Recently,Kelly and colleagues[1],inspired by computed tomography(CT),report a“volumetric additive manufacturing”technology via a computed axial lithography(CAL)approach.A related US patent application[2]has also bee...Recently,Kelly and colleagues[1],inspired by computed tomography(CT),report a“volumetric additive manufacturing”technology via a computed axial lithography(CAL)approach.A related US patent application[2]has also been filed.The cumulative light exposure solidifies the material in the target area,while the other area remains uncured,resulting in only specific points in the designed 3D objects being printed.This technology significantly improves the capability of the digital light processing(DLP)technique.Meanwhile,the lithography approach based on a similar algorithm was already proposed by Xiang Wu in a patent(application No.PCT/CN2016/080097)in 2016[3].展开更多
Currently,flight delays are common and they propagate from an originating flight to connecting flights,leading to large disruptions in the overall schedule.These disruptions cause massive economic losses,affect airli...Currently,flight delays are common and they propagate from an originating flight to connecting flights,leading to large disruptions in the overall schedule.These disruptions cause massive economic losses,affect airlines’reputations,waste passengers’time and money,and directly impact the environment.This study adopts a network science approach for solving the delay propagation problem by modeling and analyzing the flight schedules and historical operational data of an airline.We aim to determine the most disruptive airports,flights,flightconnections,and connection types in an airline network.Disruptive elements are influential or critical entities in an airline network.They are the elements that can either cause(airline schedules)or have caused(historical data)the largest disturbances in the network.An airline can improve its operations by avoiding delays caused by the most disruptive elements.The proposed network science approach for disruptive element analysis was validated using a case study of an operating airline.The analysis indicates that potential disruptive elements in a schedule of an airline are also actual disruptive elements in the historical data and they should be considered to improve operations.The airline network exhibits small-world effects and delays can propagate to any part of the network with a minimum of four delayed flights.Finally,we observed that passenger connections between flights are the most disruptive connection type.Therefore,the proposed methodology provides a tool for airlines to build robust flight schedules that reduce delays and propagation.展开更多
The scarcity and high cost of lithium resources drive the search for sustainable alternatives,positioning potassium-ion batteries(KIBs)as promising energy storage solutions due to the natural abundance and advantageou...The scarcity and high cost of lithium resources drive the search for sustainable alternatives,positioning potassium-ion batteries(KIBs)as promising energy storage solutions due to the natural abundance and advantageous electrochemical properties of the potassium.This study investigates the enhancement of KIB anodes through phase transformation and electronic structure engineering of monolayer 1T-MoS_(2),achieved via doping with highly electronegative non-metal elements:carbon(C),nitrogen(N),oxygen(O),and fluorine(F).Density functional theory(DFT)simulations reveal that electronegative atom doping enhances phase stability,structural robustness,and thermal resilience,which are key properties for highperformance KIB anodes.Among the doped configurations,F and N-doped 1T-MoS_(2)(MoS_(2-)F and MoS_(2)-N)exhibit superior electrochemical performance,showing optimal adsorption energies and significantly improved electronic conductivity,attributable to favorable charge redistribution and increased active potassium adsorption sites.Specifically,MoS_(2)-F and MoS_(2)-N achieve the highest specific capacities of339.65 and 339.17 mAh/g,respectively,while maintaining stability within an ideal open circuit voltage range,outperforming undoped MoS_(2).This work undersco res the potential of electronegative atom doping in 1T-MoS_(2)to enable sustainable,high-capacity energy storage solutions,offering key advancements in the electrochemical and structural properties of KIB anodes.展开更多
During rock drilling and blasting activities,stemming blast holes is to prevent high-pressure explosive gases from the holes,thereby enhancing the overall blasting effectiveness.Hence,it is imperative to investigate t...During rock drilling and blasting activities,stemming blast holes is to prevent high-pressure explosive gases from the holes,thereby enhancing the overall blasting effectiveness.Hence,it is imperative to investigate the dynamic mechanical properties of the stem-ming materials.In this study,impact compression tests were conducted on self-swelling cartridges(SSCs)using a split Hopkinson pres-sure bar(SHPB),aiming to evaluate dynamic performances across strain rate range of 20 to 65 s^(−1).Test results indicate that the dynamic compressive strength of SSCs exhibits the following trends:it increases with increasing density of SSC,decreases with an increase in insertion gap,and follows an initial rise and subsequent fall trend with an increase in water absorption.The order of significance among these factors is density>water absorption>insertion gaps.SSCs exhibit a pronounced strain-rate strengthening dependence in dynamic compressive strength.Furthermore,both the compressive peak stress and peak strain of SSCs follow a well-defined quadratic upward trend with increasing strain rates.As the strain rate increases,the degree of fragmentation,absorbed energy,and dynamic increase factor exhibit an upward trend.Model experimental results indicate that,compared to cementitious stemming materials,SSCs can prolong the duration of gas explosion action.Therefore,SSCs are more suitable for high strain-rate applications such as blasting stemming and rock burst control.展开更多
In this work,we aim to develop a novel post-treatment process combining cryogenic and pulsed electric field treatment to enhance WC-Co cemented carbides.The results show a 15.62%increase in hardness from 1831.38 to 21...In this work,we aim to develop a novel post-treatment process combining cryogenic and pulsed electric field treatment to enhance WC-Co cemented carbides.The results show a 15.62%increase in hardness from 1831.38 to 2117.38 HV30,a 9.60%rise in fracture toughness from 9.06 to 9.93 MPa·m^(1/2),while the friction coefficient decreases from 0.63 to 0.47.Through the residual stress evolution,WC orientation change and the martensitic transformation of Co,and the internal enhancement mechanism of cryogenic combined with pulsed electric field treatment are revealed.The electron wind generated by the pulsed electric field can efficiently reduce the residual stress induced by cryogenic process.The evolution of residual stress promotes the base slip of WC,increasing the degree of{0001}orientation.In addition,the degree of martensitic transformation of Co intensifies,with the hcp-Co/fcc-Co ratio rising from 0.41%to 17.86%.The enhanced WC{0001}orientation and increased hcp-Co content contribute to significant improvements in hardness and wear resistance.This work provides a novel efficient enhancement strategy for ceramics and alloys,with the potential to be a mainstream strengthening method in the future.展开更多
This study is to determine the support mechanism of pre-stressed expandable props for the stope roof in room- and-pillar mining, which is crucial for maintaining stability and preventing roof collapse in mines. Utiliz...This study is to determine the support mechanism of pre-stressed expandable props for the stope roof in room- and-pillar mining, which is crucial for maintaining stability and preventing roof collapse in mines. Utilizing an engineering case from a gold mine in Dandong, China, a laboratory-based similar test is conducted to extract the actual roof characteristic curve. This test continues until the mining stope collapses due to a U-shaped failure. Concurrently, a semi-theoretical method for obtaining the roof characteristic curve is proposed and verified against the actual curve. The semi-theoretical method calculated that the support force and vertical displacement at the demarcation point between the elastic and plastic zones of the roof characteristic curve are 5.0 MPa and 8.20 mm, respectively, corroborating well with the laboratory-based similar test results of 0.22 MPa and 0.730 mm. The weakening factor for the plastic zone in the roof characteristic curve was semi-theoretically estimated to be 0.75. The intersection between the actual roof characteristic curve and the support characteristic curves of expandable props, natural pillars, and concrete props indicates that the expandable prop is the most effective “yielding support” for the stope roof in room-and-pillar mining. That is, the deformation and failure of the stope roof can be effectively controlled with proper release of roof stress. This study provides practical insights for optimizing support strategies in room-and-pillar mining, enhancing the safety and efficiency of mining operations.展开更多
High-temperature confocal scanning laser microscopy(HT-CSLM)is a potent methodology for investigating various phenomena in the field of metallurgy.Initially applied to the observation of solid phase transformations an...High-temperature confocal scanning laser microscopy(HT-CSLM)is a potent methodology for investigating various phenomena in the field of metallurgy.Initially applied to the observation of solid phase transformations and solidification,this method has gained traction in the field of non-metallic inclusion in steels in recent years.An overview of the experimental capabilities of HT-CSLM and the most important results of recent investigations regarding the topics of clean steel production are provided.It includes the formation of intragranular acicular ferrite(IAF)from the surface of non-metallic inclusions during the continuous cooling and heat treatment,which can be especially beneficial in the toughness of heat-affected zones of welded pieces.Furthermore,the investigation of agglomeration mechanisms of non-metallic inclusions(NMIs)in liquid steel is discussed to improve the insight into attraction forces between particles and clogging phenomena during continuous casting.Also,the dissolution of NMIs in various steelmaking slags can be observed by HT-CSLM to compare dissolution rates and mechanisms of NMI,where significant influences of temperature and chemical composition of the slag were shown.Last but not least,the experimental work regarding the interface between steel and slag is discussed,where novel techniques are currently being developed.A comprehensive summary of experimental techniques using HT-CSLM equipment to investigate different interactions of NMIs with steel and slag phases is compiled.展开更多
Tensile cracking is a predominant mode of failure in rocks within underground resource excavation and engineering structures,where rocks are frequently subjected to dynamic disturbances while simultaneously experienci...Tensile cracking is a predominant mode of failure in rocks within underground resource excavation and engineering structures,where rocks are frequently subjected to dynamic disturbances while simultaneously experiencing in-situ stresses.This paper proposes a new dynamic split tension setup utilising a cubic specimen to investigate the dynamic behaviour of rocks across various tensile strain rates and confining pressures.The objective is to extend the applicability of the triaxial Hopkinson bar in studying dynamic behaviour of geomaterials.For comparison,the dynamic Brazilian disc(BD)tests were performed using three rock types(e.g.,sandstone,granite and marble)under different strain rates ranging from 10^(−3)∼10^(2) s^(−1).Besides,the Digital Image Correlation(DIC)technique was adopted to measure full-field real-time tensile strain of rocks and demonstrated that tensile crack initiated at the middle part and split the specimen into two similar halves.Effects of specimen size,geometry,loading rate as well as the confining pressure are investigated in detail.The dynamic fracture behaviours,including dynamic tensile strength,tensile strain,time to fracture and dynamic increase factor(DIF),were characterised for the rocks.It is found that dynamic tensile strength of rock minimal dependence on size and geometry but is significantly influenced by loading rate and confinement.It exhibited a linear increase with strain rate(10^(0)∼10^(2) s^(−1))and demonstrated a nonlinear growth with lateral confinement from 0 to 15 MPa.The nonlinear dependency on confinement can be attributed to the restriction imposed on the opening and propagation of tensile cracks due to the presence of confinement.These findings enhance our understanding of the safety aspects associated with underground rock excavations,particularly in situations where considering in-situ stress is crucial for evaluating the dynamic tensile failure of rocks.展开更多
Dissolution kinetics of CaO·2Al_(2)O_(3)(CA_(2))particles in a synthetic CaO-Al_(2)O_(3)-SiO_(2)steelmaking slag system have been investigated using the high-temperature confocal laser scanning microscope.Effects...Dissolution kinetics of CaO·2Al_(2)O_(3)(CA_(2))particles in a synthetic CaO-Al_(2)O_(3)-SiO_(2)steelmaking slag system have been investigated using the high-temperature confocal laser scanning microscope.Effects of temperature(i.e.,1500,1550,and 1600℃)and slag composition on the dissolution time of CA_(2)particles are investigated,along with the time dependency of the projection area of the particle during the dissolution process.It is found that the dissolution rate was enhanced by either an increase in temperature or a decrease in slag viscosity.Moreover,a higher ratio of CaO/Al_(2)O_(3)(C/A)leads to an increased dissolution rate of CA_(2)particle at 1600℃.Thermodynamic calculations suggested the dissolution product,i.e.,melilite,formed on the surface of the CA_(2)particle during dissolution in slag with a C/A ratio of 3.8 at 1550℃.Scanning electron microscopy equipped with energy dispersive X-ray spectrometry analysis of as-quenched samples confirmed the dissolution path of CA_(2)particles in slags with C/A ratios of 1.8 and 3.8 as well as the melilite formed on the surface of CA_(2)particle.The formation of this layer during the dissolution process was identified as a hindrance,impeding the dissolution of CA_(2)particle.A valuable reference for designing or/and choosing the composition of top slag for clean steel production is provided,especially using calcium treatment during the secondary refining process.展开更多
Recently,Mueller matrix(MM)polarimetric imaging-assisted pathology detection methods are showing great potential in clinical diagnosis.However,since our human eyes cannot observe polarized light directly,it raises a n...Recently,Mueller matrix(MM)polarimetric imaging-assisted pathology detection methods are showing great potential in clinical diagnosis.However,since our human eyes cannot observe polarized light directly,it raises a notable challenge for interpreting the measurement results by pathologists who have limited familiarity with polarization images.One feasible approach is to combine MM polarimetric imaging with virtual staining techniques to generate standardized stained images,inheriting the advantages of information-abundant MM polarimetric imaging.In this study,we develop a model using unpaired MM polarimetric images and bright-field images for generating standard hematoxylin and eosin(H&E)stained tissue images.Compared with the existing polarization virtual staining techniques primarily based on the model training with paired images,the proposed Cycle-Consistent Generative Adversarial Networks(CycleGAN)-based model simplifies data acquisition and data preprocessing to a great extent.The outcomes demonstrate the feasibility of training CycleGAN with unpaired polarization images and their corresponding bright-field images as a viable approach,which provides an intuitive manner for pathologists for future polarization-assisted digital pathology.展开更多
Analysis of the energy balance of various parts during the basic oxygen furnace(BOF)steelmaking is of vital importance for revealing the blowing characteristics of the swirl-type oxygen lance.The energy transfer behav...Analysis of the energy balance of various parts during the basic oxygen furnace(BOF)steelmaking is of vital importance for revealing the blowing characteristics of the swirl-type oxygen lance.The energy transfer behavior between the oxygen jet and the molten bath in the top-blowing steelmaking process was investigated using the volume of fluid method.The energy of the reflected jet and the slag was introduced,and the energy balance model of the BOF converter was modified.The influences of lance height and operation pressure on energy transfer were analyzed.Compared with the traditional oxygen lance,the energy of reflected jet,splashing,and cavity formation of the swirl-type oxygen lance was decreased.However,the energy of jet attenuation,slag,and molten steel increased.The energy proportion of the reflected jet was about 8%,while the energy of slag was 15%of molten steel.The maximum energy was transferred from the jet to the slag and molten steel at H=40de(H is lance height and de is outlet diameter).When the operation pressure increased from 0.8P0 to 1.2P0(P0 is the designed pressure),the energy of slag and molten steel was increased by 33%and 25.9%,respectively.展开更多
Thermal runaway(TR)in lithium-ion batteries(LIBs)involves a complicated multiphysics process with potentially catastrophic consequences,highlighting the importance of investigating effective prevention strategies.This...Thermal runaway(TR)in lithium-ion batteries(LIBs)involves a complicated multiphysics process with potentially catastrophic consequences,highlighting the importance of investigating effective prevention strategies.This study employs a lumped model integrating electrochemical and decomposition reaction kinetics to predict the evolution of the TR of LIBs triggered by axial nail penetration,validated by experimental tests.A computational fluid dynamics(CFD)-based turbulent flow model is further employed to simulate the thermal runaway propagation(TRP)behavior induced by high-temperature gases within the battery module.A parameterized analysis based on numerical simulation is conducted to quantify the impact of thermal insulation material properties on thermal diffusion and heat accumulation within the module.The results indicate that damage to the battery vent significantly increases the risk of sidewall rupture during TR.The incorporation of thermal barriers is essential in the thermal design of battery modules to prevent heat transfer via convection from the thermal exhaust caused by sidewall rupture to adjacent cells.In addition,a reduction in the thermal diffusivity of the thermal barrier material is required to minimize thermal exchange between battery cells.By adopting insulating materials with thermal diffusivity lower than 0.3 mm^(2)/s,the TRP of batteries can be mitigated under non-enclosed conditions.These findings contribute to improved battery safety and inform the development of more effective thermal protection measures and safety standards.展开更多
Cleanliness control of advanced steels is of vital importance for quality control of the products.In order to understand and control the inclusion removal during refining process in molten steel,its motion behaviors a...Cleanliness control of advanced steels is of vital importance for quality control of the products.In order to understand and control the inclusion removal during refining process in molten steel,its motion behaviors at the multiple steel/gas/slag interfaces have attracted the attention much of metallurgical community.The recent development of the agglomeration of non-metallic inclusions at the steel/Ar and steel/slag interfaces has been summarized,and both the experimental as well as theoretical works have been surveyed.In terms of in situ observation of high-temperature interfacial phenomena in the molten steel,researchers utilized high-temperature confocal laser scanning microscopy to observe the movement of more types of inclusions at the interface,i.e.,the investigated inclusion is no longer limited to Al_(2)O_(3)-based inclusions but moves forward to rare earth oxides,MgO-based oxides,etc.In terms of theoretical models,especially the model of inclusions at the steel/slag interface,the recent development has overcome the limitations of the assumptions of Kralchevsky-Paunov model and verified the possible errors caused by the model assumptions by combining the water model and the physical model.Last but not least,the future work in this topic has been suggested,which could be in combination of thermal physical properties of steels and slag,as well as utilize the artificial intelligence-based methodology to implement a comprehensive inclusion motion behaviors during a comprehensive metallurgical process.展开更多
Selective oxidation of amines to imines through electrocatalysis is an attractive and efficient way for the chemical industry to produce nitrile compounds,but it is limited by the difficulty of designing efficient cat...Selective oxidation of amines to imines through electrocatalysis is an attractive and efficient way for the chemical industry to produce nitrile compounds,but it is limited by the difficulty of designing efficient catalysts and lack of understanding the mechanism of catalysis.Herein,we demonstrate a novel strategy by generation of oxyhydroxide layers on two-dimensional iron-doped layered nickel phosphorus trisulfides(Ni1-xFexPS_(3))during the oxidation of benzylamine(BA).In-depth structural and surface chemical characterizations during the electrocatalytic process combined with theoretical calculations reveal that Ni(1-x)FexPS_(3) undergoes surface reconstruction under alkaline conditions to form the metal oxyhydroxide/phosphorus trichalcogenide(NiFeOOH/Ni1-xFexPS_(3))heterostructure.Interestingly,the generated heterointerface facilitates BA oxidation with a low onset potential of 1.39 V and Faradaic efficiency of 53%for benzonitrile(BN)synthesis.Theoretical calculations further indicate that the as-formed NiFeOOH/Ni1-xFexPS_(3) heterostructure could offer optimum free energy for BA adsorption and BN desorption,resulting in promising BN synthesis.展开更多
Soft robots have partially or entirely provided versatile opportunities for issues or roles that cannot be addressed by conventional machine robots,although most studies are limited to designs,controls,or physical/mec...Soft robots have partially or entirely provided versatile opportunities for issues or roles that cannot be addressed by conventional machine robots,although most studies are limited to designs,controls,or physical/mechanical motions.Here,we present a transformable,reconfigurable robotic platform created by the integration of magnetically responsive soft composite matrices with deformable multifunctional electronics.Magnetic compounds engineered to undergo phase transition at a low temperature can readily achieve reversible magnetization and conduct various changes of motions and shapes.Thin and flexible electronic system designed with mechanical dynamics does not interfere with movements of the soft electronic robot,and the performances of wireless circuit,sensors,and devices are independent of a variety of activities,all of which are verified by theoretical studies.Demonstration of navigations and electronic operations in an artificial track highlights the potential of the integrated soft robot for on-demand,environments-responsive movements/metamorphoses,and optoelectrical detection and stimulation.Further improvements to a miniaturized,sophisticated system with material options enable in situ monitoring and treatment in envisioned areas such as biomedical implants.展开更多
Perinatal hypoxic-ischemic-encephalopathy significantly contributes to neonatal death and life-long disability such as cerebral palsy. Advances in signal processing and machine learning have provided the research comm...Perinatal hypoxic-ischemic-encephalopathy significantly contributes to neonatal death and life-long disability such as cerebral palsy. Advances in signal processing and machine learning have provided the research community with an opportunity to develop automated real-time identification techniques to detect the signs of hypoxic-ischemic-encephalopathy in larger electroencephalography/amplitude-integrated electroencephalography data sets more easily. This review details the recent achievements, performed by a number of prominent research groups across the world, in the automatic identification and classification of hypoxic-ischemic epileptiform neonatal seizures using advanced signal processing and machine learning techniques. This review also addresses the clinical challenges that current automated techniques face in order to be fully utilized by clinicians, and highlights the importance of upgrading the current clinical bedside sampling frequencies to higher sampling rates in order to provide better hypoxic-ischemic biomarker detection frameworks. Additionally, the article highlights that current clinical automated epileptiform detection strategies for human neonates have been only concerned with seizure detection after the therapeutic latent phase of injury. Whereas recent animal studies have demonstrated that the latent phase of opportunity is critically important for early diagnosis of hypoxic-ischemic-encephalopathy electroencephalography biomarkers and although difficult, detection strategies could utilize biomarkers in the latent phase to also predict the onset of future seizures.展开更多
Metal–organic frameworks(MOFs)with high microporosity and relatively high thermal stability are potential thermal insulation and flame-retardant materials.However,the difficulties in processing and shaping MOFs have ...Metal–organic frameworks(MOFs)with high microporosity and relatively high thermal stability are potential thermal insulation and flame-retardant materials.However,the difficulties in processing and shaping MOFs have largely hampered their applications in these areas.This study outlines the fabrication of hybrid CNF@MOF aerogels by a stepwise assembly approach involving the coating and cross-linking of cellulose nanofibers(CNFs)with continuous nanolayers of MOFs.The cross-linking gives the aerogels high mechanical strength but superelasticity(80%maximum recoverable strain,high specific compression modulus of^200 MPa cm3 g−1,and specific stress of^100 MPa cm3 g−1).The resultant lightweight aerogels have a cellular network structure and hierarchical porosity,which render the aerogels with relatively low thermal conductivity of^40 mW m−1 K−1.The hydrophobic,thermally stable MOF nanolayers wrapped around the CNFs result in good moisture resistance and fire retardancy.This study demonstrates that MOFs can be used as efficient thermal insulation and flame-retardant materials.It presents a pathway for the design of thermally insulating,superelastic fire-retardant nanocomposites based on MOFs and nanocellulose.展开更多
To investigate the stability of rock mass in high geostress underground powerhouse caverns subjected to excavation,a microseismic(MS)monitoring system was established and the discrete element method(DEM)-based numeric...To investigate the stability of rock mass in high geostress underground powerhouse caverns subjected to excavation,a microseismic(MS)monitoring system was established and the discrete element method(DEM)-based numerical simulation was carried out.The tempo-spatial damage characteristics of rock mass were analyzed.The evolution laws of MS source parameters during the formation of a rock collapse controlled by high geostress and geological structure were investigated.Additionally,a three-dimensional DEM model of the underground powerhouse caverns was built to reveal the deformation characteristics of rock mass.The results indicated that the MS events induced by excavation of high geostress underground powerhouse caverns occurred frequently.The large-stake crown of the main powerhouse was the main damage area.Prior to the rock collapse,the MS event count and accumulated energy release increased rapidly,while the apparent stress sharply increased and then decreased.The amount and proportion of shear and mixed MS events remarkably increased.The maximum displacement was generally located near the spandrel areas.The MS monitoring data and numerical simulation were in good agreement,which can provide significant references for damage evaluation and disaster forecasting in high geostress underground powerhouse caverns.展开更多
Viscoelastic dampers are now among some of the preferred energy dissipation devices used for passive seismic response control.To evaluate the performance of structures installed with viscoelastic dampers,different ana...Viscoelastic dampers are now among some of the preferred energy dissipation devices used for passive seismic response control.To evaluate the performance of structures installed with viscoelastic dampers,different analytical models have been used to characterize their dynamic force deformation characteristics.The fractional derivative models have received favorable attention as they can capture the frequency dependence of the material stiffness and damping properties observed in the tests very well.However,accurate analytical procedures are needed to calculate the response of structures with such damper models.This paper presents a modal analysis approach,similar to that used for the analysis of linear systems,for solving the equations of inotion with fractional derivative terms for arbitrary forcing functions such as those caused by earthquake induced ground motions.The uncoupled modal equations still have fractional derivatives,but can be solved by numerical or analytical procedures.Both numerical and analytical procedures are formulated.These procedures are then used to calculate the dynamic response of a multi-degree of fleedom shear beam structure excited by ground motions. Numerical results demonstrating the response reducing effect of viscoelastic dampers are also presented.展开更多
Rock mass large deformation in underground powerhouse caverns has been a severe hazard in hydropower engineering in Southwest China.During the development of rock mass large deformation,a sequence of fractures was gen...Rock mass large deformation in underground powerhouse caverns has been a severe hazard in hydropower engineering in Southwest China.During the development of rock mass large deformation,a sequence of fractures was generated that can be monitored using microseismic(MS)monitoring techniques.Two MS monitoring systems were established in two typical underground powerhouse caverns featuring distinct geostress levels.The MS b-values associated with rock mass large deformation and their temporal variation are analysed.The results showed that the MS bvalue in course of rock mass deformation was less than 1.0 in the underground powerhouse caverns at a high stress level while larger than 1.5 at a low stress level.Prior to the rock mass deformation,the MS b-values derived from both the high-stress and low-stress underground powerhouse caverns show an incremental decrease over 10%within 10 d.The results contribute to understanding the fracturing characteristics of MS sources associated with rock mass large deformation and provide a reference for early warning of rock mass large deformation in underground powerhouse caverns.展开更多
基金support by Key Research and Development Projects of Zhejiang Province(Grant No.2017C01054)National Key Research and Development Program of China(2018YFA0703000)+1 种基金Natural Science Foundation of China(Grant Nos.51875518,51821093)the Fundamental Research Funds for the Central Universities(Grant Nos.2019XZZX003-02,2019FZA4002).
文摘Recently,Kelly and colleagues[1],inspired by computed tomography(CT),report a“volumetric additive manufacturing”technology via a computed axial lithography(CAL)approach.A related US patent application[2]has also been filed.The cumulative light exposure solidifies the material in the target area,while the other area remains uncured,resulting in only specific points in the designed 3D objects being printed.This technology significantly improves the capability of the digital light processing(DLP)technique.Meanwhile,the lithography approach based on a similar algorithm was already proposed by Xiang Wu in a patent(application No.PCT/CN2016/080097)in 2016[3].
基金part of a BOEING project“Airline Performance and Disruption Management Across Extended Networks(APEMEN)”funded with research(Grant No.:46599).
文摘Currently,flight delays are common and they propagate from an originating flight to connecting flights,leading to large disruptions in the overall schedule.These disruptions cause massive economic losses,affect airlines’reputations,waste passengers’time and money,and directly impact the environment.This study adopts a network science approach for solving the delay propagation problem by modeling and analyzing the flight schedules and historical operational data of an airline.We aim to determine the most disruptive airports,flights,flightconnections,and connection types in an airline network.Disruptive elements are influential or critical entities in an airline network.They are the elements that can either cause(airline schedules)or have caused(historical data)the largest disturbances in the network.An airline can improve its operations by avoiding delays caused by the most disruptive elements.The proposed network science approach for disruptive element analysis was validated using a case study of an operating airline.The analysis indicates that potential disruptive elements in a schedule of an airline are also actual disruptive elements in the historical data and they should be considered to improve operations.The airline network exhibits small-world effects and delays can propagate to any part of the network with a minimum of four delayed flights.Finally,we observed that passenger connections between flights are the most disruptive connection type.Therefore,the proposed methodology provides a tool for airlines to build robust flight schedules that reduce delays and propagation.
基金financial support provided by the NORPART-2021/10355 project,funded by the Norwegian Directorate for Higher Education and Skills(HK-Dir)。
文摘The scarcity and high cost of lithium resources drive the search for sustainable alternatives,positioning potassium-ion batteries(KIBs)as promising energy storage solutions due to the natural abundance and advantageous electrochemical properties of the potassium.This study investigates the enhancement of KIB anodes through phase transformation and electronic structure engineering of monolayer 1T-MoS_(2),achieved via doping with highly electronegative non-metal elements:carbon(C),nitrogen(N),oxygen(O),and fluorine(F).Density functional theory(DFT)simulations reveal that electronegative atom doping enhances phase stability,structural robustness,and thermal resilience,which are key properties for highperformance KIB anodes.Among the doped configurations,F and N-doped 1T-MoS_(2)(MoS_(2-)F and MoS_(2)-N)exhibit superior electrochemical performance,showing optimal adsorption energies and significantly improved electronic conductivity,attributable to favorable charge redistribution and increased active potassium adsorption sites.Specifically,MoS_(2)-F and MoS_(2)-N achieve the highest specific capacities of339.65 and 339.17 mAh/g,respectively,while maintaining stability within an ideal open circuit voltage range,outperforming undoped MoS_(2).This work undersco res the potential of electronegative atom doping in 1T-MoS_(2)to enable sustainable,high-capacity energy storage solutions,offering key advancements in the electrochemical and structural properties of KIB anodes.
基金supported by the National Natural Science Foundation of China(Nos.51874068 and 52074062)the Open Funds from the Key Laboratory of Ministry of Education on Safe Mining of Deep Metal Mines,Northeastern University,China(No.DM2023B03).
文摘During rock drilling and blasting activities,stemming blast holes is to prevent high-pressure explosive gases from the holes,thereby enhancing the overall blasting effectiveness.Hence,it is imperative to investigate the dynamic mechanical properties of the stem-ming materials.In this study,impact compression tests were conducted on self-swelling cartridges(SSCs)using a split Hopkinson pres-sure bar(SHPB),aiming to evaluate dynamic performances across strain rate range of 20 to 65 s^(−1).Test results indicate that the dynamic compressive strength of SSCs exhibits the following trends:it increases with increasing density of SSC,decreases with an increase in insertion gap,and follows an initial rise and subsequent fall trend with an increase in water absorption.The order of significance among these factors is density>water absorption>insertion gaps.SSCs exhibit a pronounced strain-rate strengthening dependence in dynamic compressive strength.Furthermore,both the compressive peak stress and peak strain of SSCs follow a well-defined quadratic upward trend with increasing strain rates.As the strain rate increases,the degree of fragmentation,absorbed energy,and dynamic increase factor exhibit an upward trend.Model experimental results indicate that,compared to cementitious stemming materials,SSCs can prolong the duration of gas explosion action.Therefore,SSCs are more suitable for high strain-rate applications such as blasting stemming and rock burst control.
基金supported by the National Natural Science Foundation of China(Nos.U21A20399 and 52274407)Liaoning Province Applied Basic Research Program(No.2022JH2/101300212).
文摘In this work,we aim to develop a novel post-treatment process combining cryogenic and pulsed electric field treatment to enhance WC-Co cemented carbides.The results show a 15.62%increase in hardness from 1831.38 to 2117.38 HV30,a 9.60%rise in fracture toughness from 9.06 to 9.93 MPa·m^(1/2),while the friction coefficient decreases from 0.63 to 0.47.Through the residual stress evolution,WC orientation change and the martensitic transformation of Co,and the internal enhancement mechanism of cryogenic combined with pulsed electric field treatment are revealed.The electron wind generated by the pulsed electric field can efficiently reduce the residual stress induced by cryogenic process.The evolution of residual stress promotes the base slip of WC,increasing the degree of{0001}orientation.In addition,the degree of martensitic transformation of Co intensifies,with the hcp-Co/fcc-Co ratio rising from 0.41%to 17.86%.The enhanced WC{0001}orientation and increased hcp-Co content contribute to significant improvements in hardness and wear resistance.This work provides a novel efficient enhancement strategy for ceramics and alloys,with the potential to be a mainstream strengthening method in the future.
基金Project(2022YFC2903801) supported by the National Key Research and Development Program of ChinaProjects(52374117, 52274115) supported by the National Natural Science Foundation of China。
文摘This study is to determine the support mechanism of pre-stressed expandable props for the stope roof in room- and-pillar mining, which is crucial for maintaining stability and preventing roof collapse in mines. Utilizing an engineering case from a gold mine in Dandong, China, a laboratory-based similar test is conducted to extract the actual roof characteristic curve. This test continues until the mining stope collapses due to a U-shaped failure. Concurrently, a semi-theoretical method for obtaining the roof characteristic curve is proposed and verified against the actual curve. The semi-theoretical method calculated that the support force and vertical displacement at the demarcation point between the elastic and plastic zones of the roof characteristic curve are 5.0 MPa and 8.20 mm, respectively, corroborating well with the laboratory-based similar test results of 0.22 MPa and 0.730 mm. The weakening factor for the plastic zone in the roof characteristic curve was semi-theoretically estimated to be 0.75. The intersection between the actual roof characteristic curve and the support characteristic curves of expandable props, natural pillars, and concrete props indicates that the expandable prop is the most effective “yielding support” for the stope roof in room-and-pillar mining. That is, the deformation and failure of the stope roof can be effectively controlled with proper release of roof stress. This study provides practical insights for optimizing support strategies in room-and-pillar mining, enhancing the safety and efficiency of mining operations.
基金the Association SSF Strategic Mobility Grant(No.SM22-0039)theÅForsk Foundation(No.23-540)for supporting the research regarding inclusion engineering.
文摘High-temperature confocal scanning laser microscopy(HT-CSLM)is a potent methodology for investigating various phenomena in the field of metallurgy.Initially applied to the observation of solid phase transformations and solidification,this method has gained traction in the field of non-metallic inclusion in steels in recent years.An overview of the experimental capabilities of HT-CSLM and the most important results of recent investigations regarding the topics of clean steel production are provided.It includes the formation of intragranular acicular ferrite(IAF)from the surface of non-metallic inclusions during the continuous cooling and heat treatment,which can be especially beneficial in the toughness of heat-affected zones of welded pieces.Furthermore,the investigation of agglomeration mechanisms of non-metallic inclusions(NMIs)in liquid steel is discussed to improve the insight into attraction forces between particles and clogging phenomena during continuous casting.Also,the dissolution of NMIs in various steelmaking slags can be observed by HT-CSLM to compare dissolution rates and mechanisms of NMI,where significant influences of temperature and chemical composition of the slag were shown.Last but not least,the experimental work regarding the interface between steel and slag is discussed,where novel techniques are currently being developed.A comprehensive summary of experimental techniques using HT-CSLM equipment to investigate different interactions of NMIs with steel and slag phases is compiled.
基金supported by the Australian Research Council(LE150100058)the Open Research Fund of State Key Laboratory of Geomechanics and Geotechnical Engineering(Z020002)State Key Laboratory of Coal Mine Disaster Dynamics and Control.The specimens were scanned at the Imaging and Medical beamline(IMBL)under the Australian Synchrotron projects(NO:M15862 and M14428).
文摘Tensile cracking is a predominant mode of failure in rocks within underground resource excavation and engineering structures,where rocks are frequently subjected to dynamic disturbances while simultaneously experiencing in-situ stresses.This paper proposes a new dynamic split tension setup utilising a cubic specimen to investigate the dynamic behaviour of rocks across various tensile strain rates and confining pressures.The objective is to extend the applicability of the triaxial Hopkinson bar in studying dynamic behaviour of geomaterials.For comparison,the dynamic Brazilian disc(BD)tests were performed using three rock types(e.g.,sandstone,granite and marble)under different strain rates ranging from 10^(−3)∼10^(2) s^(−1).Besides,the Digital Image Correlation(DIC)technique was adopted to measure full-field real-time tensile strain of rocks and demonstrated that tensile crack initiated at the middle part and split the specimen into two similar halves.Effects of specimen size,geometry,loading rate as well as the confining pressure are investigated in detail.The dynamic fracture behaviours,including dynamic tensile strength,tensile strain,time to fracture and dynamic increase factor(DIF),were characterised for the rocks.It is found that dynamic tensile strength of rock minimal dependence on size and geometry but is significantly influenced by loading rate and confinement.It exhibited a linear increase with strain rate(10^(0)∼10^(2) s^(−1))and demonstrated a nonlinear growth with lateral confinement from 0 to 15 MPa.The nonlinear dependency on confinement can be attributed to the restriction imposed on the opening and propagation of tensile cracks due to the presence of confinement.These findings enhance our understanding of the safety aspects associated with underground rock excavations,particularly in situations where considering in-situ stress is crucial for evaluating the dynamic tensile failure of rocks.
基金the Natural Sciences and Engineering Research Council of Canada(NSERC)for funding this researchThis research used a high temperature confocal laser scanning microscope-VL2000DX-SVF17SP funded by Canada Foundation for Innovation John Evans Leaders Fund(CFI JELF,Project Number:32826),a PANalytical X’Pert diffraction instrument located at the Centre for crystal growth,Brockhouse Institute for Materials Research,and a scanning electron microscope-JEOL 6610 located at the Canadian Centre for Electron Microscopy at McMaster University.W.Mu would like to acknowledge Swedish Iron and Steel Research Office(Jernkonteret),STINT and SSF for supporting the time for international collaboration research regarding clean steel.
文摘Dissolution kinetics of CaO·2Al_(2)O_(3)(CA_(2))particles in a synthetic CaO-Al_(2)O_(3)-SiO_(2)steelmaking slag system have been investigated using the high-temperature confocal laser scanning microscope.Effects of temperature(i.e.,1500,1550,and 1600℃)and slag composition on the dissolution time of CA_(2)particles are investigated,along with the time dependency of the projection area of the particle during the dissolution process.It is found that the dissolution rate was enhanced by either an increase in temperature or a decrease in slag viscosity.Moreover,a higher ratio of CaO/Al_(2)O_(3)(C/A)leads to an increased dissolution rate of CA_(2)particle at 1600℃.Thermodynamic calculations suggested the dissolution product,i.e.,melilite,formed on the surface of the CA_(2)particle during dissolution in slag with a C/A ratio of 3.8 at 1550℃.Scanning electron microscopy equipped with energy dispersive X-ray spectrometry analysis of as-quenched samples confirmed the dissolution path of CA_(2)particles in slags with C/A ratios of 1.8 and 3.8 as well as the melilite formed on the surface of CA_(2)particle.The formation of this layer during the dissolution process was identified as a hindrance,impeding the dissolution of CA_(2)particle.A valuable reference for designing or/and choosing the composition of top slag for clean steel production is provided,especially using calcium treatment during the secondary refining process.
基金Shenzhen Key Fundamental Research Project(No.JCYJ20210324120012035).
文摘Recently,Mueller matrix(MM)polarimetric imaging-assisted pathology detection methods are showing great potential in clinical diagnosis.However,since our human eyes cannot observe polarized light directly,it raises a notable challenge for interpreting the measurement results by pathologists who have limited familiarity with polarization images.One feasible approach is to combine MM polarimetric imaging with virtual staining techniques to generate standardized stained images,inheriting the advantages of information-abundant MM polarimetric imaging.In this study,we develop a model using unpaired MM polarimetric images and bright-field images for generating standard hematoxylin and eosin(H&E)stained tissue images.Compared with the existing polarization virtual staining techniques primarily based on the model training with paired images,the proposed Cycle-Consistent Generative Adversarial Networks(CycleGAN)-based model simplifies data acquisition and data preprocessing to a great extent.The outcomes demonstrate the feasibility of training CycleGAN with unpaired polarization images and their corresponding bright-field images as a viable approach,which provides an intuitive manner for pathologists for future polarization-assisted digital pathology.
基金financially supported by the Natural Science Foundation of Liaoning Province,China(Grant No.2024-BS-219)the Education Department Project of Liaoning Province(JYTMS20230932)+3 种基金the National Natural Science Foundation of China(U20A20272)the Department of Science&Technology of Liaoning Province(Grant No.2022JH2/101300079)the Fundamental Research Funds for the Liaoning Universities(LJ212410146002)the National Natural Science Foundation of China(NSFC52074151).
文摘Analysis of the energy balance of various parts during the basic oxygen furnace(BOF)steelmaking is of vital importance for revealing the blowing characteristics of the swirl-type oxygen lance.The energy transfer behavior between the oxygen jet and the molten bath in the top-blowing steelmaking process was investigated using the volume of fluid method.The energy of the reflected jet and the slag was introduced,and the energy balance model of the BOF converter was modified.The influences of lance height and operation pressure on energy transfer were analyzed.Compared with the traditional oxygen lance,the energy of reflected jet,splashing,and cavity formation of the swirl-type oxygen lance was decreased.However,the energy of jet attenuation,slag,and molten steel increased.The energy proportion of the reflected jet was about 8%,while the energy of slag was 15%of molten steel.The maximum energy was transferred from the jet to the slag and molten steel at H=40de(H is lance height and de is outlet diameter).When the operation pressure increased from 0.8P0 to 1.2P0(P0 is the designed pressure),the energy of slag and molten steel was increased by 33%and 25.9%,respectively.
基金the Faraday Institution’s SafeBatt(https://www.safebatt.ac.uk/)project[grant numbers:EP/S003053/1,FIRG061]DSIT and the Royal Academy of Engineering,under the Chair in Emerging Technologies Scheme(CiET1718/59)。
文摘Thermal runaway(TR)in lithium-ion batteries(LIBs)involves a complicated multiphysics process with potentially catastrophic consequences,highlighting the importance of investigating effective prevention strategies.This study employs a lumped model integrating electrochemical and decomposition reaction kinetics to predict the evolution of the TR of LIBs triggered by axial nail penetration,validated by experimental tests.A computational fluid dynamics(CFD)-based turbulent flow model is further employed to simulate the thermal runaway propagation(TRP)behavior induced by high-temperature gases within the battery module.A parameterized analysis based on numerical simulation is conducted to quantify the impact of thermal insulation material properties on thermal diffusion and heat accumulation within the module.The results indicate that damage to the battery vent significantly increases the risk of sidewall rupture during TR.The incorporation of thermal barriers is essential in the thermal design of battery modules to prevent heat transfer via convection from the thermal exhaust caused by sidewall rupture to adjacent cells.In addition,a reduction in the thermal diffusivity of the thermal barrier material is required to minimize thermal exchange between battery cells.By adopting insulating materials with thermal diffusivity lower than 0.3 mm^(2)/s,the TRP of batteries can be mitigated under non-enclosed conditions.These findings contribute to improved battery safety and inform the development of more effective thermal protection measures and safety standards.
基金the National Natural Science Foundation of China(Grant No.52074179)for the financial supportNational Key Research and Development Program of China(2024YFB3713705)is also acknowledged.
文摘Cleanliness control of advanced steels is of vital importance for quality control of the products.In order to understand and control the inclusion removal during refining process in molten steel,its motion behaviors at the multiple steel/gas/slag interfaces have attracted the attention much of metallurgical community.The recent development of the agglomeration of non-metallic inclusions at the steel/Ar and steel/slag interfaces has been summarized,and both the experimental as well as theoretical works have been surveyed.In terms of in situ observation of high-temperature interfacial phenomena in the molten steel,researchers utilized high-temperature confocal laser scanning microscopy to observe the movement of more types of inclusions at the interface,i.e.,the investigated inclusion is no longer limited to Al_(2)O_(3)-based inclusions but moves forward to rare earth oxides,MgO-based oxides,etc.In terms of theoretical models,especially the model of inclusions at the steel/slag interface,the recent development has overcome the limitations of the assumptions of Kralchevsky-Paunov model and verified the possible errors caused by the model assumptions by combining the water model and the physical model.Last but not least,the future work in this topic has been suggested,which could be in combination of thermal physical properties of steels and slag,as well as utilize the artificial intelligence-based methodology to implement a comprehensive inclusion motion behaviors during a comprehensive metallurgical process.
基金National Natural Science Foundation of China,Grant/Award Number:22179029Fundamental Research Funds for the Central Universities,Grant/Award Number:buctrc202324+2 种基金Young Elite Scientists Sponsorship Program by BAST,Grant/Award Number:BYESS2023093Ministero dell'Istruzione,dell'Universitàe della Ricerca,Grant/Award Number:2022FNL89YKempestiftelserna。
文摘Selective oxidation of amines to imines through electrocatalysis is an attractive and efficient way for the chemical industry to produce nitrile compounds,but it is limited by the difficulty of designing efficient catalysts and lack of understanding the mechanism of catalysis.Herein,we demonstrate a novel strategy by generation of oxyhydroxide layers on two-dimensional iron-doped layered nickel phosphorus trisulfides(Ni1-xFexPS_(3))during the oxidation of benzylamine(BA).In-depth structural and surface chemical characterizations during the electrocatalytic process combined with theoretical calculations reveal that Ni(1-x)FexPS_(3) undergoes surface reconstruction under alkaline conditions to form the metal oxyhydroxide/phosphorus trichalcogenide(NiFeOOH/Ni1-xFexPS_(3))heterostructure.Interestingly,the generated heterointerface facilitates BA oxidation with a low onset potential of 1.39 V and Faradaic efficiency of 53%for benzonitrile(BN)synthesis.Theoretical calculations further indicate that the as-formed NiFeOOH/Ni1-xFexPS_(3) heterostructure could offer optimum free energy for BA adsorption and BN desorption,resulting in promising BN synthesis.
基金supported by the Korea Institute of Science and Technology(KIST)Institutional Program(Project No.2E32501-23-106)the National Research Foundation of Korea(NRF)grant funded by the Korea government(the Ministry of Science,ICT,MSIT)(RS-2022-00165524)+2 种基金the development of technologies for electroceuticals of National Research Foundation(NRF)funded by the Korean government(MSIT)(RS-2023-00220534)ICT Creative Consilience program through the Institute of Information&Communications Technology Planning&Evaluation(IITP)grant funded by the Korea government(MSIT)(IITP-2024-2020-0-01819)Start up Pioneering in Research and Innovation(SPRINT)through the Commercialization Promotion Agency for R&D Outcomes(COMPA)grant funded by the Korea government(Ministry of Science and ICT)(1711198921).
文摘Soft robots have partially or entirely provided versatile opportunities for issues or roles that cannot be addressed by conventional machine robots,although most studies are limited to designs,controls,or physical/mechanical motions.Here,we present a transformable,reconfigurable robotic platform created by the integration of magnetically responsive soft composite matrices with deformable multifunctional electronics.Magnetic compounds engineered to undergo phase transition at a low temperature can readily achieve reversible magnetization and conduct various changes of motions and shapes.Thin and flexible electronic system designed with mechanical dynamics does not interfere with movements of the soft electronic robot,and the performances of wireless circuit,sensors,and devices are independent of a variety of activities,all of which are verified by theoretical studies.Demonstration of navigations and electronic operations in an artificial track highlights the potential of the integrated soft robot for on-demand,environments-responsive movements/metamorphoses,and optoelectrical detection and stimulation.Further improvements to a miniaturized,sophisticated system with material options enable in situ monitoring and treatment in envisioned areas such as biomedical implants.
基金supported by the Auckland Medical Research Foundation,No.1117017(to CPU)
文摘Perinatal hypoxic-ischemic-encephalopathy significantly contributes to neonatal death and life-long disability such as cerebral palsy. Advances in signal processing and machine learning have provided the research community with an opportunity to develop automated real-time identification techniques to detect the signs of hypoxic-ischemic-encephalopathy in larger electroencephalography/amplitude-integrated electroencephalography data sets more easily. This review details the recent achievements, performed by a number of prominent research groups across the world, in the automatic identification and classification of hypoxic-ischemic epileptiform neonatal seizures using advanced signal processing and machine learning techniques. This review also addresses the clinical challenges that current automated techniques face in order to be fully utilized by clinicians, and highlights the importance of upgrading the current clinical bedside sampling frequencies to higher sampling rates in order to provide better hypoxic-ischemic biomarker detection frameworks. Additionally, the article highlights that current clinical automated epileptiform detection strategies for human neonates have been only concerned with seizure detection after the therapeutic latent phase of injury. Whereas recent animal studies have demonstrated that the latent phase of opportunity is critically important for early diagnosis of hypoxic-ischemic-encephalopathy electroencephalography biomarkers and although difficult, detection strategies could utilize biomarkers in the latent phase to also predict the onset of future seizures.
文摘Metal–organic frameworks(MOFs)with high microporosity and relatively high thermal stability are potential thermal insulation and flame-retardant materials.However,the difficulties in processing and shaping MOFs have largely hampered their applications in these areas.This study outlines the fabrication of hybrid CNF@MOF aerogels by a stepwise assembly approach involving the coating and cross-linking of cellulose nanofibers(CNFs)with continuous nanolayers of MOFs.The cross-linking gives the aerogels high mechanical strength but superelasticity(80%maximum recoverable strain,high specific compression modulus of^200 MPa cm3 g−1,and specific stress of^100 MPa cm3 g−1).The resultant lightweight aerogels have a cellular network structure and hierarchical porosity,which render the aerogels with relatively low thermal conductivity of^40 mW m−1 K−1.The hydrophobic,thermally stable MOF nanolayers wrapped around the CNFs result in good moisture resistance and fire retardancy.This study demonstrates that MOFs can be used as efficient thermal insulation and flame-retardant materials.It presents a pathway for the design of thermally insulating,superelastic fire-retardant nanocomposites based on MOFs and nanocellulose.
基金Project(2017YFC1501100)supported by the National Key R&D Program of ChinaProjects(51809221,51679158)supported by the National Natural Science Foundation of China。
文摘To investigate the stability of rock mass in high geostress underground powerhouse caverns subjected to excavation,a microseismic(MS)monitoring system was established and the discrete element method(DEM)-based numerical simulation was carried out.The tempo-spatial damage characteristics of rock mass were analyzed.The evolution laws of MS source parameters during the formation of a rock collapse controlled by high geostress and geological structure were investigated.Additionally,a three-dimensional DEM model of the underground powerhouse caverns was built to reveal the deformation characteristics of rock mass.The results indicated that the MS events induced by excavation of high geostress underground powerhouse caverns occurred frequently.The large-stake crown of the main powerhouse was the main damage area.Prior to the rock collapse,the MS event count and accumulated energy release increased rapidly,while the apparent stress sharply increased and then decreased.The amount and proportion of shear and mixed MS events remarkably increased.The maximum displacement was generally located near the spandrel areas.The MS monitoring data and numerical simulation were in good agreement,which can provide significant references for damage evaluation and disaster forecasting in high geostress underground powerhouse caverns.
基金the National Science Foundation through Grant No.CMS-9987469.
文摘Viscoelastic dampers are now among some of the preferred energy dissipation devices used for passive seismic response control.To evaluate the performance of structures installed with viscoelastic dampers,different analytical models have been used to characterize their dynamic force deformation characteristics.The fractional derivative models have received favorable attention as they can capture the frequency dependence of the material stiffness and damping properties observed in the tests very well.However,accurate analytical procedures are needed to calculate the response of structures with such damper models.This paper presents a modal analysis approach,similar to that used for the analysis of linear systems,for solving the equations of inotion with fractional derivative terms for arbitrary forcing functions such as those caused by earthquake induced ground motions.The uncoupled modal equations still have fractional derivatives,but can be solved by numerical or analytical procedures.Both numerical and analytical procedures are formulated.These procedures are then used to calculate the dynamic response of a multi-degree of fleedom shear beam structure excited by ground motions. Numerical results demonstrating the response reducing effect of viscoelastic dampers are also presented.
基金Projects(51809221,51679158)supported by the National Natural Science Foundation of ChinaProject(KFJJ20-06M)supported by the State Key Laboratory of Explosion Science and Technology(Beijing Institute of Technology),China。
文摘Rock mass large deformation in underground powerhouse caverns has been a severe hazard in hydropower engineering in Southwest China.During the development of rock mass large deformation,a sequence of fractures was generated that can be monitored using microseismic(MS)monitoring techniques.Two MS monitoring systems were established in two typical underground powerhouse caverns featuring distinct geostress levels.The MS b-values associated with rock mass large deformation and their temporal variation are analysed.The results showed that the MS bvalue in course of rock mass deformation was less than 1.0 in the underground powerhouse caverns at a high stress level while larger than 1.5 at a low stress level.Prior to the rock mass deformation,the MS b-values derived from both the high-stress and low-stress underground powerhouse caverns show an incremental decrease over 10%within 10 d.The results contribute to understanding the fracturing characteristics of MS sources associated with rock mass large deformation and provide a reference for early warning of rock mass large deformation in underground powerhouse caverns.
