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
The lifetime of an artificial satellite moving in the circular orbit under the action of nonuniform rotating atmospheric drag is studied from an energy point of view in this paper. The angular velocity of atmospheric ...The lifetime of an artificial satellite moving in the circular orbit under the action of nonuniform rotating atmospheric drag is studied from an energy point of view in this paper. The angular velocity of atmospheric rotation decreases with height according to hydrodynamics. The atmospheric density decreases with height according to the exponential formula. The expression for the lifetime of a satellite in the instantaneous circular orbit in the above-mentioned rotating atmospheric model is derived, and the numerical estimation for the lifetime of a concrete satellite has been made. The result shows clearly that the satellite lifetime calculated by this paper is shorter than that calculated by the uniform rotating atmospheric model.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.
文摘The lifetime of an artificial satellite moving in the circular orbit under the action of nonuniform rotating atmospheric drag is studied from an energy point of view in this paper. The angular velocity of atmospheric rotation decreases with height according to hydrodynamics. The atmospheric density decreases with height according to the exponential formula. The expression for the lifetime of a satellite in the instantaneous circular orbit in the above-mentioned rotating atmospheric model is derived, and the numerical estimation for the lifetime of a concrete satellite has been made. The result shows clearly that the satellite lifetime calculated by this paper is shorter than that calculated by the uniform rotating atmospheric model.
