In this paper,the influence of the limited-tension interface between lid and soil on the undrained bearing capacity of the wide-shallow bucket foundation is examined by finite element(FE)analysis.The interface between...In this paper,the influence of the limited-tension interface between lid and soil on the undrained bearing capacity of the wide-shallow bucket foundation is examined by finite element(FE)analysis.The interface between the lid and the soil is modeled using a simplified approach called the surface-based cohesive behavior,with the aim of simulating the limited-tension interface.Initially,the interaction between the lid and the soil is explored under the zero-and unlimited-tension conditions by small-scale experiments.Afterward,the effects of the embedment ratio,soil strength heterogeneity,and lid-soil interface on the bearing capacity are outlined,and the failure mechanisms are explained by FE analysis.A modified closed-form formula is given to compute the moment bearing capacity with the limited-tension interface between the lid and the soil for different embedment ratios and soil strength heterogeneities.The numerical results reveal that the existing approximating solutions,which assume fully bonded interaction,accurately exhibit the shape of the normalized failure envelopes in hm and vh load space for the limited-tension interface.However,the shape of the vm envelopes differs,requiring a novel solution to estimate the combined bearing capacity of the bucket foundation based on the embedment ratio and soil strength heterogeneity with a zero-tension interface between the lid and the soil.展开更多
Apparent critical current density(j_(Ac)^(a))of garnet all-solid-state lithium metal symmetric cells(ASSLSCs)is a fundamental parameter for designing all-solid-state lithium metal batteries.Nevertheless,how much the p...Apparent critical current density(j_(Ac)^(a))of garnet all-solid-state lithium metal symmetric cells(ASSLSCs)is a fundamental parameter for designing all-solid-state lithium metal batteries.Nevertheless,how much the possible maximum apparent current density that a given ASSLSC system can endure and how to reveal this potential still require study.Herein,a capacity perturbation strategy aiming to better measure the possible maximum j_(Ac)^(a)is proposed for the first time.With garnet-based plane-surface structure ASSLSCs as an exemplification,the j_(Ac)^(a)is quite small when the capacity is dramatically large.Under a perturbed capacity of 0.001 mA h cm^(-2),the j_(Ac)^(a)is determined to be as high as 2.35 mA cm^(-2)at room temperature.This investigation demonstrates that the capacity perturbation strategy is a feasible strategy for measuring the possible maximum j_(Ac)^(a)of Li/solid electrolyte interface,and hopefully provides good references to explore the critical current density of other types of electrochemical systems.展开更多
BACKGROUND Brain-computer interface(BCI)technology is rapidly advancing in psychiatry.Informed consent competency(ICC)assessment among psychiatric patients is a pivotal concern in clinical research.AIM To analyze the ...BACKGROUND Brain-computer interface(BCI)technology is rapidly advancing in psychiatry.Informed consent competency(ICC)assessment among psychiatric patients is a pivotal concern in clinical research.AIM To analyze the assessment of ICC and form a framework with multi-dimensional elements involved in ICC of BCI clinical research among psychiatric disorders.METHODS A systematic review of studies regarding ICC assessments of BCI clinical research in patients with six kinds of psychiatric disorders was conducted.A systematic literature search was performed using PubMed,ScienceDirect,and Web of Science.Peer-reviewed articles and full-text studies were included in the analysis.There were no date restrictions,and all studies published up to February 27,2025,were included.RESULTS A total of 103 studies were selected for this review.Fifty-eight studies included ICC factors,and forty-five were classified in ICC related ethical issues of BCI research in six kinds of psychiatric disorders.Executive function impairment is widely recognized as the most significant factor impacting ICC,and processing speed deficits are observed in schizophrenia,mood disorders,and Alzheimer’s disease.Memory dysfunction,particularly episodic and working memory,contributes to compromised ICC.Five core ethical issues in BCI research should be addressed:BCI specificity,vulnerability,autonomy,dynamic ICC,comprehensiveness,and uncertainty.CONCLUSION A Five-Dimensional evaluative framework,including clinical,ethical,sociocultural,legal,and procedural dimensions,is constructed and proposed for future ICC research in BCI clinical research involving psychiatric disorders.展开更多
It is quite common for fill slopes such as embankments and airport foundations to be constructed in mountainous areas.Steep fill–rock interfaces in such areas undergo tensile failure owing to differences in the stiff...It is quite common for fill slopes such as embankments and airport foundations to be constructed in mountainous areas.Steep fill–rock interfaces in such areas undergo tensile failure owing to differences in the stiffness values and tensile strengths of the soil and hard rock.In this study,a new anchor system,termed“radial cable,”is proposed to increase the pullout capacity of cables in the fill;this in turn helps control tensile deformation in the fill slope along the interface.In a radial cable,the steel ropes of a conventional cable are equally and symmetrically separated into three sub-cables(a central sub-cable and two branch sub-cables)with a radial distribution starting from the position of the interface.Moreover,each of the sub-cables is fixed in the fill using short U-shaped rigid rods along the cable length and a rigid baffle at its end to further increase pullout resistance.Experimental and numerical uplift tests were conducted to analyze the pullout capacity and anchoring behavior of the radial cables in soil to study the effect of branching.The reinforcement effect of the radial cables was also examined using a case study.展开更多
Transition metal sulfide(TMS)anodes exhibit the characteristics of phase stability and high capacity for lithium/sodium-ion batteries(LIBs/SIBs).However,the TMS anodes often suffer from poor electronic conductivity,lo...Transition metal sulfide(TMS)anodes exhibit the characteristics of phase stability and high capacity for lithium/sodium-ion batteries(LIBs/SIBs).However,the TMS anodes often suffer from poor electronic conductivity,low ionic diffusion and large volume expansion during Li/Na-ion intercalation significantly impairing the Li/Na-storage performance.Herein,a long chain heterostructure composed of the Co_(9)S_(8) and SnS are first reported,which can generate rich phase interfaces,and small crystal domains.The unique structure can facilitate the properties of reactivity,conductivity and ionic diffusion.In addition,the heterostructure surface is modified by the N-doped carbon(N-DC@(CoSn)S),successfully improving the structural stability.The synergistic effects of Co_(9)S_(8)/SnS heterostructure and coated carbon layer effectively increase the capacity and cycling stability.The N-DC@(CoSn)S anode delivers enhanced high specific capacities of 820.6 mAh·g^(−1) at 1.0 A·g^(–1) after 500 cycles for LIBs and 339.2 mAh·g^(–1)at 0.5 A·g^(–1) after 1000 cycles for SIBs,respectively.This work is expected to provide a material design idea for preparing LIBs/SIBs with high capacity and long cycling life.展开更多
Use of metallic Li anode raises serious concerns on the safety and operational performance of Li-S batteries due to uncontrolled hazard of Li dendrite formation, which is difficultly eliminated as long as the metallic...Use of metallic Li anode raises serious concerns on the safety and operational performance of Li-S batteries due to uncontrolled hazard of Li dendrite formation, which is difficultly eliminated as long as the metallic Li exists in the cells. Pairing lithium sulfide (Li2S) cathode with currently available metallic Lifree high-capacity anodes offers an alternative solution to this challenge. However, the performance of Li2S cathode is primarily restricted by high activation barrier upon initial charge, low active mass utilization and sluggish redox kinetics. Herein, a MXene-induced multifunctional collaborative interface is proposed to afford superb activity towards redox solid-liquid/liquid-liquid phase transformation, strong chemisorption, high conductivity and fast ionic/charge transport in high Li2S loading cathode. Applying collaborative interface effectively reduces initial voltage barrier of Li2S activation and regulates the kinetic behavior of redox polysulfide conversion. Therefore, stable operation of additive-free Li2S cathode with high areal capacities at high Li2S loading up to 9 mg cm^-2 can be achieved with less sacrifice of high capacity and rate capability in Li-S batteries. Rechargeable metallic Li-free batteries are successfully constructed by pairing this high-performance Li2S cathode with high-capacity metal oxide anodes, which delivers superior energy density to current Li-ion batteries.展开更多
Reinforced concrete (RC) constructions are the innovation of sustainable constructions replacing masonry constructions. Despite this, the use of concrete and steel to improve the performance of structural members in s...Reinforced concrete (RC) constructions are the innovation of sustainable constructions replacing masonry constructions. Despite this, the use of concrete and steel to improve the performance of structural members in service is a recurring problem due to the immediate or overtime appearance of cracks. The objective of this work was therefore to assess the damage phenomena of the steel-concrete interface in order to assess the performance of an RC structure. Samples of approximately 30 cm of reinforcement attacked by rust were taken from broken reinforced concrete columns and beams in order to determine the impact of corrosion on high adhesion steel (HA) and therefore on its ability to resist. The experimental results have shown that the corrosion degradation rates of reinforcing bars of different diameters increase as the diameter of the reinforcing bars decreases: 5% for HA12;23.75% for HA8 and 50% for HA6. Using the approach proposed by Mangat and Elgalf on the bearing capacity as a function of the progress of the corrosion phenomenon, these rates made it possible to assess the new fracture limits of corroded HA steels. For HA6 respectively HA8 and HA12, their initial limit resistances will decrease by 4/4, 3/4 and 1/4. Based on the results of this study and in order to guarantee their durability, an RC structure can be dimensioned by taking into account the effects of reinforcement corrosion.展开更多
The internal friction and the damping behaviors of in situ TiC p/2024 composites have been investigated in comparison with those of 2024 matrix alloy. The results showed that the damping properties of the TiC p/2024 c...The internal friction and the damping behaviors of in situ TiC p/2024 composites have been investigated in comparison with those of 2024 matrix alloy. The results showed that the damping properties of the TiC p/2024 composites are superior to those of the matrix alloy and increase with increasing temperature and volume fraction of TiC. It was found that the damping properties were sensitive to frequency and temperature, and the dislocation damping and interface damping were the main factors which influence the damping behaviors of the composites. When the temperature was lower than 200 ℃, the dislocation damping was the main factor; when the temperature was higher than 200 ℃, the interface and boundary damping was the main factor.展开更多
The bored cast-in-place pile is the common foundation of bridge in recent years, but during the boring, the slurry effect the quality of pile a lot. Interface grouting is the method of injecting the grout to the base ...The bored cast-in-place pile is the common foundation of bridge in recent years, but during the boring, the slurry effect the quality of pile a lot. Interface grouting is the method of injecting the grout to the base of pile through the embedded pipes after its concrete finished, to increase carrying capacity and reduce the settlement. This article will introduce the method to engineers in constuctions.展开更多
The techniques of pressurized mining and hydraulic fracturing are often used to improve gas well productivity at the later development stage of low-permeability carbonate gas reservoirs,but reservoirs are watered out ...The techniques of pressurized mining and hydraulic fracturing are often used to improve gas well productivity at the later development stage of low-permeability carbonate gas reservoirs,but reservoirs are watered out and a great number of micro fractures are produced.Therefore,one of the key factors for underground gas storages(UGS)rebuilt from low-permeability fractured gas reservoirs with CO_(2) as the cushion gas is how to expand storage capacity effectively by injecting CO_(2) to displace water and to develop control strategies for the stable migration of gas-water interface.In this paper,a mathematical model was established to simulate the gas-water flow when CO_(2) was injected into dual porosity reservoirs to displace water.Then,the gas-water interface migration rules while CO_(2) was injected in the peripheral gas wells for water displacement were analyzed with one domestic UGS rebuilt from fractured gas reservoirs as the research object.And finally,discussion was made on how CO_(2) dissolution,bottom hole flowing pressure(BHFP),CO_(2) injection rate and micro fracture parameters affect the stability of gas-water interface in the process of storage capacity expansion.It is shown that the speed of capacity expansion reaches the maximum value at the fifth cycle and then decreases gradually when UGS capacity is expanded in the pattern of more injection and less withdrawal.Gasewater interface during UGS capacity expansion is made stable due to that the solubility of CO_(2) in water varies with the reservoir pressure.When the UGS capacity is expanded at constant BHFP and the flow rate,the expansion speed can be increased effectively by increasing the BHFP and the injection flow rate of gas wells in the central areas appropriately.In the reservoir areas with high permeability and fracture-matrix permeability ratio,the injection flow rate should be reduced properly to prevent gas-water interface fingering caused by a high-speed flow.Furthermore,it is necessary to monitor strictly the migration of gas-water interface by using observation wells to prevent gas escape through the edge water or water breakthrough at high-permeability zones.These research results provide a technical and theoretical support for water displacement and capacity expansion of UGS rebuilt from low-permeability fractured gas reservoirs with CO_(2) as the cushion gas.展开更多
In this paper,we propose and analyze two second-order accurate finite difference schemes for the one-dimensional heat equation with concentrated capacity on a computa-tional domain=[a,b].We first transform the target ...In this paper,we propose and analyze two second-order accurate finite difference schemes for the one-dimensional heat equation with concentrated capacity on a computa-tional domain=[a,b].We first transform the target equation into the standard heat equation on the domain excluding the singular point equipped with an inner interface matching(IIM)condition on the singular point x=ξ∈(a,b),then adopt Taylor’s ex-pansion to approximate the IIM condition at the singular point and apply second-order finite difference method to approximate the standard heat equation at the nonsingular points.This discrete procedure allows us to choose different grid sizes to partition the two sub-domains[a,ξ]and[ξ,b],which ensures that x=ξ is a grid point,and hence the pro-posed schemes can be generalized to the heat equation with more than one concentrated capacities.We prove that the two proposed schemes are uniquely solvable.And through in-depth analysis of the local truncation errors,we rigorously prove that the two schemes are second-order accurate both in temporal and spatial directions in the maximum norm without any constraint on the grid ratio.Numerical experiments are carried out to verify our theoretical conclusions.展开更多
The problem related to bearing capacity of footing either on pure soil or on pure rock mass has been investigated over the years.Currently,no study deals with the bearing capacity of strip footing on a cohesive soil l...The problem related to bearing capacity of footing either on pure soil or on pure rock mass has been investigated over the years.Currently,no study deals with the bearing capacity of strip footing on a cohesive soil layer overlying rock mass.Therefore,by implementing the lower bound finite element limit analysis in conjunction with the second-order cone programming and the power cone programming,the ultimate bearing capacity of a strip footing located on a cohesive soil overlying rock mass is determined in this study.By considering the different values of interface adhesion factor(α_(cr))between the cohesive soil and rock mass,the ultimate bearing capacity of strip footing is expressed in terms of influence factor(I _(f))for different values of cohesive soil layer cover ratio(T_(cs)/B).The failure of cohesive soil is modeled by using Mohr−Coulomb yield criterion,whereas Generalized Hoek−Brown yield criterion is utilized to model the rock mass at failure.The variations of I_(f) with different magnitudes of α_(cr) are studied by considering the influence of the rock mass strength parameters of beneath rock mass layer.To examine stress distribution at different depths,failure patterns are also plotted.展开更多
随着锂电池在动力和储能等领域得到广泛应用,锂电池的寿命问题成为限制其发展的重要桎梏。电池处于存储状态时也会发生性能衰退而影响寿命,因此,研究电池自放电过程中的阻抗变化以表征内部电化学反应与结构相变过程,对于电池寿命模型完...随着锂电池在动力和储能等领域得到广泛应用,锂电池的寿命问题成为限制其发展的重要桎梏。电池处于存储状态时也会发生性能衰退而影响寿命,因此,研究电池自放电过程中的阻抗变化以表征内部电化学反应与结构相变过程,对于电池寿命模型完善有十分重要的意义。基于此,该文通过容量增量曲线对电池容量衰减的内因展开分析;在不同影响因素下自放电过程中电池阻抗谱变化规律的基础上,利用弛豫时间分布法进行理论原理分析;最后,在电池自放电老化过程的原理推导的基础上总结电池容量衰减量随时间的变化规律,并结合实验数据建立不同影响因素下电池容量衰减模型。结果表明,在存储过程中,电池的固体电解质界面(solid electrolyte interface,SEI)膜内阻增大,且存储温度越高、初始充电状态(state of charge,SOC)越大,相应的阻抗增加幅度越大。自放电过程电池老化主要原因是可循环活性锂离子的消耗和SEI膜的生长。同时该文推导出电池容量损失与时间近似呈0.5次方关系,并利用实验数据拟合得到电池在不同初始SOC和不同存储温度影响下的容量变化模型,为锂电池寿命模型预测提供更进一步的参考。展开更多
基金support funded by the National Natural Science Foundation of China Joint Fund Projects(No.U21A20164)。
文摘In this paper,the influence of the limited-tension interface between lid and soil on the undrained bearing capacity of the wide-shallow bucket foundation is examined by finite element(FE)analysis.The interface between the lid and the soil is modeled using a simplified approach called the surface-based cohesive behavior,with the aim of simulating the limited-tension interface.Initially,the interaction between the lid and the soil is explored under the zero-and unlimited-tension conditions by small-scale experiments.Afterward,the effects of the embedment ratio,soil strength heterogeneity,and lid-soil interface on the bearing capacity are outlined,and the failure mechanisms are explained by FE analysis.A modified closed-form formula is given to compute the moment bearing capacity with the limited-tension interface between the lid and the soil for different embedment ratios and soil strength heterogeneities.The numerical results reveal that the existing approximating solutions,which assume fully bonded interaction,accurately exhibit the shape of the normalized failure envelopes in hm and vh load space for the limited-tension interface.However,the shape of the vm envelopes differs,requiring a novel solution to estimate the combined bearing capacity of the bucket foundation based on the embedment ratio and soil strength heterogeneity with a zero-tension interface between the lid and the soil.
基金the financial support from the Natural Science Foundation for Distinguished Young Scholars of Hunan Province(2020JJ2047)the science and technology innovation Program of Hunan Province(2022RC3048)+2 种基金the Program of Huxiang Young Talents(2019RS2002)the Innovation-Driven Project of Central South University(2020CX027)the Fundamental Research Funds for the Central Universities of Central South University(2021zzts0125)。
文摘Apparent critical current density(j_(Ac)^(a))of garnet all-solid-state lithium metal symmetric cells(ASSLSCs)is a fundamental parameter for designing all-solid-state lithium metal batteries.Nevertheless,how much the possible maximum apparent current density that a given ASSLSC system can endure and how to reveal this potential still require study.Herein,a capacity perturbation strategy aiming to better measure the possible maximum j_(Ac)^(a)is proposed for the first time.With garnet-based plane-surface structure ASSLSCs as an exemplification,the j_(Ac)^(a)is quite small when the capacity is dramatically large.Under a perturbed capacity of 0.001 mA h cm^(-2),the j_(Ac)^(a)is determined to be as high as 2.35 mA cm^(-2)at room temperature.This investigation demonstrates that the capacity perturbation strategy is a feasible strategy for measuring the possible maximum j_(Ac)^(a)of Li/solid electrolyte interface,and hopefully provides good references to explore the critical current density of other types of electrochemical systems.
基金Supported by the Ministry of Science and Technology of the People's Republic of China(2021ZD0201900)Project 5,No.2021ZD0201905Capital’s Funds for Health Improvement and Research,No.CFH 2022-2-4115.
文摘BACKGROUND Brain-computer interface(BCI)technology is rapidly advancing in psychiatry.Informed consent competency(ICC)assessment among psychiatric patients is a pivotal concern in clinical research.AIM To analyze the assessment of ICC and form a framework with multi-dimensional elements involved in ICC of BCI clinical research among psychiatric disorders.METHODS A systematic review of studies regarding ICC assessments of BCI clinical research in patients with six kinds of psychiatric disorders was conducted.A systematic literature search was performed using PubMed,ScienceDirect,and Web of Science.Peer-reviewed articles and full-text studies were included in the analysis.There were no date restrictions,and all studies published up to February 27,2025,were included.RESULTS A total of 103 studies were selected for this review.Fifty-eight studies included ICC factors,and forty-five were classified in ICC related ethical issues of BCI research in six kinds of psychiatric disorders.Executive function impairment is widely recognized as the most significant factor impacting ICC,and processing speed deficits are observed in schizophrenia,mood disorders,and Alzheimer’s disease.Memory dysfunction,particularly episodic and working memory,contributes to compromised ICC.Five core ethical issues in BCI research should be addressed:BCI specificity,vulnerability,autonomy,dynamic ICC,comprehensiveness,and uncertainty.CONCLUSION A Five-Dimensional evaluative framework,including clinical,ethical,sociocultural,legal,and procedural dimensions,is constructed and proposed for future ICC research in BCI clinical research involving psychiatric disorders.
基金financially supported by the National Natural Science Foundation of China (Nos. 41672300 and 41807279)
文摘It is quite common for fill slopes such as embankments and airport foundations to be constructed in mountainous areas.Steep fill–rock interfaces in such areas undergo tensile failure owing to differences in the stiffness values and tensile strengths of the soil and hard rock.In this study,a new anchor system,termed“radial cable,”is proposed to increase the pullout capacity of cables in the fill;this in turn helps control tensile deformation in the fill slope along the interface.In a radial cable,the steel ropes of a conventional cable are equally and symmetrically separated into three sub-cables(a central sub-cable and two branch sub-cables)with a radial distribution starting from the position of the interface.Moreover,each of the sub-cables is fixed in the fill using short U-shaped rigid rods along the cable length and a rigid baffle at its end to further increase pullout resistance.Experimental and numerical uplift tests were conducted to analyze the pullout capacity and anchoring behavior of the radial cables in soil to study the effect of branching.The reinforcement effect of the radial cables was also examined using a case study.
基金This study was financially supported by the National Natural Science Foundation of China(Nos.52271211 and 52171207)the HORIZON-Marie Skłodowska-Curie Actions-2021-PF(No.101065098)+2 种基金Hunan Provincial Natural Science Foundation of China(No.2022JJ40162)the Scientific Research Fund of Hunan Provincial Education Department(No.21B0406)the science and technology innovation Program of Hunan Province(No.2022RC3037).
文摘Transition metal sulfide(TMS)anodes exhibit the characteristics of phase stability and high capacity for lithium/sodium-ion batteries(LIBs/SIBs).However,the TMS anodes often suffer from poor electronic conductivity,low ionic diffusion and large volume expansion during Li/Na-ion intercalation significantly impairing the Li/Na-storage performance.Herein,a long chain heterostructure composed of the Co_(9)S_(8) and SnS are first reported,which can generate rich phase interfaces,and small crystal domains.The unique structure can facilitate the properties of reactivity,conductivity and ionic diffusion.In addition,the heterostructure surface is modified by the N-doped carbon(N-DC@(CoSn)S),successfully improving the structural stability.The synergistic effects of Co_(9)S_(8)/SnS heterostructure and coated carbon layer effectively increase the capacity and cycling stability.The N-DC@(CoSn)S anode delivers enhanced high specific capacities of 820.6 mAh·g^(−1) at 1.0 A·g^(–1) after 500 cycles for LIBs and 339.2 mAh·g^(–1)at 0.5 A·g^(–1) after 1000 cycles for SIBs,respectively.This work is expected to provide a material design idea for preparing LIBs/SIBs with high capacity and long cycling life.
基金supported by the National Natural Science Foundation of China (NSFC, No. 51522203, 51772040)Fok Ying Tung Education Foundation (No. 151047)+2 种基金the Recruitment Program of Global Youth ExpertsXinghai Scholarship of Dalian University of Technologythe Fundamental Research Funds for the Central Universities (No. DUT18LAB19)
文摘Use of metallic Li anode raises serious concerns on the safety and operational performance of Li-S batteries due to uncontrolled hazard of Li dendrite formation, which is difficultly eliminated as long as the metallic Li exists in the cells. Pairing lithium sulfide (Li2S) cathode with currently available metallic Lifree high-capacity anodes offers an alternative solution to this challenge. However, the performance of Li2S cathode is primarily restricted by high activation barrier upon initial charge, low active mass utilization and sluggish redox kinetics. Herein, a MXene-induced multifunctional collaborative interface is proposed to afford superb activity towards redox solid-liquid/liquid-liquid phase transformation, strong chemisorption, high conductivity and fast ionic/charge transport in high Li2S loading cathode. Applying collaborative interface effectively reduces initial voltage barrier of Li2S activation and regulates the kinetic behavior of redox polysulfide conversion. Therefore, stable operation of additive-free Li2S cathode with high areal capacities at high Li2S loading up to 9 mg cm^-2 can be achieved with less sacrifice of high capacity and rate capability in Li-S batteries. Rechargeable metallic Li-free batteries are successfully constructed by pairing this high-performance Li2S cathode with high-capacity metal oxide anodes, which delivers superior energy density to current Li-ion batteries.
文摘Reinforced concrete (RC) constructions are the innovation of sustainable constructions replacing masonry constructions. Despite this, the use of concrete and steel to improve the performance of structural members in service is a recurring problem due to the immediate or overtime appearance of cracks. The objective of this work was therefore to assess the damage phenomena of the steel-concrete interface in order to assess the performance of an RC structure. Samples of approximately 30 cm of reinforcement attacked by rust were taken from broken reinforced concrete columns and beams in order to determine the impact of corrosion on high adhesion steel (HA) and therefore on its ability to resist. The experimental results have shown that the corrosion degradation rates of reinforcing bars of different diameters increase as the diameter of the reinforcing bars decreases: 5% for HA12;23.75% for HA8 and 50% for HA6. Using the approach proposed by Mangat and Elgalf on the bearing capacity as a function of the progress of the corrosion phenomenon, these rates made it possible to assess the new fracture limits of corroded HA steels. For HA6 respectively HA8 and HA12, their initial limit resistances will decrease by 4/4, 3/4 and 1/4. Based on the results of this study and in order to guarantee their durability, an RC structure can be dimensioned by taking into account the effects of reinforcement corrosion.
文摘The internal friction and the damping behaviors of in situ TiC p/2024 composites have been investigated in comparison with those of 2024 matrix alloy. The results showed that the damping properties of the TiC p/2024 composites are superior to those of the matrix alloy and increase with increasing temperature and volume fraction of TiC. It was found that the damping properties were sensitive to frequency and temperature, and the dislocation damping and interface damping were the main factors which influence the damping behaviors of the composites. When the temperature was lower than 200 ℃, the dislocation damping was the main factor; when the temperature was higher than 200 ℃, the interface and boundary damping was the main factor.
文摘The bored cast-in-place pile is the common foundation of bridge in recent years, but during the boring, the slurry effect the quality of pile a lot. Interface grouting is the method of injecting the grout to the base of pile through the embedded pipes after its concrete finished, to increase carrying capacity and reduce the settlement. This article will introduce the method to engineers in constuctions.
文摘The techniques of pressurized mining and hydraulic fracturing are often used to improve gas well productivity at the later development stage of low-permeability carbonate gas reservoirs,but reservoirs are watered out and a great number of micro fractures are produced.Therefore,one of the key factors for underground gas storages(UGS)rebuilt from low-permeability fractured gas reservoirs with CO_(2) as the cushion gas is how to expand storage capacity effectively by injecting CO_(2) to displace water and to develop control strategies for the stable migration of gas-water interface.In this paper,a mathematical model was established to simulate the gas-water flow when CO_(2) was injected into dual porosity reservoirs to displace water.Then,the gas-water interface migration rules while CO_(2) was injected in the peripheral gas wells for water displacement were analyzed with one domestic UGS rebuilt from fractured gas reservoirs as the research object.And finally,discussion was made on how CO_(2) dissolution,bottom hole flowing pressure(BHFP),CO_(2) injection rate and micro fracture parameters affect the stability of gas-water interface in the process of storage capacity expansion.It is shown that the speed of capacity expansion reaches the maximum value at the fifth cycle and then decreases gradually when UGS capacity is expanded in the pattern of more injection and less withdrawal.Gasewater interface during UGS capacity expansion is made stable due to that the solubility of CO_(2) in water varies with the reservoir pressure.When the UGS capacity is expanded at constant BHFP and the flow rate,the expansion speed can be increased effectively by increasing the BHFP and the injection flow rate of gas wells in the central areas appropriately.In the reservoir areas with high permeability and fracture-matrix permeability ratio,the injection flow rate should be reduced properly to prevent gas-water interface fingering caused by a high-speed flow.Furthermore,it is necessary to monitor strictly the migration of gas-water interface by using observation wells to prevent gas escape through the edge water or water breakthrough at high-permeability zones.These research results provide a technical and theoretical support for water displacement and capacity expansion of UGS rebuilt from low-permeability fractured gas reservoirs with CO_(2) as the cushion gas.
基金supported by the National Natural Science Foundation of China(Grant No.11571181)by the Natural Science Foundation of Jiangsu Province(Grant No.BK20171454).
文摘In this paper,we propose and analyze two second-order accurate finite difference schemes for the one-dimensional heat equation with concentrated capacity on a computa-tional domain=[a,b].We first transform the target equation into the standard heat equation on the domain excluding the singular point equipped with an inner interface matching(IIM)condition on the singular point x=ξ∈(a,b),then adopt Taylor’s ex-pansion to approximate the IIM condition at the singular point and apply second-order finite difference method to approximate the standard heat equation at the nonsingular points.This discrete procedure allows us to choose different grid sizes to partition the two sub-domains[a,ξ]and[ξ,b],which ensures that x=ξ is a grid point,and hence the pro-posed schemes can be generalized to the heat equation with more than one concentrated capacities.We prove that the two proposed schemes are uniquely solvable.And through in-depth analysis of the local truncation errors,we rigorously prove that the two schemes are second-order accurate both in temporal and spatial directions in the maximum norm without any constraint on the grid ratio.Numerical experiments are carried out to verify our theoretical conclusions.
文摘The problem related to bearing capacity of footing either on pure soil or on pure rock mass has been investigated over the years.Currently,no study deals with the bearing capacity of strip footing on a cohesive soil layer overlying rock mass.Therefore,by implementing the lower bound finite element limit analysis in conjunction with the second-order cone programming and the power cone programming,the ultimate bearing capacity of a strip footing located on a cohesive soil overlying rock mass is determined in this study.By considering the different values of interface adhesion factor(α_(cr))between the cohesive soil and rock mass,the ultimate bearing capacity of strip footing is expressed in terms of influence factor(I _(f))for different values of cohesive soil layer cover ratio(T_(cs)/B).The failure of cohesive soil is modeled by using Mohr−Coulomb yield criterion,whereas Generalized Hoek−Brown yield criterion is utilized to model the rock mass at failure.The variations of I_(f) with different magnitudes of α_(cr) are studied by considering the influence of the rock mass strength parameters of beneath rock mass layer.To examine stress distribution at different depths,failure patterns are also plotted.
文摘随着锂电池在动力和储能等领域得到广泛应用,锂电池的寿命问题成为限制其发展的重要桎梏。电池处于存储状态时也会发生性能衰退而影响寿命,因此,研究电池自放电过程中的阻抗变化以表征内部电化学反应与结构相变过程,对于电池寿命模型完善有十分重要的意义。基于此,该文通过容量增量曲线对电池容量衰减的内因展开分析;在不同影响因素下自放电过程中电池阻抗谱变化规律的基础上,利用弛豫时间分布法进行理论原理分析;最后,在电池自放电老化过程的原理推导的基础上总结电池容量衰减量随时间的变化规律,并结合实验数据建立不同影响因素下电池容量衰减模型。结果表明,在存储过程中,电池的固体电解质界面(solid electrolyte interface,SEI)膜内阻增大,且存储温度越高、初始充电状态(state of charge,SOC)越大,相应的阻抗增加幅度越大。自放电过程电池老化主要原因是可循环活性锂离子的消耗和SEI膜的生长。同时该文推导出电池容量损失与时间近似呈0.5次方关系,并利用实验数据拟合得到电池在不同初始SOC和不同存储温度影响下的容量变化模型,为锂电池寿命模型预测提供更进一步的参考。
