Classification and spectrum optimization method of grease based on infrared spectrum

The infrared(IR)absorption spectral data of 63 kinds of lubricating greases containing six different types of thickeners were obtained using the IR spectroscopy.The Kohonen neural network algorithm was used to identify the type of the lubricating grease.The results show that this machine learning method can effectively eliminate the interference fringes in the IR spectrum,and complete the feature selection and dimensionality reduction of the high-dimensional spectral data.The 63 kinds of greases exhibit spatial clustering under certain IR spectrum recognition spectral bands,which are linked to characteristic peaks of lubricating greases and improve the recognition accuracy of these greases.The model achieved recognition accuracy of 100.00%,96.08%,94.87%,100.00%,and 87.50%for polyurea grease,calcium sulfonate composite grease,aluminum(Al)-based grease,bentonite grease,and lithium-based grease,respectively.Based on the different IR absorption spectrum bands produced by each kind of lubricating grease,the three-dimensional spatial distribution map of the lubricating grease drawn also verifies the accuracy of classification while recognizing the accuracy.This paper demonstrates fast recognition speed and high accuracy,proving that the Kohonen neural network algorithm has an efficient recognition ability for identifying the types of the lubricating grease.

Polarization properties in helical metamaterials

In the last few years, there has been growing interest in the research of helical metamaterials due to the advantages of giant circular dichroism; broad operation bands, and compact structures. However, most of the researches were in the cases of single-, circular-helical metamaterials, and normal incidences. In this paper, we reviewed recent simulation works in the helical metama- terials with the finite-difference time-domain （FDTD） method, which mainly included the optical performances of double-, three-, four-helical metamaterials, perfor- mances of elliptical-helical metamaterials, and the polar- ization properties under the condition of oblique incidences. The results demonstrate that the double-helical metamaterials have operation bands more than 50%, which is broader than those of the single-helical structures. But both of them have low signal-to-noise ratios about 10 dB. The three- and four-helical metamaterials have significant improvement in overall performance. For elliptical- helixes, simulation results suggest that the transmitted light can have elliptical polarization states. On the condition of oblique incidences, the novel property of tunable polarization states occurred in the helical metama- terials, which could have much broader potential applica- tions such as tunable optical polarizers, tunable beam splitters, and tunable optical attenuators.