With aids of corpus linguistics technology, WordSmith Tools, Range, and other software such as Coh-Metrix, this paper attempts to give a scientific analysis on lexical proficiency of writings in placement test for vocational college majors of arts and those of science. First, there exist huge lexical proficiency discrepancies between the students, and they should be implanted more stylistic knowledge in writing and be input more original English materials to enlarge their English vocabulary size. Second, those using more referential cohesive devices and more difficult words tend to score lower in their writings, and the students should be instructed to pay attention to the surface coherence, but also to focus more attention to the global coherence. Finally, the students of arts do better than those of science in deep cohesion, and can score higher, despite that their words are usually the basic common words, suggesting that global coherence is of the greatest importance in all types of writings.

In the process of producing covered yarn, a single outer wrapping yarn forms a balloon when it rotates at high speed. In this work, we used a mathematical model of a balloon formed by polyamide,which is a common outer wrapping yarn, and verified its feasibility with a group of experimental data. The effects of yarn tension, rotation speed, balloon height and turntable radius on the balloon shape were analysed and the correctness simultaneously demonstrated.

During the processing of covered yarn, the stability of the tension of the yarn unwinding from the package directly affects the quality of the covered yarn. In this work, a mathematical model of the yarn unwinding balloon was established, and the influence of Coriolis force and air resistance on the balloon was considered. Further, the balloon shape of the yarn at different unwinding linear speeds was studied. An experimental observation platform for the yarn balloon morphology was built. The comparative analysis of the balloon shape obtained using the experimental observation and the theoretical research results showed that the mathematical model of the yarn unwinding balloon is correct. The phenomenon of scratching the upper edge of the package during the unwinding of spandex should be avoided. Finally, in order to maximize the diameter of the spandex package, the taper of the core yarn bobbin and the minimum yarn guide distance was determined based on the guidance of the theoretical simulations and experimental analysis. The research results provide a design base for the layout and structural dimensions of the follow-up elastic fiber passive precision tension control device.

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For the stability of composite fibre spinning, the difference in and distribution of the polymer melt velocity during the spinning are among the factors of importance. Based on the basic equation for the control of composite spinning dynamics, boundary conditions are identified and reported in this paper. A mathematical model for the symmetric and asymmetric distribution of the melt flow velocity in the microhole of the spinneret of the composite spinning assembly was developed. The accuracy of the mathematical model was also ascertained. It gives a theoretical basis for the designing of a composite spinning assembly.