When the vehicle is flying in the atmosphere at high speed, the optical head and the atmosphere will have severe friction, thus forming a complex flow field, which makes the target image shift in the optical imaging system. The influence of altitude on aero-optical imaging deviation is studied in this paper. The geometric modeling and mesh generation of a typical blunt nosed high-speed vehicle were carried out, and the three-dimensional(3 D) flow field density was obtained by a large amount of computational fluid dynamic calculation. In order to complete the optical calculation, the backward ray tracing method and the backward ray tracing stop criterion were used. The results show that as the height increases, the imaging deviation decreases gradually, and the imaging deviation slope increases and tends to be flat and close to zero.
A Raman spectroscopy method combined with neural network is used for the invasive and rapid detection of echinococcosis. The Raman spectroscopy measurements are performed on two groups of blood serum samples,which are from 28 echinococcosis patients and 38 healthy persons,respectively. The normalized Raman reflection spectra show that the reflectivity of the echinococcosis blood serum is higher than that of the normal human blood serum in the wavelength ranges of 101—175 nm and 1 801—2 701 nm. Then the principal component analysis(PCA) and back propagation neural network(BPNN) model are used to obtain the diagnosis results. The diagnosis rates for healthy persons and echinococcosis persons are 93.333 3% and 90.909 1%,respectively,so the average final diagnosis rate is 92.121 2%. The results demonstrate that the Raman spectroscopy analysis of blood serum combined with PCA-BPNN has considerable potential for the non-invasive and rapid detection of echinococcosis.
Aero-optic imaging is a kind of optical effect,which describes the imaging deviation on the imaging plane.In this paper,the effect of the change of Mach number of blunt aircraft on the aero-optic imaging deviation is studied.The imaging deviations of Mach number 0.5—3 are analyzed systematically.The results show that with the increase of Mach number,imaging deviation increases gradually,and the increase rate is gradually slow.Imaging deviation slope decreases gradually with the increase of Mach number,and gradually tends to be zero,suggesting that imaging deviation is not sensitive to the change of the larger Mach number.In other words,the Mach number of smaller changes can lead to larger imaging deviation.As the Mach number of the aircraft increases,the slope of the imaging offset tends to be closer and closer to 0.When the Mach number of the aircraft increases to a certain extent,the change of the imaging offset will not have much influence.Therefore,in order to reduce the impact of flight speed on imaging migration,the aircraft should fly at a higher Mach number.
