The significance of laser-driven polarized beam acceleration has been increasingly recognized in recent years.We propose an efficient method for generating polarized proton beams from a pre-polarized hydrogen halide g...The significance of laser-driven polarized beam acceleration has been increasingly recognized in recent years.We propose an efficient method for generating polarized proton beams from a pre-polarized hydrogen halide gas jet,utilizing magnetic vortex acceleration enhanced by a laser-driven plasma bubble.When a petawatt laser pulse passes through a pre-polarized gas jet,a bubble-like ultra-nonlinear plasma wave is formed.As a portion of the particles constituting this wave,background protons are swept by the acceleration field of the bubble and oscillate significantly along the laser propagation axis.Some of the pre-accelerated protons in the plasma wave are trapped by the acceleration field at the rear side of the target.This acceleration field is intensified by the transverse expansion of the laser-driven magnetic vortex,resulting in energetic polarized proton beams.The spin of energetic protons is determined by their precession within the electromagnetic field,which is described using the Thomas-Bargmann-Michel-Telegdi equation in analytical models and particle-in-cell simulations.Multidimensional simulations reveal that monoenergetic proton beams with an energy of hundreds of MeV,a beam charge of hundreds of pC,and a beam polarization of tens of percent can be produced at laser powers of several petawatts.Such laser-driven polarized proton beams have promise for application in polarized beam colliders,where they can be utilized to investigate particle interactions and to explore the properties of matter under extreme conditions.展开更多
Since the initial observation of carbon nanotubes(CNTs)and graphene platelets(GPLs)in the 1990 and 2000s,the demand for high-performance structural applications and multifunctional materials has driven significant int...Since the initial observation of carbon nanotubes(CNTs)and graphene platelets(GPLs)in the 1990 and 2000s,the demand for high-performance structural applications and multifunctional materials has driven significant interest in composite structures reinforced with GPLs and CNTs.Incorporating these nanofillers into matrix materials markedly enhances the mechanical properties of the structures.To further improve efficiency and functionality,func-tionally graded(FG)distributions of CNTs and GPLs have been proposed.This study presents an extensive review of computational approaches developed to predict the global behavior of composite structural components enhanced with CNT and GPL nanofillers.The analysis focuses on key structural elements,such as plate-type configurations,cylindrical and curved shells,and beams,emphasizing the computational techniques utilized to simulate their mechanical behavior.The utilization of three-dimensional elasticity theories and equivalent single-layer(ESL)frameworks,which are widely employed in the modeling and analysis of these composites,is comprehensively discussed.Additionally,the paper examines various mechanical performance aspects,including static,buckling,post-buckling,vibrational,and dynamic responses for the mentioned structures.The unique features of hybrid nanocomposites,combining CNTs and GPLs,are also analyzed.Furthermore,the study delves into the fabrication and processing techniques of these materials,with a particular focus on strategies to mitigate nanofiller agglomeration.The review extends to cover thermal and electrical properties,durability under environmental exposure,fatigue resistance,and vibration-damping characteristics.In conclusion,the paper underscores the necessity for ongoing advancements in computational modeling to facilitate improved design,analysis,and optimization of nanocomposite structures.Future research opportunities in this rapidly advancing domain are also outlined.展开更多
A self-centering bridge bent equipped with energy-dissipation(ED)beams is proposed.Quasi-static tests are conducted on self-centering bridge bents,both with and without ED beams,to validate the accuracy of the corresp...A self-centering bridge bent equipped with energy-dissipation(ED)beams is proposed.Quasi-static tests are conducted on self-centering bridge bents,both with and without ED beams,to validate the accuracy of the corresponding numerical models.The effects of various param-eters,such as the web area of ED beams,prestressing force of tendons,tendon arrangements,and number of column segments,on the seismic performance of self-centering bridge bents with ED beams are evaluated using the validated numerical model.The results demonstrate that the nu-merical models accurately replicate the quasi-static test results,with average errors in the lateral force remaining below 9.6%.The web area of ED beams significantly affects the strength,cumulative energy dissipation,and relative self-centering index(RSI)of the self-centering bridge bents.Increasing the prestressing force enhances the lateral force and self-centering capability of the bridge bents but has minimal effect on their ED capacity.Reducing the num-ber of segments in each column enhances the lateral force and cumulative hysteretic energy dissipation of the self-centering bridge bents while exerting an insignificant effect on the RSI.Thus,the proposed novel system is highly suitable for doubleor multicolumn piers supporting bridges in regions prone to strong earthquakes.展开更多
Correction to:Nuclear Science and Techniques(2025)36:66 https://doi.org/10.1007/s41365-025-01662-y.In this article,the author’s name Hui-Ling Wei was incorrectly written as Hui-Ling We.The original article has been c...Correction to:Nuclear Science and Techniques(2025)36:66 https://doi.org/10.1007/s41365-025-01662-y.In this article,the author’s name Hui-Ling Wei was incorrectly written as Hui-Ling We.The original article has been corrected.展开更多
This paper proposes a method to generate Bessel-like collimated beams with suppressed side lobes using the flexural vibration modes of a fixed boundary circular plate,which is excited by a longitudinally vibrating tra...This paper proposes a method to generate Bessel-like collimated beams with suppressed side lobes using the flexural vibration modes of a fixed boundary circular plate,which is excited by a longitudinally vibrating transducer in a ring excitation manner.The factors affecting the generation of Bessel-like collimated beams are investigated by theoretical analysis,numerical simulation and experimental methods.The results indicate that Bessel-like wave can be generated by a thin circular plate with fixed boundaries.The third-order mode of the circular plate can be modified to generate a collimated beam with suppressing side lobes when it is excited in a ring excitation manner and the excitation position lies between the first two nodal circles of the plate.As the excitation radius increases,the main lobe width of the resulting Bessel-like collimated beam decreases,the extent of the focusing region increases,and the amplitude of the side lobes initially increases and then decreases.Based on the simulation results,a prototype Bessel-like collimated beam generation system is made and measured experimentally.The experimental results are in good agreement with the numerical results.The Bessel-like collimated beam can be generated by the proposed system,which has potential application in the fields of long-range detection,imaging of highly attenuated materials,and airflow acceleration.展开更多
This article reviews the latest advances in the generation and control of perfect vector beams using metasurfaces.In recent years,metasurfaces have garnered increasing interest due to their simple fabrication and easy...This article reviews the latest advances in the generation and control of perfect vector beams using metasurfaces.In recent years,metasurfaces have garnered increasing interest due to their simple fabrication and easy integration.Perfect vortex beams(PVBs),as a type of vector beams,exhibit complex polarization states that require the superposition of multiple phases for their generation.The use of metasurfaces provides a compact platform for the generation of perfect vortex beams and enables more complex vortex beam control tasks,which are quite challenging for traditional optics.This paper begins by introducing the principle of perfect vortex beam generation using metasurfaces,followed by a discussion on the generation of complex perfect vortex beams,including multi-channel and grafted perfect vortex beams.Subsequently,it explores the applications of perfect vortex beams in particle trapping and optical communication.Finally,the paper summarizes the key findings,highlights the limitations of metasurfaces in perfect vortex beam applications,and provides insights into potential future research directions and applications.展开更多
In this study,we design and numerically investigate a novel all optical D flip-flop(AODFF)based on linear photonic crystal(LPhC)structure that is composed of optical waveguides using the finite difference time domain(...In this study,we design and numerically investigate a novel all optical D flip-flop(AODFF)based on linear photonic crystal(LPhC)structure that is composed of optical waveguides using the finite difference time domain(FDTD)method.The proposed structure has the hexagonal close packed of 16×20 circular rods that are suspended in the air substrate with a lattice constant of 606 nm.The plane wave expansion(PWE)method is used to obtain the band diagram for AODFF at an operating wavelength of 1550 nm.The proposed optical flip-flop achieves a low delay time of 0.2 ps and a high contrast ratio(CR)of 10.33 dB.The main advantage of this design is that the input power as low as 1 mW/μm^(2) is sufficient for its operation,since no nonlinear rods are included.In addition,the footprint of the proposed AODFF is 100μm^(2),which is smaller compared to the structures reported in the literature,and it has a fast switching frequency of 5 Tbit/s.展开更多
We introduce a scheme aiming at the generation of quasi-monochromatic carbon ion bunches from laser-solid interaction.The proposed scheme is an extension of the“peeler”acceleration originally proposed for proton acc...We introduce a scheme aiming at the generation of quasi-monochromatic carbon ion bunches from laser-solid interaction.The proposed scheme is an extension of the“peeler”acceleration originally proposed for proton acceleration,which involves irradiating the narrow(submicrometer)side of a tape target.This results in the generation of a surface plasma wave and the subsequent acceleration of a proton bunch with high peak energy,quasi-monochromaticity,low energy bandwidth,and low divergence by the electrostatic field induced at the target rear.Up to now,the higher-Z(e.g.,carbon)ion bunches obtained with the peeler scheme have been found to exhibit an exponentially decaying thermal-like energy spectrum.To achieve a low energy bandwidth,we place a mass-limited carbon structure at the rear of the target.Using 3D particle-in-cell simulations,we show that a quasi-monochromatic carbon bunch can indeed be obtained.With a multi-PW laser pulse,10^(8) carbon ions with peak energy~110 MeV/u and with a divergence of 20° in the vertical plane and~1° in the horizontal plane can be generated.The quasi-monochromaticity,together with the low duration of the beam and in combination with the versatility of high-power laser facilities,should make this scheme attractive for practical applications such as heavy ion cancer therapy and higher-resolution diagnostics of extreme plasma states.展开更多
[Background]Traveling-wave tubes(TWTs)are widely applied in radar,imaging,and military systems owing to their excellent amplification characteristics.Miniaturization and integration are critical to the future of TWTs,...[Background]Traveling-wave tubes(TWTs)are widely applied in radar,imaging,and military systems owing to their excellent amplification characteristics.Miniaturization and integration are critical to the future of TWTs,with multi-channel slow-wave structures(SWSs)forming the foundation for their realization in high-power vacuum electronic devices.[Purpose]To provide design insights for multi-channel TWTs and simultaneously enhance their output power,a W-band folded-waveguide TWT with dual electron beams and H-plane power combining was proposed.[Methods]Three-dimensional electromagnetic simulations in CST were conducted to verify the highfrequency characteristics,electric field distribution,and amplification performance of the proposed SWS,thereby confirming the validity of the design.[Results]Results indicate that the designed TWT achieves a transmission bandwidth of 10 GHz.With an electron beam voltage of 17.9 kV and a current of 0.35 A,the output power reaches 450 W at 94 GHz,corresponding to an efficiency of 7.18%and a gain of 23.5 dB.Moreover,under fixed beam voltage and current,the TWT delivers over 200 W output power across 91–99 GHz,with a 3 dB bandwidth of 91–98.5 GHz.The particle voltage distribution after modulation further validates the mode analysis.[Conclusions]These results demonstrate the feasibility of compact dual-beam power-combining structures and provide useful guidance for the design of future multi-channel TWTs.展开更多
By introducing noncanonical vortex pairs to partially coherent beams, spatial correlation singularity (SCS) and orbital angular momenta (OAM) of the resulting beams are studied using the Fraunhofer diffraction integra...By introducing noncanonical vortex pairs to partially coherent beams, spatial correlation singularity (SCS) and orbital angular momenta (OAM) of the resulting beams are studied using the Fraunhofer diffraction integral. The effect of noncanonical strength, off-axis distance and vortex sign on spatial correlation singularities in far field is stressed. Furthermore, far-field OAM spectra and densities are also investigated, and the OAM detection and crosstalk probabilities are discussed. The results show that the number of dislocations of SCS always equals the sum of absolute values of topological charges for canonical or noncanonical vortex pairs. Although the sum of the product of each OAM mode and its power weight equals the algebraic sum of topological charges for canonical vortex pairs, the relationship no longer holds in the noncanonical case except for opposite-charge vortex pairs. The changes of off-axis distance, noncanonical strength or coherence length can lead to a more dominant power in adjacent mode than that in center detection mode, which also indicates that crosstalk probabilities of adjacent modes exceed the center detection probability. This work may provide potential applications in OAM-based optical communication, imaging, sensing and computing.展开更多
The test results of eight concrete beams reinforced with carbon fiber reinforced polymer （CFRP） sheets subjected to an aggressive environment under a sustained load are presented. The beams are 1 700 mm long with a ...The test results of eight concrete beams reinforced with carbon fiber reinforced polymer （CFRP） sheets subjected to an aggressive environment under a sustained load are presented. The beams are 1 700 mm long with a rectangular cross-section of 120- mm width and 200-mm depth. The beams are precracked with a four-point flexural load, bonded CFRP sheets, and placed into wet-dry saline water（ NaCl） either in an unstressed state or loaded to about 30% or 60% of the initial ultimate load. The individual and coupled effects of wet-dry saline water and sustained bending stresses on the long term behaviour of concrete beams reinforced with the CFRP are investigated. The test results show that the coupled action of wet-dry saline water and sustained bending stresses appears to significantly affect the load capacity and the failure mode of beam strengthened with CFRP, mainly due to the degradation of the bond between CFRP and concrete. However, the stiffness is not affected by the coupled action of wet-dry cycles and a sustained load.展开更多
This paper investigates the free vibration and transient response of interconnected structures including double curved beams and intermediate straight beams,which are all constructed from functionally graded porous(FG...This paper investigates the free vibration and transient response of interconnected structures including double curved beams and intermediate straight beams,which are all constructed from functionally graded porous(FGP)materials.The strain potential and kinetic energies of each beam along with the work done by the external force are calculated.Additionally,a higher-order beam element is introduced to derive stiffness and mass matrices,along with the force vector.The curved and straight beams are discretized,and their assembled stiffness,mass matrices,and force vectors,are obtained.Continuity conditions at the joints are used to derive the total matrices of the entire structure.Subsequently,the natural frequencies and transient response of the system are determined.The accuracy of the mathematical model and the self-developed computer program is validated through the comparison of the obtained results with those of the existing literature and commercial software ANSYS,demonstrating excellent agreement.Furthermore,a comprehensive study is conducted to investigate the effects of various parameters on the free vibration and transient response of the considered structure.展开更多
This investigation aims to analyze thermal buckling and post-buckling behavior of functionally graded graphene nanoplateletreinforced composite(FG-GPLRC)beams.The beams are classified into two types of ideal and non-i...This investigation aims to analyze thermal buckling and post-buckling behavior of functionally graded graphene nanoplateletreinforced composite(FG-GPLRC)beams.The beams are classified into two types of ideal and non-ideal FG-GPLRC beams in which the ideal beams have smooth profiles of material distributions and another beams have layer-wise distributions of materials.The material profiles of the ideal beams are utilized as the controlling tracks for producing the material distributions of the non-ideal beams via a layer-to-layer integration technique.This technique confirms that the overall weight fraction of the materials is the same for both types of beams.The proposed models can be used to determine the material properties of the beams for further investigation on thermal buckling and post-buckling of the beams.Third-order shear deformation theory is employed to construct the energy equations of the problems,and then they are solved by the implementation of the Jacobi-Ritz method cooperating with the direct iteration procedure and Newton-Raphson technique.From our investigation,it can be disclosed that when non-ideal beams are created using ideal beams parabolic profile,the results differ significantly.However,the differences between the results of ideal and non-ideal beams can be eliminated by adding more layers.展开更多
Glue-laminated timber(GLT)is an engineered wood product widely used in mass timber construction for its strong structural and fire-resistant properties.However,the fire performance of GLT varies significantly due to t...Glue-laminated timber(GLT)is an engineered wood product widely used in mass timber construction for its strong structural and fire-resistant properties.However,the fire performance of GLT varies significantly due to the natural and uncertain phenomena(moisture,exposure time,isotropic,homogenous properties,etc.)of fire and timber.This makes it difficult to predict the fire behaviour of the GLT structural elements.To ensure building safety,it is crucial to assess GLT’s fire behaviour and post-fire structural integrity during the design stages.This study conducted the experimental tests of GLT beams(280 mm×560 mm)without loading(1.4 m)and under a four-point bending load(5.4 m).Tests identified thermal behaviour and charring rates of GLT beam.Then,the residual stiffness of the GLT beam was calculated,and the charring rates of the beams were compared with Australian and European standards.Reliability analysis was conducted for beams for a fire exposure of 120 min,considering the charring rates observed through the analysis and simulating the fire insulations.Results show that the charring rate of GLT made with spruce pine timber varied between 0.43 and 0.81 mm/min,with a mean rate of 0.7 mm/min,aligning with both Australian and European standards.However,considering timber density and moisture content,the charring rates in Australian standards were conservative.The study also found that structural capacity significantly degrades under fire,with a 22%reduction in flexural stiffness after 120 min of exposure.Additionally,GLT beams can safely function for 30 min under 75%of their design moment capacity and for 60 min under 50%capacity.展开更多
Steel-concrete composite beams,due to their superior mechanical properties,are widely utilized in engineering structures.This study systematically investigates the calculation methods for internal forces and load-bear...Steel-concrete composite beams,due to their superior mechanical properties,are widely utilized in engineering structures.This study systematically investigates the calculation methods for internal forces and load-bearing capacity of composite beams based on elastic theory,with a focus on the transformed section method and its application under varying neutral axis positions.By deriving the geometric characteristics of the transformed section and incorporating a reduction factor accounting for slip effects,a computational model for sectional stress and ultimate load-bearing capacity is established.The results demonstrate that the slip effect significantly influences the flexural load-bearing capacity of composite beams.The proposed reduction factor,which considers the influence of the steel beam’s top flange thickness,offers higher accuracy compared to traditional methods.These findings provide a theoretical foundation for the design and analysis of composite beams,with significant practical engineering value.展开更多
On-chip devices for generating pre-designed vectorial optical fields(VOFs)under surface wave(SW)excitations are highly desired in integrated photonics.However,conventional devices are usually of large footprints,low e...On-chip devices for generating pre-designed vectorial optical fields(VOFs)under surface wave(SW)excitations are highly desired in integrated photonics.However,conventional devices are usually of large footprints,low efficiencies,and limited wave-control capabilities.Here,we present a generic approach to design ultra-compact on-chip devices that can efficiently generate pre-designed VOFs under SW excitations,and experimentally verify the concept in terahertz(THz)regime.We first describe how to design SW-excitation metasurfaces for generating circularly polarized complex beams,and experimentally demonstrate two meta-devices to realize directional emission and focusing of THz waves with oppo-site circular polarizations,respectively.We then establish a systematic approach to construct an integrated device via merging two carefully designed metasurfaces,which,under SW excitations,can separately produce pre-designed far-field patterns with different circular polarizations and generate target VOF based on their interference.As a proof of con-cept,we demonstrate experimentally a meta-device that can generate a radially polarized Bessel beam under SW excita-tion at~0.4 THz.Experimental results agree well with full-wave simulations,collectively verifying the performance of our device.Our study paves the road to realizing highly integrated on-chip functional THz devices,which may find many ap-plications in biological sensing,communications,displays,image multiplexing,and beyond.展开更多
The dynamics of beams subjected to moving loads are of practical importance since the responses caused by these loads can be greater than those under equivalent static loads in some cases.In this work,a novel inertial...The dynamics of beams subjected to moving loads are of practical importance since the responses caused by these loads can be greater than those under equivalent static loads in some cases.In this work,a novel inertial nonlinear energy sink(NES)is applied for the first time to achieve vibration suppression in beams under moving loads.Based on the Timoshenko beam theory,the nonlinear motion equations of a beam with an inertial NES are derived using the energy method and Lagrange equations.The Newmark-βmethod combined with the Heaviside step function is adopted to calculate the responses of the beam under moving loads of constant amplitude and harmonic excitation.The accuracy of the modelling derivation and solution methodology are validated through comparisons with results from other studies.The results demonstrate that the velocity and excitation frequency of the moving load significantly affect the response of the beam as well as the performance of the inertial NES.To enhance its effectiveness under various moving load conditions,parametric optimization is numerically performed.The optimized inertial NES can achieve good performance by efficiently reducing the maximum deflection of the beam.The findings of this study contribute to advancing the understanding and application of NESs in mitigating structural vibrations caused by moving loads.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.12075081 and 12404395)the Innovation Group Project of the Natural Science Foundation of Hubei Province of China(Grant No.2024AFA038)Bin Liu acknowledges the support of Guangdong High Level Innovation Research Institute Project,Grant No.2021B0909050006.
文摘The significance of laser-driven polarized beam acceleration has been increasingly recognized in recent years.We propose an efficient method for generating polarized proton beams from a pre-polarized hydrogen halide gas jet,utilizing magnetic vortex acceleration enhanced by a laser-driven plasma bubble.When a petawatt laser pulse passes through a pre-polarized gas jet,a bubble-like ultra-nonlinear plasma wave is formed.As a portion of the particles constituting this wave,background protons are swept by the acceleration field of the bubble and oscillate significantly along the laser propagation axis.Some of the pre-accelerated protons in the plasma wave are trapped by the acceleration field at the rear side of the target.This acceleration field is intensified by the transverse expansion of the laser-driven magnetic vortex,resulting in energetic polarized proton beams.The spin of energetic protons is determined by their precession within the electromagnetic field,which is described using the Thomas-Bargmann-Michel-Telegdi equation in analytical models and particle-in-cell simulations.Multidimensional simulations reveal that monoenergetic proton beams with an energy of hundreds of MeV,a beam charge of hundreds of pC,and a beam polarization of tens of percent can be produced at laser powers of several petawatts.Such laser-driven polarized proton beams have promise for application in polarized beam colliders,where they can be utilized to investigate particle interactions and to explore the properties of matter under extreme conditions.
文摘Since the initial observation of carbon nanotubes(CNTs)and graphene platelets(GPLs)in the 1990 and 2000s,the demand for high-performance structural applications and multifunctional materials has driven significant interest in composite structures reinforced with GPLs and CNTs.Incorporating these nanofillers into matrix materials markedly enhances the mechanical properties of the structures.To further improve efficiency and functionality,func-tionally graded(FG)distributions of CNTs and GPLs have been proposed.This study presents an extensive review of computational approaches developed to predict the global behavior of composite structural components enhanced with CNT and GPL nanofillers.The analysis focuses on key structural elements,such as plate-type configurations,cylindrical and curved shells,and beams,emphasizing the computational techniques utilized to simulate their mechanical behavior.The utilization of three-dimensional elasticity theories and equivalent single-layer(ESL)frameworks,which are widely employed in the modeling and analysis of these composites,is comprehensively discussed.Additionally,the paper examines various mechanical performance aspects,including static,buckling,post-buckling,vibrational,and dynamic responses for the mentioned structures.The unique features of hybrid nanocomposites,combining CNTs and GPLs,are also analyzed.Furthermore,the study delves into the fabrication and processing techniques of these materials,with a particular focus on strategies to mitigate nanofiller agglomeration.The review extends to cover thermal and electrical properties,durability under environmental exposure,fatigue resistance,and vibration-damping characteristics.In conclusion,the paper underscores the necessity for ongoing advancements in computational modeling to facilitate improved design,analysis,and optimization of nanocomposite structures.Future research opportunities in this rapidly advancing domain are also outlined.
基金The National Natural Science Foundation of China(No.52278189)Zhejiang Provincial Natural Science Foundation of China(No.LY24E080002).
文摘A self-centering bridge bent equipped with energy-dissipation(ED)beams is proposed.Quasi-static tests are conducted on self-centering bridge bents,both with and without ED beams,to validate the accuracy of the corresponding numerical models.The effects of various param-eters,such as the web area of ED beams,prestressing force of tendons,tendon arrangements,and number of column segments,on the seismic performance of self-centering bridge bents with ED beams are evaluated using the validated numerical model.The results demonstrate that the nu-merical models accurately replicate the quasi-static test results,with average errors in the lateral force remaining below 9.6%.The web area of ED beams significantly affects the strength,cumulative energy dissipation,and relative self-centering index(RSI)of the self-centering bridge bents.Increasing the prestressing force enhances the lateral force and self-centering capability of the bridge bents but has minimal effect on their ED capacity.Reducing the num-ber of segments in each column enhances the lateral force and cumulative hysteretic energy dissipation of the self-centering bridge bents while exerting an insignificant effect on the RSI.Thus,the proposed novel system is highly suitable for doubleor multicolumn piers supporting bridges in regions prone to strong earthquakes.
文摘Correction to:Nuclear Science and Techniques(2025)36:66 https://doi.org/10.1007/s41365-025-01662-y.In this article,the author’s name Hui-Ling Wei was incorrectly written as Hui-Ling We.The original article has been corrected.
基金Project supported by the National Natural Science Foundation of China(Grant No.12474440).
文摘This paper proposes a method to generate Bessel-like collimated beams with suppressed side lobes using the flexural vibration modes of a fixed boundary circular plate,which is excited by a longitudinally vibrating transducer in a ring excitation manner.The factors affecting the generation of Bessel-like collimated beams are investigated by theoretical analysis,numerical simulation and experimental methods.The results indicate that Bessel-like wave can be generated by a thin circular plate with fixed boundaries.The third-order mode of the circular plate can be modified to generate a collimated beam with suppressing side lobes when it is excited in a ring excitation manner and the excitation position lies between the first two nodal circles of the plate.As the excitation radius increases,the main lobe width of the resulting Bessel-like collimated beam decreases,the extent of the focusing region increases,and the amplitude of the side lobes initially increases and then decreases.Based on the simulation results,a prototype Bessel-like collimated beam generation system is made and measured experimentally.The experimental results are in good agreement with the numerical results.The Bessel-like collimated beam can be generated by the proposed system,which has potential application in the fields of long-range detection,imaging of highly attenuated materials,and airflow acceleration.
基金supported by the Natural Science Foundation of Zhejiang Province(China)under Grant LY22F050001in part by the Science and technology innovation leading talent project of special support plan for high-level talents in Zhejiang Province(China)(2021R52032)in part by the National Natural Science Foundation of China under grant No.62175224.
文摘This article reviews the latest advances in the generation and control of perfect vector beams using metasurfaces.In recent years,metasurfaces have garnered increasing interest due to their simple fabrication and easy integration.Perfect vortex beams(PVBs),as a type of vector beams,exhibit complex polarization states that require the superposition of multiple phases for their generation.The use of metasurfaces provides a compact platform for the generation of perfect vortex beams and enables more complex vortex beam control tasks,which are quite challenging for traditional optics.This paper begins by introducing the principle of perfect vortex beam generation using metasurfaces,followed by a discussion on the generation of complex perfect vortex beams,including multi-channel and grafted perfect vortex beams.Subsequently,it explores the applications of perfect vortex beams in particle trapping and optical communication.Finally,the paper summarizes the key findings,highlights the limitations of metasurfaces in perfect vortex beam applications,and provides insights into potential future research directions and applications.
文摘In this study,we design and numerically investigate a novel all optical D flip-flop(AODFF)based on linear photonic crystal(LPhC)structure that is composed of optical waveguides using the finite difference time domain(FDTD)method.The proposed structure has the hexagonal close packed of 16×20 circular rods that are suspended in the air substrate with a lattice constant of 606 nm.The plane wave expansion(PWE)method is used to obtain the band diagram for AODFF at an operating wavelength of 1550 nm.The proposed optical flip-flop achieves a low delay time of 0.2 ps and a high contrast ratio(CR)of 10.33 dB.The main advantage of this design is that the input power as low as 1 mW/μm^(2) is sufficient for its operation,since no nonlinear rods are included.In addition,the footprint of the proposed AODFF is 100μm^(2),which is smaller compared to the structures reported in the literature,and it has a fast switching frequency of 5 Tbit/s.
基金the support of the Romanian Government and the European Union through the European Regional Development Fund–the Competitiveness Operational Programme (1/07.07.2016, COP, Grant ID No. 1334) Phases Ⅱthe Romanian Ministry of Research, Innovation and Digitalization: Program Nucleu Grant No. PN23210105+6 种基金supported by the IOSIN Funds for Research Infrastructures of National Interest funded by the Romanian Ministry of Research, Innovation and Digitalizationsupported by Project No. ELI-RO/DFG/2023_001 ARNPhot funded by the Institute of Atomic Physics (Romania), the European Union, the Romanian Governmentthe Health Program, within the project “Medical Applications of High-Power Lasers–Dr. LASER,” SMIS Code 326475by Grant Nos. ELI-RO/RDI/2024_14 SPARC and ELI-RO/RDI/2024_8 AMAPBMBF Grant No. 05P24PF2 (Germany)the EuroHPC Joint Undertaking for awarding us access to Karolina at IT4Innovations (VAB-TU), Czechia under Project No. EHPCREG-2023R02-006 (Grant No. DD-23-157)Ministry of Education, Youth and Sports of the Czech Republic through e-INFRA CZ (Grant ID No. 90140)
文摘We introduce a scheme aiming at the generation of quasi-monochromatic carbon ion bunches from laser-solid interaction.The proposed scheme is an extension of the“peeler”acceleration originally proposed for proton acceleration,which involves irradiating the narrow(submicrometer)side of a tape target.This results in the generation of a surface plasma wave and the subsequent acceleration of a proton bunch with high peak energy,quasi-monochromaticity,low energy bandwidth,and low divergence by the electrostatic field induced at the target rear.Up to now,the higher-Z(e.g.,carbon)ion bunches obtained with the peeler scheme have been found to exhibit an exponentially decaying thermal-like energy spectrum.To achieve a low energy bandwidth,we place a mass-limited carbon structure at the rear of the target.Using 3D particle-in-cell simulations,we show that a quasi-monochromatic carbon bunch can indeed be obtained.With a multi-PW laser pulse,10^(8) carbon ions with peak energy~110 MeV/u and with a divergence of 20° in the vertical plane and~1° in the horizontal plane can be generated.The quasi-monochromaticity,together with the low duration of the beam and in combination with the versatility of high-power laser facilities,should make this scheme attractive for practical applications such as heavy ion cancer therapy and higher-resolution diagnostics of extreme plasma states.
基金National Key Research and Development Program of China(2022YFF0707602)National Natural Science Foundation of China(62471097,62471115,62471101)National Natural Science Foundation of Sichuan(2025ZNSFSC0537)。
文摘[Background]Traveling-wave tubes(TWTs)are widely applied in radar,imaging,and military systems owing to their excellent amplification characteristics.Miniaturization and integration are critical to the future of TWTs,with multi-channel slow-wave structures(SWSs)forming the foundation for their realization in high-power vacuum electronic devices.[Purpose]To provide design insights for multi-channel TWTs and simultaneously enhance their output power,a W-band folded-waveguide TWT with dual electron beams and H-plane power combining was proposed.[Methods]Three-dimensional electromagnetic simulations in CST were conducted to verify the highfrequency characteristics,electric field distribution,and amplification performance of the proposed SWS,thereby confirming the validity of the design.[Results]Results indicate that the designed TWT achieves a transmission bandwidth of 10 GHz.With an electron beam voltage of 17.9 kV and a current of 0.35 A,the output power reaches 450 W at 94 GHz,corresponding to an efficiency of 7.18%and a gain of 23.5 dB.Moreover,under fixed beam voltage and current,the TWT delivers over 200 W output power across 91–99 GHz,with a 3 dB bandwidth of 91–98.5 GHz.The particle voltage distribution after modulation further validates the mode analysis.[Conclusions]These results demonstrate the feasibility of compact dual-beam power-combining structures and provide useful guidance for the design of future multi-channel TWTs.
文摘By introducing noncanonical vortex pairs to partially coherent beams, spatial correlation singularity (SCS) and orbital angular momenta (OAM) of the resulting beams are studied using the Fraunhofer diffraction integral. The effect of noncanonical strength, off-axis distance and vortex sign on spatial correlation singularities in far field is stressed. Furthermore, far-field OAM spectra and densities are also investigated, and the OAM detection and crosstalk probabilities are discussed. The results show that the number of dislocations of SCS always equals the sum of absolute values of topological charges for canonical or noncanonical vortex pairs. Although the sum of the product of each OAM mode and its power weight equals the algebraic sum of topological charges for canonical vortex pairs, the relationship no longer holds in the noncanonical case except for opposite-charge vortex pairs. The changes of off-axis distance, noncanonical strength or coherence length can lead to a more dominant power in adjacent mode than that in center detection mode, which also indicates that crosstalk probabilities of adjacent modes exceed the center detection probability. This work may provide potential applications in OAM-based optical communication, imaging, sensing and computing.
基金The National Natural Science Foundation of China(No.50608013)Special Prophase Project on Basic Research of the National Department of Science and Technology(No.2004CCA04100)
文摘The test results of eight concrete beams reinforced with carbon fiber reinforced polymer （CFRP） sheets subjected to an aggressive environment under a sustained load are presented. The beams are 1 700 mm long with a rectangular cross-section of 120- mm width and 200-mm depth. The beams are precracked with a four-point flexural load, bonded CFRP sheets, and placed into wet-dry saline water（ NaCl） either in an unstressed state or loaded to about 30% or 60% of the initial ultimate load. The individual and coupled effects of wet-dry saline water and sustained bending stresses on the long term behaviour of concrete beams reinforced with the CFRP are investigated. The test results show that the coupled action of wet-dry saline water and sustained bending stresses appears to significantly affect the load capacity and the failure mode of beam strengthened with CFRP, mainly due to the degradation of the bond between CFRP and concrete. However, the stiffness is not affected by the coupled action of wet-dry cycles and a sustained load.
文摘This paper investigates the free vibration and transient response of interconnected structures including double curved beams and intermediate straight beams,which are all constructed from functionally graded porous(FGP)materials.The strain potential and kinetic energies of each beam along with the work done by the external force are calculated.Additionally,a higher-order beam element is introduced to derive stiffness and mass matrices,along with the force vector.The curved and straight beams are discretized,and their assembled stiffness,mass matrices,and force vectors,are obtained.Continuity conditions at the joints are used to derive the total matrices of the entire structure.Subsequently,the natural frequencies and transient response of the system are determined.The accuracy of the mathematical model and the self-developed computer program is validated through the comparison of the obtained results with those of the existing literature and commercial software ANSYS,demonstrating excellent agreement.Furthermore,a comprehensive study is conducted to investigate the effects of various parameters on the free vibration and transient response of the considered structure.
基金supported by the Thailand Science Research and Innovation Fund(Grant No.FRB660041/0227).
文摘This investigation aims to analyze thermal buckling and post-buckling behavior of functionally graded graphene nanoplateletreinforced composite(FG-GPLRC)beams.The beams are classified into two types of ideal and non-ideal FG-GPLRC beams in which the ideal beams have smooth profiles of material distributions and another beams have layer-wise distributions of materials.The material profiles of the ideal beams are utilized as the controlling tracks for producing the material distributions of the non-ideal beams via a layer-to-layer integration technique.This technique confirms that the overall weight fraction of the materials is the same for both types of beams.The proposed models can be used to determine the material properties of the beams for further investigation on thermal buckling and post-buckling of the beams.Third-order shear deformation theory is employed to construct the energy equations of the problems,and then they are solved by the implementation of the Jacobi-Ritz method cooperating with the direct iteration procedure and Newton-Raphson technique.From our investigation,it can be disclosed that when non-ideal beams are created using ideal beams parabolic profile,the results differ significantly.However,the differences between the results of ideal and non-ideal beams can be eliminated by adding more layers.
文摘Glue-laminated timber(GLT)is an engineered wood product widely used in mass timber construction for its strong structural and fire-resistant properties.However,the fire performance of GLT varies significantly due to the natural and uncertain phenomena(moisture,exposure time,isotropic,homogenous properties,etc.)of fire and timber.This makes it difficult to predict the fire behaviour of the GLT structural elements.To ensure building safety,it is crucial to assess GLT’s fire behaviour and post-fire structural integrity during the design stages.This study conducted the experimental tests of GLT beams(280 mm×560 mm)without loading(1.4 m)and under a four-point bending load(5.4 m).Tests identified thermal behaviour and charring rates of GLT beam.Then,the residual stiffness of the GLT beam was calculated,and the charring rates of the beams were compared with Australian and European standards.Reliability analysis was conducted for beams for a fire exposure of 120 min,considering the charring rates observed through the analysis and simulating the fire insulations.Results show that the charring rate of GLT made with spruce pine timber varied between 0.43 and 0.81 mm/min,with a mean rate of 0.7 mm/min,aligning with both Australian and European standards.However,considering timber density and moisture content,the charring rates in Australian standards were conservative.The study also found that structural capacity significantly degrades under fire,with a 22%reduction in flexural stiffness after 120 min of exposure.Additionally,GLT beams can safely function for 30 min under 75%of their design moment capacity and for 60 min under 50%capacity.
文摘Steel-concrete composite beams,due to their superior mechanical properties,are widely utilized in engineering structures.This study systematically investigates the calculation methods for internal forces and load-bearing capacity of composite beams based on elastic theory,with a focus on the transformed section method and its application under varying neutral axis positions.By deriving the geometric characteristics of the transformed section and incorporating a reduction factor accounting for slip effects,a computational model for sectional stress and ultimate load-bearing capacity is established.The results demonstrate that the slip effect significantly influences the flexural load-bearing capacity of composite beams.The proposed reduction factor,which considers the influence of the steel beam’s top flange thickness,offers higher accuracy compared to traditional methods.These findings provide a theoretical foundation for the design and analysis of composite beams,with significant practical engineering value.
基金the financial support from National Natural Science Foundation of China (Nos. 62192771, 12374344, 12221004)National Key Research and Development Program of China (2022YFA1204700, 2020YFA0710100)+1 种基金Natural Science Foundation of Shanghai (Grant No. 23dz2260100)China Postdoctoral Science Foundation 2021TQ0077
文摘On-chip devices for generating pre-designed vectorial optical fields(VOFs)under surface wave(SW)excitations are highly desired in integrated photonics.However,conventional devices are usually of large footprints,low efficiencies,and limited wave-control capabilities.Here,we present a generic approach to design ultra-compact on-chip devices that can efficiently generate pre-designed VOFs under SW excitations,and experimentally verify the concept in terahertz(THz)regime.We first describe how to design SW-excitation metasurfaces for generating circularly polarized complex beams,and experimentally demonstrate two meta-devices to realize directional emission and focusing of THz waves with oppo-site circular polarizations,respectively.We then establish a systematic approach to construct an integrated device via merging two carefully designed metasurfaces,which,under SW excitations,can separately produce pre-designed far-field patterns with different circular polarizations and generate target VOF based on their interference.As a proof of con-cept,we demonstrate experimentally a meta-device that can generate a radially polarized Bessel beam under SW excita-tion at~0.4 THz.Experimental results agree well with full-wave simulations,collectively verifying the performance of our device.Our study paves the road to realizing highly integrated on-chip functional THz devices,which may find many ap-plications in biological sensing,communications,displays,image multiplexing,and beyond.
基金supported by the National Natural Science Foundation of China(Grant Nos.12102015 and 12472003)the General Program of Science and Technology Development Project of the Beijing Municipal Education Commission(Grant No.KM202110005030)the Key Research Project of Zhejiang Market Supervision Administration(Grant No.ZD2024013).
文摘The dynamics of beams subjected to moving loads are of practical importance since the responses caused by these loads can be greater than those under equivalent static loads in some cases.In this work,a novel inertial nonlinear energy sink(NES)is applied for the first time to achieve vibration suppression in beams under moving loads.Based on the Timoshenko beam theory,the nonlinear motion equations of a beam with an inertial NES are derived using the energy method and Lagrange equations.The Newmark-βmethod combined with the Heaviside step function is adopted to calculate the responses of the beam under moving loads of constant amplitude and harmonic excitation.The accuracy of the modelling derivation and solution methodology are validated through comparisons with results from other studies.The results demonstrate that the velocity and excitation frequency of the moving load significantly affect the response of the beam as well as the performance of the inertial NES.To enhance its effectiveness under various moving load conditions,parametric optimization is numerically performed.The optimized inertial NES can achieve good performance by efficiently reducing the maximum deflection of the beam.The findings of this study contribute to advancing the understanding and application of NESs in mitigating structural vibrations caused by moving loads.
