The expansibility and mechanical properties of shale are significantly influenced by water-based muds(WBMs);thus,it is necessary to mitigate this effect to avoid borehole instabilities in drilling operation.Potassium ...The expansibility and mechanical properties of shale are significantly influenced by water-based muds(WBMs);thus,it is necessary to mitigate this effect to avoid borehole instabilities in drilling operation.Potassium chloride(KCl)is usually used as inhibitor to reduce hydration of shales.In this study,we investigated the inhibitory efficiency of KCl on shale through a series of experiments,including dynamic linear swelling(DLS)tests and uniaxial compressive strength(UCS)tests,to provide reference for the design of WBMs.These tests were conducted on shale samples soaked in KCl solution for 24,48,72,and 96 h with saline concentrations of 0%,2%,4%,6%,and 8%.Experimental results show that samples with microcracks and bedding fissures have the highest swelling increase and the largest strength reduction after immersion in solution.The swelling potential decreased with increasing KCl concentration.In addition,KCl exhibited a certain inhibitory effect on the weakening of the mechanical properties of samples.An increase in the KCl concentration increases the compressive strength and elastic modulus,and decreases the Poisson's ratio.However,in terms of homogeneous samples,the UCS test results show that exposure to water is weakly related to weakening of the mechanical properties of shale samples.We found that immersing the shale in KCl solution for a longer time decreases the compressive strength,increases the Poisson's ratio,and decreases the elastic modulus.展开更多
We investigate the null tests of cosmic accelerated expansion by using the baryon acoustic oscillation(BAO)data measured by the dark energy spectroscopic instrument(DESI)and reconstruct the dimensionless Hubble parame...We investigate the null tests of cosmic accelerated expansion by using the baryon acoustic oscillation(BAO)data measured by the dark energy spectroscopic instrument(DESI)and reconstruct the dimensionless Hubble parameter E(z)from the DESI BAO Alcock-Paczynski(AP)data using Gaussian process to perform the null test.We find strong evidence of accelerated expansion from the DESI BAO AP data.By reconstructing the deceleration parameter q(z) from the DESI BAO AP data,we find that accelerated expansion persisted until z■0.7 with a 99.7%confidence level.Additionally,to provide insights into the Hubble tension problem,we propose combining the reconstructed E(z) with D_(H)/r_(d) data to derive a model-independent result r_(d)h=99.8±3.1 Mpc.This result is consistent with measurements from cosmic microwave background(CMB)anisotropies using the ΛCDM model.We also propose a model-independent method for reconstructing the comoving angular diameter distance D_(M)(z) from the distance modulus μ,using SNe Ia data and combining this result with DESI BAO data of D_(M)/r_(d) to constrain the value of r_(d).We find that the value of r_(d),derived from this model-independent method,is smaller than that obtained from CMB measurements,with a significant discrepancy of at least 4.17σ.All the conclusions drawn in this paper are independent of cosmological models and gravitational theories.展开更多
There is an urgent need to develop magnesium-matrix materials that exhibit both high thermal conductivity and low thermal expansion to ensure compatibility with chips.This study aims to develop a Mg-Zn-Cu alloy with h...There is an urgent need to develop magnesium-matrix materials that exhibit both high thermal conductivity and low thermal expansion to ensure compatibility with chips.This study aims to develop a Mg-Zn-Cu alloy with high thermal conductivity.Furthermore,it explores the preparation of AlN_(P)/Mg-Zn-Cu composites featuring low coefficients of thermal expansion.The stir casting method was utilized to fabricate the composites and an investigation was conducted to examine their microstructure and thermal properties.Results indicate that the addition of AlN_(P)reduces the thermal expansion coefficient while maintaining relatively high thermal conductivity.Specifically,the AlN_(P)/Mg-0.5Zn-0.5Cu composite with 30wt.%AlN_(P)achieves a thermal conductivity of 132.7 W·m^(-1)·K^(-1)and a thermal expansion coefficient of 18.5×10^(-6)K^(-1),rendering it suitable for electronic packaging applications where thermal management is critical.展开更多
The cement-fly ash composite expansive stable grout was prepared to deal with the problems of poor stability and volume shrinkage of ordinary cement grout,and the effects of fly ash ratio and water-binder ratio on the...The cement-fly ash composite expansive stable grout was prepared to deal with the problems of poor stability and volume shrinkage of ordinary cement grout,and the effects of fly ash ratio and water-binder ratio on the properties of the grout and its consolidation were analyzed.In addition,the mineral composition and microstructural characteristics of grout consolidation with different mixing ratios were investigated.The experimental results indicate that fly ash and the increase of water-binder ratio reduce the strength of the grout consolidation,and increase the fluidity,bleeding rate,and setting time of the composite grout.However,the magnitude of the fly ash-induced strength reduction decreases with time.And the effect of fly ash on the setting time and compressive strength becomes more significant with the water-binder ratio.The later expansion performance of grout consolidation(after 7-42 d)is improved by fly ash.But the expansibility of consolidation with fly ash decreases at the early curing stage,and the reduction amplitude of expansion rate is smaller and the reduction age is shorter with the water-binder ratio increase.Fly ash improves the corrosion resistance performance of grout consolidation,and the corrosion resistance coefficient rises first and then falls with the fly ash ratio.And for 0.6:1 water-binder ratio,the corrosion resistance coefficient of the samples mixed with fly ash are greater than 100%.XRD and SEM show that fly ash inhibited the formation of ettringite in the early stage,which is unfavorable to the expansion of the slurry,and with the increase of age,this effect gradually weakened.展开更多
Purpose–The bridge expansion joint(BEJ)is a key device for accommodating spatial displacement at the beam end,and for providing vertical support for running trains passing over the gap between the main bridge and the...Purpose–The bridge expansion joint(BEJ)is a key device for accommodating spatial displacement at the beam end,and for providing vertical support for running trains passing over the gap between the main bridge and the approach bridge.For long-span railway bridges,it must also be coordinated with rail expansion joint(REJ),which is necessary to accommodate the expansion and contraction of,and reducing longitudinal stress in,the rails.The main aim of this study is to present analysis of recent developments in the research and application of BEJs in high-speed railway(HSR)long-span bridges in China,and to propose a performance-based integral design method for BEJs used with REJs,from both theoretical and engineering perspectives.Design/methodology/approach–The study first presents a summary on the application and maintenance of BEJs in HSR long-span bridges in China representing an overview of their state of development.Results of a survey of typical BEJ faults were analyzed,and field testing was conducted on a railway cable-stayed bridge in order to obtain information on the major mechanical characteristics of its BEJ under train load.Based on the above,a performance-based integral design method for BEJs with maximum expansion range 1600 mm(±800 mm),was proposed,covering all stages from overall conceptual design to consideration of detailed structural design issues.The performance of the novel BEJ design thus derived was then verified via theoretical analysis under different scenarios,full-scale model testing,and field testing and commissioning.Findings–Two major types of BEJs,deck-type and through-type,are used in HSR long-span bridges in China.Typical BEJ faults were found to mainly include skewness of steel sleepers at the bridge gap,abnormally large longitudinal frictional resistance,and flexural deformation of the scissor mechanisms.These faults influence BEJ functioning,and thus adversely affect track quality and train running performance at the beam end.Due to their simple and integral structure,deck-type BEJs with expansion range 1200 mm(±600 mm)or less have been favored as a solution offering improved operational conditions,and have emerged as a standard design.However,when the expansion range exceeds the above-mentioned value,special design work becomes necessary.Therefore,based on engineering practice,a performance-based integral design method for BEJs used with REJs was proposed,taking into account four major categories of performance requirements,i.e.,mechanical characteristics,train running quality,durability and insulation performance.Overall BEJ design must mainly consider component strength and the overall stiffness of BEJ;the latter factor in particular has a decisive influence on train running performance at the beam end.Detailed BEJ structural design must stress minimization of the frictional resistance of its sliding surface.The static and dynamic performance of the newlydesigned BEJ with expansion range 1600 mm have been confirmed to be satisfactory,via numerical simulation,full-scale model testing,and field testing and commissioning.Originality/value–This research provides a broad overview of the status of BEJs with large expansion range in HSR long-span bridges in China,along with novel insights into their design.展开更多
High-finesse optical reference cavities are essential tools for fundamental research.In response to China’s historical reliance on importing high-finesse optical reference cavities,we successfully developed a cavity ...High-finesse optical reference cavities are essential tools for fundamental research.In response to China’s historical reliance on importing high-finesse optical reference cavities,we successfully developed a cavity using ultralow expansion glass(ULE)materials and processed it entirely in China.Using the method of measuring the cavity linewidth,a finesse of approximately 480000 was obtained in our experiments.We adopted a relatively simple and effective approach to test the optical reference cavity,which involved measuring the resonant points using an ultrastable laser.Remarkably,an expansion coefficient of the Chinese ULE optical reference cavity reached up to the order of 10^(-9)/K within the temperature range of 27℃to 40℃,with the zero expansion point occurring at approximately 34oC.These findings demonstrate China’s independent capability to develop high-finesse optical reference cavities,which is a significant advancement in precision optics.展开更多
Obtaining high-quality 10000-meter-deep seafloor sediment samples is the prerequisite and foundation for conducting deep-sea geological and environmental scientific research.The bottom structure of the deep seafloor i...Obtaining high-quality 10000-meter-deep seafloor sediment samples is the prerequisite and foundation for conducting deep-sea geological and environmental scientific research.The bottom structure of the deep seafloor is complex,and the physical and mechanical properties and disturbance resistance of sediments of different lithologies vary greatly,so the sediment sampler inevitably disturbs the sediments during the sampling process and affects the quality of the sediment samples.A new type of deep-sea sediment pressure retaining sampler is introduced,the force state and elastic–plastic state of the sampler destroying sediments are analyzed,the radial disturbance model of sediment coring based on the spherical cavity expansion theory is established,and the radius of sediments undergoing plastic deformation around the spherical holes is used as an index for evaluating the radial disturbance of sediments.The distribution of stress and strain fields in the sediments during the expansion of the spherical cavity and the influencing factors of the radius of the radially disturbed region(plastic region)are analyzed using an arithmetic example,and the influence law is analyzed.A sediment disturbance experimental platform was built indoors to simulate the sediment coring process.The radial stress field and pore water pressure of the sediment during the coring process were monitored by sensors arranged inside the sediment,and the results of indoor tests verified the correctness of the perturbation theory model.The sampler was carried aboard the deep-sea manned submersible FENDOUZHE and conducted on-site tests at depths of 9298.4 and 9142.8 m in the Kuril-Kamchatka Trench.Pressure-preserved sediment samples were retrieved,with preservation rates of 94.21%and 92.02%,respectively,which are much higher than the current technical indicator of 80%of pressure-holding ratio for deep-sea sediments.The retrieved sediments have obvious stratification characteristics and little disturbance.展开更多
Due to batteries inconsistencies and potential faults in battery management systems,slight overcharging remains a common yet insufficiently understood safety risk,lacking effective warning methods.To illuminate the de...Due to batteries inconsistencies and potential faults in battery management systems,slight overcharging remains a common yet insufficiently understood safety risk,lacking effective warning methods.To illuminate the degradation behavior and failure mechanism of various overcharged states(100%SOC,105%SOC,110%SOC,and 115%SOC),multiple advanced in-situ characterization techniques(accelerating rate calorimeter,electrochemical impedance spectroscopy,ultrasonic scanning,and expansion instrument)were utilized.Additionally,re-overcharge-induced thermal runaway(TR)tests were conducted,with a specific emphasis on the evolution of the expansion force signal.Results indicated significant degradation at 110%SOC including conductivity loss,loss of lithium inventory,and loss of active material accompanied by internal gas generation.These failure behaviors slow down the expansion force rate during reovercharging,reducing the efficacy of active warnings that depend on rate thresholds of expansion force.Specifically,the warning time for 115%SOC battery is only 144 s,which is 740 s shorter than that for fresh battery,and the time to TR is advanced by 9 min.Moreover,the initial self-heating temperature(T1)is reduced by 62.4℃compared to that of fresh battery,reaching only 70.8℃.To address the low safety of overcharged batteries,a passive overcharge warning method utilizing relaxation expansion force was proposed,based on the continued gas generation after stopping charging,leading to a sustained increase in force.Compared to active methods that rely on thresholds of expansion force rate,the passive method can issue warnings 115 s earlier.By combining the passive and active warning methods,guaranteed effective overcharge warning can be issued 863-884 s before TR.This study introduces a novel perspective for enhancing the safety of batteries.展开更多
Sulfate attack-induced expansion of cement-treated aggregates in seasonally frozen regions is a well-known issue which causes continuous expansion in railway subgrades,and particularly in high-speed railways.According...Sulfate attack-induced expansion of cement-treated aggregates in seasonally frozen regions is a well-known issue which causes continuous expansion in railway subgrades,and particularly in high-speed railways.Accordingly,we investigated the influence of material proportions,the number of freeze-thaw(FT)cycles,and temperature gradients on the expansion mechanism of sulfate attack on cement-treated aggregates subjected to FT cycles.The conditions,laws,and dominant factors causing the expansion of aggregates were analyzed through swelling tests.The results indicate that under FT cycles,3%content cement-treated graded macadam only experiences slight deformation.The maximum strain of graded macadam attacked by 1%sodium sulfate content in each FT cycle is significantly larger than that of 3%content cement-treated graded macadam attacked by 1%sodium sulfate content.Using scanning electron microscopy,needle-like crystals were observed during sulfate attack of cement-treated graded macadam.Through quantitative analysis,we determined the recoverable and unrecoverable deformations of graded macadam under FT cycles.For graded macadam under sulfate attack,the expansion is mainly induced by periodic frost heave and salt expansion,as well as salt migration.For cement-treated graded macadam under sulfate attack,the expansion is mainly induced by chemical attack and salt migration.This study can serve as a reference for future research on the mechanics of sulfate attack on cement-treated aggregates that experience FT cycles,and provide theoretical support for methods that remediate the expansion induced by sulfate attack.展开更多
Negative thermal expansion(NTE)is a notable physical property where a material’s volume decreases instead of increasing when heated.The identification of NTE materials is crucial for thermal expansion control enginee...Negative thermal expansion(NTE)is a notable physical property where a material’s volume decreases instead of increasing when heated.The identification of NTE materials is crucial for thermal expansion control engineering.Most NTE materials exhibit NTE only within a narrow temperature range,restricting their applications.Achieving NTE across a broad temperature range remains a significant challenge.This study developed a novel PbTiO_(3)-based system,(1-x)PbTiO_(3–x)BiLuO_(3),incorporating rare-earth elements,using a distinctive high-pressure and high-temperature synthesis technique.We achieved NTE across a broad temperature range by coupling lattice(c/a)with ferroelectric order parameters.The incorporation of BiLuO_(3)resulted in distinctive ferroelectric characteristics,including increased tetragonality,spontaneous polarization,and NTE over a broad temperature range.NTE over an extended temperature range has been achieved in 0.95PbTiO_(3)–0.05BiLuO_(3)(■=−1.7×10^(–5)K^(−1),300–840 K)and 0.90PbTiO_(3)–0.10BiLuO_(3)(■=−1.4×10^(–5)K^(−1),300–860 K),compared to pristine PbTiO_(3)(■=−1.99×10^(–5)K^(−1),300–763 K).The improved tetragonalities and broader NTE temperature range result from the strong hybridization of Pb/Bi–O and Ti/Lu–O atoms,as demonstrated by combined experimental and theoretical analyses,including high-energy synchrotron X-ray diffraction,Raman spectroscopy,and density functional theory calculations.This study introduces a novel example of NTE over a broad temperature range,highlighting its potential as a high-performance thermal expansion compensator.Additionally,it presents an effective method for incorporating rare-earth elements to achieve NTE in PbTiO_(3)-based perovskites across a wide temperature range.展开更多
Minimizing the thermal expansion coefficient(TEC)mismatch between the cathode and electrolyte in solid oxide fuel cells is crucial for achieving stable,durable operation and high performance.Recently,materials with ne...Minimizing the thermal expansion coefficient(TEC)mismatch between the cathode and electrolyte in solid oxide fuel cells is crucial for achieving stable,durable operation and high performance.Recently,materials with negative thermal expansion(NTE)have at-tracted significant attention as effective additives for tailoring the thermomechanical properties of electrodes and enhancing cell durability.In this work,for the first time,single-phase NTE perovskite Sm_(0.85)Zn_(0.15)MnO_(3−δ)(SZM15)was successfully synthesized via the sol-gel method,eliminating the unwanted ZnO phase typically observed in materials obtained through the conventional solid-state reaction route.The sol-gel approach proved highly advantageous,offering low cost,robustness,excellent chemical homogeneity,precise compositional control,and high phase purity.After optimization of synthesis parameters,a negative TEC of approximately−6.5×10^(−6)K^(−1)was achieved in the 400-850℃range.SZM15 was then incorporated as an additive(10wt%-50wt%)into a SmBa0.5Sr0.5CoCuO_(5+δ)(SBSCCO)cathode to tune the thermomechanical properties with a La_(0.8)Sr_(0.2)Ga_(0.8)Mg_(0.2)O_(3−δ)(LSGM)electrolyte,achieving a minimal TEC mismatch of only 1%.Notably,the SBSCCO+10wt%SZM15 composite cathode exhibited the lowest polarization resistance of 0.019Ω·cm^(2)at 900℃,showing approximately 70%lower than that of the pristine cathode.Excellent long-term stability after 100 h of operation was achieved.In addition,a high peak power density of 680 mW·cm^(−2)was achieved in a Ni-YSZ(yttria-stabilized zirconia)|YSZ|Ce_(0.9)Gd_(0.1)O_(2−δ)(GDC10)|SBSCCO+10wt%SZM15 anode-supported fuel cell at 850℃,highlighting the effectiveness of incorporating NTE materials as a promising strategy for regulating the thermomechanical properties and improving the long-term stability of intermediate temperature solid oxide fuel cells(IT-SOFCs).展开更多
This paper investigates ruin,capital injection,and dividends for a two-dimensional risk model.The model posits that surplus levels of insurance companies are governed by a perturbed composite Poisson risk model.This m...This paper investigates ruin,capital injection,and dividends for a two-dimensional risk model.The model posits that surplus levels of insurance companies are governed by a perturbed composite Poisson risk model.This model introduces a dependence between the two surplus levels,present in both the associated perturbations and the claims resulting from common shocks.Critical levels of capital injection and dividends are established for each of the two risks.The surplus levels are observed discretely at fixed intervals,guiding decisions on capital injection,dividends,and ruin at these junctures.This study employs a two-dimensional Fourier cosine series expansion method to approximate the finite time expected discounted operating cost until ruin.The ensuing approximation error is also quantified.The validity and accuracy of the method are corroborated through numerical examples.Furthermore,the research delves into the optimal capital allocation problem.展开更多
Introduction The predominant characteristics of high-altitude climates include low air pressure,low humidity,and large diurnal temperature fluctuations.In practical engineering scenarios in high-altitude regions,many ...Introduction The predominant characteristics of high-altitude climates include low air pressure,low humidity,and large diurnal temperature fluctuations.In practical engineering scenarios in high-altitude regions,many pier surface cracks only appear several months after erection,and cyclic thermal stress is identified as the main trigger for such cracking.The thermal stress in concrete structures has been investigated for decades but remains incompletely understood.Structural engineers typically regard concrete as an isotropic material and calculate the thermal stress using code-specified coefficients of thermal expansion(CTEs)along with temperature conditions and constraints.Because the CTE of hardened cement paste is more than twice that of many aggregates,reducing the CTE of coarse aggregates can further exacerbate the thermal deformation incompatibility between the coarse aggregate and mortar matrix.In this paper,a comprehensive thermal-elastic mechanics model for pier concrete was developed to analysis the temperature-induced surface stress.Methods A series of mechanical and thermophysical tests were conducted on the diorite aggregate,ITZ cement paste,and mortar,and concrete.A test pier was constructed on open ground near the Yarlung Zangbo River at an altitude of 3800 m.The pier had a diameter of 1.8 m and height of 2 m.Temperature sensors were embedded in the cross-section at a height of 1 m,positioned along the southnorth and east-west directions.The embedding depths(distances from the pier surface)were 0,1.5,3,4.5,6,7.5,9,12,15,20,25,30,35,40,50,60,70,80 cm,and 90 cm.A model of the bridge pier concrete for surface-level analysis was constructed.The model consists of a concrete unit formed as a sphere-shell-shell composite,including the aggregate,ITZ,and mortar layers,embedded in the surface layer of a bridge pier.Outside this unit,the pier concrete was treated as an isotropic,homogeneous elastic material.The real-time internal temperature fields of high-altitude concrete bridge piers,measured on-site,were incorporated into the model.By applying thermoelastic mechanics theory and finite element solutions for plane strain problems,the three-dimensional thermal stresses on the surface layer of high-altitude bridge piers were analyzed Results and discussion During the experimental period,the lowest and highest temperatures on the bridge pier in the high-altitude region were 9.6 ℃ and 42.6 ℃,respectively.These occurred before sunrise and sunset on sunny days,respectively,corresponding to the local maximum temperature gradients during the surface heating and cooling stages,as well as the maximum temperature difference between the surface and center during these stages.The thermal stress on the pier concrete surface was obtained by superimposing the stresses caused by the uneven distribution of the internal temperature field and those caused by the incompatible thermal deformation among the different components in the surface concrete Before the erection of the upper structures,the absolute values of the tangential and vertical stresses were the same;therefore,only one curve was observed.From 22:00 to 8:00,the pier concrete surface was in tension,whereas from 11:00 to 22:00,the pier concrete surface was in compression.The surface of the pier concrete was subjected to biaxial forces of equal magnitude with a maximum compressive stress of 12.52 MPa and maximum tensile stress of 2.15 MPa,respectively at 18:00 and 8:00.According to the fatigue equation,the concrete was predicted to crack after 21 d of temperature cycling.Moreover,if humidity-induced stress is added on top of this,the tensile stress may approach or even exceed the concrete's tensile strength,thereby posing a significant risk of cracking.After the erection of upper structures,the tangential and vertical stresses no longer coincide because the upper structures have been erected.The curve of the tangential stress is unchanged,whereas the curve of the vertical stress is translated downwards by 1.57 MPa due to the structural deadweight.Therefore,the maximum tangential compressive stress remained 12.52 MPa,whereas the maximum vertical compressive stress increased to 14.09 MPa.Additionally,the maximum tangential tensile stress was 2.15 MPa,and the maximum vertical tensile stress was 0.58 MPa.According to Appendix C of GB/T 50010 and the fatigue equation,stresses are unlikely to cause cracking of the pier concrete surface.Although a higher CTE of the coarse aggregate slightly increased the maximum compressive stress,the differences among the three groups of concrete were minimal and could be ignored.Specifically,the maximum compressive stresses on the pier concrete surface were 12.54,12.45 MPa,and 12.56 MPa when using diorite,limestone,and basalt,respectively.By contrast,a lower CTE of the coarse aggregate results in a greater maximum tensile stress on the pier concrete surface.For example,when using limestone,which has a low CTE,the maximum tensile stress on the pier concrete surface is 2.28 MPa,compared to 2.17 MPa when using diorite and 2.14 MPa when using basalt.The finite element simulation results indicated that the maximum compressive stress on the pier concrete surface was 11.72 MPa,whereas the maximum tensile stress was 2.10 MPa.These results are approximately consistent with the theoretical calculations.This consistency provides mutual verification.Conclusions Surface cracking in pier concrete occurs predominantly before the erection of upper structures.Under sunny conditions,the orthogonal decomposition of the superficial stress revealed that the maximum compressive stress during the day was approximately 12.52 MPa,whereas the maximum tensile stress was approximately 2.15 MPa.This tensile stress approached the tensile strength of the C35 concrete under biaxial tension.The risk of cracking increased significantly when humidity-induced stress was considered.After the erection of upper structures,the maximum tangential tensile stress on the pier surface remained at 2.15 MPa while the maximum vertical stress decreased to 0.58 MPa,both of which are well below the tensile strength of C35 concrete under biaxial tension.Although the use of coarse aggregates with a lower coefficient of thermal expansion reduced the tensile stress induced by temperature gradients,it increased the stress owing to material deformation incompatibility,leading to a slight increase in the maximum tensile stress on the pier concrete surface.展开更多
For the Sylvester continued fraction expansions of real numbers,FAN et al.(2007)proved that,for almost all real numbers,the nth partial quotient grows exponentially with respect to the product of the first n-1 partial...For the Sylvester continued fraction expansions of real numbers,FAN et al.(2007)proved that,for almost all real numbers,the nth partial quotient grows exponentially with respect to the product of the first n-1 partial quotients.In this paper,we establish the Hausdorff dimension of the exceptional set where the growth rate is a general function.展开更多
As a negative electrode material for lithium-ion batteries,silicon monoxide(SiO)suffers from dramatic volume changes during cycling,causing excessive stress within the electrode and resulting in electrode deformation ...As a negative electrode material for lithium-ion batteries,silicon monoxide(SiO)suffers from dramatic volume changes during cycling,causing excessive stress within the electrode and resulting in electrode deformation and fragmentation.This ultimately leads to a decrease in cell capacity.The trends of volume expansion and capacity change of the SiO/graphite(SiO/C)composite electrode during cycling were investigated via in situ expansion monitoring.First,a series of expansion test schemes were designed,and the linear relationship between negative electrode expansion and cell capacity degradation was quantitatively analyzed.Then,the effects of different initial pressures on the long-term cycling performance of the cell were evaluated.Finally,the mechanism of their effects was analyzed by scanning electron microscope.The results show that after 50 cycles,the cell capacity decreases from 2.556 mAh to 1.689 mAh,with a capacity retention ratio(CRR)of only 66.08%.A linear relationship between the capacity retention ratio and thickness expansion was found.Electrochemical measurements and scanning electron microscope images demonstrate that intense stress inhibits the lithiation of the negative electrode and that the electrode is more susceptible to irreversible damage during cycling.Overall,these results reveal the relationship between the cycling performance of SiO and the internal pressure of the electrode from a macroscopic point of view,which provides some reference for the application of SiO/C composite electrodes in lithium-ion batteries.展开更多
In this paper,we establish common fixed point theorems for expansive map?pings on b-metric-like space and coincidence point for f-weakly isotone increasing mappings in partially ordered b-metric-like space.The main re...In this paper,we establish common fixed point theorems for expansive map?pings on b-metric-like space and coincidence point for f-weakly isotone increasing mappings in partially ordered b-metric-like space.The main results generalize and extend several well-known comparable results from the existing literature.Moreover,some examples are provided to illustrate the main results.展开更多
The expansion of construction land on slopes in mountainous cities like Lanzhou has addressed the shortage of flat land but compromised slope stability,leading to uneven land subsidence and risks to infrastructure.Thi...The expansion of construction land on slopes in mountainous cities like Lanzhou has addressed the shortage of flat land but compromised slope stability,leading to uneven land subsidence and risks to infrastructure.This study assessed the land subsidence before and after urban expansion in five areas of Lanzhou by using slope spectrum construction method and gradient expansion intensity measurement that integrated with SBAS-InSAR technology.The results show that construction land on slopes over 20°increased significantly,accounting for 16%of new construction land.The average slope spectrum index was 4.02,with the upper slope limit rising by 8.2°.The land subsidence rate threshold increased by 10 mm/a,and the proportion of pixels experiencing subsidence greater than 5 mm/year rose from 3.63%to 5.24%.Increased construction intensity on slopes caused higher and faster subsidence,which diminished with greater distance from the expansion areas.Areas with slopes between 10°and 25°saw the greatest acceleration in subsidence.Geological composition,building density,groundwater exploitation,and cut-and-fill thickness collectively influence land subsidence rates.This study provides a scientific basis for mitigating geological disaster risks and promoting safe urban development in mountainous cities.展开更多
Silicon-based materials are considered as the next generation anode to replace graphite due to their low cost and ultra-high theoretical capacity.However,significant volume expansion and contraction occur during charg...Silicon-based materials are considered as the next generation anode to replace graphite due to their low cost and ultra-high theoretical capacity.However,significant volume expansion and contraction occur during charging and discharging processes,leading to the instability of electrode structure and susceptibility to peeling and damage,limiting its application.Constructing controllable molecular artificial solid electrolyte interphase(CMASEI)is an effective approach to address the commercialization of silicon-based anode materials[1].Improving the performance of silicon-based anodes through CMASEI is a multifaceted outcome.展开更多
TheγδT cells are an emerging class of immune effectors with potent antitumor activity,bridging innate and adaptive immunity.Their unique ability to recognise stress-induced ligands independently of major histocompat...TheγδT cells are an emerging class of immune effectors with potent antitumor activity,bridging innate and adaptive immunity.Their unique ability to recognise stress-induced ligands independently of major histocompatibility complex restriction makes them attractive candidates for cancer immunotherapy.However,the clinical application ofγδT cells requires efficient in vitro expansion strategies to generate large numbers of functional cells.This mini-review explores the latest advancements inγδT cell expansion protocols,focusing on key activation stimuli,cytokine support,and culture conditions that optimise proliferation and cytotoxicity.展开更多
基金This work was financially supported by the Foundation of National Natural Science Foundation of China(No.511774248 and 51504208)the Open Research Fund of the Key Laboratory of Deep Undergroud Science and Engineering(Sichuan University)Minstry of Education,China and the Open Research Fund of the State Key Laboratory of Geomechanics and Geotechnical Engineering,Institute of Rock and Soil Mechanics,Chinese Academy of Sciences,China(No.Z016013).
文摘The expansibility and mechanical properties of shale are significantly influenced by water-based muds(WBMs);thus,it is necessary to mitigate this effect to avoid borehole instabilities in drilling operation.Potassium chloride(KCl)is usually used as inhibitor to reduce hydration of shales.In this study,we investigated the inhibitory efficiency of KCl on shale through a series of experiments,including dynamic linear swelling(DLS)tests and uniaxial compressive strength(UCS)tests,to provide reference for the design of WBMs.These tests were conducted on shale samples soaked in KCl solution for 24,48,72,and 96 h with saline concentrations of 0%,2%,4%,6%,and 8%.Experimental results show that samples with microcracks and bedding fissures have the highest swelling increase and the largest strength reduction after immersion in solution.The swelling potential decreased with increasing KCl concentration.In addition,KCl exhibited a certain inhibitory effect on the weakening of the mechanical properties of samples.An increase in the KCl concentration increases the compressive strength and elastic modulus,and decreases the Poisson's ratio.However,in terms of homogeneous samples,the UCS test results show that exposure to water is weakly related to weakening of the mechanical properties of shale samples.We found that immersing the shale in KCl solution for a longer time decreases the compressive strength,increases the Poisson's ratio,and decreases the elastic modulus.
基金supported in part by the National Key Research and Development Program of China (Grant No.2020YFC2201504)the National Natural Science Foundation of China (Grant Nos.12588101 and 12535002)。
文摘We investigate the null tests of cosmic accelerated expansion by using the baryon acoustic oscillation(BAO)data measured by the dark energy spectroscopic instrument(DESI)and reconstruct the dimensionless Hubble parameter E(z)from the DESI BAO Alcock-Paczynski(AP)data using Gaussian process to perform the null test.We find strong evidence of accelerated expansion from the DESI BAO AP data.By reconstructing the deceleration parameter q(z) from the DESI BAO AP data,we find that accelerated expansion persisted until z■0.7 with a 99.7%confidence level.Additionally,to provide insights into the Hubble tension problem,we propose combining the reconstructed E(z) with D_(H)/r_(d) data to derive a model-independent result r_(d)h=99.8±3.1 Mpc.This result is consistent with measurements from cosmic microwave background(CMB)anisotropies using the ΛCDM model.We also propose a model-independent method for reconstructing the comoving angular diameter distance D_(M)(z) from the distance modulus μ,using SNe Ia data and combining this result with DESI BAO data of D_(M)/r_(d) to constrain the value of r_(d).We find that the value of r_(d),derived from this model-independent method,is smaller than that obtained from CMB measurements,with a significant discrepancy of at least 4.17σ.All the conclusions drawn in this paper are independent of cosmological models and gravitational theories.
基金financially supported by National Natural Science Foundation of China(No.52175321)the Fund of Key Laboratory of High Temperature Electromagnetic Materials and Structure of MOE(No.KB202505)。
文摘There is an urgent need to develop magnesium-matrix materials that exhibit both high thermal conductivity and low thermal expansion to ensure compatibility with chips.This study aims to develop a Mg-Zn-Cu alloy with high thermal conductivity.Furthermore,it explores the preparation of AlN_(P)/Mg-Zn-Cu composites featuring low coefficients of thermal expansion.The stir casting method was utilized to fabricate the composites and an investigation was conducted to examine their microstructure and thermal properties.Results indicate that the addition of AlN_(P)reduces the thermal expansion coefficient while maintaining relatively high thermal conductivity.Specifically,the AlN_(P)/Mg-0.5Zn-0.5Cu composite with 30wt.%AlN_(P)achieves a thermal conductivity of 132.7 W·m^(-1)·K^(-1)and a thermal expansion coefficient of 18.5×10^(-6)K^(-1),rendering it suitable for electronic packaging applications where thermal management is critical.
基金Funded by the National Natural Science Foundation of China(No.51979153)the Yunnan Key Research and Development Program(No.202103AA080016)。
文摘The cement-fly ash composite expansive stable grout was prepared to deal with the problems of poor stability and volume shrinkage of ordinary cement grout,and the effects of fly ash ratio and water-binder ratio on the properties of the grout and its consolidation were analyzed.In addition,the mineral composition and microstructural characteristics of grout consolidation with different mixing ratios were investigated.The experimental results indicate that fly ash and the increase of water-binder ratio reduce the strength of the grout consolidation,and increase the fluidity,bleeding rate,and setting time of the composite grout.However,the magnitude of the fly ash-induced strength reduction decreases with time.And the effect of fly ash on the setting time and compressive strength becomes more significant with the water-binder ratio.The later expansion performance of grout consolidation(after 7-42 d)is improved by fly ash.But the expansibility of consolidation with fly ash decreases at the early curing stage,and the reduction amplitude of expansion rate is smaller and the reduction age is shorter with the water-binder ratio increase.Fly ash improves the corrosion resistance performance of grout consolidation,and the corrosion resistance coefficient rises first and then falls with the fly ash ratio.And for 0.6:1 water-binder ratio,the corrosion resistance coefficient of the samples mixed with fly ash are greater than 100%.XRD and SEM show that fly ash inhibited the formation of ettringite in the early stage,which is unfavorable to the expansion of the slurry,and with the increase of age,this effect gradually weakened.
基金National Key R&D Program of China(2022YFB2602900)R&D Fund Project of China Academy of Railway Sciences Corporation Limited(2021YJ084)+2 种基金Project of Science and Technology R&D Program of China Railway(2016G002-K)R&D Fund Project of China Railway Major Bridge Reconnaissance&Design Institute Co.,Ltd.(2021)R&D Fund Project of China Railway Shanghai Group(2021141).
文摘Purpose–The bridge expansion joint(BEJ)is a key device for accommodating spatial displacement at the beam end,and for providing vertical support for running trains passing over the gap between the main bridge and the approach bridge.For long-span railway bridges,it must also be coordinated with rail expansion joint(REJ),which is necessary to accommodate the expansion and contraction of,and reducing longitudinal stress in,the rails.The main aim of this study is to present analysis of recent developments in the research and application of BEJs in high-speed railway(HSR)long-span bridges in China,and to propose a performance-based integral design method for BEJs used with REJs,from both theoretical and engineering perspectives.Design/methodology/approach–The study first presents a summary on the application and maintenance of BEJs in HSR long-span bridges in China representing an overview of their state of development.Results of a survey of typical BEJ faults were analyzed,and field testing was conducted on a railway cable-stayed bridge in order to obtain information on the major mechanical characteristics of its BEJ under train load.Based on the above,a performance-based integral design method for BEJs with maximum expansion range 1600 mm(±800 mm),was proposed,covering all stages from overall conceptual design to consideration of detailed structural design issues.The performance of the novel BEJ design thus derived was then verified via theoretical analysis under different scenarios,full-scale model testing,and field testing and commissioning.Findings–Two major types of BEJs,deck-type and through-type,are used in HSR long-span bridges in China.Typical BEJ faults were found to mainly include skewness of steel sleepers at the bridge gap,abnormally large longitudinal frictional resistance,and flexural deformation of the scissor mechanisms.These faults influence BEJ functioning,and thus adversely affect track quality and train running performance at the beam end.Due to their simple and integral structure,deck-type BEJs with expansion range 1200 mm(±600 mm)or less have been favored as a solution offering improved operational conditions,and have emerged as a standard design.However,when the expansion range exceeds the above-mentioned value,special design work becomes necessary.Therefore,based on engineering practice,a performance-based integral design method for BEJs used with REJs was proposed,taking into account four major categories of performance requirements,i.e.,mechanical characteristics,train running quality,durability and insulation performance.Overall BEJ design must mainly consider component strength and the overall stiffness of BEJ;the latter factor in particular has a decisive influence on train running performance at the beam end.Detailed BEJ structural design must stress minimization of the frictional resistance of its sliding surface.The static and dynamic performance of the newlydesigned BEJ with expansion range 1600 mm have been confirmed to be satisfactory,via numerical simulation,full-scale model testing,and field testing and commissioning.Originality/value–This research provides a broad overview of the status of BEJs with large expansion range in HSR long-span bridges in China,along with novel insights into their design.
基金supported by the National Natural Science Foundation of China(Grant Nos.12103059 and 12033007)the National Major Science and Technology Infrastructure Project of China(Grant No.2017-000052-73-01-002401)+3 种基金Xi’an Science and Technology Bureau(Grant No.E019XK1S04)Sanqin Talents’Special Support Program(Grant No.09R0557A00)the Youth Innovation Promotion Association of the Chinese Academy of Science(Grant No.1188000XGJ)the Innovation Program for Quantum Science and Technology(Grant No.2021ZD0300900)。
文摘High-finesse optical reference cavities are essential tools for fundamental research.In response to China’s historical reliance on importing high-finesse optical reference cavities,we successfully developed a cavity using ultralow expansion glass(ULE)materials and processed it entirely in China.Using the method of measuring the cavity linewidth,a finesse of approximately 480000 was obtained in our experiments.We adopted a relatively simple and effective approach to test the optical reference cavity,which involved measuring the resonant points using an ultrastable laser.Remarkably,an expansion coefficient of the Chinese ULE optical reference cavity reached up to the order of 10^(-9)/K within the temperature range of 27℃to 40℃,with the zero expansion point occurring at approximately 34oC.These findings demonstrate China’s independent capability to develop high-finesse optical reference cavities,which is a significant advancement in precision optics.
基金supported by the National Key Research and Development Program of China(Nos.2023YFC2809304 and 2022YFC2805904).
文摘Obtaining high-quality 10000-meter-deep seafloor sediment samples is the prerequisite and foundation for conducting deep-sea geological and environmental scientific research.The bottom structure of the deep seafloor is complex,and the physical and mechanical properties and disturbance resistance of sediments of different lithologies vary greatly,so the sediment sampler inevitably disturbs the sediments during the sampling process and affects the quality of the sediment samples.A new type of deep-sea sediment pressure retaining sampler is introduced,the force state and elastic–plastic state of the sampler destroying sediments are analyzed,the radial disturbance model of sediment coring based on the spherical cavity expansion theory is established,and the radius of sediments undergoing plastic deformation around the spherical holes is used as an index for evaluating the radial disturbance of sediments.The distribution of stress and strain fields in the sediments during the expansion of the spherical cavity and the influencing factors of the radius of the radially disturbed region(plastic region)are analyzed using an arithmetic example,and the influence law is analyzed.A sediment disturbance experimental platform was built indoors to simulate the sediment coring process.The radial stress field and pore water pressure of the sediment during the coring process were monitored by sensors arranged inside the sediment,and the results of indoor tests verified the correctness of the perturbation theory model.The sampler was carried aboard the deep-sea manned submersible FENDOUZHE and conducted on-site tests at depths of 9298.4 and 9142.8 m in the Kuril-Kamchatka Trench.Pressure-preserved sediment samples were retrieved,with preservation rates of 94.21%and 92.02%,respectively,which are much higher than the current technical indicator of 80%of pressure-holding ratio for deep-sea sediments.The retrieved sediments have obvious stratification characteristics and little disturbance.
基金supported by the National Natural Science Foundation of China(52476200,52106244)the Guangdong Basic and Applied Basic Research Foundation(2024A1515030124)+1 种基金the Science and Technology Project of China Southern Power Grid under Grant GDKJXM20230246(030100KC23020017)the Fundamental Research Funds for the Central Universities。
文摘Due to batteries inconsistencies and potential faults in battery management systems,slight overcharging remains a common yet insufficiently understood safety risk,lacking effective warning methods.To illuminate the degradation behavior and failure mechanism of various overcharged states(100%SOC,105%SOC,110%SOC,and 115%SOC),multiple advanced in-situ characterization techniques(accelerating rate calorimeter,electrochemical impedance spectroscopy,ultrasonic scanning,and expansion instrument)were utilized.Additionally,re-overcharge-induced thermal runaway(TR)tests were conducted,with a specific emphasis on the evolution of the expansion force signal.Results indicated significant degradation at 110%SOC including conductivity loss,loss of lithium inventory,and loss of active material accompanied by internal gas generation.These failure behaviors slow down the expansion force rate during reovercharging,reducing the efficacy of active warnings that depend on rate thresholds of expansion force.Specifically,the warning time for 115%SOC battery is only 144 s,which is 740 s shorter than that for fresh battery,and the time to TR is advanced by 9 min.Moreover,the initial self-heating temperature(T1)is reduced by 62.4℃compared to that of fresh battery,reaching only 70.8℃.To address the low safety of overcharged batteries,a passive overcharge warning method utilizing relaxation expansion force was proposed,based on the continued gas generation after stopping charging,leading to a sustained increase in force.Compared to active methods that rely on thresholds of expansion force rate,the passive method can issue warnings 115 s earlier.By combining the passive and active warning methods,guaranteed effective overcharge warning can be issued 863-884 s before TR.This study introduces a novel perspective for enhancing the safety of batteries.
基金National Natural Science Foundation of China(Nos.42171130 and 42301158)Pilot Project of China’s Strength in Transportation for the Central Research Institute(No.QG2021-1-4-7)National Key Technology Research and Development Program of the Ministry of Science and Technology of China(No.2021YFB2601200).
文摘Sulfate attack-induced expansion of cement-treated aggregates in seasonally frozen regions is a well-known issue which causes continuous expansion in railway subgrades,and particularly in high-speed railways.Accordingly,we investigated the influence of material proportions,the number of freeze-thaw(FT)cycles,and temperature gradients on the expansion mechanism of sulfate attack on cement-treated aggregates subjected to FT cycles.The conditions,laws,and dominant factors causing the expansion of aggregates were analyzed through swelling tests.The results indicate that under FT cycles,3%content cement-treated graded macadam only experiences slight deformation.The maximum strain of graded macadam attacked by 1%sodium sulfate content in each FT cycle is significantly larger than that of 3%content cement-treated graded macadam attacked by 1%sodium sulfate content.Using scanning electron microscopy,needle-like crystals were observed during sulfate attack of cement-treated graded macadam.Through quantitative analysis,we determined the recoverable and unrecoverable deformations of graded macadam under FT cycles.For graded macadam under sulfate attack,the expansion is mainly induced by periodic frost heave and salt expansion,as well as salt migration.For cement-treated graded macadam under sulfate attack,the expansion is mainly induced by chemical attack and salt migration.This study can serve as a reference for future research on the mechanics of sulfate attack on cement-treated aggregates that experience FT cycles,and provide theoretical support for methods that remediate the expansion induced by sulfate attack.
基金financially supported by the National Natural Science Foundation of China(Nos.22271309,12425403 and 12261131499)the National Key R&D Program of China(No.2021YFA1400300)+2 种基金financial support from the Science and Technology Development Fund from Macao SAR(No.0062/2023/ITP2)Macao Polytechnic University(No.RP/FCA-03/2023)Synchrotron X-ray powder diffraction experiments were conducted at SPring-8,approved by the Japan Synchrotron Radiation Research Institute(Nos.2024A1506,2024A1695 and 2024B1807)
文摘Negative thermal expansion(NTE)is a notable physical property where a material’s volume decreases instead of increasing when heated.The identification of NTE materials is crucial for thermal expansion control engineering.Most NTE materials exhibit NTE only within a narrow temperature range,restricting their applications.Achieving NTE across a broad temperature range remains a significant challenge.This study developed a novel PbTiO_(3)-based system,(1-x)PbTiO_(3–x)BiLuO_(3),incorporating rare-earth elements,using a distinctive high-pressure and high-temperature synthesis technique.We achieved NTE across a broad temperature range by coupling lattice(c/a)with ferroelectric order parameters.The incorporation of BiLuO_(3)resulted in distinctive ferroelectric characteristics,including increased tetragonality,spontaneous polarization,and NTE over a broad temperature range.NTE over an extended temperature range has been achieved in 0.95PbTiO_(3)–0.05BiLuO_(3)(■=−1.7×10^(–5)K^(−1),300–840 K)and 0.90PbTiO_(3)–0.10BiLuO_(3)(■=−1.4×10^(–5)K^(−1),300–860 K),compared to pristine PbTiO_(3)(■=−1.99×10^(–5)K^(−1),300–763 K).The improved tetragonalities and broader NTE temperature range result from the strong hybridization of Pb/Bi–O and Ti/Lu–O atoms,as demonstrated by combined experimental and theoretical analyses,including high-energy synchrotron X-ray diffraction,Raman spectroscopy,and density functional theory calculations.This study introduces a novel example of NTE over a broad temperature range,highlighting its potential as a high-performance thermal expansion compensator.Additionally,it presents an effective method for incorporating rare-earth elements to achieve NTE in PbTiO_(3)-based perovskites across a wide temperature range.
基金supported by the research project within the program“Excellence Initiative-Research University”for the AGH University of Krakow(IDUB AGH,Action 21)Kun Zheng acknowledges financial support from AGH University of Krakow(No.16.16.210.476).
文摘Minimizing the thermal expansion coefficient(TEC)mismatch between the cathode and electrolyte in solid oxide fuel cells is crucial for achieving stable,durable operation and high performance.Recently,materials with negative thermal expansion(NTE)have at-tracted significant attention as effective additives for tailoring the thermomechanical properties of electrodes and enhancing cell durability.In this work,for the first time,single-phase NTE perovskite Sm_(0.85)Zn_(0.15)MnO_(3−δ)(SZM15)was successfully synthesized via the sol-gel method,eliminating the unwanted ZnO phase typically observed in materials obtained through the conventional solid-state reaction route.The sol-gel approach proved highly advantageous,offering low cost,robustness,excellent chemical homogeneity,precise compositional control,and high phase purity.After optimization of synthesis parameters,a negative TEC of approximately−6.5×10^(−6)K^(−1)was achieved in the 400-850℃range.SZM15 was then incorporated as an additive(10wt%-50wt%)into a SmBa0.5Sr0.5CoCuO_(5+δ)(SBSCCO)cathode to tune the thermomechanical properties with a La_(0.8)Sr_(0.2)Ga_(0.8)Mg_(0.2)O_(3−δ)(LSGM)electrolyte,achieving a minimal TEC mismatch of only 1%.Notably,the SBSCCO+10wt%SZM15 composite cathode exhibited the lowest polarization resistance of 0.019Ω·cm^(2)at 900℃,showing approximately 70%lower than that of the pristine cathode.Excellent long-term stability after 100 h of operation was achieved.In addition,a high peak power density of 680 mW·cm^(−2)was achieved in a Ni-YSZ(yttria-stabilized zirconia)|YSZ|Ce_(0.9)Gd_(0.1)O_(2−δ)(GDC10)|SBSCCO+10wt%SZM15 anode-supported fuel cell at 850℃,highlighting the effectiveness of incorporating NTE materials as a promising strategy for regulating the thermomechanical properties and improving the long-term stability of intermediate temperature solid oxide fuel cells(IT-SOFCs).
基金supported by the Shihezi University High-Level Talents Research Startup Project(Project No.RCZK202521)the National Natural Science Foundation of China(Grant Nos.12271066,11871121,12171405)+1 种基金the Chongqing Natural Science Foundation Joint Fund for Innovation and Development Project(Project No.CSTB2024NSCQLZX0085)the Chongqing Normal University Foundation(Grant No.23XLB018).
文摘This paper investigates ruin,capital injection,and dividends for a two-dimensional risk model.The model posits that surplus levels of insurance companies are governed by a perturbed composite Poisson risk model.This model introduces a dependence between the two surplus levels,present in both the associated perturbations and the claims resulting from common shocks.Critical levels of capital injection and dividends are established for each of the two risks.The surplus levels are observed discretely at fixed intervals,guiding decisions on capital injection,dividends,and ruin at these junctures.This study employs a two-dimensional Fourier cosine series expansion method to approximate the finite time expected discounted operating cost until ruin.The ensuing approximation error is also quantified.The validity and accuracy of the method are corroborated through numerical examples.Furthermore,the research delves into the optimal capital allocation problem.
文摘Introduction The predominant characteristics of high-altitude climates include low air pressure,low humidity,and large diurnal temperature fluctuations.In practical engineering scenarios in high-altitude regions,many pier surface cracks only appear several months after erection,and cyclic thermal stress is identified as the main trigger for such cracking.The thermal stress in concrete structures has been investigated for decades but remains incompletely understood.Structural engineers typically regard concrete as an isotropic material and calculate the thermal stress using code-specified coefficients of thermal expansion(CTEs)along with temperature conditions and constraints.Because the CTE of hardened cement paste is more than twice that of many aggregates,reducing the CTE of coarse aggregates can further exacerbate the thermal deformation incompatibility between the coarse aggregate and mortar matrix.In this paper,a comprehensive thermal-elastic mechanics model for pier concrete was developed to analysis the temperature-induced surface stress.Methods A series of mechanical and thermophysical tests were conducted on the diorite aggregate,ITZ cement paste,and mortar,and concrete.A test pier was constructed on open ground near the Yarlung Zangbo River at an altitude of 3800 m.The pier had a diameter of 1.8 m and height of 2 m.Temperature sensors were embedded in the cross-section at a height of 1 m,positioned along the southnorth and east-west directions.The embedding depths(distances from the pier surface)were 0,1.5,3,4.5,6,7.5,9,12,15,20,25,30,35,40,50,60,70,80 cm,and 90 cm.A model of the bridge pier concrete for surface-level analysis was constructed.The model consists of a concrete unit formed as a sphere-shell-shell composite,including the aggregate,ITZ,and mortar layers,embedded in the surface layer of a bridge pier.Outside this unit,the pier concrete was treated as an isotropic,homogeneous elastic material.The real-time internal temperature fields of high-altitude concrete bridge piers,measured on-site,were incorporated into the model.By applying thermoelastic mechanics theory and finite element solutions for plane strain problems,the three-dimensional thermal stresses on the surface layer of high-altitude bridge piers were analyzed Results and discussion During the experimental period,the lowest and highest temperatures on the bridge pier in the high-altitude region were 9.6 ℃ and 42.6 ℃,respectively.These occurred before sunrise and sunset on sunny days,respectively,corresponding to the local maximum temperature gradients during the surface heating and cooling stages,as well as the maximum temperature difference between the surface and center during these stages.The thermal stress on the pier concrete surface was obtained by superimposing the stresses caused by the uneven distribution of the internal temperature field and those caused by the incompatible thermal deformation among the different components in the surface concrete Before the erection of the upper structures,the absolute values of the tangential and vertical stresses were the same;therefore,only one curve was observed.From 22:00 to 8:00,the pier concrete surface was in tension,whereas from 11:00 to 22:00,the pier concrete surface was in compression.The surface of the pier concrete was subjected to biaxial forces of equal magnitude with a maximum compressive stress of 12.52 MPa and maximum tensile stress of 2.15 MPa,respectively at 18:00 and 8:00.According to the fatigue equation,the concrete was predicted to crack after 21 d of temperature cycling.Moreover,if humidity-induced stress is added on top of this,the tensile stress may approach or even exceed the concrete's tensile strength,thereby posing a significant risk of cracking.After the erection of upper structures,the tangential and vertical stresses no longer coincide because the upper structures have been erected.The curve of the tangential stress is unchanged,whereas the curve of the vertical stress is translated downwards by 1.57 MPa due to the structural deadweight.Therefore,the maximum tangential compressive stress remained 12.52 MPa,whereas the maximum vertical compressive stress increased to 14.09 MPa.Additionally,the maximum tangential tensile stress was 2.15 MPa,and the maximum vertical tensile stress was 0.58 MPa.According to Appendix C of GB/T 50010 and the fatigue equation,stresses are unlikely to cause cracking of the pier concrete surface.Although a higher CTE of the coarse aggregate slightly increased the maximum compressive stress,the differences among the three groups of concrete were minimal and could be ignored.Specifically,the maximum compressive stresses on the pier concrete surface were 12.54,12.45 MPa,and 12.56 MPa when using diorite,limestone,and basalt,respectively.By contrast,a lower CTE of the coarse aggregate results in a greater maximum tensile stress on the pier concrete surface.For example,when using limestone,which has a low CTE,the maximum tensile stress on the pier concrete surface is 2.28 MPa,compared to 2.17 MPa when using diorite and 2.14 MPa when using basalt.The finite element simulation results indicated that the maximum compressive stress on the pier concrete surface was 11.72 MPa,whereas the maximum tensile stress was 2.10 MPa.These results are approximately consistent with the theoretical calculations.This consistency provides mutual verification.Conclusions Surface cracking in pier concrete occurs predominantly before the erection of upper structures.Under sunny conditions,the orthogonal decomposition of the superficial stress revealed that the maximum compressive stress during the day was approximately 12.52 MPa,whereas the maximum tensile stress was approximately 2.15 MPa.This tensile stress approached the tensile strength of the C35 concrete under biaxial tension.The risk of cracking increased significantly when humidity-induced stress was considered.After the erection of upper structures,the maximum tangential tensile stress on the pier surface remained at 2.15 MPa while the maximum vertical stress decreased to 0.58 MPa,both of which are well below the tensile strength of C35 concrete under biaxial tension.Although the use of coarse aggregates with a lower coefficient of thermal expansion reduced the tensile stress induced by temperature gradients,it increased the stress owing to material deformation incompatibility,leading to a slight increase in the maximum tensile stress on the pier concrete surface.
基金Supported by Projects from Chongqing Municipal Science and Technology Commission(CSTB2022NSCQ-MSX0445)。
文摘For the Sylvester continued fraction expansions of real numbers,FAN et al.(2007)proved that,for almost all real numbers,the nth partial quotient grows exponentially with respect to the product of the first n-1 partial quotients.In this paper,we establish the Hausdorff dimension of the exceptional set where the growth rate is a general function.
基金supported by the Fundamental Research Funds for the Central Universities(WK2090000055)Anhui Provincial Natural Science Foundation of China(2308085QG231).
文摘As a negative electrode material for lithium-ion batteries,silicon monoxide(SiO)suffers from dramatic volume changes during cycling,causing excessive stress within the electrode and resulting in electrode deformation and fragmentation.This ultimately leads to a decrease in cell capacity.The trends of volume expansion and capacity change of the SiO/graphite(SiO/C)composite electrode during cycling were investigated via in situ expansion monitoring.First,a series of expansion test schemes were designed,and the linear relationship between negative electrode expansion and cell capacity degradation was quantitatively analyzed.Then,the effects of different initial pressures on the long-term cycling performance of the cell were evaluated.Finally,the mechanism of their effects was analyzed by scanning electron microscope.The results show that after 50 cycles,the cell capacity decreases from 2.556 mAh to 1.689 mAh,with a capacity retention ratio(CRR)of only 66.08%.A linear relationship between the capacity retention ratio and thickness expansion was found.Electrochemical measurements and scanning electron microscope images demonstrate that intense stress inhibits the lithiation of the negative electrode and that the electrode is more susceptible to irreversible damage during cycling.Overall,these results reveal the relationship between the cycling performance of SiO and the internal pressure of the electrode from a macroscopic point of view,which provides some reference for the application of SiO/C composite electrodes in lithium-ion batteries.
基金Supported by the National Natural Science Foundation of China(12001249)the Natural Science Foundation of Jiangxi Province(20232BAB211004)the Educational Commission Science Programm of Jiangxi Province(GJJ2200523)。
文摘In this paper,we establish common fixed point theorems for expansive map?pings on b-metric-like space and coincidence point for f-weakly isotone increasing mappings in partially ordered b-metric-like space.The main results generalize and extend several well-known comparable results from the existing literature.Moreover,some examples are provided to illustrate the main results.
基金National Natural Science Foundation of China(Grant No.42271214)National Key R&D Program of China(Grant No.2022YFC3800700)+1 种基金Key Research Program of Gansu Province(Grant No.23ZDKA0004)Natural Science Foundation of Gansu Province(Grant No.21JR7RA281).
文摘The expansion of construction land on slopes in mountainous cities like Lanzhou has addressed the shortage of flat land but compromised slope stability,leading to uneven land subsidence and risks to infrastructure.This study assessed the land subsidence before and after urban expansion in five areas of Lanzhou by using slope spectrum construction method and gradient expansion intensity measurement that integrated with SBAS-InSAR technology.The results show that construction land on slopes over 20°increased significantly,accounting for 16%of new construction land.The average slope spectrum index was 4.02,with the upper slope limit rising by 8.2°.The land subsidence rate threshold increased by 10 mm/a,and the proportion of pixels experiencing subsidence greater than 5 mm/year rose from 3.63%to 5.24%.Increased construction intensity on slopes caused higher and faster subsidence,which diminished with greater distance from the expansion areas.Areas with slopes between 10°and 25°saw the greatest acceleration in subsidence.Geological composition,building density,groundwater exploitation,and cut-and-fill thickness collectively influence land subsidence rates.This study provides a scientific basis for mitigating geological disaster risks and promoting safe urban development in mountainous cities.
基金supported by the Nanxun Scholars Program for Young Scholars of ZJWEU(No.RC2023021315)the start-up funding for Scientific Research for High-level Talents(No.88106324004)the National Natural Science Foundation of China(No.62304070).
文摘Silicon-based materials are considered as the next generation anode to replace graphite due to their low cost and ultra-high theoretical capacity.However,significant volume expansion and contraction occur during charging and discharging processes,leading to the instability of electrode structure and susceptibility to peeling and damage,limiting its application.Constructing controllable molecular artificial solid electrolyte interphase(CMASEI)is an effective approach to address the commercialization of silicon-based anode materials[1].Improving the performance of silicon-based anodes through CMASEI is a multifaceted outcome.
基金Supported by National Science Center of Poland,No.2019/35/N/NZ6/02973.
文摘TheγδT cells are an emerging class of immune effectors with potent antitumor activity,bridging innate and adaptive immunity.Their unique ability to recognise stress-induced ligands independently of major histocompatibility complex restriction makes them attractive candidates for cancer immunotherapy.However,the clinical application ofγδT cells requires efficient in vitro expansion strategies to generate large numbers of functional cells.This mini-review explores the latest advancements inγδT cell expansion protocols,focusing on key activation stimuli,cytokine support,and culture conditions that optimise proliferation and cytotoxicity.
