Necessary and sufficient conditions for the exact controllability and exact observability of a descriptor infinite dimensional system are obtained in the sense of distributional solution.These general results are used...Necessary and sufficient conditions for the exact controllability and exact observability of a descriptor infinite dimensional system are obtained in the sense of distributional solution.These general results are used to examine the exact controllability and exact observability of the Dzektser equation in the theory of seepage and the exact controllability of wave equation.展开更多
Magnetic semiconductors have been demonstrated to work at low temperatures, but not yet at room temperature for spin electronic applications. In contrast to the p-type diluted magnetic semiconductors, n-type diluted m...Magnetic semiconductors have been demonstrated to work at low temperatures, but not yet at room temperature for spin electronic applications. In contrast to the p-type diluted magnetic semiconductors, n-type diluted magnetic semiconductors are few. Using a combined method of the density function theory and quantum Monte Carlo simulation, we briefly discuss the recent progress to obtain diluted magnetic semiconductors with both p- and n-type carriers by choosing host semiconductors with a narrow band gap. In addition, the recent progress on two-dimensional intrinsic magnetic semiconductors with possible room temperature ferromangetism and quantum anomalous Hall effect are also discussed.展开更多
A novel aperiodically intermittent impulse control(AIIC)method is proposed to investigate the exponential synchronization in mean square(ESMS)of a class of impulsive stochastic infinite-dimensional systems with Poisso...A novel aperiodically intermittent impulse control(AIIC)method is proposed to investigate the exponential synchronization in mean square(ESMS)of a class of impulsive stochastic infinite-dimensional systems with Poisson jumps(ISIDSP).The AIIC control strategy inherits the flexibility of aperiodically intermittent control,including the variable control period,adjustable control interval length,and the discretization of impulsive control.In addition,this article introduces a novel mild Itô's formula.By leveraging semigroup theory,the contraction mapping principle,and graph theory,along with constructing the Lyapunov function,the criterion for the existence and uniqueness of a mild solution of ISIDSP is thereby established.Furthermore,the mean-square exponential synchronization problem of the above systems is resolved,and the constraints within the mild solution domain are alleviated.These criteria clarify the impact of control parameters,control intervals and network topology on ESMS.The theoretical results are subsequently applied to a class of neural networks with reaction-diffusion processes,and the validity of the results is verified using numerical simulations.展开更多
The two-dimensional kagome lattice serves as a prototypical platform for exploring quantum spin liquids owing to its pronounced geometric frustration.Substantial advancements have been achieved in herbertsmithite and ...The two-dimensional kagome lattice serves as a prototypical platform for exploring quantum spin liquids owing to its pronounced geometric frustration.Substantial advancements have been achieved in herbertsmithite and its structural analogs.These quantum spin liquid candidates exhibit large superexchange interactions yet resist magnetic ordering down to the lowest measurable temperatures,which are typically three or four orders of magnitude below the energy scale of the primary exchange energies.Nevertheless,the existence of unavoidable intrinsic interlayer magnetic impurities leads to persistent debates on their ground states.A breakthrough emerged with the discovery of YCu_(3)(OH)_(6+x)X_(3-x)(X=Cl,Br),a novel material family rigorously verifed to eliminate magnetic impurity interference.This short review highlights critical advances in these materials,emphasizing experimental signatures consistent with a Dirac quantum spin liquid and the observation of a oneninth magnetization plateau and possible quantum oscillations.Local structural characteristics play a crucial role in clarifying the complex emergent quantum phenomena of these materials.Collectively,these fndings establish this material class as a promising platform for investigating quantum spin liquid behavior in two-dimensional kagome lattices.展开更多
Gas turbine rotors are complex dynamic systems with high-dimensional,discrete,and multi-source nonlinear coupling characteristics.Significant amounts of resources and time are spent during the process of solving dynam...Gas turbine rotors are complex dynamic systems with high-dimensional,discrete,and multi-source nonlinear coupling characteristics.Significant amounts of resources and time are spent during the process of solving dynamic characteristics.Therefore,it is necessary to design a lowdimensional model that can well reflect the dynamic characteristics of high-dimensional system.To build such a low-dimensional model,this study developed a dimensionality reduction method considering global order energy distribution by modifying the proper orthogonal decomposition theory.First,sensitivity analysis of key dimensionality reduction parameters to the energy distribution was conducted.Then a high-dimensional rotor-bearing system considering the nonlinear stiffness and oil film force was reduced,and the accuracy and the reusability of the low-dimensional model under different operating conditions were examined.Finally,the response results of a multi-disk rotor-bearing test bench were reduced using the proposed method,and spectrum results were then compared experimentally.Numerical and experimental results demonstrate that,during the dimensionality reduction process,the solution period of dynamic response results has the most significant influence on the accuracy of energy preservation.The transient signal in the transformation matrix mainly affects the high-order energy distribution of the rotor system.The larger the proportion of steady-state signals is,the closer the energy tends to accumulate towards lower orders.The low-dimensional rotor model accurately reflects the frequency response characteristics of the original high-dimensional system with an accuracy of up to 98%.The proposed dimensionality reduction method exhibits significant application potential in the dynamic analysis of highdimensional systems coupled with strong nonlinearities under variable operating conditions.展开更多
In recent years,the research on superconductivity in one-dimensional(1D)materials has been attracting increasing attention due to its potential applications in low-dimensional nanodevices.However,the critical temperat...In recent years,the research on superconductivity in one-dimensional(1D)materials has been attracting increasing attention due to its potential applications in low-dimensional nanodevices.However,the critical temperature(T_(c))of 1D superconductors is low.In this work,we theoretically investigate the possible high T_(c) superconductivity of(5,5)carbon nanotube(CNT).The pristine(5,5)CNT is a Dirac semimetal and can be modulated into a semiconductor by full hydrogenation.Interestingly,by further hole doping,it can be regulated into a metallic state with the sp^(3)-hybridized σ electrons metalized,and a giant Kohn anomaly appears in the optical phonons.The two factors together enhance the electron–phonon coupling,and lead to high-T_(c) superconductivity.When the hole doping concentration of hydrogenated-(5,5)CNT is 2.5 hole/cell,the calculated T_(c) is 82.3 K,exceeding the boiling point of liquid nitrogen.Therefore,the predicted hole-doped hydrogenated-(5,5)CNT provides a new platform for 1D high-T_(c) superconductivity and may have potential applications in 1D nanodevices.展开更多
Monitoring waterbirds is vital for evaluating the ecological health of wetlands,and object detection offers an automated solution for identifying birds in monitoring imagery.However,conventional detection methods ofte...Monitoring waterbirds is vital for evaluating the ecological health of wetlands,and object detection offers an automated solution for identifying birds in monitoring imagery.However,conventional detection methods often overlook the multi-scale nature of bird targets,limiting their ability to capture rich contextual information across different scales.To address this,we propose a cross-dimensional attention network(CDA-Net)for bird detection that integrates spatial and channel information to improve species recognition.The proposed CDA-Net partitions feature maps into multiple channel wise sub-features.Spatial and channel attention are applied to each subfeature,and the resulting features are fused using the Hadamard product.The fused features are then forwarded to the detection head to generate the final detection results.This approach effectively captures and integrates information across spatial and channel dimensions.Experiments on our self-constructed Nanhai Wetland Waterbird Dataset and the public CUB-200-2011 dataset yield precision scores of 91.32%and 81.99%,respectively,outperforming existing methods.Our approach effectively handles scale variation in bird detection and provides a valuable tool for advancing automated wetland waterbird monitoring.展开更多
Compared to the well-studied two-dimensional(2D)ferroelectricity,the appearance of 2D antiferroelectricity is much rarer,where local dipoles from the nonequivalent sublattices within 2D monolayers are oppositely orien...Compared to the well-studied two-dimensional(2D)ferroelectricity,the appearance of 2D antiferroelectricity is much rarer,where local dipoles from the nonequivalent sublattices within 2D monolayers are oppositely oriented.Using NbOCl_(2) monolayer with competing ferroelectric(FE)and antiferroelectric(AFE)phases as a 2D material platform,we demonstrate the emergence of intrinsic antiferroelectricity in NbOCl_(2) monolayer under experimentally accessible shear strain,along with new functionality associated with electric field-induced AFE-to-FE phase transition.Specifically,the complex configuration space accommodating FE and AFE phases,polarization switching kinetics,and finite temperature thermodynamic properties of 2D NbOCl_(2) are all accurately predicted by large-scale molecular dynamics simulations based on deep learning interatomic potential model.Moreover,room temperature stable antiferroelectricity with low polarization switching barrier and one-dimensional collinear polarization arrangement is predicted in shear-deformed NbOCl_(2) monolayer.The transition from AFE to FE phase in 2D NbOCl_(2) can be triggered by a low critical electric field,leading to a double polarization–electric(P–E)loop with small hysteresis.A new type of optoelectronic device composed of AFE-NbOCl_(2) is proposed,enabling electric“writing”and nonlinear optical“reading”logical operation with fast operation speed and low power consumption.展开更多
Neurodegenerative disorders represent an increasingly pertinent public health crisis.As a greater proportion of the population ages,neurodegenerative disorders and other diseases of aging place undue burdens on patien...Neurodegenerative disorders represent an increasingly pertinent public health crisis.As a greater proportion of the population ages,neurodegenerative disorders and other diseases of aging place undue burdens on patients,caregivers,and healthcare workers.Alzheimer’s disease(AD)and Parkinson’s disease represent the two most common neurodegenerative disorders in the population,affecting over 65 million people,worldwide.展开更多
Dear Editor,This letter studies the problem of stealthy attacks targeting stochastic event-based estimation,alongside proposing measures for their mitigation.A general attack framework is introduced,and the correspond...Dear Editor,This letter studies the problem of stealthy attacks targeting stochastic event-based estimation,alongside proposing measures for their mitigation.A general attack framework is introduced,and the corresponding stealthiness condition is analyzed.To enhance system security,we advocate for a single-dimensional encryption method,showing that securing a singular data element is sufficient to shield the system from the perils of stealthy attacks.展开更多
The original online version of this article was revised:The layout update for Article 758 has impacted the page range in the published issue,but did not affect the scholarly content.To ensure consistency with the orig...The original online version of this article was revised:The layout update for Article 758 has impacted the page range in the published issue,but did not affect the scholarly content.To ensure consistency with the originally assigned pages(2595-2614),we will need to publish an erratum to correct the article and restore the original page range.The original article has been corrected.展开更多
Water-cooled system have significantly enhanced the power generation efficiency of offshore wind turbines.However,these innovative systems are susceptible to substantial biological fouling,maintenance challenges,and h...Water-cooled system have significantly enhanced the power generation efficiency of offshore wind turbines.However,these innovative systems are susceptible to substantial biological fouling,maintenance challenges,and high upkeep costs.Therefore,the development of a specialized front-end filter tailored for direct current water-cooled system is importance.This involves the integration of dimensionally stable anode(DSA)and nickel alloy cathode,valued for their corrosion resistance in seawater,into a novel front-end filter system for Water-cooled applications.This system has the dual capability of generating hydrogen and chlorine for self-cleaning purposes.Implementing a flushing pulse electrolysis mode,it effectively mitigates electrode failure induced by cathodic calcium and magnesium deposition,thereby significantly prolonging electrode lifespan.Laboratory tests comprising system assembly and performance evaluations were conducted,with the system programmed to operate for 5 minutes every 24 hours under continuous flushing by natural seawater to simulate real-world conditions.After more than 11 months of continuous flushing,observations reveal that the DSA mesh and nickel alloy mesh maintain intact structural integrity and normal functioning.Subsequent 1꞉1 physical prototype Sea trial further validated the soundness of the system design and electrolytic control parameters.展开更多
In this manuscript,we consider a non-autonomous dynamical system.Using the Carathéodory structure,we define a BS dimension on an arbitrary subset and obtain a Bowen’s equation that illustrates the relation of th...In this manuscript,we consider a non-autonomous dynamical system.Using the Carathéodory structure,we define a BS dimension on an arbitrary subset and obtain a Bowen’s equation that illustrates the relation of the BS dimension to the Pesin-Pitskel topological pressure given by Nazarian[24].Moreover,we establish a variational principle and an inverse variational principle for the BS dimension of non-autonomous dynamical systems.Finally,we also get an analogue of Billingsley’s theorem for the BS dimension of non-autonomous dynamical systems.展开更多
The pore structure of shale oil reservoir significantly affects the occurrence and mobility of hydrocarbons.The potential of a new type of alkaline lake shale oil has been demonstrated,but there are few reports on the...The pore structure of shale oil reservoir significantly affects the occurrence and mobility of hydrocarbons.The potential of a new type of alkaline lake shale oil has been demonstrated,but there are few reports on the pore system of alkaline lake shale,which restricts the efficient exploration and development of shale oil.This study investigates the Fengcheng Formation shale in the Mahu sag of the Junggar Basin,employing methods such as low-temperature nitrogecn adsorption(LTNA),mercury intrusion capillary pressure(MICP),and nuclear magnetic resonance(NMR)to quantitatively characterize the multi-scale pore structure and fractal characteristics of shale,while evaluating the applicability of these methods.Based on a comprehensive analysis of material composition,different pore types,and fractal dimensions,the controlling factors for the development of different pore types and their seepage capacity are discussed.The results indicate that inorganic mineral pores are the main development in alkaline lake shale,with the pore morphology being characterized by slit-like and ink-bottle shapes.The multi-scale pore size distribution(PSD)shows that Ⅱ-micropores(10-100 nm)and mesopores(100–1000 nm)are the main contributors to the pore system.The development of Ⅱ-micropores is associated with feldspar and calcareous minerals,the development of Ⅰ-micropores(<10 nm)and mesopores is related to quartz content,while large pores are mainly found in interlayer fissures of clay minerals.The development of Ⅰ-micropores increases the roughness of pore surface and enhances the adsorption capacity of the pores,while the development of Ⅱ-micropores associated with calcareous minerals hinders pore seepage capacity.Mesopores and macropores(>1000 nm)exhibit good flowability.The high content of siliceous minerals plays a positive role in the pore system of alkaline lake shale.The shale with higher fractal dimension Dmin exhibits greater adsorption capacity,which hinders the accumulation of free-state shale oil.Different types of pore space play different roles in the occurrence of shale oil,with free-state shale oil primarily occurring in micro-fractures and inorganic mineral pores,and the pore size is exceeding 10 nm.展开更多
Owing to their global search capabilities and gradient-free operation,metaheuristic algorithms are widely applied to a wide range of optimization problems.However,their computational demands become prohibitive when ta...Owing to their global search capabilities and gradient-free operation,metaheuristic algorithms are widely applied to a wide range of optimization problems.However,their computational demands become prohibitive when tackling high-dimensional optimization challenges.To effectively address these challenges,this study introduces cooperative metaheuristics integrating dynamic dimension reduction(DR).Building upon particle swarm optimization(PSO)and differential evolution(DE),the proposed cooperative methods C-PSO and C-DE are developed.In the proposed methods,the modified principal components analysis(PCA)is utilized to reduce the dimension of design variables,thereby decreasing computational costs.The dynamic DR strategy implements periodic execution of modified PCA after a fixed number of iterations,resulting in the important dimensions being dynamically identified.Compared with the static one,the dynamic DR strategy can achieve precise identification of important dimensions,thereby enabling accelerated convergence toward optimal solutions.Furthermore,the influence of cumulative contribution rate thresholds on optimization problems with different dimensions is investigated.Metaheuristic algorithms(PSO,DE)and cooperative metaheuristics(C-PSO,C-DE)are examined by 15 benchmark functions and two engineering design problems(speed reducer and composite pressure vessel).Comparative results demonstrate that the cooperative methods achieve significantly superior performance compared to standard methods in both solution accuracy and computational efficiency.Compared to standard metaheuristic algorithms,cooperative metaheuristics achieve a reduction in computational cost of at least 40%.The cooperative metaheuristics can be effectively used to tackle both high-dimensional unconstrained and constrained optimization problems.展开更多
This paper introduces a computationally efficient global sensitivity analysis method for quantifying the influence of uncertain clamp support conditions on the natural frequencies of aero-engine pipe systems.The dynam...This paper introduces a computationally efficient global sensitivity analysis method for quantifying the influence of uncertain clamp support conditions on the natural frequencies of aero-engine pipe systems.The dynamic model is based on a three-dimensional Timoshenko beam finite element formulation,with clamps represented as distributed spring elements possessing anisotropic stiffness.To overcome the prohibitive cost of traditional Monte Carlo simulation,the multiplicative dimensional reduction method(M-DRM)is integrated with variance decomposition theory.This approach approximates the high-dimensional frequency response function as a product of univariate components,enabling rapid computation of Sobol’sensitivity indices with a computational cost reduced by three orders of magnitude.Numerical case studies on a planar Z-shaped pipe and a spatial series-parallel configuration reveal that clamp position parameters dominate the system’s natural frequency characteristics.For critical clamps,Sobol’indices exceed 0.8 across multiple vibration modes,whereas stiffness parameters exhibit negligible influence.The proposed methodology provides a rigorous and efficient tool for identifying dominant uncertainty sources,guiding tolerance allocation in manufacturing,and informing robust support design for vibration-sensitive piping systems.展开更多
Based on the theory of multibody system dynamics, the spatial kinematics analysis of the Mcpherson independent suspension widely used in the car was carried out. A practical and simpler method was provided to reduce t...Based on the theory of multibody system dynamics, the spatial kinematics analysis of the Mcpherson independent suspension widely used in the car was carried out. A practical and simpler method was provided to reduce the number of the generalized coordinates and constraint functions. By solving the nonlinear equations, the motion of any points in the whole suspension and wheel system can be predicted, including the spatial changes of the wheel alignment parameters which are of great importance to the car performances.展开更多
The focusing tomography is presented to reconstruct 3 dimensional irradiance distribution. A 3 dimensional luminous body could be considered as the combination of many 2 dimensional parallel luminous sections. Focu...The focusing tomography is presented to reconstruct 3 dimensional irradiance distribution. A 3 dimensional luminous body could be considered as the combination of many 2 dimensional parallel luminous sections. Focus on these discrete sections respectively by a single camera, a group of images would be captured to form governing equations of irradiance. After inversion procedure, the irradiance distribution of different sections could be decoded. In this experimentation two lightbulbs are used to simulate two luminous sections. Reasonable results demonstrate that this technique could be a useful method in irradiance reconstruction after further development.展开更多
In this paper, the global controllability for a class of high dimensional polynomial systems has been investigated and a constructive algebraic criterion algorithm for their global controllability has been obtained. B...In this paper, the global controllability for a class of high dimensional polynomial systems has been investigated and a constructive algebraic criterion algorithm for their global controllability has been obtained. By the criterion algorithm, the global controllability can be determined in finite steps of arithmetic operations. The algorithm is imposed on the coefficients of the polynomials only and the analysis technique is based on Sturm Theorem in real algebraic geometry and its modern progress. Finally, the authors will give some examples to show the application of our results.展开更多
This paper deals with the output regulation problem for a class of SISO infinite dimensional systems with an uncertain exosystem.For these systems,a concept of relative degree is firstly introduced and used to constru...This paper deals with the output regulation problem for a class of SISO infinite dimensional systems with an uncertain exosystem.For these systems,a concept of relative degree is firstly introduced and used to construct a transformation which leads to the canonical form of output feedback systems.Then,based on this canonical form,by means of an internal model and a recursive adaptive control,the authors obtain an adaptive regulator which solves the problem.It should be pointed out that the proposed regulator is finite dimensional while it is usually infinite dimensional in existing literatures.展开更多
基金This work was supported by the National Natural Science Foundation of China(11926402,61973338).
文摘Necessary and sufficient conditions for the exact controllability and exact observability of a descriptor infinite dimensional system are obtained in the sense of distributional solution.These general results are used to examine the exact controllability and exact observability of the Dzektser equation in the theory of seepage and the exact controllability of wave equation.
基金supported by NSFC (Grant No. Y81Z01A1A9)CAS (Grant No. Y929013EA2)+3 种基金UCAS (Grant No.110200M208)the Strategic Priority Research Program of CAS (Grant No. XDB28000000)the National Key R&D Program of China (Grant No.11834014)Beijing Municipal Science & Technology Commission (Grant No. Z181100004218001)
文摘Magnetic semiconductors have been demonstrated to work at low temperatures, but not yet at room temperature for spin electronic applications. In contrast to the p-type diluted magnetic semiconductors, n-type diluted magnetic semiconductors are few. Using a combined method of the density function theory and quantum Monte Carlo simulation, we briefly discuss the recent progress to obtain diluted magnetic semiconductors with both p- and n-type carriers by choosing host semiconductors with a narrow band gap. In addition, the recent progress on two-dimensional intrinsic magnetic semiconductors with possible room temperature ferromangetism and quantum anomalous Hall effect are also discussed.
基金supported in part by the National Natural Science Foundation of China(12471422,62573274,12371173)the Natural Science Foundation of Shandong Province of China(ZR2022LLZ003,ZR2024MF001)the Funding for Visiting Studies and Research by Teachers in Ordinary Undergraduate Colleges and Universities in Shandong Province。
文摘A novel aperiodically intermittent impulse control(AIIC)method is proposed to investigate the exponential synchronization in mean square(ESMS)of a class of impulsive stochastic infinite-dimensional systems with Poisson jumps(ISIDSP).The AIIC control strategy inherits the flexibility of aperiodically intermittent control,including the variable control period,adjustable control interval length,and the discretization of impulsive control.In addition,this article introduces a novel mild Itô's formula.By leveraging semigroup theory,the contraction mapping principle,and graph theory,along with constructing the Lyapunov function,the criterion for the existence and uniqueness of a mild solution of ISIDSP is thereby established.Furthermore,the mean-square exponential synchronization problem of the above systems is resolved,and the constraints within the mild solution domain are alleviated.These criteria clarify the impact of control parameters,control intervals and network topology on ESMS.The theoretical results are subsequently applied to a class of neural networks with reaction-diffusion processes,and the validity of the results is verified using numerical simulations.
文摘The two-dimensional kagome lattice serves as a prototypical platform for exploring quantum spin liquids owing to its pronounced geometric frustration.Substantial advancements have been achieved in herbertsmithite and its structural analogs.These quantum spin liquid candidates exhibit large superexchange interactions yet resist magnetic ordering down to the lowest measurable temperatures,which are typically three or four orders of magnitude below the energy scale of the primary exchange energies.Nevertheless,the existence of unavoidable intrinsic interlayer magnetic impurities leads to persistent debates on their ground states.A breakthrough emerged with the discovery of YCu_(3)(OH)_(6+x)X_(3-x)(X=Cl,Br),a novel material family rigorously verifed to eliminate magnetic impurity interference.This short review highlights critical advances in these materials,emphasizing experimental signatures consistent with a Dirac quantum spin liquid and the observation of a oneninth magnetization plateau and possible quantum oscillations.Local structural characteristics play a crucial role in clarifying the complex emergent quantum phenomena of these materials.Collectively,these fndings establish this material class as a promising platform for investigating quantum spin liquid behavior in two-dimensional kagome lattices.
基金supported by the China Postdoctoral Science Foundation(No.2024M764171)the Postdoctoral Research Start-up Funds,China(No.AUGA5710027424)+1 种基金the National Natural Science Foundation of China(No.U2341237)the Development and construction funds for the School of Mechatronics Engineering of HIT,China(No.CBQQ8880103624)。
文摘Gas turbine rotors are complex dynamic systems with high-dimensional,discrete,and multi-source nonlinear coupling characteristics.Significant amounts of resources and time are spent during the process of solving dynamic characteristics.Therefore,it is necessary to design a lowdimensional model that can well reflect the dynamic characteristics of high-dimensional system.To build such a low-dimensional model,this study developed a dimensionality reduction method considering global order energy distribution by modifying the proper orthogonal decomposition theory.First,sensitivity analysis of key dimensionality reduction parameters to the energy distribution was conducted.Then a high-dimensional rotor-bearing system considering the nonlinear stiffness and oil film force was reduced,and the accuracy and the reusability of the low-dimensional model under different operating conditions were examined.Finally,the response results of a multi-disk rotor-bearing test bench were reduced using the proposed method,and spectrum results were then compared experimentally.Numerical and experimental results demonstrate that,during the dimensionality reduction process,the solution period of dynamic response results has the most significant influence on the accuracy of energy preservation.The transient signal in the transformation matrix mainly affects the high-order energy distribution of the rotor system.The larger the proportion of steady-state signals is,the closer the energy tends to accumulate towards lower orders.The low-dimensional rotor model accurately reflects the frequency response characteristics of the original high-dimensional system with an accuracy of up to 98%.The proposed dimensionality reduction method exhibits significant application potential in the dynamic analysis of highdimensional systems coupled with strong nonlinearities under variable operating conditions.
基金supported by the National Natural Science Foundation of China (Grant Nos.12074213 and 11574108)the Major Basic Program of Natural Science Foundation of Shandong Province (Grant No.ZR2021ZD01)the Natural Science Foundation of Shandong Province (Grant No.ZR2023MA082)。
文摘In recent years,the research on superconductivity in one-dimensional(1D)materials has been attracting increasing attention due to its potential applications in low-dimensional nanodevices.However,the critical temperature(T_(c))of 1D superconductors is low.In this work,we theoretically investigate the possible high T_(c) superconductivity of(5,5)carbon nanotube(CNT).The pristine(5,5)CNT is a Dirac semimetal and can be modulated into a semiconductor by full hydrogenation.Interestingly,by further hole doping,it can be regulated into a metallic state with the sp^(3)-hybridized σ electrons metalized,and a giant Kohn anomaly appears in the optical phonons.The two factors together enhance the electron–phonon coupling,and lead to high-T_(c) superconductivity.When the hole doping concentration of hydrogenated-(5,5)CNT is 2.5 hole/cell,the calculated T_(c) is 82.3 K,exceeding the boiling point of liquid nitrogen.Therefore,the predicted hole-doped hydrogenated-(5,5)CNT provides a new platform for 1D high-T_(c) superconductivity and may have potential applications in 1D nanodevices.
基金supported by the National Natural Science Foundation of China(32371874,32401569)supported by Beijing Natural Science Foundation(6244053)。
文摘Monitoring waterbirds is vital for evaluating the ecological health of wetlands,and object detection offers an automated solution for identifying birds in monitoring imagery.However,conventional detection methods often overlook the multi-scale nature of bird targets,limiting their ability to capture rich contextual information across different scales.To address this,we propose a cross-dimensional attention network(CDA-Net)for bird detection that integrates spatial and channel information to improve species recognition.The proposed CDA-Net partitions feature maps into multiple channel wise sub-features.Spatial and channel attention are applied to each subfeature,and the resulting features are fused using the Hadamard product.The fused features are then forwarded to the detection head to generate the final detection results.This approach effectively captures and integrates information across spatial and channel dimensions.Experiments on our self-constructed Nanhai Wetland Waterbird Dataset and the public CUB-200-2011 dataset yield precision scores of 91.32%and 81.99%,respectively,outperforming existing methods.Our approach effectively handles scale variation in bird detection and provides a valuable tool for advancing automated wetland waterbird monitoring.
基金supported by the National Natural Science Foundation of China (Grant No.11574244 for G.Y.G.)the XJTU Research Fund for AI Science (Grant No.2025YXYC011 for G.Y.G.)the Hong Kong Global STEM Professorship Scheme (for X.C.Z.)。
文摘Compared to the well-studied two-dimensional(2D)ferroelectricity,the appearance of 2D antiferroelectricity is much rarer,where local dipoles from the nonequivalent sublattices within 2D monolayers are oppositely oriented.Using NbOCl_(2) monolayer with competing ferroelectric(FE)and antiferroelectric(AFE)phases as a 2D material platform,we demonstrate the emergence of intrinsic antiferroelectricity in NbOCl_(2) monolayer under experimentally accessible shear strain,along with new functionality associated with electric field-induced AFE-to-FE phase transition.Specifically,the complex configuration space accommodating FE and AFE phases,polarization switching kinetics,and finite temperature thermodynamic properties of 2D NbOCl_(2) are all accurately predicted by large-scale molecular dynamics simulations based on deep learning interatomic potential model.Moreover,room temperature stable antiferroelectricity with low polarization switching barrier and one-dimensional collinear polarization arrangement is predicted in shear-deformed NbOCl_(2) monolayer.The transition from AFE to FE phase in 2D NbOCl_(2) can be triggered by a low critical electric field,leading to a double polarization–electric(P–E)loop with small hysteresis.A new type of optoelectronic device composed of AFE-NbOCl_(2) is proposed,enabling electric“writing”and nonlinear optical“reading”logical operation with fast operation speed and low power consumption.
基金supported by the Canadian Institutes of Health Research(DFD-181599)the National Institutes of Health(T32AG058527)to RJB and R0190106435 to VM.
文摘Neurodegenerative disorders represent an increasingly pertinent public health crisis.As a greater proportion of the population ages,neurodegenerative disorders and other diseases of aging place undue burdens on patients,caregivers,and healthcare workers.Alzheimer’s disease(AD)and Parkinson’s disease represent the two most common neurodegenerative disorders in the population,affecting over 65 million people,worldwide.
基金supported by the National Natural Science Foundation of China(62303353,62273030,62573320)。
文摘Dear Editor,This letter studies the problem of stealthy attacks targeting stochastic event-based estimation,alongside proposing measures for their mitigation.A general attack framework is introduced,and the corresponding stealthiness condition is analyzed.To enhance system security,we advocate for a single-dimensional encryption method,showing that securing a singular data element is sufficient to shield the system from the perils of stealthy attacks.
文摘The original online version of this article was revised:The layout update for Article 758 has impacted the page range in the published issue,but did not affect the scholarly content.To ensure consistency with the originally assigned pages(2595-2614),we will need to publish an erratum to correct the article and restore the original page range.The original article has been corrected.
基金Supported by the Project of Design of Anti-corrosion and Anti-fouling Solutions for Offshore Wind Power Water-Cooled Systems(No.E428161)the National Natural Science Foundation of China(No.42176047)。
文摘Water-cooled system have significantly enhanced the power generation efficiency of offshore wind turbines.However,these innovative systems are susceptible to substantial biological fouling,maintenance challenges,and high upkeep costs.Therefore,the development of a specialized front-end filter tailored for direct current water-cooled system is importance.This involves the integration of dimensionally stable anode(DSA)and nickel alloy cathode,valued for their corrosion resistance in seawater,into a novel front-end filter system for Water-cooled applications.This system has the dual capability of generating hydrogen and chlorine for self-cleaning purposes.Implementing a flushing pulse electrolysis mode,it effectively mitigates electrode failure induced by cathodic calcium and magnesium deposition,thereby significantly prolonging electrode lifespan.Laboratory tests comprising system assembly and performance evaluations were conducted,with the system programmed to operate for 5 minutes every 24 hours under continuous flushing by natural seawater to simulate real-world conditions.After more than 11 months of continuous flushing,observations reveal that the DSA mesh and nickel alloy mesh maintain intact structural integrity and normal functioning.Subsequent 1꞉1 physical prototype Sea trial further validated the soundness of the system design and electrolytic control parameters.
基金supported by the NSFC(12461012)and the NSF of Chongqing(CSTB2024NSCQ-MSX1246).
文摘In this manuscript,we consider a non-autonomous dynamical system.Using the Carathéodory structure,we define a BS dimension on an arbitrary subset and obtain a Bowen’s equation that illustrates the relation of the BS dimension to the Pesin-Pitskel topological pressure given by Nazarian[24].Moreover,we establish a variational principle and an inverse variational principle for the BS dimension of non-autonomous dynamical systems.Finally,we also get an analogue of Billingsley’s theorem for the BS dimension of non-autonomous dynamical systems.
基金financially supported by the National Natural Science Foundation of China(Nos.42272137,42202160)AAPG Foundation Grants-in-Aid and the Strategic Cooperation Technology Projecti of CNPC and CUPB(No.ZLZX2020-01-05)。
文摘The pore structure of shale oil reservoir significantly affects the occurrence and mobility of hydrocarbons.The potential of a new type of alkaline lake shale oil has been demonstrated,but there are few reports on the pore system of alkaline lake shale,which restricts the efficient exploration and development of shale oil.This study investigates the Fengcheng Formation shale in the Mahu sag of the Junggar Basin,employing methods such as low-temperature nitrogecn adsorption(LTNA),mercury intrusion capillary pressure(MICP),and nuclear magnetic resonance(NMR)to quantitatively characterize the multi-scale pore structure and fractal characteristics of shale,while evaluating the applicability of these methods.Based on a comprehensive analysis of material composition,different pore types,and fractal dimensions,the controlling factors for the development of different pore types and their seepage capacity are discussed.The results indicate that inorganic mineral pores are the main development in alkaline lake shale,with the pore morphology being characterized by slit-like and ink-bottle shapes.The multi-scale pore size distribution(PSD)shows that Ⅱ-micropores(10-100 nm)and mesopores(100–1000 nm)are the main contributors to the pore system.The development of Ⅱ-micropores is associated with feldspar and calcareous minerals,the development of Ⅰ-micropores(<10 nm)and mesopores is related to quartz content,while large pores are mainly found in interlayer fissures of clay minerals.The development of Ⅰ-micropores increases the roughness of pore surface and enhances the adsorption capacity of the pores,while the development of Ⅱ-micropores associated with calcareous minerals hinders pore seepage capacity.Mesopores and macropores(>1000 nm)exhibit good flowability.The high content of siliceous minerals plays a positive role in the pore system of alkaline lake shale.The shale with higher fractal dimension Dmin exhibits greater adsorption capacity,which hinders the accumulation of free-state shale oil.Different types of pore space play different roles in the occurrence of shale oil,with free-state shale oil primarily occurring in micro-fractures and inorganic mineral pores,and the pore size is exceeding 10 nm.
基金funded by National Natural Science Foundation of China(Nos.12402142,11832013 and 11572134)Natural Science Foundation of Hubei Province(No.2024AFB235)+1 种基金Hubei Provincial Department of Education Science and Technology Research Project(No.Q20221714)the Opening Foundation of Hubei Key Laboratory of Digital Textile Equipment(Nos.DTL2023019 and DTL2022012).
文摘Owing to their global search capabilities and gradient-free operation,metaheuristic algorithms are widely applied to a wide range of optimization problems.However,their computational demands become prohibitive when tackling high-dimensional optimization challenges.To effectively address these challenges,this study introduces cooperative metaheuristics integrating dynamic dimension reduction(DR).Building upon particle swarm optimization(PSO)and differential evolution(DE),the proposed cooperative methods C-PSO and C-DE are developed.In the proposed methods,the modified principal components analysis(PCA)is utilized to reduce the dimension of design variables,thereby decreasing computational costs.The dynamic DR strategy implements periodic execution of modified PCA after a fixed number of iterations,resulting in the important dimensions being dynamically identified.Compared with the static one,the dynamic DR strategy can achieve precise identification of important dimensions,thereby enabling accelerated convergence toward optimal solutions.Furthermore,the influence of cumulative contribution rate thresholds on optimization problems with different dimensions is investigated.Metaheuristic algorithms(PSO,DE)and cooperative metaheuristics(C-PSO,C-DE)are examined by 15 benchmark functions and two engineering design problems(speed reducer and composite pressure vessel).Comparative results demonstrate that the cooperative methods achieve significantly superior performance compared to standard methods in both solution accuracy and computational efficiency.Compared to standard metaheuristic algorithms,cooperative metaheuristics achieve a reduction in computational cost of at least 40%.The cooperative metaheuristics can be effectively used to tackle both high-dimensional unconstrained and constrained optimization problems.
基金funded by the Major Projects of Aero-Engines and Gas Turbines grant number J2019-I-0008-0008.
文摘This paper introduces a computationally efficient global sensitivity analysis method for quantifying the influence of uncertain clamp support conditions on the natural frequencies of aero-engine pipe systems.The dynamic model is based on a three-dimensional Timoshenko beam finite element formulation,with clamps represented as distributed spring elements possessing anisotropic stiffness.To overcome the prohibitive cost of traditional Monte Carlo simulation,the multiplicative dimensional reduction method(M-DRM)is integrated with variance decomposition theory.This approach approximates the high-dimensional frequency response function as a product of univariate components,enabling rapid computation of Sobol’sensitivity indices with a computational cost reduced by three orders of magnitude.Numerical case studies on a planar Z-shaped pipe and a spatial series-parallel configuration reveal that clamp position parameters dominate the system’s natural frequency characteristics.For critical clamps,Sobol’indices exceed 0.8 across multiple vibration modes,whereas stiffness parameters exhibit negligible influence.The proposed methodology provides a rigorous and efficient tool for identifying dominant uncertainty sources,guiding tolerance allocation in manufacturing,and informing robust support design for vibration-sensitive piping systems.
文摘Based on the theory of multibody system dynamics, the spatial kinematics analysis of the Mcpherson independent suspension widely used in the car was carried out. A practical and simpler method was provided to reduce the number of the generalized coordinates and constraint functions. By solving the nonlinear equations, the motion of any points in the whole suspension and wheel system can be predicted, including the spatial changes of the wheel alignment parameters which are of great importance to the car performances.
文摘The focusing tomography is presented to reconstruct 3 dimensional irradiance distribution. A 3 dimensional luminous body could be considered as the combination of many 2 dimensional parallel luminous sections. Focus on these discrete sections respectively by a single camera, a group of images would be captured to form governing equations of irradiance. After inversion procedure, the irradiance distribution of different sections could be decoded. In this experimentation two lightbulbs are used to simulate two luminous sections. Reasonable results demonstrate that this technique could be a useful method in irradiance reconstruction after further development.
基金supported by the Natural Science Foundation of China under Grant Nos.60804008,61174048and 11071263the Fundamental Research Funds for the Central Universities and Guangdong Province Key Laboratory of Computational Science at Sun Yat-Sen University
文摘In this paper, the global controllability for a class of high dimensional polynomial systems has been investigated and a constructive algebraic criterion algorithm for their global controllability has been obtained. By the criterion algorithm, the global controllability can be determined in finite steps of arithmetic operations. The algorithm is imposed on the coefficients of the polynomials only and the analysis technique is based on Sturm Theorem in real algebraic geometry and its modern progress. Finally, the authors will give some examples to show the application of our results.
基金supported by the National Natural Science Foundation of China under Grant No.61273090
文摘This paper deals with the output regulation problem for a class of SISO infinite dimensional systems with an uncertain exosystem.For these systems,a concept of relative degree is firstly introduced and used to construct a transformation which leads to the canonical form of output feedback systems.Then,based on this canonical form,by means of an internal model and a recursive adaptive control,the authors obtain an adaptive regulator which solves the problem.It should be pointed out that the proposed regulator is finite dimensional while it is usually infinite dimensional in existing literatures.
