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
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
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
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
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
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
In order to solve the problems of low overload power in MEMS cantilever beams and low sensitivity in traditional MEMS fixed beams,a novel MEMS microwave power detection chip based on the dual-guided fixed beam is desi...In order to solve the problems of low overload power in MEMS cantilever beams and low sensitivity in traditional MEMS fixed beams,a novel MEMS microwave power detection chip based on the dual-guided fixed beam is designed.A gap between guiding beams and measuring electrodes is designed to accelerate the release of the sacrificial layer,effectively enhanc-ing chip performance.A load sensing model for the MEMS fixed beam microwave power detection chip is proposed,and the mechanical characteristics are analyzed based on the uniform load applied.The overload power and sensitivity are investi-gated using the load sensing model,and experimental results are compared with theoretical results.The detection chip exhibits excellent microwave characteristic in the 9-11 GHz frequency band,with a return loss less than-10 dB.At a signal fre-quency of 10 GHz,the theoretical sensitivity is 13.8 fF/W,closely matching the measured value of 14.3 fF/W,with a relative error of only 3.5%.These results demonstrate that the proposed load sensing model provides significant theoretical support for the design and performance optimization of MEMS microwave power detection chips.展开更多
The elliptic integral method(EIM) is an efficient analytical approach for analyzing large deformations of elastic beams. However, it faces the following challenges.First, the existing EIM can only handle cases with kn...The elliptic integral method(EIM) is an efficient analytical approach for analyzing large deformations of elastic beams. However, it faces the following challenges.First, the existing EIM can only handle cases with known deformation modes. Second,the existing EIM is only applicable to Euler beams, and there is no EIM available for higher-precision Timoshenko and Reissner beams in cases where both force and moment are applied at the end. This paper proposes a general EIM for Reissner beams under arbitrary boundary conditions. On this basis, an analytical equation for determining the sign of the elliptic integral is provided. Based on the equation, we discover a class of elliptic integral piecewise points that are distinct from inflection points. More importantly, we propose an algorithm that automatically calculates the number of inflection points and other piecewise points during the nonlinear solution process, which is crucial for beams with unknown or changing deformation modes.展开更多
In order to more accurately calculate the fatigue damage and fatigue life of steel-concrete composite beam under standard vehicle load,the steel beam components of a large-span steel-concrete composite beam suspension...In order to more accurately calculate the fatigue damage and fatigue life of steel-concrete composite beam under standard vehicle load,the steel beam components of a large-span steel-concrete composite beam suspension bridge were taken as the research object.Based on the S-N curve and linear fatigue damage theory,a standard segment model was established.Accordingly,the welding position of the secondary longitudinal beam was identified as the focus fatigue point,and the stress time course calculation was done for the point.The results showed that when the vehicle mass increases from 50 t to 100 t,the amount of fatigue damage will increase by more than 5 times in the same period of time,and the increase in the vehicle mass will reduce the fatigue life of the bridge structure.The fatigue damage of bridge structures increases with the increase of vehicle speed.The increase rate of fatigue damage is greater at low speeds,and the increase rate of fatigue damage slows down at high speeds.展开更多
Electron beam fluorescence technology is an advanced non-contact measurement in rarefied flow fields,and the fluorescence signal intensity is positively correlated with the electron beam current.The ion bombardment se...Electron beam fluorescence technology is an advanced non-contact measurement in rarefied flow fields,and the fluorescence signal intensity is positively correlated with the electron beam current.The ion bombardment secondary emission electron gun is suitable for the technology.To enhance the beam current,COMSOL simulations and analyses were conducted to examine plasma density distribution in the discharge chamber under the effects of various conditions and the electric field distribution between the cathode and the spacer gap.The anode shape and discharge pressure conditions were optimized to increase plasma density.Additionally,an improved spacer structure was designed with the dual purpose of enhancing the electric field distribution between the cathode-spacer gaps and improving vacuum differential effects.This design modification aims to increase the pass rate of secondary electrons.Both simulation and experimental results demonstrated that the performance of the optimized electron gun was effectively enhanced.When the electrode voltage remains constant and the discharge gas pressure is adjusted to around 8 Pa,the maximum beam current was increased from 0.9 mA to 1.6 mA.展开更多
Without knowing the emittance value, it is difficult to optimize ion beam optics for minimum beam loss during transmission, especially considering the very high emittance values of electron cyclotron resonance(ECR) io...Without knowing the emittance value, it is difficult to optimize ion beam optics for minimum beam loss during transmission, especially considering the very high emittance values of electron cyclotron resonance(ECR) ion sources.With this in mind, to measure the emittance of the ion beams produced by the mVINIS ECR, which is part of the FAMA facility at the Vin?a Institute of Nuclear Sciences, we have developed a pepper-pot scintillator screen system combined with a CMOS camera. The application, developed on the Lab VIEW platform, allows us to control the camera's main attribute settings, such as the shutter speed and the gain, record the images in the region of interest, and process and filter the images in real time. To analyze the data from the obtained image, we have developed an algorithm called measurement and analysis of ion beam luminosity(MAIBL) to reconstruct the four-dimensional(4D) beam profile and calculate the root mean square(RMS) emittance. Before measuring emittance, we performed a simulated experiment using the pepper-pot simulation(PPS) program. An exported file(PPS) gives a numerically generated raw image(mock image) of a beam with a predefined emittance value after it has passed through a pepper-pot mask. By analyzing data from mock images instead of the image obtained by the camera and putting it into the MAIBL algorithm, we can compare the calculated emittance with PPS's initial emittance value. In this paper, we present our computational tools and explain the method for verifying the correctness of the calculated emittance values.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.
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.
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.
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.
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.
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supported by the National Natural Science Foundation of China(61904089)the Province Natural Science Foundation of Jiangsu(BK20190731).
文摘In order to solve the problems of low overload power in MEMS cantilever beams and low sensitivity in traditional MEMS fixed beams,a novel MEMS microwave power detection chip based on the dual-guided fixed beam is designed.A gap between guiding beams and measuring electrodes is designed to accelerate the release of the sacrificial layer,effectively enhanc-ing chip performance.A load sensing model for the MEMS fixed beam microwave power detection chip is proposed,and the mechanical characteristics are analyzed based on the uniform load applied.The overload power and sensitivity are investi-gated using the load sensing model,and experimental results are compared with theoretical results.The detection chip exhibits excellent microwave characteristic in the 9-11 GHz frequency band,with a return loss less than-10 dB.At a signal fre-quency of 10 GHz,the theoretical sensitivity is 13.8 fF/W,closely matching the measured value of 14.3 fF/W,with a relative error of only 3.5%.These results demonstrate that the proposed load sensing model provides significant theoretical support for the design and performance optimization of MEMS microwave power detection chips.
基金supported by the National Natural Science Foundation of China (Nos. 12172388 and 12472400)the Guangdong Basic and Applied Basic Research Foundation of China(No. 2025A1515011975)the Scientific Research Project of Guangdong Polytechnic Normal University of China (No. 2023SDKYA010)
文摘The elliptic integral method(EIM) is an efficient analytical approach for analyzing large deformations of elastic beams. However, it faces the following challenges.First, the existing EIM can only handle cases with known deformation modes. Second,the existing EIM is only applicable to Euler beams, and there is no EIM available for higher-precision Timoshenko and Reissner beams in cases where both force and moment are applied at the end. This paper proposes a general EIM for Reissner beams under arbitrary boundary conditions. On this basis, an analytical equation for determining the sign of the elliptic integral is provided. Based on the equation, we discover a class of elliptic integral piecewise points that are distinct from inflection points. More importantly, we propose an algorithm that automatically calculates the number of inflection points and other piecewise points during the nonlinear solution process, which is crucial for beams with unknown or changing deformation modes.
文摘In order to more accurately calculate the fatigue damage and fatigue life of steel-concrete composite beam under standard vehicle load,the steel beam components of a large-span steel-concrete composite beam suspension bridge were taken as the research object.Based on the S-N curve and linear fatigue damage theory,a standard segment model was established.Accordingly,the welding position of the secondary longitudinal beam was identified as the focus fatigue point,and the stress time course calculation was done for the point.The results showed that when the vehicle mass increases from 50 t to 100 t,the amount of fatigue damage will increase by more than 5 times in the same period of time,and the increase in the vehicle mass will reduce the fatigue life of the bridge structure.The fatigue damage of bridge structures increases with the increase of vehicle speed.The increase rate of fatigue damage is greater at low speeds,and the increase rate of fatigue damage slows down at high speeds.
文摘Electron beam fluorescence technology is an advanced non-contact measurement in rarefied flow fields,and the fluorescence signal intensity is positively correlated with the electron beam current.The ion bombardment secondary emission electron gun is suitable for the technology.To enhance the beam current,COMSOL simulations and analyses were conducted to examine plasma density distribution in the discharge chamber under the effects of various conditions and the electric field distribution between the cathode and the spacer gap.The anode shape and discharge pressure conditions were optimized to increase plasma density.Additionally,an improved spacer structure was designed with the dual purpose of enhancing the electric field distribution between the cathode-spacer gaps and improving vacuum differential effects.This design modification aims to increase the pass rate of secondary electrons.Both simulation and experimental results demonstrated that the performance of the optimized electron gun was effectively enhanced.When the electrode voltage remains constant and the discharge gas pressure is adjusted to around 8 Pa,the maximum beam current was increased from 0.9 mA to 1.6 mA.
基金funded by the Ministry of Education, Science and Technological Development of the Republic of Serbia via the FAMA project (research topic “Physics and chemistry with ion beams”)。
文摘Without knowing the emittance value, it is difficult to optimize ion beam optics for minimum beam loss during transmission, especially considering the very high emittance values of electron cyclotron resonance(ECR) ion sources.With this in mind, to measure the emittance of the ion beams produced by the mVINIS ECR, which is part of the FAMA facility at the Vin?a Institute of Nuclear Sciences, we have developed a pepper-pot scintillator screen system combined with a CMOS camera. The application, developed on the Lab VIEW platform, allows us to control the camera's main attribute settings, such as the shutter speed and the gain, record the images in the region of interest, and process and filter the images in real time. To analyze the data from the obtained image, we have developed an algorithm called measurement and analysis of ion beam luminosity(MAIBL) to reconstruct the four-dimensional(4D) beam profile and calculate the root mean square(RMS) emittance. Before measuring emittance, we performed a simulated experiment using the pepper-pot simulation(PPS) program. An exported file(PPS) gives a numerically generated raw image(mock image) of a beam with a predefined emittance value after it has passed through a pepper-pot mask. By analyzing data from mock images instead of the image obtained by the camera and putting it into the MAIBL algorithm, we can compare the calculated emittance with PPS's initial emittance value. In this paper, we present our computational tools and explain the method for verifying the correctness of the calculated emittance values.
