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Ti-6Al-4V has a wide range of applications, especially in the aerospace field; however, it is a difficultto-cut material. In order to achieve sustainable machining of Ti-6Al-4V, multiple objectives considering not only economic and technical requirements but also the environmental requirement need to be optimized simultaneously. In this work, the optimization design of process parameters such as type of inserts, feed rate, and depth of cut for Ti-6Al-4V turning under dry condition was investigated experimentally. The major performance indexes chosen to evaluate this sustainable process were radial thrust, cutting power, and coefficient of friction at the toolchip interface. Considering the nonlinearity between the various objectives, grey relational analysis (GRA) was first performed to transform these indexes into the corresponding grey relational coefficients, and then kernel principal component analysis (KPCA) was applied to extract the kernel principal components and determine the corresponding weights which showed their relative importance. Eventually, kernel grey relational grade (KGRG) was proposed as the optimization criterion to identify the optimal combination of process parameters. The results of the range analysis show that the depth of cut has the most significant effect, followed by the feed rate and type of inserts. Confirmation tests clearly show that the modified method combining GRA with KPCA outperforms the traditional GRA method with equal weights and the hybrid method based on GRA and PCA.

This paper studies the taxonomy of the myrmecophilous genus Lomechusa Gravenhorst, 1806 from China and describes four new species: Lomechusa elegans Chen & Zhou, n. sp. from Beijing, Lomechusa brevicornis Chen & Zhou, n. sp. from Beijing, Lomechusa seticornis Chen & Zhou, n. sp. from Hunan, and Lomechusa parva Chen & Zhou, n. sp. from Tibet. A key to all seven Chinese species of the genus Lomechusa is provided.

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