Synthetic aperture radar (SAR) is theoretically based on uniform rectilinear motion. But in real situations, the flight cannot be kept in a uniform rectilinear motion due to many factors. Therefore, the motion compens...Synthetic aperture radar (SAR) is theoretically based on uniform rectilinear motion. But in real situations, the flight cannot be kept in a uniform rectilinear motion due to many factors. Therefore, the motion compensation is needed to achieve the high-resolution image. This paper proposes an improved motion information sensor (MIS)-based on global navigation statellite system (GNSS) and strapdown inertial navigation system (SINS) for SAR motion compensation. MIS can provide the long-term absolute accuracy, and the short-term high relative accuracy during SAR imaging. Many issues related to MIS, such as system design, error models and navigation algorithms, are stressed. Experimental results show that MIS can provide accurate navigation information (position, velocity and attitude) to meet the requirements of SAR motion compensation. Especially, MIS is suitable for the case: the accuracy of airplane master inertial navigation system is too low or not configured.展开更多
Both the grand canonical Monte Carlo and molecular dynamics simulation methods are used to investigate the adsorption and diffusion of carbon dioxide confined in a 1.86 nm slit carbon pore at 4 temperatures from subcr...Both the grand canonical Monte Carlo and molecular dynamics simulation methods are used to investigate the adsorption and diffusion of carbon dioxide confined in a 1.86 nm slit carbon pore at 4 temperatures from subcritical (120 K) to supercritical (313 K) conditions. Layering transition, capillary condensation and adsorption hysteresis are found at 120 K. The microstructure of carbon dioxide fluid in the slit carbon pore is analyzed. The diffusion coefficients of carbon dioxide parallel to the slit wall are significantly larger than those normal to the slit wall.展开更多
PU （phase unwrapping） is the key step and important problem in DEM （digital elevation model） extraction and the measurement of surface deformation of InSAR （Interferometric synthetic aperture radar）. The CKFPUA ...PU （phase unwrapping） is the key step and important problem in DEM （digital elevation model） extraction and the measurement of surface deformation of InSAR （Interferometric synthetic aperture radar）. The CKFPUA （conventional Kalman filter phase unwrapping algorithm） can obtain reliable results in the flat terrain areas, but it caused error transmission not making the accurate inversion of surface deformation information in the steep terrain. Considering this situation, so it needs to introduce topographic information for guiding phase unwrapping. Here the 90 m resolution DEM data have been used and it is obtained by SRTM （shuttle radar topography mission） measured jointly by NASA （National Aeronautics and Space Administration） and NIMA （National Imaging Mapping Agency） of U.S. Department of Defense. This paper presents a SD-KFPUA （Kalman filter phase unwrapping algorithm） based on SRTM DEM. With SRTM DEM directing InSAR image to implement phase unwrapping, the speed and accuracy are improved. By analyzing with the conventional Kalman filter phase unwrapping algorithms, it is shown that the proposed method can achieve good results in particular to improve unwrapping accuracy in the low coherence region.展开更多
A series of porous resins (PYR) with different content of pyridyl group were prepared,and their physical structure and adsorption properties on the stevia glycosides werestudied in detail. Afler the selective adsorpti...A series of porous resins (PYR) with different content of pyridyl group were prepared,and their physical structure and adsorption properties on the stevia glycosides werestudied in detail. Afler the selective adsorption of PYR resins, the rebaudioside A couldbe separated hem the other components of the stevia glycosides, and a new methodforobtaining pure rebaudioside A is reported.展开更多
A reliability based analysis method for a drilled shaft stabilized slope system is presented in this paper. The drilled shaft stabilization mechanisms for the slope were treated as the drilled shaft induced soil archi...A reliability based analysis method for a drilled shaft stabilized slope system is presented in this paper. The drilled shaft stabilization mechanisms for the slope were treated as the drilled shaft induced soil arching, which was quantified by the load transfer factor in the limited equilibrium analysis. However, due to the inherent uncertainties of the soil properties and the model error of the semi-empirical load transfer equation, an extension modification of the deterministic method into a probabilistic method is developed in this paper. The MCS （Monte Carlo simulation） with log-normal random variables has been employed to calculate the probability of failure （Pf） for the drilled shafts/slope system. The developed theories were coded into a computer program for analyzing complex slope geometry and slope profile conditions. Finally, a case study has been performed to illustrate the application analysis of the developed probability approach in drilled shafts/slope system.展开更多
We examine the high density limit of the adsorption isotherms of hydrogen on MOF-5. The isotherms are calculated using quantum GCMC simulations over the pressure range： 0-150 atm （1 atm = 1.01325 ~ 105 Pa） in the s...We examine the high density limit of the adsorption isotherms of hydrogen on MOF-5. The isotherms are calculated using quantum GCMC simulations over the pressure range： 0-150 atm （1 atm = 1.01325 ~ 105 Pa） in the subcritical and supercritical state at 30, 50, 77, 113, 196 and 296 K. The fluid phase density in the pores for each temper- ature is calculated and shown to reach values higher than normal liquid density. The fluid phase density obtained at 30 K is observed to correspond to a highly compressed liquid. The radial distribution function of the adsorbed phase at 30 and 50 K are calculated. The adsorption isotherms are compared with available experimental data at 30, 50, 77 and 298 K.展开更多
Two-phase flow in two digital cores is simulated by the color-gradient lattice Boltzmann method.This model can be applied totwo-phase flow with high-density ratio(on order of 1000).The first digital core is an artific...Two-phase flow in two digital cores is simulated by the color-gradient lattice Boltzmann method.This model can be applied totwo-phase flow with high-density ratio(on order of 1000).The first digital core is an artificial sandstone core,and itsthree-dimensional gray model is obtained by Micro-CT scanning.The gray scale images are segmented into discrete phases(solid particles and pore space) by the Otsu algorithm.The second one is a digital core of shale,which is reconstructed usingMarkov Chain Monte Carlo method with segmented SEM scanning image as input.The wettability of solid wall and relativepermeability of a cylindrical tube are simulated to verify the model.In the simulations of liquid and gas two phase flow in digital cores,density ratios of 100,200,500 and 1000 between liquid and gas are chosen.Based on the gas distribution in the digital core at different times,it is found that the fingering phenomenon is more salient at high density ratio.With the density ratioincreasing,the displacement efficiency decreases.Besides,due to numerous small pores in the shale,the displacement efficiency is over 20% less than that in the artificial sandstone and the difference is even about 30% when density ratio is greaterthan 500.As the density ratio increases,the gas saturation decreases in big pores,and even reaches zero in some small pores orbig pores with small throats.Residual liquid mainly distributes in the small pores and the edge of big pores due to the wettability of liquid.Liquid recovery can be enhanced effectively by decreasing its viscosity.展开更多
文摘Synthetic aperture radar (SAR) is theoretically based on uniform rectilinear motion. But in real situations, the flight cannot be kept in a uniform rectilinear motion due to many factors. Therefore, the motion compensation is needed to achieve the high-resolution image. This paper proposes an improved motion information sensor (MIS)-based on global navigation statellite system (GNSS) and strapdown inertial navigation system (SINS) for SAR motion compensation. MIS can provide the long-term absolute accuracy, and the short-term high relative accuracy during SAR imaging. Many issues related to MIS, such as system design, error models and navigation algorithms, are stressed. Experimental results show that MIS can provide accurate navigation information (position, velocity and attitude) to meet the requirements of SAR motion compensation. Especially, MIS is suitable for the case: the accuracy of airplane master inertial navigation system is too low or not configured.
基金Supported by the State Key Fundamental Research Plan of China (No. G2000048010) and National High Performance Computing Foundation of China (No. 99118).
文摘Both the grand canonical Monte Carlo and molecular dynamics simulation methods are used to investigate the adsorption and diffusion of carbon dioxide confined in a 1.86 nm slit carbon pore at 4 temperatures from subcritical (120 K) to supercritical (313 K) conditions. Layering transition, capillary condensation and adsorption hysteresis are found at 120 K. The microstructure of carbon dioxide fluid in the slit carbon pore is analyzed. The diffusion coefficients of carbon dioxide parallel to the slit wall are significantly larger than those normal to the slit wall.
基金Acknowledgments The research is supported by the National Science Foundation of China （40874001） and National 863 plans projects of China （2009AA12Z147）. The authors would like to express thanks to ESA （European Space Agency） for providing ENVISAT satellite data.
文摘PU （phase unwrapping） is the key step and important problem in DEM （digital elevation model） extraction and the measurement of surface deformation of InSAR （Interferometric synthetic aperture radar）. The CKFPUA （conventional Kalman filter phase unwrapping algorithm） can obtain reliable results in the flat terrain areas, but it caused error transmission not making the accurate inversion of surface deformation information in the steep terrain. Considering this situation, so it needs to introduce topographic information for guiding phase unwrapping. Here the 90 m resolution DEM data have been used and it is obtained by SRTM （shuttle radar topography mission） measured jointly by NASA （National Aeronautics and Space Administration） and NIMA （National Imaging Mapping Agency） of U.S. Department of Defense. This paper presents a SD-KFPUA （Kalman filter phase unwrapping algorithm） based on SRTM DEM. With SRTM DEM directing InSAR image to implement phase unwrapping, the speed and accuracy are improved. By analyzing with the conventional Kalman filter phase unwrapping algorithms, it is shown that the proposed method can achieve good results in particular to improve unwrapping accuracy in the low coherence region.
文摘A series of porous resins (PYR) with different content of pyridyl group were prepared,and their physical structure and adsorption properties on the stevia glycosides werestudied in detail. Afler the selective adsorption of PYR resins, the rebaudioside A couldbe separated hem the other components of the stevia glycosides, and a new methodforobtaining pure rebaudioside A is reported.
文摘A reliability based analysis method for a drilled shaft stabilized slope system is presented in this paper. The drilled shaft stabilization mechanisms for the slope were treated as the drilled shaft induced soil arching, which was quantified by the load transfer factor in the limited equilibrium analysis. However, due to the inherent uncertainties of the soil properties and the model error of the semi-empirical load transfer equation, an extension modification of the deterministic method into a probabilistic method is developed in this paper. The MCS （Monte Carlo simulation） with log-normal random variables has been employed to calculate the probability of failure （Pf） for the drilled shafts/slope system. The developed theories were coded into a computer program for analyzing complex slope geometry and slope profile conditions. Finally, a case study has been performed to illustrate the application analysis of the developed probability approach in drilled shafts/slope system.
基金support of Natural Sciences and Engineering Research Council of Canadaof the H2Can strategic network and the Centre québécois sur les matériaux fonctionnels(CQMF/Fonds de recherche du Que′bec-Nature et technologies)
文摘We examine the high density limit of the adsorption isotherms of hydrogen on MOF-5. The isotherms are calculated using quantum GCMC simulations over the pressure range： 0-150 atm （1 atm = 1.01325 ~ 105 Pa） in the subcritical and supercritical state at 30, 50, 77, 113, 196 and 296 K. The fluid phase density in the pores for each temper- ature is calculated and shown to reach values higher than normal liquid density. The fluid phase density obtained at 30 K is observed to correspond to a highly compressed liquid. The radial distribution function of the adsorbed phase at 30 and 50 K are calculated. The adsorption isotherms are compared with available experimental data at 30, 50, 77 and 298 K.
基金supported by the National Natural Science Foundation of China(Grant No.51234007,51404291)Program for Changjiang Scholars and Innovative Research Team in University(Grant No.IRT1294)Introducing Talents of Discipline to Universities(Grant No.B08028)
文摘Two-phase flow in two digital cores is simulated by the color-gradient lattice Boltzmann method.This model can be applied totwo-phase flow with high-density ratio(on order of 1000).The first digital core is an artificial sandstone core,and itsthree-dimensional gray model is obtained by Micro-CT scanning.The gray scale images are segmented into discrete phases(solid particles and pore space) by the Otsu algorithm.The second one is a digital core of shale,which is reconstructed usingMarkov Chain Monte Carlo method with segmented SEM scanning image as input.The wettability of solid wall and relativepermeability of a cylindrical tube are simulated to verify the model.In the simulations of liquid and gas two phase flow in digital cores,density ratios of 100,200,500 and 1000 between liquid and gas are chosen.Based on the gas distribution in the digital core at different times,it is found that the fingering phenomenon is more salient at high density ratio.With the density ratioincreasing,the displacement efficiency decreases.Besides,due to numerous small pores in the shale,the displacement efficiency is over 20% less than that in the artificial sandstone and the difference is even about 30% when density ratio is greaterthan 500.As the density ratio increases,the gas saturation decreases in big pores,and even reaches zero in some small pores orbig pores with small throats.Residual liquid mainly distributes in the small pores and the edge of big pores due to the wettability of liquid.Liquid recovery can be enhanced effectively by decreasing its viscosity.
