China has improved its social security system in recent decades,with the aim of achieving universal coverage and improving the equity of income distribution.Based on data from the five rounds of Chinese Household Inco...China has improved its social security system in recent decades,with the aim of achieving universal coverage and improving the equity of income distribution.Based on data from the five rounds of Chinese Household Income Project surveys from 1988 to 2018,this paper examines the long-term redistributive effects of social security programs in China.Our results show that social security programs have reduced income inequality consistently,and the positive redistributive effects have been improving for the past 30 years.Social security transfers have had an increasingly essential role in rural areas,especially after 2002 when China started to establish a comprehensive rural social safety net and expanded the coverage of the social security program.The redistributive efficiency of the social security system has also increased recently.展开更多
Oxygen evolution reaction(OER)is widely recognized as a bottleneck of water electrolysis.To determine the underlying reaction mechanisms,particularly the relative contribution of the adsorbate evolution mechanism(AEM)...Oxygen evolution reaction(OER)is widely recognized as a bottleneck of water electrolysis.To determine the underlying reaction mechanisms,particularly the relative contribution of the adsorbate evolution mechanism(AEM)and lattice-oxygen participation mechanism(LOM),we conduct a comprehensive investigation combining Density Functional Theory(DFT)calculations and experimental validation.Our theoretical analysis of doped RuO_(2)catalysts reveals that heteroatom doping(Ni,Cu,and Zn)induces significant local charge transfer,leading to the increased charge state of Ru and the downshifted d-band center.This,in turn,enables the mechanism switching from the conventional AEM to the more efficient LOM,and finally improves OER activity.We also establish a simple yet powerful descriptor,Ne of Ru(representing charge density of Ru sites),which enables accurate prediction of both catalytic activity and stability.Guided by these theoretical predictions,we successfully synthesize a Ni-doped RuO_(2)catalyst,which exhibits excellent OER activity and stability in acidic media,achieving an overpotential of just 156 mV and maintaining stability for 4000 h at 10 mA cm^(−2),significantly surpassing the performance of the commercial RuO_(2).These findings not only provide fundamental insights into the mechanism-switching behavior in OER catalysis but also offer a practical strategy for designing high-performance,stable electrocatalysts for acidic water electrolysis.展开更多
Poly(phenylene oxide)(PPO)exhibits excellent dielectric properties,making it an ideal substrate for high-frequency,high-speed copper-clad laminates.The phenolic hydroxyl group at the end of PPO plays a key role in its...Poly(phenylene oxide)(PPO)exhibits excellent dielectric properties,making it an ideal substrate for high-frequency,high-speed copper-clad laminates.The phenolic hydroxyl group at the end of PPO plays a key role in its reactivity.Accurately quantifying the phenolic hydroxyl content in PPO is essential but challenging.In this study,we proposed a method for measuring the phenolic hydroxyl content of PPO using differential UV absorption spectroscopy.In alkaline solutions,the phenolic hydroxyl in PPO completely ionizes to form phenoxide ions,leading to a significant increase in UV absorbance at approximately 250 and 300 nm.Notably,the differential UV absorbance at approximately 300 nm was directly proportional to the phenolic hydroxyl concentration.Using 2,6-dimethylphenol as a standard,a calibration curve was established to relate the phenolic hydroxyl concentration to differential UV absorbance at approximately 300 nm,providing a precise and straightforward method for phenolic hydroxyl quantification in PPO with distinct advantages over conventional techniques.展开更多
The rapid recombination of photogenerated charge carriers and the poor stability of metal sulfides remain bottlenecks limiting their practical applications. In this study, sulfur vacancies were introduced into an S-sc...The rapid recombination of photogenerated charge carriers and the poor stability of metal sulfides remain bottlenecks limiting their practical applications. In this study, sulfur vacancies were introduced into an S-scheme AgIn_(5)S_(8)/Bi_(2)S_(3) heterojunction via an in situ hydrothermal method. The sulfur vacancies induced charge density redistribution within the heterojunction and generated efficient active sites for electrons, thereby creating a localized electron-rich environment. The synergistic effects of the sulfur vacancies, internal electric field, and defect energy levels accelerated the separation and transfer of photogenerated charge carriers via the S-scheme pathway, thereby enhancing the visible-light photocatalytic performance, by achieving a Cr(Ⅵ) reduction efficiency of 99.6%. More importantly, the long-term stability and excellent anti-interference capability of the S-scheme AgIn_(5)S_(8)/Bi_(2)S_(3) heterojunction demonstrate its practical application potential, achieving 98.9% Cr(Ⅵ) removal from real electroplating wastewater and meeting discharge standards. This work provides a theoretical basis for constructing highly-catalytic S-scheme heterojunctions and serves as a promising solution for Cr(VI)-containing electroplating wastewater treatment.展开更多
Edge structures are ubiquitous in the processing and fabrication of various optoelectronic devices.Novel physical properties and enhanced light–matter interactions are anticipated to occur at crystal edges due to the...Edge structures are ubiquitous in the processing and fabrication of various optoelectronic devices.Novel physical properties and enhanced light–matter interactions are anticipated to occur at crystal edges due to the broken spatial translational symmetry.However,the intensity of first-order Raman scattering at crystal edges has been rarely explored,although the mechanical stress and edge characteristics have been thoroughly studied by the Raman peak shift and the spectral features of the edge-related Raman modes.Here,by taking Ga As crystal with a well-defined edge as an example,we reveal the intensity enhancement of Raman-active modes and the emergence of Raman-forbidden modes under specific polarization configurations at the edge.This is attributed to the presence of a hot spot at the edge due to the redistributed electromagnetic fields and electromagnetic wave propagations of incident laser and Raman signal near the edge,which are confirmed by the finite-difference time-domain simulations.Spatially-resolved Raman intensities of both Raman-active and Raman-forbidden modes near the edge are calculated based on the redistributed electromagnetic fields,which quantitatively reproduce the corresponding experimental results.These findings offer new insights into the intensity enhancement of Raman scattering at crystal edges and present a new avenue to manipulate light–matter interactions of crystal by manufacturing various types of edges and to characterize the edge structures in photonic and optoelectronic devices.展开更多
This study aimed to investigate the moment redistribution in continuous glass fiber reinforced polymer(GFRP)-concrete composite slabs caused by concrete cracking and steel bar yielding in the negative bending moment z...This study aimed to investigate the moment redistribution in continuous glass fiber reinforced polymer(GFRP)-concrete composite slabs caused by concrete cracking and steel bar yielding in the negative bending moment zone.An experimental bending moment redistribution test was conducted on continuous GFRP-concrete composite slabs,and a calculation method based on the conjugate beam method was proposed.The composite slabs were formed by combining GFRP profiles with a concrete layer and supported on steel beams to create two-span continuous composite slab specimens.Two methods,epoxy resin bonding,and stud connection,were used to connect the composite slabs with the steel beams.The experimental findings showed that the specimen connected with epoxy resin exhibited two moments redistribution phenomena during the loading process:concrete cracking and steel bar yielding at the internal support.In contrast,the composite slab connected with steel beams by studs exhibited only one-moment redistribution phenomenon throughout the loading process.As the concrete at the internal support cracked,the bending moment decreased in the internal support section and increased in the midspan section.When the steel bars yielded,the bending moment further decreased in the internal support section and increased in the mid-span section.Since GFRP profiles do not experience cracking,there was no significant decrease in the bending moment of the mid-span section.All test specimens experienced compressive failure of concrete at the mid-span section.Calculation results showed good agreement between the calculated and experimental values of bending moments in the mid-span section and internal support section.The proposed model can effectively predict the moment redistribution behavior of continuous GFRP-concrete composite slabs.展开更多
The quest for sustainable energy solutions has intensified the need for efficient water electrolysis techniques,pivotal for hydrogen production.However,developing effective bifunctional electrocatalysts capable of dri...The quest for sustainable energy solutions has intensified the need for efficient water electrolysis techniques,pivotal for hydrogen production.However,developing effective bifunctional electrocatalysts capable of driving the hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)remains a formidable challenge.Addressing this,we introduce a novel built-in electric field(BEF)strategy to synthesize NiCoP–Co nanoarrays directly on Ti_(3)C_(2)T_(x) MXene substrates(NiCoP–Co/MXene).This approach leverages a significant work function difference(ΔΦ),propelling these nanoarrays as adept bifunctional electrocatalysts for comprehensive water splitting.MXene,in this process,plays a dual role.It acts as a conductive support,enhancing the catalyst’s overall conductivity,and facilitates an effective charge transport pathway,ensuring efficient charge transfer.Our study reveals that the BEF induces an electric field at the interface,prompting charge transfer from Co to NiCoP.This transfer modulates asymmetric charge distributions,which intricately control intermediates’adsorption and desorption dynamics.Such regulation is crucial for enhancing the reaction kinetics of both HER and OER.Furthermore,under oxidative conditions,the NiCoP–Co/MXene catalyst undergoes a structural metamorphosis into Ni(Co)oxides/hydroxides/MXene,increasing OER performance.This research demonstrates the BEF’s role in fine-tuning interfacial charge redistribution and underscores its potential in crafting more sophisticated electrocatalytic designs.The insights gained here could pave the way for the next generation of electrocatalysis,with far-reaching implications for energy conversion and storage technologies.展开更多
In sulfidic anoxic environments,iron sulfides are widespread solid phases that play an important role in the arsenic(As)biogeochemical cycle.This work investigated the transformation process of FeS-As coprecipitates,t...In sulfidic anoxic environments,iron sulfides are widespread solid phases that play an important role in the arsenic(As)biogeochemical cycle.This work investigated the transformation process of FeS-As coprecipitates,the concurrent behavior,and the speciation of associated As under anoxic conditions.The results showed that FeS-As coprecipitates could convert to greigite and pyrite.The transformation degree of the produced solid phases was dependent upon the pH conditions and initial As species.These results showed that the As mobilization was closely associated with the solid phase transformation.The solid phase transformationwent from disordered mackinawite to crystallinemackinawite,then greigite and finally pyrite.The As in the coprecipitates underwent a process of release,fixation,and release again.Both reduction of As(Ⅴ)and oxidation of As(Ⅲ)were observed in the aqueous and solid phases during reactions.Our study may have important implications for further understanding of As behavior and Fe/S cycling thatmay occur under an anoxic environment more comprehensively.展开更多
Hydrogen embrittlement(HE)in 2 GPa-grade press-hardened steel(PHS)has posed a great risk to its lightweighting application in automotive crash-resistant components.While conventional slow strain rate tensile tests sho...Hydrogen embrittlement(HE)in 2 GPa-grade press-hardened steel(PHS)has posed a great risk to its lightweighting application in automotive crash-resistant components.While conventional slow strain rate tensile tests show that the precharged hydrogen concentration of 3.5 wppm induces a severe loss in strength and ductility,the high strain rate tests conducted at 1–103 s−1 that simulate the crash condition demonstrate no loss in strength and a minimal loss in ductility.Such strain rate dependency cannot be exclusively explained via hydrogen diffusion and redistribution to susceptible prior austenite grain boundaries,as the tensile testing of precharged samples with jumping strain rates offers a sufficient redistribution period at slow-strain-rate loading,but does not necessarily lead to a high level of HE afterwards.Detailed fractography analysis acknowledges that hydrogen-induced microcracks nucleated within early deformation stages are directly responsible for the high HE susceptibility of all test conditions.A phase-field simulation comprising 2 GPa-grade PHS's microstructure features and the hydrogen diffusion under tested loading conditions is applied.The calculation reveals that the hydrogen redistribution behavior is spatially confined to the crack tip areas but to a much greater extent.It thus facilitates continuous crack growth following the main crack with minimal plastic deformation and avoids branching to form secondary cracks.The combined experiments and modeling highlight the vital role of microcracks in the HE performance of 2 GPa-grade PHS,upon which the safety factor of HE in high-strength martensitic steels shall be established.展开更多
In order to investigate the segregation process and clarify its effect on the formation of TiN during the solidification of a micro-alloy steel containing titanium(Ti),a new mathematical model concerning solute transp...In order to investigate the segregation process and clarify its effect on the formation of TiN during the solidification of a micro-alloy steel containing titanium(Ti),a new mathematical model concerning solute transportation,solidification,as well as TiN precipitation was successfully established and verified.The transportation of solute elements was described using the Brody-Fleming microsegregation model,while the thermodynamic principles governing the precipitation of TiN were derived within the framework of the model.Additionally,the model accounts for variations in the diffusion coefficient due to phase transition and the influence of non-equilibrium solidification on solute distribution.High-temperature tests were conducted to validate the mathematical model.Results show that during solidification,due to selective crystallization,there is positive segregation of Ti and N in the solidifying front.What’s more,due to the high cooling rate near the surface of this steel,negative segregation is easier to be formed in the surface area.The highest concentration of TiN precipitation is found in the 1/4 width of this steel.High-temperature experiment shows that when the solidifying front reaches the 1/4 width of the specimen,the concentration product of Ti and N elements biased at the solidifying front reaches the thermodynamic conditions of TiN precipitation,and exists a higher concentration of TiN distributed in this region.To address this phenomenon,a comparative analysis of the effects of cooling rate and initial solute element content on TiN precipitation behavior was conducted.An increase in the surface cooling rate accelerates the progression of the solidification front and diminishes solute segregation near the front,thereby reducing TiN precipitation.However,with the increase of the initial solute element content,the concentration product of Ti and N elements rises,then the content of TiN precipitation increases.The results of this model provide important insight into the micro segregation and TiN precipitation mechanism of the micro-alloy steels bearing titanium.展开更多
With the upgrade of armor protection materials,higher requirements are put forward for the penetration performance of tungsten alloy kinetic energy armor-piercing projectiles,and the penetration performance is closely...With the upgrade of armor protection materials,higher requirements are put forward for the penetration performance of tungsten alloy kinetic energy armor-piercing projectiles,and the penetration performance is closely related to the adiabatic shear band under extreme stress conditions.Here,the detailed analysis of the adiabatic shear band microstructure evolution of a dual-phase 90W-Ni-Fe alloy under a high strain rate was conducted by combining advanced electron microscopic characterization,while discussing shear fracture from a mechanical perspective under thermoplastic instability.The high temperature and high stress environment inside the adiabatic shear band led to the refinement of the W phase andγ-(Ni,Fe)phase grains to the submicron level,and induced the elements redistribution of W,Ni,and Fe to precipitate W nanocrystalline with hardness as high as 11.7 GPa along the recrystallization grain boundaries of theγ-(Ni,Fe)phase.Mechanical incompatibility caused by the hardness difference between W nanocrystalline andγ-(Ni,Fe)phases led to a strain gradient at the interface.The microvoids preferentially nucleated at the W nanocrystalline/γ-(Ni,Fe)phase interface,then merged to form microcracks and grew further,leading to shear failure.展开更多
Overpressure prediction for exploratory drilling has become robust in most basins with increasing well control,high-quality seismic datasets,and proactive real-time overpressure monitoring while drilling.However,accur...Overpressure prediction for exploratory drilling has become robust in most basins with increasing well control,high-quality seismic datasets,and proactive real-time overpressure monitoring while drilling.However,accurate overpressure prediction remains challenging in offshore Northwest Borneo despite several decades of drilling experience.This paper focuses on two exploration wells drilled by Brunei Shell Petroleum 40 years apart that faced similar challenges with overpressure prediction and well control.An integrated lookback study is attempted using seismic and well-log data to explore the causes of the unsatisfactory Pore Pressure Prediction(PPP)outcome in pre-drill and real-time operation settings for thesewells.Our study indicates that the misprediction of overpressures is due to real differences in shale pressure(basis of pre-drill work and monitoring)and sand pressure(source of drill kick and well control chal-lenges)due to large-scale vertical leak or expulsion of deep-seated fluids into pre-compacted normally pressured overlying sediments in several regions through a mix of shear and tensile failure mechanisms.Such migrated fluids inflate the sand pressure in the normally compacted shallower sequences with the shale pressure remaining low.A predictive framework for upward fluid expulsion was attempted but found impracticable due to complex spatial and temporal variations in the horizontal stress field responsible for such leakage.As such,it is proposed that these migratory overpressures are essentially'unpredictable'from conventional PPP workflows viewed in the broad bucket of compaction disequi-librium(undercompaction)and fluid expansion(unloading)mechanisms.Further study is recommended to understand if such migrated overpressures in the sand can produce a discernible and predictable geophysical or petrophysical signature in the abutting normally compacted shales.The study highlights the possibility of large lateral variability in the sand overpressure within the same stratigraphic unit in regions with complex tectonostratigraphic evolution like Northwest Borneo.展开更多
Type 2 diabetes mellitus,particularly when accompanied by obesity,has become a major global public health burden.Visceral adipose tissue accumulation contributes to insulin resistance,lipotoxicity,and chronic inflamma...Type 2 diabetes mellitus,particularly when accompanied by obesity,has become a major global public health burden.Visceral adipose tissue accumulation contributes to insulin resistance,lipotoxicity,and chronic inflammation,thereby accelerating metabolic deterioration.Although pharmacological agents such as pioglitazone and metformin are effective in modulating fat distribution and improving metabolic parameters,their roles in adipose tissue remodeling remain insufficiently elucidated.Recent advances in regenerative medicine have highlighted the therapeutic potential of adipose-derived stem cells,owing to their differentiation capacity,anti-inflammatory secretory profile,and involvement in metabolic homeostasis.This review summarized current pharmacological and stem cell-based strategies targeting adipose tissue dysfunction in patients with obesity and type 2 diabetes mellitus with a particular focus on the mechanistic roles of adipokines,mitochondrial dysfunction,and extracellular matrix remodeling in visceral adipose tissue.It further discussed the potential synergistic benefits of adipose-derived stem cell-based combination interventions.Finally,the review envisioned future directions for integrating molecularly targeted drugs with cell therapies in the personalized management of metabolic disorders.展开更多
The “well factory” mode's high-density well placement and multi-stage hydraulic fracturing technology enable efficient development of unconventional oil and gas resources.However,the deployment of platform wells...The “well factory” mode's high-density well placement and multi-stage hydraulic fracturing technology enable efficient development of unconventional oil and gas resources.However,the deployment of platform wells in the “well factory” model results in small wellbore spacing,and the stress disturbances caused by fracturing operations may affect neighboring wells,leading to inter-well interference phenomena that cause casing deformation.This study investigates the issue of inter-well interference causing casing deformation or even failure during multi-stage hydraulic fracturing in the “well factory”model,and predicts high-risk locations for casing failure.A flow-mechanics coupled geomechanical finite element model with retaining geological stratification characteristics was established.Based on the theory of hydraulic fracturing-induced rock fragmentation and fluid action leading to the degradation of rock mechanical properties,the model simulated the four-dimensional evolution of multi-well fracturing areas over time and space,calculating the disturbance in the regional stress field caused by fracturing operations.Subsequently,the stress distribution of multiple well casings at different time points was calculated to predict high-risk locations for casing failure.The research results show that the redistribution of the stress field in the fracturing area increases the stress on the casing.The overlapping fracturing zones between wells cause significant stress interference,greatly increasing the risk of deformation and failure.By analyzing the Mises stress distribution of multi-well casings,high-risk locations for casing failure can be identified.The conclusion is that the key to preventing casing failure in platform wells in the “well factory” model is to optimize the spatial distribution of fracturing zones between wells and reasonably arrange well spacing.The study provides new insights and methods for predicting casing failure in unconventional oil and gas reservoirs and offers references for optimizing drilling and fracturing designs.展开更多
The load profile is a key characteristic of the power grid and lies at the basis for the power flow control and generation scheduling.However,due to the wide adoption of internet-of-things(IoT)-based metering infrastr...The load profile is a key characteristic of the power grid and lies at the basis for the power flow control and generation scheduling.However,due to the wide adoption of internet-of-things(IoT)-based metering infrastructure,the cyber vulnerability of load meters has attracted the adversary’s great attention.In this paper,we investigate the vulnerability of manipulating the nodal prices by injecting false load data into the meter measurements.By taking advantage of the changing properties of real-world load profile,we propose a deeply hidden load data attack(i.e.,DH-LDA)that can evade bad data detection,clustering-based detection,and price anomaly detection.The main contributions of this work are as follows:(i)We design a stealthy attack framework that exploits historical load patterns to generate load data with minimal statistical deviation from normalmeasurements,thereby maximizing concealment;(ii)We identify the optimal time window for data injection to ensure that the altered nodal prices follow natural fluctuations,enhancing the undetectability of the attack in real-time market operations;(iii)We develop a resilience evaluation metric and formulate an optimization-based approach to quantify the electricity market’s robustness against DH-LDAs.Our experiments show that the adversary can gain profits from the electricity market while remaining undetected.展开更多
Intense rainfall infiltration is one of the primary triggers for landslides.Developing a robust model for rainfall infiltration analysis is crucial for mitigating landslide disasters.Although the numerical solution of...Intense rainfall infiltration is one of the primary triggers for landslides.Developing a robust model for rainfall infiltration analysis is crucial for mitigating landslide disasters.Although the numerical solution of Richard's equation provides high computational accuracy,it often encounters convergence issues.In contrast,the Green-Ampt(GA)model,which is more computationally efficient,lacks accuracy in dealing with the non-uniform distribution of the initial volumetric water content(VWC)and the pore-water redistribution process.Therefore,this study proposes a novel model for analyzing the slope rainfall infiltration process based on the GA model.The proposed model discretizes both the geological layers of the slope and the rainfall event in spatial and temporal scales,respectively,improving accuracy by adjusting step sizes of discretization adaptively.The proposed model is applied to analyze the permeability,stability and reliability of heterogeneous infinite slopes considering uncertainties in multiple parameters.Comparative studies with the numerical solution of Richard's equation and other models demonstrate that the proposed model can provide high computational accuracy and superior analysis convergence in rainfall infiltration modeling.It also indicates that neglecting the pore-water redistribution underestimates the probability of slope failure,overestimates the factor of safety(FOS)of the slope,and inaccurately estimates the depth of the critical slip surface.Moreover,the uncertainties in shear strength parameters may overshadow the influence of initial VWC uncertainties on the slope reliability.This study provides a theoretical basis for the analysis of rainfall infiltration on heterogeneous slopes and the formulation of strategies for landslide disaster prevention.展开更多
With the evolution of nickel-based single crystal superalloys,there is an increase in heavy elements such as Re and Ru.This has made solutal convection more pronounced during the directional solidification process,lea...With the evolution of nickel-based single crystal superalloys,there is an increase in heavy elements such as Re and Ru.This has made solutal convection more pronounced during the directional solidification process,leading to solute redistribution and increasing the risk of casting defects such as low-angle grain boundaries.To avoid casting defects,downward directional solidification(DWS)method is adopted to eliminate solutal convection and change solute redistribution.However,there is currently no in-situ characterization or quantitative simulation studying the solute redistribution during DWS and upward directional solidification(UWS)processes.A multicomponent phase field simulation coupled with lattice Boltzmann method was employed to quantitatively investigate changes in dendrite morphology,solutal convection and deviation of dendrite tips from the perspective of solute redistribution during UWS and DWS processes.The simulation of microstructure agrees well with the experimental results.The mechanism that explains how solutal convection affects side branching behavior is depicted.A novel approach is introduced to characterize dendrite deviation,elucidating the reasons why defects are prone to occur under the influence of natural convection and solute redistribution.展开更多
Hydroxyl radical(·OH)formation from Fe(Ⅱ)-bearing clay mineral oxygenation in the shallow subsurface has been well documented under moderate environmental conditions.However,the impact of freezing processes on t...Hydroxyl radical(·OH)formation from Fe(Ⅱ)-bearing clay mineral oxygenation in the shallow subsurface has been well documented under moderate environmental conditions.However,the impact of freezing processes on the·OH production capability of Fe(Ⅱ)-bearing clay minerals for organic contaminant degradation,particularly in seasonally frozen soils,remains unclear.In this study,we investigated the influence of pre-freezing durations on the mineral proprieties,·OH production,and phenol degradation during the oxygenation of reduced Fe-rich nontronite(rNAu-2)and Fe-poor montmorillonite(rSWy-3).During the freezing process of reduced clay minerals(1 mM Fe(Ⅱ)),the content of edge surface Fe and Fe(Ⅱ)decreased by up to 46%and 58%,respectively,followed by a slight increased as clay mineral particles aggregated and subsequently partially disaggregated.As the edge surface Fe(Ⅱ)is effective in O_(2) activation but less effective in the transformation of H_(2)O_(2) to·OH,the redistribution of edge surface Fe(Ⅱ)leads to that·OH production and phenol degradation increased initially and then decreased with pre-freezing durations ranging from 0 to 20 days.Moreover,the rate constants of phenol degradation for both the rapid and slow reaction phases also first increase and then decrease with freezing time.However,pre-freezing significantly influenced the rapid phase of phenol degradation by rNAu-2 but affected the slow phase by rSWy-3 due to the much higher edge-surface Fe(Ⅱ)content in rNAu-2.Overall,these findings provide novel insights into the mechanism of·OH production and contaminant degradation during the freeze-thaw processes in clay-rich soils.展开更多
Lithium-carbon dioxide(Li-CO_(2))batteries with high theoretical energy density are regarded as promising energy storage system toward carbon neutrality.However,bidirectional catalysts design for improving the sluggis...Lithium-carbon dioxide(Li-CO_(2))batteries with high theoretical energy density are regarded as promising energy storage system toward carbon neutrality.However,bidirectional catalysts design for improving the sluggish CO_(2)reduction reaction(CO_(2)RR)/CO_(2)evolution reaction(CO_(2)ER)kinetics remains a huge challenge.In this work,an advanced catalyst with fast-interfacial charge transfer was subtly synthesized through element segregation,which significantly improves the electrocatalytic activity for both CO_(2)RR and CO_(2)ER.Theoretical calculations and characterization analysis demonstrate local charge redistribution at the constructed interface,which leads to optimized binding affinity towards reactants and preferred Li_(2)CO_(3)decomposition behavior,enabling excellent catalytic activity during CO_(2)redox.Benefiting from the enhanced charge transfer ability,the designed highly efficient catalyst with dual active centers and large exposed catalytic area can maintain an ultra-small voltage gap of 0.33 V and high energy efficiency of 90.2%.This work provides an attractive strategy to construct robust catalysts by interface engineering,which could inspire further design of superior bidirectional catalysts for Li-CO_(2)batteries.展开更多
Space-division multiplexing(SDM)offers a promising route to scaling data throughput in fiber-optic networks,but it also introduces challenges such as mode-dependent loss(MDL)and intermodal crosstalk,which increase the...Space-division multiplexing(SDM)offers a promising route to scaling data throughput in fiber-optic networks,but it also introduces challenges such as mode-dependent loss(MDL)and intermodal crosstalk,which increase the computational load on digital signal processing(DSP).Periodic mode mixing has been shown to mitigate these effects by redistributing loss and gain across modes and shortening the effective temporal impulse response over which crosstalk accumulates.In this work,we present a novel and compact mode-scrambling device,3D printed directly onto the facet of a few-mode fiber.展开更多
基金supported financially by the National Social Science Foundation of China(No.18ZDA080)Humanities and Social Sciences Project from the Ministry of Education of the People’s Republic of China(Nos.17JJD790023 and 20YJC790153)the National Natural Science Foundation of China(No.71703188).
文摘China has improved its social security system in recent decades,with the aim of achieving universal coverage and improving the equity of income distribution.Based on data from the five rounds of Chinese Household Income Project surveys from 1988 to 2018,this paper examines the long-term redistributive effects of social security programs in China.Our results show that social security programs have reduced income inequality consistently,and the positive redistributive effects have been improving for the past 30 years.Social security transfers have had an increasingly essential role in rural areas,especially after 2002 when China started to establish a comprehensive rural social safety net and expanded the coverage of the social security program.The redistributive efficiency of the social security system has also increased recently.
基金supported by the National Natural Science Foundation of China(22472104)Guangdong Basic and Applied Basic Research Foundation(2024A1515012075,2024A1515010028)the Postdoctoral Fellowship Program of CPS Funder(GZC20241083,2025M771117)。
文摘Oxygen evolution reaction(OER)is widely recognized as a bottleneck of water electrolysis.To determine the underlying reaction mechanisms,particularly the relative contribution of the adsorbate evolution mechanism(AEM)and lattice-oxygen participation mechanism(LOM),we conduct a comprehensive investigation combining Density Functional Theory(DFT)calculations and experimental validation.Our theoretical analysis of doped RuO_(2)catalysts reveals that heteroatom doping(Ni,Cu,and Zn)induces significant local charge transfer,leading to the increased charge state of Ru and the downshifted d-band center.This,in turn,enables the mechanism switching from the conventional AEM to the more efficient LOM,and finally improves OER activity.We also establish a simple yet powerful descriptor,Ne of Ru(representing charge density of Ru sites),which enables accurate prediction of both catalytic activity and stability.Guided by these theoretical predictions,we successfully synthesize a Ni-doped RuO_(2)catalyst,which exhibits excellent OER activity and stability in acidic media,achieving an overpotential of just 156 mV and maintaining stability for 4000 h at 10 mA cm^(−2),significantly surpassing the performance of the commercial RuO_(2).These findings not only provide fundamental insights into the mechanism-switching behavior in OER catalysis but also offer a practical strategy for designing high-performance,stable electrocatalysts for acidic water electrolysis.
基金the“Pioneer”and“Leading Goose”R&D Program of Zhejiang(No.2023C01072)the Institute of Zhejiang University-Quzhou for their financial support。
文摘Poly(phenylene oxide)(PPO)exhibits excellent dielectric properties,making it an ideal substrate for high-frequency,high-speed copper-clad laminates.The phenolic hydroxyl group at the end of PPO plays a key role in its reactivity.Accurately quantifying the phenolic hydroxyl content in PPO is essential but challenging.In this study,we proposed a method for measuring the phenolic hydroxyl content of PPO using differential UV absorption spectroscopy.In alkaline solutions,the phenolic hydroxyl in PPO completely ionizes to form phenoxide ions,leading to a significant increase in UV absorbance at approximately 250 and 300 nm.Notably,the differential UV absorbance at approximately 300 nm was directly proportional to the phenolic hydroxyl concentration.Using 2,6-dimethylphenol as a standard,a calibration curve was established to relate the phenolic hydroxyl concentration to differential UV absorbance at approximately 300 nm,providing a precise and straightforward method for phenolic hydroxyl quantification in PPO with distinct advantages over conventional techniques.
基金supported by the National Natural Science Foundation of China (Grant No.52470078)the Natural Science Foundation of Jiangxi Province (Grant No.20252BAC250042)the Key Laboratory of Jiangxi Province for Persistent Pollutants Prevention Control and Resource Reuse (Grant No.2023SSY02061)。
文摘The rapid recombination of photogenerated charge carriers and the poor stability of metal sulfides remain bottlenecks limiting their practical applications. In this study, sulfur vacancies were introduced into an S-scheme AgIn_(5)S_(8)/Bi_(2)S_(3) heterojunction via an in situ hydrothermal method. The sulfur vacancies induced charge density redistribution within the heterojunction and generated efficient active sites for electrons, thereby creating a localized electron-rich environment. The synergistic effects of the sulfur vacancies, internal electric field, and defect energy levels accelerated the separation and transfer of photogenerated charge carriers via the S-scheme pathway, thereby enhancing the visible-light photocatalytic performance, by achieving a Cr(Ⅵ) reduction efficiency of 99.6%. More importantly, the long-term stability and excellent anti-interference capability of the S-scheme AgIn_(5)S_(8)/Bi_(2)S_(3) heterojunction demonstrate its practical application potential, achieving 98.9% Cr(Ⅵ) removal from real electroplating wastewater and meeting discharge standards. This work provides a theoretical basis for constructing highly-catalytic S-scheme heterojunctions and serves as a promising solution for Cr(VI)-containing electroplating wastewater treatment.
基金Project supported by the National Key Research and Development Program of China(Grant No.2023YFA1407000)the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB0460000)+4 种基金the National Natural Science Foundation of China(Grant Nos.12322401,12127807,and 12393832)CAS Key Research Program of Frontier Sciences(Grant No.ZDBS-LY-SLH004)Beijing Nova Program(Grant No.20230484301)Youth Innovation Promotion Association,Chinese Academy of Sciences(Grant No.2023125)CAS Project for Young Scientists in Basic Research(Grant No.YSBR-026)。
文摘Edge structures are ubiquitous in the processing and fabrication of various optoelectronic devices.Novel physical properties and enhanced light–matter interactions are anticipated to occur at crystal edges due to the broken spatial translational symmetry.However,the intensity of first-order Raman scattering at crystal edges has been rarely explored,although the mechanical stress and edge characteristics have been thoroughly studied by the Raman peak shift and the spectral features of the edge-related Raman modes.Here,by taking Ga As crystal with a well-defined edge as an example,we reveal the intensity enhancement of Raman-active modes and the emergence of Raman-forbidden modes under specific polarization configurations at the edge.This is attributed to the presence of a hot spot at the edge due to the redistributed electromagnetic fields and electromagnetic wave propagations of incident laser and Raman signal near the edge,which are confirmed by the finite-difference time-domain simulations.Spatially-resolved Raman intensities of both Raman-active and Raman-forbidden modes near the edge are calculated based on the redistributed electromagnetic fields,which quantitatively reproduce the corresponding experimental results.These findings offer new insights into the intensity enhancement of Raman scattering at crystal edges and present a new avenue to manipulate light–matter interactions of crystal by manufacturing various types of edges and to characterize the edge structures in photonic and optoelectronic devices.
基金supported by National Natural Science Foundation of China(Project No.51878156,received by Wen-Wei Wang) and EPC Innovation Consulting Project for Longkou Nanshan LNG Phase I Receiving Terminal(Z2000LGENT0399,received by Wen-Wei Wang and ZhaoJun Zhang).
文摘This study aimed to investigate the moment redistribution in continuous glass fiber reinforced polymer(GFRP)-concrete composite slabs caused by concrete cracking and steel bar yielding in the negative bending moment zone.An experimental bending moment redistribution test was conducted on continuous GFRP-concrete composite slabs,and a calculation method based on the conjugate beam method was proposed.The composite slabs were formed by combining GFRP profiles with a concrete layer and supported on steel beams to create two-span continuous composite slab specimens.Two methods,epoxy resin bonding,and stud connection,were used to connect the composite slabs with the steel beams.The experimental findings showed that the specimen connected with epoxy resin exhibited two moments redistribution phenomena during the loading process:concrete cracking and steel bar yielding at the internal support.In contrast,the composite slab connected with steel beams by studs exhibited only one-moment redistribution phenomenon throughout the loading process.As the concrete at the internal support cracked,the bending moment decreased in the internal support section and increased in the midspan section.When the steel bars yielded,the bending moment further decreased in the internal support section and increased in the mid-span section.Since GFRP profiles do not experience cracking,there was no significant decrease in the bending moment of the mid-span section.All test specimens experienced compressive failure of concrete at the mid-span section.Calculation results showed good agreement between the calculated and experimental values of bending moments in the mid-span section and internal support section.The proposed model can effectively predict the moment redistribution behavior of continuous GFRP-concrete composite slabs.
基金supported by Guangdong Basic and Applied Basic Research Foundation(Nos.2021A1515010261 and 2023A1515140153)Guangdong Special Innovative Projects of General Universities(No.2022KTSCX136)+1 种基金the Major and Special Project in the Field of Intelligent Manufacturing of the Universities in Guangdong Province(No.2020ZDZX2067)the Innovative Team Project of the Universities in Guangdong Province(No.2023KCXTD035).
文摘The quest for sustainable energy solutions has intensified the need for efficient water electrolysis techniques,pivotal for hydrogen production.However,developing effective bifunctional electrocatalysts capable of driving the hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)remains a formidable challenge.Addressing this,we introduce a novel built-in electric field(BEF)strategy to synthesize NiCoP–Co nanoarrays directly on Ti_(3)C_(2)T_(x) MXene substrates(NiCoP–Co/MXene).This approach leverages a significant work function difference(ΔΦ),propelling these nanoarrays as adept bifunctional electrocatalysts for comprehensive water splitting.MXene,in this process,plays a dual role.It acts as a conductive support,enhancing the catalyst’s overall conductivity,and facilitates an effective charge transport pathway,ensuring efficient charge transfer.Our study reveals that the BEF induces an electric field at the interface,prompting charge transfer from Co to NiCoP.This transfer modulates asymmetric charge distributions,which intricately control intermediates’adsorption and desorption dynamics.Such regulation is crucial for enhancing the reaction kinetics of both HER and OER.Furthermore,under oxidative conditions,the NiCoP–Co/MXene catalyst undergoes a structural metamorphosis into Ni(Co)oxides/hydroxides/MXene,increasing OER performance.This research demonstrates the BEF’s role in fine-tuning interfacial charge redistribution and underscores its potential in crafting more sophisticated electrocatalytic designs.The insights gained here could pave the way for the next generation of electrocatalysis,with far-reaching implications for energy conversion and storage technologies.
基金supported by the National Key Research and Development Program of China(No.2022YFC3701301)the National Natural Science Foundation of China(Nos.42173063 and 42377251)+1 种基金the Youth Innovation Promotion Association CAS(No.2020200)the Fundamental Research Funds for the Central Universities.
文摘In sulfidic anoxic environments,iron sulfides are widespread solid phases that play an important role in the arsenic(As)biogeochemical cycle.This work investigated the transformation process of FeS-As coprecipitates,the concurrent behavior,and the speciation of associated As under anoxic conditions.The results showed that FeS-As coprecipitates could convert to greigite and pyrite.The transformation degree of the produced solid phases was dependent upon the pH conditions and initial As species.These results showed that the As mobilization was closely associated with the solid phase transformation.The solid phase transformationwent from disordered mackinawite to crystallinemackinawite,then greigite and finally pyrite.The As in the coprecipitates underwent a process of release,fixation,and release again.Both reduction of As(Ⅴ)and oxidation of As(Ⅲ)were observed in the aqueous and solid phases during reactions.Our study may have important implications for further understanding of As behavior and Fe/S cycling thatmay occur under an anoxic environment more comprehensively.
基金support from the National Natural Science Foundation of China(No.52130102)the National Key Research and Development Program of China(No.2019YFA0209900)+5 种基金the Research Grants Council of Hong Kong(No.R7066–18)the Guangzhou Municipal Science and Technology Project(No.202007020007)the Guangdong Basic and Applied Basic Research Foundation of China(No.2020B1515130007)Lunhua He and Mingxin Huang acknowledge the support from the International Partnership Program of the Chinese Academy of Sciences(No.113111KYSB20190029)the key program of the Chinese Academy of Sciences(CAS)China Spallation Neutron Source(CSNS)is acknowledged for supporting neutron diffraction experiments using the General Purpose Powder Diffractometer(GPPD).
文摘Hydrogen embrittlement(HE)in 2 GPa-grade press-hardened steel(PHS)has posed a great risk to its lightweighting application in automotive crash-resistant components.While conventional slow strain rate tensile tests show that the precharged hydrogen concentration of 3.5 wppm induces a severe loss in strength and ductility,the high strain rate tests conducted at 1–103 s−1 that simulate the crash condition demonstrate no loss in strength and a minimal loss in ductility.Such strain rate dependency cannot be exclusively explained via hydrogen diffusion and redistribution to susceptible prior austenite grain boundaries,as the tensile testing of precharged samples with jumping strain rates offers a sufficient redistribution period at slow-strain-rate loading,but does not necessarily lead to a high level of HE afterwards.Detailed fractography analysis acknowledges that hydrogen-induced microcracks nucleated within early deformation stages are directly responsible for the high HE susceptibility of all test conditions.A phase-field simulation comprising 2 GPa-grade PHS's microstructure features and the hydrogen diffusion under tested loading conditions is applied.The calculation reveals that the hydrogen redistribution behavior is spatially confined to the crack tip areas but to a much greater extent.It thus facilitates continuous crack growth following the main crack with minimal plastic deformation and avoids branching to form secondary cracks.The combined experiments and modeling highlight the vital role of microcracks in the HE performance of 2 GPa-grade PHS,upon which the safety factor of HE in high-strength martensitic steels shall be established.
基金supported by the National Natural Science Foundation of China(Grant Nos.52174321,52274339,52204348)the Jiangsu Achievement Transformation Fund Project(Grant No.SBA2023030047)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(Grant No.KYCX24_3310).
文摘In order to investigate the segregation process and clarify its effect on the formation of TiN during the solidification of a micro-alloy steel containing titanium(Ti),a new mathematical model concerning solute transportation,solidification,as well as TiN precipitation was successfully established and verified.The transportation of solute elements was described using the Brody-Fleming microsegregation model,while the thermodynamic principles governing the precipitation of TiN were derived within the framework of the model.Additionally,the model accounts for variations in the diffusion coefficient due to phase transition and the influence of non-equilibrium solidification on solute distribution.High-temperature tests were conducted to validate the mathematical model.Results show that during solidification,due to selective crystallization,there is positive segregation of Ti and N in the solidifying front.What’s more,due to the high cooling rate near the surface of this steel,negative segregation is easier to be formed in the surface area.The highest concentration of TiN precipitation is found in the 1/4 width of this steel.High-temperature experiment shows that when the solidifying front reaches the 1/4 width of the specimen,the concentration product of Ti and N elements biased at the solidifying front reaches the thermodynamic conditions of TiN precipitation,and exists a higher concentration of TiN distributed in this region.To address this phenomenon,a comparative analysis of the effects of cooling rate and initial solute element content on TiN precipitation behavior was conducted.An increase in the surface cooling rate accelerates the progression of the solidification front and diminishes solute segregation near the front,thereby reducing TiN precipitation.However,with the increase of the initial solute element content,the concentration product of Ti and N elements rises,then the content of TiN precipitation increases.The results of this model provide important insight into the micro segregation and TiN precipitation mechanism of the micro-alloy steels bearing titanium.
基金supported by the National Natural Science Foundation of China(No.51931012)the Science and Technology Innovation Program of Hunan Province(No.2023RC3068).
文摘With the upgrade of armor protection materials,higher requirements are put forward for the penetration performance of tungsten alloy kinetic energy armor-piercing projectiles,and the penetration performance is closely related to the adiabatic shear band under extreme stress conditions.Here,the detailed analysis of the adiabatic shear band microstructure evolution of a dual-phase 90W-Ni-Fe alloy under a high strain rate was conducted by combining advanced electron microscopic characterization,while discussing shear fracture from a mechanical perspective under thermoplastic instability.The high temperature and high stress environment inside the adiabatic shear band led to the refinement of the W phase andγ-(Ni,Fe)phase grains to the submicron level,and induced the elements redistribution of W,Ni,and Fe to precipitate W nanocrystalline with hardness as high as 11.7 GPa along the recrystallization grain boundaries of theγ-(Ni,Fe)phase.Mechanical incompatibility caused by the hardness difference between W nanocrystalline andγ-(Ni,Fe)phases led to a strain gradient at the interface.The microvoids preferentially nucleated at the W nanocrystalline/γ-(Ni,Fe)phase interface,then merged to form microcracks and grew further,leading to shear failure.
文摘Overpressure prediction for exploratory drilling has become robust in most basins with increasing well control,high-quality seismic datasets,and proactive real-time overpressure monitoring while drilling.However,accurate overpressure prediction remains challenging in offshore Northwest Borneo despite several decades of drilling experience.This paper focuses on two exploration wells drilled by Brunei Shell Petroleum 40 years apart that faced similar challenges with overpressure prediction and well control.An integrated lookback study is attempted using seismic and well-log data to explore the causes of the unsatisfactory Pore Pressure Prediction(PPP)outcome in pre-drill and real-time operation settings for thesewells.Our study indicates that the misprediction of overpressures is due to real differences in shale pressure(basis of pre-drill work and monitoring)and sand pressure(source of drill kick and well control chal-lenges)due to large-scale vertical leak or expulsion of deep-seated fluids into pre-compacted normally pressured overlying sediments in several regions through a mix of shear and tensile failure mechanisms.Such migrated fluids inflate the sand pressure in the normally compacted shallower sequences with the shale pressure remaining low.A predictive framework for upward fluid expulsion was attempted but found impracticable due to complex spatial and temporal variations in the horizontal stress field responsible for such leakage.As such,it is proposed that these migratory overpressures are essentially'unpredictable'from conventional PPP workflows viewed in the broad bucket of compaction disequi-librium(undercompaction)and fluid expansion(unloading)mechanisms.Further study is recommended to understand if such migrated overpressures in the sand can produce a discernible and predictable geophysical or petrophysical signature in the abutting normally compacted shales.The study highlights the possibility of large lateral variability in the sand overpressure within the same stratigraphic unit in regions with complex tectonostratigraphic evolution like Northwest Borneo.
基金Special Fund Project for Clinical Medicine of Zhejiang Medical Association,No.2024ZYC-Z30Zhejiang Provincial Traditional Chinese Medicine Science and Technology Program,No.2025ZL144.
文摘Type 2 diabetes mellitus,particularly when accompanied by obesity,has become a major global public health burden.Visceral adipose tissue accumulation contributes to insulin resistance,lipotoxicity,and chronic inflammation,thereby accelerating metabolic deterioration.Although pharmacological agents such as pioglitazone and metformin are effective in modulating fat distribution and improving metabolic parameters,their roles in adipose tissue remodeling remain insufficiently elucidated.Recent advances in regenerative medicine have highlighted the therapeutic potential of adipose-derived stem cells,owing to their differentiation capacity,anti-inflammatory secretory profile,and involvement in metabolic homeostasis.This review summarized current pharmacological and stem cell-based strategies targeting adipose tissue dysfunction in patients with obesity and type 2 diabetes mellitus with a particular focus on the mechanistic roles of adipokines,mitochondrial dysfunction,and extracellular matrix remodeling in visceral adipose tissue.It further discussed the potential synergistic benefits of adipose-derived stem cell-based combination interventions.Finally,the review envisioned future directions for integrating molecularly targeted drugs with cell therapies in the personalized management of metabolic disorders.
基金supported by the National Natural Science Foundation of China (No.52104008&No.52274042)the Natural Science Foundation of Sichuan,China (No.2024NSFSC0963)。
文摘The “well factory” mode's high-density well placement and multi-stage hydraulic fracturing technology enable efficient development of unconventional oil and gas resources.However,the deployment of platform wells in the “well factory” model results in small wellbore spacing,and the stress disturbances caused by fracturing operations may affect neighboring wells,leading to inter-well interference phenomena that cause casing deformation.This study investigates the issue of inter-well interference causing casing deformation or even failure during multi-stage hydraulic fracturing in the “well factory”model,and predicts high-risk locations for casing failure.A flow-mechanics coupled geomechanical finite element model with retaining geological stratification characteristics was established.Based on the theory of hydraulic fracturing-induced rock fragmentation and fluid action leading to the degradation of rock mechanical properties,the model simulated the four-dimensional evolution of multi-well fracturing areas over time and space,calculating the disturbance in the regional stress field caused by fracturing operations.Subsequently,the stress distribution of multiple well casings at different time points was calculated to predict high-risk locations for casing failure.The research results show that the redistribution of the stress field in the fracturing area increases the stress on the casing.The overlapping fracturing zones between wells cause significant stress interference,greatly increasing the risk of deformation and failure.By analyzing the Mises stress distribution of multi-well casings,high-risk locations for casing failure can be identified.The conclusion is that the key to preventing casing failure in platform wells in the “well factory” model is to optimize the spatial distribution of fracturing zones between wells and reasonably arrange well spacing.The study provides new insights and methods for predicting casing failure in unconventional oil and gas reservoirs and offers references for optimizing drilling and fracturing designs.
基金supported by the project Major Scientific and Technological Special Project of Guizhou Province([2024]014).
文摘The load profile is a key characteristic of the power grid and lies at the basis for the power flow control and generation scheduling.However,due to the wide adoption of internet-of-things(IoT)-based metering infrastructure,the cyber vulnerability of load meters has attracted the adversary’s great attention.In this paper,we investigate the vulnerability of manipulating the nodal prices by injecting false load data into the meter measurements.By taking advantage of the changing properties of real-world load profile,we propose a deeply hidden load data attack(i.e.,DH-LDA)that can evade bad data detection,clustering-based detection,and price anomaly detection.The main contributions of this work are as follows:(i)We design a stealthy attack framework that exploits historical load patterns to generate load data with minimal statistical deviation from normalmeasurements,thereby maximizing concealment;(ii)We identify the optimal time window for data injection to ensure that the altered nodal prices follow natural fluctuations,enhancing the undetectability of the attack in real-time market operations;(iii)We develop a resilience evaluation metric and formulate an optimization-based approach to quantify the electricity market’s robustness against DH-LDAs.Our experiments show that the adversary can gain profits from the electricity market while remaining undetected.
基金supported by the National Natural Science Foundation of China(Grant Nos.52179103 and 52222905)Jiangxi Provincial Natural Science Foundation(Grant No.20242BAB24001).
文摘Intense rainfall infiltration is one of the primary triggers for landslides.Developing a robust model for rainfall infiltration analysis is crucial for mitigating landslide disasters.Although the numerical solution of Richard's equation provides high computational accuracy,it often encounters convergence issues.In contrast,the Green-Ampt(GA)model,which is more computationally efficient,lacks accuracy in dealing with the non-uniform distribution of the initial volumetric water content(VWC)and the pore-water redistribution process.Therefore,this study proposes a novel model for analyzing the slope rainfall infiltration process based on the GA model.The proposed model discretizes both the geological layers of the slope and the rainfall event in spatial and temporal scales,respectively,improving accuracy by adjusting step sizes of discretization adaptively.The proposed model is applied to analyze the permeability,stability and reliability of heterogeneous infinite slopes considering uncertainties in multiple parameters.Comparative studies with the numerical solution of Richard's equation and other models demonstrate that the proposed model can provide high computational accuracy and superior analysis convergence in rainfall infiltration modeling.It also indicates that neglecting the pore-water redistribution underestimates the probability of slope failure,overestimates the factor of safety(FOS)of the slope,and inaccurately estimates the depth of the critical slip surface.Moreover,the uncertainties in shear strength parameters may overshadow the influence of initial VWC uncertainties on the slope reliability.This study provides a theoretical basis for the analysis of rainfall infiltration on heterogeneous slopes and the formulation of strategies for landslide disaster prevention.
基金supported by the stable support project and the Major National Science and Technology Project(2017-VII-0008-0101).
文摘With the evolution of nickel-based single crystal superalloys,there is an increase in heavy elements such as Re and Ru.This has made solutal convection more pronounced during the directional solidification process,leading to solute redistribution and increasing the risk of casting defects such as low-angle grain boundaries.To avoid casting defects,downward directional solidification(DWS)method is adopted to eliminate solutal convection and change solute redistribution.However,there is currently no in-situ characterization or quantitative simulation studying the solute redistribution during DWS and upward directional solidification(UWS)processes.A multicomponent phase field simulation coupled with lattice Boltzmann method was employed to quantitatively investigate changes in dendrite morphology,solutal convection and deviation of dendrite tips from the perspective of solute redistribution during UWS and DWS processes.The simulation of microstructure agrees well with the experimental results.The mechanism that explains how solutal convection affects side branching behavior is depicted.A novel approach is introduced to characterize dendrite deviation,elucidating the reasons why defects are prone to occur under the influence of natural convection and solute redistribution.
基金supported by the National Natural Science Foundation of China(Nos.U22A20591,42077185,42107217)the Sichuan Province Science and Technology Program for Distinguished Young Scholars(No.2022JDJQ0010)+1 种基金the Sichuan Science and Technology Program(No.2024NSFSC0842)the State Key Laboratory of Geohazard Prevention and Geoenvironment Protection(No.SKLGP2020Z002)。
文摘Hydroxyl radical(·OH)formation from Fe(Ⅱ)-bearing clay mineral oxygenation in the shallow subsurface has been well documented under moderate environmental conditions.However,the impact of freezing processes on the·OH production capability of Fe(Ⅱ)-bearing clay minerals for organic contaminant degradation,particularly in seasonally frozen soils,remains unclear.In this study,we investigated the influence of pre-freezing durations on the mineral proprieties,·OH production,and phenol degradation during the oxygenation of reduced Fe-rich nontronite(rNAu-2)and Fe-poor montmorillonite(rSWy-3).During the freezing process of reduced clay minerals(1 mM Fe(Ⅱ)),the content of edge surface Fe and Fe(Ⅱ)decreased by up to 46%and 58%,respectively,followed by a slight increased as clay mineral particles aggregated and subsequently partially disaggregated.As the edge surface Fe(Ⅱ)is effective in O_(2) activation but less effective in the transformation of H_(2)O_(2) to·OH,the redistribution of edge surface Fe(Ⅱ)leads to that·OH production and phenol degradation increased initially and then decreased with pre-freezing durations ranging from 0 to 20 days.Moreover,the rate constants of phenol degradation for both the rapid and slow reaction phases also first increase and then decrease with freezing time.However,pre-freezing significantly influenced the rapid phase of phenol degradation by rNAu-2 but affected the slow phase by rSWy-3 due to the much higher edge-surface Fe(Ⅱ)content in rNAu-2.Overall,these findings provide novel insights into the mechanism of·OH production and contaminant degradation during the freeze-thaw processes in clay-rich soils.
基金supported by the National Key Research and Development Program of China(2019YFA0705700)Guangdong Innovative and Entrepreneurial Research Team Program(2021ZT09L197)+2 种基金Shenzhen Science and Technology Program(KQTD20210811090112002)Interdisciplinary Research and Innovation Fund of Tsinghua Shenzhen International Graduate School,National Natural Science Foundation of China(No.52373233)the SIAT International Joint Lab Project(No.E3G113).
文摘Lithium-carbon dioxide(Li-CO_(2))batteries with high theoretical energy density are regarded as promising energy storage system toward carbon neutrality.However,bidirectional catalysts design for improving the sluggish CO_(2)reduction reaction(CO_(2)RR)/CO_(2)evolution reaction(CO_(2)ER)kinetics remains a huge challenge.In this work,an advanced catalyst with fast-interfacial charge transfer was subtly synthesized through element segregation,which significantly improves the electrocatalytic activity for both CO_(2)RR and CO_(2)ER.Theoretical calculations and characterization analysis demonstrate local charge redistribution at the constructed interface,which leads to optimized binding affinity towards reactants and preferred Li_(2)CO_(3)decomposition behavior,enabling excellent catalytic activity during CO_(2)redox.Benefiting from the enhanced charge transfer ability,the designed highly efficient catalyst with dual active centers and large exposed catalytic area can maintain an ultra-small voltage gap of 0.33 V and high energy efficiency of 90.2%.This work provides an attractive strategy to construct robust catalysts by interface engineering,which could inspire further design of superior bidirectional catalysts for Li-CO_(2)batteries.
基金Horizon 2020 Framework Programme(619732)Ministry of Innovation,Science and Technology,Fulbright U.S.Scholar Program。
文摘Space-division multiplexing(SDM)offers a promising route to scaling data throughput in fiber-optic networks,but it also introduces challenges such as mode-dependent loss(MDL)and intermodal crosstalk,which increase the computational load on digital signal processing(DSP).Periodic mode mixing has been shown to mitigate these effects by redistributing loss and gain across modes and shortening the effective temporal impulse response over which crosstalk accumulates.In this work,we present a novel and compact mode-scrambling device,3D printed directly onto the facet of a few-mode fiber.
