprogrammed desorption(TPD)chamber,quick load-lock chamber,and in situ reaction cell.The preparation chamber was equipped with setups based on the surface science techniques used for standard sample preparation and characterization,including an Ar+sputter gun,Auger electron spectrometer,and a low-energy electron diffractometer.After a well-defined model catalyst was prepared,the sample was transferred to a TPD chamber to investigate the adsorption and desorption of the probe molecule,or to the reaction cell,to measure the catalytic activity.A thermal desorption experiment for methanol on a clean Cu(111)surface was conducted to demonstrate the functionality of the preparation and TPD chambers.Moreover,the repeatability of the in situ reaction cell experiment was verified by CO_(2) hydrogenation on the Ni(110)surface.At a reaction pressure of 800 Torr at 673 K,turnover frequencies for the methanation reaction and reverse water-gas shift reaction were 0.15 and 7.55 Ni atom^(-1) s^(-1),respectively.展开更多
This study aims to clarify the effects of curing regimes and lightweight aggregate(LWA)on the morphology, width and mechanical properties of the interfacial transition zone(ITZ) of ultra-high performance concrete(UHPC...This study aims to clarify the effects of curing regimes and lightweight aggregate(LWA)on the morphology, width and mechanical properties of the interfacial transition zone(ITZ) of ultra-high performance concrete(UHPC), and provide reference for the selection of lightweight ultra-high performance concrete(L-UHPC) curing regimes and the pre-wetting degree LWA. The results show that, under the three curing regimes(standard curing, steam curing and autoclaved curing), LWA is tightly bound to the matrix without obvious boundaries. ITZ width increases with the water absorption of LWA and decreases with increasing curing temperature. The ITZ microhardness is the highest when water absorption is 3%, and the microhardness value is more stable with the distance from LWA. Steam and autoclaved curing increase ITZ microhardness compared to standard curing. As LWA pre-wetting and curing temperatures increase, the degree of hydration at the ITZ increases, generating high-density CSH(HD CSH) and ultra-high-density CSH(UHD CSH), and reducing unhydrated particles in ITZ. ITZ micro-mechanical properties are optimized due to hydration products being denser.展开更多
Ultra-high temperature ceramic coatings have ultra-high melting points,excellent mechanical properties and high temperature ablation resistance.These unique performance combinations turn it into a promising material f...Ultra-high temperature ceramic coatings have ultra-high melting points,excellent mechanical properties and high temperature ablation resistance.These unique performance combinations turn it into a promising material for use in extreme environment structures in rockets and hypersonic vehicles,particularly nozzles,leading edges and engine components.In this paper,various preparation methods of ultra-high temperature ceramic coatings were reviewed,including plasma spraying,chemical vapor deposition,pack cementation,slurry sintering,hot pressing and their research progress.Meanwhile,some new preparation methods of high temperature coatings,such as ion beam deposition,ultrasonic spraying,metal organic frame work coating,and magnetron sputtering,were introduced.The development trend of ultra-high temperature coatings was prospected as well.展开更多
[Objectives]This study was conducted to establish an uncertainty evaluation method for the determination of ethyl maltol by ultra-high performance liquid chromatograph-mass spectrometer(UPLC-MS).[Methods]A mathematica...[Objectives]This study was conducted to establish an uncertainty evaluation method for the determination of ethyl maltol by ultra-high performance liquid chromatograph-mass spectrometer(UPLC-MS).[Methods]A mathematical model of uncertainty was established by analyzing the method for determining ethyl maltol using UPLC-MS.The sources of uncertainty were analyzed,and the components of uncertainty were calculated to evaluate the expanded uncertainty of the method.[Results]When the content of ethyl maltol in edible vegetable oil was 1657μg/kg,the expanded uncertainty was 22.4μg/kg(K=2,P=95%).[Conclusions]The uncertainty in this evaluation model mainly came from standard solution preparation,sample weighing,dilution of sample to constant volume,standard curve fitting,and repeated measurement.展开更多
A two-dimensional mathematical model is used to simulate the influence of water flow on the piers of a bridge for different incidence angles.In particular,a finite volume method is used to discretize the Navier-Stokes...A two-dimensional mathematical model is used to simulate the influence of water flow on the piers of a bridge for different incidence angles.In particular,a finite volume method is used to discretize the Navier-Stokes control equations and calculate the circumferential pressure coefficient distribution on the bridge piers’surface.The results show that the deflection of the flow is non-monotonic.It first increases and then decreases with an increase in the skew angle.展开更多
Hidden by several layers of white paint,the almost forgotten polychromy of Nervi’s exhibition halls emerges from historical images,not necessarily intended to document the complex,but rather as a setting for exhibiti...Hidden by several layers of white paint,the almost forgotten polychromy of Nervi’s exhibition halls emerges from historical images,not necessarily intended to document the complex,but rather as a setting for exhibitions,fairs or film and advertising sets.Historical documentation reveals Nervi’s presence on the building site and his desire to supervise the finishing phases.The first stratigraphic investigations also testify to his attention color,as well as the subsequent transformations of use.Specific theoretical and technical issues regarding the conservation of the pictorial layers in relation to the conservation of the reinforced concrete elements are outlined.Furthermore,the use of polychromy in combination with the original employment of natural and artificial light sources introduces new facets into the analysis of Nervi’s work,offering the opportunity for original reflection.This is particularly true if we consider the impact of the interventions carried out so far,even those considered non-invasive,such as routine maintenance operations and some technological upgrades.展开更多
文摘The objective of this paper is to propose and illustrate feasibility, approach, validation as per prevailing codes and design standards, specification to rehabilitate bridge pier cap by using Ultra-High Performance Concrete (UHPC). The evaluation of existing pier caps and bearings indicates that the complete removal of existing bearing is undesirable due to 1) massive size of bearing 2) difficulty in cutting through the thick components of existing bearing 3) deeply anchored lower shoe of existing bearings 4) huge cost and time required to erect temporary support system for superstructure to facilitate the construction of new piers. To overcome these difficulties, UHPC could be cast around the lower shoe up to the existing bearing pin. This UHPC cast could be used to support jacks and temporary bearings. The new low height permanent bearing could then be installed after removing the upper shoe of the existing bearing. In the present research, first properties of UHPC are summarized followed by evaluation of case studies to check feasibility of the solution to rehabilitate pier cap by using UHPC. The complex load paths in pier cap are idealized by using validated strut and tie model as per prevailing AASHTO LRFD Bridge Design Specification.
基金Funed by the National Natural Science Foundation of China(No.U21A20149)the Ecological Environment Scientific Research Project of Anhui Province(No.2023hb0014)+2 种基金the Research Reserve of Anhui Jianzhu University(No.2022XMK01)the Excellent Scientific Research and Innovation Team in Colleges and Universities of Anhui Province(No.2022AH010017)Research on the preparation technology of self compacting concrete with strength grade C100.
文摘We developed ultra-high performance concrete(UHPC)incorporating mullite sand and brown corundum sand(BCS),and the quartz sand UHPC was utilized to prepare for comparison.The properties of compressive strength,elastic modulus,ultrasonic pulse velocity,flexural strength,and toughness were investigated.Scanning electron microscopy and nanoindentation were also conducted to reveal the underlying mechanisms affecting macroscopic performance.Due to the superior interface bonding properties between mullite sand and matrix,the compressive strength and flexural toughness of UHPC have been significantly improved.Mullite sand and BCS aggregates have higher stiffness than quartz sand,contributing to the excellent elastic modulus exhibited by UHPC.The stiffness and volume of aggregates have a more significant impact on the elastic modulus of UHPC than interface performance,and the latter contributes more to the strength of UHPC.This study will provide a reference for developing UHPC with superior elastic modulus for structural engineering.
基金supports from National Natural Science Foundation of China (Grant No.62205117,52275429)National Key Research and Development Program of China (Grant No.2021YFF0502700)+3 种基金Young Elite Scientists Sponsorship Program by CAST (Grant No.2022QNRC001)West Light Foundation of the Chinese Academy of Sciences (Grant No.xbzg-zdsys-202206)Knowledge Innovation Program of Wuhan-Shuguang,Innovation project of Optics Valley Laboratory (Grant No.OVL2021ZD002)Hubei Provincial Natural Science Foundation of China (Grant No.2022CFB792).
文摘Interactive holography offers unmatched levels of immersion and user engagement in the field of future display.Despite of the substantial progress has been made in dynamic meta-holography,the realization of real-time,highly smooth interactive holography remains a significant challenge due to the computational and display frame rate limitations.In this study,we introduced a dynamic interactive bitwise meta-holography with ultra-high computational and display frame rates.To our knowledge,this is the first reported practical dynamic interactive metasurface holographic system.We spa-tially divided the metasurface device into multiple distinct channels,each projecting a reconstructed sub-pattern.The switching states of these channels were mapped to bitwise operations on a set of bit values,which avoids complex holo-gram computations,enabling an ultra-high computational frame rate.Our approach achieves a computational frame rate of 800 kHz and a display frame rate of 23 kHz on a low-power Raspberry Pi computational platform.According to this methodology,we demonstrated an interactive dynamic holographic Tetris game system that allows interactive gameplay,color display,and on-the-fly hologram creation.Our technology presents an inspiration for advanced dynamic meta-holography,which is promising for a broad range of applications including advanced human-computer interaction,real-time 3D visualization,and next-generation virtual and augmented reality systems.
基金National Natural Science Foundation of China under Grant Nos.51921006 and 51725801Fundamental Research Funds for the Central Universities under Grant No.FRFCU5710093320Heilongjiang Touyan Innovation Team Program。
文摘Reinforcement corrosion is the main cause of performance deterioration of reinforced concrete(RC)structures.Limited research has been performed to investigate the life-cycle cost(LCC)of coastal bridge piers with nonuniform corrosion using different materials.In this study,a reliability-based design optimization(RBDO)procedure is improved for the design of coastal bridge piers using six groups of commonly used materials,i.e.,normal performance concrete(NPC)with black steel(BS)rebar,high strength steel(HSS)rebar,epoxy coated(EC)rebar,and stainless steel(SS)rebar(named NPC-BS,NPC-HSS,NPC-EC,and NPC-SS,respectively),NPC with BS with silane soakage on the pier surface(named NPC-Silane),and high-performance concrete(HPC)with BS rebar(named HPC-BS).First,the RBDO procedure is improved for the design optimization of coastal bridge piers,and a bridge is selected to illustrate the procedure.Then,reliability analysis of the pier designed with each group of materials is carried out to obtain the time-dependent reliability in terms of the ultimate and serviceability performances.Next,the repair time of the pier is predicted based on the time-dependent reliability indices.Finally,the time-dependent LCCs for the pier are obtained for the selection of the optimal design.
基金funded by SINOPEC Science and Technology Project P18080by National Energy Administration Research and Development Center Project.
文摘An accurate mapping and understanding of remaining oil distribution is very important for water control and stabilize oil production of mature oilfields in ultra-high water-cut stage.Currently,the Tuo-21 Fault Block of the Shengtuo Oilfield has entered the stage of ultra-high water cut(97.2%).Poor adaptability of the well pattern,ineffective water injection cycle and low efficiency of engineering measures(such as workover,re-perforation and utilization of high-capacity pumps)are the significant problems in the ultra-high water-cut reservoir.In order to accurately describe the oil and water flow characteristics,relative permeability curves at high water injection multiple(injected pore volume)and a semiquantitative method is applied to perform fine reservoir simulation of the Sand group 3e7 in the Block.An accurate reservoir model is built and history matching is performed.The distribution characteristics of remaining oil in lateral and vertical directions are quantitatively simulated and analyzed.The results show that the numerical simulation considering relative permeability at high injection multiple can reflect truly the remaining oil distribution characteristics after water flooding in an ultrahigh water-cut stage.The distribution of remaining oil saturation can be mapped more accurately and quantitatively by using the‘four-points and five-types’classification method,providing a basis for potential tapping of various remaining oil types of oil reservoirs in late-stage of development with high water-cut.
基金funded by the Key R&D Program of Jilin Province(20220201132GX)the Key R&D Program of Hubei Province(2022BAA084)the Open Funds of the State Key Laboratory of Rare Earth Resource Utilization(RERU2023008)。
文摘Ultra-high nickel cobalt-free lithium layered oxides are promising cathode material for lithium-ion batteries(LIBs)because of their relatively high capacity and low cost.Nevertheless,the high nickel content would induce bulk structure degradation and interfacial environment deterioration,and the absence of Co element reduces the lithium diffusion kinetics,severely limiting the performance liberation of this kind of cathodes.Herein,a multifunctional Ti/Zr dual cation co-doping strategy has been employed to improve the lithium storage performance of LiNi_(0.9)Mn_(0.1)O_(2)(NM91)cathode.On the one hand,the Ti/Zr co-doping weakens the Li^(+)/Ni^(2+)mixing through magnetic interactions due to the inexistence of unpaired electrons for Ti^(4+)and Zr^(4+),increasing the lithium diffusion rate and suppressing the harmful coexistence of H1 and H2 phases.On the other hand,they enhance the lattice oxygen stability because of the strong Ti-O and Zr-O bonds,inhibiting the undesired H3 phase transition and lattice oxygen loss,improving the bulk structure and cathode-electrolyte interface stability.As a result,the Ti/Zr co-doped NM91(NMTZ)exhibits a 91.2%capacity retention rate after 100 cycles,while that of NM91 is only82.9%.Also,the NMTZ displays better rate performance than NM91 with output capacities of 115 and93 mA h g^(-1)at a high current density of 5 C,respectively.Moreover,the designed NMTZ could enable the full battery to deliver an energy density up to 263 W h kg^(-1),making the ultra-high nickel cobaltfree lithium layered oxide cathode closer to practical applications.
文摘Local scour around bridge piers and abutments is one of the most significant causes of bridge failure.Despite a plethora of studies on scour around individual bridge piers or abutments,few studies have focused on the joint impact of a pier and an abutment in proximity to one another on scour.This study conducted laboratory experiments and flow analyses to examine the interaction of piers and abutments and their effect on clear-water scour.The experiments were conducted in a rectangular laboratory flume.They included 18 main tests(with a combination of different types of piers and abutments)and five control tests(with individual piers or abutments).Three pier types(a rectangular pier with a rounded edge,a group of three cylindrical piers,and a single cylindrical pier)and two abutment types(a wingewall abutment and a semicircular abutment)were used.An acoustic Doppler velocimeter was used to measure the three-dimensional flow velocity for analyses of streamline,velocity magnitude,vertical velocity,and bed shear stress.The results showed that the velocity near the pier and abutment increased by up to 80%.The maximum scour depth around the abutment increased by up to 19%.In contrast,the maximum scour depth around the pier increased significantly by up to l71%.The presence of the pier in the vicinity of the abutment led to an increase in the scour hole volume by up to 87%relative to the case with a solitary abutment.Empirical equations were also derived to accurately estimate the maximum scour depth at the pier adjacent to the abutment.
文摘The seismic behavior of horizontally curved bridges,particularly with unequal height piers,is more complicated than that of straight bridges due to their geometric properties.In this study,the seismic responses of several horizontally curved single-column-bent viaducts with various degrees of curvature and different pier heights have been investigated,employing three different analysis approaches:namely,modal pushover analysis,uniform load method,and nonlinear time history analysis.Considering the investigated bridge configurations and utilizing the most common regularity indices,the results indicate that viaducts with 45-degree and 90-degree deck subtended angles can be categorized as regular and moderately irregular,respectively,while the bridges with 180-degree deck subtended angle are found to be highly irregular.Furthermore,the viaducts whose pier heights are asymmetric may be considered as irregular for almost all ranges of the deck subtended angles.The effects of higher transverse and longitudinal modes are discussed and the minimum analysis requirements are identified to assess the seismic response of such bridge configurations for design purposes.Although the Regularity Indices used here are useful tools to distinguish between regular and irregular bridges,further studies are needed to improve their reliability.
基金National Natural Science Foundation of China under Grant No.51608488Scientific and Technological Project of Henan Province,China under Grant No.222102320006+1 种基金Zhengzhou University 2022 Annual Basic Research Foundation for Young Teachers,China under Grant No.JC22547025Postdoctoral Research Grant in Henan Province。
文摘The deterioration of the performance of offshore bridges is particularly prominent due to the complex natural environment,including the coupling effects of earthquake and seawater erosion.In particular,bridge piers are the main energy-consuming and load-bearing components,so that excellent seismic capacity of bridge piers is the key to avoiding bridge damage.Although earthquake resistant behavior of ordinary reinforced concrete bridge piers(ordinary pier)can be improved by increasing the section size and reinforcement ratio of piers,the improvement of the earthquake resistant behavior is limited.To further improve the earthquake resistant behavior of bridge piers,high-tensile reinforcement engineered cementitious composite(ECC)bridge piers are utilized and time-varying seismic fragility analysis are conducted in this study.The refined model of a bridge pier is built by OpenSees.First,the influence of ECC replacement height on pier curvature is analyzed to determine the reasonable ECC height.Then,the time-varying fragility analysis of high-tensile reinforcement ECC piers(ECC composite piers)with durability damage are evaluated considering the time-varying law of materials.Four damage states,slight damage,moderate damage,extensive damage and complete collapse,are utilized in the study.These fragility curves indicate the durability damage can debase the earthquake resistant behavior of piers continually,the exceedance probability of the same state of destruction increases with the increase of peak ground acceleration(PGA)and service time of pier.The results also indicate that the corrosion level of chloride ion to pier is small during the early service period,and the bridge pier vulnerable curve is similar to that of the new bridge pier.As the level of chlorine ion corrosion deepens,transcendental probability is increased.Compared with the ordinary pier,the exceedance probability in each limit state of ECC composite piers is significantly reduced.The proposed ECC composite pies leads to better realistic time-varying earthquake resistant behavior.
基金National Natural Science Foundation of China under Grant Nos.U21A20154 and 52078436the Sichuan Science and Technology Program under Grant Nos.2022JDRC0012,2023YFG0064 and 2023YFS0429the Opening Funding Project of the Key Laboratory of Earthquake Engineering Simulation and Seismic Resilience of the China Earthquake Administration。
文摘Conventional reinforced concrete piers are vulnerable to severe compressive damage under strong earthquake conditions and are difficult to quickly rehabilitate.This paper develops a new type of composite pier,consisting of ultra-high-performance concrete(UHPC)and reinforced concrete(RC).This UHPC-RC composite pier uses a UHPC cover outside of an RC core to achieve a high load-carrying capacity and mitigate compressive damage.An experiment is performed to evaluate the performance of the UHPC-RC composite pier under cyclic deformation.The crack development,ultimate failure modes,and load-carrying capacities of the pier are observed.Because of the extraordinary compressive strength of UHPC,the composite pier suffers little compressive damage under large lateral deformations.The composite pier fails as a result of fracturing of the reinforcement.A numerical model is developed to reproduce the cyclic behavior of the composite pier.On the basis of the verified numerical model,a parametric analysis is used to investigate the influence of the thickness of the UHPC cover and the axial load ratio.Finally,an approach is recommended for designing composite piers.
基金supported by the National Natural Science Foundation of China (Grant Nos.52179060 and 51909024).
文摘Various regions are becoming increasingly vulnerable to the increased frequency of floods due to the recent changes in climate and precipitation patterns throughout the world.As a result,specific infrastructures,notably bridges,would experience significant flooding for which they were not intended and would be submerged.The flow field and shear stress distribution around tandem bridge piers under pressurized flow conditions for various bridge deck widths are examined using a series of three-dimensional(3D)simulations.It is indicated that scenarios with a deck width to pier diameter(Ld/p)ratio of 3 experience the highest levels of turbulent disturbance.In addition,maximum velocity and shear stresses occur in cases with Ld/p equal to 6.Results indicate that increasing the number of piers from 1 to 2 and 3 results in the increase of bed shear stress by 24%and 20%respectively.Finally,five machine learning algorithms,including Decision Trees(DT),Feed Forward Neural Networks(FFNN),and three Ensemble models,are implemented to estimate the flow field and the turbulent structure.Results indicated that the highest accuracy for estimation of U,and W,were obtained using AdaBoost ensemble with R2=0.946 and 0.951,respectively.Besides,the Random Forest algorithm outperformed AdaBoost slightly in the estimation of V and turbulent kinetic energy(TKE)with R2=0.894 and 0.951,respectively.
基金supported by Fok Ying-Tong Education Foundation(Grant No.171043)Sichuan Science and Technology Program(Award No.2020YFQ0036).
文摘Polymer gels have been accepted as a useful tool to address many sealing operations such as drilling and completion,well stimulation,wellbore integrity,water and gas shutoff,etc.Previously,we developed an ultra-high strength gel(USGel)for medium to ultra-low temperature reservoirs.However,the removal of USGel is a difficult problem for most temporary plugging operations.This paper first provides new insights into the mechanism of USGel,where multistage network structure and physical entanglement are the main reasons for USGel possessing ultra-high strength.Then the effects of acid breakers,encapsulated breakers,and oxidation breakers(including H_(2)O_(2),Na_(2)S_(2)O_(8),Ca(ClO)_(2),H_(2)O_(2)+NaOH,Na_(2)S_(2)O_(8)+NaOH,and Ca(ClO)_(2)+NaOH)were evaluated.The effects of component concentration and temperature on the breaking solution were studied,and the corrosion performance,physical simulation and formation damage tests of the breaking solution were carried out.The final formulation of 2%-4%NaOH+4.5%-6%H_(2)O_(2) breaking solution was determined,which can make USGel completely turn into water at 35e105C.The combinations of“acid t breaking solution”,“acid+encapsulated breaker”and“encapsulated breaker+breaking solution”were evaluated for breaking effect.The acid gradually reduced the volume of USGel,which increased the contact area between breaking solution and USGel,and the effect of“4%acid+breaking solution”was 23 times higher than that of breaking solution alone at 35C.However,the acid significantly reduced the strength of USGel.This paper provides new insights into the breaking of high-strength gels with complex network structures.
基金National Natural Science Foundation of China under Grant Nos.51978656 and 51478459the Key Research and Development Project of Xuzhou under Grant No.KC22282the Open Fund of Jiangsu Key Laboratory of Environmental Impact and Structural Safety in Civil Engineering,China University of Mining and Technology under Grant No.KFJJ202004。
文摘Considering the desirable behavior of concrete filled steel tube(CFT)columns and the complicated behavior of segmental double-column piers under cyclic loads,three post-tensioned precast segmental CFT double-column pier specimens were tested to extend their application in moderate and high seismicity areas.The effects of the number of CFT segments and the steel endplates as energy dissipaters on the seismic behavior of the piers were evaluated.The experimental results show that the segmental piers exhibited stable hysteretic behavior with small residual displacements under cyclic loads.All the tested specimens achieved a drift ratio no less than 13%without significant damage and strength deterioration due to the desirable behavior of CFT columns.Since the deformation of segmental columns was mainly concentrated at the column-footing interfaces,the increase of the segment numbers for each column had no obvious effects on the loading capacity but reduced the initial stiffness of the specimens.The use of steel endplates improved the bearing capacity,stiffness and energy dissipation of segmental piers,but weakened their self-centering capacity.Fiber models were also proposed to simulate the hysteretic behavior of the tested specimens,and the influences of segment numbers and prestress levels on seismic behavior were further studied.
基金supported by the National Natural Science Foundation of China (Nos.21802096,21832004,21902179,21991152,and 21991150)the Shanghai XFEL Beamline Project (SBP) (31011505505885920161A2101001)the support of the Shanghai Sailing Program (19YF1455600)。
文摘An in-depth understanding of the structure-activity relationship between the surface structure,chemical composition,adsorption and desorption of molecules,and their reaction activity and selectivity is necessary for the rational design of high-performance catalysts.Herein,we present a method for studying catalytic mechanisms using a combination of in situ reaction cells and surface science techniques.The proposed system consists of four parts:preparation chamber,temperatureprogrammed desorption(TPD)chamber,quick load-lock chamber,and in situ reaction cell.The preparation chamber was equipped with setups based on the surface science techniques used for standard sample preparation and characterization,including an Ar+sputter gun,Auger electron spectrometer,and a low-energy electron diffractometer.After a well-defined model catalyst was prepared,the sample was transferred to a TPD chamber to investigate the adsorption and desorption of the probe molecule,or to the reaction cell,to measure the catalytic activity.A thermal desorption experiment for methanol on a clean Cu(111)surface was conducted to demonstrate the functionality of the preparation and TPD chambers.Moreover,the repeatability of the in situ reaction cell experiment was verified by CO_(2) hydrogenation on the Ni(110)surface.At a reaction pressure of 800 Torr at 673 K,turnover frequencies for the methanation reaction and reverse water-gas shift reaction were 0.15 and 7.55 Ni atom^(-1) s^(-1),respectively.
基金Funded by the National Natural Science Foundation of China (Nos.U21A20149, 51878003, 51908378)Research Reserve of Anhui Jianzhu University (No.2022XMK01)Excellent Scientific Research and Innovation Team in Colleges and Universities of Anhui Province(No. 2022AH010017)。
文摘This study aims to clarify the effects of curing regimes and lightweight aggregate(LWA)on the morphology, width and mechanical properties of the interfacial transition zone(ITZ) of ultra-high performance concrete(UHPC), and provide reference for the selection of lightweight ultra-high performance concrete(L-UHPC) curing regimes and the pre-wetting degree LWA. The results show that, under the three curing regimes(standard curing, steam curing and autoclaved curing), LWA is tightly bound to the matrix without obvious boundaries. ITZ width increases with the water absorption of LWA and decreases with increasing curing temperature. The ITZ microhardness is the highest when water absorption is 3%, and the microhardness value is more stable with the distance from LWA. Steam and autoclaved curing increase ITZ microhardness compared to standard curing. As LWA pre-wetting and curing temperatures increase, the degree of hydration at the ITZ increases, generating high-density CSH(HD CSH) and ultra-high-density CSH(UHD CSH), and reducing unhydrated particles in ITZ. ITZ micro-mechanical properties are optimized due to hydration products being denser.
基金supported by the Henan College Students Innovation and Entrepreneurship Training Program(202211070009 and 202211070016).
文摘Ultra-high temperature ceramic coatings have ultra-high melting points,excellent mechanical properties and high temperature ablation resistance.These unique performance combinations turn it into a promising material for use in extreme environment structures in rockets and hypersonic vehicles,particularly nozzles,leading edges and engine components.In this paper,various preparation methods of ultra-high temperature ceramic coatings were reviewed,including plasma spraying,chemical vapor deposition,pack cementation,slurry sintering,hot pressing and their research progress.Meanwhile,some new preparation methods of high temperature coatings,such as ion beam deposition,ultrasonic spraying,metal organic frame work coating,and magnetron sputtering,were introduced.The development trend of ultra-high temperature coatings was prospected as well.
文摘[Objectives]This study was conducted to establish an uncertainty evaluation method for the determination of ethyl maltol by ultra-high performance liquid chromatograph-mass spectrometer(UPLC-MS).[Methods]A mathematical model of uncertainty was established by analyzing the method for determining ethyl maltol using UPLC-MS.The sources of uncertainty were analyzed,and the components of uncertainty were calculated to evaluate the expanded uncertainty of the method.[Results]When the content of ethyl maltol in edible vegetable oil was 1657μg/kg,the expanded uncertainty was 22.4μg/kg(K=2,P=95%).[Conclusions]The uncertainty in this evaluation model mainly came from standard solution preparation,sample weighing,dilution of sample to constant volume,standard curve fitting,and repeated measurement.
文摘A two-dimensional mathematical model is used to simulate the influence of water flow on the piers of a bridge for different incidence angles.In particular,a finite volume method is used to discretize the Navier-Stokes control equations and calculate the circumferential pressure coefficient distribution on the bridge piers’surface.The results show that the deflection of the flow is non-monotonic.It first increases and then decreases with an increase in the skew angle.
文摘Hidden by several layers of white paint,the almost forgotten polychromy of Nervi’s exhibition halls emerges from historical images,not necessarily intended to document the complex,but rather as a setting for exhibitions,fairs or film and advertising sets.Historical documentation reveals Nervi’s presence on the building site and his desire to supervise the finishing phases.The first stratigraphic investigations also testify to his attention color,as well as the subsequent transformations of use.Specific theoretical and technical issues regarding the conservation of the pictorial layers in relation to the conservation of the reinforced concrete elements are outlined.Furthermore,the use of polychromy in combination with the original employment of natural and artificial light sources introduces new facets into the analysis of Nervi’s work,offering the opportunity for original reflection.This is particularly true if we consider the impact of the interventions carried out so far,even those considered non-invasive,such as routine maintenance operations and some technological upgrades.