As a cleaner,high-efficiency,and low-carbon fuel,natural gas has been an important fuel resource for China.To achieve a substantial increase in natural gas demand,China has sought to reform its natural gas pricing mec...As a cleaner,high-efficiency,and low-carbon fuel,natural gas has been an important fuel resource for China.To achieve a substantial increase in natural gas demand,China has sought to reform its natural gas pricing mechanism.Employing a set of unbalanced panel data for China’s 30 provinces covering 1999-2015,this study aims to estimate the evolving price and income elasticities of natural gas demand and explore the effect of natural gas price reform in China.For this purpose,a series of econometric techniques allowing for cross-sectional dependence and slope homogeneity is utilized.The results suggest that although natural gas demand in China still lacks negative price elasticity,the phenomenon is improving.Moreover,the estimates suggest that natural gas demand in China is indeed becoming increasingly sensitive to income changes.Our estimates also provide strong evidence in favor of the effect of natural gas price reform on the change in price elasticity as the price elasticity decreases in five of the seven regions.In addition,the results indicate large variations in the change in price and income elasticities of natural gas demand across China’s regions.Natural gas demand is becoming more price inelastic in Southwest China and Northwest China,while such demand in North China and East China responds less sensitively to income changes.These findings offer several policy suggestions for the reform of China’s natural gas market at the national and regional levels.展开更多
Elasticity of substitution is traditionally estimated while ignoring technical and allocative inefficiencies,which could bias the estimates.We estimate elasticity of substitution for Chinese energy-intensive sectors b...Elasticity of substitution is traditionally estimated while ignoring technical and allocative inefficiencies,which could bias the estimates.We estimate elasticity of substitution for Chinese energy-intensive sectors by incorporating these inefficiencies.The results show most of the sectors are low substitutes between input factors and stress important differences among energy-intensive sectors.Concerning the cross-price elasticity for energy,with respect to capital(labor),the sectors are mainly characterized by weak substitutability or complementary.These imply the production structure is quite rigid and capital cannot be so readily used as a substitute for energy.展开更多
Urban metabolism is a complex system of materials, energy, population and environment, which usually can be measured by the Emergy Synthesis(ES) and the Slacks-Based Measure(SBM) approach. In this paper, by employing ...Urban metabolism is a complex system of materials, energy, population and environment, which usually can be measured by the Emergy Synthesis(ES) and the Slacks-Based Measure(SBM) approach. In this paper, by employing the two approaches of ES and SBM, as well as metabolic evolution index, urban metabolic stocks, efficiencies and elasticity of 31 Chinese cities are evaluated in a systematic way. The results imply that over the last decade(2000–2010), most of the cities, such as Chongqing, Nanjing, Shijiazhuang, Hangzhou, were experiencing drastic urban metabolic efficiency decline accompanied with a moderate decrease of industrial outputs. By contrast, metropolises and specialized cities have improved their urban metabolic performances, with higher output-input ratio and fewer undesirable outputs. However, their exported emergy experienced a substantial increase as well. It is concluded that local urban management might develop policies to diversify urban renewable supplies and address the undesirable output problems. The urban emergy of renewable resources should be specified as a prime focus for future research. In addition, mechanisms of different urban metabolic models will also be necessary for researchers.展开更多
This paper presents a general framework that can be used to estimate direct and cross elasticities for freight transport using a network model. This methodology combines operational research (network assignments in a ...This paper presents a general framework that can be used to estimate direct and cross elasticities for freight transport using a network model. This methodology combines operational research (network assignments in a geographical information system) with more classical econometrics (multinomial logit choice models). The application of the method to a real-world case is illustrated by a simple model that relies on the generalized cost of transport as the only explanatory variable in the utility function. The methodological framework allows, however, for the implementation of more complex functions. Beside the generalized cost functions for road, rail and inland waterways transport, the network model needs origin-destination matrixes and digitized networks. They are imported from ETIS Plus, a European transport policy information system. A set of direct and cross elasticities is presented. The estimated values are obtained using two methods: the first computes standard elasticities, while the second estimates arc elasticities. Figures are presented for Europe and for a large region around the Benelux countries, where more competition exists between the three modes of interest.展开更多
This paper classifies total fixed capital into three categories,namely,economic infrastructure capital,social infrastructure capital and non-infrastructure capital,and then offers complete and detailed estimates of th...This paper classifies total fixed capital into three categories,namely,economic infrastructure capital,social infrastructure capital and non-infrastructure capital,and then offers complete and detailed estimates of the national time series data(1981-2012) and the provincial panel data of 31 administrative regions(1997-2012).On this basis,this paper estimates the output elasticities of the three categories of capital and then tests whether or not the production function of China shows constant returns to scale.展开更多
Which rule of mixture is the best for predicting the overall elastic properties of polyphase rocks based on the elastic properties and volume fractions of their constituents? In order to address this question, we sint...Which rule of mixture is the best for predicting the overall elastic properties of polyphase rocks based on the elastic properties and volume fractions of their constituents? In order to address this question, we sintered forsterite-enstatite polycrystalline aggregates with a varied forsterite volume fraction (0, 0.2, 0.4, 0.5, 0.6, 0.8, and 1.0). Elastic properties (shear, bulk, and Young’s moduli) of these synthesized composites were measured as a function of pressure up to 3.0 GPa in a liquid-medium piston-cylinder apparatus using a high-precision ultrasonic interferometric technique. The experimental data can be much better described by the shear-lag model than by the commonly used simple models such as Voigt, Ruess and Hill averages, Hashin-Shtrikman bounds, Ravichandran bounds, Halpin-Tsai equations, and Paul’s calculations. We attributed this to the fact that the elastic interaction and stress transfer between phases are neglected in all the models except for the shear-lag model. In particular,展开更多
Oxygen carriers play a fundamental role in chemical looping combustion(CLC).Iron-based carriers have been extensively investigated owing to their abundance and environmentally friendly.However,the reactivity and separ...Oxygen carriers play a fundamental role in chemical looping combustion(CLC).Iron-based carriers have been extensively investigated owing to their abundance and environmentally friendly.However,the reactivity and separability of iron-based carriers require further enhancement.This study investigates the effect of the concentration of Mn doping on reactivity,elastic properties and magnetic properties based on density functional theory(DFT)calculations.Theoretical results demonstrate that Mn doping effectively enhances reactivity by reducing the oxygen vacancy formation energy(E_(vac))from 2.33 to 0.87 eV.However,Mn doping introduces HV/EV Ms lattice distortions that deteriorate elastic properties,thereby reducing wear resistance,as evidenced by a 54.54%decrease in the hardness-to-Young's modulus ratio(H_(v)/E_(v))forα-Fe_(2)O_(3)and an 83.33%reduction for Fe_(3)O_(4).Furthermore,Mn doping also modifies magnetic properties.The maximum of saturation magnetization(M_(s))of Fe_(3)O_(4)reaches 121.02 emu/g at 33.33%Mn doping concentration.Finally,systematic evaluation identifies 33.33%as the optimal Mn doping concentration,achieving a balance in enhanced reactivity,superior magnetic performance,and retained elastic stability.展开更多
Dear Editor,This letter presents a model predictive control(MPC)scheme for human-robot interaction(HRI)in a multi-joint exoskeleton robot(ER)driven by series elastic actuator(SEA).The proposed scheme in robot-in-charg...Dear Editor,This letter presents a model predictive control(MPC)scheme for human-robot interaction(HRI)in a multi-joint exoskeleton robot(ER)driven by series elastic actuator(SEA).The proposed scheme in robot-in-charge(RIC)mode facilitates the ER driven by SEA to provide the required assistance and support for the subject.展开更多
The testing of large structures is limited by high costs and long cycles, making scaling methods an attractive solution. However, the scaling process of elastic rings introduces complexities in multi-parameter geometr...The testing of large structures is limited by high costs and long cycles, making scaling methods an attractive solution. However, the scaling process of elastic rings introduces complexities in multi-parameter geometric distortions, leading to a diminution in the predictive accuracy of the distorted similitude. To address this challenge, this study formulates a novel set of scaling laws, tailored to account for the intricate geometric distortions associated with elastic rings. The proposed scaling laws are formulated based on the intrinsic deformation characteristics of elastic rings, rather than the traditional systemic governing equations. Numerical and experimental cases are conducted to assess the efficacy and precision of the proposed scaling laws, and the obtained results are compared with those achieved by traditional methods. The outcomes demonstrate that the scaling laws put forth by this study significantly enhance the predictive capabilities for deformations of elastic rings.展开更多
To investigate the influence of coarse aggregate parent rock properties on the elastic modulus of concrete,the mineralogical properties and stress-strain curves of granite and dolomite parent rocks,as well as the stre...To investigate the influence of coarse aggregate parent rock properties on the elastic modulus of concrete,the mineralogical properties and stress-strain curves of granite and dolomite parent rocks,as well as the strength and elastic modulus of mortar and concrete prepared with mechanism aggregates of the corresponding lithology,and the stress-strain curves of concrete were investigated.In this paper,a coarse aggregate and mortar matrix bonding assumption is proposed,and a prediction model for the elastic modulus of mortar is established by considering the lithology of the mechanism sand and the slurry components.An equivalent coarse aggregate elastic modulus model was established by considering factors such as coarse aggregate particle size,volume fraction,and mortar thickness between coarse aggregates.Based on the elastic modulus of the equivalent coarse aggregate and the remaining mortar,a prediction model for the elastic modulus of the two and three components of concrete in series and then in parallel was established,and the predicted values differed from the measured values within 10%.It is proposed that the coarse aggregate elastic modulus in highstrength concrete is the most critical factor affecting the elastic modulus of concrete,and as the coarse aggregate elastic modulus increases by 27.7%,the concrete elastic modulus increases by 19.5%.展开更多
Background Computed tomography(CT) and cone-beam computed tomography(CBCT) image registration play pivotal roles in computer-assisted navigation for orthopedic surgery. Traditional methods often apply uniform deformat...Background Computed tomography(CT) and cone-beam computed tomography(CBCT) image registration play pivotal roles in computer-assisted navigation for orthopedic surgery. Traditional methods often apply uniform deformation models, neglecting the biomechanical differences between rigid structures and soft tissues, which compromises registration accuracy, especially during significant bone displacements. Method To address this issue, we introduce RE-Reg, a rigid-elastic CT-CBCT image registration framework that jointly learns rigid bone motion and soft tissue deformation. RE-Reg incorporates a rigid alignment(RA) module to estimate global bone motion and an elastic deformation(ED) module to model soft tissue deformation, preserving bony structures through bone shape preservation(BSP) loss. Result Our comprehensive evaluation on publicly available datasets demonstrates that RE-Reg significantly outperforms existing methods in terms of registration accuracy and rigid bone structure preservation, achieving a 1.3% improvement in Dice similarity coefficient(DSC) and a 23% reduction in rigid bone deformation(%Δvol) compared with the best baseline. Conclusion This framework not only enhances anatomical fidelity but also ensures biomechanical plausibility and provides a valuable tool for image-guided orthopedic surgery. This code is available athttps://github.com/Zq-Huang/RE-Reg.展开更多
The contact deformation and buckling of elastic rods against rigid surfaces represent a prevalent phenomenon in applications such as oil drilling,arterial stents,and energy harvesting.This has attracted widespread att...The contact deformation and buckling of elastic rods against rigid surfaces represent a prevalent phenomenon in applications such as oil drilling,arterial stents,and energy harvesting.This has attracted widespread attention from researchers.In this paper,the deformation and buckling behaviors of a circular arch subject to compression by a rigid plate are investigated with a planar elastic rod model that incorporates tension,shearing,and bending.In comparison with the existing models that solely consider the bending energy,the deflection curve,the internal force distribution,and the critical load of the present model show good agreement with the finite element results.Through the dimensional analysis and order-of-magnitude estimation,we examine the factors influencing the critical load.The study reveals that the semi-central angle of the arch has the most significant effect.The dimensionless geometric parameter describing arch slenderness becomes prominent when the semi-central angle is less than 30°,while Poisson's ratio and the cross-sectional shear correction factor exhibit negligible influence.Furthermore,the variation in the proportions of strain energy components during critical buckling is presented with respect to the semi-central angle and the geometric parameter,thereby delineating the applicable ranges of both the original model(OM)and the modified model(MM).展开更多
Uncertain parameters are widespread in engineering systems.This study investigates the modal analysis of a fluid-conveying pipe subjected to elastic supports with unknown-but-bound parameters.The governing equation fo...Uncertain parameters are widespread in engineering systems.This study investigates the modal analysis of a fluid-conveying pipe subjected to elastic supports with unknown-but-bound parameters.The governing equation for the elastically supported fluid-conveying pipe is transformed into ordinary differential equations using the Galerkin truncation method.The Chebyshev interval approach,integrated with the assumed mode method is then used to investigate the effects of uncertainties of support stiffness,fluid speed,and pipe length on the natural frequencies and mode shapes of the pipe.Additionally,both symmetrical and asymmetrical support stiffnesses are discussed.The accuracy and effectiveness of the Chebyshev interval approach are verified through comparison with the Monte Carlo method.The results reveal that,for the same deviation coefficient,uncertainties in symmetrical support stiffness have a greater impact on the first four natural frequencies than those of the asymmetrical one.There may be significant differences in the sensitivity of natural frequencies and mode shapes of the same order to uncertain parameters.Notably,mode shapes susceptible to uncertain parameters exhibit wider fluctuation intervals near the elastic supports,requiring more attention.展开更多
In this work,a computational modelling and analysis framework is developed to investigate the thermal buckling behavior of doubly-curved composite shells reinforced with graphene-origami(G-Ori)auxetic metamaterials.A ...In this work,a computational modelling and analysis framework is developed to investigate the thermal buckling behavior of doubly-curved composite shells reinforced with graphene-origami(G-Ori)auxetic metamaterials.A semi-analytical formulation based on the First-Order Shear Deformation Theory(FSDT)and the principle of virtual displacements is established,and closed-form solutions are derived via Navier’s method for simply supported boundary conditions.The G-Ori metamaterial reinforcements are treated as programmable constructs whose effective thermo-mechanical properties are obtained via micromechanical homogenization and incorporated into the shell model.A comprehensive parametric study examines the influence of folding geometry,dispersion arrangement,reinforcement weight fraction,curvature parameters,and elastic foundation support on the critical buckling temperature(CBT).The results reveal that,under optimal folding geometry and reinforcement alignment with principal stress trajectories,the CBT can increase by more than 150%.Furthermore,the combined effect of G-Ori reinforcement and elastic foundation substantially enhances thermal buckling resistance.These findings establish design guidelines for architected composite shells in applications such as aerospace thermal skins,morphing structures,and thermally-responsive systems,and illustrate the potential of auxetic graphene metamaterials for multifunctional,lightweight,and thermally robust structural components.展开更多
Carbonate reservoirs are vital energy storage spaces,including for oil,shale gas,geothermal,and hydrogen energy.Accurate prediction of reservoir characteristics such as permeability and saturated fluid types through n...Carbonate reservoirs are vital energy storage spaces,including for oil,shale gas,geothermal,and hydrogen energy.Accurate prediction of reservoir characteristics such as permeability and saturated fluid types through noninvasive approaches is crucial for optimal storage capability.In this paper,we combine a linear Boolean model and a discrete Fourier transform approach to generate pore‐and fracturepore‐type carbonate rocks.Elastic wave velocity information is necessary to predict permeability in different rock geometry models.Permeability is calculated using the lattice Boltzmann method,and the elastic wave velocity is calculated using a finite element method based on a minimal energy approach.Saturated fluids that contain oil and gas were both considered.Our simulated results reveal that,for pore‐type carbonate,empirical formulas were proposed to estimate permeability through elastic data.However,in fracture‐pore carbonate rocks,the precision of the empirical formula is compromised due to the presence of significant conductive channels within the rock matrix.We also find that using S‐wave velocity and permeability relationships to distinguish oil and gas is better than using P‐wave velocity and permeability relationships under low‐porosity conditions.展开更多
Alkali-free SiO_(2)-Al_(2)O_(3)-CaO-MgO with different SiO_(2)/Al_(2)O_(3)mass ratios was prepared by conventional melt quenching method.The glass network structure,thermodynamic properties and elastic modulus changes...Alkali-free SiO_(2)-Al_(2)O_(3)-CaO-MgO with different SiO_(2)/Al_(2)O_(3)mass ratios was prepared by conventional melt quenching method.The glass network structure,thermodynamic properties and elastic modulus changes with SiO_(2)and Al_(2)O_(3)ratios were investigated using various techniques.It is found that when SiO_(2)is replaced by Al_(2)O_(3),the Q^(4) to Q^(3) transition of silicon-oxygen network decreases while the aluminum-oxygen network increases,which result in the transformation of Si-O-Si bonds to Si-O-Al bonds and an increase in glass network connectivity even though the intermolecular bond strength decreases.The glass transition temperature(T_(g))increases continuously,while the thermal expansion coefficient increases and high-temperature viscosity first decreases and then increases.Meanwhile,the elastic modulus values increase from 93 to 102 GPa.This indicates that the elastic modulus is mainly affected by packing factor and dissociation energy,and elements with higher packing factors and dissociation energies supplant those with lower values,resulting in increased rigidity within the glass.展开更多
The development of β-titanium alloys with bone-mimicking elastic moduli remains a significant challenge.Although machine learning has the potential to accelerate alloy discovery,traditional methods often face data li...The development of β-titanium alloys with bone-mimicking elastic moduli remains a significant challenge.Although machine learning has the potential to accelerate alloy discovery,traditional methods often face data limitations such as sparsity,compositional discontinuity,and feature heterogeneity,leading to overfitting and restricting the exploration of novel compositional spaces.In this study,we introduce a domain-adversarial neural network framework that balances predictive accuracy with the generalization ability of unexplored composition space through integrated feature alignment and adversarial training.Using this approach,we successfully developed a non-intuitiveβ-Ti alloy with an ultra-low elastic modulus of 28±3 GPa,providing new insights beyond conventionally designed biomedical titanium alloys.This work establishes a screening framework for materials discovery in small-sample data spaces,with broad implications for the design of biomedical and other alloy systems.展开更多
This study addresses the challenge of directly determining the elastic modulus of complex shaped ceramic products—such as gas turbine combustor tiles—using conventional standardized methods,which are limited by spec...This study addresses the challenge of directly determining the elastic modulus of complex shaped ceramic products—such as gas turbine combustor tiles—using conventional standardized methods,which are limited by specimen geometry.A rapid,non-destructive testing method based on the impulse excitation technique(IET)and a shape factor coefficient was proposed.Three types of shaped ceramic tiles were selected.The elastic modulus of standard rectangular specimens obtained by destructive sampling was used as the reference value,and the shape factor coefficient for each tile type was calibrated by combining the mass and fundamental frequency of the whole tile.Using this coefficient,the elastic modulus of whole tiles was calculated solely from non-destructively measured mass and frequency.The results show that the deviation between the elastic modulus derived from the proposed method and that from destructive testing is less than 5%,confirming the accuracy and reliability of the approach.The method overcomes the shape restrictions inherent in traditional testing,offering a fast,non-destructive solution suitable for onsite quality assessment and process control during the production of shaped ceramic components.展开更多
As the types of traffic requests increase,the elastic optical network(EON)is considered as a promising architecture to carry multiple types of traffic requests simultaneously,including immediate reservation(IR)and adv...As the types of traffic requests increase,the elastic optical network(EON)is considered as a promising architecture to carry multiple types of traffic requests simultaneously,including immediate reservation(IR)and advance reservation(AR).Various resource allocation schemes for IR/AR requests have been designed in EON to reduce bandwidth blocking probability(BBP).However,these schemes do not consider different transmission requirements of IR requests and cannot maintain a low BBP for high-priority requests.In this paper,multi-priority is considered in the hybrid IR/AR request scenario.We modify the asynchronous advantage actor critic(A3C)model and propose an A3C-assisted priority resource allocation(APRA)algorithm.The APRA integrates priority and transmission quality of IR requests to design the A3C reward function,then dynamically allocates dedicated resources for different IR requests according to the time-varying requirements.By maximizing the reward,the transmission quality of IR requests can be matched with the priority,and lower BBP for high-priority IR requests can be ensured.Simulation results show that the APRA reduces the BBP of high-priority IR requests from 0.0341 to0.0138,and the overall network operation gain is improved by 883 compared to the scheme without considering the priority.展开更多
The application of polymer electrolytes is expected to revitalize solidstate lithium metal batteries(SSLMBs)with high energy density and enhanced safety.However,practical deployment faces challenges from inadequate me...The application of polymer electrolytes is expected to revitalize solidstate lithium metal batteries(SSLMBs)with high energy density and enhanced safety.However,practical deployment faces challenges from inadequate mechanical properties of electrolyte and unstable interfaces in high-voltage SSLMB s.Herein,we design an asymmetric composite solid-state electrolyte(ACSE)composed of a cellulose framework in situ self-assembled with zeolitic imidazolate framework nanosheets(CP@MOF)embedded in a polymer matrix.The CP@MOF network provides the electrolyte with an elastic modulus of 1.19 GPa,effectively resisting Li dendrite penetration.Furthermore,theoretical calculations guided the compositional design of ACSE to address asynchronous interfacial requirements at cathode/electrolyte and anode/electrolyte interfaces,facilitating stable interphase formation and thus ensuring prolonged cycling of SSLMBs.Consequently,Li symmetric cells achieve extended cycling stability(>5000 h)with minimal polarization.The NCM811|Li full cell maintains 84.9%capacity retention after 350 cycles.Notably,assembled NCM811 pouch cells deliver practical energy densities of 337.9 Wh kg^(-1)and 711.7 Wh L^(-1),demonstrating exceptional application potential.This work provides novel insights into the application of ACSEs for high-energy-density SSLMBs.展开更多
基金Financial support from the National Social Science Foundation of China (Grant Nos.17BGL014 and 18VDL017)
文摘As a cleaner,high-efficiency,and low-carbon fuel,natural gas has been an important fuel resource for China.To achieve a substantial increase in natural gas demand,China has sought to reform its natural gas pricing mechanism.Employing a set of unbalanced panel data for China’s 30 provinces covering 1999-2015,this study aims to estimate the evolving price and income elasticities of natural gas demand and explore the effect of natural gas price reform in China.For this purpose,a series of econometric techniques allowing for cross-sectional dependence and slope homogeneity is utilized.The results suggest that although natural gas demand in China still lacks negative price elasticity,the phenomenon is improving.Moreover,the estimates suggest that natural gas demand in China is indeed becoming increasingly sensitive to income changes.Our estimates also provide strong evidence in favor of the effect of natural gas price reform on the change in price elasticity as the price elasticity decreases in five of the seven regions.In addition,the results indicate large variations in the change in price and income elasticities of natural gas demand across China’s regions.Natural gas demand is becoming more price inelastic in Southwest China and Northwest China,while such demand in North China and East China responds less sensitively to income changes.These findings offer several policy suggestions for the reform of China’s natural gas market at the national and regional levels.
基金financial support provided by the China Natural Science Funding:[Grant Number71673134]sponsored by Qing Lan Project and the Fundamental Research Funds for the Central Universities:[Grant Number NJ20150035]
文摘Elasticity of substitution is traditionally estimated while ignoring technical and allocative inefficiencies,which could bias the estimates.We estimate elasticity of substitution for Chinese energy-intensive sectors by incorporating these inefficiencies.The results show most of the sectors are low substitutes between input factors and stress important differences among energy-intensive sectors.Concerning the cross-price elasticity for energy,with respect to capital(labor),the sectors are mainly characterized by weak substitutability or complementary.These imply the production structure is quite rigid and capital cannot be so readily used as a substitute for energy.
基金National Natural Science Foundation of China(No.41530634,41530751)Key Consulting Project of the Chinese Academy of Science and Technology Strategic Consulting(No.Y02015001)+1 种基金Open Project Funding of Beijing Modern Industrial New Area Development Research Base in 2015(No.JD2015002)Youth Innovation Promotion Association of Chinese Academy of Sciences(No.2014042)
文摘Urban metabolism is a complex system of materials, energy, population and environment, which usually can be measured by the Emergy Synthesis(ES) and the Slacks-Based Measure(SBM) approach. In this paper, by employing the two approaches of ES and SBM, as well as metabolic evolution index, urban metabolic stocks, efficiencies and elasticity of 31 Chinese cities are evaluated in a systematic way. The results imply that over the last decade(2000–2010), most of the cities, such as Chongqing, Nanjing, Shijiazhuang, Hangzhou, were experiencing drastic urban metabolic efficiency decline accompanied with a moderate decrease of industrial outputs. By contrast, metropolises and specialized cities have improved their urban metabolic performances, with higher output-input ratio and fewer undesirable outputs. However, their exported emergy experienced a substantial increase as well. It is concluded that local urban management might develop policies to diversify urban renewable supplies and address the undesirable output problems. The urban emergy of renewable resources should be specified as a prime focus for future research. In addition, mechanisms of different urban metabolic models will also be necessary for researchers.
文摘This paper presents a general framework that can be used to estimate direct and cross elasticities for freight transport using a network model. This methodology combines operational research (network assignments in a geographical information system) with more classical econometrics (multinomial logit choice models). The application of the method to a real-world case is illustrated by a simple model that relies on the generalized cost of transport as the only explanatory variable in the utility function. The methodological framework allows, however, for the implementation of more complex functions. Beside the generalized cost functions for road, rail and inland waterways transport, the network model needs origin-destination matrixes and digitized networks. They are imported from ETIS Plus, a European transport policy information system. A set of direct and cross elasticities is presented. The estimated values are obtained using two methods: the first computes standard elasticities, while the second estimates arc elasticities. Figures are presented for Europe and for a large region around the Benelux countries, where more competition exists between the three modes of interest.
基金the financial supports of the Natural Science Foundation for Distinguished Young Scholars of Zhejiang Province(Grant No.LR14G03001)the National Natural Science Foundation of China(Grant No.71673237)
文摘This paper classifies total fixed capital into three categories,namely,economic infrastructure capital,social infrastructure capital and non-infrastructure capital,and then offers complete and detailed estimates of the national time series data(1981-2012) and the provincial panel data of 31 administrative regions(1997-2012).On this basis,this paper estimates the output elasticities of the three categories of capital and then tests whether or not the production function of China shows constant returns to scale.
文摘Which rule of mixture is the best for predicting the overall elastic properties of polyphase rocks based on the elastic properties and volume fractions of their constituents? In order to address this question, we sintered forsterite-enstatite polycrystalline aggregates with a varied forsterite volume fraction (0, 0.2, 0.4, 0.5, 0.6, 0.8, and 1.0). Elastic properties (shear, bulk, and Young’s moduli) of these synthesized composites were measured as a function of pressure up to 3.0 GPa in a liquid-medium piston-cylinder apparatus using a high-precision ultrasonic interferometric technique. The experimental data can be much better described by the shear-lag model than by the commonly used simple models such as Voigt, Ruess and Hill averages, Hashin-Shtrikman bounds, Ravichandran bounds, Halpin-Tsai equations, and Paul’s calculations. We attributed this to the fact that the elastic interaction and stress transfer between phases are neglected in all the models except for the shear-lag model. In particular,
基金Supported by National Natural Science Foundation of China(50976032,51776070)。
文摘Oxygen carriers play a fundamental role in chemical looping combustion(CLC).Iron-based carriers have been extensively investigated owing to their abundance and environmentally friendly.However,the reactivity and separability of iron-based carriers require further enhancement.This study investigates the effect of the concentration of Mn doping on reactivity,elastic properties and magnetic properties based on density functional theory(DFT)calculations.Theoretical results demonstrate that Mn doping effectively enhances reactivity by reducing the oxygen vacancy formation energy(E_(vac))from 2.33 to 0.87 eV.However,Mn doping introduces HV/EV Ms lattice distortions that deteriorate elastic properties,thereby reducing wear resistance,as evidenced by a 54.54%decrease in the hardness-to-Young's modulus ratio(H_(v)/E_(v))forα-Fe_(2)O_(3)and an 83.33%reduction for Fe_(3)O_(4).Furthermore,Mn doping also modifies magnetic properties.The maximum of saturation magnetization(M_(s))of Fe_(3)O_(4)reaches 121.02 emu/g at 33.33%Mn doping concentration.Finally,systematic evaluation identifies 33.33%as the optimal Mn doping concentration,achieving a balance in enhanced reactivity,superior magnetic performance,and retained elastic stability.
基金supported in part by the National Natural Science Foundation of China(62173048,62373065,61873304,62106023)the Key Science and Technology Projects of Jilin Province,China(20230204081YY)the Research and Innovation Team of Anhui Province(2024AH010023)。
文摘Dear Editor,This letter presents a model predictive control(MPC)scheme for human-robot interaction(HRI)in a multi-joint exoskeleton robot(ER)driven by series elastic actuator(SEA).The proposed scheme in robot-in-charge(RIC)mode facilitates the ER driven by SEA to provide the required assistance and support for the subject.
基金Project supported by the National Natural Science Foundation of China(Nos.52405095,12272089,and 92360305)the Guangdong Basic and Applied Basic Research Foundation of China(No.2023A1515110557)+4 种基金the Natural Science Foundation of Liaoning Province of China(No.2023-BSBA-102)the Open Fund of National Key Laboratory of Particle Transport and Separation Technology of China(No.WZKF-2024-6)the Open Project of Guangxi Key Laboratory of Automobile Components and Vehicle Technology of China(Nos.2024GKLACVTKF07 and 2024GKLACVTKF06)the Basic Research Projects of Liaoning Provincial Department of Education of China(No.JYTQN2023162)the Fundamental Research Funds for the Central Universities of China(No.N2403022)。
文摘The testing of large structures is limited by high costs and long cycles, making scaling methods an attractive solution. However, the scaling process of elastic rings introduces complexities in multi-parameter geometric distortions, leading to a diminution in the predictive accuracy of the distorted similitude. To address this challenge, this study formulates a novel set of scaling laws, tailored to account for the intricate geometric distortions associated with elastic rings. The proposed scaling laws are formulated based on the intrinsic deformation characteristics of elastic rings, rather than the traditional systemic governing equations. Numerical and experimental cases are conducted to assess the efficacy and precision of the proposed scaling laws, and the obtained results are compared with those achieved by traditional methods. The outcomes demonstrate that the scaling laws put forth by this study significantly enhance the predictive capabilities for deformations of elastic rings.
基金Funded by State Railway Administration Research Project(No.2023JS007)National Natural Science Foundation of China(No.52438002)+1 种基金Research and Development Programs for Science and Technology of China Railways Corporation(No.J2023G003)New Cornerstone Science Foundation through the XPLORER PRIZE。
文摘To investigate the influence of coarse aggregate parent rock properties on the elastic modulus of concrete,the mineralogical properties and stress-strain curves of granite and dolomite parent rocks,as well as the strength and elastic modulus of mortar and concrete prepared with mechanism aggregates of the corresponding lithology,and the stress-strain curves of concrete were investigated.In this paper,a coarse aggregate and mortar matrix bonding assumption is proposed,and a prediction model for the elastic modulus of mortar is established by considering the lithology of the mechanism sand and the slurry components.An equivalent coarse aggregate elastic modulus model was established by considering factors such as coarse aggregate particle size,volume fraction,and mortar thickness between coarse aggregates.Based on the elastic modulus of the equivalent coarse aggregate and the remaining mortar,a prediction model for the elastic modulus of the two and three components of concrete in series and then in parallel was established,and the predicted values differed from the measured values within 10%.It is proposed that the coarse aggregate elastic modulus in highstrength concrete is the most critical factor affecting the elastic modulus of concrete,and as the coarse aggregate elastic modulus increases by 27.7%,the concrete elastic modulus increases by 19.5%.
基金Supported by the National Natural Science Foundation of China(Grant Nos.62025104,62331005,and U22A2052)the Beijing Natural Science Foundation(Grant No.L242100).
文摘Background Computed tomography(CT) and cone-beam computed tomography(CBCT) image registration play pivotal roles in computer-assisted navigation for orthopedic surgery. Traditional methods often apply uniform deformation models, neglecting the biomechanical differences between rigid structures and soft tissues, which compromises registration accuracy, especially during significant bone displacements. Method To address this issue, we introduce RE-Reg, a rigid-elastic CT-CBCT image registration framework that jointly learns rigid bone motion and soft tissue deformation. RE-Reg incorporates a rigid alignment(RA) module to estimate global bone motion and an elastic deformation(ED) module to model soft tissue deformation, preserving bony structures through bone shape preservation(BSP) loss. Result Our comprehensive evaluation on publicly available datasets demonstrates that RE-Reg significantly outperforms existing methods in terms of registration accuracy and rigid bone structure preservation, achieving a 1.3% improvement in Dice similarity coefficient(DSC) and a 23% reduction in rigid bone deformation(%Δvol) compared with the best baseline. Conclusion This framework not only enhances anatomical fidelity but also ensures biomechanical plausibility and provides a valuable tool for image-guided orthopedic surgery. This code is available athttps://github.com/Zq-Huang/RE-Reg.
基金Project supported by the National Natural Science Foundation of China(Nos.124B2043,U2241267,12172155,and 12302278)the Science and Technology Leading Talent Project of Gansu Province of China(No.23ZDKA0009)the Natural Science Foundation of Gansu Province of China(Nos.24JRRA473 and 24JRRA489)。
文摘The contact deformation and buckling of elastic rods against rigid surfaces represent a prevalent phenomenon in applications such as oil drilling,arterial stents,and energy harvesting.This has attracted widespread attention from researchers.In this paper,the deformation and buckling behaviors of a circular arch subject to compression by a rigid plate are investigated with a planar elastic rod model that incorporates tension,shearing,and bending.In comparison with the existing models that solely consider the bending energy,the deflection curve,the internal force distribution,and the critical load of the present model show good agreement with the finite element results.Through the dimensional analysis and order-of-magnitude estimation,we examine the factors influencing the critical load.The study reveals that the semi-central angle of the arch has the most significant effect.The dimensionless geometric parameter describing arch slenderness becomes prominent when the semi-central angle is less than 30°,while Poisson's ratio and the cross-sectional shear correction factor exhibit negligible influence.Furthermore,the variation in the proportions of strain energy components during critical buckling is presented with respect to the semi-central angle and the geometric parameter,thereby delineating the applicable ranges of both the original model(OM)and the modified model(MM).
基金supported by the National Natural Science Foundation of China(Grant Nos.12272211,12072181,and 12121002).
文摘Uncertain parameters are widespread in engineering systems.This study investigates the modal analysis of a fluid-conveying pipe subjected to elastic supports with unknown-but-bound parameters.The governing equation for the elastically supported fluid-conveying pipe is transformed into ordinary differential equations using the Galerkin truncation method.The Chebyshev interval approach,integrated with the assumed mode method is then used to investigate the effects of uncertainties of support stiffness,fluid speed,and pipe length on the natural frequencies and mode shapes of the pipe.Additionally,both symmetrical and asymmetrical support stiffnesses are discussed.The accuracy and effectiveness of the Chebyshev interval approach are verified through comparison with the Monte Carlo method.The results reveal that,for the same deviation coefficient,uncertainties in symmetrical support stiffness have a greater impact on the first four natural frequencies than those of the asymmetrical one.There may be significant differences in the sensitivity of natural frequencies and mode shapes of the same order to uncertain parameters.Notably,mode shapes susceptible to uncertain parameters exhibit wider fluctuation intervals near the elastic supports,requiring more attention.
文摘In this work,a computational modelling and analysis framework is developed to investigate the thermal buckling behavior of doubly-curved composite shells reinforced with graphene-origami(G-Ori)auxetic metamaterials.A semi-analytical formulation based on the First-Order Shear Deformation Theory(FSDT)and the principle of virtual displacements is established,and closed-form solutions are derived via Navier’s method for simply supported boundary conditions.The G-Ori metamaterial reinforcements are treated as programmable constructs whose effective thermo-mechanical properties are obtained via micromechanical homogenization and incorporated into the shell model.A comprehensive parametric study examines the influence of folding geometry,dispersion arrangement,reinforcement weight fraction,curvature parameters,and elastic foundation support on the critical buckling temperature(CBT).The results reveal that,under optimal folding geometry and reinforcement alignment with principal stress trajectories,the CBT can increase by more than 150%.Furthermore,the combined effect of G-Ori reinforcement and elastic foundation substantially enhances thermal buckling resistance.These findings establish design guidelines for architected composite shells in applications such as aerospace thermal skins,morphing structures,and thermally-responsive systems,and illustrate the potential of auxetic graphene metamaterials for multifunctional,lightweight,and thermally robust structural components.
基金Chengdu University of Technology Youth Teaching Backbone Project,Grant/Award Number:10912-JXGG2023-09458Sichuan Province Overseas Returnees Science and Technology Excellence Project,Grant/Award Number:10900-23BZ28-02+1 种基金Physics-informed machine learning for coupled modelling of carbon storage,Grant/Award Number:SKLGME021002Chengdu University of Technology Research Start-up Fund,Grant/Award Number:10912-KYQD2022-09458。
文摘Carbonate reservoirs are vital energy storage spaces,including for oil,shale gas,geothermal,and hydrogen energy.Accurate prediction of reservoir characteristics such as permeability and saturated fluid types through noninvasive approaches is crucial for optimal storage capability.In this paper,we combine a linear Boolean model and a discrete Fourier transform approach to generate pore‐and fracturepore‐type carbonate rocks.Elastic wave velocity information is necessary to predict permeability in different rock geometry models.Permeability is calculated using the lattice Boltzmann method,and the elastic wave velocity is calculated using a finite element method based on a minimal energy approach.Saturated fluids that contain oil and gas were both considered.Our simulated results reveal that,for pore‐type carbonate,empirical formulas were proposed to estimate permeability through elastic data.However,in fracture‐pore carbonate rocks,the precision of the empirical formula is compromised due to the presence of significant conductive channels within the rock matrix.We also find that using S‐wave velocity and permeability relationships to distinguish oil and gas is better than using P‐wave velocity and permeability relationships under low‐porosity conditions.
基金Supported by the National Key Research Program(No.2024-1129-954-112)National Natural Science Foundation of China(No.52372033)Guangxi Science and Technology Major Program(No.AA24263054)。
文摘Alkali-free SiO_(2)-Al_(2)O_(3)-CaO-MgO with different SiO_(2)/Al_(2)O_(3)mass ratios was prepared by conventional melt quenching method.The glass network structure,thermodynamic properties and elastic modulus changes with SiO_(2)and Al_(2)O_(3)ratios were investigated using various techniques.It is found that when SiO_(2)is replaced by Al_(2)O_(3),the Q^(4) to Q^(3) transition of silicon-oxygen network decreases while the aluminum-oxygen network increases,which result in the transformation of Si-O-Si bonds to Si-O-Al bonds and an increase in glass network connectivity even though the intermolecular bond strength decreases.The glass transition temperature(T_(g))increases continuously,while the thermal expansion coefficient increases and high-temperature viscosity first decreases and then increases.Meanwhile,the elastic modulus values increase from 93 to 102 GPa.This indicates that the elastic modulus is mainly affected by packing factor and dissociation energy,and elements with higher packing factors and dissociation energies supplant those with lower values,resulting in increased rigidity within the glass.
基金supported by the Guangdong S&T Program(Grant No.2025B1111130003).
文摘The development of β-titanium alloys with bone-mimicking elastic moduli remains a significant challenge.Although machine learning has the potential to accelerate alloy discovery,traditional methods often face data limitations such as sparsity,compositional discontinuity,and feature heterogeneity,leading to overfitting and restricting the exploration of novel compositional spaces.In this study,we introduce a domain-adversarial neural network framework that balances predictive accuracy with the generalization ability of unexplored composition space through integrated feature alignment and adversarial training.Using this approach,we successfully developed a non-intuitiveβ-Ti alloy with an ultra-low elastic modulus of 28±3 GPa,providing new insights beyond conventionally designed biomedical titanium alloys.This work establishes a screening framework for materials discovery in small-sample data spaces,with broad implications for the design of biomedical and other alloy systems.
基金National Key Research and Development Program of China(2023YFB3711200)Key Research and Development Project of Henan Province(231111230700).
文摘This study addresses the challenge of directly determining the elastic modulus of complex shaped ceramic products—such as gas turbine combustor tiles—using conventional standardized methods,which are limited by specimen geometry.A rapid,non-destructive testing method based on the impulse excitation technique(IET)and a shape factor coefficient was proposed.Three types of shaped ceramic tiles were selected.The elastic modulus of standard rectangular specimens obtained by destructive sampling was used as the reference value,and the shape factor coefficient for each tile type was calibrated by combining the mass and fundamental frequency of the whole tile.Using this coefficient,the elastic modulus of whole tiles was calculated solely from non-destructively measured mass and frequency.The results show that the deviation between the elastic modulus derived from the proposed method and that from destructive testing is less than 5%,confirming the accuracy and reliability of the approach.The method overcomes the shape restrictions inherent in traditional testing,offering a fast,non-destructive solution suitable for onsite quality assessment and process control during the production of shaped ceramic components.
文摘As the types of traffic requests increase,the elastic optical network(EON)is considered as a promising architecture to carry multiple types of traffic requests simultaneously,including immediate reservation(IR)and advance reservation(AR).Various resource allocation schemes for IR/AR requests have been designed in EON to reduce bandwidth blocking probability(BBP).However,these schemes do not consider different transmission requirements of IR requests and cannot maintain a low BBP for high-priority requests.In this paper,multi-priority is considered in the hybrid IR/AR request scenario.We modify the asynchronous advantage actor critic(A3C)model and propose an A3C-assisted priority resource allocation(APRA)algorithm.The APRA integrates priority and transmission quality of IR requests to design the A3C reward function,then dynamically allocates dedicated resources for different IR requests according to the time-varying requirements.By maximizing the reward,the transmission quality of IR requests can be matched with the priority,and lower BBP for high-priority IR requests can be ensured.Simulation results show that the APRA reduces the BBP of high-priority IR requests from 0.0341 to0.0138,and the overall network operation gain is improved by 883 compared to the scheme without considering the priority.
基金the financial support from the National Natural Science Foundation of China(52072307,22408198)the Fundamental Research Funds for the Central Universities(XJJSKYQD202533)。
文摘The application of polymer electrolytes is expected to revitalize solidstate lithium metal batteries(SSLMBs)with high energy density and enhanced safety.However,practical deployment faces challenges from inadequate mechanical properties of electrolyte and unstable interfaces in high-voltage SSLMB s.Herein,we design an asymmetric composite solid-state electrolyte(ACSE)composed of a cellulose framework in situ self-assembled with zeolitic imidazolate framework nanosheets(CP@MOF)embedded in a polymer matrix.The CP@MOF network provides the electrolyte with an elastic modulus of 1.19 GPa,effectively resisting Li dendrite penetration.Furthermore,theoretical calculations guided the compositional design of ACSE to address asynchronous interfacial requirements at cathode/electrolyte and anode/electrolyte interfaces,facilitating stable interphase formation and thus ensuring prolonged cycling of SSLMBs.Consequently,Li symmetric cells achieve extended cycling stability(>5000 h)with minimal polarization.The NCM811|Li full cell maintains 84.9%capacity retention after 350 cycles.Notably,assembled NCM811 pouch cells deliver practical energy densities of 337.9 Wh kg^(-1)and 711.7 Wh L^(-1),demonstrating exceptional application potential.This work provides novel insights into the application of ACSEs for high-energy-density SSLMBs.
