We present a robust and fiducial-marker-free algorithm that can identify and correct stick-slip distortion caused by nonuniform rotation(or beam scanning)in distally scanned catheters for endoscopic optical coherence ...We present a robust and fiducial-marker-free algorithm that can identify and correct stick-slip distortion caused by nonuniform rotation(or beam scanning)in distally scanned catheters for endoscopic optical coherence tomography(OCT)images.This algorithm employs spatial fre-quency analysis to select and remove distortions.We demonstrate the feasibility of this algorithm on images acquired from ex vivo rat colon with a distally scanned DC motor-based endoscope.The proposed algorithm can be applied to general endoscopic OCT images for correcting non-uniform rotation distortion.展开更多
In this paper,a high-order distortion model is proposed for analyzing the rotating stall inception process induced by inlet distortion in axial compressors.A distortion-generating screen in the compressor inlet is con...In this paper,a high-order distortion model is proposed for analyzing the rotating stall inception process induced by inlet distortion in axial compressors.A distortion-generating screen in the compressor inlet is considered.By assuming a quadratic function for the local flow total pressure-drop,the existing Mansoux model is extended to include the effects of static inlet distortion,and a new high-order distortion model is derived.To illustrate the effectiveness of the distortion model,numerical simulations are performed on an eighteenth-order model.It is demonstrated that long length-scale disturbances emerge out of the distorted background flow,and further induce the onset of rotating stall in advance.In addition,the circumferential non-uniform distribution and time evolution of the axial flow are also shown to be consistent with the existing features.It is thus shown that the high-order distortion model is capable of describing the transient behavior of stall inception and will contribute further to stall detection under inlet distortion.展开更多
This paper represents numerical simulation of flow inside an axial transonic compressor subject to inlet flow distortion,to evaluate its effect on compressor performance and stability.Two types of inlet distortion,nam...This paper represents numerical simulation of flow inside an axial transonic compressor subject to inlet flow distortion,to evaluate its effect on compressor performance and stability.Two types of inlet distortion,namely inlet swirl and total pressure distortion are investigated.To study the effect of combined distortion patterns,different combinations of inlet swirl and total pressure distortion are also studied.Results for cases with total pressure distortion indicate that hub radial distortion improves stability range of the compressor while tip radial distortion deteriorates it.An explanation for this observation is presented based on redistribution of flow parameters caused by distortion and the way it interacts with stall inception mechanisms in a transonic axial compressor.Results also show that while co-swirl patterns slightly improve stability range of the compressor,counter-swirl patterns diminish it.Study of combined distortion cases reveals that superimposition of effects of each individual pattern could predict the effect of a combined pattern on compressor's performance within an accuracy of 1%.However,it is unable to predict the associated effect on compressor's stability.展开更多
基金supported in part by the National Institutes of Health under the grant No.R01 HL121788The Wallace H.Coulter FoundationMaryland Innovation Initiative(MII)Fund from TEDCO
文摘We present a robust and fiducial-marker-free algorithm that can identify and correct stick-slip distortion caused by nonuniform rotation(or beam scanning)in distally scanned catheters for endoscopic optical coherence tomography(OCT)images.This algorithm employs spatial fre-quency analysis to select and remove distortions.We demonstrate the feasibility of this algorithm on images acquired from ex vivo rat colon with a distally scanned DC motor-based endoscope.The proposed algorithm can be applied to general endoscopic OCT images for correcting non-uniform rotation distortion.
基金co-supported by the National Major Scientific Instruments Development Project of China(No.61527811)the National Science Fund for Distinguished Young Scholars of China(No.61225014)+3 种基金the Guangdong Inovative Project(No.2013KJCX0009)the Guangdong Provice Natural Science Foundation(No.2014A030312005)the Guangdong Provice Key Laboratory of Biomedical Engineeringthe Space Intelligent Control Key Laboratory of Science and Technology for National Defense
文摘In this paper,a high-order distortion model is proposed for analyzing the rotating stall inception process induced by inlet distortion in axial compressors.A distortion-generating screen in the compressor inlet is considered.By assuming a quadratic function for the local flow total pressure-drop,the existing Mansoux model is extended to include the effects of static inlet distortion,and a new high-order distortion model is derived.To illustrate the effectiveness of the distortion model,numerical simulations are performed on an eighteenth-order model.It is demonstrated that long length-scale disturbances emerge out of the distorted background flow,and further induce the onset of rotating stall in advance.In addition,the circumferential non-uniform distribution and time evolution of the axial flow are also shown to be consistent with the existing features.It is thus shown that the high-order distortion model is capable of describing the transient behavior of stall inception and will contribute further to stall detection under inlet distortion.
文摘This paper represents numerical simulation of flow inside an axial transonic compressor subject to inlet flow distortion,to evaluate its effect on compressor performance and stability.Two types of inlet distortion,namely inlet swirl and total pressure distortion are investigated.To study the effect of combined distortion patterns,different combinations of inlet swirl and total pressure distortion are also studied.Results for cases with total pressure distortion indicate that hub radial distortion improves stability range of the compressor while tip radial distortion deteriorates it.An explanation for this observation is presented based on redistribution of flow parameters caused by distortion and the way it interacts with stall inception mechanisms in a transonic axial compressor.Results also show that while co-swirl patterns slightly improve stability range of the compressor,counter-swirl patterns diminish it.Study of combined distortion cases reveals that superimposition of effects of each individual pattern could predict the effect of a combined pattern on compressor's performance within an accuracy of 1%.However,it is unable to predict the associated effect on compressor's stability.
