Defect inspection of specular curved surface is a challenging job. Taking steel balls for example, a new method based on reflected pattern integrity recognition is put forward. The specular steel ball surfac...Defect inspection of specular curved surface is a challenging job. Taking steel balls for example, a new method based on reflected pattern integrity recognition is put forward. The specular steel ball surface will totally reflect the patterns when it is placed inside a dome-shaped light source, whose inner wall is modified by patterns with certain regular. Distortion or intermittence of reflected pattern will occur at the defective part, which indicates the pattern has lost its integrity. Based on the integrity analysis of reflected pattern images？ surface defects can be revealed. In this paper, a set of concentric circles are used as the pattern and an image processing algorithm is customized to extract the surface defects. Results show that the proposed method is effective for the specular curved surface defect inspection展开更多
A sensing system is developed to measure the weld pool boundary and pool suoface deformation in gas tungsten arc welding. LaserStrobe technique is used to eliminate the strong arc light inteoference, and specular refl...A sensing system is developed to measure the weld pool boundary and pool suoface deformation in gas tungsten arc welding. LaserStrobe technique is used to eliminate the strong arc light inteoference, and specular reflection from the pool suoface is sensed to describe the relation between the deformed stripes and pool surface depression. Clear images of both the pool boundary and the deformed stripes edges are obtained during gas tungsten arc welding process, which lays foundation for realtime monitoring the pool suoface depression and weld penetration.展开更多
It is well known that the sea return echo contains contributions from at least two scattering mechanisms. In addition to the resonant Bragg scattering, the specular point scattering plays an important role as the inci...It is well known that the sea return echo contains contributions from at least two scattering mechanisms. In addition to the resonant Bragg scattering, the specular point scattering plays an important role as the incidence angle becomes smaller （≥ 20°）. Here, in combination with the Kirchhoff integral equation of scattering field and the stationary phase approximation, analytical expressions for Doppler shift and spectral bandwidth of specular point scattering, which are insensitive to the polarization state, are derived theoretically. For comparison, the simulated results related to the two-scale method （TSM） and the method of moment （MOM） are also presented. It is found that the Doppler shift and the spectral bandwidth given by TSM are insufficient at small incidence angles. However, a comparison between the analytical results and the numerical simulations by MOM in the backscatter configuration shows that our proposed formulas are valid for the specular point scattering case. In this work, the dependences of the predicted results on incidence angle, radar frequency, and wind speed are also discussed. The obtained conclusions seem promising for a better understanding of the Doppler spectra of the specular point scattering fields from time-varying sea surfaces.展开更多
The paper applies a mathematical model[1] for specular reflection to plain-knitted fabrics by using a three-dimensional analysis. Computer simulation of goniophotometric curves is generated based oa the model. Correct...The paper applies a mathematical model[1] for specular reflection to plain-knitted fabrics by using a three-dimensional analysis. Computer simulation of goniophotometric curves is generated based oa the model. Correction factors are introduced by taking into consideration of geometry of the instrument used. Comparison between the simulated and the measured curves of a straight monofilament yarn with various orientation angles is carried out and reasonable agreement has been obtained.展开更多
Top and bottom NiO-pinning spin valves of Si/Ta/NiO/Co/Cu/Co/Ta and Si/Ta/Co/Cu/Co/NiO/Ta were prepared by magnetron sputtering, and X-ray diffraction and giant magnetoresistance （GMR） ratio were measured in the tem...Top and bottom NiO-pinning spin valves of Si/Ta/NiO/Co/Cu/Co/Ta and Si/Ta/Co/Cu/Co/NiO/Ta were prepared by magnetron sputtering, and X-ray diffraction and giant magnetoresistance （GMR） ratio were measured in the temperature range from 5 to 300 K. For the bottom spin valve, the interracial roughness at NiO/Co is much smaller than that of Co/NiO in the top one. The Co/Cu and Cu/Co interfaces have the same roughness in the bottom and the top spin valves. NiO, Co, and Cu layers have （111） preferred orientations in the top one and random orientations in the bottom one. The GMR ratio of the bottom spin valve is larger than that of the top one at all temperatures and their difference increases with decreasing temperature.展开更多
Radio propagation in dense and super dense wireless networks as well as indoor-to-outdoor picocell networks can have multiple line-of-sight or multiple specular components. The performance of a dual-hop decode-and-for...Radio propagation in dense and super dense wireless networks as well as indoor-to-outdoor picocell networks can have multiple line-of-sight or multiple specular components. The performance of a dual-hop decode-and-forward relaying system over multiple specular components fading channels(MSCC)with multiple Rayleigh distributed co-channel interferers in an interference-limited environment is investigated. The MSCC fading model is designed to allow direct and meaningful comparisons to be made between line-of-sight channels and non-line-of-sight channels, with exact parameter correspondences. Comparisons of outage and bit error performance between Nakagami-m/Rayleigh and MSCC/Rayleigh fading environments show that the MSCC model is needed to describe line-of-sight channels that cannot be accurately modeled by the Nakagami-m, or other fading models.展开更多
AIM:To determine the impact of age on the morphology of endothelial cells and central corneal thickness(CCT)in Chinese tree shrew.METHODS:One-hundred and twenty eyes of 60 healthy Chinese tree shrews were studied.Base...AIM:To determine the impact of age on the morphology of endothelial cells and central corneal thickness(CCT)in Chinese tree shrew.METHODS:One-hundred and twenty eyes of 60 healthy Chinese tree shrews were studied.Based on age,the tree shrews were divided into four groups.After general anesthesia,the images of endothelium were acquired using non-contact specular microscope Topcon 3000 P.Eight parameters of corneal endothelial cells were measured by built-in software,including CCT,endothelial cell density(ECD),percent hexagonality(HG%),coeffi cient of variability(CV),size of minimal cell(Smin),size of maximal cell(Smax),average cells size(Savg)and size standard deviation(Ssd).Data were analyzed using STATA software.The differences of eight parameters among groups and correlations with age were analyzed.RESULTS:In all studied animals,the average CCT was 249.6±2.29μm(202-301μm),ECD was 3080.72±460.76 cells/mm^2(1239.6-4047.6 cells/mm^2)and CV was 29.10±7.60(13.6-54.6).CV was significantly different among different groups(P〈0.001).Strong correlation with age was found in ECD,Smax,Savg,Ssd and CV.CONCLUSION:Cornea of Chinese tree shrews had half CCT of human cornea and similar ECD,CV and size of corneal endothelial cells.Young adult tree shrews had higher ECD,HG%and low CV.ECD,Smax,Savg,Ssd and CV correlated with age signifi cantly.展开更多
Specular detection and removal has been a hot topic in the field of computer vision. Most of the existing methods are mainly for color images, but grayscale images are widely used. For a single grayscale image with on...Specular detection and removal has been a hot topic in the field of computer vision. Most of the existing methods are mainly for color images, but grayscale images are widely used. For a single grayscale image with only intensity information, highlight detection and removal becomes a difficult issue. To solve this problem, the single grayscale image highlight detection and removal method based on Markov random field is presented. Each reflection component modeling is estimated by geometric relation of surface normal in diffuse and specular reflection component in the framework of Markov random field. Their maximum a posteriori estimation is calculated under Bayesian formula and highlight area is detected. Finally, image inpainting method based on the BSCB model removes highlights. Experiment reveals that this method can effectively detect grayscale image specular reflection area, improve highlight areas the repair rate.展开更多
Specular hematite concentrate,characterized by predominantly intermediate particle size distribution with minimal ultrafine fractions and a dense,smooth surface texture,exhibits poor granulation performance,resulting ...Specular hematite concentrate,characterized by predominantly intermediate particle size distribution with minimal ultrafine fractions and a dense,smooth surface texture,exhibits poor granulation performance,resulting in a significantly lower proportion in sinter mixtures.The granulation behavior of iron ore blends containing 40%Canadian specular hematite concentrate was systematically investigated,focusing on the effects of nuclei types,adhering fines and binders on the packed bed permeability and adhesion load,and solutions were developed for improving its granulation performance.The results revealed that the granulation effectiveness of specular hematite concentrate is influenced more significantly by the type of adhering fines than by the type of nuclei.Specifically,adhering fines with higher maximum molecular moisture content(e.g.,goethite-type LO-F)and elevated proportions of−0.01 mm ultrafine particles help improve the adhering performance,while particles with higher microhardness(e.g.,magnetite MO-F)hinder adhesion.The addition of quicklime and bentonite as binders further enhances the adhesion,and the specular hematite concentrate adhesion load increases by 4.4%with a combination of quicklime and bentonite,accompanied by 33%enhancement in packed bed permeability.An optimized strategy recommends selecting adhering fines with high molecular water content and low microhardness,combined with binders,to improve sintering efficiency and support low-carbon ironmaking transitions.展开更多
The lack of data is constraining research on the bistatic ballistic target(BT).In the bistatic radar system,the angle between the target axis and the radar line of sight(RLOS)is generally large,which means that the sp...The lack of data is constraining research on the bistatic ballistic target(BT).In the bistatic radar system,the angle between the target axis and the radar line of sight(RLOS)is generally large,which means that the specular scattering center(SSC)is likely to be present with the target's micro-motion.This results in a brief flash in the time-frequency representation(TFR)but has been less frequently reported.We propose a micro-motion echo simulation method with SSC by calculating its position vector and modeling its visible coefficient.Furthermore,the model with four estimated parameters is utilized to optimize the simulated TFR.The simulation results intuitively and numerically agree well with the TFR obtained by electromagnetic calculation.展开更多
Specular highlight detection and removal is a fundamental problem in computer vision and image processing.In this paper,we present an efficient endto-end deep learning model for automatically detecting and removing sp...Specular highlight detection and removal is a fundamental problem in computer vision and image processing.In this paper,we present an efficient endto-end deep learning model for automatically detecting and removing specular highlights in a single image.In particular,an encoder–decoder network is utilized to detect specular highlights,and then a novel Unet-Transformer network performs highlight removal;we append transformer modules instead of feature maps in the Unet architecture.We also introduce a highlight detection module as a mask to guide the removal task.Thus,these two networks can be jointly trained in an effective manner.Thanks to the hierarchical and global properties of the transformer mechanism,our framework is able to establish relationships between continuous self-attention layers,making it possible to directly model the mapping between the diffuse area and the specular highlight area,and reduce indeterminacy within areas containing strong specular highlight reflection.Experiments on public benchmark and real-world images demonstrate that our approach outperforms state-of-the-art methods for both highlight detection and removal tasks.展开更多
Euler-Euler two-fluid model is used to simulate the hydrodynamics of gas-solid flow in a bubbling flu- idized bed with Geldert B particles where the solid property is calculated by applying the kinetic theory of granu...Euler-Euler two-fluid model is used to simulate the hydrodynamics of gas-solid flow in a bubbling flu- idized bed with Geldert B particles where the solid property is calculated by applying the kinetic theory of granular flow （KTGF）. Johnson and Jackson wall boundary condition is used for the particle phase, and different amount of slip between particle and wall is given by varying the specularity coefficient （φ） from 0 to 1. The simulated particle velocity, granular temperature and particle volume fraction are compared to investigate the effect of different wall boundary conditions on the hydrodynamic behavior, Some of the results are also compared with the available experimental data from the literature. It was found that the model predictions are sensitive to the specularity coefficient. The hydrodynamic behavior deviated sig- nificantly for φ = 0 and φ = 0.01 with maximum deviation found at φ = 0 i.e. free-slip condition. However, the overall bed height predicted by all the conditions is similar.展开更多
Photometric stereo is a fundamental technique in computer vision known to produce 3D shape with high accuracy. It uses several input images of a static scene taken from one and the same camera position but under varyi...Photometric stereo is a fundamental technique in computer vision known to produce 3D shape with high accuracy. It uses several input images of a static scene taken from one and the same camera position but under varying illumination. The vast majority of studies in this 3D reconstruction method assume orthographic projection for the camera model.In addition, they mainly use the Lambertian reflectance model as the way that light scatters at surfaces.Thus, providing reliable photometric stereo results from real world objects still remains a challenging task. We address 3D reconstruction by use of a more realistic set of assumptions, combining for the first time the complete Blinn–Phong reflectance model and perspective projection. Furthermore, we compare two different methods of incorporating the perspective projection into our model. Experiments are performed on both synthetic and real world images; the latter do not benefit from laboratory conditions. The results show the high potential of our method even for complex real world applications such as medical endoscopy images which may include many specular highlights.展开更多
The relations between the specular reflection component of the intensity scattered by random surfaces and the height distributions of the surfaces are analyzed theoretically. In the extraction of the height distributi...The relations between the specular reflection component of the intensity scattered by random surfaces and the height distributions of the surfaces are analyzed theoretically. In the extraction of the height distribution, both the phase and the amplitude of the specular wave are required. The measured specular intensity data versus the perpendicular component of the wave vector are used for the retrieval of the phase distribution of the specular wave, in which the Gerchberg-Saxton iterative algorithm is employed, and the characterization of the height distribution of random surfaces is accomplished. In the experiment, two samples with Gaussian and quasi-two level height distributions, respectively, are practically measured and the results of the height probability density function obtained by light scattering method are in good accordance with those by atomic force microscopy. The method of this paper is of important significance for the characterizations and studies of random surfaces.展开更多
Propelled by the rapidly growing demand for function incorporation and performance improvement,various specular components with complex structured surfaces are broadly applied in numerous optical engineering arenas.Fo...Propelled by the rapidly growing demand for function incorporation and performance improvement,various specular components with complex structured surfaces are broadly applied in numerous optical engineering arenas.Form accuracy of the structured surfaces directly impacts the functioning of the specular components.Because the scales of these structures and/or the importance of their functions are usually designed differently,the structures require different measurement demands in scale,lateral resolution,and accuracy.In this paper,a multiscale form measurement technique is proposed based on triple-sensor phase measuring deflectometry for measuring structured specular surfaces.The proposed technique contains two sub-phase measuring deflectometry(PMD)-systems.Each sub-system works as a single segmentation PMD(SPMD)system and is designed to have different measurement scales,lateral resolutions,and accuracies to meet the measurement demands of the targeted surfaces.Two imaging sensors in the proposed technique cover the measured full-scale surface.The specular surface is separated into several continuous segments through algorithms and the spatial relationship of the continuous segments is established based on absolute depth data calculated through the triangular relationship between the two imaging sensors.The third imaging sensor with a long working distance only captures thefield of the small-scale structures and reconstructs the structures based on gradient data to improve the structures’reconstruction resolution and accuracy.In order to make it suitable for portable and embedded measurement,a compact configuration is explored to reduce system volume.Data fusion techniques are also studied to combine the measurement data of the two sub-systems.Experimental results demonstrate the validity of a portable prototype developed based on the proposed technique by measuring a concave mirror with small-scale structures.展开更多
基金Tianjin Research Program of Application Foundation and Advanced Technology(No.14JCYBJC18600,No.14JCZDJC39700)National Key Scientific Instrument and Equipment Development Project(No.2013YQ17053903)
文摘Defect inspection of specular curved surface is a challenging job. Taking steel balls for example, a new method based on reflected pattern integrity recognition is put forward. The specular steel ball surface will totally reflect the patterns when it is placed inside a dome-shaped light source, whose inner wall is modified by patterns with certain regular. Distortion or intermittence of reflected pattern will occur at the defective part, which indicates the pattern has lost its integrity. Based on the integrity analysis of reflected pattern images？ surface defects can be revealed. In this paper, a set of concentric circles are used as the pattern and an image processing algorithm is customized to extract the surface defects. Results show that the proposed method is effective for the specular curved surface defect inspection
文摘A sensing system is developed to measure the weld pool boundary and pool suoface deformation in gas tungsten arc welding. LaserStrobe technique is used to eliminate the strong arc light inteoference, and specular reflection from the pool suoface is sensed to describe the relation between the deformed stripes and pool surface depression. Clear images of both the pool boundary and the deformed stripes edges are obtained during gas tungsten arc welding process, which lays foundation for realtime monitoring the pool suoface depression and weld penetration.
基金Project supported by the Young Scientists Fund of the National Natural Science Foundation of China(Grant No.40906088)the Specialized Research Fund for the Doctoral Program of Higher Education,China(Grant No.200804231021)
文摘It is well known that the sea return echo contains contributions from at least two scattering mechanisms. In addition to the resonant Bragg scattering, the specular point scattering plays an important role as the incidence angle becomes smaller （≥ 20°）. Here, in combination with the Kirchhoff integral equation of scattering field and the stationary phase approximation, analytical expressions for Doppler shift and spectral bandwidth of specular point scattering, which are insensitive to the polarization state, are derived theoretically. For comparison, the simulated results related to the two-scale method （TSM） and the method of moment （MOM） are also presented. It is found that the Doppler shift and the spectral bandwidth given by TSM are insufficient at small incidence angles. However, a comparison between the analytical results and the numerical simulations by MOM in the backscatter configuration shows that our proposed formulas are valid for the specular point scattering case. In this work, the dependences of the predicted results on incidence angle, radar frequency, and wind speed are also discussed. The obtained conclusions seem promising for a better understanding of the Doppler spectra of the specular point scattering fields from time-varying sea surfaces.
文摘The paper applies a mathematical model[1] for specular reflection to plain-knitted fabrics by using a three-dimensional analysis. Computer simulation of goniophotometric curves is generated based oa the model. Correction factors are introduced by taking into consideration of geometry of the instrument used. Comparison between the simulated and the measured curves of a straight monofilament yarn with various orientation angles is carried out and reasonable agreement has been obtained.
基金the National Natural Science Foundation of China （Grant No. 10174014, 60271013, 10321003, 60490290） the State Key Project of Fundamental Research （No. 001CB610602 , 2002CB613504） the Hong Kong RGC Grant （HKUST6165/01P）.
文摘Top and bottom NiO-pinning spin valves of Si/Ta/NiO/Co/Cu/Co/Ta and Si/Ta/Co/Cu/Co/NiO/Ta were prepared by magnetron sputtering, and X-ray diffraction and giant magnetoresistance （GMR） ratio were measured in the temperature range from 5 to 300 K. For the bottom spin valve, the interracial roughness at NiO/Co is much smaller than that of Co/NiO in the top one. The Co/Cu and Cu/Co interfaces have the same roughness in the bottom and the top spin valves. NiO, Co, and Cu layers have （111） preferred orientations in the top one and random orientations in the bottom one. The GMR ratio of the bottom spin valve is larger than that of the top one at all temperatures and their difference increases with decreasing temperature.
基金supported by Fundamental Research Funds for the Central Universities No. 2014JBZ001the NSFC project No.11171016the National Program No.2015AA01A709
文摘Radio propagation in dense and super dense wireless networks as well as indoor-to-outdoor picocell networks can have multiple line-of-sight or multiple specular components. The performance of a dual-hop decode-and-forward relaying system over multiple specular components fading channels(MSCC)with multiple Rayleigh distributed co-channel interferers in an interference-limited environment is investigated. The MSCC fading model is designed to allow direct and meaningful comparisons to be made between line-of-sight channels and non-line-of-sight channels, with exact parameter correspondences. Comparisons of outage and bit error performance between Nakagami-m/Rayleigh and MSCC/Rayleigh fading environments show that the MSCC model is needed to describe line-of-sight channels that cannot be accurately modeled by the Nakagami-m, or other fading models.
基金Supported by the Natural Science Foundation of Yunnan Province[No.2017FE467(-195)]the National Science and Technology Support Program(No.2014BAI01B01)Yunnan Joint Support for National Program(No.2015GA009)
文摘AIM:To determine the impact of age on the morphology of endothelial cells and central corneal thickness(CCT)in Chinese tree shrew.METHODS:One-hundred and twenty eyes of 60 healthy Chinese tree shrews were studied.Based on age,the tree shrews were divided into four groups.After general anesthesia,the images of endothelium were acquired using non-contact specular microscope Topcon 3000 P.Eight parameters of corneal endothelial cells were measured by built-in software,including CCT,endothelial cell density(ECD),percent hexagonality(HG%),coeffi cient of variability(CV),size of minimal cell(Smin),size of maximal cell(Smax),average cells size(Savg)and size standard deviation(Ssd).Data were analyzed using STATA software.The differences of eight parameters among groups and correlations with age were analyzed.RESULTS:In all studied animals,the average CCT was 249.6±2.29μm(202-301μm),ECD was 3080.72±460.76 cells/mm^2(1239.6-4047.6 cells/mm^2)and CV was 29.10±7.60(13.6-54.6).CV was significantly different among different groups(P〈0.001).Strong correlation with age was found in ECD,Smax,Savg,Ssd and CV.CONCLUSION:Cornea of Chinese tree shrews had half CCT of human cornea and similar ECD,CV and size of corneal endothelial cells.Young adult tree shrews had higher ECD,HG%and low CV.ECD,Smax,Savg,Ssd and CV correlated with age signifi cantly.
基金This work was financially supported by National Natural Science Foundation of China (61440025), the research project of science and technology of Heilongjiang provincial education department (12541119).
文摘Specular detection and removal has been a hot topic in the field of computer vision. Most of the existing methods are mainly for color images, but grayscale images are widely used. For a single grayscale image with only intensity information, highlight detection and removal becomes a difficult issue. To solve this problem, the single grayscale image highlight detection and removal method based on Markov random field is presented. Each reflection component modeling is estimated by geometric relation of surface normal in diffuse and specular reflection component in the framework of Markov random field. Their maximum a posteriori estimation is calculated under Bayesian formula and highlight area is detected. Finally, image inpainting method based on the BSCB model removes highlights. Experiment reveals that this method can effectively detect grayscale image specular reflection area, improve highlight areas the repair rate.
基金financial support of the China Baowu Low Carbon Metallurgy Innovation Foundation(BWLCF202216).
文摘Specular hematite concentrate,characterized by predominantly intermediate particle size distribution with minimal ultrafine fractions and a dense,smooth surface texture,exhibits poor granulation performance,resulting in a significantly lower proportion in sinter mixtures.The granulation behavior of iron ore blends containing 40%Canadian specular hematite concentrate was systematically investigated,focusing on the effects of nuclei types,adhering fines and binders on the packed bed permeability and adhesion load,and solutions were developed for improving its granulation performance.The results revealed that the granulation effectiveness of specular hematite concentrate is influenced more significantly by the type of adhering fines than by the type of nuclei.Specifically,adhering fines with higher maximum molecular moisture content(e.g.,goethite-type LO-F)and elevated proportions of−0.01 mm ultrafine particles help improve the adhering performance,while particles with higher microhardness(e.g.,magnetite MO-F)hinder adhesion.The addition of quicklime and bentonite as binders further enhances the adhesion,and the specular hematite concentrate adhesion load increases by 4.4%with a combination of quicklime and bentonite,accompanied by 33%enhancement in packed bed permeability.An optimized strategy recommends selecting adhering fines with high molecular water content and low microhardness,combined with binders,to improve sintering efficiency and support low-carbon ironmaking transitions.
基金supported by the National Natural Science Foundation of China(Nos.62071475 and 62401580).
文摘The lack of data is constraining research on the bistatic ballistic target(BT).In the bistatic radar system,the angle between the target axis and the radar line of sight(RLOS)is generally large,which means that the specular scattering center(SSC)is likely to be present with the target's micro-motion.This results in a brief flash in the time-frequency representation(TFR)but has been less frequently reported.We propose a micro-motion echo simulation method with SSC by calculating its position vector and modeling its visible coefficient.Furthermore,the model with four estimated parameters is utilized to optimize the simulated TFR.The simulation results intuitively and numerically agree well with the TFR obtained by electromagnetic calculation.
基金This work was partially funded by the National Natural Science Foundation of China(U21A20515,62172416,62172415,U2003109)Youth Innovation Promotion Association of the Chinese Academy of Sciences(2022131).
文摘Specular highlight detection and removal is a fundamental problem in computer vision and image processing.In this paper,we present an efficient endto-end deep learning model for automatically detecting and removing specular highlights in a single image.In particular,an encoder–decoder network is utilized to detect specular highlights,and then a novel Unet-Transformer network performs highlight removal;we append transformer modules instead of feature maps in the Unet architecture.We also introduce a highlight detection module as a mask to guide the removal task.Thus,these two networks can be jointly trained in an effective manner.Thanks to the hierarchical and global properties of the transformer mechanism,our framework is able to establish relationships between continuous self-attention layers,making it possible to directly model the mapping between the diffuse area and the specular highlight area,and reduce indeterminacy within areas containing strong specular highlight reflection.Experiments on public benchmark and real-world images demonstrate that our approach outperforms state-of-the-art methods for both highlight detection and removal tasks.
基金the support of Department of Science&Technology(Govt.of India)through PURSE scheme
文摘Euler-Euler two-fluid model is used to simulate the hydrodynamics of gas-solid flow in a bubbling flu- idized bed with Geldert B particles where the solid property is calculated by applying the kinetic theory of granular flow （KTGF）. Johnson and Jackson wall boundary condition is used for the particle phase, and different amount of slip between particle and wall is given by varying the specularity coefficient （φ） from 0 to 1. The simulated particle velocity, granular temperature and particle volume fraction are compared to investigate the effect of different wall boundary conditions on the hydrodynamic behavior, Some of the results are also compared with the available experimental data from the literature. It was found that the model predictions are sensitive to the specularity coefficient. The hydrodynamic behavior deviated sig- nificantly for φ = 0 and φ = 0.01 with maximum deviation found at φ = 0 i.e. free-slip condition. However, the overall bed height predicted by all the conditions is similar.
基金supported by the Deutsche Forschungsgemeinschaft under grant number BR2245/4–1
文摘Photometric stereo is a fundamental technique in computer vision known to produce 3D shape with high accuracy. It uses several input images of a static scene taken from one and the same camera position but under varying illumination. The vast majority of studies in this 3D reconstruction method assume orthographic projection for the camera model.In addition, they mainly use the Lambertian reflectance model as the way that light scatters at surfaces.Thus, providing reliable photometric stereo results from real world objects still remains a challenging task. We address 3D reconstruction by use of a more realistic set of assumptions, combining for the first time the complete Blinn–Phong reflectance model and perspective projection. Furthermore, we compare two different methods of incorporating the perspective projection into our model. Experiments are performed on both synthetic and real world images; the latter do not benefit from laboratory conditions. The results show the high potential of our method even for complex real world applications such as medical endoscopy images which may include many specular highlights.
基金This work was supported by the National Natural Science Foundation of China (Grant No. 69978012)the National Key Basic Research Special Foundation (NKBRSF) of China (Grant No. G1999075200)
文摘The relations between the specular reflection component of the intensity scattered by random surfaces and the height distributions of the surfaces are analyzed theoretically. In the extraction of the height distribution, both the phase and the amplitude of the specular wave are required. The measured specular intensity data versus the perpendicular component of the wave vector are used for the retrieval of the phase distribution of the specular wave, in which the Gerchberg-Saxton iterative algorithm is employed, and the characterization of the height distribution of random surfaces is accomplished. In the experiment, two samples with Gaussian and quasi-two level height distributions, respectively, are practically measured and the results of the height probability density function obtained by light scattering method are in good accordance with those by atomic force microscopy. The method of this paper is of important significance for the characterizations and studies of random surfaces.
基金supported by the UK’s Engineering and Physical Sciences Research Council(EPSRC)funding of“The EPSRC Future Advanced Metrology Hub”(EP/P006930/1)the funding of“A Multiscale Digital Twin-Driven Smart Manufacturing System for High Value-Added Products”(EP/T024844/1).
文摘Propelled by the rapidly growing demand for function incorporation and performance improvement,various specular components with complex structured surfaces are broadly applied in numerous optical engineering arenas.Form accuracy of the structured surfaces directly impacts the functioning of the specular components.Because the scales of these structures and/or the importance of their functions are usually designed differently,the structures require different measurement demands in scale,lateral resolution,and accuracy.In this paper,a multiscale form measurement technique is proposed based on triple-sensor phase measuring deflectometry for measuring structured specular surfaces.The proposed technique contains two sub-phase measuring deflectometry(PMD)-systems.Each sub-system works as a single segmentation PMD(SPMD)system and is designed to have different measurement scales,lateral resolutions,and accuracies to meet the measurement demands of the targeted surfaces.Two imaging sensors in the proposed technique cover the measured full-scale surface.The specular surface is separated into several continuous segments through algorithms and the spatial relationship of the continuous segments is established based on absolute depth data calculated through the triangular relationship between the two imaging sensors.The third imaging sensor with a long working distance only captures thefield of the small-scale structures and reconstructs the structures based on gradient data to improve the structures’reconstruction resolution and accuracy.In order to make it suitable for portable and embedded measurement,a compact configuration is explored to reduce system volume.Data fusion techniques are also studied to combine the measurement data of the two sub-systems.Experimental results demonstrate the validity of a portable prototype developed based on the proposed technique by measuring a concave mirror with small-scale structures.
