During the continuous casting process of high-Mn high-Al steels,various types of gases such as Ar need to escape through the top of the mold.In which,the behavior of bubbles traversing the liquid slag serves as a rest...During the continuous casting process of high-Mn high-Al steels,various types of gases such as Ar need to escape through the top of the mold.In which,the behavior of bubbles traversing the liquid slag serves as a restrictive link,closely associated with viscosity and the thickness of liquid slag.In contrast to two-dimensional surface observation,three-dimensional(3D)analysis method can offer a more intuitive,accurate,and comprehensive information.Therefore,this study employs a 3D X-ray microscope(3D-XRM)to obtained spatial distribution and 3D morphological characteristics of residual bubbles in mold flux under different basicity of liquid slag,different temperatures,and different holding times.The results indicate that as basicity of slag increases from 0.52 to 1.03,temperature increases from 1423 to 1573 K,the viscosity of slag decreases,the floating rate of bubbles increases.In addition,when holding time increases from 10 to 30 s,the bubbles floating distance increases,and the volume fraction and average equivalent sphere diameter of the bubbles solidified in the mold flux gradually decreases.In one word,increasing the basicity,temperature,and holding time leading to an increase in the removal rate of bubbles especially for the large.These findings of bubbles escape behavior provide valuable insights into optimizing low basicity mold flux for high-Mn high-Al steels.展开更多
We theoretically investigate the extended Bose-Hubbard model using a three-dimensional cubic lattice.In the framework of the dynamical Gutzwiller mean-field theory,we identify a checkerboard supersolid phase.By consid...We theoretically investigate the extended Bose-Hubbard model using a three-dimensional cubic lattice.In the framework of the dynamical Gutzwiller mean-field theory,we identify a checkerboard supersolid phase.By considering the repulsive interactions between next-nearest-neighbor lattice sites,we further discover an exotic type of supersolid state,whose site occupancies show a stereoscopically arrayed and staggered distribution rather than checkerboard ordering.Intriguingly,if the physical observations of two neighboring layers were superimposed,they would give rise to a checkerboard configuration.This novel structure is convincingly induced by the simultaneous existence of nearest-neighbor and nextnearest-neighbor interactions.We also identify arrayed stripes in the ground state,as well as arrayed holes in the pattern of occupancies.展开更多
The motion of gas bubbles beneath a free surface will lead to a spike of fluid on the free surface. The distance of the bubbles to the free surface is the key factor to different phenomena. When the inception distance...The motion of gas bubbles beneath a free surface will lead to a spike of fluid on the free surface. The distance of the bubbles to the free surface is the key factor to different phenomena. When the inception distance varies in some range, crown phenomenon would happen after the impact of weak buoyancy bubbles, so this kind of spike is defined as crown spike in the present paper. Based on potential flow theory, a three-dimensional numerical model is established to simulate the motion of the free-surface spike generated by one bubble or a horizontal line of two in-phase bubbles. After the downward jet formed near the end of the collapse phase, the simulation of the free surface is performed to study the crown spike without regard to the toroidal bubble＇s effect. Calculations about the interaction between one bubble and free surface agree well with the experimental results conducted with a high-speed camera, and relative error is within 15%. Crown spike in both single- and two-bubble cases are simulated numerically. Different features and laws of the motion of crown spike, depending on the bubble-boundary distances and the inter-bubble distances, have been investigated.展开更多
The interaction of two underwater explosion bubbles was mathematically analyzed in this paper. Based on the assumption of potential flow, high-order curved elements were used to discretize the boundary integral equati...The interaction of two underwater explosion bubbles was mathematically analyzed in this paper. Based on the assumption of potential flow, high-order curved elements were used to discretize the boundary integral equation and solve it. Assuming that gas inside the bubble follows the isentropic rule, the Euler-Lagrange method was used to trace the evolution of the bubble, and when calculating the singular integral, the singularity of the double-layer singular integral was eliminated by reconstructing a principal-value integral of double-layer potential so that a more precise result could be obtained. Elastic mesh technique (EMT) was also used when tracing the evolution of the bubble interface, and numerical smoothing wasn't needed. A comparison of calculations using this three-dimensional model with results of the Reyleigh-Plesset bubble model shows that the three-dimensional model and calculation method in this paper is practical. This three-dimensional model was applied to simulate the interaction of two bubbles under the action of gravity, and the dynamic characteristics of two bubbles near the surface was also analyzed. Bubbles influenced by surface effects and gravity present severe non-linearity. This paper provides a reference for research into the dynamics of multi-bubbles.展开更多
It is very important for underwater robots to accurately detect and locate target objects. However,under many circumstances,it is difficult to clearly observe the target object due to the existence of bubble noise. In...It is very important for underwater robots to accurately detect and locate target objects. However,under many circumstances,it is difficult to clearly observe the target object due to the existence of bubble noise. In this paper,we proposed a method to solve this problem. First,we used the LK optical flow algorithm to calculate the motion vector of the image background and compensate for the background motion.Then,the optical flow field of the bubbles was calculated by the HS optical flow algorithm,and the area where the bubble existed was obtained by binarizing the image. Finally,we used the adjacent frame image to repair the bubble area. We carried out a bubble noise removal experiment. The results show that this method can effectively remove the bubble noise in the image.展开更多
We show that giant asymmetric transmission and optical rotation for linear polarizations can be achieved by a chiral three-dimensional metamaterial composed of L-shaped and C-shaped metallic particles. Numerical calcu...We show that giant asymmetric transmission and optical rotation for linear polarizations can be achieved by a chiral three-dimensional metamaterial composed of L-shaped and C-shaped metallic particles. Numerical calcu- lations on the electric field distributions indicate that the coupling between the electric dipolar and quadrupolar resonances in the L- and C-shaped metallic particles contributes to these effects.展开更多
In optical three-dimensional shape measurement, a method of improving the measurement precision for phase reconstruction without phase unwrapping is analyzed in detail. Intensities of any five consecutive pixels that ...In optical three-dimensional shape measurement, a method of improving the measurement precision for phase reconstruction without phase unwrapping is analyzed in detail. Intensities of any five consecutive pixels that lie in the x-axis direction of the phase domain are given. Partial derivatives of the phase function in the x- and y-axis directions are obtained with a phase-shifting mechanism, the origin of which is analysed. Furthermore, to avoid phase unwrapping in the phase reconstruction, we derive the gradient of the phase function and perform a two-dimensional integral along the x- and y-axis directions. The reconstructed phase can be obtained directly by performing numerical integration, and thus it is of great convenience for phase reconstruction. Finally, the results of numerical simulations and practical experiments verify the correctness of the proposed method.展开更多
An optical encryption of three-dimensional (3D) object with digital holography was implemented. In the process of encryption, two holograms involved recording key information and 3D object were obtained. In the proces...An optical encryption of three-dimensional (3D) object with digital holography was implemented. In the process of encryption, two holograms involved recording key information and 3D object were obtained. In the process of decryption, the 3D object was reconstructed from the two holograms by extracting the object and key information, followed by multiplication of the two holograms and inverse Fresnel transform numerically. The robustness of the method was also tested for different occlusions attacks and Gaussian noises. The results showed that the method was able to encrypt and decrypt the 3D object while being robust under different occlusions attacks and Gaussian noises.展开更多
A high optical magnification three-dimensional imaging system is proposed using an optic microscope whose ocular （eyepiece） is retained and the structure of the transmission mode is not destroyed. The elemental imag...A high optical magnification three-dimensional imaging system is proposed using an optic microscope whose ocular （eyepiece） is retained and the structure of the transmission mode is not destroyed. The elemental image array is captured through the micro lens array. Due to the front diffuse transmission element, each micro lens sees a slightly different spatial perspective of the scene, and a different independent image is formed in each micro lens channel. Each micro lens channel is imaged by a Fourier lens and captured by a CCD. The design translating the stage in x or y provides no parallax. Compared with the conventional integral imaging of micro-objects, the optical magnification of micro-objects in the proposed system can enhanced remarkably. The principle of the enhancement of the image depth is explained in detail and the experimental results are presented.展开更多
Background:Traditional imaging approaches to keratoconus(KCN)have thus far failed to produce a standardized approach for diagnosis.While many diagnostic modalities and metrics exist,none have proven robust enough to b...Background:Traditional imaging approaches to keratoconus(KCN)have thus far failed to produce a standardized approach for diagnosis.While many diagnostic modalities and metrics exist,none have proven robust enough to be considered a gold standard.This study aims to introduce novel metrics to differentiate between KCN and healthy corneas using three-dimensional(3D)measurements of surface area and volume.Methods:This retrospective observational study examined KCN patients along with healthy control patients between the ages of 20 and 79 years old at the University of Maryland,Baltimore.The selected patients underwent a nine-line raster scan anterior segment optical coherence tomography(AS-OCT).ImageJ was used to determine the central 6 mm of each image and each corneal image was then divided into six 1 mm segments.Free-D software was then used to render the nine different images into a 3D model to calculate corneal surface area and volume.A two-tailed Mann-Whitney test was used to assess statistical significance when comparing these subsets.Results:Thirty-three eyes with KCN,along with 33 healthy control,were enrolled.There were statistically significant differences between the healthy and KCN groups in the metric of anterior corneal surface area(13.927 vs.13.991 mm^(2),P=0.046),posterior corneal surface area(14.045 vs.14.173 mm^(2),P<0.001),and volume(8.430 vs.7.773 mm3,P<0.001)within the central 6 mm.Conclusions:3D corneal models derived from AS-OCT can be used to measure anterior corneal surface area,posterior corneal surface area,and corneal volume.All three parameters are statistically different between corneas with KCN and healthy corneas.Further study and application of these parameters may yield new methodologies for the detection of KCN.展开更多
Comprehensive numerical and experimental analyses of the effect of viscosity on cavitation oscillations are performed. This numerical approach is based on the Rayleigh-Plesset equation. The model predictions are compa...Comprehensive numerical and experimental analyses of the effect of viscosity on cavitation oscillations are performed. This numerical approach is based on the Rayleigh-Plesset equation. The model predictions are compared with experimental results obtained by using a fibre-optic diagnostic technique based on optical beam deflection （OBD）. The maximum and minimum bubble radii as well as the oscillation times for each oscillation cycle are determined according to the characteristic signals. It is observed that the increasing of viscosity decreases the maximum bubble radii but increases the minimum bubble radii and the oscillation time. These experimental results are consistent with numerical results.展开更多
In this paper, the flow field is assumed to be inviscid, irrotational and incompressible, triangular elements are adopted to discretize the boundary of flow field, the boundary integral method is used to solve the flo...In this paper, the flow field is assumed to be inviscid, irrotational and incompressible, triangular elements are adopted to discretize the boundary of flow field, the boundary integral method is used to solve the flow field and the Mixed-Eulerian-Lagrangian method is applied to simulate the evolution of bubble. Three-dimensional smoothing method is used to smooth the bubble surface and the velocity potential to make the computing process more accurate and stable. In the analysis process, three-dimensional model simulates the dynamics of a bubble in the free field, gravitational field and near the rigid wall respectively, and the calculated results coincide well with the exact results and experimental data, which show that the algorithm and 3D model in this paper are of high accuracy. Calculation process indicates that bubble takes on strong non-linear under the combine effect of gravity and rigid wall.展开更多
Bubble plumes are important during the process of air-sea exchange,and optical-fiber phase detection is a suitable way to observe bubble plumes entrained by breaking waves.This paper designs a new optical-fiber probe(...Bubble plumes are important during the process of air-sea exchange,and optical-fiber phase detection is a suitable way to observe bubble plumes entrained by breaking waves.This paper designs a new optical-fiber probe(OFP)made of sapphire to overcome the limitations of existing materials(e.g.,high brittleness,poor corrosion resistance,and narrow bandwidth)and thereby enhance the detection performance of the OFP by improving its structure.Based on total internal reflection and light refraction,a simulation model of the probe is established in the Zemax optical design software to optimize the probe tip and matching mode of the two probe tips.The results show that the optimum OFP tip is a conical sapphire one with a cone angle of 35°.Tests are then conducted on a bespoke OFP sensor,the results of which are consistent with those predicted theoretically.The simulation results lay the foundation for the integrated design of OFP sensors and the optimization of their internal optics.The findings could also be applied to OFPs with multiple tips.展开更多
Object identification and three-dimensional reconstruction techniques are always attractive research interests in machine vision,virtual reality,augmented reality,and biomedical engineering.Optical computing metasurfa...Object identification and three-dimensional reconstruction techniques are always attractive research interests in machine vision,virtual reality,augmented reality,and biomedical engineering.Optical computing metasurface,as a two-dimensional artificial design component,has displayed the supernormal character of controlling phase,amplitude,polarization,and frequency distributions of the light beam,capable of performing mathematical operations on the input light field.Here,we propose and demonstrate an all-optical object identification technique based on optical computing metasurface,and apply it to 3D reconstruction.Unlike traditional mechanisms,this scheme reduces memory consumption in the processing of the contour surface extraction.The identification and reconstruction of experimental results from high-contrast and low-contrast objects agree well with the real objects.The exploration of the all-optical object identification and 3D reconstruction techniques provides potential applications of high efficiencies,low consumption,and compact systems.展开更多
Based on the theory of compressible fluid, a three-dimension boundary element method is utilized to research the motion of bubble. The far-field noise radiation during the growth and contraction is calculated by the K...Based on the theory of compressible fluid, a three-dimension boundary element method is utilized to research the motion of bubble. The far-field noise radiation during the growth and contraction is calculated by the Kirchhoff formula and the Ffowcs Williams-Hawkings （FW-H） formula with a fixed radiation surface being arranged at the near-field of bubble as a new acoustic source. The results show that the amplitude of the sound pressure induced by non-spherical bubble is lower than that of spherical bubble in the contraction phase. The retardance effect is more obvious when the observer is farther away from the bubble. In the anaphase of contraction, the observer with the maximum amplitude of sound pressure moves up with the obvious jet. Larger buoyance parameters will generate lower sound pressure amplitudes in the anaphase, while larger intensive parameters will cause higher sound pressure amplitudes in the whole procedure of bubble motion.展开更多
The hydrogen evolution reaction(HER)in electrochemical water splitting is crucial for green hydrogen production,yet its efficiency is limited by bubble dynamics at the electrode surface.Accumulated bubbles can block a...The hydrogen evolution reaction(HER)in electrochemical water splitting is crucial for green hydrogen production,yet its efficiency is limited by bubble dynamics at the electrode surface.Accumulated bubbles can block active sites,hinder mass transport,and increase local resistance,causing energy loss.Thus,precise bubble monitoring is crucial for understanding performance limitations and optimizing catalyst design.Conventional bubble monitoring techniques,such as optical microscopy,high-speed imaging,and electrochemical impedance,are constrained by real-time accuracy,complex post-processing,or signal interference at high current densities.Here,we present an in situ fiber optic sensing system that enables precise,real-time monitoring of bubble dynamics during HER.Unlike traditional methods,this system leverages the sensitivity and real-time capability of fiber optic sensors to quantify key parameters,such as growth rate,detachment rate,intake/output ratio,and detaching size.Its reliability and adaptability were validated using two different Pt/C-loaded carbon paper catalysts with distinct catalytic properties.Notably,the system also achieves a bubble detection limit of 79μm,which meets the spatial resolution requirements for monitoring bubble dynamics relevant to electrocatalytic activity in HER.This sensing platform establishes a practical framework for connecting interfacial gas evolution to electrochemical performance,offering valuable insight for optimizing HER efficiency through catalyst design.展开更多
Fusion of bubbles is a common and significant phenomenon in the nature. In this work, the potential flow theory and the boundary integral method are employed to simulate the fusion of underwater explosion bubbles. Bas...Fusion of bubbles is a common and significant phenomenon in the nature. In this work, the potential flow theory and the boundary integral method are employed to simulate the fusion of underwater explosion bubbles. Based on the numerical and experimental results in the literature, a three-dimensional model of bubble fusion is established. A good agreement is shown between the numerical results and experimental data. Influences of characteristic parameters such as distance and depth are specifically investigated by using the developed three-dimensional program, resulting in favorable curves and conclusions. This work provides references for the relevant research on fusion mechanics and dynamic characteristics of bubbles.展开更多
A new aspheric surface pre-collimation lenses system for the optical antenna of three-dimensional （3D） imaging of lidar has been optimally designed and simulated by optical design software CODE-V.Four kinds of asphe...A new aspheric surface pre-collimation lenses system for the optical antenna of three-dimensional （3D） imaging of lidar has been optimally designed and simulated by optical design software CODE-V.Four kinds of aspheric surfaces spherical lenses including the sections of spherical,elliptical,hyperbola,and parabola have been researched.The optical system,including the elliptical cylinder lenses collimation and the optical antenna,can be realized less than 5 rad collimation angle for dot source semiconductor laser beam.展开更多
In order to meet the requirements of nondestructive testing of true 3D topography of micro-nano structures,a novel three-dimensional atomic force microscope(3D-AFM)based on flared tip is developed.A high-precision sca...In order to meet the requirements of nondestructive testing of true 3D topography of micro-nano structures,a novel three-dimensional atomic force microscope(3D-AFM)based on flared tip is developed.A high-precision scanning platform is designed to achieve fast servo through moving probe and sample simultaneously,and several combined nanopositioning stages are used to guarantee linearity and orthogonality of displacement.To eliminate the signal deviation caused by AFM-head movement,a traceable optical lever system is designed for cantilever deformation detection.In addition,a method of tailoring the cantilever of commercial probe with flared tip is proposed to reduce the lateral force applied on the tip in measurement.The tailored probe is mounted on the 3D-AFM,and 3D imaging experiments are conducted on different samples by use of adaptive-angle scanning strategy.The results show the roob-mean-square value of the vertical displacement noise(RMS)of the prototype is less than 0.1 nm and the high/width measurement repeatability(peak-to-peak)is less than 2.5 nm.展开更多
Recently published in Joule,Feng Liu and colleagues from Shanghai Jiaotong University reported a record-breaking 20.8%power conversion efficiency in organic solar cells(OSCs)with an interpenetrating fibril network act...Recently published in Joule,Feng Liu and colleagues from Shanghai Jiaotong University reported a record-breaking 20.8%power conversion efficiency in organic solar cells(OSCs)with an interpenetrating fibril network active layer morphology,featuring a bulk p-in structure and proper vertical segregation achieved through additive-assisted layer-by-layer deposition.This optimized hierarchical gradient fibrillar morphology and optical management synergistically facilitates exciton diffusion,reduces recombination losses,and enhances light capture capability.This approach not only offers a solution to achieving high-efficiency devices but also demonstrates the potential for commercial applications of OSCs.展开更多
基金financially supported by the National Natural Science Foundation of China(Nos.52274315 and 52374320)the Fundamental Research Funds for the Central Universities(Nos.FRF-TP-22-011A1 and FRF-DF22-16)。
文摘During the continuous casting process of high-Mn high-Al steels,various types of gases such as Ar need to escape through the top of the mold.In which,the behavior of bubbles traversing the liquid slag serves as a restrictive link,closely associated with viscosity and the thickness of liquid slag.In contrast to two-dimensional surface observation,three-dimensional(3D)analysis method can offer a more intuitive,accurate,and comprehensive information.Therefore,this study employs a 3D X-ray microscope(3D-XRM)to obtained spatial distribution and 3D morphological characteristics of residual bubbles in mold flux under different basicity of liquid slag,different temperatures,and different holding times.The results indicate that as basicity of slag increases from 0.52 to 1.03,temperature increases from 1423 to 1573 K,the viscosity of slag decreases,the floating rate of bubbles increases.In addition,when holding time increases from 10 to 30 s,the bubbles floating distance increases,and the volume fraction and average equivalent sphere diameter of the bubbles solidified in the mold flux gradually decreases.In one word,increasing the basicity,temperature,and holding time leading to an increase in the removal rate of bubbles especially for the large.These findings of bubbles escape behavior provide valuable insights into optimizing low basicity mold flux for high-Mn high-Al steels.
基金supported by the Hainan Provincial Natural Science Foundation of China(Grant No.525QN342)the Scientific Research Foundation of Hainan Tropical Ocean University(Grant No.RHDRC202301).
文摘We theoretically investigate the extended Bose-Hubbard model using a three-dimensional cubic lattice.In the framework of the dynamical Gutzwiller mean-field theory,we identify a checkerboard supersolid phase.By considering the repulsive interactions between next-nearest-neighbor lattice sites,we further discover an exotic type of supersolid state,whose site occupancies show a stereoscopically arrayed and staggered distribution rather than checkerboard ordering.Intriguingly,if the physical observations of two neighboring layers were superimposed,they would give rise to a checkerboard configuration.This novel structure is convincingly induced by the simultaneous existence of nearest-neighbor and nextnearest-neighbor interactions.We also identify arrayed stripes in the ground state,as well as arrayed holes in the pattern of occupancies.
基金Project supported by the Major Basic Research Project of National Security of China(Grant No.613157)the Excellent Young Scientists Fund of China(Grant No.51222904)
文摘The motion of gas bubbles beneath a free surface will lead to a spike of fluid on the free surface. The distance of the bubbles to the free surface is the key factor to different phenomena. When the inception distance varies in some range, crown phenomenon would happen after the impact of weak buoyancy bubbles, so this kind of spike is defined as crown spike in the present paper. Based on potential flow theory, a three-dimensional numerical model is established to simulate the motion of the free-surface spike generated by one bubble or a horizontal line of two in-phase bubbles. After the downward jet formed near the end of the collapse phase, the simulation of the free surface is performed to study the crown spike without regard to the toroidal bubble＇s effect. Calculations about the interaction between one bubble and free surface agree well with the experimental results conducted with a high-speed camera, and relative error is within 15%. Crown spike in both single- and two-bubble cases are simulated numerically. Different features and laws of the motion of crown spike, depending on the bubble-boundary distances and the inter-bubble distances, have been investigated.
文摘The interaction of two underwater explosion bubbles was mathematically analyzed in this paper. Based on the assumption of potential flow, high-order curved elements were used to discretize the boundary integral equation and solve it. Assuming that gas inside the bubble follows the isentropic rule, the Euler-Lagrange method was used to trace the evolution of the bubble, and when calculating the singular integral, the singularity of the double-layer singular integral was eliminated by reconstructing a principal-value integral of double-layer potential so that a more precise result could be obtained. Elastic mesh technique (EMT) was also used when tracing the evolution of the bubble interface, and numerical smoothing wasn't needed. A comparison of calculations using this three-dimensional model with results of the Reyleigh-Plesset bubble model shows that the three-dimensional model and calculation method in this paper is practical. This three-dimensional model was applied to simulate the interaction of two bubbles under the action of gravity, and the dynamic characteristics of two bubbles near the surface was also analyzed. Bubbles influenced by surface effects and gravity present severe non-linearity. This paper provides a reference for research into the dynamics of multi-bubbles.
基金Sponsored by the National Natural Science Foundation of China(Grant No.61673138)the National Key Basic Research Development Plan Project(Grant No.2013CB035502)the Self-Planned Task of State Key Laboratory of Robotics and System(HIT)(Grant No.SKLRS201804B)
文摘It is very important for underwater robots to accurately detect and locate target objects. However,under many circumstances,it is difficult to clearly observe the target object due to the existence of bubble noise. In this paper,we proposed a method to solve this problem. First,we used the LK optical flow algorithm to calculate the motion vector of the image background and compensate for the background motion.Then,the optical flow field of the bubbles was calculated by the HS optical flow algorithm,and the area where the bubble existed was obtained by binarizing the image. Finally,we used the adjacent frame image to repair the bubble area. We carried out a bubble noise removal experiment. The results show that this method can effectively remove the bubble noise in the image.
基金Supported by the International Science and Technology Cooperation Program of Anhui Province under Grant No 1403062027the Anhui Provincial Natural Science Foundation under Grant Nos KJ2014A195 and 1308085MA13the Undergraduate Scientific and Technological Innovation Project under Grant Nos AH201310371022,2013jyxml36,2013ZYJS04 and FS201310371082
文摘We show that giant asymmetric transmission and optical rotation for linear polarizations can be achieved by a chiral three-dimensional metamaterial composed of L-shaped and C-shaped metallic particles. Numerical calcu- lations on the electric field distributions indicate that the coupling between the electric dipolar and quadrupolar resonances in the L- and C-shaped metallic particles contributes to these effects.
基金Project supported by the National Natural Science Foundation of China (Grant No. 61144006)
文摘In optical three-dimensional shape measurement, a method of improving the measurement precision for phase reconstruction without phase unwrapping is analyzed in detail. Intensities of any five consecutive pixels that lie in the x-axis direction of the phase domain are given. Partial derivatives of the phase function in the x- and y-axis directions are obtained with a phase-shifting mechanism, the origin of which is analysed. Furthermore, to avoid phase unwrapping in the phase reconstruction, we derive the gradient of the phase function and perform a two-dimensional integral along the x- and y-axis directions. The reconstructed phase can be obtained directly by performing numerical integration, and thus it is of great convenience for phase reconstruction. Finally, the results of numerical simulations and practical experiments verify the correctness of the proposed method.
文摘An optical encryption of three-dimensional (3D) object with digital holography was implemented. In the process of encryption, two holograms involved recording key information and 3D object were obtained. In the process of decryption, the 3D object was reconstructed from the two holograms by extracting the object and key information, followed by multiplication of the two holograms and inverse Fresnel transform numerically. The robustness of the method was also tested for different occlusions attacks and Gaussian noises. The results showed that the method was able to encrypt and decrypt the 3D object while being robust under different occlusions attacks and Gaussian noises.
基金Supported by the Scientific Research Fund Project of the Education Department of Shaanxi Province under Grant No 15JK1732the Natural Science Foundation of Shaanxi Province under Grant No2014JQ1044the Science Foundation of Northwest University under Grant No 12NW01
文摘A high optical magnification three-dimensional imaging system is proposed using an optic microscope whose ocular （eyepiece） is retained and the structure of the transmission mode is not destroyed. The elemental image array is captured through the micro lens array. Due to the front diffuse transmission element, each micro lens sees a slightly different spatial perspective of the scene, and a different independent image is formed in each micro lens channel. Each micro lens channel is imaged by a Fourier lens and captured by a CCD. The design translating the stage in x or y provides no parallax. Compared with the conventional integral imaging of micro-objects, the optical magnification of micro-objects in the proposed system can enhanced remarkably. The principle of the enhancement of the image depth is explained in detail and the experimental results are presented.
文摘Background:Traditional imaging approaches to keratoconus(KCN)have thus far failed to produce a standardized approach for diagnosis.While many diagnostic modalities and metrics exist,none have proven robust enough to be considered a gold standard.This study aims to introduce novel metrics to differentiate between KCN and healthy corneas using three-dimensional(3D)measurements of surface area and volume.Methods:This retrospective observational study examined KCN patients along with healthy control patients between the ages of 20 and 79 years old at the University of Maryland,Baltimore.The selected patients underwent a nine-line raster scan anterior segment optical coherence tomography(AS-OCT).ImageJ was used to determine the central 6 mm of each image and each corneal image was then divided into six 1 mm segments.Free-D software was then used to render the nine different images into a 3D model to calculate corneal surface area and volume.A two-tailed Mann-Whitney test was used to assess statistical significance when comparing these subsets.Results:Thirty-three eyes with KCN,along with 33 healthy control,were enrolled.There were statistically significant differences between the healthy and KCN groups in the metric of anterior corneal surface area(13.927 vs.13.991 mm^(2),P=0.046),posterior corneal surface area(14.045 vs.14.173 mm^(2),P<0.001),and volume(8.430 vs.7.773 mm3,P<0.001)within the central 6 mm.Conclusions:3D corneal models derived from AS-OCT can be used to measure anterior corneal surface area,posterior corneal surface area,and corneal volume.All three parameters are statistically different between corneas with KCN and healthy corneas.Further study and application of these parameters may yield new methodologies for the detection of KCN.
基金supported by the National Natural Science Foundation of China (Grant No 60578015)the Teaching and Research Award Program for Outstanding Young Teachers in Higher Education Institute of China (2003-2008)the National Key Opening Experiment Foundation of Laser Technology of China (Grant No 2005)
文摘Comprehensive numerical and experimental analyses of the effect of viscosity on cavitation oscillations are performed. This numerical approach is based on the Rayleigh-Plesset equation. The model predictions are compared with experimental results obtained by using a fibre-optic diagnostic technique based on optical beam deflection （OBD）. The maximum and minimum bubble radii as well as the oscillation times for each oscillation cycle are determined according to the characteristic signals. It is observed that the increasing of viscosity decreases the maximum bubble radii but increases the minimum bubble radii and the oscillation time. These experimental results are consistent with numerical results.
文摘In this paper, the flow field is assumed to be inviscid, irrotational and incompressible, triangular elements are adopted to discretize the boundary of flow field, the boundary integral method is used to solve the flow field and the Mixed-Eulerian-Lagrangian method is applied to simulate the evolution of bubble. Three-dimensional smoothing method is used to smooth the bubble surface and the velocity potential to make the computing process more accurate and stable. In the analysis process, three-dimensional model simulates the dynamics of a bubble in the free field, gravitational field and near the rigid wall respectively, and the calculated results coincide well with the exact results and experimental data, which show that the algorithm and 3D model in this paper are of high accuracy. Calculation process indicates that bubble takes on strong non-linear under the combine effect of gravity and rigid wall.
文摘Bubble plumes are important during the process of air-sea exchange,and optical-fiber phase detection is a suitable way to observe bubble plumes entrained by breaking waves.This paper designs a new optical-fiber probe(OFP)made of sapphire to overcome the limitations of existing materials(e.g.,high brittleness,poor corrosion resistance,and narrow bandwidth)and thereby enhance the detection performance of the OFP by improving its structure.Based on total internal reflection and light refraction,a simulation model of the probe is established in the Zemax optical design software to optimize the probe tip and matching mode of the two probe tips.The results show that the optimum OFP tip is a conical sapphire one with a cone angle of 35°.Tests are then conducted on a bespoke OFP sensor,the results of which are consistent with those predicted theoretically.The simulation results lay the foundation for the integrated design of OFP sensors and the optimization of their internal optics.The findings could also be applied to OFPs with multiple tips.
基金support from the National Natural Science Foundation of China(Grant Nos.12174097 and 12304321)the Natural Science Foundation of Hunan Province(Grant Nos.2021JJ10008 and 2023JJ40202)the Research Foundation of Education Bureau of Hunan Province(Grant No.22B0871).
文摘Object identification and three-dimensional reconstruction techniques are always attractive research interests in machine vision,virtual reality,augmented reality,and biomedical engineering.Optical computing metasurface,as a two-dimensional artificial design component,has displayed the supernormal character of controlling phase,amplitude,polarization,and frequency distributions of the light beam,capable of performing mathematical operations on the input light field.Here,we propose and demonstrate an all-optical object identification technique based on optical computing metasurface,and apply it to 3D reconstruction.Unlike traditional mechanisms,this scheme reduces memory consumption in the processing of the contour surface extraction.The identification and reconstruction of experimental results from high-contrast and low-contrast objects agree well with the real objects.The exploration of the all-optical object identification and 3D reconstruction techniques provides potential applications of high efficiencies,low consumption,and compact systems.
基金supported by the Key Program of the National Natural Science Foundation of China(No.50939002)the National Defense Basic Scientific Research Program of China(No.613157)the Excellent Young Science Foundation of the National Natural Science Foundation of China(No.51222904)
文摘Based on the theory of compressible fluid, a three-dimension boundary element method is utilized to research the motion of bubble. The far-field noise radiation during the growth and contraction is calculated by the Kirchhoff formula and the Ffowcs Williams-Hawkings （FW-H） formula with a fixed radiation surface being arranged at the near-field of bubble as a new acoustic source. The results show that the amplitude of the sound pressure induced by non-spherical bubble is lower than that of spherical bubble in the contraction phase. The retardance effect is more obvious when the observer is farther away from the bubble. In the anaphase of contraction, the observer with the maximum amplitude of sound pressure moves up with the obvious jet. Larger buoyance parameters will generate lower sound pressure amplitudes in the anaphase, while larger intensive parameters will cause higher sound pressure amplitudes in the whole procedure of bubble motion.
基金supported by the following:the National Natural Science Foundation of China(Nos.62405141 and 22479079)Natural Science Research Start-up Foundation of Recruiting Talents of Nanjing University of Posts and Telecommunications(No.NY222178).
文摘The hydrogen evolution reaction(HER)in electrochemical water splitting is crucial for green hydrogen production,yet its efficiency is limited by bubble dynamics at the electrode surface.Accumulated bubbles can block active sites,hinder mass transport,and increase local resistance,causing energy loss.Thus,precise bubble monitoring is crucial for understanding performance limitations and optimizing catalyst design.Conventional bubble monitoring techniques,such as optical microscopy,high-speed imaging,and electrochemical impedance,are constrained by real-time accuracy,complex post-processing,or signal interference at high current densities.Here,we present an in situ fiber optic sensing system that enables precise,real-time monitoring of bubble dynamics during HER.Unlike traditional methods,this system leverages the sensitivity and real-time capability of fiber optic sensors to quantify key parameters,such as growth rate,detachment rate,intake/output ratio,and detaching size.Its reliability and adaptability were validated using two different Pt/C-loaded carbon paper catalysts with distinct catalytic properties.Notably,the system also achieves a bubble detection limit of 79μm,which meets the spatial resolution requirements for monitoring bubble dynamics relevant to electrocatalytic activity in HER.This sensing platform establishes a practical framework for connecting interfacial gas evolution to electrochemical performance,offering valuable insight for optimizing HER efficiency through catalyst design.
基金Project supported by the National Natural Science Foundation of China (Nos. 50939002, 50779007)the Combination of the National Natural Science Foundation and Chinese Academy of Engineering Physics (No. 10976008)+1 种基金National Science Foundation for Young Scientists of China (No. 50809018)the National Science Foundation for Post-Doctoral Scientists of China (No. 200801104)
文摘Fusion of bubbles is a common and significant phenomenon in the nature. In this work, the potential flow theory and the boundary integral method are employed to simulate the fusion of underwater explosion bubbles. Based on the numerical and experimental results in the literature, a three-dimensional model of bubble fusion is established. A good agreement is shown between the numerical results and experimental data. Influences of characteristic parameters such as distance and depth are specifically investigated by using the developed three-dimensional program, resulting in favorable curves and conclusions. This work provides references for the relevant research on fusion mechanics and dynamic characteristics of bubbles.
基金supported by Pre-research Foundation under Grant No. G020104PJ09DZ0246the National Natural Science Foundation of China under Grant No. 11004024
文摘A new aspheric surface pre-collimation lenses system for the optical antenna of three-dimensional （3D） imaging of lidar has been optimally designed and simulated by optical design software CODE-V.Four kinds of aspheric surfaces spherical lenses including the sections of spherical,elliptical,hyperbola,and parabola have been researched.The optical system,including the elliptical cylinder lenses collimation and the optical antenna,can be realized less than 5 rad collimation angle for dot source semiconductor laser beam.
基金National Key Research and Development Pragram of China(No.2016YFF0200602)National Natural Science Foundation of China(No.61973233)。
文摘In order to meet the requirements of nondestructive testing of true 3D topography of micro-nano structures,a novel three-dimensional atomic force microscope(3D-AFM)based on flared tip is developed.A high-precision scanning platform is designed to achieve fast servo through moving probe and sample simultaneously,and several combined nanopositioning stages are used to guarantee linearity and orthogonality of displacement.To eliminate the signal deviation caused by AFM-head movement,a traceable optical lever system is designed for cantilever deformation detection.In addition,a method of tailoring the cantilever of commercial probe with flared tip is proposed to reduce the lateral force applied on the tip in measurement.The tailored probe is mounted on the 3D-AFM,and 3D imaging experiments are conducted on different samples by use of adaptive-angle scanning strategy.The results show the roob-mean-square value of the vertical displacement noise(RMS)of the prototype is less than 0.1 nm and the high/width measurement repeatability(peak-to-peak)is less than 2.5 nm.
基金Technology Development Program of Jilin Province(YDZJ202201ZYTS640)the National Key Research and Development Program of China(2022YFB4200400)funded by MOST+4 种基金the National Natural Science Foundation of China(52172048 and 52103221)Shandong Provincial Natural Science Foundation(ZR2021QB024 and ZR2021ZD06)Guangdong Basic and Applied Basic Research Foundation(2023A1515012323,2023A1515010943,and 2024A1515010023)the Qingdao New Energy Shandong Laboratory open Project(QNESL OP 202309)the Fundamental Research Funds of Shandong University.
文摘Recently published in Joule,Feng Liu and colleagues from Shanghai Jiaotong University reported a record-breaking 20.8%power conversion efficiency in organic solar cells(OSCs)with an interpenetrating fibril network active layer morphology,featuring a bulk p-in structure and proper vertical segregation achieved through additive-assisted layer-by-layer deposition.This optimized hierarchical gradient fibrillar morphology and optical management synergistically facilitates exciton diffusion,reduces recombination losses,and enhances light capture capability.This approach not only offers a solution to achieving high-efficiency devices but also demonstrates the potential for commercial applications of OSCs.
