Honeycomb structure composites are taking an increasing proportion in aircraft manufacturing because of their high strength-to-weight ratio, good fatigue resistance, and low manufacturing cost. However, the hollow structure is very prone to liquid ingress. Here, we report a fast and automatic classification approach for water, alcohol, and oil filled in glass fiber reinforced polymer (GFRP) honeycomb structures through terahertz time-domain spectroscopy (THz-TDS). We propose an improved one-dimensional convolutional neural network (1D-CNN) model, and compared it with long short-term memory (LSTM) and ordinary 1D-CNN models, which are classification networks based on one dimension sequenced signals. The automated liquid classification results show that the LSTM model has the best performance for the time-domain signals, while the improved 1D-CNN model performed best for the frequency-domain signals.

Low-energy ion beam erosion has been shown to be a promising alternative approach for generation of self-organized patterns on crystal surfaces. In addition to the removal of material from the surface due to sputtering caused by energy and momentum transfer from the incoming ions to target atoms, the interplay between sputter-induced roughening (result in a rough surface) and various surface relaxation mechanisms(result in a smooth surface) can lead to a wide range of well ordered patterns on the surface. In the experiments the Low-energy Ar+ ion beam were produced in a cleaning ion source on the magnetron sputter equipment from Belarus, and dot and ripple patterns have obtained at the different ion beam incidence. The FFT method is used to analyze the obtained nanostructures. In this paper results on self-organized patterns formed during low energy Ar+ ion beam erosion on Si surfaces are presented. It is analyzed the influence of ion beam parameters, such as the ion incidence angle, ion flux, and ion energy, to the self-organized nanostructures, and given the patterns formed on the Si surfaces in the case without sample rotation . The experimental results show periodic structures are depended deeply on the incidence angle of ion beams, and ripple patterns transferred from dot patterns with the increasing in ion beam incidence angle, which coincided with the Bradley-Harper theory of ripple formation.