The optical memory effect is an interesting phenomenon that has attracted considerable attention in recent decades. Here, we present a new physical picture of the optical memory effect, in which the memory effect and ...The optical memory effect is an interesting phenomenon that has attracted considerable attention in recent decades. Here, we present a new physical picture of the optical memory effect, in which the memory effect and the conventional spatial shift invariance are united. Based on this picture we depict the role of thickness, scattering times, and anisotropy factor and derive equations to calculate the ranges of the angular memory effect(AME) of different scattering components(ballistic light, singly scattered, doubly scattered, etc.), and hence a more accurate equation for the real AME ranges of volumetric turbid media. A conventional random phase mask model is modified according to the new picture. The self-consistency of the simulation model and its agreement with the experiment demonstrate the rationality of the model and the physical picture, which provide powerful tools for more sophisticated studies of the memory-effect-related phenomena and wavefront-sensitive techniques, such as wavefront shaping, optical phase conjugation, and optical trapping in/through scattering media.展开更多
To study the seismic responses produced by gas hydrate bubble plumes in the cold seepage active region, we constructed a plume water body model based on random medium theory and acoustic velocity model of bubble mediu...To study the seismic responses produced by gas hydrate bubble plumes in the cold seepage active region, we constructed a plume water body model based on random medium theory and acoustic velocity model of bubble medium. The plume water body model was forward simulated by finite difference. Seismic records of single shot show the scattered waves produced by the plume. The scattered wave energy is strong where the plume exists. Where the scattered wave energy is stronger, the minimum of travel time is always above the plume, which has no relationship with the shot's position. Seismic records of shot gathers were processed by prestack time migration. The migration section shows that the scattered waves produced by plumes can be imaged distinctly with higher accuracy. These researches laid a foundation for further study on the seismic responses produced by plumes and provided a new approach for the identification of gas hydrate.展开更多
Based on the definition of MQ-B-Splines,this article constructs five types of univariate quasi-interpolants to non-uniformly distributed data. The error estimates and the shape-preserving properties are shown in detai...Based on the definition of MQ-B-Splines,this article constructs five types of univariate quasi-interpolants to non-uniformly distributed data. The error estimates and the shape-preserving properties are shown in details.And examples are shown to demonstrate the capacity of the quasi-interpolants for curve representation.展开更多
Using the occurrence characteristics of bubble plumes in the South China Sea as a reference, this paper continues to study the seismic responses produced by bubble plumes in the cold seepage active region. To make the...Using the occurrence characteristics of bubble plumes in the South China Sea as a reference, this paper continues to study the seismic responses produced by bubble plumes in the cold seepage active region. To make the plume modelling scheme more reasonable, we modified the original modelling scheme and reconstructed a plume water body model based on the variation of its radius as bubbles rise in seawater. The plume seismic records of shot gathers were obtained by forward simulation. The seismic records of single shot show obvious characteristics of a scattering wave field and the periodic characteristics of the model. Seismic records of shot gathers were processed using prestack depth migration. The boundary of its imaging section has a good convergence effect. The migration sections can be imaged distinctly with higher accuracy. The aforementioned studies once again laid a foundation for the further study of the seismic responses produced by plumes. They also gradually probed a more suitable seismic data processing method for plumes and provided a theoretical guidance for the identification of plumes.展开更多
The microstructure and misorientation of ultrathin hot strip were analyzed by CSP technology using electron back scattered diffraction (EBSD) method and Autoforge finite element program. The experimental results showe...The microstructure and misorientation of ultrathin hot strip were analyzed by CSP technology using electron back scattered diffraction (EBSD) method and Autoforge finite element program. The experimental results showed that the finishing hot rolling microstructures were the mixture of recrystallized and deformed austenite. After phase transformation, ferrite grains embody substructures and dislocations, leading to the high strength and relatively low elongation rate of the ultrathin hot strip. The FEM simulation of strain mode and distribution in deformation area has been fulfilled. The simulation results are in good agreement with the theoretical analysis and experimental results.展开更多
An improved self-organizing feature map (SOFM) neural network is presented to generate rectangular and hexagonal lattic with normal vector attached to each vertex. After the neural network was trained, the whole scatt...An improved self-organizing feature map (SOFM) neural network is presented to generate rectangular and hexagonal lattic with normal vector attached to each vertex. After the neural network was trained, the whole scattered data were divided into sub-regions where classified core were represented by the weight vectors of neurons at the output layer of neural network. The weight vectors of the neurons were used to approximate the dense 3-D scattered points, so the dense scattered points could be reduced to a reasonable scale, while the topological feature of the whole scattered points were remained.展开更多
The scattered fields of plane waves in a solid from a cylinder or sphere are critical in determining its acoustic characteristics as well as in engineering applications. This paper investigates the scattered field dis...The scattered fields of plane waves in a solid from a cylinder or sphere are critical in determining its acoustic characteristics as well as in engineering applications. This paper investigates the scattered field distributions of different incident waves created by elastic cylinders embedded in an elastic isotropic medium. Scattered waves, including longitudinal and transverse waves both inside and outside the cylinder, are described with specific modalities under an incident plane wave. A model with a scatterer embedded in a structural steel matrix and filled with aluminum is developed for comparison with the theoretical solution. The frequency of the plane wave ranged from 235 kHz to 2348 kHz, which corresponds to scaling factors from 0.5 to 5. Scattered field distributions in matrix materials blocked by an elastic cylindrical solid have been obtained by simulation or calculated using existing parameters. The simulation results are in good agreement with the theoretical solution, which supports the correctness of the simulation analysis. Furthermore, ultrasonic phased arrays are used to study scattered fields by changing the characteristics of the incident wave. On this foundation, a partial preliminary study of the scattered field distribution of double cylinders in a solid has been carried out, and the scattered field distribution at a given distance has been found to exhibit particular behaviors at different moments. Further studies on directivities and scattered fields are expected to improve the quantification of scattered images in isotropic solid materials by the phased array technique.展开更多
In this study,the effects of hybridizing micron-sized titanium particles with nano-sized boron carbide particles on the microstructural and mechanical properties of Mg-Ti composite were investigated.Microstructural ch...In this study,the effects of hybridizing micron-sized titanium particles with nano-sized boron carbide particles on the microstructural and mechanical properties of Mg-Ti composite were investigated.Microstructural characterization revealed grain refinement attributed to the presence of uniformly distributed micro-Ti particles embedded with nano-B_(4)C particulates.Electron back scattered diffraction(EBSD)analyses of the Mg-(Ti+B_(4)C)BM hybrid composite showed relatively more localized recrystallized grains and lesser tensile twin fraction,when compared to Mg-Ti.The evaluation of mechanical properties indicated that the best combination of strength and ductility was observed in the Mg-(Ti+B_(4)C)BM hybrid composite.The superior properties of the Mg-(Ti+B_(4)C)BM hybrid composite when compared to Mg-Ti can be attributed to the presence of nano-reinforcement,the uniform distribution of the hybridized particles and the better interfacial bonding between the matrix and the reinforcement particles achieved by nano-B_(4)C addition.展开更多
The effect of carbonation treatment and mixing method on the mechanical properties and interfacial transition zone（ITZ） properties of recycled aggregate concrete（RAC） was investigated. Properties of recycled concr...The effect of carbonation treatment and mixing method on the mechanical properties and interfacial transition zone（ITZ） properties of recycled aggregate concrete（RAC） was investigated. Properties of recycled concrete aggregate（RCA） were tested firstly. Then, five types of concretes were made and slump of fresh concrete was measured immediately after mixing. Compressive strength and splitting tensile strength of hardened concrete were measured at 28 d. Meanwhile, the microstructure of RAC was analyzed by backscattered electron（BSE） image. It was found that the water absorption ratio of carbonated recycled concrete aggregate（CRCA） was much lower when compared to the untreated RCA. Comparatively, the apparent density of CRCA was not significantly modified. The concrete strength results indicate that the mix CRAC-2 prepared with CRCA by adopting two-stage mixing approach shows the highest compressive strength value compared to the other mixes. The microstructural analysis demonstrate that the mix CRAC-2 has a much denser old ITZ than the untreated RAC because of the chemical reaction between CO2 and the hydration products of RCA. This study confirms that the ITZ microstructure of RAC can be efficiently modified by carbonation treatment of RCA and encourages broadening the application of construction and demolition wastes.展开更多
Taking AutoCAD2000 as platform, an algorithm for the reconstruction ofsurface from scattered data points based on VBA is presented. With this core technology customerscan be free from traditional AutoCAD as an electro...Taking AutoCAD2000 as platform, an algorithm for the reconstruction ofsurface from scattered data points based on VBA is presented. With this core technology customerscan be free from traditional AutoCAD as an electronic board and begin to create actual presentationof real-world objects. VBA is not only a very powerful tool of development, but with very simplesyntax. Associating with those solids, objects and commands of AutoCAD 2000, VBA notably simplifiesprevious complex algorithms, graphical presentations and processing, etc. Meanwhile, it can avoidappearance of complex data structure and data format in reverse design with other modeling software.Applying VBA to reverse engineering can greatly improve modeling efficiency and facilitate surfacereconstruction.展开更多
Terahertz(THz)technologies have become a focus of research in recent years due to their prominent role in envisioned future communication and sensing systems.One of the key challenges facing the field is the need for ...Terahertz(THz)technologies have become a focus of research in recent years due to their prominent role in envisioned future communication and sensing systems.One of the key challenges facing the field is the need for tools to enable agile engineering of THz wave fronts.Here,we describe a reconfigurable metasurface based on GaN technology with an array-of-subarrays architecture.This subwavelength-spaced array,under the control of a 1-bit digital coding sequence,can switch between an enormous range of possible configurations,providing facile access to nearly arbitrary wave front control for signals near 0.34 THz.We demonstrate wide-angle beam scanning with 1°of angular precision over 70 GHz of bandwidth,as well as the generation of multi-beam and diffuse wave fronts,with a switching speed up to 100 MHz.This device,offering the ability to rapidly reconfigure a propagating wave front for beam-forming or diffusively scattered wide-angle coverage of a scene,will open new realms of possibilities in sensing,imaging,and networking.展开更多
In this paper, we use a univariate multiquadric quasi-interpolation scheme to solve the one-dimensional nonlinear sine-Gordon equation that is related to many physical phenomena. We obtain a numerical scheme by using ...In this paper, we use a univariate multiquadric quasi-interpolation scheme to solve the one-dimensional nonlinear sine-Gordon equation that is related to many physical phenomena. We obtain a numerical scheme by using the derivative of the quasi-interpolation to approximate the spatial derivative and a difference scheme to approximate the temporal derivative. The advantage of the obtained scheme is that the algorithm is very simple so that it is very easy to implement. The results of numerical experiments are presented and compared with analytical solutions to confirm the good accuracy of the presented scheme.展开更多
To study the bubble plume's seismic response characteristics,the model of a plume water body has been built in this article using the bubble-contained medium acoustic velocity model and the stochastic medium theor...To study the bubble plume's seismic response characteristics,the model of a plume water body has been built in this article using the bubble-contained medium acoustic velocity model and the stochastic medium theory based on an analysis of both the acoustic characteristics of a bubble-contained water body and the actual features of a plume.The finite difference method is used for forward modelling,and the single-shot seismic record exhibits the characteristics of a scattered wave field generated by a plume.A meaningful conclusion is obtained by extracting seismic attributes from the pre-stack shot gather record of a plume.The values of the amplitude-related seismic attributes increase greatly as the bubble content goes up,and changes in bubble radius will not cause seismic attributes to change,which is primarily observed because the bubble content has a strong impact on the plume's acoustic velocity,while the bubble radius has a weak impact on the acoustic velocity.The above conclusion provides a theoretical reference for identifying hydrate plumes using seismic methods and contributes to further study on hydrate decomposition and migration,as well as on distribution of the methane bubble in seawater.展开更多
Passive inter-modulation （PIM） is a form of nonlinear distortion caused by the inherent nonlinearities of the passive devices and components in RF/microwave system. It will degenerate the performance of communicatio...Passive inter-modulation （PIM） is a form of nonlinear distortion caused by the inherent nonlinearities of the passive devices and components in RF/microwave system. It will degenerate the performance of communication system with broad-band channel and high-sensitivity receiver. Therefore, it is necessary to construct a model to simulate this process in order to predict the level of PIM. This paper is aimed at constructing some plate models with one-dimensional and two-dimensional contact nonlinearity sections illuminated by two-tone waves, and calculating the scattered field at a fixed-point in space using time-domain physical optics method. By taking fast Fourier transform （FFT）, we get the spectrum of the scattered field and then analyze the generated PIM products. At the end of this paper, some numerical examples are presented to show the influence rules of the relative factors on PIM. The results indicate the variation of the level of PIM with the number of the nonlinear regions, the nonlinear spacing, and the incident power levels.展开更多
Fully polarized Compton scattering from a beam of spin-polarized electrons is investigated in plane-wave backgrounds in a broad intensity region from the perturbative to the nonperturbative regimes.In the perturbative...Fully polarized Compton scattering from a beam of spin-polarized electrons is investigated in plane-wave backgrounds in a broad intensity region from the perturbative to the nonperturbative regimes.In the perturbative regime,polarized linear Compton scattering is considered for investigating polarization transfer from a single laser photon to a scattered photon,and in the high-intensity region,the polarized locally monochromatic approximation and locally constant field approximation are established and are employed to study polarization transfer from an incoming electron to a scattered photon.The numerical results suggest an appreciable improvement of about 10%in the scattering probability in the intermediate-intensity region if the electron’s longitudinal spin is parallel to the laser rotation.The longitudinal spin of the incoming electron can be transferred to the scattered photon with an efficiency that increases with laser intensity and collisional energy.For collision between an optical laser with frequency1 eV and a 10 GeV electron,this polarization transfer efficiency can increase from about 20%in the perturbative regime to about 50%in the nonperturbative regime for scattered photons with relatively high energy.展开更多
This paper proposed a deep-learning-based method to process the scattered field data of transmitting antenna,which is unmeasurable in inverse scattering system because the transmitting and receiving antennas are multi...This paper proposed a deep-learning-based method to process the scattered field data of transmitting antenna,which is unmeasurable in inverse scattering system because the transmitting and receiving antennas are multiplexed.A U-net convolutional neural network(CNN)is used to recover the scattered field data of each transmitting antenna.The numerical results proved that the proposed method can complete the scattered field data at the transmitting antenna which is unable to measure in the actual experiment and can also eliminate the reconstructed error caused by the loss of scattered field data.展开更多
Moving from the county seat of Danba,Garze Prefecture,Sichua Province,the car turned to a small lane,just aside of a steep canyon,and then moved toward a nearby village.Before long,a charming village appeared in front...Moving from the county seat of Danba,Garze Prefecture,Sichua Province,the car turned to a small lane,just aside of a steep canyon,and then moved toward a nearby village.Before long,a charming village appeared in front of audiences.Row after row white painted houses were scattered to covering the mountain valley,as if a fictitious land of peace.This is Zhailong Village,an especially renowned place thanks to the local traditional music and dance culture.展开更多
The present study was aimed at the inlet particle spatial distribution of a gas-solid separator with high solid loading and investigated its effects on cyclone performance and the inner flow pattern.The flow fields of...The present study was aimed at the inlet particle spatial distribution of a gas-solid separator with high solid loading and investigated its effects on cyclone performance and the inner flow pattern.The flow fields of a cyclone with different rectangular particle flow areas on the inlet surface were numerically simulated using a four-way coupling method.The simulated results indicate that reducing the inlet particle flow area and lowing the inlet particle position can effectively reduce the scattered particles inside the cyclone separator and enhance the separation performance.Vertically gathering the particles to the centerline can also weaken the particle back-mixing.The particles near the roof account for the swirling particle ceiling phenomenon.The inlet particle spatial distribution affects the pressure drop mainly by affecting the gas tangential velocity in the cylinder body.Moreover,compared to the hori-zontal particle distribution on the inlet surface,the vertical particle distribution has greater effects on cyclone performance.展开更多
基金National Key Research and Development Program of China Stem Cell and Translational Research(2016YFC0100602)
文摘The optical memory effect is an interesting phenomenon that has attracted considerable attention in recent decades. Here, we present a new physical picture of the optical memory effect, in which the memory effect and the conventional spatial shift invariance are united. Based on this picture we depict the role of thickness, scattering times, and anisotropy factor and derive equations to calculate the ranges of the angular memory effect(AME) of different scattering components(ballistic light, singly scattered, doubly scattered, etc.), and hence a more accurate equation for the real AME ranges of volumetric turbid media. A conventional random phase mask model is modified according to the new picture. The self-consistency of the simulation model and its agreement with the experiment demonstrate the rationality of the model and the physical picture, which provide powerful tools for more sophisticated studies of the memory-effect-related phenomena and wavefront-sensitive techniques, such as wavefront shaping, optical phase conjugation, and optical trapping in/through scattering media.
基金supported by National Basic Research Program of China(Grant No. 2009CB219505)Program for Science and Technology Development of Zhanjiang (Grant No. 2011C3107006)the Talents Introduction Special Project of Guangdong Ocean University (Grant No. 0812182)
文摘To study the seismic responses produced by gas hydrate bubble plumes in the cold seepage active region, we constructed a plume water body model based on random medium theory and acoustic velocity model of bubble medium. The plume water body model was forward simulated by finite difference. Seismic records of single shot show the scattered waves produced by the plume. The scattered wave energy is strong where the plume exists. Where the scattered wave energy is stronger, the minimum of travel time is always above the plume, which has no relationship with the shot's position. Seismic records of shot gathers were processed by prestack time migration. The migration section shows that the scattered waves produced by plumes can be imaged distinctly with higher accuracy. These researches laid a foundation for further study on the seismic responses produced by plumes and provided a new approach for the identification of gas hydrate.
基金Supported by the National Natural Science Foundation of China( 1 9971 0 1 7,1 0 1 2 5 1 0 2 )
文摘Based on the definition of MQ-B-Splines,this article constructs five types of univariate quasi-interpolants to non-uniformly distributed data. The error estimates and the shape-preserving properties are shown in details.And examples are shown to demonstrate the capacity of the quasi-interpolants for curve representation.
基金The National Natural Science Foundation under contract No.41306050the Science and Technology Project of Guangdong Province under contract No.2014A010103030+1 种基金the Natural Science Foundation of Guangdong Province under contract No.2015A030313617the National Marine Important Charity Special Foundation under contract No.201305019
文摘Using the occurrence characteristics of bubble plumes in the South China Sea as a reference, this paper continues to study the seismic responses produced by bubble plumes in the cold seepage active region. To make the plume modelling scheme more reasonable, we modified the original modelling scheme and reconstructed a plume water body model based on the variation of its radius as bubbles rise in seawater. The plume seismic records of shot gathers were obtained by forward simulation. The seismic records of single shot show obvious characteristics of a scattering wave field and the periodic characteristics of the model. Seismic records of shot gathers were processed using prestack depth migration. The boundary of its imaging section has a good convergence effect. The migration sections can be imaged distinctly with higher accuracy. The aforementioned studies once again laid a foundation for the further study of the seismic responses produced by plumes. They also gradually probed a more suitable seismic data processing method for plumes and provided a theoretical guidance for the identification of plumes.
基金This research is supported by the State Foundation for Key Projects, Fundamental Research on New Generation of Steels (No.G1998061500)
文摘The microstructure and misorientation of ultrathin hot strip were analyzed by CSP technology using electron back scattered diffraction (EBSD) method and Autoforge finite element program. The experimental results showed that the finishing hot rolling microstructures were the mixture of recrystallized and deformed austenite. After phase transformation, ferrite grains embody substructures and dislocations, leading to the high strength and relatively low elongation rate of the ultrathin hot strip. The FEM simulation of strain mode and distribution in deformation area has been fulfilled. The simulation results are in good agreement with the theoretical analysis and experimental results.
基金Supported by Science Foundation of Zhejiang (No. 599008) ZUCC Science Research Foundation
文摘An improved self-organizing feature map (SOFM) neural network is presented to generate rectangular and hexagonal lattic with normal vector attached to each vertex. After the neural network was trained, the whole scattered data were divided into sub-regions where classified core were represented by the weight vectors of neurons at the output layer of neural network. The weight vectors of the neurons were used to approximate the dense 3-D scattered points, so the dense scattered points could be reduced to a reasonable scale, while the topological feature of the whole scattered points were remained.
基金Supported by National Key R&D Program of China(Grant No.2016YFF0203000)State Key Program of National Natural Science Foundation of China(Grant No.11834008)+5 种基金National Natural Science Foundation of China(Grant Nos.11774167,61571222)Fundamental research funds for the Central Universities(Grant No.020414380001)State Key Laboratory of Acoustics,Chinese Academy of Science(Grant No.SKLA201809)Key Laboratory of Underwater Acoustic Environment,Chinese Academy of Sciences(Grant No.SSHJ-KFKT-1701)AQSIQ technology R&D program(Grant No.2017QK125)Innovative Talents Program of Far East NDT New Technology&Application Forum
文摘The scattered fields of plane waves in a solid from a cylinder or sphere are critical in determining its acoustic characteristics as well as in engineering applications. This paper investigates the scattered field distributions of different incident waves created by elastic cylinders embedded in an elastic isotropic medium. Scattered waves, including longitudinal and transverse waves both inside and outside the cylinder, are described with specific modalities under an incident plane wave. A model with a scatterer embedded in a structural steel matrix and filled with aluminum is developed for comparison with the theoretical solution. The frequency of the plane wave ranged from 235 kHz to 2348 kHz, which corresponds to scaling factors from 0.5 to 5. Scattered field distributions in matrix materials blocked by an elastic cylindrical solid have been obtained by simulation or calculated using existing parameters. The simulation results are in good agreement with the theoretical solution, which supports the correctness of the simulation analysis. Furthermore, ultrasonic phased arrays are used to study scattered fields by changing the characteristics of the incident wave. On this foundation, a partial preliminary study of the scattered field distribution of double cylinders in a solid has been carried out, and the scattered field distribution at a given distance has been found to exhibit particular behaviors at different moments. Further studies on directivities and scattered fields are expected to improve the quantification of scattered images in isotropic solid materials by the phased array technique.
文摘In this study,the effects of hybridizing micron-sized titanium particles with nano-sized boron carbide particles on the microstructural and mechanical properties of Mg-Ti composite were investigated.Microstructural characterization revealed grain refinement attributed to the presence of uniformly distributed micro-Ti particles embedded with nano-B_(4)C particulates.Electron back scattered diffraction(EBSD)analyses of the Mg-(Ti+B_(4)C)BM hybrid composite showed relatively more localized recrystallized grains and lesser tensile twin fraction,when compared to Mg-Ti.The evaluation of mechanical properties indicated that the best combination of strength and ductility was observed in the Mg-(Ti+B_(4)C)BM hybrid composite.The superior properties of the Mg-(Ti+B_(4)C)BM hybrid composite when compared to Mg-Ti can be attributed to the presence of nano-reinforcement,the uniform distribution of the hybridized particles and the better interfacial bonding between the matrix and the reinforcement particles achieved by nano-B_(4)C addition.
基金Funded by the National Natural Science Foundation of China(Nos.51278073,51678081,51678143)State Key Laboratory for Geo-mechanics and Deep Underground Engineering,China University of Mining&Technology(No.SKLGDUEK1704)
文摘The effect of carbonation treatment and mixing method on the mechanical properties and interfacial transition zone（ITZ） properties of recycled aggregate concrete（RAC） was investigated. Properties of recycled concrete aggregate（RCA） were tested firstly. Then, five types of concretes were made and slump of fresh concrete was measured immediately after mixing. Compressive strength and splitting tensile strength of hardened concrete were measured at 28 d. Meanwhile, the microstructure of RAC was analyzed by backscattered electron（BSE） image. It was found that the water absorption ratio of carbonated recycled concrete aggregate（CRCA） was much lower when compared to the untreated RCA. Comparatively, the apparent density of CRCA was not significantly modified. The concrete strength results indicate that the mix CRAC-2 prepared with CRCA by adopting two-stage mixing approach shows the highest compressive strength value compared to the other mixes. The microstructural analysis demonstrate that the mix CRAC-2 has a much denser old ITZ than the untreated RAC because of the chemical reaction between CO2 and the hydration products of RCA. This study confirms that the ITZ microstructure of RAC can be efficiently modified by carbonation treatment of RCA and encourages broadening the application of construction and demolition wastes.
文摘Taking AutoCAD2000 as platform, an algorithm for the reconstruction ofsurface from scattered data points based on VBA is presented. With this core technology customerscan be free from traditional AutoCAD as an electronic board and begin to create actual presentationof real-world objects. VBA is not only a very powerful tool of development, but with very simplesyntax. Associating with those solids, objects and commands of AutoCAD 2000, VBA notably simplifiesprevious complex algorithms, graphical presentations and processing, etc. Meanwhile, it can avoidappearance of complex data structure and data format in reverse design with other modeling software.Applying VBA to reverse engineering can greatly improve modeling efficiency and facilitate surfacereconstruction.
基金This work was financially supported by National Key Research and Development Program of China(2021YFA1401000)National Natural Science Foundation of China(U20A20212,61931006,62131007,61921002,62101111 and 61901093)+2 种基金Fundamental Research Funds for the Central Universities(ZYGX2020ZB011)China Postdoctoral Science Foundation(2020M683285)the US National Science Foundation grant(1923782,1954780 and 2211616).
文摘Terahertz(THz)technologies have become a focus of research in recent years due to their prominent role in envisioned future communication and sensing systems.One of the key challenges facing the field is the need for tools to enable agile engineering of THz wave fronts.Here,we describe a reconfigurable metasurface based on GaN technology with an array-of-subarrays architecture.This subwavelength-spaced array,under the control of a 1-bit digital coding sequence,can switch between an enormous range of possible configurations,providing facile access to nearly arbitrary wave front control for signals near 0.34 THz.We demonstrate wide-angle beam scanning with 1°of angular precision over 70 GHz of bandwidth,as well as the generation of multi-beam and diffuse wave fronts,with a switching speed up to 100 MHz.This device,offering the ability to rapidly reconfigure a propagating wave front for beam-forming or diffusively scattered wide-angle coverage of a scene,will open new realms of possibilities in sensing,imaging,and networking.
基金supported by the State Key Development Program for Basic Research of China (Grant No 2006CB303102)Science and Technology Commission of Shanghai Municipality,China (Grant No 09DZ2272900)
文摘In this paper, we use a univariate multiquadric quasi-interpolation scheme to solve the one-dimensional nonlinear sine-Gordon equation that is related to many physical phenomena. We obtain a numerical scheme by using the derivative of the quasi-interpolation to approximate the spatial derivative and a difference scheme to approximate the temporal derivative. The advantage of the obtained scheme is that the algorithm is very simple so that it is very easy to implement. The results of numerical experiments are presented and compared with analytical solutions to confirm the good accuracy of the presented scheme.
基金financially supported by the National Natural Science Foundation of China(No.41306050)the Science and Technology Project of Guangdong Province of China(No.2014A010103030)+1 种基金the Natural Science Foundation of Guangdong Province under contract(No.2015A030313617)the National Marine Important Charity Special Foundation of China(No.201305019)
文摘To study the bubble plume's seismic response characteristics,the model of a plume water body has been built in this article using the bubble-contained medium acoustic velocity model and the stochastic medium theory based on an analysis of both the acoustic characteristics of a bubble-contained water body and the actual features of a plume.The finite difference method is used for forward modelling,and the single-shot seismic record exhibits the characteristics of a scattered wave field generated by a plume.A meaningful conclusion is obtained by extracting seismic attributes from the pre-stack shot gather record of a plume.The values of the amplitude-related seismic attributes increase greatly as the bubble content goes up,and changes in bubble radius will not cause seismic attributes to change,which is primarily observed because the bubble content has a strong impact on the plume's acoustic velocity,while the bubble radius has a weak impact on the acoustic velocity.The above conclusion provides a theoretical reference for identifying hydrate plumes using seismic methods and contributes to further study on hydrate decomposition and migration,as well as on distribution of the methane bubble in seawater.
文摘Passive inter-modulation （PIM） is a form of nonlinear distortion caused by the inherent nonlinearities of the passive devices and components in RF/microwave system. It will degenerate the performance of communication system with broad-band channel and high-sensitivity receiver. Therefore, it is necessary to construct a model to simulate this process in order to predict the level of PIM. This paper is aimed at constructing some plate models with one-dimensional and two-dimensional contact nonlinearity sections illuminated by two-tone waves, and calculating the scattered field at a fixed-point in space using time-domain physical optics method. By taking fast Fourier transform （FFT）, we get the spectrum of the scattered field and then analyze the generated PIM products. At the end of this paper, some numerical examples are presented to show the influence rules of the relative factors on PIM. The results indicate the variation of the level of PIM with the number of the nonlinear regions, the nonlinear spacing, and the incident power levels.
基金The authors are supported by the National Natural Science Foundation of China(Grant Nos.12104428,12075081,12375240,and 12265024).
文摘Fully polarized Compton scattering from a beam of spin-polarized electrons is investigated in plane-wave backgrounds in a broad intensity region from the perturbative to the nonperturbative regimes.In the perturbative regime,polarized linear Compton scattering is considered for investigating polarization transfer from a single laser photon to a scattered photon,and in the high-intensity region,the polarized locally monochromatic approximation and locally constant field approximation are established and are employed to study polarization transfer from an incoming electron to a scattered photon.The numerical results suggest an appreciable improvement of about 10%in the scattering probability in the intermediate-intensity region if the electron’s longitudinal spin is parallel to the laser rotation.The longitudinal spin of the incoming electron can be transferred to the scattered photon with an efficiency that increases with laser intensity and collisional energy.For collision between an optical laser with frequency1 eV and a 10 GeV electron,this polarization transfer efficiency can increase from about 20%in the perturbative regime to about 50%in the nonperturbative regime for scattered photons with relatively high energy.
基金National Natural Science Foundation of China(No.61971036)Fundamental Research Funds for the Central Universities(No.2023CX01011)Beijing Nova Program(No.20230484361)。
文摘This paper proposed a deep-learning-based method to process the scattered field data of transmitting antenna,which is unmeasurable in inverse scattering system because the transmitting and receiving antennas are multiplexed.A U-net convolutional neural network(CNN)is used to recover the scattered field data of each transmitting antenna.The numerical results proved that the proposed method can complete the scattered field data at the transmitting antenna which is unable to measure in the actual experiment and can also eliminate the reconstructed error caused by the loss of scattered field data.
文摘Moving from the county seat of Danba,Garze Prefecture,Sichua Province,the car turned to a small lane,just aside of a steep canyon,and then moved toward a nearby village.Before long,a charming village appeared in front of audiences.Row after row white painted houses were scattered to covering the mountain valley,as if a fictitious land of peace.This is Zhailong Village,an especially renowned place thanks to the local traditional music and dance culture.
基金supported by the Key Project of the National Fourteen-Five Year Research Program of China(grant No.2022YFB4100303).
文摘The present study was aimed at the inlet particle spatial distribution of a gas-solid separator with high solid loading and investigated its effects on cyclone performance and the inner flow pattern.The flow fields of a cyclone with different rectangular particle flow areas on the inlet surface were numerically simulated using a four-way coupling method.The simulated results indicate that reducing the inlet particle flow area and lowing the inlet particle position can effectively reduce the scattered particles inside the cyclone separator and enhance the separation performance.Vertically gathering the particles to the centerline can also weaken the particle back-mixing.The particles near the roof account for the swirling particle ceiling phenomenon.The inlet particle spatial distribution affects the pressure drop mainly by affecting the gas tangential velocity in the cylinder body.Moreover,compared to the hori-zontal particle distribution on the inlet surface,the vertical particle distribution has greater effects on cyclone performance.
