Injection-production coupling(IPC) technology holds substantial potential for boosting oil recovery and enhancing economic efficiency.Despite this potential,discussion on gas injection coupling,especially in relation ...Injection-production coupling(IPC) technology holds substantial potential for boosting oil recovery and enhancing economic efficiency.Despite this potential,discussion on gas injection coupling,especially in relation to microscopic mechanisms,remains relatively sparse.This study utilizes microscopic visualization experiments to investigate the mechanisms of residual oil mobilization under various IPC scenarios,complemented by mechanical analysis at different stages.The research quantitatively assesses the degree of microscopic oil recovery and the distribution of residual oil across different injection-production methods.Findings reveal that during the initial phase of continuous gas injection(CGI),the process closely mimics miscible displacement,gradually transitioning to immiscible displacement as CO_(2)extraction progresses.Compared to CGI,the asynchronous injection-production(AIP) method improved the microscopic oil recovery rate by 6.58%.This enhancement is mainly attributed to significant variations in the pressure field in the AIP method,which facilitate the mobilization of columnar and porous re sidual oil.Furthermo re,the synchronous cycle injection(SCI) method increased microscopic oil recovery by 13.77% and 7.19% compared to CGI and AIP,respectively.In the SCI method,membrane oil displays filame ntary and Karman vo rtex street flow patterns.The dissolved and expanded crude oil te nds to accumulate and grow at the oil-solid interface due to adhesive forces,thereby reducing migration resistance.The study findings provide a theoretical foundation for improving oil recovery in lowpermeability reservoirs.展开更多
The utilization of multi-field coupling simulation methods has become a pivotal approach for the investigation of intricate fracture behavior and interaction mechanisms of rock masses in deep strata.The high temperatu...The utilization of multi-field coupling simulation methods has become a pivotal approach for the investigation of intricate fracture behavior and interaction mechanisms of rock masses in deep strata.The high temperatures,pressures and complex geological environments of deep strata frequently result in the coupling of multiple physical fields,including mechanical,thermal and hydraulic fields,during the fracturing of rocks.This review initially presents an overview of the coupling mechanisms of these physical fields,thereby elucidating the interaction processes ofmechanical,thermal,and hydraulic fields within rockmasses.Secondly,an in-depth analysis ofmulti-field coupling is conducted from both spatial and temporal perspectives,with the introduction of simulation methods for a range of scales.It emphasizes cross-scale coupling methodologies for the transfer of rock properties and physical field data,including homogenization techniques,nested coupling strategies and data-driven approaches.To address the discontinuous characteristics of the rock fracture process,the review provides a detailed explanation of continuousdiscontinuous couplingmethods,to elucidate the evolution of rock fracturing and deformationmore comprehensively.In conclusion,the review presents a summary of the principal points,challenges and future directions of multi-field coupling simulation research.It also puts forward the potential of integrating intelligent algorithms with multi-scale simulation techniques to enhance the accuracy and efficiency of multi-field coupling simulations.This offers novel insights into multi-field coupling simulation analysis in deep rock masses.展开更多
Sandwich piezoelectric semiconductor(PS)structures have significant applications in multi-functional semiconductor devices.The analysis of multi-field coupling behaviors of PS structures is of fundamental importance i...Sandwich piezoelectric semiconductor(PS)structures have significant applications in multi-functional semiconductor devices.The analysis of multi-field coupling behaviors of PS structures is of fundamental importance in developing novel PS devices.In this paper,we develop a general temperature-deformation-polarization-carrier(TDPC)coupling model for sandwich-type PS beams involving pyroelectricity under thermal loadings,based on three-dimensional(3D)basic equations of the thermo-piezoelectric semiconductor(TPS).We derive analytical solutions for extensional,bending,and buckling deformations of simply-supported sandwich n-type PS beams subjected to open-circuit and electrically isolated boundary conditions.The accuracy of the proposed model in this paper is verified through finite element simulations implemented in the COMSOL software.Numerical results show that the initial electron concentration and the thickness ratio of the PS layer to the beam's total thickness have a significant effect on thermally induced extensional and bending responses,as well as critical buckling mechanical and thermal loadings.This study provides a theoretical framework and guidance for designing semiconductor devices based on sandwich PS beam structures.展开更多
This study presents a comprehensive mechanical analysis of P110S oil tubing subjected to thermal and chemical coupling effects,with particular attention to the presence of rectangular corrosion defects.Drawing on the ...This study presents a comprehensive mechanical analysis of P110S oil tubing subjected to thermal and chemical coupling effects,with particular attention to the presence of rectangular corrosion defects.Drawing on the material’s stress–strain constitutive behavior,thermal expansion coefficient,thermal conductivity,and electrochemical test data,the research incorporates geometric nonlinearities arising from large deformations induced by corrosion.A detailed three-dimensional finite element(FE)model of the corroded P110S tubing is developed to simulate its response under complex loading conditions.The proposed model is rigorously validated through full-scale burst experiments and analytical calculations based on theoretical formulations.Building upon this validation,the Extended Finite Element Method(XFEM)and a failure criterion grounded in damage evolution mechanics are applied to investigate the mechanical behavior of the tubing under the coupled influences of temperature,stress,and chemical corrosion.Special emphasis is placed on the role of rectangular corrosion features in determining failure mechanisms.To further elucidate the impact of multiple interacting parameters,a sensitivity analysis is performed by integrating grey correlation theory with simulation outcomes.Based on these findings,the study systematically explores the elastic–plastic deformation process,crack initiation and propagation behavior,and the burst failure response of tubing specimens with varying axial lengths and depths of corrosion.The proposed methodology provides a robust predictive framework for petroleum engineers to evaluate fracture pressure,diagnose failure modes,assess operational risks,and optimize production strategies.展开更多
In this study,a series of triaxial tests are conducted on sandstone specimens to investigate the evolution of their mechanics and permeability characteristics under the combined action of immersion corrosion and seepa...In this study,a series of triaxial tests are conducted on sandstone specimens to investigate the evolution of their mechanics and permeability characteristics under the combined action of immersion corrosion and seepage of different chemical solutions.It is observed that with the increase of confining pressure,the peak stress,dilatancy stress,dilatancy stress ratio,peak strain,and elastic modulus of the sandstone increase while the Poisson ratio decreases and less secondary cracks are produced when the samples are broken.The pore pressure and confining pressure have opposite influences on the mechanical properties.With the increase of the applied axial stress,three stages are clearly identified in the permeability evolution curves:initial compaction stage,linear elasticity stage and plastic deformation stage.The permeability reaches the maximum value when the highest volumetric dilatancy is obtained.In addition,the hydrochemical action of salt solution with pH=7 and 4 has an obvious deteriorating effect on the mechanical properties and induces the increase of permeability.The obtained results will be useful in engineering to understand the mechanical and seepage properties of sandstone under the coupled chemical-seepage-stress multiple fields.展开更多
Hydraulic fracturing technology has played an important role in the exploitation of unconventional oil and gas resources,however,its application to gas hydrate reservoirs has been rarely studied.Currently,there is sti...Hydraulic fracturing technology has played an important role in the exploitation of unconventional oil and gas resources,however,its application to gas hydrate reservoirs has been rarely studied.Currently,there is still limited understanding of the propagation and extension of fractures around the wellbore during the fracturing process of horizontal wells in hydrate reservoirs,as well as the stress interference patterns between fractures.This study simulates hydraulic fracturing processes in hydrate reservoirs using a fluidsolid coupling discrete element method(DEM),and analyzes the impacts of hydrate saturation and geological and engineering factors on fracture extension and stress disturbance.The results show that hydraulic fracturing is more effective when hydrate saturation exceeds 30%and that fracture pressure increases with saturation.The increase in horizontal stress differential enhances the directionality of fracture propagation and reduces stress disturbance.The distribution uniformity index(DUI)reveals that injection pressure is directly proportional to the number of main fractures and inversely proportional to fracturing time,with fracturing efficiency depending on the spacing between injection points and the distance between wells.This work may provide reference for the commercial exploitation of natural gas hydrates.展开更多
Permafrost regions of Qilian Mountains in China are rich in gas hydrate resources.Once greenhouse gases in deep frozen layer are released into the atmosphere during hydrate mining,a series of negative consequences occ...Permafrost regions of Qilian Mountains in China are rich in gas hydrate resources.Once greenhouse gases in deep frozen layer are released into the atmosphere during hydrate mining,a series of negative consequences occur.This study aims to evaluate the impact of hydrate thermal exploitation on regional permafrost and carbon budgets based on a multi-physical field coupling simulation.The results indicate that the permeability of the frozen soil is anisotropic,and the low permeability frozen layer can seal the methane gas in the natural state.Heat injection mining of hydrates causes the continuous melting of permafrost and the escape of methane gas,which transforms the regional permafrost from a carbon sink to a carbon source.A higher injection temperature concentrates the heat and causes uneven melting of the upper frozen layer,which provides a dominant channel for methane gas and results in increased methane emissions.However,dense heat injection wells cause more uniform melting of the lower permafrost layer,and the melting zone does not extend to the upper low permeability formation,which cannot provide advantageous channels for methane gas.Therefore,a reasonable and dense number of heat injection wells can reduce the risk of greenhouse gas emissions during hydrate exploitation.展开更多
Metal–organic gel(MOG)derived composites are promising multi-functional materials due to their alterable composition,identifiable chemical homogeneity,tunable shape,and porous structure.Herein,stable metal–organic h...Metal–organic gel(MOG)derived composites are promising multi-functional materials due to their alterable composition,identifiable chemical homogeneity,tunable shape,and porous structure.Herein,stable metal–organic hydrogels are prepared by regulating the complexation effect,solution polarity and curing speed.Meanwhile,collagen peptide is used to facilitate the fabrication of a porous aerogel with excellent physical properties as well as the homogeneous dispersion of magnetic particles during calcination.Subsequently,two kinds of heterometallic magnetic coupling systems are obtained through the application of Kirkendall effect.FeCo/nitrogen-doped carbon(NC)aerogel demonstrates an ultra-strong microwave absorption of−85 dB at an ultra-low loading of 5%.After reducing the time taken by atom shifting,a FeCo/Fe3O4/NC aerogel containing virus-shaped particles is obtained,which achieves an ultra-broad absorption of 7.44 GHz at an ultra-thin thickness of 1.59 mm due to the coupling effect offered by dual-soft-magnetic particles.Furthermore,both aerogels show excellent thermal insulation property,and their outstanding radar stealth performances in J-20 aircraft are confirmed by computer simulation technology.The formation mechanism of MOG is also discussed along with the thermal insulation and electromagnetic wave absorption mechanism of the aerogels,which will enable the development and application of novel and lightweight stealth coatings.展开更多
Tailoring grain size can improve the strength of polycrystals by regulating the proportion of grains to grain boundaries and the interaction area.As the grain size decreases to the nanoscale,the deformation mechanism ...Tailoring grain size can improve the strength of polycrystals by regulating the proportion of grains to grain boundaries and the interaction area.As the grain size decreases to the nanoscale,the deformation mechanism in polycrystals shifts from being primarily mediated by dislocations to deformation occurring within the grains and grain boundaries.However,the mechanism responsible for fine-grain strengthening in ferroelectric materials remains unclear,primarily due to the complex multi-field coupling effect arising from spontaneous polarization.Through molecular dynamics simulations,we investigate the strengthening mechanism of barium titanate(BaTiO3),with extremely fine-grain sizes.This material exhibits an inverse Hall–Petch relationship between grain size and strength,rooting in the inhomogeneous concentration of atomic strain and grain rotation.Furthermore,we present a theoretical model to predict the transition from the inverse Hall–Petch stage to the Hall–Petch stage based on strength variations with size,which aligns well with the simulation results.It has been found that the piezoelectric properties of the BaTiO3 are affected by polarization domain switching at various grain sizes.This study enhances our understanding of the atomic-scale mechanisms that contribute to the performance evolution of fine-grain nano-ferroelectric materials.It also provides valuable insights into the design of extremely small-scale ferroelectric components.展开更多
Minin-induced water inrush from a confined aquifer due to subsided floor karst collapse column(SKCC)is a type of serious disaster in the underground coal extraction.Karst collapse column(KCC)developed in a confined aq...Minin-induced water inrush from a confined aquifer due to subsided floor karst collapse column(SKCC)is a type of serious disaster in the underground coal extraction.Karst collapse column(KCC)developed in a confined aquifer occurs widely throughout northern China.A water inrush disaster from SKCC occurred in Taoyuan coal mine on February 3,2013.In order to analyze the effect of the KCC influence zone’s(KCCIZ)width and the entry driving distance of the water inrush through the fractured channels of the SKCC,the stress,seepage,and impact dynamics coupling equations were used tomodel the seepage rule,and a numerical FLAC3D model was created to determine the plastic zones,the vertical displacement development of the rockmass surrounding the entry driving working face(EDWF),and the seepage vector and water inflow development of the seepage field.The hysteretic mechanism of water inrush due to SKCC in Taoyuan coal mine was investigated.The results indicate that a water inrush disaster will occur when the width of the KCCIZ exceeds 16 m under a driving,which leads to the aquifer connecting with the fractured zones of the entry floor.Hysteretic water inrush disasters are related to the stress release rate of the surrounding rocks under the entry driving.When the entry driving exceeds about 10 m from the water inrush point,the stress release rate reaches about 100%,and a water inrush disaster occurs.展开更多
There were differences between real boundary and blast hole controlling boundary of irregular mined-out area in underground metal mines. There were errors in numerical analysis of stability for goaf, if it was analyze...There were differences between real boundary and blast hole controlling boundary of irregular mined-out area in underground metal mines. There were errors in numerical analysis of stability for goaf, if it was analyzed as regular 3D mined-out area and the influence of coupling stress-seepage-disturbance was not considered adequately. Taking a lead zinc mine as the background, the model was built by the coupling of Surpac and Midas-Gts based on the goaf model precisely measured by CMS.According to seepage stress fundamental equations based on the equivalent continuum mechanical and the theory about equivalent load of dynamic disturbance in deep-hole blasting, the stability of mined-out area under multi-field coupling of stress-seepage-dynamic disturbance was numerically analyzed. The results show that it is more consistent between the numerical analysis model based on the real model of irregular 3D shape goaf and the real situation, which could faithfully reappear the change rule of stress–strain about the surrounding rock under synthetic action of blasting dynamic loading and the seepage pressure. The mined-out area multi-field coupling formed by blasting excavation is stable. Based on combination of the advantages of the CMS,Surpac and Midas-Gts, and fully consideration of the effects of multi-field coupling, the accurate and effective way could be provided for numerical analysis of stability for mined-out area.展开更多
Human activities, such as blasting excavation, bolting, grouting and impounding of reservoirs, will lead to disturbances to rock masses and variations in their structural features and material properties. These engine...Human activities, such as blasting excavation, bolting, grouting and impounding of reservoirs, will lead to disturbances to rock masses and variations in their structural features and material properties. These engineering disturbances are important factors that would alter the natural evolutionary processes or change the multi-field interactions in the rock masses from their initial equilibrium states. The concept of generalized multi-field couplings was proposed by placing particular emphasis on the role of engineering disturbances in traditional multi-field couplings in rock masses. A mathematical model was then developed, in which the effects of engineering disturbances on the coupling-processes were described with changes in boundary conditions and evolutions in thermo-hydro-mechanical （THM） properties of the rocks. A parameter, d, which is similar to damage variables but has a broader physical meaning, was conceptually introduced to represent the degree of engineering disturbances and the couplings among the material properties. The effects of blasting excavation, bolting and grouting in rock engineering were illustrated with various field observations or theoretical results, on which the degree of disturbances and the variations in elastic moduli and permeabilities were particularly focused. The influences of excavation and groundwater drainage on the seepage flow and stability of the slopes were demonstrated with numerical simulations. The proposed approach was further employed to investigate the coupled hydro-mechanical responses of a high rock slope to excavation, bolting and impounding of the reservoir in the dam left abutment of Jinping I hydropower station. The impacts of engineering disturbances on the deformation and stability of the slope during construction and operation were demonstrated.展开更多
In order to study the multi-field coupling mechanical behavior of the simply-supported conductive rectangular thin plate under the condition of an externally lateral strong impulsive magnetic field, that is the dynami...In order to study the multi-field coupling mechanical behavior of the simply-supported conductive rectangular thin plate under the condition of an externally lateral strong impulsive magnetic field, that is the dynamic buckling phenomenon of the thin plates in the effect of the magnetic volume forces produced by the interaction between the eddy current and the magnetic fields, a FEM analysis program is developed to characterize the phenomena of magnetoelastic buckling and instability of the plates. The critical values of magnetic field for the three different initial vibrating modes are obtained, with a detailed discussion made on the effects of the lengththickness ratio a/h of the plate and the length-width ratio a/b as well as the impulse parameter on the critical value BOcr of the applied magnetic field.展开更多
Sandwiched functionally-graded piezoelectric semiconductor(FGPS)plates possess high strength and excellent piezoelectric and semiconductor properties,and have significant potential applications in micro-electro-mechan...Sandwiched functionally-graded piezoelectric semiconductor(FGPS)plates possess high strength and excellent piezoelectric and semiconductor properties,and have significant potential applications in micro-electro-mechanical systems.The multi-field coupling and free vibration of a sandwiched FGPS plate are studied,and the governing equation and natural frequency are derived with the consideration of electron movement.The material properties in the functionally-graded layers are assumed to vary smoothly,and the first-order shear deformation theory is introduced to derive the multi-field coupling in the plate.The total strain energy of the plate is obtained,and the governing equations are presented by using Hamilton’s principle.By introducing the boundary conditions,the coupling physical fields are solved.In numerical examples,the natural frequencies of sandwiched FGPS plates under different geometrical and physical parameters are discussed.It is found that the initial electron density can be used to modulate the natural frequencies and vibrational displacement of sandwiched FGPS plates in the case of nano-size.The effects of the material properties of FGPS layers on the natural frequencies are also examined in detail.展开更多
The 14th Five-Year Plan period is a critical period for China to achieve high-quality development. Based on super-efficiency slacks-based measure(SBM) model, grey-related analysis(GRA) and other models, this paper stu...The 14th Five-Year Plan period is a critical period for China to achieve high-quality development. Based on super-efficiency slacks-based measure(SBM) model, grey-related analysis(GRA) and other models, this paper studies the heterogeneity of the coupling relationship among technological innovation, industrial transformation and environmental efficiency in the Huaihai Economic Zone during the period of 2005-2019. In addition, it analyzes the coupling mechanism of single and binary systems to the ternary system, which is of great significance for the collaborative symbiosis among systems. The findings are as follows. 1) The technological innovation, industrial transformation and environmental efficiency(TIE) systems of the Huaihai Economic Zone had significant spatial-temporal heterogeneity. Although their evaluation value fluctuated, the development trends are all positive. Ultimately, technological innovation is characterized by being high in the northeast and low in the southwest around Xuzhou, while other systems are relatively staggered in space. 2) The coupling of TIE systems is in transition, lack of orderly integration and benign interaction. However, the developing trend of interaction is also upward, and a spatial pattern driven by Xuzhou and Linyi as the dual cores has gradually formed. Moreover, the coupling is mostly manifested as outdated technological innovation and industrial transformation. Except for the final coordination of regenerative cities, the other resource types are all in transition. Cities in all traffic locations are still in transition. The overall system interaction of cities on Longhai Line(Lanzhou-Lianyungang Railway) is relatively optimal, and cities on Xinshi Line(Xinxiang-Rizhao Railway) are accelerating toward synergy. 3) The coupling status of TIE systems depends on the development of the single system and the interaction of the binary(2E) system. The coupling is closely related to technological innovation and Technology-Industry system,and is hindered by the inefficient interaction of Technology-Environment system. Specifically, the synergy of regenerative cities is attributed to the advantage of a single system and the effective integration of 2E systems. Beneficial from the advantages of environmental efficiency, the cities on Xinshi Line promote the synergy of the 2E and TIE systems. Therefore, while the Huaihai Economic Zone stimulates the development potential of the single and 2E systems, it is necessary to amplify the superimposition effect of systems in accordance on the basis of resource and location.展开更多
We propose a multi-field implicit finite element method for analyzing the electromechanical behavior of dielectric elastomers. This method is based on a four-field variational principle, which includes displacement an...We propose a multi-field implicit finite element method for analyzing the electromechanical behavior of dielectric elastomers. This method is based on a four-field variational principle, which includes displacement and electric potential for the electromechanical coupling analysis, and additional independent fields to address the incompressible constraint of the hyperelastic material. Linearization of the variational form and finite element discretization are adopted for the numerical implementation. A general FEM program framework is devel- oped using C＋＋ based on the open-source finite element library deal.II to implement this proposed algorithm. Numerical examples demonstrate the accuracy, convergence properties, mesh-independence properties, and scalability of this method. We also use the method for eigenvalue analysis of a dielectric elastomer actuator subject to electromechanical loadings. Our finite element implementation is available as an online supplementary material.展开更多
The fault caused by a pantograph-catenary arc is the main factor that threatens the stability of high-speed railway energy transmission.Pantograph-catenary arc vertical drift is more severe than the case under normal ...The fault caused by a pantograph-catenary arc is the main factor that threatens the stability of high-speed railway energy transmission.Pantograph-catenary arc vertical drift is more severe than the case under normal pressure,as it is easy to develop the rigid busbar,which may lead to the flashover occurring around the support insulators.We establish a pantograph-catenary arc experiment and diagnosis platform to simulate low pressure and strong airflow environment.Meanwhile,the variation law of arc drift height with time under different air pressures and airflow velocities is analyzed.Moreover,arc drift characteristics and influencing factors are explored.The physical process of the arc column drifting to the rigid busbar with the jumping mechanism of the arc root on the rigid busbar is summarized.In order to further explore the mechanism of the above physical process,a multi-field stress coupling model is built,as the multi-stress variation law of arc is quantitatively evaluated.The dynamic action mechanism of multi-field stress on arc drifting characteristics is explored,as the physical mechanism of arc drifting under low pressure is theoretically explained.The research results provide theoretical support for arc suppression in high-altitude areas.展开更多
The marine biopharmaceutical industry(MBI)has been considered as an important part of the blue economy.The high-quality development of this industry depends on the high-level coordinated development of technological i...The marine biopharmaceutical industry(MBI)has been considered as an important part of the blue economy.The high-quality development of this industry depends on the high-level coordinated development of technological innovation system(TIS).In the present study,the coupling mechanism of industrial innovation input subsystem and innovation output subsystem was analyzed for the first time.On this basis,the development level and coupling coordination level of TIS in China’s MBI during 2008-2018 were empirically evaluated with the capacity coupling coordination model.Then,the obstacle factors were diagnosed and recognized with the obstacle model.The results showed that the innovation input index fluctuated at a low level in China’s MBI.The innovation output index has basically maintained a growth trend,whereas the quality of development was not high.Although the coupling coordination level of TIS showed a positive change as mild disordered→primary coordinated→well-coordinated,the development type of innovation system has changed from the lagging output of innovation into the lagging input of innovation.Insufficient input of innovation factors remained the main obstacle to the improvement of coordination level.Based on the above analysis,suggestions were put forward from the perspectives of policy and fund guarantees to improve the coupling coordination level in China’s MBI.展开更多
As an important part of buoy-type ocean monitoring systems,the inductively coupled mooring chain solves the problem of data cotransmission through the multinode sensors that it carries,which is significant for the rap...As an important part of buoy-type ocean monitoring systems,the inductively coupled mooring chain solves the problem of data cotransmission through the multinode sensors that it carries,which is significant for the rapid acquisition of fish,hydrology,and other information.This paper is based on a seawater channel transmission model with a depth of 300 m and a bandwidth of 2 MHz.An orthogonal frequency division multiplexing(OFDM)technology is used to overcome the multipath effect of signal transmission on a seawater medium.The adaptive technology is integrated into the OFDM,and an improved joint subcarrier and bit power allocation algorithm is proposed.This algorithm solves the problem of dynamic subcarrier allocation during the cotransmission of underwater multinode user data in seawater channels.The results show that the algorithm complexity can be reduced by 0.18126×10^(-2)s during one complete OFDM system data transmission by the improved greedy algorithm,and a total of 216 bits are transmitted by the OFDM.The normalized channel capacity can be improved by 0.012 bit s^(-1)Hz^(-1).At the bit error ratio(BER)of 10^(-3),the BER performance can be improved by approximately 6 d B.When the numbers of users are 4 and 8,the improved algorithm increases the channel capacity,and the higher the number of users,the more evident the channel capacity improvement effect is.The results of this paper have an important reference value for enhancing the transmission performance of inductively coupled mooring chain underwater multinode data.展开更多
Objective: To explore the potential predictors of a live birth (LB) outcome among subfertile couples of Asian ethnicity undergoing the first fertility treatment cycle;to assess the cumulative live birth rates after su...Objective: To explore the potential predictors of a live birth (LB) outcome among subfertile couples of Asian ethnicity undergoing the first fertility treatment cycle;to assess the cumulative live birth rates after successive cycles;and to determine the incidence rate of spontaneous conception (SC).Methods:Subfertile couples were grouped according to treatment modalities at the first fertility treatment cycle: intrauterine insemination (IUI),in vitro fertilization (IVF), intracytoplasmic sperm injection (ICSI) and no treatment, and were followed-up for duration up to seven years. Multivariable logistic regression analysis was used for statistical analyses. Results: Age of female subjects [35-38 years, odds ratio (OR): 0.39;≥39 years, OR: 0.14], uterine factor subfertility (OR: 5.24), and treatment modalities (ORs: IUI 0.25, IVF 2.33 and ICSI 1.91) significantly predicted a LB outcome (P<0.05). The cumulative live birth rates were 11.7% IUI, 41.5% IVF, 27.5% ICSI and 22.6% from frozen embryo transfer cycles. The cumulative SC rate was 24.6% in the non-treated group and 10.7% in the treated group. All LBs from IVF cycles were delivered by the second cycle and within four years, compared to SC delivery of within five years in the non-treated group and six years in the treated group. Conclusions:Age of female subject, uterine factor and modalities of treatment are significant predictors for LB outcome at the first cycle. Higher delivery rates could be achieved following fewer successive IVF cycles and within a shorter duration compared to SC.展开更多
基金supported by the National Natural Science Foundation of China (Nos.52374064,51974347,52474072)the Shandong Provincial Universities Youth Innovation and Technology Support Program (2022KJ065)。
文摘Injection-production coupling(IPC) technology holds substantial potential for boosting oil recovery and enhancing economic efficiency.Despite this potential,discussion on gas injection coupling,especially in relation to microscopic mechanisms,remains relatively sparse.This study utilizes microscopic visualization experiments to investigate the mechanisms of residual oil mobilization under various IPC scenarios,complemented by mechanical analysis at different stages.The research quantitatively assesses the degree of microscopic oil recovery and the distribution of residual oil across different injection-production methods.Findings reveal that during the initial phase of continuous gas injection(CGI),the process closely mimics miscible displacement,gradually transitioning to immiscible displacement as CO_(2)extraction progresses.Compared to CGI,the asynchronous injection-production(AIP) method improved the microscopic oil recovery rate by 6.58%.This enhancement is mainly attributed to significant variations in the pressure field in the AIP method,which facilitate the mobilization of columnar and porous re sidual oil.Furthermo re,the synchronous cycle injection(SCI) method increased microscopic oil recovery by 13.77% and 7.19% compared to CGI and AIP,respectively.In the SCI method,membrane oil displays filame ntary and Karman vo rtex street flow patterns.The dissolved and expanded crude oil te nds to accumulate and grow at the oil-solid interface due to adhesive forces,thereby reducing migration resistance.The study findings provide a theoretical foundation for improving oil recovery in lowpermeability reservoirs.
基金supported by the National Natural Science Foundation of China(Grant Nos.42477185,41602308)the Zhejiang Provincial Natural Science Foundation of China(Grant No.LY20E080005)the Postgraduate Course Construction Project of Zhejiang University of Science and Technology(Grant No.2021yjskj05).
文摘The utilization of multi-field coupling simulation methods has become a pivotal approach for the investigation of intricate fracture behavior and interaction mechanisms of rock masses in deep strata.The high temperatures,pressures and complex geological environments of deep strata frequently result in the coupling of multiple physical fields,including mechanical,thermal and hydraulic fields,during the fracturing of rocks.This review initially presents an overview of the coupling mechanisms of these physical fields,thereby elucidating the interaction processes ofmechanical,thermal,and hydraulic fields within rockmasses.Secondly,an in-depth analysis ofmulti-field coupling is conducted from both spatial and temporal perspectives,with the introduction of simulation methods for a range of scales.It emphasizes cross-scale coupling methodologies for the transfer of rock properties and physical field data,including homogenization techniques,nested coupling strategies and data-driven approaches.To address the discontinuous characteristics of the rock fracture process,the review provides a detailed explanation of continuousdiscontinuous couplingmethods,to elucidate the evolution of rock fracturing and deformationmore comprehensively.In conclusion,the review presents a summary of the principal points,challenges and future directions of multi-field coupling simulation research.It also puts forward the potential of integrating intelligent algorithms with multi-scale simulation techniques to enhance the accuracy and efficiency of multi-field coupling simulations.This offers novel insights into multi-field coupling simulation analysis in deep rock masses.
基金Project supported by the National Natural Science Foundation of China(No.11672265)。
文摘Sandwich piezoelectric semiconductor(PS)structures have significant applications in multi-functional semiconductor devices.The analysis of multi-field coupling behaviors of PS structures is of fundamental importance in developing novel PS devices.In this paper,we develop a general temperature-deformation-polarization-carrier(TDPC)coupling model for sandwich-type PS beams involving pyroelectricity under thermal loadings,based on three-dimensional(3D)basic equations of the thermo-piezoelectric semiconductor(TPS).We derive analytical solutions for extensional,bending,and buckling deformations of simply-supported sandwich n-type PS beams subjected to open-circuit and electrically isolated boundary conditions.The accuracy of the proposed model in this paper is verified through finite element simulations implemented in the COMSOL software.Numerical results show that the initial electron concentration and the thickness ratio of the PS layer to the beam's total thickness have a significant effect on thermally induced extensional and bending responses,as well as critical buckling mechanical and thermal loadings.This study provides a theoretical framework and guidance for designing semiconductor devices based on sandwich PS beam structures.
文摘This study presents a comprehensive mechanical analysis of P110S oil tubing subjected to thermal and chemical coupling effects,with particular attention to the presence of rectangular corrosion defects.Drawing on the material’s stress–strain constitutive behavior,thermal expansion coefficient,thermal conductivity,and electrochemical test data,the research incorporates geometric nonlinearities arising from large deformations induced by corrosion.A detailed three-dimensional finite element(FE)model of the corroded P110S tubing is developed to simulate its response under complex loading conditions.The proposed model is rigorously validated through full-scale burst experiments and analytical calculations based on theoretical formulations.Building upon this validation,the Extended Finite Element Method(XFEM)and a failure criterion grounded in damage evolution mechanics are applied to investigate the mechanical behavior of the tubing under the coupled influences of temperature,stress,and chemical corrosion.Special emphasis is placed on the role of rectangular corrosion features in determining failure mechanisms.To further elucidate the impact of multiple interacting parameters,a sensitivity analysis is performed by integrating grey correlation theory with simulation outcomes.Based on these findings,the study systematically explores the elastic–plastic deformation process,crack initiation and propagation behavior,and the burst failure response of tubing specimens with varying axial lengths and depths of corrosion.The proposed methodology provides a robust predictive framework for petroleum engineers to evaluate fracture pressure,diagnose failure modes,assess operational risks,and optimize production strategies.
基金Projects(12072102,12102129)supported by the National Natural Science Foundation of ChinaProject(DM2022B01)supported by the Key Laboratory of Safe Mining of Deep Metal Mines,Ministry of Education,ChinaProject(JZ-008)supported by the Six Talent Peaks Project in Jiangsu Province,China。
文摘In this study,a series of triaxial tests are conducted on sandstone specimens to investigate the evolution of their mechanics and permeability characteristics under the combined action of immersion corrosion and seepage of different chemical solutions.It is observed that with the increase of confining pressure,the peak stress,dilatancy stress,dilatancy stress ratio,peak strain,and elastic modulus of the sandstone increase while the Poisson ratio decreases and less secondary cracks are produced when the samples are broken.The pore pressure and confining pressure have opposite influences on the mechanical properties.With the increase of the applied axial stress,three stages are clearly identified in the permeability evolution curves:initial compaction stage,linear elasticity stage and plastic deformation stage.The permeability reaches the maximum value when the highest volumetric dilatancy is obtained.In addition,the hydrochemical action of salt solution with pH=7 and 4 has an obvious deteriorating effect on the mechanical properties and induces the increase of permeability.The obtained results will be useful in engineering to understand the mechanical and seepage properties of sandstone under the coupled chemical-seepage-stress multiple fields.
基金financially supported by the National Key Research and Development Plan(2023YFC2811001)the National Natural Science Foundation of China(42206233)the Taishan Scholars Program(tsqn202312280,tsqn202306297)。
文摘Hydraulic fracturing technology has played an important role in the exploitation of unconventional oil and gas resources,however,its application to gas hydrate reservoirs has been rarely studied.Currently,there is still limited understanding of the propagation and extension of fractures around the wellbore during the fracturing process of horizontal wells in hydrate reservoirs,as well as the stress interference patterns between fractures.This study simulates hydraulic fracturing processes in hydrate reservoirs using a fluidsolid coupling discrete element method(DEM),and analyzes the impacts of hydrate saturation and geological and engineering factors on fracture extension and stress disturbance.The results show that hydraulic fracturing is more effective when hydrate saturation exceeds 30%and that fracture pressure increases with saturation.The increase in horizontal stress differential enhances the directionality of fracture propagation and reduces stress disturbance.The distribution uniformity index(DUI)reveals that injection pressure is directly proportional to the number of main fractures and inversely proportional to fracturing time,with fracturing efficiency depending on the spacing between injection points and the distance between wells.This work may provide reference for the commercial exploitation of natural gas hydrates.
基金supported by the Second Tibetan Plateau Scientific Expedition and Research Program(STEP)(No.2019QZKK0904)the National Natural Science Foundation of China(Nos.42107190,41972287 and 42277144)。
文摘Permafrost regions of Qilian Mountains in China are rich in gas hydrate resources.Once greenhouse gases in deep frozen layer are released into the atmosphere during hydrate mining,a series of negative consequences occur.This study aims to evaluate the impact of hydrate thermal exploitation on regional permafrost and carbon budgets based on a multi-physical field coupling simulation.The results indicate that the permeability of the frozen soil is anisotropic,and the low permeability frozen layer can seal the methane gas in the natural state.Heat injection mining of hydrates causes the continuous melting of permafrost and the escape of methane gas,which transforms the regional permafrost from a carbon sink to a carbon source.A higher injection temperature concentrates the heat and causes uneven melting of the upper frozen layer,which provides a dominant channel for methane gas and results in increased methane emissions.However,dense heat injection wells cause more uniform melting of the lower permafrost layer,and the melting zone does not extend to the upper low permeability formation,which cannot provide advantageous channels for methane gas.Therefore,a reasonable and dense number of heat injection wells can reduce the risk of greenhouse gas emissions during hydrate exploitation.
基金the National Natural Science Foundation of China(22265021)the Aeronautical Science Foundation of China(2020Z056056003).
文摘Metal–organic gel(MOG)derived composites are promising multi-functional materials due to their alterable composition,identifiable chemical homogeneity,tunable shape,and porous structure.Herein,stable metal–organic hydrogels are prepared by regulating the complexation effect,solution polarity and curing speed.Meanwhile,collagen peptide is used to facilitate the fabrication of a porous aerogel with excellent physical properties as well as the homogeneous dispersion of magnetic particles during calcination.Subsequently,two kinds of heterometallic magnetic coupling systems are obtained through the application of Kirkendall effect.FeCo/nitrogen-doped carbon(NC)aerogel demonstrates an ultra-strong microwave absorption of−85 dB at an ultra-low loading of 5%.After reducing the time taken by atom shifting,a FeCo/Fe3O4/NC aerogel containing virus-shaped particles is obtained,which achieves an ultra-broad absorption of 7.44 GHz at an ultra-thin thickness of 1.59 mm due to the coupling effect offered by dual-soft-magnetic particles.Furthermore,both aerogels show excellent thermal insulation property,and their outstanding radar stealth performances in J-20 aircraft are confirmed by computer simulation technology.The formation mechanism of MOG is also discussed along with the thermal insulation and electromagnetic wave absorption mechanism of the aerogels,which will enable the development and application of novel and lightweight stealth coatings.
基金supported by the National Natural Science Foundation of China(Nos.12172117,12372154)National Science and Technology Major Project(No.J2019-1II-0010-0054)+1 种基金National Numerical Windtunnel(No.NNW2019-JT01-023)High-Performance Computing Center of Hebei University。
文摘Tailoring grain size can improve the strength of polycrystals by regulating the proportion of grains to grain boundaries and the interaction area.As the grain size decreases to the nanoscale,the deformation mechanism in polycrystals shifts from being primarily mediated by dislocations to deformation occurring within the grains and grain boundaries.However,the mechanism responsible for fine-grain strengthening in ferroelectric materials remains unclear,primarily due to the complex multi-field coupling effect arising from spontaneous polarization.Through molecular dynamics simulations,we investigate the strengthening mechanism of barium titanate(BaTiO3),with extremely fine-grain sizes.This material exhibits an inverse Hall–Petch relationship between grain size and strength,rooting in the inhomogeneous concentration of atomic strain and grain rotation.Furthermore,we present a theoretical model to predict the transition from the inverse Hall–Petch stage to the Hall–Petch stage based on strength variations with size,which aligns well with the simulation results.It has been found that the piezoelectric properties of the BaTiO3 are affected by polarization domain switching at various grain sizes.This study enhances our understanding of the atomic-scale mechanisms that contribute to the performance evolution of fine-grain nano-ferroelectric materials.It also provides valuable insights into the design of extremely small-scale ferroelectric components.
基金supported by the National Natural Science Foundation of China(Project Nos.51708185,41807209 and 51778215,SC,http://www.nsfc.gov.cn)the Young Teacher Foundation of HPU(Project No.2019XQG-19,SC,http://www6.hpu.edu.cn/rsc)+1 种基金the Henan Provincial Youth Talent Promotion Program(Project No.2020HYTP003,SC,http://www.hast.net.cn:82)the Doctor Foundation of Henan Polytechnic University(Project No.B2017-51 and B2017-53,SC,http://kxc.hpu.edu.cn).
文摘Minin-induced water inrush from a confined aquifer due to subsided floor karst collapse column(SKCC)is a type of serious disaster in the underground coal extraction.Karst collapse column(KCC)developed in a confined aquifer occurs widely throughout northern China.A water inrush disaster from SKCC occurred in Taoyuan coal mine on February 3,2013.In order to analyze the effect of the KCC influence zone’s(KCCIZ)width and the entry driving distance of the water inrush through the fractured channels of the SKCC,the stress,seepage,and impact dynamics coupling equations were used tomodel the seepage rule,and a numerical FLAC3D model was created to determine the plastic zones,the vertical displacement development of the rockmass surrounding the entry driving working face(EDWF),and the seepage vector and water inflow development of the seepage field.The hysteretic mechanism of water inrush due to SKCC in Taoyuan coal mine was investigated.The results indicate that a water inrush disaster will occur when the width of the KCCIZ exceeds 16 m under a driving,which leads to the aquifer connecting with the fractured zones of the entry floor.Hysteretic water inrush disasters are related to the stress release rate of the surrounding rocks under the entry driving.When the entry driving exceeds about 10 m from the water inrush point,the stress release rate reaches about 100%,and a water inrush disaster occurs.
基金Project(2012BAK09B02-05)supported by the National"Twelfth Five"Science and Technology Support Program,ChinaProject(51274250)supported by the National Natural Science Foundation of China+2 种基金Project(2013zzts057)supported by the Fundamental Research Funds for the Central Universities,ChinaProject(11KF02)supported by the Research Fund of the State Key Laboratory of Coal Resources and Mine safety,CUMT,ChinaProject(2012M511417)supported by China Postdoctoral Science Foundation
文摘There were differences between real boundary and blast hole controlling boundary of irregular mined-out area in underground metal mines. There were errors in numerical analysis of stability for goaf, if it was analyzed as regular 3D mined-out area and the influence of coupling stress-seepage-disturbance was not considered adequately. Taking a lead zinc mine as the background, the model was built by the coupling of Surpac and Midas-Gts based on the goaf model precisely measured by CMS.According to seepage stress fundamental equations based on the equivalent continuum mechanical and the theory about equivalent load of dynamic disturbance in deep-hole blasting, the stability of mined-out area under multi-field coupling of stress-seepage-dynamic disturbance was numerically analyzed. The results show that it is more consistent between the numerical analysis model based on the real model of irregular 3D shape goaf and the real situation, which could faithfully reappear the change rule of stress–strain about the surrounding rock under synthetic action of blasting dynamic loading and the seepage pressure. The mined-out area multi-field coupling formed by blasting excavation is stable. Based on combination of the advantages of the CMS,Surpac and Midas-Gts, and fully consideration of the effects of multi-field coupling, the accurate and effective way could be provided for numerical analysis of stability for mined-out area.
基金Supported by the National Natural Science Fund for Distinguished Young Scholars of China(50725931)the National Natural Science Foundation of China(50839004,51079107)the Supporting Program of the "Eleventh Five-year Plan" for Sci & Tech Research of China(2008BAB29B01)
文摘Human activities, such as blasting excavation, bolting, grouting and impounding of reservoirs, will lead to disturbances to rock masses and variations in their structural features and material properties. These engineering disturbances are important factors that would alter the natural evolutionary processes or change the multi-field interactions in the rock masses from their initial equilibrium states. The concept of generalized multi-field couplings was proposed by placing particular emphasis on the role of engineering disturbances in traditional multi-field couplings in rock masses. A mathematical model was then developed, in which the effects of engineering disturbances on the coupling-processes were described with changes in boundary conditions and evolutions in thermo-hydro-mechanical （THM） properties of the rocks. A parameter, d, which is similar to damage variables but has a broader physical meaning, was conceptually introduced to represent the degree of engineering disturbances and the couplings among the material properties. The effects of blasting excavation, bolting and grouting in rock engineering were illustrated with various field observations or theoretical results, on which the degree of disturbances and the variations in elastic moduli and permeabilities were particularly focused. The influences of excavation and groundwater drainage on the seepage flow and stability of the slopes were demonstrated with numerical simulations. The proposed approach was further employed to investigate the coupled hydro-mechanical responses of a high rock slope to excavation, bolting and impounding of the reservoir in the dam left abutment of Jinping I hydropower station. The impacts of engineering disturbances on the deformation and stability of the slope during construction and operation were demonstrated.
基金Project supported by the National Natural Sciences Foundation of China (Nos. 10132010 and 90405005).
文摘In order to study the multi-field coupling mechanical behavior of the simply-supported conductive rectangular thin plate under the condition of an externally lateral strong impulsive magnetic field, that is the dynamic buckling phenomenon of the thin plates in the effect of the magnetic volume forces produced by the interaction between the eddy current and the magnetic fields, a FEM analysis program is developed to characterize the phenomena of magnetoelastic buckling and instability of the plates. The critical values of magnetic field for the three different initial vibrating modes are obtained, with a detailed discussion made on the effects of the lengththickness ratio a/h of the plate and the length-width ratio a/b as well as the impulse parameter on the critical value BOcr of the applied magnetic field.
基金supported by the National Natural Science Foundation of China(Nos.12172236 and 12202289)。
文摘Sandwiched functionally-graded piezoelectric semiconductor(FGPS)plates possess high strength and excellent piezoelectric and semiconductor properties,and have significant potential applications in micro-electro-mechanical systems.The multi-field coupling and free vibration of a sandwiched FGPS plate are studied,and the governing equation and natural frequency are derived with the consideration of electron movement.The material properties in the functionally-graded layers are assumed to vary smoothly,and the first-order shear deformation theory is introduced to derive the multi-field coupling in the plate.The total strain energy of the plate is obtained,and the governing equations are presented by using Hamilton’s principle.By introducing the boundary conditions,the coupling physical fields are solved.In numerical examples,the natural frequencies of sandwiched FGPS plates under different geometrical and physical parameters are discussed.It is found that the initial electron density can be used to modulate the natural frequencies and vibrational displacement of sandwiched FGPS plates in the case of nano-size.The effects of the material properties of FGPS layers on the natural frequencies are also examined in detail.
基金Under the auspices of National Natural Science Foundation of China(No.41971158)National Social Science Foundation of China(No.20BJL106)+1 种基金Cultural Experts and Four batches Talents Independently Selected Topic Project(No.ZXGZ[2018]86)Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.KYCX21_0357)。
文摘The 14th Five-Year Plan period is a critical period for China to achieve high-quality development. Based on super-efficiency slacks-based measure(SBM) model, grey-related analysis(GRA) and other models, this paper studies the heterogeneity of the coupling relationship among technological innovation, industrial transformation and environmental efficiency in the Huaihai Economic Zone during the period of 2005-2019. In addition, it analyzes the coupling mechanism of single and binary systems to the ternary system, which is of great significance for the collaborative symbiosis among systems. The findings are as follows. 1) The technological innovation, industrial transformation and environmental efficiency(TIE) systems of the Huaihai Economic Zone had significant spatial-temporal heterogeneity. Although their evaluation value fluctuated, the development trends are all positive. Ultimately, technological innovation is characterized by being high in the northeast and low in the southwest around Xuzhou, while other systems are relatively staggered in space. 2) The coupling of TIE systems is in transition, lack of orderly integration and benign interaction. However, the developing trend of interaction is also upward, and a spatial pattern driven by Xuzhou and Linyi as the dual cores has gradually formed. Moreover, the coupling is mostly manifested as outdated technological innovation and industrial transformation. Except for the final coordination of regenerative cities, the other resource types are all in transition. Cities in all traffic locations are still in transition. The overall system interaction of cities on Longhai Line(Lanzhou-Lianyungang Railway) is relatively optimal, and cities on Xinshi Line(Xinxiang-Rizhao Railway) are accelerating toward synergy. 3) The coupling status of TIE systems depends on the development of the single system and the interaction of the binary(2E) system. The coupling is closely related to technological innovation and Technology-Industry system,and is hindered by the inefficient interaction of Technology-Environment system. Specifically, the synergy of regenerative cities is attributed to the advantage of a single system and the effective integration of 2E systems. Beneficial from the advantages of environmental efficiency, the cities on Xinshi Line promote the synergy of the 2E and TIE systems. Therefore, while the Huaihai Economic Zone stimulates the development potential of the single and 2E systems, it is necessary to amplify the superimposition effect of systems in accordance on the basis of resource and location.
基金the support under A*STAR SERC grant (132-183-0025)
文摘We propose a multi-field implicit finite element method for analyzing the electromechanical behavior of dielectric elastomers. This method is based on a four-field variational principle, which includes displacement and electric potential for the electromechanical coupling analysis, and additional independent fields to address the incompressible constraint of the hyperelastic material. Linearization of the variational form and finite element discretization are adopted for the numerical implementation. A general FEM program framework is devel- oped using C＋＋ based on the open-source finite element library deal.II to implement this proposed algorithm. Numerical examples demonstrate the accuracy, convergence properties, mesh-independence properties, and scalability of this method. We also use the method for eigenvalue analysis of a dielectric elastomer actuator subject to electromechanical loadings. Our finite element implementation is available as an online supplementary material.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51707166,51922090,U1966602,and U19A20105)the Sichuan Science and Technology General Project(Grant Nos.2019YJ0213 and2019JDJQ0019)。
文摘The fault caused by a pantograph-catenary arc is the main factor that threatens the stability of high-speed railway energy transmission.Pantograph-catenary arc vertical drift is more severe than the case under normal pressure,as it is easy to develop the rigid busbar,which may lead to the flashover occurring around the support insulators.We establish a pantograph-catenary arc experiment and diagnosis platform to simulate low pressure and strong airflow environment.Meanwhile,the variation law of arc drift height with time under different air pressures and airflow velocities is analyzed.Moreover,arc drift characteristics and influencing factors are explored.The physical process of the arc column drifting to the rigid busbar with the jumping mechanism of the arc root on the rigid busbar is summarized.In order to further explore the mechanism of the above physical process,a multi-field stress coupling model is built,as the multi-stress variation law of arc is quantitatively evaluated.The dynamic action mechanism of multi-field stress on arc drifting characteristics is explored,as the physical mechanism of arc drifting under low pressure is theoretically explained.The research results provide theoretical support for arc suppression in high-altitude areas.
基金supported by the National Natural Science Foundation of China(Nos.42176126,42076221)the Department of Marine Strategic Planning and Economy,Ministry of Natural Resources of China,and Marine Development Research Society of China(No.CAMA201817).
文摘The marine biopharmaceutical industry(MBI)has been considered as an important part of the blue economy.The high-quality development of this industry depends on the high-level coordinated development of technological innovation system(TIS).In the present study,the coupling mechanism of industrial innovation input subsystem and innovation output subsystem was analyzed for the first time.On this basis,the development level and coupling coordination level of TIS in China’s MBI during 2008-2018 were empirically evaluated with the capacity coupling coordination model.Then,the obstacle factors were diagnosed and recognized with the obstacle model.The results showed that the innovation input index fluctuated at a low level in China’s MBI.The innovation output index has basically maintained a growth trend,whereas the quality of development was not high.Although the coupling coordination level of TIS showed a positive change as mild disordered→primary coordinated→well-coordinated,the development type of innovation system has changed from the lagging output of innovation into the lagging input of innovation.Insufficient input of innovation factors remained the main obstacle to the improvement of coordination level.Based on the above analysis,suggestions were put forward from the perspectives of policy and fund guarantees to improve the coupling coordination level in China’s MBI.
基金the National Natural Science Foundation of China(No.62071329)the National Science Foundation of Tianjin(No.20JCYB JC00130)。
文摘As an important part of buoy-type ocean monitoring systems,the inductively coupled mooring chain solves the problem of data cotransmission through the multinode sensors that it carries,which is significant for the rapid acquisition of fish,hydrology,and other information.This paper is based on a seawater channel transmission model with a depth of 300 m and a bandwidth of 2 MHz.An orthogonal frequency division multiplexing(OFDM)technology is used to overcome the multipath effect of signal transmission on a seawater medium.The adaptive technology is integrated into the OFDM,and an improved joint subcarrier and bit power allocation algorithm is proposed.This algorithm solves the problem of dynamic subcarrier allocation during the cotransmission of underwater multinode user data in seawater channels.The results show that the algorithm complexity can be reduced by 0.18126×10^(-2)s during one complete OFDM system data transmission by the improved greedy algorithm,and a total of 216 bits are transmitted by the OFDM.The normalized channel capacity can be improved by 0.012 bit s^(-1)Hz^(-1).At the bit error ratio(BER)of 10^(-3),the BER performance can be improved by approximately 6 d B.When the numbers of users are 4 and 8,the improved algorithm increases the channel capacity,and the higher the number of users,the more evident the channel capacity improvement effect is.The results of this paper have an important reference value for enhancing the transmission performance of inductively coupled mooring chain underwater multinode data.
文摘Objective: To explore the potential predictors of a live birth (LB) outcome among subfertile couples of Asian ethnicity undergoing the first fertility treatment cycle;to assess the cumulative live birth rates after successive cycles;and to determine the incidence rate of spontaneous conception (SC).Methods:Subfertile couples were grouped according to treatment modalities at the first fertility treatment cycle: intrauterine insemination (IUI),in vitro fertilization (IVF), intracytoplasmic sperm injection (ICSI) and no treatment, and were followed-up for duration up to seven years. Multivariable logistic regression analysis was used for statistical analyses. Results: Age of female subjects [35-38 years, odds ratio (OR): 0.39;≥39 years, OR: 0.14], uterine factor subfertility (OR: 5.24), and treatment modalities (ORs: IUI 0.25, IVF 2.33 and ICSI 1.91) significantly predicted a LB outcome (P<0.05). The cumulative live birth rates were 11.7% IUI, 41.5% IVF, 27.5% ICSI and 22.6% from frozen embryo transfer cycles. The cumulative SC rate was 24.6% in the non-treated group and 10.7% in the treated group. All LBs from IVF cycles were delivered by the second cycle and within four years, compared to SC delivery of within five years in the non-treated group and six years in the treated group. Conclusions:Age of female subject, uterine factor and modalities of treatment are significant predictors for LB outcome at the first cycle. Higher delivery rates could be achieved following fewer successive IVF cycles and within a shorter duration compared to SC.
