KEYWORDS: Super resolution, Image restoration, Feature extraction, Convolutional neural networks, Deep learning, Data modeling, Data acquisition, Target recognition, Signal to noise ratio, Image quality
With the rapid advancement of hypersonic flight technology, the high-precision measurement of hypersonic flow field parameters has become an urgent issue. The computational fluid dynamics (CFD) method for obtaining high-resolution flow field data requires high grid quality and involves complex numerical solving processes, leading to significant computational costs. There is a growing need to quickly obtain high-resolution flow field data with less effort. Leveraging the powerful nonlinear fitting capabilities of neural networks, it is possible to perform fine super-resolution reconstruction of low-resolution flow field data in a data-driven manner. In this study, we propose an improved Enhanced Super-resolution Convolutional Neutral Network (ESRCNN) model tailored for hypersonic target flow fields. This enhanced model is applied to the super-resolution reconstruction of low-resolution flow fields of blunt body aircraft targets and compared with interpolation methods and traditional deep learning methods. Peak Signal-to-Noise Ratio (PSNR) and Structural Similarity Index (SSIM) are used as evaluation metrics. The results validate the accuracy and superiority of this model in reconstructing hypersonic target flow fields. This method provides an effective approach for the precise measurement and reconstruction of hypersonic flow fields, thereby contributing to the advancement of hypersonic flight technology.
An experimental scheme based on interferometry is designed to measure the orbital angular momentum spectrum of vortex beam perturbed by turbulence. The orbital angular momentum spectrum of vortex beam can be calculated by using four light intensity images. The laser beam is modulated by a spatial light modulator to obtain a vortex beam, and then passes through another spatial light modulator loaded with a turbulent phase perturbation hologram to interfere with the reference beam. The orbital angular momentum spectrum of the vortex beam can be obtained by making use of two interference patterns and the intensity patterns of the vortex beam and the reference beam. The results show that the experimental scheme can measure the orbital angular momentum spectrum of the vortex beam affected by turbulence.
Aiming at the requirement of accurate simulation of near-space atmospheric infrared background radiation, this paper simulates near-space infrared atmospheric background radiance according to atmospheric parameters detected by satellites. The multi-channel infrared radiometer SABER (Sound of the Atmosphere using Broadband Emission Radiometry) carried by TIMED satellite (Thermosphere, Ionosphere Mesosphere Energetics and Dynamics) is used to acquire atmospheric profile. Combined with limb observation model and atmospheric background radiance calculation model, the transmittance and spectral radiance of infrared atmospheric background were simulated. The spectral radiance of atmospheric background under the standard atmospheric model and satellite atmospheric profiles was compared to analyze the difference between the two atmospheric parameter. In the infrared band, the atmospheric profile has a great impact on atmospheric background radiance. For the accurate simulation calculation of infrared background spectral radiance in different regions, the influence of atmospheric profile parameters should be taken into account.
At high temperatures, typical species in the rocket exhaust plume produce spectral radiation signals in a specific spectrum due to high-temperature vibration-rotation transitions. This signal level strongly depend on the working condition of the rocket engine. In this paper, based on the statistic-narrow-band (SNB) model and the latest version of the HITEMP2010 line-by-line database, a database of spectral radiation calculation parameters for methane combustion products, H2O and CO2, is established. By comparing the experimental results and the line-by-line method, the correctness of the model verified. Based on this database, considering the atmospheric detection band of the typical rocket plume infrared radiation signals, the un-attenuated and attenuated by the long atmospheric path are predicted, (2.7 and 4.3μm band) spectral radiance of the high temperature mixed gases (H2O and CO2) at different altitude are predicted. The model prediction results compared with the experimental results, and good results obtained accurately
Atmospheric transmittance is a significant parameter in the research of atmospheric radiation transmission. To research the impact of atmospheric profile on the simulation of infrared atmospheric transmittance, multichannel infrared radiometer SABER (Sounding of the Atmosphere using Broadband Emission Radiometry) carried by TIMED satellite (Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics) is used to acquire atmospheric profile. The infrared limb atmospheric transmittance of the South China Sea area (105°E-118°E,4°N-21°N) and MODTRAN standard atmospheric model are simulated. The differences between the two models are analyzed that in infrared spectral band, the variation of atmospheric profile has a great impact on the simulation of atmospheric transmittance. The atmospheric transmittance of the arbitrary region can be obtained by this method, which is more accurate than the standard atmospheric model.
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