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
Insufficient metallurgical compatibility between Zr and Ni can lead to the formation of brittle welds and introduce thermal stress-related challenges during the electron beam welding process.Through the implementation...Insufficient metallurgical compatibility between Zr and Ni can lead to the formation of brittle welds and introduce thermal stress-related challenges during the electron beam welding process.Through the implementation of beam deflection and vibration,a transformation was achieved in the primary Ni_(5)Zr dendrite structure,transitioning from a mass into a layered configuration,consequently resulting in the formation of an ultrafine-grained eutectic−dendrite complex structure.It is revealed that the enhanced strength−ductility synergy of this structure significantly contributes to the high tensile strength and improved plasticity observed in the welded joints.As a result,the welding cracks are effectively mitigated,and notable advancements are achieved in the mechanical properties of Zr/Ni joints,elevating the tensile strength of the joints from 36.4 to 189 MPa.This research not only highlights the potential of this technique in enhancing the strength and ductility of Zr/Ni welded joints but also serves as a valuable reference for future investigations involving welding applications of dissimilar metals.展开更多
Conventionally,the spatially structured light beams produced by metasurfaces primarily highlight the polarization modulation of the beams propagating along the optical axis or the beams'spatial transmission trajec...Conventionally,the spatially structured light beams produced by metasurfaces primarily highlight the polarization modulation of the beams propagating along the optical axis or the beams'spatial transmission trajectory.In particular,along the optical axis,the polarization state is either constant or varies continuously in each output plane.Here,we develop innovative spatially structured light beams with continually changing polarization along any arbitrary spatial transmission trajectories.With tri-layer metallic metasurfaces,the geometric characteristics of each layer structure can be adjusted to modulate the phase and polarization state of the incident terahertz(THz)wave.The beam will converge to the predefined trajectory along several paths to generate a Bessel-like beam with longitudinal polarization changes.We demonstrate the versatility of the approach by designing two THz-band structured light beams with varying polarization states along the spatial helical transmission trajectory.Continuous linear polarization changes and linear polarization to right circular polarization(RCP)and back to linear polarization changes are realized respectively.The experimental results are basically consistent with the simulated results.Our proposal for arbitrary trajectory structured light beams with longitudinally varying polarization offers a practical method for continuously regulating the characteristics of spatial structured light beams with non-axial transmission.This technique has potential uses in optical encryption,particle manipulation,and biomedical imaging.展开更多
A pin-like beam is a kind of structured light with a special intensity distribution that can be against diffraction,which can be seen as a kind of quasi-nondiffracting beam(Q-NDB).Due to its wide applications,recently...A pin-like beam is a kind of structured light with a special intensity distribution that can be against diffraction,which can be seen as a kind of quasi-nondiffracting beam(Q-NDB).Due to its wide applications,recently,numerous researchers have used optical lenses or on-chip integrated optical diffractive elements to generate this kind of beam.We theoretically verify and experimentally demonstrate an all-fiber solution to generate a subwavelength inverted pin beam by integrating a simple plasma structure on the fiber end surface.The output beams generated by two kinds of plasma structures,i.e.,nanoring slot and nanopetal structure,are investigated and measured experimentally.The results show that both the structures are capable of generating subwavelength beams,and the beam generated using the nanopetal structure has the sidelobe suppression ability along the x-axis direction.Our all-fiber device can be flexibly inserted into liquid environments such as cell cultures,blood,and biological tissue fluids to illuminate or stimulate biological cells and molecules in them.It provides a promising fiber-integrated solution for exploring light–matter interaction with subwavelength resolution in the field of biological research.展开更多
Vector structured beams(VSBs)offer infinite eigenstates and open up new possibilities for highcapacity optical and quantum communications by the multiplexing of the states.Therefore,the sorting and measuring of VSBs a...Vector structured beams(VSBs)offer infinite eigenstates and open up new possibilities for highcapacity optical and quantum communications by the multiplexing of the states.Therefore,the sorting and measuring of VSBs are extremely important.However,the efficient manipulations of a large number of VSBs have simultaneously remained challenging up to now,especially in integrated optical systems.Here,we propose a compact spin-multiplexed diffractive metasurface capable of continuously sorting and detecting arbitrary VSBs through spatial intensity separation.By introducing a diffractive optical neural network with cascaded metasurface systems,we demonstrate arbitrary VSBs sorters that can simultaneously identify Laguerre–Gaussian modes(l=−4 to 4,p=1 to 4),Hermitian–Gaussian modes(m=1 to 4,n=1 to 3),and Bessel–Gaussian modes(l=1 to 12).Such a sorter for arbitrary VSBs could revolutionize applications in integrated and high-dimensional optical communication systems.展开更多
Through the Galerkin method the nonlinear ordinary differential equations （ODEs） in time are obtained from the nonlinear partial differential equations （PDEs） to describe the mo- tion of the coupled structure of a...Through the Galerkin method the nonlinear ordinary differential equations （ODEs） in time are obtained from the nonlinear partial differential equations （PDEs） to describe the mo- tion of the coupled structure of a suspended-cable-stayed beam. In the PDEs, the curvature of main cables and the deformation of cable stays are taken into account. The dynamics of the struc- ture is investigated based on the ODEs when the structure is subjected to a harmonic excitation in the presence of both high-frequency principle resonance and 1：2 internal resonance. It is found that there are typical jumps and saturation phenomena of the vibration amplitude in the struc- ture. And the structure may present quasi-periodic vibration or chaos, if the stiffness of the cable stays membrane and frequency of external excitation are disturbed.展开更多
Electron beam melting(EBM) process is an additive manufacturing process largely used to produce complex metallic components made of high-performance materials for aerospace and medical applications.Especially,lattice ...Electron beam melting(EBM) process is an additive manufacturing process largely used to produce complex metallic components made of high-performance materials for aerospace and medical applications.Especially,lattice structures made by Ti-6A1-4V have represented a hot topic for the industrial sectors because of having a great potential to combine lower weights and higher performances that can also be tailored by subsequent heat treatments.However,the little knowledge about the mechanical behaviour of the lattice structures is limiting their applications.The present work aims to provide a comprehensive review of the studies on the mechanical behaviour of the lattice structures made of Ti-6A1-4V.The main steps to produce an EBM part were considered as guidelines to review the literature on the lattice performance:(1) design,(2) process and(3) post-heat treatment.Thereafter,the correlation between the geometrical features of the lattice structure and their mechanical behaviour is discussed.In addition,the correlation among the mechanical performance of the lattice structures and the process precision,surface roughness and working temperature are also reviewed.An investigation on the studies about the properties of heat-treated lattice structure is also conducted.展开更多
In this paper, a novel method of a subwavelength binary simple periodic rectangular structure is presented to realize even beam splitting by combining the rigorous couple-wave analysis with the genetic algorithm. Seve...In this paper, a novel method of a subwavelength binary simple periodic rectangular structure is presented to realize even beam splitting by combining the rigorous couple-wave analysis with the genetic algorithm. Several even splitters in the terahertz region were designed and one of the silicon-based beam splitters designed to separate one incident beam into four emergent beams has total efficiency up to 92.23 %. Zero-order diffraction efficiency was reduced to less than 0.192 % and the error of uniformity decreased to 6.51 9 10-6. These results break the limitation of even beam splitting based on the traditional scalar theory. In addition, the effects of the incident angle, wavelength, as well as the polarizing angle on the diffraction efficiency and uniformity were also investigated.展开更多
Deep beam anchorage structures based on spatial distribution analysis of the cable prestressed field have been proposed for roadway roof support, Stability and other factors that influence deep beam structures are stu...Deep beam anchorage structures based on spatial distribution analysis of the cable prestressed field have been proposed for roadway roof support, Stability and other factors that influence deep beam structures are studied in this paper using mechanical calculations, numerical analysis and field measurements, A mechanical model of deep beam structure subjected to multiple loading is established, including analysis of roof support in the return airway of S1203 working face in the Yuwu coal mine, China, The expression of maximum shear stress in the deep beam structure is deduced according to the stress superposition criterion, It is found that the primary factors affecting deep beam structure stability are deep beam thickness, cable pre-tension and cable spacing, The variation of maximum shear stress distribution and prestressed field diffusion effects according to various factors are analyzed using Matlah and FLAC3DTM software, and practical support parameters of the S1203 return airway roof are determined, According to the observations of rock pressure, there is no evidence of roof separation, and the maximum values of roof subsidence and convergence of wall rock are 72 and 48 mm, respectively, The results show that the proposed roof support design with a deep beam structure is feasible and achieves effective control of the roadway roof,展开更多
The paper investigated the equivalent continuum modeling of beam-like repetitive truss structures considering the flexibility of joints,which models the contact between the truss member and joint by spring-damper with...The paper investigated the equivalent continuum modeling of beam-like repetitive truss structures considering the flexibility of joints,which models the contact between the truss member and joint by spring-damper with six directional stiffnesses and dampings.Firstly,a two-node hybrid joint-beam element was derived for modeling the truss member with flexible end joints,and a condensed model for the repeating element with flexible joints was obtained.Then,the energy equivalence method was adopted to equivalently model the truss structure with flexible joints and material damping as a spatial viscoelastic anisotropic beam model.Afterwards,the equations of motion for the equivalent beam model were derived and solved analytically in the frequency domain.In the numerical studies,the correctness of the presented method was verified by comparisons of the natural frequencies and frequency responses evaluated by the equivalent beam model with the results of the finite element method model.展开更多
The Beijing spectrometer Ⅲ （BESⅢ） beam pipe is in the center of the BESⅢ, which is the detector of the upgrade project of Beijing electron and positron collider （BEPC Ⅱ）. Electrons and positrons collide in the...The Beijing spectrometer Ⅲ （BESⅢ） beam pipe is in the center of the BESⅢ, which is the detector of the upgrade project of Beijing electron and positron collider （BEPC Ⅱ）. Electrons and positrons collide in the BESⅢ beam pipe. According to the demands of the BEPC Ⅱ, a key program of Chinese Academy of Sciences, the BESⅢ beam pipe is designed based on the finite elements analysis. The BESIII beam pipe is installed in the inner cylinder of the BESⅢ drift chamber. As a vacuum tube, the BESIII beam pipe is designed as 1 000 mm in length, 63 mm in inner diameter and 114 mm in outer diameter, respectively. The BESIII beam pipe consists of a central beryllium pipe cooled by EDM-1, the oil No.1 for electric discharge machining, and two extended copper pipes cooled by deionized water （DW）. The three parts are jointed by vacuum welding. Factors taken into account in the design are as follows. ① The wall thickness of the central beryllium pipe should be designed as small as possible to reduce the multi-scattering and improve the particle momentum resolution. And the wall thickness of the extended copper pipe should be designed as large as possible to protect the detectors from the backgrounds. ②The BESⅢ beam pipe must be sufficiently cooled to avoid the damage and prevents its influence to the BESⅢ drift chamber （DC） operation. The inner surface temperature of the DC inner cylinder must be maintained at 293±2 K. ③ The magnetic permeability of the materials used in the BESⅢ beam pipe must be less than 1.05 H/m to avoid large magnetic field distortions. ④ The static pressure of the vacuum chamber of the BESⅢ beam pipe must be less than 800 μPa. The simulating results show that the designed structure of the BESⅢ beam pipe satisfies the requirements mentioned above. The structure design scheme is evaluated and adonted hv the headouarters of BEPCⅡ.展开更多
Combined multi-body dynamics with structural dynamics, a new discrete element with flexible connector, which is applicable for 3-D beam structures, is developed in this paper. Both the generalized elastic coefficient ...Combined multi-body dynamics with structural dynamics, a new discrete element with flexible connector, which is applicable for 3-D beam structures, is developed in this paper. Both the generalized elastic coefficient matrix of the flexible connector and the mass matrix of discrete element may be off-diagonal in a general case. The zero-length rigid element is introduced to simulate the node at which multiple elements are jointed together. It may also be effective when the axes of adjacent elements are not in the same line. The examples for eigenvalue calculation show that the model is successful. It can be extended to the geometric nonlinear response analysis.展开更多
The analysis of the microstructural characterization and phase composition of electron beam welded joint zones of Ti- 43Al-9V-O. 3Y alloy has been done in this study. The welded seam is mainly composed of B2 phase, th...The analysis of the microstructural characterization and phase composition of electron beam welded joint zones of Ti- 43Al-9V-O. 3Y alloy has been done in this study. The welded seam is mainly composed of B2 phase, the partial γ ＋ α2 twophase lamellar structure and granular γm phase. And the lanthanon Y existed as YAl2 phase and served as grain refined. The impact of different cooling rates on joint microstructure, fracture characteristic and tensile strength were investigated. The high cooling rate restrained the structural transformation and resulted in the ordering structure. The fracture of the joint was brittle cleavage fracture because the ordering structure went against restraining the crack propagation. With the decrease of cooling rate, the transformation amounts of lamellar structure increased, and the fracture presented the layered and crosslayered characteristic.展开更多
Based on the method of reverberation ray matrix（MRRM）, a reverberation matrix for planar framed structures composed of anisotropic Timoshenko（T） beam members containing completely hinged joints is developed for st...Based on the method of reverberation ray matrix（MRRM）, a reverberation matrix for planar framed structures composed of anisotropic Timoshenko（T） beam members containing completely hinged joints is developed for static analysis of such structures.In the MRRM for dynamic analysis, amplitudes of arriving and departing waves for joints are chosen as unknown quantities. However, for the present case of static analysis, displacements and rotational angles at the ends of each beam member are directly considered as unknown quantities. The expressions for stiffness matrices for anisotropic beam members are developed. A corresponding reverberation matrix is derived analytically for exact and unified determination on the displacements and internal forces at both ends of each member and arbitrary cross sectional locations in the structure. Numerical examples are given and compared with the finite element method（FEM） results to validate the present model. The characteristic parameter analysis is performed to demonstrate accuracy of the present model with the T beam theory in contrast with errors in the usual model based on the Euler-Bernoulli（EB） beam theory. The resulting reverberation matrix can be used for exact calculation of anisotropic framed structures as well as for parameter analysis of geometrical and material properties of the framed structures.展开更多
Adopting a steel-anchor beam and steel corbel composite structure in the anchor zone on pylon is one of the key techniques for the design of Jintang bridge, a cable-stayed bridge in Zhoushan, China. In order to ensure...Adopting a steel-anchor beam and steel corbel composite structure in the anchor zone on pylon is one of the key techniques for the design of Jintang bridge, a cable-stayed bridge in Zhoushan, China. In order to ensure the safety of the steel-concrete composite structure, a stud connector model for the joint section was put forward. Experiments were conducted to obtain the relation between load and slip of specimen, the failure pattern of stud connector, the yield bearing capacity and ultimate bearing capacity of a single stud, etc. The whole process of the structural behavior of the specimen was comprehensively analyzed. The features of the internal force distribution in the steel-concrete composite structure and the strain distribution of stud connector under different loads were emphatically studied. The test results show that the stud connector is applicable for the steel-concrete composite structure for pylon of Jintang bridge. The stud has a good ductility performance and a obvious yield process before its destruction. The stud connector basically works in a state of elasticity under a load less than the yield load.展开更多
The new Ni-Co-based superalloy featuring a"fusion structure"was produced utilizing electron beam smelting layered solidification technology(EBSL).Experimental examination of hot compression deformation with ...The new Ni-Co-based superalloy featuring a"fusion structure"was produced utilizing electron beam smelting layered solidification technology(EBSL).Experimental examination of hot compression deformation with varied settings for EBSL and conventional duplex process melting Ni-Co superalloys was performed.As per the study,EBSL-Ni-Co superalloys exhibited enhanced recrystallization susceptibility during hot deformation.Furthermore,elevating deformation temperature,lowering strain rate,and augmenting strain collectively contribute to enlarging the volume fraction of dynamically recrystallized grains.Aberrant growth of grains occurred when the deformation temperature equaledγ′sub-solvus temperature and the strain rate was slower.Moreover,exceeding theγ′solvus temperature during deformation significantly increases the particle size of dynamic recrystallization(DRX)grains.Theγ′phase can effectively modulate the DRX grain size through the pegging effect.Additionally,it was revealed that the presence of the fusion structure aids in the generation of continuous dynamic recrystallization,discontinuous dynamic recrystallization,and twinning-induced dynamic recrystallization while the alloy undergoes hot deformation.This mechanism promotes DRX granule formation and permits complete recrystallization.Ultimately,the fusion structure was identified as playing a catalytic role in the dynamic recrystallization process of the new Ni-Co superalloy.展开更多
This paper extends Le van＇s work to the case of nonlinear problem and the complicated configuration. The wrinkling stress distribution and the pressure effects are also included in our analysis. Pseudo-beam method is...This paper extends Le van＇s work to the case of nonlinear problem and the complicated configuration. The wrinkling stress distribution and the pressure effects are also included in our analysis. Pseudo-beam method is presented based on the inflatable beam theory to model the inflatable structures as a set of inflatable beam elements with a prestressed state. In this method, the discretized nonlinear equations are given based upon the virtual work principle with a 3-node Timoshenko＇s beam model. Finite element simulation is performed by using a 3-node BEAM189 element incorporating ANSYS nonlinear program. The pressure effect is equivalent included in our method by modifying beam element cross-section parameters related to pressure. A benchmark example, the bending case of an inflatable cantilever beam, is performed to verify the accuracy of our proposed method. The comparisons reveal that the numerical results obtained with our method are close to open published analytical and membrane finite element results. The method is then used to evaluate the whole buckling and the loadcarrying characteristics of an inflatable support frame subjected to a compression force. The wrinkling stress and region characteristics are also shown in the end. This method gives better convergence characteristics, and requires much less computation time. It is very effective to deal with the whole load-carrying ability analytical problems for large scale inflatable structures with complex configuration.展开更多
In this study, a new method for conversion of solid finite element solution to beam finite element solution is developed based on the meta-modeling theory which constructs a model consistent with continuum mechanics. ...In this study, a new method for conversion of solid finite element solution to beam finite element solution is developed based on the meta-modeling theory which constructs a model consistent with continuum mechanics. The proposed method is rigorous and efficient compared to a typical conversion method which merely computes surface integration of solid element nodal stresses to obtain cross-sectional forces. The meta-modeling theory ensures the rigorousness of proposed method by defining a proper distance between beam element and solid element solutions in a function space of continuum mechanics. Results of numerical verification test that is conducted with a simple cantilever beam are used to find the proper distance function for this conversion. Time history analysis of the main tunnel structure of a real ramp tunnel is considered as a numerical example for the proposed conversion method. It is shown that cross-sectional forces are readily computed for solid element solution of the main tunnel structure when it is converted to a beam element solution using the proposed method. Further, envelopes of resultant forces which are of primary importance for the purpose of design, are developed for a given ground motion at the end.展开更多
The cellular structured titanium alloys have attracted significant attention for implants because of their lower Young’s modulus,which is comparable to human bone and has the capability of providing space for bone ti...The cellular structured titanium alloys have attracted significant attention for implants because of their lower Young’s modulus,which is comparable to human bone and has the capability of providing space for bone tissue in-growth.However,there is a gap in the knowledge in regard to the relationship between the pore characteristics and the electrochemical performance of open-cellular structured titanium alloys.In this study,we elucidate the influence of pore characteristics on the electrochemical performance of open-cellular structured Ti-6Al-4V alloys produced by electron beam melting(EBM).Intriguingly,the passive film formed on cellular structured Ti-6Al-4V alloy with a larger pore size was more stable and protective,and the corrosion performance was superior compared to the samples with a smaller pore size in phosphate buffered saline(PBS),mainly because of relatively smaller exposed surface area and unlimited flow of electrolyte.However,in acidic PBS containing fluoride ions,the pore characteristics did not play an important role in the corrosion resistance.It was considered that the protective film breaks down such that the corrosion performance of cellular structured alloys was comparable to each other in this harsh environment.展开更多
We realize broadband acoustic focusing effect by employing two symmetric Airy beams generated from phased arrays,in which the units of the phased arrays consist of different numbers of cavity structures, each of which...We realize broadband acoustic focusing effect by employing two symmetric Airy beams generated from phased arrays,in which the units of the phased arrays consist of different numbers of cavity structures, each of which is composed of a square cavity and two inclined channels in air. The exotic phenomenon arises from the energy overlapping of the two symmetric Airy beams. Besides, we demonstrate the focusing performance with high self-healing property, and discuss the effects of structure parameters on focusing performance, and present the characteristics of the cavity structure with straight channels. Compared with other acoustic lenses, the proposed acoustic lens has advantages of broad bandwidth（about 1.4 kHz）, high self-healing property of focusing performance, and free adjustment of focal length. Our finding should have great potential applications in ultrasound imaging and medical diagnosis.展开更多
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 National Natural Science Foundation of China(No.52375322).
文摘Insufficient metallurgical compatibility between Zr and Ni can lead to the formation of brittle welds and introduce thermal stress-related challenges during the electron beam welding process.Through the implementation of beam deflection and vibration,a transformation was achieved in the primary Ni_(5)Zr dendrite structure,transitioning from a mass into a layered configuration,consequently resulting in the formation of an ultrafine-grained eutectic−dendrite complex structure.It is revealed that the enhanced strength−ductility synergy of this structure significantly contributes to the high tensile strength and improved plasticity observed in the welded joints.As a result,the welding cracks are effectively mitigated,and notable advancements are achieved in the mechanical properties of Zr/Ni joints,elevating the tensile strength of the joints from 36.4 to 189 MPa.This research not only highlights the potential of this technique in enhancing the strength and ductility of Zr/Ni welded joints but also serves as a valuable reference for future investigations involving welding applications of dissimilar metals.
基金supported by the National Natural Science Foundation of China(Grant Nos.12074094 and 121774271)the Sino-German Mobility Program of the Sino-German Center for Science Funding(Grant No.M-0225)the Capacity Building for Science&Technology Innovation-Fundamental Scientific Research Funds(Grant No.00820531120017).
文摘Conventionally,the spatially structured light beams produced by metasurfaces primarily highlight the polarization modulation of the beams propagating along the optical axis or the beams'spatial transmission trajectory.In particular,along the optical axis,the polarization state is either constant or varies continuously in each output plane.Here,we develop innovative spatially structured light beams with continually changing polarization along any arbitrary spatial transmission trajectories.With tri-layer metallic metasurfaces,the geometric characteristics of each layer structure can be adjusted to modulate the phase and polarization state of the incident terahertz(THz)wave.The beam will converge to the predefined trajectory along several paths to generate a Bessel-like beam with longitudinal polarization changes.We demonstrate the versatility of the approach by designing two THz-band structured light beams with varying polarization states along the spatial helical transmission trajectory.Continuous linear polarization changes and linear polarization to right circular polarization(RCP)and back to linear polarization changes are realized respectively.The experimental results are basically consistent with the simulated results.Our proposal for arbitrary trajectory structured light beams with longitudinally varying polarization offers a practical method for continuously regulating the characteristics of spatial structured light beams with non-axial transmission.This technique has potential uses in optical encryption,particle manipulation,and biomedical imaging.
基金supported by the National Natural Science Foundation of China (Grant Nos.62205079,62065006,62125503,and 62261160388)the Natural Science Foundation of Hubei Province of China (Grant No.2023AFA028)+1 种基金the Innovation Project of GUET Graduate Education (Grant No.2023YCXS214)the Innovation Project of Optics Valley Laboratory (Grant No.OVL2021BG004).
文摘A pin-like beam is a kind of structured light with a special intensity distribution that can be against diffraction,which can be seen as a kind of quasi-nondiffracting beam(Q-NDB).Due to its wide applications,recently,numerous researchers have used optical lenses or on-chip integrated optical diffractive elements to generate this kind of beam.We theoretically verify and experimentally demonstrate an all-fiber solution to generate a subwavelength inverted pin beam by integrating a simple plasma structure on the fiber end surface.The output beams generated by two kinds of plasma structures,i.e.,nanoring slot and nanopetal structure,are investigated and measured experimentally.The results show that both the structures are capable of generating subwavelength beams,and the beam generated using the nanopetal structure has the sidelobe suppression ability along the x-axis direction.Our all-fiber device can be flexibly inserted into liquid environments such as cell cultures,blood,and biological tissue fluids to illuminate or stimulate biological cells and molecules in them.It provides a promising fiber-integrated solution for exploring light–matter interaction with subwavelength resolution in the field of biological research.
基金supported by the National Natural Science Foundation of China(Grant No.12274105)the Heilongjiang Natural Science Funds for Distinguished Young Scholars(Grant No.JQ2022A001)+1 种基金the Fundamental Research Funds for the Central Universities(Grant No.HIT.OCEF.2021020)the Joint Guidance Project of the Natural Science Foundation of Heilongjiang Province(Grant No.LH2023A006).
文摘Vector structured beams(VSBs)offer infinite eigenstates and open up new possibilities for highcapacity optical and quantum communications by the multiplexing of the states.Therefore,the sorting and measuring of VSBs are extremely important.However,the efficient manipulations of a large number of VSBs have simultaneously remained challenging up to now,especially in integrated optical systems.Here,we propose a compact spin-multiplexed diffractive metasurface capable of continuously sorting and detecting arbitrary VSBs through spatial intensity separation.By introducing a diffractive optical neural network with cascaded metasurface systems,we demonstrate arbitrary VSBs sorters that can simultaneously identify Laguerre–Gaussian modes(l=−4 to 4,p=1 to 4),Hermitian–Gaussian modes(m=1 to 4,n=1 to 3),and Bessel–Gaussian modes(l=1 to 12).Such a sorter for arbitrary VSBs could revolutionize applications in integrated and high-dimensional optical communication systems.
基金supported by the National Natural Science Foundation of China(Nos.10672121 and 11072125)
文摘Through the Galerkin method the nonlinear ordinary differential equations （ODEs） in time are obtained from the nonlinear partial differential equations （PDEs） to describe the mo- tion of the coupled structure of a suspended-cable-stayed beam. In the PDEs, the curvature of main cables and the deformation of cable stays are taken into account. The dynamics of the struc- ture is investigated based on the ODEs when the structure is subjected to a harmonic excitation in the presence of both high-frequency principle resonance and 1：2 internal resonance. It is found that there are typical jumps and saturation phenomena of the vibration amplitude in the struc- ture. And the structure may present quasi-periodic vibration or chaos, if the stiffness of the cable stays membrane and frequency of external excitation are disturbed.
文摘Electron beam melting(EBM) process is an additive manufacturing process largely used to produce complex metallic components made of high-performance materials for aerospace and medical applications.Especially,lattice structures made by Ti-6A1-4V have represented a hot topic for the industrial sectors because of having a great potential to combine lower weights and higher performances that can also be tailored by subsequent heat treatments.However,the little knowledge about the mechanical behaviour of the lattice structures is limiting their applications.The present work aims to provide a comprehensive review of the studies on the mechanical behaviour of the lattice structures made of Ti-6A1-4V.The main steps to produce an EBM part were considered as guidelines to review the literature on the lattice performance:(1) design,(2) process and(3) post-heat treatment.Thereafter,the correlation between the geometrical features of the lattice structure and their mechanical behaviour is discussed.In addition,the correlation among the mechanical performance of the lattice structures and the process precision,surface roughness and working temperature are also reviewed.An investigation on the studies about the properties of heat-treated lattice structure is also conducted.
基金supported by grants from the Natural Science Foundation of China(Nos.61275167,60878036and 60178023)the Basic Research Project of Shenzhen(Nos.JCYJ20130329103020637,JCYJ20120613112628842,JCYJ20140418095735591 and JC201005280533A)
文摘In this paper, a novel method of a subwavelength binary simple periodic rectangular structure is presented to realize even beam splitting by combining the rigorous couple-wave analysis with the genetic algorithm. Several even splitters in the terahertz region were designed and one of the silicon-based beam splitters designed to separate one incident beam into four emergent beams has total efficiency up to 92.23 %. Zero-order diffraction efficiency was reduced to less than 0.192 % and the error of uniformity decreased to 6.51 9 10-6. These results break the limitation of even beam splitting based on the traditional scalar theory. In addition, the effects of the incident angle, wavelength, as well as the polarizing angle on the diffraction efficiency and uniformity were also investigated.
基金provided by the National Natural Science Foundation of China (Nos. 51504259 and 51234005)the Fundamental Research Funds for the Central Universities (No. 2010QZ06)
文摘Deep beam anchorage structures based on spatial distribution analysis of the cable prestressed field have been proposed for roadway roof support, Stability and other factors that influence deep beam structures are studied in this paper using mechanical calculations, numerical analysis and field measurements, A mechanical model of deep beam structure subjected to multiple loading is established, including analysis of roof support in the return airway of S1203 working face in the Yuwu coal mine, China, The expression of maximum shear stress in the deep beam structure is deduced according to the stress superposition criterion, It is found that the primary factors affecting deep beam structure stability are deep beam thickness, cable pre-tension and cable spacing, The variation of maximum shear stress distribution and prestressed field diffusion effects according to various factors are analyzed using Matlah and FLAC3DTM software, and practical support parameters of the S1203 return airway roof are determined, According to the observations of rock pressure, there is no evidence of roof separation, and the maximum values of roof subsidence and convergence of wall rock are 72 and 48 mm, respectively, The results show that the proposed roof support design with a deep beam structure is feasible and achieves effective control of the roadway roof,
基金This work was supported by the National Natural Science Foundation of China(Grants 11702146,11732006 and 11827801)the Equipment Pre-research Foundation(Grant 6140210010202).
文摘The paper investigated the equivalent continuum modeling of beam-like repetitive truss structures considering the flexibility of joints,which models the contact between the truss member and joint by spring-damper with six directional stiffnesses and dampings.Firstly,a two-node hybrid joint-beam element was derived for modeling the truss member with flexible end joints,and a condensed model for the repeating element with flexible joints was obtained.Then,the energy equivalence method was adopted to equivalently model the truss structure with flexible joints and material damping as a spatial viscoelastic anisotropic beam model.Afterwards,the equations of motion for the equivalent beam model were derived and solved analytically in the frequency domain.In the numerical studies,the correctness of the presented method was verified by comparisons of the natural frequencies and frequency responses evaluated by the equivalent beam model with the results of the finite element method model.
基金Key Programs of Chinese Academy of Sciences(No.KJ95T-03)
文摘The Beijing spectrometer Ⅲ （BESⅢ） beam pipe is in the center of the BESⅢ, which is the detector of the upgrade project of Beijing electron and positron collider （BEPC Ⅱ）. Electrons and positrons collide in the BESⅢ beam pipe. According to the demands of the BEPC Ⅱ, a key program of Chinese Academy of Sciences, the BESⅢ beam pipe is designed based on the finite elements analysis. The BESIII beam pipe is installed in the inner cylinder of the BESⅢ drift chamber. As a vacuum tube, the BESIII beam pipe is designed as 1 000 mm in length, 63 mm in inner diameter and 114 mm in outer diameter, respectively. The BESIII beam pipe consists of a central beryllium pipe cooled by EDM-1, the oil No.1 for electric discharge machining, and two extended copper pipes cooled by deionized water （DW）. The three parts are jointed by vacuum welding. Factors taken into account in the design are as follows. ① The wall thickness of the central beryllium pipe should be designed as small as possible to reduce the multi-scattering and improve the particle momentum resolution. And the wall thickness of the extended copper pipe should be designed as large as possible to protect the detectors from the backgrounds. ②The BESⅢ beam pipe must be sufficiently cooled to avoid the damage and prevents its influence to the BESⅢ drift chamber （DC） operation. The inner surface temperature of the DC inner cylinder must be maintained at 293±2 K. ③ The magnetic permeability of the materials used in the BESⅢ beam pipe must be less than 1.05 H/m to avoid large magnetic field distortions. ④ The static pressure of the vacuum chamber of the BESⅢ beam pipe must be less than 800 μPa. The simulating results show that the designed structure of the BESⅢ beam pipe satisfies the requirements mentioned above. The structure design scheme is evaluated and adonted hv the headouarters of BEPCⅡ.
基金The project was financially supported by the National Natural Science Foundation of China
文摘Combined multi-body dynamics with structural dynamics, a new discrete element with flexible connector, which is applicable for 3-D beam structures, is developed in this paper. Both the generalized elastic coefficient matrix of the flexible connector and the mass matrix of discrete element may be off-diagonal in a general case. The zero-length rigid element is introduced to simulate the node at which multiple elements are jointed together. It may also be effective when the axes of adjacent elements are not in the same line. The examples for eigenvalue calculation show that the model is successful. It can be extended to the geometric nonlinear response analysis.
文摘The analysis of the microstructural characterization and phase composition of electron beam welded joint zones of Ti- 43Al-9V-O. 3Y alloy has been done in this study. The welded seam is mainly composed of B2 phase, the partial γ ＋ α2 twophase lamellar structure and granular γm phase. And the lanthanon Y existed as YAl2 phase and served as grain refined. The impact of different cooling rates on joint microstructure, fracture characteristic and tensile strength were investigated. The high cooling rate restrained the structural transformation and resulted in the ordering structure. The fracture of the joint was brittle cleavage fracture because the ordering structure went against restraining the crack propagation. With the decrease of cooling rate, the transformation amounts of lamellar structure increased, and the fracture presented the layered and crosslayered characteristic.
基金Project supported by the Program for New Century Excellent Talents in Universities(NCET)by the Ministry of Education of China(No.NCET-04-0373)
文摘Based on the method of reverberation ray matrix（MRRM）, a reverberation matrix for planar framed structures composed of anisotropic Timoshenko（T） beam members containing completely hinged joints is developed for static analysis of such structures.In the MRRM for dynamic analysis, amplitudes of arriving and departing waves for joints are chosen as unknown quantities. However, for the present case of static analysis, displacements and rotational angles at the ends of each beam member are directly considered as unknown quantities. The expressions for stiffness matrices for anisotropic beam members are developed. A corresponding reverberation matrix is derived analytically for exact and unified determination on the displacements and internal forces at both ends of each member and arbitrary cross sectional locations in the structure. Numerical examples are given and compared with the finite element method（FEM） results to validate the present model. The characteristic parameter analysis is performed to demonstrate accuracy of the present model with the T beam theory in contrast with errors in the usual model based on the Euler-Bernoulli（EB） beam theory. The resulting reverberation matrix can be used for exact calculation of anisotropic framed structures as well as for parameter analysis of geometrical and material properties of the framed structures.
文摘Adopting a steel-anchor beam and steel corbel composite structure in the anchor zone on pylon is one of the key techniques for the design of Jintang bridge, a cable-stayed bridge in Zhoushan, China. In order to ensure the safety of the steel-concrete composite structure, a stud connector model for the joint section was put forward. Experiments were conducted to obtain the relation between load and slip of specimen, the failure pattern of stud connector, the yield bearing capacity and ultimate bearing capacity of a single stud, etc. The whole process of the structural behavior of the specimen was comprehensively analyzed. The features of the internal force distribution in the steel-concrete composite structure and the strain distribution of stud connector under different loads were emphatically studied. The test results show that the stud connector is applicable for the steel-concrete composite structure for pylon of Jintang bridge. The stud has a good ductility performance and a obvious yield process before its destruction. The stud connector basically works in a state of elasticity under a load less than the yield load.
基金the financial support from the National Key Research and Development Program of China(Grant No.2019YFA0705300)the National Natural Science Foundation of China(Grant No.52004051)the Innovation Team Project for Key Fields of Dalian(Grant No.2019RT13).
文摘The new Ni-Co-based superalloy featuring a"fusion structure"was produced utilizing electron beam smelting layered solidification technology(EBSL).Experimental examination of hot compression deformation with varied settings for EBSL and conventional duplex process melting Ni-Co superalloys was performed.As per the study,EBSL-Ni-Co superalloys exhibited enhanced recrystallization susceptibility during hot deformation.Furthermore,elevating deformation temperature,lowering strain rate,and augmenting strain collectively contribute to enlarging the volume fraction of dynamically recrystallized grains.Aberrant growth of grains occurred when the deformation temperature equaledγ′sub-solvus temperature and the strain rate was slower.Moreover,exceeding theγ′solvus temperature during deformation significantly increases the particle size of dynamic recrystallization(DRX)grains.Theγ′phase can effectively modulate the DRX grain size through the pegging effect.Additionally,it was revealed that the presence of the fusion structure aids in the generation of continuous dynamic recrystallization,discontinuous dynamic recrystallization,and twinning-induced dynamic recrystallization while the alloy undergoes hot deformation.This mechanism promotes DRX granule formation and permits complete recrystallization.Ultimately,the fusion structure was identified as playing a catalytic role in the dynamic recrystallization process of the new Ni-Co superalloy.
基金supported by the Specialized Fund for the Doctoral Program of Higher Education of China (200802131046)China Postdoctoral Science Foundation Funded Major Project (200801290)+1 种基金Development Program of Outstanding Young Teachers in Harbin Institute of Technology (HITQNJS.2008.004)Specialized Fund for Innovation Talents of Science and Technology in Harbin (2008RFQXG057).
文摘This paper extends Le van＇s work to the case of nonlinear problem and the complicated configuration. The wrinkling stress distribution and the pressure effects are also included in our analysis. Pseudo-beam method is presented based on the inflatable beam theory to model the inflatable structures as a set of inflatable beam elements with a prestressed state. In this method, the discretized nonlinear equations are given based upon the virtual work principle with a 3-node Timoshenko＇s beam model. Finite element simulation is performed by using a 3-node BEAM189 element incorporating ANSYS nonlinear program. The pressure effect is equivalent included in our method by modifying beam element cross-section parameters related to pressure. A benchmark example, the bending case of an inflatable cantilever beam, is performed to verify the accuracy of our proposed method. The comparisons reveal that the numerical results obtained with our method are close to open published analytical and membrane finite element results. The method is then used to evaluate the whole buckling and the loadcarrying characteristics of an inflatable support frame subjected to a compression force. The wrinkling stress and region characteristics are also shown in the end. This method gives better convergence characteristics, and requires much less computation time. It is very effective to deal with the whole load-carrying ability analytical problems for large scale inflatable structures with complex configuration.
文摘In this study, a new method for conversion of solid finite element solution to beam finite element solution is developed based on the meta-modeling theory which constructs a model consistent with continuum mechanics. The proposed method is rigorous and efficient compared to a typical conversion method which merely computes surface integration of solid element nodal stresses to obtain cross-sectional forces. The meta-modeling theory ensures the rigorousness of proposed method by defining a proper distance between beam element and solid element solutions in a function space of continuum mechanics. Results of numerical verification test that is conducted with a simple cantilever beam are used to find the proper distance function for this conversion. Time history analysis of the main tunnel structure of a real ramp tunnel is considered as a numerical example for the proposed conversion method. It is shown that cross-sectional forces are readily computed for solid element solution of the main tunnel structure when it is converted to a beam element solution using the proposed method. Further, envelopes of resultant forces which are of primary importance for the purpose of design, are developed for a given ground motion at the end.
基金partial support from the National Key Research and Development Program of China(Nos.2017YFC1104902,2016YFC1100502 and 2018YFC1105503)the National Natural Science Foundation of China(Nos.51871220 and 51631007)+3 种基金the Key Research Program of Frontier Sciences,CAS(No.QYZDJ-SSW-JSC031-02)the Natural Science Foundation of Liaoning Province of China(No.2019-MS-327 and 2020-KF-14-01)the State Key Laboratory of Light Alloy Casting Technology for Highend Equipment(No.LACT-007)the Shenyang Talents Program(No.RC200230)。
文摘The cellular structured titanium alloys have attracted significant attention for implants because of their lower Young’s modulus,which is comparable to human bone and has the capability of providing space for bone tissue in-growth.However,there is a gap in the knowledge in regard to the relationship between the pore characteristics and the electrochemical performance of open-cellular structured titanium alloys.In this study,we elucidate the influence of pore characteristics on the electrochemical performance of open-cellular structured Ti-6Al-4V alloys produced by electron beam melting(EBM).Intriguingly,the passive film formed on cellular structured Ti-6Al-4V alloy with a larger pore size was more stable and protective,and the corrosion performance was superior compared to the samples with a smaller pore size in phosphate buffered saline(PBS),mainly because of relatively smaller exposed surface area and unlimited flow of electrolyte.However,in acidic PBS containing fluoride ions,the pore characteristics did not play an important role in the corrosion resistance.It was considered that the protective film breaks down such that the corrosion performance of cellular structured alloys was comparable to each other in this harsh environment.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11774137 and 11404147)the Major Program of the National Natural Science Foundation of China(Grant No.51239005)+2 种基金the Natural Science Foundation of Jiangsu Province,China(Grant Nos.BK20140519 and BK20140523)the Jiangsu Qing Lan Project,Chinathe Practice Innovation Training Program Projects for Industrial Center of Jiangsu University,China
文摘We realize broadband acoustic focusing effect by employing two symmetric Airy beams generated from phased arrays,in which the units of the phased arrays consist of different numbers of cavity structures, each of which is composed of a square cavity and two inclined channels in air. The exotic phenomenon arises from the energy overlapping of the two symmetric Airy beams. Besides, we demonstrate the focusing performance with high self-healing property, and discuss the effects of structure parameters on focusing performance, and present the characteristics of the cavity structure with straight channels. Compared with other acoustic lenses, the proposed acoustic lens has advantages of broad bandwidth（about 1.4 kHz）, high self-healing property of focusing performance, and free adjustment of focal length. Our finding should have great potential applications in ultrasound imaging and medical diagnosis.
