The joint of clay core-wall and concrete cut-off wall is one of the weakest parts in high earth and rockftll dams.A kind of highly plastic clay is always fixed on the joint to fit the large shear deformation between c...The joint of clay core-wall and concrete cut-off wall is one of the weakest parts in high earth and rockftll dams.A kind of highly plastic clay is always fixed on the joint to fit the large shear deformation between clay core-wall and concrete cut-offwall,so the hydro-mechanical coupling mechanisms on the joint under high stress,high hydraulic gradient,and large shear deformation are of great importance for the evaluation of dam safety.The hydro-mechanical coupling characteristics of the joint of the highly plastic clay and the concrete cut-off wall in a high earth and rockfill dam in China were studied by using a newly designed soil-structure contact erosion apparatus.The experimental results indicate that：1） Shear failure on the joint is due to the hydro-mechanical coupling effect of stress and seepage failure.The seepage failure will induce the final shear failure when the ratio of deviatoric stress to confining pressure is within 1.0-1.2; 2） A negative exponential permeability empirical model for the joint denoted by a newly defined principal stress function,which considers the coupling effect of confining pressure and axial pressure on the permeability,is established based on hydro-mechanical coupling experiments.3） The variation of the settlement before and after seepage failure is very different.The settlement before seepage failure changes very slowly,while it increases significantly after the seepage failure.4） The stress-strain relationship is of a strain softening type.5） Flow along the joint still follows Darcian flow rule.The results will provide an important theoretical basis for the further evaluation on the safety of the high earth and rockfill dam.展开更多
The transient finite element technique is applied, and a transient heat conduction model of wet brake friction disk is established. For obtaining the accurate heat flow density mathematic model and avoiding possibly i...The transient finite element technique is applied, and a transient heat conduction model of wet brake friction disk is established. For obtaining the accurate heat flow density mathematic model and avoiding possibly instable thermoelastic stress produced by the non uniform contact pressure of friction pair, a test method is applied to collect accurate contact pressure between the dual sheet steel and friction disk in the combining process. And then the heat-flow density and transient ther mo mechanical coupling simulation are analyzed. At the same time all possible boundary conditions are considered, such as the heat generation, heat conduction problem, relation between friction and contact, variation in load and heat change problem etc. The simulation results show that the me chanical model of thermo mechanical coupling can express well the dynamic characteristics of fric tion disk, and gives perfect reference for more study on thermoelastic distortion of brake friction pairs.展开更多
Based on fluid mechanics, thermodynamics and damage mechanics, thermal-hydro-mechanical （THM） coupling damage model of brittle rock is established by analyzing THM coupling mechanism, where THM coupling damage varia...Based on fluid mechanics, thermodynamics and damage mechanics, thermal-hydro-mechanical （THM） coupling damage model of brittle rock is established by analyzing THM coupling mechanism, where THM coupling damage variable DTHM is dominated by TH coupling damage variable DTH, TM coupling damage variable DTM and HM coupling damage variable DHM, and DTH is firstly expressed in term of dimensionless total thermal conductivity of the water Nu. Permeability test, uni-axial compression test and THM coupling test are conducted to measure the permeability, elastic modulus and THM coupling stress-strain curves of brittle rock. The tested values of THM coupling elastic modulus E＇HM are in good agreement with the predicted values of THM coupling elastic modulus ETHM, which can verify the newly established THM coupling damage model.展开更多
The development of advanced magnetoelectric(ME)composites necessitates high-performance materials that arecapable of achieving high levels of ME coupling,minimal magnetic loss,and absence or limited reliance on extern...The development of advanced magnetoelectric(ME)composites necessitates high-performance materials that arecapable of achieving high levels of ME coupling,minimal magnetic loss,and absence or limited reliance on externalexcitation sources.In this paper,a(2-2)connectivity ME laminate integrates multiple layers of FeSiB alloy(Metglas)andPb(Mg,Nb)O_(3)-PbTiO_(3)(PMN-PT)single crystal,achieving a remarkable ME coupling coefficient of 2033.4 V/Oe·cm(sevenfold rise)by laser thermal annealing treatment.Here,the laser-induced nanostructures on Metglas,with anoxidized insulation layer and soft and hard magnetic dipole layer improve the Magneto-electric-mechanical couplingwith a mechanical quality factor(Q_(m))exceeding 350.More importantly,the interaction between amorphous andnanocrystalline dipoles triggers an Exchange Bias(EB)effect,leading to a self-biasing performance of 67.45 V/Oe·cm.Furthermore,the composite exhibits an excellent passive DC magnetic detection limit of 22 nT,and an improved weakAC magnetic detection limit down to 383 fT.These explorations offer the potential to enhance passive currentmeasurement,and underwater communication,extend weak magnetic positioning and brain magnetic detection.展开更多
With policy support for carbon capture,utilization,and storage(CCUS),an integrated approach that combines energy storage fracturing,CO_(2)-enhanced oil recovery(EOR),and storage emerges as a promising direction for th...With policy support for carbon capture,utilization,and storage(CCUS),an integrated approach that combines energy storage fracturing,CO_(2)-enhanced oil recovery(EOR),and storage emerges as a promising direction for the shale oil industry.The process of energy storage fracturing induces significant changes in the pressure and saturation of the medium.However,conventional simulations often overlook the effects of fracturing and shut-in operations on the seepage field and production performance.Furthermore,fractured shale reservoirs exhibit complex non-Darcy flow characteristics due to intricate pore structures and multi-scale porous media.A comprehensive understanding of flow mechanisms is essential for effective reservoir development and CO_(2) storage.This study establishes a multi-component simulation model that encompasses the life-cycle of fracturing,shut-in,production,and CO_(2) huff-n-puff processes,thereby ensuring the continuity of the seepage field.The model accounts for the effect of nano-confinement on phase behavior by modifying the equation of state.Furthermore,the flux term is adjusted to incorporate Maxwell–Stefan diffusion,pre-/post-Darcy flow,and stress sensitivity.The embedded discrete fracture model(EDFM)is employed to simulate multiphase flow within multi-scale media,and the results from the validation model align satisfactorily with those derived from ECLIPSE.Mechanism analysis indicates that the interaction of multiple mechanisms significantly influences both production and storage performance.Under the multi-mechanism coupling,the cumulative oil production increased by 12.01%,while the utilization and storage factors increased by 62.93%and 8.93%,respectively.The role of molecular diffusion in shale oil reservoirs may be overstated,contributing only a 0.26% enhancement in oil production.Simulation results show that the energy storage fracturing strategy can increase oil production and net present value by 12.47%and 15.07%,respectively.Sensitivity analysis indicates that the CO_(2) injection rate is the main factor affecting the recovery factor,followed by CO_(2) injection time and the number of cycles,with fracturing fluid volume having the least impact.This study develops a multi-process,multi-mechanism simulation framework for multi-scale shale oil reservoirs.This framework provides a robust evaluation system for CCUS-EOR,facilitating informed decision-making in fracturing stimulation,development planning,and parameter optimization.展开更多
Multimodal ultrasonic vibration(UV)assisted micro-forming has been widely investigated for its advantages of further reducing forming loads and improving forming quality.However,the influence mechanism of different UV...Multimodal ultrasonic vibration(UV)assisted micro-forming has been widely investigated for its advantages of further reducing forming loads and improving forming quality.However,the influence mechanism of different UV modes on microstructure evolution and mechanical properties was still unclear.Mul-timodal UV assisted micro-compression tests on T2 copper with different grains and sample sizes were conducted in this study.The microstructure evolution for different UV modes was observed by EBSD.The results showed that the true stress reduction caused by UV was increased sequentially with tool ultrasonic vibration(TV),mold ultrasonic vibration(MV)and compound ultrasonic vibration(CV).The region of grain deformation was shifted along the direction of UV,and the MV promoted the uniform distribution of deformation stress.The grain refinement,fiber streamline density,grain deformation and rotation degree were further enhanced under CV,due to the synergistic effect of TV and MV.Additionally,a coupled theoretical model considering both acoustic softening effect and size effect was proposed for describing the mechanical properties.And a physical model of dislocation motion in different UV modes was developed for describing the microstructure evolution.The maximum error between the theoretical and experimental results was only 2.39%.This study provides a theoretical basis for the optimization of UV assisted micro-forming process.展开更多
De-icing technology has become an increasingly important subject in numerous applications in recent years.However,the direct numerical modeling and simulation the physical process of thermomechanical deicing is limite...De-icing technology has become an increasingly important subject in numerous applications in recent years.However,the direct numerical modeling and simulation the physical process of thermomechanical deicing is limited.This work is focusing on developing a numerical model and tool to direct simulate the de-icing process in the framework of the coupled thermo-mechanical peridynamics theory.Here,we adopted the fully coupled thermo-mechanical bond-based peridynamics(TM-BB-PD)method for modeling and simulation of de-icing.Within the framework of TM-BB-PD,the ice constitutive model is established by considering the influence of the temperature difference between two material points,and a modified failure criteria is proposed,which takes into account temperature effect to predict the damage of quasi-brittle ice material.Moreover,thermal boundary condition is used to simulate the thermal load in the de-icing process.By comparing with the experimental results and the previous reported finite element modeling,our numerical model shows good agreement with the previous predictions.Based on the numerical results,we find that the developed method can not only predict crack initiation and propagation in the ice,but also predict the temperature distribution and heat conduction during the de-icing process.Furthermore,the influence of the temperature for the ice crack growth pattern is discussed accordingly.In conclusion,the coupled thermal-mechanical peridynamics formulation with modified failure criterion is capable of providing a modeling tool for engineering applications of de-icing technology.展开更多
3-D rigid-viscoplastic FEM of compressible materials was applied to analyze the deformation behavior during twist compression forming of axisymmetrical body at high temperatures. When calculating the temperature fiel...3-D rigid-viscoplastic FEM of compressible materials was applied to analyze the deformation behavior during twist compression forming of axisymmetrical body at high temperatures. When calculating the temperature fields, considering the thermo mechanical coupling effect between temperature and deformation, 2-D FEM and CNG methods were adopted, and the up winding technique was used to avoid the influences of numerical instability on calculated results.展开更多
The novel process of hydrogen-based shaft furnaces(HSFs)has attracted considerable attention because of their significant reduction of CO_(2)emissions.In this study,the interaction of H_(2)and CO with Fe_(tet1)-and Fe...The novel process of hydrogen-based shaft furnaces(HSFs)has attracted considerable attention because of their significant reduction of CO_(2)emissions.In this study,the interaction of H_(2)and CO with Fe_(tet1)-and Fe_(oct2)-terminated Fe_(3)O_(4)(111)surfaces under HSF conditions,including their adsorption and reduction behaviors,was investigated using the density functional theory method.The results indicated that the H_(2)molecule adsorbed onto the Fe_(tet1)-terminated surface with an adsorption energy(AE)of-1.36 eV,whereas the CO molecule preferentially adsorbed on the Fe_(oct2)-terminated surface with an AE of-1.56 eV.Both H_(2)and CO can readily undergo reduction on the Fe_(tet1)-terminated surface(corresponding to energy barriers of 0.83 eV and 2.23 eV,respectively),but kinetically the reaction of H2is more favorable than that of CO.With regard to the thermodynamics at 400-1400 K,the H_(2)was easy to be adsorbed,while the CO would like to react on the Fe_(tet1)-terminated surface.These thermodynamically tendencies were reversed on the Fe_(oct2)-terminated surface.The thermodynamic disadvantage of the reaction of H_(2)on the Fe_(tet1)-terminated surface was offset by an increase in the temperature.Furthermore,the adsorption of H2 and CO on the Fe_(tet1)-terminated surface was competitive,whereas the adsorption of them on the Fe_(oct2)-terminated surface was synergistic.Therefore,iron ores with a higher proportion of Fe_(tet1)-terminated surface can be applied for the HSF process.In conjunction with the increases in the reduction temperature and the ratio of H_(2)in the reducing gas would promote efficient HSF smelting.These observations provide effective guidance for optimizing the practical operation parameters and advancing the development of the HSF process.展开更多
Land use transition refers to the changes in land use morphology （both dominant morphology and recessive morphology） of a certain region over a certain period of time driven by socio-economic change and innovation, ...Land use transition refers to the changes in land use morphology （both dominant morphology and recessive morphology） of a certain region over a certain period of time driven by socio-economic change and innovation, and it usually corresponds to the transition of socio-economic development phase. In China, farmland and rural housing land are the two major sources of land use transition. This paper analyzes the spatio-temporal coupling characteristics of farmland and rural housing land transition in China, using high-resolution Landsat TM （Thematic Mapper） data in 2000 and 2008, and the data from the Ministry of Land and Resources of China. The outcomes indicated that： （1） during 2000-2008, the correlation coefficient of farmland vs. rural housing land change is -0.921, and it shows that the change pattern of farmland and rural housing land is uncoordinated; （2） the result of Spearman rank correlation analysis shows that rural housing land change has played a major role in the mutual transformation of farmland and rural housing land; and （3） it shows a high-degree spatial coupling between farmland and rural housing land change in southeast China during 2000-2008. In general, farmland and rural housing land transition in China is driven by socio-economic, bio-physical and managerial three-dimensional driving factors through the interactions among rural population, farmland and rural housing land. However, the spatio-temporal coupling phenomenon and mechanism of farmland and rural housing land transition in China are largely due to the ＂dual-track＂ structure of rural-urban development.展开更多
A debris flow forecast model based on a water-soil coupling mechanism that takes the debrisflow watershed as a basic forecast unit was established here for the prediction of disasters at the watershed scale.This was a...A debris flow forecast model based on a water-soil coupling mechanism that takes the debrisflow watershed as a basic forecast unit was established here for the prediction of disasters at the watershed scale.This was achieved through advances in our understanding of the formation mechanism of debris flow.To expand the applicable spatial scale of this forecasting model,a method of identifying potential debris flow watersheds was used to locate areas vulnerable to debris flow within a forecast region.Using these watersheds as forecasting units and a prediction method based on the water-soil coupling mechanism,a new forecasting method of debris flow at the regional scale was established.In order to test the prediction ability of this new forecasting method,the Sichuan province,China was selected as a study zone and the large-scale debris flow disasters attributable to heavy rainfall in this region on July 9,2013 were taken as the study case.According to debris flow disaster data on July 9,2013 which were provided by the geo-environmental monitoring station of Sichuan province,there were 252 watersheds in which debris flow events actually occurred.The current model predicted that 265 watersheds were likely to experience a debris flow event.Among these,43 towns including 204 debrisflow watersheds were successfully forecasted and 24 towns including 48 watersheds failed.The false prediction rate and failure prediction rate of thisforecast model were 23% and 19%,respectively.The results show that this method is more accurate and more applicable than traditional methods.展开更多
A barrier-free wheelchair robot with a mechanism coupled by wheel and track is presen- ted in this paper. Using the wheelchair, the lower limb disabled persons could be more relaxed to take part in outdoor activities ...A barrier-free wheelchair robot with a mechanism coupled by wheel and track is presen- ted in this paper. Using the wheelchair, the lower limb disabled persons could be more relaxed to take part in outdoor activities whether on flat ground or stairs and obstacles in the city. The wheel- track coupling mechanism is designed and the stability of the bodywork of the wheelchair robot on the stairs is analyzed. In order to obtain the stability of wheelchair robot when it climbs obstacles, centroid projection method is applied to analyze the static stability, stability margin is proposed to provide the stability under some dynamic forces, and the push rod rotation angle in terms of the guaranteed stability margin is given. Finally, the dynamic model of the wheelchair robot based on Lagrange equation is established, which can be a theoretical foundation for the wheelchair control system design.展开更多
To probe the coupling effect of the electron and Li ion conductivities in Ni-rich layered materials(LiNi0.8Co0.15Al0.05O2,NCA),lithium lanthanum titanate(LLTO)nanofiber and carbon-coated LLTO fiber(LLTO@C)materials we...To probe the coupling effect of the electron and Li ion conductivities in Ni-rich layered materials(LiNi0.8Co0.15Al0.05O2,NCA),lithium lanthanum titanate(LLTO)nanofiber and carbon-coated LLTO fiber(LLTO@C)materials were introduced to polyvinylidene difluoride in a cathode.The enhancement of the conductivity was indicated by the suppressed impedance and polarization.At 1 and 5 C,the cathodes with coupling conductive paths had a more stable cycling performance.The coupling mechanism was analyzed based on the chemical state and structure evolution of NCA after cycling for 200 cycles at 5 C.In the pristine cathode,the propagation of lattice damaged regions,which consist of high-density edge-dislocation walls,destroyed the bulk integrity of NCA.In addition,the formation of a rock-salt phase on the surface of NCA caused a capacity loss.In contrast,in the LLTO@C modified cathode,although the formation of dislocation-driven atomic lattice broken regions and cation mixing occurred,they were limited to a scale of several atoms,which retarded the generation of the rock-salt phase and resulted in a pre-eminent capacity retention.Only NiO phase“pitting”occurred.A mechanism based on the synergistic transport of Li ions and electrons was proposed.展开更多
As the oil or gas exploration and development activities in deep and ultra- deep waters become more and more, encountering gas hydrate bearing sediments （HBS） is almost inevitable. The variation in temperature and p...As the oil or gas exploration and development activities in deep and ultra- deep waters become more and more, encountering gas hydrate bearing sediments （HBS） is almost inevitable. The variation in temperature and pressure can destabilize gas hydrate in nearby formation around the borehole, which may reduce the strength of the formation and result in wellbore instability. A non-isothermal, transient, two-phase, and fluid-solid coupling mathematical model is proposed to simulate the complex stability performance of a wellbore drilled in HBS. In the model, the phase transition of hydrate dissociation, the heat exchange between drilling fluid and formation, the change of mechanical and petrophysical properties, the gas-water two-phase seepage, and its interaction with rock deformation are considered. A finite element simulator is developed, and the impact of drilling mud on wellbore instability in HBS is simulated. Results indicate that the re- duction in pressure and the increase in temperature of the drilling fluid can accelerate hydrate decomposition and lead to mechanical properties getting worse tremendously. The cohesion decreases by 25% when the hydrate totally dissociates in HBS. This easily causes the wellbore instability accordingly. In the first two hours after the formation is drilled, the regions of hydrate dissociation and wellbore instability extend quickly. Then, with the soaking time of drilling fluid increasing, the regions enlarge little. Choosing the low temperature drilling fluid and increasing the drilling mud pressure appropriately can benefit the wellbore stability of HBS. The established model turns out to be an efficient tool in numerical studies of the hydrate dissociation behavior and wellbore stability of HBS.展开更多
Some settlements were located in unsuitable regions due to limited land resources in mountainous areas,some settlements were even even constructed in areas prone to geological hazards in Southwest China.Therefore,it w...Some settlements were located in unsuitable regions due to limited land resources in mountainous areas,some settlements were even even constructed in areas prone to geological hazards in Southwest China.Therefore,it was important to evaluate the spatial appropriateness of a region and determine the areas that were unsuitable for settlements,and then find out the settlements located in unsuitable regions.It will assist in decision making associated with the relocation of settlements.Furthermore,it will be the key to ensure the safety of inhabitants and promoting sustainable development in mountainous areas.This study explored the coupling mechanism between suitable space and rural settlements in the upper Minjiang River basin,which is an ecologically fragile area with high-frequency of natural hazards.Firstly,we identified relief degree of land surface(RDLS),elevation,and disaster risk as the limiting factors.Then,by determining the thresholds of these limiting factors,we recognized the suitable areas for inhabitation in the upper Minjiang River basin with GIS.Finally,using the distribution map of rural settlements and that of suitable space,the distribution of rural settlements located at unsuitable area was obtained by coupling relationship analysis.Consequently,an in-depth understanding of this relationship was achieved as follows:(1)The suitable space of the upper Minjiang River basin is 13.7 thousand km2,accounting for 54.9%of the total land space;(2)There were 196 settlements located in the unsuitable area,the total area of these settlements was 125.27 km2,and there were 68000 people in these settlements,accounting for 17.65%of the total population;(3)There were 65 settlements located near mountain hazard areas,accounting for 4.9%of the total.These findings suggest that it was necessary to carefully investigate settlements with risks and develop targeted relocation policies to help find the most effective way of using land safely and to good effect.The details are as follows:(1)Fully consider the safety of residents:For the 196 settlements distributed in the unsuitable region,the government should undertake a point-by-point survey and classify these settlements into different categories for relocation;(2)For the 65 settlements closely related with mountain hazards,professional geological prospecting teams should be organized to conduct a field survey at each point;(3)Besides considering the safety of residents during the relocation process,it is necessary to pay more attention to the cultural customs of inhabitants and livelihood sustainability.展开更多
Comprehensive analysis of the Economy-Energy-Carbon Emission(EECE)system is beneficial for promoting sustainable social development.This study analyzes the system development of major watersheds in China from 2010 to ...Comprehensive analysis of the Economy-Energy-Carbon Emission(EECE)system is beneficial for promoting sustainable social development.This study analyzes the system development of major watersheds in China from 2010 to 2019.The research fully considers the system’s internal and external inputs and outputs and proposes an evaluation index system for regional EECE coupling and coordinated development.Then,using the difference in system weight allocation to improve the coupling and coordination model,the study explores the dynamic system’s coupling and coordination.The results show that(1)The development of the system structure is relatively stable,but the overall development status is not ideal;(2)The downstream of China’s main river basins has obvious economic advantages,while the energy system fluctuates greatly.The efficiency of the carbon emission system will decrease in areas with rapid economic development.The coupling and coordination level of the EECE system is better in the Yangtze River Basin than in the Yellow River Basin;(3)From the perspective of dynamic coordinated development,the main river basins have been divided into two states since 2012,but it is relatively stable overall.Regional dynamic coordination is often at a disadvantage in regions with rapid economic and energy development;(4)The coupling coordination degree of the two river basins has significant positive spatial autocorrelation.Most provinces’significant spatial clustering characteristics of the coupling coordination degree are High-High type.Low-Low type provinces are mainly concentrated downstream.The research process has certain reference significance for the collaborative governance of complex regional systems.展开更多
In recent years,most studies of complex networks have focused on a single network and ignored the interaction of multiple networks,much less the coupling mechanisms between multiplex networks.In this paper we investig...In recent years,most studies of complex networks have focused on a single network and ignored the interaction of multiple networks,much less the coupling mechanisms between multiplex networks.In this paper we investigate synchronization phenomena in multilayer networks with nonidentical topological structures based on three specific coupling mechanisms:assortative,disassortative,and anti-assortative couplings.We find rich and complex synchronous dynamic phenomena in coupled networks.We also study the behavior of effective frequencies for layers I and II to understand the underlying microscopic dynamics occurring under the three different coupling mechanisms.In particular,the coupling mechanisms proposed here have strong robustness and effectiveness and can produce abundant synchronization phenomena in coupled networks.展开更多
The coupling mechanism of saturated concrete subjected to simultaneous 4-point fatigue loading and freeze-thaw cycles was, for the first time, experimentally studied by strain technology. The coupling strain, temperat...The coupling mechanism of saturated concrete subjected to simultaneous 4-point fatigue loading and freeze-thaw cycles was, for the first time, experimentally studied by strain technology. The coupling strain, temperature strain and fatigue strain of concrete specimens were measured at the same time from one sample with stain analysis method and the relationship among these three kinds of strains was studied by fitting data to present coupling mechanism at macro level. The results showed that there was no interaction between fatigue strain and temperature strain and the coupling strain could be written by linear superposition of temperature strain and fatigue strain.展开更多
This work presents a novel radio frequency(RF)narrowband Si micro-electro-mechanical systems(MEMS)filter based on capacitively transduced slotted width extensional mode(WEM)resonators.The flexibility of the plate lead...This work presents a novel radio frequency(RF)narrowband Si micro-electro-mechanical systems(MEMS)filter based on capacitively transduced slotted width extensional mode(WEM)resonators.The flexibility of the plate leads to multiple modes near the target frequency.The high Q-factor resonators of around 100000 enable narrow bandwidth filters with small size and simplified design.The 1-wavelength and 2-wavelength WEMs were first developed as a pair of coupled modes to form a passband.To reduce bandwidth,two plates are coupled with aλ-length coupling beam.The 79.69 MHz coupled plate filter(CPF)achieved a narrow bandwidth of 8.8 kHz,corresponding to a tiny 0.011%.The CPF exhibits an impressive 34.84 dB stopband rejection and 7.82 dB insertion loss with near-zero passband ripple.In summary,the RF MEMS filter presented in this work shows promising potential for application in RF transceiver front-ends.展开更多
A hybrid metamaterial with the integration of molybdenum disulfide(MoS_(2))overlayer is proposed to manipulate the terahertz(THz)wave.The simulated results indicate that the introduction of MoS_(2) layer could signifi...A hybrid metamaterial with the integration of molybdenum disulfide(MoS_(2))overlayer is proposed to manipulate the terahertz(THz)wave.The simulated results indicate that the introduction of MoS_(2) layer could significantly modify the resonant responses with large resonance red-shift and bandwidth broadening due to the depolarization field effect,especially for the structure on the small permitivity substrate.Additionally,the wide-band modulator in off-resonant region and a switch effect at resonance can be achieved by varying the conductivity of MoS_(2) layer.Further theoretical calculations based on the Lorentz coupling model are consistent with the simulated results,explicating the response behaviors originate from the coupling between MoS_(2) overlayer and the metastructure.Our results could provide a possibility for active control THz modulator and switchable device based on the MoS_(2) overlayer and advance the understanding of the coupling mechanism in hybrid structures.展开更多
基金Projects(51009053,51079039)supported by the National Natural Science Foundation of ChinaProject(20100094120004)supported by the Doctoral Program of Higher Education of China
文摘The joint of clay core-wall and concrete cut-off wall is one of the weakest parts in high earth and rockftll dams.A kind of highly plastic clay is always fixed on the joint to fit the large shear deformation between clay core-wall and concrete cut-offwall,so the hydro-mechanical coupling mechanisms on the joint under high stress,high hydraulic gradient,and large shear deformation are of great importance for the evaluation of dam safety.The hydro-mechanical coupling characteristics of the joint of the highly plastic clay and the concrete cut-off wall in a high earth and rockfill dam in China were studied by using a newly designed soil-structure contact erosion apparatus.The experimental results indicate that：1） Shear failure on the joint is due to the hydro-mechanical coupling effect of stress and seepage failure.The seepage failure will induce the final shear failure when the ratio of deviatoric stress to confining pressure is within 1.0-1.2; 2） A negative exponential permeability empirical model for the joint denoted by a newly defined principal stress function,which considers the coupling effect of confining pressure and axial pressure on the permeability,is established based on hydro-mechanical coupling experiments.3） The variation of the settlement before and after seepage failure is very different.The settlement before seepage failure changes very slowly,while it increases significantly after the seepage failure.4） The stress-strain relationship is of a strain softening type.5） Flow along the joint still follows Darcian flow rule.The results will provide an important theoretical basis for the further evaluation on the safety of the high earth and rockfill dam.
基金Supported by the National Basic Research Program of China("973"Program)(613002)
文摘The transient finite element technique is applied, and a transient heat conduction model of wet brake friction disk is established. For obtaining the accurate heat flow density mathematic model and avoiding possibly instable thermoelastic stress produced by the non uniform contact pressure of friction pair, a test method is applied to collect accurate contact pressure between the dual sheet steel and friction disk in the combining process. And then the heat-flow density and transient ther mo mechanical coupling simulation are analyzed. At the same time all possible boundary conditions are considered, such as the heat generation, heat conduction problem, relation between friction and contact, variation in load and heat change problem etc. The simulation results show that the me chanical model of thermo mechanical coupling can express well the dynamic characteristics of fric tion disk, and gives perfect reference for more study on thermoelastic distortion of brake friction pairs.
基金Project(11072269) supported by the National Natural Science Foundation of ChinaProject(20090162110066) supported by the Research Fund for the Doctoral Program of Higher Education of China
文摘Based on fluid mechanics, thermodynamics and damage mechanics, thermal-hydro-mechanical （THM） coupling damage model of brittle rock is established by analyzing THM coupling mechanism, where THM coupling damage variable DTHM is dominated by TH coupling damage variable DTH, TM coupling damage variable DTM and HM coupling damage variable DHM, and DTH is firstly expressed in term of dimensionless total thermal conductivity of the water Nu. Permeability test, uni-axial compression test and THM coupling test are conducted to measure the permeability, elastic modulus and THM coupling stress-strain curves of brittle rock. The tested values of THM coupling elastic modulus E＇HM are in good agreement with the predicted values of THM coupling elastic modulus ETHM, which can verify the newly established THM coupling damage model.
基金supported by the National Key Research and Development Program(Grant No.2021YFB3201800)the Natural Science Foundation of China(Grants 62131017,U22A2019)the Key R&D Project of Shaanxi Province-University Joint Project(2023GXLH-020).
文摘The development of advanced magnetoelectric(ME)composites necessitates high-performance materials that arecapable of achieving high levels of ME coupling,minimal magnetic loss,and absence or limited reliance on externalexcitation sources.In this paper,a(2-2)connectivity ME laminate integrates multiple layers of FeSiB alloy(Metglas)andPb(Mg,Nb)O_(3)-PbTiO_(3)(PMN-PT)single crystal,achieving a remarkable ME coupling coefficient of 2033.4 V/Oe·cm(sevenfold rise)by laser thermal annealing treatment.Here,the laser-induced nanostructures on Metglas,with anoxidized insulation layer and soft and hard magnetic dipole layer improve the Magneto-electric-mechanical couplingwith a mechanical quality factor(Q_(m))exceeding 350.More importantly,the interaction between amorphous andnanocrystalline dipoles triggers an Exchange Bias(EB)effect,leading to a self-biasing performance of 67.45 V/Oe·cm.Furthermore,the composite exhibits an excellent passive DC magnetic detection limit of 22 nT,and an improved weakAC magnetic detection limit down to 383 fT.These explorations offer the potential to enhance passive currentmeasurement,and underwater communication,extend weak magnetic positioning and brain magnetic detection.
基金the National Natural Science Foundation of China(No.52341401)the National Key Research and Development Program of China under grant(No.2022YFE0206700)+4 种基金the National Natural Science Foundation of China(No.42302272)the State-funded Postdoctoral Fellowship Program(No.GZB20230862)the Science Foundation of China University of Petroleum,Beijing(No.2462023XKBH006)the Science Foundation of China University of Petroleum,Beijing(No.2462021YJRC012)the Open Project Program of Key Laboratory of Groundwater Resources and Environment(Jilin University),Ministry of Education(No.202306ZDKF05).
文摘With policy support for carbon capture,utilization,and storage(CCUS),an integrated approach that combines energy storage fracturing,CO_(2)-enhanced oil recovery(EOR),and storage emerges as a promising direction for the shale oil industry.The process of energy storage fracturing induces significant changes in the pressure and saturation of the medium.However,conventional simulations often overlook the effects of fracturing and shut-in operations on the seepage field and production performance.Furthermore,fractured shale reservoirs exhibit complex non-Darcy flow characteristics due to intricate pore structures and multi-scale porous media.A comprehensive understanding of flow mechanisms is essential for effective reservoir development and CO_(2) storage.This study establishes a multi-component simulation model that encompasses the life-cycle of fracturing,shut-in,production,and CO_(2) huff-n-puff processes,thereby ensuring the continuity of the seepage field.The model accounts for the effect of nano-confinement on phase behavior by modifying the equation of state.Furthermore,the flux term is adjusted to incorporate Maxwell–Stefan diffusion,pre-/post-Darcy flow,and stress sensitivity.The embedded discrete fracture model(EDFM)is employed to simulate multiphase flow within multi-scale media,and the results from the validation model align satisfactorily with those derived from ECLIPSE.Mechanism analysis indicates that the interaction of multiple mechanisms significantly influences both production and storage performance.Under the multi-mechanism coupling,the cumulative oil production increased by 12.01%,while the utilization and storage factors increased by 62.93%and 8.93%,respectively.The role of molecular diffusion in shale oil reservoirs may be overstated,contributing only a 0.26% enhancement in oil production.Simulation results show that the energy storage fracturing strategy can increase oil production and net present value by 12.47%and 15.07%,respectively.Sensitivity analysis indicates that the CO_(2) injection rate is the main factor affecting the recovery factor,followed by CO_(2) injection time and the number of cycles,with fracturing fluid volume having the least impact.This study develops a multi-process,multi-mechanism simulation framework for multi-scale shale oil reservoirs.This framework provides a robust evaluation system for CCUS-EOR,facilitating informed decision-making in fracturing stimulation,development planning,and parameter optimization.
基金supported by the National Key Research and Development Program(No.2022YFB4602502)the Guangdong Basic and Applied Basic Research Foundation(No.2021A1515011991)+2 种基金the Key Research and Development Program Fund of Hubei Province(No.2022BAA057)the state Key Lab-oratory of Solidification Processing in NPU(No.SKLSP202325)the China Scholarship Council Visiting PhD Program(No.202306410136).
文摘Multimodal ultrasonic vibration(UV)assisted micro-forming has been widely investigated for its advantages of further reducing forming loads and improving forming quality.However,the influence mechanism of different UV modes on microstructure evolution and mechanical properties was still unclear.Mul-timodal UV assisted micro-compression tests on T2 copper with different grains and sample sizes were conducted in this study.The microstructure evolution for different UV modes was observed by EBSD.The results showed that the true stress reduction caused by UV was increased sequentially with tool ultrasonic vibration(TV),mold ultrasonic vibration(MV)and compound ultrasonic vibration(CV).The region of grain deformation was shifted along the direction of UV,and the MV promoted the uniform distribution of deformation stress.The grain refinement,fiber streamline density,grain deformation and rotation degree were further enhanced under CV,due to the synergistic effect of TV and MV.Additionally,a coupled theoretical model considering both acoustic softening effect and size effect was proposed for describing the mechanical properties.And a physical model of dislocation motion in different UV modes was developed for describing the microstructure evolution.The maximum error between the theoretical and experimental results was only 2.39%.This study provides a theoretical basis for the optimization of UV assisted micro-forming process.
基金the University of California at Berkeley.Ms.Y.Song gratefully acknowledges the financial support from the Chinese Scholar Council(CSC Grant No.201706680094).
文摘De-icing technology has become an increasingly important subject in numerous applications in recent years.However,the direct numerical modeling and simulation the physical process of thermomechanical deicing is limited.This work is focusing on developing a numerical model and tool to direct simulate the de-icing process in the framework of the coupled thermo-mechanical peridynamics theory.Here,we adopted the fully coupled thermo-mechanical bond-based peridynamics(TM-BB-PD)method for modeling and simulation of de-icing.Within the framework of TM-BB-PD,the ice constitutive model is established by considering the influence of the temperature difference between two material points,and a modified failure criteria is proposed,which takes into account temperature effect to predict the damage of quasi-brittle ice material.Moreover,thermal boundary condition is used to simulate the thermal load in the de-icing process.By comparing with the experimental results and the previous reported finite element modeling,our numerical model shows good agreement with the previous predictions.Based on the numerical results,we find that the developed method can not only predict crack initiation and propagation in the ice,but also predict the temperature distribution and heat conduction during the de-icing process.Furthermore,the influence of the temperature for the ice crack growth pattern is discussed accordingly.In conclusion,the coupled thermal-mechanical peridynamics formulation with modified failure criterion is capable of providing a modeling tool for engineering applications of de-icing technology.
文摘3-D rigid-viscoplastic FEM of compressible materials was applied to analyze the deformation behavior during twist compression forming of axisymmetrical body at high temperatures. When calculating the temperature fields, considering the thermo mechanical coupling effect between temperature and deformation, 2-D FEM and CNG methods were adopted, and the up winding technique was used to avoid the influences of numerical instability on calculated results.
基金financially supported by the Key Program of National Natural Science Foundation of China(No.U23A20608)the Liaoning Province Science and Technology Plan Joint Program(Key Research and Development Program Project),China(No.2023JH2/101800058)+3 种基金the Science&Technology Plan Project of Hebei Province,China(No.23314601L)the Project of Hydrogen-Based Shaft Furnace Reduction-Electric Furnace Melting And Separation Technology Research and Application for High-Titanium Magnetite Iron Ore(No.HG2023239)the General Program of National Natural Science Foundation of China(No.52274253)the Special Project for Major Scientific and Technological Achievements Transformation in Hebei Province,China(No.23284101Z)。
文摘The novel process of hydrogen-based shaft furnaces(HSFs)has attracted considerable attention because of their significant reduction of CO_(2)emissions.In this study,the interaction of H_(2)and CO with Fe_(tet1)-and Fe_(oct2)-terminated Fe_(3)O_(4)(111)surfaces under HSF conditions,including their adsorption and reduction behaviors,was investigated using the density functional theory method.The results indicated that the H_(2)molecule adsorbed onto the Fe_(tet1)-terminated surface with an adsorption energy(AE)of-1.36 eV,whereas the CO molecule preferentially adsorbed on the Fe_(oct2)-terminated surface with an AE of-1.56 eV.Both H_(2)and CO can readily undergo reduction on the Fe_(tet1)-terminated surface(corresponding to energy barriers of 0.83 eV and 2.23 eV,respectively),but kinetically the reaction of H2is more favorable than that of CO.With regard to the thermodynamics at 400-1400 K,the H_(2)was easy to be adsorbed,while the CO would like to react on the Fe_(tet1)-terminated surface.These thermodynamically tendencies were reversed on the Fe_(oct2)-terminated surface.The thermodynamic disadvantage of the reaction of H_(2)on the Fe_(tet1)-terminated surface was offset by an increase in the temperature.Furthermore,the adsorption of H2 and CO on the Fe_(tet1)-terminated surface was competitive,whereas the adsorption of them on the Fe_(oct2)-terminated surface was synergistic.Therefore,iron ores with a higher proportion of Fe_(tet1)-terminated surface can be applied for the HSF process.In conjunction with the increases in the reduction temperature and the ratio of H_(2)in the reducing gas would promote efficient HSF smelting.These observations provide effective guidance for optimizing the practical operation parameters and advancing the development of the HSF process.
基金National Natural Science Foundation of China, No.41171149 No.41130748 Knowledge Innovation Program of the Chinese Academy of Sciences, No.KZCX2-YW-QN304
文摘Land use transition refers to the changes in land use morphology （both dominant morphology and recessive morphology） of a certain region over a certain period of time driven by socio-economic change and innovation, and it usually corresponds to the transition of socio-economic development phase. In China, farmland and rural housing land are the two major sources of land use transition. This paper analyzes the spatio-temporal coupling characteristics of farmland and rural housing land transition in China, using high-resolution Landsat TM （Thematic Mapper） data in 2000 and 2008, and the data from the Ministry of Land and Resources of China. The outcomes indicated that： （1） during 2000-2008, the correlation coefficient of farmland vs. rural housing land change is -0.921, and it shows that the change pattern of farmland and rural housing land is uncoordinated; （2） the result of Spearman rank correlation analysis shows that rural housing land change has played a major role in the mutual transformation of farmland and rural housing land; and （3） it shows a high-degree spatial coupling between farmland and rural housing land change in southeast China during 2000-2008. In general, farmland and rural housing land transition in China is driven by socio-economic, bio-physical and managerial three-dimensional driving factors through the interactions among rural population, farmland and rural housing land. However, the spatio-temporal coupling phenomenon and mechanism of farmland and rural housing land transition in China are largely due to the ＂dual-track＂ structure of rural-urban development.
基金supported by the foundation of the Research Fund for Commonweal Trades (Meteorology) (Grant No. GYHY201006039)the International Cooperation Project of the Department of Science and Technology of Sichuan Province (Grant No. 2009HH0005)
文摘A debris flow forecast model based on a water-soil coupling mechanism that takes the debrisflow watershed as a basic forecast unit was established here for the prediction of disasters at the watershed scale.This was achieved through advances in our understanding of the formation mechanism of debris flow.To expand the applicable spatial scale of this forecasting model,a method of identifying potential debris flow watersheds was used to locate areas vulnerable to debris flow within a forecast region.Using these watersheds as forecasting units and a prediction method based on the water-soil coupling mechanism,a new forecasting method of debris flow at the regional scale was established.In order to test the prediction ability of this new forecasting method,the Sichuan province,China was selected as a study zone and the large-scale debris flow disasters attributable to heavy rainfall in this region on July 9,2013 were taken as the study case.According to debris flow disaster data on July 9,2013 which were provided by the geo-environmental monitoring station of Sichuan province,there were 252 watersheds in which debris flow events actually occurred.The current model predicted that 265 watersheds were likely to experience a debris flow event.Among these,43 towns including 204 debrisflow watersheds were successfully forecasted and 24 towns including 48 watersheds failed.The false prediction rate and failure prediction rate of thisforecast model were 23% and 19%,respectively.The results show that this method is more accurate and more applicable than traditional methods.
基金Supported by State Key Laboratory of Robotics and Systems(HIT)(SKLRS-2010-ZD-04)Capital Medical Development Scientific Research Fund(20092098)
文摘A barrier-free wheelchair robot with a mechanism coupled by wheel and track is presen- ted in this paper. Using the wheelchair, the lower limb disabled persons could be more relaxed to take part in outdoor activities whether on flat ground or stairs and obstacles in the city. The wheel- track coupling mechanism is designed and the stability of the bodywork of the wheelchair robot on the stairs is analyzed. In order to obtain the stability of wheelchair robot when it climbs obstacles, centroid projection method is applied to analyze the static stability, stability margin is proposed to provide the stability under some dynamic forces, and the push rod rotation angle in terms of the guaranteed stability margin is given. Finally, the dynamic model of the wheelchair robot based on Lagrange equation is established, which can be a theoretical foundation for the wheelchair control system design.
基金This work was financially supported by the National Natural Science Foundation of China(Nos.51571182 and 51001091)the Fundamental Research Program from the Ministry of Science and Technology of China(No.2014CB931704)the Program for Innovative Research Team(in Science and Technology)in University of Henan Province(No.21IRTSTHN003).This work was also partially supported by the Provincial Scientific Research Program of Henan(No.182102310815).
文摘To probe the coupling effect of the electron and Li ion conductivities in Ni-rich layered materials(LiNi0.8Co0.15Al0.05O2,NCA),lithium lanthanum titanate(LLTO)nanofiber and carbon-coated LLTO fiber(LLTO@C)materials were introduced to polyvinylidene difluoride in a cathode.The enhancement of the conductivity was indicated by the suppressed impedance and polarization.At 1 and 5 C,the cathodes with coupling conductive paths had a more stable cycling performance.The coupling mechanism was analyzed based on the chemical state and structure evolution of NCA after cycling for 200 cycles at 5 C.In the pristine cathode,the propagation of lattice damaged regions,which consist of high-density edge-dislocation walls,destroyed the bulk integrity of NCA.In addition,the formation of a rock-salt phase on the surface of NCA caused a capacity loss.In contrast,in the LLTO@C modified cathode,although the formation of dislocation-driven atomic lattice broken regions and cation mixing occurred,they were limited to a scale of several atoms,which retarded the generation of the rock-salt phase and resulted in a pre-eminent capacity retention.Only NiO phase“pitting”occurred.A mechanism based on the synergistic transport of Li ions and electrons was proposed.
基金supported by the Major National Science and Technology Program(Nos.2008ZX05026-00411 and 2011ZX05026-004-08)the Program for Changjiang Scholars and Innovative Research Team in University(No.RT1086)
文摘As the oil or gas exploration and development activities in deep and ultra- deep waters become more and more, encountering gas hydrate bearing sediments （HBS） is almost inevitable. The variation in temperature and pressure can destabilize gas hydrate in nearby formation around the borehole, which may reduce the strength of the formation and result in wellbore instability. A non-isothermal, transient, two-phase, and fluid-solid coupling mathematical model is proposed to simulate the complex stability performance of a wellbore drilled in HBS. In the model, the phase transition of hydrate dissociation, the heat exchange between drilling fluid and formation, the change of mechanical and petrophysical properties, the gas-water two-phase seepage, and its interaction with rock deformation are considered. A finite element simulator is developed, and the impact of drilling mud on wellbore instability in HBS is simulated. Results indicate that the re- duction in pressure and the increase in temperature of the drilling fluid can accelerate hydrate decomposition and lead to mechanical properties getting worse tremendously. The cohesion decreases by 25% when the hydrate totally dissociates in HBS. This easily causes the wellbore instability accordingly. In the first two hours after the formation is drilled, the regions of hydrate dissociation and wellbore instability extend quickly. Then, with the soaking time of drilling fluid increasing, the regions enlarge little. Choosing the low temperature drilling fluid and increasing the drilling mud pressure appropriately can benefit the wellbore stability of HBS. The established model turns out to be an efficient tool in numerical studies of the hydrate dissociation behavior and wellbore stability of HBS.
基金funded by The National Natural Science Foundation of China(Grant NOs.41801140,41930651 and 41771194)。
文摘Some settlements were located in unsuitable regions due to limited land resources in mountainous areas,some settlements were even even constructed in areas prone to geological hazards in Southwest China.Therefore,it was important to evaluate the spatial appropriateness of a region and determine the areas that were unsuitable for settlements,and then find out the settlements located in unsuitable regions.It will assist in decision making associated with the relocation of settlements.Furthermore,it will be the key to ensure the safety of inhabitants and promoting sustainable development in mountainous areas.This study explored the coupling mechanism between suitable space and rural settlements in the upper Minjiang River basin,which is an ecologically fragile area with high-frequency of natural hazards.Firstly,we identified relief degree of land surface(RDLS),elevation,and disaster risk as the limiting factors.Then,by determining the thresholds of these limiting factors,we recognized the suitable areas for inhabitation in the upper Minjiang River basin with GIS.Finally,using the distribution map of rural settlements and that of suitable space,the distribution of rural settlements located at unsuitable area was obtained by coupling relationship analysis.Consequently,an in-depth understanding of this relationship was achieved as follows:(1)The suitable space of the upper Minjiang River basin is 13.7 thousand km2,accounting for 54.9%of the total land space;(2)There were 196 settlements located in the unsuitable area,the total area of these settlements was 125.27 km2,and there were 68000 people in these settlements,accounting for 17.65%of the total population;(3)There were 65 settlements located near mountain hazard areas,accounting for 4.9%of the total.These findings suggest that it was necessary to carefully investigate settlements with risks and develop targeted relocation policies to help find the most effective way of using land safely and to good effect.The details are as follows:(1)Fully consider the safety of residents:For the 196 settlements distributed in the unsuitable region,the government should undertake a point-by-point survey and classify these settlements into different categories for relocation;(2)For the 65 settlements closely related with mountain hazards,professional geological prospecting teams should be organized to conduct a field survey at each point;(3)Besides considering the safety of residents during the relocation process,it is necessary to pay more attention to the cultural customs of inhabitants and livelihood sustainability.
基金supported by the Chengdu University of Technology“Double First-Class”initiative Construction Philosophy and Social Sciences Key Construction Project(No.ZDJS202202)the Research on the realization path and strategy of strategic mineral resources supply security under the new road of Chinese modernization(No.SCKCZY2023-ZD002)The Second Tibetan Plateau Scientific Expedition and Research(No.2021QZKK0305)。
文摘Comprehensive analysis of the Economy-Energy-Carbon Emission(EECE)system is beneficial for promoting sustainable social development.This study analyzes the system development of major watersheds in China from 2010 to 2019.The research fully considers the system’s internal and external inputs and outputs and proposes an evaluation index system for regional EECE coupling and coordinated development.Then,using the difference in system weight allocation to improve the coupling and coordination model,the study explores the dynamic system’s coupling and coordination.The results show that(1)The development of the system structure is relatively stable,but the overall development status is not ideal;(2)The downstream of China’s main river basins has obvious economic advantages,while the energy system fluctuates greatly.The efficiency of the carbon emission system will decrease in areas with rapid economic development.The coupling and coordination level of the EECE system is better in the Yangtze River Basin than in the Yellow River Basin;(3)From the perspective of dynamic coordinated development,the main river basins have been divided into two states since 2012,but it is relatively stable overall.Regional dynamic coordination is often at a disadvantage in regions with rapid economic and energy development;(4)The coupling coordination degree of the two river basins has significant positive spatial autocorrelation.Most provinces’significant spatial clustering characteristics of the coupling coordination degree are High-High type.Low-Low type provinces are mainly concentrated downstream.The research process has certain reference significance for the collaborative governance of complex regional systems.
基金Project supported by the National Natural Science Foundation of China(Grants Nos.71801066 and 71704046)the Natural Science Foundation of Anhui Province,China(Grant Nos.1808085QG225 and 1908085MA22)+1 种基金the FundamentalResearch Funds for the Central Universities,China(Grant Nos.JZ2020HGTB0021 and JZ2021HGTB0065)the Outstanding Young Talent Support Program in Universities of Anhui Province in 2020 year。
文摘In recent years,most studies of complex networks have focused on a single network and ignored the interaction of multiple networks,much less the coupling mechanisms between multiplex networks.In this paper we investigate synchronization phenomena in multilayer networks with nonidentical topological structures based on three specific coupling mechanisms:assortative,disassortative,and anti-assortative couplings.We find rich and complex synchronous dynamic phenomena in coupled networks.We also study the behavior of effective frequencies for layers I and II to understand the underlying microscopic dynamics occurring under the three different coupling mechanisms.In particular,the coupling mechanisms proposed here have strong robustness and effectiveness and can produce abundant synchronization phenomena in coupled networks.
基金Funded by the Major State Basic Research Development Program of China(No.2009CB623202)the National Natural Science Foundation of China(No.5107-8081)
文摘The coupling mechanism of saturated concrete subjected to simultaneous 4-point fatigue loading and freeze-thaw cycles was, for the first time, experimentally studied by strain technology. The coupling strain, temperature strain and fatigue strain of concrete specimens were measured at the same time from one sample with stain analysis method and the relationship among these three kinds of strains was studied by fitting data to present coupling mechanism at macro level. The results showed that there was no interaction between fatigue strain and temperature strain and the coupling strain could be written by linear superposition of temperature strain and fatigue strain.
基金supported by the National Natural Science Foundation of China(61734007)National Key Research and Development Program of China(2022YFF0706100).
文摘This work presents a novel radio frequency(RF)narrowband Si micro-electro-mechanical systems(MEMS)filter based on capacitively transduced slotted width extensional mode(WEM)resonators.The flexibility of the plate leads to multiple modes near the target frequency.The high Q-factor resonators of around 100000 enable narrow bandwidth filters with small size and simplified design.The 1-wavelength and 2-wavelength WEMs were first developed as a pair of coupled modes to form a passband.To reduce bandwidth,two plates are coupled with aλ-length coupling beam.The 79.69 MHz coupled plate filter(CPF)achieved a narrow bandwidth of 8.8 kHz,corresponding to a tiny 0.011%.The CPF exhibits an impressive 34.84 dB stopband rejection and 7.82 dB insertion loss with near-zero passband ripple.In summary,the RF MEMS filter presented in this work shows promising potential for application in RF transceiver front-ends.
基金Beijing Natural Science Foundation of China(Grant No.4181001)the National Natural Science Foundation of China(Grant Nos.62075142 and 61875140).
文摘A hybrid metamaterial with the integration of molybdenum disulfide(MoS_(2))overlayer is proposed to manipulate the terahertz(THz)wave.The simulated results indicate that the introduction of MoS_(2) layer could significantly modify the resonant responses with large resonance red-shift and bandwidth broadening due to the depolarization field effect,especially for the structure on the small permitivity substrate.Additionally,the wide-band modulator in off-resonant region and a switch effect at resonance can be achieved by varying the conductivity of MoS_(2) layer.Further theoretical calculations based on the Lorentz coupling model are consistent with the simulated results,explicating the response behaviors originate from the coupling between MoS_(2) overlayer and the metastructure.Our results could provide a possibility for active control THz modulator and switchable device based on the MoS_(2) overlayer and advance the understanding of the coupling mechanism in hybrid structures.
