The optimal imaging time selection of ship targets for shore-based inverse synthetic aperture radar (ISAR) in high sea conditions is investigated. The optimal imaging time includes opti- mal imaging instants and opt...The optimal imaging time selection of ship targets for shore-based inverse synthetic aperture radar (ISAR) in high sea conditions is investigated. The optimal imaging time includes opti- mal imaging instants and optimal imaging duration. A novel method for optimal imaging instants selection based on the estimation of the Doppler centroid frequencies (DCFs) of a series of images obtained over continuous short durations is proposed. Combined with the optimal imaging duration selection scheme using the image contrast maximization criteria, this method can provide the ship images with the highest focus. Simulated and real data pro- cessing results verify the effectiveness of the proposed imaging method.展开更多
A wide range of techniques has been developed to image biological samples at high spatial and temporal resolution.In this paper,we report recent results from deep-UV confocal fAuorescence microscopy to image inherent ...A wide range of techniques has been developed to image biological samples at high spatial and temporal resolution.In this paper,we report recent results from deep-UV confocal fAuorescence microscopy to image inherent emission from fuorophores such as tryptophan,and structured ilumination microscopy(SIM)of biological materials.One motivation for developing deep-UV fhuorescence imaging and SIM is to provide methods to complement our measurements in the emerging field of X-ray coherent diffractive imaging.展开更多
In our previous work, a novel algorithm to perform robust pose estimation was presented. The pose was estimated using points on the object to regions on image correspondence. The laboratory experiments conducted in th...In our previous work, a novel algorithm to perform robust pose estimation was presented. The pose was estimated using points on the object to regions on image correspondence. The laboratory experiments conducted in the previous work showed that the accuracy of the estimated pose was over 99% for position and 84% for orientation estimations respectively. However, for larger objects, the algorithm requires a high number of points to achieve the same accuracy. The requirement of higher number of points makes the algorithm, computationally intensive resulting in the algorithm infeasible for real-time computer vision applications. In this paper, the algorithm is parallelized to run on NVIDIA GPUs. The results indicate that even for objects having more than 2000 points, the algorithm can estimate the pose in real time for each frame of high-resolution videos.展开更多
The electrical capacitance tomography (ECT) with neural network multi-criteria image reconstruction technique (NN-MOIRT) is developed for real time imaging of a gas-solid fluidized bed using FCC particles with eva...The electrical capacitance tomography (ECT) with neural network multi-criteria image reconstruction technique (NN-MOIRT) is developed for real time imaging of a gas-solid fluidized bed using FCC particles with evaporative liquid injection. Some aspects of the fundamental characteristics of the gas-solid flow with evaporative liquid injection including real time and time averaged cross-sectional solids concentration distributions, the cross-sectional solids concentration fluctuations and the quasi-3D flow structures are studied. A two-region model and a direct image calculation are proposed to describe the dynamic behavior in both the bubble/void phase and the emulsion phase based on the tomographic images. Comparisons are made between the fundamental behaviors of the gas-solid flows with and without evaporative liquid injection for various gas velocities ranging from bubbling to turbulent fluidization regimes. Significant differences are observed in the behavior of the gas-solid flow with the evaporative liquid injection compared to the fluidized bed without liquid injection.展开更多
Satellite-based wetland mapping faces challenges due to the high spatial heterogeneity and dynamic characteristics of seasonal wetlands.Although normalized difference vegetation index(NDVI)time series(NTS)shows great ...Satellite-based wetland mapping faces challenges due to the high spatial heterogeneity and dynamic characteristics of seasonal wetlands.Although normalized difference vegetation index(NDVI)time series(NTS)shows great potential in land cover mapping and crop classification,the effectiveness of various NTS with different spatial and temporal resolution has not been evaluated for seasonal wetland classification.To address this issue,we conducted comparisons of those NTS,including the moderate-resolution imaging spectroradiometer(MODIS)NTS with 500 m resolution,NTS fused with MODIS and Landsat data(MOD_LC8-NTS),and HJ-1 NDVI compositions(HJ-1-NTS)with finer resolution,for wetland classification of Poyang Lake.Results showed the following:(1)the NTS with finer resolution was more effective in the classification of seasonal wetlands than that of the MODIS-NTS with 500-m resolution and(2)generally,the HJ-1-NTS performed better than that of the fused NTS,with an overall accuracy of 88.12%for HJ-1-NTS and 83.09%for the MOD_LC8-NTS.Future work should focus on the construction of satellite image time series oriented to highly dynamic characteristics of seasonal wetlands.This study will provide useful guidance for seasonal wetland classification,and benefit the improvements of spatiotemporal fusion models.展开更多
Large-eddy simulation(LES) with fully resolved rotor method(FRM) is applied to explore the turbulent wake flow characteristics and vortex evolution laws of a two-bladed horizontal-axis wind turbine. Relevant wind tunn...Large-eddy simulation(LES) with fully resolved rotor method(FRM) is applied to explore the turbulent wake flow characteristics and vortex evolution laws of a two-bladed horizontal-axis wind turbine. Relevant wind tunnel experiments have been done based on time resolved particle image velocimetry(TRPIV) technique. The simulation results are validated by the experimental data and they are in good agreement. The axial average velocity, turbulent kinetic energy, shear Reynolds stress, and vortex structure of the wind turbine wake are analyzed based on the comparison of LES results and experimental data. It is observed that the wake diameter of wind turbine enlarges with the increase of tip speed ratio(TSR). Turbulent kinetic energy meets its minimum value when x/R=2.0. Shear Reynolds stress appears a positive peak in the near wake when x/R<2.0, and the value of shear Reynolds stress decreases along the axial direction. The blade tip vortex dissipates more quickly than the central vortex in the wind turbine wake, and the gradient of the relationship curve between the blade tip vortex core position and the vortex age decreases as the TSR increases. With the increase of TSR, the thrust coefficient increases, and the power coefficient increases first and then decreases.The present work proves that LES with FRM could calculate wind turbine turbulent wake flow with a high accuracy.展开更多
Let X(t) be an N parameter generalized Lévy sheet taking values in Rd with a lower index α,sR = {(s,t] = ∏iN=1(si,ti],si < ti},E(x,Q) = {t ∈ Q: X(t) = x},Q ∈ sR be the level set of X at x and X(Q) = {x: (E)t...Let X(t) be an N parameter generalized Lévy sheet taking values in Rd with a lower index α,sR = {(s,t] = ∏iN=1(si,ti],si < ti},E(x,Q) = {t ∈ Q: X(t) = x},Q ∈ sR be the level set of X at x and X(Q) = {x: (E)t ∈ Q such that X(t) = x} be the image of X on Q.In this paper,the problems of the existence and increment size of the local times for X(t) are studied.In addition,the Hausdorff dimension of E(x,Q) and the upper bound of a uniform dimension for X(Q) are also established.展开更多
Imaging sea-bed sediment layers from echo data, which are collected by a system composed of a seismic profiler and a hydrophone streamer towed behind the profiler, is a way to reconstruct the structure of sedimeat lay...Imaging sea-bed sediment layers from echo data, which are collected by a system composed of a seismic profiler and a hydrophone streamer towed behind the profiler, is a way to reconstruct the structure of sedimeat layers with acoustic wav equation. The equation which describes the wave propagation is used for backward extrapolation of echo data observed at sea surface. When the medium is homogeneous or horizontally layered, time imaging approach is valid. However, in the case where a considerable lateral variation in velocity exists, the image section processed with the time approach does not represent the real structure, because of distortions caused by thin-lens effect similar as in optics. In this case, depth imaging approach must be used for both the time-shift correction of refraction terms and the convergence of diffractions simultaneously as wavefields are downward continued. As a result, the good image can be derived to determine the structure of sea-bed sediment layers.展开更多
Streak tube imaging lidar (STIL) is an active imaging system that has a high range accuracy with tile use of a pulsed lapser transmitter and streak tube receiver to produce 3D range inlages. This work investigates t...Streak tube imaging lidar (STIL) is an active imaging system that has a high range accuracy with tile use of a pulsed lapser transmitter and streak tube receiver to produce 3D range inlages. This work investigates the effect of tile time bin size oil the range accuracy of STIL systems based on the peak detection algorithm. The nunlerical simulation indicates that the time bin size has a significant effect on the range aceuracy, resulting in a modified analytical estimate of the range error. An indoor experilnent with a planar target is carried out to validate the theory that shows the linear relationship between tile range error and the time bin size. Finer 3D depth iinages of a fist model are acquired by using a smaller time bin size and the best range error of 0.003 In is achieved with the optimal time bin size of 0.07 ns.展开更多
基金supported by the Innovation Foundation for Scientific Research Base(NJ20140008NJ20150018)+1 种基金the Aeronautical Science Foundation of China(20132052035)the National Defense Basic Scientific Research(B2520110008)
文摘The optimal imaging time selection of ship targets for shore-based inverse synthetic aperture radar (ISAR) in high sea conditions is investigated. The optimal imaging time includes opti- mal imaging instants and optimal imaging duration. A novel method for optimal imaging instants selection based on the estimation of the Doppler centroid frequencies (DCFs) of a series of images obtained over continuous short durations is proposed. Combined with the optimal imaging duration selection scheme using the image contrast maximization criteria, this method can provide the ship images with the highest focus. Simulated and real data pro- cessing results verify the effectiveness of the proposed imaging method.
基金We acknowledge the support of the Australian Research Council for the Center of Excellence for Coherent X-ray Science(CE0561787).
文摘A wide range of techniques has been developed to image biological samples at high spatial and temporal resolution.In this paper,we report recent results from deep-UV confocal fAuorescence microscopy to image inherent emission from fuorophores such as tryptophan,and structured ilumination microscopy(SIM)of biological materials.One motivation for developing deep-UV fhuorescence imaging and SIM is to provide methods to complement our measurements in the emerging field of X-ray coherent diffractive imaging.
文摘In our previous work, a novel algorithm to perform robust pose estimation was presented. The pose was estimated using points on the object to regions on image correspondence. The laboratory experiments conducted in the previous work showed that the accuracy of the estimated pose was over 99% for position and 84% for orientation estimations respectively. However, for larger objects, the algorithm requires a high number of points to achieve the same accuracy. The requirement of higher number of points makes the algorithm, computationally intensive resulting in the algorithm infeasible for real-time computer vision applications. In this paper, the algorithm is parallelized to run on NVIDIA GPUs. The results indicate that even for objects having more than 2000 points, the algorithm can estimate the pose in real time for each frame of high-resolution videos.
基金support of the National Science Foundation on the development of the ECT used in this study is gratefully acknowledged
文摘The electrical capacitance tomography (ECT) with neural network multi-criteria image reconstruction technique (NN-MOIRT) is developed for real time imaging of a gas-solid fluidized bed using FCC particles with evaporative liquid injection. Some aspects of the fundamental characteristics of the gas-solid flow with evaporative liquid injection including real time and time averaged cross-sectional solids concentration distributions, the cross-sectional solids concentration fluctuations and the quasi-3D flow structures are studied. A two-region model and a direct image calculation are proposed to describe the dynamic behavior in both the bubble/void phase and the emulsion phase based on the tomographic images. Comparisons are made between the fundamental behaviors of the gas-solid flows with and without evaporative liquid injection for various gas velocities ranging from bubbling to turbulent fluidization regimes. Significant differences are observed in the behavior of the gas-solid flow with the evaporative liquid injection compared to the fluidized bed without liquid injection.
基金the Major Special Project-the China High-Resolution Earth Observation System[grant number 30-Y20A37-9003-15/17]The National Natural Science Foundation of China[grant number 41271423].
文摘Satellite-based wetland mapping faces challenges due to the high spatial heterogeneity and dynamic characteristics of seasonal wetlands.Although normalized difference vegetation index(NDVI)time series(NTS)shows great potential in land cover mapping and crop classification,the effectiveness of various NTS with different spatial and temporal resolution has not been evaluated for seasonal wetland classification.To address this issue,we conducted comparisons of those NTS,including the moderate-resolution imaging spectroradiometer(MODIS)NTS with 500 m resolution,NTS fused with MODIS and Landsat data(MOD_LC8-NTS),and HJ-1 NDVI compositions(HJ-1-NTS)with finer resolution,for wetland classification of Poyang Lake.Results showed the following:(1)the NTS with finer resolution was more effective in the classification of seasonal wetlands than that of the MODIS-NTS with 500-m resolution and(2)generally,the HJ-1-NTS performed better than that of the fused NTS,with an overall accuracy of 88.12%for HJ-1-NTS and 83.09%for the MOD_LC8-NTS.Future work should focus on the construction of satellite image time series oriented to highly dynamic characteristics of seasonal wetlands.This study will provide useful guidance for seasonal wetland classification,and benefit the improvements of spatiotemporal fusion models.
基金supported by the Foundation of Key Laboratory for Wind and Solar Power Energy Utilization Technology,Ministry of Education and Inner Mongolia Construction(Grant No.201503)the National Natural Science Foundation of China(Grant No.51346006)
文摘Large-eddy simulation(LES) with fully resolved rotor method(FRM) is applied to explore the turbulent wake flow characteristics and vortex evolution laws of a two-bladed horizontal-axis wind turbine. Relevant wind tunnel experiments have been done based on time resolved particle image velocimetry(TRPIV) technique. The simulation results are validated by the experimental data and they are in good agreement. The axial average velocity, turbulent kinetic energy, shear Reynolds stress, and vortex structure of the wind turbine wake are analyzed based on the comparison of LES results and experimental data. It is observed that the wake diameter of wind turbine enlarges with the increase of tip speed ratio(TSR). Turbulent kinetic energy meets its minimum value when x/R=2.0. Shear Reynolds stress appears a positive peak in the near wake when x/R<2.0, and the value of shear Reynolds stress decreases along the axial direction. The blade tip vortex dissipates more quickly than the central vortex in the wind turbine wake, and the gradient of the relationship curve between the blade tip vortex core position and the vortex age decreases as the TSR increases. With the increase of TSR, the thrust coefficient increases, and the power coefficient increases first and then decreases.The present work proves that LES with FRM could calculate wind turbine turbulent wake flow with a high accuracy.
基金This work was partially supported by the National Natural Science Foundation of China(Grant No.10571159)China Postdoctoral Science Foundation.
文摘Let X(t) be an N parameter generalized Lévy sheet taking values in Rd with a lower index α,sR = {(s,t] = ∏iN=1(si,ti],si < ti},E(x,Q) = {t ∈ Q: X(t) = x},Q ∈ sR be the level set of X at x and X(Q) = {x: (E)t ∈ Q such that X(t) = x} be the image of X on Q.In this paper,the problems of the existence and increment size of the local times for X(t) are studied.In addition,the Hausdorff dimension of E(x,Q) and the upper bound of a uniform dimension for X(Q) are also established.
文摘Imaging sea-bed sediment layers from echo data, which are collected by a system composed of a seismic profiler and a hydrophone streamer towed behind the profiler, is a way to reconstruct the structure of sedimeat layers with acoustic wav equation. The equation which describes the wave propagation is used for backward extrapolation of echo data observed at sea surface. When the medium is homogeneous or horizontally layered, time imaging approach is valid. However, in the case where a considerable lateral variation in velocity exists, the image section processed with the time approach does not represent the real structure, because of distortions caused by thin-lens effect similar as in optics. In this case, depth imaging approach must be used for both the time-shift correction of refraction terms and the convergence of diffractions simultaneously as wavefields are downward continued. As a result, the good image can be derived to determine the structure of sea-bed sediment layers.
基金supported by the National Key Scientific Instrument and Equipment Development Projects of China under Grant No.2012YQ040164
文摘Streak tube imaging lidar (STIL) is an active imaging system that has a high range accuracy with tile use of a pulsed lapser transmitter and streak tube receiver to produce 3D range inlages. This work investigates the effect of tile time bin size oil the range accuracy of STIL systems based on the peak detection algorithm. The nunlerical simulation indicates that the time bin size has a significant effect on the range aceuracy, resulting in a modified analytical estimate of the range error. An indoor experilnent with a planar target is carried out to validate the theory that shows the linear relationship between tile range error and the time bin size. Finer 3D depth iinages of a fist model are acquired by using a smaller time bin size and the best range error of 0.003 In is achieved with the optimal time bin size of 0.07 ns.