The original nonlinear chirp scaling(NCS) algorithm was extended for high precision processing of the highly squinted curvilinear trajectory synthetic aperture radar(CTSAR).Based on the analysis of slant range model a...The original nonlinear chirp scaling(NCS) algorithm was extended for high precision processing of the highly squinted curvilinear trajectory synthetic aperture radar(CTSAR).Based on the analysis of slant range model and the frequency spectrum characteristics of the echo signal,a novel nonlinear chirp scaling function and more complex phase compensation factors with both velocity and acceleration parameters were proposed in the new algorithm for accommodation to curvilinear trajectory.The processing flow and computational complexity of modified NCS algorithm were fundamentally the same as the original NCS algorithm.However,the higher order phase compensation,range cell migration correction(RCMC) and range-variant secondary range compression(SRC) caused by the non-linear aperture and the severe range-azimuth coupling were accomplished accurately and efficiently without interpolation.Simulation results show that data acquired with a curvilinear aperture and a squint angle up to about 50° for X-band can be processed with no evident degradation of impulse response function.展开更多
The uncertainties of some key influence factors on coal crushing,such as rock strength,pore pressure and magnitude and orientation of three principal stresses,can lead to the uncertainty of coal crushing and make it v...The uncertainties of some key influence factors on coal crushing,such as rock strength,pore pressure and magnitude and orientation of three principal stresses,can lead to the uncertainty of coal crushing and make it very difficult to predict coal crushing under the condition of in-situ reservoir.To account for the uncertainty involved in coal crushing,a deterministic prediction model of coal crushing under the condition of in-situ reservoir was established based on Hoek-Brown criterion.Through this model,key influence factors on coal crushing were selected as random variables and the corresponding probability density functions were determined by combining experiment data and Latin Hypercube method.Then,to analyze the uncertainty of coal crushing,the firstorder second-moment method and the presented model were combined to address the failure probability involved in coal crushing analysis.Using the presented method,the failure probabilities of coal crushing were analyzed for WS5-5 well in Ningwu basin,China,and the relations between failure probability and the influence factors were furthermore discussed.The results show that the failure probabilities of WS5-5 CBM well vary from 0.6 to 1.0; moreover,for the coal seam section at depth of 784.3-785 m,the failure probabilities are equal to 1,which fit well with experiment results; the failure probability of coal crushing presents nonlinear growth relationships with the increase of principal stress difference and the decrease of uniaxial compressive strength.展开更多
基金Project(61171133) supported by the National Natural Science Foundation of ChinaProject(61101182) supported by the National Natural Science Foundation for Young Scientists of ChinaProject(11JJ1010) supported by the Natural Science Foundation for Distinguished Young Scholars of Hunan Province,China
文摘The original nonlinear chirp scaling(NCS) algorithm was extended for high precision processing of the highly squinted curvilinear trajectory synthetic aperture radar(CTSAR).Based on the analysis of slant range model and the frequency spectrum characteristics of the echo signal,a novel nonlinear chirp scaling function and more complex phase compensation factors with both velocity and acceleration parameters were proposed in the new algorithm for accommodation to curvilinear trajectory.The processing flow and computational complexity of modified NCS algorithm were fundamentally the same as the original NCS algorithm.However,the higher order phase compensation,range cell migration correction(RCMC) and range-variant secondary range compression(SRC) caused by the non-linear aperture and the severe range-azimuth coupling were accomplished accurately and efficiently without interpolation.Simulation results show that data acquired with a curvilinear aperture and a squint angle up to about 50° for X-band can be processed with no evident degradation of impulse response function.
基金Project(51204201)supported by the National Natural Science Foundation of ChinaProjects(2011ZX05036-001,2011ZX05037-004)supported by the National Science and Technology Major Program of China+1 种基金Project(2010CB226706)supported by the National Basic Research Program of ChinaProject(11CX04050A)supported by the Fundamental Research Funds for the Central Universities of China
文摘The uncertainties of some key influence factors on coal crushing,such as rock strength,pore pressure and magnitude and orientation of three principal stresses,can lead to the uncertainty of coal crushing and make it very difficult to predict coal crushing under the condition of in-situ reservoir.To account for the uncertainty involved in coal crushing,a deterministic prediction model of coal crushing under the condition of in-situ reservoir was established based on Hoek-Brown criterion.Through this model,key influence factors on coal crushing were selected as random variables and the corresponding probability density functions were determined by combining experiment data and Latin Hypercube method.Then,to analyze the uncertainty of coal crushing,the firstorder second-moment method and the presented model were combined to address the failure probability involved in coal crushing analysis.Using the presented method,the failure probabilities of coal crushing were analyzed for WS5-5 well in Ningwu basin,China,and the relations between failure probability and the influence factors were furthermore discussed.The results show that the failure probabilities of WS5-5 CBM well vary from 0.6 to 1.0; moreover,for the coal seam section at depth of 784.3-785 m,the failure probabilities are equal to 1,which fit well with experiment results; the failure probability of coal crushing presents nonlinear growth relationships with the increase of principal stress difference and the decrease of uniaxial compressive strength.
