In the past two decades,extensive and in-depth research has been conducted on Time Series InSAR technology with the advancement of high-performance SAR satellites and the accumulation of big SAR data.The introduction ...In the past two decades,extensive and in-depth research has been conducted on Time Series InSAR technology with the advancement of high-performance SAR satellites and the accumulation of big SAR data.The introduction of distributed scatterers in Distributed Scatterers InSAR(DS-InSAR)has significantly expanded the application scenarios of InSAR geodetic measurement by increasing the number of measurement points.This study traces the history of DS-InSAR,presents the definition and characteristics of distributed scatterers,and focuses on exploring the relationships and distinctions among proposed algorithms in two crucial steps:statistically homogeneous pixel selection and phase optimization.Additionally,the latest research progress in this field is tracked and the possible development direction in the future is discussed.Through simulation experiments and two real InSAR case studies,the proposed algorithms are compared and verified,and the advantages of DS-InSAR in deformation measurement practice are demonstrated.This work not only offers insights into current trends and focal points for theoretical research on DS-InSAR but also provides practical cases and guidance for applied research.展开更多
Locally resonant sonic materials, due to their ability to control the propagation of low-frequency elastic waves, have become a promising option for underwater sound absorption materials. In this paper, the finite ele...Locally resonant sonic materials, due to their ability to control the propagation of low-frequency elastic waves, have become a promising option for underwater sound absorption materials. In this paper, the finite element method is used to investigate the absorption characteristics of a viscoelastic panel periodically embedded with a type of infinite-long noncoaxially cylindrical locally resonant scatterers(LRSs). The effect of the core position in the coating layer of the LRS on the low-frequency(500 Hz–3000 Hz) sound absorption property is investigated. With increasing the longitudinal core eccentricity e, there occur few changes in the absorptance at the frequencies below 1500 Hz, however, the absorptance above 1500 Hz becomes gradually better and the valid absorption(with absorptance above 0.8) frequency band(VAFB)of the viscoelastic panel becomes accordingly broader. The absorption mechanism is revealed by using the displacement field maps of the viscoelastic panel and the steel slab. The results show two typical resonance modes. One is the overall resonance mode(ORM) caused by steel backing, and the other is the core resonance mode(CRM) caused by LRS. The absorptance of the viscoelastic panel by ORM is induced mainly by the vibration of the steel slab and affected little by core position. On the contrary, with increasing the core eccentricity, the CRM shifts toward high frequency band and decouples with the ORM, leading to two separate absorption peaks and the broadened VAFB of the panel.展开更多
According to the model of equivalent dipoles for active molecules, the analysisof inelastic EM scattering by active molecules embedded in a sphere is given by the method ofdyadic Green’s functions at the first, and t...According to the model of equivalent dipoles for active molecules, the analysisof inelastic EM scattering by active molecules embedded in a sphere is given by the method ofdyadic Green’s functions at the first, and then based on the theory of elastic multiple scattering byrandomly distributed spherical scatterers, a new theory for analysis of inelastic multiple scatteringby active molecules embedded in randomly distributed spherical scatterers also is developed. Thistheory gives the expansions of the multiple scattering fields in all space region in terms of vectorspherical wave functions in which the expansion coefficients can be solved from a set of coupledlinear equations.展开更多
Starting from the basic integral equation for multiple scattered fields,a set of coupledlinear equations for the expansion coefficients of elastic multiple scattered fields by randomlydistributed spherical scatterers ...Starting from the basic integral equation for multiple scattered fields,a set of coupledlinear equations for the expansion coefficients of elastic multiple scattered fields by randomlydistributed spherical scatterers has been derived by using the expansions of the fields and thetranslational addition theorems of vector spherical wave functions.Thus,a new theory for thiskind of problems is developed.Different from the others,this theory gives the multiple elasticallyscattered fields in all space regions.展开更多
The acoustic properties of anechoic layers with a singly periodic array of cylindrical scatterers are investigated. A method combined plane wave expansion and finite element analysis is extended for out-of-plane incid...The acoustic properties of anechoic layers with a singly periodic array of cylindrical scatterers are investigated. A method combined plane wave expansion and finite element analysis is extended for out-of-plane incidence. The reflection characteristics of the anechoic layers with cavities and locally resonant scatterers are discussed. The backing is a steel plate followed by an air half space. Under this approximate zero transmission backing condition, the reflection reduction is induced by the absorption enhancement. The absorption mechanism is explained by the scattering/absorption cross section of the isolated scatterer. Three types of resonant modes which can induce efficient absorption are revealed. Due to the fact that the frequencies of the resonant modes are related to the size of the scatterers, anechoic layers with scatterers of mixed size can broaden the absorption band. A genetic optimization algorithm is adopted to design the anechoic layer with scatterers of mixed size at a desired frequency band from 2 kHz to l0 kHz for normal incidence, and the influence of the incident angle is also discussed.展开更多
Based on the diffraction theory model for hot-image formation, the evolution of hot-images induced by multiscatterers located in the same plane perpendicular to the propagation axis is numerically simulated. The simul...Based on the diffraction theory model for hot-image formation, the evolution of hot-images induced by multiscatterers located in the same plane perpendicular to the propagation axis is numerically simulated. The simulation results show that hot-images induced by coplanar multi-scatterers are also coplanar no matter whether they exist simultaneously or severally. However, if they exist simultaneously the peak intensity of the primary hot-images is weaker than if they exist severally. The unequal competition for energy between the scattered beams from the scatterers leads to the fact that part of the corresponding hot-images are relatively enhanced and the others are restrained. The results show that the hot-images of certain scatterers become stronger when any of these parameters, i.e. amplitude modulation coefficient, phase modulation coefficient and size of the surrounding scatterer, decrease.展开更多
Synthetic aperture radar(SAR) is able to detect surface changes in urban areas with a short revisit time, showing its capability in disaster assessment and urbanization monitoring.Most presented change detection metho...Synthetic aperture radar(SAR) is able to detect surface changes in urban areas with a short revisit time, showing its capability in disaster assessment and urbanization monitoring.Most presented change detection methods are conducted using couples of SAR amplitude images. However, a prior date of surface change is required to select a feasible image pair. We propose an automatic spatio-temporal change detection method by identifying the temporary coherent scatterers. Based on amplitude time series, χ^(2)-test and iterative single pixel change detection are proposed to identify all step-times: the moments of the surface change. Then the parameters, e.g., deformation velocity and relative height, are estimated and corresponding coherent periods are identified by using interferometric phase time series. With identified temporary coherent scatterers, different types of temporal surface changes can be classified using the location of the coherent periods and spatial significant changes are identified combining point density and F values. The main advantage of our method is automatically detecting spatio-temporal surface changes without prior information. Experimental results by the proposed method show that both appearing and disappearing buildings with their step-times are successfully identified and results by ascending and descending SAR images show a good agreement.展开更多
Calculating the current distribution in circular loop scatterers commonly involves complicated computation. In this paper, based on the theory of Maxwellian circuits （MC）, we propose a fast algorithm by solving a wa...Calculating the current distribution in circular loop scatterers commonly involves complicated computation. In this paper, based on the theory of Maxwellian circuits （MC）, we propose a fast algorithm by solving a wave equation with constant parameters corresponding to the circular loop. Our method prodeces similar results compared to the methods using method of moments （MoM） with lower computational complexity. It is effective when there are parallel multiple circular loop scatterers. Experimental results show accuracy of the method.展开更多
Passive daytime radiative cooling(PDRC)exhibits efficient cooling performance to reduce global fossil energy consumption and has attracted enormous interest.An efficient PDRC technology for achieving daytime subambien...Passive daytime radiative cooling(PDRC)exhibits efficient cooling performance to reduce global fossil energy consumption and has attracted enormous interest.An efficient PDRC technology for achieving daytime subambient cooling is supposed to exhibit ultra-high solar reflectivity and infrared emissivity within atmospheric windows,among which ultra-high solar reflectivity is the principal property.In most PDRC technologies,spherical particles are selected as scatterers to achieve high solar reflectivity because the Mie scattering effect of spherical scatterers can provide a high scattering efficiency.However,the weak backward scattering of spherical scatterers remains a drawback.In this study,several nonspherical scatterers with strong backward scattering are introduced and researched systematically.The numerical analysis results indicate that pyramidal scatterers provide the strongest backward scattering and square/circular scatterers exhibit the highest scattering efficiency.Besides,by considering scattering efficiency and asymmetry factor comprehensively,a dimensionless evaluation parameter is proposed,which can be employed as a quantitative design criterion to achieve the optimal-object-oriented designing of superior scatterers.This work can provide an innovative strategy for designing efficient passive daytime radiative cooling materials.展开更多
We experimentally study the wavelength dependence of light propagation in a water suspension of lithium niobate microcrystalline particles.First,the ballistic transmission in the visible range of the suspension is mea...We experimentally study the wavelength dependence of light propagation in a water suspension of lithium niobate microcrystalline particles.First,the ballistic transmission in the visible range of the suspension is measured.The nonlinear relationship is observed between the transport mean free path and the wavelength of the incident light.Secondly,we measure the coherent backscattering (CBS) of the sample at different wavelengths.The full width at half maximum of the CBS cone at 532 nm is about 1.24 times as large as that at 671 nm.The results indicate that the light with a long wavelength propagates further than the short wavelength light and the localization state of the short one is stronger.Finally,we investigate the light-controllable CBS experiments in the disordered materials of anisotropic scatterers,which show that the configuration of pump light with the longer wavelength and the probe light with the shorter wavelength performs better.展开更多
The radiative transfer from a model of multi-layer random media embedded by multiple components, size-distributed, dense spherical scatterers is studied. The size distribution of spherical scatterers as ice grains and...The radiative transfer from a model of multi-layer random media embedded by multiple components, size-distributed, dense spherical scatterers is studied. The size distribution of spherical scatterers as ice grains and the effective radius are discussed by use of a snow sample. By using Gaussian quadrature, discrete ordinate and eigenanalysis methods, two vector radiative transfer equations of dense scatterers and four coupling boundary conditions are numerically solved. The polarized brightness temperature and the functional dependence on various parameters are obtained, which are well compared with experimental data from remote sensing of dry and wet snow.展开更多
In DEM generation using interferometric synthetic aperture radar(InSAR),the ground control points(GCPs)for refinement and reflattening are usually selected by manual selection,field surveying,GPS points and existing b...In DEM generation using interferometric synthetic aperture radar(InSAR),the ground control points(GCPs)for refinement and reflattening are usually selected by manual selection,field surveying,GPS points and existing basemaps,which may not be completely suitable for consequent processes.We proposed a new method(auto-PS-GCP)of GCP selection based on permanent scatterers,which automatically defines the thresholds for the coherence,amplitude,and amplitude dispersion index to select permanent scatterer as the GCPs.The GCP thinning(auto-PS-GCP-Thin)was further conducted considering the point density,distances among points and terrain conditions.We used a three-stage assessment that includes:(1)phase stability and intensity of the GCPs,(2)RMSEs of the elevations between GCPs and homonymous points in the reference DEM,and(3)generated DEM accuracy.Three areas respectively in the plain,hilly and mountainous regions were selected to verify the proposed methods.The assessment using both SRTM DEM andICESat-2 points shows that the DEM accuracy of auto-PS-GCP-Thin was improved by 20%∼30%for different areas compared to the manual,where the best DEM accuracy of 4.71 m was found in the plain area.It is concluded that the proposed methods are effective and reliable in various areas with different terrain conditions.展开更多
In this paper, firstly presented a geometrically based statistical channel model with scatterers that are with an inverted parabolic spatial distribution around mobile station （MS） within a circle wherein the base s...In this paper, firstly presented a geometrically based statistical channel model with scatterers that are with an inverted parabolic spatial distribution around mobile station （MS） within a circle wherein the base station （BS） and MS are included. This paper proposed a technique to simply derive probability density functions （PDFs） of angle of arrival （AOA）, time of arrival （TOA） and Doppler spectra to characterize the outdoor macrocell and microcell environments by employing various distances between BS and MS, or different size of circular region. Employing this channel model, we analyze the impacts of a directional antenna at BS with the main-lobe width 2~z on the fading and the Doppler spectra.展开更多
Ultraslow-light effects in two-dimensional hexagonal-lattice coupled waveguide with moon-like scat- terers were theoretically studied using the plane-wave expansion method. For symmetric structures, simulations showed...Ultraslow-light effects in two-dimensional hexagonal-lattice coupled waveguide with moon-like scat- terers were theoretically studied using the plane-wave expansion method. For symmetric structures, simulations showed that slow light with high group index can be achieved by shifting the scatterers and adjusting the radius of moon-like scatterers. The maximum group index was over 8.0 × 10^4. For asymmetric structures, simulations showed that slow light with flat band and high group index can be obtained by shifting the scatterers, adjusting the radius of moon-like scatterers, and rotating the scatterers. The maximum group index was over 5.7 ×10^5 with a ＂saddle-like＂ relationship between the frequency and group index.展开更多
Exceptional points have given rise to many intriguing optical phenomena that are of fundamental importance for a variety of breakthrough technologies.The pre-defined Mie scatterers can bring a resonator to an exceptio...Exceptional points have given rise to many intriguing optical phenomena that are of fundamental importance for a variety of breakthrough technologies.The pre-defined Mie scatterers can bring a resonator to an exceptional point,and result in enhanced quality factor through coherently suppressing the backward scattering.展开更多
High-resolution seeing through complex scattering media such as turbid water,biological tissues,and mist is a significant challenge because the strong scattering scrambles the light paths and forms the scattering wall...High-resolution seeing through complex scattering media such as turbid water,biological tissues,and mist is a significant challenge because the strong scattering scrambles the light paths and forms the scattering wall.We propose an active polarized iterative optimization approach for high-resolution imaging through complex scattering media.By acquiring a series of sub-polarized images,we can capture the diverse pattern-illuminated images with various high-frequency component information caused by the Brownian motion of complex scattering materials,which are processed using the common-mode rejection of polarization characteristics to extract target information from scattering medium information.Following that,our computational reconstruction technique employs an iterative optimization algorithm that commences with patternilluminated Fourier ptychography for reconstructing the high-resolution scene.It is extremely important that our approach for high-resolution imaging through complex scattering media is not limited by priori information and optical memory effect.The proposed approach is suitable for not only dynamic but also static scattering media,which may find applications in the biomedicine field,such as skin abnormalities,non-invasive blood flow,and superficial tumors.展开更多
Glucose molecules are of great significance being one of the most important molecules in metabolic chain.However,due to the small Raman scattering cross-section and weak/non-adsorption on bare metals,accurately obtain...Glucose molecules are of great significance being one of the most important molecules in metabolic chain.However,due to the small Raman scattering cross-section and weak/non-adsorption on bare metals,accurately obtaining their"fingerprint information"remains a huge obstacle.Herein,we developed a tip-enhanced Raman scattering(TERS)technique to address this challenge.Adopting an optical fiber radial vector mode internally illuminates the plasmonic fiber tip to effectively suppress the background noise while generating a strong electric-field enhanced tip hotspot.Furthermore,the tip hotspot approaching the glucose molecules was manipulated via the shear-force feedback to provide more freedom for selecting substrates.Consequently,our TERS technique achieves the visualization of all Raman modes of glucose molecules within spectral window of 400-3200 cm^(-1),which is not achievable through the far-field/surface-enhanced Raman,or the existing TERS techniques.Our TERS technique offers a powerful tool for accurately identifying Raman scattering of molecules,paving the way for biomolecular analysis.展开更多
Persistent toxic substances(PTS)represent a paramount environmental issue in the 21st century.Understanding the concentrations and forms of PTS in the environment is crucial for accurately assessing their environmenta...Persistent toxic substances(PTS)represent a paramount environmental issue in the 21st century.Understanding the concentrations and forms of PTS in the environment is crucial for accurately assessing their environmental health impacts.This article presents a concise overview of the components of PTS,pertinent environmental regulations,and conventional detection methodologies.Additionally,we offer an in-depth review of the principles,development,and practical applications of surface-enhanced Raman scattering(SERS)in environmental monitoring,emphasizing the advancements in detecting trace amounts of PTS in complex environmental matrices.Recent progress in enhancing SERS sensitivity,improving selectivity,and practical implementations are detailed,showcasing innovative materials and methods.Integrating SERS with advanced algorithms are highlighted as pivotal areas for future research.展开更多
We investigate theoretically the enhancement of mechanical squeezing in a multimode optomechanical system by introducing a coherent phonon–photon interaction via the backward stimulated Brillouin scattering(BSBS)proc...We investigate theoretically the enhancement of mechanical squeezing in a multimode optomechanical system by introducing a coherent phonon–photon interaction via the backward stimulated Brillouin scattering(BSBS)process.The coherent photon–phonon interaction where two optical modes couple to a Brillouin acoustic mode with a large decay rate provides an extra channel for the cooling of a Duffing mechanical oscillator.The squeezing degree and the robustness to the thermal noises of the Duffing mechanical mode can be enhanced greatly.When the Duffing nonlinearity is weak,the squeezing degree of the mechanical mode in the presence of BSBS can be improved by more than one order of magnitude compared with that in the absence of BSBS.Our scheme may be extended to other quantum systems to study novel quantum effects.展开更多
In this study,we developed a single-beam optical trap-based surface-enhanced Raman scattering(SERS)optofluidic molecular fingerprint spectroscopy detection system.This system utilizes a single-beam optical trap to con...In this study,we developed a single-beam optical trap-based surface-enhanced Raman scattering(SERS)optofluidic molecular fingerprint spectroscopy detection system.This system utilizes a single-beam optical trap to concentrate free silver nanoparticles(AgNPs)within an optofluidic chip,significantly enhancing SERS performance.We investigated the optical field distribution characteristics within the tapered fiber using COMSOL simulation software and established a MATLAB simulation model to validate the single-beam optical trap's effectiveness in capturing AgNPs,demonstrating the theoretical feasibility of our approach.To verify the particle capture efficacy of the system,we experimentally controlled the optical trap's on-off state to manage the capture and release of particles precisely.The experimental results indicated that the Raman signal intensity in the capture state was significantly higher than in the non-capture state,confirming that the single-beam optical trap effectively enhances the SERS detection capability of the optofluidic detection system.Furthermore,we employed Raman mapping techniques to investigate the impact of the capture area on the SERS effect,revealing that the spectral intensity of molecular fingerprints in the laser-trapping region is significantly improved.We successfully detected the Raman spectrum of crystal violet at a concentration of 10^(−9)mol/L and pesticide thiram at a concentration of 10^(−5)mol/L,further demonstrating the ability of the single-beam optical trap in enhancing the molecular fingerprint spectrum identification capability of the SERS optofluidic chips.The optical trapping SERS optofluidic detection system developed in this study,as a key component of an integrated optoelectronic sensing system,holds the potential for integration with portable high-power lasers and high-performance Raman spectrometers.This integration is expected to advance highly integrated technologies and significantly enhance the overall performance and portability of optoelectronic sensing systems.展开更多
基金National Natural Science Foundation of China(No.42374013)National Key Research and Development Program of China(Nos.2019YFC1509201,2021YFB3900604-03)。
文摘In the past two decades,extensive and in-depth research has been conducted on Time Series InSAR technology with the advancement of high-performance SAR satellites and the accumulation of big SAR data.The introduction of distributed scatterers in Distributed Scatterers InSAR(DS-InSAR)has significantly expanded the application scenarios of InSAR geodetic measurement by increasing the number of measurement points.This study traces the history of DS-InSAR,presents the definition and characteristics of distributed scatterers,and focuses on exploring the relationships and distinctions among proposed algorithms in two crucial steps:statistically homogeneous pixel selection and phase optimization.Additionally,the latest research progress in this field is tracked and the possible development direction in the future is discussed.Through simulation experiments and two real InSAR case studies,the proposed algorithms are compared and verified,and the advantages of DS-InSAR in deformation measurement practice are demonstrated.This work not only offers insights into current trends and focal points for theoretical research on DS-InSAR but also provides practical cases and guidance for applied research.
基金supported by the National Natural Science Foundation of China(Grant No.51275519)
文摘Locally resonant sonic materials, due to their ability to control the propagation of low-frequency elastic waves, have become a promising option for underwater sound absorption materials. In this paper, the finite element method is used to investigate the absorption characteristics of a viscoelastic panel periodically embedded with a type of infinite-long noncoaxially cylindrical locally resonant scatterers(LRSs). The effect of the core position in the coating layer of the LRS on the low-frequency(500 Hz–3000 Hz) sound absorption property is investigated. With increasing the longitudinal core eccentricity e, there occur few changes in the absorptance at the frequencies below 1500 Hz, however, the absorptance above 1500 Hz becomes gradually better and the valid absorption(with absorptance above 0.8) frequency band(VAFB)of the viscoelastic panel becomes accordingly broader. The absorption mechanism is revealed by using the displacement field maps of the viscoelastic panel and the steel slab. The results show two typical resonance modes. One is the overall resonance mode(ORM) caused by steel backing, and the other is the core resonance mode(CRM) caused by LRS. The absorptance of the viscoelastic panel by ORM is induced mainly by the vibration of the steel slab and affected little by core position. On the contrary, with increasing the core eccentricity, the CRM shifts toward high frequency band and decouples with the ORM, leading to two separate absorption peaks and the broadened VAFB of the panel.
文摘According to the model of equivalent dipoles for active molecules, the analysisof inelastic EM scattering by active molecules embedded in a sphere is given by the method ofdyadic Green’s functions at the first, and then based on the theory of elastic multiple scattering byrandomly distributed spherical scatterers, a new theory for analysis of inelastic multiple scatteringby active molecules embedded in randomly distributed spherical scatterers also is developed. Thistheory gives the expansions of the multiple scattering fields in all space region in terms of vectorspherical wave functions in which the expansion coefficients can be solved from a set of coupledlinear equations.
文摘Starting from the basic integral equation for multiple scattered fields,a set of coupledlinear equations for the expansion coefficients of elastic multiple scattered fields by randomlydistributed spherical scatterers has been derived by using the expansions of the fields and thetranslational addition theorems of vector spherical wave functions.Thus,a new theory for thiskind of problems is developed.Different from the others,this theory gives the multiple elasticallyscattered fields in all space regions.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.1100429 and 51275519)
文摘The acoustic properties of anechoic layers with a singly periodic array of cylindrical scatterers are investigated. A method combined plane wave expansion and finite element analysis is extended for out-of-plane incidence. The reflection characteristics of the anechoic layers with cavities and locally resonant scatterers are discussed. The backing is a steel plate followed by an air half space. Under this approximate zero transmission backing condition, the reflection reduction is induced by the absorption enhancement. The absorption mechanism is explained by the scattering/absorption cross section of the isolated scatterer. Three types of resonant modes which can induce efficient absorption are revealed. Due to the fact that the frequencies of the resonant modes are related to the size of the scatterers, anechoic layers with scatterers of mixed size can broaden the absorption band. A genetic optimization algorithm is adopted to design the anechoic layer with scatterers of mixed size at a desired frequency band from 2 kHz to l0 kHz for normal incidence, and the influence of the incident angle is also discussed.
基金supported by the Joint Foundation of National Natural Science Foundation of China and the Science Foundation of the Chinese Academy of Engineering Physics,China(Grant No 10576023)the Doctorate Foundation of Northwestern Polytechnical University,China(Grant No CX200714)
文摘Based on the diffraction theory model for hot-image formation, the evolution of hot-images induced by multiscatterers located in the same plane perpendicular to the propagation axis is numerically simulated. The simulation results show that hot-images induced by coplanar multi-scatterers are also coplanar no matter whether they exist simultaneously or severally. However, if they exist simultaneously the peak intensity of the primary hot-images is weaker than if they exist severally. The unequal competition for energy between the scattered beams from the scatterers leads to the fact that part of the corresponding hot-images are relatively enhanced and the others are restrained. The results show that the hot-images of certain scatterers become stronger when any of these parameters, i.e. amplitude modulation coefficient, phase modulation coefficient and size of the surrounding scatterer, decrease.
基金supported by the National Natural Science Foundation of China (42074022)。
文摘Synthetic aperture radar(SAR) is able to detect surface changes in urban areas with a short revisit time, showing its capability in disaster assessment and urbanization monitoring.Most presented change detection methods are conducted using couples of SAR amplitude images. However, a prior date of surface change is required to select a feasible image pair. We propose an automatic spatio-temporal change detection method by identifying the temporary coherent scatterers. Based on amplitude time series, χ^(2)-test and iterative single pixel change detection are proposed to identify all step-times: the moments of the surface change. Then the parameters, e.g., deformation velocity and relative height, are estimated and corresponding coherent periods are identified by using interferometric phase time series. With identified temporary coherent scatterers, different types of temporal surface changes can be classified using the location of the coherent periods and spatial significant changes are identified combining point density and F values. The main advantage of our method is automatically detecting spatio-temporal surface changes without prior information. Experimental results by the proposed method show that both appearing and disappearing buildings with their step-times are successfully identified and results by ascending and descending SAR images show a good agreement.
基金Project supported by the Shanghai Leading Academic Discipline Project (Grant No.S30108)the Science and Technology of Commission of Shanghai Municipality (Grant No.08DZ2231100)
文摘Calculating the current distribution in circular loop scatterers commonly involves complicated computation. In this paper, based on the theory of Maxwellian circuits （MC）, we propose a fast algorithm by solving a wave equation with constant parameters corresponding to the circular loop. Our method prodeces similar results compared to the methods using method of moments （MoM） with lower computational complexity. It is effective when there are parallel multiple circular loop scatterers. Experimental results show accuracy of the method.
基金supported by the National Natural Science Foundation of China(Grant Nos.52076064,52211530089)the Fundamental Research Funds for the Central Universities(Grant No.HIT.DZJJ.2023095)+1 种基金the National Key Research and Development Program of China(Grant No.2018YFA0702300)Taishan Scholar Foundation of Shandong Province(Grant No.tsqn201812105).
文摘Passive daytime radiative cooling(PDRC)exhibits efficient cooling performance to reduce global fossil energy consumption and has attracted enormous interest.An efficient PDRC technology for achieving daytime subambient cooling is supposed to exhibit ultra-high solar reflectivity and infrared emissivity within atmospheric windows,among which ultra-high solar reflectivity is the principal property.In most PDRC technologies,spherical particles are selected as scatterers to achieve high solar reflectivity because the Mie scattering effect of spherical scatterers can provide a high scattering efficiency.However,the weak backward scattering of spherical scatterers remains a drawback.In this study,several nonspherical scatterers with strong backward scattering are introduced and researched systematically.The numerical analysis results indicate that pyramidal scatterers provide the strongest backward scattering and square/circular scatterers exhibit the highest scattering efficiency.Besides,by considering scattering efficiency and asymmetry factor comprehensively,a dimensionless evaluation parameter is proposed,which can be employed as a quantitative design criterion to achieve the optimal-object-oriented designing of superior scatterers.This work can provide an innovative strategy for designing efficient passive daytime radiative cooling materials.
基金supported by the National Natural Science Foundation of China (Grant Nos. 10874093 and 10804055)the National Basic Research Program of China (Grant Nos. 2007CB307002 and 2010CB934101)+1 种基金the 111 Project (Grant No. B07013)the Program for NCET
文摘We experimentally study the wavelength dependence of light propagation in a water suspension of lithium niobate microcrystalline particles.First,the ballistic transmission in the visible range of the suspension is measured.The nonlinear relationship is observed between the transport mean free path and the wavelength of the incident light.Secondly,we measure the coherent backscattering (CBS) of the sample at different wavelengths.The full width at half maximum of the CBS cone at 532 nm is about 1.24 times as large as that at 671 nm.The results indicate that the light with a long wavelength propagates further than the short wavelength light and the localization state of the short one is stronger.Finally,we investigate the light-controllable CBS experiments in the disordered materials of anisotropic scatterers,which show that the configuration of pump light with the longer wavelength and the probe light with the shorter wavelength performs better.
基金Project Supported by the National Natural Science Foundation of China
文摘The radiative transfer from a model of multi-layer random media embedded by multiple components, size-distributed, dense spherical scatterers is studied. The size distribution of spherical scatterers as ice grains and the effective radius are discussed by use of a snow sample. By using Gaussian quadrature, discrete ordinate and eigenanalysis methods, two vector radiative transfer equations of dense scatterers and four coupling boundary conditions are numerically solved. The polarized brightness temperature and the functional dependence on various parameters are obtained, which are well compared with experimental data from remote sensing of dry and wet snow.
基金Supported by the National Key R&D Program of China(2021YFB3900105-2)the National Natural Science Foundation of China(42071371).
文摘In DEM generation using interferometric synthetic aperture radar(InSAR),the ground control points(GCPs)for refinement and reflattening are usually selected by manual selection,field surveying,GPS points and existing basemaps,which may not be completely suitable for consequent processes.We proposed a new method(auto-PS-GCP)of GCP selection based on permanent scatterers,which automatically defines the thresholds for the coherence,amplitude,and amplitude dispersion index to select permanent scatterer as the GCPs.The GCP thinning(auto-PS-GCP-Thin)was further conducted considering the point density,distances among points and terrain conditions.We used a three-stage assessment that includes:(1)phase stability and intensity of the GCPs,(2)RMSEs of the elevations between GCPs and homonymous points in the reference DEM,and(3)generated DEM accuracy.Three areas respectively in the plain,hilly and mountainous regions were selected to verify the proposed methods.The assessment using both SRTM DEM andICESat-2 points shows that the DEM accuracy of auto-PS-GCP-Thin was improved by 20%∼30%for different areas compared to the manual,where the best DEM accuracy of 4.71 m was found in the plain area.It is concluded that the proposed methods are effective and reliable in various areas with different terrain conditions.
基金supported by the National Natural Science Foundation of China(61072137)the Scientific & Technological Support Project (Industry) of Jiangsu Province(BE2011298)the National overseas study support Foundation Item(20071108)
文摘In this paper, firstly presented a geometrically based statistical channel model with scatterers that are with an inverted parabolic spatial distribution around mobile station （MS） within a circle wherein the base station （BS） and MS are included. This paper proposed a technique to simply derive probability density functions （PDFs） of angle of arrival （AOA）, time of arrival （TOA） and Doppler spectra to characterize the outdoor macrocell and microcell environments by employing various distances between BS and MS, or different size of circular region. Employing this channel model, we analyze the impacts of a directional antenna at BS with the main-lobe width 2~z on the fading and the Doppler spectra.
基金Acknowledgements This work was supported by the National Natural Science Foundation of China （Grant Nos. 11144007 and 61307050）.
文摘Ultraslow-light effects in two-dimensional hexagonal-lattice coupled waveguide with moon-like scat- terers were theoretically studied using the plane-wave expansion method. For symmetric structures, simulations showed that slow light with high group index can be achieved by shifting the scatterers and adjusting the radius of moon-like scatterers. The maximum group index was over 8.0 × 10^4. For asymmetric structures, simulations showed that slow light with flat band and high group index can be obtained by shifting the scatterers, adjusting the radius of moon-like scatterers, and rotating the scatterers. The maximum group index was over 5.7 ×10^5 with a ＂saddle-like＂ relationship between the frequency and group index.
文摘Exceptional points have given rise to many intriguing optical phenomena that are of fundamental importance for a variety of breakthrough technologies.The pre-defined Mie scatterers can bring a resonator to an exceptional point,and result in enhanced quality factor through coherently suppressing the backward scattering.
基金supported by the National Natural Science Foundation of China(Grant Nos.62205259,62075175,62105254,and 62375212)the National Key Laboratory of Infrared Detection Technologies(Grant No.IRDT-23-06)+1 种基金the Fundamental Research Funds for the Central Universities(Grant Nos.XJSJ24028,XJS222202,ZYTS24097,and ZYTS24095)the Open Research Fund of Beijing Key Laboratory of Advanced Optical Remote Sensing Technology.
文摘High-resolution seeing through complex scattering media such as turbid water,biological tissues,and mist is a significant challenge because the strong scattering scrambles the light paths and forms the scattering wall.We propose an active polarized iterative optimization approach for high-resolution imaging through complex scattering media.By acquiring a series of sub-polarized images,we can capture the diverse pattern-illuminated images with various high-frequency component information caused by the Brownian motion of complex scattering materials,which are processed using the common-mode rejection of polarization characteristics to extract target information from scattering medium information.Following that,our computational reconstruction technique employs an iterative optimization algorithm that commences with patternilluminated Fourier ptychography for reconstructing the high-resolution scene.It is extremely important that our approach for high-resolution imaging through complex scattering media is not limited by priori information and optical memory effect.The proposed approach is suitable for not only dynamic but also static scattering media,which may find applications in the biomedicine field,such as skin abnormalities,non-invasive blood flow,and superficial tumors.
基金supported by National Natural Science Foundation of China(12374358,91950207)Guangdong Basic and Applied Basic Research Foundation(2024A1515010420).
文摘Glucose molecules are of great significance being one of the most important molecules in metabolic chain.However,due to the small Raman scattering cross-section and weak/non-adsorption on bare metals,accurately obtaining their"fingerprint information"remains a huge obstacle.Herein,we developed a tip-enhanced Raman scattering(TERS)technique to address this challenge.Adopting an optical fiber radial vector mode internally illuminates the plasmonic fiber tip to effectively suppress the background noise while generating a strong electric-field enhanced tip hotspot.Furthermore,the tip hotspot approaching the glucose molecules was manipulated via the shear-force feedback to provide more freedom for selecting substrates.Consequently,our TERS technique achieves the visualization of all Raman modes of glucose molecules within spectral window of 400-3200 cm^(-1),which is not achievable through the far-field/surface-enhanced Raman,or the existing TERS techniques.Our TERS technique offers a powerful tool for accurately identifying Raman scattering of molecules,paving the way for biomolecular analysis.
基金supported by the National Natural Science Foundation of China(Nos.42077299,and U21A20290)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB0750400)the Ordos Key Research and Development Program(No.YF20240037).
文摘Persistent toxic substances(PTS)represent a paramount environmental issue in the 21st century.Understanding the concentrations and forms of PTS in the environment is crucial for accurately assessing their environmental health impacts.This article presents a concise overview of the components of PTS,pertinent environmental regulations,and conventional detection methodologies.Additionally,we offer an in-depth review of the principles,development,and practical applications of surface-enhanced Raman scattering(SERS)in environmental monitoring,emphasizing the advancements in detecting trace amounts of PTS in complex environmental matrices.Recent progress in enhancing SERS sensitivity,improving selectivity,and practical implementations are detailed,showcasing innovative materials and methods.Integrating SERS with advanced algorithms are highlighted as pivotal areas for future research.
基金Project supported by the Scientific and Technological Research Program of Chongqing Municipal Education Commission(Grant No.KJQN202400624)the Natural Science Foundation of Chongqing CSTC(Grant No.CSTB2022NSCQBHX0020)+3 种基金the China Electronics Technology Group Corporation 44th Research Institute(Grant No.6310001-2)the Project Grant“Noninvasive Sensing Measurement based on Terahertz Technology”from Province and MOE Collaborative Innovation Centre for New Generation Information Networking and Terminalsthe Key Research Program of CQUPT on Interdisciplinary and Emerging Field(A2018-01)the Venture&Innovation Support program for Chongqing Overseas Returnees Year 2022。
文摘We investigate theoretically the enhancement of mechanical squeezing in a multimode optomechanical system by introducing a coherent phonon–photon interaction via the backward stimulated Brillouin scattering(BSBS)process.The coherent photon–phonon interaction where two optical modes couple to a Brillouin acoustic mode with a large decay rate provides an extra channel for the cooling of a Duffing mechanical oscillator.The squeezing degree and the robustness to the thermal noises of the Duffing mechanical mode can be enhanced greatly.When the Duffing nonlinearity is weak,the squeezing degree of the mechanical mode in the presence of BSBS can be improved by more than one order of magnitude compared with that in the absence of BSBS.Our scheme may be extended to other quantum systems to study novel quantum effects.
基金financial supports from National Natural Science Foundation of China(62175023).
文摘In this study,we developed a single-beam optical trap-based surface-enhanced Raman scattering(SERS)optofluidic molecular fingerprint spectroscopy detection system.This system utilizes a single-beam optical trap to concentrate free silver nanoparticles(AgNPs)within an optofluidic chip,significantly enhancing SERS performance.We investigated the optical field distribution characteristics within the tapered fiber using COMSOL simulation software and established a MATLAB simulation model to validate the single-beam optical trap's effectiveness in capturing AgNPs,demonstrating the theoretical feasibility of our approach.To verify the particle capture efficacy of the system,we experimentally controlled the optical trap's on-off state to manage the capture and release of particles precisely.The experimental results indicated that the Raman signal intensity in the capture state was significantly higher than in the non-capture state,confirming that the single-beam optical trap effectively enhances the SERS detection capability of the optofluidic detection system.Furthermore,we employed Raman mapping techniques to investigate the impact of the capture area on the SERS effect,revealing that the spectral intensity of molecular fingerprints in the laser-trapping region is significantly improved.We successfully detected the Raman spectrum of crystal violet at a concentration of 10^(−9)mol/L and pesticide thiram at a concentration of 10^(−5)mol/L,further demonstrating the ability of the single-beam optical trap in enhancing the molecular fingerprint spectrum identification capability of the SERS optofluidic chips.The optical trapping SERS optofluidic detection system developed in this study,as a key component of an integrated optoelectronic sensing system,holds the potential for integration with portable high-power lasers and high-performance Raman spectrometers.This integration is expected to advance highly integrated technologies and significantly enhance the overall performance and portability of optoelectronic sensing systems.
