This paper presents a new criterion for determining the unloading points quantitatively and consistently in a multi-stage triaxial test.The radial strain gradient(RSG)is first introduced as an arc tangent function of ...This paper presents a new criterion for determining the unloading points quantitatively and consistently in a multi-stage triaxial test.The radial strain gradient(RSG)is first introduced as an arc tangent function of the rate of change of radial strain to time.RSG is observed to correlate closely with the stress state of a compressed sample,and reaches a horizontal asymptote as approaching failure.For a given rock type,RSG value at peak stress is almost the same,irrespective of the porosity and permeability.These findings lead to the development of RSG criterion:Unloading points can be precisely determined at the time when RSG reaches a pre-determined value that is a little smaller than or equal to the RSG at peak stress.The RSG criterion is validated against other criteria and the single-stage triaxial test on various types of rocks.Failure envelopes from the RSG criterion match well with those from single-stage tests.A practical procedure is recommended to use the RSG criterion:an unconfined compression or single-stage test is first conducted to determine the RSG at peak stress for one sample,the unloading point is then selected to be a value close to the RSG at peak stress,and the multi-stage test is finally performed on another sample using the pre-selected RSG unloading criterion.Generally,the RSG criterion is applicable for any type of rocks,especially brittle rocks,where other criteria are not suitable.Further,it can be practically implemented on the most available rock mechanical testing instruments.展开更多
Cyclic changes in the internal pressure of compressed air energy storage reservoirs in abandoned coal mines result in complex alternating loads on the rocks surrounding the energy storage reservoirs.These complex alte...Cyclic changes in the internal pressure of compressed air energy storage reservoirs in abandoned coal mines result in complex alternating loads on the rocks surrounding the energy storage reservoirs.These complex alternating loads can be regarded as multi-stage constant-amplitude cyclic loads following simplification.In this paper,the mechanical responses and acoustic emission(AE)characteristics of red sandstone with five bedding dip angles(0°,30°,45°,60°,and 90°)under such loads are investigated,and the damage evolution processes of the five specimens are revealed from both quantitative and microscopic perspectives.The results show that the fatigue deformation characteristics of the specimens are affected by the bedding dip angle.Under cyclic loads,the axially irreversible plastic deformations of the rocks increase,their elastic stiffness increases,their crack volumetric strain increases and then decreases,and their AE cumulative count/energy curves exhibit a ladder shape.A damage evolution model based on the crack volumetric strain is proposed,and the damage evolution process is divided into two stages:a rapid increase stage and a tendency toward stabilization stage.Through cluster analysis,the AE events are used to classify the damage into three categories:small-sized localized damage,large-sized tensile damage,and large-sized shear damage.Finally,the MohreCoulomb criterion is applied to analyze the relationship between the failure modes of the red sandstone specimens and the dip angle of the bedding.The results of this study will help to predict the stability and safety of compressed air energy storage reservoirs in abandoned coal mines.展开更多
The application of machine learning for pyrite discrimination establishes a robust foundation for constructing the ore-forming history of multi-stage deposits;however,published models face challenges related to limite...The application of machine learning for pyrite discrimination establishes a robust foundation for constructing the ore-forming history of multi-stage deposits;however,published models face challenges related to limited,imbalanced datasets and oversampling.In this study,the dataset was expanded to approximately 500 samples for each type,including 508 sedimentary,573 orogenic gold,548 sedimentary exhalative(SEDEX)deposits,and 364 volcanogenic massive sulfides(VMS)pyrites,utilizing random forest(RF)and support vector machine(SVM)methodologies to enhance the reliability of the classifier models.The RF classifier achieved an overall accuracy of 99.8%,and the SVM classifier attained an overall accuracy of 100%.The model was evaluated by a five-fold cross-validation approach with 93.8%accuracy for the RF and 94.9%for the SVM classifier.These results demonstrate the strong feasibility of pyrite classification,supported by a relatively large,balanced dataset and high accuracy rates.The classifier was employed to reveal the genesis of the controversial Keketale Pb-Zn deposit in NW China,which has been inconclusive among SEDEX,VMS,or a SEDEX-VMS transition.Petrographic investigations indicated that the deposit comprises early fine-grained layered pyrite(Py1)and late recrystallized pyrite(Py2).The majority voting classified Py1 as the VMS type,with an accuracy of RF and SVM being 72.2%and 75%,respectively,and confirmed Py2 as an orogenic type with 74.3% and 77.1%accuracy,respectively.The new findings indicated that the Keketale deposit originated from a submarine VMS mineralization system,followed by late orogenic-type overprinting of metamorphism and deformation,which is consistent with the geological and geochemical observations.This study further emphasizes the advantages of Machine learning(ML)methods in accurately and directly discriminating the deposit types and reconstructing the formation history of multi-stage deposits.展开更多
The high proportion of uncertain distributed power sources and the access to large-scale random electric vehicle(EV)charging resources further aggravate the voltage fluctuation of the distribution network,and the exis...The high proportion of uncertain distributed power sources and the access to large-scale random electric vehicle(EV)charging resources further aggravate the voltage fluctuation of the distribution network,and the existing research has not deeply explored the EV active-reactive synergistic regulating characteristics,and failed to realize themulti-timescale synergistic control with other regulatingmeans,For this reason,this paper proposes amultilevel linkage coordinated optimization strategy to reduce the voltage deviation of the distribution network.Firstly,a capacitor bank reactive power compensation voltage control model and a distributed photovoltaic(PV)activereactive power regulationmodel are established.Additionally,an external characteristicmodel of EVactive-reactive power regulation is developed considering the four-quadrant operational characteristics of the EVcharger.Amultiobjective optimization model of the distribution network is then constructed considering the time-series coupling constraints of multiple types of voltage regulators.A multi-timescale control strategy is proposed by considering the impact of voltage regulators on active-reactive EV energy consumption and PV energy consumption.Then,a four-stage voltage control optimization strategy is proposed for various types of voltage regulators with multiple time scales.Themulti-objective optimization is solved with the improvedDrosophila algorithmto realize the power fluctuation control of the distribution network and themulti-stage voltage control optimization.Simulation results validate that the proposed voltage control optimization strategy achieves the coordinated control of decentralized voltage control resources in the distribution network.It effectively reduces the voltage deviation of the distribution network while ensuring the energy demand of EV users and enhancing the stability and economic efficiency of the distribution network.展开更多
E-commerce, as an emerging marketing mode, has attracted more and more attention and gradually changed the way of our life. However, the existing layout of distribution centers can＇t fulfill the storage and picking d...E-commerce, as an emerging marketing mode, has attracted more and more attention and gradually changed the way of our life. However, the existing layout of distribution centers can＇t fulfill the storage and picking demands of e-commerce sufficiently. In this paper, a modified miniload automated storage/retrieval system is designed to fit these new characteristics of e-commerce in logistics. Meanwhile, a matching problem, concerning with the improvement of picking efficiency in new system, is studied in this paper. The problem is how to reduce the travelling distance of totes between aisles and picking stations. A multi-stage heuristic algorithm is proposed based on statement and model of this problem. The main idea of this algorithm is, with some heuristic strategies based on similarity coefficients, minimizing the transportations of items which can not arrive in the destination picking stations just through direct conveyors. The experimental results based on the cases generated by computers show that the average reduced rate of indirect transport times can reach 14.36% with the application of multi-stage heuristic algorithm. For the cases from a real e-commerce distribution center, the order processing time can be reduced from 11.20 h to 10.06 h with the help of the modified system and the proposed algorithm. In summary, this research proposed a modified system and a multi-stage heuristic algorithm that can reduce the travelling distance of totes effectively and improve the whole performance of e-commerce distribution center.展开更多
Large-scale geological energy storage plays a crucial role in balancing the intermittency of renewable energy.As an energy storage medium,soaked sandstone has a wide range of applications in geological energy storage....Large-scale geological energy storage plays a crucial role in balancing the intermittency of renewable energy.As an energy storage medium,soaked sandstone has a wide range of applications in geological energy storage.Understanding the damage characteristics in soaked sandstones is essential for ensuring the stability and longevity of these energy storage systems.This study involved multi-stage cyclic loading tests conducted on soaked sandstone to explore the damage evolution throughout the loading process.The findingsreveal several important insights:(1)The plastic hysteresis loops observed during multi-stage cyclic loading evolved from dense to sparse.An increase in stress level led to greater damage in the rock,as evidenced by an increase in accumulated peak/plastic strains.(2)Energy density and stress level are related by quadratic polynomial relationships.The elastic and dissipated energy densities are related by a linear law.The average energy storage coefficientdecreased by up to 24.1%with increasing stress amplitude,reflectingchanges in energy dynamics within the samples.(3)AE counts,amplitude,and frequency provided critical insights into rock damage and fracture patterns.The greater the loading rate and stress amplitude,the lower the proportion of high-amplitude,high-peak frequency,and shear-type fractures.Increasing stress amplitude caused a maximum 16.63%reduction in the AE bvalue,indicating shifts in fracture behavior under varying stress conditions.(4)The increase in loading rate and stress amplitude promotes the transformation of micropores and mesopores to macropores/microcracks.(5)Damage variables,definedin terms of cumulative dissipation energy,aligned closely with the fatigue damage model under multi-stage cyclic loading.Accelerated damage primarily occurred during the finalstages of fatigue loading,highlighting critical periods in the degradation of soaked sandstones.This study can offer guidance for designing operational parameters for energy storage geological bodies dominated by soaked sandstones.展开更多
Although previous researchers have attempted to decipher ore genesis and mineralization in the Erdaokan Ag-Pb-Zn deposit,some uncertainties regarding the mineralization process and evolution of both ore-forming fluids...Although previous researchers have attempted to decipher ore genesis and mineralization in the Erdaokan Ag-Pb-Zn deposit,some uncertainties regarding the mineralization process and evolution of both ore-forming fluids and magnetite types still need to be addressed.In this study,we obtained new EPMA,LA-ICP-MS,and in situ Fe isotope data from magnetite from the Erdaokan deposit,in order to better understand the mineralization mechanism and evolution of both magnetite and the ore-forming fluids.Our results identified seven types of magnetite at Erdaokan:disseminated magnetite(Mag1),coarse-grained magnetite(Mag2a),radial magnetite(Mag2b),fragmented fine-grained magnetite(Mag2c),vermicular gel magnetite(Mag3a1 and Mag3a2),colloidal magnetite(Mag3b)and dark gray magnetite(Mag4).All of the magnetite types were hydrothermal in origin and generally low in Ti(<400 ppm)and Ni(<800 ppm),while being enriched in light Fe isotopes(δ^(56)Fe ranging from−1.54‰to−0.06‰).However,they exhibit different geochemical signatures and are thus classified into high-manganese magnetite(Mag1,MnO>5 wt%),low-silicon magnetite(Mag2a-c,SiO_(2)<1 wt%),high-silicon magnetite(Mag3a-b,SiO_(2)from 1 to 7 wt%)and high-silicon-manganese magnetite(Mag4,SiO_(2)>1 wt%,MnO>0.2 wt%),each being formed within distinct hydrothermal environments.Based on mineralogy,elemental geochemistry,Fe isotopes,temperature trends,TMg-mag and(Ti+V)vs.(Al+Mn)diagrams,we propose that the Erdaokan Ag-Pb-Zn deposit underwent multi-stage mineralization,which can be broken down into four stages and nine sub-stages.Mag1,Mag2a-c,Mag3a-b and Mag4 were formed during the first sub-stage of each of the four stages,respectively.Additionally,fluid mixing,cooling and depressurization boiling were identified as the main mechanisms for mineral precipitation.The enrichment of Ag was significantly enhanced by the superposition of multi-stage ore-forming hydrothermal fluids in the Erdaokan Ag-Pb-Zn deposit.展开更多
A new hang-off system has been proposed to improve the security of risers in hang-off modes during typhoons.However,efficient anti-typhoon evacuation strategies have not been investigated.Optimiza-tion model and metho...A new hang-off system has been proposed to improve the security of risers in hang-off modes during typhoons.However,efficient anti-typhoon evacuation strategies have not been investigated.Optimiza-tion model and method for the anti-typhoon evacuation strategies should be researched.Therefore,multi-objective functions are proposed based on operation time,evacuation speed stability,and steering stability.An evacuation path model and a dynamic model of risers with the new hang-off system are developed for design variables and constraints.A multi-objective optimization model with high-dimensional variables and complex constraints is established.Finally,a three-stage optimization method based on genetic algorithm,least square method,and the penalty function method is proposed to solve the multi-objective optimization model.Optimization results show that the operation time can be reduced through operation parameter optimization,especially evacuation heading optimization.The optimal anti-typhoon strategy is evacuation with all risers suspended along a variable path when the direction angle is large,while evacuation with all risers suspended along a straight path at another di-rection angle.Besides,the influencing factors on anti-typhoon evacuation strategies indicate that the proposed optimization model and method have strong applicability to working conditions and remarkable optimization effects.展开更多
Nano zero-valent iron(nZVI)is a promising phosphate adsorbent for advanced phosphate removal.However,the rapid passivation of nZVI and the low activity of adsorption sites seriously limit its phosphate removal perform...Nano zero-valent iron(nZVI)is a promising phosphate adsorbent for advanced phosphate removal.However,the rapid passivation of nZVI and the low activity of adsorption sites seriously limit its phosphate removal performance,accounting for its inapplicability to meet the emission criteria of 0.1 mg P/L phosphate.In this study,we report that the oxalate modification can inhibit the passivation of nZVI and alter the multi-stage phosphate adsorption mechanism by changing the adsorption sites.As expected,the stronger antipassivation ability of oxalate modified nZVI(OX-nZVI)strongly favored its phosphate adsorption.Interestingly,the oxalate modification endowed the surface Fe(III)sites with the lowest chemisorption energy and the fastest phosphate adsorption ability than the other adsorption sites,by in situ forming a Fe(III)-phosphate-oxalate ternary complex,therefore enabling an advanced phosphate removal process.At an initial phosphate concentration of 1.00 mg P/L,pH of 6.0 and a dosage of 0.3 g/L of adsorbents,OX-nZVI exhibited faster phosphate removal rate(0.11 g/mg/min)and lower residual phosphate level(0.02 mg P/L)than nZVI(0.055 g/mg/min and 0.19 mg P/L).This study sheds light on the importance of site manipulation in the development of high-performance adsorbents,and offers a facile surface modification strategy to prepare superior iron-basedmaterials for advanced phosphate removal.展开更多
The effectiveness of horizontal well multi-stage and multi-cluster fracturing in the fractured soft coal seam roof for coalbed methane(CBM) extraction has been demonstrated.This study focuses on the geological charact...The effectiveness of horizontal well multi-stage and multi-cluster fracturing in the fractured soft coal seam roof for coalbed methane(CBM) extraction has been demonstrated.This study focuses on the geological characteristics of the No.5 and No.11 coal seams in the Hancheng Block,Ordos Basin,China.A multi-functional,variable-size rock sample mold capable of securing the wellbore was developed to simulate layered formations comprising strata of varying lithology and thicknesses.A novel segmented fracturing simulation method based on an expandable pipe plugging technique is proposed.Large-scale true triaxial experiments were conducted to investigate the effects of horizontal wellbore location,perforation strategy,roof lithology,and vertical stress difference on fracture propagation,hydraulic energy variation,and the stimulated reservoir volume in horizontal wells targeting the soft coal seam roof.The results indicate that bilateral downward perforation with a phase angle of 120° optimizes hydraulic energy conservation,reduces operational costs,enhances fracture formation,and prevents fracturing failure caused by coal powder generation and migration.This perforation mode is thus considered optimal for coal seam roof fracturing.When the roof consists of sandstone,each perforation cluster tends to initiate a single dominant fracture with a regular geometry.In contrast,hydraulic fractures formed in mudstone roofs display diverse morphology.Due to its high strength,the sandstone roof requires significantly higher pressure for crack initiation and propagation,whereas the mudstone roof,with its strong water sensitivity,exhibits lower fracturing pressures.To mitigate inter-cluster interference,cluster spacing in mudstone roofs should be greater than that in sandstone roofs.Horizontal wellbore placement critically influences fracturing effectiveness.For indirect fracturing in sandstone roofs,an optimal position is 25 mm away from the lithological interface.In contrast,the optimal location for indirect fracturing in mudstone roofs is directly at the lithological interface with the coal seam.Higher vertical stress coefficients lead to increased fractu ring pressures and promote vertical,layer-penetrating fractures.A coefficient of 0.5 is identified as optimal for achieving effective indirect fracturing.This study provides valuable insights for the design and optimization of staged fracturing in horizontal wells targeting crushed soft coal seam roofs.展开更多
Studies of wave-current interactions are vital for the safe design of structures.Regular waves in the presence of uniform,linear shear,and quadratic shear currents are explored by the High-Level Green-Naghdi model in ...Studies of wave-current interactions are vital for the safe design of structures.Regular waves in the presence of uniform,linear shear,and quadratic shear currents are explored by the High-Level Green-Naghdi model in this paper.The five-point central difference method is used for spatial discretization,and the fourth-order Adams predictor-corrector scheme is employed for marching in time.The domain-decomposition method is applied for the wave-current generation and absorption.The effects of currents on the wave profile and velocity field are examined under two conditions:the same velocity of currents at the still-water level and the constant flow volume of currents.Wave profiles and velocity fields demonstrate substantial differences in three types of currents owing to the diverse vertical distribution of current velocity and vorticity.Then,loads on small-scale vertical cylinders subjected to regular waves and three types of background currents with the same flow volume are investigated.The maximum load intensity and load fluctuation amplitude in uniform,linear shear,and quadratic shear currents increase sequentially.The stretched superposition method overestimates the maximum load intensity and load fluctuation amplitude in opposing currents and underestimates these values in following currents.The stretched superposition method obtains a poor approximation for strong nonlinear waves,particularly in the case of the opposing quadratic shear current.展开更多
Data center industries have been facing huge energy challenges due to escalating power consumption and associated carbon emissions.In the context of carbon neutrality,the integration of data centers with renewable ene...Data center industries have been facing huge energy challenges due to escalating power consumption and associated carbon emissions.In the context of carbon neutrality,the integration of data centers with renewable energy has become a prevailing trend.To advance the renewable energy integration in data centers,it is imperative to thoroughly explore the data centers’operational flexibility.Computing workloads and refrigeration systems are recognized as two promising flexible resources for power regulationwithin data centermicro-grids.This paper identifies and categorizes delay-tolerant computing workloads into three types(long-running non-interruptible,long-running interruptible,and short-running)and develops mathematical time-shifting models for each.Additionally,this paper examines the thermal dynamics of the computer room and derives a time-varying temperature model coupled to refrigeration power.Building on these models,this paper proposes a two-stage,multi-time scale optimization scheduling framework that jointly coordinates computing workloads time-shift in day-ahead scheduling and refrigeration power control in intra-day dispatch to mitigate renewable variability.A case study demonstrates that the framework effectively enhances the renewable-energy utilization,improves the operational economy of the data center microgrid,and mitigates the impact of renewable power uncertainty.The results highlight the potential of coordinated computing workloads and thermal system flexibility to support greener,more cost-effective data center operation.展开更多
The multi-pass intermittent local loading process,which features a more flexible processing path,can further enhance the second material distribution during local loading,improve the formability of components,and redu...The multi-pass intermittent local loading process,which features a more flexible processing path,can further enhance the second material distribution during local loading,improve the formability of components,and reduce forming loads.However,the absence of compatible forming equipment makes it difficult to control the constraint in the unloaded zones during the forming process.This difficulty complicates coordination and control of deformation,particularly for asymmetric rib-web components.Additionally,the current implementation involves multi-fire heating,a long process flow,and high energy consumption,which limits the popularization and application of the local loading process.In this study,a new multi-pass local loading hydraulic forming apparatus that can quickly and reliably switch between heavy-load deformation and low-load constraint for different local loading sub-dies was developed.A 10-tonne laboratory prototype was developed,and the forming characteristics during the forming process as well as the response characteristics of the hydraulic system during the multi-pass intermittent local loading of rib-web component were investigated using numerical simulations and physical experiments.Results indicated that,compared to a whole loading process with the same initial geometry of billet,the total forming load(i.e.,the sum of loaded and restrained loads)is reduced by more than 40%with the local loading process,and by nearly 50%with multi-pass local loading.The multi-pass local loading process allows for more effective control of material flow compared to single-pass local loading,leading to improved cavity filling and reduced flow line disturbance.For a large-scale,complex titanium alloy bulkhead,the cavity filling problem was addressed by optimizing the multi-pass local loading path with an unequal thickness billet.The dynamic performance of the multi-pass local loading hydraulic system was found to be robust,with stable pressure transitions during motion and load switching for the sub-die(s).The dynamic characteristic of the hydraulic cylinder when switching from non-moving/unloaded state to a moving/loading state are consistent whether a load is present or not.However,the dynamic characteristics differ when switching from a moving/loading state to non-moving/unloaded state,showing opposite behavior.The developed hydraulic drive mechanism provides a way for implementation of multi-pass local loading without auxiliary operation and extra heating.The results of the study provide a foundation for the industrial production of large-scale,complex components with reduced force requirement and low-energy consumption.展开更多
Unbonded post-tensioned(PT)concrete systems are widely used in safety-critical structures,yet model-ing practices for prestress implementation and tendon-concrete interaction remain inconsistent.This study investigate...Unbonded post-tensioned(PT)concrete systems are widely used in safety-critical structures,yet model-ing practices for prestress implementation and tendon-concrete interaction remain inconsistent.This study investigates the effects of sheath(duct)implementation and confinement assumptions through nonlinear finite element analysis.Four modeling cases were defined,consisting of an explicit sheath without tendon-concrete confinement(S)and three no-sheath variants with different confinement levels(X,N,A).One-way beams and two-way panels were analyzed,and panel blast responses were validated against experimental results.In both beams and panels,average initial stress levels were similar across models,through local stress concentrations appeared when the sheath was modeled.Under blast loading,these local effects became critical,and the sheath-implemented model reproduced experimental behavior most accurately,whereas non-implemented models deviated.Reduced blast intensity diminished the differences among models,thereby reaffirming that sheath-induced localization and damage propagation are critical factors.These findings highlight the importance of explicit sheath implementation for realistic numerical assessment of unbonded PT structures under extreme loads.展开更多
This paper investigates the detection and mitigation of coordinated cyberattacks on Load Frequency Control(LFC)systems integrated with Battery Energy Storage Systems(BESS).As renewable energy sources gain greater pene...This paper investigates the detection and mitigation of coordinated cyberattacks on Load Frequency Control(LFC)systems integrated with Battery Energy Storage Systems(BESS).As renewable energy sources gain greater penetration,power grids are becoming increasingly vulnerable to cyber threats,potentially leading to frequency instability and widespread disruptions.We model two significant attack vectors:load-altering attacks(LAAs)and false data injection attacks(FDIAs)that corrupt frequency measurements.These are analyzed for their impact on grid frequency stability in both linear and nonlinear LFC models,incorporating generation rate constraints and nonlinear loads.A coordinated attack strategy is presented,combining LAAs and FDIAs to achieve stealthiness by concealing frequency deviations from system operators,thereby maximizing disruption while evading traditional detection.To counteract these threats,we propose an Unknown Input Observer(UIO)-based detection framework for linear and nonlinear LFCs.The UIO is designed using linear matrix inequalities(LMIs)to estimate system states while isolating unknown attack inputs,enabling attack detection through monitoring measurement residuals against a predefined threshold.For mitigation,we leverage BESS capabilities with two adaptive strategies:dynamic mitigation for dynamic LAAs,which tunes BESS parameters to enhance the system’s stability margin and accelerate convergence to equilibrium;and staticmitigation for static LAAs and FDIAs.Simulations show that the UIO achieves high detection accuracy,with residuals exceeding thresholds promptly under coordinated attacks,even in nonlinear models.Mitigation strategies reduce frequency deviations by up to 80%compared to unmitigated cases,restoring stability within seconds.展开更多
With the growing global demand for energy,deep underground salt caverns are emerging as a potential solution for large-scale energy storage.In this study,multistage cyclic loading tests were conducted on rock salt at ...With the growing global demand for energy,deep underground salt caverns are emerging as a potential solution for large-scale energy storage.In this study,multistage cyclic loading tests were conducted on rock salt at different temperatures in combination with real-time acoustic emission(AE)monitoring.The results show that the cumulative AE count increases stepwise with increasing cyclic stress.The peak frequency is concentrated primarily in the medium-frequency range,exhibiting a band distribution across low-,medium-,and high-frequency ranges.As the temperature increases,the proportion of low-frequency signals decreases from 14.32%to 5.76%,whereas the proportion of medium-frequency signals increases from 85.48%to 94.1%.The proportion of high-frequency signals remains relatively constant between 0.1%and 0.2%.The amplitude-count relationship of the AE signals demonstrates a strong negative power-law correlation.Furthermore,with increasing temperature,the negative power-law exponent of the amplitude gradually decreases,with the b value decreasing from 1.096 to 0.837 and the a value decreasing from 7.4871 to 6.6982.Under all four temperature conditions,the dominant failure mode in rock salt is tensile cracking.However,as the temperature increases,the proportion of tensile cracks decreases from 88.59%to 75.12%,whereas the proportion of shear cracks at 80℃is nearly double that at 20℃.This finding indicates that as the temperature increases,the ductility of the material increases,and the crack propagation mode shifts from tensile to shear.This research provides valuable insights for the design and stability assessment of salt cavern reservoirs for deep underground energy storage systems.展开更多
This study investigates the performance of high-strength cable bolts under impact loading conditions representative of rock bursts in underground environments.Although widely used,the dynamic behaviour of these cable ...This study investigates the performance of high-strength cable bolts under impact loading conditions representative of rock bursts in underground environments.Although widely used,the dynamic behaviour of these cable bolts has received limited experimental attention,and their effectiveness in seismically active zones remains a subject of ongoing debate.To address this gap,a reverse pull-out test machine integrated with a drop hammer rig was employed.Tests were conducted on 70-t SUMO bulbed and non-bulbed cable bolts with encapsulation lengths of 300 and 450 mm,subjected to an impact energy of 14.52 k J.Results indicate that non-bulbed cables,despite showing lower initial peak loads(average 218 vs.328 k N for bulbed cables at 300 mm encapsulation),demonstrated superior energy absorption(average 11.26 vs.8.75 k J)and displacement capacity(average 48.40 vs.36.25 mm).Increasing the encapsulation length for bulbed cables led to a reduction in initial peak load but improved displacement and energy absorption.The dominant failure mechanism was debonding at the cable-grout interface,characterised by frictional sliding and cable rotation.These findings provide new insights into the energy dissipation mechanisms of cables and support the development of more resilient ground support systems for dynamically active conditions.展开更多
This study establishes and validates a method for the precise quantification of aquatic microbial loads using microbial diversity absolute quantitative sequencing.By adding synthetic spike-in DNA to water samples from...This study establishes and validates a method for the precise quantification of aquatic microbial loads using microbial diversity absolute quantitative sequencing.By adding synthetic spike-in DNA to water samples from the Dahei River prior to DNA extraction and 16S rRNA gene sequencing,it generates standard curves to convert sequencing data into absolute microbial copy numbers.The method,which is proved highly accurate(R^(2)>0.99),reveals a clear contrast between the river sites:the upstream community has not only a significantly higher total microbial load but also a completely different makeup of species compared to the downstream site.This approach effectively overcomes the limitations of relative abundance analysis,providing a powerful tool for environmental monitoring,and proposes key steps for future standardization to ensure data comparability and integration.展开更多
This study examined non-uniform loading in goaf cantilever rock masses via testing,modeling,and mechanical analysis to solve instantaneous fracture and section buckling from mining abutment pressure.The study investig...This study examined non-uniform loading in goaf cantilever rock masses via testing,modeling,and mechanical analysis to solve instantaneous fracture and section buckling from mining abutment pressure.The study investigates the non-uniform load gradient effect on fracture characteristics,including load characteristics,fracture location,fracture distribution,and section roughness.A digital model for fracture interface buckling analysis was developed,elucidating the influence of non-uniform load gradients on Fracture Interface Curvature(FIC),Buckling Rate of Change(BRC),and Buckling Domain Field(BDF).The findings reveal that nonlinear tensile stress concentration and abrupt tensile-compressive-shear strain mutations under non-uniform loading are fundamental mechanisms driving fracture path buckling in cantilever rock mass structures.The buckling process of rock mass under non-uniform load can be divided into two stages:low load gradient and high gradient load.In the stage of low gradient load,the buckling behavior is mainly reflected in the compression-shear fracture of the edge.In the stage of high gradient load,a buckling band along the loading direction is gradually formed in the rock mass.These buckling principles establish a theoretical basis for accurately characterizing bearing fractures,fracture interface instability,and vibration sources within overlying cantilever rock masses in goaf.展开更多
Theauthor proposes a dual layer source grid load storage collaborative planning model based on Benders decomposition to optimize the low-carbon and economic performance of the distribution network.The model plans the ...Theauthor proposes a dual layer source grid load storage collaborative planning model based on Benders decomposition to optimize the low-carbon and economic performance of the distribution network.The model plans the configuration of photovoltaic(3.8 MW),wind power(2.5 MW),energy storage(2.2 MWh),and SVC(1.2 Mvar)through interaction between upper and lower layers,and modifies lines 2–3,8–9,etc.to improve transmission capacity and voltage stability.The author uses normal distribution and Monte Carlo method to model load uncertainty,and combines Weibull distribution to describe wind speed characteristics.Compared to the traditional three-layer model(TLM),Benders decomposition-based two-layer model(BLBD)has a 58.1%reduction in convergence time(5.36 vs.12.78 h),a 51.1%reduction in iteration times(23 vs.47 times),a 8.07%reduction in total cost(12.436 vs.13.528 million yuan),and a 9.62%reduction in carbon emissions(12,456 vs.13,782 t).After optimization,the peak valley difference decreased from4.1 to 2.9MW,the renewable energy consumption rate reached 93.4%,and the energy storage efficiency was 87.6%.Themodel has been validated in the IEEE 33 node system,demonstrating its superiority in terms of economy,low-carbon,and reliability.展开更多
文摘This paper presents a new criterion for determining the unloading points quantitatively and consistently in a multi-stage triaxial test.The radial strain gradient(RSG)is first introduced as an arc tangent function of the rate of change of radial strain to time.RSG is observed to correlate closely with the stress state of a compressed sample,and reaches a horizontal asymptote as approaching failure.For a given rock type,RSG value at peak stress is almost the same,irrespective of the porosity and permeability.These findings lead to the development of RSG criterion:Unloading points can be precisely determined at the time when RSG reaches a pre-determined value that is a little smaller than or equal to the RSG at peak stress.The RSG criterion is validated against other criteria and the single-stage triaxial test on various types of rocks.Failure envelopes from the RSG criterion match well with those from single-stage tests.A practical procedure is recommended to use the RSG criterion:an unconfined compression or single-stage test is first conducted to determine the RSG at peak stress for one sample,the unloading point is then selected to be a value close to the RSG at peak stress,and the multi-stage test is finally performed on another sample using the pre-selected RSG unloading criterion.Generally,the RSG criterion is applicable for any type of rocks,especially brittle rocks,where other criteria are not suitable.Further,it can be practically implemented on the most available rock mechanical testing instruments.
基金supported by the National Natural Science Foundation of China(Grant No.52374078)the Fundamental Research Funds for the Central Universities(Grant No.2023CDJKYJH021)the Sichuan-Chongqing Science and Technology Innovation Cooperation Program Project(Grant No.2024TIAD-CYKJCXX0011).
文摘Cyclic changes in the internal pressure of compressed air energy storage reservoirs in abandoned coal mines result in complex alternating loads on the rocks surrounding the energy storage reservoirs.These complex alternating loads can be regarded as multi-stage constant-amplitude cyclic loads following simplification.In this paper,the mechanical responses and acoustic emission(AE)characteristics of red sandstone with five bedding dip angles(0°,30°,45°,60°,and 90°)under such loads are investigated,and the damage evolution processes of the five specimens are revealed from both quantitative and microscopic perspectives.The results show that the fatigue deformation characteristics of the specimens are affected by the bedding dip angle.Under cyclic loads,the axially irreversible plastic deformations of the rocks increase,their elastic stiffness increases,their crack volumetric strain increases and then decreases,and their AE cumulative count/energy curves exhibit a ladder shape.A damage evolution model based on the crack volumetric strain is proposed,and the damage evolution process is divided into two stages:a rapid increase stage and a tendency toward stabilization stage.Through cluster analysis,the AE events are used to classify the damage into three categories:small-sized localized damage,large-sized tensile damage,and large-sized shear damage.Finally,the MohreCoulomb criterion is applied to analyze the relationship between the failure modes of the red sandstone specimens and the dip angle of the bedding.The results of this study will help to predict the stability and safety of compressed air energy storage reservoirs in abandoned coal mines.
基金the National Key Research and Development Program of China(2021YFC2900300)the Natural Science Foundation of Guangdong Province(2024A1515030216)+2 种基金MOST Special Fund from State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences(GPMR202437)the Guangdong Province Introduced of Innovative R&D Team(2021ZT09H399)the Third Xinjiang Scientific Expedition Program(2022xjkk1301).
文摘The application of machine learning for pyrite discrimination establishes a robust foundation for constructing the ore-forming history of multi-stage deposits;however,published models face challenges related to limited,imbalanced datasets and oversampling.In this study,the dataset was expanded to approximately 500 samples for each type,including 508 sedimentary,573 orogenic gold,548 sedimentary exhalative(SEDEX)deposits,and 364 volcanogenic massive sulfides(VMS)pyrites,utilizing random forest(RF)and support vector machine(SVM)methodologies to enhance the reliability of the classifier models.The RF classifier achieved an overall accuracy of 99.8%,and the SVM classifier attained an overall accuracy of 100%.The model was evaluated by a five-fold cross-validation approach with 93.8%accuracy for the RF and 94.9%for the SVM classifier.These results demonstrate the strong feasibility of pyrite classification,supported by a relatively large,balanced dataset and high accuracy rates.The classifier was employed to reveal the genesis of the controversial Keketale Pb-Zn deposit in NW China,which has been inconclusive among SEDEX,VMS,or a SEDEX-VMS transition.Petrographic investigations indicated that the deposit comprises early fine-grained layered pyrite(Py1)and late recrystallized pyrite(Py2).The majority voting classified Py1 as the VMS type,with an accuracy of RF and SVM being 72.2%and 75%,respectively,and confirmed Py2 as an orogenic type with 74.3% and 77.1%accuracy,respectively.The new findings indicated that the Keketale deposit originated from a submarine VMS mineralization system,followed by late orogenic-type overprinting of metamorphism and deformation,which is consistent with the geological and geochemical observations.This study further emphasizes the advantages of Machine learning(ML)methods in accurately and directly discriminating the deposit types and reconstructing the formation history of multi-stage deposits.
基金funded by the State Grid Corporation Science and Technology Project(5108-202218280A-2-391-XG).
文摘The high proportion of uncertain distributed power sources and the access to large-scale random electric vehicle(EV)charging resources further aggravate the voltage fluctuation of the distribution network,and the existing research has not deeply explored the EV active-reactive synergistic regulating characteristics,and failed to realize themulti-timescale synergistic control with other regulatingmeans,For this reason,this paper proposes amultilevel linkage coordinated optimization strategy to reduce the voltage deviation of the distribution network.Firstly,a capacitor bank reactive power compensation voltage control model and a distributed photovoltaic(PV)activereactive power regulationmodel are established.Additionally,an external characteristicmodel of EVactive-reactive power regulation is developed considering the four-quadrant operational characteristics of the EVcharger.Amultiobjective optimization model of the distribution network is then constructed considering the time-series coupling constraints of multiple types of voltage regulators.A multi-timescale control strategy is proposed by considering the impact of voltage regulators on active-reactive EV energy consumption and PV energy consumption.Then,a four-stage voltage control optimization strategy is proposed for various types of voltage regulators with multiple time scales.Themulti-objective optimization is solved with the improvedDrosophila algorithmto realize the power fluctuation control of the distribution network and themulti-stage voltage control optimization.Simulation results validate that the proposed voltage control optimization strategy achieves the coordinated control of decentralized voltage control resources in the distribution network.It effectively reduces the voltage deviation of the distribution network while ensuring the energy demand of EV users and enhancing the stability and economic efficiency of the distribution network.
文摘E-commerce, as an emerging marketing mode, has attracted more and more attention and gradually changed the way of our life. However, the existing layout of distribution centers can＇t fulfill the storage and picking demands of e-commerce sufficiently. In this paper, a modified miniload automated storage/retrieval system is designed to fit these new characteristics of e-commerce in logistics. Meanwhile, a matching problem, concerning with the improvement of picking efficiency in new system, is studied in this paper. The problem is how to reduce the travelling distance of totes between aisles and picking stations. A multi-stage heuristic algorithm is proposed based on statement and model of this problem. The main idea of this algorithm is, with some heuristic strategies based on similarity coefficients, minimizing the transportations of items which can not arrive in the destination picking stations just through direct conveyors. The experimental results based on the cases generated by computers show that the average reduced rate of indirect transport times can reach 14.36% with the application of multi-stage heuristic algorithm. For the cases from a real e-commerce distribution center, the order processing time can be reduced from 11.20 h to 10.06 h with the help of the modified system and the proposed algorithm. In summary, this research proposed a modified system and a multi-stage heuristic algorithm that can reduce the travelling distance of totes effectively and improve the whole performance of e-commerce distribution center.
基金sponsored by National Natural Science Foundation of China(Grant Nos.U22B6003 and 52304070)Key Laboratory of Geomechanics and Geotechnical Engineering Safety,Chinese Academy of Sciences(Grant No.SKLGME-JBGS2404).
文摘Large-scale geological energy storage plays a crucial role in balancing the intermittency of renewable energy.As an energy storage medium,soaked sandstone has a wide range of applications in geological energy storage.Understanding the damage characteristics in soaked sandstones is essential for ensuring the stability and longevity of these energy storage systems.This study involved multi-stage cyclic loading tests conducted on soaked sandstone to explore the damage evolution throughout the loading process.The findingsreveal several important insights:(1)The plastic hysteresis loops observed during multi-stage cyclic loading evolved from dense to sparse.An increase in stress level led to greater damage in the rock,as evidenced by an increase in accumulated peak/plastic strains.(2)Energy density and stress level are related by quadratic polynomial relationships.The elastic and dissipated energy densities are related by a linear law.The average energy storage coefficientdecreased by up to 24.1%with increasing stress amplitude,reflectingchanges in energy dynamics within the samples.(3)AE counts,amplitude,and frequency provided critical insights into rock damage and fracture patterns.The greater the loading rate and stress amplitude,the lower the proportion of high-amplitude,high-peak frequency,and shear-type fractures.Increasing stress amplitude caused a maximum 16.63%reduction in the AE bvalue,indicating shifts in fracture behavior under varying stress conditions.(4)The increase in loading rate and stress amplitude promotes the transformation of micropores and mesopores to macropores/microcracks.(5)Damage variables,definedin terms of cumulative dissipation energy,aligned closely with the fatigue damage model under multi-stage cyclic loading.Accelerated damage primarily occurred during the finalstages of fatigue loading,highlighting critical periods in the degradation of soaked sandstones.This study can offer guidance for designing operational parameters for energy storage geological bodies dominated by soaked sandstones.
基金financially supported by the Heilongjiang Provincial Key R&D Program Project(No.GA21A204)Heilongjiang Provincial Natural Science Foundation of China(No.LH2022D031)the Research Project of Heilongjiang Province Bureau of Geology and Mineral Resources(No.HKY202302).
文摘Although previous researchers have attempted to decipher ore genesis and mineralization in the Erdaokan Ag-Pb-Zn deposit,some uncertainties regarding the mineralization process and evolution of both ore-forming fluids and magnetite types still need to be addressed.In this study,we obtained new EPMA,LA-ICP-MS,and in situ Fe isotope data from magnetite from the Erdaokan deposit,in order to better understand the mineralization mechanism and evolution of both magnetite and the ore-forming fluids.Our results identified seven types of magnetite at Erdaokan:disseminated magnetite(Mag1),coarse-grained magnetite(Mag2a),radial magnetite(Mag2b),fragmented fine-grained magnetite(Mag2c),vermicular gel magnetite(Mag3a1 and Mag3a2),colloidal magnetite(Mag3b)and dark gray magnetite(Mag4).All of the magnetite types were hydrothermal in origin and generally low in Ti(<400 ppm)and Ni(<800 ppm),while being enriched in light Fe isotopes(δ^(56)Fe ranging from−1.54‰to−0.06‰).However,they exhibit different geochemical signatures and are thus classified into high-manganese magnetite(Mag1,MnO>5 wt%),low-silicon magnetite(Mag2a-c,SiO_(2)<1 wt%),high-silicon magnetite(Mag3a-b,SiO_(2)from 1 to 7 wt%)and high-silicon-manganese magnetite(Mag4,SiO_(2)>1 wt%,MnO>0.2 wt%),each being formed within distinct hydrothermal environments.Based on mineralogy,elemental geochemistry,Fe isotopes,temperature trends,TMg-mag and(Ti+V)vs.(Al+Mn)diagrams,we propose that the Erdaokan Ag-Pb-Zn deposit underwent multi-stage mineralization,which can be broken down into four stages and nine sub-stages.Mag1,Mag2a-c,Mag3a-b and Mag4 were formed during the first sub-stage of each of the four stages,respectively.Additionally,fluid mixing,cooling and depressurization boiling were identified as the main mechanisms for mineral precipitation.The enrichment of Ag was significantly enhanced by the superposition of multi-stage ore-forming hydrothermal fluids in the Erdaokan Ag-Pb-Zn deposit.
基金supported by the National Natural Science Foundation of China(Grant No:52271300,52071337)National Key Research and Development Program of China(2022YFC2806501)+1 种基金High-tech Ship Research Projects Sponsored by MIIT(CBG2N21-4-25)Program for Changjiang Scholars and Innovative Research Team in University(Grant No.IRT14R58).
文摘A new hang-off system has been proposed to improve the security of risers in hang-off modes during typhoons.However,efficient anti-typhoon evacuation strategies have not been investigated.Optimiza-tion model and method for the anti-typhoon evacuation strategies should be researched.Therefore,multi-objective functions are proposed based on operation time,evacuation speed stability,and steering stability.An evacuation path model and a dynamic model of risers with the new hang-off system are developed for design variables and constraints.A multi-objective optimization model with high-dimensional variables and complex constraints is established.Finally,a three-stage optimization method based on genetic algorithm,least square method,and the penalty function method is proposed to solve the multi-objective optimization model.Optimization results show that the operation time can be reduced through operation parameter optimization,especially evacuation heading optimization.The optimal anti-typhoon strategy is evacuation with all risers suspended along a variable path when the direction angle is large,while evacuation with all risers suspended along a straight path at another di-rection angle.Besides,the influencing factors on anti-typhoon evacuation strategies indicate that the proposed optimization model and method have strong applicability to working conditions and remarkable optimization effects.
基金supported by the National Key Research and Development Program of China(Nos.2022YFA1205602,and 2023YFC3707801)the National Natural Science Foundation of China(Nos.U22A20402,22376073,21936003 and 22306119)China Postdoctoral Science Foundation(No.2023T160419).
文摘Nano zero-valent iron(nZVI)is a promising phosphate adsorbent for advanced phosphate removal.However,the rapid passivation of nZVI and the low activity of adsorption sites seriously limit its phosphate removal performance,accounting for its inapplicability to meet the emission criteria of 0.1 mg P/L phosphate.In this study,we report that the oxalate modification can inhibit the passivation of nZVI and alter the multi-stage phosphate adsorption mechanism by changing the adsorption sites.As expected,the stronger antipassivation ability of oxalate modified nZVI(OX-nZVI)strongly favored its phosphate adsorption.Interestingly,the oxalate modification endowed the surface Fe(III)sites with the lowest chemisorption energy and the fastest phosphate adsorption ability than the other adsorption sites,by in situ forming a Fe(III)-phosphate-oxalate ternary complex,therefore enabling an advanced phosphate removal process.At an initial phosphate concentration of 1.00 mg P/L,pH of 6.0 and a dosage of 0.3 g/L of adsorbents,OX-nZVI exhibited faster phosphate removal rate(0.11 g/mg/min)and lower residual phosphate level(0.02 mg P/L)than nZVI(0.055 g/mg/min and 0.19 mg P/L).This study sheds light on the importance of site manipulation in the development of high-performance adsorbents,and offers a facile surface modification strategy to prepare superior iron-basedmaterials for advanced phosphate removal.
基金support from China National Natural Science Foundation (11672333)。
文摘The effectiveness of horizontal well multi-stage and multi-cluster fracturing in the fractured soft coal seam roof for coalbed methane(CBM) extraction has been demonstrated.This study focuses on the geological characteristics of the No.5 and No.11 coal seams in the Hancheng Block,Ordos Basin,China.A multi-functional,variable-size rock sample mold capable of securing the wellbore was developed to simulate layered formations comprising strata of varying lithology and thicknesses.A novel segmented fracturing simulation method based on an expandable pipe plugging technique is proposed.Large-scale true triaxial experiments were conducted to investigate the effects of horizontal wellbore location,perforation strategy,roof lithology,and vertical stress difference on fracture propagation,hydraulic energy variation,and the stimulated reservoir volume in horizontal wells targeting the soft coal seam roof.The results indicate that bilateral downward perforation with a phase angle of 120° optimizes hydraulic energy conservation,reduces operational costs,enhances fracture formation,and prevents fracturing failure caused by coal powder generation and migration.This perforation mode is thus considered optimal for coal seam roof fracturing.When the roof consists of sandstone,each perforation cluster tends to initiate a single dominant fracture with a regular geometry.In contrast,hydraulic fractures formed in mudstone roofs display diverse morphology.Due to its high strength,the sandstone roof requires significantly higher pressure for crack initiation and propagation,whereas the mudstone roof,with its strong water sensitivity,exhibits lower fracturing pressures.To mitigate inter-cluster interference,cluster spacing in mudstone roofs should be greater than that in sandstone roofs.Horizontal wellbore placement critically influences fracturing effectiveness.For indirect fracturing in sandstone roofs,an optimal position is 25 mm away from the lithological interface.In contrast,the optimal location for indirect fracturing in mudstone roofs is directly at the lithological interface with the coal seam.Higher vertical stress coefficients lead to increased fractu ring pressures and promote vertical,layer-penetrating fractures.A coefficient of 0.5 is identified as optimal for achieving effective indirect fracturing.This study provides valuable insights for the design and optimization of staged fracturing in horizontal wells targeting crushed soft coal seam roofs.
基金Supported by the Development and Application Project of Ship CAE Software.
文摘Studies of wave-current interactions are vital for the safe design of structures.Regular waves in the presence of uniform,linear shear,and quadratic shear currents are explored by the High-Level Green-Naghdi model in this paper.The five-point central difference method is used for spatial discretization,and the fourth-order Adams predictor-corrector scheme is employed for marching in time.The domain-decomposition method is applied for the wave-current generation and absorption.The effects of currents on the wave profile and velocity field are examined under two conditions:the same velocity of currents at the still-water level and the constant flow volume of currents.Wave profiles and velocity fields demonstrate substantial differences in three types of currents owing to the diverse vertical distribution of current velocity and vorticity.Then,loads on small-scale vertical cylinders subjected to regular waves and three types of background currents with the same flow volume are investigated.The maximum load intensity and load fluctuation amplitude in uniform,linear shear,and quadratic shear currents increase sequentially.The stretched superposition method overestimates the maximum load intensity and load fluctuation amplitude in opposing currents and underestimates these values in following currents.The stretched superposition method obtains a poor approximation for strong nonlinear waves,particularly in the case of the opposing quadratic shear current.
基金supported by Science and Technology Standard Project of Guangdong Electric Power Design Institute(ER11301W,ER11811W).
文摘Data center industries have been facing huge energy challenges due to escalating power consumption and associated carbon emissions.In the context of carbon neutrality,the integration of data centers with renewable energy has become a prevailing trend.To advance the renewable energy integration in data centers,it is imperative to thoroughly explore the data centers’operational flexibility.Computing workloads and refrigeration systems are recognized as two promising flexible resources for power regulationwithin data centermicro-grids.This paper identifies and categorizes delay-tolerant computing workloads into three types(long-running non-interruptible,long-running interruptible,and short-running)and develops mathematical time-shifting models for each.Additionally,this paper examines the thermal dynamics of the computer room and derives a time-varying temperature model coupled to refrigeration power.Building on these models,this paper proposes a two-stage,multi-time scale optimization scheduling framework that jointly coordinates computing workloads time-shift in day-ahead scheduling and refrigeration power control in intra-day dispatch to mitigate renewable variability.A case study demonstrates that the framework effectively enhances the renewable-energy utilization,improves the operational economy of the data center microgrid,and mitigates the impact of renewable power uncertainty.The results highlight the potential of coordinated computing workloads and thermal system flexibility to support greener,more cost-effective data center operation.
基金the supports of the National Natural Science Foundation of China(Grant No.52375378)。
文摘The multi-pass intermittent local loading process,which features a more flexible processing path,can further enhance the second material distribution during local loading,improve the formability of components,and reduce forming loads.However,the absence of compatible forming equipment makes it difficult to control the constraint in the unloaded zones during the forming process.This difficulty complicates coordination and control of deformation,particularly for asymmetric rib-web components.Additionally,the current implementation involves multi-fire heating,a long process flow,and high energy consumption,which limits the popularization and application of the local loading process.In this study,a new multi-pass local loading hydraulic forming apparatus that can quickly and reliably switch between heavy-load deformation and low-load constraint for different local loading sub-dies was developed.A 10-tonne laboratory prototype was developed,and the forming characteristics during the forming process as well as the response characteristics of the hydraulic system during the multi-pass intermittent local loading of rib-web component were investigated using numerical simulations and physical experiments.Results indicated that,compared to a whole loading process with the same initial geometry of billet,the total forming load(i.e.,the sum of loaded and restrained loads)is reduced by more than 40%with the local loading process,and by nearly 50%with multi-pass local loading.The multi-pass local loading process allows for more effective control of material flow compared to single-pass local loading,leading to improved cavity filling and reduced flow line disturbance.For a large-scale,complex titanium alloy bulkhead,the cavity filling problem was addressed by optimizing the multi-pass local loading path with an unequal thickness billet.The dynamic performance of the multi-pass local loading hydraulic system was found to be robust,with stable pressure transitions during motion and load switching for the sub-die(s).The dynamic characteristic of the hydraulic cylinder when switching from non-moving/unloaded state to a moving/loading state are consistent whether a load is present or not.However,the dynamic characteristics differ when switching from a moving/loading state to non-moving/unloaded state,showing opposite behavior.The developed hydraulic drive mechanism provides a way for implementation of multi-pass local loading without auxiliary operation and extra heating.The results of the study provide a foundation for the industrial production of large-scale,complex components with reduced force requirement and low-energy consumption.
基金supported by the Nuclear Safety Research Program through the Korea Foundation of Nuclear Safety(KoFONS)using the financial resource granted by the Nuclear Safety and Security Commission(NSSC)of the Republic of Korea[RS-2025-02310881]the Korea Institute of Energy Technology Evaluation and Planning[KETEP]grant funded by the Ministry of Trade,Industry and Energy(MOTIE)[RS-2025-25447272].
文摘Unbonded post-tensioned(PT)concrete systems are widely used in safety-critical structures,yet model-ing practices for prestress implementation and tendon-concrete interaction remain inconsistent.This study investigates the effects of sheath(duct)implementation and confinement assumptions through nonlinear finite element analysis.Four modeling cases were defined,consisting of an explicit sheath without tendon-concrete confinement(S)and three no-sheath variants with different confinement levels(X,N,A).One-way beams and two-way panels were analyzed,and panel blast responses were validated against experimental results.In both beams and panels,average initial stress levels were similar across models,through local stress concentrations appeared when the sheath was modeled.Under blast loading,these local effects became critical,and the sheath-implemented model reproduced experimental behavior most accurately,whereas non-implemented models deviated.Reduced blast intensity diminished the differences among models,thereby reaffirming that sheath-induced localization and damage propagation are critical factors.These findings highlight the importance of explicit sheath implementation for realistic numerical assessment of unbonded PT structures under extreme loads.
基金supported by the Natural Science Foundation of China No.62303126the project Major Scientific and Technological Special Project of Guizhou Province([2024]014).
文摘This paper investigates the detection and mitigation of coordinated cyberattacks on Load Frequency Control(LFC)systems integrated with Battery Energy Storage Systems(BESS).As renewable energy sources gain greater penetration,power grids are becoming increasingly vulnerable to cyber threats,potentially leading to frequency instability and widespread disruptions.We model two significant attack vectors:load-altering attacks(LAAs)and false data injection attacks(FDIAs)that corrupt frequency measurements.These are analyzed for their impact on grid frequency stability in both linear and nonlinear LFC models,incorporating generation rate constraints and nonlinear loads.A coordinated attack strategy is presented,combining LAAs and FDIAs to achieve stealthiness by concealing frequency deviations from system operators,thereby maximizing disruption while evading traditional detection.To counteract these threats,we propose an Unknown Input Observer(UIO)-based detection framework for linear and nonlinear LFCs.The UIO is designed using linear matrix inequalities(LMIs)to estimate system states while isolating unknown attack inputs,enabling attack detection through monitoring measurement residuals against a predefined threshold.For mitigation,we leverage BESS capabilities with two adaptive strategies:dynamic mitigation for dynamic LAAs,which tunes BESS parameters to enhance the system’s stability margin and accelerate convergence to equilibrium;and staticmitigation for static LAAs and FDIAs.Simulations show that the UIO achieves high detection accuracy,with residuals exceeding thresholds promptly under coordinated attacks,even in nonlinear models.Mitigation strategies reduce frequency deviations by up to 80%compared to unmitigated cases,restoring stability within seconds.
基金supported by the Major Research Development Program of Hubei Province,China(Grant Nos.2022BAA093 and 2022BAD163)the Open Research Fund of the State Key Laboratory of Geomechanics and Geotechnical Engineering,Institute of Rock and Soil Mechanics,Chinese Academy of Sciences(Grant No.SKLGME023008).
文摘With the growing global demand for energy,deep underground salt caverns are emerging as a potential solution for large-scale energy storage.In this study,multistage cyclic loading tests were conducted on rock salt at different temperatures in combination with real-time acoustic emission(AE)monitoring.The results show that the cumulative AE count increases stepwise with increasing cyclic stress.The peak frequency is concentrated primarily in the medium-frequency range,exhibiting a band distribution across low-,medium-,and high-frequency ranges.As the temperature increases,the proportion of low-frequency signals decreases from 14.32%to 5.76%,whereas the proportion of medium-frequency signals increases from 85.48%to 94.1%.The proportion of high-frequency signals remains relatively constant between 0.1%and 0.2%.The amplitude-count relationship of the AE signals demonstrates a strong negative power-law correlation.Furthermore,with increasing temperature,the negative power-law exponent of the amplitude gradually decreases,with the b value decreasing from 1.096 to 0.837 and the a value decreasing from 7.4871 to 6.6982.Under all four temperature conditions,the dominant failure mode in rock salt is tensile cracking.However,as the temperature increases,the proportion of tensile cracks decreases from 88.59%to 75.12%,whereas the proportion of shear cracks at 80℃is nearly double that at 20℃.This finding indicates that as the temperature increases,the ductility of the material increases,and the crack propagation mode shifts from tensile to shear.This research provides valuable insights for the design and stability assessment of salt cavern reservoirs for deep underground energy storage systems.
文摘This study investigates the performance of high-strength cable bolts under impact loading conditions representative of rock bursts in underground environments.Although widely used,the dynamic behaviour of these cable bolts has received limited experimental attention,and their effectiveness in seismically active zones remains a subject of ongoing debate.To address this gap,a reverse pull-out test machine integrated with a drop hammer rig was employed.Tests were conducted on 70-t SUMO bulbed and non-bulbed cable bolts with encapsulation lengths of 300 and 450 mm,subjected to an impact energy of 14.52 k J.Results indicate that non-bulbed cables,despite showing lower initial peak loads(average 218 vs.328 k N for bulbed cables at 300 mm encapsulation),demonstrated superior energy absorption(average 11.26 vs.8.75 k J)and displacement capacity(average 48.40 vs.36.25 mm).Increasing the encapsulation length for bulbed cables led to a reduction in initial peak load but improved displacement and energy absorption.The dominant failure mechanism was debonding at the cable-grout interface,characterised by frictional sliding and cable rotation.These findings provide new insights into the energy dissipation mechanisms of cables and support the development of more resilient ground support systems for dynamically active conditions.
基金supported by the National Natural Science Foundation of China(Grant No.32160172)the Key Science-Technology Project of Inner Mongolia(2023KYPT0010)+1 种基金the Natural Science Foundation of Inner Mongolia Autonomous Region of China(Grant No.2025QN03006)the 2023 Inner Mongolia Public Institution High-level Talent Introduction Scientific Research Support Project.
文摘This study establishes and validates a method for the precise quantification of aquatic microbial loads using microbial diversity absolute quantitative sequencing.By adding synthetic spike-in DNA to water samples from the Dahei River prior to DNA extraction and 16S rRNA gene sequencing,it generates standard curves to convert sequencing data into absolute microbial copy numbers.The method,which is proved highly accurate(R^(2)>0.99),reveals a clear contrast between the river sites:the upstream community has not only a significantly higher total microbial load but also a completely different makeup of species compared to the downstream site.This approach effectively overcomes the limitations of relative abundance analysis,providing a powerful tool for environmental monitoring,and proposes key steps for future standardization to ensure data comparability and integration.
基金support provided by the National Natural Science Foundation of China(No.52274077)the Natural Science Foundation of Henan(No.242300421072)+2 种基金the Youth Elite Teachers Cultivation Program for Higher Education Institutions in Henan Province(No.2024GGJS036)the Funds for Distinguished Young Scholars of Henan Polytechnic University(No.J2023-3)the Young Core Teacher Funding Scheme of Henan Polytechnic University(No.2023XQG-09).
文摘This study examined non-uniform loading in goaf cantilever rock masses via testing,modeling,and mechanical analysis to solve instantaneous fracture and section buckling from mining abutment pressure.The study investigates the non-uniform load gradient effect on fracture characteristics,including load characteristics,fracture location,fracture distribution,and section roughness.A digital model for fracture interface buckling analysis was developed,elucidating the influence of non-uniform load gradients on Fracture Interface Curvature(FIC),Buckling Rate of Change(BRC),and Buckling Domain Field(BDF).The findings reveal that nonlinear tensile stress concentration and abrupt tensile-compressive-shear strain mutations under non-uniform loading are fundamental mechanisms driving fracture path buckling in cantilever rock mass structures.The buckling process of rock mass under non-uniform load can be divided into two stages:low load gradient and high gradient load.In the stage of low gradient load,the buckling behavior is mainly reflected in the compression-shear fracture of the edge.In the stage of high gradient load,a buckling band along the loading direction is gradually formed in the rock mass.These buckling principles establish a theoretical basis for accurately characterizing bearing fractures,fracture interface instability,and vibration sources within overlying cantilever rock masses in goaf.
文摘Theauthor proposes a dual layer source grid load storage collaborative planning model based on Benders decomposition to optimize the low-carbon and economic performance of the distribution network.The model plans the configuration of photovoltaic(3.8 MW),wind power(2.5 MW),energy storage(2.2 MWh),and SVC(1.2 Mvar)through interaction between upper and lower layers,and modifies lines 2–3,8–9,etc.to improve transmission capacity and voltage stability.The author uses normal distribution and Monte Carlo method to model load uncertainty,and combines Weibull distribution to describe wind speed characteristics.Compared to the traditional three-layer model(TLM),Benders decomposition-based two-layer model(BLBD)has a 58.1%reduction in convergence time(5.36 vs.12.78 h),a 51.1%reduction in iteration times(23 vs.47 times),a 8.07%reduction in total cost(12.436 vs.13.528 million yuan),and a 9.62%reduction in carbon emissions(12,456 vs.13,782 t).After optimization,the peak valley difference decreased from4.1 to 2.9MW,the renewable energy consumption rate reached 93.4%,and the energy storage efficiency was 87.6%.Themodel has been validated in the IEEE 33 node system,demonstrating its superiority in terms of economy,low-carbon,and reliability.
