An upper estimate of the new curvature entropy is provided,via the integral inequality of a concave function.For two origin-symmetric convex bodies in R^(n),this bound is sharper than the log-Minkowski inequality of c...An upper estimate of the new curvature entropy is provided,via the integral inequality of a concave function.For two origin-symmetric convex bodies in R^(n),this bound is sharper than the log-Minkowski inequality of curvature entropy.As its application,a novel proof of the log-Minkowski inequality of curvature entropy in the plane is given.展开更多
Identifying key nodes in complex networks is crucial for understanding and controlling their dynamics. Traditional centrality measures often fall short in capturing the multifaceted roles of nodes within these network...Identifying key nodes in complex networks is crucial for understanding and controlling their dynamics. Traditional centrality measures often fall short in capturing the multifaceted roles of nodes within these networks. The Page Rank algorithm, widely recognized for ranking web pages, offers a more nuanced approach by considering the importance of connected nodes. However, existing methods generally overlook the geometric properties of networks, which can provide additional insights into their structure and functionality. In this paper, we propose a novel method named Curv-Page Rank(C-PR), which integrates network curvature and Page Rank to identify influential nodes in complex networks. By leveraging the geometric insights provided by curvature alongside structural properties, C-PR offers a more comprehensive measure of a node's influence. Our approach is particularly effective in networks with community structures, where it excels at pinpointing bridge nodes critical for maintaining connectivity and facilitating information flow. We validate the effectiveness of C-PR through extensive experiments. The results demonstrate that C-PR outperforms traditional centrality-based and Page Rank methods in identifying critical nodes. Our findings offer fresh insights into the structural importance of nodes across diverse network configurations, highlighting the potential of incorporating geometric properties into network analysis.展开更多
As oil and gas exploration moves into deeper waters,marine risers are subjected to increasingly complex service conditions,including vessel motions,ocean currents,seabed-soil interactions,and internal flow effects.Thi...As oil and gas exploration moves into deeper waters,marine risers are subjected to increasingly complex service conditions,including vessel motions,ocean currents,seabed-soil interactions,and internal flow effects.This work establishes a dynamic behavior model of steel catenary risers(SCRs)with varying curvatures subjected to internal flow and external currents and considers the effects of pipe-soil interactions on the curvature profile.The governing equation is solved via the generalized integral transform technique(GITT),which yields a semi-analytical solution of a high-order nonlinear partial differential equation.Parametric studies are then performed to analyze the effects of varying curvature on the vibration frequency and amplitude of SCRs.The vibration frequency and amplitude increase with the touchdown angle and hang-off angle,although the effect of the hang-off angle is negligible.Additionally,as the curvature increases along the centerline axis,the position of the maximum amplitude of the SCR moves upward.展开更多
The elastic properties of membranes are typically characterized by a few phenomenological parameters,including bending and Gaussian curvature moduli measuring the membrane rigidity against its deformation and topologi...The elastic properties of membranes are typically characterized by a few phenomenological parameters,including bending and Gaussian curvature moduli measuring the membrane rigidity against its deformation and topological change,as well as spontaneous curvature arising from the asymmetry between the two leaflets in the lipid bilayers.Though tether-based and fluctuationbased experiments are commonly utilized to measure the bending modulus,measuring the Gaussian curvature modulus and the spontaneous curvature of the membrane is considered to be much more difficult.In this paper,we study the buckling process of a circular membrane with nonzero spontaneous curvature under compressive stresses.It is found that when the stress exceeds a critical value,the circular membrane will transform from a spherical cap to a buckled shape,with its buckling degree enhanced with the increase of stress until its base is constricted to almost zero.As the stress-strain relationship of the buckled membrane strongly depends on the Gaussian curvature modulus and the spontaneous curvature,we therefore propose a method to determine the Gaussian curvature modulus and the spontaneous curvature simultaneously by measuring its stress-strain relationship during a buckling process.展开更多
Metal-free carbon catalysts have garnered significant attention since their inception.Despite substantial advancements,including widely adopted strategies such as heteroatom doping and defect engineering,their catalyt...Metal-free carbon catalysts have garnered significant attention since their inception.Despite substantial advancements,including widely adopted strategies such as heteroatom doping and defect engineering,their catalytic performance remains inferior to that of metal-based catalysts.In this study,we have predicted and demonstrated that the curvature of carbon plays a pivotal role in the adsorption of acetylene and the overall catalytic performance.First-principles calculations suggest that a tip-enhanced local electric field at the defect site on the curved carbon catalyst enhances the reaction kinetics for acetylene hydrochlorination.The experimental results highlight the structural advantages of the curved defect site,revealing that high-curvature defective carbon(HCDC)demonstrates an adsorption capacity for acetylene that is almost two orders of magnitude higher than that of defective carbon.Notably,HCDC achieves an acetylene conversion of up to 90%at 220℃under a gas hourly space velocity of 300 h^(-1),significantly surpassing the performance of the benchmark 0.25%Au/AC catalyst.This proof-of-concept study reveals the fundamental mechanisms driving the superior performance of carbon catalysts with curved nanostructures and presents a straightforward,environmentally friendly method for large-scale production of carbon materials with precisely controlled nanostructures.It highlights the potential for commercializing metal-free carbon catalysts in acetylene hydrochlorination and related heterogenous catalytic reactions.展开更多
In this paper,we study scalar curvature rigidity of non-smooth metrics on smooth manifolds with non-positive Yamabe invariant.We prove that if the scalar curvature is not less than the Yamabe invariant in the distribu...In this paper,we study scalar curvature rigidity of non-smooth metrics on smooth manifolds with non-positive Yamabe invariant.We prove that if the scalar curvature is not less than the Yamabe invariant in the distributional sense,then the manifold must be isometric to an Einstein manifold.This result extends Theorem 1.4 in Jiang,Sheng and Zhang[27],from a special case where the manifolds have zero Yamabe invariant to general cases where the manifolds have non-positive Yamabe invariant.展开更多
Crystal defects and morphological modifications are popular strategies to enhance the catalytic activity of heterogeneous semiconductor photocatalysts.Despite defect engineering and morphology control show their succe...Crystal defects and morphological modifications are popular strategies to enhance the catalytic activity of heterogeneous semiconductor photocatalysts.Despite defect engineering and morphology control show their successful applications in ZnO,the effects of curved surface modifications on the photocatalytic performance of ZnO and their interplay with the defect formation remain unclear.To resolve this puzzle,we systemically investigate the joint effects of curvature and defect formation on the electronic structure,optoelectronic properties,and photocatalytic performance of ZnO slabs using first-principles calculations.We find that curvature deformation effectively narrows the electronic bandgap by up to 1.6 eV and shifts the p-/d-band centers,thereby enhancing light absorption in the visible and near-ultraviolet regions.Besides,curvature deformation stimulates self-polarization,facilitating the separation of photogenerated electrons and holes.Also,curvature deformation promotes the formation of defects by reducing defect formation energy(by up to 1.0 eV),thus creating abundant reaction sites for photocatalysis.Intriguingly,the synergistic interaction between curvature and defect deformation further strengthens the self-polarization,narrows the electronic bandgaps,adjusts the p-/d-band centers to improve the optoelectronic properties,and influences the dissociation and free energy barriers of intermediates.Consequently,our findings reveal that this synergy substantially enhances the photocatalytic performance of ZnO slabs,providing deeper insights into the role of defect engineering and morphology control on photocatalysis.展开更多
Berry curvature describes the intrinsic geometric property of electronic band structure,crucial for governing emergent transport phenomena.As a typical Berry-curvature-related property,the anomalous Nernst effect prob...Berry curvature describes the intrinsic geometric property of electronic band structure,crucial for governing emergent transport phenomena.As a typical Berry-curvature-related property,the anomalous Nernst effect probes local Berry curvature near the Fermi surface,whereas the anomalous Hall effect integrates contributions across all occupied states.Thus,the anomalous Nernst effect is a superior probe for detecting subtle evolution of Berry curvature near the Fermi level;however,their relation remains elusive.Here,we demonstrate giant anomalous Nernst angles induced by Berry curvature in layered itinerant ferromagnets Fe_(3)GaTe_(2)and Fe_(5)GeTe_(2).Their maximum values(≈0.33 for Fe_(3)GaTe_(2)and≈0.41 for Fe_(5)GeTe_(2))are one order of magnitude larger than those of traditional ferromagnets(θ_(AN)^(max)<0.02).Scaling analysis of anomalous Hall effect in these two systems further suggests these giant angles originate from intrinsic Berry curvature.These findings indicate Berrycurvature-dominated regimes,and establish these materials for high-performance spin-caloritronic devices.展开更多
Nanomaterials have garnered recognition for their notable surface effects and demonstration of superior mechanical properties.Previous studies on the surface effects of nanomaterials,employing the finite element metho...Nanomaterials have garnered recognition for their notable surface effects and demonstration of superior mechanical properties.Previous studies on the surface effects of nanomaterials,employing the finite element method,often relied on simplified twodimensional models due to theoretical complexities.Consequently,these simplified models inadequately represent the mechanical properties of nanomaterials and fail to capture the substantial impact of surface effects,particularly the curvature dependence of nanosurfaces.This study applies the principle of minimum energy and leverages the Steigmann-Ogden surface theory of nanomaterials to formulate a novel finite element surface element that comprehensively accounts for surface effects.We conducted an analysis of the stress distribution and deformation characteristics of four typical 2D and 3D nanomaterial models.The accuracy of the developed surface element and finite element calculation method was verified through comparison with established references.The resulting finite element model provides a robust and compelling scientific approach for accurately predicting the mechanical performance of nanomaterials.展开更多
Low-temperature lithium sulfur(Li-S)batteries have attracted increasing attention,but lithium polysulfide(LiPSs)clu stering and tardy ionic mobility have been challenging issues,which could be exacerbated under high s...Low-temperature lithium sulfur(Li-S)batteries have attracted increasing attention,but lithium polysulfide(LiPSs)clu stering and tardy ionic mobility have been challenging issues,which could be exacerbated under high sulfur loading and lean electrolyte.The distinct behaviors of sulfur cathode in lowtemperature Li-S batteries call for special regulations of the sulfur host to improve the electrochemical performances.Here,a three-dimensional Ti_(3)C_(2)micro-cage(TCC)with an interfacial structure modulated by rich curvatures has been fabricated to propel the sulfur electrochemistry at subzero temperatures.Spectroscopic/microscopic analyses and theoretical calculations elucidate that the precipitation of ultrafine Ti-metal particles on the in-situ generated Ti_(3)C_(2)nanoribbons could trigger the self-scrolling of Ti_(3)C_(2)nanoribbons into TCC.Moreover,in-situ ultraviolet-visible spectra collected at low temperature and theoretical calculations verified that the TCC regulated by rich curvatures have effectively alleviated the Li+dissociation barrier,reduced the energy barrier for charge transfer at the electrode-electrolyte interface,and restrained the clustering and shuttling of LiPSs,thus accelerating the electrochemical conversion kinetics of sulfur species at low temperatures.The performances of the carbon-free TCC-S cathode at low temperatures have been also compared from the aspects of cathode configuration and measurement condition,to demonstrate the potential of TCC.This work can not only provide new methodology for regulating the interfacial structure of MXene to enrich the materials library for low-temperature Li-S batteries,but also expand understanding about the role of interfacial structure of sulfur host in Li-S batteries.展开更多
Metal-nitrogen-carbon(M-N-C)single-atom catalysts are widely utilized in various energy-related catalytic processes,offering a highly efficient and cost-effective catalytic system with significant potential.Recently,c...Metal-nitrogen-carbon(M-N-C)single-atom catalysts are widely utilized in various energy-related catalytic processes,offering a highly efficient and cost-effective catalytic system with significant potential.Recently,curvature-induced strain has been extensively demonstrated as a powerful tool for modulating the catalytic performance of M-N-C catalysts.However,identifying optimal strain patterns using density functional theory(DFT)is computationally intractable due to the high-dimensional search space.Here,we developed a graph neural network(GNN)integrated with an advanced topological data analysis tool-persistent homology-to predict the adsorption energy response of adsorbate under proposed curvature patterns,using nitric oxide electroreduction(NORR)as an example.Our machine learning model achieves high accuracy in predicting the adsorption energy response to curvature,with a mean absolute error(MAE)of 0.126 eV.Furthermore,we elucidate general trends in curvature-modulated adsorption energies of intermediates across various metals and coordination environments.We recommend several promising catalysts for NORR that exhibit significant potential for performance optimization via curvature modulation.This methodology can be readily extended to describe other non-bonded interactions,such as lattice strain and surface stress,providing a versatile approach for advanced catalyst design.展开更多
Radiofrequency ablation(RFA)is a form of minimally invasive procedure that precisely ablates abnormal lesions or hyperplastic tissues through thermal energy generated by the radiofrequency current at the tip electrode...Radiofrequency ablation(RFA)is a form of minimally invasive procedure that precisely ablates abnormal lesions or hyperplastic tissues through thermal energy generated by the radiofrequency current at the tip electrode of the flexible catheter,which aims to partially or fully restore the function of the corresponding tissues or organs.Accurate prediction and control of thermal fields are crucial for clinical thermal ablation to ensure precise control of the ablation lesion size and prevent excessive burning of healthy tissues.In this study,an axisymmetric analytical model is developed for the electrothermal analysis of RFA in the cambered tissue surface and verified with the finite element analysis(FEA),which incorporates both the thermal field induced by the radiofrequency current and Pennes'biothermal effect.This model utilizes analytically derived electric and thermal fields to accurately predict the increase in the tissue temperature and the time-varying size of ablation lesion in the tissue.Furthermore,the parameters such as the input current density,curvature,and convective heat transfer coefficient of blood have a significant effect on the thermal field and thus the ablation lesion size.This electrothermal analytical model with a large curvature may provide a theoretical foundation and guidance for the future RFA applications on large-curvature biological surfaces,thereby enhancing accuracy,reducing the need for re-ablation,and lowering the costs associated with the design and production of ablation catheters.展开更多
To solve the problem of false edges in a flat region of l_(1)norm total variational TV model,an edge extractor based on non-local idea is proposed in this paper.The new edge extractor can effectively suppress the infl...To solve the problem of false edges in a flat region of l_(1)norm total variational TV model,an edge extractor based on non-local idea is proposed in this paper.The new edge extractor can effectively suppress the influence of noise and extract the edge information of the image.The new edge extractor is used as the adaptive function and the weighting function of the l_(p) norm variational model to control the noise reduction ability of the model,and a new model 1 is obtained.Considering that the new model 1 only uses the gradient mode as the image feature operator,which is insufficient to express the image texture information,a new level set curvature gradient variational model 2 combined with the edge extractor is proposed.The new model 2 uses the idea of minimum curvature of the level set of clear images to obtain noise reduction images.By coupling new model 1 and new model 2 to smooth the noise and protect more textures,a new Non-local level set denoising model(NLSDM)for image noise reduction is obtained.The experimental results show that compared with the noise reduction model,the new model has significantly improved the peak signal-to-noise ratio and structural similarity,and the effect of noise reduction and edge preservation is better.展开更多
Cloud coverage has become a significant factor affecting the availability of remote-sensing images in many applications.To mitigate the adverse impact of cloud coverage and recover ground information obscured by cloud...Cloud coverage has become a significant factor affecting the availability of remote-sensing images in many applications.To mitigate the adverse impact of cloud coverage and recover ground information obscured by clouds,this paper presents a curvature-driven cloud removal method.Considering that each image can be regarded as a curved surface and the curvature can reflect the texture information well due to its dependence on the surface’s undulation degree,the presented method transforms image from natural domain to curvature domain for information reconstruction to maintain details of reference image.In order to improve the overall consistency and continuity of cloud removal results,the optimal boundary for cloud coverage area replacement is determined first to make the boundary pass through pixels with minimum curvature difference.Then,the curvature of missing area is reconstructed based on the curvature of reference image,and the reconstructed curvature is inversely transformed to natural domain to obtain a cloud-free image.In addition,considering the possible significant radiometric differences between different images,the initial cloud-free result will be further refined based on specific checkpoints to improve the local accuracy.To evaluate the performance of the proposed method,both simulated experiments and real data experiments are carried out.Experimental results show that the proposed method can achieve satisfactory results in terms of radiometric accuracy and consistency.展开更多
AIM:To analyze the distribution of refractive status in school-age children with different corneal curvatures(CC)and the correlation between CC and refractive status.METHODS:A total of 2214 school-aged children of gra...AIM:To analyze the distribution of refractive status in school-age children with different corneal curvatures(CC)and the correlation between CC and refractive status.METHODS:A total of 2214 school-aged children of grade 4 in Hangzhou who were screened for school myopia were included.Uncorrected distance visual acuity(UCDVA),non-cycloplegic refraction,axial length(AL),horizontal and vertical corneal curvature(K1,K2)were measured and spherical equivalent(SE),corneal curvature radius(CCR)and axial length/corneal radius of curvature ratio(AL/CR)were calculated.UCDVA<5.0 and SE≤-0.50 D were classified as school-screening myopia.According to the different CCRs,the patients were divided into the lower corneal curvature(LCC)group(CCR≥7.92)and the higher corneal curvature(HCC)group(CCR<7.92).Each group was further divided into the normal AL subgroup and the long AL subgroup.The refractive parameters were compared to identify any differences between the two groups.RESULTS:Both SE and AL were greater in the LCC group(P=0.013,P<0.001).The prevalence of myopia was 38% in the LCC group and 44% in the HCC group(P<0.001).The proportion of children without screening myopia was higher in the LCC group(62%)than in the HCC group(56%).Among these children without screening myopia,the proportion of long AL in the LCC group(24%)was significantly higher than that in the HCC group(0.012%;P<0.001).The change of SE in the LCC group was less affected by the increase of AL than that in the HCC group.CONCLUSION:School-aged children in the LCC group have a lower incidence of screening myopia and longer AL.Low CC can mask SE reduction and AL growth to some extent,and the change of AL growth change more in children with low CC than high CC.Before the onset of myopia,its growth rate is even faster than that after the onset of myopia.展开更多
In this article,we study Kahler metrics on a certain line bundle over some compact Kahler manifolds to find complete Kahler metrics with positive holomorphic sectional(or bisectional)curvatures.Thus,we apply a strateg...In this article,we study Kahler metrics on a certain line bundle over some compact Kahler manifolds to find complete Kahler metrics with positive holomorphic sectional(or bisectional)curvatures.Thus,we apply a strategy to a famous Yau conjecture with a co-homogeneity one geometry.展开更多
In this note,we prove a logarithmic Sobolev inequality which holds for compact submanifolds without a boundary in manifolds with asymptotically nonnegative sectional curvature.Like the Michale-Simon Sobolev inequality...In this note,we prove a logarithmic Sobolev inequality which holds for compact submanifolds without a boundary in manifolds with asymptotically nonnegative sectional curvature.Like the Michale-Simon Sobolev inequality,this inequality contains a term involving the mean curvature.展开更多
Using the harmonic map theory,we study the geometry of conformal minimal twospheres immersed in Q_(6),or a real Grassmannian manifold G(2,8;R)equivalently.Then we classify the linearly full reducible conformal minimal...Using the harmonic map theory,we study the geometry of conformal minimal twospheres immersed in Q_(6),or a real Grassmannian manifold G(2,8;R)equivalently.Then we classify the linearly full reducible conformal minimal immersions with constant Gaussian curvature from S^(2)to Q_(6)under some conditions.We also construct specific examples of non-congruent two-spheres with the same Gaussian curvature,up to SO(8)-equivalence,for each case.展开更多
The gravitational curvatures(GC,the third-order derivatives of the gravitational potential)in gravity field modeling are gaining increased interest in geosciences.The crustal effects of the GC and Moho variation sense...The gravitational curvatures(GC,the third-order derivatives of the gravitational potential)in gravity field modeling are gaining increased interest in geosciences.The crustal effects of the GC and Moho variation sensed by the GC are not fully evaluated for the current study.In this contribution,the effects of the GC induced by topographic and anomalous crustal masses are investigated based on ETOPO1 and CRUST1.0 models using the tesseroids.By adopting the gravitational stripping correction,the residual GC sensed by the CRUST1.0 Moho depths are presented globally to examine whether the GC can sense crustal mass anomalies at the satellite altitude of 260 km.The spatial analysis using the Pearson correlations coefficient(PCC)between the residual GC and the CRUST1.0 Moho depths is performed.Among the 10 residual GC functionals,the PCC value of the residual radial-radial-radial componentδT^(res)_(zzz)is largest with 0.31,where this value is highly dependent on the spectral content removed from the EGM2008,e.g.signals assumed to relate to deeper mass anomalies.Numerical experiments show that with the increased order of the derivatives up to third-order,the fineness level of different global Moho sensed crustal mass anomalies increases correspondingly.Taking the Tibetan plateau for example,the values of theδT^(res)_(zzz)can better reveal the detailed features of the Tibetan plateau’s Moho depth than these of the lower-order residual radial functionals(i.e.disturbing potentialδTres,disturbing radial gravity vectorδT^(res)_(z),and disturbing radial-radial gravity gradient tensorδT^(res)_(zz)),especially for the Qaidam,Sichuan,Tarim,and Turpan basins.Numerical results over the Himalayan region demonstrate that the GC componentδT^(res)^(z)has some potential in geophysical inversion.These residual GC functionals would help to get a better knowledge of the internal structures of the Earth and other planetary objects.展开更多
基金supported by the NSFC(12171378)supported by the Characteristic innovation projects of universities in Guangdong province(2023K-TSCX381)+3 种基金supported by the Young Top-Talent program of Chongqing(CQYC2021059145)the Major Special Project of NSFC(12141101)the Science and Technology Research Program of Chongqing Municipal Education Commission(KJZD-K202200509)the Natural Science Foundation Project of Chongqing(CSTB2024NSCQ-MSX0937).
文摘An upper estimate of the new curvature entropy is provided,via the integral inequality of a concave function.For two origin-symmetric convex bodies in R^(n),this bound is sharper than the log-Minkowski inequality of curvature entropy.As its application,a novel proof of the log-Minkowski inequality of curvature entropy in the plane is given.
基金Project partially supported by the National Natural Science Foundation of China (Grant Nos. 61672298 and 62373197)the Major Project of Philosophy and Social Science Research in Colleges and Universities in Jiangsu Province,China (Grant No. 2018SJZDI142)the Postgraduate Research & Practice Innovation Program of Jiangsu Province,China (Grant No. KYCX23 1045)。
文摘Identifying key nodes in complex networks is crucial for understanding and controlling their dynamics. Traditional centrality measures often fall short in capturing the multifaceted roles of nodes within these networks. The Page Rank algorithm, widely recognized for ranking web pages, offers a more nuanced approach by considering the importance of connected nodes. However, existing methods generally overlook the geometric properties of networks, which can provide additional insights into their structure and functionality. In this paper, we propose a novel method named Curv-Page Rank(C-PR), which integrates network curvature and Page Rank to identify influential nodes in complex networks. By leveraging the geometric insights provided by curvature alongside structural properties, C-PR offers a more comprehensive measure of a node's influence. Our approach is particularly effective in networks with community structures, where it excels at pinpointing bridge nodes critical for maintaining connectivity and facilitating information flow. We validate the effectiveness of C-PR through extensive experiments. The results demonstrate that C-PR outperforms traditional centrality-based and Page Rank methods in identifying critical nodes. Our findings offer fresh insights into the structural importance of nodes across diverse network configurations, highlighting the potential of incorporating geometric properties into network analysis.
基金financially supported by the National Natural Science Foundation of China(Grant No.52201312).
文摘As oil and gas exploration moves into deeper waters,marine risers are subjected to increasingly complex service conditions,including vessel motions,ocean currents,seabed-soil interactions,and internal flow effects.This work establishes a dynamic behavior model of steel catenary risers(SCRs)with varying curvatures subjected to internal flow and external currents and considers the effects of pipe-soil interactions on the curvature profile.The governing equation is solved via the generalized integral transform technique(GITT),which yields a semi-analytical solution of a high-order nonlinear partial differential equation.Parametric studies are then performed to analyze the effects of varying curvature on the vibration frequency and amplitude of SCRs.The vibration frequency and amplitude increase with the touchdown angle and hang-off angle,although the effect of the hang-off angle is negligible.Additionally,as the curvature increases along the centerline axis,the position of the maximum amplitude of the SCR moves upward.
基金the financial support from the National Natural Science Foundation of China under Grant Nos.12174323 and 12474199Fundamental Research Funds for Central Universities of China under Grant No.20720240144(RM)111 project B16029。
文摘The elastic properties of membranes are typically characterized by a few phenomenological parameters,including bending and Gaussian curvature moduli measuring the membrane rigidity against its deformation and topological change,as well as spontaneous curvature arising from the asymmetry between the two leaflets in the lipid bilayers.Though tether-based and fluctuationbased experiments are commonly utilized to measure the bending modulus,measuring the Gaussian curvature modulus and the spontaneous curvature of the membrane is considered to be much more difficult.In this paper,we study the buckling process of a circular membrane with nonzero spontaneous curvature under compressive stresses.It is found that when the stress exceeds a critical value,the circular membrane will transform from a spherical cap to a buckled shape,with its buckling degree enhanced with the increase of stress until its base is constricted to almost zero.As the stress-strain relationship of the buckled membrane strongly depends on the Gaussian curvature modulus and the spontaneous curvature,we therefore propose a method to determine the Gaussian curvature modulus and the spontaneous curvature simultaneously by measuring its stress-strain relationship during a buckling process.
文摘Metal-free carbon catalysts have garnered significant attention since their inception.Despite substantial advancements,including widely adopted strategies such as heteroatom doping and defect engineering,their catalytic performance remains inferior to that of metal-based catalysts.In this study,we have predicted and demonstrated that the curvature of carbon plays a pivotal role in the adsorption of acetylene and the overall catalytic performance.First-principles calculations suggest that a tip-enhanced local electric field at the defect site on the curved carbon catalyst enhances the reaction kinetics for acetylene hydrochlorination.The experimental results highlight the structural advantages of the curved defect site,revealing that high-curvature defective carbon(HCDC)demonstrates an adsorption capacity for acetylene that is almost two orders of magnitude higher than that of defective carbon.Notably,HCDC achieves an acetylene conversion of up to 90%at 220℃under a gas hourly space velocity of 300 h^(-1),significantly surpassing the performance of the benchmark 0.25%Au/AC catalyst.This proof-of-concept study reveals the fundamental mechanisms driving the superior performance of carbon catalysts with curved nanostructures and presents a straightforward,environmentally friendly method for large-scale production of carbon materials with precisely controlled nanostructures.It highlights the potential for commercializing metal-free carbon catalysts in acetylene hydrochlorination and related heterogenous catalytic reactions.
基金Supported by the National Key Research and Development Program of China(2022YFA1005501)the Natural Science Foundation of Jiangsu Province(BK20241433).
文摘In this paper,we study scalar curvature rigidity of non-smooth metrics on smooth manifolds with non-positive Yamabe invariant.We prove that if the scalar curvature is not less than the Yamabe invariant in the distributional sense,then the manifold must be isometric to an Einstein manifold.This result extends Theorem 1.4 in Jiang,Sheng and Zhang[27],from a special case where the manifolds have zero Yamabe invariant to general cases where the manifolds have non-positive Yamabe invariant.
基金supported by the National Key R&D Program of China(No.2021YFA1502300)the National Natural Science Foundation of China(Nos.22103012,22173105)+2 种基金the Natural Science Foundation of Fujian Province(Nos.2024J01456,2024J01191)the Selfdeployment Project Research Program of Haixi Institutes,Chinese Academy of Sciences(No.CXZX-2022-GH10)the CAS Youth Interdisciplinary Team.
文摘Crystal defects and morphological modifications are popular strategies to enhance the catalytic activity of heterogeneous semiconductor photocatalysts.Despite defect engineering and morphology control show their successful applications in ZnO,the effects of curved surface modifications on the photocatalytic performance of ZnO and their interplay with the defect formation remain unclear.To resolve this puzzle,we systemically investigate the joint effects of curvature and defect formation on the electronic structure,optoelectronic properties,and photocatalytic performance of ZnO slabs using first-principles calculations.We find that curvature deformation effectively narrows the electronic bandgap by up to 1.6 eV and shifts the p-/d-band centers,thereby enhancing light absorption in the visible and near-ultraviolet regions.Besides,curvature deformation stimulates self-polarization,facilitating the separation of photogenerated electrons and holes.Also,curvature deformation promotes the formation of defects by reducing defect formation energy(by up to 1.0 eV),thus creating abundant reaction sites for photocatalysis.Intriguingly,the synergistic interaction between curvature and defect deformation further strengthens the self-polarization,narrows the electronic bandgaps,adjusts the p-/d-band centers to improve the optoelectronic properties,and influences the dissociation and free energy barriers of intermediates.Consequently,our findings reveal that this synergy substantially enhances the photocatalytic performance of ZnO slabs,providing deeper insights into the role of defect engineering and morphology control on photocatalysis.
基金supported by the National Key Research and Development Program of China(Grant Nos.2024YFA1408104,2021YFA1202901,and 2022YFA1204001)the National Natural Science Foundation of China(Grant Nos.92365203,U24A6002,52302180,and U21A2086)+1 种基金the Natural Science Foundation of Jiangsu Province(Grant No.BK20243011)the Hebei Natural Science Foundation No.E2023203002).
文摘Berry curvature describes the intrinsic geometric property of electronic band structure,crucial for governing emergent transport phenomena.As a typical Berry-curvature-related property,the anomalous Nernst effect probes local Berry curvature near the Fermi surface,whereas the anomalous Hall effect integrates contributions across all occupied states.Thus,the anomalous Nernst effect is a superior probe for detecting subtle evolution of Berry curvature near the Fermi level;however,their relation remains elusive.Here,we demonstrate giant anomalous Nernst angles induced by Berry curvature in layered itinerant ferromagnets Fe_(3)GaTe_(2)and Fe_(5)GeTe_(2).Their maximum values(≈0.33 for Fe_(3)GaTe_(2)and≈0.41 for Fe_(5)GeTe_(2))are one order of magnitude larger than those of traditional ferromagnets(θ_(AN)^(max)<0.02).Scaling analysis of anomalous Hall effect in these two systems further suggests these giant angles originate from intrinsic Berry curvature.These findings indicate Berrycurvature-dominated regimes,and establish these materials for high-performance spin-caloritronic devices.
基金supported by the Jiangsu Funding Program for Excellent Postdoctoral Talent (Grant No.2023ZB397)the Project funded by China Postdoctoral Science Foundation (Grant No.2023M732986).
文摘Nanomaterials have garnered recognition for their notable surface effects and demonstration of superior mechanical properties.Previous studies on the surface effects of nanomaterials,employing the finite element method,often relied on simplified twodimensional models due to theoretical complexities.Consequently,these simplified models inadequately represent the mechanical properties of nanomaterials and fail to capture the substantial impact of surface effects,particularly the curvature dependence of nanosurfaces.This study applies the principle of minimum energy and leverages the Steigmann-Ogden surface theory of nanomaterials to formulate a novel finite element surface element that comprehensively accounts for surface effects.We conducted an analysis of the stress distribution and deformation characteristics of four typical 2D and 3D nanomaterial models.The accuracy of the developed surface element and finite element calculation method was verified through comparison with established references.The resulting finite element model provides a robust and compelling scientific approach for accurately predicting the mechanical performance of nanomaterials.
基金support from the National Natural Science Foundation of China for financial support(22175054)the Distinguished Project for Scientific Research in Universities of Anhui Province(2024AH020011)+2 种基金the Key Project for Cultivation of Outstanding Young Scholars in Universities of Anhui Province(YQZD2024015)the Key Project of Provincial Natural Science Research Foundation of Anhui Universities,China(No.2022AH050406)the Anhui Province Research Funding for Outstanding Young Talents in Colleges and Universities,China(No.gxyq2022021)。
文摘Low-temperature lithium sulfur(Li-S)batteries have attracted increasing attention,but lithium polysulfide(LiPSs)clu stering and tardy ionic mobility have been challenging issues,which could be exacerbated under high sulfur loading and lean electrolyte.The distinct behaviors of sulfur cathode in lowtemperature Li-S batteries call for special regulations of the sulfur host to improve the electrochemical performances.Here,a three-dimensional Ti_(3)C_(2)micro-cage(TCC)with an interfacial structure modulated by rich curvatures has been fabricated to propel the sulfur electrochemistry at subzero temperatures.Spectroscopic/microscopic analyses and theoretical calculations elucidate that the precipitation of ultrafine Ti-metal particles on the in-situ generated Ti_(3)C_(2)nanoribbons could trigger the self-scrolling of Ti_(3)C_(2)nanoribbons into TCC.Moreover,in-situ ultraviolet-visible spectra collected at low temperature and theoretical calculations verified that the TCC regulated by rich curvatures have effectively alleviated the Li+dissociation barrier,reduced the energy barrier for charge transfer at the electrode-electrolyte interface,and restrained the clustering and shuttling of LiPSs,thus accelerating the electrochemical conversion kinetics of sulfur species at low temperatures.The performances of the carbon-free TCC-S cathode at low temperatures have been also compared from the aspects of cathode configuration and measurement condition,to demonstrate the potential of TCC.This work can not only provide new methodology for regulating the interfacial structure of MXene to enrich the materials library for low-temperature Li-S batteries,but also expand understanding about the role of interfacial structure of sulfur host in Li-S batteries.
基金supported by the Natural Science Foundation of Xiamen,China(3502Z202472001)the National Natural Science Foundation of China(22402163,22021001,21925404,T2293692,and 22361132532)。
文摘Metal-nitrogen-carbon(M-N-C)single-atom catalysts are widely utilized in various energy-related catalytic processes,offering a highly efficient and cost-effective catalytic system with significant potential.Recently,curvature-induced strain has been extensively demonstrated as a powerful tool for modulating the catalytic performance of M-N-C catalysts.However,identifying optimal strain patterns using density functional theory(DFT)is computationally intractable due to the high-dimensional search space.Here,we developed a graph neural network(GNN)integrated with an advanced topological data analysis tool-persistent homology-to predict the adsorption energy response of adsorbate under proposed curvature patterns,using nitric oxide electroreduction(NORR)as an example.Our machine learning model achieves high accuracy in predicting the adsorption energy response to curvature,with a mean absolute error(MAE)of 0.126 eV.Furthermore,we elucidate general trends in curvature-modulated adsorption energies of intermediates across various metals and coordination environments.We recommend several promising catalysts for NORR that exhibit significant potential for performance optimization via curvature modulation.This methodology can be readily extended to describe other non-bonded interactions,such as lattice strain and surface stress,providing a versatile approach for advanced catalyst design.
基金Project supported by the National Natural Science Foundation of China(Nos.U23A20111 and 12372160)。
文摘Radiofrequency ablation(RFA)is a form of minimally invasive procedure that precisely ablates abnormal lesions or hyperplastic tissues through thermal energy generated by the radiofrequency current at the tip electrode of the flexible catheter,which aims to partially or fully restore the function of the corresponding tissues or organs.Accurate prediction and control of thermal fields are crucial for clinical thermal ablation to ensure precise control of the ablation lesion size and prevent excessive burning of healthy tissues.In this study,an axisymmetric analytical model is developed for the electrothermal analysis of RFA in the cambered tissue surface and verified with the finite element analysis(FEA),which incorporates both the thermal field induced by the radiofrequency current and Pennes'biothermal effect.This model utilizes analytically derived electric and thermal fields to accurately predict the increase in the tissue temperature and the time-varying size of ablation lesion in the tissue.Furthermore,the parameters such as the input current density,curvature,and convective heat transfer coefficient of blood have a significant effect on the thermal field and thus the ablation lesion size.This electrothermal analytical model with a large curvature may provide a theoretical foundation and guidance for the future RFA applications on large-curvature biological surfaces,thereby enhancing accuracy,reducing the need for re-ablation,and lowering the costs associated with the design and production of ablation catheters.
基金funded by National Nature Science Foundation of China,grant number 61302188.
文摘To solve the problem of false edges in a flat region of l_(1)norm total variational TV model,an edge extractor based on non-local idea is proposed in this paper.The new edge extractor can effectively suppress the influence of noise and extract the edge information of the image.The new edge extractor is used as the adaptive function and the weighting function of the l_(p) norm variational model to control the noise reduction ability of the model,and a new model 1 is obtained.Considering that the new model 1 only uses the gradient mode as the image feature operator,which is insufficient to express the image texture information,a new level set curvature gradient variational model 2 combined with the edge extractor is proposed.The new model 2 uses the idea of minimum curvature of the level set of clear images to obtain noise reduction images.By coupling new model 1 and new model 2 to smooth the noise and protect more textures,a new Non-local level set denoising model(NLSDM)for image noise reduction is obtained.The experimental results show that compared with the noise reduction model,the new model has significantly improved the peak signal-to-noise ratio and structural similarity,and the effect of noise reduction and edge preservation is better.
基金supported by the National Natural Science Foundation of China[grant number 41971422 and 42090011]Key Research and Development Plan Project of Hubei Province[grant number 2020BIB006]+1 种基金Hubei Provincial Natural Science Foundation[grant number 2020CFA001]LIESMARS Special Research Funding.
文摘Cloud coverage has become a significant factor affecting the availability of remote-sensing images in many applications.To mitigate the adverse impact of cloud coverage and recover ground information obscured by clouds,this paper presents a curvature-driven cloud removal method.Considering that each image can be regarded as a curved surface and the curvature can reflect the texture information well due to its dependence on the surface’s undulation degree,the presented method transforms image from natural domain to curvature domain for information reconstruction to maintain details of reference image.In order to improve the overall consistency and continuity of cloud removal results,the optimal boundary for cloud coverage area replacement is determined first to make the boundary pass through pixels with minimum curvature difference.Then,the curvature of missing area is reconstructed based on the curvature of reference image,and the reconstructed curvature is inversely transformed to natural domain to obtain a cloud-free image.In addition,considering the possible significant radiometric differences between different images,the initial cloud-free result will be further refined based on specific checkpoints to improve the local accuracy.To evaluate the performance of the proposed method,both simulated experiments and real data experiments are carried out.Experimental results show that the proposed method can achieve satisfactory results in terms of radiometric accuracy and consistency.
基金Supported by Key Research and Development Projects of Zhejiang Science and Technology Plan(No.2021C03103).
文摘AIM:To analyze the distribution of refractive status in school-age children with different corneal curvatures(CC)and the correlation between CC and refractive status.METHODS:A total of 2214 school-aged children of grade 4 in Hangzhou who were screened for school myopia were included.Uncorrected distance visual acuity(UCDVA),non-cycloplegic refraction,axial length(AL),horizontal and vertical corneal curvature(K1,K2)were measured and spherical equivalent(SE),corneal curvature radius(CCR)and axial length/corneal radius of curvature ratio(AL/CR)were calculated.UCDVA<5.0 and SE≤-0.50 D were classified as school-screening myopia.According to the different CCRs,the patients were divided into the lower corneal curvature(LCC)group(CCR≥7.92)and the higher corneal curvature(HCC)group(CCR<7.92).Each group was further divided into the normal AL subgroup and the long AL subgroup.The refractive parameters were compared to identify any differences between the two groups.RESULTS:Both SE and AL were greater in the LCC group(P=0.013,P<0.001).The prevalence of myopia was 38% in the LCC group and 44% in the HCC group(P<0.001).The proportion of children without screening myopia was higher in the LCC group(62%)than in the HCC group(56%).Among these children without screening myopia,the proportion of long AL in the LCC group(24%)was significantly higher than that in the HCC group(0.012%;P<0.001).The change of SE in the LCC group was less affected by the increase of AL than that in the HCC group.CONCLUSION:School-aged children in the LCC group have a lower incidence of screening myopia and longer AL.Low CC can mask SE reduction and AL growth to some extent,and the change of AL growth change more in children with low CC than high CC.Before the onset of myopia,its growth rate is even faster than that after the onset of myopia.
文摘In this article,we study Kahler metrics on a certain line bundle over some compact Kahler manifolds to find complete Kahler metrics with positive holomorphic sectional(or bisectional)curvatures.Thus,we apply a strategy to a famous Yau conjecture with a co-homogeneity one geometry.
基金Supported by the NSFC(11771087,12171091 and 11831005)。
文摘In this note,we prove a logarithmic Sobolev inequality which holds for compact submanifolds without a boundary in manifolds with asymptotically nonnegative sectional curvature.Like the Michale-Simon Sobolev inequality,this inequality contains a term involving the mean curvature.
基金Supported by the National Natural Science Foundation of China(Grant No.12371055)。
文摘Using the harmonic map theory,we study the geometry of conformal minimal twospheres immersed in Q_(6),or a real Grassmannian manifold G(2,8;R)equivalently.Then we classify the linearly full reducible conformal minimal immersions with constant Gaussian curvature from S^(2)to Q_(6)under some conditions.We also construct specific examples of non-congruent two-spheres with the same Gaussian curvature,up to SO(8)-equivalence,for each case.
基金supported by National Natural Science Foundation of China[Grant Nos.42030105,41721003,41804012,41631072,41874023].
文摘The gravitational curvatures(GC,the third-order derivatives of the gravitational potential)in gravity field modeling are gaining increased interest in geosciences.The crustal effects of the GC and Moho variation sensed by the GC are not fully evaluated for the current study.In this contribution,the effects of the GC induced by topographic and anomalous crustal masses are investigated based on ETOPO1 and CRUST1.0 models using the tesseroids.By adopting the gravitational stripping correction,the residual GC sensed by the CRUST1.0 Moho depths are presented globally to examine whether the GC can sense crustal mass anomalies at the satellite altitude of 260 km.The spatial analysis using the Pearson correlations coefficient(PCC)between the residual GC and the CRUST1.0 Moho depths is performed.Among the 10 residual GC functionals,the PCC value of the residual radial-radial-radial componentδT^(res)_(zzz)is largest with 0.31,where this value is highly dependent on the spectral content removed from the EGM2008,e.g.signals assumed to relate to deeper mass anomalies.Numerical experiments show that with the increased order of the derivatives up to third-order,the fineness level of different global Moho sensed crustal mass anomalies increases correspondingly.Taking the Tibetan plateau for example,the values of theδT^(res)_(zzz)can better reveal the detailed features of the Tibetan plateau’s Moho depth than these of the lower-order residual radial functionals(i.e.disturbing potentialδTres,disturbing radial gravity vectorδT^(res)_(z),and disturbing radial-radial gravity gradient tensorδT^(res)_(zz)),especially for the Qaidam,Sichuan,Tarim,and Turpan basins.Numerical results over the Himalayan region demonstrate that the GC componentδT^(res)^(z)has some potential in geophysical inversion.These residual GC functionals would help to get a better knowledge of the internal structures of the Earth and other planetary objects.
